Lithium selenide

The reaction of tetrachlorodisilane with chalcogenation reagents is one of the synthetic methods to bis-nor-adamantane or double-decker type compounds. When a solution of di-terf-butyltetrachlorodisilane 66 in THF is refluxed together with one equivalent of lithium sulfide or stirred with lithium selenide at room temperature, the tetra(ferf-butylsilicon)pentachalcogenides 67 and 68, respectively, are formed (Scheme 18)6. Each pentachalcogenide exhibits one resonance of a ferf-butyl group in the H and 13C NMR spectra. Most likely, the bis-nor-adamantane derivatives 69 and 70 are initially formed. Insertion of a sulfur or selenium atom into one of the two strained Si—Si bonds would then lead to the observed products. 

Selenanes containing electron-withdrawing groups on the 2- and 6-positions 142 were prepared by treatment of the corresponding dihalo compounds with sodium and lithium selenides (Equation 54) <1999J(P1)1155>. Preparation of selenanes such as 142 proved to be a key step in the preparation of dihydroselenines, 477-selenines, and selenaben-zenes (see Equations 47 and 39 Scheme 2). 

By writing Li2Se and Li2Te for lithium selenide and lithium telluride, we do not wish to claim that the exact nature of these molecular formulae is known. 

Selenides.—The chemistry, and particularly the preparative aspects, of the chalcogenides has been reviewed.321 The heat of the reaction between F2 and Li2Se has been used322 to determine the heat of formation of lithium selenide. Some difficulty was experienced in this study in the preparation of the pure selenide, the method used being the direct reaction of liquid lithium with selenium vapour. It was concluded that the product contained some hydrated lithium hydroxide which had been formed whilst handling the selenide in a dry-box with a water and oxygen content of less than 5 p.p.m. by volume. 

Silastannathianes containing the unit SiSSn can be prepared from the reaction of a mixture of tin halide and silicon halide with hydrogen sulfide in the presence of an amine, and the corresponding selenium and tellurium compounds from a similar reaction using lithium selenide or lithium telluride.14... 

Only anhydrous lithium selenides have been considered. 

Diselenane (31) was first obtained in very low yield by the reaction of lithium selenide and bis(2-chlorodiethyl)selenide (30) in acetone (Equation (5)) <51JA1105>. A better approach is to heat a mixture of aluminum selenide and 1,2-dibromoethane at 80-140°C over some hours. Even using this method, the yield is only 10% <56JA5825>. 

Dialkyl selemdes dialkyi diselenides. Reaction of selenium with 2.1 equiv. of this hydride in THF gives a suspension of milky white lithium selenide. On addition of alkyl halides dialkyl selenides are formed in 60-95% yield (equation I). 

Lithium selenide reacts with o-chloroacetophenone in aprotic medium to give unexpectedly a significant amount (25%) of selenoindoxyl <88TL6ll9>. Reaction of HjSe with ketoepoxide (61) gives 12% of the selenolane derivative besides a tetrahydroselenopyran derivative (Equation (17)) <91ZOR942>. 

Synthesis of Bis(trimethylsilyl) Selenide. In the initial studies, bis(trimethylsilyl) selenide was synthesized by the following two methods silylation of sodium selenide (or lithium selenide ) with chlorotrimethylsilane (eq 1) or reaction of bromobenzene, magnesium, and selenium with chlorotrimethylsilane (eq 2). ... 

However, the former method requires the troublesome manipulation involved in preparing sodium selenide (or lithium selenide) in liquid ammonia and conducting the silylation in benzene (or diethyl ether). The latter method is inefficient and results in a low yield of the desired disilyl selenide. Thus a one-pot, high-yield procedure based on the lithium triethylborohydride reduction of elemental selenium has been developed, as depicted in eq 3. In this method, both preparation of Li2Se and silylation with MesSiCl are performed in THE Technically important is the use of selenium shot if selenium powder is utilized, the yield of Li2Se decreases sharply. Moreover, addition of small amount of boron trifluoride etherate (1.6 mol %) accelerates the silylation of Li2Se. ... 

The striking example is the reactivity of lithium with IE-VI layered compounds such as the decomposition of Li intercalated InSe with the formation of lithium selenide, Li2Se, observed by Raman spectroscopy on specimens prepared by various intercalation methods. The insertion of Li into M0S2 appears more stable with the occurrence of a superlattice formation at x(Li) 0.25 but a structural transformation from 2H-M0S2 (P-phase) to IT-M0S2 (a-phase) occurs for x l. This process is irreversible but the intercalation-deintercalation reaction is possible with the IT-M0S2, which could act as a positive electrode in rechargeable lithium batteries after formation of the cells. 

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