W0097

Solid State Reactivity of Aquabis(3-butenoato)Calcium. Michael J. Vela and Bruce M. Foxman, Department of Chemistry, Brandeis University, Waltham, MA 02254-9110 USA

For the past several years we have been studying the behavior of salts and complexes of various metals with trans-2-butenoic acid (crotonic acid). ⁶⁰Co _-irradiation of solid metal trans-2-butenoates leads stereospecifically to acyclic trimers or to cyclic dimers. We now report the solid-state chemistry of the calcium salt of 3-butenoic acid (vinylacetic acid). The crystal structure of aquabis(3-butenoato)calcium was solved and refined using restrained refinement techniques available in the Oxford University CRYSTALS software package. The local coordination environment of the calcium ion, which is seven-coordinate, is shown in the accompanying Figure. The X- ray structure determination indicated that the terminal carbon on each of the carboxylates is disordered over two sites, as represented by the shaded/unshaded atoms in the Figure. ⁶⁰Co _-irradiation of solid aquabis(3-butenoato)calcium (305 kGy) leads to > 95% conversion to calcium poly(3-butenoate). The molecular weight distribution of the polymer is bimodal with maxima at 10⁵ and 10⁶ g/mol. The presentation will include a discussion of the structural chemistry of this phase (the calcium coordination polymer), the likely reaction pathway (as deduced from structure-reactivity relationships), and the characterization of the product. To the best of our knowledge, it is not possible to synthesize this polymer by solution techniques.