Alkali metal carbonylmetallate

Approximately 25 years after Mond and co-workers had prepared the first carbonyl of cobalt, Co2(CO)8 (78), Hieber obtained HCo(CO)4 by the acidification of salts containing [Co(CO)4] (79), one of the first established carbonylmetallates (80). In 1941, Behrens, a student of Hieber, initiated his important and extensive investigations on the reduction of metal carbonyls and their derivatives by alkali and alkaline earth metals in liquid ammonia (81). At this time he established that various salts of [Co(CO)4]-, including Na[Co(CO)4] and K[Co(CO)4], could be obtained from the neutralization of HCo(CO)4 or the reduction of Cd[Co(CO)4]2 by sodium or potassium in liquid ammonia (4). On the basis of Behrens pioneering studies, we were... 

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