799270-29-4Relevant academic research and scientific papers
Bis(imino)pyridine iron alkyls containing β-hydrogens: Synthesis, evaluation of kinetic stability, and decomposition pathways involving chelate participation
Trovitch, Ryan J.,Lobkovsky, Emil,Chirik, Paul J.
, p. 11631 - 11640 (2009/05/30)
Bis(imino)pyridine iron alkyl complexes bearing β-hydrogens, ( iPrPDI)FeR ((iPrPDI = 2,6-(2,6-iPr 2-C6H3N=CMe)2C5H 3N; R = Et, nBu, iBu, CH2 cycloC5H9; 1-R), were synthesized either by direct alkylation of (iPrPDI)FeCl (1-Cl) with the appropriate Grignard reagent or more typically by oxidative addition of the appropriate alkyl bromide to the iron bis(dinitrogen) complex, (iPrPDI)Fe(N 2)2 (1-(N2)2). In the latter method, the formal oxidative addition reaction produced (iPrPDI)FeBr (1-Br), along with the desired iron alkyl, 1-R. Elucidation of the electronic structure of 1-Br and related 1-R derivatives by magnetic measurements, structural studies and NMR spectroscopy established high spin ferrous compounds antiferromagnetically coupled to chelate radical anions. Thus, the formal oxidative process is bis(imino)pyridine ligand-based (one electron is formally removed from each chelate, not the iron) during oxidative addition. The kinetic stability of each 1-R compound was assayed in benzene-d6 solution and found to produce a mixture of the corresponding alkane and alkene. The kinetic stability of the iron alkyl complexes was inversely correlated with the number of β-hydrogens present. For example, the iron ethyl complex, 1-Et, underwent clean loss of ethane over the course of three hours, whereas the corresponding 1-iBu compound had a half-life of over 12 h under identical conditions. The mechanism of the decomposition was studied with a series of deuterium labeling experiments and support a pathway involving initial β-hydrogen elimination followed by cyclometalation of an isopropyl methyl group, demonstrating an overall transfer hydrogenation pathway. The relevance of such pathways to chain transfer in bis(imino)pyridine iron catalyzed olefin polymerization reactions is also presented.
Preparation and molecular and electronic structures of iron(0) dinitrogen and silane complexes and their application to catalytic hydrogenation and hydrosilation
Bart, Suzanne C.,Lobkovsky, Emil,Chirik, Paul J.
, p. 13794 - 13807 (2007/10/03)
Reduction of the five-coordinate iron(II) dihalide complexes ( iPrPDI)FeX2 (iPrPDI = ((2,6-CHMe 2)2C6H3N=CMe)2C 5H3N; X = Cl, Br) with sodium amalgam under 1 atm of dinitrogen afforded the square pyramidal, high spin iron(0) bis(dinitrogen) complex (iPrPDI)Fe(N2)2. In solution, ( iPrPDI)Fe(N2)2 loses 1 equiv of N2 to afford the mono(dinitrogen) adduct (iPrPDI)Fe(N2) 2. Both dinitrogen compounds serve as effective precatalysts for the hydrogenation and hydrosilation of olefins and alkynes. Effecient catalytic reactions are observed with low catalyst loadings (≤0.3 mol %) at ambient temperature in nonpolar media. The catalytic hydrosilations are selective in forming the anti-Markovnikov product. Structural characterization of a high spin iron(0) alkyne and a bis(silane) σ-complex has also been accomplished and in combination with isotopic labeling studies provides insight into the mechanism of both catalytic C-H and catalytic C-Si bond formation.
