Crystal structures of [Pb(NO3)6]4– and [Ba(NO3)6]4– salts of 24-pyrimidinium crown 6 {5,12,19,26,33,40-hexaamino-3,10,17,24,31,38-hexamethyl [1.6](1,5)pyrimidiniophane}

Abstract

Reflux of thiamin [3-(4-amino-2-methylpyrimidin-5-ylmethyl)-5-(2-hydroxyethyl)-4-methylthiazolium] mononitrate in methanol for 2 h, followed by recrystallization from water, produced single crystals of [L][NO₃]₆{L = 5,12,19,26,33,40-hexaamino-3,10,17,24,31,38-hexamethyl[1.₆](1,5)-pyrimidiniophane or 24-pyrimidinium crown 6}. Addition of a saturated aqueous solution of M(NO₃)₂(M = Ba or Pb) to a saturated aqueous solution of [L][NO₃]₆ yielded single crystals of [L][Ba(NO₃)₆][NO₃]₂·6H₂O and [L][Pb(NO₃)₆][NO₃]₂·6H₂O respectively. Both compounds crystallize in the trigonal space group R: Ba, a=b= 14.265(3), c= 25.206(9)Å, Z= 3, R= 0.0435, R′= 0.0586, 1169 independent reflections with F > 6.0σ(F); Pb, a=b= 14.228(5), c=25.24(1)Å, Z= 3, R= 0.0343, R′= 0.0354, 1263 independent reflections with F > 1.0σ(F). The M²⁺ ions in these isomorphous structures lie on a three-fold axis and are co-ordinated to 12 nitrate oxygen atoms, with a co-ordination polyhedron resembling a distorted cuboctahedron.