Synthesis and chemistry of 1,3-dihydrotellurolo[3,4-b]quinoxaline and derivatives: crystal and molecular structure of 1,3-dihydro-2,2-di-iodo-2λ4-tellurolo[3,4-b]quinoxaline–2,3-bis(iodomethyl)quinoxaline (1:1)

Abstract

The reaction of 2,3-bis(bromomethyl)quinoxaline with tellurium and sodium iodide (2 h) gave the violet compound 1,3-dihydro-2,2-di-iodo-2λ⁴-tellurolo[3,4-b]quinoxaline, which may be reduced to 1,3-dihydrotellurolo[3,4-b]quinoxaline (m.p. 158–160 °C). The latter compound readily forms a black 1 : 1 complex with 7,7,8,8-tetracyanoquinodimethane. The u.v., n.m.r., i.r., and mass spectra of the new organotellurium heterocycles are presented and discussed. 2,3-Bis(bromomethyl)quinoxaline also reacts with tellurium and potassium iodide (1 h) to give a yellow material for which elemental analysis, n.m.r., and mass spectroscopy suggest a 1 : 1 adduct of the above di-iodo-complex and 2,3-bis(iodomethyl)quinoxaline. Sodium hydrogentelluride reduces 2,3-bis(bromomethyl)quinoxaline to 2,3-dimethylquinoxaline. The crystal and molecular structure of the 1 : 1 adduct of 1,3-dihydrotelluro[3,4-b]quinoxaline, C₁₀H₈l₂N₂Te, with 2,3-bis(iodomethyl)quinoxaline, C₁₀H₈l₂N₂, has been determined. Crystals of the compound are triclinic, space group P, with a= 7.667(2), b= 11.826(4), c= 13.739(4)Å, α= 93.26(3), β= 98.37(2), γ= 83.29(2)°, and Z= 2. Final R= 0.059 for 2 998 observed reflections. The structure consists of discrete molecules of C₁₀H₈I₂N₂Te and C₁₀H₈I₂N₂, a pair of each being linked into centrosymmetric dimers by weak Te ⋯ I linkages. The co-ordination about tellurium is a distorted octahedron with two Te–C bonds [2.14(1)Å], two axial Te–I bonds [2.886(2), 2.911 (2)Å] and two longer equatorial Te–I bonds trans to Te–C [3.761 (2), 3.788(2)Å], the longer contact being to an iodine of the organic di-iodide. Large deviations of bond angle from the ideal octahedral angles occur. A further very weak interaction links the dimers into chains along x. No abnormal features are observed in the organic moieties.