Nitrogen reaction with tungsten

The cycloaddition reactions of chiral 2-amino-l, 3-dienes with Fischer-type carbene complexes have been examined by Barluenga et al. Reactions with tungsten vinyl carbene complexes A and with boron-nitrogen-chelated chromium complexes B lead very selectively to cyclohexanone derivatives. However, when employing chromium vinyl carbene complexes in acetonitrile at room temperature in these reactions, cycloheptadienes were obtained selectively by cyclopropanation and subsequent Cope rearrangement. 

Tungsten alkynyl Fischer carbene complexes are excellent dienophile partners in the classical Diels-Alder reaction with 1-azadienes (see Sect. 2.9.2.1). On the contrary, the chromium-derived complexes exhibit a different behaviour and they react through a [4S+3C] heterocyclisation reaction to furnish azepine derivatives [116] (Scheme 68). The reaction is initiated by a 1,2-addition of the nitrogen lone pair to the carbene carbon followed by a [l,2]-Cr(CO)5 shift-pro-... 

Methyl benzoate, anisole, and diphenyl ether each give sandwich compounds with chromium vapor, although in rather low yield (32, 55, 110). Chromium appears to attack alkyl ethers and this deoxygenation probably competes with complexation with the aromatic oxygen compounds. No simple product has been isolated from chromium atoms and aniline, but bis(7V,7V-dimethylaniline)chromium has been prepared (32). The behavior of molybdenum and tungsten vapors closely resembles that of chromium in reactions with oxygen- and nitrogen-substituted arenes (113). 

SAFETY PROFILE Chronic inhalation causes lung damage in humans. Ignites at 600°C in nitrogen oxide atmospheres. Violent reaction with F2, CIF3, NOx, IF5, Pb02, NO2, N2O. See also TUNGSTEN COMPOUNDS. 

Nitrides usually form by reaction of tungsten with dry ammonia (formation of atomar nitrogen in-situ nitrogen pressures in the range of 10 -10 bar). Exceptions are reactions in a nitrogen jet stream or chemical and physical vapor deposition (plasma-aided formation). 

Molybdenum m) and Tungsten m). Reaction of [Mo(H20) ] with NO3 has been used to investigate the reduction of NO to NOJ by nitrate reductase. " The formation of [Mo204(H20)g] " and NOJ was observed spectrophotometrically and implies that the system involves the two electron transfer couple Mo VMo. A synthesis of MoCl3(THP)3 has appeared and its reactions with phosphines and reduction to Mo in a nitrogen atmosphere investigated. The equilibrium... 

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