Reduction of A[Co(CO)4] by three equivalents of A (A = sodium or potassium) in liquid ammonia provides salts containing tricarbonylcobaltate(3 -). A satisfactorily pure sodium compound, Na3[Co(CO)3] is described for the first time. Reactions of A3[Co(CO)3] with two equivalents of Ph3ECl (E = Ge, Sn, Pb) provides 50-70% yields of trans-(Ph3E)2Co(CO)3- which have been isolated as analytically pure Et4N+ salts. Treatment of liquid ammonia slurries of K3[Co(CO)3] with three equivalents of NH4Cl in the presence of PR3 or CNR, results in evolution of hydrogen gas and the formation of Co(CO)3L-. In the case of L = t-BuNC, the first such isocyanide substituted carbonylcobaltate(1 -) species was prepared and isolated in a 67% yield by this procedure. A possible pathway for the formation of Co(CO)3L- from K3[Co(CO)3] is discussed in light of similar protonation reactions reported for other carbonylmetallate trianions.
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We thank the donors of the Petroleum Research Fund, administered by the American Chemistry Society, and the National Science Foundation for continuing support of this research.