Structure of Cu(II) and Pd(II) complexes with 2-(2,2-dimethylhydrazone)pentanone-4

Article abstract of DOI:10.1134/S0022476617050213

Palladium(II) and copper(II) complexes with 2-(2,2-dimethylhydrazone) pentanone-4 are synthesized for the first time. The compounds are characterized by IR and NMR spectroscopy, elemental and single crystal X-ray diffraction analyses. The palladium complex crystallizes in the space group I4₁/a; the copper complex crystallizes in the space group P1?. Both compounds are molecular; the palladium chelate core has a distorted square geometry and that of copper has a distorted tetrahedral geometry. The average M–O and M–N bond lengths are respectively 1.9808(15) ? and 2.0427(17) ? for M = Pd, 1.915(8) ? and 1.97(1) ? for M = Cu. The chelate O–M–N angles are 88.32(7)-91.67(7)° for M = Pd, 93.37(4)-99.02(5)° for M = Cu.

Full text of DOI:10.1134/S0022476617050213

Journal of Structural Chemistry. Vol. 58, No. 5, pp. 1004-1008, 2017.
Original Russian Text © 2017 N. V. Kuratieva, E. S. Vikulova, A. D. Shushanyan, N. S. Nikolaeva, S. I. Dorovskikh, N. S. Mikhaleva,
N. B. Morozova.
STRUCTURE OF Cu(II) AND Pd(II) COMPLEXES
WITH 2-(2,2-DIMETHYLHYDRAZONE)PENTANONE-4
1,2 1
N. V. Kuratieva , E. S. Vikulova ,
UDC 546.98:546.562:543.442.3:543.57
1,2 1
A. D. Shushanyan , N. S. Nikolaeva *,
1,2 1
S. I. Dorovskikh , N. S. Mikhaleva ,
1
and N. B. Morozova
Palladium(II) and copper(II) complexes with 2-(2,2-dimethylhydrazone) pentanone-4 are synthesized for
the first time. The compounds are characterized by IR and NMR spectroscopy, elemental and single crystal
X-ray diffraction analyses. The palladium complex crystallizes in the space group I4 /a; the copper
1
complex crystallizes in the space group P1 . Both compounds are molecular; the palladium chelate core has
a distorted square geometry and that of copper has a distorted tetrahedral geometry. The average M–O and
M–N bond lengths are respectively 1.9808(15) Å and 2.0427(17) Å for M = Pd, 1.915(8) Å and 1.97(1) Å
for M = Cu. The chelate O–M–N angles are 88.32(7)-91.67(7)° for M = Pd, 93.37(4)-99.02(5)° for M = Cu.
DOI: 10.1134/S0022476617050213
Keywords: palladium(II), copper(II), β-iminoketone, single crystal X-ray diffraction.
INTRODUCTION
Bimetallic Pd–Cu coatings have been actively employed as contact materials, catalysts and are among the most
promising functional membrane layers for hydrogen purification, etc. [1-3]. Metal organic chemical vapor deposition
(MOCVD) is one of the methods used to produce composite Pd–Cu layers on various substrates [4, 5]. For bimetallic
coatings to be formed within one experiment (in co-deposition), MOCVD precursors should not only meet the standard
requirements [6], but also have compatible thermochemical characteristics, in particular, overlapping ranges of vapor
pyrolysis temperatures on a heated surface. Thus, to select precursor combinations in controlled MOCVD processes for the
preparation of bimetallic layers in different deposition temperature ranges, it is necessary to expand a series of volatile
palladium and copper complexes. It should also be noted that today, owing to their high volatility, the complexes with
fluorinated ligands are most often used as palladium and copper precursors [6-8]. However, aggressive fluorine-containing
products can form during the thermal decomposition of the precursor vapor [9, 10].
Therefore, it is topical to create new volatile compounds of the considered metals without halogens. One of the
possible approaches to this issue can be implemented based on β-iminoketone ligands by introducing a dimethylamino group
at the nitrogen atom in order to loose packing and reduce the crystal lattice energy [11].
1
Nikolaev Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia;
2
nikolaeva@niic.nsc.ru. Novosibirsk National Research State University, Russia. Translated from Zhurnal Strukturnoi
*
Khimii, Vol. 58, No. 5, pp. 1042-1046, June-July, 2017. Original article submitted December 28, 2016.
1004
0022-4766/17/5805-1004 © 2017 by Pleiades Publishing, Ltd.

Against this background, this work deals with the synthesis and the structural study of new palladium(II) and
copper(II) complexes with the proposed-type β-iminoketone: 2-(2,2-dimethylhydrazone)pentanone-4 (Hdmha).
EXPERIMENTAL
The CHN elemental analysis was performed on a Carlo-Erba 1108 device (measurement error did not exceed 0.5%).
–1
IR spectra of the samples (pellets with KBr) were measured on a Scimitar FTS 2000 spectrometer in a range 375-4000 cm .
1
3
H NMR spectra of the solutions of individual compounds in CDCl were recorded on Bruker Avance-500 (operating
frequency 500 MHz). Hexamethyldisiloxane (0.04 ppm of TMS) was used as the internal standard.
Hdmha was synthesized by the acetylacetone interaction with dimethylhydrazone in a 1:1 molar ratio according to
a modified procedure from [12] and purified by distillation (fraction at Т = 193-198 °C, yield 80-85%). IR spectrum
–1
1
(
ν, cm ): 3460, 3220, 2990, 2960, 2860, 2820, 2780, 1610, 1570, 1510, 1430, 750. H NMR: δ = 1.80 s (3H, CH
3H, CH ), δ = 2.35 s (6H, N(CH )), δ = 4.67 s (1H, CH), δ = 10.93 s (1H, NH).
The Pd(dmha) complex (1) was prepared using the procedure described in [13]: PdCl (0.30 g, 1.69 mmol) was
3
), δ = 1.83 s
(
3
3
2
2
dissolved in 30 ml of acetonitrile, then a solution of Hdmha (0.55 g, 3.87 mmol) in 10 ml of acetonitrile was added. Next,
a portion of KOH (0.2 g, 3.56 mmol) dissolved in a minimum amount of water was added to the reaction mixture. In 10 min,
the target product was precipitated with water (500 ml). The precipitate was filtered off, dried in air, and purified by vacuum
–2
sublimation (T = 100 °C, P = 2⋅10 Torr). Yield was 50%. The elemental analysis (wt.%) for PdC14
H
26
N
4
O
2
(1): calculated N
–1
1
1
4.4, C 43.3, H 7.9; found N 13.8, C 41.5, H 6.8. IR spectrum (ν, cm ): 3100, 3060, 2930, 2890, 2780, 1570, 1510, 1455,
1
400, 760. H NMR: δ = 1.82 (6H, 2CH
3 3 3 3 2
), δ = 2.00 (6H, 2CH ), δ = 2.78 (12H, 4CH , 2N(CH ) ), δ = 4.65 (2H, 2CH).
The Cu(dmha) complex (2) was synthesized using the procedure described in [14]. Aqueous solutions of
2
2 2 2
CuCl ⋅2H O (1.296 g, 7.73 mmol) and NaOH (0.155 g, 3.87 mmol) were mixed; the resulting precipitate of Cu(OH) was
filtered off, washed with acetone, and added to a Hdmha (1.00 g, 7.03 mmol) solution in isopropanol (20 ml). After
evaporation of alcohol, the target product was extracted with chloroform and purified by vacuum sublimation (T = 90 °C,
–2
26 4 2
P = 2⋅10 Torr). Yield was 65%. The elemental analysis (wt.%) for CuC14H N O (2) calculated N 16.2, C 48.5, H 7.5,
–1
found N 16.0, C 48.4, H 7.6. IR spectrum (ν, cm ): 3430, 2980, 2945, 2860, 2780, 1575, 1500, 1460, 1400, 750.
Crystals suitable for X-ray diffraction (XRD) were obtained by slow evaporation of hexane solutions of 1 and 2.
Single crystal XRD was performed according to the standard procedure on an automated Bruker APEX DUO four-circle
α
diffractometer (CCD area detector, Т = 150(2) K, MoK radiation, λ = 0.71073 Å, graphite monochromator). Absorption
correction was applied empirically from the intensities of equivalent reflections using the SADABS software [15]. The
structures were solved by a direct method and refined by the full-matrix least-squares technique in the anisotropic
approximation for all non-hydrogen atoms using the SHELXTL software [15]. The sites of hydrogen atoms were found
geometrically and refined in a riding model.
The crystallographic data for complex (1) are as follows: chemical formula PdC14
crystal system, space group I4 /a, a = 18.4603(6) Å, c = 10.0181(3) Å, V = 3414.00(19) Å , Z = 8, dcalc = 1.513 g/cm ,
μ = 1.097 mm . The crystal size is 0.22×0.20×0.15 mm. In total, 14995 reflections (θ from 2.21° to 28.33°) were measured,
including 2120 independent and 1883 observable (I ≥ 2σ(I)), R = 0.0246, wR = 0.0629.
For complex (2): chemical formula CuC14 , М = 345.93, triclinic crystal system, space group P1 ,
a = 10.8311(4) Å, b = 11.0271(3) Å, c = 16.4623(5) Å, α = 86.234(1)°, β = 84.481(1)°, γ = 61.481(1)°, V = 1719.21(9) Å ,
26 4 2
H N O , М = 388.79, tetragonal
3
3
1
–1
1
2
26 4 2
H N O
3
3 –1
Z = 4, dcalc = 1.336 g/cm , μ = 1.280 mm . The crystal size is 0.40×0.36×0.10 mm. In total, 16714 reflections (θ from 2.40°
to 28.38°) were measured, including 8557 independent and 7358 observable (I ≥ 2σ(I)), R = 0.0266, wR = 0.0692.
1 2
The CIF files containing full information on the studied structures have been deposited with CCDC under numbers
524700 and 1524701 (www.ccdc.cam.ac.uk/data_reguest/cif).
1
1005

RESULTS AND DISCUSSION
Compounds 1 and 2 were synthesized according to the following scheme:
Complex 1 was prepared by the interaction of Pd(CH
3 2 2 2
CN) Cl generated in situ on dissolving PdCl in acetonitrile with
Hdmha in the presence of KOH; compound 2 was prepared by the interaction of a Hdmha solution in isopropanol with a 10%
2
excess of freshly precipitated Cu(OH) . The synthesized substances are yellow (1) or dark purple (2) powders; complex 2 is
unstable when stored in air.
Both complexes typically form island molecular crystal structures. Compound 1 crystallizes in the high-symmetry
space group I4 /a, therefore the asymmetric unit of the structure contains a half of the molecule and the palladium atom is in
1
a system of inversion centers. The asymmetric unit of the unit cell of compound 2 contains two molecules of the complex.
Some geometric parameters of the molecules are given in Table 1. The molecules of complexes 1 and 2 have similar
–
structures (Figs. 1, 2). The coordination environment of metal atoms is formed by oxygen and nitrogen atoms of two dmha
ligands rotated to the trans-position by substituents and coordinated in bidentate cyclic mode. The Pd atom in complex 1 has
a nearly square coordination environment and both Cu atoms in compound 2 have a distorted coordination sphere, where the
angle between the planes of two chelate cycles is intermediate between the square and tetrahedral coordination (46.3° and
52.9°). In complex 1 the metallocycles are planar; in the molecules of 2 they are close to planar (bend angles along the N…O
line are in a range 2.8-18.7°). Therewith, in the structure of 2 the metallocycles were observed to be flattened for the
molecule with a larger rotation of the coordination chelate cycles: 2.8° and 8.2° against 14.0° and 18.7°.
TABLE 1. Main Interatomic Distances (Å) and Angles (deg) in Complexes 1 and 2
Complex
1
2
Complex
1
2
Bond length, d
1.9082(10)-1.9168(10)
.915(8)*
1.9559(11)-1.9750(12)
.97(1)*
1.2808(19)-1.2908(17)
.287(9)*
1.453(2)-1.4723(18)
1.46(2)*
M–O
M–N
1.9808(15)
2.0427(17)
N′–N
1.460(2)
1.313(3)
1.413(3)
1.372(3)
1.4408(16)-1.4468(16)
1.443(5)*
1
α
N–C ′
1.3097(18)-1.3156(18)
1.314(5)*
1
O–C
α
1.286(3)
C
α
–C
γ
1.420(2)-1.426(2)
1.423(3)*
1
N′–C
1.460(3)-1.476(4)
Cγ–C
α
′
1.369(2)-1.383(2)
1.468(4)*
Angle, ω
138.93(5)-141.77(5)
40(2)*
93.37(4)-99.02(5)
95(3)*
O–M–O
O–M–N
180.00
N–M–N
180.00
144.88(5)-152.46(5)
149(3)*
1
88.32(7)-91.67(7)
0(2)*
9
*
Average value.
1006

Fig. 1. Structure of the Pd(dmha) molecular complex
2
with the asymmetric unit numbering. Thermal
displacement ellipsoids are drawn at the 50%
probability level.
Fig. 2. Structure of the Cu(dmha)2 molecular complex with the asymmetric unit
numbering. Thermal displacement ellipsoids are drawn at the 50% probability level.
In the crystal packing of 1 the planes of the coordination squares are mutually perpendicular for the nearest
neighbors. On the whole, the molecular packing in 1 corresponds to a two-layer hexagonal close sphere packing (CSP) in the
(0 1 1) family of planes with partial (1 of 6) vacancies in CSP and partial occupation of octahedral voids by the molecules of
the complex that draws apart and distorts the packing layers. In the case of compound 2, a zigzag chain ordering of complex
molecules in the b direction is observed. The shortest distance between the metal atoms is 6.991(1) Å in the structure of 1 and
6.331(1) Å in 2.
A comparison of the structures of 1, 2 with the complexes of the studied metals with 4-(N-
methylimino)pentanedione-2 M(Mei-acac)
2
(M = Pd 3 [16], Cu 4 [14]) allows us to conclude that, for copper(II) compounds,
007
1

the replacement of methyl substituent at the ligand nitrogen atom by a bulky dimethylamino group leads to greater
differences in the Cu–O and Cu–N bond lengths (0.035 Å in 2 and 0.052 Å in 4), a stronger distortion of the coordination
polyhedron, and a larger deformation of the chelate metallocycles. On the contrary, for the palladium complexes (compounds
1
and 3), the differences in the structure of the coordination site are insignificant. At the same time, in both cases the
considered modification of the ligand fundamentally changes the crystal packing. For instance, the molecular packing of 3
and 4 corresponds to distorted double hexagonal CSP; at that, for 3 the plane of the molecule coincides with that of the layer.
For the palladium complexes, a decrease in the calculated density of compound 1 with its greater molecular weight should
also be noted.
Therefore, the structural characteristics of palladium(II) and copper(II) complexes with 4-(N,N-
dimethylhydrazone)pentanedione-2 are determined. The introduction of a bulky dimethylamino group at nitrogen is shown to
loosen the crystal packing. Sublimation characteristics of the compounds suggest their possible use in MOCVD processes.
The work was supported by the Russian Science Foundation (Project No. 15-13-10014).
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