Organometallics 2009, 28, 6841–6844 6841
DOI: 10.1021/om900821c
Microwave Synthesis of Benchmark Organo-Iron Complexes
Sean M. Garringer, Andrew J. Hesse, John R. Magers, Kristopher R. Pugh,
Stacy A. O’Reilly, and Anne M. Wilson*
Clowes Department of Chemistry, Butler University, 4600 Sunset Avenue, Indianapolis, Indiana 46208
Received September 21, 2009
Summary: Microwave-assisted reaction techniques have been
applied to the formation of a variety of organo-iron species.
The species synthesized include ferrocene and acetylferrocene,
piano stool complexes such as CpFe(CO)2I, CpFe(PPh3)-
(CO)I, and CpFe(PPh3)(CO)(COMe), and bisphosphine iron
complexes. The use of microwave-assisted reactions has de-
creased reaction times while maintaining or improving yields as
compared to traditional methods.
complexes; and phosphine tricarbonyl complexes. Several
compounds from each of these classes were chosen for this
study. Classical preparations of the sandwich compounds
ferrocene5 and acetyl ferrocene6 are known in the literature.
Cyclopentadienyl iron carbonyl dimers [CpFe(CO)2]2 (Fp-
Fp, Cp = C5H5) and [Cp*Fe(CO)2]27 (Fp*-Fp*, Cp* = C5-
(CH3)5) are common starting materials for other iron
carbonyl reagents. Piano stool compounds CpFe(CO)2I,8
CpFe(PPh3)(CO)I,9 and CpFe(PPh3)(CO)(COMe)10 are
also well-known compounds. Lastly, the phosphine carbonyl
complexes,11 especially bis-phosphine complexes of iron,12
have also been reported, characterized, and utilized as
reactive intermediates in the chemical literature. Many of
these classical preparations require refluxing solvent condi-
tions for substantial amounts of time, some even requiring
days, in order to make these compounds in yields ranging
from poor to excellent. However, we sought to reduce the
time required for the synthesis of these complexes to minutes
or hours rather than days, as well as improve the yields for
some of the poor-yielding processes.
Ever since the first reports of ferrocene,1 organo-iron
complexes have become staples of classical organometallic
synthesis. The ease of formation, commercial availability,
relative cost, and synthetic utility of many organo-iron
reagents make these ubiquitous compounds available to
inorganic and organic chemists alike.2 However, the forma-
tion of many of these fundamental compounds requires long
reaction times and high heat. These reaction conditions are
ideal conditions to exploit microwave-assisted synthesis.
Since microwave synthesis was introduced in the litera-
ture, there has been an explosion of applications to organic
synthesis, inorganic synthesis, and organometallic synth-
esis.3 Of these, applications to the synthesis of transition
metal complexes have been relatively underexploited.4 Re-
action sequences requiring a long time at elevated tempera-
tures are ideal candidates for the application of microwave
heating.
Experimental Section
General Procedures. All reagents were purchased from che-
mical suppliers (Aldrich Chemical Co.) and used without further
purification. Infrared spectra were taken with a Nicolet/Thermo
Electron Avatar 370 FTIR spectrometer. Nuclear magnetic
When evaluating organo-iron compounds as targets for
microwave synthesis, three classes of compounds were ideal
candidates: sandwich complexes; cyclopentadienyl carbonyl
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*Corresponding author. E-mail: amwilson@butler.edu.
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