Tungsten carbonyl complexes reactions

Tungsten carbonyl complexes are also effective catalysts, showing some preference for nucleophile addition at the more hindered position of an unsymmetrical allyl ligand (equations 69 and 70). Other allylic alkylation reactions... 

The rearrangement of a tungsten carbonyl-complexed 7-phosphanorbomadiene to its 7-phosphatricyclo[3.2.0 ]hept-2-ene complex has been analysed by ab initio MO calculations, and it has been shown that the reactions of molybdenum and tungsten metallates of the type [CpM(CO)2CNR] with methyl iodide yield methyl complexes of the composition [CpM(CO)2(CNR)], which subsequently rearrange to / -iminoacyls and / -l-azaallyls depending on the nature of the metal, the isocyanide R substituent, and the solvent used. ... 

Further studies of the reaction of molybdenum and tungsten carbonyl complexes with Lewis acids have been reported and several interesting new adducts characterized. [Mg(py)4][(7r-Cp)Mo(CO)3]2 has been obtained by a metal-exchange reaction from [Hg Mo(7t-Cp)(CO)3 2] in THF, followed by recrystallization from pyridine. X-Ray crystallographic studies have shown the compound to possess the units (67), the dimensions of which suggest that an... 

Across other double bonds Isocyanates also undergo [2+2] cycloaddition reactions with metal/carbon double bonds. For example, liganded tungsten carbonyl complexes 143 add... 

Phosphorus pentachloride also has been used as an oxidant for molybdenum and tungsten carbonyl complexes. 25 por example, the reaction of [W (CO)3(Me)Cp l with PQ5 in dichloromethane S leads to formation of the dimer, [Cp Win a yield of 90%. Organophosphorus halides, R3PX2, have been used as mild oxidants in inorganic syntheses. The reagents are synthesized by the direct reactions of tertiary phosphines with halogens. 

Molybdenum and tungsten carbonyl hydride complexes were shown (Eqs. (16), (17), (22), (23), (24) see Schemes 7.5 and 7.7) to function as hydride donors in the presence of acids. Tungsten dihydrides are capable of carrying out stoichiometric ionic hydrogenation of aldehydes and ketones (Eq. (28)). These stoichiometric reactions provided evidence that the proton and hydride transfer steps necessary for a catalytic cycle were viable, but closing of the cycle requires that the metal hydride bonds be regenerated from reaction with H2. 

Sulfoxide adducts of chromium, molybdenum, and tungsten carbonyls have been studied as catalysts for the polymerization of monomers such as vinyl chloride (248). Simple adducts of the type [M(CO)5(Me2SO)] may be prepared by carbonyl displacement from the corresponding hexacarbonyl. Photochemical reactions are frequently necessary to cause carbonyl displacement in this manner, many carbonyl complexes of higher sulfoxides have been prepared (255, 256). Infrared (257) and mass spectral studies (154) of these complexes have appeared, and infrared data suggest that S-bonding may occur in Cr(0) sulfoxide complexes, although definitive studies have not been reported. 

There are two general procedures for the preparation of monomeric W11 complexes.269 In one, substituted tungsten carbonyls are oxidized by halogens under controlled conditions as exemplified by equations (18) and (19). In the second, W(CO)6 is first oxidized by Cl2 or Br2 at low temperature, followed by reaction of the oxidized product with the appropriate ligands. This preparative procedure is exemplified by equation (20). 

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