Activation of Single-Component Nickel(II) Polyethylene Catalysts via Phase Transfer of Fluorous Phosphine Ligands

The nickel salicylaldiminato phosphine complexes [1,2,3-C₆H₃(9-anthracenyl)O(CH=N(2,6-C₆H₃(iPr)₂)]Ni(Me)[P(4-C₆H₄R)₃] (4; R = a, (CH₂)₂R_f8; b, (CH₂)₃R_f8; c, H (R_f8 = (CF₂)₇CF₃)) are prepared from the corresponding phosphines 3a-c and nickel NCMe adduct (46-68%). These are applied as catalysts for ethylene polymerization in toluene and fluorous/toluene liquid/liquid biphasic mixtures. Under the latter conditions, the fluorous phosphines 3a,b that must dissociate to generate the active catalyst migrate to the fluorous phase (partition coefficients 97.5:2.5 and 66.6:33.4 vs <0.5:>99.5 for 4a,b). Catalysts 4a,b show marked accelerations under biphasic conditions, but 4c (which has a lipophilic phosphine ligand) does not. Under all conditions, 4a,b are faster catalysts than the Ni(Ph)(PPh₃) analogue, a previously reported benchmark.