Additions and intramolecular migrations of nucleophiles in cationic diruthenium μ-allenyl complexes

The diruthenium μ-allenyl complex [Ru2(CO)(NCMe)(μ-CO){μ-η1:η2-C(H)double bond; length as m-dashCdouble bond; length as m-dashC(Me)(Ph)}(Cp)2][BF4], 3b, reacts with halide anions to yield the neutral derivatives [Ru2(CO)2(X){μ-η1:η2-C(H)double bond; length as m-dashCdouble bond; length as m-dashC(Me)(Ph)}(Cp)2] [X = Cl, 4b; X = Br, 4c; X = I, 4d]. Complex 4b undergoes isomerization to the unprecedented bridging vinyl-chlorocarbene species [Ru2(CO)(μ-CO){μ-η1:η3- C(Cl)C(H)double bond; length as m-dashC(Me)(Ph)}(Cp)2], 10, upon filtration of a CH2Cl2 solution through an alumina column. Complex 3b reacts with an excess of NaBH4 to give five products: the allene complex [Ru2(CO)2{μ-η2:η2- CH2double bond; length as m-dashCdouble bond; length as m-dashC(Me)(Ph)}(Cp)2], 5; the hydride species trans-[Ru2(CO)2(μ-H){μ-η1:η2-CHdouble bond; length as m-dashCdouble bond; length as m-dashC(Me)(Ph)}(Cp)2], 6, and cis-[Ru2(CO)2(μ-H){μ-η1:η2-CHdouble bond; length as m-dashCdouble bond; length as m-dashC(Me)(Ph)}(Cp)2], 8; the vinyl-alkylidene [Ru2(CO)(μ-CO){μ-η1:η3- C(H)C(H)double bond; length as m-dashC(Me)(Ph)}(Cp)2], 9; and the cluster [Ru3(CO)3(μ-H)3(Cp)3], 7. Studies on the thermal stabilities of 5, 6, 8 and 9 have suggested a plausible mechanism for the formation of these complexes and for the synthesis of 10.