Nickel(II)−Methyl Complexes with Water-Soluble Ligands L [(salicylaldiminato-κ2N,O)NiMe(L)] and Their Catalytic Properties in Disperse Aqueous Systems

Neutral (salicylaldiminato)nickel(II) methyl complexes [{6-C(H)NAr-2,4-I2C6H2O-κ2N,O}NiMe(L)] (Ar = 2,6-{3,5-(F3C)2C6H3}2C6H3) with different water-soluble ligands L (2a, L = 1,3,5-triaza-7-phosphaadamantane; 2b, L = hexamethylenetetramine (urotropine); 2c, L = tetraethylammonium pyridine-3-sulfonate; 2d, L = amino-terminated poly(ethylene glycol) monomethoxy ether) were prepared. 2a−d are potentially water-soluble catalyst precursors for ethylene polymerization, which form a water-insoluble active site [{κ2-N,O}NiR(ethylene)] (R = growing chain). Only complex 2d was found to be water-soluble (>2 mmol L-1); 2c is soluble in water/2-propanol mixtures. In toluene as a reaction medium, only the relatively weakly coordinated tertiary amine complex 2b is polymerization active (1.7 × 104 TO). In aqueous systems 2c,d are also active due to compartmentalization of the active site in the polymer particles and of L in the aqueous phase. Polyethylene particle sizes vary from 18 nm (dispersions formed with 2d) to ove...