Rhenium acyl complexes reaction

Cyclic cobalt-acyl complexes can be deprotonated, and subsequent reaction of these enolates with aldehydes gives predominantly the anti/threo product (Scheme 63). Rhenium-acyl complexes can be deprotonated in the same manner. These lithium enolates can be alkylated or can react with [M(CO)5(OTf)] (M = Re, Mn) to give the corresponding enolates (Scheme Many transition metal enolates of type (21) or (22) are known, - but only a few have shown normal enolate behavior , e.g. aldol reaction, reaction with alkyl halides, etc. Particularly useful examples have been developed by Molander. In a process analogous to the Reformatsky reaction, an a-bromo ester may be reduced with Smia to provide excellent yields of condensation products (Scheme 65) which are generated through intermediacy of a samarium(III) enolate. ... 

The electrophilicity of the alkylidyne carbon in cationic complexes of manganese and rhenium such as 154 or 157 is well established. A study by Chen et al. established that the carbonyl ligands are also potential sites for nucleophilic attack (157,158). Reaction of 154 with the bulky carborane anion LiCjBioH, results in the formation of two products the carbene complex 156, resulting from attack at the alkylidyne carbon, and the alkylidyne acyl complex 155, resulting from attack at a carbonyl ligand [Eq. (135)]. At room temperature complex 155 transforms into complex 156. 

The acyl complex of reaction (i) undergoes decarbonylation above its melting pont (182-184°C) to give the corresponding compound containing a rhenium-silicon bond . 

Acids, acyl, and aroyl halides all react with [ReCl(N2)(PMe2Ph)4]. However, protonation occurs at the metal to give the hydride [ReClH(N2)-(PMe2Ph)4], whereas slow acylation and aroylation occur at the end nitrogen atom. Interestingly, this latter reaction is the reverse of the preparation of the rhenium dinitrogen complexes. Alkyl halides do not react with rhenium complexes of dinitrogen. 

Further studies on the reaction of CH3Mn(CO)s with MnfCOls indicated that these species are in equilibrium with an anionic acyl complex which can be trapped as a carbene complex by O-alkylation (Anderson and Casey, 1971). The corresponding reaction of Re(CO)5 with CH3Mn(CO)s did not produce the expected manganese-carbene complex (VIII), but gave the rhenium-... 

Whilst reaction of acyl chloride 303 with Na[Co(CO)3(PEt3)] affords the oxocyclobut-enyl complex 306" by ring expansion and CO loss, analogous treatment with NaRe(CO)5 delivers the non-fluxional // -cyclopropenylrhenium compound 305" . In the latter case, compound 304 loses carbon monoxide with concomitant migration of the cyclopropenyl moiety from carbonyl to rhenium as an allylic rearrangement rather than a 1,2-shift. 

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