MIXED-VALENCE COINAGE METAL-CLUSTERS WITH 1,1-THIOPERTHIO LIGANDS - SYNTHESES AND MOLECULAR-STRUCTURES OF THE [CU4L3]2-, [CU5L4]-, AND [AUCU4L4]- ANIONS (L = 1,1-DICARBO-TERT-BUTOXYETHYLENE-2,2-THIOPERTHIOLATE) - A GEOMETRICALLY-LOCKED, CHARGE-SEPARATED VALENCE STATE IN THE [CU5L4]- ANION

Sulfur addition to the coordinated dithiolene ligands in the known [Cu8((t)BuDED)6]4- cluster results in the formation of the {[Cu4(StBuDED)3]n}m-''sulfur-rich'' clusters. The molecularity of the seclusters depends on the nature of the counterions. With Bu4N+ as counterions, n = 2 and m = 4 (I), while with K+ as one of the counterions, n = 1 and m = 2 (II). The oxidation of either I or II with Cu(II) ions or with HAuCl4.3H2O affords the mixed-valence [Cu5(StBuDED)4]-(III) and the mixed-valence, mixed-coinage metal [Cu4Au(StBuDED)4]-(IV) clusters. The crystal and molecular structures of K(Ph4P)[Cu4(StBrDED)3].[(CH3)2C=O]3, (BzPh3P)[Cu5(StBuDED)4, and (Bu4N)2[Cu4A-Au(StBuDED)4].CuCl2.(CH2Cl2)0.5 have been determined. The compounds that contain II, III, and IV crystallize in the space groups R3m, P2(1)/n, and C2/c, respectively. The cell dimensions for II are a = 12.846(2) angstrom, alpha = beta = gamma = 83.92(1)degrees, and Z = 1, for III, a = 17.042(4) angstrom, b = 31.133(10) angstrom, c = 18.326(5) angstrom, beta = 97.03(2)degrees, and Z = 4, and for IV, a = 39.172(6) angstrom, b = 9.8553(9) angstrom, c = 30.745(4) angstrom, beta = 108.69(1)degrees, and Z = 4. Crystallographic data for the three structures were obtained on an automatic diffractometer employing Mo Kalpha radiation for II and III and Cu K(alpha) for IV. The refinement of the structures by full-matrix least-squares methods was based on 2507 unique reflections (2theta(max) = 40-degrees, I > 3sigma(I)) for II, on 4215 unique reflections (2theta(max) = 40-degrees, I> 3sigma(I)) for III, and on 4172 unique reflections (20. = 103-degrees, 1 > 3sigma(I)) for IV. Refinements on 206 parameters for 11, 551 parameters for III, and 477 parameters for IV, with all atoms present in the asymmetric units, have converged to R values of 0.049, 0.109, and O.085, respectively. The structure of II shows a tetrahedral Cu4 core with three StBuDED ligands in a symmetric fashion roughly bisecting three of the Cu4 tetrahedron faces. The arrangement of the ligands results in a unique Cu(I) atom that is located on a 3-fold axis of symmetry with the three other Cu atoms situated in a plane perpendicular to the 3-fold axis. The S-S ''arms'' of the sulfur-rich ligands are used to bridge the Cu atoms in this plane. The mean Cu-Cu distance of II is 2.729 angstrom, and the Cu-S distances range from 2.211(3) angstrom (involving the S atoms bridging the Cu atoms in the plane perpendicular to the 3-fold axis) to 2.268(3) angstrom (involving the S atoms bridging the unique axial copper to the basal copper atoms). The potassium cation in II is located on the 3-fold axis of symmetry and is coordinated to three carbonyl groups, one from each ligand, and to the three acetone molecules of solvation. The structures of III and IV consist of rectangular pyramidal Cu5 and Cu4Au cores. Each of the square pyramidal faces are bisected by the StBuDED ligands. The persulfido S-S arm of each ligand binds to the unique axial atoms (Cu(III) in III and Au(III) in IV) and bridges these atoms to the basal Cu(I) atoms. The other sulfur donor of each ligand bridges the basal Cu(I) atoms to give an octagonal Cu(I)4S4 crown with alternating Cu and S atoms. The basal Cu atoms are three coordinate and planar with Cu-S bonds within the Cu(1)4S4 crown that range from 2.181(5) to 2.229(9) angstrom. The axial Cu(III) and Au(III) atoms are four coordinate and planar with Cu(III)-S and Au(III)-S bonds of 2.283(9) and 2.400 angstrom, respectively, for III and IV. The mean Cu(III)-Cu(I) bonds in III and the Cu(III)-Au(III) bonds in IV are 2.83(2) and 3.029(7) angstrom, respectively. The reactions of III with thiolate ions result in the formation of the new [Cu4(StBuDED)4]4- cluster, V. This cluster is proposed to be structurally similar to III and IV and is obtained by the reductive removal of the axial Cu(III) to Au(III) ions. The 13C-NMR spectra of III, IV, and V are discussed in terms of their structural electronic and solution dynamic characteristics.