Reactions of the methylmercury cation with xanthine and crystal structures of μ-(xanthinato-N3,N7,N9)tris(methylmercury(II)) nitrate and μ-(xanthinato-N1,N3,N7,N9)tetrakis(methylmercury(II)) nitrate

Publisher Website
Google Scholar
Abstract
Compounds of the types [(CH3Hg)X], [(CH3Hg)4X]Z, and [(CH3Hg)3(HX)]Z (where Z = NO3-,ClO4-) were obtained by reacting the methylmercury cation with xanthine (H3X) in aqueous media. The 3 acidic protons of H3X at N(1), N(3) and N(7) are substituted by CH3Hg+ groups in [(CH3Hg)3X1.cntdot.2H2O. Crystals of [(CH3Hg)3(HX)]NO3.cntdot.H2O belong to the triclinic P.hivin.1 space group, with a = 7.319(3), b= 9.466(8), c = 12.004(3) .ANG., .alpha. = 96,06(5), .beta. = 95,00(3), .gamma. = 97.69(5).degree., and Z = 2. The structure was refined on 1610 nonzero reflections to an R factor of 0.038. The CH3Hg+ groups are linearly coordinated to N(3), N(7), and N(9) of a dianionic xanthine retaining its N(1).sbd.H proton (mean Hg.sbd.N = 2.07(3) .ANG.). The [(CH3Hg)4X]NO3 compound is monoclinic, space group C2/c, a = 24.55(2), b = 17.016(4), c = 19.108(9) .ANG., .beta. = 110.26(5).degree., Z = 16. The structure was refined on 1418 nonzero reflections to R = 0.046. The 2 independent [(CH3Hg)4X]+ ions possess methylmercury groups linearly coordinated to the 4 nitrogen atoms of the X3 anion (mean Hg.sbd.N = 2.07(5) .ANG.). The compounds prepared were characterized by IR spectroscopy, and by 1H and 13C NMR. The [(CH3Hg)3X].cntdot.2H2O and [(CH3Hg)4X]Z compounds remain undissociated in DMSO [dimethyl sulfoxide] solution. The [(CH3Hg)3(HX)]+ salts disproportionated to some extent into [(CH3Hg)4X]+ and a lower complex which was identified as the N(7),N(9)-bonded [(CH3Hg)2(H2X)]+ ion.