Cobalt carbonyls green

Mankind has produced acetic acid for many thousand years but the traditional and green fermentation methods cannot provide the large amounts of acetic acid that are required by today s society. As early as 1960 a 100% atom efficient cobalt-catalyzed industrial synthesis of acetic acid was introduced by BASF, shortly afterwards followed by the Monsanto rhodium-catalyzed low-pressure acetic acid process (Scheme 5.36) the name explains one of the advantages of the rhodium-catalyzed process over the cobalt-catalyzed one [61, 67]. These processes are rather similar and consist of two catalytic cycles. An activation of methanol as methyl iodide, which is catalytic, since the HI is recaptured by hydrolysis of acetyl iodide to the final product after its release from the transition metal catalyst, starts the process. The transition metal catalyst reacts with methyl iodide in an oxidative addition, then catalyzes the carbonylation via a migration of the methyl group, the "insertion reaction". Subsequent reductive elimination releases the acetyl iodide. While both processes are, on paper, 100%... 

ChIorotris(triphenylphosphine)cobalt, CoCUPCQH,),], (1). This bright green, moderately air-stable complex is obtained by reaction of CoClitPlQHjljJj with P(C6Hs) and Zn in CHjCN. The reagent reacts with benzocyclobutenediones to insert the metal between the two carbonyl groups. 

From the absorption spectra of the various green solutions produced by the reaction of hydrogen peroxide on a cobaltous salt in the presence of potassium (or sodium) bicarbonate, acetate, tartrate, citrate or oxalate, Durrant - concluded that the green color depended on complex ions with the >Co O Co < nucleus, and that the differences in tint of green and in absorption spectra depended probably on the various association of carbonyl groups attached to the nucleus. On account of his detailed study, the reaction discovered by Field has been called Field-Durrant reaction ... 

---