Structural analyses of 2-triorganylsilyl- and 2-triorganylstannyl derivatives of...

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Journal of Organometallic Chemistry 751 (2014) 579e590

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Journal of Organometallic Chemistry

journal homepage: www.elsevier .com/locate/ jorganchem

Structural analyses of 2-triorganylsilyl- and2-triorganylstannyl derivatives of 5-alkyl-[1,3,5]-dithiazinanes.Do S/Si and S/Sn interactions exist?

Raúl Colorado-Peralta a,b, Carlos Guadarrama-Pérez a, Luis A. Martínez-Chavando a,Juan Carlos Gálvez-Ruiz c, Angélica M. Duarte-Hernández a, Galdina V. Suárez-Moreno a,Aurora Vásquez-Badillo a, Sonia A. Sánchez-Ruiz a, Rosalinda Contreras a,Angelina Flores-Parra a,*

aDepartamento de Química, Cinvestav, A.P. 14-740, México, D.F. 07000, Mexicob Facultad de Ciencias Químicas, Universidad Veracruzana, Orizaba, Veracruz, MexicocDepartamento de Ciencias Químico-Biológicas, Universidad de Sonora, Hermosillo, Sonora, Mexico

a r t i c l e i n f o

Article history:Received 7 June 2013Received in revised form18 July 2013Accepted 18 July 2013

Keywords:2-R3Si-[1,3,5]-dithiazinanes2-R3Sn-[1,3,5]-dithiazinanesN-borane adductsS/Si and S/Sn weak interactionsConformational analyses

* Corresponding author.E-mail address: aflores@cinvestav.mx (A. Flores-Pa

0022-328X/$ e see front matter � 2013 Elsevier B.V.http://dx.doi.org/10.1016/j.jorganchem.2013.07.058

a b s t r a c t

A series of 2� R03E (E ¼ Si or Sn; R0 ¼ Me or Ph) derivatives of 5-R-[1,3,5]-dithiazinanes (R ¼ Me, iPr, tBu)

are reported, as well as some of their NeBH3 adducts. Structures were determined by 29Si, 119Sn, 11B, 13Cand 1H NMR and X ray diffraction analyses. Minimum energy conformations were calculated by HF/6-31þþG(d,p) and B3LYP/6-31þþG(d,p) methods. Preferred conformations and steric and stereo-electronic interactions are analyzed. In the solid state the ring conformation is a chair with the NeRgroup in axial and the 2-substituents in equatorial position. The Si or Sn atoms linked to C-2 have shortdistances to the two sulfur atoms, interpreted as Si/S and Sn/S stabilizing contacts. The 119Sn NMRchemical shifts and 1J(13C,119Sn) coupling constants evidenced weak S/Sn coordination bonds. Substi-tution reactions at C2 performed in NeBH3 adducts of 2-lithium-5-methyl-[1,3,5]-dithiazinanes ofanchored conformation proceed with retention of C2 configuration.

� 2013 Elsevier B.V. All rights reserved.

1. Introduction

Following our research program on the chemistry of [1,3,5]-dithiazinanes [1e8], we have synthesized a series of [1,3,5]-dithiazinanes bearing triorganylsilane or triorganyltin groups atC2. It has been reported that 2-trialkylsilyl and 2-trialkylstannylsubstituents have more preference for the equatorial position in1,3-dithianes than in cyclohexane [9], however until now there wasno explanation for this relevant fact, which we attributed to Si/Sand Sn/S stabilizing interactions. Our interest in sulfur weak in-teractions [4,5,10e12] motivated us to explore the structure of 2-substituted [1,3,5]-dithiazinanes by NMR, X-ray diffraction andab-initio theoretical studies [HF/6-31þþG(d,p)] in order to analyzeif Si/S or Sn/S short contacts could account for conformationalstabilization. We are also interested in having clues about the ste-reochemistry of C2 substitution reactions in 5-alkyl-[1,3,5]-dithia-zinanes of blocked conformation by N-borane coordination.

rra).

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2. Results and discussion

The synthesis and structural analyses of series of 2-R3Si-[1,3,5]-dithiazinanes (4e9) and 2-R3Sn-[1,3,5]-dithiazinanes (10e15)(R ¼ methyl or phenyl) derived from 5-methyl-[1,3,5]-dithiazinane(1), 5-isopropyl-[1,3,5]-dithiazinane (2) and 5-tertbutyl-[1,3,5]-dithiazinane (3) are reported. The reactions of dithiazinanes 1e3with tBuLi in THF followed by addition of SiMe3Cl or SiPh3Cl gavethe organosilyl compounds 4e9 respectively, whereas the reactionswith SnMe3Cl and SnPh3Cl afforded the organotin derivatives 10e15, Scheme 1.

Organometallic compounds 4e15 were obtained in good yields.They were purified by CH2Cl2 extraction and washed with water.Structures were determined by NMR, elemental analyses and (þ)TOF mass spectra. X-ray diffraction analyses were performed forcompounds 4e7, 9, 10 and 14.

The silicon and tin derivatives 4, 5, 10, 11 and 13 were treatedwith BH3eTHF to give the corresponding N-borane adducts (16e20). In order to check the stereochemistry of the substitution re-actions at C2, the N-borane adduct (1BH3) of the starting dithiazi-nane 1was submitted to reactionwith tertbutyllithium followed by

1 R = Me2 R = iPr3 R = tBu

1) tBuLi, THF

R

R'3E

R

E = Si E = Sn R' = Me R' = Ph R' = Me R' = PhR = Me 4 7 10 13

R = iPr 5 8 11 14

R = tBu 6 9 12 15

2) R'3ECl, THF

Scheme 1. Synthesis of silicon 4e9 and tin [1,3,5]-dithiazinanes 10e15.

21 22

Cl-

Me Me

Me3Me3C

Scheme 3. Compounds 21 and 22.

R. Colorado-Peralta et al. / Journal of Organometallic Chemistry 751 (2014) 579e590580

trialkylsilane chloride and trialkylstannane chloride to give com-pounds 16, 17 and 20, Scheme 2.

Compounds 1e3 are in conformational equilibrium in solutionat room temperature, whereas their N-alkyl group is maintained inaxial position [13]. The X-ray diffraction analyses of compounds 1e3 [3,13] show that sulfur atoms are partially sp3 hybridized [w33e40%] in consequence the sulfur orbitals containing the lone pairshave equatorial and axial incipient lobes and produce anti-periplanar effects on vicinal axial CeH protons.

We were unable to synthesize the 2-tertbutyl-[1,3,5]-dithiazi-nane (21, Scheme 3), however data of the calculated structure [13]wERE compared with its silicon (4) and tin (10) analogs, vide infra.Crystals of Me3Si-[1,3,5]-dithiazinanium chloride (22) were ob-tained as subproducts in the synthesis of compound 4, Scheme 3.The X-ray analysis of compound 22 was performed.

2.1. 2-Silicon and tin organometallic derivatives 4e15

2.1.1. NMR analysesNMR analyses of silicon and tin compounds 4e15 indicate that

all of them are in a preferred conformation as was deduced fromthe 1He1H coupling pattern, Table 1. Evidence for the equatorialposition of the organometallic group was found in the couplingconstants of tin atoms with the equatorial C4eH protons and3J(13C,119Sn) with the C4 and C6 atoms, Table 2. In compounds 10e12 coupling constants values 3J(13C,119Sn) from 19.2 to 22.1 Hz are inagreement with data of 2-Me3Sn-1,3-dithiane and confirm theassigned conformation [9,14]. Results also coincide with previousreports of the equatorial preference of R3E (E ¼ Si, Sn or Pb) groupsin the C2 carbon of 1,3-dithianes, in contrast of cyclohexanesubstituted by the same groups [9].

The presence of Me3Si- (4e6) or Me3Sn- (10e12) groups affectsonly the 1H resonances of axial C2eH protons, 0.5 and 0.2 ppmshifts toward lower frequencies respectively, Table 1. However, inPh3Si- (7e9) and Ph3Sn- (13e15) compounds, the C2eHprotons areshifted toward higher frequencies, between 0.34 and 0.55 ppm forsilicon derivatives and 0.7 ppm for tin compounds.

1) nBuLi2) R'3ECl 16, 17, 20

1BH3

R R

R'3

16 E= Si, R = Me, R' = Me17 E= Sn, R = Me, R' = Me18 E= Si, R = iPr, R' = Me19 E= Sn, R = iPr, R' = Me20 E= Sn, R = Me, R' = Ph

R'3

4, 5, 10, 11, 13

H3B-THF

Scheme 2. Synthesis of NeBH3 adducts of tin and silicon compounds 16e20.

Examination of 13C NMR chemical shifts of C2 in compounds 4e9 indicates that the silyl groups do not produce any significant ef-fect on the signals, whereas the 13C spectra of the stannane de-rivatives 10e15 show for C2 a moderate shielding effect, w2 ppmfor Ph3Sn- and w5 ppm for Me3Sn- derivatives, Table 1.

The 29Si chemical shifts of compounds 4e6 vary from þ2.8to þ3.3 ppm (CDCl3, Table 3). They show a slightly shielding effect,when compared to the signals of RSeCH(SiMe3)SR (when R is Me,d 29Si ¼ þ4.98 ppm and when R is (CH2)3, d 29Si ¼ þ4.32 ppm [15]).Same effect was observed for Ph3Si- compounds 7e9, their d 29Siresonances are slightly shifted to lower frequencies (d variesfrom �13.7 to �14.1 ppm, CDCl3) when compared to the signal ofSiMePh3 (d 29Si ¼ �11.9 ppm [16]). It indicates that the dithiazi-nanyl ring has only a small effect on the 29Si chemical shift.

The 119Sn chemical shifts of Me3Sn derivatives 10e12 are in therange of �2.0 to þ1.6 ppm, values not very different from theresonance of Me3Snecyclohexane (d 119Sn ¼ ¼ �4.7 ppm, CH2Cl2[17]). However, the 119Sn chemical shifts of the Ph3Sn- compounds13e15, where the tin atoms are more acidic, appear in the rangeof �146.1 to �148.4 ppm (CDCl3), far from the Ph3Snecyclohexaneresonance (d ¼ �113.7 ppm, CHCl3 [17]). These shifts may beattributed to “through the space S/Sn interactions” in agreementwith the S/Sn short distances found in X-ray diffraction structures,as we will discuss below.

The fact that in Me3Sn compounds, the 1J(13C,119Sn) couplingconstants with the methyl carbon [10 (352.7 Hz), 11 (351.2 Hz) and12 (351.7 Hz), Table 2] are bigger than the equivalent couplingconstant in Me3Snecyclohexane (299.4 Hz [17]) clearly indicatesthat the tin atom has weak coordinative interactions with the sulfuratoms.

The 1J(13C,119Sn) coupling constants with C2 [10 (281.9 Hz), 11(285.1 Hz) and 12 (291.5 Hz)] are smaller than the correspondingcoupling constant (403.8 Hz) in Me3Snecyclohexane, it is aconsequence of the sulfur atoms presence. 1J(13C,119Sn) couplingconstants are bigger in triphenyltin compounds 13 (321.1 Hz) and14 (307.6 Hz) than in trimethyltin derivatives due to the moreelectronegative tin substituents, Table 4. The nitrogen coordinationto borane in compound 17 decreases the nitrogen lone pair elec-troattractive effect which is reflected at the 1J(13C,119Sn) couplingconstant with C2 (214.0 Hz) [16]

The 2J(1H,119Sn) coupling constants of H2 are sensitive to the tinsubstituents (40.2e42.0 Hz in SnMe3 and 44.5e47.8 Hz in SnPh3compounds) and to the N / BH3 coordination bond in compound17 (38.6 Hz), Tables 2 and 4. Some 29Si coupling constants are re-ported in Table 5.

2.1.2. X-ray diffraction analyses of compounds 4e7, 9, 10, 14 and 22Compounds 4e7, 9, 10, 14 and 22 have similar structures,

Figs. 1e6. Selected bond lengths and angles are given in Tables 6and 7, respectively. The silicon and tin groups are placed in equa-torial position and the N-substituents in axial position. The C2eE(Si or Sn) bond has an alternated conformation. The S/Si (between3.03 and 3.09�A) and S/Sn (between 3.27 and 3.29�A) distances areshorter than the sum of the van der Waals radii (SrvdW 3.9 �A for[Si/S] and 4.05 �A for [Sn/S] [18]), Table 8. The spacefill repre-sentation of sulfur and silicon atoms in 4 is shown in Fig. 1. Com-parison of the bond lengths in the silicon and tin derivatives with

Table 11H and 13C NMR data [d in ppm and J(1He1H) in Hz] of compounds 1e20.

2

Cpd R E R0 H2eq H2ax H4eq,H6eq H4ax,H6ax C2 C4,C6

Dithianea H H Lone pair 3.81(m) 3.81(m) 2.86(m) 2.86(m)1(�80�C),b Me H Lone pair 3.56(dt)c,d 4.60(d)c 3.93(dt)e,d 4.95(d)e 34.3 60.01BH3

a Me H BH3 3.40(dt)f,g 4.05(d)f 3.85(dt)h,g 4.37(d)h 30.2 62.12(�95�C),b iPr H Lone pair 3.64(br d)h 4.65(d)h 4.29(d)i 4.80(d)i 34.0 56.43(�95�C),b tBu H Lone pair 3.68(br s) 4.72(br s) 4.78(br s) 4.55(br s) 35.1 54.3

Cpd R E R0 H2ax H4eq,H6eq H4ax,H6ax C2 C4,C6

4 Me Me3Si Lone pair 4.07(s) 3.92(d)m 4.83(d)m 37.1 60.75 iPr Me3Si Lone pair 4.13(s) 4.27(d)n 4.69(d)n 36.6 57.36 tBu Me3Si Lone pair 4.19(s) 4.45(d)n 4.63(d)n 37.5 55.17 Me Ph3Si Lone pair 4.94(s) 3.94(d)h 4.96(d)h 35.0 61.48 iPr Ph3Si Lone pair 5.04(s) 4.32(d)n 4.81(d)n 34.9 58.19 tBu Ph3Si Lone pair 5.27(s) 4.66(d)n 4.94(d)n 35.7 56.110 Me Me3Sn Lone pair 4.42(s) 3.82(d)m 4.92(d)m 29.5 61.511 iPr Me3Sn Lone pair 4.47(s) 4.16(d)n 4.72(d)n 29.2 58.412 tBu Me3Sn Lone pair 4.49(s) 4.33(d)n 4.66(d)n 29.6 56.113 Me Ph3Sn Lone pair 5.29(s) 3.94(d)m 5.11(d)m 32.0 62.014 iPr Ph3Sn Lone pair 5.35(s) 4.33(d)h 5.01(d)h 32.0 59.015 tBu Ph3Sn Lone pair 5.43(s) 4.50(d)o 4.98(d)o 32.5 56.816b Me Me3Si BH3 3.60(s) 3.87(d)f 4.33(d)f 32.6 63.018b iPr Me3Si BH3 3.67(s) 4.15(d)f 4.60(d)f 37.0 57.717b Me Me3Sn BH3 3.74(s) 3.75(d)f 4.28(d)f 23.9 63.419b iPr Me3Sn BH3 3.85(s) 3.92(d)e 3.98(d)e 27.3 62.920b Me Ph3Sn BH3 4.50(s) 3.85(d)q 4.47(d)q 26.9 63.9

(a) In CDCl3; (b) in THF-d8; 2J(1H,1H)¼ 13.3 (c), 12.6 (e), 13.9 (f), 13.2 (h), 12.2 (i), 13.0 (m), 13.3 (n), 13.5 (o), 13.9 (p), 12.4 (q); 4J(1H,1H)¼ 2.6 (d), 2.0 (g); 3J(1H,1H)¼ 6.7 (j), 5.5(k), 6.9 (l) Hz.

R. Colorado-Peralta et al. / Journal of Organometallic Chemistry 751 (2014) 579e590 581

those of starting heterocycles indicates that substituents do notalter the bond lengths [3].

As expected, compound 5 is similar to 4, some CeH/S distancesare shown in Fig. 2. Intermolecular CeH/S hydrogen bonds in 5-tertbutyl-[1,3,5]-dithiazinane 6 are shown in Fig. 3. The solid statestructures of triphenylsilanes derivatives bearing N-Me (7) and N-tBu groups (9) are represented in Fig. 4, with some CeH/S dis-tances and S/p contacts for 9.

The solid state structures of tin compounds 10 and 14 (Fig. 5) aresimilar to those of silyl derivatives 5 and 7. The Sn/S distances incompounds 10 and 14 are 3.20 and 3.27 �A and 3.25 and 3.27 �A,respectively.

The ionic compound 22 bearing a protonated nitrogen atom has,as expected, a slightly more tetrahedral nitrogen atom, as can bededuced from the angles around the nitrogen atom: C6eNeC4111.37�; C6eNeC7 113.70�; C4eNeC7 115.15�, compared to neutraldithiazinane 4 (C6eNeC4 112.53; C6eNeC7 114.61; C4eNeC7113.93�). However, the S/HeC hydrogen bondmakes themoleculeto adopt closer angles, Fig. 6.

Table 2Coupling constants (Hz) of SnMe3 compounds 10e12 and 17.

Cpd 2J(1H,119Sn) H2 4J(1H,119Sn) (H4/H6)eq 2J(1H,1

Cyclohexanyl-SnMe3 [20]10 42.0 18.7 54.811 40.8 19.8 55.5; 512 40.2 21.7 54.717 38.6 52.0

a Coupling constant with 117Sn.

2.1.3. Ab-initio calculationsThe minimum energy chair conformations of compounds 4e6,

9e13 and 15e21 were calculated, silicon compounds by the B3LYP6-31þþG(d,p) method, whereas the tin compounds by B3LYP 3-21G. The electrostatic potential representations of compound 1[13], the equatorial and axial conformers of 4, 10 and 21 arein Supplementary material.

In order to check the accuracy of the theoretical analyses, wehave calculated the energy difference (A ¼ �DGo ¼ RT ln K in kJ/mol) between the axial and equatorial conformers in Me3Ce,Me3Sie and Me3Snecyclohexanes. It was found that A values were22.8,17.2 and 6.6 kJ/mol respectively. The different values are due tothe different substituents volume. The Me3Snecyclohexane haslonger bonds and in consequence the smallest energy differencedue to lesser hindrance of the equatorial and axial substituents. Thecalculated values agree reasonably well with those experimental orcalculated values found in the literature. The experimental A valuesfor Me3Cecyclohexane are 22.6 kJ/mol [19] and 20.5 kJ/mol [20],whereas the calculated A values are 25.6 and 22.8 kJ/mol [21]. The

19Sn) CH3Sn 1J(13C,119Sn) C2 3J(13C,119Sn) C4/C6 1J(13C,119Sn) CH3Sn

403.8 299.4281.9; 269.9a 19.2 352.7; 343.1a

3.7a 285.1; 272.9a 20.0 351.2; 335.9a

291.5; 276.4a 22.1 351.7; 336.6a

214.0; 204.5a 29.2 359.0; 347.4a

Table 329Si and 119Sn chemical shifts [ppm, CDCl3] of compounds 4e20.

2

Cpd E R R0 29Si Cpd E R R0 119Sn

4 Me3Si Me Lone pair þ3.3 10 Me3Sn Me Lone pair þ1.65 Me3Si iPr Lone pair þ3.2 11 Me3Sn iPr Lone pair �1.86 Me3Si tBu Lone pair þ2.8 12 Me3Sn tBu Lone pair �2.07 Ph3Si Me Lone pair �13.4 13 Ph3Sn Me Lone pair �146.18 Ph3Si iPr Lone pair �13.7 14 Ph3Sn iPr Lone pair �146.69 Ph3Si tBu Lone pair �14.0 15 Ph3Sn tBu Lone pair �148.416a Me3Si Me BH3 þ5.9 17a Me3Sn Me BH3 þ20.018a Me3Si iPr BH3 þ5.7 19a Me3Sn iPr BH3 þ16.7

20a Ph3Sn Me BH3 �126.6

a In THF-d8.

R. Colorado-Peralta et al. / Journal of Organometallic Chemistry 751 (2014) 579e590582

experimental A value reported for Me3Siecyclohexane is 10.5 kJ/mol [22], whereas its calculated A value is 14.3 kJ/mol [23] andfinally the experimental Avalues for Me3Snecyclohexane are 4.4 kJ/mol [24] and 3.8 kJ/mol [9]

Similar calculations in 5-methyl-[1,3,5]-dithiazinanes bearing inC2, Me3C- (21), Me3Si- (4) and Me3Sn- groups (10) gave 13.3, 13.0and 6.9 kJ/mol Avalues, respectively. Calculations performed for thecorresponding anchored molecules bearing the N / BH3 groupafforded 11.6 (2-tertbutyl-5-borane-5-methyl-[1,3,5]-dithiazinane),12.5 (16) and 7.0 (17) kJ/mol.

Calculated data in [1,3,5]-dithiazinanes are not far from those ofexperimental data in [1,3]-dithianes, as observed for the experi-mental A value of 2-Me3C-[1,3]-dithiane (11.4 kJ/mol [25]) and 2-Me3Sn-[1,3]-dithiane (9.0 kJ/mol [9]). It is evident that the size ofthe substituents influences the value of A. On the other side, the Avalue of Me3C-[1,3,5]-dithiazinane 21 (13.3 kJ/mol) is smaller thanthose of Me3Cecyclohexane (22.8 kJ/mol), whereas the differencebetween the A values of Me3Si-dithiazinane 4 (13.0 kJ/mol) andMe3Siecyclohexane (17.2 kJ/mol) is only 4.2 kJ/mol. The A value ofMe3Sn-[1,3,5]-dithiazinane 10 (6.9 kJ/mol) is similar to that ofMe3Snecyclohexane (6.6 kJ/mol). The distances between the car-bon, silicon and tin atoms and the axial protons in cyclohexane(3.35, 3.34 and 3.23 �A, respectively) and in 5-methyl-[1,3,5]-dithiazinane (3.66, 3.52 and 3.43 �A) were measured in order toanalyze the repulsion between the C2 axial substituent and theaxial hydrogen atoms nearby, it was found that the shorter dis-tances in cyclohexane could explain the energy difference betweencyclohexanes and [1,3,5]-dithiazinanes.

The spacefill models of the calculated equatorial conformer of 2-tertbutyl derivative 21 and the X-ray diffraction structures of silane(4) and stannane (5) analogs show their crowded shape, Fig. 7,while in derivative 21 the methyl groups of the tertbutyl are closerto the sulfur atoms.

The steric effect produced by axial substituents can also beappreciated in the spacefill models of the calculated axial con-formers of 21, 4 and 10, Fig. 8.

Table 4Coupling constants (Hz) of SnPh3 compounds 13e15.

Cpd 2J(1H,119Sn) H2 4J(1H,119Sn) (H4/H6)eq 1J(13C,119Sn)

13 47.8 22.9 321.114 44.6 19.6 307.615 44.5 22.9 e

Data suggest that the steric effect is not the only reason for theenergy difference between the axial and equatorial conformers inC2 substituted molecules 21, 4 and 10. Another explanation couldbe found in the electronic stabilizing interactions between thesubstituent in axial or in equatorial and the sulfur atoms. Analysisof the EeCeS (E ¼ C, Si or Sn) angles in the calculated equatorialconformers of 4 [111.4�] and 10 [110.0�] and those obtained fromtheir X-ray diffraction structures [111.1(1)� and 110.3(2)� (4);111.2(2)� and 110.3(2)� (10)] indicate that in spite of the steric strainproduced by the big size of the silicon and tin substituents, the Me

CeS angles are not very different from the ideal values of a tetra-hedral geometry (109.5�). On the other side, the EeCeS (E¼ C, Si orSn) angles in the calculated axial conformers of 4 and 10 are 116.3�

and 115.3�. These angles are also not so open in spite of the hin-drance produced by the axial position of the bulky groups. Stabi-lizing interactions between the C, Si or Sn and the sulfur atomscould be invoked for the equatorial and the axial conformers. Inboth, the C, Si or Sn, the C2 and the two sulfur atoms could have arelationship that reminds a tetrahedral cluster. The distances be-tween the sulfur and the substituent atoms in equatorial or in axialposition are described in Table 8. It can be observed from thecalculated minimum energy structures of equatorial and axialconformers of Me3C (21), Me3Si (4) and Me3Sn (10) compounds,that the atomic distances E/S (E ¼ C, Si or Sn) are shorter than thesum of the van der Walls and therefore a stabilizing interaction ispossible in both cases. The X-ray analysis of the tetra[5-isopropyl-[1,3,5]-dithiazinan-2-yl]stannane [26] shows a tin atom linked tofour 5-isopropyl-[1,3,5]-dithiazinanes by the C2. The interestingfeature is that two dithiazinyl groups were equatorially bound tothe tin whereas the other two were axially linked. The explanationfor this unusual conformation is that the packing forces determinedthe conformation because the energy difference for both tin posi-tions, axial or equatorial, is only 6.9 kJ/mol. The axial conformer isless stable. The distances between the sulfur and the silicon or tinatoms (a) and the distances between the two sulfur atoms (d) fordithiazinanyl groups with tin in equatorial or in axial positions,

C2 2J(13C,119Sn) Co 3J(13C,119Sn) Cm 4J(13C,119Sn) Cp

36.3 52.2 28.149.2 68.4 15.829.2 60.8 13.8

Fig. 2. X-ray diffraction analysis structures of silicon compound 5.

Table 529Si Coupling constants (Hz) of compounds 4e6.

Cpd 1J(1H,29Si) H2 1J(1H,29Si) MeSi 1J(13C,29Si) C-2 1J(13C,29Si) MeSi

4 6.4 6.5 47.5 53.45 e e 47.6 53.46 5.8 e 47.6 53.4

R. Colorado-Peralta et al. / Journal of Organometallic Chemistry 751 (2014) 579e590 583

found in the X-ray diffraction analysis of tetra[5-isopropyl-[1,3,5]-dithiazinan-2-yl]stannane, are described in Table 8. The distancesare even shorter than in the calculated structures. This findingsupports the existence of stabilizing interactions between the sul-fur and the C2-substituent, Fig. 9.

2.2. N-borane adducts of 2-silicon and 2-tin organometalliccompounds 4, 5, 10 and 11

Reaction of borane with compounds 1e3 give the equatorial N-borane adducts (1BH3e3BH3) [27]. Their stability depends on thesteric hindrance of the N-alkyl substituent. The N-methyl derivative1BH3 is the most stable [13]. We have previously reported thestrong effect of N-borane in blocking the dithiazinane ring inver-sion and giving a fixed configuration of the nitrogen and the ring.This phenomenon is attributed to proton-hydride cooperative in-teractions [28,29]. The conformationally blocked N-borane adductsare therefore suitable models for the stereochemical analyses of theC2eH proton substitution, Scheme 2. The energy difference (A)between the two chair conformers (BH3 axial and BH3 equatorial) of1BH3 is 42.3 kJ/mol, where the equatorial borane is the most stable.Therefore it was of interest to calculate the A values between thechair conformers of compounds 16 and 17, Scheme 4. Calculationsindicate that the most stable conformers have the C2 substituentand the N-BH3 in equatorial. The A value between isomers I and II is12.5 kJ/mol for the silanyl derivatives and 7.0 kJ/mol for the tincompounds in agreement with A values for the chair conformers in4 and 10. The higher energy conformers are those with BH3 in axialposition. Fig. 10 shows the two calculated isomers (6-31þþG) I andII of compound 18.

Calculations of the corresponding four conformers of 2 and 2BH3anions were performed, Scheme 5. Results indicate that the moststable conformer of the anion 2 has the C2 and nitrogen lone pairsin equatorial, while in the anion of 2BH3, the C2-lone pair and theborane are in equatorial. The conformer of highest energy in anion2 has both lone pairs in axial position, while in 2BH3, the C2-lonepair and borane are also in axial position. The electrostatic poten-tial of the four conformers (IeIV) of anion 2 are includedin Supplementary material.

The electrostatic potential representation of the most stableconformer (I) of the anion 2 shows that the electronegative area isfound at the C2 and the two sulfur atoms which stabilize theequatorial position of the lithium [13], silicon and tin atoms.

Reactions of the lithium derivative 1BH3 (Scheme 2) withMe3SnCl, Ph3SnCl and Me3SiCl occur stereoselectively with

Fig. 1. Representation of van der Waals radii of sulfur and silicon atoms and S/Sidistances (Srvdw[Si/S] ¼ 3.9 �A) for compound 4.

retention of the configuration at C2 as was previously observed foralkylation of compounds 1e3 [13]. The configuration of C2 of theorganometallic compounds 16e20 was confirmed by synthesizingthem by BH3 addition to the silicon or tin compounds 4, 5,10,11 and13 with a blocked conformation. As it is reported in a previouspaper [30], borane is added to the equatorial position of NeiPrdithiazinanes. Therefore a similar stereochemistry is expected forcompounds 18 and 19. The configuration of the nitrogen can beassessed by analyzing the 13C and 11B NMR chemical shifts [2]. The11B signals of N(Me)BH3 adducts 16, 17 and 20 appears atw�8.5 ppm, whereas those of N(iPr)BH3 in compounds 18 and 19are shifted at �19 ppm due to the steric effect of isopropyl group,Scheme 2. Attempts to synthesize the NeBH3 adduct of compound12 bearing an N-tertbutyl group were unsuccessful, due to the factthat this adduct is weak and dissociates very easily.

It is important to mention that adducts 2BH3 and 3BH3 cannotbe isolated because they decompose after some time in THF, givingreduced products. It is known that the ring reduction has an in-termediate borate (Scheme 6), with a negative sulfur atom availablefor BH3 coordination, which is a probable step in the total ringreduction [31]. The electrostatic potential representation of theborate intermediate in the reduction of 2,5-dimethyl-5-boranedithiazinane is included in Supplementary material. The SeBH2sulfur atom is the more negative and therefore the place for thesecond borane coordination.

A remarkable fact in N-isopropyl compounds bearing R3Si- (18)and R3Sn- (19) substituents is that they are resistant to ring openingby BH3 reduction, and are preserved several weeks in THF solutionin contrast to non-substituted parent compounds. The onlyobserved reaction in compounds 18 and 19 is the very slowdissociation of the NeBH3 bond. The noteworthy stability of tin and

Fig. 3. Solid state structure of silicon compound 6. Intermolecular CeH/S hydrogenbonding is shown.

Fig. 4. Solid state structures of Ph3Si compounds 7 (left) and 9 (right).

Fig. 5. Solid state structures of tin compounds 10 and 14.

R. Colorado-Peralta et al. / Journal of Organometallic Chemistry 751 (2014) 579e590584

silicon compounds (4e15) to BH3 reduction in contrast to parentheterocycles could be explained by assuming that sulfur interactionwith the silicon or tin atoms inhibits the ring opening and the sulfurability for BH3 coordination. The electrostatic potential represen-tations of compounds 17 and 20, are included in Supplementarymaterial, and reveal the steric protection of the Me3Sn- group aswell as the presence of non basic sulfur atoms.

The stability of compounds 16e20 provided by the silicon andtin substituents allowed to obtain the NMR data of NReBH3 (whereR is a bulky group) and to analyze the borane electronic effect inthose rings.

3. Conclusion

A series of 1,3,5-dithiazinanes with triorganylsilanyl- or tri-organylstannyl- groups in C2 were obtained. The new compounds

Fig. 6. Structure of compound 22 found by X-ray diffraction analysis. Distances of theCeH protons to sulfur atoms are shown.

were studied by 1H, 13C, 29Si and 119Sn NMR. The C2 substitutionanchors the ring inversion allowing a valuable collection of NMRdata, useful for the conformational study and stereoelectronicbehavior of the new compounds.

The X-ray diffraction analyses revealed that the preferredconformation of compounds has the NeR group (R¼Me, iPr or tBu)in axial and the 2-substituents in equatorial. The X-ray diffractionstructures showed that the silicon or tin bound to C2 presenteddistances to the two sulfur atoms shorter than the sum of the vander Waals radii. It was deduced that these short distances produceweak stabilizing interactions S/Si and S/Sn. The presence of R3Si-and R3Sn- groups makes the heterocycles resistant to the boranereduction, which is attributed to the silicon and tin interactionswith the sulfur atoms. Evidence for the S/Sn stabilizing contactsare also found in 119Sn NMR shifts and 1J(13C,119Sn) couplingconstants.

Substitution reactions in NeBH3 adducts of [1,3,5]-dithiazinaneswith a blocked conformation and configuration let know us thatthese reactions occur with retention of the organolithium config-uration. Calculations confirm that N-borane groups prefer theequatorial position, even in the presence of N-bulky groups.

4. Experimental

4.1. General comments

Reagents were commercial and used without purification. Vac-uum line techniques were employed for moisture sensitive com-pounds. THF was dried by distillation from sodium/benzophenone

Table 6Selected bond lengths (�A) for compounds 4e7, 9, 10, 14 and 22.

22

1

3

1

3

9

9

7

R7 R9

4 Me SiMe35 iPr SiMe36 tBu SiMe37 Me SiPh3

6

7

4

R7 R9

9 tBu SiPh310 Me SnMe314 iPr SnPh3

6

2

42

Cpd C2eE S1eC2 S3eC2 S1eC6 S3eC4 C4eN5 C6eN5

4 1.885(4) 1.809(4) 1.803(4) 1.840(6) 1.833(4) 1.410(6) 1.427(5)5 1.885(3) 1.808(3) 1.803(3) 1.847(3) 1.831(3) 1.437(3) 1.438(3)6 1.888(3) 1.811(4) 1.809(3) 1.845(4) 1.844(4) 1.440(4) 1.429(4)

1.882(4) 1.805(3) 1.803(3) 1.850(5) 1.828(4) 1.428(5) 1.439(5)7 1.900(2) 1.815(2) 1.810(2) 1.844(3) 1.835(3) 1.433(3) 1.427(3)9 1.902(3) 1.922(3) 1.802(3) 1.842(4) 1.840(4) 1.437(4) 1.441(5)10 2.180(3) 1.800(4) 1.799(4) 1.837(4) 1.836(4) 1.436(5) 1.441(5)14 2.175(4) 1.802(3) 1.796(4) 1.842(5) 1.826(5) 1.445(5) 1.438(6)22 1.901(2) 1.812(2) 1.807(2) 1.792(2) 1.789(2) 1.498(2) 1.495(2)

R. Colorado-Peralta et al. / Journal of Organometallic Chemistry 751 (2014) 579e590 585

under a nitrogen atmosphere prior to use. Dry CDCl3, DMSO-d6 andTHF-d8, were purchased from Aldrich and used without furtherpurification. Compounds 1e3 [3], 1BH3 [27] were synthesized ac-cording to the literature.

Melting points were obtained on a Mel-Temp II apparatus andare uncorrected. Mass spectra in the EI mode were recorded at20 eV on a Hewlett-Packard HP 5989A spectrometer. High resolu-tion mass spectra were obtained by LC/MSD TOF on an AgilentTechnologies instrument with ESI as ionization source. Elementalanalyses were performed on Flash (EA) 1112 series, equipment.NMR spectrawere obtained on a Jeol GSX-270, Jeol Eclipse 400MHzand Bruker Avance 300 MHz. 1H, 13C [X 25.145020, Si(CH3)4], 29Si [X19.867187, Si(CH3)4] and 119Sn [X 37.290665, Sn(CH3)4].

Crystallographic data were measured on a Nonius KappaCCD instrument with a CCD area detector using graphite-monochromated MoKa radiation. Intensities were measured using4þu scans. Crystal data are described inTable 9. The structuresweresolved using direct methods with SHELX-97 [32], Sir 2002 and Sir2004 [33]. The refinement for all structures (based on F2 of all data)was performed by full matrix least-squares techniqueswith Crystals12.84 [34]. All non-hydrogen atoms were refined anisotropically.Calculations were performed in order to obtain the molecular ge-ometries using the Gaussian 98 package [35]. Geometries werechecked to be the minimal by means of the frequency analysis.

Table 7Selected bond angles (�) of compounds 4e7, 9, 10, 14 and 22.

1

3

9

R7 R9

4 Me SiMe35 iPr SiMe36 tBu SiMe37 Me SiPh3

7

9 tB10 M14 iP

6

42

SeC2eS

4 (E ¼ Si) 112.4(2)5 (E ¼ Si) 112.0(1)6 (E ¼ Si) 112.3(2)

111.6(2)7 (E ¼ Si) 111.5(1)9 (E ¼ Si) 112.4(1)10 (E ¼ Sn) 112.5(2)14 (E ¼ Sn) 113.1(2)22 (E ¼ Si) 111.3(1)

4.2. Syntheses

4.2.1. (5-Methyl-[1,3,5]-dithiazinan-2-yl)-trimethylsilane (4).General procedure for the preparation of compounds 4e15

To a solution of compound 1 (250 mg, 1.85 mmol), 1 M tBuLisolution in hexane at �78 �C, Me3SiCl (0.2 mL, 3.7 mmol) wasslowly added and themixture stirred for 20min. Then, water (5mL)was added and the mixture extracted with CH2Cl2 (3 � 30 mL).Compound 4 was crystallized from CHCl3 (340 mg, 87.5%). Mp 49e50 �C. NMR (CDCl3, 25 �C, d ppm), 1H: 2.65 (s, 3H, H7), 0.12 (s, 9H,H9); 13C: 37.5 (C7), �3.5 (C9); 29Si: þ3.26. (þ)TOF m/z (amu) calcd.for (C7H18NS2Si)þ, m/z (amu): 208.0649; found 208.0648. Anal.calcd. for (C7H17NS2Si): C, 40.57; H, 8.27; N, 6.76. Found: C, 40.34; H,8.07; N, 6.91.

4.2.2. (5-isoPropyl-[1,3,5]-dithiazinan-2-yl)-trimethylsilane (5)Compound 2 (250 mg, 1.53 mmol), tBuLi (1.54 mmol, 1.54 g) and

Me3SiCl (0.32 mL, 3.0 mmol). Compound 5 was crystallized fromCHCl3 (300 mg, 84%). Mp 48e49 �C. NMR (CDCl3, 25 �C, d ppm), 1H:3.79 (sept, 3J(1H,1H) 6.5 Hz,1H, H7),1.10 (d, 3J(1H,1H) 6.5 Hz, 6H, H8),0.11 (s, 9H, H10); 13C: 44.8 (C7), 20.7 (C8), �3.5 (C10); 29Si: þ3.17.(þ)TOF m/z (amu) calcd. for (C9H22NS2Si)þ, m/z (amu): 236.0962;found 236.0957. Anal. calcd. for (C9H21NS2Si): C, 45.94; H, 9.00; N,5.96. Found: C, 46.32; H, 9.13; N, 6.03.

22

1

3

9

7

6

4

R7 R9

u SiPh3e SnMe3r SnPh3

2

S1eC2-E S3eC2eE C2eS3eC4 C2eS1eC6

111.1(1) 110.3(2) 100.4(2) 99.5(2)112.6(1) 109.9(1) 99.6(3) 98.6(1)110.5(2) 110.3(2) 99.4(2) 96.5(2)111.7(2) 110.6(2) 98.8(2) 97.9(2)113.0(1) 111.0(1) 98.3(1) 97.2(1)112.3(1) 110.7(1) 98.2(1) 99.3(1)111.2(2) 110.3(2) 98.0(2) 98.4(2)109.6(2) 110.3(2) 98.2(2) 97.9(2)111.9(1) 109.2(1) 100.3(1) 99.0(1)

Table 8[E/S], [C/C], [S/C] and [S/S] atomic distances (�A) in compounds 4e7, 9, 10, 14, 21 and 22.

S

SE

H

a

b c

d

S

SH

E

ab

c d

Data from X-ray diffraction analyses

a b c d

4 3.03, 3.05 1.88 1.81, 1.80 3.005 3.02, 3.07 1.88 1.80, 1.80 2.996 3.04, 3.03 1.89 1.81, 1.81 3.017 3.06, 3.09 1.90 1.81, 1.81 3.009 3.08, 3.06 1.91 1.82, 1.81 3.0310 3.29, 3.27 2.17 1.80, 1.80 2.9914 3.25, 3.27 2.17 1.80, 1.80 3.0022 3.03, 3.07 1.90 1.82, 1.81 3.00

Data from the solid state structure of tetra[5-isopropyl-[1,3,5]-dithiazinan-2-yl]stannane [26].

a b c d

Equatorial 3.25 2.19 1.81 2.993.27

Axial 3.37 2.20 1.81 3.013.42

Distances from optimized conformers of compounds 4, 10 and 21.

Equatorial Axial

a b c d a b c d

21 2.84 1.54 1.85 3.06 21 2.91 1.56 1.86 3.104 3.10 1.93 1.84 3.08 4 3.21 1.93 1.85 3.1010 3.36 2.20 1.91 3.17 10 3.48 2.20 1.92 3.19

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4.2.3. (5-tertButyl-[1,3,5]-dithiazinan-2-yl)-trimethylsilane (6)Compound 3 (250 mg, 1.41 mmol), tBuLi (1.42 mmol, 1.42 mL)

and Me3SiCl (0.3 mL, 2.82 mmol). Compound 6 was crystallizedfrom CHCl3 (300 mg, 86%). Mp 47e48 �C. NMR (CDCl3, 25 �C,d ppm), 1H: 1.29 (s, 9H, H8), 0.08(s, 9H, H10); 13C: 54.3 (C7), 37.6(C2), 29.8 (C8), �3.5 (C10); 29Si: þ2.75. (þ)TOFm/z (amu) calcd. for(C10H24NS2Si)þ, m/z (amu): 250.1119; found 250.1113. Anal. calcd.

Fig. 7. Spacefill model of calculated equatorial conf

Fig. 8. Spacefill models of the calculated axial conf

for (C10H23NS2Si): C, 48.17; H, 9.31; N, 5.62. Found: C, 47.86; H, 9.61;N, 5.27.

4.2.4. (5-Methyl-[1,3,5]-dithiazinan-2-yl)-triphenylsilane (7)Compound 1 (250 mg, 1.85 mmol), tBuLi (1.9 mmol, 1.9 mL) and

Ph3SiCl (950 mg, 3.1 mmol). Compound 7 was crystallized fromCHCl3 (440 mg, 60%). Colorless crystals, Mp 180e181 �C. NMR

ormers of compounds 21 (a), 4 (b) and 10 (c).

ormers of compounds 21 (a), 4 (b) and 10 (c).

iPr

Y

:

. .

Y = BH3 or lone pair

iPr

Y

iPr

iPr:

. .

YY

I II

IIIIV

Scheme 5. For the anion of 2 (Y ¼ lone pair), conformer I is more stable than II by15.4 kJ/mol. I is more stable than III by 24.3 kJ/mol, and I is more stable than IV by98.7 kJ/mol. For the anion of 2BH3 (Y ¼ BH3), the corresponding energies are 23.5, 52.7and 75.9 kJ/mol, respectively.

Fig. 9. X-ray diffraction analysis of tetra[5-isopropyl-[1,3,5]-dithiazinan-2-yl]stannane[26].

Me3E BH3

I II

IIIIVMe3E

Me3E

Me3E

BH3

BH3 BH3

Scheme 4. When E ¼ Si (16), I is more stable than II for 12.5 kJ/mol. I is more stablethan III for 34.3 kJ/mol and I is more stable than IV for 48.5 kJ/mol. When E ¼ Sn (17),the corresponding A values are 7.0, 41 and 50.2 kJ/mol, respectively.

R. Colorado-Peralta et al. / Journal of Organometallic Chemistry 751 (2014) 579e590 587

(CDCl3, 25 �C, d ppm), 1H: 2.72 (s, 3H, H7), 7.71 (d, 3J(1H,1H) 7.1 Hz,6H, Ho), 7.47 (d, 3J(1H,1H) 6.9 Hz, 6H, Hp), 7.41 (dd, 3J(1H,1H) 7.1 Hz,3J(1H,1H) 6.9 Hz, 3H, Hm); 13C: 37.8 (C7), 136.6 (Co), 131.6 (Ci), 130.2(Cp), 127.8 (Cm). 29Si: �14.1. MS (20 eV) m/z (%): 394(2), 350(10),276(3), 259(84), 226(3), 181(8), 167(2), 134(4), 101(46), 89(4),57(100), 44(17). (þ)TOF calcd. for (C22H24NS2Si)þ, m/z (amu):394.1119; found: 394.1113. Anal. calcd. for (C22H23NS2Si): C, 67.16;H, 5.90; N, 3.56. Found: C, 66.75; H, 6.01; N, 3.48.

4.2.5. (5-isoPropyl-[1,3,5]-dithiazinan-2-yl)-triphenylsilane (8)Compound 5 (250 mg, 1.53 mmol), tBuLi (1.54 mmol, 1.54 mL)

and Ph3SiCl (790 mg, 3.1 mmol). Compound 11 was obtained asviscous oil (430mg, 67%). NMR (CDCl3, 25 �C, d ppm), 1H: 3.96 (sept,3J(1H,1H) 6.4 Hz, 1H, H7), 1.20 (d, 3J(1H,1H) 6.4 Hz, 6H, H8), 7.73 (d,

Fig. 10. Calculated isomers I

3J(1H,1H) 7.4 Hz, 6H, Ho), 7.52 (d, 3J(1H,1H) 6.6 Hz, 6H, Hp), 7.41 (dd,3J(1H,1H) 7.1 and 6.9 Hz, 3H, Hm). 13C: 45.4 (C7), 20.9 (C8), 136.8 (Co),131.8 (Ci), 130.3 (Cp), 128.1 (Cm). 29Si: �13.7. MS (20 eV) m/z (%):421(1), 397(3), 350(7), 319(5), 276(58), 259(38), 199(100), 154(5),129(35), 85(61), 70(9), 57(9), 43(26). (þ)TOF calcd. for(C24H28NS2Si)þ, m/z (amu): 422.1432; found: 422.1434. Anal. calcd.for (C24H27NS2Si$CH2Cl2): C, 59.28; H, 5.78; N, 2.77. Found: C, 60.12;H, 6.05; N, 3.13.

4.2.6. (5-tertButyl-[1,3,5]-dithiazinan-2-yl)-triphenylsilane (9)Compound 3 (250 mg, 1.41 mmol), tBuLi (1.42 mmol, 1.42 mL)

and Ph3SiCl (730 mg, 2.82 mmol). Compound 9 was crystallizedfrom CHCl3 (550 mg, 90%). Mp 134e135 �C. NMR (CDCl3, 25 �C,d ppm), 1H: 1.54 (s, 9H, H8), 7.95-7.42 (m, 15H, Ph). 13C: 55.8 (C7),30.1 (C8), 137.0 (Co), 132.1 (Ci), 130.4 (Cp), 128.0 (Cm). 29Si:�14.0. (þ)TOF calcd. for (C25H30NS2Si)þ, m/z (amu): 436.1588; found:436.1583. Anal. calcd. for (C25H29NS2Si): C, 68.94; H, 6.72; N, 3.22.Found: C, 69.33; H, 6.96; N, 3.05.

4.2.7. (5-Methyl-[1,3,5]-dithiazinan-2-yl)-trimethylstannane (10)Compound 1 (250 mg, 1.85 mmol), tBuLi (1.86 mmol, 1.86 mL)

and Me3SnCl (740 mg, 3.7 mmol). Compound 10 was crystallizedfrom CHCl3 (0.44 g, 80%). Mp 51e52 �C. NMR (CDCl3, 25 �C, d ppm),1H: 2.73 (s, 3H, H7), 0.23 (s, 9H, H9). 13C: 37.7 (C7), �10.4 (C9).119Sn: þ1.72. (þ)TOF calcd. for (C7H18NS2Sn)þ, m/z (amu):299.9902; found: 299.9897. Anal. calcd. for (C7H17NS2Sn): C, 28.21;H, 5.75; N, 4.70. Found: C, 28.60; H, 5.93; N, 4.92.

and II of compound 18.

reduced products

Scheme 6. Isomerization of 2,5-dimethyl-5-borane dithiazinane and borane reduction of the 2,5,5-trimethyl-[1,3,5,6]-dithiazaborata.

Table 9Crystal data of compounds 4e7, 9, 10, 14 and 22.

22

R'= Ph 7 E= Si, R= Me9 E= Si, R= tBu 14 E= Sn, R= iPr

R'= Me 4 E= Si, R= Me 5 E= Si, R= iPr 6 E= Si, R= tBu10 E= Sn, R= Me

Compound 4 5 6 7 9 10 14 22Empirical formula C7H17NS2Si C9H21NS2Si C20H46N2S4Si2 C22H23NS2Sn C22H23N2S2Si C7H17NS2Sn C24H27NS2Sn C7H18NS2SiClMolecular weight 207.43 235.48 499.01 393.62 435.7 298.04 512.28 243.90Crystal size [mm] 0.45 � 0.33

� 0.210.3 � 0.3� 0.22

0.3 � 0.15� 0.15

0.3 � 0.25� 0.15

0.45 � 0.23� 0.2

0.3 � 0.3� 0.3

0.25 � 0.18� 0.03

0.25 � 0.20� 0.10

Crystal shape Prism Prism Prism Fragment Fragment Prism Needle PlateCrystal color Colorless Colorless Colorless Colorless Colorless Colorless Colorless ColorlessCrystal system Monoclinic Orthorhombic Monoclinic Triclinic Triclinic Orthorhombic Monoclinic MonoclinicSpace group P21/c Pcab P21/n P-1 P-1 P212121 P21/c C2/ca [�A] 8.8496 (6) 9.656 12.332 10.1879 (3) 9.8739(1) 6.5335 (4) 20.5041 (6) 33.329b [�A] 10.4769 (7) 12.883 22.236 10.3342 (3) 11.2600(2) 6.7814 (4) 16.3136 (4) 7.002c [�A] 12.7765 (10) 22.583 12.583 10.6834 (4) 12.0226(2) 26.8742 (16) 7.1274 (2) 11.618a [�] 90 90 90 71.817 (1) 85.241(1) 90 90 90b [�] 105.887 (4) 90 119.01 89.545 (1) 65.687(1) 90 99.661 (1) 94.85g [�] 90 90 90 78.688 (2) 74.141(1) 90 90 90V [�A3] 1139.34 (14) 2809.3 3017.5 1046.15 (6) 1171.09(3) 1190.70 (12) 2350.27 (11) 2701.6Z 4 8 4 2 2 4 4 8r (calcd.) [Mg/m3] 1.209 1.114 1.098 1.25 1.236 1.662 1.448 1.199m [mm�1] 0.52 0.43 0.40 0.32 0.29 2.45 1.27 0.64F(000) 448 1024 1088 416 464 592 1040 1040Temperature [K] 198 293 293 293 293 293 293 293q Range for data

collection7.0e53.4 3.4e27.5 3.4e27.5 2.9e27.5 2.9e27.5 1.5e29.5 2.9e27.5 2.9e27.5

Index ranges �10 � h � 9 �10 � h � 12 �15 � h � 16 �12 � h � 12 �12 � h � 12 �8 � h � 8 �24 � h � 24 �42 � h � 42�13 � k � 13 �16 � k � 16 �25 � k � 28 �12 � k � 13 �14 � k � 14 �8 � k � 8 �17 � k � 19 �9 � k � 7�16 � l � 16 �26 � l � 29 �12 � l � 16 �13 � l � 13 �15 � l � 15 �30 � l � 33 �7 � l � 8 �15 � l � 15

Reflections collected 4377 22,193 25,807 11,080 22,147 7004 14,667 18,747Independent reflections 2329 3191 6845 4677 5346 2456 4003 2962Observed reflections

[I > 2s(l)]1527 1453 3937 2885 4254 2269 3162 2417

R (int) 0.037 0.090 0.040 0.043 0.037 0.027 0.049 0.039Number of variables 169 126 305 240 265 151 263 181Weighting scheme

R/wR0.0426/1.184 0.0507/0.1997 0.0499/1.7503 0.0404/0.2045 0.0368/0.4349 0.0227/0.7448 0.0363/1.0326

Goodness-of-fit 1.04 1 1.02 1.01 1.04 0.95 1.02 1.05R [F2 > 2s(F2)] 0.057 0.049 0.062 0.050 0.037 0.023 0.030 0.033wR (F2) 0.135 0.128 0.156 0.116 0.093 0.028 0.066 0.084Largest residual

peak [e/�A3]0.34, �0.46 0.22, �0.23 0.42, �0.28 0.21, �0.18 0.27, �0.26 0.35, �0.40 0.41, �0.34 0.25, �0.24

Where w ¼ 1=½s2ðF2o Þ þ ðaPÞ2 þ bP�: P ¼ ðF2o þ 2F2c Þ=3.

R. Colorado-Peralta et al. / Journal of Organometallic Chemistry 751 (2014) 579e590588

4.2.8. (5-isoPropyl-[1,3,5]-dithiazinan-2-yl)-trimethylstannane(11)

Compound 2 (250 mg, 1.53 mmol), tBuLi (1.54 mmol, 1.54 mL)and Me3SnCl (600 mg, 3.0 mmol). Compound 11 is a yellowviscous liquid (420 mg, 84%). NMR (CDCl3, 25 �C, d ppm), 1H 3.86(sept, 3J(1H,1H) 6.3 Hz, 1H, H7), 1.03 (d, 3J(1H,1H) 6.3 Hz, 6H, H8),0.14 (s, 9H, H10). 13C: 44.9 (C7), 20.9 (C8), �10.4 (C10).119Sn: �0.88. MS (20 eV) m/z (%): 326(18), 312(43), 310(33),298(5), 284(1), 266(1), 247(6), 241(3), 215(5), 201(2), 170(20),155(14), 129(57), 100(4), 86(100), 70(3), 43(2). (þ)TOF calcd. for(C9H22NS2Sn)þ, m/z (amu): 328.0215; found: 328.0215. Anal.

calcd. for (C9H21NS2Sn$1/2CH2Cl2): C, 31.98; H, 6.24; N, 4.03.Found: C, 32.30; H, 6.40; N, 3.90.

4.2.9. (5-tertButyl-[1,3,5]-dithiazinan-2-yl)-trimethylstannane (12)Compound 3 (250 mg, 1.41 mmol), tBuLi (1.42 mmol, 1.42 mL)

and Me3SnCl (560 mg, 2.82 mmol). Compound 12 was obtained asyellow oil (400 mg, 83%). NMR (CDCl3, 25 �C, d ppm), 1H: 1.27 (s, 9H,H8), 0.16 (s, 9H, H10). 13C: 55.7 (C7), 29.8 (C8), �10.4 (C10).119Sn: �4.06. MS (20 eV), m/z (%): 340(1), 326(9), 322(4), 241(5),238(1), 183(1), 165(6), 143(18), 119(2), 99(38), 86(2), 75(2), 70(2),57(19), 43(100). (þ)TOF calcd. for (C10H24NSSn)þ, m/z (amu):

R. Colorado-Peralta et al. / Journal of Organometallic Chemistry 751 (2014) 579e590 589

342.0372, found 342.0366. Anal. calcd. for (C10H23NS2Sn): C, 35.31;H, 6.82; N, 4.12. Found: C, 35.30; H, 6.88; N, 3.90.

4.2.10. (5-Methyl-[1,3,5]-dithiazinan-2-yl)-triphenylstannane (13)Compound 1 (250mg,1.85mmol), tBuLi (1.86mmol,1.86mL) and

Ph3SnCl (1.3 g, 3.7 mmol). Compound 13 is a viscous liquid (770 mg,86%). NMR (CDCl3, 25 �C, d ppm), 1H: 7.82e7.33 (m,15H, Ph), 2.89 (s,3H, H7). 13C: 38.0 (C7), 139.2 (Ci), 137.6 (Co), 129.7 (Cp), 128.8 (Cm).119Sn: �147.4. MS (20 eV) m/z (%): 484(1), 426(1), 383(16), 365(10),351(39), 333(6), 287(5), 197(6), 181(6), 167(5), 134(31), 114(8),101(22), 57(100), 42(19). (þ)TOF calcd. for (C22H24NS2Sn)þ, m/z(amu): 486.0372, found: 486.0366. Anal. calcd. for (C22H23NS2Sn): C,54.56; H, 4.79; N, 2.89. Found: C, 54.23; H, 4.93; N, 2.70.

4.2.11. (5-isoPropyl-[1,3,5]-dithiazinan-2-yl)-triphenylstannane(14)

Compound 2 (250 mg, 1.53 mmol), tBuLi (1.54 mmol, 1.54 mL)and Ph3SnCl (1.1 g, 3.0 mmol). Compound 14 was crystallized fromCHCl3 (710mg, 90%). Mp 98e100 �C. NMR (CDCl3, 25 �C, d ppm), 1H:7.83e7.34 (m, 15H, Ph), 4.16 (sept, 3J(1H,1H) 6.3 Hz, 1H, H7), 1.27 (d,3J(1H,1H) 6.3 Hz, 6H, H8). 13C: 138.1 (Ci), 137.7 (Co), 129.6 (Cp), 128.9(Cm), 45.5 (C7), 21.1 (C8). 119Sn: �146.6. MS (20 eV) m/z (%): 512(1),436(3), 404(3), 383(10), 351(23), 349(17), 333(6), 287(3), 274(2),256(3), 197(8), 181(13), 162(31), 154(5), 129(37), 118(5), 85(100),57(19), 43(65). (þ)TOF calcd. for (C24H28NS2Sn)þ, m/z (amu):514.0685. Found: 514.0679. Anal. calcd. for (C24H27NS2Sn): C, 56.26;H, 5.32; N, 2.74. Found: C, 56.60; H, 5.21; N, 2.98.

4.2.12. (5-tertButyl-[1,3,5]-dithiazinan-2-yl)-triphenylstannane(15)

Compound 3 (250 mg, 1.41 mmol) and Ph3SnCl (1.0 g,2.82 mmol). Compound 15 is a viscous liquid (700 mg, 95%). NMR(CDCl3, 25 �C) d (ppm), 1H: 7.79e7.33 (m, 15H, Ph), 1.43 (s, 9H, H8).13C: 139.2 (Ci), 136.6 (Co), 130.7 (Cp), 129.4 (Cm), 55.9 (C7), 30.0 (C8).119Sn: �148.6. MS (20 eV) m/z (%) 526(1), 355(8), 351(48), 309(18),231(6), 154(100), 100(17), 86(5), 77(6), 57(6), 43(11). (þ)TOF calcd.for (C25H30NS2Sn)þ, m/z (amu): 528.0841; found: 528.0828. Anal.calcd. for (C25H29NS2Sn$1/2CH2Cl2): C, 55.38; H, 5.43; N, 2.56.Found: C, 55.40; H, 5.51; N, 2.69.

4.2.13. 5-Borane-5-methyl-2-trimethylsilanyl-[1,3,5]-dithiazinane(16)

Procedure A. To a solution of dithiazinane 4 (166 mg, 0.8 mmol)in dry THF (20 mL) at �78 �C, a 2 M BH3eDMS solution (0.4 mL,0.8 mmol) was added. The reaction mixture was stirred for 5 minand the solvent evaporated. Compound 16 was obtained quantita-tively as a moisture sensitive colorless solid (170 mg, 98%).

Procedure B. To a solution of dithiazinane 1 (200 mg, 1.5 mmol)in THF (40 mL) at �78 �C, a 2 M BH3eDMS solution (1.6 mmol) wasadded. The reaction mixture was stirred for 15 min and the solventevaporated. Then, the solid was analyzed by NMR and the adduct1BH3 formation was confirmed. The solid was dissolved in THF(40 mL) and the solution cooled at �78 �C, then a 1.8 M tBuLi so-lution in hexane (2 mL, 1.92 mmol) was added. The mixture wasstirred for 30 min at �78 �C, and Me3SiCl (0.15 mL, 1.47 mmol) wasadded. The reaction mixture was stirred at �78 �C for 2 h. Thesolvents were evaporated in vacuum. A moisture sensitive colorlesssolid was obtained (300 mg, 98%). NMR (CDCl3, 27 �C, d ppm), 1H:2.86 (s, 3H, H7), 0.18 (s, 9H, H8). 13C: 42.9 (C7),�3.1 (C8). 29Si:þ5.90(s). 11B: �8.5 (br q).

4.2.14. 5-Borane-5-methyl-2-trimethylstannanyl-[1,3,5]-dithiazinane (17)

Compound 17 was prepared following the procedure A from 10(240 mg, 0.8 mmol) and BH3eDMS (0.4 mL, 0.8 mmol). A moisture

sensitive colorless solid was obtained (240 mg, 98%). Reaction byprocedure B, from compound 1 (200 mg, 1.5 mmol), tBuLi(1.6 mmol, 1.6 mL) and Me3SnCl (300 mg, 1.5 mmol), yield 440 mg,98%. NMR (CDCl3, 27 �C, d ppm), 1H: 2.89 (s, 3H, H7), 0.31 (s, 9H;2J(119Sn,1H) 56.9 Hz, H8). 13C: 42.7 (C7), �9.5 (C-8). 119Sn: þ20 (s).11B: �8.8 (q, 1J(11B,1H) 98 Hz). Anal. calcd. for [C7H20NS2SnB](311.89): C, 26.95; H, 6.80; N, 4.49. found: C, 26.75; H, 6.96; N, 4.20.

4.2.15. 5-Borane-5-isopropyl-2-trimethylsilanyl-[1,3,5]-dithiazinane (18)

Compound 18 was prepared following the procedure A from 5(190 mg, 0.8 mmol) and BH3eDMS (0.4 mL, 0.8 mmol). A moisturesensitive colorless solid was obtained (190 mg, 97%) and by pro-cedure B, from compound 2 (250 mg, 1.5 mmol), tBuLi (1.6 mmol,1.6 mL) and Me3SiCl (0.16 mL, 1.5 mmol), yield 340 mg, 98%. NMR(CDCl3, 27 �C, d ppm), 1H: 4.60 (sept, 3J(1H,1H) 6.7 Hz, 1H, H7), 1.20(d, 3J(1H,1H) 6.7, 6H, H8), 0.14 (s, 9H, H9). 13C: 44.8 (C7), �3.2 (C9).28Si: 5.7 (s). 11B: �19.0 [q, 1J(11B,1H) 98 Hz].

4.2.16. 5-Borane-5-isopropyl-2-trimethylstannanyl-[1,3,5]-dithiazinane (19)

Compound 19 was prepared following the procedure A from 11(260 mg, 0.8 mmol) and BH3eDMS (0.4 mL, 0.8 mmol). A moisturesensitive colorless solid was obtained (260 mg, 97%). By procedureB from 2 (250 mg, 1.5 mmol), tBuLi (1.6 mmol, 1.6 mL) and Me3SnCl(300 mg, 1.5 mmol), yield 480 mg, 98%. NMR (CDCl3, 27 �C, d ppm),1H: 3.73 (sept, 3J(1H,1H) 6.7 Hz, 1H, H7), 1.09 (d, 3J(1H,1H) 6.7 Hz, 6H,H8), 0.14 (s, 9H, H8). 13C: 49.6 (C-7), 24.4 (C8), �2.9 (C9).119Sn: þ16.7(s). 11B: �11.0 (q, 98 Hz).

4.2.17. 5-Borane-5-methyl-2-triphenylstannanyl-[1,3,5]-dithiazinane (20)

Compound 20 was prepared following the procedure B, fromcompound 1 (200 mg, 1.5 mmol), tBuLi (1.6 mmol, 1.6 mL) andPh3SnCl (500 mg, 1.5 mmol). A moisture sensitive colorless solidwas obtained (710 mg, 97%). NMR (CDCl3, 27 �C, d ppm), 1H: 7.9e7.4(m,15H, Ph), 2.96 (s, 3H, H7). 13C: 38.0 (C7), 138.0 (Ci, br s), 137.6 (Co,br s), 129.4 (Cp, br s), 128.2 (Cm, br s).

4.2.18. (5-Methyl-5[H]-[1,3,5]-dithiazinium-2-yl)-trimethylsilane22

From a solution of compound 4 (200 mg, 1.0 mmol) in THF(30 mL), and 1 M aq. HCl solution (1.5 mL). Compound 22 wascrystallized from CHCl3 (200 mg, 98%). Mp 180e182 �C. NMR(CDCl3, 27 �C, d ppm), 1H: 2.86 (d, 3H, [3J(1H,1H) 5.19 Hz] H7), �0.13(s, 9H, H8). 13C: 44.6 (C7), �3.5 (C8). 29Si: þ4.24 (s). (þ)TOF calcd.for (C7H18NS2Si)þ, m/z (amu): 208.0649; found: 208.0649.

Acknowledgments

We thank Prof. Heinrich Nöth for the X-ray diffraction analysis ofcompound 10. We thank also Prof. Angeles Paz-Sandoval for helpfuldiscussions. We are grateful to Cinvestav for the use of CGSTIC su-percomputer HPC-cluster Xiuhcoatl, and to Conacyt for financialsupport (Project 128411 and A.M.D.-H. thanks for a scholarship).

Appendix A. Supplementary material

CCDC 933843 (for 4), CCDC 933844 (5), CCDC 933845 (6), CCDC933846 (7), CCDC 933847 (9), CCD C933840 (10), CCDC 933841 (14),and CCDC 933842 (22) contain the supplementary crystallographicdata for this paper. These data can be obtained free of charge fromThe Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.

R. Colorado-Peralta et al. / Journal of Organometallic Chemistry 751 (2014) 579e590590

Supplementary material associated with this article can be foundin the online version, at http://dx.doi.org/10.1016/j.jorganchem.2013.07.058.

References

[1] A. Flores-Parra, S.A. Sánchez-Ruiz, Heterocycles 51 (1999) 2079.[2] A. Flores-Parra, S.A. Sánchez-Ruiz, C. Guadarrama-Pérez, Eur. J. Inorg. Chem.

(1999) 2063.[3] G. Cadenas-Pliego, L.M.R. Martínez-Aguilera, A.M. Bello-Ramírez, M.J. Rosales-

Hoz, R. Contreras, J.C. Daran, S. Halut, A. Flores-Parra, Phosphorus Sulfur Sil-icon 81 (1993) 111.

[4] J.C. Gálvez-Ruiz, H. Nöth, A. Flores-Parra, Inorg. Chem. 42 (2003) 7569.[5] J.C. Gálvez-Ruiz, C. Guadarrama-Pérez, H. Nöth, A. Flores-Parra, Eur. J. Inorg.

Chem. (2004) 601.[6] J.C. Gálvez Ruiz, J.C. Jaen-Gaspar, I.G. Castellanos-Arzola, R. Contreras,

A. Flores-Parra, Heterocycles 63 (2004) 2269.[7] R. Colorado-Peralta, A. Xotlanihua-Flores, J.C. Gálvez-Ruíz, S.A. Sánchez-Ruíz,

R. Contreras, A. Flores-Parra, J. Mol. Struct. 981 (2010) 21.[8] R. Colorado-Peralta, C.A. López-Rocha, S.A. Sánchez-Ruiz, R. Contreras,

A. Flores-Parra, Heteroat. Chem. 22 (2011) 59.[9] G.M. Drew, W. Kitching, J. Org. Chem. 46 (1981) 558.

[10] F. Téllez, A. Cruz, H. López-Sandoval, I. Ramos-García, U. Gayosso, R. Castillo-Sierra, B. Paz-Michel, H. Nöth, A. Flores-Parra, R. Contreras, Eur. J. Org. Chem.(2004) 4203.

[11] A. Esparza-Ruiz, A. Peña-Hueso, J. Hernández-Díaz, A. Flores-Parra,R. Contreras, Cryst. Growth Des. 7 (2007) 2031.

[12] A. Peña-Hueso, F. Téllez, R. Vieto-Peña, R.O. Esquivel, A. Esparza-Ruiz,I. Ramos-García, R. Contreras, N. Barba-Behrens, A. Flores-Parra, J. Mol. Struct.984 (2010) 409.

[13] R. Colorado-Peralta, C. Guadarrama-Pérez, J.C. Galvez-Ruiz, S.A. Sánchez-Ruiz,R. Contreras, A. Flores-Parra, J. Mol. Struct. 1047 (2013) 149.

[14] E.L. Eliel, V.S. Rao, F.G. Riddell, J. Am. Chem. Soc. 98 (1976) 3583.[15] Ch Rim, H. Zhang, D.Y. Son, Inorg. Chem. 47 (2008) 11993.[16] C.R. Ernst, L. Spialter, G.R. Buell, D.L. Wilhite, J. Am. Chem. Soc. 96 (1974) 5375.[17] B. Wrackmeyer, Annu. Rep. NMR Spectrosc. 16 (1985) 73.[18] S.S. Batsanov, Inorg. Mater. 37 (2001) 871.[19] W. Klyne, V. Prelog, Experientia 16 (1960) 521.[20] M. Manoharan, E.L. Eliel, Tetrahedron Lett. 25 (1984) 3267.

[21] F. Freeman, Z.M. Tsegai, M.L. Kasner, W.J. Hehre, J. Chem. Educ. 77 (2000) 661.[22] W. Kitching, H.A. Olszowy, G.M. Drew,W.J. Adcock, J. Org. Chem. 47 (1982) 5153.[23] R.J. Ouellette, D. Baron, J. Stolfo, A. Rosenblum, P. Weber, Tetrahedron 28

(1972) 2163.[24] W. Kitching, D. Doddrell, J.B. Grutzner, J. Organomet. Chem. 107 (1976) C5.[25] E.L. Eliel, R.O. Hutchins, J. Am. Chem. Soc. 91 (1969) 2703.[26] P. Montes-Tolentino, R Colorado-Peralta, L.A. Martínez-Chavando, E Mijangos,

A.M. Duarte-Hernández, G.V. Suarez-Moreno, R. Contreras, A. Flores-Parra, J.Organomet. Chem.

[27] A. Flores-Parra, G. Cadenas-Pliego, L.M.R. Martínez-Aguilera, M.L. García-Nares, R. Contreras, Chem. Ber. 126 (1993) 863.

[28] A. Flores-Parra, S.A. Sánchez-Ruiz, C. Guadarrama-Pérez, H. Nöth, R. Contreras,Eur. J. Inorg. Chem. (1999) 2069.

[29] M. Güizado-Rodríguez, A. Flores-Parra, S.A. Sánchez-Ruiz, R. Tapia-Benavides,R. Contreras, V.I. Bakhmutov, Inorg. Chem. 40 (2001) 3243.

[30] G. Cadenas-Pliego, M.-J. Rosales-Hoz, R. Contreras, A. Flores-Parra, Tetrahe-dron: Asymmetry 5 (1994) 633.

[31] C. Guadarrama-Pérez, G. Cadenas-Pliego, L.M.R. Martínez-Aguilera, A. Flores-Parra, Chem. Ber. 130 (1997) 813.

[32] G.M. Sheldrick, SHELX 97-2 Users Manual, University of Göttingen, Germany,1977.

[33] P.W. Betteridge, J.R. Carruthers, R.I. Cooper, K. Prout, D.J.J. Watkin, J. Appl.Crystallogr. 36 (2003) 1487.

[34] M. Camalli, M.C. Burla, B. Carrozzini, G.L. Cascarano, C. Giacovazzo, G. Polidori,R. Spagna, J. Appl. Crystallogr. 36 (2003) 1103.

[35] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb,J.R. Cheeseman, J.A. Montgomery Jr., T. Vreven, K.N. Kudin, J.C. Burant,J.M. Millam, S.S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi,G. Scalmani, N. Rega, G.A. Petersson, H. Nakatsuji, M. Hada, M. Ehara,K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda,O. Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox, H.P. Hratchian, J.B. Cross,V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev,A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma,G.A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S. Dapprich,A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck,K. Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S. Clifford,J. Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi,R.L. Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara,M. Challacombe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong,C. Gonzalez, J.A. Pople, Gaussian 03, Revision C.02, Gaussian, Inc., Wall-ingford, CT, 2004.