Physicochemical behaviour of copper(II) complexes of chelated dianune ligands: Catalytic role of diaquabis(ethylenediamine)copper(II) perchlorate in acylal formation

Abstract

Preparation and propertics of a few chelated diarnine complexes of copper(II) are reported. Thc compounds, [Cu(en)₂(H₂O)₂](C lO₄)₂ (1), [Cu(tmen)₂(H₂O)₂](C lO₄)₂ (2), [Cu(en)₂Cl₄]ո (3) and [Cu(en)₂(SO₄)₂(H₂O)₄].2H₂O (4) have been prepared in moderate to excellent yields and characterized by various physicochemical techniques. The structure of [Cu₂(en)₂Cl₄]n (3) has been determined by single crystal X-ray diffraction. Complex 3 crystallizes in monoclinic space group P2l/m, with unit cell parameters a = 6.7850 (14) Aº, b = 5.7600(12)Aº, c = 8.2240(l6)Aº, β = 93.75(3)º, V = 320.7(1)Aº³. The structurc has been solved by direct method and refined by full-matrix least squares to final R₁ = 0.0460, wR₂ = 0.1249 and GooF = 1.135 for all 8 I 8 reflections. Each copper atom in complex 3 is present in a distorted octahedral environment creatcd by a chelating ethylenediamine ligand and four chlorine atoms. Two adjacent parallel -Cu-Cl-Cu- chains joined by short Cu-C1 bonds give rise to a zigzag ribbon-like polymer. Complex 1has been studied as a catalyst 1'01' thc conversion of aromatic aldehydes to acylals under solvent-free conditions at room temperature.