Direct synthesis of titanium complexes with chelating cis-9, 10dihydrophenanthrenediamide ligands through sequential C-C bondforming reactions from o-metalated arylimines

Article abstract of DOI:10.1002/chem.200903017

A series of new titanium(IV) complexes with o-metalated arylimine and/or d.v-9,10-dihydrophenanthrenediamide ligands, [o-C₆H₄(CH= NR)TiCl₃] (R = 2,6-iPr₂C₆H₃ (3a), 2,6Me₂C₆H₃ (3 b), tBu (3c)), [cis-9,10PhenH₂(NR)₂TiCl₂] (PhenH₂ = 9,10-dihydrophenanthrene; R = 2,6-iPr₂C₆H₃ (4a), 2,6-Me₂C₆H₃ (4b), tBu (4c)), [{m-9,10-PhenH₂(NR)₂|{o-C₆H₄(HC= NR))TiCl] (R = 2,6-iPr₂C₆H₃ (5a), 2,6Me ₂C₆H₃ (5b), tBu (5c)), have been synthesised from the reactions of TiCl₄ with o-C₆H₄(CH=NR) Li (R = 2,6iPr₂C₆H₃, 2,6-Me₂C ₆H₃, tBu). Complexes 4 and 5 were formed unexpectedly from the reactions of TiCl₄ with two or three equivalents of the corresponding o-C₆H₄(CH=NR)Li followed by sequential intramolecular C-C bond-forming reductive elimination and oxidative coupling reactions. Attempts to isolate the intermediates, [{oC₆H ₄(CH=NR)]₂TiCl₂] (2), were unsuccessful. All complexes were characterised by ¹H and ¹³C NMR spectroscopy, and the molecular structures of 3 a, 4ac, 5a, and 5c were determined by Xray crystallography.

Full text of DOI:10.1002/chem.200903017

DOI: 10.1002/chem.200903017
Direct Synthesis of Titanium Complexes with Chelating cis-9,10-
À
Dihydrophenanthrenediamide Ligands through Sequential C C Bond-
Forming Reactions from o-Metalated Arylimines
Dapeng Zhao, Wei Gao, Ying Mu,* and Ling Ye[a]
À
Abstract: A series of new titanium(IV)
complexes with o-metalated arylimine
and/or cis-9,10-dihydrophenanthrene-
synthesised from the reactions of TiCl4
with o-C6H4A(CH=NR)Li (R=2,6-
iPr2C6H3, 2,6-Me2C6H3, tBu). Com-
plexes 4 and 5 were formed unexpect-
edly from the reactions of TiCl4 with
two or three equivalents of the corre-
by sequential intramolecular C C
G
bond-forming reductive elimination
and oxidative coupling reactions. At-
tempts to isolate the intermediates, [{o-
diamide
ligands,
[o-C6H4ACTHNGUTERNNU(G CH=
NR)TiCl3] (R=2,6-iPr2C6H3 (3a), 2,6-
Me2C6H3 (3b), tBu (3c)), [cis-9,10-
PhenH2(NR)2TiCl2] (PhenH2 =9,10-di-
hydrophenanthrene; R=2,6-iPr2C6H3
(4a), 2,6-Me2C6H3 (4b), tBu (4c)),
[{cis-9,10-PhenH2(NR)2}ACHTNUGTRENNUG{o-C6H4ACHUTNGTREN(NUGN HC=
NR)}TiCl] (R=2,6-iPr2C6H3 (5a), 2,6-
Me2C6H3 (5b), tBu (5c)), have been
C6H4ACHTUGNTERNNU(G CH=NR)}2TiCl2] (2), were unsuc-
cessful. All complexes were character-
1
sponding o-C6H
N
ised by H and 13C NMR spectroscopy,
and the molecular structures of 3a, 4a–
c, 5a, and 5c were determined by X-
ray crystallography.
À
Keywords: C C coupling
amines · domino reactions · synthet-
ic methods · titanium
·
di-
Introduction
through the reductive elimination process, although the cou-
pling of alkyl, acyl, and 1-alkenyl groups is the most com-
À
Carbon–carbon bond-forming reactions have been one of
the most active research areas in organic and organometallic
chemistry.[1] In particular, transition-metal-mediated carbon–
carbon bond-forming reactions have been studied extensive-
ly for construction of the basic carbon backbone of small or-
ganic molecules and extended polymeric structures.[2] Mech-
anistic studies of such reactions indicate that the stoichio-
monly observed C C bond-forming reductive elimination
involving Group 4 metal complexes.[5] Very few examples of
aryl–aryl bond-forming reductive eliminations mediated by
Group 4 metals have been reported so far,[6] although the
analogous process is well documented for Group 10
metals.[7] Yet the oxidative coupling of unsaturated organic
compounds to low-valent Group 4 metals is an efficient
pathway for construction of carbon–carbon bonds.[8] In oxi-
dative coupling reactions, the compounds of low-valent
Group 4 metals such as TiII or ZrII are usually generated by
treatment of TiIV or ZrIV complexes with Grignard or orga-
nolithium reagents, followed by a reductive elimination pro-
cess.[9] In principle, both the reductive elimination and oxi-
dative coupling processes can be used to construct carbon–
carbon bonds. However, there are no examples of formation
À
metric and catalytic C C bond-forming reactions mediated
by mid- and late-transition metals can follow several path-
ways, such as reductive elimination, oxidative coupling, mi-
gratory insertion, and s-bond or p-bond metathesis,[3]
whereas reactions mediated by Group 4 metals go mainly
through the migratory insertion pathway, which does not re-
quire redox changes at the metal centre such as those that
happen in Ziegler–Natta polymerisation reactions.[4] The
À
À
Group 4 metals also mediate C C bond-forming reactions
of two C C bonds in one molecule by means of the sequen-
tial reductive elimination and oxidative coupling reactions.
Recently, in an attempt to synthesise [{o-C6H4ACHTUNGTRENNUNG(CH=
NR)}2TiCl2] complexes as potential olefin polymerisation
catalysts, some new titanium complexes with a cis-9,10-dihy-
drophenanthrenediamide ligand were obtained in high
yields. Clearly the latter complexes are produced through
[a] Dr. D. Zhao, Dr. W. Gao, Prof. Y. Mu, L. Ye
State Key Laboratory of Supramolecular Structure and Materials
School of Chemistry, Jilin University
Chang Chun 130012 (China)
À
sequential C C bond-forming reductive elimination and oxi-
Fax : (+86)431-85193421
E-mail: ymu@jlu.edu.cn
dative coupling from the originally formed [{o-C6H
4A
4394
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Chem. Eur. J. 2010, 16, 4394 – 4401

FULL PAPER
NR)}2TiCl2]. To the best of our knowledge, this is the first
À
time that such a sequential C C bond-forming process has
Reaction of TiCl4 with o-C6H4ACHTNGUETRNNU(G CH=NR)Li: Reactions of the
been used to synthesise complexes of this type. The new
chemistry may supply a simple and efficient method of syn-
thesizing complexes with various diamide ligands directly
from easily obtained imine compounds. The rare titanium-
mediated aryl–aryl bond-forming reductive elimination in-
volved in the process makes this chemistry especially inter-
esting.
o-bromoimine compounds 1a–c with nBuLi (1 equiv) in
hexane resulted in formation of the corresponding o-lithiat-
ed imine derivatives.[11] The reactions were carried out at
08C to minimise the formation of by-products, as the lithia-
tion reactions are usually rapid and exothermic. The prod-
ucts were isolated in high yields as air- and moisture-sensi-
tive precipitates, which were washed with hexanes to
remove residual nBuLi. In toluene, the o-lithiated imine de-
rivative from 1b has good solubility whereas those from 1a
and 1c are sparingly soluble. Reactions of these derivatives
with TiCl4 were studied in detail (Scheme 1): TiCl4 with one
equivalent of any of the o-lithiated imine reagents in tolu-
ene gives the corresponding complex 3 in high yields (ca.
85%). However, attempts to synthesise complexes 2 by the
reactions of TiCl4 with two equivalents of a corresponding
o-lithiated imine reagent were unsuccessful. Surprisingly,
when reactions were investigated in different solvents, such
as toluene, diethyl ether, and THF, at different tempera-
tures, unexpected complexes 4 with a cis-9,10-dihydrophe-
nanthrenediamide ligand were always isolated instead of 2.
To our knowledge, no similar chemistry has been reported
for Group 4 metals. TiIV and ZrIV complexes with two o-
metalated acetophenone imine ligands (see Scheme 2) simi-
Herein we report the synthesis of the new titanium(IV)
complexes with o-metalated arylimine and/or cis-9,10-dihy-
drophenanthrenediamide ligands, [o-C6H
(R=2,6-iPr2C6H3 (3a), 2,6-Me2C6H3 (3b), tBu (3c)), [cis-
9,10-PhenH2(NR)2TiCl2] (PhenH2 =9,10-dihydrophenan-
threne; R=2,6-iPr2C6H3 (4a), 2,6-Me2C6H3 (4b), tBu (4c)),
[{cis-9,10-PhenH2(NR)2}{o-C6H4A(CH=NR)}TiCl] (R=2,6-
iPr2C6H3 (5a), 2,6-Me2C6H3 (5b), tBu (5c)), and the at-
tempted synthesis of intermediate complexes [{o-C6H4A(CH=
NR)}2TiCl2] (2) from the reaction of TiCl4 with o-C6H4Li-
(CH=NR) (R=2,6-iPr2C6H3, 2,6-Me2C6H3, tBu), as well as
4ACHTUNGTRENUN(NG CH=NR)TiCl3]
G
CHTUNGTRENNUNG
CTHUNGTRENNUNG
ACHTUNGTRENNUNG
their spectroscopic characterisation and crystal structure
analysis of complexes 3a, 4a–c, 5a, and 5c.
Results and Discussion
Synthesis of imine compounds: The imine compounds o-
C6H4ACHTUNGTRENNUNG(CH=NR)Br (1a–c) were prepared according to a liter-
ature procedure[10] in high yields by condensation of o-bro-
mobenzaldehyde with the corresponding amine (1 equiv) in
hexane (Scheme 1). Compound 1a was isolated as yellow
crystals, whereas 1b and 1c were obtained as pale yellow
oils. These compounds are soluble in most common organic
solvents. Compounds 1a–c were characterised by 1H and
13C NMR spectroscopy and elemental analysis. Their
1H NMR spectra exhibit resonances in the region of d=
8.58–8.64 ppm for the CH=N imine protons, with the corre-
sponding 13C NMR resonances occurring in the range d=
154.5–162.0 ppm.
Scheme 2. TiIV and ZrIV complexes with two o-metalated acetophenone
imine ligands similar to 2.
lar to 2 were reported recently.[12] These complexes were
found to be stable even when heated to 608C in solution
and no reductive elimination
À
or oxidative coupling C C
bond-forming process was ob-
served. Why complexes
2
could not be isolated from our
reaction system is not very
clear. It is possible that the less
bulky ligands used in our reac-
tion system facilitate the re-
ductive elimination and oxida-
À
tive coupling C C bond-form-
ing processes. It was found that
the synthetic yields of com-
plexes 4a–c (50–70%) depend
on reaction conditions and the
solvent system, and the yield
for a specific complex decreas-
es with the solvent in the order
Scheme 1. Synthesis of complexes 1, 3, 4, and 5.
Chem. Eur. J. 2010, 16, 4394 – 4401
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4395

Y. Mu et al.
À
toluene>diethyl ether>THF. To examine if the initial C C
coupling reaction is caused by light, the reactions were also
lengths of 2.231 ꢁ in 4a and 2.276 ꢁ in 4c are comparable
to those reported for related titanium chloride complex-
es.[15,2b] The terminal Ti Cl bond length (2.277 (2) ꢁ) in 4b
À
tested in the dark; complexes 4 were obtained in similar
yields, indicating that the C C coupling process is not a pho-
À
À
is similar to those in 4a and 4c, whereas the bridged Ti Cl
tochemical reaction. From reactions at molar ratio TiCl4/o-
lithiated imine=1:3, complexes 5a and 5c were isolated in
high yields (>85%), but 5b could be obtained only in low
yields as an oily crude product. Attempts to synthesise tita-
nium complexes with two 9,10-dihydrophenanthrenediamide
ligands by treating TiCl4 with four or more equivalents of an
o-lithiated imine reagent were not successful, and complexes
5 were always obtained. Complexes 5 could also be formed
in the reactions of TiCl4 with two equivalents of an o-lithiat-
ed imine if the reaction conditions (temperature and con-
centration) were not properly controlled. Crystallographic
analysis of complexes 4a–c, 5a, and 5c indicates that the
9,10-dihydrophenanthrenediamide ligands in these com-
plexes are all in a cis configuration.
bond lengths (2.3946(16) and 2.6059(16) ꢁ) in 4b are much
longer than normal ones. Because of the dimeric structure
of 4b, the bond angles of N1-Ti-N2 in 4a (88.08(19)8) and
4c (90.21(9)8) are larger than that (85.60(17)8) in 4b. For
the same reason, the Cl1-Ti-Cl2 bond angles in 4a
(108.56(9)8) and 4c (113.55(4)8) are also quite different
from those in 4b (78.11 (5), 86.37 (6), and 127.67(7)8). The
N1-C1-C14-N2 torsion angle in 4c (50.4(2)8) is clearly larger
than the corresponding ones in 4a (36.3(5)8) and 4b
(39.66(2)8). Similarly, the C2-C7-C8-C13 torsion angle in 4c
(23.0 (4)8) is also larger than those in 4a (20.1(9)8) and 4b
(18.25(4)8). These results reveal that the two tBu groups in
4c impose a greater effect on forcing the molecule to twist
than the 2,6-diisopropylphenyl and 2,6-dimethylphenyl
1
Complexes 3, 4 and 5 are all soluble in toluene, CH2Cl2,
and THF, but less soluble in petroleum ether and hexanes.
Complexes 3 are air- and moisture-sensitive in both the
solid state and solution, whereas complexes 4 and 5 show
relatively good stability to air and moisture, and can be ex-
posed to air for several hours without obvious decomposi-
tion. Complexes 3, 4 and 5 show good thermal stability in
solution and can be heated in boiling toluene for hours with-
out decomposition. Complexes 3, 4, and 5 were all charac-
groups in 4a and 4b. These torsion-angle data agree with H
and 13C NMR analyses of these complexes, indicating that
the bulky tBu groups in 4c block the transformation be-
tween two different conformations in solution.
In complexes 5a and 5c the metal centre is five-coordi-
nate, adopting a distorted square pyramidal geometry. The
À
average Ti NACTHUNTGRNEUNG(amide) bond lengths (1.900 ꢁ in 5a and
1.906 ꢁ in 5c) are in the normal range found in other titani-
um complexes with a diamide ligand.[2b,15] The Ti N
bond lengths (2.447(3) ꢁ in 5a and 2.3806(17) ꢁ in 5c) are
(imine)
À
1
terised by elemental analysis and H and 13C NMR spectros-
copy, and satisfactory analytical results were obtained.
close to those in related titanium complexes with imine li-
gands reported in the literature.[14b] The Ti Cl bond lengths
À
À
(2.3218(13) ꢁ in 5a and 2.3682(8) ꢁ in 5c) and Ti C bond
Crystal structures: Crystals of 3a, 4a–c, 5a, and 5c suitable
for X-ray crystal structure determination were grown from
CH2Cl2/n-hexane at room temperature. The ORTEP draw-
ings of their molecular structures are shown in Figure 1, and
selected bond lengths and angles are given in Table 1. The
X-ray diffraction analysis reveals that the solid-state struc-
ture of 3a has a Cs symmetry and adopts a distorted trigonal
bipyramidal geometry around the metal centre with two
chlorine atoms and one carbon atom on the equator and the
other chlorine atom and the nitrogen atom in the apical po-
lengths (2.178 (4) ꢁ in 5a and 2.144 (2) ꢁ in 5c) are compa-
rable to those reported for related titanium complexes, and
longer than the corresponding ones in 3a and 4a–c. As dis-
cussed above for 4a and 4c, the torsion angles of N1-C1-
C14-N2 (53.88(2)8) and C2-C7-C8-C13 (23.41(4)8) in 5c are
clearly larger than the corresponding ones in 5a (27.9(4)8
and 18.6(6)8) due to the relatively large steric effect of tBu
groups in 5c.
À
sitions (Figure 1a; Table 1). The average Ti Cl bond length
NMR analysis of complexes: All new complexes were char-
acterised by 1H and 13C NMR spectroscopy; for selected
NMR data, see Table 3. For complexes 3a–c, the resonances
(2.214 ꢁ) is close to those reported in the literature.[13,2b]
À
À
The Ti C (2.109(2) ꢁ) and Ti NACTHNUTRGENUGN(imine) bond lengths (2.255
(18) ꢁ) are comparable to those reported for related titani-
1
for the CH=N protons (d=8.28–8.40 ppm) in the H NMR
um complexes.[14]
spectra shift 0.23–0.31 ppm toward high field compared to
their corresponding signals in free imine compounds, while
the resonances (d=169.5–179.0 ppm) for the CH=N carbon
atoms in the 13C NMR spectra shift to low field compared
with their corresponding signals in free imine compounds.[16]
Resonances for other protons and carbon atoms are in
normal positions. Complexes 4a–c could be identified readi-
In the molecular structures of 4a and 4c, the titanium
atom is four-coordinate and the geometry around it can be
described as a distorted tetrahedron. Complex 4b exists in a
dimeric form in the solid state, in which titanium atom is
five-coordinate and adopts a distorted trigonal bipyramidal
À
geometry. The average Ti N bond lengths (1.853 ꢁ in 4a,
1.888 ꢁ in 4b, and 1.861 ꢁ in 4c) are all in normal range
1
ly by H and 13C NMR spectroscopy. A sharp singlet was ob-
1
found in other titanium complexes with a diamide li-
served at d=6.18 and 6.39 ppm in the H NMR spectra of
gand.[15,2b] The Ti N bond lengths in 4b are longer than
complexes 4a and 4b, respectively, which is representative
À
À
À
those in 4a and 4c because the dimeric structure of 4b
makes the molecule more crowded. The average Ti Cl bond
of the CHN protons in the 9,10-dihydrophenanthrene
À
À
À
ring. The corresponding CHN carbon resonances were
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Chem. Eur. J. 2010, 16, 4394 – 4401

Synthesis of Titanium Complexes
FULL PAPER
Figure 1. Perspective view of complexes 3a (a), 4a (b), 4b (c), 4c (d), 5a (e), and 5c (f) with thermal ellipsoids drawn at 30% probability level. Hydro-
gen atoms are omitted for clarity. See Table 2 for a summary of the crystallographic data.
observed at d=72.6 and 71.5 ppm in their 13C NMR spectra.
Two sets of doublets (at d=4.95 and 6.05 ppm) in the
1H NMR spectrum of complex 4c and two resonances (at
d=66.1 and 68.9 ppm) in its 13C NMR spectrum were ob-
served, indicating that the two CHN groups in the 9,10-
dihydrophenanthrene ring of 4c are inequivalent, probably
because the bulky tBu groups at the N atoms block the con-
formation transformation of the six-membered ring. Com-
À
À
Chem. Eur. J. 2010, 16, 4394 – 4401
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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4397

Y. Mu et al.
Table 1. Selected bond lengths [ꢁ] and angles [8] for 3a, 4a–c, 5a, and 5c.
3a
4a
4b
4c
5a
5c
À
Ti Cl
À
Ti C
2.203(9)–2.233(8)
2.109(2)
2.255(18) (imine)
2.228(2)–2.233(2)
–
1.842(4),
2.277(2)–2.6059(16)
–
1.875(4),
2.2762(9)
–
1.852(2),
1.870(2) (amide)
2.3218(13)
2.178(4)
1.882(3),
1.919(3) (amide);
2.447(3) (imine)
83.33(15)–157.10(13)
–
27.9(4)
18.6(6)
29.7(4)
2.3682(8)
2.144(2)
À
Ti N
1.8963(16),
1.9168(16) (amide);
2.3806(17) (imine)
88.68(7)–164.74(6)
–
48.27(4)
23.41(4)
53.88(2)
1.864(4) (amide)
1.901(4) (amide)
N-Ti-N
Cl-Ti-Cl
N-C-C-N
C2-C7-C8-C13
C2-C1-C14-C13
–
88.08(19)
108.56(9)
36.3(5)
20.1(9)
40.1(6)
85.60(17)
78.11(5)–127.67(7)
39.66(2)
18.25(4)
44.33(2)
90.21(9)
113.55(4)
50.4(2)
23.0(4)
56.2(3)
90.37(7)–118.94(4)
–
–
–
Table 2. Summary of crystallographic data for complexes 3a, 4a–c, 5a and 5c.
3a
4a
4b
4c
5a
5c
formula
Fw
crystal system
space group
a [ꢁ]
b [ꢁ]
c [ꢁ]
a [8]
b [8]
C19H22Cl3NTi
418.63
monoclinic
P21/n
9.6194(8)
14.0367(11)
15.6617(12)
90
99.2860(10)
90
2087.0(3)
4
0.795
0.0160
1.041
C38H38Cl2N2Ti·0.5C5H12
C33H35Cl2N2Ti
578.43
C22H28Cl2N2Ti
439.24
C57H66ClN3Ti·0.5CH2Cl2
C33H42ClN3Ti
564.05
monoclinic
Cc
10.532(3)
19.111(5)
15.133(4)
90
96.254(4)
90
3027.8(15)
4
683.63
monoclinic
C2/c
19.139(6)
17.273(6)
23.121(5)
90
91.48(3)
90
7641(4)
8
0.392
0.1227
1.016
0.1005
0.2299
918.94
monoclinic
Cc
13.075(4)
20.681(7)
19.572(5)
90
97.583(11)
90
5246(3)
4
0.303
0.0415
1.027
0.0734
0.2008
triclinic
triclinic
¯
¯
P1
P1
10.287(2)
12.568(3)
13.028(3)
68.23(3)
82.22(3)
83.11(3)
1545.4(5)
2
0.473
0.0633
1.089
0.1030
8.3734(7)
10.2708(9)
13.9754(12)
99.8470(10)
101.9480(10)
105.4350(10)
1100.39(16)
2
g [8]
V [ꢁ3]
Z
m [mmÀ1
Rint
]
0.641
0.0178
1.030
0.0617
0.397
0.0148
1.059
0.0295
0.0728
GOOF
R1
wR2
0.0431
0.1163
0.2869
0.1166
1
Table 3. Selected H NMR data for complexes 3a–c, 4a–c, and 5a–c.[a]
3a
3b
3c
4a
4b
4c
5a
5b
8.43
5c
À
À
CH=N
8.28
8.40
8.37
–
–
–
7.92
G
R
G
G
ACHTUNGTRENNUNG
3
3
À
CHN
À
6.18
6.39
4.95 (d, J=
4.68 (d, J=
G
E
3.9 Hz, 1H);
A
4.2 Hz, 1H);
6.53 (d, J=
3
3
6.05 (d, J=
3.9 Hz, 1H)
1.09 (s, 9H);
1.61 (s, 9H)
4.2 Hz, 1H)
1.17
ACHTUNGTRENNUNG(s, 9H);
3
3
3
À
CH3
1.12 (d, J=
2.58
(s, 6H)
1.67
(s, 9H)
1.11 (d, J=
0.44 (d, J=6.6 Hz, 6H);
2.19
(s, 12H);
2.60
3
6.6 Hz, 6H);
G
N
6.6 Hz, 12H);
N
0.52 (d, J=6.6 Hz, 6H);
R
3
3
3
1.34 (d, J=
1.20 (d, J=
0.70 (d, J=6.6 Hz, 6H);
1.43
1.75
3
6.6 Hz, 6H)
6.6 Hz, 12H)
0.90 (d, J=6.6 Hz, 6H);
E
N
3
1.28 (d, J=6.6 Hz, 6H);
3
1.50 (d, J=6.6 Hz, 6H)
ACHTUNGTRENNUNG
3
3
3.29 (sept, 3J=
6.6 Hz, 4H)
–
–
2.27 (sept, J=6.6 Hz, 2H);
3.37 (sept, J=6.6 Hz, 2H);
3.65 (sept, J=6.6 Hz, 2H)
À
CH
(CH3)2 3.52 (sept, J=
–
–
3
6.6 Hz, 2H)
3
[a] d values in ppm referred to TMS; measurements were carried out at room temperature.
1
plexes 5a and 5c could also be readily identified by H and
0.12 ppm toward high field compared to the corresponding
signal in complex 4a. The resonances for the CH=N and
13C NMR spectroscopy. The presence of resonances for both
À
À
À
À
the CHN protons and the CH=N protons in their
1H NMR spectra confirms the structures of 5a and 5c.[17]
The resonance for the CH=N proton in complex 5a (d=
7.92 ppm) shifts 0.36 ppm toward high field compared to the
corresponding signal in complex 3a, while the resonance for
CHN carbon atoms in complexes 5a all shift toward high
field compared to the corresponding signals in complexes 3a
and 4a. As observed for complex 4c, two sets of doublets
À
À
(d=4.68 and 6.53 ppm) were observed for the CHN pro-
tons in complex 5c for the same reason. For complexes 3a,
4a and 5a, two sets of doublets were observed for the two
À
À
the CHN protons in complex 5a (d=6.06 ppm) shifts
4398
www.chemeurj.org
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 4394 – 4401

Synthesis of Titanium Complexes
FULL PAPER
methyl groups in the isopropyl unit, indicating that the rota-
tion about the N-aryl bond is blocked in these complexes,
which results in inequivalence of the two methyl groups.
have the two imine carbon atoms close to each other[19] and
the oxidative coupling reaction can therefore take place
easily to form the cis-diamide ligands. The cis selectivity of
this reaction system may also be related to the smaller
atomic radius of titanium, as trans-diamide ligands were ob-
tained in similar imine oxidative couplings mediated by sa-
marium reagents.[20]
Mechanistic aspects of the coupling reactions: As mentioned
above, complexes 4 were always obtained instead of 2 from
the reactions of TiCl4 with two equivalents of the corre-
sponding o-lithiated imine reagents. On the basis of the
known chemistry and the structure of complexes 4, it can
reasonably be speculated that the complexes 2 must be
formed first in these reactions and then converted to com-
Conclusions
À
plexes 4 in situ through the sequential C C bond-forming
reductive elimination and oxidative coupling reactions
In attempts to synthesise the titanium complexes [{o-C6H4-
ACHTUNGTERN(UNGN CH=NR)}2TiCl2] (2), chelating cis-9,10-dihydrophenanthre-
nediamide complexes of titanium (4 and 5) have been ob-
tained by the reactions of
shown in Scheme 3. Although the TiIV complexes 2 were not
TiCl4 with two or three equiva-
lents of the corresponding o-
C6H4ACTHNUTRGNE(NUG CH=NR)Li, followed by
À
sequential intramolecular C C
bond-forming reductive elimi-
nation and oxidative coupling.
Attempts to isolate the inter-
mediates 2 were unsuccessful.
No trans-9,10-dihydrophenan-
threnediamide complex has
been obtained from these reac-
tions. The synthetic yields of
Scheme 3. The proposed mechanism for the formation of 4. RE =reductive elimination, OC=oxidative cou-
pling.
isolated from our reactions, probably because of their low
stability, similar TiIV and ZrIV complexes with two o-metalat-
ed acetophenone imine ligands (Scheme 2) have been ob-
tained previously from the reaction of TiCl4 or ZrCl4 with
two equivalents of bulky o-lithiated acetophenone imine
ligand, and the crystal structure of the ZrIV complex has
been determined.[12] Only a few examples of the TiIV-mediat-
ed aryl–aryl bond-forming reductive elimination have been
reported so far.[6,18] One is the formation of biphenyl and
[(C6H5)2TiII] from [(C6H5)4Ti].[18] Another related example is
the formation of [Cp2TiII(2,2’-biquinoline)] from [Cp2TiIV(2-
quinoline)2] (Cp=cyclopentadienyl).[6b] Attempts to isolate
the TiII intermediates from our reactions by lowering the re-
action temperature or adding an additional ligand, such as
pyridine, to the reaction system to stabilise the intermedi-
ates have been unsuccessful so far. Since the titanium(II) in-
termediates are coordinately unsaturated species with a
strong tendency to lose two electrons, the two imine groups
in these TiII intermediates would coordinate to the TiII atom
and undergo oxidative coupling immediately to form the
complexes 4 as shown in Scheme 3. The TiII- and ZrII-medi-
complexes 4 were found to change in the order 4a>4c>
4b. The cis configurations of complexes 4a–c, 5a and 5c
were confirmed by X-ray crystallographic analysis. H and
1
13C NMR spectroscopic analysis revealed asymmetric struc-
tures for complexes 4c and 5c in solution, probably because
the bulky tBu groups at the N atoms block the transforma-
tion between different conformations. A possible reaction
mechanism was proposed, based on the structures of com-
plexes 4 and 5.
Experimental Section
General: All manipulations of air- and water-sensitive compounds were
performed under an inert atmosphere of nitrogen by using standard
Schlenk-line or glove-box techniques. Solvents were dried and purified
by known procedures and distilled under nitrogen before use. nBuLi and
TiCl4 were purchased from Aldrich and used as received without further
purification. 1H and 13C NMR spectra were measured on either a Varian
Mercury-300 or a Bruker Avance-500 NMR spectrometer. Elemental
analysis was performed on a Perkin-Elmer 2400 analyzer.
Synthesis of o-C6H4(CH=NC6H3iPr2-2,6)Br (1a): A mixture of o-bromo-
benzaldehyde (8.71 g, 47.1 mmol), 2,6-diisopropylaniline (8.9 mL,
47.1 mmol) and MgSO4 (1.0 g) in n-hexane (30 mL) was stirred for 2 h.
The mixture was filtered and the filtrate was evaporated to dryness in
vacuo to give the crude product as a yellow solid. Pure product (13.8 g,
40.1 mmol, 85%) was obtained as yellowish-green crystals by recrystalli-
sation from ethanol at À208C. 1H NMR (300 MHz, CDCl3, 258C, TMS):
À
ated C C bond-forming reactions of alkenes, alkynes, car-
bonyls, and imines have been well documented.[17a,19] From
the proposed mechanism shown in Scheme 3, 9,10-dihydro-
phenanthrenediamide ligands with both cis and trans config-
À
urations may be formed in the oxidative coupling C C
d=1.20 (d, 3J
6.9 Hz, 2H; CHACHTUNGTRENNUNG
G
(CH3)2), 2.98 (sept, 3J
ACHUTGTNRNEUNG ACHTUNGTRENNUNG(H,H)=
bond-forming step. However, only the titanium complexes
with cis-9,10-dihydrophenanthrenediamide ligands have
been obtained so far. It is possible that only the intermedi-
ate with the two imine bonds in a coplanar position can
À
À
À
À
À
7.45 (t, 1H; Ph H), 7.65 (d, 1H; Ph H), 8.29 (d, 1H; Ph H), 8.59 ppm
(s, 1H; CH=NAr); 13C NMR (300 MHz, CDCl3, 258C, TMS): d=23.5-
ACHUTNGRENU(NG CH3),27.9 (CHCAHUTNGTREN(NGUN CH3)2), 123.1,124.4,125.7, 127.7, 128.8, 132.3, 133.1,
Chem. Eur. J. 2010, 16, 4394 – 4401
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4399

Y. Mu et al.
134.6, 137.5, 148.9, 161.3 ppm (CH=NAr); elemental analysis calcd (%)
for C19H22NBr: C 66.28, H 6.44, N 4.07; found: C 66.17, H 6.49, N 4.11.
(521 mg, 0.79 mmol, 68%), m.p. 207–2098C; 1H NMR (300 MHz, CDCl3,
3
3
258C, TMS): d=1.11 (d, JAHTCGNUTREN(NUGN H,H)=6.6 Hz, 12H; CH3), 1.20 (d, JACHTUNGTRENNUNG
6.6 Hz, 12H; CH3), 3.29 (sept, 3J
ACTHNUGTRENN(UNG H,H)=6.6 Hz, 4H; CHACTHUNGTRENNNUG
Synthesis of o-C6H4(CH=NC6H3Me2-2,6)Br (1b): Compound 1b was pre-
pared in the same manner as 1a with 2,6-dimethylaniline (5.8 mL,
47.1 mmol) as starting material. Pure product (11.5 g, 39.9 mmol, 79%)
was obtained as a yellowish oil by distillation under reduced pressure at
82–838C/10 mmHg. 1H NMR (300 MHz, CDCl3, 258C, TMS): d=2.18 (s,
À
À
2H; CHN), 6.88 (d, 2H; Ph H), 7.00–7.40 (m, 10H; Ph H), 7.85 ppm (d,
2H; Ph H); 13C NMR (300 MHz, CDCl3, 258C, TMS): d=25.0 (CH3),
À
27.0 (CH3), 29.4 (CH
(CH3)2), 72.6 (CHN), 123.8, 124.9, 125.1, 127.3,
128.5, 129.3, 129.4, 132.3, 134.7, 140.4 ppm; elemental analysis calcd (%)
for C38H44N2Cl2Ti: C 70.48, H 6.85, N 4.33; found: C 70.45, H 6.83, N
4.31.
À
À
6H; CH3), 6.96–7.11 (m, 3H; Ph H), 7.37(t, 1H; Ph H), 7.45 (t, 1H;
À
À
À
Ph H), 7.64 (d, 1H; Ph H), 8.28 (d, 1H; Ph H), 8.63 ppm (s, 1H; CH=
NAr); 13C NMR (300 MHz, CDCl3, 258C, TMS): d=18.5
AHCTUNGTRENNUNG
Synthesis of [{cis-9,10-(NC6H3Me2-2,6)2-9,10-dihydrophenanthrene}TiCl2]
(4b): Complex 4b was synthesised in the same manner as 3a with 1b
(630 mg, 2.2 mmol), nBuLi (2.2 mmol) and TiCl4 (209 mg, 1.0 mmol) as
starting materials or reagents. Pure 4b was obtained as red crystals
(273 mg, 0.54 mmol, 54%), m.p. 190–1918C; 1H NMR (300 MHz, CDCl3,
125.8, 127.0, 127.8, 128.3, 128.8, 132.4, 133.2, 134.8, 151.0, 162.0 ppm
(CH=NAr); elemental analysis calcd (%) for C15H14NBr: C 62.52, H
4.90, N 4.86; found: C 62.54, H 4.93, N 4.82.
Synthesis of o-C6H4ACHTUNGTRENNUNG(CH=NtBu)Br (1c): Compound 1c was prepared in
À
258C, TMS): d=2.42 (s, 12H; CH3), 6.39 (s, 2H; CHN), 6.84 (d, 2H; Ph
the same manner as 1a with tert-butylaniline (5.9 mL, 56.5 mmol) as
starting material. Pure product (11.1 g, 46.2 mmol, 89%) was obtained as
a light yellow oil by distillation under reduced pressure at 54–558C/
10 mmHg. 1H NMR (300 MHz, CDCl3, 258C, TMS): d=1.31 (s, 9H; C-
H), 7.00–7.40 (m, 10H; Ph H), 7.85 ppm (d, 2H; Ph H); 13C NMR
(300 MHz, CDCl3, 258C, TMS): d=19.9 (CH3), 71.5 (CHN), 123.3, 127.7,
128.3, 128.9, 129.2, 129.3, 129.5, 131.0, 132.3, 134.7 ppm; elemental analy-
sis calcd (%) for C30H28N2Cl2Ti : C 67.31, H 5.27, N 5.23; found: C 67.30,
H 5.26, N 5.21.
À
À
À
À
À
ACHTUNGTRENNUNG(CH3)3), 7.20 (t, 1H; Ph H), 7.30 (t, 1H; Ph H), 7.52 (d, 1H; Ph H),
7.99 (d, 1H; Ph H), 8.60 ppm (s, 1H; CH=NAr); 13C NMR (300 MHz,
À
CDCl3, 258C, TMS): d=29.6 (CH3), 57.9 (C
(CH3)3), 125.0, 127.4, 128.5,
Synthesis of [{cis-9,10-(NtBu)2-9,10-dihydrophenanthrene}TiCl2] (4c).
Complex 4c was synthesised in the same manner as 3a with 1c (530 g,
2.2 mmol), nBuLi (2.2 mmol), and TiCl4 (209 mg, 1.1 mmol) as starting
materials or reagents. Pure 4c was obtained as red crystals (334 mg,
131.2, 132.6, 135.3, 154.5 ppm (CH=NAr); elemental analysis calcd (%)
for C11H14NBr: C 55.0, H 5.88, N 5.83; found: C 55.1, H 5.86, N 5.84.
Synthesis of [{o-C6H4(CH=NC6H3iPr2-2,6)}TiCl3] (3a):
A solution of
0.81 mmol, 65%), m.p. 185–1868C; 1H NMR (300 MHz, CDCl3, 258C,
nBuLi (2.2 mmol) was added dropwise to a solution of 1a (760 mg,
2.2 mmol) in n-hexane (20 mL) at 08C. The reaction mixture was allowed
to warm to room temperature and stirred for 3 h. The lithium salt of 1a
formed was collected on a frit, washed with n-hexane (2ꢂ5 mL), and
dried under vacuum. The lithium salt (570 mg, 2.1 mmol) obtained was
dissolved in toluene (20 mL) and added to a solution of TiCl4 (398 mg,
2.1 mmol) in toluene (10 mL) at À788C. The reaction mixture was al-
lowed to warm to room temperature and stirred for 6 h. The precipitate
was filtered off, and the solvent was removed to leave a red solid. Re-
crystallisation from CH2Cl2/hexane gave the pure 3a as red crystals
(810 mg, 1.9 mmol, 87%), m.p. 109–1108C; 1H NMR (300 MHz, CDCl3,
3
TMS): d=1.09 (s, 9H; CH3), 1.61 (s, 9H; CH3), 4.95 (d, J
N
3
1H; CHN), 6.05 (d, JACTHNUTRGNEUNG(H,H)=3.9 Hz, 1H; CHN), 7.20–7.80 ppm (m, 8H;
Ph H); 13C NMR (300 MHz, CDCl3, 258C, TMS): d=28.0 (CH3), 29.4
À
(CH3), 63.1 (C
A
G
124.6, 127.5 128.3, 130.3, 130.9, 131.3, 132.5, 135.4, 136.4, 137.6,
139.1 ppm; elemental analysis calcd (%) for C22H28N2Cl2Ti: C 60.16; H
6.43; N 6.38; found: C 60.15; H 6.42; N 6.39.
Synthesis of [{cis-9,10-(NC6H3iPr2-2,6)2-9,10-dihydrophenanthrene}ACHTUNGTRENNUNG{o-
C6H4(CH=NC6H3iPr2-2,6)}TiCl] (5a): Complex 5a was synthesised in the
same manner as 3a with 1a (760 mg, 2.2 mmol), nBuLi (2.2 mmol), and
TiCl4 (133 mg, 0.7 mmol) as starting materials or reagents. Pure 5a was
obtained as red crystals (561 mg, 0.62 mmol, 89%), m.p. 135–1368C;
258C, TMS): d=1.12 (d, 3J
3J (CH3)2), 3.52 (sept, 3J
(H,H)=6.6 Hz, 6H; CH
(CH3)2), 7.24–7.56 (m, 6H; Ph H), 8.15 (d, 1H; Ph H), 8.28 ppm (s, 1H;
CH=NAr); 13C NMR (300 MHz, CDCl3, 258C, TMS): d=23.1 (CH3),
26.2 (CH3), 29.0 (CH(CH3)2), 123.0, 124.1, 127.4, 128.5, 131.9, 135.9,
A
ACHTUGNTREN(UNNG CH3)2), 1.34 (d,
A
R
ACHTUNGTRENNUNG
1H NMR (300 MHz, CDCl3, 258C, TMS): d=0.44 (d, 3J
6H; CH (H,H)=6.6 Hz, 6H; CH
(CH3)2), 0.52 (d, 3J
3J (CH3)2), 0.90 (d, 3J
(H,H)=6.6 Hz, 6H; CH (H,H)=6.6 Hz, 6H; CH-
(CH3)2), 1.28 (d, 3J (CH3)2), 1.50 (d, 3J
(H,H)=6.6 Hz, 6H; CH (H,H)=
6.6 Hz, 6H; CH (H,H)=6.6 Hz, 2H; CH(CH3)2),
(CH3)2), 2.27 (sept, 3J
3.37 (sept, 3J (CH3)2), 3.65 (sept, 3J
(H,H)=6.6 Hz, 2H; CH (H,H)=
6.6 Hz, 2H; CH(CH3)2), 6.06 (s, 2H; CHN), 6.30 (d, 2H; Ph H), 6.72–
AHCTUNGTRENNUNG
À
À
ACHTUNGTRENNUNG
A
U
ACHTUNGTRENNUNG
A
R
ACHTUNGTRENNUNG
140.4, 141.5, 142.6, 146.3, 177.8 ppm (CH=NAr); elemental analysis calcd
(%) for C19H22NCl3Ti: C 54.51, H 5.30, N 3.35; found: C 54.49, H 5.32, N
3.37.
A
E
N
ACHTUNGTRENNUNG
A
R
ACHTUNGTRENNUNG
A
R
ACHTUNGTRENNUNG
À
AHCTUNGTRENNUNG
Synthesis of [{o-C6H4(CH=NC6H3Me2-2,6)}TiCl3] (3b): Complex 3b was
synthesised in the same manner as 3a with 1b (630 mg, 2.2 mmol), nBuLi
(2.2 mmol), and TiCl4 (398 mg, 2.1 mmol) as starting materials or re-
agents. Pure 3b was obtained as a red crystalline solid (650 mg, 1.8 mmol,
82%), m.p. 95–968C; 1H NMR (300 MHz, CDCl3, 258C, TMS): d=2.58
À
À
7.39 (m, 18H; Ph H), 7.88 (d, 1H; Ph H), 7.92 ppm (s, 1H; CH=NAr);
13C NMR (300 MHz, CDCl3, 258C, TMS): d=22.3 (CH3), 23.0 (CH3),
25.4 (CH3), 25.9 (CH3), 26.2 (CH3), 26.4 (CH3), 28.1 (CH
ACHTUGNTRNEN(UNG CH3)2), 28.2
(CH(CH3)2), 28.9 (CH(CH3)2), 72.2 (CHN), 122.8, 123.6, 123.7, 125.7,
A
ACHTUNGTRENNUNG
À
À
126.1, 126.5, 126.9, 127.3, 128.4, 128.7, 130.1, 130.9, 132.8, 137.0, 137.9,
140.9, 141.1, 145.5, 148.9, 178.1, 191.3 ppm (CH=NAr); elemental analysis
calcd (%) for C57H66N3ClTi : C78.11, H7.59, N4.79; found: C78.13,
H7.57, N4.81.
(s, 6H; CH3), 7.15–7.65 (m, 6H; Ph H), 8.24 (d, 1H; Ph H), 8.40 ppm
(s, 1H; CH=NAr); 13C NMR (300 MHz, CDCl3, 258C, TMS): d=19.6
(CH3), 124.1, 125.3, 126.8, 127.6, 128.2, 129.0, 131.7, 132.9, 135.8, 142.4,
179.0 ppm (CH=NAr); elemental analysis calcd (%) for C15H14NCl3Ti: C
49.70, H 3.89, N 3.86; found: C 49.08, H 3.82, N 3.78.
Synthesis of [{cis-9,10-(NC6H3Me2-2,6)2-9,10-dihydrophenanthrene}ACHTUNGTRENNUNG{o-
C6H4(CH=NC6H3Me2-2,6)}TiCl] (5b): Complex 5b was synthesised in the
same manner as 3a with 1b (630 mg, 2.2 mmol), nBuLi (2.2 mmol), and
TiCl4 (133 mg, 0.7 mmol) as starting materials or reagents. Complex 5b
was obtained as an oily crude product. Pure product has not been ob-
tained yet. 1H NMR (300 MHz, CDCl3, 258C, TMS): d=2.19 (s, 12H;
Synthesis of [{o-C6H4ACHTUNGTRENNUNG(CH=NtBu)}TiCl3] (3c): Complex 3c was synthes-
ised in the same manner as 3a with 1c (530 mg, 2.2 mmol), nBuLi
(2.2 mmol) and TiCl4 (398 mg, 2.1 mmol) as starting materials or re-
agents. Pure 3c was obtained as a red crystalline solid (592 mg, 1.9 mmol,
85%), m.p. 89–918C; 1H NMR (300 MHz, CDCl3, 258C, TMS): d=1.67
À
À
À
À
CH3), 2.60 (s, 6H; CH3), 6.17 (s, 2H; CHN), 6.90–7.60 (m, 20H; Ph H),
(s, 9H; CH3), 7.26 (t, 1H; Ph H), 7.68 (t, 1H; Ph H), 7.80 (d, 1H; Ph
H), 7.98 (d, 1H; Ph H), 8.37 ppm (s, 1H; CH=NAr); 13C NMR
À
À
8.00 (d, 1H; Ph H), 8.43 ppm (s, 1H; CH=NAr).
(300 MHz, CDCl3, 258C, TMS): d=31.8 (CH3), 63.1 (C
(CH3)3), 124.2,
Synthesis of [{cis-9,10-(NtBu)2-9,10-dihydrophenanthrene}ACHTNUTRGENN{UG o-C6H4ACHTUNGTRENNUNG(CH=
127.9, 128.8, 132.4, 133.7, 140.4, 169.5 ppm (CH=NAr); elemental analysis
calcd (%) for C11H14NCl3Ti: C 42.01, H 4.49, N 4.45; found: C 42.11, H
4.39, N 4.37.
NtBu)}TiCl] (5c): Complex 5c was synthesised in the same manner as 3a
with 1c (530 mg, 2.2 mmol), nBuLi (2.2 mmol), and TiCl4 (133 mg,
0.7 mmol) as starting materials or reagents. Pure 5c was obtained as red
1
Synthesis of [{cis-9,10-(NC6H3iPr2-2,6)2-9,10-dihydrophenanthrene}TiCl2]
(4a): Complex 4a was synthesised in the same manner as 3a with 1a
(760 mg, 2.2 mmol), nBuLi (2.2 mmol), and TiCl4 (209 mg, 1.1 mmol) as
starting materials or reagents. Pure 4a was obtained as red crystals
crystals (362 mg, 0.61 mmol, 87%), m.p. 127–1288C; H NMR (300 MHz,
CDCl3, 258C, TMS): d=1.17 (s, 9H; C
1.75 (s, 9H; C (H,H)=4.2 Hz, 1H; CHN), 6.53 (d,
(CH3)3), 4.68 (d, 3J
3J
(H,H)=4.2 Hz, 1H; CHN), 7.20–7.65 (m, 8H; Ph H), 7.76 (t, 2H; Ph
ACHTUNTGRENNGU(CH3)3), 1.43 (s, 9H; CACHTUNGTRENNUNG(CH3)3),
A
ACHTUNGTRENNUNG
À
À
AHCTUNGTRENNUNG
4400
www.chemeurj.org
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 4394 – 4401

Synthesis of Titanium Complexes
FULL PAPER
H), 7.86 (t, 2H; Ph H), 8.49 ppm (s, 1H; CH=NAr); 13C NMR
(300 MHz, CDCl3, 258C, TMS): d=28.0 (CH3), 29.2 (CH3), 31.6 (CH3),
[5] a) R. Beckhaus, J. Oster, I. Strauss, M. Wagner, Synlett 1997, 241–
249; b) P. Stepnicka, R. Gyenpes, I. Cisarova, M. Horacek, J. Kubis-
ta, K. Mach, Organometallics 1999, 18, 4869–4880; c) U. Rosenthal,
Angew. Chem. 2004, 116, 3972–3977; Angew. Chem. Int. Ed. 2004,
43, 3882–3887; d) G. Erker, Acc. Chem. Res. 1984, 17, 103–109;
e) R. Beckhaus, K. H. Thiele, J. Organomet. Chem. 1986, 317, 23–
31; f) J. Campora, S. L. Buchwald, E. Gutierrez-Puebla, A. Monge,
Organometallics 1995, 14, 2039–2046.
À
59.9 (CACHTUNGTRENNUNG(CH3)3), 60.3 (CACHTUNGTRENNUNG(CH3)3), 62.0 (CACHTNUGTREN(UNGN CH3)3), 64.9 (CHN), 75.1 (CHN),
122.4, 124.6, 125.9, 125.7, 127.5, 127.7, 127.9, 128.1, 128.5, 129.5, 129.8,
129.9, 130.7, 131.2, 137.3, 137.8, 141.7, 142.2, 171.1, 190.2 ppm (CH=
NAr); elemental analysis calcd (%) for C33H42N3ClTi : C 70.27, H 7.51, N
7.45; found: C 70.28, H 7.52, N 7.44.
X-ray structure determinations of 3a, 4a–c, 5a and 5c: Single crystals of
3a, 4a–c, 5a and 5c suitable for X-ray structural analysis were obtained
from the CH2Cl2/hexane mixture. The data were collected at 293 K on a
Bruker SMART CCD diffractometer using graphite-monochromated
MoKa radiation (l=0.71073 ꢁ) for 3a, 4c, and 5c, and on a Rigaku R-
AXIS RAPID IP diffractometer equipped with graphite-monochromated
MoKa radiation (l=0.71073 ꢁ) for 4a, 4b and 5a. The structures were
solved by direct methods[21] and refined by full-matrix least-squares on
F2. All non-hydrogen atoms were refined anisotropically, and the hydro-
gen atoms were included in idealised positions. All calculations were per-
formed using the SHELXTL[22] crystallographic software packages. De-
tails of the crystal data, data collections, and structure refinements are
summarised in Table 2. CCDC-739019 (3a), 739020 (4a), 739021 (4b),
739022 (4c), 739023 (5a), and 739024 (5c) contain the supplementary
crystallographic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
[6] a) S. Kraft, R. Beckhaus, D. Haase, W. Saak, Angew. Chem. 2004,
116, 1609–1614; Angew. Chem. Int. Ed. 2004, 43, 1583–1587;
b) I. M. Piglosiewicz, R. Beckhaus, W. Saak, D. Haase, J. Am. Chem.
Soc. 2005, 127, 14190–14191; c) M. R. Haneline, A. F. Heyduk, J.
Am. Chem. Soc. 2006, 128, 8410–8411.
[7] a) R. K. Merwin, R. C. Schnabel, J. D. Koola, D. M. Roddick, Org-
nometallics 1992, 11, 2972–2978; b) Z. Z. Qiu, Z. W. Xie, Angew.
Chem. 2008, 120, 6674–6677; Angew. Chem. Int. Ed. 2008, 47, 6572–
6575.
[8] a) A. Kasatkin, T. Nakagawa, S. Okamoto, F. Sato, J. Am. Chem.
Soc. 1995, 117, 3881–3882; b) S. L. Buchwald, B. T. Watson, M. W.
Wannamaker, J. C. Dewan, J. Am. Chem. Soc. 1989, 111, 4486–
4494; c) S. O. Agustsson, C. H. Hu, U. Englert, T. Marx, L. Wese-
mann, C. Ganter, Organometallics 2002, 21, 2993–3000.
[9] R. B. Grossman, S. L. Buchwald, J. Org. Chem. 1992, 57, 5803–5805.
[10] P. G. Hayes, G. C. Welch, D. J. H. Emslie, C. L. Noack, W. E. Piers,
M. Parvez, Organometallics 2003, 22, 1577.
[11] V. Snieckus, Chem. Rev. 1990, 90, 879–933.
[12] T. I. Baiz, J. A. R. Schmidt, Organometallics 2007, 26, 4094–4097.
[13] a) M. Mitani, R. Furuyama, J. I. Mohri, J. Saito, S. Ishii, H. Terao, T.
Nakano, H. Tanaka, T. Fujita, J. Am. Chem. Soc. 2003, 125, 4293–
4305; b) Y. T. Zhang, J. H. Wang, Y. Mu, Z. Shi, C. S. Lꢃ, Y. R.
Zhang, L. J. Qiao, S. H. Feng, Organometallics 2003, 22, 3877–3883.
[14] a) G. D. Smith, P. E. Fanwick, I. P. Rothwell, Inorg. Chem. 1990, 29,
3221–3226; b) J. Zhang, Y. J. Lin, G. X. Jin, Organometallics 2007,
26, 4042–4047.
[15] a) N. A. Ketterer, J. W. Ziller, A. L. Rheingold, A. F. Heyduk, Orga-
nometallics 2007, 26, 5330–5338; b) M. E. G. Skinner, T. Toupance,
D. A. Cowhig, B. R. Tyrrell, P. Mountford, Organometallics 2005, 24,
5586–5603.
[16] a) K. P. Bryliakov, E. A. Kravtsov, D. A. Pennington, S. J. Lancaster,
M. Bochmann, H. H. Brintzinger, E. P. Talsi, Organometallics 2005,
24, 5660–5664; b) A. F. Mason, G. W. Coates, J. Am. Chem. Soc.
2004, 126, 16326–16327.
[17] a) M. G. Thorn, J. E. Hill, S. A. Waratuke, E. S. Johnson, P. E. Fan-
wick, I. P. Rothwell, J. Am. Chem. Soc. 1997, 119, 8630–8641; b) C.
Lefeber, P. Arndt, A. Tillack, W. Baumann, R. Kempe, V. V. Burla-
kov, U. Rosenthal, Organometallics 1995, 14, 3090–3093.
[18] a) D. F. Herman, W. R. Nelson, J. Am. Chem. Soc. 1953, 75, 3877–
3882; b) D. F. Herman, W. R. Nelson, J. Am. Chem. Soc. 1953, 75,
3882–3887.
Acknowledgements
This work was supported by the National Natural Science Foundation of
China (Nos. 20674024 and 20772044).
[1] Selected reviews: a) V. Ritleng, C. Sirlin, M. Pfeffer, Chem. Rev.
2002, 102, 1731–1769; b) L. Resconi, L. Cavallo, A. Fait, F. Piemon-
tesi, Chem. Rev. 2000, 100, 1253–1345; c) T.-Y. Luh, M. K. Leung,
K. T. Wong, Chem. Rev. 2000, 100, 3187–3204; d) G. J. P. Britovsek,
V. C. Gibson, D. F. Wass, Angew. Chem. 1999, 111, 448–468; Angew.
Chem. Int. Ed. 1999, 38, 428–447; e) I. Ojima, M. Tzamarioudaki,
Z. Li, R. J. Donovan, Chem. Rev. 1996, 96, 635–662.
[2] a) A. Motta, I. L. Fragala, T. J. Marks, J. Am. Chem. Soc. 2007, 129,
7327–7338; b) J. D. Scollard, D. H. McConville, N. C. Payne, J. J.
Vittal, Macromolecules 1996, 29, 5241–5243; c) J. C. Sierra, D. Hꢃer-
lꢄnder, M. Hill, G. Kehr, G. Erker, R. Frçhlich, Chem. Eur. J. 2003,
9, 3618–3622; d) M. B. Bertrand, J. D. Neukom, J. P. Wolfe J. Org.
Chem. 2008, 73, 8851–8860; e) H. R. Bigmore, S. R. Dubberley, M.
Kranenburg, S. C. Lawrence, A. J. Sealey, J. D. Selby, M. A. Zuide-
veld, A. R. Cowley, P. Mountford, Chem. Commun. 2006, 118, 436–
438.
[19] L. D. Durfee, A. K. McMullen, I. P. Rothwell, J. Am. Chem. Soc.
1988, 110, 1463–1467.
[3] a) S. B. Jhaveri, K. R. Carter, Chem. Eur. J. 2008, 14, 6845–6848;
b) T. Nagano, T. Hayashi, Org. Lett. 2005, 7, 491–493; c) J. D. Scol-
lard, D. H. McConville, J. Am. Chem. Soc. 1996, 118, 10008–10009;
d) N. Borduas, D. A. Powell, J. Org. Chem. 2008, 73, 7822–7825;
e) F. Rosenfeldt, G. Erker, Tetrahedron Lett. 1980, 21, 1637–1640;
f) S. A. Cummings, R. Radford, G. Erker, G. Kehr, R. Frçhlich, Or-
ganometallics 2006, 25, 839–842.
[4] a) J. W. Strauch, G. Erker, G. Kehr, R. Frçhlich, Angew. Chem.
2002, 114, 2662–2664; Angew. Chem. Int. Ed. 2002, 41, 2543–2546;
b) R. J. Long, V. C. Gibson, A. J. P. White, Organometallics 2008, 27,
235–245; c) L. Rocchigiani, C. Zuccaccia, D. Zuccaccia, A. Mac-
chioni, Chem. Eur. J. 2008, 14, 6589–6592; d) A. Motta, I. L. Fraga-
la, T. J. Marks, J. Am. Chem. Soc. 2007, 129, 7327–7338; e) X. H.
Yang, X. L. Sun, F. B. Han, B. Liu, Y. Tang, Z. Wang, M. L. Gao,
Z. W. Xie, S. Z. Bu, Organometallics 2008, 27, 4618–4624.
[20] a) N. Taniguchi, T. Hata, M. Uemura Angew. Chem. 1999, 111,
1311–1314; Angew. Chem. Int. Ed. 1999, 38, 1232–1235; Angew.
Chem. Int. Ed. 1999, 38, 1232–1235; b) A. O. Larsen, R. A. Talor,
P. S. White, M. R. Gagn, Organometallics 1999, 18, 5157–5162; c) R.
Yanada, N. Negoro, M. Okaniwa, Y. Miwa, T. Taga, K. Yanada, T.
Fujita, Synlett 1999, 537–540.
[21] SHELXTL; PC Siemens Analytical X-ray Instruments: Madison
WI, 1993.
[22] G. M. Sheldrick, SHELXTL Structure Determination Programs,
Version 5.0; PC Siemens Analytical Systems: Madison, WI, 1994.
Received: November 2, 2009
Published online: March 5, 2010
Chem. Eur. J. 2010, 16, 4394 – 4401
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4401