GROUP IB ORGANOMETALLIC CHEMISTRY .29. SYNTHETIC AND STRUCTURAL ASPECTS OF POLYNUCLEAR ARYLCOPPERLITHIUM COMPOUNDS AR4CU2LI2(ARYLCUPRATES) AND INTERAGGREGATE EXCHANGE PHENOMENA IN AR4CU4-AR4LI4-AR4CU2LI2 SYSTEMS

The thermally stable arylmetal-IB-lithium compounds (2-Me2NCHZC6H4)4M2Li2 (M = Cu, Ag or Au; Z = H or Me) and (2-Me2NC6H4)4M2Li2 have been prepared by a 2 1 molar reaction of the aryllithium compounds with the corresponding metal-IB halide (Cu or Ag) or metal-lB halide phosphine complex (BrAuPPh3). 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 M2Li2 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 1H and 13C NMR spectroscopic data (J(AgC(1)), J(LiC(1)) of solutions of these tetranuclear compounds as well as on the 197Au Mössbauer data of solid (2-Me2NC6H4)4Au2Li2 (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 M2Ar bond cleavage. Some aspects of the organic reactions in which organocuprates are involved as intermediates are discussed in terms of the novel structural information. © 1979.