Reactions tungsten-nitrogen

Phthalocyanines are excellent lubricants at temperatures of 149—343°C (191). Combinations with other lubricants, like grease, molybdenum, or tungsten sulfides, have found appHcations in the automotive industry or professional drilling equipment (192—195). Further uses include indicators for iron(Il), molybdenum(V), and uranium(IV) (196) or redox reactions (197), medical appHcations like hemoglobin replacements (198) or sterilisation indicators (199), or uses like in gas filters for the removal of nitrogen oxides from cigarette smoke (200). 

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-... 

Alkylation of sp3 C-H bonds adjacent to a heteroatom such as nitrogen and oxygen is possible. The early works using tungsten or iridium complexes involved the reaction of dimethylamine with 1-pentene (Equation (29)) and the alkylation of a C-H bond adjacent to oxygen with / r/-butylethylene.34,34a,34b... 

In contrast to the palladium-catalyzed reactions, little attention has been paid to other transition-metal catalysts. Recently some efficient reactions using copper(i or 11), gold(m), platinum(n), and tungsten(O) have been developed for the synthesis of nitrogen-heterocycles. The copper-catalyzed cyclizations of 2-alkynylaniline derivatives into... 

Differential scanning calorimetry has been used to measure89,90 the enthalpy of reaction for the displacement of a nitrogen donor ligand, L, from tungsten complexes [W(CO)6 L ] by carbon monoxide under isobaric conditions. The reaction is described by the equation... 

Selective Catalytic Reduction (SCR) process is very similar to SNCR with the exception that a catalyst is used to accelerate the reactions at lower temperatures allowing it to be applied to both full and partial-burn regenerators. An SCR system consists of a catalyst bed installed in the flue gas line of a combustion system. Ammonia is injected into the flue gas with air in the presence of a catalyst. The catalyst is typically oxide forms of vanadium and tungsten. The ammonia selectively reacts with NOx to form molecular nitrogen and water via an exothermic reaction that has achieved > 90% reduction in NO when applied to an FCCU. 

In addition to the successful reductive carbonylation systems utilizing the rhodium or palladium catalysts described above, a nonnoble metal system has been developed (27). When methyl acetate or dimethyl ether was treated with carbon monoxide and hydrogen in the presence of an iodide compound, a trivalent phosphorous or nitrogen promoter, and a nickel-molybdenum or nickel-tungsten catalyst, EDA was formed. The catalytst is generated in the reaction mixture by addition of appropriate metallic complexes, such as 5 1 combination of bis(triphenylphosphine)-nickel dicarbonyl to molybdenum carbonyl. These same catalyst systems have proven effective as a rhodium replacement in methyl acetate carbonylations (28). Though the rates of EDA formation are slower than with the noble metals, the major advantage is the relative inexpense of catalytic materials. Chemistry virtually identical to noble-metal catalysis probably occurs since reaction profiles are very similar by products include acetic anhydride, acetaldehyde, and methane, with ethanol in trace quantities. 

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