Molecular and Intracomplex Dioxomolybdenum(VI) Compounds with Substituted R1-Salycilidene-N-methylimines (HL): Crystal Structure of Three [MoO2(L)2] Complexes (R1 = H, 5-Br, 5-Cl)

Article abstract of DOI:10.1134/S003602361808020X

The synthesis and IR spectroscopic and X-ray diffraction studies of three [MoO₂(Lⁿ)₂] complexes with n = 1 (R = H, repeatedly) (I), n = 4 (R = Br) (II), and n = 3 (R = Cl) (III) have been performed. The molybdenum atoms in

Full text of DOI:10.1134/S003602361808020X

ISSN 0036-0236, Russian Journal of Inorganic Chemistry, 2018, Vol. 63, No. 8, pp. 1026–1031. © Pleiades Publishing, Ltd., 2018.
Original Russian Text © V.S. Sergienko, V.L. Abramenko, Yu.E. Gorbunova, 2018, published in Zhurnal Neorganicheskoi Khimii, 2018, Vol. 63, No. 8, pp. 989–995.
COORDINATION
COMPOUNDS
Molecular and Intracomplex Dioxomolybdenum(VI) Compounds
with Substituted R1-Salycilidene-N-methylimines (HL):
Crystal Structure of Three [MoO2(L)2]
Complexes (R1 = H, 5-Br, 5-Cl)
V. S. Sergienkoa, b, *, V. L. Abramenkoc, and Yu. E. Gorbunovaa
aKurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Moscow, 119991 Russia
bAll-Russia Institute of Scientific and Technical Information, Russian Academy of Sciences, Moscow, 125315 Russia
cDal’ East Ukrainian National University, Lugansk, 91034 Ukraine
*e-mail: sergienko@igic.ras.ru
Received August 7, 2017
Abstract⎯The synthesis and IR spectroscopic and X-ray diffraction studies of three [MoO2(Ln)2] complexes
with n = 1 (R = H, repeatedly) (I), n = 4 (R = Br) (II), and n = 3 (R = Cl) (III) have been performed. The
molybdenum atoms in the structures of complexes I–III have a typical octahedral coordination with dioxo
ligands in cis-positions, atoms N(Ln) in trans-positions to О(oxo), and atoms О(Ln) in cis-positions to oxo
ligands. Ligands Ln are bidentate chelate (N, O).
DOI: 10.1134/S003602361808020X
compounds, such as [МоО2(L1)2] (I), [МоО2(L4)2]
Salicylideneimines (о-oxyazomethines) (Scheme 1)
in the reaction with Lewis acids MLn form complexes
of two types, such as adducts or molecular complexes
(MCs) containing neutral ligand molecules and che-
lates representing intracomplex compounds (ICCs),
whose ligands are coordinated to the central atom in
the form of deprotonated anions. For Group VIB oxo
and dioxocations, the complexes with salicylidene-N-
aryl- and hetarylimines are best studied, but much less
attention has been paid to their complexes with sali-
cylidene-N-alkylimines. A major part of papers is
devoted to the synthesis and structural study of intra-
complex compounds [1]. The synthesis of intracom-
plex compounds was performed via the ligand
exchange between dioxomolybdenum(VI) acetylacet-
onate and a corresponding azomethine in boiling
alcohol. However, the reaction between molybdenum
dioxodichloride and salicylideneimines in a medium
of low-polarity solvents yields molecular complexes
[2–4].
(II), and [МоО2(L3)2] (III) were characterized by
X-ray diffraction. The structure of compound I was
determined anew (see below for details).
OH
N Me
Z
HLn : R1 = H (n = 1); 3-OMe (n = 2);
5-Cl (n = 3); 5-Br (n = 4); 3-NO2 (n = 5);
5-NO2 (n = 6); 3-OMe-5-Br (n = 7);
3,5-Br2 (n = 8); 5,6-cyclo-С4Н4 (n = 9).
Scheme 1.
EXPERIMENTAL
Synthesis. Salicylidene-N-methylimines were syn-
thesized via the coupling of corresponding substituted
salicylic aldehydes and methylamine in boiling etha-
nol. After recrystallization from ethanol, they repre-
sented crystalline lemon powders (HL1 is a liquid at
room temperature, and HL2 is orange crystals).
For the further study of conditions for the synthesis
of complex compounds of different types and the
broadening of information about the structure of com-
plexes formed by Group VIB dioxocations with о-oxy-
azomethines, the synthesis of dioxomolybdenum(VI)
Molecular complexes like МоО2Сl2 ⋅ 2HLn were
complexes with imines, derivatives of substituted sali- synthesized by the immediate reaction between
cylic aldehydes and methylamine (HLn) was per-
МоО2Сl2 and о-oxyazomethines in a medium of low-
formed, and their structures and properties were polarity solvents. In diethyl ether, these complexes are
investigated. The structures of three intracomplex formed with a nearly quantitative yield. To a solution
1026

MOLECULAR AND INTRACOMPLEX DIOXOMOLYBDENUM(VI) COMPOUNDS
1027
Table 1. Crystallographic data and selected characteristics of X-ray diffraction experiment for the structures of complexes
I–III
Parameter
I
II
III
Formula weight
Color, habit
Crystal size
Symmetry system, space group
396.25
Yellow, block
0.15 × 0.10 × 0.05
Orthorhombic, P212121
6.631(1)
554.05
Yellow, block
0.18 × 0.08 × 0.05
Monoclinic, С2/c
19.312(1)
465.13
Yellow, block
0.18 × 0.09 × 0.05
Monoclinic, С2/c
18.976(1)
a, Å
b, Å
c, Å
β, deg
Z
12.841(1)
19.501(1)
9.398(1)
13.595(1)
131.30(1)
9.561(2)
13.481(1)
132.24(3)
90
4
4
4
ρ
calcd, g/cm3
1.586
1.985
1.706
Mo, mm–1
9.810
800
5.041
1.042
926
μ
F(000)
1072
Radiation (λ, Å)
Т, K
Scanning type
Range of θ, deg
Index ranges
MoKα (0.71073), graphite monochromator
393
ω
2.58–25.96
2.09–27.97
2.58–26.00
–1 ≥ h ≥ 8, –1 ≥ k ≥ 16,
–23 ≥ l ≥ 23
–1 ≥ h ≥ 23, –1 ≥ k ≥ 11,
–16 ≥ l ≥ 13
–18 ≥ h ≥ 14, –9 ≥ k ≥ 9,
–1 ≥ l ≥ 12
Total number of reflections/
5507/3945 [0.0690]
2247/1989 [0.0647]
1906/850 [0.0525]
independent [R(int)]
Completeness over θ, %
Number of reflections
98.7
1713
100.0
851
100.0
688
with I ≥ 2σ(I)
Absorption correction
Tmin/Tmax
Semiempirical, by equivalents
0.8881/0.9606
209
0.4639/0.7867
115
0.8346/0.9497
110
Number of refined parameters
GOOF on F2
0.920
0. 849
1.104
R [I ≥ 2σ(I)]
R (all data)
R1 = 0.0289, wR2 = 0.0655 R1 = 0.0319, wR2 = 0.0769 R1 = 0.0991, wR2 = 0.2125
R1 = 0.1930, wR2 = 0.0886 R1 = 0.1472, wR2 = 0.2095 R1 = 0.1148, wR2 = 0.2285
Residual electron density
(max/min), e/Å3
0.493/–1.159
0.606/–0.852
2.430/–2.576
of molybdenum dioxodichloride (0.199 g, 0.001 mol) reaction mixture was boiled for 10–15 min and
in absolute diethyl ether (20 mL), a solution of corre- allowed to stand at room temperature for crystalliza-
sponding azomethine (0.002 mol) was added drop by tion. The settled crystals of complexes were filtered out,
drop under stirring on a magnetic agitator. The formed washed on a filter with cold methanol, and dehumidi-
precipitates of complexes were separated out on a fied first in a dry air flow and then in vacuum desiccator
Schott glass filter equipped with a drying system, over СаСl2. The yield of complexes was 85–90%.
washed with ether, and dehumidified in a dry argon
Elemental analysis for molybdenum, chlorine, and
flow.
nitrogen was performed as described in [4] by standard
The intracomplex compounds [МоО2(Ln)2] were
methods.
synthesized via the ligand exchange between molybde-
IR spectra were recorded on an IKS-29 spectrom-
eter as Nujol mulls.
num acetylacetonate and corresponding azomethines.
To a hot solution of МоО2(Асас)2 (0.326 g, 0.001 mol)
in methanol (20 mL) a methanol solution of azome-
X-ray diffraction analysis. Experimental data for
thine (0.002 mol) was added drop by drop, and the crystals of complexes I–III were obtained on an
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1028
SERGIENKO et al.
Table 2. Selected bond lengths and bond angles in the
structure of complex I
Enraf-Nonius CAD-4 automatic diffractometer. The
structures were solved by direct methods (SHELXS-86)
[5] and refined by the least-squares technique in the
full-matrix anisotropic approximation for all non-
hydrogen atoms (SHELXL-97) [6]. The positions of
hydrogen atoms were calculated geometrically and
included into refinement “as riding”. It has been
established that a crystal of complex I is a racemic twin
(0.52(2) : 0.48(6)). The low quality of a crystal of com-
plex III (and its obvious propensity to twinning) leads
to high R-factors. Unit cell parameters and selected
characteristics of X-ray diffraction experiment for the
structures of complexes I–III are given in Table 1,
bond length and bond angles are listed in Table 2 for
complex I and Table 3 for complexes II and III. Com-
plete crystallographic data were deposited with the
Cambridge Structure Database (nos. 1565270 (I),
1562990 (II), and 1565241 (III); http://www.ccdc.
cam.ac.uk/deposit/.
Bond
d, Å
Bond
d, Å
Mo(1)–O(1)
Mo(1)–O(2)
Mo(1)–O(4)
Mo(1)–O(3)
Mo(1)–N(1)
Mo(1)–N(2)
1.698(4)
1.700(4)
1.940(4)
1.963(3)
2.322(5)
2.341(4)
O(3)–C(1)
O(4)–C(7)
N(1)–C(13)
N(1)–C(15)
N(2)–C(14)
N(2)–C(16)
1.345(6)
1.337(6)
1.282(6)
1.463(6)
1.279(6)
1.475(6)
Angle
ω, deg
Angle
ω, deg
O(1)Mo(1)O(2) 107.56(19) N(2)C(14)C(8) 125.7(5)
O(1)Mo(1)O(4) 96.53(17) C(1)O(3)Mo(1) 127.4(3)
N(1)Mo(1)N(2) 76.30(15) C(13)N(1)Mo(1) 122.7(4)
O(3)Mo(1)N(2) 84.03(17) C(7)O(4)Mo(1) 133.3(3)
O(2)Mo(1)O(4) 97.59(17) C(13)N(1)C(15) 116.1(5)
O(1)Mo(1)O(3) 94.94(18) C(15)N(1)Mo(1) 121.2(4)
O(2)Mo(1)O(3) 96.03(16) C(14)N(2)C(16) 116.5(5)
O(4)Mo(1)O(3) 158.64(18) C(14)N(2)Mo(1) 122.8(4)
O(1)Mo(1)N(1) 89.07(18) C(16)N(2)Mo(1) 120.6(3)
RESULTS AND DISCUSSION
Independently of the ratio between reacting com-
ponents, the reaction of МоО2Сl2 with salicylidene-
N-methylimines in a low-polarity solvents results in
molecular complexes of the only composition
МоО2Сl2 ⋅ 2HLn (Table 4) representing amorphous
powders, which are hydrolyzable in air and readily sol-
uble in methanol with the formation of electrically
conductive solutions.
O(2)Mo(1)N(1) 163.22(18) O(3)C(1)C(2)
O(4)Mo(1)N(1) 82.39(18) O(3)C(1)C(6)
O(3)Mo(1)N(1) 79.85(18) O(4)C(7)C(8)
119.3(5)
121.2(5)
121.7(5)
O(1)Mo(1)N(2) 165.30(16) O(4)C(7)C(12) 118.5(5)
O(2)Mo(1)N(2) 87.13(17) N(1)C(13)C(6) 125.6(5)
O(4)Mo(1)N(2) 80.32(16) N(2)C(14)C(8) 125.7(5)
In contrast to the molecular complexes, the slow crys-
tallization of intracomplex compounds [МоО2(Ln)2]
from methanol solutions results in well-shaped crys-
tals melting at a much higher temperature than the
corresponding adducts. The studied intracomplex
compounds are stable in air and poorly soluble in cold
polar solvents, but well soluble in methanol under
heating, dimethyl sulfoxide, and dimethyl sulfamide
to form electrically unconducive solutions.
the stretching vibrations of the C=N bond of ben-
zenoid (enolimine) tautomer a (Scheme 2):
MXn
MXn
OH
O
H
N
N
Certain information necessary to determine the
type of formed complex and the position of coordina-
tion bonds between metals and azomethines can be
acquired by studying their IR spectra in the region of
1500–1700 cm–1, in which several absorption bands
can be distinguished for non-coordinated salicylide-
neimines. Of the greatest interest is the high-fre-
quency band at 1620–1635 cm–1 assigned to the
stretching vibrations of the С=N azomethine group
[7]. When an intracomplex compound is formed, the
ν(С=N) absorption band shiftstoward lower frequen-
cies, thus indicating that the nitrogen atom of the
С=N group participates in donor–acceptor interac-
tion. The same region in the spectra of molecular
complexes contains an intense band at ~1650 cm–1,
which should be assigned with the highest probability
to the downshifted band of quinoid (ketoamine) tau-
Z
R
R
Z
m
m
а
b
Scheme 2.
The available scanty literature data on the X-ray
diffraction analysis of molecular complexes of some
metals with о-oxyazomethines [8–11] also confirms
the coordination of ligands in quinoid tautomeric
form b.
The intense absorption bands in the region of 900–
950 cm–1 can be assigned to the symmetric and anti-
symmetric stretching vibrations of the Мо=О bond in
the cis-МоО2 group [12]. New absorption bands
appear in the low-frequency region of the IR spectra
of these complexes at 565–590 cм–1 (MC spectra) and
tomer b instead of the complexation upshifted band of 520–540, 470–475 cm–1 (ICC spectra) and should be
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Table 3. Selected bond lengths (d) and bond angles (ω) in the structures of complexes II and III*
II
Bond
d, Å
Bond
d, Å
Mo(1)–O(2)
Mo(1)–N(1)
O(1)–C(1)
N(1)–C(8)
1.689(4)
2.332(5)
1.342(7)
1.481(8)
Mo(1)–O(1)
Br(1)–C(4)
N(1)–C(7)
1.950(4)
1.901(7)
1.272(8)
Angle
ω, deg
Angle
ω, deg
O(1)#1Mo(1)O(2)
O(1)Mo(1)N(1)
O(2)Mo(1)O(1)#1
O(2)Mo(1)N(1)
O(2)Mo(1)O(1)
O(1)#1Mo(1)O(1)
O(2)Mo(1)N(1)#1
O(1)Mo(1)N(1)#1
N(1)C(7)C(6)
108.4(3)
79.5 (2)
95.7(2)
86.8(2)
96.6(2)
158.9(2)
164.6(2)
84.2(2)
125.9(6)
C(1)O(1)Mo(1)
C(7)N(1)C(8)
C(7)N(1)Mo(1)
C(8)N(1)Mo(1)
O(1)C(1)C(3)
O(1)C(1)C(6)
C(3)C(4)Br(1)
C(5)C(4)Br(1)
128.3(3)
117.5(5)
121.9(4)
120.3(4)
118.0(5)
122.6(5)
118.1(5)
120.4(5)
III
Bond
d, Å
Bond
d, Å
Mo(1)–O(2)
Mo(1)–N(1)
N(1)–C(8)
1.687(9)
2.329(11)
1.465(19)
Mo(1)–O(1)
N(1)–C(7)
O(1)–C(6)
1.978(8)
1.291(19)
1.334(16)
Angle
ω, deg
Angle
ω, deg
O(2)#1Mo(1)O(2)
O(2)#1Mo(1)O(1)
O(2)Mo(1)O(1)
O(1)Mo(1)O(1)#1
O(2)Mo(1)N(1)
O(1)Mo(1)N(1)
O(1)Mo(1)N(1)#1
C(4)O(1)Mo(1)
108.7(6)
96.9(4)
95.9(4)
157.9(5)
86.8(4)
79.4(4)
83.4(4)
129.5(7)
O(2)C(6)C(5)
O(1)C(6)C(1)
C(7)N(1)C(8)
C(7)N(1)Mo(1)
C(8)N(1)Mo(1)
O(2)Mo(1)N(1)#1
O(1)Mo(1)N(1)#1
N(1)C(7)C(1)
119.3(12)
119.3(12)
117.5(11)
121.0(8)
121.2(10)
164.5(4)
79.4(4)
125.6(12)
* Symmetry codes in the structures of complexes II and III: #1 –x, y, –z + 1/2.
assigned to the stretching vibrations of the Мо–ОHL
and Мо–NL, Мо–ОL bonds [4], respectively.
,
tonated hydroxo groups of salicylideneimines in trans-
positions to each other.
The structures of intracomplex compounds I–III
were established by X-ray diffraction. The crystal
structure of compound I was characterized earlier by a
photographic method (Ia) [15] at a low precision
(R-factor = 7%). Our study is more precise (R = 3.2%)
despite the twin nature of a single crystal of compound I.
Crystals of compounds II and III are isostructural.
Since the structure of a twin crystal of compound III
was determined at a low precision, we shall operate
with the data on the structure of compound II in the
discussion of results. The molybdenum atoms in com-
pounds I–III have an octahedral coordination. The
structures of complexes I and III are shown in Fig. 1
Based on the obtained experimental results and the
literature data [13], it is possible to conclude that the
studied dioxomolybdenum(VI) MCs and ICCs with
substituted salicylidene-N-methylimines have an
octahedral structure with two multiply bonded oxo
ligands in cis-positions as typical for Group VIB oxo-
and dioxocations. In addition to the terminal oxygen
atoms, the vertices of MC octahedra are occupied by
two carbonyl oxygen atoms of the quinoide tautomeric
form of oxoazomethines in trans-positions to oxo
ligands according to the “self-consistency rule” [14]
and two chlorine atoms in trans-positions to each
other. The vertices of ICC octahedra are occupied by and Fig. 2, respectively. Similarly to all the other dioxo
complexes of Group V–VII metals d0-M5 + x (x = 0–2;
two multiply bonded terminal oxygen atoms in cis-
positions, two donating nitrogen atoms in trans-posi-
M = V5+, Nb5+, Mo6+, W6+, Tc7+, Re7+), the O(oxo)
tions to oxo ligands, and two oxygen atoms of depro- ligands in compounds I–III are in cis-positions to
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MOLECULAR AND INTRACOMPLEX DIOXOMOLYBDENUM(VI) COMPOUNDS
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different antisymmetric conformation. In a crystal of
compound I, the neighboring Мо(1) and N(1) atoms
of the Mo(1)–N(1)–C(1)–C(2)–C(3)–O(3) chelate
ring deviate at 1.136 and 0.304 Å, respectively, in the
same direction from the plane of nearly coplanar
( 0.003–0.063 Å) О(3) and С(1)–C(3) atoms, while
the neighboring Мо(1) and О(4) atoms of the Мо(1)–
N(2)–C(11)–C(12)–C(17)–О(4) chelate ring deviate
at –0.506 and +0.148 Å, respectively, in different
directions from the plane of nearly coplanar ( 0.015–
0.033 Å) N(2), C(11), C(12), and С(17) atoms. The
similar Мо(1)–N(1)–C(7)–C(6)–C(1)–O(1) che-
late ring in the structure of complex II has a “sofa”
conformation, where the Mo(1) atom deviates at 0.896 Å
from the plane of the other five nearly coplanar
( 0.022–0.077 Å) atoms.
С(9)
С(14)
N(2)
С(10)
С(8)
С(16)
O(2)
С(11)
O(3)
С(7)
O(4)
С(12)
Mo(1)
N(1)
С(1)
С(5)
С(2)
С(4)
O(1)
С(13)
С(15)
С(3)
С(6)
Fig. 1. Structure of complex I.
The structures of compounds I–III contain no
short intermolecular contacts that would correspond
to hydrogen bonds.
Br(1)
С(5)
С(4)
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Translated by E. Glushachenkova
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 63 No. 8 2018