Titanium amido- and imido-complexes supported by a tridentate pyrrolyl ligand: Syntheses, characterisation and catalytic activities

Article abstract of DOI:10.3184/174751912X13324293828161

The complexes [Ti(NMe₂)₂(pmpmi)] [H₂pmpmi = (2-pyrrolylmethene)-(2-pyrrolylmethyl)imine], [Ti(N^tBu)(pmpmi)(py) ₂], [Ti(N^tBu)(pmpmi)(dpy)] and [Ti(NPh)(pmpmi)(py) ₂] have been prepared, characterised and shown to be pre-catalysts for the hydroamination of phenylacetylene with aniline and p-chloroaniline. The X-ray structures of [Ti(NMe₂)₂(pmpmi)], [Ti(N ^tBu)(pmpmi)(dpy)] and [Ti(NPh)(pmpmi)(py)₂] have been determined.

Full text of DOI:10.3184/174751912X13324293828161

JOURNAL OF CHEMICAL RESEARCH 2012
MAY, 249–253
RESEARCH PAPER 249
Titanium amido- and imido-complexes supported by a tridentate pyrrolyl
ligand: syntheses, characterisation and catalytic activities
a,b
b
b
a
b
a
a
Zhou Chen , Lei Li , Yanmei Chen , Bin Hu , Jian Wu , Xiufang Wang , Tao Lei and
b,c
Yahong Li *
a
Key Laboratory of Salt Lake Resources and Chemistry of Chinese Academy of Sciences, Qinghai Institute of Salt Lakes, Xining 810008,
P. R. China.
b
Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow
University, Suzhou 215006, P. R. China.
c
State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou, 730000, P. R. China
t
Thecomplexes[Ti(NMe
[
2
)
2
(pmpmi)][H
Ti(N Bu)(pmpmi)(dpy)] and [Ti(NPh)(pmpmi)(py)
forthehydroaminationofphenylacetylenewithanilineandp-chloroaniline.TheX-raystructuresof[Ti(NMe
2
pmpmi=(2-pyrrolylmethene)-(2-pyrrolylmethyl)imine],[Ti(N Bu)(pmpmi)(py)
2
],
t
2
] have been prepared, characterised and shown to be pre-catalysts
2 2
) (pmpmi)],
t
[
Ti(N Bu)(pmpmi)(dpy)] and [Ti(NPh)(pmpmi)(py) ] have been determined.
2
Keywords: titanium, imines, X-ray structure, hydroamination
1
Studies of preparation and characterisation of titanium amido-
and imido- complexes have largely been driven by investiga-
tion of hydroamination reaction, in which an amine is added
across an unsaturated C–C bond to form imines, enamines
and N-containing heterocycles. Since this process circumvents
the formation of byproducts and provides an attractive strategy
for the preparation of industrially important N-containing
compounds, both inter- and intra-molecular hydroamination
graphite-monochromatised Mo Kα radiation (λ = 0.71073 Å).
H
1
3
and C NMR spectra were recorded on a Varian Inova-300 or
VXR-500 spectrometer. GC/MS spectra were recorded with a
GCMS-QP2010.
Crystals grown from concentrated solutions at room temperature
were quickly selected and mounted on a glass fibre in wax. The data
collections were carried out on a Bruker AXS three-circle goniometer
with a CCD detector equipped with graphite-monochromated MoKα
radiation by using the w/ω scan technique at room temperature. The
1
–7
have attracted attention for more than 20 years. A variety of
32,33
structures were solved by direct methods with SHELXS-97.
The
2
complexes are known to effect such transformations. Amongst
hydrogen atoms were assigned with common isotropic displacement
factors and included in the final refinement by use of geometrical
restraints. A full-matrix least-squares refinement on F was carried out
using SHELXL-97. The structures shown in Figs 1–3 were produced
using ORTEP, and ellipsoids are at the 30% probability level.
these, titanium complexes have been proved to be some of the
most useful catalysts for the hydroamination of alkynes due
to their enhanced stability and improved functional group
tolerance. Titanium-catalysed hydroamination of alkynes has
2
8
–14
been extensively studied by many groups around the world.
Preparation of Li pmpmi
2
This research has indicated that the ligand chelating to the metal
centre plays a key role in controlling the regioselectivity of the
hydroamination products. In general, anti-Markonikov products
n
–1
BuLi (1.25 mL, 1.6 mol L , 2 mmol) in hexane (3 mL) was added
dropwise to a solution of H pmpmi (0.1732 g, 1 mmol) in THF
3 mL) cooled to –35 °C. A white precipitate formed immediately.
The resulting mixture was allowed to warm to room temperature
and stirred for 3 h, then used as the lithiated salt without further
purification.
2
(
1
5–18
are preferentially obtained with titanocene catalysts;
in
contrast, Markovnikov isomers are formed with pyrrolyl
19–24
ligands.
As a continuation of our efforts on studying the
hydroamination of alkynes catalysed by pyrrolyl ligand-chelated
2
5–27
Preparation of [Ti(NMe ) (pmpmi)] (1)
2 2
titanium compounds,
we are exploring the syntheses and
H pmpmi (0.1732 g, 1 mmol) in THF (3 mL) was added dropwise
2
catalytic activities of titanium amido- or imido-complexes
chelated by H pmpmi [H pmpmi = (2-pyrrolylmethene)-(2-
to a solution of [Ti(NMe ) ] (0.2242 g, 1 mmol) in THF (3 mL) cooled
2
4
2
2
8–29
to –35 °C. The reaction mixture was allowed to warm to room
2
pyrrolylmethyl)imine].
H pmpmi is a tridentate, dianionic
2
pyrrolyl Schiff base ligand, that potentially forms a bisamido-
complex with [Ti(NMe ) ], and provides a straightforward
2
4
access to titanium imido- complexes.
We now describe the syntheses and structural characterisa-
tion of three titanium imido-complexes and one titanium
bisamido-complex. The catalytic activities of four complexes
towards intermolecular hydroamination of alkynes are also
reported.
Experimental
All manipulations of air-sensitive compounds were carried out in an
MBraun drybox under a purified dinitrogen atmosphere. Hexane,
toluene and THF were purchased from commercial suppliers
and dried over purple sodium benzophenone ketyl. Pyridine and
liquid primary amines were pre-dried by CaH and distilled prior
2
t
30
31
to use. [Ti(N Bu)Cl (py) ], 2-cyanopyrrole and H pmpmi were
2
2
2
prepared according to the literature procedures. Elemental analyses
C, H, N) were performed with a Carlo-Erba EA 1110 CHNO-S
(
microanalyser. Crystal structure determination was performed with
a Bruker SMART APEX II CCDC diffractometer equipped with
Fig. 1 ORTEP structural drawing of 1. Ellipsoids are drawn at
the 30% probability level, and hydrogen atoms are omitted for
clarity.
*
Correspondent. E-mail: liyahong@suda.edu.cn

2
50 JOURNAL OF CHEMICAL RESEARCH 2012
temperature and stirred for 16 h, after which time the volatiles were
removed under reduced pressure to produce a red solid. The solid was
dissolved in toluene, the precipitate filtered away, and the filtrates
were dried under reduced pressure, yielding 2 as a red solid. Yield:
0
.368 g (82%).
t
Preparation of [Ti(N Bu)(pmpmi)(dpy)] (3)
Method A: 2,2′-dipyridyl (0.164 g, 1.05 mmol) and Bu NH (1 mL)
t
2
was added to a solution of 1 (0.3072 g, 1 mmol) in THF (3 mL). The
reaction mixture was stirred for 32 h, after which time the volatiles
were removed under reduced pressure to afford a yellow solid. The
solid was washed with hexane and dried under reduced pressure.
1
Yield: 0.344 g (77%). H NMR (300 MHz, C D ): δ = 8.39 (2H,
6
6
d, 6-dpy), 7.50 (2H, s, 3-dpy), 7.33 (1H, s, CH=N), 6.94 (1H, t,
5
4
-C H N), 6.90 (2H, d, 4-dpy), 6.80 (3H, 3,5-C H N), 6.66 (1H, d,
4
3
4
3
-C H N), 6.47 (2H, t, 5-dpy), 6.28 (1H, s, 4-C H N), 4.08 (1H,
4
3
4
3
13
Fig. 2 ORTEP structural drawing of 3. Ellipsoids are drawn at
the 30% probability level, and hydrogen atoms are omitted for
clarity.
d, CH -N), 1.14 (9H, s, CH ) ppm. C NMR (75 MHz, CDCl ):
2
3
3
δ = 160.4, 154.9, 151.8, 142.1, 141.2, 140.2, 139.6, 133.1, 127.8,
122.8, 115.6, 113.4, 110.0, 101.5, 67.9, 58.6, 34.2 ppm. Anal.
Calcd for C H N Ti: C, 64.68; H, 5.77; N, 18.83. Found: C, 65.23;
24
26
6
H, 6.01; N, 18.00%.
Method B: A solution of 2,2′-dipyridyl (0.164 g, 1.05 mmol) in
t
THF (2 mL) was added dropwise to a solution of [Ti(N Bu)Cl (py) ]
2
2
(
0.3482 g, 1 mmol) in THF (3 mL). A yellow precipitate was formed.
The reaction mixture was stirred at room temperature for 8 h, after
which time the volatiles were removed under reduced pressure to
produce a yellow solid. The solid was dissolved in THF (3 mL) and
cooled to –35 °C, then a solution of Li pmpmi (1 mmol), cooled to
2
–
35 °C, was added. The reaction mixture was allowed to warm to
room temperature and stirred for 16 h, after which time the volatiles
were removed under reduced pressure to generate a yellow solid.
The solid was dissolved in toluene, the white precipitates filtered
away, and the filtrate was dried under reduced pressure, yielding 3 as
a yellow solid. Yield: 0.388 g (87%).
Preparation of [Ti(NPh)(pmpmi)(py) ] (4)
2
Method A:Aniline (0.0931 g, 1 mmol) in THF (3 mL) was added drop-
wise to a solution of 1 (0.3072 g, 1 mmol) in THF (3 mL), cooled to
Fig. 3 ORTEP structural drawing of 4. Ellipsoids are drawn at
the 30% probability level, and hydrogen atoms are omitted for
clarity.
–35 °C,. The reaction mixture was allowed to warm to room tempera-
ture and stirred for 12 h, after which time the volatiles were removed
under reduced pressure to afford a brown solid. The solid was dis-
solved in the mixture of THF (3 mL) and pyridine (1 mL). The result-
ing mixture was stirred for 6 h, after which time the volatiles were
removed under reduced pressure to provide a red solid. The solid was
temperature and stirred for 16 h, after which time the volatiles
were removed under reduced pressure to generate a red solid. Yield:
washed with hexane and dried under reduced pressure. Yield: 0.422 g
0
.289 g (94%). Red single crystals of 1 were grown from a saturated
1
(
(
(
(
(
(
1
90%). H NMR (300 MHz, CDCl ): δ = 8.10 (4H, d, 2-C H N), 7.97
3
5
5
THF solution left standing at –35 °C in a vibration-free environment.
1H, s, CH=N), 7.89 (1H, s, 5-C H N), 7.84 (1H, s, 5-C H N), 7.59
2H, t, 4-C H N ), 7.16 (4H, t, 3-C H N), 7.04 (2H, t, 3-C H N), 6.84
2H, d, 2-C H N), 6.70 (1H, t, 4-C H N), 6.60 (1H, s, 3-C H N), 6.40
1H, t, 4-C H N), 6.36 (1H, t, 4-C H N), 5.98 (1H, s, 3-C H N), 4.65
1H, s, CH ) ppm. C NMR (75 MHz, CDCl ): δ = 159.1, 152.1,
43.1, 142.4, 139.9, 139.1, 130.8, 130.4, 126.7, 126.5, 126.0, 122.1,
1
4
3
4
3
H NMR (300 MHz, CDCl ): δ = 8.12 (1H, s, CH=N), 7.29 (1H,
3
5
5
5
5
6
5
s, 5-C H N), 6.87 (2H, s, 5-C H N), 6.64 (1H, d, 3-C H N), 6.26
4
3
4
3
4
3
6
5
6
5
4
3
(
(
1H, t, 4-C H N), 6.22 (1H, t, 4-C H N), 5.98 (1H, s, 3-C H N), 5.01
4 3 4 3 4 3
4
3
4
3
4
3
13
2H, s, CH ), 3.25 (12H, s, CH ) ppm. C NMR (75 MHz, CDCl ):
13
2
3
3
2
3
δ = 161.1, 142.4, 141.9, 139.1, 127.6, 117.9, 113.9, 111.0, 101.9,
5
6.7, 46.8 ppm. Anal. Calcd for C H N Ti: C, 54.73; H, 6.89; N,
14 21 5
116.8, 113.4, 110.5, 102.4, 53.8 ppm. Anal. Calcd for C H N Ti: C,
26 24 4
2
2.80. Found: C, 54.23; H, 7.01; N, 22.52%.
6
6.67; H, 5.16; N, 17.94. Found: C, 66.31; H, 5.01; N, 17.73%.
Method B: A solution of aniline (0.0931 g, 1 mmol) in THF (2 mL)
t
Preparation of [Ti(N Bu)(pmpmi)(py) ] (2)
t
2
was added dropwise to a solution of [Ti(N Bu)Cl (py) ] (0.3482 g,
t
2
2
Method A: BuNH (10 mL) was added to a solution of (1) (0.3072 g,
mmol) in THF. The reaction mixture was heated at 55 °C for 16 h,
2
1
mmol) in THF (3 mL) cooled to –35 °C. The reaction mixture was
1
stirred at room temperature for 16 h, after which time volatiles were
removed under reduced pressure to provide a brown solid. The solid
was dissolved in THF (3 mL) and cooled to –35 °C, then a solution
after which time the volatiles were removed under reduced pressure to
produce a red oil. The oil was dissolved in a mixture of THF (3 mL)
and pyridine (1.58 g, 20 mmol). The resulting mixture was stirred
for 6 h, after which time the volatiles were removed under reduced
pressure to provide a red solid. The solid was washed with hexane,
of Li pmpmi (1 mmol), cooled to –35 °C, was added. The resulting
2
reaction mixture was allowed to warm to room temperature and stirred
for 16 h, after which time the volatiles were removed under reduced
pressure to generate a brown solid. The solid was dissolved in toluene,
the white precipitates filtered away, and the filtrate was dried under
reduced pressure, yielding 4 as a red solid. Yield: 0.197 g (42%).
1
and dried under reduced pressure. Yield: 0.399 g (89%). H NMR
(
300 MHz, CDCl ): δ = 8.03 (4H, d, 2-C H N), 7.93 (1H, s, CH=N),
3
5
5
7
7
6
0
1
6
.80 (1H, s, 5-C H N), 7.73 (1H, s, 5-C H N), 7.61 (2H, t, 4-C H N),
4 3 4 3 5 5
.17 (4H, t, 3-C H N), 6.53 (1H, d, 3-C H N), 6.40 (1H, t, 4-C H N),
.37 (1H, t, 4-C H N), 5.94 (1H, s, 3-C H N), 4.46 (2H, s, CH –N),
.90 (9H, s, CH ) ppm. C NMR (75 MHz, CDCl ): δ = 158.2, 152.4,
43.3, 142.5, 139.4, 139.1, 131.6, 126.2, 116.0, 112.9, 110.0, 102.1,
8.2, 53.5, 34.1 ppm. Anal. Calcd for C H N Ti: C, 64.29; H, 6.29;
5
5
4
3
4
3
Catalytic reactions; general procedure
4
3
4
3
2
13
The pre-catalyst (0.3 mmol), amine (4.5 mmol), alkyne (3 mmol) and
toluene (5 mL) was added to a 50 mL pressure tube in a drybox.
The pressure tube was sealed with a teflon screw cap, taken out of
the drybox and heated at 100 °C for 16 h. Then at 0 °C the reaction
3
3
2
4
28
6
N, 18.74. Found: C, 64.01; H, 6.66; N, 18.53%.
Method B: Li pmpmi (1 mmol) solution was added dropwise to
solution was carefully added to a suspension of LiAlH in toluene and
the mixture was refluxed for 3 h. After cooling the solution to 0 °C,
2
4
t
a solution of [Ti(N Bu)Cl (py) ] (0.3482 g, 1 mmol) in THF (3 mL)
2
2
cooled to –35 °C. The reaction mixture was allowed to warm to room
the excess amount of LiAlH was hydrolysed with aqueous NaOH
4

JOURNAL OF CHEMICAL RESEARCH 2012 251
–
1
(
3 mol L ). The mixture was then extracted with CH Cl (3 × 30 mL),
bond lengths reveals that the Ti–N(NMe ) bond distances in
2
2
2
and the combined organic layers were dried with MgSO and concen-
trated under vacuum. Column chromatography of the residue on silica
gel afforded the pure amine derivatives.
N-Phenylphenethylamine (7a): H NMR (300 MHz, CDCl ):
δ = 7.59–7.79 (8H, Ph), 6.89–7.00 (2H, p–Ph), 4.12 (1H, NH), 3.79
2H, PhCH ), 3.29–3.37 (2H, NHCH ) ppm. C NMR (75 MHz,
CDCl ): δ = 145.5, 138.0, 128.1, 127.8, 127.7, 125.5, 120.8, 113.0,
4.0, 34.3 ppm. MS (GC/MS of PhN=CHCH Ph, determined before
1 are relatively short, averaging 1.870(3) Å.
4
t
In the presence of pyridine and using BuNH as the solvent,
2
1
was completely converted to 2 after heating at 55 °C for
1
3
16 h. Complex 2 was also synthesised by adding Li pmpmi
2
t
to 1 equiv. of [Ti(N Bu)Cl (py) ] (Scheme 2). Unfortunately, a
2
2
13
(
1
2
2
single-crystal of 2 was not successfully cultivated. The H
3
t
NMR spectrum of 2 shows signals for a N Bu group and two
4
2–
2
pyridine molecules. The signals of the pmpmi ligand can
+
being reduced to PhNHCH CH Ph): m/z (%) = 195 (50) [M ], 104
1
13
2
2
be also observed. The solution H NMR, C NMR spectra and
elemental analysis data are fully consistent with the structure
+
+
+
(
100) [C H N=CH ], 91 (25) [C H CH ], 77 (62) [C H ].
6 5 6 5 2 6 5
1
N-4-Chlorophenylphenethylamine(7b): HNMR(300 MHz, CDCl ):
δ = 7.88–7.96 (8H, Ph), 7.37 (1H, p-Ph), 4.27 (1H, NH), 4.03 (2H,
PhCH ), 3.54 (2H, NHCH ) ppm. C NMR (75 MHz, CDCl ):
δ = 147.0, 138.3, 128.3, 127.8, 127.6, 125.4, 116.5, 112.0, 44.0, 34.4
ppm. MS (GC/MS of p-ClPhN=CHCH Ph, determined before being
reduced to p-ClPhNHCH CH Ph): m/z (%) = 229 (52) [M ], 138 (100)
3
of 2.
t
13
Addition of 2,2′-dipyridyl and BuNH
2
to a solution of 1 in
2
2
3
THF yielded 3. Complex 3 was also synthesised by adding
t
Li pmpmi to the mixture of [Ti(NBu)Cl (py) ] and 2,2′-dipyridyl
2
2
2
2
+
(Scheme 3).
2
2
+
+
+
Complex 3 was structurally characterised by single-crystal
[
ClC H N=CH ], 111 (42) [ClC H ], 91 (24) [C H CH ].
6 4 6 4 6 5 2
X-ray diffraction (Fig. 2). The titanium atom was coordinated
t
by one nitrogen atom of a N Bu group by a double bond, two
Results and discussion
Treatment of a [Ti(NMe ) ] solution with 1 equiv. of H pmpmi
nitrogen atoms from 2,2′-dipyridyl, and three nitrogen atoms
2–
2
4
2
from one pmpmi ligand. The six nitrogen atoms around the
leads to near quantitative transamination generating [Ti(NMe2)
2
titanium atom display a pseudo-octahedral geometry. The
2
–
(
pmpmi) ] (1) with loss of 2 equiv. of HNMe (Scheme 1). The
compound is readily isolated as a red solid and red single
crystals of 1 were grown at –35 °C.
2
three nitrogen atoms of the pmpmi ligand are not coplanar.
The Ti1=N6 bond distance is the shortest [1.696(3) Å]. Simi-
2
–
lar to 1, the donor amine of the pmpmi ligand exhibits the
longest Ti1–N2 bond (2.267(3) Å). The two Ti–N (dipyridyl)
bond lengths are slightly shorter than that of the donor amine
Single-crystal X-ray diffraction studies reveal that com-
plex 1 crystallises in the triclinic crystal system of the
P-1 space group. The overall structure of 1 is remarkably
close to a distorted square pyramid (Fig. 1), with one amide
nitrogen atom axial and the other four equatorial. The angles
between the equatorial nitrogen atoms add up to 343.13°.
The three nitrogen atoms of the pmpmi ligand are nearly
coplanar. As expected, the donor amine exhibits the longest
Ti1–N2 bond (2.184(3) Å). The averaged Ti–N(pyrrolyl)
bond distance is found to be 0.195 Å longer than the aver-
aged Ti–N(dimethylamide) bond length. An analysis of the
known and crystallographically determined Ti–N(NMe2)
2
–
Ti–N bond of the pmpmi ligand. The averagedTi–N(pyrrolyl)
bond length is 2.102(3) Å.
Addition of 1 equiv. of PhNH to 1 followed by adding
2
an excess of pyridine yielded 4 in 90% isolated yield.
2
–
Alternatively, treatment of Li pmpmi with a mixture of
2
t
[
(
Ti(N Bu)Cl (py) ] and aniline, produced 4 in good yield
2
2
Scheme 4).
An ORTEP structural representation derived from single-
crystal X-ray diffraction on 4 (Fig. 3) showed that the complex
is pseudo-octahedral, with the three coplanar nitrogen atoms
2–
of the pmpmi ligand facially occupying three sites. The angle
of N1–Ti1–N2 is 148.46(9). The opposite position of the
2
–
pmpmi ligand is occupied by a NPh group, and the angle of
N3–Ti1–N4 is 177.07(10), which indicates that the nitrogen
atom of the NPh group and the three nitrogen atoms of the
2
–
pmpmi ligand are nearly coplanar too. The two axial posi-
tions of the distorted octahedron were occupied by two
pyridine nitrogen atoms. As expected, the Ti–N(pyrrolyl),
Ti–N(pyrrolylmethene), Ti–N(phenyl) and Ti–N(pyridine)
bond distances in 4 are similar with those of in complex 3.
Scheme 1 Synthesis of 1.
Scheme 2 Synthesis of 2.
Scheme 3 Synthesis of 3.

2
52 JOURNAL OF CHEMICAL RESEARCH 2012
Scheme 4 Synthesis of 4.
Catalytic intermolecular hydroamination of alkynes with amines
Table 2 Selected bond lengths (Å) and angles (°) for com-
plexes 1, 3 and 4 · Tol
The successful preparation of the titanium bisamido-complex
1
and imido-complexes 2–4 prompted us to explore the cata-
1
lytic activity of 1–4 in the hydroamination of alkynes (5) by
amines (6). Initially, we investigated the reaction of aniline
with three alkynes (phenylacetylene, 3-hexyne and diphenyl-
acetylene) catalysed by 10 mol % of 1. For comparison
purpose, the catalytic reactions were carried out at 100 °C
in toluene for 24 h with a 1:1.5 molar ratio of alkyne and
aniline. Because the resulting imines were not stable to column
chromatography, the hydroamination products were directly
Ti(1)–N(1)
Ti(1)–N(3)
N(2)–C(5)
N(2)–C(6)
N(5)–Ti(1)–N(4)
N(5)–Ti(1)–N(2)
2.081(3) Ti(1)–N(2)
2.048(3) Ti(1)–N(4)
1.332(4) Ti(1)–N(5)
1.396(4)
104.88(11) N(4)–Ti(1)–N(2)
109.76(11)
2.184(3)
1.883(3)
1.857(2)
145.21(10)
3
Ti(1)–N(1)
Ti(1)–N(3)
Ti(1)–N(5)
N(2)–C(5)
N(6)–Ti(1)–N(1)
N(6)–Ti(1)–N(3)
N(1)–Ti(1)–N(2)
N(4)–Ti(1)–N(2)
2.093(3) Ti(1)–N(2)
2.110(3) Ti(1)–N(4)
2.247(3) Ti(1)–N(6)
2.267(3)
2.252(3)
1.696(3)
reduced to amines by LiAlH . The results are shown in
4
Table 3. As can be seen in Table 3, complex 1 could promote
the hydroamination of phenylacetylene and afforded the
desired amines (7 and 8) with good yield (62%; Table 3,
entry 1). No hydroamination products were determined for
1.444(5)
N(2)–C(10)
1.284(4)
104.30(12) N(6)–Ti(1)–N(4)
101.25(12) N(6)–Ti(1)–N(5)
71.29(11) N(3)–Ti(1)–N(2)
93.48(10)
93.79(11)
96.60(12)
73.68(11)
3
-hexyne and diphenylacetylene (Table 3, entries 2, 3).
The anti-Markovnikov product is the exclusive product of
hydroamination of phenylacetylene with aniline.
Then we probed the hydroamination of phenylacetylene by
two aromatic amines (aniline and p-chloroaniline) catalysed
by 1–4 (Table 3, entries 4, 6–11). All of the catalysts could
mediate the hydroamination of phenylacetylene and provided
4
· Tol
Ti(1)–N(1)
Ti(1)–N(3)
Ti(1)–N(5)
N(3)–C(5)
N(1)–Ti(1)–N(3)
N(3)–Ti(1)–N(5)
N(4)–Ti(1)–N(1)
N(4)–Ti(1)–N(5)
2.089(2) Ti(1)–N(2)
2.216(2) Ti(1)–N(4)
2.245(2) Ti(1)–N(6)
2.074(2)
1.728(2)
2.252(2)
1.388(4)
74.04(9)
82.88(8)
105.87(10)
94.20(9)
1.348(3)
74.47(9)
87.62(9)
N(3)–C(10)
N(2)–Ti(1)–N(3)
N(3)–Ti(1)–N(6)
7
a and 7b with good yields. In all cases, the anti-Markovnikov
product was favoured, often in excess of 94:6, over the
Markovnikov product.
105.67(10) N(4)–Ti(1)–N(2)
95.30(10) N(4)–Ti(1)–N(6)
Table 1 Crystallographic data and structure refinement for complexes 1, 3 and 4 · Tol
1
3
4 · Tol
Formula
Fw
Crystal system
Space group
a (Å)
b (Å)
c (Å)
C
14
H
21
N
5
Ti
C
24
H
26
N
6
Ti
33 32 6
C H N Ti
560.52
307.23
Triclinic
P-1
446.41
Orthorhombic
P b c a
17.583(4)
15.334(3)
20.516(4)
90.00
90.00
90.00
5531.4(19)
8
1.072
Monoclinic
P 2/c
13.582(3)
10.688(2)
21.733(7)
90.00
112.69(2)
90.00
2910.7(13)
4
8.9025(18)
9.6471(19)
10.725(2)
107.22(3)
94.11(3)
116.35(3)
765.9(3)
2
α (°)
β (°)
γ (°)
V (Å )
3
Z
D
–3
calcd (g cm )
1.332
1.279
F(000)
Crystal size(mm )
µ/mm
324
1872
0.40 x 0.17 x 0.09
0.328
1176
0.30 x 0.22 x 0.13
0.327
3
0.36 x 0.28 x 0.12
0.557
–1
Theta range for data collection
Limiting indices
2.05 to 25.70
–10 ≤ h ≤ 10
1.99 to 25.00
–20 ≤ h ≤ 20
–18 ≤ k ≤ 18
–24 ≤ l ≤ 22
4859/0/297
0.898
2.03 to 26.23
–15 ≤ h ≤ 16
–10 ≤ k ≤ 13
–26 ≤ l ≤ 26
5854/21/356
1.046
–
–
11 ≤ k ≤ 11
13 ≤ l ≤ 13
Data/restraints/parameters
GOF
2896/0/185
1.082
No. of total Reflns
No. of unique Reflns (Rint)
10458
23786
21527
2896 [0.0432]
0.0473, 0.1362
0.0641, 0.1477
0.679 and –0.499
4859 [0.0684]
0.0599, 0.1512
0.1039, 0.1704
0.307 and –0.261
5854 [0.0482]
0.0519, 0.1234
0.0923, 0.1421
0.650 and –0.436
1
2
R ,WR [I>2a(I)]
1
2
R ,WR [all data]
–
3
Largest diff. peak and hole(e Å )

JOURNAL OF CHEMICAL RESEARCH 2012 253
Table 3 The hydroamination of alkynes with amines catalysed by 1–4a
b
Entry
Alkyne
R3NH
2
Catalyst
Products
Isolated yield, reduction
Ratio (7)/(8)
product of (7) /%
1
2
3
4
5
6
7
Phenylacetylene
3-Hexyne
Diphenylacetylene
Phenylacetylene
Phenylacetylene
Phenylacetylene
Phenylacetylene
Phenylacetylene
Phenylacetylene
Phenylacetylene
Phenylacetylene
Aniline
1
1
1
1
1
2
2
3
3
4
4
7a, 8
–
62
nr
98/2
–
Aniline
Aniline
–
nr
–
p-Chloroaniline
tert-Butylamine
Aniline
7b, 8
7c
7a, 8
7b, 8
7a, 8
7b, 8
7a, 8
7b, 8
54
88/12
100/0
98/2
97/3
97/3
98/2
97/3
94/6
trace
57
p-Chloroaniline
Aniline
p-Chloroaniline
Aniline
59
8
9
65
63
64
54
1
1
0
1
p-Chloroaniline
a
Isolated yields of the corresponding amines. Reaction conditions: (1) alkyne (3.0 mmol), amine (4.5 mmol), 10 mol% catalyst,
toluene (5 mL), 100 °C, 20 h; (2) Reduced by LiAlH , followed by column chromatography.
4
Determined by GC–MS analyses prior to the reduction.
b
4
5
6
7
8
9
0
A.L. Odom, Dalton Trans., 2005, 225.
P.W. Roesky and T.E. Müller, Angew. Chem., Int. Ed., 2003, 42, 2708.
F. Pohlki and S. Doye, Chem. Soc. Rev., 2003, 32, 104.
T.E. Müller and M. Beller, Chem. Rev., 1998, 98, 675.
Complex 1 catalysed hydroamination of phenylacetylene
with tert-butylamine was examined and trace amount of
hydroamination product (7c) was detected (Table 3, entry 5).
H. Shen and Z. Xie, J. Am. Chem. Soc., 2010, 132, 11473.
D.L. Swartz Ii, R.J. Staples and A.L. Odom, Dalton Trans., 2011, 40, 7762.
L. Ackermann, R.G. Bergman and R.N. Loy, J. Am. Chem. Soc., 2003, 125,
Conclusions
1
1
1
1956.
G. Zi, F. Zhang, L. Xiang, Y. Chen, W. Fang and H. Song, Dalton Trans.,
010, 39, 4048.
Four titanium complexes incorporating a tridentate, dianionic
pyrrolyl ligand have been synthesised and characterised.
The catalytic activities of 1–4 towards the hydroamination of
alkynes have been studied. Complexes 1–4 were active pre-
catalysts for the hydroamination reactions of phenylacetylene
with aniline and p-chloroaniline.
CCDC-763963 (1), 792053 (3) and 763962 (4·Tol) contain
the supplementary crystallographic data for this paper. These
data can be obtained free of charge via www.ccdc.cam.ac.uk/
conts/retrieving.html (or from the Cambridge Crystallographic
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; Fax: +44
1
2
12 T. Janssen, R. Severin, M. Diekmann, M. Friedemann, D. Haase, W. Saak,
S. Doye and R. Beckhaus, Organometallics, 2010, 29, 1806.
A. Tillack, I.G. Castro, C.G. Hartung and M. Beller, Angew. Chem., Int.
Ed., 2002, 41, 2541.
1
3
14 J.A. Bexrud, C. Li and L.L. Schafer, Organometallics, 2007, 26, 6366.
15 E. Haak, I. Bytschkov and S. Doye, Angew. Chem., Int. Ed., 1999, 38, 3389.
6
7
1
1
A. Heutling, F. Pohlki and S. Doye, Chem. Eur. J., 2004, 10, 3059.
M.A. Esteruelas, A.M. Lopez, A.C. Mateo and E. Onate, Organometallics,
2
006, 25, 1448.
18 J.A. Bexrud, C. Li and L.L. Schafer, Organometallics, 2007, 26, 6366.
9
0
1
2
D.L. Swartz II and A.L. Odom, Organometallics, 2006, 25, 6125.
Y. Shi, C. Hall, J.T. Ciszewski, C. Cao and A.L. Odom, Chem. Commun.,
1
223 336-033; or deposit@ccdc.cam.ac.uk).
2
003, 586.
2
2
2
1
2
3
Y. Shi, J.T. Ciszewski and A.L. Odom, Organometallics, 2001, 20, 3967.
C. Cao, J.T. Ciszewski and A.L. Odom, Organometallics, 2001, 20, 5011.
S. Majumder and A.L. Odom, Organometallics, 2008, 27, 1174.
The authors appreciate the financial supports of Hundreds of
Talents Program of Chinese Academy of Sciences (2005012),
Natural Science Foundation of China (20872105), and ‘Qinglan
Project’ of Jiangsu Province (Bu109805).
24 C. Cao, Y. Li, Y. Shi and A.L. Odom, Chem. Commun., 2004, 10, 2002.
25 F. Zhou, M. Lin, L. Li, X. Zhang, Z. Chen, Y. Li, Y. Zhao and W. Li,
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X. Han, Y. Li, H. Wei and Y. Zhang, Chin. J. Chem., 2007, 25, 1334.
Y. Zhao, M. Lin, Z. Chen, H. Pei, Y. Li, Y. Chen, X. Wang, L. Li, Y. Cao, Y.
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N. Putochin, Ber, 1926, 59, 1987.
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Received 28 October 2011; accepted 23 February 2012
Paper 1100958 doi: 10.3184/174751912X13324293828161
Published online: 10 May 2012
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