Fig. 4 Raman spectra of Mo(CO)6 in PPh3 as a function of time upon
microwave irradiation (in the region 2400–1500 cm21).
Our results show the potential for using in situ Raman
spectroscopy as a tool for monitoring the progress of organome-
tallic reactions performed using microwave heating. Work is now
underway to broaden the scope of the method for organometallic
reactions as well as expand it to organic and metal-mediated
catalytic transformations.
Fig. 2 Raman spectra of Mo(CO)6 in pyridine as a function of time
upon microwave irradiation (in the region 2400–1500 cm21).
Enwave Optronics is thanked for supplying the Raman
spectroscopy module. The University of Connecticut is acknowl-
edged for funding.
Notes and references
1 For recent reviews on the general area of microwave-promoted organic
synthesis see: (a) C. O. Kappe, Angew. Chem., Int. Ed., 2004, 43, 6250;
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2 For examples see: (a) S. L. VanAtta, B. A. Duclos and D. B. Green,
Organometallics, 2000, 19, 2397; (b) M. Ardon, G. Hogarth and
D. T. W. Oscroft, J. Organomet. Chem., 2004, 689, 2429; (c)
D. R. Baghurst, D. M. P. Mingos and J. Watson, J. Organomet.
Chem., 1989, 368, C43; (d) D. R. Baghurst, S. R. Cooper, D. L. Greene,
D. M. P. Mingos and S. M. Reynolds, Polyhedron, 1990, 9, 893; (e)
N. Kuhnert and T. N. Danks, J. Chem. Res., 2002, 66.
3 For a review see: G. A. Tompsett, W. C. Conner and K. S. Yngvesson,
ChemPhysChem, 2006, 7, 296.
4 G. R. Robb, A. Harrison and A. G. Whittaker, Phys. Chem. Commun.,
2002, 135.
5 W. H. Dokter, T. P. M. Beelen, H. F. Vangarderen, R. A. Vansanten,
W. Bras, G. E. Derbyshire and G. R. Mant, J. Appl. Crystallogr., 1994,
27, 901.
6 S. Y. Yang and A. Navrotsky, Chem. Mater., 2004, 16, 3682.
7 S. Hocde´, C. Pledel-Boussard, D. Le Coq, G. Fonteneau and J. Lucas,
Proc. SPIE-Int. Soc. Opt. Eng., 1999, 3849, 50.
8 D. E. Pivonka and J. R. Empfield, Appl. Spectrosc., 2004, 58, 41.
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1998, 177, 201; (b) J. R. Schoonover and G. F. Strouse, Chem. Rev.,
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10 For recent examples see: (a) A. Gabrielsson, F. Hartl, H. Zhang,
J. R. Lindsay Smith, M. Towrie, A. Vlcek and R. N. Perutz, J. Am.
Chem. Soc., 2006, 128, 4253; (b) I. V. Rubtsov, Y. K. Kang,
N. P. Redmore, R. M. Allen, J. Zheng, D. N. Beratan and
M. J. Therien, J. Am. Chem. Soc., 2004, 126, 5022; (c)
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Fig. 3 Raman spectra of Mo(CO)6 in octylamine as a function of time
upon microwave irradiation (in the region 2400–1500 cm21).
Mo(CO)3(py)3. Holding the reaction mixture at 180 uC for a
further 1 min resulted in further conversion to Mo(CO)3(py)3.
The results of a similar study using octylamine (oct) are shown
in Fig. 3. Formation of Mo(CO)5(oct) (2072 cm21 and 1976 cm21
)
and some Mo(CO)4(oct)2 (1899 cm21) was observed after 20 s
microwave heating. Heating for 1 min leads to the formation of
more Mo(CO)4(oct)2 but prolonging the microwave irradiation to
3 min leads to extensive decomposition.
We also performed the reaction using triphenylphosphine as a
ligand. The reaction mixture was heated from 100 uC to 160 uC
over a period of 60 s using a microwave power of 150 W and
monitoring the Raman spectrum in the region 2400–1500 cm21
(Fig. 4). The bands from the parent hexacarbonyl decreased in
intensity and three new bands grew in at 2073 cm21, 1988 cm21
and 1943 cm21 (the band at 1584 cm21 originates from
triphenylphosphine). By comparison with literature data,11 the
three bands can be attributed to the formation of Mo(CO)5(PPh3).
Holding the reaction mixture at 160 uC for a further 1 min has
little effect.
11 T. N. Day, P. J. Hendra, A. J. Rest and A. J. Rowlands, Spectrochim.
Acta, Part A, 1991, 47A, 1251.
3616 | Chem. Commun., 2006, 3615–3616
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