Iron Phosphinimide and Phosphinimine Complexes: Catalyst Precursors for Ethylene Polymerization

Reaction of Li[NPt-Bu 3 ] with FeCl 2 affords [Cl 3 Fe 2 (μ-NPt-Bu 3 ) 2 ] 1 in 71% yield. This mixed valent Fe(III)-Fe(II) undergoes reversibly one-electron oxidation to generate [Cl 3 Fe 2 (μ-NPt-Bu 3 ) 2 ] + . Chemical oxidationwith [Cp 2 Fe]PF 6 yields [Cl 2 Fe(μ-NPt-Bu 3 )] 2 2. The reaction of Li[NPt-Bu 3 ] with FeBr 3 affords [Br 4 Fe 2 (μ-NPt-Bu 3 ) 2 ] 3, while the reaction of FeCl 3 with Me 3 -SiNPCy 3 gives [Cl 2 Fe(μ-NPCy 3 )] 2 4. Hydrolysis of 3 yields the species [(t-Bu 3 PNH)Br 2 Fe] 2 -(μ-O) 5. These species have also been evaluated as catalysts for the polymerization of ethylene and copolymerization of ethylene/octene. These species were found to be single-site catalysts even under rather demanding conditions (50-160 °C, 100-300 psig ethylene), although the activities are generally low. Compound 5 affords polymer similar to that produced by 3, suggesting that MAO dehydrates 5 generating a catalyst similar to that derived from 3. Compounds 1, 2, 4, and 5 have been crystallographically characterized.