Intramolecular C - H bond activation by lanthanoid complexes bearing a bulky aminopyridinato ligand

Article abstract of DOI:10.1002/ejic.200900723

The present work is aimed towards the synthesis of C - H activation products of various group 3 and lanthanoid metals bearing a bulky aminopyridinato ligand, (2,6-diisopropylphenyl) [6-(2,6-dimethylphenyl)pyridin- 2-yl]amine ( 1, Ap′H). Deprotonation of 1 using KH leads to polymeric [Ap′K]_n (2), which undergoes clean salt metathesis reaction with MX₃ [M = Sc, Nd and Sm, and X. = Cl or M = La and X = Br] forming mono thf adducts [Ap′₂ScCl(thf)] (3), [Ap′₂LaBr(thf)] (4), [Ap′₂NdCl(thf)] (5), and [Ap′₂SmCl(thf)] (6). However, reacting 2 with LuCl₃ leads to mono- as well as bis(aminopyridinato)lutetium complexes [Ap′LuCl₂(thf)₂] (7) and [Ap′ ₂LuCl(thf)] (8), respectively, while the analogous reaction with LaCl₃ at 50 °C produces the tris(aminopyridinatojlanthanum complex [Ap′₃La] (9). For the selective synthesis of 8 in good yield amine elimination route was adopted. X-ray diffraction studies revealed a distorted octahedral coordination for the bis(aminopyridinato) complexes 3, 4 and 6, despite the differences in their ionic radii. Alkylation of the bis(aminopyridinato) monohalide complexes with equimolar amounts of LiCH ₂SiMe₃ in hexane allowed the isolation of the corresponding alkyl derivatives. For the smaller metals like Sc and Lu affording [Ap′₂ScCH₂SiMe₃(UIf)] (10) and [Ap′₂LuCH₂SiMe₃(thf)] (11), respectively. However, lanthanoids with large ionic radii such as La and Nd resulted in the formation of methyl group C - H bond activation, products [Ap′(Ap′ _-H)La(thf)₂] (12) and [Ap′(Ap′_-H) Nd(thf)] (13), respectively. Most likely an alkyl species was formed which then undergoes intramolecular C - H activation and. C - H activation runs fast with regard to the rate of alkyl complex, formation. The alkylation of 6 (Sm) with LiCH₂SiMe₃ did not give a clear product. The reaction of 11 with PhSiH₃ (Ph = phenyl) led via intramolecular C - H bond activation to [Ap′(Ap′_-H)Lu(thf)] (14). In this case most likely a hydride species was formed which then undergoes rapid C - H activation. The alkyl complex 10 (Sc) did not react with PhSiH₃. The molecular structures of 11, 12 and 13 have been confirmed by X-ray crystal structure analysis.

Full text of DOI:10.1002/ejic.200900723

FULL PAPER
DOI: 10.1002/ejic.200900723
Intramolecular C–H Bond Activation by Lanthanoid Complexes Bearing a
Bulky Aminopyridinato Ligand
Sadaf Qayyum,[a] Grigorii G. Skvortsov,[b] Georgii K. Fukin,[b] Alexander A. Trifonov,*[b]
Winfried P. Kretschmer,[a] Christian Döring,[a] and Rhett Kempe*[a]
Keywords: Lanthanoids / C-H bond activation / N ligands / Aminopyridinato ligands
The present work is aimed towards the synthesis of C–H acti-
vation products of various group 3 and lanthanoid metals
with equimolar amounts of LiCH2SiMe3 in hexane allowed
the isolation of the corresponding alkyl derivatives. For the
smaller metals like Sc and Lu affording [ApЈ2ScCH2-
SiMe3(thf)] (10) and [ApЈ2LuCH2SiMe3(thf)] (11), respec-
tively. However, lanthanoids with large ionic radii such as La
and Nd resulted in the formation of methyl group C–H bond
activation products [ApЈ(ApЈ–H)La(thf)2] (12) and [ApЈ-
(ApЈ–H)Nd(thf)] (13), respectively. Most likely an alkyl species
was formed which then undergoes intramolecular C–H acti-
vation and C–H activation runs fast with regard to the rate
of alkyl complex formation. The alkylation of 6 (Sm) with
LiCH2SiMe3 did not give a clear product. The reaction of 11
with PhSiH3 (Ph = phenyl) led via intramolecular C–H bond
activation to [ApЈ(ApЈ–H)Lu(thf)] (14). In this case most likely
a hydride species was formed which then undergoes rapid
bearing
a
bulky aminopyridinato ligand, (2,6-diiso-
propylphenyl)[6-(2,6-dimethylphenyl)pyridin-2-yl]amine (1,
ApЈH). Deprotonation of 1 using KH leads to polymeric
[ApЈK]n (2), which undergoes clean salt metathesis reaction
with MX3 [M = Sc, Nd and Sm, and X = Cl or M = La and X
=
Br] forming mono thf adducts [ApЈ2ScCl(thf)] (3),
[ApЈ2LaBr(thf)] (4), [ApЈ2NdCl(thf)] (5), and [ApЈ2SmCl(thf)]
(6). However, reacting 2 with LuCl3 leads to mono- as well
as bis(aminopyridinato)lutetium complexes [ApЈLuCl2(thf)2]
(7) and [ApЈ2LuCl(thf)] (8), respectively, while the analogous
reaction with LaCl3 at 50 °C produces the tris(aminopyridin-
ato)lanthanum complex [ApЈ3La] (9). For the selective syn-
thesis of 8 in good yield amine elimination route was
adopted. X-ray diffraction studies revealed a distorted octa- C–H activation. The alkyl complex 10 (Sc) did not react with
hedral coordination for the bis(aminopyridinato) complexes
3, 4 and 6, despite the differences in their ionic radii. Alky-
lation of the bis(aminopyridinato) monohalide complexes
PhSiH3. The molecular structures of 11, 12 and 13 have been
confirmed by X-ray crystal structure analysis.
itself, could be activated by lanthanocene complexes such
as (Cp*)2LuCH3 (Cp* = pentamethylcyclopentadienyl).[4]
Consequently, intermolecular alkyl group C–H activation
of spectator ligands of lanthanoid complexes has been ob-
served for a variety of ligands, for instance, for methyl
groups of the Cp* ligand.[5] Similar alkyl group C–H acti-
vation reactions have been described for non-metallocene
lanthanoid complexes.[6]
Introduction
The activation of C–H bonds and in particular the acti-
vation of the C–H bonds of inert alkyls by transition metal
and lanthanoid complexes is a reaction of general interest
due to its relevance for the functionalization of organic
molecules.[1] The chemistry of lanthanoid metals is charac-
terized by their high electrophilicity, their tendency to high
coordination numbers and their unique feature of varying
the sizes of the rare earth atom[2] with a nearly identical
coordination chemical behavior. Complexes of these metals
are strong Lewis acids which may attack the electron den-
sity of C–H bonds, thus forming agostic[3] interactions and
activate C–H bonds. Watson has even shown that methane,
Aminopyridinato ligands[7] have been used successfully
for the stabilization of early transition metals and lanthano-
ids and we started recently a research program to investi-
gate the reactivity of metal complexes coordinated by very
bulky aminopyridinates.[8] In the course of these studies we
observed that alkyl and hydrido yttrium complexes sup-
ported by the aminopyridinato ligand ApЈ {ApЈH =
(2,6-diisopropylphenyl)[6-(2,6-dimethylphenyl)pyridin-2-yl]-
amine, Figure 1} undergo methyl group C–H activation of
one of the methyl groups of the 2,6-dimethylphenly moiety
of the ApЈ ligand.[8i]
[a] Lehrstuhl Anorganische Chemie II, Universität Bayreuth,
95440 Bayreuth, Germany
Fax: +49-921552157
E-mail: kempe@uni-bayreuth.de
[b] G. A. Razuvaev Institute of Organometallic Chemistry of the
Russian Academy of Sciences,
The alkyl complex [ApЈ2YCH2SiMe3] undergoes this C–
H activation rather slowly and the corresponding hydride
does it more than 500 times faster.
Tropinina 49, GSP-445, 603950 Nizhny Novgorod, Russian
Federation
E-mail: trif@iomc.ras.ru
248
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Intramolecular C–H Bond Activation
Compound 8 was synthesized in (90%) yield by reacting
four equivalents of 1 with [(R2N)2LuCl(thf)]2 where R =
diisopropyl (Scheme 3).
Figure 1. Used aminopyridine.
Since yttrium mimics the size of the late lanthanoids
quite well we became interested in how this ligand metalla-
tion proceeds for early lanthanoids as well as for Lu and
Sc. Herein we report on synthesis and characterization of
lanthanoid monohalide complexes stabilized by bulky ApЈ
ligands, their alkylation with LiCH2SiMe3 which leads – de-
pending on the size of the lanthanoid ion – to C–H acti-
vation products or to (rather) stable alkyl complexes
(Scheme 1).
Scheme 3. Amine elimination synthesis of 8.
The thf ligand is labile and a thf-free derivative of com-
pound 3 was isolated after work up in toluene. However,
crystals suitable for X-ray analysis were grown from con-
centrated toluene solution after adding a few drops of thf
which coordinates to the vacant site of the metal centre.
Compound 4 is isolated as yellow crystalline material from
hexane in moderate yield. Compound 6 and 8 were isolated
as yellow crystals by slow diffusion of hexane or toluene
into a saturated thf solution of these complexes. This series
of compounds is a rare example of lanthanoid complexes
with the same ligand environment for which the same coor-
dination number is observed despite their different ionic ra-
dii. The coordination of the bis(aminopyridinato)-
lanthanoid halide complexes is best described as a distorted
octahedron arising from the two bidentate aminopyrid-
inates, the chloro/bromo as well the thf ligand, as shown in
Figures 2, 3, 4, and 5. Crystallographic details of all struc-
tures are listed in Tables 1 and 2. It has been observed that
in all cases the aminopyridinato ligands induce distortion
Scheme 1. Ligand metallation (methyl group C–H activation) reac-
tion of ApЈ2Y-alkyl and -hydride complexes.
Results and Discussion
Polymeric 2 was prepared according to the literature re-
ported procedure.[8a] Two equivalents of 2 were treated with
MX3 [M = Sc, Nd, and Sm, and X = Cl or M = La and X =
Br] in a salt metathesis reaction to afford the corresponding
bis(aminopyridinato) complexes [ApЈ2ScCl(thf)] (3),
[ApЈ2LaBr(thf)]
(4),
[ApЈ2NdCl(thf)][8b]
(5),
and
[ApЈ2SmCl(thf)] (6) in good yields (Scheme 2).
from the ideal octahedral symmetry.
Npyridine–M–
Namido angles of 60.21, 52.98, 55.16 and 57.7° in 3, 4, 6
and 8, respectively, were observed and are comparable to
previously published 5 [54.5°].[8b] The longer M–Npyridine
bond lengths compared to M–Namido bond length is indica-
tive of the localization of the anionic function of the ligand
at the amido N-atoms.[9]
The compound 7 is dimeric in solid state and the coordi-
nation around each Lu can be best described as distorted
pentagonal bipyramid (Figure 6). The two chloro ligands,
Scheme 2. Synthesis of bis(aminopyridinato) halide complexes.
However, in case of Lu both mono- as well as bis(amino- the pair of nitrogen atoms and one thf ligand form the pen-
pyridinato)lutetium complexes [ApЈLuCl2(thf)2] (7) and tagonal (equatorial) plane and the remaining chloro and thf
[ApЈ2LuCl(thf)] (8) were observed, respectively. Due to the ligands occupy the axial positions of the polyhedron. The
poor solubility of 8 in hexane 7 can be separated easily in distortion is caused by the small N–Lu–N angle of 56.5(2)°
24% yield if extracted with hexane. Residue 8 was extracted due to the strained binding mode of the ligand. It leads to
with toluene in a yield of 20%. Due to the poor yield of 8 a situation in which all other angles in the pentagonal plane
we became interested in using an amine elimination route. are over 72°. The N1–Lu–Cl2 and O2–Lu–Cl2 cis angles
Eur. J. Inorg. Chem. 2010, 248–257
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249

A. A. Trifonov, R. Kempe et al.
FULL PAPER
Figure 2. Molecular structure of 3; selected bond lengths [Å] and
angles [°]: N1–Sc1 2.109(5), N2–Sc1 2.403(6), N3–Sc1 2.151(6),
N4–Sc1 2.314(5), O1–Sc1 2.190(5) Cl2–Sc1 2.365(2); N1–Sc1–N3
105.9(2), N1–Sc1–O1 101.61(19), N3–Sc1–O1 149.00(18), N1–Sc1–
N4 160.4(2), N3–Sc1–N4 60.57(19), O1–Sc1–N4 89.09(19), N1–
Sc1–Cl2 92.25(16), N3–Sc1–Cl2 101.97(16), O1–Sc1–Cl2 90.88(15),
N4–Sc1–Cl2 104.05(16), N1–Sc1–N2 59.85(19), N3–Sc1–N2
94.0(2), O1–Sc1–N2 87.57(19), N4–Sc1–N2 104.89(19), Cl2–Sc1–
N2 150.99(14).
Figure 4. Molecular structure of 6; selected bond lengths [Å] and
angles [°]: N1–Sm1 2.334(2), N2–Sm1 2.572(2), N3–Sm1 2.352(2),
N4–Sm1 2.519(2), O1–Sm1 2.4064(18), Cl1–Sm1 2.5681(6); N1–
Sm1–N4 156.85(7), N1–Sm1–O1 103.58(7), N4–Sm1–O1 89.57(7),
N1–Sm1–N3 107.83(7), N4–Sm1–N3 55.63(7), O1–Sm1–N3
144.80(7), N1–Sm1–N2 54.69(6), N4–Sm1–N2 107.57(6), O1–Sm1–
N2 88.88(6), N3–Sm1–N2 96.43(7), N1–Sm1–Cl1 89.50(5), N4–
Sm1–Cl1 109.53(5), O1–Sm1–Cl1 90.98(5), N3–Sm1–Cl1 104.61(5),
N2–Sm1–Cl1 142.90(5).
Figure 3. Molecular structure of 4; selected bond lengths [Å] and
angles [°]: N1–La1 2.418(3), N2–La1 2.650(4), N3–La1 2.639(3),
N4–La1 2.433(3), O1–La1 2.525(3), Br1–La1 2.8625(6); N1–La1–
N4 104.46(11), N1–La1–O1 110.29(11), N4–La1–O1 144.13(11),
N1–La1–N3 151.20(11), N4–La1–N3 53.04(11), O1–La1–N3
91.22(10), N1–La1–N2 52.92(12), N4–La1–N2 102.77(11), O1–
La1–N2 91.42(10), N3–La1–N2 109.73(11), N1–La1–Br1 89.59(9),
N4–La1–Br1 103.33(8), O1–La1–Br1 85.80(7), N3–La1–Br1
111.59(8), N2–La1–Br1 138.63(8).
Figure 5. Molecular structure of 8; selected bond lengths [Å] and
angles [°]: [A°] and angles [°]: N1–Lu1 2.248(7), N2–Lu1–2.422(8),
N3–Lu1 2.246(8), N4–Lu1 2.462(10), O1–Lu1 2.297(6), Cl1–Lu1
2.479(3); N1–Lu1–N4 95.0(3), N1–Lu1–O1 147.8(3), N4–Lu1–O1
88.5(4), N1–Lu1–N3 105.8(3), N4–Lu1–N3 56.7(3), O1–Lu1–N3
102.8(3), N1–Lu1–N2 58.7(2), N4–Lu1–N2 107.1(3), O1–Lu1–N2
89.7(3), N3–Lu1–N2 158.6(3), N1–Lu1–Cl1 102.8(3), N4–Lu1–Cl1
146.8(19), O1–Lu1–Cl1 90.9(2), N3–Lu1–Cl1 91.3(2), N2–Lu1–Cl1
106.1(2).
are 77.13(18) and 72.66(15)°. The N2–Lu–O2 angle is the
widest [81.5(2)°] of all. The O1ax–Lu–O2eq and Clax–Lu–
O2eq angles are 80.63(18) and 90.05(14)°, respectively.
[D8]toluene solution to 273 K afforded the splitting of the
Although structurally very similar, complexes 3 and 4 above signal into two broad resonances. Further cooling
demonstrated different dynamic behaviour in solution. We resulted first in sharpening of these signals (253 K) and
essentially attribute this to the different radii of the lan- then again into the broadening and splitting of each of
thanoid ions. In 3 the signals of the two methyl groups are them to a new pair of signals (233 K). Most likely, two dy-
well separated as two sharp peaks at room temperature. At namic processes are present, first the exchange of the posi-
330 K a very slow exchange between two methyl groups is tions of the two Ap ligand and secondly the freezing out of
observed. The exchange becomes faster at 350 K but the the rotation of the 2,6-dimethylphenyl substituent Figure 7.
signals still remain inequivalent. The 1H NMR spectrum of
Reacting two equivalents of 2 with LaCl3 in thf at 65 °C
compound 4 at room temperature consists of one broad without stirring it at room temperature leads to a homolep-
signal corresponding to methyl group. The cooling of the tic complex, [ApЈ3La] (9) in overall yield of 37%
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Intramolecular C–H Bond Activation
Table 1. Details of the X-ray crystal structure analyses.
3
4 · 1/2(C6H14)
6
Crystal system
Space group
triclinic
P1
triclinic
P1
triclinic
P1
¯
¯
¯
a [Å]
b [Å]
c [Å]
α [°]
12.6930(11)
14.030(12)
14.1790(12)
73.880(10)
79.920(10)
88.820(5)
2391.2(4)
0.22ϫ0.17ϫ0.15
1.205
12.2880(7)
12.3570(7)
19.3060(11)
99.975(5)
90.309(5)
113.791
2632.8(3)
0.21ϫ0.20ϫ0.19
1.322
12.8440(7)
13.9910(8)
14.2110(8)
104.986(4)
99.473(4)
90.957(4)
2428.5(2)
0.49ϫ0.36ϫ0.22
1.330
β [°]
γ [°]
V [Å3]
Crystal size [mm]
ρcalcd [gcm–3]
µ [mm–1] (Mo-Kα)
T [K]
0.252
191(2)
1.611
191(2)
1.305
133(2)
θ range [°]
1.55 to 25.69
3681
22008
550
0.222
1.82 to 24.69
6434
28979
562
0.080
1.51 to 25.75
8251
31719
562
0.071
Number of reflections unique
Number of reflections obsd. [I Ͼ 2σ(I)]
Number of parameters
wR2 (all data)
R value [I Ͼ 2σ(I)]
0.087
0.042
0.027
Table 2. Details of the X-ray crystal structure analyses.
7
8
9
Crystal system
Space group
monoclinic
P21/n
triclinic
P1
monoclinic
P21/n
¯
a [Å]
b [Å]
c [Å]
α [°]
10.222(5)
18.663(5)
17.437(5)
12.7414(9)
13.9751(13)
14.1997(10)
105.467(7)
99.750(7)
90.090(7)
2898.8(3)
0.23ϫ0.20ϫ0.18
1.381
13.7710(4)
22.5550(8)
20.1650(7)
β [°]
93.047(5)
91.11(3)
γ [°]
V [Å3]
3322(2)
0.17ϫ0.08ϫ0.07
1.495
0.71
193(2)
6262.2(4)
0.59ϫ0.50ϫ0.35
1.285
0.73
191(2)
Crystal size [mm]
ρcalcd [gcm–3]
µ [mm–1] (Mo-Kα)
T [K]
2.155
133(2)
θ range [°]
1.60 to 26.15
2790
6538
361
0.064
1.51 to 25.70
4437
6249
544
0.139
1. 35 to 25.7
10335
81811
881
0.076
Number of reflections obsd. [I Ͼ 2σ(I)]
Number of reflections
Number of parameters
wR2 (all data)
R value [I Ͼ 2σ(I)]
0.033
0.057
0.030
(Scheme 4). Crystals of 9 suitable for X-ray analysis (crys- studies to various other lanthanoids. We observed that 3
tallographic details are listed in Table 2) were grown by slow and 8 comprised of smaller lanthanoids like Sc and Lu can
condensation of hexane into a saturated thf solution of 9. be alkylated successfully by reacting them with one equiva-
The coordination around La can best be described as dis- lent of LiCH2SiMe3 in hexane to give the corresponding
torted trigonal prism as shown in Figure 8. The slightly alkyl complexes [ApЈ2ScCH2SiMe3] (10) and [ApЈ2LuCH2-
elongated La–Npyridine bond length in 9 (2.745 Å, averaged SiMe3(thf)] (11) in good yields of 62% and 86%, respec-
value) indicates some steric overcrowding. The averaged tively (Scheme 5).
1
La–pyridine distance is 2.703 (47 values taken from the
CSD version 5.30).
In the H NMR spectrum of complex 10 we observed a
singlet at δ = 0.13 ppm for the protons of the –SiMe3 group
As we have previously shown for yttrium[8i] that such bis- and a broad singlet at δ = 0.22 ppm for the methylene pro-
(aminopyridinato)lanthanoid halide complexes can be suc- tons. In the 13C NMR we observed a sharp signal for the –
cessfully alkylated using LiCH2SiMe3. The reaction of these SiMe3 group at δ = 3.62 ppm, however a signal for methyl-
alkyls with PhSiH3 to form the intramolecular C–H bond ene carbon could not be observed since the carbon signals
activation products is fast compared to the slow decomposi- of scandium alkyls are usually broad due to the 7/2 spin of
tion of the parent alkyls (Scheme 1). In order to investigate Sc. Complex 10 is quite stable in solution and doesnЈt show
the role of the size of the used metal to form such intramo- any detectable decomposition when its C6D6 solution was
lecular C–H bond activation products we extended our monitored for several weeks. Compound 11 (Figure 9) was
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A. A. Trifonov, R. Kempe et al.
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Figure 6. Molecular structure of 7; selected bond lengths [Å] and
angles [°]: Lu1–N1 2.283(5), Lu1–O1 2.341(5), Lu1–O2 2.375(5),
Lu1–N2 2.474(6), Lu1–Cl1 2.516(2), Lu1–Cl2 2.675(2), Lu1–Cl2
2.718(2), 3.556; N1–Lu1–O1 86.21(17), O1–Lu1–O2 80.63(18), N1–
Lu1–N2 56.5(2), O1–Lu1–N2 85.93(17), O2–Lu1–N2 81.5(2), N1–
Lu1–Cl1 98.79(12), O1–Lu1–Cl1 170.23(13), O2–Lu1–Cl1
90.05(14), N2–Lu1–Cl1 89.83(14), N1–Lu1–Cl2 77.13(18), O1–
Lu1–Cl2 94.14(12), O2–Lu1–Cl2 144.41(14), Cl1–Lu1–Cl2
95.16(7), O1–Lu1–Cl2 85.57(12), O2–Lu1–Cl2 72.66(15), N2–Lu1–
Cl2 153.81(14), Cl1–Lu1–Cl2 94.48(7), Cl2–Lu1–Cl2 71.85(7).
Figure 8. Molecular structure of 9; selected bond lengths [Å] and
angles [°]: N1–La 2.7249(17), N2–La 2.4446(18), N3–La
2.7302(17), N4–La 2.4478(19), N5–La 2.7815(17), N6–La
2.4365(18), N4–La–N2 96.75(6), N4–La–N6 98.69(6), N2–La–N6
100.64(6), N4–La–N1 144.11(6), N2–La–N1 52.31(6), N6–La–N1
104.22(6) N4–La–N3 52.24(5), N2–La–N3 103.74(6), N6–La–N3
143.72(6), N1–La–N3 111.92(5), N4–La–N5 105.61(6), N2–La–N5
146.32(6), N6–La–N5 51.84(6), N1–La–N5 110.25(5), N3–La–N5
109.84(5).
Scheme 5. Synthesis of 10 and 11 [10: M = (Sc, X = no thf); 11:
M = (Lu, X = thf), (R = CH2SiMe3)].
in the crystal. The structure refinement data are listed in
Table 3. The coordination sphere of the lutetium atom is set
up by four nitrogen atoms of two aminopyridinato ligands,
one carbon atom of the alkyl group and one oxygen atom
of the thf molecule resulting in the coordination number
of six. The Lu–C bond length of 2.323(14) Å is slightly
shorter than the values reported for related anilido phos-
phinimino (2.370 Å), 4,4,4ЈЈ-tri-tert-butyl-2,2Ј:6Ј,2ЈЈ-terpyr-
idine (2.378 Å) and β-ketoiminato (2.402 Å) ligand com-
plexes.[10]
1
Figure 7. Variable-temperature H NMR of 4 in C7D8.
1
In the H NMR spectrum of complex 11 the hydrogen
atoms of the methylene group attached to the lutetium atom
appear as a broad singlet at δ = –0.65 ppm whereas in the
13C NMR the appropriate carbon appears at δ = 47.8 ppm.
Scheme 4. Synthesis of tris(aminopyridinato)lanthanum complex 9.
1
Similarly in the H NMR spectrum the nine protons of the
SiMe3 group appear as a singlet at δ = 0.15 ppm. It is note-
crystallized by slow cooling of its concentrated hexane solu- worthy that the signal sets corresponding to the aminopyr-
1
tion when layered with thf to –20 °C. X-ray analysis show idinate fragments in the H NMR spectrum of 11 is quite
one thf molecule per molecule of [ApЈ2LuCH2SiMe3(thf)] different from its parent chloro complex 7. In the latter pro-
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Eur. J. Inorg. Chem. 2010, 248–257

Intramolecular C–H Bond Activation
In contrast to Sc and Lu the alkylation of the chloro
complexes 4 and 5 comprised of the larger lanthanoids La
and Nd with one equivalent of LiCH2SiMe3 did not yield
the desired alkyl complexes and led directly to the intramo-
lecular C–H bond activated products [ApЈ(Ap–HЈ)La(thf)]
(12) and [ApЈ(Ap–HЈ)Nd(thf)] (13), in good yields of 61%
and 63%, respectively (Scheme 6).
Figure 9. Molecular structure of 11; selected bond lengths [Å] and
angles [°]: N1–Lu1 2.536(9), N2–Lu1 2.242(9), N3–Lu1 2.426(9),
N4–Lu1 2.310(10), O1–Lu1 2.294(9), C1–Lu1 2.323(14); N1–Lu1–
N4 94.1(3), N1–Lu1–O1 84.3(3), N4–Lu1–O1 148.2(3), N1–Lu1–
N3 108.3(3), N4–Lu1–N3 56.8(3), O1–Lu1–N3 93.5(3), N1–Lu1–
N2 58.2(3), N4–Lu1–N2 101.3(3), O1–Lu1–N2 104.6(3), N3–Lu1–
N2 155.3(3), N1–Lu1–C1 154.2(4), N4–Lu1–C1 100.1(4), Si1–Lu1–
C1 149.8(7), O1–Lu1–C1 94.4(4), N3–Lu1–C1 97.5(4), N2–Lu1–
C1 97.7(4).
Scheme 6. Synthesis of C–H activation products [12: M = La, n =
2; 13: M = Nd, n = 1; 14: M = Lu, n = 1].
Orange crystals of 12 were grown by slow cooling of a
concentrated thf/hexane (1:2) solution to –20 °C whereas
brown crystals of 13 suitable for X-ray analysis were grown
from a mixture of thf/pentane (1:10) at low temperature.
The molecular structures of 12 and 13 are depicted in Fig-
tons of the methyl substituents appear as a singlet at δ = ures 10 and 11, respectively. In 12 one extra thf coordi-
2.90 ppm whereas the same group of protons in 11 gives nates to the La compared to the parent 4 increasing the
two individual singlets at δ = 1.46 and 2.46 ppm. This dif- coordination number to seven. Complex 13 shows strongly
ferent behavior can be explained in terms of the steric bulk distorted octahedral coordination. The bond lengths of
of the alkyl group introduced that slows down the ligand 2.601(4) and 2.519 (10) Å in 12 and 13, respectively, be-
exchange process due to increased hindrance to rotation. tween the corresponding metal (lanthanum/neodymium)
Complex 11 does not coordinate thf during the course of and the “benzylic” carbon are elongated as expected com-
the reaction and results in the thf adduct if a few drops of pared to previously reported Y–C bond [2.420(11) Å].[8i] In
thf are added during crystallization process. Compound 11 comparison to the averaged bond length of La–C bonds
can be stored in solid state without decomposition at which is 2.797 Å (averaged from 48 La···methyl distances,
–20 °C while in solution it decomposes quite slowly at room CSD version 5.30) and the corresponding Nd distance
temperature compared to its yttrium analogue eliminating 2.649 Å (average of 55 distances, CSD version 5.30) the Ln–
SiMe4.[8i]
C bond lengths in 12 and 13 are a little shorter. Unlike the
Table 3. Details of the X-ray crystal structure analyses.
11 · C4H8O
12
13
Crystal system
Space group
triclinic
P1
monoclinic
P21/c
monoclinic
P2(1)
¯
a [Å]
b [Å]
c [Å]
α [°]
12.5940(10)
12.6940(13)
18.972(2)
75.789(8)
89.453(5)
83.858(7)
2922.9(5)
0.14ϫ0.11ϫ0.06
1.274
12.2350(5)
23.4280(11)
18.6550(8)
9.7600(6)
20.8890(12)
12.2070(7)
β [°]
103.847(3)
107.083(4)
γ [°]
V [Å3]
5191.9(4)
0.28ϫ0.25ϫ0.23
1.276
0.87
133(2)
2378.9(2)
0.15ϫ0.15ϫ0.11
1.299
1.13
173(2)
Crystal size [mm]
ρcalcd [gcm–3]
µ [mm–1] (Mo-Kα)
T [K]
1.753
133(2)
θ range [°]
1.63 to 25.7
5084
9976
638
0.154
1.42 to 25.6
6999
61178
588
0.087
1.75 to 25.7
6044
25156
522
0.110
Number of reflections obsd. [I Ͼ 2σ(I)]
Number of reflections
Number of parameters
wR2 (all data)
R value [I Ͼ 2σ(I)]
0.071
0.038
0.062
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253

A. A. Trifonov, R. Kempe et al.
FULL PAPER
chloro compounds 4 and 5, in complexes 12 and 13 one
aminopyridinato ligand is bidentate, while the second one
becomes tridentate due to metallation of the methyl group
of one of the Me2C6H3 fragments and formation of the new
M–C σ-bond. The interesting features of 12 and 13 are the
different ways of coordination of the aminopyridinato li-
gands. We have observed in the chloro complexes that both
of the ligands have amidopyridine binding modes. The type
of coordination of the bidentate ApЈ ligand is similar to
that observed in chloro complexes: one short M–N bond
with amido nitrogen atom [La1–N1 2.489(3) and Nd1–N4
2.416(6)] Å and one long with the nitrogen atom of pyridine
fragment [La1–N2 2.700(7) and Nd1–N3 2.556(8) Å]. In the
tridentate Ap–HЈ ligand formation of the M–C bond influ-
ences dramatically the bonding situation: the covalent bond
between metal and amido nitrogen atom [La1–N4 2.565(3)
and Nd1–N1 2.499(7) Å] becomes longer than the coordi-
nation bond between metal and pyridine nitrogen atom
[La1–N3 2.528(3) and Nd1–N2 2.448(7) Å] which means a
switch from the amidopyridine to the aminopyridinato
form is observed.[9]
Figure 11. Molecular structure of 13; selected bond lengths [Å] and
angles [°]: N1–Nd1 2.499(7), N2–Nd1 2.448(7), N3–Nd1 2.556(8),
N4–Nd1 2.416(6), O1–Nd1 2.462(6), C1–Nd1 2.519(10); N1–Nd1–
N4 107.8(2), N1–Nd1–O1 91.3(2), N4–Nd1–O1 127.8(2), N1–Nd1–
N3 147.6(2), N4–Nd1–N3 54.4(2), O1–Nd1–N3 83.7(2), N1–Nd1–
N2 53.8(2), N4–Nd1–N2 148.9(2), O1–Nd1–N2 81.0(2), N3–Nd1–
N2 154.1(2), N1–Nd1–C1 107.9(3), N4–Nd1–C1 99.8(3), O1–Nd1–
C1 120.2(3), N3–Nd1–C1 102.3(3), N2–Nd1–C1 68.6(3).
as a synthetic approach to bis(aminopyridinato)lanthanoid
hydrides or intramolecular C–H bond activation products.
We observed that 10 was quite inert towards phenylsilane
and did not undergo any observable change when the reac-
tion was monitored by 1H NMR spectroscopy. However
stirring of 11 in toluene with phenylsilane for three days at
room temperature and then cooling to –20 °C allowed the
isolation of complex [ApЈ(Ap–HЈ)Lu(thf)] (14) in 60% yield
(Scheme 6).
In order to understand the role of the size of the used
lanthanoid we studied the formation of complex 14 on
NMR scale in [D6]benzene at 296 K in the presence of
phenylsilane. We observed that for lutetium the rate of for-
mation of the C–H activation product is about twenty times
slower than for the comparatively larger yttrium based on
Figure 10. Molecular structure of 12; selected bond lengths [Å] and
angles [°]: N1–La1 2.489(3), N2–La1 2.700(3), N3–La1 2.528(3),
N4–La1 2.565(3), O1–La1 2.554(2), O2–La1 2.609(2), C1–La1
2.601(4); La–C1–C2 117.4(2), N1–La1–N4 107.81(9), N1–La1–O1
90.44(9), N4–La1–O1 155.45(9), N1–La1–N3 119.46(9), N4–La1–
N3 52.97(8), O1–La1–N3 131.32(8), N1–La1–N2 51.83(9), N4–
La1–N2 99.29(8), O1–La1–N2 78.87(8), N3–La1–N2 149.74(8),
N1–La1–C1 70.5(3), N4–La1–C1 112.37(10), O1–La1–C1
87.36(10), N3–La1–C1 66.43(10), N2–La1–C1 125.78(10), N1–
La1–O2 159.17(9), N4–La1–O2 88.91(9), O2–La1–N3 80.39(11),
O2–La1–N2 114.44(8), O1–La1–C1 117.7(3), O1–La1–O2 70.21(8),
C1–La1–O2 109.18(10).
1
half-times.[8i] The H NMR spectrum did not indicate the
presence of a hydride specie in the reaction mixture.
Conclusions
Several conclusions can be made from this study. The
bulky aminopyridinato ligand ApЈ affords isostructural bis-
We observe a broad singlet at δ = 1.35 ppm for the La– aminopyridinate monohalide complexes from La to Sc de-
1
CH2 protons in the H NMR spectrum that coincides with spite of the large difference in the ionic radii of the metals.
the signal of coordinated thf. However the respective signals The corresponding alkyl complexes, synthesized via salt me-
were observed as a singlet at δ = 68.9 ppm in the 13C NMR tathesis starting from the monohalides, can be unstable and
spectrum. In case of 13 the paramagnetic nature of the can undergo intramolecular methyl group C–H activation
complex excludes the observations of this resonance.
depending on the size of the lanthanoids used. For larger
We know from our previous studies that such C–H acti- lanthanoids the rate of decomposition of the parent alkyl
vated products are accessible if the parent alkyl is reacted at room temperature is fast and precludes the isolation of
with equimolar amount of PhSiH3 therefore for smaller these alkyls. Gradual decrease of the metal size enables the
scandium and lutetium the σ-bond metathesis reactions of isolation of stable alkyl complexes which may undergo in-
alkyl complexes 10 and 11 with phenylsilane were employed tramolecular C–H activation via a transient hydride species
254
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Intramolecular C–H Bond Activation
ford bright yellow crystals suitable for X-ray analysis after 48 h at
room temperature; yield (1.066 g, 53%). C54H66BrLaN4O
(1005.94): calcd. C 64.47, H 6.61, N 5.57; found C 64.60, H 7.07,
at reasonable rates at room temperature. C–H activation of
2,6-dimethylphenyl moieties can be avoided by using 2,6-
dichlorophenyl instead.[11]
1
N 5.10. H NMR (250 MHz, C6D6, 298 K): δ = 0.96–1.39 [m, 28
H, (4 H, β-CH2, thf), 24 H, H23,24,25,26], 2.12 [br., s, 12 H, H13,14],
3.32 [br., s, 4 H, α-CH2, thf], 3.45 [sept, 4 H, H21,22], 5.57 [d, 2 H,
J = 8.5 Hz, H3], 5.75 [d, 2 H, J = 7.0 Hz, H5], 6.70 [dd, 2 H, H4],
6.88–7.21 [m,12 H, H9,10,11,17,18,19] ppm. 13C NMR (C6D6, 298 K):
δ = 20.6 [C13,14], 25.0 [C23,24,25,26], 25.3 [β-CH2, thf], 28.7 [C21,22],
70.1 [α-CH2, thf], 107.7 [C3/5], 109.8 [C3/5], 124.2 [C17,19], 124.9
[C9,11], 127.8 [C10,18], 136.3 [C8,12], 139.5 [C7], 140.3 [C4], 144.0
[C16,20], 144.8 [C15], 155.8 [C6], 170.4 [C2] ppm.
Experimental Section
General Procedures: All reactions and manipulations with air-sensi-
tive compounds were performed under dry argon, using standard
Schlenk and glovebox techniques. Non halogenated solvents were
distilled from sodium benzophenone ketyl and halogenated sol-
vents from P2O5. Deuterated solvents were obtained from Cam-
bridge Isotope Laboratories and were degassed, dried and distilled
prior to use. All chemicals were purchased from commercial ven-
dors and used without further purification. Compound
[ApЈ2NdCl(thf)] (5) was prepared according to previously pub-
lished procedure.[8b] NMR spectra were obtained using either a
Bruker ARX 250 or Varian Inova Unity 400 spectrometer. Chemi-
cal shifts are reported in ppm relative to the deuterated solvent; an
atom numbering scheme for signal assignments is given in Scheme
7. X-ray crystal structure analyses were performed by using a
STOE-IPDS I or II equipped with an Oxford Cryostream low-tem-
perature unit. Structure solution and refinement were accomplished
using SIR97,[12] SHELXL-9[13] and WinGX.[14] Crystallographic
details are summarized in Tables 1, 2 and 3. Elemental analyses
were carried out by means of a Vario elementar EL III or Leco
CHN-932 elemental analyser.
Synthesis of 6: A solution of 2 (0.34 g, 0.86 mmol) in thf (30 mL)
was added to a suspension of SmCl3 (0.11 g, 0.43 mmol) in thf
(5 mL) and the reaction mixture was stirred for 7 h at 50 °C. After
cooling to the room temperature thf was evaporated in vacuo and
the remaining residue was extracted with toluene (30 mL). The ex-
tracts were filtered and the solvent was removed under vacuum and
the resulting yellow solid was redissolved in thf. Slow condensation
of hexane into concentrated thf solution afforded complex 6 as
yellow crystals. The crystals were washed with cold hexane and
dried in vacuo at room temperature; yield (0.33 g, 81%).
C54H66ClN4OSm (972.94): calcd. C 66.66, H 6.84, N 5.76; found
C 66.11, H 6.88, N 5.64.
Synthesis of 7 and 8: thf (40 mL) was added to LuCl3 (0.562 g,
2.00 mmol) and 2, (1.58 g, 4.00 mmol) in a Schlenk flask. The re-
sulting yellow colour reaction mixture was stirred overnight. The
solvent was removed under vacuum and hexane (30 mL) was
added. The yellow reaction mixture was filtered and on standing
at room temperature for 48 h, yellow crystals (suitable for X-ray
analysis) of the title compound 7 were formed; yield (0.37 g, 24%).
C66H90Cl4Lu2N4O4 (1495.19): calcd. C 53.02, H 6.07, N 3.75;
found C 52.85, H 5.96, N 3.74. 1H NMR (250 MHz, C6D6, 298 K):
δ = 0.50–1.09 [br. m, 24 H, 24 H, H23,24,25,26], 1.22 [br. s, 16 H, (4
H, β-CH2, thf) H13,14], 2.40 [br. s, 12 H, H13,14], 3.76 [br. s, 16 H,
α-CH2, thf], 4.09 [sept, 4 H, H21,22], 5.82 [br. d, 4 H, H3/5], 6.87–
7.25 [m,14 H, H4,9,10,11,17,18,19] ppm. 13C NMR (C6D6, 298 K): δ =
23.83 [C13,14], 24.88 [C23,24,25,26], 25.2 and 25.4 [β-CH2, thf], 28.7
[C21,22], 71.9 [α-CH2, thf], 106.7 [C3/5], 107.5 [C3/5], 124.1 [C17,19],
125.2 [C9,11], 127.4 [C10,18], 128.2 [C8,12], 139.9 [C7], 140.8 [C4],
143.1 [C16,20], 145.8 [C15], 155.1[C6], 168.1 [C2] ppm.
Scheme 7. Numbering scheme for NMR labelling.
Synthesis of Lanthanoid Complexes
Synthesis of 3: thf (40 mL) was added to ScCl3 (0.302 g, 2.00 mmol)
and 2 (1.586 g, 4.00 mmol) in a Schlenk flask. The resulting bright
yellow coloured reaction mixture was stirred overnight. The solvent
was evaporated under vacuum and the product was extracted with
toluene (30 mL). Toluene was fully evaporated and the resulting
product was washed with hexane; yield (0.9 g, 52%). Crystals suit-
able for X-ray analysis were grown by adding a few drops of thf to
a concentrated toluene solution. C54H66ClN4OSc (867.5): calcd. for
thf coordinated crystals C 74.76, H 7.67, N 6.46; found. C 74.26,
Toluene (30 mL) was added to the residue of the reaction. The
mixture was filtered and the filtrate was concentrated. A few drops
of thf were added to afford bright yellow crystals of 8 suitable for
X-ray analysis after 24 h at room temperature; yield (0.200 g, 20%).
C54H66ClLuN4O (997.55): calcd. C 65.02, H 6.67, N 5.62; found C
64.15, H 6.80, N 5.33. 1H NMR (400 MHz, C7D8, 298 K): δ =
0.88–1.11 [m, 28 H, (4 H, β-CH2, thf), 24 H, H23,24,25,26], 2.92 [s,
12 H, H13,14], 3.28–3.59 [br., sept, 8 H, (4 H, α-CH2, thf, 4 H,
1
H 8.01, N 6.46. H NMR (250 MHz, C6D6, 298 K): δ = 0.81–1.26
H21,22)], 5.79 [br. d, 4 H, H3/5], 6.74–7.19 [m,14 H, H4,9,10,11,17,18,19
]
[m, 24 H, H23,24,25,26], 1.47 [s, 6 H, H13,14], 2.34 [s, 6 H, H13,14], 3.28
ppm. 13C NMR (C7D8, 298 K): δ = 20.4 [C13,14], 21.3 [C23,24,25,26],
23.8 and 24.9 [β-CH2, thf], 28.1 [C21,22], 72.7 [α-CH2, thf], 104.2
[C3/5], 109.9 [C3/5], 124.2 [C17,19], 125.2 [C9,11], 129.2 [C10,18], 135.9
[C8,12], 139.5 [C7], 141.3 [C4], 144.3 [C16,20], 148.0 [C15], 156.4 [C6],
157.4 [C2] ppm.
[sept, 4 H, H21,22], 5.60 [d, J = 8.4 Hz, 2 H, H3], 5.68 [d, J = 7.2 Hz,
2 H, H5], 6.67 [dd, 2 H, H4], 7.02–7.18 [m, 12 H, H9,10,11,17,18,19
]
ppm. 13C NMR (C6D6, 298 K): δ = 19.2 [C13,14], 24.7 [C23,24,25,26],
29.9 [C13,14], 104.8 [C3/5], 110.6 [C3/5], 124.1 [C17,19], 124.4 [C9,11],
129.2 [C10,18], 135.7 [C8,12], 137.3 [C7], 141.6 [C16,20], 144.0 [C4],
144.5 [C15], 156.1 [C6], 168.7 [C2] ppm.
Selective Synthesis of 8: {[(R2N)2LuCl (thf)]2} (R = diisopropyl;
Synthesis of 4: thf (40 mL) was added to LaBr3 (0.757 g, 0.539 g, 1.11 mmol) and 1 (0.800 g, 2.23 mmol) were loaded to-
2.00 mmol) and 2 (1.58 g, 4.00 mmol) in a Schlenk flask. The re-
sulting bright yellow colour reaction mixture was stirred overnight.
The solvent was removed under vacuum and the product was ex-
tracted with hexane (30 mL). The filtrate was concentrated to af-
gether into a Schlenk flask in glove box. Toluene (40 mL) was
added to the yellow reaction mixture. The mixture was stirred over-
night. Toluene was fully removed in vacuo to yield 8. The product
was washed with hexane; yield (1.00 g, 90%).
Eur. J. Inorg. Chem. 2010, 248–257
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255

A. A. Trifonov, R. Kempe et al.
FULL PAPER
Synthesis of 9: A solution of 2 (0.49 g, 1.24 mmol) in thf (30 mL)
of was added to a suspension of LaCl3 (0.152 g, 0.61 mmol) in thf
(5 mL) and the reaction mixture was stirred for 20 h at 65 °C. After
cooling to the room temperature thf was evaporated in vacuo and
the remaining residue was extracted with toluene (30 mL). The sol-
vent was removed under vacuum and the resulting solid residue
was redissolved in thf. Slow condensation of hexane into concen-
trated thf solution afforded complex 9 as brown crystals. The crys-
tals were washed with cold hexane and dried in vacuo at room
temperature; yield (0.12 g, 32%). C75H87LaN6 (1211.44): calcd. C
for 30 min at room temperature and for 1 h at 50 °C. After cooling
to room temperature the mixture was filtered and toluene was re-
moved in vacuo. The solid residue was dissolved in thf/hexane mix-
ture (≈ 1:2). Slow cooling of the concentrated solution of complex
12 to –20 °C afforded brown crystals of 12. The crystals were sepa-
rated from the mother liquor by decantation, washed with cold
hexane and dried in vacuo at room temperature (30 min); yield
(0.28 g, 61%). C58H73LaN4O2 (997.1): calcd. C 69.86, H 7.38, N
5.62; found C 69.73, H 7.81, N 5.66. 1H NMR (400 MHz, C6D6,
25 °C): δ = 1.03, 1.21, 1.27 [d, J = 6.8 Hz, 24 H, H,23,24,25,26], 1.35
74.36, H 7.24, N 6.94; found C 73.81, H 7.42, N 7.10. 1H NMR [br. s together, 10 H, β-CH2, thf, CH2La], 2.27, 2.42 [s, 9 H, H13,14],
(250 MHz, C6D6, 298 K): δ = 0.57–1.16 [br. m, 36 H, H23,24,25,26],
1.59 [br. s, 6 H, H13,14], 2.24 [br. s, 6 H, H13,14], 2.34 [br. s, 6 H,
H13,14], 2.83 [sept, J = 6.7 Hz, 2 H, H21,22], 3.33 [sept, J = 6.7 Hz,
4 H, H21,22], 5.57 [d, J = 8.7 Hz, 3 H, H3], 5.78 [d, J = 7.0 Hz, 3
3.33 [br. s, 2 H, H21,22], 3.48 [m, 2 H, H21,22], 3.51 [br. s, 8 H, α-
CH2, thf], 5.79, 5.81 [d, J = 8.4 Hz, 2 H, H3], 5.94, 6.46 [d, J =
7.2 Hz, 2 H, H5,], 6.56–7.35 [m, 14 H, H4,9,10,11,17,18,19] ppm. 13C
NMR (100 MHz, C6D6, 25 °C): δ = 20.4, 22.4 [C13,14], 24.1, 25.1
H, H5], 6.61 [dd, J = 8.7, J = 7.1 Hz, 3 H, H4], 6.82–7.23 [m,18 H, [C23,24,25,26], 25.2 [β-CH2, thf], 28.4, 28.5 [C21,22], 68.8[α-CH2, thf],
H9,10,11,17,18,19] ppm. 13C NMR (C6D6, 298 K): δ = 20.5 [C13,14]; 68.9 [s, CH2], 106.4, 108.4 [C3], 108.0, 109.0 [C5], 118.2, 122.8,
24.7, 26.5, 26.7 [C23,24,25,26]; 28.8, 29.1 [C21,22], 109.0 123.6, 123.8, 124.0, 127.4, 127.5, 127.6, 128.1 [C9,10,11,17,18,19],
[C3/5], 112.0 [C3/5], 124.5 [C17,19], 125.0 [C9,11], 125.3 [C10,18], 138.1
[C8,12], 140.9 [C7], 144.0 [C4], 145.7 [C16,20], 145.9 [C15], 156.0 [C6],
171.0 [C2] ppm.
138.4, 139.3 [C4], 134.3, 136.0, 141.7, 143.2, 143.6, 146.4, 147.1,
153.1 [C7,8,12,15,16,20], 153.7, 155.8 [C6], 166.7, 170.4 [C2] ppm.
Synthesis of 13: A solution of LiCH2SiMe3 (0.045 g, 0.48 mmol) in
(30 mL) hexane was added to
a suspension of 5 (0.464 g,
Synthesis of 10: LiCH2SiMe3 (0.105 g, 1.11 mmol) in hexane
0.48 mmol) in hexane (20 mL) and the reaction mixture was stirred
for 1 h. The mixture was filtered and hexane was removed in vacuo.
The solid residue was dissolved in a thf/pentane mixture (≈ 1:10).
Slow cooling of the concentrated solution of complex 13 to –20 °C
afforded brown crystals of 13. The crystals were separated from the
mother liquor by decantation, washed with cold hexane and dried
in vacuo at room temperature; yield (0.29 g, 63%). C54H65N4NdO
(930.36): calcd. C 69.71, H 7.04, N 6.02; found C 69.05, H 7.44, N
6.04.
(30 mL) was added to
a stirred suspension of 3 (0.886 g,
1.11 mmol) in hexane and the reaction mixture was stirred for 24 h.
The mixture was filtered and volume of the filtrate was reduced
under vacuum. A light yellow crystalline material deposited at
–25 °C after standing overnight; yield (0.572 g, 62%).
C54H69N4ScSi (847.19): calcd. C 76.56, H 8.21, N 6.61; found C
77.25, H 7.82, N 6.72. 1H NMR (250 MHz, C6D6, 298 K): δ = 0.13
[s, 9 H, CH2Si(CH3)3], 0.22 [s, 2 H, CH2Si(CH3)3], 0.81–1.27 [m,
24 H, H23,24,25,26], 1.45 [s, 6 H, H13,14], 2.18 [s, 6 H, H13,14], 3.18–
3.44 [sept, 4 H, H21,22], 5.62 [br., dd, 4 H, H3/5], 6.65 [br., dd, 2 H,
H4], 7.01–7.37 [m, 12 H, H9,10,11,17,18,19] ppm. 13C NMR (C6D6,
298 K): δ = 3.62 [Si(CH3)3], 21.26 [C13,14], 23.66 [C13,14], 24.7 and
24.8 [C23,24,25,26], 25.1 and 25.4 [C21,22], 29.2 [C21,22], 105.5 [C3/5],
110.4 [C3/5], 124.4 [C17,19], 125.9 [C9,11], 128.4 [C10,18], 136.3
[C8,12],139.4 [C7], 142.8 [C16,20], 144.1 [C4], 144.1 [C15], 144.5 [C6],
169.2 [C2] ppm. (CH2 signal could not be observed).
Synthesis of 14: A solution of PhSiH3 (0.061 g, 0.57 mmol) in tolu-
ene solution (3 mL) was added to a solution of 11 (0.600 g,
0.57 mmol) in toluene (30 mL) at room temperature and the reac-
tion mixture was stirred for 72 h. The solution was concentrated
to small volume and cooled to –25 °C affording yellow crystalline
material; yield (0.319 g, 60%). C54H65LuN4O (961.09): calcd. C
67.48, H 6.82, N 5.83; found C 67.28, H 7.20, N 5.99. 1H NMR
(400 MHz, C7D8, 298 K): δ = 0.80–1.58 [m, together 32 H,
H23,24,25,26, β-CH2, thf, CH2Lu],1.78–2.33 [m,together 9 H, H13,14],
3.19–3.45 [br., sept, 8 H, (4 H, α-CH2, thf) (4 H, H21,22)], 5.64 [m,
4 H, H3/5], 6.63–7.27 [m,14 H, H4,9,10,11,17,18,19] ppm. 13C NMR
(C7D8, 298 K): δ = 20.3, 20.5 [C13,14], 23.0, 25.0 [C23,24,25,26], 25.2
[β-CH2, thf], 28.1,28.6 [C21,22], 68.6 [α-CH2, thf], 72.1 [s,CH2],
103.7, 108.8 [C3/5], 110.1, 114.5 [C3/5], 124.2, 124.3, 124.8, 125.0,
127.5, 127.7, 128.5, 129.7 [C9,10,11,17,18,19], 134.7, 135.2 [C4], 135.9,
136.0, 138.9, 139.5, 140.8, 141.8, 144.4 [C7,8,12,15,16,20], 148.0, 156.3
[C6], 159.3, 159.9 [C2] ppm.
Synthesis of 11: LiCH2SiMe3 (0.094 g, 1.00 mmol) in hexane
(30 mL) was added to a stirred suspension of 8 (1.0 g, 1.00 mmol)
in hexane and the reaction mixture was stirred for 24 h. The mix-
ture was filtered and yellow crystals of 11 suitable for X-ray analy-
sis were obtained by slow cooling of the concentrated mixture thf/
hexane (1:5). The crystals were dried under vacuum for two hours
for elemental analysis; yield (0.900 g, 86%). C58H77LuN4OSi
(1049.31): calcd. C 66.39, H 7.40, N 5.34; found C 66.73, H 7.29,
N 5.71. 1H NMR (250 MHz, C6D6, 298 K): δ = –0.65 [s, 2 H,
CH2Si(CH3)3], 0.15 [s, 9 H, CH2Si(CH3)3], 0.92–1.22 [m, 24 H,
H23,24,25,26], 1.40 [br. s, 4 H, -CH2, thf], 1.46 [s, 6 H, H13,14], 2.16
[s, 6 H, H13,14], 3.29 [sept, J = 6.8 Hz, 4 H, H21,22], 3.59 [thf, 4 H,
β-CH2], 5.62 [d, J = 8.4 Hz, 2 H, H3/5], 5.67 [d, J = 6.9 Hz, 2
H, H3/5], 6.70 [br., H4, J = 7.9 Hz, 2 H, dd], 6.96–7.22 [m, 12 H,
H9,10,11,17,18,19] ppm. 13C NMR (C6D6, 298 K): δ = 4.34 [Si(CH3)3],
CCDC-740977 (for 7), -740978 (for 4), -740979 (for 13),
-740980 (for 11), -740981 (for 3), -740982 (for 9), -740983 (for 6),
-740984 (for 12) and -741180 (for 8) contain the supplementary
Crystallographic details for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data centre
via: www.ccdc.cam.ac.uk/conts/retrieving.html.
19.5 [C13,14], 21.1 [C13,14], 24.1[C23,24,25,26], 24.7[C23,24,25,26
]
25.0[C23,24,25,26] 25.7 [β-CH2, thf], 28.0 [C21,22], 29.3 [C21,22],
47.8[CH2], 68.4 [β-CH2, thf], 106.3 [C3/5], 109.8 [C3/5], 124.1 [C17,19],
124.4 [C17,19], 125.4 [C9,11], 127.8 [C9,11],128.5 [C10,18], 135.7 [C8,12],
136.2 [C8,12], 139.4 [C7], 140.8 [C4], 144.1 [C15], 144.2 [C16,20], 156.0
[C6], 168.0 [C2] ppm.
Acknowledgments
Financial support from the Deutsche Forschungsgemeinschaft
(DFG) (Schwerpunktprogramm 1166 “Lanthanoid-spezifische
Funktionalitäten in Molekül und Material), the Russian Founda-
tion for Basic Research (Grant No 08-03-00391, 06-03-32728), the
RFBR-DFG grant (08-03-91953) is gratefully acknowledged.
Synthesis of 12: A toluene solution of LiCH2SiMe3 (0.043 g,
0.46 mmol) in (30 mL) was added to a suspension of 4 (0.46 g,
0.46 mmol) in toluene (5 mL) and then reaction mixture was stirred
256
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Eur. J. Inorg. Chem. 2010, 248–257

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Received: July 27, 2009
Published Online: November 24, 2009
Eur. J. Inorg. Chem. 2010, 248–257
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