Synthesis, structure, and reactivity of rare-earth metallocene η3-propargyl/allenyl complexes

Article abstract of DOI:10.1021/om800547n

The reaction of the alkyl complexes Cp*₂LnCH(SiMe ₃)₂ (Ln = Y 1-Y, Ce 1-Ce, La 1-La; Cp* = η⁵-C₅Me₅) and Me₂Si(η ⁵-C₅Me₄)₂LnCH(SiMe₃) ₂ (Ln = Ce 5-Ce) with 1-methylalk-2-ynes CH₃C≡CR (R = Me 3a, Et 3b, ⁿPr 3c, ^tBu 3d, SiMe₃ 3e, Ph 3f, C₆H₄Me-2 3g, C₆H₃Me ₂-2,6 3h, C₆H₃ⁱPr₂-2,6 3i, C₆F₅ 3j) affords the corresponding η³-propargyl/allenyl complexes Cp*₂LnCH ₂CCR (4a-j-Ln) and Me₂Si(η⁵-C ₅Me₄)₂CeCH₂CCR (6a-j-Ce) via propargylic metalation. The hydride complexes [Cp*₂Ln(μ-H)] ₂ (Ln = Y 2-Y, Ce 2-Ce, La 2-La) react rapidly with 3 to produce mixtures of insertion and propargylic metalation products, and the relative rate of these processes depends on the metal and alkyne substituent. Selected η³-propargy/allenyl complexes Cp*₂YCH ₂CCR (R = Me 4a-Y, Ph 4f-Y), Cp*₂CeCH₂CCR (R = Me 4a-Ce, Ph 4f-Ce), Cp*₂CeCH(Me)CCEt (9b-Ce), Cp*₂LaCH₂CCR (R = Ph 4f-La, C₆H ₃Me₂-2,6 4h-La) are obtained on a preparative scale and characterized by NMR spectroscopy, IR spectroscopy, and cryoscopy. Compounds 4f-Y and 4f-La are also characterized by single-crystal X-ray diffraction. The reactions of the η³-propargyl/allenyl complexes with Bronsted acids, such as alcohols and acetylenes, afford the corresponding substituted allenes (RCH=C=CH₂) and 1-methylalk-2-ynes (CH ₃C≡CR) as organic products. The reactions of 4f-Y and 4f-La with Lewis bases, such as pyridine and THF, yield die corresponding base adducts. The adduct 4f-La · py is characterized by single-crystal X-ray diffraction, revealing an η³-coordinated propargyl/allenyl ligand.

Full text of DOI:10.1021/om800547n

5672
Organometallics 2008, 27, 5672–5683
Synthesis, Structure, and Reactivity of Rare-Earth Metallocene
η3-Propargyl/Allenyl Complexes
Victor F. Quiroga Norambuena, Andre´ Heeres, Hero J. Heeres, Auke Meetsma,
Jan H. Teuben, and Bart Hessen*
Center for Catalytic Olefin Polymerization, Stratingh Institute for Chemistry and Chemical Engineering,
UniVersity of Groningen, Nijenborgh 4, NL-9747 AG Groningen, The Netherlands
ReceiVed June 12, 2008
The reaction of the alkyl complexes Cp*2LnCH(SiMe3)2 (Ln ) Y 1-Y, Ce 1-Ce, La 1-La; Cp* )
η5-C5Me5) and Me2Si(η5-C5Me4)2LnCH(SiMe3)2 (Ln ) Ce 5-Ce) with 1-methylalk-2-ynes CH3Ct CR
n
t
i
(R ) Me 3a, Et 3b, Pr 3c, Bu 3d, SiMe3 3e, Ph 3f, C6H4Me-2 3g, C6H3Me2-2,6 3h, C6H3 Pr2-2,6 3i,
C6F5 3j) affords the corresponding η3-propargyl/allenyl complexes Cp*2LnCH2CCR (4a-j-Ln) and
Me2Si(η5-C5Me4)2CeCH2CCR (6a-j-Ce) via propargylic metalation. The hydride complexes [Cp*2Ln(µ-
H)]2 (Ln ) Y 2-Y, Ce 2-Ce, La 2-La) react rapidly with 3 to produce mixtures of insertion and propargylic
metalation products, and the relative rate of these processes depends on the metal and alkyne substituent.
Selected η3-propargyl/allenyl complexes Cp*2YCH2CCR (R ) Me 4a-Y, Ph 4f-Y), Cp*2CeCH2CCR (R
) Me 4a-Ce, Ph 4f-Ce), Cp*2CeCH(Me)CCEt (9b-Ce), Cp*2LaCH2CCR (R ) Ph 4f-La, C6H3Me2-2,6
4h-La) are obtained on a preparative scale and characterized by NMR spectroscopy, IR spectroscopy,
and cryoscopy. Compounds 4f-Y and 4f-La are also characterized by single-crystal X-ray diffraction.
The reactions of the η3-propargyl/allenyl complexes with Brønsted acids, such as alcohols and acetylenes,
afford the corresponding substituted allenes (RCHdCdCH2) and 1-methylalk-2-ynes (CH3Ct CR) as
organic products. The reactions of 4f-Y and 4f-La with Lewis bases, such as pyridine and THF, yield
the corresponding base adducts. The adduct 4f-La · py is characterized by single-crystal X-ray diffraction,
revealing an η3-coordinated propargyl/allenyl ligand.
is known about related rare-earth metal compounds.2 In general,
Introduction
η1-allenyl (I) and -propargyl (III) metal complexes (Chart 1)
In contrast to allenyl and propargyl derivatives of transition
metals, alkali metals, and alkaline earth metals,1 relatively little
are known to exhibit interesting structural features and unusual
reactivity.3 An aspect that has received much recent attention
is their tautomeric behavior, as metal η1-propargyls have been
shown to undergo both reversible and irreversible tautomeriza-
tion into metal η1-allenyls. In addition, various well-character-
ized delocalized π-bonded η3-allenyl/propargyl complexes (II)
are known.4
The first reported rare-earth metal allenyl and propargyl
derivatives were made from the reaction of Cp*2LuMe with
allene and 2-butyne, both yielding allenyl products.5 A facile
1,3-metal shift in the propargyl intermediate to yield the
observed allenyl was proposed, but no experimental evidence
was given. A decade later, Heeres et al. reported spectroscopi-
* Corresponding author. E-mail: b.hessen@rug.nl.
(1) (a) Klein, J. In The Chemistry of the Carbon-Carbon Triple Bond;
Patai, S., Ed.; Wiley: New York, 1978; Part 1; Chapter 9, p 343. (b) Moreau,
J. In The Chemistry of Ketenes, Allenes and Related Compounds; Patai, S.,
Ed.; Wiley: New York, 1980; Part 1; p 363. (c) Brandsma, L.; Verkruijsse,
H. D. Synthesis of Acetylenes, Allenes and Cumulenes. A Laboratory
Manual; Elsevier: Amsterdam; 1981. (d) Bielmann, J.-F.; Ducep, J.-B. Org.
React. 1982, 27, 1. (e) Landor, P. D. In The Chemistry of the Allenes;
Landor, R. S., Ed.; Academic Press: London, 1982; p 19. (f) Epsztein, R.
In ComprehensiVe Carbanion Chemistry; Buncel, E., Durst, T., Eds.;
Elsevier: Amsterdam, 1984; Part B; p 107. (g) Schuster, H. F.; Coppola,
G. M. Allenes in Organic Chemistry; Wiley: New York, 1984; Chapter 10.
(h) Yamamoto, H. In ComprehensiVe Organic Synthesis; Trost, B. M.,
Fleming, I., Eds.; Pergamon Press: Oxford, 1991; Vol. 2; p 81. (i) Tsuji, J.;
Mandai, T. Angew. Chem., Int. Ed. Engl. 1995, 34, 2589.
(2) For general reviews of organo rare-earth metal chemistry, see: (a)
Marks, T. J.; Ernst, R. D. In ComprehensiVe Organometallic Chemistry;
Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon Press: Oxford,
U.K., 1982; Chapter 21. (b) Evans, W. J. AdV. Organomet. Chem. 1985,
24, 131–177. (c) Schaverien, C. J. AdV. Organomet. Chem. 1994, 36, 283–
362. (d) Edelmann, F. T. In ComprehensiVe Organometallic Chemistry;
Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon Press: Oxford,
U.K., 1995; Vol. 4,Chapter 2. (e) Schumann, H.; Meese-Marktscheffel, J. A.;
Esser, L. Chem. ReV. 1995, 95, 865–986. (f) Anwander, R.; Herrmann, W. A.
Top. Curr. Chem. 1996, 179, 1. (g) Edelmann, F. T. Top. Curr. Chem.
1996, 179, 247. (h) Molander, G. A. Chemtracts: Org. Chem. 1998, 18,
237–263. (i) Edelmann, F. T. In Metallocenes; Togni, A., Halterman, R. L.,
Eds.; Wiley-VCH: Weinheim, 1998; Vol. 1,Chapter 2. (j) Chirik, P. J.,
Bercaw, J. E. In Metallocenes; Togni, A., Halterman, R. L., Eds.; Wiley-
VCH: Weinheim, 1998; Vol. 1,Chapter 3. (k) Edelmann, F. T.; Freckmann,
D. M. M.; Schumann, H. Chem. ReV. 2002, 102, 1851–1896. (l) Arndt, S.;
Okuda, J. Chem. ReV. 2002, 102, 1953–1976. (m) Shibasaki, M.; Yoshikawa,
N. Chem. ReV. 2002, 102, 2187–2210. (n) Inanaga, J.; Furuno, H.; Hayano,
T. Chem. ReV. 2002, 102, 2211–2226.
(3) For reviews, see: (a) Wojcicki, A.; Shuchart, C. E. Coord. Chem.
ReV. 1990, 105, 35. (b) Welker, M. E. Chem. ReV. 1992, 92, 97. (c) Doherty,
S.; Corrigan, J. F.; Carty, A. J.; Sappa, E. AdV. Organomet. Chem. 1995,
37, 39. (d) Wojcicki, A. New J. Chem. 1994, 18, 61. (e) Chen, J.-T. Coord.
Chem. ReV. 1999, 190-192, 1143. (f) Wojcicki, A. Inorg. Chem. Commun.
2002, 5, 82.
(4) For examples, see: (a) Mo: Krivykh, V. V.; Taits, E. S.; Petrovskii,
P. V.; Struchkov, Y. T.; Yanovski, A. I. MendeleeV Commun. 1991, 103.
(b) Zr: Blosser, P. W.; Gallucci, J. C.; Wojcicki, A J. Am. Chem. Soc. 1993,
115, 2994. (c) Re: Casey, C. P.; Yi, C. S J. Am. Chem. Soc. 1992, 114,
6597. (d) Pt: Huang, T.-M.; Chen, J.-T.; Lee, G. H.; Wang, Y. J. Am. Chem.
Soc. 1993, 115, 1170. (e) Pt: Blosser, P. W.; Schimpff, D. G.; Gallucci,
J. C.; Wojcicki, A Organometallics 1993, 12, 1993. (f) Pt: Stang, P. J.;
Critell, C. M.; Arif, A. M Organometallics 1993, 12, 4799. (g) Pd: Baize,
M. W.; Blosser, P. W.; Plantevin, V.; Schimpff, Gallucci, J. C.; Wojcicki,
A. Organometallics 1996, 15, 164. (h) Zr: Rodriguez, G.; Bazan, G. C.
J. Am. Chem. Soc. 1997, 119, 343.
(5) Watson, P. L. In SelectiVe Hydrogen Carbon ActiVation. Principles
and Progress; Davies, J. A., Watson, P. L., Greenberg, A., Liebman, J. F.,
Eds.; VCH: Weinheim, 1990; Chapter 4, p 78.
10.1021/om800547n CCC: $40.75
2008 American Chemical Society
Publication on Web 10/07/2008

Rare-Earth Metallocene η3-Propargyl/Allenyl Complexes
Organometallics, Vol. 27, No. 21, 2008 5673
Chart 1. Structural Isomerism in Allenyl/Propargyl Metal
Complexes
rare-earth metallocenes toward Lewis bases and Brønsted acids
was also investigated.
Results and Discussion
Reactions with 1-Methyl-alk-2-ynes on NMR Tube
Scale. In this section, the reactions of rare-earth metallocene
alkyl and hydride complexes with 1-methylalk-2-ynes on an
NMR tube scale are described. Isolation and full characterization
of the organometallic products of selected examples are reported
in a following section.
Scheme 1. Catalytic Cyclodimerization of 1-Methylalk-1-ynes
(a) Metallocene Alkyls. The alkyl derivatives
Cp*2LnCH(SiMe3)2 (1) (Ln ) Y 1-Y, Ce 1-Ce, La 1-La) reacted
with equimolar amounts of 1-methylalk-2-ynes CH3CCR (R )
n
t
Me 3a, Et 3b, Pr 3c, Bu 3d, SiMe3 3e, Ph 3f, C6H4Me-2 3g,
i
C6H3Me2-2,6 3h, C6H3 Pr2-2,6 3i, C6F5 3j) to afford the
cally characterized alkyl- and silyl-substituted rare-earth met-
allocene 2-alkynyls Cp*2LnCH2CCR that were implicated as
the active catalyst in the organolanthanide-catalyzed cyclodimer-
ization of alkyl- and silyl-substituted 1-methylalk-2-ynes
CH3CCR (Scheme 1).6 The reactivity of these species remained
unexplored and the exact nature of their bonding was unknown,
as structural data were lacking.
corresponding 2-alkynyl complexes Cp*2LnCH2CCR (4a-j)
and CH2(SiMe3)2, as indicated by in situ NMR spectroscopy
(Scheme 2). A correlation between the rate of proton transfer
and the (kinetic) acidity of the 1-methylalk-2-ynes might be
expected.12 In this study, the rate of propargylic metalation was
found to decrease considerably upon increasing the size of the
alkyne substituent R and decreasing the ionic size of the metal
Ln.13 For example, the reactions of the cerium (1-Ce) and
lanthanum (1-La) derivatives with 2-butyne (3a) were complete
within a few hours at room temperature. The smaller yttrium
derivative 1-Y, on the other hand, was unreactive toward 3a,
even after prolonged heating at 80 °C. The rate of propargylic
metalation could be increased by employing a large molar excess
of substrate, but then propargylic metalation was accompanied
by competing catalytic cyclodimerization of the substrate for
the reactions of 1-Ce and 1-La with less sterically encumbered
1-methylalk-2-ynes. No reaction was observed for 1-Ce and
1-La with the more crowded internal alkyne 3-hexyne (7b), even
after prolonged heating at 50 °C. Nevertheless, for the analogous
reactions of 1-Ce and 1-La with 2-pentyne (3b) and 2-hexyne
(3c), respectively, complete conversion of 1-Ce and 1-La into
the corresponding 2-alkynyl derivatives was observed after 15
days at 50 °C. As alkyl groups do not differ significantly in
their electronic substituent effects, these reactions appear to be
under steric control.14
Since then, only three studies involving well-defined allenyl/
propargyl rare-earth metal complexes have appeared in literature,
including the spectroscopically characterized yttrium η1-allenyl
species A, which is reported to be in a rapid equilibrium with
its η1-propargyl isomer A′,7 some structurally characterized η3-
propargyl samarium half-sandwich complexes (e.g., B), incor-
porating a chelating allenyl/propargyl ligand system,8 and a
divalent ytterbium η3-propargyl (C), which was also structurally
characterized (Chart 2).9 The only other reports regarding
propargyl and/or allenyl rare-earth metal complexes involve
proposed reactive intermediates in metal-mediated organic
synthesis, prepared in situ by transmetalation reactions of rare-
earth metal salts with organopalladium intermediates10 or
Grignard reagents.11
A study on the synthesis, structure, and reactivity of these
complexes was initiated to elucidate the nature of the bonding
in 2-alkynyl rare-earth metallocenes and investigate their reactive
chemistry.ThereactionsofCp*2LnCH(SiMe3)2(1)and[Cp*2Ln(µ-
H)]2 (2) with several 1-methylalk-1-ynes (3) were probed as
routes toward Lewis-base-free 2-alkynyl rare-earth metal com-
plexes Cp*2LnCH2CCR (4). The effects of the metal, ancillary
ligand, and alkyne substituent on the rate and selectivity of these
reactions are discussed, as well as the structure of the resulting
2-alkynyl rare-earth metal complexes. The reactivity of 2-alkynyl
Reactions of the ansa-metallocene alkyl Me2Si(η5-
C5Me4)2CeCH(SiMe3)2 (5-Ce) with 1-methylalk-2-ynes 3a-j
were conducted in order to investigate the effect of opening
(12) A Hammett plot with a reaction constant F of 1.3 was found for
the propargylic metalation of substituted 1-phenyl-1-propynes by n-BuLi,
indicating that this reaction is only mildly accelerated by electron-
withdrawing substituents; see: Becker, J. Y. J. Organomet. Chem. 1976,
118, 247.
(6) (a) Heeres, H. J.; Heeres, A.; Teuben, J. H. Organometallics 1990,
9, 1508. (b) Heeres, H. J. Ph.D. Thesis, University of Groningen,
1990,Chapter 5.
(13) Ionic radii for eight-coordinate complexes: La3+ (1.160 Å), Ce3+
(1.143 Å), and Y3+, see: Shannon, R. D Acta Crystallogr., Sect. A 1976,
A32, 751.
(7) Hajela, S.; Schaefer, W. P.; Bercaw, J. E. J. Organomet. Chem. 1997,
532, 45.
(8) Ihara, E.; Tanaka, M.; Yasuda, H.; Kanehisa, N.; Maruo, T.; Kai,
Y. J. Organomet. Chem. 2000, 613, 26.
(9) Ferrence, G. M.; McDonald, R.; Takats, J. Angew. Chem., Int. Ed.
1999, 38, 2233.
(10) For examples, see: (a) Tabuchi, T.; Inanag, J.; Yamaguchi, M.
Tetrahedron Lett. 1986, 27, 5237. (b) Tabuchi, T.; Inanag, J.; Yamaguchi,
M. Chem. Lett. 1987, 2275. (c) Makioka, Y.; Koyama, K.; Nishiyama, T.;
Takaki, K.; Taniguchi, Y.; Fujiwara, Y. Tetrahedron Lett. 1995, 36, 6283.
(d) Mikami, K.; Yoshida, A.; Matsumoto, S.; Feng, F.; Matsumoto, Y.;
Sugino, A.; Hanamoto, T.; Inanag, J. Tetrahedron Lett. 1995, 36, 907. (e)
Makioka, Y.; Saiki, A.; Takaki, K.; Taniguchi, Y.; Kitamura, T.; Fujiwara,
Y. Chem. Lett. 1997, 27.
(14) (a) Hansch, C.; Leo, A.; Taft, R. W. Chem. ReV. 1991, 91, 165.
(b) Isaacs, N. S. Physical Organic Chemistry, 2nd ed.; Longman: Essex,
1996. (c) Charton, M. Prog. Phys. Org. Chem. 1981, 13, 119.
(15) Many examples exist in the literature, demonstrating that the rates
of insertion and σ-bond metathesis are greatly influenced upon linking the
cyclopentadienyl ligands by a Me2Si group; see:(a) Hajela, S.; Bercaw, J. E.
Organometallics 1994, 13, 1147. (b) Jeske, G.; Schock, L. E.; Swepston,
P. N.; Schumann, H.; Marks, T. J. J. Am. Chem. Soc. 1985, 107, 8103. (c)
Jeske, G.; Lauke, H.; Mauermann, H.; Schumann, H.; Marks, T. J. J. Am.
Chem. Soc. 1985, 107, 8111. (d) Gagne´, M. R.; Marks, T. J. J. Am. Chem.
Soc. 1989, 111, 4108. (e) Giardello, M. A.; Conticello, V. P.; Brard, L.;
Gagne´, M. R.; Marks, T. J. J. Am. Chem. Soc. 1994, 116, 10241. (f) Shin,
J. H.; Parkin, G. Chem. Commun. 1999, 887. (g) Fendrick, C. M.; Schertz,
L. D.; Day, V. W.; Marks, T. J. Organometallics 1988, 7, 1828. (h) Dash,
A. K.; Gourevich, I.; Wang, J. Q.; Wang, J.; Kapon, M.; Eisen, M. S.
Organometallics 2001, 20, 5084. (i) Fontaine, F. G.; Tilley, D. T.
Organometallics 2005, 24, 4340.
(11) (a) Eckenberg, P.; Groth, U.; Kohler, T. Liebigs Ann. Chem. 1994,
673. (b) Ruan, R.; Zhang, J.; Zhou, X.; Cai, R. Chem. Commun. 2002,
538.

5674 Organometallics, Vol. 27, No. 21, 2008
Chart 2. Examples of Rare-Earth Metal Propargyl and Allenyl Species
Quiroga Norambuena et al.
Scheme 2. Reactions of the Alkyl Derivatives 1 and 5 with 1-Methylalk-2-ynes CH3CCR (3a-j) Affording the 2-Alkynyl
Derivatives 4a-j and 6a-j, Respectively
the metal coordination sphere at the σ-ligand equatorial girdle.15
Although the scope of the propargylic metalation of 5-Ce toward
3a-j was similar to that of 1-Ce and 1-La, the solubility of the
formed 2-alkynyl derivatives was very low. For example,
the addition of excess 2-butyne (3a) to 5-Ce resulted in the
quantitative formation of CH2(SiMe3)2 and the deposition of
orange crystalline [Me2Si(η5-C5Me4)2CeCH2CCMe]n (6a-Ce),
suggesting the formation of an oligomeric product. Unfortu-
nately, the quality of the crystals was insufficient for single-
crystal X-ray diffraction. Further heating of the reaction mixture
led to catalytic cyclodimerization of 3a at a reaction rate
comparable to the same reaction catalyzed by Cp*2LaCH2CCMe
(4a-La).6
(b) Metallocene Hydrides. In general, the hydride derivatives
[Cp*2Ln(µ-H)]2 (2) react rapidly with aliphatic and aromatic
1-methylalk-2-ynes to yield complex, time-dependent reaction
mixtures. Reaction mixtures contained significant amounts of
cis-alkenes in most cases and the relative amount of the cis-
alkene depended on the metal and the alkyne substituent.16 The
reactions of 2-Y with 3a-j were generally less selective for
the formation of the corresponding 2-alkynyl derivative than
those of 2-Ce and 2-La. Also, the composition of the reaction
mixtures with 2-Y did not change in time, contrary to reactions
with 2-Ce and 2-La.17 The reactions of 2 with 1-pentafluo-
rophenyl-1-propyne (3j) were more complicated, as product
analysis indicated that multiple nonselective insertions of the
alkyne take place.18
reaction mixtures could not be identified unambiguously,
quenching experiments with methanol-d4 afforded cis-1-phenyl-
1-propene-d1, suggestive of the presence of Cp*2LnC-
(Ph)dC(Me)H (8fa) and Cp*2LnC(Me)dC(Ph)H (8af).
These results can be rationalized by three separate pathways
by which a monomeric hydride derivative Cp*2LnH reacts with
3f (Scheme 3).19 Analogous to the above alkyls, Cp*2LnH may
react with 3f via propargylic C-H activation, forming
Cp*2LnCH2CCPh (4f-Ln) and dihydrogen. The formation of
2-La from the reaction of 4f-La with excess dihydrogen suggests
that propargylic C-H activation by Cp*2LaH is reversible.20
Contrary to the above alkyls, however, insertion of Cp*2LnH
into the carbon-carbon triple bond of 3f may also take place:
1,2- and 2,1-insertion give rise to the 1-phenylprop-1-en-2-yl
8fa and the 1-phenylprop-1-en-1-yl 8af derivative, respectively.
This process is exemplified by the reaction of [Cp*2La(µ-H)]2
(2-La) with diphenylethyne, producing the alkenyl derivative
Cp*2LaC(Ph)dC(Ph)H (8ff-La) in high isolated yield. The
reaction of 8af and 8fa with 3f yields 4f-Ln and cis-1-
phenylprop-1-ene. Evidence for this process is provided by the
reaction of 8ff-La with 3f, producing 4f-La and cis-diphe-
nylethene. Other routes to the formation of cis-1-phenylprop-
1-ene are plausibly the reactions of 8af and 8fa with dihydrogen,
formed from propargylic C-H activation of 3f by Cp*2LaH.
Preparative Scale Reactions. The yellow Cp*2YCH2CCMe
(4a-Y) and orange Cp*2YCH2CCPh (4f-Y) yttrium derivatives,
the green cerium compounds Cp*2CeCH2CCMe (4a-Ce),
Cp*2CeCH2CCPh (4f-Ce), and Cp*2CeCH(Me)CCEt (9b-Ce),
and the red lanthanum compounds Cp*2LaCH2CCPh (4f-La)
and Cp*2LaCH2CCC6H3Me2-2,6 (4h-La) were obtained as
crystalline materials by addition of excess 1-methylalk-2-yne
to pentane suspensions of the corresponding hydrides and
subsequent crystallization by cooling. The isolated yields of the
NMR tube reactions of the hydride derivatives [Cp*2Ln(µ-
H)]2 (2) (Ln ) Y 2-Y, Ce 2-Ce, La 2-La) with molar excesses
of 1-phenyl-1-propyne (3f) produced mixtures that appear to
contain three metallocene species, one of them being
Cp*2LnCH2CCPh (4f), and cis-1-phenyl-1-propene. The con-
centration of 4f and cis-1-phenylprop-1-ene gradually increased
over time. Even though the two additional metallocenes in these
(19) Ample evidence exists in the literature that hydride derivatives of
rare-earth metallocenes [Cp*2Ln(µ-H)]2 (2-Ln) are present in solution as
an equilibrium mixture of dimer and monomer. Dissociation of the dimer
[Cp*2Y(µ-H)]2 to the monomer Cp*2YH in reactions of [Cp*2Y(µ-H)]2 with
alkenes has been studied in detail; see: Casey, C. P.; Tunge, J. A.; Lee,
T.-Y.; Carpenetti, D. W., III. Organometallics 2002, 21, 389.
(20) The reversible nature of propargylic metalation was demonstrated
by the reaction of Cp*2LaCH2CCPh (4f-La) with excess dihydrogen (1 atm).
4f-La was consumed within several hours, giving rise to n-propylbenzene
and [Cp*2La(µ-H)2] (2-La) over the course of 1 day at room temperature.
(16) See the Supporting Information.
(17) These results are in accordance with the much lower hydrogenation
activity of alkenes by 2-Y relative to 2-La and 2-Ce; see: Jeske, G.; Lauke,
H.; Mauermann, H.; Schumann, H.; Marks, T. J. J. Am. Chem. Soc. 1985,
107, 8111.
(18) GC/GC-MS and NMR analyses indicate the presence of 1-(pen-
tafluorophenyl)prop-1-ene-d1 and 2,4-bis(pentafluorophenyl)-3-methylhexa-
2,4-diene-d1 after deuterolysis, pointing to mono- and double-insertion
products.16

Rare-Earth Metallocene η3-Propargyl/Allenyl Complexes
Organometallics, Vol. 27, No. 21, 2008 5675
Scheme 3. Proposed Reaction Sequences for the Reaction of the Hydride Derivatives [Cp*2Ln(µ-H)]2 (2) with
1-Phenyl-1-propyne (3f)
Scheme 4. Reactions of 4f-Y and 4f-La with THF and
Pyridine
alkyl-substituted derivatives were relatively low, due to the high
solubility of the compounds in both aliphatic and aromatic
solvents. Molecular weight determinations (cryoscopy in ben-
zene) showed that 4a-Y, 4f-Y, 4a-Ce, 4f-La, and 9b-Ce are
monomeric in solution.
The phenyl-substituted 2-alkynyl derivatives Cp*2LnCH2-
CCPh (4f) could be prepared in high isolated yields by
performing the reaction of the hydride 2 with 1-phenyl-1-
propyne (3f) while removing the H2 formed by the reaction by
repeated brief evacuations. A more convenient preparative
method involves the in situ formation of the hydride 2 from
the alkyl 1. This is achieved by replacing the nitrogen
atmosphere of a pentane solution of 1 by hydrogen (1 atm),
subsequent stirring for 12 h at 0 °C, replacing the hydrogen
atmosphere again by nitrogen, and addition of alkyne. A
crystalline solid was obtained after complete in Vacuo removal
of the organic compounds in the crude product mixture (e.g.,
cis-1-phenylprop-1-ene, CH2(SiMe3)2, unreacted 3f).
electrophilic metal center. On the basis of the upfield shift of
the propargylic CH2 carbon resonance vs 4f-La (∆δ -1.37 ppm)
and the similarity of the NMR spectral parameters with the
crystallographically characterized pyridine adduct Cp*2La(η3-
CH2CCPh) · C5H5N (Vide infra), an η3-propargyl/allenyl struc-
ture is favored for Cp*2LaCH2CCPh · C4H8O (4f-La · THF).
(b) Pyridine. A clean and quantitative reaction was also
observed for the reaction of Cp*2LaCH2CCPh (4f-La) with an
equimolar amount of pyridine (Scheme 4) with in situ 1H NMR
spectroscopy. The formation of the corresponding adduct (4f-
La · py) is indicated by the upfield shifts of the pyridine proton
(∆δ -0.12, -0.17, and -0.19 ppm for R-, ꢀ-, and γ-CH,
respectively) and carbon resonances (∆δ -0.55, -0.30, and
+1.77 ppm for R-, ꢀ-, and γ-CH, respectively) upon metal
coordination. The changes of the 1H and 13C NMR resonances
of 4f-La are similar to those observed previously for 4f-
La · THF. A single-crystal X-ray analysis study of 4f-La · py
established unambiguously that the bonding of the propargyl/
allenyl ligand in 4f-La · py is trihapto (Vide infra).
The reaction of Cp*2YCH2CCPh (4f-Y) with pyridine was
studied to investigate the effect of metal size on the bonding
mode of the η3-propargyl/allenyl ligand upon Lewis base
coordination. NMR spectroscopy indicated that the addition of
pyridine (1 equiv) to 4f-Y led to the rapid and clean formation
of the corresponding Lewis base adduct 4f-Y · py. The Lewis
base adduct Cp*2YCH2CCPh · C5H5N (4f-Y · py) was isolated
in reasonable yield (63%) as an off-white thermolabile solid.
The increased thermolability of 4f-Y · py as compared to 4f-
La · py may be explained by an increased nucleophilic character
of the propargyl methylene group in the former due to a stonger
distortion of the η3-bonding of the propargyl/allenyl ligand upon
coordination of pyridine to the smaller metal. This increased
nucleophilicity could induce reactivity with the coordinated
The putative oligomeric 2-butynyl compound [Me2Si(η5-
C5Me4)2CeCH2CCMe]n (6a-Ce) was synthesized by addition
of excess 2-butyne (3a) to a benzene solution of Me2Si(η5-
C5Me4)2CeCH(SiMe3)2 (5-Ce). Its low solubility impeded the
use of NMR spectroscopy and cryoscopy, but elemental analysis,
infrared spectroscopy, and its reactivity with 2,6-di-tert-butyl-
4-methylphenol confirmed its identity (Vide infra).21
Reactivity toward Lewis Bases. (a) Tetrahydrofuran. The
reaction of Cp*2LaCH2CCPh (4f-La) with an equimolar amount
of tetrahydrofuran (THF) in benzene-d6 revealed a rapid and
clean reaction without color change, as indicated by in situ 1H
NMR spectroscopy (Scheme 4).16 The upfield shifts of the THF
1H and 13C NMR resonances versus free THF (e.g., ∆δ -0.55
and -0.04 ppm for the R- and ꢀ-carbon, respectively, in the
13C NMR spectrum) are consistent with the coordination to the
(21) Attempts to dissolve [Me2Si(η5-C5Me4)2CeCH2CCMe]n (6a-Ce) in
THF-d8 resulted in the formation of free 2-butyne and several broad
resonances in the-25 to 15 ppm range of the 1H NMR spectrum. C-O
bond activation of THF-d8 and the formation of a ring-bridged µ-oxo
compound, [Me2Si(η5-C5Me4)2Ce(THF)]2(µ-O), is well-possible; see: Booij,
M. Ph.D. Thesis 1989, University of Groningen, Chapter 2.
(22) (a) Watson, P. L. J. Chem. Soc., Chem. Commun. 1983, 276. (b)
Thompson, M. E.; Baxter, S. M.; Bulls, A. R.; Burger, B. J.; Nolan, M. C.;
Santarsiero, B. D.; Schaefer, W. P.; Bercaw, J. E. J. Am. Chem. Soc. 1987,
109, 203. (c) Thompson, M. E.; Bercaw, J. E. Pure Appl. Chem. 1984,
105, 6491. (d) Duchateau, R.; van Wee, C. T.; Teuben, J. H. Organome-
tallics 1996, 15, 2291. (e) Ringelberg, S. N. Ph.D. Thesis, University of
Groningen, 2001. (f) Arndt, S.; Elvidge, B. R.; Zeimentz, P. M.; Spaniol,
T. P.; Okuda, J. Organometallics 2007, 25, 793. (g) Jantunen, K. C.; Scott,
B. L.; Gordon, J. L.; Kiplinger, J. L. Organometallics 2007, 26, 2777.

5676 Organometallics, Vol. 27, No. 21, 2008
Quiroga Norambuena et al.
arrangement of the metal center with the η3-propargyl/allenyl
carbon backbone is seen (atom displacements from the least-
squares plane relative to 4f-La · py: La ∆ +0.002, C26 ∆
+0.010, C27 ∆ +0.018, C28 ∆ +0.010 Å). An apparent shift
toward a more propargyl-like structure is also observed, as
evidenced by the increased distances between lanthanum and
the terminal carbon (∆ 0.08(1) Å).
Spectroscopic Characterization. (a) NMR Spectroscopy.
Selected 1H and 13C NMR resonances of several
Cp*2LnCH2CCR complexes are shown in Table 2. The dia-
magnetic yttrium and lanthanum Cp*2LnCH2CCR complexes
1
exhibit equivalent Cp* and CH2 resonances in the H and 13C
1
NMR spectrum. No H and 13C NMR resonances attributable
to distinct η1-propargyl and η1-allenyl forms of Cp*2YCH2CCPh
(4f-Y), Cp*2LaCH2CCPh (4f-La), and Cp*2LaCCC6H3Me2-2,6
(4h-La) were observed at temperatures down to -80 °C. These
observations, together with the solid-state structures of 4f-La
and 4f-Y, suggest that the Cp*2LnCH2CCR compounds have a
static η3-propargyl structure and do not exist as a rapid
equilibrium mixture of distinct η1-propargyl and η1-allenyl
species in solution, but additional experiments would be needed
to settle this issue more rigorously. The NMR data of the present
rare-earth metal complexes compare well with those of reported
(phenyl-substituted) allenyl and propargyl transition metal
complexes3,4 and are consistent with an η3-allenyl/propargyl
structure.14,25
Figure 1. Thermal ellipsoid plot of Cp*2LaCH2CCPh (4f-La)
(drawn at a 50% probability level). Hydrogen atoms are omitted
for clarity.
pyridine ligand, as is observed frequently for rare-earth metal
alkyl and hydride species.22 Attempts to obtain single crystals
of 4f-Y · py suitable for X-ray analysis failed. Freshly prepared
4f-Y · py turned dark red within hours upon standing at room
temperature, and the decomposition products defied unambigu-
ous characterization.
X-ray Crystal Structures of Cp*2YCH2CCPh (4f-Y),
Cp*2LaCCPh (4f-La), and Cp*2LaCH2CCPh · py (4f-La · py).
The geometries of the bent metallocene fragments in 4f-Y, 4f-
La, and 4f-La · py are similar to that in other lanthanum23 and
lanthanide metallocenes.24 However, the Cp* ligands are in the
less common eclipsed conformation in 4f-La · py. The molecular
structure of 4f-La is shown in Figure 1, and selected bond
distances and angles for 4f-Y and 4f-La are given in Table 1.
The phenyl-substituted propargyl/allenyl ligands are clearly
bound in an η3-mode.3 The backbone of the η3-propargyl/allenyl
ligands is virtually coplanar with the metal center (e.g., atom
displacements from the least-squares plane: La 0.000, C21 0.001,
C22 0.003, C23 0.002 Å for 4f-La). This structural feature is
believed to be typical of η3-propargyl/allenyl complexes.3d-f
The crystallographic C21-C22 and C22-C23 bond distances
of 1.36(1) and 1.23(1) Å, respectively, are intermediate between
those generally accepted for C-C single (1.45 Å) and double
(1.31 Å) and double and triple (1.20 Å) bonds, respectively,
and the C3 ligand backbone is thus consistent with resonance
between propargyl and allenyl structures. The bond angles
C21-C22-C23 of 156° and 159° for 4f-Y and 4f-La, respec-
tively, indicate a considerable deviation from linearity at the
central carbon atom, which is typical for η3-propargyl/allenyl
complexes.3d-f
Although the chemical shifts of the CH2 propargyl carbon
resonances (C-1, δ 42-56 ppm) of the Cp*2LnCH2CCR
complexes are in the range of metal-bound sp3 carbons in rare-
earth metallocenes, such as Cp*2Y(CH2C6H3Me2-3,5)26 (δ 47.35
ppm, 1JCH ) 133.4 Hz) and Cp*2LaCH(SiMe3)227 (δ 44.64 ppm,
1JCH ) 93.0 Hz), the corresponding first-order carbon-hydrogen
1
coupling constants JCH (156.7-162.5 Hz) are significantly
larger. These unusually large 1JCH values suggest that the C-H
bonds of the propargylic carbon have considerably more s
character and are close to that of an sp2 carbon (typically 156
Hz).28
Yttrium-89 has a nucleus with I ) 1/2 in a natural abundance
of 100%, and coupling interactions in Cp*2YCH2CCR (R )
Me 4a-Y, Ph 4f-Y) are observed with the propargyl (C-1) and
terminal carbon atom (C-3) of the CH2CCR ligand (Table 2).
The absence of an observable JYC on the central carbon (C-2)
of CH2CCR is in agreement with the nature of metal η3-
(25) Extensive studies in organolithium chemistry have shown that the
central carbon (C-2, δ 165-180 ppm for allenyl) and the propargyl carbon
(C-1, δ 90-100 ppm) are very sensitive indicators of allenylic and
propargylic structures. For examples, see:(a) Reich, H. J.; Holladay, J. E.
Angew. Chem., Int. Ed. Engl. 1996, 35, 2365. (b) Reich, H. J.; Thompson,
J. L. Org. Lett. 2000, 2, 783. (c) Reich, H. J.; Holladay, J. E.; Walker,
T. G.; Thompson, J. L. J. Am. Chem. Soc. 1999, 121, 9769. (d) Reich,
H. J.; Holladay, J. E.; Mason, J. D.; Sikorsko, W. H. J. Am. Chem. Soc.
1995, 117, 12137. (e) Reich, H. J.; Holladay, J. E. J. Am. Chem. Soc. 1995,
117, 8470. (f) Lambert, C.; von Rague´ Schleyer, P.; Wu¨rthwein, E.-U. J.
Org. Chem. 1993, 58, 6377.
The solid-state molecular structure of 4f-La · py is depicted
in Figure 2, and selected bond distances and angles are given
in Table 1. It is interesting to note that pyridine coordinates at
the more substituted side of the η3-propargyl/allenyl ligand,
suggesting that the coordination of Lewis bases is controlled
by electronic factors rather than steric factors. The solid-state
structures of 4f and 4f-La · py reveal several changes upon
pyridine coordination. First, a slight distortion of the coplanar
(26) den Haan, K. H. Ph.D. Thesis, University of Groningen, 1986,
Chapter 6.
(27) Booij, M. Ph.D. Thesis, University of Groningen, 1989, Chapter
7.
(23) (a) Heeres, H. J.; Meetsma, A.; Teuben, J. H. Angew. Chem., Int.
Ed. Engl. 1990, 29, 420. (b) Scholz, A.; Smola, A.; Scholz, J.; Loebel, J.;
Schumann, H.; Thiele, K.-H. Angew. Chem., Int. Ed. Engl. 1991, 30, 435.
(c) Gagne´, M. R.; Stern, C. L.; Marks, T. J. J. Am. Chem. Soc. 1992, 114,
275. (d) Thiele, K.-H.; Bambirra, S.; Sieler, J. Angew. Chem., Int. Ed. 1998,
37, 2886. (e) Evans, W. J.; Davis, B. L.; Nyce, G. W.; Perotti, J. M.; Ziller,
J. W. J. Organomet. Chem. 2003, 677, 89.
(28) Such an unambiguous interpretation is complicated by the fact that
1
inductive/field effects originating from polar substituents influence JCH
values to such an extent that the 1JCH values mostly do not reflect the true
hybridization state of the carbon; see: (a) Kalinowski, H.-O.; Berger, S.;
Braun, S. Carbon-13 NMR Spectroscopy; Wiley: Chichester, 1991; Chapter
4. (b) Friebolin, H. Basic One- and Two-Dimensional NMR Spectroscopy;
Wiley-VCH: Weinheim, 1998; Chapter 3.3; p 97.
(24) Evans, W. J.; Foster, S. E. J. Organomet. Chem. 1992, 433, 79.

Rare-Earth Metallocene η3-Propargyl/Allenyl Complexes
Organometallics, Vol. 27, No. 21, 2008 5677
Table 1. Selected Bond Lengths (Å) and Angles (deg) in Cp*2LnCH2CCPh (Ln ) Y 4f-Y, La 4f-La) and Cp*2LaCH2CCPh(C5H5N) (4f-La · py)a
4f-Y
4f-La
4f-La · py
Bond Lengths
C21-C22
C22-C23
C23-C24
Y-C21
1.366(4)
1.268(4)
1.462(4)
2.653(3)
2.529(3)
2.560(3)
2.654(4)
2.652(4)
2.362(3)
2.362(3)
C21-C22
C22-C23
C23-C24
La-C21
La-C22
La-C23
1.362(10)
1.234(10)
1.465(9)
2.811(6)
2.695(7)
2.740(7)
2.806(16)
2.780(16)
2.535(3)
2.509(4)
C26-C27
C27-C28
C28-C29
La-C26
1.356(4)
1.248(4)
1.454(4)
2.822(3)
2.726(3)
2.823(3)
2.841(7)
2.852(7)
2.571
Y-C22
La-C27
Y-C23
av Y-C(Cp*)
La-C28
av La-C(Cp*)
av La-C(Cp*)
La-Ct1
av La-C(Cp*)
av La-C(Cp*)
La-Ct1
Y-Ct1
Y-Ct2
La-Ct2
La-Ct2
La-N
2.584
2.743(2)
Bond Angles
Ct1-Y-Ct2
139.3(1)
Ct1-La-Ct2
137.1(1)
Ct1-La-Ct2
134.2
C21-C22-C23
C22-C23-C24
Y-C21-C22
Y-C23-C22
155.9(3)
141.5(3)
70.2(2)
74.7(2)
C21-C22-C23
C22-C23-C24
La-C21-C22
La-C23-C22
159.3(7)
141.2(7)
71.0(4)
74.9(4)
C26-C27-C28
C27-C28-C29
La-C26-C27
La-C28-C27
161.0(3)
142.8(3)
71.9(2)
72.7(2)
a Cp*1 ) C1-C5, Cp*2 ) C11-C15, Ct ) centroid.
relations are not evident.33 Nonetheless, practically all protons
are observable in the 1H NMR spectra, exhibiting correct
integrated intensities.14 Noteworthy are the strongly high-field
shifted R-carbon protons of Cp*2CeCH2CCMe (4a-Ce) and
Cp*2CeCH2CCPh (4f-Ce), at δ -30.5 (lw ) 38 Hz, lw ) line
width of the resonances at half-maximum) and δ -35.4 ppm
(lw ) 78 Hz), respectively. The R-proton of Cp*2CeCH(Me)-
CCEt (9b-Ce) is found at δ -11.2 ppm (lw ) 43 Hz). The
NMR data for 9b-Ce clearly demonstrate that the R-carbon is
asymmetric, resulting in diastereotopic CH2 protons and in-
equivalent Cp* rings.
The 1H and 13C NMR resonances of 4f-La shift in a similar
fashion upon coordination of pyridine or THF. The upfield shift
of the propargylic CH2 carbon resonance and the increase in
its corresponding first-order carbon, hydrogen coupling constant
(1JCH) suggest an increase in propargylic character of the η3-
CH2CCPh ligand in 4f-La · py and 4f-La · THF relative to 4f-
La (Table 2). The upfield shifts of the CH2CC carbon resonances
upon coordination of pyridine are larger for 4f-Y · py than for
4f-La · py, suggesting that the shift toward more propargylic
character of the CH2CCPh ligand in Cp*2LnCH2CCPh · py is
influenced by steric factors. IR spectroscopy also points to a
substantial increase of propargylic character in 4f-Y upon
coordination of pyridine (Vide infra), but the overall η3-
coordination of the CH2CCPh ligand in 4f-Y · py is clearly
indicated by the coupling between yttrium and the propargyl
and terminal carbon atoms.
Figure 2. Molecular structure of 4f-La · py with thermal ellipsoids
drawn at the 50% probability level. The hydrogen atoms are omitted
for clarity.
CH2CCR bonding.29 The yttrium-carbon couplings of the
propargyl carbon CH2 (8.1 Hz for 4a-Y and 5.2 Hz for 4f-Y)
are notably smaller than those of yttrocene-bound sp3 carbons,
such as Cp*2Y(CH2C6H3Me2-3,5)30 (1JYC ) 23.2 Hz) and
31
Cp*2YCH(SiMe3)2 (1JYC ) 36.6 Hz), but are comparable to
those of the terminal carbons of the allyl group in Cp*2Y(η3-
C3H5)32 (1JYC ) 3.8 Hz).
(b) Infrared Spectroscopy. Infrared spectroscopy has been
widely used as a diagnostic tool in determining the relative
contribution of allenylic and propargylic structures.1 In the
1890-2000 cm-1 region of the infrared spectrum, strong and
medium absorptions were observed for the present
The NMR spectra of the paramagnetic cerium compounds
show strongly shifted and broadened resonances. Proton-proton
coupling cannot be observed in most cases, and shift-structure
(29) According to several molecular orbital studies, the η3-CH2CCR
ligand binds mainly through its terminal carbons, while the π-bond of the
carbon-carbon triple bond does not interact significantly with the metal
fragment. For examples, see:(a) Jemmis, E. D.; Chandrasekhar, J.; von
Rague´ Schleyer, P. J. Am. Chem. Soc. 1979, 101, 2848. (b) Carfagna, C.;
Deeth, R. J.; Green, M.; Mahon, M. F.; McInnes, J. M.; Pellegrini, S.;
Woolhouse, C. B. J. Chem. Soc., Dalton Trans. 1995, 3975. (c) Graham,
J. P.; Wojcicki, A.; Bursten, B. E. Organometallics 1999, 18, 837.
(30) (a) den Haan, K. H. Ph.D. Thesis, University of Groningen,
1986,Chapter 6. (b) den Haan, K. H.; Wielstra, Y.; Teuben, J. H.
Organometallics 1987, 6, 2053.
(31) den Haan, K. H.; de Boer, J. L.; Teuben, J. H. Organometallics
1986, 5, 1726.
(32) Evans, W. J.; Kozimor, S. A.; Brady, J. C.; Davis, B. L.; Nyce,
G. W.; Seibel, C. A.; Ziller, J. W.; Doedens, R. J. Organometallics 2005,
24, 2269.
(33) (a) Evans, W. J.; Meadows, J. M.; Kosta, A. G.; Gloss, G. L.
Organometallics 1985, 4, 324. (b) Fischer, R. D. Fundamental and
Technological Aspects of Organo-f-Element Chemistry; T. J. Marks, I. L.
Fragala, Eds.; D. Reidel: Dordrecht, 1985; p 277. (c) Evans, W. J.; Hozbor,
M. A. J. Organomet. Chem. 1987, 326, 299.
(34) Infrared absorptions at 1850-1900 cm-1 are assigned to allenyl
structures and those >2000 cm-1 to propargyl structures in organolithium
chemistry; see:(a) Jaffe, F. J. Organomet. Chem. 1970, 23, 53–62. (b)
Priester, W.; West, R.; Chwang, T. L. J. Am. Chem. Soc. 1976, 98, 8413.
(c) West, R.; Jones, P. C. J. Am. Chem. Soc. 1969, 91, 6156. (d) Klein, J.;
Becker, J. Y. J. Chem. Soc., Chem. Commun. 1973, 576. For examples of
organozinc and -magnesium compounds, see: (e) ref 1b. For examples of
organotitanium compounds, see: (f) Ishiguro, M.; Ikeda, N.; Yamamoto,
H. J. Org. Chem. 1982, 47, 2225. (g) Furuta, K.; Ishiguro, M.; Haruta, R.;
Ikeda, N.; Yamamoto, H. Bull. Chem. Soc. Jpn. 1984, 57, 2768.

5678 Organometallics, Vol. 27, No. 21, 2008
Quiroga Norambuena et al.
Table 2. NMR Data for Selected Cp*2LnCH2CCR Complexesa
entry
Cp*2LnCH2CCR
CH2
C-1 (1JCH
,
1JYC
)
C-2
C-3 (1JYC
)
1
2
3
4
5
6
7
8
9
Cp*2YCH2CCMe (4a-Y)
Cp*2YCH2CCPh (4f-Y)
Cp*2YCH2CCPh · C5H5N (4f-Y · py)
Cp*2LaCH2CCMe (4a-La)
2.16
2.82
2.71
2.30
2.82
2.95
3.16
2.71
2.68
3.08
42.0 (154, 8.1)
137.3
155.1
151.6
139.7
152.2
n.o.
152.2
149.3
145.6
165.2
94.9 (8.0)
106.8 (11.9)
104.9
102.5
112.8
n.o.
n.o.
105.8
100.3
49.3 (159.1, 5.2)
47.2 (157.2, 7.7)
50.9 (155)
54.0 (158.3)
52.6 (n.d.)
51.1 (159.5)
49.0 (156.9)
47.7 (156.7)
55.8 (162.5)
Cp*2LaCH2CCPh (4f-La)
Cp*2LaCH2CCPh · C4H8O (4f-La · THF)
Cp*2LaCH2CCPh · C5H5N (4f-La · py)
Cp*2LaCH2CCC6H3Me2-2,6 (4h-La)
i
Cp*2LaCH2CCC6H3 Pr2-2,6 (4i-La)
10
Cp*2LaCH2CCC6F5 (4j-La)
108.8
a NMR measurements in C6D6 at 25 °C under a nitrogen atmosphere. The chemical shifts are reported in ppm and the coupling constants in Hz. n.d.
) not determined, n.o. ) not observed.
Scheme 5. Hybridization of the Terminal Carbon Atoms in
the Limiting Structures of the Prop-2-ynyl/Allenyl Anion
Scheme 6. Reaction of Cp*2Ln(η3-CH2CCR) with Methanol-d4
to Produce Acetylenic and Allenylic Protonolysis Products
131.4) < 3j (C6F5, 133.0).14,36 In this light, structurally
diagnostic spectroscopic parameters of the Cp*2LaCH2CCR
complexes, such as (1) the proton chemical shift of the CH2
group, (2) the carbon chemical shifts of the η3-CH2CCR ligand,
and (3) the first-order carbon-hydrogen coupling constant of
the CH2 group, correlate well with the σ-electron-withdrawing
ability of the ligand, revealing that the bonding character of
the η3-CH2CCR ligand in Cp*2LaCH2CCR complexes is mainly
influenced by the electronic effects of the alkyne substitu-
ent R.37 The (steric) effect of the di-ortho-isopropyl groups in
3i as compared to the di-ortho-methyl groups in 3h is relatively
small on the above structurally diagnostic spectroscopic
parameters.
Cp′2LnCH2CCR complexes.14 Comparison with reported data
indicates that these values are intermediate of those typically
observed for η1-propargyl (2100-2215 cm-1) and η1-allenyl
metal complexes (1800-1920 cm-1).34
A shift of the Ct C stretch from 1944 cm-1 to 1973 cm-1 is
observed upon coordination of pyridine to the metal center in
4f-La, indicating an increase in the propargylic bonding
character of the η3-CH2CCPh ligand. A larger shift from 1923
cm-1 to 2148 cm-1 points to an even higher degree of
propargylic character of the η3-CH2CCPh ligand in 4f-Y upon
coordination of pyridine.
Reactions with Brønsted Acids. (a) Methanol. When the
Cp*2LnCH2CCR complexes were allowed to react with methanol-
d4, rapid reactions occurred, as indicated by instantaneous color
changes to light yellow. The organic reaction products were
identified as the acetylenic (RCCCH2D) and allenylic
(RCDdCdCH2) deuterolysis products of the η3-CH2CCR ligand
(Scheme 6). Analogous reactions with methanol were conducted,
and the ratios of acetylenic and allenylic products were
determined by in situ 1H NMR spectroscopy (using appropriate
long pulse delays to avoid signal saturation under the present
anaerobic conditions). The results reveal that the influence of
metal size (entries 1and 2, Table 3) and the electronic substituent
effect of the alkyne substituent (entries 2 and 6) is small on the
relative amount of acetylenic quenching product. More pro-
nounced effects are observed for the steric effect of the alkyne
substituent (entries 2 and 5).
(c) Substituent Effects. The 1H NMR data of the propargyl
derivatives Cp*2LnCH2CCR reveal that the propargylic CH2
resonances move upfield with increasing ortho-substitution in
i
the Cp*2LaCH2CCC6H3R2-2,6 (R ) H 4f-La, Me 4h-La, Pr
4i-La) series, while substitution of the phenyl group by a
pentafluorophenyl group has the opposite effect (Table 2). The
13C NMR data of the η3-CH2CCR ligand of the Cp*2LaCH2CCR
complexes show a similar trend. The CH2 and CH2CC reso-
nances shift upfield, while the CH2CC resonances shift down-
field upon increasing the steric bulk at the ortho-positions of
the phenyl group. A reverse change is observed (i.e., the CH2
and CH2CC resonances shift downfield and the CH2CC reso-
nance shifts upfield), when the phenyl group in
Cp*2LaCH2CCPh is replaced by a pentafluorophenyl group.
The first-order carbon-hydrogen couplings (1JCH in Hz) of
the propargylic carbon in the Cp*2LaCH2CCR series decrease
in the following order: C6F5 (163) > C6H5 (158) > C6H3Me2-
(36) The validity of the linear relationship between the rate of proton
transfer from a carbon acid and the first-order carbon-hydrogen coupling
constant of the corresponding carbon (1JCH) has been demonstrated by many
studies. For reviews on carbon acids, see: (a) Cram, D. J. Fundamentals of
Carbanion Chemistry; Academic Press: New York, 1965. (b) Jones, J. R.
The Ionisation of Carbon Acids; Academic Press: London, 1973. (c) Reutov,
O. A.; Beletskaya, I. P.; Butin, K. P. CH-Acids; Pergamon Press: Oxford,
1978. (d) Stewart, R. The Proton: Applications to Organic Chemistry;
Academic Press: New York, 1985. (e) For examples, see: Closs, G. L.;
Closs, L. E. J. Am. Chem. Soc. 1963, 85, 2022. (f) Closs, G. L.; Larrabee,
R. B. Tetrahedron Lett. 1965, 287. (g) Streitweiser, A., Jr.; Caldwell, R. A.;
Young, W. R. J. Am. Chem. Soc. 1969, 91, 529. (h) Maksic´, Z. B.; Eckert-
Maksic´, M. Tetrahedron 1969, 25, 5113. (i) Maksic´, Z. B.; Randic´, M.
J. Am. Chem. Soc. 1973, 95, 6522. (j) Luh, T.-Y.; Stock, L. M. J. Am.
Chem. Soc. 1974, 96, 3712.
i
2,6 (157) > C6H3 Pr2-2,6 (157).14 Under the assumption that
the polar effects of the metal center are constant in the series
Cp*2LaCH2CCR, this decrease in 1JCH arguably reflects a change
in hybridization, pointing to a change from a sp2-type carbon
in E and F to a more sp3-type carbon in D (Scheme 5).35
On the basis of the 1JCH value of the methyl group, the relative
σ-electron-withdrawing ability of the substituent R on the
alkynes CH3CCR was found to increase in the following order:
i
3h (C6H3Me2-2,6, 131.0) ≈ 3i (C6H3 Pr2-2,6, 131.0) < 3f (Ph,
(37) Electronic substituent effects in propargyl-allenyl equilibria are
not without precedent; see: Miao, W.; Chung, L. W.; Wu, Y.-D.; Chan,
T. H. J. Am. Chem. Soc. 2004, 126, 13326.
(35) Bushby, R. J.; Patterson, A. S.; Ferber, G. J.; Duke, A. J.; Whitham,
G. H. J. Chem. Soc., Perkin Trans. 2 1978, 807.

Rare-Earth Metallocene η3-Propargyl/Allenyl Complexes
Organometallics, Vol. 27, No. 21, 2008 5679
Table 3. Alkyne/Allene Ratios for the Reaction of Cp*2LnCH2CCR (4) with Methanol (MeOH), 2,6-Di-tert-butyl-4-methylphenol (ArOH), and
Phenylacetylene (PhCCH)a
entry
compound
alkyne:allene (MeOH)
alkyne:allene (ArOH)
alkyne:allene (PhCCH)
1
2
3
4
5
6
Cp*2YCH2CCPh (4f-Y)
1.0:1.0
1.1:1.0
n.d.
1.1:1.0
0.6:1.0
1.2:1.0
0.8:1.0
1.0:1.0
1.0:1.0
n.d.
n.d.
n.d.
n.d.
0.2:1.0
n.d.
n.d.
n.d.
Cp*2LaCH2CCPh (4f-La)
Cp*2CeCH2CCPh (4f-Ce)
Cp*2LaCH2CCC6H3Me2-2,6 (4h-La)
i
Cp*2LaCH2CCC6H3 Pr2-2,6 (4i-La)
Cp*2LaCH2CCC6F5 (4j-La)
n.d.
a Reactions conducted in benzene-d6 at room temperature. The ratios were determined by in situ 1H NMR spectroscopy. n.d. ) not determined.
Scheme 7. Reaction of Cp*2La(η3-CH2CCPh) (4f-La) with
base coordination (Scheme 8). Nucleophilic attack at the metal
Phenylacetylene to Produce Acetylenic and Allenylic
Protonolysis Products alongside Products from Catalytic
Dimerization of Phenylacetylene
center may take place at the substituted side or at the unsub-
stituted side of the η3-propargyl/allenyl ligand.39 The formation
of the Lewis base adducts is plausibly followed by the
electrophilic attack of the hydroxyl proton on the most polarized
carbon of the η3-propargyl/allenyl ligand. As a result, the η1-
allenyl-like Lewis base adduct G, formed from nucleophilic base
attack at the unsubstituted side of the η3-propargyl/allenyl ligand,
will give rise to the allenylic quenching product upon proto-
nolysis, and the η1-propargyl-like Lewis base adduct H, formed
from nucleophilic base attack at the substituted side of the η3-
propargyl/allenyl ligand, will give rise to the acetylenic quench-
ing product.
The solid-state structure of Cp*2LaCH2CCPh · C5H4N (4f-
La · py) showed that pyridine is coordinated to the metal center
at the more substituted side of the η3-propargyl/allenyl ligand
(Vide supra). Although this finding suggests that the coordination
of Lewis bases is controlled by electronic factors rather than
steric factors, more experiments are needed to determine whether
the regioselectivity of the protonolysis reaction of the
Cp′2LnCH2CCR complexes is under electronic or steric control.
It should be noted that the catalytic cyclodimerization of
1-methylalk-2-ynes is presently believed to involve alkyne
insertion into the propargylic Ln-CH2 bond and the allenylic
La-CH(R) bond of Cp′2LnCH2CCR complexes.40 As alkyne
insertion reasonably proceeds via initial Lewis base coordina-
tion,41 the side of Lewis base coordination at the metal center
may also control the regioselectivity of the reaction of 4f-La
with 1-methylalk-2-ynes.
(b) 2,6-Di-tert-butyl-4-methylphenol. To study the effect of
a sterically more hindered alcohol than methanol, analogous
reactions with 2,6-di-tert-butyl-4-methylphenol (HOAr) were
performed. These reactions were also rapid, forming the
corresponding Cp*2LnOAr (10) compounds quantitatively. The
results reveal that the effect of a sterically more hindered alcohol
is small on the regioselectivity of the protonolysis reaction
(entries 1 and 2, Table 3).
(c) Phenylacetylene. When a stoichiometric amount of
phenylacetylene was added to a benzene-d6 solution of 4f-La
at room temperature, the orange solution turned immediately
dark red. Only 57% of 4f-La was consumed upon complete
conversion of phenylacetylene, as determined by in situ 1H NMR
spectroscopy. NMR and GC-MS analysis revealed products
previously observed in the lanthanocene-catalyzed oligomer-
ization reaction of phenylacetylene (Scheme 7),38 while the
protonated η3-propargyl/allenyl ligand was converted into
phenylallene and 1-phenyl-1-propyne in a 1.00:0.20 ratio,
respectively. When 4f-La was allowed to react with a 2- and
10-fold molar excess of phenylacetylene, the complete con-
sumption of phenylacetylene was accompanied by a mere 80%
and 88% conversion of 4f-La, respectively. It seems therefore
that protonolysis of 4f-La by phenylacetylene is slow relative
to oligomerization of phenylacetylene catalyzed by monomeric
Cp*2LaCCPh.
Conclusions
Novel rare-earth metallocene η3-propargyl/allenyl derivatives
have been prepared via the reactions of the alkyl derivatives
Cp*2LnCH(SiMe3)2 or hydride derivatives[Cp*2Ln(µ-H)]2 with
the corresponding 1-methylalk-2-ynes CH3CCR. Spectral and
structural analysis provided evidence for a static η3-bonding
description of the propargylic/allenylic ligand in
Cp*2LnCH2CCR. NMR spectroscopy revealed that changes
toward a more propargylic or a more allenylic character of the
η3-CH2CCR ligand in Cp*2LaCH2CCR complexes are brought
about mainly by the electronic effects of the alkyne substituent
R. Despite the η3-bonding of the propargyl/allenyl ligands, the
compounds can still accommodate an additional Lewis base
ligand. Reactions of the Cp*2LnCH2CCR complexes with
Brønsted acids produce both acetylenic (CH3Ct CR) and
(d) Mechanism. The formation of allenylic and acetylenic
quenching products in the reaction of Cp′2LnCH2CCR com-
plexes with Brønsted acids may be rationalized by initial Lewis
(38) (a) Ge, S.; Norambuena, V. F.; Hessen, B. Organometallics 2007,
26, 6508. (b) Quiroga Norambuena, V. F. Ph.D. Thesis, 2006, University
of Groningen, Chapter 4. Electronic copy available at http://irs.ub.rug.nl/
ppn/297799576.
(39) Coordination of Lewis bases along the line perpendicular to the
Cp(centroid)-Ln-Cp(centroid) plane allows for a good overlap between
the lowest unoccupied molecular orbital (LUMO), approximately of a z2
type, and the lone pair of the Lewis base, as demonstrated by MO analyses
of d0 metallocenes and Cp2Y(η3-CH2CCPh).14 For examples, see:(a) Lauher,
J. W.; Hoffmann, R. J. Am. Chem. Soc. 1976, 98, 1729. (b) Steigerwald,
M. L.; Goddard, W. A., III. J. Am. Chem. Soc. 1984, 106, 308. (c) Ortiz,
J. V.; Hoffmann, R. Inorg. Chem. 1985, 24, 2095. (d) Rabaaˆ, H.; Saillard,
J.-Y.; Hoffmann, R. J. Am. Chem. Soc. 1986, 108, 4327. (e) Rappe´, A. K.
J. Am. Chem. Soc. 1987, 109, 5605.
(40) (a) Quiroga Norambuena, V. F.; Hessen, B. Manuscript in prepara-
tion. (b) Quiroga Norambuena, V. F. Ph.D. Thesis, 2006, University of
Groningen, Chapter 3. Electronic copy available at http://irs.ub.rug.nl/ppn/
297799576.
(41) (a) Casey, C. P.; Lee, T.-Y.; Tunge, J. A.; Carpenetti, D. W., II.
J. Am. Chem. Soc. 2001, 123, 10762. (b) Stoebenau, E. J., III; Jordan, R. F.
J. Am. Chem. Soc. 2004, 126, 11170. (c) Stoebenau, E. J., III; Jordan, R. F.
Organometallics 2006, 25, 3379. (d) Sydora, O. L.; Kilyanek, S. M.; Jordan,
R. F. J. Am. Chem. Soc. 2007, 129, 112952.

5680 Organometallics, Vol. 27, No. 21, 2008
Quiroga Norambuena et al.
Scheme 8. Proposed Mechanism for the Reactions of the Cp*2Ln(η3-CH2CCR) Complexes with Alcohol R′OH
1H NMR spectra were referenced to resonances of residual protons
in deuterated solvents and reported in ppm relative to tetrameth-
allenylic (CH2dCdCHR) protonolysis products. Rare-earth
metallocene η3-propargyl/allenyl species are likely to be in-
ylsilane (δ 0.00 ppm). The coupling constants J and the line width
volved in the catalytic cyclodimerization of 1-methylalk-1-ynes.
The catalytic cyclodimerization of methylarylalkynes by these
compounds will be reported separately.
(lw) of the resonances at half-maximum are given in Hz. The 13
C
NMR spectra were referenced to carbon resonances of deuterated
solvents. 19F NMR spectra were referenced internally to hexafluo-
robenzene in CDCl3 (δ -163.0 ppm). IR spectra of pure compounds
and KBr pellets or Nujol solutions of the samples were recorded
on a Mattson 4020 Galaxy FT-IR or a Pye-Unicam SP3-300
spectrophotometer. The elemental analyses were performed by H.
Kolbe, Mikroanalytisches Laboratorium, Mu¨lheim an der Ruhr, or
the Microanalytical Department of the University of Groningen.
All found percentages are the average of at least two independent
determinations. GC analyses were performed on a HP 6890
instrument with a HP-1 dimethylpolysiloxane column (19095
Z-123). GC-MS spectra were recorded at 70 eV using a HP 5973
mass-selective detector attached to a HP 6890 GC as described
above. Vacuum sublimations were carried out by using a homemade
sublimation apparatus. Molecular weights were determined by
cryoscopy in benzene.
Experimental Section
General Considerations. All reactions and manipulations of air-
and moisture-sensitive compounds were performed under a nitrogen
atmosphere using standard Schlenk, vacuum line, and glovebox
techniques. Deuterated solvents were dried over Na/K alloy prior
to use. Other solvents were dried by percolation over columns of
aluminum oxide, BASF R3-11-supported Cu oxygen scavenger, and
molecular sieves (4 Å) (pentane) or by distillation from Na/K alloy
(THF, cyclohexane). The compounds Cp*2LnCH(SiMe3)2 (Ln )
Y,42 Ce,43 La44), [Cp*2Ln(µ-H)]2 (Ln
)
Ce,40 La41),
Me2Si(Cp′′H)2,45 LiCH(SiMe3)2,46 2-(prop-1-ynyl)toluene,47 2,6-
dimethyliodobenzene,48 1-(2,6-dimethylphenyl)-1-propyne,44 n-
butyl nitrite,49 copper bronze,50 and propynyl copper(I)51 were
prepared according to literature procedures. Reagents were pur-
chased from Aldrich and Acros Organics and were used as received
unless stated otherwise. Hydrogen (Hoek-Loos, 99.995%) was dried
by passing the gas over a column filled with LiAlH4. Diphenyl-
ethyne (Aldrich) was purified by sublimation before use. Dimethyl
sulfoxide was dried at least three times on freshly activated 4 Å
molecular sieves.52
Preparation of [Me2Si(η5-C5Me4)2Ce(µ-Cl)]2. A suspension of
2.76 g (11.2 mmol) of CeCl3 and 3.83 g (12 mmol) of Me2Si(η5-
C5Me4)2Li2 in THF (200 mL) was heated under reflux for 5 days.
The resulting orange suspension was evaporated to dryness and
sublimed under vacuum (0.01 mmHg) at 225 °C. This afforded
0.84 g (0.9 mmol, 16%) of [Me2Si(η5-C5Me4)2Ce(µ-Cl)]2 as pink
crystals.
Physical and Analytical Measurements. NMR spectra were
recorded on a Varian VXR-300 (FT, 300 MHz, 1H; 75 MHz, 13C),
a Varian XL-400 (FT, 400 MHz, 1H; 100 MHz, 13C), or a Varian
Inova 500 (FT, 500 MHz, 1H; 125.7 MHz, 13C) spectrometer. NMR
experiments on air-sensitive samples were conducted in flame-
sealable tubes or tubes equipped with a Teflon valve (Young). The
IR (Nujol, [cm-1]): 2700 (w), 2120 (w), 1310 (m), 1250 (m),
1140 (m), 1120 (m), 1010 (m), 840 (s), 800 (s), 770 (m), 750 (m),
680 (s), 450 (s). Anal. Calcd for C20H30CeClSi: C, 50.65; H, 6.38.
Found: C, 50.20; H, 6.52. [Me2Si(η5-C5Me4)2Ce(µ-Cl)]2 is insuf-
ficiently soluble for NMR and cryoscopy.
Preparation of Me2Si(η5-C5Me4)2CeCH(SiMe3)2 (5-Ce). A 381
mg (0.40 mmol) amount of [Me2Si(η5-C5Me4)2Ce(µ-Cl)]2 and 128
mg (0.77 mmol) of LiCH(SiMe3)2 were suspended in toluene (20
mL). After stirring for 24 h at room temperature, a red-purple
solution containing a white precipitate had formed. The solvent
was removed in Vacuo, and the residue was extracted with pentane
(30 mL). Concentration and cooling to -80 °C gave 261 mg (0.44
mmol) of 5-Ce as purple crystals. A second workup gave another
31 mg. Total yield: 292 mg (0.49 mmol, 61%).
(42) den Haan, K. H.; de Boer, J. L.; Teuben, J. H.; Spek, A. L.; Kojicˆ-
Prodicˆ, B.; Hays, G. R.; Huis, R. Organometallics 1986, 5, 1726.
(43) Heeres, H. J.; Renkema, J.; Meetsma, A.; Teuben, J. H. Organo-
metallics 1988, 7, 2495.
(44) Jeske, G.; Lauke, H.; Mauermann, H.; Swepston, P. N.; Schumann,
H.; Marks, T. J. J. Am. Chem. Soc. 1985, 107, 8091.
(45) Jutzi, P.; Dickbreder, R. Chem. Ber. 1986, 119, 1750.
(46) Davidson, D. J.; Harris, D. H.; Lappert, M. F. J. Chem. Soc., Dalton
Trans. 1976, 2268.
1H NMR (300 MHz, C6D6, 21 °C): δ 10.76 (s, CH3, 6 H, lw )
12 Hz), 3.96 (s, CH3, 6 H, lw ) 20 Hz), -3.09 (m, CH3, 6 H, lw
) 31 Hz), -4.92 (s, CH3, 6 H, lw ) 14 Hz), -8.57 (s, SiCH3, 18
H, lw ) 37 Hz), -13.97 (s, CH3, 6 H, lw ) 22 Hz). The resonance
due to CeCH was not observed. IR (Nujol, [cm-1]): 2710 (w), 2130
(w), 1310 (m), 1250 (m), 1240 (m), 1120 (m), 1060 (m), 1020
(sh), 840 (s), 820 (s), 810 (sh), 770 (m), 750 (m), 680 (m), 570
(m), 460 (m). Anal. Calcd for C27H49CeSi3: C, 54.22; H, 8.26; Ce,
23.43. Found: C, 54.49; H, 8.35; Ce, 23.82.
(47) Negishi, E.; Kotora, M.; Xu, C. D J. Org. Chem. 1997, 62, 8957.
(48) Ohno, A.; Tsutsumi, A.; Yamazaki, N.; Okamura, M.; Mikata, Y.;
Fujii, M. Bull. Chem. Soc. Jpn. 1996, 69, 1679.
(49) Vogel, A. I.; Rogers, V.; Hannaford, A. J.; Furniss, B. S. Vogel’s
Textbook of Practical Organic Chemistry, 4th ed.; Longman: London, 1978;
p 409.
(50) Vogel, A. I.; Rogers, V.; Hannaford, A. J.; Furniss, B. S. Vogel’s
Textbook of Practical Organic Chemistry, 4th ed.; Longman: London, 1981;
p 285.
(51) For propynylcopper, see: (a) Atkinson, R. E.; Curtis, R. F. J. Chem.
Soc. (C) 1967, 578. (b) Bossenbroek, B.; Sanders, D. C.; Curry, H. M.;
Shechter, H J. Am. Chem. Soc. 1969, 91, 371. For a detailed experimental
procedure, see Supporting Information.
Preparation of 2,6-Diisopropyliodobenzene. A 500 mL, three-
neck, round-bottomed flask, equipped with a gas-inlet adaptor, drop
funnel, and a Teflon-coated stir bar, was charged with 2 g of freshly
(52) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of
Laboratory Chemicals, 2nd ed.; Pergamon Press: Oxford, 1980.

Rare-Earth Metallocene η3-Propargyl/Allenyl Complexes
Organometallics, Vol. 27, No. 21, 2008 5681
prepared copper bronze and placed in a nitrogen atmosphere. A
16.52 g (99.5 mmol) sample of KI, 8.30 g (32.7 mmol) of iodine,
and 50 mL of dry DMSO were added, and the resulting mixture
was stirred and heated to 60 °C. After addition of 20 g of freshly
prepared n-butylnitrite a solution of 12.1 g (68.2 mmol) of 2,6-
diisopropylaniline in 30 mL of DMSO was added dropwise. The
reaction mixture was stirred for 2 h at 60 °C. The reaction was
stopped by adding aqueous solutions of sodium chloride and sodium
bisulfite. Filtration, separation, drying over MgSO4, and rotatory
evaporation gave a yellow oil, which was purified with column
chromatography (silica, hexanes). Yield: 15.2 g (78%) of a light
yellow, viscous liquid.
the tubes were flame-sealed and kept at room temperature. The
reactions were monitored by H NMR spectroscopy.
1
Preparation of Cp*2YCH2CCMe (4a-Y). A solution of 694
mg (1.34 mmol) of Cp*2YCH(SiMe3)2 in pentane (35 mL) was
stirred under H2 (1 atm) for 3 h at room temperature, during which
a white precipitate of [Cp*2Y(µ-H)]2 was formed. The hydrogen
atmosphere was replaced by nitrogen, and 2-butyne (0.85 mL, 11
mmol) was added at 0 °C. The reaction mixture was stirred for 15
min, during which hydrogen evolved and a clear yellow solution
was formed. Concentration and cooling to -80 °C gave 107 mg
(0.26 mg) of 4a-Y as pale yellow crystals. A second crop gave
another 45 mg (0.11 mmol). Total yield: 152 mg (0.37 mmol, 28%).
Complex 4a-Y is extremely soluble, and this hampers purification
and isolation considerably.
1H NMR (300 MHz, CDCl3, 25 °C): δ 7.20 (m, CH, 1 H), 7.04
3
3
(m, CH, 2 H), 3.37 (septet, JHH ) 6.8 Hz, 2 H), 1.20 (d, JHH
)
6.8 Hz, 6 H). 13C NMR (125.7 MHz, CDCl3, 25 °C): δ 23.37 (q,
IR (cm-1): 2720 (w), 1975 (m), 1930 (w), 1230 (w), 1020 (m),
1JCH ) 126.8 Hz, CH3), 39.41 (d, JCH ) 128.2 Hz, CH), 109.14
1
1
710 (m), 600 (w). H NMR (300 MHz, C6D6, 21 °C): δ 1.54 (t,
(m, CI), 123.79 (d, 1JCH ) 156.4 Hz, CH), 128.30 (d, 1JCH ) 160.2
Hz, CH), 151.12 (m, C). IR (neat, [cm-1]): 2950 (m), 2915 (m),
2850 (m), 2230 (w), 1907 (w), 1665 (w), 1490 (m), 1463 (m), 1365
(m), 1105 (w), 1020 (m), 910 (m), 872 (m), 835 (s), 790 (m), 728
(s). GC-MS, m/z (relative intensity): 290 (1), 289 (9), 288 (M+,
70), 274 (13), 273 (M+ - CH3, 100), 146 (10), 145 (8), 133 (9),
131 (33), 128 (14), 117 (21), 115 (23), 105 (10), 91 (28). Anal.
Calcd for C12H17I (288.17): C, 50.02; H, 5.95. Found: C, 50.15; H,
6.07.
5JHH ) 2.6 Hz, 3 H, CH3), 1.92 (s, 30 H, Cp*), 2.16 (t, 5JHH ) 2.6
Hz, 2JYH ) 0.6 Hz, 2 H, CH2). 13C NMR (75 MHz, C6D6, 21 °C):
δ 8.4 (q, 1JCH ) 130 Hz, CH3), 11.0 (q, 1JCH ) 125 Hz, C5(CH3)5),
42.33 (dt, 1JCH ) 154 Hz, 1JYC ) 8.1 Hz, CH2Ct C), 94.9 (d, 1JYC
) 8.0 Hz, CH2Ct C), 116.9 (s, C5Me5), 137.3 (s, Ct CCH3). Anal.
Calcd for C24H35Y (412.45): C, 69.89; H, 8.55. Found: C, 69.54;
H, 8.41; MW, 433 ( 34.
Preparation of Cp*2CeCH2CCMe (4a-Ce). 2-Butyne (1.7 mL,
23 mmol) was added to a solution of 1.02 g (1.79 mmol) of
Cp*2CeCH(SiMe3)2 in benzene (25 mL). After stirring for 16 h at
room temperature, a green solution had formed. Concentration and
crystallization at 10 °C gave 51 mg (0.11 mmol, 6%) of 4a-Ce as
sticky green crystals. Complex 4a-Ce is extremely soluble, and this
hampers purification and isolation considerably. IR (cm-1): 2140
(m), 1965 (m), 1260 (m), 1080 (m), 1010 (s), 800 (m), 670 (w),
620 (w), 570 (s). 1H NMR (300 MHz, C6D6, 21 °C): δ 2.5 (s, Cp*,
30 H, lw ) 14 Hz), -9.6 (s, CH3, 3 H, lw ) 3 Hz), -30.5 (s, 2 H,
CH2, lw ) 80 Hz). Anal. Calcd for C24H35Ce (463.66): C, 62.17;
H, 7.61. Found: C, 61.68; H, 7.28.
Preparation of 1-(2,6-Diisopropylphenyl)-1-propyne (3i). A
8.6 g (84 mmol) amount of freshly prepared propynyl copper(I)
was brought in a 400 mL Schlenk flask, equipped with a Teflon-
coated stir bar, and evacuated. After addition of 240 mL of dry
pyridine and 3.0 g (10 mmol) of 2,6-diisopropyliodobenzene the
reaction mixture was heated at reflux at 120 °C for 10 days. The
mixture was quenched with water. Addition of petroleum ether
(40-60), filtration, extraction of the organic layer with petroleum
ether (40-60), drying over MgSO4, and rotatory evaporation
afforded a yellow oil, which was purified by means of column
chromatography (neutral alumina) with petroleum ether. Yield:
1.58 g (76%) of a colorless oil.
Preparation of Cp*2CeCH(Me)C(Et) (9b-Ce). 3-Hexyne (1
mL, 8.8 mmol) was added to a suspension of 369 mg (0.45 mmol)
of [Cp*2Ce(µ-H)]2 in pentane (5 mL). The mixture was stirred for
60 h at room temperature, during which a green solution and a
small amount of a green solid were formed. Filtration, concentration
(to ∼3 mL), and cooling to -80 °C gave 203 mg (0.41 mmol,
46%) of 9b-Ce as green crystals. IR (cm-1): 2720 (w), 2130 (w),
1890 (s), 1570 (w), 1380 (m), 1310 (w), 1060 (w), 1020 (m), 910
1H NMR (500 MHz, CDCl3, 25 °C): δ 1.24 (d, 3JHH ) 6.9 Hz,
3
CH(CH3)2, 6 H), 2.13 (s, ArCCH3, 3 H), 3.52 (septet, JHH ) 6.9
3
Hz, CHMe2, 2 H), 7.18 (d, JHH ) 7.8 Hz, m-CH, 2 H), 7.30 (t,
3JHH ) 7.8 Hz, p-CH, 1 H). 13C NMR (125.7 MHz, CDCl3, 25
1
1
°C): δ 4.55 (q, JCH ) 131.4 Hz, CCCH3), 23.61 (qdq, JCH
)
125.8 Hz, 2JCH ) 5.1 Hz, 3JCH ) 5.1 Hz, CH3), 31.92 (dsept, 1JCH
2
2
1
) 128.7 Hz, JCH ) 4.0 Hz, CHMe2), 76.73 (q, JCH ) 4.6 Hz,
(w), 800 (w), 720 (m), 590 (w), 520 (w), 460 (w). H NMR (300
3
CH3C), 93.76 (q, JCH ) 10.7 Hz, ArC), 121.64 (m, i-C), 122.32
MHz, C6D6, 21 °C): δ 3.16 (s, Cp*, 15 H, lw ) 11 Hz), 2.54 (s,
Cp*, 15 H, lw ) 11 Hz), -2.73 (s, 3 H, CH3, lw ) 13 Hz), -4.29
(s, 1 H, CH2, lw ) 31 Hz), -6.32 (s, 1 H, CH2, lw ) 32 Hz),
-11.2 (s, 1 H, CH, lw ) 43 Hz), -13.2 (s, 3 H, CH3, lw ) 9 Hz).
1
2
3
(ddd,, JCH ) 158.5 Hz, JCH ) 4.8 Hz, JCH ) 7.9 Hz, m-CH),
1
127.55 (d, JCH ) 159.9 Hz, p-CH), 150.52 (m, o-C). IR (neat,
[cm-1]): 2962 (s), 2870 (m), 2243 (w), 1575 (w), 1463 (m), 1362
(m), 1253 (w), 1179 (w), 1107 (w), 1060 (w), 935 (w), 801 (m),
754 (m), 483 (s). GC-MS, m/z (relative intensity): 201 (8), 200
(M+, 51), 185 (M+ - CH3, 33), 158 (12), 157 (67), 156 (11), 155
(15), 154 (9), 153 (19), 152 (16), 151 (4), 144 (14), 143 (100), 141
(37), 129 (38), 128 (70), 115 (36), 91 (9). HR-MS: C15H20, calc.
200.15650, found 200.15734.
1
13C NMR (75 MHz, C6D6, 21 °C): δ -13.3 (t, JCH ) 134 Hz,
1
1
CH2), 7.8 (q, JCH ) 125 Hz, C5(CH3)5), 11.0 (q, JCH ) 125 Hz,
1
1
C5(CH3)5), 27.9 (q, JCH ) 126 Hz, CH3), 132.8 (d, JCH ) 153
Hz, CH), 146.5 (s, C′), 201.3 (s, C5(CH3)5), 216.6 (s, C5(CH3)5),
390.0 (s, C′), 480.1 (q, JCH ) 123 Hz, CH3). Anal. Calcd for
1
C26H39Ce (491.71): C, 63.51; H, 8.00; Ce, 28.50; MW, 491.69.
Found: C, 63.38; H, 7.94; Ce, 28.36; MW, 491 ( 32 (cryoscopy
in benzene).
Reactions of Cp*2LnCH(SiMe3)2 (Ln ) Y, Ce, La) and Me2Si(η5-
C5Me4)2CeCH(SiMe3)2 with Excess MeCCR (R ) Me, Et, Pr,
t
Preparation of [Me2Si(η5-C5Me4)2CeCH2CCMe]n (6a-Ce).
2-Butyne (0.5 mL, 6.4 mmol) was added to a solution of Me2Si(η5-
C5Me4)2CeCH(SiMe3)2 (118 mg, 0.20 mmol) in benzene (10 mL).
The solution was stirred at room temperature for 24 h, during which
orange crystals deposited. Isolation gave 65 mg (0.13 mmol, 65%)
of 6a-Ce as orange crystals. IR and elemental analysis indicated
the presence of lattice benzene (1/3 C6H6/Ce). IR (cm-1): 2720
(w), 2000 (s), 1400 (w), 1310 (m), 1245 (m), 1230 (m), 1120 (w),
1000 (m), 830 (s), 815 (s), 770 (m), 750 (m), 670 (s), 590 (m),
520 (s), 460 (s). The compound is insufficiently soluble for NMR
Ph, SiMe3, and Bu). NMR tubes were loaded with solutions of
∼0.05 mmol of Cp*2LnCH(SiMe3)2 and Me2Si(η5-C5Me4)2-
CeCH(SiMe3)2 in 0.5 mL of benzene-d6. Excess MeCCR (∼0.9
mmol) was added, and the tubes were flame-sealed and kept in an
oven at 80 °C. The reactions were monitored by 1H NMR
spectroscopy.
Reactions of [Cp*2Ln(µ-H)]2 (Ln ) Y, Ce, La) with Excess
MeCCR (R ) Me, Et, Pr, Ph, SiMe3, and tBu). NMR tubes were
loaded with solutions of ∼0.03 mmol of [Cp*2Ln(µ-H)]2 in 0.5
mL of benzene-d6. Excess MeCCR (∼0.15 mmol) was added, and

5682 Organometallics, Vol. 27, No. 21, 2008
Quiroga Norambuena et al.
and cryoscopy. Anal. Calcd for C26H37CeSi (517.78): C, 60.30; H,
7.20; Ce, 27.06. Found: C, 60.42; H, 7.08; Ce, 26.29.
760 (s), 690 (m), 600 (s), 450 (m). Anal. Calcd for C29H37La
(524.52): C, 66.41; H, 7.11. Found: C, 66.24; H, 7.00.
Preparation of Cp*2YCH2CCPh (4f-Y). Hydrogen at a pressure
of 1 bar was supplied to a solution of Cp*2YCH(SiMe3)2 (0.58 g,
1.12 mmol) in hexanes (5 mL). Stirring for 3 h at room temperature
produced a light yellow suspension. The hydrogen atmosphere was
replaced by nitrogen, and 1-phenyl-1-propyne (0.2 mL, 1.60 mmol)
was added. Immediately, a red suspension formed. The suspension
was stirred for 30 min at room temperature, during which it was
degassed several times. The solid was separated by decantation and
filtration. Subsequent in Vacuo removal of the solvent yielded a
red crystalline material (0.49 g, 92% yield). Crystals suitable for
X-ray analysis were obtained by recrystallization in toluene at low
temperature.
Preparation of Cp*2LaCH2CCC6H3Me2-2,6 (4h-La). Hydro-
gen (1 bar) was applied to a solution of Cp*2LaCH(SiMe3)2 (0.56
g, 0.98 mmol) in hexanes (5 mL). The yellow suspension was stirred
for 2 h at room temperature. The hydrogen atmosphere was replaced
by nitrogen, and 1-(2,6-dimethylphenyl)-1-propyne (0.21 g, 1.46
mmol) was added. The suspension was stirred overnight at room
temperature and degassed several times. After overnight stirring,
the suspension turned deep red. The reaction mixture was extracted
with hexanes and evaporated to dryness, forming a deep red oil.
Crystallization from hexanes at low temperature yielded a red
crystalline material (0.12 g, 22% yield). Crystals suitable for X-ray
analysis were obtained by recrystallization in toluene and cooling
the solution.
1H NMR (500 MHz, C6D6, 25 °C): δ 1.93 (s, Cp*, 30 H), 2.82
1H NMR (300 MHz, C6D6, 25 °C): δ 1.92 (s, Cp*, 30 H), 2.18
(s, CH3, 6 H), 2.71 (s, CH2, 2 H), 6.94 (s, CH, 3 H). 13C NMR
(125.7 MHz, C6D6, 25 °C): δ 11.10 (q, 3JCH ) 124.8 Hz, C5(CH3)5),
3
3
(s, CH2, 2 H), 6.98 (t, JHH ) 7.5 Hz, p-Ph, 1 H), 7.09 (t, JHH
)
7.5 Hz, m-Ph, 2 H), 7.19 (d, 3JHH ) 7.8 Hz, o-Ph, 2 H). 13C NMR
(125.7 MHz, C6D6, 25 °C): δ 11.15 (q, 1JCH ) 125.6 Hz, C5(CH3)5),
49.33 (dt, 1JCH ) 159.1 Hz, 1JYC ) 5.2 Hz, CH2Ct C), 106.79 (d,
3
1
22.36 (q, JCH ) 125.5 Hz, CH3), 49.12 (t, JCH ) 156.9 Hz,
3
1JYC ) 11.9 Hz, CH2Ct C), 117.78 (m, C5Me5), 126.69 (dt, JCH
1
CH2Ct C), 105.81 (t, JCH ) 7.0 Hz, CH2Ct C), 119.04 (m,
C5Me5), 127.14 (d, 1JCH ) 159.0, p-CH), 128.31 (d, 1JCH ) 156.9,
) 160.8, 3JCH ) 7.7 Hz, p-CH), 128.60 (dd, 1JCH ) 159.4 Hz,3JCH
2
1
3
m-CH), 130.96 (m, i-CH), 140.74 (m, o-CH), 149.28 (t, JCH
)
) 7.6 Hz, m-CH), 132.40 (dtd, JCH ) 159.1 Hz, JCH ) 7.1 Hz,
4JCH ) 1.4 Hz, o-CH), 132.77 (tdd, 2JCH ) 3.7 Hz, 3JCH ) 8.1 Hz,
4JCH ) 2.0 Hz, i-C), 155.09 (t, 2JCH ) 2.5 Hz, CH2Ct C). IR (Nujol,
[cm-1]): 2924 (m), 2856 (m), 2727 (m), 1923 (m), 1592 (m), 1544
(m), 1455 (m), 1378 (m), 1269 (m), 1154 (m), 1065 (m), 1021
(m), 916 (w), 846 (w), 768 (m), 698 (m), 627 (m), 482 (s). Anal.
Calcd for C29H37Y (474.52): C, 73.41; H, 7.86. Found: C, 73.24;
H, 7.89.
2.6 Hz, CH2Ct C). IR (Nujol, [cm-1]): 2925 (s), 2853 (s), 2725
(w), 1975 (m), 1786 (w), 1566 (w), 1465 (s), 1377 (m), 1260 (w),
1168 (w), 1093 (w), 1020 (m), 779 (m), 720 (m), 500 (s). Anal.
Calcd for C31H41La (552.57): C, 67.38; H, 7.48. Found: C, 67.29;
H, 7.54.
Preparation of Cp*2LaC(Ph)dC(Ph)H (8ff-La). To a suspen-
sion of [Cp*2La(µ-H)]2 (35.0 mg, 42.6 µmol) in cyclohexane (5
mL) was added diphenylacetylene (15.2 mg, 85.3 µmol). The light
yellow suspension turned into an orange solution immediately.
Removal of the solvent in Vacuo gave a yellow solid in quantitative
yield. Isolated yield: 49.2 mg (98%).
Preparation of Cp*2CeCH2CCPh (4f-Ce). 1-Phenyl-1-propyne
(0.5 mL 4.00 mmol) was added to a suspension of 374 mg (0.46
mmol) of [Cp*2Ce(µ-H)]2 in pentane (20 mL). After stirring for
3 h at room temperature, a grass-green solution was formed.
Filtration, concentration, and cooling to -80 °C gave 268 mg (0.51
mmol, 56%) of 4f-Ce as green crystals. IR (cm-1): 3050 (w), 2710
(w), 2120 (w), 1930 (s), 1580 (m), 1550 (w), 1480 (m), 1150 (w),
1060 (w), 1020 (w), 900 (w), 760 (s), 740 (m), 710 (w), 690 (s),
1H NMR (500 MHz, C7D14, 25 °C): δ 7.40 (s, D), 7.22 (t, G),
7.20 (t, A), 7.07 (m, F), 6.95 (m, B), 6.91 (d, E), 6.73 (m, C), 1.77
(s, Cp*, 30 H). 13C NMR (125.7 MHz, C7D14, 25 °C): δ 10.51 (q,
1
1JCH ) 125.4 Hz, C5Me5), 120.60 (s, C5Me5), 122.97 (dt, JCH
)
1
3
600 (w), 510 (w), 450 (w). H NMR (300 MHz, C6D6, 21 °C): δ
148.6 Hz, JCH ) 7.1 Hz, 3), 124.25 (d, overlap hampered
3
determination of coupling constants, 2), 125.53 (ddd, 1JCH ) 153.5
3.53 (t, JHH ) 7.0 Hz, 1 H, p-CH, lw ) 3 Hz), 2.91 (s, Cp*, 30
3
3
1
H, lw ) 28 Hz), 2.8 (s, 2 H, m-CH, lw ) 10 Hz), -7.65 (s, 2 H,
o-CH, lw ) 20 Hz), -35.4 (s, 2 H, CH2, lw ) 78 Hz). Anal. Calcd
for C29H37Ce (525.73): C, 66.25; H, 7.09; Ce, 26.65; MW, 525.71.
Found: C, 67.23; H, 7.07; Ce, 25.86; MW, 530 ( 31 (cryoscopy
in benzene).
Hz, JCH ) 6.2 Hz, JCH ) 6.2 Hz, 8), 126.18 (dt, JCH
162.2 Hz, 3JCH ) 7.3 Hz, 9), 129.58 (dd, 1JCH ) 156.1 Hz, 3JCH
)
)
7.9 Hz, 1), 130.83 (dd, 1JCH ) 158.6 Hz, 3JCH ) 7.9 Hz, 10), 133.72
(dt, 1JCH ) 147.5 Hz, 3JCH ) 4.1 Hz, 6), 146.25 (q, 3JCH ) 6.6, 7),
150.83 (q, 3JCH ) 7.5 Hz, 4), 217.47 (s, 5). 1H-13C gHSQC (500.0
MHz, 125.7 MHz, C7D14, 25 °C): A1, B2, C3, D6, E8, F8, G10.
Preparation of Cp*2LaCH2CCPh (4f-La). Hydrogen at a
pressure of 1 bar was supplied to a solution of Cp*2LaCH(SiMe3)2
(0.82 g, 1.42 mmol) in pentane (5 mL). Stirring for 2 h at room
temperature produced a yellow suspension. The hydrogen atmo-
sphere was replaced by nitrogen, and 1-phenyl-1-propyne (0.4 mL,
3.20 mmol) was added. Immediately, a deep red suspension formed.
The suspension was stirred for 1 h at room temperature, during
which it was degassed several times. The solid was separated by
decantation and filtration. Subsequent in Vacuo removal of the
solvent yielded a red crystalline material (0.68 g, 91% yield).
Crystals suitable for X-ray analysis were obtained by recrystalli-
zation in toluene at low temperature.
1H-13C gHMBC (500.1 MHz, 125.7 MHz, C7D14, 25 °C): A2-4
,
B1,3, C1-5,
D3-8, E6-9, F8,10, G7-9. Anal. Calcd for C34H41La
(588.61): C, 69.38; H, 7.02. Found: C, 69.51; H, 6.90.
Reactions of Cp′2LnCH2CCR with MeOH, CD3OD, and
ArOH. NMR Scale. Samples (0.04-0.08 mmol) of methanol,
methanol-d4, or 2,6-di-tert-butyl-4-methylphenol (ArOH) were
added to equimolar amounts of Cp′2LnCH2CCR at room temper-
ature in benzene-d6 (0.5 mL). Reaction took place immediately,
and Cp*2LnOAr compounds were formed quantitatively together
with a mixture of allenylic and acetylenic quenching products (Table
3). These reaction products were identified by comparison with
literature or authentic samples.
1H NMR (300 MHz, C6D6, 25 °C): δ 1.92 (s, Cp*, 30H), 2.82
3
3
(s, CH2, 2H), 6.99 (t, JHH ) 7.3 Hz, p-H, 1 H), 7.12 (dd, JHH
)
Preparation of Cp*2YOAr (10-Y). To a stirred pentane solution
of Cp*2YCH(SiMe3)2 (302 mg, 0.58 mmol) was added 128 mg
(0.58 mmol) of ArOH. The solution was stirred for 48 h at room
temperature. A slightly orange solution had formed, which was
concentrated to ∼1 mL and subsequently cooled to -80 °C.
Isolation gave 205 mg (0.35 mmol, 60%) of the title compound as
7.2 Hz, 3JHH ) 7.3 Hz, m-H, 2 H), 7.24 (d, 3JHH ) 7.2 Hz, o-H, 2
H). 13C NMR (125.7 MHz, C6D6, 25 °C): δ 10.61 (q, 1JCH ) 124.5
1
Hz, C5(CH3)5), 54.02 (t, JCH ) 158.3 Hz, CH2Ct C), 112.76 (m,
CH2Ct C), 119.46 (m, C5Me5), 126.19 (dt, 1JCH ) 161.8 Hz, 3JCH
) 7.4 Hz, p-CH), 128.71 (dd,1JCH ) 153.0 Hz, 3JCH ) 8.0, m-CH),
130.84 (dtd,1JCH ) 159.9 Hz, 3JCH ) 7.0 Hz, 2JCH ) 1.4 Hz, o-CH),
132.39 (t,3JCH ) 7.1 Hz, i-C), 152.19 (s, CH2Ct C). IR (Nujol,
[cm-1]): 2920 (m), 2850 (m), 1944 (s), 1587 (m), 1550 (w), 1455
(s), 1380 (m), 1260 (w), 1090 (w), 1065 (w), 1020 (m), 900 (w),
1
white crystals. H NMR (C6D6): δ 7.13 (s, 2H, m-C6H2), 2.37 (s,
3H, p-Me), 1.88 (s, 30H, C5Me5); 1.46 (s, 18H, t-Bu). 13C NMR
(C6D6): δ 160.5 (s, i-C6H2), 135.2 (s, o-C6H2), 125.8 (d, J ) 151
Hz, m-C6H2), 123.5 (s, p-C6H2), 119.4 (s, C5Me5), 35.6 (s, t-Bu),

Rare-Earth Metallocene η3-Propargyl/Allenyl Complexes
Organometallics, Vol. 27, No. 21, 2008 5683
Table 4. Summary of Crystallographic Data of
Cp*2Ln(η3-CH2CCPh) (Ln ) Y 4f-Y, La 4f-La) and
[Cp*2La(η3-CH2CCPh)(NC5H5)] (4f-La · py)
31.6 (q, J ) 124 Hz, t-Bu), 21.6 (q, J ) 124 Hz, p-Me), 11.6 (q,
J ) 125 Hz, C5Me5). Anal. Calcd for C35H53YO (578.71): C, 72.64;
H, 9.23; Y, 15.36. Found: C, 72.40; H, 9.16; Y, 15.57.
4f-Y
4f-La
4f-La · py
Preparation of Cp*2CeOAr (10-Ce). Aryloxide 10-Ce was
prepared by a similar procedure to 10-Y by using 1.809 g (3.2
mmoL) of Cp*2CeCH(SiMe3)2 and 698 mg (3.2 mmol) of ArOH.
Workup gave 10-Ce as red crystals in 68% yield (1.36 g, 2.2 mmol).
IR (cm-1): 2730 (w), 2130 (w), 2120 (w), 1740 (w), 1600 (w),
1410 (s), 1370 (m), 1260 (s), 1240 (s), 1210 (m), 1110 (m), 1010
(m), 860(m), 820 (m), 800 (m), 520 (m). 1H NMR (benzene-d6): δ
8.39 (s, 2 H, lw ) 2 Hz, m-C6H2), 3.31 (s, 3 H, lw ) 2 Hz, p-Me),
2.71 (s, 30 H, lw ) 5 Hz, C5Me5), -7.12 (s, 18 H, lw ) 35 Hz,
t-Bu). Anal. Calcd for C35H53CeO (629.92): C, 66.73; H, 8.48; Ce,
22.25. Found: C, 66.81; H, 8.45; Ce, 22.29.
Preparation of Cp*2LaOAr (10-La). To a stirred solution of
Cp*2LaCH(SiMe3)2 (219 mg, 0.38 mmol) in pentane (20 mL) was
added 82 mg (0.37 mmol) of ArOH. The reaction mixture was
stirred for 2 h at room temperature. Concentration to ca. 3 mL and
cooling to -80 °C gave 101 mg (0.16 mmol, 43%) of 25 as white
crystals. IR (cm-1): 2720 (w), 1750 (w), 1590 (w), 1425 (s), 1360
(m), 1260 (s), 1230 (s), 1210 (m), 1120 (m), 1020 (w), 860 (m),
820 (m), 800 (m), 530 (m), 510 (w). 1H NMR (benzene-d6, 21
°C): δ 7.14 (s, 2 H, m-C6H2), 2.35 (s, 3 H, p-Me), 1.89 (s, 30 H,
C5Me5), 1.44 (s, 18 H, t-Bu). 13C NMR (benzene-d6, 21 °C): δ
158.4 (s, i-C6H2), 135.5 (s, o-C6H2, 125.8 (d, J ) 151 Hz, m-C6H2),
123.6 (s, p-C6H2), 120.9 (s, C5Me5), 35.1 (s, CMe3), 32.0 (q, J )
125 Hz, CMe3), 21.5 (q, J ) 125 Hz, p-Me), 11.1 (q, J ) 125 Hz,
C5Me5). Anal. Calcd for C35H53LaO (628.71): C, 66.86; H, 8.50;
La, 22.09. Found: C, 66.60; H, 8.32; La, 21.96.
molecular formula
fw
T, K
cryst syst
space group
a, Å
b, Å
c, Å
R, deg
ꢀ, deg
γ, deg
V, Å3
C29H37Y
474.52
100(1)
C29H37La
524.52
100(1)
C34H42LaN
603.62
100(1)
orthorhombic orthorhombic triclinic
Pca2a1
16.4646(9)
10.5009(6)
14.7315(8)
j
Pna21
P1
20.064(1)
10.051(2)
12.233(3)
8.7176(4)
9.6510(4)
18.4634(9)
78.405(1)
87.337(1)
72.103(1)
1447.86(11)
2
1.385
620
14.97
2.26, 28.28
0.0666
2547.0(2)
4
1.237
1000
23.02
2.30, 28.28
0.0685
6224
2466.9(8)
4
1.412
1072
17.44
2.27, 27.48
0.0990
5124
Z
F
calc, g cm-1
F(000)
µ(Mo KR), cm-1
θ range, deg
wR(F2)
refined reflns
refined params
6986
493
0.0307
1.028
419
276
R(F) for Fo > 4.0 σ(Fo) 0.0297
0.0463
1.025
0.0, 0.0
GooF
weighting (a, b)
1.030
0.0393, 0.0
0.0316, 0.0
Scheme 9. Numbering Scheme of Cp*2LaC(Ph)dCH(Ph)
(8ff-La)
Preparation of Cp*2La(η3-CH2CCPh)(py) (4f-La · py). Pyri-
dine (8.0 µL, 98 µmol) was added with a microsyringe to a solution
of Cp*2LaCH2CCPh (50 mg, 95 mmol) in hexanes (2 mL) in the
glovebox. Stirring for 2 h at room temperature produced a clear,
light yellow solution. Cooling and concentrating the solution in
Vacuo afforded yellow crystals suitable for X-ray analysis. Isolated
yield: 52 mg (90%).
Data collection and structure solution were conducted at the
University of Groningen. The structures were solved by Patterson
methods, and extension of the model was accomplished by direct
methods applied to difference structure factors using the program
DIRDIF.54 Relevant crystal and data collection parameters are given
in Table 4.
1H NMR (300 MHz, C6D6, 25 °C): δ 1.94 (s, Cp*, 30H), 3.16
(s, CH2, 2H), 6.51 (ddd, 3JHH ) 7.7 Hz, 3JHH ) 4.5 Hz, 4JHH ) 1.5
Hz, ꢀ-H, 2 H), 6.81 (tt, 3JHH ) 7.6 Hz, 4JHH ) 1.9 Hz, γ-H, 1 H),
6.96 (tt, 3JHH ) 7.4 Hz, 4JHH ) 1.2 Hz, p-H, 1 H), 7.13 (d, 3JHH
)
3
7.4 Hz, m-H, 2 H), 7.24 (d, JHH ) 7.9 Hz, o-H, 2 H), 8.40 (dd,
3JHH ) 4.5 Hz, 3JHH ) 1.9 Hz, R-H, 2 H). 13C NMR (125.7 MHz,
Acknowledgment. We thank the Council for Chemical
Sciences of The Netherlands Foundation for Scientific
Research (NWO-CW) for financial support.
1
C6D6, 25 °C): δ 11.55 (q, JCH ) 125.1 Hz, C5(CH3)5), 51.07 (t,
1JCH ) 159.5 Hz, CH2CC), 117.96 (m, C5Me5), 123.72 (d, 1JCH
)
153.6 Hz, p-CH), 123.79 (d, 1JCH ) 165.6 Hz, ꢀ-CH), 128.58 (m-
and o-CH), 136.43 (m, i-C), 137.04 (d,1JCH ) 163.3 Hz, R-CH),
152.16 (s, CH2Ct C). The signal corresponding to CH2CC was not
observed. IR (Nujol, [cm-1]): 2923 (s), 2853 (s), 2713 (m), 1973
(m), 1741 (w), 1653 (w), 1591 (m), 1459 (s), 1377 (m), 1215 (m),
1150 (m), 1067 (m), 1021 (m), 898 (m), 838 (m), 748 (m), 694
(m), 686 (m), 477 (s). Anal. Calcd for C34H42LaN (603.62): C,
67.65; H, 7.01. Found: C, 67.51; H, 6.90.
Supporting Information Available: More detailed experimental
procedures are given, as well as spectroscopic data of representative
transition metal complexes (for reference) and aromatic 1-methy-
lalk-2-ynes. Graphic representations of the dependence of the proton
chemical shift of the CH2 group, the carbon chemical shifts of the
C3 ligand, and the first-order carbon-hydrogen coupling constant
of the CH2 group in Cp*2LaCH2CCR complexes versus the first-
order carbon-hydrogen coupling constant of the CH3 group of the
corresponding neutral ligand CH3CCR. The solid-state structure of
Cp*2Y(η3-CH2CCPh) (4f-Y) is shown as well. This material is
available free of charge via the Internet at http://pubs.acs.org.
X-ray Crystallography. In the glovebox, the crystals were
transferred from the reaction vessels to a Petri dish filled with a
small amount of light mineral oil. A suitable crystal was chosen
by examination under a microscope. This crystal was attached to
glass fiber, which was mounted in a cold nitrogen stream on a
Bruker53 SMART APEX CCD diffractometer for data collection.
OM800547N
(54) Beurskens, P. T.; Beurskens, G.; De Gelder, R.; Garc´ıa-Granda,
S.; Gould, R. O.; Israe¨l, R.; Smits, J. M. M. The DIRDIF-99 Program
System; University of Nijmegen, The Netherlands, 1999.
(53) SMART, SAINT, SADABS, XPREP, and SHELXK/NT. Smart Apex
Software Reference Manuals; Bruker AXS Inc.: Madison, WI, 2000.