RHENIUM SELENIUM CHLORINE SOLID-PHASES - CLUSTER EXCISION AND CORE SUBSTITUTION-REACTIONS OF MOLECULAR-SPECIES

Removal of intact clusters from the ternary phases Re6Se4+qCl10-2q (q = 1-3) by the method of cluster excision has been investigated. The q = 1 phase Re6Se5Cl8 (Re6Sei5Cli3Cla4Cla-a2/2) has a one-dimensional (chainlike) structure, the q = 2 phase Re6Se6Cl6 (Re6Sei6Cli2Cla2Cla-a4/2) a two-dimensional (sheetlike) structure, and the q = 3 phase Re6Se7Cl4 (Re6Sei7CliCla-a6/2) a three-dimensional lattice. Treatment of Re6Se5Cl9 and Re6Se6Cl6 with excess R4NCl in hot DMF or acetonitrile results in solubilization of the solid-state clusters, which were isolated in the molecular forms (R4N) [Re6Se5Cl9] (R = Et, Pr (1), Bu (7)) and (R4N)2[Re6Se6Cl8] (R = Et (4), Pr (5)), respectively, in 78-85% yields. The structures of the clusters in these compounds were determined by X-ray analysis. Core Se/Cl atoms are disordered. Compound 1 crystallizes in the triclinic space group P1BAR with a = 8.894 (2) angstrom, b = 10.082 (2) angstrom, c = 18.540 (4) angstrom, alpha = 80.87 (1)-degrees, beta = 87.65 (2)-degree, gamma = 87.36 (2)-degrees, and Z = 2. The cluster [Re6Se5Cl9]-contains an Re6 octahedron which is face-capped to form a [Re6(mu3-Se)5(mu3-Cl)3]5+ core; each Re atom is bonded to a terminal chloride. Compound 5 crystallizes in the tetragonal space group P4(2)/mnm with a = 11.939 (3) angstrom, c = 16.806 (4) angstrom, and Z = 2. The cluster [Re6Se6Cl8]2- has the [Re6Se6Cl2]4+ core and an analogous structure; the clusters in 4 and 5 are isostructural. These results demonstrate excision of the clusters known to be present in the solid phases by Re-Cla-a bond rupture with chloride. Excision of clusters from Re6Se7Cl4 has not been achieved. Reactions resulting in substitution of core chloride atoms have been performed. The molecular phase Re6Se4Cl10 reacts with water in Pr4NCl/DMF at 60-degrees-C to give two isomeric clusters formulated as (Pr4N)2[alpha-Re6Se4O2Cl8] (2) and (Pr4N)2[beta-Re6Se4O2Cl8] (3) by X-ray structure determinations. Compound 2-2DMF crystallizes in the monoclinic space group P2(1)/n with a = 12.146 (3) angstrom, b = 12.158 (2) angstrom, c = 19.316 (4) angstrom, 104.59 (2)-degrees and Z = 2. Compound 3 is obtained in monoclinic space group C2/c with a = 22.610 (6) angstrom, b = 14.335 (4) angstrom, c = 17.399 (7) angstrom, beta = 126.45 (3)-degrees, and Z = 4. Both clusters contain the [Re6Se4O2Cl2]4+ core but differ in position of the oxygen atoms; in the alpha-isomer they are at opposite ends of a body diagonal of the core whereas in the beta-isomer they are trans on the same core face. Reaction of 1 or 7 with Li2Se in THF affords a material identical to the excision product 5 or (Bu4N)2[Re6Se6Cl8] (6), respectively. The structure of 6 was confirmed by an X-ray structure determination. These results demonstrate Cl/Se core substitution. Substitution reactions of [M6L8]z cores are summarized; halide/chalcogenide replacements should be capable of extension and lead to new cluster types.