INSTITUTO POLITÉCNICO NACIONAL

Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada

“Catalytic activity of mixed metal hexacyanocobaltates in oxidation process”

Tema que para obtener el grado de Doctora en Tecnología Avanzada

Presenta: M.C. Alma Lilia García Ortiz

Director de Tesis:

Dr. Edilso F. Reguera Ruiz

Julio, 2015.

INDEX FIGURE INDEX ____________________________________________________________________________________ 4 TABLE INDEX _____________________________________________________________________________________ 5 SCHEME INDEX ___________________________________________________________________________________ 5 1. INTRODUCTION _____________________________________________________________________________ 6 2. STATE OF THE ART _________________________________________________________________________ 9

2.1 Heterogeneous catalysis _____________________________________________________________________ 9 2.1.1. Concept ______________________________________________________________________________________________ 9 2.1.2. Adsorption _________________________________________________________________________________________ 10 2.1.2.1. Physisorption _____________________________________________________________________________________ 10 2.1.2.2. Chemisorption ____________________________________________________________________________________ 11 2.1.3. Acid - Base properties ____________________________________________________________________________ 13

2.2 Oximes _______________________________________________________________________________________ 14 2.2.1. Oxidation example ______________________________________________________________________________ 15

2.3. bis-naphthalenethiol and bis-naphthol _________________________________________________ 15 2.3.1. Bis- naphthalenethiol reactions ________________________________________________________________ 16 2.3.1.1. Preparative methods _____________________________________________________________________________ 16 2.3.1.2. Reactions example ________________________________________________________________________________ 16 2.3.2. Bis- naphthol reactions __________________________________________________________________________ 17 2.3.2.1. Preparative methods _____________________________________________________________________________ 17 2.3.2.2. Reactions example ________________________________________________________________________________ 18 2.3.3. C-C Coupling _______________________________________________________________________________________ 19

3. MATERIALS AND METHODS______________________________________________________________ 22

3.1 Synthesis of Hexacyanocobaltates _______________________________________________________ 22

3.2 Reactors and reactions ____________________________________________________________________ 22 3.2.1. The reactor ________________________________________________________________________________________ 22 3.2.2. Reaction performance ___________________________________________________________________________ 23

3.3 Evaluation of catalytic activity and monitoring by GC ________________________________ 24 3.3.1. Theoretical foundations _________________________________________________________________________ 24 3.3.1.1. Definition __________________________________________________________________________________ 24 3.3.1.2. Equipment _________________________________________________________________________________ 24 3.3.2. Standard internal and external ________________________________________________________________ 26 3.3.2.1. Internal standard _________________________________________________________________________ 26 3.3.2.2. External standard _________________________________________________________________________ 26 3.3.3. Response factor calculations ____________________________________________________________________ 27 3.3.3.1. Calculated example from naphthalenethiol ______________________________________________ 27 3.3.4. Conversion and yield calculations ______________________________________________________________ 28 3.5.6. Equipment characteristics ______________________________________________________________________ 29

4. RESULTS AND DISCUSSION_______________________________________________________________ 31

4.1 Characterization of Hexacyanocobaltates ______________________________________________ 31

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4.1.1. Powder X-ray diffraction ________________________________________________________________________ 31 4.1.2. Infrared spectra __________________________________________________________________________________ 32 4.1.3. Thermogravimetric curves ______________________________________________________________________ 33 4.1.4. X-ray fluorescence spectroscopy _______________________________________________________________ 34

4.2 Oxidation of oximes ________________________________________________________________________ 35 4.2.1. Ciclohexanone oxime _____________________________________________________________________________ 35 4.2.2. Acetophenone oxime _____________________________________________________________________________ 36 4.2.3. Other oximes ______________________________________________________________________________________ 41 4.2.4. Mechanism proposal _____________________________________________________________________________ 42

4.3 Oxidative coupling of naphthalenethiol and naphthol ________________________________ 45 4.3.1. Oxidative coupling of naphthalenethiol _______________________________________________________ 45 4.3.1.1. Characterization of Bis-naphthalenethiol ________________________________________________ 49 4.3.1. Oxidative coupling of naphthol _________________________________________________________________ 53

5. CONCLUSIONS ______________________________________________________________________________ 55 6. PERSPECTIVES _____________________________________________________________________________ 56 7. SUPPLEMENTARY INFORMATION ______________________________________________________ 57

7.1. Isomerism scheme _________________________________________________________________________ 57

7.2 X-Ray Power Diffraction ___________________________________________________________________ 58

7.3 TG Curves ____________________________________________________________________________________ 64

7.4 X-ray fluorescence spectroscopy _________________________________________________________ 70

7.5. Monitoring of oxidative coupling from naphthalenethiol ___________________________ 75

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FIGURE INDEX Figure 2. 1. Process of the reaction with catalyst and without catalyst ___________ 9 Figure 2. 2. Defects and associated coordinate unsaturation ______________________ 13 Figure 2. 3. Back donation in the Co–C≡N–T chain___________________________________ 13 Figure 2. 4. Structure from a) aldoxime and b) ketoxime __________________________ 14 Figure 2. 5.a) Structure of bis-naphthalenethiol, b) Structure of bis-naphthol _ 15 Figure 3. 1.Reinforced glass semi continuous reactor ______________________________ 23 Figure 3. 2. Chromatograph components______________________________________________ 24 Figure 3. 3. Chromatogram ______________________________________________________________ 25 Figure 4.1. a)Power XRD of Co1.4Cu1.6[Co(CN)6]8H2O. b)Crystal structure of hexacyanocobaltates showing the lattice and the dimensions of cubic pores __ 32 Figure 4. 2. Infrared spectra of Co1.4Cu1.6[Co(CN)6]2 8H2O _________________________ 32 Figure 4. 3. TG curve for Co1.4Cu1.6[Co(CN)6]2∙8H2O ________________________________ 33 Figure 4. 4. X-ray fluorescence spectroscopy of FeCu2[Co(CN)6]2 ∙7.5H2O ______ 34 Figure 4. 5. Conversion plots for the oxidation of acetophenone oxime to acetophenone ______________________________________________________________________________ 38 Figure 4. 6. Time-percentage plot for the oxidation of acetophenone oxime by FeCu2[Co(CN)6]2 as catalyst _____________________________________________________________ 39 Figure 4. 7. Time-yield plot for the consecutive runs _______________________________ 40 Figure 4. 8. XRD pattern of FeCu2[Co(CN)6]2 reuses. ________________________________ 41 Figure 4. 9. Time-yield plots for the oxidation of acetophenone oxime __________ 43 Figure 4.10.Conversion plots for the oxidative coupling of naphthalenethiol __ 46 Figure 4. 11. Time - percentage plot for the oxidative coupling of naphthalenethiol __________________________________________________________________________ 47 Figure 4. 12. Time-yield plot for the consecutive runs ______________________________ 48 Figure 4. 13. Powder XRD pattern of FeCu2[Co(CN)6]2 reuses _____________________ 48 Figure 4. 14. X-Ray pattern from Bis-naphthalenethiol _____________________________ 49 Figure 4. 15. IR spectra from 2-naphtalenethiol and Bis-naphthalenethiol _____ 50 Figure 4.16. Peaks from Bis-naphthalenethiol isomers _____________________________ 51 Figure 4.17. Fragmentation pattern from Bis-naphthalenethiol __________________ 52 Figure 4.18. Fragmentation pattern publish in SDBS No. 16326 __________________ 52 Figure 4.19. Conversion-plot from naphthol to bis-nathpthol _____________________ 54 Figure 4. 20. Chromatographic sequence of oxidative coupling from naphthol to bis-naphthol _______________________________________________________________________________ 54

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TABLE INDEX Table 1. 1. Historical background of catalytic processes ____________________________ 6 Table 2. 1. BET surface area and pore volume from hexacyanocobaltates ______ 11 Table 3. 1. Solution from naphthalenethiol to FR ____________________________________ 27 Table 3. 2. Experimental areas from each sample ___________________________________ 28 Table 3. 3. Response factor from naphthalenethiol _________________________________ 28 Table 3. 4. PM theoretical and experimental weight ________________________________ 29 Table 3. 5. Kinetic data from oxidative coupling reaction of naphthalenethiol to Bis-naphthalenethiol _____________________________________________________________________ 29 Table 4. 1. Infrared vibrations wavenumber for the materials under study ____ 33 Table 4. 2. Oxidation of the cyclohexanone oxime by molecular oxygen _________ 35 Table 4. 3. Influence of the solvent on the performance of Cu3[Co(CN)6]2 as catalyst ______________________________________________________________________________________ 36 Table 4. 4. Catalytic activity for the conversion of acetophenone oxime to acetophenone ______________________________________________________________________________ 37 Table 4. 5. Additive substances at the reaction to perform the mechanism _____ 42 Table 4. 6.Oxidative coupling from naphthalenethiol to bis-naphthalenethiol _ 45 Table 4. 7. Elemental Analysis from formula: C10H14S2 _____________________________ 51 Table 4. 8. Oxidative coupling from naphthol to bis-naphthol _____________________ 53

SCHEME INDEX Scheme 2. 1. Use of bis-naphthalenethiol from obtaining of a cyclic diene ______ 17 Scheme 2. 2. Example of a route from resolution of racemic bis-naphthol ______ 18 Scheme 2. 3. Crown ether derivative from Bis-naphthol____________________________ 18 Scheme 2. 4. Categories of dual activation. ____________________________________________ 19 Scheme 2. 5. Mechanism of the Heck reaction ________________________________________ 20 Scheme 2. 6. Mechanism of the Suzuki reaction _______________________________________ 2 Scheme 4. 1. Conversion of cyclohexanone oxime to cyclohexanone 35 Scheme 4. 2. Conversion of acetophenone oxime to acetophenone _______________ 37 Scheme 4. 3. a) Conversion of benzophenone oxime to benzophenone; b) Conversion of carvone oxime to carvone ______________________________________________ 41 Scheme 4. 4. Proposed mechanism for the aerobic oxidation of oximes to carboxylic compound in the presence of mixed double metal cyanides. _________ 44 Scheme 4. 5. Oxidative coupling from 2-naphthalenethiol to bis-naphthalenethiol. _________________________________________________________________________ 45 Scheme 4. 6. Bis-naphthalenethiol with a torsion angle of 90° ____________________ 50

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1. INTRODUCTION Catalysis is an important field in the chemistry which almost 90% of chemical processes involving catalysts in at least one of their steps. In the table 1.1 is illustrated a historical background of some catalytic processes. Table 1. 1. Historical background of catalytic processes1

Catalytic process Catalyst Main author Year Sulfuric acid Lead chamber Roebuck 1746

Dehydration of alcohols Acid Priestley 1778 Esterification of organic acids Acid Scheele 1782

Dehydrogenation of alcohols (ethanol) Metal Van Marum 1796 Oxidation of alcohol Pt black Priestley &

Döbereiner 1810

Decomposition of H2 O2 and NH3 Metals Thénard 1813 Hydrolysis of starch to glucose Acid Kirchoff 1814

Combustion Pt Davy 1817 Decomposition NH3 Fe > Cu > Ag > Au > Pt Dulong 1823

Oxidation Pt Fusinieri 1824 Oxidation SO2 to SO3 (contact process) Pt Phillips 1831

Definition of catalysis Berzelius 1836 Oxidation of NH3 to nitric acid Pt Kuhlmann 1838

HCl + O2 → Cl2 Cu Deacon 1875 Esterification of acid Acid Bertholet 1879

Sulfuric acid V2 O5 1875 Friedel-Crafts reactions Lewis acids (AlCl ) Friedel & Crafts 1877

Nitric acid synthesis Pt gauzes 1904 NH3 synthesis from N2 and H2 under

high pressure Fe Haber 1909

Hydrogenation Ni Sabatier 1912 Active site concept Michaelis 1913

Theory of adsorption Langmuir 1915 Industrial process of NH3 synthesis

under pressure Fe Haber 1918

CO + H2 → CH3 OH ZnO-chromia BASF 1923 CO + H2 → hydrocarbons Fe, Co Fischer & Tropsch 1923 Contact catalysis theory Taylor 1925

Hydrogenation vegetable oils Ni Raney 1926 Catalytic cracking of petroleum Acid Houdry 1930

Synthesis gas Bergius & Bosch 1931 Alkylation reaction for gasoline fuel Acid Ipatieff & Pines 1940

Synthetic zeolites Barrer & Breck 1946

Exhaust gas treatment General Motors & Ford 1976

1. I. Fechete, Y. Wang, J. C. Védrine, Catal. Today, 189 (2012) 2

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The focus of the catalysis is the transformation of organic or inorganic substances in other more important or relevant, although, at present, due to environmental issues and our dependence on fossil fuels such as coal, petroleum, and natural gas, the fuel production is the industry as major demand of novel catalytic materials. However, world reserves are diminishing inexorably and this situation cannot last for long time so are urgently needed promoting materials of new energies, for example those that are capable of producing electricity, breaking H2O bonds with the separation of H2 and O2, and storing the energy either in batteries or as molecular hydrogen. Catalytic processes more efficient, require improvements in the catalytic activity and selectivity whereby it becomes important to tailor the design of catalytic materials with the desired structures and the desired dispersion of active sites, which can be found in materials such as zeolites1, LDHs2 (Layered double hydroxides), CNTs3 (Carbon nanotubes), PILC4 (Pillared interlayer clays), MOFs5 (Metal organic frameworks), offer a variety of these possibilities, with controlled large and accessible surface areas of the catalysts. These materials may possess specific chemical properties, such as acid-base, redox, dehydrogenating, hydrogenating, oxidizing and physical properties like porosity, high surface area, thermal and electrical conductivity. On the other hand, scientist also search that the catalysts being inexpensive and easily obtained to multigram scale.

Recently, hexacyanometallates, which are a serial of materials with molecular formula MII[MIII(CN)6]2∙nH2O, have been used as heterogeneous catalysts for the industrial ring epoxide aperture with alcohols leading to polyetherols.6 However, these material offer many other possibilities as polycarbonates and poly-oles synthesis7-9 and for hydroamination of alkenes and alkynes.10, 11 All of these reactions with high catalytic activity. Once exposed above, has been suggested as thesis subject, the evaluation of catalytic activity in oxidation reactions, of a serie of hexacyanocobaltates which contain mixture of divalent metals such as Mn2+, Fe2+, Co2+, Ni2+ and Cu2+.

1. B. Smit, T. L. M. Maesen, Nature 451 (2008) 671 2. R. Yang, Y. Gao, J. Wanga, Q. Wang, Dalton Trans., 43 (2014) 10317 3. N. I. Andersen, A. Serov, P. Atanassov, Appl Catal. B: Envir. 163, (2015) 623 4. J. G. Mei, S. M. Yu, J. Cheng, Catal. Comm., 5 (2004) 437 5. J. Lee, O. K. Farha, J. Roberts, K. A. Scheidt, T. Nguyena, J. T. Hupp, Chem. Soc. Rev., 38 (2009) 1450 6. Yu, Guangzhou Huaxue 29 (2004) 47 7. X.-K. Sun, X.-H. Zhang, S. Chen, B.-Y. Du, Q. Wang, Z.-Q. Fan, G.-R. Qi, Polymer 51 (2010) 5719 8. I. Kim, M.J. Yi, S.H. Pyun, D.W. Park, C.-S. Ha, Stud. Surf. Sci. Catal. 153 (2004) 239 9. J.L. Garcia, E.J. Jang, H. Alper, J. Appl. Polym. Sci. 86 (2002) 1553 10. A. Peeters, P. Valvekens, R. Ameloot, G. Sankar, C.E.A. Kirschhock, D. De Vos, ACS Catal. 3 (2013) 597 11. A. Peeters, P. Valvekens, F. Vermoortele, R. Ameloot, C. Kirschhock, D. De Vos, Chem. Commun. 47 (2011) 4114

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These materials were made in order to have present in the solid hexacyanocobaltates, ions that can provide the structural integrity and also they can interact with oxygen and introduce Lewis acidity to bind some organic molecules that contain Lewis bases sites.

For which arise the next general objective:

Synthesis, characterization and evaluation by gases chromatography of catalytic activity of hexacyanocobaltates in oxidation process.

And as specific objectives:

Synthesis of hexacyanocobaltates of formula MAXMB3-X[Co(CN)6]2∙nH2O with metal divalent mixture of Mn2+, Fe2+, Co2+, Ni2+ and Cu2+ by precipitation technique.

Characterization of hexacyanocobaltates by means of:

-Infrared spectroscopy -X-ray diffraction -Thermogravimetric analysis -X-ray Fluorescence

Evaluation of catalytic activity of hexacyanocobaltates as heterogeneous catalyst and monitoring the process of reactions by Gases Chromatography in: -Oxidation reaction of Oximes to ketones -Oxidative coupling of naphthalenethiol and naphthalene Characterization of products by separation with Gases Chromatography and their identification by Mass Spectrometry.

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2. STATE OF THE ART

2.1 Heterogeneous catalysis 2.1.1. Concept Catalysis is a term that was defined in 1836 by J.J. Berzelius to describe the property of substances called catalyst which, being in small quantities, increase the rate of a chemical reactions and decreasing the activation energy without being consumed in them. However, the catalyst enhances the rate of the reaction, it cannot modify the thermodynamics or the equilibrium. Reaction features are shown in figure 2.1.

Figure 2. 1. Process of the reaction with catalyst and without catalyst

In Heterogeneous catalysis are present different phases during the reaction, usually the catalyst are in solid state, whereby, are typically more tolerant of extreme operating conditions and the main advantage of this, is the relative ease of catalyst separation from the products and this aids in the creation of continuous chemical processes. Heterogeneous catalytic reaction involves a serie of process such as:

- O. Deutschmann, K. Kochloefl, Heterogeneous Catalysis and Solid Catalysts, Wiley-VCH Verlag GmbH & Co., Weinheim, Germany, 2009 - P. Stoltze, Introduction to heterogeneous catalysis, Department of Chemistry and Applied Engineering Science, Aalborg, Denmark.

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• Adsorption of reactants from a gas phase onto a solid surface • Surface reaction of adsorbed species • Desorption of products into the fluid phase

2.1.2. Adsorption First step in a heterogeneous catalytic reaction involves activation of a reactant molecule by adsorption onto a catalyst surface. There are two main classes of adsorption: physisorption and chemisorption. 2.1.2.1. Physisorption Is also known as Van der Waals adsorption which remains under a relatively weak interaction between the adsorbate and the adsorbent surface. More than one layer of molecules can be physisorbed on a surface. Some adsorption measurements indicate the extent of the solid surface area and provide information on the pore structure of the solid. One method of surface-area measurement was developed by Brunauer, Emett and Teller, (BET). Their equation can be written in the form:

𝑥𝑥𝑉𝑉(1 − 𝑥𝑥)

= 1𝑉𝑉𝑚𝑚𝐶𝐶

+ (𝐶𝐶 − 1)𝑥𝑥𝑉𝑉𝑚𝑚𝐶𝐶

Where x is the relative pressure p/p°, for the adsorbate, V is the volume of gas adsorbed at relative pressure x; Vm is the volume of adsorbate required to form a monolayer on the surface of the adsorbent, and C is a constant which depends of the heat of adsorption in the first layer, the heat of liquefaction of the adsorbate, the gas constant and the absolute temperature. The use of the BET method for obtaining values for the surface area of a solid involves estimating the area covered by each adsorbed molecule, based on the next assumptions:

- O. Deutschmann, K. Kochloefl, Heterogeneous Catalysis and Solid Catalysts, Wiley-VCH Verlag GmbH & Co., Weinheim, Germany, 2009 - P. H. Emmett, Catalysis: Fundamental Principles (PART 1), Book division Reinhold Publishing Corporation, New York, 1954

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- The adsorbate molecules area held in two dimensional close packing on the surface.

- The area occupied by each molecule being the cross-section of the molecular volumes calculated from the density of the liquefied adsorbate.

𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 𝑝𝑝𝐴𝐴𝐴𝐴 𝐴𝐴𝑎𝑎𝑎𝑎𝐴𝐴𝑎𝑎𝐴𝐴𝑎𝑎𝐴𝐴 𝑚𝑚𝑎𝑎𝑚𝑚𝐴𝐴𝑚𝑚𝑚𝑚𝑚𝑚𝐴𝐴 = 4(. 866) �𝑀𝑀

4 √2 𝐴𝐴𝑎𝑎 �2/3

Where: M is the molecular weight of the gas, A is Avogrado´s number and d is the density of the liquefied adsorbate. In previous works,1 were measured the superficial area and the pore size from the hexacyanocobaltates presented in this study and the data are summarize in the table 2.1.

Table 2. 1. BET surface area and pore volume from hexacyanocobaltates

Structural Formula

BET surface area(m2g-1)

Pore volume (cm3g-1)

Cu3[Co(CN)6]2 773 0.32 MnCu2[Co(CN)6]2 787 0.34

Ni1.3Cu1.7[Co(CN)6]2 808 0.36 FeCu2[Co(CN)6]2 782 0.33

Ni3[Co(CN)6]2 834 0.36 Co3[Co(CN)6]2 795 0.39

Mn1.2Fe1.8[Co(CN)6]2 769 0.37 Fe1.4Ni1.6[Co(CN)6]2 781 0.35

Mn3[Co(CN)6]2 803 0.39 Co1.5Ni1.5(Co(CN)6)2 811 0.38 Co1.4Cu1.6(Co(CN)6)2 797 0.36 Fe1.4Co1.6(Co(CN)6)2 783 0.40

2.1.2.2. Chemisorption In chemisorption, the adsorbed molecules are held to the surface by valence forces of the same nature as those which bind atoms together in molecules. From this concept, is developed the Sabatier´s principle that proposes the existence of an unstable intermediate compound formed between the catalyst surface and at least one of the reactants. This intermediate must be stable enough to be formed in sufficient quantities and labile enough to decompose to yield the final product or products.

1. J. Roque, E. Reguera, J. Balmaseda, J. Rodríguez-Hernández, L. Reguera, L.F. del Castillo, Microporous and Mesoporous Materials, 103, 2007, 57.

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Some special features are considered, since they are of great importance in connection with the kinetics of surface reaction.

• UNIMOLECULAR LAYER The fact is that after a surface has become covered with a single layer of adsorbed molecules it is saturated whereby, cannot take place an additional chemisorption so is formed a unimolecular layer. This concept was emphasized theoretically by Langmuir where is assumed an array of sites which are energetically identical and which would adsorb just one molecule from the gas phase in a localized mode. The Langmuir adsorption isotherm results from this model and the sites involved can be considered to be active sites.

• ACTIVATED ADSORPTION The second feature was suggested by Taylor and it exposes that the process may often have a considerable activation energy, and hence may sometimes be a slow process. It has been found, that heats of adsorption are frequently small at low temperatures and large at higher temperatures; this is because the Van der Waal adsorption is more important at the lower temperatures in which the chemisorption process being slow. When the temperature increase, the chemisorption with its large heat is predominant.

• SURFACE HETEROGENEITY Finally, the third feature depicts the heterogeneity of sites on the surface, this means that even the most carefully polished surfaces are not perfect, whereby their surface consists of atoms with a variety of unsaturated sites along the edges or plane surface, where preferentially, the adsorption would take place, and in which the catalytic activity is highest. These sites are denominated “active centers”. In this context, the variation of coordination numbers of surface atoms will lead to different reactivities and activities of the corresponding sites.

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1. http://www.tececo.com/technical.reactive_magnesia.php (13/08/15) 2. G. Autié-Castro, M. A. Autié, E. Rodríguez-Castellón, J. Santamaría-González, and E. Reguera, J of Surf. and Interf. of Mat., 2, 2014, 220

Figure 2. 2. Defects and associated coordinate unsaturation1

2.1.3. Acid - Base properties As it was mentioned above, the heterogeneity of active sites provides to the systems a variety of properties, which can be exploited in different areas such as catalysis. In this sense, the next analysis of the surface acid – base property in some hexacyanocobaltates, early reported, is relevant for the present work. It was found that in the cubic phase the material shows definite acidic features, with KA(0.32) which was ascribed to the availability of metal centers with an incomplete coordination sphere as Lewis acid sites. The relatively small value for KA is probably related to the charge redistribution within the · · · T–N≡C–Co–C≡N–T· · · chain in the 3D framework; in this case for T=Co. The CN ligand subtracts electron density, via back donation, from the metal linked at the C end, it is located at the N end, the most electronegative atom in the CN bridge group, and finally partially donated to the metal coordinated to the N atom. (Figure 2.3)

Figure 2. 3. Back donation in the Co–C≡N–T chain

In the present work M= Co3+ and T =Mn2+, Fe2+, Co2+, Ni2+ and Cu2+.

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The net effect is a reduction of the effective polarizing power for the metal found at the cavity surface, whereby diminishing its acidic features due to that the N–T–N bond has an angle of 180° and hence the charge distribution is favorable. This bond angle leads to an effective overlapping between orbitals of similar symmetry properties, σ in the ligand and eg in the metal T. Through this mechanism, the acid-base properties of these porous materials must be modulated by the nature of the metals linked at both atoms, the C and N ends of the CN group. Once the properties have been established with respect to the materials used as catalysts; in the following sections will been discussed the results informed in the literature about the reactions presented in this thesis.

2.2 Oximes The oximes are chemical compounds belonging to the imines, with the general formula R1R2C=N-OH, where R1 is an organic chain and R2 have two possibilities, may be hydrogen, forming an aldoxime, or another organic group, forming a ketoxime. Figure 2.4

a) b)

Figure 2. 4. Structure from a) aldoxime and b) ketoxime

These kinds of molecules are generated throughout the reaction between the hydroxylamine and aldehydes or ketones, or via ammoxidation of ketones in the presence of hydrogen peroxide. Due to the ease with which crystalize and are manipulate, their derivates are prepared, usually as a purification medium and characterization of liquid ketones or aldehydes.1,2 Particularly, acetone oxime is an excellent corrosion inhibitor with lower toxicity and greater stability compared to the common agent hydrazine. Other oxime compounds are used as antidotes for nerve agents which inactivates acetylcholinesterase molecules by phosphorylation of the molecule. Oxime compounds can reactivate acetylcholinesterase by attaching to the phosphorus atom and forming an oxime-phosphonate, which then splits away from the acetylcholinesterase molecule. The most

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1. J. McMurry, Química orgánica, 7ª edición, CENGAGE Learning, México, 2008 2. X. Liang, Z. Mi, Y. Wang, L. Wang, X. Zhang, Reaction Kinetics and Catalysis Letters, 82, 2004, 333 3. J. Kassa, Clinical Toxicology, 40, 2002, 803. 4. M.A. Mantegazza, A. Cesana, M. Pastori, Catalysis of Organic Reactions, Marcel Dekker INC. New York, 1996. 5. F. P. Ballistreri, U. Chiacchio, A. Rescifina, G. Tomaselli, R. M. Toscano, Molecules, 13, 2008, 1230 Toscano

effective oxime nerve-agent antidotes are pralidoxime, also known as 2-PAM, obidoxime and methoxime.3 2.2.1. Oxidation example In the literature are developed a serie of examples from oxime oxidation reaction in which stoichiometric amounts of transition metal oxidation reagents (titanium silicalite)4 have been used to perform oxidation of oximes with H2O2 as auxiliary and other organic compounds (Tetrakis(oxodiperoxotungsteno) Phosphate, PCWP)5 and although this type of reaction does not require catalysts, they generated, frequently, toxic wastes. In contrast, oxidation only with oxygen is characterized by high activation barriers and poor selectivity toward as single product. Is for this reason, that catalytic oxidative deoximation using a combination of O2 and good catalysts is a well-established method to obtain the corresponding and selective ketone.

2.3. bis-naphthalenethiol and bis-naphthol Bis-naphthalenethiol, bis-naphthol (figure 2.5) and their derivatives are larger class of atropisomeric chiral molecules with C2-symmetry that have been used as chiral auxiliaries in asymmetric synthesis, also called enantioselective synthesis in which is preserved, induced or favored a specific chirality. (See figure 7.1 in attachments for more information about isomerism)

a) b) Figure 2. 5 a) Structure of bis-naphthalenethiol, b) Structure of bis-naphthol

C2 C2

OHOH

SHSH

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1. De Lucchi, O. J. Pharm. Sci. 74, 1993, 195. 2. S. Murata; T.Suzuki, A. Yanagisawa, S. Suga, Heterocycl. Chem. 28, 1991, 433 3. D. Fabbri, G. Delogu, O. De Lucchi, Org. Chem. 58, 1993, 1748. 4. S. Cossu, G.Delogu, O. De Lucchi, D. Fabbri, Org. Synth. Coll., 79, 1989, 3431. 5. F. Di Furia, G. Licini, G. Modena, O. De Lucchi, Tetrahedron Lett. 30, 1989, 2575. 6. L. A. Paqette, Handbook of Reagents for Organic Synthesis Chiral Reagents for Asymmetric Synthesis John-Wiley & Sons, England, 2003

These kinds of synthesized molecules, provide more advantages that the natural chiral molecules for example the ease of resolution of isomers, the ease of extraction and the stability in further manipulations and other conditions. 2.3.1. Bis- naphthalenethiol reactions This molecule is used as reagent for the preparation of chiral atropisomeric organosulfur reagents more complexes with the same symmetry1 and as chiral ligand and in the preparation of chiral crown ethers.

2.3.1.1. Preparative methods

The original procedure used was the Ullman coupling of l-bromo-2-naphthalenesulfonic acid. The intermediate binaphthalene-2,2-sulfonic acid can be resolved with strychnine. Lithiation of 2,2'-dibromo- 1,1'-binaphthalene with t-butyllithium, quenching with sulfur2 and reduction of the resulting disulfide is an alternative preparation of the racemic dithiol. More practical procedures entail Newman-Kwart rearrangement of the thioester derived from binaphthol and dimethylthiocarbamoyl chloride, followed by hydrolysis.3, 4 Use of enantiomerically pure binaphthol as starting material gives the enantiomerically pure reagent.3 Another resolution procedure involves enantioselective oxidation of sulfides which can be further transformed into the dithiol.5

2.3.1.2. Reactions example

In scheme 2.1 is showed an example. The dithiocine tetraoxide is derived from cyclocondensation of bis-naphthalenethiol with (Z)-dichloroethylene and oxidation. This product is a chiral version of the bis(phenylsulfony)ethylenes that are useful in cycloaddition reactions and allows the preparation of optically active hydrocarbons which would be difficult to prepare by classical methods. The dithiocine tetroxide reacts with nonsymmetric dienes to give a single crystalline diastereomeric adduct in most cases and it could be obtained cyclic dienes.6

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1. A. McKillop, A.G. Turrell, D. Young, E.C. Taylor, Am. Chem. Soc. 102, 1980, 6504. 2. M. Smrcina, J. Polakova, S. Vyskocil, P. Kocovsky, Org. Chem. 58, 1993, 4534. 3. T-S Li, H-Y Duan, B-Z Li, B. B. Tewari, S-H Li, J. Chem. Soc., Perkin Trans., 1, 1999, 291 4. M. Matsushita, K. Kamata, K. Yamaguchi, N. Mizuno, J. Am. Chem. Soc., 127, 2005, 6632 5. B. Gong, W. Chen, B. Hu, Org. Chem., 56, 1991, 423 6. L. A. Paqette, Handbook of Reagents for Organic Synthesis Chiral Reagents for Asymmetric Synthesis, John-Wiley & Sons, England, 2003

SHSH

EtONa, EtOH(Z)-CHCl=CHCl

78°C93% S

S

S

SO2

O2

m- CPBA

CHCl3, reflux82%

dithiocine tetroxide

O2

O2

S

S

R1

R2

diastereomeric adduct

Scheme 2. 1. Use of bis-naphthalenethiol from obtaining of a cyclic diene.

2.3.2. Bis- naphthol reactions Similarly at bis- naphthalenethiol, this molecule is used mainly as reagent for the preparation of chiral atropisomeric reagents. 2.3.2.1. Preparative methods The most common preparation method to racemic Bis-naphthol (BINOL) is from the oxidative coupling reaction of 2-naphthol in the presence of transition metal complexes among which are Cu, Fe, Rh.1-4 As it was showed in scheme 2.2, the resolution of racemic BINOL with cinchonine may be performed via the cyclic phosphate.5, 6

17

1 L. A. Paqette, Handbook of Reagents for Organic Synthesis Chiral Reagents for Asymmetric Synthesis, John-Wiley & Sons, England, 2003

Scheme 2. 2. Example of a route from resolution of racemic bis-naphthol

2.3.2.2. Reactions example A bis-naphthol derived crown ethers have been reported.1 This containing 3,3´-disubstituted BINOL derivatives are particularly effective for asymmetric synthesis. Thus complexes of these crown ethers (e.g. 18-Crown-6) with Potassium Amide or Potassium t-Butoxide catalyze asymmetric Michael additions. The reaction of methyl l-oxo-2- indancarboxylate with methyl vinyl ketone with the 3,3´-dimethyl-BINOL-crown ether/KO-t-Bu complex gives the Michael product in 48% yield and with 99% ee.

Scheme 2. 3. Crown ether derivative from Bis-naphthol

18

S. Takizawa, T. Katayama, H. Somei, Y. Asano, T. Yoshida, C. Kameyama, D. Rajesh, K. Onitsuka, T. Suzuki, M. Mikami, H. Yamatakay, D. Jayaprakash, H. Sasai, Tetrahedron 64 (2008) 3361

2.3.3. C-C Coupling As was mentioned, one of the most used via to obtain these bis molecules is through C-C coupling and since is an important procedure have been object of Nobel Prizes in Chemistry to Grignard in 1912, Diels-Alder in 1950, Witting in 1979, Schrock in 2005 and finally Suzuki-Negishi-Heck in 2010, these last using Pd- complexes as catalysts in a cross coupling reaction. Has been mentioned in the literature, three categories of dual activation systems to form C-C bond which lead to enhanced reaction rates and more specific control of the transition structure (scheme 2.4): a) dual activation using two different kinds of catalysts; b) conjugated-type dual activation with a functional group such as a phosphate, which has both acidic and basic sites in one functionality, and c) dual activation by two catalytic sites in a single catalyst.

Scheme 2. 4. Categories of dual activation.

The principle of palladium-catalyzed cross couplings in the Heck or Suzuki reactions is that two organic molecules are coordinated on the metal in a formation of metal-carbon bonds, as is observed in the case b in scheme 2.4. In this way the carbon atoms bound to palladium are brought very close to one another. In the next step they couple and this leads to the formation of a new carbon-carbon single bond. The scheme 2.5 illustrate the proposal mechanism to Heck reaction.

b)

a)

c)

19

The royal swedish academy of sciences, Scientific Background on the Nobel Prize in Chemistry 2010

Scheme 2. 5. Mechanism of the Heck reaction The reaction begins when the active Pd(0)-complex catalyst reacts with the organohalide RX in a called oxidative addition. In this reaction the oxidation state of palladium formally changes from Pd(0) to Pd(II) with the formation of an organopalladium compound RPdX. Then is formed a new palladium-carbon bond. In the next step the olefin is also coordinated to palladium, and the olefin and R group are now assembled on the metal and can react. In the next step the R group on palladium migrates to one of the carbons of the coordinated olefin and palladium will shift to the other carbon of the olefin. This process is called a migratory insertion and generates the carbon-carbon bond. Finally, the release of the organic group occurs via a β-hydride elimination which forms the new olefin in which the R group from the organohalide RX has replaced a hydrogen atom on the substrate olefin. In this step a short-lived HPdX species is formed, which loses HX to regenerate Pd(0). On the other hand in the Negishi and Suzuki cross-coupling reaction an organozinc or organoboron compound, couples with an organohalide or an analogous compound such as an organotriflate or a diazo compound, in the presence of a catalytic amount of a Pd(0) complex. The mechanism is presented in scheme 2.6.

20

Scheme 2. 6. Mechanism of the Suzuki reaction

The first step is identical to that the Heck reaction, the formation of organopallidium complex through an oxidative addition; i the second step the organic group, R on zinc or boron, is transferred to palladium in a process called transmetallation. In this way the two organic groups are assembled on the same palladium atom via palladium-carbon bonds. In the final step the R’ and R groups couple with one another to give a new carbon-carbon single bond and R-R’ is released from palladium With the previous review is possible to see the importance of molecules studied in the present work. In the next chapters, the contribution from the catalysts used will be described as well as the advantages, reproducibility and inexpensive obtaining method.

21

1. S.S. Kaye, J.R. Long, J. Am. Chem. Soc., 127, 2005, 6506 2. C.P. Krap, J. Balmaseda, C.L.F. del, B. Zamora, E. Reguera, Energy Fuels, 24, 2010, 581.

3. MATERIALS AND METHODS All reagents and solvents used in the process of this work have been bought and employed without previous purification. Except Bis-naphthalenethiol which was obtained and purify in the reaction.

3.1 Synthesis of Hexacyanocobaltates

Hexacyanocobaltates are obtained through a simple synthetic procedure consisting in the precipitation of potassium hexacyanometallate solutions (0.01M of potassium hexacyanocobaltate) by addition of an aqueous solution of the appropriate mixture from divalent metals MA, MB =Mn2+, Fe2+, Co2+, Ni2+ and Cu2+ (0.05M of sulfate salts of metals) under constant stirring and at room temperature; The resulting precipitates were aged for 24 h within the mother liquor, followed by its separation by centrifugation and washed with distilled water and centrifuged.1,2 The samples characterization is presented in the next chapters. 3.2 Reactors and reactions 3.2.1. The reactor To this work, the catalytic reactions were carried out in a reinforced glass semi continuous reactor (2mL) equipped with pressure control, and a cannula which allows sampling at a certain time. The reactor was deeply introduced into a stirring and temperature controller that was preheated at the reaction temperature. Figure 3.1

22

Figure 3. 1.Reinforced glass semi continuous reactor 3.2.2. Reaction performance The mixture of the reaction was placed into the reactor together with appropriate amount of catalyst (catalyst/ substrate ratio 1-5 mol%), substrate 0.5 mmol in 2mL solvent at 100-110 °C. Add, in the cases were solvent was different to water, 0.2 mmol of dodecane almost were placed as internal standard, in the other hand, in cases were water was used as solvent, dodecane was placed as external standard weighting it in each sample. After sealing the reactor, air was purged by filling the reactor with oxygen since 5 bar and pumping out three times before final pressurization of the reactor with O2 or air at 5 bar. During the experiment, the pressure was maintained constant and the reaction mixture was magnetically stirred at 1200 rpm. Aliquots were taken from the reactor at different reaction times, the sample were analyzed by GC. The products were identified by GC–MS and also by comparing their retention time with that of commercial pure samples when they were available.

1 11

2

3

4

5 6

7

8

9

1 10

2

3

4

5 6

7

8

9

1 10

23

1. http://old.lf3.cuni.cz/chemie/english/practical_trainings/task_B2.htm 2. O. Orio, Cromatografía en fase gaseosa, Cuadernos GEMINIS, Buenos Aires Argentina, 1986. 3. I. Fowlis, Gas Chromatography, ACOL, John Wiley and Sons, England, 1995.

3.3 Evaluation of catalytic activity and monitoring by GC

3.3.1. Theoretical foundations 3.3.1.1. Definition The base of the chromatographic separation is the sample distribution between two faces in a dynamic system. In gas chromatography (GC), the mobile phase is a gas and the stationary phase could be liquid or solid. The technique was developed in the late 1950s with packed column although developed of capillary columns progressed at the same time.

3.3.1.2. Equipment The figure 3.2 shows the components from the chromatograph.

Figure 3. 2. Chromatograph components1

- CARRIER GAS It is the gas used to carry the sample through the chromatographic system. - DETECTOR GAS They are the requested gases that detector need to work. In the case of FID (Flame Ionization Detector) are used H2, Air, and N2. This detector has a sensibility of 1ppm. -INJECTOR Place where the sample is introduced at the system, and is vaporized.

24

1. http://www.knauer.net/en/application/separation_of_clindamycin_qc.html

-COLUMN The column is the place in which the separation of the components take place and it is located into an oven which is possible programing with a temperature ramp to do the most efficient separation. -DETECTOR It is the place that recognize and give response at the components that eluted. In FID detector, the compounds are burning in a flame and ions are produced, collected and transformed in current. -INTEGRATOR It transform the signal from the detector in a chromatogram. In this technic the components from the sample are transported through the column by an inert gas, and they are separated due to the interactions that are generated between each component and the stationary phase, for example polarity or molecular weight. The result of this process is the chromatogram, (figure 3.3), where peaks with retention time major correspond to molecules with most interaction.

Figure 3. 3. Chromatogram1

There are some factors that determined the reliability of the analysis and which are observed in the chromatogram, such as, retention time, that is characteristic from each molecule under certain experimental conditions; the resolution of the peaks, that it indicates the degree of separation of the components in the mixture and finally the width of the peak that lets it allows to establish a relationship of area under the curve with the concentration of the analyte. With which is possible quantify each component. In this work, was used two methods to quantify the analytes, they are discussed below.

25

3.3.2. Standard internal and external In a standardization method is relationship a select area from a peak with the concentration or quantity from a component. In any case, the standard substance should not react with any compound in the medium of analysis, it should resolve of the other peaks, elute near to interest peak and its concentration should be similar to the analyte. 3.3.2.1. Internal standard This method is also known as relative calibration method or indirect. Where are prepared a serial of solutions with weight ratios known from sample and standard substance, and their chromatograms obtained. The peak areas are measured (integrated) and area ratios are plotted versus the weight ratios. In the unknown sample is added an exactly known amount of internal standard and the chromatography is done, the area from the standard is measured and with its relationship with the area of the substance unknown is possible to obtain its amount. The advantage of this method is that the injected amount that not need be exactly measure. 3.3.2.2. External standard In particular to this work, was necessary the use of external standard in the case in which water/ethanol mixture was used in the reaction, and the process was next. It was weighting each component in the reaction to obtain the total, whereby the concentration is known, on the other hand, the concentration from standard is also known and is added to each sample, and in the same way that internal standard with the chromatogram is measure the relation between the area and the concentration to obtain of the substance unknown.

26

3.3.3. Response factor calculations Due to all compounds has different responses in a detector is necessary to normalize it because the areas are not directly proportional to the percentages of composition whereby is calculated a correction factor which change in other detector, column or chromatograph condition. This factor is calculated as following:

𝐹𝐹𝑅𝑅 = (𝜂𝜂𝑠𝑠𝑠𝑠)( 𝐴𝐴𝑟𝑟𝑟𝑟𝑎𝑎𝑐𝑐) (𝜂𝜂𝑟𝑟𝑟𝑟𝑎𝑎𝑐𝑐)( 𝐴𝐴𝑠𝑠𝑠𝑠)

where: ηst mol standard; Ast area of standard ηreac mol reactive; Areac area of reactive

3.3.3.1. Calculated example from naphthalenethiol Were prepared three solution of naphthalenethiol with the amounts described in table 3.1.

Table 3. 1. Solution from naphthalenethiol to FR THIOL

(mg) standard

(mg) THIOL (mol)

standard (mol)

vial 1 40.3 42.9 0.2514 0.2518 vial 2 21.1 12.8 0.1316 0.0751 vial 3 10.5 33.5 0.0655 0.1966

(MW; thiol /dodecano: 160.24/170.33 mg/mmol) Each sample was injected per triplicate and was obtained the chromatogram and the areas are showed in table 3.2.

27

Table 3. 2. Experimental areas from each sample AREAS VIAL 1 AREA VIAL 2 AREA VIAL3 AREA

a B c a b c a b c THIOL 13123.6 9854.3 11394.1 7160.6 6477.4 6983.7 3208.5 2998.8 3419.6

standard 18128.4 13265.2 16664.7 5583.4 4746.7 5699.7 13060.6 13533.6 14042.1

And finally, with these areas were calculated the FR of each sample and obtain the average in weight and mole to use them in the conversion and yield calculations. (Table 3.3) Table 3. 3. Response factor from naphthalenethiol VIAL 1 VIAL 2 VIAL 3 Average

a B c a b c a b c FR=

(weight) 0.77062 0.79079 0.72783 0.77799 0.82782 0.74329 0.78378 0.70695 0.77696 0.76613

FR=(mol) 0.72497 0.74395 0.68472 0.73191 0.77878 0.69926 0.73735 0.66507 0.73093 0.72075 So, in the case the FR of naphthalenethiol correspond to 0.7207, which is used to calculate conversions and yield 3.3.4. Conversion and yield calculations Fists, with the FR, is necessary calculate the mol of the reactive, in this case naphthalenethiol, in every sample (time: 5, 15, 30 minutes, and 1, 2, 3 hours) and also from each component, used next equation.

𝜂𝜂𝑟𝑟𝑟𝑟𝑎𝑎𝑐𝑐 = (𝜂𝜂𝑠𝑠𝑠𝑠)( 𝐴𝐴𝑟𝑟𝑟𝑟𝑎𝑎𝑐𝑐)

(𝐹𝐹𝑅𝑅)( 𝐴𝐴𝑠𝑠𝑠𝑠)

Once that is obtained, is calculated the conversion with:

%𝐶𝐶𝑎𝑎𝐶𝐶𝐶𝐶 =𝜂𝜂𝐴𝐴𝐴𝐴𝐴𝐴𝑚𝑚𝑠𝑠𝑡𝑡 − 𝜂𝜂𝐴𝐴𝐴𝐴𝐴𝐴𝑚𝑚𝑠𝑠1

𝜂𝜂𝐴𝐴𝐴𝐴𝐴𝐴𝑚𝑚𝑠𝑠𝑡𝑡 × 100

28

Avoided in the case of this thesis, is observed the formation of one single product so the final conversion is related with the yield. As an example of these calculates are taken dates from oxidative coupling reaction of naphthalenethiol to Bis-naphthalenethiol with 5%mol of catalyst Ni1.3Cu1.7[Co(CN)6]2. Initial data table 3.4

Table 3. 4. PM theoretical and experimental weight PM

(mg/mmol) mg

exp. mmol exp.

DODECANO 170.33 34.4 0.2019 TIOL 160.24 80 0.4992

BITIOL 318.45

Table 3. 5. Kinetic data from oxidative coupling reaction of naphthalenethiol to Bis-naphthalenethiol

Dodecane (4.47s)

Thiol (8.4s)

Bis-thiol (21.8s)

HOURS AREA AREA MOLES %Conver. AREA MOLES

0.05 528.7 1519.4 0.8061 100 192.4 0.03 0.25 1489.1 4324.6 0.8046 99.9 408.9 0.015 0.5 1213.6 3546.4 0.8006 99 443.8 0.047 1 745.7 1806 0.6793 84.2 378.6 0.165 2 853.6 985.6 0.3238 40.1 795.9 0.337

3.5 519.8 167.9 0.0906 11.2 1780.5 0.396 4 557.7 58.6 0.0294 3.6 2176.5 0.399 5 753.3 12 0.0044 0.5 3159.6 0.41

Data in parenthesis correspond at Time retentions in the chromatogram 3.5.6. Equipment characteristics IR spectra were recorded in an FT-IR spectrophotometer Nicolet 710 at Spain and FT-IR spectrophotometer PerkinElmer at Mexico. XRD powder patterns were obtained with Cu Kα radiation in an HZG-4 diffractometer (from Carl Zeiss) and their evaluation carried out using Dicvol program at Spain and with Bruker D8 ADVANCE diffractometer at Mexico. X-ray Fluorescence analysis was done in a Bruker S2 Ranger with Aluminum filter 500µm, 40KV.

TG curves were analyzed in a METTLER TOLEDO TGA/SDTA851 and the specific surface area and porosity of the materials was analyzed in a Micromeritics ASAP 2010 by N2 at 77 K at Spain.

29

Elemental analyses of metals in the liquid phase were performed by inductively coupled plasma-optical emission spectroscopy (ICP-OES) in a Varian 715-ES, after solid dissolution in HNO3/HCl/HF aqueous solution. (Spain) Elemental analyses of organic compounds were performed in a microanalyzer PerkinElmer 2400 serie II using acetanilide as standard. Gas chromatography (GC) was performed using He as carrier gas, with a Varian 3900 apparatus equipped with an TRB-5MS column (5% phenyl, 95% polymethylsiloxane, 30 m x 0.25 mm x 0.25 mm, Teknokroma). GC/MS analyses were performed on an Agilent spectrometer equipped with the same column as the GC and operated under the same conditions at Spain. Gas chromatography (GC) was performed using He as carrier gas, with a Agilent 6890 apparatus equipped with an PE-5 column (5% phenyl, 95% polymethylsiloxane, 30 m x 0.32 mm x 0.25 mm, PerkinElmer). GC/MS analyses were performed on Perkin Elmer Auto system XL chromatograph/ Perkin Elmer AutoMass spectrometer under EI+ analysis, equipped with the same column as the GC and operated under the same conditions.

30

4. RESULTS AND DISCUSSION

4.1 Characterization of Hexacyanocobaltates

4.1.1. Powder X-ray diffraction For this study, a serie of twelve hexacyanocobaltates, were prepared with general formula MAXMB3-X[Co(CN)6]2∙nH2O, these compounds were obtained by precipitation from hexacyanocobaltate solution and an aqueous solution of a divalent metal (Mn2+, Fe2+, Co2+, Ni2+ and Cu2+) as well as mixtures of two of these divalent metals. Hexacyanocobaltates have a cubic crystal structure, determined by powder X-ray diffraction and which usually belong to the Fm3m space group. The characteristic pattern of these materials and their miller index are showing in figure 4.1a to Co1.4Cu1.6[Co(CN)6]2∙8H2O material The structure is constituted by octahedral building blocks in which a trivalent cobalt is octahedrally coordinated through C atoms of six cyanide ligands while a second divalent transition metal cation is also coordinates octahedrally, by the N atoms of the cyanide ligands of the building units. The Figure 4.1b shows the porous structure, with windows approximately 4.5 Å, (micro porous materials, according with IUPAQ) in the cubic arrangement of their lattice, where is possible to observe the larger pores which result from formed by systematic vacancies for the building block about 8.5 Å. In the crystal structures of these metal hexacyanides the divalent metals are randomly distributed in their structural position to form solid solutions.

-G.W. Beall, D.F. Mullica, W.O. Milligan, Inorg. Chem. 19 (1980) 2876 -D.F. Mullica, W.O. Milligan, G.W. Beall, W.L. Reeves, Acta Crystallogr., Sect. B. B34(1978)3558. -M.R. Hartman, V.K. Peterson, Y. Liu, S.S. Kaye, J.R. Long, Chem. Mater. 18 (2006) 3221 -S.S. Kaye, J.R. Long, J. Am. Chem. Soc. 127 (2005) 6506 - J. Roque, E. Reguera, J. Balmaseda, J. Rodríguez-Hernández, L. Reguera, C.L.F. Microporous Mesoporous Mater. 103 (2007) 57.

31

a) Figure 4. 1. a)Power X-ray diffraction of Co1.4Cu1.6[Co(CN)6]8H2O. b)Crystal structure of hexacyanocobaltates showing the lattice and the dimensions of cubic pores 4.1.2. Infrared spectra Infrared spectra of cobaltates present two outstanding vibrations that correspond to ν(CN) and ν(CoC) around of 2180 and 460 cm-1 respectively, a weak vibration to δ(CoCN) near to 700 cm-1 and finally, bands that confirm the presence of coordination and crystallization water in 3600, 3400 and 1600 cm-1 shown in Figure 4.2 for Co1.4Cu1.6[Co(CN)6]2⋅8H2O. In table 4.1 are summarized the list of the materials prepared and their principal vibrations.

4000 3500 3000 2500 2000 1500 1000 500

60

80

δ (CoCN)

δ (OH)

v(OH)

cm-1

Co1.4Cu1.6[Co(CN)6]2 8H2O

%T

v(CN)

ν (CoC)

Figure 4. 2. Infrared spectra of Co1.4Cu1.6[Co(CN)6]2 8H2O

-K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds, John-Wiley & Sons, New York, Chichester, Brisbane, Toronto,Singapore, 1986 - A.G. Sharpe, The Chemistry of Cyano Complexes of the Transition Metals, Academic Press, New York, 1976. Articulo 11

Co

MA

MB

C

N

b) (2,0

,0)

(2,2

,0)

(4,0

,0)

(4,2

,0)

(4,2

,2)

(4,4

,0)

32

10 20 30 40 50 60 70 80

2θ

Inte

nsity

Co1.4Cu1.6[Co(CN)6]2 8H2O

Table 4. 1. Infrared vibrations wavenumber for the materials under study

Structural Formula ν (CN) (cm-1) v(CoC) (cm-1) Cu3[Co(CN)6]2 ∙5H2O 2181 475

MnCu2[Co(CN)6]2∙8H2O 2171 465 Ni1.3Cu1.7[Co(CN)6]2∙8H2O 2191 465 FeCu2[Co(CN)6]2∙7.5H2O 2181 475

Ni3[Co(CN)6]2∙7H2O 2181 454 Co3[Co(CN)6]2∙8H2O 2171 450

Mn1.2Fe1.8[Co(CN)6]2∙8H2O 2173 462 Fe1.4Ni1.6[Co(CN)6]2∙7.5H2O 2170 454

Mn3[Co(CN)6]2∙8H2O 2171 454 Co1.5Ni1.5(Co(CN)6)2∙8H2O 2181 454 Co1.4Cu1.6(Co(CN)6)2∙8H2O 2181 465 Fe1.4Co1.6(Co(CN)6)2∙8H2O 2171 465

4.1.3. Thermogravimetric curves The number of water molecules and the thermal stability of these materials were determined by TG curves (pink curve) and the first derivate (blue curve) where the zero slope indicates the temperature in the loss of water; figure 4.3 is an example, wherein a first loss is observed until 225°C that corresponds to water molecules. After this point the decomposition of materials begins.

200 400 60045

50

55

60

65

70

75

80

85

90

95

100

-18.2706%597.44°C

-7.0796%364.25°C

-24.1448%225.81°C

Co1.4Cu1.6[Co(CN)6]2 8H2O

%

T (°C)

2.0290mg

Figure 4. 3. TG curve for Co1.4Cu1.6[Co(CN)6]2∙8H2O

33

4.1.4. X-ray fluorescence spectroscopy To determine the ratio between the divalent metals in the materials, X-ray fluorescence spectroscopy in powder were realized. The spectrum in figure 4.4, shows the characteristic peaks Kα and Kβ from the heaviest atoms so that only the metals that the sample contains are showed. The area and intensity correspond well with the formula FeCu2[Co(CN)6]2∙7.5H2O.

30 25 20 15 10 5 00

500

1000

1500

2000

2500

3000

3500

Cps

KeV

FeCu2[Co(CN)6]2 7.5H2O

9 8 7 6

Cu Kβ1

Co Kα1

Co Kβ1

Fe Kβ1

Cu Kα1

Co Kα1

Fe Kα1

Figure 4. 4. X-ray fluorescence spectroscopy of FeCu2[Co(CN)6]2 ∙7.5H2O

The supplementary information provide a collection of powder XRD pattern, X-ray fluorescence spectra and the TG curves for all materials. The features and properties physical and chemical as thermal stability and the acidity discussed previously that are presented by these hexacyanometallate suggest that can be used as catalysts in oxidation of organic molecules processes, as discussed below in the oxidation of oximes and subsequently in the oxidative coupling of naphthalenethiol and naphthol.

34

4.2 Oxidation of oximes 4.2.1. Ciclohexanone oxime As a first stage of oxidation of oximes, were screened the catalytic activity and optimal quantity (mol%) of the series of cobaltates aforementioned for the oxidation of cyclohexanone oxime and oxygen at 5 bar of pressure and in a mixture of ethanol-water (1:1) as solvent. The results that show the oxime conversion and cyclohexanone yield at final reaction times are presented in the table 4.2. The scheme 4.1 present the reaction. Scheme 4. 1. Conversion of cyclohexanone oxime to cyclohexanone. GC-MS: m/z data for Ciclohexanone: 98

Table 4. 2. Oxidation of the cyclohexanone oxime by molecular oxygen. Reaction conditions: Cyclohexanone oxime: 0.5 mmol, catalyst/substrate ratio: 5 mol%, solvent: 2 ml EtOH/H2O 1:1, temperature: 100 °C, oxygen pressure: 5 bar.

Catalyst Time

(h) Conv.

% Yield

% Cu3[Co(CN)6]2 1 94 82

MnCu2[Co(CN)6]2 2 55 42 Ni1.3Cu1.7[Co(CN)6]2 1 100 82a

FeCu2[Co(CN)6]2 2 96 77a Ni3[Co(CN)6]2 30.5 20 28 Co3[Co(CN)6]2 30.5 39 37

Mn1.2Fe1.8[Co(CN)6]2 23 38 30 Fe1.4Ni1.6[Co(CN)6]2 23 17 36

Mn3[Co(CN)6]2 18 20 13 Co1.5Ni1.5(Co(CN)6)2 3 5 7 Co1.4Cu1.6(Co(CN)6)2 3 100 100 Fe1.4Co1.6(Co(CN)6)2 23 33 36

a The reaction with NiCu and CuFe catalysts presents the formation of 1,1-diethoxycyclohexanone

O2 / Solvent

Catalyst

NOH

O

35

In this first screening, is possible to observe that those cobaltates containing Cu were the most efficient ones and, therefore, they were selected for additional studies. As was mentioned in previous chapters, in the heterogeneous catalysis, the organic reaction takes place on the external surface of the material due to the small pore size. The solvent may play a role in the process by reversible adsorption on the metallic sites competing in this way with the substrate modulating the reaction rate, whereby several amounts of catalyst and solvents were tested as reaction medium. In the table 4.3 the results can be seen. In all cases Cu3[Co(CN)6]2∙5H2O was used as catalyst. Cyclohexanone oxime conversion and ketone selectivity were lower when the reaction is carried out in toluene or in pure ethanol in comparison with mixtures ethanol-water (1:1). It was found that a convenient reaction media is a mixture of ethanol-water. Table 4. 3. Influence of the solvent on the performance of Cu3[Co(CN)6]2 as catalyst. Reaction conditions: Cyclohexanone oxime: 0.5 mmol, solvent: 2 ml, temperature: 100 °C, oxygen pressure: 5 bar.

Entry Catalyst mol %

Time (h) Solvent Conv. % Yield %

1 10 22 Toluene 79 49 2 10 5 EtOH 48 31a 3 5 1 EtOH/H2O 1:1b 94 82 4c 5 21 H2O/EtOH 1:1d 46 35 5 5 6 H2O/EtOH 1:1 74 59 6 5 2 EtOH/H2O 1.5:0.5 82 63a 7 3 16 H2O/EtOH 1:1 76 62 8 3 23 EtOH/H2O 1:1 70 55 9 1 28 EtOH/H2O 1:1 48 43

a Formation of 1,1-dietoxycyclohexanone was observed. b Ethanol was added before that water. c Air at 5 bar. d Water was added before Ethanol

4.2.2. Acetophenone oxime Once reaction media and optimal catalyst amount were found it was proposed the use of more complex oxime in this case acetophenone oxime was testing as substrate, the reaction was carried out in the mixture of ethanol–water 1:1 as a reaction media and the best MCu-cobaltates which was identified in the first step were used as catalysts at 5 mol%. (Scheme 4.2)

36

Scheme 4. 2 Conversion of acetophenone oxime to acetophenone. GC-MS m/z data for Acetophenone: 120

In this evaluation, it was possible to observe that the chosen catalysts promote high conversion at final reaction times and that the selectivity to acetophenone is <99% in all cases. The results are contained in table 4.4. Additionally, the reaction was carried out under air pressure instead of pure oxygen with a decrease in conversion. Table 4. 4. Catalytic activity for the conversion of acetophenone oxime to acetophenone. Reaction conditions: Acetophenone oxime: 0.5 mmol, catalyst/substrate ratio: 5 mol%, solvent: EtOH/H2O 1:1; 2 ml, temperature: 100 °C, O2 pressure: 5 bar.

a The reaction was perform with air. In the next plot can be observe despite of high conversion results at final reaction times, that were exhibited for the materials, the temporal profile of the reaction was remarkably different depending on the catalyst. (Figure 4.5) In the case of Ni1.3Cu1.7[Co(CN)6]2 and Co1.4Cu1.6[Co(CN)6]2 the reaction in the first hour occurred in a very low extent, indicating the existence of an induction period for the process, while FeCu2[Co(CN)6]2, did not present an induction period in any case with oxygen or air.

Catalyst Time (h)

Conversion of oxime

(%)

Yield to acetophenone

(%) Cu3[Co(CN)6]2 3 11 8

Ni1.3Cu1.7[Co(CN)6]2 3 97 97 FeCu2[Co(CN)6]2 3 100 100

Co1.4Cu1.6[Co(CN)6]2 3 96 92 FeCu2[Co(CN)6]2 25a 80 74

Catalyst

O2 / Solvent

NOH O

37

Figure 4. 5. Conversion plots for the oxidation of acetophenone oxime to acetophenone catalyzed by FeCu2[Co(CN)6]2 (), Co1.4Cu1.6[Co(CN)6]2 (), Ni1.3Cu1.7[Co(CN)6]2 (), Cu3[Co(CN)6]2 (), FeCu2[Co(CN)6]2 () air. Reaction conditions: Acetophenone oxime: 0.5 mmol, catalyst/substrate ratio: 5 mol%, solvent: 2 ml of EtOH/H2O 1:1, temperature: 100 °C, O2 pressure: 5 bar.

To the catalyst FeCu2[Co(CN)6]2 the rate of the reaction was estimated as 48mmol h-1 in air pressure and 49mmol h-1 with pure oxygen which means that initially the reaction is of zero order with respect to the oxygen pressure under the present conditions. However, when air is used, the long time required and final conversion indicate that the catalyst undergoes some deactivation. On the other hand, to understand the origin of the induction period observed for NiCu and CoCu catalysts, some experiments were performed. The first test, the solvent was mixed with the catalyst under the experimental reaction conditions, but in the absence of acetophenone oxime. After three hours, the liquid phase was separated an analyzed by ICP-OES to registred the presence of dissolved metal ions. Amounts below 1% of Cu or Co were found. The solid was submitted to X-ray diffraction.The results showed that the solid catalyst maintains its crystal structure. These measurements exclude the possibility that the induction period could be due to the leaching of metal ions from the solid to the solution or to the partial dissolution of the solid. In the second experiment, the reaction was initiated under the typical reaction conditions but in the absence of acetophenone oxime and this substrate was added after 90 minutes. The reaction was carried out as usual and analyzed for conversion and selectivity.

0

30

60

90

0 1 2 3Time (h)

Yiel

d (%

) FeCu2[Co(CN)6]2 (), Co1.4Cu1.6[Co(CN)6]2 () Ni1.3Cu1.7[Co(CN)6]2 () Cu3[Co(CN)6]2 () FeCu2[Co(CN)6]2 () air

38

The result exhibit an induction period similar to that shown in the figure 4.5. Therefore, the induction period observed in the time-conversion plot for NiCu and CoCu catalysts likely reflect probably changes on the surface of the crystal, probably by coordination of the substrate or by the interaction with molecular oxygen forming peroxo species. This surface conditioning would not take place or would be much faster in the case of FeCu catalyst. Is for this reason that FeCu catalyst was selected for the next studies. The process of oxidation of acetophenone oxime in the presence of FeCu2[Co(CN)6]2 as catalyst is shown in the figure 4.6, as pseudo first-order kinetics since while is observed the disappearance of the acetophenone oxime, only is perceived the formation of acetophenone because of this product is the unique and stable product of the reaction.

Figure 4. 6. Time-percentage plot for the oxidation of acetophenone oxime by FeCu2[Co(CN)6]2 as catalyst. Conversion of acetophenone oxime (), yield of acetophenone (). Reaction conditions: Acetophenone oxime: 0.5 mmol, catalyst/substrate ratio: 5 mol%, solvent: 2 ml of EtOH/H2O 1:1; temperature: 100 °C, oxygen pressure: 5 bar.

In any kind of catalysis is determinant the reusability of catalyst, therefore were performed the kinetics of two consecutive reuses of the same FeCu catalyst. After each run, the solid catalyst was recovered by filtration, washed with pure ethanol and reused for a consecutive reaction without further treatment accumulating 9 h (figure 4.7). In the temporal profiles of the reused samples, an induction period of about 15 minutes was observed, after which, the initial reaction rate and final conversion of the fresh and

0

30

60

90

0 1 2 3Time (h)

Perc

enta

ge(%

)

Conversion of acetophenone oxime () Yield of acetophenone ()

39

first and second reuses, are almost coincident, indicating the stability thermal and chemical, and recyclability of the FeCu as catalyst. Figure 4. 7. Time-yield plot for the consecutive runs using the same FeCu as catalyst; first run: (); second run: (); third run (). Reaction conditions: Acetophenone oxime: 0.25 mmol, catalyst/substrate ratio: 5 mol%, solvent: 1 ml of EtOH/H2O 1:1; temperature: 100 °C, oxygen pressure: 5 bar.

Although the appearance of the induction period could be a sign of deactivation, the catalyst was analyzed for crystallinity by XRPD. They were measurement under the same conditions in step and time after its third consecutive use and the same diffraction pattern was observed, indicating the stability of the FeCu material under the present reaction conditions. Figure 4.8

First run: () Second run: () Third run ()

0

30

60

90

0 1 2 3

Yiel

d(%

)

Time (h)

40

Figure 4. 8. XRD pattern of FeCu2[Co(CN)6]2 reuses. a) Before of the reaction, b) First run, c) Second run, d) Third run. Reaction conditions: Acetophenone oxime: 0.25 mmol, catalyst/substrate ratio: 5 mol%, solvent: 1 ml of EtOH/H2O 1:1; temperature: 100 °C, oxygen pressure: 5 bar. 4.2.3. Other oximes

Besides cyclohexanone and acetophenone oximes, the catalytic activity of FeCu2[Co(CN)6]2 was probed on more bulky oximes as benzophenone and more relevant as carvone oximes conversion and yield > 90%. Schem 4.3. a) b) Scheme 4. 3 .a) Conversion of benzophenone oxime to benzophenone; b) Conversion of carvone oxime to carvone. Reaction conditions: Oxime: 0.5 mmol, catalyst/substrate ratio: 5 mol%, solvent: 2 ml of EtOH/H2O 1:1; temperature: 100°C, oxygen pressure: 5 bar. GC-MS m/z data for Benzophenone: 182 and GC-MS m/z data for Carvone: 150

Catalyst

O2 / Solvent

Catalyst

O2 / Solvent

OHN

O

NOH O

(2,0

,0)

(2,2

,0)

(4,0

,0)

(4,2

,0)

(4,2

,2)

10 20 30 40 50 60 70

FeCu2[Co(CN)6]2 7.5H2O

c)

b)Inte

nsity

2θ

a)

d)

41

It should be noted that carvone is used in the fragrance industry and one of the commercial synthetic routes is based on deoximation of carvone oxime. In spite of the larger molecular dimension of these substrates also almost a full conversion to benzophenone and carvone were achieved indicating that FeCu2[Co(CN)6]2 catalyst is also efficient for the oxidation of bulk aromatic oximes. This reactivity of benzophenone and carvone oxime demostrate that the reaction take places exclusively on the external surface of the hexacyanocobaltates, since both oximes are absolutely excluded from intracrystalline diffusion. 4.2.4. Mechanism proposal In an attempt to understand how the reaction takes place, the oxidation of acetophenone oxime in the presence of small percentages of different substances was performed, such as: radical quenchers (hydroquinone), carboxylic acids (ascorbic and benzoic acid), and carboxylate anion (NaAcO). This data are collected in table 4.5 Table 4. 5. Additive substances at the reaction to perform the mechanism The time-conversion plot presented in figure 4.9 shows that the hydroquinone leads to the appearance of an induction period that can be interpreted as the time required to produce the oxidation of hydroquinone. According to this, the reaction mechanism is likely to involve some radical species, as peroxo groups, that could be quenched by the oxidation of hydroquinone that occurs in competence. On the other hand, the presence of carboxylic acids increases the reaction rate, suggesting that protonation of acetophenone oxime or a possible intermediate accelerates the reaction. On the contrary, addition of acetate (1%) leads to a complete quenching of the reaction that can be interpreted as arising from the strong adsorption to the acetate on the Lewis acid sites of the catalyst.

Additive Quantity (mol%) Conversion Hydroquinone 10 97 Ascorbic acid 10 99 Benzoic acid 5 87

NaAcO 1 0 Any - 98

42

Figure 4. 9. Time-yield plots for the oxidation of acetophenone oxime in the presence of hydroquinone 10 mol% (), ascorbic acid 10 mol% (), benzoic acid 5 mol% (), NaAcO 1 mol% () and with any additive (). Reaction conditions: Acetophenone oxime: 0.25 mmol, catalyst/substrate ratio: 5 mol%, solvent: EtOH/H2O 1:1; 2 ml, temperature: 100 °C, oxygen pressure: 5 bar. Amount of additive: hydroquinone, 2.8mg; ascorbic acid, 4.5mg; benzoic acid, 3mg; NaAcO, 0.4mg.

According to the previous discussion in the scheme 4.4 is presented a mechanistic proposal to describe the catalytic activity of double metal hexacyanocobaltates as solid catalysts in the aerobic oxidation of oximes.

0

30

60

90

0 0.5 1

Yiel

d (%

)

Time (h)

Hydroquinone 10 mol% (), Ascorbic acid 10 mol% (), Benzoic acid 5 mol% (), NaAcO 1 mol% () Any additive ()

43

Scheme 4. 4. Proposed mechanism for the aerobic oxidation of oximes to carboxylic compound in the presence of mixed double metal cyanides.

In this mechanism the first step is the adsorption of the substrates on the material the oxime will bind to the most acidic metal ion Fe2+, while Cu2+ will interact with oxygen and the combination of these two metal sites adsorbing the oxime (Fe2+) and the oxidizing reagent (Cu2+) with the formation of the peroxo group that could interact with the C from C=NH+ where the N is protonated will result in the oxidative breakdown of C=N, such that the corresponding oxazyridine could be the reaction intermediate that finalized with the formation of the carbonyl compound. The role of the internal hexacyanocobaltate units in this mechanism will be just structural, maintaining the crystallinity of the material. In agreement with this proposal, other double metal hexacyanocobaltates less efficient to interact with the oxime will exhibit lower catalytic activity and the solid containing exclusively copper ions will also be almost inactive due to the low affinity to bind the oxime. However, the ability of Cu2+ ions to bind molecular O2 will be reflected in the need for this transition metal to cooperate and in consequence have a high active catalyst.

44

4.3 Oxidative coupling of naphthalenethiol and naphthol 4.3.1. Oxidative coupling of naphthalenethiol In order to understand more about of the behavior of hexacyanocobaltates as catalysts, it was performed the study of their catalytic activity in oxidative coupling reaction from 2-naphthalenethiol to bis-naphthalenethiol, (Scheme 4.5) at 4.5 bar of pressure in dichloromethane as solvent. In the table 4.6 are summarized the results.

Scheme 4. 5.Oxidative coupling from 2-naphthalenethiol to bis-naphthalenethiol. GC-MS: m/z data for Bis-naphtahlenethiol: 318

Is important to mention that a screening of solvents was not necessary due to the substrate, 2-naphthalenethiol is poorly soluble in majority of solvents, therefore with a previous solubility test was choose the work solvent.

Table 4. 6. Oxidative coupling from naphthalenethiol to bis-naphthalenethiol. Reaction conditions: 2-Naphthalenethiol: 0.5 mmol, catalyst/substrate ratio: 5 mol%, solvent: 2 ml of CH2Cl2, temperature: 110 °C, O2 pressure: 4.5 bar.

Catalyst Time

(h) Conv.

% Yield

% Cu3[Co(CN)6]2 5 35 34

Ni1.3Cu1.7[Co(CN)6]2 5 99 98 FeCu2[Co(CN)6]2 3 100 100 FeCu2[Co(CN)6]2a 5 100 100

Fe1.4Ni1.6[Co(CN)6]2 5.5 100 100 Co1.4Cu1.6(Co(CN)6)2 5 97 97 Fe1.4Co1.6(Co(CN)6)2 5 100 99

Fe3(Co(CN)6)2 2 100 100 a This reaction was carryout at 90°C

Catalyst

O2 / Solvent

SHSH

S H

45

It is possible to observe that those cobaltates that present a metal mixture were very efficient while in the case of Cu, the catalytic activity of this material was drastically reduced probably because here does not exist the cooperative behavior between different metals observed in the other cases and finally in the case of Fe, the catalytic activity is attributed to its affinity with the sulfur in the organic molecule. Figure 4.10 presents the differences in the yield-plots for each catalyst regardless final conversion. In the case of Ni1.3Cu1.7[Co(CN)6]2 and Co1.4Cu1.6[Co(CN)6]2 it was observed an induction period, which also was present in the reaction with oximes; on the other hand, Fe1.4Ni1.6[Co(CN)6]2, Fe1.4Co1.6[Co(CN)6]2 and FeCu2[Co(CN)6]2 at 90°C, showed a low activity until the last hour where they presented the major activity with total conversion, and finally, FeCu2[Co(CN)6]2 and Fe3[Co(CN)6]2 with high conversion in less time.

Figure 4. 10. Conversion plots for the oxidative coupling of naphthalenethiol catalyzed by FeCu2[Co(CN)6]2 at 90°C (), FeCu2[Co(CN)6]2 (●), Co1.4Cu1.6[Co(CN)6]2 (), Ni1.3Cu1.7[Co(CN)6]2 (─), Cu3[Co(CN)6]2 (), Fe1.4Ni1.6[Co(CN)6]2 (), Fe1.4Co1.6[Co(CN)6]2 (), Fe3[Co(CN)6]2 (+), Reaction conditions: 2-Naphthalenethiol: 0.5 mmol, catalyst/substrate ratio: 5 mol%, solvent: 2 ml of CH2Cl2, temperature: 110 °C, O2 pressure: 4.5 bar.

0

20

40

60

80

100

0 1 2 3 4 5

Yiel

d (

%)

Time

FeCu2[Co(CN)6]2 () at 90°C, FeCu2[Co(CN)6]2 (●) Co1.4Cu1.6[Co(CN)6]2 () Ni1.3Cu1.7[Co(CN)6]2 (─) Cu3[Co(CN)6]2 () Fe1.4Ni1.6[Co(CN)6]2 () Fe1.4Co1.6 [Co(CN)6]2 () Fe3[Co(CN)6]2 (+)

46

As is showed in figure 4.11, the process oxidative coupling of naphtalenethiol in the presence of Fe3[Co(CN)6]2 as catalyst is a pseudo first-order kinetics. It is means that to the disappearance of naphthalenethiol, the unique and stable product of the reaction is Bis-naphthalethiol. The chromatograms for this reaction are available in supplementary information

Figure 4. 11. Time-percentage plot for the oxidative coupling of naphthalenethiol by Fe3[Co(CN)6]2 as catalyst. Oxidative coupling of naphthalenethiol (●), yield of Bis-naphthalenothiol (). Reaction conditions: 2-naphthalenethiol: 0.5 mmol, catalyst/substrate ratio: 5 mol%, solvent: 2 ml of CH2Cl2; temperature: 110 °C, oxygen pressure: 4.5 bar

As previously mentioned, one the most important point in catalysis is to determine the reusability of catalyst, so in this case the kinetic of one consecutive reuses of the same FeCu catalyst was performed. Due to Fe catalyst presented difficulties in its separation from the reaction media because it is presented as a powder extremely fine and a stable dispersion is formed. After each run, the solid FeCu catalyst was recovered by filtration, washed with pure CH2Cl2 and reused for a consecutive reaction under the same conditions and without further treatment accumulated 6h of use, in tow reactions as it can see in figure 4.12 In the temporal profiles from the reuse, an induction period was not observed but the process is slower than the first run although the final conversion is the same and it keeps its high catalytic activity.

0

30

60

90

0 0.5 1 1.5 2Time (h)

Yiel

d(%

)

47

Figure 4. 12. Time-yield plot for the consecutive runs using the same FeCu as catalyst; first run: (●); second run: (). Reaction conditions: 2-naphthalenethiol: 0.5 mmol, catalyst/substrate ratio: 5 mol%, solvent: 2 ml of CH2Cl2; temperature: 110 °C, oxygen pressure: 4.5 bar

In the same context, it is equally important that the catalyst maintains its catalytic activity as its structure therefore it was analyzed the crystallinity before and after for the reaction. In figure 4.13 shows the XRD from the samples where it is observe that the structure is stable, at reactions conditions.

5 10 15 20 25 30 35 40 45 50 55 60

c)After run

2θ

Inte

nsit

y b)First run

a) Before

Figure 4. 13. Powder XRD pattern of FeCu2[Co(CN)6]2 reuses. a) Before of the reaction, b) First run, c) After first run. Reaction conditions: 2-naphthalenethiol: 0.5 mmol, catalyst/substrate ratio: 5 mol%, solvent: 2 ml of CH2Cl2; temperature: 110 °C, oxygen pressure: 4.5 bar

0

30

60

90

0 1 2 3

yiel

d (%

)

Time (h)

48

4.3.1.1. Characterization of Bis-naphthalenethiol One of the greatest contributions of this work was the synthesis of Bis-naphthalenothiol and not its oxidated form which present an S-S bond. It is important because in the in literature only the obtaining of the oxidation form has been informed and then is carry out the reduction reaction as it was presented in state of the art chapter. The presence of bis-naphthalenethiol was corroborated by the characterization: XRD, IR, Elemental Analysis and GC-Mass. The organic compound was obtained from one reaction in the same conditions, the catalyst was filtered and the liquid was evaporated, the resulting powder was recrystallized of pure CH2Cl2. In the first stage of characterization the XRD powder was analyzed (figure 4.14) where the crystallinity of the organic compound is observed, but unfortunately, it was not possible to obtain the structure resolution because it was not possible index the patter.

Figure 4. 14. X-Ray pattern from Bis-naphthalenethiol In the comparison of Infrared spectra from 2-naphtalenethiol and Bis-naphthalenethiol (figure 4.15) it can see that aromatics area from 700 cm-1 to 1000 is practically the same in both cases; although, the assigned band from νSH near 2600 cm-1 is not observed in Bis-naphthalethiol spectra due to is so weak.1

5 10 15 20 25 30 35 40 45 50

Inte

nsity

2θ

Bis-naphthalenothiol

49

1. C. Gautier, T. Bü rgi, J. Phys. Chem. C, 114, 2010, 15897

Figure 4. 15. Infrared spectra from 2-naphtalenethiol and Bis-naphthalenethiol Gautier and coworkers have done an extended theoretical and experimental IR study about the Bis-naphthalenethiol and their possible arrangements and in comparison with the oxidized molecule. They concluded that in the case of the reduced molecule S-H groups are coplanar to the corresponding naphthyl groups and the torsion angle between these groups is measured by comprising carbon atoms 2, 1, 1′, and 2′ (Scheme 4.6) the most stable structure is in all cases very close to 90°, and this this arrangement of molecule generates weak bands which are not observed in the oxidized form, in 1190, 1350 and 1625 cm-1.

Scheme 4. 6. Bis-naphthalenethiol with a torsion angle of 90°

The elemental analysis theoretical and experimental is presented in table 4.7. Both data correspond with the reduced molecule, C10H14S2

3500 3000 2500 2000 1500 1000 500

40

60

80

% T

cm-1

naphthalenethiol Bis-naphthalenethiol

2 2´

1´ 1

νS-H

1800 1600 1400 1200 1000

cm-1

119013501625

50

Table 4. 7. Elemental Analysis from formula: C10H14S2 %C %H %S

Theoretical 75.43 4.43 20.13 Experimental 75.46 4.45 19.69

Also the sample was measured by polarimetry, and the result from the angular rotation was 0, which it is indicates that the sample is a racemic mixture from both possible isomers (R, S). Finally to the characterization of this compound, were carried out in Gas Chromatography-Mass Spectrometry study, under the same conditions that in the case of CG, where were observed a composition of two peaks that correspond to bis-naphthalenethiol isomers. (Figure 4.16) Isomer R Isomer S

Figure 4.16. Peaks from Bis-naphthalenethiol isomers

The fragmentation pattern to this organic molecule is presented in figure 4.17. This pattern shows the molecular ion m/z in 318 that correspond at molecular weight of Bis-naphthalenothiol, and their later fragments.

SHSH

SH

SH

51

http://sdbs.db.aist.go.jp/sdbs/cgi-bin/direct_frame_top.cgi 15 junio 2015

Figure 4.17. Fragmentation pattern from Bis-naphthalenethiol

The result was compared with the previously reported in SDBS (Spectral Data Base for Organic Compounds) and it corresponds in each fragment observed, (figure 4.18)

100 200 3000

50

100

63 89

115

128

159

254

285

Rala

tive

Inte

nsity

m/z

Mass of molecular ion: 318Formule: C20H14S2Di (2-naphthyl)disulfide SDBS NO. 16326

318

Figure 4.18. Fragmentation pattern publish in SDBS No. 16326

52

With the comparison above, is corroborated that this compound is the single and stable product obtained under the reaction conditions presented in the development of this work. In order to understand the behavior of catalysts, were tested the use of the catalysts with major catalytic activity in the oxidative coupling from 2-naphthol. 4.3.1. Oxidative coupling of naphthol The reactions were performance under the same conditions, nevertheless, due to low solubility of naphthol in CH2Cl2 were necessary the use of ethanol has solvent. The reaction is presented in scheme 4.7.

Scheme 4.7. Oxidative coupling from 2-naphthol to bis-naphtol. GC-MS: m/z data for Bis-naphthol: 286 The summary of results are presented in table 4.8. None of the catalysts examined showed an important catalytic activity (less 50% convertion), even at increasing temperature, nor longer reaction times. Table 4. 8. Oxidative coupling from naphthol to bis-naphthol. Reaction conditions: 2-Naphthol:0.5 mmol, catalyst/substrate ratio:5 mol%, solvent:2 ml, O2 pressure: 4.5 bar.

Catalyst t (h) solvent T (°C)

Fe1.4Co1.6[Co(CN)6]2 35 EtOH 110 FeCu2[Co(CN)6]2 20 EtOH 100

Cu3[Co(CN)6]2 20 EtOH 100 Ni1.3Cu1.7[Co(CN)6]2 46 EtOH 100 Co1.4Cu1.6(Co(CN)6)2 24 EtOH 100

FeCu2[Co(CN)6]2 28 Toluene 100 FeCu2[Co(CN)6]2 92 EtOH 120

As one example, the results from the formation of bis-naphtol were taken, using FeCu2[Co(CN)6]2 as catalyst, where the total reaction had a total time of 92 hours in

Catalyst

O2 / Solvent

OHOH

O H

53

comparison with the same catalyst in the oxidative coupling from naphthalenethiol where the total reaction (99% yield) was in 3 hours.(Figure 4.19)

Figure 4.19. Conversion - plot from naphthol to bis-nathpthol by FeCu2[Co(CN)6]2 as catalyst. Reaction conditions: 2-Naphthol: 0.5 mmol, catalyst/substrate ratio: 5 mol%, solvent: 2 ml of EtOH, temperature: 120 °C, O2 pressure: 4.5 bar. Finally, in order to do a descriptive transformation of 2-naphthol, in figure 4.20, is showed the chromatographic sequence throughout the analysis time.

Figure 4. 20. Chromatographic sequence of oxidative coupling from naphthol to bis-naphthol, in presence of FeCu2[Co(CN)6]2 as catalyst.

0

30

60

90

0 20 40 60 80 100

Conv

ersi

on (%

)

t (h)

8 10 12 14 16 18 20 22 24

8 10 12 14 16 18 20 22 24

8 10 12 14 16 18 20 22 24

8 10 12 14 16 18 20 22 24

8 10 12 14 16 18 20 22 24

8 10 12 14 16 18 20 22 24

5min

2h

21h

49h

92h

64h

Inte

nsity

OHOH

O H

54

5. CONCLUSIONS

This work demonstrates the high catalytic activity that hexacyanocobaltates material with formula TAx TB3-x [Co(CN)6]2 could have in the promotion of oxidation reactions using molecular oxygen.

It was observed that, due to the pore size of 4 Å approximately, the substrates are out of reach to carry out the reaction into the material whereby is concluded that the external surface is catalytically the most important site and it is the place where the reaction is accomplished.

The ease in obtaining and the thermal stability that the materials TAx TB3-x [Co(CN)6]2

show, make feasible their use as heterogeneous catalysts. Additionally, the potential of those depends on the combination and cooperativity between the divalent metals to interact preferably, one with organic molecule and the other with oxygen molecule. As it was show in the proposal mechanism.

Particularly, the hexacyanocobaltates with combination of Cu, NiCu, FeCu and CoCu metals, presented the major catalytic activity and high conversion rate, and selectivity toward ketones, being FeCu the most active with short time conversions. An induction period was observed in the case of CoCu and NiCu which depends of the slow interaction between the surface and substrate.

The consecutive reactions performed, using the same catalyst (FeCu) show a minimal decrease in catalytic activity from this material, under the same reaction conditions. It is means that the material maintains its crystallinity and structure.

On the other hand, in the case of bis-naphthalenethiol, the hexacyanocobaltates of combinations Cu, NiCu, CoCu, FeCu, FeNi, FeCo and Fe presented major catalytic activity with high conversion and selectivity toward bis-naphthalenethiol, being FeCu and Cu the most actives, however, due to short particle size, its separation from the reaction was difficult. One of the major contributions from this part of work is the obtaining of the reducing molecule and not the oxidized.

Finally, due to the acidic decrease in the Lewis acid places, these materials do not present high catalytic activity in sides with major basicity as in the case of naphthol.

55

6. PERSPECTIVES

In this work, was demonstrate the capacity of hexacyanocobaltates to transform organic molecules in their oxidized derivatives with high conversion. The organic molecules had a common feature, the functional group that acts as Lewis base is, in the Pearson concept, a soft or borderline base that could interact, in principle, with any soft or borderline acids as are the divalent metals used. In this sense, is proposed the idea of testing the hexacyanocobaltates as heterogeneous catalysts in the oxidation reaction of amines to nitro compounds. In the other hand, is probably that oxide-reduction processes have place into the material, since the divalent metals can change their oxidation state relatively easy, so is viable the use of them in reduction reactions, it is means that change the oxygen atmosphere for hydrogen atmosphere. Finally, because of these materials contain transition metals and they present transitions in UV-Vis range, is possible that the material can be photocatalytically actives radiating with this magnitude of energy.

56

7. SUPPLEMENTARY INFORMATION

7.1. Isomerism scheme

ISOMERS

Stereoisomers

Enantiomers Diasteroisomers

Conformers

Atropisomers

Cis-Trans Isomers

Structurals

Chain, position

57

7.2 X-Ray Power Diffraction

20 40 60

500

1000

1500

Co3[Co(CN)6)]2 8H2O

Inte

nsity

2θ

XRD pattern of Co3[Co(CN)6]2

20 40 60 80

400

800

1200

Co1.4Cu1.6[Co(CN)6]2 8H2O

Inte

nsity

2θ

XRD pattern of Co1.4Cu1.6(Co(CN)6)2

58

20 40 60

100

200

300

Cu3[Co(CN)6)]2 8H2OIn

tens

ity

2θ

XRD pattern of Cu3[Co(CN)6]2

20 40 60300

600

900

Fe1.4Co1.6[Co(CN)6)]2 8H2O

Inte

nsity

2θ

XRD pattern of Fe1.4Co1.6(Co(CN)6)2

59

20 40 60

200

400

FeCu2[Co(CN)6]2 7.5H2O

Inte

nsity

2θ

XRD pattern of FeCu2[Co(CN)6]2

20 40 60

700

1400

2100

Mn3[Co(CN)6]2 8H2O

Inte

nsity

2θ

60

XRD pattern of Mn3[Co(CN)6]2

20 40 60

400

800

1200

MnCu2[Co(CN)6]2 8H2O

Inte

nsity

2θ

XRD pattern of MnCu2[Co(CN)6]2

20 40 60300

600

900

Ni3[Co(CN)6)2] 7H2O

Inte

nsity

2θ

XRD pattern of Ni3[Co(CN)6]2

61

20 40 60

400

600

800

Co1.5Ni1.5[Co(CN)6]2 8H2O

Inte

nsity

2θ

XRD pattern of Co1.5Ni1.5(Co(CN)6)2

20 40 60

400

800

1200

Ni1.3Cu1.7[Co(CN)6]2 8H2O

Inte

nsity

2θ

XRD pattern of Ni1.3Cu1.7[Co(CN)6]2

62

20 40 60

100

200

300

400Fe1.4Ni1.6[Co(CN)6)2] 7.5H2O

Inte

nsity

2θ

XRD pattern of Fe1.4Ni1.6[Co(CN)6]2

20 40 60

400

800

1200

Mn1.2Fe1.8[Co(CN)6)2] 8H2O

Inte

nsity

2θ

XRD pattern of Mn1.2Fe1.8[Co(CN)6]2

63

7.3 TG Curves

TERMOGRAVIMETRIC CURVES

TG curves of Co3[Co(CN)6]2

64

TG curves of Co1.4Cu1.6(Co(CN)6)2

TG curves of Cu3[Co(CN)6]2

TG curves of Fe1.4Co1.6(Co(CN)6)2

65

TG curves of FeCu2[Co(CN)6]2

TG curves of Mn3[Co(CN)6]2

66

. TG curves of MnCu2[Co(CN)6]2

TG curves of Ni3[Co(CN)6]2

67

TG curves of Co1.5Ni1.5(Co(CN)6)2

TG curves of Ni1.3Cu1.7[Co(CN)6]2

68

TG curves of Fe1.4Ni1.6[Co(CN)6]2

Fe1.8Mn1.2[Co(CN)6]2

69

7.4 X-ray fluorescence spectroscopy

30 25 20 15 10 5 0

0

500

1000

K Kα1

Cu Kβ1

Cu Kα1

Co Kβ1

Co Kα1

Cps

KeV

Cu3[Co(CN)6)]2 8H2O

30 25 20 15 10 5 0

0

500

1000

1500

Cu Kβ1

Cu Kα1

Mn Kβ1

MnCu2[Co(CN)6]2 8H2O

Cps

KeV

Mn Kα1

Co Kα1

Co Kβ1

70

30 25 20 15 10 5 0

0

500

1000

1500

Cu Kβ1

Cu Kα1

Ni Kα1

Co Kα1Ni1.3Cu1.7[Co(CN)6]2 8H2O

Cps

KeV

30 25 20 15 10 5 00

1000

2000

3000

4000

5000Ni3[Co(CN)6)2] 7H2O

Cps

KeV

Co Kα1

Ni Kβ1

Ni Kα1

71

30 25 20 15 10 5 00

1000

2000

3000

Co Kα2

Cps

KeV

Co3[Co(CN)6)]2 8H2OCo Kα1

30 25 20 15 10 5 0

0

500

1000

1500

Mn Kα1

Mn1.2Fe1.8[Co(CN)6)]2 8H2O

Cps

KeV

Fe Kα1Co Kα1

Co Kβ1

72

30 25 20 15 10 5 0

0

1000

2000

Mn3[Co(CN)6)]2 8H2O

Cps

KeV

Co Kβ1

Mn Kα1

Mn Kβ1

Co Kα1

30 25 20 15 10 5 00

2000

4000

Cu Kβ1

Co Kβ1

Cu Kα1

Co Kα1

Cps

KeV

Co1.4Cu1.6[Co(CN)6]2 8H2O

73

30 25 20 15 10 5 00

1000

2000

3000

Fe Kα1

Co Kα1

Co Kβ1

Cps

KeV

Fe1.4Co1.6[Co(CN)6)]2 8H2O

30 25 20 15 10 5 0

0

500

1000

1500 Fe Kα1

Fe3[Co(CN)6)]2 8H2O

Cps

KeV

Co Kα2

Co Kα1

74

7.5. Monitoring of oxidative coupling from naphthalenethiol

5 10 15 20

time (min)

0.05 hour

0.25hour

Inte

nsity 0.5 hour

1 hour

2 hours

Chromatogram for Fe3[Co(CN)6]2

Internal standar

75