Unsymmetrical Saturated Ketones Resulting from Activations of Hydrocarbon C(sp³)–H and C(sp²)–H Bonds Effected by Cp*W(NO)(H)(η³‑allyl) Complexes

C–H activations of a C­(sp²)–H bond in benzene or a C­(sp³)–H bond in mesitylene at 80 °C under CO pressure in undried solvents without rigorous exclusion of air and moisture can be effected with the 18e complexes Cp*W­(NO)­(H)­(η³-CH₂CHCMe₂) (<b>1</b>), Cp*W­(NO)­(H)­(η³-CH₂CHCHMe) (<b>2</b>), and Cp*W­(NO)­(H)­(η³-CH₂CHCHPh) (<b>3</b>) (Cp* = η⁵-C₅Me₅). These activations are regiospecific and afford in the case of complex <b>1</b> good yields of the unsymmetrical saturated ketones 4-methyl-1-phenylpentan-1-one (<b>5</b>) and 1-(3,5-dimethylphenyl)-5-methylhexan-2-one (<b>8</b>), respectively, in which the alkyl groups result from hydrogenation of the allyl ligand in the organometallic reactant. Complex <b>2</b> reacts similarly, but complex <b>3</b> only produces the ketone from its reaction with CO in benzene. Theoretical calculations indicate that the key mechanistic feature of these conversions is the formation of a 16e η²-alkene complex which is generated by the regiospecific migration of the hydride ligand onto the tertiary carbon of the allyl ligand. The 16e Cp*W­(NO)­(η²-CH₂CHCHMe₂) and Cp*W­(NO)­(η²-MeCHCHPh) intermediate complexes formed in this manner by complexes <b>1</b> and <b>3</b>, respectively, have been trapped as the corresponding 18e CO adducts Cp*W­(NO) (CO)­(η²-CH₂CHCHMe₂) (<b>10</b>) and Cp*W­(NO) (CO)­(η²-MeCHCHPh) (<b>11</b>). All new complexes have been characterized by conventional spectroscopic and analytical methods, and the solid-state molecular structures of two isomers of <b>11</b> have been established by single-crystal X-ray crystallographic analyses. This new and facile method of synthesizing saturated unsymmetrical ketones via C–C bond formation not only is atom economical but also is part of a complete synthetic cycle, since Cp*W­(NO)­(CO)₂ (<b>4</b>) is the final organometallic product formed in all cases, and it can be readily reconverted to the hydrido allyl reactants <b>1</b>–<b>3</b> in three steps via Cp*W­(NO)­Cl<sub>2