Tungsten cyclopentadienyl derivatives

Bisalkyne cyclopentadienyl derivatives of molybdenum and tungsten have been prominent in the development of Group VI alkyne chemistry in the 1980s. Unlike the dithiocarbamate systems where addition of a second alkyne produces a substitutionally inert bisalkyne derivative, interconversion of monoalkyne and bisalkyne cyclopentadienyl complexes is facile and synthetically useful. 

For cyclopentadienyl tungsten(II) derivatives barriers of 18-19 kcal/mol characterize alkyne rotation in both the alkyl and acyl cases (67,69,161). Extended Huckel calculations indicate that steric factors play a role in these complexes in addition to the standard dir orbital electronic factors (147). Smaller barriers attend replacement of CO in CpW(CO)-(HC=CH)X complexes with either P(OMe)3 or PMe3. No alkyne rotation... 

Kinetics of acid hydrolysis of a series of pyridioraethyl-carbonyl and -TT-cyclopentadienyl derivatives of molybdenum, tungsten, manganese, and iron have been reported. In the case of the 4-pyridiomethyl derivatives the mechanism is dissociative, and may be described either as 51 1 with respect to the metal or 5 eI with respect to the carbon of the pyridiomethyl ligand. For the 3-pyridiomethyl derivatives homolysis is important. ... 

C. Miscellaneous Chromium, Molybdenum, and Tungsten Carbonyl Anions Other Than Cyclopentadienyl Derivatives... 

The active species responsible for metathesis polymerization of cyclic alkanes has also been identified by NMR spectroscopy. These species (tungsten carbenes and tungsten cyclobutane derivatives) can form simultaneously (equation 9). The equilibria conditions involving these species have not yet been established. The living, ring-opening polymerization of norbornene with bis(cyclopentadienyl)titanacyclobutane derivatives was also followed by NMR spectroscopy. ... 

T. S. Piper, and G. Wilkinson, Alkyl and Aryl Derivatives of 7i-Cyclopentadienyl Compounds of Chromium, Molydenum, Tungsten, and Iron, J. Inorg. Nucl. Chem. 3, 104-124 (1956). 

Fig. 14. Apparatus for the acidification of the alkali metal derivatives of the cyclopentadienyl carbonyl hydrides of chromium, molybdenum, and tungsten.

WC6H6(C0)3H Cyclopentadienyl-tungsten tricarbonyl, hydride, and derivatives, 7 136, 139 [WC5H5(CO)3]s Cyclopentadienyl-tungsten tricarbonyl, dimer, 7 139... 

Reactions of thioketones with nucleophilic reagents have been studied to some extent. Thiobenzophenone (20) and its 4,4 -substituted derivatives react with cyclopentadienyliron dicarbonyl anion and cyclopentadienyl-molybdenum or -tungsten tricarbonyl anion at room temperature to give fulvenes. Phase-transfer catalysis conditions improve the yields. An electron-transfer mechanism has been proposed for this desulphurization and coupling reaction. An electron-transfer mechanism has also been proposed for the reduction of thiopivalophenone (54) by 1-benzyl-1,4-dihydronicotinamide in acetonitrile. 2,3-Diphenylcyclopropene-thione (55) reacts with 7V-methylarylamines to give the bicyclic thioamides (56). The formation of a thioketen as an intermediate has been suggested. A similar reaction scheme has also been proposed for the reaction of (55) with 3,4-dihydroisoquinoline. ... 

A. Chaloyard and N. El Murr, Inorg. Chem., 1980, 19, 3217. Synthesis of ring-substituted derivatives of cyclopentadienyl tricarbonyl complexes of molybdenum and tungsten. 

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