Vanadate complexes bearing an imidazolidine-bridged bis(aryloxido) ligand: Synthesis and solid state and solution structure

Article abstract of DOI:10.1039/c2dt30153a

A new imidazolidine-bridged bis(aryloxido) ligand precursor (H ₂L) [H₂L = 2,2′-(imidazolidine-1,3- diylbis(methylene))bis(4-(1,1,3,3-tetramethylbutyl-2-yl)phenol)] was prepared in a relatively high yield (～60%) via a single-step Mannich condensation of 4-(1,1,3,3-tetramethylbutyl)phenol, ethylenediamine and paraformaldehyde at 2:1:3 molar ratio and characterized by chemical and physical techniques including X-ray crystallography. Reactions of H₂L with [VO(OEt) ₃] at 1:1 and 1:2 molar ratios in toluene afforded [V(L-κ³O,N,N,O)(O)(OEt)] (1) and [V₂(μ-L- κ⁴O,N,N,O)(μ-OEt)₂(O)₂(OEt) ₂] (2), respectively. Alcoholysis of 1 with EtOH enables elimination of one molecule of H₂L and the formation of 2. Compounds 1 and 2 were characterized by IR and NMR spectroscopy as well as ES-MS experiments. The definitive molecular structure of 2 was provided by a single-crystal analysis and revealed its dinuclear nature, featuring two octahedral vanadium centres bridged by both OEt groups and the L ligand. The ⁵¹V, ¹H and ¹³C NMR spectra as well as ES-MS showed that 2 does not stay intact in solution and undergoes dissociation to give 1 and [VO(OEt) ₃].

Full text of DOI:10.1039/c2dt30153a

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PAPER
Vanadate complexes bearing an imidazolidine-bridged bis(aryloxido) ligand:
synthesis and solid state and solution structure†
Ewa Kober, Tomasz Nerkowski, Zofia Janas* and Lucjan B. Jerzykiewicz
Received 20th January 2012, Accepted 8th March 2012
DOI: 10.1039/c2dt30153a
A new imidazolidine-bridged bis(aryloxido) ligand precursor (H2L) [H2L = 2,2′-(imidazolidine-1,3-
diylbis(methylene))bis(4-(1,1,3,3-tetramethylbutyl-2-yl)phenol)] was prepared in a relatively high yield
(∼60%) via a single-step Mannich condensation of 4-(1,1,3,3-tetramethylbutyl)phenol, ethylenediamine
and paraformaldehyde at 2 : 1 : 3 molar ratio and characterized by chemical and physical techniques
including X-ray crystallography. Reactions of H2L with [VO(OEt)3] at 1 : 1 and 1 : 2 molar ratios in
toluene afforded [V(L-κ3O,N,N,O)(O)(OEt)] (1) and [V2(μ-L-κ4O,N,N,O)(μ-OEt)2(O)2(OEt)2] (2),
respectively. Alcoholysis of 1 with EtOH enables elimination of one molecule of H2L and the formation
of 2. Compounds 1 and 2 were characterized by IR and NMR spectroscopy as well as ES-MS
experiments. The definitive molecular structure of 2 was provided by a single-crystal analysis and
revealed its dinuclear nature, featuring two octahedral vanadium centres bridged by both OEt groups and
the L ligand. The 51V, 1H and 13C NMR spectra as well as ES-MS showed that 2 does not stay intact in
solution and undergoes dissociation to give 1 and [VO(OEt)3].
dinuclear titanium,6 and mono- and dinuclear rare-earth metal
Introduction
complexes5b,7 have been synthesized and structurally character-
Vanadium complexes have received considerable attention from
the point of view of their different applications in catalysis or
biologically active systems.1,2 A new trend in vanadium chem-
istry concerns the incorporation of ligands that could create
vanadium systems useful either for catalytic processes or for
model compounds, mimicking the coordination sphere of the
active sites in vanadium-dependent enzymes. Among them, che-
lating, dianionic [ONNO]-type diaminebis(aryloxido) ligands
derived from di-Mannich bases, when associated with vanadium
complexes, have proven, upon activation with aluminium alkyls,
to be efficient catalysts for ethene-α-olefin copolymerization,
producing poly(ethene-co-1-hexene) and poly(ethene-co-norbor-
nene) with high α-olefin content.3 Besides, this type of
vanadium complex in the presence of H2O2 or organic hydroper-
oxides perfectly mimics the vanadium-dependent haloperoxidase
functionalities in selective sulfoxidation.3a,4
The modification of di-Mannich bases by including an
additional single hydrocarbon bridge between the two N-donors
leads to the creation of stable and rigid imidazolidine-bridged bis
(aryloxido) ligands. Such di-Mannich bases have only scarcely
been investigated and further, only a few single-crystal structures
have been reported to date.5 Consequently, published results on
the ability of the imidazolidine-bridged bis(aryloxido) ligands to
form complexes are limited. Up to date, tetranuclear sodium,5b
ized. However, there are no reports in the literature concerning
vanadium chemistry of the imidazolidine-bridged bis(aryloxido)
ligands. Since for many years our interest has laid strongly in
vanadium chemistry with various supporting ligand environ-
ments [aryloxide, thiolate, thiobis(aryloxide)],2e,8 this has
prompted us to extend our studies to the vanadium complexes
with (ONNO)-type ligands. In the present paper, we report
the synthesis, structure and spectroscopic characterization of
both the 2,2′-(imidazolidine-1,3-diylbis(methylene))bis(4-(1,1,3,
3-tetramethylbutyl-2yl)phenolate) ligand precursor H2L and its
oxovanadium(V) complexes.
Results and discussion
The synthesis of H2L was based on a single-step Mannich con-
densation between ethylenediamine, paraformaldehyde and 4-
(1,1,3,3-tetramethylbutyl)phenol in a 1 : 3 : 2 molar ratio accord-
ing to a previously published procedure with the essential
modifications (Scheme 1).5b
The product of this reaction strongly depends on the stoichio-
metry, used solvent and temperature. When the reaction proceeds
by refluxing of the corresponding reagents in methanol and with
an excess of CH2O, a mixture of H2L and a bridged benzoxazine
is formed. The same preparative problems have been reported by
Shen and coworkers,5b who tried to obtain 1,4-bis(2-hydroxy-
3,5-di-tert-butyl-benzyl)-imidazolidine) using the procedure
described by Kol and coworkers.9 Finally, H2L was isolated as
the major colourless product (∼60%) when the reaction pro-
ceeded in CH3CN or EtOH under reflux at a controlled tempera-
ture (351 K). The compound was fully characterized by
Faculty of Chemistry, University of Wrocław, 14 F. Joliot-Curie Street,
50-383 Wrocław, Poland. E-mail: zofia.janas@chem.uni.wroc.pl; Fax:
+48 71 3282348; Tel: +48 71 3757480
†CCDC 855050 for H2L. For crystallographic data in CIF or other elec-
tronic format see 10.1039/c2dt30153a
5188 | Dalton Trans., 2012, 41, 5188–5192
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Scheme 1
Evaporation of volatiles under reduced pressure yielded the
chemically pure product of the corresponding oxo–ethoxo
complex [V(L-κ3O,N,N,O)(O)(OEt)] (1) (Scheme 1). Compound
1 is very soluble in common organic solvents, except CH3CN,
but attempts to obtain it in crystalline form suitable for the
crystal structure determination unfortunately failed. The structure
1
of 1 was confirmed on the basis of H, 13C and 51V NMR spec-
troscopy and elemental analyses, as well as ES-MS. The 51V
NMR spectrum of 1 in C6D6 shows only one signal at
−485 ppm – the range typical for vanadium complexes with an
O, N donor set (Fig. 2).2b,c
In the 1H NMR spectrum the methylene protons of both
ArCH2N units are inequivalent and give rise to two doublets at
2
4.60 and 2.46 ppm, with a J coupling constant of 12.2 Hz, and
one broad singlet at 3.80 ppm, which compares well to the
singlet in the free ligand (3.89 ppm). These suggest that one of
the ArCH2N units has a rigid configuration in solution while the
nitrogen atom of the other one does not participate in coordi-
nation to the vanadium center. Similarly, the methylene reson-
ances of the bridging imidazolidine unit display three resonances
at 4.53, 4.50 and 1.78 ppm for the NCH2CH2N unit and two
doublets with a 2J coupling constant of 4.4 Hz at 3.45 and
1.98 ppm for the NCH2N group (3.54 ppm in free ligand). Also,
two sets of resonances for the protons of the Ar groups are
observed in the NMR spectrum of 1, confirming the coordination
mode of the ligand shown in Scheme 1. Variable-temperature
NMR studies on this system did not show any significant differ-
ences (in toluene-d8, from 213 to 313 K) suggesting that only
one species exists in solution within the temperature range
studied. These results and the mass spectrum with m/z: 619.4
corresponding to the {[VOL(OEt)]+H}+ species allowed us to
propose the mononuclear nature of 1 in solution with the five-
coordinate vanadium center. However, the dimeric structure of 1
in the solid state is not excluded, taking into consideration that
Fig. 1 Molecular structure of H2L with thermal ellipsoids drawn at the
50% probability level. Selected parameters (bonds, Å; angles, °): N1–C1
1.484(2), N1–C2 1.470(2), N1–C4 1.474(2), N2–C1 1.473(2), N2–C3
1.472(2), N2–C19 1.471(2), O1–H1⋯N1 2.679(2), O2–H2⋯N2 2.718
(2), O1–H1⋯N1 153(2), O2–H2⋯N2 149(2).
1
elemental analysis, NMR, IR and ES-MS. The IR and H NMR
spectra showed a broad absorption at 2910 cm−1 and a broad
singlet at 10.22 ppm, respectively, suggesting the presence of
intramolecular hydrogen OH⋯N bonds. In order to confirm
these structural characteristics an X-ray crystallographic analysis
was performed. The molecular structure of H2L is shown in
Fig. 1 and hydrogen bond lengths are given in the caption. The
structure revealed evidence for an intramolecular hydrogen-bond
interaction between O1–H1⋯N1 [2.679(2) Å, 153(2)°] and
O2–H2⋯N2 [2.718(2) Å, 149(2)°], which, at least in part, may
contribute to the arrangement of two phenol moieties in an
extended transoidal manner. The five membered imidazolidine
ring adopts an envelope conformation with C(1) lying 0.5 Å out
of the plane defined by N(1), C(2), C(3), and N(2).
The reaction of the ligand precursor H2L with one molar
equivalent of [VO(OEt)3] in toluene gave a pink-red solution.
the
2,2′-{(hexahydro-1H-benzo[d]imidazole-1,3(2H)-diyl)bis-
(methylene)}phenol (H2L) forms the dinuclear titanium complex
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Fig. 3 Molecular
structure
of
[V2(μ-L-κ4O,N,N,O)
(O)2(μ-OEt)2(OEt)2] (2) with thermal ellipsoids drawn at the 50% prob-
ability level. Selected parameters (bonds, Å; angles, °): V1–O3 1.597
(2), V1–O8 1.808(2), V1–O1 1.842(3), V1–O5 1.989(3), V1–O6 2.008
(2), V1–N1 2.472(3), V2–O4 1.595(2), V2–O7 1.800(3), V2–O2 1.851
(2), V2–O5 2.003(2), V2–O6 2.009(3), V2–N2 2.457(3), O3–V1–O8
98.89(11), O8–V1–O1 101.20(11), O3–V1–O5 99.58(11), O5–V1–O6
73.62(9), O3–V1–N1 179.34(11), O1–V1–N1 83.87(9), O4–V2–O7
99.17(12), O7–V2–O2 100.11(11), O5–V2–O6 73.32(9), O4–V2–N2
178.96(11), O2–V2–N2 84.32(9), O6–V2–N2 82.22(9).
Fig. 2 300 MHz 51V NMR spectra of 1 (a) and 2 (b) in C6D6.
[Ti2(μ-L-κ4O,N,N,O)(OPr)4], containing the five-coordinate
metal centers, which is unstable in solution.6
When compound 1 was dissolved in EtOH and allowed to
stand at room temperature for one month a mixture of dark-
violet and colorless crystals, identified as a new vanadate com-
pound [V2(μ-L-κ4O,N,N,O)(μ-OEt)2(O)2(OEt)2] (2) and the
ligand precursor H2L, respectively, were obtained (Scheme 1).
This result indicates that compound 1 is not stable in EtOH and
undergoes nucleophilic substitution resulting in the elimination
of one molecule of H2L. The analytically pure 2 was obtained
with a relatively high yield (∼60%) in a direct reaction of
[VO(OEt)3] and H2L at a stoichiometric ratio in n-hexane.
Single crystals of 2 suitable for single-crystal X-ray crystallogra-
phy were grown from saturated solution in EtOH at room temp-
erature. An ORTEP presentation of the structure and selected
bond lengths and angles are presented in Fig. 3.
The structure reveals a dinuclear species of the formula
[V2(μ-L-κ4O,N,N,O)(μ-OEt)2(O)2(OEt)2], where two vanadium
centres are bridged by a single chelating ligand and two OEt
groups. Each vanadium centre is bound to one aryloxide oxygen
and one nitrogen of the L ligand and two μ-O atoms of OEt
groups. The rest of the coordination sphere is occupied by one
oxo and one OEt terminal group, resulting in a distorted octa-
hedral geometry around each vanadium centre. It is worthy to
underline that the –V–O–V–O– array is almost planar with a
V(1)–O(6)–V(2)–O(5) torsion angle of 1.65(2)° [maximal devi-
ation of oxygen atoms up to 0.02(1)]. A similar structural feature
was observed for [Ti2(μ-L-κ4O,N,N,O)(μ-OiPr)2(OiPr)4] [H2L =
1,4-bis(2-hydroxy-3,5-di-tert-butyl-benzyl)-imidazolidine] (torsion
angle of 0.6°).6 The V–O bond distances, either oxo or aryloxo,
as well as alkoxo, are in the normal range for such bonds.3b,4,10
However, since there are no examples of vanadium complexes
with an imidazolidine-bridged bis(aryloxido) ligand, we can
only notice that the V–N bond lengths of av. 2.467 Å are – as
expected – considerably longer than those found for the tripodal
and linear diaminebis(aryloxido)vanadate(V) complexes (2.213–
2.400 Å).3b,4,11
To our knowledge, complex 2 is the first crystallographically
characterized example of a vanadium compound bearing an imi-
dazolidine-bridged bis(aryloxido) ligand.
Interestingly, attempts to substitute of the terminal OEt groups
bound to vanadium centres in 2 by a second dianionic L ligand,
even when an excess of H2L was used and the reaction was
carried out at a higher temperature, failed. Similar behavior was
demonstrated for [Ti2(μ-L-κ4O,N,N,O)(μ-OiPr)2(OiPr)4] and elu-
t
cidated as a result of the large Bu groups in an imidazolidine-
bridged bis(aryloxido) ligand, which precluded binding of a
second tetradentate ligand.6 However, the lack of substituents at
ortho positions in our L ligand makes this explanation not con-
vincing. It seems most likely that it is not steric factors on the
imidazolidine-bridged-bis(aryloxido) ligands but mainly satur-
ation of the coordination sphere around the small vanadium(V)
centers that prevents addition of a second rigid L ligand.
The 51V NMR spectrum of 2 in C6D6 exhibits two signals,
one at −485 ppm and the second at −602 ppm, which compare
well with those obtained in the same solvents for 1 and
1
[VO(OEt)3] (Fig. 2). Also, the H NMR experiment evidently
confirms the presence of the analogous sets of resonances as
those detected for 1 and for [VO(OEt)3] (δ 4.94 and 1.39 ppm).
These studies suggest that the structure of 2 does not stay
intact in solution and undergoes dissociation to produce 1 and
[VO(OEt)3] (Scheme 1).
Conclusions
New imidazolidine-bridged bis(aryloxido) ligand precursor H2L,
H2L = 2,2′-(imidazolidine-1,3-diylbis(methylene)bis(4-(1,1,3,3-
tetramethylbutyl-2-yl)phenol), has been prepared in a relatively
5190 | Dalton Trans., 2012, 41, 5188–5192
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high yield and structurally characterized. Reaction of H2L with
[VO(OEt)3], depending on the stoichiometry, resulted in the for-
mation of the dinuclear mixed-ligand complexes [V(L-κ3O,N,N,
O)(O)(OEt)] (1) and [V2(μ-L-κ4O,N,N,O)(μ-OEt)2(O)2(OEt)2]
(2), the structural features of which have been determined by
NMR spectra in solution and a single-crystal X-ray diffraction
study in the solid state for 2. These vanadate complexes rep-
resent the first examples of imidazolidine-bridged bis(aryloxido)
vanadium compounds. The structure of 2 reveals that in the solid
state a single chelating ligand bridges the two octahedral
vanadium centres, providing one oxygen and one nitrogen to
each metal centre, which are additionally linked by two OEt
CH2C(CH3)3], 33.1 [ArC(CH3)2CH2C(CH3)3], 32.6 [ArC(CH3)2
CH2C(CH3)3], 32.0 [ArC(CH3)2CH2C(CH3)3]. ES-MS: m/z:
509.4 [H2L + H]+. IR (Nujol mulls, cm−1): ν(O–H), 2910 (br).
Crystals suitable for the crystal structure determination were
obtained via recrystallization of the crude product from a
mixture of EtOH–MeOH (1 : 1).
Preparation of [V(μ-L-κ3O,N,N,O)(O)(OEt)] (1)
To a colorless suspension of H2L (1.43 g, 2.81 mmol) in toluene
(30 cm3) was added [VO(OEt)3] (0.5 cm3, 2.81 mmol) and the
mixture was stirred at room temperature for 2 h. Then, the pink-
red solution was evaporated to dryness to give a dark-red solid
of 1 (1.41 g, 81.6%). Anal. calcd for C35H55N2O4V: C, 67.92;
1
groups. The 51V, H and 13C NMR spectra, as well as ES-MS,
showed that compound 2 does not stay intact in solution and
undergoes dissociation to produce 1 and [VO(OEt)3].
1
H, 8.96; N, 4.53. Found: C, 67.87; H, 8.95; N, 4.51. H NMR
3
4
The presented results indicate that the imidazolidine-bridged
bis(aryloxido) L ligand might not have significant potential for
the design and synthesis of the vanadate well defined single-site
catalysts for homogeneous olefin polymerization, particularly in
the case of 1. However, the application of 1 and 2 as hetero-
geneous catalytic systems is not excluded and is being tested in
our laboratory, together with their potential in the oxidation of
organic materials with peroxides.
(600 MHz, C6D6, 298 K): δ 7.20 (dd, 4H, J = 8.7 Hz, J = 2.3
3
4
Hz, ArH), 7.17 (dd, 4H, J = 8.7 Hz, J = 2.3 Hz, ArH), 7.04
(dd, 4H, J = 8.7 Hz, J = 2.3 Hz, ArH), 7.02 (d, 4H, J = 2.3
Hz, ArH), 6.96 (d, 4H, J = 2.3 Hz, ArH), 6.77 (d, 4H, J = 2.3
Hz, ArH), 6.64 (d, 2H, J = 8.2 Hz, ArH), 6.55 (d, 2H, J = 8.2
Hz, ArH), 5.90 (q, 4H, J = 6.9 Hz, OCH2CH3), 5.63 (q, 4H, J
= 6.6 Hz, OCH2CH3), 4.60 (d, J = 12.2 Hz, 2H, NCH2Ar),
3
4
4
4
4
3
3
3
3
2
4.53 [d, J = 6.3 Hz, NCH2CH2N], 4.50 [m, 4H, NCH2CH2N],
2
3.80 (br, s, 2H, NCH2Ar), 3.45 [d, J = 4.4 Hz, 1H, N(CH2)N],
2
2
2.46 (d, J = 12.2 Hz, 2H, NCH2Ar), 1.98 [d, J = 4.5 Hz, 1H,
Experimental
2
N(CH2)N], 1.78 (d, J = 6.4 Hz, 1H, NCH2CH2N), 1.65, 1.57
All operations were carried out under a dry dinitrogen atmos-
phere, using standard Schlenk techniques. All the solvents were
distilled under dinitrogen from the appropriate drying agents
prior to use. Ethylenediamine, paraformaldehyde, 4-(1,1,3,3-
tetramethylbutyl)phenol and [VO(OEt)3] were obtained from the
Aldrich Chemical Co. and used without further purification
unless stated otherwise. Infrared spectra were recorded on a
Perkin-Elmer 180 spectrophotometer in Nujol mulls. NMR
spectra were performed on Bruker ARX 300 and Bruker Avance
III 600 spectrometers. The electrospray mass spectra (ES-MS)
were recorded on a Bruker MicrOTOF-Q mass spectrograph.
Microanalyses were conducted with a ASA-1 (GDR, Karl-Zeiss-
Jena) instrument (in-house).
[s, 2H, ArC(CH3)2CH2C(CH3)3], 1.37 [t, 3H, 3J = 6.8 Hz,
OCH2CH3 overlap with ArC(CH3)2CH2C(CH3)3], 1.30 [s, 12H,
ArC(CH3)2CH2C(CH3)3], 1.27 [s, 12H, ArC(CH3)2CH2C-
3
(CH3)3], 0.80 [t, 3H, J = 6.8 Hz, OCH2CH3 overlap with ArC
(CH3)2CH2C(CH3)3], 0.67 [s, 9H, ArC(CH3)2CH2C(CH3)3]. 13
C
NMR (600 MHz, C6D6, 298 K): δ 163.5, 163.3, 143.6, 143.5,
138.6, 138.4, 129.7, 129.1, 126.9, 126.3, 117.2, 117.0 (C6H3),
83.9 (OCH2CH3), 76.2, (NCH2N), 75.4 (NCH2CH2N), 70.5
(NCH2CH2N), 60.7 (NCH2N), 58.3, 58.1 [ArC(CH3)2CH2C-
(CH3)3], 54.0 (ArCH2N), 38.8, 38.7 [ArC(CH3)2CH2C(CH3)3],
33.1, 33.0 [ArC(CH3)2CH2C(CH3)3], 32.7 32.6 [ArC-
(CH3)2CH2C(CH3)3], 32.4, 32.0 [ArC(CH3)2CH2C(CH3)3], 20.1
(OCH2CH3). 51V NMR (300 MHz, C6D6, 298 K) δ −485.
ES-MS: m/z: 619.4 {[VOL(OEt)]+H}+. IR (Nujol mulls, cm−1):
ν(VvO), 964 (s, shr).
Preparation of H2L
A
mixture of 4-(1,1,3,3-tetramethylbutyl)phenol (10 g,
Preparation of [V2(μ-L-κ4O,N,N,O)(O)2(μ-OEt)2(OEt)2] (2)
48.5 mmol), paraformaldehyde (2.19 g, 72.8 mmol) and
ethylenediamine (1.6 cm3, 24.2 mmol) in CH3CN or EtOH
(100 cm3) was stirred under reflux for one day at 351 K. A white
precipitate formed was filtered, washed with ice-cold CH3CN or
EtOH (3 × 20 cm3) and dried in vacuo to yield a fine white
powder (7.26 g, 59.0%). Anal. calcd for C33H52N2O2: C, 77.90;
H, 10.30; N, 5.51. Found: C, 77.77; H, 10.12; N, 5.40. 1H NMR
(600 MHz, CDCl3, 298 K): δ 10.10 (br s, 2H, ArOH), 7.16 (dd,
Method 1: The synthesis of compound 2 was carried out using a
similar preparation as for 1 starting from H2L (2.87 g,
5.63 mmol) and [VO(OEt)3] (2 cm3, 11.27 mmol) in toluene to
give a dark-violet solid (2.85 g, 61.7%). Anal. calcd for
C41H70N2O8V2: C, 59.97; H, 8.60; N, 3.41. Found: C, 59.83; H,
1
8.58; N, 3.40. H NMR (600 MHz, C6D6, 298 K): δ 7.20 (dd,
3
4
3
4H, J = 8.7 Hz, J = 2.3 Hz, ArH), 7.17 (dd, 4H, J = 8.7 Hz,
3
4
4
2H, J = 8.4 Hz, J = 2.3 Hz, ArH), 6.95 (d, 2H, J = 2.3 Hz,
4J = 2.3 Hz, ArH), 7.04 (dd, 4H, 3J = 8.7 Hz, 4J = 2.3 Hz, ArH),
7.02 (d, 4H, J = 2.3 Hz, ArH), 6.96 (d, 4H, J = 2.3 Hz, ArH),
3
4
4
ArH), 6.76 (d, 2H, J = 8.4 Hz, ArH), 3.89 (s, 4H, NCH2Ar),
4
3
3.54 [s, 2H, N(CH2)N], 2.95 [s, 4H, N(CH2CH2)N], 1.65 [s, 4H,
ArC(CH3)2CH2C(CH3)3], 1.32 [s, 12H, ArC(CH3)2CH2C
(CH3)3], 0.68 (s, 18H, ArC(CH3)2CH2C(CH3)3]. 13C NMR
(600 MHz, CDCl3, 298 K): δ 156.7, 140.9, 128.9, 127.7, 126.7,
121.7, 116.8 (C6H3), 74.8 (NCH2N), 59.2 (ArCH2N), 57.9 [ArC
(CH3)2CH2C(CH3)3], 51.9 (NCH2CH2N), 38.6 [ArC(CH3)2-
6.77 (d, 4H, J = 2.3 Hz, ArH), 6.64 (d, 2H, J = 8.2 Hz, ArH),
6.55 (d, 2H, 3J = 8.2 Hz, ArH), 5.90 (q, 4H, 3J = 6.9 Hz,
3
OCH2CH3), 5.63 (q, 4H, J = 6.6 Hz, OCH2CH3), 4.94 (q, 4H,
3J = 6.6 Hz, OCH2CH3, [VO(OEt)3]), 4.60 (d, 2J = 12.2 Hz, 2H,
NCH2Ar), 4.53 [d, J = 6.3 Hz, NCH2CH2N)], 4.50 (m, 4H,
2
NCH2CH2N), 3.80 (br, s, 2H, NCH2Ar), 3.45 [d, J = 4.4 Hz,
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1H, N(CH2)N], 2.46 (d, 2J = 12.2 Hz, 2H, NCH2Ar), 1.98 [d, 2J
= 4.5 Hz, 1H, N(CH2)N], 1.78 (d, 2J = 6.4 Hz, 1H,
NCH2CH2N), 1.65, 1.57 [s, 2H, ArC(CH3)2CH2C(CH3)3], 1.39
Table 1 Crystallographic data for H2L and 2
Compound
H2L
2
3
3
(t, 3H, J = 6.8 Hz, OCH2CH3, [VO(OEt)3]), 1.37 [t, 3H, J =
6.8 Hz, OCH2CH3 overlap with ArC(CH3)2CH2C(CH3)3], 1.30
[s, 12H, ArC(CH3)2CH2C(CH3)3], 1.27 [s, 12H, ArC-
(CH3)2CH2C(CH3)3], 0.80 [t, 3H, 3J = 6.8 Hz, OCH2CH3
overlap with ArC(CH3)2CH2C(CH3)3], 0.67 [s, 9H, ArC-
(CH3)2CH2C(CH3)3]. 13C NMR (600 MHz, C6D6, 298 K): δ
163.5, 163.3, 143.6, 143.5, 138.6, 138.4, 129.7, 129.1, 126.9,
126.3, 117.2, 117.0 (C6H3), 83.9 (OCH2CH3), 82.0 (OCH2CH3)
[VO(OEt)3]) 76.2, (NCH2N), 75.4 (NCH2CH2N), 70.5
(NCH2CH2N), 60.7 (NCH2N), 58.3 [ArC(CH3)2CH2C(CH3)3],
58.1 [ArC(CH3)2CH2C(CH3)3], 54.0 (ArCH2N), 38.8, 38.7
[ArC(CH3)2CH2C(CH3)3], 33.1, 33.0 [ArC(CH3)2CH2C(CH3)3],
32.7, 32.6 [ArC(CH3)2CH2C(CH3)3], 32.4, 32.0 [ArC-
(CH3)2CH2C(CH3)3], 20.1 (OCH2CH3), 18.8 (OCH2CH3, [VO-
(OEt)3]). 51V NMR (300 MHz, C6D6, 298 K) δ −485, −602.
ES-MS: m/z: 619.4 {[VOL(OEt)]+H}+. IR (Nujol mulls, cm−1):
ν(VvO), 965 (s, shr).
Formula
Fw
Crystal system
Space group
a (Å)
b (Å)
c (Å)
C
33H52N2O2
C41H70N2O8V2
820.71
Monoclinic
C2/c
26.977(6)
15.717(4)
23.165(5)
90.00
115.54(5)
90.00
8862(4)
8
1.230
0.21 × 0.11 × 0.05
0.47
2 to 27
48 380
7834
0.093
3912
0.0444, 0.0973
0.0905, 0.1190
0.995
508.77
Triclinic
P1
ˉ
6.492(3)
11.653(5)
22.139(9)
98.79(5)
96.86(5)
93.90(5)
1637(1)
2
α (°)
β (°)
γ (°)
V (Å3)
Z
Dc (Mg m−3
)
1.032
0.28 × 0.18 × 0.15
0.06
Crystal size (mm3)
μ (mm−1
θ (°)
)
3 to 37
Reflections collected
Unique reflections
R(int)
18 377
7505
0.043
4722
Parameters
Final R1, wR2 [I > σ(I)]
Final R1, wR2 (all data)
Goodness-of-fit (S)
0.0635, 0.1362
0.1199, 0.1488
1.068
Crystals suitable for the crystal structure determination were
grown from saturated solution in EtOH at room temperature for
several weeks.
Method 2. Compound 1 was dissolved in EtOH and left for
crystallization at room temperature. After one month a mixture
of dark-violet and colorless crystals of 2 and H2L, respectively,
settled down. These were filtered off, washed with cold EtOH
and dried in vacuo. Crystals of both compounds were separated
by hand for identification.
Notes and references
1 For a recent review on vanadium used in polymerization catalysis see:
(a) C. Redshaw, Dalton Trans., 2010, 39, 5595; (b) S. Gambarotta,
Coord. Chem. Rev., 2003, 237, 147; (c) H. Hagen, J. Boersma and G. van
Koten, Chem. Soc. Rev., 2002, 31, 357.
2 For vanadium complexes in bioinorganic chemistry see for example:
(a) V. Conte and B. Floris, Dalton Trans., 2011, 40, 1419; (b) D. Rehder,
Bioinorganic Vanadium Chemistry, John Wiley & Sons, Ltd., New York,
2008; (c) A. S. Tracey, G. r. Willsky and E. S. Takeuchi, Chemistry, Bio-
chemistry, Pharmacology and Practical Applications, CRC Press, Taylor
& Francis Group, Boca Raton, FL, 2007; (d) D. C. Crans, J. J. Smee,
E. Gaidamauskas and L. Yang, Chem. Rev., 2004, 104, 849; (e) Z. Janas
and P. Sobota, Coord. Chem. Rev., 2005, 249, 2144; (f) C. Bolm, Coord.
Chem. Rev., 2003, 237, 245.
3 (a) O. Wichmann, R. Sillanpää and A. Lehtonen, Coord. Chem. Rev.,
2012, 256, 371; (b) F. Wolff, C. Lorber, R. Choukroun and
B. Donnadieu, Inorg. Chem., 2003, 27, 7839; (c) F. Wolff, C. Lorber,
R. Choukroun and B. Donnadieu, Eur. J. Inorg. Chem., 2004, 2861;
(d) C. Lorber, F. Wolff, R. Choukroun and L. Vendier, Eur. J. Inorg.
Chem., 2005, 2850; (e) C. Lorber, Pure Appl. Chem., 2009, 81, 1205.
4 S. Barroso, P. Adâo, F. Madeira, M. Teresa Duarte, Joâo Costa Pessoa and
Ana M. Martins, Inorg. Chem., 2010, 49, 7452.
5 (a) H.-T. Xia, Y.-F. Liu, S.-P. Yang and D.-Q. Wang, Acta Crystallogr.,
Sect. E: Struct. Rep. Online, 2007, 63, o680; (b) X. Xu, Y. Yao, Y. Zhang
and Q. Shen, Inorg. Chem., 2007, 46, 3743; (c) A. Rivera, D. Quiroga,
J. Ríos-Motta, J. Carda and G. Peris, J. Chem. Crystallogr., 2009, 39, 827;
(d) A. Rivera, D. Quiroga, J. Ríos-Motta, M. Dušek and K. Fejfarová, Acta
Crystallogr., Sect. E: Struct. Rep. Online, 2010, 66, o2643.
6 C. M. Manna, M. Shavit and E. Y. Tshuva, J. Organomet. Chem., 2008,
693, 3947.
X-Ray crystallography
Data for H2L were collected on an Xcalibur PX diffractometer
with CCD Onyx and for 2 on a KM4 diffractometer with a CCD
sapphire camera and Mo Kα radiation (λ = 0.710 73 Å). Data
reduction and analysis were carried out with the Kuma Diffrac-
tion programs.12 The structures were solved by direct methods13
and refined by the full-matrix least-squares method on all F2
data using the SHELXTL software.13 Carbon bonded hydrogen
atoms were included in calculated positions and refined in the
riding mode using SHELXTL default parameters. All non-
hydrogen atoms were refined with anisotropic displacement par-
ameters. In both structures the 1,1,3,3-tetramethylbutyl substitu-
ents at the phenyl groups were constrained as a rigid group
owing to their disorder as seen in the difference map. A correc-
tion for diffuse effects due to the inclusion of disordered solvent
molecules in the crystal structures was made for H2L and 2
using the SQUEEZE option of PLATON.14 The total potential
solvent volume per unit cell was calculated to be 141.4 Å3
(8.6% of the cell volume) for H2L and 758.3 Å3 (8.6% of the
cell volume) for 2. Table 1 lists the key crystallographic par-
ameters for H2L and 2.
7 Z. Zhang, X. Xu, W. Li, Y. Yao, Y. Zhang, Q. Shen and Y. Luo, Inorg.
Chem., 2009, 48, 5715.
8 Z. Janas, D. Wiśniewska, L. B. Jerzykiewicz, P. Sobota, K. Drabent and
K. Szczegot, Dalton Trans., 2007, 2065.
9 E. Y. Tshuva, N. Gendeziuk and M. Kol, Tetrahedron Lett., 2001, 42,
6405.
10 W. A. Nugent and J. M. Mayer, Metal-Ligand Multiple Bonds, Wiley-
Interscience, New York, 1988.
11 Z. Janas, E. Kober, T. Nerkowski and L. B. Jerzykiewicz, – in
preparation.
Acknowledgements
12 Oxford Diffraction, CrysAlis CCD and CrysAlis RED, versions 1.171.33,
Oxford Diffraction Poland, Wroclaw, Poland, 2009.
13 G. M. Sheldrick, Acta Crystallogr., Sect. A, 2008, 64, 112.
14 A. L. Spek, J. Appl. Crystallogr., 2003, 36, 7.
The authors thank the State Committee for Scientific Research
(Poland) for financial support of this work (grant no. N N204
028238).
5192 | Dalton Trans., 2012, 41, 5188–5192
This journal is © The Royal Society of Chemistry 2012