Tungsten reactions with

Schmidt reaction of ketones, 7, 530 from thienylnitrenes, 4, 820 tautomers, 7, 492 thermal reactions, 7, 503 transition metal complexes reactivity, 7, 28 tungsten complexes, 7, 523 UV spectra, 7, 501 X-ray analysis, 7, 494 1 H-Azepines conformation, 7, 492 cycloaddition reactions, 7, 520, 522 dimerization, 7, 508 H NMR, 7, 495 isomerization, 7, 519 metal complexes, 7, 512 photoaddition reactions with oxygen, 7, 523 protonation, 7, 509 ring contractions, 7, 506 sigmatropic rearrangements, 7, 506 stability, 7, 492 N-substituted mass spectra, 7, 501 rearrangements, 7, 504 synthesis, 7, 536-537... 

Tungsten, tricarbonyleyelopentadienylhydrido-reaction with ynamines, 1, 666 Turpin reaction, 3, 1033 Tylophorine occurrence, 4, 478 synthesis, 4, 472, 475 Tylosin... 

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]. 

Tungsten alkynyl Fischer carbene complexes are excellent dienophile partners in the classical Diels-Alder reaction with 1-azadienes (see Sect. 2.9.2.1). On the contrary, the chromium-derived complexes exhibit a different behaviour and they react through a [4S+3C] heterocyclisation reaction to furnish azepine derivatives [116] (Scheme 68). The reaction is initiated by a 1,2-addition of the nitrogen lone pair to the carbene carbon followed by a [l,2]-Cr(CO)5 shift-pro-... 

Kitatani et al. found that tungsten(VI) chloride would catalyse the formation of a range of oxazoles from benzoyl(phenyl)diazomethane and nitriles (Scheme 17).<74TL1531, 77BCJ1647> The reaction with acetonitrile was studied with a range of other metal chlorides, but all proved less satisfactory than WCle. They attributed the catalytic nature of tungsten(Vl) chloride to both its Lewis acidity and the affinity of tungsten for carbenes. 

Scheme 8 Addition reactions with tungsten carbenes...

During the preparation of the hexamethoxides of rhenium, molybdenum and tungsten by co-condensation with excess tetramethoxysilane on a cold surface, simultaneous co-condensation is necessary to avoid the danger of explosion present when sequential condensation of the reactants is employed. In the latter case, the high concentrations of hexafluoride at the interface leads to violent reaction with the silane. 

Aspects of the apparatus for the synthesis using metal atoms are described. The reactions of the atoms of rhenium, tungsten, and osmium with hydrocarbons including alkanes are described. It is shown that metal atom reactions with alkanes can give isolable organometallic compounds including l-alkylidene compounds. 

Figure 7 Reaction of tungsten atoms with cyclopentane, (i and iv) Co-condensation at -196 °C (ii) Cyclopenta-diene in benzene at 60 °C and (iii) Dihydrogen at 50 atm.

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