New acetylide migration and oxygen transfer reactions in ruthenium complexes containing an acetyl-substituted Cp ligand

Article abstract of DOI:10.1021/om010893j

Formation of [η⁵:η¹-C₅H₄C(CH₃) =C(Ph)C(O)](PPh₃)2Ru (3a) from the reaction of (η⁵-C₅H₄-COCH₃)(PPh₃) ₂RuCl (2a) with PhC≡CH proceeds via the vinylidene intermediate [(η⁵-C₅H₄-COCH₃)(PPh₃ )₂Ru=C=CHPh]Cl (4a). In this reaction the oxygen atom of the pendant acetyl group in the cyclopentadienyl ligand of 4a is transferred to C_α of the vinylidene ligand, and this transfer is accompanied by formation of a C=C bond, giving 3a. Treatment of 2a with LiC≡CPh affords (η⁵-C₅H₄C(CCPh)(OH)CH₃)(PPh ₃)₂RuCl (6a), and passing 6a through a column packed with alumina also gives 3a. The latter transformation involves a new migration of an acetylide group from exocyclic C_α of a substituted cyclopentadienyl ligand to the Ru center followed by the same oxygen transfer process. The metal acetylide (η⁵-C₅H₄COCH₃)(BINAP)RuC=CPh (5c), resulting from the same migration but with no oxygen transfer, is isolated when two PPh₃ ligands are replaced by BINAP. The structures of complexes 3a and 6b, a chirophos analogue of 6a, have been determined by X-ray diffraction analysis.