2-(2-PYRIDYL)PHENYL SELENIUM-COMPOUNDS - SYNTHESIS AND PROPERTIES - THE CRYSTAL-STRUCTURE OF 2-(2-PYRIDYL)PHENYL-SELENIUM(II) TRIBROMOMERCURATE(II)

The reaction of RHgCl (R = 2-(2-pyridyl)phenyl-) with SeX4 (X = Cl, Br) involves both trans-metallation and redox processes, the final product being 2-(2-pyridyl)phenylselenium(II) tribromomercurate(II). Variation of the reaction conditions allows isolation of materials that appear to be intermediates in the trans-metallation process; the nature of these intermediates is discussed. Routes to compounds of the types RSeBr3 and RR′Se (R′ = p-ethoxyphenyl-) are described. The crystal and molecular structure of the title compound was determined. Disorder in the structure prevented differentiation of the CSe and NSe bonds, which apparently had the same length of 1.91(3) Å within the cation, which can be regarded as electronically equivalent to dibenzoselenophene. The packing of the tribromomercurate ions [HgBr 2.52(1), 2.49(1) Å] results in two additional Hg...Br contacts (3.43(1) Å) that complete trigonal bipyramidal co-ordination. There are weak (3.21(1) Å) Se...Br contacts. © 1990.