Some new complexes of nickel(II) halides with N,N′-disubstituted thioureas

Structural Characterization of Thermochromic and Spin Equilibria in Solid-State Ni(detu)4Cl2 (detu = N,N′-Diethylthiourea)

“…A C 4 -symmetric [Ni­(datu) 4 ] 2+ cation was found: symmetry-equivalent Ni–S bond lengths were 2.221(4) Å; cis and trans S–Ni–S angles were 88.1(1)° and 159.1(1)°, respectively; the nickel atom was displaced 0.40 Å out of the equatorial (S) 4 plane toward a proximal axial iodide at a Ni···I distance of 3.74 Å; and the second distal iodide was disposed linearly from the opposite face at a Ni···I distance of 6.64 Å. This structure is analogous to [Ni­(detu) 4 ]­Cl 2 ; however, spin equilibria were not reported for Ni­(datu) 4 X 2 (X = Cl, Br, I) . Of related interest is blue [Ni­(dmtu) 4 ]­Br 2 ·2H 2 O (dmtu = N , N ′-dimethylthiourea; MTUNIB.cif), , which is apparently distinct from the blue-green anhydride reported to exhibit spin crossover .…”

“…Although the spin equilibrium is endothermic (Figures and ), factors likely contributing to a favorable entropy are the higher spin multiplicity and elongation of Ni–S bonds in the high-spin isomer. , As previously reported, − the temperature range of the spin crossover is strongly affected by the N , N ′-dialkyl substituents (i.e., n Bu < Et < Me). The detu ligands also support a pattern of N–H···Cl hydrogen bonding that controls the disposition of the critical proximal chloride in the spin equilibrium and frames the lattice structure through equatorial interactions with the distal chloride.…”

“…Ni­(detu) 4 Cl 2 was obtained according to literature syntheses. − ,, Under ordinary air at room temperature, N , N ′-diethylthiourea (8.82 g, 66.7 mmol) was dissolved in n -butanol (100 mL), and NiCl 2 ·6H 2 O (3.99 g, 16.8 mmol) was added to the solution with stirring. After 30 min, a green precipitate was recovered by filtration and recrystallized by vapor diffusion of diethyl ether into an ethanol solution.…”

“…An early review by Barefield et al highlighted five other examples of nickel­(II) complexes that exhibit “anomalous magnetism”, particularly temperature-dependent solid-state susceptibilities attributed to thermal spin equilibria. − None of the relevant spin isomers were structurally characterized, although X-ray structures of derivative complexes were consistent with tetragonal distortion as a basis for spin equilibria (Scheme ). − Our particular attention was drawn to a family of N , N ′-dialkylthiourea halide complexes Ni­(R 2 tu) 4 X 2 that display spin equilibria over a range of temperatures depending on the ligand substituents (R = n Bu < Et < Me) and the halide (X = Cl < Br < I). − The lead complex of this type, Ni­(detu) 4 Cl 2 was reported by Holt, Bouchard, and Carlin as the prototypical example of solid-state spin crossover for nickel­(II), with T 1/2 = 383 K (Figure ). Spin crossover in response to applied pressure was also reported for Ni­(detu) 4 X 2 in 1990 by Bray and Drickamer .…”

Structural properties and potential reactivity of substituted 3- aroyldithiocarbazates

“…A third intense band appears at -32.5 kK, which undergoes a hypsochromic shift with increasing solvent polarity. It is therefore assigned to a n --+ r* transition of the carbonyl group [29,30].…”