Synthesis, structures, and solution behavior of Di- and trinuclear titanium(IV)-cyclophosphato complexes

Article abstract of DOI:10.1021/ic049206h

The reaction of the cyclotetraphosphate ion (P₄O ₁₂^4-) with [Cp*TiCl₃] (Cp* = η⁵-C₅Me₅) gives [(Cp*Ti) ₂(P₄O₁₂)₂]^2- where the P₄O₁₂ ligands adopt a saddle conformation, while that with [(Cp*TiCl)₃(μ-O)₃] leads to [(Cp*Ti) ₃(μ-O)₃(P₄O₁₂)]^- containing a crown form P₄O₁₂ ligand; both products feature their unique cage structures. On the other hand, the reactions of the cyclotriphosphate ion (P₃O₉^3-) with [(Cp*TiCl₂)₂(μ-O)] and [(Cp*TiCl) ₃(μ-O)₃] afford [(Cp*Ti)₂(μ-O) (P₃O₉)₂]^2- and [(Cp*Ti) ₃(μ-O)₃Cl(P₃O₉)]^-, respectively, and in both cases the P₃O₉ ligands bridge two titanium centers with an η²:η¹ mode.

Full text of DOI:10.1021/ic049206h

Inorg. Chem. 2004, 43, 6127−6129
Synthesis, Structures, and Solution Behavior of Di- and Trinuclear
Titanium(IV) Cyclophosphato Complexes
−
Sou Kamimura,† Tsukasa Matsunaga,† Shigeki Kuwata,‡ Masakazu Iwasaki,§ and Youichi Ishii*,|
Institute of Industrial Science, The UniVersity of Tokyo, Komaba, Meguro-ku,
Tokyo 153-8505, Japan, Department of Applied Chemistry, Graduate School of Science and
Engineering, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8552, Japan,
Department of Applied Chemistry, Faculty of Engineering, Saitama Institute of Technology,
Okabe, Saitama 369-0293, Japan, and Department of Applied Chemistry, Faculty of Science
and Engineering, Chuo UniVersity, Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan
Received June 18, 2004
4
-
The reaction of the cyclotetraphosphate ion (P4O12
)
with
blocks. In contrast, structural diversity of oxo-bridged inor-
ganic-organometallic hybrids based on inorganic polyphos-
phates, especially that of oxophilic early transition metal
derivarives, has been much less explored.7,8 In this Com-
munication, we disclose that the di- and trinuclear Ti(IV)
complexes built up with Cp*Ti units and cyclophosphato
ligand(s) possess unique three-dimensional structures, where
the cyclophosphato ligands take coordination structures
considerably different from those observed in late transition
metal complexes.
[Cp*TiCl3] (Cp* ) η5-C5Me5) gives [(Cp*Ti)2(P4O12)2]2 where the
-
P4O12 ligands adopt
a
saddle conformation, while that with
[(Cp*TiCl)3( -O)3] leads to [(Cp*Ti)3(
µ
µ
-O)3(P4O12)]- containing a
crown form P4O12 ligand; both products feature their unique cage
structures. On the other hand, the reactions of the cyclotriphosphate
3
ion (P3O9 -) with [(Cp*TiCl2)2(
µ
-O)] and [(Cp*TiCl)3(
-O)(P3O9)2]2- and [(Cp*Ti)3( -O)3Cl(P3O9)]-, respectively,
and in both cases the P3O9 ligands bridge two titanium centers
with an η2 η1 mode.
µ-O)3] afford
[(Cp*Ti)2(
µ
µ
When (PPN)4(P4O12)‚5H2O7b (PPN ) (PPh3)2N+) was
allowed to react with 1 equiv of [Cp*TiCl3] in CH2Cl2 at
room temperature, the dianionic dinuclear complex (PPN)2-
[(Cp*Ti)2(P4O12)2] (1) was obtained as red crystals in 28%
yield (Scheme 1).9 The 31P{1H} NMR spectrum of 1 shows
a singlet at δ -30.3 assignable to the P4O12 ligand, while
:
Organotransition metal complexes with O-donor ligands
have recently been attracting considerable attention, because
they serve as molecular models of metal species bound on
oxo surfaces of heterogeneous catalysts.1 They are also
expected to provide effective single source precursors for
structurally controlled inorganic materials.2 In this context,
a variety of three-dimensional coordination structures have
successfully been constructed by using monophosphates,3
monophosphonates,4-6 and monophosphinates6 as building
1
the H NMR spectrum shows a Cp* signal at δ 2.17 (s),
suggesting that the complex has a highly symmetric structure.
The solid-state structure of 1‚2C2H4Cl2 has been established
by an X-ray diffraction study (Figure 1a).10 The molecule
has a crystallographic center of symmetry. The anionic part
of 1 is composed of two Cp*Ti and two P4O12 units, where
* To whom correspondence should be addressed. E-mail: ishii@
chem.chuo-u.ac.jp.
(6) Guerrero, G.; Mehring, M.; Mutin, P. H.; Dahan, F.; Vioux, A. J.
Chem. Soc., Dalton Trans. 1999, 1537.
† The University of Tokyo.
(7) Several cyclophosphato complexes of late transition metals have been
synthesized by us and others. (a) Kamimura, S.; Kuwata, S.; Iwasaki,
M.; Ishii, Y. Dalton Trans. 2003, 2666. (b) Kamimura, S.; Kuwata,
S.; Iwasaki, M.; Ishii, Y. Inorg. Chem. 2004, 43, 399. (c) Besecker,
C. J.; Day, V. W.; Klemperer, W. G. Organometallics 1985, 4, 564.
(d) Day, V. W.; Klemperer, W. G.; Main, D. J. Inorg. Chem. 1990,
29, 2345. (e) Klemperer, W. G.; Main, D. J. Inorg. Chem. 1990, 29,
2355. (f) Day, V. W.; Klemperer, W. G.; Lockledge, S. P.; Main, D.
J. J. Am. Chem. Soc. 1990, 112, 2031. (g) Day, V. W.; Eberspacher,
T. A.; Klemperer, W. G.; Planalp, R. P.; Schiller, P. W.; Yagasaki,
A.; Zhong, B. Inorg. Chem. 1993, 32, 1629. (h) Klemperer, W. G.;
Zhong, B. Inorg. Chem. 1993, 32, 5821. (i) Han, K.-N.; Whang, D.;
Lee, H.-J.; Do, Y.; Kim, K. Inorg. Chem. 1993, 32, 2597. (j) Attanasio,
D.; Bachechi, F.; Suber, L. J. Chem. Soc., Dalton Trans. 1993, 2373.
(8) Ryu, S.; Whang, D.; Kim, J.; Yeo, W.; Kim, K. J. Chem. Soc., Dalton
Trans. 1993, 205.
‡ Tokyo Institute of Technology.
§ Saitama Institute of Technology.
| Chuo University.
(1) (a) Feher, F. J.; Budzichowski, T. A. Polyhedron 1995, 14, 3239. (b)
Gouzerh, P.; Proust, A. Chem. ReV. 1998, 98, 77. (c) Murugavel, R.;
Voigt, A.; Walawalkar, M. G.; Roesky, H. W. Chem. ReV. 1996, 96,
2205.
(2) Walawalkar, M. G.; Roesky, H. W. Acc. Chem. Res. 1999, 32, 117.
(3) Lugmair, C. G.; Tilley, T. D. Inorg. Chem. 1998, 37, 1821.
(4) Walawalkar, M. G.; Horchler, S.; Dietrich, S.; Chakraborty, D.;
Roesky, H. W.; Scha¨fer, M.; Schmidt, H.-G.; Sheldrick, G. M.;
Murugavel, R. Organometallics 1998, 17, 2865.
(5) (a) Chakraborty, D.; Chandrasekhar, V.; Bhattacharjee, M.; Kratzner,
R.; Roesky, H. W.; Noltemeyer, M.; Schmidt, H.-G. Inorg. Chem.
2000, 39, 23. (b) Guzyr, O. I.; Siefken, R.; Chakraborty, D.; Roesky,
H. W.; Teichert, M. Inorg. Chem. 2000, 39, 1680. (c) Mehring, M.;
Guerrero, G.; Dahan, F.; Mutin, P. H.; Vioux, A. Inorg. Chem. 2000,
39, 3325.
(9) Although the formation of 1 and 2 seemed to be clean, difficulty in
isolating them by recrystallization resulted in the significant loss of
the yield.
10.1021/ic049206h CCC: $27.50
Published on Web 09/08/2004
© 2004 American Chemical Society
Inorganic Chemistry, Vol. 43, No. 20, 2004 6127

COMMUNICATION
Scheme 2
yield (Scheme 1).9 An X-ray diffraction study of
2‚0.5CH2Cl2 has revealed that the core of complex 2 is a
cage composed of a crown form P4O12 ligand and a Ti3O3
six-membered ring (Figure 1b).10 One of the three titanium
centers (Ti(1)) adopts a four-legged piano stool geometry,
while the geometry of the other two is a three-legged piano
stool. It should be pointed out that 1 and 2 are rare examples
of P4O12 complexes,7b and to the best of our knowledge, 2
provides the first example of the coordination compound
containing a crown conformation P4O12 ligand.
Figure 1. ORTEP drawings for the anionic parts of 1‚2C2H4Cl2 (a) and
2‚0.5C6H5CH3 (b). Thermal ellipsoids are drawn at the 30% probability
level. Hydrogen atoms are omitted for clarity. Selected bond distances (Å)
for 1‚2C2H4Cl2: Ti-O(1), 1.963(3); Ti-O(2), 1.980(3); Ti-O(9)*, 1.969-
(3); Ti-O(11)*, 1.995(2). For 2‚0.5C6H5CH3: Ti(1)-O(1), 1.921(2);
Ti(1)-O(3), 1.906(2); Ti(1)-O(4), 2.011(2); Ti(1)-O(5), 2.023(2);
Ti(2)-O(1), 1.774(2); Ti(2)-O(2), 1.833(2); Ti(2)-O(6), 1.927(2);
Ti(3)-O(2), 1.834(2); Ti(3)-O(3), 1.780(2); Ti(3)-O(7), 1.916(2).
Scheme 1
1
In the 31P{1H} and H NMR spectra of 2 in CD2Cl2 at
room temperature, only one broad signal at δ -33.6 (s) for
the P4O12 ligand and one singlet at δ 2.15 for the Cp* groups
are observed, respectively. These spectral features, which
are inconsistent with the local Cs symmetry of the anion of
2 in the solid state, indicate that the complex 2 is fluxional
in solution. In fact, the broad 31P{1H} NMR signal coalesces
at -20 °C and splits to two pseudodoublets (δ -30.3 (J )
32 Hz), -37.0 (J ) 32 Hz)) at -80 °C in the variable
temperature 31P{1H} NMR spectra (162 MHz), though there
is no apparent change in the 1H NMR over this temperature
range. This fluxionality is rationalized by the rotation of the
Ti3O3 unit on the P4O12 platform, and the ∆Gq value for the
(10) Crystal data for 1‚2C2H4Cl2 follow: formula C96H98Cl4N2O24P12Ti2,
M ) 2273.17, triclinic, a ) 12.28(1) Å, b ) 14.16(2) Å, c )
15.65(2) Å, R ) 87.08(4)°, â ) 72.44(2)°, γ ) 85.39(4)°, V )
2585(5) Å3, P1h, Z ) 1, µ ) 5.15 cm-1, Dc ) 1.460 g cm-3, 50474
reflections measured, 11675 unique (Rint ) 0.041), R1 ) 0.047, wR2
) 0.123. For 2‚0.5C6H5CH3: formula C69.5H79NO15P6Ti3, M )
1497.93, triclinic, a ) 11.2743(9) Å, b ) 13.313(1) Å, c ) 26.442(2)
Å, R ) 79.799(3)°, â ) 89.912(5)°, γ ) 65.218(2)°, V ) 3534.6(5)
Å3, P1h, Z ) 2, µ ) 5.32 cm-1, Dc ) 1.407 g cm-3, 31333 reflections
measured, 15682 unique (Rint ) 0.040), R1 ) 0.055, wR2 ) 0.121.
For 3‚CH2Cl2: formula C93H92Cl2N2O19P10Ti2, M ) 2018.20, tri-
clinic, a ) 13.021(3) Å, b ) 19.841(4) Å, c ) 19.899(5) Å, R )
98.981(10)°, â ) 105.971(13)°, γ ) 105.740(11)°, V ) 4607.0(17)
Å3, P1h, Z ) 2, µ ) 4.76 cm-1, Dc ) 1.455 g cm-3, 68686 reflections
measured, 19935 unique (Rint ) 0.040), R1 ) 0.050, wR2 ) 0.098.
For 4‚0.5C2H4Cl2: formula C67H77Cl2NO12P5Ti3, M ) 1457.82,
triclinic, a ) 11.44(1) Å, b ) 14.128(4) Å, c ) 22.247(8) Å, R )
94.55(4)°, â ) 97.81(4)°, γ ) 92.84(4)°, V ) 3544.6(4) Å3, P1h, Z )
2, µ ) 5.76 cm-1, Dc ) 1.366 g cm-3, 16918 reflections measured,
16914 unique (Rint ) 0.045), R ) 0.051, Rw ) 0.056 [7948 data I >
3σ(I)].
each P4O12 ligand takes a saddle conformation and bridges
the two titanium atoms to form an unprecedented cage
structure. Interestingly, the cage structure of 1 has a chan-
nel which penetrates the two side faces defined by the
characteristic 12-membered Ti2P4O6 rings. Considering the
van der Waals radius of oxygen (1.4 Å) as well as the
O(5)‚‚‚O(7)*, O(1)‚‚‚O(11), and Ti‚‚‚Ti* interatomic dis-
tances at 3.683(4), 4.783(3), and 6.134(1) Å, respectively,
the size of the rectangular entrance of the channel is estimated
to be 0.9 Å × 2.0 Å.
On the other hand, the reaction of (PPN)4(P4O12)‚5H2O
with 1 equiv of the oxo-bridged trinuclear complex
[(Cp*TiCl)3(µ-O)3]11 afforded the monoanionic complex
(PPN)[(Cp*Ti)3(µ-O)3(P4O12)] (2) as orange crystals in 28%
(11) Carofiglio, T.; Floriani, C.; Sgamellotti, A.; Rosi, M.; Chiesi-Villa,
A.; Rizzoli, C. J. Chem. Soc., Dalton Trans. 1992, 1081.
6128 Inorganic Chemistry, Vol. 43, No. 20, 2004

COMMUNICATION
Scheme 3
Finally, treatment of (PPN)3(P3O9)‚H2O with [(Cp*TiCl)3-
(µ-O)3] resulted in the formation of the monoanionic complex
(PPN)[(Cp*Ti)3(µ-O)3Cl(P3O9)] (4) in 84% yield (Scheme
2). The structure of the anion is shown in Figure 2b. In
contrast to the P4O12 complex 2, only two of the three
titanium centers are bound to the terminal oxygen atoms of
the P3O9 ligand in 4, and the remaining titanium atom
(Ti(3)) remains coordinated by a chloro ligand (Figure 2b).10
Again, the P3O9 ligand adopts a κ2O,O′:κO′′ coordination
mode, making the trititanium core unsymmetrical. Con-
versely, the 31P{1H} NMR spectra (CDCl3) of 4 exhibit one
triplet (δ -23.4, J ) 15 Hz) and one doublet (δ -26.7, J )
1
15 Hz) assignable to the P3O9 ligand, and the H NMR
Figure 2. ORTEP drawings for the anionic parts of 3‚CH2Cl2 (a) and
4‚0.5C2H4Cl2 (b). Thermal ellipsoids are drawn at the 30% probability level.
Hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles
(deg) for 3‚CH2Cl2: Ti(1)-O(1), 1.859(3); Ti(1)-O(2), 2.046(2); Ti(1)-
O(3), 2.028(3); Ti(1)-O(11), 2.061(3); Ti(2)-O(1), 1.819(2); Ti(2)-O(4),
2.044(2); Ti(2)-O(12), 2.025(2); Ti(2)-O(13), 2.041(2); Ti(1)‚‚‚Ti(2),
3.120(1); Ti(1)-O(1)-Ti(2), 116.1(1). For 4‚0.5C2H4Cl2: Ti(1)-O(7),
2.103(4); Ti(1)-O(9), 2.025(4); Ti(1)-O(10), 1.910(4); Ti(1)-O(11), 1.882-
(4); Ti(2)-O(8), 1.926(4); Ti(2)-O(11), 1.791(4); Ti(2)-O(12), 1.816(4);
Ti(3)-Cl, 2.319(2); Ti(3)-O(10), 1.771(4); Ti(3)-O(12), 1.828(4).
spectra display two Cp* singlets at δ 2.10 (30H) and 2.09
(15H), suggesting an apparent Cs symmetry of the complex
in solution. Although no temperature dependence of the
spectra was observed over the range 20 to -60 °C, these
spectral features are explained by the fast migration of the
specific oxygen atom (O*) between the titanium centers
Ti(1) and Ti(2) (Scheme 3), but not by the rotation of the
P3O9 ligand as observed in the P4O12 complex 2.
In summary, we have disclosed that cyclophosphate anions
are versatile building blocks to construct organotitanium-
phosphate hybrids with diversified structures, in which the
P4O12 and P3O9 ligands take unique coordination modes. The
closed cage structures have been found for the P4O12
complexes, while more open structures have been observed
with the P3O9 ligands.
rotation at the coalescence temperature (-20 °C) is estimated
to be 45(2 kJ/mol (see Supporting Information).
The P3O9 ligand exhibited rather different coordination
behavior. Although the reaction of (PPN)3(P3O9)‚H2O with
[Cp*TiCl3] failed to give isolable products, that with 0.5
equiv of [(Cp*TiCl2)2(µ-O)]12 in CH2Cl2 at room temperature
afforded the dianionic complex (PPN)2[(Cp*Ti)2(µ-O)-
(P3O9)2] (3) as red crystals in 80% yield (Scheme 2). Its
31P{1H} NMR spectrum (CDCl3) clearly shows the presence
of three nonequivalent phosphorus atoms in the P3O9 ligand
(δ -21.4 (dd, J ) 14 Hz, J ) 19 Hz), -24.4 (dd, J ) 14
Hz, J ) 24 Hz), -26.7 (dd, J ) 19 Hz, J ) 24 Hz)), while
Acknowledgment. This work was supported by a Grant-
in-aid for Scientific Research from the Ministry of Education,
Culture, Sports, Science and Technology, Japan, and by a
grant from the Research Institute of Science and Engineering,
Chuo University, Japan.
1
the H NMR spectrum displays one singlet at δ 2.16 (s)
Supporting Information Available: Experimental details de-
scribing the synthesis and characterization data; a table of crystal
data for 1-4; complete X-ray structural data for 1-4 in CIF format.
This material is available free of charge via the Internet at
http://pubs.acs.org.
assignable to the Cp* ligand. The molecular structure of
3‚CH2Cl2 has been confirmed by an X-ray study (Figure
2a).10 In complex 3, each P3O9 ligand bridges the two
titanium atoms in a κ2O,O′:κO′′ fashion. It should be noted
that in the P3O9 complexes reported so far only the
monomeric κ3- or κ2-coordination mode has been observed;
the above bridging coordination mode is unprecedented for
the P3O9 ligand.
IC049206H
(12) Palacious, F.; Royo, P.; Serrano, R. J. Organomet. Chem. 1989, 375,
51.
Inorganic Chemistry, Vol. 43, No. 20, 2004 6129