Reaction of Trihydridostannyl Complexes with SO2: Preparation of

Jan 16, 2009 - Abstract Image. The complexes [Re2{Sn2(μ-S)(μ-SO3)2}(CO)4L2{PPh(OEt)2}4] (L = PPh(OEt)2 (1), (CH3)3CNC (2)) were prepared by reaction...
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Reaction of Trihydridostannyl Complexes with SO2: Preparation of [Re2{Sn2(µ-S)(µ-SO3)2}(CO)4L2{PPh(OEt)2}4] (L ) PPh(OEt)2, (CH3)3CNC) Gabriele Albertin,*,† Stefano Antoniutti,† Jesu´s Castro,‡ and Gianluigi Zanardo† Dipartimento di Chimica, UniVersita` Ca’ Foscari Venezia, Dorsoduro 2137, 30123 Venezia, Italy, and Departamento de Quı´mica Inorga´nica, UniVersidade de Vigo, Facultade de Quı´mica, Edificio de Ciencias Experimentais, 36310 Vigo (Galicia), Spain ReceiVed October 22, 2008 Summary: The complexes [Re2{Sn2(µ-S)(µ-SO3)2}(CO)4L2{PPh(OEt)2}4] (L ) PPh(OEt)2 (1), (CH3)3CNC (2)) were prepared by reaction of the trihydridostannyl compounds Re(SnH3)(CO)2L[PPh(OEt)2]2 with SO2 under mild conditions. The complexes were characterized by spectroscopy and by X-ray crystal structure determination of [Re2{Sn2(µ-S)(µ-SO3)2}(CO)4{PPh(OEt)2}6] and [Re2{Sn2(µ-S)(µ-SO3)2}(CO)4{(CH3)3CNC}2{PPh(OEt)2}4]. Previous reports1 from our laboratories have dealt with studies on the synthesis and reactivity of the tin trihydride complexes [M]-SnH3 (M ) Mn, Re, Ru, Os) with CO2, which gave new mono- and dinuclear stannyl derivatives. We have now extended our studies of such SnH3 complexes to their reactivity with SO2 and found a new reaction, giving unprecedented complexes containing (µ-sulfide)(µ-sulfite)stannyl as a bridging ligand. Although stannyl complexes of transition metals have been reported2,3 with a large number of organic and inorganic substituents at the tin atom, [M]-SnR3, those containing the Sn-S bond are very rare and, to the best of our knowledge, only involve the sulfur-substituted stannyl complexes4 Ru(SnMe2SH)I(CO)(4-CH3C6H4NC)(PPh3)2 and Os{SnMe(1,2S2C2H4)}(η2-S2CNMe2)(CO)(PPh3)2. No example of either sulfide-stannyl or sulfite-stannyl complexes has ever been described. We now report the reaction of the rhenium complexes Re(SnH3)(CO)2L[PPh(OEt)2]2 (L ) PPh(OEt)2, (CH3)3CNC) with SO2, which resulted in the formation of novel thiostannyl complexes.

Experimental Section General Comments. All synthetic work was carried out under an appropriate atmosphere (Ar) using standard Schlenk techniques * To whom correspondence should be addressed. Fax: +39 041 234 8917. E-mail: [email protected]. † Universita` Ca’ Foscari Venezia. ‡ Universidade de Vigo. (1) (a) Albertin, G.; Antoniutti, S.; Bacchi, A.; Bortoluzzi, M.; Pelizzi, G.; Zanardo, G. Organometallics 2006, 25, 4235–4237. (b) Albertin, G.; Antoniutti, S.; Castro, J.; Garcı´a-Fonta´n, S.; Zanardo, G. Organometallics 2007, 26, 2918–2930. (c) Albertin, G.; Antoniutti, S.; Bacchi, A.; Pelizzi, G.; Zanardo, G. Organometallics 2008, 27, 4407–4418. (2) (a) Mackay, K. M.; Nicholson, B. K. In ComprehensiVe Organometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon Press: New York, 1982, Vol. 2, pp 1043-1114. (b) Holt, M. S.; Wilson, W. L.; Nelson, J. H. Chem. ReV. 1989, 89, 11–49. (c) Lappert, M. F.; Rowe, R. S. Coord. Chem. ReV. 1990, 100, 267–292. (d) Davies, A. G. In ComprehensiVe Organometallic Chemistry,; Stone, F. G. A., Abel, E. W., Wilkinson, G., Eds.; Pergamon Press: New York, 1995; Vol. 2, pp 218-297. (e) Davies, A. G. Organotin Chemistry; Wiley-VCH: Weinheim, Germany, 2004. (f) Roper, W. R.; Wright, L. J. Organometallics 2006, 25, 4704–4718.

or in an inert-atmosphere drybox. Once isolated, the complexes were found to be relatively stable in air but were stored under nitrogen at -25 °C. All solvents were dried over appropriate drying agents, degassed on a vacuum line, and distilled into vacuum-tight storage flasks. Re2(CO)10 was a Pressure Chemical Co. product, used as received. The phosphonite PPh(OEt)2 was prepared by the method of Rabinowitz and Pellon.5 Other reagents were purchased from commercial sources in the highest available purity and used as received. Infrared spectra were recorded on Nicolet Magna 750 or Perkin-Elmer Spectrum-One FT-IR spectrophotometers. NMR spectra (1H, 31P, 13C, 119Sn) were obtained on AC200 and AVANCE 300 Bruker spectrometers at temperatures between -90 and +30 °C, unless otherwise noted. 1H and 13C spectra are referenced to internal tetramethylsilane, 31P{1H} chemical shifts are reported with respect to 85% H3PO4, and 119Sn spectra are referenced with respect to Sn(CH3)4; in all cases downfield shifts are considered positive. COSY, HMQC, and HMBC NMR experiments were performed (3) (a) Sullivan, R. J.; Brown, T. L. J. Am. Chem. Soc. 1991, 113, 9155– 9161. (b) Buil, M. L.; Esteruelas, M. A.; Lahoz, F. J.; On˜ate, E.; Oro, L. A. J. Am. Chem. Soc. 1995, 117, 3619–3620. (c) Nakazawa, H.; Yamaguchi, Y.; Miyoshi, K. Organometallics 1996, 15, 1337–1339. (d) Schubert, U.; Grubert, S. Organometallics 1996, 15, 4707–4713. (e) Akita, M.; Hua, R.; Nakanishi, S.; Tanaka, M.; Moro-oka, Y. Organometallics 1997, 16, 5572– 5584. (f) Utz, T. L.; Leach, P. A.; Geib, S. J.; Cooper, N. J. Chem. Commun. 1997, 847–848. (g) Baya, M.; Crochet, P.; Esteruelas, M. A.; GutierrezPuebla, E.; Ruiz, N. Organometallics 1999, 18, 5034–5043. (h) Rickard, C. E. F.; Roper, W. R.; Woodman, T. J.; Wright, L. J. Chem. Commun. 1999, 837–838. (i) Adams, H.; Broughton, S. G.; Walters, S. J.; Winter, M. J. Chem. Commun. 1999, 1231–1232. (j) Chen, Y.-S.; Ellis, J. E. Inorg. Chim. Acta 2000, 300-302, 675–682. (k) Clark, A. M.; Rickard, C. E. F.; Roper, W. R.; Woodman, T. J.; Wright, L. J. Organometallics 2000, 19, 1766–1774. (l) Hermans, S.; Johnson, B. F. G. Chem. Commun. 2000, 1955– 1956. (m) Turki, M.; Daniel, C.; Za´lis, S.; Vlcˆek, A., Jr.; van Slageren, J.; Stufkens, D. J. J. Am. Chem. Soc. 2001, 123, 11431–11440. (n) Christendat, D.; Wharf, I.; Lebuis, A.-M.; Butler, I. S.; Gilson, D. F. G. Inorg. Chim. Acta 2002, 329, 36–44. (o) Neale, N. R.; Tilley, T. D. J. Am. Chem. Soc. 2002, 124, 3802–3803. (p) Esteruelas, M. A.; Lledos, A.; Maseras, F.; Oliva´n, M.; On˜ate, E.; Tajada, M. A.; Toma`s, J. Organometallics 2003, 22, 2087–2096. (q) Adams, R. D.; Captain, B.; Smith, J. L., Jr.; Hall, M. B.; Beddie, C. L.; Webster, C. E. Inorg. Chem. 2004, 43, 7576–7578. (r) Neale, N. R.; Tilley, T. D. J. Am. Chem. Soc. 2005, 127, 14745–14755. (s) Adams, R. D.; Captain, B.; Herber, R. H.; Johansson, M.; Nowik, I.; Smith, J. L.; Smith, M. D. Inorg. Chem. 2005, 44, 6346–6358. (t) Eguillor, B.; Esteruelas, M. A.; Olivan, M.; On˜ate, E. Organometallics 2005, 24, 1428–1438. (u) Sagawa, T.; Ohtsuki, K.; Ishiyama, T.; Ozawa, F. Organometallics 2005, 24, 1670–1677. (v) Adams, R. D.; Captain, B.; Hollandsworth, C. B.; Johansson, M.; Smith, J. L., Jr. Organometallics 2006, 25, 3848–3855. (w) Alvarez, M. A.; Garcia, M. E.; Ramos, A.; Ruiz, M. A. Organometallics 2006, 25, 5374–5380. (x) Braunschweig, H.; Bera, H.; Geibel, B.; Do¨rfler, R.; Go¨tz, D.; Seeler, F.; Kupfer, T.; Radacki, K. Eur. J. Inorg. Chem. 2007, 3416–3424. (y) Albertin, G.; Antoniutti, S.; Castro, J.; Garcı´a-Fonta´n, S.; Noe´, M. Dalton Trans. 2007, 5441–5452. (z) Carlton, L.; Fernandes, M. A.; Sitabule, E. Proc. Natl. Acad. Sci. 2007, 104, 6969–6973. (4) (a) Clark, G. R.; Flower, K. R.; Roper, W. R.; Wright, L. J. Organometallics 1993, 12, 3810–3811. (b) Clark, A. M.; Rickard, C. E. F.; Roper, W. R.; Woodman, T. J.; Wright, L. J. Organometallics 2000, 19, 1766–1774. (5) Rabinowitz, R.; Pellon, J. J. Org. Chem. 1961, 26, 4623–4626.

10.1021/om801013s CCC: $40.75  2009 American Chemical Society Publication on Web 01/16/2009

Notes with standard programs. The SwaN-MR and iNMR software packages6 were used to treat NMR data. The conductivities of 10-3 mol dm-3 solutions of the complexes in CH3NO2 at 25 °C were measured on a Radiometer CDM 83 instrument. Elemental analyses were determined by the Microanalytical Laboratory of the Dipartimento di Scienze Farmaceutiche, University of Padova, Padova, Italy. Synthesis of Complexes. The trihydridostannyl complexes Re(SnH3)(CO)2[PPh(OEt)2]3 and Re(SnH3)(CO)2[(CH3)3CNC][PPh(OEt)2]2 were prepared by following the reported methods.1b,7 [Re2{Sn2(µ-S)(µ-SO3)2}(CO)4{PPh(OEt)2}6] (1). A solution of the trihydridostannyl complex Re(SnH3)(CO)2[PPh(OEt)2]3 (0.2 g, 0.21 mmol) in 10 mL of toluene was stirred under a SO2 atmosphere (1 atm) at 0 °C for 30 min. The solvent was removed under reduced pressure to give an oil, which was triturated with ethanol (3 mL). A pale yellow solid slowly separated out, whose precipitation was completed by adding hexane (5 mL). The solid was filtered and crystallized from toluene and hexane; yield g80%. IR (KBr): νCO 1990, 1928 cm-1 (s). 1H NMR (CD3C6D5, 25 °C): δ 8.05-6.96 (m, 30H, Ph), 4.18, 4.02, 3.80 (m, 24H, CH2), 1.41, 1.29, 1.27 (t, 36H, CH3, J ) 7 Hz). 31P{1H} NMR (CD3C6D5, 25 °C): AB2 spin system, δA 137.0, δB 132.7, JAB ) 35.5 Hz (J31PA117Sn ) 317.0, J31PB117Sn ) 276.5 Hz). 13C{1H} NMR (CD3C6D5, 25 °C): δ 193.2, 192.7 (m, CO), 141-128 (m, Ph), 63.4 (m, CH2), 16.2 (m, CH3). 119Sn NMR (CD3C6D5, 25 °C): AB2M spin system, δM -151.7, JAM ) 329.5, JBM ) 288.0 Hz. Anal. Calcd for C64H90O22P6Re2S3Sn2: C, 36.55; H, 4.31. Found: C, 36.38; H, 4.44. Mp: 147-149 °C dec. [Re2{Sn2(µ-S)(µ-SO3)2}(CO)4{(CH3)3CNC}2{PPh(OEt)2}4] (2). This complex was prepared exactly like the related complex 1, starting from Re(SnH3)(CO)2[(CH3)3CNC][PPh(OEt)2]2 and using a reaction time of 40 min; yield g85%. IR (KBr): νCN 2163 (s); νCO 1976, 1923 cm-1 (s). 1H NMR (CD2Cl2, 25 °C): δ 7.78-7.45 (m, 20H, Ph), 4.08, 3.97, 3.88 (m, 16H, CH2), 1.41, 1.35 (t, 24H, CH3 phos, J ) 7 Hz), 1.16 (s, 18H, CH3 But). 31P{1H} NMR (CD2Cl2, 25 °C): A2 spin system, δ 137.2 (J31P117Sn ) 244.5 Hz). 13C{1H} NMR (CD2Cl2, 25 °C): δ 193.9 (t, CO, JCP ) 10.6), 191.1 (t, CO, JCP ) 9.4 Hz), 141-128 (m, Ph), 134.9 (br, CN), 63.4 (d, CH2), 58.2 (s, C(CH3)3), 30.1 (s, C(CH3)3), 11.3 (d, CH3 phos). 119Sn NMR (CD2Cl2, 25 °C): A2M spin system, δM -126.8, JAM ) 256.0 Hz. Anal. Calcd for C54H78N2O18P4Re2S3Sn2: C, 34.63; H, 4.20; N, 1.50. Found: C, 34.85; H, 4.32; N, 1.41. Mp: 133-135 °C dec. Crystal Structure Determination of 1 and 2. Crystallographic data were collected on a Bruker Smart 1000 CCD diffractometer at CACTI (Universidade de Vigo) using graphite-monochromated Mo KR radiation (λ ) 0.710 73 Å) and were corrected for Lorentz and polarization effects. The software SMART8 was used for collecting frames of data, indexing reflections, and determining lattice parameters, SAINT9 for integrating the intensity of reflections and scaling, and SADABS10 for empirical absorption correction. The structures were solved and refined with the Oscail program11 by Patterson methods and refined by full-matrix least squares based (6) Balacco, G. J. Chem. Inf. Comput. Sci. 1994, 34, 1235–1241. (http:// www.inmr.net/). (7) Albertin, G.; Antoniutti, S.; Castro, J.; Zanardo, G. Manuscript in preparation. (8) SMART Version 5.054, Instrument Control and Data Collection Software; Bruker Analytical X-ray Systems Inc., Madison, WI, 1997. (9) SAINT Version 6.01, Data Integration Software Package; Bruker Analytical X-ray Systems Inc., Madison, WI, 1997. (10) Sheldrick, G. M. SADABS, An Empirical Absorption Correction Program for Area Detector Data; University of Go¨ttingen, Go¨ttingen, Germany, 1996. (11) McArdle, P. J. Appl. Crystallogr. 1995, 28, 65–65.

Organometallics, Vol. 28, No. 4, 2009 1271 on F2.12 For the compound 2, the Squeeze program was used to correct the reflection data for the diffuse scattering due to disordered toluene solvent.13 Non-hydrogen atoms were refined with anisotropic displacement parameters, except, in compound 1, for the atoms labeled as C(1) and C(4), which were refined with isotropic displacement parameters. For compound 2 the S-O bond distance of the terminal oxygen atom O(5) bonded to the sulfur in the sulfite was fixed to a chemically accepted value. In the case of 1 all of the phenyl rings were constrained to be planar. Hydrogen atoms were included in idealized positions and refined with isotropic displacement parameters. Crystal data and details of the structural refinement are given in Table 1.

Results and Discussion The trihydridostannyl complexes Re(SnH3)(CO)2L[PPh(OEt)2]2 (L ) PPh(OEt)2, (CH3)3CNC) react with sulfur dioxide under mild conditions (0 °C, 1 atm) to give, as final products, the binuclear compounds [Re2{Sn2(µ-S)(µ-SO3)2}(CO)4L2{PPh(OEt)2}4] (1, 2) containing both sulfide (µ-S)2- and sulfite (µ-SO3)2- bridging stannyl ligands (Scheme ). The reaction proceeds with reduction of SO2 to sulfide, S2-, through a complicated mechanism which probably involves the hydrides of the SnH3 ligand as the reducing agent. Two sulfite anions, SO32-, are also formed in the reaction and, together with S2-, act as bridging groups between the tin atoms. The progress of the reaction between the [Re]-SnH3 complexes and SO2 in CD3C6D5 was monitored by NMR spectroscopy, but no clear information on either the stoichiometry of the reaction or the nature of the intermediates was obtained. The reaction was very fast, even at low temperature (-20 °C), and the 1H NMR spectra did not show any new signals except for those of the starting and final complexes 1 and 2. This also seems to exclude the formation of free H2,14 whose presence should be shown by a slightly broad signal at ca. 4.6 ppm.15 The 31P NMR spectra of the reaction mixture showed that the signal of the [Re]-SnH3 precursors disappeared with the concurrent appearance of the resonance of dinuclear complex 1 or 2. Some signals of low intensity, probably intermediates, were also observed, but they disappeared at the end of the reaction and did not give any information on its path. The reduction of SO2 to sulfide (S2-) by tin hydrides involves 6e for each sulfur atom and is really a complicated reaction, which probably proceeds through a series of steps. However, whatever the mechanism may be, the reaction gave the unprecedented dinuclear complexes 1 and 2, containing (µsulfide)(µ-sulfite)stannyl as ligand, which were very stable and were isolated as pale yellow solids and fully characterized. It was also noted that substituting one PPh(OEt)2 with tert-butyl isocyanide in Re(SnH3)(CO)2[PPh(OEt)2]3 did not change the reaction with SO2, giving the same dinuclear bis(stannyl) complex 2, stabilized by the isocyanide ligand. Although analytical and spectroscopic data (IR and 1H, 31P, 13 C, and 119Sn NMR) matched the proposed formulations of the complexes, their geometry was deduced by X-ray crystal structure determinations of [Re2{Sn2(µ-S)(µ-SO3)2}(CO)4{PPh(12) Sheldrick, G. M. SHELX-97, Program for the Solution and Refinement of Crystal Structures; University of Go¨ttingen, Go¨ttingen, Germany, 1997. (13) Spek, A. L. Acta Crystallogr. 1990, A46, C34. (14) The absence of H2 seems to exclude the simple stoichiometry: 2[Re]-SnH3 + 3SO2 f [Re]2-Sn2(µ-S)(µ-SO3)2 + 3H2. Other species containing hydrogen and/or sulfur, which were not identified, probably also formed in the reaction. (15) Crabtree, R. H.; Lavin, M.; Bonneviot, L. J. Am. Chem. Soc. 1986, 108, 4032–4037.

1272 Organometallics, Vol. 28, No. 4, 2009

Notes

Table 1. Crystal Data and Structure Refinement Details for 1 and 2 1 empirical formula formula wt temp, K wavelength, Å crystal syst space group unit cell dimens a, Å b, Å c, Å β, deg V, Å3 Z calcd density, Mg/m3 abs coeff, mm-1 F(000) cryst size. mm θ range for data collecn, deg index ranges no. of rflns collected no. of indep rflns no. of obsd rflns (>2σ) data completeness abs cor max, min transmission refinement method no. of data/ restraints/params goodness of fit on F2 final R indices (I > 2σ(I)) R indices (all data) largest diff peak, hole, e Å-3

2

C64H90O22P6Re2S3Sn2 2103.14 293(2) 0.710 73 monoclinic P21/c

C54H78N2O18P4Re2S3Sn2 1873.02 293(2) 0.710 73 monoclinic C2/c

12.0145(14) 29.314(3) 25.998(3) 115.140(5) 8289.0(16) 4 1.685 3.763 4152 0.25 × 0.08 × 0.07 1.39-20.82

15.347(7) 16.615(7) 31.222(14) 93.489(9) 7946(6) 4 1.566 3.873 3672 0.45 × 0.25 × 0.13 1.81-27.90

-11 e h e 12; -29 e k e 29; -19 e h e 19; -12 e k e 21; -21 e l e 25 -41 e l e 40 29 497 25 074 8654 (R(int) ) 0.1240) 9289 (R(int) ) 0.0441) 4999 5643 0.999 0.978 semiempirical from equivalents 1.000, 0.768 1.000, 0.695 full-matrix least squares on F2 8654/0/798 9289/1/391 0.968 R1 ) 0.0670, wR2 ) 0.1552 R1 ) 0.1282, wR2 ) 0.1944 1.692, -0.945

Scheme 1a

a [Re] ) Re(CO) [PPh(OEt) ] 2 2 3 (1), Re(CO) 2[(CH 3) 3CNC][PPh(OEt)2]2 (2).

Figure 1. View of compound 1 drawn at the 30% probability level. The phenyl rings and the ethoxy groups are not shown.

(OEt)2}6] (1) and [Re2{Sn2(µ-S)(µ-SO3)2}(CO)4{(CH3)3CNC}2{PPh(OEt)2}4] (2), whose ORTEP drawings are shown in Figures 1 and S1 (Supporting Information), respectively. Selected bond distances and angles for 1 and 2 are given in Table 2.

0.928 R1 ) 0.0394, wR2 ) 0.0920 R1 ) 0.0753, wR2 ) 0.1032 0.849, -0.983

Compounds 1 and 2 consist of dimeric units of two rhenium atoms connected by the novel bridging ditin ligand (µsulfide)bis(µ-sulfite-κO,O′)ditin. This moiety consists of two tin atoms connected by two SO32- (sulfite ions) and a S2- (sulfide ion), forming a structure which may be defined as a bicyclo[3.3.1]nonane where both bridgeheads are tin atoms. In both cases, the oxygen atoms of the sulfite ions out of the bicycle are directed toward the sulfide atoms, like the wings of the bicycle, leaving the nonbonding electronic pairs almost parallel, as the legs of the bicycle (see Figure S2 in the Supporting Information). However, this assessment should be made with care, since the positions of the oxygen atoms are not well established (at least for 2; see the Experimental Section). The tin atoms are the donor atoms of this bridging ligand and coordinate to two rhenium atoms. In the case of 1, the coordination sphere of the rhenium atoms is completed by two cis carbonyl ligands and three mer diethoxyphenylphosphonite ligands. In complex 2, one diethoxyphenylphosphonite ligand was substituted by a tert-butyl isocyanide molecule, in such a way that the remaining phosphonite ligands were mutually trans and the tert-butyl isocyanide ligand was trans to a carbonyl ligand. Both molecules have a symmetry axis, which is crystallographic (symmetry operation 1 - x, y, 0.5 - z) in the case of 2 and makes the two rhenium atoms quite similar in their geometrical parameters. However, the spatial disposition of the ligands is different in both cases. In 2, they are related by the symmetry operation (1 - x, y, 0.5 - z) and the consequence is an isocyanide-Re-Re-isocyanide or carbonyl-Re-Re-carbonyl torsion angle close to 90° (average 91.8(3)°) (see Figure S3 in the Supporting Information), but for 1 the corresponding torsion angles are close to 180° (average 160.3(9)°) (see Figure S3).

Notes

Organometallics, Vol. 28, No. 4, 2009 1273 Table 2. Selected Bond Lengths (Å) and Angles (deg)

Re(1)-C(1) Re(1)-C(2) Re(1)-P(1) Re(1)-P(3) Re(1)-P(2) Re(1)-Sn(1) C(1)-O(1) C(2)-O(2) Sn(1)-O(1S) Sn(1)-O(3S) Sn(1)-S(3) S(1)-O(3S) S(1)-O(4S) S(1)-O(5S) C(1)-Re(1)-C(2) C(2)-Re(1)-P(1) C(1)-Re(1)-P(3) C(1)-Re(1)-P(1) C(2)-Re(1)-P(2) P(2)-Re(1)-P(3) C(1)-Re(1)-Sn(1) P(1)-Re(1)-Sn(1) P(2)-Re(1)-Sn(1) P(3)-Re(1)-Sn(1) C(2)-Re(1)-P(3) P(1)-Re(1)-P(2) C(2)-Re(1)-Sn(1) P(3)-Re(1)-P(1) C(1)-Re(1)-P(2) O(1)-C(1)-Re(1) O(2)-C(2)-Re(1) O(3S)-Sn(1)-O(1S) O(1S)-Sn(1)-S(3) O(3S)-Sn(1)-S(3) O(1S)--Sn(1)-Re(1) O(3S)-Sn(1)-Re(1) S(3)-Sn(1)-Re(1) Re-C(1) Re-C(2) Re-P(1) Re-P(2) Re-C(31) Re-Sn C(1)-O(1) C(2)-O(2) C(1)-Re-C(2) C(2)-Re-C(31) C(1)-Re-P(1) C(1)-Re-P(2) C(2)-Re-P(1) C(31)-Re-P(1) C(1)-Re-Sn P(1)-Re-Sn P(2)-Re-Sn C(31)-Re-Sn C(31)-Re-P(2) C(2)-Re-P(2) C(2)-Re-Sn

Compound 1 1.86(2) Re(2)-C(4) 1.81(2) Re(2)-C(3) 2.381(6) Re(2)-P(4) 2.372(6) Re(2)-P(6) 2.416(6) Re(2)-P(5) 2.7285(17) Re(2)-Sn(2) 1.22(2) C(3)-O(3) 1.21(2) C(4)-O(4) 2.084(15) Sn(2)-O(2S) 2.055(15) Sn(2)-O(4S) 2.400(6) Sn(2)-S(3) 1.569(15) S(2)-O(1S) 1.573(16) S(2)-O(2S) 1.458(18) S(2)-O(6S) 90.1(9) 89.1(6) 85.8(6) 88.5(6) 93.9(7) 94.7(2) 85.0(6) 86.03(14) 90.99(15) 95.18(15) 89.2(6) 91.1(2) 173.1(7) 174.0(2) 176.0(6) 175.0(17) 178.7(18) 89.8(7) 103.0(4) 102.7(4) 113.9(4) 106.8(4) 132.01(15)

C(3)-Re(2)-C(4) C(4)-Re(2)-P(4) C(4)-Re(2)-P(6) C(3)-Re(2)-P(5) C(3)-Re(2)-P(6) P(5)-Re(2)-P(6) C(4)-Re(2)-Sn(2) P(6)-Re(2)-Sn(2) P(4)-Re(2)-Sn(2) P(5)-Re(2)-Sn(2) C(3)-Re(2)-P(4) P(4)-Re(2)-P(5) C(3)-Re(2)-Sn(2) P(4)-Re(2)-P(6) C(4)-Re(2)-P(5) O(3)-C(3)-Re(2) O(4)-C(4)-Re(2) O(4S)-Sn(2)-O(2S) O(2S)-Sn(2)-S(3) O(4S)-Sn(2)-S(3) O(2S)-Sn(2)-Re(2) O(4S)-Sn(2)-Re(2) S(3)-Sn(2)-Re(2)

Compound 2 1.948(7) Sn-S(1) 1.944(6) Sn-O(3) 2.3881(17) Sn-O(4) 2.3856(17) S(2)-O(4i) 2.065(6) S(2)-O(5) 2.7383(12) S(2)-O(3) 1.152(7) N(31)-C(32) 1.141(7) C(31)-N(31) 91.8(3) 92.7(2) 89.7(2) 89.5(2) 87.2(2) 90.93(17) 92.91(18) 94.32(4) 88.61(4) 82.65(16) 90.01(17) 89.9(2) 175.1(2)

P(1)-Re-P(2) C(1)-Re-C(31) O(2)-C(2)-Re O(1)-C(1)-Re O(3)-Sn-O(4) O(3)-Sn-S(1) O(4)-Sn-S(1) O(3)-Sn-Re O(4)-Sn-Re S(1)-Sn-Re C(31)-N(31)-C(32) N(31)-C(31)-Re

1.92(2) 1.88(2) 2.375(6) 2.381(6) 2.411(6) 2.7316(16) 1.14(2) 1.15(2) 2.051(15) 2.041(16) 2.415(6) 1.537(17) 1.533(15) 1.45(2) 92.2(9) 88.2(7) 84.2(7) 83.4(7) 89.9(6) 96.6(2) 87.9(6) 90.11(15) 91.12(14) 96.51(13) 88.9(6) 90.8(2) 179.9(6) 172.3(2) 175.5(7) 177(2) 175(2) 90.9(7) 101.2(5) 100.8(4) 113.3(5) 119.2(4) 125.06(14) 2.4165(17) 2.060(5) 2.067(5) 1.470(5) 1.274(14) 1.503(5) 1.489(8) 1.152(7) 177.02(5) 175.6(2) 179.3(7) 178.6(7) 93.7(3) 103.35(15) 97.89(15) 113.11(14) 113.40(14) 129.04(5) 172.2(6) 178.2(5)

In conclusion, the substitution of a phosphonite ligand by a isocyanide ligand causes important spatial changes in the molecule. It is important to note that the tin atoms are out of the Re-Re axis, since the different sulfur bridges in the ditin ligand cause a large bending of this axis, up to Re-Sn-Sn-Re torsion angles of 7.2(8)° for 1 and 30.2(2)° for 2. This effect is more evident when the dihedral angles formed by the equatorial coordination planes are calculated, and they are 23.8(5)° for 1 and 30.68(9)° for 2. The environment of the rhenium atoms in both complexes may be described as that of a slightly distorted octahedron. Bond lengths around rhenium atoms have values similar to those found

in the literature.1b,7,16-22 In 1, the rhenium atom labeled as Re(2) is slightly distorted with respect to Re(1), due to the steric effect on one of the phosphonites of the bridging sulfite. The substitution of a phosphonite ligand by a isocyanide ligand causes more differences in the compounds. In 2, the mutually trans phosphonite ligands are almost perfectly staggered, with an average C-P-P-C or O-P-P-O torsion angle of 176.4(3)°. However, for 1, the mutually trans phosphonite ligands are almost perfectly eclipsed, with average C-P-P-C or O-P-P-O torsion angles of 18.9(9)° for Re(1) and 4.0(9)° for Re(2). In addition, neither rhenium atom has the same spatial arrangement. For that labeled Re(1), the phenyl group is almost perpendicular to the carbonyl trans to the tin atoms (average torsion angle C-P-Re(1)-C(2) of 79.5(1)°) whereas an average torsion angle C-P-Re(2)-C(3) of 6.7(1)° shows an almost parallel arrangement of the phenyl group in Re(2). The phosphonite ligand trans to a carbonyl group in 1 has a P-O bond almost parallel to the Re-Sn vector, with torsion angles of 164.6(6)° (Re(1)-Sn(1)-P(1)-O(11)) and 172.9(6)° (Re(2)-Sn(2)-P(5)-O(51)). The IR and NMR data of both thiostannyl complexes 1 and 2 indicate that a geometry of type I (Scheme ), like that observed in the solid state, also occurs in solution. The IR spectra of both compounds 1 and 2 show two νCO bands, fitting the mutually cis position of the two carbonyl ligands. In the spectrum of 2, a strong band at 2163 cm-1, attributed to the νCN of the isocyanide, is also present. The 13C NMR spectra of both compounds indicate the magnetic inequivalence of the two CO groups, showing two well-separated multiplets for the carbonyl carbon resonances at 193.2-193.9 and 192.7-191.1 ppm. At temperatures between +30 and -80 °C, the 31P NMR spectra of 1 is an AB2 multiplet, indicating that two phosphonites are magnetically equivalent and different from the third. Instead, the 31P spectra of complex 2 is a sharp singlet, fitting the magnetic equivalence of the two phosphonite ligands. 119Sn spectra appear either as a complicated multiplet at -151.7 ppm (1) or as a triplet at -126.8 ppm (2), due to the coupling with the phosphorus nuclei of the phosphonites. Simulations with either an AB2M (1) or an A2M (2) model (M ) 119Sn) gave an excellent fit between experimental and calculated spectra (see Figures S4 and S5 in the Supporting Information). On the basis of these data, a geometry of type I may be proposed in solution for dinuclear complexes 1 and 2.

Acknowledgment. Mrs. Daniela Baldan is gratefully acknowledged for technical assistance. Supporting Information Available: CIF files and Figures S1-S3, giving crystallographic data for compounds 1 and 2, and Figures S4 and S5, giving 119Sn{1H} NMR data. This material is available free of charge via the Internet at http://pubs.acs.org. OM801013S (16) Albertin, G.; Antoniutti, S.; Castro, J.; Garcı´a-Fonta´n, S.; Zanardo, G. Organometallics 2008, 27, 2789–2794. (17) Albertin, G.; Antoniutti, S.; Bravo, J.; Castro, J.; Garcı´a-Fonta´n, S.; Marı´n, M. C.; Noe`, M. Eur. J. Inorg. Chem. 2006, 3451–3462. (18) Albertin, G.; Antoniutti, S.; Bacchi, A.; Celebrin, A.; Pelizzi, G.; Zanardo, G. Dalton Trans. 2007, 661–668. (19) Carballo, R.; Losada-Gonza´lez, P.; Va´zquez-Lo´pez, E. M. Z. Anorg. Allg. Chem. 2003, 629, 249–254. (20) Garcia, R.; Paulo, A.; Domingos, A.; Santos, I.; Pietzsch, H.-J. Synth. React. Inorg. Nano-Met. Chem. 2005, 35, 35–42. (21) Nieto, S.; Pe´rez, J.; Riera, L.; Riera, V.; Miguel, D.; Golen, J. A.; Rheingold, A. L. Inorg. Chem. 2007, 46, 3407–3418. (22) Huynh, L.; Wang, Z.; Yang, J.; Stoeva, V.; Lough, A.; Manners, I.; Winnik, M. A. Chem. Mater. 2005, 17, 4765–4773.