SYNTHESIS OF [2-(PYRIDIN-2'-YL)PHENYL]-MERCURY(II) ARYLTHIOSEMICARBAZONATES - AN UNUSUAL COORDINATION MODE OF A DEPROTONATED 2-FORMYL-(2-HYDROXY-BENZENE)-THIOSEMICARBAZONE

The reactions of [2-(pyridin-2'-yl)phenyl]mercury(II) acetate with 2-f ormyl-benzene-(Hbtsc), 2-formyl-(2-hydroxybenzene)-(H(2)stsc) and 2-fo rmyl-(4-methoxybenzene)-(Hmbtsc) thiosemicarbazones in ethanol in 1:1 ratio at room temperature formed [Hg(C6H4C5H4N)L] (L=btsc, 1; Hstsc, 2 ; mbtsc, 3). The derivative [Hg(C6H4C5H4N)L] 2 crystallises in the tri clinic space group P/1 (n. 2), Z = 2, R = 0.0353 and V = 906.8(3)Angst rom(3). Mercury is bonded strongly only to sulphur atom of thiosemicar bazonate anion [Hg-S, 2,357(2)Angstrom] and Hg...N(3) distance of 3.12 6(6)Angstrom, slightly less than the sum of the van der Waal's radii ( 3.28 Angstrom) shows a weak interaction. The pyridyl nitrogen binds st rongly to Hg [Hg-N(4), 2.575(6)Angstrom] with a short C(9)HgN(4) bite angle of 74.6(2)degrees, but Hg retains near linearity in CPhHgS bond angle [177.8(2)degrees]. H-1 and Hg-199 NMR spectra in CDCl3 solution reveal two isomers (A and B) for each of 1-3 and probably also a third isomer (C) for 2. The similarity of H-1 and Hg-199 data of B isomers (minor for 1 and 3; major for 2) clearly support that thiosemicarbazon es are unidentate S-donors as established for crystallized B isomer of 2 (major) by X-ray study, with pyridyl nitrogen of 2-pyridylphenyl co ordinating to Hg. The A isomers (major for 1 and 3;minor for 2) have p resumably N-3,S-coordinated thiosemicarbazonates with weak Hg-N(pyridy l) interaction and the Hg atom formally tetracoordinated. (C) 1998 Els evier Science Ltd. All rights reserved.