BaP4Te2--a ternary telluride with P-Te bonds and a structural fragment of black phosphorus.

The new telluride BaP(4)Te(2) was synthesized in form of gleaming black needles by heating stochiometric mixtures of the elements to 475 degrees C for 100 h. The crystal structure was determined by single-crystal Xray methods. BaP(4)Te(2) crystallizes orthorhombically, space group Pnma with a=16.486(8), b=6.484(2), c=7.076(4) A, and Z=4. A main feature of the so far unknown crystal structure type are P(4)Te(2) chains that consist of condensed six-membered rings of phosphorus. These strands are equivalent to a structural fragment of black phosphorus, in which each of the lateral atoms is connected to a tellurium atom. The chains running along [0 1 0] are separated from each other by barium atoms, that is, linked through Ba-Te and Ba-P bonds. BaP(4)Te(2) is an electron precise compound according to the Zintl concept, and the formula can be split ionically as follows: BaP(4)Te(2) identical with Ba(2+)(P(0))(4)(Te(-))(2). The remarkable Te-P bonds have been analyzed by electronic structure calculations using the electron localization function (ELF) and the crystal orbital Hamiltonian population (COHP) methods.