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

Problems
10. At 11 °C, the proton decoupled 13 C n.m.r. spectrum of (ry'-C 7 H 7 )Mn(C0) 3
contains four signals due to the hydrocarbon ligand as shown below. At 3 5°C,
these broaden in the manner shown. Assign these 13 C resonances and explain in
detail the reason for the differential broadening at 35"C.
35•c
11 ·c
b 129.7 107.4 98.0 77.1
9
'
-
Mn(C0)3
'
[For the interpretation of the n.m.r. data ignore ali nuclei except 1 3 C (I = %-. 1%
abundant) ].
(University of Southampton).
11. Reaction of the pentamethylcyclopentadienyl complex (C,Me,)Rh(C0) 2
with HBF 4 affords a salt A. Treatment of A with NaOMe yields the red solid B,
which gives Con heating. Propose structures for A, B and C using the data below,
and comment on the bonding in C.
A:-
Mass spectrum
M+ jamu
B: 560
C: 532
vco/cm- 1
2026,1739
1951. 1778
1732
Proton n.m.r. ( <:5 relative ta
TMS)
2.03(singlet, 30H), - 10.40 (triplet,
J = 19Hz, 1H).
1. 91 (singlet).
1. 6 5 ( singlet).
Analysis of A gave 42.6% C, 31.8% Rh and 1.67% B.
Isotopic abundances: 1 H, 100%. I = i: 10 B, 1 9%. I = 3, 11 B, 81%. 1 = f; 12 C,
98.9%.1 =O; 13 C, 1.1 %. 1 = η 16 0, 100%.1 =O; 19 F, 100%.1 = -i-: 103 Rh, 100%. I
=H
(University of Southampton).
12. The molar magnetic susceptibility (X~rr) of 1.1'-dimethylmanganocene,
corrected for diamagnetism, varies with temperature as shown below. Given that
the magnetic moment f.l.eff = 797.7 (x~rr.T)1 12 , calculate f.l.eff at each temperature.
Plot x~rr VS T and f.l.eff vs T.
T/K 214 235 253 285 310 331 366 371
7.527 8.394 8.771 9.814 9.953 9.840 9.525 9.576
1,1'-Dimethylmanganocene exists as an equilibrium mixture of high spin (hs)
309