Migratory insertion reactions of nickel and palladium σ-alkyl complexes with a phosphinito-imine ligand

摘要

Ligand exchange reactions have been used for the synthesis of metallacyclic complexes of Ni and Pd of the type [M(CH2CMe2-o-C6H4)(P¿N)], where P¿N is the phosphinito-imine ligand P(iPr)2OC(Me)N(2,6-C6H3(iPr)2. The protic acid [H(OEt2)(BAr¿4)] (Ar¿ = 3,5-C6H3(CF3)2) selectively cleaves one of the two ¿ metal¿carbon bonds, affording cationic monoalkyl complexes. Nickel monoalkyls stabilized with Et2O or MeCN ligands are thermally unstable and spontaneously undergo a decomposition process that ultimately leads to the breakdown of the phosphinito-imine ligand. In contrast, cationic alkylpalladium derivatives are thermally very stable, allowing the isolation of a formally unsaturated monoalkyl complex stabilized by an intramolecular ¿-arene interaction. Although monoalkynickel and -palladium phosphinito-imine derivatives are inactive as ethylene polymerization or copolymerization catalysts, they readily experience migratory insertion reactions. A palladium chelate arising from the successive insertion of CO and ethylene has been isolated and characterized.