Complexes of methylmercury(II) with 1-methylcytosine and crystal structure of μ-(1-methylcytosinato-N3,N4)bis(methylmercury(II)) nitrate

Abstract

Two types of solid complexes are isolated by reaction of CH 3 HgX (X = NO 3 and ClO 4 ) with 1-methylcytosine (MCy). The CH 3 Hg + ion is probably bonded to N(3) in the [CH 3 Hg(MCy)]X compounds. Mercury binding to N(3) and the deprotonated amino group in [(CH 3 Hg) 2 (MCy—H)]X is confirmed by X-ray work on the nitrate salt. The crystals are orthorhombic, space group Pbca, with a = 12.014, b = 13.573, c = 16.353 Å, and Z = 8. The structure was refined on 962 independent reflections to an R factor of 0.038. The CH 3 Hg + groups are arranged in a syn configuration and the angles around the mercury-bonded nitrogen atoms are severely distorted to prevent short Hg … Hg contacts. N(3)-coordination in the 1:1 complexes introduces minor changes in the infrared spectra, but the substitution of an amino proton in the 1:2 compounds produces important modifications. 1 H nmr data in DMSO-d 6 are reported for both types of compounds. This work emphasizes the important acidity enhancement experienced by the amino protons upon initial coordination to N(3), which facilitates further reaction of CH 3 Hg + by proton displacement even in acidic media.