Reactions of organolithium complexes with elemental selenium: insertion producing [PhCCSeLi·TMEDA·THF] 1 and cyclisation producing [{PhC}4Se] 2 (TMEDA=[Me2NCH2]2)

A mechanistic study of the activation of small molecules (H2 and C2H2) by group 14 analogues of selenophene

In this study, the reactivity influenced by group 14 elements (E = C, Si, Ge, Sn, and Pb), which are used as substituents in heterocyclic five-membered rings, was theoretically examined by using density functional theory (B3PW91/def2-SVP).

Isoselenocarbonyl complexes

The salt elimination reactions of [NEt₄][Mo(CSe)(CO)₂(Tp*)] ([NEt₄][2], Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) with a range of metal halide complexes (ClML_n) have been investigated as a possible route to isoselenocarbonyl complexes [Mo(CSeML_n)(CO)₂(Tp*)].

AI SeC2 H (AI =K, Rb, Cs): Crystalline Compounds with the Elusive - Se-C≡C-H Anion

By reaction of alkali metal acetylides, A^I C₂ H (A^I =K, Rb, Cs), with elemental selenium in liquid ammonia highly crystalline powders of A^I SeC₂ H were obtained. The structure analysis based on the resulting synchrotron powder diffraction data revealed that all compounds crystallize in an orthorhombic unit cell (Cmc2₁ , Z=4) exhibiting the elusive ^- SeC₂ H anion, which is unprecedented in a crystalline compound up to now. Elemental analysis and IR spectroscopic data confirm this finding. Upon heating, A^I SeC₂ H compounds release acetylene based on DSC/TGA experiments resulting in powders with the proposed composition A^I ₂ Se₂ (C₂ ). The resulting powders were indexed with small cubic unit cells, but a reasonable structural model could not be developed up to now. Upon exposure of A^I SeC₂ H compounds to water elemental selenium is formed again.

Synthesis and reactivity of selenium functionalised allylidynes and propargylidynes

The reactions of the trimethylsilylpropargylidyne [W([triple bond, length as m-dash]CC[triple bond, length as m-dash]CSiMe3)(CO)2(Tp*)] (1: Tp* = hydrotris(dimethylpyrazolyl)borate) towards selenium centred reagents when treated with tetrabutylammonium fluoride (TBAF) were explored in order to prepare alkynylselenolato propargylidynes, e.g., [W([triple bond, length as m-dash]CC[triple bond, length as m-dash]CSePh)(CO)2(Tp*)]. Treating 1 with TBAF and PhSeSePh resulted in E and Z isomers of the vinylcarbyne (allylidyne) complex [W{[triple bond, length as m-dash]CC(SePh)[double bond, length as m-dash]CHSePh}(CO)2(Tp*)] in addition to traces of the trisubstituted derivative [W{[triple bond, length as m-dash]CC(SePh)[double bond, length as m-dash]C(SePh)2}(CO)2(Tp*)]. Reactions with PhSeCl resulted in the isolation of bimetallic bis-substituted allylidyne complex [(Tp*)(CO)2W[triple bond, length as m-dash]CC(SePh)[double bond, length as m-dash]C(SePh)C[triple bond, length as m-dash]CC[triple bond, length as m-dash]W(CO)2(CO)2(Tp*)] as well as the desired selenolatopropargylidyne [W([triple bond, length as m-dash]CC[triple bond, length as m-dash]CSePh)(CO)2(Tp*)].

2,5-Digermaselenophenes: Germanium Analogues of Selenophenes

A stable crystalline 2,5-digermaselenophene was synthesized. In contrast to hitherto reported selenophenes, this digermaselenophene exhibits a trans-pyramidalized structure, which is due to its electronic properties. The practical utility of this 2,5-digermaselenophene is reflected in its ability to activate dihydrogen and acetylene at room temperature in the absence of a transition-metal complex, and this behavior can be rationalized on the basis of its physicochemical properties, which are characterized by considerable electron-donating and -accepting abilities.

Monodentate coordination of the normally chelating chiral diamine (R,R)-TMCDA

After isolating an unusual binuclear, but monosolvated NaHMDS complex [{(R,R)-TMCDA}·(NaHMDS)₂]_∞ which polymerises via intermolecular electrostatic NaMe_HMDS interactions, further (R,R)-TMCDA was added to produce the discrete binuclear amide [{κ²-(R,R)-TMCDA}·(NaHMDS)₂{κ¹-(R,R)-TMCDA}], whose salient feature is the unique monodentate coordination of one of the chiral diamine ligands.

Synthesis of novel 2,5-diarylselenophenes from selenation of 1,4-diarylbutane-1,4-diones or methanol/arylacetylenes

Reaction of 2,4-bis(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide [PhP(Se)(mu-Se)](2) (Woollins' reagent, WR) with one equivalent of 1,4-diarylbutane-1,4-diones 1a-g in refluxing toluene affords the corresponding 2,5-diarylselenophenes 2a-g in excellent yields (up to 99%). Alternatively, the 2,5-diarylselenophenes (2a and 2b) can be obtained in 70-80% yields from the reaction of arylacetylene with an equivalent of O-methyl Se-hydrogen phenylphosphonodiselenoate; the latter was derived from WR and methanol. The first X-ray structure of 2,5-diarylselenophenes is presented along with characterisation of their redox properties.