Decomplexation of phosphirane and phosphirene complexes

Article abstract of DOI:10.1021/om060570t

Novel transient phosphinidene complex Ph-P=Mo(CO)₄PMe ₃, generated from a 7-phosphanorbornadiene precursor, adds to C=C and C≡C bonds to give Mo(CO)₄PMe₃-complexed phosphiranes and phosphirenes. The cis-PMe₃ ligand weakens the interaction between the molybdenum complex and the three-membered ring. Under mild CO pressure the Mo(CO)₄PMe₃ transition metal group detaches from the phosphorus center of the ring structure by selective CO substitution. The resulting byproduct Mo(CO)₅PMe₃ can be reused in the synthesis of the phosphinidene precursor.

Full text of DOI:10.1021/om060570t

5286
Organometallics 2006, 25, 5286-5291
Decomplexation of Phosphirane and Phosphirene Complexes
Sander G. A. van Assema, Frans J. J. de Kanter, Marius Schakel, and Koop Lammertsma*
Department of Chemistry, Faculty of Sciences, Vrije UniVersiteit, De Boelelaan 1083, NL-1081 HV
Amsterdam, The Netherlands
ReceiVed June 28, 2006
Novel transient phosphinidene complex Ph-PdMo(CO)4PMe3, generated from a 7-phosphanor-
bornadiene precursor, adds to CdC and CtC bonds to give Mo(CO)4PMe3-complexed phosphiranes
and phosphirenes. The cis-PMe3 ligand weakens the interaction between the molybdenum complex and
the three-membered ring. Under mild CO pressure the Mo(CO)4PMe3 transition metal group detaches
from the phosphorus center of the ring structure by selective CO substitution. The resulting byproduct
Mo(CO)5PMe3 can be reused in the synthesis of the phosphinidene precursor.
Scheme 1. Synthesis of Uncomplexed Phosphiranes
Introduction
Phosphirane (1), the phosphorus homologue of cyclopropane,
has received much attention in the past two decades as new
synthetic routes became available that made use of the stabiliza-
tion rendered by transition metal groups.1 Whereas uncomplexed
phosphiranes can be obtained, for example, from the reaction
of a metal phosphide and a diol ditosylate (see Scheme 1),2
their limited thermal stability and sensitivity toward oxidation
not only complicates their isolation but also restricts the
versatility of the reaction. Phosphiranes have also been synthe-
sized by carbene addition to a phosphaalkene, by salt elimination
from the reaction of RPX2 with 1,2-dimetallic derivatives of
alkanes, and by cyclization of C-P-C units.3 The stability of
phosphiranes improves with bulky substituents on the phos-
phorus atom, but they remain photolytically labile4 and subject
to [2+1] cycloreversion,5 retro-electrocyclization,6 and ring-
chain rearrangement.7
Scheme 2. Two Phosphinidene Precursors
Scheme 3. Addition Reactions of a Phosphinidene
Transition Metal Complex
Phosphiranes with a transition metal complex coordinated to
the phosphorus center are intrinsically more stable. Several
methods have been reported to obtain these complexed hetero-
cycles. A popular method is the addition of a transient
electrophilic phosphinidene R-PdM(CO)5 (M ) Cr, Mo, W)
to the CdC bond of a suitable substrate. The most widely used
precursor, 7-phosphanorbornadiene complex 2, generates this
phosphinidene through thermal cheletropic elimination.8 Re-
cently, a new precursor was developed, 3H-3-benzophosphepine
complex 3 (Scheme 2),9 that offers more flexibility in the choice
of the transition metal complex. It has also been shown that
transient R2N-PdFe(CO)4, generated from Collman’s reagent,
adds to double bonds, albeit only to terminal ones.10 Still other
precursors have been reported that are capable of transferring
(trapping) electrophilic phosphinidene complexes by addition
to olefins and alkynes to generate isomeric phosphiranes 5 and
phosphirenes 4 (Scheme 3). Azaphosphirene complexes11 and
1-amino-phosphirane and -phosphirene complexes12 have also
been used to generate electrophilic phosphinidenes.
(1) For recent reviews: (a) Lammertsma, K. Top. Curr. Chem. 2003,
229, 95. (b) Lammertsma, K.; Vlaar, M. J. M. Eur. J. Org. Chem. 2002,
1127. (c) Mathey, F.; Tran Huy, N. H.; Marinetti, A. HelV. Chim. Acta
2001, 84, 2938.
(2) Li, X.; Robinson, K. D.; Gaspar, P. P. J. Org. Chem. 1996, 61, 7702.
(3) Mathey, F. Phosphorus-Carbon Heterocyclic Chemistry: The Rise
of a New Domain; Pergamon: Amsterdam, 2001; pp 40-51.
(4) Recent reviews: (a) Dillon, K. B.; Mathey, F.; Nixon, J. F.
Phosphorus: the Carbon Copy; Wiley: New York, 1998; p 182. (b) Mathey,
F.; Regitz, M. ComprehensiVe Heterocyclic Chemistry II; Padwa, A., Ed.;
Elsevier: Amsterdam, 1996; p 277.
(5) Li, X.; Weissman, S. I.; Lin, T.-S.; Gaspar, P. P. J. Am. Chem. Soc.
1994, 116, 7899.
(6) Chaquin, P.; Gherbri, A. J. Org. Chem. 1995, 60, 3723.
(7) (a) Nguyen, M. T.; Landuyt, L.; Vanquickenborne, L. G. J. Chem.
Soc., Faraday Trans. 1994, 90, 1771. (b) Wang, B.; Lake, C. H.;
Lammertsma, K. J. Am. Chem. Soc. 1996, 118, 1690.
There are only a few methods to remove a transition metal
complex from the three-membered heterocycles, but none works
reliably and consistently for all systems, possibly in part due to
the perceived sensitivity of the uncomplexed products. Decom-
(9) Borst, M. L. G.; Bulo, R. E.; Winkel, C. W.; Gibney, D. J.; Ehlers,
A. W.; Schakel, M.; Lutz, M.; Spek, A. L.; Lammertsma, K. J. Am. Chem.
Soc. 2005, 127, 5800.
(10) (a) Wit, J. B. M.; van Eijkel, G. T.; de Kanter, F. J. J.; Schakel, M.;
Ehlers, A. W.; Lutz, M.; Spek, A. L.; Lammertsma, K. Angew. Chem. 1999,
111, 2716; Angew. Chem., Int. Ed. 1999, 38, 2596. (b) Wit, J. B. M.; van
Eijkel, G. T.; Schakel, M.; Lammertsma, K. Tetrahedron 2000, 56, 137.
(11) (a) Streubel, R.; Wilkens, H.; Ostrowski, A.; Neumann, C.; Ruthe,
F.; Jones, P. G. Angew. Chem. 1997, 109, 1549; Angew. Chem., Int. Ed.
Engl. 1997, 36, 1492. (b) Wilkens, H.; Ruthe, F.; Jones, P. G.; Streubel, R.
Chem. Commun. 1998, 1529.
(8) (a) Marinetti, A.; Mathey, F.; Fischer, J.; Mitschler, A. J. Am. Chem.
Soc. 1982, 104, 4484. (b) Marinetti, A.; Mathey, F. Organometallics 1982,
1, 1488.
(12) Mercier, F.; Deschamps, B.; Mathey, F. J. Am. Chem. Soc. 1989,
111, 9098.
10.1021/om060570t CCC: $33.50 © 2006 American Chemical Society
Publication on Web 09/28/2006

Decomplexation of Phosphirane and Phosphirene Complexes
Organometallics, Vol. 25, No. 22, 2006 5287
Scheme 4. Synthesis of a Novel Phosphinidene Precursor
plexation of the W(CO)5 group has been explored most. One
approach is the selective oxidation with iodine to weaken the
W-P bond followed by ligand exchange with N-methylimida-
zole.13 In a variation of this method, pyridinium tribromide is
used for the oxidation of W(0) to W(II) and 2,2′-bipyridine for
the displacement of the phosphine.14 The use of this method
for the decomplexation of sensitive compounds such as phos-
phiranes is very limited, and to the best of our knowledge, only
one such example has been reported.15
Direct exchange for a bidentate diphosphine ligand has been
reported to work only for very stable phosphiranes, as high
temperatures (∼150 °C) are needed.16a With this method,
phospholes and 1-chlorophosphirenes can also be demetalated.16b,c
Trimethylamine N-oxide has been reported as a reagent for
oxidative decomplexation of a P-W(CO)5 complex to the
corresponding phosphoryl compound.17 Finally, the electro-
chemical decomplexation of phosphine-W(CO)5 complexes has
been reported for phosphole compounds.18
Photodissociation of the transition metal group has received
little attention, probably because the reverse process is used to
exchange CO for phosphine ligands in metal carbonyl com-
plexes.19 However, TD-DFT calculations on (C2H4)PH-Cr-
(CO)5 and H3P-Cr(CO)5 suggested that photochemical decom-
plexation may be a viable option.20 PB88/TZP calculations also
indicated that the phosphirane-Mo(CO)5 complex weakens by
4 kcal/mol on replacing a CO for a PH3 ligand.
this phosphinidene will be added to olefins and alkynes. Such
phosphiranes coordinated to a transition metal carbonyl complex
carrying an additional phosphine ligand are rare. We are aware
of only a phosphirane Fe complex with a bidentate diphosphine
ligand22 and bidentate phosphine Mo complexes in which the
second phosphine is linked to the phosphirane ring.23 Finally,
the demetalation from the phosphiranes and phosphirenes will
be discussed.
Synthesis of Phosphinidene Precursor 8. This phosphanor-
bornadiene derivative can be obtained by cycloaddition of an
acetylene derivative and 3,4-dimethylphosphole-Mo(CO)4PMe3
complex 7. The synthesis of 7 was pursued first by the addition
of both phosphorus ligands 1-phenyl-3,4-dimethylphosphole and
PMe3 to cis-Mo(CO)4(piperidine)2, but surprisingly this
reaction yielded mostly bis-trimethylphosphine complex cis-
Mo(CO)4(PMe3)2. Sequential addition, starting with the phos-
phole followed by PMe3, gave mixtures of phosphine complexes
with cis-Mo(CO)4(PMe3)2 as the major product. A more
successful procedure started with the synthesis of Mo(CO)5PMe3,
6 (75% yield), from Mo(CO)6 by oxidation with trimethylamine
N-oxide, followed by replacement of the in-situ-formed aceto-
nitrile complex with trimethylphosphine. Exchange of a cis-
CO ligand for 1-phenyl-3,4-dimethylphosphole by UV irradia-
tion in THF gave the desired Mo complex 7 (61% yield). Its
31P NMR spectrum shows doublets (2J(P,P) ) 24.5 Hz) at
+33.6 ppm for the phosphole ligand and at -15.3 ppm for the
PMe3 ligand. Diels-Alder reaction of 7 with dimethyl acetyl-
enedicarboxylate yielded phosphinidene precursor 8 in 50%
isolated yield (Scheme 4).
Phosphinidene Additions. Heating a toluene solution of
phosphanorbornadiene complex 8 and diphenylacetylene at 70
°C results in the rapid addition of transient PhPdMo(CO)4PMe3
to the CtC bond to give the Mo-complexed phosphirene 9 in
39% yield (Scheme 5). This yield is slightly higher than the
29% yield reported for the addition of transient PhPdMo(CO)5,
which is generated at 120 °C.14 Generally, because of the
stronger W-P bond, higher yields are obtained with tungsten
phosphinidene complexes. Only very recently was a higher yield
of 66% reported by using a benzophosphepine phosphinidene
precursor (Scheme 2, M ) Mo) at 75-80 °C.9 However, we
could not use this precursor because it lacks the additional PMe3
ligand. The 31P NMR resonance at -130.0 ppm is normal for
To expand the access to metal-free phosphorus heterocycles,
which have potential in asymmetric catalysis,21 we report on a
decomplexation procedure that is based on pressurized reactions
in a CO atmosphere. As proof of principle, we use as substrates
phosphirene and phosphirane molybdenum carbonyl complexes
carrying one additional phosphine ligand.
Results and Discussion
The first step is the synthesis of phosphinidene precursor 8,
based on the 7-phosphanorbornadiene unit, having
a
Mo(CO)4PMe3 group coordinated to the phosphorus atom. Next
(13) (a) Marinetti, A.; Mathey, F.; Fischer, J.; Mitschler, A. J. Chem.
Soc., Chem. Commun. 1984, 45. (b) A recent example: van Eis, M. J.;
Zappey, H.; de Kanter F. J. J.; de Wolf, W. H.; Lammertsma, K.;
Bickelhaupt, F. J. Am. Chem. Soc. 2000, 122, 3386.
(14) Marinetti, A.; Fischer, J.; Mathey, F. J. Am. Chem. Soc. 1985, 107,
5001.
(15) (a) Krill, S.; Wang, B.; Hung, J. -T.; Horan, C. J.; Gray, G. M.;
Lammertsma. K. J. Am. Chem. Soc. 1997, 119, 8432.
(16) (a) Slootweg, J. C.; Schakel, M.; de Kanter, F. J. J.; Ehlers, A. W.;
Kozhushkov, S. I.; De Meijere, A.; Lutz, M.; Spek, A. L.; Lammertsma,
K. J. Am. Chem. Soc. 2004, 126, 3050. (b) Deschamps, B.; Mathey, F.
Synthesis 1995, 941. (c) Espinosa-Ferao, A.; Deschamps, B.; Mathey, F.
Bull. Soc. Chim. Fr. 1993, 130, 695.
(17) Tran Huy, N. H.; Mathey, F. J. Org. Chem. 2000, 65, 652.
(18) Yakhvarov, D. G.; Budnikova, Y. H.; Tran Huy, N. H.; Ricard, L.;
Mathey, F. Organometallics 2004, 23, 1961.
(19) (a) Wrighton, M. S. Chem. ReV. 1974, 74, 401. (b) Geoffroy, G.
L.; Wrighton, M. S. Organometallic Chemistry; Academic Press: New York,
1974; Chapter 2. (c) For a recent example, see: Darensbourg, D. J.; Ortiz,
C. G.; Kamplain, J. W. Organometallics 2004, 23, 1747.
(20) Goumans, T. P. M.; Ehlers, A. W.; van Hemert, M. C.; Rosa, A.;
Baerends, E. J.; Lammertsma, K. J. Am. Chem. Soc. 2003, 125, 3558.
(21) (a) Marinetti, A.; Mathey, F.; Ricard, L. Organometallics 1993, 12,
1207. (b) Liedtke, J.; Loss, S.; Widauer, C.; Gru¨tzmacher, H. Tetrahedron
2000, 56, 143.
(22) Bader, A.; Kang, Y. B.; Pabel, M.; Pathak, D. D.; Willis, A. C.;
Wild, S. B. Organometallics 1995, 14, 1434.
(23) (a) van Assema, S. G. A.; Ehlers, A. W.; de Kanter, F. J. J.; Schakel,
M.; Spek, A. L.; Lutz, M.; Lammertsma, K. Chem. Eur. J. 2006, 12, 4333.
(b) Vlaar, M. J. M.; van Assema, S. G. A.; de Kanter, F. J. J.; Schakel, M.;
Spek, A. L.; Lutz, M.; Lammertsma, K. Chem. Eur. J. 2002, 8, 58.

5288 Organometallics, Vol. 25, No. 22, 2006
Van Assema et al.
Scheme 6. Synthesis of Phosphirane Complexes
Scheme 5. Synthesis of a Phosphirene Complex
a Mo-complexed phosphirene, and that at -14.2 ppm for PMe3
is similar to that of 8; the 2J(P,P) coupling constant of 32.4 Hz
is normal for cis-diphosphine compounds.
The reaction of 8 with the CdC bond of trans-stilbene gave
phosphirane complex 10, but in low isolated yield (21%) due
to product decomposition during the reaction. Reaction of 8 with
styrene resulted in the formation (51%) of a mixture of
diastereomeric phosphiranes 11a and 11b (ratio 8:1) in which
the Mo(CO)4PMe3 group is oriented respectively anti and syn
to the phenyl substituent of the ring. The products could be
separated by crystallization. The anti assignment of the major
isomer is based on steric considerations, as we were unable to
grow suitable crystals for an X-ray crystal structure determi-
nation. Addition reactions to sterically more hindered alkenes,
Scheme 7. Phosphirene Decomplexation
Scheme 8. Phosphirane Decomplexation
t
such as Ph2CdCH2 and BuCHdCH2, did not result in the
formation of the desired phosphiranes. The 31P NMR resonances
of phosphirane complexes 10 (-89.5) and 11 (a -125.6; b
-124.6) are similar to those of the W(CO)5 complexes.24 During
the synthesis of 10 and 11 small amounts (<5%) of the
demetalated products were detected by their 31P NMR reso-
nances at -147 and -182 ppm, respectively. This suggests that
mild heating may suffice to remove the transition metal group,
which can be captured by CO under pressurized condition.
Demetalation. The decomplexation of Mo complex 9 occurs
already at 60 °C to give over 48 h the known free triphen-
ylphosphirene 1215 in 94% isolated yield. Also the metal
fragment is nearly quantitatively recovered as Mo(CO)5PMe3
(6) and can be reused in the synthesis of 8. Removal of the
transition metal group results in a 57 ppm shielding of the 31P
NMR chemical shift to -187.4. ppm. Free PMe3 is not observed
under the reaction conditions.
Scheme 9. Possible Reaction Path for Decomplexation
Decomplexation of phosphirane 10 occurs likewise, but more
care has to be exercised because of the sensitivity of the product
to oxygen. Thus, heating 10 (δ(31P) -88.6 and -15.2 ppm,
2J(P,P) 30.5 Hz) at 60 °C for 24 h resulted in the near
quantitative formation of free triphenylphosphirane 13 (δ(31P)
) -147.5 ppm) and Mo(CO)5PMe3 (δ(31P) ) -15.1 ppm). Also
Scheme 10. Thermolysis of Phosphirene-Transition Metal
Complexes
2
complex 11a (δ(31P) -125.6 and -14.6 ppm, J(P,P) ) 31.4
Hz) is converted at 60 °C to the free phosphirane (14, δ(31P)
-182.2 ppm) without isomerization. Monitoring the decom-
plexing of a 11a,b mixture by 31P NMR shows the formation
of both phosphirane isomers 14 (δ(31P) ) -182.2 and -197.2
ppm) in the same ratio. Phosphirane 14 is thermally not very
stable and undergoes slow degradation at 60 °C, thereby
lowering the observed ratio of phosphirane to Mo(CO)5PMe3.
Decomplexation of phosphiranes 10 and 11 was performed on
a 5 mg scale. Due to the instability of the free phosphiranes,
we reduced the reaction time by increasing the ratio of CO to
phosphirane complex. In our experimental setup, suited for
monitoring the reactions, this could be achieved only by
reducing the amount of phosphirane complex to 5 mg. An
autoclave and higher CO pressures are recommended for larger
scale reactions.
equilibrium between the complex of the three-membered
heterocycle and its free form. Indicative is the rapid formation
of small amounts of the decomplexed phosphirene and phos-
phiranes at the slightly higher temperature of 80 °C. The
presence of CO dissolved in the reaction mixture is apparently
capable of capturing the possible intermediate 15, thereby
driving the decomplexation to completion.
The reaction is remarkable, as thermolysis of M(CO)5-
complexed phosphirene 16 (M ) Cr, Mo, W) has been reported
by Mathey et al.14 to give ring enlargement via carbonylation
of a phosphorus-carbon bond (Scheme 10). The mechanism
involves intermediate 1-phospha-2-metallacyclobutene 17, which
is carbonylated in modest yield (8-43%) to phosphete complex
18. We did not observe this reaction with the Mo(CO)4PMe3-
complexed phosphirene, which illustrates that the PMe3 ligand
contributes to the weakened coordination of the transition metal
to the heterocycle.
A possible explanation for the mild decomplexation of the
Mo(CO)4PMe3 group at 60 °C could be the existence of an
(24) Marinetti, A.; Mathey, F. Organometallics 1984, 3, 456.

Decomplexation of Phosphirane and Phosphirene Complexes
Organometallics, Vol. 25, No. 22, 2006 5289
Mp: 69-70 °C. 31P NMR (CDCl3): δ -15.3 (d, 2J(P,P) ) 24.5
Conclusions
2
1
Hz; P(CH3)3), 33.6 (d, J(P,P) ) 24.5 Hz; phosphole). H NMR
(CDCl3): δ 1.28 (d, 2J(P,H) ) 7.0 Hz; 9H, P(CH3)3), 2.10 (s, 6H,
Transient phosphinidene complex Ph-PdMo(CO)4PMe3 is
generated at only 70 °C from its 7-phosphanorborandiene
precursor and adds to olefinic and acetylenic bonds to form
Mo(CO)4PMe3-complexed phosphiranes and phosphirenes, re-
spectively. The phosphine ligand reduces the PdMo bond
strength as compared to the all-carbonyl complex. The transition
metal group is readily removed under mild CO pressure by
selective replacement of the three-membered PCC rings for CO.
Byproduct Mo(CO)5PMe3 of this reaction is used photochemi-
cally to generate Mo(CO)4PMe3-complexed phosphole 7, from
which phosphinidene precursor 8 is obtained in a mild Diels-
Alder reaction with dimethyl acetylenedicarboxylate.
2
CH3), 6.52 (d, J(P,H) ) 36.0 Hz; 2H, CdCH), 7.28-7.54 (m,
3
5H, Ph). 13C NMR (CDCl3): δ 17.3 (d, J(C,P) ) 9.7 Hz; CH3),
1
3
20.5 (dd, J(C,P) ) 22.6 Hz; J(C,P) ) 2.0 Hz; P(CH3)3), 128.4
3
4
(d, J(C,P) ) 9.4 Hz; m-Ph), 129.3 (d, J(C,P) ) 2.0 Hz; p-Ph),
1
3
131.0 (dd, J(C,P) ) 34.3 Hz; J(C,P) ) 8.1 Hz; P-Cd), 131.1
(d, 2J(C,P) ) 12.0 Hz; o-Ph), 133.2 (dd, 1J(C,P) ) 33.1 Hz; 3J(C,P)
) 2.8 Hz; ipso-Ph), 148.8 (d, 3J(C,P) ) 7.7 Hz; CHCCH3), 209.8
2
2
(dd, J(C,P) ) 10.4 Hz; J(C,P) ) 9.2 Hz; cis-CO), 214.6 (dd,
2J(C,P) ) 23.9 Hz; 2J(C,P) ) 8.4 Hz; trans-CO), 215.0 (dd, 2J(C,P)
2
) 22.1 Hz; J(C,P) ) 9.0 Hz; trans-CO). IR (CH2Cl2): ν(CO) )
2017 (w), 1903 (vs), 1880 (sh) cm-1. HR-MS: calcd for C19H22O4P2-
Mo 474.0047, found 474.0046.
Synthesis of cis-(Trimethylphosphine)(5,6-dimethyl-2,3-bis-
(methoxycarbonyl)-7-phenyl-7-phosphanorbornadiene)tetracar-
bonylmolybdenum, 8. A mixture of complex 7 (1.60 g, 3.39 mmol)
and dimethyl acetylenedicarboxylate (10 mL, 82.6 mmol) was
stirred at 50 °C for 22 h. Column chromatography (silica gel,
starting with pentane and gradually converting to dichloromethane)
gives a yellow solid. Recrystallization from dichloromethane/hexane
resulted in 1.02 g (49%) of 8 as orange crystals.
Mp: 120-121 °C (dec). 31P NMR (CDCl3): δ -14.6 (d, 2J(P,P)
) 27.7 Hz; P(CH3)3), 253.2 (d, 2J(P,P) ) 27.7 Hz; 7-phosphanor-
bornadiene). 1H NMR (CDCl3): δ 1.34 (d, 2J(P,H) ) 6.8 Hz; 9H,
P(CH3)3), 2.02 (s, 6H, CH3), 3.63 (s, 6H, CO2CH3), 3.85 (d, 2J(P,H)
) 3.5 Hz; 2H, dC-CH-C)), 7.14-7.30 (m, 5H, Ph). 13C NMR
Experimental Section
All experiments were performed under an atmosphere of dry
nitrogen. Solids were dried in a vacuum, and liquids were distilled
under N2 prior to use. Toluene was distilled over sodium, and THF
was dried by successive distillation over LiAlH4 and sodium/
benzophenone. CH2Cl2 was dried over P2O5. 1-Phenyl-3,4-dimeth-
ylphosphole25 was prepared according to literature procedures. NMR
spectra were recorded on a Bruker WM 250 spectrometer (1H, 13C),
internally referenced to residual solvent resonances and 85% H3PO4
(31P) as external standard. IR spectra were recorded on a Mattson
6030 Galaxy FT-IR spectrophotometer and high-resolution mass
spectra (HR-MS) on a Finnigan Mat 900 spectrometer (EI, 70 eV).
Fast atom bombardment (FAB) mass spectrometry was carried out
using a JEOL JMS SX/SX 102A four-sector mass spectrometer,
coupled to a JEOL MS-MP9021D/UPD system program. Samples
were loaded in a matrix solution (3-nitrobenzyl alcohol) onto a
stainless steel probe and bombarded with xenon atoms with an
energy of 3 keV. During the high-resolution FAB-MS measurements
a resolving power of 10 000 (10% valley definition) was used.
Column chromatography was performed using silica gel (SiliaFlash
P60, Silicycle) using indicated solvents as determined with TLC.
Thin-layer chromatography was performed using silica gel plates
(silica gel 60 F254 plates, Merck). Melting points were measured
on samples in unsealed capillaries and are uncorrected.
3
1
(CDCl3): δ 15.9 (d, J(C,P) ) 1.7 Hz; CH3), 21.5 (dd, J(C,P) )
3
23.1 Hz; J(C,P) ) 2.5 Hz; P(CH3)3), 51.6 (s, OCH3), 60.5 (dd,
3
1J(C,P) ) 14.1 Hz; J(C,P) ) 2.3 Hz; P-CH-Cd), 127.9 (d,
3J(C,P) ) 6.3 Hz; m-Ph), 128.6 (d, 2J(C,P) ) 9.3 Hz; o-Ph), 128.7
(s, p-Ph), 137.3 (d, 1J(C,P) ) 17.4 Hz; ipso-Ph), 142.2 (d, 2J(C,P)
) 3.5 Hz; CdC-CH3), 145.6 (d, 2J(C,P) ) 17.4 Hz; CdC-CO2-
CH3), 165.2 (d, 3J(C,P) ) 2.2 Hz; CO2CH3), 208.7 (dd, 2J(C,P) )
2
2
10.4 Hz; J(C,P) ) 8.1 Hz; cis-CO), 214.1 (dd, J(C,P) ) 11.5
2
2
Hz; J(C,P) ) 2.5 Hz; trans-CO), 214.5 (dd, J(C,P) ) 9.2 Hz;
2J(C,P) ) 4.5 Hz; trans-CO). IR (CH2Cl2): ν(CO) ) 2021 (w),
1913 (vs), 1889 (sh) cm-1. HR-MS (FAB+): calcd for C25H28O8P2-
Mo 616.0313, found 616.0296.
Synthesis of cis-(Trimethylphosphine)(1,2,3-triphenylphos-
phirene)tetracarbonylmolybdenum, 9. A mixture of 8 (500 mg,
0.81 mmol) and diphenylacetylene (470 mg, 2.64 mmol) dissolved
in 15 mL of dry toluene was stirred at 70 °C for 5.25 h. Column
chromatography (silica gel, pentane/dichloromethane, 7:3) and
recrystallization from dichloromethane/hexane gave 9 (190 mg,
39%) as yellow crystals.
Synthesis of (Trimethylphosphine)pentacarbonylmolybdenum,
6. Mo(CO)6 (3.00 g, 11.4 mmol) and Me3N+O-‚2H2O (1.27 g,
11.5 mmol) were added to 50 mL of a 1:1 mixture of dichlo-
romethane and acetonitrile. The reaction mixture was stirred for
1.5 h at room temperature. A 11.4 mL portion of 1 M PMe3 in
toluene was slowly added to the reaction mixture. Stirring was
continued for 1.5 h at room temperature. Evaporation to dryness
and column chromatography (silica gel, pentane/dichloromethane,
5:1) gave 6 (2.80 g, 79%) as a white solid.
Mp: 143-144 °C. 31P NMR (CDCl3): δ -130.0 (d, 2J(P,P) )
32.4 Hz; phosphirene), -14.2 (d, 2J(P,P) ) 34.2 Hz; P(CH3)3). 1H
NMR (CDCl3): δ 1.24 (d, 2J(P,H) ) 6.8 Hz; 9H, P(CH3)3), 7.43-
7.93 (m, 15H, Ph). 13C NMR (CDCl3): δ 20.7 (dd, 1J(C,P) ) 22.7
Hz; 3J(C,P) ) 2.8 Hz; P(CH3)3), 127.9 (d, 3J(C,P) ) 6.3 Hz; m-Ph),
31P NMR (CDCl3): δ -15.3 (s, P(CH3)3). The 1H and 13C NMR
data are identical to those in ref 26.
Synthesis of cis-(Trimethylphosphine)(3,4-dimethyl-1-phen-
ylphosphole)tetracarbonylmolybdenum, 7. Mo(CO)5PMe3 (6)
(2.40 g, 8.01 mmol) was dissolved in 200 mL of dry THF. Nitrogen
was bubbled through the solution, and 1.65 g (9.00 mmol) of
1-phenylphosphole was added. The reaction mixture was stirred
for 44 h while being irradiated with a high-pressure Philips Hg
lamp (0.9 A, Type 93110E). UV light was filtered out using a 0.1
cm thick glass plate. Evaporation to dryness, column chromatog-
raphy (silica gel, pentane/dichloromethane, 5:1), and recrystalliza-
tion from dichloromethane/hexane gave 2.32 g (61%) of 7 as yellow
crystals.
2
128.6 (d, J(C,P) ) 9.3 Hz; o-Ph), 128.2-31.4 (m, Ph), 140.0 (d,
1J(C,P) ) 6.1 Hz; ipso-Ph), 209.7 (dd, 2J(C,P) ) 10.5 Hz; 2J(C,P)
2
2
) 11.4 Hz; cis-CO), 213.9 (dd, J(C,P) ) 35.6 Hz; J(C,P) ) 8.9
Hz; trans-CO), 214.5 (dd, 2J(C,P) ) 23.3 Hz; 2J(C,P) ) 10.1 Hz;
trans-CO). IR (CH2Cl2): ν(CO) ) 2020 (w), 1908 (vs), 1882 (sh)
cm-1. HRMS (70 eV): m/z (%)572 (2) [M+], 516 (1) [M+ - 2CO],
488 (1) [M+ - 3CO], 460 (4) [M+ - 4CO], 384 (6) [M+ - 4CO
- P(CH3)3], 314 (18) [PhPMo(CO)4], 286 (22) [M+ - Mo(CO)4P-
(CH3)3], 178 (100) [PhCCPh]. HR-MS: calcd for C27H24O4P2Mo,
572.02039; found, 572.01932.
Synthesis of cis-(Trimethylphosphine)(1,2,3-triphenylphos-
phirane)tetracarbonylmolybdenum, 10. A mixture of 8 (500 mg,
0.81 mmol) and trans-stilbene (517 mg, 2.87 mmol) dissolved in
15 mL of dry toluene was stirred at 70 °C for 5.75 h. 31P NMR
spectroscopy showed that the precursor-to-product ratio was ca.
(25) Breque, A.; Mathey, F.; Savignac, Ph. Synthesis 1981, 983.
(26) (a) Grobe, J.; Kunik, H. Z. Anorg. Allg. Chem. 1984, 518, 36. (b)
Grobe, J.; Kunik, H. Z. Anorg. Allg. Chem. 1993, 619, 47. (c) Pastore, H.
O.; Ozin, G. A.; Poe, A. J. J. Am. Chem. Soc. 1993, 115, 1215.

5290 Organometallics, Vol. 25, No. 22, 2006
Van Assema et al.
Figure 1. 31P NMR spectrum of phosphirene decomplexation.
1:1. Column chromatography (silica gel, pentane/dichloromethane,
7:3) and recrystallization from dichloromethane/hexane gave 10 (99
mg, 21%) as colorless crystals. Mp: 127-128 °C. 31P NMR
(CDCl3): δ -89.5 (d, 2J(P,P) ) 30.0 Hz; phosphirane), -15.3 (d,
2J(P,P) ) 30.0 Hz; P(CH3)3). 1H NMR (CDCl3): δ 1.19 (d, 2J(P,H)
Chart 1. Schematic View of Equipment for Decomplexation
Reactions
2
3
) 6.9 Hz; 9H, P(CH3)3), 3.45 (dd, J(P,H) ) 3.1 Hz; J(H,H) )
2
3
10.0 Hz; 1H, P-CHPh), 3.85 (dd, J(P,H) ) 7.5 Hz; J(H,H) )
10.0 Hz; 1H, P-CHPh), 7.00-7.50 (m, 15H, Ph). 13C NMR
(CDCl3): δ 20.7 (dd, 1J(C,P) ) 23.0 Hz; 3J(C,P) ) 2.7 Hz;
P(CH3)3), 33.4 (dd, 1J(C,P) ) 20.4 Hz; 3J(C,P) ) 1.6 Hz;
P-CHPh), 35.7 (dd, 1J(C,P) ) 21.9 Hz; 3J(C,P) ) 3.9 Hz;
P-CHPh), 126.2-133.2 (m, Ph), 135.7 (d, 3J(C,P) ) 7.0 Hz; ipso-
Ph), 137.4 (s; ipso-Ph), 208.7 (t, 2J(C,P) ) 10.3 Hz; cis-CO), 214.2
(m; trans-CO). IR (CH2Cl2): ν(CO) ) 2022 (w), 1913 (vs), 1881
(sh) cm-1. HRMS (70 eV): m/z (%) 574 (2) [M+], 394 (3) [PhPMo-
(CO)4P(CH3)3], 366 (4) [PhPMo(CO)3P(CH3)3], 338 (4) [PhPMo-
(CO)2P(CH3)3], 310 (7) [PhPMo(CO)P(CH3)3], 288 (10) [M+
-
Mo(CO)4P(CH3)3], 179 (100) [PhCHCHPh]. HR-MS: calcd for
C27H26O4P2Mo, 574.03601; found, 574.03559.
2
Minor isomer: 31P NMR (CDCl3) δ -124.6 (d, J(P,P) ) 31.4
2
Hz; phosphirane), -14.9 (d, J(P,P) ) 31.4 Hz; P(CH3)3).
Synthesis of cis-(Trimethylphosphine)(1,2-diphenylphos-
phirane)tetracarbonylmolybdenum, 11. A mixture of 8 (400 mg,
0.65 mmol) and styrene (0.75 mL, 6.50 mmol) dissolved in 15 mL
of dry toluene was stirred at 70 °C for 9.5 h. Column chromatog-
raphy (silica gel, pentane/dichloromethane, 7:3) and recrystallization
from dichloromethane/hexane gave 11 (165 mg, 51%) as colorless
crystals. Two diastereomers were formed in a 8:1 ratio. The two
isomers can be separated by slow recrystallization from dichlo-
romethane/hexane. The minor isomer was not obtained in pure form.
Major isomer: mp 66-67 °C. 31P NMR (CDCl3): δ -125.6 (d,
Decomplexation of Phosphirene-Mo(CO)4PMe3, 9. A NMR
tube was charged with phosphirene complex 9 (89 mg, 0.15 mmol)
and 1.5 mL of dry THF. The tube was pressurized at 25 bar of CO
and heated for 48 h at 60 °C. 31P NMR showed complete conversion
of the complex to the free phosphirene (see Figure 1). The reaction
mixture was filtered over a short silica gel column. Recrystallization
from pentane gave 12 (40 mg, 94%). Mp: 76-77 °C (lit. 73 °C).
31P NMR (CDCl3): δ -187.2 (s). H NMR (CDCl3): δ 7.19-
1
7.25 (m, 3H; Ph), 7.40-7.51 (m, 8H; Ph), 7.84-7.88 (m, 4H; Ph).
The spectroscopic data are identical to those of ref 15.
Decomplexation of Phosphirane-Mo(CO)4PMe3, 10. A NMR
tube was charged with phosphirane complex 10 (5 mg, 9 µmol)
and 0.75 mL of dry THF. The tube was pressurized at 25 bar of
CO and heated for 24 h at 60 °C. 31P NMR showed complete
conversion of the complex to the free phosphirane 13. Upon
prolonged heating, thermal degradation of the phosphirane was
observed.
31P NMR [intensity] (THF): δ -147.5 (s, phosphirane) [0.995],
-15.1 (s, Mo(CO)5PMe3) [1.000].
Decomplexation of Phosphirane-Mo(CO)4PMe3, 11a. A
NMR tube was charged with phosphirane complex 11a (5 mg, 10
µmol) and 0.75 mL of dry THF. The tube was pressurized at 25
2
2J(P,P) ) 31.4 Hz; phosphirane), -14.6 (d, J(P,P) ) 31.4 Hz;
1
2
P(CH3)3). H NMR (CDCl3): δ 1.34 (d, J(P,H) ) 6.8 Hz; 9H,
P(CH3)3), 1.74-1.82 (m, 1H, P-CH), 2.22-2.32 (m, 1H, P-CH),
2.89-2.96 (m, 1H, P-CH), 6.81-6.85 (m; 2H, Ph), 7.00-7.15
(m, 8H, Ph). 13C NMR (CDCl3): δ 14.3 (dd, J(C,P) ) 16.1 Hz;
1
3J(C,P) ) 2.0 Hz; PCH2), 21.0 (dd, 1J(C,P) ) 22.9 Hz; 3J(C,P) )
2.8 Hz; P(CH3)3), 30.8 (dd, 1J(C,P) ) 20.8 Hz; 3J(C,P) ) 3.6 Hz;
P-CHPh), 126.1-133.4 (m, Ph), 133.8 (d, 1J(C,P) ) 15.9 Hz; ipso-
Ph), 136.0 (d, 2J(C,P) ) 5.5 Hz; ipso-Ph), 209.0 (t, 2J(C,P) ) 10.4
2
2
Hz; cis-CO), 214.5 (dd, J(C,P) ) 24.3 Hz, J(C,P) ) 11.0 Hz;
trans-CO), 214.5 (dd, 2J(C,P) ) 34.3 Hz, 2J(C,P) ) 8.8 Hz; trans-
CO). IR (CH2Cl2): ν(CO) ) 2021 (w), 1907 (vs), 1889 (sh) cm-1
.
HR-MS: calcd for C21H22O4P2Mo 498.0047, found 498.0043.

Decomplexation of Phosphirane and Phosphirene Complexes
Organometallics, Vol. 25, No. 22, 2006 5291
bar of CO and heated for 10 h at 60 °C. 31P NMR showed clean
conversion of the complex to the free phosphirane. The conversion
of complex to free phosphine was 1:3, but without formation of
byproducts. Upon prolonged heating, thermal degradation of the
phosphirane 14 was observed.
Acknowledgment. This work has been supported by The
Netherlands Organization for Scientific Research, Chemical
Sciences (NWO-CW).
Supporting Information Available: NMR spectra (31P, 1H, and
13C) for compounds 7, 8, 9, 10, and 11a/b. This material is available
free of charge via the Internet at http://pubs.acs.org.
31P NMR [intensity] (THF): δ -182.2 (s, free phosphirane)
2
[1.00], -125.7 (d, J(P,P) ) 31.4 Hz; complex) [0.35], -14.9 (s,
2
Mo(CO)5PMe3) [1.05], -14.5 (d, J(P,P) ) 31.4 Hz; complex)
[0.37].
OM060570T