SPLITTING DIOXYGEN WITH MESITYLCOPPER(I) - AN ARYLCOPPER(I) INTERMEDIATE, FORMED IN A COUPLING REACTION, CONTAINING 2 TRAPPED TRIGONAL PYRAMIDALLY COORDINATED OXIDES

Oxidatively induced reductive coupling of mesityl from mesitylcopper(I ) effected by dioxygen is shown to result in an intermediate, [Cu10O2( Mes)6], containing oxide ligands trapped in an unusual coordination mo de on the surface of the cluster. [Cu10O2(Mes)6] crystallizes in the m onoclinic space group C2/c with a = 16.452(5) angstrom, b = 33.947(8) angstrom, c = 12.902(5) angstrom, beta = 125.66(1)-degrees, and Z = 4. The complex has approximate D3h symmetry such that the two oxide liga nds and a central copper(I) are situated on the approximate 3-fold axi s while the remaining nine copper(I) centers form three wings, each wi th three copper(I) atoms participating in 2 electron-3 center bonds wi th two mesityl groups. Cu...Cu distances involved in the latter intera ctions range from 2.376(8) to 2.439(6) angstrom. The oxide ligands are trigonal pyramidally coordinated by four copper(I) atoms at distances of 1.81(2)-1.90(2) angstrom and are slightly displaced (0.1 angstrom) from the cluster surface, i.e. from the trigonal coordination plane, toward the central copper(I). The unusual coordination mode of oxygen on the surface of the cluster, the extreme instability of the complex, and its color are discussed in the context of extended Huckel (EHT) c alculations.