Synthesis and study of rutheniun silylene complexes of the type [(eta(5)-C5Me5)(Me3P)(2)Ru=SiX2](+) (X = thiolate, Me, and Ph)

Various ruthenium silyl complexes of the type Cp*(Me3P)(2)RuSiR3 (Cp* = eta (5)-C5Me5; SiR3 = SiCl3 (1), Si(NMe2)(3) (2), Si(SEt)(3) (3), Si(S-a-Naph)( 8) (4), Si[S(CH2)(3)S]Ph (5), Si(SCy)(2)Cl (B), and Si(SMes)(2)Cl (7, Mes = 2,4,6-trimethylphenyl)) were prepared by the reaction of Cp*(Me3P)(2)RuCH2 SiMe3 with the appropriate silane HSiR3. Compound 3 was converted to the tr iflate Cp*(Me3P)(2)RuSi(SEt)(2)OTf (8) by the reaction of 3 with Me3SiOTf. Similar reactions produced Cp*(Me3P)(2)RuSi(NMe2)(2)OTf (13), Cp*(Me3P)(2)R uSi(NMe2)(OTf)(2) (14), Cp*(Me3P)(2)RuSi(SMes)(2)OTf (18), and Cp*(Me3P)(2) RuSi(SMes)(Cl)OTf (19). By NMR spectroscopy, compound 8 in dichloromethane solution appears to possess a labile triflate group. Reactions of the trifl ates 8 and Cp*(Me3P)(2)RuSi(S-p-Tol)(2)OTf (10) with NaBPh4 provided the si lylene complexes [Cp*(Me3P)(2)RuSi(SR)(2)][BPh4] (20, R = Et; 21, R = p-Tol ). Similarly, the reaction of 6 with NaBPh4 gave [Cp*(Me3P)(2)RuSi(SCy)(2)] [BPh4] (22), and the reaction of 4 with B(C6F5)(3) produced [Cp*(Me3P)(2)Ru Si(S-2-Naph)(2)][MeB(C6F5)(3)] (23). Silylene complexes 20-23 display chara cteristic Si-29 NMR shifts in the region of delta 250-270. The non-heteroat om-stabilized silylene complexes [Cp*(Me3P)(2)RuSiR2][B(C6F5)(4)] (24, R = Me; 25, R = Ph), obtained:via reactions of (Et2O)LiB(C6F5)(4) with Cp*(Me3P )(2)RuSiR2OTf (11, R = Me; 12, R = Ph) exhibit Si-29 NMR shifts around delt a 300. The crystal structure of 24 revealed a Ru-Si distance of 2.238(2) An gstrom, and the Cp*(centroid)-Ru-Si-Me dihedral angle is 34 degrees. Compou nd 24 reacts quantitatively with 1 equiv of PMe3 or PPh3 in dichloromethane -d(2) to form the base-stabilized silylene complexes [Cp*(Me3P)(2)RuSiMe2(P R3)][B(C6F5)(4)] (28, R = Me; 29, R = Ph), identified by H-1 and P-31 NMR s pectroscopy. These complexes are thermally labile and decompose with elimin ation of the dimethylsilylene fragment to give [Cp*(Me3P)(2)RuPR3][B(C6F5)( 4)] (R = Me, Ph). The ylide CH2PPh3 reacts with 24 to form [Cp*(Me3P)(2)RuS iMe2CH2PPh3][B(C6F5)(4)] (32a), and the characterization of [Cp*(Me3P)(2)Ru SiMe2CH2PPh3][OTf] (32b) by X-ray crystallography suggests that the complex is best viewed as a ruthenium silyl derivative with the positive charge lo calized on the "ylide" phosphorus atom. Reactions of 20 and 24 with hydroge n proceed slowly and result in relatively complex product mixtures that con tain various ruthenium hydride species. The reaction involving 20 also prod uced HSi(SEt)(3), perhaps via redistribution of initially formed H2Si(SEt)( 2). For the reaction of 24 with hydrogen, no H2SiMe2 was detected in the produc t mixture. The reaction of 20 with H2SiSiPh3 gave [Cp*(Me3P)(2)Ru(H)(SiH2Si Ph3)][BPh4] (35) and HSi(SEt)(3), and the corresponding reaction of H(3)SiM es in dichloromethane gave [Cp*(Me3P)(2)RuHCl][BPh4] (34), BPh3, and H(2)Si Mes(SEt), among other products. By NMR spectroscopy, the intermediate [Cp*( Me3P)(2)Ru(H)(SiH(2)Mes)][BPh4] (36) was observed for the latter process. C ompound 36, generated independently by reaction of [Cp*(Me3P)(2)Ru(NCMe)][B Ph4] with H(3)SiMes, was shown to react with HSi(SEt)(3) to give H(2)SiMes( SEt).