Unexpected tandem reactions of tris(cyclopentadieny1)lanthanide with diphenylketene and regeneration of the η5-bonding mode: One-pot synthesis of heteroleptic yttrocenes from simple (C5H 5)3Y precursors

Article abstract of DOI:10.1021/om1002045

Unprecedented tandem insertion/cycloaddition/isomerization reactions of Cp₃Y with diphenylketene have been revealed, by which a general method for assembling one or two anionic side chains to the cyclopentadienyl ring bound to lanthanide metals in a one-pot procedure is established.

Full text of DOI:10.1021/om1002045

3298 Organometallics 2010, 29, 3298–3302
DOI: 10.1021/om1002045
Unexpected Tandem Reactions of Tris(cyclopentadieny1)lanthanide with
Diphenylketene and Regeneration of the η5-Bonding Mode: One-Pot
Synthesis of Heteroleptic Yttrocenes from Simple (C5H5)3Y Precursors
Xiaoqing Li,† Ruiting Liu,† Zhengxing Zhang,† Xiaoming Mu,§ Linhong Weng,† and
Xigeng Zhou*,†,‡
†Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials,
Fudan University, Shanghai 200433, People’s Republic of China, ‡State Key Laboratory of Organometallic
Chemistry, Shanghai 200032, People’s Republic of China, and §Department of Environmental Chemical
Engineering, Luoyang Institute of Science and Technology, Luoyang 471023, People’s Republic of China
Received March 17, 2010
Unprecedented tandem insertion/cycloaddition/isomerization reactions of Cp3Y with diphenyl-
ketene have been revealed, by which a general method for assembling one or two anionic side chains
to the cyclopentadienyl ring bound to lanthanide metals in a one-pot procedure is established.
Lanthanide complexes containing cyclopentadienyl and re-
lated ligands have played a dominant role in the development of
organolanthanide chemistry1 and continue to attract consider-
able attention because of their great potential as catalysts2 or
useful intermediates3 in the synthesis of chemicals and materials
with interesting properties. The role of cyclopentadienyl ligands
in the fine-tuning of the chemical and physical properties of
organolanthanide compounds illustrates the need for the devel-
opment of new functionalized cyclopentadienyl structures and
new methods for their construction.2c,3c,4 It has been well
known that many functionalized cyclopentadienyl complexes
of transition metals can be synthesized by direct modification of
the corresponding cyclopentadienyl complexes.5 In spite of
considerable additional research efforts along these lines, no
viable method for ring modification of lanthanocene complexes
has been reported, with the exception of examples based on the
side chain modification of prefunctionalized cyclopentadienyl
ligands.6 The failure is mainly ascribed to the increased Lewis
acidity of the lanthanide metals, leading to facile decomposition
pathways under the reaction conditions involved.7 As a result,
the substituents on the cyclopentadienyl ring are generally
accreted before application in the lanthanocene synthesis,4,8
which not only limits the substituent scope but could also
require expensive and/or toxic reagents as well as laborious
separations. Therefore, the development of a basic strategy
capable of constructing functionalized lanthanocene frame-
works, especially the mixed cyclopentadienyl ring systems,
directly from a rather simple lanthanocene precursor represents
a highly desirable but challenging target.
*To whom correspondence should be addressed. E-mail: xgzhou@
fudan.edu.cn.
(1) Selected reviews, see: (a) Edelmann, F. T. Coord. Chem. Rev.
2009, 253, 343–409. (b) Gottfriedsen, J.; Edelmann, F. T. Coord. Chem. Rev.
Although organolanthanide complexes containing cyclo-
pentadienyl and related ligands have been investigated ex-
tensively, the parent cyclopentadienyl (C5H5) ligand that is
most important and ubiquitous in organolanthanide chem-
istry is usually an inert spectator ligand or a removed group
in previously reported reactions of these complexes.1,9
As part of a continuing effort in our laboratory toward the
development of new methods for synthesis of lanthanocene
derivatives,9 we became interested in the possibility of devel-
oping a one-pot synthesis of functionalized cyclopentadienyl
lanthanide complexes from a rather simple lanthanocene
~
2007, 251, 142–202. (c) Prashar, S.; Antinolo, A.; Otero, A. Coord. Chem.
Rev. 2006, 250, 133–154. (d) Arndt, S.; Okuda, J. Chem. Rev. 2002, 102,
1953–1976. (e) Evans, W. J.; Davis, B. L. Chem. Rev. 2002, 102, 2119–2136.
(f) Molander, G. A.; Romero, J. A. C. Chem. Rev. 2002, 102, 2161–2185.
(g) Siemeling, U. Chem. Rev. 2000, 100, 1495–1526. (h) Schumann, H.;
Meese-Marktscheffel, J. A.; Esser, L. Chem. Rev. 1995, 95, 865–986.
(2) (a) Cui, D.; Nishiura, M.; Tardif, O.; Hou, Z. Organometallics
2008, 27, 2428–2435. (b) Luo, Y.; Baldamus, J.; Hou, Z. J. Am. Chem. Soc.
2004, 126, 13910–13911. (c) Arndt, S.; Okuda, J. Adv. Synth. Catal. 2005,
347, 339–354. (d) Hong, S.; Marks, T. J. Acc. Chem. Res. 2004, 37, 673–
686. (e) Trifonov, A. A.; Van de Weghe, P.; Collin, J.; Domingos, A.; Santos, I.
J. Organomet. Chem. 1997, 527, 225–237.
(3) (a) Cui, D.; Tardif, O.; Hou, Z. J. Am. Chem. Soc. 2004, 126, 1312–
1313. (b) Tardif, O.; Hashizume, D.; Hou, Z. J. Am. Chem. Soc. 2004, 126, 8080–
8081. (c) Arndt, S.; Spaniol, T. P.; Okuda, J. Organometallics 2003, 22, 775–781.
(d) Qian, C.; Wang, B.; Deng, D.; Hu, J.; Chen, J.; Wu, G.; Zheng, P. Inorg. Chem.
1994, 33, 3382–3388. (e) Deng, D.; Zheng, X.; Qian, C.; Sun, J.; Zhang, L.
J. Organomet. Chem. 1994, 466, 95–100. (f) Laske, D. A.; Duchateau, R.;
Teuben, J. H.; Spek, A. L. J. Organomet. Chem. 1993, 462, 149–153.
(4) (a) Zhang, W.; Nishiura, M.; Mashiko, T.; Hou, Z. Chem.;Eur.
J. 2008, 14, 2167–2179. (b) Zhang, L.; Luo, Y.; Hou, Z. J. Am. Chem. Soc.
2005, 127, 14562–14563. (c) Nishiura, M.; Hou, Z.; Wakatsuki, Y.; Yamaki,
T.; Miyamoto, T. J. Am. Chem. Soc. 2003, 125, 1184–1185.
(6) (a) Hao, J.; Song, H.; Cui, C. Organometallics 2009, 28, 3970–3972.
(b) Zhou, X.; Zhu, M.; Zhang, L.; Zhu, Z.; Pi, C.; Pang, Z.; Weng, L.; Cai, R.
Chem. Commun. 2005, 2342–2344. (c) Schumann, H.; Heim, A.; Demtschuk,
J.;M€uhle, S.H. Organometallics 2003, 22, 118–128. (d) Arndt, S.; Spaniol, T. P.;
Okuda, J. Organometallics 2003, 22, 775–781. (e) Evans, W. J.; Brady, J. C.;
Ziller, J. W. J. Am. Chem. Soc. 2001, 123, 7711–7712. (f) Booij, M.; Meetsma,
A.; Teuben, J. H. Organometallics 1991, 10, 3246–3252.
(7) (a) Evans, W. J.; Lee, D. S.; Johnston, M. A.; Ziller, J. W.
Organometallics 2005, 24, 6393–6397. (b) Qian, C.; Qiu, A.; Huang, Y.;
Chen, W. J. Organomet. Chem. 1991, 412, 53–59. (c) Schumann, H.; Jeske,
G. Angew. Chem., Int. Ed. Engl. 1985, 24, 225–226.
(5) For examples, see: (a) Braunschweig, H.; Kupfer, T.; Lutz, M.;
Radacki, K. J. Am. Chem, Soc. 2007, 129, 8893–8906. (b) Braunschweig,
H.; Kupfer, T.; Radacki, K. Angew. Chem., Int. Ed. 2007, 46, 1630–1633.
(8) (a) Braunschweig, H.; Breitling, F. M. Coord. Chem. Rev. 2006,
250, 2691–2720. (b) Xie, Z. Acc. Chem. Res. 2003, 36, 1–9. (c) Wang, B.;
Deng, D.; Qian, C. New J. Chem. 1995, 19, 515–524.
€
(c) Erker, G.; Kehr, G.; Frohlich, R. Organometallics 2008, 27, 3–14.
(d) Butler, D. C. D.; Richards, C. J. Organometallics 2002, 21, 5433–5436.
r
pubs.acs.org/Organometallics
Published on Web 07/14/2010
2010 American Chemical Society

Article
Organometallics, Vol. 29, No. 15, 2010 3299
Scheme 1
Figure 1. Thermal ellipsoid (30%) plot of complex 2. Hydro-
gen atoms are omitted for clarity. Key bond lengths (A)
and angles (deg): Y(1)-O(1) 2.106(2), Y(1)-O(2) 2.340(2),
O(1)-C(24) 1.327(4), O(2)-C(30) 1.208(4), C(17)-C(24)
1.360(4), C(24)-C(25) 1.513(4), C(25)-C(26) 1.513(4), C(26)-
C(27) 1.327(4), C(27)-C(28) 1.496(4), C(28)-C(29) 1.544(4),
C(29)-C(30) 1.541(4), C(28)-C(31) 1.575(4), C(30)-C(31)
1.541(4); O(1)-Y(1)-O(2) 78.6(1), sum of angles at C(30) 359.5(3).
crystallography analysis. The pseudotetrahedral coordination
sphere about Y in 2 is comprised of two η5-cyclopentadienyl
groups and two oxygen donors of the newly formed bicyclo-
[3.2.0]heptenone-substituted enolate ligand. Within the dike-
tone anion ligand, the C-C distances are in the normal range.
To our surprise, the simple coordination of THF can
promote 2 to undergo intramolecular insertion of a carbonyl
into the Y-O bond, forming the hemiketal complex 3. The
driving force might be from the ease of forming hemiketals
and their stability. Compared to the well-known Ln-X (X =
H, C, N, S) insertions,8b,9f,9i-9k,10,11 examples of insertions of
unsaturated molecules into Ln-O bonds are very rare,2a,3b,12
probably due to the high Ln-O bond enthalpy.13
It was unexpected that heating a toluene solution of 2 at
110 °C led to the ring-opening of the cyclobutanone, afford-
ing 4 in 65% isolated yield. To see if the four-membered-ring
unit of complex 3 is also thermally sensitive, the thermal
rearrangement of 3 was examined. Interestingly, complex 4
could also be obtained by heating 3 in refluxing toluene.
Cycloaddition and ring-opening reactions are essential tools
for organic synthesis, offering not only substrate flexibility
but also rapid increase of molecular complexity. It is un-
expected that the cyclopentadienyl ligand bound to a rare
earth metal undergoes a tandem insertion/cycloaddition with
unsaturated molecules to form highly strained and acylated
bicyclo[3.2.0]heptanone. To the best of our knowledge, the
ring-opening mode of cyclobutanone shown herein is also
unprecedented.14
precursor. Herein, we report the first example of authen-
ticated cyclopentadienyl-based reactions of lanthanocene
complexes with ketene and their application in one-pot
syntheses of mono- and difunctionalized cyclopentadienyl
lanthanide derivatives directly from (C5H5)3Ln precursors,
representing a new strategy for functionalization of the Cp
rings bound to metals.
Treatment of Cp3Y with 1 equiv of Ph2CCO generated the
doubly functionalized product 2 as the main metal-containing
product with recovery of some Cp3Y. Employment of Cp3Yand
Ph2CCO in a 1:2 ratio led to the isolation of 2 in 85% yield
(Scheme 1). Complex 2 was characterized by elemental analysis
and spectroscopic methods. In the IR spectra of 2, the carbonyl
characteristic stretching frequency was observed at 1712 cm-1
.
The 1H NMR data for 2 were consistent with the incorporation
of 2 equiv of Ph2CCO. Furthermore, the formulation of com-
pound 2 (Figure 1) was unambiguously determined via X-ray
(10) Selected review, see: (a) Zhou, X.; Zhu, M. J. Organomet. Chem.
2002, 647, 28–49. (b) Evans, W. J.; Davis, B. L. Chem. Rev. 2002, 102,
2119–2136.
(9) (a) Zheng, P.; Hong, J.; Liu, R.; Zhang, Z.; Pang, Z.; Weng, L.; Zhou,
X. Organometallics 2010,29, 1284–1289. (b) Sun, Y.; Zhang, Z.; Wang, X.; Li, X.;
Weng, L.; Zhou, X. Dalton Trans. 2010, 39, 221–226. (c) Sun, Y.; Zhang, Z.;
Wang, X.; Li, X.; Weng, L.; Zhou, X. Organometallics 2009, 28, 6320–6330. (d)
Pi, C.; Zhu, Z.; Weng, L.; Chen, Z.; Zhou, X. Chem. Commun. 2007, 2190–2192.
(e) Pi, C.; Zhang, Z.; Pang, Z.; Zhang, J.; Luo, J.; Chen, Z.; Weng, L.; Zhou, X.
Organometallics 2007, 26, 1934–1946. (f) Zhang, J.; Cai, R.; Chen, Z.; Zhou, X.
Inorg. Chem. 2007, 46, 321–327. (g) Pi, C.; Zhang, Z.; Liu, R.; Weng, L.; Chen, Z.;
Zhou, X. Organometallics 2006, 25, 5165–5172. (h) Zhang, C.; Liu, R.; Zhang, J.;
Chen, Z.;Zhou, X. Inorg. Chem. 2006, 45, 5867–5877. (i) Liu, R.; Zhang, C.; Zhu,
Z.; Luo, J.; Zhou, X.; Weng, L. Chem.;Eur. J. 2006,12, 6940–6952. (j) Zhang, J.;
Cai, R.; Weng, L.; Zhou, X. Organometallics 2004, 23, 3303–3308. (k) Zhang, J.;
Cai, R.; Weng, L.; Zhou, X. J. Organomet. Chem. 2003, 672, 94–99.
(11) (a) Li, H.; Yao, Y.; Shen, Q.; Weng, L. Organometallics 2002, 21,
2529–2532. (b) Zhang, C.; Liu, R.; Zhou, X.; Chen, Z.; Weng, L.; Lin, Y.
Organometallics 2004, 23, 3246–3251. (c) Nishiura, M.; Hou, Z. J. Mol.
Catal. A: Chem. 2004, 213, 101–106. (d) Robert, D.; Trifonov, A. A.; Voth,
P.; Okuda, J. J. Organomet. Chem. 2006, 691, 4393–4399.
(12) (a) Seo, S. Y.; Yu, X. H.; Marks, T. J. J. Am. Chem. Soc. 2009,
131, 263–276. (b) Yu, X. H.; Seo, S. Y.; Marks, T. J. J. Am. Chem. Soc. 2007,
129, 7244–7245.
(13) Nolan, S. P.; Stern, D.; Marks, T. J. J. Am. Chem. Soc. 1989, 111,
7844–7853.
(14) (a) Lee-Ruff, E.; Mladenova, G. Chem. Rev. 2003, 103, 1449–
1483. (b) Namyslo, J. C.; Kaufmann, D. E. Chem. Rev. 2003, 103, 1485–
1537.

3300 Organometallics, Vol. 29, No. 15, 2010
Li et al.
Figure 2. Thermal ellipsoid (30%) plot of complex 3. Hydrogen
atoms are omitted for clarity. Selected bond distances (A) and angles
(deg): Y(1)-O(1) 2.082(3), Y(1)-O(3) 2.325(4), O(1)-C(11)
1.324(5), O(2)-C(11) 1.483(5), O(2)-C(18) 1.364(5), C(11)-C(12)
1.599(6), C(12)-C(13) 1.575(6), C(13)-C(14) 1.461(7), C(13)-
C(17) 1.560(6), C(11)-C(17) 1.537(6), C(14)-C(15) 1.314(7),
C(15)-C(16) 1.503(6), C(16)-C(17) 1.542(6), C(16)-C(18)
1.499(6), C(18)-C(19) 1.340(6); O(1)-Y(1)-O(3) 92.97(14),
O(1)-C(11)-O(2) 108.9(3).
Figure 4. Thermal ellipsoid (30%) plot of 5. Key bond lengths
(A) and angles (deg): Y(1)-O(1) 2.362(3), Y(1)-O(2) 2.292(3),
Y(1)-O(3) 2.334(3), Y(1)-O(4) 2.398(3), Y(2)-O(1) 2.296(3),
Y(2)-O(3) 2.232(3), Y(3)-O(2) 2.269(3), Y(3)-O(4) 2.224(3),
Y(1)-C(1) 2.783(5), Y(1)-C(2) 2.681(5), C(1)-C(6) 1.506(6),
O(1)-C(6) 1.380(5), O(2)-C(20) 1.392(6), C(6)-C(7) 1.310(6),
O(5)-Li(1) 1.86(1); O(2)-Y(1)-O(1) 83.9(1), O(3)-Y(1)-O(4)
83.4(1), sum of angles at C(6) 360.0(5).
Given the expectation that the cyclopentadiene bridge of 4
might undergo deprotonation, we were interested in the
possibility of regeneration of the η5-bonding between the
metal and the resulting bifunctionalized cyclopentadiene
ring and thus developing a basic and versatile strategy for
ring modification of cyclopentadienyl ligands bound to rare
earth metals. Significantly, treatment of 4 with 2 equiv of
LiMe gave a rare trianionic bifunctionalized cyclopenta-
dienyl complex (5) in 43% isolated yield (Scheme 1). Single
crystals of the byproduct C5H5Li (6)16 were also obtained by
dissolving the residue in THF and subsequently diffusing
hexane into the THF solution.
As shown in Figure 4, compound 5 contains three yttriums,
one lithium, four unaltered C5H5 ligands, two trianionic di-
functionalized C5H5 ligands, and one coordinated THF mole-
cule. Three Y atoms are coordinated with two types of environ-
ments, in which the center Y(1) is bonded to four enolate
oxygen atoms, one η5-cyclopentadienyl, and one bridging η2-
cyclopentadienyl, while the Y(2) and Y(3) are coordinated to
two enolate oxygen atoms and two η5-cyclopentadienyl ligands
to form a distorted tetrahedral geometry, respectively. The Liþ
ion is coordinated by a bridging η5-C5H3(C(O)CPh2)2 ligand
and one THF molecule. Each of four enolate oxygen atoms
bridges two Y atoms. One difunctionalized cyclopentadienyl
ligand is bonded to four metals, while another is bonded to
three. The Y(1) is respectively linked to Y(2) and Y(3) by two
oxygen bridges. The Y-O bond distances are between 2.224(3)
and 2.398(3) A, and the average Y-O distance of 2.301(3) A is
comparable with the values reported for other Y-O(bridging)
distances.17 The Y(1)-C(1) and Y(1)-C(2) distances of
2.783(5) and 2.681(5) A are significantly shorter than the corres-
ponding values in [(C5H5)2Pr(μ2-η5:η2-C5H5)]4 (av3.04 A)18 and
Figure 3. Thermal ellipsoid (30%) plot of complex 4. Hydrogen
atoms are omitted for clarity. Key bond lengths (A) and angles
(deg): Y(1)-O(1) 2.173(3), Y(1)-O(2) 2.183(3), O(1)-C(11)
1.248(5), O(2)-C(30) 1.246(5), C(29)-C(30) 1.414(6), C(11)-
C(25) 1.437(6), C(25)-C(26) 1.371(6), C(26)-C(27) 1.354(6),
C(27)-C(28) 1.375(7), C(28)-C(29) 1.400(6), C(25)-C(29)
1.487(6); O(1)-Y(1)-O(2) 80.4(1), sum of angles at C(11)
359.8(5), sum of angles at C(25) 360.0(5).
The molecular structures of 3 (Figures 2) and 4 (Figures 3)
were also determined by X-ray structural analysis. Character-
istically, the endocyclic C-C distances of the four-membered-
ring moiety in 3 are between 1.537(6) and 1.599(6) A, which are
similar to the values found in other four-membered-ring com-
pounds(1.533-1.604 A) and significantly longer than the
common C-C single bond lengths due to ring tension.15 The
view of the structure shows that compound 4 has two Ph2CHC-
(O) substituents bonded to the cyclopentadiene ring. The bond
parameters of 4 indicate an appreciable degree of π-delocali-
zation across the bifunctional ligands (Figure 3). Metric para-
meters within the (C5H5)2Y part are unexceptional.
(16) Complex 6 is identical to that previously reported: Dinnebier,
R. E.; Behrens, U.; Olbrich, F. Organometallics 1997, 16, 3855–3858.
(17) Boyle, T. J.; Ottley, L. A. M.; Daniel-Taylor, S. D.; Tribby, L. J.;
Bunge, S. D.; Costello, A. L.; Alam, T. M.; Gordon, J. C.; McCleskey,
T. M. Inorg. Chem. 2007, 46, 3705–3713.
(18) Hinrichs, W.; Melzer, D.; Rehwoldt, M.; Jahn, W.; Fischer,
R. D. J. Organomet. Chem. 1983, 251, 299–305.
(15) (a) Marrero, J.; Rodrıguez, A. D.; Baran, P.; Raptis, R. G.;
´
ꢀ
Sanchez, J. A.; Ortega-Barria, E.; Capson, T. L. Org. Lett. 2004, 6, 1661–
1664. (b) Hassner, A.; Naidorf-Meir, S.; Gottlieb, H. E.; Goldberg, I. J. Org.
Chem. 1992, 57, 2442–2445. (c) Mihova, T. R.; Trifonov, L. S.; Dimitrov,
V. S.; Orahovats, A. S.; Linden, A.; Heimgartner, H. Helv. Chim. Acta 1991,
74, 1011–1026.

Article
Organometallics, Vol. 29, No. 15, 2010 3301
Scheme 2
[(C5H4Me)2La(μ2-η5:η2-C5H4Me)]4 (av 3.033(6) A),19 when the
difference in metallic radii is considered. This difference is due to
the chelating effect of the side chains. The structural features
within the two enolate units of the bifunctionalized cyclopenta-
dienyl ligands are essentially identical.
To confirm that complex 2 was formed by the insertion and
subsequent cycloaddition (Scheme 1, path A) rather than by
1,2-cycloaddition of one ketene function to a C5H5 ring followed
by insertion of a second ketene function into a Y-C bond
(Scheme 1, path B), we first checked the hydrolyzed products of
the fast 1:1 reaction of Cp3Y with Ph2CCO at -30 °C for 15 min
by LC analysis, indicating the presence of a small amount of
Ph2CHCOC5H5 without the observation of 7,7-diphenylbi-
cyclo[3.2.0]hept-2-en-6-one. However, attempts to isolate the
intermediate 1 were unsuccessful. Furthermore, we examined
whether the cycloaddition of 1 with Ph2CCO could be prevented
by a suitable base (e.g., alkyllithium) and thus if it should
offer the opportunity to explore a new simple, one-pot route
to assemble linked cyclopentadienyl/enolate lanthanide com-
plexes from a simple Cp3Ln precursor. To our delight, reaction
of Cp3Y with Ph2CCO in the presence of LiMe in toluene/THF
and subsequent fractional recrystallization in THF/toluene/
hexane gave the first linked cyclopentadienyl enolate lanthanide
complex, [Cp3Y2(μ-O)(μ-η1:η1:η5-OC(CPh2)C5H4)]2Li2(THF)8
(8), in 25% isolated yield accompanied by the elimination of
C5H5Li (6) and unexpected allene product 7. The formation of
complex 8 might be interpreted as one PhCCO insertion into the
Y-C5H5 bond and subsequent deprotonation followed by the
elimination of CpLi and Ph2CdCdC5H4 (7), as shown in
Scheme 2. Compound 7 was confirmed by GC-MS analysis of
the organic products. It is well known that lithium alkyls do not
abstract the hydrogen on the C5H5 ring directly bonded to a
lanthanide center;7c therefore, the possibility that compound 8
results from the ring metalation and subsequent addition with
ketene can be excluded.
Figure 5. Thermal ellipsoid (30%) plot of complex 8. Key bond
lengths (A) and angles (deg): Y(1)-O(2A) 2.199(4), Y(1)-O(2)
2.220(5), Y(1)-O(1) 2.769(5), Y(2)-O(1) 2.170(6), Y(2)-O(2)
2.147(4), C(3)-C(6) 1.497(11), C(6)-C(7) 1.364(10), O(1)-C(6)
1.351(9); O(1)-C(6)-C(7) 123.6(8), O(1)-C(6)-C(3) 113.2(7),
C(7)-C(6)-C(3) 123.1(8), sum of angles at O(1) 329.0(4), sum
of angles at O(2), 359.9(2).
and η5-cyclopentadienyl. The coordination geometry at Y(2) is
best described as a distorted tetrahedron, while that at Y(1) is a
distorted trigonal bipyramid. The average Y-O(μ3-oxide) bond
length in 8 is 2.189 A, which is slightly longer than that observed
for the μ3-oxide group in [(C5Me4SiMe3)Y]4(μ3-O)2(μ-H)4-
(THF) (av 2.161 A).20 The Y(2)-O(1) distance of 2.170(6) A
is in the low end of the range (2.206-2.290 A) typical for
[Cp2Y(μ-OR)]2.21 Characteristically, there is a very weak inter-
action between Y(1) and O(1).
In summary, a series of unprecedented reactions of (C5H5)3-
Ln with diphenylketene have been established. Furthermore, by
applying these new reactions as the key step, we have developed
an efficient and versatile method for assembling one and two
anionic side chains on the sensitive lanthanocene frameworks in
a one-pot procedure, which are impossible to carry out by other
methods. Further studies into the scope and limitations of the
An X-ray crystallographic study unambiguously confirmed 8
to be a tetrametallic structure (Figure 5). Coordinated THF
molecules allow the lithium ion to be of preferred dissociated
state. The linked cyclopentadienyl/enolate dianion ligands co-
ordinate to two yttrium atoms through one bridging oxygen
(20) Shima, T.; Hou, Z. J. Am. Chem. Soc. 2006, 128, 8124–8125.
(21) (a) Evans, W. J.; Sollberger, M. S.; Shreeve, J. L.; Olofson, J. M.;
Hain, J. H.; Ziller, J. W. Inorg. Chem. 1992, 31, 2492–2501. (b) Evans,
W. J.; Dominguez, R.; Hanusa, T. P. Organometallics 1986, 5, 1291–1296.
(c) Schierwater, K.; Hanika-Heidl, H.; Bollmann, M.; Fischer, R. D.; Harris,
R. K.; Apperley, D. C. Coord. Chem. Rev. 2003, 242, 15–31. (d) Sun, H.;
Chen, S.; Yao, Y.; Shen, Q.; Yu, K. Appl. Organomet. Chem. 2006, 20, 310–
314.
(19) Eggers, S. H.; Kopf, J.; Fisher, R. D. Organometallics 1986, 5,
383–385.

3302 Organometallics, Vol. 29, No. 15, 2010
Li et al.
functionalization at the cyclopentadienyl and related rings of
sensitive lanthanocenes are underway.
described for method A, heating 3 (0.275 g, 0.37 mmol) in refluxing
toluene afforded 4 (0.102 g) in 41% yield.
Preparation of (C5H5)4Y3[μ-η1:η1:η5-C5H3(COCPh2)2-1,2]-
[μ-η1:η1:η2:η5-C5H3(COCPh2)2-1,2]Li(THF) (5). MeLi (1.6 M
in hexane, 1.70 mL, 2.72 mmol) was added dropwise to a toluene
solution (20 mL) of 4 (0.915 g, 1.36 mmol) at -30 °C. After stirring
for 30 min at -30 °C, the mixture was slowly warmed to room
temperature and an orange precipitate was slowly formed. The
solution was removed and the precipitate was dissolved in 20 mL of
THF. THF was removed under vacuum, and the resulting solid was
extracted with 40 mL of toluene. The extraction was evaporated to
Experimental Section
General Procedures. All manipulations were conducted under
a nitrogen-filled atmosphere using standard Schlenk or glove-
box techniques. All organic solvents (including deuterated
solvents for the NMR measurements) were predried over
sodium wire and distilled from sodium/benzophenone under
dinitrogen prior to use. (C5H5)3Y22 and Ph2CCO23 were pre-
pared according to literature methods. Melting points were
determined in sealed nitrogen-filled capillaries and were not
corrected. Elemental analyses for C and H were carried out on a
Rapid CHN-O analyzer. Infrared spectra were obtained on
a Nicolet FT-IR 360 spectrometer with samples prepared
as Nujol mulls. 1H NMR data were obtained on a Bruker
DRX-400NMR spectrometer.
ca. 10 mL, and pale yellow crystals of 5 1/2toluene (0.304 g, 43%
3
based on Y) were obtained at room temperature. The residue was
dissolved in THF, and diffusion of n-hexane to the solution afforded
colorless crystals of [C5H5Li]n (6). Mp: 207-209 °C (dec). IR
(Nujol): 3072w, 1616s, 1591s, 1307m, 1264w, 1188s, 1092s,
1041m, 1013m, 941s, 773s, 700m cm-1. Anal. Calcd for C93.5H78-
LiO5Y3 (%): C, 72.21; H, 5.06. Found: C, 72.02; H, 5.01.
Synthesis of [(C5H5)3Y2(μ3-O)(μ-η1:η1:η5-C5H4COCPh2)]2-
[Li(THF)4]2 (8). To a solution of (C5H5)3Y (0.291 g, 1.02 mmol)
in a mixed solvent of THF (10 mL) and toluene (30 mL) was
added Ph2CCO (0.200 g, 1.02 mmol) at 0 °C. After the reaction
mixture was stirred for 5 min, LiCH3 (1.60 M, 0.64 mL) was
added at 0 °C. The solution was slowly warmed to ambient
temperature and continued to stir for 24 h. The solution was
then concentrated to ca. 8 mL under reduced pressure. Yellow
Preparation of (C5H5)2Y(η2-[OC(CPh2-4)-(Ph2-7,7)-(O-6)-
{3.2.0}] (2). To a 20 mL toluene solution of (C5H5)3Y (0.375 g,
1.32 mmol) was added Ph2CCO (0.512 g, 2.64 mmol) at -30 °C.
The solution changed color from colorless to red immediately.
After being stirred for 30 min, the mixture was warmed to room
temperature and continued to stir for 12 h. Then, the solution was
concentrated and cooled to -15 °C for several days to afford 2 as
orange crystals. Yield: 0.755 g (85%). Mp: 210-212 °C (dec). 1H
NMR (400 MHz, C6D6, 25 °C): 7.81(d, 2H, Ph), 7.79 (d, 2H, Ph),
7.38-7.04 (m, 16H, Ph), 6.42 (brs, 5H, C5H5), 5.93-4.99 (brsþm,
6H, C5H5þCHdC), 5.14 (m, 1H, CHdC), 4.06 (m, 1H, CH), 3.62
(m, 1H, CH), 3.56 (t, 1H, CH). IR (Nujol): 3056 m, 1712vs, 1596s,
1575vs, 1560vs, 1439s, 1327m, 1282s, 1262vs, 1209m, 1008vs, 965m,
912m, 846m, 774vs, 749vs, 704vs, 668s cm-1. Anal. Calcd for
C43H35O2Y (%): C, 76.78; H, 5.24. Found: C, 76.15; H, 5.19.
Preparation of (C5H5)2Y(OCOC33H25)(THF) (3). Recrystal-
lization of 2 (0.397 g, 0.59 mmol) in a mixed solvent of THF and
n-hexane afforded 3 as colorless crystals. Yield: 0.338 g (77%).
Mp: 150-152 °C (dec). 1H NMR (400 MHz, C6D6, 25 °C):
7.77(d, 2H, Ph), 7.34-7.01 (m, 18H, Ph), 6.14 (s, 10H, C5H5),
5.80 (t, 1H, CH), 5.25 (t, 1H, CH), 4.11 (t, 1H, CH), 3.63 (t, 1H,
CH), 3.57-3.43 (m, 5H, CH þ THF), 5.84 (m, 4H, THF). IR
(Nujol): 3053m, 2927s, 2853s, 1625s, 1598s, 1465m, 1444s,
1314vs, 1255m, 1202m, 1137m, 1040m, 1016m, 958m, 940m,
838m, 778vs, 733m, 704m, 607m cm-1. Anal. Calcd for C47H43-
O3Y (%): C, 75.80; H, 5.82. Found: C, 75.55; H, 5.69.
crystals of 8 THF were obtained by vapor diffusion of hexane
3
into the solution. Yield: 0.125 g (25% based on Y). Mp: 242 °C
(dec). IR (Nujol): 3054w, 1541s, 1340m, 1260m, 1042s, 1013w,
890m, 764s, 700m cm-1. Anal. Calcd for C104H130Li2O13Y4
(%): C, 63.81; H, 6.69. Found: C, 63.42; H, 6.56.
Crystal Structure Determination. Suitable single crystals were
sealed under N2 in thin-walled glass capillaries. X-ray diffraction
data were collected on a SMART APEX CCD diffractometer
(graphite-monochromated Mo KRradiation, φ-ω-scan technique,
λ = 0.71073 A). The intensity data were integrated by means of the
SAINT program.24 SADABS25 was used to perform area-detector
scaling and absorption corrections. The structures were solved by
direct methods and were refined against F2 using all reflections with
the aid of the SHELXTL package.26 All non-hydrogen atoms were
found from the difference Fourier syntheses and refined anisotropi-
cally. All hydrogen atoms were assigned in idealized posi-
tions with isotropic thermal parameters related to those of the sup-
porting carbon atoms but were not included in the refinement. Two
heavily disordered solvated THF in the cationic part of 8were found.
All calculations were performed using the Bruker Smart program.
Preparation of (C5H5)2Y[η1:η1-C5H3(COCHPh2)2-1,2] (4).
Method A: A 20 mL toluene solution of 2 (0.841 g, 1.25 mmol)
was warmed to 110 °C and stirred for another 8 h at this
temperature. The solution changed color from red to dark red
slowly. Then, the solution was cooled to room temperature and
concentrated. After storing at -15 °C for one week, 4 was isolated
as yellow crystals (0.549 g, 65%). Mp: 245-247 °C (dec). 1H NMR
(400 MHz, C6D6, 25 °C): 7.61 (d, 2H, CH), 7.23 (d, 8H, Ph), 7.11
(t, 8H, Ph), 7.04 (m, 4H, Ph), 6.29 (t, 1H, CH), 5.99 (s, 2H, CHPh2),
5.84 (s, 10H, C5H5). IR (Nujol): 3052m, 1553vs, 1289m, 1254m,
1108s, 1057s, 1031m, 1010s, 941s, 850m, 820m, 778vs, 739vs, 610vs,
628s cm-1. Anal. Calcd for C43H35O2Y (%): C, 76.78; H, 5.24.
Found: C, 76.32; H, 5.20. Method B: Following the same procedure
Acknowledgment. We thank the NNSF of China, 973
program (2009CB825300), NSF of Shanghai, and Shang-
hai Leading Academic Discipline Project for financial
support (B108).
Supporting Information Available: CIF files for complexes of
2-5 and 8. This material is available free of charge via the
Internet at http://pubs.acs.org.
(24) Bruker. SAINTPlus Data Reduction and Correction Program v.
6.02 a; Bruker AXS: Madison, WI, 2000.
(25) Sheldrick, G. M. SADABS, A Program for Empirical Absorption
(22) Birmingham, J. M.; Wilkinson, G. J. Am. Chem. Soc. 1956, 78,
€
€
42–44.
Correction; University of Gottingen: Gottingen, Germany, 1998.
(26) Sheldrick, G. M. SHELXL-97, Program for the Refinement of
(23) Baigrie, L. M.; Seiklay, H, R.; Tidwell, T. T. J. Am. Chem. Soc.
1985, 107, 5391–5396.
€
€
Crystal Structures; University of Gottingen: Gottingen, Germany, 1997.