Synthesis of CAAC Complexes by Oxidative Addition of 2-Chloro-3,3-dimethyl-N-ethylindoleninium Cations to Carbonylmetalates and Subsequent Transmetalation

2-Chloro-3,3-dimethyl-N-ethylindoleninium tetrafluoroborate has been oxidatively added to three carbon-ylmetalates Na2[M(CO)n] (M = Fe, n = 4; M = Cr, W, n = 5) to yield the neutral carbonyl complexes [2]-[4] bearing a benzannu-lated cyclic (alkyl)(amino)carbene (CAAC) ligand. The chromium complex was subsequently used for the transmetalation of the CAAC ligand to gold(I) to give [Au(CAAC)(Cl)] complex [5]. Complex [5] was reacted with 1,3-diisopropylbenzimidazolium tetrafluoroborate (bimy center dot HBF4) in the presence of K2CO3 as a base to give the hetero-bis-NHC-Au complex [Au(bimy)(CAAC)]BF4, [6]BF4. The Huynh electronic parameter (HEP) was determined from the 13C NMR spectrum of [6]BF4 to obtain quantitative information about the sigma- donor properties of the CAAC ligand.