Tungsten hexacarbonyl complexes reactions

Molybdenum and tungsten hexacarbonyls are able to form anionic complexes (AsPli4)2[(OC)4M( -pz)2M(CO)4] upon reaction with sodium pyrazolate and PluAsCl (72CB3203). The cationic complexes [(rj -Cp)2Mo(/Lt-pz)2Mo(rj -Cp)2] " (n = 2, 3) are known as well (74HCA1988). The other representatives of the complexes containing an exobidentate ligand (26) are derived from 4//-pyrazoles [70ZAAC(379)169]. 

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. 

The heat of formation of [MolCOlg] has been determined as -960 + 12 kJ mol by measuring its heat of decomposition. The Mossbauer parameters for the 100 keV transition of in [W(CO)g] and some tungsten(vi) complexes have been measured and discussed in terms of known bonding and structure. Secondary ions [M (CO) ] (M = Mo, m = I or 2 M = W, m = 1—4 n = 0—14) formed by ion-molecule reactions have been observed in the mass spectra of the hexacarbonyls. A mixt u re of [Cr(CO) ] and [MolCO) ] vapours affords [CrMo(CO) ] ( = 5—7). [MofCOl ] and [WICO) ] catalyse the condensation of isocyanates with aldehydes to give imines in high yields. ... 

The crystal structure of 2-lithiated l-methyl-l,3-benzazaphosphole 35 showed it to have a dimeric structure with two THF molecules associated with each lithium. The two lithium atoms and the two C-2 atoms form a four-membered ring <20020M912>. In contrast, the N-lithiated derivative of 2,5-dimethyl-l//-l,3-benzazaphosphole exists as a monomeric species 36 in the solid state <2002JOM(646)113>. The carbene-type complex 37 derived from the lithiated species 35 on reaction with tungsten hexacarbonyl was also studied by X-ray crystallography. 

A copper-catalyzed tandem reaction between 2-alkynylarylideneanilines 135 and alcohols provided a novel route to A-(alkyloxybenzyl)indoles 136 <04TL35>. A stable tungsten carbene complex was isolated from a reaction involving 135 (R, = Me), f-butyl vinyl ether, and tungsten hexacarbonyl <04CL16>. 2,3-Disubstituted indoles were prepared by the cyclization of 2-... 

A number of attempts have been made over the years to develop reproducible synthetic routes to six- and seven-coordinate isocyanide complexes of molybdenum and tungsten. Two of the older methods, namely, the reaction of the hexacarbonyls with halogens in the presence of an isocyanide (775,116) or reactions of the salt Ag4Mo(CN)8 with isocyanides (74), have given six- and seven-coordinate products. Recently, however, the discovery of the reductive or nonreductive cleavage of multiple metal - metal bonds in dinuclear group VIA compounds by isocyanides has provided a facile route to the synthesis of a variety of homoleptic and related isocyanide complexes of these metals in reasonable yields. 

Upon UV irradiation in hydrocarbon solution, the hexacarbonyls of chromium, molybdenum, and tungsten react differently with conjugated dienes like 1,3-butadiene (la), ( )-l,3-pentadiene (lb), 2-methyl-1,3-butadiene (lc), ( , )-2,4-hexadiene (Id), ( )-2-methyl-l,3-pentadiene (le), 2-ethyl-1,3-butadiene (If), or 1,3-cyclohexadiene (Ig). Chromium hexacarbonyl (2) yields, with the acyclic dienes la-lf, tetracarbonyl-r/2-dienechromium(0) complexes (3a-3f) in a smooth reaction (8-10). With 1,3-cyclohexadiene, in addition to 3g, dicarbonylbis(>/4-l,3-cyclohexadiene)chromium(0) (4g) is obtained [Eqs. (7) and (8)j. During chromatography on silica gel, the 1,3-cyclohexadiene complex 3g dismutates readily to [Cr(CO)6] and 4g [Eq. (9)]. Under the same conditions with 2 1,3-cyclopentadiene (lh) yields, in a hydrogen-transfer reaction, the stable dicarbonyl- / 5-cyclopentadienyl-r/ 3-cyclopent-enylchromium (5) (11-13) [Eq. (10)]. 

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