Crystal structure of a dimeric 1-methylcytosine mercuric chloride complex

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Abstract
Di-.mu.-chloro-bis[chloro(1-methylcytosine-O,N3)mercury(II)] belongs to space group P21/c with cell dimensions a = 9.932(2), b = 14.051(3), c = 9.198(2) .ANG., and .beta. = 135.41(2).degree.. The structure was solved by the heavy-atom method and refined to an R factor of 0.027 for 1271 independent reflections. The crystal is composed of centrosymmetric dimeric molecules in which 2 Hg atoms are attached by a pair of symmetrical Cl bridges. The 1-methylcytosine ligand is bidentate via N(3) and O(2). The metal atom has a (2 + 3) coordination with a very distorted trigonal bipyramid geometry. A Cl atom at 2.322(3) .ANG. and ring Nitrogen (N(3) at 2.17(1) .ANG. form strong axial bonds with Hg. Two bridging Cl atoms at 2.719(2) and 2.745(3) .ANG., and carbonyl oxygen O(2) at 2.84(1) .ANG. form weaker equatorial bonds. The amino group is H-bonded to a bridging Cl of the same molecule (N.cntdot..cntdot..cntdot.Cl = 3.23(1) .ANG. and a carbonyl O of a neighboring molecule (N.cntdot..cntdot..cntdot.O = 2.86(2) .ANG.).