Monoalkyl and monoanilide yttrium complexes containing tridentate pyridyl-1-azaallyl dianionic ligands

Article abstract of DOI:10.1039/c0dt01539c

A series of pyridyl-1-azaallyl ligand precursors (HL1-HL5) were synthesized via condensation of pyridine ketones with anilines. The alkane elimination reactions between Y(CH₂SiMe₃)₃(THF)₂ and HL4 or HL5 gave the monoalkyl complexes (L4-H)YCH₂SiMe ₃(THF) (1) and (L5-H)YCH₂SiMe₃(THF) (2) supported by new tridentate pyridyl-1-azaallyl dianionic ligands. The reactions of monoalkyl complexes, 1 and 2, with one equivalent of 2,6-diisopropylaniline produced the corresponding monoanilide complexes, (L4-H)YNHAr(THF) (3) and (L5-H)YNHAr(THF) (4) (Ar = 2,6-(ⁱPr)₂C₆H ₃), via highly selective protonolysis of the terminal alkyl Y-CH ₂SiMe₃ bond. Complexes 1-4 are active for intramolecular hydroamination of aminoalkenes.

Full text of DOI:10.1039/c0dt01539c

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PAPER
Monoalkyl and monoanilide yttrium complexes containing tridentate
pyridyl-1-azaallyl dianionic ligands†
Erli Lu,a Wei Gana,b and Yaofeng Chen*a
Received 4th November 2010, Accepted 29th November 2010
DOI: 10.1039/c0dt01539c
A series of pyridyl-1-azaallyl ligand precursors (HL1–HL5) were synthesized via condensation of
pyridine ketones with anilines. The alkane elimination reactions between Y(CH2SiMe3)3(THF)2 and
HL4 or HL5 gave the monoalkyl complexes (L4–H)YCH2SiMe3(THF) (1) and (L5–H)YCH2SiMe3-
(THF) (2) supported by new tridentate pyridyl-1-azaallyl dianionic ligands. The reactions of monoalkyl
complexes, 1 and 2, with one equivalent of 2,6-diisopropylaniline produced the corresponding
monoanilide complexes, (L4–H)YNHAr(THF) (3) and (L5–H)YNHAr(THF) (4) (Ar =
2,6-(iPr)2C6H3), via highly selective protonolysis of the terminal alkyl Y–CH2SiMe3 bond. Complexes
1–4 are active for intramolecular hydroamination of aminoalkenes.
cyanide.13,14,15 Recently, rare-earth metal complexes supported by
aminopyridinate ligands have received considerable attention.16
Herein we report the synthesis of pyridyl-1-azaallyl ligand pre-
cursors by condensation of pyridine ketones with anilines, the
monoalkyl and monoanilide yttrium complexes supported by
exceptional pyridyl-1-azaallyl dianionic ligands and their catalytic
behavior for intramolecular hydroamination of aminoalkenes.
Introduction
Due to their rich and diversified coordinating properties and
reactivities, organometallic complexes of rare-earth metals have
received growing attention.1,2,3 The most widely investigated
organometallic complexes of rare-earth metals are those bearing
Cp-type ligands. Recently, there is a tendency to explore “non-
Cp” ligands and their application in rare-earth organometallic
chemistry.4 Among the “non-Cp” ligands, b-diketiminato ligands
are one of the most promising ligand families.5 Numerous
b-diketiminato rare-earth organometallic complexes have been
prepared, and some have shown interesting structural features
and good catalytic activities.6,7,8,9,10,11 Pyridyl-1-azaallyl ligands are
close relatives of the b-diketiminato ligands, which introduce a
neighboring fused six-membered nitrogen heterocyclic ring into
the backbone of the primitive b-diketiminato.5,12 The pyridine ring,
with its electronic delocalization and steric rigidity, may introduce
some special structural features and interesting catalytic activities
into the primitive b-diketiminato based metal complexes. Pyridyl-
1-azaallyl ligands have been used in early transition metal,13
late transition metal14 as well as main-group metal15 chemistry.
However, the pyridyl-1-azaallyl ligands have not been introduced
into rare-earth metal chemistry. From another aspect, in contrast
with the diversified synthetic pathways to b-diketiminato ligands,
the method reported for the synthesis of pyridyl-1-azaallyl ligands
is the insertion reaction between lithiated 2-alkyl substituted
pyridines and cyanides, such as phenyl cyanide and trimethylsilyl
Results and discussion
A series of pyridyl-1-azaallyl ligand precursors (HL1–HL5) were
readily synthesized via condensation of pyridine ketones with
anilines in the presence of p-toluenesulfonic acid in toluene (or
benzene) with removal of water by azeotropic distillation (Scheme
1). These compounds were characterized by NMR (1H and 13C)
and HRMS spectroscopy.
Scheme 1 Synthesis of HL1–HL5.
The 1H NMR spectral monitoring of reactions between
the ligand precursors (HL1–HL3) and one equivalent of
Y(CH2SiMe3)3(THF)2 in C6D6 showed that all the reactions led to
complicated mixtures within several hours at room temperature.
We then turned to the ligand precursors (HL4 and HL5), which
have more sterically demanding trimethylsilyl (for HL4) or phenyl
(for HL5) substituents on the pyridine ring. The 1H NMR
spectral monitoring showed that HL4 and HL5 were nearly
aState Key Laboratory of Organometallic Chemistry, Shanghai Institute
of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road,
Shanghai, 200032, China. E-mail: yaofchen@mail.sioc.ac.cn; Fax: 86-21-
64166128
bDepartment of Chemistry, Northwest University, 229 Taibai North Avenue,
Xi’an, 710069, China
† CCDC reference numbers 789698–789700. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/c0dt01539c
2366 | Dalton Trans., 2011, 40, 2366–2374
This journal is
The Royal Society of Chemistry 2011
©

completely converted into new complexes 1 and 2, respectively,
at room temperature in 24 h, with concomitant disappearance of
Y(CH2SiMe3)3(THF)2 and formation of two equivalents of Me4Si.
The reactions were then scaled up in hexane, 1 and 2 were isolated
as yellow crystalline solids (77% and 71% yield, respectively).
1H NMR spectra of 1 and 2 in C6D6 show the existence of
a pyridyl-1-azaallyl ligand fragment, a –CH2SiMe3 alkyl group
(-0.42 and 0.17 ppm for 1, -0.43 and 0.09 ppm for 2) and a THF
molecule in each complex. For 1, a broad signal is observed at
0.61 ppm with an area of 6 H, which can be assigned as two
methyls on the Si atom of the ligand. However, the signal of the
third methyl on the Si atom is absent, while a broad peak with an
area of 2 H at -0.36 ppm is observed, which is suspected to be the
Scheme
Y(CH2SiMe3)3(THF)2.
2
Reactions of HL4 and HL5 with one equivalent of
1
signal of YCH2. For 2, in its H NMR spectrum, the signals in
the aromatic region are too complicated to allow an unambiguous
assignment, while the 13C NMR spectrum is more informative. A
doublet is observed at 187.5 ppm with a 2JYC coupling constant of
46.4 Hz, which is suspected to be the signal of YCAr.
To obtain an unambiguous characterization of the structures
of 1 and 2, single crystals of the complexes were grown from
the toluene solutions and characterized by X-ray diffraction
studies (Fig. 1 and 2). Complexes 1 and 2 are the monoalkyl
yttrium complexes with new tridentate pyridyl-1-azaallyl dian-
ionic ligands, as shown in Scheme 2. Therefore, the reactions
of Y(CH2SiMe3)3(THF)2 with HL4 or HL5 not only lead to
the deprotonation of the b-diketimine backbone but also the
activation of a sp3 C–H bond of a trimethylsilyl substituent (for
HL4) or a sp2 C–H bond of a phenyl substituent (for HL5)
on the pyridine ring of the ligand precursors. Both 1 and 2
are five-coordinate monomers. In 1, the Y(III) center adopts a
distorted trigonal bipyramidal geometry with a nitrogen atom
of the imine group, a carbon atom of the –CH2SiMe2 group,
and a carbon atom of the –CH2SiMe3 alkyl ligand forming the
equatorial plane, and a nitrogen atom on the pyridine ring and
an oxygen atom of the THF occupying the axial positions. The
˚
Y–N2 distance of 2.385(3) A is significantly longer than the Y–N1
˚
distance (2.285(3) A). Although the C2–N1 and C4–N2 distances
˚
(1.362(5) and 1.364(5) A, respectively) are almost the same, the
˚
C2–C3 distance (1.366(5) A) is shorter than the C3–C4 distance
˚
(1.416(6) A), and the N1, C2, C3, C4 and N4 atoms are not well
fit in a plane. Therefore, the b-diketiminato backbone is better
described as the partially delocalized electronic structure. The
pyridine ring’s plane forms a dihedral angle of 8.27◦ with the
N1–C2–C3–C4–N2 plane. The yttrium ion sits above the N1–
˚
C2–C3–C4–N2 ligand plane by 0.743 A; the distances from the
˚
yttrium ion to the atoms C2, C3 and C4 (>3.31 A) are too long
Fig. 1 Molecular structure of 1 with thermal ellipsoids at 30% probability
level. Isopropyl groups on the Ar substituents and hydrogen atoms
˚
for effective interaction. The Y–C25 distance (2.403(4) A) is close
to the Y–C31 distance (2.371(4) A). For the Y–N2–C8–Si1–C25
five-membered ring, the atoms N2, C8, Si1 and C25 are nearly
coplanar with the yttrium ion 1.117 A out of the plane to adopt
˚
˚
have been removed for clarity. Selected bond lengths (A) and angles
(◦): Y–C31 2.371(4), Y–C25 2.403(4), Y–N1 2.285(3), Y–N2 2.385 (3),
Y–O 2.367(3), N1–C2 1.362(5), N2–C4 1.364(5), C2–C3 1.366(5), C3–C4
1.416(6), C31–Y–C25 114.20(14).
˚
a folded-like conformation. The THF is bonded to the metal ion
˚
with a reasonable Y–O separation of 2.367(3) A.
The structural features of 2 are very similar to those of 1,
and the distances from the yttrium ion to the coordinated atoms
in these two complexes are nearly the same. For 2, it’s worthy
1
noting that the h coordinated phenyl ring is nearly coplanar
with the pyridine ring. It’s also interesting to do a brief structural
comparison between 2 and a yttrium hydrido complex supported
by a tridentate phenyl substituted amidopyridinate dianionic
ligand reported by Trifonov et al., where a sp2 C–H bond of
a phenyl substituent on the pyridine ring is also activated and
1
the phenyl ring is h coordinated to the metal center.16f In 2,
the dianionic ligand forms one six-membered ring and one five-
membered ring with the metal center, while in Trifonov’s complex,
the dianionic ligand forms two five-membered rings with the
metal center. The Y–CAr and Y–NPy distances in 2 (2.396(3)
Fig. 2 Molecular structure of 2 with thermal ellipsoids at 30% probability
level. Isopropyl groups on the Ar substituents and hydrogen atoms
˚
have been removed for clarity. Selected bond lengths (A) and angles
˚
(◦): Y–C31 2.360(3), Y–C24 2.396(3), Y–N1 2.273(3), Y–N2 2.371(3),
Y–O 2.355(2), N1–C2 1.344(4), N2–C4 1.367(4), C2–C3 1.362(4), C3–C4
1.426(4), C31–Y–C24 112.40(12).
and 2.371(3) A, respectively) are shorter than those in Trifonov’s
˚
complex (2.469(2) and 2.4252(17) A, respectively), while the other
˚
˚
Y–N distance is longer in 2 (2.273(3) A vs. 2.2205(18) A). The
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 2366–2374 | 2367
©

Table 1 Hydroamination of A catalyzed by 1–4a
yttrium ion in 2 sits more out of the N–N–C plane than that
˚
˚
in Trifonov’s complex (0.977 A vs. 0.696 A). Alkyl complexes 1
and 2 are stable at room temperature for several days. When the
temperature is elevated to 60 ◦C, the decomposition of 1 is less
than 20% in C6D6 in 5.5 h; 2 is more stable and show less than
10% decomposition in C6D6 in 12 h.
Entry Catalyst [Cat.]/[Sub.] (%) Time (min) Conv. (%)b TOF (h-1)c
As shown in Scheme 2, besides a terminal Y–CH2SiMe3 bond,
3
2
1 and 2 have a metallacyclic Y–Csp (Y–CH2SiMe2) or Y–Csp
(Y–CAr) bond, respectively. How the terminal and metallacyclic
Y–C bonds differentiate in reactivity should be an intriguing
question. To answer the question, protonolysis reactions of 1 and
2 with one equivalent of a Brønsted acid 2,6-diisopropylaniline
were carried out. 1H NMR spectral monitoring of the reactions in
C6D6 showed that 1 and 2 were nearly completely converted into
anilide complexes 3 and 4 with concomitant disappearance of the
terminal –YCH2SiMe3 functional group in the metal complexes
and formation of one equivalent of Me4Si in 6 h (for 1) and
3 h (for 2) at room temperature. The experiments demonstrated
that the terminal Y–CH2SiMe3 bond is more reactive than the
metallacyclic Y–C bond. The reactions were then scaled up in
toluene, 3 and 4 were isolated as yellow crystalline solids in 55%
and 64% yield, respectively (Scheme 3).
1
2
3
4
1
2
3
4
2.5
2.5
2.5
2.5
60
35
120
70
96
97
97
98
38.4
66.5
19.4
33.6
a 15.3 mmol L-1 [cat.], 0.0613 mol L-1 [Cp2Fe], 0.613 mol L-1 [sub.], 60 ◦C,
0.46 mL of C6D6 as solvent. b NMR conv. determined relative to ferrocene
internal standard. c Turnover frequency.
Fig. 3 Molecular structure of 4 with thermal ellipsoids at 30% probability
level. Isopropyl groups on the Ar substituents and hydrogen atoms (except
anilide hydrogen atom◦) have been removed for clarity. Selected bond
˚
lengths (A) and angles ( ): Y–N3 2.197(5), Y–N1 2.281(4), Y–N2 2.361(4),
Y–C24 2.424(6), Y–O 2.355(3), N1–C2 1.342(6), N2–C4 1.371(7), C2–C3
1.383(8), C3–C4 1.397(7), Y–N3–C29 154.9(4).
behavior of complexes 1–4 for intramolecular hydroamination
were initially tested by employing 2,2-dimethyl-1-aminopent-4-
ene (A) as substrate (Table 1). A solution of the yttrium complex,
the standard ferrocene and substrate in C6D6 was loaded into an
NMR tube, and the reaction process was monitored by 1H NMR
spectroscopy.
Scheme 3 Protonolysis reactions of 3 and 4 with one equivalent of
2,6-diisopropylaniline.
1
When alkyl complexes 1 and 2 were used as catalysts, the H
NMR spectrum showed a rapid protonolysis of the terminal
alkyl by amine with a release of Me4Si. A clean formation
of 2,4,4-trimethylpyrrolidine, the Markovnikov-selective product,
was observed in several minutes. No traces of other heterocyclic
regioisomers were detected through the proceeding. Intriguingly,
anilide complexes 3 and 4 also exhibited good catalytic activities
for the intramolecular hydroamination, and the regioselectivity
was identical with that catalyzed by the alkyl complexes. The
hydroaminations of A catalyzed by 1–4 could be completed within
2 h at 60 ◦C, with a catalyst loading of 2.5 mol% (Table 1). The alkyl
complexes 1 and 2 are more active than the corresponding anilide
complexes 3 and 4; the complexes with the phenyl substituted
ligand L5–H, 2 and 4, are more active than the corresponding
ones with the silyl substituted ligand L4–H, 1 and 3. The catalytic
activity order is as the following: 2 > 1 > 4 > 3.
Single crystals of 4 were grown from the toluene solution and
characterized by X-ray diffraction studies (Fig. 3). The structure
of 4 takes great resemblance to its alkyl precursor 2, while the
terminal alkyl functional group in 2 is replaced by the anilide
functional group in 4. The Y–Nanilide distance is 2.197(5) A, and
˚
the ∠Y–Nanilide–C29 is 154.9(4)◦. The anilide complexes 3 and 4 are
stable at room temperature for several days. When the temperature
is elevated to 60 ◦C, the decomposition of 3 is less than 15% in C6D6
in 5.5 h; 4 is more stable and shows less than 5% decomposition
in C6D6 in 12 h.
Catalytic behavior for intramolecular hydroamination of
aminoalkenes
Intramolecular hydroamination of aminoalkenes offers an efficient
and atom-economical method to construct nitrogen heterocycles
that are important for the fine chemicals and pharmaceuticals.
Rare-earth metal complexes have been employed as one of the
most promising catalysts for this transformation.2,17,18 The catalytic
To investigate the initiation of catalytic reaction in detail,
experiments with a high [cat.]/[sub.] mole ratio of 1/5 were per-
formed in C6D6 at room temperature and monitored by 1H NMR
spectroscopy. In the case of alkyl complex 1, the protonolysis
2368 | Dalton Trans., 2011, 40, 2366–2374
This journal is
The Royal Society of Chemistry 2011
©

of the terminal alkyl with concomitant appearance of one
equivalent of Me4Si was observed immediately. The protonolysis
of metallacyclic Y–CH2SiMe2 bond was observed immediately,
which was evidenced by the disappearance of the Y–CH2SiMe2
signal. For anilide complex 3, there was no observation of 2,6-
diisopropylanilide throughout the reaction; but, similar to that
of the alkyl complex 1, the protonolysis of the metallacyclic
Y–CH2SiMe2 bond was observed immediately. The foregoing
observations suggested that in the hydroamination catalyzed by
alkyl complex 1, both the terminal Y–CH2SiMe3 bond and the
metallacyclic Y–CH2SiMe2 bond initiated the reaction; while in
the hydroamination catalyzed by anilide complex 3, the metal-
lacyclic Y–CH2SiMe2 bond initiated the reaction solely, and the
Y–Nanilide bond was retained. Complexes 2 and 4, which bear the
phenyl substituted ligand, showed similar behavior to complexes
1 and 3. In the case of alkyl complex 2, the protonolysis of the
terminal alkyl with concomitant appearance of one equivalent
of Me4Si and dramatic changes of the proton signals for the
aromatic rings were observed immediately. For anilide complex 4,
2,6-diisopropylanilide was not observed throughout the reaction,
while the proton signals for the aromatic rings immediately
changed dramatically. Thus in the hydroamination catalyzed by
alkyl complex 2, both the terminal Y–CH2SiMe3 bond and
the metallacyclic Y–CAr bond initiated the reaction; while in
the hydroamination catalyzed by the anilide complex 4, the
metallacyclic Y–CAr bond initiated the reaction solely. These
observations indicated that the alkyl complexes (1 and 2) and
the anilide complexes (3 and 4) have a different number of active
sites, which is responsible for the difference in activity between the
alkyl complexes and the anilide complexes.
Fig. 5 Plots showing ln[c]t/[c]0 versus time of hydroamination reactions
of A catalyzed by 1–4 ([cat.] = 15.3 mmol L-1) at 60 ◦C.
rearrangement of the insertion product to the secondary amide
cannot be rule out a priori).18g,19
Complexes 1 and 2, which have higher catalytic activity, were
subsequently applied for the intramolecular hydroamination of
a series of aminoalkenes (B–D) (Table 2). As observed in the
intramolecular hydroamination of substrate A, 2 showed higher
catalytic activity than 1. Under mild conditions (60 ◦C) with
a rather low catalyst loading (2.5 mol% 2), all substrates were
converted to the cyclic products in high conversions within short
reaction times (0.5 to 7 h). According to Baldwin’s rule for ring
closure20 that the formation of a six-membered ring is less favorable
than that of a five-membered ring, a longer reaction time was
needed for completing the reaction of substrate B in comparison
to that for substrate A (Table 2, entries 1 and 2 vs. Table 1, entries
1 and 2). The internal alkene’s intramolecular hydroamination is
still challenging. As shown in Table 2, 2 is also highly active to
the internal alkenes C and D. For substrate C, the cyclic product
was formed nearly quantitatively with 2.5 mol% 2 in 7 h (Table 2,
entry 4). For substrate D, bearing bulky phenyl substituents in the
b-position to the amino group, the reaction rate was accelerated.
The substrate was converted to the cyclic product in 98% yield
within 0.5 h (Table 2, entry 6), this observed rate enhancement is
consistent with the Thorpe–Ingold effect.21
Kinetic studies of 1–4 cata◦lyzed intramolecular hydroamination
1
of A were carried out at 60 C by in situ H NMR spectroscopy.
Fig. 4 presents substrate concentration decay curves for the
reactions catalyzed by 1–4. All of the four substrate decay curves
deviate from the typical zero-order dependence on substrate
concentration and show a decrease in rate at low substrate
concentrations. Actually, the reactions catalyzed by complexes 1
and 3 were about first-order dependent on substrate concentration
(Fig. 5), suggesting the protonation of the insertion product by
the substrate is rate limiting (although a preceding intramolecular
Conclusions
A variety of pyridyl-1-azaallyl ligand precursors (HL1–HL5) can
be readily synthesized via condensation of pyridine ketones with
anilines in the presence of p-toluenesulfonic acid. The alkane
elimination reactions of Y(CH2SiMe3)3(THF)2 with HL1–HL3
gave complicated mixtures, while that with the more sterically
demanding HL4 or HL5 afforded the monoalkyl complexes 1 and
2 supported by new tridentate pyridyl-1-azaallyl dianionic ligands.
Thus not only the deprotonation of the b-diketimine backbone but
also the activation of a sp3 C–H bond of trimethylsilyl substituent
(for HL4) or a sp2 C–H bond of phenyl substituent (for HL5)
on the pyridine ring of the ligand precursors were involved in
Fig. 4 Substrate concentration decay curves for hydroamination reac-
tions of A catalyzed by 1–4 ([cat.] = 15.3 mmol L-1) at 60 ◦C.
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 2366–2374 | 2369
©

Table 2 Hydroamination of aminoalkenes catalyzed by 1 and 2a
Entry
Substrate
Product
Catalyst
[Cat.]/[Sub.] (%)
Time (h)
Conv. (%)b
TOF (h-1)c
1
2
1
2
2.5
2.5
36
3
60
97
0.67
12.9
3
4
1
2
2.5
2.5
24
7
85
98
1.42
5.60
5
6
1
2
2.5
2.5
0.75
0.5
97
98
51.7
78.4
◦
a 15.3 mmol L-1 [cat.], 0.0613 mol L-1 [Cp2Fe], 0.613 mol L-1 [sub.], 60 C, 0.46 mL of C6D6 as solvent. b NMR conv. determined relative to ferrocene
internal standard. c Turnover frequency.
the reactions. The protonolysis reactions of 1 and 2 with one
equivalent of 2,6-diisopropylaniline were highly selective and gave
the corresponding monoanilide complexes (L4–H)YNHAr(THF)
(3) and (L5–H)YNHAr(THF) (4). Complexes 1–4 showed moder-
ate to good catalytic activities for intramolecular hydroamination
of a series of aminoalkenes to give the Markovnikov-selective
product. In the hydroamination catalyzed by the alkyl complexes,
both the terminal Y–CH2SiMe3 bond and the metallacyclic
Y–CH2SiMe2 (or Y–CAr) bond of the complexes initiated the
reaction; while in the hydroamination catalyzed by the anilide
complexes, the metallacyclic Y–CH2SiMe2 (or Y–CAr) bond of the
complexes initiated the reaction solely, and the Y–Nanilide bond was
retained.
(1-(6-Trimethylsilyl-pyridin-2-yl)propan-2-one). 2-Methyl-6-
trimethylsilanyl-pyridine (4.01 g, 24.0 mmol) was dissolved in
30 mL of dry Et2O, and was then cooled to -70 ◦C. The pentane
solution of tBuLi (1.6 M, 15 mL, 24.0 mmol) was added dropwise
into the ether solution at -70 ◦C. After the addition, the reaction
mixture was kept at -70 ◦C for an additional 30 min, then N,N-
dimethyl-acetamide (2.10 g, 2.25 mL, 24.0 mmol) was added
dropwise at -70 ◦C. The slurry brown mixture was warmed to
room temperature, stirred for 2 h, and quenched by 10 mL of
water. The mixture was extracted by dichloromethane (20 mL ¥ 3),
washed with brine, and dried over anhydrous Na2SO4 overnight.
The solvent was removed under vacuum, and the residues was
purified by flash column chromatography to give the desired
product as a yellow oil (1.83 g, 37% yield) (Scheme 4). The product
existed as a mixture of two isomers, a (1-(6-trimethylsilyl-pyridin-
2-yl)propan-2-one) and b (1-(6-trimethylsilyl-pyridin-2-yl)prop-
Experimental
1
1-en-2-ol), at room temperature. H NMR (300 MHz, CDCl3,
◦
3
General procedures
25 C): d (ppm) 7.45 (t, JHH = 7.5 Hz, 0.6 H, ArH of a), 7.28
3
3
(t, JHH = 7.2 Hz, 0.6 H, ArH of a), 7.26 (t, JHH = 6.9 Hz,
All operations were carried out under an atmosphere of ar-
gon using standard Schlenk techniques or in a nitrogen filled
glovebox. THF was distilled from Na-benzophenoneketyl, and
degassed by freeze–thaw–vacuum prior to use. Toluene, hexane
and C6D6 were dried over Na/K alloy, followed by vacuum
transfer and stored in the glovebox. 2,6-Diisopropylaniline for
the protonolysis reaction was purchased from Aldrich, dried
3
1H, ArH of b), 7.01 (d, JHH = 7.8 Hz, 0.6 H, ArH of a), 6.72
3
3
(d, JHH = 6.6 Hz, 1H, ArH of b), 6.61 (d, JHH = 8.7 Hz, 1H,
ArH of b), 5.20 (s, 1H, CCH C(OH)(CH3) of b), 3.85 (s, 1.2H,
CH2C O(CH3) of a), 2.16 (s, 1.8 H, CH2C O(CH3) of a), 2.02
(s, 3H, CCH C(OH)(CH3) of b), 0.30 (s, 9H, SiMe3 of b), 0.24
(s, 5.5 H, SiMe3 of a). 13C NMR (75 MHz, CDCl3, 25 ◦C): d
(ppm) 206.1 (CH2C O(CH3)), 181.1 (CH C(OH)CH3), 168.1,
156.3, 154.8, 154.6, 135.7, 134.2, 126.5, 122.6, 120.1, 120.0
(ArC), 91.1 (CH C(OH)CH3), 53.5 (CH2C O(CH3)), 29.6
(CH2C O(CH3)), 25.6 (CH C(OH)CH3), -2.0, -2.5 (SiMe3).
HRMS (EI) calcd for C11H17NOSi (M+) 207.1079; found 207.1074.
˚
over 4 A molecular sieves, distilled under vacuum, and degassed
by freeze–thaw–vacuum prior to use. 2-Methyl-6-aminopyridine,
trimethylchlorosilane and phenylboronic acid were purchased
from Acros and used without further purification. 1-(6-
Methyl-pyridin-2-yl)-propan-2-one, 2-(6-methyl-pyridin-2-yl)-1-
23
phenyl-ethanone,22 2-methyl-6-trimethylsilanyl-pyridine and 2-
24
methyl-6-phenyl-pyridine
were synthesized according to lit-
erature procedures. Y(CH2SiMe3)3(THF)2 was synthesized as
reported.25 1H and 13C NMR spectra were recorded on a Varian
Mercury 300 MHz or a Varian 400 MHz spectrometer. All
chemical shifts were reported in d units with references to the
residual solvent resonance of the deuterated solvents for proton
and carbon chemical shifts. Elemental analysis was performed
by the Analytical Laboratory of Shanghai Institute of Organic
Chemistry.
Scheme 4 Synthesis of 1-(6-trimethylsilyl-pyridin-2-yl)propan-2-one.
1-(6-Phenyl-pyridin-2-yl)propan-2-one. The procedure de-
scribed for (1-(6-trimethylsilyl-pyridin-2-yl)propan-2-one) was
used, but with 2-methyl-6-phenyl-pyridine (2.04 g, 12.0 mmol)
2370 | Dalton Trans., 2011, 40, 2366–2374
This journal is
The Royal Society of Chemistry 2011
©

t
and BuLi (1.6 M, 7.5 mL, 12.0 mmol), and the reaction time
extended to 20 h. HL3 was obtained as a yellow solid (9.16 g, 87%
yield). 1H NMR (400 MHz, CDCl3, 25 ◦C): d (ppm) 11.62 (s, 1H,
NH), 7.44 (t, 3JHH = 8.0 Hz, 1H, Py-H), 7.19–7.23 (m, 2H, ArH),
7.11–7.17 (m, 4H, ArH), 7.05 (d, 3JHH = 8.0 Hz, 2H, ArH), 6.89 (d,
3JHH = 8.0 Hz, 1H, Py-H), 6.75 (d, 3JHH = 7.6 Hz, 1H, Py-H), 5.40
(s, 1H, CH), 3.41 (sp, 3JHH = 6.8 Hz, 2H, ArCHMe2), 2.46(s, 3H,
was extended to 6 h. 1-(6-Phenyl-pyridin-2-yl)propan-2-one was
obtained as a yellow oil (1.31 g, 52% yield) (Scheme 5). 1H NMR
◦
3
(300 MHz, CDCl3, 25 C): d (ppm) 7.95 (d, JHH = 7.5 Hz, 2H,
ArH), 7.64 (t, 3JHH = 7.8 Hz, 1H, ArH), 7.57–7.54 (m, 1H, ArH),
3
7.44–7.35 (m, 3H, ArH), 7.09 (d, JHH = 7.5 Hz, 1H, ArH), 3.93
(s, 2H, CH2C O(CH3)), 2.22 (s, 3H, CH2C O(CH3)). 13C NMR
(75 MHz, CDCl3, 25 ◦C): d (ppm) 205.6 (CH2C O(CH3)), 156.9,
154.5, 139.0, 137.2, 128.8, 128.7, 126.8, 122.2, 118.5 (ArC), 53.2
(CH2C O(CH3)), 29.9 (CH2C O(CH3)). HRMS (EI) calcd for
C14H13NO (M+) 211.0997; found 211.1000.
Py-CH3), 1.16 (d, 3JHH = 6.8 Hz, 6H, ArCHMe2), 0.98 (d, 3JHH
=
6.8 Hz, 6H, ArCHMe2). 13C NMR (100 MHz, CDCl3, 25 ◦C):
d (ppm) 159.3 (imine C), 155.4, 152.8, 145.8, 137.8, 136.1, 135.9,
128.2, 127.7, 127.5, 126.1, 122.9, 119.0, 116.4 (PyC and ArC), 96.6
(MeC(NH)CH), 28.3, 25.6, 24.5, 21.8 (ArMe2 and PyMe). HRMS
(EI) calcd for C26H30N2 (M+) 370.2409; found 370.2413.
HL4. The procedure described for HL1 was used, but with
2,6-diisopropylaniline (1.56 g, 8.84 mmol), a mixture of 1-(6-
trimethylsilyl-pyridin-2-yl)propan-2-one and 1-(6-trimethylsilyl-
pyridin-2-yl)prop-1-en-2-ol (1.83 g, 8.84 mmol), a catalytic
amount of p-toluenesulfonic acid (300 mg) in benzene (30 mL),
and the reaction time was extended to 24 h. HL4 was obtained
Scheme 5 Synthesis of 1-(6-phenyl-pyridin-2-yl)propan-2-one.
1
as a yellow oil (1.50 g, 47% yield). H NMR (400 MHz, CDCl3,
◦
25 C): d (ppm) 11.51 (s, 1H, MeC(NH)CH), 7.41–7.37 (m, 1H,
HL1. 1-(6-Methyl-pyridin-2-yl)-propan-2-one
(6.01
g,
ArH), 7.28–7.26 (m, 1H, ArH), 7.19–7.17 (m, 2H, ArH), 7.02 (d,
40.2 mmol), 2,6-diisopropylaniline (4.87 g, 40.2 mmol), p-
toluenesulfonic acid (6.92 g, 36.4 mmol) and toluene (60 mL)
were introduced into a 150 mL flask equipped with Dean–Stark
apparatus. After refluxing for 15 h, the solvent was removed
under vacuum. The orange viscous residue was dissolved in
100 mL of dichloromethane, washed by saturated aqueous
Na2CO3 (100 mL), and dried over anhydrous Na2SO4 overnight.
The solvent was removed under vacuum, and the residue was
purified by flash column chromatography to give HL1 as a yellow
3JHH = 6.8 Hz, 1H, ArH), 6.85 (d, 3JHH = 7.8 Hz, 1H, ArH), 5.15
3
(s, 1H, MeC(NH)CH), 3.31 (sept, JHH = 6.8 Hz, 2H, CHMe2),
1.68 (s, 3H, MeC(NH)CH), 1.22 (d, 3JHH = 6.8 Hz, 6H, CHMe2),
3
1.14 (d, JHH = 6.8 Hz, 6H, CHMe2), 0.21 (s, 9H, SiMe3). 13C
NMR (100 MHz, CDCl3, 25 ◦C): d (ppm) 164.3 (imine C), 160.3,
150.8, 147.6, 135.6, 133.5, 127.2, 122.8, 121.5, 120.3 (ArC), 93.1
(MeC(NH)CH), 28.2 (MeC(NH)CH), 24.8, 22.9, 20.1 (AriPr),
-1.7 (SiMe3). HRMS (ESI) calcd for C23H35N2Si (M+) 367.2564;
found 367.2561.
oil (6.24 g, 62% yield). H NMR (300 MHz, CDCl3, 25 ◦C): d
1
3
(ppm) 11.34 (s, 1H, MeC(NH)CH), 7.52 (t, JHH = 7.8 Hz, 1H,
HL5. The procedure described for HL1 was used, but with
2,6-diisopropylaniline (1.16 g, 6.55 mmol), 1-(6-phenyl-pyridin-
2-yl)propan-2-one (1.38 g, 6.55 mmol), p-toluenesulfonic acid
(0.997 g, 5.24 mmol) and benzene (30 mL), and the reaction time
was extended to 24 h. HL5 was obtained as a yellow solid (0.70 g,
3
3
ArH), 6.88 (d, JHH = 8.1 Hz, 1H, ArH), 6.81 (d, JHH = 7.5 Hz,
1H, ArH), 5.31 (s, 1H, CH), 2.58 (s, 3H, Py-CH3), 2.45 (s, 6H,
ArCH3), 1.86 (s, 3H, CH3). 13C NMR (75 MHz, CDCl3, 25 ◦C):
d (ppm) 159.6 (imine C), 155.3, 150.0, 139.3, 137.2, 135.7, 127.9,
126.1, 117.7, 115.5 (ArC), 93.7(CH), 24.6, 20.0, 18.6 (ArMe,
PyMe and MeC). HRMS (EI) calcd for C17H20N2 (M+) 252.1626;
found 252.1630.
◦
1
29% yield). H NMR (300 MHz, CDCl3, 25 C): d (ppm) 11.34
3
(s, 1H, MeC(NH)CH), 7.82 (d, JHH = 7.8 Hz, 2H, ArH), 7.50
(t, JHH = 8.1 Hz, 1H, ArH), 7.32–7.14 (m, 6H, ArH), 6.86 (d,
3
3JHH = 8.1 Hz, 1H, ArH), 5.20 (s, 1H, MeC(NH)CH), 3.28 (sept,
3JHH = 6.6 Hz, 2H, CHMe2), 1.68 (s, 3H, MeC(NH)CH), 1.20 (d,
3JHH = 6.6 Hz, 6H, CHMe2), 1.04 (d, 3JHH = 6.6 Hz, 6H, CHMe2).
13C NMR (75 MHz, CDCl3, 25 ◦C): d (ppm) 159.9 (imine C),
154.9, 151.0, 147.6, 136.1, 135.6, 128.5, 128.3, 127.2, 126.4, 123.1,
119.4, 113.4 (ArC), 93.2 (MeC(NH)CH), 28.3 (MeC(NH)CH),
25.0, 22.5, 20.2 (AriPr). HRMS (ESI) calcd for C26H31N2 (MH+)
371.2482; found 371.2495.
HL2. The procedure described for HL1 was used, but with
2-(6-methyl-pyridin-2-yl)-1-phenyl-ethanone (4.20 g, 19.9 mmol),
2,6-dimethylaniline (2.41 g, 19.9 mmol), p-toluenesulfonic acid
(3.42 g, 18.0 mmol) in toluene (60 mL), and the reaction time was
extended to 22 h. HL2 was obtained as a ◦yellow solid (5.08 g,
81% yield). 1H NMR (400 MHz, CDCl3, 25 C): d (ppm) 11.58 (s,
3
1H, PhC(NH)CH), 7.43 (t, JHH = 7.6 Hz, 1H, ArH), 7.26–7.28
(m, 1H, ArH), 7.24–7.26 (m, 1H, ArH), 7.12–7.20 (m, 3H, ArH),
3
6.90–6.96 (m, 3H, ArH), 6.88 (d, JHH = 8.0 Hz, 1H, ArH), 6.75
(L4-H)YCH2SiMe3(THF) (1). HL4 (270 mg, 0.738 mmol) and
Y(CH2SiMe3)3(THF)2 (400 mg, 0.811 mmol) were dissolved in
5 mL of hexane at room temperature. The reaction mixture was
allowed to stand at room temperature for 24 h. The volatiles were
removed under vacuum, and the residue was extracted by hexane
(3 mL ¥ 3). The extract was concentrated to approximately 1 mL,
3
(d, JHH = 7.2 Hz, 1H, ArH), 5.43 (s, 1H, CH), 2.49 (s, 3H,◦Py-
CH3), 2.22 (s, 6H, ArCH3). 13C NMR (100 MHz, CDCl3, 25 C):
d (ppm) 159.0 (imine C), 155.5, 152.2, 139.7, 138.6, 135.9, 134.6,
128.2, 128.0, 127.9, 127.8, 127.6, 124.7, 119.2, 116.7 (ArC), 97.8
(MeC(NH)CH), 24.6, 19.1 (ArMe and PyMe). HRMS (EI) calcd
for C22H22N2 (M+) 314.1783; found 314.1784.
◦
stored at -35 C for 24 h to afford 1 as a pale yellow crys◦talline
1
HL3. The procedure described for HL1 was used, but with
2-(6-methyl-pyridin-2-yl)-1-phenyl-ethanone (6.01 g, 28.4 mmol),
2,6-diisopropylaniline (5.47 g, 28.4 mmol), p-toluenesulfonic acid
(4.90 g, 25.8 mmol) in toluene (100 mL), and the reaction time was
solid (348 mg, 77% yield). H NMR (400 MHz, C6D6, 25 C): d
(ppm) 7.07–7.03 (m, 1H, ArH), 7.00 (s, 3H, ArH), 6.93 (d, 3JHH
=
7.2 Hz, 1H, ArH), 6.80 (d, 3JHH = 7.2 Hz, 1H, ArH), 5.36 (s, 1H,
MeC(N)CH), 3.50–3.05 (br, 6H, THF-Ha and CHMe2), 1.73 (s,
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 2366–2374 | 2371
©

3H, MeC(N)CH), 1.21–1.09 (m, br, 16H, THF-Hb and CHMe2),
0.61 (br, 6H, Si(CH3)2), 0.17 (s, 9H, CH2SiMe3), -0.36 (s, br, 2H,
Me2SiCH2Y), -0.42 (d, 2JYH = 2.8 Hz, 2H, YCH2SiMe3). 13C NMR
Table 3 Crystallographic data and refinement for complexes 1, 2, and 4
Complex
1
2
4
◦
(100 MHz, C6D6, 25 C): d (ppm) 171.3 (imine C), 158.0, 157.4,
Empirical formula
Formula weight
Colour
C31H51N2OSi2Y C34H47N2OSiY C42H54N3OY
143.8, 135.5, 125.4, 124.0, 123.1, 121.3 (ArC), 96.0 (MeC(N)CH),
69.5 (THF-Ca ), 38.4 (d, 1JYC = 43.2 Hz, YCH2SiMe3), 28.1 (AriPr),
25.1 (br, YCH2SiMe2), 24.9, 23.7, 23.4, 23.0 (AriPr, CMe and
THF-Cb). 3.6 (SiMe3 and SiMe2). Elemental analysis (%) calcd
for C31H51N2OSi2Y: C 60.76, H 8.39, N 4.57; found: C 60.32, H
8.50, N 4.41.
612.83
Yellow
Orthorhombic
P212121
9.2709(11)
17.719(2)
21.296(2)
90
616.74
705.79
Yellow
Monoclinic
P21
9.6805(11)
17.3700(19)
11.7004(13)
90
Yellow
Monoclinic
P21/c
12.1821(11)
13.4126(12)
20.8185(18)
90
Crystal system
Space group
˚
a/A
˚
b/A
˚
c/A
a/◦
b/◦
g /◦
90
90
95.134(2)
90
98.877(2)
90
(L5-H)YCH2SiMe3(THF) (2). HL5 (217 mg, 0.587 mmol) and
Y(CH2SiMe3)3(THF)2 (289 mg, 0.587 mmol) were dissolved in
5 mL of hexane at room temperature. The reaction mixture was
allowed to stand at room temperature for 24 h. The volatiles were
removed under vacuum, and the residue was washed by hexane
(1.5 mL ¥ 4) to afford 2 as a yellow solid (258 mg, 71% yield). 1H
NMR (300 MHz, C6D6, 25 ◦C): d (ppm) 7.96–7.93 (m, 1H, ArH),
7.60–7.58 (m, 1H, ArH), 7.38–7.27 (m, 3H, ArH), 7.20–7.15 (m,
3
˚
Volume/A
3498.2(7)
4
3388.0(5)
4
1.209
1943.9(4)
2
1.206
Z
Density (calculated)/ 1.164
g cm-3
F(000)
1304
1.50–27.50
1304
748
q range/◦
1.96–27.00
19537
7358
1.76–25.50
10141
6841
Reflections collected 21215
Unique reflections
Unique reflections
(I > 2s(I))
7892
3954
3157
4156
1H, ArH), 6.97 (s, 3H, ArH), 6.85 (d, 3JHH = 8.1 Hz, ArH), 5.51
3
(s, 1H, MeC(N)CH), 3.33 (br, 4H, THF-Ha ), 3.27 (sept, JHH
=
Parameters
344
401
448
Goodness of fit
Final R indices [I > 0.0420, 0.0722
0.863
0.835
0.821
6.6 Hz, 2H, CHMe2), 1.79 (s, 3H, MeC(N)CH), 1.13 (br, 4H,
0.0453, 0.0712 0.0503, 0.0996
3
3
THF-Hb), 1.06 (d, JHH = 7.2 Hz, 6H, CHMe2), 0.98 (d, JHH
=
=
2s(I)]
6.9 Hz, 6H, CHMe2), 0.09 (s, 9H, YCH2SiMe3), -0.43 (d, 1JYH
-3
˚
Drmax,min/e A
0.506, -0.320
0.618, -0.337 0.487, -0.388
◦
3.3 Hz, 2H, YCH2SiMe3). 13C NMR (75 MHz, C6D6, 25 C): d
(ppm) 187.5 (YCAr, 2JYC = 46.4 Hz), 161.2 (imine C), 157.7, 157.2,
148.7, 145.9, 142.8, 137.7, 135.9, 126.8, 126.7, 125.5, 124.8, 124.0,
121.9, 109.9 (ArC), 96.3 (MeC(N)CH), 70.1 (THF-Ca ), 38.0 (d,
1JYC = 43.0 Hz, YCH2SiMe3), 27.9 (AriPr), 25.5, 25.2, 24.0, 23.8
(AriPr, CMe and THF-Cb), 3.6 (CH2SiMe3). Elemental analysis
(%) calcd for C34H47N2OSiY: C 66.21, H 7.68, N 4.54; found: C
65.74, H 7.48, N 4.32.
64% yield). 1H NMR (400 MHz, C6D6, 25 ◦C): d (ppm) 7.91–7.89
(m, 1H, ArH), 7.61–7.58 (m, 1H, ArH), 7.33–7.31 (m, 2H, ArH),
7.20–7.18 (m, 1H, ArH), 7.09–7.05 (m, 3H, ArH), 6.99 (s, 3H,
3
3
ArH), 6.79 (t, JHH = 7.6 Hz, 1H, ArH), 6.73 (d, JHH = 7.8 Hz,
1H, ArH), 5.48 (s, 1H, MeC(N)CH), 4.96 (s, br, 1H, YNHAr),
3.33 (br, 6H, THF-Ha and CHMe2), 2.93 (sept, 3JHH = 6.4 Hz, 2H,
CHMe2), 1.84 (s, 3H, MeC(N)CH), 1.19 (d, 3JHH = 6.8 Hz, 12H,
CHMe2), 1.25–0.95 (m, br, 16H, CHMe2 and THF-Hb). 13C NMR
(L4-H)Y[NH(2,6-iPr2–C6H3)](THF) (3). A toluene solution of
1 (150 mg, 0.245 mmol, 1 mL) was added to 2,6-diisopropylaniline
(43.4 mg, 0.245 mmol) at room temperature. The reaction mixture
was allowed to stand at room temperature for 6 h. The volatiles
were removed under vacuum, the residue was extracted by 2 mL
of toluene. The volatiles were removed under vacuum, and the
residues was washed by hexane (0.5 mL ¥ 3) to afford 3 as a yellow
crystalline solid (95.0 mg, 55% yield). 1H NMR (400 MHz, C6D6,
◦
2
(100 MHz, C6D6, 25 C): d (ppm) 186.0 (YCAr, JYC = 48.4 Hz),
161.1 (imine C), 161.0, 158.4, 156.8, 152.5, 152.4, 149.0, 145.5,
143.8, 137.6, 136.3, 132.4, 127.0, 126.5, 125.3, 124.4, 123.9, 122.8,
121.3, 115.4, 109.9 (ArC), 96.1 (MeC(N)CH), 70.6 (THF-Ca ),
31.2, 28.3, 25.5, 25.3, 24.3, 24.0, 23.0 (AriPr, CMe and THF-Cb).
Elemental analysis (%) calcd for C42H54N3OY: C 71.47, H 7.71, N
5.95; found: C 71.31, H 7.76, N 5.91.
◦
3
25 C): d (ppm) 7.12 (d, JHH = 7.6 Hz, 2H, ArH), 7.00 (s, 3H,
ArH), 6.96–6.94 (m, 1H, ArH), 6.85–6.83 (m, 2H, ArH), 6.72–
6.69 (m, 1H, ArH), 5.32 (s, MeC(N)CH), 4.75 (s, br, 1H, YNHAr),
General procedure for intramolecular hydroamination. The
yttrium complex, aminoalkene and the standard ferrocene were
mixed in C6D6 and transferred into an NMR tube. The NMR
tube was heated at 60 ◦C, and the process of the reaction was
monitored by 1H NMR.
3.35 (br, 2H, CHMe2), 3.21 (br, 4H, THF-Ha ), 2.98 (sept, 3JHH
=
6.8 Hz, 2H, CHMe2), 1.76 (s, 3H, MeC(N)CH), 1.40–0.90 (m, br,
24H, CHMe2), 1.05 (m, 4H, THF-Hb), 0.68 (br, 3H, YCH2SiMe2),
0.49 (br, 3H, YCH2SiMe2), -0.20 – -0.28 (br, 2H, YCH2SiMe2).
13C NMR (100 MHz, C6D6, 25 ◦C): d (ppm) 171.3 (imine C), 158.1,
158.0, 151.8, 144.5, 135.1, 132.9, 125.3, 124.9–123.9 (br), 122.9,
122.7, 121.0, 115.5 (ArC), 96.3 (MeC(N)CH), 70.4 (THF-Ca ),
30.7, 28.3, 24.8, 24.7, 24.3, 23.4 (AriPr, CMe and THF-Cb), 20.9
(d, 1JYC = 37.7 Hz, YCH2SiMe2), 4.6–4.4 (br, YCH2SiMe2), 2.0–1.8
(br, YCH2SiMe2). Elemental analysis (%) calcd for C39H58N3OSiY:
C 66.74, H 8.33, N 5.99; found: C 67.47, H 8.43, N 6.11.
Kinetic studies of intramolecular hydroamination. The yttrium
complex, aminoalkene and the standard ferrocene were mixed in
C6D6 and transferred into an NMR tube The tube was immediately
inserted into the probe of the Varian 400 MHz spectrometer, which
had been previously set to 60 0.1 ◦C. Data were corrected using
four scans per time interval with a 5 s delay to ensure accurate
integration. The substrate concentration was measured from the
olefin peak area standardized to the area of Cp2Fe (4.00 ppm in
C6D6).
(L5-H)Y[NH(2,6-iPr2–C6H3)](THF) (4). Following the proce-
dure described for 3, but with 2 (100 mg, 0.162 mmol) and 2,6-
diisopropylaniline (29.0 mg, 0.162 mmol), and the reaction time
was 3 h. 4 was obtained as a yellow crystalline solid (74.0 mg,
X-Ray crystallography†. Suitable single crystals of 1, 2 and
4 were sealed in thin-walled glass capillaries, and data collection
was performed at 20 ◦C on a Bruker SMART diffractometer with
2372 | Dalton Trans., 2011, 40, 2366–2374
This journal is
The Royal Society of Chemistry 2011
©

˚
graphite-monochromated Mo-Ka radiation (l = 0.71073 A). The
S. M. Humphrey and M. Bochmann, Organometallics, 2005, 24, 3792;
(c) D. V. Vitanova, F. Hampel and K. C. Hultzsch, Dalton Trans., 2005,
1565; (d) X. L. Liu, X. M. Shang, T. Tang, N. H. Hu, F. K. Pei, D. M.
Cui, X. S. Chen and X. B. Jing, Organometallics, 2007, 26, 2747.
10 (a) Y. M. Yao, Y. Zhang, Q. Shen and K. B. Yu, Organometallics, 2002,
21, 819; (b) Y. M. Yao, Y. Zhang, Z. Q. Zhang, Q. Shen and K. B. Yu,
Organometallics, 2003, 22, 2876; (c) Z. Q. Zhang, Y. M. Yao, Y. Zhang,
Q. Shen and W. T. Wong, Inorg. Chim. Acta, 2004, 357, 3173; (d) M. Q.
Xue, Y. M. Yao, Q. Shen and Y. Zhang, J. Organomet. Chem., 2005,
690, 4685; (e) Y. M. Yao, Z. Q. Zhang, H. M. Peng, Y. Zhang, Q. Shen
and J. Lin, Inorg. Chem., 2006, 45, 2175; (f) R. Jiao, X. D. Shen, M. Q.
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SMART program package was used to determine the unit-cell
parameters. The absorption correction was applied using SAD-
ABS. The structures were solved by direct methods and refined
on F2 by full-matrix least squares techniques with anisotropic
thermal parameters for non-hydrogen atoms. Hydrogen atoms
were placed at calculated positions and were included in the
structure calculation excepted for the hydrogen atom of anilide
functional group in 4, which was located in Fourier map. All
calculations were carried out using the SHELXL-97 program. The
software used is listed in the references.26,27,28,29 Crystallographic
data and refinement for 1, 2 and 4 are listed in Table 3.
11 (a) X. Xu, X. Y. Xu, Y. F. Chen and J. Sun, Organometallics, 2008, 27,
758; (b) E. L. Lu, W. Gan and Y. F. Chen, Organometallics, 2009, 28,
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This work was supported by the National Natural Science Foun-
dation of China (Grant Nos. 20872164, 20821002 and 21072209),
Chinese Academy of Sciences, and Shanghai Municipal Commit-
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