Tungsten carbonyl complexes characterization

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... 

Although Mo (II) and W(II) exhibit the most extensive seven-coordinate chemistry yet known (consistent with the application of the effective atomic number rule to these systems), a survey of the substituted metal carbonyl complexes of molybdenum and tungsten reveals no structural data for compounds of the type M(00)3(6-6)2 where 6-6 is a bidentate monoanionic ligand. No tungsten tricarbonyls of this type have been reported to date, but McDonald and co-workers have synthesized and studied the closely related W(CO)2(PPh3) (6-6)2 compounds where 6-6 is a chelating dithiocarbamate (7), xanthate, or dithiophos-phate (8). For molybdenum, the compounds Mo(CO)3(dtc)2(dtc = R2NCS2") (9) are examples of the M(CO)3(6-6)2 type as is Mo(CO)3-[S2P(i-Pr)2]2 (10), which has been well characterized in solution. 

In a study of reductive McMurry-type coupling of carbonyl compounds with (OR)3WsW(OR)3 (R = 2,2-dimethylpropyl), a dinuclear cyclopropylmethylidene complex 14 was isolated and structurally characterized by X-ray.The cyclopropyl group remained intact (also in subsequent coupling reactions with other carbonyl compounds) thus, no long-lived carbene intermediate (or cation or anion) is involved and the tungsten carbon bond must have considerable covalent [Pg.1893]

Lappert and Poland (1969) were the first authors who reported on the discovery and characterization of mononuclear alkyldiazenido complexes by reaction of (tri-methylsilyl)diazomethane with tricarbonyl(cyclopentadienyl)molybdenum hydride and the analogous tungsten hydride. Scheme (10-18) demonstrates that these reactions are not simple substitutions of a carbonyl by a diazenido ligand, but that they are insertions of the diazoalkane into the M-H bond (see also Lappert and Lorberth, 1967). 

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