Further chemistry of ruthenium butatrienylidene complexes

Several complexes have been obtained from reactions carried out in early attempts to prepare the diynyl complexes Ru(Ctriple bond; length of mdashCCtriple bond; length of mdashCR)(dppe)Cp* (R = H, SiMe3). These have been identified crystallographically as the acyl complex Ru{Ctriple bond; length of mdashCC(O)Me}(dppe)Cp* (3), the cationic imido complex [Ru{Ctriple bond; length of mdashCC(double bond; length as m-dashNH2)Me}(dppe)Cp*]PF6 (4), the binuclear butenynylallenylidene [{Ru(dppe)Cp*}2{μ-Ctriple bond; length of mdashCC(OMe)double bond; length as m-dashCHCMedouble bond; length as m-dashCdouble bond; length as m-dashCdouble bond; length as m-dash}]PF6 (5), and the bis(ethynyl)cyclobutenylidene [{Ru(dppe)Cp*}2{μ-Ctriple bond; length of mdashCC4H2(SiMe3)Ctriple bond; length of mdashC}]PF6 (6). NMR studies of 5 have revealed the existence of two isomers. Plausible routes for their formation from the putative butatrienylidene intermediate [Ru(double bond; length as m-dashCdouble bond; length as m-dashCdouble bond; length as m-dashCdouble bond; length as m-dashCH2)(dppe)Cp*]+ (A) are discussed.