SYNTHESIS, CHARACTERIZATION, AND REACTIVITIES OF DIRUTHENIUM COMPLEXES CONTAINING A MU-SILANE LIGAND AND STRUCTURAL STUDIES OF THE MU-SILANE COMPLEX [CP'RU(CO)](2)(MU-ETA(2)ETA(2)-H(2)SI(T)BU(2))

The diruthenium complex [Cp'Ru(mu-H)](2)(mu-eta(2):eta-H(2)Si(t)Bu(2)) (4; Cp' = eta(5)-C(5)Me(5)), containing a mu-silane ligand, was synthesized by the reaction of Cp'Ru(mu-H)(4)RuCp' (1) with (t)Bu(2)SiH(2). The unusual coordination mode of di-tert-butylsilane was confirmed by means of H-1, C-13, and Si-29 NMR and IR spectroscopy. Treatment of 4 with 1 atm of CO affords a mixture of the mu-silane complex [Cp'Ru(CO)](2)(mu-eta(2):eta(2)-H(2)Si(t)Bu(2)) (5) and the mu-silyl complex [Cp'Ru(CO)](2)(mu-eta(2)-HSi(t)Bu(2))(H) (6). The mu-silane complex 5 is in equilibrium in solution with hydrido-mu-silyl species 6. The equilibrium constant K, where K = [6]/[5], was determined to be 1.3 at 303 K in benzene-d(6). Variable-temperature 1H NMR measurements yielded thermodynamic parameters for conversion of 5 to 6: Delta H = 1.2 +/- 0.1 kcal/mol and Delta S = 4.5 +/- 0.1 eu/mol. The reaction of 4 with 5 equiv of PhSiH(3) yields the mixed-bridge bis(mu-silyl) complex [Cp'Ru](2)(mu-eta(2)-HSi(t)Bu(2))(mu-eta(2)-HSiPhH)(mu-H)(H) (7b). When 4 is treated with 12 equiv of Et(2)SiH(2), the mixed-bridge bis(mu-silyl) complex [Cp'Ru](2)(mu-eta(2)-HSi(t)Bu(2))(mu-eta(2)-HSiEtH)(mu-H)(H) (7a) is obtained via Si-C bond fission. The molecular structure of 5, 7a, and 7b were determined by single-crystal X-ray diffraction studies.