Synthesis, Structures, and Reactivity of Ruthenium(II) Nitrosyl Tri- and

(8) It is believed that the Ir(bpy)-catalyzed borylation involves the oxidative addition ... Chemical shifts (δ, ppm) were reported with reference to...
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5794

Organometallics 2009, 28, 5794–5801 DOI: 10.1021/om900598j

Synthesis, Structures, and Reactivity of Ruthenium(II) Nitrosyl Tri- and Dialkyl Complexes Ka-Wang Chan, Enrique Kwan Huang, Ian D. Williams, and Wa-Hung Leung* Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, People’s Republic of China Received July 9, 2009

Treatment of Ru(dtbpy)(NO)Cl3 (dtbpy=4,40 -di-tert-butyl-2,20 -bipyridyl) (1) with Me3SiCH2MgCl afforded the trialkyl compound mer-Ru(dtbpy)(NO)(CH2SiMe3)3 (2), which exhibits νNO at 1741 cm-1 in the IR spectrum. The solid-state structure of 2 shows a mer arrangement for the three alkyl groups and that the nitrosyl is trans to dtbpy. Protonation of 2 with HX afforded the dialkyl compounds cis, cis-Ru(dtbpy)(CH2SiMe3)(NO)X (X=Cl (3), OTs (4)), in which X is trans to an alkyl group. Treatment of 3 with AgOTf (OTf-=triflate) afforded cis,cis-Ru(dtbpy)(CH2SiMe3)2(NO)(OTf) (5), which reacted with amines RNH2 to give the adducts cis,cis-[Ru(dtbpy)(CH2SiMe3)2(NO)(NH2R)][OTf] (R=meistyl (6), 4-tol (7)). Substitution of 5 with NaOR led to the isolation of cis,trans-Ru(dtbpy)(CH2SiMe3)2(NO)(OR) (R=Ph (8), SiMe3 (9), SiPh3 (10)), in which the nitrosyl is trans to OR-, whereas that with NaSR gave cis,cis-Ru(dtbpy)(CH2SiMe3)2(NO)(SR) (R=2,6-Me2C6H4 (11), SiPh3 (12)). Treatment of 5 with K[OsO3N] afforded the bimetallic complex cis,cis-Ru(dtbpy)(CH2SiMe3)2(NO)(NOsO3) (13), containing an unsymmetrical Os(VIII)tN-Ru(II) bridge. The crystal structures of 2-5, 7-10, 12, and 13 have been determined. Introduction Ruthenium complexes with polypyridyl ligands, notably 2,20 -bipyridyl (bpy), are of interest due to their applications to redox and photochemical catalysis.1 While the coordination chemistry of Ru(bpy)n (n = 1, 2, 3) compounds has been studied extensively, Ru(bpy) compounds with σ-alkyl ligands are rather uncommon.2,3 To our knowledge, Ru(bpy) trialkyl compounds have not been synthesized to date, although Ru poly-alkyl/aryl compounds such as Ru2R6 (R= CH2CMe3, CH2SiMe3),4 RuR4 (R = o-tol, mesityl),5 [Li(tmed)2][RuMe6],6 and [Ru(N)RnX4-n]- (R=Me, CH2SiMe3)7 are known. Our interest in bpy-supported transition-metal alkyl compounds is stimulated by recent reports that Ir(bpy) compounds can catalyze selective borylation of arenes with borane and *To whom correspondence should be address. E-mail: [email protected]. (1) (a) Balzani, V.; Juris, A.; Venturi, M.; Campagna, S.; Serroni, S. Chem. Rev. 1996, 96, 759. (b) Juris, A.; Balzani, V.; Barigelletti, F.; Campagna, S.; Belser, P.; von Zelewsky, A. Coord. Chem. Rev. 1988, 84, 85. (2) (a) Nieuwenhuis, H. A.; Stufkens, D. J.; Oskam, A. Inorg. Chem. 1994, 3212. (b) Rohde, W.; tom Dieck, H. J. Organomet. Chem. 1987, 328, 209. (c) tom Dieck, H.; Rohde, W.; Behrens, U. Z. Narurforsch. 2 1989, 44B, 158. (3) Black, S. I.; Skapski, A. C.; Young, G. B. J. Chem. Soc., Chem. Commun. 1989, 911. (4) Tooze, R.; Wilkinson, G.; Motevalli, M.; Hursthouse, M. B. J. Chem. Soc., Dalton Trans. 1986, 2711. (5) (a) Savage, P. D.; Wilkinson, G.; Motevalli, M.; Hursthouse, M. B. J. Chem. Soc., Dalton Trans. 1988, 669. (b) Hay-Motherwell, R. S.; Wilkinson, G.; Hussain-Bates, B.; Hursthouse, M. B. J. Chem. Soc., Dalton Trans. 1992, 3477. (6) Hay-Motherwell, R. S.; Wilkinson, G.; Hussain-Bates, B.; Hursthouse, M. B. Polyhedron 1990, 9, 2071. (7) Shapley, P. A.; Kim, H. S.; Wilson, S. R. Organometallics 1988, 7, 928. pubs.acs.org/Organometallics

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diboron reagents under mild conditions.8 It is believed that the Ir(bpy)-catalyzed borylation involves the oxidative addition of arene C-H bonds with Ir(III) boryl intermediates.9 This suggests that electron-donating bpy can serve as a good spectator ligand for high-valent transition-metal alkyl/aryl complexes. Recently, we have isolated Ir and Rh alkyl and aryl compounds with 4,40 -di-tert-butyl-2,20 -bipyridyl (dtbpy) that were found to exhibit interesting reactivity, e.g., C-H activation and C-Si cleavage.10 This prompted us to synthesize analogous Ru(dtbpy) trialkyl compounds and investigate their organometallic chemistry. A common method to synthesize Ru σ-alkyl compounds involves transmetalation of Ru chloride compounds with alkylating agents such as alkyl lithium and Grignard reagents. Young and co-workers synthesized the dialkyl compounds Ru(dtbpy)2R2 (R = Me, Et, CH2-cyclo-C6H11, CH2SiMe2CHdCH2, CH2SiMe3, CH2SiMe2Ph, CH2CMe2Ph) from Ru(dtbpy)2Cl2 and the corresponding Grignard reagents.3 However, Ru(dtbpy)Cl3, which is a precursor to Ru trialkyl compounds, is unknown. We then turned our attention to Ru(NO)(dtbpy)R3 because Ru(bpy) nitrosyl complexes are usually photolabile and the nitrosyl ligand (8) (a) Ishiyama, T.; Takagi, J.; Hartwig, J. F.; Miyaura, N. Angew. Chem., Int. Ed. 2002, 41, 3056. (b) Ishiyama, T.; Takagi, J.; Ishida, K.; Miyaura, N.; Anastasi, N.; Hartwig, J. F. J. Am. Chem. Soc. 2002, 124, 390. (c) Ishiyama, T.; Miyaura, N. J. Organomet. Chem. 2003, 680, 3. (9) (a) Kunz, D.; Hartwig, J. F.; Webster, C. E.; Fan, Y. B.; Hall, M. B. J. Am. Chem. Soc. 2003, 125, 858. (b) Tamura, H.; Yamazaki, H.; Sato, H.; Sakaki, S. J. Am. Chem. Soc. 2003, 125, 16114. (c) Boller, T. M.; Murphy, J. M.; Hapke, M.; Ishiyama, T.; Miyaura, N.; Hartwig, J. F. J. Am. Chem. Soc. 2005, 127, 14263. (10) (a) Sau, Y. K.; Chan, K. W.; Zhang, Q. F.; Williams, I. D.; Leung, W. H. Organometallics 2007, 26, 6338. (b) Sau, Y. K.; Lee, H. K.; Williams, I. D.; Leung, W. H. Chem.-Eur. J. 2006, 12, 9323. r 2009 American Chemical Society

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can be easily removed by photolysis.11 In addition, photoactive Ru nitrosyl compounds are important in their own right because they can function as NO donors under biological conditions.12 Although organometallic nitrosyl compounds are well documented,13 Ru nitrosyl compounds with σ-alkyl ligands are rather rare.14 Herein, we describe the synthesis and structure of the first Ru nitrosyl trialkyl compounds, mer-Ru(dtbpy)(NO)(CH2SiMe3)3. The protonation of mer-Ru(dtbpy)(NO)(CH2SiMe)3 with acids to give dialkyl complexes has been studied. The synthesis and crystal structures of Ru(dtbpy) dialkyl complexes with siloxide, phenoxide, and thiolate ligands as well as a bimetallic nitridobridged Ru(II)/Os(VIII) complex will also be reported.

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Scheme 1. Syntheses of Ru(dtbpy) Tri- and Dialkyl Complexes

Experimental Section General Considerations. All manipulations were carried out under nitrogen by standard Schlenk techniques. Solvents were purified, distilled, and degassed prior to use. NMR spectra were recorded on a Varian Mercury 300 spectrometer operating at 300 and 282.4 MHz for 1H and 19F, respectively. Chemical shifts (δ, ppm) were reported with reference to SiMe4 (1H) and C6H5CF3 (19F). Infrared spectra were recorded on a PerkinElmer 16 PC FT-IR spectrophotometer; mass spectra, on a Finnigan TSQ 7000 spectrometer. Elemental analyses were performed by Medac Ltd., Surrey, UK. Ru(NO)Cl3 3 xH2O and 4,40 -di-tert-butyl-2,20 -bipyridyl (dtbpy) were obtained from Strem and Aldrich Ltd., respectively. K[OsO3N] was synthesized according to a literature method.15 A hydrogen atom labeling scheme of the dtbpy ligand is shown in Scheme 1. Preparation of Ru(dtbpy)(NO)Cl3 (1). To a solution of Ru(NO)Cl3 3 xH2O (200 mg, 0.78 mmol) in MeOH (2 mL) was added dtbpy (210 mg, 0.78 mmol), and the mixture was heated at reflux for 1 h. The precipitate was collected and washed with methanol (3  2 mL) and Et2O (3  2 mL). Recrystallization from CH2Cl2/hexane afforded a dark pink powder. Yield: 272 mg (69%). 1H NMR (300 MHz, CD2Cl2): δ 1.49 (s, 18H, t-Bu), 7.78 (d, J=5.9 Hz, 2H, H5), 8.22 (s, 2H, H3), 9.52 (d, J=6.2 Hz, 2H, H6). IR (KBr, cm-1): 1871 (νNO). MS (FAB): m/z 470 (Mþ - Cl). Anal. Calcd for C18H24Cl3N3ORu 3 1/4CH2Cl2: C, 41.57; H, 4.69; N, 7.97. Found: C, 42.06; H, 4.17; N, 7.42. Preparation of mer-Ru(dtbpy)(NO)(CH2SiMe3)3 (2). To a suspension of 1 (100 mg, 0.20 mmol) in tetrahydrofuran (THF) (6 mL) was added Me3SiCH2MgCl (0.54 mL of a 1.3 M solution in THF, 0.70 mmol) at -78 °C. The mixture was stirred at room temperature for 5 h, and the volatiles were removed in vacuo. The residue was extracted with hexane. Concentration and cooling at -4 °C gave deep red crystals, which were suitable for X-ray analysis. Yield: 84 mg (65%). 1H NMR (300 MHz, C6D6): δ -0.55 (d, J=12.5 Hz, 2H, CH2SiMe3), 0.02 (s, 18H, CH2SiMe3), 0.71 (s, 9H, CH2SiMe3), 0.85 (s, 9H, t-Bu), 1.01 (s, 9H, t-Bu), 1.24 (d, J=12.5 Hz, 2H, CH2SiMe3), 1.59 (s, 2H, CH2SiMe3), 6.49 (d, J=6.2 Hz, 1H, H5), 6.66 (d, J=5.7 Hz, 1H, H5), 7.81 (s, 1H, H3), 7.96 (s, 1H, H3), 8.60 (d, J=6.2 Hz, 1H, H6), 8.97 (d, J=5.7 Hz, 1H, H6). IR (KBr, cm-1): 1741 (νNO). MS (FAB): m/z 574 (11) (a) Callahan, R. W.; Meyer, T. J. Inorg. Chem. 1977, 16, 574. (b) Sauaia, M. G.; Oliveira, F. S.; Tedesco, A. C.; da Silva, R. S. Inorg. Chim. Acta 2003, 355, 191. (c) Sauaia, M. G.; de Lima, R. G.; Tedesco, A. C.; da Silva, R. S. J. Am. Chem. Soc. 2003, 125, 14718. (12) (a) Rose, M. J.; Mascharak, P. K. Coord. Chem. Rev. 2008, 252, 2093. (b) Tfouni, E.; Krieger, M.; McGarvey, B. R.; Franco, D. W. Coord. Chem. Rev. 2003, 236, 57. (13) Hayton, T. W.; Legzdins, P.; Sharp, W. B. Chem. Rev. 2001, 101, 935. (14) (a) Chang, J.; Seidler, M. D.; Bergman, R. G. J. Am. Chem. Soc. 1989, 111, 3258. (b) Chang, J.; Bergman, R. G. J. Am. Chem. Soc. 1987, 109, 4298. (c) Seidler, M. D.; Bergman, R. G. J. Am. Chem. Soc. 1984, 106, 6110. (d) Hodge, S. J.; Wang, L.-S.; Khan, M. A.; Young, V. G., Jr; Richter-Addo, G. B. Chem. Commun. 1996, 2283. (15) Clifford, A. F.; Kobayashi, C. S. Inorg. Synth. 1960, 6, 204.

(Mþ - CH2SiMe3 þ 1). Despite several attempts, we have not been able to obtain satisfactory elemental analysis (particularly the carbon content). Nevertheless, this compound has been well characterized by spectroscopic methods and X-ray diffraction. Preparation of cis,cis-Ru(dtbpy)(CH2SiMe3)2(NO)Cl (3). To a solution of 2 (138 mg, 0.21 mmol) in hexane (4 mL) was added HCl (0.06 mL of a 3.5 M solution in Et2O, 0.21 mmol) at -78 °C, and the mixture was stirred at room temperature for 3 h. The red precipitate was collected, washed with hexane, and recrystallized from CH2Cl2/Et2O/hexane to give reddish-brown crystals, which were suitable for X-ray analysis. Yield: 109 mg (85%). 1H NMR (300 MHz, C6D6): δ -0.11 (s, 9H, CH2SiMe3), 0.62 (d, J= 12.9 Hz, 2H, CH2SiMe3), 0.76 (s, 9H, CH2SiMe3), 0.85 (s, 9H, tBu), 0.94 (s, 9H, t-Bu), 1.89 (d, J=12.9 Hz, 1H, CH2SiMe3), 2.06 (d, J = 9.4 Hz, 1H, CH2SiMe3), 2.84 (d, J = 9.4 Hz, 1H, CH2SiMe3), 6.54 (d, J = 7.9 Hz, 1H, H5), 6.72 (d, J = 7.6 Hz, 1H, H5), 7.70 (s, 1H, H3), 7.80 (s, 1H, H3), 8.70 (d, J=6.2 Hz, 1H, H6), 8.75 (d, J=5.9 Hz, 1H, H6). IR (KBr, cm-1): 1773 (νNO). Anal. Calcd for C26H46ClN3ORuSi2 3 3/4CH2Cl2: C, 47.73; H, 7.12; N, 6.25. Found: C, 47.84; H, 7.19; N, 6.34. Preparation of cis,cis-Ru(dtbpy)(CH2SiMe3)2(NO)(OTs) (OTs= tosylate) (4). To a solution of 2 (100 mg, 0.15 mmol) in hexane was added p-toluenesulfonic acid (24 mg, 0.15 mmol) at -78 °C, and the mixture was stirred at room temperature for 24 h. The purple precipitate was collected and washed with Et2O and hexane. Recrystallization from CH2Cl2/Et2O/hexane afforded purple crystals that were suitable for X-ray analysis. Yield: 75 mg (72%). 1H NMR (300 MHz, C6D6): δ -0.11 (s, 9H, CH2SiMe3), 0.61 (s, 9H, CH2SiMe3), 0.85 (s, 9H, t-Bu), 1.03 (s, 9H, t-Bu), 1.29 (d, J = 12.6 Hz, 1H, CH2SiMe3), 1.73 (d, J=12.6 Hz, 1H, CH2SiMe3), 1.83 (s, 3H, Me), 1.96 (d, J = 10.0 Hz, 1H, CH2SiMe3), 2.06 (d, J = 10.0 Hz, 1H, CH2SiMe3), 6.57 (d, J=5.6 Hz, 1H, H5), 6.67 (d, J= 7.9 Hz, 2H, Ho of tosyl), 6.96 (d, J=5.9 Hz, 1H, H5), 7.79 (s, 1H, H3), 7.88 (d, J=7.9 Hz, 2H, Hm of tosyl), 7.92 (s, 1H, H3), 8.68 (d, J=6.2 Hz, 1H, H6), 9.14 (d, J=5.9 Hz, 1H, H6). IR (KBr, cm-1): 1803 (νNO). Anal. Calcd for C33H53N3O4RuSSi2: C, 53.20; H, 7.17; N, 5.64. Found: C, 53.21; H, 7.53; N, 5.48. Preparation of cis,cis-Ru(dtbpy)(CH2SiMe3)2(NO)(OTf) (5). To a solution of 3 (172 mg, 0.28 mmol) in CH2Cl2 (4 mL) was added AgOTf (75 mg, 0.29 mmol). The mixture was stirred at room temperature for 5 h and filtered and evaporated to dryness. Recrystallization from hexane at -4 °C gave purple crystals that were suitable for X-ray analysis. Yield: 162 mg

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(80%). 1H NMR (300 MHz, C6D6): δ -0.20 (s, 9H, CH2SiMe3), 0.61 (s, 9H, CH2SiMe3), 0.77 (d, J=12.9 Hz, 2H, CH2SiMe3), 0.86 (s, 9H, t-Bu), 0.95 (d, J = 12.9 Hz, 2H, CH2SiMe3), 1.01 (s, 9H, t-Bu), 1.83 (d, J=10.0 Hz, 2H, CH2SiMe3), 1.95 (d, J= 10.0 Hz, 2H, CH2SiMe3), 6.59 (d, J=5.3 Hz, 1H, H5), 6.91 (d, J= 7.6 Hz, 1H, H5), 7.83 (s, 1H, H3), 7.96 (s, 1H, H3), 8.58 (d, J= 6.2 Hz, 1H, H6), 8.80 (d, J = 5.3 Hz, 1H, H6). 19F NMR (282 MHz, C6D6): δ -78.24 (OTf). IR (KBr, cm-1): 1809 (νNO). Anal. Calcd for C27H46F3N3O4RuSSi2 3 0.5C6H14: C, 47.04; H, 6.97; N, 5.49. Found: C, 47.00; H, 7.15; N, 5.36. Preparation of cis,cis-[Ru(dtbpy)(CH2SiMe3)2(NO)(NH2R)][OTf] (R = 2,4,6-Me3C6H2 (6), 4-tol (7)). To a solution of 5 (40 mg, 0.055 mmol) in THF (10 mL) was added NH2R (0.057 mmol), and the mixture was stirred at room temperature for 3 h. The volatiles were removed in vacuo, and the residue was washed with hexane. Recrystallization from CH2Cl2/ hexane at -30 °C gave a brown solid. For 6: Yield: 28 mg (60%). 1H NMR (300 MHz, C6D6): δ -0.21 (s, 9H, CH2SiMe3), 0.57 (s, 9H, CH2SiMe3), 0.78 (m, 3H, NH2C6H2Me3 and CH2SiMe3), 0.91 (s, 9H, t-Bu), 1.06 (s, 9H, t-Bu), 1.19 (d, J=13.0 Hz, 1H, CH2SiMe3), 1.79 (d, J=12.3 Hz, 1H, CH2SiMe3), 1.90 (s, 6H, NH2), 1.95 (d, J = 13.1 Hz, 1H, CH2SiMe3), 2.20 (s, 3H, Me), 6.63 (br s, 1H, H5), 6.73 (s, 2H, Hm of p-tol), 6.90 (d, J=6.0 Hz, 1H, H5), 7.91 (br s, 1H, H3), 8.03 (br s, 1H, H3), 8.55 (d, J=6.0 Hz, 1H, H6), 8.72 (br s, 1H, H6). 19 F NMR (282 MHz, C6D6): δ -78.13 (OTf). IR (KBr, cm-1): 1786 (νNO). Anal. Calcd for C36H59F3N4O4RuSSi2: C, 50.38; H, 6.93; N, 6.53. Found: C, 50.20; H, 7.37; N, 6.58. For 7: Yield: 25 mg (54%). 1H NMR (300 MHz, C6D6): δ -0.32 (s, 9H, CH2SiMe3), 0.29 (s, 9H, CH2SiMe3), 0.55 (br s, 2H, NH2), 1.16 (s, 9H, t-Bu), 1.26 (s, 9H, t-Bu), 1.65 (m, 2H, CH2SiMe3), 1.75 (d, J=10.5 Hz, 1H, CH2SiMe3), 2.04 (s, 3H, Me), 4.78 (d, J= 10.5 Hz, 1H, CH2SiMe3), 6.02 (d, J=10.8 Hz, 1H, H5), 6.41 (d, J= 6.0 Hz, 1H, H5), 6.50 (d, J=8.4 Hz, 2H, Hm of p-tol), 6.65 (d, J= 8.3 Hz, 2H, Ho of p-tol), 7.61 (d, J=5.7 Hz, 1H, H6), 8.37 (s, 1H, H3), 8.44 (s, 1H, H3), 8.54 (d, J=6.0 Hz, 1H, H6). 19F NMR (282 MHz, C6D6): δ -77.80 (OTf). IR (KBr, cm-1): 1779 (vNO). Anal. Calcd for C34H55F3N4O4RuSSi2 3 1/4CH2Cl2: C, 48.32; H, 6.58; N, 6.58. Found: C, 48.02; H, 6.51; N, 6.74. Preparation of cis,trans-Ru(dtbpy)(CH2SiMe3)2(NO)(OPh) (8). To a solution of 5 (100 mg, 0.14 mmol) in THF was added NaOPh (16 mg, 0.14 mmol) at -78 °C. The mixture was stirred for 12 h at room temperature, and the volatiles were removed in vacuo. The residue was washed with hexane and extracted with toluene. Concentration and cooling at -4 °C gave orange crystals that were suitable for X-ray analysis. Yield: 18 mg (19%). 1H NMR (300 MHz, C6D6): δ 0.61 (s, 18H, CH2SiMe3), 0.95 (s, 18H, t-Bu), 2.11 (d, J=12.6 Hz, 2H, CH2SiMe3), 2.37 (d, J=12.6 Hz, 2H, CH2SiMe3), 5.82 (d, J=8.5 Hz, 2H, H5), 6.29 (d, J=7.0 Hz, 1H, OPh), 6.55 (t, J=7.3 Hz, 2H, phenyl), 6.69 (dd, J=5.9 and 2.0 Hz, 2H, phenyl), 7.50 (s, 2H, H3), 8.85 (d, J= 5.6 Hz, 2H, H6). IR (KBr, cm-1): 1771 (νNO). Anal. Calcd for C32H51N3O2RuSi2: C, 57.62; H, 7.71; N, 6.30. Found: C, 57.21; H, 7.98; N, 6.18. Preparation of cis,trans-Ru(dtbpy)(CH2SiMe3)2(NO)(OSiR3) (R=Me (9), Ph (10). To a solution of 5 (100 mg, 0.14 mmol) in THF was added NaOSiR3 (0.14 mmol) at -78 °C. The mixture was stirred for 12 h at room temperature, and the volatiles were removed in vacuo. The residue was washed with hexane and was then extracted with toluene. Concentration and cooling at -4 °C gave orange crystals that were suitable for X-ray analysis. For 9: Yield: 64 mg (69%). 1H NMR (300 MHz, C6D6): δ -0.35 (s, 9H, OSiMe3), 0.62 (s, 18H, CH2SiMe3), 0.95 (s, 18H, t-Bu), 1.93 (d, J=13.2 Hz, 2H, CH2SiMe3), 2.10 (d, J=13.2 Hz, 2H, CH2SiMe3), 6.86 (dd, J=7.2 Hz and 1.8 Hz, 2H, H5), 7.84 (d, J=1.5 Hz, 2H, H3), 8.97 (d, J=2.9 Hz, 2H, H6). IR (KBr, cm-1): 1768 (vNO) Anal. Calcd for C29H55N3O2RuSi3: C, 52.53; H, 8.36; N, 6.34. Found: C, 52.08; H, 8.38; N, 6.61. For 10: Yield: 74 mg (61%). 1H NMR (300 MHz, C6D6): δ 0.55 (s, 18H, CH2SiMe3), 0.97 (s, 18H, t-Bu), 2.01 (d, J=13.2 Hz, 2H,

Chan et al. CH2SiMe3), 2.45 (d, J=13.2 Hz, 2H, CH2SiMe3), 6.82 (dd, J= 7.7 and 1.7 Hz, 2H, H5), 7.01-7.07 (m, 9H, phenyl), 7.41 (dd, J= 7.4 and 1.9 Hz, 6H, Ph), 7.59 (d, J=1.7 Hz, 2H, H3), 8.89 (d, J= 5.5 Hz, 2H, H6). IR (KBr, cm-1): 1766 (νNO). Anal. Calcd for C44H61N3O2RuSi3: C, 62.22; H, 7.24; N, 4.95. Found: C, 62.15; H, 7.26; N, 4.86. Preparation of cis,cis-Ru(dtbpy)(CH2SiMe3)2(NO)(SC6H3Me2-2,6) (11). To a solution of 2,6-dimethylbenzenethiol (7.6 mg, 0.055 mmol) in THF was added NaH (5 mg, 0.13 mmol, 60% in mineral oil). The reaction mixture was stirred at room temperature for 30 min, and a solution of 5 (40 mg, 0.055 mmol) in THF (10 mL) was added at 0 °C. The resulting mixture was stirred at room temperature for 12 h. The solvent was removed in vacuo, and the residue was extracted with Et2O/hexane (1:1, v/v). Concentration and cooling at -4 °C gave an orange powder. Yield: 27 mg (72%). 1H NMR (300 MHz, C6D6): δ 0.13 (s, 9H, CH2SiMe3), 0.22 (d, J = 12.6 Hz, 1H, CH2SiMe3), 0.80 (s, 9H, CH2SiMe3), 0.90 (s, 9H, t-Bu), 0.99 (s, 9H, t-Bu), 1.67 (d, J=12.8 Hz, 1H, CH2SiMe3), 1.85 (d, J=9.6 Hz, 1H, CH2SiMe3), 1.94 (br s, 6H, Me), 2.42 (d, J=9.6 Hz, 1H, CH2SiMe3), 6.36 (d, J=1.8 Hz, 1H, H5), 6.39 (d, J = 1.9 Hz, 1H, H5), 6.48 (d, J = 6.6 Hz, 2H, phenyl), 7.01 (t, J=6.6 Hz, 1H, phenyl), 7.32 (d, J=1.5 Hz, 1H, H3), 7.54 (d, J=1.8 Hz, 1H, H3), 8.43 (d, J=6.0 Hz, 1H, H6), 8.66 (d, J=6.3 Hz, 1H, H6). IR (KBr, cm-1): 1760 (νNO). Anal. Calcd for C34H55N3ORuSSi2: C, 57.43; H, 7.80; N, 5.91. Found: C, 57.53; H, 8.29; N, 6.11. Preparation of cis,cis-Ru(dtbpy)(CH2SiMe3)2(NO)(SSiPh3) (12). This compound was prepared similarly to complex 11 using Ph3SiSH in place of 2,6-dimethylbenzenethiol. Yield: 38 mg (80%). 1H NMR (300 MHz, C6D6): δ -0.21 (s, 9H, CH2SiMe3), -0.01 (d, J=12.6 Hz, 1H, CH2SiMe3), 0.79 (s, 9H, CH2SiMe3), 0.92 (s, 9H, t-Bu), 0.95 (s, 9H, t-Bu), 1.65 (d, J= 12.6 Hz, 1H, CH2SiMe3), 1.88 (d, J=9.6 Hz, 1H, CH2SiMe3), 2.48 (d, J=9.6 Hz, 1H, CH2SiMe3), 6.46 (d, J=5.8 Hz, 1H, H5), 6.51 (d, J=6.0 Hz, 1H, H5), 7.05 (m, 9H, phenyl), 7.41 (s, 1H, H3), 7.43 (s, 1H, H3), 7.77 (m, 6H, phenyl), 8.03 (d, J=5.7 Hz, 1H, H6), 8.72 (d, J = 6.3 Hz, 1H, H6). IR (KBr, cm-1): 1775 (νNO). Anal. Calcd for C44H61N3ORuSSi3 3 1/2H2O: C, 60.44; H, 7.15; N, 4.81. Found: C, 60.44; H, 7.21; N, 4.64. Preparation of cis,cis-Ru(dtbpy)(CH2SiMe3)2(NO)(NOsO3) (13). To a solution of 5 (50 mg, 0.07 mmol) in THF was added KOsO3N (20 mg, 0.07 mmol) at -78 °C. The mixture was stirred for 12 h at room temperature, and the volatiles were removed in vacuo. The residue was washed with hexane and extracted with toluene. Concentration and cooling at -4 °C gave red crystals that were suitable for X-ray analysis. Yield: 20 mg (35%). 1H NMR (300 MHz, C6D6): δ -0.12 (s, 9H, CH2SiMe3), 0.29 (s, 2H, CH2SiMe3), 0.59 (s, 9H, CH2SiMe3), 0.78 (d, J=12.6 Hz, 1H, CH2SiMe3), 0.91 (s, 9H, t-Bu), 0.97 (s, 9H, t-Bu), 1.63 (d, J= 12.6 Hz, 1H, CH2SiMe3), 6.63 (dd, J=5.9 and 1.8 Hz, 1H, H5), 6.77 (dd, J=5.9 and 2.1 Hz, 1H, H5), 7.91 (d, J=1.8 Hz, 1H, H3), 7.98 (d, J=1.6 Hz, 1H, H3), 8.37 (d, J=5.7 Hz, 1H, H6), 8.44 (d, J=5.7 Hz, 1H, H6). IR (KBr, cm-1): 1806 (νNO), 1030 (νOsN), 901, 886 (νOsO). Anal. Calcd for C26H46N4O4OsRuSi2: C, 37.80; H, 5.61; N, 6.78. Found: C, 37.69; H, 5.60; N, 6.76. X-ray Crystallography. Preliminary examinations and intensity data collection were carried out on a Bruker SMART-APEX 1000 area-detector diffractometer using graphite-monochromated Mo KR radiation (λ=0.70173 A˚). The collected frames were processed with the software SAINT.16 The data were corrected for absorption using the program SADABS.17 Structures were solved by direct methods and refined by full-matrix least-squares on F2 using the SHELXTL software package.17 Unless stated otherwise, non-hydrogen atoms were refined with anisotropic displacement parameters. Carbon-bonded hydrogen atoms were included in (16) Sheldrick, G. M. SADABS; University of G€ottingen: Germany, 1997. (17) Sheldrick, G. M. SHELXTL-Plus V5.1 Software Reference Manual; Bruker AXS Inc.: Madison, WI, 1997.

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calculated positions and refined in the riding mode using SHELXL97 default parameters. In 3, one of the t-Bu groups of dtbpy was found to be disordered, and each of the carbon atoms C(22), C(23), and C(24) was split into two sites with occupancies of 0.55 and 0.45. In 5, the fluorine atoms F(1), F(2), and F(3) of the triflate ligand were found to be 50:50 disordered. In 7, the C(28) of the p-tolNH2 ligand, C(37) of dtbpy, and F(1)-F(3) and O(2)O(4) atoms of the triflate counteranion were found to be 50:50 disordered. In 10, one of the t-Bu groups in dtbpy was found to be disordered. Each of the carbon atoms C(42)-C(44), C(47), and C(48) was split into two sites with occupancies of 0.75 and 0.25, while C(46) was split into three sites with occupancies of 0.65, 0.25, and 0.1.

Results and Discussion Ruthenium Trialkyl Complex. Alkylation of the trichloride compound Ru(dtbpy)(NO)Cl3 (1) with a variety of alkylating agents including alkyl lithium and Grignard reagents has been attempted. In most cases, dark intractable materials were formed. However, for the alkylation of 1 with Me3SiCH2MgCl, a red crystalline, hexane-soluble product was obtained. Recrystallization from hexane afforded single crystals identified as mer-Ru(dtbpy)(NO)(CH2SiMe3)3 (2) in 65% yield. 2 is moderately air stable in the solid state, but air sensitive in solutions. The 1H NMR spectrum showed two singlets at δ 1.01 and 1.81 due to the tert-butyl groups of the dtbpy ligand. The methyl protons of the equatorial and axial alkyl groups appeared as two singlets in a 1:2 ratio at δ 0.88 and 0.98, indicative of the mer arrangement of the three alkyl groups. The two doublets at δ -0.55 and 1.24 were assigned to the methylene protons of the axial alkyl groups, whereas a singlet at δ 2.60 was observed for those of the equatorial one. The positive-ion FAB spectrum of 2 showed a molecular ion peak at m/z 574 corresponding to [Mþ - CH2SiMe3 þ 1]. Ruthenium Dialkyl Complexes. Protonation of 2 with HCl in hexane led to formation of a red precipitate characterized as the dialkyl compound cis,cis-Ru(dtbpy)(CH2SiMe3)2(NO)Cl (3). Di- or trichloride compounds were not formed even when excess HCl was used for the protonation. Unlike 2, 3 is air stable in both the solid state and solution. In the 1H NMR spectrum, the SiMe3 protons appeared as two singlets at δ -0.11 and 0.76 and the methylene protons appeared as four doublets at δ 0.62, 1.89, 2.06, and 2.84, indicating that the two alkyl groups are cis to each other. Similarly, protonation of 2 with p-toluenesulfonic acid (HOTs) afforded the dialkyl compound cis,cis-Ru(dtbpy)(CH2SiMe3)2(NO)(OTs) (4), which exhibited a similar 1H NMR spectrum to that of 3 (except for resonances of the tosylate ligand). Attempts to prepare mixed alkyl compounds, Ru(dtbpy)(CH2SiMe3)2(NO)(R), by alkylation of 3 or 4 with alkylating agents such as PhMgBr and PhLi were unsuccessful. Treatment of 3 with silver triflate (AgOTf) in CH2Cl2 afforded the triflate compound cis,cis-Ru(dtbpy)(CH2SiMe3)2(NO)(OTf) (5), which could also be prepared by direct protonation of 2 with triflic acid. It may be noted that the reactions of 2 with HX (X=Cl, OTs, OTf) resulted in selective cleavage of the axial rather than equatorial Ru-C bond. The selective reactivity of 2 with HX can be explained in terms of the relative Ru-C bond strength and/or carbanion character of the alkyl groups. The Ru-C(trans to C) bonds in 2 are longer (as indicated in the solid-state structure, vide infra) and weaker than the Ru-C(trans to N) bond due to the trans influence of the alkyl group, and thus the cleavage of the former is thermodynamically preferred.

Figure 1. Molecular structure of mer-Ru(dtbpy)(NO)(CH2SiMe3)3 (2). Hydrogen atoms are omitted for clarity. The ellipsoids are drawn at the 40% probability level. Selected bond lengths (A˚) and angles (deg): Ru(1)-N(1) 1.693(2), Ru(1)-N(10) 2.139(2), Ru(1)-N(21) 2.128(2), Ru(1)-C(31) 2.188(3), Ru(1)-C(32) 2.132(3), Ru(1)-C(33) 2.202(3); Ru(1)-N(1)-O(1) 175.5(2).

Substitution of 5 with Amines. The triflate ligand in 5 is labile and can be readily replaced by heteroatom ligands. Substitution reactions of 5 are summarized in Scheme 1. Treatment of 5 with amines NH2R afforded the cationic amine complexes cis, cis-[Ru(dtbpy)(CH2SiMe3)2(NO)(NH2R)][OTf] (R = mesityl (6), 4-tol (7)). 1H NMR spectroscopy indicates that the two alkyl groups in each of 6 and 7 are inequivalent and mutually cis, consistent with the solid-state structure (vide infra). Attempts to prepare Ru amido complexes by treatment of 6 and 7 with bases such as n-BuLi and NaN(SiMe3)2 were unsuccessful. Substitution of 5 with Anionic Ligands. Treatment of 5 with sodium phenoxide afforded the phenoxide compound cis, trans-Ru(dtbpy)(CH2SiMe3)2(NO)(OPh) (8). The 1H NMR spectrum of 8 showed two singlets at δ 0.95 and 0.61 assignable to the t-Bu and SiMe3 groups, respectively, indicating that the two cisoid alkyl groups are opposite to the dtbpy ligand. The phenoxide in 8 is situated opposite the nitrosyl apparently due to the “push-pull” effect19 between the π-donating phenoxide and π-accepting nitrosyl ligands. The existence of Ru-O π interaction is also evidenced by the observed short Ru-O distance and large Ru-O-C angle (vide infra). Attempts to replace the triflate in 5 with other alkoxides such as methoxide and tert-butoxide were unsuccessful. However, treatment of 5 with NaOSiR3 led to isolation of the siloxide complexes cis,trans-Ru(dtbpy)(CH2SiMe3)2(NO)(OSiR3) (R=Me (9), Ph (10)). Similar to 8, 1H NMR spectroscopy indicates that in 9 and 10 the two alkyl groups are opposite dtbpy and the nitrosyl is trans to the π-donating siloxide group. Treatment of 5 with NaSR afforded the thiolate compounds cis,cis-Ru(dtbpy)(CH2SiMe3)2(NO)(SR) (R = 2,6-Me2C6H3 (18) Leung, W. H.; Chim, J. L. C.; Wong, W. T. J. Chem. Soc., Dalton Trans. 1997, 3227. (19) (a) Poulton, J. T.; Sigalas, M. P.; Felting, K.; Streib, W. E.; Eisenstein, O.; Caulton, K. G. Inorg. Chem. 1994, 33, 1476. (b) Poulton, J. T.; Folting, K.; Streib, W. E.; Caulton, K. G. Inorg. Chem. 1992, 31, 3190.

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Figure 2. Molecular structure of cis,cis-Ru(dtbpy)(CH2SiMe3)2(NO)Cl (3). Hydrogen atoms are omitted for clarity. The ellipsoids are drawn at the 40% probability level. Selected bond lengths (A˚) and angles (deg): Ru(1A)-N(1A) 1.707(3), Ru(1A)-N(10A) 2.133(3), Ru(1A)-N(21A) 2.144(3), Ru(1A)-C(1A) 2.114(3), Ru(1A)-C(5A) 2.138(4), Ru(1A)-Cl(1A) 2.4759(10), O(1A)N(1A)-Ru(1A) 171.2(3).

Figure 3. Molecular structure of cis,cis-Ru(dtbpy)(NO)(CH2SiMe3)2(NO)(OTs) (4). Hydrogen atoms are omitted for clarity. The ellipsoids are drawn at the 40% probability level. Selected bond lengths (A˚) and angles (deg): Ru(1)-N(1) 1.712(2), Ru(1)-N(10) 2.154(2), Ru(1)-N(20) 2.138(2), Ru(1)-C(1) 2.127(3), Ru(1)C(5) 2.104(3), Ru(1)-O(2) 2.2045(18), O(1)-N(1)-Ru(1) 172.1(2). 1

(11) and SiPh3 (12)). H NMR spectroscopy indicates that in 11 and 12 the alkyl groups are inequivalent and the nitrosyl is cis to the thiolate ligand. This suggests that for the Ru(II) system thiolate is a weaker donor ligand than the oxygen analogue, and therefore the trans arrangement between nitrosyl and thiolate is not favored. Treatment of 5 with K[OsO3N] afforded the nitridobridged Ru(II)/Os(VIII) bimetallic complex cis,cis-Ru(dtbpy)(CH2SiMe3)2(NO)(NOsO3) (13). 13 exhibited a similar 1 H NMR spectrum to 5, indicating that the nitridoosmate ligand is cis to the nitrosyl. The cis arrangement between

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Figure 4. Molecular structure of cis,cis-Ru(dtbpy)(CH2SiMe3)2(NO)(OTf) (5). Hydrogen atoms are omitted for clarity. The ellipsoids are drawn at the 25% probability level. Selected bond lengths (A˚) and angles (deg): Ru(1)-N(1) 1.728(3), Ru(1)-N(10) 2.145(3), Ru(1)-N(21) 2.160(3), Ru(1)-C(2) 2.107(4), Ru(1)C(6) 2.100(4), Ru(1)-O(2) 2.266(3); O(1)-N(1)-Ru(1) 172.8(4).

Figure 5. Molecular structure of the cation cis,cis-[Ru(dtbpy)(CH2SiMe3)2(NO)(4-tolNH2)]þ in 7. Hydrogen atoms are omitted for clarity. The ellipsoids are drawn at the 40% probability level. Selected bond lengths (A˚) and angles (deg): Ru(1)-N(1) 1.705(3), Ru(1)-N(2) 2.131(2), Ru(1)-N(3) 2.151(2), Ru(1)-C(1) 2.141(3), Ru(1)-C(5) 2.127(3), Ru(1)-N(31) 2.263(3); O(1)-N(1)-Ru(1) 172.1(2), C(31)-N(31)-Ru(1) 117.35(19).

[OsO3N]- and nitrosyl suggests the Ru-N(Os) π interaction in 13 is not significant, consistent with the solid-state structure (vide infra). Infrared Spectroscopy. The IR spectrum of 2 displayed the N-O band at 1741 cm-1, which is considerably lower than that of 1 (1871 cm-1), reflecting the electron-donating ability of the alkyl ligand. To our knowledge, this is among the lowest N-O stretching frequencies found for Ru(II) linear nitrosyl complexes. The N-O stretching frequencies for the dialkyl compounds cis,cis-Ru(dtbpy)(CH2SiMe3)2(NO)X (X = Cl, OTs, OTf, amine, thiolate) are lower than that of 1 and lie in the range 1760-1809 cm-1. On the basis of the

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Figure 6. Molecular structure of cis,trans-Ru(dtbpy)(CH2SiMe3)2(NO)(OPh) (8). Hydrogen atoms are omitted for clarity. The ellipsoids are drawn at the 40% probability level. Selected bond lengths (A˚) and angles (deg): Ru(1)-N(1) 1.7095(13), Ru(1)-N(10) 2.2161(12), Ru(1)-N(21) 2.2019(12), Ru(1)-C(31) 2.1151(14), Ru(1)-C(35) 2.1160(14), Ru(1)-O(2) 2.0212(9); O(1)-N(1)-Ru(1) 172.65(14), C(1)-O(2)-Ru(1) 128.72(9).

Figure 7. Molecular structure of cis,trans-Ru(dtbpy)(CH2SiMe3)2(NO)(OSiMe3) (9). Hydrogen atoms are omitted for clarity. The ellipsoids are drawn at the 40% probability level. Selected bond lengths (A˚) and angles (deg): Ru(1A)-N(1A) 1.690(6), Ru(1A)-N(20A) 2.221(4), Ru(1A)-N(30A) 2.230(4), Ru(1A)C(4A) 2.127(5), Ru(1A)-C(8A) 2.121(5), Ru(1A)-O(2A) 1.974(4); O(1A)-N(1A)-Ru(1A) 175.3(4), Si(1A)-O(2A)-Ru(1A) 149.1(2).

IR data, the donor strength of X is ranked in the order 2,6Me2C6H3S->Ph3SiS->Cl>p-tolNH2>OTs>[OsO3N]-> OTf-. The measured νNO for 13 is similar to that for the triflate compound 5, indicating the absence of Ru-N(Os) π interaction in 13 and that [NOsO3]- behaves like a weakly coordinating ligand. The Os-N (1030 cm-1) and Os-O (910 and 886 cm-1) stretching frequencies are higher than those for the free [OsO3N]- (1023 and 890, and 858 cm-1, respectively), suggesting that the Os-N and Os-O bonds in [OsO3N]- are strengthened upon coordination to Ru(II). A similar result has been found for related heterometallic nitridoosmate complexes.18 The N-O stretching frequencies for cis,trans-Ru(dtbpy)(CH2SiMe3)2(NO)X (X=phenoxide, siloxide) complexes (1768-1774 cm-1) are similar to those of the thiolate complexes despite Ru-O π interactions. On the

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Figure 8. Molecular structure of cis,trans-Ru(dtbpy)(CH2SiMe3)2(NO)(OSiPh3) (10). Hydrogen atoms are omitted for clarity. The ellipsoids are drawn at the 40% probability level. Selected bond lengths (A˚) and angles (deg): Ru(1)-N(1) 1.715(3), Ru(1)-N(30) 2.224(3), Ru(1)-N(40) 2.200(3), Ru(1)-C(19) 2.116(4), Ru(1)C(23) 2.113(4), Ru(1)-O(2) 1.994(2); O(1)-N(1)-Ru(1) 177.6(3), Si(1)-O(2)-Ru(1) 150.51(15).

Figure 9. Molecular structure of cis,cis-Ru(dtbpy)(CH2SiMe3)2(NO)(SSiPh3) (12). Hydrogen atoms are omitted for clarity. The ellipsoids are drawn at the 40% probability level. Selected bond lengths (A˚) and angles (deg): Ru(1)-N(1) 1.7114(17), Ru(1)-N(2) 2.1387(16), Ru(1)-N(3) 2.1451(16), Ru(1)-C(51) 2.117(2), Ru(1)-C(55) 2.156(2), Ru(1)-S(1) 2.4941(6); O(1)-N(1)-Ru(1) 172.20(16), Si(1)-S(1)-Ru(1) 115.37(3).

basis of the measured νNO, the donor strength of X in cis, trans-Ru(dtbpy)(CH2SiMe3)2(NO)X is ranked in the order Me3SiO- >PhO- >Ph3SiO-. It may noted that for related trans-Ru(CO)X(H)(Pt-Bu2Me)2 complexes a slightly different trend of ligand donor strength (Me3SiO- > Ph3SiO- > PhO-) was found.19 Crystal Structures. Complexes 2-5, 7-10, 12, and 13 have been characterized by X-ray diffraction, and their structures are shown in Figures 1-10, respectively. In 2, the geometry around Ru is pseudo-octahedral with the nitrosyl opposite to

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Figure 10. Structures of a pair of optical isomers of cis,cis-Ru(dtbpy)(CH2SiMe3)2(NO)(NOsO3) (13). Hydrogen atoms are omitted for clarity. The ellipsoids are drawn at the 40% probability level. Selected bond lengths (A˚) and angles (deg): Ru(1A)-N(1A) 1.689(13), Ru(1B)-N(1B) 1.747(14), Ru(1A)-C(1A) 2.101(14), Ru(1A)-C(5A) 2.106(19), Ru(1B)-C(1B) 2.157(18), Ru(1B)-C(5B) 2.134(15), Os(1A)-N(2A) 1.654(11), Os(1B)-N(2B) 1.742(13), Os-O 1.687(13)-1.760(11); O(4A)-N(1A)-Ru(1A) 167.9(13), O(4B)N(1B)-Ru(1B) 175.3(14), Os(1A)-N(2A)-Ru(1A) 163.7(7); Os(1B)-N(2B)-Ru(1B) 162.6(8).

a pyridyl group, and the three alkyls adopt a mer arrangement. The fac-trialkyl complex is not formed possibly because the trans arrangement between strong π-accepting nitrosyl and trans-directing alkyl ligand is not favored, although trans Ru nitrosyl alkyl compounds, e.g., transRu(OEP)(NO)(C6H4F-p) (OEP2-=octaethylporphyrin dianion), in which the Ru-N-O linkage is bent and tilted,14d,20 are known. It may also be noted that related nitrosyl trihydride complexes MH3(NO)L2 (M = Ru, Os; L = PR3) also exhibit a mer geometry. However, in MH3(NO)(PR3)2 the nitrosyl is trans to a hydride instead of L.21 Such a geometry is not possible for 2 because of the bidentate binding mode of dtbpy. As expected, the Ru-C distances for the axial alkyls (2.188(2) and 2.202(3) A˚) are longer than the equatorial one (2.132(3) A˚). The C(axial)-Ru-C0 (axial) unit is slightly bent, with an angle of 165.49(10)o presumably due to mutual trans influence of the alkyl ligands. Also, the Ru-C(axial) bonds are slightly bent away from the Ru-NO bond with the C(axial)-Ru-NO angles of 98.33(12)° and 95.12(12)o. The Ru-NO distance of 1.693(2) A˚ and the Ru-N-O angle of 175.5(2)o are typical for Ru(II) linear nitrosyl complexes. Complexes 3-5, 7, and 12 exhibit cis,cis geometry with the alkyls cis to each other and the nitrosyl opposite a pyridyl group. The Ru-C distances in these complexes are in the range 2.100(4)-2.156(2) A˚, which are similar to the RuC(equatorial) distance in 2. The Ru-Cl distance (2.4759(10) A˚) in 3 is rather long due to the trans influence of the alkyl. (20) Richter-Addo, G. B.; Wheeler, R. A; Hixson, C. A.; Chen, L.; Khan, M. A.; Ellison, M. K.; Schulz, C. E.; Scheidt, W. R. J. Am. Chem. Soc. 2001, 123, 6314. (21) Yandulov, D. V.; Huang, D. J.; Huffman, J. C.; Caulton, K. G. Inorg. Chem. 2000, 39, 1919. (22) Soong, S.-L.; Hain, J. H., Jr.; Millar, M.; Koch, S. A. Organometallics 1988, 7, 556.

The Ru-S distance of 2.4941(6) A˚ in 12 is longer than that in [Ru(NO)(SAr)4]- (Ar=mesityl) (2.385 A˚).22 The relatively small Ru-S-C angle (115.37(3)o) suggests that Ru-S π interactions, if any, are not signficant. Complexes 8-10 exhibit a cis,trans geometry with the nitrosyl opposite the phenoxide/siloxide ligand and the two cisoid alkyl groups opposite dtbpy. The Ru-C distances in the range 2.113(4)-2.127(5) A˚ are similar to those of the cis, cis-complexes. The Ru-O distance in 8 (2.0212(9) A˚) is shorter than that in TpRu(PMe3)2(OPh) (Tp- = hydridotrispyrazolylborate) (2.102(2) A˚), while the Ru-O-C angle in the former (128.72(9)o) is smaller than that of the latter (133.2(2)o).23 The Ru-O distance in 9 (1.974(4) A˚) is similar to those in cis-[RuIII(L)(OSiMe3)2]þ (L = 3,6-hexamethyl3,6-diazaoctane-1,8-diamine) (1.977 A˚),24 but the Ru-O-Si angle (149.1(2)o) is smaller than those of the latter (av 172.5°). The Ru-O distance in 10 (1.994(2) A˚) is slightly shorter than that in Ru(OSiPh3)(CO)(H)(Pt-Bu2Me)2 (av 2.057(4) A˚), in which the siloxide is trans to carbonyl,19 but the Ru-O-Si angle (150.51(15)o) is smaller that that in the latter (av 165.5°). The observed large Ru-O-C/Si bond angles in 8-10 are indicative of Ru-O π interactions. The Ru-NO distances (1.690(6)-1.715(3) A˚) and Ru-N-O angles (172.65(14)-177.6(3)o) in 8-10 are similar to those in 2 and rather insensitive to the trans ligand X. Complex 13 exhibits a cis,cis geometry with the [OsO3N]ligand trans to an alkyl. Unlike the crystal structures of the above cis,cis-Ru(dtbpy)R2(NO)X complexes, the asymmetric unit of 13 consists of a pair of molecules that are optical isomers of each other. The Ru-N-Os unit is roughly

(23) Feng, Y.; Lail, M.; Foley, N. A.; Gunnoe, T. B.; Barakat, K. A.; Cundari, T. R.; Petersen, J. L. J. Am. Chem. Soc. 2006, 128, 7982. (24) Chiu, W.-H.; Che, C.-M.; Mak, T. C. W. Polyhedron 1996, 15, 1129.

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linear (av 163.2°). The rather long Ru-N(nitride) and short Os-N distances (av 2.104 and 1.698 A˚, respectively) indicate that Ru-N(Os) π interaction is not significant, and 13 is best described as an unsymmetrically nitrido-bridged Ost NfRu complex. By comparison, the Ru-N and Os-N distances in trans-Ru(OEP)(NO)(NOsO3), which exhibits substantial Ru-N(Os) π interactions, are 1.83(2) and 1.79(1) A˚, respectively.25 The Os-N and Os-O distances of the [OsO3N]- ligand in 13 (av 1.698 and 1.732 A˚, respectively) are similar to those in free [OsO3N]- (1.67(2) and 1.744(1) A˚).26

Conclusions We have synthesized and structurally characterized the first Ru(II) nitrosyl mer-trialkyl compound with a 2,20 -bipyridyl ligand. One of the mutually trans Ru-C bonds in 2 can be (25) Leung, W.-H.; Chim, J. L. C.; Lai, W.; Lam, L.; Wong, W.-T.; Chan, W.-H.; Yeung, C.-H. Inorg. Chim. Acta 1999, 290, 28. (26) Kafitz, W.; Weller, F.; Dehnicke, K. Z. Anorg. Allg. Chem. 1982, 590, 175.

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easily cleaved by Brønsted acids to give cis-dialkyl complexes. The triflate complex 5 proved to be a good starting material for preparations of Ru(II) alkyl complexes containing heteroatom ligands. Substitution of 5 with amines and thiolate affords dialkyl complexes with the nitrosyl opposite a pyridyl group, whereas that with phenoxide and siloxide resulted in trans nitrosyl phenoxide/siloxide complexes. The study of organometallic chemistry and catalytic activity of Ru di- and trialkyl complexes with dtbpy is underway.

Acknowledgment. This work has been supported by the Hong Kong Research Grants Council (project number 601708). We thank Dr. Herman H. Y. Sung for solving the crystal structures. Supporting Information Available: Tables of crystal data, final atomic coordinates, anisotropic thermal parameters, and complete bond lengths and angles for complexes 2, 3 3 0.25C7H8, 4 3 0.5H2O, 5, 7 3 1.5H2O, 8, 9 3 0.25C4H8O, 10, 12 3 C6H14, and 13. This material is available free of charge via the Internet at http:// pubs.acs.org.