Bis(η5-pentamethylcyclopentadienyl)cobalt(II)

The crystal structure of the title compound, decamethylcobaltocene, [Co(C10H15)2], has been determined. High-quality single crystals were grown from a cold saturated hexamethyldisiloxane solution. The structure is related to the manganese and iron analogs. The molecule has D 5d symmetry, with the Co atom in a crystallographic 2/m position. The cobalt–centroid(C5) distance is 1.71Å and the centroid(C5)–Co–centroid(C5) angle is 180°, by symmetry.

The crystal structure of the title compound, decamethylcobaltocene, [Co(C 10 H 15 ) 2 ], has been determined. Highquality single crystals were grown from a cold saturated hexamethyldisiloxane solution. The structure is related to the manganese and iron analogs. The molecule has D 5d symmetry, with the Co atom in a crystallographic 2/m position. The cobalt-centroid(C 5 ) distance is 1.71Å and the centroid(C 5 )-Co-centroid(C 5 ) angle is 180 , by symmetry.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: SJ2590).
to grow single crystals from toluene and hexane, the latter from which Robbins reported having grown crystals, resulted in very poor quality specimens that were unsuitable for X-ray diffraction experiments. A cold (-38 ° C) saturated hexamethyldisiloxane solution of (I) afforded excellent crystals that resulted in a high quality structural determination.

Experimental
All operations were performed under an inert atmosphere (dinitrogen). Hexamethyldisiloxane was stirred over CaH 2 and vacuum transferred from sodium benzophenone ketyl. (I) was purchased from Sigma-Aldrich and used as is. Hexamethyldisiloxane (1 ml) was added to (I) (10 mg, 30 µmol), most of which dissolved over the course of a few hours at room temperature. After filtration through Celite, the filtrate was stored at -38 °C, resulting in dark yellow-brown crystals of (I) after a few hours.

Refinement
Hydrogen atoms were found from the difference Fourier map and refined independently from their respective carbon atoms with individual isotropic displacement parameters.  Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.