Solid state structures of AsCl 5 and SbCl 5

Abstract

Arsenic pentachloride has a trigonal bipyramidal structure in the solid state with As-Cl eq = 210.6,211.9 pm, As-Cl ax 220.7 pm, space group Pmmn, a = 706.2 (1); b = 760.3 (2), c = 623.3 (1) pm. Antimony pentachloride exists in two modifications: above - 54.1°C it is also trigonal bipyramidal with Sb-Cl eq = 227.0 and Sb-Cl ax = 233.3 pm, space group P6 3/mmc, a = 741.4 (1), c = 799.0(2)pm. Below -54.1°C it changes reversibly into a double chlorine bridged dimer resulting in an edge shared double octahedral structure, space group P2 1/c, a = 952.4 (1), b = 1189.9 (1), c = 1219.7 (1) pm, β = 108,27 (1): In presence of water the formation of AsCl 5 is hindered, two salts containing the octahedral anion AsCl 6- have been isolated, [(H 5O 2+) 5AsCl 6-(Cl -) 4], space group C2/c, a = 1416.9 (2), b = 1316.6 (3), c = 1215.3 (2) pm, β = 94.96 (1)°, and [(H 5O 2+)(AsCl 6-) ·AsOCl 3], space group P2 1/n, a = 771.6 (3), b = 904.5 (3), c = 2140.7(2)pm, β = 100.21(1). The AsOCl 3 moiety in this compound appears as a monomer, in contrast to pure AsOCl 3, which is a doubly oxygen bridged dimer in the solid state.