Cocrystallized mixtures and multiple geometries: Syntheses, structures, and NMR spectroscopy of the Re-6 clusters [NMe(4)](4)[Re-6(Te8-nSen)(CN)(6)] (n=0-8)

The mixed tellurium/selenium Re-6 clusters [NMe(4)](4)[Res(Te8-nSen)(CN)(6)] (n = 0-8) have been prepared from the reactions of Re6Te15 with the appropriate stoichiometry of NaCN and Se at 600 degrees C, followed by cation exchange with NMe(4)Br. A typical anion comprises an Re-6 octahedron with its eight faces capped by mu(3)-chalcogen atoms to form a pseudocube, and each Re atom has a terminal cyanide ligand. These anions have essentially idealized cubic symmetry. In the [Re6Te8(CN)(6)](4-) anion, Re-Re bond distances range from 2.673(1) to 2.690(1) Angstrom and Re-(mu(3)-Te) distances range from 2.683(1) to 2.705(1) Angstrom. In the [Re6Te8(CN)(6)](4-) anion the Re-Re and Re-(mu(3)-Se) distances range from 2.622(2) to 2.638(2) Angstrom and 2.520(3) to 2.550(3) Angstrom respectively. The ''[Re6Te4.34Se3.66(CN)(6)](4-n) anion, with disordered Se/Te positions, displays intermediate bond distances with Re-Re distances ranging from 2.653(1) to 2.665(1) Angstrom and Re-(mu(3)-Q) (Q = Se, Te) distances ranging from 2.581(1) to 2.673(1) Angstrom. Whereas single-crystal X-ray diffraction results provide the barest indication of the complicated nature of the mixed Te/Se crystalline products, NMR spectroscopy indicates that they comprise cations and mixtures of geometric isomers of [Re-6(Te8-nSen)(CN)(6)](4-) anions(Te-125 NMR (delta, ppm): [NMe(4)](4)[Re6Te8(CN)(6)], -1112; [NMe(4)](4)[Re6Te7Se(CN)(6)], greater than or equal to 10 peaks, -643 to -1231; [NMe(4)](4)[Re6Te4Se4(CN)(6)], greater than or equal to 18 peaks, -705 to -1234; [NMe(4)](4)[Re6TeSe7(CN)(6)], greater than or equal to 12 peaks, -648 to -1114. Se-77 NMR (delta, ppm): [NMe(4)](4)[Re6TeSe7(CN)(6)], greater than or equal to 8 peaks, 928 to 966; [NMe(4)](4)[Re-6-Se-8(CN)(6)] . 3(1/3)H(2)O, 933).