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Experiment
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Spillage & disposalClear area, shut off all sources
of ignition. Organise effective ventilation and allow to
evaporate. Diethyl ether should be placed in the
non-chlorinated waste container for
central disposal.
Experimental Procedure
IMPORTANT!!!! SAFETY NOTE: Chromium hexacarbonyl and the chromium
complexes you
prepare are extremely toxic and may cause cancer. Chromium hexacarbonyl is a volatile solid,
which must be handled and weighed out within a fume hood, wearing nitrile gloves.
The evaporation step
must be carried out on a rotary evaporator situated in a fume hood (rear of the
Perkin laboratory).
A
mixture of di-n-butyl ether (purified by distillation
from sodium-benzophenone (60ml),5THF (purified by distillation from
sodium-benzophenone (6ml),5the arene you have been assigned
(10ml) and chromium
hexacarbonyl (1.0g) are placed, together with a magnetic
stirrer bar,in a 100ml round bottomed flask and
attached to the Strohmeier apparatus. The assembly is connected to the vacuum line/nitrogen manifold using
semipressure tubing and a magnetic stirrer and a heating bath on a lab jack, placed
beneath the round bottomed flask.
Check that all joints are
sealed then evacuate the apparatus by carefully turning the
3-way tap on the frame (see
APPENDIX for the vacuum line/nitrogen manifold system). As soon as the solvent begins to boil, let in the dry,
oxygen free nitrogen viathe 3-way tap. Repeat this cycle nine more times to ensure that the system is
completely anaerobic. With the system maintained under a slight
positive pressure of
nitrogen by the manifold commence stirring and heating the
contents of the flask.
Maintain the solution at a steady reflux for [!] 24 h.
At the end of this time,
the flask is cooled then detached from the Strohmeier
apparatus. In the fume hood, the solution is
chromatographed over a short (~-5cm) column of silica gel 60
using diethyl ether to
complete the elution of the yellow/orange complex. Evaporation of the solvents,
using a cardice
Büchi evaporator situated in a fume hood with
minimal bath heating, yields the product.
Record
the m.p. of your product and record and interpret the i.r. and
n.m.r. spectra.
Write Up
The write up should
conform to the style of Organic and Biomolecular Chemistry, style (Title, Abstract, Introduction, Results and Discussion, Experimental,
References). Your
introduction must include
discussion of the following points:
a)Three recent (1998 or later) examples of synthetic
applications of arenetricarbonylchromium
complexes from the primary literature. Extra marks
for originality and breadth of chemistry! b)Two other recent (1998 or later) examples from the
primary literature of the use of other
types of metal carbonyl complex in organic
synthesis (ieNOT
arenetricarbonylchromium
complexes).
References and Notes
1.For broad
surveys see: "Comprehensive Organometallic Chemistry"
Eds G.Wilkinson,
F.G.A.Stone and E.W.Abel, Pergamon Press, Oxford,
1982, Vols 7 and 8; S.G.Davies,
"Organotransitionmetal Chemistry: Applications
to Organic Synthesis" Pergamon Press,
Oxford, 1982; "Organometallics in Organic
Synthesis" by E.-I. Negishi, Wiley-
Interscience, New York, 1980.