CBr versus CH bond activation in palladium(II) cyclopalladated compounds.: Crystal and molecular structure of [Pd{C 6H 4C(H)NCy}(MeCOCHCOMe)

Abstract

Treatment of N-(2-bromobenzylidene)cyclohexylamine, 2-BrC 6H 4C(H)NCy ( a), with tris(dibenzylideneacetone)palladium(0) in refluxing benzene gave the cyclometallated compound [Pd{C 6H 4C(H)NCy}(Br)] 2 ( 1). Treatment of 1 with thallium acetylacetonate gave the mononuclear cyclometallated compound [Pd{C 6H 4C(H)NCy}(MeCOCHCOMe)] ( 2). Reaction of a with palladium(II) acetate in refluxing acetic acid gave the dinuclear Pd(II) compound [Pd{2-BrC 6H 3C(H)NCy}(O 2CMe)] 2 ( 3). Treatment of 3 with aqueous sodium chloride gave the dimer complex [Pd{2-BrC 6H 3C(H)NCy}(Cl)] 2 ( 4). Reaction of 4 with tertiary phosphines gave the cyclometallated complexes [Pd{2-BrC 6H 3C(H)NCy}(L)] ( 5: L=PPh 3; 6: L=PEtPh 2; 7: L=PMePh 2), with the phosphine ligand trans to the imine nitrogen atom. Treatment of 2-Br4,5-(MeO) 2C 6H 2C(H)NCH 2CH 2NMe 2 ( b), with palladium(II) chloride in refluxing octane or with tris(dibenzylideneacetone)palladium(0) gave [Pd{4,5-(MeO) 2C 6H 2C(H)NCH 2CH 2NMe 2}(X)] ( 8: X=Cl; 16: X=Br, respectively) and with the ligand as [C, N, N] terdentate. Treatment of 8 with tertiary phosphines gave [Pd{4,5-(MeO) 2C 6H 2C(H)NCH 2CH 2NMe 2}(Cl)(L)] ( 9: L=PPh 3; 10: L=PEtPh 2; 11: L=PMePh 2). Reaction of 1,4-{2-Br4,5-(MeO) 2C 6H 2C(H)N} 2C 6H 4 ( c), with PdCl 2, Li 2[PdCl 4] or K 2[PdCl 4] gave the tetranuclear compound [1,4-{Pd[4,5-(MeO) 2C 6H 2C(H)N](Cl)} 2C 6H 4] 2 ( 12), which when treated with tertiary phosphines gave the dinuclear species 13– 15. The molecular structure of 2 has been determined by X-ray crystallography.