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

The trichloro- and tribromo-acetato derivatives of copper(II) of general fo rmula Cu-2(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 c hloro derivative, which has also been obtained from CuO in the presence of CCl3CO2H/(CCl3CO)(2)O, has been characterized by variable-temperature magne tic measurements and by X-ray diffraction. The trifluoroacetato carbonyl de rivative of copper(I), Cu(CF3CO2)(CO), has been prepared: (a) by reaction o f Cu2O with CF3CO2H/(CF3CO)(2)O in the presence of CO; (b) by direct carbon ylation of Cu(CF3CO2) in toluene or in the solid state; (c) by synproportio nation 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 obta ined by the synproportionation of Cu-2(CCl3CO2)(4)(CCl3CO2H)(2) and copper under a CO atmosphere in toluene. No carbonyl derivative was observed in so lution with Cu-2(CBr3CO2)(4)(CBr3CO2H)(2) under similar conditions. On stan ding, hydrocarbon solutions of Cu(CCl3CO2)(CO) slowly gave CuCl(CO) and a m ixed-valence, polynuclear carbonyl derivative of formula [Cu-4(CCl3CO2)(6)( CHCl2CO2H)(CO)(2)](n) which has fully been characterized by variable temper ature magnetic measurements and by X-ray diffraction.