New salan and salen vanadium complexes: Syntheses and application in sulfoxidation catalysis

Article abstract of DOI:10.1016/j.jorganchem.2018.06.011

New diamine bis-phenol compounds of salan- (HOPh'CHNH(CH₂)₂NHCHPh'OH, Ph’ = 2,4-(CMe₂Ph)C₆H₂, H₂L1) and salen-type (HOPh’’CHN(CHPh)₂NCHPh’’OH, Ph’’ = 2,4-^tBuC₆

Full text of DOI:10.1016/j.jorganchem.2018.06.011

Accepted Manuscript
New salan and salen vanadium complexes: Syntheses and application in
sulfoxidation catalysis
Minaxi S. Maru, Sónia Barroso, Pedro Adão, Luis G. Alves, Ana M. Martins
PII:
S0022-328X(18)30481-9
10.1016/j.jorganchem.2018.06.011
JOM 20470
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 20 April 2018
Revised Date: 1 June 2018
Accepted Date: 15 June 2018
Please cite this article as: M.S. Maru, Só. Barroso, P. Adão, L.G. Alves, A.M. Martins, New salan
and salen vanadium complexes: Syntheses and application in sulfoxidation catalysis, Journal of
Organometallic Chemistry (2018), doi: 10.1016/j.jorganchem.2018.06.011.
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ACCEPTED MANUSCRIPT
New Salan and Salen Vanadium Complexes: Syntheses
and Application in Sulfoxidation Catalysis
Minaxi S. Maru, Sónia Barroso, Pedro Adão, Luis G. Alves and Ana M. Martins*
Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001
Lisboa, Portugal
E-mail: ana.martins@tecnico.ulisboa.pt
Abstract
New diamine bis-phenol compounds of salan- (HOPh’CHNH(CH2)2NHCHPh’OH, Ph’ = 2,4-(CMe2Ph)C6H2, H2L1)
and salen-type (HOPh’’CHN(CHPh)2NCHPh’’OH, Ph’’
=
2,4-tBuC6H2, H2L2 and HOPh’’CHN(1,1’-2-
binaphthyl)NCHPh’’OH, Ph’’ = 2,4-tBuC6H2, H2L3), as well as their oxido vanadium derivatives are described.
VO(OiPr)3 was used as starting material for the preparation of [VO(OiPr)(L1)], 1, [VO(OiPr)(L2)], 3, and (µ-
O){[VO(OiPr)(µ-O)(L3)VO]}2, 5. An intramolecular redox process involving the reduction of V(V) to V(IV) converts
3 into [VO(L2)], 4. The reactions of 1 and 5 with Me3SiCl give [VOCl(L1)], 2, and [VOCl(L3)], 6, respectively. All
complexes were tested as catalysts for the sulfoxidation of thioanisole using H2O2 as oxidant. In general, the
compounds display high activity and selectivity, although salan-type complexes (1 and 2) perform better.
Comparison of complexes 5 and 6 shows the monomeric species is more active and selective. Well-defined
complexes, 5 and 6, display better catalytic performance than systems using 1:1.5 [VO(acac)2] and H2L3.
Introduction
Sulfoxides are an important class of compounds that may be obtained by catalytic oxidation of thioethers using
transition metal complexes as catalysts [1]. Among other early transition metals used, vanadium catalyzed
sulfoxidation reactions gained prominence, as vanadium is a cheap metal, present in biological systems, and
active when H2O2 is used as oxidant [2]. Despite the important contributions given to this research field, which
include the implementation of bio-inorganic methodologies as well as successful kinetic resolution processes [3],
the use of well-defined asymmetric sulfoxidation catalysts still presents several drawbacks [4]. The requirement
of laborious and expensive separation procedures and the use of chlorinated solvents, low temperature and
controlled addition of oxidants are some of the issues that need further development [4,5]. The implementation of
new catalytic systems and a better understanding of their reactivity, through the identification of the species
involved and the study of the reactions’ mechanisms, using either computational or experimental methods, is
thus an essential strategy to attain more efficient sulfoxidation systems.
As part of our research in transition metal catalyzed oxidation reactions [6], we focused on catalytic sulfoxidation
of thioethers and described tripodal diamine bis(phenolate) oxidovanadium(V) complexes that are very selective
(up to 98%) towards thioanisole sulfoxidation using H2O2 as oxidant, without requiring the use of chlorinated
solvents [7,8].
Aiming to evaluate the properties of new vanadium complexes in sulfoxidation of thioanisole, we report here the
synthesis of new salen- and salan-type vanadium complexes with different ligand frames as binaphthyl and
phenyl groups, along with bulky o-phenolate substituents.
Results and Discussion
Synthesis and characterization
The ligand precursors used in this work are depicted in Figure 1. H2L1 is a salan-type diamine bisphenol that was
prepared by a single step Mannich condensation reaction of 2,4-(CMe2Ph)2PhOH, formaldehyde and ethylene
1
diamine, adapting a literature procedure [9]. The H and 13C-{1H} NMR spectra of H2L1 are in agreement with a
Cs-symmetric species, displaying only two sets of resonances for the Me and for the Ar-CH groups, one singlet
for the ArCH2N groups and one singlet for the NCH2CH2N moiety. H2L2 and H2L3 are salen-type diimine
bisphenols that were synthesized through reactions of 3,5-di-tert-butyl-2-hydroxybenzaldehyde with the

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corresponding diamines, following reported procedures [10]. H2L3 was prepared from the racemic mixture of 1,1’-
bi(2-naphthylamine), and H2L2 was prepared from meso-(R,S)-diphenylethylenediamine.
Figure 1. Ligand precursors used in this study
Crystals of H2L2 suitable for X-ray diffraction were obtained by slow evaporation of an EtOH solution. The
compound crystallizes in the monoclinic system, space group P21/c, with one half-molecule in the asymmetric
unit. The structure is stabilized by the formation of intramolecular hydrogen bonds between the OH groups of the
phenols and the N atoms of the diimine moieties. Such interactions display O(1)-H(1O)...N(1) bond lengths of
1.73(2) Å and define two 6-member heterocycles. The two phenyl rings linked to the two stereocenters of the
molecule are placed in an anti periplanar conformation. The overall distances and angles fit the usual values
reported in the literature for organic molecules [11].
Figure 2. ORTEP diagram of H2L2 using 30% probability level ellipsoids. Hydrogen bonds are represented by
dashed lines. Equivalent atoms (i) are generated using the symmetry transformation –x+1, -y, -z+2.
As shown in Scheme 1, treatment of VO(OiPr)3 with one equivalent of H2L1 in THF at room temperature afforded
[VO(OiPr)(L1)], 1, in 70% yield. The 1H and 13C-{1H} NMR spectra of 1 revealed the formation of a C1-symmetric
complex, displaying mutually-trans coordination of the phenolate rings to the metal. The ligand displays an
overall cis-α coordination mode that is probably determined by the bulkiness of the dimethylphenyl substituents
on the phenol groups [12]. As expected for an asymmetric species, the proton NMR spectrum of 1 displays 8
resonances for the Me groups of the CMe2Ph moiety, 2 doublets and 1 septet for methyl and methyne protons of
the isopropoxido ligand, 2 AX spin systems for the benzyl protons ArCH2N, 4 doublets for the aromatic protons of

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the phenol rings and several multiplets for the phenyl groups. The 51V NMR spectrum of 1 in C6D6 displays one
broad peak at δ -563 ppm, which is in agreement with the values reported for monomeric alkoxido
oxidovanadium complexes supported by other amine phenolate donor sets [7,13].
1
The reaction of 1 with excess of Me3SiCl in CH2Cl2 gave [VO(Cl)(L1)], 2, in 60% yield (Scheme 1). The H and
13C-{1H} NMR spectra of 2 are very similar to those of 1, in agreement with a C1-symmetric species. The 51V
NMR spectrum of 2 displays one broad peak at δ -413 ppm in C6D6, which is in accordance with the values
obtained for related complexes [7,12,13].
Scheme 1. Complexes synthesized
The reaction of VO(OiPr)3 with H2L2 also led to the formation of a vanadium(V) complex, [VO(L2)(OiPr)], 3, but,
together with this compound, a vanadium(IV) species, [VO(L2)], 4, was also formed (Scheme 1). The reduction of
V(V) to V(IV) is the result of a spontaneous intramolecular redox process that is accompanied by the oxidation of
the isopropoxido ligand to acetone [14]. It is known that the V(V)O(salen)+ species have a pronounced oxidative
character, as evidenced by the highly positive V(V)O(salen)+/V(IV)O(salen) and V(V)O(salen)+/V(III)(salen)+
redox couples [15].. Literature reports regarding the redox activity of isopropanol indicate that the onset of the
oxidation to acetone can occur at potentials as low as 0.2 V vs. RHE (reversible hydrogen electrode) [16].
Therefore, the spontaneous oxidation of the isopropoxido ligand by the V(V)O(salen) core is possible from an
electrochemical standpoint. Compound 3 and H2L2 where identified by NMR but 4, which is a d1 species, was
identified by single-crystal X-ray diffraction analysis of the crystals that grew in the bulk solution (see below). The
1H and 13C NMR spectra of 3 are consistent with its formulation as a C1 symmetry species and the 51V NMR
resonance comes up at -479.9 ppm. The ESI-MS spectrum in CH3CN shows a peak at m/z 709.70 (100%), that
is assigned to [VO(L2)]+.
Compound 4 was also independently synthesized in moderate yield by the reaction of VOCl2·2H2O with H2L2.
The first derivative of the EPR spectrum of 4, measured in DMF at 77 K, is shown in Figure 3. The spin
Hamiltonian parameters, gxy= 1.977, gz= 1.949, Axy= 55.3 × 10-4 cm-1, Az= 160.6 × 10-4 cm-1, were obtained by
simulation of the experimental spectrum. The value obtained for the z-component of the hyperfine coupling
constant, Az, is consistent with the equatorial donor atom set of two imines and two phenolate oxygens [17].

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Figure 3. First derivative of the X-band EPR spectra of frozen solutions of 4, measured at 77 K in DMF.
Compound 4 crystallizes in the triclinic system, P-1 space group, with two chemically identical but
crystallographically independent molecules. An ORTEP diagram of one molecule is presented in Figure 4 and
selected bond distances and angles are shown in Table 1. The coordination geometry of vanadium in 4 is
square-pyramidal, typical of salen-type vanadium(IV) complexes. The basal plane is defined by the two nitrogen
atoms and the two oxygen atoms of the salen ligand and the apical position is occupied with the oxido ligand.
The bond distances V=O (1.597(5) Å), V-Ophenolate (1.910(6) and 1.925(6) Å) and V-Nimine (2.036(7) and 2.052(8)
Å) are within the ranges reported for other oxidovanadium(IV) complexes anchored by salen-type ligands [18].
Table 1. Selected bond lengths (Å) and angles (deg.) for compounds 4 and 5.
4
5
Distances (Å)
V(1)-N(1)
V(1)-N(2)
V(1)-O(1)
V(1)-O(2)
V(1)-O(3)
V(1)-O(4)
V(2)-O(4)
V(2)-O(5)
V(2)-O(6)
V(2)-O(7A)
V1(1)-eq. pla
2.052(8)
2.325(7)
2.147(7)
1.846(5)
1.896(6)
1.601(5)
1.846(6)
1.725(6)
1.598(7)
1.766(2)
1.715(7)
0.298(3)
2.036(7)
1.910(6)
1.925(6)
1.597(5)
-
-
-
-
-
0.598(3)
Angles (°)
O(1)-V(1)-O(2)
O(1)-V(1)-O(3)
O(2)-V(1)-O(3)
O(4)-V(1)-O(1)
O(4)-V(1)-O(2)
O(3)-V(1)-O(4)
O(1)-V(1)-N(1)
O(2)-V(1)-N(1)
O(3)-V(1)-N(1)
O(4)-V(1)-N(1)
O(1)-V(1)-N(2)
O(2)-V(1)-N(2)
O(3)-V(1)-N(2)
O(4)-V(1)-N(2)
N(1)-V(1)-N(2)
O(5)-V(2)-O(7A)
O(5)-V(2)-O(4)
O(7)-V(2)-O(4)
O(5)-V(2)-O(6)
O(7A)-V(2)-O(6)
O(4)-V(2)-O(6)
V(2)-O(6)-V(2i)
θb
89.4(3)
95.5(2)
103.2(2)
95.3(2)
91.3(2)
160.3(2)
101.1(3)
82.8(2)
79.0(3)
172.2(3)
83.6(3)
161.5(2)
82.1(3)
95.3(2)
85.5(3)
78.7(2)
102.6(5)
109.7(3)
109.7(3)
107.6(4)
109.9(4)
112.1(3)
177.6(6)
120.0(3)
111.8(3)
107.0(3)
-
-
-
85.9(3)
148.5(2)
103.6(3)
-
139.8(3)
85.9(3)
107.6(3)
-
77.7(3)
-
-
-
-
-
-
-
162.2(4)

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Equivalent atoms (i) are generated using the symmetry transformation –x+1, y, -z+1/2.
a The equatorial plane is defined by atoms O1, O2, N1 and N2 in 4 and by O1, O2, O4 and N4 in 5. b θ is the dihedral angle
between the planes containing the phenolate rings.
The reaction of H2L3 with VO(OiPr)3 (Scheme 1) gives a mixture of several species. The analysis of 1D and 2D
NMR data revealed the presence of free ligand and several minor vanadium species containing isopropoxido
ligands. The major vanadium species is a rare tetranuclear vanadium(V) compound, (µ-O){[VO(OiPr)(µ-
O)(L3)VO]}2, 5, which was identified by single-crystal X-ray diffraction (Figure 5) and by NMR. The 1H and
13C{1H} NMR spectra of 5 are rather simple. In the (L3)V=O fragments the ligand is coordinated to the metal in
the cis-β binding mode [12], and the NMR spectra show C1 symmetry. The 1H NMR spectrum displays 4
resonances for the tert-butyl substituents of the phenolate moieties, 2 singlets (δ 7.78 and 7.69 ppm) assigned to
the N=CH protons, several singlets and multiplets in the aromatic region due to the phenolate and binaphthyl
moieties and 1 septet and two doublets (δ 4.41, 0.88 and 0.39 ppm, respectively) due to the OCHMe2 ligands.
The 51V NMR spectrum of 5 displays one small broad peak at δ -475 ppm assigned to [VO(L3)(OiPr)] and two
intense peaks at δ -636 and -652 assigned to µ-oxido vanadium dimers. These assignments take into account
the fact that replacing the chlorido ligand with more electronegative donors and increasing the steric bulk of the
OR ligand coordinated to the V(V)O core shifts the 51V signals upfield [19]. The values obtained are in agreement
with those found for other oxidovanadium complexes supported by amine phenolate ligands [7,13].
Figure 4. ORTEP diagram of 4 using 30% probability level ellipsoids. Hydrogen atoms are omitted for clarity.
Compound 5 crystallizes in the monoclinic system, C2/c space group, with half molecule of 5 and two co-
crystallized molecules of Et2O in the asymmetric unit. An ORTEP diagram of 5 is presented in Figure 5 and
selected bond distances and angles are listed in Table 1. This is the first structurally characterized vanadium
complex bearing a binaphthyl-based salen-type ligand. The coordination geometry around V1 is distorted
octahedral with the equatorial plane defined by atoms O1, O2 and N2 of the salen ligand and the bridging oxygen
atom O4, while the axial positions are occupied by the oxido ligand O3 and atom N3 of ligand L3. The
coordination geometry of V2 is tetrahedral, defined by two bridging oxygen atoms, one terminal oxido ligand, and
one oxygen atom of the isopropoxido ligand. Differently from other salen vanadium complexes, which display
trans-phenolate moieties, the binding mode of L3 in 5 is cis-β.
The V=O (1.601(5) Å) and V-Ophenolate (1.846(5) and 1.896(6) Å) bond distances are in agreement with the values
reported for other oxidovanadium(V) complexes with salen ligands [20] while the V-Nimine (2.325(7) and 2.147(7)
Å) bond distances are longer than those reported in other oxidovanadium(V) complexes (typical values range
from 2.054 to 2.114 Å) [21], possibly due to the cis-β binding mode of the ligand in 5. The long V1-N1 bond
distance, in comparison with V1-N2 (2.325(7) vs. 2.147(7) Å) is due to the trans effect of the oxido ligand O3. The
V-Obridging bond lengths are in accordance with values reported [18, 20].
The appearance of a small signal in the 51V NMR spectrum assigned to [VO(L3)(OiPr)] might be indicative that
similarly to [VO(L2)(OiPr)], the compound is spontaneously reduced to V(IV). However, it is surprising that in the
current experimental conditions, the final product is not the [VO(L3)] species, analogous to 4, but a compound
that may be described as a bridging oxido dimer of two divanadium moieties, namely (µ-O){[VO(OiPr)(µ-
O)(L3)VO]}2.

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Figure 5. ORTEP diagram of 5 using 30% probability level ellipsoids. Hydrogen atoms, atoms belonging to B fraction of
disordered isopropoxido ligand and tert-butyl substituents from phenolate groups are omitted for clarity. The inset shows the
tetranuclear vanadium(V) core. Equivalent atoms (i) are generated using the symmetry transformation –x+1, y, -z+1/2.
The reaction of H2L3 with VO(OiPr)3 in THF followed by addition of SiMe3Cl in CH2Cl2 led, upon recrystallization
from n-hexane, to the isolation of pure [VO(L3)Cl], 6, in 55% yield. The NMR spectra of 6 are in agreement with a
C1-symmetric species. The 1H NMR spectrum displays 4 resonances for the CH3 protons of the tert-butyl groups,
2 singlets at δ 8.07 and 8.06 ppm assigned to the N=CH protons and several multiplets in the range δ 7.81-8.06
ppm for the aromatic protons of the phenolate and binaphthyl moieties. The 51V NMR spectrum of 6 displays one
broad peak at δ -321 ppm in C6D6, which is in agreement with the values obtained for 1 and other chloride
oxidovanadium(V) complexes supported by amine phenolate ligands [7,13].
Catalytic Studies
The vanadium complexes prepared were evaluated for their catalytic potential in the sulfoxidation of thioanisole.
Control reactions were made to test for the lack of thioanisole oxidation in the absence of metal and confirm the
role of vanadium complexes as catalysts. The results are listed in Table 2.
Using a ratio of 100:1 between substrate and catalyst precursor, all complexes led to high substrate conversions
and product selectivity, although complexes [VO(X)(L1)], X = OiPr, 1, and X = Cl, 2, present the best
performances. Both compounds display the same catalytic features, which is not surprising considering that in
the presence of H2O2 they should originate identical active species. The comparison of the solvents showed that
in acetone the reactions are faster than in other solvents and, if the reaction is kept at 0 °C, the amounts of
sulfone are, in general, very low. It is worth noting that complexes 1 and 2 afforded nearly complete conversions
after 3 h at 0 °C. Comparatively, complex 6 exhibited a lower activity at 0 °C, with 85 % conversion after 3 h,
although over oxidation to sulfone was not observed. Complexes 4 and 5 required longer reaction times in order
to afford comparable conversions, although selectivities towards sulfoxide were lower. These results are in line
with those previously reported for tripodal diamine bis(phenolate) vanadium complexes and, as observed for
those systems, the reactions proceed without O2 release [7].
The comparison between complexes 5 and 6 points out that the latter leads to a faster and more selective
catalytic system. It is important to note that the inclusion of a binaphthyl moiety in the ancillary ligand frame of 6
led to 100% selectivity in sulfoxide. If, as expected, in the presence of H2O2 the V-O-V bridges of 5 are broken,
the fragments resulting from the V1 centres may originate a catalytic active species that is close to the one
formed from 6, which implies that the lower selectivity obtained with 5 is likely associated to the V2 centres.
Finally, it is clear that the in situ methodology (entries 11 and 12) affords comparable yields, but lower
selectivities than the pre-formed complex 6.

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Table 2. Catalytic data for sulfoxidation of thioanisolea
mol %
cat.
conv.
(%)
Entry
1b
Catalyst
Solvent
T/ºC
0
t (h)
sulfoxide (%)
93
sulfone (%)
6
1
(CH3)2CO
1
3
99
2c
3c
4c
1
1
1
CH3Cl3
EtOAc
EtOH
1
1
1
24
24
24
1
1
1
96
93
97
84
73
82
12
20
15
5b
2
(CH3)2CO
1
0
3
>99
95
5
6b
7b
4
4
5
5
6
(CH3)2CO
DCE
1
1
1
1
1
0
0
0
0
0
24
24
24
24
3
94
88
93
77
85
89
84
78
60
85
5
4
8b
(CH3)2CO
DCE
15
17
0
9b
10b
(CH3)2CO
11b
12b
VO(acac)2/H2L3
VO(acac)2/ H2L3
(CH3)2CO
DCE
1/1.5
1/1.5
0
0
24
97
97
87
87
10
10
24
a Thioanisole (1 mmol); 1.2 eq. oxidant H2O2 20% (w/v) aqueous solution, 4 mL solvent.
b Conversion and yields determined by HPLC.
c Conversion and yields determined by NMR.
Concusions
[VO(X)(L1)], X = OiPr, 1, and X = Cl, 2, are salan-type diamine bisphenolate V(V) complexes that display very
bulky dimethylphenyl substituents on the phenolate groups. Attempts to obtain pure [VO(OiPr)(L2)], 3, and
[VO(OiPr)(L3)], both displaying salen-type ligands, were hampered by spontaneous reduction to V(IV) via an
intramolecular redox process that is accompanied by the oxidation of the isopropoxido ligand to acetone.
Analysis of the literature reports concerning the redox activity of either V(V)O-(salen)X species and isopropanol
indicates that this spontaneous intramolecular process is feasible [15,16]. In the case of L2, the resulting V(IV)
complex is stable and displays a square-pyramidal geometry that is typical of vanadium(IV) oxido salen
complexes. A more complex process leads to the formation of 5. It may be speculated that transient formation of
[VO(OiPr)(L3)] is followed by reduction to V(IV) by a process similar to the formation of 4. However, this
compound reacts further with VO(OiPr)3 to originate the tetra-vanadium complex (µ-O){[VO(OiPr)(µ-O)(L3)VO]}2,
5. [VO(Cl)(L3)], 6, was obtained in more than 50% yield upon addition of Me3SiCl to the mixture resulting from
the reaction of H2L3 and VO(OiPr)3.
In general, all complexes catalyse the sulfoxidation of thioanisole, although well-defined monomeric complexes,
(1, 2 and 6), display the better performances considering either activity and selectivity. It is noteworthy that the
inclusion of the binaphthyl moiety in the ancillary ligand frame of 6 leads to 100% selectivity in sulfoxide.
The results also pointed out that the addition of salen-type ligand precursors to VO(OiPr)3, often used as
vanadium(V) starting material for the syntheses of oxido vanadium complexes, led to concomitant reduction to
V(IV). The latter may or not undergo subsequent reactions, leading to polynuclear vanadium complexes. These
react with H2O2 to give V(V) species that are sulfoxidation catalysts. The higher selectivity displayed by
monomeric precatalysts is likely associated to the presence of only one type of active species in solution.
Experimental Section
General
All reactions were carried out under inert atmosphere. Unless stated otherwise all reagents were purchased from
commercial suppliers (e. g. Aldrich, Acrös, Fluka) and used as received. Chlorotrimethylsilane (TMSCl) was

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distilled before use. THF, CH2Cl2 and n-hexane were dried by standard methods (sodium/benzophenone for
THF; calcium hydride for CH2Cl2 and n-hexane) and distilled prior to use. H2L3 was prepared following a
literature procedure [10]. NMR samples of air/moisture sensitive compounds were prepared in a glovebox under
inert atmosphere using NMR tubes equipped with J-Young stopcocks. C6D6 was dried over Na and distilled under
reduced pressure. 1D NMR (1H, 13C-{1H}, 13C-{1H} APT) and 2D NMR (COSY, NOESY, HSQC) spectra were
recorded on Bruker Advance II+ 300 or 400 MHz (UltraShield Magnet) spectrometers, at ambient temperature.
1H and 13C chemical shifts (δ) are expressed in ppm relative to Me4Si. EPR experiments were run in a Bruker
EMX EPR Spectrometer and calibrated using a DPPH (2,2-diphenyl-1-picrylhydrazyl) solution as internal
standard. The experimental spectra (1st derivative X-band EPR) were simulated with the computer program
developed by Rockenbauer and Korecz [22]. The analysis of the products obtained in catalytic reactions was
done by HPLC, using a Jasco system equipped with a Daicel Chiralpak IA column, a 870-UV Intelligent UV-Vis
detector, two 880-PU Intelligent HPLC Pumps, a 2-line degasser 880-51 and a Rheodyne 725i injector (5 µL).
The system uses Borwin software for data acquisition and analysis.
Synthesis of H2L1
Ethylene diamine (0.901 g, 15 mmol) and 37 % aqueous solution formaldehyde (3.2 mL, 43.5 mmol) were added
to a solution of 2,4-bis(2-phenylpropan-2-yl)phenol (10.9 g, 33 mmol) in EtOH (100 mL). The mixture was
refluxed for 48h leading to an off-white solid precipitate that was filtered off, washed with cold ethanol and dried
in vacuum. The solid was suspended in ethanol (50 mL) and the pH adjusted to <1 by dropwise addition of 6M
HCl solution. The clear solution obtained was refluxed for 3 h and the solvent was then removed through
evaporation. The residue was washed with Et2O and dissolved in a 1:1 mixture of EtOH and water until a clear
solution was obtained. The solution was then neutralized with a 1M Na2CO3 solution to give an off-white
precipitate, which was filtered off, washed with ethanol and dried under vacuum (8.7 g, 78% yield). The product
1
4
was recrystallized from CH2Cl2. H NMR (400 MHz, C6D6, ppm): δ 7.32-7.28 (m, 8H, CH-Ar), 7.26 (d, JHH = 1.8
4
Hz, 2H, CH-Ar), 7.23-7.15 (m, 10H, CH-Ar), 7.12-7.07 (m, 2H, CH-Ar), 6.74 (d, JHH = 1.9 Hz, CH-Ar), 3.72 (s,
4H, ArCH2N), 2.47 (s, 4H, N(CH2)2N), 1.72 (s, 12H, C(CH3)2Ph), 1.66 (s, 12H, C(CH3)2Ph). 13C-{1H} NMR (101
MHz, C6D6, ppm): δ 153.7, 151.43, 151.40, 140.3 and 135.5 (Cipso-Ar), 128.0, 127.8, 126.9, 125.8, 125.7 and
125.6 (CH-Ar), 125.1 and 125.0 (CH-Ar), 121.8 (Cipso-Ar), 52.6 (ArCH2N), 47.2 (N(CH2)2N), 42.6 and 42.1
(C(CH3)2Ph), 31.2 and 29.6 (C(CH3)2Ph). ESI-MS (CH3CN): m/z = 745 (M+), 100%. EA calcd. for
C52H60N2O2 0.2(CH2Cl2): C, 82.28; H, 7.99; N, 3.68. Found: C, 82.34; H, 8.28; N, 3.65.
Synthesis of H2L2
meso-1,2-diphenylethane-1,2-diamine (0.212 g, 1 mmol) was dissolved in 10 mL of EtOH and 3,5-di-tert-butyl-2-
hydroxybenzaldehyde (0.469 g, 2 mmol) was then added. The mixture was refluxed for 20 h leading to a light
yellow precipitate that was filtered off, washed with cold ethanol and dried under vacuum (0.412 g, 88%).
Colourless crystals of H2L2 suitable for X-ray diffraction were obtained by slow evaporation of an EtOH solution
at room temperature. 1H NMR (300 MHz, C6D6, ppm): δ 14.01 (s, 2H, OH), 7.83 (s, 2H, N=CH), 7.56 (d, 2H, 4JHH
4
= 1.9 Hz, CH-Ar), 7.28 (m, 4H, CH-Ph), 7.07 (m, 4H, CH-Ph), 6.98 (m, 2H, CH-Ph), 6.88 (d, 2H, JHH = 2.1 Hz,
CH-Ar), 4.54 (s, 2H, NCH), 1.64 (s, 18H, C(CH3)3), 1.28 (s, 18H, C(CH3)3). 13C-{1H} NMR (101 MHz, C6D6, ppm):
δ 167.3 (N=CH), 158.8, 140.3, 140.1, 137.1 (Cipso-Ar), 128.6, 127.9, 127.5, 126.9 (CH-Ar), 118.6 (Cipso-Ar), 80.2
(N-CH), 35.5 and 34.3 (C(CH3)3), 31.7 and 29.8 (C(CH3)3). EA calcd. for C44H56N2O2: C, 81.94; H, 8.75; N, 4.34.
Found: C, 81.75; H, 9.09; N, 4.35. ESI-MS (CH3CN): m/z = 416 (M+), 100%.
Synthesis of [VO(L1)(OiPr)], 1
A THF solution of VO(OiPr)3 (0.244 g, 1 mmol) was added dropwise, with continuous stirring at room
temperature, to a solution of H2L1 (0.744 g, 1 mmol) in the same solvent. The initially colorless solution turned
dark purple while it was stirred for 18 h, after which the solvent was evaporated to dryness. The compound was
recrystallized from n-hexane at –20 °C to give a purple crystalline solid (0.608 g, 70 % yield). 1H NMR (300 MHz,
4
C6D6, ppm): δ 7.56 (d, JHH = 1.9 Hz, 1H, CH-Ar), 7.51 (d, 4JHH = 2.1 Hz, 1H, CH-Ar), 7.46-7.41 (m, 2H, CH-Ar),
4
7.39-7.28 (m, 4H, CH-Ar), 7.26-7.18 (m, 6H, CH-Ar), 7.11-7.02 (m, 2H, CH-Ar), 6.95 (d, JHH = 2.4 Hz, 1H, CH-
4
3
Ar), 6.96-6.86 (m, 4H, CH-Ar), 6.84 (d, JHH = 1.9 Hz, 1H, CH-Ar), 6.81-6.72 (m, 2H), 5.88 (sept, JHH = 6.1 Hz,
1H, CH(CH3)2), 4.66 (d, 2JHH = 12.5 Hz, 1H, NCH2Ar), 4.33 (d, 2JHH = 13.7 Hz, 1H, NCH2Ar), 3.16 (d, 2JHH = 14.1
2
Hz, 1H, NCH2Ar), 2.89 (d, JHH = 14.3 Hz, 1H, NCH2Ar), 2.18 (s, 3H, C(CH3)2Ph), 1.90 (s, 3H, C(CH3)2Ph), 1.81
(s, 3H, C(CH3)2Ph), 1.79 (s, 3H, C(CH3)2Ph), 1.74 (s, 3H, C(CH3)2Ph), 1.73 (s, 3H, C(CH3)2Ph), 1.52 (s, 6H,
3
C(CH3)2Ph), 1.48 (m, 2H, N(CH2)2N), 1.43 (d, JHH = 6.1 Hz, 3H, CH(CH3)2), 1.37 (m, 2H, N(CH2)2N), 1.34 (d,
3JHH = 6.1 Hz, 3H, CH(CH3)2). 13C-{1H} NMR (101 MHz, C6D6, ppm): δ 154.8, 154.3, 151.9, 151.6, 140.0 and
139.6 (Cipso-Ar), 128.5, 127.4, 127.3, 127.2, 126.7, 126.5, 126.2, 126.0, 125.9, 124.1, 124.0, 123.5 and 123.3
(CH-Ar), 122.9 (Cipso-Ar), 85.2 (CH(CH3)2), 56.1 and 52.3 (NCH2Ar), 45.8 and 43.6 (N(CH2)2N), 42.92, 42.88,

ACCEPTED MANUSCRIPT
42.7 and 42.5 (C(CH3)2Ph), 33.0, 32.7, 31.6, 31.6, 31.5, 31.5, 26.1 and 26.0 (C(CH3)2Ph), 25.9 and 25.8
(CH(CH3)2). 51V NMR (79 MHz, C6D6, ppm): δ -563.4. FT-IR (KBr, cm−1): ν(V=O) 801. EA calcd. for
C55H65N2O4V 0.6(CH2Cl2): C, 72.59; H, 7.25; N, 3.04. Found: C, 72.54; H, 7.44; N, 3.10. ESI-MS (CH3CN): m/z =
809.53 [VVO(L1)]+, ca. 70%; 849.86 (M+), 100%; 1636.13 {[VVO(L1)]2O}+, ca. 20%.
Synthesis of [VO(L1)Cl], 2
1 (0.608 g, 0.7 mmol) was suspended in 10 mL of CH2Cl2 and three equivalents of SiMe3Cl (0.179 g, 2.1 mmol)
were added dropwise at room temperature. The mixture was stirred for 18 h to give a dark violet solution. The
solvent was evaporated to dryness under vacuum to give a dark violet powder that was recrystallized from n-
hexane at -20 °C (0.355 g, 60 % yield. 1H NMR (300 MHz, C6D6, ppm): δ 7.61 (s, 1H, CH-Ar), 7.46-7.31 (m, 7H,
CH-Ar), 7.25-7.17 (m, 6H, CH-Ar), 7.10-7.04 (m, 2H, CH-Ar), 6.97-6.89 (m, 2H, CH-Ar), 6.87-6.64 (m, 5H, CH-
Ar), 6.58-6.53 (m, 1H, CH-Ar), 4.92 (d, 2JHH = 14.1 Hz, 1H, NCH2Ar), 4.52 (d, 2JHH = 13.7 Hz, 1H, NCH2Ar), 3.08
2
2
(d, JHH = 14.5 Hz, 1H, NCH2Ar), 2.84 (d, JHH = 14.5 Hz, 1H, NCH2Ar), 2.10 (s, 3H, C(CH3)2Ph), 2.05 (s, 3H,
C(CH3)2Ph), 1.79 (s, 3H, C(CH3)2Ph), 1.77 (s, 3H, C(CH3)2Ph), 1.70 (s, 3H, C(CH3)2Ph), 1.68 (s, 3H, C(CH3)2Ph),
1.49 (s, 3H, C(CH3)2Ph), 1.36 (m, 1H, N(CH2)2N), 1.36 (s, 3H, C(CH3)2Ph), 1.32 (m, 2H, N(CH2)2N), 1.18 (m, 1H,
N(CH2)2N). 13C-{1H} NMR (101 MHz, C6D6, ppm): δ 162.1, 159.0, 154.4, 153.8, 150.9, 146.0, 141.8, 137.5 and
136.3 (Cipso-Ar), 128.6, 128.5, 127.2, 127.1, 126.7, 126.5, 126.3, 126.2, 126.1, 124.4, 124.1, 123.8 and 123.3
(CH-Ar), 119.2 (Cipso-Ar), 57.8 and 52.0 (NCH2Ar), 47.1 and 44.3 (N(CH2)2N), 43.2, 43.0, 42.8 and 42.6
(C(CH3)2Ph), 32.7, 32.6, 31.6, 31.3, 26.6 and 26.1 (C(CH3)2Ph). 51V NMR (79 MHz, C6D6, ppm): δ -413. FT-IR
(KBr, cm−1): ν(V=O) 802. EA calcd. for C52H58ClN2O3V 2.8(CH2Cl2): C, 60.76; H, 5.92; N, 2.59. Found: C, 60.61;
H, 6.33; N, 2.56. ESI-MS (CH3CN): m/z = 843.01 (M–), 100%; 878.58 {[VVO(L1)(Cl)]Cl}–, ca. 45%; 905.65
{[VVO2(H2L1)Cl]CH3CN}–, ca. 40%.
Reaction of H2L2 with VO(OiPr)3
A THF solution of VO(OiPr)3 (0.122 g, 0.5 mmol) was added dropwise to a solution of H2L2 (0.318 g, 0.5 mmol) in
the same solvent, at room temperature. The initially colorless solution turned to dark blue and, after being stirred
for 18 h, it was evaporated to dryness to give a blue crystalline powder. A THF solution of the powder at -20 ºC
gave green crystals of 4 suitable for X-ray diffraction. The NMR analysis of the remaining solid revealed the
1
presence of H2L2 and [VO(L2)(OiPr)], 3, in 1:4 ratio. Data for 3: H NMR (300 MHz, CDCl3, ppm): δ 8.29 (s, 1H,
N=CH), 8.14 (s, 1H, N=CH), 7.56 (s, 2H, CH-Ar), 7.40-7.14 (m, 4H, CH-Ph), 7.07 (2H, CH-Ar), 7.04-6.93 (m, 4H
CH-Ph), 6.57 (m, 2H, CH-Ph), 6.35 (d, J = 6.0 Hz, 1H, NCH), 6.20 (sept, 3JHH = 6.0 Hz, 1H, OCH(CH3)2), 5.03 (d,
3JHH = 6.0 Hz, 1H, NCH), 1.61 (s, 9H, C(CH3)3), 1.48 (s, 9H, C(CH3)3), 1.44 (d, 3H, CH(CH3)2), 1.30 (s, 9H,
C(CH3)3), 1.26 (s, 9H, C(CH3)3), 1.24 (d, 3H, CH(CH3)2). 13C-{1H} NMR (101 MHz, C6D6, ppm): δ 167.0 (N=CH),
166.8 (Cipso-Ar), 160.7 (N=CH), 158.1, 141.3, 139.4, 138.9, 138.4 and 132.3 (Cipso-Ar), 132.1 (CH-Ph), 130.44
(CH-Ar), 129.6 (CH-Ph), 129.2, 129.0 and 128.9 (CH-Ar), 128.54, 128.45, 128.4, 128.3, 128.2 and 125.7 (CH-
Ph), 122.3 and 121.8 (Cipso-Ph), 89.6 (CH(CH3)2), 76.1 and 75.4 (NCH), 35.69, 35.68, 34.4 and 34.3 (C(CH3)3),
31.6, 31.5, 30.5 and 30.2 (C(CH3)3), 26.6 and 26.4 (CH(CH3)2). 51V NMR (79 MHz, C6D6, ppm): δ –480. ESI-MS
(CH3CN): m/z = 709.70 [VVO(L1)]+, 100%.
Synthesis of [VO(L2)], 4
H2L2 (0.432 g, 0.67 mmol) in EtOH was added to an aqueous solution 50 % (w/v) of VOCl2·2H2O (0.18 mL, 0.67
mmol) and the mixture was stirred for 0.5 h at room temperature leading to a green/grey solution. Addition of a
solution of NaOH 1M in water till pH ~ 8 led to the formation of a light green precipitate that was separated by
filtration and dried in vacuum (0.290 g, 61%). EPR (DMF, 77 K): gz= 1.949, Az= 160.6 × 10-4 cm-1. Elemental
analysis: Calcd. for C44H54N2O3V 0.8(H2O); C, 72.97; H, 7.74; N, 3.87; Found: C, 72.96; H, 7.24; N, 3.82.
Reaction of H2L3 with VO(OiPr)3
A THF solution of VO(OiPr)3 (0.122 g, 0.5 mmol) was added dropwise to a solution of H2L3 (0.406 g, 0.5 mmol) in
the same solvent, at room temperature. The initially colorless solution turned to dark blue and, after 18 h, it was
evaporated to dryness to give a blue crystalline powder. The NMR analysis of the powder revealed the presence
of several species including H2L3, [VO(L3)(OiPr)] and (µ-O){[VO(OiPr)(µ-O)(L3)VO]}2,5. An Et2O solution of the
1
mixture at -20 ºC gave blue crystals of 5 in 30% yield, suitable for X-ray diffraction. Data for 5: H NMR (300
MHz, C6D6, ppm): δ 9.25 (d, J = 8.5 Hz, 1H, CH-Ar), 8.48 (d, J = 8.4 Hz, 1H, CH-Ar), 8.34 (d, J = 8.5 Hz, 1H, CH-
Ar), 7.88 (s, 1H, N=CH), 7.76 (s, 1H, CH-Ar), 7.69 (s, 1H, N=CH), 7.58 (s, 2H, CH-Ar), 7.36-7.18 (m, 4H, CH-Ar),
3
7.04-6.86 (m, 3H CH-Ar), 6.81 (d, J = 8.5 Hz, 2H, CH-Ar), 6.62 (s, 1H, CH-Ar), 4.41 (sept, JHH = 6.1 Hz, 2H,
OCH(CH3)2), 2.19 (s, 18H, C(CH3)3), 1.72 (s, 9H, C(CH3)3), 1.29 (s, 9H, C(CH3)3), 1.04 (s, 9H, C(CH3)3), 0.88 (d,
6H, CH(CH3)2), 0.39 (d, 6H, CH(CH3)2). 13C-{1H} NMR (101 MHz, C6D6, ppm): δ 168.0 and 166.2 (Cipso-Ar), 165.7

ACCEPTED MANUSCRIPT
and 164.1 (N=CH), 149.6, 149.2, 144.4, 141.1, 137.8, 136.1 134.0, 133.6, 133.4 (Cipso-Ar), 132.2 (CH-Ar), 132.1
(Cipso-Ar), 130.9, 129.8, 129.4, 128.6, 127.1, 127.0, 126.7, 126.4 and 125.4 (CH-Ar), 125.2 and 125.1 (Cipso-Ar),
124.7 (CH-Ar), 119.9 (Cipso-Ar), 82.6 (CH(CH3)2), 36.3, 35.8, 34.7 and 34.2 (C(CH3)3), 31.6, 31.4, 30.8 and 30.4
(C(CH3)3), 25.9 and 25.3 (CH(CH3)2). 51V NMR (79 MHz, C6D6, ppm): δ –475, –636, –652. ESI-MS (CH3CN): m/z
= 781.55 [VVO(L2)]+, 100%.
Synthesis of [VO(L3)Cl], 6
A solution of H2L3 (0.500 g, 0.7 mmol) in THF was slowly added to a solution of VO(OiPr)3 (0.171 g, 0.7 mmol) in
the same solvent and stirred for 18 h at room temperature. The solvent was removed under reduced pressure
and the dark blue powder that formed was suspended in 10 mL of CH2Cl2. SiMe3Cl (0.179 g, 2.1 mmol) was then
added dropwise to the suspension and the mixture was stirred at room temperature for 18 h. The solvent was
evaporated under reduced pressure and the dark blue residue dried under vacuum. The compound was
1
recrystallized from n-hexane at -20 ºC (0.321 g, 55 % yield). H NMR (300 MHz, C6D6, ppm): δ 8.07 (s, 1H,
N=CH), 8.06 (s, 1H, N=CH), 7.81-7.55 (m, 6H, CH-Ar), 7.44-7.22 (d, 3H, CH-Ar), 7.13 (m, 1H, CH-Ar), 6.99 (m,
1H, CH-Ar), 6.93-6.76 (m, 5H, CH-Ar), 1.81 (s, 9H, C(CH3)3), 1.58 (s, 9H, C(CH3)3), 1.16 (s, 9H, C(CH3)3), 1.00
(s, 9H, C(CH3)3). 13C-{1H} NMR (101 MHz, C6D6, ppm):
δ 168.4 and 167.0 (Cipso-Ar), 165.53 and 165.49 (N=CH),
150.2, 149.3, 145.7, 142.2, 136.6, 134.7, 132.9, 132.8, 132.5 and 131.9 (Cipso-Ar), 130.9, 129.3, 128.7, 128.5,
128.4, 128.2 and 126.9 (CH-Ar), 126.9 (Cipso-Ar), 126.7, 126.6, 126.53 and 126.49 (CH-Ar), 125.9 (Cipso-Ar),
125.6, 125.2, 125.1 and 124.7 (CH-Ar), 124.1 and 120.2 (Cipso-Ar), 35.5, 35.1, 34.3 and 33.8 (C(CH3)3), 31.0,
30.8, 30.2 and 30.0 (C(CH3)3). 51V NMR (79 MHz, C6D6, ppm): δ -321. Elemental analysis: Calcd. for
C53H61N2O4V (CH2Cl2); C, 71.32; H, 6.48; N, 3.32; Found: C, 71.35; H, 6.39; N, 3.05. ESI-MS (CH3CN): m/z =
781.63 [VVO(L2)]+, 100%; 1656.70 {Na[VVO(L2)(Cl)]2}+, ca. 30%.
General Procedure for the solution sulfoxidation of thioanisole
The catalytic experiments were carried out at atmospheric pressure, at a constant temperature, in a glass vessel,
equipped with magnetic stirrer, thermometer and condenser. In a typical run, the solid catalyst (1 mol%) and
thioanisole (1 mmol) were dissolved in the appropriate solvent (4 mL). Then the oxidant (1.2 mmol), hydrogen
peroxide (20 wt% aqueous solution) was added to the mixture under stirring. Control experiments were carried
out in the absence of catalyst. Samples of the reaction mixture were withdrawn periodically and analyzed on a
Jasco HPLC system equipped with a Daicel Chiralpak IA column. The eluent used was hexane:ethyl acetate
(60:40) with a flow of 1 mL/min. The calibration curves for each reagent and product, namely sulfide, sulfoxide
and sulfone, were determined using similar HPLC procedures and these calibrations used for the quantitative
analyses. Diphenylsulfone was used as an internal standard [4e].
General Procedure for X-ray Crystallography
Crystals suitable for single-crystal X-ray analysis were obtained for H2L2, 4 and 5 as described in the
experimental procedures. The data were collected using graphite monochromated Mo-Kα radiation (λ = 0.71073
Å) on a Bruker AXS-KAPPA APEX II diffractometer equipped with an Oxford Cryosystem open-flow nitrogen
cryostat. Cell parameters were retrieved using Bruker SMART software and refined using Bruker SAINT on all
observed reflections. Absorption corrections were applied using SADABS [23]. The structures were solved using
direct methods with programs SHELX-XS [24] and SIR2004 [25] and refined with program SHELXL [24], included
in the WINGX-Version 1.80.01 [25] system of programs. All non-hydrogen atoms were refined anisotropically and
the hydrogen atoms were inserted in idealized positions and allowed to refine riding on the parent carbon atom.
The crystals of 4 and 5 had poor diffracting power leading to poor quality data; even so, the structures have been
unequivocally determined. The molecular diagrams were drawn with ORTEP-3 for Windows [27] included in the
software package. For crystallographic experimental data and structure refinement parameters see Table 3.
Table 3. Selected crystallographic experimental data and structure refinement parameters for H2L2, 4 and 5.
H2L2
C44H56N2O2
644.90
4
5
C106H122N4O13V4·
Empirical formula
Formula weight
Temperature (K)
Crystal system
C44H54N2O3V
709.83
4(C4H10O)
2160.31
150(2)
150(2)
150(2)
Monoclinic
Triclinic
Monoclinic

ACCEPTED MANUSCRIPT
Space group
P21/c
17.2649(9)
11.1317(6)
10.4440(5)
90
P-1
14.564(3)
15.406(3)
20.454(3)
93.228(11)
101.993(10)
98.017(10)
4428.1(13)
4, 1.065
C2/c
24.146(3)
27.289(3)
18.3902(19)
90
a(Å)
b(Å)
c(Å)
α(°)
104.493(3)
90
92.886(6)
90
β(°)
γ(°)
V(Å3)
1943.34(17)
2, 1.102
0.066
12102(2)
4, 1.186
0.361
Z, ρcalc (gcm-3)
(mm-1)
0.260
µ
Crystal size
Crystal colour
Crystal shape
Refl. collected
Unique refl. [R(int)]
R1 [I>2σ(I)]
0.30×0.26×0.20
colourless
prism
0.10×0.04×0.02
green
0.16×0.16×0.16
blue
plate
block
36138
34664
48184
4309 [0.0793]
0.0602
15552 [0.2563]
0.1068
10605 [0.1798]
0.1100
0.1814
0.2230
0.2638
wR2 [I>2σ(I)]
GooF
1.099
0.808
1.009
Supporting Information
Data for the structures of H2L2, 4 and 5 were deposited in CCDC under the deposit numbers CCDC 1833347-
1833349 and can be obtained free of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.uk/data_request/cif.
Acknowledgements
The authors thank the Fundação para
(SFRH/BPD/73941/2010, SFRH/BPD/79778/2011,
a
Ciência
e
a
Tecnologia, Lisbon, Portugal, for funding
UID/QUI/00100/2013 and
SFRH/BPD/86815/2012,
RECI/QEQ-QIN/0189/2012) and IST-UL Centers of the Portuguese NMR and Mass Spectrometry Networks
(REM2013, RNNMR).
References
[1]
K. P. Bryliakov, Chem. Rev. 117 (2017) 11406-11459.

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[2]
a) H. Pellisier, Coord. Chem. Rev. 284 (2015) 93-110; b) S. Dekar, K. Ouari, S. Bendia, D. Hannachi, J. Weiss,
J. Organometal. Chem. (doi.org/10.1016/j.jorganchem.2018.04.015); c) W. A. Zoubi, Y. G. Ko, Appl. Organomet.
Chem. 31 (2017) e3574.
[3]
[4]
a) F. v. d. Velde, I. W. C. E. Arends, R. A. Sheldon, J. Inorg. Biochem. 80 (2000) 81-89; b) S. Takizawa, H.
Gröger, H. Sasai, Chem. Eur. J. 21 (2015) 8992-8997.
a) K. Nakajima, M. Kojima, J. Fujita, Chem. Lett. (1986) 1483-1486; b) P. Bravo, M. Crucianelli, A. Farina, S. V.
Meille, A. Volonterio, M. Zanda, Eur. J. Org. Chem. (1998) 435-440; c) S. Nakamura, Y. Watanabe, T. Toru, J.
Chem. Soc., Perkin Trans. 1 (1999) 3403-3404; d) H. Cotton, T. Elebring, M. Larsson, L. Li, H. Sorensen, S. v.
Unge, Tetrahedron: Asymm. 11 (2000) 3819-3825; e) M. Mba, M. Pontini, S. Lovat, C. Zonta, G. Bernardinelli,
P. E. Kundig, G. Licini, Inorg. Chem. 47 (2008) 8616-8618; f) P. Adão, J. C. Pessoa, R. T. Henriques, M. L.
Kuznetsov, F. Avecilla, M. R. Maurya, U. Kumar, I. Correia, Inorg. Chem. 48 (2009) 3542-3561.
a) S. Nakamura, Y. Watanabe, T. Toru, J. Chem. Soc., Perkin Trans. 1 (1999) 3403-3404; b) H. Cotton, T.
Elebring, M. Larsson, L. Li, H. Sorensen, S. v. Unge, Tetrahedron: Asymm. 11 (2000) 3819-3825.
F. Madeira, S. Barroso, S. Namorado, P. M. Reis, B. Royo, A. M. Martins, Inorg. Chim. Acta 383 (2012) 152-
156; b) S. Barroso, A. M. Coelho, P. Adão, M. J. Calhorda, A. M. Martins, Dalton Trans. 2017,46, 9692-9704; c) S.
Barroso, F. Madeira, M. J. Calhorda, M. J. Ferreira, M. T. Duarte, A. M. Martins, Inorg. Chem., 2013, 52, 9427-9439.
a) C. Bolm, F. Bienewald, Angew. Chem. Intl. Ed. 34 (1995) 2640-2641; b) J. Skarzewski, E. Ostrycharz, R.
Siedlecka, Tetrahedron: Asymm. 10 (1999) 3457-3461; c) A. G. J. Ligtenbarg, R. Hage, B. L. Feringa, Coord.
Chem. Rev. 237 (2003) 89-101; d) C. Drago, L. Caggiano, R. F. W. Jackson, Angew. Chem. Intl. Ed. 44 (2005)
7221-7223; e) M. Hinch, O. Jacques, C. Drago, L. Caggiano, R. F. W. Jackson, C. Dexter, M. S. Anson, S. J. F.
MacDonald, J. Mol. Catal. A: Chemical 251 (2006) 123-128; f) H. Liu, M. Wang, Y. Wang, R. Yin, W. Tian, L.
Sun, Appl. Organometal. Chem. 22 (2008) 253-257; g) Y. Wang, M. Wang, X. Wang, L. Wang, L. Sun, J. Catal.
273 (2010) 177-181; h) S. Barroso, P. Adão, F. Madeira, M. T. Duarte, J.C. Pessoa, A. M. Martins, Inorg. Chem.
49 (2010) 7452-7463.
[5]
[6]
[7]
[8]
a) C. J. Schneider, J. E. Penner-Hahn, V. L. Pecoraro, J. Am. Chem. Soc. 130 (2008) 2712-2713; b) V. Conte,
A. Coletti, B. Floris, G. Licini, C. Zonta, Coord. Chem. Rev. 255 (2011) 2165-2177; c) D. Balcells, F. Maseras, G.
Ujaque, J. Am. Chem. Soc. 127 (2005) 3624-3634.
[9]
a) R. Sanzenbacher, A. Bottcher, H. Elias, Inorg. Chem. 35 (1996) 7493-7499; b) C. S. Higham, D. P. Dowling,
J. L. Shaw, A. Cetin, C. J. Ziegler, J. R. Farrell, Tetrahedron Lett. 47 (2006) 4419-4423.
a) K. Bernardo, A. Robert, F. Dahan, B. Meunier, New J. Chem. 19 (1995) 129-131; b) K. Bernardo, S. Leppard,
A. Robert, G. Commenges, F. Dahan, B. Meunier, Inorg. Chem. 35 (1996) 387-396; c) P. Muthupandi, S. K.
Alamsetti, G. Sekar, Chem. Commun. (2009) 3288-3290; d) N. Madoux, T. Roisnel, V. Dorcet, J. F. Carpentier,
Y. Sarazin, Chem. Eur. J. 20 (2014) 6131-6147.
[10]
[11]
[12]
F. H. Allen, O. Kennard, D. G. Watson, L. Brammer, A. G. Orpen, R. Taylor, J. Chem. Soc. Perkin Trans. 2
(1987) S1-S19.
P. Adão, R. Maurya, U. Kumar, F. Avecilla, R. T. Henriques, M. L. Kusnetsov, J. C. Pessoa, I. Correia, Pure
Appl. Chem. 81 (2009) 1279-1296.
[13]
[14]
F. Wolff, C. Lorber, R. Choukroun, B. Donnadieu, Inorg. Chem. 42 (2003) 7839-7845.
a) S. K. Hanson, R. T. Baker, J. C. Gordon, B. L. Scott, A. D. Sutton, D. L. Thorn, J. Am. Chem. Soc. 131 (2009)
428-429; b) S. K. Hanson, R. T. Baker, J. C. Hanson, B. L. Scott, L. A. Silks, D. L. Thorn, J. Am. Chem. Soc.
132 (2010) 17804-17816; c) S. K. Hanson, R. Wu. L. A. Silks, Org. Lett. 13 (2011) 1908-1911; d) G. Zhang, B.
L. Scott, R. Wu, L. A. Silks, S. K. Hanson, Inorg. Chem. 51 (2012) 7354-7361.
[15]
[16]
Z. Liu, F. C. Anson, Inorg. Chem. 39 (2000) 274-280.
a) A. Santalo, F. J. Vidal-Iglesias, J. Solla-Gullón, A. Berná, T. Kallio, J. M. Feliu, Electrochim. Acta 54 (2009)
6576-6583; b) A. Santalo-Aarnio, Y. Kwon, E. Ahlberg, K. Kontturi, T. Kalliu, M. T. M. Koper, Electrochem.
Commun. 13 (2011) 466-469.

ACCEPTED MANUSCRIPT
[17]
[18]
a) K. Wüthrich, Helv. Chim. Acta 48 (1965) 1012-1017; b) N. D. Chasteen, In Biological Magnetic Resonance;
Berliner, L. J., Reuben, J., Eds.; Plenum Press: New York, 1981; Vol. 3, pp 53−119; c) T. S. Smith II, R.
LoBrutto, V. L. Pecoraro, Coord. Chem. Rev. 228 (2002) 1-18.
a) M. Kojima, H. Taguchi, M. Tsuchimoto, K. Nakajima, Coord. Chem. Rev. 237 (2003) 183-196; b) O. Taheri,
M. Behzad, A. Ghaffari, M. Kubicki, G. Dutkiewicz, A. Bezaatpour, H. Nazari, A. Khaleghian, A. Mohammadi, M.
Salehi, Transition Met. Chem. 39 (2014) 253-259.
[19]
[20]
a) W. Priebsch, D. Rehder, Inorg. Chem. 29 (1990) 3013-3019; b) D. C. Crans, R. A. Felty, H. Chen, H. Eckert,
N. Das, Inorg. Chem. 33 (1994) 2427-2438.
a) P. B. Chatterjee, S. Bhattacharya, A. Audhya, K.-Y. Choi, A. Endo, M. Chaudhury, Inorg. Chem. 47 (2008)
4891-4902; b) Y. N. Belokon, W. Clegg, R. W. Harrington, V. I. Maleev, M. North, M. O. Pujol, D. L. Usanov, C.
Young, Chem. Eur. J. 15 (2009) 2148-2165.
[21]
A search using CCDC ConQuest program version 1.19 returned 38 hits with the following bond distance ranges
for oxidovanadium(V) salen complexes: V=O 1.539 – 1.609 Å, V-Ophenolate 1.786 – 2.011 Å, V-Oimine 2.054 –
2.114 Å.
[22]
[23]
A. Rockenbauer, L. Korecz, Appl. Magn. Reson. 10 (1996) 29-43.
G. M. Sheldrick, SADABS, Program for Empirical Absorption Correction; University of Göttingen: Göttingen,
Germany, 1996.
[24]
[25]
a) G. M. Sheldrick, , SHELXL-97 – Programs for Crystal Structure Analysis (Release 97-2), Göttingen,
Germany, 1998; b) G. M. Sheldrick, Acta Crystallogr. A64 (2008) 112-122.
M. C. Burla, R. Caliandro, M. Camalli, B. Carrozzini, G. L. Cascarano, L. De Caro, C. Giacovazzo, G. Polidori,
R. Spagna, J. Appl. Crystallogr. 38 (2005) 381-388.
[26]
[27]
L. J. Farrugia, J. Appl. Crystallogr. 32 (1999) 837-838.
L. J. Farrugia, J. Appl. Crystallogr. 30 (1997) 565-565.

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Text for TOC
New salan- and salen-vanadium complexes display high activity and selectivity in sulfoxidation of thioanisole.
Salan-type complexes perform better. Well-defined binaphthyl-based salen complexes display better catalytic
performance than in-situ prepared systems using [VO(acac)2] and the ligand precursor.
Graphical Abstract

ACCEPTED MANUSCRIPT
New Salan and Salen Vanadium Complexes: Syntheses
and Application in Sulfoxidation Catalysis
Minaxi S. Maru, Sónia Barroso, Pedro Adão, Luis G. Alves and Ana M. Martins*
Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001
Lisboa, Portugal
E-mail: ana.martins@tecnico.ulisboa.pt
Highlights:
•
•
•
•
New vanadium complexes of salan- and salen-types are described
Salen V(V) complexes spontaneously reduce to V(IV) through intramolecular redox processes
Vanadium salen and salan oxido complexes were assessed as sulfoxidation catalysts
The inclusion of a binaphthyl moiety in the ancillary ligand frame led to 100% selectivity in sulfoxide