INOR 239 |
| John P. Fackler Jr., Ahmed A. Mohamed, Hanan E. Abdou, and Michael D. Irwin. Department of Chemistry, Texas A&M University, College Station, TX 77843-3255 |
| The formation of metal-metal bonded Au(II) compounds has included a wide variety of ligands dominated by the ylides, carbon atom bonded ligands which effectively donate electron density to the metal centers to produce a HOMO that is antibonding between the metal atoms and a LUMO which is bonding. Mixed S, C and P, C ligand systems (atoms bonded to gold) and at least one S, S ligand system also gives Au(II)-Au(II) species which have been structurally characterized. The shortest Au(II)-Au(II) distances previously observed are about 2.55Å. No Au(II) compounds have been reported structurally with N, N or even mixed N, C coordination although trinuclear species which undergo oxidation addition to form Au(III) species are well established. These compounds do not form Au(II) products. With tetranuclear gold compounds the situation remains unclear. Tetranuclear species have been formed with bridging P, S, and P, N ligands in which the Au(I)...Au(I) distances are around 3 Å. Unlike the trinuclear species in which the formation of a Au(II)-Au(II) bond is sterically unfavorable, the tetranuclear species do not have this problem. By using special anionic N, N ligands with short N...N ‘bite” distances, we have prepared a dinuclear complex which gives a very short Au(II)-Au(II) bond, 2.45Å, with terminal chlorine atoms. With a similar N, N ligand, a tetranuclear Au(I) species is produced which has Au(I)...Au(I) distances under 3.0Å. Cyclic voltammetry shows this material to have three reversible oxidation waves. A trinuclear species also has been characterized which appears to be an intermediate to the formation of the tetranuclear complex. |
|
Contemporary Aspects of Chemical Bonding
8:40 AM-12:00 PM, Monday, September 8, 2003 Javits Convention Center -- 1A26/1A27, Oral
Division of Inorganic Chemistry |