The preparation and characterization of Cp(PR3)2RuSiX3 [PR3 = PPhMe2, SiX3 = SiCl3 (1), SiHCl2 (2), SiH2Cl (3), SiHMeCl (4), SiH3 (7), SiMeH2 (8), SiMe3 (9); PR3 = PPh2Me, SiX3 = SiCl3 (10), SiHCl2 (5), SiH2Cl (6), SiMeCl2 (11)] are described. Ruthenium silyl complexes 1−6 are prepared by the reaction of the ruthenium hydrides, Cp(PR3)2RuH, with the corresponding chlorosilane, ClSiX3; the ruthenium dihydrides [Cp(PR3)2RuH2]Cl were obtained as coproducts. Increasing the steric demand of the phosphine decreased the reactivity of the corresponding ruthenium hydride toward chlorosilanes. Silyl complexes 1−4 undergo chloride/hydride exchange with LiAlH4 to give the corresponding ruthenium hydrosilyl complexes Cp(PPhMe2)2RuSiHX2 [SiHX2 = SiH3 (7), SiMeH2 (8)]. Methylation of 1 with AlMe3 produces Cp(PPhMe2)2RuSiMe3 (9). Complexes 10 and 11 were prepared by the reaction of Cp(PPh2Me)2RuMe with neat hydrosilanes HSiX3 (SiX3 = SiCl3, SiMeCl2) at 100 °C. The effects of the silicon substituents on the spectroscopic properties of 1−11 and the related Cp(PMe3)2RuSiX3 complexes were examined as a function of Tolman's electronic parameter (χ i ) for the substituents on silicon. The NMR resonance PR3 δ(31P) and the NMR coupling constants, 1 J SiH and 2 J SiP, exhibit a linear relationship with ∑χ i (SiX3). On the other hand, the silyl groups differentiated into three classes, dichlorosilyl, monochlorosilyl, and “non-chlorosilyl”, when the NMR resonances SiX3 δ(29Si), SiH δ(1H), and SiMe δ(13C) were examined as a function of ∑χ i (SiX3). This “chloro effect” was attributed to Ru−Si silylene character from d(Ru)−σ*(Si−Cl) π-back-bonding interactions. Surprisingly, changing the phosphine attached to ruthenium had no effect on the spectroscopic properties of the silyl group.

Protonation of Cp(PMe3)2RuSiCl3 (1) leads to the formation of [Cp(PMe3)2Ru(η2-HSiCl3)]+ (2 + ), a rare example of a cationic η2-silane complex. The η2-silane coordination in 2 + is confirmed by an X-ray crystallographic study. The short Ru−H and long Si−H interactions in 2 + model the latter stages of hydrosilane oxidative addition to a metal center.

The structures for a series of Cp(PR 3 ) 2 RuSiX 3 {PR 3 ) PMe 3 , SiX 3 ) SiCl 3 , SiMeCl 2 , SiPhCl 2 ; PR 3 ) PMe 2 Ph, SiX 3 ) SiCl 3 } complexes were determined and compared. The Ru-Si and Si-Cl distances in these complexes increased when Cl was replaced with Me or Ph groups and correlated with the observed spectroscopic properties of these complexes. The structural variations were explained by d(Ru)-σ*(Si-Cl) π-back-bonding interactions.

The ruthenium chloride and hydride complexes Cp(PR 3 ) 2 RuH {X ) Cl; PR 3 ) PMe 3 (1), PMe 2 Ph (2), PMePh 2 (3), PPh 3 (4); X = H; PR 3 ) PMe 3 (5), PMe 2 Ph (6), PMePh 2 (7), PPh 3 (8)} were studied by spectroscopy and solution calorimetry. The structures of 2 and 3 are reported and complete the structural characterization of the series 1-4. In this series, the Ru-Cl distance (2.449 ( 0.007 Å) remains constant, while the Ru-PR 3 distance increases in the order 1 < 2 < 3 < 4. The ruthenium hydrides 5-8 were prepared from the reaction of the corresponding ruthenium chloride with KOMe in methanol. Spectroscopic data on hydrides 5-8 indicated that the ruthenium hydride interaction decreases in the order 5 > 6 > 7 > 8. Enthalpies of reaction for the hydride/chloride metatheses of 5-8 with chlorocarbons (CHCl 3 or CCl 4 ) were studied by solution calorimetry and allowed for the determination of Ru-Cl bond disruption enthalpies (BDEs) relative to the corresponding Ru-H BDEs. [BDE(Ru-Cl) -BDE(Ru-H)] values covered a 6 kcal/mol range with an average of 21.4 ( 2.5 kcal/mol. The magnitude of [BDE(Ru-Cl) -BDE(Ru-H)] correlated with the number of methyl groups on the phosphine and was dependent on the electronic and steric properties of the phosphine.