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Crystal structures of trans-[Ta_6Cl_(12)(OH)_4(H_2O)_2]×10H_2O and (NMe_4)_2[Ta_6Cl_(12)(OH)_6]×21H_2O

The compounds trans-[Ta_6Cl_(12)(OH)_4(H_2O)_2]×10H_2O (1), (NMe_4)_2[Ta_6Cl_(12)(OH)_6]×21H_2O (2) and Na_2[Ta_6Cl_(12)(OH)_6]×16H_2O (3) containing octahedral tantalum chloro clusters were isolated from alkaline methanol/water solutions of [Ta_6Cl_(12)]^(4+). Crystal structures were solved for 1 and 2. Crystal data: (1), monoclinic, space group P2_1/c (No. 14), a = 938.5(2) pm, b = 1220.3(2) pm, c = 1391.7(4) pm, beta = 103.87(2)°, V = 1547.5(6)x10^6 pm^3, Z = 2 ; (2), rhombohedral, space group R-3 (No. 148), a = 1201.4(2) pm, c = 3110.8(6) pm, V = 3888.5(12)x10^6 pm^3, Z = 3 ; (3), cubic F lattice, a = 1451(2) pm, V = 3055(13)x10^6 pm^3, Z = 4. The cluster in 1 contains the neutral, mixed-coordinated trans-[Ta_6Cl_(12)(OH)_4(H_2O)_2] cluster with Ta-OH and Ta-OH_2 distances of 210.4(5) pm and 214.5(5) pm respectively. One coordinated H_2O molecule from one cluster and a coordinated OH^- group from a neighbouring cluster form H_3O_2^- intercluster bridges with the O...H-O distance 253.7(7) pm. Twelve Ta-Cl (bridging) distances range from 244.1(2) to 245.2(2) pm. The structure of 2 is built of [Ta_6Cl_(12)(OH)_6]^(2-) anions, NMe_4^+ cations and water molecules, the latter linked to the anions by the hydrogen bonds.

Hexanuclear tantalum chloro cluster; tantalum cluster hydroxide; mixed coordinated clusters; intercluster bridges; crystal structures

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