Cis-trans isomerism in square planar [TeX2(stu)(2)] complexes (X = Br-, I-) with bulky substituted thiourea (stu) ligands. Syntheses and structures of four new tellurium(II) complexes
PHOSPHORUS SULFUR AND SILICON AND THE RELATED ELEMENTS
Authors: Husebye, S; Mughannam, D; Tornroos, KW
Abstract
The complexes were synthesised by adding a hot solution of the appropriate substituted thiourea in MeOH (Br- complexes) or DMF (I- complexes) to a solution of TeO2 dissolved in hot conc. HCl. The structures of the resulting four-coordinate square planar complexes, cis-[TeBr2{((PrNH)-Pr-i)(2)CS}(2)] (1), cis-[TeBr2{((BuNH)-Bu-i)(2)CS}(2)] (2), trans[Tel(2){((PrNH)-Pr-i)(2)CS}(2)](3), and trans-[Tel(2){((BuNH)-Bu-i)(2)CS}(2)](4), were studied by means of X-ray crystallographic methods. The average Te-S bond length in 1 and 2 is 2.5364 Angstrom. The corresponding average Te-Br bond length is 2.9639 Angstrom, reflecting the stronger trans influences of the two thioureas as compared to that of bromide. In 3 and 4 where there is no trans influence affecting the Te-ligand bonds, the average Te-S and Te-I bond lengths are 2.6926 and 2.9761 Angstrom respectively. Tetraalkyl- or aryl-substituted thioureas alone as well as bulky disubstituted thioureas together with I- ligands seem to favor formation of trans complexes.
Observation of Te center dot center dot center dot pi and X center dot center dot center dot X bonding in para-substituted diphenyltellurium dihalides, (p-Me2NC6H4)(p-(YCH4)-H-6)TeX2 (X = Cl, Br, I; Y=H, EtO, Me2N)
AUSTRALIAN JOURNAL OF CHEMISTRY
Authors: Beckmann, J; Dakternieks, D; Duthie, A; Mitchell, C; Schurmann, M
Abstract
The supramolecular association of the previously described para-dimethylaminophenyl-substituted diorganotellurium dihalides (p-Me2NC6H4)(2)TeX2 (X = Cl ( 1), Br ( 2), I ( 3)) and (p-Me2NC6H4) RTeCl2 (R= Ph ( 4), p-EtOC6H4 ( 5)), was investigated by X-ray crystallography. Unlike almost all other structurally characterized diorganotellurium dihalides, (p-Me2NC6H4)(2)TeX2 (X = Cl ( 1), Br ( 2), I ( 3)) reveal no secondary Te ... X interactions, but X ... X interactions. The structure of (p-Me2NC6H4) PhTeCl2 ( 4) resembles that of Ph2TeCl2 and shows one secondary Te ... Cl contact, whereas (p-Me2NC6H4)(p-EtOC6H4) TeCl2 ( 5) exhibits neither secondary Te ... Cl nor Cl ... Cl interactions. The unusual structural characteristics of 1 - 5 are attributed to the occurrence of intermolecular Te ... pi and pi...pi contacts associated with quinoid pi-electron delocalization across the para-dimethylaminophenyl ( 1 - 5) and para-ethoxyphenyl ( 5) groups.
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