Mechanistic studies on Ni(dppe)Cl(2)-catalyzed chain-growth polymerizations: evidence for rate-determining reductive elimination.
The mechanisms for Ni(dppe)Cl(2)-catalyzed chain-growth polymerization of 4-bromo-2,5-bis(hexyloxy)phenylmagnesium chloride and 5-bromo-4-hexylthiophen-2-ylmagnesium chloride were investigated. Rate studies utilizing IR spectroscopy and gas chromatography revealed that both polymerizations exhibit a first-order dependence on the catalyst concentration but a zeroth-order dependence on the monomer concentration. (31)P NMR spectroscopic studies of the reactive organometallic intermediates suggest that the resting states are unsymmetrical Ni(II)-biaryl and Ni(II)-bithiophene complexes. In combination, the data implicate reductive elimination as the rate-determining step for both monomers. Additionally, LiCl was found to have no effect on the rate-determining step or molecular weight distribution in the arene polymerization.
Department of Chemistry and Macromolecular Science and Engineering Program, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, USA.
Erica L
EL
Lanni
Anne J
AJ
McNeil
D002384:Catalysis; D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D010647:Phenyl Ethers / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism; D013876:Thiophenes / Q000138:chemical synthesis* / Q000737:chemistry
C547018:4-bromo-2,5-bis(hexyloxy)phenylmagnesium; C547019:5-bromo-4-hexylthiophen-2-ylmagnesium; D056831:Coordination Complexes; D009942:Organometallic Compounds; D010647:Phenyl Ethers; D013876:Thiophenes