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 (Me2Dt0) and N,N’-diisopropyl piperazine 2,3-dithione(iPr2Dt0) ligands are reported. These ligands were used in synthesizing bis- and tris-dithione nickel(II) complexes as tetrafluroborate or hexafluorophosphate salts i.e., [Ni(iPr2Dt0)2][BF4]2 ([1a][BF4]2), [Ni(iPr2Dt0)2][PF6]2 ([1a][PF6]2), [Ni(Me2Dt0)2][BF4]2 ([1b][BF4]2), [Ni(iPr2Dt0)3][BF4]2 ([2a][BF4]2) and [Ni(iPr2Dt0)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 volt-ammograms 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 inter-valence charge transfer (IVCT) transition as a spectroscopic signature of the mixed-valence [Ni(iPr2Dt0)(iPr2Dt1−)]− species. Analysis of this IVCT band suggests this ligand based mixed valence complex, [Ni(iPr2Dt0)(iPr2Dt1−)]−, 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.

Large Ligand Folding Distortion in an Oxomolybdenum Donor–Acceptor Complex

“…Dithiolene ligands have been extensively used as donor ligands in the synthesis of complexes that possess LL′CT and mixed-metal LL′CT (MMLL′CT) transitions. 1–7 These generalized Donor-Acceptor LL′CT complexes display interesting photophysical processes related to the formation of charge separated excited states that formally possess dithiolene radical (i.e. hole) and acceptor ligand radical (i.e.…”

A mixed valence zinc dithiolene system with spectator metal and reactor ligands

“…This level of theory was chosen due to its well documented ability to model metal dithiolenes. [20, 21] The vibrational frequency calculations were performed to (a) confirm that structures were true minima and (b) to aid in the assignment of molecular vibrational modes. The calculated infrared spectrum for 4 is presented in Figure 4.…”

“…Recently, it has become increasingly clear that redox active metals may function as a spectator anchoring point for interaction between two redox active ligands. [20] To this end, we have been engaged in studying metal-ligand interactions using a dithione ligand, i.e., the fully oxidized π-accepting ligand using a redox-active metal. [20, 21] In the case presented, an electron rich π-donating dithiolate ligand is added alongside a dithione ligand, and a molecular system with built-in electron rich and electron deficient moieties can be created, a situation made possible by the redox versatility of the dithione ligand.…”

“…[20] To this end, we have been engaged in studying metal-ligand interactions using a dithione ligand, i.e., the fully oxidized π-accepting ligand using a redox-active metal. [20, 21] In the case presented, an electron rich π-donating dithiolate ligand is added alongside a dithione ligand, and a molecular system with built-in electron rich and electron deficient moieties can be created, a situation made possible by the redox versatility of the dithione ligand. Because of the presence of potential ligand to ligand charge transfer (LLCT) transitions, these electronic donor-acceptor systems are of great interest as materials for information storage and switching.…”

“…[20] Herein we report another four coordinate metal system where the two dithiolene ligands are in varying redox states. An inherently redox inactive d 10 Zn(II) ion serves as the metal center in the present case.…”