Ruthenium silyl complexes containing the Cp(PMe3)(2)Ru moiety: Preparation, substituent effects, and silylene character in the Ru-Si bond

The preparation and characterization of new ruthenium(II) silyl complexes c ontaining the Cp(PM3)(2)Ru moiety are described. The ruthenium(II) hydride Cp(PMe3)(2)RuH reacts with a variety of chlorosilanes to produce the ruthen ium(II) silyl complexes Cp(PMe3)(2)RuSiR3 [SiR3 = SiCl3 (1), SiHCl2 (2), Si H2Cl (3), SiMeCl2 (4), SiMeHCl (5), SiMe2Cl (6)] and the ruthenium(IV) dihy dride [Cp(PMe3)(2)RuH2]Cl. Silyl complexes 1-6 undergo chloride/hydride exc hange with LiAlH4 to give the corresponding ruthenium(II) hydrosilyl comple xes Cp(PMe3)(2)RuSiHR2 [SiHR2 = SiH3 (7), SiMeH2 (8), SiMe2H (9)]. Methylat ion of 6 with AlMe3 produces Cp(PMe3)(2)RuSiMe3 (10). A method for recoveri ng the Cp(PMe3)(2)Ru moiety is described. The structure of 1 was determined by X-ray crystallography. Complexes 1-10 represent the first complete set of metal silicon compounds that contain every possible combination of H, Cl , and Me groups on silicon. The effects of the substituents on the spectros copic properties of 1-10 were examined as a function of Tolman's electronic parameter (chi(i)) for the substituents on silicon. The infrared stretchin g frequency, nu(Si-H), and the NMR coupling constants, (2)J(SiP) and (1)J(S iH), exhibit a linear relationship with Sigma chi(i), consistent with Bent' s rule. However, when the NMR resonances SiR3 delta(Si-29), SiH delta(H-1), and SiMe delta(C-13) were examined as a function of Sigma chi(i), the sily l groups differentiated into three classes: dichlorosilyl, monochlorosilyl, and "non-chlorosilyl"; within each class a linear but inverse relationship with Sigma chi(i) was observed. Silylene character in the Ru-Si bond resul ting from d(Ru)-sigma*(Si-Cl) pi-back-bonding interactions was used to expl ain the origin of the three silyl classes.