Acetic acid mediated synthesis of phosphonate-substituted titanium oxo clusters

Article abstract of DOI:10.1002/ejic.201400051

New phosphonate/acetate-substituted titanium oxo/alkoxo clusters were prepared from Ti(OiPr)₄ and bis(trimethylsilyl) phosphonates in the presence of acetic acid, which served to generate water in situ through ester formation. The process led to clusters with a higher degree of condensation than in previously known phosphonate-substituted titanium oxo clusters. The clusters [Ti₆O₄(OiPr)₁₀(OAc)₂(O ₃PR)₂] (OAc = acetate) were obtained for a large variety of functional and non-functional groups R under a range of reaction conditions. This cluster type, which is also retained in solution, therefore appears to be very robust. Two other clusters, [Ti₅O(OiPr)₁₁(OAc)(O ₃PCH₂CH₂CH₂Br)₃] and [Ti₅O₃(OiPr)₆(OAc)₄(O ₃P-xylyl)₂], were only isolated in special cases. Several acetate/phosphonate-substituted titanium cage compounds were obtained from the reaction of titanium isopropoxide with bis(trimethylsilyl) phosphonates in the presence of acetic acid as water generator.

Full text of DOI:10.1002/ejic.201400051

FULL PAPER
DOI:10.1002/ejic.201400051
Acetic Acid Mediated Synthesis of Phosphonate-
Substituted Titanium Oxo Clusters
Matthias Czakler,[a] Christine Artner,[a] and Ulrich Schubert*[a]
Keywords: Cluster compounds / Cage compounds / Titanium / P ligands / Hydrolysis
New phosphonate/acetate-substituted titanium oxo/alkoxo
clusters were prepared from Ti(OiPr)4 and bis(trimethylsilyl)
phosphonates in the presence of acetic acid, which served to
generate water in situ through ester formation. The process
led to clusters with a higher degree of condensation than in
previously known phosphonate-substituted titanium oxo
clusters. The clusters [Ti6O4(OiPr)10(OAc)2(O3PR)2] (OAc =
acetate) were obtained for a large variety of functional and
non-functional groups R under a range of reaction conditions.
This cluster type, which is also retained in solution, therefore
appears to be very robust. Two other clusters, [Ti5O(OiPr)11
-
(OAc)(O3PCH2CH2CH2Br)3] and [Ti5O3(OiPr)6(OAc)4(O3P-
xylyl)2], were only isolated in special cases.
pared with the corresponding phosphonic acids, the esters
have the advantage that they are soluble in organic solvents.
Their reaction with alcohol liberates phosphonic acid,
which substitutes part of the OR groups of Ti(OR)4 in a
relatively fast reaction. Oxo groups are generated in situ
by esterification of either coordinated or non-coordinated
phosphonic acid, as in the case of carboxylic acids. How-
ever, because esterification of phosphonic acids appears to
be slow, oxo clusters with a low degree of condensation (de-
fined O/Ti ratio of the Ti/O core[7]) (0.25 or 0.29) were ob-
tained, although higher degrees of condensation can be
achieved under solvothermal conditions.[8]
In this article we report the results of experiments in
which Ti(OiPr)4 was treated with mixtures of various bis-
(trimethylsilyl) esters of phosphonic acids and acetic acid.
The fundamental idea was to increase the proportion of in
situ generated water by taking advantage of the easier ester
formation of acetic acid. We will show that this approach
leads to the formation of titanium oxo clusters substituted
by both phosphonate and acetate ligands with an increased
degree of condensation.
Introduction
Metal alkoxides are often substituted by less easily hy-
drolyzable organic groups to moderate their reactivity in
sol-gel processes and to introduce functional or non-func-
tional organic groups for inorganic–organic hybrid materi-
als.[1] Such substituted metal alkoxide derivatives are ob-
tained by reacting metal alkoxides with a protic compound,
such as β-diketonates, amino alcohols, or oximes. Reaction
with carboxylic acids is a special case because this normally
does not result in carboxylate-substituted metal alkoxides
but, instead, in carboxylate-substituted metal oxo clusters.
This is due to the fact that carboxylic acids not only provide
carboxylate ligands but also act as an in situ water source
through esterification with the eliminated alcohol. Such oxo
clusters have been used as nanosized building blocks for the
construction of inorganic–organic hybrid polymers or as
linker units in metal–organic frameworks (MOF).[2]
Whereas carboxylate-substituted oxo/alkoxo clusters of
titanium have been particularly well investigated,[3] only a
few phosphonate-substituted derivatives are known.[4,5] The
latter are interesting for hybrid materials because of the
strong Ti–O–P bonds, especially when phosphonate ligands
with functional organic groups are employed.[6]
Results and Discussion
We have recently shown that titanium oxo clusters can
be easily prepared by using bis(trimethylsilyl) esters.[5] Com-
Reaction of one molar equivalent of bis(trimethylsilyl)
ethylphosphonate with two equivalents of acetic acid and
four equivalents of Ti(OiPr)4 led to the centrosymmetric
cluster [Ti6(μ3-O)2(μ2-O)2(μ2-OiPr)4(OiPr)6(OAc)2(O3PEt)2]
(1; Figure 1, OAc = acetate), with a high degree of conden-
sation (0.67). The cluster was, to the best of our knowledge,
also the first mixed carboxylate-phosphonate titanium oxo
cluster to be characterized. This new cluster type consists
of a Ti6O4 cluster core with two parallel Ti3O triangles con-
[a] Institute of Materials Chemistry, Vienna University of
Technology,
Getreidemarkt 9, 1060 Wien, Austria
E-mail: Ulrich.Schubert@tuwien.ac.at
http://www.imc.tuwien.ac.at
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201400051.
© 2014 The Autors. Published by Wiley-VCH Verlag GmbH & Co.
KGaA. This is an open access article under the terms of the Creative
Commons Attribution License, which permits use, distribution and re-
production in any medium, provided the original work is properly cited. nected by μ2-oxo and phosphonate bridges. The nearly cu-
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bic Ti6P2O10 core resembles that of polyhedral oligomeric distorted trigonal bipyramidal coordination sphere. Be-
silsesquioxanes (POSS) with a Si8O12 core. The titanium cause of the asymmetric substitution of the Ti3O triangle,
and phosphorus atoms form a distorted parallelepiped the μ3-oxygen (O1) is not in the center of the triangle but
(Figure 2).
has instead a significantly shorter distance to Ti3 [190.61(6)
pm] than to the octahedrally coordinated atoms Ti1 and
Ti2 [198.04(6) and 199.58(5) pm]. Otherwise, the Ti–O bond
lengths at the five-coordinate Ti3 are longer than the corre-
sponding distances of Ti1 and Ti2.
The core of the structure of 1 is comparable to that of
[Ti6(μ3-O)2(μ2-O)2(μ2-OiPr)4(OiPr)6(O3SiFlMe)2(PhNH2)2]
(Fl = 9-methylfluorenyl),[9] although all titanium atoms in
the titanasiloxane structure are five-coordinate.
In contrast to reactions of Ti(OiPr)4 with bis(trimethyl-
silyl) phosphonates in the absence of acetic acid,[5] a series
of isostructural clusters [Ti6O4(OiPr)10(OAc)2(O3PR)2] was
obtained both with much bulkier groups at the phosphorus
atom, such as R = CH2–naphthyl (2), and with functional
organic groups, such as R = vinyl (3), allyl (4), or
CH2CH2CH2Cl (5) [Equation (1)]. This cluster type there-
fore appears to be rather robust. With one exception (see
below) we obtained this cluster type for the RPO3H/HOAc/
Ti(OiPr)4 ratio of 1:1:2. In some cases this ratio was varied
slightly for the preparation of 1–5, from 1:1:2 to 1:2:3 and
1:2:4, but the same cluster was always obtained. Note that,
in each case, the molar ratio of (RPO3H + HOAc) did not
exceed that of Ti(OiPr)4.
Figure 1. Molecular structure of [Ti6(μ3-O)2(μ2-O)2(μ2-OiPr)4-
(OiPr)6(OAc)2(O3PEt)2] (1). Hydrogen atoms are omitted for clar-
ity.
Figure 2. Core structure of the carboxylate-phosphonate-substi-
tuted titanium oxo clusters 1–7. Isopropoxo and acetate ligands as
well as the substituents at the phosphorus atoms are omitted for
clarity.
(1)
In contrast to the previously obtained clusters with sym-
Clusters 1–5 crystallized from the reaction mixture at
metrical, phosphonate-substituted Ti3(μ3-O)(μ2-OiPr)3- room temperature within several weeks. To obtain the clus-
(OiPr)3 units as the basic structural motif,[4,5] the structure ter faster and in higher yield, the synthesis of 1, as an exam-
of 1 is based on unsymmetrically substituted Ti3(μ3-O)(μ2- ple, was repeated by heating the reaction mixture (1:2:3) to
OiPr)2(OiPr)3(μ2-OAc) units. Two Ti atoms (Ti1 and Ti2) reflux overnight. The NMR spectra of the resulting powder
of this unit are bridged by both an OiPr and an acetate were the same as those of the sample prepared at room
ligand, whereas Ti1 and Ti3 are singly bridged by a μ2-OiPr temperature. With this faster preparation process, the iso-
group. A terminal OiPr ligand is coordinated to each Ti structural clusters
6 (R = CH2Ph) and 7 (R =
atom. The two Ti3O triangles are connected through a μ2- CH2CH2CH2Br)2 were additionally obtained. It can be as-
O unit between Ti2 and Ti3* (* denotes the symmetry-re- sumed that clusters 2–5 can also be more rapidly obtained
lated atom in the second Ti3O unit) as well as two phos- by this modification of the synthesis. Cluster 7 was only
phonate ligands connecting Ti2, Ti3 and Ti1* (and Ti2*, obtained for RPO3H/HOAc/Ti(OiPr)4 ratios of 1:2:4 or
Ti3*, Ti1, respectively). The acetate-bridged atoms Ti1 and 1:2:3; surprisingly, for a 1:1:2 ratio another cluster was ob-
Ti2 are thus octahedrally coordinated, whereas Ti3 has a tained (see below for cluster 8).
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Clusters 1–7 were well-soluble in organic solvents. Their group is replaced by a Ti2(μ2-OiPr)(OiPr)4(μ2-OAc) moiety.
NMR spectra were very similar, and were consistent with Two of the phosphonate ligands are coordinated to only
the solid-state structures (see the Supporting Information), one Ti atom of the Ti2 unit, whereas the third bridges both
which shows that the clusters are stable in solution and are of them. This phosphonate ligand has a binding mode of
not in equilibrium with other structures. The 1H NMR 4.211 (w.xyz refers to the number of metal atoms to which
spectroscopic data of 1–7 show five doublets for the CH3 the phosphonate ligand is coordinated [w], and the number
of the OiPr ligands, although the signals of two bridging of metal atoms to which each oxygen is coordinated
OiPr ligands overlap at about 1.7 ppm; the other three dou- [x,y,z][10]), whereas the other two phosphonate ligands, as
blets partly overlap at 1.3–1.5 ppm. For the CH group of well as those in the cluster 1–7, have a 3.111 binding mode.
the OiPr ligands, three different multiplets were found, in a The Ti2(μ2-OiPr)(OiPr)4(μ2-OAc) moiety in 8 is structurally
few cases two of them partly overlap. The singlet for the related to Ti2(OR)6(μ2-OOCRЈ)2.[11]
CH3 group of the acetate ligands was observed at about
The solution 1H NMR spectrum showed several overlap-
2.0 ppm. Only one signal between 10 and 30 ppm was ob- ping signals in the region of 1.2–2.0 ppm that can be as-
served in the 31P NMR spectra, indicating that the clusters signed to the CH3 groups of OiPr as well as to the PCH2
are centrosymmetric in solution. 13C NMR spectra were in group. The CH signals of OiPr appear at 4.6–5.4 ppm as
good agreement with the 1H NMR spectroscopic data, with five multiplets. The two well-separated triplets for the
six signals for the CH3 groups at 23–26 ppm, three signals CH2Br group at δ = 3.52 and 3.71 ppm have an intensity
for the CH groups at 76–79 ppm, and one signal at around ratio of 1:2. The same is true for the two resonances at δ =
180 ppm for the carboxylate ligand.
27.44 and 30.34 ppm in the 31P NMR spectrum. This is in
Upon reaction of the aforementioned bis(trimethylsilyl) good agreement with the structure in the crystalline state.
phosphonates with acetic acid and Ti(OiPr)4 in a 1:1:2 ratio, Solution 13C NMR spectroscopic data confirm the 1H
in one case another cluster type was obtained. Reaction of NMR spectroscopic data, with corresponding signals at 23–
bis(trimethylsilyl) 3-bromopropylphosphonate at room tem- 25 ppm for CH3 and 77–80 ppm for CH groups. Two dou-
perature reproducibly resulted in the cluster [Ti5(μ3-O)(μ2- blets were found for each CH2 group of the bromopropyl
OiPr)4(OiPr)7(OAc)(O3PCH2CH2CH2Br)3] (8), the struc- moiety; the signals of the P-CH2 groups could not be une-
ture of which (Figure 3) is related to those of previously quivocally assigned.
observed clusters [Ti4(μ3-O)(μ2-OiPr)3(OiPr)5(O3PR)3L] (L
Another Ti5 cluster was obtained from the reaction of
= neutral ligand).[4,5] The latter consist of a symmetrical bis(trimethylsilyl) 3,5-dimethylphenylphosphonate with
Ti3(μ3-O)(μ2-OiPr)3(OiPr)3 unit to which a Ti(OiPr)2L Ti(OiPr)4andaceticacid(1:2:2).[Ti5(μ3-O)2(μ2-O)(μ2-OiPr)2-
group is connected by means of three phosphonate ligands (OiPr)4(OAc)4(O3P-xylyl)2] (9; Figure 4) consists of five oc-
coordinating to two of the Ti atoms of the Ti3O triangle tahedrally coordinated titanium atoms that form two cor-
and the capping Ti atom. In 8, the capping Ti(OiPr)2L ner-sharing Ti3O triangles (Ti1, Ti2, Ti3 and Ti3, Ti4, Ti5),
tilted by 52.2°. The cluster has a noncrystallographic C2
Figure 3. Molecular structure of [Ti5(μ3-O)(μ2-OiPr)4(OiPr)7(OAc)-
Figure 4.Molecularstructure of[Ti5(μ3-O)2(μ2-O)(μ2-OiPr)2(OiPr)4-
(O3PCH2CH2CH2Br)3] (8). Hydrogen atoms are omitted for clarity. (OAc)4(O3P-xylyl)2] (9). Hydrogen atoms are omitted for clarity.
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axis passing through the μ2-oxygen O3 and Ti5, thus ren- tion of acetic acid compared with phosphonic acids. The
dering the two Ti3O units chemically equivalent. The Ti3O higher condensation ratio goes hand in hand with incorpo-
units have the composition Ti3(μ3-O)(μ2-OiPr)(OiPr)2(μ2- ration of acetate ligands in the coordination sphere of the
OAc)2 and can be derived from the basic structural motif clusters; the new titanium oxo clusters are the first examples
Ti3(μ3-O)(μ2-OiPr)3(OiPr)3 in the previously obtained acet- of a mixed ligand sphere containing carboxylate, phos-
ate-free clusters[4,5] and in 8, and the monosubstituted unit phonate and alkoxo ligands.
Ti3(μ3-O)(μ2-OiPr)2(OiPr)3(μ2-OAc) in 1. The Ti3O tri-
Whereas reactions of Ti(OR)4 with carboxylic acids lead
angles are connected with each other by one μ2-O and two to a great variety of cluster types, depending on the OR
phosphonate ligands in a 3.111 binding mode. The central group, the acid, and the Ti(OR)4/acid ratio,[3] the reaction
Ti3 atom is coordinated by an oxygen atom of both phos- with various phosphonates and acetic acid led to the same
phonate ligands and the other four Ti atoms are coordi- cluster type [Ti6O4(OiPr)10(OAc)2(O3PR)2] (1–7), which
nated by the oxygen atoms of just one phosphonate ligand. therefore appears to be a rather robust structural entity. The
Cluster 9 has another degree of condensation (0.6) and cluster core has an inversion center, and therefore the phos-
a higher proportion of acetate ligands than the Ti5 cluster phonate ligands are opposite to each other. Because phos-
8 or the Ti6 clusters 1–7. This is attributed to the higher phonate ligands with functional organic groups are easily
amount of acetic acid used for the preparation, which ap- introduced, reactions of these groups should be possible,
parently led to the higher proportion of acetate ligands in e.g., polymerization, thiol-en or addition reactions, by
the product. The steric hindrance and the increased acidity which chains of clusters and hybrid materials with aniso-
of xylylphosphonic acid (aromatic phosphonic acids are tropic structures could be generated.
slightly more acidic) possibly play an additional role. In pre-
vious experiments, when only phosphonates were treated
Experimental Section
with Ti(OiPr)4, the steric bulk of the phosphonate substitu-
ents had a significant influence on the cluster structure.[5]
General Methods: Manipulations were carried out under an argon
The approximate C2 symmetry is retained in solution be-
atmosphere using standard Schlenk and glove box techniques. Di-
ethyl ethylphosphonate, diethyl (3-bromopropyl)phosphonate, di-
ethyl vinylphosphonate, allyl bromide, 1-bromo-3-chloropropane,
benzyl bromide, 1-bromo-3,5-dimethylbenzene, 2-(bromomethyl)-
naphthalene, triethyl phosphite and Ti(OiPr)4 were purchased from
Sigma–Aldrich and used as received. Diethyl (3,5-dimethylphenyl)-
phosphonate was prepared as reported.[12] Other diethyl phos-
phonates were prepared by reaction of the corresponding bromide
with triethyl phosphite for 16 h in a Dean–Stark apparatus at
150 °C and purified by distillation.
cause only one signal was observed in the 31P NMR spec-
1
trum. The solution H NMR spectrum show three singlets
for the xylyl CH groups at δ = 6.91, 8.03 and 8.08 ppm and
three multiplets for the isopropoxo CH groups at δ = 5.07,
5.22 and 5.66 ppm. One singlet at δ = 2.18 ppm was as-
signed to the CH3 groups of the xylyl moieties and two
singlets at δ = 1.95 and 1.98 ppm to the two acetate ligands.
These signals are consistent with respect to shift, number
and intensity with the solid-state structure.
Five doublets were found for the CH3 groups of the OiPr
ligands. Their total intensity corresponded to the calculated
value, but only three were expected because of the C2 sym-
metry. Two doublets at δ = 1.90 and 1.91 ppm overlap with
a shift difference of only 0.01 ppm and can be assigned to
the two bridging OiPr ligands, which should be symmetry-
equivalent. It is therefore assumed that rotation around the
O–CH bond is hindered, resulting in different chemical
shifts for the two CH3 groups. The same can be assumed
for one of the terminal CH3 groups (possibly interacting
with each other) leading to two doublets at δ = 1.46 and
1.51 ppm. The other two terminal OiPr ligands show a
doublet at δ = 1.54 ppm. The same observations were made
in the 13C NMR spectrum. The increased number of signals
The bis(trimethylsilyl) esters were prepared by adding bromotri-
methylsilane (3 equiv.) to a solution of the corresponding diethyl
phosphonate (1 equiv.) in CH2Cl2 followed by removing all vola-
tiles in vacuo and characterization of the compounds by 31P and
1H NMR spectroscopy.
Isopropyl alcohol was dried by heating to reflux over sodium and
distillation. Samples for NMR measurements were obtained by
washing the crystalline compounds with isopropyl alcohol and dry-
ing. Acetic acid was purified by distillation from P4O10.
The given yields refer to crystallized compounds. No attempts were
made to increase the crystal crop; i.e., the actual yields were higher.
[Ti6O4(OiPr)10(OAc)2(O3PEt)2] (1): Bis(trimethylsilyl) ethylphos-
phonate (184 mg, 0.72 mmol) was added to Ti(OiPr)4 (840 μL,
2.9 mmol) in isopropyl alcohol (3 mL). Acetic acid (83 μL,
1.4 mmol) was then quickly added. Cluster 1 crystallized after eight
1
in the CH3 region is also attributed to sterically hindered weeks, yield 200 mg (43%). H NMR (250 MHz, C6D6): δ = 1.30–
1.48 (m, 4 H, CH2CH3), 1.37 (d, J = 5.98 Hz, 12 H, CHCH3), 1.40
(d, J = 6.05 Hz, 12 H, CHCH3), 1.52 (d, J = 6.08 Hz, 12 H,
CHCH3), 1.63–1.79 (m, 4 H, CH2), 1.78 (d, J = 6.28 Hz, 12 H,
CHCH3), 1.84 (d, J = 6.30 Hz, 12 H, CHCH3), 2.00 (s, 6 H, CCH3),
4.84 (m, J = 6.20 Hz, 2 H, CH), 5.03 (m, J = 6.12 Hz, 4 H, CH),
5.36 (m, J = 6.28 Hz, 4 H, CH) ppm. 31P NMR (101.2 MHz,
C6D6): δ = 18.0 ppm. 13C NMR (62.9 MHz, C6D6): δ = 7.45 (d, J
= 6.73 Hz, CH3), 20.00 (d, J = 158.1 Hz, CH2), 23.62 (s, CH3),
23.97 (s, CH3), 24.25 (s, CH3), 24.70 (s, CH3), 25.22 (s, CH3), 25.31
(s, CH3), 77.48 (s, CH), 78.45 (s, CH), 79.21 (s, CH), 177.87 (s,
rotation of the OiPr groups.
Conclusions
We have shown that addition of acetic acid to an appro-
priate mixture of reactants does indeed result in a higher
degree of condensation of the obtained oxo clusters com-
pared with the clusters prepared from only bis(trimethyl-
silyl)phosphonates. This is attributed to the easier esterifica- COO) ppm.
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[Ti6O4(OiPr)10(OAc)2(O3PCH2C10H7)2] (2): Ti(OiPr)4 (627 μL, CD2Cl2): δ = 1.13 (d, J = 6.00 Hz, 12 H, CHCH3), 1.21 (d, J =
2.16 mmol) was added to a solution of CH3COOH (62 μL,
1.08 mmol) and bis(trimethylsilyl) (naphthylmethyl)phosphonate
5.95 Hz, 12 H, CHCH3), 1.35 (d, J = 6.05 Hz, 12 H, CHCH3), 1.45
(d, J = 5.80 Hz, 12 H, CHCH3), 1.47 (d, J = 5.33 Hz, 12 H,
(396 mg, 1.08 mmol) in isopropyl alcohol (2 mL). After 5 min stir- CHCH3), 1.71 (m, JH,H = 7.30, JP,H = 18.72 Hz, 4 H, PCH2), 1.92
ring, the flask allowed to stand for crystallization at room tempera-
ture. Crystals of 2 were obtained after three months, yield 200 mg
(25%). 1H NMR (400 MHz, C6D6): δ = 1.30 (d, J = 5.68 Hz, 12
(s, 6 H, CCH3), 2.15 (m, 4 H, CH2), 3.75 (t, J = 6.71 Hz, 4 H,
CH2Cl), 4.76 (m, J = 6.58 Hz, 6 H, CH), 4.98 (m, J = 6.16 Hz, 4
H, CH) ppm. 31P NMR (101.2 MHz, CD2Cl2): δ = 15.44 ppm. 13
C
H, CHCH3), 1.41 (d, J = 6.16 Hz, 12 H, CHCH3), 1.44 (d, J = NMR (62.9 MHz, CD2Cl2): δ = 23.59 (s, CH3), 23.91 (s, CH3),
5.32 Hz, 12 H, CHCH3), 1.61 (d, J = 6.04 Hz, 12 H, CHCH3), 1.67 24.25 (s, CH3), 24.37 (d, J = 157.3 Hz, PCH2), 24.71 (s, CH3), 25.28
(d, J = 5.32 Hz, 12 H, CHCH3), 1.89 (s, 6 H, CCH3), 3.32 (d, (s, CH3), 27.57 (d, J = 4.94 Hz, CH2), 44.94 (d, J = 12.97 Hz,
JP–H = 22.65 Hz, 4 H, PCH2), 4.85 (m, J = 6.16 Hz, 2 H, CH),
4.95 (m, 4 H, CH), 5.23 (m, J = 6.06 Hz, 4 H, CH), 7.33 (t, J =
7.43 Hz, 2 H, CHAr), 7.39 (t, J = 7.63 Hz, 2 H, CHAr), 7.76 (d, J
= 8.00 Hz, 2 H, CHAr), 7.84 (d, J = 9.04 Hz, 2 H, CHAr), 7.85 (d,
J = 6.61 Hz, 2 H, CHAr), 7.89 (d, J = 7.72 Hz, 4 H, CHAr) ppm.
CH2Cl), 77.82 (s, CH), 78.70 (s, CH), 79.54 (s, CH), 178.13 (s,
COO) ppm.
[Ti6O4(OiPr)10(OAc)2(O3PCH2Ph)2] (6): Ti(OiPr)4 (2.8 mL,
9.5 mmol) and acetic acid (365 μL, 6.4 mmol) were added to a solu-
tion of bis(trimethylsilyl) benzylphosphonate (1 g, 3.2 mmol) in iso-
propyl alcohol (20 mL). After heating to reflux overnight and cool-
ing to room temperature, a cloudy mixture was obtained. The sus-
pension was concentrated under vacuum and filtered. After wash-
ing two times with small portions of iPrOH and drying, a white
powder of 6 was obtained. Part of the powder was crystallized from
CH2Cl2, yield 1 g (45%). 1H NMR (250 MHz, CDCl3): δ = 1.34
(d, J = 6.13 Hz, 12 H, CHCH3), 1.42 (d, J = 6.20 Hz, 12 H,
CHCH3), 1.47 (d, J = 6.10 Hz, 12 H, CHCH3), 1.67 (d, J =
6.25 Hz, 12 H, CHCH3), 1.73 (d, J = 6.23 Hz, 12 H, CHCH3), 1.98
(s, 6 H, CCH3), 3.19 (d, JP,H = 22.54 Hz, 4 H, PCH2), 4.87 (m, J
= 6.21 Hz, 2 H, CH), 4.97 (m, J = 6.04 Hz, 4 H, CH), 5.25 (m, J
= 6.24 Hz, 4 H, CH), 7.2 (m, 2 H, CHPh), 7.33 (t, J = 7.66 Hz, 4
H, CHPh), 7.64 (d, J = 7.49 Hz, 4 H, CHPh) ppm. 31P NMR
(101.2 MHz, CDCl3): δ = 23.6 ppm. 13C NMR (62.9 MHz, C6D6):
δ = 23.62 (CHCH3), 23.84 (CHCH3), 24.20 (CHCH3), 24.86
(CHCH3), 25.35 (CCH3), 34.94 (d, J = 152.2 Hz, PCH2), 77.73
31P NMR (162 MHz, C6D6):
δ =
11.58 ppm. 13C NMR
(100.6 MHz, C6D6): δ = 23.49 (CHCH3), 23.81 (CHCH3), 24.16
(CHCH3), 24.87 (CHCH3), 25.31 (CCH3), 35.23 (d, J = 151.8 Hz,
PCH2), 77.75 (CHCH3), 78.71 (CHCH3), 79.27 (CHCH3), 125.10
(CHAr), 125.54 (CHAr), 127.25 (CHAr), 128.74 (d, J = 8.78 Hz,
CHAr), 129.32 (d, J = 4.61 Hz, CCH2Ar), 132.48 (CHAr), 132.56
(CHAr), 132.64 (d, J = 9.67 Hz, CHAr), 133.87 (CAr), 133.92 (CAr),
177.95 (COO) ppm.
[Ti6O4(OiPr)10(OAc)2(O3P-vinyl)2] (3): Bis(trimethylsilyl) vinyl-
phosphonate (0.45 m in CH2Cl2, 2 mL, 0.9 mmol) was added to
Ti(OiPr)4 (522 μL, 1.8 mmol) in isopropyl alcohol (1 mL). Acetic
acid (51.5 μL, 0.9 mmol) was then quickly added. After five months
the CH2Cl2 was removed, and after an additional two weeks, crys-
tals of 3 were obtained, yield 80 mg (21%). 1H NMR (250 MHz,
CDCl3): δ = 1.38 (d, J = 6.16 Hz, 12 H, CHCH3), 1.39 (d, J =
6.16 Hz, 12 H, CHCH3), 1.52 (d, J = 6.10 Hz, 12 H, CHCH3), 1.80
(d, J = 6.32 Hz, 12 H, CHCH3), 1.84 (d, J = 6.32 Hz, 12 H, (CHCH3), 78.69 (CHCH3), 79.16 (CHCH3), 125.83 (d, J = 2.96 Hz,
CHCH3), 1.99 (s, 6 H, CCH3), 4.85 (m, J = 6.20 Hz, 2 H, CH),
5.05 (m, J = 6.12 Hz, 4 H, CH), 5.38 (m, J = 6.28 Hz, 4 H, CH),
5.72 (ddd, JP,H = 49.52, Jtrans = 12.00, Jtrans = 3.48 Hz, 4 H,
CHPh), 130.51 (d, J = 6.82 Hz, CHPh), 134.91 (d, J = 9.07 Hz,
ArCH2), 177.88 (COO) ppm.
C
[Ti6O4(OiPr)10(OAc)2(O3PCH2CH2CH2Br)2]
(7):
Ti(OiPr)4
CH=CH2), 6.21–6.56 (m,
4
H, CH=CH2) ppm. 31P NMR
(29 mL, 100 mmol) and acetic acid (3.83 mL, 67 mmol) were added
to a solution of bis(trimethylsilyl) (3-bromopropyl)phosphonate
(11.63 g, 33.4 mmol) in iPrOH (50 mL). After heating to reflux
overnight and cooling to room temperature, a cloudy mixture was
obtained. The suspension was concentrated under vacuum and fil-
tered. After washing two times with n-hexane and drying, a white
powder of 7 was obtained. For single-crystal measurements, part
of the powder was crystallized from CH2Cl2, yield 8 g (33%). 1H
NMR (250 MHz, C6D6): δ = 1.37 (d, J = 6.15 Hz, 12 H, CHCH3),
1.41 (d, J = 6.40 Hz, 12 H, CHCH3), 1.51 (d, J = 6.08 Hz, 12 H,
CHCH3), 1.71 (m, 4 H, PCH2), 1.76 (d, J = 6.16 Hz, 12 H,
CHCH3), 1.82 (d, J = 5.90 Hz, 12 H, CHCH3), 2.04 (s, 6 H, CCH3),
(101.2 MHz, C6D6): δ = 15.80 ppm. 13C NMR (62.9 MHz, C6D6):
δ = 23.61 (CHCH3), 23.97 (CHCH3), 24.28 (CHCH3), 24.72
(CHCH3), 25.26 (CHCH3), 25.32 (CCH3), 77.78 (CHCH3), 78.66
(CHCH3), 79.49 (CHCH3), 128.95 (s, CH2), 130.69 (d, J =
203.96 Hz, CH=CH2), 177.98 (COO) ppm.
[Ti6O4(OiPr)10(OAc)2(O3P-allyl)2] (4): Bis(trimethylsilyl) allylphos-
phonate (400 mg, 1.6 mmol) was added to Ti(OiPr)4 (930 μL,
3.2 mmol) in isopropyl alcohol (2 mL), then acetic acid (91 μL,
1.6 mmol) was quickly added. Crystals of 4 were obtained after
1
three weeks, yield 500 mg (48%). H NMR (250 MHz, CD2Cl2): δ
= 1.11 (d, J = 6.13 Hz, 12 H, CHCH3), 1.20 (d, J = 6.10 Hz, 12
H, CHCH3), 1.34 (d, J = 6.23 Hz, 12 H, CHCH3), 1.43 (d, J = 2.35 (m, JH,H = 7.23, JP,H = 17.30 Hz, 4 H, CH2), 3.52 (t, J =
6.33 Hz, 12 H, CHCH3), 1.47 (d, J = 6.48 Hz, 12 H, CHCH3), 1.90
(s, 6 H, CCH3), 2.43 (dd, JH,H = 7.4, JP,H = 23.0 Hz, 4 H,
CH=CH2), 4.73 (m, 6 H, CH), 4.97 (m, 4 H, CH), 5.09 (m, 4 H,
7.35 Hz, 4 H, CH2Br), 4.85 (m, J = 6.20 Hz, 2 H, CH), 5.00 (m, J
= 6.00 Hz, 4 H, CH), 5.33 (m, J = 6.28 Hz, 4 H, CH) ppm. 31P
NMR (101.2 MHz, C6D6): δ = 15.5 ppm. 13C NMR (62.9 MHz,
CH=CH2), 5.90 (m, 2 H, CH=CH2) ppm. 31P NMR (101.2 MHz, C6D6): δ = 23.64 (s, CH3), 23.91 (s, CH3), 24.25 (s, CH3), 24.74 (s,
CD2Cl2): δ = 11.9 ppm. 13C NMR (62.9 MHz, CD2Cl2): δ = 23.38
(s, CH3), 23.61 (s, CH3), 23.76 (s, CH3), 24.38 (s, CH3), 24.77 (s,
CH3), 25.29 (s, CH3), 25.33 (s, CH3), 25.71 (d, J = 157.2 Hz,
PCH2), 27.85 (d, J = 4.49 Hz, CH2), 33.71 (d, J = 12.98 Hz,
CH3), 24.89 (s, CH3), 32.85 (d, J = 154.13 Hz, PCH2), 77.21 (s, CH2Br), 77.83 (s, CH), 78.70 (s, CH), 79.54 (s, CH), 178.14 (s,
CH), 78.52 (s, CH), 80.05 (s, CH), 117.12 (d, J = 14.96 Hz, CH2), COO) ppm.
130.66 (d, J = 11.47 Hz, CH), 177.70 (s, COO) ppm.
[Ti5O(OiPr)11(OAc)(O3PCH2CH2CH2Br)3] (8): Bis(trimethylsilyl)
[Ti6O4(OiPr)10(OAc)2(O3PCH2CH2CH2Cl)2] (5): Bis(trimethyl- (3-bromopropyl)phosphonate (233 mg, 0.67 mmol) was added to
silyl) (3-chloropropyl)phosphonate (224 mg, 0.74 mmol) was added
to Ti(OiPr)4 (860 μL, 3.0 mmol) in isopropyl alcohol (3 mL), then
acetic acid (85 μL, 1.5 mmol) was quickly added. Cluster 5 crys-
tallized after three weeks, yield 100 mg (20%). 1H NMR (250 MHz,
Ti(OiPr)4 (388 μL, 1.34 mmol) in isopropyl alcohol (2 mL), then
acetic acid (38.3 μL, 0.67 mmol) was quickly added. Cluster 8 crys-
tallized after 12 weeks, yield 100 mg (26%). H NMR (250 MHz,
1
C6D6): δ = 1.38 (d, J = 7.90 Hz, 6 H, CHCH3), 1.41 (d, J = 6.40 Hz,
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6 H, CHCH3), 1.45 (d, J = 6.15 Hz, 18 H, CHCH3), 1.51 (d, J = 24.26 (s, CH3), 24.49 (s, CH3), 24.74 (s, CH3), 24.81 (s, CH3), 25.22
6.05 Hz, 6 H, CHCH3), 1.63 (d, J = 6.30 Hz, 12 H, CHCH3), 1.79 (s, CH3), 25.31 (s, CH3), 26.95 (d, J = 4.52 Hz, CH2), 27.86 (d, J
(m, 18 H, CHCH3), 1.85–2.01 (m, 6 H, PCH2), 2.04 (s, 3 H, CCH3), = 4.99 Hz, CH2), 33.73 (d, J = 12.59 Hz, CH2Br), 35.82 (d, J =
2.29–2.54 (m, 6 H, CH2), 3.52 (t, J = 7.23 Hz, 2 H, CH2Br), 3.71
(t, J = 6.40 Hz, 4 H, CH2Br), 4.69 (m, J = 6.20 Hz, 2 H, CH), 4.84
(m, J = 6.28 Hz, 1 H, CH), 5.00 (m, J = 6.16 Hz, 2 H, CH), 5.16
(m, J = 6.44 Hz, 3 H, CH), 5.33 (m, J = 6.24 Hz, 3 H, CH) ppm.
15.06 Hz, CH2Br), 77.84 (s, CH), 78.49 (s, CH), 78.73 (s, CH),
79.57 (s, CH), 79.82 (s, CH), 178.17 (s, COO) ppm.
[Ti5O3(OiPr)6(OAc)4(O3P-xylyl)2] (9): Bis(trimethylsilyl) xylyl-
31P NMR (101.2 MHz, C6D6): δ = 27.44 (1 P), 30.34 (2 P) ppm. phosphonate (100 mg, 0.30 mmol) was added to a solution of
13C NMR (62.9 MHz, C6D6): δ = 23.65 (s, CH3), 23.96 (s, CH3), Ti(OiPr)4 (176 μL, 0.61 mmol) in isopropyl alcohol (1 mL), then
Table 1. Crystal data and structure refinement details for 1–9.
1
2
3
Empirical formula
Formula weight
Crystal system
Space group
a [pm]
b [pm]
c [pm]
C38H86O24P2Ti6
1276.22
monoclinic
P 21/n
1226.23(6)
1649.58(9)
1464.69(7)
90
C56H94O24P2Ti6
1500.65
monoclinic
C 2/c
2259.5(2)
1682.61(13)
1830.97(15)
90
C38H82O24P2Ti6
1272.38
monoclinic
P 21/n
1206.87(6)
1664.31(8)
1460.95(8)
90
α [°]
β [°]
98.272(3)
90
2931.9(3)
2
1.446
0.904
91.538(3)
90
6958.5(10)
4
1.432
0.774
97.193(2)
90
2911.4(3)
2
1.451
0.91
γ [°]
V (pm3·106)
Z
Dx [Mgm–3]
μ [mm–1]
Crystal size [mm]
Measured reflections
Observed reflections
[IϾ2σ(I)]
0.5ϫ0.5ϫ0.5
121208
16514
0.5ϫ0.5ϫ0.4
93315
10942
0.5ϫ0.4ϫ0.3
43475
5034
θmax. [°]
42.84
33.22
26.41
R [F2 Ͼ2σ(F)], wR(F2), S
Reflections/parameters
Weighting scheme[a]
0.0323, 0.0862, 1.037
21197/418
0.0356, 0.1004, 1.043
13284/408
0.0424, 0.1002, 1.106
5971/448
w = 1/[σ2(Fo2) + (0.0344P)2 +
1.21P]
w = 1/[σ2(Fo2) + (0.0417P)2 +
14.8148P]
w = 1/[σ2(Fo2) + (0.0344P)2 +
9.7385P]
δρmax.,min. [e·10–6 pm–3]
0.885, –1.307
1.246, –0.424
1.641, –0.957
2
2
[a] P = (Fo + 2Fc )/3.
Table 2. Crystal data and structure refinement details for 4–6.
4
5
6
Empirical formula
Formula weight
Crystal system
Space group
a [pm]
b [pm]
c [pm]
C40H86O24P2Ti6
1300.43
C40H88Cl2O24P2Ti6
1373.34
monoclinic
P 21/n
1376.54(5)
1571.04(5)
1653.85(5)
90
112.1300(10)
90
3313.13(19)
2
C50H94Cl4O24P2Ti6
1570.39
monoclinic
P21/c
2643.8(3)
1259.66(14)
2280.3(3)
90
108.761(4)
90
7190.8(14)
4
triclinic
¯
P 1
1146.80(9)
1223.83(10)
1228.22(10)
106.880(4)
110.202(3)
97.601(4)
1495.2(2)
1
α [°]
β [°]
γ [°]
V (pm3·106)
Z
Dx [Mgm–3]
μ [mm–1]
1.444
0.888
1.377
0.883
1.451
0.896
Crystal size [mm]
Measured reflections
Observed reflections
[IϾ2σ(I)]
0.3ϫ0.3ϫ0.3
62482
12261
0.5ϫ0.4ϫ0.4
88173
5416
0.32ϫ0.27ϫ0.23
287456
16780
θmax. [°]
36.35
28.95
30.58
R [F2 Ͼ2σ(F)], wR(F2), S 0.0263, 0.0726, 1.036
0.0647, 0.2177, 1.094
8720/443
0.044, 0.1256, 1.068
21997/894
Reflections/parameters
14474/336
Weighting scheme[a]
w = 1/[σ2(Fo2) + (0.0313P)2 +
0.6556P]
w = 1/[σ2(Fo2) + (0.0889P)2 +
3.5722P]
w = 1/[σ2(Fo2) + (0.0517P)2 +
11.3637P]
δρmax.,min. [e·10–6 pm–3]
1.272, –0.362
0.741, –0.477
1.5, –1.368
2
2
[a] P = (Fo + 2Fc )/3.
Eur. J. Inorg. Chem. 2014, 2038–2045
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Table 3. Crystal data and structure refinement details for 7–9.
7
8
9
Empirical formula
Formula weight
Crystal system
Space group
a [pm]
b [pm]
c [pm]
C40H88Br2O24P2Ti6
1462.26
orthorhombic
P b c a
1632.40(3)
1585.18(3)
2401.10(4)
90
90
90
6213.2(2)
4
1.563
C44H98Br3O23P3Ti5
1567.36
monoclinic
P 21/n
1308.99(7)
2291.37(13)
2346.81(13)
90
102.299(2)
90
6877.4(7)
4
C42H72O23P2Ti5
1246.44
triclinic
¯
P 1
1210.96(6)
1284.46(7)
1908.81(11)
101.464(3)
96.661(3)
96.627(3)
2860.8(3)
2
α [°]
β [°]
γ [°]
V (pm3·106)
Z
Dx [Mgm–3]
1.514
2.434
1.447
0.797
μ [mm–1]
2.142
Crystal size [mm]
Measured reflections
Observed reflections
[IϾ2σ(I)]
θmax. [°]
0.6ϫ0.5ϫ0.5
196724
10744
0.6ϫ0.4ϫ0.35
127718
13683
0.7ϫ0.6ϫ0.4
137433
19253
36.37
34.37
28.32
R [F2 Ͼ2σ(F)], wR(F2), S 0.0222, 0.0571, 1.049
0.0567, 0.1487, 1.031
16623/727
0.063, 0.1544, 1.084
27635/789
Reflections/parameters
13047/345
Weighting scheme[a]
w = 1/[σ2(Fo2) + (0.0251P)2 +
2.6246P]
w = 1/[σ2(Fo2) + (0.0552P)2 +
46.4092P]
w = 1/[σ2(Fo2) + (0.0160P)2 +
9.9669P]
δρmax.,min. [e·10–6 pm–3]
0.681, –0.423
5.461, –5.769
1.701, –1.112
2
2
[a] P = (Fo + 2Fc )/3.
CH3COOH (35 μL, 0.61 mmol) was added. After 15 weeks, crystals
of 9 were obtained, yield 200 mg (48%). 1H NMR (250 MHz,
C6D6): δ = 1.46 (d, J = 6.15 Hz, 6 H, CHCH3), 1.51 (d, J = 6.78 Hz,
6 H, CHCH3), 1.54 (d, J = 6.33 Hz, 12 H, CHCH3), 1.90 (d, J =
6.20 Hz, 6 H, CHCH3), 1.91 (d, J = 6.32 Hz, 6 H, CHCH3), 1.95
(s, 6 H, CCH3), 1.98 (s, 6 H, CCH3), 2.18 (s, 12 H, CH3(Xyl)), 5.07
(m, J = 6.20 Hz, 2 H, CH), 5.22 (m, J = 6.12 Hz, 2 H, CH), 5.66
(m, J = 6.32 Hz, 2 H, CH), 6.91 (s, 2 H, CHXyl), 8.03 (s, 2 H,
CHXyl), 8.08 (s, 2 H, CHXyl) ppm. 31P NMR (101.2 MHz, C6D6):
δ = 15.92 ppm. 13C NMR (62.9 MHz, C6D6): δ = 20.92 (CH3),
22.90 (CH3), 23.30 (CH3), 23.93 (CH3), 24.05 (CH3), 24.11 (CH3),
24.16 (CH3), 24.60 (CH3), 24.77 (CH3), 25.19 (CH3), 80.57
(CHCH3), 81.41 (CHCH3), 82.27 (CHCH3), 129.80 (d, J = 10.0 Hz,
CH), 131.44 (d, J = 201.0 Hz, PC), 132.53 (d, J = 2.8 Hz, CH),
137.24 (d, J = 16.3 Hz, C), 177.87 (COO), 180.11 (COO) ppm.
ligands and one chloropropyl group of 5; four OiPr ligands and
one dichloromethane of 6; four OiPr ligands of 9.
CCDC-981140 (for 1), -981141 (for 2), -981142 (for 3), -981143 (for
4), -981144 (for 5), -981145 (for 6), -981146 (for 7), -981147 (for 8),
and -981148 (for 9) contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Center via
www.ccdc.cam.ac.uk/data_request/cif.
Supporting Information (see footnote on the first page of this arti-
1
cle): Copies of H and 13C NMR spectra.
Acknowledgments
This work was supported by the Austrian Fonds zur Förderung der
wissenschaftlichen Forschung (FWF) (project number P22915).
X-ray measurements were carried out within the X-ray Center of
the Vienna University of Technology.
X-ray Structure Analyses: All measurements were performed at
100 K using Mo-Kα (λ = 71.073 pm) radiation. Data were collected
with a Bruker AXS SMART APEX II four-circle diffractometer
with κ-geometry. Crystals of 5 cracked when cooled to 100 K; ap-
parently a phase transition took place at about 180 K. The mea-
surements of 5 were therefore carried out at 213 K. Data were col-
lected with φ and ω-scans and different frame widths. The data
were corrected for polarization and Lorentz effects, and an empiri-
cal absorption correction (SADABS) was employed. The cell di-
mensions were refined with all unique reflections. SAINT PLUS
software (Bruker Analytical X-ray Instruments, 2007) was used to
integrate the frames. Details of the X-ray investigations are given
in Table 1 (for 1–3), Table 2 (for 4–6), and Table 3 (for 7–9). The
structures were solved by the Patterson method (SHELXS97[13]).
Refinement was performed by the full-matrix least-squares method
based on F2 (SHELXL97) with anisotropic thermal parameters for
all non-hydrogen atoms. Hydrogen atoms were inserted in calcu-
lated positions and refined by riding with the corresponding atom.
Positions of disordered carbon and halogen atoms were refined
with two sites, with about 50% occupancy each. Disordered
groups: three OiPr ligands of 1; one vinyl group of 3; three OiPr
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Published Online: March 11, 2014
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© 2014 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim