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

Allyl and diene complexes
volatile,low-melting solid A of empirica! formula C 7 H 6 0 3 Fe. The mass spectrum of
A contained a strong parent ion peak at m/z 194 and there were other strong
peaks at m/z 166, 138 and 110.
The 1 H n.m.r. spectrum of A consisted of o ne sharp singlet. The 13 C spectrum
consisted of two singlets and a triplet: under conditions of complete proton
decoupling the triplet became a singlet, but the spectrum was otherwise
unaltered.
When A was dissolved in strong acid, and then CI- was added to the solution, a
covalent compound B was isolated. B was found to possess the empirica! formula
C 7 H 7 0 3 ClFe. The 1 H n.m.r. spectrum of B contained three singlet resonances of
relative are a 3: 2: 2. B could also be prepared by the reaction of H 2 C=CMeCH 2 CI
with Fe 2 (C0) 9 •
Suggest structures for compounds A and B, showing them tobe consistent with
the spectroscopic data. Comment as fully as you can on the bonding between
metal and organic ligands in A and B. Show that both A and B can be regarded as
'obeying the 18-electron rule'.
(University of York).
5. Some chemistry of sodium cyclopentadienyltricarbonyltungstate is shown
below:
Na[(C,H,)W(C0) 3 ] + CH 2 =CH-CH 2 Cl -----> A ~ D
Elemental analysis for B gave 35.4% W, 25.4%C. 5.96%P.
Mass spectrum
M+ (based on
184 W) amu
A: 374
B:
C: 376
D: 346
Vco/cm-1
2019, 1950, 1904
2107, 2053, 2007
2005, 1947. 1905
1960, 1880
Proton nmr ( 1J relative to TMS,
relative intensities in parentheses)
6.0(1H), 5.25(5H), 4.6(1H), 4.5(1H),
2.32(2H).
5.99(5H), 4.36(1H). 3.29(1H),
3.20(1H). 2.22(3H).
4.59(5H), 2.78(1H), 1.55(6H).
4.63( 5H) 3.2 5(1H) 2.48(2H),
1.12(2H).
(a) Propose structures for A to D, showing how you have used the data above.
(b) Comment on the reactions in the scheme.
(c) Describe the bonding of the acyclic hydrocarbon ligand to the metal in D.
(University of Southampton).
6. (a) Make a qualitative sketch of the proton n.m.r. spectrum of (tJ 4 -1, 3-
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