Supramolecular chemistry of gold(I) thiocyanate complexes with thiophene, phosphine and isocyanide ligands, and the structure of 2,6-dimethylphenyl isocyanide

Abstract

The reaction of equivalent quantities of (L)AuCl (L = tetrahydrothiophene, trimethylphosphine, 2,6-xylyl isocyanide or mesityl isocyanide) and KSCN in CH₂Cl₂–water gave (L)Au(SCN) in excellent yield. The products were formed through Cl ↔ (SCN) anion exchange in the two-phase systems. Crystals of (THT)Au(SCN) contain short inter-ion Au ⋯ Au contacts (3.006 Å) within chain polymers of alternating cations [Au(THT)₂]⁺ and anions [(NCS)₂Au]⁻. The crystal structure of (Me₃P)Au(SCN) exhibits dimers based on short Au ⋯ Au contacts of 3.099 Å. The dimers appear to aggregate further by long Au ⋯ S contacts giving a tetrameric motif. Molecules of (2,6-Me₂C₆H₃NC)Au(SCN) crystallise as flat, centrosymmetric dimers with long intermolecular Au ⋯ Au and Au ⋯ S contacts. Although the general aurophilic motif of (2,4,6-Me₃C₆H₂NC)Au(SCN) is similar to (2,6-Me₃C₆H₃NC)Au(SCN), its structure has two different dimers formed from similar monomers. The crystal structure of 2,6-Me₂C₆H₃NC was also characterised and (consistent with bonding theory of metal isocyanides) exhibited a CN bond which is slightly longer than in the gold(I) complex.