Synthesis and reactivity of new palladium alkyl complexes containing PMe 3 ligands: Insertion reactions and formation of bis(pyrazolyl)borate derivatives

Abstract

The complex PdCl 2(cod) (cod = 1,4-cyclooctadiene) reacts with one equivalent of R(Mg)Cl (R = CH 2CMe 2Ph, CH 2SiMe 3, CH 2C 6H 4- 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 PMe 3 to generate Pd(R)Cl(L 2) (L 2 = (PMe 3) 2, dmpe) of which, the complex Pd(CH 2CMe 2Ph)Cl(PMe 3) 2 thermally isomerizes to the palladium aryl Pd(C 6H 4- o-CMe 3)Cl(PMe 3) 2 in the presence of catalytic amounts of NEt 3. 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(PMe 3) 2 complexes. During the course of these reactions one equivalent of PMe 3 is liberated. The complex Bp ∗Pd(CH 2SiMe 3)(PMe 3) has been structurally characterized by X-ray crystallography.