Zirconium complexes stabilized by amine-bridged bis(phenolato) ligands as precatalysts for intermolecular hydroamination reactions

Article abstract of DOI:10.1039/c5dt02643a

A series of zirconium complexes bearing amine-bridged bis(phenolato) ligands of different steric and electronic properties have been synthesized, and their activities in catalyzing intermolecular hydroamination reactions have been studied and compared. In

Full text of DOI:10.1039/c5dt02643a

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DOI: 10.1039/C5DT02643A
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Zirconium Complexes Stabilized by Amine-Bridged Bis(phenolato)
Ligands as Precatalysts for Intermolecular Hydroamination
Reactions †
Received 00th January 20xx,
Accepted 00th January 20xx
Qiu Sun, Yaorong Wang, Dan Yuan,* Yingming Yao,* and Qi Shen
DOI: 10.1039/x0xx00000x
A series of zirconium complexes bearing amine-bridged bis(phenolato) ligands of different steric and electronic properties
have been synthesized, and their activities in catalyzing intermolecular hydroamination reactions have been studied and
compared. In general, hexacoordinate zirconium dibenzyl complexes 1-4 stabilized by [ONNO]- or [ONOO]-type ligands
were found to be less active than pentacoordinate complexes 5 and 7 that carry [ONO]-type ligands, which clearly imply
that amine-bridged bis(phenolato) ligands play crucial roles in influencing catalytic activities. Complex 5 showed good
activities and regioselectivities in catalysing reactions of various primary amines and alkynes. Moreover, reactions of
challenging substrates, including secondary amines, internal alkynes, and hydrazines, were achieved with in situ generated
cationic species from complex 5 and [Ph3C][B(C6F5)4].
www.rsc.org/
Introduction
Hydroamination reactions are direct addition of N–H bonds wide range of main group and transition metal complexes
across C–C unsaturated bonds, which provide a highly atom bearing bis(phenolato) ligands have been synthesized,7 and are
economic strategy to prepare compounds containing nitrogen mainly applied in promoting ring-opening polymerization of
atoms.1 The transformation can be promoted by a wide range olefin,7c-k lactide,7l-s epoxide,7t-u and some other monomers.7v-x
of complexes of transition metals,2 lanthanides,1h,3 and main Recently, we reported a zirconium complex stabilized by an
group elements,1h, 4 which allow these processes to be [ONNO]-type tetradentate ligand, which was found to be a
performed under relatively mild conditions. As one type of good precatalyst for intermolecular hydroamination reactions
low-toxic and easily available metal species, group 4 metal of primary amines in the presence of cationic reagent
complexes1c,d,f,h,5,6 have attracted much interest due to their [Ph3C][B(C6F5)4].8 However, it failed to catalyze reactions with
generally high reactivity in catalysing both intra-5 and secondary amines. In remarkable contrast,
intermolecular6 hydroamination reactions. However, the complex bearing an [ONO]-type tridentate ligand proved
a zirconium
limitation of group
4 metal catalysed intermolecular efficient in catalysing intermolecular hydroamination reactions
hydroamination reactions lies in the narrow substrate scope, of secondary amines.9 Apparently, a small change in ancillary
which is mainly restricted to primary amines. As an exception, ligands leads to significant differences in catalytic performance
Schafer et al. reported a tethered zirconium bis(ureate) of complexes. We thus extended our investigations to a series
complex which showed good activities in catalysing the of bis(phenolato) ligands of different steric and electronic
hydroamination of aliphatic secondary amines.6w
properties, and carried out a systematic study on their
Modification of ligands is a practical strategy to tune the influence on complex formation and catalytic activities of
catalytic activities of metal complexes. Bis(phenolato) ligands resulting complexes.
have been intensively studied, due to their good capacities in
stabilizing metal centres, as well as their structural diversity
which enables a detailed study on the correlation between
Results and discussion
structures and catalytic activities of resulting complexes. A
Synthesis of zirconium complexes.
Amine-bridged bis(phenol) L1H2
–
L4H2 bearing coordinating
sidearms were synthesized (Figure 1), with the fourth donor
Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry,
Chemical Engineering and Materials Science, Dushu Lake Campus, Soochow
University, Suzhou 215123, People’s Republic of China
*To whom correspondence should be addressed. Email: yuandan@suda.edu.cn;
yaoym@suda.edu.cn
being nitrogen or oxygen atoms. Precursors L5H2 L7H2 of
–
potentially tridentate ligands carrying non-coordinating
sidearms were also prepared. Moreover, different substituents
on phenyl rings, including methyl, tert-butyl and cumyl groups,
were introduced to exert different spatial environments for
†
Electronic supplementary information: X-ray crystallographic data for
6
(CCDC
1410748) in CIF format, 1H and 13C NMR spectra of complexes
hydroamination products and 1H NMR spectra for kinetic studies.
2, 3, 6, 7 and
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metal centers. All ligand precursors were synthesized through 90-95% yields (Scheme 1). However, the reaction of n-
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Mannich condensation reactions from readily available starting butylamine-bridged bis(phenol) L6HD2 OI: c10a.r1r0y3i9n/gC5DTm02e6t4h3yAl
materials, namely primary amines, formaldehyde, and substituents with ZrBn4 in 1:1 ratio gave rise to homoleptic
substituted phenols.10
zirconium complex 6 in 49% yield accompanied with unreacted
ZrBn4. Various reaction conditions, including different ratios of
starting materials, different sequences of reactant addition,
and different temperatures (r.t. or -78
C), resulted in complex
6
as the sole product. Reaction of the correct stoichiometry at
room temperature led to an almost quantitative yield of 97%.
The formation of the homoleptic complex may be ascribed to
two reasons: 1) the sterically less-hindered methyl
substituents on phenyl rings; 2) the absence of the fourth
coordinating site from the bis(phenolato) ligand.11 1H NMR
Figure 1. Ligand precursors
spectrum of complex
6 shows signals corresponding to one set
Metathesis reactions of ZrBn4 and bis(phenol) at room
temperature provide an easy access to zirconium dialkyl
of ligand L6, revealing a symmetric structure.
complexes. Complexes 1-5, and 7 were isolated as expected in
Scheme 1. Synthesis of zirconium complexes
Figure 2. Molecular structure of 6PhCH3 showing 30% probability ellipsoids; hydrogen
atoms and solvent molecules are omitted for clarity. A summary of crystallographic
data is given in ref.12. Selected bond lengths (Å) and bond angles (deg): Zr1-O1
2.0014(15), Zr1-O2 1.9941(15) Zr(1)-N(1) 2.4197(17); O(2)-Zr(1)-O(2’) 91.50(10), O(2)-
Zr(1)-O(1) 159.47(6), O(2’)-Zr(1)-O(1) 91.30(7), O(1)-Zr(1)-O(1’) 93.17(9), O(2)-Zr(1)-N(1)
80.42(6), O(2’)-Zr(1)-N(1) 101.30(6), O(1)-Zr(1)-N(1) 79.09(6), O(1)-Zr(1)-N(1’) 99.22(6),
N(1)-Zr(1)-N(1’) 177.58(8), C(5)-O(1)-Zr(1) 144.30(13), C(14)-O(2)-Zr(1) 138.53(14), C(1)-
N(1)-C(11) 112.24(17), C(1)-N(1)-C(20) 111.91(16), C(11)-N(1)-C(20) 105.59(16), C(1)-
N(1)-Zr(1) 108.64(12), C(11)-N(1)-Zr(1) 107.61(12), C(20)-N(1)-Zr(1) 110.77(13), N(1)-
C(1)-C(2) 117.36(18).
Solid state structure of
6 (depicted in Figure 2) obtained
from X-ray diffraction analyses on single crystals supports that
the two amine-bridged bis(phenolato) ligands coordinate to
the metal center through two N and four O donors. The overall
coordination geometry is octahedral.
Hydroamination reactions of alkynes and primary amines.
Catalytic behaviors of complexes 1-7 were evaluated and
compared in catalyzing the hydroamination reaction between
aniline and phenylacetylene (Table 1). Analogous to the
previously reported zirconium amide stabilized by the same
ligand L1,8 complex
110
1
failed to catalyze this transformation at

C (Table 1, entry 1). Similarly, complexes and carrying
2
3
different substituents on phenyl rings showed no activity
(entry 2 and 3). Changing the tetradentate [ONNO]-type
bis(phenolato) ligand to [ONOO]-type ligand L4 proved not
helpful, as complex
4 did not show any activity under identical
conditions (entry 4). In contrast, mixtures of complexes
1-4
and [Ph3C][B(C6F5)4] (TB) efficiently catalyzed the reaction, and
led to the desired product 10a in almost quantitative yields
(entry 5-8) within a short period of 1-2 h. Cationic species
derived from reactions of 1-4 with TB are believed to play
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crucial roles in catalyzing this transformation, which may be
attributed to the enhanced Lewis acidity of metal centers, as
well as larger coordination sites for the substrates.8 Moreover,
Markovnikov products formed exclusively, revealing 100%
regioselectivity of these reactions.
Table 1. Hydroamination/reduction reactions of aniline and phenylacetylene catalyzed
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by different complexesa
DOI: 10.1039/C5DT02643A
In stark contrast to the above-discussed findings, the
pentacoordinate complex
5 itself worked well in catalyzing the
reaction between aniline and phenylacetylene, and 98% of the
expected product 10a formed (entry 9). It is noteworthy that
21% of Z-enyne 11a resulting from the dimerization of
phenylacetylene was isolated as well (entry 9). The sequence
of starting material addition proved crucial in determining
product distributions. If alkyne was mixed with the precatalyst
5
followed by the addition of amine, hydroamination reaction
occurred exclusively (entry 10), while the reversed sequence
led to a mixture of 10a and 11a (entry 9). Reactions of
phenylacetylene and aniline in the ratio of 2:1 gave the same
trends (entry 11 and 12). This finding resembles that reported
by Schafer et al., which discloses that a dibenzyl tethered
bis(ureate) zirconium precatalyst in the presence of aniline
efficiently catalyzed the dimerization of phenylacetylene.13
Changing the ratio of starting materials to 1:1 resulted in 96%
and 97% yields of 10a in either chlorobenzene (entry 13) or
a Conditions unless otherwise stated: precatalyst (0.1 mmol), [Ph3C][B(C6F5)4] (TB),
(0.1 mmol) if necessary, 8a (desired amount) and 9a (0.091 mL,1 mmol) was
added successively into chlorobenzene (2 mL), and the mixture was heated at 110
C for desired time. b The initially formed imine was reduced by LiAlH4 to give
corresponding secondary amines. c Isolated yield. No anti-Markovnikov product
was detected. d 9a was mixed with 5 in solution for 1 h followed by the addition
of 8a. The mixture was heated for another 3 h. e 8a was mixed with 5 in solution
toluene (entry 14). The homoleptic complex
in catalyzing this reaction (entry 15), while complex
similar activity to that of (entry 16). The activity differences
between hexacoordinate complexes and pentacoordinate
complexes and clearly reveal the important role of
6
proved inactive
7
showed
5
f
1-4
for 1 h followed by the addition of 9a. The mixture was heated for another 3 h.
Yield is based on 9a.
5
7
bis(phenolato) ligands in influencing the catalytic activities of
respective complexes. The absence of the fourth coordination
Complex
5 was then tested in catalysing the intermolecular
hydroamination reactions between various alkynes and aniline
(Chart 1). Excellent yields of 94-99% were obtained from
reactions of phenylacetylene derivatives bearing either
electron-withdrawing or donating groups at ortho-, meta-, or
site in complexes
5 and 7 makes the metal centers more Lewis
acidic and renders coordination sites for substrates to bind,
which may be the major reasons that are responsible for
enhanced activities of pentacoordinate complexes. This finding
is different from previous reports by Kol, Goldschmidt and co-
workers, in which hexacoordinate complexes are found to be
more active than pentacoordinate counterparts in initiating
the polymerization of 1-hexene.10 Borates [Ph3C][B(C6F5)4] (TB),
[PhMe2NH][B(C6F5)4], and [Et3NH][BPh4] have been tested in
the absence of zirconium complexes, and no desired product
was detected (entry 17-19), which verifies the essential role of
zirconium complexes in catalyzing the transformation.
para-positions (10b-f). The reaction with 2-ethynylthiophene
also proceeded smoothly, and afforded the desired product
10g in 96% yield. Aliphatic alkynes, including 3-phenyl-1-
propyne, 1-hexyne, and cyclohexylacetylene, reacted
straightforwardly with aniline under optimal conditions, and
gave rise to secondary amines 10h-j after reduction in almost
quantitative yields of 95-99%. All products 10b
-
j
formed
following Markovnikov rules.
For reactions of internal alkynes catalysed by complex
conversion was detected at all after 12 h of reaction at 110 °C.
However, in situ generated cationic species from complex
5
, no
5
and [Ph3C][B(C6F5)4] (TB) efficiently catalysed reactions
between aniline and diphenylacetylene or 1-phenyl-1-propyne,
and afforded the desired products in 93% (10k) and 89% (10l
+
10l’) yields, respectively. It is noteworthy that for the
unsymmetrical substrate 1-phenyl-1-propyne, a mixture of 10l
and 10l’ resulting from different directions of the addition
reaction was obtained.
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good yields of 79-90% (12s
of TB.
-
u
) were obtained in the presence
Chart 1. Hydroamination/reduction reactions of aniline and various alkynes catalyzed
by 5a,b
View Article Online
DOI: 10.1039/C5DT02643A
Chart 2. Hydroamination/reduction reactions of phenylacetylene and various amines
catalyzed by complex 5a,b
a
Conditions unless otherwise stated: 8 (1 mmol) was mixed with 5 (0.070 g, 0.1
mmol) in toluene (2 mL) for 1 h followed by the addition of 9a (0.091 mL, 1 mmol).
The mixture was heated at 110 C for another 3 h. b Isolated yield. c The alkyne is
e
3-phenyl-1-propyne. d In the presence of TB in PhCl. The alkyne is 1-phenyl-1-
propyne.
Hydroamination reactions between phenylacetylene and
various anilines catalyzed by complex
and results are summarized in Chart 2. For mono-substituted
anilines, good yields of 85-99% were obtained 12b ),
5 have also been studied,
(
-j
regardless there are ortho-, meta-, or para- substitutes which
are electron-withdrawing or donating. It is noteworthy that
reactions with 4- and 2-anisidines that contain coordinating
oxygen atoms proceeded smoothly, and generated the desired
products in 95% (12h) and 85% (12i) yields, respectively. No
significant catalyst deactivation was observed. For comparison,
a much lower yield (11%) of 12h was obtained from the
reaction catalyzed by cationic species, probably due to the
stronger binding of the substrate with the more Lewis acidic
center that leads to deactivation of catalytically active
a Conditions unless otherwise stated: 8a (0.11 mL, 1 mmol) was mixed with 5
(0.070 g, 0.1 mmol) in toluene (2 mL) for 1 h followed by the addition of 9 (1
mmol). The mixture was heated at 110 C for another 3 h. b Isolated yield. c 24 h
reaction time. d In the presence of TB in PhCl.
Hydroamination reactions of alkynes and secondary amines.
As previously communicated, the mixture of complex
5 and TB
showed good activities in catalyzing the reaction of secondary
amines and alkynes, which is the first group 4 metal based
catalyst in mediating intermolecular hydroamination reactions
species.8 2-tert-butylaniline that carries
a bulky ortho-
substituent reacted with phenylacetylene under optimal
conditions, and afforded 12o in 93% yield. For anilines that
bear more than one substituent, their reactions with
phenylacetylene led to different results. Reactions with 2,6-
of amines bearing both aryl and alkyl N-substituents.9
A
comparative study with other complexes revealed that
mixtures of complexes 1-4 and TB failed to catalyze
hydroamination reactions of 1,2,3,4-tetrahydroquinoline
dimethylaniline
and
2,4,6-trimethylaniline
worked
straightforwardly, and afforded desired products in 99% (12k
)
(Table 2, entry 1-4). Complex
5 itself did not catalyze this
and 98% (12l) yields, respectively. As the substituents get
bulkier, no product was detected from the reaction with 2,6-
diisopropylaniline (9m). No reaction occurred with aniline
bearing more than one electron-withdrawing group, i.e., 3,5-
bis(trifluoromethyl)aniline (9n) and pentafluoroaniline (9o),
transformation (entry 5), which is different from the result
obtained in the presence of TB (entry 6). The homoleptic
complex
6
proved inactive (entry 7), and complex
7 showed
similar activity as that of
5
(entry 8). These findings are
consistent with those of primary amines (vide supra) that
enhanced Lewis acidities of metal centers and suitable
coordination sites for substrates to bind are essential for
complexes of higher activities in catalyzing hydroamination
reactions, which can be achieved by modification of the
amine-bridged bis(phenlato) ligands. Similarly, borates showed
negligible activities in catalyzing the hydroamination reactions
even after prolonged reaction time. Complex
5 also failed to
catalyze reactions involving primary aliphatic amines such as
benzylamine (9p), hexylamine (9q) and tert-butyl amine (9r).
Reactions with substrates 9n-r have also been tested in the
presence of TB, however, to no avail. Hydrazines have also
been studied in reactions with phenylacetylene and 3-phenyl-
1-propyne. No reaction occurred in the absence of TB, while
of secondary amines (entry 9-11) (vide supra). As complex
5
exhibited limited activity in catalyzing reactions of aliphatic
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secondary amines,9 complex
ARTICLE
7
was tested in catalyzing
piperidine, 1,2,3,4-
View Article Online
DOI: 10.1039/C5DT02643A
reactions of pyrrolidine,
tetrahydroisoquinoline and morpholine with phenylacetylene.
However, no desired product was detected.
Table 2. Hydroamination/reduction reactions of 1,2,3,4-Tetrahydroquinoline and
phenylacetylene catalyzed by different complexesa
Figure 3. Plot of ln[8e]0/[8e] versus time (s) for the hydroamination reaction of p-
tolylacetylene 8e and aniline 9a catalyzed by 10 mol% of complex 5. Conditions: [8e]0
0.3636 mol·L−1, [9a]0 = 3.6374 mol·L−1; 10 mol% of complex 5, PhCH3-d8, 110 °C.
=
Plausible mechanism.
Based on the above-discussed experimental findings,
a
plausible mechanism has been proposed. Since the mechanism
of cationic species catalysed transformations has been
communicated,9 only the mechanism of neutral complexes
catalysed reactions is depicted in Figure 4. An imido
a Conditions unless otherwise stated: Catalyst (0.1 mmol), [Ph3C][B(C6F5)4] (TB)
intermediate
A has been proposed, which explains why neutral
(0.1 mmol) if necessary, 13a (0.125mL, 1 mmol), 8a (0.22 mL, 2 mmol), solvent (2
b
mL), 110 C. The initially formed enamine was reduced by LiAlH4 to give
complexes failed to catalyse hydroamination reactions of
secondary amines. Coordination of alkynes took place,
followed by the [2 + 2] cycloaddition and aminolysis, which
gave rise to hydroamination products. Meanwhile, a zirconium
corresponding tertiary amines. c Isolated yield. No anti-Markovnikov product was
detected.
alkynyl species
E may form, which led to the dimerization of
Kinetic study.
phenylacetylene.13
Kinetic study was conducted in order to gain further insights
into the catalytic process. As previously reported, the reaction
of primary amines which is catalyzed by cationic zirconium
complex stabilized by ligand L1 showed first order dependence
on [alkyne], while a reversed-first order dependence on
[amine].8 The behavior of complex
compared.
5 was then investigated and
The kinetic experiment was carried out with ten-fold of
aniline 9a under pseudo-first order conditions, and the
concentration of p-tolylacetylene 8e was monitored as a
function of time by 1H NMR spectroscopy (Scheme 2). A
representative plot of ln([8e]0/[8e]) versus time shows a first-
14
order disappearance (Figure 3).6p,q,
Meanwhile, the
concentration of amine (1, 2 and 10 equiv.) did not influence
the reaction rate, suggesting a zero-order dependence on
amines. Overall, the rate law is deduced as

~
[alkyne]1[amine]0. The different order of [amine] comparing to
that of cationic species catalyzed system may be ascribed to
the stronger binding of amine to more Lewis acidic metal
centers in the latter, which shuts down the catalytic cycle for
certain extent.
Figure 4. A plausible mechanism.
Conclusions
In summary, a series of zirconium complexes stabilized by
amine-bridged bis(phenolato) ligands have been prepared, and
Scheme 2. Model Reaction for Kinetic Study of Complex 5.
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their behaviors in catalyzing intermolecular hydroamination 59.7(PhCH2), 50.8(PhCH2), 31.6(NCH2CH2N), 22.7(NCH2CH2N),
View Article Online
reactions have been studied and compared. Hexacoordinate 20.4 (p-PhCH3), 16.3 (o-PhCH3), 14.0 (N(DCOHI3:)120)..1A03n9a/Cl.5CDaTl0c2d64f3oAr
zirconium complexes
type ligands were found to be less active than pentacoordinate 7.01; N, 4.49
complexes and bearing [ONO]-type ligands, revealing the
ZrBn2L3 (3). Complex
important role that ligands play in influencing catalytic NMR (400 MHz, C6D6): δ 7.66-7.59 (m, 4H, Ar-H), 7.40 (m, 9H,
activities. Complex efficiently catalyzed the intermolecular Ar-H), 7.26-7.01 (m, 16H, Ar-H), 6.68-6.62 (m, 4H, Ar-H), 6.50-
1-4 bearing either [ONNO]- or [ONOO]- C36H44N2O2Zr: C, 68.85; H, 7.06; N, 4.46. Found: C, 68.83; H,
1
5
7
3 was isolated in 2.88 g (92% yield). H
5
hydroamination reactions of various primary amines and 6.47 (m, 1H, Ar-H), 6.14-6.13 (m, 2H, Ar-H), 2.92-2.89 (d, 2H, J
alkynes, and showed good regiocontrol. Reactions of = 13.08Hz, ArCH2), 2.47 (s, 2H, PhCH2), 2.29 (s, 2H, PhCH2),
challenging substrates, such as internal alkynes, hydrazines, 2.21-2.18 (d, 2H, J = 13.48Hz, ArCH2), 1.98 (s, 6H, p-PhCH3),
and secondary amines, were achieved with in situ generated 1.87 (s, 6H, o-PhCH3), 1.68 (s, 12H, PhCH3), 1.68 (m, 2H, NCH2C),
cationic species from complex
5
and [Ph3C][B(C6F5)4]. Further 1.68 (m, 2H, CCH2N), 1.37 (s, 6H, N(CH3)2). 13C{1H} NMR (100
study on development of group 4 metal complexes as MHz, C6D6): 156.9, 150.7, 150.3, 148.5, 145.6, 139.9, 135.4,
precatalysts in catalyzing atom economic transformations is 127.8, 127.5, 126.7, 126.3, 126.0, 125.9, 125.2, 125.0, 120.5,
on-going in our laboratory
119.6, (Ar-C), 70.6 (ArCH2N), 66.6 (ArCH2N), 63.7 (PhCH2), 59.1
(PhCH2), 41.9 (p-PhCH3), 31.1 (NCH2CH2N), 30.7 (NCH2CH2N),
30.6 (o-PhCH3), 28.8 (N(CH3)2). Anal. Calcd for C68H76N2O2Zr: C,
78.19; H, 7.33; N, 2.68. Found: C, 78.22; H, 7.31; N, 4.27
Experimental section
General considerations.
Zr(L6)2 (6). Complex
6
was isolated in 2.78 g (97% yield) 1H
NMR (400 MHz, C6D6): δ 7.16-7.12 (m, 4H, Ar-H), 7.07-7.05 (m,
2H, Ar-H), 7.02-7.01 (m, 4H, Ar-H), 6.96-6.92 (m, 4H, Ar-H),
6.83-6.81 (m, 4H, Ar-H), 4.69-4.64 (m, 4H, ArCH2), 3.43-3.37 (t,
4H, NCH2), 2.88-2.84 (m, 4H, ArCH2), 2.29 (s, 6H, p-PhCH3), 2.26
(s, 6H, p-PhCH3), 2.26 (s, 6H, o-PhCH3), 2.21 (s, 6H, PhCH3),
1.95 (s, 6H, o-PhCH3), 1.41-1.37 (m, 4H, NCCH2), 0.83-0.69 (m,
4H, NCCCH2), 0.55-0.51 (m, 6H, NCCCCH3).13C{1H} NMR (100
MHz, C6D6): 158.1, 158.0, 137.5, 131.8, 129.0, 128.2, 126.4,
126.0, 125.3, 124.8, 124.7, 122.1, 121.9 (Ar-C), 58.4, 58.0
(ArCH2N), 45.9 (NCCH2), 21.1(ArCH3), 20.6(PhCH3), 20.5, 19.7
(ArCH3), 16.4 (NCH2CH2), 16.1 (NCH2CH2CH2), 13.1
All manipulations of air- and/or moisture-sensitive compounds
were performed under nitrogen atmosphere using standard
1
Schlenk or glovebox techniques. H and 13C NMR spectra were
recorded on a Varian XL 400 MHz spectrometer. Carbon,
hydrogen, and nitrogen analyses were performed by direct
combustion with a Carlo-Erba EA-1110 instrument. X-ray
crystallographic data were collected using a Bruker AXS D8 X-
ray diffractometer. Toluene and hexane were freshly distilled
by refluxing over sodium/benzophenone ketyl and distilled
prior to use. C6H5Cl, C6D6, PhMe-d8 and C6D5Cl were degassed
and distilled over CaH2. [Ph3C][B(C6F5)4] purchased from Strem
Chemicals, Inc. was used without purification. ZrBn4 and ligand
precursors L1H2 - L7H2 were prepared according to reported
(NCH2CH2CH2CH2). Anal. Calcd for C44H58N2O4Zr
72.99; H, 7.82; N, 2.94. Found: C, 73.14; H, 7.90; N, 2.88.
ZrBn2L7 (7). Complex was isolated in 2.78 g (90% yield). 1H
2PhCH3: C,
procedures.10 Compounds
1, 4, 5 and all of hydroamination
7
1
NMR (400 MHz, C6D6): δ 7.60-7.59 (m, 2H, Ar-H), 7.34-7.32 (m,
4H, Ar-H), 7.30-7.27 (m, 4H, Ar-H), 7.19-7.00 (m, 16H, Ar-H),
6.91-6.89 (m, 2H, Ar-H), 6.70-6.67 (m, 4H, Ar-H), 6.45-6.43 (m,
2H, Ar-H), 2.98-2.94 (d, 2H, J = 13.8Hz, ArCH2), 2.57-2.54 (d, 2H,
J = 13.92Hz, ArCH2), 1.94 (s, 6H, p-PhCH3), 1.80 (s, 6H, o-PhCH3),
1.85(s, 2H, PhCH2), 1.83-1.80 (m, 2H NCH2), 1.67 (s, 12H,
PhCH3), 1.55 (s, 2H, PhCH2), 0.77-0.71 (m, 2H, NCCH2), 0.57-
0.52(m, 5H, NCCCH2CH3). 13C{1H} NMR (100 MHz, C6D6): 157.3,
156.5, 151.2, 150.7, 150.4, 149.0, 146.0, 140.3, 135.9, 128.3,
128.0, 127.1, 126.8, 126.5, 125.7, 125.5, 121.0, 120.0 (Ar-C),
71.1 (ArCH2N), 61.1 (ArCH2N), 64.1 (PhCH2), 59.5 (PhCH2), 50.2
(NCH2), 31.6 (p-PhCH3), 31.2 (NCH2CH2), 29.3 (NCH2CH2CH2),
22.7 (PhCH3), 14.0 (NCH2CH2CH2CH2). Anal. Calcd for
C68H75NO2Zr: C, 79.33; H, 7.34; N, 1.36. Found: C, 79.29; H,
7.31; N, 1.30.
products were confirmed by comparing H NMR spectra with
literature data.8,9,10,15 Amines were distilled over CaH2. Alkynes
were degassed, flushed with argon and stored over molecular
sieves (4 Å).
General procedure for zirconium complexes synthesis.10
To a solution of ZrBn4 (3 mmol) in toluene (10 mL) was added
dropwise LnH2 (n = 1-5 and 7) (3 mmol) or L6H2 (6 mmol) in
toluene (5 mL) at room temperature over 15 min. After stirring
for 12 hours at room temperature, toluene was removed
under reduced pressure and the residue was washed with
hexane (2
toluene solution, while complexes
toluene and hexane solution. Complexes
as yellow solids, and were obtained as colourless solids.
ZrBn2L2 (2). Complex was isolated in 1.70 g (90% yield). 1H

5 mL). Complexes
1
-
4
were recrystallized from
were recrystallized from
were obtained
5-7
1 - 4
5-7
2
General procedure for hydroamination reactions of primary
NMR (400 MHz, C6D6): δ 7.54-7.52 (d, 2H, J = 13.1 Hz, Ar-H),
7.05-7.01 (m, 2H, Ar-H), 7.34-7.31 (m, 2H, Ar-H), 6.95-6.88 (m,
7H, Ar-H), 6.66-6.63 (m, 1H, Ar-H), 6.52 (s, 2H, Ar-H), 3.61-3.57
(d, 2H, J = 13.48 Hz, ArCH2), 2.65(s, 2H, PhCH2), 2.48-2.45 (d,
2H, J = 11.68Hz, PhCH2), 2.45(s, 6H, p-PhCH3), 2.41(s, 2H,
PhCH2), 2.20(s, 6H, o-PhCH3), 1.87 (m, 2H, NCH2C), 1.54 (s, 6H,
N(CH3)2), 1.27(m, 2H, CCH2N). 13C{1H} NMR (100 MHz,
C6D6):156.7, 149.6, 146.2, 131.9, 128.0, 128.2, 128.1, 127.9,
126.7, 125.0, 122.0, 119.9 (Ar-C), 65.5 (ArCH2N), 63.5 (ArCH2N),
amines catalyzed by 5.8
In a glovebox filled with nitrogen,
the toluene solution (2 mL) of
followed by the addition of (1mmol). The resulting mixture
was stirred at 110 C for the desired time. After the mixture
was cooled to 0 C, LiAlH4 (76 mg, 2 mmol) was added, and the
resulting mixture was stirred at 60 C for 2 hours. The reaction
8
(1 mmol) was mixed with
5
(78 mg, 0.1 mmol) for 1 h,
9



was quenched by the aqueous solution of NaOH (6 M). The
6 | J. Name., 2012, 00, 1-3
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Journal Name
product was extracted with toluene (3
shown in Chart 1-2 were isolated by column chromatography
(petroleum ether/ethyl acetate =100/1, Al2O3) as viscous
colorless oil and characterized by 1H and 13C NMR
spectroscopy.
ARTICLE
2
(a) N. Nishina, Y. Yamamoto, Top Organomet. Chem. 2013,

1 mL). All amines
43, 115 and references therein. (b) S. WeVrkiemw AeritsictleeOr,nlinSe.
DOI: 10.1039/C5DT02643A
Fleischer, S. Zhou, K. Junge, M. Beller, ChemSusChem, 2012,
5
, 777.
3
4
S. Hong, T. J. Marks, Acc. Chem. Res., 2004, 37, 673.
(a) M. R. Crimmin, I. J. Casely and M. S. Hill, J. Am. Chem. Soc.,
2005, 127, 2042. (b) F. Hild and S. Dagorne, Organometallics,
2012, 31, 1189. (c) C. Brinkmann, A. G. M. Barrett, M. S. Hill
and P. A. Procopiou, J. Am. Chem. Soc., 2012, 134, 2193.
Selective reports on group 4 metal complexes catalyzed
intramolecular hydroamination reactions: (a) P. L. McGrane,
M. Jensen, T. Livinghouse, J. Am. Chem. Soc., 1992, 114, 5459.
General procedure for hydroamination reactions of secondary
amines catalyzed by 5.9
In a glovebox filled with nitrogen, PhCl solution (1 mL) of
[Ph3C][B(C6F5)4] (92 mg, 0.01 mmol) was added to PhCl
5
solution (2 mL) of
5 (70 mg, 0.01 mmol) under stirring. A color
(b) P. L. McGrane, T. Livinghouse, J. Org. Chem., 1992, 57
,
change from orange to colorless was observed immediately.
After 5 min, 13a (0.125mL, 1 mmol) and 8a (0.22 mL, 2 mmol)
were added to the mixture successively. The resulting solution
1323. (c) H. Kim, P. H. Lee, T. Livinghouse, Chem. Commun.,
2005, 5205. (d) J. A. Bexrud, J. D. Beard, D. C. Leitch, L. L.
Schafer, Org. Lett., 2005, 7, 1959. (e) E. Chong, S. Qayyum, L.
was stirred at 110
was cooled to 0 C, LiAlH4 (76 mg, 2 mmol) was added, and the
resulting mixture was stirred at 60 C for 2 hours. The reaction
was quenched by the aqueous solution of NaOH (6 M).The
product was extracted with toluene (3 1 mL). The crude
C for the desired time. After the mixture
L. Schafer, R. Kempe, Organometallics, 2006, 25, 6125. (f) K.
Born, S. Doye, Eur. J. Org. Chem., 2012, 764. (g) R. K.
Thomson, J. A. Bexrud, L. L. Schafer, Organometallics, 2006,
25, 4069. (h) B. D. Stubbert, T. J. Marks, J. Am. Chem. Soc.,
2007, 129, 6149. (i) J. Cho, T. K. Hollis, T. R. Helgert, E. J.
Valente, Chem. Commun., 2008, 5001. (j) C. Müller, W. Saak,
S. Doye, Eur. J. Org. Chem., 2008, 2731. (k) J. A. Bexrud, L. L.
Schafer, Dalton Trans., 2010, 39, 361. (l) D. C. Leitch, R. H.
Platel, L. L. Schafer, J. Am. Chem. Soc., 2011, 133, 15453. (m)
R. O. Ayinla, L. L. Schafer, Dalton Trans., 2011, 40, 7769. (n) E.
Chong, S. Qayyum, L. L. Schafer, R. Kempe, Organometallics,
2013, 32, 1858. (o) P. R. Payne, R. K. Thomson, D. M.



product obtained after removal of solvent was isolated by
column chromatography (petroleum ether, silica gel, 0.5% NEt3)
as viscous colorless oil and characterized by H and 13C NMR
1
spectroscopy
X-Ray crystallographic structure determination.
Suitable single crystals of complex
6 were sealed in a thin-
Medeiros, G. Wan, L. L. Schafer, Dalton Trans., 2013, 42
,
walled glass capillary for determination the single-crystal
structures. Intensity data were collected with a Rigaku
15670. (p) J. M. P. Lauzon, L. L. Schafer, Z. Anorg. Allg. Chem.,
2015, 641, 128.
6
Selective reports on group 4 metal complexes catalyzed
intermolecular hydroamination reactions: (a) P. J. Walsh, A.
Mercury CCD area detector in
 scan mode using Mo-Kα
radiation ( = 0.71070 Å). The diffracted intensities were

M. Baranger, R. G. Bergman, J. Am. Chem. Soc., 1992, 114
,
corrected for Lorentz/ polarization effects and empirical
absorption corrections.
1708. (b) E. Haak, I. Bytschkov, S. Doye, Angew. Chem. Int.
Ed., 1999, 38, 3389. (c) J. S. Johnson, R. G. Bergman, J. Am.
Chem. Soc., 2001, 123, 2923. (d) F. Pohlki, S. Doye, Angew.
Chem. Int. Ed., 2001, 40, 2305. (e) B. F. Straub, R. G. Bergman,
Angew. Chem. Int. Ed., 2001, 40, 4632. (f) Y. Shi, J. T.
Ciszewski, A. L. Odom, Organometallics, 2001, 20, 3967. (g) C.
The structures were solved by direct methods and refined
by full-matrix least-squares procedures based on |F|2.The
hydrogen atoms in these complexes were generated
geometrically, assigned appropriate isotropic thermal
parameters, and allowed to ride on their parent carbon atoms.
All of the hydrogen atoms were held stationary and included in
the structure factor calculation in the final stage of full-matrix
least-squares refinement. The structures were solved and
refined using SHELEXL-97 programs.
Cao, J. T. Ciszewski, A. L. Odom, Organometallics, 2001, 20
,
5011. (h) A. Tillack, I. G. Castro, C. G. Hartung, M. Beller,
Angew. Chem. Int. Ed., 2002, 41, 2541. (i) A. Heutling, S.
Doye, J. Org. Chem., 2002, 67, 1961. (j) V. Khedkar, A. Tillack,
M. Beller, Org. Lett., 2003,
Gillon, B. O. Patrick, L. L. Schafer, Chem. Commun., 2003, 586.
(l) Z. Zhang, L. L. Schafer, Org. Lett., 2003, , 4733. (m) Y. Shi,
5, 4767. (k) C. Li, R. K. Thomson, B.
5
C. Hall, J. T. Ciszewski, C. Cao, A. L. Odom, Chem. Commun.,
2003, 2462. (n) L. L. Anderson, J. Arnold, R. G. Bergman, Org.
Lett., 2004,
6, 2519. (o) A. Tillack, V. Khedkar, M. Beller,
Acknowledgements
Tetrahedron Lett., 2004, 45, 8875. (p) A. Heutling, F. Pohlki, S.
Doye, Chem. Eur. J., 2004, 10, 3059. (q) A. Tillack, H. Jiao, I. G.
Castro, C. G. Hartung, M. Beller, Chem. Eur. J., 2004, 10, 2409.
(r) A. Tillack, V. Khedkar, H. Jiao, M. Beller, Eur. J. Org. Chem.,
2005, 5001. (s) K. Marcseková, B. Wegener, S. Doye, Eur. J.
Org. Chem., 2005, 4843. (t) E. Chong, S. Qayyum, L. L. Schafer,
R. Kempe, Organometallics, 2006, 25, 6125. (u) A. V. Lee, L. L.
Schafer, Organometallics, 2006, 25, 5249. (v) Z. Zhang, D. C.
Leitch, M. Lu, B. O. Patrick, L. L. Schafer, Chem. Eur. J., 2007,
13, 2012. (w) D. C. Leitch, P. R. Payne, C. R. Dunbar, L. L.
Schafer, J. Am. Chem. Soc., 2009, 131, 18246. (x) K. S.
Weitershau, B. D. Ward, R. Kubiak, C. Müller, H. Wadepohl, S.
Doye, L. H. Gade, Dalton Trans., 2009, 4586. (y) D. C. Leitch,
Financial support from the National Natural Science
Foundation of China (21402135), the Natural Science
Foundation of the Jiangsu Higher Education Institutions of
China (14KJB150021), PAPD, and the Qing Lan Project is
gratefully acknowledged.
Notes and references
1
(a) T. E. Müller and M. Beller, Chem. Rev., 1998, 98, 675. (b) F.
Alonso, I. P. Beletskaya, M. Yus, Chem. Rev., 2004, 104, 3079.
(c) S. Doye, Synlett, 2004, 1653. (d) Odom A. L. Dalton Trans.,
2005, 225. (e) R. Severin, and S. Doye, Chem. Soc. Rev., 2007,
36, 1407. (f) A. V. Lee and L. L. Schafer, Eur. J. Inorg. Chem.,
2007, 2243. (g) T. E. Müller, K. C. Hultzsch, M. Yus, F. Foubelo,
M. Tada, Chem. Rev., 2008, 108, 3795. (h) L. R. Alexander, K.
C. Hultzsch, Top Organomet. Chem., 2013, 43, 51.
C. S. Turner, L. L. Schafer, Angew. Chem. Int. Ed., 2010, 49
,
6382. (z) II, D. L. Swartz, R. J. Staples, A. L. Odom, Dalton
Trans., 2011, 40, 7762. (aa) K. Born, S. Doye, Eur. J. Org.
Chem., 2012, 764. (bb) I. A. Tonks, J. C. Meier, J. E. Bercaw,
Organometallics, 2013, 32, 3451. (cc) C. Brahms, P. Tholen,
This journal is © The Royal Society of Chemistry 20xx
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Page 8 of 9
ARTICLE
Journal Name
W. Saak, S. Doye, Eur. J. Org. Chem., 2013, 33, 7583. (dd) J. C. 14 (a) D. L. Swartz II, A. L. Odom, Organometallics, 2006, 25
,
View Article Online
–H. Yim, J. A. Bexrud, R. O. Ayinla, D. C. Leitch, L. L. Schafer, J.
Org. Chem., 2014, 79, 2015.
6125. (b) F. Hild, S. Dagorne, Organometallics, 2012, 31,
DOI: 10.1039/C5DT02643A
1189.
7
For recent reports: (a) E. Despagnet-Ayoub, M. K. Takase, J. A. 15 A. Lalitha, K. Pitchumani and C. Srinivasan, Green Chemistry,
Labinger, J. E. Bercaw, J. Am. Chem. Soc., 2015, DOI:
10.1021/jacs.5b06695. (b) A. C. Behrle, J. R. Levin, J. E. Kim, J.
M. Drewett, C. L. Barnes, E. J. Schelter, J. R. Walensky,
Dalton Trans., 2015, 44, 2693. (c) E. Bisz, M. Bialek, B.
Zarychta, Appl. Catal. A-Gen., 2015, 503, 26 (d) H. Schroeder,
B. R. Lake, S. Demeshko, M. P. Shaver, M. Buback,
Macromolecules, 2015, 48, 4329. (e) F. Bonnet, H. E. Dyer, Y.
El Kinani, C. Dietz, P. Roussel, M. Bria, M. Visseaux, P. Zinck, P.
Mountford, Dalton Trans., 2015, 44, 12312. (f) J-B. Wang, L-P.
1999, 1, 173.
Lu, J-Y. Liu, H-L. Mu, Y-S. Li, J. Mol. Catal. A-Chem., 2015, 398
,
289. (g) M. Tschage, S. Jung, T. P. Spaniol, J. Okuda,
Macromol. Rapid. Comm. 2015, 36, 219. (h) M. R. Radlauer, T.
Agapie, Organometallics, 2014, 33, 3247. (i) C. Hohberger, T.
P. Spaniol, J. Okuda, Macromol. Chem. Phys. 2014, 205, 2011.
(j) S. Xiong, D. K. Steelman, G. A. Medvedev, W. N. Delgass,
M. M. Abu-Omar, J. M. Caruthers, ACS Catal., 2014, 4, 1162.
(k) L. Chiang, L. N. Allan, J. Alcantara, M. P. Wang, T. Storr, M.
P. Shaver, Dalton Trans., 2014, 43, 4295. (l)T. Zeng, Q. Qian,
B. Zhao, D. Yuan, Y. Yao, Q. Shen, RSC Adv., 2015, 5, 53161.
(m) T. R. Forder, M. D. Jones, New. J. Chem. 2015, 39, 1974.
(n) M. Zhang, X. Ni, Z. Shen, Organometallics, 2014, 33, 6861.
(o) Y. Chapurina, J. Klitzke, O. J. Casagrande, M. Awada, V.
Dorcet, E. Kirillov, J-F Carpentier, Dalton Trans., 2014, 43
,
14322. (p) K. Nie, T. Feng, F. Song, Y. Zhang, H. Sun, D. Yuan,
Y. Yao, Q. Shen, Sci. China. Chem. 2014, 57, 1106. (q) C.
Romain, C. Fliedel, S. Bellemin-Laponnaz, S. Dagorne,
Organometallics, 2014, 33, 5730. (r) J. S. Klitzke, T. Roisnel, E,
Kirillov, de L. Casagrande, J. Osvaldo, J-F. Carpentier,
Organometallics, 2014, 33, 309. (s) S. Yang, K. Nie, Y. Zhang,
M. Xue, Y. Yao, Q. Shen, Inorg. Chem., 2014, 53, 105. (t) M.
Taherimehr, J. P. C. C. Serta, A. W. Kleij, C. J. Whiteoak, P. P.
Pescarmona, ChemSusChem, 2015,
8
, 1034. (u)H. Chen, L. N.
, 1547. (v) T.
Dawe, C. M. Kozak, Catal. Sci. Technol., 2014,
4
Zeng, Y. Wang, Q. Shen, Y. Yao, Y. Luo, D, Cui,
Organometallics, 2014, 33, 6803. (w) W, Guerin, A. K. Diallo,
E. Kirilov, M. Helou, M. Slawinski, J-M. Brusson, J-F.
Carpentier, S. M. Guillaume, Macromolecules, 2014, 47, 4230.
(x) C. G. Jaffredo, Y. Chapurina, S. M. Guillaume, J. F.
Carpentier, Angew. Chem. Int. Ed., 2014, 53, 2687.
Q. Sun, Y. Wang, D. Yuan, Y. Yao, Q. Shen, Organometallics,
2014, 33, 994.
8
9
Q. Sun, Y. Wang, D. Yuan, Y. Yao, Q. Shen, Chem. Commun.,
2015, 51, 7633.
10 (a) E.Y. Tshuva, I. Goldberg, M. Kol, Z. Goldschmidt,
Organometallics, 2001, 20, 3017. (b) E.Y. Tshuva, I. Goldberg,
M. Kol, H. Weitman, Z. Goldschmidt, Chem. Commun., 2000,
379. (c) E.Y. Tshuva, I. Goldberg, M. Kol, Z. Goldschmidt,
Inorg. Chem. Commun., 2000, 3, 611.
11 (a) E.Y. Tshuva, I. Goldberg, M. Kol, Z. Goldschmidt, Inorg.
Chem., 2001, 40, 4263. (b) E.Y. Tshuva, M. Versano, I.
Goldberg, M. Kol, H. Weitman, Z. Goldschmidt, Inorg. Chem.
Commun., 1999,
2, 371.
12 Selected X-ray crystallographic data for zirconium complex
6
:
Formula, C44H58N2O4Zr, C7H8; fw, 862.28; color, colorless;
habit, prism; cryst size [mm], 0.60×0.50×0.40; temp [K],
223(2); crystsyst, monoclinic; space group, P2(1)/c; a [Å],
19.1566(9); b [Å], 16.0193(6); c [Å], 16.0089(7);
 [deg],
110.2047(5)˚; V[Å3], 4610.4(3); Z, 4; Dc [g cm-3], 1.242;
radiation used, Mo Kα; μ [mm-1], 0.283; θ range, 2.85-26.37;
no. of unique data, 4712; max, min transm, 1.000, 0.8600;
final R indices [I> 2(I)], R1 = 0.0395, wR2 = 0.1094; R indices
(all data), R1 = 0.0470wR2 = 0.1157; goodness-of-fit on F2,
1.091; peak/hole [e Å3], 0.764/-0.623.
13 R. H. Platel, L. L. Schafer, Chem. Commun., 2012, 48, 10609.
8 | J. Name., 2012, 00, 1-3
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View Article Online
DOI: 10.1039/C5DT02643A
Pentacoordinate zirconium complexes 5 and 7 stabilized by amine-bridged
bis(phenolato) ligands are more active than hexacoordinate complexes 1-4 in
catalyzing intermolecular hydroamination reactions.