CRYSTAL AND MOLECULAR-STRUCTURE AT 298-K AND 183-K OF HEXAKIS(PYRIDINE)MERCURY(II) TRIFLUOROMETHANESULFONATE, [HG(NC5H5)6](CF3SO3)2, AND THERMAL ANALYSES OF HEXAPYRIDINE SOLVATES OF MERCURY(II)

The compound [Hg(NC5H-5)6](CF3SO3)2 crystallizes with two formula units in its unit cell in the triclinic space group PBAR1 with a = 10.890(4) [10.799(5)], b = 11.206(6) [11.128(8)], c = 17.736(7) [17.695(5)] angstrom, alpha = 85.10(4) [85.14(7)], beta = 89.38(3) [89.32(4)], gamma = 60.57(3) [59.90(4)-degrees], V = 1877(2) [1832(2)] angstrom-3 at 298 [183] K. The structural parameters were refined by least-squares methods to conventional R-values of 0.045 [0.030]. The structure is built up from discrete hexakis(pyridine)-mercury(II) complex ions and trifluoromethanesulfonate ions. The six Hg-N bonds in the range 2.42-2.48 [2.402-2.499] angstrom, at 298 [183] K form a tetragonally elongated octahedron with two opposite Hg-N bonds somewhat longer (average value 2.48(5) [2.50] angstrom) than the other four (average 2.44 [2.42] angstrom). The structural feature appears to be consistent with a thermogravimetric (TG) analysis, which showed that the pyridine molecules leave in pairs in a stepwise decomposition leading to [Hg(NC5H-5)2](CF3SO3)2. A similar behaviour was found for the hexakis(pyridine)-mercury(II) perchlorate.