Reduction of several metal carbonyl dimers including Mn2](CO)10, [C5H5Fe(C0)2]2, Co2(CO)8, and [C5H5M(CO)3]2 (M = Cr, Mo and W) by sodium-potassium alloy (NaK) in tetrahydrofuran at room temperature provides a rapid and clean method for the production of the corresponding metal carbonyl anions in high yield. Isolation and characterization of [n-Bu4N] [Fe(CO)2C5H5] from the iron dimer reduction is described. Reductions of other carbonyls including M(CO)6 (M = Cr, Mo and W) and Re2(CO)10 proceed more slowly than previously established methods and provide principally M2(CO)102- and Re(CO)55-. Methods for the preparation of Re(CO)5- are critically considered. The reaction of NaK with [C5H5NiCO]2 is discussed in relation to previously reported results. Infrared solution spectra of a number of carbonyl anions in THF, obtained in a special infrared solution cell, are reported.
Bibliographical noteFunding Information:
We are grateful to the donors of the Petroleum Research Fund administered by the American Chemical Society and to the University of Minnesota Graduate School for partial support of this work. We also thank Mr. Robert A. Fal-tynek for help on studying the nickel reductions.