Group 1B organometallic chemistry XXIX. Synthetic and structural aspects of polynuclear arylcopperlithium compounds Ar4Cu2Li2 ('arylcuprates') and interaggregate exchange phenomena in Ar4Cu4/Ar4Li4/Ar4Cu2Li2 systems

Abstract

The thermally stable arylmetal-IB-lithium compounds (2-Me{2}NCHZC{6}H{4}){4}M{2}Li{2} (M = Cu, Ag or Au; Z = H or Me) and (2-Me{2}NC{6}H{4}){4}M{2}Li{2} have been prepared by a 21 molar reaction of the aryllithium compounds with the corresponding metal-IB halide (Cu or Ag) or metal-lB halide phosphine complex (BrAuPPh{3}). These tetranuclear complexes were also made by an interaggregate exchange reaction of the pure arylmetal-IB clusters with the aryllithium compound.The structure of these compounds in solution consists of aryl groups bridging one metal-lB and one lithium atom of a trans M{2}Li{2} core. The four built-in ligands coordinate to lithium resulting in two-coordination at M and four-coordination at Li. These conclusions were based on }1{H and }1{}3{C NMR spectroscopic data (J(Ag@?C(1)), J(Li@?C(1)) of solutions of these tetranuclear compounds as well as on the }1{}9{}7{Au Mossbauer data of solid (2-Me{2}NC{6}H{4}){4}Au{2}Li{2} (IS 5.65 mm/s and QS 12.01 mm/s).The interaggregate exchange between the tetranuclear species is discussed in terms of an associative mechanism involving formation of an octanuclear intermediate in which the aryl groups can migrate via (3c-2e)edge-(2c-2e)corner(3c-2e)edge movements without M{2}@?Ar bond cleavage.Some aspects of the organic reactions in which organocuprates are involved as intermediates are discussed in terms of the novel structural information.