| Abstrakt: |
The X-ray structure determination of (η5-C5H5)Ta(η2-C2H4)Cl2(PMe2Ph)2 has revealed that the compound crystallizes in the orthorhombic space groupFdd2 witha=21.098(9),b=29.848(9),c=7.694(3) Å, andDc=1.70g cm−3 forZ=8. Least-squares refinement based on 893 independent observed reflections resulted in a finalR value of 0.026. The molecule resides on a crystallographic two-fold axis, with disordered ethylene and cyclopentadienyl groups. The Ta-Cl and Ta-P separations are 2.473(4) and 2.649(3) Å, respectively. Since the two carbon atoms of the ethylene molecule are indistinguishable from two of the cyclopentadienyl carbon atoms, the Ta-C bond lengths are 2.37(1) and 2.39(2) Å for the ethylene and for two of the cyclopentadienyl carbon atoms. The other three Ta-C(cyclopentadienyl) distances are much longer: 2.54(3), 2.54(3), and 2.62(3) Å. In order to achieve 18e− at the tantalum atom, the cyclopentadienyl ligand must be viewed in an η5-bonding mode. The variation of the Ta-C lengths is thus considered to be steric in origin. The carbon atoms of the C5H5− group are planar to 0.03 Å. |
Full text from SpringerLink