Dinuclear Ruthenium Ethylene Complexes: Syntheses, Structures, and Catalytic Applications in ATRA and ATRC Reactions
摘要:
The complexes [(p-cymene)Ru(mu-Cl)(3)RuCl(C2H4)(PR3)] (PR3 = PPh3, Pn-Bu-3) were synthesized by reaction of [(p-cymene)RuCl(mu-Cl)](2) with the respective phosphine ligand in the presence of ethylene. Structurally related complexes containing the tricyclopentylphosphine (PCyp(3)) or the isobutylphobane ligand (phobane = 9-phosphabicyclo[3.3.1]nonane) were obtained by reaction of [(arene)RuCl(mu-Cl)](2) (arene = p-cymene, 1,3,5-i-Pr3C6H3) with 2 equiv of [(arene)RuCl2(PCyp(3))] or [(arene)RuCl2(isobutylphobane)] in the presence of ethylene. The structures of the dinuclear complexes [(p-cymene)Ru(mu-Cl)(3)RuCl-(C2H4)(PPh3)] and [(1,3,5-i-Pr3C6H3)Ru(mu-Cl)(3)RuCl(C2H4)(isobutylpliobane)] as well as of the mononuclear precursors [(p-cymene)RuCl2(isobutylphobane)], [(1,3,5-i-Pr3C6H3)RuCl2(isobutylphobane)], and [(p-cymene)RuCl2(PCyp(3))] were determined by single-crystal X-ray analyses. Kinetic analyses of the atom transfer radical addition reaction of CCl4 to styrene revealed that the catalytic activity of the dinuclear complexes was strongly dependent on the nature of the phosphine ligand but only slightly affected by the nature of the arene ligand. Addition of Mg to the reaction mixture was found to increase the lifetime of the catalyst significantly. With Mg as the cocatalyst, mixed-valence Ru(II)-Ru(III) complexes of the general formula [(arene)Ru(mu-Cl)(3)RuCl2(PR3)] were found to be equally potent catalyst precursors when compared to the Ru(II)-Ru(II) complexes [(arene)Ru(mu-Cl)(3)RuCl(C2H4)(PR3)].
Synthesis and evaluation of new RuCl2(p-cymene)(ER2R′) and (η1:η6-phosphinoarene)RuCl2 complexes as ring-opening metathesis polymerization catalysts
摘要:
New RuCl2(p-cymene)(ER2R') complexes (E = P, As, Sb; R, R' = H, alkyl, arylalkyl) have been synthesized and used as catalyst precursors for the ring-opening metathesis polymerization (ROMP) of cyclooctene, cyclopentene, and norbornene. When ER2R' was a phosphinoarene, the p-cymene ligand could be displaced upon heating and tethered (eta(1):eta(6)-phosphinoarene)RuCl2 complexes were obtained. Simple thermogravimetric analysis (TGA) of the complexes provided clear-cut indication on their potential catalytic activity in ROMP. (C) 2000 Elsevier Science S.A. All rights reserved.