Diphenylthallium(III) thiosemicarbazonates: flexibility of coordination in the solid state and polymorphism in chloroform solution

摘要

The reactions of diphenylthallium(III) hydroxide in water-ethanol at room temperature with thiosemicarbazones HL = R = N(3)-N(2)H-C(l)(S)-N(l)H-2 (RO = cyclopentanone, benzaldehyde, 2-hydroxybenzaldehyde, 4-methoxybenzaldehyde, acetophenone, furan-2-carbaldehyde, pyridine-2-formaldehyde and pyridine-2-acetaldehyde) afforded novel diphenylthallium(III) thiosemicarbazonates of stoichiometry [TIPh2(L)] (compounds 1-8, respectively) that were characterised with the help of analytical data, physical properties. IR spectrometry, multinuclear (H-1, C-13 and Tl-205) NMR spectroscopy and X-ray studies of 1, 7 and 8. In crystals of 1 (and probably also in those of 2, 4, 5 and 6), Tl(III) is bound to two phenyl carbons and to the N(3) and S atoms of the monodeprotonated thiosemicarbazone in a distorted trigonal bipyramidal coordination polyhedron with one vacant site in the equatorial plane, In 3 the metal atom is S,N(3),O-coordinated. In 7 and 8 there are three independent molecules: all three have distorted trigonal bipyramidal coordination with Tl coordinated to two carbon atoms and to the N(Py), N(3) and S atoms of the deprotonated thiosemicarbazones. but they differ significantly in their bonding parameters. The Tl-205 NMR spectra suggest that for 1-6 more than one coordination mode is present in solution in chloroform. whereas for 7 and 8 there is only one species. Low temperature proton NMR studies of 7 and 8 showed that the energy barrier to rotation of the amino groups about the C-1-N-1 bond correlated with the bonding parameters of the thioamide group in the solid state: in both cases the barrier is somewhat higher than in thiosemicarbazonates of PhHg(II). 2002 Elsevier Science B.V. All rights reserved. [References: 36]