Exploring the reactivity of a coordinatively unsaturated Cp*Ru(κ2-P,O) complex with small molecule substrates: application in E–H bond activation (E = H, B, and Si)

Abstract

Treatment of [Cp*RuCl]₄ with 1-diisopropylphosphino-2-indanone (1) afforded Cp*Ru(Cl)(κ²-P,O-1) (2) in 96% isolated yield. Dehydrohalogenation of 2 under an atmosphere of N₂ provided the dinuclear complex 4 (78% isolated yield), which is comprised of two coordinatively unsaturated Cp*Ru(κ²-P,O) fragments (3) linked by an end-on coordinated μ-N₂ ligand. Although complex 3 has not been observed directly, reactivity studies demonstrated that 4 can serve as a convenient source of 3. Isolable adducts of 3 were prepared via exposure of 4 to an atmosphere of CO (93% yield, 5a) or two equivalents of PhCN (91% yield, 5b). Exposure of 4 to an atmosphere of H₂ afforded the adduct 3·(σ-H₂) (6) quantitatively; the clean conversion of 6 back into 4 occurred upon evacuation and re-introduction of a N₂ atmosphere. Treatment of 4 with two equivalents of PhSiH₃ or Ph₂SiH₂ afforded products featuring (H)₂Ru–SiPhX–O fragments (7a and 7b, respectively; both 95% isolated yield) corresponding to net double geminal Si–H bond activation of the organosilane in which the extruded silylene fragment has inserted into the Ru–O bond of the putative intermediate 3. Similar reactivity was observed upon treatment of 4 with two equivalents of mesitylborane to give 8 (82% isolated yield). While minimal Ru–H⋯Si interactions were identified for 7a,b in solution and the solid state, the hydride ligands in 8 were observed to bridge ruthenium and boron. Crystallographic characterization data were obtained for 2·0.5C₆H₆, 4, 7b, and 8.