_P.-Powell-auth.-Principles-of-Organometallic-Chemistry-Springer-Netherlands-1988

References
In the salt [K+(diglyme)][Ce(C 8 H 8 );] the anion has staggered D 8 d symmetry.
The cerium system is unusual for a lanthanide complex in showing two oneelectron
oxidation-reduction steps.
K
Ce(CaHal2 diglyme
Block needles Green
Streitwieser noticed that the HOMOs of C 8 H~- ha ve the correct symmetry to
interact with the Sf orbitals of an actinide (or 4f of a lanthanide). This led to the
preparation of the sandwich complex bis( cyclooctatetraene )uranium ( uranocene).
Uranocene is pyrophoric in air, but it thermally very robust. It forms deep
green crystals which can be sublimed under vacuum. X-ray diffraction shows
that the rings are parallel and eclipsed (D 8 h).
The extent of electrostatic (ionic) and orbita! (covalent) considerations in
determining the structures of such compounds oflanthanides, actinides and early
d-block transition elements is not clear. As with Cp 4 M (M =Ti, Zr. Th, U) the
complexes M(C 8 H 8 ) 2 show structural trends apparently related to the size of the
metal atom.
Q Q Q
t0
~(]
16-electron, rings 18e
ropidly interconvert
in solution.
-...:::::::
6
Formal Coord.No 6 8 8
Th
20 e
13.5 References
Evans, W.J. (1985) Organolanthanide chemistry. Adv. Organomet. Chem .. 24. 131.
Marks, T.J. (1978) Prog. Inorg. Chem., 24. 51; (1979) Prog. Inorg. Chem., 25. 223. Reviews
of early work.
Watson, P.L. and Parshall, G. W. (1985) Organolanthanides in catalysis. Ace. Chem. Res ..
18. 51.
403