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.
