The compounds 4,5-dimethyl-N,N′-bis(2,6-diisopropylphenyl)imidazol-2-ylidene silver chloride [AgCl(IPrMe)] 3and 4,5-dimethyl-N,N′-bis(2,6-diisopropylphenyl)imidazol-2-ylidene gold(I) chloride [AuCl(IPrMe)] 4have been synthesized. The attempted synthesis of the corresponding 4,5-dimethyl-N,N′-bis(2,6-diisopropylphenyl)imidazol-2-ylidene gold(III) chloride by oxidative addition of chlorine gas on 4allowed for the formation of the expected complex, concomitantly with 6, resulting from a chlorination of a methyl group situated in the backbone of the NHC (N-heterocyclic carbene). Additionally, the buried volume %Vburof the IPrMeligand in [AgCl(IPrMe)] 3and [AuCl(IPrMe)] 4complexes was calculated and compared to %Vburof more classical NHCs. This quantification of the steric hinderance of the IPrMeligand reveals the influence of the substituent modulation in the backbone of NHCs. [ABSTRACT FROM AUTHOR]