Monosulfoniumsalze und neue stabile Ylid-Salze aus 2-substituierten 1,3-dithianen

Trialkyloxonium-tetrafluoroborate reacts with 2-substituted 1,3-dithianes to yield sterically uniform monosulfonium salts. Bis-sulfonium salts obtained likewise lead after deprotonation to new stable ylid salts.     

Über neue Verbindungen in den Systemen EuF2–EuF3 und SrF2–EuF3

New compounds in the Systems EuF₂–EuF₃ and SrF₂–EuF₃ Four new compounds were found in the system EuF₂–EuF₃: Eu₃F₇, Eu₁₄F₃₃,Eu₂₇F₆₄ and Eu₁₃F_32-δ. These anion-excess fluorite-superstructure phase are member of the homologous series Eu_mF_2m+5 with m = 15, 14 und 13. Eu₂₇F₆₄is a combination of the phase with m = 13 and m = 14. The analogous isotypic compounds exist also in the structurally related system SrF₂–EuF₃:Sr₂EuF₇,Sr₉Eu₅F₃₃, and Sr 17 Eu₁₀F 64 , and Sr_7+δEu_6-δF_32-δ.     

Eine neue Modifikation von Lanthanmonosilicid – lT-LaSi

A New Modification of Lanthanum Monosilicide – lT-LaSi La metal and silicon react at 950 °C in the presence of LaBr₃ to form LaSi with the hitherto unknown low temperature modification (lT-LaSi). lT-LaSi crystallizes in Cmcm with a = 456.21(2), b = 1348.03(5), c = 662.59(6) pm. The Si atoms are connected to form cis-trans-cis-trans chains with alternating distances of d_Si–Si = 248 and 260 pm. They are coordinated in a trigonal prismatic fashion by the La atoms. lT-LaSi shows metallic conductivity.     

RbGa3S5 und CsGa3S5 – Zwei neue Strukturtypen

RbGa₃S₅ and CsGa₃S₅ – Two New Structure Types The title compounds RbGa₃S₅ and CsGa₃S₅ were synthesized by a solid state reaction starting from GaS, S and MN₃ (M = Rb, Cs) as alkaline metal source. They crystallize in the space group P2₁/c with comparable lattice parameters but with completely different structures (RbGa₃S₅: a = 7,1530(6), b = 12,715(1), c = 10,1282(9) Å, β = 102,43(1)°, Z = 4; CsGa₃S₅: a = 10,6717(8), b = 12,763(1), c = 6,9265(6) Å, β = 91,168(9)°, Z = 4). In RbGa₃S₅ Rb together with S shows the topology of a hexagonal close packing in which Ga occupies 3/12 of the tetrahedral holes. The GaS₄ tetrahedra are connected by common corners and edges forming a 3D‐network. The structure of CsGa₃S₅ is characterized by corrugated layers of edge‐ and corner‐sharing GaS₄‐tetrahedra. Both compounds represent so far unknown structure types and thus two further structural alternatives for compounds with the composition MM₃′Ch₅.