Novel tribochemically active metal chelates of aromatic azo ligands

Article abstract of DOI:10.1134/S1070328406090119

Novel Cu(II) and Pd(II) complexes with o-phenylaminoazo compounds were synthesized and studied by X-ray diffraction. Distorted tetrahedral chelate complex of Cu contains two six-membered CuN₃C₂ metal cycles. The complexes under study

Full text of DOI:10.1134/S1070328406090119

ISSN 1070-3284, Russian Journal of Coordination Chemistry, 2006, Vol. 32, No. 9, pp. 686–691. © Pleiades Publishing, Inc., 2006.
Original Russian Text © A.S. Burlov, A.I. Uraev, K.A. Lysenko, G.G. Chigarenko, A.G. Ponomarenko, P.V. Matuev, S.A. Nikolaevskii, E.D. Garnovskaya, G.S. Borodkin,
A.D. Garnovskii, 2006, published in Koordinatsionnaya Khimiya, 2006, Vol. 32, No. 9, pp. 714–719.
Novel Tribochemically Active Metal Chelates
of Aromatic Azo Ligands
a
a
b
c
a
a
A. S. Burlov , A. I. Uraev , K. A. Lysenko , G. G. Chigarenko , A. G. Ponomarenko , P. V. Matuev ,
a
a
a
a
S. A. Nikolaevskii , E. D. Garnovskaya , G. S. Borodkin , and A. D. Garnovskii
a
Institute of Physical and Organic Chemistry, Rostov State University, pr. Stachki 194/3, Rostov-on-Don, 344104 Russia
b
Nesmayanov Institute of Organoelement Compounds, Russian Academy of Sciences,
ul. Vavilova 28, Moscow, 119991 Russia
c
Invek RD Ltd., Rostov-on-Don, Russia
Received June 3, 2005
Abstract—Novel Cu(II) and Pd(II) complexes with o-phenylaminoazo compounds were synthesized and stud-
ied by X-ray diffraction. Distorted tetrahedral chelate complex of Cu contains two six-membered CuN C metal
3
2
cycles. The complexes under study can be used as industrial lubricant additives.
DOI: 10.1134/S1070328406090119
Complex compounds of azo ligands are always in
Metal complexes of azo compounds have wide prac-
the focus of researchers’ attention [1–4]. Azo ligand tical application, including the production of dyes and
chelate complexes were used to establish and develop pigments [1, 8, 9].
important theoretical concepts about chelate isomeriza-
In this work, the most poorly studied atomatic azo
tion (realization of metal cycles with different members chelates with the MN coordination core are synthe-
4
in the molecule of a complex) [3–5], about stabilization sized and their structures are determined by X-ray dif-
as a result of complexation of different tautomeric fraction. Their tribochemical activity (the possibility of
forms of the ligand systems [4], and isolation of cis- using as lubricant addivites) is shown. Azo chelates are
trans-isomers [6, 7].
obtained by the following scheme:
Ph
Ph
N H
N M/2
5
6
T, °C
N N
R + MAc2
N N
R
(I)
(II)
2
+
2+
R = Me, M = Cu (a); R = Cl, M = Pd (b).
EXPERIMENTAL
reaction mixture was boiled on a water bath for 1 h and
cooled. The obtained precipitates of the complexes
were filtered off, washed twice with 5-ml portions of
methanol.
The complexes were recrystallized and their crystals
for X-ray diffraction analysis were grown from methyl-
Synthesis of ligands. The starting compounds I
were prepared according to the known procedures [1,
1
0], i.e., by diazotization of p-toluidine or p-chloroa-
niline and coupling with N-phenyl-2-naphthylamine.
Synthesis of complex compounds II. To a solution ene chloride–methanol mixture (1 : 2).
of 4-(2'-N-phenylaminonaphthylazo)toluene (0.67 g,
IIa. Dark brown crystals, í = 232–233°ë.
m
2
mmol) in 50 ml methanol, a solution of Cu acetate
monohydrate (0.2 g, 1 mmol) in 20 ml methanol was
added (IIa, M = Cu) or to a solution of 4-(2'-N-pheny-
laminonaphthylazo)chlorobenzene (0.72 g, 2 mmol) in
For ë ç N Cu
4
6
36
6
Anal. calcd. (%): ë 75.12; ç 4.95; N 11.35; Cu 8.55.
Found (%): ë 75.02; ç 4.93; N 11.41; Cu 8.63.
5
1
0 ml methanol, a solution of Pd acetate (0.22 g,
mmol) in 10 ml acetone was added (IIb, M = Pd). The
6
86

NOVEL TRIBOCHEMICALLY ACTIVE METAL CHELATES
687
IIb. Dark brown crystals, T = 203–204°C.
Table 1. The main crystallographic parameters and summa-
ry of data collection for structures IIa and IIb
m
For C H N ClPd
Value
44 30 6
Parameter
Anal. calcd. (%): C 64.51; H 3.70;N10.15; Cl 8.76;Pd 12.88.
IIa
IIb
Found (%):
C 64.44;H 3.69; N10.25; Cl 8.65;Pd 12.98.
M
736.35
Monoclinic
C2/c
820.04
Crystal system
Monoclinic
1
ç NMR, 300 MHz, ëDël , ppm: 4-(2'-N-pheny- Space group
P2 /c
3
1
laminonaphthylazo)chlorobenzene (Ib), 12.91 (1H, s,
NH), 8.88 (1H, d, J = 8.4 Hz, ç ), 7.88–7.23 (14H, m,
T, K
120
120
2
3
8
Z
8
4
H C H , 5ç ë ç , 5ç ë ç ); Pd complex IIb, 8.30
6 4 6 5 10 5
2H, d, J = 8.6 Hz, ç ) 7.79–6.83(28H, m, 8H C H ;
3
a, Å
b, Å
c, Å
β, deg
25.919(2)
12.3992(8)
23.476(2)
105.113(2)
7283.8(8)
1.343
8.4146(3)
17.4835(6)
12.2616(5)
97.987(1)
1786.4(1)
1.525
(
8
6
4
1
0H ë ç , 10ç ë ç ).
6
5
10
5
X-ray diffraction analysis. The experimental data
for single crystals IIa and IIb were collected on a
Bruker AXS SMART 1000 diffractometer equipped V, Å3
with CCD-detector (MoK radiation, λ = 0.71073 Å,
ρ (calcd), g cm–3
µ, cm–1
α
graphite monochromator, ω scan mode). The experi-
mental data were processed and averaged with the
SAINT-Plus program package [11], the absorption was
corrected by semiempirical method from equivalent
reflections [12].
6.42
7.12
2θmax, deg
58
58
Number of measured
reflections (Rint)
22550 (0.0358) 13638 (0.0253)
Number of independent
reflections
9614
6073
480
4715
3906
245
Structures IIa and IIb were solved by the direct
2
method and refined on F by least-squared method in
hkl
Number of reflections
anisotropic approximation for non-hydrogen atoms. with I > 2σ(I)
The H atoms were located geometrically and refined in
Number of refined pa-
rameters
the rider model. The main crystallographic parameters
and summary of data collection are presented in
Table 1. All calculations were performed with the
SHELXTL-Plus program package [13].
GOOF
0.982
0.0513
1.070
0.0597
R1
wR2
0.1251
0.0851
1
The H NMR spectra were measured on a Varian
∆
ρmax/∆ρmin, eÅ–3
0.77/–0.28
1.246/–0.891
Unity-300 instrument in CDël solution (300 MHz).
3
Tribochemical study was performed on a friction-test-
ing machine of AE-5 type.
coordination cores in analogous Ni complexes with
4
-aryl-5-aminopyrazoles (III) [16].
RESULTS AND DISCUSSION
R3
1
R = iso-Pr, Ph;
Me
N
N
Metal chelates II were synthesized by the direct
reaction of components, i.e., azo compound I and metal
acetates [5].
2
R = Ph, C H Me-p,
6
4
Ni/2
C H OMe-p, C H COOMe-p;
N
6
3
4
6
4
N
R2
N
R1
(
R = C H Me-p, C D .
6
4
6
5
1
The H NMR spectrum of Ib exhibits a pronounced
singlet from a proton of the NH group at 12.91 ppm,
which is absent in the case of the Pd complex IIb. This
fact indicates the formation of chelate structures of
type II.
III)
The question of stereochemistry of chelates II also
remained open [4, 6, 7]. These questions were solved in
the course of X-ray diffraction analysis of complexes IIa
2+
2+
Taking into account the literature data, the com- (M = Cu , R = CH ) and IIb (M = Pd , R = Cl). The
3
plexes under consideration were expected to contain data obtained showed that in the structures of chelates
five- and(or) six-membered metal cycles [3–7, 14]. In IIa (Fig. 1) and IIb (Fig. 2), as in the case with com-
the previous publication [15], Price proposed the for- plexes of type III and analogous complexes of azome-
mation of five-membered chelate rings in the Co com- thin series [4, 17, 18], two six-membered metal rings
2+
plexes similar to II (R = H, M = Co ), which were are closed. The analysis of bond lengths and bond
described in manual [1]. At the same time, X-ray dif- angles in structures IIa and IIb showed that aryl sub-
fraction data confirmed the formation of six-membered stituents contained in the ligands at atoms N(1) and
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 32 No. 9 2006

6
88
BURLOV et al.
C(20') C(21')
C(1M)
C(15)
C(14)
C(16)
C(11)
C(19')
C(22')
C(17')
C(9)
C(5)
C(13)
C(3')
C(10)
C(18')
N(2)
C(8)
C(7)
C(12)
C(4')
C(5')
C(6)
C(1)
N(1)
C(2')
C(1')
N(3')
C(7')
C(9')
Cu(1)
N(3)
C(6')
C(8')
C(2)
N(1')
C(16')
C(4)
N(2')
C(11')
C(3)
C(18)
C(17)
C(22)
C(10')
C(15')
C(12')
C(19)
C(14')
C(21)
C(13')
C(20)
C(1M')
Fig. 1. General view of complex IIa (the H atoms are omitted).
Cl(1A)
C(15A)
C(19)
C(14A)
C(13A)
C(20)
C(16A)
C(18)
C(21)
C(11A)
C(12A)
C(22)
N(2A)
C(9A)
C(10A)
C(6A)
C(4)
C(7) C(5)
C(17)
C(3)
C(2)
N(1A)
N(3)
Pd(1)
N(1)
C(8A)
C(1A)
C(6)
C(8)
N(3A)
C(1)
N(2)
C(2A)
C(7A)
C(5A)
C(4A)
C(17A)
C(11)
C(9) C(10)
C(3A)
C(12)
C(22A)
C(21A)
C(13)
C(14)
C(16)
C(18A)
C(20A)
C(19A)
C(15)
Cl(1)
Fig. 2. General view of complex IIb (the H atoms are omitted).
N(2) make these complexes sterically overloaded, as a aryl substituents of the neighboring chelates:
result of which their geometry is distorted.
ë(11)···ë(17') (ë(11')···ë(17)) 3.217(3) Å in IIa,
C(11)···C(17A) 3.074(3) Å in IIb. Note that the letter con-
Indeed, in both complexes, the aromatic substituents at
the N atoms have “face-to-face” arrangement, such that a tact is shorter than the contact between the planes of aro-
number of shortened contacts are realized between the matic rings in [2.2]-paracyclophane (3.099(1) Å) [19].
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 32 No. 9 2006

NOVEL TRIBOCHEMICALLY ACTIVE METAL CHELATES
689
Table 2. Selected bond lengths in structures IIa and IIb
IIa
IIb
bond
d, Å
bond
d, Å
bond
d, Å
Cu(1)–N(1)
Cu(1)–N(1')
Pd(1)–N(1)
1
.934(2)
1.947(2)
1.946(2)
1.297(2)
1.350(3)
1.330(3)
1.440(3)
1.470(3)
1.446(3)
1.349(3)
1.421(3)
1.402(3)
1.419(3)
1.403(3)
1.356(4)
1.395(4)
2.017(2)
2.029(2)
1.299(3)
1.339(3)
1.331(3)
1.446(3)
1.462(3)
1.461(3)
1.355(3)
1.423(4)
1.413(3)
1.407(3)
1.409(3)
1.382(4)
1.404(4)
Cu(1)–N(3)
N(1)–N(2)
N(2)–C(1)
N(3)–C(2)
C(1)–C(2)
C(1)–C(6)
C(2)–C(3)
C(3)–C(4)
C(4)–C(5)
C(5)–C(6)
C(5)–C(7)
C(6)–C(10)
C(7)–C(8)
C(8)–C(9)
1.940(2)
1.289(2)
1.353(3)
1.341(3)
1.433(3)
1.467(3)
1.446(3)
1.353(3)
1.425(3)
1.402(3)
1.423(3)
1.407(3)
1.375(3)
1.402(3)
Cu(1)–N(3')
N(1')–N(2')
N(2')–C(1')
N(3')–C(2')
C(1')–C(2')
C(1')–C(6')
C(2)–C(3)
C(3')–C(4')
C(4')–C(5')
C(5')–C(6')
C(5')–C(7')
C(6')–C(10')
C(7')–C(8')
C(8')–C(9')
Pd(1)–N(3)
N(1)–N(2)
N(2)–C(1)
N(3)–C(2)
C(1)–C(2)
C(1)-C(6)
C(2)–C(3)
C(3)–C(4)
C(4)–C(5)
C(5)–C(6)
C(5)–C(7)
C(6)–C(10)
C(7)–C(8)
C(8)–C(9)
Minimization of steric repulsion of substituents in base [20]) indicated that the violation of planarity of a
the complexes under study is realized due to distortion ring observed in IIb (the torsional angles
of the Cu coordination polyhedron in complex IIa and C(6)C(1)C(2)C(3) and C(1)C(2)C(3)C(4) are equal to
distortion of chelate in complex IIb.
21.1° and 18.3°) is maximum. In particular, analogous
torsional angles in IIa are 0.9° and 1.6°.
Thus, in complex IIa, the coordination polyhedron
of the Cu(1) atom is significantly distorted: the dihedral
angle between the planes Cu(1)N(1)N(2) and
Cu(1)N(1')N(2') is equal to 88.8°, the bond angles at the
Cu(1) atom vary within a range of 92.04(7)°–
In addition to the above mentioned distortions of
naphthalene ring, complex IIb also exhibits significant
twisting about the double bond N(1)=N(2) (the torsional
angles Pd(1)N(1)N(2)C(1) and C(1)N(1)N(2)C(11) are
equal to 28.3° and 167°, respectively). For comparison,
the corresponding torsional angles in IIa are equal to
1
38.94(8)°. In this case, six-membered metal rings
Cu(1)N(1)N(2)N(3)C(1)C(2)
and
8.6°–9.9° and 178°, respectively.
Cu(1)N(1')N(2)N(3')C(1')C(2') in IIa are sufficiently
flattened to give chair conformation with 0.36 and
Despite the observed ligand distortions, the bond
lengths in IIa and IIb are close: the differences for the
0
.27 Å deviation of the Cu(1) atom from the N C
3
2
plane, respectively. The angles of bending along the C(1)–C(6) ring do not exceed 0.015 Å (Table 2). Hence,
N(1)···N(3) and N(1')···N(3') lines are 9.6° and 11.3°, violation in the naphthalene ring planarity and twisting
respectively.
On the contrary, the Pd atom in complex IIb lies in
about the double bonds N=N do not result in weakening
of the π-system coupling of a ligand.
In order to study in detail the nature of intramolecu-
lar interactions in complexes II, we performed the
quantum-chemical calculations of chelate IIa in terms
of DFT (UPBEPBE/DGDZVP/DGA1). The full opti-
mization of the molecular geometry and further calcu-
lation of the electron density distribution function
the symmetry center and has ordinary square coordina-
tion, whereas metal rings and naphthalene fragment are
significantly distorted (Fig. 2). Unlike complex IIa, the
metal ring Pd(1)N(1)N(2)C(1)C(2)N(3) in complex IIb
has the conformation of a slightly twisted boat with the
Pd(1) and C(1) atoms deviating by 0.87 and 0.23 Å
from the plane N(1)N(2)C(2)N(3), respectively. The
angle of bending along the N(1)···N(3) line is equal to
(
r(r)) were performed with the G03W program pack-
age [21]. The topological analysis of ρ(r) in terms of
the Bader “atoms in molecules” (AM) theory [22] was
carried out with the MORPHY-98 program [23]. The
3
5.7°. As a result of the metal ring distortion, the naph-
thalene ring C(1)–C(6) in IIb is also distorted and
acquires the boat conformation with the C(2) and C(6) geometry of IIa obtained in the quantum-chemical cal-
atoms deviating from the plane C(1)C(3)C(4)C(5) by culation agrees well with the experimental data. Thus,
0
.22 and 0.10 Å, respectively. The analysis of molecules the Cu–N and N(1)–N(2) bond lengths in an isolated
containing analogous disubstituted naphthalene frag- complex are equal to 1.984–1.992 and 1.301 Å, respec-
ment (as follows from the Cambridge Structural Data- tively. A significant tetragonal distortion of the Cu
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 32 No. 9 2006

6
90
BURLOV et al.
polyhedron is also retained: the dihedral angle
Cu(1)N(1)N(2)/Cu(1)N(1')N(2') is equal to 72.4°,
while the bond angles NCuN vary within 92.9°–132.3°.
Note that the metal ring in an isolated molecule is flat-
tened and the angle of bending along the N(1)···N(3)
line does not exceed 3°. The metal ring flattening sub-
stantially strengthens the intramolecular contact
between the aryl substituents (ë(11)…ë(17') 3.457 Å).
Therefore, one can assume that flattening of a six-mem-
bered metal cycle confirmed by X-ray diffraction data
for complex IIa arises, first of all, due to steric repul-
sion of the aryl substituents.
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3
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