Synthesis, structure and characterization of dinuclear pentacoordinate molybdenuni(V) complexes with thiosemicarbazone ligands

Article abstract of DOI:10.1002/zaac.200801290

New dinuclear pentacoordinate molybdenum(V) complexes, [Mo₂ ^vO₃L₂] [L = thiosemicarbazonato ligand: C ₆H₄(O)CH:NN:C(S)NHR' and C₁₀H ₆(O)CH:NN:C(S)NHR'; R' = H, CH

Full text of DOI:10.1002/zaac.200801290

ARTICLE
DOI: 10.1002/zaac.200801290
Synthesis, Structure and Characterization of Dinuclear Pentacoordinate
Molybdenum(V) Complexes with Thiosemicarbazone Ligands
[a]
[a]
[a]
[a]
ˇ
ˇ
´
´
´
´
Visnja Vrdoljak,* Dalibor Milic, Marina Cindric, Dubravka Matkovic-Calogovic,
[a]
[a]
[a]
´
Jana Pisk, Marina Markovic, and Predrag Novak
Keywords: Molybdenum; Thiosemicarbazones; Coordination chemistry; Dinuclear complexes; Oxo-bridged complexes
Abstract. New dinuclear pentacoordinate molybdenum(V)
complexes, [Mo2VO3L2] [L
thiosemicarbazonato ligand: Crystal and molecular structure of [Mo2O3{C6H4(O)-
C6H4(O)CH:NN:C(S)NHRЈ and C10H6(O)CH:NN:C(S)NHRЈ; CH:NN:C(S)NHC6H5}2]·CH3CN has been determined by the
[Mo2O3(acac)4] in the reaction with the corresponding ligands H2L.
ϭ
RЈ ϭ H, CH3, C6H5) were obtained either by oxygen atom abstrac-
single-crystal X-ray diffraction method.
tion from MoVIO2L with triphenylphosphine or by using
deprotonated thiosemicarbazonato ligand. Although a
large number of molybdenum(V) complexes containing the
Mo2O34ϩ core are known, only a few complexes containing
pentacoordinate molybdenum have been synthesized and
structurally characterized so far [13Ϫ16].
Introduction
Oxomolybdenum compounds have been extensively stud-
ied as models for molybdoenzymes that catalyze oxygen
atom transfer (OAT) [1Ϫ5]. It is known that OAT reactions
proceed in steps: a) transfer of an oxygen atom from
MoVIO2L to an appropriate substrate (PR3) and formation
of the corresponding MoIVOL complex, and b) transfer of
an oxo-group from an oxo-donor substrate (DMSO, pyri-
dine N-oxide, or O2) to MoIVOL and regeneration of the
initial MoVIO2L complex. The oxomolybdenum complexes
of interest are those which can provide completion of the
catalytic cycle. However, the OAT cycle is in some cases
accompanied by the formation of a dinuclear oxo-bridged
molybdenum(V) complex, usually inactive toward further
oxo-transfer:
Results and Discussion
The molybdenum(V) complexes having the general
formula [Mo2VO3L2] (1Ϫ6) [L ϭ thiosemicarbazonato
ligand: C6H4(O)CH:NN:C(S)NHRЈ and C10H6(O)CH:NN:
C(S)NHRЈ; RЈ ϭ H, CH3, C6H5] have been prepared by
two alternative ways (Scheme 1). Either by oxygen atom
abstraction from [MoVIO2L]n (1aϪ6a) with triphenylphos-
phine in acetonitrile (method A) or by the reaction of
[Mo2O3(acac)4] (acac ϭ acetylacetonate ion) with the corre-
sponding thiosemicarbazone ligands, H2L (method B).
Complexes prepared by either of the methods were of the
MoO2ϩ ϩ MoO2 p Mo2O3
2ϩ
4ϩ
There are only rare examples of complexes with the same formula, as proven not only by comparison of their
Mo2O34ϩ core that take part in oxo-transfer reactions. They spectral and elemental analyses, but also by the X-ray pow-
were found to have a labile bonded molecule trans to the der diffraction.
terminal MoϭO bond [6Ϫ8].
Dark red-brown products were characterized as novel
Recently, we have published syntheses, as well as struc- dinuclear five-coordinate molybdenum(V) complexes, with
tural and spectral properties of several molybdenum(VI) ligands coordinated to molybdenum as tridentate ONS-
complexes with thiosemicarbazones [9Ϫ12]. In the continu- donors through phenolic-oxygen, imine-nitrogen and thiol-
ation of our research we report herein the synthesis sulfur atoms. The existence of MoV instead of MoIV in the
and characterization of several pentacoordinate molyb- OAT process was proven by EPR spectroscopy [17]. For all
denum(V) complexes, [Mo2O3L2], in which L represents a complexes a similar spectrum was obtained and therefore
just one representative example is given in Figure 1.
These compounds are very soluble in coordinating sol-
vents D such as CH3OH, dmf, dmso, picoline or py and
* Prof. V. Vrdoljak
only moderately soluble in acetonitrile. Their solutions are
quite sensitive to traces of oxygen resulting in color change
form dark red to orange. This change of the coloration is a
consequence of oxidation of the [Mo2VO3L2] complexes to
E-Mail: visnja@chem.pmf.hr
[a] Department of Chemistry
Faculty of Science, University of Zagreb
Horvatovac 102a
10000 Zagreb, Croatia
1242
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2009, 635, 1242Ϫ1248

Dinuclear Pentacoordinate Molybdenum(V) Complexes with Thiosemicarbazone Ligands
Scheme 1.
[Mo2VO3L2] (1Ϫ6), these bands are shifted to a single
strong absorption in the region 763Ϫ746 cmϪ1, indicative
for MoϪOϪMo bridging [13, 19]. The molybdenum(V)
complexes 1Ϫ6 exhibit a single strong absorption band
around 960 cmϪ1 assigned to terminal MoϭO groups. The
[MoVIO2LD] (1bϪ6b) complexes obtained by the oxidation
of [Mo2VO3L2] were identified by the appearance of the
νasym(MoO2) and νsym(MoO2) around 930 cmϪ1 and
895 cmϪ1, respectively, and by absence of the band indica-
tive of metalϪoxygen bridging [9Ϫ11, 20].
˜
˜
The stretching frequencies found at about 1545 cmϪ1 and
two strong bands at about 1595 and 1575 cmϪ1 were attri-
buted to CϪOphenolic and CϭN, respectively. The remaining
frequencies in the IR spectra were due to the vibrations
within the ligand.
Figure 1. EPR spectrum of molybdenum(V) complex 2.
Thermal Analyses
the mononuclear [MoVIO2LD] (1bϪ6b) complexes, ad-
ditionally coordinated by a solvent molecule D (Scheme 1).
The molybdenum(VI) complexes [MoVIO2LD] obtained by
this procedure are identical to those known from our pre-
vious investigations [9Ϫ12, 18].
The advantage of pentacoordinated molybdenum(V)
complexes is their capability of regenerating the initial di-
oxomolybdenum(VI) complexes so that catalytic cycle can
be accomplished. It is reasonable to suppose that the ar-
rangement around molybdenum gives the opportunity for
a ready access to the sixth coordination place around the
molybdenum atom by an appropriate substrate.
Upon heating of the [Mo2VO3L2] complexes in the atmos-
phere of pure oxygen weight gain occurred [in the range
173Ϫ200 °C (2); 195Ϫ201 °C (3); 174Ϫ192 °C (4);
192Ϫ198 °C (5); 173Ϫ199 °C (6)], that was related to the
oxidation of molybdenum and formation of the molyb-
denum(VI) thiosemicarbazonato complexes. This thermal
oxidation was followed on further heating by significant
weight losses [in the range 237Ϫ460 °C (1); 248Ϫ569 °C (2);
228Ϫ540 °C (3); 219Ϫ499 °C (4); 206Ϫ555 °C (5);
247Ϫ569 °C (6)] that were indicative of complex decompo-
sition resulting in the solid residue identified as MoO3.
The first step in the thermogravimetric curve of the
[Mo2O3{C6H4(O)CH:NN:C(S)NHC6H5}2]·CH3CN
(3)
Infrared Spectra
(weight loss within the range 60Ϫ170 °C) was related to the
In the polymeric complexes [MoVIO2L]n (1aϪ6a) there loss of solvent of crystallization. The other complexes were
are intense bands in the region 799Ϫ834 cmϪ1 associated unsolvated or they were loosing their molecules of crystalli-
with the MoϭO···Mo interaction. In complexes zation already at room temperature.
Z. Anorg. Allg. Chem. 2009, 1242Ϫ1248
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
1243

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V. Vrdoljak, D. Milic, M. Cindric, D. Matkovic-Calogovic, J. Pisk, M. Markovic, P. Novak
ARTICLE
Table 1. Selected bond lengths and angles for 3.
˚
Bond lengths /A
Bond angles / °
x ϭ 1
x ϭ 2
x ϭ 1
x ϭ 2
MoxϪSx
2.3560(14)
1.977(3)
1.669(3)
1.851(4)
2.140(4)
1.753(5)
1.342(6)
1.401(6)
1.311(7)
1.319(7)
1.361(7)
1.422(7)
2.3573(14)
1.964(3)
1.683(4)
1.872(4)
2.146(4)
1.767(5)
1.351(6)
1.395(6)
1.296(7)
1.316(7)
1.341(7)
1.408(6)
SxϪMoxϪO1x
SxϪMoxϪO2x
SxϪMoxϪO3x
SxϪMoxϪN1x
O1xϪMoxϪO2x
O1xϪMoxϪO3x
O1xϪMoxϪN1x
O2xϪMoxϪO3x
O2xϪMoxϪN1x
O3xϪMoxϪN1x
Mo1ϪO3ϪMo2
139.48(10)
107.07(11)
89.15(10)
78.22(12)
112.15(14)
87.93(14)
84.33(15)
108.48(17)
101.55(16)
149.72(16)
137.02(12)
109.35(14)
88.70(10)
78.07(12)
112.39(18)
87.16(14)
83.91(16)
109.13(18)
101.75(17)
148.97(16)
177.7(2)
MoxϪO1x
MoxϪO2x
MoxϪO3x
MoxϪN1x
SxϪC3x
O1xϪC5x
N1xϪN2x
N1xϪC1x
N2xϪC3x
N4xϪC3x
N4xϪC15x
Table 2. Hydrogen bonding arrangement in 3.
˚
˚
˚
DϪH···A
d(DϪH) /A
d(H···A) /A
d(D···A) /A
Є(DϪH···A) /°
N41ϪH41N···N5
N42ϪH42N···O21i
0.88(3)
0.85(3)
2.13(3)
2.23(4)
3.006(7)
3.017(5)
172(4)
153(4)
Symmetry code: (i) Ϫx, 2 Ϫy, Ϫz.
Crystal Structure of 3
(H2L3) bonded through an oxygen atom (O1x) from the
deprotonated phenolic group, imine nitrogen atom (N1x),
and sulfur atom (Sx) from the deprotonated thiol group
(Figure 2). The two thiosemicarbazonato ligands are bound
in a quasi-centrosymmetrical mode regarding the bridging
oxo group and each of them forms a five- and six-mem-
bered chelate ring with the MoV atom. The coordination
arrangement around MoV is distorted tetragonal-pyramidal
with the terminal oxo group in the apical position and
with the other coordinating atoms defining the basal plane
An ORTEP plot of the asymmetric unit of 3 is shown in
Figure 2 and the selected geometrical parameters are
presented in Table 1. In compound 3, molecules of the
dinuclear molybdenum(V) complex [Mo2O3{C6H4(O)-
CH:NNC(S)NHC6H5}2] co-crystallize with molecules of
acetonitrile.
of the pyramid {τ1 ϭ 0.17 and τ2 ϭ 0.20; τx
ϭ
ΗЄ(SxϪMoxϪO1x) Ϫ Є(O3ϪMoxϪN1x)Η/60° [21]}. The
maximum deviation from the least-squares plane defined by
Sx, N1x, O1x, O3 in both parts is that of O1x being
˚
˚
0.114(3) A for x ϭ 1 and 0.128(4) A for x ϭ 2. Mo1 and
Mo2 are moved out of the corresponding basal plane by
˚
˚
0.6210(5) A and 0.6505(5) A, respectively. The molyb-
denum-donor bond lengths are similar to those observed
for this type of complexes [15, 22].
Each thiosemicarbazonato ligand consists of three
(nearly) planar parts: salicyl (atoms C1x, C5xϪC10x and
O1x), thiosemicarbazonyl (Sx, N1x, N2x, C3x and N4x)
and N-phenyl (C15xϪC20x) moiety. Dihedral angles be-
tween the least-squares planes of the salicyl and the thiose-
micarbazonyl moieties are 5.14(18)° and 3.44(18)° for the
ligand molecules bound to Mo1 and Mo2, respectively, thus
allowing a high degree of π-electron delocalization through-
out these parts (as observed in the values of bond lengths).
Whereas the N-phenyl part in the ligand molecule coordin-
ating Mo2 is basically coplanar with the thiosemicarba-
zonyl moiety [dihedral angle between the least-squares
planes is 1.8(2)°] and thus extending the delocalized π-elec-
tron system, in the other ligand the N-phenyl moiety is in-
clined by 21.7(3)° in respect to the thiosemicarbazonyl part,
Figure 2. An asymmetric unit of 3 with the numbering scheme and
displacement ellipsoids drawn at the 50 % probability level. A
molecule of acetonitrile is connected to molecule of the dinuclear
complex by the hydrogen bond represented by the dashed line.
4ϩ
The complex consists of an anti-Mo2O3 core with an
oxo-bridge being almost linear [Є(Mo1ϪO3ϪMo2) ϭ
177.7(2)°], but slightly asymmetrical [d(Mo1ϪO3)
ϭ
V
˚
˚
1.851(4) A and d(Mo2ϪO3) ϭ 1.872(4) A]. Each Mo is
coordinated by a bridging (O3) and one terminal (O2x; x ϭ
1 or 2) oxo group and by the tridentate doubly depro-
tonated salicylaldehyde 4-phenylthiosemicarbazone ligand so the π-electron delocalization between these two moieties
1244
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2009, 1242Ϫ1248

Dinuclear Pentacoordinate Molybdenum(V) Complexes with Thiosemicarbazone Ligands
is slightly interrupted (cf. N4xϪC3x bond lengths; Table
1). In contrast to the crystal structure of salicylaldehyde 4-
phenylthiosemicarbazone [23], in which molecules of the
free ligand (three per asymmetric unit) are found in the
thioketo tautomeric form with CϭS distances in the range
˚
1.662(3)Ϫ1.680(2) A and CϪN(amino) distances ranging
˚
from 1.347(3) to 1.356(3) A, the analogous C3xϪSx dis-
˚
tances in 3 are much longer [1.753(5) and 1.767(5) A],
˚
whereas C3xϪN2x are shorter [1.319(7) and 1.316(7) A] as
consistent with the thiolate form. In comparison to the free
thiosemicarbazone ligand [23], the formally double bonds
in the bound ligand in 3 are significantly elongated, whereas
the formally single bonds are significantly shortened thus
suggesting a higher degree of π-electron delocalization in
the complex.
Figure 3. The crystal packing in 3. Hydrogen atoms bound to
carbon atoms are omitted for clarity. Hydrogen bonds are shown
by the dashed lines. Symmetry code: (i) Ϫx, 2Ϫy, Ϫz.
In the crystal structure of 3, a molecule of acetonitrile
is bonded to a molecule of the dinuclear complex by the
N41ϪH41N···N5 hydrogen bond (Figure 2; Table 2). Two
molecules of the complex are mutually connected by
N42ϪH42N···O21 (Ϫx, 2Ϫy, Ϫz) hydrogen bonds (Figure
3; Table 2) thus forming a centrosymmetrical dimer and a
ring described by a graph-set notation as R22(16).
flecting intramolecular hydrogen bonding interactions that
was consistent with the previous results. According to the
chemical shifts, all ligands exist in the hydroxy-thione tau-
tomeric form in [D6]DMSO as found in the solid state.
The absence of OH and NH-2 protons observed for com-
pounds 1Ϫ6 corroborates the formation of complexes. As a
consequence, the NH-4 protons experience an up-field shift
NMR Spectroscopy
Assignments of proton and carbon chemical shifts in of approximately 1 ppm. The coordination-induced chemi-
[D6]DMSO were made by using standard one- (1H and cal shifts are more profound for carbon atoms. The largest
APT) and two-dimensional (COSY, HMQC and HMBC) change was observed for carbons C-1, C-3 being the two
NMR experiments. Chemical shifts of the ligands most effected interacting sites. These effects are down-field
H2L1ϪH2L6 (Scheme 2) as well as their MoV complexes (up to 14.55 ppm) for the former and up-field (up to
1Ϫ6 are given in Table 3 and Table 4.
15.32 ppm) for the later site. The observed shielding and
The 1H and 13C chemical shift values are similar to those deshielding effects are a consequence of electron redistri-
previously reported for the related ligands and their MoVI bution upon complexation. The total effect at C-3 is a
complexes [10, 11, 24]. A relatively broad OH resonance superposition of a coordination-induced effect and the for-
was observed for all ligands at approximately 10 ppm, re- mation of an imine instead of a thiocarbonyl bond.
Scheme 2.
Z. Anorg. Allg. Chem. 2009, 1242Ϫ1248
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
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V. Vrdoljak, D. Milic, M. Cindric, D. Matkovic-Calogovic, J. Pisk, M. Markovic, P. Novak
ARTICLE
1
Table 3. H and 13C chemical shifts /ppm of ligands H2L1ϪH2L3 and their molybdenum(V) complexes 1Ϫ3.
H2L1
1
H2L2 *
2
H2L3 *
3
atom
1H
13C
1H
13C
1H
13C
1H
13C
1H
13C
1H
13C
1
2
3
4
5
6
7
8
8.39
11.39
Ϫ
8.17 / 7.92
Ϫ
6.88
7.22
6.83
7.92
Ϫ
139.55
Ϫ
177.56
Ϫ
156.28
115.92
130.97
119.15
126.65
120.22
8.45
Ϫ
Ϫ
7.14
Ϫ
6.85
7.40
6.98
7.58
Ϫ
150.82
Ϫ
166.18
Ϫ
158.82
118.00
133.27
120.84
133.48
121.22
8.37
11.47
Ϫ
8.42
Ϫ
6.87
7.22
6.83
7.95
Ϫ
139.09
Ϫ
177.68
Ϫ
156.46
116.16
131.09
119.32
126.72
120.62
30.96
8.57
Ϫ
Ϫ
7.45
Ϫ
6.85
7.41
6.98
7.60
Ϫ
151.68
Ϫ
164.60
Ϫ
158.67
118.01
133.31
120.83
133.52
121.19
30.89
8.48
11.75
Ϫ
10.03
Ϫ
6.88
7.23
6.84
8.08
Ϫ
139.95
Ϫ
175.61
Ϫ
8.81
Ϫ
Ϫ
9.69
Ϫ
6.87
7.47
7.03
7.69
Ϫ
154.50
Ϫ
161.08
Ϫ
156.49
115.92
131.20
119.10
129.96
120.15
139.04
125.56
127.90
125.04
127.90
125.56
Ϫ
158.83
117.98
133.95
120.85
133.95
120.69
140.52
119.64
128.54
122.35
128.54
119.64
Ϫ
9
10
11
12
13
14
15
16
OH
3.01
2.81
Ϫ
Ϫ
7.57
7.36
7.19
7.36
7.57
9.96
7.75
7.31
7.01
7.31
7.75
Ϫ
9.88
Ϫ
Ϫ
Ϫ
9.87
Ϫ
Ϫ
Ϫ
1
* The H and 13C chemical shift values for H2L2 and H2L3 are taken from ref. [11] and [24], respectively.
1
Table 4. H and 13C chemical shifts /ppm of ligands H2L4ϪH2L6 and their molybdenum(V) complexes 4Ϫ6.
H2L4
4
H2L5
5
H2L6 *
6
atom
1H
13C
1H
13C
1H
13C
1H
13C
1H
13C
1H
13C
1
2
3
4
5
6
7
8
9.05
11.39
Ϫ
8.21
Ϫ
7.20
7.88
Ϫ
7.85
7.38
7.56
8.51
Ϫ
143.18
Ϫ
178.20
Ϫ
9.26
Ϫ
Ϫ
7.22
Ϫ
7.14
8.00
Ϫ
7.91
7.45
7.60
8.26
Ϫ
146.09
Ϫ
165.64
Ϫ
9.05
11.40
Ϫ
8.34
Ϫ
7.21
7.89
Ϫ
7.86
7.39
7.57
8.45
Ϫ
142.59
Ϫ
177.28
Ϫ
9.31
Ϫ
Ϫ
7.49
Ϫ
7.14
7.99
Ϫ
7.91
7.45
7.60
8.30
Ϫ
Ϫ
2.88
147.00
Ϫ
164.45
Ϫ
9.20
11.79
Ϫ
10.11
Ϫ
7.25
7.92
Ϫ
7.87
7.39
7.60
8.51
Ϫ
143.65
Ϫ
175.85
Ϫ
9.59
Ϫ
Ϫ
9.71
Ϫ
7.19
8.05
Ϫ
7.93
7.46
7.65
8.45
Ϫ
150.11
Ϫ
160.53
Ϫ
156.75
118.49
132.62
128.21
128.82
123.54
128.02
123.59
131.66
110.10
159.46
119.81
133.67
128.53
128.55
124.08
127.99
121.13
132.02
112.02
156.24
118.29
132.25
128.01
128.61
123.38
127.74
122.58
131.50
109.74
31.15
159.33
119.87
133.74
128.56
128.85
1224.11
128.00
121.29
132.08
112.11
30.82
156.78
118.63
132.73
128.19
128.87
123.62
127.95
122.62
131.76
109.83
139.32
125.22
128.33
125.22
128.33
125.22
Ϫ
159.98
119.36
134.76
128.62
128.95
124.35
128.19
121.59
132.33
111.98
140.63
119.76
128.69
122.36
128.69
119.76
Ϫ
9
10
11
12
13
14
15
16
17
18
19
20
OH
Ϫ
Ϫ
Ϫ
3.04
Ϫ
Ϫ
Ϫ
Ϫ
7.62
7.41
7.21
7.41
7.62
10.68
7.88
7.36
7.03
7.36
7.88
Ϫ
10.49
Ϫ
Ϫ
Ϫ
10.51
Ϫ
Ϫ
Ϫ
1
* The H and 13C chemical shift values for H2L6 are taken from ref. [10].
analyses were measured with a Mettler TG 50 thermobalance using
aluminum crucibles under oxygen atmosphere within the tempera-
ture range from 25 to 600 °C. All experiments were recorded with
a heating rate of 5 °C minϪ1 in a dynamic atmosphere with a flow
rate of 200 cm3 minϪ1. The results were developed by applying the
Mettler STARe 6.1 program. EPR spectra were measured at 293 K
with a Varian E-109 spectrometer operating at 100 kHz modu-
lation, equipped with dual sample cavity. As a g-factor standard
2,2-diphenyl-1-picrylhydrazyl (DPPH, g ϭ 2.0036) was used. X-ray
diffraction powder data were obtained using Cu-Kα radiation (λ ϭ
Experimental Section
Thiosemicarbazones H2L1ϪH2L6 were prepared analogously to the
procedure described by Purohit et al. [20]. The starting complex
[Mo2O3(acac)4] was prepared as described in the literature [25, 26].
The [MoO2L]n complexes (1aϪ6a) were synthesized by the reaction
of [MoO2(acac)2] with the appropriate ligands H2L in acetonitrile,
or by dissolving of [MoO2L(CH3OH)] in acetonitrile [9, 11, 18].
Acetonitrile was dried with P2O5.
C, H, N and S analyses were provided by the Analytical Services
1.5406 A) with a Philips XPERT PW 3710 diffractometer. Data were
˚
ˇ
´
Laboratory of Rudjer Boskovic Institute, Zagreb. Infrared spectra
collected in the 5 < 2θ < 70° range, in the θ-2θ step scan mode
were recorded in KBr with the PerkinϪElmer 502 spectrophoto-
meter in the 4500Ϫ450 cmϪ1 region. Thermogravimetric (TG) with Δ2θ ϭ 0.02° and t ϭ 12 s.
1246
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2009, 1242Ϫ1248

Dinuclear Pentacoordinate Molybdenum(V) Complexes with Thiosemicarbazone Ligands
H2L5). C26H22Mo2N6O5S2 (Mr ϭ 754.502): C 41.39; H 2.94; N
11.14; S 8.50; Found: C 41.18; H 2.85; N 11.29; S 8.31. TG: 37.89 %
Synthesis of the Molybdenum(V) Complexes [Mo2O3L2]
All syntheses were performed under dry argon atmosphere by the
following methods:
MoO3 (Calcd. 38.15 %). Selected IR data: ν˜ ϭ 1594, 1575 (CϭN),
1547 (CϪO), 959 (Mo ϭ O), 747 (MoϪOϪMo) cmϪ1
.
Method A. [MoO2L]n (0.25 mmol) was suspended in dry aceto-
nitrile and PPh3 (0.1 g, 0.38 mmol) was added. The solution was
warmed up for 5 h during which a dark red-brown microcrystalline
product deposited. It was collected by filtration, washed with aceto-
nitrile and dried.
Synthesis of [Mo2O3{C10H6(O)CH:NN:C(S)NHC6H5}2]
(6)
Yield: 0.09 g, 42 % (method A, obtained from 6a). Yield: 0.07 g,
51 % (method B, obtained from the reaction of [Mo2O3(acac)4] with
H2L6). C36H26Mo2N6O5S2 (Mr ϭ 878.64): C 49.21; H 2.98; N 9.56;
S 7.30, Found: C 49.58; H 2.96; N 10.07; S 7.11. TG: 32.28 %
MoO3 (Calcd. 32.76 %). Selected IR data: ν˜ ϭ 1593, 1573 (CϭN),
Method B. [Mo2O3(acac)4] (0.15 mmol) was dissolved in dry aceto-
nitrile (25 mL) and appropriate thiosemicarbazone ligand H2L
(0.3 mmol) was added. The mixture was warmed for 5 h. A dark
red-brown product obtained from the solution was filtered off,
washed with acetonitrile and dried.
1540 (CϪO), 959 (Mo ϭ O), 752 (MoϪOϪMo) cmϪ1
.
Synthesis of [Mo2O3{C6H4(O)CH:NN:C(S)NH2}2] (1)
Single-Crystal X-ray Structural Analysis
Yield: 0.05 g, 20 % (method A, obtained from 1a). Yield: 0.06 g,
43 % (method B, obtained from the reaction of [Mo2O3(acac)4] with
H2L1). C16H14Mo2N6O5S2 (Mr ϭ 626.331): C 30.68; H 2.25; N
13.42; S 10.24; Found: C 30.25; H 2.44; N 13.28; S 10.13. TG:
46.01 % MoO3 (calcd. 45.96 %). Selected IR data: ν˜ ϭ 1601, 1582
The X-ray diffraction data from the single crystal of 3 were col-
lected at 295(2) K with the Oxford Diffraction Xcalibur 3 CCD
diffractometer with graphite-monochromated Mo-Kα radiation
˚
(λ ϭ 0.71073 A). Crystallographic data for 3: C30H25Mo2N7O5S2,
¯
Mr ϭ 819.57, red plate, 0.40 ϫ 0.06 ϫ 0.02 mm, triclinic, P1 (no.
(CϭN), 1546 (CϪO), 962 (Mo ϭ O), 760 (MoϪOϪMo) cmϪ1
.
˚
˚
˚
3
2), a ϭ 10.0221(12) A, b ϭ 12.2577(12) A, c ϭ 14.1225(13) A, Ͱ ϭ
˚
74.333(8)°, β ϭ 83.969(9)°, γ ϭ 77.162(10)°, V ϭ 1626.8(3) A , Z ϭ
2, Dcalc ϭ 1.673 g·cmϪ3, μ ϭ 0.950 mmϪ1, θmax ϭ 25.0°, 13939
measured reflections, 5637 unique reflections, Ϫ11 Յ h Յ 11, Ϫ14
Յ k Յ 14, Ϫ16 Յ l Յ 16, 3359 reflections with I > 2σ(I), 422
parameters refined, R1 ϭ 0.0425 [I > 2σ(I)] and 0.0869 (all data),
wR2 ϭ 0.0895 [I > 2σ(I)] and 0.1031 (all data), S ϭ 0.925, the
Synthesis of
[Mo2O3{C6H4(O)CH:NN:C(S)NHCH3}2] (2)
Yield: 0.07 g, 42 % (method A, obtained from 2a). Yield: 0.07 g,
66 % (method B, obtained from the reaction of [Mo2O3(acac)4] with
H2L2). C18H18Mo2N6O5S2 (Mr ϭ 654.381): C 33.04; H 2.77; N
12.84; S 9.80; Found: C 33.28; H 2.25; N 13.38; S 10.24. TG:
43.59 % MoO3 (calcd. 43.99 %). Selected IR data: ν˜ ϭ 1598, 1580
largest difference peak and hole 1.40 and Ϫ0.49 e·AϪ3. The data
˚
reduction (including the multi-scan absorption correction: Tmin
ϭ
0.690, Tmax ϭ 0.981) was performed using the CrysAlis software
package [27]. Solution, refinement and analysis of the structure
were done using the programs integrated in WinGX system [28].
The structures were solved by the direct methods (SHELXS) [29]
and refined by the full-matrix least-squares method based on F2
against all reflections (SHELXL-97) [30]. The non-hydrogen atoms
were refined anisotropically. All hydrogen atoms were located in
the difference Fourier maps; those bound to nitrogen atoms were
refined using restraints on the NϪH distances, whereas others were
refined using the riding model. All hydrogen atoms were assigned
isotropic thermal parameters, Uiso(H) ϭ 1.2Ueq(parent atom). Geo-
metrical calculations were performed using PLATON [31] and the
structural figures were made using PLATON and ORTEP-3 [32].
(CϭN), 1548 (CϪO), 972 (MoϭO), 763 (MoϪOϪMo) cmϪ1
.
Synthesis of
[Mo2O3{C6H4(O)CH:NN:C(S)NHC6H5}2]·CH3CN (3)
Yield: 0.06 g, 31 % (method A, obtained from 3a). Yield: 0.084 g,
73 % (method B, obtained from the reaction of [Mo2O3(acac)4] with
H2L3). C30H25Mo2N7O5S2 (Mr ϭ 819.57): C 43.96; H 3.07; N
11.96; S 7.83. Found: C 43.40; H 2.85; N 11.79; S 8.24. TG: 4.79 %
CH3CN (calcd. 5.01 %); 34.98 % MoO3 (calcd. 35.13 %). Selected
IR data: ν˜ ϭ 1599, 1579 (CϭN), 1543 (CϪO), 967 (MoϭO), 755
(MoϪOϪMo) cmϪ1
.
NMR Spectroscopy
Synthesis of [Mo2O3{C10H6(O)CH:NN:C(S)NH2}2] (4)
One- and two-dimensional (1H, APT, gCOSY, gHSQC and
gHMBC) NMR spectra were recorded at ambient temperature with
the Avance DRX500 spectrometer using a 5 mm diameter inverse
detection probe with z-gradient. The spectra were recorded in
[D6]DMSO and CDCl3 with the sample concentration of 20 mg
mLϪ1 and TMS as the internal standard.
Yield: 0.09, 47 % (method A, obtained from 4a). Yield: 0.04 g, 36 %
(method B, obtained from the reaction of [Mo2O3(acac)4] with
H2L4). C24H18Mo2N6O5S2 (Mr ϭ 726.449): C 39.68; H 2.50; N
11.57; S 8.83; Found: C 39.20; H 2.75; N 11.39; S 8.45. TG: 39.38 %
MoO3 (calcd. 39.63 %). Selected IR data: ν˜ ϭ 1594, 1575 (CϭN),
1543 (CϪO), 959 (Mo ϭ O), 746 (MoϪOϪMo) cmϪ1
.
Typical spectral conditions for one-dimensional 1H and 13C (APT)
spectra were as follows. The spectra were recorded using 64K data
points and spectral widths of 6200 Hz and 20000 Hz for proton
and carbon (APT) experiments, respectively. Digital resolution was
Synthesis of [Mo2O3{C10H6(O)CH:NN:C(S)NHCH3}2]
(5)
Yield: 0.08 g, 43 % (method A, obtained from 5a). Yield: 0.07 g,
62 % (method B, obtained from the reaction of [Mo2O3(acac)4] with was 8Ϫ16 for H and 1000Ϫ3000 for APT spectra.
0.10 Hz and 0.30 Hz per point, respectively. The number of scans
1
Z. Anorg. Allg. Chem. 2009, 1242Ϫ1248
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
1247

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V. Vrdoljak, D. Milic, M. Cindric, D. Matkovic-Calogovic, J. Pisk, M. Markovic, P. Novak
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increments. Spectra were zero-filled in the f1 dimension to 1 K and
processed using an unshifted sine bell window function. Digital
resolution was 3.91 Hz per point in both dimensions.
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acquisition matrix of 1 K x 256 with 32 scans and processed with
2 K ϫ 1 K transformed matrix. The sweep width was 7500 Hz in
f2 dimension and 31500 Hz in f1 dimension for both experiments.
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and linear prediction. Digital resolution was 3.25 Hz per point and
30.70 Hz per point in f2 and f1, respectively. HMBC spectra were
recorded using transfer delay for the evolution of long range CϪH
couplings of 60 ms.
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CCDC-683830 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
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Acknowledgement
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We thank Dr. Z. Veksli, Rudjer Boskovic Institute, Zagreb for
recording the EPR spectra. This research was supported by the
Ministry of Science, Education and Sports of the Republic of
Croatia, Grants nos. 119-1191342-1082, 119-1191342-1083 and
119-1193079-1084.
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Received: September 09, 2008
Published Online: May 11, 2009
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2009, 1242Ϫ1248