Synthesis and structural investigations of Ni(II)- and Pd(II)-coordinated α-diimines with chlorinated backbones

Novel square planar Pd(II) α-diimines [PdX2{ArNC(Cl)}2], where Ar = C6H5, (2,6-Me2C6H3), (2,6-iPr2C6H3) and X = Cl or Br, and the octahedral Ni(II) complex [NiBr2{(C6H5)NC(Cl)}2(THF)2] have been prepared and characterised by spectroscopic methods. For two of the Pd(II) complexes and the Ni(II) complex the crystal structures were determined by X-ray crystallography. A further insight into the geometry and electronic structure of [PdBr2{(2,6-Me2C6H3)NC(Cl)}2] was gained using density functional theoretical calculations (DFT). This compound resembles structurally and electronically typical olefin polymerisation pre-catalysts supported by α-diimines incorporating methyl- and 1,8-naphtalenyl substituents at the ligand backbone. The chlorine-substituted backbone of the free ligand [2,6-Me2C6H3NC(Cl)]2 can be employed in further alkylation reactions to generate new multifunctional ligand prototypes with potential uses as ansa-metallocene/diimines building blocks for catalytic applications of heterobimetallic complexes.