화학공학소재연구정보센터
Inorganic Chemistry, Vol.57, No.24, 15600-15609, 2018
Reactions of Low-Coordinate Cobalt(0)-N-Heterocyclic Carbene Complexes with Primary Aryl Phosphines
Aiming to get knowledge on the reactivity of low-coordinate cobalt(0) species toward primary phosphines, the reactions of [(IPr)Co-(vtms)(2)] and [(ICy)(2)Co(vtms)] (IPr = 1,3-bis(2',6'-diisopropylphenyl)-imidazol-2-ylidene, ICy = 1,3-dicyclohexylimidazol-2-ylidene, and vtms = vinyltrimethylsilane) with several primary aryl phosphines have been examined. The reactions of [(IPr)Co(vtms)(2)] and [(ICy)(2)Co(vtms)] with H(2)PDmp (Dmp = 2,6-dimesitylphenyl) at 80 degrees C furnish the diamagnetic cobalt(I) phosphido complexes [(NHC)Co(PHDmp)] (NHC = IPr, 1; ICy, 2) that feature the Co (eta(6)-mesityl) interaction. Complex 1 can coordinate CO to generate the terminal phosphido complex [(IPr)Co(CO)(3)(PHDmp)] (3) and can be oxidized by [Cp2Fe] [BAr4F] to yield the cobalt(II) phosphido complex [(IPr)Co(PHDmp)][BAr4F] (4, BAr4F = tetrakis(3,5-di(trifluoromethyl)phenyl)borate). For the reactions with sterically less-hindered primary phosphines, [(IPr)Co(vtms)(2)] is inert toward H2PC6H2-2,4,6-Me-3 (H(2)PMes) at room temperature, whereas [(ICy)(2)Co(vtms)] can react with H(2)PMes at room temperature to produce the cobalt(II) phosphido alkyl complex trans-[(ICy)(2)Co(CH2CH2SiMe3)(PHMes)](5). At 80 degrees C, the cobalt(0) alkene complexes [(IPr)Co(vtms)(2)] and [(ICy)(2)Co(vtms)] and also the cobalt phosphido complexes, 1, 2, and 5 can serve as precatalysts for the dehydrocoupling reaction of H(2)PMes to afford MesHPPHMes. NHC-Co(I)-phosphido species are proposed as the in-cycle intermediates for these cobalt-catalyzed dehydrocoupling reactions.