SYNTHESES OF (ME4N)2[(MU-EPH)6(MX)4] (M = CD, ZN, E = S, SE, X = CL, BR, I] - CRYSTAL AND MOLECULAR-STRUCTURES OF (ME4N)2[(MU-SPH)6(CDBR)4], (ME4N)2[(MU-SEPH)6(CDBR)4] AND CHARACTERIZATION OF [(MU-EPH)6(CDX)4]2- IN SOLUTION BY CD-113 AND SE-77 NMR

The direct, quantitative reaction of the adamantanoid anions [μ-EPh)6(MEPh)4]2- (M = Cd, Zn; E = S, Se) with X2 (X = Cl, Br, I) in acetone or MeCN or, for X = Cl, PhICl2 in MeCN, provides a simple route to the new complexes [M4(EPh)6X4]2- isolated as Me4N+ salts in high yield. The structurally representative salts (Me4N)2[Cd4(EPh)6Br4] (E = S, Se) have been fully characterized by single-crystal X-ray diffractometry techniques. Both crystallize in the cubic space group P213 with four formula units in the cell. The dimensions are a = 17.869 (2) Å for (Me4N)2[Cd4(SPh)6Br4] (1) and a = 18.062 (2) Å for (Me4N)2-[Cd4(SePh)6Br4] (2). The structures have been refined by full-matrix least-squares techniques on F to agreement factors R = 0.033 (1343 observations with Fo > 5σ(Fo)) for 1 and R = 0.033 (989 observations with Fo > 5σ(F0)) for 2. In each salt, both cations and anions lie on a crystallographic threefold axis. In the chiral [(μ-EPh)6(CdBr)4] anions in 1 and 2, the Cd4E6Br4 core consists of a Cd4 tetrahedron, regular within experimental error, inscribed in a slightly irregular octahedron defined by the bridging E atoms in an adamantanoid cage. Each Cd atom is tetrahedrally coordinated by one terminal Br and three bridging E atoms. The average Cd···Cd distance is 4.166 (3) for 1 and 4.251 (6) Å for 2, the Cd–Br distances are 2.559 (3) and 2.565 (2) Å for 1 and 2.568 (4) and 2.581 (2) Å for 2, the Cd–S distances are in the range 2.541 (3)—2.554 (3) Å for 1, and the Cd–Se distances are in the range 2.627 (2)–2.654 (2) Å for 2. The anions in 1 and 2 represent the first examples containing the M4(μ-EPh)6 core in which the axial/equatorial dispositions of the EPh groups in the tetracyclic structure are aaa, aee, aee, aee. The absolute structures of 1 and 2 have been determined by measurement of Bijvoet pairs. NMR (113Cd, 77Se) studies of [Cd4(EPh)6X4]2- show the persistence of fully terminally halogen substituted tetranuclear structures in solution. At reduced temperatures, exchange of both chalcogenates and halogens between clusters is slow on the NMR time scale. In addition, a slow-exchange 77Se NMR spectrum has been observed for [(μ-SePh)6(CdSePh)4]2-. © 1987, American Chemical Society. All rights reserved.