Gold(I) Complexes Bearing Sterically Imposing, Saturated Six- and Seven-Membered Expanded Ring N-Heterocyclic Carbene Ligands

The synthesis and characterization of novel six- and seven-membered expanded ring N-heterocyclic carbene (NHC) complexes of the general formula [Au­(NHC)­Cl] are described. The key structural parameters of complexes <b>1</b>, <b>2</b>, and <b>4</b> have been evaluated by solid-state analysis and by means of the percent buried volume (%<i>V</i>_bur) analysis. Complex <b>4</b> is found to demonstrate the largest %<i>V</i>_bur value of any gold­(I) NHC complex reported to date, with a value of 52.6. All complexes <b>1</b>–<b>4</b> have been evaluated in a preliminary catalytic survey of the hydration of internal alkynes