Synthesis, structure, and bonding of A5Cd2Tl11, A = Cs, Rb. Naked pentagonal antiprismatic columns centered by cadmium.
A new anionic thallium cluster chain 1 infinity[Cd2Tl11(5-)] has been discovered in the A-Cd-Tl systems for A = Cs, Rb. The compounds are synthesized by direct fusion of the elements at 700 degrees C and equilibration of the quenched product at 200 degrees C for 1 month. The thallides crystallize in the orthorhombic space group Amm2, Z = 2, a = 56107(7) and 55999(6) A, b = 18090(3) and 17603(3) A, c = 13203(3) and 12896(2) A for A = Cs and Rb, respectively, and contain chains of face-sharing pentagonal Tl10 antiprisms embedded in a matrix of alkali metal cations. Cadmium atoms occupy the center of the antiprisms and donate electrons to the anionic chain. Additional four-bonded Tl atoms on one side of the chain make the structure acentric. The compounds are diamagnetic (chi 296 = -08, -40 (x 10(-4) emu/mol, respectively) and metallic (10-20 mu omega cm at 275 K), and the indirect band gap energy of both compounds is close to zero according to extended Hückel calculations on the isolated chain.
Kaskel
S
S
Ames Laboratory-DOE, Iowa, USA.
Corbett
J D
JD