Redetermination of the cobaltocene crystal structure at 100 K and 297 K: comparison with ferrocene and nickelocene.
The mol. and crystal structures of the monoclinic modification of cobaltocene Cp2Co were detd. at 100 K and 297 K with new sets of x-ray diffraction data. At 297 K the structure is disordered (similar to the isomorphous ferrocene and nickelocene) with two distinct orientations of the ring, differing in occupancy factors (80% and 20%) and by a rotation angle in the ring plane of approx. 34 Deg. Just as for nickelocene but in contrast to ferrocene, no sharp phase transition was found on cooling Cp2Co to 100 K, but an essential ordering of the Cp-ring position was detected with a decrease of the contribution of the second minor orientation to nearly 10%. On the basis of a careful anal. of the mol. geometry, crystal packing, and anisotropic at. displacement parameters, a dynamic temp.-dependent nature of the disorder in Cp2Co is assumed.
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