Crystal and molecular structures of 1,4-butylenediamine-bis(1,2-ethylenediamine)cobalt(III) pentachloromercurate(II) [Co(En)(2)Tmd]HgCl5

The crystal structure of the [Co(En)(2)Tmd]HgCl5 complex (where En is 1,2-e thylenediamine, and Tmd is 1,4-butylenediamine) is determined by X-ray diff raction analysis. The crystals are monoclinic [a = 11.669(1), b = 10.243(1) , and c = 17.190(1) Angstrom; beta = 103.09(1)degrees; Z = 4; space group P 2(1)/c; and R = 0.0408 for 2618 reflections] and involve the discrete catio nic complexes [Co(En)(2)Tmd](3+) and the pentachloromercurate(II) anions [H gCl5](3-). In the octahedral cationic complex, the Co-N bond lengths range between 1.96 and 1.98 Angstrom. In the [HgCl5](3-) anion, each Hg atom is s urrounded by five Cl atoms that occupy vertices of a tetragonal pyramid, an d the Hg-Cl bond lengths are equal to 2.395-2.887 Angstrom. Such a tetragon al-pyramidal form of the pentachloromercurate(II) ions is observed for the first time.