HIGHLY REDUCED ORGANOMETALLICS .28. SYNTHESIS, ISOLATION, AND CHARACTERIZATION OF [K(CRYPTAND 2.2.2)]2[HF(CO)6], THE 1ST SUBSTANCE TO CONTAIN HAFNIUM IN A NEGATIVE OXIDATION-STATE - STRUCTURAL CHARACTERIZATION OF [K(CRYPTAND 2.2.2)]2[M(CO)6].PYRIDINE (M = TI, ZR, AND HF)

Reductive carbonylation of M(CO)4|CH3C(CH2PMe2)3], M = Ti, Zr, and Hf, by [K(cryptand 2.2.2)] [naphthalene] at -70 followed by warming provides practically quantitative yields of the thermally robust salts [K(cryptand 2.2.2)]2[M(CO)6], include previously inaccessible [Hf(CO)6]2-. X-ray crystal structure analyses show the presence of essentially unperturbed octahi nexacarbonyl metal units in all three salts. This study represents the first structural characterization of “pure” carbonyimetallates of the group 4 elements and establishes the existence of a compound containing hafnium in a negative (-2) oxidation state for the first time. © 1990, American Chemical Society. All rights reserved.