Reduced Zirconium Halide Clusters in Aqueous Solution

Reduced hexazirconium halide cluster compounds have good solubility and stability in strongly acidic and/or
halide-rich aqueous solutions. Cyclic voltammetric (CV) measurements in aqueous media established that
[(Zr6BCl12)(H2O)6]2+/+ and [(Zr6BBr12)(H2O)6]2+/+ exhibited positive half-wave potentials (E1/2 = 0.059V and
0.160 V, respectively) vs the SHE, indicating that these clusters are only modestly reducing. Several new crystalline
cluster compounds have been isolated from cold 12 M HCl solutions; the structures of each contain extended
hydrogen-bonding water networks. Crystallographic data for these compounds are reported as follows:  [Rb0.44(H3O)4.56][(Zr6BCl12)Cl6]·19.44H2O (3), cubic, Im3̄m, a = 13.8962(3) Å, Z = 2; (H3O)5[(Zr6BeCl12)Cl6]·19H2O
(4), cubic, Im3̄m, a = 13.8956(4) Å, Z = 2; (H3O)5[(Zr6MnCl12)Cl6]·19H2O (5), cubic, Im3̄m, a = 14.029(3) Å,
Z = 2; (H3O)4[(Zr6BCl12)Cl6]·12.97H2O (6), tetragonal, P42/mnm, a = 11.5373(2) Å, c = 15.7169(4) Å, Z = 2;
(H3O)4[(Zr6BCl12)Br6]·13.13H2O (7), tetragonal, P42/mnm, a = 11.7288(6) Å, c = 15.931(1) Å, Z = 2.