Synthesis, structure, and catalytic activity of TiIV and Zr IV complexes derived from (R)-2,2′-diamino-1,1′- binaphthyl-based N4-donor ligands

Article abstract of DOI:10.1002/ejic.200701105

Reaction of (R)-bis(pyrrol-2-ylmethyleneamino)-1,1′-binaphthyl (1H₂) or (R)-N,N′-bis(pyridin-2-ylmethyl)-1,1′- binaphthyl-2,2′-diamine (2H₂) with Zr(NMe₂) ₄ (1 equiv.) gives chiral zirconium amides 1-Zr(NMe

Full text of DOI:10.1002/ejic.200701105

FULL PAPER
DOI: 10.1002/ejic.200701105
Synthesis, Structure, and Catalytic Activity of TiIV and ZrIV Complexes
Derived from (R)-2,2Ј-Diamino-1,1Ј-binaphthyl-Based N4-Donor Ligands
Li Xiang,[a] Haibin Song,[b] and Guofu Zi*[a]
Keywords: Titanium / Zirconium / N ligands / Asymmetric catalysis / Hydroamination
Reaction of (R)-bis(pyrrol-2-ylmethyleneamino)-1,1Ј-binaph-
thyl (1H2) or (R)-N,NЈ-bis(pyridin-2-ylmethyl)-1,1Ј-binaph-
thyl-2,2Ј-diamine (2H2) with Zr(NMe2)4 (1 equiv.) gives chiral
zirconium amides 1-Zr(NMe2)2·C7H8 (4·C7H8) or 2-Zr-
(NMe2)2 (6) in good yields, respectively. Under similar condi-
tions, 1H2 reacts with Ti(NMe2)4 (1 equiv.) to give chiral tita-
nium amide 1-Ti(NMe2)2·C6H6 (3·C6H6), whereas treatment
of 2H2 with Ti(NMe2)4 (1 equiv.) leads to the isolation of bis-
(ligated) product (2)2-Ti·C7H8 (5·C7H8) in 74% yield. All com-
plexes were characterized by various spectroscopic tech-
niques, elemental analysis, and X-ray diffraction analysis.
Zirconium amides 4 and 6 are active catalysts for the asym-
metric hydroamination/cyclization of aminoalkenes, and cy-
clic amines were obtained in good-to-excellent yields with
moderate ee values (up to 59%); titanium amides 2 and 5
were not active under the reaction conditions.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
asymmetric hydrogenation of aromatic ketones, although
this complex was not isolated.[13] In this paper, we report
on some observations concerning the chemistry of ligands
1H2 and 2H2 with titanium(IV) and zirconium(IV) amides
and the use of the resulting complexes as catalysts in asym-
metric hydroamination/cyclization reactions.
Introduction
Hydroamination is a highly atom-economical process in
which an amine N–H bond adds to an unsaturated carbon–
carbon bond to form nitrogen heterocycles, which can be
found in numerous biologically active compounds.[1] There-
fore, it is not surprising that recent efforts have focused on
the development of chiral catalysts for intramolecular
asymmetric alkene hydroamination.[2–10] Since the pioneer-
ing work of Marks in 1992,[3a,3b] many chiral catalysts based
on lanthanide metals, main group metals, group 4 metals,
and late-transition metals have been widely studied,[2–10] but
only a small number of highly enantioselective reactions
(Ͼ90%ee) have been reported.[7a,9c,9e,10e–10g] Thus, the devel-
opment of new catalysts for asymmetric alkene hydroamin-
ation is a desirable and challenging goal. In recent years,
we have developed a series of chiral non-Cp multidentate
ligands, and it was shown that their IrI, RhI, TiIV, AgI, ZnII,
and lanthanide complexes are useful catalysts for a wide
range of transformations.[11] In our endeavors to further ex-
plore the coordination chemistry of the chiral (R)-bis-
(pyrrol-2-ylmethyleneamino)-1,1Ј-binaphthyl (1H2) and
(R)-N,NЈ-bis(pyridin-2-ylmethyl)-1,1Ј-binaphthyl-2,2Ј-di-
amine (2H2) N4-ligands, we recently extended our research
work to titanium(IV) and zirconium(IV) chemistry.[12] In
the only other literature report featuring ligand 2H2, it was
shown that its RuII complex is a useful catalyst for the
Results and Discussion
Synthesis
Group 4 metal amide complexes can be efficiently pre-
pared by amine elimination of M(NMe2)4 with protic rea-
gents.[14] It is rational to propose that two acidic protons in
ligands 1H2 and 2H2 would allow a similar amine elimi-
nation reaction to occur between 1H2 or 2H2 and metal
amides. In fact, treatment of 1H2 or 2H2 with Zr(NMe2)4
(1 equiv.) gives desired chiral zirconium amides 1-Zr-
(NMe2)2·C7H8 (4·C7H8) (Scheme 1) or 2-Zr(NMe2)2 (6)
(Scheme 2), respectively, in good yields. Under similar con-
ditions, the reaction of 1H2 with Ti(NMe2)4 (1 equiv.) gives
chiral titanium amide 1-Ti(NMe2)2·C6H6 (3·C6H6)
(Scheme 1). However, treatment of 2H2 with Ti(NMe2)4
[a] Department of Chemistry, Beijing Normal University,
Beijing 100875, China
Fax: +86-10-5880-2075
E-mail: gzi@bnu.edu.cn
[b] State Key Laboratory of Elemento-Organic Chemistry, Nankai
University,
Tianjin 300071, China
Scheme 1. Synthesis of complexes 3 and 4.
Eur. J. Inorg. Chem. 2008, 1135–1140
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(1 equiv.) does not yield expected compound 2-Ti- Table 1. Selected bond lengths [Å] and bond angles [°] for 3–6.
(NMe2)2; instead, bis(ligated) product (2)2-Ti·C7H8
(5·C7H8) was isolated in 74% yield (Scheme 2).
Compound 3·C6H6
Ti1–N1
2.278(2)
2.143(2)
1.890(2)
72.70(8)
72.81(8)
111.3(2)
123.39(19)
122.84(19)
Ti1–N2
Ti1–N4
Ti1–N6
N1–Ti1–N3
N5–Ti1–N6
C31–N5–Ti1
C33–N6–C34 110.1(2)
C34–N6–Ti1
2.286(2)
2.129(2)
1.895(2)
73.73(8)
101.99(10)
124.75(19)
Ti1–N3
Ti1–N5
N1–Ti1–N2
N2–Ti1–N4
C31–N5–C32
C32–N5–Ti1
C33–N6–Ti1
127.0(2)
torsion (aryl–aryl) 71.2(2)
Compound 4·C7H8
Zr1–N1
Zr1–N3
Zr1–N5
N1–Zr1–N2
N3–Zr1–N4
C31–N5–C32
C32–N5–Zr1
C33–N6–Zr1
2.291(5)
2.377(4)
2.038(5)
70.01(15)
69.47(14)
112.5(6)
120.8(5)
117.4(5)
Zr1–N2
Zr1–N4
Zr1–N6
N2–Zr1–N3
N5–Zr1–N6
C31–N5–Zr1
C33–N6–C34 114.8(6)
C34–N6–Zr1
2.377(4)
2.280(4)
2.041(5)
72.33(13)
108.1(2)
126.4(5)
127.3(5)
torsion (aryl–aryl) 67.7(5)
Scheme 2. Synthesis of complexes 5 and 6.
Compound 5·C7H8
Ti1–N1
Ti1–N3
Ti1–N6
N1–Ti1–N2
N5–Ti1–N6
C34–N5–C53
C53–N5–Ti1
C44–N6–Ti1
2.072(4)
2.315(4)
1.969(4)
97.32(15)
96.12(16)
114.6(4)
123.2(3)
119.5(3)
Ti1–N2
Ti1–N5
Ti1–N7
N1–Ti1–N3
N5–Ti1–N7
C34–N5–Ti1
C44–N6–C59 114.6(3)
C59–N6–Ti1
1.976(4)
2.018(4)
2.294(4)
74.67(13)
73.72(16)
120.1(3)
These complexes are stable in a dry-nitrogen atmosphere,
but they are very sensitive to moisture. They are soluble in
organic solvents such as THF, DME, pyridine, toluene, and
benzene, and they are only slightly soluble in n-hexane.
They were characterized by various spectroscopic tech-
niques, elemental analysis, and X-ray diffraction analysis.
117.4(3)
1
The H NMR spectra of 3, 4, and 6 support that the ratio
torsion (aryl–aryl) 62.8(3)
of the NMe2 amino group and ligand anion 1 or 2 is 2:1;
analysis also established that one benzene molecule for 3
and one toluene molecule for 4 per ligand anion 1, respec-
67.2(3)
Compound 6
Zr1–N1
Zr1–N2
Zr1–N3
N1–Zr1–N1A
N3–Zr1–N3A
C17–N3–Zr1
2.2155(19)
Zr1–N1A
Zr1–N2A
Zr1–N3A
N1–Zr1–N2
C18–N3–C17 111.6(2)
C18–N3–Zr1 121.94(19)
2.2155(19)
2.4204(19)
2.0866(19)
69.25(7)
1
tively, cocrystallized in the lattice. The H NMR spectrum
2.4204(19)
2.0866(19)
83.08(9)
113.72(12)
126.30(19)
of 5 confirmed that the ratio of toluene and ligand anion
2 is 1:2. The 13C NMR spectra are consistent with these
conclusions.
torsion (aryl–aryl) 66.5(2)
Molecular Structures
Complexes 3–6 were characterized by single-crystal X-
ray diffraction analysis. Selected bond lengths and angles
are listed in Table 1. Single-crystal X-ray diffraction analy-
sis showed that there are two 1-M(NMe2)2 molecules and
two solvate benzene molecules for 3 and two solvate toluene
molecules for 4 in the lattice. In each 1-M(NMe2)2 mole-
cule, the M4+ is σ bound to four nitrogen atoms from ligand
anion 1 and two nitrogen atoms from the NMe2 groups
in a distorted-octahedron geometry (Figures 1 and 2); the
average distance are M–N 2.104(2) Å for Ti and 2.234(5) Å
for Zr. The short distances of M–NMe2 [Ti–N5 1.890(2) Å,
Ti–N6 1.895(2) Å for Ti and Zr–N5 2.038(5) Å, Zr–N6
2.041(5) Å for Zr] and the planar geometry around the N5
and N6 atoms indicate that both sp2-hybridized nitrogen
atoms are engaged in N(pπ)ǞM(dπ) interactions. These
structural data are very close to those found in the litera-
ture.[14] The twisting between the naphthylene rings has a
torsion angle of 71.2(2)° for Ti and 67.7(5)° for Zr, which
are comparable to those found in 1-YCl(dme) [70.1(3)°] and
1-Y[N(SiMe3)2](thf) [67.3(4)°].[11f]
Figure 1. Molecular structure of 3 (thermal ellipsoids drawn at the
35% probability level).
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 1135–1140

TiIV and ZrIV Complexes Derived from Binaphthyl-Based N4-Donor Ligands
Figure 4. Molecular structure of 6 (thermal ellipsoids drawn at the
35% probability level).
Figure 2. Molecular structure of 4 (thermal ellipsoids drawn at the
35% probability level).
Asymmetric Hydroamination/Cyclization
Single-crystal X-ray diffraction analysis of 5 revealed
that there are two molecules of 5 and two toluene solvent
molecules in the lattice. In each molecule of 5, the Ti4+ is σ
bound to the six nitrogen atoms from two ligand anions 2 in
a distorted-octahedron geometry (Figure 3) with an average
distance of Ti–N 2.107(4) Å, which is close to that found in
3 [2.104(2) Å]. The twisting between the naphthylene rings
occurs with torsion angles of 62.8(3) and 67.2(3)°, which
are smaller than that found in 3 [71.2(2)°].
To examine the catalytic ability of complexes 3–6, the
asymmetric hydroamination/cyclization of unactivated ter-
minal aminoalkenes was tested under the conditions given
in Table 2. The results of the hydroamination/cyclization of
2,2-dimethylpent-4-enylamine show that the zirconium
amides are active catalysts for this transformation (Table 2,
Entries 2 and 4). Complex 4 gives a noticeably better ee
value (59%; Table 2, Entry 2), whereas complex 6 shows
poor enantioselectivity (only 14%) for this transformation.
Under similar reaction conditions, no detectable hydro-
amination activity was observed for titanium complexes 3
and 5, even at 120 °C for one week (Table 2, Entries 1 and
3). The reaction of substrate 8a was fast, but the ee values
were low (Table 2, Entries 5 and 6). We were encouraged to
find that formation of a six-membered ring could also be
performed with our zirconium catalysts (Table 2, Entries 7
and 8), and that the reaction, mediated by catalyst 6, pro-
ceeded with moderate enantioselectivity (up to 49%;
Table 2, Entry 8). It can be concluded that the rate of cycli-
Table 2. Enantioselective hydroamination/cyclization of aminoal-
kenes.[a]
Figure 3. Molecular structure of 5 (thermal ellipsoids drawn at the
35% probability level).
The solid-state structure of 6 shows that the Zr4+ is σ
bound to four nitrogen atoms from ligand anion 2 and two
nitrogen atoms from the NMe2 groups in a distorted-octa-
hedron geometry (Figure 4) with an average distance of Zr–
N 2.2408(19) Å. The short Zr–N3 and Zr–N3A bond
lengths [2.0866(19) and 2.0866(19) Å, respectively] and the
planar geometry around the N3 and N3A atoms indicate
that both sp2-hybridized nitrogen atoms are engaged in
N(pπ)ǞZr(dπ) interactions. The twisting between the naph-
thylene rings has a torsion angle of 66.5(2)°. These struc-
tural data are close to those found in 4.
[a] Conditions: C6D6 (0.70 mL), aminoalkene (0.16 mmol), catalyst
(0.016 mmol), at 120 °C. [b] Determined by 1H NMR spectroscopy
on the basis of tetramethylsilane (TMS) as the internal standard.
[c] Determined by 1H NMR spectroscopy of its diastereomeric (S)-
(+)-O-acetylmandelic acid salt on the basis of tetramethylsilane
(TMS) as the internal standard.[6,8g]
Eur. J. Inorg. Chem. 2008, 1135–1140
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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L. Xiang, H. Song, G. Zi
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ane[8a] 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 with an Avatar 360 Fourier trans-
zation of the aminoalkenes follows the order 5 Ͼ 6, which
is consistent with classical, stereoelectronically controlled,
cyclization processes. Our results show that the catalytic ac-
tivities of zirconium amides 4 and 6 resemble those of zirco-
nium bis(amido) catalysts,[10d] whereas the enantiomeric ex-
cesses of the resulting cyclic amines are similar to those
obtained with bis(phenolate).[10a] Although the enantio-
meric excesses obtained are moderate, it should be noted
that there are only a few catalysts available that give signifi-
cant ee values for these reactions.
1
form spectrometer. H and 13C NMR spectra were recorded with
a Bruker AV 500 spectrometer at 500 and 125 MHz, respectively.
All chemical shifts are reported in δ units with reference to the
residual protons of the deuterated solvents or protons of tetrameth-
ylsilane [TMS; contained 1% (v/v) in C6D6], which are internal
standards, for proton and carbon chemical shifts. Melting points
were measured with an X-6 melting point apparatus and are uncor-
rected. Elemental analyses were performed with a Vario EL ele-
mental analyzer.
Conclusions
1-Ti(NMe2)2·C6H6 (3·C6H6): A toluene solution (10 mL) of 1H2
(0.22 g, 0.5 mmol) was slowly added to a toluene solution (10 mL)
of Ti(NMe2)4 (0.11 g, 0.5 mmol) with stirring at room temperature.
The solution was warmed to 60 °C and kept for 1 d at this tempera-
ture. The solution was filtered, and the solvent was removed under
reduced pressure. The resulting red solid was recrystallized from a
benzene solution to give 3·C6H6 as red crystals. Yield: 0.29 g (90%).
A series of chiral organotitanium(IV) and organozirconi-
um(IV) amide complexes was synthesized from the reaction
of M(NMe2)4 (M = Ti, Zr) with chiral N4 ligands, (R)-
bis(pyrrol-2-ylmethyleneamino)-1,1Ј-binaphthyl (1H2) and
(R)-N,NЈ-bis(pyridin-2-ylmethyl)-1,1Ј-binaphthyl-2,2Ј-di-
amine (2H2). Their use as catalysts in asymmetric hydro-
amination/cyclization reactions was studied. The zirconium
amides showed good-to-excellent catalytic activity in the re-
actions of representative aminoalkenes, whereas the tita-
nium amides did not.
By changing the pyrrol-2-ylmethylene group to a pyridin-
2-ylmethyl one, ligands 1H2 and 2H2 exhibited different re-
activity patterns. For example, reaction of Ti(NMe2)4 with
1H2 gave expected complex 1-Ti(NMe2)2 (3), whereas that
of 2H2 afforded bis(ligated) complex (2)2-Ti (5). Zirconium
complex 4 (with ligand anion 1) showed moderate enantio-
selectivity (up to 59%ee) for the asymmetric hydroamin-
ation/cyclization of 2,2-dimethylpent-4-enylamine, whereas
zirconium complex 6 (with ligand anion 2) did not, which
might indicate that very precise control of the metal coordi-
nation sphere is required for this asymmetric transforma-
tion to be a realistic prospect. Our ligand set, which in-
volves a peripheral binaphthylene unit coupled to pyrrole or
pyridine ligation in multidentate systems, does not provide
sufficient rigidity of the dative N-donor ligand to achieve
this goal; however, in contrast to the chiral biphenyl-based
N2O2 ligand system,[10e,f] the present results should signifi-
cantly expand the range of possibilities that can be used in
the design of catalysts not only for hydroamination but also
for many other reactions.[12] Further exploration of these
catalysts towards other types of transformations and the
optimization of the ligand architecture to improve the enan-
tiomeric excess for this transformation are still underway.
1
M.p. 143–145 °C (dec.). H NMR (500 MHz, C6D6): δ = 7.70 (m,
4 H, CH=N and aryl H), 7.60 (m, 4 H, aryl H), 7.50 (m, 2 H, aryl
H), 7.28 (m, 4 H, aryl H), 7.18–7.15 (m, 8 H, aryl and pyrrolyl H),
6.43 (d, J = 1.6 Hz, 2 H, pyrrolyl H), 6.13 (d, J = 3.4 Hz, 2 H,
pyrrolyl H), 3.52 [s, 12 H, N(CH3)2] ppm. 13C NMR (125 MHz,
C6D6): δ = 159.9, 148.5, 138.0, 137.9, 134.4, 131.8, 128.6. 128.5,
128.3, 128.1, 127.1, 126.7, 124.9, 122.7, 117.5, 112.8 (aryl C), 47.3
[N(CH ) ] ppm. IR (KBr): ν = 2962 (s), 2923 (m), 2850 (m), 1592
˜
3 2
(w), 1567 (vs), 1504 (s), 1390 (s), 1260 (s), 1036 (vs), 804 (s) cm–1.
C40H38N6Ti (650.64): calcd. C 73.84, H 5.89, N 12.92; found C
73.55, H 5.78, N 12.71.
1-Zr(NMe2)2·C7H8 (4·C7H8): This compound was prepared by a
similar procedure to that described for 3·C6H6. Orange crystals
were obtained from the reaction of 1H2 (0.22 g, 0.5 mmol) with
Zr(NMe2)4 (0.14 g, 0.5 mmol) in toluene (20 mL) and recrystalli-
zation from a toluene solution. Yield: 0.30 g (86%). M.p. 170–
172 °C (dec.). 1H NMR (500 MHz, C6D6): δ = 7.55–7.33 (m, 10 H,
CH=N and aryl H), 7.15–7.10 (m, 7 H, aryl H), 7.04 (m, 4 H, aryl
and pyrrolyl H), 6.26 (m, 2 H, pyrrolyl H), 6.10 (d, J = 2.7 Hz, 2
H, pyrrolyl H), 3.21 [s, 12 H, N(CH3)2], 2.10 (s, 3 H, C6H5CH3)
ppm. 13C NMR (125 MHz, C6D6): δ = 160.7, 147.2, 139.9, 138.9,
134.4, 132.1, 129.3, 129.2, 128.9, 128.5, 128.3, 127.7, 127.1, 127.0,
125.6, 125.3, 123.0, 120.4, 113.8 (aryl C), 42.7 [N(CH3)2], 21.4
(C H CH ) ppm. IR (KBr): ν = 2961 (s), 2923 (m), 2850 (m), 1599
˜
6
5
3
(s), 1575 (vs), 1392 (s), 1286 (s), 1260 (s), 1037 (vs), 800 (s) cm–1.
C41H40N6Zr (708.02): calcd. C 69.55, H 5.68, N 11.87; found C
69.72, H 5.66, N 11.68.
(2)2-Ti·C7H8 (5·C7H8): This compound was prepared by a similar
procedure to that described for 3·C6H6. Red crystals were obtained
from the reaction of 2H2 (0.23 g, 0.5 mmol) with Ti(NMe2)4
(0.11 g, 0.5 mmol) in toluene (20 mL) and recrystallization from a
toluene solution. Yield: 0.20 g (74%; base on ligand 2H2). M.p. 10
8–110 °C (dec.). 1H NMR (500 MHz, C6D6): δ = 8.19 (d, J =
9.0 Hz, 2 H, aryl H), 7.98 (m, 4 H, aryl H), 7.80 (d, J = 8.7 Hz, 2
H, aryl H), 7.69 (d, J = 8.4 Hz, 2 H, aryl H), 7.54 (d, J = 7.8 Hz,
2 H, aryl H), 7.50 (d, J = 5.3 Hz, 2 H, aryl H), 7.29–7.08 (m, 13
H, aryl H), 7.01 (d, J = 8.6 Hz, 2 H, aryl H), 6.86 (m, 2 H, aryl
H), 6.68 (d, J = 7.9 Hz, 2 H, aryl H), 6.50 (m, 2 H, aryl H), 6.34
(m, 4 H, aryl H), 6.22 (m, 2 H, aryl H), 6.11 (d, J = 16.7 Hz, 2 H,
aryl H), 5.61 (t, J = 6.3 Hz, 2 H, aryl H), 5.52 (d, J = 5.2 Hz, 2 H,
NCH2), 5.49 (s, 2 H, NCH2), 4.75 (d, J = 20.4 Hz, 2 H, NCH2),
4.32–4.20 (m, 2 H, NCH2), 2.23 (s, 3 H, C6H5CH3) ppm. 13C NMR
Experimental Section
General Methods: All experiments were performed under an atmo-
sphere of dry nitrogen with rigid exclusion of air and moisture by
using standard Schlenk or cannula techniques, or the experiments
were performed in a glovebox. All organic solvents were freshly
distilled from sodium benzophenone ketyl immediately prior to
use. (R)-Bis(pyrrol-2-ylmethyleneamino)-1,1Ј-binaphthyl (1H2),[11f]
(R)-N,NЈ-bis(pyridin-2-ylmethyl)-1,1Ј-binaphthyl-2,2Ј-diamine
(2H2),[11c] M(NMe2)4,[15] 2,2-dimethylpent-4-enylamine,[6] 2,2Ј-di-
methylhex/5-enylamine,[6] and 1-(aminomethyl)-1-allylcyclohex-
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TiIV and ZrIV Complexes Derived from Binaphthyl-Based N4-Donor Ligands
(125 MHz, C6D6): δ = 161.6, 161.2, 156.6, 150.2, 149.2, 148.4,
148.0, 136.0, 135.7, 135.1, 128.5, 128.4, 128.3, 128.2, 128.1, 127.4,
127.3, 126.9, 125.7, 122.5, 122.3, 120.3, 120.2, 120.1, 118.8, 114.2
(aryl C), 64.5 (NCH2), 62.6 (NCH2), 49.0 (NCH2), 21.2 (C6H5CH3)
conversion (based on TMS) from 2,2-dimethylpent-4-enylamine to
2,4,4-trimethylpyrrolidine (7b) was determined. 1H NMR
(500 MHz, C6D6): δ = 3.10 (m, 1 H, NCH), 2.64 (m, 1 H, NCHH),
2.50 (m, 1 H, NCHH), 1.50 (m, 1 H, CHH), 1.18 (br. s, 1 H, NH),
1.07 (d, J = 6.2 Hz, 3 H, CH3), 0.98 (s, 3 H, CH3), 0.96 (s, 3 H,
CH3) ppm. These data were in agreement with those reported in
the literature.[6,8g] The cyclic amine 2,4,4-trimethylpyrrolidine (7b)
was vacuum transferred from the J. Young NMR tube into a 25-
mL Schlenk flask, which contained (S)-(+)-O-acetylmandelic acid
(31 mg, 0.16 mmol). This transfer was quantitated by washing the
NMR tube with a small amount of CDCl3. The resulting mixture
was stirred at room temperature for 2 h, and the volatiles were then
removed in vacuo. The resulting diastereomeric salt was then dis-
solved in CDCl3, and the enantiomeric excess was determined by
1H NMR spectroscopy (59%ee). 1H NMR (500 MHz, CDCl3)
(major isomer): δ = 7.50 (d, J = 7.2 Hz, 2 H, aryl H), 7.31–7.24
(m, 3 H, aryl H), 5.74 (s, 1 H, CHOAc), 3.52 (m, 1 H, NCH), 2.84
(d, J = 11.4 Hz, 1 H, NCHH), 2.68 (q, J = 11.0 Hz, 1 H, NCHH),
2.13 (s, 1 H, CH3CO), 1.65 (m, 1 H, CHCH2), 1.27 (t, J = 11.4 Hz,
1 H, CHCH2), 1.22 (d, J = 6.5 Hz, 3 H, NHCH3), 1.05 (s, 1 H,
CH3), 0.96 (s, 1 H, CH3) ppm. 1H NMR (500 MHz, CDCl3) (minor
isomer): δ = 7.50 (d, J = 7.2 Hz, 2 H, aryl H), 7.31–7.24 (m, 3 H,
aryl H), 5.74 (s, 1 H, CHOAc), 3.35 (m, 1 H, NCH), 2.84 (d, J =
11.4 Hz, 1 H, NCHH), 2.68 (q, J = 11.0 Hz, 1 H, NCHH), 2.13 (s,
1 H, CH3CO), 1.65 (m, 1 H, CHCH2), 1.27 (t, J = 11.4 Hz, 1 H,
CHCH2), 1.15 (d, J = 6.5 Hz, 3 H, NHCH3), 1.05 (s, 1 H, CH3),
0.96 (s, 1 H, CH3) ppm. These data were in agreement with those
reported in the literature.[6,8g]
ppm; other carbon resonances overlapped. IR (KBr): ν = 3053 (m),
˜
2961 (m), 2920 (m), 1614 (s), 1590 (s), 1503 (s), 1422 (s), 1325 (s),
1260 (s), 1091 (s), 806 (s) cm–1. C71H56N8Ti (1069.13): calcd. C
79.76, H 5.28, N 10.48; found C 79.64, H 5.36, N 10.24.
2-Zr(NMe2)2 (6): This compound was prepared by a similar pro-
cedure to that described for 3·C6H6. Orange crystals were obtained
from the reaction of 2H2 (0.23 g, 0.5 mmol) with Zr(NMe2)4
(0.14 g, 0.5 mmol) in toluene (20 mL) and recrystallization from a
1
toluene solution. Yield: 0.24 g (76%). M.p. 158–160 °C (dec.). H
NMR (500 MHz, C6D6): δ = 8.24 (d, J = 5.2 Hz, 2 H, aryl H),
7.82 (m, 4 H, aryl H), 7.59 (d, J = 8.4 Hz, 4 H, aryl H), 7.21 (t, J
= 7.3 Hz, 2 H, aryl H), 7.11 (t, J = 7.9 Hz, 2 H, aryl H), 6.78 (t, J
= 7.5 Hz, 2 H, aryl H), 6.52 (t, J = 6.2 Hz, 2 H, aryl H), 6.27 (d,
J = 7.8 Hz, 2 H, aryl H), 5.10 (d, J = 19.2 Hz, 2 H, NCH2), 4.61
(d, J = 19.2 Hz, 2 H, NCH2), 3.04 [s, 12 H, N(CH3)2] ppm. 13C
NMR (125 MHz, C6D6): δ = 166.8, 154.2, 147.9, 136.9, 135.2,
129.6, 128.3, 127.3, 127.1, 126.7, 125.5, 124.9, 122.2, 120.8, 120.6
(aryl C), 62.5 (NCH ), 43.8 [N(CH ) ] ppm. IR (KBr): ν = 3046
˜
2
3 2
(w), 2919 (m), 2757 (s), 1607 (s), 1588 (s), 1499 (s), 1421 (s), 1332
(s), 1260 (s), 1017 (vs), 930 (s), 804 (s) cm–1. C36H36N6Zr (643.94):
calcd. C 67.15, H 5.64, N 13.05; found C 67.48, H 5.48, N 12.87.
General Procedure for the Asymmetric Hydroamination/Cyclization
Reaction: The cyclization of 2,2-dimethylpent-4-enylamine (7a) cat-
alyzed by catalyst 4 is representative (Table 2, Entry 2). In a nitro-
gen-filled glovebox, 1-Zr(NMe2)2·C7H8 (4·C7H8; 11.3 mg, X-ray Crystallography: Single-crystal X-ray diffraction measure-
0.016 mmol), C6D6 [0.7 mL; contains 1% (v/v) TMS], and 2,2-di- ments were carried out with a Rigaku Saturn CCD diffractometer
methylpent-4-enylamine (7a; 18 mg, 22.6 µL, 0.16 mmol) were in-
troduced sequentially into a J. Young NMR tube equipped with a
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. After heating for 80 h, 87%
at 113(2) K by using graphite monochromated Mο-Kα radiation (λ
= 0.71070 Å). An empirical absorption correction was applied by
using the SADABS program.[16] All structures were solved by direct
methods and refined by full-matrix least-squares on F2 with the use
of the SHELXL-97 program package.[17] All hydrogen atoms were
Table 3. Crystal data and experimental parameters for compounds 3–6.
Compound
3·C6H6
4·C7H8
5·C7H8
6
Formula
Formula weight
Crystal system
Space group
a [Å]
b [Å]
c [Å]
C40H38N6Ti
650.66
orthorhombic
P21212
22.910(1)
30.511(1)
9.661(1)
90
C41H40N6Zr
708.01
orthorhombic
C2221
9.878(1)
20.895(3)
35.945(4)
90
C71H56N8Ti
1069.14
monoclinic
P1211
15.263(6)
19.815(8)
21.584(9)
90
C36H36N6Zr
643.93
trigonal
P3221
11.591(1)
11.591(1)
20.734(3)
90
α [°]
β [°]
90
90
6752.7(4)
8
1.280
0.292
0.12ϫ0.10ϫ0.08
2736
90
90
102.88(1)
90
6363(4)
4
1.116
0.180
90
120
2412.5(5)
3
1.330
0.376
0.24ϫ0.20ϫ0.18
1002
γ [°]
V [Å3]
7419.1(17)
8
1.268
0.333
0.24ϫ0.20ϫ0.16
2944
Z
Dcalcd. [gcm–3]
µ [mm–1]
Size [mm]
F(000)
0.20ϫ0.20ϫ0.20
2240
2θ range [°]
No. of reflections, collected 64197
3.20 to 55.74
3.90 to 52.82
21150
3.42 to 50.00
47836
4.06 to 52.86
13630
No. of unique reflections
No. of observed reflections
15991 (Rint = 0.0689)
7605 (Rint = 0.0388)
7605
1.00, 0.69
0.052
20129 (Rint = 0.0590)
20129
0.96, 0.80
0.069
3312 (Rint = 0.0377)
3312
0.94, 0.92
0.027
15991
0.98, 0.97
0.053
Abscorr (Tmax, Tmin
)
R
Rw
Rall
Gof
0.115
0.067
1.04
0.132
0.081
1.06
0.166
0.078
1.08
0.057
0.038
1.09
Eur. J. Inorg. Chem. 2008, 1135–1140
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1139

L. Xiang, H. Song, G. Zi
FULL PAPER
[9]
For asymmetric hydroaminations with the use of late-transi-
tion-metal catalysts, see: a) O. Löber, M. Kawatsura, J. F. Hart-
wig, J. Am. Chem. Soc. 2001, 123, 4366–4367; b) N. T. Patil,
L. M. Lutete, H. Wu, N. K. Pahadi, I. D. Gridnev, Y. Yamam-
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B. D. Sherry, E. J. Kang, F. D. Toste, J. Am. Chem. Soc. 2007,
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Widenhoefer, J. Am. Chem. Soc. 2007, 129, 14148–14149.
geometrically fixed by using the riding model. The crystal data and
experimental data for 3–6 are summarized in Table 3. Selected
bond lengths and angles are listed in Table 1.
CCDC-663456 (for 3), -663457(for 4), -663458 (for 5), and -663459
(for 6) contain the supplementary crystallographic data for this pa-
per. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
[10]
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Knight, I. Munslow, P. N. O’Shaughnessy, P. Scott, Chem.
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K. C. Hultzsch, F. Hampel, Chem. Commun. 2006, 2221–2223;
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2006, 25, 4731–4733; e) M. C. Wood, D. C. Leitch, C. S. Yeung,
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S. Tsuchida, T. Shimizu, A. Kaneshige, K. Tomioka, Tetrahe-
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Acknowledgments
This work was supported by the National Natural Science Founda-
tion of China (20602003), and SRF for ROCS, SEM.
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Received: October 13, 2007
Published Online: January 7, 2008
1140
www.eurjic.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 1135–1140