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Crystal and molecular structure of bis(pyridine)bis(saccharinato)-mercury(II), [Hg(py)_2(sac)_2]

Within our extensive research of the structural properties of saccharinato salts and complexes, the crystal structures of Hg(sac)_2 (1) [B. Kamenar et al., Cryst. Struct. Comm., 11 (1982) 263], HgCl(sac) (2) [G. Jovanovski et al., Acta Cryst., C44 (1988) 616] and Hg(bpy)(sac)_2 (3) [A. Hergold-Brundić et al., Acta Cryst., C45 (1989) 556] were previously reported. Our recent attempts to synthesize a pyridine adduct of mercury(II) saccharinate using HgCl_2 yielded the complex [HgCl(py)(sac)]_2 (4) [O. Grupče et al., Croat. Chem. Acta, 72, No. 2 (1999) in press]. The use of Hg(OAc)_2, however, gave the expected pyridine adduct, bis(pyridine)bis(saccharinato)mercury(II) (5), whose crystal and molecular structure is reported here. Crystal data. C_24H_18HgN_4O_6S_2, triclinic, P-1, M_r = 723.13, a = 10.1763(7), b = 10.2652(8), c = 12.7153(10) A, a = 101.734(7), b = 95.528(9), c = 94.389(9) ^o, V = 1288.15(17) A^3, D_c= 1.864 gˇcm^-^3, Z = 2, l(MoK_a) = 0.71073 A, R = 0.118, wR = 0.163 for 4004 reflections with Inet * 2sInet out of 5593 independent intensity data. (based on the non-absorption correction data; the refinement is in progress). The structure consists of discrete [Hg(py)_2(sac)_2] molecules. Mercury atom is in the general position, being tetrahedrally coordinated by two pyridine as well as two saccharinato nitrogen atoms. The value of the dihedral angle between the planes of the pyridine rings is 103.0(16)^o, while that between the saccharinato ligands amounts 59.6(6)^o. The Hg-N(py) distances in 5 [2.30(3) and 2.34(3) A] are larger than that in 4 [2.021(8) A], but very similar to the Hg-N(bpy) distances in 3 [2.328(4) and 2.393(3) A]. The Hg-N(sac) bond lengths in 5 [2.156(24) and 2.148(22) A], as well as in the other tetrahedral mercury(II) saccharinato adducts, 3 [2.141(4) and 2.120(4) A] and 4 [2.106(7) A], are all longer than the corresponding bonds in the digonal compounds 1 [2.03(1), 2.04(2), 2.05(2) and 2.06(1) A] and 2 [2.021(8) A]. No other interactions, but the usual van der Waals contacts, were observed among the individual molecules.

Metal saccharinates; mercury(II) compounds; X-ray structure determination

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