Metalla-azaspirophosphanes: Synthesis, structure, and reactivity

Article abstract of DOI:10.1002/anie.200250772

The reaction of a trichloro iminophosphorane (Cl₃P=NtBu) and either a zirconaindane phospholane or an azazirconaindane phosphane proceeds in an unexpected fashion, with the trapping of a transient chlorophosphaimine species (Cl-P=NtBu), and the formation of unique metalla-azaspirophosphanes (see picture).

Full text of DOI:10.1002/anie.200250772

Communications
functionalities that differ only slightly in their steric and/or
electronic environment.[2] However, studies of interactions
between main-group elements and, more precisely, phospho-
rus derivatives and zirconium compounds have not been so
frequently reported.[3,4] We recently reported the formation of
mono- or tricyclic diphosphanes by exchange reactions
between monochlorophosphanes or dichlorophosphanes
and, for example, the zirconaindane phospholane (phospho-
lanozirconaindane) 1 to obtain compounds 2 and 3 in good
yields[5,6] and even in an enantiomerically pure form for one of
these derivatives.[7] Functionalization of these ligands and
their grafting on polymer supports or on dendrimers should
open up interesting perspectives in catalysis. At first glance,
an easy method of functionalization may involve the direct
reaction of 1 with trichlorophosphane oxide or sulfide in
order to synthesize monohalogenated tricyclic ligands such as
4. However treatment of 1 with (S)PCl3 or (O)PCl3 gave
numerous phosphorus species, as attested by the complexity
of 31P NMR spectra of the resulting mixtures. Unexpectedly,
an unprecedented reaction was observed when 1 was treated
with the trichloro iminophosphorane 5 leading to the first
metallaspirophosphane 6. We report here the full character-
ization of this unique compound including X-ray diffraction
studies. The extension of this surprising reaction to the
synthesis of another metalla-azaspirophosphane is described,
as well as details concerning the mechanism of formation of
these species and preliminary results concerning their reac-
tivity.
Zirconium Spirophosphanes
Metalla-Azaspirophosphanes: Synthesis, Struc-
ture, and Reactivity**
Krzysztof Owsianik, Maria Zablocka,*
Bruno Donnadieu, and Jean-Pierre Majoral*
Zirconium derivatives play central roles in a number of
technologically important processes including, for example,
the Ziegler–Natta-type polymerization of olefins.[1] The
group IV metallocene derivatives have been the target of a
range of studies directed either at the generation and
trapping, or the isolation of a large number of significant
species in organic and organometallic chemistry. A number of
new methodologies in synthesis has been found that give easy
access to useful starting materials, such as various hetero-
cycles, chiral ligands, or more sophisticated molecules. Indeed
the success of organozirconium reagents in organic, inorganic,
and organometallic chemistry can be explained in terms of
chemo-, regio-, diastereo-, and enantioselectivity. These
reagents are generally able to discriminate between similar
Ph
R2P
P
P
P
Ph
Ph
R'
X
2
3 X = lone pair; R' = alkyl, NR2, ...
4 X = O, S; R' = Cl
Treatment of the zirconaindane phospholane 1 (2 equiv)
¼ ꢀ
with Cl3P N tBu (5; 1 equiv) in toluene at room temperature
resulted in the formation of two phosphorus species 6 and 7
and [Cp2ZrCl2] (Scheme 1, Cp = h5-C5H5). The 31P {1H} NMR
spectrum of 6, which was isolated in 52% yield, exhibits two
doublets at d = 3.7 and 1.1 ppm (2JPP = 22.4 Hz), while a signal
at d = ꢀ10 ppm is attributed to the phospholane 7.[8] In
addition to the signals from the carbon–phosphorus tricyclic
[*] Dr. J.-P. Majoral, B. Donnadieu
Laboratoire de Chimie de Coordination
CNRS
205 route de Narbonne, 31077 Toulouse cedex 4 (France)
Fax: (+33)5-6155-3003
Ph
E-mail: majoral@lcc-toulouse.fr
P
7
Ph
Dr. M. Zablocka, K. Owsianik
Centre of Molecular and Macromolecular Studies
Polish Academy of Sciences
Cl3P
N
+
+
Zr
Cp2
– [Cp2ZrCl2]
P
5
Ph
N
P
Cl
1
Sienkiewicza 112, 90-363 Lodz (Poland)
8
+ 1
[**] This work was performed with the support of the Laboratoire
EuropØen AssociØ (L.E.A) financed by C.N.R.S. (France), the Polish
Committee for Scientific Research (KBN grant 3TO9A03619), and
the European Community Marie Curie Fellowship (contract
No. HPMT-CT-2001-00398).
P
P
Ph
N
ZrCp2
Cl
6
Supporting information for this article is available on the WWW
under http://www.angewandte.org or from the author.
Scheme 1. Synthesis of the zircona–azaspirophosphane 6. Solvent and
conditions: toluene, 08C, 30 min.
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DOI: 10.1002/anie.200250772
Angew. Chem. Int. Ed. 2003, 42, 2176 – 2179

Angewandte
Chemie
backbone and from the tert-butyl group linked to the nitrogen
atom, two doublets are detected at d = 6.05 (JHP = 1.7 Hz) and
6.09 ppm (JHP = 1.7 Hz) in the 1H NMR spectrum of 6, which
are characteristic of coupling of the cyclopentadienyl protons
with a phosphorus atom when a direct phosphorus–zirconium
bond is formed.[9,10] Other 1H NMR data as well as 13C NMR
data are in agreement with the proposed structure for 6, the
first metalla-azaspirophosphane derivative reported to date.
The solid-state structure of 6 has been corroborated by a
single-crystal X-ray diffraction study.[11] An ORTEP diagram
of 6 is shown in Figure 1 with selected bond lengths and
angles.
N
Me2P
[Cp2ZrMe2] +
N
Cl P
– 40°C
Cp2ZrCl
9
10
N
Me2P
N
Me2P
Cp2ZrCl
11
H
12
Scheme 2. Addition of the chloro iminophosphane 9 to [Cp2ZrMe2].
phosphane 12 through cleavage of the nitrogen–zirconium
bond (Scheme 2).
In order to provide additional arguments in favor of the
mechanism involving 1 and 5, 1 was reacted with the stable
chlorophospha-imine 9 in a 1:1 ratio in toluene at 08C. Such a
reaction allowed the isolation of the bisphosphane 13,
obtained as only one isomer, and arising from the insertion
of 9 into a zirconium–carbon bond of 1 with release of a
{Cp2ZrCl} fragment after mild hydrolysis of the nitrogen–
zirconium bond (Scheme 3). Indeed, this experiment corrob-
orates the proposed mechanism for the formation of 6 in
which the trapping of an analogous chlorophospha-imine is
postulated.
N
Cl P
+
Zr
P
N
Cp2
9
Ph
P
1
P
P
P
H2O
Ph
ZrCp2Cl
Ph
N
Figure 1. ORTEP drawing of complex 6. Selected bond lengths [Š] and
angles [8]: Zr-N 2.204(2), Zr-P(1) 2.5805(9), P1-N 1.615(2), P1-C1
1.865(2), P1-C10 1.807(3); N-Zr-P1 38.44(5), N-P1-Zr 58.05(7), P1-N-
Zr 83.51(9), C10-P1-C1 92.9(12), N-P1-C1 123.54(11).
H
13
Scheme 3. Addition of the chloro iminophosphane 9 to the tricyclic
system 1.
As a first approach, one can postulate that the trichloro
iminophosphorane 5 reacts with the first equivalent of 1 (with
removal of [Cp2ZrCl2]) to form the transient chlorophospha-
As well as representing the preparation of an unique
metalla-azaspirophosphane, these preliminary experiments
show that in the presence of 1, the trichloro iminophosphor-
ane 5 can be regarded as a precursor of the unstable
chlorophospha-imine 8, a potentially useful new reagent in
organophosphorus chemistry.
A question remains: Is it possible to generalize such a
reaction? In other words, can other zircona complexes act in a
similar fashion to 5? To answer this question, the azazirco-
nacyclopentene 14[12] (2 equiv) was heated at 508C for 2 h in
the presence of 5 (1 equiv); in these conditions the expected
metalla-bisazaspirophosphane 15 was isolated in 49% yield
(Scheme 4). Therefore, the presence of a N-Zr-C linkage in
the starting reagent 14, instead of the C-Zr-C unit in 1, does
not prevent the reaction from taking place.
ꢀ ¼ ꢀ
imine Cl P N tBu (8), which reacts further with the second
ꢀ
equivalent of 1 by insertion into an intracyclic Zr C bond
with concomitant migration of the chlorine atom from the
phosphorus to the zirconium center. Rearrangement then
leads to the stable 18 electron metalla-species 6. Such an
assumption is supported by previous work[10] in which the
reaction of an analogous chlorophospha-imine
9 with
[Cp2ZrMe2] was reported. In this latter experiment the
ꢀ
reaction proceeded by insertion of 9 into a Zr Me bond
followed by migration of the chlorine atom from the
phosphorus to zirconium center and concomitant migration
of the second methyl group in the opposite direction to give
the kinetic product 10, with the reaction observed only at
ꢀ408C. Migration of a {Cp2ZrCl} fragment to nitrogen
occurred, which led to the thermodynamic product 11 which
is extremely water-sensitive and gave the final amino
Such unusual complexes offer the opportunity to study
their versatile behavior since several possible reactions can be
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ꢀ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2177

Communications
two isomers in a 9:1 ratio (major product: d = 57.9 (d, PPh)
and 67.8 ppm (d, PN) with 2JPP = 7.8 Hz; minor product: 57.5
(d, PPh) and 65.5 ppm (d, PN) with JPP = 4.4 Hz). Dissoci-
P(NiPr2)2
P(NiPr2)2
2
+
N
Cl3P
N
2
N
– [Cp2ZrCl2]
Zr
Cp2
P
5
ation of the strong zirconium–chlorine bond and retention of
the ring system was observed when NaBPh4 was added to a
solution of 6 in acetonitrile. 31P NMR spectra show the
disappearance of the two doublets that arise from complex 6,
and two new doublets at d = 4.4 (PN) and 6.3 ppm (PPh) with
2JPP = 32 Hz. Proof of ring retention is given by a small
coupling constant (JHP = 1.5 Hz) in the 1H NMR spectrum
that results from interactions between cyclopentadienyl
protons and the phosphorus center. However, the resulting
new cationic zirconium azaspirophosphane 20 is highly
unstable and decomposes to several unidentified products.
14
N
ZrCp2
Cl
15
Scheme 4. Synthesis of the zircona-bisazaspirophosphane 15.
envisaged, including regiospecific reactions on one or both of
ꢀ
ꢀ
the phosphorus atoms, selective cleavage of P N or P Zr
bonds, and specific reactions at the zirconium center.
Preliminary results obtained from experiments conducted
with the metalla-azaspirophosphane 6 are shown in Scheme 5.
ꢀ
ꢀ
Indeed, the presence of P Zr and N Zr bonds does not
significantly help in the stabilization of 20. Nevertheless a
specific reaction at the zirconium center can be emphasized at
this stage.
H2O
P
P
Ph
H
O
16
In conclusion, the reaction of a trichloro iminophosphor-
ane with two different zirconaindane complexes led to unique
metallaspirophosphanes. The extension of such a method-
ology to other trichloro iminophosphoranes and to other
zirconium complexes should provide a range of new metalla-
spirophosphanes; their versatile behavior would allow the
preparation of useful reagents for organometallic chemistry
and catalysis.
[AuCl(tht)]
P
P
Ph
Au–Cl
N
ZrCp2
Cl
17
P
P
Ph
N
ZrCp2
Cl
S8
i) S8
P
P
Ph
S
ii) H2O
6
P
P
Ph
S
N
S
N
ZrCp2
Cl
19
H
Received: December 16, 2002 [Z50772]
18
NaBPh4
Keywords: bimetallic complexes · phosphanes · phosphorus ·
spiro compounds · zirconium
.
CH3CN
– NaCl
P
+
P
Ph
–
N
BPh4
ZrCp2
N
C
20
[1] See for example: a) “Metallocene and Single Site Olefin
Catalysts”: J. Mol. Catal. A 1998, 128, 1 (Ed.: R. F. Jordan);
b) W. E. Piers, Chem. Eur. J. 1998, 4, 13, and references therein.
[2] See for example: a) “Recent Advances in the Chemistry of
Zirconocene and Related Compounds:”Tetrahedron 1995, 51,
15, 4255 (Guest Ed.: E. I. Negishi); b) J. A. Labinger in
Comprehensive Organic Synthesis, Vol. 8 (Ed.: B. M. Trost, I.
Fleming), Pergamon, Oxford, 1991, p. 667; c) E. I. Neghishi in
Comprehensive Organic Synthesis, Vol. 5 (Ed.: B. M. Trost, L. A.
Paquette), Pergamon, Oxford, 1991, p. 1163; d) R. H. Grubbs,
H. S. Pine in Comprehensive Organic Synthesis, Vol. 5 (Ed.:
B. M. Trost, L. A. Paquette), Pergamon, Oxford, 1991, p. 1115;
e) C. Ferreri, G Palumbo in Comprehensive Organic Synthesis,
Vol. 1 (Ed.: B. M. Trost, S. L. Schreiber), Pergamon, Oxford,
1991, p. 139; f) A. D. Ryabov, Chem. Rev. 1990, 90, 403; g) J. E.
McMurry, Chem. Rev. 1989, 89, 1513; G. Erker, M. Aulbach, M.
Mena, R. Ptaff, F. Sosna, Chem. Scr. 1989, 29, 451; h) S. L.
Buchwald, R. B. Nielsen, Chem. Rev. 1988, 88, 1047; i) E. I.
Negishi, T. Takahashi,Aldrichimica Acta 1985, 18, 31.
[3] a) “New Aspects in Phosphorus Chemistry:”J. P. Majoral, A.
Igau, V. Cadierno, M. Zablocka, Top. Curr. Chem. 2002, 220, 54;
b) J. P. Majoral, P. Meunier, A. Igau, N. Pirio, M. Zablocka, A.
Skowronska, S. Bredeau, Coord. Chem. Rev. 1998, 178–180, 145;
c) J. P. Majoral, A. Igau, Coord. Chem. Rev. 1998, 176, 1.
[4] a) O. J. Scherer, M. Swarowsky, H. Swarowsky, G. Wolmer-
shauser, Angew. Chem. 1988, 100, 738; Angew. Chem. Int. Ed.
Engl. 1988, 27, 694; b) D. W. Stephan, Angew. Chem. 2000, 112,
322; Angew. Chem. Int. Ed. 2000, 39, 314; c) P. J. Chirik, J. A.
Pool, E. Lobkovsky, Angew. Chem. 2002, 114, 3613; Angew.
Chem. Int. Ed. 2002, 41, 3463.
CH3
Scheme 5. Reactivity of the zircona-azaspirophosphane 6.
Indeed, several observations can be made. Hydrolysis occur-
red, as expected, at the “central” phosphorus moiety with
ꢀ
ꢀ
concomitant P N and P Zr bond cleavage that led to a new
tricyclic ligand 16, obtained as two isomers (cis and trans with
respect to the position of the substituents on phosphorus
atoms, that is, the proton and the phenyl group) in a 9:1 ratio
and characterized by 31P NMR (major product: d = 3.4 (brd,
2
2JPP = 143 Hz, PPh) and 51.3 ppm (d of brd, JPP = 143 Hz,
1JPH = 488 Hz, PN); minor product: d = ꢀ7.9 (brd, JPP
=
2
53 Hz, PPh) and 37.4 ppm (d of brd, 2JPP = 53 Hz, JPH
=
1
1
488 Hz, PN)), H and 13C NMR spectroscopy, as well as by
mass spectrometry. Addition of [AuCl(tht)] (tht = tetrahy-
drothiophene) to 6 occurred at the phospholane ring, that is,
on the external trivalent phosphorus atom, to form a unique
bimetallic complex 17. Treatment of6 with two equivalents of
sulfur initially afforded the derivative 18 resulting from
sulfuration of the “external” phosphorus atom. The reaction
can be monitored by 31P NMR (doublets at d = 60.3 (P(S)Ph)
and ꢀ0.5 ppm (PN) with 2JPP = 26 Hz). Sulfuration of the
central phosphorus moiety then occurred with cleavage of the
ꢀ
ꢀ
dative P Zr bond followed by mild hydrolysis of the N Zr
bond to form the disulfide adduct 19, which was obtained as
2178
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Angewandte
Chemie
[5] M. Zablocka, A. Igau, B. Donnadieu, J. P. Majoral, A. Skow-
ronska, P. Meunier, Chem. Commun. 1997, 1239.
[6] M. Zablocka, N. Cenac, A. Igau, B. Donnadieu, J. P. Majoral, A.
Skowronska, P. Meunier, Organometallics 1996, 15, 5436.
[7] M. Zablocka, B. Donnadieu, J. P. Majoral, M. Achard, G. Buono,
Tetrahedron Lett., in press.
[8] The phospholane 7 was isolated and characterized as its sulfide
adduct. Main characteristic data: 31P{1H} NMR (C6D6,
162 MHz): d = 55.1 ppm. 13C{1H} NMR (C6D6, 100.6 MHz): d =
29.8 (d, 1JCP = 66.8 Hz; CH2P), 32.7 (d, 2JCP = 3.7 Hz; CH2), 37.5
(d, 1JCP = 66.5 Hz; CH2P), 45.3 (d, 2JCP = 11.6 Hz; CH), 126.7 (s),
127.0 (s), 128.8 (s), 128.9 (d, JCP = 11.1 Hz; o-Ph or m-Ph), 129.9
(d, JCP = 9.8 Hz; m-Ph or o-Ph), 131.9 ppm (s, p-Ph).
[9] a) M. Zablocka, F. Boutonnet, A. Igau, F. Dahan, J. P. Majoral,
K. M. Pietrusiewicz, Angew. Chem. 1993, 105, 1846; Angew.
Chem. Int. Ed. Engl. 1993, 32, 1735; b) V. Cadierno, M.
Zablocka, B. Donnadieu, A. Igau, J. P. Majoral, A. Skowronska,
J. Am. Chem. Soc. 1999, 121, 11086.
[10] A. Igau, N. Dufour, A. Mahieu, J. P. Majoral, Angew. Chem.
1993, 105, 76; Angew. Chem. Int. Ed. Engl. 1993, 32, 95.
[11] CCDC-199652 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge via
www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cam-
bridge Crystallographic Data Centre, 12, Union Road, Cam-
bridge CB21EZ, UK; fax: (+ 44)1223-336-033; or deposit@
ccdc.cam.ac.uk).
[12] V. Cadierno, B. Donnadieu, A. Igau, J. P. Majoral, Eur. J. Inorg.
Chem. 2000, 417.
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