Synthesis, structure, and catalytic activity of group 4 complexes with new chiral biaryl-based NO2 ligands

Article abstract of DOI:10.1016/j.jorganchem.2010.03.014

A new series of chiral bis-ligated group 4 complexes have been prepared from the reaction between M(NMe₂)₄ (M = Ti, Zr) and C₁-symmetric biaryl-based NO₂ ligands, (R)-2-(mesitoylamino)-2′-methoxy-1,1′-binaphthyl (1H), (R)-2-(mesitoylamino)-2′-methoxy-6,6′-dimethyl-1,1′-biphenyl (2H), (S)-5,5′,6,6′,7,7′,8,8′-octahydro-2-(mesitoylamino)-2′-methoxy-1,1′-binaphthyl (3H), (R)-2-(3,5-di-tert-butyl-2-hydroxyphenylmethyleneamino)-2′-methoxy-1,1′-binaphthyl (4H), (R)-2-(3-tert-butyl-2-hydroxyphenylmethyleneamino)-2′-methoxy-6,6′-dimethyl-1,1′-biphenyl (5H), which are derived from (R)-2-amino-2′-methoxy-1,1′-binaphthyl, (R)-2-amino-2′-methoxy-6,6′-dimethyl-1,1′-biphenyl or (S)-5,5′,6,6′,7,7′,8,8′-octahydro-2-amino-2′-methoxy-1,1′-binaphthyl. Treatment of M(NMe₂)₄ with 2 equiv. of mesitoylamides 1H, 2H or 3H gives, after recrystallization from a toluene or n-hexane solution, the bis-ligated chiral titanium amides (1)₂Ti(NMe₂)₂ (6), (2)₂Ti(NMe₂)₂ (8), (3)₂Ti(NMe₂)₂ (10), and zirconium amides (1)₂Zr(NMe₂)₂ (7), (2)₂Zr(NMe₂)₂ (9), (3)₂Zr(NMe₂)₂ (11), respectively, in good yields. Under similar reaction conditions, treatment of M(NMe₂)₄ with 2 equiv. of Schiff base ligands 4H or 5H gives, after recrystallization from a toluene solution, the chiral bis-ligated titanium complex {(R)-2-[3,5-(Me₃C)₂-2-O-C₆H₂CH(NMe₂)N]-2′-(MeO)-1,1′-C₂₀H₁₂}₂Ti (12) and zirconium complex {(R)-2-[3-Me₃C-2-O-C₆H₃CH(NMe₂)N]-2′-(MeO)-1,1′-(6-Me-C₆H₃)₂}(5)ZrNMe₂ (13), respectively, in good yields. All new compounds have been characterized by various spectroscopic techniques, and elemental analyses. The solid-state structures of compounds 1H, 6, 8, 9, 12 and 13 have further been confirmed by X-ray diffraction analyses. The titanium and zirconium amides are active catalysts for the asymmetric hydroamination/cyclization of aminoalkenes, affording cyclic amines in moderate to excellent yields with good ee values.

Full text of DOI:10.1016/j.jorganchem.2010.03.014

Journal of Organometallic Chemistry 695 (2010) 1583–1591
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis, structure, and catalytic activity of group 4 complexes with new
chiral biaryl-based NO2 ligands
Qiuwen Wang a, Haibin Song b, Guofu Zi a,
*
a Department of Chemistry, Beijing Normal University, Beijing 100875, China
b State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A new series of chiral bis-ligated group 4 complexes have been prepared from the reaction between
M(NMe2)4 (M = Ti, Zr) and C1-symmetric biaryl-based NO2 ligands, (R)-2-(mesitoylamino)-20-
methoxy-1,10-binaphthyl (1H), (R)-2-(mesitoylamino)-20-methoxy-6,60-dimethyl-1,10-biphenyl (2H),
Received 5 February 2010
Received in revised form 10 March 2010
Accepted 12 March 2010
(S)-5,50,6,60,7,70,8,80-octahydro-2-(mesitoylamino)-20-methoxy-1,10-binaphthyl
(3H),
(R)-2-(3,5-di-
Available online 16 March 2010
tert-butyl-2-hydroxyphenylmethyleneamino)-20-methoxy-1,10-binaphthyl (4H), (R)-2-(3-tert-butyl-2-
hydroxyphenylmethyleneamino)-20-methoxy-6,60-dimethyl-1,10-biphenyl (5H), which are derived from
(R)-2-amino-20-methoxy-1,10-binaphthyl, (R)-2-amino-20-methoxy-6,60-dimethyl-1,10-biphenyl or (S)-
5,50,6,60,7,70,8,80-octahydro-2-amino-20-methoxy-1,10-binaphthyl. Treatment of M(NMe2)4 with 2 equiv.
of mesitoylamides 1H, 2H or 3H gives, after recrystallization from a toluene or n-hexane solution, the
bis-ligated chiral titanium amides (1)2Ti(NMe2)2 (6), (2)2Ti(NMe2)2 (8), (3)2Ti(NMe2)2 (10), and zirconium
amides (1)2Zr(NMe2)2 (7), (2)2Zr(NMe2)2 (9), (3)2Zr(NMe2)2 (11), respectively, in good yields. Under sim-
ilar reaction conditions, treatment of M(NMe2)4 with 2 equiv. of Schiff base ligands 4H or 5H gives, after
recrystallization from a toluene solution, the chiral bis-ligated titanium complex {(R)-2-[3,5-(Me3C)2-2-
O-C6H2CH(NMe2)N]-20-(MeO)-1,10-C20H12}2Ti (12) and zirconium complex {(R)-2-[3-Me3C-2-O-C6H3CH
(NMe2)N]-20-(MeO)-1,10-(6-Me-C6H3)2}(5)ZrNMe2 (13), respectively, in good yields. All new compounds
have been characterized by various spectroscopic techniques, and elemental analyses. The solid-state
structures of compounds 1H, 6, 8, 9, 12 and 13 have further been confirmed by X-ray diffraction analyses.
The titanium and zirconium amides are active catalysts for the asymmetric hydroamination/cyclization
of aminoalkenes, affording cyclic amines in moderate to excellent yields with good ee values.
Ó 2010 Elsevier B.V. All rights reserved.
Keywords:
2-Amino-20-hydroxy-1,10-binaphthyl
Chiral group 4 metal complexes
Synthesis
Crystal structure
Asymmetric hydroamination/cyclization
1. Introduction
In recent years, 2-amino-20-hydroxy-1,10-binaphthyl (NOBIN) as
its (R) or (S) enantiomer has been modified to give variants which
Chiral group 4 metal complexes have been widely studied in the
past decades [1–14]. Among these, the development of group 4
metal catalysts for intramolecular asymmetric alkene hydroamin-
ation has received growing attention in recent years [11–14], be-
cause the hydroamination is a highly atom economical process in
which an amine N–H bond is added to an unsaturated carbon–car-
bon bond leading to the formation of nitrogen heterocycles that are
prevalent in naturally occurring and/or biologically active mole-
cules. To date, the chiral group 4 metal catalysts have been shown
promising for this transformation [15–30], however, successful
catalysts affording significant enantioselectivity (>90% ee) are still
scarcely reported, and those high enantioselective inductions are
observed only for one or two substrates [20,21,30]. Thus, the devel-
opment of new chiral group 4 metal catalysts for asymmetric al-
kene hydroamination is a desirable and challenging goal.
bear appropriate structural and electronic features for intended spe-
cific reactions, and its derivatives have exhibited good to excellent
enantioselectivities in a number of asymmetric transformations
[31–33]. However, few examples of chiral early transition metal cat-
alysts based on NOBIN have been reported [31–33]. More recently,
we have developed a series of early transition metal complexes
based on chiral NOBIN, and found they are useful catalysts in the
polymerization of methyl methacrylate (MMA), the ring-opening
polymerization of rac-lactide, and the hydroamination/cyclization
of the aminoalkenes [34–37]. In our endeavors to further explore
the chiral NOBIN ligand system, and in our previous study we found
that the group 4 complexes with chiral biaryl-based mesitoylamidate
ligands [25,30] are more effective chiral catalysts for asymmetric
hydroamination/cyclization than other ligated catalysts [24,28,29],
we therefore have recently extended our research work to new
chiral C1-symmetric versatile mesitoylamide ligands, (R)-2-(mes-
itoylamino)-20-methoxy-1,10-binaphthyl (1H) and (S)-5,50,6,60,7,70,
8,80-octahydro-2-(mesitoylamino)-20-methoxy-1,10-binaphthyl (3H),
* Corresponding author. Tel.: +86 10 5880 7843; fax: +86 10 5880 2075.
E-mail address: gzi@bnu.edu.cn (G. Zi).
0022-328X/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.03.014

1584
Q. Wang et al. / Journal of Organometallic Chemistry 695 (2010) 1583–1591
each ligand contains two
r-donating oxygen atoms and one
r
-
(s), 815 (s), 749 (s). Anal. Calc. for C31H27NO2: C, 83.57; H, 6.11;
donating nitrogen atom that can act in a bidentate or tridentate fash-
ion. Herein, we report the synthesis and properties of the new chiral
ligands, their use in the coordination chemistry of titanium(IV) and
zirconium(IV), and the applications of the resulting complexes as
catalysts for the asymmetric hydroamination/cyclization of
aminoalkenes. For better understanding and comparison, the new
ligands (R)-2-(mesitoylamino)-20-methoxy-6,60-dimethyl-1,10-biphenyl
(2H), (R)-2-(3,5-di-tert-butyl-2-hydroxyphenylmethyleneamino)-20-
methoxy-1,10-binaphthyl (4H) and (R)-2-(3-tert-butyl-2-hydroxyphe-
nylmethyleneamino)-20-methoxy-6,60-dimethyl-1,10-biphenyl (5H)
will be also included in this contribution.
N, 3.14. Found: C, 83.53; H, 6.03; N, 3.18%.
2.3. Preparation of (R)-2-(mesitoylamino)-20-methoxy-6,60-dimethyl-
1,10-biphenyl (2H)
This compound was prepared as a white solid from the reaction
of mesitoyl chloride (0.91 g, 5.0 mmol) with (R)-2-amino-20-meth-
oxy-6,60-dimethyl-1,10-biphenyl (1.14 g, 5.0 mmol) in the presence
of pyridine (2 mL, 25.3 mmol) in dry toluene (30 mL) at reflux and
purification by flash column chromatography (n-hexane/ethyl ace-
tate = 10:1) using a similar procedure as in the synthesis of 1H.
Yield: 1.70 g (91%). M.p.: 52–54 °C. 1H NMR (CDCl3): d 8.28 (d,
J = 8.2 Hz, 1H, aryl), 7.38 (t, J = 7.9 Hz, 1H, aryl), 7.27 (m, 1H, aryl),
7.15 (d, J = 7.5 Hz, 1H, aryl), 6.92 (d, J = 7.5 Hz, 1H, aryl), 6.81 (m,
4H, NH and aryl H), 3.69 (s, 3H, OCH3), 2.26 (s, 3H, CH3), 2.18 (s,
6H, CH3), 1.97 (s, 3H, CH3), 1.96 (s, 3H, CH3). 13C NMR (CDCl3): d
168.6, 156.8, 138.6, 138.5, 137.2, 135.7, 135.2, 134.3, 129.3,
128.6, 128.2, 127.9, 126.2, 124.3, 122.9, 119.5, 108.5, 55.5, 21.0,
2. Experimental
2.1. General methods
Group 4 complexes and catalytic reactions were performed un-
der an atmosphere of dry dinitrogen with rigid exclusion of air and
moisture using standard Schlenk or cannula techniques, or in a
glovebox. Allorganicsolventswerefreshlydistilledfromsodiumben-
zophenone ketyl immediately prior to use. (R)-2-Amino-20-methoxy-
1,10-binaphthyl [37], (R)-2-amino-20-methoxy-6,60-dimethyl-1,
10-biphenyl [37], (S)-5,50,6,60,7,70,8,80-octahydro-2-amino-20-meth-
oxy-1,10-binaphthyl [37], 2,2-dimethylpent-4-enylamine [38],
2,20-dimethylhex-5-enylamine [38], and 1-(aminomethyl)-1-allyl-
cyclohexane [39] were prepared according to literature methods.
All chemicals were purchased from Aldrich Chemical Co. and Beijing
Chemical Co., and used as received unless otherwise noted. Infrared
spectra were obtained from KBr pellets on an Avatar 360 Fourier
transform spectrometer. 1H and 13C NMR spectra were recorded
on a Bruker AV 400 spectrometer at 400 and 100 MHz, respectively.
All chemical shifts are reported in d units with reference to the resid-
ual protons of the deuterated solvents for proton and carbon chem-
ical shifts. Melting points were measured on an X-6 melting point
apparatus and were uncorrected. Elemental analyses were
performed on a Vario EL elemental analyzer.
19.9, 19.6, 18.8. IR (KBr, cmꢁ1):
m 3397 (s), 3061 (w), 2920 (m),
1680 (s), 1579 (s), 1513 (s), 1465 (s), 1410 (s), 1292 (s), 1256 (s),
1080 (s), 799 (s). Anal. Calc. for C25H27NO2: C, 80.40; H, 7.29; N,
3.75. Found: C, 80.34; H, 7.38; N, 3.73%.
2.4. Preparation of (S)-5,50,6,60,7,70,8,80-octahydro-2-(mesitoylamino)-
20-methoxy-1,10-binaphthyl (3H)
This compound was prepared as a white solid from the reaction
of mesitoyl chloride (0.91 g, 5.0 mmol) with (S)-5,50,6,60,7,70,8,80-
octahydro-2-amino-20-methoxy-1,10-binaphthyl (1.54 g, 5.0 mmol)
in the presence of pyridine (2 mL, 25.3 mmol) in dry toluene
(30 mL) at reflux and purification by flash column chromatography
(n-hexane/ethyl acetate = 10:1) using a similar procedure as in the
synthesis of 1H. Yield: 1.84 g (81%). M.p.: 56–58 °C. 1H NMR
(CDCl3): d 8.02 (d, J = 8.3 Hz, 1H, aryl), 7.09 (d, J = 8.3 Hz, 1H, aryl),
6.96 (d, J = 8.4 Hz, 1H, aryl), 6.66 (m, 4H, NH and aryl H), 3.56 (s,
3H, OCH3), 2.75 (m, 2H, CH2), 2.64 (m, 2H, CH2), 2.16 (s, 3H, CH3),
2.06 (s, 6H, CH3), 1.98 (m, 4H, CH2), 1.68–1.51 (m, 8H, CH2). 13C
NMR (CDCl3): d 167.5, 153.4, 137.3, 136.0, 134.8, 134.7, 133.3,
133.2, 131.6, 129.4, 128.9, 127.8, 127.6, 127.1, 122.9, 118.7,
107.6, 54.4, 28.7, 28.3, 28.2, 26.2, 26.1, 22.2, 22.0, 21.9, 20.0,
2.2. Preparation of (R)-2-(mesitoylamino)-20-methoxy-1,10-binaphthyl
(1H)
17.8. IR (KBr, cmꢁ1):
m 3395 (s), 2926 (s), 2855 (w), 1680 (s),
Mesitoyl chloride (0.91 g, 5.0 mmol) was mixed with
(R)-2-amino-20-methoxy-1,10-binaphthyl (1.50 g, 5.0 mmol) in
dry toluene (30 mL). Pyridine (2 mL, 25.3 mmol) was added,
and the solution was refluxed for two days. The solvent was re-
moved and the residue was decomposed with H2O (20 mL) and
extracted with ethyl acetate (20 mL ꢀ 3) and washed with brine
(20 mL). The combined organic layers were dried with anhydrous
Na2SO4 and the solvent was removed under reduced pressure to
give a white solid, which was further purified by flash column
chromatography (n-hexane/ethyl acetate = 10:1) to give 1H as a
white solid. Colorless crystals suitable for X-ray structure analysis
were grown from a toluene solution at room temperature. Yield:
1.78 g (80%). M.p.: 148–150 °C. 1H NMR (CDCl3): d 8.62 (d,
J = 8.8 Hz, 1H, aryl), 8.05 (d, J = 9.0 Hz, 1H, aryl), 7.99 (d,
J = 9.0 Hz, 1H, aryl), 7.93 (d, J = 8.2 Hz, 1H, aryl), 7.86 (d,
J = 8.1 Hz, 1H, aryl), 7.42 (m, 2H, aryl), 7.34 (m, 1H, aryl), 7.23
(m, 2H, aryl), 7.10 (d, J = 8.5 Hz, 1H, aryl), 7.05 (d, J = 8.5 Hz,
1H, aryl), 7.00 (s, 1H, NH), 6.68 (s, 2H, aryl), 3.74 (s, 3H, OCH3),
2.18 (s, 3H, CH3), 1.94 (s, 6H, CH3). 13C NMR (CDCl3): d 168.8,
154.9, 138.5, 134.8, 134.3, 134.1, 133.8, 133.1, 131.4, 130.8,
129.2, 128.6, 128.1, 128.0, 127.4, 126.3, 125.7, 125.0, 124.8,
124.1, 124.0, 123.1, 121.9, 117.1, 113.3, 56.3, 21.0, 18.6. IR
1593 (s), 1504 (s), 1479 (s), 1440 (s), 1260 (s), 1085 (s), 803 (s).
Anal. Calc. for C31H35NO2: C, 82.08; H, 7.78; N, 3.09. Found: C,
81.92; H, 7.68; N, 3.13%.
2.5. Preparation of (R)-2-(3,5-di-tert-butyl-2-hydroxyphenyl-
methyleneamino)-20-methoxy-1,10-binaphthyl (4H)
3,5-Di-tert-butyl-2-hydroxybenzaldehyde (2.34 g, 10.0 mmol)
was mixed with (R)-2-amino-20-methoxy-1,10-binaphthyl (2.99 g,
10.0 mmol) in dry toluene (50 mL). A few 4 Å molecular sieves
were added, and the solution was warmed up to 70 °C and kept
for two days at this temperature. The solution was filtered and
the solvent was removed under reduced pressure. The residue
was purified by recrystallization from an n-hexane solution to give
4H as a yellow solid. Yield: 3.40 g (66%). M.p.: 190–192 °C. 1H NMR
(C6D6): d 13.57 (s, 1H, OH), 8.38 (s, 1H, CH@N), 7.98 (d, J = 9.0 Hz,
1H, aryl), 7.88 (m, 3H, aryl), 7.69 (d, J = 8.4 Hz, 1H, aryl), 7.55 (d,
J = 2.4 Hz, 1H, aryl), 7.43 (d, J = 8.4 Hz, 1H, aryl), 7.31 (m, 3H, aryl),
7.23 (d, J = 7.2 Hz, 1H, aryl), 7.14 (m, 2H, aryl), 6.99 (d, J = 2.4 Hz,
1H, aryl), 3.44 (s, 3H, OCH3), 1.55 (s, 9H, CH3), 1.37 (s, 9H, CH3).
13C NMR (C6D6): d 162.4, 159.1, 155.1, 144.1, 139.9, 137.0, 134.5,
134.4, 133.1, 130.1, 129.8, 129.6, 129.3, 128.4, 127.6, 127.4,
127.1, 127.0, 126.9, 126.8, 125.9, 125.5, 123.8, 120.4, 118.9,
(KBr, cmꢁ1):
1596 (s), 1488 (s), 1426 (s), 1351 (s), 1266 (s), 1251 (s), 1082
m 3399 (s), 3056 (w), 2956 (m), 1682 (s), 1612 (s),
117.7, 113.7, 55.8, 35.2, 34.2, 31.6, 29.5. IR (KBr, cmꢁ1):
m 3432

Q. Wang et al. / Journal of Organometallic Chemistry 695 (2010) 1583–1591
1585
(m), 3054 (w), 2957 (s), 1623 (s), 1610 (s), 1578 (s), 1508 (s), 1465
(s), 1250 (s), 1171 (s), 1084 (s), 804 (s), 746 (s). Anal. Calc. for
C36H37NO2: C, 83.85; H, 7.23; N, 2.72. Found: C, 83.96; H, 7.28;
N, 2.73%.
1085 (s), 1020 (s), 799 (s). Anal. Calc. for C66H64N4O4Zr: C, 74.19;
H, 6.04; N, 5.24. Found: C, 74.05; H, 6.21; N, 5.23%.
2.9. Preparation of (2)2Ti(NMe2)2 (8)
This compound was prepared as red crystals from the reaction
of 2H (0.37 g, 1.0 mmol) with Ti(NMe2)4 (0.11 g, 0.5 mmol) in tol-
uene (20 mL) at room temperature and recrystallization from a tol-
uene solution by a similar procedure as in the synthesis of 6. Yield:
0.32 g (72%). M.p.: 196–198 °C (dec.). 1H NMR (C6D6): d 7.54 (d,
J = 5.5 Hz, 2H, aryl), 7.43 (s, 2H, aryl), 7.11 (s, 2H, aryl), 7.01 (d,
J = 7.6 Hz, 2H, aryl), 6.93 (d, J = 7.2 Hz, 2H, aryl), 6.53 (m, 2H, aryl),
6.49 (m, 2H, aryl), 6.46 (m, 2H, aryl), 3.62 (s, 12H, NMe2), 3.09 (s,
6H, OCH3), 2.16 (s, 6H, CH3), 2.08 (s, 12H, CH3), 1.94 (s, 12H,
CH3). 13C NMR (C6D6): d 181.7, 157.8, 144.2, 137.4, 133.3, 131.8,
129.0, 128.3, 128.2, 127.7, 127.6, 127.2, 126.4, 126.2, 124.6,
2.6. Preparation of (R)-2-(3-tert-butyl-2-hydroxyphenyl-
methyleneamino)-20-methoxy-6,60-dimethyl-1,10-biphenyl (5H)
This compound was prepared as a yellow solid from the reac-
tion of 3-tert-butyl-2-hydroxybenzaldehyde (1.78 g, 10.0 mmol)
with (R)-2-amino-20-methoxy-6,60-dimethyl-1,10-biphenyl (2.27 g,
10.0 mmol) in the presence of 4 Å molecular sieves in dry toluene
(50 mL) at 70 °C and purification by recrystallization from an n-
hexane solution using a similar procedure as in the synthesis of
4H. Yield: 3.14 g (81%). M.p.: 118–120 °C. 1H NMR (C6D6): d
13.82 (s, 1H, OH), 8.33 (s, 1H, CH@N), 7.32 (m, 1H, aryl), 7.22 (m,
1H, aryl), 7.18 (d, J = 7.6 Hz, 1H, aryl), 7.12 (m, 1H, aryl), 7.01 (d,
J = 7.6 Hz, 1H, aryl), 6.96 (d, J = 7.6 Hz, 1H, aryl), 6.90 (d,
J = 7.6 Hz, 1H, aryl), 6.79 (t, J = 7.6 Hz, 1H, aryl), 6.70 (d, J = 8.2 Hz,
1H, aryl), 3.34 (s, 3H, OCH3), 2.17 (s, 3H, CH3), 2.08 (s, 3H, CH3),
1.59 (s, 9H, CH3). 13C NMR (C6D6): d 162.1, 161.3, 157.0, 147.1,
138.3, 137.7, 137.5, 133.7, 130.6, 130.2, 129.3, 128.6, 128.5,
127.4, 122.9, 119.6, 118.1, 115.6, 108.6, 55.1, 35.1, 29.5, 20.0,
122.1, 107.4, 54.4, 47.9, 20.8, 20.7, 20.6, 20.3. IR (KBr, cmꢁ1):
m
2961 (m), 2921 (m), 1653 (s), 1609 (s), 1575 (s), 1464 (s), 1260
(s), 1081 (s), 1020 (s), 944 (s), 796 (s). Anal. Calc. for C54H64N4O4Ti:
C, 73.62; H, 7.32; N, 6.36. Found: C, 73.58; H, 7.44; N, 6.33%.
2.10. Preparation of (2)2Zr(NMe2)2 (9)
19.8. IR (KBr, cmꢁ1):
m 3434 (m), 3000 (m), 2955 (s), 2918 (m),
This compound was prepared as yellow crystals from the reac-
tion of 2H (0.37 g, 1.0 mmol) with Zr(NMe2)4 (0.14 g, 0.5 mmol) in
toluene (20 mL) at room temperature and recrystallization from a
toluene solution by a similar procedure as in the synthesis of 6.
Yield: 0.32 g (70%). M.p.: 202–204 °C (dec.). 1H NMR (C6D6): d
7.51 (d, J = 7.8 Hz, 2H, aryl), 7.13 (m, 4H, aryl), 7.04 (m, 2H, aryl),
6.93 (d, J = 6.7 Hz, 2H, aryl), 6.48 (m, 2H, aryl), 6.42 (m, 2H, aryl),
6.36 (m, 2H, aryl), 3.17 (s, 12H, NMe2), 3.06 (s, 6H, OCH3), 2.06
(s, 18H, CH3), 1.83 (s, 12H, CH3). 13C NMR (C6D6): d 182.4, 157.6,
143.1, 137.7, 137.6, 133.3, 132.2, 129.1, 128.3, 128.2, 127.7,
127.6, 126.5, 126.4, 125.2, 122.3, 107.5, 54.6, 42.3, 22.8, 21.2,
2827 (m), 1625 (s), 1610 (s), 1569 (s), 1467 (s), 1429 (s), 1255
(s), 1201 (s), 1114 (s), 1086 (s), 754 (s). Anal. Calc. for C26H29NO2:
C, 80.59; H, 7.54; N, 3.61. Found: C, 80.66; H, 7.48; N, 3.63%.
2.7. Preparation of (1)2Ti(NMe2)2 (6)
A toluene solution (10 mL) of 1H (0.45 g, 1.0 mmol) was slowly
added into
a toluene solution (10 mL) of Ti(NMe2)4 (0.11 g,
0.5 mmol) with stirring at room temperature. The solution was
stirred at room temperature for one day. The solution was filtered
and the solvent was removed under reduced pressure. The result-
ing red solid was recrystallized from a toluene solution to give 6 as
red crystals. Yield: 0.38 g (75%). M.p.: 246–248 °C (dec.). 1H NMR
(C6D6): d 7.94 (d, J = 8.8 Hz, 2H, aryl), 7.86 (m, 4H, aryl), 7.76 (m,
4H, aryl), 7.10 (m, 8H, aryl), 6.91 (t, J = 7.5 Hz, 2H, aryl), 6.67 (s,
4H, aryl), 6.34 (s, 2H, aryl), 5.99 (s, 2H, aryl), 3.60 (s, 12H, NMe2),
3.28 (s, 6H, OCH3), 2.11 (s, 6H, CH3), 1.98 (s, 6H, CH3), 1.67 (s, 6H,
CH3). 13C NMR (C6D6): d 180.6, 155.2, 142.8, 137.4, 136.6, 135.4,
134.1, 132.9, 131.7, 129.7, 129.1, 128.9, 128.2, 127.4, 127.2,
127.0, 126.3, 126.0, 125.9, 125.8, 125.4, 124.4, 122.2, 119.5,
20.6, 20.2. IR (KBr, cmꢁ1):
m 2921 (m), 1676 (s), 1609 (s), 1577
(s), 1508 (s), 1465 (s), 1390 (s), 1259 (s), 1079 (s), 1021 (s), 947
(s), 773 (s). Anal. Calc. for C54H64N4O4Zr: C, 70.17; H, 6.98; N,
6.06. Found: C, 70.05; H, 6.81; N, 6.13%.
2.11. Preparation of (3)2Ti(NMe2)2 (10)
This compound was prepared as red microcrystals from the
reaction of 3H (0.45 g, 1.0 mmol) with Ti(NMe2)4 (0.11 g,
0.5 mmol) in toluene (20 mL) at room temperature and recrystalli-
zation from an n-hexane solution by a similar procedure as in the
synthesis of 6. Yield: 0.42 g (80%). M.p.: 130–132 °C (dec.). 1H NMR
(C6D6): d 7.51 (d, J = 8.2 Hz, 2H, aryl), 7.15 (d, J = 7.6 Hz, 2H, aryl),
7.06 (m, 4H, aryl), 6.5 (m, 2H, aryl), 6.40 (m, 2H, aryl), 3.58 (s,
12H, NMe2), 3.03 (s, 6H, OCH3), 2.85 (m, 4H, CH2), 2.60 (m, 4H,
CH2), 2.27 (m, 4H, CH2), 2.20 (s, 6H, CH3), 2.02 (s, 6H, CH3), 2.01
(s, 6H, CH3), 1.85 (m, 4H, CH2), 1.60 (m, 16H, CH2). 13C NMR
(C6D6): d 183.0, 155.7, 142.0, 137.6, 135.7, 135.5, 133.6, 132.9,
131.4, 129.0, 128.9, 128.6, 128.3, 126.5, 125.4, 124.4, 107.6, 54.3,
48.3, 29.9, 29.7, 27.5, 25.6, 23.6, 22.9, 21.1, 20.9, 20.8, 20.5. IR
112.6, 55.2, 47.3, 20.9, 20.7, 20.2. IR (KBr, cmꢁ1):
m 2963 (m),
1652 (s), 1592 (s), 1447 (s), 1260 (vs), 1083 (vs), 1020 (vs), 799
(s). Anal. Calc. for C66H64N4O4Ti: C, 77.33; H, 6.29; N, 5.47. Found:
C, 77.18; H, 6.48; N, 5.45%.
2.8. Preparation of (1)2Zr(NMe2)2 (7)
This compound was prepared as yellow microcrystals from the
reaction of 1H (0.45 g, 1.0 mmol) with Zr(NMe2)4 (0.14 g,
0.5 mmol) in toluene (20 mL) at room temperature and recrystalli-
zation from a toluene solution by a similar procedure as in the syn-
thesis of 6. Yield: 0.37 g (70%). M.p.: 196–198 °C (dec.). 1H NMR
(C6D6): d 7.96 (m, 2H, aryl), 7.85 (m, 4H, aryl), 7.75 (t, J = 7.2 Hz,
4H, aryl), 7.14 (m, 8H, aryl), 6.90 (t, J = 7.2 Hz, 2H, aryl), 6.66 (s,
4H, aryl), 6.34 (s, 2H, aryl), 5.97 (s, 2H, aryl), 3.35 (s, 6H, OCH3),
3.28 (s, 12H, NMe2), 2.17 (s, 6H, CH3), 1.98 (s, 6H, CH3), 1.51 (s,
6H, CH3). 13C NMR (C6D6): d 181.9, 155.0, 141.9, 137.6, 136.4,
135.3, 134.1, 132.6, 131.7, 129.7, 129.1, 128.9, 128.3, 128.2,
127.4, 127.2, 127.0, 126.4, 126.2, 125.8, 125.4, 124.5, 122.3,
(KBr, cmꢁ1):
m 2922 (m), 1680 (s), 1591 (s), 1495 (s), 1446 (s),
1259 (s), 1085 (s), 1034 (s), 798 (s). Anal. Calc. for C66H80N4O4Ti:
C, 76.13; H, 7.74; N, 5.38. Found: C, 76.05; H, 7.62; N, 5.33%.
2.12. Preparation of (3)2Zr(NMe2)2 (11)
This compound was prepared as yellow microcrystals from the
reaction of 3H (0.45 g, 1.0 mmol) with Zr(NMe2)4 (0.14 g,
0.5 mmol) in toluene (20 mL) at room temperature and recrystalli-
zation from an n-hexane solution by a similar procedure as in the
synthesis of 6. Yield: 0.45 g (84%). M.p.: 142–144 °C (dec.). 1H NMR
(C6D6): d 7.61 (d, J = 8.2 Hz, 2H, aryl), 7.24 (d, J = 7.6 Hz, 2H, aryl),
119.4, 112.9, 55.5, 42.0, 21.0, 20.8, 20.7. IR (KBr, cmꢁ1):
(m), 1675 (s), 1609 (s), 1594 (s), 1502 (s), 1425 (s), 1260 (s),
m 2962

1586
Q. Wang et al. / Journal of Organometallic Chemistry 695 (2010) 1583–1591
7.14 (m, 4H, aryl), 6.79 (m, 2H, aryl), 6.56 (m, 2H, aryl), 3.34 (s,
12H, NMe2), 2.93 (s, 6H, OCH3), 2.89–2.69 (m, 12H, CH2), 2.30 (m,
4H, CH2), 2.26 (s, 6H, CH3), 2.24 (s, 6H, CH3), 2.10 (s, 6H, CH3),
1.89–1.64 (m, 16H, CH2). 13C NMR (C6D6): d 180.3, 155.6, 140.8,
137.6, 137.3, 137.2, 135.8, 133.5, 133.4, 133.3, 131.7, 129.1,
128.8, 126.2, 125.4, 124.8, 107.7, 54.4, 43.0, 29.9, 27.5, 27.0, 23.8,
6H, OCH3), 2.42 (s, 6H, NMe2), 2.18 (s, 6H, CH3), 1.86 (s, 6H, CH3),
1.39 (s, 18H, C(CH3)3). 13C NMR (C6D6): d 162.3, 157.6, 151.9,
140.4, 139.4, 138.4, 134.2, 129.9, 129.0, 127.5, 127.3, 127.0,
126.3, 124.1, 123.8, 123.5, 117.4, 107.7, 87.9, 54.7, 45.2, 44.3,
35.2, 30.0, 21.1, 20.7. IR (KBr, cmꢁ1):
m 2948 (m), 2772 (w), 1623
(w), 1594 (s), 1546 (s), 1465 (s), 1424 (s), 1319 (s), 1250 (s),
1189 (s), 1080 (s), 1027 (s), 938 (s), 868 (s), 756 (s). Anal. Calc.
for C56H68N4O4Zr: C, 70.62; H, 7.20; N, 5.88. Found: C, 70.45; H,
7.21; N, 5.83%.
23.5, 23.2, 22.9, 22.8, 20.8, 20.7. IR (KBr, cmꢁ1):
m 2923 (m), 1675
(s), 1583 (s), 1496 (s), 1477 (s), 1448 (s), 1258 (s), 1084 (s), 1002
(s), 799 (s). Anal. Calc. for C66H80N4O4Zr: C, 73.09; H, 7.43; N,
5.17. Found: C, 73.05; H, 7.21; N, 5.23%.
2.15. General procedure for asymmetric hydroamination/cyclization
2.13. Preparation of {(R)-2-[3,5-(Me3C)2-2-O-C6H2CH(NMe2)N]-20-
(MeO)-1,10-C20H12}2Ti (12)
In a nitrogen-filled glove box, precatalyst (0.016 mmol), C6D6
(0.7 mL), and aminoalkene (0.16 mmol) were introduced sequen-
tially into a Young NMR tube equipped with Teflon screw cap.
The reaction mixture was subsequently kept at 120 °C to achieve
hydroamination, and the reaction was monitored periodically by
1H NMR spectroscopy. The cyclic amine was vacuum transferred
from the Young NMR tube into a 25 mL Schlenk flask which con-
tained 31 mg (0.16 mmol) of (S)-(+)-O-acetylmandelic acid. The
resulting mixture was stirred at room temperature for 2 h and
the volatiles were removed in vacuo. The resulting diastereomeric
salt was then dissolved in CDCl3 and the enantiomeric excesses
were determined by 1H NMR spectroscopy [38].
This compound was prepared as red crystals from the reaction
of 4H (0.52 g, 1.0 mmol) with Ti(NMe2)4 (0.11 g, 0.5 mmol) in tol-
uene (20 mL) at room temperature and recrystallization from a tol-
uene solution by a similar procedure as in the synthesis of 6. Yield:
0.35 g (60%). M.p.: 178–180 °C (dec.). 1H NMR (C6D6): d 7.95–7.85
(m, 4H, aryl), 7.78–7.66 (m, 4H, aryl), 7.57 (m, 2H, aryl), 7.49 (m,
4H, aryl), 7.46 (m, 4H, aryl), 7.05 (m, 4H, aryl), 6.71 (m, 4H, aryl),
5.77 (s, 2H, aryl), 4.77 (s, 2H, CH), 3.67 (s, 6H, OCH3), 2.22 (s,
12H, NMe2), 1.81 (s, 18H, C(CH3)3), 1.59 (s, 18H, C(CH3)3). 13C
NMR (C6D6): d 160.8, 159.1, 155.6, 155.5, 150.9, 150.4, 141.2,
140.0, 134.6, 134.3, 133.7, 133.6, 132.0, 130.0, 126.6, 125.6,
124.7, 124.3, 120.3, 87.6, 56.6, 43.7, 35.2, 34.3, 31.9, 29.8. IR (KBr,
cmꢁ1):
m 2962 (m), 2915 (m), 2850 (m), 1578 (m), 1349 (s), 1260
Table 2
(s), 1197 (s), 1082 (s), 1054 (s), 1018 (s), 800 (s). Anal. Calc. for
C76H84N4O4Ti: C, 78.33; H, 7.27; N, 4.81. Found: C, 78.18; H,
7.48; N, 4.75%.
Selected bond distances (Å) and bond angles (°) for compounds 6, 8, 9, 12 and 13.
Compound
6 (Ti)
8 (Ti)
9 (Zr)
12 (Ti)
13 (Zr)
M–N (av.)
M–N(1)
M–N(2)
M–N(3)
M–N(4)
2.027(6)
2.155(4)
2.141(4)
1.904(6)
1.907(6)
2.136(5)
2.525(6)
2.021(1)
2.125(1)
2.143(1)
1.907(1)
1.909(1)
2.131(1)
2.536(2)
2.300(2)
2.278(2)
2.283(2)
2.052(2)
2.044(2)
2.224(2)
2.670(2)
2.122(2)
1.954(2)
2.247(2)
2.006(2)
2.282(2)
1.901(2)
2.260(1)
2.373(1)
2.139(1)
2.482(1)
2.048(1)
2.047(1)
2.14. Preparation of {(R)-2-[3-Me3C-2-O-C6H3CH(NMe2)N]-20-(MeO)-
1,10-(6-Me-C6H3)2}(5)ZrNMe2 (13)
M–O (av.)
M–C (av.)
This compound was prepared as yellow crystals from the reac-
tion of 5H (0.39 g, 1.0 mmol) with Zr(NMe2)4 (0.14 g, 0.5 mmol) in
toluene (20 mL) at room temperature and recrystallization from a
toluene solution by a similar procedure as in the synthesis of 6.
Yield: 0.33 g (70%). M.p.: 212–214 °C (dec.). 1H NMR (C6D6): d
8.47 (s, 1H, CH@N), 7.45–7.34 (m, 4H, aryl), 6.99–6.77 (m, 4H, aryl),
6.72–6.56 (m, 6H, aryl), 6.48 (t, J = 7.6 Hz, 2H, aryl), 6.43 (d,
J = 8.2 Hz, 2H, aryl), 4.92 (s, 1H, CH), 3.26 (s, 6H, ZrNMe2), 3.00 (s,
Sum angles of N
N(3):
359.5(6)
N(4):
N(3):
359.3(1)
N(4):
N(3):
360.0(2)
N(4):
N(1):
350.7(2)
N(3):
N(2):
357.8(1)
N(4):
359.9(6)
360.0(1)
359.5(2)
354.6(2)
359.2(2)
Torsion (aryl–aryl)
69.1(6)
71.9(6)
73.3(1)
69.3(1)
69.7(2)
71.3(2)
82.8(2)
89.0(2)
83.5(1)
84.5(1)
Table 1
Crystal data and experimental parameters for compounds 1H, 6, 8, 9, 12 and 13.
Compound
1H
6
8
9
12
13
Formula
Formula weight
Crystal system
Space group
a (Å)
C31H27NO2
445.54
C66H64N4O4Ti
1025.11
Monoclinic
P1211
15.071(3)
9.199(2)
19.282(4)
94.83(2)
2663.7(10)
2
C54H64N4O4Ti
880.99
C54H64N4O4Zr
924.31
C76H84N4O4Ti
C56H68N4O4Zr
952.36
1165.37
Orthorhombic
P212121
16.181(5)
36.786(1)
12.400(1)
90
7380.3(4)
4
1.049
Orthorhombic
P212121
8.023(2)
17.250(3)
20.727(4)
90
2868.5(10)
4
1.032
Orthorhombic
P212121
9.344(2)
19.234(4)
26.737(5)
90
4805.5(17)
4
1.218
Orthorhombic
P212121
9.224(1)
19.226(2)
27.295(3)
90
4840.3(9)
4
1.268
Orthorhombic
P212121
15.270(2)
15.260(1)
21.788(2)
90
5077.2(9)
4
1.246
b (Å)
c (Å)
b (°)
V (Å3)
Z
Dcalc. (g cmꢁ3
Size (mm)
F(0 0 0)
)
1.278
0.26 ꢀ 0.24 ꢀ 0.22
0.22 ꢀ 0.20 ꢀ 0.12
0.28 ꢀ 0.26 ꢀ 0.22
0.16 ꢀ 0.14 ꢀ 0.10
0.26 ꢀ 0.22 ꢀ 0.18
0.26 ꢀ 0.20 ꢀ 0.18
944
1084
1880
1952
2488
2016
2h Range (°)
3.94–55.70
29 063
3839(0.0481)
3443
4.60–135.98
17 328
8386(0.0777)
5869
3.04–55.76
27 672
11 344(0.0275)
10 035
3.66–55.80
36 281
11 436(0.0528)
10 489
2.74–55.76
50 397
17 339(0.0437)
15 207
20.01–55.78
58 779
11 478(0.0417)
11 324
No. of reflections collected
No. of unique reflections (Rint
No. of observed reflections
)
Absorbed corrections (Tmax, Tmin
R
)
0.99, 0.98
0.049
0.81, 0.69
0.079
0.95, 0.94
0.033
0.97, 0.96
0.038
0.97, 0.96
0.056
0.95, 0.93
0.027
Rw
0.138
0.142
1.19
0.175
0.228
1.09
0.078
0.081
1.03
0.083
0.086
1.04
0.148
0.154
1.03
0.061
0.061
1.06
wR2 (all data)
Goodness-of-fit (GOF)

Q. Wang et al. / Journal of Organometallic Chemistry 695 (2010) 1583–1591
1587
2.16. X-ray crystallography
rical on the NMR timescale, which are consistent with their C1-
symmetric structures. The infrared spectra of these compounds ex-
hibit peaks corresponding to aromatic stretches in addition to N–H
stretches at about 3390 cmꢁ1, and strong C@O stretches at about
1680 cmꢁ1 for 1H, 2H and 3H, and O–H stretches at about
3430 cmꢁ1, and strong C@N stretches at about 1620 cmꢁ1 for 4H
and 5H. The solid-state structure of compound 1H has been further
confirmed by X-ray diffraction analysis.
The single-crystal X-ray diffraction analysis shows that the
binaphthyl groups of the compound 1H arrange in a staggered
geometry (Fig. 1). The twisting between the naphthyl rings of tor-
sion angle is 77.9(3)°, which is smaller than that found in 2-amino-
20-hydroxy-1,10-binaphthyl (87.9(1)°) [42].
Single-crystal X-ray diffraction measurements were carried out
on a Rigaku Saturn CCD diffractometer at 113(2) K using graphite
monochromated Mo Ka radiation (k = 0.71 075 Å) or Cu Ka radia-
tion (k = 1.54 187 Å). An empirical absorption correction was ap-
plied using the SADABS program [40]. All structures were solved by
direct methods and refined by full-matrix least squares on F2 using
the SHELXL-97 program package [41]. All the hydrogen atoms were
geometrically fixed using the riding model. The crystal data and
experimental data for 1H, 6, 8, 9, 12 and 13 are summarized in Ta-
ble 1. Selected bond lengths and angles are listed in Table 2.
3. Results and discussion
3.2. Synthesis and characterization of complexes
3.1. Synthesis and characterization of ligands
Group 4 metal amide complexes can be efficiently prepared via
amine elimination reaction between M(NMe2)4 and protic re-
agents. For example, treatment of M(NMe2)4 with 2 equiv. of mes-
The C1-symmetric mesitoylamide ligands, (R)-2-(mesitoylami-
no)-20-methoxy-1,10-binaphthyl (1H), (R)-2-(mesitoylamino)-20-
methoxy-6,60-dimethyl-1,10-biphenyl (2H) and (S)-5,50,6,60,7,70,8,
80-octahydro-2-(mesitoylamino)-20-methoxy-1,10-binaphthyl (3H),
are readily prepared in good yields by treatment of mesitoyl chlo-
ride with 1 equiv. of (R)-2-amino-20-methoxy-1,10-binaphthyl, (R)-
2-amino-20-methoxy-6,60-dimethyl-1,10-biphenyl or (S)-5,50,6,60,
7,70,8,80-octahydro-2-amino-20-methoxy-1,10-binaphthyl, respec-
tively, in the presence of an excess of pyridine in toluene at reflux,
after purification by flash column chromatography (Schemes 1–3).
The C1-symmetric Schiff base ligands, (R)-2-(3,5-di-tert-butyl-2-
hydroxyphenylmethyleneamino)-20-methoxy-1,10-binaphthyl (4H),
(R)-2-(3-tert-butyl-2-hydroxyphenylmethyleneamino)-20-methoxy-
6,60-dimethyl-1,10-biphenyl (5H), are also readily prepared in good
yields by condensation of the starting materials (R)-2-amino-20-
methoxy-1,10-binaphthyl, (R)-2-amino-20-methoxy-6,60-dimethyl-
1,10-biphenyl with 1 equiv. of 3,5-di-tert-butyl-2-hydroxybenzalde-
hyde or 3-tert-butyl-2-hydroxybenzaldehyde, respectively, in the
presence of molecular sieves in toluene at 70 °C, followed by recrys-
tallization from an n-hexane solution (Schemes 1 and 2).
itoylamides,
(R)-2-(mesitoylamino)-20-methoxy-1,10-binaphthyl
(1H), (R)-2-(mesitoylamino)-20-methoxy-6,60-dimethyl-1,10-biphe-
nyl (2H) or (S)-5,50,6,60,7,70,8,80-octahydro-2-(mesitoylamino)-20-
methoxy-1,10-binaphthyl (3H) gives, after recrystallization from a
toluene or n-hexane solution, the bis-ligated chiral titanium
amides (1)2Ti(NMe2)2 (6), (2)2Ti(NMe2)2 (8), (3)2Ti(NMe2)2 (10),
and zirconium amides (1)2Zr(NMe2)2 (7), (2)2Zr(NMe2)2 (9),
(3)2Zr(NMe2)2 (11), respectively, in good yields (Schemes 1–3).
Our previous work has shown that interaction between the
Schiff base ligand (R)-2-(pyrrol-2-ylmethyleneamino)-20-methoxy-
1,10-binaphthyl and M(NMe2)4 (M = Ti, Zr) gives the bis-ligated
amides
[(R)-1,10-C20H12-20-(MeO)-2-(NCH-2-C4H3N)]2M(NMe2)2
[37]. However, under similar reaction conditions, treatment of
Ti(NMe2)4 with 2 equiv. of the Schiff base ligand (R)-2-(3,5-
di-tert-butyl-2-hydroxyphenylmethyleneamino)-20-methoxy-1,10-
binaphthyl (4H) does not lead to the expected bis-ligated amide
complex (4)2Ti(NMe2)2, instead, a chiral bis-ligated titanium com-
plex
{(R)-2-[3,5-(Me3C)2-2-O-C6H2CH(NMe2)N]-20-(MeO)-1,10-
All the new ligands are air-stable, and soluble in CH2Cl2, CHCl3,
toluene, benzene, and n-hexane. They have been fully character-
ized by various spectroscopic techniques and elemental analyses.
Their 1H and 13C NMR spectra indicate that they are non-symmet-
C20H12}2Ti (12) has been isolated in 60% yield (Scheme 1),
where {(R)-2-[3,5-(Me3C)2-2-O-C6H2CH(NMe2)N]-20-(MeO)-1,10-
2ꢁ
C20H12
}
is a tridentate ligand resulting from the insertion of
the anion Me2Nꢁ at the imine unit of 4H. The 1,2-migratory inser-
tBu
OH
O
tBu
HO
N
H
tBu
COCl
NH2
tBu
O
N
H
OMe
OMe
OMe
C7H8/m.s.
pyridine
4H
Ti(NMe2)4
1
H
C7H8
M(NMe2)4
tBu
tBu
C7H8
OMe
tBu
tBu
MeO
O
Me
Me
N
O
N
OMe
Me
OMe
N
OO
N
Me
N
N
Ti
M
Me2N
NMe2
12
M = Ti (6), Zr (7)
Scheme 1.

1588
Q. Wang et al. / Journal of Organometallic Chemistry 695 (2010) 1583–1591
tBu
OH
O
tBu
HO
N
COCl
H
O
N
H
OMe
NH2
pyridine
OMe
OMe
C7H8/m.s.
2H
5H
Zr(NMe2)4
M(NMe2)4
C7H8
Me
C7H8
tBu
tBu
MeO
OMe
O
O
N
OMe
Me
OMe
O
O
N
N
N
N
Zr
M
NMe2
13
Me2N
NMe2
8
9
M = Ti ( ), Zr ( )
Scheme 2.
NH2
OMe
pyridine
COCl
O
N
H
OMe
3
H
M(NMe2)4
C7H8
MeO
OMe
OO
N
N
Fig. 1. Molecular structure of 1H (thermal ellipsoids drawn at the 35% probability
level).
M
Me2N
NMe2
bis-ligated complexes 6–11. Unlike the titanium amides 6, 8 and
10, the 1H NMR spectrum of 12 does not exhibit a singlet resonance
at about 3.60 ppm attributable to the TiNMe2 groups, while a sin-
glet resonance appears at about 2.22 ppm attributable to the
RNMe2 groups, supporting the formation of the bis-ligated com-
plex 12. The 1H NMR spectrum of 13 exhibits two singlet reso-
nances with the ratio of 1:1 at about 3.26 ppm and 2.42 ppm
attributable to the ZrNMe2 and RNMe2 groups, respectively, sup-
porting the formation of the mixed-bis-ligated complex 13. These
results are consistent with their 13C NMR spectra. The solid-state
structures of the complexes 6, 8, 9, 12 and 13 have further been
confirmed by X-ray diffraction analyses.
M = Ti (10), Zr (11)
Scheme 3.
tion of the anion Me2Nꢁ at the imine unit has been also observed in
the reaction between the Schiff base ligand (R)-2-(3-tert-butyl-
2-hydroxyphenylmethyleneamino)-20-methoxy-6,60-dimethyl-1,
10-biphenyl (5H) and Zr(NMe2)4, results in the isolation of the
complex {(R)-2-[3-Me3C-2-O-C6H3CH(NMe2)N]-20-(MeO)-1,10-(6-
Me-C6H3)2}(5)ZrNMe2 (13) in 70% yield (Scheme 2).
These complexes are stable in dry nitrogen atmosphere, while
they are very sensitive to moisture. They are soluble in organic sol-
vents such as THF, DME, pyridine, toluene, and benzene, and only
slightly soluble in n-hexane. They have been characterized by var-
ious spectroscopic techniques, and elemental analyses. The 1H
NMR spectra of 6–11 support that the ratio of amino group NMe2
and ligand anion 1, 2 or 3 is 1:1, supporting the formation of the
The single-crystal X-ray diffraction analyses confirm that 8 and
9
are isostructural. In each molecule of (1)2Ti(NMe2)2 or
(2)2M(NMe2), the substituted MeO group is far away from the me-
tal center, and the M4+ is
-bound to two nitrogen atoms and two
r
oxygen atoms from the two ligands 1, or 2 and two nitrogen atoms
from amino groups NMe2 in a distorted-octahedron geometry
(Figs. 2 and 3) with the average distance of Ti–N (2.027(6) Å) for

Q. Wang et al. / Journal of Organometallic Chemistry 695 (2010) 1583–1591
1589
Fig. 2. Molecular structure of 6 (thermal ellipsoids drawn at the 35% probability
level).
Fig. 4a. Molecular structure of 12 (thermal ellipsoids drawn at the 35% probability
level).
Fig. 3. Molecular structure of 8 (M = Ti) and 9 (M = Zr) (thermal ellipsoids drawn at
the 35% probability level).
Fig. 4b. Core structure of 12 (thermal ellipsoids drawn at the 35% probability level).
The solid-state structure of 13 shows that the Zr4+ is
two nitrogen atoms and one oxygen atom from the anion {(R)-2-[3-
Me3C-2-O-C6H3CH(NMe2)N]-20-(MeO)-1,10-(6-Me-C6H3)2}2ꢁ
and
r-bound to
6, Ti–N (2.021(1) Å) for 8, Zr–N (2.300(2) Å) for 9, respectively, and
the average distance of Ti–O (2.136(5) Å) for 6, Ti–O (2.131(1) Å)
for 8, Zr–O (2.224(2) Å) for 9, respectively. The short M–N(3) and
M–N(4) bond distances (1.904(6) and 1.907(6) Å for 6, 1.907(1)
and 1.909(1) Å for 8, 2.052(2) and 2.044(2) Å for 9) and the planar
geometry around the N(3) and N(4) nitrogen atoms indicate that
the nitrogen atoms with sp2 hybridization are engaged in
,
two nitrogen atoms and one oxygen atom from the ligand 5 in a dis-
torted-octahedron geometry (Fig. 5) with the average distance of
Zr–N (2.260(1) Å) and the average distance of Zr–O (2.047(1) Å).
The short Zr–N(2) and Zr–N(4) bond distances (2.139(1) and
2.048(1) Å) and the planar geometry around the N(2) and N(4)
nitrogen atoms indicate that both nitrogen atoms with sp2 hybrid-
ization are engaged in N(p ) ? Zr(d ) interactions. The twisting be-
N(p ) ? M(d ) interactions. These structural data are very close
p
p
to those found in the literatures [43–49]. The aryl rings are twisted
by 69.1(6)° and 71.9(6)° for 6, 73.3(1)° and 69.3(1)° for 8, 69.7(2)°
and 71.3(2)° for 9, which are comparable to those found in 1H
(77.9(3)°), [(R)-1,10-C20H12-20-(MeO)-2-(NCH-2-C4H3N)]2Ti(NMe2)2
(89.7(9)° and 87.2(9)°) [37], [(R)-(6-Me-C6H3)2-20-(MeO)-2-(NCH-
2-C4H3N)]2Ti(NMe2)2 (78.2(4)° and 86.4(4)°) [37] and [(R)-(6-Me-
C6H3)2-20-(MeO)-2-(NCH-2-C4H3N)]2Zr(NMe2)2 (84.9(4)° and 89.7
(4)°) [37].
p
p
tween the binaphthyl rings of torsion angles are 83.5(1)° and
84.5(1)°, which are larger than those found in 8 (73.3(1)° and
69.3(1)°) and 9 (69.7(2)° and 71.3(2)°).
3.3. Asymmetric hydroamination/cyclization
The solid-state structure of 12 shows that the Ti4+ is
r-bound
To evaluate the catalytic ability of the complexes 6–13, the
asymmetric hydroamination/cyclization of unactivated terminal
aminoalkenes has been tested under the conditions given in Table
3. The results of the hydroamination/cyclization of 2,2-dimethyl-
pent-4-enylamine clearly show that the zirconium amidates are
active catalysts for this transformation (Table 3, entries 2, 4 and
6), and the complex 7 shows more effective catalyst for this
asymmetric transformation with a good enantioselectivity (up
to 61%; Table 3, entry 2). When more bulky ligand 3 is used,
the ee value decreases significantly (Table 3, entry 6). However,
when the Ti4+ ion is used (Table 3, entry 1), the ee value increases
slightly (up to 68%) but the rate decreases. Complex 13 can medi-
to four nitrogen atoms and two oxygen atoms from two ligand
anions {(R)-2-[3,5-(Me3C)2-2-O-C6H2CH(NMe2)N]-20-(MeO)-1,10-
2ꢁ
C20H12
}
in a distorted-octahedron geometry (Fig. 4a and b) with
the average distance of Ti–N (2.122(2) Å) and the average dis-
tance of Ti–O (1.901(2) Å). The short Ti–N(1) and Ti–N(3) bond
distances (1.954(2) and 2.006(2) Å) and the planar geometry
around the N(1) and N(3) nitrogen atoms indicate that both nitro-
gen atoms with sp2 hybridization are engaged in N(p ) ? Ti(d )
p
p
interactions. The twisting between the binaphthyl rings of torsion
angles are 82.8(2)° and 89.0(2)°, which are larger than those
found in 1H (77.9(3)°) and 6 (69.1(6)° and 71.9(6)°).

1590
Q. Wang et al. / Journal of Organometallic Chemistry 695 (2010) 1583–1591
man and others [19,20,22]. Substrate 15a reacts fast but the ee
values are moderate (Table 3, entries 9–14). The formation of
six-membered ring can also be performed with our amidate cat-
alysts (Table 3, entries 15–20), and a moderate enantioselectivity
(up to 25%), mediated by the catalyst 6, has been obtained (Table
3, entry 15). Our results show that the bis-ligated amidate group
4 complexes are more effective chiral catalysts for the asymmet-
ric hydroamination/cyclization than those ligated by Schiff base
ligands [37], but less than those coordinated by C2-symmetric
bis-amidate ligands [20,21,30]. Although the enantiomeric ex-
cesses obtained remain moderate to good, it should be noted that
there are only few group 4 catalysts for these reactions that give a
significant ee (>90%) at all [20,21,30].
4. Conclusions
In conclusion, a new series of chiral bis-ligated group 4 metal
complexes have been readily prepared from the reactions between
M(NMe2)4 (M = Ti, Zr) and chiral C1-symmetric ligands, 1H, 2H, 3H,
4H and 5H, and the bis-ligated amidate complexes have been
shown more effective chiral catalysts for asymmetric hydroamina-
tion/cyclization than those ligated by Schiff base ligands [37].
When changes are made from pyrrol-2-ylmethyleneamino group
to mesitoylamino group, and to phenylmethyleneamino group,
the ligands (R)-2-(pyrrol-2-ylmethyleneamino)-20-methoxy-1,
10-binaphthyl [37], (R)-2-(mesitoylamino)-20-methoxy-1,10-binaph-
thyl (1H) and (R)-2-(3,5-di-tert-butyl-2-hydroxyphenylmethyle-
neamino)-20-methoxy-1,10-binaphthyl (4H) exhibit different
reactivity patterns. For example, reaction of the Schiff base ligand
(R)-2-(pyrrol-2-ylmethyleneamino)-20-methoxy-1,10-binaphthyl or
amidate ligand 1H with Ti(NMe2)4 gives the bis-ligated titanium
Fig. 5. Molecular structure of 13 (thermal ellipsoids drawn at the 35% probability
level).
ate the cyclization of 2,2-dimethylpent-4-enylamine (Table 3, en-
try 8), but the conversion ceases after 1 or 2 days due to the
decomposition by the intermediacy of the metal alkyl species
via 1,2-migratory insertion at the imine unit [50]. Under similar
reaction conditions, no detectable hydroamination activity is ob-
served for titanium complex 12 even heated at 120 °C for one
week, and none of the complexes described above is effective cat-
alyst for the cyclization of 1-aminopent-4-ene into 2-methylpyr-
rolidine, presumably due to a lack of a Thorpe–Ingold effect
[51,52] from the unsubstituted aminoalkene, and none of the cat-
alysts is effective catalyst for the cyclization of aminoalkenes con-
taining secondary amine groups such as the substrate 1-(N-
methylamino)-2,2-dimethylpent-4-ene into the corresponding
heterocycles, which is in agreement with the amine elimination
followed by [2+2] cycloaddition mechanism postulated by Berg-
amides
[(R)-1,10-C20H12-20-(MeO)-2-(NCH-2-C4H3N)]2Ti(NMe2)2
[37] and (1)2Ti(NMe2)2 (6), respectively, while reaction of the Schiff
base ligand 4H with Ti(NMe2)4 affords a bis-ligated complex {(R)-
2-[3,5-(Me3C)2-2-O-C6H2CH(NMe2)N]-20-(MeO)-1,10-C20H12}2Ti (12)
in which the amide complex is decomposed by the dimethylamino
via 1,2-migratory insertion at the imine unit of 4H. The Schiff base
ligated titanium amide [(R)-1,10-C20H12-20-(MeO)-2-(NCH-2-
C4H3N)]2Ti(NMe2)2 shows no catalytic activity for the enantiose-
lective hydroamination/cyclization reaction [37], while the
Table 3
Enantioselective hydroamination/cyclization of aminoalkenes.a
Entry
Catalyst (M)
Substrate
NH2
Product
Time (h)
Conv. (%)b
ee (%)c
1
2
3
4
5
6
7
8
6 (Ti)
7 (Zr)
8 (Ti)
9 (Zr)
10 (Ti)
11 (Zr)
12 (Ti)
13 (Zr)
48
24
48
24
48
24
160
48
93
100
96
100
86
100
N.R.
24
68
61
51
43
46
38
N.A.
15
H
N
14a
14b
9
6 (Ti)
7 (Zr)
8 (Ti)
9 (Zr)
10 (Ti)
11 (Zr)
36
16
36
16
36
16
100
100
100
100
100
100
52
43
46
39
42
36
NH2
NH
10
11
12
13
14
15b
15a
15
16
17
18
19
20
6 (Ti)
7 (Zr)
8 (Ti)
9 (Zr)
10 (Ti)
11 (Zr)
48
24
48
24
48
24
98
25
20
24
21
23
19
NH2
NH
100
100
100
90
16a
16b
100
a
b
c
Conditions: C6D6 (0.70 mL), aminoalkene (0.16 mmol), catalyst (0.016 mmol), at 120 °C.
Determined by 1H NMR based on p-xylene as the internal standard. N.R., no reaction.
Determined by 1H NMR of its diastereomeric (S)-(+)-O-acetylmandelic acid salt [38]. N.A., not applicable.

Q. Wang et al. / Journal of Organometallic Chemistry 695 (2010) 1583–1591
[12] K.C. Hultzsch, Adv. Synth. Catal. 347 (2005) 367–391.
1591
titanium amidate (1)2Ti(NMe2)2 (6) does, and in some cases, the
corresponding heterocyclic products have been obtained with
good ee values (up to 68%) by this modified chiral 2-amino-20-hy-
droxy-1,10-binaphthyl ligand. Although the titanium amidates
show more enantioselective than zirconium amidates for the
hydroamination/cyclization reaction, they exhibit less effective
catalytic activity than zirconium amidates. How to fully optimize
both the rate and selectivity remains a question for the asymmetric
hydroamination. We are planning to synthesize similar tridentate
or bidentate chiral biaryl embedded in a C1-symmetric chiral scaf-
fold in order to obtain more effective and stereoselective chiral li-
gands (including 3,30-substituted NOBIN) and to utilize those novel
chiral ligands in this transformation and other catalytic asymmet-
ric reactions. Work along these lines is in progress.
[13] I. Aillaud, J. Collin, J. Hannedouche, E. Schulz, Dalton Trans. (2007) 5105–5118.
[14] G. Zi, Dalton Trans. (2009) 9101–9109.
[15] P.D. Knight, I. Munslow, P.N. O’Shaughnessy, P. Scott, Chem. Commun. (2004)
894–895.
[16] D.V. Gribkov, K.C. Hultzcsh, Angew. Chem., Int. Ed. 43 (2004) 5542–5546.
[17] F. Pohlki, I. Bytschkov, H. Siebeneicher, A. Hertling, W.A. König, S. Doye, Eur. J.
Org. Chem. (2004) 1967–1972.
[18] J.M. Hoover, J.R. Petersen, J.H. Pikul, A.R. Johnson, Organometallics 23 (2004)
4614–4620.
[19] D.A. Watson, M. Chiu, R.G. Bergman, Organometallics 25 (2006) 4731–4733.
[20] M.C. Wood, D.C. Leitch, C.S. Yeung, J.A. Kozak, L.L. Schafer, Angew. Chem., Int.
Ed. 46 (2007) 354–358.
[21] A.L. Gott, A.J. Clarke, G.J. Clarkson, P. Scott, Organometallics 26 (2007) 1729–
1737.
[22] A.L. Gott, A.J. Clarke, G.J. Clarkson, P. Scott, Chem. Commun. (2008) 1422–1424.
[23] A.L. Gott, G.J. Clarkson, R.J. Deeth, M.L. Hammond, C. Morton, P. Scott, Dalton
Trans. (2008) 2983–2990.
[24] L. Xiang, H. Song, G. Zi, Eur. J. Inorg. Chem. (2008) 1135–1140.
[25] G. Zi, X. Liu, L. Xiang, H. Song, Organometallics 28 (2009) 1127–1137.
[26] A.J. Hickman, L.D. Hughs, C.M. Jones, H. Li, J.E. Redford, S.J. Sobelman, J.A.
Kouzelos, A.R. Johnson, Tetrahedron: Asymmetry 20 (2009) 1279–1285.
[27] A.L. Reznichenko, K.C. Hultzsch, Organometallics 29 (2010) 24–27.
[28] G. Zi, F. Zhang, X. Liu, L. Ai, H. Song, J. Organomet. Chem. 695 (2010) 730–739.
[29] L. Xiang, F. Zhang, J. Zhang, H. Song, G. Zi, Inorg. Chem. Commun. (2010),
doi:10.1016/j.inoche.2010.03.015.
Acknowledgements
This work was supported by the National Natural Science Foun-
dation of China (20972018), Scientific Research Foundation of Bei-
jing Normal University (2009SD-13), and Beijing Municipal
Commission of Education.
[30] G. Zi, F. Zhang, L. Xiang, Y. Chen, W. Fang, H. Song, Dalton Trans. (2010),
doi:10.1039/b923457h.
ˇ
´
ˇ
ˇ
[31] P. Kocovsky, Š. Vykocil, M. Smrcina, Chem. Rev. 103 (2003) 3213–3246.
[32] K. Ding, X. Li, B. Ji, H. Guo, M. Kitamura, Curr. Org. Synth. 2 (2005) 499–545.
[33] K. Ding, H. Guo, X. Li, Y. Yuan, Y. Wang, Top. Catal. 35 (2005) 105–116.
[34] Q. Wang, L. Xiang, H. Song, G. Zi, Inorg. Chem. 47 (2008) 4319–4328.
[35] Q. Wang, L. Xiang, G. Zi, J. Organomet. Chem. 693 (2008) 68–76.
[36] Q. Wang, L. Xiang, H. Song, G. Zi, J. Organomet. Chem. 694 (2009) 691–696.
[37] G. Zi, Q. Wang, L. Xiang, H. Song, Dalton Trans. (2008) 5930–5944.
[38] J.Y. Kim, T. Livinghouse, Org. Lett. 7 (2005) 1737–1739.
[39] D. Riegert, J. Collin, A. Meddour, E. Schulz, A. Trifonov, J. Org. Chem. 71 (2006)
2514–2517.
[40] G.M. Sheldrick, SADABS, Program for Empirical Absorption Correction of Area
Detector Data, University of Göttingen, Göttingen, Germany, 1996.
[41] G.M. Sheldrick, SHELXL-97, Program for the Refinement of Crystal Structure from
Diffraction Data, University of Göttingen, Göttingen, Germany, 1997.
[42] H. Mahmoud, Y. Han, B.M. Segal, L. Cai, Tetrahedron: Asymmetry 9 (1998)
2035–2042.
Appendix A. Supplementary data
CCDC 760930, 760931, 760932, 760933, 760934, and 760935
contain the supplementary crystallographic data for 1H, 6, 8, 9,
12 and 13, respectively. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif. Supplementary data associ-
ated with this article can be found, in the online version, at
doi:10.1016/j.jorganchem.2010.03.014.
References
[43] G. Zi, H.-W. Li, Z. Xie, Organometallics 21 (2002) 3850–3855.
[44] Z.J. Tonzetich, R.R. Schrock, A.S. Hock, P. Müller, Organometallics 24 (2005)
3335–3342.
[45] S. Majumder, A.L. Odom, Organometallics 27 (2008) 1174–1177.
[46] J.A. Bexrud, C. Li, L.L. Schafer, Organometallics 26 (2007) 6366–6372.
[47] Z. Zhang, D.C. Leitch, M. Lu, B.O. Patrick, L.L. Schafer, Chem.-Eur. J. 13 (2007)
2012–2022.
[48] R.K. Thomson, F.E. Zahariev, Z. Zhang, B.O. Patrick, Y.A. Wang, L.L. Schafer,
Inorg. Chem. 44 (2005) 8680–8689.
[49] P.N. O’Shaughnessy, K.M. Gillespie, C. Morton, I. Westmoreland, P. Scott,
Organometallics 21 (2002) 4496–4504.
[1] M. North, D.L. Usanov, C. Young, Chem. Rev. 108 (2008) 5146–5226.
[2] K. Maruoka, T. Ooi, in: M. Christmann, S. Braese (Eds.), Asymmetric Synthesis,
Wiley–VCH, Weinheim, 2007, pp. 121–125.
[3] D.J. Ramon, M. Yus, Chem. Rev. 106 (2006) 2126–2208.
[4] C.-M. Che, J.-S. Jie, Coord. Chem. Rev. 242 (2003) 97–113.
[5] F. Chen, X. Feng, Y. Jiang, ARKIVOC (2003) 21–31.
[6] H. Groeger, Chem. Rev. 103 (2003) 2795–2827.
[7] A.H. Hoveyda, in: I. Marek (Ed.), Titanium and Zirconium in Organic Synthesis,
Wiley–VCH, Weinheim, 2002, pp. 180–229.
[8] K. Mikami, M. Terada, in: H. Yamamoto (Ed.), Lewis Acid Reagents, Oxford
University Press, Oxford, 1999, pp. 93–136.
[9] A. Hafner, R.O. Duthaler, in: G.R. Stephenson (Ed.), Advanced Asymmetric
Synthesis, Chapman and Hall, London, 1996, pp. 231–259.
[10] R.O. Duthaler, A. Hafner, Chem. Rev. 92 (1992) 807–832.
[11] K.C. Hultzsch, Org. Biomol. Chem. 3 (2005) 1819–1824.
[50] P.R. Woodman, N.W. Alcock, I.J. Munslow, C.J. Sanders, P. Scott, J. Chem. Soc.,
Dalton Trans. (2000) 3340–3346.
[51] R.M. Beesley, C.K. Ingold, J.F. Thorpe, J. Chem. Soc. 107 (1915) 1080–1106.
[52] C.K. Ingold, J. Chem. Soc. 119 (1921) 305–329.