Correlation between the structure and reactivity of the selenide dihalide of the new reducing reagent NaBH₄–R₂SeX₂on the highly selective reduction of amides. X-Ray molecular structure of bis-(2-chloroethyl)selenium dichloride

Reaction of tertiary phosphine selenides, R3PSe (R = Me2N, Et2N or C6H11), with dibromine. The first reported examples of 1∶1 addition

“…The phosphorus-selenium distances again fall within the range expected for single bonds, 2.271 (6) Although no compound of formula R 3 PSeBr 2 has previously been reported, a few related R 2 SeBr 2 compounds have been studied by single crystal X-ray diffraction. 7,11, 12 The Se-Br bond lengths for these compounds are similar to or a little shorter than those in the R 3 PSeBr 2 compounds described herein [e.g. d (Se-Br) for Me 2 SeBr 2 = 2.546(4) and 2.551(4) Å].…”

Why Nature Chose Selenium

“…For example, the hypervalent sulfurane 12-S decomposes at −67 °C with a half-life of 46 min, while the selenurane 12-Se has to be “heated” to 0 °C before the decomposition rate is comparable, corresponding to a difference in activation energy of 2.9 kcal/mol . The addition product of chlorine and dialkyl sulfides (e.g., the Corey-Kim reagent) is an ionic structure 13 , whereas that of dialkyl selenides is covalent ( 14 ) . Another occurrence of stronger Se–X bonds occurs in bonding to metals.…”

Crystallographic characterisation of dihalogenodimethylselenium compounds, Me2SeX2 (X = Cl, Br or I) and the dependence of their structures on the nature of the halogen

“…For example, the diphenyl derivatives, Ph 2 SeX 2 (X = Cl 2 or Br 3 ), both adopt a ψ-trigonal-bipyramidal geometry, as does bis(2-chloroethyl)selenium dichloride. 4 From spectroscopic evidence, mainly infrared and Raman, it appears that two distinct structural motifs occur and are dependent on the nature of the halogen. For example, Hayward and Hendra 5 concluded that Me 2 SeBr 2 adopts a ψ-trigonalbipyramidal structure, shown by X-ray crystallography to occur for Ph 2 SeBr 2 , but that Me 2 SeI 2 adopts the charge-transfer Me 2 Se᎐I᎐I structure.…”