Toluene tungsten complex

A nuxture of tungsten(Vl) oxytetrachloride (0.43 g, 1.3 mmol), toluene (10 mL), and 2,6-dibromOphenol (0.63 g, 2.5 mmol) is heated under reflux for 1 h and then concentrated under reduced pressure. The solid residue is broken up with a spatula and dried under high vacuum for 15 min. Toluene (75 mL), diethyl diallylmalonate (15.0 g, 62.4 mmol), and tetraethyllead (0.81 g, 2.5 mmol) are added to the crude tungsten complex and the resulting mixture is heated to 90 °C... 

The physical and solubility properties of the tungsten complex are similar to those of the molybdenum analog, except that it is less photosensitive. The HNMR spectrum at room temperature (toluene-tig) shows this complex to be stereochemically rigid, but at 60 °C, a binomial quintet is observed at d — 1.72 for the W—H protons ( ph = 31 Hz). 

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. 

With the Ru dimers, [ Ru(bpy)2 2(M-L)], ESR data indicate that these binuclear semiquinone complexes are near the borderline between anion radical complexes and metal-centered mixed-valence species/ The thermal reaction between [W(CO)6] and tetrachloro-l,2-benzoquinone in toluene produces the tris(quinone) tungsten complex/ Features of the molecule indicate that the quinones are coordinated as catecholate ligands and the tungsten ions are in a formal +6 oxidation state. Quinones trapped within a polymeric electrode film can act as electron sinks and/or sources. IJ/I and [FeCCN) ] " " have been utilized as charge-release mediators. 

Using an electron-gun source, tungsten atoms were reacted with benzene, toluene, or mesitylene at 77 K, to form the expected (arene)2W complex (42) in a yield of 30%, compared with the —2% yield from the previously published, bis(benzene)W synthesis (32). These arene complexes are reversibly protonated, to give the appropriate [(T7-arene)2WH] species. By using the same technique, the analogous, niobium complexes were isolated (43). 

If olehn metathesis is to be conducted in solution, solvents of low Lewis-basicity will generally give the best results (CH2CI2 > toluene > THF). As discussed above, metathesis is initiated by the formation of a jt-complex between the metal and the alkene. Hence, other nucleophiles will compete with the alkene for these coordination sites and in some systems even THF can lead to complete deactivation of the catalyst [786]. Tungsten-based catalysts which can even metathesize allyl thioethers have, however, been described [787]. 

Most of the work has been done with RUCI3, OSCI3 or IrCl3 as catalysts at 50-80 °C in water, aqueous emulsion, an aromatic solvent, or mixtures of an alcohol and water. Tungsten or molybdenum carbene complexes in toluene are effective at 20 °C with monomers that do not contain hydroxyl groups. Thus 8W (R = Me) gives polymers of very high... 

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