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}A H(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}A HCN}] 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

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ring.