Further reactions of some bis(vinylidene)diruthenium complexes

Whereas {1Ru(dppm)Cp*}(2)(mu-CdropCCdropC) (2) is the only product formed by deprotonation of [{Ru(dppm)Cp*}(2)-{mu(=C=CHCH=C=)}](+) with dbu, a mixture of 2 with Ru{CdropCCH=CH(PPh2)(2)[RuCp*]}(dppm)Cp* (3) and {Cp*Ru(PPh2-CHC=CH-)}(2) (4) is obtained with KOBu1. A similar reaction with [{Ru(dppm)Cp*}(2){mu=C=CMeCMe=C=)}](+) (5) gave Ru{CdropCCMe=CH(PPh2)(2)[RuCp*]}(dppm)Cp* (6). X-ray structures of 4, 5 and 6 confirm the presence of the 1-ruthena-2,4-diphosphabicyclo[1.1.1]pentane moiety, which is likely formed by an intramolecular attack of the deprotonated dppm ligand on C(1) of the vinylidene ligand. Protonation of {Ru(dppe)Cp*}(2)(mu(-CdropCCdropC) (8-Ru) regenerates its precursor [{Ru(dppe)Cp*}(2)-{mu(=C=CHCH=C=)}](2+) (7-Ru). Ready oxidation of the bis(vinylidene) complex affords the cationic carbonyl [Ru(CO) (dppe)Cp*]PF6 (9) (X-ray structure). (C) 2004 Elsevier B.V. All rights reserved.