An investigation into the electronic and structural properties of nickel complexes of tetradentate N2S2 ligands

Synthesis, spectroscopic and electrochemical study of nickel-(II) and -(I) complexes with Schiff-base ligands giving a NN′OS co-ordination sphere

“…In addition, the spectroscopic characteristics of the oxidized solutions are indicative that a complex mixture of products is formed, indicating that probably decomposition of the complexes occurs after electron transfer. This behaviour is similar to that reported for nickel() complexes with ligands containing the dithioester fragment, 3,7, 8 showing that, as commonly observed for unhindered thiolate ligands, the dithiocarboxylate moiety is a non-innocent redox ligand. In contrast, chemical or electrochemical oxidation of [Ni(salen)] and derivatives in co-ordinating solvents was found to yield nickel() species, 16 although oxygen-based ligands are not expected to be as efficient as thiolate donors in the stabilization of high oxidation states.…”

“…The low-energy band observed in the electronic spectra is characteristic of low-spin square-planar nickel() complexes, with co-ordination spheres N 2 O 2 , 15,17-19 and N 2 S 2 , 17,20 while the next three bands have been assigned to S→Ni charge-transfer transitions in related NiN 2 S 2 complexes. 7, 8 Analysis of Table 2 reveals that the position of both the d-d band and the MLCT bands is only slightly affected by the substituents of the ligand; the larger variations for [Ni(cdMe 2salpd)], [Ni(cdMeMeOsalpd)] and [Ni(cdnappd)] are probably due to poor determination of band maxima as they are masked by the MLCT bands. Nevertheless, these small changes cannot be correlated directly with the electron-donor or -acceptor ability of the substituents, since they may be caused by different tetrahedral distortions.…”

“…Crystal data and data collection parameters. [Ni(cdsalpd)],C 17 H 20 N 2 NiOS 2 , M = 391.16, monoclinic, space group P2 1 /n, a = 8.924(5), b = 16.889(8), c = 12.051(6) Å, β = 97.94(2)Њ, U = 1799(2) Å 3 (by least-squares refinement on diffractometer angles from 23 centred reflections, 13.71 < θ < 25.03), T = 203 K, graphite-monochromated Mo-Kα radiation, λ = 0.710 73 Å, Z = 4, D c = 1.444 Mg m Ϫ3 , F(000) = 816, brown prism with dimensions 0.40 × 0.20 × 0.10 mm, µ(Mo-Kα) = 1.287 mm Ϫ1 , empirical absorption correction based on ψ scans, transmission factors 0.3354-0.3727, STOE STADI IV diffractometer, 2θ-ω scans, data collection range 3.41 < 2θ < 54.00Њ, ±h, ±k, ±l, three standard reflections measured every 90 min showed no significant variation in intensity; 4091 reflections measured, 3713 unique (R int = 0.0233) which were used in all calculations.…”

Nickel(II) and copper(II) complexes of 2-(2-pyridyl)benzimidazole: synthesis and structural characterization

“…The bioinorganic chemistry of copper(II) and nickel(II) has become increasingly important, and nickel(II) has been shown to lie at the active site of several important classes of metalloenzymes including, most notably, nickel(II) hydrogenases. Copper salts and their complexes are also well known for their antifungal and antibacterial properties [25][26][27]. Extensive research efforts have been centered on N,N 0 -donor ligand metal complexes, showing luminescence from charge-transfer excited states.…”

Chapter 13. The coordination chemistry of open-chain polydentate ligands

“…Reaction of [CuI2(232)I2+, in which each Cu' occupies an N3 binding pocket, with O2 causes oxygenation of the phenyl group to give a (p-phenolato)(phydroxo)bis-Cu" core. If the phenyl ring is halogenated, as in [Cu'(233)I2', the same product arises via oxidative dehalogenation.266 [ C U ' ~L ] ~+ (L = 234,235) react similarly with O2 to give C U " ~( ~-O R ) ~ cores (R = H, alkyl).…”