¹⁵N and ⁷⁷Se Nuclear Magnetic Resonance Study of Selenium Diimides and Aminoselenanes

Abstract

Selenium Diimides, Aminoselenanes, l5N N M R , 77Se N M R , Coupling C onstants / ( 77Se15N) Selenium diimides R(NSeN)R [R = 'Bu (la ), 'Oct (1 b)], the eight-membered heterocycle 'BuN(SeSeSe)2N'Bu (2) and the aminoselenanes of the type [R(Cl3Si)N]2Se (4a,b) and [(Me3Si)2N]2Se (5) were studied by multinuclear N M R with emphasis on l5N N M R for detec tion of coupling constants J(77Se15N). The selenium diimides possess the largest values of '/ ( 77Sel5N) observed so far ( la : 158.4 and 163.5 Hz; lb : 158.6 and 162.8 Hz). Com pound lb was found to be much more stable than 1 a, the heterocycle 2 being the m ajor decomposition product of la . The selenium diimides ( la ,b ) react readily with hexachlorodisilane to give the bis[alkyl(trichlorosilyl)amino]selenanes 4a,b. The solid state 13C, 15N, 29Si and 77Se CP/M AS N M R spectra of bis[bis(trimethylsilyl)amino]selenane (5) gave results in accord with the known crystal structure, and there is agreement with the solution state N M R data.

Solid-state selenium-77 NMR

“…10h for structure), gives a 77 Se CP MAS NMR peak at 41 ppm at room temperature, which differs from the value found at À40°C in solution, 4.3 ppm, and the difference has been interpreted as evidence for structural differences [200]. The NASeAN moiety produces a broad peak at 1113 ppm in the 77 [201]. The eight-membered ring system 1,5-Se 2 S 2 N 4 possesses an alternating nitrogen-chalcogen pattern and the two 77 Se chemical shifts obtained, 1409 and 1455 ppm, are two of the most deshielded selenium environments found by solid-state 77 Se NMR [202].…”

Experimental and Theoretical Investigations of Structural Trends for Selenium(IV) Imides and Oxides: X-ray Structure of Se3(NAd)2

“…56 This is consistent with the experimental observations that 1a and 1b are monomeric species. 8,11 It has recently been shown that the difference in reaction energies for sulfur and selenium diimides can be ascribed to the lower -bond energies of Se=N bonds which makes the coupling of the two fragments energetically more preferable. 10 Figure 3 shows that the cyclodimerization and cycloaddition energies are rather independent of the identity of the R group (H, Me and t Bu derivatives).…”

“…8 Monomeric structures are also found exclusively for sulfur(IV) diimides. 1 By contrast, the corresponding tellurium(IV) imide, t BuNTe(-N t Bu)2TeN t Bu, is dimeric in solution and in the solid state.…”

“…10 In a preliminary communication we showed by X-ray crystallography that Se(NAd)2 (1b, Ad = 1-adamantyl) is a syn,anti-monomer in the solid state, 11 in agreement with the conclusions of solution NMR studies of 1a. 8 Interestingly, the hybrid imido-oxo system (seleninyl amine) OSe(-N t Bu)2SeO (2a) first reported by Herberhold in 1986, 12 forms a dimer with the oxo ligands in a cis configuration in the solid state. 11 The third member of this isoelectronic series, (SeO2)∞ (3), has a polymeric chain structure.…”

4. Selenium– and tellurium–nitrogen reagents

“…However, the generation of selenium-rich systems must involve elemental selenium, which is formed during the thermal decomposition as evinced by the detection of t BuN=N t Bu as a byproduct[79]. A more versatile route to the generation of cyclic selenium imides is provided by cyclocondensation reactions of SeCl2 with t BuNH2, since the stoichiometry can be controlled () diimides readily undergo insertion reactions into the Si-Si bond of hexachlorodisilane (eq 14)[80]. Insertion into the C-B bond of triethylborane occurs at low temperatures, but the initially formed cyclic product t BuN(µ-SeEt)(µ-BEt2)N t Bu decomposes at -50 o C[81].…”