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

Abstract Treatment of N -(2-bromobenzylidene)cyclohexylamine, 2-BrC 6 H 4 C(H)NCy ( a ), with tris(dibenzylideneacetone)palladium(0) in refluxing benzene gave the cyclometallated compound [Pd{C 6 H 4 C(H)NCy}(Br)] 2 ( 1 ). Treatment of 1 with thallium acetylacetonate gave the mononuclear cyclometallated compound [Pd{C 6 H 4 C(H)NCy}(MeCOCHCOMe)] ( 2 ). Reaction of a with palladium(II) acetate in refluxing acetic acid gave the dinuclear Pd(II) compound [Pd{2-BrC 6 H 3 C(H)NCy}(O 2 CMe)] 2 ( 3 ). Treatment of 3 with aqueous sodium chloride gave the dimer complex [Pd{2-BrC 6 H 3 C(H)NCy}(Cl)] 2 ( 4 ). Reaction of 4 with tertiary phosphines gave the cyclometallated complexes [Pd{2-BrC 6 H 3 C(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) 2 C 6 H 2 C(H)NCH 2 CH 2 NMe 2 ( b ), with palladium(II) chloride in refluxing octane or with tris(dibenzylideneacetone)palladium(0) gave [Pd{4,5-(MeO) 2 C 6 H 2 C(H)NCH 2 CH 2 NMe 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) 2 C 6 H 2 C(H)NCH 2 CH 2 NMe 2 }(Cl)(L)] ( 9 : L=PPh 3 ; 10 : L=PEtPh 2 ; 11 : L=PMePh 2 ). Reaction of 1,4-{2-Br4,5-(MeO) 2 C 6 H 2 C(H)N} 2 C 6 H 4 ( c ), with PdCl 2 , Li 2 [PdCl 4 ] or K 2 [PdCl 4 ] gave the tetranuclear compound [1,4-{Pd[4,5-(MeO) 2 C 6 H 2 C(H)N](Cl)} 2 C 6 H 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.