Structural Diversity of Pentafluorophenylcopper Complexes. First Evidence of π-Coordination of Unsupported Arenes to Organocopper Aggregates

Abstract

The binding behavior of arenes toward pentafluorophenylcopper was investigated. Crystallization of pentafluorophenylcopper from a mixture of 1,2-dichloroethane and cyclohexane affords the homoleptic tetrameric complex [Cu(C6F5)]4, whereas a π-complex, [Cu(C6F5)]4(η2-toluene)2, is obtained from toluene solution. The unique coordination of two toluene molecules in [Cu(C6F5)]4(η2-toluene)2 leads to major structural changes as the regular square planar tetramer is distorted toward a butterfly structure with one short and one long diagonal Cu···Cu distance of 2.5935(3) and 3.955(1) A, respectively. The toluene molecules are bound in an unsymmetrical η2-coordination mode with the shortest contacts observed between copper and the meta carbon atoms (d(Cu−C) = 2.271(2), 2.298(2) A) and slightly longer distances to the para positions (d(Cu−C) = 2.339(2), 2.455(4) A). Multinuclear NMR studies show that complexation to the intact tetrameric cluster species also occurs in neat solution of the aromatic species. Strongl...