Rhenium pentacarbonyl halides

The decacarbonyls of manganese, technetium, and rhenium, of formula M2(CO)io, have terminal carbonyl groups and a metal-metal bond. The molecular symmetry is D d with the two M(CO)s fragments in a staggered conformation. The heterodinuclear decacarbonyl MnRe(CO)io is also known as obtained by the redox reaction of a rhenium pentacarbonyl halide with the pentacarbonylmanganate(-I) anion at room temperature (at 160 °C or higher, the heterodinuclear carbonyl tends to form the homodinuclear compounds with an equilibrium constant close to the statistical value ). The X-ray diffraction stndy of MnRe(CO)io has shown the Mn-Re distance of 2.909 A to be shorter than the sum of the covalent radii obtained from the homodinuclear compounds (Table 3). 

The synthesis of pentacarbonyl rhenium(I) halides, Re(CO)5X, succeeded from simple and complex rhenium halides below 200 atm of CO at 200° C. The compounds are extraordinarily stable and form easily, often quantitatively, from carbon monoxide and rhenium metal in the presence of other heavy metal halides or halogen sources such as CC14. Later we prepared the corresponding carbonyl halides of manganese (67) and technetium (68) from their respective carbonyls. It was found that the corresponding binuclear tetracarbonyl halides [M(CO)4X]2 (M = Mn, Re) could be made by heating the mononuclear M(CO)5X complexes (15, 69), as well as by other methods. 

Vanhoye and coworkers [402] synthesized aldehydes by using the electrogenerated radical anion of iron pentacarbonyl to reduce iodoethane and benzyl bromide in the presence of carbon monoxide. Esters can be prepared catalytically from alkyl halides and alcohols in the presence of iron pentacarbonyl [403]. Yoshida and coworkers reduced mixtures of organic halides and iron pentacarbonyl and then introduced an electrophile to obtain carbonyl compounds [404] and converted alkyl halides into aldehydes by using iron pentacarbonyl as a catalyst [405,406]. Finally, a review by Torii [407] provides references to additional papers that deal with catalytic processes involving complexes of nickel, cobalt, iron, palladium, rhodium, platinum, chromium, molybdenum, tungsten, manganese, rhenium, tin, lead, zinc, mercury, and titanium. 

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