Structure of molecular adducts of inorganic salts. IV. Comparison of the Cd(ReO4)2 · 2 Urea and Cd(ReO4)2 · 2H2O structures 1

Abstract

Abstract Cadmium perrhenate diureate crystallizes in the monoclinic space group P21/c with a = 15.185(3) Å, b = 10.257(2) Å, c = 7.561(5) Å, β = 93.69(2)°, Z = 4 and dcalc = 3.658g · cm−3. The hydrated cadmium perrhenate is triclinic with space group P[unk], a = 7.828(1) Å, b = 8.631(1) Å, c = 13.863(1) Å, α = 73.34(1)°, β = 89.39(1)°, γ = 70.42(1)°, Z = 4 and dcalc = 5.119 g · cm−3. The two compounds are built up of topologically equal but differently oriented and interlinked chains of the type [unk][MT2]φ 2, M = Cd, T = ReO4, φ = Urea and H2O respectively. In Cd(ReO4)2 · 2 Urea they are parallel and linked by H-bonds only while in Cd(ReO4)2 · 2H2O the chains lie in alternating layers with crossed orientation. Both bond valence calculations and low-range Raman spectroscopic measurements and estimate pointed out to a stronger Cd–OUrea in comparison to Cd–OH2O bonding.