PENTAMETHYLCYCLOPENTADIENYLRHODIUM BIS-CARBOXYLATES - MONOHAPTO CARBOXYLATE COORDINATION, DIHAPTO CARBOXYLATE COORDINATION, AND WATER COORDINATION TO CP-ASTERISK-RH

Reaction between [CpRhCl2](2) and silver carboxylates in anhydrous, n on-coordinating solvents produces CpRh(eta(2)-O(2)CR)(eta(1)-O(2)CR) complexes with the unusual feature of having both the eta(2) and eta(1 ) carboxylate ligands bound to the same metal. The benzoate complex Cp Rh(eta(2)-O(2)CPh)(eta(1)-O(2)CPh) was characterized crystallographic ally and its structure is discussed. CpRh(eta(2)-O(2)CPh)(eta(1)-O(2) CPh) was found to crystallize in the monoclinic space group P2(1)/c wi th a=11.658(3), b=14.574(4), c=26.248(6) Angstrom, beta=101.87(2)degre es and V=4364(2) Angstrom(3) for Z=8. These bis-carboxylate compounds are very hygroscopic, reacting with water quite readily to form the aq uo complexes, CpRh(OH2)(eta(1)-O(2)CR)(2). The acetate aquo complex C pRh(OH2)(eta(1)-O(2)CMe)(2) was characterized crystallographically an d was found to crystallize in the monoclinic space group P2(1)/c with a=8.910(2), b=12.854(4), c=14.710(3) Angstrom, beta=106.82(2)degrees a nd V=1612.6(7) Angstrom(3) for Z=4. The water molecule in CpRh(OH2)(e ta(1)-O(2)CMe)(2) was found to internally hydrogen bond to the coordin ated acetate groups. The coordination of water in CpRh(OH2)(eta(1)-O( 2)CMe)(2) is unusual in that the Rh-O bond is perpendicular to the pla ne of the water molecule. The geometry of water coordination in these CpRh complexes is compared with geometries found for water coordinate d to other non-classical, organometallic compounds.