Thermolysis of Cp*W(NO)(CH2CMe3)(eta(3)-CH2CHCHMe) (1) at ambient temperatures leads to the loss of neopentane and the formation of the eta(2)-diene intermediate, Cp*W(NO)(eta(2)-CH2=CHCH=CH2) (A), which has been isolated as its 18e PMe3 adduct. In the presence of linear alkanes, A effects C-H activations of the hydrocarbons exclusively at their terminal carbons and forms 18e Cp*W(NO)(n-alkyl)(eta(3)-CH2CHCHMe) complexes. Similarly, treatments of 1 with methylcyclohexane, chloropentane, diethyl ether, and triethylamine all lead to the corresponding terminal C-H activation products. Furthermore, a judicious choice of solvents permits the C-H activation of gaseous hydrocarbons (i.e., propane, ethane, and methane) at ambient temperatures under moderately elevated pressures. However, reactions between intermediate A and cyclohexene, acetone, 3-pentanone, and 2-butyne lead to coupling between the eta(2)-diene ligand and the site of unsaturation on the organic molecule. For example, Cp*W(NO)(eta(3),eta(1)-CH2CHCHCH2C(CH2CH3)2O) is formed exclusively in 3-pentanone. When the site of unsaturation is sufficiently sterically hindered, as in the case of 2,3-dimethyl-2-butene, C-H activation again becomes dominant, and so the C-H activation product, Cp*W(NO)(eta(1)-CH2CMe=CMe2)(eta(3)-CH2CHCHMe), is formed exclusively from the alkene and 1. All new complexes have been characterized by conventional spectroscopic and analytical methods, and the solid-state molecular structures of most of them have been established by X-ray crystallographic analyses. Finally, the newly formed alkyl ligands may be liberated from the tungsten centers in the product complexes by treatment with iodine. Thus, exposure of a CDCl3 solution of the n-pentyl allyl complex, Cp*W(NO)(n-C5H11)(eta(3)-CH2CHCHMe), to I2 at -60 degrees C produces n-C5H11I in moderate yields.

A potential catalytic cycle for the formation of new C-C and C-O linkages from hydrocarbon feedstocks and readily available olefin and ketone substrates mediated by Cp′M(NO)(L) (M ) Mo, W; Cp′ ) Cp*, Cp; L ) Lewis base) fragments has been investigated. The cycle is based on three steps: (1) oxidative addition of the hydrocarbon substrate to the metal center, (2) subsequent hydrometalation of the olefin or the ketone, and (3) final reductive elimination of the coupled product. Of the various Cp′M-(NO)(L) groups examined, the Cp*W(NO)(PPh 3 ) fragment has been found to be the best candidate for mediating these catalytic steps since it is not prone to form unreactive Cp*W(NO)(PPh 3 ) 2 as are some of the other fragments that readily decompose to 18e Cp′M(NO)L 2 complexes. Hence, Cp*W(NO)(PPh 3 ) has been utilized to determine if the oxidative addition and hydrometalation steps can occur sequentially under one-pot experimental conditions. However, olefins are too π-acidic and readily form stable 18e Cp*W(NO)(PPh 3 )(η 2 -olefin) adducts, which prevent oxidative addition of the hydrocarbon substrate to the tungsten center. Similarly, benzophenone, Ph 2 CO, and diisopropyl ketone, i Pr 2 CO, also form 1:1 η 2 -CdO adducts with the π-basic tungsten center in the 16e fragment. Nevertheless, oxidative addition and hydrometalation do occur sequentially to form the desired aryl alkoxide complex, Cp*W(NO)(OCH i -Pr 2 )(Ph), in addition to the Cp*W(NO)(η 2 -OC i Pr 2 )(PPh 3 ) adduct, when benzene and diisopropyl ketone are employed as the two substrates. The solid-state molecular structures of cis-Cp*W(NO)[η 2 -(CH 2 -NMe)P(NMe 2 ) 2 ](H), Cp*W(NO)(OCH i Pr 2 )(Ph), and Cp*W(NO)(η 2 -OC i Pr 2 )(PPh 3 ) have been established by single-crystal X-ray crystallographic analyses.

Cp*W(NO)(CH 2 CMe 3 ) 2 (1) and Cp*W(NO)(CH 2 SiMe 3 )(η 2 -CPhCH 2 ) (2), two complexes which initiate the catalytic ring-retaining oligomerization of cyclic olefin substrates from cyclopentene to cyclooctene, have been reacted with analogous heteroatom-containing cyclic olefins under thermolytic conditions. These reactions with 2,5-dihydrofuran, 3,4-dihydro-2H-pyran, and 1,2,3,6-tetrahydropyridine do not result in the formation of oligomeric organic products but, rather, afford organometallic complexes resulting from alternate modes of substrate reactivity, such as ring-opening C-O bond cleavage and N-H activation.