Palladium chemistry related to benzyl bromide carbonylation: Mechanistic studies

Palladium(II) complexes of the general formula PdCl2 (PR3)(2) with PR3 = P( OPh)(3) P(O4-MeC6H4)(3), P(O-2-MeC6H4)(3), and PPh2(OBu) were reduced by NE t3 in chloroform or benzene to Pd(0) complexes Pd(PR3)(4) and Pd(PR3)(x)(NE t3)(4-x). The same reaction performed in the presence of air gave CH3CHO or CH3CH2CHO when NPr3 was used instead of NEt3. PdCP(OPh)(3))(4) reacted wit h benzyl bromide affording the oxidative addition product cis-PdBr(CH2Ph)(P (OPh)(3))(2). The reaction of PdCl2(P(OPh)(3))(2) with benzyl bromide was o bserved only in the presence of NEt3, and a dimeric complex of [PdBr(CH2Ph) (P(OPh)(3))](2) was identified as the reaction product. Both benzyl complex es reacted fast with CO (1 atm) to form acyl complexes exhibiting,nu (CO) b ands at 1709 and 1650 cm(-1).