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(κ2(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(κ1(P)-Ph2PCH2CH2OMe)(Cl)(CCHR) (3a–c) and RuTp(κ1(P)-Ph2PCH2CH2OMe)(Cl)(CO) (4). The κ1(P) bonding mode of the phosphinoether testifies to its hemilabile nature. Complex 3a reacts with lithium diisopropylamide to give the neutral α-acetylide complex RuTp(κ2(P,O)-Ph2PCH2CH2OMe)(CCPh) (5) which couples with stoichiometric amounts of HCCPh to give RuTp(κ1(P)-Ph2PCH2CH2OMe)(C(Ph)CHCCPh) (6), featuring a σ,η2-bound enynyl ligand. Treatment of 3a with AgCF3SO3 affords the cationic vinylidene complex [RuTp(κ2(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.