Tellurium derivatives of 3-acetyl-2,5-dimethylthiophene: Synthetic and structural aspects

Oxidative addition of α-bromo-3-acetyl-2,5-dimethylthiophene to elemental tellurium and aryltellurium(II) bromide provides direct routes to (2,5-dimethyl-3-thiophenoylmethyl)tellurium(IV) dibromides, (Me2TpnCOCH2)2TeBr2 (1a; Me2Tpn = 2,5-Me2-3-C4HS) and Ar(Me2TpnCOCH2)TeBr2 (Ar = 1-C10H7, Npl, 2a; 2,4,6-Me3C6H2, Mes, 3a). The chloro analogs of 2a and 3a, Ar(Me2TpnCOCH2)TeCl2 (Ar = Npl, 2b; Mes, 3b) and derivative when Ar = Anisyl (anisyl = 4-MeOC6H4, 4b) were prepared by the condensation reaction of methyl ketone, Me2TpnCOCH3 with NplTeCl3, MesTeCl3 and anisylTeCl3 respectively while the chloro analog of 1a, bis(2,5-dimethyl-3-thiophenoylmethyl)tellurium(IV) dichloride, (Me2TpnCOCH2)2TeCl2 (1b) was obtained by the condensation reaction of methyl ketone, Me2TpnCOCH3 with TeCl4. Metathesis of these products (1a–b, 2a–b, 3a–b and 4b) with an alkali iodide affords the iodo analogs 1c, 2c, 3c and 4c. These diorganotellurium dihalides are reduced with aqueous bisulfite to diorganotellurides 1–4, which can be oxidized readily with dihalogens to the desired diorganotellurium(IV) dihalides. The crystal structures of the Te(IV) compounds 1b, 2a, 3c and 4b have been studied and all the Te(IV) compounds, the carbonyl functionalized organic moiety, show intramolecular 1,4–Te⋯O secondary bonding interaction (SBI). In the crystal lattice of 2a, the intermolecular Te⋯Br secondary bonding interactions are evident and result in a dimer. They get further associated via C–H⋯Br secondary interactions to form a 3D supramolecular motifs. In 1b, 3c and 4b supramolecular motifs are formed through C–H⋯O and C–H⋯Cl interactions.

New tellurium(II) and (IV) derivatives of 3-acetyl-2,5-dimethylthiophene were synthesized. Preparation of (Me2TpnCOCH2)2TeBr2 and Ar(Me2-TpnCOCH2)TeBr2 involved oxidative addition of α-bromo-3-acetyl-2,5-dimethylthiophene to tellurium and aryltellurium(II) bromide. The chloro analogs were prepared by condensation of methyl ketone with TeCl4 and ArTeCl3. A centrosymmetric dimeric structure of Npl(Me2TpnCOCH2)TeBr2 formed due to intermolecular Te⋯Br interactions.Figure optionsDownload as PowerPoint slideHighlights
► 1H, 13C, 125Te NMR data of 2,5-Me2-3-thiophenoylmethyl compounds of Te are reported.
► Crystal structures of 2,5-Me2-3-thiophenoylmethyltellurium(IV) derivatives are studied.
► Me2TpnCOCH2 – moiety in Te(IV) compounds, behaves as a (C, O) chelating ligand.
►  In 2a, centrosymmetric dimeric unit was realized via reciprocatory Te⋯Br1 SBIs.