Phosphite complexes of copper(II) carboxylates and their derivatives. Crystal structure of penta-µ-acetato-bis(triethyl phosphite)tricopper-(I,II)

Abstract

Copper(II) alkanecarboxylates, [Cu₂(O₂CR¹)₄](R¹= Me, Et, or Prⁿ), react with trialkyl phosphites, P(OR²)₃(R²= Me, Et, or Prⁱ), in equimolar proportions in alcohol (R²OH) solution to form pale blue-green [Cu₂(O₂CR¹)₅{P(OR²)₃}₂] complexes, which have been characterised by microanalysis, spectroscopic (i.r., ¹H and ³¹P n.m.r., e.s.r., u.v.–visible), and magnetic susceptibility measurements. The crystal structure of [Cu₃(O₂CMe)₅{P(OEt)₃}₂] has been determined from X-ray diffractometer data by Patterson and Fourier methods. Crystals are monoclinic, space group C_c, with Z= 4 in a unit cell of dimensions a= 13.77(4), b= 19.10(3), c= 17.08(4)Å, and β= 125.6(2)°. The structure was refined by least-squares methods to R 0.10 for 651 reflections. The structure shows that a Cu₂(O₂CMe)₄ unit provides a monoatomic syn-anti bridge through oxygen to a Cu(O₂CMe){P(OEt)₃}₂ unit, the acetate group of which provides an anti-anti bridge between Cu₂(O₂CMe)₄ units to form a polymeric chain. In alcohol solution the chain is broken and the solvated fluxional monomeric [Cu₃(O₂CMe)₅{P(OR²)₃}₂](R²= Me or Et) units rearrange so that the copper(I) atom is connected to one of the copper(II) atoms through two unidentate bridging acetates. In alcohol solution [Cu₃(O₂CMe)₅{P(OR²)₃}₂](R = Me or Et) reacts with unidentate oxygen- or nitrogen-donor ligands, L, to form [Cu₂(O₂CMe)₄L₂] and [{Cu(O₂CMe)[P(OR²)₃]₂}₂]. The dimeric copper(I) complexes react with bidentate nitrogen- and phosphorus-donor ligands, L′, to form [Cu(O₂CMe){P(OR²)₃}L′][L′= 2,2′-bipyridine, 1,10-phenanthroline, 1,2-diaminoethane, or 1,2-bis(diphenylphosphino)ethane] which exist as fluxional monomers in solution.