Syntheses and characterizations of homovalent and heterovalent dinuclear gold ylide metallocycles

Abstract

Homovalent and heterovalent derivatives of the gold ylide metallocycle (Au[4(CH2)2PPh2l ) 2(l) have been synthesized. Substitution reactions with the potentially bidentate ligands methylenediphenylthiophosphinate (mtp) and diphenyldithio phosphinate (dtp) have been carried out using dihalide, tetrahalide, and A-frame derivatives of 1. Some of these reactions proceeded as metathesis reactions, while others involved the reduction of the gold atoms and the formation of a gold-gold bond The molecular structures of f Au[ii-(CH2)2PPh2l ) 2(dtP)2 (4), Au[@(CH2)2pMe2l)2(MtP)2(6), anti-[AuBr(mtp)[4-(CH2)2pPh2l 12 (7), Au[4 (CH2)2pPh2l)2(Mtp)Br (8), t AU2([i-CH2)[4-(CH2)2pPh2]2)(dtP)2 (10), and Au[4(CH2)2pph2]l2(MtP)l (II) have been obtained by X-ray crystallography. The structural trans influence on the Au-Br bond lengths of 7 and 8 were compared to each other and to other structurally characterized derivatives of 1. The synthesis of a new gold acyl complex has been reported. NNM and IR spectra supported the formation of an asymmetrical Au'-Au' metallocycle. The presence of cyanide ligands greatly affects the chemistry of 1. When cyanide ligands have been involved in either the substitution of halides or in oxidative addition, the production of mixed-valence, Au/Au', metallocycles were observed. The series of structural isomers possible for the halide derivatives of I was completed with the structural determination of the mixed-valence complex cis-AuAuBr2[4 (CH2)2PPh2]2) (15). Compound 15 was produced in the presence of cyanide. Ligand exchanges, geometrical isomenzation, and single-center reductions may all be occurring due to the presence of cyanide ligands.