GENERATION OF VINYLCARBYNE COMPLEXES FROM REACTION OF THE PROPYNYL COMPLEX [CP(CO)(PPH3)MNC-EQUIVALENT-TO-CME]- WITH ALDEHYDES AND KETONES

The highly nucleophilic propynyl complex Li+[Cp(CO)(PPh3)MnC=CMe]- (2) reacts with a variety of aldehydes and ketones in the presence of BF3 .Et2O to give, after quenching with MeOH, a series of cationic vinylca rbyne complexes of the general form [Cp (CO) (PPh3)Mn=C-C(Me)=C(R)(R') ]BF4. The reactions of the R,R' = Ph derivative (5a) with a series of nucleophiles (LiAlH4, RMgX, Bu(t)C=CLi) have been studied, and additio n occurs to both the a-carbon of the vinylcarbyne ligand to form vinyl carbene complexes [Cp(CO)(PPh3)Mn=C(R)C(Me)=CPh2] (R = H, Me, Et, -C=C Bu(t)) and to the gamma-carbon to give vinylidene complexes, with addi tion to C(alpha) being electronically preferred but with addition to C , being favored sterically because of the bulky PPh3 ligand. The vinyl carbyne complexes that have an acidic proton on the C(gamma) substitue nt undergo facile deprotonation to give vinylvinylidene derivatives of the general form Cp(CO)(PPh3)Mn=C=C(Me)C(R)=C(R')2 (R' = H, R = p-Tol (14c), Bu(t); R' = Me, R = H). The propynyl complex 2 also adds to th e gamma-carbon of 5a to form the binuclear bis(vinylidene) complex [Cp (CO)(PPh3)Mn=C=C(Me)-]2{C(Ph)2) as a separable mixture of diastereomer s. The related binuclear bis(vinylidene) complex [Cp(CO)(PPh3)Mn=C=C(M e)-]2{C(H)(Et)} (13) was also isolated in low yield from the reaction of propynyl complex 2 with both MeOH and Me3SiCl. Also described is th e preparation of the new PPh3-substituted carbyne complexes [Cp(CO)(PP h3)Mn=CR]X (R = Et, Ph, CH2Ph; X = BF4, OTf), and complexes 5a, 13, an d 14c have been crystallographically characterized.