Vinylidene complexes of transition metals : II. A new method of synthesis of vinylidene complexes. Cymantrene derivatives containing phenylvinylidene ligands

A rearrangement of transition metal acetylenic π-complexes into compounds with vinylidene n-ligands has been established. Compounds CpMn(CCHPh)-(CO)₂ and Cp₂Mn₂(μ-CCHPh)(CO)₄ with terminal and bridging phenylvinylidene (benzylidenecarbene) ligands respectively were obtained from the π-complexes CpMn(CO)₂(PhCCR) where R  H, Ph₃Ge or Ph₃Sn. Reactions leading to conversion of the terminal CCHPh group into a bridging ligand and vice versa were studied. Under the action of L  Ph₃P, (EtO)₃P or (PhO)₃P, substitution of CO groups in vinylidene complexes takes place and compounds CpMn(CCHPh)-(CO)L are formed. IR, ¹H and ¹³C NMR spectra of the novel complexes are discussed. The data obtained indicate an electron-withdrawing property of the CCHPh ligand and stronger bonding of this ligand to the metal as compared with a CO group.