SYNTHESIS AND CHARACTERIZATION OF IRON METALLOCARBOXYLATES

The synthesis and characterization of hydrated metallocarboxylate anion salts (eta-5-C5H5)Fe(CO)(PPh3)COO-M+.xH2O (M = Li, Na, K) and (eta-5-C5Me5)Fe(CO)(PPh3)COO-K+.xH2O together with the anhydrous analogues (eta-5-C5H5)Fe(CO)(PPh3)COO-M+ (M = Li, K) and (eta-5-C5Me5)Fe(CO)(PPh3)COO-K+ are reported. Comparisons of the reactions of these salts toward equimolar amounts of acids or methylating agents show that there is competitive cleavage of the carboxylate C-O and O-M bonds. The more oxophilic cations promote C-O bond cleavage; the more electron-donating pentamethylcyclopentadienyl ligand also promotes C-O bond cleavage when compared to the cyclopentadienyl-substituted compound. Hydration appears to strengthen the O-M bond slightly. Reactions of the potassium salts with an electrophilic cation Mn(CO)5(PPh3)+BF4- result in oxide transfer whereas reactions of the same metallocarboxylates with Ph3SnCl yield bimetallic CO2-bridged complexes. The anhydrous salts are more thermally stable than the hydrates. All of the metallocarboxylate salts bind CO2 strongly; decomposition occurs as a result of hydrolysis to the corresponding metallocarboxylic acids.