title: Solution, Solid, and Gas Phase Studies on a Nickel Dithiolene System: Spectator Metal and Reactor Ligand.
abstract: The syntheses of cationic nickel complexes using N,N'-dimethyl piperazine 2,3-dithione (Me2Dt(0)) and N,N'-diisopropyl piperazine 2,3-dithione ((i)Pr2Dt(0)) ligands are reported. These ligands were used in synthesizing bis and tris(dithione)Ni(II) complexes as tetrafluoroborate or hexafluorophosphate salts, i.e., [Ni((i)Pr2Dt(0))2][BF4]2 ([1a][BF4]2), [Ni((i)Pr2Dt(0))2][PF6]2 ([1a][PF6]2), [Ni(Me2Dt(0))2][BF4]2 ([1b][BF4]2), [Ni((i)Pr2Dt(0))3][BF4]2 ([2a][BF4]2), and [Ni((i)Pr2Dt(0))3][PF6]2 ([2a][PF6]2), respectively. Complex [2a][PF6]2 was isolated from a methanolic solution of [1a][PF6]2. Compound [1a][BF4]2 crystallizes in a trigonal crystal system (space group, P31/c) and exhibits unique packing features, whereas [2a][BF4]2 crystallizes in a monoclinic (P21/n) space group. Cyclic voltammograms of [1a][BF4]2 and [1b][BF4]2 are indicative of four reduction processes associated with stepwise single-electron reduction of the ligands. Spectroelectrochemical experiments on [1a][BF4]2 exhibit an intervalence charge transfer (IVCT) transition as a spectroscopic signature of the mixed-valence [Ni((i)Pr2Dt(0))((i)Pr2Dt(1-))](-) species. Analysis of this IVCT band suggests that this ligand based mixed valence complex, [Ni((i)Pr2Dt(0))((i)Pr2Dt(1-))](-), behaves more like a traditional class II/III metal based mixed-valence complex. The density functional theory (DFT) and time dependent DFT calculations provide a theoretical framework for understanding the electronic structures and the nature of excited states of the target compounds that are consistent with their spectroscopic and redox properties. Vibrational spectra of [1a](2+) and [2a](2+) were investigated as discrete species in the gas phase using infrared multiple photon dissociation (IRMPD) spectroscopy.
authors.affiliation: †Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282, United States.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Mogesa
authors.affiliation: †Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282, United States.
authors.forename: Eranda
authors.initials: E
authors.lastname: Perera
authors.affiliation: ‡Department of Chemistry and Biochemistry, University of Minnesota-Duluth, Duluth, Minnesota 55812, United States.
authors.forename: Hannah M
authors.initials: HM
authors.lastname: Rhoda
authors.affiliation: §Chemical Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, United States.
authors.forename: John K
authors.initials: JK
authors.lastname: Gibson
authors.affiliation: ∥Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7c, 6525ED Nijmegen, The Netherlands.
authors.forename: Jos
authors.initials: J
authors.lastname: Oomens
authors.affiliation: ∥Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7c, 6525ED Nijmegen, The Netherlands.
authors.forename: Giel
authors.initials: G
authors.lastname: Berden
authors.affiliation: †Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282, United States.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: van Stipdonk
authors.affiliation: ‡Department of Chemistry and Biochemistry, University of Minnesota-Duluth, Duluth, Minnesota 55812, United States.
authors.forename: Victor N
authors.initials: VN
authors.lastname: Nemykin
authors.affiliation: †Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282, United States.
authors.forename: Partha
authors.initials: P
authors.lastname: Basu
mesh_terms: D005740:Gases / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D009532:Nickel / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D011789:Quantum Theory; D012996:Solutions; D013455:Sulfur / Q000737:chemistry*; D014732:Vibration
chemical_list: D005740:Gases; D008024:Ligands; D009942:Organometallic Compounds; D012996:Solutions; D013455:Sulfur; D009532:Nickel