X‑ray Crystallographic, Multifrequency Electron Paramagnetic Resonance, and Density Functional Theory Characterization of the Ni(P<sup>Cy</sup><sub>2</sub>N<sup><i>t</i>Bu</sup><sub>2</sub>)<sub>2</sub><sup><i>n</i>+</sup> Hydrogen Oxidation Catalyst in the Ni(I) Oxidation State

Abstract

The Ni­(I) hydrogen oxidation catalyst [Ni­(P<sup>Cy</sup><sub>2</sub>N<sup><i>t</i>Bu</sup><sub>2</sub>)<sub>2</sub>]<sup>+</sup> (<b>1</b><sup>+</sup>; P<sup>Cy</sup><sub>2</sub>N<sup><i>t</i>Bu</sup><sub>2</sub> = 1,5-di­(<i>tert</i>-butyl)-3,7-dicyclohexyl-1,5-diaza-3,7-diphosphacyclooctane) has been studied using a combination of electron paramagnetic resonance (EPR) techniques (X-, Q-, and D-band, electron–nuclear double resonance, hyperfine sublevel correlation spectroscopy), X-ray crystallography, and density functional theory (DFT) calculations. Crystallographic and DFT studies indicate that the molecular structure of <b>1</b><sup>+</sup> is highly symmetrical. EPR spectroscopy has allowed determination of the electronic <b>g</b> tensor and the spin density distribution on the ligands, and revealed that the Ni­(I) center does not interact strongly with the potentially coordinating solvents acetonitrile and butyronitrile. The EPR spectra and magnetic parameters of <b>1</b><sup>+</sup> are found to be distinctly different from those for the related compound [Ni­(P<sup>Ph</sup><sub>2</sub>N<sup>Ph</sup><sub>2</sub>)<sub>2</sub>]<sup>+</sup> (<b>4</b><sup>+</sup>). One significant contributor to these differences is that the molecular structure of <b>4</b><sup>+</sup> is unsymmetrical, unlike that of <b>1</b><sup>+</sup>. DFT calculations on derivatives in which the R and R′ groups are systematically varied have allowed elucidation of structure/substituent relationships and their corresponding influence on the magnetic resonance parameters

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Last time updated on 12/02/2018

This paper was published in FigShare.

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