Rare-earth metal alkyl, amido, and cyclopentadienyl complexes supported by Lmidazolin-2-iminato ligands: Synthesis, structural characterization, and catalytic application

Article abstract of DOI:10.1021/ic9024052

The rare earth metal dichlorides [(1)MCl₂(THF)₃] (2a, M = Sc; 2b, M = Y; 2c, M = Lu) and the gadolinium complex [(1)GdCl ₂(THF)₂]·[LiCl(THF)₂] (2d), containing the 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-iminato ligand 1, proved to be versatile starting materials for the preparation of trimethylsilylmethyl ("neosilyl") and bis(thmethylsilyl)amido complexes [(1)M(CH ₂SiMe₃)₂(THF)₂] (3a-3d) and [(1)M(HMDS)₂(THF)] [4a-4d, HMDS = hexamethyldisilazide, N(SiMe ₃)₂] and for the preparation of the benzyl complex [(1)Lu(CH₂Ph)₂(THF)₂] (5c) by the reaction with LiCH₂SiMe₃, Na[N(SiMe₃)₂], and KCH₂Ph, respectively. Treatment of 2a-2c with KCp* afforded the mono(pentamethylcyclopentadienyl) complexes [(1)Sc(Cp*)Cl(THF)] (6a), [(1)Y(Cp*)Cl(THF)₂] (6b), and [(1)Lu(Cp*)Cl(THF)] (6c). In contrast, the gadolinocene complex [(1)Gd(Cp*)₂(THF)] (7) was isolated from the reaction of 2d with 2 equiv of KCp*. The molecular structures of 3a-3d, 4b-THF, 4d, 5c, 6a, 6c, and 7-THF were determined by X-ray diffraction analyses, revealing the presence of exceptionally short metal-nitrogen bonds. The neosilyl complexes 3b and 3c showed high catalytic activity in the intramolecular hydroamination of aminoalkenes and aminoalkynes and in the hydrosilylation of 1-hexene and 1-octene with PhSiH3.

Full text of DOI:10.1021/ic9024052

Inorg. Chem. 2010, 49, 2435–2446 2435
DOI: 10.1021/ic9024052
Rare-Earth Metal Alkyl, Amido, and Cyclopentadienyl Complexes Supported by
Imidazolin-2-iminato Ligands: Synthesis, Structural Characterization, and Catalytic
Application^
Alexandra G. Trambitas,† Tarun K. Panda,† Jelena Jenter,‡ Peter W. Roesky,*,‡ Constantin Daniliuc,†
Cristian G. Hrib,† Peter G. Jones,† and Matthias Tamm*,†
†
€
Institut fu€r Anorganische und Analytische Chemie, Technische Universitat Carolo-Wilhelmina, Hagenring 30,
38106 Braunschweig, Germany, and ‡Institut fu€r Anorganische Chemie, Karlsruher Institut fu€r Technologie
(KIT), Engesserstrasse 15, 76128 Karlsruhe, Germany
Received December 4, 2009
The rare earth metal dichlorides [(1)MCl2(THF)3] (2a, M = Sc; 2b, M = Y; 2c, M = Lu) and the gadolinium complex
[(1)GdCl2(THF)2] [LiCl(THF)2] (2d), containing the 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-iminato ligand 1,
3
proved to be versatile starting materials for the preparation of trimethylsilylmethyl (“neosilyl”) and bis-
(trimethylsilyl)amido complexes [(1)M(CH2SiMe3)2(THF)2] (3a-3d) and [(1)M(HMDS)2(THF)] [4a-4d, HMDS =
hexamethyldisilazide, N(SiMe3)2] and for the preparation of the benzyl complex [(1)Lu(CH2Ph)2(THF)2] (5c) by the
reaction with LiCH2SiMe3, Na[N(SiMe3)2], and KCH2Ph, respectively. Treatment of 2a-2c with KCp* afforded
the mono(pentamethylcyclopentadienyl) complexes [(1)Sc(Cp*)Cl(THF)] (6a), [(1)Y(Cp*)Cl(THF)2] (6b), and
[(1)Lu(Cp*)Cl(THF)] (6c). In contrast, the gadolinocene complex [(1)Gd(Cp*)2(THF)] (7) was isolated from the
reaction of 2d with 2 equiv of KCp*. The molecular structures of 3a-3d, 4b THF, 4d, 5c, 6a, 6c, and 7 THF were
3
3
determined by X-ray diffraction analyses, revealing the presence of exceptionally short metal-nitrogen bonds. The
neosilyl complexes 3b and 3c showed high catalytic activity in the intramolecular hydroamination of aminoalkenes and
aminoalkynes and in the hydrosilylation of 1-hexene and 1-octene with PhSiH3.
Introduction
not themselves participate in chemical transformations, these
homoleptic Cp complexes do usually not display particularly
interesting catalytic reactivity, and the interest in this class of
compounds is mainly justified from a historic and structural point
of view.5 Accordingly, bis(cyclopentadienyl) complexes of the
type [(Cp)2M(X)(L)n] (X = anionic ligand, L = neutral ligand)
play a much more prominent role with regard to the application
of rare earth metal complexes in homogeneous catalysis,6 and in
the past, numerous metallocene or lanthanocene complexes have
been developed that were able to catalyze efficiently organic
transformations such as the polymerization of olefins, dienes,
acrylates, and alkynes7 and the hydrogenation,8 hydroami-
nation,9 hydrosilylation,10 and hydroboration11 of alkenes
and alkynes.12 In contrast, significantly less use has been
made of mono(cyclopentadienyl) complexes of the type
Ever since the preparation of the first tris(cyclopentadienyl)
rare earth metal complexes, [(η-C5H5)3M], by Wilkinson and
Birmingham in 1954,1 the organometallic chemistry of the rare
earth elements has been dominated by cyclopentadienyl
ligands (Cp), or by ligands that may be regarded as Cp
analogues.2-4 As cyclopentadienides normally serve as proto-
typical ancillary ligands that stabilize a metal complex but do
*Corresponding author. E-mail: m.tamm@tu-bs.de (M.T.); roesky@
kit.edu (P.W.R.).
^ We dedicate this paper, in memoriam, to our mentor Prof. Dr. Herbert
Schumann.
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r
2010 American Chemical Society
Published on Web 01/26/2010
pubs.acs.org/IC

2436 Inorganic Chemistry, Vol. 49, No. 5, 2010
Trambitas et al.
[(Cp)M(X)2(L)n] in homogeneous catalysis, since the selec-
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made difficult by the greater thermodynamic stability of the
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Figure 1. Selection of monoanionic ancillary ligands in rare-earth metal
chemistry.
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Scheme 1. Mesomeric Structures for the Imidazolin-2-imide 1 (Dipp =
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important ligands for the application of rare earth metal
complexes in homogeneous catalysis and material science.
Recently, we and others25 have introduced monoanionic
imidazolin-2-iminato ligands such as ImDippN (1)26 to this
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of catalytically active transition metal and rare earth metal
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[(1)MCl2(THF)3] (2) and [(η8-C8H8)M(1)(THF)n] revealed
in all cases the presence of terminal imidazolin-2-iminato
ligands with exceptionally short metal-nitrogen bonds.29,30
The potential of imidazolin-2-iminato ligands such as 1to form
particularly strong metal-nitrogen bonds is illustrated by the
two limiting resonance structures 1A and 1B (Scheme 1),26,31
indicating that the ability of the imidazolium ring to stabilize a
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Article
Inorganic Chemistry, Vol. 49, No. 5, 2010 2437
Scheme 2. Preparation of Imidazolin-2-iminato Rare-Earth Metal Complexes
electron-donating capacity toward early transition metals
or metals in a higher oxidation state. In these cases, the
imidazolin-2-iminato ligands are able to display their full
potential as 2σ,4π-electron donors and can thus be regarded
as monodentate analogues of cyclopentadienyls, C5R5, and
as monoanionic imido ligands in a similar fashion to that
described for related phosphoraneiminato ligands.16,32 Ac-
cordingly, we aimed at the preparation of complexes with
one, two or three imidazolin-2-iminato ligands for compar-
ison with the corresponding mono-, bis- and tris(cyclo-
pentadienyl) complexes. With this contribution, we begin
by reporting the synthesis and structural characterization of
various mono(imidazolin-2-iminato) complexes of the type
[(1)M(X)2(THF)n] (M = Sc, Y, Gd, Lu) with X = trimethyl-
silylmethyl (CH2SiMe3), benzyl (CH2Ph), bis(trimethylsilyl)-
amido [(Me3Si)2N], and pentamethylcyclopentadienyl (Cp*).
In addition, the application of several neosilyl (CH2SiMe3)
complexes as catalyts for hydrosilylation and hydroamina-
tion reactions is presented.
Results and Discussion
Preparation and Structural Characterization of Imidazolin-
2-iminato Neosilyl Complexes. In most cases, bis(neosilyl)
rare earth metal complexes have been prepared by the
reaction of [M(CH2SiMe3)3(THF)2] with the protonated
form of a desired ancillary ligand, which is accompanied by
release of tetramethylsilane (TMS).33 In our hands, how-
ever, the dichloro complexes [(1)MCl2(THF)3] (2a, M = Sc;
2b, M = Y; 2c, M = Lu) proved to be superior starting
materials,30 and their reaction with two equivalents of
LiCH2SiMe3 afforded the bis(neosilyl) complexes [(1)Sc-
(CH2SiMe3)2(THF)] (3a), [(1)Y(CH2SiMe3)2(THF)2] (3b),
and [(1)Lu(CH2SiMe3)2(THF)2] (3c) as pale yellow solids
in high yield (Scheme 2). In contrast, the corresponding
gadolinium complex [(1)Gd(CH2SiMe3)2(THF)2] (3d) was
obtained from the ate complex [(1)GdCl2(THF)2] [LiCl-
3
(THF)2] (2d) by treatment with the neosilyl lithium reagent
(Scheme 3). All complexes showed good solubility in com-
mon organic solvents, such as THF, pentane, and toluene.
Well-resolved NMR spectra are obtained for the diamag-
netic scandium, yttrium, and lutetium complexes 3a-3c, and
each complex shows one set of 1H and 13C NMR resonances
for the CH2SiMe3 and THF moieties. Additionally, each 1H
NMR spectrum exhibits two doublet resonances for the
diasterotopic isopropyl CH3 groups, indicating that rotation
around the C-N-metal axis is fast on the NMR time scale.
The methylene protons of the neosilyl groups in complexes 3a
and 3c are observed as singlet peaks at -0.37 and -1.03 ppm,
respectively, whereas the yttrium complex 3b shows a doublet
at -0.97 ppm because of 89Y-1H coupling (2JY-H =2.8Hz).
Accordingly, this methylene group in 3b gives rise to a
doublet at 26.2 ppm in the 13C {1H} NMR with a 89Y-13C
coupling of 1JY-C = 36.4 Hz; these values fall in the range that
was previously reported for yttrium-neosilyl complexes.28,34
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2438 Inorganic Chemistry, Vol. 49, No. 5, 2010
Trambitas et al.
Scheme 3. Preparation of Imidazolin-2-iminato Gadolinium Com-
plexes
(CH3)(NHtBu)] B(C6F5)3 [1.969(3) A] with nacnac =
3
[Dipp-NC(tBu)CHC(tBu)N-Dipp].38
The larger ionic radii39 allow the yttrium, lutetium, and
gadolinium atoms in 3a-3d to accommodate an addi-
tional THF ligand, and in agreement with the NMR data,
complexes of the type [(1)M(CH2SiMe3)2(THF)2] are
formed. 3b and 3c are isostructural and crystallize in the
orthorhombic space group P212121, whereas 3d crystal-
lizes in the space group Pna21. As representatives, the
molecular structures of 3b and 3d are shown in Figures 3
and 4; all three complexes exhibit a five-coordinate metal
atom with a trigonal-bipyramidal coordination sphere, in
which the THF ligands adopt the axial positions, albeit
with a pronounced deviation of the O1-M-O2 angles
from 180ꢀ [160.50(4)ꢀ (3b), 161.15(8)ꢀ (3c), 165.73(4)ꢀ
(3d)]. Because the C28-M-C32 angles in 3b-3d are
larger than the N1-M-C28/C32 angles, the orientation
of the equatorial ligands deviates significantly from an
ideal trigonal-planar geometry; however, the sum of these
angles is in all cases almost exactly 360ꢀ, thus indicating a
nearly perfect coplanarity with the metal atom.
The isostructural complexes 3b and 3c exhibit almost
linear M-N1-C1 angles with metal-nitrogen bond
lengths of 2.1255(13) and 2.089(3) A that are shorter than
those observed for the dichlorides 2b and 2c.30 For
yttrium, we are only aware of one complex featuring an
even shorter Y-N distance (2.116(6) A), and this is a
tetranuclear Cp-yttrium complex containing μ3-ethylimido
ligands.40 In contrast, the Lu-N bond length in 3c is
shorter than any other previously published Lu-N bonds,
and the previous shortest Lu-N distances of 2.145(2) and
2.149(4) A were found in benzamidinate and amido com-
plexes, respectively.40,41 Nevertheless, it should be noted
thatthe value in3cisreduced evenfurtherin5cand 6c(vide
infra). 3d features a gadolinium-nitrogen distance of
2.1643(13) A, which is slightly longer than that found for
the ate complex 2d [2.153(3) A].30 Therefore, the latter
value still represents the shortest Gd-N bond ever re-
ported; the previous shortest Gd-N distances ranging
from 2.190(3) to 2.240(3) A were observed for five-mem-
bered amidolanthanide heterocycles.42
Preparation and Structural Characterization of Imida-
zolin-2-iminato Bis(trimethylsilyl)amido Complexes. In a
similar fashion to that described for bis(neosilyl) rare
earth metal complexes, related diamido complexes are
usually prepared from the triamides [M{N(SiRMe2)2}3-
(THF)2] (R = Me, H), which release one amine HN-
(SiRMe2)2 upon treatment with the protonated form
of an appropriate ancillary ligand.43 Again, the reaction
of the dichlorides [(1)MCl2(THF)3] (2a, M = Sc; 2b, M =
Y; 2c, M = Lu) with two equivalents of [Na{N(SiMe3)2}]
in THF proved to be a superior method, and the com-
plexes 4a-4c of the composition [(1)M(HMDS)2(THF)]
[HMDS= hexamethyldisilazide, N(SiMe3)2] were isolated
3b was additionally characterized by 89Y NMR spectro-
scopy, affording a resonance at 813.8 ppm, which is
upfield from the resonance at 882.7 ppm reported
for [Y(CH2SiMe3)3(THF)2].35 This high-field shift is in
agreement with the trend derived for other yttrium
complexes upon substitution of alkyl groups by π-donor
ligands.36
The solid-state structures of complexes 3a-3d were
determined by X-ray diffraction analyses, and selected bond
lengths and angles are summarized in Table 1. The molecular
structure of the scandium complex 3a is shown in Figure 2,
revealing the formation of a mono(tetrahydrofuran) com-
plex [(1)Sc(CH2SiMe3)2(THF)]. Accordingly, the scandium
atom in 3a is only four-coordinate and displays a strongly
distorted tetrahedral coordination sphere with scandium-
carbon and scandium-oxygen distances of 2.223(3) A
(Sc-C28), 2.225(3) A (Sc-C32), and 2.1593(18) A (Sc-O)
that are similar to those found in related four-coordinate
complexes of the type [Sc(X)(CH2SiMe3)2(THF)] (X =
anionic ligand).33g,j The imidazolin-2-iminato ligand co-
ordinates in an essentially linear fashion [Sc-N1-C1 =
178.90(18)ꢀ], and the Sc-N bond length of 1.9520(18) A is
shorter than observed for the six-coordinate dichloride
2a.30 In fact, there is only one complex featuring a shorter
Sc-N distance of 1.9366(14) A, and that is the AlMe3
adduct of the transient scandium-imido complex [(PNP)-
Sc(N-Dipp)] containing the PNP pincer ligand bis
(2-diisopropylphosphino-4-methylphenyl)amide.37 The
only other Sc-N bond lengths that also lie below 2 A have
been observed in 2a and in the β-diketiminato complexes
[(nacnac)ScCl(NHtBu)] [1.986(2) A] and [(nacnac)Sc-
(38) (a) Knight, L. K.; Piers, W. E.; Fleurat-Lessard, P.; Parvez, M.;
McDonald, R. Organometallics 2004, 23, 2087. (b) Knight, L. K.; Piers, W. E.;
McDonald, R. Organometallics 2006, 25, 3289.
(39) Shannon, R. D.; Prewit, C. T. Acta Crystallogr., Sect. B 1969, B25,
925.
(40) Cui, D.; Nishiura, M.; Hou, Z. Angew. Chem., Int. Ed. 2005, 44, 959.
(41) Nishiura, M.; Hou, Z.; Wakatsuki, Y.; Yamaki, T.; Miyamoto, T.
J. Am. Chem. Soc. 2003, 125, 1184.
(35) Arndt, S.; Okuda, J. Adv. Synth. Catal. 2005, 347, 339.
(36) (a) Schaverien, C. J. Organometallics 1994, 13, 69. (b) White, R. E.;
Hanusa, T. P. Organometallics 2006, 25, 5621.
(37) Scott, J.; Basuli, F.; Fout, A. R.; Huffman, J. C.; Mindiola, D. J.
Angew. Chem., Int. Ed. 2008, 47, 8502.
(42) Shah, S. A. A.; Dorn, H.; Roesky, H. W.; Lubini, P.; Schmidt, H.-G.
Inorg. Chem. 1997, 36, 1102.

Article
Inorganic Chemistry, Vol. 49, No. 5, 2010 2439
Table 1. Selected Bond Lengths (A) and Angles (deg) in Complexes 3-5
3a (M = Sc)
3b (M = Y)
3c (M = Lu)
3d (M = Gd)
4b THF (M = Y)
3
4d (M = Gd)
5c (M = Lu)
M-N1
1.9520(18)
2.1593(18)
2.1255(13)
2.3629(10)
2.3697(10)
2.4469(15)
2.089(3)
2.3138(17)
2.327(2)
2.399(3)
2.1643(13)
2.444(3)
2.428(3)
2.135(2)
2.3314(16)
2.172(5)/2.180(5)
2.366(4)/2.392(4)
2.0752(18)
2.3102(15)
2.3117(16)
M-O1
M-O2
M-C28
2.223(3)
2.225(3)
2.4795(17)
M-N4
2.264(2)
2.294(2)
2.316(5)/2.180(5)
2.311(5)/2.275(5)
M-C36
2.428(2)
M-C32
2.4334(17)
2.391(3)
2.4983(17)
M-N5
M-C43
2.427(2)
1.267(3)
178.27(16)
101.04(6)
103.11(6)
155.82(6)
N1-C1
1.271(3)
178.90(18)
106.61(7)
1.2653(19)
176.85(12)
97.85(5)
101.61(5)
160.50(4)
135.84(6)
1.268(3)
176.4(2)
97.64(9)
101.19(9)
161.15(8)
136.22(10)
1.2678(19)
170.85(12)
96.60(14)
97.42(14)
165.73(4)
130.79(6)
1.261(3)
166.08(17)
97.50(7)
1.242(7)/1.259(8)
164.9(4)/166.1(5)
97.75(17)/95.71(17)
M-N1-C1
N1-M-O1
N1-M-O2
O1-M-O2
C28-M-C32
N4-M-N5
C36-M-C43
N1-M-C28
N1-M-N4
N1-M-C36
N1-M-C32
N1-M-N5
N1-M-C43
N2-C1-N3
109.82(15)
115.00(11)
118.81(12)
102.61(16)
117.70(8)
111.81(7)
124.40(18)/115.68(18)
114.51(18)/113.321(18)
130.96(8)
111.60(8)
114.37(5)
109.77(5)
101.64(13)
114.21(9)
109.56(9)
101.4(2)
113.86(6)
115.35(5)
101.72(13)
126.30(8)
118.42(18)/113.32(18)
102.4(5)/102.2(5)
117.31(8)
102.22(16)
101.93(18)
Figure 2. ORTEP diagram of 3a with thermal displacement parameters
drawn at the 15% probability level.
Figure 4. ORTEP diagram of 3d with thermal displacement parameters
drawn at the 30% probability level.
as off-white crystalline solids in good yield after extraction
with pentane. The H NMR spectra (in C6D6) of the
1
diamagnetic complexes 4a-4c exhibit in all cases one
singlet resonance for the SiCH3 groups and, similarly to
complexes 3a-3c, two doublet resonances for the diastero-
topic isopropyl CH3 groups. In contrast, the paramagnetic
nature of the gadolinium complex 4d prevents its charac-
terization by NMR spectroscopy.
(43) (a) Aspinall, H. C.; Bradley, D. C.; Hursthouse, M. B.; Sales, K. D.;
Walker, N. P. C.; Hussain, B. Dalton Trans. 1989, 623. (b) Hermann, W. A.;
Anwander, R.; Munck, F. C.; Scherer, W.; Dufaud, V.; Huber, N. W.; Artus,
G. R. J. Z. Naturforsch. 1994, 49b, 1789. (c) Karl, M.; Harms, K.; Dehnicke, K.
€
Z. Anorg. Allg. Chem. 1999, 625, 1774. (d) Klimpel, M. G.; Gorlitzer, H. W.;
Tafipolsky, M.; Spiegler, M.; Scherer, W.; Anwander, R. J. Organomet. Chem.
€
2002, 647, 236. (e) Niemeyer, M. Inorg. Chem. 2006, 45, 9085. (f) Rastatter, M.;
€
Zulys, A.; Roesky, P. W. Chem. Commun. 2006, 874. (g) Rastatter, M.; Zylus, A.;
€
Figure 3. ORTEP diagram of 3b with thermal displacement parameters
drawn at the 30% probability level.
Roesky, P. W. Chem.;Eur. J. 2007, 13, 3606. (h) Doring, C.; Kempe, R. Eur.
J. Inorg. Chem. 2009, 412.

2440 Inorganic Chemistry, Vol. 49, No. 5, 2010
Trambitas et al.
Figure 5. ORTEP diagram of 4b in 4b THF with thermal displacement
parameters drawn at the 30% probability level; selected bond lengths (A):
Y-H37B, 2.73(4); Y-H37C, 2.82(3).
Figure 6. ORTEP diagram of 4d (one of two independent molecules)
with thermal displacement parameters drawn at the 30% probability level;
selected bond lengths (A): Gd1-H37A, 2.64; Gd1-H37C, 2.65; Gd2-
H87A, 2.59; Gd2-H87C, 2.84.
3
The high solubility of complexes 4a-4d in aromatic
and aliphatic solvents suggested the formation of mono-
nuclear metal complexes, which was confirmed for the
yttrium and gadolinium complexes 4b and 4d via X-ray
diffraction analysis. Suitable single crystals were obtained
from THF/pentane solution at -30 ꢀC; the yttrium
complex 4b crystallizes as a THF solvate in the space
group P1, whereas the gadolinium complex 4d crystallizes
without an additional THF solvate molecule in the space
group P212121 with two independent molecules in the
asymmetric unit. In both cases, the metal atoms attain a
coordination number of four, being coordinated by
one imidazolin-2-iminato ligand, two bis(trimethylsilyl)-
amido groups and one THF unit, and thus, the coordina-
tion spheres around the metal atoms could be described as
distorted tetrahedral geometries. However, in both cases,
the imidazolin-2-iminato ligands exhibit significantly
shorter metal-nitrogen distances in comparison with the
HMDS ligands; however, they are slightly longer than
those found for the neosilyl complexes 3b and 3d (Table 1).
Preparation and Structural Characterization of an Imi-
dazolin-2-iminato Benzyl Complex. Benzyl (CH2Ph) com-
plexes are also very common in organolanthanide
chemistry and are often encountered as precatalysts in
various rare earth metal catalyzed organic transforma-
tions;46 therefore, the possibility of introducing benzyl
ligands was tested for the lutetium dichloride 2c as an
alternative to the established preparation from tribenzyl
complexes of the type [M(CH2Ph)3(THF)n].47 Accord-
ingly, the dibenzyl complex 5c was synthesized by treat-
ment of 2c with two equivalents of benzylpotassium
(KCH2Ph) in THF solution and was isolated as a white
crystalline solid by crystallization from THF/pentane
short intramolecular C-H M contacts are observed
3 3 3
with the methyl groups of one HMDS ligand as is
commonly found for related silylamido rare earth metal
complexes (Figures 5 and 6).44,45 Because the methyl
groups involved in these weak agostic interactions
are located trans to the THF ligand, the metal coordina-
tion spheres in 4b and 4d should preferably be described
as distorted trigonal-bipyramidal with the nitrogen
ligands adopting the equatorial positions. As expected,
solution at -30 ꢀC in 66% yield. The 1H NMR and 13
C
NMR spectra show one set of signals for the CH2Ph
ligands with the methylene resonances appearing as sing-
lets at 1.52 and 59.5 ppm, respectively. The NMR spectro-
scopic data and the elemental analysis suggested the
composition [(1)M(CH2Ph)2(THF)2], which was also
confirmed by X-ray diffraction analysis (Figure 7). The
two benzyl ligands are coordinated in a monohapto
fashion, and, in a similar fashion to that described for
complexes 3b-3d (vide supra), the lutetium metal in 5c is
five-coordinate with the ligands forming a distorted
trigonal-bipyramidal coordination sphere. Again, the
(44) For yttrium complexes, see: (a) Haan, K. H.; de Boer, J. L.; Teuben,
J. H. Organometallics 1986, 5, 1726. (b) Klooster, W. T.; Brammer, L.;
Schaverien, C. J.; Budzelaar, H. M. J. Am. Chem. Soc. 1999, 121, 1381. (c)
Fryzuk, M. D.; Jafarpour, L.; Kerton, F. M.; Love, J. B.; Patrick, B. O.; Rettig, S. J.
Organometallics 2001, 20, 1387. (d) Matsuo, Y.; Mashima, K.; Tani, K.
Organometallics 2001, 20, 3510. (e) Douglas, M. R.; Ogasawara, M.; Hong,
S.; Metz, M.; Marks, T. J. Organometallics 2002, 21, 283. (f) Kim, Y. K.;
Livinghouse, T.; Horino, Y. J. Am. Chem. Soc. 2003, 125, 9560. (g) Arnold, P. L.;
Mungur, S. A.; Blake, A. J.; Wilson, C. Angew. Chem., Int. Ed. 2003, 42, 5981.
(h) Hultzsch, K. C.; Gribkov, D. V.; Hampel, F. J. Organomet. Chem. 2005, 690,
4441. (i) Arnold, P. L.; Liddle, S. T. Organometallics 2006, 25, 1485. (j)
Edworthy, I. S.; Blake, A. J.; Wilson, C.; Arnold, P. L. Organometallics 2007,
26, 3684. (k) Zhou, S.; Wang, S.; Yang, G.; Li, Q.; Zhang, L.; Yao, Z.; Zhou, Z.;
Song, H. Organometallics 2007, 26, 3755. (l) Xiang, L.; Wang, Q.; Song, H.; Zi,
G. Organometallics 2007, 26, 5323.
(46) (a) Evans, W. J; Ulibarri, T. A.; Ziller, J, W. Organometallics 1991,
10, 134. (b) Mandel, A.; Magull, J. Z. Anorg. Allg. Chem. 1996, 622, 1913. (c)
Bambirra, S.; Brandsma, M. J. R.; Brussee, E. A. C.; Meetsma, A.; Hessen, B.;
Teuben, J. H. Organometallics 2000, 19, 3197. (d) Hayes, P. G.; Piers, W. E.; Lee,
L. W. M.; Knight, L. K.; Parvez, M.; Elsegood, M. R. J.; Clegg, W. Organo-
metallics 2001, 20, 2533. (e) Avent, A. G.; Cloke, G. N.; Elvidge, B. R.; Hitchcock,
P. B. Dalton Trans. 2004, 1083. (f) Bambirra, S.; Meetsma, A.; Hessen, B.
Organometallics 2006, 25, 3454. (g) Hitzbleck, J.; Beckerle, K.; Okuda, J.
J. Organomet. Chem. 2007, 692, 4702. (h) Carver, C. T.; Monreal, M. J.;
Diaconescu, P. L. Organometallics 2008, 27, 363.
(45) For gadolinium, see: (a) Aspinall, H. C.; Bradley, D. C.; Hursthouse,
M. B.; Sales, K. D.; Walker, N. P. C. J. Chem. Soc. 1985, 1585. (b) Tardif, O.;
Kaita, S. Dalton Trans. 2008, 2531.
(47) Meyer, N.; Roesky, P. W.; Bambirra, S.; Meetsma, A.; Hessen, B.;
Salin, K.; Takas, J. Organometallics 2008, 27, 1501.

Article
Inorganic Chemistry, Vol. 49, No. 5, 2010 2441
Figure 7. ORTEP diagram of 5c with thermal displacement parameters
drawn at the 30% probability level.
Figure 8. ORTEP diagram of 6a with thermal displacement parameters
drawn at the 30% probability level.
stable, chiral-at-metal complexes.49 Consequently, two
septets are observed for the CHCH3 protons for 6a
and 6c, in agreement with the presence of diastereotopic
isopropyl groups; 6a also shows the required four doublets
for the CHCH3 protons, whereas 6c exhibits only three
doublets in a 6:6:12 ratio with two isochronous methyl
resonances as confirmed by two-dimensional 1H-1H
COSY experiments (see the Supporting Information). In
contrast, the 1H NMR spectrum of 6b indicates the coordi-
nation of a second THF ligand, and only two doublets are
observed for the diastereotopic isopropyl methyl groups.
It should be noted, however, that the resonances are rather
broad at room temperature, suggesting a higher fluxionality
of the yttrium system 6b on the NMR time scale.
The molecular structures of 6a and 6c were addi-
tionally established by single-crystal X-ray diffraction;
both complexes are isostructural and crystallize in the
space group P21/c. As a representative, the molecular
structure of 6a is shown in Figure 8, confirming the
spectroscopically derived pseudotetrahedral geometry.
Yet again, the Sc-N and Lu-N bond lengths of
1.9575(10) and 2.0697(18) A are very short, with the latter
being the shortest ever reported for lutetium-nitrogen
systems (Table 2). The metal-carbon distances range
from 2.4752(13)-2.5305(12) A in 6a and from 2.565(2)-
2.618(2) A in 6c, which is comparable to the values found
for related Cp* complexes.33g,50
O1-Lu-O2 angle of 155.82(6)ꢀ deviates significantly
from a linear orientation, which can be mainly attributed
to the steric demand of the diisopropylphenyl substitu-
ents of the imidazolin-2-iminato ligand. This ligand co-
ordinates to the lutetium atom in an almost linear fashion
[Lu-N1-C1 = 178.27(16)ꢀ] with a very short Lu-N1
bond of 2.0752(18) A, which falls below the values found
for 2c and 3c. The two benzyl ligands point away from
each other, and the Lu-C distances of 2.428(2) and
2.427(2) A fall in the range observed for other benzyl
lutetium complexes.48
Preparation and Structural Characterization of Imida-
zolin-2-iminato Cyclopentadienyl Complexes. In view of
the isolobal relationship between imidazolin-2-iminato
and cyclopentadienyl (Cp) ligands, we also pursued the
reaction of the dichlorides 2a-2d with pentamethylcy-
clopentadienyl potassium (KCp*). To introduce two Cp*
ligands, we treated the complexes [(1)MCl2(THF)3] (2)
with 2 equiv of KCp* in THF for 12 h at ambient
temperature. White solids were isolated from the reac-
tions of 2a, 2b, and 2c after extraction with toluene
followed by evaporation, and their spectroscopic char-
acterization indicated the formation of mono(penta-
methylcyclopentadienyl) complexes [(1)Sc(Cp*)Cl(THF)]
(6a), [(1)Y(Cp*)Cl(THF)2] (6b), and [(1)Lu(Cp*)Cl(THF)]
(6c). In contrast, the product obtained from the reaction of
2d with KCp* could be extracted with pentane, and an
elemental analysis indicated that [(1)Gd(Cp*)2(THF)] (7)
has formed and that the larger gadolinium ion is able to
accommodate two Cp* ligands. The 1H NMR spectra (in
C6D6) of the Sc and Lu complexes 6a and 6c are very
similar, indicating the coordination of just one sterically
demanding Cp* ligand (δ = 1.91 ppm for 6a, δ = 1.93
ppm for 6c) and one THF ligand. In both complexes, the
THF ligand gives rise to four resonances, indicating non-
fluxional behavior and strong coordination to the metal
atom, which results in the formation of configurationally
The highly paramagnetic nature of the gadolinium
complexes prohibited the use of NMR spectroscopy for
the characterization of 7; however, its solid-state struc-
ture could be established by X-ray diffraction, confirming
that a complex with two Cp* ligands had formed. The
coordination sphere around the Gd atom is completed by
the imidazolin-2-iminato and one THF ligand to afford a
(49) These structures are closely related to chiral three-legged half-
sandwich transition metal complexes of the type [(Cp)ML1L2L3], see:(a)
Brunner, H. Angew. Chem., Int. Ed. 1999, 38, 1194. (b) Brunner, H. Eur.
J. Inorg. Chem. 2001, 905. (c) Brunner, H.; Tsuno, T. Acc. Chem. Res. 2009, 42,
1501.
(48) (a) Meyer, N.; Roesky, P. W. Z. Anorg. Allg. Chem. 2008, 634, 2171.
(b) Lin, D.; Chen, J.; Luo, C.; Zhang, Y.; Yao, Y.; Luo, Y. J. Organomet. Chem.
2009, 694, 2976.
(50) Van der Heijden, H.; Pasman, P; de Boer, R. J. M.; Schaverien, C. J.
Organometallics 1989, 8, 1459.

2442 Inorganic Chemistry, Vol. 49, No. 5, 2010
Table 2. Selected Bond Lengths (A) and Angles (deg) in Complexes 6 and 7
6a (M = Sc)
Trambitas et al.
6c (M = Lu)
7 THF (M = Gd)
3
M-N1
M-O
1.9575(10)
2.173(09)
2.4100(4)
2.4752(13)-2.5302(12)
2.0697(18)
2.2529(15)
2.4951(6)
2.565(2)-2.618(2)
2.2388(13)
2.4227(11)
M-Cl
M-Ct1a
2.6877(13)-2.7228(14)
2.7327(14)-2.8604(14)
1.2640(18)
174.57(11)
97.62(4)
M-Ct2a
N1-C1
1.2707(15)
169.72(9)
104.01(4)
106.28(3)
123.64
1.262(3)
171.24(17)
104.25(6)
108.33(5)
124.33
M-N1-C1
N1-M-O
N1-M-Cl
N1-M-Ct1a
N1-M-Ct2a
Cl-M-O
N2-C1-N3
Ct1-M-Ct2a
Ct1-M-Cla
108.68
112.40
90.30(3)
102.42(9)
91.05(4)
102.09(17)
100.22(10)
130.94
114.71
113.85
a Ct1, Ct2 = centroids of the five-membered rings.
distorted pseudotetrahedral geometry (Figure 9). The pre-
sence of two bulky Cp* rings leads to an elongation of the
Gd-N bond [2.2388(13) A] in comparison with the pre-
viously described imidazolin-2-iminato gadolinium com-
plexes such as 2d, 3d, 4d (vide supra), and [(η8-C8H8)Gd-
(1)(THF)2].30 The lanthanocene moiety is bent with a
centroid-Gd-centroid angle of 130.94ꢀ, and the Gd-C
distances range from 2.6877(13) to 2.8604(14) A (Table 2),
which isingoodagreement with the datareported for other
complexes containing a (Cp)2Gd fragment.51
Catalytic Hydroamination and Hydrosilylation Studies.
Rare earth metal complexes have proven to be favorable
catalysts for a number of catalytic applications ranging
from polymerization to small molecule activation.9,12,52
In particular, organo-rare earth metal complexes were
found to be suitable catalysts for the hydroamination of
alkenes or alkynes.9,53 Typical catalytic systems for hy-
droamination contain a trivalent (þ3 oxidation state)
metal atom and at least one kinetically labile, σ-bonded
ligand (e.g., H, CH(SiMe3)2, CH2SiMe3, CH2Ph, N-
(SiMe3)2), which can be replaced by the amine substrate
to generate a metal-amido species. The mechanism of
Figure 9. ORTEP diagram of 7 with thermal displacement parameters
drawn at the 30% probability level.
the lanthanocene-catalyzed hydroamination/cyclization reac-
tion was established some years ago by Marks et al.9,54
Thereby, cyclopentadienyl-based lanthanide complexes
played a pioneering role; however, in recent years,20,43g,43h,55
a number of active noncyclopentadienyl lanthanide catalysts
with amido44f,56 and alkoxide44h,57 ligands have been deve-
loped. Herein, we report a study of the intramolecular
hydroamination/cyclization reaction of terminal amino-
alkenes and of one aminoalkyne using catalytic amounts of
the yttrium and lutetium bis(neosilyl) complexes 3b and 3c,
with the intention of evaluating their catalytic activity in
comparison with other rare earth metal complexes.
The rigorously anaerobic reaction between the com-
plexes 3b and 3c and dry, degassed aminoalkene or amino-
alkyne proceeded regiospecifically, leading in almost all
cases to full conversion into the cyclic products (Table 3).
Kinetic studies were undertaken by in situ 1H NMR
spectroscopy. The reaction behavior of a 20-fold molar
excessofthe substrate withconstantcatalystconcentration
was monitored until complete substrate consumption was
(51) (a) Ibers, J. A.; Pernin, C. G. Inorg. Chem. 2000, 39, 1216. (b) Zhang,
J.; Zhou, X.; Cai, R.; Weng, L. Inorg. Chem. 2005, 44, 716. (c) Daniel, S. D;
Lehn, J.-S. M.; Van der Heide, P.; Wang, Y.; Hoffmann, D. M Inorg. Chim. Acta
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Article
Inorganic Chemistry, Vol. 49, No. 5, 2010 2443
achieved. The decrease inthe substratepeak was integrated
vs the product signals. Additionally, ferrocene was used as
internal standard. The hydroamination/cyclization reac-
tion could be achieved in high yields at room temperature
(entries 1, 4, 5), at 60 ꢀC (entry 3) or at 120 ꢀC (entry 2),
respectively. The substrates bearing bulky geminal substit-
uents in the β-position to the amino group could be
cyclized with 5 mol % catalyst loading in good reaction
time (5 min) at room temperature. In contrast, when the
substrate bears small substituents in the β-position, the
reaction time increases, and also a higher reaction tem-
perature is required. This could be explained by the
Thorpe-Ingold effect,58 an effect observed in organic
synthesis where increasing the size of two substituents at
a tetrahedral center leads to enhanced reaction rates
between parts of the other two substituents.
Table 3. Catalytic Hydroamination Reactionsa
The dependency of the rate on the ionic radius of the
metal center (Ln3þ) was demonstrated first for the me-
tallocene catalysts of the lanthanides,53 and the rates
increase with increasing ionic radii.39 In the present
contribution, however, the difference in activity between
the yttrium and lutetium catalysts is not significant. A
comparison of complexes 3b and 3c using substrates from
entry 1, 4, and 5 (see Table 3) with noncyclopentadienyl
complexes, for example [La{N(SiHMe2)2}2{CH(PPh2-
NSiMe3)}],55d shows a significantly higher turnover for
the first catalysts“, albeit at different reaction conditions.
In comparison with the corresponding metallocene cata-
lysts, for example [(Cp*)2Ln{CH(SiMe3)2}]54 (Ln = La,
Sm, Nd), the rates for the hydroamination/cyclization
reaction, using as catalysts complexes 3b and 3c, are
rather slower.
In addition, compounds 3b and 3c were also screened for
the catalytic hydrosilylation of alkenes, because this reac-
tion represents an important and efficient method for the
synthesis of alkylsilanes and for the production of organo-
silanes on an industrial scale.23b,59 It could be demon-
strated that rare-earth metal complexes with Cp10,60 and
non-Cp55,61 ligands are efficient catalysts or precatalysts
for the hydrosilylation of olefins, and the mechanism is
generally believed to involve the insertion of the olefin into
the M-Si or M-H bond of a metal-silyl or metal-
a Conditions: Cat. 15-20 mg, C6D6. b Calculated by 1H NMR.
c Ferrocene as internal standard
hydride species, followed by σ-bond metathesis.10e,60b,62
In our hands, the bis(neosilyl) complexes 3b and 3c proved
to be highly efficient precatalysts for the intermolecular
hydrosilylation of hexene and octene using a small excess
(4%) of phenylsilane (PhSiH3) and 2 mol% catalyst load-
ings. In all cases, the reaction went essentially to comple-
tion in <5 min at ambient temperature as judged by
1H NMR spectroscopy. Full selectivity for the anti-
Markovnikov products and no side reactions were ob-
served (for example hydrogenation, alkene dimerization,
and/or dehydrogenative coupling of organosilanes).
With regard to reaction temperature, catalyst loadings,
and yields, the activity of compounds 3b and 3c is higher
than that reported for metallocene complexes, and for
instance, a TOF of 120 h-1 was reported for the hydro-
silylation of 1-hexene in the presence of [Me2Si(C5Me5)2-
SmCH(SiMe3)2] at room temperature.60b It is not surpris-
ing that the activities of 3b and 3c fall in the range that was
recently observed for closely related organoyttrium cata-
lysts of the type [{PhC(NAr)2}Y(CH2SiMe3)2(THF)] and
[{Me2NC(NAr)2}Y(CH2SiMe3)2(THF)] with sterically
demanding amidinate and guanidinate ligands, which were
shown to be excellent catalysts for the hydrosilylation of
various terminal alkenes (see Table 4) with phenylsilane
and which displayed higher turnover frequencies than any
other rare-earth or early transition metal catalysts.61d
(58) (a) Beesley, R. M.; Inglod, C. K.; Thorpe, J. F. J. Chem . Soc. 1915,
107, 1080. (b) Ingold, C. K. J. Chem. Soc. 1921, 119, 305. (c) Kirby, A. J. Adv.
Phys. Org. Chem. 1980, 17, 183. (d) Jung, M. E.; Gervay, J. J. Am. Chem. Soc.
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Trost, B. M., Ed.; Pergamon Press: Oxford, U.K., 1991; Vol. 8, Chapter 3, p 12. (b)
Marciniec, B. In Comprehensive Handbook on Hydrosilylation; Pergamon
Press: Oxford, U.K., 1992. (c) Ojima, I.; Li, Z.; Zhu, J. In Chemistry of Organic
Silicon Compounds; Rappoport, Z., Apeloig, Y., Eds; Wiley: Chichester, U.K.,
1998; Vol. 2, p 1687. (d) Marcinies, B. In Applied Homogenous Catalysis with
Organometallic Compunds; Cornils, B., Herrmann, W. A., Eds.; Wiley: Weinheim,
Germany, 2002; Vol. 1, p 491. (e) Edelmann, F. T. In Comprehensive Organo-
metallic Chemistry II; Pergamon Press: Oxford, U.K., 1995; Vol. 4, pp 11-210.
(60) (a) Sakakura, Y; Lautenschlager, H. J.; Tanaka, M. J. Chem.
Commun. 1991, 40. (b) Fu, P.-F.; Brard, L.; Li, Y.; Marks, T. J. J. Am. Chem.
Soc. 1995, 117, 7157. (c) Hou, Z.; Zhang, Y.; Tardif, O.; Wakatsuki, Y. J. Am.
Chem. Soc. 2001, 123, 9216. (d) Voskoboynikov, A. Z.; Shestakova, A. K.;
Beletskaya, I. P. Organometallics 2001, 20, 2794. (e) Tardif, O.; Nishiura, M.;
Hou, Z. Tetrahedron 2003, 59, 10525. (f) Robert, D.; Trifonov, A. A.; Voth, P.;
Okuda, J. J. Organomet. Chem. 2006, 691, 4393.
Conclusions
The present study showed that the rare earth metal dichlor-
ides 2 are convenient starting materials for the preparation of
alkyl, amido, and cyclopentadienyl complexes containing
ancillary imidazolin-2-iminato ligands, which are capable of
forming particularly short and strong metal-nitrogen bonds.
(61) (a) Takaki, K.; Sonoda, K.; Kousaka, T.; Koshoji, G.; Shishido, T.;
Takehira, K. Tetrahedron Lett. 2001, 42, 9211. (b) Gribkov, D. V.; Hampel, F.;
Hultzsch, K. C. Eur. J. Inorg. Chem. 2004, 4091. (c) Konkol, M.; Kondracka, M.;
Voth, P.; Spaniol, T. P.; Okuda, J. Organometallics 2008, 27, 3774. (d) Ge, S.;
Meetsma, A.; Hessen, B. Organometallics 2008, 27, 3131.
(62) Horino, Y.; Livinghouse, T. Organometallics 2004, 23, 12.

2444 Inorganic Chemistry, Vol. 49, No. 5, 2010
Trambitas et al.
In all cases, the steric bulk of the ImDippN ligand (1) supports
the formation of mononuclear rare earth metal complexes,
which, in an inert atmosphere, are easy to handle and stable in
solution and in the solid state. In addition, it was shown that
efficient catalysts for hydroamination and hydrosilylation
reactions can be developed based on the imidazolin-2-iminato
rare earth metal scaffold, thus demonstrating that this ligand
class represents a useful addition to the growing number of
noncyclopentadienyl ligands in organolanthanide chemistry.
Table 4. Catalytic Hydrosilylation Reactions
Experimental Section
General Information. All manipulations of air-sensitive mate-
rials were performed with the rigorous exclusion of oxygen and
moisture in flame-dried Schlenk-type glassware either on a dual
manifold Schlenk line, interfaced to a high vacuum (1 ꢀ 10-4
Torr) line, or in an argon-filled glovebox (MBraun 200B). All
solvents were purified by a solvent purification system from
MBraun and stored over molecular sieve (4 A) prior to use.
Deuterated solvents were obtained from Sigma Aldrich (all g99
atom % D) and were degassed, dried, and stored in the argon-
filled glovebox. NMR spectra were recorded on Bruker DPX 200
and Bruker DRX 400 devices. The chemical shifts are expressed in
parts per million (ppm) using tetramethylsilane (TMS) as internal
standard (1H, 13C). 89Y NMR spectra were obtained on a Bruker-
a Calculated by 1H NMR. b AM = anti-Markovnikov; M = Mar-
kovnikov.
Analytical Data for [(1)Y(CH2SiMe3)2(THF)2] (3b). Yield:
390 mg (97%). Anal. Calcd for [C43H74N3O2Si2Y]: C, 63.75; H,
9.21; N, 5.19. Found: C, 62.19; H, 9.00; N, 5.20. 1H NMR
(C6D6, 400 MHz, 25 ꢀC): δ 7.06-7.04 (m, 6H, m-H, p-H), 5.81
(s, 2H, NCH), 3.43-3.39 (m, 4H, THF), 3.35 (sept., 4H,
CHMe2), 1.40 (d, 12H, CHCH3), 1.32-1.29 (m, 4H, THF),
1.21 (d, 12H, CHCH3), 0.27 (s, 18H, SiMe3), -0.97 (d, 4H,
Y-CH2, 2J89Y,H = 2.8 Hz) ppm. 13C NMR (C6D6, 50.3 MHz,
25 ꢀC): δ 149.1 (o-C), 137.6 (ipso-C), 136. 128.4 (p-C), 123.7
(m-C), 112.9 (NCH), 70.1 (THF), 28.8 (CHMe2), 26.2 (Y-CH2,
400 spectrometerandwereexternally referencedtoY(NO3)3 H2O
3
in D2O. Elemental analysis (C, H, N) succeeded by combustion
and gas chromatographically analysis with an Elementar vario
MICRO. Some results gave low values for carbon content, despite
acceptable H and N measurements. As observed by other
groups,63 this might be ascribed to the extreme sensitivity of the
complexes and to the possibility of metal carbide formation during
combustion. 1,3-Bis(2,6-diisopropylphenyl)midazolin-2-iminato
rare earth metal dichlorides [(1)MCl2(THF)3] (2a-c, M = Sc,
J
89Y,C = 36.4 Hz), 25.5 (THF), 24.3 (CHCH3), 23.3 (CHCH3),
5.04 (SiMe3) ppm; the NCN resonance was not observed. 89Y
NMR (C6D6, 400 MHz; 25 ꢀC): δ 813.8 ppm.
Analytical Data for [(1)Lu(CH2SiMe3)2(THF)2] (3c). Yield:
435 mg (97%). Anal. Calcd for [C43H74LuN3O2Si2]: C, 57.63; H,
8.32; N, 4.69. Found: C, 57.52; H, 8.13; N, 5.02. 1H NMR
(C6D6, 200 MHz, 25 ꢀC): δ 7.09-7.06 (m, 6H, m-H, p-H), 5.87
(s, 2H, NCH), 3.44-3.38 (m, 4H, THF), 3.34 (sept., 4H,
CHMe2), 1.41 (d, 12H, CHCH3), 1.31-1.26 (m, 4H, THF),
1.22 (d, 12H, CHCH3), 0.25 (s, 18H, SiMe3), -1.03 (s, 4H,
Lu-CH2) ppm. 13C NMR (C6D6, 50.3 MHz, 25 ꢀC): δ 148.4
(o-C), 137.0 (ipso-C), 127.9 (p-C), 123.3 (m-C), 112.94 (NCH),
69.4 (THF), 36.3 (Lu-CH2), 28.3 (CHMe2), 25.0 (THF), 24.7
(CHCH3), 23.6 (CHCH3), 4.48 (SiMe3) ppm; the NCN reso-
nance was not observed.
Y, Lu) and [(1)GdCl2(THF)2] [LiCl(THF)2] (2d),30 [KCH2Ph],64
3
[KC5Me5],65 and [LiCH2SiMe3]66 were prepared according to
published procedures. [Na{N(SiMe3)2}] was purchased from
Sigma-Aldrich and used as received.
General Procedure for the Preparation of Imidazolin-2-iminato
Rare-Earth Metal Neosilyl Complexes [(1)M(CH2SiMe3)2(THF)n]
(3a, M = Sc, n= 1; 3b, M = Y, n=2;3c, M=Lu,n= 2, 3d, M =
Gd, n = 2). To a THF solution of 0.5 mmol of [(1)MCl2(THF)3]
(M = Sc, Y, Lu) or [(1)GdCl2(THF)2] [LiCl(THF)2], 94 mg
3
Analytical Data for [(1)Gd(CH2SiMe3)2(THF)2] (3d). Yield:
427 mg (97%). Anal. Calcd for [C43H74GdN3O2Si2]: C, 58.79; H,
8.49; N, 4.78. Found: C, 56.74; H, 8.02; N, 4.96. Because of the
highly paramagnetic nature of the compound, no NMR spectra
were recorded. We were unable to obtain a satisfactory elemental
analysis, presumably because incomplete combustion.
(1.0 mmol) of LiCH2SiMe3 in THF (5 mL) was added dropwise
at ambient temperature and then the reaction mixture was
stirred for 12 h. The solvent was evaporated and subsequently
the compound was extracted with pentane. After filtration
and evaporation, the complexes were crystallized from THF/
pentane at -30 ꢀC.
General Procedure for the Preparation of Imidazolin-2-iminato
Rare-Earth Metal Amides [(1)M(HMDS)2(THF)] (4a, M = Sc;
4b, M = Y; 3c, M = Lu; 3d, M = Gd). To a THF solution of
0.5 mmol of [(1)MCl2(THF)3] (M = Sc, Y, Lu) or [(1)GdCl2-
Analytical Data for [(1)Sc(CH2SiMe3)2(THF)] (3a). Yield:
326 mg (94%). Anal. Calcd for [C39H66N3OSi2Sc]: C, 67.49; H,
9.58; N, 6.05. Found: C, 66.56; H, 9.41; N, 6.12. 1H NMR
(C6D6, 400 MHz, 25 ꢀC): δ 7.18-7.08 (m, 6H, m-H, p-H), 5.86
(s, 2H, NCH), 3.34 (br, 4H, THF), 3.24 (sept., 4H, CHMe2), 1.41
(d, 12H, CHCH3), 1.18 (d, 12H, CHCH3), 1.32-1.11 (br, 4H,
THF), 0.18 (s, 18H, SiMe3), -0.37 (s, 4H, Sc-CH2) ppm. 13C
NMR (C6D6, 400 MHz, 25 ꢀC): δ 148.1 (o-C), 135.7 (ipso-C),
128.6 (p-C), 123.5 (m-C), 113.5 (NCH), 70.8(THF), 34.5(Sc-CH2),
28.6 (CHMe2), 24.8 (THF), 23.9 (CHCH3), 23.8 (CHCH3), 3.8
(SiMe3) ppm; the NCN resonance was not observed.
(THF)2] [LiCl(THF)2] was added 183 mg (1.0 mmol) of
3
[Na{N(SiMe3)2}] in THF (5 mL) dropwise at ambient tempera-
ture and then the reaction mixture was stirred for 12 h. The
solvent was evaporated and subsequently the compound was
extracted with pentane. After filtration and evaporation, the
complexes were crystallized from THF/pentane at -30 ꢀC.
Analytical Data for [(1)Sc(HMDS)2(THF)] (4a). Microcrys-
talline product was obtained. Yield: 345 mg (82%). Anal. Calcd
for [C43H80N5OSi4Sc]: C, 61.45; H, 9.59; N, 8.33. Found: C,
1
(63) Elvidge, B. R.; Arndt, S.; Spaniol, T. P.; Okuda, J. Dalton Trans.
2006, 890, and references cited therein.
(64) Schlosser, M.; Hartmann, J. Angew. Chem. 1973, 85, 544. (b)
Schlosser, M.; Hartmann, J. Angew. Chem., Int. Ed. 1973, 12, 508.
(65) Schumann, H.; Albrecht, I.; Loebel, J.; Hahn, E.; Hossain, M. B.;
van der Helm, D. Organometallics 1986, 5, 1296.
61.11; H, 9.36; N, 8.07. H NMR (C6D6, 200 MHz, 25 ꢀC): δ
7.24-7.17 (m, 4H, m-H), 7.12-7.10 (m, 2H, p-H), 5.86 (s, 2H,
NCH), 3.58 (br, 4H, THF), 3.23 (sept., 4H, CHMe2), 1.45 (d,
12H, CHCH3), 1.32-1.20 (m, 4H, THF), 1.16 (d, 12H,
CHCH3), 0.23 (s, 36H, SiMe3) ppm. 13C NMR (C6D6, 50.3
MHz, 25 ꢀC): δ 148.2 (o-C), 137.5 (ipso-C), 128.3 (p-C), 123.6
(m-C), 113.1 (NCH), 69.2 (THF), 28.3 (CHMe2), 25.2 (THF),
(66) Vaughn, G. D.; Krein, K. A.; Gladysz, J. A. Organometallics 1986, 5,
936.

Article
Inorganic Chemistry, Vol. 49, No. 5, 2010 2445
24.1 (CHCH3), 23.3 (CHCH3), 5.7 (SiMe3) ppm; the NCN
resonance was not observed.
Analytical Data for [(1)Y(HMDS)2(THF)] (4b). Yellow crys-
tals were obtained. Yield: 360 mg (81%). Anal. Calcd for
[C43H80N5OSi4Y]: C, 58.39; H, 9.11; N, 7.91. Found: C, 57.96;
H, 8.87; N, 7.59. 1H NMR (C6D6, 200 MHz, 25 ꢀC): δ 7.21-7.16
(m, 4H, m-H), 7.13-7.10 (m, 2H, p-H), 5.98 (s, 2H, NCH), 3.46
(sept., 4H, CHMe2), 1.47 (d, 12H, CHCH3), 1.21 (d, 12H,
CHCH3), 0.27 (s, 36H, SiMe3) ppm. 13C NMR (C6D6, 50.3
MHz, 25 ꢀC): δ 148.8 (o-C), 138.1 (ipso-C), 127.9 (p-C), 123.2
(m-C), 113.7 (NCH), 69.1 (THF), 28.4 (CHMe2), 24.9 (THF),
24.1 (CHCH3), 23.1 (CHCH3), 5.9 (SiMe3) ppm; the NCN
resonance was not observed.
Analytical Data for [(1)Lu(HMDS)2(THF)] (4c). Microcrys-
talline compounds were obtained. Yield: 364 mg (75%). Anal.
Calcd for [C43H80LuN5OSi4]: C, 53.22; H, 8.30; N, 7.21. Found:
C, 52.86; H, 7.91; N, 7.01. 1H NMR (C6D6, 200 MHz, 25 ꢀC): δ
7.22-7.16 (m, 4H, m-H), 7.13-7.11 (m, 2H, p-H), 6.01 (s, 2H,
NCH), 3.52 (sept., 4H, CHMe2), 1.47 (d, 12H, CHCH3), 1.21 (d,
12H, CHCH3), 0.36 (s, 36H, SiMe3) ppm. 13C NMR (C6D6,
50.3 MHz, 25 ꢀC): δ 149.1 (o-C), 137.1 (ipso-C), 128.4 (p-C),
123.2 (m-C), 113.5 (NCH), 69.5 (THF), 28.7 (CHMe2), 25.1
(THF), 24.3 (CHCH3), 23.4 (CHCH3), 5.6 (SiMe3) ppm; the
NCN resonance was not observed.
Analytical Data for [(1)Gd(HMDS)2(THF)] (4d). Colorless
crystals were obtained. Yield: 371 mg (78%). Anal. Calcd for
[C43H80GdN5OSi4]: C; 54.20; H, 8.46; N, 7.35. Found: C, 53.86;
H, 8.11; N, 7.13. Because of the highly paramagnetic nature of
the compound, no NMR spectra were recorded.
Preparation of the Imidazolin-2-iminato Lutetium Benzyl
Complex [(1)Lu(CH2Ph)2(THF)2] (5c). To a 10 mL THF solu-
tion of 432 mg (0.5 mmol) of [(1)LuCl2(THF)3] was added
145 mg (1.0 mmol) of KCH2Ph in 10 mL THF dropwise at
ambient temperature, and the product was extracted with
pentane. After filtration and evaporation, the complex was
crystallized from THF/pentane at -30 ꢀC. Yield: 300 mg
(66%). Anal. Calcd for [C49H66LuN3O2]: C, 65.10; H, 7.36; N,
4.64. Found: C, 64.86; H, 7.11; N, 4.41. 1H NMR (C6D6,
200 MHz, 25 ꢀC): δ 7.24-7.18 (m, 8H, o-Bz, m-Dipp),
3
7.14-7.6.99 (m, 2H, p-Dipp), 6.84 (d, JHH = 6.0 Hz, 4H,
o-Bz), 6.56 (t, 3JHH = 8.0 Hz, 2H, p-Bz), 5.90 (s, 2H, NCH), 3.34
(br, 4H, CHMe2), 1.52 (s, 4H, Lu-CH2), 1.33 (d, 12H, CHCH3),
1.21 (d, 12H, CHCH3) ppm. 13C NMR (C6D6, 50.3 MHz,
25 ꢀC): δ 149.6 (o-C), 148.5 (Bz, ipso-C), 137.3 (ipso-C), 129.1
(Bz, o/m-C),127.5 (p-C), 124.5 (Bz, o/m-C), 123.2 (m-C), 119.0
(Bz, p-C), 113.3 (NCH), 59.5 (Lu-CH2), 28.7 (CHMe2), 25.7
(CHCH3), 24.4 (CHCH3) ppm; the NCN resonance was not
observed.
General Procedure for the Preparation of Imidazolin-2-iminato
mono(pentamethylcyclopentadienyl) Complexes [(1)M(C5Me5)-
Cl(THF)n] (6a, M = Sc, n = 1; 6b, M = Y, n = 2; 6c, M = Lu,
n = 1). To a 10 mL THF solution of 481 mg (0.5 mmol) of
[(1)MCl2(THF)3] (M = Sc, Lu, Y) 87.5 mg (0.5 mmol) of KCp*
in 10 mL THF was added dropwise at ambient temperature, and
the reaction mixture was stirred for 12 h. The solvent was
evaporated and subsequently the compound was extracted with
pentane/toluene solution. After filtration and evaporation, the
complexes were crystallized from THF/pentane at -30 ꢀC.
Analytical Data for [(1)Sc(C5Me5)Cl(THF)] (6a). Yield:
321 mg (93%). Anal. Calcd for [C41H59ClN3OSc]: C, 71.33; H,
8.61; N 6.09. Found: C, 70.35; H, 8.51; N, 6.10. 1H NMR (C6D6,
400 MHz, 25 ꢀC): δ 7.10-7.08 (m, 6H, m-H, p-H), 5.86 (s, 2H,
NCH), 3.58 (sept, 2H, CHMe2), 3.53-3.45 (m, 2H, THF), 3.26
(sept, 2H, CHMe2), 2.66-2.60 (m, 2H, THF), 1.91 (s, 15H,
C5Me5), 1.53 (d, 6H, CHCH3), 1.47 (d, 6H, CHCH3), 1.22 (d,
6H, CHCH3), 1.20 (d, 6H, CHCH3), 1.14-1.05 (m, 4H, THF)
ppm. 13C NMR (C6D6, 400 MHz, 25 ꢀC): δ 149.0 (o-C), 148.5
(o-C), 137.0 (ipso-C), 128.6 (p-C), 124.2 (m-C), 123.7 (m-C),
118.9 (C5Me5) 113.7 (NCH), 72.2 (THF), 28.9 (CHMe2), 28.7

2446 Inorganic Chemistry, Vol. 49, No. 5, 2010
Trambitas et al.
(CHMe2), 25.8 (THF), 24.9 (CHCH3), 24.5 (CHCH3), 24.1
(CHCH3), 23.7 (CHCH3), 11.6 (C5Me5) ppm; the NCN reso-
nance was not observed
en-1-amine,53b 2,2-diphenyl-pent-4-enylamine,66 [1-(pent-2-ynyl)-
cyclohexyl]methanamine43h were synthesized according to the
literature procedures. 1H NMR spectra of 3-methyl-2-aza-spiro-
[4.5]decane,66 2,5-dimethylpyrrolidine,67 2,4,4-trimethylpyrro-
lidine,53b 2-methyl-4,4-diphenylpyrrolidine,66 and 3-propyl-2-
azaspiro[4.5]dec-2-ene43h conform with the literature.
Analytical Data for [(1)Y(C5Me5)Cl(THF)2] (6b). Yield:
242 mg (86%). Anal. Calcd for [C45H67ClN3O2Y]: C, 67.02;
H, 8.37; N, 5.21. Found: C, 67.23; H, 8.20; N, 5.82. H NMR
1
(C6D6, 400 MHz, 25 ꢀC): δ 7.14-7.06 (m, 6H, m-H, p-H), 5.89
(s, 2H, NCH), 3.56-3.34 (m, br, 8H, THF), 3.11 (sept, br, 4H,
CHMe2), 1.94 (s, 15H, C5Me5), 1.48 (d, 12H, CHCH3), 1.22 (d,
12H, CHCH3), 1.19-1.15 (br, 8H, THF) ppm. 13C NMR
(C6D6, 400 MHz, 25 ꢀC): δ 148.7 (o-C), 138.9 (NCN), 136.9
(ipso-C), 128.6 (p-C), 123.3 (m-C), 117.5 (C5Me5) 113.2 (NCH),
70.9 (THF), 28.7 (CHMe2), 25.7 (THF), 24.4 (CHCH3), 24.3
(CHCH3), 11.0 (C5Me5) ppm.
General Procedure for Catalytic Hydrosilylation of Alkenes.
An NMR tube was charged in the glovebox with 3b or 3c
(7 μmol), PhSiH3 (0.36 mmol), olefin (1-hexene or 1-octene,
0.35 mmol), and C6D6 (3 mL). The tube was closed and taken
out of the glovebox. The disappearance of the substrates and
formation of new organosilanes can be conveniently monitored
by 1H NMR spectroscopy.
X-ray Crystal Structure Determinations. Data were recorded
on various area detectors (Oxford Diffraction or Bruker) at low
temperature using Mo KR radiation. Absorption corrections
were performed on the basis of multiscans. Structures were
refined anisotropically using the program SHELXL-97.69
Hydrogen atoms were included using rigid methyl groups or a
riding model. Numerical details are summarized in Table 5.
Special details and exceptions: Compound 3a diffracted weakly
and was also mechanically unstable at very low temperature
(presumably because of a phase change). Data were accordingly
measured with Cu KR radiation at -100 ꢀC. However, the U
values are large and one SiMe3 group is disordered, so molecular
dimensions should be interpreted with caution. Compounds 3b,
3d, 4d, and 7 crystallize by chance in chiral space groups; in each
case, the chirality was determined unambiguously, but applies
only to the measured crystal and not to the bulk material.
Compound 3c crystallizes as a racemic twin in the noncentro-
symmetric space group Pna21, but all atom positions except
for the trimethylsilyl and isopropyl groups correspond to the
centrosymmetric space group Pnam; the refinement is therefore
less stable because of near-singularity effects, and U values of
light atoms were restrained to be approximately isotropic. Two
carbons of one THF ligand in 5c are disordered over two sites.
Analytical Data for [(1)Lu(C5Me5)Cl(THF)] (6c). Yield:
397 mg (97%). Anal. Calcd for [C41H59LuN3ClO]: C 60.03,
H 7.25, N 5.12. Found C 60.02, H 7.29, N 5.16. 1H (C6D6,
400 MHz, 25 ꢀC): δ 7.15-7.09 (m, 6H, m-H, p-H), 5.91 (s, 2H,
NCH), 3.51 (sept., 2H, CHMe2), 3.40-3.31 (m, 2H, THF), 3.26
(sept., 2H, CHMe2), 2.68-2.62 (m, 2H, THF), 1.93 (s, 15H,
C5Me5), 1.50 (d, 16H, CHCH3), 1.47 (d, 6H, CHCH3), 1.22 (d,
12H, CHCH3), 1.14-1.05 (m, 4H, THF) ppm. 13C NMR (C6D6,
400 MHz, 25 ꢀC): δ 149.0 (o-C), 148.6 (o-C), 142.3 (NCN), 137.1
(ipso-C), 128.6 (p-C), 124.1 (m-C), 123.6 (m-C), 116.8 (C5Me5)
113.3 (NCH), 72.0 (THF), 28.9 (CHMe2), 28.7 (CHMe2), 25.7
(THF), 24.6 (CHCH3), 24.5 (CHCH3), 24.4 (CHCH3), 23.9
(CHCH3), 11.1 (C5Me5) ppm.
Preparation of the Imidazolin-2-iminato Bis(pentamethyl-
cyclopentadienyl) Complex [(1)Gd(C5Me5)2(THF)] (7). To a
10 mL THF solution of 481 mg (0.5 mmol) of [(1)GdCl2-
(THF)2] [LiCl(THF)2] was added 175 mg (1.0 mmol) of KC5Me5
3
in 10 mL THF dropwise at ambient temperature and the reaction
mixture was stirred for 12 h. The solvent was evaporated and
subsequently the compound was extracted from pentane. After
filtration and evaporation, the complex was crystallized from
THF/pentane at -30 ꢀC. Yield: 350 mg (71%). Anal. Calcd for
[C55H82GdN3O2]: C, 67.78; H, 8.48; N, 4.31. Found: C, 67.16; H,
8.18; N, 4.11. Because of the highly paramagnetic nature of the
compound, no NMR spectra were recorded.
The agostic Y H contacts in 4b were established by free
3 3 3
refinement of the relevant methyl H atoms. However, the data
for 4d did not allow free hydrogen refinement (probably because
of the noncentrosymmetric space group) so the usual idealized
methyl geometry was assumed; metal-hydrogen distances are
therefore less reliable.
General Procedure for Catalytic Hydroamination of Alkenes.
The catalyst was weighed in a glovebox under argon gas into an
NMR tube. C6D6 (∼ 0.5 mL) was condensed into the NMR
tube, and the mixture was frozen to -196 ꢀC. The reactant was
injected onto the solid mixture, and the whole sample was
melted and mixed just before insertion into the core of the
NMR machine (t0). The ratio between the reactant and the
product was calculated by comparison of the integrations of the
corresponding signals. Ferrocene was used as internal standard
for the kinetic measurements. The substrates C-(1-allyl-cyclo-
hexyl)-methylamine,67 2-amino-5-hexene68 2,2-dimethylpent-4-
Acknowledgment. This work was supported by the
Deutsche Forschungsgemeinschaft (DFG) through the pro-
€
gram “Lanthanoidspezifische Funktionalitat in Molekul und
€
Material” (SPP 1166).
Supporting Information Available: Presentation of selected
NMR spectra (PDF) and crystallographic information files
(CIF). This material is available free of charge via the Internet
at http://pubs.acs.org.
(67) Horrillo Martı
2006, 2221.
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