Assessment of the Electronic Structure of 2,2′-Pyridylpyrrolides as Ligands

Abstract

The ligand class 2,2'-pyridylpyrrolide is surveyed, both for its structural features and its electronic structure, when attached to monovalent K, Cu, Ag, Au, and Rh. The influence of pyrrolide ring substituents is studied, as well as the question of push/pull interaction between the pyridyl and pyrrolide halves. The π donor ability of the pyrrolide is found to be less than that of an analogous phenyl. However, in contrast to the phenyl analog, the HOMO is pyrrolide π in character for pyridylpyrrolide complexes of copper and rhodium, while it is conventionally metal localized for planar, d(8) rhodium pyridylphenyl. Monovalent three-coordinate copper complexes show great deviations from Y-shaped toward T-shaped structures, including cases where the pyridyl ligand bonds only weakly.

Direct Transformation of Molecular Dinitrogen into Ammonia Catalyzed by Cobalt Dinitrogen Complexes Bearing Anionic PNP Pincer Ligands

“…For dissociation of dinitrogen from the cobalt center in the singlet state, the free energy changes at 195 K (Δ G 195 ) in Et 2 O were calculated to be 19.1 kcal mol −1 for 1 a and 16.5 kcal mol −1 for 5 . The moderate σ‐donating ability of the PNP ligand might be essential in the effective catalytic transformation of dinitrogen into ammonia by 1 a , although the exact role of the PNP ligand has not yet been clarified…”

Direct Transformation of Molecular Dinitrogen into Ammonia Catalyzed by Cobalt Dinitrogen Complexes Bearing Anionic PNP Pincer Ligands

“…= 0.64). For dissociation of dinitrogen from the cobalt center in the singlet state,the free energy changes at 195 K( DG 195 )inE t 2 Owere calculated to be 19.1 kcal mol À1 for 1a and 16.5 kcal mol À1 for 5.The moderate s-donating ability of the PNP ligand [24] might be essential in the effective catalytic transformation of dinitrogen into ammonia by 1a,a lthough the exact role of the PNP ligand has not yet been clarified. [25] In summary,w eh ave designed new cobalt dinitrogen complexes with anionic PNP-type pincer ligands that are effective catalysts for the reduction of molecular dinitrogen into ammonia under mild reaction conditions.W hereas molybdenum-and iron-catalyzed variants have been reported previously, [26] this is the first clear-cut example of cobaltcatalyzed direct formation of ammonia from dinitrogen under mild reaction conditions.W ebelieve that the present findings provide valuable insight for the development of nitrogen fixation systems using transition-metal dinitrogen complexes as catalysts.…”

Photoluminescence of Seven‐Coordinate Zirconium and Hafnium Complexes with 2,2′‐Pyridylpyrrolide Ligands

“…Inspired by theser esults, we sought to furtheri nvestigate the luminescentp roperties of group 4c oordination compounds containing electron-rich N-heterocycle ligands.D ue to their close relationship to the pyridine dipyrrolide (PDP) ligand system,s ubstituted 2,2'-pyridylpyrrolide ligands (PMP = pyridine monopyrrolide) were identifieda s promisingc andidatest os upport photoluminescence via LMCT. While various favorable aspects of the coordination chemistry of PMP compounds including rich redox chemistry, [63][64][65] stabilization of high oxidations tates, [66,67] and photoluminescent properties [68][69][70] have been reported for late transition metals, few reportsa re available for early metals. [71] Here we describe the synthesis and characterization of seven-coordinate zirconium and hafnium species carrying three Me PMP Me ligands( Me PMP Me = 3,5-dimethyl-2-(2-pyridyl)pyrrolide).T hese complexesa re rare examples of group 4c ompounds exhibiting photoluminescence in solution at room temperature.…”