Oxidative Dimerization of Arylalkynyl–Ruthenium Complexes

Chemical oxidation of Ru(CCPh)(PPh3)2Cp with [FeCp2]PF6 affords the binuclear cationic complexes [Cp(PPh3)2Ru{CCHC6H4CPhC}Ru(PPh3)2Cp](PF6)2 (2) and [Cp(PPh3)2Ru{CC(C6H4)CPhC}Ru(PPh3)2Cp]PF6 (3) by radical coupling at sites shown to be electron-rich by DFT studies, particularly involving the acetylide Cβ and Ph Cpara atoms and, to a lesser extent, the Cp carbon atoms. Complexes 2 and 3 are related by facile deprotonation/protonation reactions. When the 4-position of the Ph group is blocked, attack by Cβ upon the Cp group occurs to give the bis(vinylidene) [Ru{CC(C6H4Me-4)-η-C5H4[Ru(PPh3)2{CCH(C6H4Me-4)}(PPh3)2Cp]}](PF6)2 (4), which can be deprotonated to give [Ru{CC(C6H4Me-4)-η-C5H4[Ru(PPh3)2{CC(C6H4Me-4)}(PPh3)2Cp]}]PF6 (5). Complex 4 is rapidly oxidized during workup to form [Ru{CC(C6H4Me)-η-C5H4[Ru(CO)(PPh3)2]}(PPh3)2Cp](PF6)2 (6). Single-crystal X-ray structure determinations of the salts 2, 3, and 6 are reported.