First ICN Adduct with a Selenium Donor (R = Se): Is It an Ionic [RSeCN]⁺I⁻ or a “T‐Shaped” R(I)SeCN Hypervalent Compound?

Abstract

The reaction between 1,3-dimethyl-4-imidazoline-2-selone (2) and ICN gave the adduct 2·ICN, whose crystal structure features dimers made up of two [2·CN] + and two I − which strongly interact. Hybrid DFT calculations on the adduct 2·ICN, on the cation [2·CN] + , and on the dimer (2·ICN) 2 ac-

A Unique Case of Oxidative Addition of Interhalogens IX (X=Cl, Br) to Organodiselone Ligands: Nature of the Chemical Bonding in Asymmetric ISeX Polarised Hypervalent Systems

“…The same criteria can be used for the interpretation of the FT-Raman spectrum of compound VIII, which is dominated by two broad partially-overlapping bands centred at 190 and 174 cm + ···X À ionic pairs. [17,29] Structural and theoretical evidence tends to suggest the presence of partial covalent character in the Se À X bond and, therefore, a hypervalent nature of the central selenium atom in these asymmetric systems as compared with the symmetric XÀSeA C H T U N G T R E N N U N G (ÀC<)ÀX (X= I, Br, Cl) moieties. The linearity observed for the IÀSeÀX [NCÀSeÀX] groups so far structurally characterised could support this view, although this is not direct evidence for the hypervalency of the selenium atom.…”

“…[29] Analysis of the QTAIM properties at the BCPs of Se À C/ Se À X bonds in 1-17: To better establish the degree of hypervalency of the selenium atom in chalcogen compounds featuring either a linear I À SeA C H T U N G T R E N N U N G ( À C<) À X (X= Br, Cl) or linear NCÀSeA C H T U N G T R E N N U N G (ÀC<)ÀI moiety and, therefore, the 3c-4e nature of these compounds, we performed a topological electron density analysis on model compounds 1-17 (Scheme 2) based on the quantum theory of atoms-in-molecules (QTAIM) [30] approach developed by Bader and already applied with success to other types of hypervalent systems. [31][32][33][34][35] Non-hypervalent compounds 1-5 have also been considered as reference compounds for comparing QTAIM parameters (see below).…”

“…4) We recently elucidated the crystal structure of compound 17, which represents a rare case of an asymmetric "T-shaped" adduct formally derived from the oxidative addition of ICN to 5. [29] We described the system as a strongly polarised selenium hypervalent adduct on the basis of the directionality of the I···Se À CN moiety, the value of the angle C À Se À CN, charge distribution and nature of the LUMO orbital in the cation [5·CN]…”

Reactions of pyridyl donors with halogens and interhalogens: an X-ray diffraction and FT-Raman investigation

“…As an example, from the reaction of 2,2 0 -bipy with IBr both the neutral CT adduct 2,2 0 -bipy AE 2IBr [22], and the salts ½Hð2; 2 0 -bipyÞ þ ðH 3 O þ Þ ðIBr À 2 Þ 2 , or ½Hð2; 2 0 -bipyÞ þ ðI 2 Br À 3 Þ [23] were obtained, depending on the reaction conditions. Following our previous investigations on chalcogen donors towards halogens [1,24,25], interhalogens [26], and the pseudo-halogen ICN [27], and encouraged by the recent results obtained with di-[2]-pyridyl-disulfide, which was able to template an infinite polyiodide 3D-network [6], we are systematically testing the reactivity towards halogens and interhalogens of polypyridyl donors, differing in their dimensions, conformations, and directionality of N-donor sites.…”

Sulfur and SeleniumActivation by Frustrated NHC/B(C6F5)3 Lewis Pairs; Conformational Flexibility of Products

“…The selenium adduct of the saturated carbene crystallised with one disordered molecule of pentane and half a disordered molecule of toluene per asymmetric unit. The structural data for the tetrahedral selenoborate unit shows a C-Se distance of 1.9187 (14)Å, which is slightly longer than 1.869 (6)Å in dimethylimidazolidin-2-selenone [31], but in the range of cationic dimethylimidazolidin-2-selenonehalogen species 1.894 -1.910Å [32]. The Se-B distance of 2.2111 (15)Å represents the first selenone-borane bond length to be determined by X-ray diffraction analysis.…”