Metal atoms acyl halides

Use of large excesses of acyl halides results in fragmentation of 2 and 4I44). The observed inertness of the bridging thiolates is not suprising, as coordination to two metal centers would be expected to substantially reduce the nucleophilic character of the thiolate sulfur. Additionally, all reasonable assignments of oxidation states indicate that the Mo atoms in 1-5 are approximately trivalent octahedrally coordinated Mo(III) (d3) would be expected to be kinetically non-labile. 

Although a variety of new preparative routes has been developed in recent years (for reviews see refs 1 -10), the transformation of the metal-carbonyl carbon bond of a metal-carbonyl complex into a metal-carbene carbon bond is still the most useful and versatile method for preparing transition-metal carbene complexes. The addition of a carbanion to the carbon atom of a carbonyl ligand yields an anionic acyl complex that subsequently can be reacted with an electrophile to give a neutral carbene complex. Thus, the syntheses of anionic acyl and neutral carbene complexes are closely related, for almost all the carbene complexes considered in this section acyl complexes are precursors, although most have not been isolated and characterized. The syntheses of acyl complexes via CO insertion (for reviews see refs. 11, 12) or by reaction of metal carbonyl anions with acyl halides is outside the scope of this section. 

Ketones can be prepared by the replacement of the halogen atom of an acyl halide (e.g. CH3COCI) by an alkyl group. This replacement can be effected as the result of the action of certain organic compounds which contain metals. The zinc alkyls or magnesium alkyl halides are generally used. Methyl ethyl ketone can be prepared in this way from acetyl chloride and magnesium ethyl iodide —... 

The N2 hgand bound to a metal atom may also be susceptible to attack by electrophilic reagents other than acids. In fact, reactions of coordinated N2 or its protonated derivatives have been extensively studied with a range of organic compounds including alkyl and acyl halides, carboxyhc anhydrides, aldehydes, ketones, and activated aryl or vinyl halides to directly form the carbon-nitrogen bonds. 

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. 

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