Reactions of Hexanuclear Niobium and Tantalum Halide Clusters with Mercury(II) Halides. I. Synthesis and structures of the semiconducting compounds [M 6 Br 12 (H 2 O) 6 ][HgBr 4 ] · 12H 2 O, MNb, Ta

A method for the preparation of new solvated clusters of the composition [M 6 Br 12 (H 2 O) 6 ][HgBr 2 X 2 ] · 12H 2 O (MNb, Ta; XCl, Br, I) is given. The cubic crystals of [Nb 6 Br 12 (H 2 O) 6 ][HgBr 4 ] · 12H 2 O 1 and [Ta 6 Br 12 (H 2 O) 6 ][HgBr 4 ] · 12H 2 O 2 were characterized by the X‐ray structure analysis: 1 : cubic, space group Fd 3 m, a = 21.0072(6) Å, Z = 8, R = 0.051 (R w = 0.066); 2 : cubic, space group Fd 3 m, a = 20.9698(1) Å, Z = 8, R = 0.038 (R w = 0.050). 1 and 2 contain octahedral cluster cation [M 6 Br 12 (H 2 O) 6 ] 2+ and tetrahedrally arranged [HgBr 4 ] 2− anion. The MM bond distances are 2.949(1) Å for 1 and 2.9000(8) Å for 2 . The HgBr bond distances in [HgBr 4 ] 2− anion are 2.614(2) Å in 1 and 2.622(2) Å in 2 . The crystal packing patterns of the isostructural clusters 1 and 2 involve the three‐dimensional hydrogen bond network; the crystalline water molecules act as donors of hydrogen to the bromine atoms of the cluster and [HgBr 4 ] 2− units, whereas the coordinated water molecules form hydrogen bonds to the crystalline water molecules. [Nb 6 Br 12 (H 2 O) 6 ][HgBr 4 ] · 12H 2 O is diamagnetic and semiconducting with the activation energy, E a = 0.20 eV.