Synthesis, spectroscopy, and electrochemistry of heterocyclic thionato complexes of divalent nickel: crystal structure of tetraethylammonium fac-[tris(benzothiazoline-2-thionato)nickelate(II)]

Abstract

The deprotonated anions derived from benzothiazoline-2-thione (C₇H₅NS₂), thiouracil (C₄H₄N₂OS) and 6-amino-2,3-dihydro-2-thioxo-(1H)-pyrimidin-4-one (C₄H₅N₃OS) react with [NEt₄]₂[NiCl₄] in acetonitrile to give [NEt₄][Ni(C₇H₄NS₂)₃], (1), [NEt₄][Ni(C₄H₃N₂OS)₃], (2), and [NEt₄][Ni(C₄H₄N₃OS)₃], (3). Crystal structure analysis shows that (1) crystallises in the monoclinic space group P2₁/n with a= 10.290(1), b= 19.137(2), c= 16.814(2)Å, β= 101.95(1)°, Z= 4, R= 0.082 from 5 336 unique reflections with F > 4σ(F). The [Ni(C₇H₄NS₂)₃]^– anion adopts the confacial isomeric form with the metal in a distorted-octahedral environment formed from three, four-membered, S,N-chelating ligands. Average Ni^II–N and Ni^II–S_thionate distances are 2.070 and 2.555 Å, respectively, and the mean N–Ni^II–S angle is 67.8°. Solid-state electronic spectra and room-temperature magnetic moments show that Ni^II is octahedrally co-ordinated in complexes (1)–(3). They also suggest that the anions have the same isomeric form. Electrochemical measurements show the complexes to be irreversibly oxidised in acetonitrile.