Nickel(II) and Palladium(II) Complexes with Tridentate [C,N,S] and [C,N,P] Ligands: Syntheses, Characterization, and Catalytic Norbornene Polymerization

A series of tridentate monoanionic
[C–,N,X] (X
= S, P) nickel­(II) complexes [(C6H4CHNPh-2-XPh)­NiBr]
(X = S (1a), PPh (1b)) and palladium­(II)
complexes [(C6H4CHNPh-2-XPh)­PdCl] (X
= S (2a), PPh (2b)) were synthesized from
the reactions of La and Lb (La = BrC6H4CHNPh-2-SPh, Lb = BrC6H4CHNPh-2-PPh2) with
(DME)­NiBr2 and (COD)­PdCl2, respectively, in
good yields. All complexes were fully characterized by IR, NMR, and
elemental analyses. Single-crystal X-ray diffraction analysis of complex 2a revealed an almost square-planar geometry of the metal
center. After activation with methylaluminoxane (MAO), the title complexes 1a,b and 2a,b can be
used as catalysts for norbornene polymerization to produce vinyl addition
type polynorbornene (PNB) with good catalytic activities. The good
catalytic activities of complexes 1b and 2b as procatalysts which contain a P atom as the third coordinated
atom can be maintained even at high temperature, demonstrating their
excellent thermal stability.