Synthesis and properties of tetracyanamidosilicates ARE[Si(CN2)4].

Tetracyanamidosilicates of the type ARE[Si(CN(2))(4)] with A = K, Rb, and Cs and RE = Y and La-Lu have been prepared by a solid-state metathesis reaction. The potassium compounds with RE = La-Gd crystallize orthorhombically in the space group P2(1)2(1)2. Rubidium as well as cesium compounds crystallize tetragonally in the space group I4. The luminescent properties of ARE[Si(CN(2))(4)]:Ln compounds with RE = Y, La, and Gd doped with 5 mol % Ln = Ce, Eu, or Tb were investigated. Temperature-dependent magnetic susceptibilities were measured for KGd[Si(CN(2))(4)]. The value of the magnetic moment is 7.3 mu(B)/Gd(3+) ion, which is in line with the expected value for the [Xe]4f(7) configuration of Gd(3+).

Crystal structures, phase-transition, and photoluminescence of rare earth carbodiimides.

Rare earth carbodiimides with the general formula RE 2(CN 2) 3 crystallize with two modifications. A monoclinic( C2/m) modification is obtained for RE = Y, Ce-Tm and a rhombohedral ( R3 c) modification for RE = Tm-Lu. The space group R3 c is confirmed by single-crystal structure determination on Lu 2(CN 2) 3 and indexed powder patterns of RE = Tm, Yb and Lu. The use of diverse chemical syntheses conditions for Tm 2(CN 2) 3 revealed the dimorphic character of this compound. In addition, pressure experiments on Tm 2(CN 2) 3 have induced a phase-transition from rhombohedral to monoclinic. This transformation comprises an increase of the coordination number of Tm from 6 to 7, and a unit-cell volume reduction in the order of 20 %. The photoluminescence behavior of lanthanide doped Gd 2(CN 2) 3:Ln samples is presented with different activators (Ln = Ce, Tb) revealing a broad band emission of Gd 2(CN 2) 3:Ce, quite similar to that of the well-known YAG:Ce.

The synthesis of phosphorus heterocycles from tetra-tert-butyltetraphosphacubane.

Tetra-tert-butyltetraphosphacubane, P(4)C(4)(t)Bu(4), reacts with water in the presence of 'GaI' to yield two products, namely 4,6,7,8-tetra-tert-butyl-1,2,3-triphospha-5-phosphoniatetracyclo[3.2.1.0(2,4).0(3,8)]oct-6-ene tetraiodogallate(III), (C(20)H(37)P(4))[GaI(4)], and triiodo(3,5,7,8-tetra-tert-butyl-1,2,4lambda(5),6-tetraphosphatetracyclo[4.1.1.0(2,5).0(7,8)]octan-4-one)gallium(III), [GaI(3)(C(20)H(38)OP(4))], both of which have been structurally characterized. The X-ray crystal structure determination of the former compound shows it to be an ion-separated salt, while the latter compound is a neutral phosphinite complex of GaI(3).