Halogen addition to NHC-gold(I) chloride complexes in the framework of the Inverted Ligand Field

The conversion of LAuX to LAuX3, where L is a neutral ligand such as a phosphane or a carbene and X = Cl, Br or I, can be performed by halogen addition reactions in mild conditions. The formation of complexes with mixed halides, such as LAuY2X, also evoking the possibility of geometrical isomerization, is less investigated. In this work the iodine and bromine addition reactions, under mild conditions, to a symmetrically disubstituted carbene 1,3-dimethyl-imidazolyl-2-yl-gold(I)chloride were considered. The molecular structures highlight the formation of the trans LAuI2Cl in the case of iodine addition and a mixture of the geometrical isomers for bromine. DFT analysis points out a stepwise addition of halogen atom to the linear gold(I) complex without a net change in metal electronic population, suggesting the occurrence of the Inverted Ligand Field.