The reaction between Pt- and Pd-cis di-chloro complexes and 4,4′-diethynylbiphenyl: synthesis and characterisation of a ‘zigzag’ metal/poly-yne polymer

The synthesis of poly-yne polymers containing transition metals inserted in the main chain has been attempted by reacting a dialkyne molecule, 4,4′-diethynylbiphenyl (or DEBP), with [PtCl2(dppe)] and [PdCl2(dppe)], the platinum- and palladium-cis square-planar di-chlorine complexes containing diphenylphosphine ethane (dppe) as bidentate ligand. The aim of this work was to obtain organometallic polymers ([Pt(dppe)DEBP]n and [Pd(dppe)DEBP]n, respectively) having an all-cis ‘zigzag’ structure, by formation of a σ-acetylide bond between the transition metal complexes and the dialkyne molecule. When [PtCl2(dppe)] was reacted with DEBP, the formation of a chlorine-terminated [Pt(dppe)DEBP]n oligomer was evidenced; in the reaction involving the Pd(II) complex, on the other hand, [PdCl2(dppe)] seems to catalyse the polymerisation of DEBP via opening of the triple bond, producing a poly-DEBP polymer containing Pd(II) atoms inserted in the main chain.