Binuclear nickel(II) complexes with 3,5-di-tert-butylbenzoate and 3,5-di-tert-butyl-4-hydroxybenzoate anions and 2,3-lutidine: the synthesis, structure, and magnetic properties

Abstract

Two novel binuclear nickel(II) complexes [Ni2(O2CR)4(2,3-lut)2] (O2CR is anion of 3,5-di(tert-butyl)benzoic acid (bzo, 1) and 4-hydroxy-3,5-di(tert-butyl)benzoic acid (hbzo, 2); 2,3-lut is 2,3-lutidine) with four carboxylate bridges were synthesized. The structure of complex 1 was determined by X-ray diffraction. Both dimers 1 and 2 were characterized by elemental analysis, IR spectroscopy, and magnetic measurements. The presence of the α-substituent in the apical lutidine ligand leads to a distortion of the geometry of the metal carboxylate core in complex 1 as a result of short steric contacts Me(Lut)…O(OOCR) (3.134(7) Å). This is apparently responsible for a considerable decrease in the exchange parameters of complexes 1 and 2 (J =–30.0 and–23.6 cm–1, respectively) as compared to known analogues. Density functional calculations of the structure and magnetic properties of 1 and 2 were carried out by the UB3LYP/6-31G(d,p) method.

Full text

Russian Chemical Bulletin, International Edition, Vol. 65, No. 12, pp. 2812—2819, December, 2016
2812
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2812—2819, December, 2016.
10665285/16/65122812 © 2016 Springer Science+Business Media, Inc.
Binuclear nickel(II) complexes with 3,5ditertbutylbenzoate
and 3,5ditertbutyl4hydroxybenzoate anions and 2,3lutidine:
the synthesis, structure, and magnetic properties*
S. A. Nikolaevskii,a M. A. Kiskin,a A. A. Starikova,b N. N. Efimov,a A. A. Sidorov,a
V. M. Novotortsev,a and I. L. Eremenkoa
aN. S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences,
31 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (495) 952 1279. Email: sanikol@igic.ras.ru
bInstitute of Physical and Organic Chemistry at Southern Federal University,
194/2 prosp. Stachki, 344090 RostovonDon, Russian Federation.
Fax: +7 (863) 243 4700. Email: alstar@ipoc.sfedu.ru
Two novel binuclear nickel(II) complexes [Ni2(O2CR)4(2,3lut)2] (O2CR is anion of
3,5di(tertbutyl)benzoic acid (bzo, 1) and 4hydroxy3,5di(tertbutyl)benzoic acid (hbzo, 2);
2,3lut is 2,3lutidine) with four carboxylate bridges were synthesized. The structure of complex
1 was determined by Xray diffraction. Both dimers 1 and 2 were characterized by elemental
analysis, IR spectroscopy, and magnetic measurements. The presence of the αsubstituent in
the apical lutidine ligand leads to a distortion of the geometry of the metal carboxylate core in
complex 1 as a result of short steric contacts Me(Lut)…O(OOCR) (3.134(7) Å). This is appar
ently responsible for a considerable decrease in the exchange parameters of complexes 1 and 2
(J = –30.0 and –23.6 cm–1, respectively) as compared to known analogues. Density functional
calculations of the structure and magnetic properties of 1 and 2 were carried out by the UB3LYP/
631G(d,p) method.
Key words: nickel(II) complexes, carboxylate complexes, Xray diffraction, magnetic prop
erties, quantum chemical calculations.
An analysis of published data on binuclear carboxyl
ates of 3d transition metals shows that these systems
are still of increased interest for researchers working
in different areas of science in spite of intensive re
search carried out in the last decades. Although the
emphasis is placed on unique catalytic1—5 and other
important properties of these complexes, recently partic
ular attention has been paid to the use of the complex
es as building blocks for chemical engineering of com
plex polynuclear architectures including coordination
polymers of different dimension,6 as well as metalorganic
frameworks.7—16 The use of magnetically active coor
dination binuclear carboxylates [LM(μO2CR)4ML]
(M = MnII, FeII, CoII, NiII, and CuII) as either pristine
or modified building blocks for chemical assembly of
more complicated polynuclear structures including com
binations in novel heteronuclear molecular architectures
suggests the possibility to design unusual molecular mag
netic systems including singlemolecule magnets. Partic
ular attention should be paid to binuclear magnetic sys
tems that exhibit magnetostructural correlations, includ
ing the possibility of varying the type and energy para
meters of spinspin exchange depending on (i) the nature,
number, and structural features of the bridging carboxyl
ate groups, (ii) the electronic structure and geometry
of the apical ligands L, and (iii) the distance between
the magnetic metal centers, which undoubtedly is of
great importance when choosing a starting binuclear
material.17—19
In this work, we studied two novel molecular binuclear
nickel(II) complexes with the 3,5di(tertbutyl) (bzo) and
4hydroxy3,5di(tertbutyl)benzoate (hbzo) anions and
2,3lutidine (2,3lut) as apical ligands, which extend
the number of known compounds of the general formula
[Ni2(O2CR)4L2].7—12,20—39 We have determined the
molecular structure of the title compounds and studied
their paramagnetic properties in the temperature range of
2—300 K. The results obtained were used to approximate
the experimental temperature dependence of χT. Quan
tum chemical calculations of the complexes were also
carried out.
* Dedicated to Academician of the Russian Academy of Sciences
R. Z. Sagdeev on the occasion of his 75th birthday.

Synthesis and structure of binuclear Ni complexes Russ.Chem.Bull., Int.Ed., Vol. 65, No. 12, December, 2016 2813
Results and Discussion
Among numerous known binuclear complexes with
four carboxylate bridges [LM(μO2CR)4ML] (M = MnII,
CoII, FeII, NiII, CuII) with various donor apical ligands,40—42
the number of structurally characterized nickel(II) deriva
tives is relatively small. This is probably due to facile
formation of a moiety with three bridges {Ni(μH2O)
(μO2CR)2Ni} in the presence of even trace amounts of
water in the reaction medium.24,26 The situation can be to
some extent changed by assembling NiII dimers with four
carboxylate bridges from carboxylate anions with bulky
substituents and bulky apical ligands, which makes the
incorporation of water molecules between nickel ions im
possible, especially if substituents at carboxylate anions as
well as apical ligands bear hydrophobic, e.g., alkyl, groups.
Therefore, in this work novel carboxylate dimers contain
ing nickel ions were synthesized using 3,5di(tertbutyl)
benzoate (bzo) and 4hydroxy3,5di(tertbutyl)benzoate
(hbzo) anions and 2,3dimethylpyridine (lutidine) contain
ing alkyl groups. It was found that, although the reaction
mixture contained nickel(II) chloride solvated by water
molecules and ethanol (96%), the reactions of nickel chloride
and potassium salts of the acids cited above afford com
plexes [Ni2(O2CR)4(2,3lut)2] (O2CR = bzo (1), hbzo (2)).
According to Xray data, compound 1 crystallizes in
the space group P1
– with no solvate molecules (Fig. 1).
The inversion center lies between the Ni(1) and Ni(1A)
atoms of the binuclear molecule. The Ni(1) atom coordi
nates four O atoms of four bridging carboxylate groups
and the N atom of the 2,3lutidine molecule, thus forming
a distorted squarepyramidal environment (nickel atom
deviates from the O4 plane by 0.251(2) Å). The bond
lengths in the coordination unit and the Ni...Ni distance
(Table 1) are typical of the dimers having four carboxylate
bridges,20—39 although, unlike most analogues, complex 1
has a distorted N—Ni—Ni—N fragment. Deviation from
linearity (Ni—Ni—N angle is 152.23(14)°) can be appar
ently caused by steric effects of the methyl group in posi
tion 2 of the 2,3lutidine molecule (Me(Lut)...O(OOCR)
distance is 3.134(7) Å).
The angles between the aromatic ring planes and carb
oxylate groups are 11.1(2)° and 4.0(4)° for C(2)—C(7)
and O(1)C(1)O(2), C(17)—C(22) and O(3)C(16)O(4),
respectively. The angle between the C(2)—C(7) and
C(17)—C(22) aromatic rings is 84.2(2)°, while the angle
between the O(1)C(1)O(2) and O(3)C(16)O(4) carboxyl
ate group planes is 89.4(7)°. The coordinated 2,3lutidine
molecule deviates from the C(2)—C(7) and C(17)—C(22)
aromatic ring planes by 60.0(2)° and 19.6(2)°, respectively.
Note that the C(37)...O(4) distance is 3.134(7) Å, being
much shorter than the sum of the corresponding van der
Waals radii (3.22 Å).43 Earlier, shortened contacts be
tween the αmethyl group of the coordinated 2,3lutidine
molecule and the nearest O donor atoms of the carboxylate
anion were observed for complex [Ni2(piv)4(2,4lut)2] (piv
is pivalate anion and 2,4lut is 2,4lutidine).21 This specif
ic interaction causes the C(35)N(1)Ni(1) angle to increase
by 13.5° compared to the C(31)N(1)Ni(1) angle. An anal
ysis of the molecular packing shows that molecules in the
complex are isolated from one another. Selected bond
lengths and bond angles in complex 1 are listed in Table 1.
Fig. 1. Molecular structure of complex 1 (hydrogen atoms are
not shown).
Note. Fig. 1 is available in full color on the web page of the
journal (http://www.link.springer.com).
C(19)
C(20)
C(21)
C(22)
C(18)
C(17)
C(32) C(31)
C(33)
C(34)
C(36) C(37)
C(35)
N(1)
O(3)
O(4)
O(1A)
O(2A)
Ni(1) O(2)
O(3A)
O(1)
O(4A)
Ni(1A) N(1)
C(37A)
C(36A)
C(34A)
C(33A)
C(32A)
C(31A)
C(35A)
Table 1. Selected bond angles (ω) and bond lengths (d) in
complex 1
Angle ω/deg Bond d/Å
O(1)—C(1)—O(2) 123.1(5) Ni(1)—O(1) 2.040(4)
O(3)—C(16)—O(4) 126.7(5) Ni(1)—O(2) 2.101(4)
O(1)—Ni(1)—O(2) 165.1(2) Ni(1)—O(3) 2.017(4)
O(1)—Ni(1)—O(3) 189.5(2) Ni(1)—O(4) 1.997(4)
O(1)—Ni(1)—O(4) 191.7(2) Ni(1)—N(1) 2.044(5)
O(2)—Ni(1)—O(3) 186.5(2) Ni(1)...Ni(1) 2.720(2)
O(2)—Ni(1)—O(4) 188.9(2) C(1)—O(1) 1.264(6)
O(3)—Ni(1)—O(4) 166.1(2) C(1)—O(2) 1.255(6)
O(1)—Ni(1)—N(1) 102.3(2) C(16)—O(3) 1.261(6)
O(2)—Ni(1)—N(1) 192.2(2) C(16)—O(4) 1.251(6)
O(3)—Ni(1)—N(1) 191.6(2) C(31)—N(1) 1.352(7)
O(4)—Ni(1)—N(1) 101.6(2) C(35)—N(1) 1.355(7)
N(1)—Ni(1)—Ni(1A) 152.23(14) C(31)—C(32) 1.362(8)
C(31)—N(1)—Ni(1) 113.7(4) C(32)—C(33) 1.374(9)
C(35)—N(1)—Ni(1) 127.2(4) C(34)—C(35) 1.399(8)

Nikolaevskii et al.2814 Russ.Chem.Bull., Int.Ed., Vol. 65, No. 12, December, 2016
We failed to obtain single crystals of complex 2 as yet,
but elemental analysis data suggest that the composition
of 2 exactly corresponds to the binuclear structure
[Ni2(hbzo)4(2,3lut)2]. An analysis of the IR spectra of 2
revealed a band at 3603 cm–1 corresponding to OH group.
Also, the spectra exhibit characteristic bands in the region
1620 cm–1 (1) and 1618 cm–1 (2), as well as at 1392 cm–1
(1) and 1384 cm–1 (2), which correspond to symmetric
(νs) and antisymmetric (νas) vibrations of carboxylate
groups. The νs – νas difference is 228 cm–1 for 1 and
234 cm–1 for 2, which is typical of the bridging coordina
tion of carboxylate groups. The absence of peaks in the
region 1700 cm–1 for both compounds suggests deproto
nation of all carboxylic groups.44,45
Our studies of the temperature dependences of the mag
netic susceptibility of compounds 1 and 2 in the tempera
ture range of 2—300 K revealed antiferromagnetic inter
actions (Fig. 2). The magnetic moment (μeff) is 4.19 μB
(χexpT = 2.20 cm3 K mol–1) for 1 and 4.20 μB
(χexpT = 2.21 cm3 K mol–1) for 2 at 300 K, being some
what higher than the theoretical value obtained for two
noninteracting Ni2+ ions (S = 1): μcalc = 4 μB (χcalcT =
= 2.02 cm3 K mol–1).46 As the temperature decreases to 2 K,
the effective magnetic moment decreases to 0.25 μB
(χexpT = 0.01 cm3 K mol–1) for 1 and 0.42 μB (χexpT =
= 0.02 cm3 K mol–1) for 2. At 100 < T < 300 K, the χ–1(T)
dependence is linear for both compounds (see Fig. 2, c, d),
being satisfactorily described by the Curie—Weiss equa
tion χM = C/(T – θ) with the parameters listed in Table 2.
The Weiss constant is highly negative for both compounds.
The considerable decrease in the magnetic moment and
the negative sign of the Weiss constant are indicative of
strong antiferromagnetic interactions in the samples.
To determine the exchange parameter, experimental
data χT(T) for the entire temperature range studied were
approximated by the van Vleck equation for S1 = S2 = 1
Fig. 2. Temperature dependences of magnetic susceptibility (1) and χT (2) of compounds 1 (a) and 2 (b) and the corresponding 1/χ(T)
plots (c, d). Closed and open circles as well as open squares denote experimental data; solid lines denote results of calculations.
1.2
0.9
0.6
0.3
χ•10–2/cm3 mol–1
2
1
0
χT/cm3 K mol–1
0 100 200 T/К
a
1.5
1.2
0.9
0.6
0.3
χ•10–2/cm3 mol–1
2
1
0
χT/cm3 K mol–1
0 100 200 T/К
b
1.4
1.2
1.0
0.8
1/χ•102/mol cm–3
200 300 T/К
с
1.4
1.2
1.0
0.8
1/χ•102/mol cm–3
200 300 T/К
d
1
2
1
2
Table 2. Bestfit parameters for approximations* for complexes 1
and 2
Com gJ/cm–1 P (%) Cθ/K
plex /cm3 K mol–1
12.35±0.03 –30±1 1 3.39 –167
22.25±0.03 –24±1 5 2.98 –106
* The g, J, P are the van Vleck equation parameters for the entire
temperature range; C, θ are the Curie—Weiss law parameters
at 100 < T < 300 K).

Synthesis and structure of binuclear Ni complexes Russ.Chem.Bull., Int.Ed., Vol. 65, No. 12, December, 2016 2815
Table 3. Geometric parameters and results of approximation of magnetochemical data for known binuclear nickel(II)
complexes of the general formula [Ni2(O2CR)4L2]
Complex* d(Ni…Ni)/ÅAngle Ni—Ni—N/deg gJReference
[Ni2(piv)4(Metquin)2] 2.754 — .— –160 20
[Ni2(piv)4(2,4lut)2]** 2.708 166.65 2.40a–194a21
2.72b–224b
[Ni2(piv)4(2,5lut)2] 2.708 166.65 2.38 –128 21
[Ni2(piv)4(EtPy)2] 2.723 166.00 2.85 –221 21, 22
[Ni2(Et2CHCOO)4(quin)2].— — 2.35 –216 21
[Ni2(Me2PhCCOO)4(PPh3)2] 2.752c172.42c2.00 –206 23
2.765c166.64c
[Ni2(Me2PhCCOO)4(quin)2] 2.734 165.70 2.03 –142 22, 23
[Ni2(piv)4(2pic)2] 2.717 169.46 2.28 –223 22, 23
[Ni2(piv)4(Py)2] 2.604 176.7 2.175 –130 18, 24
[Ni2(PhCO2)4(NITpPy)2] 2.6454 172.9 2.02 –29.45 33
[Ni2(atc)4(Py)2] 2.700d171.9d2.20 –537 36
2.651d175.2d
[Ni2(L)2(4,4´bpy)2] 2.700 180.0 2.20 –103.56 37
[Ni2(dpa)2(MeOH)2] 2.582 167.8e2.2 –103 38
[Ni2(RCOO)4(4,4´bpy)2] 2.694 165.17 2.26 –190.03 39
[Ni2(bzo)4(2.3lut)2] 2.720 152.23 2.35 –30 ***
[Ni2(hbzo)4(2.3lut)2].— — 2.25 –24 ***
* Metquin is 2methylquinoline; 2,4lut is 2,4lutidine; 2,5lut is 2,5lutidine; EtPy is 2ethylpyridine; quin is quinoline;
2pic is 2picoline; Py is pyridine; NITpPy is 2(4pyridyl)4,4,5,5tetramethylimiadzoline1oxyl3oxide; atc is
9anthracenecarboxylate anion; 4,4´bpy is 4,4´bipyridyl; H2L is 2,4dibenzoylisophthalic acid; H2dpa is 2(2
carboxyphenyl)benzoic acid; and RCOOH is 4,4´pyridine2,6diyldiisophthalic acid.
** Parameters of exchange interactions for this complex were calculated using two mathematical models for the low
temperature region (a) and hightemperature region (b); Ni...Ni interatomic distances and Ni—Ni—P angles in two
independent molecules of the complex (c); Ni...Ni interatomic distances and Ni—Ni—N angles in two independent
molecules of the complex (d); and the Ni—Ni—O(MeOH) angle (e).
*** This work.
taking into account noninteracting paramagnetic
Ni2+ ions:
where N is the Avogadro constant, μB is the Bohr magne
ton, k is the Boltzmann constant, J is the exchange inte
gral, P is the proportion of noninteracting paramagnetic
Ni2+ centers, C is the Curie constant, and θ is the Weiss
constant.
The bestfit parameters are g = 2.35±0.03, J =
= –30.0±0.4 cm–1 for 1 and g = 2.25±0.03, J =
= –23.6±0.1 cm–1 for 2. The proportion of noninteracting
paramagnetic centers (P) is at most 1% for 1 and 5% for 2.
Emphasize that only a few studies on the magnetic
behavior of nickel complexes with four carboxylate bridges
[Ni2(RCO2)4L2] are available.18,20,21,23,24,33—39 Quantita
tive interpretation of exchange interactions was performed
for fourteen compounds only18,20,21,23,33,36—39 (Table 3).
However, an analysis of these data reveals no reliable cor
relations between the efficiency of exchange interactions
of nickel(II) ions and the Ni...Ni distance, geometry of the
metal carboxylate core, parameters of substituents at carb
oxylate groups, etc.
According to our density functional calculations car
ried out by the UB3LYP/631G(d,p) method, the opti
mized geometries of the compounds synthesized corre
spond to a known structure with four carboxylate bridges,
typical of this type of compounds20—39 (Fig. 3). This is in
good agreement with the results of Xray study of com
pound 1. The largest deviation for the bond lengths (at
most 0.02 Å) was predicted for the Ni...Ni distance. Energy
minima located on the quintet potential energy surface
(PES) of the complexes in the highspin (HS) state, 1HS
and 2HS, possess similar characteristics of the coordina
tion units.
The J values calculated for the optimized geometries
of 1 and 2 are respectively –34 and –37 cm–1, which
indicates a weak antiferromagnetic coupling of the un
paired electrons of nickel(II) ions and is in agreement with
the values obtained using the results of magnetochemical
studies (–30 and –24 cm–1, respectively). An analysis of
the magnetic orbitals (αSOMO+βSOMO) of com
pounds 1 and 2 in the "broken symmetry" (BS) state shows

Nikolaevskii et al.2816 Russ.Chem.Bull., Int.Ed., Vol. 65, No. 12, December, 2016
(Fig. 4, a) that the observed magnetic properties are due to
channels of antiferromagnetic exchange involving carbox
ylate bridges. According to calculations, the spin density
in complex 1 (Fig. 4, b) is localized on the metal and
oxygen atoms. This confirms the conclusions about the
role of carboxylate ligands in antiferromagnetic coupling
of nickel atoms.18
An analysis of the results of studies of the binuclear
NiII carboxylates (see Table 3) shows a record high J value
of –537 cm–1 for [Ni2(atc)4(Py)2].36 The results of single
point calculations of the complex in different approxima
tions disclose a strong antiferromagnetic exchange between
unpaired electrons of nickel ions (about –390 cm–1). Hav
ing analyzed our results and the available published data
Fig. 3. Optimized geometries of complexes 1 and 2 obtained from DFT UB3LYP/631g(d,p) calculations (hydrogen atoms are
omitted).
2.064
2.023
99°
2.741
2.125
153°
1
2.069
2.022
99°
2.732
2.125
152°
2
Fig. 4. Magnetic orbitals (αSOMO+βSOMO) of complex 1 in the BS state (a) and typical spin density distribution for compounds 1
and 2 (b).
ab

Synthesis and structure of binuclear Ni complexes Russ.Chem.Bull., Int.Ed., Vol. 65, No. 12, December, 2016 2817
and based on the assumption that oxygen atoms occupy
vertices of a rectangular parallelepiped, one can assume
improved efficiency of spinspin exchange between NiII
magnetic ions in the undistorted metal carboxylate core
{Ni2(O2CR)4}.
Summing up, we synthesized two novel binuclear com
plexes [Ni2(O2CR)4(2,3lut)2] (O2CR = bzo (1), hbzo (2)).
The structure of 1 was determined by Xray analysis.
Structural distortion of the tetracarboxylate moiety
{Ni2(O2CR)4} in molecule 1 is due to steric effects caused
by the αsubstituent in the coordinated 2,3lutidine mole
cule. An analysis of magnetic data for 1 and 2 revealed
antiferromagnetic interactions between nickel(II) magnetic
ions (S = 1) with close values of gfactors and exchange
integrals (g = 2.35±0.03, J = –30.0±0.4 cm–1 for 1;
g = 2.25±0.03, J = –23.6±0.1 cm–1 for 2). According to
quantum chemical calculations, the magnetic behavior of
the complexes in question is governed by the antiferro
magnetic exchange channel formed as a result of the over
lap of the magnetic orbitals including four carboxylate
ligands. Based on these results and published data (see
Table 3), one can assume that the parameter J of the
binuclear nickel(II) complexes with four carboxylate bridges
correlates with the geometric parameters of the magneto
active fragment {Ni(μO2CR)4Ni}. It seems quite probable
that steric effects can be used as an important tool for
controlling the magnetic properties of the magnetically
active dinickel unit with four carboxylate bridges taking
into account structural features of the apical ligand.
Experimental
The novel complexes were synthesized in air from commer
cially available reactants, namely, ethanol (96%), 3,5di(tert
butyl)benzoic acid (>99%), 4hydroxy3,5di(tertbutyl)benzoic
acid (98%), 2,3lutidine (>99%), NiCl2•6H2O (>99.8%), and
KOH (>99%). IR spectra of the compounds were recorded on
a Perkin Elmer Spectrum 65 spectrophotometer equipped with
a Quest ATR Accessory (Specac) by the attenuated total reflec
tance (ATR) in the range of 400—4000 cm–1. Elemental analysis
was performed on a Euro EA3000 (Euro Vektor) automated
C,H,N,Sanalyzer. Powder Xray diffraction study was done on
a Bruker D8 Advance diffractometer (CuKα, Ni filter, LYNXEYE
detector, reflection geometry).
The magnetic properties of powders of compounds 1 and 2
were measured on a Quantum Design PPMS9 automated phys
ical property measurement system. Temperature dependences
of the magnetization were measured in the temperature range
from 2 to 300 K in an external magnetic field (H) of 5 kOe.
A correction for paramagnetic properties of the sample holder
was applied. The diamagnetic correction was made using Pascal´s
constants.46
Quantum chemical calculations were carried out within the
framework of the density functional theory (DFT) using the
Gaussian 09 program47 and the UB3LYP functional,48 which
correctly reproduces the parameters of openshell coordination
compounds,49—51 and the 631g(d,p) basis set. Stationary points
on the PES were located by full geometry optimization of mo
lecular structures followed by stability tests for the DFT wave
function. Exchange interactions between unpaired electrons of
paramagnetic centers were evaluated using the "broken symme
try" (BS) approach.52 The exchange parameters (J/cm–1) were
calculated using the Yamaguchi formula.53 Graphic images of
the molecular structures shown in Figs 3 and 4 were drawn using
the ChemCraft program54 for which corresponding Cartesian
atomic coordinates obtained from quantum chemical calcula
tions served as the input parameters.
Bis(2,3dimethylpyridineκκ
κκ
κNtetrakis[μμ
μμ
μO,O´3,5di(tert
butyl)benzoato]dinickel(II), [Ni2(bzo)4(2,3lut)2] (1). To a solu
tion of NiCl2•6H2O (0.238 g, 1 mmol) in ethanol (15 mL), a hot
solution of potassium salts of 3,5di(tertbutyl)benzoic acid, ob
tained by reaction of 3,5di(tertbutyl)benzoic acid (1.17 g,
5 mmol) with potassium hydroxide (0.28 g, 5 mmol) in ethanol
(30 mL), was added. The reaction mixture was refluxed for 5 min,
cooled to 60 °C, and kept at this temperature for additional
15 min. Potassium chloride precipitate was filtered off. 2.3Luti
dine (0.1072 g, 1 mmol) was added to the filtrate. The mixture
was stirred at 60 °C for 1 h, transferred to a Schlenk vessel, and
the solvent was gradually (over a period of 4 h) concentrated to
20 mL. A week later, a lightgreen residue formed. The residue
was filtered and washed with hot ethanol (3×5 mL). The yield of
complex 1 was 71% (calculated with respect to the initial amount
of NiCl2•6H2O). Darkgreen crystals suitable for Xray study
were grown within two weeks by slow evaporation of mother
liquor at a reduced pressure. The identity of the single crystals
and the residue isolated earlier was confirmed by powder
Xray diffraction. Found (%): C, 70.48; H, 8.42; N, 2.02.
C74H102N2Ni2O8. Calculated (%): C, 70.26; H, 8.13; N, 2.21.
IR, ν/cm–1: 2962 (m), 2903 (vw), 2865 (vw), 1620 (s), 1583 (vs),
1475 (vw), 1439 (s), 1392 (vs), 1361 (w), 1287 (m), 1247 (m),
1194 (w), 1162 (vw), 1133 (w), 1026 (vw), 995 (vw), 892 (m),
822 (m), 788 (s), 741 (vs), 723 (m), 704 (s), 604 (w), 535 (m),
492 (m), 424 (m), 413 (m).
Bis(2,3dimethylpyridineκκ
κκ
κNtetrakis[μμ
μμ
μO,O´4hydroxy
3,5di(tertbutyl)benzoato]dinickel(II), [Ni2(hbzo)4(2,3lut)2] (2)
was synthesized analogously using 4hydroxy3,5di(tertbutyl)
benzoic acid (1.25 g, 5 mmol) instead of 3,5di(tertbutyl)benzoic
acid. Transfer of the reaction mixture to the Schlenk vessel and
concentration of the solution to 20 mL was followed by precipi
tation of lightgreen residue of 2. The yield of complex 2 was 89%
(calculated with respect to the initial amount of NiCl2•6H2O).
We failed to grow single crystals suitable for Xray study due to low
solubility of the reaction product in common organic solvents.
Recrystallization of the complex from DMF afforded bright
red single crystals of 3.3´,5.5´tetra(tertbutyl)1.1´biphenyl
idene4.4´quinone.55 Found (%): C, 66.68; H, 7.97; N, 2.14.
C74H102N2Ni2O12. Calculated (%): C, 66.88; H, 7.74; N 2.11.
IR, ν/cm–1: 3603 (s), 2957 (m), 2903 (vw), 2865 (vw), 1618 (s),
1597 (m), 1574 (s), 1472 (m), 1449 (m), 1384 (vs), 1318 (s), 1281 (m),
1233 (s), 1202 (m), 1152 (s), 1133 (m), 1116 (s), 1024 (w),
616 (w), 890 (m), 821 (w), 782 (s), 787 (s), 750 (w), 722 (m), 701 (vs),
648 (m), 604 (w), 552 (m), 516 (m), 460 (s), 451 (s), 438 (s), 412 (m).
Singlecrystal Xray study of complex 1 was performed on
a Bruker Apex II diffractometer (CCD detector, MoKα,
λ = 0.71073 Å, graphite monochromator).56 A semiempirical
absorption correction57 was applied. The structure was solved by
the direct methods and refined in the fullmatrix anisotropic
approximation for all nonhydrogen atoms. Hydrogen atoms at

Nikolaevskii et al.2818 Russ.Chem.Bull., Int.Ed., Vol. 65, No. 12, December, 2016
carbon atoms of organic ligands were located geometrically and
refined in the riding model. Calculations were carried out using
the SHELX97 software.58 Crystallographic parameters of com
plex 1: M = 1265.00, crystal dimensions 0.08×0.06×0.06 mm,
green, cubic, T = 184(2) K, triclinic, P1
–, a = 11.203(5),
b = 12.548(5), c = 12.662(5) Å, α = 88.946(7)°, β = 84.820(7)°,
γ = 78.346(7)°, V = 1736.1(12) Å3, Z = 1, ρ = 1.210 g cm–3,
μ = 0.596 mm–1, θ = 1.61—28.38°, –14 ≤ h ≤ 14, –16 ≤ k ≤ 16,
–16 ≤ l ≤ 16; a total of 18102 reflections, 8553 unique reflec
tions, 4388 reflections with I > 2σ(I), Rint = 0.0901, Tmin/Tmax =
= 0.9538/0.9651, S = 1.171, R1 = 0.0915, wR2 = 0.2574 (for the
whole data array), R1 = 0.0915, wR2 = 0.2161 (for I ≥ 2σ(I)),
Δρmin/Δρmax = –0.984/2.153 e Å–3. Full Xray data array was
deposited at the Cambridge Structural Database (CCDC No.
1499784; deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.
ac.uk/data_request/cif).
Singlecrystal and powder Xray diffraction studies and
C,H,Nanalysis were performed at the Center of Collective use
of the Kurnakov Institute of General and Inorganic Chemistry,
Russian Academy of Sciences.
This work was financially supported by the Presidium
of the Russian Academy of Sciences and by the Federal
Agency for Scientific Organizations. S. A. Nikolaevskii,
M. A. Kiskin, and I. L. Eremenko express their gratitude
to the Russian Science Foundation for financial support
of Xray studies carried out in this work (Project No. 14
2300176).
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Received August 31, 2016;
in revised form October 26, 2016