Tungsten tris complex

In the case of other Group 6 metals, the polymerization of olefins has attracted little attention. Some molybdenum(VI) and tungsten(VI) complexes containing bulky imido- and alkoxo-ligands have been mainly used for metathesis reactions and the ring-opening metathesis polymerization (ROMP) of norbornene or related olefins [266-268]. Tris(butadiene) complexes of molybdenum ) and tungsten(O) are air-stable and sublimable above 100°C [269,270]. At elevated temperature, they showed catalytic activity for the polymerization of ethylene [271]. 

Tungsten aryloxo complexes have been shown to catalyze the intramolecular metathesis reactions of di- and tri-substituted co-unsaturated glucose and glucosamine derivatives to yield bicyclic carbohydrate-based compounds containing 12- and 14-membered rings [108,214,215]. An example is shown in Eq. 37. The tolerance for amides and esters is noteworthy, as are the yields and the size of the rings that are formed. 

Irradiation of 69 in chlorinated solvents in the presence of tri-methylphosphine gives rise to the oxidized products 70. The reaction was postulated to proceed via short-lived 17-electron carbyne complex intermediates. Electrochemical evidence for the existence of 17-electron species was reported. In the absence of trimethylphosphine no products could be characterized for the molybdenum phenylcarbyne complex. In the absence of trimethylphosphine the tungsten cyclopropylcarbyne complex affords W( / -C5H5)Cl3(CO)[P(OMe)3] and cyclopentenone [Eq. (59)] (99). 

Toluene-3,4-dithiol (dithiol 30) gives complexes with many metals (e.g. Bi, Sb , Co, Cu, Ni and Pb in acid solution Mn, Fe, Tl, V and Ru in alkaline, aqueous pyridine solution). The yellow-green tris complex with molybdenum can be separated from tungsten(VI) by extraction into pentyl acetate from 3.7 M HCl. The blue-green tungsten complex extracts if the acidity is lowered. Sn also gives a yellow-red complex. 

CARBONYL HALIDE TUNGSTEN(II) COMPLEXES OF TRIS(3,5-DIMETHYLPYRAZOLYL)HYDROBORATE... 

Reduction of TpW(NO)(PMe3)(Br) (Tp=hydrido-tris(pyrazolyl)borate) with sodium in the presence of thiophene yielded a mixture of tungsten-containing complexes, exhibiting distinct chemical properties, which could be partially hydrogenated to dihydrothiophene complexes with combined yields of 22% in a 1 1 ratio of two diastereoisomers (Scheme 130). The coordinate binding fashion is less common for 16-electron metal complex than the or S-bound form [144]. 

Tungsten(ni) tris(dithiocarbamate) complexes are not known. However, in one report a related tungsten(III) complex, [W(S2CH)(S2CNMe2)2] (152), has been reported prepared as a side product of the addition of carbon disulfide and sulfur to [W2(NMe2)6] (1051). 

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