Synproportionation reactions between copper(II) trihalogenoacetates Cu(CX3CO2)2, X = F, Cl or Br, and copper in the presence of carbon monoxide

Abstract

The trichloro- and tribromo-acetato derivatives of copper(II) of general formula Cu₂(CX₃CO₂)₄(CX₃CO₂H)₂ have been prepared by exchange reactions from Cu(CF₃CO₂)₂ and CX₃CO₂H (X = Cl or Br) in a hydrocarbon solvent. The chloro derivative, which has also been obtained from CuO in the presence of CCl₃CO₂H/(CCl₃CO)₂O, has been characterized by variable-temperature magnetic measurements and by X-ray diffraction. The trifluoroacetato carbonyl derivative of copper(I), Cu(CF₃CO₂)(CO), has been prepared: (a) by reaction of Cu₂O with CF₃CO₂H/(CF₃CO)₂O in the presence of CO; (b) by direct carbonylation of Cu(CF₃CO₂) in toluene or in the solid state; (c) by synproportionation of Cu(CF₃CO₂)₂ and copper in the presence of CO in MeOH, DME, THF or toluene at room temperature. Solutions of Cu(CCl₃CO₂)(CO) have been obtained by the synproportionation of Cu₂(CCl₃CO₂)₄(CCl₃CO₂H)₂ and copper under a CO atmosphere in toluene. No carbonyl derivative was observed in solution with Cu₂(CBr₃CO₂)₄(CBr₃CO₂H)₂ under similar conditions. On standing, hydrocarbon solutions of Cu(CCl₃CO₂)(CO) slowly gave CuCl(CO) and a mixed-valence, polynuclear carbonyl derivative of formula [Cu₄(CCl₃CO₂)₆(CHCl₂CO₂H)(CO)₂]_n which has fully been characterized by variable temperature magnetic measurements and by X-ray diffraction.