Twisting the arm: Structural Constraints in Bicyclic Expanded-Ring N-Heterocyclic Carbenes - data

A series of diaryl, mono-aryl/alkyl and dialkyl mono- and bicyclic expanded-ring N-heterocyclic carbenes (ER-NHCs) have been prepared and their complexation to Au(I) investigated through the structural analysis of fifteen Au(NHC)X and/or [Au(NHC)2]X complexes. The substituted diaryl 7-NHCs are the most sterically encumbered with large buried volume (%VB) values of 40-50% with the less flexible six-membered analogues having %VB values at least 5% smaller. Although the bicyclic systems containing fused 6- and 7-membered rings (6,7-NHCs) are constrained with relatively acute NCN bond angles, they have the largest %VB values of the dialkyl derivatives reported here, a feature related to the fixed conformation of the heterocyclic rings and the compressional effect of a pre-set methyl substituent. The data presented are text files containing details of the single-crystal X-ray diffraction collection and solution. They contain fractional coordinate data based on cartesian axes that can be read by specialist software (Ortep, Mercury etc) to generate views of the molecular structures.