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Published on: May 28, 2014
Dinuclear Gold(I) and Gold(III) Complexes of Janus Di-N-heterocyclic Carbenes
Jia Nuo Leung1, Han Vinh Huynh1
1Department of Chemistry, Faculty of Science, National University of Singapore, 3 Science Drive 3, Singapore 117453, Republic of Singapore.
Abstract:
A series of Janus-type hetero-tetrakis(NHC) dinuclear gold(I) complexes of the general formula [Au2I(NHC)2(μ-Janus diNHC)]X2 {NHC = 1,3-diisopropyl-benzimidazolin-2-ylidene (iPr2-bimy) or 1,3-bis(2,6-diisopropylphenyl)-imidazolin-3-ylidene (IPr); X = BF4, PF6, OTf} were synthesized. These complexes contain 1,2,4-triazolidin-3,5-diylidene (ditz), benzobis(imidazolin-2-ylidene) (BBI) and the mesoionic pyrazolidin-3,5-diylidene (dipy) as distinct Janus-type diNHCs. Some of the complexes were susceptible to ligand redistribution, which was fastest for the mesoionic dipy digold(I) complex. Introduction of the bulky IPr ligand could significantly slow down this process. The respective gold(III) counterparts [Au2IIIBr4(NHC)2(μ-Janus diNHC)]X2 were obtained by oxidation of the homonuclear gold(I) complexes with elemental bromine further increasing stability. Comparison of the IPr carbene resonances in the dinuclear gold complexes show an increasing trend for the Janus diNHC system 1,2,4-triazolidin-3,5-diylidene (ditz) < benzobis(imidazolin-2-ylidene) (BBI) < mesoionic pyrazolidin-3,5-diylidene (dipy), which is in line with their increasing donicities.
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