W0219

Single-Crystal Neutron Diffraction and the Study of Metal-Hydrogen Interactions. Thomas F. Koetzle, IPNS Div., Argonne National Laboratory, Argonne, IL 60439 and Chemistry Dept., Brookhaven National Laboratory, P.O. Box 5000, Upton, NY 11973.

In studies stretching back to the 1960’s, single-crystal neutron diffraction has been exploited to reveal details of metal-hydrogen interactions in a variety of molecular crystals. These studies take advantage of neutron diffraction’s unique sensitivity to light atoms, including hydrogen. The structures of transition metal hydride (M-H) and dihydrogen (M-H₂) complexes have been of great interest here because of their central importance in hydrogen activation and chemical catalysis. Recent studies in this area will be discussed, including several where novel hydrogen-bonding modes have been uncovered that might be expected to form the basis for extended motifs.

In the past, applications of single-crystal neutron diffraction frequently have been limited by the requirement for large crystals, greater than 1 mm³. Revolutionary improvements are expected with the advent of a new generation of powerful neutron sources now under construction or in the planning stage, including the Spallation Neutron Source (SNS) that is scheduled to become operational at Oak Ridge in 2006. At the SNS, it should be possible to work with much smaller crystals, approaching the size commonly used in laboratory single-crystal X-ray studies, thus greatly expanding the range of materials that will be open to investigation. Some speculations will be offered on the exciting new possibilities that are envisioned for the single-crystal diffractometer (SCD) now being planned for SNS.

Argonne and Brookhaven National Laboratories are operated under contracts W-31-109-ENG-38 and DE-AC02-98CH10886, respectively, with the U.S. Department of Energy.