Synthesis, characterization, and norbornene polymerization of eta(3)-benzylnickel(II) complexes of N-heterocyclic carbenes

Abstract

Neutral eta(1)-benzylnickel carbene complexes, [Ni(eta(1)-CH(2)C(6)H(5))(IiPr)(PMe(3))(Cl)] (3) (IiPr = 1,3-bis-(2, 6-diisopropylphenyl)imidazol-2-ylidene) and [Ni(eta(1)-CH(2)C(6)H(5))(SIiPr)(PMe(3))(Cl)] (4) (SIiPr = 1,3-bis-(2, 6-diisopropylphenyl)imidazolin-2-ylidene), were prepared by the reaction between [Ni(eta(3)CH(2)C(6)H(5))(PMe(3))(Cl)] and an equivalent amount of the corresponding free N-heterocyclic carbene. The preparation of eta(3)-benzylnickel carbene complexes, [Ni(eta(3)-CH(2)C(6)H(5))(IiPr)(Cl)] (5) and [Ni(eta(3)CH(2)C(6)H(5))( SIiPr)(Cl)] (6) were carried out by the abstraction of PMe3 from 3 and 4 by the treatment of B(C(6)F(5))(3). The treatment of AgX on 5 and 6 produced the anion-exchanged complexes, [Ni(eta(3)CH(2)C(6)H(5))( NHC)(X)] (7, NHC = IiPr, X = O(2)CCF(3); 8, NHC = IiPr, X = O(3)SCF(3); 9, NHC = SIiPr, X = O(2)CCF(3); 10, NHC = SIiPr, X = O3SCF3). The solid state structures of 3 and 10 were determined by X-ray crystallography. The eta(3)-benzyl complexes of IiPr (5, 7, and 8) alone, in the absence of any activators such as borate and MAO, showed good catalytic activity towards the vinyl-type norbornene polymerization. The catalyst was thermally robust and the activity increases as the temperature rises to 130 degrees C.