COORDINATION CHARACTERISTICS OF DIVALENT TETRAHEDRAL (TD AND D2D) TETRAHALOMETALATE ANIONS OF 3D ELEMENTS AND SOLID-STATE 18C6 REORIENTATIONS

The MX4(2-) compounds (M = 3d element, X = halogen) are good ligands for [A18C6]n+ cations (A = Rb, Tl, Ba). The regular MX4(2-) tetrahedra (T(d)) coordinate via the triangular faces (facial ligation), while the flattened MCl4(2-) tetrahedra (D2d) prefer edge ligation. The cryogenic structure of [(Tl18C6)4CuBr4][TlBr4]2 (1) confirms solid-state reorientational motion of coordinated 18C6 previously detected in some metal and metal-free host-guest crystals by variable-temperature solid-state H-1 and C-13 NMR (Chem. Abstr. 1989, 111, 56905b). The motions generating the reorientations are very sensitive to the detailed crystal environment; dependence on crystal water and nature of the 3d element is evident. Crystal data: [(Tl18C6)4CuBr4][TlBr4]2 (1) cryogenic (115 K), cubic, space group F23 with a = 20.674(3) angstrom, V = 8837(1) angstrom3, Z = 4, 700 reflections (I > 3sigma(I)), and R = 0.054; [(Tl18C6)4MnCl4]-[TlCl4]2 (2), cubic, space group F23 with a = 20.789(2) angstrom, V = 8985.2(9) angstrom3, Z = 4, 693 reflections (I > 1sigma(I)), and R = 0.036; (Ba18C6)CoCl4.2H2O (3), triclinic, space group P1BAR with a = 8.769(1) angstrom, b = 10.383(2) angstrom, c = 13.912(1) angstrom, alpha = 98.29(1)-degrees, beta = 89.77(1)-degrees, gamma = 113.64(1)-degrees, V = 1146.2(6) angstrom3, Z = 2, 6156 reflections (I > 3sigma(I)), and R = 0.033; Rb(15C5)2TlBr4 (4), orthorhombic, space group Cmcm, with a = 13.630(1) angstrom, b = 11.631(1) angstrom, c = 22.021(1) angstrom, V = 3491.0(7) angstrom3, Z = 4, 847 reflections (I > 1sigma(I)), and R = 0.054.