4-(Dimethylamino)phenyl ethynyl telluride

The title compound, C10H11NTe, is the first organyl ethynyl telluride, R—Te—C C—H, to be structurally characterized. In the L-shaped molecule, the aryl moiety, viz. Me2NC6H4Te, is almost perpendicular to the Te—C C—H fragment. The Te—Csp 2 bond [2.115 (3) Å] is significantly longer than the Te—Csp bond [2.041 (4) Å]. The Te—C C group is approximately linear [Te—C—C = 178.5 (4)° and C C = 1.161 (5) Å], while the coordination at the Te atom is angular [C—Te—C = 95.92 (14)°]. In the crystal structure, there are Csp—H⋯N hydrogen bonds which are perpendicular to the CNMe2 group; the N atom displays some degree of pyramidalization. Centrosymmetrically related pairs of molecules are linked by Te⋯π(aryl) interactions, with Te⋯Cg = 3.683 (4) Å and Csp—Te⋯Cg = 159.1 (2)° (Cg is the centroid of the benzene ring). These interactions lead to the formation of zigzag ribbons which run along c and are approximately parallel to (110).

The title compound, C 10 H 11 NTe, is the first organyl ethynyl telluride, R-Te-C C-H, to be structurally characterized. In the L-shaped molecule, the aryl moiety, viz. Me 2 NC 6 H 4 Te, is almost perpendicular to the Te-C C-H fragment. The Te-Csp 2 bond [2.115 (3) Å ] is significantly longer than the Te-Csp bond [2.041 (4) Å ]. The Te-C C group is approximately linear [Te-C-C = 178.5 (4) and C C = 1.161 (5) Å ], while the coordination at the Te atom is angular  ]. In the crystal structure, there are Csp-HÁ Á ÁN hydrogen bonds which are perpendicular to the CNMe 2 group; the N atom displays some degree of pyramidalization. Centrosymmetrically related pairs of molecules are linked by TeÁ Á Á(aryl) interactions, with TeÁ Á ÁCg = 3.683 (4) Å and Csp-TeÁ Á ÁCg = 159.1 (2) (Cg is the centroid of the benzene ring). These interactions lead to the formation of zigzag ribbons which run along c and are approximately parallel to (110).

Comment
Although organotellurium compounds have attracted considerable interest as reagents and intermediates in organic synthesis (Petragnani, 1994), only a limited number of compounds with mono-and ditelluroethyne cores, R-Te-C≡CH and R-Te-C≡C-Te-R', have been reported, in spite of the potential reactivity of the acetylene unit towards addition reactions. We recently reported the syntheses and crystal structures of several symmetrical (R = R') bis(aryltelluro)ethynes, Ar-Te-C≡C-Te-Ar (Farran et al., 2002). On the other hand, only five R-Te-C≡CH derivatives have been prepared so far, with R = Me, Et, i Pr, n-Bu and Ph (Kauffmann & Ahlers, 1983;Dabdoub et al., 1998;Potapov & Trofimov, 2005;Yoshimatsu, 2005), and none has been structurally characterized (in addition, molecular orbital calculations for R = HC≡C were carried out by Murai et al., 1994). Here we describe the crystal structure of the title compound (R = p-Me 2 NC 6 H 4 ), the first of an organyl ethynyl telluride to be reported.
The structure analysis showed that the crystal contains discrete L-shaped molecules of the title compound (Figure 1), in which the aryl moiety, Me 2 NC 6 H 4 Te, is almost perpendicular to the Te-C≡C-H fragment (cf. C-Te-C angle, Table   1), but bent ca 13° towards the C12-C13 side of the ring (cf. C-Te-C-C angles, Table 1), probably to optimize the C-H···N interaction (see below).
In the crystal structure the molecules are linked by C(sp)-H···N hydrogen bonds (Table 2)

Experimental
Ethynyl magnesium bromide, HC≡CMgBr, was prepared according to published procedures (Brandsma, 1988). The corresponding diaryl ditelluride, (Me 2 NC 6 H 4 Te) 2 , was synthesized as reported elsewhere (Petragnani et al., 1975). A dark solution supplementary materials sup-2 of the diaryl ditelluride (2.0 mmol, 0.94 g) in 40 ml of THF was treated dropwise with bromine (2.0 mmol, 0.32 g, 0.10 ml) in 10 ml of benzene, at 0°C, in N 2 atmosphere, while efficient cooling was applied. The Grignard reagent was then added dropwise. Gradual disappearance of the dark color of the solution was observed until it finally became almost colorless when about 10% excess of the reagent was added. After stirring for 30 min at room temperature, the solution was diluted with 50 ml of low boiling point petroleum ether, treated with aqueous NH 4 Cl and washed with brine. The organic layer was dried over magnesium sulfate and the solvents were evaporated. The residue was purified by flash chromatography (silica gel/hexane). Yield 51%. Crystals suitable for X-ray analysis were obtained by slow evaporation of a chloroform solution.
The specimen used for data collection was air-protected with a thin coat of Loctite epoxy adhesive.

Refinement
Hydrogen atoms were placed in calculated positions using a riding atom model with fixed C-H distances [0.93 Å for C(sp) and C(sp 2 ), 0.96 Å for C(sp 3 )] and U iso = p U eq (parent atom) [p = 1.2 for C(sp) and C(sp 2 ), 1.5 for C(sp 3 )]. Fig. 1. Molecular structure of the title compound showing the atomic numbering. Displacement ellipsoids are drawn at 50% probability level.