REVOLUTIONARY ADVANCES IN CRYSTALLOGRAPHIC ANALYSES OF HIGH-NUCLEARITY TRANSITION METAL CLUSTERS: FROM POINT-DETECTOR TO CCD AREA-DETECTOR SYSTEMS. Lawrence F. Dahl¹, Masaki Kawano¹, Jeffrey W. Bacon¹, John M. Bemis¹, Peter D. Mlynek¹, Nguyet T. Tran¹, Charles F. Campana², ¹Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706 ²Siemens Analytical X-Ray Instruments, 6300 Enterprise Lane, Madison, WI 53719

The availability of the SMART charge-coupled-device (CCD) area detector system approximately two years ago for collecting single-crystal X-ray diffraction data with MoK[[alpha]] radiation has proven to be crucial for our current research on giant-sized metallic and bimetallic clusters. This lecture will illustrate: (1) the much greater capability of the CCD system relative to a point-detector system in determining both the molecular architectures and stoichiometries of a number of geometrically unprecedented close-packed bimetallic Ni/Pd and Ni/Cu clusters, especially for weakly diffracting and/or small crystals; and (2) crystallographic problems that bedevil modern X-ray diffraction analysis of large metal clusters.