SOME REACTIONS OF THE OCTAHALODIRHENATE(III) IONS .10. FURTHER STUDY OF THE TETRAKIS(PIVALATO)DIRHENIUM DIHALIDES

The previously known compounds Re2(O2CCMe3)4Cl2 and Re2(O2CCMe3)4Br2 have been further studied structurally and spectroscopically. The two compounds are isomorphous, crystallizing in the space group I4/m with Z = 2 and the following cell dimensions, where those for the bromide follow those for the chloride in each case: a = 11.469 (4), 11.601 (3) Å, c= 10.733 (1), 11.154 (3) Å, V= 1411.8 (2), 1501.1 (2) Å 3. The molecules have crystallographically imposed 4/m (C4h) symmetry and, neglecting the rotational orientations of the CMe3 groups, approximate very closely to Z)4h symmetry. The XReReX groups are perfectly linear and parallel to the crystal c axis. The most important molecular dimensions are as follows: for the chloride Re-Re = 2.236 (1) Å, Re-Cl = 2.477 (3) Å, Re-O = 2.025 (4) Å, Re-Re-0 = 89.82 (9)°; for the bromide Re-Re = 2.234 (1) Å, Re-Br = 2.603 (1) Å, Re-0 = 2.029 (5) Å, Re-Re-0 = 89.54 (10)°. The visible spectra are also reported and discussed in a preliminary way. © 1979, American Chemical Society. All rights reserved.