Metal carbonyls Arene chromium complexes

The intermediate cyclooctene complex appears to be more reactive with respect to CS coordination and more sensitive to oxidation when the arene ring bears electron-withdrawing groups (e.g., C02CH3). Dicarbonyl(methyl rj6-benzoate)-thiocarbonyl)chromium is air stable in the solid state and reasonably stable in solution.9 The infrared spectrum exhibits metal carbonyl absorptions at 1980 and 1935 cm"1 and a metal thiocarbonyl stretch at 1215 cm"1 (Nujol) (these occur at 1978, 1932, and 1912 cm"1 in CH2C12 solution).10 Irradiation of the compound in the presence of phosphite or phosphine leads to slow substitution of CO by these ligands, whereas the CS ligand remains inert to substitution. The crystal structure has been published."... 

Metal carbonyls Acylcobaltate complexes, 101 Arene(tricarbonyl)chromium complexes, 19... 

Heterometal alkoxide precursors, for ceramics, 12, 60-61 Heterometal chalcogenides, synthesis, 12, 62 Heterometal cubanes, as metal-organic precursor, 12, 39 Heterometallic alkenes, with platinum, 8, 639 Heterometallic alkynes, with platinum, models, 8, 650 Heterometallic clusters as heterogeneous catalyst precursors, 12, 767 in homogeneous catalysis, 12, 761 with Ni—M and Ni-C cr-bonded complexes, 8, 115 Heterometallic complexes with arene chromium carbonyls, 5, 259 bridged chromium isonitriles, 5, 274 with cyclopentadienyl hydride niobium moieties, 5, 72 with ruthenium—osmium, overview, 6, 1045—1116 with tungsten carbonyls, 5, 702 Heterometallic dimers, palladium complexes, 8, 210 Heterometallic iron-containing compounds cluster compounds, 6, 331 dinuclear compounds, 6, 319 overview, 6, 319-352... 

Apart from bis(benzene)chromium and other bis(arene) metal compounds, a huge number of mono(arene) transition metal complexes were also prepared in the golden 1950s . In 1957, Fischer and Ofele reported the synthesis of (C6H6)Cr(CO)3, the first representative of the family of arene metal carbonyls [64], The original preparative procedure (a sealed-tube reaction of Cr(CO)6 and Cr(C6H6)2 at 220°C) was soon replaced by a more convenient synthesis, based... 

Arene(tricarbonyl)chromium complexes undergo a number of synthetically important transformations not usually observed for uncomplexed arenes. The chromium tricarbonyl moiety facilitates nucleophilic, electrophilic, and radical reactions at the benzylic position. Upon complexation, one side of the aromatic ring and adjacent functionalities is blocked by the metal carbonyl moiety and highly stereoselective reactions are usually observed even at relatively remote positions. In addition, the protons of the complexed aromatic ring have a substantially higher acidity and are readily removed and further substituted by electrophiles. Finally, the aromatic ring is activated toward addition reactions using a variety of nucleophiles. 

Following this initial discovery, several additional routes to benzene-chromium tricarbonyl and related complexes were developed, the most convenient of which involves the simple refluxing of the metal carbonyl and arene with concurrent loss of carbon monoxide 96, 97,184, 187). 

Schlogl K (1989) Stereochemistry of arenetricarbonylchromium complexes—useful intermediates for stereoselective synthesis. In Werner H, Erker G (eds) Organometal-lics in organic synthesis 2. Springer, Berlin Heidelberg New York, p 63 Solladi -Cavallo A (1989) Chiral arene-chromium-carbonyl complexes in asymmetric synthesis. In Liebeskind LS (ed) Advances in metal organic chemistry, vol 1. Jai Press, London, p 99... 

Chiral Catalysts Containing Group 6 Metals (Cr, Mo, and W). Although all the three metals have important role in organometallic chemistry (eg, carbonyl complexes), their catalytic properties are scarcely investigated in the past few years. The tricarbonyl(jj -arene)chromium structural unit (see Fig. 16)... 

Low Oxidation State Chromium Compounds. Cr(0) compounds are TT-bonded complexes that require electron-rich donor species such as CO and C H to stabilize the low oxidation state. A direct synthesis of Cr(CO)g, from the metal and CO, is not possible. Normally, the preparation requires an anhydrous Cr(III) salt, a reducing agent, an arene compound, carbon monoxide that may or may not be under high pressure, and an inert atmosphere (see Carbonyls). 

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