Carbonyl metallates, redox condensation reactions

Related synthetic routes include the redox condensation reaction of carbonylate anions with neutral carbonyls, e.g., Eq. (12) (55), metal exchange reactions between carbonylate anions, e.g., Eq. (13) (56), and direct reductive carbonylation of metal halides, e.g., Eq. (14) (57). The stoichiometry of the products are not rational, and the mechanisms clearly are very complicated, though once again these reactions, under experimental optimization, can provide very useful synthetic routes. 

The reaction of a carbonylmetalate with a neutral metal carbonyl has been labeled a redox condensation by Chini et al. (40, 41) and has been as widely used as a pyrolysis reaction for synthesizing mixed-metal clusters. Carbonylmetalates usually react rapidly with most neutral carbonyls, even under very mild conditions. A large number of mixed-metal hydride clusters have been formed via this type of reaction, primarily because the initial products are anionic clusters that in many cases may be protonated to yield the neutral hydride derivative. 

Redox condensation is not restricted to the reaction of a carbonylmetal-ate with a neutral carbonyl, and it is possible to condense the carbonyl-metalate with other simple cationic species for example (35,102),... 

Few successful reactions are known by which an organometallic nitrosyl product has been formed from the condensation of mononuclear metal nitrosyl complexes. The unique cluster (Tj -C5H5)3Mn3(NO)4 (39), which contains the only i3-NO known (7) (40), is prepared using photochemical or thermal (41) decarbonylation of (Tj -C5H5)2Mn2(CO)2(NO)2 [Eq. (25)]. The use of the redox condensation of a nitrosyl carbonylmetallate with a neutral metal carbonyl cluster to produce a nitrosyl cluster has... 

The reaction of metal carbonyl complexes with carbonyl anions is a widely used technique for synthesis of mixed-metal clusters. This reaction is also termed reductive condensation or redox condensation. The metal carbonyl anion may be generated in situ or may be separately isolated. The mixed-metal product is usually an anion protonation can be used to generate a neutral cluster hydride. 

---