Uranocene crystal structure

Also crystallizing in space group P2 ]c, uranocene has two molecules per unit cell, so that the U(CsH8)2 molecule occupies a special position of site symmetry 1. In other words, the molecule has an eclipsed conformation, and it may be assigned to special position 2(a). Similarly, the two halves of the [Re2Clg]2- dianion in K2 [Rc2C lmolecular dimensions (indicating that the symmetry of the dianion is Z>4h within experimental error) and crystal structure are shown in Fig. 9.6.5. 

Many substituted uranocenes have been made and there is a substantial body of organometallic chemistry of uranocene derivatives now known 16, 17). Some of this chemistry will be mentioned in passing but wiU not be covered in a systematic way since other reviews of the organic chemistry are available 18). The only other actinide cyclooctatetraene complex structurally characterized to date is bis[(l,3,5,7-tetramethylcyclooctatetraenyl]uranium(IV) 19), which was of interest because the presence of methyl groups allowed the planarity and relative orientation of the dianion rings to be determined. Crystal and molecular parameters for these three actinide compounds are summarized in Table 1. 

The molecular structure of uranocene has been determined by single-crystal x-ray diffraction and is shown in Fig. 22.15 [130,131]. The molecule possesses rigorous Dg), symmetry with the eight-membered rings arranged in an eclipsed conformation. The mean U-C bond distance is 2.647(4) A, and the mean C-C bond distance is 1.392(13) A. TheCgHi rings are planar to within experimental error. 

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