title: Redox non-innocence of a N-heterocyclic nitrenium cation bound to a nickel-cyclam core.
abstract: The redox properties of Ni complexes bound to a new ligand, [DMC-nit](+), where a N-heterocyclic nitrenium group is anchored on a 1,4,8,11-tetraazacyclotetradecane backbone, have been examined using spectroscopic and DFT methods. Ligand-based [(DMC-nit)Ni](2+/+) reduction and metal-based [(DMC-nit)Ni](2+/3+) oxidation processes have been established for the [(DMC-nit)Ni](+/2+/3+) redox series, which represents the first examples of nitrenium nitrogen (N(nit))-bound first-row transition-metal complexes. An unprecedented bent binding mode of N(nit) in [(DMC-nit)Ni](2+) is observed, which possibly results from the absence of any N(nit)→Ni σ-donation. For the corresponding [(DMC-nit)Ni(F)](2+) complex, σ-donation is dominant, and hence a coplanar arrangement at N(nit) is predicted by DFT. The binding of the triazolium ion to Ni enables new chemistry (formate oxidation) that is not observed in a derivative that lacks this functional group. Thus the N-heterocyclic nitrenium ligand is a potentially useful and versatile reagent in transition-metal-based catalysis.
authors.affiliation: Institut für Chemie, Humboldt-Universität zu Berlin , Brook-Taylor-Straße 2, D-12489 Berlin, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Heims
authors.forename: Florian Felix
authors.initials: FF
authors.lastname: Pfaff
authors.forename: Sarah-Luise
authors.initials: SL
authors.lastname: Abram
authors.forename: Erik R
authors.initials: ER
authors.lastname: Farquhar
authors.forename: Maurizio
authors.initials: M
authors.lastname: Bruschi
authors.forename: Claudio
authors.initials: C
authors.lastname: Greco
authors.forename: Kallol
authors.initials: K
authors.lastname: Ray
mesh_terms: D002412:Cations / Q000737:chemistry; D006571:Heterocyclic Compounds / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D011789:Quantum Theory
chemical_list: D002412:Cations; D006571:Heterocyclic Compounds; D009942:Organometallic Compounds; C024560:cyclam; D009532:Nickel; D009584:Nitrogen