Synthesis and characterisation of four- and eight-membered ring auralactam complexes

The reactions of the cyclo-aurated gold(III) dihalide complex [{C6H3(CH2NMe2)-2-(OMe)-5}AuCl2] with N-cyanoacetylurethane [NCCH2C(O)NHCO2Et], 2-benzoylacetanilide [PhC(O)CH2C(O)NHPh] and acetoacetanilide [MeC(O)CH2C(O)NHPh], and [{C6H4(CH2NMe2)-2}AuCl2] with acetoacetanilide in dichloromethane with excess silver(I) oxide gives the first examples of auralactam complexes, containing (O)CHR′ four-membered rings. A single-crystal X-ray diffraction study on the complex [{C6H4(CH2NMe2)-2}AH(COMe)}] reveals similar structural features to related metallalactam complexes of platinum(II) and palladium(II). When a CDCl3 solution of the complex [{C6H3(CH2NMe2)-2-(OMe)-5}AHCN}] is allowed to stand for 18 h, a novel dimerisation reaction occurs, giving the insoluble product [{C6H3(CH2NMe2)-2-(OMe)-5}Au{N(CO2Et)C(O)CHCN}]2·2CDCl3, characterised by an X-ray structure determination. The dimer contains an eight-membered A ring.