SYNTHESIS, STRUCTURE, AND REACTIVITY OF POLYMETALLIC SODIUM AND LANTHANUM 4-METHYLPHENOXIDE COMPLEXES

LaCl3 reacts with 4.5 equiv of sodium 4-methylphenoxide, 1, in THF to form La2Na3(mu4-OR)3(mu-OR)6(THF)5, 2, in 80% yield (R = C6H4Me-4). Compound 2 crystallizes from toluene in the orthorhombic space group Pcca with a = 18.159(6) angstrom, b = 18.474(17) angstrom, c = 25.145(18) angstrom, V = 8435(9) angstrom3, and D(calcd) = 1.32 g cm-3 for Z = 8. The five metal atoms in this complex define a trigonal bipyramid with lanthanum in the axial positions and sodium in the equatorial positions. Bridging aryloxide ligands are located at each of the nine edges of the trigonal bipyramid, and each metal is ligated by a terminal THF. When 2 is crystallized from THF/benzene/dioxane, a dioxane-solvated complex is formed in 88% yield: {[La2Na3 (mu4-OR)3(mu-OR)6](mu-dioxane) 2(dioxane)3](dioxane)}n, 3. Compound 3 crystallizes in the monoclinic space group P2(1)/c with a = 18.854(3) angstrom, b = 16.624(2) angstrom, c = 29.561(5) angstrom, beta = 108.36(1)-degrees, V = 8793(2) angstrom3, and D(calcd) = 1.39 g cm-3 for Z = 4. Least-squares refinement on the basis of 8127 observed reflections led to a final RF= 4.9%. The connectivity of the metals and aryloxide ligands in 2 is retained in 3. However, dioxane molecules replace the THF in 2 and link the trigonal bipyramids together through Na-(mu-dioxane)-La bridges. Crystallization of 2 from dimethoxyethane (DME) generates the salt [Na(DME)3]-[La2Na2(mu3-OR)3(mu-OR)4(OR) 2(THF) 2(DME)2](DME),4,in 90% yield. Compound 4 crystallizes in the monoclinic space group P2(1) with a = 13.604(3) angstrom, b = 15.463(4) angstrom, c = 48.572(12) angstrom, beta = 92.29(2)-degrees, V = 10209(4) angstrom3, and D(calcd) = 1.38 g CM-3 for Z = 2. The structure of 4 appears to derive from 2 by removal of one sodium atom which becomes solvated with DME and exists in the crystal as the Na(DME)3+ countercation. Compounds 3 and 4 are quantitatively converted back into 2 in THF. Complex 2 reacts with Me4NCl to generate [Me4}{La2Na2(mu4-OR)(mu3-OR)2(mu-OR)4(OR)2(THF)5](THF), 5, in quantitative yield. Complex 5 crystallizes from THF in the triclinic space group P1BAR with a = 14.726(3) angstrom, b = 16.274(3) angstrom, c = 20.121(3) angstrom, alpha = 99.98(1)-degrees, beta = 90.98(1)-degrees, gamma = 94.77(1)-degrees, V = 4730(l) angstrom3, and D(calcd) = 1.31 g CM-3 for Z = 2. Least-squares refinement on the basis of 15 205 observed reflections led to a final RF = 3.6%. The structure of 5 is similar to that of 4 with the noncoordinating NMe4+ cation in place of the solvated sodium countercation. When a THF solution of 2 is infused with hexanes, crystals of 1 form in the orthorhombic space group Pccn with a = 21.941(6) angstrom, b = 10.744(6) angstrom, c = 5.626(2) angstrom, V = 1326.4(9) angstrom3, and D(calcd) = 1.30 g CM-3 for Z = 8. Least-squares refinement on the basis of 761 observed reflections led to a final RF= 7.9%. The crystal structure of 1 can be described as [Na(mu4-eta1:eta1:eta1:eta6-OR)]n. It can be viewed as a stacked array of interpenetrating Na4 and O4 tetrahedra offset such that a Na4O4 cube is not present. Each 4-methylphenoxide ligand bridges three sodium atoms within a Na4 tetrahedron with its oxygen donor atom and interacts with a sodium atom of an adjacent Na4 tetrahedron via an eta6-arene-Na interaction. When 5 was crystallized from DME, crystals of [Na(DME)]4(mu3-OR)4, 6, were recovered. Complex 6 crystallizes in the tetragonal space group P42(1)cBAR with a = 14.362(1) angstrom, c = 12.254(l) angstrom, V = 2527.7(4) angstrom3, and D(calcd) = 1.16 g cm-3 for Z = 2. Least-squares refinement on the basis of 934 observed reflections led to a final R(F) = 5.4%. The structure of 6 consists of interpenetrating Na4 and O4 tetrahedra arranged to generate a cube.