A study of the co-ordination behaviour of various 2-pyridylketones. Part II. Rhodium(III) complexes of 2-benzoylpyridine

Abstract

Reaction of rhodium trichloride and 2-benzoylpyridine (PhCOpy) in ethanol affords the complex Rh(PhCOpy)₂Cl₂,Rh(PhCOpy)Cl₄. The cation has been obtained as perchlorate in yellow and orange isomeric forms. Both isomers have trans chloride ligands. Reaction of any of these compounds with boliing water gives Rh(PhCOpy)₂Cl₂,OH, a neutral six-co-ordinate rhodium(III) complex containing one unidentate 2-benzoyl-pyridine molecule co-ordinated via oxygen. Reflexing the last compound in aqueous ethanol gives a further neutral complex, Rh(PhCOpy)₂Cl₃ containing one molecule of benzoylpyridine co-ordinated through nitrogen only Another neutral complex [Rh(PhCOpy)Cl₂,H₂O],H₂O is considered to arise from the aquation of the Rh(PhCOpy)Cl₄ ^– anion. Corresponding bromo-complexes have been prepared and spectroscopic data, including assignments of rhodium–halogen stretching frequencies, are presented.