Investigation in the coupling of zirconocene complexes and trimethylsilyl(diphenylphosphino)acetylene. P-C bond cleavage chemistry from protonolysis reactions

Article abstract of DOI:10.1016/j.jorganchem.2003.12.034

The regioselectivity of the coupling reactions of the internal acetylenic derivative Ph₂P-C≡C-SiMe₃ (2) and the benzyne complex [Cp₂Zr(η²- C₆H₄)] (1) resulted preferentially in the formation of the zirconaindene metallacycle with the metal α-carbanions stabilized by the trimethylsilyl group. We have been able to structurally characterize the two regiosomers. The unusual acute Zr-C-P angle and the short Zr-P distance revealed that a significant Lewis-base/Lewis-acid σ-P-Zr interaction occurs in the α-phosphino zirconaindene metallacycle. Addition of HCl·Et₂O on the cyclic α-silyl zirconindene complex led to competition reactions between (i) the nucleophilic attack of the lone pair of the phosphino group followed by P-C cleavage to form Ph₂PH and Ph-C≡C-SiMe₃ (7) and (ii) protonolysis of the Zr-CSi bond to give the Z-vinyl silyl phosphino product Ph₂PC(Ph)=C(H) SiMe₃ (8). When the lone electron pair of the phosphino group is engaged intramolecularly with the metal center to achieve the stable 18-electron configuration protonolysis reaction on the Zr-C bonds to give the Z-vinyl silyl phosphino product Ph₂PC(H)=C(Ph)SiMe₃ (9) is the unique process observed. Protonolysis reaction on the complexes prepared in situ from the addition of 2 and zirconocene like reagents [Cp₂Zr] gave Ph₂PH, H-C≡C-SiMe₃, and Ph₂PC(H)=C(H)SiMe₃ (18) which resulted from the competitive P-C and Zr-C bond cleavage processes of the transient alkyne complex Cp₂Zr(η²-Ph₂ P-C≡C-SiMe₃)] (14).

Full text of DOI:10.1016/j.jorganchem.2003.12.034

Journal of Organometallic Chemistry 689 (2004) 953–964
www.elsevier.com/locate/jorganchem
Investigation in the coupling of zirconocene complexes and
trimethylsilyl(diphenylphosphino)acetylene. P–C bond
cleavage chemistry from protonolysis reactions
*
Yamna El Harouch, Victorio Cadierno, Alain Igau , Bruno Donnadieu,
*
Jean-Pierre Majoral
Laboratoire de Chimie de Coordination du CNRS, 205 route de Narbonne, 31077 Toulouse Cedex, France
Received 12 November 2003; accepted 12 December 2003
Abstract
The regioselectivity of the coupling reactions of the internal acetylenic derivative Ph2P–CBC–SiMe3 (2) and the benzyne complex
[Cp2Zr(g2-C6H4)] (1) resulted preferentially in the formation of the zirconaindene metallacycle with the metal a-carbanions sta-
bilized by the trimethylsilyl group. We have been able to structurally characterize the two regiosomers. The unusual acute Zr–C–P
angle and the short Zr–P distance revealed that a significant Lewis-base/Lewis-acid r-P–Zr interaction occurs in the a-phosphino
zirconaindene metallacycle. Addition of HCl ꢀ Et2O on the cyclic a-silyl zirconindene complex led to competition reactions between
(i) the nucleophilic attack of the lone pair of the phosphino group followed by P–C cleavage to form Ph2PH and Ph–CBC–SiMe3 (7)
and (ii) protonolysis of the Zr–CSi bond to give the Z-vinyl silyl phosphino product Ph2PC(Ph)@C(H)SiMe3 (8). When the lone
electron pair of the phosphino group is engaged intramolecularly with the metal center to achieve the stable 18-electron configu-
ration protonolysis reaction on the Zr–C bonds to give the Z-vinyl silyl phosphino product Ph2PC(H)@C(Ph)SiMe3 (9) is the unique
process observed. Protonolysis reaction on the complexes prepared in situ from the addition of 2 and zirconocene like reagents
‘‘[Cp2Zr]’’ gave Ph2PH, H–CBC–SiMe3, and Ph2PC(H)@C(H)SiMe3 (18) which resulted from the competitive P–C and Zr–C bond
cleavage processes of the transient alkyne complex Cp2Zr(g2-Ph2P–CBC–SiMe3)] (14).
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Zirconium; C–C coupling; Phosphorus; Cleavage reactions
1. Introduction
reactions with 1 [4], While using the trimethylsilyl group
R–CBC–SiMe3 as a proton surrogate, these authors
observed that the silyl fragment was ending in a-position
to the metal center (Scheme 1, equation (a)) regardless
of the nature of the R group. Both electronic (silyl
groups are known to stabilize a-carbanions) [5] and
steric factors (the a-position is probably less hindered
than the b-position) [1c] were invoked to rationalize
the regioselectivity of such coupling reactions. More
recently, we found that addition of the terminal diph-
enylphosphinoacetylene Ph2P–CBCH to the benzyne
zirconocene complex 1 leads to the formation of only
one regioisomer where the phosphorus fragment occu-
pie an a position relative to the zirconocene moiety
(Scheme 1, equation (b)) [6]. We proposed that the
phosphino moiety Ph2P– acts as a two electrons L type
ligand which directs the approach of the acetylenic
The reductive coupling of unsaturated organic mol-
ecules with low-valent group 4 complexes to yield me-
tallacyclic compounds is well documented [1,2]. In
particular, alkynes are known to act as suitable coupling
partners in association with the benzyne zirconocene
complex [Cp2Zr(g2-C6H4)] 1, to produce the corre-
sponding zirconaindene complexes [2]. The regiochem-
istry of the insertion process was investigated by
Buchwald and Nielsen [3], who also noted that terminal
alkynes, R–CBC–H, do not undergo clean coupling
* Corresponding authors. Tel.: +33-5-61-33-31-23; fax: +33-5-61-55-
30-03.
E-mail addresses: igau@lcc-toulouse.fr (A. Igau), majoral@
lcc-toulouse.fr (J.-P. Majoral).
0022-328X/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2003.12.034

954
Y. El Harouch et al. / Journal of Organometallic Chemistry 689 (2004) 953–964
Scheme 1.
moiety, thus preventing the formation of the alternate
b-regioisomer.
sistent with their formulation as two regioisomers, 3 and
4, of the expected zirconaindene complexes (Scheme 2).
The 31P NMR spectrum of the crude reaction mixture
displays a singlet at )8.5 ppm for the major isomer. By
1H and 13C NMR, g5-cyclopentadienyl (Cp) and trim-
ethylsilyl (Me3Si) groups appear as one singlet. In ad-
dition to the signals corresponding to the aryl carbons,
the deshielded chemical shift at 244.8 (JCP ¼ 26:8 Hz)
ppm observed in the 13C NMR spectrum is indicative of
the occurrence of a Zr–C bond [7]. Moreover, in the 1H–
13C{31P} HMBC experiment, correlations were ob-
served between the Zr–C sp2-carbon atom and the
protons of the silyl fragment. The signal at 152.0
(JCP ¼ 39:8 Hz) ppm corresponds to the carbon atom
linked to the phosphorus substituent. The minor isomer
exhibits characteristic signal at ꢁ67:5 ppm in the 31P
NMR spectrum. The 13C NMR shows the sp2-C signals
linked to phosphorus and silyl fragments at 191.7
(JCP ¼ 10:5 Hz) and 189.9 (JCP ¼ 11:8 Hz) ppm, re-
spectively. All NMR assignments are in favor of the
formation of the two zirconaindenes with the major
component corresponding to the complex 3 bearing the
silyl fragment in a-position relative to the zirconium
atom, and the minor product 4 corresponding to the
reverse regioisomer. Variable temperature NMR exper-
iments provided no evidence for any fluxional process.
Addition of L type ligands (L ¼ PMe3, pyridine,
CH3CN) to 4 did not modify its 31P NMR chemical
shift. Also noteworthy in the 31P NMR spectrum is a
With the aim to gain more insight into the regio-se-
lectivity of the insertion process, we were led to use
trimetylsilyldiphenylphosphinoacetylene Me3Si–CBC–
PPh2 (2) as a reacting substrate for the benzyne zirc-
onocene complex 1. This led us to identify two isomeric
zirconocene complexes whose X-ray structure analyses
are reported here. In addition, protonolysis reactions
carried out on such derivatives reveals the occurrence of
competitive P–C and Zr–C bond cleavage reactions.
These competitive P–C and Zr–C bond cleavage pro-
cesses were also observed after the protonolysis reaction
carried out on the complexes obtained from the addition
of the internal acetylenic derivative 2 with zirconocene
synthons ‘‘[Cp2Zr]’’.
2. Results and discussion
2.1. Synthesis and X-ray crystal structure of zirconaind-
ene complexes 3 and 4
The synthesis was carried out by direct reaction of
Me3Si–CBC–PPh2 (2) with the benzyne zirconocene
complex 1, generated in situ from Cp2ZrPh2 in refluxing
toluene for 2 h, leading to two compounds in a 10:1
ratio. After their separation and purification, elemental
analyses and mass spectra on pure samples were con-
Scheme 2.

Y. El Harouch et al. / Journal of Organometallic Chemistry 689 (2004) 953–964
955
Table 2
Crystal data and structure refinement for 3 and 4
large Dd of 60 ppm observed between the two regioi-
somers 3 and 4 depending on whether the silyl group is
placed at the a or b position relative to the zirconium
center. Large chemical shift differenciations between
phosphino zirconaindene regioisomers have been al-
ready observed in our earlier studies (Table 1) [6,8]. It is
also noteworthy that the 31P chemical shift of b-phos-
phino zirconaindenes, is not significantly affected by the
nature of the substituent in a position to the metal
center, in marked contrast with the alternate case of a-
phosphino zirconaindenes, for which the 31P resonance
is highly dependent on the nature of the substituent
placed in b position.
Let us specify that prolonged reflux of a mixture of
the regioisomers 3 and 4 in toluene in the presence or
absence of phosphines (PMe3, PhPMe2, Ph2PMe) or
pyridine as two electron donor ligands did not modify
the initial ratio [3].
The X-ray structure analyses of the compounds 3 and
4 are reported (Table 2). The structural diagrams of
these complexes, shown in Figs. 1 and 2, respectively,
are revealing interesting features. Selected bond dis-
tances and angles are presented in Table 3. The bonding
parameters at the pseudotetrahedral bent metallocene
moiety for 3 and 4 are as usually observed in a num-
ber of other Zr(IV)-containing zirconocene deriva-
tives [9]. In both structures the atoms Zr, C1–C8 are
almost perfectly coplanar. The C1–C2, C2–C3, and
C3–C8 bond lengths in 3 and 4 are not significantly
perturbed by the nature of the substituents linked to the
C1 and C2 atoms, and compare well with the other
zirconaindene complexes reported in the literature
([6,10], also for phosphonium–zirconaindeneate com-
plexes, see [11]). The Zr–C8 aromatic bond lengths
3
4
Formula
C33H33PSiZr
579.87
C33H33PsiZr
579.87
Formula weight
Crystal size (mm)
Crystal system
Space group
0.27 ꢂ 0.22 ꢂ 0.07
monoclinic
P21=c
0.52 ꢂ 0.12 ꢂ 0.07
triclinic
ꢁ
P1
293
Temperature (K)
ꢀ
Wavelength (A)
180
0.71073
9.1354(12)
38.617(5)
8.7101(12)
90.0
0.71073
10.2451(16)
10.3288(16)
14.813(3)
70.290(19)
72.510(19)
82.921(18)
1407.0(4)
2
ꢀ
a (A)
ꢀ
b (A)
ꢀ
c (A)
a (°)
b (°)
c (°)
113.422(15)
90.0
3
ꢀ
V (A )
2819.6(7)
4
1.366
Z (mg mꢁ3
)
Calculated density
(mg mꢁ3
Absorption coefficient
1.369
)
0.509
0.510
(mmꢁ1
)
F ð000Þ
1200
45.2
600
52.5
2hmax (°)
Reflections measured
total: 12 994
unique: 3670
Rint ¼ 0:0478
3670
total: 13 360
unique: 5108
Rint ¼ 0:0274
5108
Reflections observed
½I > 2ðIÞꢃ
Number of variables
Tmin ꢁ Tmax
328
0.403–0.797
1.038
328
0.507–0.844
1.048
GOF on F 2
R1ðF Þ½I > 2rðIÞꢃ
R1ðF 2Þ (all data)
wR2ðF 2Þ (all data)
0.0386
0.0530
0.0987
0.0289
0.0360
0.0780
ꢀ
measured in 3 (2.258(3) A) is within the expected range
for tetra-coordinated zirconocene complexes of the
type CpZr(X)(Y) (as for example in the structurally
Table 1
31P NMR chemical shifts (ppm) of a- and b-phosphinozirconaindenes
a-P-zirconaindenes
d
31P
b-P-zirconaindenes
d
31P
Dd
Ref.
[6]
7
ꢁ36
ꢁ10
26
[8]
ꢁ56ðPaÞ
ꢁ67
ꢁ10ðPbÞ
ꢁ7
46
60
[8]
Current

956
Y. El Harouch et al. / Journal of Organometallic Chemistry 689 (2004) 953–964
Table 3
ꢀ
Selected bond distances (A) and angles (°) for 3 and 4
3
4
X
Y
SiMe3
PPh2
PPh2
SiMe3
Zr–C1
Zr–C8
2.279(3)
2.254(2)
2.258(3)
1.345(5)
1.502(5)
1.414(5)
1.877(3)
1.856(3)
2.357(2)
1.352(3)
1.493(3)
C1–C2
C2–C3
C3–C8
C1–X
1.420(3)
1.751(2)
C2–Y
Zr–P
1.895(2)
2.7784(6)
68.77(7)
–
C1–Zr–C8
Zr–C1–C2
Zr–C8–C3
Zr–C1–X
C1–C2–Y
X–C1–C2
78.01(12)
111.4(2)
111.8(2)
126.67(15)
116.87(14)
86.87(9)
123.03(16)
116.0(3)
125.60(26)
127.09(16)
144.89(18)
Fig. 1. Molecular structure of 3 (ORTEP drawing with thermal ellip-
soids at 50% probability).
the formally open-shell Zr and its phosphine substituent
avoid interacting with one another. The Zr–C–P angle in
II is open at 130.1° and the closest Zr–P approach in the
ꢀ
crystal is the intramolecular distance of 3.75 A [12].
ꢀ
Therefore, the Zr–P distance of 2.7784(6) A in 4 lies in
the limit of those observed in zirconocene(IV) phosphine
complexes of the type Cp2Zr(X)(Y)(PR3) (Zr–P 2.65–
ꢀ
2.85 A) [13,14], it is reasonable to propose that a
significant Lewis-base/Lewis-acid r-P–Zr interaction
occurs in 4.
2.2. Protonolysis reaction of zirconaindenes complexes 3
and 4
Treatment of the isolated a-trimethylsilyl zircona-
indene regioisomer 3 with 2 equiv. of HCl ꢀ OEt2 in THF
at 25 °C led to the clean formation of two phosphines
which were identified by 31P NMR as Ph2PH (d )40
1
ppm, JPH ¼ 273 Hz), and the vinyl phosphine 8 (d 0.8
Fig. 2. Molecular structure of 4 (ORTEP drawing with thermal ellip-
soids at 50% probability).
ppm) in 10:1 ratio, respectively. The 1H NMR spectrum
for 8 revealed the characteristic resonance of the vinylic
@CH proton at d 6.88 ppm, whereas the 13C NMR
spectrum showed signals at 153.5 (@CHSi) and 155.9
(PC@) ppm in the expected region for olefinic sp2 car-
bon atoms. In addition, the acetylenic organic product
Me3Si–CBC–Ph (7) was also identified from the crude
reaction mixture by NMR and GC–MS analysis
(Scheme 3).
Clearly, the incipient alkenyl phosphine 8 is resulting
from the expected protonolysis of the two Zr–C bonds
of the zirconaindene complex 3 [3,14]. However, in order
to rationalize the formation in the crude reaction of the
primary phosphine Ph2PH it is reasonable to propose
that protonation at the phosphorus atom generates the
transient phosphonium–zirconate complex 9 which re-
arranges after cleavage of the P–C bond to form Ph2PH
characterized zirconaindene I) [10]. It is in marked
contrast with the Zr–C8 distance found in 4 of 2.357(2)
ꢀ
A which is in favor with a five-coordinated zirconocene
metal fragment of the type CpZr(X)(Y)(L) [11]. Phenyl
substituents at the phosphorus atom adopt an orienta-
tion as to minimize their steric interaction with the
metallocene fragment. Moreover, the Zr–C1–P angle in
4 at 86.9° is unusually acute. It is much smaller than
those observed in unsaturated five-membered ring zir-
conocenes, which are as expected around a sp2-carbon
atom as for example Zr–C1–Si angle (123.0°) in 3.
Interestingly the X-ray structure of the diphenylphos-
phinomethanechlorozirconocene complex Cp2Zr(Cl)CH2
PPh2 (II) is remarkable in revealing the degree to which

Y. El Harouch et al. / Journal of Organometallic Chemistry 689 (2004) 953–964
957
Scheme 3.
and 5 (Scheme 3). b-Elimination reaction with halogen
as leaving group in zirconacyclopentadiene complexes to
afford the corresponding alkynyl zirconation product
was lately observed by Takahashi and coll [15]. More-
over P–C bond cleavage in b-phosphorus zirconocene
complexes was already exemplified [16]. We also pro-
posed earlier that isolation of the homoallylic phosphine
compound PhP(H)(CH2)2CH@CH2 after addition of
HCl to the starting b-zirconocene phospholane complex
may arise from the transient formation of the corre-
sponding phosphonium zirconocene complex followed
by P–C bond cleavage (Eq. (1)) [17].
(1JCP ¼ 38:2 Hz) ppm corresponds to the other ole-
finic sp2-carbon atom bound to the phosphino sub-
1
stituent and the aryl group. Thus, H and 13C NMR
data confirm that 6 results from the cleavage of the
Zr–C(Si) bond of the starting zirconacyclopentadiene
3. For 6, the deshielded 31P NMR chemical shift at
20 ppm strongly suggests an intramolecular r-P–Zr in-
teraction forming a highly favorable five-membered
ring [18]. Note that these experimental conditions
(1 equiv., HCl ꢀ OEt2) did not allow us to fully charac-
terize the zirconocene complex 5 from the crude reaction
mixture.
The vinyl phosphine derivative 10 was the unique
phosphorus compound observed by 31P NMR after
addition of 2 equiv. of HCl ꢀ OEt2 on 4 (Scheme 3).
Compound 10 resulted in the expected protonolysis re-
action of the two Zr–C bonds of the corresponding
zirconaindene complex 4 [14]. In marked contrast to the
case of the a-trimethylsilyl zirconaindene 3, it was not
possible to observe the formation of any complex re-
sulting from the mono addition of HCl ꢀ OEt2. It is in-
teresting to note that it has been previously
demonstrated [19] that JHP coupling constants in vinyl
diphenylphosphine derivatives make assignment for the
ð1Þ
Addition of only 1 equiv. of HCl ꢀ OEt2 to 3 allowed
us to identify from the crude solution the formation of
Ph2PH and 6 (d 31P 20 ppm). All the resonances in the
1H and 13C NMR spectra for 6 were attributed by ho-
monuclear decoupling experiments. 13C NMR assign-
1
3
ments were confirmed by inverse gradient H–13C{31P}
the different regioisomers unambiguous as JHP (6:
3
2
HMQC and 31P–1H INEPT NMR experiments, re-
vealing that the Me3Si-group in 6 is connected to the
sp2-carbon atom of the vinylic @CH fragment (d 1H
7.42 ppm, d 13C 142.1 ppm). The signal at 152.3
3JHP ¼ 29:3 Hz, 8: JHP 52.4 Hz) are larger than JHP
2
(10: JHP 2.8 Hz).
The reactivity of the a-phosphino zirconaindene
complex 4 with HCl ꢀ OEt2 is in full agreement with

958
Y. El Harouch et al. / Journal of Organometallic Chemistry 689 (2004) 953–964
the r-P–Zr interaction observed by X-diffraction stud-
ies. No nucleophilic attack of the lone pair of the
phosphorus substituent may be envisaged in 4 as it in-
teracts with the single acceptor 1a1 orbital of the zirc-
onocene(IV) fragment to achieve the stable 18-electron
configuration. Therefore, no P–C bond cleavage is ob-
served in marked contrast to the reactivity of the reverse
b-phosphino zirconaindene regioisomer 3 where the lone
pair of the phosphorus atom is available for a proton-
ation by the incoming proton Hþ.
synthon. Attempts to isolate 12 and 13 led to their de-
composition with regeneration of 2 and formation of
several unidentified zirconocene products. Nevertheless,
12 and 13 could be unambiguously characterized in situ
by 1D and 2D (DQF-COSY, NOESY, HMQC, HMBC)
NMR experiments. In addition to the signals corre-
sponding to the diphenylphosphino substituents, 1H
NMR experiments reveal the presence for compounds
12 and 13 of g5-cyclopentadienyl ligands and trimeth-
ylsilyl groups in 1:2 and 1:1 ratio, respectively. The de-
shielded chemical shifts for 12 at d 205.5 (JCP ¼ 68:5 Hz)
ppm and 189.7 (JCP ¼ 9:4 Hz) ppm observed in the 13C
NMR spectra are indicative of carbon atoms directly
linked to the metallocene fragment [22]. These signals
correspond to the ZrCP and ZrCSi carbon atoms of the
cyclic zirconacyclopropene skeleton. The deshielded 31P
NMR resonance at d 13.6 ppm for this a-phosphino
three-membered zirconacycle may indicate the presence
of a Lewis-base/Lewis-acid r-interaction between the
lone electron pair of the phosphorus atom and the va-
cant coordination site of the zirconium metal center to
form a stable dimeric complex with a six-membered ring
[23]. A number of zirconacyclopropenes have been
prepared and stabilized as 18-electron metal complexes
using phosphine ligands [13b,13c,22].
2.3. Synthesis and protonolysis reaction of zirconacycle
complexes 12 and 13
Alkynes are known to undergo dimerization at the
zirconocene unit ‘‘[Cp2Zr]’’ to give the corresponding
zirconacyclopentadiene [1,20]. The zirconocene like re-
agent [Cp2Zr(g2-1-butene)] (11) [21] (1 equiv.) reacts
with 2 (2 equiv.) in THF to yield a mixture of com-
pounds 12 and 13 in 1:1 ratio which appear by 31P
NMR at d ¼ 13:6 and 21.0 ppm, respectively (Scheme
4). Surprisingly unreacted phosphino acetylenic reagent
2 is still present in the solution. Careful control of re-
action stoichiometry (11 (1 equiv.); 2 (1.5 equiv.)) al-
lowed us to observe the total disappearance of 2 to form
the dimeric zirconacyclopropene 12 and the zirconacy-
clopentadiene 13 complexes in quasi quantitative yield
according to NMR spectroscopy. Identical results were
observed starting with [Cp2Zr(g2-Me3Si–CBC–Si-
Me3)(THF)] complex as the zirconocene ‘‘[Cp2Zr]’’
In the 13C NMR spectra, the signal at d 192.8
(JCP ¼ 36:1 Hz) ppm observed for 13 is indicative of the
sp2-CZr carbon atom of the zirconacyclopentadiene
skeleton [24]. As expected, the resonance at 171.2 ppm
corresponding to the carbon atom placed in b-position
Scheme 4.

Y. El Harouch et al. / Journal of Organometallic Chemistry 689 (2004) 953–964
959
relative to the zirconium center in the five-membered
ring and connected to the phosphino group appears as a
doublet of doublet with coupling constants JCP of 58.3
and 10.2 Hz. The deshielded 31P NMR chemical shift of
this unprecedented b; b0-phosphino zirconacyclopent-
adiene complex 13 is in accord with the deshielded
chemical shift observed in b-phosphino zirconaindene
complexes (Table 1). Note that no dynamic equilibrium
between 12 and 13 was observed in solution by variable
temperature NMR.
vinyl zirconocene complex 16 (Scheme 4). The 1H NMR
CHSi absorption was observed at low field (d 8.06). 13C
NMR spectra showed a high field SiCH vinyl chemical
shift at 106.7 ppm and a reduced 1JCH coupling constant
of 109.0 Hz. All these NMR data are in accord with a
significant agostic Zr–H–C interactions between the vi-
nyl C–H bond and the unsaturated Zr(IV) center in
complex 16 [13a,25].
According to the products resulting from the pro-
tonolysis reaction, the dimeric complex 12 and the
zirconacyclopentadiene compound 13 were found to
react with HCl ꢀ OEt2 under the monomeric form 14. As
already reported in the literature [22b,26] rapid bis(g2-
alkyne)zirconocene to zirconacyclopentadiene conver-
sion is sometimes a readily reversible reaction despite
the fact that the equilibrium lies far over on the side of
the metallacycle. Reactive (g2-alkyne)zirconocene be-
comes available by shifting the equilibrium by adding a
suitable scavenger as for example a phosphine. This b–
b0-carbon–carbon bond cleavage in five-membered
zirconacycles was largely exploited synthetically [27]
Such a ring-opening equilibration is facilitated by bulky
alkyne substituents like the trimethylsilyl group –SiMe3.
Therefore, it is reasonable to propose that in the pres-
ence of HCl ꢀ OEt2, 13 rearranges to 14 after elimination
of 2. Then, competitive P–C and Zr–C bond cleavage
reactions occurred. Nucleophilic attack of the phosph-
ino group Ph2P– to form a P–H phosphonium–zirconate
intermediate 15 which rearranges after ring opening
process following P–C bond cleavage to give 17 and
Ph2PH (Scheme 4, path (a)). Compound 16 results from
the protonolysis reaction of the Zr–CSi bond of the
corresponding zirconacyclopropene intermediate 14
(Scheme 4, path (b)).
Protonolysis reaction of the crude reaction mixture
with 2 equiv. of HCl ꢀ OEt2 at 25 °C of in situ generated
(g2-diphenylphosphinotrimethylsilylacetylene)zircono-
cene dimer 12 and the zirconacyclopentadiene complex
13 led, beside the formation of Cp2ZrCl2, to 2, Ph2PH,
the vinyl phosphine 18 and trimethylsilylacetylene H–
CBC–SiMe3 (Scheme 4). All these compounds were
unambiguously identified by NMR spectroscopy and
GC-MS analysis. 31P NMR spectrum showed the pres-
ence of 2 (d ꢁ33 ppm), Ph2PH (d ꢁ40 ppm), and 18 (d
ꢁ21 ppm) as the sole phosphorus products of the reac-
tion. The vinyl phosphine compound 18 was indepen-
dently prepared by hydrozirconation reaction, with the
SchwartzÕs reagent [Cp2ZrHCl]n (19), on 2 at room
temperature followed by protonolysis of the Zr–C bond
of the corresponding zirconocene complex 20 (Scheme
1
4). The H and 13C NMR vinyl CH resonances appear,
respectively, at 6.82 and 151.2 ppm for the @CHSi
fragment and at 7.24 and 147.2 ppm for the @CHP
fragment and compare well with the chemical shifts
obtained for 8 and 10 (Table 4).
Careful addition of 1 equiv. of HCl ꢀ OEt2 at 25 °C to
the crude reaction mixture of 12 and 13 allowed us to
observe by 31P NMR the formation of Ph2PH and the
Table 4
Comparison of olefinic @CH agostic and non-agostic chemical shift (ppm) and JCH (Hz) coupling constant in vinyl trimethylsilyl-phosphine
derivatives
1
Zirconocene vinyl phosphines
Vinyl phosphines
(@CH)
1H
(@CH)
1H
d
d
13C
d
1JCH
d
d
13C
d
1JCH
6.88
153.5
130
8.06
106.7
109
7.00
144.5
154
8.40
110.5
129
(@CHSi)
151.2
6.81
7.24
135
155
(@CH)
147.2

960
Y. El Harouch et al. / Journal of Organometallic Chemistry 689 (2004) 953–964
Interestingly, characterization of the hydrozircona-
3.2. Preparation of zirconaindene complexes 3 and 4
tion product 20 by NMR spectroscopy revealed that the
bulky trimethylsilyl substituent is located at the a-posi-
tion relative to the metal fragment. The presence of a
marked agostic alkenyl b-C–H–Zr interaction was ob-
vious from the characteristic spectroscopic features. The
To a solution of Cp2ZrPh2 (0.144 g, 0.51 mmol) in
toluene (2 ml) was added at room temperature Me3Si–
CBC–PPh2 (2) (0.192 g, 0.51 mmol). The mixture was
heated under reflux for 2h; then the reaction mixture
was allowed to cool down to room temperature. Sol-
vents were evaporated in vacuo. 31P NMR of the crude
mixture showed the presence of the two regioisomers 3
and 4 in 10/1 ratio, respectively, as the sole phosphorus
compounds of the reaction. The residue was dissolved in
a minimum of THF (ꢄ1 ml), then pentane was slowly
added to the THF solution (ꢄ9 ml). The precipitate
formed was filtered and corresponds to 3 which was
isolated as a yellow powder in 85% yield. The volatiles
were removed to give 4 as a red powder in 9% yield.
Recrystallization of the regioisomers in toluene/CH2Cl2
gave 3 as yellow crystals and 4 as red crystals. 3. Fp:
148–150 °C. C33H33PSiZr (579.87): Anal. Calc. C 68.35,
H 5.73. Found: C 68.52, H 5.54%. 31P{1H} NMR (101
1
Zr–C@C–H unit shows a H NMR signal at rather low
field (d 8.40). The 13C NMR absorption of ZrC signal is
at d 232.6, whereas the PCH signal is located upfield at d
1
110.5. The low JCH coupling constant (129 Hz) is a
strong indication for the presence of the agostic Zr–C–H
moiety.
1
For zirconocenes 16 and 20 the JCH is 20–25 Hz
smaller than in the corresponding non-metal vinyl
1
phosphine Ph2PCH@CHSiMe3 (18). Moreover, the H
and 13C NMR resonances of the @CH fragment for 16
1
and 20 are significantly deshielded (Dd H 1.2–1.3 ppm)
and shielded (Dd 13C 37–45 ppm) by comparison with
vinyl phosphines 8, 10, and 18 (Table 4). Therefore,
whatever the metal fragment ZrCp2Cl is located on
the carbon–carbon double bond, both of the two P,
Si-heterosubstituted vinyl zirconocene regioisomers 16
and 20 showed strong evidences for Zr–H–C agostic
interactions.
1
MHz, CDCl3, 25 °C): d )8.5 (s) ppm. H NMR (250
MHz, CDCl3, 25 °C): d 0.17 (s, 9H, SiMe3), 6.42 (s,
10H, Cp), 6.43–7.55 (m, 14H, CHaryl) ppm. 13C{1H}
NMR (62 MHz, CDCl3, 25 °C): d 3.3 (s, SiMe3), 112.5
(s, Cp), 123.5, 124.0, 126.8, 135.8 (s, CHarom), 128.2 (s, o-
3
PPh), 128.7 (s, p-PPh), 130.9 (d, JCP ¼ 16:0 Hz, m-Ph),
1
3. Experimental
138.6 (d, JCP ¼ 25:0 Hz, i-Ph), 143.9 (s, ZrCC), 152.0
1
(d, JCP ¼ 39:8 Hz, ZrCCP), 188.2 (s, ZrC), 244.8 (d,
3.1. General procedures
2JCP ¼ 26:8 Hz, ZrCSi) ppm. 4. Fp: 161–163 °C.
31P{1H} NMR (101 MHz, CDCl3, 25 °C): d ꢁ67:5 (s)
ppm. 1H NMR (250 MHz, CDCl3, 25 °C): d 0.19 (s, 9H,
SiMe3), 5.56 (d, 3JHP ¼ 0:8 Hz, 10H, Cp), 6.42–7.55 (m,
14H, CHaryl) ppm. 13C{1H} NMR (62 MHz, CDCl3, 25
°C): d 1.1 (s, SiMe3), 105.2 (s, Cp), 122.8, 126.1, 126.2,
141.8 (s, CHarom), 128.6 (d, 2JCP ¼ 7:9 Hz, o-PPh), 129.2
All manipulations were conducted under an argon
atmosphere with standard Schlenk techniques. Nuclear
magnetic resonance (NMR) spectra were recorded on
Bruker MSL 400, AM-250, AC-200, and AC-80 Fourier
transform spectrometers. Positive chemical shifts are
given downfield relative to Me4Si (1H, 13C, 29Si) or
3
(s, p-PPh), 130.9 (d, JCP ¼ 11:3 Hz, m-Ph), 135.0 (s, i-
1
3
H3PO4 (31P), respectively. All the H and 13C signals
Ph), 164.3 (d, JCP ¼ 43:4 Hz,ZrCC), 189.9 (d,
were assigned on the basis of chemical shifts, spin–spin
coupling constants, splitting patterns and signal inten-
2JCP ¼ 11:8 Hz, ZrCCSi), 191.0 (s, ZrC), 191.7 (d,
1JCP ¼ 10:5 Hz, ZrCP) ppm.
1
1
sities, and by using H–1H COSY45, H–13C HMQC
and 1H–13C HMBC experiments. GC–MS (electron
impact, EI) analyses were carried out on a Hewlett–
Packard 5890 gas chromatograph on capillary column
(HP-5MS, 30 m, Ø 0.25 mm) coupled to a 5970 Hewlett–
Packard mass-selective detector. Elemental analyses
were performed by the analytical service of the Labo-
ratoire de Chimie de Coordination (LCC) of the CNRS
on a Perkin–Elmer 2400 series II instrument. Solvents
were freshly distilled from sodium/benzophenone ketyl
(toluene, THF), P2O5 (CH2Cl2) or lithium aluminum
hydride (pentane). CD2Cl2, and CDCl3 were treated
with CaH2, distilled, and stored under argon. Cp2ZrCl2,
BuLi, THF-d8 and HCl ꢀ OEt2 were purchased from
Aldrich and used without further purification. Ph2P–
CBC–SiMe3[28], Cp2ZrPh2 [29], and [Cp2ZrHCl]n [30]
were prepared according to literature procedure.
3.3. Addition of HCl (1 equiv.) on b-phosphino zircona-
indene complex 3
To a solution of 3 (0.064 g, 0.11 mmol) in toluene (1
ml) was added 1 equiv. of HCl (0.11 ml, 1 M in Et2O).
1
31P, H, and 13C NMR spectra showed the presence of
three products in the reaction mixture: Ph2PH (d 31P
)40 ppm, JPH ¼ 230 Hz), 5, and 6 which were identified
in situ. 6. 31P{1H} NMR (101 MHz, THF-d8, 25 °C): d
1
19.9 (s) ppm. H NMR (250 MHz, CDCl3, 25 °C): d
ꢁ0:41 (s, 9H, SiMe3), 5.77 (s, 10H, Cp), 7.42 (d,
3JHP ¼ 29:3 Hz, 1H, @CHSi), 7.31–7.52 (m, 14H,
CHaryl) ppm. 13C{1H} NMR (62 MHz, CDCl3, 25 °C): d
0.3 (s, SiMe3), 111.9 (s, Cp), 126.1, 127.4, 133.3, 134.7 (s,
3
CHaryl), 124.7 (d, JCP ¼ 8:7 Hz, m-Ph), 128.1 (d,
1
2JCP ¼ 8:3 Hz, o-Ph), 130.3 (d, JCP ¼ 11:3 Hz, i-Ph),

Y. El Harouch et al. / Journal of Organometallic Chemistry 689 (2004) 953–964
961
2
3
142.1 (d, JCP ¼ 3:6 Hz, @CHSi), 142.7 (d, JCP ¼ 5:8
SiMe3), 127.0, 128.3, 128.5, 129.0, 129.1 (s, CHPh), 133.0
2
Hz, PCCC H), 152.3 (d, 1JCP ¼ 38:2 Hz, PC@), 157.5 (d,
(d, JCP ¼ 18:3 Hz, o-PPh), 140.2 (d, JCP ¼ 10:1 Hz, i-
3
2JCP ¼ 32:3 Hz, PCC), 182.1 (d, JCP ¼ 2:2 Hz, ZrC)
Ph), 144.5 (d, JCP ¼ 11:8 Hz, PCH), 148.2 (d, JCP
¼
3
1
1
2
ppm. It was not possible from the reaction mixture to
unambiguously identified the carbon and proton aryl
17:1 Hz, i-PPh), 165.1 (d, JCP ¼ 40:2 Hz, SiCPh) ppm.
1
signals for complex 5: H NMR (250 MHz, CDCl3, 25
3.6. Formation of complexes [Cp2Zr(g2-Ph2-PC2Si-
Me3)]2 (12) and Cp2ZrC(SiMe3)@C(PPh2)–C(PPh2)@
C(SiMe3) (13)
°C): d 0.18 (s, 9H, SiMe3), 5.94 (s, 10H, Cp); 13C{1H}
NMR (62 MHz, CDCl3, 25 °C): d 0.6 (s, SiMe3), 109.2
(s, Cp), 96.4 (s, PhCC), 104.9 (s, SiC C) ppm.
To a solution of 11 (prepared from Cp2ZrCl2 (0.031
g, 0.11 mmol) in THF and 2 equiv. of t-BuLi (0.082 ml,
2.7 M) cooled to ꢁ78°C and stirred for 2 h) was added
1.5 equiv. of 2 (0.0042 g, 0.15 mmol) in THF. The re-
action mixture was stirred at room temperature for 3 h.
According to NMR spectroscopy complexes 12 and 13
were formed in 1:1 ratio. Attempts to isolate 12 and 13
lead to a multitude of compounds. However, they were
unambiguously identified by NMR spectroscopy, in
situ, following the same experimental procedure using
THF-d8. 12: 31P{1H} NMR (162 MHz, THF-d8,
3.4. Addition of HCl (2 equiv.) on b-phosphino zircona-
indene complex 3
To a solution of 3 (0.064 g, 0.11 mmol) in toluene (1
ml) was added 2 equiv. of HCl (0.22 ml, 1 M in Et2O).
1
31P, H, 13C NMR spectra and GC–MS analysis on the
crude reaction mixture showed the presence of Ph2PH (d
31P )40 ppm, JPH ¼ 230 Hz), 7, and 8 in 10/10/1 ratio,
respectively, as the sole products of the reaction. Com-
pounds 7 and 8 were also obtained after addition of HCl
(1 equiv.) on complexes 5 and 6 obtained from the pro-
cedure described above (cf. addition of HCl (1 equiv.) on
3). 7: 1H NMR (400 MHz, CD2Cl2, 25 °C): d 0.25 (s, 9H,
SiMe3), 7.20–7.50 (m, 5H, Ph) ppm. 13C{1H} NMR (101
MHz, CD2Cl2, 25 °C): d 0.0 (s, SiMe3), 94.0 (s, CSiMe3),
105.1 (s, CPh), 123.0, 128.1, 128.4, 131.9 (s, Ph) ppm. 8:
31P{1H} NMR (162 MHz, CD2Cl2, 25 °C): d 0.8 (s) ppm.
1H NMR (400 MHz, CD2Cl2, 25 °C): d 0.38 (d,
5JHP ¼ 1:2 Hz, 9H, SiMe3), 6.88 (d, 3JHP ¼ 52:4 Hz, 1H,
CHSi), 7.25–7.58 (m, 15H, CHaryl) ppm. 13C{1H} NMR
1
ꢁ30°C): d 13.6 (s) ppm. H NMR (400 MHz, THF-d8,
ꢁ30°C): d 0.10 (s, 18H, SiMe3), 5.86 (s, 10H, Cp), 6.06
(s, 10H, Cp), 7.31–7.40, 7.63–7.66 (m, 20H, Ph) ppm.
13C{1H} NMR (101 MHz, THF-d8, ꢁ30°C): d 1.2 (s,
SiMe3), 110.4, 111.7 (s, Cp), 127.7 (d, 2JCP ¼ 5:4 Hz, m-
2
Ph), 133.8 (d, JCP ¼ 17:2 Hz, o-Ph), 144.2 (d,
4JCP ¼ 13:0 Hz, i-PPh), 189.7 (d, 2JCP ¼ 9:4 Hz, ZrCSi),
1
205.5 (d, JCP ¼ 68:5 Hz, ZrCP) ppm, p-Ph was not
detected. 13: 31P{1H} NMR (162 MHz, THF-d8,
1
ꢁ30°C): d 21.0 (s) ppm. H NMR (400 MHz, THF-d8,
4
(101 MHz, CD2Cl2, 25 °C): d 1.1 (d, JCP ¼ 7:0 Hz,
ꢁ30°C): d 0.34 (s, 18H, SiMe3), 5.38 (s, 10H, Cp), 7.31–
7.40, 7.63–7.66 (m, 20H, Ph) ppm. 13C{1H} NMR (101
MHz, THF-d8, ꢁ30°C): d 2.3 (s, SiMe3), 106.5 (s, Cp),
128.1 (d, 3JCP ¼ 5:6 Hz, m-Ph), 133.8 (d, 2JCP ¼ 17:2 Hz,
SiMe3), 126.6, 127.7, 128.0, 128.5, 128.5 (s, CHPh), 133.2
2
1
(d, JCP ¼ 18:1 Hz, o-PPh), 137.1 (d, JCP ¼ 13:2 Hz, i-
2
PPh), 153.5 (d, JCP ¼ 54:3 Hz, CHSi), 155.9 (d,
4
1JCP ¼ 22:1 Hz, PCPh) ppm. GC–MS analysis (He, 1.5
ml mnꢁ1, from 35 to 80 °C (2 °C mnꢁ1) then from 80 to
280 °C (10 °C mnꢁ1); MS (EI, 70 eV) m/z): (7) 174 (Mþ,
25%), 159 (100%); (Ph2PH) 186 (Mþ, 186%), 108 (100%);
(8) 360 (Mþ, 46%), 345 (20%), 175 (38%), 73 (100%).
o-Ph), 140.8 (d, JCP ¼ 14:5 Hz, i-PPh), 171.2 (dd,
2
1JCP ¼ 58:3 Hz, JCP ¼ 10:2 Hz, ZrCCP), 192.8 (d,
2JCP ¼ 36:1 Hz, ZrCSi) ppm, p-Ph was not detected.
3.7. Addition of HCl (1 equiv.) on 12 and 13
3.5. Addition of HCl (2 equiv.) on b-phosphino zircona-
indene complex 4
On the complexes 12 and 13 prepared from the above
experimental procedure was added 1 equiv. of HCl (0.11
ml, 1 M in Et2O). 31P, 1H, and 13C NMR spectra
showed the presence of three products in the reaction
mixture corresponding to Ph2PH (d 31P ꢁ40 ppm,
JPH ¼ 230 Hz), 16, and 17. Complex 16 was identified in
situ. Formation of complex 17 was identified after pro-
tonolysis of the Zr–C bond to give the corresponding
alkyne compound H–CBC–SiMe3 (cf. following exper-
imental procedure). 16: 31P{1H} NMR (162 MHz,
To a solution of 4 (0.162 g, 0.28 mmol) in toluene (3
ml) was added at room temperature 2 equiv. of HCl
(0.56 ml, 1 M in Et2O). The reaction mixture was stirred
for 30 mn and the solution turned yellow. The resulting
residue was extracted with pentane and filtered. Re-
moval of the solvent in vacuo from the colourless so-
lution gave 10 in 85% yield. C23H25PSi (360.51): Anal.
Calc. C 76.63, H 6.99. Found: C 77.09, H 6.72%.
31P{1H} NMR (162 MHz, CD2Cl2, 25 °C): d ꢁ22:0 (s)
1
CD2Cl2, 25 °C): d 7.3 (s) ppm. H NMR (400 MHz,
CD2Cl2, 25 °C): d 0.10 (s, 9H, SiMe3), 5.85 (s, 10H, Cp),
1
3
ppm. H NMR (400 MHz, CD2Cl2, 25 °C): d 0.34 (d,
7.40–7.42, 7.66–7.70 (m, 10H, Ph), 8.06 (d, JHP ¼ 42:1
2
5JHP ¼ 1:2 Hz, 9H, SiMe3), 7.00 (d, JHP ¼ 2:8 Hz, 1H,
Hz, 1H, SiCH) ppm. 13C{1H} NMR (101 MHz,
CHP), 7.25–7.58 (m, 15H, CHaryl) ppm. 13C{1H} NMR
CD2Cl2, 25 °C): d 0.0 (d, JCP ¼ 2:9 Hz, SiMe3), 106.7
4
4
2
(101 MHz, CD2Cl2, 25 °C): d 1.8 (d, JCP ¼ 8:9 Hz,
(d, JCP ¼ 23:2 Hz, SiCH), 111.0 (s, Cp), 127.7 (d,

962
Y. El Harouch et al. / Journal of Organometallic Chemistry 689 (2004) 953–964
3
2JCP ¼ 5:4 Hz, o-PPh), 134.6 (d, JCP ¼ 20:2 Hz, m-
The reaction mixture was stirred at room temperature
for 1 h and then evaporated to dryness. The resulting
residue was extracted with pentane and filtered. Re-
moval of the solvent in vacuo from the colourless so-
lution gave 18 in 90% yield. Anal. Calc. for C17H21PSi
(284.41): C, 71.79; H, 7.44. Found: C, 71.96; H, 7.28%.
1
PPh), 139.5 (d, JCP ¼ 7:3 Hz, i-PPh), 225.9 (d,
1JCP ¼ 41:4 Hz, ZrCP) ppm; p-PPh was not observed.
3.8. Addition of HCl (2 equiv.) on 12 and 13
On the complexes 12 and 13 prepared from the above
experimental procedure was added 2 equiv. of HCl (0.22
ml, 1 M in Et2O). 31P, 1H, and 13C NMR spectra showed
the total disappearance of the starting complexes and the
formation in the reaction mixture of four compounds
corresponding to 2, Ph2PH (d 31P ꢁ40 ppm, JPH ¼ 230
Hz), 18, and H–CBC–SiMe3. Compounds 18 and H–
CBC–SiMe3 were also formed after addition of HCl (1
equiv.) on complexes 16 and 17 prepared from the pro-
cedure described above (cf. Addition of HCl (1 equiv.) on
12 and 13). 18: 31P{1H} NMR (101 MHz, CDCl3, 25 °C):
d ꢁ20:7 (s) ppm. 1H NMR (250 MHz, CDCl3, 25 °C): d
0.30 (d, 5JHP ¼ 0:6 Hz, 9H, SiMe3), 6.82 (dd, 3JHP ¼ 45:4
Hz, 3JHH ¼ 15:1 Hz, 1H, SiCH), 7.24 (dd, 2JHP ¼ 1:6 Hz,
3JHH ¼ 15:1 Hz, 1H, PCH), 7.32–7.48 (m, 10H, Ph) ppm.
13C{1H} NMR (62 MHz, CDCl3, 25 °C): d 0.5 (d,
4JCP ¼ 6:2 Hz, SiMe3), 128.2 (s, p-Ph), 132.4 (d,
3.11. X-ray analysis of zirconaindene complexes 3 and 4
For complexes 3 and 4 data collection have been
collected on a Stoe imaging plate diffraction system
(IPDS), equipped with an Oxford cryosystems cryo-
stream cooler device and using a graphite-monochro-
ꢀ
mated Mo Ka radiation (k ¼ 0:71073 A), at low
temperature for 3 and room temperature for 4. Final
unit cell parameters were obtained by means of a least-
squares refinement of a set of 5000 well-measured re-
flections, and a crystal decay was monitored in the
course of data collection by measuring 200 reflections by
image, any significant fluctuations of intensities have
been observed during measurements. Structures have
been solved by means of direct methods using the pro-
gram SIR92 [31] and subsequent differences Fourier
maps, then refined by least-squares procedures on a F2
by using the program SHELXL-97 [32]; atomic scattering
factors were taken from International Tables for X-ray
crystallography [33]. All hydrogen atoms were located
on a difference Fourier maps, but introduced in the re-
finement as fixed contributors by using a riding model
and with an isotropic thermal parameter fixed at 20%
higher than those of the C-sp2 atoms and 50% for the C-
sp3 atoms to which they were connected, the methyl
groups were refined with the torsion angle as free vari-
able. All non-hydrogens atoms were anisotropically re-
fined, and in the last cycles of refinement weighting
schemes have been used, where weights are calculated
2
3JCP ¼ 17:8 Hz, m-Ph), 128.3 (d, JCP ¼ 6:1 Hz, o-Ph),
139.4 (d, 1JCP ¼ 10:1 Hz, i-Ph), 147.2 (d, 1JCP ¼ 11:2 Hz,
2
PCH), 151.2 (d, JCP ¼ 41:9 Hz, SiCH) ppm. GC-MS
analysis (He, 1.5 ml mnꢁ1, from 35 to 80 °C (2 °C mnꢁ1
)
then from 80 to 280 °C (10 °C mnꢁ1); MS (EI, 70 eV) m/
z): (H–CBC–SiMe3) 98 (Mþ, 8%), 83 (100%), 53 (11%);
(Ph2PH) 186 (Mþ, 58%), 108 (100%); (18) 284 (Mþ,
85%), 269 (50%), 100 (100%).
3.9. Preparation of Z–Ph2PC(H)@C(ZrCp2Cl)SiMe3
(20)
A solution of 2 (0.226 g, 0.80 mmol) in THF (10 ml)
was added at ꢁ20°C to a suspended solution of
[Cp2ZrHCl]n (19) (0.206 g, 0.80 mmol) in THF (10 ml).
The reaction mixture was stirred at room temperature
for 2 h. Removal of the solvent in vacuo from the yellow
solution gave 20 in nearly quantitative yield. 31P{1H}
2
from the following formula: w ¼ 1=½r2ðFo2Þ þ ðaPÞ þ
bPꢃ where P ¼ ðFo2 þ 2Fc2Þ=3. Criteria for a satisfactory
complete analysis were the ratios of root mean square
shift standard deviation being less than 0.1 and no sig-
nificant features in final difference Fourier maps.
Drawings of molecules are performed by using the
program ORTEP3 [34] with 50% probability displace-
ment ellipsoids for non-hydrogen atoms.
1
NMR (162 MHz, CD2Cl2, 25 °C): d ꢁ21:0 (s) ppm. H
NMR (400 MHz, CD2Cl2, 25 °C): d 0.44 (s, 9H, SiMe3),
6.00 (s, 10H, Cp), 7.38–7.43, 7.64–7.67 (m, 10H, Ph),
8.40 (s, 1H, PCH) ppm. 13C{1H} NMR (101 MHz,
4
CD2Cl2, 25 °C): d 1.8 (d, JCP ¼ 5:1 Hz, SiMe3), 110.5
1
(d, JCP ¼ 40:9 Hz, PCH), 111.7 (s, Cp), 128,1 (s, p-
4. Conclusions
2
PPh), 129.0 (d, JCP ¼ 5:4 Hz, o-PPh), 133.3 (d,
1
3JCP ¼ 18:4 Hz, m-PPh), 139.3 (d, JCP ¼ 14:3 Hz, i-
We have demonstrated that coupling reactions of the
internal acetylenic derivative Ph2P–CBC–SiMe3 (2) with
both the benzyne complex 1 and the zirconocene like
reagent, take place regioselectively to produce primarily
metallacyclic derivatives where the a-carbanion is sta-
bilized by the trimethylsilyl group. Quite surprisingly,
this regiochemical outcome appears to be much more
favourable than the alternate situation where the
2
PPh), 232.6 (d, JCP ¼ 8:6 Hz, ZrCSi) ppm.
3.10. Preparation of Z–Ph2PC(H)@C(H)SiMe3 (18)
from 20
To a solution of 20 (0.184 g, 0.34 mmol) in THF (4
ml) was added 1 equiv. of HCl (0.34 ml, 1 M in Et2O).

Y. El Harouch et al. / Journal of Organometallic Chemistry 689 (2004) 953–964
963
(c) W.A. Nugent, D.L. Thorn, R.L. Harlow, J. Am. Chem. Soc.
109 (1987) 2788.
chemically unsaturated metal fragment is yet stabilized
by the lone pair of the phosphino group Ph2P–. Nev-
ertheless, we have been able to isolate and structurally
characterize the two regioisomers 3 and 4. The structure
of 4 represents the first reported example of an a-
phosphino zirconacycle. Significantly, the existence of a
Lewis-base/Lewis-acid r-P–Zr interaction is confirmed
here by the occurrence of an unusually acute Zr–C–P
angle.
Interestingly, further protonation reactions follow
different pathways depending on the nature of the initial
regioisomer. Typically, when the phosphino substituent
is placed in b-position relative to the metal center, ad-
dition of HCl leads to a competition between (i) pro-
tonation at the lone pair of the phosphino group
followed by P–C cleavage, and (ii) protonolysis of the
Zr–CSi bond. Alternatively, when the lone electron pair
of the phosphino group is protected by interaction with
the metal center thus achieving a stable 18-electron
configuration, protonolysis takes place exclusively at the
Zr–C bonds thus releasing the corresponding organic
moiety.
[2] (a) R.D. Broene, S.L. Buchwald, Science 261 (1993) 1696;
(b) S.L. Buchwald, R.B. Nielsen, Chem. Rev. 88 (1988) 1047, and
references therein;
(c) J.P. Majoral, P. Meunier, A. Igau, N. Pirio, M. Zablocka, A.
Skowronska, S. Bredeau, Coord. Chem. Rev. 178–180 (1998) 145.
[3] S.L. Buchwald, R. Nielsen, J. Am. Chem. Soc. 111 (1989) 2870.
[4] S.L. Buchwald, Q. Fang, J. Org. Chem. 54 (1989) 2793.
[5] P.D. Magnus, T. Sarkar, S. Djuruc, in: G. Wilkinson, F.G.A.
Stone, E.W. Abel (Eds.), Comprehensive Organometallic Chem-
istry, vol. 7, Pergamon Press, Oxford, 1982, p. 520.
[6] Y. Miquel, A. Igau, B. Donnadieu, J.P. Majoral, L. Dupuis, N.
Pirio, P. Meunier, Chem. Commun. (1997) 279.
€
€
[7] M. Westerhausen, M.H. Digeser, C. Guckel, H. Noth, J. Kniezek,
W. Ponikwar, Organometallics 18 (1999) 2491.
[8] Y. Miquel, Dissertation, University Paul Sabatier, Toulouse III,
1998.
[9] (a) D.J. Cardin, M.F. Lappert, C.L. Raston, Chemistry of
Organo-Zirconium and Hafnium Compounds, Wiley, New York,
1986, and references cited therein;
(b) J.W. Lauher, R. Hoffmann, J. Am. Chem. Soc. 98 (1976) 1729;
(c) P. Hofmann, P. Stauffert, N. Shore, Chem. Ber. 115 (1982)
2153.
[10] A. Kanj, P. Meunier, B. Gautheron, J. Organomet. Chem. 454
(1993) 51.
[11] (a) Y. Miquel, A. Igau, B. Donnadieu, J.P. Majoral, N. Pirio, P.
Meunier, J. Am. Chem. Soc. 120 (1998) 3504;
(b) Y. Miquel, V. Cadierno, B. Donnadieu, A. Igau, J.P. Majoral,
Organometallics 19 (2000) 54.
Our future research efforts in this area will examine
the synthetic utility of the phosphorus–carbon bond
cleavage in metallacyclic group 4 complexes for the
specific synthesis of unsaturated organic derivatives that
are difficult to prepare by alternate procedures.
[12] N.E. Schore, H. Hope, J. Am. Chem. Soc. 102 (1980) 4251.
[13] (a) K.A. Kreutzer, R.A. Fisher, W.M. Davis, E. Spaltenstein,
S.L. Buchwald, Organometallics 10 (1991) 4031;
(b) S.L. Buchwald, B. Watson, J.C. Huffman, J. Am. Chem. Soc.
109 (1987) 2544;
(c) S.L. Buchwald, B. Watson, J.C. Huffman, J. Am. Chem. Soc.
108 (1986) 7411;
5. Supplementary material
(d) H.H. Karsch, G. Grauvogl, M. Kawecki, P. Bissinger,
Organometallics 12 (1993) 2757;
(e) H.H. Karsch, B. Deubelly, G. Grauvogl, J. Lachmann, G.
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC Nos. 215453 and 215454 com-
pounds for 3 and 4, respectively. Copies of this infor-
mation may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK (fax: +44-1223/336-033; e-mail: deposit@ccdc.cam.
ac.uk or www: http//www.ccdc.cam.ac.uk).
€
Muller, Organometallics 11 (1992) 4245;
(f) H.H. Karsch, G. Grauvogl, B. Deubelly, G. Muller,
Organometallics 11 (1992) 4238.
€
[14] T. Takahashi, D.R. Swanson, E. Negishi, Chem. Lett. (1987) 623.
[15] Y. Liu, Z. Zhong, K. Nakajima, T. Takahashi, J. Org. Chem. 67
(2002) 7451.
[16] U. Segerer, S. Blaurock, J. Sieler, E. Hey-Hawkins, Organomet-
allics 18 (1999) 2838.
ꢃ
[17] (a) N. Cenac, M. Zablocka, A. Igau, J.P. Majoral, M.
Pietrusiewicz, Organometallics 13 (1994) 5166;
ꢃ
(b) N. Cenac, M. Zablocka, A. Igau, G. Commenges, J.P.
Acknowledgements
Majoral, A. Skowronska, Organometallics 15 (1996) 1208.
[18] Even though intermolecular r-P–Zr interaction cannot be totally
ruled out for 6 it is rather unlikely as it would form an unfavorable
8-membered ring.
This work was supported by the CNRS (France) and
ꢂ
the Ministere de la Recherche et de lÕEnseignement
ꢃ
Superieur (Ph.D. fellowship for Y.E.H.). VC thanks the
[19] T.N. Mitchell, K. Heesche, J. Organomet. Chem. 409 (1991) 163.
[20] V. Skibbe, G. Erker, J. Organomet. Chem. 241 (1983) 15.
[21] (a) E. Negishi, F.E. Cederbaum, T. Takahashi, Tetrahedron Lett.
27 (1986) 2829;
Spanish Ministerio de Educacion y Cultura for post-
doctoral fellowship.
€
(b) P. Binger, P. Muller, R. Benn, A. Rufinska, B. Gabor, C.
Kruger, P. Betz, Chem. Ber. 122 (1989) 1035.
€
References
€
[22] (a) U. Rosenthal, A. Ohff, M. Michalik, H. Gorls, V.V. Burlakov,
V.B. Shur, Angew. Chem., Int. Ed. 32 (1993) 1193;
(b) G. Erker, R. Zwettler, J. Organomet. Chem. 409 (1991) 179.
[23] (a) Despite we cannot totally ruled out the formation of a trimer
for 12, dimers leading to 6 membered ring with PCZr as monomer
skeleton are favoured over larger cyclic structure: see ref [13d] and
[1] (a) E. Negishi, T. Takahashi, Acc. Chem. Res. 27 (1994) 124;
(b) E. Negishi, in: B.M. Trost, I. Fleming (Eds.), Comprehensive
Organic Synthesis, vol. 5, Pergamon Press, Oxford, UK, 1991, p.
1163;

964
Y. El Harouch et al. / Journal of Organometallic Chemistry 689 (2004) 953–964
(a) L. Weber, Angew. Chem., Int. Ed. 35 (1996) 271, and [28] C. Charrier, W. Chodkiewicz, P. Cadiot, Bull. Soc. Chim. Fr. 167
references therein;
(b) P. Rosa, P. Le Floch, L. Ricard, F. Mathey, J. Am. Chem.
Soc. 119 (1997) 9417.
(1966) 1002.
[29] E. Samuel, M.D. Rausch, J. Am. Chem. Soc. 95 (1973)
6263.
€
[24] N. Metzler, H. Noth, M. Thomann, Organometallics 12 (1993)
2423.
[25] (a) I. Hyla-Kryspin, R. Gleiter, C. Kruger, R. Zwettler, G. Erker,
[30] S.L. Buchwald, S.J. LaMaire, R.B. Nielsen, B.T. Watson, S.M.
King, Tetrahedron Lett. 28 (1987) 3895.
€
[31] (a) SIR92 – A Program for Crystal Structure Solution: A.
Altomare, G. Cascarano, C. Giacovazzo, A. Guargliardi, J. Appl.
Cryst. 26 (1993) 343;
Organometallics 9 (1990) 517;
(b) G. Erker, R. Zwettler, C. Kruger, I. Hyla-Kryspin, R. Gleiter,
€
Organometallics 9 (1990) 524.
[26] (a) C. McDade, J.E. Bercaw, J. Organomet. Chem. 279 (1985)
281–315;
(b) SIR97 – A. Altomare, M.C. Burla, M. Camalli, G. Cascarano,
C. Giacovazzo, A. Guargliardi, A.G.G. Moliterni, G. Polidori, R.
Spagna, J. Appl. Cryst. 32 (1999) 115.
(b) G. Erker, U. Dorf, A.L. Rheingold, Organometallics 7 (1988)
138–143;
[32] G.M. Sheldrick, SHELX97 [Includes SHELXS97, SHELXL97, CIF-
TAB] – Programs for Crystal Structure Analysis (Release 97-2),
€
Germany, 1998.
€
€ €
Institut fur Anorganische Chemie der Universitat, Gottingen,
(c) R.H. Grubbs, A. Miyashita, J. Am. Chem. Soc. 100 (1978)
1300.
[27] (a) T. Takahashi, M. Kotora, R. Hara, Z. Xi, Bull. Chem. Soc.
Jpn. 72 (1999) 2591;
[33] International Tables for X-Ray Crystallography, vol. IV, Kynoch
Press, Birmingham, UK, 1974.
(b) T. Takahashi, Z. Xi, M. Kageyama, R. Fisher, K. Nakajima,
E. Negishi, J. Org. Chem. 63 (1998) 6802.
[34] ORTEP3 for Windows L.J. Farrugia, J. Appl. Crystallogr. 30
(1997) 565.