While recent spectroscopic studies have established the presence of an interstitial carbon atom at the center of the iron–molybdenum cofactor (FeMoco) of MoFe-nitrogenase, its role is unknown. We have pursued Fe–N2 model chemistry to explore a hypothesis whereby this C-atom (previously denoted as a light X-atom) may provide a flexible trans interaction with an Fe center to expose an Fe–N2 binding site. In this context, we now report on Fe complexes of a new tris(phosphino)alkyl (CPiPr3) ligand featuring an axial carbon donor. It is established that the iron center in this scaffold binds dinitrogen trans to the Calkyl-atom anchor in three distinct and structurally characterized oxidation states. Fe–Calkyl lengthening is observed upon reduction, reflective of significant ionic character in the Fe–Calkyl interaction. The anionic (CPiPr3)FeN2– species can be functionalized by a silyl electrophile to generate (CPiPr3)Fe–N2SiR3. (CPiPr3)FeN2– also functions as a modest catalyst for the reduction of N2 to NH3 wh...

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Catalytic reduction of N2 to NH3 by an Fe-N2 complex featuring a C-atom anchor.

New Element‐Carbon (p‐p)π Bonds

Classical structural formulas often convey the impression only those relationships between the atoms are of importance which hold a molecule together as symbolized by the chemical bonds. However, many interactions between atoms or groups of atoms are not adequately denoted in this manner. Nevertheless, their existence can have important consequences for ground state energies (cis-difluoroethylene is more stable than trans-difluoroethylene), conformations (the syn form of methyl vinyl ether is more stable than the anti form), reactivities (an endo cyclopropane ring in 7-anti-norbornyl derivatives accelerates solvolysis by a factor of 1014), UV spectra (“superposition” of the π-systems of acridine and purine-bonded through a four-membered chain-results in hypochromism), CD spectra (the inherently symmetrical but dissymmetrically perturbed chromophore of 2-deuterionorbornadiene allows the observation of three transitions in the near UV), and ESR spectra (the long-range coupling with H-4 in the bridgehead bicyclo[2.1.1]hex-1-yl radical equals 22.5 G). Since orbital interactions are involved in most intramolecular effects of this kind, photoelectron spectroscopy has proven an informative and valuable extension to other methods.

Proximity Effects in Organic Chemistry—The Photoelectron Spectroscopic Investigation of Non‐Bonding and Transannular Interactions

Syntheses of chromenes and chromanes via o-quinone methide intermediates

Theory and application of photoelectron spectroscopy

A photoelectron spectroscopic study of keto-enol tautomerism in acetylacetones - a new application of photoelectron spectroscopy

Theory and application of photoelectron spectroscopy. 61. Detection of rotational isomers by variable temperature photoelectron spectroscopy. A new technique in the realm of molecular conformational analysis

Hans Vermeer

Papers

A photoelectron spectroscopic study of keto-enol tautomerism in acetylacetones - a new application of photoelectron spectroscopy

Theory and application of photoelectron spectroscopy. 61. Detection of rotational isomers by variable temperature photoelectron spectroscopy. A new technique in the realm of molecular conformational analysis

Dibenz[b,e]arsenin (9-Arsaanthracen)†

Synthesis and application of precursors of hetero-anthracenes : 2-halo- and 2,2′-dihalodiphenylmethanes and methine substituted derivatives

Theory and application of photoelectron spectroscopy. 77. Use of photoelectron spectroscopy in studying rotational isomerism in tetramethyldiphosphine