LSU Historical Dissertations and Theses

1988

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Chemistry

Joel Selbin

Abstract

Seven new coinage metal cluster compounds were synthesized and their single-crystal X-ray structures were determined. The novel gold cluster, hexakis(o-methyldithiobenzoato)hexagold(I), (Au$\sb6$ (o-CH$\sb3$C$\sb6$H$\sb4$CS$\sb2$)$\sb6$), has six gold atoms that are coplanar to within 0.14A. Each gold(I) forms two nearly linear bonds to bridging ligands alternately above and below the cluster plane. In addition to the multitude of Au-Au interactions within the hexameric cluster, a close intermolecular contact exists, thereby forming chains of these hexamers. The other gold cluster is a dimer, bis(2,4,6-trimethyldithiobenzoato)digold(I), (Au$\sb2\{$2,4,6-(CH$\sb3$)$\sb3$C$\sb6$H$\sb2$CS$\sb2\}\sb2$). However, there are three crystallographically independent dimers in the unit cell which are positioned such that a gold atom from each dimer lies at the vertices of a triangle that connects the three dimers. Of the three silver cluster compounds, one (n-Pr$\sb4$N)$\sb2$ (Ag$\sb4\{$2,4,6-(CH$\sb3$)$\sb3$C$\sb6$H$\sb2$CS$\sb2$ $\}\sb6$) $\cdot$1/2DMF$\cdot$H$\sb2$O, has a square-planar array of silver atoms, whereas the other two, (Ag$\sb4\{$2,4,6-(CH$\sb3$)$\sb3$C$\sb6$H$\sb2$CS$\sb2\}\sb4$(py)$\sb3$) $\cdot$1/2py and (Ag$\sb4$(o-CH$\sb3$C$\sb6$H$\sb4$CS$\sb2$)$\sb4$(py)$\sb4$), have distorted tetrahedral structures. The two trithioperoxybenzoate copper clusters, (Cu$\sb4\{$2,4,6-(CH$\sb3$)$\sb3$C$\sb6$H$\sb2$CS$\sb2$S$\}\sb4$) and Cu$\sb4$ (o-CH$\sb3$C$\sb6$H$\sb4$CS$\sb2$S)$\sb4$), exhibit distorted tetrahedral coordination. Triphenylphosphine was reacted with these clusters and resulted in seven monomeric derivatives with the formula (M(L)(PPh$\sb3$)$\sb{\rm x}$) where M = Au, L = o-CH$\sb3$C$\sb6$H$\sb4$CS$\sb2$, x = 1; M = Au, L = 2,4,6-(CH$\sb3$)$\sb3$C$\sb6$H$\sb2$CS$\sb2$, x = 1 or 2; M = Ag or Cu, L = o-CH$\sb3$C$\sb6$H$\sb4$CS$\sb2$ or 2,4,6-(CH$\sb3$)$\sb3$C$\sb6$H$\sb2$CS$\sb2$, x = 2. When x = 1, the gold compounds are linearly coordinated and the ligands are monodentate. When x = 2, the metals are all tetrahedrally coordinated and the ligands are bidentate. In addition to the above, seven other gold(I) complexes were synthesized using similar ligands, but solubility problems prevented single crystal growth and structural determinations. These ligands originated from tetraalkylammonium salts of the following substituted dithiobenzoates: p-methoxy-, p-fluoro-, p-phenyl-, p-benzoyl-, p-formyl-, p-acetyldithiobenzoate, and 1-dithionaphthoate. In order to further characterize some of these compounds, solid-state $\sp{13}$C CP-MAS NMR spectra were obtained for the o-methyl-, 2,4,6-trimethyl-, p-methoxy-, and p-fluorodithiobenzoatogold(I) complexes. All the gold(I) dithiobenzoate compounds were characterized by infrared and visible-ultraviolet spectroscopy. A discussion of the anomalous behavior of the p-phenyldithiobenzoate ligand in reactions with gold(III) and copper(II) is presented. No new light is shed on a continuing controversy regarding metal-metal bonding, its relative strength or even existence, in coinage metal clusters.

345

COinS