Reactions of η2-Acyl Ligands in Tp'(CO)2Mo2-C(O)R> Complexes To Form Complexed Enolates and Enones, Allyls, and Alkyne Insertion Products

Article abstract of DOI:10.1021/ja00189a029

Elaboration of the η²-acyl ligand in hydridotris(3,5-dimethylpyrazolyl)borate (Tp') complexes of the type Tp'(CO)2Mo<η²-C(O)R> (R=Me, Et) has been accomplished by deprotonation to form enolates which react with electrophiles such as MeI, PhCH2Br, and PhCHO.Two enolate complexes, K and K, have been characterized by NMR spectroscopy.Photolysis of an acetonitrile solution of the achiral dicarbonyl reagent, Tp'(CO)2Mo<η²-C(O)R>, followed by addition of triphenyl phosphite forms racemic Tp'(CO)Mo.Excellent diastereoselectivity characterizes the addition of benzyl bromide (BzBr) to the enolate of Tp'(CO)Mo<η²-C(O)CH2CH3>; the Tp'(CO)Mo(η²-C(O)CHMeBz) product has been structurally characterized.Condensation of enolate complexes with benzaldehyde or benzophenone produces unsaturated η²-enone complexes.The structure of Tp'(CO)2Mo<η²-C(O)CH=CPh2> is reported.The η²-enone complexes undergo conjugate addition reactions to form saturated η²-acyl products, e.g., nucleophilic addition of MeLi to Tp'(CO)2Mo(η²-C(O)CH=CHPh) followed by acidification yields Tp'(CO)2Mo<η²-C(O)CH2CHMePh>.Heating Tp'(CO)2Mo(η²-C(O)CMe=CHPh) in toluene yields a ?-allyl complex, Tp'(CO)2Mo(η³-CH2CHCHPh).Insertion of alkynes (RC<*>CR, R = Et or Ph) into the metal-carbon bond of the η²-acyl ligand in Tp'(CO)(CH3CN)Mo(η²-C(O)Et) under carbon monoxide forms oxametallacycles of the Tp'(CO)2Mo<*>(CRCRC(O<*>)Et) (R = Et or Ph).The structure of Tp'(CO)2Mo<*>(CEtCEt(O<*>)Et) has been determined.