Syntheses, characterizations, and single-crystal X-ray structures of soluble titanium alkoxide phosphonates

Article abstract of DOI:10.1021/ic000002k

Reactions of Ti(O(i)Pr)₄ with different phosphonic acids RPO₃H₂ (R = Ph, 4-CNPh, Me, (t)Bu) in organic solvents have been investigated. In the presence of small amounts of water, the new molecular titanium oxide alkoxide phosphonates [Ti₄(μ₃-O)(O(i)Pr)₅(μ-O(i)Pr)₃(RPO₃)₃]·DMSO [R = Ph (1), Me (2), (t)Bu (3), 4-CNPh (4.)] were isolated. The single-crystal X-ray structure analyses of 1 and 2 revealed hexacoordinated titanium atoms and a connectivity of (111) for each phosphonate. Under rigorous exclusion of water, the reaction of Ti(O(i)Pr)₄ with tert-butylphosphonic acid in toluene gave the titanium phosphonate tetramer [Ti(O(i)Pr)₂((t)BuPO₃)]₄ (5). A single-crystal X-ray structure analysis of 5 revealed a 5 + 1 coordination of the titanium atoms as a result of the (112) connectivity of each phosphonate; such a coordination mode has never been reported for a titanium phosphate, phosphonate, or phosphinate. Compounds 1-5 were characterized by FT-IR, ³¹P MAS NMR, and solution multinuclear NMR (¹H, ¹³C{¹H}, ³¹P{¹H}) spectroscopies. ¹³C CP MAS NMR experiments were carried out on arylphosphonates 1 and 4. Solution NMR experiments were also used to investigate the exchange reaction between 1 and 2 and the conversion of 5 to [Ti₄(μ₃-O)(O(i)Pr)₅(μ-O(i)Pr)₃((t)BuPO₃)₃]·(i)PrOH by partial hydrolysis in the presence of Ti(O(i)Pr)₄. The phosphonate clusters 1-5 are soluble in organic solvents and are likely intermediates in the sol-gel processing of inorganic-organic hybrids based on titanium oxide and phosphonate groups that we are currently developing.

Full text of DOI:10.1021/ic000002k

Inorg. Chem. 2000, 39, 3325-3332
3325
Syntheses, Characterizations, and Single-Crystal X-ray Structures of Soluble Titanium
Alkoxide Phosphonates
Michael Mehring,‡ Gilles Guerrero, Franc¸oise Dahan,§ P. Hubert Mutin,* and Andre´ Vioux
UMR CNRS 5637, Chimie Mole´culaire et Organisation du Solide, Case 007, Universite´ de Montpellier
II, 34095 Montpellier Cedex 5, France, and UPR CNRS 8241, Laboratoire de Chimie de Coordination
du CNRS, 205 Route de Narbonne, 31077 Toulouse Cedex 4, France
ReceiVed January 5, 2000
t
Reactions of Ti(OiPr)4 with different phosphonic acids RPO3H2 (R ) Ph, 4-CNPh, Me, Bu) in organic solvents
have been investigated. In the presence of small amounts of water, the new molecular titanium oxide alkoxide
phosphonates [Ti4(µ3-O)(OiPr)5(µ-OiPr)3(RPO3)3]‚DMSO [R ) Ph (1), Me (2), tBu (3), 4-CNPh (4)] were isolated.
The single-crystal X-ray structure analyses of 1 and 2 revealed hexacoordinated titanium atoms and a connectivity
of (111) for each phosphonate. Under rigorous exclusion of water, the reaction of Ti(OiPr)4 with tert-butylphosphonic
acid in toluene gave the titanium phosphonate tetramer [Ti(OiPr)2(tBuPO3)]4 (5). A single-crystal X-ray structure
analysis of 5 revealed a 5 + 1 coordination of the titanium atoms as a result of the (112) connectivity of each
phosphonate; such a coordination mode has never been reported for a titanium phosphate, phosphonate, or
phosphinate. Compounds 1-5 were characterized by FT-IR, 31P MAS NMR, and solution multinuclear NMR
(1H, 13C{1H}, 31P{1H}) spectroscopies. 13C CP MAS NMR experiments were carried out on arylphosphonates 1
and 4. Solution NMR experiments were also used to investigate the exchange reaction between 1 and 2 and the
conversion of 5 to [Ti4(µ3-O)(OiPr)5(µ-OiPr)3(tBuPO3)3]‚iPrOH by partial hydrolysis in the presence of Ti(OiPr)4.
The phosphonate clusters 1-5 are soluble in organic solvents and are likely intermediates in the sol-gel processing
of inorganic-organic hybrids based on titanium oxide and phosphonate groups that we are currently developing.
Introduction
use of bidentate diorganophosphinic acids (R2PO2H) or tridentate
organophosphonic acids (RPO3H2) to prepare molecular titanium
Metal alkoxides play an important role as precursors to metal
oxide materials prepared by sol-gel processing or metal-
organic chemical vapor deposition (MOCVD).1-4 In the sol-
gel process, chemical modifiers such as â-diketonate or
carboxylate ligands are usually allowed to react with the metal
alkoxides prior to hydrolysis:5-8 the partial replacement of
alkoxy groups by these ligands decreases the reactivity and thus
permits control of the formation of sols and gels. Furthermore,
it allows the introduction of organic functionalities for organic-
inorganic hybrid materials applications.2,9
Partial hydrolysis and condensation reactions of (modified)
transition metal alkoxides lead to the formation of oxide
alkoxides, which serve as models for the initial stages in the
sol-gel process as well as molecular building blocks for novel
advanced materials.10-13 Several molecular titanium oxide
alkoxide clusters have been prepared by reactions of titanium
alkoxides with bidentate carboxylic acids.14-19 However, the
(oxide) alkoxide clusters remains mainly unexplored,20,21 al-
though phosphato, phosphonato, and phosphinato ligands have
been widely used to prepare polynuclear oxo anions such as
vanadates and molybdates,22-24 layered titanium phosphates and
phosphonates,25 and polymeric titanium alkoxide phosphinates.26
To date, the only crystallographically characterized molecular
titanium phosphonates are the titanium alkoxo anion in
(10) Day, V. W.; Eberspacher, T. A.; Klemperer, W. G.; Park, C. W. J.
Am. Chem. Soc. 1993, 115, 8469-8470.
(11) Chen, Y. W.; Klemperer, W. G.; Park, C. W. Mater. Res. Symp. Proc.
1992, 271, 57-63.
(12) Campana, C. F.; Chen, Y.; Day, V. W.; Klemperer, W. G.; Sparks,
R. A. J. Chem. Soc., Dalton Trans. 1996, 691-702.
(13) Day, V. W.; Eberspacher, T. A.; Chen, Y.; Hao, J.; Klemperer, W.
G. Inorg. Chim. Acta 1995, 229, 391-405.
(14) Papiernik, R.; Hubert-Pfalzgraf, L. G.; Vaissermann, J.; Goncalves,
M. J. Chem. Soc., Dalton Trans. 1998, 2285-2287.
(15) Boyle, T. J.; Todd, M. A.; Tafoya, C. J.; Scott, B. L. Inorg. Chem.
1998, 37, 5588-5594.
(16) Lei, X.; Shang, M.; Fehlner, T. P. Organometallics 1997, 16, 5289-
5301.
* Corresponding author. E-mail: mutin@crit.univ-montp2.fr.
‡ Present address: Universita¨t Dortmund, Otto Hahn Str. 6, 44227
Dortmund, Germany.
(17) Schubert, U.; Tewinkel, S.; Mo¨ller, F. Inorg. Chem. 1995, 34, 995-
§ UPR CNRS 8241.
997.
(1) Hubert-Pfalzgraf, L. G. Polyhedron 1994, 13, 1181-1195.
(2) Schubert, U.; Hu¨sing, N.; Lorenz, A. Chem. Mater. 1995, 7, 2010-
2027.
(3) Sanchez, C.; Ribot, F. New J. Chem. 1994, 18, 1007-1047.
(4) Mehrotra, R. C.; Singh, A. Chem. Soc. ReV. 1996, 25, 1-13.
(5) Scolan, E.; Sanchez, C. Chem. Mater. 1998, 10, 3217-3223.
(6) Leaustic, A.; Babonneau, F.; Livage, J. Chem. Mater. 1989, 1, 240-
247.
(18) Kickelbick, G.; Schubert, U. Eur. J. Inorg. Chem. 1998, 159-161.
(19) Doeuff, S.; Dromzee, Y.; Taulelle, F.; Sanchez, C. Inorg. Chem. 1989,
28, 4439-4445.
(20) Errington, J. R.; Ridland, J.; Willett, K. J.; Clegg, W.; Coxall, R. A.;
Heath, S. L. J. Organomet. Chem. 1998, 550, 473-476.
(21) Guerrero, G.; Mehring, M.; Mutin, P. H.; Dahan, F.; Vioux, A. J.
Chem. Soc., Dalton Trans. 1999, 1537-1538.
(22) Zubieta, J. Comments Inorg. Chem. 1994, 16, 153-183.
(23) Chang, Y. D.; Zubieta, J. Inorg. Chim. Acta 1996, 245, 177-198.
(24) Pope, M. T. Heteropoly and Isopoly Oxometalates; Springer-Verlag:
Berlin, 1983; Vol. 8.
(7) Leaustic, A.; Babonneau, F.; Livage, J. Chem. Mater. 1989, 1, 248-
252.
(8) Doeuff, S.; Henry, M.; Sanchez, C.; Livage, J. J. Non-Cryst. Solids
1987, 89, 206-216.
(9) Judeinstein, P.; Sanchez, C. J. Mater. Chem. 1996, 6, 511-525.
(25) Clearfield, A. Prog. Inorg. Chem. 1998, 47, 371-510.
(26) Dahl, G. H.; Block, B. P. Inorg. Chem. 1967, 6, 1439-1443.
10.1021/ic000002k CCC: $19.00 © 2000 American Chemical Society
Published on Web 07/06/2000

3326 Inorganic Chemistry, Vol. 39, No. 15, 2000
Mehring et al.
[Ti2(OMe)6(O3PPh)2][nBu4N]2 and the partially hydrolyzed
20
Table 1. Crystallographic Collection Data for
[Ti(µ3-O)(OiPr)5(µ-OiPr)3(MePO3)3]‚DMSO (2) and
[Ti(OiPr)2(tBuPO3)]4 (5)
complexes [(Cp*TiO3PR)4(µ-O)2] (R ) Me, Ph) and [(Cp*Ti)3-
(tBuPO3)2{tBuPO2(OH)}(µ-O)2].27
2
5
The condensation of titanium alkoxides with carboxylic acids
as well as with phosphinic and phosphonic acids results in the
formation of alcohols. In the case of carboxylic acids, esteri-
fication of unreacted acids by the liberated alcohols leads to
the formation of water. Under the same conditions, the esteri-
fication of phosphonic or phosphinic acids by the liberated
alcohols does not take place; hence, no water forms, which
allows a better control of the formation of oxo bridges.
We recently reported a promising sol-gel route to novel
inorganic-organic hybrids based on metal oxide and phospho-
nate groups. This sol-gel route involves the nonhydrolytic
condensation between a metal alkoxide and an organophospho-
rus acid, followed by a controlled hydrolysis-condensation of
the remaining alkoxy groups.28
empirical formula
fw
C29H71O19P3STi4
1040.43
C40H92O20P4Ti4
1208.62
space group
a, Å
b, Å
P21/c (No. 14)
19.743(3)
12.6777(11)
19.896(3)
90
91.019(15)
90
P1 (No. 2)
14.1115(17)
19.819(2)
21.784(3)
92.677(16)
92.369(16)
92.074(14)
6076.1(14)
4
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
4979.1(10)
4
λ, Å
0.710 73
160 ( 2
0.710 73
160 ( 2
1.321
0.675
0.0304, 0.0569
0.0548, 0.0601
T, K
F
calcd, Mg/m3
1.388
µ(Mo KR), mm-1
R:a obsd, all
0.819
0.0218, 0.0344
0.0451, 0.0488
The present contribution deals with the reaction of Ti(OiPr)4
with different phosphonic acids (phenylphosphonic acid, (4-
cyanophenyl)phosphonic acid, methylphosphonic acid, and tert-
butylphosphonic acid), resulting in the formation of novel,
organic-soluble molecular titanium phosphonates. The syntheses
and characterizations of the titanium oxide alkoxide phospho-
nates [Ti4(µ3-O)(OiPr)5(µ-OiPr)3(RPO3)3]‚DMSO [R ) Ph (1),
Rw:b obsd, all
a R ) ∑||Fo| - |Fc||/∑|Fo|. b Rw ) [∑w(|Fo | - |Fc2|)2/∑w|Fo | ]1/2
.
2
2 2
and high-power proton decoupling. 31P MAS NMR spectra were
recorded without cross-polarization (CP) using a 45° flip angle and a
10 s recycling delay; chemical shifts are referenced to H3PO4 (85% in
water). 13C CP-MAS NMR spectra were recorded using cross-
polarization (CP) with a 5 s recycling delay; chemical shifts are
referenced to Me4Si. FT-IR spectra were obtained on a Perkin-Elmer
Spectrum 2000 spectrophotometer with the KBr pellet technique.
X-ray Data Collections and Structure Determinations for 2 and
5. The data were collected31 on a Stoe imaging plate diffractometer
system (IPDS), equipped with an Oxford Cryosystems cooler device,
at 160 K using Mo KR radiation with a graphite monochromator (λ )
0.710 73 Å). In both cases, the data were collected with a crystal-to-
detector distance of 80 mm, in the 2θ range 2.9-48.4° with a æ rotation
movement (æ ) 0.0-249.6° and ∆æ ) 1.3° for 2; æ ) 0.0-250.5°
and ∆æ ) 1.5° for 5). No absorption corrections were made. The
structures were solved using direct methods32 and refined33 by full-
matrix least-squares techniques based on F2. All non-hydrogen atoms
were refined anisotropically. Hydrogen atoms were found on difference
Fourier maps and introduced into calculations with riding models, where
t
Me (2), Bu (3), 4-CNPh (4)] and the titanium alkoxide
phosphonate [Ti(OiPr)2(tBuPO3)]4 (5) are presented. In a
preliminary communication, the X-ray single-crystal structure
of 1 was reported.21 In this work, we present the X-ray single-
crystal structures of the methyl analogue 2 and of the first
example of a molecular phosphonate-bridged titanium alkoxide
5. We also present the characterizations of compounds 1-5 by
IR spectroscopy, variable-temperature multinuclear NMR spec-
troscopy (1H, 13C, 31P) in solution, and 31P solid-state NMR
spectroscopy, which shows 3 and 4 to be analogues of 1 and 2.
Experimental Section
General Methods. All manipulations were carried out under an
atmosphere of dry argon using standard Schlenk and glovebox
techniques. Solvents were purified by conventional procedures and
distilled prior to use. DMSO was distilled two times from CaH2 and
stored over molecular sieve (4 Å). Elemental analyses were performed
by the microanalysis laboratory of the CNRS in Vernaison. The melting
points were measured under argon in sealed capillaries on a Bu¨chi B
450 melting point apparatus and are reported uncorrected. All manipu-
lations were carried out under an inert atmosphere. Ti(OiPr)4 (Aldrich)
was distilled prior to use. Methylphosphonic and phenylphosphonic
acids (Aldrich), tert-butylphosphonic acid (Lancaster), and 4-(cy-
anophenyl)phosphonic acid29,30 were dried under high vacuum prior to
use.
Uiso was equal to 1.1 times Uiso of the atom of attachment. The atomic
scattering factors and anomalous dispersion terms were taken from the
standard compilation.34 The crystallographic data are summarized in
Table 1, and the non-carbon fractional coordinates for 2 and 5 are listed
in Tables 2 and 3, respectively.
[Ti4(µ3-O)(OiPr)5(µ-OiPr)3(PhPO3)3]‚DMSO (1). This compound
was prepared as described previously.21 Anal. Calcd for C44H77O19P3-
1
STi4: C, 43.08; H, 6.32. Found: C, 42.85; H, 6.52. H NMR (200.1
i
MHz, THF, 23 °C), δ (ppm): 0.33 (d, 12H, MeO Pr), 0.71 (d, 18H,
i
i
MeO Pr), 0.80 (d, 18H, MeO Pr), 1.83 (s, 6H, MeDMSO), 4.03 (sep, 3H,
i
i
i
CHO Pr), 4.26 (sep, 2H, CHO Pr), 4.40 (sep, 3H, CHO Pr), 6.60-6.71
(complex pattern, 12H, Haryl), 7.16-7.28 (complex pattern, 6H, Haryl).
Spectroscopies. Solution 1H and 31P NMR experiments were
performed using a Bruker DPX200 spectrometer. When THF was used
as the solvent for NMR experiments, samples were transferred under
an argon atmosphere into a 5 mm NMR tube and an acetone-d6 capillary
13C{1H} NMR (50.3 MHz, THF, 23 °C), δ (ppm): 24.0, 24.2 (MeO Pr),
i
38.8 (MeDMSO), 77.6, 78.4 (CHO Pr), 126.9 (d, J(13C-31P) ) 15 Hz,
3
i
4
2
C
aryl/meta), 129.0 (d, J(13C-31P) ) 3 Hz, Caryl/para), 130.6 (d, J(13C-
31P) ) 9 Hz, Caryl/ortho), 135.5 (d, 1J(13C-31P) ) 203 Hz, Caryl/ipso). 31P-
{1H} NMR (101.3 MHz, THF, 23 °C), δ (ppm): 6.8. 31P{1H} NMR
(101.3 MHz, THF, -40 °C), δ (ppm): 6.7, 6.5 (2:1). 31P{1H} MAS
NMR (solid state, 121.5 MHz), δ (ppm): 5.84, 6.20, 7.25 (1:1:1). 13C-
{1H} MAS NMR (solid state, 75.5 MHz), δ (ppm): 24.0, 25.1, 25.7,
1
was used as a lock standard. H NMR chemical shifts are referenced
to Me4Si and 31P NMR chemical shifts to H3PO4 (85% in water). Solid-
state NMR spectra were obtained with a Bruker Avance DPX300
spectrometer, using magic angle spinning (MAS) (spinning rate 10 kHz)
(27) Walawalkar, M. G.; Horchler, S.; Dietrich, S.; Chakraborty, D.;
Roesky, H. W.; Schafer, M.; Schmidt, H. G.; Sheldrick, G. M.;
Murugavel, R. Organometallics 1998, 17, 2865-2868.
(28) (a) Mutin, P. H.; Delenne, C.; Medoukali, D.; Corriu, R.; Vioux, A.
Mater. Res. Symp. Proc. 1998, 519, 345-350. (b) Guerrero, G.; Mutin,
P. H.; Vioux, A. Chem. Mater. 2000, 12, 1268-1272.
(29) Hirao, T.; Masunaga, T.; Oshiro, Y.; Toshio, A. Synthesis 1981, 56-
57.
(31) Stoe. IPDS Manual, Version 2.87; Stoe & Cie: Darmstadt, Germany,
1997.
(32) Sheldrick, G. M. SHELXS-97: Program for Crystal Structure Solution;
University of Go¨ttingen: Go¨ttingen, Germany, 1990.
(33) Sheldrick, G. M. SHELXL-97: Program for the Refinement of Crystal
Structures from Diffraction Data; University of Go¨ttingen, Go¨ttingen,
Germany, 1997.
(30) McKenna, C. E.; Higa, M. T.; Cheung, N. H.; McKenna, M.-C.
Tetrahedron Lett. 1977, 2, 155-158.
(34) International Tables for Crystallography; Kluwer Academic Publish-
ers: Dordrecht, The Netherlands, 1992; Vol. C.

Soluble Titanium Alkoxide Phosphonates
Inorganic Chemistry, Vol. 39, No. 15, 2000 3327
Table 2. Selected Positional and Equivalent Isotropic Displacement
Parameters (Å2 × 102) and Their Esd’s for
Table 3. Selected Positional and Equivalent Isotropic Displacement
Parameters (Å2 × 102) and Their Esd’s for [Ti(OiPr)2(tBuPO3)]4 (5)
[Ti(µ3-O)(OiPr)5(µ-OiPr)3(MePO3)3]‚DMSO (2)
a
x
y
z
Ueq
a
x
y
z
Ueq
Ti(1A)
Ti(2A)
Ti(3A)
Ti(4A)
P(1A)
P(2A)
P(3A)
0.87566(3)
0.83416(3)
0.79120(3)
0.61346(3)
0.95297(5)
0.72813(5)
0.78773(5)
0.64422(5)
0.9014(1)
0.9349(1)
0.9148(1)
0.7111(1)
0.8229(1)
0.7360(1)
0.8710(1)
0.7508(1)
0.6994(1)
0.7476(1)
0.6555(1)
0.5915(1)
0.9974(1)
0.8369(1)
0.9106(1)
0.7885(1)
0.8301(1)
0.7883(1)
0.5339(1)
0.5422(1)
0.21336(3)
0.25293(4)
0.42685(4)
0.16535(4)
0.40180(6)
0.09118(5)
0.31436(5)
0.25200(6)
0.2991(1)
0.3891(1)
0.4515(1)
0.1398(1)
0.1122(1)
0.1297(1)
0.3086(1)
0.3305(1)
0.2186(1)
0.2904(1)
0.3386(1)
0.1682(1)
0.2587(1)
0.1391(1)
0.2210(2)
0.2476(2)
0.4963(2)
0.5063(2)
0.0435(1)
0.2083(2)
0.53824(2)
0.35688(2)
0.49948(2)
0.55461(2)
0.46107(3)
0.44118(3)
0.61990(3)
0.42679(3)
0.46827(7)
0.38583(7)
0.50634(7)
0.50575(7)
0.45789(8)
0.37895(8)
0.60196(8)
0.56160(7)
0.63449(8)
0.41232(8)
0.47229(8)
0.46259(8)
0.53821(8)
0.59971(8)
0.32237(8)
0.28002(8)
0.43856(9)
0.56974(9)
0.56049(8)
0.59058(9)
1.12488(2)
0.95891(2)
0.92619(2)
0.95869(2)
1.03903(4)
1.01517(3)
1.05626(3)
0.85923(3)
1.05880(9)
0.98398(9)
1.01139(9)
1.01730(8)
1.08745(8)
0.96219(8)
1.11098(8)
0.98603(8)
1.04584(8)
0.90882(9)
0.85101(9)
0.88569(8)
1.19667(8)
1.16725(8)
1.0133(1)
0.34760(2)
0.24889(2)
0.11874(2)
0.25781(2)
0.21287(3)
0.34979(3)
0.23969(3)
0.16949(3)
0.27400(7)
0.19416(7)
0.16317(7)
0.31574(7)
0.38624(7)
0.30667(7)
0.28180(7)
0.19447(7)
0.27683(7)
0.18749(7)
0.11397(7)
0.22091(7)
0.37325(7)
0.40189(7)
0.30414(7)
0.21142(7)
0.06473(7)
0.07066(8)
0.31934(8)
0.20047(8)
0.26890(2)
0.37502(2)
0.23021(2)
0.14636(2)
0.33465(3)
0.28911(3)
0.15683(3)
0.23978(4)
0.31993(8)
0.38136(8)
0.27773(9)
0.22747(7)
0.31751(7)
0.33092(8)
0.20781(8)
0.18017(8)
0.11950(8)
0.29201(8)
0.20036(9)
0.20286(8)
0.31534(8)
0.21656(8)
0.43630(9)
0.41339(9)
0.2810(1)
1.66(1)
1.45(1)
1.95(1)
1.87(1)
1.42(1)
1.58(1)
1.99(2)
1.80(2)
1.28(4)
1.62(4)
1.68(4)
1.81(4)
1.78(4)
1.79(4)
1.94(4)
1.76(4)
2.33(4)
1.79(4)
2.28(4)
1.99(4)
2.25(4)
2.58(4)
1.97(4)
2.23(4)
2.71(4)
2.99(5)
2.49(4)
2.76(4)
2.09(1)
3.10(1)
3.22(1)
2.59(1)
3.05(2)
2.12(2)
2.42(2)
3.03(2)
2.76(4)
3.62(5)
3.44(5)
2.14(4)
2.21(4)
2.83(4)
2.50(4)
2.82(4)
2.73(4)
3.17(5)
3.55(5)
2.89(4)
2.70(4)
2.56(4)
4.02(5)
4.47(6)
4.22(5)
4.05(5)
3.41(5)
3.99(5)
Ti(1)
Ti(2)
Ti(3)
Ti(4)
S(1)
P(1)
P(2)
0.25164(2)
0.30721(2)
0.32514(2)
0.09730(2)
-0.00852(3)
0.15666(3)
0.18158(2)
0.26186(3)
0.17379(7)
0.19208(6)
0.18687(7)
0.00680(7)
0.26087(6)
0.31354(6)
0.33079(7)
0.25046(7)
0.22060(7)
0.35642(7)
0.28751(7)
0.38143(7)
0.30275(7)
0.38835(7)
0.24982(6)
0.13256(6)
0.11846(7)
0.05553(6)
0.07822(7)
0.33956(3)
0.56442(3)
0.46501(3)
0.60588(3)
0.41890(4)
0.51395(4)
0.37147(4)
0.68918(4)
0.3962(1)
0.3033(1)
0.6718(1)
0.5280(1)
0.4814(1)
0.4144(1)
0.3247(1)
0.2136(1)
0.5779(1)
0.6320(1)
0.6903(1)
0.5286(1)
0.6091(1)
0.4394(1)
0.4081(1)
0.4608(1)
0.5587(1)
0.72315(9)
0.6274(1)
0.11894(2)
0.09055(2)
0.23228(2)
0.21244(2)
0.22391(2)
0.05957(2)
0.25523(2)
0.21728(2)
0.06800(6)
0.19250(6)
0.22113(7)
0.19543(7)
0.15828(6)
0.05497(6)
0.18433(6)
0.07960(7)
0.04339(6)
0.03074(7)
0.14511(7)
0.15815(7)
0.26046(7)
0.29518(7)
0.28468(6)
0.24150(6)
0.11764(6)
0.18192(6)
0.30058(6)
2.62(1)
2.60(1)
2.69(1)
2.16(1)
3.09(1)
2.58(1)
2.57(1)
3.11(1)
3.14(3)
2.94(3)
3.61(3)
3.25(3)
2.64(3)
2.99(3)
3.10(3)
3.59(3)
3.41(3)
3.73(3)
3.87(4)
3.24(3)
3.68(3)
3.40(3)
2.85(3)
2.62(3)
2.80(3)
2.42(3)
3.11(3)
P(4A)
O(1A)
O(2A)
O(3A)
O(4A)
O(5A)
O(6A)
O(7A)
O(8A)
O(9A)
O(10A)
O(11A)
O(12A)
O(13A)
O(14A)
O(15A)
O(16A)
O(17A)
O(18A)
O(19A)
O(20A)
Ti(1B)
Ti(2B)
Ti(3B)
Ti(4B)
P(1B)
P(3)
O(1)
O(2)
O(3)
O(4)
O(5)
O(6)
O(7)
O(8)
O(9)
O(10)
O(11)
O(12)
O(13)
O(14)
O(15)
O(16)
O(17)
O(18)
O(19)
a Ueq ) one-third of the trace of the orthogonalized Uij tensor.
i
i
26.3, 26.9 (MeO Pr), 37.7, 38.9 (MeDMSO), 78.5, 79.0, 79.1, 82.8 (CHO Pr),
125.6-134.9 (broad, Caryl), 136.5 (d, 1J(13C-31P) ) 201 Hz, Caryl/ipso),
137.2 (d, J(13C-31P) ) 208 Hz, Caryl/ipso). FT-IR (Nujol), cm-1: 602
1
P(2B)
P(3B)
P(4B)
(m), 623 (m), 618 (m), 697 (m), 719 (w), 750 (m), 838 (m), 854 (m),
958 (s), 972 (s), 1003 (sh), 1010 (vs), 1035 (m), 1068 (w), 1094 (s),
1137 (vs), 1164 (sh), 1194 (s), 1316 (w), 1327 (w).
O(1B)
O(2B)
O(3B)
O(4B)
O(5B)
O(6B)
O(7B)
O(8B)
O(9B)
O(10B)
O(11B)
O(12B)
O(13B)
O(14B)
O(15B)
O(16B)
O(17B)
O(18B)
O(19B)
O(20B)
[Ti4(µ3-O)(OiPr)5(µ-OiPr)3(MePO3)3]‚DMSO (2). To a solution of
methylphosphonic acid (270 mg, 2.81 mmol) in 3.5 mL of DMSO was
added Ti(OiPr)4 (1.60 g, 5.63 mmol), giving a colorless precipitate.
Addition of water (17 µL, 0.94 mmol) in 3 mL of THF and stirring for
10 min at room temperature gave a cloudy solution. A 5 mL portion
of THF was added, and the reaction mixture was heated until a clear
solution was observed. The solvent was evaporated until a cloudy
solution was obtained. Colorless crystals appeared in this solution after
several days at 0 °C. These crystals were filtered off, washed with two
5 mL portions of Et2O, and dried in vacuo, giving 593 mg (61% yield)
of 2. Mp: 140-142 °C. Anal. Calcd for C29H71O19P3STi4: C, 33.48;
1
H, 6.83. Found: C, 33.38; H, 6.81. H NMR (200.1 MHz, THF, 23
°C), δ (ppm): 0.42-0.64 (broad complex pattern, 21H, MePMe, MeOiPr),
i
i
0.8808(1)
0.8797(1)
0.9278(1)
0.95830(9)
0.90876(9)
0.68 (d, 18H, MeO Pr), 0.81 (d, broad, 18H, MeO Pr), 1.92 (s, 6H,
i
MeDMSO), 4.00 (sep, 3H, CHO Pr), 4.23-4.45 (broad complex pattern,
0.16845(9)
0.12167(8)
0.08502(9)
5H, CHO Pr). 13C{1H} NMR (50.3 MHz, THF, 23 °C), δ (ppm): 12.1
i
(d, 1J(13C-31P) ) 158 Hz, MePMe), 23.7, 24.0 (MeO Pr), 39.3 (MeDMSO),
i
76.9, 77.2, 77.8 (CHO Pr). 31P{1H} NMR (81.0 MHz, THF, 23 °C), δ
i
(ppm): 17.2, 19.2 (1:2). 31P{1H} NMR (81.0 MHz, CH2Cl2/CD2Cl2,
23 °C), δ (ppm): 20.7, 21.5 (1:2). 31P{1H} MAS NMR (solid state,
a Ueq ) one-third of the trace of the orthogonalized Uij tensor.
121.5 MHz), δ (ppm): 14.7, 16.7, 17.6 (1:1:1). FT-IR (Nujol), cm-1
:
gave a clear yellow solution. Colorless crystals were obtained from
this solution after several days. These crystals were filtered off and
dried under high vacuum, giving 670 mg (53% yield) of 3 as an
amorphous powder. Mp: 187-190 °C. No satisfactory elemental
analysis was obtained for 3, probably as a result of the high sensitivity
608 (m), 769 (w), 776 (w), 798 (w), 835 (w), 854 (w), 890 (vw), 954
(m), 1008 (vs), 1036 (w), 1066 (s), 1104 (s), 1132 (s), 1164 (sh), 1195
(sh), 1303 (w), 1327 (vw).
Reaction of 1 with 2. Crystals of 1 (118 mg, 0.096 mmol) and 2
(100 mg, 0.096 mmol) were mixed in 1.5 mL of THF at room
temperature. A cloudy solution formed, and the 31P NMR analysis
showed signals at 20.8 (1%), 20.1 (8%), 19.6 (12%), 17.7 (20%), 8.5
(6%), and 7.3 ppm (53%). No assignment was made.
1
of this fine, amorphous powder to hydrolysis. H NMR (200.1 MHz,
CD2Cl2, 23 °C), δ (ppm): 1.20 (d, 3J(1H-31P) ) 15 Hz, 27H, MePtBu),
i
i
i
1.23 (d, 12H, MeO Pr), 1.37 (d, 18H, MeO Pr), 1.48 (d, 18H, MeO Pr),
i
i
2.61 (s, 6H, MeDMSO), 4.65 (sep, 3H, CHO Pr), 4.87 (sep, 3H, CHO Pr),
[Ti4(µ3-O)(OiPr)5(µ-OiPr)3(tBuPO3)3]‚DMSO (3). To a solution of
tert-butylphosphonic acid (450 mg, 3.25 mmol) in 5 mL of DMSO
was added Ti(OiPr)4 (1.80 g, 6.33 mmol), giving two liquid phases.
Addition of water (20 µL, 1.11 mmol) in 3 mL of THF and heating
5.15 (m, 2H, CHO Pr). 13C{1H} NMR (50.3 MHz, CD2Cl2, 23 °C), δ
i
(ppm): 25.1, 26.0, 26.1 (MeO Pr), 26.7 (d, 2J(13C-31P) ) 2 Hz, MePtBu),
i
31.3 (d, 1J(13C-31P) ) 153 Hz, CPtBu), 41.5 (MeDMSO), 77.7, 79.8
(CHO Pr), 80.3 (broad, CHO Pr). 31P{1H} NMR (81.0 MHz, THF, 23 °C),
i
i

3328 Inorganic Chemistry, Vol. 39, No. 15, 2000
Mehring et al.
δ (ppm): 28.8. 31P{1H} NMR (101.3 MHz, CD2Cl2, 23 °C), δ (ppm):
27.3. 31P{1H} NMR (101.3 MHz, CD2Cl2, -70 °C), δ (ppm): 24.3,
25.0 (1:2). 31P{1H} MAS NMR (solid state, 121.5 MHz), δ (ppm):
23.6, 24.5 (1:2) (from the deconvolution of overlapping signals). FT-
IR (Nujol), cm-1: 606 (s), 694 (w), 827 (sh), 835 (m), 853 (m), 954
(s), 1004 (vs), 1044 (s), 1056 (m), 1070 (m), 1104 (s), 1127 (s), 1164
(sh), 1204 (vw), 1233 (vw), 1308 (w), 1326 (w).
Scheme 1
[Ti4(µ3-O)(OiPr)5(µ-OiPr)3(4-CNPhPO3)3]‚DMSO (4). Water (30
µL, 1.67 mmol) was added to a solution of (4-cyanophenyl)phosphonic
acid (771 mg, 9.85 mmol) in 3 mL of DMSO. The addition of Ti-
(OiPr)4 (2.80 g, 9.85 mmol) gave a clear yellow solution. Colorless
crystals were obtained from this solution after several days. These
crystals were filtered off, washed with two 4 mL portions of Et2O, and
dried in vacuo, giving 1.05 g (57% yield) of 4. Mp: >240 °C dec.
Anal. Calcd for C47H74N3O19P3STi4: C, 43.37; H, 5.73; N, 3.22.
1
Found: C, 43.18; H, 5.93; N, 3.11. H NMR (200.1 MHz, THF, 23
i
i
°C), δ (ppm): 0.33 (d, 12H, MeO Pr), 0.71 (d, 18H, MeO Pr), 0.79 (d,
i
i
18H, MeO Pr), 1.84 (s, 6H, MeDMSO), 4.02 (sep, 3H, CHO Pr), 4.22 (sep,
i
i
2H, CHO Pr), 4.41 (sep, 3H, CHO Pr), 7.01-7.08 (complex pattern, 6H,
H
aryl), 7.27-7.38 (complex pattern, 6H, Haryl). 13C{1H} NMR (50.3
i
MHz, THF, 23 °C), δ (ppm): 23.8, 23.9, 24.0 (MeO Pr), 39.1 (MeDMSO),
4
78.3, 79.2 (CHO Pr), 113.3 (d, J(13C-31P) ) 3.4 Hz, Caryl/para), 117.7
(d, 5J(13C-31P) ) 1.6 Hz, CN), 130.9 (d, 3J(13C-31P) ) 15 Hz, Caryl/meta),
131.1 (d, 2J(13C-31P) ) 10 Hz, Caryl/ortho), 140.6 (d, 1J(13C-31P) ) 200
Hz, Caryl/ipso). 31P{1H} NMR (101.3 MHz, THF, 23 °C), δ (ppm): 4.5.
31P{1H} NMR (101.3 MHz, THF, -40 °C), δ (ppm): 4.6, 4.3 (2:1).
31P{1H} MAS NMR (solid state, 121.5 MHz), δ (ppm): 3.1, 4.4 (1:2).
FT-IR (Nujol), cm-1: 606 (s), 631 (s), 778 (vw), 795 (vw), 834 (s),
854 (s), 952 (s), 982 (s), 1005 (vs), 1049 (s), 1090 (s), 1129 (vs), 1160
(s), 1181 (w), 1205 (s), 1298 (vw), 1321 (w), 1328 (w) 2229 (m).
[Ti(OiPr)2(tBuPO3)]4 (5). Ti(OiPr)4 (3.64 g, 12.81 mmol) was added
dropwise to a suspension of tert-butylphosphonic acid (910 mg, 6.59
mmol) in 60 mL of toluene, giving a clear solution. This solution was
heated at 80 °C for 2 h, and 45 mL of toluene was distilled off. Colorless
crystals were isolated from this solution after 2 weeks at 0 °C. The
crystals were dried in vacuo, giving 0.60 g (30% yield) of 5. Mp: >260
°C dec. Anal. Calcd for C40H92O20P4Ti4: C, 39.77; H, 7.62. Found: C,
39.31; H, 7.57. 1H NMR (200.1 MHz, CD2Cl2, 23 °C), δ (ppm): 1.30
i
When THF was used as the solvent instead of DMSO, the
reaction of phenylphosphonic acid, water, and Ti(OiPr)4 gave a
1
clear solution. The 31P NMR and H NMR data of the crude
reaction mixture indicated the formation of [Ti(µ3-O)(OiPr)5-
(µ-OiPr)3(PhPO3)3]‚THF.
The reaction of Ti(OiPr)4 with a DMSO solution of tert-
butylphosphonic acid gave two liquid phases. Upon addition
of THF and water, a yellow solution was obtained and
crystallization began after several hours. When (4-cyanophenyl)-
phosphonic acid, water, and Ti(OiPr)4 were allowed to react in
DMSO, no precipitate was observed, in contrast to what was
observed with phenylphosphonic acid. Compound 4 crystallized
after several days from a concentrated DMSO solution.
Attempts to isolate a nonhydrolyzed titanium alkoxide
phosphonate from DMSO or THF solutions failed, and the
addition of water was required to prepare the partially hydro-
lyzed compounds 1-4 in significant yields. If an insufficient
amount of water was used for the preparation of 1, the 31P NMR
spectrum of the crude reaction mixture was indicative of a
complex mixture containing several products. Further addition
of water gave a 31P NMR spectrum showing one main signal
for the cluster at δ 6.8 ppm (ca. 70-80%) and two signals in
the region of δ 16 ppm (ca. 30-20%) (unidentified compounds).
When the ratio of Ti(OiPr)4 to phenylphosphonic acid was varied
between 1.33 and 10, the 31P NMR spectra of the crude reaction
mixtures did not vary significantly and 1 was always obtained
as the main product.
(d, 12H, MeO Pr), 1.36 (d, 3J(1H-31P) ) 17 Hz, 9H, MePtBu), 5.35 (sep,
i
2H, CHO Pr). 13C{1H} NMR (50.3 MHz, CD2Cl2, 23 °C), δ (ppm): 25.8
i
1
(MeO Pr), 25.9 (MePtBu), 32.3 (d, J(13C-31P) ) 137 Hz, CPtBu), 83.0
i
(CHO Pr). 31P{1H} NMR (101.3 MHz, CD2Cl2, 23 °C), δ (ppm): 40.2.
i
31P{1H} NMR (101.3 MHz, THF, 23 °C), δ (ppm): 39.3. 31P{1H} MAS
NMR (solid state, 121.5 MHz), δ (ppm): 36.9, 37.9, 38.0, 38.7, 39.0,
39.1. FT-IR (Nujol), cm-1: 605 (m), 668 (vw), 834 (w), 854 (w), 1002
(vs), 1010 (s), 1075 (sh), 1096 (m), 1126 (m), 1162 (w), 1204 (vw),
1235 (vw), 1224 (w).
Reaction of 5 with H2O in the Presence of Ti(OiPr)4. Pure [Ti-
(OiPr)2(tBuPO3)]4 (5) (320 mg, 0.265 mmol) was dissolved in 0.6 mL
of CD2Cl2, and Ti(OiPr)4 (115 mg, 0.405 mmol) was added. To this
solution was added water (6 µL, 0.33 mmol) in three steps, leading to
a cloudy solution after the addition of the third portion of water. After
each addition, the 31P and 1H NMR spectra were recorded. The initial
Despite a certain sensitivity to hydrolysis, the arylphospho-
nates 1 and 4 may be handled in air for short periods of time
without notable decomposition: the 31P MAS NMR spectra of
1 and 4 recorded after exposure to atmospheric moisture for 2
h were unchanged compared to the initial 31P MAS NMR
spectra. This was not the case for the alkylphosphonates 2 and
3, which showed much higher sensitivity to hydrolysis.
The titanium alkoxide phosphonate [Ti(OiPr)2(tBuPO3)]4 (5)
(Scheme 2) was prepared by adding Ti(OiPr)4 to a suspension
of tert-butylphosphonic acid in toluene, giving a clear solution.
After heating, the 31P NMR spectrum of the crude reaction
mixture showed one main signal at δ 39.4 ppm corresponding
to 5 and several signals of minor intensity in the region of δ
20-40 ppm. 5 was crystallized from this solution on standing
at 0 °C for several days.
1
signal of 5 disappeared, and the 31P and H NMR spectra showed the
formation of [Ti4(µ3-O)(OiPr)5(µ-OiPr)3(tBuPO3)3]‚HOiPr and 2-pro-
panol, together with minor, unidentified phosphonate products.
Results
Syntheses. The titanium oxide alkoxide phosphonates [Ti4(µ3-
t
O)(OiPr)5(µ-OiPr)3(RPO3)3]‚DMSO [R ) Ph (1), Me (2), Bu
(3), 4-CNPh (4)] were each prepared by adding Ti(OiPr)4 and
small amounts of water to a DMSO solution of the appropriate
organophosphonic acid (Scheme 1). In the case of the phenyl-
and methylphosphonic acids, an amorphous precipitate was
formed first, which was dissolved by adding small amounts of
THF followed by a slight warming of the reaction mixture.
Crystallization of colorless needles of 1 and 2 from the light
yellow solution was observed after several days, depending on
the amount of THF added.
Single-Crystal X-ray Structures of [Ti4(µ3-O)(OiPr)5(µ-
OiPr)3(MePO3)3]‚DMSO (2) and [Ti(OiPr)2(tBuPO3)]4 (5).
The structures of 2 (Figure 1) and 5 (Figure 2) are molecular

Soluble Titanium Alkoxide Phosphonates
Inorganic Chemistry, Vol. 39, No. 15, 2000 3329
Figure 2. ORTEP view of one molecule of 5 (A). Hydrogen atoms
have been omitted for clarity. Thermal ellipsoids are drawn at 50%
probability. The geometry of the other molecule is essentially the same.
Figure 1. ORTEP view of 2. Hydrogen atoms have been omitted for
clarity. Thermal allipsoids are drawn at 50% probability.
Table 4. Selected Bond Lengths (Å) and Angles (deg) for
[Ti4(µ3-O)(OiPr)5(µ-OiPr)3(MePO3)3]‚DMSO (2)
Scheme 2
Bond Lengths
Ti(1)-O(1)
Ti(1)-O(2)
Ti(1)-O(5)
Ti(1)-O(6)
Ti(1)-O(7)
Ti(1)-O(8)
Ti(4)-O(3)
Ti(4)-O(4)
1.962(1)
1.949(1)
1.968(1)
2.017(1)
2.024(1)
1.778(1)
1.961(1)
2.064(1)
Ti(4)-O(16)
Ti(4)-O(17)
Ti(4)-O(18)
Ti(4)-O(19)
P(1)-O(1)
2.047(1)
2.029(1)
1.800(1)
1.821(1)
1.539(2)
1.539(1)
1.502(1)
1.527(1)
P(1)-O(9)
P(1)-O(17)
S(1)-O(4)
Bond Angles
O(1)-Ti(1)-O(2)
O(1)-Ti(1)-O(5)
O(1)-Ti(1)-O(6)
O(1)-Ti(1)-O(7)
O(1)-Ti(1)-O(8)
O(2)-Ti(1)-O(5)
O(2)-Ti(1)-O(6)
O(2)-Ti(1)-O(7)
O(2)-Ti(1)-O(8)
O(5)-Ti(1)-O(6)
O(5)-Ti(1)-O(7)
O(5)-Ti(1)-O(8)
O(6)-Ti(1)-O(7)
O(6)-Ti(1)-O(8)
O(7)-Ti(1)-O(8)
O(3)-Ti(4)-O(4)
O(3)-Ti(4)-O(16)
89.81(6) O(3)-Ti(4)-O(17)
86.40(5) O(3)-Ti(4)-O(18)
88.84(6) O(3)-Ti(4)-O(19)
162.70(6) O(4)-Ti(4)-O(16)
95.59(6) O(4)-Ti(4)-O(17)
88.26(5) O(4)-Ti(4)-O(18)
164.88(6) O(4)-Ti(4)-O(19)
87.97(5) O(16)-Ti(4)-O(17)
90.41(6)
94.88(6)
93.05(6)
84.57(5)
84.17(5)
87.12(6)
92.08(6)
85.58(5)
96.63(6) O(16)-Ti(4)-O(18) 171.48(6)
76.63(5) O(16)-Ti(4)-O(19)
76.39(5) O(17)-Ti(4)-O(18)
86.42(5)
91.75(5)
with no significant intermolecular contacts in their respective
crystal lattices. The molecular structure of 2 is similar to that
of the phenylphosphonate analogue 1, with the four Ti atoms
forming a trigonal pyramid (Scheme 1). Selected bond lengths
and angles for 2 are displayed in Table 4. The three titanium
atoms of the base, Ti(1), Ti(2), and Ti(3), have similar
coordination geometries, formed by two oxygen atoms of two
different phosphonato groups [Ti-O 1.943(1)-1.973(2) Å], one
terminal isopropoxy group [Ti-O 1.771(1)-1.781(2) Å], two
bridging isopropoxy groups [Ti-O 2.017(1)-2.035(2) Å], and
the µ3-oxygen atom [Ti-O 1.938(1)-1.968(1) Å]. The Ti-
O(iPr) and the Ti-O(P) bond distances compare well with those
reported for titanium oxide alkoxides13 and titanium phospho-
nates,20,27 respectively. The distorted octahedral geometry of Ti-
(1)-Ti(3) is demonstrated by the O-Ti-O trans angles in the
range 162.70(6)-174.72(6)° and the O-Ti-O cis angles in the
range 76.26(5)-101.71(6)°. The µ3-oxygen atom symmetrically
bridges the titanium centers Ti(1), Ti(2), and Ti(3), and the Ti-
µ3-O-Ti angles are almost identical [105.03(6)-105.89°]. The
six-coordinate titanium atom Ti(4) of the apex is bonded to the
Ti3O(OiPr)6 fragment of the base by three bridging phosphonato
groups. Two of the phosphonato oxygen atoms are trans to
174.72(6) O(17)-Ti(4)-O(19) 171.45(6)
88.85(5) O(18)-Ti(4)-O(19)
98.49(6) O(1)-P(1)-O(9)
101.71(6) O(1)-P(1)-O(17)
174.28(6) O(9)-P(1)-O(17)
93.23(6)
95.74(6)
110.74(8)
113.26(7)
112.76(8)
terminal isopropoxy groups [Ti-O 1.800(1)-1.821(1) Å], and
the corresponding Ti-O(P) bonds are slightly shorter [Ti-O
2.047(1)/2.029(1) Å] than the Ti(4)-O(3)(P) bond [Ti-O 1.961-
(1) Å], which is trans to the coordinated DMSO molecule. The
distortion of the octahedral coordination geometry of Ti(4) is
shown by the O-Ti-O trans and cis angles in the ranges
171.45(6)-174.28(6) and 84.17(5)-95.74(6)°, respectively. In
this cluster, the phosphonate groups act as tridentate bridging
ligands. Each of the phosphonate units is bonded to three
different titanium atoms, and the connectivity is noted (111).35
Nevertheless, two groups of distinct O-P-O angles are found.
Those bridging the titanium atoms of the central Ti3O unit
(35) Massiot, D.; Drumel, S.; Janvier, P.; Bujoli-Doeuff, M.; Bujoli, B.
Chem. Mater. 1997, 9, 6-7.

3330 Inorganic Chemistry, Vol. 39, No. 15, 2000
Mehring et al.
Table 5. Selected Bond Lengths (Å) and Angles (deg) for
[Ti(OiPr)2(tBuPO3)]4 (5) (Molecule A)
Bond Distances
Ti(1)-O(1)
Ti(1)-O(4)
Ti(1)-O(5)
Ti(1)-O(7)
Ti(1)-O(13)
2.122(2)
2.450(2)
1.972(2)
1.955(2)
1.784(2)
Ti(1)-O(14)
P(1)-O(1)
P(1)-O(2)
P(1)-O(3)
1.775(2)
1.547(2)
1.537(2)
1.531(2)
Bond Angles
O(1)-Ti(1)-O(4)
O(1)-Ti(1)-O(5)
O(1)-Ti(1)-O(7)
O(1)-Ti(1)-O(13)
80.96(6) O(4)-Ti(1)-O(14)
83.89(6) O(5)-Ti(1)-O(7)
82.77(6) O(5)-Ti(1)-O(13)
90.65(7) O(5)-Ti(1)-O(14)
90.96(7)
149.94(7)
101.62(7)
97.24(7)
105.35(8)
91.82(7)
98.31(8)
O(1)-Ti(1)-O(14) 170.51(8) O(7)-Ti(1)-O(13)
O(4)-Ti(1)-O(5)
O(4)-Ti(1)-O(7)
64.89(6) O(7)-Ti(1)-O(14)
86.44(7) O(13)-Ti(1)-O(14)
O(4)-Ti(1)-O(13) 164.65(7)
[O-P-O average 110.6°] are slightly smaller than those
connecting Ti(4) to the Ti3O unit [O-P-O average 112.8°]. In
the same way, the P-O bonds that are directed toward Ti(1),
Ti(2), and Ti(3) [P-O average 1.537 Å] are slightly longer than
the P-O bonds which are directed toward Ti(4) [P-O average
1.504 Å].
The asymmetric unit of [Ti(OiPr)2(tBuPO3)]4 (5) contains two
independent molecules, 5A and 5B, which are chemically
identical in composition and do not differ significantly in
structure. The central Ti4O12P4 core of 5 is formed by four
titanium and four phosphorus atoms that occupy the alternate
vertexes of a highly distorted cube (Scheme 2). This three-
dimensional Ti-O-P core is surrounded by eight terminal
isopropoxy groups and four tert-butyl groups, making the
organic-inorganic cluster compound highly soluble in common
organic solvents. Selected bond lengths and angles for 5 are
given in Table 5. The Ti-O bond distances of the terminal
isopropoxy groups [Ti-O 1.760(2)-1.794(2) Å] are comparable
to those reported for titanium (oxide) alkoxides.13
The phosphonato groups in 5 present a (112) connectivity.35
Thus, two of the oxygens of the phosphonate units are bonded
to one titanium atom only; the corresponding Ti-O(P) bond
distances [Ti-O(P) 1.948(2)-1.982(2) Å] are comparable to
those found for 2 or for other titanium phosphonates where the
phosphonato groups are in a (111) connectivity.21,27 The third
oxygen of the phosphonate units is bonded to two titanium atoms
on the same face of the distorted Ti4O12P4 cube; the corre-
sponding Ti-O(P) bond distances are in the ranges 2.120(2)-
2.141(2) and 2.401(2)-2.454(2) Å, respectively. Note that the
longest Ti-O(P) bonds are across a face of the Ti4O12P4 cube.
The P-O bond distances (P-O(Ti) 1.523(2)-1.552(2) Å) are
comparable to those of previously reported molecular titanium
phosphonates and show no particularities. On the other hand,
the O-P-O angles are significantly larger in the bridging
coordination mode (average 112.4°) than in the chelating
coordination mode (average 102.6°).
Figure 3. FT-IR spectra of compounds 1-5.
3). For all of the titanium phosphonates 1-5, the FT-IR spectra
showed no absorptions corresponding to P-OH or PdO groups,
suggesting RP(O-Ti)3 units in all cases.36-39 The ν(Ti-O)
absorption frequencies of 1-5 are observed in the 602-608
cm-1 range. Furthermore, all compounds show characteristic
absorptions at 1126-1137 and 1162-1164 cm-1 assigned to
the iso-branching vibrations of the isopropoxy groups.40 Another
general spectral feature of compounds 1-5 is a strong band
observed in the range 1090-1104 cm-1 which may be ascribed
to a ν(P-O) absorption frequency. The IR spectra of the
arylphosphonates 1 and 4 also exhibit strong ν(P-O) absorption
bands at 972 and 982 cm-1, respectively, which are well
separated from the ν(C-O) bands at 1010 cm-1 (1) and 1005
cm-1 (4). In the IR spectra of 2, 3, and 5, these P-O absorption
bands overlap with the ν(C-O) bands in the range 1002-1008
cm-1; the resulting ν(P-O)/ν(C-O) overlap bands are very
intense, especially for 5. The characteristic absorption of the
CN group in [Ti4(µ3-O)(OiPr)5(µ-OiPr)3(4-CNPhPO3)3]‚DMSO
(4) is observed as a sharp band at 2229 cm-1
.
(b) Solid-State NMR. 31P MAS NMR experiments for the
cluster compounds 1-5 and 13C CP-MAS NMR experiments
on the arylphosphonates 1 and 4 were undertaken to obtain
further structural information. The crystal structures of 1 and 2
Owing to the (112) connectivity of the phosphonate groups,
the titanium atoms are hexacoordinated: they are bonded to
three different phosphonate groups via four Ti-O(P) bonds and
to two terminal alkoxy groups. The resulting coordination
polyhedron is a highly distorted TiO6 octahedron, as shown by
the O-Ti-O cis angle range (64.55(7)-05.68(9)° and the
O-Ti-O trans angle range (149.11(7)-171.99(7)°).
(36) Jaimez, E.; Bortun, A.; Hix, G. B.; Garcia, J. R.; Rodriguez, J.; Slade,
R. C. T. J. Chem. Soc., Dalton Trans. 1996, 2285-2292.
(37) Palvadeau, P.; Queignec, M.; Venien, J. P.; Bujoli, B.; Villieras, J.
Mater. Res. Bull. 1988, 23, 1561-1573.
Spectroscopic Characterizations. (a) Infrared Spectros-
copy. The FT-IR spectra of the titanium alkylphosphonates 2
and 3 as well as the FT-IR spectra of the arylphosphonates 1
(38) Bujoli, B.; Palvadeau, P.; Queignec, M. Eur. J. Solid State Inorg.
Chem. 1992, 29, 141-159.
(39) Persson, P.; Laiti, E.; O¨ ham, L.-O. J. Colloid Interface Sci. 1997,
190, 341-349.
and 4 do not differ significantly in the region 900-1300 cm-1
,
(40) Lynch, C. T.; Mazdiyasni, K. S.; Smith, J. S.; Crawford, W. J. Anal.
Chem. 1964, 36, 2332-2337.
which is ascribed to their similar Ti-O-P frameworks (Figure

Soluble Titanium Alkoxide Phosphonates
Inorganic Chemistry, Vol. 39, No. 15, 2000 3331
reveal a different chemical environment for each of the three
phosphonate groups due to different bond distances and angles
and to the coordinated DMSO molecule. Indeed, three sharp
signals are observed in the 31P MAS NMR spectra of well-
crystallized samples of 1 and 2, at δ 5.8, 6.2, 7.3 ppm and δ
14.7, 16.7, 17.0 ppm, respectively. For less crystalline powders
of 1 and 2, the line widths of the signals increase slightly and
the signals at δ 5.8 and 6.2 ppm for 1 and at δ 16.7 and 17.0
ppm for 2 are no longer separated, leading to broader resonances
with double the intensity. The same effect is observed in the
31P MAS NMR spectra of 3 and 4: two signals with a 1:2
integral ratio are observed at δ 23.6 and 24.5 ppm for 3 and at
δ 3.1 and 4.4 ppm for 4.
The 31P MAS NMR chemical shifts of the molecular titanium
phosphonates 1 and 2 are low-field-shifted compared to those
of layered titanium phenyl- and methylphosphonates (δ -4.0
and 9.0 ppm, respectively).36 These low-field shifts are probably
the result of different O-P-O bond angles, since the RPO3
connectivity is (111) in all cases.
The 31P MAS NMRspectrum of 5 shows several overlapping
resonances in the range δ 36.9-39.1 ppm as a result of the
presence of two independent molecules in its crystal structure
which both contain slighlty inequivalent phosphonate groups.
The 31P NMR resonance of [Ti(OiPr)2(tBuPO3)]4 (5) is signifi-
cantly low-field-shifted (∆δ = 14 ppm) compared to that of
[Ti4(O)(OiPr)8(tBuPO3)3]‚DMSO (3). This is ascribed to the
different coordination modes of the phosphonate groups which
are (111) in 3 and (112) in 5. A similar effect was previously
reported for zinc phosphonates.38
At -40 °C, in the 31P{1H} NMR spectrum of 4, two signals at
δ 4.6 and 4.3 ppm (2:1) are observed, whereas the 31P{1H} NMR
spectrum of 3 at -70 °C shows a broad signal at δ 24.3 ppm
with a shoulder centered at 25.0 ppm. Surprisingly, the
methylphosphonate 2 exhibits the expected two signals at δ 17.2
(broad) and δ 19.2 ppm with an integral ratio of 1:2 at room
temperature, indicating a slower exchange process.
The 31P NMR chemical shift of 5 in solution is similar to the
one observed in the solid state, which shows that the (112)
connectivity of the phosphonate groups is maintained in solution.
In the pyramidal clusters 1-4, three different types of
isopropoxo ligands are expected: three bridging and three
terminal ones bonded to the three Ti atoms of the base and two
1
terminal ones bonded to the Ti atom of the apex. In the H
NMR spectra of phosphonates 1-4, the three expected doublets
i
of MeO Pr can easily be distinguished (see Experimental Section),
although for methylphosphonate 2 the doublets overlap with
the signals of the methyl groups of PPMe. In the 13C NMR spectra
of tert-butylphosphonate 3 and (4-cyanophenyl)phosphonate 4,
i
three resonances of MeO Pr are observed at δ 25.1, 26.0 (broad),
and 26.1 ppm (3) and at δ 23.8, 23.9, and 24.0 ppm (4), whereas
only two signals can be distinguished for 1 (δ 24.0, 24.2 ppm)
and 2 (δ 23.7, 24.0 ppm). The 13C NMR signals of CHO Pr (1-
i
4) are also found in a narrow range and partially overlap. For
the arylphosphonates 1 and 4, only two signals are observed at
δ 77.6, 78.4 ppm and at δ 78.3, 79.2 ppm, respectively, whereas
three signals are found in the 13C NMR spectra of the
alkylphosphonates 2 and 3 (2 δ 76.9, 77.2, 77.8 ppm; 3 δ 77.7,
i
79.8, 80.3 ppm). However, the CHO Pr resonances at δ 77.2 ppm
13C CP-MAS NMR experiments were performed on a well-
crystallized sample of 1 and an amorphous powder of 4. The
spectrum of 1 exhibits five well-resolved 13C NMR signals
for 2 and at δ 79.8 ppm for 3 associated with the isopropoxo
ligands bonded to the apex of the pyramid are broadened, which
suggests that these ligands are involved in an exchange process.
i
around δ 25 ppm for MeO Pr whereas the spectrum of 4 shows
This exchange is probably the result of a trace amount of
iPrOH in the NMR solution. Upon the addition of a small
only one broad signal at δ 25.8 ppm. The corresponding
i
resonances of the CHO Pr groups are located around δ 80 ppm.
i
1
amount of PrOH to the H NMR solution of 1, the signals
In both spectra, the signals of the aromatic ipso carbons are
well separated from those in the broad aromatic region around
δ 125-135 ppm. In the spectrum of 1, two distinct doublets
are observed at δ 136.5 and δ 137.2 ppm, the former being of
double intensity. As a result of the lower crystallinity of 4,
overlapping signals are observed in the δ 140-145 ppm region
for the ipso carbons. Furthermore, the signals of the aromatic
para carbons overlap with the CN resonances at δ 113.3-115.3
ppm. Interestingly, the methyl groups of the coordinated DMSO
in 1 give rise to two separated resonances at δ 37.6 and 38.9
ppm, reflecting the different chemical environment of MeDMSO
found in the crystal structure; on the other hand, only one broad
signal at δ 40 ppm is observed in the case of 4.
i
assigned to the terminal isopropxy ligands (CHO Pr δ 4.26 ppm;
MeO Pr δ 0.33 ppm) bonded to the apex of the pyramid disappear,
i
whereas the resonances attributed to the isopropoxy groups
i
i
bonded to the Ti3O base (CHO Pr δ 4.03, 4.40 ppm; MeO Pr
δ
0.71, 0.80 ppm) are unaffected. This behavior shows that iPrOH
exchanges rapidly only with the terminal OiPr ligands of the
titanium atom of the apex.
For [Ti(OiPr)2(tBuPO3)]4 (5), only one type of isopropoxy
group is observed in the 1H NMR spectrum (MeO Pr δ 1.30 ppm;
i
CHO Pr δ 5.35 ppm) as well as in the 13C{1H} NMR spectrum
i
i
i
(MeO Pr δ 25.8 ppm; CHO Pr δ 83.0 ppm). The addition of a small
amount of iPrOH does not affect the signals of 5, which indicates
that no isoproxide ligand exchange occurs.
(c) Multinuclear NMR Experiments in Solution. 31P{1H},
1H, and 13C{1H} NMR studies in solution were performed on
all compounds. In contrast to the solid state 31P MAS NMR
spectrum, the 31P{1H} NMR spectrum of 1 in THF (room
temperature) displays only one single resonance at δ 6.8 ppm,
which we ascribe to a fast exchange of coordinated solvent
molecules. A variable-temperature 31P{1H} NMR experiment
showed the single resonance to split into two well-separated
signals at δ 6.7 and 6.5 ppm as a result of a slower exchange
process of coordinated solvent molecules. These chemical shifts
are comparable to those previously reported for titanium
phenylphosphonates: [Ti2(OMe)6(O3PPh)2][nBu4N]2,20 δ 8.2
ppm; [(Cp*TiO3PPh)4(µ-O)2],27 δ 7.4 ppm. A similar coordina-
tion behavior in solution is observed for compounds 3 and 4:
At room temperature, their 31P{1H} NMR spectra each show
only one sharp resonance at δ 28.8 and 4.3 ppm, respectively.
Reactivity of the Clusters. (a) Exchange Reaction of 1 with
2. We were intrigued by a possible scrambling reaction between
the phenylphosphonate 1 and the methylphosphonate 2, which
present similar structures. A mixture of 1 and 2 in THF gave a
cloudy solution. Nevertheless, in the 31P NMR spectrum of the
reaction mixture, six signals at 20.8 (1%), 20.1 (8%), 19.6
(12%), 17.7 (20%), 8.5 (6%), and 7.3 ppm (52%) were observed.
Although no assignment of the NMR signals was made, this
experiment suggests that exchange processes involving Ti-O-P
bond cleavage are operative.
(b) Reaction of 5 with Water and Titanium Isopropoxide.
We were also interested in the possible conversion of 5 into
cluster 3a (having the same structure as 3 but coordinated by
iPrOH instead of DMSO). Indeed, the Ti-O-P frameworks of
both clusters are related: the replacement of one tridentate

3332 Inorganic Chemistry, Vol. 39, No. 15, 2000
Mehring et al.
Table 6. Comparison between Bond Lengths Predicted by the Bond
Scheme 3
Valence Method (dBV) and Observed Average Bond Lengths (dobsd
)
compd
bond
va
dBV,b Å
dhobsd, Å
1
Ti-O(Ti)
0.667
0.667
1.333
0.667
0.667
1.333
0.667
0.467
0.200
1.333
2.00
2.00
1.53
2.00
2.00
1.53
2.00
2.13
2.45
1.53
1.96
1.99
1.53
1.98
1.53
Ti-O(P)
P-O(Ti)
2
5
Ti-O(Ti)
Ti-O(P)
P-O(Ti)
Ti-O(P)(short)
Ti-O(P)(medium)
Ti-O(P)(long)
P-O(Ti)
1.97
2.13
2.43
1.54
a Bond order. b Bond length calculated by the formula d ) d0 - b
ln(v) where b ) 0.37 Å, d0 ) 1.85 Å for Ti-O, and d0 ) 1.64 Å for
P-O.27
nated titanium atoms was previously described for [(Cp*TiO3-
PR)4(µ-O)2] (R ) Me, Ph)27 although two opposite faces of
the cubic core were capped by two µ2-oxygen atoms. In
compound 5, the sixth coordination to the Ti atoms comes from
the (112) connectivity of the phosphonate groups, unusual for
a titanium phosphonate. This connectivity leads to three sets of
Ti-O(P) bond lengths: the phosphonato oxygens bonded to
one titanium atom give “short” (average 1.97 Å) Ti-O(P) bonds,
and the phosphonato oxygen bonded to two titanium atoms gives
one “medium” (average 2.13 Å) and one “long” (average 2.43
Å) Ti-O(P) bond. These Ti-O(P) bond lengths are in good
agreement with the lengths predicted by the bond valence
method, assuming apparent bond valences of 0.667-0.2 and
of 0.2 for the “medium” and “long” Ti-O(P) bonds, respectively
(Table 6).
phosphonate group in 5 by one µ3-oxygen atom leads to the
framework of 3a (Scheme 3).
According to the 31P and 1H NMR spectra, the addition of 1
equiv of water to a solution of 5 gave 2-propanol and several
unidentified hydrolysis products, but the formation of cluster
3a was not observed. On the other hand, addition of 1 equiv of
water to a solution of 5 and Ti(OiPr)4 gave 2-propanol and
compound 3a as the major product (65% based on 31P NMR),
1
as indicated by the H and 31P NMR spectra. Note that after
The (112) connectivity of the phosphonate groups in 5
accounts for the significant difference between the 31P NMR
chemical shift of 5 and the chemical shifts of 3 and other
molecular tert-butylphosphonates of titanium27 and group 13
metals42 which all present a (111) connectivity.
Interestingly, in the presence of water and Ti(OiPr)4, com-
pound 5 was converted into the titanium oxide alkoxide phos-
phonate 3a, with the same Ti-O-P framework as that of com-
pounds 1-4. This conversion probably involves Ti-O-P/
Ti-O-Ti bond exchanges between the titanium alkoxide
phosphonate 5 and titanium oxide alkoxide species formed by
partial hydrolysis-condensation of Ti(OiPr)4. The formation of
clusters 1-4 could follow a similar mechanism.
The reported titanium phosphonate clusters are major inter-
mediates in the sol-gel processing of titanium oxide/phospho-
nate hybrid materials.28 Furthermore, they are promising single-
source sol-gel precursors for the preparation of organic-
inorganic hybrids, as they are well-defined compounds, soluble
in common organic solvents, and can be condensed by hydroly-
sis-condensation of the remaining Ti-OiPr groups. The isola-
tion of the cyanophenyl derivative 4 illustrates the possibility
of introducing functional organic groups for hybrid materials
applications and for the design of self-assembled nanostruc-
tured materials.
the addition of 0.66 equiv of water, both the starting material 5
and cluster 3a were present.
Discussion and Conclusion
The reactions of Ti(OiPr)4 with different organophosphonic
acids RPO3H2 (R ) Ph, 4-CNPh, Me, tBu) gave two novel types
of molecular titanium phosphonates which are highly soluble
in organic solvents. Interestingly, under the same reaction con-
ditions the same cluster framework, [Ti4(µ3-O)(OiPr)2(OiPr)3-
(µ-OiPr)3(RPO3)3], formed regardless of the organic group R
t
bonded to phosphorus [R ) Ph (1), Me (2), Bu (3), 4-CNPh
(4)]. The main driving forces for the cluster geometry seem to
be the tendency of titanium to be hexacoordinated, the stability
of the Ti3(µ3-O)(µ2-OR)3 fragment which is present in several
titanium oxoalkoxides,13,15 and the (111) coordination mode of
the phosphonato ligands found in most titanium phosphonates.
In contrast, the reactions of Cp*TiMe3 with RPO3H2 led to two
different structures, depending on the organic group R (R )
t
Me, Ph; R ) Bu).27 As already reported for other titanophos-
phonate clusters,27 the average Ti-O and P-O bond lengths
in clusters 1 and 2 are in good agreement with the lengths
predicted by the bond valence method41 (Table 6).
A novel type of titanium phosphonate cluster, [Ti(OiPr)2-
(tBuPO3)]4 (5), was isolated by reacting tert-butylphosphonic
acid and Ti(OiPr)4 in toluene under strictly anhydrous conditions.
Single-crystal X-ray analysis revealed that 5 consists of an
M4P4O12 framework. This fragment is often found for typically
tetracoordinated metals, for instance in group 13 metal phos-
phonates,42,43 but is unexpected for a typically hexacoordinated
metal. A similar structural arrangement involving pentacoordi-
Acknowledgment. M.M. is grateful to the Centre National
de la Recherche Scientifique for a postdoctoral fellowship.
Supporting Information Available: X-ray crystallographic files,
in CIF format, for 2 and 5. This material is available free of charge via
the Internet at http://pubs.acs.org.
IC000002K
(41) O’Keefe, M. Struct. Bonding 1989, 71, 161.
(42) Walawalkar, M. G.; Roesky, H. W.; Murugavel, R. Acc. Chem. Res.
1999, 32, 117-126.
(43) Mason, M. R. J. Cluster Sci. 1998, 9, 1-23.