In 1836 the first organoselenium compound, diethyl selenide, was prepared by Löwig,1 and it was isolated in the pure form in 1869.2 Early selenium chemistry involved the synthesis of simple aliphatic compounds such as selenols (RSeH), selenides (RSeR), and diselenides (RSeSeR); however, because of their malodorous nature, these compounds were difficult to handle. This, combined with the instability of certain derivatives and difficulties in purification, meant that selenium chemistry was slow to develop. By the 1950s, the number of known selenium compounds had increased significantly, but it was not until the 1970s, when several new reactions leading to novel compounds with unusual properties were discovered, that selenium chemistry began to attract more general interest.3-9 Aryl-substituted compounds were synthesized that were found to be less volatile and more pleasant to handle than the earlier aliphatic compounds. Compounds containing selenium in high oxidation states are relatively easy to manipulate using modern techniques.4c Organoselenium chemistry has now become a well-established field of research, and recent advances have been brought about by the potential technical applications of selenium compounds. Today selenium compounds find application in many areas including organic synthesis,4 biochemistry,5 xerography,6 the synthesis of conducting materials7 and semiconductors,8 and ligand chemistry.4c,9 Many of these aspects of selenium chemistry are wellcovered elsewhere in the literature; however, the subject of hypervalency has not attracted much attention and is the focus of this review.10

Organoselenium chemistry: role of intramolecular interactions.

Recent developments in the coordination chemistry of selenoether and telluroether ligands

Synthesis, antioxidant properties, biological activity and molecular modelling of a series of chalcogen analogues of the 5-lipoxygenase inhibitor DuP 654

Synthesis, structure, and reactivity of organochalcogen (Se, Te) compounds derived from 1-(N,N-dimethylamino)naphthalene and N,N-dimethylbenzylamine

Mercury(II) and gold(III) derivatives of 2-phenyl pyridines and 2-phenyl-4-(methylcarboxylato)quinoline

The syntheses and spectroscopic data (13C n.m.r.) for some new organyltellurium ligands are described. Thus trans metallation of 2-(2-pyridyl)phenyl-(R) or 2-(quinolin-2-yl)phenyl-(R′) mercury(II) chloride with TeBr4 gives the organyltellurium tribromides RTeBr3 and R′TeBr3, which may be reduced to the organyltellurium bromides RTeBr and R′TeBr, some metathesis reactions of which are described; or, in the presence of excess hydrazine, to diorganyl ditellurides, R2Te2 and R′2Te2. Reduction of RTeBr3X with NaBH4 gave a novel tritelluride, R2Te3; a method of preparation for R′2Te3 was also devised. Syntheses of the tellurides R2Te, R′2Te, and RTe(C6H4OEt-p) were developed and the intermediacy of ionic compounds [R2TeBr][HgClBr2] and [R2TeCl][HgCl3] noted. The crystal structures of 2-(2-pyridyl)phenyltellurium(IV) tribromide, (1), dimethyldithiocarbamato [2-(2-pyridyl)phenyl]tellurium(II), (2), and p-ethoxyphenyl 2-(2-pyridyl)phenyltelluride, (3), have been determined from three-dimensional X-ray counter data. Complex (1) is triclinic, space group P with a= 6.953(6), b= 8.382(1), c= 12.133(2)A, α= 78.68(1), β= 82.87(4), γ= 87.14(4)°, and Z= 2; R= 0.0735 for 1 963 observed reflections. The co-ordination about Te is octahedral with a vacant equatorial position, two Br atoms apical, the third Br and the organic group equatorial [Te–C, 2.110(19); Te–N, 2.244(14)A]. The compound is essentially monomeric, with a weak association between Te and Br [3.596(3)A] in a neighbouring molecule. Complex (2) is triclinic, space group P with a= 8.809(3), b= 9.032(5), c= 10.727(4)A, α= 83.06(4), β= 86.49(3), γ= 63.68(4), and Z= 2; R= 0.0417 for 2 502 observed reflections. The co-ordination about Te is trigonal bipyramidal, C(1) and two lone pairs of Te comprising the equatorial co-ordination and the S(1) atom together with the pyridyl-N atom axial [Te–C, 2.111(5); Te–N, 2.354(4)A]. No significant intermolecular contacts occur. Complex (3) is monoclinic, space group P21/c with a= 13.422(2), b= 16.469(3), c= 7.711(3)A, β= 91.01(2)°, and Z= 4; R= 0.0415 for 2 014 observed reflections. The Te atom is bonded to two C atoms. The N atom of the pyridyl ring is twisted away from Te [Te–N, 2.695(4)A] by rotation of the pyridyl ring about the pyridyl–phenyl bond by 23.2(3)°, a manifestation of the trans effect of the Te–C(ethoxyphenyl) covalent bond.

2-Pyridyl- and quinolin-2-yl-functionalised organyltellurium ligands. The stabilisation of diorganyl tritellurides. The crystal and molecular structures of 2-(2-pyridyl)phenyltellurium(IV) tribromide, dimethyldithiocarbamato[2-(2-pyridyl)phenyl]tellurium(II), and p-ethoxyphenyl 2-(2-pyridyl)phenyl telluride

Najih Al-Salim

Papers

Bis(2-(2-pyridyl)phenyl)tritelluride - synthesis and crystal structure

The ligand chemistry of 2-(4-Ethoxyphenyltelluro)benzoate