Preparation and structural characterisation of isocyanide gold(I) nitrates, [Au(NO3)(CNR)] (R = Et, But or C6H3Me2-2,6); new auriophilic motifs†

Abstract

The first examples of isocyanide gold(I) nitrates, [Au(NO₃)(CNR)] (R = Et, Bu^t or C₆H₃Me₂-2,6) have been prepared from the corresponding chlorides and AgNO₃. Full characterisation included crystal structure determinations for each example. The structures of the analogous compounds [AuCl(CNR)] (R = Et or C₆H₃Me₂-2,6) were also determined for comparison. All species show Au· · ·Au interactions in the solid state, but with different modes of aggregation; [AuCl(CNEt)] and [Au(NO₃)(CNBu^t)] have infinite zigzag chains, [AuCl(CNC₆H₃Me₂-2,6)] has a ‘broken’ chain of tetrameric units, [Au(NO₃)(CNEt)] has a linked chain of tetrameric units, while [Au(NO₃)(CNC₆H₃Me₂-2,6)] has a highly compressed chain. In each instance the Au· · ·Au interactions for [Au(NO₃)(CNR)] are shorter than for the analogous [AuCl(CNR)], suggesting NO₃^– enhances these secondary bonds. This is in direct contrast to previous theoretical predictions. The structure of the solvated ionic compound [Au(CNC₆H₃Me₂-2,6)₂]NO₃ has also been determined.