Metal carbonyl anions halide bridged

These carbonyl anions are strong nucleophiles (see Nucleophile) and can be used to form a diverse range of new compounds. Protonation gives the /t-hydride (see Bridging Ligand) [(/u.-H) Mo(CO)5 ]. Reactions with other metal carbonyls lead to CO substitution and the formation of metal metal-bonded heteronuclear anions, for example, [Mo(CO)s Fe(CO)4] and [Mo(CO)5-Co(CO)4] . Reaction with main group halides is shown in Scheme 1. The dianion reacts similarly. 

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