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Organometallics 2009, 28, 1582–1585
Behavior of OsH2Cl2(PiPr3)2 in Acetonitrile: The Importance of the Small Details Miguel A. Esteruelas,* Sara Fuertes, Montserrat Oliva´n, and Enrique On˜ate Departamento de Quı´mica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n, UniVersidad de Zaragoza-CSIC, 50009 Zaragoza, Spain ReceiVed NoVember 3, 2008 Summary: The behaVior of OsH2Cl2(PiPr3)2 (1) in acetonitrile as solVent is studied. Acetonitrile coordinates to the metal center of 1 and promotes the dihydride-dihydrogen transformation of its OsH2 unit to giVe the trans-Cl2 compound OsCl2(η2H2)(CH3CN)(PiPr3)2 (2a), which eVolVes to its cis-Cl2 isomer 2b. Treatment of 1 with TlPF6 in acetonitrile leads to the PF6 salt of the cis-bis(acetonitrile) cation [OsCl(η2-H2)(CH3CN)2(PiPr3)2]+ (3a), which is transformed into its trans-bis(acetonitrile) isomer 3b. The addition of Et3N to the PF6 salts of 3a,b in acetonitrile giVes [OsH(CH3CN)3(PiPr3)2]PF6 (4). Reaction of 4 with 1,5-cyclooctadiene (COD) in refluxing toluene affords [OsH(COD)(CH3CN)2(PiPr3)]PF6 (5). The X-ray structures of 3b and 5 are also reported. Equilibrium positions of chemical reactions, including intramolecular redox processes, are solvent-dependent. Responsible for this medium effect are the different solvations of reactants and products.1 One of the most relevant redox processes in transition-metal chemistry is dihydride-dihydrogen tautomerization.2 The interactions within the MH2 units play a main role in the reactions of the complexes containing two hydrogen atoms bonded to the metal center and the unsaturated organic molecules.3 The unsaturated complex OsH2Cl2(PiPr3)2 (1) is one of the cornerstones in the development of modern osmium organometallic chemistry. Its solid-state structure, significantly distorted from octahedral, has only C2 symmetry and can be described as a square antiprism with two missing vertexes.4 In noncoordinanting solvents the metal center keeps its oxidation state. Thus,itexistsastworapidlyinterconvertingdihydride-osmium(IV) isomers, one having C2 symmetry and the other with no symmetry.5 We have now observed that, however, in acetonitrile the metal center is reduced to form complex mixtures of dihydrogen-osmium(II) species (Scheme 1). The 1H NMR spectrum of the freshly prepared solutions of 1 in acetonitrile-d3 is consistent with the formation of the trans-Cl2 complex OsCl2(η2-H2)(CH3CN)(PiPr3)2 (2a), which results from * To whom correspondence should be addressed. E-mail: maester@ unizar.es. (1) See for example: (a) Weaver, M. J. Chem. ReV. 1992, 92, 463. (b) Richardt, C. Chem. ReV. 1994, 94, 2319. (c) Bolan˜o, T.; Castarlenas, R.; Esteruelas, M. A.; On˜ate, E. Organometallics 2007, 26, 2037, and references therein. (2) (a) Esteruelas, M. A.; Oro, L. A. Chem. ReV. 1998, 92, 577. (b) Kubas, G. J. Chem. ReV. 2007, 107, 4152. (c) Szymczak, N. K.; Tyler, D. R. Coord. Chem. ReV. 2008, 252, 212. (d) Morris, R. H. Coord. Chem. ReV. 2008, 252, 2381. (3) Castro-Rodrigo, R.; Esteruelas, M. A.; Lo´pez, A. M.; On˜ate, E. Organometallics 2008, 27, 3547, and references therein. (4) Aracama, M.; Esteruelas, M. A.; Lahoz, F. J.; Lo´pez, J. A.; Meyer, U.; Oro, L. A.; Werner, H. Inorg. Chem. 1991, 30, 288. (5) Gusev, D. G.; Kuhlman, R.; Rambo, J. R.; Berke, H.; Eisenstein, O.; Caulton, K. G. J. Am. Chem. Soc. 1995, 117, 281.
Scheme 1
the coordination of a solvent molecule to the osmium atom of 1 and the redox dihydride-dihydrogen transformation of the OsH2 unit. According to this, there are marked differences between the spectra of the acetonitrile-d3 and dichloromethane-d2 solutions (Figure 1). In acetonitrile-d3, the PiPr3 methyl groups display a doublet of virtual triplets instead of the characteristic double doublet in dichloromethane-d2, whereas the OsH2 resonance appears at -6.20 ppm, shifted by more than 10 ppm to lower field with regard to that in dichloromethane solution (-16.34 ppm). The movement toward lower field is accompanied by a reduction of the H-P coupling constant from 35.0 to 8.7 Hz. The 31P{1H} NMR spectra are also sensitive to the transformation. In acetonitrile, a singlet at 2.4 ppm is observed, which appears shifted by 42.1 ppm toward higher field with regard to that of the dichloromethane solutions (44.5 ppm). After a few minutes a yellow solid precipitates from the acetonitrile solutions of 1. Its elemental analysis is consistent with 2a. At room temperature, the 1H NMR spectrum in dichloromethane-d2 of the solid contains the resonances of 1 and that of 1 equiv of free acetonitrile. In benzene-d6, the spectrum shows a mixture of 2a, 1, and acetonitrile in a 1:2:2 molar ratio. These observations indicate a solvent-dependent equilibrium between 2a and 1 plus acetonitrile. The stereochemistry of 2a was inferred from the shape of the PiPr3 methyl resonance, which is characteristic for an octahedral structure with two symmetry planes. One of them is
10.1021/om801057z CCC: $40.75 2009 American Chemical Society Publication on Web 01/26/2009
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Organometallics, Vol. 28, No. 5, 2009 1583
Figure 1. 1H NMR spectra of freshly prepared solutions of 1 in CD3CN (a) and CD2Cl2 (b) at 293 K.
perpendicular to the P-Os-P direction and makes the phosphine ligands equivalent. The other plane is perpendicular to the Cl-Os-Cl direction and makes the methyl groups of each isopropyl group equivalent. The nonclassical character of the OsH2 unit is supported by its 1H NMR resonance, which at 248 K has a 400 MHz T1(min) value of 30 ( 1 ms. This value corresponds to a hydrogen-hydrogen distance of 1.2 Å (slow spinning),6 which agrees well with the H-D coupling constant of 15.7 Hz, obtained from the species containing the partially deuterated ligand η2-HD,7 and lies in the reported range (1.0-1.5 Å) for elongated dihydrogen derivatives.2 The mutually trans disposition of the chloride ligands is the stereochemistry expected from a kinetically controlled formation of 2a.8 In accordance with this, after 30 min, the 1H and 31P{1H} spectra of the acetonitrile solutions show 1:3 mixtures of 2a and its cis-Cl2 isomer 2b, along with small amounts of the cisbis(acetonitrile) cation [OsCl(η2-H2)(CH3CN)2(PiPr3)2]+ (3a). The formation of 2b is strongly supported by the PiPr3 methyl signal in the 1H NMR spectrum that, in agreement with diasterotopic methyl groups, appears as two doublets of virtual triplets at 1.32 and 1.31 ppm. The OsH2 resonance is observed at -9.90 ppm, as a triplet with a H-P coupling constant of 11.5 Hz. In this case a H-D coupling constant of 17.1 Hz was found in the partially deuterated species, which corresponds to a hydrogen-hydrogen distance of 1.1 Å. A singlet at 1.0 ppm in the 31P{1H} NMR spectrum is also characteristic of 2b. The cation 3a results from the displacement of one of the mutually trans disposed chloride ligands of 2a by a solvent molecule. In agreement with this, its PF6 salt can be easily formed by addition of 1.0 equiv of TlPF6 to the freshly prepared solutions of 1 in acetonitrile (i.e., to 2a) and isolated as a white solid in 72% yield.9 The mutually cis disposition of the acetonitrile ligands was inferred from the presence of two singlets, at 2.72 and 2.67 ppm, in the 1H NMR spectrum and four singlets, at 126.2 and 123.1 (CN) ppm and 3.8 and 3.4 (6) (a) Earl, K. A.; Jia, G.; Maltby, P. A.; Morris, R. H. J. Am. Chem. Soc. 1991, 113, 3027. (b) Desrosiers, P. J.; Caı¨, L.; Lin, Z.; Richards, R.; Halpern, J. J. Am. Chem. Soc. 1991, 113, 4173. (c) Jessop, P. G.; Morris, R. H. Coord. Chem. ReV. 1992, 121, 155. (7) Maltby, P. A.; Schlaf, M.; Steinbeck, M.; Lough, A. J.; Morris, R. H.; Klooster, W. T.; Koetzle, T. F.; Srivastava, R. C. J. Am. Chem. Soc. 1996, 118, 5396. (8) (a) Esteruelas, M. A.; Lahoz, F. J.; Oro, L. A.; On˜ate, E.; Ruiz, N. Inorg. Chem. 1994, 33, 787. (b) Esteruelas, M. A.; Ferna´ndez-Alvarez, F. J.; On˜ate, E. J. Am. Chem. Soc. 2006, 128, 13044. (c) Esteruelas, M. A.; Ferna´ndez-Alvarez, F. J.; On˜ate, E. Organometallics 2007, 26, 5239. (9) Under the same conditions, the treatment of the acetone solutions of 1 with 1.0 equiv of TlPF6 leads to the dimer cation [(PiPr3)2H2Os(µCl)3OsH2(PiPr3)2]+, which has been previously prepared by protonation of 1 with CF3SO3H in diethyl ether. See: Kuhlman, R.; Streib, W. E.; Caulton, K. G. Inorg. Chem. 1995, 34, 1788.
Figure 2. 31P{1H} NMR spectrum of the acetonitrile-d3 solutions of 1 after 15 h at 293 K.
(CH3) ppm, in the 13C{1H} NMR spectrum. The nonclassical nature of the OsH2 unit is supported by the 1H NMR spectrum. Its resonance appears at -8.99 ppm, as a triplet with a H-P coupling constant of 9.8 Hz. As expected, the substitution of the chloride by an acetonitrile molecule produces a slight shortening of the hydrogen-hydrogen distance.2 Thus, the H-D coupling constant in the partially deuterated species increases with regard to that of 2a. The obtained value of 24.7 Hz corresponds to a hydrogen-hydrogen separation of 1.0 Å, which is 0.2 Å shorter than that of 2a. The 31P{1H} NMR spectrum contains a singlet at 5.8 ppm. After 15 h, the 1H and 31P{1H} NMR spectra of the acetonitrile-d3 solutions of 1 reveal the presence of the neutral dihydrogen isomers 2a,b, the dihydrogen cations 3a and its trans-bis(acetonitrile) isomer 3b, and the monohydride cation [OsH(CH3CN)3(PiPr3)2]+ (4). Figure 2 shows the 31P{1H} NMR spectrum of the mixture. The cation 3b could be the result of the displacement of the chloride ligand of 2b disposed trans to acetonitrile by a solvent molecule or, alternatively, it could be formed from 3a by isomerization. In agreement with the latter process, the PF6 salt of 3b can be generated by heating of an acetonitrile solution of the PF6 salt of 3a, at 60 °C during 2 h, and isolated as a white solid in 78% yield. Figure 3 shows a view of the structure of 3b. The geometry around the osmium atom can be described as a distorted octahedron with trans phosphines (P(1)-Os-P(2) ) 179.88(3)°) and trans acetonitriles (N(1)-Os-N(2) ) 179.38(9)°). The coordinated hydrogen molecule lies trans to the chloride ligand, and it is disposed almost parallel to the P-Os-P direction. The H(01)-H(02) distance is 1.07(4) Å. The 1H and 31P{1H} NMR spectra of 3b are consistent with the structure shown in Figure 3. In the 1H NMR spectrum, the most noticeable feature is the OsH2 resonance, which appears at -10.29 ppm as a triplet with a H-P coupling constant of
1584 Organometallics, Vol. 28, No. 5, 2009
Notes
Figure 3. Molecular diagram of cation 3b. Selected bond lengths (Å): Os-P(1) ) 2.4327(9), Os-P(2) ) 2.4423(9), Os-Cl ) 2.4525(9), H(01)-H(02) ) 1.07(4).
Figure 4. Molecular diagram of the cation of 5. Selected bond lengths (Å): Os-C(1) ) 2.213(6), Os-C(2) ) 2.218(6), Os-C(5) ) 2.171(5), Os-C(6) ) 2.159(5), C(1)-C(2) ) 1.386(8), C(5)-C(6) ) 1.398(8).
10.4 Hz. The H-D coupling constant in the partially deuterated species of 19.3 Hz allows us to calculate a hydrogen-hydrogen separation of 1.1 Å, which agrees well with that obtained from the X-ray diffraction analysis. In accordance with the presence of equivalent phosphines in the complex, the 31P{1H} NMR shows a singlet at 5.5 ppm. After 3 days, the 1H and 31P{1H} NMR spectra of the acetonitrile-d3 solutions of 1 show the resonances of a 3:1 mixture of 3b and 4. Cation 4 is the result of the elimination of HCl from 3a and/or 3b and the coordination of a solvent molecule to the metal center. When the HCl that forms can be leaked out, cation 3b evolves into 4. Thus, on a Schlenk-tube scale, 4 is formed in almost quantitative yield by refluxing the acetonitrile solutions of 1. The PF6 salt of 410 can be isolated in about 80% yield from the reactions at room temperature of the PF6 salts of 3a,b with triethylamine in acetonitrile. The behavior of 1 in acetonitrile determines the reactions in this solvent, and therefore, there are marked differences in the obtained product depending upon the solvent used. For instance, the reaction of 1 with 1,5-cyclooctadiene (COD) in toluene under reflux gives cyclooctene and the isopropenyldiisopropylphosphine derivative OsCl2(η4-COD){[η2-CH2dC(CH3)]PiPr2} in high yield,11 while in acetonitrile under reflux the generated cation 4 does not undergo the productive dissociation of solvent molecules solvating the metal center12 and, as a result, it is inert. The reaction of 4 with the diene requires toluene as solvent. Thus, the treatment in refluxing toluene of the PF6 salt of 4 with 3.0 equiv of 1,5-cyclooctadiene affords a complex mixture of products, from which [OsH(η4-COD)(CH3CN)2(PiPr3)]PF6 (5) is separated as a white solid in 23% yield (eq 1).
rationalized as being derived from a highly distorted octahedron with cis acetonitriles and the phosphine disposed trans to the C(1)-C(2) double bond of the diene. The 1,5-cyclooctadiene ligand takes its customary “tub” conformation. The C(1)-C(2) and C(5)-C(6) bond lengths of 1.386(8) and 1.398(8) Å lie within the range reported for transition-metal complexes (1.340-1.455 Å).13 They are statistically identical and are longer than those found in the free 1,5-cyclooctadiene molecule (1.34 Å),14 in agreement with the usual Chatt, Dewar, and Duncanson metal-bonding scheme. The osmium diene coordination exhibits Os-C distances between 2.159 (5) and 2.218(6) Å, which agree well with those found in other osmium-olefin complexes (2.13-2.28 Å).15 The 1H, 13C{1H}, and 31P{1H} spectra of 5 in dichloromethane-d2 are consistent with the structure shown in Figure 4. In agreement with the presence of the hydride ligand, the 1H NMR spectrum shows at -10.99 ppm a doublet with a H-P coupling constant of 21.4 Hz. The vinyl protons of the diene display three multiplets at 4.10, 3.35, and 3.07 ppm, whereas in the 13C{1H} NMR spectrum the C(sp2) resonances appear as doublets at 75.3 (JC-P ) 9.1 Hz) and 74.7 (JC-P ) 13.6 Hz) ppm and as singlets at 60.9 and 57.9 ppm. The 31P{1H} NMR spectrum contains a singlet at 10 ppm. In conclusion, the choice of solvent in the planning of the chemical reactions of transition-metal complexes is a crucial step. This is due not only to the fact that some solvents saturate unsaturated species, displace coordinated ligands, and prevent dissociation processes but also because they can promote intramolecular redox reactions. The behavior of the dihydrideosmium(IV) compound OsH2Cl2(PiPr3)2 in acetonitrile is a good example of these four solvent effects on the same complex.
Experimental Section All reactions were carried out with rigorous exclusion of air using Schlenk-tube techniques. Solvents were dried by the usual proce-
Figure 4 shows a view of the structure of the cation of 5. The coordination geometry around the osmium atom can be (10) The BF4 salt of 4 has been previously prepared via [OsH(η2H2)(CH3CN)2(PiPr3)2]BF4 by protonation in acetonitrile of OsH6(PiPr3)2 with HBF4. See: Smith, K.-T.; Tilset, M.; Kuhlman, R.; Caulton, K. G. J. Am. Chem. Soc. 1995, 117, 9473. (11) Edwards, A. J.; Esteruelas, M. A.; Lahoz, F. J.; Lo´pez, A. M.; On˜ate, E.; Oro, L. A.; Tolosa, J. I. Organometallics 1997, 16, 1316. (12) Although the acetonitrile ligands of 5 exchange with the solvent10 and unsaturated species could be proposed as intermediates of the exchange, solvent coordination appears to be faster than diene coordination.
(13) Allen, F. H.; Davies, J. E.; Galloy, J. J.; Johnson, O.; Kennard, O.; Macrae, C. F.; Mitchell, E. M.; Mitchell, G. F.; Smith, J. M.; Watson, D. G. J. Chem. Inf. Comput. Sci. 1991, 31, 187. (14) Churchill, M. R.; Bezman, S. A. Inorg. Chem. 1973, 12, 531. (15) See for example: (a) Johnson, T. J.; Albinati, A.; Koetzle, T. F.; Ricci, J.; Eisenstein, O.; Huffman, J. C.; Caulton, K. G. Inorg. Chem. 1994, 33, 4966. (b) Buil, M. L.; Esteruelas, M. A.; Garcı´a-Yebra, C.; Gutie´rrezPuebla, E.; Oliva´n, M. Organometallics 2000, 19, 2184. (c) Esteruelas, M. A.; Gonza´lez, A. I.; Lo´pez, A. M.; On˜ate, E. Organometallics 2003, 22, 414. (d) Baya, M.; Buil, M. L.; Esteruelas, M. A.; On˜ate, E. Organometallics 2004, 23, 1416. (e) Baya, M.; Buil, M. L.; Esteruelas, M. A.; On˜ate, E. Organometallics 2005, 24, 2030. (f) Esteruelas, M. A.; Garcı´a-Yebra, C.; Oliva´n, M.; On˜ate, E. Inorg. Chem. 2006, 45, 10162.
Notes dures and distilled under argon prior to use. The starting materials OsH2Cl2(PiPr3)2 (1)4 and OsD2Cl2(PiPr3)2 (1-d2)8c were prepared in accord with methods reported in the literature. 1H, 31P{1H}, and 13 C{1H} NMR spectra were recorded on a Varian Gemini 2000, a Bruker Avance 300 MHz, or a Bruker Avance 400 MHz instrument. Chemical shifts (expressed in parts per million) are referenced to residual solvent peaks (1H, 13C{1H}) or external H3PO4 (31P{1H}). Coupling constants, J and N, are given in hertz. Infrared spectra were run on a Perkin-Elmer Spectrum One instrument (Nujol mulls on polyethylene sheets). C, H, and N analyses were carried out in a Perkin-Elmer 2400 CHNS/O analyzer. Preparation of trans-OsCl2(η2-H2)(CH3CN)(PiPr3)2 (2a). A solution of 1 (160 mg, 0.274 mmol) in 5 mL of acetonitrile was stirred at room temperature for 5 min. The resulting yellow solid was separated by decantation and dried in vacuo. Yield: 124 mg (72%). Anal. Calcd for C20H47NCl2OsP2: C, 38.45; H, 7.58; N, 2.24. Found: C, 38.30; H, 7.41; N, 2.28. IR (Nujol, cm-1): ν(CtN) 2287 (w). 1H NMR (300 MHz, CD3CN, 293 K): δ 2.63 (m, 6H, PCH), 1.96 (s, 3H, CH3CN), 1.29 (dvt, N ) 12.6, JH-H ) 7.2, 36H, PCHCH3), -6.20 (t, JH-P ) 8.7, 2H, OsH2). 31P{1H} NMR (121.4 MHz, CD3CN, 293 K): δ 2.4 (s). 13C{1H} NMR-APT (75.4 MHz, toluene-d8, 253 K): δ 115.9 (s, CN), 22.9 (vt, N ) 11.6, PCH), 19.2 (s, PCHCH3), 1.8 (s, CH3CN). T1(min) (ms, toluene-d8, 400 MHz, -6.15, 248 K): 30 ((1) f dH-H(calcd) ) 1.2 Å. Determination of the JH-D Value for 2a. An NMR tube was charged with 1-d2 (30 mg, 0.051 mmol), and CD3CN (0.5 mL) was added at 273 K. The 1H{31P} NMR spectra of this solution exhibit in the hydride region the resonances due to a mixture of the [Os](η2H-D) and the [Os](η2-H-H) 2a species. JH-D ) 15.7 f dH-H(calcd) ) 1.15 Å. Formation and Characterization of cis-OsCl2(η2-H2)(CH3CN)(PiPr3)2 (2b). An NMR tube was charged with 1 (30 mg, 0.051 mmol) and CD3CN (0.6 mL). The mixture was left for 30 min at room temperature. The 1H NMR spectrum showed the presence of trans-OsCl2(η2-H2)(CH3CN)(PiPr3)2 (2a) and cis-OsCl2(η2H2)(CH3CN)(PiPr3)2 (2b) as the only detectable Os species. 1H NMR (300 MHz, CD3CN, 293 K): δ 2.65 (m, 6H, PCH), 2.09 (s, 3H, CH3CN), 1.32 (dvt, N ) 13.3, JH-H ) 6.1, 18H, PCHCH3),1.31 (dvt, N ) 12.7, JH-H ) 5.5, 18H, PCHCH3), -9.90 (t, JH-P ) 11.5, 2H, OsH2). 31P{1H} NMR (121.4 MHz, CD3CN, 293 K): δ 1.0 (s). Determination of the JH-D Value for 2b. An NMR tube was charged with 1-d2 (30 mg, 0.051 mmol), and CD3CN (0.5 mL) was added. After 1.5 h, the 1H{31P} NMR spectra of this solution exhibit in the hydride region the resonances due to a mixture of the [Os](η2H-D) and the [Os](η2-H-H) 2b species. JH-D ) 17.1 f dH-H(calcd) ) 1.13 Å. Preparation of cis-[OsCl(η2-H2)(CH3CN)2(PiPr3)2]BF4 ([3a]BF4). A solution of 1 (481 mg, 0.824 mmol) in 15 mL of acetonitrile was treated with AgBF4 (160 mg, 0.824 mmol) in the absence of light. After the mixture was stirred for 4 h at room temperature, the suspension was filtered through Celite and the filtrate was evaporated to dryness. The residue was washed with diethyl ether (4 × 5 mL) to afford a white solid. Yield: 426 mg (72%). Anal. Calcd for C22H50BF4ClN2OsP2: C, 36.84; H, 7.02; N, 3.90. Found: C, 36.78; H, 7.12; N, 3.99. IR (Nujol, cm-1): ν(CtN) 2283 (w); ν(Os-H2) 2106 (br); ν(BF) 1051 (vs). 1H NMR (300 MHz, CD2Cl2, 293 K): δ 2.72 and 2.67 (both s, 6H, CH3CN), 2.61 (m, 6H, PCH), 1.33 (dvt, N ) 13.2, JH-H ) 6.9, 18H, PCHCH3), 1.32 (dvt, N ) 13.3, JH-H ) 7.0, 18H, PCHCH3), -8.99 (t, JH-P ) 9.8, 2H, OsH2). 31 P{1H} NMR (121.4 MHz, CD2Cl2, 293 K): δ 5.8 (s). 13C{1H} NMR (75.4 MHz, CD2Cl2, 293 K): δ 126.2 and 123.1 (both s, CN), 22.5 (vt, N ) 25.0, PCH), 18.3 and 18.2 (both s, PCHCH3), 3.8 and 3.4 (both s, CH3CN). T1(min) (ms, CD2Cl2, 400 MHz, -9.08, 228 K): 21 ((1) f dH-H(calcd) ) 1.1 Å. Determination of the JH-D Value for 3a. An NMR tube was charged with 1-d2 (30 mg, 0.051 mmol) and CD3CN (0.5 mL). After
Organometallics, Vol. 28, No. 5, 2009 1585 1.5 h, the 1H{31P} NMR spectra of this solution exhibit in the hydride region the resonances due to a mixture of the [Os](η2H-D) and the [Os](η2-H-H) 2b and 3a species. JH-D ) 24.7 f dH-H(calcd) ) 1.00 Å. Preparation of cis-[OsCl(η2-H2)(CH3CN)2(PiPr3)2]PF6 ([3a]PF6). Compound [3a]PF6 was prepared in the same way as [3a]BF4, with TlPF6 (102 mg, 291 mmol) and 1 (170 mg, 291 mmol). Yield: 162 mg (75%). Preparation of trans-[OsCl(η2-H2)(CH3CN)2(PiPr3)2]PF6 ([3b]PF6). A solution of 1 (506 mg, 0.866 mmol) in 15 mL of acetonitrile was treated with TlPF6 (302 mg, 0.866 mmol) in the absence of light. After the mixture was stirred for 4 h at room temperature, the suspension was filtered through Celite. The resulting solution was heated at 60 °C for 2 h and evaporated to dryness. The residue was washed with diethyl ether (5 × 5 mL) to afford a white solid. Yield: 524 mg (78%). Anal. Calcd for C22H50F6ClN2OsP3: C, 34.08; H, 6.50; N, 3.61. Found: C, 34.02; H, 6.46; N, 3.75. IR (Nujol, cm-1): ν(CtN) 2282 (m); ν(Os-H2) 2135 (w), 2162 (w); ν(PF6) 843 (vs), 557 (vs). 1H NMR (300 MHz, CD2Cl2, 293 K): δ 2.62 (m, 6H, PCH), 2.51 (s, 6H, CH3CN), 1.34 (dvt, N ) 13.6, JH-H ) 7.0, 36H, PCHCH3), -10.29 (t, JH-P ) 10.4, 2H, OsH2). 31P{1H} NMR (121.4 MHz, CD2Cl2, 293 K): δ 5.5 (s). 13C{1H} NMR (100.6 MHz, CD2Cl2, 293 K): δ 120.1 (s, CN), 23.5 (vt, N ) 21.0, PCH), 19.6 (s, PCHCH3), 4.1 (s, CH3CN). T1(min) (ms, CD2Cl2, 400 MHz, -10.55, 228 K): 23 ((1) f dH-H(calcd) ) 1.1 Å. Determination of the JH-D Value for 3b. An NMR tube was charged with 1-d2 (30 mg, 0.051 mmol) and CD3CN (0.5 mL). After 2 h at 60 °C, the 1H{31P} NMR spectra of this solution exhibit in the hydride region the resonances due to a mixture of the [Os](η2H-D) and the [Os](η2-H-H) 3b species. JH-D ) 19.3 f dH-H(calcd) ) 1.09 Å. Preparation of [OsH(η4-COD)(CH3CN)2(PiPr3)]PF6 (5). A solution of 4 (250 mg, 0.320 mmol) and 1,5-cyclooctadiene (118 µL, 0.959 mmol) in toluene (15 mL) was refluxed for 4 h. After that time, the mixture was evaporated to dryness and 20 mL of CH2Cl2 was added. The suspension was filtered through Celite. The resulting solution was evaporated to dryness. The residue was washed with methanol (2 × 5 mL) and diethyl ether (2 × 5 mL) to afford a white solid. Yield: 51 mg (23%). Anal. Calcd for C21H40P2F6N2Os: C, 36.72; H, 5.87; N, 4.07. Found: C, 36.48; H, 5.98; N, 3.71. IR (Nujol, cm-1): ν(CtN) 2280 (w); ν(Os-H) 2126 (w); ν(PF6) 828 (vs), 554 (vs). 1H NMR (400 MHz, CD2Cl2, 293 K): δ 4.10 (m, 1H, CH-COD), 3.35 (m, 2H, CH-COD), 3.07 (m, 1H, CH-COD), 2.61 and 2.45 (both s, 6H, CH3CN), 2.33 (m, 2H, CH2-COD), 2.25-1.80 (m, 6H, CH2-COD), 2.13 (m, 3H, PCH), 1.19 (dd, JH-P ) 12.8, JH-H ) 6.8, 9H, PCHCH3), 1.17 (dd, JH-P ) 13.2, JH-H ) 6.4, 9H, PCHCH3), -10.99 (d, JH-P ) 21.4, 1H, OsH). 31P{1H} NMR (161.9 MHz, CD2Cl2, 293 K): δ 10.0 (s). 13C{1H} NMR (100.6 MHz, CD2Cl2, 293 K): δ 127.1 and 122.6 (both s, CN), 75.3 (d, JC-P ) 9.1, CH-COD), 74.7 (d, JC-P ) 13.6, CH-COD), 60.9 and 57.9 (both s, 2H, CH-COD), 35.9 (d, JC-P ) 3.4, CH2-COD), 33.4 (s, CH2-COD), 32.5 (d, JC-P ) 3.9, CH2-COD), 27.0 (d, JC-P ) 1.8, CH2-COD), 25.0 (d, JC-P ) 23.8, PCH), 19.6 (s, PCHCH3), 19.2 (d, JC-P ) 1.6, PCHCH3), 4.3 and 4.0 (both s, CH3CN).
Acknowledgment. Financial support from the MICINN of Spain (Project No. CTQ2008-00810 and Consolider Ingenio 2010 CSD2007-00006) and the Diputacio´n General de Arago´n (E35) is acknowledged. Supporting Information Available: Text giving details of the X-ray analysis and crystal structure determination and a CIF file giving crystal data for 3b and 5. This material is available free of charge via the Internet at http://pubs.acs.org. OM801057Z
