301658-91-3Relevant academic research and scientific papers
Arene coordination in bis(imino)pyridine iron complexes: Identification of catalyst deactivation pathways in iron-catalyzed hydrogenation and hydrosilation
Archer, Andrew M.,Bouwkamp, Marco W.,Cortez, Maria-Patricia,Lobkovsky, Emil,Chirik, Paul J.
, p. 4269 - 4278 (2008/10/09)
The phenyl-substituted bis(imino)pyridine iron bis(dinitrogen) complex (iPrPhPDI)Fe(N2)2 (iPrPhPDI = 2,6-(2,6-iPr2-C6H3N=CPh) 2C5H3N) was prepared by sodium amalgam reduction of the corresponding ferrous dichloride precursor under 4 atm of dinitrogen. Comparison of the infrared stretching frequencies of the bis(dinitrogen), mono(dinitrogen), and related dicarbonyl derivatives to those of the corresponding bis(imino)pyridine iron compounds bearing the methyl-substituted ligand, (iPrPDI)Fe(L)n ( iPrPDI = 2,6-(2,6-iPr2-C6H 3N=CMe)2C5H3N; L = CO, n = 2; L = N2, n = 1, 2), established a more electrophilic iron center for the phenyl-substituted cases. Comparing the productivity of (iPrPhPDI) Fe(N2)2 to (iPrPDI)Fe(N2) 2 in the catalytic hydrogenation and hydrosilation of 1-hexene demonstrated higher turnover frequencies for (iPrPhPDI)Fe(N 2)2. For more hindered substrates such as cyclohexene and (+)-(R)-limonene, the opposite trend was observed, where the methyl-substituted precursor, (iPrPDI)Fe(N2)2, produced more rapid conversion. The difference in catalytic performance resulted from competitive, irreversible formation of η6-aryl and -phenyl compounds with the phenyl-substituted complex. Addition of coordinating solvents such as cyclohexene or THF resulted in exclusive formation of the η6- phenyl derivative. When alkoxide substituents are introduced in the bis(imino)pyridine ligand backbone, the formation of η6-aryl compounds was exclusive, as alkali metal reduction of (iPrROPDI) FeBr2 (iPrROPDI = 2,6-(2,6-iPr 2-C6H3N=C(OR))2C5H 3N, R = Me, Et) yielded only the catalytically inactive η6-aryl species.
Chelate bis(imino)pyridine cobalt complexes: Synthesis, reduction, and evidence for the generation of ethene polymerization catalysts by Li+ cation activation
Kleigrewe, Nina,Steffen, Winfried,Bloemker, Tobias,Kehr, Gerald,Froehlich, Roland,Wibbeling, Birgit,Erker, Gerhard,Wasilke, Julia-Christina,Wu, Guang,Bazan, Guillermo C.
, p. 13955 - 13968 (2007/10/03)
Treatment of the bis(iminobenzyl)pyridine chelate Schiff-base ligand 8 (ligPh) with FeCl2 or CoCl2 yielded the corresponding (ligPh)MCl2 complexes 9 (Fe) and 10 (Co). The reaction of 10 with methyllithium or "butadiene-magnesium" resulted in reduction to give the corresponding (ligPh)Co(I)Cl product 11. Similarly, the bis(aryliminoethyl)pyridine ligand (ligMe) was reacted with CoCl2 to yield (ligMe)CoCl2 (12). Reduction to (ligMe)CoCl (13) was effected by treatment with "butadiene-magnesium". Complex 13 reacted with Li[B(C 6F5)4] in toluene followed by treatment with pyridine to yield [(ligMe)Co+-pyridine] (15). The reaction of the Co(II) complexes 10 or 12 with ca. 3 molar equiv of methyllithium gave the cobalt(I) complexes 16 and 17, respectively. Treatment of the (lig Me)CoCH3 (17) with Li[B(C6F5) 4] gave a low activity ethene polymerization catalyst. Likewise, complex 16 produced polyethylene (activity = 33 g(PE) mmol(cat)-1 h-1 bar-1 at room temperature) upon treatment with a stoichiometric amount of Li[B(C6F5)4]. A third ligand (ligOMe) was synthesized featuring methoxy groups in the ligand backbone (22). Coordination to FeCl2 and CoCl2 yielded the desired compounds 23 and 24. Reaction with MeLi gave (lig OMe)CoMe (25/26). Treatment of 25/26 with excess B(C 6F5)3 gave the η6-arene cation complex 27, where one Co-N linkage was cleaved. Activation of 25/26 with Li[B(C6F5)4] again gave a catalytically active species.
