5

Inorganic and Organometallic Chemistry

Introduction

The activities on this research area can be summarized as the synthesis,

characterization and reactivity studies of inorganic, organometallic and intermetallic

compounds of lanthanides and actinides. The main goal of the research is to understand the

influence of the electronic configuration and of the size of these elements in the chemical

behaviour of their compounds, particularly in the lanthanide series* .

The main activity of the group during several years concerned the synthesis and

characterization of organocompounds of f elements and a few examples are given on the

following pages. The reactivity of the compounds towards several organic substrates has been

studied in order to test their capability to promote stoichiometric or catalytic transformations

in organic substrates. Facilities for handling air sensitive compounds, X-ray diffraction

analysis for structural studies and termochemical studies for acquisition and analysis of metal-

ligand bond disruption enthalpies in order to get insights into reaction patterns in

organometallic chemistry and catalysis are some of the techniques available as a result of this

activity.

More recently, we have been using the synthetic chemistry expertise and the

availability of standard characterization techniques to develop the chemistry of rhenium.

Reactivity studies of the rhenium complexes showed that they could be used as intermediates

in reactions directed to organic synthesis. This activity has also been used to train people

working in the preparation of radiopharmaceuticals – 99m

Tc.

The next step is to start studies on the reactivity of the synthesized compounds

towards small molecules such as CO2 and CH4. Our motivation is to increase the value of the

natural gas, the methane being its major component (C-H activation and conversion in

methanol), and the environmental problems concerning the greenhouse effect (carbon dioxide

activation, methanol and/or carbonates production).

Gas-phase reactions of metallic, intermetallic and oxide ions involving lanthanides

and actinides with saturated and unsaturated hydrocarbons by means of Fourier transform ion

cyclotron resonance spectroscopy (FTICR) is under intense study in our group. Special

attention will be given to reactions that can act as models of homogeneous and heterogeneous

catalytic processes.

Research Team

Researchers – 9 (8 PhD)

Research Students – 4

Technicians – 2

Publications:

Journals – 11

Proceedings – 2

Special Publ. – 1

Conf. Commun.: 8

Theses:

PhD – 1

* The actinides studied in our Laboratories are thorium and uranium. Other more toxic ones are studied, in some

cases and when ever possible in collaboration with European Institutes that have adequate facilities.

6

Lic. – 2

f - Element Chemistry

Chemical and structural aspects of uranium compounds containing the

fragment "UL2" (L=HB(pz)3 and B(pz)4)

M. Paula Campello, Ângela Domingos, A.Pires de Matos and Isabel Santos Departamento de Química, ITN, 2686 Sacavém CODEX, Portugal

Abstract

[UCl2{B(pz)4}2] (1) is a suitable material for preparing compounds of the type

[U{B(pz)4}2ClX] (X=OtBu (2), OC6H2-2,4,6-Me3 (3), OC(Me)2CH2SiMe3 (4)). Reactions

with LiCH2SiMe3 did not give characterizable products. X-ray crystallographic analysis of 1

and 3 showed that the poly(pyrazolyl)borate ligands are tridentate; the uranium is eight-

coordinated and displays distorted SAP and BCTP coordination geometries in 1 and 3,

respectively. Two dynamic processes occur in solution: one which equilibrates the

coordinated pyrazolyl rings and another which equilibrates coordinated and uncoordinated

rings.

Journal of Rare Earths 2 (1995) 513.

Synthesis and reactivity of hydrotris(pyrazolyl)borate -hydrocarbyl

uranium(IV) complexes

Manuela Silva, Noémia Marques, A. Pires de Matos Departamento de Química, Instituto Tecnológico e Nuclear, Estrada Nacional 10, 2686 Sacavém

Codex,Portugal

Abstract

Stable -hydrocarbyl uranium (IV) compounds could not be obtained by simple metathesis

reactions of [UCl3L*.THF] (L* = HB(3,5-Me2pz)3) with LiMe, LiC6H5, or LiCH2C6H5.THF.

The reactions with LiMe resulted in uncharacterizable mixtures of products and the reactions

with LiCH2C6H5.THF or LiC6H5 yielded a known reduced uranium compound, {UCl2L*}x.

Decomposition pathways could be prevented by using a second ancillary ligand as Cp or by

introducing a voluminous substituent on the aromatic ring of the benzyl or phenyl ligand.

Reactions of [UCl2CpL*] with MeLi gave [UCl2-xCpMexL*] (x = 1 (1) or 2 (2)) depending

of the stoichiometric ratio of the reagents and the reactions of [UCl3L*.THF] with Li-o-

CH2C6H4NMe2 or Li-o-C6H4CH2NMe2 yielded the compounds [UCl2(o-CH2C6H4NMe2)L*]

(3) and [UCl2(o-C6H4CH2NMe2)L*] (4), respectively. Compounds 3 and 4 display fluxional

behaviour in solution at room temperature, but static spectra were obtained at low

temperature. The observed dynamic behaviour can be explained by dissociation followed by

recoordination of the U-N donor bond of the internally chelating (o-CH2C6H4NMe2) and (o-

C6H4CH2NMe2) ligands.

J. Organomet. Chem. 493 (1995) 129.

7

Synthesis, characterization and reactivity of lanthanide (II) poly(pyrazol-

1-yl)borates (Ln = Sm, Eu, and Yb). Fluorescence studies of [EuL2(THF)2]

(L = B(pz)4, HB(pz)3)

Ângela Domingosa, Joaquim Marçalo

a, Noémia Marques

a, and A. Pires de Matos

a, Adelino

Galvãob, P. C. Isolani

c, G. Vicentini

c, and K. Zinner

c

aDepartamento de Química, ICEN/INETI, 2686 Sacavém Codex, Portugal

bC. Q. E., Complexo 1, Instituto Superior Técnico, Av. Rovisco Pais 1096 Lisboa Codex, Portugal

cInstituto de Química, Universidade de S. Paulo, P. O. Box 20780, São Paulo, Brazil 01498-970

Abstract

The reactions of [LnI2(THF)x] (Ln = Sm, Eu, Yb) with 2 equiv of K[B(pz)4] (pz = pyrazolyl)

in THF result in the formation of [Ln{B(pz)4}2(THF)2] complexes. The molecular structure

of [Eu{B(pz)4}2(THF)2] has been determined by single-crystal X-ray diffraction analysis.

The compound crystallizes in the orthorhombic space group Pnma, with a=17.707(1) Å,

b=14.141(1) Å, c=14.726(1) Å, V=3687(1) Å3, Z=4. The [Sm{B(pz)4}2(THF)2] and

[Yb{B(pz)4}2(THF)2] complexes are fluxional in solution as indicated by the equivalence of

the pyrazolyl rings in the 1H NMR spectra at room temperature. A static spectrum could be

obtained for the Sm compound at -68 ºC with a pattern that is in accordance with the geometry

found for the Eu complex, in the solid state. The complexes [Ln{HB(pz)3}2(THF)2] (Ln =

Sm, Eu, Yb) have been prepared by the procedure used to synthesize the

[Ln{B(pz)4}2(THF)2] complexes. The THF molecules can be replaced by 1,2-

dimethoxyethane yielding the compounds [Ln{HB(pz)3}2(DME)] (Ln = Sm, Yb).

[Sm{B(pz)4}2(THF)2] and [Yb{B(pz)4}2(THF)2] react readily with alkyl halides, alcohols

or alkynes to yield Ln(III) complexes, that disproportionate to the [Ln{B(pz)4}3] complexes.

The crystal and molecular structure of the compound [Yb{B(pz)4}3].C2H5OH obtained in the

reaction of [Yb{B(pz)4}2(THF)2] with ethanol was determined by X-ray diffraction analysis.

The compound crystallizes in the monoclinic space group P21/c, with a=14.663(6) Å,

b=13.755(1) Å, c=23.312(9) Å, =106.49(2), V=4508(3) Å3, Z=4. Fluorescence studies on

the Eu compounds are also reported.

Polyhedron 14 (1995) 3067.

8

Synthesis and characterization of a tetramethylurea adduct of a

biscyclopentadienyl ytterbium(II) complex. X-ray crystal structure of

YbCp2.2TMU

M. G. Silva-Valenzuelaa, Lea Barbieri Zinner

a, Ângela Domingos

b, Noémia Marques

b, A.

Pires de Matosb

aUniversidade de S. Paulo, Instituto de Química, Caixa Postal 20780, CEP 01498-970, S. Paulo,

Brasil

b Departamento de Química, ICEN, INETI, 2686 Sacavém Codex,

Portugal

Abstract

The complex YbCp2.3TMU (TMU = 1,1,3,3-tetramethylurea) has been synthesized by

addition of (CH3)2NCON(CH3)2 to YbCp2.2THF, obtained by reduction of YbCp2Cl.THF

with sodium naphtalenide. The characterization was done by metal analysis, IR and 1H NMR

spectroscopies. Orange-reddish crystals of YbCp2.2TMU, were obtained by slow evaporation

of a benzene solution of YbCp2.3TMU. The compound crystallizes in the monoclinic space

group C2/c with four molecules in a unit cell of dimensions a=14.892(4), b=12.792(2),

c=12.484(4) Å, =99.37(1)º and V=2346(1) Å3 (R=0.033, Rw=0.037 for 125 parameters and

2127 reflections with Fo>3(Fo)).

J. Alloys and Comp. 225 (1995) 331.

Recent advances in the chemistry of f-element poly(pyrazolyl)borate

complexes

Isabel Santos and Noémia Marques Departamento de Química, ICEN-INETI, 2686 Sacavém Codex, Portugal

Abstract

This paper presents an overview of the chemical progress involving f-elements and

poly(pyrazolyl)borate ligands. This includes compounds of lanthanides (III) and (II) as well as

actinides (IV) and (III). Because of its close similarity, yttrium is also included. Synthetic,

chemical, structural, and solution behaviour of these compounds are reviewed.

The plan of the review is :

1. Introduction

2. Synthetic and Chemical Aspects

2.1 Lanthanides (III)

2.2 Lanthanides (II)

2.3 Actinides (IV)

2.4 Actinides (III)

3. Structural Aspects and Solution Behaviour

4. Concluding Remarks

5. Abbreviations and References

New J. Chem. 19 (1995) 551.

9

High-temperature oxidation of LnCu2 intermetallics and their catalytic

behaviour in 4-methyl-2-pentanol decomposition

Danielle. Ballivet-Tkatchenko

a, Joaquim Branco

b,A. P. Matos

b

a Laboratoire de Chimie de Coordination du CNRS, 205 route de Narbonne, 31077 Toulouse Cedex,

France b Departamento de Química, Instituto Tecnológico e NuclearP-2686 Sacavém Codex, Portugal

Abstract.

The air-oxidation of the intermetallic compounds LaCu2, CeCu2, PrCu2 and NdCu2 was

followed by thermogravimetry. The mass uptake occured over a wide range of temperature

(423-1100 K) leading to two stoichiometries according to the lanthanide : CeCu2O4 and

LnCu2O3.5 (Ln = La, Pr, Nd). The characterization by powder X-ray diffraction, scanning

electron microscopy/energy dispersive X-ray analysis, and surface area mesurements showed

that segregation took placed with the formation of CuO along with CeO2 or Ln2CuO4 (Ln=La,

Pr, Nd). Therefore, the oxidized intermetallics are better described by the formulas

CeO2.2CuO and Ln2CuO4.3CuO. The oxidation process noticeably increased the surface areas

and promoted CuO migration to the surface. These systems exhibed selectivities in 4-methyl-

2-pentanol decomposition, which are associated with the lanthanide.

J. Phys. Chem. 99 (1995) 5481.

Synthesis of lanthanide complexes coordinated by an asymetric

cyclopentadienyl ligand

Alexander A. Trifonova, Pierre Van de Weghe

a, Jacqueline Collin

a, Isabel Santos,

b Angela

Domingosb

aLaboratoire de Synthèse Asymétrique, URA 1497, ICMO, Université Paris -Sud, 91405 Orsay,

France bDepartamento de Química, ITN, 2686 Sacavém Codex, Portugal

Syntheses and characterization of bis and monocyclopentadienyl lanthanides iodides (S)-

C´p2LnI (Ln=Sm, 3; Ln=La, 4) and (S)-C´pLnI2(THF)n, (Ln=Sm, n=3, 5; Ln=La, n=2, 6)

coordinated by an asymmetric cyclopentadienyl ligand (C´p=C5H4CH2CH(CH3)OCH2Ph)

have been carried out. Variable temperature NMR studies of compounds 3 and 4 reveal a

fluxional process in solution. X-ray crystal structure analysis of 3 shows a bent metallocene

structure with intramolecular coordination of both cyclopentadienyl ligands. 3 crystallizes in

space group C2221 with a=9.415 (1) Å, b=13.869 (1) Å, c=12.732(2) Å, V=5580 (1) Å3 and

Z=8 for Dcal=1.676 gcm-3

. For monocyclopentadienyl complexes intramolecular coordination

is observed only for the lanthanum complex 6. All compounds exhibit activity for the catalysis

of Diels-Alder reactions.

10

Hydrocarbyl derivatives of [UCl2{HB(pz)3}2]: synthesis, characterization

and reactivity studies towards protic substrates and ketones

M. Paula C. Campello, Ângela Domingos, João Paulo Leal, A.Pires de Matos and Isabel

Santos Departamento de Química, ITN, 2686 Sacavém Codex, Portugal

The reaction of [UCl2{HB(pz)3}2] (1) with lithium alkyls LiR (R=Me, CH2SiMe3, C6H5-o-

CH2NMe2) in the 1:1 or 1:2 molar ratio affords the compounds [UClR{HB(pz)3}2] (R=Me

(2), CH2SiMe3 (3), C6H5-o-CH2NMe2 (4)) and [UR2{HB(pz)3}2] (R=Me (5), CH2SiMe3

(6)), respectively. Complex 2 can also be obtained in a reasonable yield (60%) by

redistribution at room temperature between the complexes 1 and 5. Compounds 2, 3 and 4

react with pzH providing [UCl(pz){HB(pz)3}2] (7) in almost quantitative yield and

compounds 5 and 6 react with the same substrate leading to [U(pz)2{HB(pz)3}2] (8). The

alkoxides [U(OC6H4-o-OMe)2{HB(pz)3}2] (9) and [U(O(CH2)4O){HB(pz)3}2] (10) were

synthesized by reacting 5 or 6 with guaiacol and 1,4-butanodiol, respectively. By reacting

ketones with hydrocarbyls the complexes [UCl(OCMe2R){HB(pz)3}2] (R=Ph (11),

CH2SiMe3(12)) and [UCl(OCMe2 CH2(C=O)Me){HB(pz)3}2] (13) have been prepared, due

to the insertion of the substrates into the metal carbon bonds or due to the activation of -CH

bonds of acetone. [U(OC6H4-o-OMe)2 {HB(pz)3}2] (9) crystalizes from toluene/hexane in

the triclinic space group P1 with unit cell dimensions a=12.295 (2) Å, b=12.640(2) Å,

c=13.994(2) Å, =76.10(1)º, =72.50(1)º, =80.71(1)º, V=2004(2) Å3; Z=2;

[UCl(OCMe2CH2SiMe3) {HB(pz)3}2] (12) crystallizes from toluene/hexane in the monoclinic

space group P21/a with cell parameters a=15.778(4) Å, b=25.922(5) Å, c=17.038(3) Å, =101.21(3)º, V=6836(3) Å

3; Z=8.

Synthesis of an uranium (III) homoleptic complex

Sandra Jorge , Ângela Domingos, A.Pires de Matos and Isabel Santos Departamento de Química, ITN, 2686 Sacavém Codex, Portugal

Uranium triiodide reacts with [KPh2B(pz)2] in the 1:3 molar ratio yielding the homoleptic

compound [U{Ph2B(pz)2}3]. This complex crystalizes from toluene/hexane in the triclinic

space group P1 with unit cell dimensions a=13.565(1) Å, b=15.715(2) Å, c=15.929(2) Å,

=118.957(9)º, =92.650(11)º, =97.356(15)º, V=2924(1) Å3; Z=2. The uranium is six-

coordinated, displaying a prism trigonal coordination geometry.

11

Synthesis and Characterization of [UCl2{HB(3,5-Me2pz)3}]2(-2:

2-

Me3SiC4SiMe3)

Manuela Silva, Noémia Marques and A. Pires de Matos Departamento de Química, Instituto Tecnológico e Nuclear, Estrada Nacional 10, 2686 Sacavém

Codex,Portugal

The reaction of [UCl2(CH2SiMe3)L*] (L*={HB(3,5-Me2pz)3}) with HCCSiMe3 yields the

compound [UCl2L*]2(-2:

2- Me3SiC4SiMe3) (1), due to carbon-carbon bond formation by

two alkyne molecules. The compound was formulated on the basis of IR, 1H NMR

spectroscopies and elemental analysis, and by protolysis with HOtBu.

Synthesis of Sm (II) and Yb (II) complexes and reactivity studies with

several unsaturated organic substrates

Irene Lopes, Noémia Marques Departamento de Química, ICEN, INETI, 2686 Sacavém Codex, Portugal

The aim of this work is to use the reducing properties of the Sm(II) and Yb (II) compounds to

promote transformations into organic substrates by means of electron transfer reactions.

We have been studying the ability of the complex SmTp*2 (Tp* = HB{3,5- Me2(pz)3}) to act

as a one-electron-transfer reagent toward R2E2 reagents (E = O, S, Se), S8, SPPh3 and

quinones. The use of E2R2 as reagents showed to be a good synthetic route for

organochalcogenate complexes of the type SmTp*2ER, but the compound SPPh3 is not

reduced under similar conditions. The quinones are readily reduced but the resulting

compounds depend on the stoichiometric ratio of the reagents and the nature of the products

formed in the reactions are still under investigation. The steric crowding around the metal and

the enhancement of electron density at the metal due to the presence of two

polypyrazolylborate ligands are perhaps responsible for the reduced reactivity of this

compound in comparison with the one observed with the SmCp*2 compound. By this reason

we are extending this work to the [Ln{HB(3-tBu,5-Mepz)3}I(THF)x]) and [Ln{HB(3-

Mspz)3}I(THF)x] complexes (Ln=Sm,Yb).

Rearrangement of hydrotris(3-mesitylpyrazol-1-yl)borate into hydrobis(3-

mesitylpyrazol-1-yl)(5-mesitylpyrazolyl-1-yl)borate. Synthesis and

structure of hydrobis(3-mesitylpyrazol-1-yl) (5- mesitylpyrazolyl-1-

yl)borato trichlorouranium(IV), UHB(3-Mspz)2(5-Mspz)Cl3

Ângela Domingosa, Noémia Marques

a, Manuela Silva

a, Josef Takats

b and Swiatoslaw

Trofimenkoc

a Departamento de Química, ITN, Estrada Nacional 10, 2686 Sacavém Codex, Portugal

b Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2

c E.I. Du Pont de Nemours & Company, Inc., Experimental Station, Wilmington, Delaware 19880-0302

The reactivity of the U-C bond of -hydrocarbyl uranium (IV) complexes of general formula

[UCl2RTpMe2] (TpMe2=HB(3,5-Me2Pz)3) (R=CH(SiMe3)2, CH2SiMe3) towards several

organic substrates has been investigated. As it was found that the reactivity patterns were

dependent of the steric bulk of the R group we decided to extend these studies to compounds

12

in which the steric coordination around the uranium centre was modified by using a

polypyrazolylborate stabilizing ligand with different steric and electronic requirements.

Here we describe the synthesis and characterization of the compound [UCl3TpMs*] (TpMs*=

hydrobis(3-mesitylpyrazol-1-yl)(5-mesitylpyrazol-1-yl)borate) obtained by reaction of UCl4

with the ligand hydrotris(3-mesitylpyrazolyl-1yl)borate

UCl4 + Tl[HB(3-Mspz)3] U[HB(3-Mspz)2(5-Mspz)]Cl3 + TlCl

The characterization of the compound by elemental analysis, IR and 1H NMR spectroscopies,

and X-ray crystal diffraction analysis indicated that the ligand [HB(3-Mspz)3] has become

[HB(3-Mspz)2(5-Mspz)] after coordination to the uranium centre. Isomerization of the [HB(3-

i-Prpz)3] to [HB(3-i-Prpz)2(5-i-Prpz)] has already been observed during the attempted

preparation of M[HB(3-i-Prpz)3]2 (M= Fe(II), Co(II), Ni(II)), in refluxing toluene.

Synthesis of lanthanide alkoxides and carboxylation reactions

Joaquim Branco, Adelaide Carvalho, Angela Domingos, Noémia Marques Departamento de Química, ICEN, INETI, 2686 Sacavém Codex, Portugal

The use of carbon dioxide as a raw material for chemical synthesis is an ecologically and

ecomically valuable purpose. In this project we intend to study the carboxylation of the

methanol to obtain dimethyl carbonate, an industrially important product, by using lanthanide

alkoxides to catalize the reaction.

Alkoxides are known for almost all the elements, but the structural chemistry of these

compounds is dominated by the formation of polymeric structures. Due to the large ionic radii

of the lanthanides, the formation of multinuclear species is still more general for lanthanide

alkoxides, leading to compounds with low solubility and reactivity. In order to overcome this

effect we decided to use donor functionalized alkoxide ligands that combine two effects: to

achieve steric overcrowding through the additional chelating bond and to increase the electron

density at the metal leading to less polarized M-O bonds.

The first alcohol that we tried was guaicol (OC6H5-o-(OCH3)). The salt metathesis reaction of

YbCl3 with 3 equiv. of the potassium salt of the guaiacol in thf led after work-up and

recrystallization from a THF/hexane mixture to crystals of a compound that was characterized

by X-ray difraction analysis as the polymetallic compound Yb8O3{OC6H5-o-(OCH3)}18.

Alkoxide chemistry: An ammoniacal synthetic route

Joaquim Branco Departamento de Química, ITN

There is a resurgence of ammoniacal synthetic routes to prepare metal alkoxides complexes,

which have been successfully employed in the synthesis of uranium and alkaline earth

alkoxide complexes. It is known that europium and ytterbium among the lanthanide metals

readily dissolve in liquid ammonia to yield a homogeneous blue solution containing

ammoniated electrons. The dissolution of europium and ytterbium in liquid ammonia enables

a novel route to lanthanide alkoxides.

Reaction of Yb or Eu metal in liquid ammonia at -780C with 3 equiv. of guaiacol (C7H8O2) in

thf produces “Ln(OR)3.thf” species after warming to room temperature. Crystals have been

obtained and an x-ray crystallographic study performed. We have not yet the results.

13

Intermetallics synthesis : An ammoniacal synthetic route

Joaquim Branco Departamento de Química, ITN

In recent years there has been a growing interest in the surface properties of lanthanide-3d

transition metal intermetallic compounds from the point of view of heterogeneous catalysis.

The lanthanide intermetallic compounds show interesting catalytic properties often superior in

terms of catalytic activity and/or selectivity. Nevertheless, they have small surface areas as a

disadvantage. The synthesis of intermetallic compounds in liquid ammonia can provide

products with large surface areas and interesting properties.

We have prepared some ytterbium compounds with copper, nickel and iron (1:1). In a typical

preparation Yb is dissolved in liquid ammonia at -78OC to form the blue solution

characteristic of the solvated electron, and the metal powders of Cu, NI or Fe were gradually

added to the solution. The blue color immediately disappeared as the result of the reaction

with the high reactive ytterbium in solution. After warming the reaction vessel to room

temperature the excess of ammonia was vaporized leaving black pyrophoric powders. These

products are courrently under analysis but an x-ray powder diffraction analysis revealed

already that they are amorphous.

14

Rhenium Chemistry

Reactivity of a tetrakis(pyrazolyl)borate oxo complex of rhenium

António Paulo, Ângela Domingos, Joaquim Marçalo, António Pires de Matos and Isabel

Santos Departamentos de Química e Radioisótopos, ICEN-INETI 2686 Sacavém Codex, Portugal

Abstract

The rhenium (VII) compound [ReO3{B(pz)4}] (1) is easily reduced by triphenylphosphine in

tetrahydrofuran providing, in 60% yield, a very reactive oxo complex of Re that, based on its

reactivity, we tentatively formulated as "[ReO(-O){B(pz)4}]2"(2). This air stable compound

is insoluble in tetrahydrofuran and water, slightly soluble in chloroform and dichloromethane

and a versatile material for the synthesis of monomeric compounds of Re(V):

[ReO{B(pz)4}Cl2] (3), [ReO(L){B(pz)4}] (L=OCH2CH2O (4), C6H4O2 (5)),

[ReO{B(pz)4}(OR)2] (R=Me (6), Et (7), Pri (8), Ph (9)), [ReO{B(pz)4}(SPh)2] (10) and [ReO(

2-OCONPh){B(pz)4}] (11). Compounds 3-11 were characterized by elemental analyses, I.R.

and 1H NMR spectroscopies and, in the case of compounds 9 and 10, by X-ray

crystallography. Compound 9 crystallizes in the triclinic space group P1 with cell parameters

a=9.611(4) Å, b=11.808(3) Å, c=12.400(5) Å, =88.69(2)º, =69.61(3)º, =74.01(3)º,

V=1264(1) Å3, Z=2, R=0.031, Rw=0.037 for 5226 reflections (Fo3(Fo)); compound 10

crystallizes in the triclinic space group P1 with cell parameters a=10.563(3) Å, b=11.768(2)

Å, c=12.149(3) Å, =94.10(2)º, =100.50(2)º,

=92.44(2)º, V =1479(1) Å3, Z=2, R=0.043, Rw=0.051, for 4721 reflections (Fo3(Fo)). For

all the compounds the characterization includes laser desorption and electron impact Fourier

transform ion cyclotron resonance mass spectroscopy. For complex 2 variable temperature 1H

NMR studies are also described.

Inorg. Chem. 34 (1995) 2113.

Co-ordination of tetrakis(pyrazolyl)borate in rhenium complexes

containing the [ReV=O]

3+ core

António Paulo, Ângela Domingos, Isabel Santos

Departamentos de Química e de Radioisótopos, ITN, 2686 Sacavém Codex, Portugal

Abstract

The complex [ReO{3-B(pz)4}(OMe)2] (1) reacts with potentially bidentate protic substrates

yielding several monomeric and dimeric oxorhenium compounds in which the

tetrakis(pyrazolyl)borate presents different coordination modes: [ReO(acac){2-

B(pz)4}(OMe)] (3), [ReO(acac){2-B(pz)4}]2(-O) (4), [ReO{

2-B(pz)4}(quinolin-8-

olate)(OMe)] (5), [ReO{2-B(pz)4}(OMe)(pz*)(pz*H)] (pz*=pz (6) or 3,5-Me2pz (7)), [ReO

{2-B(pz)4}(-pz*)]2(-O) (pz*=pz (9) or 3,5-Me2pz (10)), [ReO(HNCH2CH2NH){

3-

B(pz)4}] (14) and [ReO(m-nitrophenyl-o-diaminate){3-B(pz)4}] (15). Using the analogous

alkoxide [ReO{3-B(pz)4}(OEt)2] (2) the compound [ReO{

2-B(pz)4}(OEt)(pz)(pzH)] (8)

has also been obtained. Compounds 3 and 5 react with trimethylsilyl chloride providing the

15

monochlorides [ReO(acac){2-B(pz)4}Cl] (12) and [ReO{

2-B(pz)4}(quinolin-8-olate)Cl]

(13), respectively. Compounds 9, 10 and 14 were also prepared by reacting [ReO(-

O){B(pz)4}]2 (11) with the respective substrates. The new compounds 3-10 and 12-15 were

characterized by elemental analysis, I.R. and 1H NMR spectroscopies. Compounds 3, 4 and 9.

have also been characterized by X-ray crystallography. Compounds 3 and 4 both crystallize in

the monoclinic space group P21/c, with a=7.862(1) Å, b=14.152(2) Å, c=19.975(3) Å,

=91.79(1)º, V=2221(1) Å3 and Z=4 (3) and a=13.547 (2), Å, b= 9.959 (1) Å, c= 15.878 (2)

Å, = 102.00 (1)º, V=2095(1) Å3 and Z=2 (4). Compound 9 crystallizes in the monoclinic

space group P21, with cell parameters a=11.086 (2) Å, b=15.269 (1) Å, c=12.133 (1) Å,

=93.51(1), V=2050 (1) Å3 and Z=2.

Inorg. Chem., in press.

Oxo complexes of Re(V) with poly(pyrazolyl)borates

António Paulo, Joaquim Marçalo, António Pires de Matos and Isabel Santos Departamentos de Química e Radioisótopos, ICEN-INETI 2686 Sacavém Codex, Portugal

Abstract

The species [ReO(-O){B(pz)4}]2 and [ReO(-O){HB(pz)3}]2 have been obtained by

reduction of [ReO3{B(pz)4}] or [ReO3{HB(pz)3}] with PPh3. The solution behaviour of these

compounds have been studied by variable temperature 1H NMR studies.

Technetium and Rhenium in Chemistry and Nuclear Medicine 4 (M. Nicolini, G.Bandoli, U.

Mazzi Eds.), Bressanone (1995) 227-230.

Study of the redox properties of tetrakis(pyrazolyl)borate rhenium(V)

complexes

M. Fernanda N.N. Carvalho

(a), Dina Nunes

(b), AntónioPaulo

(b), Armando J.L.Pombeiro

(a) and

Isabel Santos(b)

(a)

Centro de Química Estrutural, Complexo I, I.S.T, Av. Rovisco Pais, 1096 Lisboa Codex, Portugal (b)

Departamentos de Química e de Radioisótopos, I.T.N., 2686 Sacavém Codex, Portugal

Abstract

The redox properties of some tetrakis(pyrazolyl)borate rhenium(V) complexes of the type

[ReO{3-B(pz)4}L] (L =

-O–O

- type ligand, 1/2L = MeO

-) and [ReO{

2-B(pz)4}(OMe)L’]

(L’ = O–O-, N–O

-, N–N

- type ligands) were studied by cyclic voltammetry. These Re(V)

complexes display generally one anodic and one cathodic waves, at values of potential which

are discussed in terms of hapticity of the pyrazolylborate ligand and of the electronic

properties of the chelating co-ligands.

Proceedings of the VII Encontro da Sociedade Portuguesa de Electroquímica-III Encontro

Ibérico de Electroquímica, Faro, Portugal, October (1995). 51-53.

16

Hydrides of rhenium (III) and rhenium (V) with modified

poly(pyrazolyl)borates: ReH2{(OR2)B(pz)2}(PPh3)2 (R = Me (1), Et (2))

and ReH4{H(OR)B(3,5-Me2pz)2}(PPh3)2 (R = Me (3), Et(4))

António Paulo,

(a) Ângela Domingos,

(a)Isabel Santos

(a) José Ascenso

(b)

(a) Departamentos de Química e de Radioisótopos, I.T.N., 2686 Sacavém Codex, Portugal

(b)C.Q.E., Complexo 1, I.S.T., Av. Rovisco Pais, 1096 Lisboa Codex, Portugal

The complex ReOCl3(PPh3)2 reacts with KH2B(pz*)2

(pz* = pyrazolyl, 3,5-

dimetilpyrazolyl) in alcohools leading, in low to moderate yield, to Re(III) and Re(V)

polyhydrides: ReH2{(OR)2B(pz)2}(PPh3)2 (R=Me (1), Et=(2)) and ReH4{H(OR)B(3,5-

Me2pz)2}(PPh3) (R=Me (3), Et=(4)). These compounds were characterized by elemental

analysis, I.R., 1H and

31P NMR spectroscopies and, in the case of 4, also by X-ray

crystallographic analysis. Compound 4 crystallizes from toluene/n-hexane in the triclinic

space group P1 with cell parameters a=9.850(1) Å, b=11.031(1) Å, c=14.870(1) Å,

=107.346(7)º, =91.426(8)º, =100.017(9), V=1514.1(3) Å3, Z=2. The solid state structure

showed that in 4 the Re is eight-coordinate by four hydrogen atoms, by the phosphine and by

two nitrogen and one oxygen atoms of the modified poly(pyrazolyl)borate.

17

Gas Phase Chemistry

Gas phase chemistry of bis(pentamethylcyclopentadienyl)samarium

Joaquim Marçaloa and António Pires de Matos

a, William J. Evans

b

aDepartamento de Química, Instituto Tecnológico e NuclearP-2686 Sacavém Codex, Portugal

bDepartment of Chemistry, University of California at Irvine, Irvine, California 92717

Abstract

The gas phase chemistry of bis(pentamethylcyclopentadienyl)samarium, (C5Me5)2Sm, was

studied by Fourier transform ion cyclotron resonance mass spectrometry (FTICR/MS). The

positive electron impact (EI) spectra showed the formation of (C5Me5)2Sm+, (C5Me5)Sm

+, and

Sm+. All three ions reacted with (C5Me5)2Sm by charge transfer, as verified by double-

resonance techniques, and (C5Me5)Sm+ also formed the (C5Me5)3Sm2

+ ion in a condensation

reaction with neutral (C5Me5)2Sm. The laser desorption/ionization (LDI) spectra showed, in

addition to (C5Me5)2Sm+, (C5Me5)Sm

+, and Sm

+, the formation of (C5Me4H)Sm

+ and

(C5Me4CH2)Sm+. The latter species most probably involves a tetramethylfulvenide ligand.

Access to all of the ionic species cited here could also be obtained by reacting laser-desorbed

Sm+ ions with pentamethylcyclopentadiene, C5Me5H. (C5Me4CH2)Sm

+, (C5Me4H)Sm

+, and

(C5Me5)Sm+ were formed as primary products, and the metallocene ion (C5Me5)2Sm

+ resulted

from the rapid addition of C5Me5H to (C5Me4CH2)Sm+.

Organometallics 15 (1996) 345-349.

The “Bare” uranyl dication UO22+

Hans H. Cornehl*, Christoph Heinemann*, Joaquim Marçalo**, António Pires de Matos**,

and Helmut Schwarz* * Institut für Organische Chemie, Technischen Universität Berlin, D-10623 Berlin

** Departamento de Química, Instituto Tecnológico e Nuclear, P-2686 Sacavém Codex

Abstract

The first synthesis and thermochemical characterization of the "bare" uranyl dication UO22+

in

the gas phase are reported. The species is generated via (i) sequential ion-molecule reactions

involving U2+

and various oxygen-donors and (ii) "charge-stripping" collisions between fast

UO2+ projectiles and O2 targets. Both UO2

2+ and UO

2+ are thermodynamically stable towards

dissociation in singly charged fragments ("Coulomb explosion"). In accordance with ab initio

pseudopotential calculations, the second ionization energy of UO2 is measured as 15.4 ± 2.6

eV, corresponding to Hfº (UO22+

) = 371 ± 60 kcal/mol.

Angewandte Chemie, in press.

18

Lanthanide, thorium and uranium oxide clusters formed by DLV/FTICR

António Pires de Matos, Joaquim Marçalo, and João Paulo Leal Departamento de Química, Instituto Tecnológico e Nuclear,P-2686 Sacavém Codex, Portugal

Abstract

In this work we report the formation of clusters of all the lanthanides (except promethium),

thorium and uranium by direct laser vaporization (DLV) of surface oxidized metallic targets

in a vacuum of about 2 x 10-8

Torr. The cluster ions were obtained using a Nd:YAG laser

pulse (ca. 30 mJ at the fundamental 1064 nm wavelength) and the ions were stored in the trap

of an Extrel (Waters) FTMS 2001-DT Fourier transform ion cyclotron resonance (FTICR)

spectrometer.

We observed for all the lanthanides (Ln) that the clusters showed a sequential addition of

Ln2O3 units in forming increasingly larger clusters, with two main series of the type [LnmO(3m-

1)/2]+ (m odd) and [LnmO(3m-2)/2]

+ (m even). Work on lanthanide clusters has been reported by

Gibson using excimer laser abalation of lanthanide oxalates in a reflectron time of flight mass

spectrometer, and by Kemp and Read, and Selbin et al. by fast atom bombardment (FAB)

mass spectrometry of lanthanide salts. In some lanthanides, and due to the high resolution of

the FTICR instrument, we could identify the two following clusters with hydrogen:

[Ln2O3H]+ and [Ln4O6H]

+ in which the fragment valence is 3 if H is present as OH. For Ce,

with the 4 valence state accessible, we observed also clusters where the valence state is larger

than 3, as for example in the series CemO(3/2)m+.

For Eu, we observed clusters of the series of the type EumO(3m-2)/2 +

(m even), EumO(3m-3)/2+

(m odd), EumO(3m-4)1/2+ (m even), EumO(3m-5)1/2

+ (m odd), EumO (3m-6)/2

+ (m even) as

previously reported by Gibson1, but in addition we found clusters with hydrogen and in

particular we mention here the clusters [Eu2O2H]+, [Eu2O3H3]

+ and [Eu3O4H3]

+ in which all

the Eu sites are in valence 2 if hydrogen is present as OH.

For Th the clusters formed showed sequential addition of ThO2, with the series [ThmO2m-1]+

approaching a fragment valence 4 with increasing m. For U, five series of clusters were

observed, UmO2m+, UmO2m-1

+, UmO3m-1

+, UmO3m-2

+, and UmO3m-3

+, showing a

sequential addition of UO3 and UO2, approaching fragment valences of 4 or 6, the most stable

oxidation states in the case of uranium. While for U the largest cluster obtained was [U5O13]+,

for Th it was possible to obtain Th11O21+. Thorium and uranium clusters have been

previously obtained by Michiels and Gijbels (m = 1,2,3) using LAMMA of oxides, and by

Jennings et al., Tench et al. , and Brown and Ismail using FAB of thorium and uranium salts.

Summarizing, in all cases the cluster composition depends on the accessibility of the metal

valence states, Ln(III) sites are dominant for the lanthanides, Ln(II) more easily accessible for

Eu, M(IV) only for Ce, Th and U, and M(VI) for U.

Communication to: 43rd

ASMS Conference on Mass Spectrometry and Allied Topics Atlanta,

Georgia, USA, May 21-26, 1995.

19

Gas phase reactions of lanthanide ions with isopropanol and phenol

José Manuel Carretas, Joaquim Marçalo and António Pires de Matos Departamento de Química, Instituto Tecnológico e Nuclear, P-2686 Sacavém Codex

Abstract

The chemistry of lanthanide alkoxides is dominated by the formation of polymetallic species,

some of which involving the presence of oxo ligands; however, the mechanisms of formation

of these species remain unclear. It is usually considered that gas phase studies of the reactions

of metallic ions with organic molecules can give hints for the understanding of the

mechanisms of condensed phase processes. Therefore, the gas phase reactions of the

lanthanide series ions Pr+ e Sm

+ with isopropanol and phenol were studied by Fourier

transform ion cyclotron resonance mass spectrometry (FT-ICR/MS), using a FT/MS 2001-DT

spectrometer. The metallic ions were produced by laser ionisation of the corresponding metals

and thermalised by collisions with argon, which was introduced in the instrument through

pulsed valves; the reagents were introduced through a “leak valve” to pressures of (1-5) 10-7

Torr.

The Pr+ e Sm

+ ions react exothermically with the two alcohols, with formation of MO

+ and

MOH+ ions as primary products, which participate in subsequent reactions that lead to

M(OR)x(HOR)y+ species, where x = 1-2 and y = 0-3. The detailed study of the reaction

sequences, of the corresponding kinetics and of the energies involved in the various steps

showed important differences between the reactions with isopropanol and with phenol, as well

as in the relative reactivity of the two metallic ions; the larger reactivity of Pr+ compared to

Sm+ with both alcohols is in agreement with the known data on the reactivity of the lanthanide

series ions with several hydrocarbons .

Communication to: 2nd

Mass Spectrometry Meeting of the Portuguese Chemical Society

Lisbon, Portugal, December 5-7, 1995.

Gas phase reactivity of thorium ions with alkanes

João Paulo Leal, Joaquim Marçalo and António Pires de Matos Departamento de Química, Instituto Tecnológico e Nuclear, P-2686 Sacavém Codex

Abstract

The gas phase reactivity of positive Th ions with alkanes (methane, ethane, propane, butane

and isobutane) was studied by Fourier transform ion cyclotron resonance mass spectrometry

(FT-ICR/MS), using a FT/MS 2001-DT spectrometer. Metallic ions were produced by laser

ionization from a metallic piece of thorium and thermalized by collision with argon molecules

introduced by a pulsed valve. Reagent gases were introduced by a leak valve and kept in the

range of (1-5) 10-7

Torr.

Th+ ions react exothermically with all studied alkanes, producing simple and multiple

dehydrogenations, implying that CH bonds are preferentially activated. In the reaction with

methane ThCH2+ is formed and, despite the low efficiency of the reaction k/kLangevin = 0.02, it

should be stressed that Th+ is one of the few ions that can activate CH bonds in (the others

are ions of the third d transition series, Ta+, W

+, Os

+, Ir

+ and Pt

+ [1]). The reaction with ethane

produces ThC2H4+ (50%) and ThC2H2

+ (50%), with k/kLangevin = 0.20. With propane the

resulting products, ThC3H6+ (30%) and ThC3H4

+ (70%), came from simple and double

dehydrogenation, with k/kLangevin = 0.32. Reactions with butane and isobutane both lead to

20

double dehydrogenation with formation of ThC4H6+, with k/kLangevin = 0.32 and 0.30,

respectively; CID experiments with the species formed in these reactions indicated the same

structure, probably Th(butadiene)+.

It should be noted that U+ reactivity with alkanes shows important differences relatively to

Th+, since U

+ doesn’t react with methane and ethane, but reacts with propane, butane and

isobutane.

Communication to: 2nd

Mass Spectrometry Meeting of the Portuguese Chemical Society

Lisbon, Portugal, December 5-7, 1995.

Ion-Molecule Equilibrium Experiments in a Fourier Transform Ion

Cyclotron Resonance (FT-ICR) Mass Spectrometer

J. P. Leal#, M. T. Fernandez*, J. A. Martinho Simões*,

# Departamento de Química, ITN

* Departamento de Química, FCUL

Abstract

Since the middle of the seventies, a considerable amount of information about neutral and

ionic species thermochemistry had been derived from equilibrium constants of gas phase ion-

molecule reactions, using a variety of methods like Fourier transform ion-cyclotron resonance

mass spectrometry (FT-ICR).

The importance of thermochemical data obtained by these methods, e.g. enthalpies of

formation of ions and bond energies, as well the fact that they are collected without solvent

effect, led to the implementation of such a method in a Fourier transform ion-cyclotron

resonance mass spectrometer (FT-ICR), located at the ITN, Sacavém.

As a calibration system was choosen the proton transfer equilibrium between benzene and

fluorobenzene, previously measured in several other laboratories. The results obtained at 301

K, agree with the ones measured by high pressure pulsed mass spectrometry (HPPMS): K =

1.780.16, 1.54, 1.690.20, 1.760.25.

(C6H6)H+ + C6H6F C6H6 + (C6H5F)H

+

Communication to: 2nd

Physical Chemistry Meeting of the Portuguese Chemical Society

Porto, Portugal, June 1995.

Theoretical and experimental study of relative basicity of limonene in gas

phase

M. T. N. Fernandez*, C. Williams

§, R. S. Mason

§, J. P. Leal

# and B. C. Cabral*

* Departamento de Química, FCUL §Chemistry Department, University College, Swansea, UK

# Dep. Química, ITN, Sacavém.

Abstract

Terpens, natural products abundant in our country, had been the subject of wide investigation,

mainly due to its application on industry. During last years the reactivity of limonene with the

most abundant species in the troposphere show a relevant increment, since they are a

21

significant part of the VOC (Volatile Organic Compounds) that came from plants.

Thermochemical data available for terpens are scarce. However, these data are very important

to build a data bank to test theoretical models that can bring some light over the protonation

mechanism.

The first step in the study of monoterpenes was the determination of the gas phase basicity of

limonene by measuring proton transfer equilibrium constants.

C10H16 + BH+ C10H16H

+ + B

C10H16 - limonene; B -acetophenone and aniline

High pressure pulsed mass spectrometry had been used and relative basicity values measured

to limonene were GB = -G0

575 = 837 1 kJ/mol and GB = -G0

474 = 838.5 1 kJ/mol with

respect to aniline and acetophenone respectively.

In an attempt to predict the structure of the C10H16H+ ion Hartree-Fock calculations were

performed and confirm a high energy value associated to the proton transfer process.

The implementation of this kind of experiment in an ICR-FTMS apparatus is in progress.

Communication to: 2nd

Mass Spectrometry Meeting of the Portuguese Chemical Society

Lisbon, Portugal, December 5-7, 1995

Periodicity in the reactivity of lanthanide ions with naphthalene and

mesitylene - thermodynamic and kinetic trends

João Paulo Leal*, Joaquim Marçalo*, A. Pires de Matos* and Alan G. Marshall

#

* Departamento de Química, ITN, 2686 Sacavém CODEX, Portugal #Department of Chemistry, Florida State University, Tallahassee, FL 32306-3006 and National High

Magnetic Field Laboratory, Florida State University,1800 East Paul Dirac Drive,Tallahassee, FL

32310, USA

Abstract

The gas phase reactivity of the lanthanide series ions Ln+ (Ln = La-Lu, except Pm) with

naphthalene and mesitylene have been studied by Fourier transform ion cyclotron resonance

mass spectrometry.

Two main types of primary products were observed in these reactions: Ln(Arene)+ adducts

and C-H activation products, depending on the metal ion and the arene involved. The most

important feature of the secondary reactions is that some Ln(Arene)+ species activate a new

arene molecule.

The patterns of reactivity along the lanthanide series can be rationalized by the magnitude of

the promotion energies from the ground state to reactive configurations. However, to explain

kinetic results some other effects, e.g. orbital sizes, should be considered in addition to the

one stated above.

The kinetic results obtained with naphthalene and mesitylene are comparable with the ones

obtained for other organic molecules.

Communication to: 8th

Sanibel Conference on Mass Spectrometry, Sanibel Island, Florida,

January 20-23, 1996.

22

Gas-phase actinide ion chemistry: reactions of Th+ and U

+ with CH4 and

C2H6

Joaquim Marçalo, João Paulo Leal, and António Pires de Matos Departamento de Química, Instituto Tecnológico e Nuclear,P-2686 Sacavém Codex, Portugal

Abstract

The gas-phase reactivity of the actinide series ions Th+ and U

+ with methane and ethane were

studied by Fourier transform ion cyclotron resonance mass spectrometry (FTICR/MS), using

an Extrel (Waters) FTMS 2001-DT spectrometer. The metal ions were produced by laser

desorption/ionization of pure metal pieces and the reagents were admitted to the instrument

through a leak valve; argon, introduced through pulsed valves, was used for collisional

cooling of the metal ions.

Th+ ions dehydrogenated methane with a rather low efficiency (k/kL = 0.014) to form ThCH2

+,

implying that D(Th+–CH2) 460 kJ/mol. With ethane, single and double dehydrogenations

were observed, producing ThC2H4+ and ThC2H2

+ (relative intensity ca. 1:1) with a moderate

efficiency (k/kL = 0.124), indicating that D(Th+–C2H4) 136 kJ/mol and D(Th

+–C2H2) 312

kJ/mol. In the absence of collisional cooling, minor products like ThH+, ThH2

+, ThCH2

+, and

ThCH3+, either endothermic or corresponding to processes with high kinetic barriers, were

also observed in the ethane reaction. The facile oxidation of the products of both reactions by

residual water and oxygen dominated the secondary steps, indicating that the primary products

of the methane and ethane reactions are unreactive with these gases.

U+ ions were found to be essentially unreactive with methane and ethane. The formation of

oxygenated products from background water and oxygen was the main process observed

either in the presence or absence of thermalization, although in this last case inefficient

formation of dehydrogenation products was also observed with both reagents.

The results obtained in the reactions of Th+ and U

+ with methane and ethane, as well as those

previously obtained with benzene and other arenes, not unexpectedly show similarities to the

reactivity of the early d transition metal cations and the lanthanide cations La+, Ce

+, and Gd

+.

However, the differences in reactivity between Th+ and U

+ reported herein, appear to indicate

that simple electronic arguments (ground state configuration of Th+ - 5f

06d

27s

1; ground state

configuration of U+ - 5f

36d

07s

2, low-lying configurations at 0.04 eV - 5f

36d

17s

1 and 0.57 eV -

5f36d

27s

0) may not be sufficient to explain the reactivities of actinide ions with hydrocarbons,

and significant electronic effects in the reactivity along the actinide series can be anticipated.

Communication to: 43rd

ASMS Conference on Mass Spectrometry and Allied Topics Atlanta,

Georgia, USA, May 21-26, 1995.

Reactivity of thorium ions with ethylene, propene, 1-butene and cyclopropane

Joaquim Marçalo, João Paulo Leal and António Pires de Matos Departamento de Química, ITN

The gas-phase reactivity of Th+ ions with ethylene, propene, 1-butene and cyclopropane was

studied by Fourier transform ion cyclotron resonance mass spectrometry (FTICR/MS), using

an FT/MS 2001-DT spectrometer. The metal ions were produced by laser

desorption/ionization of pure metal pieces and the reagents were admitted to the instrument

through a leak valve; argon, introduced through pulsed valves, was used for collisional

cooling of the metal ions.

Th+ ions dehydrogenated ethylene to form ThC2H2

+ as primary product, with a rather high

23

efficiency k/kL = 0.46, and sequentially dehydrogenated further ethylene molecules up to

ThC8H8+, with lower efficiencies of 0.08, 0.20 and 0.05 for each subsequent step.

With propene ThCH2+ (55%), ThC3H4

+ (25%) and ThC3H2

+ (20%) were formed as primary

products, with a reaction efficiency k/kADO = 0.48; the primary ions reacted with new propene

molecules inducing single and double dehydogenations.

In the reaction with 1-butene the primary products were ThCH2+ (20%), ThC2H2

+ (40%),

ThC4H6+ (10%) and ThC4H4

+ (30%), and the efficiency k/kADO = 0.46; again, the primary

products reacted with new 1-butene molecules, up to ThC9Hx+ species.

The reaction with cyclopropane yielded as primary products ThCH2+ (70%), ThC3H4

+ (15%)

and ThC3H2+ (15%), with an efficiency k/kL = 0.33, and further reactions of these ions with

cyclopropane were observed.

This study showed that, as in the case of saturated hydrocarbons, Th+ ions are more reactive

than U+ ions.

Reactivity of lanthanide metal and oxide ions with pentamethylcyclo-

pentadiene and related studies

Joaquim Marçaloa and António Pires de Matos

a, William J. Evans

b

aDepartamento de Química, ITN

bDepartment of Chemistry, University of California, Irvine

The gas-phase reactivity of Sc+, Y

+ and Ln

+ (Ln = La - Lu) ions with

pentamethylcyclopentadiene was studied by Fourier transform ion cyclotron resonance mass

spectrometry (FTICR/MS), using an FT/MS 2001-DT spectrometer. The metal and oxide ions

were produced by laser desorption/ionization of metal pieces and the reagents were admitted

to the instrument through a leak valve; argon, introduced through pulsed valves, was used for

collisional cooling of the reagent ions.

The reactivity of Eu+, Tm

+ and Yb

+ was similar to the one observed for Sm

+, namely the

formation of the fulvenide ion (C5Me4CH2)M+ as main primary product and of the

metallocene ion (C5Me5)2M+ as main secondary product. With Sc

+, Y

+ and the remaining

lanthanide series ions, several other species were observed in the primary reactions,

corresponding to multiple neutral losses. These differences in reactivity, as well as the

kinetics, are in agreement with previous observations on the reactivity of the lanthanide ions

with hydrocarbons, which strongly depends on the accessibility of reactive excited state

electron configurations of the metal ions.

In the case of the metal oxide ions MO+ (M = Sc, Y , Ln), the reactivity with

pentamethylcyclopentadiene appeared to be determined by the strength of the M+ – O bonds.

The ions with the strongest bonds to oxygen, La+, Ce

+ and Pr

+, formed (C5Me5)(OH)M

+ as

sole primary product, which then reacted further, eliminating water, to give the metallocene

ion (C5Me5)2M+. Sc

+, Y

+ and the remaining lanthanide series ions yielded other primary

products besides (C5Me5)(OH)M+ like (C5Me4CH2)MO

+ and (C5Me4CH2)M

+, and as

secondary products (C5Me4CH2)2M+ and (C5Me5)2M

+. The kinetics also showed a dependency

on the strength of the M+ – O bonds.

In related work, the reactivity of Y+, Sm

+ and Eu

+ with indene was studied using the same

methodology. In the case of the less reactive metal ions Sm+ and Eu

+, a single primary

product, the indenyl ion (C9H7)M+, was observed, and as secondary product only the

condensation product (C9H8)(C9H7)M+ formed. In the case of Y

+, the main primary product

was due to dehydrogenation of indene, (C9H6)M+, which then yielded the bis(indenyl) ion

24

(C9H7)2M+ in a secondary reaction. The study of reactions of the remaining Ln

+ ions with

indene is in progress.

Reactivity of lanthanide oxide cluster ions with unsaturated hydrocarbons

Joaquim Marçalo,a António Pires de Matos,

a Hans H. Cornehl,

b Christoph Heinemann

b and

Helmut Schwarz b

a Departamento de Química, ITN

bInstitut für Organische Chemie, Technischen Universität Berlin

The gas-phase reactivity of lanthanide oxide cluster ions of the type LnxOy+ (Ln = La - Lu)

with unsaturated hydrocarbons was studied by Fourier transform ion cyclotron resonance mass

spectrometry (FTICR/MS), using an FT/MS 2001-DT spectrometer. The lanthanide oxide

cluster ions were produced by direct laser desorption/ionization of surface oxidized metal

pieces and the reagents were admitted to the instrument through a leak valve; argon,

introduced through pulsed valves, was used for collisional cooling of the reagent ions and also

for CID studies.

2-butene was used as a model substrate for the reactivity studies, that involved oxide cluster

ions with different compositions, namely Ln3O4+, Ln6O8

+ and Ln7O10

+, of all the lanthanide

series metals. In all cases, no reactions with 2-butene were observed; the only process that

could be detected was the sequential coordination to the cluster ions of water molecules,

present in the background of the mass spectrometer. For some cluster ions containing

representative lanthanide series metals, the reaction with 1,4-cyclohexadiene, for which the

formation of benzene plus hydrogen is by itself exothermic, was also tried, but again no

reactions were observed. These reactivity studies indicate that the lanthanide oxide cluster

ions are closed-shell species with very stable structures, a fact that is corroborated by CID

studies in which fragmentation of the cluster ions could only be observed for high excitation

energies of the ions.

FTICR mass spectrometric study of nucleosides

Joaquim Marçalo,a Anna Napoli,

b Giovanni Sindona,

b Maria Alzira Almoster Ferreira

c

a Departamento de Química, ITN

b Università della Calabria, Cosenza

c Faculdade de Ciências da Universidade de Lisboa

In this work, we tried to use Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

(FTICR/MS) to determine the proton affinity of natural nucleosides, namely 2’-

deoxyguanosine (dG), 2’-deoxyadenosine (dA), 2’-deoxycytosine (dC) and 2’-deoxyuridine

(dU), either by an adaptation of the “kinetic method” to the FTICR/MS technique, or by

“bracketing” methods. However, with the available experimental conditions, it was not

possible to accomplish this objective, as the Laser Desorption (LD) spectra always showed the

attachement of metal cations present in the background (Na+, K

+ or Cr

+) to the nucleoside, and

no formation of (M + H)+ species, necessary for the proposed experiments.

From the LD spectra obtained with a mixture of nucleosides it was possible to establish a

relative ordering of their affinities towards sodium: dA dU > dG >> dC.

25

FTICR mass spectrometric study of arsenic compounds

Joaquim Marçalo,a M. Helena Florêncio,

b A. M. de Bettencourt

b

a

Departamento de Química, ITN Faculdade de Ciências da Universidade de Lisboa b Departamento de Ecologia, Universidade de Évora

Laser Desorption Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (LD-

FTICR/MS) was used to analyse several organometallic and inorganic arsenic compounds,

namely arsenocoline, arsenobetaine, sodium methylarseniates and tetramethylarsonium iodide,

with the purpose of their future use in the identification of “refractory” organometallic arsenic

compounds present in water samples from the Tagus estuary.

FTICR mass spectrometric analysis of organic and organometallic compounds

Joaquim Marçalo and João Paulo Leal Departamento de Química , ITN

The analysis of several organic and organometallic compounds was performed using Laser

Desorption (LD) and Electron Impact (EI) Fourier Transform Ion Cyclotron Resonance Mass

Spectrometry (FT-ICR/MS) as a result of informal collaborations with research groups in

Instituto Nacional de Engenharia e Tecnologia Industrial (INETI), Instituto Superior Técnico

(IST) and Faculdade de Ciências da Universidade de Lisboa (FCUL). These analyses

involved, in some cases, exact mass measurements for structure confirmation.

Equilibrium studies of phenols in gas phase

João Paulo Leal, J. A. Martinho Simões and Teresa Fernandez Departamento de Química, ITN

Departamento Química, FCUL

The equilibrium of PhOH and p-MeOPhOH was studied using a FT-ICR mass spectrometer.

The preliminary results obtained are in a fairly good agreement with the literature values.

After some minor modification, the procedure will be used to study other gas phase equilibria

that will lead to a relative gas phase acidity scale.

26

Metal Vapour Synthesis

Synthesis, NMR and FTICR mass spectrometric characterization of Ti, Cr,

Mo and W Bis(fluorene) complexes

Alberto Romão Diasa, João Luís Ferreira da Silva,

a Joaquim Marçalo,

b António Pires de

Matos, b

F. G. N. Clokec

aCentro de Química Estrutural, Instituto Superior Técnico Av. Rovisco Pais, 1096 Lisboa Codex,

Portugal b Departamento de Química, Instituto Tecnológico e Nuclear P-2686 Sacavém Codex, Portugal

cSchool of Chemistry and Molecular Sciences, University of Sussex Brighton, BN1 9RQ, U.K.

Abstract

The title complexes were prepared using the Metal Vapour Synthesis technique, by

cocondensing metal and fluorene vapours on a glass reactor cooled with liquid nitrogen.

NMR studies of solutions of these complexes in d-benzene show that fluorene coordinates 6

to the metals, producing a 1:1 isomer mixture. They also demonstrate the variations in

backdonation for the different metals.

The complexes were also characterised by Fourier transform ion cyclotron resonance mass

spectrometry (FTICR/MS), using both electron impact (EI) and laser desorption/ionization

(LDI). The experiments were performed with an Extrel FTMS (Waters Corp.) Model 2001-

DT FTICR mass spectrometer, interfaced to a Spectra-Physics pulsed Nd:YAG laser,

operating at the fundamental wavelength (1064 nm). The air-sensitive complexes were

transferred to the automatic solids probe of the instrument under argon.

Positive EI mass spectra could only be obtained for the volatile Cr and Mo complexes, at

probe temperatures of ~ 100 ºC, and showed prominent molecular ion peaks at low electron

beam energies. Positive LDI mass spectra were obtained for all the compounds and showed a

close relation to their thermal stabilities. The spectra of the more stable Cr and Mo complexes

were dominated by the molecular ion peaks, while for the less stable W complex both the

W(fluorene)2+ and the W(fluorenyl)2

+ ions were formed. In the case of the Ti complex only

the Ti(fluorenyl)2+ ion could be observed.

The laser desorption/ionization process also induced, for all the compounds studied, the

formation of other interesting species, namely M(fluorene)(fluorenyl)2+, M2(fluorene)2

+,

M2(fluorenyl)2+, M2(fluorene)(fluorenyl)2

+ and M2(fluorene)3

+. In the case of Cr, the

formation of the presumed “triple-decker sandwich” species Cr2(fluorene)3+ could also be

observed by reacting Cr(fluorene)+, produced by EI, with neutral Cr(fluorene)2.

Communication to: XIth

FECHEM Conference on Organometallic Chemistry Parma, Italy,

September 10-15, 1995.

Metal vapour synthesis of europium alkoxides

J.M. Carretas, J. Marçalo, J.C. Waerenborgh and A. Pires de Matos Departamento de Química, ITN

Metal vapour synthesis of several europium alkoxides have been studied. Eu(II) species were

identified by Mössbauer spectroscopy. Tentatives to grow crystals are in progress.

27

Surface Studies

Photon stimulated ion desorption from polyatomic molecules in the VUV:

C2H4/ graphite

J.M. Coquel,

a T. Almeida Gasche,

b J. Wilkes,

a,c C.M.Friedrich,

d C.L.A. Lamont, M.A.

c

MacDonald, e R.E. Palmer,

a A.M.C. Moutinho

f

aNanoscale Physics Research Laboratory, Scholl of Physics and Space Research, University of

Birmingham, Birmingham B15 2TT, UK bDepartamento de Química, Instituto Tecnológico e Nuclear Estrada Nacional 10, 2686 Sacavém

Codex, Portugal cSchool of Applied Sciences, University of Huddersfield Huddersfield HD1 3DH, UK

dCavendish Laboratory, University of Cambridge Madingley Rd, Cambridge CB3 OHE, UK CLRC,

eDaresbury Laboratory Warrington WA4 4AD, UK GIDS,

fDepartamento de Física, Faculdade de Ciências e Tecnologia Universidade Nova de Lisboa, 2825

Monte da Caparica, Portugal

Abstract

VUV light sources offers new routes to chemically selective surface modification.

Photodesorption measurements allow us to address a key issue in this area-the mechanism of

molecular dissociation or desorption. We have investigated photon stimulated ion desorption

from C2H4 physisorbed on highly ordered pyrolytic graphite using VUV synchroton radiation

in the enrgy range 13-40 eV. In contrast with the gas phase photodissociation measurements,

only H+ ions are detected. This result is attributed to the image potential barrier to desorption

from the surface and the unequal distribution of kinetic energy amongst the molecular

photofragments. The yield of desorbed H+ ions shows a threshold at 20.5 eV, a resonance at

24 eV and a further threshold at 28 eV. This behaviour differs significantly from the gas phase

and is attributed to selective quenching of excited molecular electronic states on the surface

and to chemical reactions between specific molecular dissociated fragments and the substrate.

J, of Physics: Condensed Matter (Surface and Interface Science Letters) (in press).

28

Thermochemistry

Determination of enthalpies of formation of potassium and cesium

alkoxides

João Paulo Leal, M. E. Minas da Piedade and Paulo Nunes Departamento de Química, ITN

Departamento de Engenharia Química, IST

Alkaline metal alkoxides MOR (M = K and Cs, R = Et, Bu and t-Bu) were synthesized and

the respective enthalpies of formation were determined by reaction-solution calorimetry,

studying the reaction of the alkoxides with water.