Rhodium complexes polynuclear species

Rhodium carbonyl clusters with encapsulated heteroatoms, e.g., CRh6(C0)i5C]2 , [RhgPtCO l12 and [Rhi7S2(C0)32]3 , have been observed to be more resistant to fragmentation under 500-1000 atm of C0 H2 than homometal lie rhodium clusters. Polynuclear species account for 95-98 and 80-85 percent, respectively, of the total rhodium content of those systems, while the greatest catalyst activity has been noted with the latter complexes. CRh(C0>4l]— Is the only fragmentation product detected In both Instances. . ... 

We have already observed that simple antonlc, e.g., CRh(C0)4] , and neutral, e.g, HRh(C0)4 or Rh2(C0)s> rhodium complexes could be involved In the fragmentation and aggregation reactions of polynuclear species. In addition, the cationic moiety "Rh(C0)2+" has been found to formally coordinate to [Rh 4(C0)2534- +0 form [Rhi 5(C0)27]3 (equation 8), or to get detached from the latter cluster by halide ligands (equation 9) JJJ under ambient conditions. 

Another simple rhodium carbonyl complex that has been shown to be involved in the aggregation and fragmentation reactions of polynuclear rhodium species is "Rh(C0)2+ ". This moiety has been shown to be involved in such reactions under ambient conditions as reported by Chinl, et al. UJ (equations 21 and 22). 

In the search for catalytically active species, heterobi-and polynuclear molecules containing both U(III) and a transition metal (palladium, platinum, rhodium, or ruthenium) strongly bonded in close proximity but without a direct metal-metal bond were synthesized. Difunctional bridging ligands like cyclopentadienylphosphido ligands were used to form such complexes. 

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