Versatile behavior of a new class of bicyclic compounds: Zirconacyclopentadiene phosphiranes

Article abstract of DOI:10.1021/om970216i

Diacetylenic phosphanes are cleanly transformed when reacted with zirconocene into zirconacyclopentadiene phosphiranes. These new cyclic systems are the source of a variety of unsaturated phosphorus compounds like phospharadialene or alkenyl alkynyl phosphanes.

Full text of DOI:10.1021/om970216i

3086
Organometallics 1997, 16, 3086-3088
Ver sa tile Beh a vior of a New Cla ss of Bicyclic
Com p ou n d s: Zir con a cyclop en ta d ien e P h osp h ir a n es
Armelle Mahieu, Yannick Miquel, Alain Igau, Bruno Donnadieu, and
J ean-Pierre Majoral*
Laboratoire de Chimie de Coordination du CNRS,
205, route de Narbonne, 31077 Toulouse Cedex, France
Received March 17, 1997X
Sch em e 1. Syn th esis of
Zir con a cyclop en ta d ien e-p h osp h ir a n es 3 (Ar )
2,4,6-t-Bu 3C6H2)
Summary: Diacetylenic phosphanes are cleanly trans-
formed when reacted with zirconocene into zirconacy-
clopentadiene phosphiranes. These new cyclic systems
are the source of a variety of unsaturated phosphorus
compounds like phospharadialene or alkenyl alkynyl
phosphanes.
Interactions between unsaturated phosphorus com-
pounds and zirconium species usually initiate a totally
different chemistry1-3 than that generally observed
when the same zirconium compounds are reacted with
the corresponding unsaturated organic or inorganic
derivatives.4 Moreover, the chemical behavior of the
resulting metalated phosphorus moieties is also unex-
pected. Thus, we have already shown that phosphorus
placed in a â position to a zirconium fragment induces
original rearrangement processes leading, for example,
to a large variety of R-functionalized substituted phos-
phanes: when phosphorus is included in a ring, an
unprecedented ring-opening reaction is observed.1
Several recent papers describe oxidative alkyne cou-
pling using [Cp2Zr] leading to a variety of metallacyclic
complexes which act as excellent sources of [Cp2Zr] or
give rise to a number of metallacycles when they are
reacted with unsaturated organic species.5 Therefore,
taking into account observations mentioned before,
investigations concerning coupling reactions involving
phosphorus alkynes and [Cp2Zr] (1) should lead to
different reactions and unexpected derivatives. Indeed,
we report here the synthesis of a new class of com-
pounds, the zirconacyclopentadiene phosphiranes 3a -
c. Preliminary experiments on the reactivity of these
species toward halogenated compounds demonstrate
their versatile behavior.6
Treatment of phosphanes 2a -c with freshly prepared
[Cp2Zr] (1) synthon in THF at -78 °C leads to the
ziconacyclopentadiene phosphiranes 3a -c isolated as
powders in 90% yield (Scheme 1).7 These derivatives
exhibit remarkably shielded 31P chemical shifts at
-300.5 (3a ) -299.7 (3b), and -244.2 (3c) ppm which
fit well with a phosphirane-type structure. Indeed, the
δ
31P value for 3a is one of the highest reported for a
molecule containing strained-membered rings and is
apparently exceeded among phosphirane derivatives
only by the parent phosphirane compound (δ: -341
(6) Part of this work was presented at IVe`me J ourne´e Grand Sud-
Ouest, Toulouse-France, November 25, 1994, and at XIIIth Interna-
tional Conference on Phosphorus Chemistry, J erusalem-Israel, J uly
16-21, 1995.
X Abstract published in Advance ACS Abstracts, J une 15, 1997.
(1) See, for example: (a) Ce´nac, N.; Zablocka, M.; Igau, A.; Majoral,
J .-P.; Skowronska, A. Organometallics 1996, 15, 1208. (b) Zablocka,
M.; Igau, A.; Ce´nac, N.; Donnadieu, B.; Dahan, F.; Majoral, J .-P.;
Pietrusiewicz, K. M. J . Am. Chem. Soc. 1995, 117, 8083. (c) Igau, A.;
Dufour, N.; Mahieu, A.; Majoral, J .-P.; Angew. Chem., Int. Ed. Engl.
1993, 32, 95 and references cited herein.
(7) General procedure for the synthesis of 3: To a solution of
dichlorozirconocene [Cp2ZrCl2] (0.292 g, 1.0 mmol) in THF (5 mL) at
-78 °C was added BuLi in hexane (0.8 mL, 2.5 M). The mixture was
stirred for 2 h at -78 °C, then 1 equiv of bis(acetylenic)phosphine in
THF (5 mL) was added via canula. The reaction mixture was warmed
slowly to room temperature and stirred for a further 3 h. The resulting
solution was evaporated to dryness. Successive extractions of the
residue with pentane (2 × 30 mL) gave compound 3 as a powder.
Satisfactory elemental analysis for 3a -c. 3a : brown powder, 31P{1H}
NMR (C6D6) δ -300.5 ppm. 1H NMR (C6D6): δ 7.62 (d, 4J (H,P) ) 3.1
Hz, 2H, CHAr), 7.35-7.33 (m, 6H, CHPh), 7.10-7.07 (m, 4H, CHPh),
5.40 (s, 5H, Cp), 5.38 (s, 5H, Cp), 1.30 (s, 18H, o-tBu), 1.19 (s, 9H,
p-tBu). 13C{1H} NMR (C6D6): δ 168.7 (d, 2J (C,P) ) 4.0 Hz, CZr), 159.1
(d, 1J (C,P) ) 5.0 Hz, i-CAr), 150.8 (s, o-CAr), 149.3 (s, m-CAr), 145.3 (s,
i-CAr), 130.3 (d, 3J (C,P) ) 15.6 Hz, i-CPh), 129.5 (s, o-CPh), 128.9 (s,
m-CPh), 123.1 (s, p-CPh), 107.3 (s, Cp), 106.9 (s, Cp), 88.5 (d, 1J (C,P) )
62.7 Hz, PCdC), 39.7 (s, p-CCH3), 34.6 (d, 3J (C,P) ) 8.6 Hz, o-CCH3),
32.3 (s, o-CCCH3), 32.0 (s, p-CCH3). 3b: yellow powder, 31P{1H} NMR
(CD2Cl2) δ -299.7. 1H NMR (CD2Cl2): δ 8.29-8.26 (m, 4H, Ph), 7.52-
7.46 (m, 6H, Ph), 5.65 (s, 5H, Cp), 5.34 (s, 5H, Cp), 0.98 (d, 3J (H,P) )
12.5 Hz, 9H, tBu). 13C{1H} NMR (CD2Cl2): δ 165.7 (d, 2J (C,P) ) 6.0
Hz, CZr), 139.7 (s, i-CPh), 128.8 (s, o-CPh), 128.1 (s, m-CPh), 127.7 (s,
p-CPh), 105.2 (s, Cp), 105.1 (s, Cp), 79.1 (d, 1J (C,P) ) 64.5 Hz, PCdC),
33.9 (d, 1J (C,P) ) 42.2 Hz, CH3C), 26.6 (d, 2J (C,P) ) 15.7 Hz, CH3C).
3c: red powder, 31P{1H} NMR (C6D6) δ -244.2. 1H NMR (C6D6): δ
8.13-8.09 (m, 4H, CHPh), 7.53-7.26 (m, 6H, CHPh), 5.65 (s, 5H, Cp),
5.43 (s, 5H, Cp), 2.75 (sept, 3J (H,H) ) 6.7 Hz, 2H, CH3CH), 1.08 (d,
3J (H,H) ) 6.7 Hz, 12H, CH3CH). 13C{1H} NMR (C6D6): δ 168.9 (d,
2J (C,P), ) 7.6 Hz, CZr), 134.1 (s, i-CPh), 129.7 (s, m-CPh), 129.5 (s, p-CPh),
129.2 (s, o-CPh), 106.0 (s, Cp), 105.9 (s, Cp), 85.5 (d, 1J (C,P) ) 71.3 Hz,
PCdC), 46.1 (d, 2J (C,P) ) 7.4 Hz, CH3CH), 24.2 and 24.1 (s, CH3CH).
(2) Reactivity of tBuCtP with zirconocene derivatives, see: (a)
Binger, P.; Wettling, T.; Schneider, R.; Zurmu¨hlen, F.; Bergstrasser,
U.; Hoffmann, J .; Maas, G.; Regitz, M. Angew. Chem., Int. Ed. Engl.
1991, 30, 207 and references cited herein.
(3) Reactivity of R3PdCH2 with group 4 metallocene derivatives, see,
for example: (a) Binger, P.; Glase, G.; Gabor, B.; Mynott, R. Angew.
Chem., Int. Ed. Engl. 1995, 34, 81 and references cited herein. (b)
Erker, G.; Dorf, U.; Czisch, P.; Petersen, J . L. Organometallics 1986,
5, 668 and references cited herein. (c) Schmidbaur, H.; Pichl, R. Z.
Naturforsch. 1985, 40b, 352 and references cited herein.
(4) Tetrahedron Symposia in print No. 57: Negishi, E. Tetrahedron
1995, 51, 4255. For reviews, see for example: (a) Annby, U.; Karlson,
S. Acta Chem. Scand. 1993, 47, 425. (b) Labinger, J . A. Comprehensive
Organic Chemistry; Trost, B. M., Fleming, I., Eds.; Pergamon Press:
New York, 1991; Vol. 8, p 667. (c) Negishi, E. In Comprehensive
Organic Chemistry; Trost, B. M., Fleming, I., Paquette, L. A., Eds.;
Pergamon Press: New York, 1991; Vol. 8, p 1163.
(5) For an overview concerning the reaction of zirconocene with bis-
(alkynyl) derivatives, see, for example: (a) Takahashi, T.; Xi, Z.; Obora,
Y.; Suzuki, N. 1995, 117, 2665. (b) Warner, B. P.; Davis, M.; Buchwald,
S. L. J . Am. Chem. Soc. 1994, 116, 5471. (c) Metzler, N.; No¨th, H.;
Thomann, M. Organometallics 1993, 12, 2423. (d) Negishi, E. I.;
Holmes, S. J .; Tour, J . M.; Miller, J . A.; Cederbaum, F. E.; Swanson,
D. R.; Takahashi, T. J . Am. Chem. Soc. 1989, 111, 3336. (e) Nugent,
W. A.; Thorn, D. L.; Harlow, R. L. J . Am. Chem. Soc. 1987, 109, 2788.
S0276-7333(97)00216-1 CCC: $14.00 © 1997 American Chemical Society

Communications
Organometallics, Vol. 16, No. 14, 1997 3087
Sch em e 2. Rea ctivity of 3b w ith Electr op h ile H+
ppm).8 Cp groups are inequivalent and appear as two
1
singlets both in the H and 13C NMR spectra. 13C NMR
spectra show a doublet at 165.7-168.9 ppm (2J CP, 4.0-
7.6 Hz) characteristic for sp2 carbon atoms bound to
zirconium9 and a doublet at 79.1-88.5 ppm (1J CP, 62.7-
71.3 Hz) characteristic for sp2 carbon atoms bound to
phosphorus. These data agree with the proposed struc-
ture. While compounds 3b and 3c are found to be stable
at room temperature for several days, in contrast, 3a
is transformed into a new derivative not yet fully
characterized overnight at room temperature.10
Attempts to get suitable crystals for X-ray structure
determinations of compounds 3a -c have failed up to
now. Therefore, in order to have a better insight of the
structure and properties of these new metalated phos-
phorus species, a preliminary study of their reactivity
was undertaken. Addition of HCl‚OEt2 to the phos-
phirane 3b in THF at -78 °C leads to a mixture of four
products: the alkenyl-alkynyl phosphanes E/Z-5 (35%)
in a 1/1 ratio, the phospharadialene 6 (35%), and the
secondary phosphane 7 (30%) (Scheme 2). All of these
compounds are fully characterized by NMR11 and mass
spectrometry. The molecular structure of Z-5 (as its
sulfide adduct 8) is also established by X-ray crystal-
lography studies12 (Figure 1), which confirms that a
selective monoreduction of one of the two alkenyl groups
of the starting phosphane 2b takes place. Interestingly,
such a selective monoreduction occurs when 3b is
reacted with HCl‚pyridine: products E/Z-5 (1/1 ratio)
are obtained in quantitative yield.
F igu r e 1. Molecular structure of 8 in the crystal. Selected
distances (Å) and angles (deg): P(1)-S(1) 1.951(1), P(1)-
C(1) 1.827(4), P(1)-C(2) 1.804(4), P(1)-C(3) 1.743(4), C(2)-
C(4) 1.307(5), C(3)-C(5) 1.204(5), C(4)-C(41) 1.462(5),
C(5)-C(51) 1.433(6), S(1)-P(1)-C(1) 113.7(1), S(1)-P(1)-
C(2) 115.2(1), P(1)-C(2)-C(4) 129.9(3), P(1)-C(3)-C(5)
173.5(4), C(1)-P(1)-C(2) 104.1(2), C(1)-P(1)-C(3)
104.8(2), C(2)-P(1)-C(3) 105.6(2), C(2)-C(4)-C(41)
131.9(4), C(3)-C(5)-C(51) 178.1(4).
diate can react with a second equivalent of HCl to give
E/Z-5 via phosphirane ring opening and 6 via substitu-
NMR data for 6 fit well with the values given for the
few phospharadialenes already reported in the litera-
ture.13 The 31P NMR spectrum exhibits a singlet at high
field (δ ) -131.1 ppm), and classical 13C resonances for
1
the cyclic (δ ) 119.5, J CP ) 40.9 Hz) and acyclic (δ )
122.8, 2J CP ) 4.6 Hz) sp2 carbon atoms are detected. The
radialene structure of 6 is unambiguously determined
by X-ray analysis12 (Figure 2) and compares well with
the unique structure of this type, 9, characterized by
X-ray analysis.14 Slightly longer intracylic P-C bonds
(1.825-1.827 Å for 6; 1.816 Å for 9) and a slightly
shorter intracyclic C-C bond (1.413 Å for 6; 1.422 Å
for 9) are found for 6.
tion of the remaining zirconium fragment.15
(11) Selected NMR data for componds E/Z-5 and 6. E-5: 31P{1H}
NMR (C6D6) δ -16.4. 1H NMR (C6D6): δ 7.72-7.65 (m, 4H, CHPh),
7.39-7.24 (m, 6H, CHPh), 7.21 (dd, 3J (H,P) ) 13.5 Hz, 3J (H,H) ) 16.9
Hz, 1H, dCHPh), 6.75 (dd, 2J (H,P) ) 14.5 Hz, 3J (H,H) ) 16.9 Hz, 1H,
PCHd), 1.30 (d, 3J (H,P) ) 13.6 Hz, 9H, tBu). 13C{1H} NMR (C6D6):
δ 143.7 (d, 2J (C,P) ) 26.0 Hz, dCHPh), 135.0 (d, 3J (C,P) ) 7.2 Hz,
i-CPh), 131.9 (s, o-CPh), 129.8 (s, p-CPh), 127.9 (s, m-CPh), 122.5 (d, 1J (C,P)
) 13.2 Hz, PCHd), 106.2 (s, tCPh), 86.2 (d, 1J (C,P) ) 16.2 Hz, PCt),
31.4 (d, 1J (C,P) ) 4.4 Hz, CH3C), 27.4 (d, 2J (C,P) ) 13.1 Hz, CH3C).
Z-5: 31P{1H} NMR (C6D6) δ -35.3. 1H NMR (C6D6): δ 7.72-7.65 (m,
4H, CHPh), dCHPh resonance hidden by phenyl signals, 7.39-7.24 (m,
Formation of E/Z-5, 6, and 7 can be easily explained
via the transient generation of the complex 10 resulting
from the cleavage of a zirconium-carbon bond and
subsequent protonation (Scheme 3). Such an interme-
3
6H, CHPh), 6.39 (dd, 2J (H,P) ) 2.5 Hz, J HH ) 12.7 Hz, 1H, PCHd),
1.28 (d, 3J (H,P) ) 13.5 Hz, 9H, tBu). 13C{1H} NMR (C6D6): δ 144.6
(d, 2J (C,P) ) 19.5 Hz, dCHPh), 136.9 (d, 3J (C,P) ) 2.2 Hz, i-CPh), 131.9
(s, o-CPh), 128.3 (s, p-CPh), 127.9 (s, m-CPh), 124.9 (d, 1J (C,P) ) 17.3
Hz, PCHd), 104.1 (s, tCPh), 87.3 (d, 1J (C,P) ) 29.4 Hz, PCt), 31.5
(d, 1J (C,P) ) 4.3 Hz, CH3C), 27.2 (d, 2J (C,P) ) 15.2 Hz, CH3C). 6:
recrystallized from THF as yellow crystals. 31P{1H} NMR (C6D6): δ
) -131.1. 1H NMR (C6D6): δ 7.72-7.65 (m, 4H, CHPh), 7.55 (d, 3J (H,P)
) 9.6 Hz, 2H, dCHPh), 7.39-7.24 (m, 6H, CHPh), 1.13 (d, 3J (H,P) )
12.7 Hz, 9H, tBu). 13C{1H} NMR (C6D6): δ 137.7 (d, 3J (C,P) ) 2.3 Hz,
i-CPh), 128.3 (s, p-CPh), 127.9 (s, m-CPh), 127.2 (d, 4J (C,P) ) 2.4 Hz,
o-CPh), 122.8 (d, 2J (C,P) ) 4.6 Hz, dCHPh), 119.5 (d, 1J (C,P) ) 40.9
Hz, PCd), 35.6 (d, 1J (C,P) ) 39.1 Hz, CH3C), 29.2 (d, 2J (C,P) ) 14.3
Hz, CH3C). Satisfactory analysis were found for E/Z-5 and 6.
(8) (a) Mathey, F. Chem. Rev. 1990, 997-1025. (b) Chan, S.;
Goldwhite, H.; Keyzer, H.; Rowsell, D. G.; Tang, R. Tetrahedron 1969,
25, 1097.
(9) Thanedar, S.; Farona, M. F. J . Organomet. Chem. 1982, 235,
65.
(10) This transformation can be easily monitored by 31P NMR since
a ∆δ of 584 ppm is detected! 13C and 1H NMR data for this new species
are not informative enough to propose, unambiguously, a structure.
Attempts to get suitable crystals for an X-ray structure determination
have failed up to now.

3088 Organometallics, Vol. 16, No. 14, 1997
Communications
Sch em e 3. P r op osed Mech a n ism for th e F or m a tion of E/Z-5, 6, a n d 7
Sch em e 4. Syn th esis of th e Secon d a r y P h osp h a n e
11
then ring opening and phosphorus carbon bond cleav-
age. Such a mechanism should be favored for a species
like 3e possessing a donor group bonded to phosphorus.
Indeed, addition of HCl‚pyridine to 3e gives rise exclu-
sively to the secondary phosphane 11 (δ 31P ) -129.0,
1J PH ) 249.9 Hz) (Scheme 4).
It has been already reported that zirconacyclopenta-
dienes react with a dichlorophosphane, such as PhPCl2,
to give the corresponding phosphole.16 This metalla-
cycle transfer is not observed when, for example, 3b is
treated with RPCl2 (R ) C6H5 or 2,4,6(tBu)3C6H2). In
this case, the bis(alkynyl)phosphane 2b is formed in
addition to either the cyclic polyphosphane (PhP)5 or the
diphosphene (tBu)3C6H2sPdPsC6H2(tBu)3. Compound
2b is also recovered when 3b is reacted with (trimeth-
ylsilyl)trifluoromethane sulfonate.
F igu r e 2. Molecular structure of 6 in the crystal. Selected
distances (Å) and angles (deg): P(1)-C(1) 1.884(3), P(1)-
C(2) 1.827(3), P(1)-C(3) 1.825(3), C(2)-C(3) 1.413(4), C(2)-
C(4) 1.330(4), C(3)-C(5) 1.327(4), C(4)-C(41) 1.454(4),
C(5)-C(51) 1.457(4), P(1)-C(2)-C(4) 150.8(2), P(1)-C(2)-
C(3) 67.1(2), P(1)-C(3)-C(2) 67.3(2), P(1)-C(3)-C(5) 151.9-
(2), C(1)-P(1)-C(2) 107.1(1), C(1)-P(1)-C(3) 107.2(1),
C(2)-P(1)-C(3) 45.5(1), C(2)-C(4)-C(41) 128.5(3), C(3)-
C(5)-C(51) 128.8(3), C(2)-C(3)-C(5) 140.8(3), C(3)-C(2)-
C(4) 142.0(3).
The formation of the secondary phosphane 7 (δ 31P )
1
-55.1, J PH ) 216.7 Hz) might involve first the proto-
nation on the phosphorus atom of the complex 10,
concomitant cleavage of the zirconium-carbon bond,
Work is in progress to extend these reactions to other
bis(alkynyl)phosphanes and to study the chemical re-
activity of phosphirane zirconacyclopentadienes species.
(12) Crystal data for Z-5 (as the sulfide adduct 8) and 6. ENRAF-
NONIUS CAD4 diffractometer with Mo KR radiation (λ ) 0.710 73
Å); graphite monochromator. Crystal data for 6: crystal dimensions
(mm) 0.9 × 0.5 × 0.125, monoclinic space group P21/n, a ) 10.809(2)
Å, b ) 6.125(2) Å, c ) 25.442(8) Å, V ) 1674 Å3, Z ) 4, Fcalcd ) 1.16 g
cm-3, F(000) ) 624.45; 3811 reflections with 3 < 2θ < 52°, 1875
reflections with I > 3.0σ(I). Structure solution and refinement for 3284
independent reflections with I > 3.0σ(I) and 191 parameters. R )
0.038; Rw ) 0.038. Residual electron density max 0.189, min -0.177
Ack n ow led gm en t. We thank the CNRS for finan-
cial support.
Su p p or tin g In for m a tion Ava ila ble: Tables giving de-
tails of the X-ray structure determinations, atomic coordinates
and isotropic thermal parameters, bond lengths and bond
angles, anisotropic displacement parameters, and hydrogen
atom coordinates for 6 and 8 (18 pages). Ordering information
is given on any current masthead page.
e Å-3
.
Crystal data for 8: crystal dimensions mm 0.3 × 0.4 × 0.2,
orthorhombic space group P212121, a ) 6.037(3)Å, b ) 14.887(3) Å, c
) 20.049(8) Å, V ) 1674 Å3, Z ) 4, Fcalcd ) 1.19 g cm-3, F(000) ) 689.88;
1845 reflections with 3 < 2θ < 50°, 1457 reflections with I > 3.0σ(I).
Structure solution and refinement for 1682 independent reflections
with I > 3.0σ(I) and 201 parameters. R ) 0.027; Rw ) 0.029. Residual
electron density max 0.189, min -0.165 e Å-3
. The structures were
solved by direct methods (SHELXS86) and refined according to the
CRYSTALS program. The positions of all hydrogen atoms were
determined from difference Fourier maps but introduced in calculated
positions (C-H ) 0.98 Å) and thermal parameters fixed 20% higher
than those of the carbon atoms to which they were attached. All non-
hydrogen atoms were anisotropically refined. Corrections for Lorentz
polarization effects and semi-empirical absorption corrections were
applied.
OM970216I
(15) Such results can be compared with those recently reported
concerning the treatment of zirconacyclopentadiene derivatives with
HCl: cleavage of the carbon-zirconium bond was also observed with
formation either of (E,E) butadiene compounds5c or alkenyl-alkynyl
derivatives.5b
(16) (a) Fagan, P. J .; Nugent, W. A. J . Am. Chem. Soc. 1988, 110,
2310. (b) Fagan, P. J .; Nugent, W. A.; Calabrese, J . C. J . Am. Chem.
Soc. 1994, 116, 1880.
(13) Maerker, A.; Brieden, W. Chem. Ber. 1991, 124, 933.
(14) Miyahara, I.; Hayashi, A.; Hirotsu, K.; Yoshifuji, M.; Yoshimura,
H.; Toyota, K. Polyhedron 1992, 3, 385.