CBr versus CH bond activation in palladium(II) cyclopalladated compounds.: Crystal and molecular structure of [Pd{C6H4C(H)NCy}(MeCOCHCOMe)]

Treatment of N-(2-bromobenzylidene)cyclohexylamine, 2-BrC6H4C(H)NCy (a), with tris(dibenzylideneacetone)palladium(0) in refluxing benzene gave the cyclometallated compound [Pd{C6H4C(H)NCy}(Br)]2 (1). Treatment of 1 with thallium acetylacetonate gave the mononuclear cyclometallated compound [Pd{C6H4C(H)NCy}(MeCOCHCOMe)] (2). Reaction of a with palladium(II) acetate in refluxing acetic acid gave the dinuclear Pd(II) compound [Pd{2-BrC6H3C(H)NCy}(O2CMe)]2 (3). Treatment of 3 with aqueous sodium chloride gave the dimer complex [Pd{2-BrC6H3C(H)NCy}(Cl)]2 (4). Reaction of 4 with tertiary phosphines gave the cyclometallated complexes [Pd{2-BrC6H3C(H)NCy}(L)] (5: L=PPh3; 6: L=PEtPh2; 7: L=PMePh2), with the phosphine ligand trans to the imine nitrogen atom. Treatment of 2-Br4,5-(MeO)2C6H2C(H)NCH2CH2NMe2 (b), with palladium(II) chloride in refluxing octane or with tris(dibenzylideneacetone)palladium(0) gave [Pd{4,5-(MeO)2C6H2C(H)NCH2CH2NMe2}(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)2C6H2C(H)NCH2CH2NMe2}(Cl)(L)] (9: L=PPh3; 10: L=PEtPh2; 11: L=PMePh2). Reaction of 1,4-{2-Br4,5-(MeO)2C6H2C(H)N}2C6H4 (c), with PdCl2, Li2[PdCl4] or K2[PdCl4] gave the tetranuclear compound [1,4-{Pd[4,5-(MeO)2C6H2C(H)N](Cl)}2C6H4]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.