title: X-ray Crystallographic, Multifrequency Electron Paramagnetic Resonance, and Density Functional Theory Characterization of the Ni(P(Cy)2N(tBu)2)2(n+) Hydrogen Oxidation Catalyst in the Ni(I) Oxidation State.
abstract: The Ni(I) hydrogen oxidation catalyst [Ni(P(Cy)2N(tBu)2)2](+) (1(+); P(Cy)2N(tBu)2 = 1,5-di(tert-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 1(+) is highly symmetrical. EPR spectroscopy has allowed determination of the electronic g 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 1(+) are found to be distinctly different from those for the related compound [Ni(P(Ph)2N(Ph)2)2](+) (4(+)). One significant contributor to these differences is that the molecular structure of 4(+) is unsymmetrical, unlike that of 1(+). 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.
authors.affiliation: †Division of Chemical Sciences and Engineering, Argonne National Laboratory, Argonne, Illinois 60439, United States.
authors.forename: Jens
authors.initials: J
authors.lastname: Niklas
authors.affiliation: ‡Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States.
authors.forename: Mark
authors.initials: M
authors.lastname: Westwood
authors.affiliation: §Department of Chemistry and Physics, Chicago State University, Chicago, Illinois 60628, United States.
authors.forename: Kristy L
authors.initials: KL
authors.lastname: Mardis
authors.affiliation: §Department of Chemistry and Physics, Chicago State University, Chicago, Illinois 60628, United States.
authors.forename: Tiara L
authors.initials: TL
authors.lastname: Brown
authors.affiliation: §Department of Chemistry and Physics, Chicago State University, Chicago, Illinois 60628, United States.
authors.forename: Anthony M
authors.initials: AM
authors.lastname: Pitts-McCoy
authors.affiliation: ‡Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Hopkins
authors.affiliation: †Division of Chemical Sciences and Engineering, Argonne National Laboratory, Argonne, Illinois 60439, United States.
authors.forename: Oleg G
authors.initials: OG
authors.lastname: Poluektov
mesh_terms: D002384:Catalysis; D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D006859:Hydrogen / Q000737:chemistry*; D008958:Models, Molecular; D009532:Nickel / Q000737:chemistry*; D010084:Oxidation-Reduction; D010758:Phosphorus / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D010758:Phosphorus; D009532:Nickel; D006859:Hydrogen