CRYO-CRYSTAL STRUCTURE ANALYSIS AND APPLICATIONS TO REACTION INTERMEDIATES. Dietmar Stalke, Inst. für Anorg. Chem., Am Hubland, D-97074 Würzburg, Germany

As a major aspect of our work, techniques have been established to handle 'short-lived' intermediates in organometallic synthesis. Key features of this work involved the introduction of new synthetic routes genera-ting the metastable target compounds, and the development of comprehensive cryotechniques to make the solid state structure investigations feasible. Although, many alkali metal species had been characterized by crystal structure analysis in the past 20 years, little was known about the nature of the thermolabile intermediates involved in their reactions. To address this problem, we developed a low temperature crystal handling technique which facilitates the x-ray structural characterization of low melting (down to -80deg.C) and/or extremely air-sensitive species (T. Kottke, D. Stalke, J. Appl. Crystallogr. 1993, 26, 615). ln a typical experiment, single crystals are grown at a temperature ranging from 0 to -120deg.C and - after cryomanipulation under a polarizing microscope - transferred to the diffractometer at the required low temperature. Applying this technique, the 'text book structures' of the classical lithium organometallics [ⁿBuLi]₆, [^tBuLi]₄, and the metastable [^tBuLi.Et₂O]₂ have been determined (T. Kottke, D. Stalke, Angew. Chem. Int. Ed. Engl. 1993, 32, 580).