Unsymmetrical Zirconacyclopentadienes from Isolated Zirconacyclopropenes with 1-Alkynylphosphine Ligands

Article abstract of DOI:10.1021/om801040t

The reaction of one equiv of 1-alkynylphosphines, R₂PC≡CR? (R = Et,ⁱPr, or Ph and R = Ph or Mes), with Cp₂Zr(pyr) (η²-Me₃SiC≡CSiMe₃) resulted in formation of monoalkyne complexes. In the ca

Full text of DOI:10.1021/om801040t

1252
Organometallics 2009, 28, 1252–1262
Unsymmetrical Zirconacyclopentadienes from Isolated
Zirconacyclopropenes with 1-Alkynylphosphine Ligands
Adam D. Miller, Samuel A. Johnson, Karl A. Tupper, Jennifer L. McBee, and
T. Don Tilley*
Department of Chemistry, UniVersity of California, Berkeley, Berkeley, California 94720-1460
ReceiVed October 29, 2008
i
The reaction of one equiv of 1-alkynylphosphines, R2PCt CR′ (R ) Et, Pr, or Ph and R′ ) Ph or
Mes), with Cp2Zr(pyr)(η2-Me3SiCt CSiMe3) resulted in formation of monoalkyne complexes. In the case
where R ) Et, iPr, or Ph and R′ ) Ph, a “ligand free” zirconacyclopropene complex is produced. These
complexes are stabilized by intermolecular donation of the phosphorus lone-pair in the dimeric complexes
i
[Cp2Zr(η2-R2PCt CPh)]2 (R ) Et, Pr, or Ph). However, with R ) Ph and R′ ) Mes, the zirconocyclo-
propene-pyridine complex Cp2Zr(pyr)(η2-Ph2PCt CMes) is formed. Homocoupling of the 1-alkynylphos-
phines was demonstrated by reaction of a second equiv of Ph2PCt CPh with [Cp2Zr(η2-Ph2PCt CPh)]2
to give the diphosphinozirconacyclopentadiene Cp2Zr[2,5-(Ph2P)2-3,4-Ph2C4] with high regioselectivity
(77%). The zirconacyclopropene complexes also react with one equiv of PhCt CPh or EtCt CEt to give
zirconacyclopentadienes in which the phosphino substituent preferentially adopts the 2-position (R) of
the zirconacyclopentadiene ring. These unsymmetrical zirconacyclopentadienes undergo substitution of
the R2PCCR′ moiety with the less bulky alkynes PhCt CPh or EtCt CEt. The substituents on the
1-alkynylphosphines significantly influence the rates of alkyne substitution such that sterically more
demanding substituents in either the R- (-PiPr2) or ꢀ- (-Mes) position of the zirconacycle lead to faster
exchange. The R-phosphinozirconacyclopentadienes were readily converted to 1-phosphinobutadienes
via reaction with benzoic acid. The zirconacyclopentadiene Cp2Zr[2-Ph2P-3,4,5-Ph3C4] was converted to
the corresponding thiophene oxide by the oxo-transfer reaction with sulfur dioxide. In the case of ((1Z,3E)-
3-ethyl-2-phenylhexa-1,3-dienyl)diphenylphosphine and (3,4,5-triphenylthiophen-2-yl oxide)diphenylphos-
phine, the molecules were isolated as their phosphine oxides. Reactions of the zirconacyclopropene
complexes [Cp2Zr(η2-Ph2PCt CPh)]2 and Cp2Zr(pyr)(η2-Ph2PCt CMes) with the diyne (F5C6)Ct C-1,4-
C6H4-Ct C(C6F5) gave bis(zirconacycle)s terminated with phosphino groups. These bis(zirconacycle)s
were converted to the corresponding phosphino-terminated oligomers by protonolysis with hydrochloric
acid. In addition, the Ph2PCCMes moiety of Cp2Zr[2-Ph2P-3-Mes-4-(C6F5)C4]-1,4-C6H4-Cp2Zr[2-Ph2P-
3-Mes-4-(C6F5)C4] was exchanged with PhCt CPh to give the phenylene(zirconacyclopentadiene)
Cp2Zr[2,3-Ph2-4-(C6F5)C4]-1,4-C6H4-Cp2Zr[2,3-Ph2-4-(C6F5)C4].
factor that determines the structure of the products in these
conversions is the regiochemistry of the alkyne coupling at
zirconium, which is known to be sensitive to both steric and
electronic factors. For example, sterically demanding groups
such as -SiMe3 and -CMe3 direct alkyne couplings such that
they adopt the less-crowded R-positions (-2 and -5) of the
zirconacyclopentadiene ring.17-19 On the other hand, electron
poor substituents (e.g., pentafluorophenyl groups) prefer the
Introduction
The reductive coupling of alkynes by zirconocene is an
important carbon-carbon bond forming reaction.1-3 The result-
ing zirconacyclopentadienes are useful precursors to a wide
range of organic molecules including (for example) dienes,4
arenes,5-9 cyclopentadienes,10-12 thiophenes,13,14 phospholes,15
thiophene oxides,16 and bicyclic compounds.17 An important
* To whom correspondence should be addressed. E-mail:
tdtilley@berkeley.edu.
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10.1021/om801040t CCC: $40.75
2009 American Chemical Society
Publication on Web 01/29/2009

Unsymmetrical Zirconacyclopentadienes
Organometallics, Vol. 28, No. 4, 2009 1253
ꢀ-positions (-3 and -4) of the zirconacyclopentadiene ring.20
The ability to control the coupling of unsymmetrical alkynes
in a regioselective manner is not only useful for the preparation
of small molecules but also for the synthesis of macrocycles21-27
and polymers20,28 via the coupling of diynes of the type
RCt C-R′-Ct CR. For the synthesis of macrocycles by this
method, another important requirement is that the alkyne
substituents promote reversibility for zirconacyclopentadiene
formation.21
via donation of the phosphorus lone pair to zirconium. In related
work by Majoral and co-workers, Ph2PCt CR alkynes were
observed to couple with the transient benzyne complex Cp2Zr(η2-
C6H4) to produce the corresponding zirconaindene complexes.36,37
In the latter compounds, the diphenylphosphino group adopts
the R-position of the metallocyclic zirconaindene ring, presum-
ably due to interaction of the lone pair on the phosphorus with
the metal center.36 It has also been proposed that 1-alkynylphos-
phines and 1-alkynylphosphonates form zirconacyclopropenes
as intermediates in zirconocene-mediated cross-couplings with
other alkynes.37,38 Takahashi and co-workers have reported that
Ph2PCt CR reacts with diethylzirconocene to form the corre-
sponding zirconacyclopentene. These species then react with a
second alkyne with displacement of ethylene and formation of
unsymmetrical zirconacyclopentadienes.39
In an attempt to further develop methodologies for the control
of regioselectivity in the cross-couplings of alkynes by zir-
conocene, 1-alkynylphosphine substrates have been examined.
To the best of our knowledge zirconacyclopropenes derived
from 1-alkynylphosphines have not been isolated and fully
characterized. This report describes such zirconacyclopropenes,
and the characterization of their structures and reactivities toward
alkynes. This chemistry has been utilized in the synthesis of
phosphino-terminated oligomers, from diynes of the type
RCt C-R′-Ct CR containing a rigid spacer R′ group. In
addition, conditions are described that allow facile substitution
of the 1-alkynylphosphine by other alkynes in a zirconacyclo-
pentadiene.
Due to the inherently high reactivity of zirconocene (Cp2Zr),
the regioselective cross-coupling of two alkynes, to form
unsymmetrical zirconacyclopentadienes, has proven difficult to
control. Generally, two alkynes may be added sequentially if
the first addition gives a relatively stable zirconacyclopropene
intermediate (A), and several different methods for the stabiliza-
tion of this monoalkyne adduct (or an analogous synthon) have
been investigated (eq 1).29-33 One approach involves the
synthesis of a zirconacyclopropene that is stabilized by coor-
dination of a Lewis base (L ) PMe3, DMAP, etc.; B).29-31
A
second equiv of alkyne may then be added to displace the Lewis
base. Another approach involves intermediate zirconacyclo-
pentenes, formed by the relatively efficient cross-coupling of
an alkyne with ethylene (C). The ethylene may then be replaced
by heating the zirconacycle in the presence of a second alkyne,
to form the desired cross-coupled product.33 An approach that
has yet to be examined is the use of an isolable, base-free
zirconacyclopropene. This approach will require use of cyclo-
pentadienyl or alkyne substituents that stabilize the inherently
reactive zirconacyclopropene.34,35
Results and Discussion
Synthesis and Structural Characterizations of
Zirconacyclopropene Complexes. The zirconacyclopropenes
used in this study were synthesized by reaction of one equiv of
i
R2PCt CR′ (R ) Et, Pr, or Ph; R′ ) Ph or Mes) with
Rosenthal’s complex Cp2Zr(pyr)(η2-Me3SiCt CSiMe3)40 in
toluene at ambient temperature. Alkyne-alkyne homocoupling
was prevented by careful control of the ratio of alkyne to Cp2Zr.
i
In the case where R ) Pr, Et, or Ph and R′ ) Ph, both the
pyridine and Me3SiCt CSiMe3 were displaced from the metal
center and a “ligand-free” zirconacyclopropene was formed
(1-3, eq 2). On the other hand, when R ) Ph and R′ ) Mes,
the pyridine is retained to stabilize the resulting zirconacyclo-
propene (4, eq 3).
Alkynes that incorporate a Lewis base, such as a phosphino
group, may be useful coupling partners in reactions of this type,
given their potential ability to form stable monoalkyne adducts
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Zirconacyclopropenes 1-3 are probably stabilized by bridg-
ing interactions involving donation of the lone-pair on the
phosphorus to the open coordination site of a zirconium center,
to give dimeric structures with a central, six-membered ring.37,41,42
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3495–3498.

1254 Organometallics, Vol. 28, No. 4, 2009
Miller et al.
The 1H NMR spectra for zirconacyclopropenes 1 and 2 contain
resonances for inequivalent Cp ligands, and inequivalent alkyl
groups on the phosphino groups suggest a dimeric or higher-
order, rigid ring structure. Zirconacyclopropene 3 has a room
temperature 1H NMR spectrum that is consistent with a
monomeric structure (single Cp resonance at 5.45 ppm and
equivalent Ph groups by 13C{1H} NMR spectroscopy). However,
this simplified spectrum could result (for example) from a
dynamic process in a dimeric structure, which would intercon-
vert axial and equatorial Cp and Ph groups of a six-membered
ring in a chair conformation. To investigate this possibility, a
variable-temperature NMR study was undertaken. By monitoring
the Cp resonance of compound 3, a coalescence temperature
of -50 °C was observed. At lower temperatures, inequivalent
Cp resonances were observed at 5.34 and 5.29 ppm. This
corresponds to a Gibb’s free energy of activation at the
coalescence temperature of 11.2(2) kcal/mol.
It has been proposed that 31P{1H} NMR chemical shifts might
be used to characterize the presence of phosphorus-zirconium
interactions in alkynylphosphine complexes of zirconocene.37
The diisopropylphosphino group of zirconacyclopropene 1 has
31P{1H} chemical shift of 37.0 ppm. The chemical shifts of
Figure 1. ORTEP depiction of the solid-state molecular structure
of 1. Hydrogen atoms are omitted for clarity. Ellipsoids are drawn
with 50% probabilities. Selected bond lengths (Å), bond angles
(deg): Zr-P′, 2.80; Zr-C1, 2.298(3); Zr-C2, 2.219(3); P-C1,
a
zirconacyclopropenes 2 and 3 are 14.6 and 18.5 ppm, respec-
tively. For all three complexes, coordination of the alkynylphos-
phine therefore results in a downfield 31P NMR shift of 50-54
ppm with respect to that of the free alkyne. The base-stabilized
zirconacyclopropene 4, which should possess little bonding
interaction between phosphorus and zirconium, exhibits a
31P{1H} chemical shift of 10.6 ppm. This corresponds to a
downfield shift of 43 ppm relative to the free alkyne. Thus,
while donation of the lone pair to the metal center may have
an affect on the chemical shift of the phosphorus, this effect is
rather subtle. In the 13C NMR spectra, the most downfield signals
are generally associated with a zirconium-bound sp2 carbon
atom.43,44 For complexes 1-3, the most downfield resonances
are in the range of 197.9-200.9 ppm and correspond to the
zirconium-bound carbon with a phenyl group substituent.
Resonances for the zirconium-bound carbon with the phosphino
group substituent appear in the range of 144.1-154.9 ppm for
these three complexes. Thus, sp2 carbon atoms with zirconium
and phenyl substituents are observed to resonate 50 ppm
downfield of sp2 carbon atoms with zirconium and phosphino
group substituents. In contrast, the base-stabilized complex 4
1.806(3); C1-C2, 1.306(4); C2-C3, 1.470(4); Cpcent-Zr-Cpcent
,
125.1; C1-Zr-C2, 33.6(1); C1-Zr-P′, 78.9; C1-C2-C3, 141.9(3);
P-C1-C2, 133.4(2).
exhibits its most downfield 13C NMR resonance at 184.4 ppm,
but this corresponds to the zirconium-bound carbon with the
phosphino group substituent. The zirconium-bound carbon with
the phenyl group substituent has a similar resonance of 184.0
ppm for compound 4. Therefore, while the 31P NMR shifts
provides little diagnostic information, it appears that the
resonance of the carbon attached to phosphorus gives some
indication that the phosphorus lone-pair is coordinated to the
metal center for zirconacyclopropenes 1-3 (Vide infra).
The solid state structures of zirconacyclopropenes 1 and 4
were determined by single-crystal X-ray crystallography, and
the ORTEP diagrams45 are shown in Figures 1 and 2. As
predicted for zirconacyclopropene 1, two Cp2Zr fragments are
i
bridged by two Pr2PCCPh groups to form a central six-
membered ring flanked by two fused, three-membered rings.
The structure is centrosymmetric and folded along the P-P′
axis by 53.4° (angle between Zr-C1-P plane and Zr′-C1′-P′
plane). The presence of a rigid, bent ring is also consistent with
the NMR data of zirconacyclopropenes 1-3. At 2.80 Å, the
Zr-P′ distance of 1 is considerably longer than that for other
phosphine-stabilized zirconacyclopropenes such as Cp2Zr(η2-
(32) Takahashi, T.; Kageyama, M.; Denisov, V.; Hara, R.; Negishi, E.
Tetrahedron Lett. 1993, 34, 687–690.
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4448.
(34) Hiller, J.; Thewalt, U.; Polasek, M.; Petrusova, L.; Varga, V.;
Sedmera, P.; Mach, K. Organometallics 1996, 15, 3752–3759.
(35) List, A. K.; Koo, K.; Rheingold, A. L.; Hillhouse, G. L. Inorg.
Chim. Acta 1998, 270, 399–404.
(36) Miquel, Y.; Igau, A.; Donnadieu, B.; Majoral, J. P.; Dupuis, L.;
Pirio, N.; Meunier, P. Chem. Commun. 1997, 279–280.
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J. P. J. Organomet. Chem. 2004, 689, 953–964.
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45, 2427–2429.
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450.
PhCt CPh)(PMe3)
(2.70
Å)
and
Cp2Zr(η2-
HCt C(CH2)3CH3)(PMe3) (2.66 Å).29,30 This is likely due to
the smaller steric demand and greater electron-donating ability
of the PMe3 ligand. The Zr-P′ distance compares well with a
similar dimeric diphosphinomethanide zirconocene complex in
which the Zr-P distance associated with the bridging
Me2PCPMe2 group is 2.75 Å.41
The structure of zirconacyclopropene 4 is very similar to that
of the related complex, Cp2Zr(pyr)(η2-Me3SiCt CSiMe3).40
These compounds are best described as pyridine-stabilized
zirconacyclopropenes. All bond distances and angles in the two
compounds compare well, including the bond distances and
angles around the metal center (Zr-Cpcent distance of 2.275 Å
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311–316.
(45) Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565.

Unsymmetrical Zirconacyclopentadienes
Organometallics, Vol. 28, No. 4, 2009 1255
coupled diphosphinozirconacyclopentadienes. For example,
reaction of zirconacyclopropene 3 with diphenyl(phenyleth-
ynyl)phosphine in toluene at 85 °C for 16 h gives zirconacyclo-
pentadiene 5 with both phosphino groups in the R-positions, as
the major product (77%, by 1H NMR spectroscopy of the crude
reaction mixture). A minor product, presumably the R,ꢀ
regiosomer (6) on the basis of its solution NMR spectra, is
formed in 23% yield (eq 4). The R,ꢀ regiosomer is characterized
1
by a H NMR Cp resonance at 5.71 ppm (JH-P ) 1.2 Hz) and
31P{1H} NMR resonances of -8.5 and -50.0 ppm (4JP-P ) 5
Hz).
Figure 2. ORTEP depiction of the solid-state molecular structure
of 4. Hydrogen atoms are omitted for clarity. Ellipsoids are drawn
with 50% probabilities. Selected bond lengths (Å), bond angles
(deg): Zr-N, 2.449(2); Zr-C1, 2.208(2); Zr-C2, 2.243(2); P-C1,
1.781(2); C1-C2, 1.314(3); C2-C3, 1.482(3); Cpcent-Zr-Cpcent
,
128.66(1);C1-Zr-C2,34.34(8);C2-Zr-N,103.12(8);C1-C2-C3,
134.7(2); P-C1-C2, 141.7(2).
The solid-state structure of zirconacyclopentadiene 5, deter-
mined by single crystal X-ray crystallography, confirmed the
expected R,R regiochemistry (Figure 3). The most notable
feature of this structure is the donation of the lone-pair of one
of the phosphorus atoms to zirconium. This results in a highly
acute Zr-C4-P2 bond angle of 89.4(1)°, which is significantly
less than the Zr-C1-P1 bond angle of 135.4(1)°. The Zr-P2
dative bond distance of 2.8219(7) Å is somewhat longer than
might be expected for complexes of the type Cp2Zr(X)(Y)(PR3)
(2.62-2.75 Å).29,30,41,54-56 A similar Zr-P interaction was
observed by Majoral and co-workers for a zirconaindene
complex with a diphenylphosphino group in the R-position
relative to zirconium.37 In contrast to this zirconaindene
and Cpcent-Zr-Cpcent bond angle of 128.7°). The C1/C2/N plane
is perpendicular to the Cpcent/Zr/Cpcent plane and bisects the
Cpcent-Zr-Cpcent angle, as is expected for an 18 electron
zirconocene complex. The most notable feature is the regio-
chemistry of the Ph2PCCMes coordination, which places the
mesityl substituent near the pyridine ligand. In addition, the
phosphino group is positioned symmetrically within the “wedge”
formed by the Cp ligands. It is possible that the greater steric
bulk of the mesityl group prevents it from approaching the Cp
ligands.
Further evidence for the dimeric structures of zirconacyclo-
propenes 1-3 in solution was obtained by DOSY NMR studies.
It was reasoned that the diffusion coefficients of the dimeric
complexes would be smaller than those for the monomeric
complex 4. The following diffusion coefficients were measured
by these investigations: 1, 1.00(3) × 10-9 m2/s; 2, 1.01(3) ×
10-9 m2/s; 3, 1.04(1) × 10-9 m2/s; 4, 1.16(5) × 10-9 m2/s. From
this it is apparent that zirconacyclopropenes 1-3 have similar
diffusion coefficients that are smaller than that measured for
monomeric complex 4. The diffusion coefficient is inversely
proportional to the hydrodynamic radius, according to the
Stokes-Einstein equation.46 To examine whether the difference
between diffusion coefficients of the dimeric and monomeric
complexes was consistent with the differences in the hydrody-
namic radii, the average molecular radii of zirconocene com-
plexes 1 and 4 were computed with Gaussian0347 at the
B3LYP48-51/LanL2DZ52 level of theory using the atomic
coordinates from the crystal structure data.53 Accordingly, the
radius of 1 is 6.07 Å and the radius of 4 is 5.35 Å. The ratio of
the diffusion coefficients of 1 to 4 is 0.86 and the ratio of the
radii of 4 to 1 is 0.88. Thus, the diffusion coefficients are
consistent with dimeric complexes in solution based on com-
parison of the radii of the two structurally characterized
complexes.
(47) Frisch, M. J. T. G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.; Kudin, K. N.;
Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.;
Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.;
Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.;
Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li,
X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken, V.; Adamo, C.;
Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.;
Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.;
Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich,
S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.;
Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.;
Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz,
P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.; AlLaham, M. A.;
Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson,
B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople, J. A.; Gaussian, revision
A.01; Gaussian, Inc.: Wallingford, CT, 2004.
(48) Becke, A. D. J. Chem. Phys. 1993, 98, 5648–5652.
(49) Vosko, S. H.; Wilk, L.; Nusair, M. Can. J. Phys 1980, 58, 1200–
1211.
(50) Lee, C. T.; Yang, W. T.; Parr, R. G. Phys. ReV. B 1988, 37, 785–
789.
(51) Krishnan, R.; Binkley, J. S.; Seeger, R.; Pople, J. A. J. Chem. Phys.
1980, 72, 650–654.
(52) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 299–310.
(53) Tight convergence criteria were used for the SCF and volume
calculations.
(54) Kreutzer, K. A.; Fisher, R. A.; Davis, W. M.; Spaltenstein, E.;
Buchwald, S. L. Organometallics 1991, 10, 4031–4035.
(55) Buchwald, S. L.; Watson, B. T.; Huffman, J. C. J. Am. Chem. Soc.
1986, 108, 7411–7413.
(56) Karsch, H. H.; Grauvogl, G.; Deubelly, B.; Muller, G. Organo-
metallics 1992, 11, 4238–4245.
Reactivity of Zirconacyclopropene Complexes with
Alkynes. Zirconacyclopropene complexes 1-4 react with a
second equivalent of 1-alkynylphosphine to form the homo-
(46) Bird, R. B.; Stewart, W. E.; Lightfoot, E. N. Transport Phenomena;
John Wiley & Sons, Inc.: New York, 1960.

1256 Organometallics, Vol. 28, No. 4, 2009
Miller et al.
Figure 3. ORTEP depiction of the solid-state molecular structure
of 5. Hydrogen atoms are omitted for clarity. Ellipsoids are drawn
with 50% probabilities. Selected bond lengths (Å), bond angles (°):
Zr-P1, 3.88; Zr-P2, 2.82; Zr-C1, 2.350(2); Zr-C4, 2.235(2);
P1-C1, 1.838(2); P2-C4, 1.744(2); C1-C2, 1.368(3); C2-C3,
1.493(3); C3-C4, 1.349(3); Cpcent-Zr-Cpcent, 132.4; C1-Zr-C4,
71.28(8); Zr-C1-P1, 135.4; Zr-C4-P2, 89.4.
Figure 4. ORTEP depiction of the solid-state molecular structure
of 8. Hydrogen atoms are omitted for clarity. Ellipsoids are drawn
with 50% probabilities. Selected bond lengths (Å), bond angles
(deg): Zr-P1, 2.78; Zr-C1, 2.366(3); Zr-C4, 2.248(3); P1-C4,
1.738(3); C1-C2, 1.344(4); C2-C3, 1.489(4); C3-C4, 1.351(4);
Cpcent-Zr-Cpcent, 129.4; C1-Zr-C4, 69.7; Zr-C4-P1, 87.4.
R-position, as determined by 1D and 2D (NOESY, HMQC,
HMBC) NMR experiments. Thus, while dimeric zirconacyclo-
propenes 1-3 required elevated temperatures to react with
3-hexyne or tolan, the reaction of tolan with complex 4 occurred
at room temperature on the same time scale. Presumably, this
difference reflects the slower rate by which the dimeric species
dissociate to give the required reaction intermediate, a mono-
meric zirconacyclopropene complex.
complex, compound 5 exhibits a bending of the zirconacyclo-
pentadiene framework which presumably enhances the interac-
tion of the phosphorus with the metal center. The resulting
envelope structure exhibits a fold angle of 28.7° along the
C1-C4 axis. This is also accompanied by an elongation of
Zr-C1 (vs Zr-C4) by 0.115(2) Å.
The room temperature NMR spectra of zirconacyclopenta-
diene 5 are consistent with a symmetrical structure, indicating
a fast dynamic process which exchanges the two phosphorus
environments. The 1H NMR Cp resonance appears as one singlet
at 5.83 ppm and there is a single 31P{1H} NMR resonance at
-16.8 ppm which is upfield from the phosphorus resonance of
zirconacyclopropene 3 by 35.3 ppm. A variable temperature
31P{1H} NMR study was undertaken to measure the activation
energy of phosphorus exchange, but decoalesence was not
observed down to -90 °C.
Cross-couplings of alkynes were investigated by reactions
of zirconacyclopropenes 1-4 with tolan and/or 3-hexyne to form
unsymmetrical zirconacyclopentadienes. Cross-couplings with
zirconacycle 1 were generally performed at 80 °C for 16 h, and
those with zirconacycle 3 were carried out at 50 °C for 16 h, to
give zirconacyclopentadienes 7-10 (eq 5). In all cases, analysis
of the crude reaction mixtures (by 1H NMR spectroscopy)
indicates that one product formed in high yield. Reaction of
zirconacyclopropene 2 with tolan was not observed until the
reaction mixture was heated to 160 °C or higher. At this elevated
temperature, control of regioselectivity was not maintained and
two products were formed in a nearly statistical ratio (11 and
1
12, eq 6). Analysis by H and 31P{1H} NMR spectroscopy
indicates that the major species is ꢀ-phosphinozirconacyclo-
The solid-state structures of the unsymmetrical zircona-
cyclopentadienes 8 and 10 (eq 5), determined by single crystal
X-ray crystallography, confirm that for each complex the
phosphino group is in the R-position (Figures 4 and 5). The
significant difference between the two structures is that 8, which
is substituted with a diisopropylphosphino group, exhibits a
Zr-P bonding interaction while for zirconacyclopentadiene 10,
containing a diphenylphosphino group, there is no interaction
of the lone-pair on phosphorus with the metal center. This
1
pentadiene (12), with a H NMR Cp resonance at 6.00 ppm
and a 31P{1H} NMR resonance at -51.0 ppm. In this case, the
minor product is R-phosphinozirconacyclopentadiene (11), with
1
a H NMR Cp resonance at 5.63 ppm (JH-P ) 1.2 Hz) and a
31P{1H} NMR resonance at -39.5 ppm. The Lewis base-
stabilized zirconacyclopropene 4 was found to readily react with
tolan at room temperature within 16 h to give 13 (eq 7). The
only observed regioisomer contains the phosphino group in the

Unsymmetrical Zirconacyclopentadienes
Organometallics, Vol. 28, No. 4, 2009 1257
Table 1. Substitution of 1-Alkynylphosphines in
Zirconacyclopentadienes 7, 9, and 13 by Tolan to Form
Cp2Zr[2,3,4,5-Ph4C4]
Figure 5. ORTEP depiction of the solid-state molecular structure
of 10. Hydrogen atoms are omitted for clarity. Ellipsoids are drawn
with 50% probabilities. Selected bond lengths (Å), bond angles
(deg): Zr-P1, 3.75; Zr-C1, 2.239(7); Zr-C4, 2.278(7); P1-C4,
1.819(7); C1-C2, 1.341(9); C2-C3, 1.509(9); C3-C4, 1.375(8);
Cpcent-Zr-Cpcent
132.4(4).
, 135.7; C1-Zr-C4, 79.4(3); Zr-C4-P1,
8. Consistent with this, zirconacycle 13 was transformed to
Cp2Zr[2,3-Ph2-4,5-Et2C4] by selective substitution of the
Ph2PCCMes group with 3-hexyne. This reaction was observed
to occur in the presence of a slight excess of 3-hexyne (1.1
equiv) at 80 °C in benzene-d6, to give free Ph2PCt CMes and
the unsymmetrical zirconacyclopentadiene Cp2Zr[2,3-Ph2-4,5-
Et2C4] (1H NMR: 5.98 ppm, Cp). Complete substitution was
observed to occur in less than 10 h, and was accompanied by
a small amount (5%) of the symmetrical tetraphenylzircona-
cyclopentadiene.
difference is consistent with a very weak Zr-P bonding
interaction for the diphenylphosphino substituent of compound
5, as observed in the VT NMR study (Vide supra). This
difference may be largely ascribed to the greater electron-
donating ability of the diisopropylphosphino group.
Zirconacyclopentadiene 8 is structurally similar to compound
5, with a Zr-P bond which is slightly shorter (2.7774(9) Å)
than that in the latter complex (2.8219(7) Å). The zircona-
cyclopentadiene framework of 8 is folded along the C1-C4
axis by 13.6°, and this appears to be associated with a
contraction of the Zr-C bond for the carbon attached to the
phosphino group, relative to the carbon attached to the ethyl
group, of 0.118(3) Å. This distortion allows for a stronger Zr-P
interaction, as reflected in the acute Zr-C4-P1 bond angle of
87.4(1)°. Zirconacyclopentadiene 10, which has no Zr-P
bonding interaction in the solid state, has a Zr-P1 distance of
3.773(2) Å and a Zr-C4-P1 bond angle of 132.4(4)°. The
structure of complex 10 is noteworthy because of the distorted
zirconacyclopentadiene framework. Unlike most zirconacyclo-
pentadienes which have a nearly planar framework, no four
atoms of the zirconacyclopentadiene ring of 10 are in the same
plane. The deviations from planarity vary from 0.1 - 0.55 Å.
The structure of zirconacycle 10 is also in contrast to the
structures of 5 and 8, which have an envelope framework with
the four carbons of the butadiene backbone in the same plane
and the Zr out of the plane by 0.89 and 0.44 Å for 5 and 8,
respectively.
To examine the influence of the substituents on the rates of
alkynylphosphine substitution in zirconacyclopentadienes, reac-
tions of 7, 9, and 13 with a slight excess of tolan were monitored
(100 °C, benzene-d6). These reactions cleanly form tetra-
phenylzirconacyclopentadiene, and substituents on the 1-alky-
nylphosphine were found to have a significant influence on the
rates of alkyne substitution (Table 1). The substitution of
Ph2PCt CPh with tolan in zirconacyclopentadiene 9 was
significantly slower than the corresponding substitution reactions
of iPr2PCt CPh and Ph2PCt CMes for zirconacycles 7 and 13,
respectively, which were observed to proceed at similar rates.
Alkyne substitutions of zirconacyclopentadienes have been
shown both experimentally59 and theoretically20,60 to proceed
dissociatively through a zirconacyclopropene intermediate.
Therefore, it might seem reasonable that sterically hindered
substituents on the leaving alkyne would lead to a faster rate of
dissociation (and therefore alkyne exchange). However, it is
worth noting that steric hindrance associated with the bis(cy-
clopentadienyl) ligand set retards such reactions.59 As shown
in Table 1, the least sterically demanding set of alkyne
Selective Alkyne-Alkyne Exchange in Zircona-
cyclopentadienes. It has previously been observed that sterically
demanding substituents, such as -SiMe3 and -CMe3, promote
reversible fragmentations of a zirconacyclopentadiene ring.19,57-59
In principle, this reactivity should allow selective transformations
of unsymmetrical zirconacyclopentadienes, as illustrated in eq
(57) Erker, G.; Zwettler, R. J. Organomet. Chem. 1991, 409, 179–188.
(58) Takahashi, T.; Kotora, M.; Hara, R.; Xi, Z. F. Bull. Chem. Soc.
Jpn. 1999, 72, 2591–2602.
(59) Miller, A. D.; McBee, J. L.; Tilley, T. D. J. Am. Chem. Soc. 2008,
130, 4992–4999.
(60) Imabayashi, T.; Fujiwara, Y.; Nakao, Y.; Sato, H.; Sakaki, S.
Organometallics 2005, 24, 2129–2140.

1258 Organometallics, Vol. 28, No. 4, 2009
Miller et al.
substituents (-PPh2 and -Ph of zirconacycle 9) corresponds
to the slowest exchange reaction. Zirconacycles with larger
substituents in the R- (-PiPr2, 7) and ꢀ- (-Mes, 13) position
undergo faster exchange reactions. Thus, for these exchange
reactions, bulky substituents on the zirconacyclopentadiene ring
appear to lower the barrier for “alkyne decoupling” at the metal
center.
absorptions assigned to phosphine oxide (1199 cm-1) and
sulfoxide (1049 cm-1) groups but no absorption was observed
for the asymmetric SdO stretch of a sulfone (1300-1335
cm-1).61
Functionalized Phosphines and Phosphine Oxides from
r-Phosphinozirconacyclopentadienes. Zirconacyclopenta-
dienes have been transformed, via metathesis reactions at the
metal-center, to a wide array of organic compounds.4-17 To
evaluate the utility of these alkyne couplings for the synthesis
of functionalized phosphorus compounds, zirconium-transfer
reactions of zirconacyclopentadienes 9 and 10 were examined.
Two types of transformations were examined: protonolysis to
form a substituted butadiene,4 and reaction of sulfur dioxide
with zirconacyclopentadienes to form substituted thiophene
oxides.16 Zirconacyclopentadiene 9 was treated with 10 equiv
of benzoic acid at room temperature to give butadienylphosphine
14 in 88% yield after purification by flash column chromatog-
raphy (eq 9). Solid 14 is stable for long periods (several months)
in air, but it significantly oxidizes within hours in solution to
the corresponding phosphine oxide as indicated by a charac-
teristic downfield shift of the phosphorus resonance in the
31P{1H} NMR spectrum (-23.6 ppm vs 18.4 ppm). However,
solutions of 14 may be handled briefly in air. This compound
was previously synthesized by Takahashi and co-workers from
the in situ generated zirconacycle 14 and was shown to have
the desired regiochemistry by single-crystal X-ray analysis.39
The butadienylphosphine oxide 15 was synthesized in a similar
manner. Zirconacyclopentadiene 10 was treated with 10 equiv
of benzoic acid and then 2 equiv of H2O2 to ensure complete
oxidation of the phosphorus (eq 10). The resulting butadi-
enylphosphine oxide was purified by flash column chromatog-
raphy to give the product in 82% yield. The resulting 31P{1H}
NMR spectrum contains a chemical shift of 17.4 ppm and the
IR spectrum has an absorption at 1168 cm-1 assigned to the
phosphine oxide (PdO).
Extended π-Systems from Reactions of Diynes with
Zirconacyclopropenes. The zirconocene-coupling of diynes has
proven to be an efficient and versatile pathway to a variety of
conjugated polymers and oligomers.4,16,20-22,28,62-66 Thus, it
was of interest to study the possible use of zirconocene-
phosphinoalkyne complexes in the construction of phosphino-
terminated, conjugated oligomers. In addition, it was thought
that oligomers derived from such zirconocene reagents might
allow a degree of “end-group control” for the synthesis of
functionalized oligomers, via alkyne-exchange reactions. Pre-
liminary results from such studies are described below.
For synthesis of a linear, conjugated system, a starting diyne
must possess a rigid, conjugated spacer group as well as
terminal, ꢀ-directing groups. It has previously been shown that
1,4-bis(pentafluorophenylethynyl)benzene is useful in this re-
gard.20 This diyne was found to react with 2 equiv of
zirconacyclopropene 3 at 50 °C, to give the bis(zirconacycle)
17. Similarly, 4 reacted with the diyne at room temperature to
produce 18 (eq 12). These compounds were purified by washing
with pentane, and were isolated in 44-67% yield. Compounds
17 and 18 are slightly soluble in aromatic solvents such as
1
benzene and toluene and were characterized by H, 31P{1H},
and 19F NMR spectroscopy and elemental analysis. The 31P{1H}
NMR chemical shifts of -27.4 ppm and -25.8 ppm for
bis(zirconacycles) 17 and 18, respectively, are indicative of a
phosphino group in the R-position of a zirconacyclopentadiene
(Vide supra).37
Bis(zirconacycles) 17 and 18 contain two zirconocene frag-
ments that may function as useful reaction centers, and terminal
phosphino groups that offer intriguing binding and/or linking
sites. Bis(zirconacycle) 17 (generated in situ) was converted to
the corresponding bis(butadienyl)benzene 19 by hydrolysis with
a degassed, aqueous HCl solution to avoid oxidation of the
phosphino group (eq 13). The product was purified by an
aqueous workup with a saturated NaHCO3 solution to remove
The synthesis of thiophene oxide 16 was accomplished by
exposure of a THF solution of zirconacyclopentadiene 9 to an
atmosphere of sulfur dioxide for 20 min. After aqueous workup
and column chromatography 16 was obtained as a bright yellow
solid in 75% yield (eq 11). In this case, oxidation of the
phosphorus moiety was a result of exposure to the ambient
atmosphere during workup. To rule out oxidation of the
phosphorus by the sulfur dioxide, an NMR scale experiment
was conducted in a sealed tube. This investigation revealed that
the reaction of 9 with SO2 cleanly gave a new compound that
exhibits a 31P{1H} NMR shift of -18.3 ppm, attributed to (3,4,5-
triphenylthiophen-2-yl oxide)diphenylphosphine. Thiophene ox-
ide 16, with the oxidized phosphorus moiety, exhibits a
downfield chemical shift of 17.3 ppm. The IR spectrum is also
consistent with the assigned structure for 16, as it contains
(61) Coates, J. Interpretation of Infrared Spectra: A Practical Approach;
Meyers, R. A., Ed.; John Wiley & Sons Ltd: Chichester, 2000.
(62) Lucht, B. L.; Buretea, M. A.; Tilley, T. D. Organometallics 2000,
19, 3469–3475.
(63) Lucht, B. L.; Mao, S. S. H.; Tilley, T. D. J. Am. Chem. Soc. 1998,
120, 4354–4365.
(64) Mao, S. S. H.; Tilley, T. D. J. Organomet. Chem. 1996, 521, 425–
428.
(65) Mao, S. S. H.; Tilley, T. D. Macromolecules 1996, 29, 6362–6364.
(66) Suh, M. C.; Jiang, B. W.; Tilley, T. D. Angew. Chem., Int. Ed.
2000, 39, 2870–2873.

Unsymmetrical Zirconacyclopentadienes
Organometallics, Vol. 28, No. 4, 2009 1259
oxygen-free solvents were used. Olefin impurities were removed
from pentane by treatment with concentrated H2SO4, 0.5 N KMnO4
in 3 M H2SO4, and saturated NaHCO3. Pentane was then dried over
MgSO4, stored over activated 4 Å molecular sieves, and distilled
from potassium benzophenone ketyl under a nitrogen atmosphere.
Toluene was purified by stirring with concentrated H2SO4, washing
with saturated NaHCO3, then drying over CaCl2 and distillation
from sodium under a nitrogen atmosphere. Spectrophotometric
grade diethyl ether and reagent grade THF were distilled from
sodium benzophenone ketyl under a nitrogen atmosphere. Aceto-
nitrile was refluxed over P2O5 and distilled under a nitrogen
atmosphere. Benzene-d6 was vacuum distilled from sodium/
potassium alloy and benzophenone.
the excess acid, and subsequent washing of the resulting organic
solid with MeOH gave the analytically pure compound in 56%
yield. The 31P{1H} NMR spectrum of 19 has a single resonance
at -22.4 ppm which is consistent with an unoxidized phosphino
group.
NMR spectra were recorded on a Bruker AVB-400 instrument
operating at 400.1 MHz (1H), 100.7 MHz (13C), 376.5 MHz (19F),
and 162 MHz (31P), with a Bruker AV-300 instrument operating at
300.1 MHz (1H), or with a Bruker DRX-500 instrument operating
at 500.1 MHz (1H) and 125.8 MHz (13C). Chemical shifts are
reported in ppm relative to SiMe4 and are referenced internally to
residual solvent resonances (1H, 13C) or externally to 85% H3PO4
(31P). 19F NMR spectra were referenced internally by a C6F6
standard relative to CFCl3 at 0 ppm. Splitting patterns are designated
as s, singlet; d, doublet; t, triplet; q, quartet; sept, septet; m,
multiplet; v, virtual. Infrared spectra were recorded as thin films
on NaCl plates or as KBr pellets using a Mattson FTIR spectrometer
at a resolution of 4 cm-1. Elemental analyses were performed by
the Microanalytical Laboratory in the College of Chemistry at the
University of California, Berkeley.
As observed for zirconacycles 7, 9, and 13, the R2PCCR′
group of the zirconacyclopentadienes may be selectively
substituted in the presence of a smaller alkyne. To demonstrate
the exchange of end groups in a conjugated bis(zirconacycle),
a solution of 18 was heated in the presence of 3 equiv of tolan
to give the slightly soluble bis(zirconacycle) 20 (eq 14). The
solid product was washed with pentane to give the analytically
pure compound in 25% yield. In general, this approach should
prove useful for the introduction of various end groups onto
oligomers obtained by zirconocene-coupling methods.
The compounds Cp2Zr(pyr)(η2-Me3SiCt CSiMe3)23 and 1,4-
bis(pentafluorophenylethynyl)benzene20 were synthesized according
to published procedures. All other chemicals were obtained from
commercial suppliers and used as received. The n-butyl lithium
reagent was used as a 1.6 M solution in hexanes.
Conclusions
Diisopropyl(phenylethynyl)phosphine. To a cold (0 °C) solu-
tion of phenylacetylene (0.69 mL, 6.3 mmol) in diethyl ether (60
mL) was added n-BuLi (3.9 mL, 6.3 mmol) dropwise via syringe.
The solution was stirred for 10 min before the ice bath was removed,
and it was then stirred for an additional 1.5 h. The reaction mixture
was then cooled with a dry ice/isopropanol bath and chlorodiiso-
propylphosphine (1.0 mL, 6.3 mmol) was added dropwise via
syringe. The reaction mixture was slowly warmed to ambient
temperature and was stirred for 16 h. The yellow solution with a
white precipitate was concentrated under reduced pressure and then
pentane (60 mL) was added and the lithium chloride precipitate
was removed by cannula filtration. The solution was concentrated
under vacuum and the resulting yellow oil was purified by short
path vacuum transfer at 0.05 mTorr and 70 °C giving a 59% yield
(0.81 g, 3.7 mmol) of the desired compound, which was spectro-
scopically identified.671H NMR (400 MHz, C6D6): δ 7.47 (m, 2H),
Zirconacyclopropenes derived from 1-alkynylphosphines are
useful reagents for the synthesis of unsymmetrical zircona-
cyclopentadienes. For either dimeric zirconacyclopropenes or
related Lewis base-stabilized adducts, efficient cross-couplings
with an additional equiv of alkyne occur regioselectively to give
a zirconacyclopentadiene containing a phosphino group in the
R-position. This regiocontrol is observed for diisopropylphos-
phino and diphenylphosphino groups, and is presumed to be
due to interaction of the phosphino group with zirconium,
possibly through a stabilizing Zr-P interaction in the transition
state. Clearly, this type of Zr-P bonding is characteristic of
several zirconacyclopentadienes with R-phosphino substituents.
However, it should be noted that it is difficult at this time to
rule out a purely steric factor, which may also direct the
phosphino groups into the R-position. Zirconacyclopentadienes
containing the R2PCCR′ group are labile, such that the 1-alky-
nylphosphines are readily substituted for a less bulky alkyne.
The observed coupling reactions also represent a potentially
useful approach for the synthesis of well-defined oligomers with
functional end groups. For example, an oligomer terminated with
an alkynyl group may be functionalized with a phosphino group
in a “click”-type reaction with a phosphine-containing zircona-
cyclopropene. Such phosphino groups may be of use in the
organization of conjugated oligomers into hybrid, metal-
containing materials.
3
3
7.01 (m, 3H), 1.93 (sept, JH-H ) 7.0 Hz, 2H), 1.34 (dd, JH-H
)
)
3
3
3
7.0 Hz, JH-P ) 11.0 Hz, 6H), 1.17 (dd, JH-H ) 7.0 Hz, JH-P
16.8 Hz, 6H). 31P{1H} NMR (162 MHz, C6D6): δ -12.5.
Diethyl(phenylethynyl)phosphine. See the preparation of di-
isopropyl(phenylethynyl)phosphine for the synthetic protocol. The
amounts of reagents used were phenylacetylene (0.49 mL, 4.5
mmol), n-BuLi (2.8 mL, 4.5 mmol), and chlorodiethylphosphine
(0.50 mL, 4.1 mmol). Purification by short path vacuum transfer
at 0.05 mTorr and 45 °C resulted in a light-yellow oil, identified
spectroscopically,67 in 52% yield (0.41 g, 2.1 mmol). 1H NMR (400
MHz, C6D6): δ 7.41 (m, 2H), 6.92 (m, 3H), 1.61 (qt, 4JH-H ) 3JH-H
4
3
) 7.6 Hz, 2H), 1.46 (qt, JH-H ) JH-H ) 7.6 Hz, 2H), 1.13 (m,
6H). 31P{1H} NMR (162 MHz, C6D6): δ -39.3.
Experimental Section
General Procedures. Unless otherwise noted, all manipulations
were performed under a dry, nitrogen atmosphere using either
standard Schlenk techniques or a nitrogen-filled glovebox. Dry,
(67) Aguiar, A. M.; Irelan, J. R. S.; Morrow, C. J.; John, J. P.; Prejean,
G. W. J. Org. Chem. 1969, 34, 2684–2686.

1260 Organometallics, Vol. 28, No. 4, 2009
Miller et al.
Diphenyl(phenylethynyl)phosphine. This procedure is a modi-
fication of a procedure described in the literature.68 To a cold (0
°C) solution of phenylacetylene (5.0 mL, 46 mmol) in 250 mL of
diethyl ether was added 28 mL of a 1.6 M solution of n-BuLi in
hexane while the mixture was efficiently stirred. The reaction
mixture was allowed to warm to room temperature over 2.5 h and
was then cooled to -78 °C in a dry ice/acetone bath. Diphenyl-
chlorophosphine (8.2 mL, 46 mmol) was then slowly added to this
solution. The dry ice/acetone bath was removed and the solution
was allowed to stir at room temperature for 3 h. The reaction
mixture was exposed to the atmosphere and the solvent was
removed under vacuum and the residue was extracted with pentane
(200 mL). The solution was filtered and the solvent was removed
under vacuum. The resulting solid was dissolved in ethanol (75
mL) and the resulting solution was then cooled to -30 °C overnight.
The white crystals that formed were collected and dried under
vacuum. Yield: 72% (9.4 g). mp: 40-41 °C (lit. 43 °C).681H NMR
(400 MHz, CDCl3): δ 7.69 (m, 4H), 7.55 (m, 2H), 7.35 (m, 9H).
31P{1H} NMR (162 MHz, CDCl3): δ -33.5. IR (cm-1): 3054 (w),
2919 (w), 2161 (w, Ct C), 1488 (m), 1434 (s), 1095 (w), 1025
(w), 838 (w), 751 (s), 691 (s), 507 (m), 451 (w).
[Cp2Zr(η2-Et2PCCPh)]2 (2). See the preparation of zircona-
cyclopropene 1 for the synthetic protocol. The amounts of reagents
used were diethyl(phenylethynyl)phosphine (0.10 g, 0.5 mmol) and
Cp2Zr(pyr)(η2-Me3SiCt CSiMe3) (0.25 g, 0.5 mmol). A yellow solid
1
was obtained in a 65% yield (0.14 g, 0.17 mmol). H NMR (400
3
MHz, C6D6): δ 7.30 (t, JH-H ) 7.6 Hz, 2H), 7.16 (overlap with
residual solvent, 2H), 7.04 (m, 1H), 5.37 (s, 5H), 5.35 (s, 5H), 2.00
2
3
2
(m, 2H), 1.65 (qd, JH-H ) JH-H ) 7.4 Hz, 1H), 1.29 (qd, JH-H
) 3JH-H ) 7.6 Hz, 1H), 0.93 (m, 3H), 0.63 (m, 3H). 13C{1H} NMR
(125.8 MHz, C6D6): δ 200.9 (vt, JC-P ) 21 Hz, Cp2Zr(η2-
2
Et2PCt CPh), 156.4 (i-Ph), 144.3 (vt, JC-P ) 30 Hz, Cp2Zr(η2-
1
Et2PCt CPh), 128.9 (m-Ph), 123.3 (p-Ph), 121.7 (o-Ph), 105.3 (Cp),
1
1
104.0 (Cp), 19.3 (Et), 18.2 (vdd, JC-P ) 24 Hz, JC-P ) 10 Hz,
Et), 9.2 (Et), 8.2 (vt, 2JC-P ) 4 Hz, Et). 31P{1H} NMR (162 MHz,
C6D6): δ 14.6. Anal. calcd for C24H29PZr: C, 64.19; H, 6.12. Found:
C, 64.40; H, 5.95.
[Cp2Zr(η2-Ph2PCCPh)]2 (3). A mixture of diphenyl(phenyl-
ethynyl)phosphine (0.30 g, 1.1 mmol) and Cp2Zr(pyr)(η2-
Me3SiCt CSiMe3) (0.50 g, 1.1 mmol) was cooled to -78 °C and
toluene (50 mL) was added via cannula. The dry ice/acetone bath
was removed and the solution was then stirred for 16 h at ambient
temperature. The solvent was removed under vacuum and then
pentane (50 mL) was added via cannula. The solution was sonicated
for 1 h and then the solvent was removed via cannula filtration, to
give a yellow solid that was then dried under vacuum. Yield: 67%
Diphenyl(mesitylethynyl)phosphine. The mesitylethyne (1.89
g, 13.1 mmol) was dissolved in ether (250 mL) and then this
solution was cooled with an ice bath. A solution of n-BuLi (8.2
mL, 13.1 mmol) in hexanes was then added dropwise, the ice bath
was removed, and the reaction mixture was allowed to stir at
ambient temperature for an hour. The reaction mixture was then
cooled with a dry ice/isopropanol bath and chlorodiphenylphosphine
(2.35 mL, 13.1 mmol) was slowly added. The reaction mixture was
allowed to slowly warm to ambient temperature while stirring over
the next 16 h. The reaction mixture was exposed to the atmosphere
and then filtered through silica gel and concentrated under vacuum.
The resulting solid was crystallized from a pentane solution at -30
°C resulting in white crystals in 62% yield (2.68 g, 8.2 mmol).
mp: 72-73.5 °C. 1H NMR (400 MHz, C6D6): δ 7.81 (m, 4H), 7.10
(m, 4H), 7.03 (m, 2H), 6.64 (s, 2H), 2.40 (s, 6H), 2.03 (s, 3H).
13C{1H} NMR (100.7 MHz, C6D6): δ 141.4 (d,3JC-P ) 1 Hz), 138.9,
1
(0.36 g, 0.35 mmol). mp: 151-153 °C, dec H NMR (400 MHz,
C6D6): δ 7.48 (m, 4H), 7.22 (m, 4H), 6.89 (m, 7H), 5.45 (s, 10H).
13C{1H} NMR (125.8 MHz, C6D6): δ 197.9 (d, JC-P ) 46 Hz,
Cp2Zr(η2-Ph2PCt CPh)), 152.7 (Ph), 144.1 (d, JC-P ) 80 Hz,
Cp2Zr(η2-Ph2PCt CPh)), 141.1 (Ph), 134.5 (Ph), 128.8 (Ph), 128.1
(m, Ph), 124.3 (Ph), 124.0 (Ph), 105.8 (Cp). 31P{1H} NMR (162
MHz, C6D6): δ 18.5. IR (cm-1): 3050 (m), 3017 (w), 2958 (w),
1681 (m), 1630 (w), 1585 (m), 1478 (m), 1434 (m), 1364 (w), 1260
(w), 1166 (w), 1089 (w), 1024 (m), 794 (s), 696 (s), 543 (w), 499
(m). Anal. calcd for C47H41PZr: C, 77.54; H, 5.68. Found: C, 77.44;
H, 5.57.
Cp2Zr(η2-Ph2PCt CMes)(pyr) (4). Diphenyl(mesitylethynyl)phos-
phine (0.469 g, 1.4 mmol) and Cp2Zr(pyr)(η2-Me3SiCt CSiMe3)
(0.706 g, 1.5 mmol) were cooled in a dry ice/isopropanol bath and
then toluene (20 mL) was added. The reaction mixture was stirred
for 0.5 h at this temperature and then the bath was removed and
the reaction mixture was stirred at ambient temperature for 16 h.
The solvent was removed under vacuum and the resulting solid
was washed with ether (30 mL) to produce an orange solid in 82%
1
2
138.1 (d, JC-P ) 8 Hz), 133.5, 133.3, 129.5, 129.3 (d, JC-P ) 7
Hz), 128.5, 120.6, 107.0 (d, 2JC-P ) 4 Hz), 94.2 (d, 1JC-P ) 6 Hz),
21.7, 21.6. 31P{1H} NMR (162 MHz, C6D6): δ -32.5. IR (cm-1):
3054 (m), 2915 (m), 2853 (w), 2148 (m, Ct C), 1609 (w), 1478
(m), 1435 (m), 1376 (w), 1227 (w), 1094 (w), 1026 (w), 853 (m),
811 (w), 740 (m), 695 (s), 579 (w), 510 (m). Anal. calcd for
C23H21P: C, 84.12; H, 6.45. Found: C, 83.97; H, 6.46.
[Cp2Zr(η2-iPr2PCCPh)]2 (1). A solution of diisopropyl(phenyl-
ethynyl)phosphine (0.40 g, 1.8 mmol) in toluene (20 mL) was
1
yield (0.73 g, 1.2 mmol). mp: 160 °C, dec H NMR (400 MHz,
C6D6): δ 8.49 (m, 2H), 7.70 (m, 4H), 7.13 (m, 4H), 7.06 (m, 2H),
6.73 (s, 2H), 6.59 (m, 1H), 6.22 (m, 2H), 5.64 (s, 10H), 2.22 (s,
3H), 2.17 (s, 6H). 13C{1H} NMR (125.8 MHz, C6D6): δ 184.4 (d,
1JC-P ) 52 Hz, Cp2Zr(η2-Ph2PCt CMes)), 184.0 (Cp2Zr(η2-
cannula-transferred to
a
flask containing Cp2Zr(pyr)(η2-
Me3SiCt CSiMe3) (0.86 g, 1.8 mmol). The reaction mixture was
then stirred at ambient temperature for 16 h. The toluene was
removed under vacuum and the resulting solid was washed with
diethyl ether (2 × 20 mL) and dried under vacuum to give a yellow
solid in 58% yield (0.46 g, 0.50 mmol). X-ray quality crystals were
grown by layering a solution of diisopropyl(phenylethynyl)phos-
phine in toluene over a toluene solution of Cp2Zr(pyr)(η2-
Me3SiCt CSiMe3) and allowing reaction to occur over 2 days. mp:
192 °C, dec 1H NMR (400 MHz, C6D6): δ 7.25 (m, 4H), 6.98 (m,
1H), 5.63 (s, 5H), 5.46 (s, 5H), 2.87 (m, 1H), 2.41 (m, 1H), 1.34
3
Ph2PCt CMes)), 154.72 (o-pyr), 144.4 (d, JC-P ) 4 Hz, i-Mes),
141.1 (d, 1JC-P ) 11 Hz, i-Ph), 137.2 (p-pyr), 134.6 (d, 2JC-P ) 20
4
Hz, o-Ph), 132.4 (d, JC-P ) 1 Hz, o-Mes), 131.8 (p-Mes), 128.7
(m-Mes), 128.4 (m-Ph), 128.1, (p-Ph), 124.0 (m-pyr), 107.9 (Cp),
5
21.9, (d, JC-P ) 6 Hz, o-Me), 21.4 (p-Me). 31P{1H} NMR (162
MHz, C6D6): δ 10.6. Anal. calcd for C38H36NPZr: C, 72.57; H,
5.77; N, 2.23. Found: C, 72.25; H, 5.58; N, 2.18.
Cp2Zr[2,5-(Ph2P)2-3,4,-Ph2C4] (5). A solution of zirconacylo-
propene 3 (0.14 g, 0.14 mmol) and diphenyl(phenylethynyl)phos-
phine (0.08 g, 0.28 mmol) in toluene (7 mL) was heated at 85 °C
for 16 h. The solvent was removed under vacuum and the resulting
solid was washed with pentane (3 × 15 mL) to produce a red-
orange solid in 73% yield (0.16 g, 0.20 mmol). 1H NMR (500 MHz,
C6D6): δ 7.56 (m, 8H), 7.20 (m, 4H), 6.97 (m, 12H), 6.75 (t, 3JH-H
) 7.8 Hz, 4H), 6.65 (m, 2H), 5.83 (s, 10H). 13C{1H} NMR (125.8
3
3
(m, 6 H), 1.16 (dd, JH-H ) 7.5 Hz, JH-P ) 14.0 Hz, 3H), 1.05
(dd, JH-H ) JH-P ) 6.5 Hz, 3H). 13C{1H} NMR (125.8 MHz,
C6D6): δ 199.2 (Cp2Zr(η2-iPr2PCt CPh)), 172.8 (Ph), 154.9 (Cp2Zr(η2-
iPr2PCt CPh)), 127.9 (Ph), 123.4 (Ph), 122.4 (Ph), 106.1 (Cp), 105.1
(Cp), 31.5 (iPr), 30.9 (iPr), 23.2 (iPr), 22.2 (iPr), 20.7 (iPr), 1.8 (iPr).
31P{1H} NMR (162 MHz, C6D6): δ 37.0. Anal. calcd for C24H29PZr:
C, 65.56; H, 6.65. Found: C, 65.51; H, 6.36.
3
3
1
3
MHz, C6D6): δ 185.7 (dd, JC-P ) 57 Hz, JC-P ) 3 Hz,
2
3
-ZrC(Ph2Ph)dC(Ph)-), 162.6 (dd, JC-P ) 20 Hz, JC-P ) 9 Hz,
-ZrC(Ph2P)dC(Ph)-), 143.6 (m, Ph), 139.1 (d, JC-P ) 8 Hz, Ph),
(68) Samb, A.; Demerseman, B.; Dixneuf, P. H.; Mealli, C. Organo-
metallics 1988, 7, 26–33.

Unsymmetrical Zirconacyclopentadienes
Organometallics, Vol. 28, No. 4, 2009 1261
134.9 (d, JC-P ) 17 Hz, Ph), 130.3 (Ph), 128.6 (Ph), 128.4 (Ph),
127.5 (Ph), 126.1 (Ph), 108.9 (Cp).31P{1H} NMR (162 MHz, C6D6):
δ -16.8. Anal. calcd for C50H40P2Zr: C, 75.63; H, 5.08. Found: C,
75.25; H, 5.00.
Cp2Zr[2-Ph2P-3-Ph-4,5-Et2C4] (10). To a solution of zircona-
cylopropene 3 (0.40 g, 0.39 mmol) in toluene (10 mL) was added
3-hexyne (94 µL, 0.83 mmol). The resulting solution was placed
in an oil bath and was heated at 50 °C for 16 h. The solvent was
removed under vacuum and to the resulting crude solid was added
pentane (2 × 20 mL). The insoluble solids were removed by cannula
filtration and the resulting solution was concentrated to 6 mL. The
solution was then cooled to -30 °C for 3 days, and then the solvent
was removed via cannula filtration. The resulting solid was dried
under vacuum to give a red-orange solid in 60% yield (0.28 g,
0.47 mmol). 1H NMR (400 MHz, C6D6): δ 7.47 (m, 4H), 7.25 (d,
Cp2Zr[2-iPr2P-3,4,5-Ph3C4] (7). A solution of zirconacyclopro-
pene 1 (0.25 g, 0.3 mmol) and tolan (0.10 g, 0.6 mmol) in toluene (10
mL) was heated at 80 °C for 16 h. The resulting solution was
concentrated to 5 mL and then pentane was added until a small amount
of precipitate formed. The solution was then cooled to -80 °C for
18 h, and then the solvent was removed via cannula filtration. The
resulting solid was dried under vacuum to give an orange solid in 58%
yield (0.20 g, 0.3 mmol). 1H NMR (300 MHz, C6D6): δ 7.37 (m, 2H),
7.16 (m, overlaps with residual solvent peak), 6.95 (m, 7H), 6.74 (tt,
3JH-H ) 7.2 Hz, 1H), 5.78 (d, 4JH-P ) 1.2 Hz, 10H), 1.98 (sept, 3JH-H
) 7.5 Hz, 2H), 1.20 (dd, 3JH-H ) 7.5 Hz, 3JH-P ) 12.9 Hz, 6H), 0.79
3
3JH-H ) 7.0 Hz, 2H), 6.98 (m, 9H), 5.82 (s, 10H), 2.31 (q, JH-H
) 7.5 Hz, 2H), 2.23 (q, 3JH-H ) 7.5 Hz, 2H), 1.12 (t, 3JH-H ) 7.5
Hz, 3H), 0.98 (t, 3JH-H ) 7.5 Hz, 3H). 13C{1H} NMR (125.8 MHz,
C6D6): δ 202.4 (d, 3JC-P ) 4 Hz, -ZrC(Et)dC(Et)-), 174.2 (d, 1JC-P
2
3
3
(dd, JH-H ) 7.5 Hz, JH-P ) 15.9 Hz, 6H). 13C{1H} NMR (125.8
) 44 Hz, -ZrC(Ph2P)dC(Ph)-), 160.8 (d, JC-P ) 10 Hz,
-ZrC(Ph2P))C(Ph)-), 145.1 (d, 3JC-P ) 18 Hz, -ZrC(Et)dC(Et)-),
144.8 (d, JC-P ) 13 Hz, Ph), 140.7 (d, JC-P ) 9 Hz, Ph), 134.7 (d,
JC-P ) 18 Hz, Ph), 129.0 (d, JC-P ) 1 Hz, Ph), 128.6 (Ph), 128.5
3
MHz, C6D6): δ 210.9 (d, JC-P ) 10 Hz, -ZrC(Ph)dC(Ph)-), 170.7
(d, JC-P ) 68 Hz, -ZrC(iPr2P)dC(Ph)-), 165.1 (d, JC-P ) 15 Hz,
1
2
-ZrC(iPr2P)dC(Ph)-), 155.9 (Ph), 154.7 (d, 3JC-P ) 29 Hz, -ZrC(Ph))
3
4
(Ph), 128.0 (Ph), 126.4 (Ph), 109.6 (Cp), 30.9 (Et), 23.8 (d, JC-P
)
C(Ph)-), 145.4 (d, JC-P ) 8 Hz, Ph), 142.6 (d, JC-P ) 5 Hz, Ph),
5 Hz, Et), 16.1 (Et), 15.1 (Et).31P{1H} NMR (162 MHz, C6D6): δ
-18.9. Anal. calcd for C36H35PZr: C, 73.30; H, 5.98. Found: C,
72.91; H, 5.82.
132.0 (Ph), 129.1 (Ph), 128.39 (Ph), 128.2 (Ph), 127.7 (Ph), 127.4
(Ph), 127.0 (Ph), 125.2 (Ph), 123.4 (Ph), 105.5 (Cp), 27.8 (d, 1JC-P
)
6 Hz, iPr), 22.2 (iPr), 21.3 (d, 2JC-P ) 8 Hz, iPr).31P{1H} NMR (162
MHz, C6D6): δ -33.3. Anal. calcd for C38H39PZr: C, 73.86; H, 6.36.
Found: C, 73.80; H, 6.30.
Cp2Zr[2-Ph2P-3-Mes-4,5-Ph2C4] (13). Zirconacyclopropene 4
(0.30 g, 0.48 mmol) and tolan (0.085 g, 0.48 mmol) were loaded
into a Schlenk flask and then cooled in a dry ice/isopropanol bath.
Toluene (10 mL) was added dropwise and the reaction mixture
was allowed to slowly reach ambient temperature. The reaction
mixture was stirred for 16 h and then the toluene was removed
under vacuum. The resulting solid was dissolved in ether (10 mL)
and this solution was cannula-filtered to remove the insoluble
impurities. The solution was then concentrated to 5 mL and cooled
to -30 °C for 72 h to give the product, isolated by filtration, as
Cp2Zr[2-iPr2P-3-Ph-4,5-Et2C4] (8). To a solution of zircona-
cylopropene 1 (0.21 g, 0.24 mmol) in toluene (10 mL) was added
3-hexyne (60 µL, 0.53 mmol). The solution was placed in an oil
bath and was heated at 80 °C for 16 h. The solvent was removed
under vacuum and to the resulting crude solid was added pentane
(15 mL). The insoluble solids were removed by cannula filtration
and the resulting solution was then cooled to -30 °C for 18 h. The
solvent was removed via cannula filtration and the solid was dried
under vacuum resulting in a red-orange solid in 72% yield (0.18 g,
0.35 mmol). 1H NMR (400 MHz, C6D6): δ 7.32 (m, 2H), 7.16 (m,
1
orange crystals in 60% yield (0.21 g, 0.29 mmol). H NMR (500
MHz, C6D6): δ 7.52 (m, 4H), 7.04 (m, 2H), 6.97 (m, 10H), 6.60
(m, 3H), 6.66 (m, 1H), 6.48 (s, 2H), 5.92 (s, 10H), 2.39 (s, 6H),
1.94 (s, 3H). 13C{1H} NMR (125.8 MHz, THF-d8): δ 205.1 (d,
3
3
2H), 7.08 (m, 1H), 5.72 (d, JC-P ) 1.2 Hz, 10H), 2.75 (q, JH-H
3
3
) 3.6 Hz, 2H), 2.43 (q, JH-H ) 3.2 Hz, 2H), 1.68 (dqq, JH-H
)
1
3JC-P ) 4 Hz, -ZrC(Ph)dC(Ph)-), 175.9 (d, JC-P ) 53 Hz,
2JH-P ) 7.2 Hz, 2H), 1.44 (t, JH-H ) 7.6 Hz, 3H), 1.02 (m, 9H),
3
2
0.91 (dd, JH-H ) 7.2 Hz, JH-P ) 15.6 Hz, 6H). 13C{1H} NMR
3
3
-ZrC(Ph2P)dC(Mes)-), 164.9 (d, JC-P ) 5 Hz, -ZrC(Ph2P)d
3
3
C(Ph)-), 152.8 (Ph), 149.8 (d, JC-P ) 23 Hz, -ZrC(Ph)dC(Ph)-),
(125.8 MHz, C6D6): δ 207.1 (d, JC-P ) 9 Hz, -ZrC(Et)dC(Et)-),
169.4 (d, JC-P ) 15 Hz, -ZrC(iPr2P))C(Ph)-), 163.6 (d, JC-P
)
2
1
142.9 (d, JC-P ) 4 Hz, Ph), 142.4 (d, JC-P ) 9 Hz, Ph), 139.4 (d,
JC-P ) 13 Hz, Mes), 135.3 (d, JC-P ) 18 Hz, Ph), 135.2 (Mes),
134.2 (d, JC-P ) 20 Hz, Ph), 131.1 (Ph), 129.3 (d, JC-P ) 1 Hz,
Mes), 128.8 (d, JC-P ) 8 Hz, Ph), 128.6 (Ph), 128.0 (Ph), 127.3
(Ph), 126.6 (Mes), 125.1 (Ph), 123.1 (Ph), 110.2 (Cp), 22.0 (d, 5JC-P
) 3 Hz, Mes), 21.2 (Mes). 31P{1H} NMR (162 MHz, C6D6): δ
-27.0. Anal. calcd. for C47H41PZr: C, 77.54; H, 5.68. Found: C,
77.44; H, 5.57.
68 Hz, -ZrC(iPr2P)dC(Ph)-), 157.9 (d, JC-P ) 30 Hz, -ZrC(Et))
3
C(Et)-), 147.2 (d, 3JC-P ) 9 Hz, i-Ph), 128.4 (Ph), 128.3 (Ph), 126.7
4
1
(p-Ph), 104.6 (Cp), 33.3 (d, JC-P ) 1 Hz, Et), 127.6 (d, JC-P
)
10 Hz, iPr), 24.0 (d, 4JC-P ) 4 Hz, Et), 22.2 (d, 5JC-P ) 2 Hz, Et),
21.6 (d, 2JC-P ) 8 Hz, iPr), 16.9 (Et), 15.5 (iPr).31P{1H} NMR (162
MHz, C6D6): δ -45.1. Anal. calcd for C30H39PZr: C, 69.05; H,
7.53. Found: C, 69.11; H, 7.60.
Reaction of Zirconacyclopentadienes with Tolan. Zircona-
cyclopentadienes 7, 9, or 13 (ca. 20 mg, 31 µmol) and tolan (6.0
mg, 34 µmol) were dissolved in benzene-d6 (ca. 500 mg) and loaded
into a Teflon-sealed NMR tube. The tubes were placed in a 100
°C oil bath and were monitored by 1H NMR spectroscopy at regular
intervals. The conversion of starting material to Cp2Zr[2,3,4,5-
Ph4C4] was calculated by comparison of the integrals of the Cp
resonances for these two species.
Cp2Zr[2-Ph2P-3,4,5-Ph3C4] (9). A solution of zirconacylopro-
pene 3 (0.50 g, 0.50 mmol) and tolan (0.18 g, 1.0 mmol) in toluene
(10 mL) was heated at 50 °C for 16 h. The solution was
concentrated until the solid persisted in solution (4 mL). This
mixture was then cooled to -30 °C for 5 days, and then the solvent
was removed via cannula filtration. The resulting solid was dried
under vacuum to give an orange solid in 66% yield (0.45 g, 0.66
1
mmol). mp: 229-231 °C. H NMR (400 MHz, C6D6): δ 7.40 (m,
4H), 7.25 (m, 4H), 7.12 (m, 4H), 6.94 (m, 9H), 6.75 (m, 4H), 5.75
((1E,3E)-2,3,4-Triphenylbuta-1,3-dienyl)diphenylphosphine
(14). Zirconacycle 9 (0.10 g, 0.15 mmol) was loaded into a Schlenk
flask and benzoic acid (0.18 g, 1.5 mmol) was added under a flow
of nitrogen. To this flask was added THF (12 mL) and the resulting
solution was stirred for 4 h. The reaction mixture was exposed to
the atmosphere, the solvent was removed, and the resulting crude
solid was purified by column chromatography (10% EtOAc in
hexanes) to give a white solid in 88% yield (0.060 g, 0.13 mmol),
which was spectroscopically identified.391H NMR (500 MHz,
CD2Cl2): δ 7.30 (m, 20H), 7.07 (m, 3H), 6.82 (m, 2H), 6.42 (s,
4
(d, JH-P ) 0.8 Hz, 10H). 13C{1H} NMR (125.8 MHz, C6D6): δ
3
2
212.1 (d, JC-P ) 10 Hz, -ZrC(Ph)dC(Ph)-), 166.4 (d, JC-P ) 9
1
Hz, -ZrC(Ph2P)dC(Ph)-), 165.5 (d, JC-P ) 68 Hz, -ZrC(Ph2P)d
C(Ph)-), 154.6 (Ph), 153.3 (d, JC-P ) 31 Hz, -ZrC(Ph)dC(Ph)-),
3
142.2 (Ph), 142.1 (d, JC-P ) 5 Hz, Ph), 135.9 (d, JC-P ) 9 Hz,
Ph), 133.8 (d, JC-P ) 13 Hz, Ph), 131.9 (Ph), 129.4 (d, JC-P ) 2
Hz, Ph), 129.2 (Ph), 129.0 (Ph), 128.9 (Ph), 127.9 (Ph), 127.8 (Ph),
127.3 (Ph), 127.0 (Ph), 125.5 (Ph), 123.6 (Ph), 107.5 (Cp).31P{1H}
NMR (162 MHz, C6D6): δ -43.6. Anal. calcd for C44H35PZr: C,
77.04; H, 5.14. Found: C, 76.79; H, 5.05.
2
1H), 6.29 (d, JH-P ) 1.8 Hz, 1H). 13C{1H} NMR (125.8 MHz,

1262 Organometallics, Vol. 28, No. 4, 2009
Miller et al.
CD2Cl2): δ 159.8 (d, JC-P ) 27 Hz), 145.3 (d, JC-P ) 7 Hz), 140.8
(d, JC-P ) 11 Hz), 140.4 (d, JC-P ) 7 Hz), 139.9, 137.3, 133.8 (d,
JC-P ) 2 Hz), 133.1, 132.9, 131.5 (d, JC-P ) 9 Hz), 130.72, 130.70,
130.1, 129.3, 128.9 (d, JC-P ) 6 Hz), 128.7, 128.3, 128.1, 128.0,
127.6. 31P{1H} NMR (162 MHz, C6D6): δ -23.6.
g, 0.086 mmol). 1H NMR (400 MHz, C6D6): δ 7.44 (m, 8H), 7.30
(d,3J ) 8.0 Hz, 4H), 6.96 (m, 18H), 6.87 (s, 4H), 5.77 (s, 20H).
19F NMR (376.5 MHz, CDCl3): δ -138.3 (m, 4F), -157.2 (t, 3JF-F
) 22.6 Hz, 2F), -163.6 (m, 4F).31P{1H} NMR (162 MHz, C6D6):
δ -27.4. IR (cm-1): 3066 (w), 3021 (w), 1511 (s), 1485 (s), 1434
(m), 1070 (m), 1015 (m), 980 (s), 880 (m), 794 (s), 736 (m), 699
(m), 500 (w). Anal. calcd for C82H54F10P2Zr2: C, 66.83; H, 3.69.
Found: C, 66.50; H, 3.75.
((1Z,3E)-3-Ethyl-2-phenylhexa-1,3-dienyl)diphenylphos-
phine oxide (15). Zirconacycle 10(0.15 g, 0.25 mmol) was loaded
into a Schlenk flask and dissolved in THF (10 mL). To the resulting
solution was added benzoic acid (0.31 g, 2.5 mmol) under a flow of
nitrogen and the reaction mixture was stirred for 4 h. The reaction
mixture was quenched with water (20 mL) and the resulting solution
was extracted with diethyl ether (20 mL). The organic layer was
collected and washed with 2N NaOH (2 × 20 mL), a saturated,
aqueous solution of NaHCO3 (20 mL), water (20 mL), and brine (20
mL). The organic layer was then transferred to a flask and a 30 wt%
hydrogen peroxide solution (52 µL, 0.51 mmol) was added via syringe
and the solution was stirred for 16 h. The solvent was removed and
the resulting crude solid was purified by column chromatography (10%
EtOAc in hexanes) to give a yellow oil in 82% yield (0.080 g, 0.21
mmol). 1H NMR (400 MHz, CDCl3): δ 7.57 (m, 4H), 7.35 (m, 2H),
Bis(zirconacycle) (18). The zirconacyclopropene 4 (0.32 g, 0.50
mmol) and 1,4-bis(pentafluorophenylethynyl)benzene (0.12 g, 0.25
mmol) were loaded into a Schlenk flask and then dissolved in
toluene (8 mL). The resulting solution was then stirred at ambient
temperature for 16 h. The volatile components were then removed
and the resulting solid was washed with pentane (3 × 5 mL) to
1
give an orange solid in 67% yield (0.26 g, 0.17 mmol). H NMR
(400 MHz, C6D6): δ 7.48 (m, 8H), 6.96 (m, 12H), 6.74 (s, 4H),
6.58 (s, 4H), 5.86 (s, 20H), 2.45 (s, 12H), 1.95 (s, 6H). 19F NMR
3
(376.5 MHz, C6D6): δ -134.3 (d, JF-F ) 22.6 Hz, 4F), -157.4
(t, 3JF-F ) 21.3 Hz, 2F), -164.3 (m, 4F).31P{1H} NMR (162 MHz,
C6D6): δ -25.8. Anal. calcd for C88H66F10P2Zr2: C, 67.85; H, 4.27.
Found: C, 66.56; H, 4.11.
2
7.28 (m, 4H), 7.03 (m, 5H), 6.43 (d, JH-P ) 19.6 Hz, 1H), 5.39 (t,
3JH-H ) 7.4 Hz, 1H), 2.33 (q, 3JH-H ) 7.6 Hz, 2H), 2.12 (dq, 3JH-H
) 7.5 Hz, 2H), 1.06 (t, 3JH-H ) 7.5 Hz, 3H), 0.92 (t, 3JH-H ) 7.4 Hz,
3H). 13C{1H} NMR (125.8 MHz, CD2Cl2): δ 163.3 (d, JC-P ) 2 Hz),
143.2 (d, JC-P ) 16 Hz), 138.4, 137.7, (d, JC-P ) 7 Hz), 135.5, 134.7,
130.7, 130.6 (d, JC-P ) 9 Hz), 129.9 (d, JC-P ) 11 Hz), 128.1 (d,
JC-P ) 12 Hz), 127.7, 127.0, 21.9, 21.1, 13.6, 13.3. 31P{1H} NMR
(202 MHz, CDCl3): δ 17.4. IR (cm-1): 3058 (m), 2924 (s), 2876 (m),
2851 (m), 1717 (s), 1593 (w), 1457 (s), 1438 (s), 1379 (w), 1168 (PdO,
s), 1118 (s), 1101 (m), 1072 (w), 751 (m), 724 (m), 696 (s), 527 (s).
FAB-MS: m/z ) 387 (M + H+). HRMS calcd for C26H28OP,
387.1878; Found, 387.1865.
1,4-Bis(1E,3E-4-diphenylphosphino-2-pentafluorophenyl-3-
phenylbuta-1,3-dienyl)benzene (19). The zirconacyclopropene 3
(0.25 g, 0.49 mmol) and 1,4-bis(pentafluorophenylethynyl)benzene
(0.11 g, 0.25 mmol) were loaded into a Schlenk flask and then
dissolved in toluene (10 mL). The flask was placed in a 90 °C oil
bath and the reaction mixture was stirred for 40 min. The reaction
mixture was then allowed to cool to ambient temperature and the
solvent was removed under vacuum. The solid was suspended in
THF (10 mL) and a degassed, 1.1 M solution of HCl (5 mL) was
added. The resulting solution was stirred for 2.5 h and then
quenched with a saturated solution of NaHCO3 (20 mL). This
solution was extracted with dichloromethane (2 × 20 mL) and the
organic layers were collected, dried with MgSO4, filtered, and
concentrated to give a crude yield of 95%. Analytically pure
samples were obtained by washing with MeOH to give a yellow
solid in 56% yield (0.14 g, 0.14 mmol). 1H NMR (400 MHz, C6D6):
δ 7.40 (m, 8H), 7.33 (m, 4H), 7.03 (m, 18H), 6.76 (s, 2H), 6.59 (d,
2JH-P ) 1.4 Hz, 2H), 6.39 (s, 4H). 19F NMR (376.5 MHz, C6D6):
(3,4,5-Triphenylthiophen-2-yloxide)diphenylphosphine oxide
(16). Zirconacycle 9 (0.10 g, 0.15 mmol) was loaded into a Schlenk
flask and then dissolved in THF (15 mL). This solution was then
exposed to an atm of SO2 for 20 min. The reaction mixture was
quenched with water (15 mL) and the resulting solution was
extracted with diethyl ether (50 mL). The organic layer was col-
lected and washed with water (50 mL) and brine (50 mL) and then
dried over MgSO4. The solvent was removed and the resulting crude
solid was purified by column chromatography (50% EtOAc in
DCM) to give a bright yellow solid in 75% yield (0.060 g, 0.11
mmol). Analytically pure samples were obtained by crystallization
3
δ -139.8 (m, 4F), -152.9 (t, JF-F ) 21.3 Hz, 2F), -161.3 (m,
4F).31P{1H} NMR (162 MHz, C6D6): δ -22.4. Anal. calcd for
C62H38F10P2: C, 71.96; H, 3.70. Found: C, 71.61; H, 3.59.
Bis(zirconacycle) (20). The bis(zirconacycle) 18 (0.10 g, 0.064
mmol) and tolan (0.034 g, 0.19 mmol) were loaded into a Schlenk
flask and suspended in toluene (4 mL). The flask was placed in a
85 °C oil bath and heated for 4 days. The reaction mixture was
allowed to cool to ambient temperature and the solvent was removed
under vacuum. The resulting solid was washed with pentane (3 ×
7 mL) to give a yellow solid in 25% yield (0.020 g, 0.016 mmol).
1H NMR (400 MHz, C6D6): δ 7.78 (m, 8H), 7.35 (m, 4H), 7.08
(m, 8H), 6.65 (s, 4H), 5.99 (s, 20H). 19F NMR (376.5 MHz, C6D6):
1
from methylene chloride/ether at -30 °C. H NMR (500 MHz,
CD2Cl2): δ 7.90 (dd, JH-P ) 12.7 Hz,3JH-H ) 7.3 Hz, 2H), 7.75
(dd, JH-P ) 12.6 Hz,3JH-H ) 7.3 Hz, 2H), 7.61 (t, 3JH-H ) 7.4 Hz,
1H), 7.55 (m, 3H), 7.46 (m, 2H), 7.29 (m, 3H), 7.25 (m, 3H), 7.14
(m, 3H), 7.01 (t, 3JH-H ) 7.6 Hz, 2H), 6.86 (m, 4H).13C{1H} NMR
(125.8 MHz, CD2Cl2): δ 159.2 (d, JC-P ) 6 Hz), 155.7 (d, JC-P
4 Hz), 140.9, 140.1, 139.3 (d, JC-P ) 10 Hz), 133.3 (d, JC-P ) 3
Hz), 132.1, 132.0, 131.8 (d, JC-P ) 4 Hz), 131.7, 129.9 (d, JC-P
)
)
3
15 Hz), 129.7, 129.2, 128.8, 128.6, 128.5, 128.4 (d, JC-P ) 9 Hz),
128.3 (d, JC-P ) 8 Hz), 128.2, 127.3. 31P{1H} NMR (162 MHz,
CD2Cl2): δ 17.3. IR (cm-1): 3057 (m), 3026 (w), 2961 (m), 2923
(s), 2852 (m), 1734 (m), 1474 (m), 1438 (s), 1261 (m), 1199 (P )
O, s), 1117 (s), 1101 (s), 1072 (s), 1049 (SdO, s), 1029 (s), 914
(w), 791 (m), 725 (s), 688 (s), 530 (m). FAB-MS: m/z ) 529 (M
+ H+). Anal. calcd for C34H25O2PS: C, 77.25; H, 4.77; S, 6.07.
Found: C, 76.91; H, 4.78; S, 6.16.
δ -138.0 (m, 4F), -157.4 (t, JF-F ) 20.7 Hz, 2F), -164.0 (m,
4F). Anal. calcd for C70H44F10Zr2: C, 66.86; H, 3.53. Found: C,
66.96; H, 3.87.
Acknowledgment. Jamin L. Krinsky of the Molecular
Graphics and Computation Facility in the College of
Chemistry for calculation of the average molecular radii of
complexes 1 and 4. This work was supported by the National
Science Foundation research grant CHE0314709.
Bis(zirconacycle) (17). The zirconacyclopropene 3 (0.20 g, 0.40
mmol) and 1,4-bis(pentafluorophenylethynyl)benzene (0.090 g, 0.20
mmol) were loaded into a Schlenk flask and then dissolved in
toluene (6 mL). The flask was placed in a 50 °C oil bath and the
reaction solution was stirred for 16 h. The reaction mixture was
then allowed to cool to ambient temperature and the solvent was
removed under vacuum. The resulting solid was washed with
pentane (3 × 5 mL) to give a yellow-gold solid in 44% yield (0.13
Supporting Information Available: Tables of bond lengths and
angles, computational results, and the X-ray crystallographic data
for compounds 1, 4, 5, 8, and 10 in the form of CIF files. This
materialisavailablefreeofchargeviatheInternetathttp://pubs.acs.org.
OM801040T