Metallocenes and metallocinium salts readily undergo temperature-induced, crystal-to-crystal, topotactic phase transformations, where mother and daughter phases are closely aligned.  The presentation will focus on a number of examples, including [Fe(C5H5)2][FeCl4] 1  , [Fe(C5H5)2]BF4 2  , [Fe(C5H5)2]PF6 3  , [Co(C5H5)2]PF6 4   and others.  Using newly-developed tools for analyzing the transformations, we will present a series of �movies� representing an accurate picture of the rearrangements.  The observed transformations are often what might be called �typical�, e.g., 2   undergoes a transformation from orthorhombic to monoclinic in which the symmetry of the mother lattice is maintained (referred to as conservative twinning).  For 3  ,   cooling leads reproducibly to a four-component twin, while isomorphous compound 4  has been previously reported to undergo a similar transformation to that of 3   without twinning.  A new determination of the behavior of 4  , as well as an analysis of the molecular displacements which occur in the transformations of 1-4  , will be reported.

Crystal-to-crystal phase transitions in metallocinium salts: Good stories for Arnie

243rd National Meeting (2012)

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