Preparation of ruthenium and osmium carbonyl complexes using microwave heating: demonstrating the use of a gas-loading accessory and real-time reaction monitoring by means of a digital camera

Article abstract of DOI:10.1021/om701099p

By using a gas-loading accessory, we show that it is possible to perform reactions involving gases and prepare organometallic complexes easily in good yields using microwave heating. The complexes Ru₃(CO)₁₂, H₄Ru₄(CO)₁₂, and H₂Os ₃(CO)₁₀ are prepared. Ligand substitution reactions of Ru₃(CO)₁₂ are also studied and, in the case of the reaction with triphenylphosphine, the reaction is monitored in real time by means of a digital camera interfaced with the microwave unit.

Full text of DOI:10.1021/om701099p

1254
Organometallics 2008, 27, 1254–1258
Preparation of Ruthenium and Osmium Carbonyl Complexes Using
Microwave Heating: Demonstrating the Use of a Gas-Loading
Accessory and Real-Time Reaction Monitoring by Means of a
Digital Camera
Nicholas E. Leadbeater* and Krista M. Shoemaker
Department of Chemistry, UniVersity of Connecticut, 55 North EagleVille Road,
Storrs, Connecticut 06269-3060
ReceiVed October 31, 2007
By using a gas-loading accessory, we show that it is possible to perform reactions involving gases and
prepare organometallic complexes easily in good yields using microwave heating. The complexes
Ru3(CO)12, H4Ru4(CO)12, and H2Os3(CO)10 are prepared. Ligand substitution reactions of Ru3(CO)12 are
also studied and, in the case of the reaction with triphenylphosphine, the reaction is monitored in real
time by means of a digital camera interfaced with the microwave unit.
same group has performed the synthesis of a range of other
transition-metal coordination compounds at atmospheric pressure
under reflux conditions.6 One reason why there have been only
a few reports is that monitoring a reaction using microwave
heating can be difficult. Generally it requires stopping the
reaction, allowing the mixture to cool, and then using standard
analysis techniques. This often makes optimization of reaction
conditions such as time and temperature a matter of trial and
error. This can be a particular problem when trying to prepare
organometallic complexes. For example, in ligand exchange
reactions, stopping a reaction after a desired number of
substitutions is difficult if the reaction cannot be continually
monitored. With conventional heating the reaction can be slow
and aliquots removed and analyzed over time, but with
microwave heating the reaction may be complete within a matter
of minutes (or even seconds) and accessing a sealed vessel
during a reaction is not possible. We have recently reported a
way to overcome this by using in situ Raman spectroscopy as
a tool. By studying some simple substitution reactions of
Mo(CO)6 with monodentate ligands, we have shown the
potential applicability of this technique.7 Although not as widely
used as infrared, Raman spectroscopy is a useful tool for probing
both molecular composition and structure in metal carbonyls.
By focusing on the νCO stretching region of the Raman spectrum,
it is possible to follow ligand substitution reactions as they occur.
Another limitation of microwave heating as a tool for the
preparation of organometallic compounds is that often gaseous
reagents are required. This is particularly the case when
preparing metal carbonyl, hydride, and olefin complexes. We
thought that, by overcoming this problem, it would be possible
to open up more avenues for microwave-promoted synthesis
of organometallics. Here we show how, by using a gas-loading
accessory we developed for organic synthesis, we can now
perform reactions involving gases and prepare organometallic
complexes. We also extend our reaction monitoring work to
Introduction
Microwave heating offers a fast, easy way to perform
chemical reactions that require heat. Synthetic organic chemists
have taken advantage of microwave heating in their work and
found that reaction times can often be reduced from hours to
minutes and yields are improved. Microwave heating occurs
on a molecular level, as opposed to relying on convection
currents and thermal conductivity when using conventional
heating methods. This offers an explanation as to why micro-
wave reactions are so much faster. With microwave irradiation,
since the energy is interacting with the molecules at a very fast
rate, the molecules do not have time to relax and the heat
generated can be, for short times, much greater than the overall
recorded temperature of the bulk reaction mixture. In essence,
there will be sites of instantaneous localized superheating where
reactions will take place much faster than in the bulk.
In the literature, there have been relatively few reports of
the use of microwave heating in preparative organometallic
chemistry. Green and co-workers have reported the microwave-
assisted synthesis of group 6 zerovalent carbonyl compounds.1
They prepared M(CO)4L complexes (M ) Cr, Mo, W; L )
bidentate amine or phosphine ligand), finding that the reaction
can be accelerated using microwave heating. Hogarth and co-
workers have also investigated the use of microwave heating
for the synthesis of group 6 carbonyl complexes.2 This work
was performed using open-vessel conditions in a domestic
microwave, where accurate temperature monitoring is not
possible. Building on this work, Chung and co-workers have
used microwave heating to prepare (η6-arene)tricarbonylchro-
mium complexes.3 Teflon autoclaves have been used by Mingos
and co-workers, who have reported the synthesis of the rhodium
and iridium(I) diolefin complexes [Cp2Rh]PF6, [(η6-C6H6)Ru(µ-
Cl)]2, [IrCl(CO)(PPh3)], and [RuCl(CO)(2,2′-bipy)2]Cl.4,5 The
* To whom correspondence should be addressed. E-mail:
nicholas.leadbeater@uconn.edu.
(4) Baghurst, D. R.; Mingos, D. M. P.; Watson, J. J. Organomet. Chem.
1989, 368, C43.
(1) VanAtta, S. L.; Duclos, B. A.; Green, D. B. Organometallics 2000,
19, 2397.
(5) Baghurst, D. R.; Cooper, S. R.; Greene, D. L.; Mingos, D. M. P.;
Reynolds, S. M. Polyhedron 1990, 9, 893.
(2) Ardon, M.; Hogarth, G.; Oscroft, D. T. W. J. Organomet. Chem.
2004, 689, 2429.
(6) Baghurst; D. R.; Mingos, D. M. P. J. Organomet. Chem. 1990, 384,
C57.
(3) Lee, Y. T.; Choi, S. Y.; Lee, S. I.; Chung, Y. K.; Kang, T. J.
Tetrahedron Lett. 2006, 47, 6569.
(7) Barnard, T. M.; Leadbeater, N. E. Chem. Commun. 2006, 3615.
10.1021/om701099p CCC: $40.75
2008 American Chemical Society
Publication on Web 02/22/2008

Ru and Os Complexes Using MicrowaVe Heating
Organometallics, Vol. 27, No. 6, 2008 1255
include watching reactions as they take place by means of a
digital camera interfaced with the microwave unit.
Results and Discussion
Many of the approaches to binary metal carbonyl complexes
involve using autoclaves, high pressures of CO, and long
reaction times at elevated temperatures. A versatile starting
material for the generation of ruthenium-containing compounds
is Ru3(CO)12 (1). It has been prepared by several routes,8–10
the most popular of which requires heating a methanol solution
of ruthenium trichloride under a high pressure of carbon
monoxide at 250 °C for several hours.11 More recently, this
and other ruthenium carbonyl clusters have been prepared under
milder conditions by a two-step process involving carbonylation
of RuCl3 · nH2O dissolved in ethylene glycol to give a mixture
of ruthenium(II) tri- and dicarbonyl species followed by addition
of specific amounts of alkali-metal carbonates and further
reductive carbonylation.12,13 A similar approach using potassium
hydroxide has also been reported. In this case, the addition of
2 equiv of KOH per Ru under 1 atm of CO at 75 °C to a mixture
of [Ru(CO)2Cl2]n and [Ru(CO)3Cl2]2, generated in situ by
carbonylation of RuCl3 · nH2O in 2-ethoxyethanol, triggers a
reaction cascade producing 1 in good yields and with shorter
reaction times.14,15 We wanted to see if we could use microwave
heating as a tool for the simple, rapid preparation of 1. Our
initial objective was to modify the original high-temperature,
high-pressure synthesis so we could attempt this using micro-
wave heating. To do this, we clearly needed to be able to load
our reaction vessel with carbon monoxide. We have developed
an apparatus for use with an 80 mL reaction vessel (Figure
1).16,17 The gas is introduced directly into the vessel, and a
pressure sensor is connected to the vessel in parallel. As a result,
the exact loading pressure can be monitored in real time. Since
the microwave apparatus is designed to contain the results of a
vessel failure under pressure, the unit together with the gas-
loading interface offers a very simple and safe way to perform
chemistry using gaseous reagents at elevated pressures. Most
commercially available microwave systems have a pressure limit
of 20–30 bar. With the combination of a pressure of reactive
gas and the autogenic pressure of solvents at elevated temper-
atures, there is a limit to the temperature to which reaction
mixtures can be heated. We needed to take this into account
when attempting to prepare 1. In our first run, we placed a
solution of RuCl3 in methanol into the reaction vessel, closed
it, and loaded it to an initial pressure of 50 psi of CO. Then,
using an initial microwave power of 300 W, we heated the
reaction mixture from room temperature to 110 °C, where we
held it for 20 min. We could not heat to a higher temperature
Figure 1. Schematic of the gas-loading interface.
Scheme 1
due to the pressure limits of the vessel. Upon cooling, analysis
of the resultant solution showed only a trace of the desired
product. This could be attributed to the fact that the reaction
temperature and CO pressure are significantly lower than in the
conventional procedure. We therefore turned our attention to
the alternative, base-mediated routes to 1. Using RuCl3 as our
ruthenium starting material, sodium carbonate as the base
(Na2CO3:RuCl3 molar ratio 3:2), methanol as the solvent, and
an initial pressure of 50 psi of CO, we obtained a 40% yield of
1 after heating to 110 °C and holding until a total time of 15
min had elapsed. An observation we made was that, even at
the end of the reaction, only a fraction of the sodium carbonate
had dissolved in the methanolic solution. It occurred to us that
this may be the contributing factor for the moderate yield of
product. We therefore turned to cesium carbonate, which we
knew was soluble in methanol. Using the same reaction
conditions, we obtained a 90% yield of 1. We were able to both
shorten the reaction time to 10 min and reduce the Cs2CO3:
RuCl3 molar ratio from 3:2 to 1:1 without a deleterious effect
on the product yield. This offers a very fast and easy route to
1 in one step (Scheme 1) and in yields comparable to or higher
than those in previous literature reports.
Having prepared 1, we next wanted to assess the use of
microwave heating as a tool for some ligand substitution
reactions.18 As a starting point, we wanted to prepare phosphine-
substituted derivatives. It is possible to replace up to three of
the carbonyl groups on 1 with phosphine ligands by simple
thermolysis in a hydrocarbon solvent.19 Since 1 and hydrocar-
bons are nonpolar, they do not heat efficiently under microwave
irradiation. Therefore, we decided to perform the chemistry
using 1,2-dichloroethane as solvent. We focused attention on
preparing the triphenylphosphine-substituted complexes
(8) Lewis, J.; Johnson, B. F. G. Inorg. Synth. 1972, 13, 92.
(9) James, B. R.; Rempel, G. L.; Teo, W. K. Inorg. Synth. 1975, 16,
45.
(10) Mantovani, A.; Cenini, S. Inorg. Synth. 1975, 16, 47.
(11) Bruce, M. I.; Jensen, C. M.; Jones, N. L. Inorg. Synth. 1990, 28,
216.
(12) Roveda, C.; Cariati, E.; Lucenti, E.; Roberto, D. J. Organomet.
Chem. 1999, 580, 117.
(13) Lucenti, E.; Cariati, E.; Dragonetti, C.; Roberto, D. J. Organomet.
Chem. 2003, 669, 44.
(14) Faure, M.; Maurette, L.; Donnadieu, B.; Lavigne, G. Angew. Chem.,
Int. Ed. 1999, 38, 518.
(15) Faure, M.; Saccavini, C.; Lavigne, G. Chem. Commun. 2003, 1578.
(16) For use of this equipment in organic chemistry, see: Kormos, C. M.;
Leadbeater, N. E. Synlett 2007, 2006.
(18) For an overview of the ligand substitution chemistry of Ru3(CO)12,
see: Bruce, M. I. In ComprehensiVe Organometallic Chemistry II; Abel,
E. W., Stone, F. G. A., Wilkinson, G., Eds.; Pergamon: Oxford, U.K., 1995;
Vol. 4, Chapter 32.5.
(19) (a) Bruce, M. I.; Shaw, G.; Stone, F. G. A. J. Chem. Soc., Dalton
Trans. 1972, 2094.
(17) For other reports of microwave equipment modified for gas-loading
in organic chemistry, see: (a) Vanier, G. S. Synlett 2007, 131. (b) Petricci,
E.; Mann, A.; Schoenfelder, A.; Rota, A.; Taddei, M. Org. Lett. 2006, 8,
3725. (c) Kormos, C. M.; Leadbeater, N. E. Synlett 2006, 1663.

1256 Organometallics, Vol. 27, No. 6, 2008
Leadbeater and Shoemaker
Scheme 2
Scheme 3
Scheme 4
Ru3(CO)12-n(PPh3)n (n ) 1-3). Heating a solution of 1 and
PPh3 in the correct molar ratio led to the formation of the desired
phosphine complexes within 1 min of microwave irradiation
(Scheme 2). Product purity was checked by performing 31P
NMR on the entire product mixture. In the case of the synthesis
of Ru3(CO)11(PPh3), some evidence for over-reaction to generate
Ru3(CO)10(PPh3)2 was observed (approximately 5%). A similar
observation was made when preparing Ru3(CO)10(PPh3)2:
Ru3(CO)9(PPh3)3 was present in the product mixture (∼10%).
This is as much, if not more, of an issue in the conventionally
heated protocol.
Since the phosphine-substituted complexes are deep orange
or red, we decided to follow the reaction in real time using a
digital camera interfaced with our microwave unit. We have
used this before to monitor macroscopic effects as organic
reactions proceed, including color and viscosity changes,
evolution of gases, and metal-mediated couplings.20 We decided
to monitor the formation of Ru3(CO)9(PPh3)3. The video is
presented in the Supporting Information. It shows that the
reaction occurs very rapidly upon starting the microwave
irradiation and the characteristic color of the product is clearly
seen growing in intensity. By monitoring reactions in real time,
we can watch for deposition of metal particles on the surface
of the glass reaction vessels as starting materials or products
decompose. These particles, if allowed to form, can superheat
in the microwave field, melt the glass, and lead to failure of
the reaction vessel. They can, to a great extent, be avoided by
ensuring that the reaction mixture is stirred efficiently throughout
the microwave heating process.
Conventionally, 2 is prepared either by passing hydrogen
through a refluxing octane solution of Ru3(CO)12 or in an
23
autoclave (25 atm of H2, 120 °C, 2 h).24 We performed a series
of test reactions using our microwave apparatus. Our attention
focused mainly on the effects of time and temperature on the
outcome of the reaction. We placed a solution of Ru3(CO)12 in
1,2-dichloroethane into our reaction vessel and, after sealing,
loaded it with 50 psi of hydrogen. When the mixture was heated
to 130 °C, we found that the reaction reached completion after
a total time of 15 min and we obtained a good yield of the
desired tetranuclear product (Scheme 4). Running for shorter
times resulted in incomplete conversion. Of added interest was
the observation that, in all of the reactions we performed, while
1
2 was the predominant product, H NMR studies showed the
presence of a second hydride-containing compound. The chemi-
cal shift correlated with the minor product being the previously
reported dihydrido complex H2Ru3(CO)10.25 Since this is a very
reactive species, it was not possible to isolate it from the reaction
mixture. Decreasing the reaction temperature to 80 °C gave
almost exclusively 2 after a reaction time of 15 min, but starting
material remained. Prolonging the reaction time to 30 min led
to better conversion.
Staying with the theme of preparing hydrido-containing
complexes, we turned our attention to the reaction of Os3(CO)12
with dihydrogen. Conventionally, passing hydrogen through a
refluxing octane solution of Os3(CO)12 results in the formation
of the unsaturated complex H2Os3(CO)10.23,26 Prolonged heating
in the presence of hydrogen leads to moderate yields of
H2Os4(CO)12. Using our approach, we converted Os3(CO)12 into
H2Os3(CO)10 nearly quantitatively after 15 min at 150 °C using
an initial hydrogen loading of 50 psi (Scheme 4). No
H2Os4(CO)12 was observed.
We next attempted to prepare the hexanuclear cluster
Ru6C(CO)17 from 1. Traditionally, this was prepared by
thermolysis27,28 or pyrolysis29 of 1. More recently, reaction of
a heptane solution of 1 with ethene under conditions of moderate
We next turned our attention to the reaction of 1 with
phenylacetylene. The interaction of trinuclear ruthenium com-
plexes with unsaturated hydrocarbons has been the subject of
considerable research interest for some years, but few general
patterns of reactivity have been uncovered.21 Terminal alkynes
react with 1 to give the hydrido complexes HRu3(CO)3(Ct CR),
in which the acetylide residue interacts with all three ruthenium
atoms. Using a 1:1 molar ratio of 1 to phenylacetylene and using
1,2-dichloroethane as solvent, we obtained a quantitative
conversion of 1 to HRu3(CO)3(Ct CPh) in 5 min at 100 °C
(Scheme 3). No mononuclear or dinuclear biproducts were
formed in the reaction, unlike the case of conventional heating,
where this can be an issue.
Having shown that ligand exchange reactions can be ef-
ficiently effected using microwave heating and can be monitored
in real time, we turned back to our gas-loading accessory with
the objective of converting 1 into the tetranuclear hydrido
complex H4Ru4(CO)12 (2). This compound finds uses as a
catalyst for a range of synthetic organic transformations.22
(22) For recent examples, see: (a) Dallmann, K.; Buffon, R. J. Mol.
Catal. A: Chem. 2001, 172, 81. (b) Bonelli, B.; Brait, S.; Deabate, S.;
Garrone, E.; Giordano, R.; Sappa, E.; Verre, F. J. Cluster Sci. 2000, 11,
307.
(23) Knox, S. A. R.; Koepke, J. W.; Andrews, M. A.; Kaesz, H. D.
J. Am. Chem. Soc. 1975, 97, 3942.
(24) Bruce, M. I.; Williams, M. I. Inorg. Synth. 1990, 28, 219.
(25) Lewis, J.; Leadbeater, N. E.; Raithby, P. R. J. Organomet. Chem.
1997, 543, 251.
(20) Bowman, M. D.; Leadbeater, N. E.; Barnard, T. M. Tetrahedron
Lett. doi:10.1016/j.tetlet. 2007.10.097.
(21) Raithby, P. R.; Rosales, M. J. AdV. Inorg. Radiochem. 1985, 29,
169.
(26) (a) Kaetz, H. D. Inorg. Synth. 1990, 28, 238. (b) Mingos, D. M. P.
Nature 1972, 236, 99. (c) Lauher, W. J. Am. Chem. Soc. 1978, 100, 5305.

Ru and Os Complexes Using MicrowaVe Heating
Organometallics, Vol. 27, No. 6, 2008 1257
was interfaced with the microwave unit by means of an access port
in the side of the microwave cavity. The face of the lens was
positioned outside the cavity wall and protected with a plastic cover.
Three white light LEDs were placed in the bottom of the microwave
cavity in order to illuminate the reaction vessel. The camera was
connected to a PC via a USB 2.0 interface and controlled using
computer software. Using this, it was possible to record temperature,
pressure, and microwave power profiles at the same time as the
video images.
Preparation of Ru3(CO)12 (1). In a dry 80 mL glass vessel
equipped with a magnetic stirbar were added RuCl3 (30 mg, 0.13
mmol), Cs2CO3 (47 mg, 0.14 mmol), and methanol (15.0 mL). The
vessel was sealed in the microwave apparatus, with a septum
containing ports for pressure and temperature measurement devices.
A pressure of 50 psi of carbon monoxide was introduced into the
vessel, the pressure sensor being kept closed. The line to the carbon
monoxide regulator was then closed and the pressure vented to the
atmosphere through the pressure sensor. This process was repeated
two more times, and then the vessel was loaded to 50 psi and sealed.
With stirring, the reaction mixture was heated to 110 °C using an
initial microwave power of 300 W and was held at this temperature
until a total reaction time of 10 min had elapsed. The reaction
mixture was then cooled to 50 °C, at which time the remaining
pressure was carefully vented. The contents of the reaction vessel
were transferred into a round-bottom flask, and the methanol was
removed on a rotary evaporator. Hexane (30 mL) was added to the
flask and heated to extract Ru3(CO)12. This was repeated three times,
and the combined hexane washings were collected. Removal of
the solvent left pure Ru3(CO)12 in 90% yield.
Reaction of Ru3(CO)12 with Phenylacetylene. In a dry 10 mL
glass vessel equipped with a magnetic stirbar were added Ru3(CO)12
(19.4 mg, 0.03 mmol), phenylacetylene (3.1 mg, 0.03 mmol), and
1,2-dichloroethane (2 mL). The vessel was sealed with a septum
and placed in the microwave apparatus. With stirring, the reaction
mixture was heated to 100 °C using an initial microwave power of
300 W and was held at this temperature for 5 min. The reaction
mixture was then cooled to 50 °C, the contents were transferred
into a round-bottom flask, and the solvent was removed on a rotary
evaporator. The residue was dissolved in dichloromethane (30 mL)
and silica gel (9.5 g) added. The solvent was then removed, leaving
the product adsorbed on the silica. The silica was washed with
hexane to remove unreacted starting materials and then with
dichloromethane to elute the product which, upon removal of the
solvent, was obtained in 98% yield.
Reaction of Ru3(CO)12 with Triphenylphosphine. In a dry 10
mL glass vessel equipped with a magnetic stirbar were added
Ru3(CO)12 (30 mg, 0.05 mmol), triphenylphosphine (36 mg, 0.15
mmol), and 1,2-dichloroethane (2 mL). The vessel was sealed with
a septum and placed in the microwave apparatus. With stirring,
the reaction mixture was heated using an initial microwave power
of 300 W for 1 min, at which point the reaction mixture had reached
110 °C. The reaction mixture was then cooled to 50 °C, the contents
were transferred into a round-bottom flask, and the solvent was
removed on a rotary evaporator. The product was isolated using
the same procedure as in the case of the reaction of Ru3(CO)12
with phenylacetylene to give Ru3(CO)9(PPh3)3 in 92% yield.
Preparation of H4Ru4(CO)12 (2). In a dry 80 mL glass vessel
equipped with a magnetic stirbar were added Ru3(CO)12 (30 mg,
0.05 mmol) and 1,2-dichloroethane (15.0 mL). The vessel was
sealed in the microwave apparatus, with a septum containing ports
for pressure and temperature measurement devices. A pressure of
50 psi of hydrogen was introduced into the vessel, the pressure
sensor being kept closed. The line to the hydrogen regulator was
then closed and the pressure vented to the atmosphere through the
pressure sensor. This process was repeated two more times, and
then the vessel was loaded to 50 psi and sealed. With stirring, the
reaction mixture was heated to 130 °C using an initial microwave
temperature and pressure (150 °C; 30 atm) has been shown to
generate Ru6C(CO)17 in substantially higher yields.30 Mecha-
nistic studies have shown that this reaction involves the
formation of “Ru(CO)3” type intermediates.31 Using our mi-
crowave apparatus, 1 as starting material, and dichloroethane
as solvent and loading the reaction vessel with ethene, we
screened a range of reaction conditions for the formation of
Ru6C(CO)17, but without success. In the majority of cases, 1
was recovered quantitatively, indicating that no reaction was
taking place. With the combination of a pressure of ethene and
the autogenic pressure of the solvent at elevated temperatures,
there is a limit to the initial loading pressure and the temperature
to which reaction mixtures can be heated. At lower loading
pressures we can reach higher reaction temperatures, and
conversely, at higher loading pressures we are limited by the
temperature to which we can heat the reaction mixture. We
believe that these limitations are preventing us from reaching
conditions under which reaction to generate the mononuclear
fragments necessary for formation of Ru6C(CO)17 will occur.
Conclusion
In summary, we have shown here how microwave heating is
a useful tool for the preparation of ruthenium and osmium
complexes. By using our gas-loading accessory, we have
developed a fast and easy route to Ru3(CO)12, H4Ru4(CO)12,
and H2Os3(CO)10. We have studied the ligand substitution
reactions of Ru3(CO)12 with triphenylphosphine and pheny-
lacetylene. In the case of the former, we followed the reaction
in real time using a digital camera interfaced with our microwave
unit. These initial results build on the limited reports in the
literature using microwave heating for the preparation of
organometallics and show the potential for the technique. Work
is now underway to prepare other important classes of orga-
nometallic complexes as well as develop routes to complexes
previously inaccessible using conventional heating.
Experimental Section
General Experimental Conditions. All reagents were obtained
from commercial suppliers and used without further purification.
1H NMR spectra were recorded at 293 K on a 300 or 400 MHz
spectrometer. IR spectra were recorded on a Jasco FT-IR-4000
spectrophotometer. Reactions were performed using a CEM Dis-
cover microwave unit. This consists of a continuous focused
microwave power delivery system with operator-selectable power
output from 0 to 300 W. Reactions were performed in either 10 or
80 mL capacity sealed tubes. The temperature of the contents of
the vessel was monitored using an IR sensor located underneath
the reaction vessel or a fiber-optic temperature probe inserted
directly into the reaction mixture. Pressure was controlled by a load
cell connected directly to the vessel. The contents of the reaction
vessel were stirred by means of an electromagnet located below
the floor of the microwave cavity and a Teflon-coated magnetic
stirbar in the vessel. Temperature, pressure, and power profiles were
monitored using commercially available software provided by the
microwave manufacturer. For real-time reaction monitoring, a CEM
Discover S-class microwave unit was used. A 1.3 megapixel camera
(27) Johnson, B. F. G.; Johnston, R. D. Lewis, J. J. Chem. Soc. A 1968,
2865.
(28) Williams, I. G. J. Chem. Soc. A 1970, 901.
(29) Eady, C. R.; Johnson, B. F. G.; Lewis, J. J. Chem. Soc., Dalton
Trans. 1975, 2606.
(30) Johnson, B. F. G.; Lewis, J.; Sankey, S. W.; Wong, K.; McPartlin,
M.; Nelson, W. J. H. J. Organomet. Chem. 1980, 191, C3.
(31) Leadbeater, N. E. Inorg. Chim. Acta 1998, 278, 250.

1258 Organometallics, Vol. 27, No. 6, 2008
Leadbeater and Shoemaker
power of 300 W and held at this temperature until a total reaction
time of 15 min had elapsed. The reaction mixture was then cooled
to 50 °C, at which point the remaining pressure was carefully
vented. The contents of the reaction vessel were transferred into a
round-bottom flask, and the solvent was removed on a rotary
evaporator. Analysis by 1H NMR spectroscopy relative to an
internal standard showed a near-quantitative conversion to the
desired product.
Preparation of H2Os3(CO)10. In a dry 80 mL glass vessel
equipped with a magnetic stirbar were added Os3(CO)12 (30 mg,
0.03 mmol) and 1,2-dichloroethane (15.0 mL). The vessel was
sealed and loaded with hydrogen in the same way as in the case of
the reaction with Ru3(CO)12. With stirring, the reaction mixture
was heated to 150 °C using an initial microwave power of 300 W
and held at this temperature until a total reaction time of 15 min
had elapsed. After cooling and removal of the solvent, analysis by
IR and 1H NMR spectroscopy showed a near-quantitative conver-
sion to the desired product.
Acknowledgment. Pfizer, the Connecticut Business &
Industry Association (CBIA), and the Petroleum Research
Foundation, administered by the American Chemical Society,
are thanked for funding and CEM Corp. is thanked for
equipment support. Input from T. Michael Barnard is
gratefully acknowledged.
Supporting Information Available: Video file for the reaction
of Ru3(CO)12 with PPh3 to form Ru3(CO)9(PPh3)3 and instructions
on how to view it. This material is available free of charge on the
Internet at http://pubs.acs.org.
OM701099P