Oximate-substituted zirconium alkoxides

Article abstract of DOI:10.1039/c0dt00384k

The reaction of acetoxime, ethyl methyl ketoxime or cyclohexanone oxime with zirconium iso-propoxide gave dimeric alkoxo oximate derivatives [Zr(OiPr)(oximate)₃]₂. The oximate ligands are side-on coordinated and the alkoxo groups bridge the two metal centres. NMR spectroscopy revealed dynamic behaviour of the compounds in solution. When exposing a reaction mixture of zirconium butoxide and cyclohexanone oxime to ambient moisture, the oxo-alkoxo derivative Zr₄O(OBu)₈(ONC ₆H₁₀)₆ was obtained.

Full text of DOI:10.1039/c0dt00384k

View Article Online / Journal Homepage / Table of Contents for this issue
Dynamic Article Links
Dalton
Transactions
Cite this: Dalton Trans., 2011, 40, 1401
www.rsc.org/dalton
PAPER
Oximate-substituted zirconium alkoxides†
Stefan O. Baumann, Michael Puchberger and Ulrich Schubert*
Received 28th April 2010, Accepted 21st November 2010
DOI: 10.1039/c0dt00384k
The reaction of acetoxime, ethyl methyl ketoxime or cyclohexanone oxime with zirconium
iso-propoxide gave dimeric alkoxo oximate derivatives [Zr(OiPr)(oximate)3]2. The oximate ligands are
side-on coordinated and the alkoxo groups bridge the two metal centres. NMR spectroscopy revealed
dynamic behaviour of the compounds in solution. When exposing a reaction mixture of zirconium
butoxide and cyclohexanone oxime to ambient moisture, the oxo-alkoxo derivative
Zr4O(OBu)8(ON C6H10)6 was obtained.
two Zr2(OBu)5(OCH2CH2NH2)3 and two Zr(OBu)4 sub-units,
which are associated by alkoxo bridges.4
Introduction
Modification of transition metal alkoxides, M(OR)n, by bi- or
tridentate organic ligands allows decreasing the high reaction rates
during sol–gel processing as well as introducing functional groups
in metal-based sol–gel materials. Effects of these modifications on
the derived gels have been discussed elsewhere.1 Acetic acid or
acetylacetone is most commonly used for modification, but also
other compounds, such as a-amino acids, hydroxycarboxylic acids,
phosphonic and phosphinic acids, sulfonic acids, as well as various
b-diketones and b-ketoesters, amino alcohols, etc. The protic
compounds can substitute one or more OR groups of M(OR)n with
concomitant ROH elimination. This results in modified precursors
M(OR)n-x(BL)x, where BL is an anionic bi- or tri-dentate ligand
which is more strongly bonded than alkoxo ligands.
The structural chemistry of Ti(OR)4-x(BL)x derivatives with
various bidentate ligands and their primary hydrolysis products,2
to a smaller extent also that of Al(OR)3-x(BL)x,3 has been
well investigated. The reason for the better knowledge on Ti
and Al derivatives is their higher crystallization tendency and
simpler structures, compared with other metal alkoxides. Both
can be traced back to the lower coordination numbers of
Ti (six, rarely five) and Al (4–6) which results in a smaller
number of possibilities how the coordination polyhedra can
be connected with each other. For this reason, the structures
of zirconium alkoxide derivatives cannot be extrapolated from
the corresponding titanium derivatives. A particularly illustrative
example are the compounds “M(OR)3(OCH2CH2NH2)” (M = Ti,
Zr). While titanium derivatives (OR = OiPr, OEt) are alkoxo-
bridged dimers with chelating aminoethanolate ligands, the Zr
compound is in fact Zr6(OBu)18(OCH2CH2NH2)6, assembled from
When used in sol–gel processes, the organically modified metal
alkoxide derivatives are the building blocks for the obtained hybrid
inorganic–organic gels. Since the latter are usually non-crystalline,
structural information must be extrapolated from the structures
of the building blocks. In this respect, partially hydrolyzed
compounds are also important, as they allow conclusions on how
the gel structures develop in the early stages of the hydrolysis
and condensation processes. Each of the structures is just a
snapshot, but common features can be extracted when comparing
all snapshots. For example, comparison of partially hydrolyzed
carboxylate- or aminoalcoholate-substituted titanium alkoxide
derivatives showed, inter alia,2,4 (i) that m3-oxygen atoms are
already formed in the very early stages of the hydrolysis process,
and (ii) that the degree of substitution (average number of BL
ligands per metal atom) and the degree of hydrolysis (average
number of oxo groups per metal atom) have a mutual influence on
the observed structural features.
Because of the lower crystallization tendency of Zr
derivatives, only few structural data on Zr(OR)4-x(BL)x
derivatives or their partial hydrolysis products are available.
Apart from “Zr(OBu)3(OCH2CH2NH2)”, the structures of
[Zr(OiPr)2(OOC-CCo3(CO)9)2]2 (one bridging carboxylate
and OiPr ligand per zirconium atom each)5 and polymeric
6
[Zr(OPr)(O3SMe)3]•
(two bridging and one chelating
sulfonate group per zirconium atom and a terminal OPr
group) are known. Structurally characterized BL-substituted
oxo-alkoxo
derivatives
are
Zr4O(OMe)4(acac)4(3,5-di-
tert-butylcatecholate)3(MeOH) (acac
=
acetylacetonate),7
Zr4O(OPr)10(acac)4,8,9 Zr10O6(OH)4(OPr)18(allylacetoacetate)6,9
[Zr3O(OBu)5(methacrylate)5]2 and [Zr3O(OMe)2(OBu)(methacry-
10
late)7]2
(oxo derivatives without residual OR groups are
Institute of Materials Chemistry, Vienna University of Technol-
ogy, Getreidemarkt 9, A-1060, Vienna, Austria. E-mail: uschuber@
mail.zserv.tuwien.ac.at; Fax: +43-1-58801-16599
† CCDC reference numbers 775285 (for 1), 775286 (for 2), 775287 (for 3),
and 775288 (for 4). For crystallographic data in CIF or other electronic
format see DOI: 10.1039/c0dt00384k
disregarded here). The b-diketonate ligands are all chelating,
while the methacrylate derivatives contain both chelating and
bridging carboxylate ligands, the two Zr3O units being bridged
by OR groups.
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 1401–1406 | 1401
©

View Article Online
Table 1 Selected distances (pm) and angles (deg) in 1–3 (atoms with an
Own recent work dealt with the modification of titanium
alkoxides with oximes,11 and the use of the oximate-substituted
precursors for sol–gel processing.12 We were able to show that the
chemistry and structures of Ti(OiPr)4-x(oximate)x derivatives are
less straightforward than has been reported in the literature. The
preferentially formed derivatives, independent of the employed
stoichiometric ratio of Ti(OiPr)4 and oxime, were the dimeric,
alkoxo-bridged compounds [Ti(OiPr)2(oximate)2]2. In this article,
we report the results of our investigations of the corresponding
zirconium oximate derivatives.
asterisk denote inversion-related atoms)
1
2
3
Zr(1)–O(1)
Zr(1)–O(1)*
Zr(1)–O(2)
218.6(3)
214.6(3)
212.7(3)
215.4(2)
218.2(2)
210.3(3)
219.2(2)
215.0(2)
212.0(3)
Zr(1)–O(3)
Zr(1)–O(4)
210.1(3)
208.4(3)
209.4(3)
208.6(2)
209.9(3)
208.0(3)
Zr(1)–N(1)
Zr(1)–N(2)
218.0(4)
223.3(4)
221.5(4)
224.2(3)
220.1(3)
223.4(3)
Zr(1)–N(3)
226.7(4)
226.4(3)
229.0(3)
O(1)–Zr(1)–N(2)
O(2)–Zr(1)–N(3)
N(1)–Zr(1)–N(3)
O(1)–Zr(1)–O(3)
O(2)–Zr(1)–O(4)
166.72(12)
167.49(13)
130.45(14)
156.50(11)
130.90(12)
168.98(10) (O1*)
165.77(9)
129.48(11)
154.39(10) (O1*)
130.53(10)
167.78(10)
163.94(10)
128.94(11)
155.37(10)
129.91(10)
Results and discussion
It was claimed in the early literature, that the whole se-
ries of compounds Zr(OiPr)4-x(oximate)x was obtained when
Zr(OiPr)4 was reacted with simple ketoximes.13 Buyuktas et al.
reported recently the formation of Zr(OBu)2(acetoximate)2 and
Zr(OBu)3(acetoximate) from Zr(OBu)4.14 They postulated from
spectroscopic data, that both derivatives are oximate-bridged
dimers with terminal butoxo groups. Contrary to this re-
port, we only obtained the dimeric, tri-substituted derivatives
[Zr(OiPr)(oximate)3]2 (1: acetoximate, 2: ethyl methyl ketoximate,
3: cyclohexanone oximate, Fig. 1) when Zr(OiPr)4 was reacted
with small ketoximes, viz. acetoxime, ethyl methyl ketoxime or
cyclohexanone oxime, in a 1 : 2 ratio. Mono- or di-substituted
compounds (i.e., one or two oximate ligands per zirconium atom)
could not be isolated even with smaller proportions of oxime.
The crystalline compounds were investigated by X-ray structure
analyses.
Fig. 2 Molecular structure of [Zr(ON C6H10)3(OiPr)]2 (3) as an exam-
ple. Thermal ellipsoids were drawn at 50% probability.
smaller c.n. of Ti is the reason for the lower degree of substitution
compared to Zr.
Two of the oximate groups in 1–3 are coordinated to the metal
centre by forming a nearly linear N–Zr–O axis (N–Zr–O 164–
169◦) similar to what was previously found for one isomer of
di-substituted titanium alkoxides [Ti(OR)2(oximate)2]2 (the other
isomer has nearly linear N–Ti–N axes).11,15 The corresponding
N(1)–Zr–N(3) and O(2)–Zr–O(4) angles are around 130◦. The
coordination sphere of the zirconium atoms is completed by a
third oximate ligand enclosing a Oalkoxo–Zr–Ooximate angle of ~156◦
while the associated nitrogen is slightly twisted out of the central
Zr2(OiPr)2 plane.
Metal alkoxides and their derivatives sometimes undergo com-
plex equilibria in solution. Any structural investigation must
therefore be complemented by NMR spectroscopy in solution. As
shown in Fig. 3 for [Zr(OiPr)(ON C(Me)2)3]2 (1) as an example,
more than one CH signal for the methine proton of the bridging
OiPr group, as expected for a compound with Ci symmetry, was
observed in CD2Cl2 solution. In this chemical shift range, an
additional signal at d = 3.99 ppm (d) was present in addition
to the expected signal at d = 4.55 ppm (b). Furthermore, two
weaker, broad signals were observed at 4.68 ppm (c) and 4.36 (a)
ppm. The EXSY spectrum (Fig. 3) shows exchange between the
different OiPr species. One possible explanation for the observed
spectrum is, that the dynamic behavior arises from site exchange
Fig. 1 Schematic structure of the [Zr(OiPr)(oximate)3]2 derivates 1–3.
The zirconium alkoxide derivatives 1–3 are centrosymmetric
dimeric compounds. The structure of 3 is shown in Fig. 2 as an
example; important bond lengths and angles are compared in
Table 1. Each zirconium atom is coordinated by three oximate
ligands (side-on) and two bridging OiPr groups. The zirconium
atoms are thus surrounded by three nitrogen and five oxygen
atoms in a distorted dodecahedron. The preference of Zr for
coordination number (c.n.) 8 may be the reason for (i) the
substitution by three oximate ligands and (ii) the formation of OR
bridges. A lower degree of substitution or formation of monomeric
Zr(OR)(oximate)3 would result in a lower c.n. For the same reason,
the di-substituted derivatives [Ti(OiPr)2(oximate)2]2 (one terminal
and one bridging OR ligand per Ti atom) are preferentially
formed from Ti(OiPr)4 under comparable conditions, viz. room
temperature reaction of the metal alkoxides with two molar
equivalents of the respective oxime. The smaller size and therefore
1402 | Dalton Trans., 2011, 40, 1401–1406
This journal is
The Royal Society of Chemistry 2011
©

View Article Online
signals almost disappeared at -80 ◦C, i.e. one of the exchange
processes is slowed down or terminated at this temperature. While
the number of methine signals was reduced, splitting of the peaks
was observed in the methyl group region upon cooling. At -80 ◦C
three sets of signals were observed for the methyl groups of the
OiPr ligands and five (larger) signals for the acetoximate protons.
The additional resonances can be explained by slowing down
the site exchange (or rotation) of the oximate ligand and thus
observation of a mixture of a Ci and a C1 symmetric species. An
alternative explanation of the observed exchange process might
be that an equilibrium between different oximate-substituted
zirconium iso-propoxide species is observed. This would be
supported by a tentative assignment of the two more intensive CH
signals from the HSQC spectrum: The signal a 3.99 ppm shows
a carbon correlation at 64.1 ppm, whereas the signal at 4.55 ppm
shows a correlation at 71.6 ppm. Therefore it appears possible
that this is an equilibrium between bridging and coordinating iso-
propoxo ligands. Other examples for such equilibria in solution
are known, such as Ti(OR)3(b-diketonate) derivatives, where
monomeric and dimeric species are in equilibrium.16 In addition
to that, [Ti(OR)3(b-diketonate)]n is in equilibrium with Ti(OR)4
and Ti(OR)2(b-diketonate)2.17 Two isomers were found in the di-
substituted titanium alkoxides derivatives [Ti(OR)2(oximate)2]2,
which differ by the mutual orientation of the oximate ligands
(parallel or antiparallel arrangement of the N–O vectors) but
interconvert in solution.11 The many possible equilibria explain the
complex NMR spectra, even if an assignment of the resonances
to specific compounds is currently not possible.
Fig. 3 EXSY spectrum of the region of the OiPr methine protons of 1 in
CD2Cl2 at room temperature.
or rotation of the oximate ligands while the OiPr ligands are only
“observing” this process (the exchange signals originate from the
changed symmetry). This would explain why there are only two
resonances for the methyl groups of the oximate ligands (between
1-2 ppm) instead of six which would be expected for a Ci symmetric
compound. Unfortunately, these resonances also partially overlap
with the methyl groups of the OiPr groups. Therefore, no further
information can be derived from this part of the spectrum.
As mentioned before, we were not able to crystallize a mono-
or di-substituted derivative [Zr(OR)4-x(ON C(Me)2)x]n (x = 1
or 2). However, when ambient moisture was allowed to diffuse
slowly into a reaction solution containing two molar equivalents
of cyclohexanone oxime and one equivalent of Zr(OBu)4, crystals
of Zr4O(OBu)8(ON C6H10)6 (4, Fig. 5) were obtained. In this
compound, half of the zirconium atoms are substituted by one or
two oximate ligands, respectively. The core of this partial hydrolysis
When the CD2Cl2 solution of 1 was cooled to -80 ◦C, the signal
pattern changed. The signals at 4.55 ppm and 3.99 ppm became
sharper between 0 ◦C and -40 ◦C (Fig. 4) before the two weak
Fig. 4 Temperature-dependent 1H NMR spectra of 1 in CD2Cl2 at three different temperatures: 25 ◦C (top), -20 ◦C (centre) and -80 ◦C (bottom). The
region of the methine protons of the OiPr ligand (left) and the methyl group region (right) is shown.
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 1401–1406 | 1403
©

View Article Online
Table 2 Selected distances (pm) and angles (◦) in 4
Zr(4) 406.4 pm) is much larger. Coordination of the oximates
occurs in side-on fashion as in the derivatives 1–3 exhibiting Zr–O
and Zr–N distances of comparable magnitude.
Zr(1)–O(1)
221.2(2)
222.9(2)
220.7(2)
220.8(2)
211.3(3)
210.3(3)
207.3(3)
210.4(3)
91.28(9)
136.54(11)
105.68(9)
Zr(4)–O(13)
Zr(4)–O(14)
Zr(1)–N(1)
210.7(3)
208.7(3)
223.2(3)
224.6(3)
224.6(3)
228.0(3)
226.4(3)
222.1(3)
104.90(9)
132.68(11)
92.54(9)
Zr(2)–O(1)
Zr(3)–O(1)
Zr(4)–O(1)
Zr(2)–N(2)
Zr(1)–O(3)
Zr(2)–O(6)
Zr(3)–N(3)
Zr(3)–N(4)
Conclusions
Zr(3)–O(9)
Zr(4)–N(5)
Zr(4)–N(6)
Zr(2)–O(1)–Zr(3)
Zr(2)–O(1)–Zr(4)
Zr(3)–O(1)–Zr(4)
Contrary to analogous reactions of Ti(OiPr)4 with oximes, where
mainly the di-substituted derivatives [Ti(OiPr)2(oximate)2]2 were
obtained, reaction of Zr(OiPr)4 with the oximes of acetone,
ethyl methyl ketone and cyclohexanone yielded tri-substituted
[Zr(OiPr)(oximate)3]2 (1–3). The Ti and Zr derivatives are struc-
turally related, a terminal iso-propoxo group in the Ti derivative
being replaced by a side-on coordinated oximate ligand. This
appears to be a consequence of the increased coordination number
of zirconium. The dimeric structure of [Zr(OiPr)(oximate)3]2 is in
stark contrast to the polymeric structure of [Zr(OPr)(O3SMe)3]•.6
The structural difference is probably due to the more pronounced
tendency of sulfonate ligands for a bridging coordination.
Zr(3)–O(10)
Zr(1)–O(1)–Zr(2)
Zr(1)–O(1)–Zr(3)
Zr(1)–O(1)–Zr(4)
In Zr4O(ON C6H10)6(OBu)8 (4), obtained from partial hydrol-
ysis, both seven- and eightfold coordinated zirconium atoms are
present forming a distorted tetrahedron around a central oxygen.
The Zr4(m4-O) motif was already found in two other oxo-alkoxo
derivatives (with different arrangements of the organic ligands,
although only a few compounds were structurally investigated.
There is again a remarkable difference to partially hydrolyzed
Ti(OR)4-x(BL)x derivatives, where Ti3(m3-O) groups develop in
early stages.2 Such groups are typical of crystalline titania modifi-
cations. By analogy, the Zr4(m4-O) motif found in 4 and the related
compounds is found in crystalline zirconia. Thus, basic building
blocks of the corresponding crystalline oxides develop in a very
early stage of the hydrolysis reactions.
Experimental
Fig. 5 Molecular structure of Zr4O(OnBu)8(ON C6H10)6 (4). Thermal
All care was taken to avoid water or other OH species during
sample preparation, viz. by working in the dry argon atmosphere
of a glovebox and silylation of the NMR tubes. The solvents
were additionally treated with basic alumina to eliminate acidic
species. Zr(OiPr)4·iPrOH (ABCR, 99.9%), Zr(OBu)4 (Aldrich,
80% in butanol), acetoxime (Aldrich, 98%), cyclohexanone oxime
(Aldrich, 97%) and ethyl methyl ketone (Aldrich, 99%) were
used as received. Ethyl methyl ketone E-oxime was synthesized
from the ketone by usual methods following a modified version
of the procedure of Bousquet.18 All solvents were dried and
purified by standard methods. The solvents for NMR spectroscopy
(Eurisotop) were degassed prior to use and stored over molecular
sieve.
ellipsoids were drawn at 50% probability.
product is built by four zirconium atoms which are located around
a central m4-oxygen by forming a distorted tetrahedron with
Zr–O bond lengths ranging from 221 to 223 pm and Zr–O–
Zr– angles from 91.3 to 136.5◦ (Table 2). The Zr4O structural
motif was already observed in Zr4O(OMe)4(acac)4(3,5-di-tert-
7
butylcatecholate)3(MeOH) and Zr4O(OPr)10(acac)4.8,9 In the
latter case it was postulated that the compound is formed by
condensation of two dimers.8 However, other mechanisms are also
imaginable.
In contrast to the latter clusters, the Zr4O core is more strongly
distorted. This is probably due to the fact that in the two acac
derivatives all edges of the Zr4 tetrahedron are bridged by organic
groups. In 4, no bridges are present between Zr(1)/Zr(3) and
Zr(2)/Zr(4). The two zirconium atoms Zr(1) and Zr(2) which are
coordinated by only one oximate each and which are connected
by two butoxo bridges have approximately the same distance
(317.50(5) pm) as Zr(3) and Zr(4) which both are surrounded
by two oximates each and are also connected by two butoxo
bridges (319.09(5) pm). The distance between the neighbouring,
differently substituted zirconium atoms bridged by one butoxo
ligand (Zr(1)-Zr(4) 352.30(5) and Zr(2)-Zr(3) 351.69(5) pm) and
the non-bridged zirconium atoms (Zr(1)-Zr(3) 410.6 and Zr(2)-
1H and 13C solution NMR spectra were recorded on a Bruker
1
13
AVANCE 250 (250.13 MHz { H}, 62.86 MHz { C}) and a Bruker
1
13
DPX 300 spectrometer (300.13 MHz { H}, 75.47 MHz { C})
equipped with a 5 mm inverse-broadband probe head and a z-
gradient unit. 2D NMR spectra were measured with Bruker stan-
dard pulse programs COSY (Correlation Spectroscopy), HSQC
(Heteronuclear Single Quantum Correlation), EXSY (Exchange
Spectroscopy; tmix = 1 s), and HMBC (Heteronuclear Multiple-
Bond Correlation; optimized for J = 140 Hz). The numbering
scheme for the carbon atoms of the oximate ligands is given in
Fig. 6.
1404 | Dalton Trans., 2011, 40, 1401–1406
This journal is
The Royal Society of Chemistry 2011
©

View Article Online
Table 3 Crystallographic and structural parameters of 1–4
1
2
3
4·CH2Cl2
Empirical formula
Formula weight
Crystal system
Space group
a/pm
C24H50N6O8Zr2
733.14
C30H62N6O8Zr2
817.30
Monoclinic
C42H74N6O8Zr2
973.51
C69H134Cl2N6O15Zr4
1723.60
Monoclinic
P21/n
1288.58(11)
2515.8(2)
Triclinic
Triclinic
¯
¯
P1
C2/c
P1
973.44(15)
1911.3(3
2044.6(3)
64.979(2)
84.170(2)
88.836(2)
3428.2(9)·106
4
1454.5(2)
1825.1(3)
1520.8(2)
1050.6(3)
1072.8(3)
1095.4(3)
100.974(4)
112.554(4)
91.132(4)
1113.5(5)·106
1
b/pm
c/pm
2561.1(2)
a (◦)
b (◦)
101.557(2)
90.299(2)
g (◦)
Volume/pm3
Z
3955.4(11)·106
4
1.372
8302.5(12)·106
4
1.379
Dc/g cm-3
1.420
0.656
0.19 ¥ 0.16 ¥ 0.09
1.10–25.00
26145/11936
11936/753
1.069
0.046
0.132
1.647/-1.005
1.452
0.525
0.23 ¥ 0.13 ¥ 0.05
2.86–28.33
14723/5509
5509/264
1.007
0.050
0.109
1.390/-1.041
Abs. coeff. m/mm-1
Crystal size/mm
H range/◦
0.577
0.613
0.55 ¥ 0.26 ¥ 0.25
2. 73–25.00
14184/3477
3477/227
1.065
0.043
0.117
0.90 ¥ 0.50 ¥ 0.30
2.26–28.29
55967/20481
20481/900
1.075
0.050
0.113
Reflections coll./unique
Data/parameters
GOF on F2
R [I > 2s(I)]
0.1317
-3
˚
Largest diff. peak/hole/e A
0.771/-0.625
1.036/-1.681
solution of 356 mg (0.92 mmol) of Zr(OiPr)4 in 3.0 mL of toluene.
The reaction mixture was refluxed for 5 min. Evaporation of the
solvent gave colourless crystals of 2 after one day of storage at
room temperature which were washed with several portions of
pentane at -20 ◦C and dried in◦vacuo. Yield 134 mg (39% rel.
Zr(OiPr)4). 1H NMR (CDCl3, 20 C): d 4.54/3.95 (q, br, J 6.2 Hz,
1H, CHMe2), 2.44/2.29 (q, J 7.6 Hz, 6H, CH2Me), 1.87 ((s),
9H, CCH3), 1.13 ((s), 6H, CH(CH3)2), 0.99 (d, br, J 6.7 Hz, 9H,
◦
1
Fig. 6 Numbering of the carbon atoms of cyclohexanone and acetoxi-
mate ligands.
CH(CH3)2) ppm. 13C{ H} NMR (CDCl3, 20 C): d 151 (C N),
77.2 (CHMe2), 29.1 (CH2Me), 24.0 (CHMe2), 15.6 (CCH3), 9.8
(CH2CH3) ppm. IR (CH2Cl2, cm-1):n 2873 (s), 2861 (s), 1683 (w),
1649 (w), 1494 (m), 1438 (w), 1375 (m), 1331 (w), 1161 (m), 1128
(m), 1083 (w), 972 (s), 942 (m), 851 (w), 813 (w), 617 (m), 592 (m).
FT-IR spectra were recorded on a Bruker Tensor 27 working in
ATR MicroFocusing MVP-QL with a ZnSe crystal or in CH2Cl2
solution, using OPUS version 4.0 software for analysis. Because of
the high moisture sensitivity of the complexes, elemental analysis
could not be obtained.
[Zr(ON C6H10)3(OiPr)]2 (3).
A
solution of 428 mg
(1.10 mmol) of Zr(OiPr)4 in 5.0 mL toluene was added dropwise
to a solution of 250 mg (2.21 mmol) of acetoxime in 1.0 mL of
toluene. The reaction mixture was stirred for 3 min. Colourless
crystals of 3 were obtained from the yellow solution after one day
which were washed with several portions of pentane at -20 ◦C
and dried in vacuo. Yield 136 mg (25% rel. Zr(OiPr)4). 1H NMR
(CDCl3, 20 ◦C): d 4.51/3.95 (q, br, J 6.1 Hz, 1H, CHMe2), 2.45 (t,
br, J 7.2 Hz, 6H, C2H), 2.29 (t, br, J 5.8 Hz, 6H, C6H), 1.51 ((s),
Syntheses
[Zr(ON C(Me)2)3(OiPr)]2 (1).
A solution of 94.6 mg
(1.29 mmol) of acetoxime in 1.0 mL of toluene was added dropwise
to a solution of 242 mg (0.63 mmol) of Zr(OiPr)4 in 2.0 mL
of toluene. The reaction mixture was stirred for 3 min. Slow
evaporation of the solvent gave colourless crystals of 1 after three
days of storage at room temperature which were washed with
several portions of pentane at -20 ◦C and dried in vacuo. Yield
132 mg (58%, rel. Zr(OiPr)4, 84% rel. oxime). 1H NMR (CDCl3,
20 ◦C): d 4.50/3.95 (q, br, J 5.9 Hz, 1H, CHMe2), 1.95 (s, 3H,
C2H), 1.91 (s, 3H, C3H), 1.13 (d, br, J 5.2 Hz, 3H, CH(CH3)2) ppm.
18H, C3–5H), 1.14 (d, br, J 6.2 Hz, 6H, CH3) ppm. 13C{ H} NMR
1
◦
(CDCl3, 20 C): d 152.0 (C N), 77.2 (CHMe2), 32.3 (C6), 27.7
(C2), 26.7/25.9/25.6 (C3–5), 24.3 (CH3) ppm. IR (CH2Cl2, cm-1):
n 2936 (s), 2859 (s), 1683 (w), 1651 (w), 1608 (w), 1451 (m), 1372
(m), 1332 (w), 1123 (m), 1089 (w), 999 (m), 968 (m), 934 (m), 884
(m), 854 (w), 558 (s).
13C{ H} NMR (CDCl3, 20 ◦C): d 147.0 (C–N), 77.2 (CHMe2),
1
25.3/23.9 (CH(CH3)2), 22.0 (C2H), 18.0 (C3H) ppm. IR (CH2Cl2,
cm-1):n 2973 (s), 2919 (s), 1684 (w), 1645 (m), 1495 (m), 1438 (m),
1378 (s), 1367 (m), 1344 (m), 1159 (m), 1128 (m), 1082 (s), 970 (s),
947 (vs), 846 (w), 814 (w), 609 (m), 590 (m).
Zr4O(ONC6H10)6(OBu)8 (4). An amount of 444 mg
(3.92 mmol) of cyclohexanone oxime was dissolved in 0.63 mL
of dichloromethane before 944 mg (1.97 mmol) of Zr(OBu)4 were
added. The reaction mixture was reduced to about three quarters
of its original volume by evaporation of the solvent in vacuo.
Storage of the yellow viscous liquid at 2 ◦C yielded crystals of
4 after three weeks upon slow diffusion of ambient moisture into
[Zr(ON C(Me)Et)3(OiPr)]2 (2). An amount of 160 mg
(1.80 mmol) of ethyl methyl ketoxime was added dropwise to a
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 1401–1406 | 1405
©

View Article Online
the reaction mixture through a perforated rubber seal. The crystals
were recrystallized from dichloromethane.
References
1 U. Schubert, Acc. Chem. Res., 2007, 40, 730; U. Schubert, J. Sol-Gel
Sci. Technol., 2003, 26, 47.
2 Review: U. Schubert, J. Mater. Chem., 2005, 15, 3701.
3 Review: R. Lichtenberger and U. Schubert, J. Mater. Chem., 2010, 20,
9287.
4 H. Fric, F. R. Kogler, M. Puchberger and U. Schubert, Z. Naturforsch
B, 2004, 59, 1241; H. Fric, M. Puchberger and U. Schubert, Eur. J.
Inorg. Chem., 2008, 1452.
5 X. Lei, M. Shang and T. P. Fehlner, Organometallics, 1997, 16, 5289.
6 A. Lorenz, G. Kickelbick and U. Schubert, Chem. Mater., 1997, 9,
2551.
7 Y. Chi, J.-W. Lan, W.-L. Ching, S.-M. Peng and G.-H. Lee, J. Chem.
Soc., Dalton Trans., 2000, 2923.
8 P. Toledano, M. In and C. Sanchez, C. R. Acad. Sci. Ser. II, 1990, 311,
1161.
9 C. Sanchez, M. In, P. Toledano and P. Griesmar, Mat. Res. Soc. Symp.
Proc., 1992, 271, 669.
10 B. Moraru, S. Gross, G. Kickelbick, G. Trimmel and U. Schubert,
Monatsh. Chem., 2001, 132, 993.
11 S. O. Baumann, M. Bendova, H. Fric, M. Puchberger, C. Visinescu and
U. Schubert, Eur. J. Inorg. Chem., 2009, 3333.
X-Ray structure analyses†
Single crystal X-ray diffraction measurements were performed
on a Siemens SMART and a Bruker-AXS KAPPA APEX II
diffractometer with CCD area detectors and a crystal-to-detector
distance of 5.5 cm using graphite-monochromated Mo-Ka radi-
ation (l = 71.073 pm). The data collection at 100 K in a stream
of cold nitrogen covered at least a hemisphere of the reciprocal
space by recording three or more sets of exposures, each of them
exhibiting a different U angle. The times for each exposure were 5
to 20 s, each of them covering 0.3◦ in w. The data were corrected
for polarization and Lorentz effects, and an empirical absorption
correction (SADABS) was applied. The structures were solved
with direct methods (SHELXS97) and refinement to convergence
was carried out with the full-matrix least-squares method based on
F2 (SHELXL97) with anisotropic structure parameters for all non-
hydrogen atoms. The hydrogen atoms were placed on calculated
positions and refined riding on their parent atoms.
12 M. Lomoschitz, S. O. Baumann, K. Zorn, S. Pabisch, H. Peterlik and
U. Schubert, J. Mater. Chem., 2010, 20, 5527; J. Yang, H. Peterlik, M.
Lomoschitz and U. Schubert, J. Non-Cryst. Solids, 2010, 356, 1217.
13 A. Singh and R. C. Mehrotra, Inorg. Chim. Acta, 1973, 7, 450.
14 B. S. Buyuktas and O. Aktas, Transition Met. Chem., 2006, 31, 56.
15 M. G. Davidson, A. L. Johnson, M. D. Jones, M. D. Lunn and M. F.
Mahon, Polyhedron, 2007, 26, 975.
A methyl group of one of the oximate ethyl groups of 2 is
disordered as well as two of the terminal butoxy groups in 4.
16 A. Le´austic, F. Babonneau and J. Livage, Chem. Mater., 1989, 1, 240.
17 J. Blanchard, S. Barboux-Doueff, J. Maquet and C. Sanchez, New J.
Chem., 1995, 19, 929; R. J. Errington, J. Ridland, W. Clegg, R. A.
Coxall and J. M. Sherwood, Polyhedron, 1998, 17, 659.
18 E. W. Bousquet, Organic Syntheses (Coll. Vol.), 1943, 2, 313.
Acknowledgements
This work was supported by the Austrian Fonds zur Fo¨rderung der
wissenschaftlichen Forschung (FWF) (Project P20750).
1406 | Dalton Trans., 2011, 40, 1401–1406
This journal is
The Royal Society of Chemistry 2011
©