From a terminal (cis-2-butene-1,4-diyl-1,4-diphosphinidene) complex to some new diphosphorus bicycles

Article abstract of DOI:10.1016/S0022-328X(98)01185-1

The reaction of the transient decacarbonylditungsten complex (3) as generated from the appropriate 7-phosphanorbornadiene precursor (2) at 60 deg C in the presence of CuCl as a catalyst with 3-hexyne, 2,3-dimethylbutadiene and pentacarbonyltungsten yields the products 5, 7 and 8. These products formally result from the <2 + 2>, <4 + 2> and <1 + 2> cycloadditions of the reagents with the P=P double bond of the <3,6-dihydro-1,2-diphosphinine>decacarbonylditungsten. However, a mechanism involving a monocondensation of the reagent onto one P of the bis-phosphinidene, followed by the insertion of the second P into the monophosphorus heterocycles thus formed is favored.

Full text of DOI:10.1016/S0022-328X(98)01185-1

Journal of Organometallic Chemistry 582 (1999) 53–57
From a terminal (cis-2-butene-1,4-diyl-1,4-diphosphinidene) complex to
some new diphosphorus bicyclesꢀ
Ngoc Hoa Tran Huy *, Louis Ricard, Franc¸ois Mathey 1
Laboratoire He´te´roe´le´ments et Coordination, Ecole Polytechnique, UMR 7653 CNRS, DCPH, F-91128 Palaiseau Cedex, France
Received 9 September 1998
Abstract
The reaction of the transient [cis-2-butene-1,4-diyl-1,4-diphosphinidene]decacarbonylditungsten complex (3) as generated from
the appropriate 7-phosphanorbornadiene precursor (2) at 60°C in the presence of CuCl as a catalyst with 3-hexyne, 2,3-
dimethylbutadiene and [phenyl(methoxy)carbene]pentacarbonyltungsten yields the products 5, 7 and 8. These products formally
result from the [2+2], [4+2] and [1+2] cycloadditions of the reagents with the PꢀP double bond of the [3,6-dihydro-1,2-diphos-
phinine]decacarbonylditungsten. However, a mechanism involving a monocondensation of the reagent onto one P of the
bis-phosphinidene, followed by the insertion of the second P into the monophosphorus heterocycles thus formed is favored.
© 1999 Elsevier Science S.A. All rights reserved.
Keywords: 1,6-Diphosphabicyclo[4,n,0] compounds; P-insertion; Phosphinidene; Carbene complex
1. Introduction
the two reactive termini, we decided to investigate the
case of a (cis-2-butene-1,4-diyl)diphosphinidene com-
plex. Due to the favorable geometry, the intermediate
For some time now, transient electrophilic terminal
phosphinidene complexes [RP“M] [M=Cr, Mo,
W(CO)5] have been developed into a highly efficient
tool for the synthesis of P–C heterocycles from alkenes,
alkynes, dienes, etc. [1]. As a next logical step toward
more elaborate structures, it was interesting to investi-
gate the chemistry of a,v-alkanediyldiphosphinidene
complexes with the hope of observing intramolecular
condensation reactions of some practical interest. A
formation of
a 3,6-dihydro-1,2-diphosphinine ring
could be envisaged in that case (Eq. (1)). The formation
of PꢀP double bonds by dimerization of terminal phos-
phinidene complexes is indeed well documented [3]. We
report here on the results of this study.
preliminary
work
concerning
1,2-ethanediphos-
phinidene complexes was reported some years ago [2].
In that case, both phosphorus functionalities react nor-
mally and independently with external reagents. In
order to favor the intramolecular interactions between
(1)
2. Results and discussion
ꢀ Dedicated to Professor Alan Cowley for his 65th birthday.
* Corresponding author.
The appropriate 7-phosphanorbornadiene precursor
2 was prepared as usual (Eq. (2)).
1 Also corresponding author.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(98)01185-1

54
N. Hoa Tran Huy et al. / Journal of Organometallic Chemistry 582 (1999) 53–57
3 (m/z 846 for 184W). The structure was solved by X-ray
analysis (Fig. 1). It shows the formation of a four-mem-
bered 1,2-dihydro-1,2-diphosphete ring. The junction
between the six- and the four-membered rings has a cis
stereochemistry. The P–P bond length is normal at
(2)
˚
2.224(2) A. The geometry of the four-membered ring is
very close to that reported previously for a cis-1,2-dihy-
dro-1,2-diphosphete complex [5]. A priori, two mecha-
nisms can account for the formation of 5. The first one
would involve a PꢀP coupling followed by a [2+2]
cycloaddition between the PꢀP double bond and the
alkyne. Such [2+2] cycloadditions have already been
described previously [3b]. The formation of 4 in the
same reaction suggests a more likely pathway involving
the initial formation of a mono-phosphirene followed
by the intramolecular insertion of the phosphinidene
into the phosphirene (Eq. (5)). Such an insertion has
also some precedent in the literature [5].
In spite of the bulkiness associated with the P–CH2–
CHꢀCH–CH2–P bridge, the cycloaddition takes place
on the phosphole side opposite to the tungsten com-
plexing group as shown by the couplings of Me–C5,
Me–C6, MeO2C–C2, MeO2C–C3 with phosphorus:
2
l(C5, C6) 139.02, J(C–P)=16.8 Hz; l(C2, C3) 145.57,
2J(C–P) ca. 0 Hz. The 2J(C–P) are indeed highly
dependent on the C–C–P–W dihedral angles and these
data correspond closely to those of the structurally
characterized 7-phosphanorbornadiene complexes [4].
All our attempts to generate the bis-phosphinidene 3
from 2 by thermal decomposition failed to give any-
thing other than polymeric products. On the contrary,
trapping experiments with various unsaturated sub-
strates gave satisfactory results. The reaction with 3-
hexyne in large excess gives the corresponding
bis-phosphirene complex 4 (Eq. (3)).
(5)
We then investigated the reaction of 2 with 2,3-
dimethylbutadiene. The reaction of terminal phos-
phinidene complexes with conjugated dienes is known
to give 2-vinylphosphirane complexes which rearrange
upon heating to the corresponding phospholenes [6]. In
the case of 2, the reaction produces two isomeric bis-
(vinylphosphirane) complexes 6a,b in minor quantities,
but the main product 7 is not a bis-phospholene com-
plex (Eq. (6)).
(3)
The bis-phosphirene is characterized by its high-field
31P resonance at −158 (CDCl3). Together with the fact
that it is impossible to get well-defined products during
the thermal decomposition of 2, this result tends to
demonstrate that the formation of the 3,6-dihydro-1,2-
diphosphinine ring from 3 by PꢀP coupling is not a
highly favored process. A more exciting result was
obtained when 3 was generated in the presence of a
limited amount of 3-hexyne. Together with the bis-
phosphirene 4, another product 5 was formed (Eq. (4))
which does not incorporate a three-membered ring as
shown by its 31P resonance at 7.5 (CDCl3).
Fig. 1. ORTEP drawing of one molecule of 5. Hydrogen atoms are
omitted for clarity. Selected bond lengths (A) and angles (°): W(1)–
˚
P(1) 2.497(1), W(2)–P(2) 2.482(1), P(1)–P(2) 2.224(2), P(1)–C(1)
1.845(4), P(1)–C(3) 1.856(6), P(2)–C(2) 1.833(4), P(2)–C(6) 1.838(5),
C(1)–C(2) 1.341(7), C(3)–C(4) 1.483(8), C(4)–C(5) 1.308(8), C(5)–
C(6) 1.509(7); W(1)–P(1)–P(2) 132.33(6), W(1)–P(1)–C(1) 123.5(2),
W(1)–P(1)–C(3) 111.7(2), P(2)–P(1)–C(1) 75.8(2), P(2)–P(1)–C(3)
100.9(2), C(1)–P(1)–C(3) 106.2(2), W(2)–P(2)–P(1) 126.43(6), W(2)–
P(2)–C(2) 124.2 (2), W(2)–P(2)–C(6) 114.5(2), P(1)–P(2)–C(2)
76.3(2), P(1)–P(2)–C(6) 101.7(2), C(2)–P(2)–C(6) 106.7(2), P(1)–
C(1)–C(2) 103.8(3), P(2)–C(2)–C(1) 103.8(3).
(4)
The mass spectrum indicates that 5 results from the
addition of one molecule of hexyne to one molecule of

N. Hoa Tran Huy et al. / Journal of Organometallic Chemistry 582 (1999) 53–57
55
−93.5 and −101.0, indicating the presence of a three-
membered ring. The mass spectrum shows a molecular
peak at m/z 884, demonstrating that 8 results from the
addition of one molecule of carbene to one molecule of
3. The postulated mechanism is depicted in Eq. (9):
(6)
(9)
The identity of 6a,b was easily ascertained. The high-
field shift of their 31P resonances at −145.6 and −
150.8 (CDCl3) establishes the presence of the
three-membered rings. The mass spectrum indicates
that 6a,b results from the addition of two molecules of
2,3-dimethylbutadiene to one molecule of 3 (m/z 928
for 184W). A close inspection of the 31P resonance of 7
at −43.9 in CDCl3 shows two 31P–183W couplings of
162.9 [1J(P–W)] and 85.7 Hz [2J(P–W)], respectively,
implying the presence of a W–P–P–W unit. The mass
spectrum of 7 displays a molecular peak at m/z 846,
indicating that 7 results from the addition of one
molecule of diene to one molecule of 3. The symmetry
of the structure is demonstrated by the 1H and 13C
spectra showing one type of CH3, two types of CH2 and
one type of vinylic CH resonances. Thus the 1,6-
diphosphabicyclo[4.4.0]deca-3,8-diene structure is es-
tablished beyond any doubt. Once again two
mechanisms of formation are possible. The first one
would involve a PꢀP coupling followed by a [4+2]
cycloaddition between the PꢀP double bond and the
diene. A similar cycloaddition involving a diphosphene
dicomplex has been described earlier [7]. However the
formation of the bis-(vinylphosphirane) complexes 6a,b
leads us to prefer the mechanism depicted in Eq. (7).
The first step mimics the formation of P=C double
bonds from phosphinidene and carbene complexes [8].
The second step is analogous to the synthesis of diphos-
phiranes from phosphaalkenes and terminal phos-
phinidene complexes [9].
Thanks to their reactive P–P bonds, the three bicy-
cles 5, 7 and 8 described in this work are interesting
starting points for the synthesis of a variety of new
seven-, eight-, and ten-membered diphosphorus rings.
Work is in progress to evaluate these possibilities.
3. Experimental
All reactions were performed under nitrogen; the
solvents were purified, dried and degassed by standard
techniques. 1H-, 13C-, and 31P-NMR spectra were
recorded on a Bruker AC 200 SY spectrometer operat-
ing at 200.13, 50.32, and 81.01 MHz, respectively. All
chemical shifts are reported in ppm downfield from
internal TMS (1H and 13C) and external 85% H3PO4
(31P). Mass spectra (EI) were obtained at 70 eV by the
direct inlet method.
3.1. [1,4-Bis-(3,4-dimethylphospholyl)-cis-2-butene]-
decarbonylditungsten (1)
(7)
The [1-lithio-3,4-dimethylphosphole]pentacarbonyl-
tungsten complex was prepared as described in a previ-
ous publication [10]. The resulting solution in THF was
allowed to react with a half equivalent of 1,4-dichloro-
cis-2-butene between −40°C and room temperature.
The bis-phospholyl complex 1 was isolated by chro-
matography on silica gel with hexane/dichloromethane
4:1 as the eluent. A yellow powder was thus obtained in
25% yield (not optimized). 31P-NMR (CDCl3): l 4.5,
We are currently checking the implications of that
hypothesis.
The reaction of 2 with Fischer carbene complexes fits
the general pattern presented in our previous mechanis-
tic speculations (Eqs. (5) and (7)). Indeed, the reaction
of
2 with (methoxy)(phenyl)carbene-pentacarbonyl-
tungsten complex leads to a diphosphirane ring (Eq.
(8)).
1
1J(31P–183W)=204.7 Hz. H-NMR (CDCl3): l 2.16 (s,
12H, Me), 2.70 (m, 4H, CH2), 5.35 (m, 2H, CHꢀCH),
2
6.24 (d, J(H–P)=36.9 Hz, 4H, ꢀCH–P). 13C-NMR
3
(8)
(CDCl3): l 17.34 (d, J(C–P)=10.6 Hz, Me), 29.61 (d,
1J(C–P)=20.9 Hz, CH2), 125.32 (s, CHꢀCH), 128.50
(d, 1J(C–P)=41.9 Hz, P–CH=), 151.80 (d, 2J(C–
P)=7.2 Hz, Me–C), 196.21 (cis CO); Mass spectrum
The product 8a,b is a mixture of two isomers as shown
by its 31P spectrum which displays two resonances at
(
184W): m/z 924 (M+, 7%), 379 (100%).

56
N. Hoa Tran Huy et al. / Journal of Organometallic Chemistry 582 (1999) 53–57
3.2. [1,4-Bis-(2,3-bis-methoxycarbonyl-5,6-dimethyl-
7-phosphanorbornadien-7-yl)-cis-2-butene]-
decacarbonylditungsten (2)
Calc. for C20H16O10P2W2: C, 28.36; H, 1.89. Found: C,
27.81; H, 2.02.
3.5. [1,4-Bis-(2-methyl-2-propenylphosphiran-1-yl)-
cis-2-butene]decacarbonylditungsten (6a,b) and
[3,4-Dimethyl-1,6-diphosphabicyclo[4.4.0]deca-3,8-
diene]decacarbonylditungsten (7)
A solution of 1 (9.3 g, 1×10−2 mol) and dimethyl
acetylenedicarboxylate (8 ml) in 30 ml of toluene was
heated at 70°C for 48 h. The product was purified by
chromatography on silica gel with dichloromethane as
the eluent. Yield 50%. 31P-NMR (CDCl3): l 207.1,
A solution of 2 (0.5 g, ca. 0.4×10−3 mol), 2,3-
dimethyl-1,3-butadiene (0.1 ml, ca. 0.8×10−3 mol),
CuCl (60 mg) in toluene (7 ml) was heated at 60°C for
2 h. The products were separated by chromatography
on silica gel with hexane as the eluent. The first fraction
contained a mixture of 6a,b (50 mg, 13%); the second
fraction contained 7 (160 mg, 45%). 6a,b 31P-NMR
(CDCl3): l −145.57 and −150.86 (1:1). MS (184W):
m/z 928 (M+, 6%), 379 (100%). 7 31P-NMR (CDCl3): l
−43.94, 1J(31P–183W)=162.9, 2J(31P–183W)=85.7
1
1J(31P–183W)=239.7 Hz. H-NMR (CDCl3): l 1.93 (s,
12H, Me), 3.14 (s, br, 4H, CH2), 3.59 (d, 2J(H–P)=2.2
Hz, 4H, P–CH), 3.78 (s, 12H, OCH3), 5.44 (m, 2H,
CHꢀCH). 13C-NMR (CDCl3): l 16.20 (s, Me), 36.03 (s,
1
P–CH2), 52.79 (s, OMe), 59.44 (d, J(C–P)=19.6 Hz,
2
P–CH), 125.28 (d, J(C–P)=9.3 Hz, CHꢀCH), 139.01
2
(d, J(C–P)=16.8 Hz, Me–C), 145.57 (s, C–CO2Me),
2
165.11 (s, CO2Me), 196.15 (d, J(C–P)=6.0 Hz, cis-
2
CO), 197.66 (d, J(C–P)=27.3 Hz, trans-CO). Anal.
1
Calc. for C38H34O18P2W2: C, 37.75; H, 2.81. Found: C,
37.58; H, 2.71.
Hz. H-NMR (CDCl3): l 1.83 (s, 6H, Me), 2.73 and
2.95 (2 m, 8H, CH2), 5.88 (m, 2H, CHꢀCH). 13C-NMR
(CDCl3): l 22.89 (pseudo t, Me), 27.93 (pseudo t,
CH2P), 35.38 (pseudo t, CH2P), 124.17 and 124.22 (2 s,
CH and C sp2; assignments checked by parity experi-
ments), 196.27 (cis CO). MS (184W): m/z 846 (M+,
22%), 650 (100%).
3.3. [1,4-Bis-(2,3-diethylphosphiren-1-yl)-cis-2-butene]-
decacarbonylditungsten (4)
A solution of 2 (0.6 g, 5×10−4 mol), 3-hexyne (0.35
ml, 3×10−3 mol), CuCl (60 mg) in 10 ml of toluene
was heated at 60°C for 2.5 h. The product was chro-
matographed on silica gel with hexane/dichloromethane
5/1 as the eluent. The bis-phosphirene 4 was isolated as
a white powder (0.15 g, 30%). 31P-NMR (CDCl3): l
−158. 1H-NMR (CDCl3): l 1.27 (t, 12H, Me), 2.40 (m,
4H, CH2), 2.65 (q, CH2 (Et)), 5.25 (m, 2H,
CHꢀCH);13C-NMR (CDCl3): l 12.51 (s, Me), 20.50 (d,
CH2–Me), 38.06 (d, 1J(C–P)=5.2 Hz, P–CH2),
125.61 (s, CHꢀCH), 133.53 (d, 1J(C–P)=14.8 Hz, P–C
3.6. [7-Methoxy-7-phenyl-1,6-diphosphabicyclo[4.1.0]-
hept-3-ene]decacarbonylditungsten (8a,b)
A solution of 2 (0.85 g, 7×10−4 mol), carbene
complex (1.7 g, 3.8×10−3 mol), CuCl (100 mg) in 20
ml of toluene was heated at 60°C for 3 h. The product
was purified by chromatography on silica gel with
hexane as the eluent. 31P-NMR (CDCl3): l −101.0 and
1
−93.5. H-NMR (CDCl3): l 3.26 and 3.33 (2 s, OMe),
5.61 and 6.34 (2 m, CHꢀCH). 13C-NMR (CDCl3): l
29.05 and 31.26 (2 s, CH2P), 55.43 and 58.19 (2 t,
3J(C–P)=7.5 and 4.5 Hz, OMe), 79.50 and 80.50 (2 t,
1J(C–P)=7.8 and 16.8 Hz, C–OMe), 126.44 (s,
CHꢀCH). MS (184W): m/z 884 (M+, 26%), 662 (100%).
Anal. Calc. for C22H14O11P2W2: C, 29.86; H, 1.58.
Found: C, 29.36; H, 1.86.
2
(Et)), 196.73 (d, J(C–P)=7.6 Hz, cis CO). MS (184W):
m/z 928 (M+, 8.6%), 437 (100%).
3.4. [7,8-Diethyl-1,6-diphosphabicyclo[4.2.0]octa-3,7-
diene]decacarbonylditungsten (5)
A solution of 2 (0.42 g, 3.5×10−4 mol), 3-hexyne
(0.12 ml, 1×10−3 mol), CuCl (40 mg) in 10 ml of
toluene was heated at 60°C for 3 h. According to the
31P spectrum of the reaction mixture, 4 and 5 were
formed in a 1:2 ratio. The products were separated by
chromatography on silica gel with hexane/
dichloromethane 10/1 as the eluent. The bicycle 5 was
isolated as a white powder (0.12 g, 40%). 31P-NMR
4. X-ray structure determination for 5
A crystal of 5 (C20H16O10P2W2, colorless cube 0.32×
0.32×0.32 mm) was grown from a dichloromethane–
pentane solution of the compound. Data were collected
at 12390.5 K on an Enraf–Nonius CAD4 diffrac-
1
˚
(CDCl3): l 7.5. H-NMR (CDCl3): l 1.06 (t, 6H, CH3),
tometer using Mo–Ka (u90.71073 A) radiation and a
2.39 (m, 4H, CH2Me), 2.68 and 3.07 (2 m, 4H, CH2P),
5.89 (m, 2H, CHꢀCH). 13C-NMR (CDCl3): l 13.49 (s,
Me), 24.19 (pseudo t, CH2Me), 35.14 (s, CH2P), 125.87
(s, CHꢀCH), 153.73 (pseudo t, P–C–Et). MS (184W):
m/z 846 (M+, 26%), 564 (M+ −10 CO, 100%). Anal.
graphite monochromator. Psi scan absorption correc-
tions (Tmin=0.59, Tmax=1.00) were applied. The crys-
tal structure was solved and refined using the
Enraf–Nonius MOLEN package. The compound crys-
˚
(
tallises in space group P1 (c2), a=7.397(1) A, b=

N. Hoa Tran Huy et al. / Journal of Organometallic Chemistry 582 (1999) 53–57
57
˚
˚
9.254(1) A, c=18.822(2) A, h=94.58(1)°, i=
posit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.
ac.uk.
3
˚
94.45(1)°, k=105.78(1)°; V=1229.30(54) A ; Z=2;
D
calc. =2.285 g cm−3; v=97.3 cm−1; F(000)=788. A
total of 6408 unique reflexions were recorded in the
range 2°5q556.1° of which 1246 were considered as
unobserved (F2B3.0|(F2)), leaving 5162 for solution
and refinement. Direct methods yielded a solution for
all atoms. The hydrogen atoms were included as fixed
contributions in the final stages of least-squares refine-
ment while using anisotropic temperature factors for all
other atoms. A non-Poisson weighting scheme was
applied with a p factor equal to 0.08. The final agree-
ment factors were R=0.027, Rw=0.049, goodness-of-
fit=1.28.
References
[1] (a) K.B. Dillon, F. Mathey, J.F. Nixon, Phosphorus: The
Carbon Copy, Wiley, Chichester, 1998, pp. 19–39. (b) A.H.
Cowley, Acc. Chem. Res. 30 (1997) 445.
[2] C. Charrier, N. Maigrot, F. Mathey, Organometallics 6 (1987)
586.
[3] (a) A. Marinetti, C. Charrier, F. Mathey, J. Fischer,
Organometallics, 4 (1985) 2134. (b) N.H. Tran Huy, Y. In-
ubushi, L. Ricard, F. Mathey, Organometallics 16 (1997) 2506.
[4] (a) A. Marinetti, F. Mathey, J. Fischer, A. Mitschler, J. Chem.
Soc. Chem. Commun. (1982) 667. (b) A. Marinetti, F. Mathey,
Organometallics 1 (1982) 1488.
[5] N.H. Tran Huy, L. Ricard, F. Mathey, Organometallics 16
(1997) 4501.
[6] (a) A. Marinetti, F. Mathey, Organometallics, 3 (1984) 456. (b)
K. Lammerstma, J.-T. Hung, P. Chand, G.M. Gray, J. Org.
Chem. 57 (1992) 6557. (c) J.-T. Hung, K. Lammertsma, J. Org.
Chem. 58 (1993) 1800.
[7] J. Borm, G. Huttner, O. Orama, J. Organomet. Chem. 282
(1985) 53.
[8] N.H. Tran Huy, L. Ricard, F. Mathey, Organometallics 7 (1988)
1791.
[9] R. Streubel, N.H. Tran Huy, F. Mathey, Synthesis (1993) 763.
[10] S. Holand, F. Mathey, J. Fischer, Polyhedron 5 (1986) 1413.
5. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC No. 103100 for 6. Copies of the
information can be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge, CB2
1EZ, UK (Fax: +44-1223-336-033; e-mail: de-
.