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

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 Angstrom) within chain polymers of alternating cations [Au(THT)(2)](+) and anions [(NCS)(2)Au](-). The crystal structure of (Me3P)Au(SCN) exhibits dimers based on short Au . . . Au contacts of 3.099 Angstrom. 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 C=N bond which is slightly longer than in the gold(I) complex.