Synthesis and structures of new niobium cluster compounds with pyridinium cations: (PyrH) 2[Nb 6Cl 18]·EtOH (Pyr: pyridine, Et: ethyl) and the cubic modification of (PyrH) 2[Nb 6Cl 18

Abstract

Slow crystallization of (PyrH) 2[Nb 6Cl 18] from hot ethanol solution affords triclinic (PyrH) 2[Nb 6Cl 18]·EtOH. Treatment of [Nb 6Cl 14(H 2O) 4]·4H 2O with pyridine in a methanol solution gives the second title compound, the cubic modification of (PyrH) 2[Nb 6Cl 18]. Both structures were determined by single crystal X-ray diffraction, (PyrH) 2[Nb 6Cl 18]·EtOH: P1¯, a=9.3475(3), b=9.3957(3), c=10.8600(3) Å, α=82.582(1)°, β=78.608(1)°, and γ=78.085(1)°, Z=1, R 1( F)/w R 2( F 2)=0.0254/0.0573, cub.-(PyrH) 2[Nb 6Cl 18]: Fd3¯m, a=19.935(2) Å, Z=8, R 1( F)/w R 2( F 2)=0.0557/0.1796. The cluster compounds contain isolated, molecular [Nb 6Cl i 12Cl a 6] 2− cluster anions with an octahedron of metal atoms edge bridged by chlorido ligands with additional ones on all the six exo positions. These cluster anions are separated by the pyridinium cations and ethanol solvent molecules, respectively. For the cubic modification of (PyrH) 2[Nb 6Cl 18], a structural comparison is given to the known rhombohedral modification using the group–subgroup relations as expressed by a Bärnighausen tree.