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 carbonylmetalates Na2[M­(CO) n ] (M = Fe, n = 4; M = Cr, W, n = 5) to yield the neutral carbonyl complexes [2]–[4] bearing a benzannulated 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·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 σ-donor properties of the CAAC ligand.