Hybrid Inorganic-Organic Host-Guest Compounds: Open-Framework Cadmium Oxalates Incorporating Novel Extended Structures of Alkali Halides

Abstract

Four unusual inorganic-organic nanocomposites containing extended alkali halide structures, present as layers or as three-dimensional units, have been synthesized by a metathetic reaction carried out under hydrothermal conditions. These compounds, with cadmium oxalate host lattices and the alkali halide structures as guests, have the compositions [RbCl][Cd-6(C2O4)(6)]. 2H(2)O, I; 2[CsBr][Cd(C2O4)].H2O, II; 2[CsBr][Cd-2(C2O4)(Br)(2)]. 2H(2)O, III; and 3[RbCl][Cd-2(C2O4)(Cl-2)].H2O, IV. Crystal data for I, rhombohedral, space group = R-3 (no. 148), a = 9.3859(3), c = 23.9086(8) Angstrom; V = 1824.05(1) Angstrom (3), z = 18, M = 1359.51, rho (calcd) = 3.702 g cm(-3), mu (Mo K alpha) = 7.375 mm(-1), R-1 = 0.04, wR(2) = 0.0904 [537 observed reflections with I > 2 sigma (I)]; for II, orthorhombic, space group Pbcm (no. 57), a = 6.0854(6), b = 11.0793(11), c = 16.889(2) Angstrom; V = 1138.7(2) Angstrom (3), Z = 8, M = 644.06, rho (calcd) = 3.745 g cm(-3), mu (Mo K alpha) = 15.219 mm(-1), R-1 = 0.04, wR(2) = 0.08 [408 observed reflections with I > 2 sigma (I)]; for III, orthorhombic, space group = Cmcm (no.63), a = 23.6151(14), b = 10.2528(6), c = 7.8199(6) Angstrom; V = 1894.2(2) Angstrom (3), Z = 16, M = 970.33, rho (calcd) = 3.374 g cm(-3), mu (Mo K alpha) = 14.487 mm(-1), R-1 = 0.03, wR(2) = 0.0744 [651 observed reflections with I > 2 sigma (I)]; for IV, monoclinic, space group = P2(1)/c (no. 14), a = 8.0648(2)(3), b = 22.9026(4), c = 9.3967(3) Angstrom; V = 1681.10(7) Angstrom (3), Z = 4, M = 782.53, rho (calcd) = 3.076 g cm(-3), mu (Mo K alpha) = 11.961 mm(-1), R-1 = 0.04, wR(2) = 0.093 [2071 observed reflections with I > 2 sigma (I)]. Compounds I-IV possess many unusual structural features. While I has interpenetrating lattices of the three-dimensional cadmium oxalate and RbCl with an expanded lattice, giving rise to a super rock-salt cell, 11 possesses alternating cadmium oxalate and CsBr layers, the latter comprising six-membered CsBr rings. Compounds III and IV have isolated cadmium oxalate units (zero-dimensional)linked and stabilized by the alkali halides.