Bimetallic Iron-Rhodium anionic carbonyl clusters [Fe2Rh(CO)x]- (x= 10 or 11), [FeRh4(CO)15]2-, [Fe2Rh4(CO)16]2- and [FeRh5(CO)16]-.

The syntheses and interconversions of mixed iron-rhodium carbonyl clusters are described; a combination of X-ray analysis and multinuclear n.m.r. measurements allowed the structural characterisation of [FeRh 4(CO)15]2-, [FeRh5(CO) 16]-, and [Fe2Rh4(CO) 16]2-, which can all be obtained from the unstable cluster, [Fe2Rh(CO)x]- (x = 10 or 11)