Abstract
M.Sc.
This study describes the synthesis of pyrazolyl palladium and nickel complexes and their applications as catalysts for the co-polymerization of olefins with carbon monoxide and also as ethylene oligomerization catalysts.
A series of compounds, 2-(3,5-dimethyl-pyrazol-1-yl)-ethyl]-pyridin-2-ylmethylene-imine (L1), 2-(3,5-di-tert-butyl-pyrazol-1-yl)-ethyl]-pyridin-2-ylmethylene-imine (L2), 2-(3,5-dimethyl-pyrazol-1-yl)-ethyl]-thiophen-2-ylmethylene-imine (L3), 2-(3,5-di-tert-butyl-pyrazol-1-yl)-ethyl]-thiphen-2-ylmethylene-imine (L4), 2-(3,5-dimethyl-pyrazol-1-yl)-ethyl]-5-bromothiophen-2-ylmethylene-imine (L5), 2-(3,5-di-tert-butyl-pyrazol-1-yl)-ethyl]-2bromothiophen-2-ylmethylene-imine (L6), 2-(3,5-dimethyl-pyrazol-1-yl)-ethyl]-pyrrol-2-ylmethylene-imine (L7) and 2-(3,5-di-tert-butyl-pyrazol-1-yl)-ethyl]-pyrrol-2-ylmethylene-imine (L8)] were prepared via Schiff base condensation of the appropriate amines and aldehydes. Reactions of L1-L6 and L8 with [PdClCH3(cod)] formed six complexes of general formula [PdClCH3(L)] {L = L1 (1), L2 (2), L3 (3), L4 (4), L5 (5) and L6 (6)} and [Pd(L8)2] (7). Complexes 1-6 were converted to the cationic compounds [PdCH3(L)]BAr4 {L = L1 (8), L2 (9), L3 (10), L4 (11), L5 (12) and L6 (13)} by the reaction of compounds 1-6 with the halide abstractor Na[BAr4] (where Ar = (3,5-(CF3)2C6H3) in a 1:1 mole ratio. For compounds 8 and 9 the cationic species were stabilized by the coordination of the pyrazolyl units of the ligands, which were uncoordinated in the parent palladium complexes 1 and 2. The cationic complexes 10-13, however, were stabilized by
v
coordination of NCCH3 to the palladium centre. Complexation of L1, L2, L5 and L6 with [PdCl2(NCCH3)2] gave the palladium dichloro complexes [PdCl2(L)], {L = L1 (14), L2 (15), L5 (16), and L6 (17)}.
Compounds L1, L2, L7 and L8 were reduced to form compounds L9-L12 respectively and were reacted with [NiBr2DME] to form complexes [NiBr2(L)] {L = L9 (18), L10 (19), L11 (20) and L12 (21).