The Effect of Hard and Soft Donors on Structural Motifs in (Isocyanide)gold(I) Complexes

Treatment of the (isocyanide)gold(I) species LAuCl (L=tBuNC, 2,6-Me2C6H3NC) with 4-mercaptobenzoic acid in the presence of NaOMe yields the complexes [Au(4-SC6H4CO2H)L] in good yield. Reaction of LAuCl with 2-HSQn (Qn=quinoline) and 2-HSPy (Py=pyridine) under the same conditions provides the thiolato compounds [Au(2-SQn)L] and [Au(2-SPy)L], respectively. A structural investigation of the pyridylthiolato compound revealed chains of molecules with alternating medium and long Au−Au interactions. Treatment of this compound with HBF4 results in the cationic species [Au(2-HSPy)(2,6-Me2C6H3NC)]+ as the BF4− salt. The same product is obtained on reaction of [AuCl(2,6-Me2C6H3NC)] with AgOTf followed by HSPy. Treatment of the gold(I) halide compounds LAuCl (L=tBuNC, 2,6-Me2C6H3NC) with potassium 1,3,4-thiadiazole-2,5-dithiolate (KSSSK) leads to the isolation of dinuclear thiolatogold complexes [(AuL)2(SSS)]. These products go on to form insoluble polymers through loss of isocyanide on standing in solution. A single crystal of [{Au(tBuNC)}2(SSS)] was obtained and the subsequent structural analysis revealed one of the most complicated networks known based solely on aurophilic interactions. A good comparison to the ‘soft' S-donation of the thiolato ligands was provided by the synthesis of a number of nitratogold(I)complexes with the anion bound through the ‘hard' O-donor. Reaction of iPrNC and CyNC with Au(tht)Cl provided the complexes [AuCl(iPrNC)] and [AuCl(CyNC)], respectively. These compounds were found to yield the respective nitrato species [Au(NO3)iPrNC)] and [(Au(NO3)(CyNC)] on treatment with AgNO3. The nitrato complexes yielded single crystals enabling a structural investigation to be carried out. While [Au(NO3)(CyNC)] has a more conventional structure with dimers aligned into strings with alternating short and long aurophilic bonding, [Au(NO3)(iPrNC)] has a unique structure based on strings of alternating, corner-sharing Au6 and Au8 units with short Au−Au contacts in edge-sharing Au3 triangles.