Pentacarbonyl metallate anion

With the preparation of Na[Cr(CO)5CN], we not only obtained the first anionic hexacoordinated, pentacarbonyl metalate(O) of Group VIB, but also initiated the extremely extensive chemistry of the [M(CO)sX]- anions. 

Klingler and co workers—impact of metal coordination on the formate pathway. Klingler and coworkers114,125 carried out studies on the cation reactivity of formate in solution at 180 °C, 7.8 mol/L of H20 with the solvent triethylene glycol, and the formate concentration was varied. It was noted that formic acid produced from the carbonylation of water is catalyzed by hydroxide anion, and rapidly builds up to close to equilibrium concentration levels under these conditions, so that they had to use gold plated stainless steel autoclaves. They obtained a first order dependency of the water-gas shift reaction rate (i.e., H2 evolution rate) with formate concentration. As a control experiment, they added metal pentacarbonyl iron to the reactor, and observed no additional rate increase, indicating that the water-gas shift... 

Both bromomanganese pentacarbonyl and bromorhenium pentacarbonyl rapidly precipitated sodium bromide at room temperature when added to a tetrahydrofuran solution of Na2[l, 2-B9C2H,]. Two equivalents of CO were evolved only after the mixture was refluxed, producing the corresponding 1,2-dicarbollyl metal tricarbonyl anion (11, 18). 

The chemistry of the metal carbonyl hydrides and metal carbonylates remained the principal research topic for Hieber until the 1960s. He mentioned in his account [25], that it was a particular pleasure for him that in his laboratory the first hydrido carbonyl complexes of the manganese group, HMn(CO)5 and HRe(CO)5, were prepared by careful addition of concentrated phosphoric acid to solid samples of the sodium salts of the [M(CO)5] anions, giving the highly volatile hydrido derivatives in nearly quantitative yield [45, 46]. In contrast to HCo(CO)4 and its rhodium and iridium analogues, the pentacarbonyl hydrido compounds of manganese and rhenium are thermally remarkably stable, and in... 

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 dmuclear carbonyls of group 7 are reduced by alkali metals in THF (equation 41). The pentacarbonylmetalate(—1) anions are appropriate entries into the hydrido- or alkyl (aryl) pentacarbonyl derivatives (see equations 42 and 43). These compounds have pseudooctahedral structures of C4 symmetry with the hydrido or alkyl (aryl) ligand occupying one of the positions within the coordination polyhedron. 

In 1962 and 1963 a pair of papers by Stolz, Dobson and Sheline [23,24] looked at the IR spectra of the then suspected pentacarbonyl intermediates of the group 6 metals chromium, molybdenum and tungsten. These papers provided early support for the idea that one CO ligand is initially lost in the first step of the photoreactions of these carbonyls. Analysis of the CO stretching vibrations managed to rule out other possible species such as the W2(CO)xq anion and the W(CO)5 anion. Analogous results were found for the pentacarbonyls of chromium and molybdenum. The chromium result is particularly relevant for the photochemistry discussed later. 

Production of metal carbonyl anions andcyclopentadienyl derivatives have received attentionand alkyl- and aryl-pentacarbonyl tungsten anions [RW(CO)j] have been prepared. The mechanisms of reduction of M(CO) (M = Mo or W) have been studied and found to be similar. ... 

The carbonylation of a benzyl halide in the presence of iron pentacarbonyl to give a phenylacetic acid may serve to exemplify the interaction of a metal carbonyl, carbon monoxide, PT catalyst, aqueous sodium hydroxide, and the substrate [79]. Fe(CO)5 is attacked by QOH at the interphase, and the species formed is extracted into the depths of the oganic phase, where it reacts with CO and benzyl halide (Eqs. 13 and 14). This new anion 3 is the actual catalyst. It reacts with a second benzyl halide to give a non-ionic intermediate 4 (Eq. 15). By insertion of CO and attack of QOH, 4 is decomposed to the reaction product under regeneration of 3 (Eq. 16). Thus, the action of the PT catalyst is twofold. Firstly it transports the metal carbonyl anion. More important seems to be its involvement in the (rate-determining) decomposition step. A basically similar mechanism was proposed for cobalt carbonyl reactions [80], which have been modified somewhat quite recently (see below). 

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