Formation, crystal structure and co-ordination chemistry of the [MnIII(oespz)(SH)] [oespz2– = 2,3,7,8,12,13,17,18-octakis(ethylsulfanyl)-5,10,15,20-tetraazaporphyrinate dianion] complex

Abstract

Reaction of [Mn(oespz)] [oespz^2– = 2,3,7,8,12,13,17,18-octakis(ethylsulfanyl)-5,10,15,20-tetraazaporphyrinate dianion (porphyrazinate)] with CS₂ and, subsequently, with THF, afforded the hydrogensulfido(1–)manganese(III) ethylsulfanylporphyrazinate [Mn(oespz)(SH)], in high yield. The S–H stretching absorptions are not observed in the IR spectrum of the complex, whereas a peak at δ 10.3 (vs. SiMe₄) ascribed to the hydrogensulfido proton resonance, is observed in the ¹H NMR spectrum. The complex was shown to be isostructural with [M(oespz)Cl] (M = Fe or Mn) by X-ray crystallography. The crystal packing of the complex consists of slipped stacks of dimeric units with the monomers positioned in a trans fashion with respect to the Mn–S_apical bond. Magnetic data are consistent with weakly antiferromagnetically coupled high spin (S = 2) manganese(III) centers. A possible pathway to the oxidative addition of CS₂ to the manganese(II) center has been proposed. In CHCl₃ [Mn(oespz)(SH)] reacts reversibly through the axial hydrosulfido ligand with the sterically hindered base 2,4,6-trimethylpyridine, whereas the complex co-ordinates 1-methylimidazole reversibly on the vacant site of manganese. Treatment of the complex with 1-methylimidazole in benzene leads to a Mn^III–Mn^II redox process, as deduced from the UV/VIS spectra.