The Missing Link: Manganese Complexes with Sterically Demanding Pyrrolyl Ligands

Kreye, Markus; Freytag, Mat­thias; Daniliuc, Constantin G.; Jones, Peter G.; Walter, Marc D.

doi:10.1002/zaac.201500555

Cited by 8 publications

(2 citation statements)

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“…Several factors have contributed to this development, including readily modifiable steric and electronic properties of the pincer architecture and the high thermal stability of the resulting metal compounds. These advantageous properties have led to many applications in small-molecule activation and catalysis. − Within this group, pincer complexes of 3d transition metals are particularly appealing and various catalysts have been developed for hydrofunctionalization, − cross-coupling, , C–H bonding, CO 2 , or N 2 activation and functionalization, − and dehydrogenation reactions. , These advances stimulated our interest in this area, and we extended our previous work on sterically encumbered pyrrolyl ligands − to pyrrolyl-based PNP pincer systems ( I ; Chart ). In 2012, the phenyl-substituted pyrrolyl-based PNP ligand was introduced independently by the groups of Tonzetich, Gade, and Mani and applied for the synthesis of nickel and palladium compounds.…”

Section: Introductionmentioning

confidence: 97%

Synthesis and Electronic Ground-State Properties of Pyrrolyl-Based Iron Pincer Complexes: Revisited

et al. 2017

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The pyrrolyl-based iron pincer compounds [(PNP)FeCl] (1), [(PNP)FeN] (2), and [(PNP)Fe(CO)] (3) were prepared and structurally characterized. In addition, their electronic ground states were probed by various techniques including solid-state magnetic susceptibility and zero-field Fe Mössbauer and X-band electron paramagnetic resonance spectroscopy. While the iron(II) starting material 1 adopts an intermediate-spin (S = 1) state, the iron(I) reduction products 2 and 3 exhibit a low-spin (S =/) ground state. Consistent with an intermediate-spin configuration for 1, the zero-field Fe Mössbauer spectrum shows a characteristically large quadrupole splitting (ΔE ≈ 3.7 mm s), and the solid-state magnetic susceptibility data show pronounced zero-field splitting (|D| ≈ 37 cm). The effective magnetic moments observed for the iron(I) species 2 and 3 are larger than expected from the spin-only value and indicate an incompletely quenched orbital angular momentum and the presence of spin-orbit coupling in the ground state. The experimental findings are complemented by density functional theory computations, which are in good agreement with the experimental data. Most notably, these calculations reveal a low-lying (S = 2) excited state for complex 1; furthermore, the computed Mössbauer parameters for all complexes studied herein are in excellent agreement with the experimental findings.

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Section: Introductionmentioning

confidence: 97%

Synthesis and Electronic Ground-State Properties of Pyrrolyl-Based Iron Pincer Complexes: Revisited

et al. 2017

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“…Bulkier ene-amides, or 1-azaallyls, were envisaged to promote bond formation by positioning the relevant carbons via sterics. There is ample precedent for synthesis of such low-coordinate amide complexes, − − whose synthesis and reactivity constitute a forefront area of first row transition metal research. In addition, iron species are emerging as targets for catalytic or stoichiometric applications toward organic synthesis, , and present a logical target as base metal, inexpensive reagents.…”

Section: Introductionmentioning

confidence: 99%

Oxidatively Triggered Carbon–Carbon Bond Formation in Ene-amide Complexes

2016

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Ene-amides have been explored as ligands and substrates for oxidative coupling. Treatment of CrCl2, Cl2Fe(PMe3)2, and Cl2Copy4 with 2 equiv of {(2,6-(i)Pr2C6H3)(1-(c)Hexenyl)N}Li afforded pseudosquare planar {η(3)-C,C,N-(2,6-(i)Pr2C6H3)(1-(c)Hexenyl)N}2Cr (1-Cr, 78%), trigonal {(2,6-(i)Pr2C6H3)(1-(c)Hexenyl)N}2Fe(PMe3) (2-Fe, 80%), and tetrahedral {(2,6-(i)Pr2C6H3)(1-(c)Hexenyl)N}2Co(py)2 (3-Co, 91%) in very good yields. The addition of CrCl3 to 1-Cr, and FeCl3 to 2-Fe, afforded oxidatively triggered C-C bond formation as rac-2,2'-di(2,6-(i)Pr2C6H3N═)2dicyclohexane (EA2) was produced in modest yields. Various lithium ene-amides were similarly coupled, and the mechanism was assessed via stoichiometric reactions. Some ferrous compounds (e.g., 2-Fe, FeCl2) were shown to catalyze C-arylation of {(2,6-(i)Pr2C6H3)(1-(c)Hexenyl)N}Li with PhBr, but the reaction was variable. Structural characterizations of 1-Cr, 2-Fe, and 3-Co are reported.

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Teaching Ferrocenium How to Relax: A Systematic Study on Spin–Lattice Relaxation Processes in tert‐Butyl‐Substituted Ferrocenium Derivatives

et al. 2016

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Sterically encumbered ferrocenium salts with four, five, or six tert-butyl substituents and a variety of counteranions ([BF 4 ] -, [SbF 6 ] -, and [PF 6 ] -) were prepared. The electronic structures of these materials were investigated by various physical techniques including electron paramagnetic resonance (EPR) and Mössbauer spectroscopy and solid-state magnetic susceptibility measurements. Spin-orbit coupling and low-symmetry distortions split the electronic ground states ( 2 E 2g ) in these compounds into two Kramers doublet states (Ψ a and Ψ b ); the energy difference between these states was evaluated by EPR spectroscopy and magnetic susceptibility measurements and decreases with increasing steric demand at the ferrocenium

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The Missing Link: Manganese Complexes with Sterically Demanding Pyrrolyl Ligands

Cited by 8 publications

References 60 publications

Synthesis and Electronic Ground-State Properties of Pyrrolyl-Based Iron Pincer Complexes: Revisited

Synthesis and Electronic Ground-State Properties of Pyrrolyl-Based Iron Pincer Complexes: Revisited

Oxidatively Triggered Carbon–Carbon Bond Formation in Ene-amide Complexes

Teaching Ferrocenium How to Relax: A Systematic Study on Spin–Lattice Relaxation Processes in tert‐Butyl‐Substituted Ferrocenium Derivatives

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