Synthesis and reactivity of new palladium alkyl complexes containing PMe3 ligands:: Insertion reactions and formation of bis(pyrazolyl) borate derivatives

The complex PdCl2(cod) (cod = 1,4-cyclooctadiene) reacts with one equivalent of R(Mg)Cl (R = CH2CMe2Ph, CH2SiMe3, CH2C6H4-o-Me) to yield monoalkyl derivatives of composition Pd(R)Cl(cod). The cyclooctadiene ligand is readily displaced by dmpe (dmpe= 1,2-bis(dimethylphosphino)ethane) and PMe3 to generate Pd(R)Cl(L-2) (L-2=(PMe3)(2), dmpe) of which, the complex Pd(CH2CMe2Ph)Cl(PMe3)(2) thermally isomerizes to the palladium aryl Pd(C6H4-o-CMe3)Cl(PMe3)(2) in the presence of catalytic amounts of NEt3. Carbonylation of the alkyl derivatives affords acyl complexes Pd(COR)Cl(L-2) and related iminoacyl derivatives have also been obtained by the analogous reaction with tert-butyl-isocyanide. New alkyl and acyl species containing bis(pyrazolyl)borate ligands have been prepared by halide metathesis in the Pd(R/COR)Cl(PMe3)(2) complexes. During the course of these reactions one equivalent of PMe3 is liberated. The complex Bp * Pd(CH2SiMe3)(PMe3) has been structurally characterized by X-ray crystallography. (C) 1997 Elsevier Science S.A.