title: Synthesis and characterization of three-coordinate Ni(III)-imide complexes.
abstract: A new family of low-coordinate nickel imides supported by 1,2-bis(di-tert-butylphosphino)ethane was synthesized. Oxidation of nickel(II) complexes led to the formation of both aryl- and alkyl-substituted nickel(III)-imides, and examples of both types have been isolated and fully characterized. The aryl substituent that proved most useful in stabilizing the Ni(III)-imide moiety was the bulky 2,6-dimesitylphenyl. The two Ni(III)-imide compounds showed different variable-temperature magnetic properties but analogous EPR spectra at low temperatures. To account for this discrepancy, a low-spin/high-spin equilibrium was proposed to take place for the alkyl-substituted Ni(III)-imide complex. This proposal was supported by DFT calculations. DFT calculations also indicated that the unpaired electron is mostly localized on the imide nitrogen for the Ni(III) complexes. The results of reactions carried out in the presence of hydrogen donors supported the findings from DFT calculations that the adamantyl substituent was a significantly more reactive hydrogen-atom abstractor. Interestingly, the steric properties of the 2,6-dimesitylphenyl substituent are important not only in protecting the Ni═N core but also in favoring one rotamer of the resulting Ni(III)-imide, by locking the phenyl ring in a perpendicular orientation with respect to the NiPP plane.
authors.affiliation: Gordon Center for Integrative Science, Department of Chemistry, University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Vlad M
authors.initials: VM
authors.lastname: Iluc
authors.forename: Alexander J M
authors.initials: AJ
authors.lastname: Miller
authors.forename: John S
authors.initials: JS
authors.lastname: Anderson
authors.forename: Marisa J
authors.initials: MJ
authors.lastname: Monreal
authors.forename: Mark P
authors.initials: MP
authors.lastname: Mehn
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Hillhouse
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D007094:Imides / Q000138:chemical synthesis* / Q000737:chemistry; D008024:Ligands; D008962:Models, Theoretical; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D013696:Temperature
chemical_list: D007094:Imides; D008024:Ligands; D009942:Organometallic Compounds; D009532:Nickel