Pentamethylcyclopentadienylrhodium bis-carboxylates: Monohapto carboxylate coordination, dihapto carboxylate coordination, and water coordination to Cp*Rh
Reaction between [Cp*RhCl2]2 and silver carboxylates in anhydrous, non-coordinating solvents produces Cp*Rh(η2-O2CR) (η1-O2CR) complexes with the unusual feature of having both the η2 and η1 carboxylate ligands bound to the same metal. The benzoate complex Cp*Rh(η2-O2CPh) (η1-O2CPh) was characterized crystallographically and its structure is discussed. Cp*Rh(η2-O2CPh) (η1-O2CPh) was found to crystallize in the monoclinic space group P21/c with a=11.658(3), b=14.574(4), c=26.248(6) Å, β=101.87(2)° and V=4364(2) Å3 for Z=8. These bis-carboxylate compounds are very hygroscopic, reacting with water quite readily to form the aquo complexes, Cp*Rh(OH2) (η1-O2CR)2. The acetate aquo complex Cp*Rh(OH2) (η1-O2CMe)2 was characterized crystallographically and was found to crystallize in the monoclinic space group P21/c with a=8.910(2), b=12.854(4), c=14.710(3) Å, β=106.82(2)° and V=1612.6(7) Å3 for Z=4. The water molecule in Cp*Rh(OH2) (η1-O2CMe)2 was found to internally hydrogen bond to the coordinated acetate groups. The coordination of water in Cp*Rh(OH2) (η1-O2CMe)2 is unusual in that the Rh-O bond is perpendicular to the plane of the water molecule. The geometry of water coordination in these Cp*Rh complexes is compared with geometries found for water coordinated to other non-classical, organometallic compounds.
Boyer, PM; Roy, CR; Bielski, JM; Merola, JS
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