Rhenium compounds carbonylation

The rhenium compound 10 is rather unreactive. Carbonylation (100°C, 200 atm) gives Cp Re(CO)3, while treatment with I2 affords Cp Re(CO)2-(I)2. It does not react with ethyne, diazomethane, or phosphines under conditions where other dimetal complexes with multiple MM bonds do so (78). The manganese complex 8, also somewhat unreactive, reacts with phosphites by Mn=Mn cleavage. In the case of P(OEt)3 the two products Cp Mn(CO)2[P(OEt)3] and CpMn(CO)[P(OEt)3]2 form in a 1 1 ratio (51). 

Allylic rearrangement in the decarbonylation of (2-cyclopropene-1 -carbonyl)rhenium compounds... 

The carbonyls are in general volatile compounds with an extensive chemistry which presents many problems as regards valence and stereochemistry. Some are reactive and form a variety of derivatives, as shown in Chart 22.1 for the iron compounds, while others are relatively inert, as for example, Cr(CO)6 etc. and Re2(CO)iQ. This rhenium compound, although converted to the carbonyl halides by gaseous halogens, is stable to alkalis and to concentrated mineral acids. A few carbonyls may be prepared by the direct action of CO on the metal, either at atmospheric pressure (Ni(C0)4) or under pressure at elevated temperatures (Fe(CO)s, Co4(CO)i2)- Others are prepared from halides or, in the case of Os and Re, from the highest oxide. The polynuclear carbonyls are prepared photo-synthetically, by heating the simple carbonyls, or by other indirect methods. 

Rhenium compounds such as Re2Sc7 are more reactive hydrogenation catalysts for the reduction of carbonyls than for olefins, except in conjugated systems . Unsaturated carbonyls have been selectively hydrogenated to unsaturated alcohols, catalyzed by a chromium-promoted finely divided Ni (Raney Ni) catalyst" ... 

The reactions of iron carbonyls with diorgano tellurides deserve mention, for example the reaction of Fe3(CO),2 with PhjTe gives Ph2TeFe(CO>4, whilst several ruthenium-carbonyl complexes have been prepared from reactions between diphenyl telluride and alcoholic carbon monoxide-saturated solutions of ruthenium trichloride hydrate. Various other ruthenium-carbonyl complexes of diorgano teUurides, including di- and tri-substituted species, have also been described. The utility of diphenyl telluride in transition metal carbonyl chemistry has also been well illustrated during studies of manganese and rhenium compounds. 

Catalyst. Two types of catalysts were used in the present study. The one is the so-called Ziegler type catalyst composed of a tungsten, molybdenum or rhenium compound (A component) and an organometallic compound (B component). The other type of catalyst is composed of a carbonyl-carbene complex of tungsten and a Lewis acid(24). 

Polynuclear Carbonyls. Several stmctures consist of dinuclear metal carbonyls as shown in stmctures (4)—(6). The metal atoms in Mn2(CO) Q, as also for technetium and rhenium, are held together by a metal—metal bond and the compound contains 10 terminal CO ligands, five coordinated to each atom. The CO ligands of Mn2(00) 0 adopt a staggered configuration as illustrated in stmcture... 

Only scare data is available in the literature on the application of rhenium containing mono- or bimetallic catalysts in the hydrogenolysis of esters to alcohols. Decades ago Broadbent and co-workers studied the hydrogenation of organic carbonyl compounds (aldehydes, ketones, esters, anhydrides, acids,... 

Schiff bases provide useful mixed donor sets. The carbonyl function of the most frequently used ligands is derived from either 1,3-dicarbonyl compounds or salicylaldehyde. Favourable combinations involve O-, N- and S-donor atoms. A range of technetium and rhenium complexes exist with bi-, tri-, tetra- and pentadentate ligands. The geometry of these complexes depends on the number and type of coordinating atoms as well as on the chain length between the donor atoms in the SchifF-base ligands. 

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