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

Problems
Mann, B.E. (1986) Fluxionality ofpolyene and polyenyl complexes. Chem. Soc. Revs .. 15.
125.
Maslowsky, A .. Jr. (1978) Metallocenes. ]. Chem. Educ., 55, 276.
Negishi, E. and Takahashi, T. (1985) Organozirconium compounds as new reagents.
Aldrichimica Acta, 18, 31.
Pearson, A.J. (1984) Iron-stabilised carbocations as intermediates for organic synthesis.
Science, 223, 895.
Werner, H. (1980) The way to novel sandwich complexes. ]. Organomet. Chem .. 200, 33 5.
(Includes triple decker and bimetallic sandwiches).
Wilkinson, G. (1975) Ferrocene. A personal account of the exciting early years. ].
Organomet. Chem., 100, 273.
Problems
1. Ferrocene, Cp 2 Fe, and cobaltocene, Cp 2 Co, can be oxidized to the cations
Cp 2 Fe + and Cp 2 Co + respectively. Discuss the metal-carbon bond distances and
magnetic moments (Jl,ff) given below in terms ofthe bonding in these compounds.
Compound M-C!A Jl,rr (298 K)
Cp 2 Fe 2.06 0.0
Cp 2 Fe+BF; 2.13 2.2
Cp 2 Co 2.12 1.7
Cp 2 Co+BF; 2.05 0.0
2. When 1. 3, 5-cycloheptatriene is heated under reflux with Fe(C0) 5
the tricarbonyliron complex A, C 10 H 8 Fe0 3 is obtained. Treatment of A with
hydrogen gas affords a second tricarbonyliron complex B, C 10 H 10 Fe0 3 • Reaction
of A with HBF 4 orB with Ph 3 C. BF 4 gives C, C 10 H 9 BF 4 Fe0 3 , which is insoluble
in non-polar solvents. The 1 H n.m.r. spectrum of C consists offive groups of lines
of relative intensity 1 : 2: 2: 2 : 2.
Propose structures for A, B, and C. giving your reasoning. Draw clear diagrams
to illustrate the conformation of the organic ligands in these complexes. Give an
interpretation of the 1 H n.m.r. spectrum.
(University of Leicester).
3. Suggest mechanisms for the reactions of cobaltocene with (a) CH 2 Cl 2
(b) PhBC1 2 •
4. Consider the following reaction scheme:
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