862169-59-3Relevant academic research and scientific papers
Bis(imino)pyridine iron(II) alkyl cations for olefin polymerization
Bouwkamp, Marco W.,Lobkovsky, Emil,Chirik, Paul J.
, p. 9660 - 9661 (2005)
Treatment of the five-coordinate ferrous dialkyl complex, (iPrPDI)Fe(CH2SiMe3)2 (iPrPDI = ((2,6-CHMe2)2C6H3N=CMe)2C5H3N), with [PhMe2NH][BPh4] in the presence of diethyl ether or tetrahydrofuran furnished the corresponding alkyl cations, where the donor ligand is coordinated in the basal plane of a distorted square pyramidal iron(II) alkyl cation. Performing the same reaction with the neutral Lewis acid, B(C6F5)3, induced methide abstraction from a silicon atom followed by rearrangement to afford the base free ferrous alkyl cation, [(iPrPDI)Fe(CH2SiMe2CH2SiMe3)][MeB(C6F5)3]. This complex is active for the polymerization of ethylene and yields polymers that are of higher molecular weight and narrower polydispersity than traditional methylalumoxane-activated catalysts. Copyright
Synthesis and electronic structure of cationic, neutral, and anionic bis(imino)pyridine iron alkyl complexes: Evaluation of redox activity in single-component ethylene polymerization catalysts
Tondreau, Aaron M.,Milsmann, Carsten,Patricks, Andrew D.,Hoyt, Helen M.,Lobkovsky, Emil,Wieghardt, Karl,Chirik, Paul J.
, p. 15046 - 15049 (2011/02/27)
A family of cationic, neutral, and anionic bis(imino)pyridine iron alkyl complexes has been prepared, and their electronic and molecular structures have been established by a combination of X-ray diffraction, Moessbauer spectroscopy, magnelochemistry, and open-shell density functional theory. For the cationic complexes, [(iPrPDI)Fe-R][BPh4] (iPrPDI = 2, 6-(2,6-iPr2-C6H3N=CMe)2C5H3N; R = CH2SiMe3, CH2CMe3, or CH3), which are known single-component ethylene polymerization catalysts, the data establish high spin ferrous compounds (SFe= 2) with neutral, redox-innocent bis(imino)pyridine chelates. One-electron reduction to the corresponding neutral alkyls, (iPrPDI)Fe(CH2SiMe3) or (iPrPDI)Fe(CH2CMe3), is chelatebased, resulting in a bis(imino)pyridine radical anion (SpDI= V2) antiferromagnetically coupled to a high spin ferrous ion (SFe= 2). The neutral neopentyl derivative was reduced by an additional electron and furnished the corresponding anion, [Li(Et2O)3][(iPrPDI)Fe(CH2CMe3)N2], with concomitant coordination of dinitrogen. The experimental and computational data establish that this S=O compound is best described as a low spin ferrous compound (SFe= O) with a closed-shell singlet bis(imino)pyridine dianion (Sprji = O), demonstrating that the reduction is ligand-based. The change in field strength of the bis(imino)pyridine coupled with the placement of the alkyl ligand into the apical position of the molecule induced a spin state change at the iron center from high to low spin. The relevance of the compounds and their electronic structures to olefin polymerization catalysis is also presented.
