Cationic rare-earth metal trimethylsilylmethyl complexes supported by THF and 12-crown-4 ligands: Synthesis and structural characterization

Article abstract of DOI:10.1021/ic0511165

To expand the limited range of rare-earth metal cationic alkyl complexes known, a series of mono- and dicationic trimethylsilylmethyl complexes supported by THF and 12-crown-4 ligands with [BPh₄]^-, [BPh ₃(CH₂SiMe₃)]^-, [B(C ₆F₅)₄]^-, [B(C₆F ₅)₃(CH₂SiMe₃)]^-, and [Al(CH₂SiMe₃)₄]^- anions were prepared from corresponding neutral precursors [Ln(CH₂SiMe ₃)₃L_n] (Ln = Sc, Y, Lu; L = THF, n = 2 or 3; L = 12-crown-4, n = 1) as solvent-separated ion pairs. The syntheses of the monocationic derivatives [Ln(CH₂SiMe₃)₂(12- crown-4)_n(THF)_m]⁺[A]^- are all high yielding and proceed rapidly in THF solution at room temperature. A one pot procedure using the neutral species directly for the syntheses of a number of lutetium and yttrium dicationic derivatives [Ln(CH ₂SiMe₃)(12-crown-4)_n(THF)_m] ²⁺[A]^-₂ with a variety of different anions, a class of compounds previously limited to just a few examples, is presented. When BPh₃ is used to generate the ion triple, the presence of 12-crown-4 is required for complete conversion. Addition of a second equiv of 12-crown-4 and a third equiv of [NMe₂PhH]⁺[B(C₆F ₅)₄]^- abstracts a third alkyl group from [Ln(CH₂SiMe₃)(12-crown-4)₂(THF) _x]²⁺[B(C₆F₅)₄] ^-₂ (Ln = Y, Lu). X-ray crystallography and variable-temperature (VT) NMR spectroscopy reveal a structural diversity within the known series of neutral 12-crown-4 supported tris-(trimethylsilylmethyl) complexes [Ln(CH₂SiMe₃)₃(12-crown-4)] (Ln = Sc, Y, Sm, Gd-Lu) in the solid and solution states. The X-ray structure of [Sc(CH₂SiMe₃)₃(12-crown-4)] exhibits incomplete 12-crown-4 coordination. VT NMR spectroscopy indicates fluxional 12-crown-4 coordination on the NMR time scale. X-ray crystallography of only the second structurally characterized dicationic rare-earth metal alkyl complex [Y(CH ₂SiMe₃)(12-crown-4)(THF)₃] ²⁺[BPh₄]^-₂ shows exocyclic 12-crown-4 coordination at the 8-coordinate metal center with well separated counteranions. ¹¹B and ¹⁹F NMR spectroscopy of all mono- and dicationic rare-earth metal complexes reported demonstrate that the anions are symmetrical and noncoordinating on the NMR time scale. A series of trends within the ¹H and ¹³C{¹H} NMR resonances arising from the Ln-CH₂ groups and, in the case of yttrium, the ¹J_YC coupling constants at the Y-CH₂ group and the ⁸⁹Y chemical shift values are discussed.

Full text of DOI:10.1021/ic0511165

Inorg. Chem. 2005, 44, 6777−6788
Cationic Rare-Earth Metal Trimethylsilylmethyl Complexes Supported by
THF and 12-Crown-4 Ligands: Synthesis and Structural Characterization
Benjamin R. Elvidge, Stefan Arndt, Peter M. Zeimentz, Thomas P. Spaniol, and Jun Okuda*
Institut fu¨r Anorganische Chemie, RWTH Aachen UniVersity, Landoltweg 1,
D-52074 Aachen, Germany
Received July 6, 2005
To expand the limited range of rare-earth metal cationic alkyl complexes known, a series of mono- and dicationic
trimethylsilylmethyl complexes supported by THF and 12-crown-4 ligands with [BPh4]-, [BPh3(CH2SiMe3)]-, [B(C6F5)4]-,
[B(C6F5)3(CH2SiMe3)]-, and [Al(CH2SiMe3)4]- anions were prepared from corresponding neutral precursors
[Ln(CH2SiMe3)3Ln] (Ln
) Sc, Y, Lu; L ) THF, n ) 2 or 3; L ) 12-crown-4, n ) 1) as solvent-separated ion pairs.
The syntheses of the monocationic derivatives [Ln(CH2SiMe3)2(12-crown-4)n(THF)m]+[A]- are all high yielding and
proceed rapidly in THF solution at room temperature. A “one pot” procedure using the neutral species directly for
the syntheses of a number of lutetium and yttrium dicationic derivatives [Ln(CH2SiMe3)(12-crown-4)n(THF)m]2+[A]-
2
with a variety of different anions, a class of compounds previously limited to just a few examples, is presented.
When BPh3 is used to generate the ion triple, the presence of 12-crown-4 is required for complete conversion.
Addition of a second equiv of 12-crown-4 and a third equiv of [NMe2PhH]+[B(C6F5)4]- abstracts a third alkyl group
from [Ln(CH2SiMe3)(12-crown-4)2(THF)x]2+[B(C6F5)4]-2 (Ln
(VT) NMR spectroscopy reveal a structural diversity within the known series of neutral 12-crown-4 supported tris-
(trimethylsilylmethyl) complexes [Ln(CH2SiMe3)3(12-crown-4)] (Ln Sc, Y, Sm, Gd Lu) in the solid and solution
) Y, Lu). X-ray crystallography and variable-temperature
)
−
states. The X-ray structure of [Sc(CH2SiMe3)3(12-crown-4)] exhibits incomplete 12-crown-4 coordination. VT NMR
spectroscopy indicates fluxional 12-crown-4 coordination on the NMR time scale. X-ray crystallography of only the
second structurally characterized dicationic rare-earth metal alkyl complex [Y(CH2SiMe3)(12-crown-4)(THF)3]2+[BPh4]-
2
shows exocyclic 12-crown-4 coordination at the 8-coordinate metal center with well separated counteranions. 11B
and 19F NMR spectroscopy of all mono- and dicationic rare-earth metal complexes reported demonstrate that the
1
anions are symmetrical and noncoordinating on the NMR time scale. A series of trends within the H and 13C
{
1H
}
1
NMR resonances arising from the Ln-CH2 groups and, in the case of yttrium, the JYC coupling constants at the
Y−
CH2 group and the 89Y chemical shift values are discussed.
Introduction
to the parent neutral species, including ethylene and R-olefin
polymerization,2a-b,e,k,m-o;3c-g styrene polymerization and
styrene-ethylene copolymerization,2j diene polymerization,1o,u,v
intramolecular hydroamination,4 and alkyne dimerization.2l
Compounds of the form [LnR2Ln]+[A]- have the advantage
that a second alkyl group is available for abstraction to give
Cationic complexes of the rare-earth metals containing
only π-bound hydrocarbyl ligands [Ln(LnX)2Lm]+[A]- 1
(Ln ) rare-earth metal, LnX ) monoanionic ligand, L )
neutral ligand, A ) anion), a single σ-bound alkyl, and
another monoanionic ligand [Ln(LnX)RLm]+[A]- 2 or two
σ-bound alkyls [LnR2Lm]+[A]- 3 have been shown to be
isolable species. Complexes in the latter group in particular
show enhanced thermal stability with respect to the neutral
tris(alkyl) precursors and often incorporate neutral macro-
cyclic ligands.3 Improved catalytic behavior has been noted
for monocationic rare-earth metal complexes in comparison
a mono(alkyl) dication of the form [LnRLn]2+[A]- , which
2
has been implicated as the active species in the polymeri-
zation of ethylene.3c-e Allyl dications have also been
discussed in the context of diene polymerization.5 Despite
the fact that cationic rare-earth metal complexes containing
a σ-bound alkyl were first reported in 1992,2c these species
still remain relatively unexplored.6 We report here a sys-
tematic multinuclear study of neutral, monocationic, and
* Corresponding author. E-mail: Jun.Okuda@ac.rwth-aachen.de.
10.1021/ic0511165 CCC: $30.25
Published on Web 08/23/2005
© 2005 American Chemical Society
Inorganic Chemistry, Vol. 44, No. 19, 2005 6777

Elvidge et al.
dicationic rare-earth metal trimethylsilylmethyl complexes
supported by THF and 12-crown-4, which expands the
relatively small number of such complexes hitherto known
in the literature. In particular, we present here that dicationic
complexes with a trimethylsilylmethyl ligand are generally
accessible and report on the second structurally authenticated
example of this type of cation.
Results and Discussion
Syntheses. We have previously reported the synthesis and
characterization of neutral rare-earth metal trimethylsilyl-
methyl complexes supported by crown ether ligands [Ln-
(CH2SiMe3)3(12-crown-4)] (Ln ) Sc (4), Y (5), and Lu (6))
via reaction of [Ln(CH2SiMe3)3(THF)n] (Ln ) Sc (1), n )
2; Y (2), n ) 2, 3, and Lu (3), n ) 2) with 12-crown-4.3a,b
We have also previously reported solution and solid-state
characterization of certain mono- and dicationic trimethyl-
silylmethyl rare-earth metal complexes incorporating solvent
separated ion pairs supported by THF and crown ether
ligands that are formed by reaction of BPh3, [NEt3H]+[BPh4]-,
or [NMe2PhH]+[BPh4]- with the appropriate THF- and
crown ether-supported neutral rare-earth metal precursors
1-6.3a-c Furthermore, the alkyl abstraction reaction of 2 with
Al(CH2SiMe3)3 resulted in the formation of the solvent-
separated, crystallographically characterized ion pair [Y(CH2-
SiMe3)2(THF)4]+[Al(CH2SiMe3)4]-.3c
(1) Cationic rare-earth metal complexes incorporating only π-bound
hydrocarbyl ligands utilize three ligand types: “Cp”: (a) Evans, W.
J.; Bloom, I.; Grate, J. W.; Hughes, L. A.; Hunter, W. E.; Atwood, J.
L. Inorg. Chem. 1985, 24, 4620. (b) Hazin, P. N.; Bruno, J. W.;
Schulte, G. K. Organometallics 1990, 9, 416. (c) Evans, W. J.; Ulibarri,
T. A.; Chamberlain, L. R.; Ziller, J. W.; Alvarez, D., Jr. Organome-
tallics 1990, 9, 2124. (d) Heeres, H. J.; Meetsma, A.; Teuben, J. H. J.
Organomet. Chem. 1991, 414, 351. (e) Evans, W. J.; Kociok-Ko¨hn,
G.; Ziller, J. W. Angew. Chem., Int. Ed. Engl. 1992, 31, 1081. (f)
Deng, D.; Zheng, X.; Qian, C.; Sun, J.; Dormond, A.; Baudry, D.;
Visseaux, M. J. Chem. Soc., Dalton Trans. 1994, 1665. (g) Schumann,
H.; Winterfeld, J.; Keitsch, M. R.; Herrmann, K.; Demtschuk, J. Z.
Anorg. Allg. Chem. 1996, 622, 1457. (h) Yuan, F.; Shen, Q.; Sun, J.
J. Organomet. Chem. 1997, 538, 241. (i) Song, X.; Thornton-Pett,
M.; Bochmann, M. Organometallics 1998, 17, 1004. (j) Evans, W.
J.; Seibel, C. A.; Ziller, J. W. J. Am. Chem. Soc. 1998, 120, 6745. (k)
Evans, W. J.; Seibel, C. A.; Forrestal, K. J.; Ziller, J. W. J. Coord.
Chem. 1999, 48, 403. (l) Xie, Z.; Liu, Z.; Chui, K.; Xue, F.; Mak, T.
C. W. J. Organomet. Chem. 1999, 588, 78. (m) Molander, G. A.;
Rzasa, R. M. J. Org. Chem. 2000, 65, 1215. (n) Evans, W. J.; Davis,
B. L.; Ziller, J. W. Inorg. Chem. 2001, 40, 6341. (o) Kaita, S.; Hou,
Z. M.; Nishiura, M.; Doi, Y.; Kurazumi, J.; Horiuchi, A. C.; Wakatsuki,
Y. Macromol. Rapid Commun. 2003, 24, 179. (p) Evans, W. J.; Perotti,
J. M.; Brady, J. C.; Ziller, J. W. J. Am. Chem. Soc. 2003, 125, 5204.
(q) Evans, W. J.; Perotti, J. M.; Ziller, J. W. J. Am. Chem. Soc. 2005,
127, 3894. “η8-C8H8”: (r) Cendrowski-Guillaume, S. M.; Nierlich,
M.; Lance, M.; Ephritikhine, M. Organometallics 1998, 17, 786. (s)
Cendrowski-Guillaume, S. M.; Le Gland, G.; Nierlich, M.; Ephri-
tikhine, M. Organometallics 2000, 19, 5654. (t) Cendrowski-Guil-
laume, S. M.; Nierlich, M.; Ephritikhine, M. Eur. J. Inorg. Chem.
2001, 1495. “allyl”: (u) Taube, R.; Maiwald, S.; Sieler, J. J.
Organomet. Chem 2001, 621, 327. (v) Kaita, S.; Hou, Z.; Wakatsuki,
Y. US2002/0119889A1.
(2) Cationic rare-earth metal complexes incorporating one σ-bound alkyl
and another different monoanionic ligand utilize four ligand types:
“LX”: (a) Bambirra, S.; van Leusen, D.; Meetsma, A.; Hessen, B.;
Teuben, J. H. Chem. Commun. 2003, 522. (b) Bambirra, S.; Bouw-
kamp, M. W.; Meetsma, A.; Hessen, B. J. Am. Chem. Soc. 2004, 126,
9182. “L2X”: (c) Schaverien, C. J. Organometallics 1992, 11, 3476.
(d) Lee, L. W. M.; Piers, W. E.; Elsegood, M. R. J.; Clegg, W.; Parvez,
M. Organometallics 1999, 18, 2947. (e) Hayes, P. G.; Piers, W. E.;
McDonald, R. J. Am. Chem. Soc. 2002, 124, 2132. (f) Hayes, P. G.;
Piers, W. E.; Parvez, M. J. Am. Chem. Soc. 2003, 125, 5622. (g) Hayes,
P. G.; Welch, G. C.; Emslie, D. J. H.; Noack, C. L.; Piers, W. E.;
Parvez, M. Organometallics 2003, 22, 1577. (h) Cameron, T. M.;
Gordon, J. C.; Michalczyk, R.; Scott, B. L. Chem. Commun. 2003,
2282. (i) Henderson, L. D.; MacInnis, G. D.; Piers, W. E.; Parvez, M.
Can. J. Chem. 2004, 82, 162. (j) Luo, Y.; Baldamus, J.; Hou, Z. J.
Am. Chem. Soc. 2004, 126, 13910. “L3X”: (k) Bambirra, S.; van
Leusen, D.; Meetsma, A.; Hessen, B.; Teuben, J. H. Chem. Commun.
2001, 637. (l) Tazelaar, C. G. J.; Bambirra, S.; van Leusen, D.;
Meetsma, A.; Hessen, B.; Teuben, J. H. Organometallics 2004, 23,
936. (m) Bambirra, S.; Boot, S. J.; van Leusen, D.; Meetsma, A.;
Hessen, B. Organometallics 2004, 23, 1891. (n) Hessen, B.; Bambirra,
S., WO2002032909. (o) Christopher, J. N.; Squire, L. R.; Canich, J.
A. M.; Schaffer, T. D., WO0018808. “L5X”: (p) Lee, L.; Berg, D. J.;
Einstein, F. W.; Batchelor, R. J. Organometallics 1997, 16, 1819.
(3) Cationic rare-earth metal complexes incorporating two σ-bound alkyls
“CH2SiMe3”: (a) Arndt, S.; Spaniol, T. P.; Okuda, J. Chem. Commun.
2002, 896. (b) Arndt, S.; Zeimentz, P. M.; Spaniol, T. P.; Okuda, J.;
Honda, M.; Tatsumi, K. Dalton Trans. 2003, 3622. (c) Arndt, S.;
Spaniol, T. P.; Okuda, J. Angew. Chem., Int. Ed. 2003, 42, 5075. (d)
Okuda, J.; Arndt, S.; Matsui, S., JP2005015579. (e) Ward, B. D.,
Bellemin-Laponnaz, S.; Gade, L. H. Angew. Chem., Int. Ed. 2005,
44, 1668. (f) Lawrence, S. C.; Ward, B. D.; Dubberley, S. R.; Kozak,
C. M.; Mountford, P. Chem. Commun. 2003, 2880. “CH3”: (g) Hajela,
S.; Schaefer, W. P.; Bercaw, J. E. J. Organomet. Chem. 1997, 532,
45.
The monocationic compounds here presented have various
anions (x ) a: [BPh4]-; b: [B(C6F5)4]-; c: [BPh3(CH2-
SiMe3)]-; d: [B(C6F5)3(CH2SiMe3)]-; e: [Al(CH2SiMe3)4]-)
and either coordinated THF ([Ln(CH2SiMe3)2(THF)n]+[A]-:
Ln ) Sc (7a): n ) 3; Y (8x): n ) 3, 4; x ) a-e; Lu (9x):
n ) 3, x ) a-d) or 12-crown-4 ligands ([Ln(CH2SiMe3)2-
(12-crown-4)(THF)n]+[A]-: Ln ) Sc (10x): n ) 0, 1; x )
a, c; Y (11x): n ) 1; x ) a-e; Lu (12x): n ) 1, x ) a-d;
Scheme 1) at the metal center. Their syntheses proceed in
74-99% yield from the neutral rare-earth metal precursors
1-6 by reaction with the Brønsted acids [NEt3H]+[BPh4]-
(a), [NMe2PhH]+[B(C6F5)4]- (b), or the Lewis acids BPh3
(c), B(C6F5)3 (d), or Al(CH2SiMe3)3 (e). All complexes are
highly soluble in THF-d8, CD2Cl2, and pyridine-d5 and show
higher thermal stability in THF-d8 than the neutral precursor
compounds. The slow appearance of tetramethylsilane in the
NMR spectrum when CD2Cl2 and pyridine-d5 are used was
assigned to decomposition processes in these solvents.7
While these monocationic compounds are in principle
useful precursor compounds for a study of dication formation,
their laborious isolation led us to consider “one-pot”
procedures. Thus all syntheses of dicationic compounds here
reported proceed from the neutral rare-earth metal precursors
1-6 by reaction with 2 or more equiv of Brønsted or Lewis
acids. Under this regimen, dicationic rare-earth mono(tri-
methylsilylmethyl) complexes of both yttrium and lutetium
with various counteranions supported by THF ([Ln(CH2-
SiMe3)(THF)n]2+[A]- : Ln ) Y (13x): n ) 5; x ) a; Lu
2
(14x): n ) 4, x ) a) and 12-crown-4 ligands ([Ln(CH2-
SiMe3)(12-crown-4)(THF)n]2+[A]- : Ln ) Y (15x): n )
2
2, 3; x ) a-c; Ln ) Lu (16b); [Ln(CH2SiMe3)(12-crown-
4)2]2+[A]- : Ln ) Y (17x): x ) b, c; Lu (18x): x ) a, b;
2
Scheme 2) were synthesized in good yields. All complexes
(4) Lauterwasser, F.; Hayes, P. G.; Bra¨se, S.; Piers, W. E.; Schafer, L. L.
Organometallics 2004, 23, 2234.
(5) Taube, R. In Metalorganic Catalysts for Synthesis and Polymerisation;
Kaminsky, W., Ed.; Springer: Berlin, Germany, 1999; p 531.
(6) Arndt, S.; Okuda, J. AdV. Synth. Catal. 2005, 347, 339.
(7) Pyridine activation processes involving rare-earth metal alkyl and
hydride complexes are known, see Kirillov, E.; Lehmann, C. W.;
Razavi, A.; Carpentier, J.-F. Eur. J. Inorg. Chem. 2004, 943 and
references therein.
6778 Inorganic Chemistry, Vol. 44, No. 19, 2005

Rare-Earth Metal Cationic Alkyl Complexes
Scheme 1
Scheme 2
are highly soluble in pyridine-d5, but their solubility in other
solvents such as THF-d8 and CD2Cl2 is highly dependent on
the choice of anion and the presence of 12-crown-4.
Compound 15a is only the second example of a crystallo-
graphically characterized alkyl dication.3c
Both 13a and its lutetium analogue 14a proceeded to 90%
conversion to the dication in THF-d8 after 1.5 h when
[NMe2PhH]+[BPh4]- was used for the synthesis.8 15a was
isolated from a mixture of 5 and 2.1 equiv of [NEt3H]+[BPh4]-
in THF as large, colorless crystals in 94% yield after standing
for 3 days at room temperature.9 The THF-free bis(12-crown-
4) dicationic lutetium compound 18a was synthesized from
a stirred equimolar mixture of 6 and 12-crown-4 with 2 equiv
of [NEt3H]+[BPh4]-.10
ported by the [B(C6F5)4]- anion were prepared in THF-d8
by reaction of 5 or 6 with 2 equiv of [NMe2PhH]+[B(C6F5)4]-.
Furthermore, the bis(12-crown-4) complexes 17b and 18b,
but notably not the mono(12-crown-4) analogues 15b and
16b, reacted with a third equiv of [NMe2PhH]+[B(C6F5)4]-
to give a trimethylsilylmethyl-free complex and a third equiv
of tetramethylsilane.11 The [B(C6F5)4]- anion afforded di-
cationic complexes of a much higher THF solubility than
the borate [BPh4]-.
When 2 equiv of BPh3 were added to 5, clean conversion
to the dication 15c was observed after 2 h at room
temperature.12 Addition of a second equiv of 12-crown-4
(9) A concentration of between 0.05 and 0.10 mol‚L-1 gave 15a in 90-
95% yield. A weaker solution (0.01 mol‚L-1) deposited only trace
15a. At 0.01 mol‚L-1 the major insoluble component was an alkyl-
free byproduct; NMR spectroscopy (pyridine-d5) indicated BPh4,
coordinated 12-crown-4 and THF, in a 2:1:1.5 ratio. The analogous
procedures with scandium and lutetium deposit only alkyl-free products
also with BPh4, coordinated 12-crown-4 and THF. Titration for Lu
content gave 12.08%; [Lu(12-crown-4)2(THF)]3+[BPh4]-3 (C92H100B3-
LuO9) requires 11.24%.
A series of dicationic mono- and bis(12-crown-4) (15b,
16b, 17b, and 18b) yttrium and lutetium complexes sup-
1
(8) The analogous scandium experiment gave a H NMR spectrum with
peaks arising from residual monocation and other unidentified
resonances. Attempted introduction of a 12-crown-4 ligand to 13a or
14a failed; 13a and 12-crown-4 in THF-d8 gave a greasy, insoluble
solid inconsistent (by 1H NMR spectroscopy in pyridine-d5) with clean
12-crown-4 incorporation.
(10) The analogous procedure for yttrium gave a mixture tentatively
assigned by NMR spectroscopy as [Y(CH2SiMe3)(12-crown-4)2]2+
-
[BPh4]-2, 15a and an alkyl-free byproduct.
Inorganic Chemistry, Vol. 44, No. 19, 2005 6779

Elvidge et al.
Table 1. Selected Bond Lengths and Angles for 4 and 15a
4
15a
Sc-C(9)
2.219(3)
2.243(3)
2.251(3)
2.276(2)
2.423(3)
3.923(3)
2.396(2)
98.63(13)
100.22(12)
105.40(12)
68.62(8)
68.77(9)
76.15(8)
157.91(11)
161.41(10)
156.46(11)
Y-C(21)
2.424(4)
2.414(3)
2.423(3)
2.491(3)
2.527(3)
2.425(2)
2.370(2)
2.396(2)
83.10(11)
75.29(9)
77.59(9)
79.58(11)
65.07(13)
64.16(9)
66.14(9)
66.63(9)
Sc-C(13)
Y-O(1)
Sc-C(17)
Y-O(2)
Sc-O(1)
Y-O(3)
Sc-O(2)
Y-O(4)
Sc-O(3)
Y-O(5)
Sc-O(4)
Y-O(6)
C(9)-Sc-C(13)
C(9)-Sc-C(17)
C(13)-Sc-C(17)
O(1)-Sc-O(4)
O(1)-Sc-O(2)
O(2)-Sc-O(4)
C(13)-Sc-O(1)
C(9)-Sc-O(2)
C(17)-Sc-O(4)
Y-O(7)
C(21)-Y-O(7)
O(7)-Y-O(6)
O(6)-Y-O(5)
O(5)-Y-C(21)
O(1)-Y-O(4)
O(4)-Y-O(3)
O(3)-Y-O(2)
O(2)-Y-O(1)
complexes including the [Sc(12-crown-4)2]3+ unit with
symmetrical exo-crown ether coordination have been reported
in which the Sc-O bond lengths lie in the region 2.160-
(8)-2.274(9) Å.15 By contrast, the monocationic complexes
Figure 1. ORTEP representation of the molecular structure of [Sc(CH2-
SiMe3)3(12-crown-4)] (4). Thermal ellipsoids are drawn at 30%, and
hydrogen atoms have been omitted for clarity.
[ScCl2(15-crown-5)]+ [CuCl4]2-, [ScCl2(18-crown-6)]+[Sb-
2
Cl6]-, and [ScCl2(benzo-15-crown-5)]+[SbCl6]- include an
almost linear ScCl2+ unit that is threaded through the crown
cavity such that the Sc and O centers are essentially planar.
Average Sc-O bond lengths for these compounds are 2.125,
2.210, and 2.188 Å, respectively.16 In [ScCl2(18-crown-6)]+-
[FeCl4]-, only five of the six oxygen atoms coordinate to
the Sc center; the average Sc-O(coordinated) bond length
is 2.215 Å.17
gave the THF-free species 17c. Both 15c and 17c were
synthesized on a preparative scale in good yield.13 Neither
of the aluminate-supported yttrium monocations 8e nor 11e
reacted with excess Al(CH2SiMe3)3 at room temperature after
7 days in THF-d8 solution.
Crystal Structures. Neutral tris(trimethylsilylmethyl)
complexes 5 and 6 adopt a three-legged “piano-stool”
geometry in the solid state, with facial 12-crown-4 coordina-
tion, as determined by X-ray crystallography.3b We have now
isolated crystals of the scandium derivative 4 suitable for
an X-ray diffraction study from dichloromethane at -30 °C.
In this case, the crown ether ligand only coordinates through
three oxygen atoms (Sc-O(1) ) 2.276(2), Sc-O(2) )
2.423(3), and Sc-O(4) ) 2.396(2) Å) to give a 6-coordinate
metal center; the fourth 12-crown-4 oxygen was found 3.923-
(3) Å from the metal center (Figure 1). The geometry at
scandium in 4 is best described as distorted octahedral, with
angles along the C13-Sc-O1, C9-Sc-O2, and C17-Sc-
O4 axes of 157.91(11)°, 161.41(10)°, and 156.46(11)°,
respectively (Table 1). The Sc-C(alkyl) separations (Sc-
C(9) ) 2.219(3), Sc-C(13) ) 2.243(3), and Sc-C(17) )
2.251(3) Å) lie within the range of distances found for other
scandium trimethylsilylmethyl complexes (2.195(3)-2.295-
(3), Table 2),14 although many of these complexes have a
lower coordination number, commonly 5. Selected crystal-
lographic data for 4 can be found in Table 3. Tricationic Sc
X-ray crystallography of single crystals of the yttrium
dication 15a confirmed the coordination of the 12-crown-4
in a face-capping manner as well as three THF units; the
geometry at the 8-coordinate yttrium center is best described
as square antiprismatic (Figure 2). There are no close
interactions between the dicationic metal center and the
borate anions in the solid state. The yttrium-carbon bond
length (Y-C(21) ) 2.424(4) Å) is very similar to that
recorded for [Y(CH3)(THF)6]2+[BPh4]- .3c Surprisingly, it is
2
also similar to the two Y-C separations in the monocationic
complex [Y(CH2SiMe3)2(THF)4]+[Al(CH2SiMe3)4]-,3c the
neutral 12-crown-4 supported tris(trimethylsilylmethyl)
[Y(CH2SiMe3)3(12-crown-4)],3b and other representative
neutral yttrium complexes (Table 4).18 The Y-O(12-crown-
4) bond lengths (2.414(3)-2.527(3) Å) are shorter than those
observed in the neutral complex 5 (2.571(7)-2.627(6) Å),3b
despite an increase in coordination number from 7 to 8 but
(14) (a) Estler, F.; Eickerling, G.; Herdtweck, E.; Anwander, R. Organo-
metallics 2003, 22, 1212. (b) Lara-Sanchez, A.; Rodriguez, A.; Hughes,
D. L.; Schormann, M.; Bochmann, M. J. Organomet. Chem. 2002,
663, 63. (c) Ward, B. D.; Dubberley, S. R.; Maisse-Francois, A.; Gade,
L. H.; Mountford, P. J. Chem. Soc., Dalton Trans. 2002, 4649. (d)
Emslie, D. J. H.; Piers, W. E.; Parvez, M.; McDonald, R. Organo-
metallics 2002, 21, 4226 and references therein. (e) Hayes, P. G.; Piers,
W. E.; Lee, L. W. M.; Knight, L. K.; Parvez, M.; Elsegood, M. R. J.;
Clegg, W. Organometallics 2001, 20, 2533.
(15) (a) Willey, G. R.; Meehan, P. R.; Drew, M. G. B. Polyhedron 1996,
15, 1397. (b) Nishihara, S.; Takamatsu, N.; Akutagawa, T.; Hasegawa,
T.; Nakamura, T. Synth. Met. 2001, 121, 1806.
(16) (a) Willey, G. R.; Lakin, M. T.; Alcock, N. W. J. Chem. Soc., Chem.
Commun. 1992, 1619. (b) Willey, G. R.; Lakin, M. T.; Alcock, N. W.
J. Chem. Soc., Dalton Trans. 1993, 3407.
(11) The alkyl-free products were tentatively assigned as [Ln(12-crown-
4)2(THF)x]3+[B(C6F5)4]-3 (Ln ) Y, Lu). The yttrium compound was
alkyl-free on a preparative scale (residual NMe2Ph was noted). The
1H and 13C{1H} NMR spectra are similar to those of the co-product
observed at low concentration in the formation of 15a. Alkyl-free
tricationic rare-earth metal borate complexes are known: (a) Sauro,
L. J.; Moeller, T. J. Inorg. Nucl. Chem. 1968, 30, 953. (b) Thomas,
R. R.; Chebolu, V.; Sen, A. J. Am. Chem. Soc. 1986, 108, 4096.
(12) Addition of two equiv of BPh3 to 6 in THF-d8 required 10 days for
complete loss of monocation resonances. The Lu analysis of the
worked-up product was 2-3% too high in Lu for the dication.
(13) A mixture of 2 and 2 equiv of BPh3 in THF-d8 gave a mixture of the
monocation 8c and another yttrium species tentatively assigned as the
dication [Y(CH2SiMe3)(THF)n]2+[BPh3(CH2SiMe3)]-2 after 2 days at
room temperature.
(17) Brown, M. D.; Levason, W.; Murray, D. C.; Popham, M. C.; Reid,
G.; Webster, M. Dalton Trans. 2003, 857.
6780 Inorganic Chemistry, Vol. 44, No. 19, 2005

Rare-Earth Metal Cationic Alkyl Complexes
Table 2. Selected Sc-C(alkyl) Bond Lengths in Neutral Tris- and Bis(alkyl) Complexes
compound
Sc-C (Å)
Neutral Tris(alkyl) Complexes
2.248(2), 2.254(2), 2.2498(19)
2.219(3), 2.243(3), 2.251(3)
Neutral Bis(alkyl) Complexes
reference
[Sc(CH2SiMe2Ph)3(THF)2]
[Sc(CH2SiMe3)3(12-crown-4)]
14d
this work
[Sc(ArNC(Ph)NAr)(CH2SiMe3)2(THF)]a
[Sc(Ar’O)(CH2SiMe3)2(THF)]b
2.229(3), 2.195(3)
2.236(2), 2.246(2)
2.2446(13), 2.1954(14)
2.229(7), 2.202(7)
2b
14b
14e
14e
[Sc{ArNC(Me)CHC(Me)NAr}(CH2SiMe3)2]a
[Sc{ArNC(tBu)CHC(tBu)NAr}(CH2SiMe3)2]a
b
a Ar ) 2,6-iPr-C6H3. Ar’O ) {2-(2,4,6-Me3C6H2NdCH)(6-tBu)C6H3O}.
Table 3. Crystal Data for 4 and 15aa
4)]+(Cl)- (2.430(3)-2.472(3) Å).19 The Y-O(THF) bond
lengths (Y-O5: 2.425(2), Y-O6: 2.370(2), and Y-O7:
2.396(2) Å) in 15a are within the range reported for
Y-O(THF) bond lengths at cationic yttrium centers (Table
5).20
4
15a
chemical formula
formula weight
C20H49O4ScSi3
482.82
C76H99B2O8SiY
1279.17
110(2) K
0.71073 Å
monoclinic,
P21/c (No. 14)
21.857(5) Å
16.632(4) Å
18.846(5) Å
90°
T
293(2) K
λ
0.71073 Å
monoclinic,
P21/n (No. 14)
10.849(4) Å
15.690(2) Å
17.256(3) Å
90°
Structures in Solution. Variable-temperature (VT) NMR
studies reveal that the coordination of 12-crown-4 in the
neutral scandium complex 4 in both CD2Cl2 and THF-d8
crystal system,
space group
a
b
c
1
solution is labile. The H NMR spectrum of 4 (CD2Cl2, 25
R
°C) showed two sharp singlets arising from the Sc-CH2
(δ -0.24 ppm) and trimethylsilyl (δ -0.06 ppm) groups as
well as a broad, poorly resolved signal at δ 4.03 ppm due to
the crown ether. At -10 °C, the broad resonance of the 12-
crown-4 changed into two higher order multiplets at δ 3.83,
4.19 ppm.21 The resonance arising from the Sc-CH2 group
was only slightly affected in its position (δ -0.28 ppm). In
THF-d8 solution, the 1H NMR spectrum at 25 °C gave sharp
singlets for the 12-crown-4 (δ 3.65 ppm) and the Sc-
methylene (δ -0.59 ppm) and trimethylsilyl (δ -0.12 ppm)
groups; the same chemical shift values were noted for the
THF-adduct 1 and free crown ether. At -60 °C, both the
above peaks and new broad peaks arising from 12-crown-4
(δ 4.01, 4.14 ppm) and Sc-CH2 (δ -0.28 ppm) and
trimethylsilyl (δ -0.09 ppm) were observed. These new
resonances are assigned to the complex with coordinated 12-
crown-4 and have a relative intensity of about 10%.
Corresponding new resonances were noted in the variable
temperature 13C{1H} NMR spectra. The 12-crown-4 ligand
in the previously reported yttrium analogue 5 is not labile
in CD2Cl2 solution (two higher-order multiplets at δ 3.74
and 4.12 ppm were noted at 25 °C) but dissociates reversibly
in THF-d8 solution, with complete coordination observed at
-80 °C.3b
â
97.50(2)°
94.451(5)°
90°
γ
90°
V
2912.2(12) Å3
4
6830(3) Å3
4
Z
Dcalc
1.101 Mg/m3
0.0503, 0.1055
0.0944, 0.1227
1.244 Mg/m3
0.0636, 0.1695
0.1171, 0.2019
2
2
R(Fo ), Rw(Fo ) [I > 2σ(I)]
R(Fo ), Rw(Fo ) (all data)
2
2
2
2
a R(Fo ) and Rw(Fo ) are defined as the final R indices [I > 2σ(I)].
All of the expected peaks for the yttrium dication 15a are
1
cleanly resolved in the H and 13C{1H} NMR spectra in
pyridine-d5. Trace Si(CH3)3(CH2D) was observed after a few
Figure 2. ORTEP representation of the molecular structure of [Y(CH2-
SiMe3)(12-crown-4)(THF)3]2+[BPh4]-2 (15a). Thermal ellipsoids are drawn
at 30%, and hydrogen atoms and borate anions have been omitted for clarity.
(19) Rogers, R. D.; Rollins, A. N.; Benning, M. M. Inorg. Chem. 1988,
27, 3826.
(20) (a) Evans, W. J.; Olofson, J. M.; Ziller, J. W. J. Am. Chem. Soc. 1990,
112, 2308. (b) Sobota, P.; Utko, J.; Szafert, S. Inorg. Chem. 1994,
33, 5203. (c) Chiu, K. Y.; Zhang, Z. Y.; Mak, T. C. W.; Xie, Z. W.
J. Organomet. Chem. 2000, 614, 107.
are comparable to those in [Y(OH2)5(12-crown-4)]3+(Cl)- ‚2
3
H2O (2.42(1)-2.59(1) Å) and [YCl2(OH2)(OHMe)(12-crown-
(18) (a) Westerhausen, M.; Hartmann, M.; Schwarz, W. Inorg. Chim. Acta
1998, 269, 91. (b) den Haan, K. H.; de Boer, J. L.; Teuben, J. H.;
Spek, A. L.; Kojicprodic, B.; Hays, G. R.; Huis, R. Organometallics
1986, 5, 1726. (c) den Haan, K. H.; de Boer, J. L.; Teuben, J. H.;
Smeets, W. J. J.; Spek, A. L. J. Organomet. Chem. 1987, 327, 31. (d)
Coughlin, E. B.; Henling, L. M.; Bercaw, J. E. Inorg. Chim. Acta
1996, 242, 205. (e) Arndt, S.; Beckerle, K.; Zeimentz, P. M.; Spaniol,
T. P.; Okuda, J. Unpublished work.
(21) Higher order downfield multiplets for crown ether ligands have been
observed in similar compounds and arise from the diastereotopic
methylene protons of the exocyclic crown ether when the coordination
is rigid on the NMR time scale (see ref 3a,b). The apparent discrepancy
with the solid-state structure can be explained by a carousel-like 12-
crown-4 oxygen rotation that is fast on the NMR time scale. A very
low intensity signal at 3.62 ppm, slightly broad at 25 °C and sharp at
-10 °C, was assigned to a trace free 12-crown-4 impurity.
Inorganic Chemistry, Vol. 44, No. 19, 2005 6781

Elvidge et al.
Table 4. Selected Y-C(alkyl) Bond Lengths in Neutral and Cationic Complexes
compound
Y-C (Å)
reference
Neutral Tris(alkyl) Complexes
[Y{CH(SiMe3)2}3]
[Y(CH2SiMe3)3(THF)3]
[Y(CH2SiMe3)3(12-crown-4)]
2.357(7) (mean)
2.427(19) (mean)
2.399(6)-2.430(6)
18a
29b
3b
Neutral Metallocenes
[Y(η5-C5Me5)2{CH(SiMe3)2}]
[Y(η5-C5Me5)2(CH3)(THF)]
2.468(7)
2.44(2)
2.418(6)
18b
18c
18d
[Y{(η5-C5Me4)2SiMe2}{CH(SiMe3)2}]
Alkyl Monocations
[Y(CH2SiMe3)2(THF)4]+[Al(CH2SiMe3)4]-
[Y(CH3)2(THF)5]+[BPh4]-
2.384(6), 2.411(6)
2.508(2), 2.526(2)
3c
18e
Alkyl Dications
[Y(CH3)(THF)6]2+[BPh4]-
2.418(3)
2.424(4)
3c
this work
2
[Y(CH2SiMe3)(12-crown-4)(THF)3]2+[BPh4]-
2
Table 5. Selected Y-O(THF) Bond Lengths in Cationic Yttrium Complexes
compound
Y-O (Å)
reference
[YCl(OCMe3)(THF)5]+[BPh4]-
[YCl2(THF)5]+[YCl4(THF)2]-
[YCl2(THF)5]+[C2B9H12]-
2.391(5)-2.422(5)
2.368(5)-2.382(6)
2.309(7)-2.401(7)
2.354(4)-2.479(4)
2.395(2)-2.418(2)
2.352(3)-2.427(3)
2.370(2)-2.425(2)
20a
20b
20c
3c
18e
[Y(CH2SiMe3)2(THF)4]+[Al(CH2SiMe3)4]-
[Y(CH3)2(THF)5]+[BPh4]-
[Y(CH3)(THF)6]2+[BPh4]-
3c
this work
2
[Y(CH2SiMe3)(12-crown-4)(THF)3]2+[BPh4]-
2
1
minutes at room temperature in the H NMR spectrum,
(Table 6). Secondary effects are seen in the difference
between 1H NMR chemical shift values of comparable
complexes with or without 12-crown-4 and between com-
plexes with different anions, from which tentative conclu-
sions about the extent of anion-cation association can also
be drawn.
We found that, on the NMR time scale as determined by
11B and 19F NMR spectroscopy, the ions are separated in
solution. The 11B nucleus gave rise to a single, cation-
independent resonance in each case of both mono- and
dicationic complexes (THF-d8, 25 °C: a: δ -6.6 ppm; b:
δ -16.7 ppm; c: δ -10.3 ppm; d: δ -14.2 ppm). These
chemical shift values show a small solvent dependency
(pyridine-d5, 25 °C: a: δ -5.7 ppm). The perfluorinated
anion d gives rise in every case to a meta-para chemical
shift difference of only δ 2.3 ppm in the 19F NMR spectrum,
which has been previously used as an indicator of solvent-
separated ion pairs.27 The 19F NMR resonances arising from
both [B(C6F5)4]- and [B(C6F5)3(CH2SiMe3)]- are clearly
cation independent.
indicating that 15a is unstable in pyridine-d5. The clear,
colorless pyridine-d5 solution of 15a reacts completely after
10 h at room temperature to give a deep yellow solution
that shows Si(CH3)3(CH2D) as the only resonance in the
δ < 1 ppm region of the 1H NMR spectrum. The resonance
arising from the Y-CH2 group was also lost in the 13C{1H}
NMR spectrum, while the peaks arising from the 12-crown-4
1
protons in the H NMR spectrum changed from a compli-
cated multiplet to a slightly higher frequency singlet after
this reaction. Rare-earth metal alkyl and hydride complexes
are known to react with pyridine, as well as other aromatic
heterocycles, to give in the case of pyridine a range of
products including ortho-metalated pyridyl complexes of the
general form [Ln(L2X)2(η2-(C,N)-C5H4N)] (L2X ) C5Me5,
Ln ) Sc,22 Y,23 Lu;24 LX2 ) C5H4R (R ) H, Me), Ln )
Y25) or, via insertion/rearrangement, 1,2- and 1,4-addition
products.25 The reaction product from 15a and pyridine-d5
was thus tentatively concluded to be [Y(η2-(C,N)-C5D4N)-
(12-crown-4)(C5D5N)n]2+[BPh4]- , based on the observed
2
formation of Si(CH3)3(CH2D) and the appearance of a low
We have found a strong effect on the 89Y frequencies
arising from the change in charge at the metal center from
the neutral complex 2 (δ 882.7 ppm) to the monocations
8a, 8c, and 8e (δ 660.0, 660.2, and 666.4 ppm) and then
intensity doublet in the 13C{1H} NMR spectrum (δ 212.6
1
ppm, JYC ) 28.9 Hz) for the pyridyl R-carbon.26
Qualitative evidence for a steady increase in positive
charge from neutral to dicationic complexes at the rare-earth
metal center can be gained from multinuclear NMR studies
1
further to the dication 13a (δ 409.2 ppm). 13C{1H} and H
NMR spectra also give similar evidence for an increase in
nuclear charge concomitant with cation formation. For
instance, the Y-CH2 13C nuclei at yttrium (δ 34.4-39.8
ppm) were recorded at a higher frequency from the neutral
precursors (δ 32.4-32.5 ppm, Table 6), an effect that has
also been noted for cationic mono(amidinate) trimethylsi-
(22) Thomson, M. E.; Baxter, S. M.; Bulls, A. R.; Burger, B. J.; Nolan,
M. C.M Santarsiero, B. D.; Schaefer, W. P.; Bercaw, J. E. J. Am.
Chem. Soc. 1987, 109, 203.
(23) Deelman, B.-J.; Stevels, W. M.; Teuben, J. H.; Lakin, M. T.; Spek,
A. L. Organometallics 1994, 13, 3881.
(24) Watson, P. L. J. Chem. Soc., Chem. Commun. 1983, 276.
(25) Evans, W. J.; Meadows, J. H.; Hunter, W. E.; Atwood, J. L. J. Am.
Chem. Soc. 1984, 106, 1291.
(27) 19F chemical shift differences between meta and para fluorine atoms
of less than 3 ppm are indicative of a noncoordinating anion for
[RB(C6F5)3]- (R ) Me, CH2Ph): Horton, A. D.; de With, J.; van der
Linden, A. J.; van de Weg, H. Organometallics 1996, 15, 2672.
(26) [YCp*2(2-pyridyl)], synthesized from [YCp*2(CH(SiMe3)2)] and pyr-
idine, gives rise to a doublet in the 13C{1H} NMR spectrum (225.5
1
ppm, JYC ) 33.2 Hz) for the pyridine R-carbon (see ref 23).
6782 Inorganic Chemistry, Vol. 44, No. 19, 2005

Rare-Earth Metal Cationic Alkyl Complexes
Table 6. Selected NMR Data for Neutral, Mono- and Dicationic Sc, Y,
THF-d8: δ -0.78 ppm; Lu-CH2, THF-d8: δ -0.99 ppm)
to dicationic (Y-CH2, THF-d8: δ -0.67 ppm; Lu-CH2,
THF-d8: δ -0.85 ppm) species. The extent of the higher
frequency shift depends on the anion used and is greater in
the case of perfluorinated borate anions than for the perpro-
tonated analogues. The Ln-CH2 groups of the monocationic
and dicationic mono(12-crown-4) yttrium and lutetium
compounds also show an anion dependency, in this case a
high-frequency shift with respect to the neutral compound
is noted for complexes with perfluorinated anions while a
low-frequency shift occurs with the perprotonated anions.
These small anion influences not detectable by 11B or 19F
NMR spectroscopy may be due to weak cation-anion
association that is fluxional on the NMR time scale.28
and Lu Complexesa
δ (1H)
δ (13C)
Ln-CH2 2JYH Ln-CH2 1JYC
δ (89Y)
compound
(ppm)
(Hz)
(ppm)
(Hz) Y (ppm) reference
Neutral Yttrium Complexes
2
5
-0.92
-0.83
2.9
2.1
32.5
32.4
35.4
35.0
882.7
29
3b
Monocationic Yttrium Complexes
8a
8b
8c
8d
-0.78
-0.69
-0.80
-0.70
-0.73
-0.89
-0.73
-0.88
-0.73
-0.73
3.3
3.2
3.2
2.9
3.1
2.9
3.1
3.0
3.4
2.8
36.9
37.4
36.7
37.3
37.2
34.4
35.3
39.8b
35.1
35.1
41.2
41.6
41.6
43.0
42.1
40.5
42.4
41.0b
40.8
40.2
660.0
660.2
666.4
8e
3c
3b
11a
11b
11c
11d
11e
3a
Conclusion
Dicationic Yttrium Complexes
0.73c
0.02c
-0.58
-0.91
-0.68
-1.05
3.3c
3.0c
3.4
2.8
2.8
3.2
44.5c
40.1c
39.0
36.9
ndd
44.9c
42.2c
37.1
43.8
409.2c
3a
We have demonstrated that a series of mono- and
dicationic rare-earth metal trimethylsilylmethyl complexes
stabilized by either THF or 12-crown-4 ligands can be
prepared from neutral tris(alkyl) precursors. We have shown
that the preparation of the monocationic complexes is general
for Sc, Y, and Lu and that a range of anions and ether ligands
can stabilize these metal centers. The syntheses of the
dicationic complexes show a strong dependency on the rare-
earth metal, anion, and ether ligand, both on the feasibility
of the reaction, its rate and the solubility of the resultant
complexes. The crystallographic study of the dicationic
complex 15a with 12-crown-4 and THF ligands revealed
well-separated ions in the crystalline state. Detailed multi-
nuclear NMR studies also indicated solvent separated ion
pairs for all mono- and dicationic complexes. These studies
also showed that there is a systematic influence of the charge
13a
15a
15b
15c
17b
17c
26.1
53.3
Neutral Lutetium Complexes
3
6
-1.15
-1.12
40.2
29
3b
39.6b
Monocationic Lutetium Complexes
9a
9b
9c
9d
12a
12b
12c
12d
-0.99
40.0
40.4
39.8
40.4
38.5
39.1
39.5b
39.1
-0.93
-1.03
-0.92
-1.12
-0.97
-1.12b
-0.97
3b
3a
Dicationic Lutetium Complexes
14a
16b
18a
18b
0.47c
-0.68
-0.17c
-0.73
44.3c
39.8
nd
at the yttrium center on the chemical shift values in the 89
Y
and 13C{1H} NMR spectra. In the case of all rare-earth metals
nd
examined, a change from THF to 12-crown-4 or to a different
Neutral Scandium Complexes
1
anion gave rise to a small variation in the H and 13C{1H}
1
4
-0.65
36.3
29
3b
-0.40b
40.0b
frequencies. Our ongoing studies in this area include the
further assessment of these novel species as catalysts for a
range of polymerizations and organic transformations or as
starting materials for the synthesis of organometallic com-
plexes inaccessible via more conventional routes.1q
Monocationic Scandium Complexes
7a
10a
10c
-0.22
-0.21
-0.21
45.0
nd
46.3
3b
a Unless otherwise noted, NMR measurements were made in THF-d8 at
25 °C. b Measured in CD2Cl2. c Measured in pyridine-d5. d nd, not detected.
Experimental Section
General Considerations. All operations were performed under
an inert atmosphere of argon using standard Schlenk-line or
glovebox techniques. THF and toluene were distilled from sodium
benzophenone ketyl. Pentane was purified by distillation from
sodium/triglyme benzophenone ketyl. Anhydrous trichlorides of
scandium, yttrium, and lutetium (ALFA or Strem) were used as
received. All other chemicals were commercially available and used
after appropriate purification. [Ln(CH2SiMe3)3(THF)n] (n ) 2 for
Ln ) Sc, Lu, n ) 3 for Ln ) Y) were prepared according to
lylmethyl complexes.2b The range of chemical shift values
for the dicationic yttrium complexes and the mono- and
dicationic lutetium compounds is much broader and reveals
no discernible trends. The JYC coupling constants are
significantly larger in the case of the monocations (δ 40.2-
43.0 Hz) than the neutral complexes (δ 35.0-35.4 Hz).
The Ln-CH2 groups of the monocationic THF-supported
scandium, yttrium, and lutetium complexes give rise to higher
frequency resonances in the 1H NMR spectrum (Sc: δ -0.22
ppm, Y: δ -0.69 to -0.80 ppm, Lu: δ -0.92 to -1.03
ppm) compared with the respective neutral species (Sc: δ
-0.65 ppm, Y: δ -0.92 ppm, Lu: δ -1.15 ppm). In situ-
generated dications 13a and 14a in THF-d8 demonstrate a
further higher frequency shift from monocationic (Y-CH2,
1
(28) Anion coordination via the phenyl group has been noted in Lewis
base-free rare-earth metal complexes with both fluorinated and
nonfluorinated anionsssee refs 1i,j,o and 2c. BPh4 coordination has
also been noted in cationic zirconium complexes: (a) Bochmann, M.;
Karger, G.; Jaggar, A. J. J. Chem. Soc., Chem. Commun. 1990, 1038.
(b) Horton, A. D.; Frijns, J. H. G. Angew. Chem., Int. Ed. Engl. 1991,
30, 1152.
Inorganic Chemistry, Vol. 44, No. 19, 2005 6783

Elvidge et al.
literature procedures.29 [Ln(CH2SiMe3)3(12-crown-4)] (Ln ) Sc,
Y, Lu) were prepared according to literature procedures.3b X-ray
diffraction data of 4 were collected with an Enraf Nonius CAD4
diffractometer, and the program system WinGX was used for the
data reduction.30 The data of 15a were collected on a Bruker CCD
platform diffractometer equipped with a CCD detector. The SMART
program package was used to determine the unit-cell parameters
and for data collection; the raw frame data was processed using
SAINT and SADABS to yield the reflection data file.31 The
structures were solved by direct methods and difference Fourier
syntheses (SHELXS-86).32 All independent reflections were used
solution. After the volatiles were removed under reduced pressure,
the resultant slightly oily solid was washed with diethyl ether (2 ×
20 mL) and pentane (2 × 20 mL) and dried under vacuum to give
colorless microcrystals (561 mg, 74%). 1H NMR (THF-d8, 25 °C):
δ -0.21 (s, 2 × 2 H, ScCH2SiCH3), -0.04 (s, 2 × 9 H, ScCH2-
SiCH3), 6.73 (t, 3JHH ) 7.0 Hz, 4 × 1 H, Ph-4), 6.87 (m, 4 × 2 H,
Ph-3), 7.28 (m (br), 4 × 2 H, Ph-2). 13C{1H} NMR (THF-d8, 25
°C): δ 3.5 (ScCH2SiCH3), 15.3 (â-CH2, NEt3), 45.0 (s (br), ScCH2-
SiCH3), 65.9 (R-CH2, NEt3), 121.6 (Ph-4), 125.4 (Ph-3), 136.7 (Ph-
1
2), 164.8 (q, JBC ) 49.3 Hz).11B{1H} NMR (THF-d8, 25 °C): δ
-6.6. Anal. Calcd for C44H66BO3Si2Sc: C, 70.00; H, 8.81; Sc, 5.95.
Found: C, 67.22; H, 8.26; Sc, 5.93.
2
in the refinement by full-matrix least-squares against all Fo data
(SHELXL-97).33 Analytical scattering factors for neutral atoms were
used throughout the analysis.34 All non-hydrogen atoms were refined
with anisotropic thermal parameters; the hydrogen atoms were
included into idealized positions. In the structure refinement of 15a,
the carbon atoms C7 and C8 were refined with split positions and
isotropic thermal parameters. For the graphical representation, the
program ORTEP-III was used as implemented in the program
system WinGX.
[Y(CH2SiMe3)2(THF)x]+[BPh4]- (8a) (x ) 3 or 4). A mixture
of 2 (1000 mg, 1884 µmol) and [NEt3H][BPh4] (794 mg, 1884
µmol) was suspended in THF (30 mL) at -78 °C and stirred at
this temperature. The reaction mixture was allowed to slowly warm
to ambient temperature and stirred for 2 h to give a colorless clear
solution. After the volatiles were removed under reduced pressure,
the resultant slightly oily solid was washed with pentane (2 × 30
mL) and dried under vacuum to give colorless microcrystals of
[Y(CH2SiMe3)2(THF)3]+[BPh4]- (1484 mg, 99%). The alternative
product [Y(CH2SiMe3)2(THF)4]+[BPh4]- can be regenerated by a
final washing with THF (5 mL) and drying under vacuum. 1H NMR
NMR spectra were recorded on a Bruker DRX 400 spectrometer
(1H, 400.1 MHz,13C, 100.6 MHz, 11B, 128.4 MHz, 19F, 376.4 MHz,
89Y 19.6 MHz) or on a Varian Unity 500 spectrometer (1H, 500
MHz, 13C, 125.6 MHz, 11B, 160.3 MHz, 19F 470.1 MHz). Chemical
shifts for 1H and 13C NMR spectra were referenced internally using
the residual solvent resonances and reported relative to tetrameth-
ylsilane. 11B NMR spectra were referenced externally to a 1 M
solution of NaBH4 in D2O. 19F NMR spectra were referenced
externally to CCl3F. 89Y spectra were referenced externally to a 1
M solution of YCl3 in D2O.
2
(THF-d8, 25 °C): δ -0.78 (d, JYH ) 3.3 Hz, 2 × 2 H, YCH2-
SiCH3), -0.06 (s, 2 × 9 H, YCH2SiCH3), 1.76 (m, 4 × 4 H, â-CH2,
3
THF), 3.60 (m, 4 × 4 H, R-CH2, THF), 6.74 (t, JHH ) 7.0 Hz,
4 × 1 H, Ph-4), 6.87 (m, 4 × 2 H, Ph-3), 7.28 (m (br), 4 × 2 H,
2
Ph-2).1H NMR (pyridine-d5, 25 °C): δ -0.08 (d, JYH ) 2.3 Hz,
2 × 2 H, YCH2SiCH3), 0.19 (s, 2 × 9 H, YCH2SiCH3), 1.65 (m,
4 × 4 H, â-CH2, THF), 3.68 (m, 4 × 4 H, R-CH2, THF), 7.12 (t,
3JHH ) 7.0 Hz, 4 × 1 H, Ph-4), 7.28 (m, 4 × 2 H, Ph-3), 8.05 (m
(br), 4 × 2 H, Ph-2). 13C{1H} NMR (THF-d8, 25 °C): δ 4.1 (YCH2-
SiCH3), 36.9 (d, 1JYC ) 41.2 Hz, YCH2SiCH3), 122.0 (Ph-4), 125.8
(Ph-3), 137.1 (Ph-2), 165.2 (q, 1JBC ) 49.3 Hz).13C NMR (pyridine-
d5, 25 °C): δ 4.5 (YCH2SiCH3), 25.8 (â-CH2, THF), 30.9 (dt,
1JYC ) 36.5 Hz, 1JCH ) 97.2 Hz, YCH2SiCH3) 67.8 (R-CH2, THF),
Elemental analyses were performed by the Microanalytical
Laboratory of the Johannes Gutenberg-University Mainz, Ger-
many. In many cases the results were not satisfactory, and the best
values from repeated runs were given. Moreover the results were
inconsistent from run to run and therefore not reproducible. We
ascribe this difficulty observed also by other workers to the extreme
sensitivity of the material.35 Metal analysis was performed by
complexometric titration.36 The sample (20-30 mg) was dissolved
in THF (2 mL) or acetonitrile (2 mL) and titrated with a 0.005 M
aqueous solution of EDTA using xylenol orange as indicator and
a 1 M ammonium acetate buffer solution (20 mL).
[Sc(CH2SiMe3)2(THF)3]+[BPh4]- (7a). A mixture of 1 (451 mg,
1.00 mmol) and [NEt3H][BPh4] (421 mg, 1.00 mmol) was
suspended in THF (50 mL) at -78 °C and stirred at this
temperature. The reaction mixture was allowed to slowly warm to
ambient temperature and stirred for 15 h to give a colorless clear
1
122.3 (Ph-4), 126.2 (Ph-3), 137.2 (Ph-2), 165.0 (q, JBC ) 49.3
Hz, Ph-1). 11B{1H} NMR (THF-d8, 25 °C): δ -6.6. 89Y NMR
(THF-d8, 25 °C): δ 660.0. Anal. Calcd for C48H74BO4Si2Y: C,
66.19; H, 8.56; Y, 10.21. Found: C, 65.91; H, 8.44; Y, 9.74.
[Y(CH2SiMe3)2(THF)x]+[B(C6F5)4]- (8b). An NMR tube was
charged with a solution of 2 (37 mg, 75 µmol) and [NMe2PhH]-
[B(C6F5)4] (60 mg, 75 µmol) in THF-d8 (0.5 mL). NMR spectra
were recorded after 40 min at 25 °C: 1H NMR (THF-d8, 25 °C):
2
δ -0.69 (d, JYH ) 3.2 Hz, 2 × 2 H, YCH2), -0.05 (s, 2 × 9 H,
YCH2SiCH3), 0.02 (s, 12 H, SiMe4), 2.87 (s, 2 × 3 H, NMe2Ph-3),
3
3
6.57 (t, JHH ) 7.2 Hz, 1 H, NMe2Ph-4), 6.65 (d, JHH ) 8.4 Hz,
2 H, NMe2Ph-2), 7.09 (m, 2 H, NMe2Ph-3). 13C{1H} NMR (THF-
d8, 25 °C): δ -0.1 (SiMe4), 3.9 (YCH2SiCH3), 37.4 (d, JYC
(29) (a) Lappert, M. F.; Pearce, R. J. Chem. Soc., Chem. Commun. 1973,
126. (b) Evans, W. J.; Brady, J. C.; Ziller, J. W. J. Am. Chem. Soc.
2001, 123, 7711. (c) Schumann, H.; Freckmann, D. M. M.; Dechert,
S. Z. Anorg. Allorg. Chem., 2002, 628, 2422.
(30) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837.
(31) Siemens. ASTRO, SAINT and SADABS. Data Collection and Process-
ing Software for the SMART System; Siemens Analytical X-ray
Instruments Inc.: Madison, WI, 1996.
(32) Sheldrick, G. M. SHELXS-86, Program for Crystal Structure Solution;
University of Go¨ttingen: Go¨ttingen, Germany, 1986.
(33) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure Refine-
ment; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(34) International Tables for X-ray Crystallography, Vol. C; Kluwer
Academic Publishers: Dordrecht, 1992.
(35) (a) Mitchell, J. P.; Hajela, S.; Brookhart, S. K.; Hardcastle, K. I.;
Henling, L. M.; Bercaw, J. E. J. Am. Chem. Soc. 1996, 118, 1045. (b)
Bambirra, S.; Brandsma, M. J. R.; Brussee, E. A. C.; Meetsma, A.;
Hessen, B.; Teuben, J. H.; Organometallics 2000, 19, 3197.
(36) Arndt, S.; Spaniol, T. P.; Okuda, J. Organometallics 2003, 22, 775
and references therein.
1
)
41.6 Hz, YCH2), 40.4 (NMe2Ph), 113.1, 116.9 (NC6H5), 125.0 (br
m, C6F5-1), 129.3 (NMe2Ph), 137.0 (d, 1JCF ) 241.6 Hz, C6F5-3),
1
1
139.0 (d, JCF ) 242.8 Hz, C6F5-4), 149.0 (d, JCF ) 243.4 Hz,
C6F5-2).11B{1H} NMR (THF-d8, 25 °C): δ -16.7. 19F NMR (THF-
d8, 25 °C): δ -168.8, -165.2, -133.1.
[Y(CH2SiMe3)2(THF)x]+[BPh3(CH2SiMe3)]- (8c) (x ) 3 or 4).
A mixture of 2 (600 mg, 1130 µmol) and BPh3 (274 mg, 1130
µmol) was suspended in THF (20 mL) at -78 °C and stirred at
this temperature. The reaction mixture was allowed to slowly warm
to ambient temperature and stirred for 6 h to give a very pale yellow
solution. After the volatiles were removed under reduced pressure,
the resultant yellow oil was washed with pentane (2 × 30 mL)
to give [Y(CH2SiMe3)2(THF)4]+[ BPh3(CH2SiMe3)]- and dried
under vacuum to give colorless microcrystals of [Y(CH2SiMe3)2-
6784 Inorganic Chemistry, Vol. 44, No. 19, 2005

Rare-Earth Metal Cationic Alkyl Complexes
(THF)3]+[BPh3(CH2SiMe3)]- (792 mg, 87%). NMR data (for x )
3): 1H NMR (THF-d8, 25 °C): δ -0.80 (d, 2JYH ) 3.2 Hz, 2 × 2
H, YCH2), -0.49 (s, 9 H, BCH2SiCH3), -0.07 (s, 2 × 9 H, YCH2-
[Lu(CH2SiMe3)2(THF)x]+[B(C6F5)4]- (9b). An NMR tube was
charged with a solution of 3 (44 mg, 75 µmol) and [NMe2PhH]-
[B(C6F5)4] (60 mg, 75 µmol) in THF-d8 (0.5 mL). Recorded spectra
after 2 h at 25 °C: 1H NMR (THF-d8, 25 °C): δ -0.93 (s, 2 × 2
H, LuCH2), -0.05 (s, 2 × 9 H, LuCH2SiCH3), 0.02 (s, 12 H,
2
3
SiCH3), 0.18 (q, JBH ) 4.8 Hz, 2 H, BCH2), 6.67 (t, JHH ) 7.1
Hz, 3 × 1 H, Ph-4), 6.83 (m, 3 × 2 H, Ph-3), 7.38 (m (br), 3 × 2
H, Ph-2). 13C{1H} NMR (THF-d8, 25 °C): δ 2.7 (BCH2SiCH3),
4.0 (YCH2SiCH3), 36.7 (d, 1JYC ) 41.6 Hz, YCH2), 121.5 (Ph-4),
3
SiMe4), 2.87 (s, 2 × 3 H, NMe2Ph), 6.57 (t, JHH ) 7.2 Hz, 1 H,
3
NMe2Ph-4), 6.66 (d, JHH ) 8.4 Hz, 2 H, NMe2Ph-2), 7.09 (m, 2
1
125.6 (Ph-3), 135.7 (Ph-2), 167.8 (q, JBC ) 48.5 Hz, Ph-1). The
H, NMe2Ph-3). 13C{1H} NMR (THF-d8, 25 °C): δ -0.1 (SiMe4),
4.1 (LuCH2SiCH3), 40.4 (LuCH2, NMe2Ph), 113.1, 116.9, (NC6H5),
125.0 (br m, C6F5-1), 129.3 (NMe2Ph), 137.0 (d, 1JCF ) 242.8 Hz,
C6F5-3), 139.0 (d, 1JCF ) 242.2 Hz, C6F5-4), 149.0 (d, 1JCF ) 241.6
Hz, C6F5-2). 11B{1H} NMR (THF-d8, 25 °C): δ -16.7. 19F NMR
(THF-d8, 25 °C): δ -168.8, -165.2, -133.1.
signal of the BCH2 group was not detected.11B{1H} NMR (THF-
d8, 25 °C): δ -10.3.89Y{1H} NMR (THF-d8, 25 °C): δ 660.2.
Anal. Calcd for C42H72BO3Si3Y: C, 62.36; H, 8.97; Y, 10.99.
Found: C, 61.52; H, 9.34; Y, 10.48.
[Y(CH2SiMe3)2(THF)x]+[B(C6F5)3(CH2SiMe3)]- (8d). An NMR
tube was charged with a solution of 2 (37 mg, 75 µmol) and
B(C6F5)3 (38 mg, 75 µmol) in THF-d8 (0.5 mL). NMR spectra were
recorded after 4 h at 25 °C and 0.5 h at 50 °C: 1H NMR (THF-d8,
25 °C): δ -0.70 (d, 2JYH ) 2.9 Hz, 2 × 2 H, YCH2), -0.38 (s, 9
H, BCH2SiCH3), -0.06 (s, 2 × 9 H, YCH2SiCH3), 0.58 (br, 2 H,
BCH2). 13C{1H} NMR (THF-d8, 25 °C): δ 1.3 (BCH2SiCH3), 3.9
(YCH2SiCH3), 37.3 (d, 1JYC ) 43.0 Hz, YCH2), 129.8 (br, C6F5-1)
[Lu(CH2SiMe3)2(THF)3]+[BPh3(CH2SiMe3)]- (9c). A mixture
of 3 (500 mg, 861 µmol) and BPh3 (209 mg, 861 µmol) was
suspended in THF (20 mL) at -78 °C and stirred at this
temperature. The reaction mixture was allowed to slowly warm to
ambient temperature and stirred for 4 h to give a very pale yellow
solution. After the volatiles were removed under reduced pressure,
the resultant yellow oil was washed with heptane (2 × 30 mL) and
dried under vacuum to give colorless microcrystals (700 mg, 91%).
1H NMR (THF-d8, 25 °C): δ -1.03 (s, 2 × 2 H, LuCH2), -0.49
(s, 9 H, BCH2SiCH3), -0.06 (s, 2 × 9 H, LuCH2SiCH3), 0.18 (q,
1
1
137.0 (d, JCF ) 243.6 Hz, C6F5-3), 138.2 (d, JCF ) 241.2 Hz,
C6F5-4), 149.1 (d, 1JCF ) 236.8 Hz, C6F5-2). The signal of the BCH2
group was not detected.11B{1H} NMR (THF-d8, 25 °C): δ -14.2.
19F NMR (THF-d8, 25 °C): δ -169.3, -167.1, -132.0.
3
2JBH ) 4.8 Hz, 2 H, BCH2), 6.67 (t, JHH ) 7.1 Hz, 3 × 1 H,
1
[Y(CH2SiMe3)2(THF)4]+[Al(CH2SiMe3)4]- (8e). A solution of
2 (100 mg, 202 µmol) in pentane (0.3 mL) was treated with THF
(72 µL, 1 mmol) and Al(CH2SiMe3)3 (73 µL, 202 µmol). After the
mixture was stirred for 5 min at 25 °C, the turbid suspension was
cooled to -40 °C. After 7 days at this temperature, colorless crystals
4-Ph), 6.83 (m (br), 3 × 2 H, Ph-3), 7.38 (br, 3 × 2 H, Ph-2). H
NMR (pyr-d5, 25 °C): δ -0.12 (s, 2 × 2 H, LuCH2), 0.04 (s, 2 ×
2
9 H, LuCH2SiCH3), 0.08 (s, 9 H, BCH2SiCH3), 0.96 (q, JBH
)
4.8 Hz, 2 H, BCH2), 1.60 (m, 3 × 4 H, â-CH2, THF), 3.64 (m,
3
3 × 4 H, R-CH2, THF), 7.06 (t, JHH ) 7.1 Hz, 3 × 1 H, 4-Ph),
7.29 (m, 3 × 2 H, Ph-3), 8.13 (m (br), 3 × 2 H, Ph-2). 13C{1H}
NMR (THF-d8, 25 °C): δ 2.8 (BCH2SiCH3), 4.2 (LuCH2SiCH3),
39.8 (LuCH2), 121.5 (Ph-4), 125.6 (Ph-3), 135.7 (Ph-2), 167.8 (q,
1JBC ) 48.7 Hz, Ph-1). The signal of the BCH2 group was not
detected.11B{1H} NMR (THF-d8, 25 °C): δ -10.3. Anal. Calcd
for C42H72BO3Si3Lu: C, 56.36; H, 8.11; Lu, 19.55. Found: C,
47.29; H, 7.67; Lu, 19.54.
1
(140 mg, 75%) formed. H NMR (THF-d8, 25 °C): δ -1.28 (br
2
m, 4 × 2 H, AlCH2), -0.73 (d, JYH ) 3.1 Hz, 2 × 2 H, YCH2),
-0.16 (s, 4 × 9 H, AlCH2SiCH3), -0.09 (s, 2 × 9 H, YCH2SiCH3),
1.75 (m, 4 × 4 H, â-CH2, THF), 3.60 (m, 4 × 4 H, R-CH2, THF).
13C{1H} NMR (THF-d8, 25 °C): δ 3.8 (YCH2SiCH3), 3.9 (AlCH2-
SiCH3), 4.4 (AlCH2), 37.2 (d, 1JYC ) 42.1 Hz, YCH2). 27Al NMR
(THF-d8, 25 °C): δ 150.9. 89Y NMR (THF-d8, 25 °C): δ 666.4.
Anal. Calcd for C40H98AlO4Si6Y: C, 51.79; H, 10.65. Found: C,
51.82; H, 10.66.
[Lu(CH2SiMe3)2(THF)x]+[B(C6F5)3(CH2SiMe3)]- (9d). An NMR
tube was charged with a solution of 3 (40 mg, 69 µmol) and
B(C6F5)3 (35 mg, 69 µmol) in THF-d8 (0.5 mL). NMR spectra were
recorded after 12 h at 40 °C: 1H NMR (THF-d8, 25 °C): δ -0.92
(s, 2 × 2 H, LuCH2), -0.37 (s, 9 H, BCH2SiCH3), -0.05 (s, 2 ×
9 H, LuCH2SiCH3), 0.59 (br, 2 H, BCH2). 13C{1H} NMR (THF-
d8, 25 °C): δ 1.3 (BCH2SiCH3), 4.1 (LuCH2SiCH3), 40.4 (LuCH2),
[Lu(CH2SiMe3)2(THF)3]+[BPh4]- (9a). A mixture of 3 (1000
mg, 1720 µmol) and [NEt3H][BPh4] (726 mg, 1720 µmol) was
suspended in THF (35 mL) at -78 °C and stirred at this
temperature. The reaction mixture was allowed to slowly warm to
ambient temperature and stirred for 2 h to give a colorless clear
solution. After the volatiles were removed under reduced pressure,
the resultant colorless solid was washed with pentane (2 × 30 mL)
and dried under vacuum to give colorless microcrystals (1485 mg,
1
129.8 (C6F5-1), 137.0 (d, JCF ) 242.8 Hz, C6F5-3), 138.3 (d,
1JCF ) 241.2 Hz, C6F5-4), 149.2 (d, 1JCF ) 226.1 Hz, C6F5-2). The
signal of the BCH2 group was not detected. 11B{1H} NMR (THF-
d8, 25 °C): δ -14.2. 19F NMR (THF-d8, 25 °C): δ -169.4, -167.1,
-132.0.
1
98%). H NMR (THF-d8, 25 °C): δ -0.99 (s, 2 × 2 H, LuCH2-
SiCH3), -0.05 (s, 2 × 9 H, LuCH2SiCH3), 1.76 (m, 3 × 4 H,
â-CH2, THF), 3.60 (m, 3 × 4 H, R-CH2, THF), 6.72 (t, 3JHH ) 7.0
Hz, 4 × 1 H, Ph-4), 6.87 (m, 4 × 2 H, Ph-3), 7.28 (m (br), 4 × 2
H, Ph-2).1H NMR (pyridine-d5, 25 °C): δ -0.10 (s, 2 × 2 H,
LuCH2SiCH3), 0.06 (s, 2 × 9 H, LuCH2SiCH3), 1.62 (m, 3 × 4 H,
â-CH2, THF), 3.66 (m, 3 × 4 H, R-CH2, THF), 7.11 (t, 3JHH ) 7.0
Hz, 4 × 1 H, Ph-4), 7.28 (m, 4 × 2 H, Ph-3), 8.06 (m (br), 4 × 2
H, Ph-2). 13C{1H} NMR (THF-d8, 25 °C): δ 4.4 (LuCH2SiCH3),
40.0 (LuCH2SiCH3), 121.9 (Ph-4), 125.7 (Ph-3), 137.0 (Ph-2), 165.0
(q, 1JBC ) 49.3 Hz).13C NMR (pyridine-d5, 25 °C): δ 3.8 (LuCH2-
[Sc(CH2SiMe3)2(12-crown-4)]+[BPh3(CH2SiMe3)]- (10c). A
solution of BPh3 (83 mg, 345 µmol) in THF (2 mL) was added to
a solution of 4 (166 mg, 345 µmol) at room temperature. The
solution was stirred at this temperature for 3 h, the solvent was
removed under reduced pressure, and the slightly sticky, off-white
crude product was washed with heptane (2 × 15 mL). Removing
the volatiles under reduced pressure gave 10c as colorless micro-
crystals (210 mg, 84%). 1H NMR (THF-d8, 25 °C): δ -0.50 (s, 9
H, BCH2SiCH3), -0.21 (s, 2 × 2 H, ScCH2), -0.10 (s, 2 × 9 H,
ScCH2SiCH3), 0.19 (q, 2JBH ) 4.9 Hz, 2 H, BCH2), 3.34, 3.65 (m,
SiCH3), 25.5 (â-CH2, THF), 42.8 (s, LuCH2SiCH3), 67.5 (R-CH2,
1
3
THF), 122.0 (Ph-4), 125.9 (Ph-3), 136.8 (Ph-2), 164.7 (q, JBC
)
2 × 8 H, 12-crown-4), 6.74 (t, JHH ) 6.8 Hz, 3 × 1 H, Ph-4),
48.9 Hz, Ph-1). 11B{1H} NMR (THF-d8, 25 °C): δ -6.6. 11B{1H}
NMR (pyridine-d5, 25 °C): δ -5.7. Anal. Calcd for C44H66BLuO3-
Si2 C, 59.72; H, 7.52; Lu, 19.77. Found: C, 59.24; H, 6.90; Lu,
19.35.
6.91 (m, 3 × 2 H, Ph-3), 7.43 (m (br), 3 × 2 H, Ph-2). 13C{1H}
NMR (THF-d8, 25 °C): δ 2.6 (BCH2SiCH3), 3.6 (ScCH2SiCH3),
14.4 (q, 1JBC ) 39.3 Hz, BCH2SiCH3), 46.3 (s(br), ScCH2SiCH3),
68.8 (12-crown-4), 121.7 (Ph-4), 125.8 (Ph-3), 135.7 (Ph-2), 167.9
Inorganic Chemistry, Vol. 44, No. 19, 2005 6785

Elvidge et al.
1
(q, JBC ) 49.1 Hz, Ph-1). 11B{1H} NMR (THF-d8, 25 °C): δ
C6F5-2). 11B{1H} NMR (THF-d8, 25 °C): δ -16.7. 19F NMR (THF-
d8, 25 °C): δ -168.3, -164.8, -132.8.
-10.4. Anal. Calcd for C38H64BO4Si3Sc: C, 62.96; H, 8.90; Sc,
6.20. Found: C, 60.64; H, 9.16; Sc, 6.24.
[Y(CH2SiMe3)2(12-crown-4)(THF)x]+[B(C6F5)4]- (11b). An
NMR tube was charged with 5 (25 mg, 47 µmol) and [NMe2PhH]-
[B(C6F5)4] (25 mg, 47 µmol) in THF-d8 (500 µL). NMR spectra
were recorded after standing for 10 min at room temperature: 1H
[Lu(CH2SiMe3)2(12-crown-4)(THF)x]+[B(C6F5)3(CH2Si-
Me3)]- (12d). An NMR tube was charged with 6 (50 mg, 82 µmol)
and B(C6F5)3 (42 mg, 82 µmol) in THF-d8 (500 µL). NMR spectra
were recorded after standing for 24 h at room temperature and 1 h
at 50 °C: 1H NMR (THF-d8, 25 °C): δ -0.97 (s, 2 × 2 H, LuCH2),
-0.36 (s, 9 H, BCH2SiCH3), -0.06 (s, 2 × 9 H, LuCH2SiCH3),
4.06, 4.20 (m, 2 × 8 H, 12-crown-4). 13C{1H} NMR (THF-d8, 25
°C): δ 1.2 (BCH2SiCH3), 4.1 (LuCH2SiCH3), 9.5 (BCH2SiCH3),
2
NMR (THF-d8, 25 °C): δ -0.73 (d, JYH ) 3.1 Hz, 2 × 2 H,
YCH2), -0.06 (s, 2 × 9 H, YCH2SiCH3), 0.00 (s, 12 H, SiMe4),
2.88 (s, 2 × 3 H, NMe2Ph), 4.08, 4.20 (m, 2 × 8 H, 12-crown-4),
3
3
6.58 (t, JHH ) 7.2 Hz, 1 H, NMe2Ph-4), 6.68 (d, JHH ) 8.4 Hz,
2 H, NMe2Ph-2), 7.11 (m, 2 H, NMe2Ph-3). 13C{1H} NMR (THF-
d8, 25 °C): δ 0.0 (SiMe4), 4.2 (YCH2SiCH3), 35.3 (d, 1JYC ) 42.4
Hz, YCH2), 40.6 (NMe2Ph), 68.9 (12-crown-4), 113.3, 117.1, 124.8
(m (br), C6F5-1), 129.5, 151.8 (NMe2Ph), 137.9 (m, C6F5-3, C6F5-
39.1 (LuCH2), 68.7 (12-crown-4), 129.8 (C6F5-1), 137.0 (d, 1JCF
)
1
242.4 Hz, C6F5-3), 138.2 (d, JCF ) 242.4 Hz, C6F5-4), 149.2 (d,
1JCF ) 237.4 Hz, C6F5-2). 11B{1H} NMR (THF-d8, 25 °C): δ
-14.2. 19F NMR (THF-d8, 25 °C): δ -168.9, -166.6, -131.6.
[Y(CH2SiMe3)(THF)5]2+[BPh4]- (13a). A mixture of 2 (400
2
4), 148.9 (d, JCF ) 247.4 Hz, C6F5-2). 11B{1H} NMR (THF-d8,
1
mg, 808 µmol) and [NEt3H][BPh4] (1022 mg, 2430 µmol) was
suspended in THF (30 mL) at -78 °C. The stirred reaction mixture
was allowed to slowly warm to ambient temperature and stirred
for 48 h. Removing small amounts of insoluble impurities by
filtration gave a colorless clear solution, the volume of which was
reduced to 10 mL under reduced pressure. Cooling to -30 °C
recovered colorless crystals of [NEt3H][BPh4] (323 mg). Evapora-
tion of the volatiles of the supernatant gave a colorless solid residue.
Washing with Et2O (2 × 20 mL) and removing the solvent under
reduced pressure yielded 13a as a colorless powder (690 mg, 77%).
1H NMR (pyridine-d5, 25 °C): δ 0.17 (s, 9 H, YCH2SiCH3), 0.73
25 °C): δ -16.7. 19F NMR (THF-d8, 25 °C): δ -168.7, -165.1,
-133.1.
[Y(CH2SiMe3)2(12-crown-4)(THF)x]+[B(C6F5)3(CH2Si-
Me3)]- (11d). An NMR tube was charged with 5 (50 mg, 95 µmol)
and B(C6F5)3 (49 mg, 95 µmol) in THF-d8 (500 µL). NMR spectra
were recorded after standing for 24 h at room temperature and 1 h
at 50 °C: 1H NMR (THF-d8, 25 °C): δ -0.73 (d, 2JYH ) 3.4 Hz,
2 × 2 H, YCH2), -0.37 (s, 9 H, BCH2SiCH3), -0.07 (s, 2 × 9 H,
YCH2SiCH3), 4.08, 4.20 (m, 2 × 8 H, 12-crown-4). 13C{1H} NMR
(THF-d8, 25 °C): δ 1.2 (BCH2SiCH3), 3.9 (YCH2SiCH3), 9.5
1
2
(BCH2SiCH3), 35.1 (d, JYC ) 40.8 Hz, YCH2), 68.7 (12-crown-
4), 129.8 (m (br), C6F5-1), 137.0 (d, JCF ) 246.2 Hz, C6F5-3),
138.3 (d, JCF ) 243.6 Hz, C6F5-4), 149.2 (d, JCF ) 238.6 Hz,
C6F5-2). 11B{1H} NMR (THF-d8, 25 °C): δ -14.2. 19F NMR (THF-
d8, 25 °C): δ -168.9, -166.6, -131.6.
(d, JYH ) 3.3 Hz, 2 H, YCH2SiCH3), 1.62 (m, 4 × 4 H, â-CH2,
1
3
THF), 3.66 (m, 4 × 4 H, R-CH2, THF), 7.10 (t, JHH ) 7.3 Hz,
1
1
8 × 1 H, Ph-4), 7.27 (m, 8 × 2 H, Ph-3), 8.06 (m (br), 8 × 2 H,
Ph-2). 13C NMR (pyridine-d5, 25 °C): δ 4.0 (YCH2SiCH3), 25.9
1
1
(â-CH2, THF), 44.5 (dt, JYC ) 44.9 Hz, JCH ) 93.8 Hz, YCH2-
SiCH3), 67.9 (R-CH2, THF), 122.4 (Ph-4), 126.2 (Ph-3), 137.1 (Ph-
[Y(CH2SiMe3)2(12-crown-4)(THF)]+[Al(CH2SiMe3)4]- (11e).
To a solution of 5 (200 mg, 380 µmol) in THF (7 mL) was added
neat Al(CH2SiMe3)3 (137 µL, 380 µmol). After the solution was
stirred overnight, the solvent was removed under reduced pressure.
The residue was washed with pentane to give colorless microcrystals
(297 mg, 92%). 1H NMR (THF-d8, 25 °C): δ -1.23 (br, 4 × 2 H,
1
2), 165.0 (q, JBC ) 49.2 Hz, Ph-1). 13C{1H} NMR (THF-d8,
25 °C): δ 3.9 (YCH2SiCH3), 25.5 (â-CH2, THF), 67.8 (R-CH2,
1
THF), 122.2 (Ph-4), 125.9 (Ph-3), 137.1 (Ph-2), 165.1 (q, JBC
)
49.2 Hz, Ph-1). The signal for the methylene group attached to
yttrium was not detected. 11B{1H} NMR (THF-d8, 25 °C): δ -6.7.
89Y NMR (THF-d8, 25 °C): δ 409.2. Anal. Calcd for C72H91B2O5-
SiY: C, 73.59; H, 7.81; Y, 7.57. Found: C, 74.62; H, 8.37;
Y, 7.16.
2
AlCH2), -0.73 (d, JYH ) 2.80 Hz, 2 × 2 H, YCH2), -0.11 (s,
4 × 9 H, AlCH2SiCH3), -0.06 (s, 2 × 9 H, YCH2SiCH3), 1.77
(m, 4 H, â-CH2, THF), 3.60 (m, 4 H, R-CH2, THF), 4.10, 4.22 (br,
1
2 × 8 H, 12-crown-4). H NMR (CD2Cl2, 25 °C): δ -1.29 (br,
[Lu(CH2SiMe3)(THF)4]2+[BPh4]-2 (14a). A mixture of 3 (290
mg, 500 µmol) and [NMe2PhH][BPh4] (552 mg, 1250 µmol) was
suspended in THF (30 mL) at -78 °C. The reaction mixture was
slowly warmed to room temperature, resulting in a clear, light brown
solution, which was stirred for 4 h. Filtration, evaporation of the
volatiles and washing with toluene (20 mL), pentane (60 mL) and
THF (5 mL) gave 14a as a colorless powder (370 mg, 62.3%). 1H
NMR (pyridine-d5, 25 °C): δ 0.12 (s, 9 H, LuCH2SiCH3), 0.47 (s,
2 H, LuCH2SiCH3), 1.60 (m, 4 × 4 H, â-CH2, THF), 3.64 (m, 4 ×
2
4 × 2 H, AlCH2), -0.70 (d, JYH ) 2.40 Hz, 2 × 2 H, YCH2),
-0.09 (s, 4 × 9 H, AlCH2SiCH3), -0.07 (s, 2 × 9 H, YCH2SiCH3),
2.11 (m, 4 H, â-CH2, THF), 3.97 (br, 8 H, 12-crown-4), 4.22 (br,
8 + 4 H, 12-crown-4 + R-CH2, THF). 13C{1H} NMR (THF-d8,
25 °C): δ 3.0 (AlCH2), 4.2 (YCH2SiCH3 + AlCH2SiCH3), 35.1
1
(d, JYC ) 40.2 Hz, YCH2), 68.9 (12-crown-4). 13C{1H} NMR
(CD2Cl2, 25 °C): δ 3.86 (YCH2SiCH3 + AlCH2SiCH3), 37.2 (d,
1JYC ) 42.0 Hz, YCH2), 72.4 (12-crown-4). Anal. Calcd for
C34H86O4.5AlSi6Y (corresponding to 0.5 THF): C, 47.96; H, 10.18.
Found: C, 47.23; H, 10.11.
3
4 H, R-CH2, THF), 7.08 (t, JHH ) 7.3 Hz, 8 × 1 H, Ph-4), 7.25
(m, 8 × 2 H, Ph-3), 8.03 (m (br), 8 × 2 H, Ph-2). 13C NMR
(pyridine-d5, 25 °C): δ 3.8 (LuCH2SiCH3), 25.5 (â-CH2, THF),
44.3 (LuCH2SiCH3), 67.5 (R-CH2, THF), 122.1 (Ph-4), 125.9 (Ph-
[Lu(CH2SiMe3)2(12-crown-4)(THF)x]+[B(C6F5)4]- (12b). An
NMR tube was charged with 6 (50 mg, 82 µmol) and [NMe2PhH]-
[B(C6F5)4] (65 mg, 82 µmol) in THF-d8 (500 µL). NMR spectra
were recorded after standing for 15 min at room temperature: 1H
NMR (THF-d8, 25 °C): δ -0.97 (s, 2 × 2 H, LuCH2), -0.06 (s,
1
3), 136.8 (Ph-2), 164.6 (q, JBC ) 49.2 Hz, Ph-1). 11B{1H} NMR
(pyridine-d5, 25 °C): δ -5.8. Anal. Calcd for C68H83B2LuO4Si:
C, 68.69; H, 7.04; Lu, 14.71. Found: C, 62.40; H, 6.78; Lu, 15.13.
2 × 9 H, LuCH2SiCH3), 0.00 (s, 12 H, SiMe4), 2.88 (s, 2 × 3 H,
[Y(CH2SiMe3)(12-crown-4)(THF)3]2+[BPh4]- (15a). A mix-
2
3
NMe2Ph), 4.04, 4.19 (m, 2 × 8 H, 12-crown-4), 6.58 (t, JHH
)
ture of 5 (44 mg, 84 µmol) and [NEt3H][BPh4] (75 mg, 178 µmol)
was dissolved in THF (1.5 mL), briefly stirred vigorously and left
at 25 °C for 3 days. 15a was isolated as large, colorless crystals,
which were separated in the glovebox from a small amount of
colorless needles (of an unidentified coproduct) and dried under
vacuum to give 15a as a white microcrystalline solid (95 mg, 94%).
7.2 Hz, 1 H, NMe2Ph-4), 6.68 (d, 3JHH ) 8.4 Hz, 2 H, NMe2Ph-2),
7.11 (m, 2 H, NMe2Ph-3). 13C{1H} NMR (THF-d8, 25 °C): δ 0.0
(SiMe4), 4.1 (LuCH2SiCH3), 39.1 (LuCH2), 40.3 (NMe2Ph), 68.8
(12-crown-4), 113.3, 117.1, 129.5, 151.8 (NMe2Ph), 125.0 (m (br),
1
C6F5-1), 137.9 (m, C6F5-3, C6F5-4), 148.9 (d, JCF ) 243.4 Hz,
6786 Inorganic Chemistry, Vol. 44, No. 19, 2005

Rare-Earth Metal Cationic Alkyl Complexes
1H NMR (pyridine-d5, 25 °C): δ -0.19 (s, 2 × 9 H, YCH2SiCH3),
(R-CH2, THF), 72.3 (12-crown-4), 122.0 (Ph-4), 126.1 (Ph-3), 135.5
(Ph-2), 167.7 (q, JBC ) 48.1 Hz, Ph-1). The signal for the BCH2
group was not detected. Anal. Calcd for C64H95B2O6Si3Y: C, 66.54;
H, 8.29; Y, 7.70. Found: C, 65.15; H, 9.12; Y 8.07.
2
1
0.02 (d, JYH ) 3.0 Hz, 2 H, YCH2), 1.62 (m, 2 × 4 H, â-CH2,
THF), 3.65 (m, 2 × 4 H, R-CH2, THF), 3.99 (m, 16 H, 12-crown-
3
4), 7.11 (t, JHH ) 7.0 Hz, 8 × 1 H, Ph-4), 7.26 (m, 8 × 2 H,
Ph-3), 8.00 (m (br), 8 × 2 H, Ph-2). 13C NMR (pyridine-d5,
[Lu(CH2SiMe3)(12-crown-4)(THF)x]2+[B(C6F5)4]-2 (16b). An
NMR tube was charged with 6 (50 mg, 82 µmol) and [NMe2PhH]-
[B(C6F5)4] (130 mg, 164 µmol) in THF-d8 (500 µL). NMR spectra
were recorded after standing for 30 min at room temperature: 1H
NMR (THF-d8, 25 °C): δ -0.68 (s, 2 H, LuCH2), -0.03 (s, 9 H,
LuCH2SiCH3), 0.00 (s, 2 × 12 H, SiMe4), 2.92 (s, 4 × 3 H, NMe2-
Ph), 4.36, 4.40 (m, 4 × 8 H, 12-crown-4), 6.66 (t, 3JHH ) 7.2 Hz,
2 × 1 H, NMe2Ph-4), 6.75 (d, 3JHH ) 8.4 Hz, 2 × 2 H, NMe2Ph-
2), 7.16 (m, 2 × 2 H, NMe2Ph-3). 13C{1H} NMR (THF-d8,
25 °C): δ 0.0 (SiMe4), 3.3 (LuCH2SiCH3), 39.8 (LuCH2), 40.6
(NMe2Ph), 70.7 (12-crown-4), 113.4, 117.5, 129.3 (NMe2Ph), 124.7
(m (br), C6F5-1), 137.9 (m, C6F5-3, C6F5-4), 149.1 (d, 1JCF ) 240.4
Hz, C6F5-2). 11B{1H} NMR (THF-d8, 25 °C): δ -16.6. 19F NMR
(THF-d8, 25 °C): δ -168.3, -164.7, -132.7.
25 °C): δ 3.2 (YCH2SiCH3), 25.5 (â-CH2, THF), 40.1 (d, 1JYC
)
42.2 Hz, YCH2SiCH3), 67.5 (R-CH2, THF), 69.4 (12-crown-4),
1
122.1 (Ph-4), 125.9 (Ph-3), 136.7 (Ph-2), 164.5 (q, JBC ) 48.9
Hz, Ph-1). 11B{1H} NMR (pyridine-d5, 25 °C): δ -5.9. Anal. Calcd
for C72H91B2O7SiY (3 × THF): C, 71.64; H, 7.60; Y, 7.37;
C68H83B2O6SiY (2 × THF): C, 71.96; H, 7.37; Y, 7.83. Found:
C, 66.61; H, 8.31; Y, 8.29.
[Y(η2-(C,N)-C5D4N)(12-crown-4)(C5D5N)n]2+[BPh4]-2. Com-
plex 15a (50 mg, 41 µmol) was dissolved in pyridine-d5 (0.5 mL).
1
NMR spectra were measured after standing for 24 h at 25 °C. H
NMR (pyridine-d5, 25 °C): δ 0.00 (s, 9 H, Si(CH3)3(CH2D)), -0.03
(t, 2JDH ) 2.1 Hz, 2 H, Si(CH3)3(CH2D)), 1.62 (m, 2 × 4 H, â-CH2,
THF), 3.65 (m, 2 × 4 H, R-CH2, THF), 4.06 (s, 16 H, 12-crown-
3
[Y(CH2SiMe3)(12-crown-4)2(THF)x]2+[B(C6F5)4]-2 (17b). An
NMR tube was charged with 5 (25 mg, 47 µmol) and [NMe2PhH]-
[B(C6F5)4] (76 mg, 95 µmol) in THF-d8 (500 µL). 12-Crown-4
(8 mg, 47 µmol) was added to the resultant clear, colorless solution.
NMR spectra were recorded after standing for 1 h at room
4), 7.11 (t, JHH ) 7.0 Hz, 8 × 1 H, Ph-4), 7.26 (m, 8 × 2 H,
Ph-3), 8.00 (m (br), 8 × 2 H, Ph-2). 13C NMR (pyridine-d5,
1
25 °C): δ -0.7 (t, JDC ) 18.2 Hz, Si(CH3)3(CH2D)), -0.3 (Si-
(CH3)3(CH2D)), 25.5 (â-CH2, THF), 67.5 (R-CH2, THF), 68.9 (12-
crown-4), 122.1 (Ph-4), 125.9 (Ph-3), 136.7 (Ph-2), 164.5 (q,
1
1JBC ) 48.9 Hz, Ph-1), 212.6 (d, JYC ) 28.9 Hz, C5D4N-2). 11B-
2
temperature: 1H NMR (THF-d8, 25 °C): δ -0.68 (d, JYH ) 2.8
{1H} NMR (pyridine-d5, 25 °C): δ -5.9.
Hz, 2 H, YCH2), -0.07 (s, 9 H, YCH2SiCH3), 0.00 (s, 2 × 12 H,
[Y(CH2SiMe3)(12-crown-4)(THF)x]2+[B(C6F5)4]- (15b). An
SiMe4), 2.89 (s, 4 × 3 H, NMe2Ph), 4.15, 4.41 (m (br), 4 × 8 H,
2
3
12-crown-4), 6.59 (t, JHH ) 7.2 Hz, 2 × 1 H, NMe2Ph-4), 6.68
NMR tube was charged with 5 (25 mg, 47 µmol) and [NMe2PhH]-
[B(C6F5)4] (76 mg, 95 µmol) in THF-d8 (500 µL). NMR spectra
were recorded after standing for 10 min at room temperature: 1H
3
(d, JHH ) 8.4 Hz, 2 × 2 H, NMe2Ph-2), 7.11 (m, 2 × 2 H,
NMe2Ph-3). 13C{1H} NMR (THF-d8, 25 °C): δ 0.0 (SiMe4), 4.0
(YCH2SiCH3), 40.6 (NMe2Ph), 71.6 (12-crown-4), 113.3, 117.1,
129.4, 151.8 (NMe2Ph), 125.0 (m (br), C6F5-1), 138.2 (m, C6F5-3,
2
NMR (THF-d8, 25 °C): δ -0.58 (d, JYH ) 3.4 Hz, 2 H, YCH2),
-0.04 (s, 9 H, YCH2SiCH3), 0.00 (s, 2 × 12 H, SiMe4), 2.94 (s,
4 × 3 H, NMe2Ph), 4.23, 4.32 (m, 4 × 8 H, 12-crown-4), 6.70 (t,
3JHH ) 7.2 Hz, 2 × 1 H, NMe2Ph-4), 6.78 (d, 3JHH ) 8.4 Hz, 2 ×
2 H, NMe2Ph-2), 7.16 (m, 2 × 2 H, NMe2Ph-3). 13C{1H} NMR
(THF-d8, 25 °C): δ 0.0 (SiMe4), 3.8 (YCH2SiCH3), 39.0 (d,
1JYC ) 37.1 Hz, YCH2), 41.0 (NMe2Ph), 70.3 (12-crown-4), 113.9,
118.2, 129.6 (NMe2Ph), 125.0 (m (br), C6F5-1), 138.2 (m, C6F5-3,
C6F5-4), 149.1 (d, 1JCF ) 242.2 Hz, C6F5-2). 11B{1H} NMR (THF-
d8, 25 °C): δ -16.6. 19F NMR (THF-d8, 25 °C): δ -168.7, -165.1,
-133.1.
1
C6F5-4), 149.1 (d, JCF ) 240.2 Hz, C6F5-2). The signal for the
YCH2 group was not detected. 11B{1H} NMR (THF-d8, 25 °C): δ
-16.6. 19F NMR (THF-d8, 25 °C): δ -168.6, -165.0, -132.1.
-
[Y(CH2SiMe3)(12-crown-4)2]2+[BPh3(CH2SiMe3)]2 (17c). A
mixture of 2 (300 mg, 606 µmol), BPh3 (294 mg, 1213 µmol), and
12-crown-4 (94 µL, 606 µmol) was suspended in THF (50 mL) at
-100 °C. The stirred suspension was allowed to slowly warm to
ambient temperature to give a clear colorless solution after 48 h.
The reaction mixture was treated with 12-crown-4 (94 µL, 606
µmol) and stirred for additional 2 h. Evaporation of the volatiles
gave a colorless solid residue. Washing with pentane and removing
the solvent under reduced pressure afforded 16c as a colorless
[Y(CH2SiMe3)(12-crown-4)(THF)2]2+[BPh3(CH2SiMe3)]-2 (15c).
A solution of 5 (200 mg, 380 µmol) and BPh3 (184 mg, 759 µmol)
in THF (1 mL) was stirred for 2 h at 25 °C. After the solvent was
removed under reduced pressure, the residue was washed with
1
powder (533 mg, 74%). H NMR (THF-d8, 25 °C): δ -1.05 (d,
2JYH ) 3.2 Hz, 2 H, YCH2), -0.48 (s, 2 × 9 H, BCH2SiCH3),
-0.14 (s, 9 H, YCH2SiCH3), 0.20 (br, 2 × 2 H, BCH2), 3.54, 3.68
1
pentane to give 15c as colorless microcrystals (371 mg, 86%). H
2
NMR (THF-d8, 25 °C): δ -0.91 (d, JYH ) 2.8 Hz, 2 H, YCH2),
3
(br, 2 × 16 H, 12-crown-4), 6.79 (t, JHH ) 7.3 Hz, 6 × 1 H,
-0.50 (s, 2 × 9 H, BCH2SiCH3), -0.10 (s, 9 H, YCH2SiCH3),
2
Ph-4), 6.95 (m, 6 × 2 H, Ph-3), 7.47 (m (br), 6 × 2 H, Ph-2).
13C{1H} NMR (THF-d8, 25 °C): δ 2.8 (BCH2SiCH3), 4.2 (YCH2-
SiCH3), 26.1 (d, 1JYC ) 53.3 Hz, YCH2SiCH3), 71.1 (br, 12-crown-
4), 122.1 (Ph-4), 126.2 (Ph-3), 136.0 (Ph-2), 168.3 (q, 1JBC ) 48.6
Hz, Ph-1). The signal for the BCH2 group was not detected. 11B-
{1H} NMR (THF-d8, 25 °C): δ -10.4. Anal. Calcd for C64H95B2O8-
Si3Y: C, 64.75; H, 8.07; Y, 7.49. Found: C, 64.63; H, 7.96; Y,
7.85.
0.18 (br q, JBH ) 5.2 Hz, 2 × 2 H, BCH2), 1.77 (m, 2 × 4 H,
â-CH2, THF), 3.16, 3.37 (br, 2 × 8 H, 12-crown-4), 3.61 (m, 2 ×
3
4 H, R-CH2, THF), 6.76 (t, JHH ) 7.2 Hz, 6 × 1 H, Ph-4), 6.92
(m, 6 × 2 H, Ph-3), 7.44 (m (br), 6 × 2 H, Ph-2). 1H NMR (CD2-
2
Cl2, 25 °C): δ -0.79 (d, JYH ) 2.8 Hz, 2 H, YCH2), -0.48 (s,
2 × 9 H, BCH2SiCH3), -0.16 (s, 9 H, YCH2SiCH3), 0.17 (br, 2 ×
2 H, BCH2), 2.00 (br, 2 × 4 H, â-CH2, THF), 2.87, 3.17 (m, 2 ×
8 H, 12-crown-4), 3.80 (br, 2 × 4 H, R-CH2, THF), 6.88 (t,
3JHH ) 7.2 Hz, 6 × 1 H, Ph-4), 7.04 (m, 6 × 2 H, Ph-3), 7.48 (m
(br), 6 × 2 H, Ph-2). 13C{1H} NMR (THF-d8, 25 °C): δ 2.75
(BCH2SiCH3), 4.03 (YCH2SiCH3), 26.4 (â-CH2, THF), 36.9 (d,
1JYC ) 43.8 Hz, YCH2), 68.3 (R-CH2, THF), 69.8 (12-crown-4),
[Lu(CH2SiMe3)(12-crown-4)2]2+[BPh4]-2 (18a) and [Lu(CH2-
SiMe3)(12-crown-4)(pyridine-d5)2]2+[BPh4]-2. A mixture of 6 (200
mg, 326 µmol), 12-crown-4 (57 µL, 362 µmol), and [NEt3H][BPh4]
(275 mg, 653 µmol) was suspended in THF (10 mL) at -100 °C.
The stirred mixture was allowed to slowly warm to ambient
temperature. After 48 h a suspension containing colorless micro-
crystals was obtained. The supernatant was filtered off, and the
precipitate was washed with Et2O (25 mL). Removing the volatiles
1
122.1 (Ph-4), 126.1 (Ph-3), 136.0 (Ph-2), 168.3 (q, JBC ) 48.1
Hz, Ph-1). The signal for the BCH2 group was not detected. 13C-
{1H} NMR (CD2Cl2, 25 °C): δ 2.26 (BCH2SiCH3), 3.37 (YCH2-
SiCH3), 25.8 (â-CH2, THF), 40.6 (d, 1JYC ) 47.7 Hz, YCH2), 69.4
Inorganic Chemistry, Vol. 44, No. 19, 2005 6787

Elvidge et al.
under reduced pressure afforded 17a as colorless microcrystals (333
mg, 82%). 1H NMR (pyridine-d5, 25 °C): δ -0.21 (s, 9 H, LuCH2-
SiCH3), -0.17 (s, 2 H, LuCH2), 3.64 (s, 16 H, 12-crown-4), 4.15
(m, 2 × 8 H, 12-crown-4), 7.10 (t, 3JHH ) 7.2 Hz, 8 × 1 H, Ph-4),
7.26 (m, 8 × 2 H, Ph-3), 8.00 (m (br), 8 × 2 H, Ph-2). 13C{1H}
NMR (pyridine-d5, 25 °C): δ 3.5 (LuCH2SiCH3), 70.2, 70.7 (12-
crown-4), 122.5 (Ph-4), 126.3 (Ph-3), 137.0 (Ph-2), 164.9 (q,
1JBC ) 49.4 Hz, Ph-1). The signal for the LuCH2 group was not
detected. 11B{1H} NMR (pyridine-d5, 25 °C): δ -6.0. Anal. Calcd
for C68H83B2LuO8Si: C, 65.18; H, 6.68; Lu, 13.96. Found: C,
64.77; H, 7.16; Lu, 14.11.
47 µmol). NMR spectra were recorded after standing for 1 h at
room temperature; no resonances due to alkyl groups at the yttrium
center were recorded. 1H NMR (THF-d8, 25 °C): δ 0.00 (s, 36 H,
SiMe4), 3.01 (s, 6 × 3 H, NMe2Ph), 4.58 (m, 4 × 8 H, 12-crown-
3
3
4), 6.84 (t, JHH ) 7.2 Hz, 3 × 1 H, NMe2Ph-4), 6.92 (d, JHH
)
8.4 Hz, 3 × 2 H, NMe2Ph-2), 7.24 (m, 3 × 2 H, NMe2Ph-3).
13C{1H} NMR (THF-d8, 25 °C): δ 0.0 (SiMe4), 42.3 (NMe2Ph),
72.3 (12-crown-4), 115.3, 120.9, 130.1, 149.6 (NMe2Ph), 125.2 (m
1
(br), C6F5-1), 138.1 (m, C6F5-3, C6F5-4), 149.1 (d, JCF ) 240.2
Hz, C6F5-2). 11B{1H} NMR (THF-d8, 25 °C): δ -16.6. 19F NMR
(THF-d8, 25 °C): δ -166.7, -163.1, -130.3.
[Lu(CH2SiMe3)(12-crown-4)2(THF)x]2+[B(C6F5)4]-2 (18b). An
NMR tube was charged with 6 (50 mg, 82 µmol) and [NMe2PhH]-
[B(C6F5)4] (130 mg, 164 µmol) in THF-d8 (500 µL). 12-Crown-4
(14 mg, 82 µmol) was added to the resultant clear, colorless
solution. NMR spectra were recorded after standing for 1 h at room
temperature: 1H NMR (THF-d8, 25 °C): δ -0.73 (2 H, LuCH2),
-0.03 (s, 9 H, LuCH2SiCH3), 0.00 (s, 2 × 12 H, SiMe4), 2.88 (s,
4 × 3 H, NMe2Ph), 3.61, 4.40 (m (br), 4 × 8 H, 12-crown-4), 6.59
Reaction between 6, 3 [NMe2PhH][B(C6F5)4] and 12-crown-4
in THF-d8. An NMR tube was charged with 6 (50 mg, 82 µmol)
and [NMe2PhH][B(C6F5)4] (130 mg, 164 µmol) in THF-d8 (500
µL). 12-Crown-4 (14 mg, 82 µmol) was added to the resultant clear,
colorless solution, followed by [NMe2HPh][B(C6F5)4] (65 mg,
82 µmol). NMR spectra were recorded after standing for 1 h at
room temperature; no resonances due to alkyl groups at the lutetium
center were recorded. 1H NMR (THF-d8, 25 °C): δ 0.00 (s, 36 H,
SiMe4), 2.95 (s, 6 × 3 H, NMe2Ph), 4.62 (s, 4 × 8 H, 12-crown-
3
3
(t, JHH ) 7.2 Hz, 2 × 1 H, NMe2Ph-4), 6.69 (d, JHH ) 8.4 Hz,
2 × 2 H, NMe2Ph-2), 7.11 (m, 2 × 2 H, NMe2Ph-3). 13C{1H}
NMR (THF-d8, 25 °C): δ 0.0 (SiMe4), 3.5, 4.1 (LuCH2SiCH3),
40.3 (NMe2Ph), 69.2, 70.8 (br, 12-crown-4), 113.3, 116.8, 129.2,
151.5 (NMe2Ph), 125.0 (m (br), C6F5-1), 137.9 (m, C6F5-3, C6F5-
3
3
4), 6.59 (t, JHH ) 7.2 Hz, 3 × 1 H, NMe2Ph-4), 6.69 (d, JHH
)
8.4 Hz, 3 × 2 H, NMe2Ph-2), 7.11 (m, 3 × 2 H, NMe2Ph-3).
13C{1H} NMR (THF-d8, 25 °C): δ 0.0 (SiMe4), 40.3 (NMe2Ph),
71.6 (12-crown-4), 113.3, 116.8, 129.2, 151.5 (NMe2Ph), 125.0 (m
1
1
4), 148.9 (d, JCF ) 242.3 Hz, C6F5-2). The signal for the LuCH2
(br), C6F5-1), 137.9 (m, C6F5-3, C6F5-4), 148.9 (d, JCF ) 242.3
group was not detected. 11B{1H} NMR (THF-d8, 25 °C): δ -16.6.
Hz, C6F5-2). 11B{1H} NMR (THF-d8, 25 °C): δ -16.6. 19F NMR
(THF-d8, 25 °C): δ -168.2, -164.6, -132.8.
19F NMR (THF-d8, 25 °C): δ -168.2, -164.6, -132.8.
Reaction between 13a and 12-crown-4 in THF-d8. 12-Crown-4
(8 µL, 49 µmol) was added to a solution of 13a (48 mg, 41 µmol)
in THF-d8, resulting in immediate deposition of an off-white, greasy
product, which failed to redissolve under ultrasonication. Soluble
fraction: 1H NMR (THF-d8, 25 °C): δ -0.87 (d, 2JYH ) 2.93 Hz,
2 × 2 H, YCH2 11), -0.75 (d, 2JYH ) 3.17 Hz, 2 × 2 H, YCH2 8),
-0.09 (s, 2 × 9 H, YCH2SiCH3 11), -0.06 (s, 2 × 9 H, YCH2-
SiCH3 8) and other associated resonances. Insoluble fraction: 1H
NMR (pyridine-d5, 25 °C): δ -0.21 (s, 2 × 9 H, YCH2SiCH3),
0.02 (d, 2JYH ) 2.0 Hz, 2 H, YCH2) and other associated resonances.
Reaction between 5, 3 [NMe2PhH][B(C6F5)4] and 12-crown-4
in THF-d8. An NMR tube was charged with 5 (25 mg, 47 µmol)
and [NMe2PhH][B(C6F5)4] (76 mg, 95 µmol) in THF-d8 (500 µL).
12-Crown-4 (8 mg, 47 µmol) was added to the resultant clear,
colorless solution, followed by [NMe2HPh][B(C6F5)4] (38 mg,
Acknowledgment. We would like to thank the Deutsche
Forschungsgemeinschaft (DFG) and the Fonds der Chemi-
schen Industrie for financial support, Prof. Dr. U. Englert
for X-ray measurements, and Dr. B. Mathiasch and Mr. T.
Gossen for NMR measurements.
Supporting Information Available: Crystallographic data for
the structural analyses of C20H49O4ScSi3 (4) and C76H99B2O8SiY
(15a). This material is available free of charge via the Internet at
http://pubs.acs.org. Copies of this information may also be obtained
free of charge from the Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ. Fax +44(1223)336-033 or e-mail deposit@
ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk.
IC0511165
6788 Inorganic Chemistry, Vol. 44, No. 19, 2005