Synthesis of the first 2H-selenete complexes, decomplexation and dimerization to dihydro-1,2-diselenine

Abstract

Pentacarbonyltungsten-coordinated selenobenzaldehydes, (CO)5W[Se=C(C6H4R-p)Hl (R = OMe, H, CF3), react with BufS-C=C-SBut by addition of the C-C t o the Se=C bond to give 2H-selenete complexes; treatment of the selenete complex (R=H) with NEt4Br affords the uncoordinated 2H-selenete and a 3,4-dihydro-1,2-diselenine.

Metal-Assisted Cycloaddition Reactions in Organotransition Metal Chemistry

“…Fischer et al have investigated the reactions of chromium and tungsten pentacarbonyl complexes of thio, seleno, and telluroaldehydes and ketones 96 [188][189][190] with yneamines (eq 27) and other donor-substituted alkynes (OR, SR, SeR). [191][192][193][194][195][196][197][198] The cycloaddition (∆H q values ca. 30 kJ/mol; ∆G q values around -150 J/(mol K) is regioselective (R 2…”

“…Reactions, as in eq 24 or 26, or the reaction of 35 to 36 in Scheme , where initially formed [2+2] cycloadducts consequently undergo a retroaddition by electrocyclic ring opening are not uncommon. Fischer et al have investigated the reactions of chromium and tungsten pentacarbonyl complexes of thio, seleno, and telluroaldehydes and ketones 96 − with yneamines (eq 27) and other donor-substituted alkynes (OR, SR, SeR). − The cycloaddition (Δ H ⧧ values ca. 30 kJ/mol; Δ G ⧧ values around −150 J/(mol K) is regioselective (R 2 = Me) and the ring opening is stereospecific (R 1 = H).…”

“…156,163,166 In the reaction of 83 with carbodiimide, the supposed initial [2+2] cycloadduct 85 undergoes a cycloreversion to the isolated isocyanide complex 86, whereas the chromium analogue of 85 160 [188][189][190] with yneamines (eq 27) and other donor-substituted alkynes (OR, SR, SeR). [191][192][193][194][195][196][197][198] 208,209 resulting from a [2+2] cycloaddition/cycloreversion sequence in the reaction of 100 (M ) Cr, W; R ) Et, Ph, t-Bu) with ethyl diethoxyacrylate, undergoes an interesting cyclization reaction to give the pyranylidene complex 109 (eq 29), from which the corresponding 6-ethoxy-2H-pyrone, formally the result of a [2+2+1] cyclization reaction, could be quantitatively released by oxidation with DMSO at room temperature. The cyclization of 108 to 109 involves the formal transfer from the diethoxymethylene group of one carbonyl group (to the metal) and one proton (to C(3) of the pyranylidene ring).…”

Selenothioic AcidS-Esters: Synthesis, Characterization, and Trend for Stability

“…Since then, the only examples of such esters have been two cyclic compounds with a selenothiocarboxyl group . Transition metal complexes of selenothioic acid S -esters, which are generally more stable than uncomplexed selenocarbonyl compounds, were not prepared until recently .…”