SYNTHESIS AND PROPERTIES OF TETRADECACARBONYLHEXACOBALTATE TETRAANION DERIVATIVES

The anion [Co6(CO)14]4- has been obtained by reducing Co4(CO)12 with an alkali metal (Li, Na, K) in tetrahydrofuran, or with cobaltocene as a homogeneous reducing agent. In both cases the initial product was the anion [Co6(CO)15]2-, which was subsequently reduced to [Co6(CO)14]4-. In toluene, cobaltocene reacted with Co2(CO)8 to give cobalticinium tetracarbonylcobaltate, while with Co4(CO)12 the brown salt {[(π-Cp)2Co][Co4(CO)11-12]}n was precipitated as the first reaction product. This anion is believed to be the first intermediate in the reduction of Co4(CO)12. The salts M4[Co6(CO)14][MK, NEt4 and (π-Cp)2Co] have been characterized by analysis. The solutions containing the anion [Co6(CO)14]4- reacted with carbon monoxide giving tetracarbonylcobaltate(1-) derivatives. The salt Na4[Co6(CO)14] has been obtained in two different isomeric forms; the considerable differences observed in the IR spectra of several salts [Li, Na, K, NEt4 and (π-Cp)2Co] are in accord with the postulated existence of several isomeric forms of the anion [Co6(CO)14]4-. © 1969.