Potassium naphthalenide reductions of [(C5R5)HfCl3] (R H, Me) in 1,2-dimethoxyethane at -60°C followed by carbonylation at atmospheric pressure provide 25-50% isolated yields of the first examples of carbonyl anions of hafnium(0), [(C5H5)Hf(Co)4]- and [(C5Me5)Hf(CO)4]-. These were isolated as tetraethylammonium salts as well as K(cryptand-2.2.2) and K(15-Crown-5)2+ salts for the latter anion and now represent two of only four presently known Hf0 carbonyls. They were characterized by elemental analyses, IR and 1H and 13C NMR spectra.
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Acknowledgement. We thank the National Science Foundation (U.S.) and the Donors of the Petroleum Research Fund, administered by the American Chemical Society for financial support.