Chalcogen Capture by an Al/P-Based Frustrated Lewis Pair: Formation of Al-E-P Bridges and Intermolecular Tellurium–Tellurium Interactions

Abstract

Reaction of the Al/P-based frustrated Lewis pair (FLP) Mes 2 P-C(CH-C 6 H 5 )-Al(CMe 3 ) 2 1 with heavier chalcogens (E = S, Se and Te) yielded by oxidation of the P atoms the respective phosphorus(V) compounds Mes 2 P(E)-C(CH-C 6 H 5 )-Al(CMe 3 ) 2 (2a, E =S, 2b, E = Se, 2c, E = Te) in good yield. The chalcogen atoms were coordinated to the Lewis-acidic Al atoms, which, in the case of the dark red Te compound 2c, resulted in a stabilization of the P−Te bond. Unique fourmembered, slightly puckered P-C-Al-E heterocycles were formed with P−E bond lengths in the normal range of terminal chalcogen atoms and comparatively long Al−E bonds, which are consistent with relatively weak Al−E interactions. Both the Se and more pronounced the Te compound formed dimers in the solid state as a result of closed-shell chalcogen−chalcogen interactions. While the Se···Se distance was only slightly shorter than the sum of the van der Waals radii (3.8 Å), the Te···Te separation (3.33 Å) was relatively short and in the characteristic range of significant intermolecular Te···Te interactions, which may result from a double donor−acceptor interaction. Quantum chemical calculations suggested a Te−Te bond energy of about −16.5 kcal/mol. The corresponding oxygen derivative could not be isolated in a pure form, but it may be formed by thermal decomposition of the new FLP adduct 1·ONMe 3 .

Reactions of a Ga/P‐Based Frustrated Lewis Pair with HX(X= F – I), HeterocumulenesR–NCY(Y= O, S) and Chalcogens–Adduct Formation and Surprising Stability towards Protolysis

“…Further typical parameters are the large 3 J PH coupling constants (>44 Hz) to the vinylic H atoms indicative of a four‐coordinate P atom and a cis ‐arrangement of P and H and the downfield shift of the t Bu resonances in the 1 H NMR spectra associated with four‐coordinate Ga atoms. The Se derivative 9b shows 77 Se satellites in the 31 P NMR spectrum and a 1 J PSe coupling constant of 459 Hz which may be compared to the respective values of other Lewis acid stabilized phosphorus chalcogenides ( 1 J PSe = 500–544 Hz), or free phosphorus selenides ( 1 J PSe = 700–793 Hz)…”

“…Compound 9a was also synthesized from 1 and propylene sulfide (see below). The Al analogue of 9a has been obtained previously in good yields from Mes 2 P–C(Al t Bu 2 )=C(H)–Ph and S or propylene sulfide …”

“…The reactions of Mes 2 P–C(Al t Bu 2 )=C(H)–Ph with the chalcogens S, Se, and Te or, in case of S, propylene sulfide, were previously shown to yield the corresponding adducts Mes 2 P(μ‐ Y )–C(Al t Bu 2 )=C(H)–Ph ( Y = S, Se, Te) in high yields . The heavier, less reactive elements Se and Te required elevated temperatures for complete conversions.…”

Reactions of an Aluminium/Phosphorus Frustrated Lewis Pair (FLP) with α,β‐Unsaturated Carbonyl Compounds: FLPs as Efficient Two‐Electron Reductants with the Formation of Enolates, a cis‐Enediolate, and an Allene

“…In most cases, the inherently high Lewis acidity of coordinatively unsaturated Al atoms does not require activation by electron‐withdrawing substituents, and simple alkyl groups are sufficient to facilitate fascinating FLP activity. These compounds have been applied for the coordination and activation of various substrates: carbonyl compounds, terminal alkynes, alkenes, boron halides, chalcogen atoms, hydrogen halides, transition‐metal atoms and so forth . They have found application in phase‐transfer catalysis with the solubilisation of alkali‐metal hydrides in toluene or the catalytic dehydrogenation of H 3 B←NHMe 2 .…”

A Structural and Spectroscopic Study of the First Uranyl Selenocyanate, [Et4N]3[UO2(NCSe)5]

“…Also present in the structure are close contacts between a coordinated selenium atom and the selenium of the non-coordinated [NCSe]´(3.427(1) Å) that are shorter than the van der Waals radii (3.64 Å) [19]. Chalcogen-chalcogen interactions have been studied both experimentally [21,22], and in the case of [NCS]´also for uranyl (S¨¨¨S = 3.536(2) Å) [15], and theoretically [23,24]. This may explain the difficulty in growing single crystals of 1 as these weak interactions may be important.…”