799270-28-3Relevant academic research and scientific papers
Iron-mediated coupling of carbon dioxide and ethylene: Macrocyclic metallalactones enable access to various carboxylates
Rummelt, Stephan M.,Zhong, Hongyu,Korobkov, Ilia,Chirik, Paul J.
supporting information, p. 11589 - 11593 (2018/09/29)
Treatment of (iPrPDI)Fe(N2)2 (iPrPDI, 2,6-(2,6-iPr2C6H3Na? CMe)2C5H3N) with CO2 and ethylene resulted in the formation of a homologous series of saturated and unsaturated iron carboxylate products, (iPrPDI)Fe(O2CR), the distribution of which depends on the ratio of the reagents. The solid-state and electronic structures of a saturated product, (iPrPDI)Fe(O2CC2H5), were elucidated. Product distributions, deuterium labeling studies, and stoichiometric experiments support initial formation of a five-membered metallalactone intermediate, which undergoes subsequent ethylene insertions to generate macrocyclic metallalactones. Competitive β-hydride elimination, CO2 insertion, or reaction with H2 determines the fate of the metallalactone, the latter accounting for formation of iron complexes with saturated carboxylates. Similar reactivity was observed upon addition of propiolactone and ethylene to (iPrPDI)Fe(N2)2, supporting C-O oxidative addition and C-C bond formation through metallacycle intermediates.
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.
Synthesis and hydrogenation of bis(imino)pyridine iron imides
Bart, Suzanne C.,Lobkovsky, Emil,Bill, Eckhard,Chirik, Paul J.
, p. 5302 - 5303 (2007/10/03)
Treatment of the iron bis(dinitrogen) complex, (iPrPDI)Fe(N2)2 (iPrPDI = (2,6-iPr2C6H3N=CMe)2C5H3N), with a series of aryl azides resulted in loss of 3 equiv of N2 and formation of the corresponding four-coordinate iron imide compounds, (iPrPDI)Fe(NAr). These complexes, two of which (Ar = 2,6-iPr2-C6H3 and 2,4,6-Me3-C6H2) have been characterized by X-ray diffraction, are significantly distorted from planarity. The metrical parameters in combination with Moessbauer spectroscopic and SQUID magnetic data suggest an intermediate spin iron(III) center antiferromagnetically coupled to a ligand-centered radical. Nitrene group transfer has been accomplished by addition of 1 atm of CO, yielding aryl isocyanates, ArNCO, and (iPrPDI)Fe(CO)2. Hydrogenation of the more sterically hindered members of the series furnished free aniline and the previously reported iron dihydrogen complex. Catalytic aryl azide hydrogenation has also been achieved, and the observed relative rates are consistent with N-H bond formation as the rate-determining step in aniline formation. Copyright
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.
