MCl(ligand) + Complexes (M = Ni, Pd, Pt) with a P,N,N Terdentate Ligand - Solid State and Solution Structures and Catalytic Activity of the PdII Derivative in the Heck Reaction

Ni-II, Pd-II and Pt-II cationic complexes of the general formula [MCl(PNN)]PF6, where PNN is the terdentate ligand N-[2(diphenylphosphanyl)benzylidene][2-(2-pyridyl)ethyl]amine, have been synthesised and fully characterised in solution by NMR spectroscopy. The diamagnetic Ni-II complex 1 shows fluxionality, which can be attributed to a conformational rearrangement of the two six-membered chelate rings. On the contrary, the Pd-II 2 and Pt-II 3 derivatives are stereochemically rigid on the NMR timescale. The crystal structures of 1 and 2 are reported, which show a planar geometry for both complexes. Complex 2 has been investigated as a precatalyst in the Heck coupling between styrene and bromobenzene. lnterestingly, the nature of the solvent has a critical role in determining the yield of the reaction product