Nickel(II) catalysed co-polymerisation of CO and ethene:Formation of polyketone vs. polyethylene - The role of co-catalysts

\u3cp\u3eThe square planar Ni complex (SP-4-3)-[Ni(2-tol)(PPh\u3csub\u3e3\u3c/sub\u3e)(N,O)] (N,O = (Z)-4,4,5,5,6,6,6-heptafluoro-3-oxo-2-(pyrrolidine-2-ylidene)- hexanenitrile) is an active catalyst for the co-polymerisation of CO and ethene yielding aliphatic polyketone. Addition of Lewis acids like BPh\u3csub\u3e3\u3c/sub\u3e or B(C\u3csub\u3e6\u3c/sub\u3eF\u3csub\u3e5\u3c/sub\u3e)\u3csub\u3e3\u3c/sub\u3e as co-catalyst accelerates the polymerisation but not the lifetime of the catalyst and leads to a mixture of polyethylene and polyketone. Addition of the Lewis base triphenylphosphane (PPh\u3csub\u3e3\u3c/sub\u3e) completely suppresses the formation of polyethylene. The polymers formed were characterised by IR spectroscopy, \u3csup\u3e13\u3c/sup\u3eC cross polarisation (CP) magic angle spinning (MAS) solid state NMR spectroscopy, differential scanning calorimetry (DSC) and size exclusion chromatography (SEC).\u3c/p\u3