Mercury complexes with 1,2,6,7-tetracyano-3,5-dihydro-3,5-diimino-pyrrolizinide

The anion 2-(5-amino-3,4-dicyano-2H-pyrrol-2-ylidene)-1,1,2-tricyanoethanide (L′, C₁₁H₂N₇⁻), after isomerization to 1,2,6,7-tetracyano-3,5-dihydro-3,5-diimino-pyrrolizinide (L), forms different metal-complexes with mercury depending on the experimental conditions. Pure compounds were isolated from the reactions HL+CH₃HgAc in CH₃CN and NaL′+HgAc₂ in AcH/H₂O. They are CH₃HgL and HgL₂. From their optical spectra, compared to those of phthalocyaninato- or other well-known pyrrolizinato-complexes, the coordination geometry of Hg(II) in these species is supposed to be trigonal planar and trigonal monopyramidal, respectively. CH₃HgL was characterized also by ¹H NMR: (CD₃CN, δ, ppm) 0.886 (CH₃), 8.733 (NH). From the reactions in water between NaL′ and HgCl₂ or HgClO₄ complex mixtures of polynuclear complexes were isolated of composition: 0.826 [Hg₂ClL₂(OH)]·0.174 [Hg₄L₃(OH)₅]·2.06 H₂O (A) or 0.588 [Hg₂L₂]·0.412 [Hg₂L(OH)₃]·3.53 H₂O (B), respectively. The formulae A and B were based on thermogravimetric and elemental analysis data. Indirect evidences, based on XPS data, for the existence of the pyrrolizinato–Hg(I) complex are also given.