New titanium complexes with symmetric or asymmetric cis-9,10- dihydrophenanthrenediamide ligands formed through sequential intramolecular C-C bond-forming reactions

Article abstract of DOI:10.1021/ic1008768

A series of new titanium(IV) complexes with symmetric or asymmetric cis-9,10-dihydrophenanthrenediamide ligands, cis-9,10-PhenH₂(NR) ₂Ti(OⁱPr)₂ [PhenH₂ = 9,10-dihydrophenanthrene, R = 2,6-ⁱ

Full text of DOI:10.1021/ic1008768

30 Inorg. Chem. 2011, 50, 30–36
DOI: 10.1021/ic1008768
New Titanium Complexes with Symmetric or Asymmetric
cis-9,10-Dihydrophenanthrenediamide Ligands Formed through
Sequential Intramolecular C-C Bond-Forming Reactions
Dapeng Zhao, Bo Gao, Wei Gao, Xuyang Luo, Duihai Tang, Ying Mu,* and Ling Ye
State Key Laboratory of Supramolecular Structure and Materials, School of Chemistry, Jilin University,
Chang Chun 130012, People’s Republic of China
Received May 4, 2010
A series of new titanium(IV) complexes with symmetric or asymmetric cis-9,10-dihydrophenanthrenediamide ligands, cis-
9,10-PhenH2(NR)2Ti(OiPr)2 [PhenH2 = 9,10-dihydrophenanthrene, R = 2,6-iPr2C6H3 (2a), 2,6-Et2C6H3 (2b), 2,6-Me2C6H3
(2c)], cis-9,10-PhenH2(NR1)(NR2)Ti(OiPr)2 [R1 = 2,6-iPr2C6H3, R2 = 2,6-Et2C6H3 (2d); R1 = 2,6-iPr2C6H3, R2 = 2,6-
Me2C6H3 (2e)], and [cis-9,10-PhenH2(NR1)2][o-C6H4(CHdNR2)]TiOiPr [R1 = 2,6-iPr2C6H3, R2 = 2,6-Et2C6H3 (3a); R1 =
2,6-iPr2C6H3, 2,6-Me2C6H3 (3b)], have been synthesized from the reactions of TiCl2(OiPr)2 with o-C6H4(CHdNR)Li [R =
2,6-iPr2C6H3, 2,6-Et2C6H3, 2,6-Me2C6H3]. The symmetric complexes 2a-2c were obtained from the reactions of
TiCl2(OiPr)2 with 2 equiv of the corresponding o-C6H4(CHdNR)Li followed by intramolecular C-C bond-forming reductive
elimination and oxidative coupling processes, while the asymmetric complexes 2d-2e were formed from the reaction of
TiCl2(OiPr)2 with two different types of o-C6H4(CHdNR)Li sequentially. The complexes 3a and 3b were also isolated from
1
the reactions for complexes 2d and 2e. All complexes were characterized by H and 13C NMR spectroscopy, and the
molecular structures of 2a, 2b, 2e, and 3a were determined by X-ray crystallography.
Introduction
reductive elimination, oxidative coupling, migratory insertion,
and σ- or π-bond metathesis.3 Group 4 metal-mediated C-C
bond-forming reactions take place usually through two princi-
pal mechanistic pathways: σ-bond metathesis and migratory
insertion, which operate without requiring redox changes at the
metal center.4 Although some examples of C-C bond-forming
reactions mediated by group 4 metals through the reductive elimi-
nation pathway are known, most of the reported C-C bond-
forming reductive elimination reactions involving group 4 metal
complexes are the coupling reactions of alkyl, acyl, 1-alkenyl,
and 1-alkynyl groups.5 For the aryl-aryl bond-forming
Studies on transition-metal-mediated C-C bond-forming
reactions have been an important research area in organic and
organometallic chemistry.1 Some of the C-C bond-forming
reactions have been well documented as efficient synthetic
methods for constructing the basic carbon backbone of small
organic molecules, metal complexes, and extended polymeric
structures.2 It has been known that most stoichiometric and
catalytic C-C bond-forming reactions mediated by transi-
tion metals can take place through several pathways, such as
€
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Piemontesi, F. Chem. Rev. 2000, 100, 1253–1345. (c) Ritleng, V.; Sirlin, C.;
Pfeffer, M. Chem. Rev. 2002, 102, 1731–1769. (d) Ojima, I.; Tzamarioudaki, M.;
Li, Z.; Donovan, R. J. Chem. Rev. 1996, 96, 635–662.
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Scollard, J. D.; McConville, D. H.; Payne, N. C.; Vittal, J. J. Macromolecules 1996,
29, 5241–5243. (c) Motta, A.; Fragala, I. L.; Marks, T. J. J. Am. Chem. Soc. 2007,
Ed. 2002, 41, 2543–2546. (b) Corradi, M. M.; Pindado, G. J.; Sarsfield, M. J.;
Thornton-Pett, M.; Bochmann, M. Organometallics 2000, 19, 1150–1159. (c)
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2008, 14, 6589–6592. (d) Motta, A.; Fragala, I. L.; Marks, T. J. J. Am. Chem. Soc.
2007, 129, 7327–7338. (e) Yang, X. H.; Sun, X. L.; Han, F. B.; Liu, B.; Tang, Y.; Wang,
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1995, 14, 2039–2046. (c) Beckhaus, R.; Oster, J.; Strauss, I.; Wagner, M. Synlett 1997,
241–249. (d) Stepnicka, P.; Gyenpes, R.; Cisarova, I.; Horacek, M.; Kubista, J.; Mach,
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pubs.acs.org/IC
Published on Web 11/29/2010
2010 American Chemical Society

Article
Inorganic Chemistry, Vol. 50, No. 1, 2011 31
reductive elimination reactions mediated by group 4 metals,
only a very few examples6 have been reported so far. On the
other hand, oxidative coupling reactions of unsaturated
organic compounds on low-valent group 4 metals have been
extensively studied as an efficient pathway for constructing the
C-C bond.7 The low-valent group 4 metals, such as titanium(II)
or zirconium(II) reagents, are usually generated by the treatment
of titanium(IV) or zirconium(IV) complexes with Grignard
or organolithium reagents, followed by a reductive elimina-
tion process.8 In principle, both the reductive elimination and
the subsequent oxidative coupling processes can be used to
construct the C-C bond. Recently, we reported such an
example of utilizing titanium-mediated sequential reductive
elimination and oxidative coupling processes to synthesize
new titanium(IV) complexes with a cis-9,10-dihydrophenan-
threnediamide ligand, cis-9,10-PhenH2(NR)2TiCl2, from the
reaction of TiCl4 with o-C6H4(CHdNR)Li.9 This reaction pro-
vides a very interesting synthetic strategy for the titanium(IV)
complexes with a complicated diamide ligand formed in situ
from easily obtained o-C6H4(CHdNR)Li reagents. How-
ever, it was found that the reaction with TiCl4 as the starting
material is relatively difficult to control because of the high
reactivity of TiCl4 and the isolated yields of the titanium(IV)
diamide complexes are usually low. To further exploit the
application of this reaction and increase the yield of the diamide
complexes, we have studied the reaction with TiCl2(OiPr)2 as
the starting material and found that both the controllability and
selectivity of the reaction are obviously improved. From the
reactions of TiCl2(OiPr)2 with o-C6H4(CHdNR)Li reagents,
both symmetric and asymmetric titanium(IV) diamide com-
plexes have been obtained in high yields. The development of
new synthetic method for the asymmetric titanium(IV) diamide
complexes is of importance, considering that the asymmetric
titanium(IV) diamide complexes might be useful as chiral
catalysts for some organic or polymerization reactions.
o-bromobenzaldehyde with 1 equiv of the corresponding
arylamine in hexane (Scheme 1).10 Of them, compounds
1a and 1c have been reported previously.9 TiCl2(OiPr)2 was
prepared according to a literature procedure11 by the reac-
tion of TiCl4 and Ti(OiPr)4 (mole radio 1:1). Pure product
was obtained as colorless crystals by recrystallization from
hexane. The treatment of compounds 1a-1c with 1 equiv of
nBuLi in hexane produced the corresponding ortho-lithiated
Schiff base derivatives o-C6H4(CHdNR)Li.12 The reactions
were carried out at 0 °C to minimize the formation of
byproducts because the lithiation reactions are usually rapid
and exothermic. The ortho-lithiated Schiff base compounds
were isolated in high yields as air- and moisture-sensitive
precipitates, which were washed with hexanes to remove
residue nBuLi. The reactions of TiCl2(OiPr)2 with these
ortho-lithiated Schiff base derivatives were studied in
detail, and a number of new symmetric and asymmetric
titanium(IV) diamide complexes 2a-2e, 3a, and 3b have
been obtained, as shown in Schemes 1 and 2. It was found
that the reactions of TiCl2(OiPr)2 with 2 equiv of an ortho-
lithiated Schiff base derivative in toluene, diethyl ether, or
tetrahydrofuran (THF) give the corresponding complexes
2a-2c in obviously higher yields (78-88%) in comparison
with those for similar complexes obtained from the corre-
sponding reactions of TiCl4.9 The synthetic yields of com-
plexes 2a-2c are quite dependent on the solvent and
decrease in the order of toluene > diethyl ether > THF. It
was also found that the reactions of TiCl2(OiPr)2 with the
ortho-lithiated Schiff base derivatives are much slower than
the corresponding reactions of TiCl4, and the selectivity for
replacing one or two chloride(s) of TiCl2(OiPr)2 with the
o-C6H4(CHdNR) ligand can be roughly controlled by the
molar ratio of the reagents. Therefore, the asymmetric com-
plexes 2d and 2e have been synthesized in good yields (57-
65%) by sequential reactions of TiCl2(OiPr)2 with two
different ortho-lithiated Schiff base reagents in toluene. In
addition to 2d and 2e, complexes 3a and 3b were also
obtained as byproducts from these reactions in low yields.
The formation of complexes 3a and 3b in these reactions
indicates that a small amount of 2a was formed in the first
step of these reactions, as shown in Scheme 2, even though
the molar ratio of TiCl2(OiPr)2 to o-C6H4[CHdN(2,6-iPr2-
C6H3)]Li was controlled as 1:1.
Herein we report the synthesis of the new titanium(IV)
complexes with symmetric and asymmetric cis-9,10-dihydro-
phenanthrenediamide ligands, cis-9,10-PhenH2(NR)2Ti(OiPr)2
[PhenH2=9,10-dihydrophenanthrene, R=2,6-iPr2C6H3 (2a),
2,6-Et2C6H3 (2b), 2,6-Me2C6H3 (2c)], cis-9,10-PhenH2(NR1)-
(NR2)Ti(OiPr)2 [R1=2,6-iPr2C6H3, R2=2,6-Et2C6H3 (2d);
R1=2,6-iPr2C6H3, R2=2,6-Me2C6H3 (2e)], and [cis-9,10-
PhenH2(NR1)2][o-C6H4(CHdNR2)]TiOiPr [R1=2,6-iPr2C6H3,
R2=2,6-Et2C6H3 (3a); R1=2,6-iPr2C6H3, 2,6-Me2C6H3 (3b)],
from the reactions of TiCl2(OiPr)2 with o-C6H4Li(CHdNR)
[R=2,6-iPr2C6H3, 2,6-Et2C6H3, 2,6-Me2C6H3], and their spec-
troscopic characterization and crystal structural analysis of
complexes 2a, 2b, 2e, and 3a.
Complexes 2a-2e, 3a, and 3b are all soluble in toluene,
CH2Cl2, and THF and less soluble in petroleum ether and
hexanes. Complexes 2a-2e are air- and moisture-sensitive
in both the solid state and solution, while complexes 3a and
3b show relatively good stability to air and moisture and can
be exposed to air for several hours without obvious decom-
position. Complexes 2a-2e, 3a, and 3b all show good
thermal stability in solution and can be heated in boiling
toluene for hours without obvious decomposition. Com-
plexes 2a-2e, 3a, and 3b were all characterized by elemental
analysis and 1H and 13C NMR spectroscopy, and satisfac-
tory analytical results were obtained. Crystallographic anal-
ysis on complexes 2a, 2b, 2e, and 3a indicates that the 9,10-
dihydrophenanthrenediamide ligands in these complexes
are all in the cis configuration.
Results and Discussion
Reaction of TiCl2(OiPr)2 with o-C6H4(CHdNR)Li. The o-
bromophenyl Schiff base compounds o-C6H4(CHdNR)Br
(1a-1c) were prepared by the condensation reaction of
(6) (a) Kraft, S.; Beckhaus, R.; Haase, D.; Saak, W. Angew. Chem., Int.
Ed. 2004, 43, 1583–1587. (b) Piglosiewicz, I. M.; Beckhaus, R.; Saak, W.; Haase,
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32 Inorganic Chemistry, Vol. 50, No. 1, 2011
Zhao et al.
Scheme 1. Synthesis of the Symmetric Complexes 2a-2c
for the TiCl4 reaction system,9 the obtained titanium com-
plexes 2a-2e, 3a, and 3b all contain cis-9,10-dihydrophe-
nanthrenediamide ligands, which indicates that the two -OiPr
groups exert little steric effect on the imine oxidative
coupling step.
Scheme 2. Synthesis of the Asymmetric Complexes 2d-2e, 3a, and 3b
NMR Analysis of the Complexes. All new complexes
were characterized by 1H and 13C NMR spectroscopy. The
complexes 2a-2e could be readily identified by 1H and 13
C
NMR spectroscopy. The disappearance of the signals of
the imine CH protons and the appearance of resonances for
the -CHN- protons in 1H NMR spectra of 2a-2e demon-
strate the formation of the titanium diamide complexes.15 A
sharp singlet at 5.81, 5.82, and 5.83 ppm was observed in the
1H NMR spectra of complexes 2a, 2b, and 2c, respectively,
which is representative of the -CHN- protons in the 9,10-
dihydrophenanthrene ring. The corresponding -CHN-
carbon resonances in these complexes were observed at
69.4, 68.8, and 66.1 ppm in their 13C NMR spectra, respec-
tively. For complexes 2d and 2e, two sets of doublets (5.75
1
and 5.91, 5.84, and 5.88 ppm) in their H NMR spectra
and two resonances (68.8 and 69.4, 66.1, and 71.0 ppm) in
their 13C NMR spectra were observed, indicating that the
two -CHN- protons and carbons in the asymmetric 9,10-
dihydrophenanthrene ring of 2d and 2e are inequivalent. The
two diastereotopic isopropoxy groups in the symmetric
complexes 2a-2c give two sets of doublets for their methyl
protons, while the four methyl groups of the two isopropoxy
groups in the asymmetric complexes 2d and 2e show four sets
of doublets because the two methyl groups in each isopropyl
group are diastereotopic in the latter cases. It should be
mentioned that the isopropyl units in the 2,6-iPr2C6H3 group
in complexes 2a, 2d, and 2e show broad signals for both the
methyl and methine protons at room temperature due
to slow rotation of the 2,6-iPr2C6H3 group about the N-aryl
bond. When the NMR experiments were carried out
at -40 °C, four sets of doublets for the methyl protons
and two sets of septets for the methine protons in the two
isopropyl units were observed because the two isopropyl
groups in one 2,6-iPr2C6H3 group are located at inequivalent
positions at low temperatures and the two methyl groups in
each isopropyl group are diastereotopic. Typical variable-
temperature 1H NMR spectra for complex 2e are shown in
Figure 1. Resonances for other protons and carbons in these
complexes are in normal positions. Complexes 3a and 3b
As mentioned above, complexes 2, instead of the inter-
mediates [o-C6H4(CHdNR)]2Ti(OiPr)2 (A), were always
obtained from the reactions of TiCl2(OiPr)2 with 2 equiv
of the corresponding ortho-lithiated Schiff base reagents,
which indicates that the intermediates A are unstable. As
discussed in the previous publication,9 the intermediates
A may be formed first in these reactions and can then be
converted to complexes 2 in situ through sequential C-C
bond-forming reductive elimination and oxidative coupling
reactions, as shown in Scheme 3. Attempts to observe the
reaction intermediates by following the reaction of TiCl2-
(OiPr)2 with 2 equiv of o-C6H4[CHdN(2,6-iPr2C6H3)]Li in
toluene-d8 at different temperatures (-30, -50, and -70 °C)
1
with H NMR were not successful probably because the
lifetime of the reaction intermediates is too short. Although
the proposed intermediates A and B have not been isolated
or observed in these reactions so far, the involved transition-
metal-mediated reductive elimination6,13 and oxidative
coupling7,14 reactions are well documented. Of course,
it is also possible for complexes 2 to be formed through
other routes, such as the direct addition of a second
o-C6H4[CHdNR]Li to the monoligated o-C6H4[CHdNR]-
TiCl(OiPr)2 to form the coupling product (rather than
through reductive elimination). As was observed previously
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S. J.; Bochmann, M.; Brintzinger, H. H.; Talsi, E. P. Organometallics 2005,
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J. C. J. Am. Chem. Soc. 1989, 111, 4486–4494.

Article
Inorganic Chemistry, Vol. 50, No. 1, 2011 33
Figure 1. Variable-temperature 1H NMR spectra of 2e in toluene-d8 at þ20, 0, -20, and -40 °C.
Scheme 3. Proposed Mechanism for the Formation of 2
could also be readily identified by 1H and 13C NMR spec-
troscopy. The presence of resonances for the -CHN-
protons (5.80 and 5.86 ppm) and the imine CH protons
(8.01 and 8.06 ppm) in their 1H NMR spectra demonstrates
the formation of titanium complexes 3a and 3b. The signals
for the ethyl group in 3a and the methyl group in 3b further
confirm their structures. For complexes 3a and 3b, four sets
of doublets for the methyl protons and two sets of septets for
the methine protons in the two isopropyl groups of the
2,6-iPr2C6H3 group were observed at room temperature,
which demonstrates that the 2,6-iPr2C6H3 rotation about the
N-aryl bond is further slowed down on the NMR time scale
in these more crowded complexes.
tetrahedral coordination environment about the titanium
˚
center. The Ti-N bond lengths of 1.913(3) and 1.901(3) A in
˚
˚
2a, 1.896(4) and 1.901(4) A in 2b, and 1.900(2) and 1.917(5) A
in 2e are in the normal range found in other titanium com-
plexes with diamide ligands.16 The Ti-O bond lengths of
˚
˚
1.787(2) and 1.781(2) A in 2a, 1.736(4) and 1.774(4) A in 2b,
˚
and 1.781(6) and 1.794(4) A in 2e are comparable to those
reported for related titanium alkoxide complexes.17 The O1-
Ti-O2 bond angles of 108.31(11)° in 2a, 111.0(2)° in 2b, and
(16) (a) Ketterer, N. A.; Ziller, J. W.; Rheingold, A. L.; Heyduk, A. F.
Organometallics 2007, 26, 5330–5338. (b) Skinner, M. E. G.; Toupance, T.;
Cowhig, D. A.; Tyrrell, B. R.; Mountford, P. Organometallics 2005, 24, 5586–
5603.
Crystal Structures. Crystals of 2a, 2b, 2e, and 3a suitable
for X-ray crystal structure determination were grown from
CH2Cl2/n-hexane at ambient temperature. The ORTEP
drawings of the molecular structures of 2a, 2b, 2e, and 3a
are shown in Figures 2-5, respectively. X-ray analysis
reveals that complexes 2a, 2b, and 2e adopt a distorted
(17) (a) Chen, H.-Y.; Liu, M.-Y.; Sutar, A. K.; Lin, C.-C. Inorg. Chem.
2010, 49, 665–674. (b) Sun, W.-H.; Liu, S. J.; Zhang, W. J.; Zeng, Y. N.; Wang, D.;
Liang, T. L. Organometallics 2010, 29, 732–741. (c) Rieger, B. J. Organomet.
Chem. 1991, 420, C17–C20. (d) Meppelder, G.-J. M.; Fan, H.-T.; Spaniol, T. P.;
Okuda, J. Inorg. Chem. 2009, 48, 7378–7388. (e) Sarsfield, M. J.; Ewart, S. W.;
Tremblay, T. L.; Roszak, A. W.; Baird, M. C. J. Chem. Soc., Dalton Trans. 1997,
3097–3104.

34 Inorganic Chemistry, Vol. 50, No. 1, 2011
Zhao et al.
Figure 2. X-ray structure of 2a with 30% probability of thermal ellip-
˚
soids. Hydrogen atoms are omitted for clarity. Selected bond distances (A)
Figure 4. X-ray structure of 2e with 30% probability of thermal ellipsoids.
˚
Hydrogen atoms are omitted for clarity. Selected bond distances (A) and
and angles (deg): Ti1-N1 = 1.913(3), Ti1-N2 = 1.901(3), Ti1-O1 =
1.787(2), Ti1-O2=1.781(2), O1-Ti1-O2 = 108.31(11), N2-Ti-N1 =
88.15(12), N1-C13-C14-N2=40.08(2), C1-C6-C7-C12=17.63(97),
C1-C13-C14-C12=40.92(3).
angles (deg): Ti1-N1=1.900(2), Ti1-N2=1.917(5), Ti1-O1=1.781(6),
Ti1-O2 = 1.794(4), O1-Ti1-O2 = 110.45(2), N2-Ti-N1 = 87.08(13),
N1-C1-C14-N2 = 39.34(5), C2-C7-C8-C13 = 13.26(9), C2-C1-
C14-C13 = 40.37(4).
Figure 3. X-ray structure of 2b with 30% probability of thermal ellipsoids.
˚
Hydrogen atoms are omitted for clarity. Selected bond distances (A) and
angles (deg): Ti1-N1=1.896(4), Ti1-N2 = 1.901(4), Ti1-O1=1.736(4),
Ti1-O2 = 1.774(4), O1-Ti1-O2 = 111.0(2), N2-Ti-N1 = 87.97(19),
N2-C1-C14-N1 = 40.80(4), C2-C1-C14-C13 = 43.22(9), C2-C7-
C8-C13=18.60(2).
Figure 5. X-ray structure of 3a with 30% probability of thermal ellipsoids.
˚
Hydrogen atoms are omitted for clarity. Selected bond distances (A) and
angles (deg): Ti1-N1=1.938(2), Ti1-N2=1.945(2), Ti1-N3=2.423(2),
Ti1-O2 = 1.8188(17), Ti1-C39 = 2.197(2), O2-Ti1-C39 = 123.65(9),
O2-Ti1-N2 = 134.37(9), N2-Ti1-C39 = 100.50(9), N1-Ti1-N3 =
173.90(8), N1-C1-C14-N2=27.2(3), C2-C7-C8-C13=16.3(4), C2-
C1-C14-C13 = 30.6(3).
110.45(5)° in 2e are close to the ideal bond angle in a tetra-
hedral coordination environment. The N1-Ti-N2 bond
angles of 88.15(12)° in 2a, 87.97(19)° in 2b, and 87.08(9)° in
2e are in line with those in their chloride analogues.9 In com-
plex 3a, the coordination environment about the titanium
atom is best described as distorted trigonal-bipyramidal,
with imine nitrogen ligands.18 The Ti-O bond length of
˚
˚
1.781(2) A and the Ti-C bond length of 2.197(2) A in 3a are
in normal range found in related titanium complexes.17,19,15a
The torsion angle of N1-C1-C14-N2 [27.3(3)°] in 3a is ob-
viously smaller than the corresponding ones in 2a [40.08(2)°],
2b [40.80(4)°], and 2a [39.34(5)°] because of the crowded
coordination environment in 3a.
where the C39, N2, and O2 atoms form the equatorial plane
P
[
angles X-Ti-Y=358.52(9)°, where X, Y=O2, C39, N2]
and the N1 and N3 atoms occupy the apical positions with an
angle of 173.90(8)° for N1-Ti-N3. The Ti-N(amide) bond
lengths of 1.938(2) and 1.945(2) A in 3a are comparable to
˚
(18) (a) Clark, K. M.; Ziller, J. W.; Heyduk, A. F. Inrog. Chem. 2010, 49,
2222–2231. (b) Zhang, J.; Lin, Y. J.; Jin, G. X. Organometallics 2007, 26, 4042–
4047. (c) Lian, B.; Spaniol, T. P.; Horrillo-Martinez, P.; Hultzsch, K. C.; Okuda, J.
Eur. J. Inorg. Chem. 2009, 429–434.
(19) Smith, G. D.; Fanwick, P. E.; Rothwell, I. P. Inorg. Chem. 1990, 29,
3221–3226.
those reported for related five-coordinate titanium complexes
with diamide ligands16 but longer than the corresponding
ones in 2a, 2b, and 2e. The Ti-N(imine) bond length of
˚
2.423(2) A in 3a is close to those in related titanium complexes

Article
Inorganic Chemistry, Vol. 50, No. 1, 2011 35
Table 1. Crystal Data and Structural Refinement Details for 2a, 2b, 2e, and 3a
2a
2b
2e
3a
formula
fw
C44H58O2N2Ti
694.82
C40H53O2N2Ti
641.74
C40H50N2O2Ti
638.72
C59H71Cl2N3OTi
956.99
cryst syst
space group
monoclinic
P2(1)/n
19.693(4)
10.332(2)
21.764(4)
90
116.54(3)
90
3962.3(14)
4
0.253
monoclinic
P2(1)/c
12.937(3)
19.908(4)
14.199(3)
90
102.68 (3)
90
3567.8(13)
4
0.275
monoclinic
P2(1)/c
17.169(1)
21.062(1)
20.082(1)
90
98.021(1)
90
7191.1(6)
8
0.273
triclinic
P1
˚
a (A)
11.236(1)
12.859(1)
18.052(1)
88.233(1)
82.722(1)
82.574(1)
2565.2(3)
2
0.314
0.0184
1.030
0.0573
0.1460
˚
b (A)
˚
c (A)
R (deg)
β (deg)
γ (deg)
3
˚
v (A )
Z
μ (mm-1
Rint
)
0.1190
1.029
0.0603
0.1259
0.2002
0.967
0.0988
0.1829
0.0410
1.009
0.0535
0.1275
GOF
R1
wR2
i
Conclusions
Synthesis of [cis-9,10-(NC6H3 Pr2-2,6)2-9,10-dihydrophenan-
threne]Ti(OiPr)2 (2a). A solution of nBuLi (2.2 mmol) was added
dropwise to a solution of 1a (0.76 g, 2.2 mmol) in n-hexane (20 mL)
at 0 °C. The reaction mixture was allowed to warm to room tem-
perature and stirred for 2 h. The formed lithium salt of 1a was
collected on a frit, washed with n-hexane (2 ꢀ 5 mL), and dried
under vacuum. The obtained lithium salt (0.57 g, 2.1 mmol) was
dissolved in toluene (20 mL) and added to a solution of TiCl2-
(OiPr)2 (1.1 mmol) in toluene (10 mL) at -20 °C. The reaction
mixture was allowed to warm to room temperature and stirred for 3
h. The precipitate was filtered off, and the solvent was removed to
leave a red solid. Recrystallization from CH2Cl2/hexane gave pure
2a as red crystals (0.67 g, 0.97 mmol, 88%). Mp: 180-181 °C. 1H
NMR (300 MHz, toluene-d8): δ 0.88 (d, J = 6.0 Hz, 6 H, OCH-
(CH3)2), 0.91 (d, J = 6.0 Hz, 6 H, OCH(CH3)2), 1.0-1.5 (br, 24 H,
CH(CH3)2), 3.4-3.7 (br, 2 H, CH(CH3)2), 3.9-4.2 (br, 2 H,
CH(CH3)2), 4.29 (sept, J = 6.0 Hz, 1 H, OCH(CH3)2), 4.34
(sept, J = 6.0 Hz, 1 H, OCH(CH3)2), 5.81 (s, 2 H, CHN), 6.80-
7.67 (m, 14 H, PhH) ppm. 13C NMR (75 MHz, toluene-d8): δ 23.5
(br, CH(CH3)2), 25.0 (br, CH(CH3)2), 25.5 (br, CH(CH3)2), 26.1
(OCH(CH3)2), 26.2 (OCH(CH3)2), 27.3 (br, CH(CH3)2), 28.2 (br,
CH(CH3)2), 29.1 (br, CH(CH3)2), 69.4 (CHN), 76.4 (OCH-
(CH3)2), 78.1 (OCH(CH3)2), 123.5, 124.3 (br), 124.9 (br), 125.5,
125.8 (br), 126.1, 126.6 (br), 127.3, 128.3, 129.7, 132.8, 138.7 ppm.
Anal. Calcd for C44H58N2O2Ti: C, 76.06; H, 8.41; N, 4.03. Found:
C, 76.01; H, 8.39; N, 4.02.
A number of new titanium complexes 2a-2e, 3a, and 3b
with an in situ formed cis-9,10-dihydrophenanthrenediamide
ligand have been directly synthesized in high yields from the
reactions of TiCl2(OiPr)2 with corresponding o-C6H4(CHd
NR)Li through sequential intramolecular C-C bond-forming
reductive elimination and oxidative coupling reactions. No
complexes with a trans-9,10-dihydrophenanthrenediamide
ligandhavebeenobtainedfromthese reactions. The reactions of
TiCl2(OiPr)2 with the o-C6H4(CHdNR)Li reagents are much
slower than the corresponding reactions of TiCl4, and the selec-
tivity for replacing one or two chloride(s) of TiCl2(OiPr)2 with
the o-C6H4(CHdNR) ligand can be controlled by the molar
ratio of the reagents. The asymmetric complexes 2d and 2e have,
therefore, been synthesized in good yields (57-65%) by sequen-
tial reactions of TiCl2(OiPr)2 with two different o-C6H4(CHd
NR)Li reagents. The cis configuration of the 9,10-dihydrophe-
nanthrenediamide ligand in these complexes was confirmed by
X-ray crystallographic analysis.
Experimental Section
General Comments. All manipulations of air- and water-
sensitive compounds were performed under an inert atmosphere
of nitrogen using standard Schlenk-line or glovebox techniques.
Solvents were dried and purified by known procedures and
distilled under nitrogen prior to use. nBuLi, Ti(OiPr)4, and TiCl4
were purchased from Aldrich and used as received without
further purification. TiCl2(OiPr)2 was prepared according to
literature methods.11 1H and 13C NMR spectra were measured
on a Varian Mercury-300 spectrometer. Elemental analysis was
performed on a Perkin-Elmer 2400 analyzer.
Synthesis of [cis-9,10-(NC6H3Et2-2,6)2-9,10-dihydrophenan-
threne]Ti(OiPr)2 (2b). Complex 2b was synthesized in the same
manner as that of 2a with compound 1b (0.70 g, 2.2 mmol), nBuLi
(2.2 mmol), and TiCl2(OiPr)2 (1.1 mmol) as starting materials or
reagents. Pure 2b was obtained as red crystals (0.57 g, 0.90 mmol,
82%). Mp: 174-175 °C. 1H NMR (300 MHz, toluene-d8): δ 0.90
(d, J = 6.0 Hz, 6 H, OCH(CH3)2), 1.04 (d, J = 6.0 Hz, 6 H, OCH-
(CH3)2), 1.35 (t, J = 7.5 Hz, 12 H, CH2CH3), 2.85-3.15 (m, J =
7.5 Hz, 8H, CH2CH3), 4.23 (sept, J = 6.0 Hz, 1 H, OCH(CH3)2),
4.32 (sept, J = 6.0 Hz, 1 H, OCH(CH3)2), 5.82 (s, 2 H, CHN),
6.80-7.80 (m, 14 H, PhH) ppm. 13C NMR (75 MHz, toluene-d8): δ
15.1 (CH2CH3), 25.2 (CH2CH3), 26.3 (OCH(CH3)2), 26.6 (OCH-
(CH3)2), 68.8 (CHN), 76.1 (OCH(CH3)2), 76.7 (OCH(CH3)2),
123.3, 124.6, 126.3, 126.6, 127.3, 127.6, 128.8, 129.5, 131.3, 137.7
ppm. Anal. Calcd for C40H50N2O2Ti: C, 75.22; H, 7.89; N, 4.38.
Found: C, 75.20; H, 7.87; N, 4.37.
Synthesis of o-C6H4Br(CHdNC6H3Et2-2,6) (1b). A mixture
of o-bromobenzaldehyde (8.71 g, 47.1 mmol), 2,6-diethylaniline
(7.8 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 (13.1 g, 41.6 mmol, 88%) was
obtained as yellowish-green crystals by recrystallization from
ethanol at -20 °C. 1H NMR (300 MHz, CDCl3): δ 1.17 (t, J=
7.5 Hz, 6 H, CH2CH3), 2.52 (q, J = 7.5 Hz, 4 H, CH2CH3),
7.04-7.12 (m, 3 H, PhH), 7.36 (t, 1 H, PhH), 7.45 (t, 1 H, PhH),
7.64 (d, 1 H, PhH), 8.28 (d, 1 H, PhH), 8.61 (s, 1 H, CHdNAr)
ppm. 13C NMR (300 MHz, CDCl3): δ 14.9 (CH3), 24.9 (CH2-
CH3), 124.3, 125.9, 126.5, 127.9, 128.3, 128.9, 132.6, 133.3,
134.6, 150.2 (CBr), 161.6 (CHdNAr) ppm. Anal. Calcd for
Synthesis of [cis-9,10-(NC6H3Me2-2,6)2-9,10-dihydrophenan-
threne]Ti(OiPr)2 (2c). Complex 2c was synthesized in the same
manner as that of 2a with compound 1c (0.63 g, 2.2 mmol), nBuLi
(2.2 mmol), and TiCl2(OiPr)2 (1.1 mmol) as starting materials or
reagents. Pure 2c was obtained as a red crystalline solid (0.50 g, 0.86
mmol, 78%). Mp: 172-173 °C. 1H NMR (300 MHz, toluene-d8):
δ 0.83 (d, J = 6.0 Hz, 6 H, OCH(CH3)2), 0.87 (d, J = 6.0 Hz,
6 H, OCH(CH3)2), 2.41 (s, 12 H, CH3), 4.20 (sept, J=6.0 Hz, 1 H,
C17H18NBr: C, 64.57; H, 5.74; N, 4.43. Found: C, 64.51; H,
5.79; N, 4.47.

36 Inorganic Chemistry, Vol. 50, No. 1, 2011
Zhao et al.
OCH(CH3)2), 4.38 (sept, J = 6.0 Hz, 1 H, OCH(CH3)2), 5.83 (s, 2
H, CHN), 6.80-7.80 (m, 14 H, PhH) ppm. 13C NMR (75 MHz,
toluene-d8): δ 23.9 (CH3), 26.4 (OCH(CH3)2), 26.7 (OCH(CH3)2),
66.1 (CHN), 71.5 (OCH(CH3)2), 76.8 (OCH(CH3)2), 123.5, 123.9,
124.0, 126.2, 127.5, 128.5, 129.7, 130.0, 130.2, 138.2 ppm. Anal.
Calcd for C36H42N2O2Ti: C, 74.22; H, 7.27; N, 4.81. Found: C,
74.20; H, 7.25; N, 4.80.
11%). Mp: 123-124 °C. 1H NMR (300 MHz, C6D6): δ 0.59 (d,
J = 6.9 Hz, 6 H, CH(CH3)2), 0.87 (d, J = 6.0 Hz, 6 H, OCH-
(CH3)2), 1.07 (d, J = 6.9 Hz, 6 H, CH(CH3)2), 1.13 (d, J = 6.9
Hz, 6 H, CH(CH3)2), 1.22 (d, J = 6.9 Hz, 6 H, CH(CH3)2), 1.27
(t, J = 7.5 Hz, 6 H, CH2CH3), 2.53 (q, J = 7.5 Hz, 4 H, CH2-
CH3), 3.58 (sept, J = 6.9 Hz, 2 H, CH(CH3)2), 3.79 (sept, J =
6.9 Hz, 2 H, CH(CH3)2), 4.22 (sept, J = 6.0 Hz, 1 H, OCH-
(CH3)2), 5.80 (s, 2 H, CHN), 6.80-7.80 (m, 21 H, PhH), 8.01 (s,
1H, CHdNAr) ppm. 13C NMR (75 MHz, C6D6): δ 14.9
(CH2CH3), 23.6, 24.8, 25.2, 25.6, 26.1, 26.6, 27.7, 28.6, 69.9
(CHN), 77.9 (OCH(CH3)2), 123.3, 123.5, 124.3, 124.6, 124.7,
124.9, 125.5, 125.9, 126.6, 127.3, 128.1, 128.2, 128.4, 128.6,
128.7, 128.9, 129.4, 129.6, 132.7, 137.6, 139.0, 162.1, 177.9
(CHdNAr) ppm. Anal. Calcd for C58H69N3OTi: C, 79.88; H,
7.98; N, 4.82. Found: C, 79.89; H, 7.96; N, 4.81.
i
Synthesis of [cis-N9(C6H3Et2-2,6)-N10(C6H3 Pr2-2,6)-9,10-dihy-
drophenanthrene]Ti(OiPr)2 (2d). The lithium salt of 1a (0.29 g,
1.1 mmol) was dissolved in toluene (10 mL), added to a solution of
TiCl2(OiPr)2 (1.1 mmol) in toluene (10 mL), and stirred for 30 min
at -25 °C. Then the lithium salt of 1b (0.25 g, 1.1 mmol) was
dissolved in toluene (10 mL) and added to the reaction mixture
at -25 °C. The reaction mixture was allowed to warm to room
temperature and also stirred for an additional 2 h. The precipitate
was filtered off, and the solvent was removed to leave a red solid.
Recrystallization from CH2Cl2/hexane gave pure 2d, obtained as a
red crystalline solid (0.48 g, 0.72 mmol, 65%). Mp: 154-155 °C. 1H
NMR (300 MHz, C6D6): δ 0.90 (d, J = 6.0 Hz, 3 H, OCH(CH3)2),
0.95 (d, J = 6.0 Hz, 3 H, OCH(CH3)2), 0.96 (d, J = 6.0 Hz, 3 H,
OCH(CH3)2), 0.97 (d, J = 6.0 Hz, 3 H, OCH(CH3)2), 0.8-1.0 (br,
3 H, CH(CH3)2), 1.1-1.5 (br, 9 H, CH(CH3)2), 1.28 (t, J = 7.5 Hz,
6 H, CH2CH3), 2.80-3.10 (m, J = 7.5 Hz, 4 H, CH2CH3), 3.7-3.9
(br, 1 H, CH(CH3)2), 3.9-4.1 (br, 1 H, CH(CH3)2), 4.20 (sept, J =
6.0 Hz, 1 H, OCH(CH3)2), 4.29 (sept, J = 6.0 Hz, 1 H, OCH-
(CH3)2), 5.75 (d, J = 7.2 Hz, 1 H, CHN), 5.91 (d, J = 7.2 Hz, 1 H,
CHN), 6.80-7.75 (m, 14 H, PhH) ppm. 13C NMR (75 MHz,
C6D6): δ 15.2 (CH2CH3), 23.5 (br, CH(CH3)2), 24.4, 24.6 (br,
CH(CH3)2), 24.7, 25.5 (br, CH(CH3)2), 25.8, 26.5 (br, CH(CH3)2),
26.8, 28.0 (br, CH(CH3)2), 28.4, 29.0 (br, CH(CH3)2), 68.8 (CHN),
69.4 (CHN), 76.2 (OCH(CH3)2), 76.9 (OCH(CH3)2), 123.3, 123.4,
123.5, 123.7, 124.5 (br), 124.6, 125.5, 125.7 (br), 126.1, 126.4, 126.5
(br), 126.7, 127.1, 127.3 (br), 127.4, 128.2, 128.8, 129.04, 129.7,
131.5, 138.8, 139.1 ppm. Anal. Calcd for C42H54N2O2Ti: C, 75.66;
H, 8.16; N, 4.20. Found: C, 75.68; H, 8.15; N, 4.21.
i
Synthesis of [cis-9,10-(NC6H3 Pr2-2,6)2-9,10-dihydrophenan-
threne][o-C6H4(CHdNC6H3Me2-2,6)]TiOiPr (3b). Complex 3b
was also isolated as a byproduct from the reaction for complex
2e. Pure 3b was obtained as a red crystalline solid (60 mg, 0.07
mmol, 13%). Mp: 118-119 °C. 1H NMR (300 MHz, C6D6): δ
0.64 (d, J = 6.9 Hz, 6 H, CH(CH3)2), 0.92 (d, J = 6.0 Hz, 6 H,
OCH(CH3)2), 1.03 (d, J = 6.9 Hz, 6 H, CH(CH3)2), 1.15 (d, J =
6.9 Hz, 6 H, CH(CH3)2), 1.27 (d, J = 6.9 Hz, 6 H, CH(CH3)2),
2.54 (s, 6 H, CH3), 3.56 (sept, J = 6.9 Hz, 2 H, CH(CH3)2), 4.15
(sept, J = 6.9 Hz, 2 H, CH(CH3)2), 4.25 (sept, J = 6.0 Hz, 1 H,
OCH(CH3)2), 5.86 (s, 2 H, CHN), 6.80-7.80 (m, 21 H, PhH),
8.06 (s, 1 H, CHdNAr) ppm. 13C NMR (75 MHz, C6D6): δ 23.9,
24.5, 26.4, 26.5, 26.6, 26.8, 28.5, 28.8, 69.8 (CHN), 76.8(OCH-
(CH3)2), 123.5, 123.8, 123.9, 124.0, 124.3, 124.9, 125.9, 126.6,
127.5, 127.7, 127.9, 128.2, 128.5, 128.8, 129.0, 129.2, 129.4,
130.0, 131.8, 134.2, 138.2, 162.4, 176.7 (CHdNAr) ppm. Anal.
Calcd for C56H65N3OTi: C, 79.69; H, 7.76; N, 4.98. Found: C,
79.68; H, 7.75; N, 4.96.
X-ray Structure Determinations of 2a, 2b, 2e, and 3a. Single
crystals of 2a, 2b, 2e, and 3a suitable for X-ray structural
analysis were obtained from the mixture of CH2Cl2/hexane.
The data were collected on a Bruker SMART-CCD diffrac-
tometer using graphite-monochromated Mo KR radiation (λ =
i
Synthesis of [cis-N9(C6H3Me2-2,6)-N10(C6H3 Pr2-2,6)-9,10-dihy-
drophenanthrene]Ti(OiPr)2 (2e). Complex 2e was synthesized in
the same manner as that of 2d with the lithium salt of 1a (0.29 g,
1.1 mmol), the lithium salt of 1c (0.21 g, 1.1 mmol), and TiCl2-
(OiPr)2 (1.1 mmol) as starting materials or reagents. Pure 2e was
obtained as red crystals (0.40 g, 0.63 mmol, 57%). Mp: 151-152 °C.
1H NMR (300 MHz, C6D6): δ 0.94 (d, J = 6.0 Hz, 6 H, OCH-
(CH3)2), 0.98 (d, J = 6.0 Hz, 3 H, OCH(CH3)2), 1.02 (d, J = 6.0
Hz, 3 H, OCH(CH3)2), 0.8-1.1 (br, 3 H, CH(CH3)2), 1.1-1.6 (br, 9
H, CH(CH3)2), 2.54 (s, 6 H, CH3), 3.6-3.8 (br, 1 H, CH(CH3)2),
4.2-4.4 (br, 1 H, CH(CH3)2), 4.25 (sept, J = 6.0 Hz, 1 H, OCH-
(CH3)2), 4.32 (sept, J = 6.0 Hz, 1 H, OCH(CH3)2), 5.84 (d, J = 7.2
Hz, 1 H, CHN), 5.88 (d, J = 7.2 Hz, 1 H, CHN), 6.80-7.80 (m, 14
H, PhH) ppm. 13C NMR (75 MHz, C6D6): δ 23-24 (br, CH-
(CH3)2), 24.0, 25-26 (br, CH(CH3)2), 26.0, 26.2, 26.3, 26.6, 27-29
(br, CH(CH3)2), 66.1 (CHN), 71.0 (CHN), 76.4 (OCH(CH3)2),
78.1 (OCH(CH3)2), 123.1, 123.6, 123.70, 123.72, 124.0 (br), 124.2,
124.5, 125.4 (br), 125.7, 127.1, 127.5 (br), 128.2, 128.7 (br), 129.4,
129.5, 129.8, 130.1, 131.3, 131.5, 133.1, 137.6, 138.3 ppm. Anal.
Calcd for C40H50N2O2Ti: C, 75.22; H, 7.89; N, 4.39. Found: C,
75.21; H, 7.88; N, 4.38.
˚
0.710 73 A) for 2e and 3a at 184.5K and on a Rigaku R-AXIS
RAPID IP diffractometer equipped with graphite-monochro-
˚
mated Mo KR radiation (λ = 0.710 73 A) for 2a and 2b at 293 K.
Details of the crystal data, data collection, and structure refine-
ments are summarized in Table 1. The structures were solved by
direct methods20 and refined by full-matrix least squares on F2.
All non-hydrogen atoms were refined anisotropically, and the
hydrogen atoms were included in idealized position. All calcula-
tions were performed using SHELXTL21 crystallographic soft-
ware packages.
Acknowledgment. This work was supported by the National
Natural Science Foundation of China (Grants 20772044 and
21074043).
Supporting Information Available: X-ray crystallographic
data in CIF format. This material is available free of charge
via the Internet at http://pubs.acs.org.
i
Synthesis of [cis-9,10-(NC6H3 Pr2-2,6)2-9,10-dihydrophenan-
(20) SHELXTL; PC Siemens Analytical X-ray Instruments: Madison, WI,
1993.
(21) Sheldrick, G. M. SHELXTL Structure Determination Programs,
version 5.0; PC Siemens Analytical Systems: Madison, WI, 1994.
threne][o-C6H4(CHdNC6H3Et2-2,6)]TiOiPr (3a). Complex 3a
was also isolated as a byproduct from the reaction for complex
2d. Pure 3a was obtained as red crystals (52 mg, 0.06 mmol,