Mono- and Bimetallic Zwitterionic Chromium(0) and Tungsten(0) Allenyls

摘要: A series of stable chiral (racemic), formally neutral, zwitterionic mono- and bimetallic M(CO)5[C(OEt)═C═CR(NHC)] (M = Cr, W) σ-allenyls are ready available by the addition N-heterocyclic carbenes (NHCs) to Cr(0) W(0) alkynyl Fischer carbene complexes. Different classes NHCs, (e.g., 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene, 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene, their six- seven-membered analogues 1,3-bis(dimethyl)imidazol-2-ylidene) were employed as nucleophiles in these C–C bond-forming reactions yielding novel complexes essentially quantitative yields. systematic experimental computational study electronic properties Cr- W-allenyls shows that UV–vis spectra directly influenced structure heterocyclic moiety derived from NHC (ring size, substituents on N atoms) nature metal fragment (Cr/W). The electron-releasing allows them participate electron-trans...