Ternary Transition Metal Acetylides AI2M0C2 (AI = K, Rb; M0 = Pd, Pt): Neutron Diffraction Studies and Electronic Properties

Cs2Cd(C2H)2(C2): A Crystalline Acetylide with Bridging C2 Units

Cs₂Cd(C₂H)₂(C₂) was synthesized by heating known Cs₂Cd(C₂H)₄ either in a dry argon atmosphere at 200 °C or under ammonothermal conditions (130 °C, ∼ 100 bar). The crystal structure of the resulting dark orange-brown microcrystalline material was solved and refined from synchrotron powder diffraction data (Cmcm, Z = 4). Cs₂Cd(C₂H)₂(C₂) is composed of Cd²⁺ cations tetrahedrally coordinated end-on by four acetylide groups. Two of them are terminating C₂H^- groups, whereas the other two positions are occupied by bridging C₂^2- anions. Thus, a polymeric _∞¹[Cd(C₂H)₂(C₂)_2/2^2-] chain-like anion results and these chains are separated by Cs⁺ cations. So obviously Cs₂Cd(C₂H)₂(C₂) is formed from Cs₂Cd(C₂H)₄ by a condensation reaction of two of its four C₂H^- groups under the release of one acetylene (C₂H₂) molecule. This reaction mechanism is supported by DSC/TGA measurements, and the crystal structure of Cs₂Cd(C₂H)₂(C₂) is further supported by IR spectroscopic investigations.

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.

The synthesis of ternary acetylides with tellurium: Li2TeC2 and Na2TeC2

Novel ternary acetylides Li₂TeC₂ and Na₂TeC₂ were synthesized via the robust direct reaction of tellurium powder and mono- or bialkali acetylides in liquid ammonia.

Alkali/coinage metals – organolithium, organocuprate chemistry

Part 1 of this chapter reviews coordination compounds of the alkali metals that contain a carbon-metal bond, looking firstly at organolithiums involving simple silanes. The use of aryl, alkynyl and N-donor ligands is also discussed. Compounds of the coinage metals - copper, silver and gold - are discussed in Part 2 of the review. Discussion is broken down by metal, with copper being considered first. Compounds containing, among others, alkene, amido and phosphido ligands are discussed, along with the significant amount of work on carbene complexes. This interest in carbene complexes is also noted within the silver and gold sections that follow, with a large number of new compounds being described. Polymeric chains and networks containing silver centres have attracted considerable interest and are described, along with the luminescent properties of a selection of novel gold species. This part of the review is completed by coverage of mixed-coinage metal structures, where the systems are found to display luminescent properties. Here again, the compounds discussed contain at least one carbon-metal bond.