Synthesis and reactivity of neutral vinylidene and σ-alkynyl complexes containing the hemilabile ligand Ph2PCH2CH2OMe -: Part 16.: Ruthenium tris(pyrazolyl)borate complexes

RuTp(COD)Cl reacts readily with Ph2PCH2CH2OMe to give the neutral complex RuTp(kappa (2)(P,O)-Ph2PCH2CH2OMe)Cl (2) which transforms with terminal alkynes HC=CR (R = Ph, n-Bu, C6H9) and carbon monoxide, respectively, into the neutral vinylidene complexes RuTp(kappa (1)(P)-Ph2PCH2CH2OMe)(Cl)(=C=CHR) (3a-c) and RuTp(kappa (1)(P)-Ph2PCH2CH2OMe)(Cl)(CO) (4). The kappa (1)(P) bonding mode of the phosphinoether testifies to its hemilabile nature. Complex 3a reacts with lithium diisopropylamide to give the neutral alpha -acetylide complex RuTp(kappa (2)(P,O)-Ph2PCH2CH2OMe)(-C=CPh) (5) which couples with stoichiometric amounts of HC=CPh to give RuTp(kappa (1)(P)-Ph2PCH2CH2OMe)(C(Ph)=CHC=CPh) (6), featuring a sigma,eta (2)-bound enynyl ligand. Treatment of 3a with AgCF3SO3 affords the cationic vinylidene complex [RuTp(kappa (2)(P,O)-Ph2PCH2CH2OMe)(=C=CHPh)]CF3SO3 (7). Complex 5 is found to catalyze the dimerization of HC=CR (R=Ph, SiMe3, n-Bu, t-Bu, C6H9) to give enynes. The structures of 3a, 4, 5 and 7 have been determined by X-ray crystallography. (C) 2001 Elsevier Science B.V. All rights reserved.