PREPARATION OF VINYLIDENERUTHENIUM COMPLEXES PROMOTED BY HEMILABILE CHELATING PHOSPHINE-LIGANDS

The octahedral ruthenium(II) complexes [RuCl2(P O)2] (3, 6) containing the P,O-bound phosphine ligands i-Pr2PCH2CH2OMe (1) and i-Pr2PCH2C(O)OMe (2) have been prepared from [RuCl2(PPh3)3] and 1 or 2 by ligand exchange. Reaction of 3 with carbon monoxide leads to the formation of [RuCl2(CO)2(eta(1)-P-i-Pr2PCH2CH2OMe)2] (4) in nearly quantitative yield. On treatment of 3 and 6 with HC = CPh or HC = CCO2Me, the vinylideneruthenium(II) complexes [RuCl2(= C = CHPh)(eta(1)-P-i-Pr2PCH2CH2OMe)(eta(2)-i-Pr2PCH2CH2OMe)] (5) and [RuCl2(= C = CHR)(eta(1)-P-i-Pr2PCH2C(O)OMe)(eta(2)-i-Pr2PCH2C(O)OMe)] (7, R = Ph; 8, R = CO2Me) are formed, which are fluxional in solution. From P-31 NMR measurements at various temperature, the free enthalpies of activation DELTA-G218 double-ended dagger = 41 kJ/mol for 5, DELTA-G275 double-ended dagger = 53 kJ/mol for 7, and DELTA-G258 double-ended dagger = 49 kJ/mol for 8 for the intramolecular rearrangement have been determined. The X-ray crystal structure analysis of 5 (monoclinic space group P2(1)/c with a = 13.129 (1) angstrom, b = 12.803 (1) angstrom, c = 18.867 (2) angstrom, and beta = 102.42 (1)-degrees reveals that in the solid state one phosphine is coordinated via phosphorus and oxygen forming a five-membered chelate whereas the other phosphine is only P-bound with a dangling CH2CH2OMe fragment. The Ru = C = C unit is almost linear with Ru-C and C-C distances of 1.749 (5) and 1.339 (7) angstrom.