N,N′-Asymmetrically substituted, methylene-linked bis(imidazol-2-ylidene) complexes have been prepared subsequent to a selective synthesis of the bis(imidazolium) salt precursors involving the quarternisation of N-alkyl and -aryl imidazoles with N-halomethyl imidazolium salts. The adaptability of the ligand precursor synthesis is illustrated through access to the N-Me/N′-Mes and N-Mes/N′-2,6-(i-Pr)2Ph systems, leading to the Pd(II) complexes [{(MeIm)(MesIm)CH2}Pd(L)2]n+, L = Cl/I (n = 0) and NCMe (n = 2), and [{(MesIm)[2,6-(i-Pr)2PhIm]CH2}Pd(L)2], L = Cl/I. The dicationic hybrid N,N′-alkyl/aryl complex was inactive in the copolymerisation of ethylene/carbon monoxide, displaying reactivity akin to N,N′-dialkyl analogues.
Dalton Transactions
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