Ethylene Polymerization and Copolymerization by Palladium and Nickel Catalysts Containing Naphthalene-Bridged Phosphine–Sulfonate Ligands

A series of naphthalene-bridged phosphine–sulfonate
ligands and the corresponding Pd­(II) complexes [κ2(P,O)-2-(R2P)-1-naphthalenesulfonato]­Pd­(Me)­(dmso)
(1, R = Ph; 2, R = o-MeO-C6H4; 3, R = Cy) and Ni­(II) complexes
[κ2(P,O)-2-(R2P)-1-naphthalenesulfonato]­Ni­(η3-C3H5) (Ni-1, R = o-MeO-C6H4; Ni-2, R = Cy) have been prepared
and characterized. The analogous benzo-bridged phosphine–sulfonate
Pd­(II) complex [κ2(P,O)-(R2P)-benzenesulfonato]­Pd­(Me)­(dmso) (2′,
R = o-MeO-C6H4) and Ni­(II)
complex [κ2(P,O)-(R2P)-benzenesulfonato]­Ni­(η3-C3H5) (Ni-1′, R = o-MeO-C6H4) were prepared for comparison. In
ethylene polymerization, complex 2 showed activity of
up to 7.5 × 106 g mol–1 h–1, which is among the most active palladium catalysts for ethylene
homopolymerization. Under the same conditions, complex 2 showed up to 1 order of magnitude higher catalytic activity than
complex 2′, generating polyethylene with slightly
smaller molecular weight and similar branching density. The Ni­(II)
complex Ni-1 was also more active than complex Ni-1′, generating polyethylene with up to 1 order of
magnitude higher molecular weight. In ethylene–methyl acrylate
copolymerization, complex 2 showed lower activity, affording
a copolymer with higher methyl acrylate incorporation and higher copolymer
molecular weight in comparison to complex 2′.