
%0 Journal Article
%A Colton, R 
%A Farthing, RH 
%A Knapp, JE 
%T Carbonyl halides of the Group VIII transition metals. IV. Halocarbonyls and halocarbonyl anions of rhodium(III) and rhodium(I)
%J Australian Journal of Chemistry
%D 1970/07/01
%V 23
%N 7
%P 1351-1358
%K 
%R https://doi.org/10.1071/CH9701351
%U https://www.publish.csiro.au/paper/CH9701351 
%X Both rhodium trichloride and tribromide are easily carbonylated and subsequently reduced by refluxing formic acid-hydrohalic acid mixture to give almost quantitative yields of the rhodium(1) halocarbonyl anions [Rh(CO)2X2]- (X = Cl,Br). It has been shown that the reaction proceeds by the intermediate formation of the rhodium(111) halocarbonyl anions [Rh(CO)X5]2- followed by slow reduction to the rhodium(1) complexes. Evaporation of the respective solutions leads to almost quantitative recovery of the new rhodium(111) halocarbonyls Rh(CO)X3 and the well known rhodium(1) compounds [Rh(C0)2X]2.   Iododicarbonylrhodium(1) could not be isolated by this method and in fact the only products which could be isolated were triiodocarbonylrhodium(111), Rh(CO)I3, and its corresponding anion; this shows that although the carbonylation reaction had occurred the subsequent reduction did not proceed. In solution the rhodium(1) complexes [Rh(C0)2X2]- oxidize to give [Rh(CO)X5]2-. Caesium salts of these rhodium(111) anions are readily isolated, but addition of caesium salts to the rhodium(1) solutions did not give the expected Cs[Rh(CO)2X2] but instead the octahedral complexes Cs2[Rh(C0)2(H2O)X3]. All of these changes in composition and oxidation state have been followed in solution, as well as in the isolated solid products, by infrared spectroscopy. 
