An unusually stable octanuclear sigma-mesityl-bridged mu(4)-oxo-copper(I) complex encapsulated by a pyrazolate-based compartmental ligand scaffold

A new compartmental pyrazole-derived chelating ligand, four equivalents of mesitylcopper and stoichiometric amounts of di-oxygen lead to the formation of a remarkably stable organometallic framework that can be described as a heteroleptic O-centered cuprate anion [(MesCu(I))(4)(mu(4)-O)](2-) linked via sigma-mesityl-bridges to two surrounding binuclear Cu(I)-pyrazolate clamps.