Synthesis of monomeric and dendritic ruthenium benzylidene cis-bis-tertiobutyl phosphine complexes that catalyze the ROMP of norbornene under ambient conditions
作者:Denise Méry、Didier Astruc
DOI:10.1016/j.molcata.2004.08.050
日期:2005.3
The synthesis of monomeric and dendritic ruthenium benzylidene cis-bis-phosphine complexes that catalyze norbornene ROMP previously reported with dicyclohexyl bis-phosphines has now been extended to monomeric and dendritic bis-tertiobutyl phosphines. The reaction of Hoveyda's catalyst [RuCl2(=CH-o-O-iPrC(6)H(4))PPh3] (1) with the diphosphine PhCH2N(CH2PtBu2)(2) (2) gives the new air-stable green ruthenium carbene complex (3) in which (2) models a dendritic branch of poly(diphosphine) dendrimers DAB-dendr-[N(CH2PtBu2)(2)](n) (G(1), n = 4; G(2).n = 8; G(3.)n = 16). Metallodendrimers DAB -dendr-[N(CH2PtBu2)(2) Ru (=CHAr)(Cl)(2)](n) (4)-(6) derived from the three first generations of DAB polyamines containing. respectively, 4, 8 and 16 ruthenium branches have been synthesized. These dendritic ruthenium-benzylidene complexes initiate the ROMP of norbornene at room temperature to form star-shaped metallodendritic polymers slightly more rapidly than the analogues with bis-cyclohexyl phosphines. Interestingly, the metallodendrimers G(1) (4) initiates the ROMP of norbornene much faster than the model ruthenium complex (3) the overall rate order being G(1) > G(2) > G(3) > model, these positive and negative dendritic effects being comparable with those found for the dicyclohexyl bis-phosphine complexes. (C) 2004 Elsevier B.V. All rights reserved.