[(2−4-η)-Butadienyl]- and [(3−5-η)-Pentatrienyl]ruthenium Complexes from Vinylidene and Allenylidene Precursors1

The vinylideneruthenium complex [C 5 H 5 RuCl( C CHCO 2 Me)(PPh 3 )] ( 2 ), which is obtained on stepwise treatment of [C 5 H 5 Ru(η 3 -C 3 H 4 Me)(PPh 3 )] ( 1 ) with HC⋮CCO 2 Me and HCl in aromatic solvents, reacts with Sn(CH CH 2 ) 4 in the presence of CuCl to give the (2−4-η)-butadienyl compound [C 5 H 5 Ru(η 3 - C H 2 C H C CHCO 2 Me)] ( 3 ) in abut 70% yield. A similar C C coupling reaction leading to the formation of the (3−5-η)-pentatrienyl metal complex [C 5 H 5 Ru{(3−5-η)- C H 2 C H C =C CPh 2 }(PPh 3 )] ( 5 ) occurs on treatment of the allenylidene compound [C 5 Me 5 RuCl( C C CPh 2 ){κ( P )- i Pr 2 PCH 2 CO 2 Me}] ( 4 ) with CH 2 CHMgBr in C 6 H 6 /THF.