First Examples of Dinickel Complexes Containing the N₃Ni(μ₂-SR)₃NiN₃ Core. Synthesis and Crystal Structures of [L₂Ni₂][BPh₄]₂ and [L₃Ni₂][BPh₄]₂ (L = 2,6-Di(aminomethyl)-4-tert-butyl-thiophenolate)

Abstract

A coordinatively unsaturated dinuclear Ni(II) complex of the tridentate ligand 2,6-di(aminomethyl)-4-tert-butyl-thiophenol (HL) has been synthesized and investigated in the context of ligand binding and oxidation state changes. The starting complex [L(2)Ni(2)][BPh(4)](2) (1) is readily prepared from NaL, NiCl(2).6H(2)O, and NaBPh(4) in methanol. Compound 1.CH(3)CN.CH(3)OH crystallizes from an acetonitrile/methanol mixed-solvent system in monoclinic space group P2(1)/n with a = 21.940(4) Å, b = 13.901(3) Å, c = 23.918(5) Å, beta = 110.00(3) degrees, and Z = 4. The structure consists of dinuclear [L(2)Ni(2)](2+) cations with two distorted planar cis-N(2)S(2)Ni coordination units joined by the thiophenolate sulfur atoms. The molecule has idealized C(2)(v)() symmetry. Complex 1 readily adds another 1 equiv of HL to afford the pale green complex [L(3)Ni(2)]Cl (2). The dinuclear structure and its formulation as a 3:2 complex (six-coordinate Ni ions) is derived from UV spectroscopy, cyclic voltammetry, and single-crystal X-ray diffraction of its oxidation product, [L(3)Ni(2)](2+). The dication was prepared by chemical oxidation of 2 with iodine in DMF and isolated as the dark brown BPh(4)(-) salt, [L(3)Ni(2)][BPh(4)](2).CH(3)OH (3), which crystallizes in monoclinic space group P2(1)/c with a = 23.678(5) Å, b = 20.090(4) Å, c = 16.797(3) Å, beta = 106.16(3) degrees, and Z = 4. Complex 3 is the first structurally characterized example that features a bioctahedral N(3)Ni(&mgr;(2)-SR)(3)NiN(3) core. Distortions from D(3)(h)() symmetry suggest that 3 is a trapped-valence Ni(II)Ni(III) compound. The Ni-S and Ni-N bond lengths vary from 2.2975(9) to 2.4486(12) Å and from 2.027(3) to 2.120(3) Å, respectively. On the CV time scale complex 2 undergoes two reversible electron-transfer reactions at E(1/2) = -0.02 and +0.44 V vs SCE, affording 3 and the transient dark green trication [L(3)Ni(2)](3+) (tau(1/2) approximately 15 min at 295 K), respectively. While 2 is EPR silent, the EPR spectrum of a powdered sample of 3 reveals g( perpendicular) = 4.0 and g( parallel) = 2.09 at 77 K, consistent with an S = (3)/(2) spin state of the mixed-valent Ni(II)Ni(III) complex.

Preparation and Characterization of Mononuclear Ni Complexes of Tetradentate Amine-thioether and Amine-thiolate Ligands

“…The infrared spectra of the complexes 9 -11 and 14 reveal mainly the various stretching and bending modes of the supporting ligands. The most significant feature in the IR spectrum of crystalline 9 is the band at 3294 cm −1 , which can be readily assigned to the N-H stretching vibrations of the coordinated amine donors [16]. Similar bands are observed for 12 and 13, but not for the complexes 10, 11, and 14 which contain only tertiary amine donors.…”

Tunable Charge Delocalization in Dinickel Quinonoid Complexes

“…Its spectrum, generated as indicated above in dry THF under N 2 and in the presence of a drop of anhydrous pyridine showed at 4 K two broad signals corresponding to g ∥ =2.13 and g ⊥ =4.16. These values are characteristic of a spin S =3/2 system in which a low‐spin Ni III ( S =1/2) would be ferromagnetically coupled to an octahedral Ni II ( S =1) 11a. Unfortunately, no hyperfine coupling to the nitrogen atoms ( 14 N) could be observed 11a.…”

Tetranuclear complexes in molecular magnetism: Targeted synthesis, high-field EPR and pulsed-field magnetization

“…The ligands HL 1 and H 3 L 4 were found to support homo-(12 [47], 13 [34], 14 [37], 15 [48]) as well as heterodinuclear complexes (16 [49], 17, 18 [37]) with a range of di-and trivalent metal ions (M = Cr, Fe, Co, and Ni). All complexes 12-18 have a face-sharing bioctahedral N 3 M(-S) 3 MN 3 core structure as illustrated in Scheme 6 and were found to undergo two reversible one-electron transfer reactions.…”

“…The full line represents the best theoretical fit[52]. (b) EPR powder spectrum of 15·2BPh4 at 77 K, apparent g values are indicated[48].Scheme 10. The structures of the dinickel(II) complexes 26 and 27[36].…”