It proved possible to selectively reduce the ester group of
the molybdenum complex 2 by diisobutylaluminum hy-
dride at ꢀ100 °C to attain the corresponding aldehyde 3 in
an acceptable yield (39%) (Scheme 2)
Scheme 2. Synthesis and Reactivity of the Phosphinine 2-Car-
boxaldehyde
Figure 2. LUMO of 2-formylphosphinine (KohnꢀSham).
complexing group without altering the aldehyde function-
ality. The use of a chelating diphosphine proved to be
uneffective. The use of carbon monoxide under pressure
proved to be satisfactory. Since the reaction is an equili-
brium, the displacement is not complete, but a conversion
of 83% was achieved under 50 bar of CO at 60 °C and 4 was
recovered in yields as high as 75% due to the very low rate of
the reverse complexation reaction at room temperature.
In 4, both the carbonyl carbon and the phosphorus are
highly electrophilic. DFT calculations on 2-formylphosphi-
nine at the RB3YP/6-311þG(D,P) level show that the
LUMO is highly localized at both P and the formyl
carbon (Figure 2). The problem was then to check
whether it is possible to perform a selective reaction
at the aldehyde. The Wittig reaction of a stabilized ylid8
with 4 afforded the corresponding alkene 5 in 91%
yield. The aldehyde 4 is thus a good building block for
the synthesis of complex structures containing phos-
phinines. Since these phosphinines have already found
numerous uses in homogeneous catalysis9 and that
some applications in conjugated materials for optoe-
lectronics are starting to appear,10 it seems clear that
this advance offers several interesting perspectives.
Complex 3 was fully characterized by NMR spectro-
scopy6 and X-ray crystal structure analysis (Figure 1). The
formyl group appears at 10.29 (3JHP = 4.6 Hz) on the
proton spectrum and at 190.67 ppm (2JCP = 27.1 Hz) on
the carbon spectrum (CDCl3). The formyl group is copla-
nar with the phosphinine ring whereas the phenyl ring is
forced to rotate out of this plane by 79.7° due to the steric
repulsion by the complexing group. The two PꢀC bonds
˚
are inequivalent at 1.719(3) [PꢀC(CHO)] and 1.729(3) A.
˚
The PꢀMo bond is relatively short at 2.4761(8) A. All of
these data are very close to those of the parent phosphinine
Mo(CO)5 complex.7 The problem then was to remove the
(5) Le Floch, P.; Carmichael, D.; Mathey, F. Organometallics 1991,
10, 2432.
(6) (3): 31P NMR (CDCl3):
δ δ
212.5; 1H NMR (CDCl3):
2.16 (d, JHP = 2.7 Hz, 3H, CH3), 2.51 (d, JHP = 5.5 Hz, 3H, CH3), 7.21ꢀ
7.51(m, 5H, Ph), 8.28(d, 3JHP = 14.6 Hz, 1H, dCH ring), 10.29 (d, 3JHP
=
4.6 Hz, 1H, CHO); 13C NMR (CDCl3): δ 20.51 (d, JCP = 4.5 Hz, CH3),
23.25 (d, JCP = 3.7 Hz, CH3), 128.38 (d, JCP = 2.4 Hz, dCH), 128.99 (d,
Acknowledgment. The authors thank the Nanyang
Technological University in Singapore for the financial
support of this work and Dr. Li Yongxin (NTU) for the
X-ray crystal structure analysis.
JCP = 1.1 Hz, dCH), 130.35 (d, JCP = 8.2 Hz, dCH), 138.17 (d, JCP
=
21.5 Hz, dC), 140.12 (d, JCP = 17.4 Hz, dC), 140.25 (d, 2JCP = 14.2 Hz,
dCH), 150.30 (d, JCP = 10.7 Hz, dC), 152.91 (d, JCP = 6.2 Hz, dC),
167.84 (d, JCP = 9.0 Hz, dC), 190.67 (d, 2JCP = 27.1 Hz, CHO), 203.21
2
2
(d, JCP = 11.0 Hz, cis-CO), 208.93 (d, JCP = 32.7 Hz, trans-CO);
HRMS m/z 464.9440 (calcd for C19H12MoO6P 464.9426) (4): 31P NMR
(CDCl3): δ 215.1; 1H NMR (CDCl3): δ 2.30 (d, JHP = 1.9 Hz, 3H, CH3),
Supporting Information Available. Experimental sec-
tion and X-ray data for 3. This material is available free of
2.53 (d, JHP = 3.3 Hz, 3H, CH3), 7.29ꢀ7.48 (m, 5H, Ph), 8.30 (d, 3JHP
=
5.0 Hz, 1H, dCH ring), 10.14 (d, 3JHP = 2.6 Hz, 1H, CHO); 13C NMR
(CDCl3): δ 19.49 (s, CH3), 23.48 (d, JCP = 2.1 Hz, CH3), 127.48 (d,
JCP = 2.0 Hz, dCH), 128.29 (s, dCH), 129.40 (d, JCP = 8.6 Hz, dCH),
136.45 (d, JCP = 13.2 Hz, dCH), 141.19 (d, JCP = 14.9 Hz, dC), 142.81
(7) Ashe, A. J., III; Butler, W.; Colburn, J. C.; Abu-Orabi, S.
J. Organomet. Chem. 1985, 282, 233.
(8) Werkhoven, T. M.; van Nispen, R.; Lugtenburg, J. Eur. J. Org.
2
(d, JCP = 25.6 Hz, dC), 146.75 (d, JCP = 10.6 Hz, dC), 160.37
(d, 1JCP = 46.9 Hz, dC;P), 171.69 (d, 1JCP = 48.4 Hz, dC;P), 193.11
(d, 2JCP = 44.9 Hz, CHO); HRMS m/z 227.0626 (calcd for C14H12OP
Chem. 1999, 2909.
1
227.0626). (5): 31P NMR (CDCl3): δ 195.2; H NMR (CDCl3): δ 1.35
(9) Mueller, C.; Vogt, D. Dalton Trans. 2007, 5505. Reetz, M. T.;
Guo, H. Synlett 2006, 2127. Le Floch, P. Coord. Chem. Rev. 2006, 250,
627. Breit, B.; Winde, R.; Mackewitz, T.; Paciello, R.; Harms, K.
Chem.;Eur. J. 2001, 7, 3106. Le Floch, P.; Knoch, F.; Kremer, F.;
Mathey, F.; Scholz, J.; Scholz, W.; Thiele, K.-H.; Zenneck, U. Eur. J.
Inorg. Chem. 1998, 119.
(10) Komath, M. S.; Gudat, D. Dalton Trans. 2010, 39, 4280.
Goettmann, F.; Moores, A.; Boissiere, C.; Le Floch, P.; Sanchez, C.
Small 2005, 1, 636. Moores, A.; Goettmann, F.; Sanchez, C.; Le Floch,
P. Chem. Commun. 2004, 2482.
3
(t, JHH = 7.1 Hz, 3H, CH3), 2.23 (d, JHP = 1.9 Hz, 3H, CH3), 2.47
(d, JHP = 3.4 Hz, 3H, CH3), 4.27(q, 2H, OCH2), 6.67 (dd, 3JHH = 15.8 Hz,
4JHP = 3.2 Hz, 1H, dCH substituent), 7.28ꢀ7.45 (m, 5H, Ph), 7.81 (d,
3JHP = 5.4 Hz, 1H, dCH ring), 7.92 (dd, 3JHH = 15.8 Hz, 3JHP = 12.2
Hz, 1H, dCH substituent); 13C NMR (CDCl3): δ 14.33 (s, CH3), 18.89
(s, CH3), 23.52 (s, CH3), 60.47 (s, OCH2), 117.61(d, JCP = 22.8 Hz,
dCH), 127.19 (s, dCH), 128.29 (s, dCH), 129.40 (d, JCP = 8.6 Hz,
dCH), 136.08 (d, JCP = 13.0 Hz, dCH), 140.71 (d, JCP = 14.4 Hz, dC),
142.56 (d, JCP = 12.2 Hz, dC), 142.95 (d, JCP = 25.5 Hz, dC), 146.77 (d,
2JCP = 29.3 Hz, dCH substituent), 159.37 (d, 1JCP = 48.2 Hz, dC;P),
166.93 (s, CO), 171.45 (d, 1JCP = 48.2 Hz, dC;P), 193.11 (d, 2JCP
=
44.9 Hz, CHO); HRMS m/z 297.1038 (calcd for C18H18O2P 297.1044).
The authors declare no competing financial interest.
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