STRUCTURES OF MOLECULAR ADDUCTS OF INORGANIC SALTS .2. CA(REO4)(2)CENTER-DOT-UREA-CENTER-DOT-H2O

Ca(ReO4)(2)C . (NH2)(2)CO . H2O, M = 618.54, triclinic, a = 7.322(2) A ngstrom, b = 9.088(3) Angstrom, c = 9.175(1) Angstrom, alpha = 111.67( 1), beta = 91.26(1), gamma = 104.89(2)degrees, V = 543.6(5) Angstrom(3 ), space group P1 $($) over bar$$ (No. 2), Z = 2, D-x = 3.778 g . cm(- 3), mu(Mok(alpha)) = 23.05 cm(-1), R = 0.031 for 2104 reflections with I > 3 sigma(I). The structure consists of (2)(infinity)[MT(2)Urea] la yers which are composed of parallel chains of alternating double M-O-M (O = urea oxygen atom) and fourfold M-T-M (T = ReO4 group) bridges. W ithin the layer the chains are interlinked by double M-T-M bridges. Th e layers are held together by H-bonds only. The coordination polyhedro n of Ca is a bi(square capped) trigonal prism with Ca-O-ave = 2.451(12 ) Angstrom. The polyhedra are coupled into centrosymmetric dimers by s haring an edge of urea oxygen atoms.