Cyclopentadienyl yttrium complexes bearing a fluorinated aryloxide functionality

Article abstract of DOI:10.1021/om0104520

The ligand C₅H₅(CH₂CAr^F₂OH) (3) (Ar^F = 3,5-C₆H₃(CF₃)₂) was prepared in moderate yield (65%) by ring opening of the epoxide Ar^F₂C(O)CH₂ (2) with NaCp. Epoxide 2 was accessible in two steps from commercially available precursors. Reaction of the dilithium salt of 3 with YCl₃ afforded the ate complex {η⁵:η¹-C₅H₄ [CH₂C(O)(3,5-C₆H₃ (CF₃)₂)₂]}₂Y^- Li⁺{THF}₂ (4a). Exposure of 4a to vacuum resulted in partial desolvation to {η⁵:η¹-C₅H₄ [CH₂C(O)(3,5-C₆H₃- (CF₃)₂)₂]}₂Y^- Li⁺ {THF} (4b). The chloride complex {η⁵:η¹-C₅H₄ [CH₂C(O)(3,5-C₆H₃ (CF₃)₂)₂]}YCl{THF}₂ (5) could only be prepared by protonolysis of {Y[N(SiMe₃)₂]₂(THF)₂(μ-Cl)}₂ with 1 equiv of 3. Metathesis reactions of 5 with 1 equiv of NaN(SiMe₃)₂, NaCp, and LiCH(SiMe₃)₂ afforded {η⁵:η¹-C₅H₄ [CH₂C(O)(3,5-C₆H₃ (CF₃)₂)₂]}Y{N(SiMe₃)₂} {THF}_n (6a, n = 2; 6b, n = 1), {η⁵:η¹-C₅H₄ [CH₂C(O)(3,5-C₆H₃ (CF₃)₂)₂]}Y{η⁵-C₅ H₅}{THF}_n (8a, n = 2; 8b, n = 1), and {η⁵:η¹-C₅H₄ [CH₂C(O)(3,5-C₆H₃ (CF₃)₂)₂]} Y{CH(SiMe₃)₂}{THF}₂ (9), respectively. Metathesis of 5 with 2 equiv of Na[N(SiMe₃)₂] or LiCH(SiMe₃)₂ afforded the anionic ate complexes {η⁵:η¹-C₅H₄ [CH₂C(O)(3,5-C₆H₃ (CF₃)₂)₂]} {N(SiMe₃)₂}₂Y^-Na⁺ {THF}₂ (7) and {η⁵:η¹-C₅ H₄[CH₂C(O)(3,5-C₆H₃ (CF₃)₂)₂]} {CH(SiMe₃)₂}₂Y^-Li⁺ {THF}₂ (10), respectively. The phenoxide {η⁵:η¹-C₅H₄ [CH₂C(O)(3,5-C₆H₃ (CF₃)₂)₂]}Y{O-2,6-t-Bu₂C₆ H₃}{THF}₂ (11) could not be prepared by salt metathesis but was isolated by protonolysis of Y[O-2,6-t-Bu₂C₆H₃][CH (SiMe₃)₂]₂[THF]₂ with 1 equiv of 3. The crystal structures of ate complex 4a and phenoxide 11 were established by X-ray crystallography.

Full text of DOI:10.1021/om0104520

Organometallics 2001, 20, 4279-4286
4279
Cyclop en ta d ien yl Yttr iu m Com p lexes Bea r in g a
F lu or in a ted Ar yloxid e F u n ction a lity
Roland A. L. Gendron,† David J . Berg,*,† Pengcheng Shao,†,§ and Tosha Barclay‡
Department of Chemistry, University of Victoria, P.O. Box 3065, Victoria,
British Columbia, Canada V8W 3V6, and Hand Lab, Mississippi State University,
Mississippi State, Mississippi 39762
Received May 30, 2001
The ligand C5H5(CH2CArF2OH) (3) (ArF ) 3,5-C6H3(CF3)2) was prepared in moderate yield
(65%) by ring opening of the epoxide ArF2C(O)CH2 (2) with NaCp. Epoxide 2 was accessible
in two steps from commercially available precursors. Reaction of the dilithium salt of 3 with
YCl3 afforded the ate complex {η5:η1-C5H4[CH2C(O)(3,5-C6H3(CF3)2)2]}2Y-Li+{THF}2 (4a ).
Exposure of 4a to vacuum resulted in partial desolvation to {η5:η1-C5H4[CH2C(O)(3,5-C6H3-
(CF3)2)2]}2Y-Li+{THF} (4b). The chloride complex {η5:η1-C5H4[CH2C(O)(3,5-C6H3(CF3)2)2]}-
YCl{THF}2 (5) could only be prepared by protonolysis of {Y[N(SiMe3)2]2(THF)2(µ-Cl)}2 with
1 equiv of 3. Metathesis reactions of 5 with 1 equiv of NaN(SiMe3)2, NaCp, and LiCH(SiMe3)2
afforded {η5:η1-C5H4[CH2C(O)(3,5-C6H3(CF3)2)2]}Y{N(SiMe3)2}{THF}n (6a , n ) 2; 6b, n )
1), {η5:η1-C5H4[CH2C(O)(3,5-C6H3(CF3)2)2]}Y{η5-C5H5}{THF}n (8a , n ) 2; 8b, n ) 1), and
{η5:η1-C5H4[CH2C(O)(3,5-C6H3(CF3)2)2]}Y{CH(SiMe3)2}{THF}2 (9), respectively. Metathesis
of 5 with 2 equiv of Na[N(SiMe3)2] or LiCH(SiMe3)2 afforded the anionic “ate” complexes
{η5:η1-C5H4[CH2C(O)(3,5-C6H3(CF3)2)2]}{N(SiMe3)2}2Y-Na+{THF}2 (7) and {η5:η1-C5H4[CH2C-
(O)(3,5-C6H3(CF3)2)2]}{CH(SiMe3)2}2Y-Li+{THF}2 (10), respectively. The phenoxide {η5:η1-
C5H4[CH2C(O)(3,5-C6H3(CF3)2)2]}Y{O-2,6-t-Bu2C6H3}{THF}2 (11) could not be prepared by
salt metathesis but was isolated by protonolysis of Y[O-2,6-t-Bu2C6H3][CH(SiMe3)2]2[THF]2
with 1 equiv of 3. The crystal structures of ate complex 4a and phenoxide 11 were established
by X-ray crystallography.
In tr od u ction
corresponding bis(cyclopentadienyl) systems. Group 4
complexes containing these ligands have been exten-
sively studied and have been widely applied to olefin
polymerization chemistry.3 In contrast, these ligands
have not been very widely investigated in yttrium or
lanthanide chemistry.2c,4,5
During the past decade there has been tremendous
development of alternative ligands to cyclopentadienyl
for early transition metal and lanthanide chemistry.1
Additionally many groups have been exploring the use
of hybrid ligands that contain both Cp and a pendant
anionic group.1c,2,3 The preparation of Cp-alkoxide and
Cp-amide mixed ligands has been particularly impor-
tant because these ligands form metal complexes with
coordination spheres that are more open than the
Many of the Cp-alkoxide ligands developed for use in
group 4 chemistry are not well suited to group 3 and
(4) (a) Mu, Y.; Piers, W. E.; MacDonald, M.-A.; Zaworotko, M. J .
Can. J . Chem. 1995, 73, 2233. (b) Hultzsch, K. C.; Spaniol, T. P.;
Okuda, J . Organometallics 1997, 16, 4845. (c) Hultzsch, K. C.; Okuda,
J . Macromol. Rapid Commun. 1997, 18, 809. (d) Hultzsch, K. C.;
Spaniol, T. P.; Okuda, J . Organometallics 1998, 17, 485. (e) Hultzsch,
K. C.; Spaniol, T. P.; Okuda, J . Angew. Chem., Int. Ed. 1999, 38, 227.
(f) Trifonov, A. A.; Kirillov, E. N.; Fischer, A.; Edelmann, F. T.;
Bochkarev, M. N. J . Chem. Soc., Chem. Commun. 1999, 2203.
(5) Cyclopentadienyl ligands bearing neutral pendant donors are
well known in yttrium and lanthanide chemistry. Literature prior to
1994 has been reviewed: Edelmann, F. T. In Comprehensive Organo-
metallic Chemistry II; Lappert, M. F., Ed.; Pergamon: London, 1995;
Vol. 4, Chapter 2. Several complexes of this type have been reported
more recently: (a) Molander, G.; Schumann, H.; Rosenthal, E. C. E.;
Demtschuk, J . Organometallics 1996, 15, 3817. (b) Qian, C.; Zhu, C.;
Lin, Y.; Xing, Y. J . Organomet. Chem. 1996, 507, 41. (c) Qian, C.; Wang,
B.; Deng, D.; Sun, J .; Hahn, F. E.; Chen, J .; Zhang, P. J . Chem. Soc.,
Dalton Trans. 1996, 955. (d) Trifonov, A. A.; van de Weghe, P.; Collin,
J .; Domingos, A.; Santos, I. J . Organomet. Chem. 1997, 527, 225. (e)
Schumann, H.; Erbstein, F.; Weimann, R.; Demtschuk, J . J . Orga-
nomet. Chem. 1997, 536, 541. (f) Schumann, H.; Rosenthal, E. C. E.;
Demtschuk, J .; Molander, G. Organometallics 1998, 17, 5324. (g) Qian,
C.; Zou, G.; Sun, J . J . Chem. Soc., Dalton Trans. 1998, 1607. (h)
Bochkarev, M. N.; Fedushkin, I. L.; Nevodchikov, V. I.; Protchenko,
A. V.; Schumann, H.; Girgsdies, F. Inorg. Chim. Acta 1998, 280, 138.
(i) Schumann, H.; Erbstein, F.; Karasiuk, D. F.; Fedushkin, I. L.;
Demtschuk, J .; Girgsdies, F. Z. Anorg. Allg. Chem. 1999, 625, 781. (j)
Qian, C.; Zou, G.; Sun, J . J . Chem. Soc., Dalton Trans. 1999, 519. (k)
Liu, Q.; Huang, J .; Qian, Y.; Chan, A. C. S. Polyhedron 1999, 18, 2345.
* To whom correspondence should be addressed.
† University of Victoria.
§ Current address: Merck Research, P.O. Box 2000, Rahway, NJ
07065.
‡ Mississippi State University.
(1) Leading references can be found in: (a) Vollmerhaus, R.; Rahim,
M.; Tomaszewski, R.; Xin, S.; Taylor, N. J .; Collins, S. Organometallics
2000, 19, 2161. (b) Martin, A.; Uhrhammer, R.; Gardner, T. G.; J ordan,
R. F.; Rogers, R. D. Organometallics 1998, 17, 382. (c) Hughes, A. K.;
Meetsma, A.; Teuben, J . H. Organometallics 1993, 12, 1936. (d) Lee,
L.; Berg, D. J .; Einstein, F. W. B.; Batchelor, R. J . Organometallics
1997, 16, 1819.
(2) For leading references see: (a) Okuda, J . Comments Inorg. Chem.
1994, 16, 185. (b) Okuda, J .; Eberle, T. In Metallocenes; Togni, A.,
Halterman, R. A., Eds.; Wiley-VCH: New York, 1998; Vol. 1, Chapter
7. (c) Hultzsch, K. C.; Voth, P.; Beckerle, P.; Spaniol, T. P.; Okuda, J .
Organometallics 2000, 19, 228.
(3) (a) Shapiro, P. J .; Cotter, W. D.; Schaefer, W. P.; Labinger, J .
E.; Bercaw, J . E. J . Am. Chem. Soc. 1994, 116, 4623. (b) Herrmann,
W. A.; Moraweitz, M. J . A. J . Organomet. Chem. 1994, 482, 1. (c)
Herrmann, W. A.; Baratta, W.; Moraweitz, M. J . A. J . Organomet.
Chem. 1995, 497, C4. (d) Herrmann, W. A.; Moraweitz, M. J . A.;
Baratta, W. J . Organomet. Chem. 1996, 506, 357. (e) Sinnema, P.-J .;
van der Veen, L.; Spek, A. L.; Veldman, N.; Teuben, J . H. Organome-
tallics 1997, 16, 4245, and references therein.
10.1021/om0104520 CCC: $20.00 © 2001 American Chemical Society
Publication on Web 08/29/2001

4280 Organometallics, Vol. 20, No. 20, 2001
Gendron et al.
mmol) in 150 mL of diethyl ether was prepared under argon
in a 500 mL Schlenk flask and cooled to -78 °C. A 2.2 M
solution of n-BuLi in hexanes (24.2 mL, 53.2 mmol) was added
via syringe over 5 min with rapid stirring. Stirring was
continued for 30 min before the cold solution was added via
cannula to a 1 L flask containing a solution of diethyl
carbonate (3.17 g, 26.6 mmol) in 100 mL of diethyl ether. After
addition was complete, the reaction mixture was allowed to
warm to 0 °C and was quenched with 200 mL of distilled water.
The mixture was extracted with 3 × 200 mL of diethyl ether,
and the combined extracts were dried over anhydrous MgSO4.
Filtration and removal of the solvent from the filtrate yielded
ketone 1 as a yellow solid. Recystallization from a mixture of
toluene and hexane afforded pure 1 as colorless crystals.
Yield: 9.08 g (75%). Mp: 136-137 °C. NMR (CDCl3): 1H δ
8.23 (s, 4H, o-arylH), 8.19 (s, 2H, p-arylH); 13C{1H} δ 205 (CO),
146.37 (ipso-arylC), 132.53 (q, m-arylC, 2J CF ) 34 Hz), 127.47
(o-arylC), 122.90 (p-arylC), 122.77 (q, CF3, 1J CF ) 272 Hz); 19F-
{1H} δ -63.30 (CF3).
1,1-Di(3,5-bis(tr iflu or om eth yl)p h en yl)eth ylen e Oxid e
(2). A solution of 1 (2.00 g, 4.41 mmol) in 50 mL of THF was
placed in a 250 mL Schlenk flask and cooled to -10 °C under
an argon atmosphere. A 0.6 M DMSO solution of Na+[CH2SO-
(CH3)2]- (7.5 mL, 4.5 mmol) was added to the flask rapidly by
syringe. The reaction mixture was quenched with ice water
10 min after the addition. The resulting mixture was extracted
with diethyl ether (3 × 100 mL), and the combined extracts
were dried over anhydrous MgSO4, filtered, and taken to
lanthanide chemistry because they possess insufficient
steric bulk to satisfy the larger coordination sphere of
these metals. In particular, many of the existing ligands
bear no substituents on the alkoxide carbon. In other
work, we have been exploring the use of perfluoroaryl-
substituted amides with group 4 and lanthanide met-
als.6 Fluorinated aryl groups are attractive substituents
because they decrease the electron donor capacity of the
heteroatom to which they are attached and they gener-
ally increase the solubility of the ligands and metal
complexes that contain them relative to their nonflu-
orinated analogues. For these reasons, we have devel-
oped a Cp-alkoxide that possesses 3,5-bis(trifluorome-
thyl)phenyl groups on the alkoxide carbon.7 An added
benefit of this ligand design is that both the Cp and the
alkoxide functions have low pKa’s, leading to improved
stability in the presence of moderately acidic substrates
(e.g., primary amines or phosphines, alkynes).8
In this contribution we report the synthesis of a new
Cp-alkoxide ligand bearing fluorinated aryl substituents
at the alkoxide carbon. The synthesis of several yttrium
complexes of this ligand and the X-ray structure of two
such complexes are described. Synthesis of the yttrium
complexes did not always proceed simply, so the prob-
lems associated with ligand incorporation by salt me-
tathesis and protonolysis are discussed in some detail.
dryness. The resulting white solid was redissolved in
a
minimum of ether and further dried over activated 4 Å
molecular sieves. After removal of solvent, the solid was
recrystallized from a hexane-toluene mixture to afford pure
epoxide 2 as colorless crystals. Yield: 1.61 g (78%). Mp: 79-
80 °C. NMR (CDCl3): 1H δ 7.90 (s, 2H, p-arylH), 7.79 (s, 4H,
o-arylH), 3.36 (s, 2H, CH2); 13C{1H} 140.4 (ipso-arylC), 132.4
(q, CCF3, 2J CF ) 34 Hz), 127.5 (o-arylC), 122.9 (p-arylC), 122.85
Exp er im en ta l Section
Gen er a l P r oced u r es. All manipulations were carried out
under an argon atmosphere, with the rigorous exclusion of
oxygen and water, using standard glovebox (Braun MB150-
GII) or Schlenk techniques. Tetrahydrofuran (THF), hexane,
and toluene were dried by distillation from sodium benzophe-
none ketyl under argon immediately prior to use. 3,5-Bis-
(trifluoromethyl)bromobenzene was purchased commercially
(Aldrich) and used as received. Yttrium tris(2,6-di-tert-bu-
tylphenoxide),9 {Y[N(SiMe3)2]2(THF)2(µ-Cl)}2,10 and Na+{CH2S-
(O)Me2}- 11 were prepared according to literature procedures.
1H (360 MHz), 13C (90.55 MHz), 19F (338.86 MHz), and 29Si
(71.54 MHz) were recorded on a Bruker AMX-360 MHz
spectrometer. All deuterated solvents were dried over activated
4 Å molecular sieves, and spectra were recorded using 5 mm
tubes fitted with a Teflon valve (Brunfeldt) at room temper-
ature unless otherwise specified. 1H and 13C NMR spectra were
referenced to residual solvent resonances. 19F NMR spectra
were referenced to external CCl3F, and 29Si NMR spectra were
referenced to external TMS. Melting points were recorded
using a Bu¨chi melting point apparatus and are not corrected.
Elemental analyses were performed by Canadian Microana-
lytical, Delta, B.C. Despite the use of co-oxidants such as V2O5
and PbO2, the analytical data for most complexes were
consistently 2-4% low in carbon. This may be due to metal
carbide formation. Mass spectra were recorded on a Kratos
Concept H spectrometer using chemical ionization (methane)
or electron impact (70 eV) methods.
1
(q, CF3, J CF ) 273 Hz), 77.2 (CO), 56.9 (CH2O); 19F{1H} δ
-63.21 (CF3).
2-Cyclopen tadien yl-1,1-di(3,5-bis(tr iflu or om eth yl)ph en -
yl)eth a n ol (3). A solution of epoxide 2 (2.90 g, 6.2 mmol) in
THF (50 mL) was placed in a 500 mL Schlenk flask and cooled
to -78 °C. To this stirred solution was added a solution of
NaCp (0.81 g, 9.2 mmol) in THF (50 mL) by cannula. The
reaction mixture was allowed to warm to room temperature,
and stirring was continued for 3 h. The reaction mixture was
quenched with distilled water (200 mL), and the organic
products were extracted with diethyl ether (3 × 200 mL). The
combined ether extracts were dried over MgSO4 and filtered,
and the solvent was removed under reduced pressure to yield
a dark red oil, which solidified on standing. The crude material
was recrystallized from hexane-toluene to yield white crystal-
line 3 as a mixture of two diene isomers in approximately 2:1
ratio. The major isomer was identified as the 1-alkyl-
substituted diene, while the minor isomer was the 2-alkyl-
substituted compound; the 5-alkyl (substituted at the sp3
carbon) isomer was not observed. Yield (based on epoxide):
2.15 g (65%). Mp: 104-105 °C. Major isomer 3a (1-alkylCp):
NMR (benzene-d6) 1H δ 7.82 (m, 4H, o-arylH), 7.60 (m, 2H,
p-arylH), 6.00 (m, 1H, Cp-H3), 5.67 (dq, 1H, Cp-H4, J ) 5.3,
1.5 Hz), 5.57 (m, 1H, Cp-H2), 2.58 (br s, 2H, CH2CO), 2.44 (q,
2H, Cp-H5), 2.16 (s, 1H, COH); 13C{1H} δ 148.40 (ipso-arylC),
139.77 (Cp-C1), 134.82 (Cp-C3), 134.19 (Cp-C4), 133.04 (Cp-
3,3′,5,5′-Tetr a k is(tr iflu or om eth yl)ben zop h en on e (1). A
solution of 3,5-bis(trifluoromethyl)bromobenzene (15.6 g, 53.2
2
(6) O’Connor, P.; Morrison, D.; Steeves, S.; Burrage, K.; Berg, D. J .
Organometallics 2001, 20, 1153.
(7) Perfluorophenyl substituents were not used in order to avoid
unwanted C-F bond activation processes observed in related zirconium
chemistry: O’Connor, P.; Berg, D. J . Unpublished results.
(8) A low pKa sulfonamido-Cp ligand has been reported: Lensink,
C. J . Organomet. Chem. 1998, 553, 387.
(9) Hitchcock, P. B.; Lappert, M. F.; Singh, A. Chem. Commun. 1983,
1499.
(10) Gendron, R. A. G.; Berg, D. J . Can J . Chem. 2000, 78, 454.
(11) Corey, E. J .; Chaykovsky, M. J . Am. Chem. Soc. 1965, 87, 1353.
C2), 132.01 (q, arylCCF3, J CF ) 33 Hz), 126.47 (o-arylCH),
123.67 (q, CF3, 1J CF ) 273 Hz), 121.66 (p-arylC), 76.02 (COH),
41.85 (Cp-C5), 41.54 (CH2CO); 19F{1H} δ -62.81 (CF3). Minor
1
isomer 3b (2-alkylCp): NMR (benzene-d6) H δ 7.79 (m, 4H,
o-arylH), 7.58 (m, 2H, p-arylH), 6.14 (dq, 1H, Cp-H3, J ) 5.4,
1.7 Hz), 5.98 (m, 1H, Cp-H4), 5.82 (m, 1H, Cp-H1), 2.58 (br s,
2H, CH2CO, overlaps major isomer), 2.17 (q, 2H, Cp-H5), 1.96
(s, 1H, COH); 13C{1H} δ 148.52 (ipso-arylC), 140.13 (Cp-C2),
2
134.15 (Cp-C1), 133.54 (Cp-C4), 132.12 (q, arylCCF3, J CF
)

Cyclopentadienyl Yttrium Complexes
Organometallics, Vol. 20, No. 20, 2001 4281
33 Hz), 131.92 (Cp-C3), 126.24 (o-arylCH), 123.64 (q, CF3, 1J CF
) 273 Hz), 121.66 (p-arylC, overlaps major isomer), 76.13
(COH), 44.58 (Cp-C5), 42.64 (CH2CO); 19F{1H} δ -62.92 (CF3).
MS (EI): 533 (M+ - H, 20%), 455 (M+ - CpCH2, 70%), 241
(3,5-C6H3(CF3)2CO, 100%) amu.
the glovebox. A solution of 3 (0.165 g, 0.31 mmol) in 20 mL
was added dropwise to the rapidly stirred solution. The
solution slowly became turbid as 5 precipitated from solution.
After 2 h, the solvent was removed under vacuum and the
white solid was recrystallized from hot hexane to afford pure
5 as a white microcrystalline powder. Yield: 90%. Mp: 196-
197 °C. NMR (THF-d8): 1H δ 8.34 (s, 4H, o-arylH), 7.68 (s,
2H, p-arylH), 5.77 (br s, 2H, CpH), 5.40 (br s, 2H, CpH), 3.65
(s, 2H, CH2CO), 3.58 (m, 8H, R-THF H), 1.73 (m, 8H, â-THF
{η5:η1-C5H4[CH2C(O)(3,5-C6H3(CF3)2)2]}2Y-Li+{THF}n (4a,
n ) 2; 4b, n ) 1): Meth od A. A 50 mL Erlenmeyer was
charged with Y[O-2,6-t-Bu2C6H3]3[THF] (0.105 g, 0.14 mmol)
in the glovebox, and 10 mL toluene was added. A solution of
LiCH2SiMe3 (0.026 g, 0.28 mmol) in 5 mL of toluene was added
to the colorless phenoxide solution at room temperature, and
the mixture was stirred for 30 min. At the end of this period,
a white precipitate of Li+[O-2,6-t-Bu2C6H3]- was evident. A 5
mL toluene solution of 3 (0.075 g, 0.14 mmol) was added
dropwise, and the white suspension was stirred for a further
30 min. The reaction mixture was filtered through Celite on a
fine sintered glass frit, and the solvent was removed from the
filtrate to yield a white powder. Recrystallization from a
minimum of toluene at -30 °C afforded colorless prisms of the
bis(THF) adduct (4a ). Exposure of this material to vacuum
resulted in partial solvent loss to afford the mono(THF) adduct
4b. Yield: 40% (based on yttrium).
2
H); 13C{1H} δ 158.06 (ipso-arylC), 131.44 (q, CCF3, J CF ) 33
1
Hz), 127.53 (o-arylC), 126.73 (Cp-C1), 124.94 (q, CF3, J CF
)
272 Hz), 120.19 (p-arylC), 111.84 (CpC), 110.18 (CpC), 91.07
(COY), 68.21 (R-THF C), 44.59 (CH2CO), 26.37 (â-THF C); 19F-
{1H} δ -63.28 (CF3). Anal. Calcd for C31H28ClF12O3Y: C, 46.49;
H, 3.52. Found: C, 45.98; H, 3.36.
{η5:η1-C5H 4[CH 2C(O)(3,5-C6H 3(CF 3)2)2]}Y{N(SiMe3)2}-
{THF }n (6a , n ) 2; 6b, n ) 1). An Erlenmeyer flask was
charged with 5 (0.131 g, 0.17 mmol) and 20 mL of toluene in
the glovebox. To the rapidly stirred white suspension was
added a 10 mL toluene solution of NaN(SiMe3)2 (0.032 g, 0.17
mmol). The suspension was stirred for 1 h at room temperature
and filtered through Celite on a glass frit, and the solvent was
removed from the filtrate to give a white powder. Recrystal-
lization of this product from a toluene-hexane mixture gave
pure 6a as small white crystals. Yield: 0.092 g (58%). Mp:
148-149 °C. NMR (benzene-d6): 1H δ 8.14 (o-arylH), 7.59 (p-
Meth od B. A solution of 3 (0.255 g, 0.48 mmol) in 30 mL of
THF was prepared under argon in a 250 mL Schlenk tube.
The flask was cooled to -78 °C, and n-BuLi (0.48 mL of 2 M
solution in hexane, 0.96 mmol) was added via syringe. The
solution was stirred for 5 min and then transferred by cannula
into a stirred suspension of YCl3 (0.093 g, 0.48 mmol) in 50
mL of THF, also cooled to -78 °C. The reaction mixture was
allowed to warm to room temperature, and stirring was
continued for a further 3 h. At the end of this period, the
solvent was removed under vacuum and 30 mL of diethyl ether
was added. Precipitated LiCl was removed by Schlenk filtra-
tion through a Celite pad, and the solvent was removed to
leave a white powder. Recrystallization from hot toluene
afforded 4a . Yield: 75%. Mp: 184-185 °C. NMR (benzene-
d6): 1H δ 8.16 (br s, 4H, o-arylHA), 7.70 (br s, 4H, o-arylHB),
7.66 (br s, 2H, p-arylHA), 7.41 (br s, 2H, p-arylHB), 6.19 (dd,
2H, Cp-H5, J ) 5.0, 2.5 Hz), 5.94 (dd, 2H, Cp-H4, J ) 5.8, 3.1
Hz), 5.65 (dd, 2H, Cp-H3, J ) 5.4, 2.6 Hz), 4.79 (dd, 2H, Cp-
3
arylH), 5.99 (t, 2H, CpH, J HH ) 2.9 Hz), 5.80 (t, 2H, CpH,
3J HH ) 2.9 Hz), 3.39 (m, 10H, R-THF H and CH2CO), 1.18 (m,
8H, â-THF H), 0.25 (s, 18H, SiMe3); 13C{1H} δ 155.37 (ipso-
arylC), 131.69 (q, CCF3, 2J CF ) 33 Hz), 130.80 (Cp-C1), 126.16
1
(o-arylC), 124.01 (q, CF3, J CF ) 273 Hz), 120.41 (p-arylC),
113.96 (CpC), 110.17 (CpC), 92.90 (COY), 70.69 (R-THF C),
42.15 (CH2CO), 24.99 (â-THF C), 4.87 (SiMe3); 19F{1H} δ
-62.49 (CF3); 29Si{1H} δ -10.20 (SiMe3).
Exposure of 6a to vacuum for extended periods of time
resulted in the loss of one THF molecule to give 6b. The NMR
data for 6b were essentially identical to those for 6a with the
exception that the THF resonances integrated to only 4H each
rather than 8H. Anal. Calcd for C33H38F12NO2Si2Y: C, 46.42;
H, 4.49; N, 1.64. Found: C, 46.41; H, 4.66; N, 1.32.
2
{η5:η1-C5H4[CH2C(O)(3,5-C6H3(CF 3)2)2]}{N(SiMe3)2}2Y--
Na +{THF }2 (7). An Erlenmeyer flask was charged with 6
(0.100 g, 0.108 mmol) and 10 mL of toluene in the glovebox.
To the rapidly stirred clear solution was added a 10 mL toluene
solution of NaN(SiMe3)2 (0.018 g, 0.108 mmol). The suspension
was stirred 4 h at room temperature and filtered through
Celite on a glass frit, and the solvent was removed from the
filtrate to give a white powder. Recrystallization of this product
from a toluene-hexane mixture gave pure 7 as small colorless
needles. Yield: 0.070 g (60%). NMR (benzene-d6): 1H δ 8.36
H2, J ) 5.5, 2.3 Hz), 3.71 (d, 2H, CHaHbCO, J HH ) 14.1 Hz),
2
2.81 (d, 2H, CHaHbCO, J HH ) 14.1 Hz), 2.41 (m, 8H, R-THF
H), 0.72 (m, 8H, â-THF H); 13C{1H} δ 155.27 (ipso-arylC),
153.49 (ipso-arylC), 132.42 (q, CCF3, 2J CF ) 33 Hz), 128.91 (q,
CCF3, 2J CF ) 33 Hz), 127.32 (Cp-C1 alkyl substituted), 126.44
1
(o-arylCA), 125.15 (o-arylCB), 123.85 (q, CF3, J CF ) 273 Hz),
1
123.46 (q, CF3, J CF ) 273 Hz), 121.61 (p-arylCA), 120.85 (p-
arylCB), 115.05 (Cp-C4), 113.09 (Cp-C3), 108.03 (Cp-C2),
107.19 (Cp-C5), 88.45 (CH2CO), 67.68 (R-THF C), 42.19 (CH2-
CO), 24.43 (â-THF C); 19F{1H} δ -62.49 (CF3), -62.96 (CF3).
Exposure of 4a to vacuum for several hours afforded the
mono(THF) adduct 4b. NMR (benzene-d6): 1H δ 8.15 (br s,
4H, o-arylHA), 7.69 (br s, 4H, o-arylHB), 7.68 (br s, 2H,
p-arylHA), 7.43 (br s, 2H, p-arylHB), 6.18 (dd, 2H, Cp-H5, J )
5.0, 2.5 Hz), 5.95 (dd, 2H, Cp-H4, J ) 5.8, 3.1 Hz), 5.63 (dd,
2H, Cp-H3, J ) 5.4, 2.6 Hz), 4.80 (dd, 2H, Cp-H2, J ) 5.5, 2.3
3
(o-arylH), 7.65 (p-arylH), 5.97 (t, 2H, CpH, J HH ) 2.9 Hz),
3
5.84 (t, 2H, CpH, J HH ) 2.9 Hz), 3.52 (m, 2H, CH2CO), 3.39
(m, 10H, R-THF H), 1.18 (m, 8H, â-THF H), 0.44 (s, 36H,
SiMe3); 13C{1H} δ 156.17 (ipso-arylC), 131.87 (q, CCF3, 2J CF
)
1
33 Hz), 129.25 (Cp-C1), 126.59 (o-arylC), 123.77 (q, CF3, J CF
) 273 Hz), 120.64 (p-arylC), 110.58 (CpC), 108.25 (CpC), 90.05
(COY), 68.87 (R-THF C), 42.41 (CH2CO), 25.06 (â-THF C), 6.15
(SiMe3); 19F{1H} δ -62.32 (CF3); 29Si{1H} δ -11.36 (SiMe3).
{η5:η1-C 5H 4[C H 2C (O )(3,5-C 6H 3(C F 3)2)2]}Y{η5-C 5H 5}-
{THF }n (8a , n ) 2; 8b, n ) 1). The cyclopentadienyl derivative
8 was prepared from 5 and NaCp using the procedure outlined
for 6. The crude product was isolated as a waxy yellow solid;
recrystallization from hexane at -30 °C initially afforded the
bis(THF) adduct 8a as colorless plates. However on removal
of the mother liquor, these crystals rapidly lost solvent to form
the mono(THF) adduct 8b as a white powder. Yield: 65%.
Mp: 168-170 °C. NMR (benzene-d6): 1H δ 8.37 (s, 2H,
o-arylH), 8.11 (s, 2H, o-arylH), 7.68 (s, 1H, p-arylH), 7.60 (s,
1H, p-arylH), 6.10 (s, 5H, C5H5), 6.07 (br s, 1H, CpH), 5.40 (br
s, 2H, CpH), 5.29 (br s, 1H, CpH), 3.48 (d, 1H, CHaHbCO, 2J HH
) 13.6 Hz), 3.05 (m, 4H, R-THF H), 2.95 (d, 1H, CHaHbCO,
2
Hz), 3.70 (d, 2H, CHaHbCO, J HH ) 14.1 Hz), 2.81 (d, 2H,
2
CHaHbCO, J HH ) 14.1 Hz), 2.36 (m, 4H, R-THF H), 0.70 (m,
4H, â-THF H); 13C{1H} δ 155.26 (ipso-arylC), 153.28 (ipso-
2
2
arylC), 132.44 (q, CCF3, J CF ) 33 Hz), 132.39 (q, CCF3, J CF
) 33 Hz), 126.47 (Cp-C1 alkyl substituted, overlaps o-aryl
resonance), 126.46 (o-arylCA), 125.11 (o-arylCB), 121.64 (p-
arylCA), 120.88 (p-arylCB), 115.04 (Cp-C4), 113.05 (Cp-C3),
108.02 (Cp-C2), 107.20 (Cp-C5), 88.44 (CH2CO), 67.64 (R-THF
C), 42.32 (CH2CO), 24.36 (â-THF C), the CF3 resonances were
not located; 19F{1H} δ -62.50 (CF3), -63.00 (CF3). Anal. Calcd
for C57H40F24LiO3Y (4b as a mono(toluene) solvate): C, 51.68;
H, 3.04. Found: C, 51.82; H, 3.38.
{η5:η1-C5H4[CH2C(O)(3,5-C6H3(CF 3)2)2]}YCl{THF }2 (5). A
50 mL Erlenmeyer flask was charged with {Y[N(SiMe3)2]2-
(THF)2(µ-Cl)}2 (0.181 g, 0.155 mmol) and 10 mL of toluene in

4282 Organometallics, Vol. 20, No. 20, 2001
Gendron et al.
2J HH ) 13.6 Hz), 1.02 (m, 4H, â-THF H); 13C{1H} δ 156.0 (ipso-
a
Sch em e 1
2
arylC), 155.5 (ipso-arylC), 131.61 (q, CCF3, J CF ) 33 Hz),
128.65 (q, CCF3, 2J CF ) 33 Hz), 128.49 (Cp-C1), 127.60 (q, CF3,
1J CF ) 275 Hz), 125.96 (o-arylC), 126.63 (o-arylC), 124.15 (q,
1
CF3, J CF ) 274 Hz), 120.40 (p-arylC), 120.20 (p-arylC), 113.4
(CpC), 110.88 (C5H5), 110.2 (CpC), 108.4 (CpC), 105.9 (CpC),
2
92.60 (d, COY, J YC ) 2.3 Hz), 71.25 (R-THF C), 43.77 (CH2-
CO), 24.99 (â-THF C); 19F{1H} δ -62.53, -62.61 (CF3). Anal.
Calcd for C32H25F12O2Y: C, 50.68; H, 3.32. Found: C, 50.45;
H, 3.31.
{η5:η1-C5H4[CH2C(O)(3,5-C6H3(CF 3)2)2]}Y{CH(SiMe3)2}-
{THF }2 (9). Crude 9 was isolated as a yellow oil using a
procedure analogous to 6 starting from 5 and LiCH(SiMe3)2
(1 equiv). Repeated recrystallization from hexane at -30 °C
produced 9 as an impure solid. Yield: 20%. NMR (benzene-
d6): 1H δ 8.13 (s, 4H, o-arylH), 7.67 (s, 2H, p-arylH), 6.31 (br
s, 2H, CpH), 6.11 (br s, 2H, CpH), 3.38 (s, 2H, CH2CO), 2.93
(m, 8H, R-THF H), 1.07 (m, 8H, â-THF H), 0.28 (s, 18H, SiMe3),
2
-1.08 (d, 1H, CH(SiMe3)2, J YH ) 2.4 Hz); 19F{1H} δ -62.33;
29Si{1H} δ -7.10 ppm.
{η5:η1-C5H4[CH2C(O)(3,5-C6H3(CF 3)2)2]} {CH(SiMe3)2}2-
Y-Li+{THF }2 (10). Crude 10 was isolated as a yellow oily solid
using a procedure analogous to 6 starting from 5 and LiCH-
(SiMe3)2 (2 equiv), but instead using hexane as solvent.
Repeated recrystallization from hexane at -30 °C produced
white crystals of 10 containing trace amounts of 9. Yield: 60%.
Mp: 97-98 °C. NMR (benzene-d6): 1H δ 8.32 (s, 4H, o-arylH),
7.65 (s, 2H, p-arylH), 6.32 (br s, 2H, CpH), 6.10 (br s, 2H, CpH),
3.52 (s, 2H, CH2CO), 2.98 (m, 8H, R-THF H), 1.07 (m, 8H,
â-THF H), 0.49 (s, 18H, SiMe3a), 0.36 (s, 18H, SiMe3b), -1.22
(br d, 2H, CHa,b(SiMe3)2); 13C{1H} δ 154.73 (ipso-arylC), 132.06
(q, CCF3, J CF ) 33 Hz), 126.59 (o-arylC), 123.99 (q, CF3, J CF
) 272 Hz), 120.95 (p-arylC), 111.75 (CpC), 108.19 (CpC), 90.50
(COY), 68.43 (R-THF C), 40.33 (CH2CO), 34.62 (d, CH(SiMe3)2,
1J C-Y ) 35 Hz), 25.07 (â-THF C), 5.99 (SiMe3a), 5.69 (SiMe3b);
19F{1H} δ -62.42; 29Si{1H} δ -6.56, -7.05. Anal. Calcd for
a
Reaction conditions: (a) (i) n-BuLi (1 equiv), -78 °C, (ii)
(EtO)2CO (0.5 equiv), -78 °C, (iii) H2O quench; (b) (i)
Na+[CH2SO(CH3)2]- (1 equiv), -10 °C, (ii) H2O; (c) (i) NaCp
(1.5 equiv), -78 °C, (ii) H2O quench.
SHELXS-9713 and refinement was done on F2. An absorption
correction was applied in both cases (abs range: 4a 0.60-1.00;
11 0.68-1.00). The final Fourier difference maps showed
maximum and minimum peaks of -0.38/+0.60 (4a ) and -0.44/
+0.67 (11) e Å-3. Thermal ellipsoid plots were drawn with
ORTEP3.14
2
1
C
37H48F12OSi4YLi: C, 47.01; H, 5.12. Found: C, 46.46; H, 5.20.
{η5:η1-C5H 4[CH 2C(O)(3,5-C6H 3(CF 3)2)2]}Y{O-2,6-t-Bu 2-
Resu lts
C6H3}{THF }2 (11). A solution of Y[O-2,6-t-Bu2C6H3][CH-
(SiMe3)2]2[THF]212 (0.27 g, 0.36 mmol) in 10 mL of toluene was
prepared in an Erlenmeyer flask in the glovebox. To this
solution, solid 3 (0.21 g, 0.36 mmol) was added and the clear
solution was stirred for 10 min. Removal of the solvent under
vacuum and recrystallization of the crude white powder from
hexanes at -30 °C afforded 11 as colorless crystals. Yield:
0.248 g (71%). Mp: 146-147 °C. NMR (benzene-d6): 1H δ 8.25
(s, 4H, o-arylH), 7.59 (s, 2H, p-arylH), 7.33 (d, 2H, m-phenoxide
H, 3J HH ) 8.1 Hz), 6.81 (t, 1H, p-phenoxide H, 3J HH ) 8.1 Hz),
The synthesis of the ligand is outlined in Scheme 1.
The formation of ketone 1 and epoxide 2 proceeded in
good yield. However, ring opening of epoxide 2 with
NaCp did not proceed in very high yield, even when
Lewis acids such as AlCl3, BF3‚Et2O, or B(C6F5)3 were
added. Nevertheless the desired alcohol 3 could be
obtained, in marked contrast to the reaction of NaCp
with the nonfluorinated diphenyl analogue of 2. In the
latter case ring opening does not occur even under
forcing conditions, demonstrating that the trifluoro-
methyl substituents activate the epoxide toward nu-
cleophilic attack, as might be expected. Although 3 is
thermally stable to at least 100 °C for days in pure form,
it decomposed to ketone 2 when the reaction mixture
was heated in attempts to increase the yield. Similarly,
we have found that 3 decomposes to ketone 2 over a
period of days when heated at 70 °C in the presence of
yttrium complexes.
3
3
6.06 (t, 2H, CpH, J HH ) 2.6 Hz), 5.84 (t, 2H, CpH, J HH ) 2.6
Hz), 3.54 (s, 2H, CH2CO), 3.32 (m, 8H, R-THF H), 1.54 (2, 18H,
CMe3), 1.07 (m, 8H, â-THF H); 13C{1H} δ 162.16 (d, ipso-
2
phenoxide C, J YC ) 4.5 Hz), 156.27 (ipso-arylC), 137.25 (o-
phenoxide C), 131.73 (q, CCF3, 2J CF ) 33 Hz), 131.08 (Cp-C1),
126.24 (m-phenoxide C), 125.84 (o-arylC), 124.04 (q, CF3, 1J CF
) 271 Hz), 120.31 (p-arylC), 116.67 (p-phenoxide C), 113.34
(CpC), 109.89 (CpC), 92.29 (COY), 71.14 (R-THF C), 42.00
(CH2CO), 35.20 (CMe3), 31.57 (CMe3), 24.98 (â-THF C); 19F-
{1H} δ -62.38 (CF3). Anal. Calcd for C45H49F12O4Y: C, 55.68;
H, 5.09. Found: C, 54.93; H, 4.80.
Reaction of the dianion of 3, formed in situ, with YCl3
in THF did not lead to the expected yttrium chloride
complex (Scheme 2). Instead, the bis(ligand) ate complex
4 was obtained as the only isolable yttrium species.
Initially, this complex was isolated from the reaction
mixture as the crystalline bis(THF) adduct 4a , and a
crystal structure was obtained, confirming this (vide
X-r a y Cr ysta llogr a p h y. Crystals of 4a and 11 were
isolated from toluene solution and a toluene-hexane mixture,
respectively. The crystals were placed in mineral oil under an
atmosphere of argon and sealed in a glass capillary. Data were
collected on a Siemens Smart 1000 CCD diffractomter equipped
with graphite-monochromated Mo KR radiation (λ ) 0.71073
Å) at 293 K. Structure solutions were carried out using
(13) Sheldrick, G. SHELX-97: Programs for Crystal Structure
Determination; University of Go¨ttingen: Germany, 1997.
(14) Farrugia, L. J . ORTEP3 for Windows. J . Appl. Crystallogr.
1997, 30, 565.
(12) This compound was prepared by reaction of 2 equiv of LiCH-
(SiMe3)2 with Y(O-2,6-t-Bu2C6H3)3 in hexane. Lee, L.; Berg, D. J .;
Gendron, R. A. L. Unpublished results.

Cyclopentadienyl Yttrium Complexes
Organometallics, Vol. 20, No. 20, 2001 4283
Sch em e 2
tion of 5 with NaN[(SiMe3)2]2 affords the silylamido
complex 6a in moderate yield (Scheme 3). The NMR
spectra of this complex are again consistent with mirror
plane symmetry for the ligand. Prolonged exposure of
6a to vacuum results in loss of one THF ligand and
formation of the less soluble mono(thf) adduct 6b.
Excess coordinating solvents such as THF must be
avoided in order to prevent redistribution to the ate
complex 4. Attempts to prepare 6a by the direct proto-
nolysis of Y[N(SiMe3)2]3 with 3 fail to give any of the
desired product. Presumably this is due to the high
degree of bulk in the tris(amido) yttrium precursor since
the less crowded dimer {Y[N(SiMe3)2]2(µ-Cl)(THF)2}2
reacts smoothly with 3 under the same conditions to
give 5. Marks et al. have reported that it is necessary
to alternately reflux and then remove the toluene
solvent during the reaction of Ln[N(SiMe3)2]3 with C5-
Me4H(SiMe2NH-t-Bu) (Ln ) Nd, Sm, Lu) in order to
deprotonate the Cp ring and prevent competitive pro-
tonolysis by HN(SiMe3)2.18 The latter reaction does not
appear to be of major concern here, judging by the
results with the bis(amido) dimer, and we cannot heat
the reaction mixture without significant ligand redis-
tribution to give 4a . It is also interesting that the
addition of another equivalent of NaN[(SiMe3)2]2 forms
the anionic species 7 in moderate yield, showing that
the metal coordination sphere in 6a and 6b is still quite
open.
Reaction of 5 with NaCp proceeds smoothly in toluene
to give the Cp derivative as the bis(THF) adduct 8a
(Scheme 3). This complex readily loses THF to form the
mono(THF) adduct 8b on standing. The 1H NMR
spectrum of 8b in benzene reveals a low-symmetry
environment where all ligand C5H4 and backbone
protons are inequivalent, indicating that the remaining
THF is not labile on the NMR time scale. Interestingly,
89Y-13C coupling (2J YC ) 2.3 Hz) is resolved for the
alkoxide carbon of the ligand in this case.
infra).15 Complex 4a loses one THF molecule, slowly on
standing and rapidly under vacuum, to give the mono-
(THF) adduct 4b as a white powder. The NMR data for
4b are consistent with C2 molecular symmetry whereby
the two ligands are related by symmetry to one another,
but all protons of the backbone and Cp unit within the
same ligand are inequivalent.
Attempts to prepare alkyl complexes by the metath-
esis reaction of 5 with lithium alkyls rapidly produced
ate complex 4 via redistribution when smaller alkyls
(Me, Et, Ph, CH2Ph) were employed; the fate of the
alkyl-containing product was not established. Reaction
with LiCH2SiMe3 also led to redistribution, but the
reaction was noticeably slower in this case. Eventually
we were able to isolate the neutral alkyl complex 9 using
the lithium salt of the bulky alkyl -CH(SiMe3)2, albeit
in low yield and moderate purity. Complex 9 was
invariably contaminated with the bis(ligand) redistribu-
tion product 4a and what proved to be the bis(alkyl) ate
complex 10. Complex 10 was isolated as the major
product of 5 with 2 equiv of LiCH(SiMe3)2 provided the
reaction was performed in noncoordinating solvents and
the reaction time was kept short (<30 min).
It is possible to isolate the chloride complex 5 in good
yield by protonolysis of the silylamido groups in dimeric
{Y[N(SiMe3)2]2(µ-Cl)(THF)2}2 using 3 (Scheme 3).16 In
this case, the complex appears to bind THF tightly as
recrystallization from hot toluene and exposure to
vacuum does not result in solvent loss. It is necessary
to use THF-d8 to dissolve 5 sufficiently to obtain NMR
data. The NMR spectra in this solvent are consistent
with mirror plane symmetry for the coordinated ligand.
Distinct C4H8O resonances are observable, well resolved
from the C4HD7O residual solvent resonances. While
this could be taken as evidence that coordinated THF
does not exchange with bulk solvent, it seems more
likely that rapid exchange is occurring and that H/ D
isotopic effects are responsible for the small chemical
shift difference observed.17
In an effort to avoid some of the problems caused by
LiCl elimination, we attempted to prepare a phenoxide
complex for use in metathesis reactions.19 However, the
direct reaction between the dilithium salt of 3 and Y[O-
Substitution of the remaining chloride in 5 can be
accomplished cleanly in some, but not all, cases. Reac-
(15) Similarly, reaction of Li2[C5Me4SiMe2NCH2CH2X] (X ) OMe
or NMe2) with LnCl3 (Ln ) Y, Lu) has been reported to afford the ate
complex Li[Ln(η5:η1-C5Me4SiMe2NCH2CH2X)2].4b
(18) Tian, S.; Arredondo, V. M.; Stern, C. L.; Marks, T. J . Organo-
metallics 1999, 18, 2568.
(16) A similar protonolysis strategy has been used to prepare Y(η5:
η1-C5Me4SiMe2NCMe2R)(CH2SiMe3)(THF) (R ) Me, Et) from C5Me4-
HSiMe2NHCMe2R and Y(CH2SiMe3)3(THF)2.2c
(19) This strategy has been used successfully in several cases: (a)
Heeres, H. J .; Meetsma, A.; Teuben, J . H.; Rogers, R. D. Organome-
tallics 1989, 8, 2637. (b) Schaverien, C. J . Organometallics 1994, 13,
69. (c) Schaverien, C. J .; Frijn, J . H. G.; Heeres, H. J .; van den Hende,
J . R.; Teuben, J . H.; Spek, A. L. J . Chem. Soc., Chem. Commun. 1991,
643.
(17) Coordinated THF has been convincingly shown to undergo rapid
exchange in solution on the NMR time scale for Y(η5:η1-C5Me4SiMe2-
NCMe2R)(CH2SiMe3)(THF) (R ) Me, Et).2c

4284 Organometallics, Vol. 20, No. 20, 2001
Gendron et al.
Sch em e 3
Sch em e 4
symmetry for the ligand in solution. The symmetry in
the solid state is lower (vide infra), suggesting that the
THF ligands are labile in solution. Not surprisingly,
given some of our earlier results, attempts to react 11
with lithium alkyls led to rapid redistribution and
formation of 4.
X-r a y Cr ysta l Str u ctu r es. The crystal structures of
the bis(THF) adduct ate complex 4a and the phenoxide
11 were obtained. Crystallographic data are given in
Table 1 while significant bond distances and angles are
collected in Table 2 for both compounds. Structural plots
for 4a and 11 are given in Figures 1 and 2, respectively.
The crystal structure of 4a shows a bimetallic system
in which the ligand alkoxide oxygens bridge between
yttrium and lithium. The coordination environment at
yttrium is a distorted pseudo-tetrahedral geometry
typical of many other Cp2YX2 systems.20 The coordina-
tion geometry at the lithium cation in 4a is quite close
to tetrahedral. The closest structural comparisons avail-
able in the literature are (η5-C5H4SiMe3)2Y(µ-O-t-Bu)2Li-
2,6-t-Bu2C6H3]3 in THF, ether, or toluene led to forma-
tion of ate complex 4. Similarly, in situ formation of Y[O-
2,6-t-Bu2C6H3][CH2SiMe3]2 from Y[O-2,6-t-Bu2C6H3]3
and LiCH2SiMe3 followed by reaction with 3 also
produced complex 4 (Scheme 2). We were able to prepare
the phenoxide 11 by direct protonolysis of Y[O-2,6-t-
Bu2C6H3][CH(SiMe3)2]2[THF]212 with 3 (Scheme 4). The
yield by this route is good provided the mixed alkyl-
alkoxide precursor is free of lithium. The phenoxide 11
crystallizes as the bis(THF) adduct according to 1H
NMR, elemental analysis, and X-ray crystallography.
The 1H NMR spectrum of 11 displays mirror plane
21
(THF)2 and the related ate complex Li[Y(η5:η1-CpR-
SiMe2NCH2CH2X)2].22 In the former structure, the
C5H4SiMe3 centroid-Y distance is longer (2.458 Å) and
(20) Edelmann, F. T. In Comprehensive Organometallic Chemistry
II; Lappert, M. F., Ed.; Pergamon: London, 1995; Vol. 4, Chapter 2.
(21) Evans, W. J .; Boyle, T. J .; Ziller, J . W. Organometallics 1993,
12, 3998.

Cyclopentadienyl Yttrium Complexes
Organometallics, Vol. 20, No. 20, 2001 4285
Ta ble 1. Su m m a r y of Cr ysta llogr a p h ic Da ta a
4a
11
formula
fw
YC60H46F24LiO4
1382.82
YC45H49F12O4
970.75
cryst size (mm)
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
0.38 × 0.51 × 0.81 0.09 × 0.27 × 0.65
orthorhombic
monoclinic
P21/n (No. 14)
12.4983(12)
16.3961(16)
23.031(2)
90
Pbcn (No. 60)
17.0844(19)
20.056(2)
18.066(2)
90
90
90
101.052(2)
90
F igu r e 1. ORTEP3 drawing14 (thermal ellipsoids 30%
probability) of complex 4a . The fluorine atoms of the ligand
CF3 groups have been omitted for clarity.
6190.1(12)
4
4632.0(8)
4
Z
F(calcd) (g cm-3
)
1.48
1.39
µ (mm-1
)
1.06
1.35
2θmax (deg)
50
50
no. reflns collected
no. of unique reflns
31228
5452
24351
8182
no. of reflns I > 2.0σ(I) 3309
4355
1992
0.048
0.112
F000
2784
0.055
0.160
0.99
R
wR2
GOF on F2
0.88
a
Data were collected on a Siemens Smart 1000 CCD diffrac-
tometer equipped with graphite-monochromated Mo KR radiation
(λ ) 0.71073 Å) at 293 K.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 4a a n d 11a
4a
11
Distances
F igu r e 2. ORTEP3 drawing14 (thermal ellipsoids 30%
probability) of complex 11. The fluorine atoms of the ligand
CF3 groups have been omitted for clarity.
Y(1)-Cp
2.372(5)
Y(1)-Cp
2.400(5)
2.128(2)
2.103(3)
2.505(3)
2.392(3)
Y(1)-O(1)
Li(1)-O(1)
Li(1)-O(S1)
Y(1)-Li(1)
2.220(2)
1.978(6)
1.979(5)
3.125(6)
Y(1)-O(1)
Y(1)-O(2)
Y(1)-O(3)
Y(1)-O(4)
will occupy equatorial sites in the TBP geometry, but
this is not possible in the present case because the CpO
ligand can only span an angle of about 95°. The large
bulk of the 2,6-di-tert-butylphenoxide ligand is accom-
modated by an opening of the equatorial Cp-phenoxide
angle to 137.01(14)° with a corresponding decrease in
the Cp-O4 (THF2) angle to 105.35(14)°. As might be
expected, the Y-O(aryloxide) distance in 11 (2.103(3)
Å), which is formally seven-coordinate, is at the long
end of the range reported for five- and six-coordinate
yttrium aryloxides (2.046(6)-2.103(10) Å).19c,23 The
angle at the aryloxide oxygen (Y(1)-O(2)-C(24) 174.6-
(2)°) is similar to that found in Y(O-t-Bu2C6H3)3 (171-
(1)-175(1)°).9
Angles
Cp-Y(1)-Cp′
Cp-Y(1)-O(1)
Cp-Y(1)-O(1)′
O(1)-Y(1)-O(1)′
Y(1)-O(1)-Li(1)
Y(1)-O(1)-C(7)
O(1)-Li(1)-O(1)′
O(1)-Li(1)-O(S1)
O(1)-Li(1)-O(S1)′
128.2(2)
95.69(14)
125.42(12) Cp-Y(1)-O(3)
78.03(12)
96.1(2)
Cp-Y(1)-O(1)
93.77(13)
137.01(14)
104.72(13)
105.35(14)
Cp-Y(1)-O(2)
Cp-Y(1)-O(4)
O(1)-Y(1)-O(2) 94.02(9)
O(1)-Y(1)-O(3) 156.19(10)
O(1)-Y(1)-O(4) 85.76(10)
124.5(2)
89.9(3)
114.22(12) O(2)-Y(1)-O(3) 82.72(9)
114.47(12) O(2)-Y(1)-O(4) 117.35(10)
O(S1)-Li(1)-O(S1)′ 108.8(4)
Li(1)-O(1)-C(7)
Y(1)-O(2)-C(24)
O(3)-Y(1)-O(4) 75.07(10)
Y(1)-O(1)-C(7) 132.7(2)
130.6(2)
174.6(2)a
a
Estimated standard deviations in parentheses. Primed atoms
are symmetry related. Cp refers to the Cp centroid.
The Cpcent-Y-O angle spanned by the ligand is
similar for both 4a (95.69(14)°) and 11 (93.77(13)°). For
comparison, the chelating η5:η1-Cp-donor ligands found
in Zr[η5:η1-t-BuC5H3(CH2CH2O)]2,24 Zr[η5:η1-C5Me4(CH2-
the Y-O distance is shorter (2.148(10), 2,157(11) Å)
than that found in 4a (2.372(5) and 2.220(2) Å, respec-
tively), but the basic coordination geometry is otherwise
very similar. The differences can be attributed to the
fact that the ligand bulk is primarily at the alkoxide
carbon in 4a , whereas it is on the C5H3SiMe3 group in
the literature complex. The latter family of complexes
display very similar Y-Cpcent distances and overall
coordination geometry to 4a .22
CH2S)]2,25 and {Ti[η5:η1-C5H4(CH2CH2O)]Cl2}2 have
26
bite angles of 99.39° (average), 102.21°, and 100.8°,
respectively. The Cp-alkoxide bite angles in 4a and 11
are closer to the values found in yttrium complexes
containing the η5:η1-CpRSiMe2NCH2CH2X series of
The geometry at yttrium in 11 is best described as a
distorted trigonal bipyramid in which the ligand alkox-
ide and one THF oxygen reside in axial positions while
the Cp centroid, phenoxide, and THF oxygens reside in
equatorial positions. Generally, the largest substituents
(23) (a) Evans, W. J .; Ansari, M. A.; Ziller, J . W. Inorg. Chem. 1995,
34, 3079. (b) Evans, W. J .; Olofson, J . M.; Ziller, J . W. Inorg. Chem.
1989, 28, 4309. (c) Evans, W. J .; Ansari, M. A.; Ziller, J . W.; Khan, S.
I. J . Organomet. Chem. 1998, 553, 141.
(24) Christoffers, J .; Bergman, R. G. Angew. Chem., Int. Ed. Engl.
1995, 34, 2266.
(25) Krut’ko, D. P.; Borzov, M. V.; Kuz’mina, L. G.; Churakov, A.
V.; Lemenovskii, D. A.; Reutov, O. A. Inorg. Chim. Acta 1982, 280,
257.
(26) Trouve´, G.; Laske, D. A.; Meetsma, A.; Teuben, J . H. J .
Organomet. Chem. 1996, 511, 255.
(22) Y-Cpcent ) 2.392(6), 2.399(6) Å (CpR ) C5Me4, X ) OMe); 2.403-
(3), 2.390(3) Å (CpR ) t-BuC5H3, X ) OMe); 2.405(3) Å (CpR ) t-BuC5H3,
X ) NMe2).4b

4286 Organometallics, Vol. 20, No. 20, 2001
Gendron et al.
ligands (95.6(2)-97.5(2)°).2c,4b,d The similarity in bite
angle between these ligands can be attributed to the
longer Si-C bond lengths, which compensates for the
shorter tether in the CpRSiMe2NR series. The angles
at C in the ligand backbone are close to tetrahedral in
both 4a and 11, suggesting that the ligand is not highly
strained to achieve the coordination geometry adopted.
However, the Y-Cp C distances are not all equal in
either complex. In both structures, the Y-Cp C dis-
tances fall into a pattern of two short, two medium, and
one long distance (4a , C4 2.634(4), C5 2.639(4), C1
2.661(4), C3 2.663(4), C2 2.692(4); 11, C1 2.621(4), C5
2.642(4), C2 2.693(4), C4 2.698(4), C3 2.733(4) Å),
although the pattern is clearly more pronounced in 11.
Thus it appears the Cp unit is tipped toward yttrium
along one edge with the carbon opposite that edge being
the furthest away from the metal center. The fact that
the alkyl tether is attached in both structures to one of
the closer carbons suggests that this effect is due to
constraints imposed by the chelate arm. A similar, but
less pronounced, effect was previously noted in {Ti[η5:
It is quite likely that these problems arise due to the
relatively open coordination sphere around yttrium.
While an open coordination sphere is desirable from a
reactivity viewpoint, the small angle spanned by the
CpO ligand is too small to allow isolation of manageable
compounds. To close down the coordination sphere
somewhat, the ligand can be modified by adding bulk
at the Cp or by extending the length of the tether by
one carbon.26,27 Although the former is a time-honored
technique in lanthanide chemistry, our attempts to
modify the ligand by using a substituted Cp have not
met with success because the ring-opening step fails
with anything other than unsubstituted Cp. While work
is still continuing in this direction, the second option
may prove to be a better choice. This is a particularly
interesting option since we have observed some ten-
dency for ligand cleavage to occur between the alkoxide
carbon and the lone CH2 group. Addition of another CH2
between the alkoxide and the Cp ring should help
stabilize the ligand by removing any resonance stabi-
lization effects involved in the ligand cleavage mecha-
nism. Work is underway to assess both of these op-
tions.
η1-C5H4(CH2CH2O)]Cl2}2 and in other systems.4b
26
Discu ssion
Ack n ow led gm en t. The support of the Natural
Sciences and Engineering Research Council of Canada
is gratefully acknowledged.
We were unable to prepare mono(ligand) derivatives
by metathesis reactions between the dilithium salt of
the ligand and an appropriate yttrium precursor (chlo-
ride or alkoxide). Redistribution to the ate complex 4
was unavoidable in all cases studied. It is possible to
isolate mono(ligand) derivatives by direct protonolysis
of a suitable yttrium complex (alkyl or amide derivative)
with ligand 3 because no lithium is present during these
reactions. Once prepared, it is sometimes possible to
convert one mono(ligand) derivative into another by
metathesis, but again, smaller alkyls in particular lead
to redistribution.
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates, bond distances and angles, and anisotropic ther-
mal parameters for 4a and 11. This material is available free
of charge via the Internet at http://pubs.acs.org.
OM0104520
(27) Fandos, R.; Meetsma, A.; Teuben, J . H. Organometallics 1991,
10, 59.