Synthetic and structural investigation of [PdBr2(CNR) 2] (R = Cy, Xyl)

Article abstract of DOI:10.1016/j.molstruc.2014.04.025

Reaction of cis-dichloro-bis-(cyclohexylisocyanide)palladium(II) ([PdCl₂(CNCy)₂], (1) or cis-dichloro-bis-(2,6- dimethylphenylisocyanide)palladium(II) ([PdCl₂(CNXyl)₂], (2) with excess of potassium bromide in acetone furnished complexes trans-dibromo-bis-(cyclohexylisocyanide)palladium(II) ([PdBr₂(CNCy) ₂], (3) or trans-dibromo-bis-(2,6-dimethylphenylisocyanide) palladium(II) ([PdBr₂(CNXyl)₂], (4), respectively. Both compounds were characterized by elemental analyses (C, H, N), high resolution ESI⁺-MS, IR, ¹H and ¹³C{¹H} NMR spectroscopies, and their crystals were analyzed by a single-crystal and powder X-ray diffraction methods. To rationalize the dependence of the structure of 1-4 on type of halogen ligands, the Gibbs free energies of corresponding cis- and trans-isomers of 1-4 were estimated at the DFT B3LYP level of theory.

Full text of DOI:10.1016/j.molstruc.2014.04.025

Accepted Manuscript
Synthetic and structural investigation of [PdBr2(CNR)2] (R = Cy, Xyl)
Mikhail A. Kinzhalov, Konstantin V. Luzyanin, Irina A. Boyarskaya, Galina L.
Starova, Vadim P. Boyarskiy
PII:
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DOI:
http://dx.doi.org/10.1016/j.molstruc.2014.04.025
MOLSTR 20532
Reference:
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2 April 2014
Please cite this article as: M.A. Kinzhalov, K.V. Luzyanin, I.A. Boyarskaya, G.L. Starova, V.P. Boyarskiy, Synthetic
and structural investigation of [PdBr2(CNR)2] (R = Cy, Xyl), Journal of Molecular Structure (2014), doi: http://
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Synthetic and structural investigation of [PdBr2(CNR)2] (R = Cy, Xyl)
Mikhail A. Kinzhalov,a Konstantin V. Luzyanin,a Irina A. Boyarskaya,a Galina L. Starova,a
Vadim P. Boyarskiya*
Department of Chemistry, Saint Petersburg State University, 198504, Petrodvorets,
Universitetskii pr. 26, Saint Petersburg, Russian Federation
(a) Saint Petersburg State University. E-mail: vadim.boyarskiy@chem.spbu.ru
Abstract
Reaction of cis-dichloro-bis-(cyclohexylisocyanide)palladium(II) ([PdCl2(CNCy)2], 1) or cis-
dichloro-bis-(2,6-dimethylphenylisocyanide)palladium(II) ([PdCl2(CNXyl)2], 2) with excess of
potassium
bromide
in
acetone
furnished
complexes
trans-dibromo-bis-
(cyclohexylisocyanide)palladium(II) ([PdBr2(CNCy)2], 3) or trans-dibromo-bis-(2,6-
dimethylphenylisocyanide)palladium(II) ([PdBr2(CNXyl)2], 4), respectively. Both compounds
1
were characterized by elemental analyses (C, H, N), high resolution ESI+-MS, IR, H and
13C{1H} NMR spectroscopies, and their crystals were analyzed by a single-crystal and powder
X-ray diffraction methods. To rationalize the dependence of the structure of 1–4 on type of
halogen ligands, the Gibbs free energies of corresponding cis- and trans-isomers of 1–4 were
estimated at the DFT B3LYP level of theory.
Keywords: Palladium-isocyanide complexes; Geometric isomerism; X-ray diffraction; Crystal
structures; DFT calculations
1

1. Introduction
In the last decade, palladium complexes with acyclic diaminocarbene ligands received attention
as catalysts for different cross-coupling transformations [1, 2]. Various strategies are available
for the generation of palladium-diaminocarbene catalysts [1, 3, 4], and the metal-mediated
coupling of palladium(II)-isocyanides with nitrogen nucleophiles is one of the most efficient and
versatile method (Scheme 1) [1, 3].
Scheme 1. Preparation of palladium complexes with acyclic diaminocarbene ligands from
corresponding cis-dichloro-bis-isocyanide species.
Among various palladium starting materials available, dichloro bis isocyanide species
attracted particular attention due to the simplicity of their preparation [1, 3, 4], while
corresponding bromide and iodide derivatives are much less explored [2, 4-7]. At the same time
it is established, that the anion ligand linked with palladium(0) affects the kinetics of the
oxidative addition to aryl halides as well as the structure and reactivity of the aryl palladium(II)
complexes produced in palladium-catalyzed coupling reactions between aryl halides and
nucleophiles [8]. Consequently, one should expect different catalytic activity for the structurally
related complexes featuring ancillary bromides (or iodides), that, in turn requires the
development of a reliable and convenient route for preparation of corresponding starting
materials, e.g. dibromo-bis-(isocyanide)palladium(II) species. Previously [PdBr2(CNCy)2] was
prepared by treatment of a benzene suspension of PdBr2 with CNCy [9] (geometry of the
complex was not indicated). The main disadvantage of this approach is the use of PdBr2 that is
less available than PdCl2. It was also reported that the complexes [PdBr2(CNR)2] (R = 3,4,5-
2

(CnH2n+1O)3C6H2, n = 4, 6, 8, 10) can be prepared from [PdCl2(CNR)2] by metathesis with KBr
[10] in acetone.
It was shown that the catalytic activity of Pd complexes in cross-couplings is affected by
the geometry of the metal core (e.g. in Sonogashira reaction, cis/trans isomerization may be the
key step of the catalytic cycle [11]) and, in particular, by the type and lability of the auxiliary
ligands (e.g. halides) [1, 2]. Geometry of both isocyanide and corresponding diaminocarbene
Pd(II) complexes depends i.a. on the halogen ligands [12]. Thus, X-ray data show that palladium
dichloride bis-isocyanide complexes are typically stabilized in the cis-form in the solid state
(Scheme 2) [7, 13-16], whereas rare reported examples of iodides [10, 17] and bromides[10]
have the trans- configuration of the isocyanide ligands.
cis-
trans-
Scheme 2. Geometry of dihalogeno-bis-isocyanide Pd(II) complexes (X = Cl, Br, I).
We report herein on synthesis of dibromo-bis-(isocyanide)palladium(II) complexes from
cis-[PdCl2(CNR)2] (R = Cy, Xyl) and KBr and full spectroscopic characterization (including X-
ray crystallography) of these Pd(II)-species. In addition, we undertook quantum chemistry
rationalization of the geometry for corresponding cis- and trans-isomers of [PdX2(CNR)2] (X =
Cl, Br; R = Cy, Xyl) aiming to understand the preference in stabilization of each form.
2. Experimental
2.1. Synthesis
Solvents, PdCl2, the isocyanides CyNC and XylNC were obtained from commercial sources and
used as received. Complexes cis-[PdCl2(CNCy)2] (1) and cis-[PdCl2(CNXyl)2] (2) were prepared
3

as previously described [17, 18]. C, H, and N elemental analyses were carried out by the
elemental analysis service at the Chemistry Department of Saint Petersburg State University on a
Euro EA 3028 HT CHNSO analyzer. Mass spectra were acquired on Bruker micrOTOF
spectrometer equipped with electrospray ionization (ESI) source, MeOH was used as the solvent.
The instrument was operated at positive ion modes using m/z range of 50–3000. The capillary
voltage of the ion source was set at –4500 V (ESI+) and the capillary exit at +(70–150) V. The
nebulizer gas pressure was 0.4 bar and drying gas flow was 4.0 L/min. The most intensive peak
in the isotopic pattern is reported. Infrared spectra were recorded on Bruker Tensor 27 FTIR
instrument (4000–200 cm–1) in KBr (4000–400 cm–1) and CsI (400–200 cm–1) pellets and CHCl3
1
solutions (4000–400 cm–1). H, 13C{1H}, and DEPT NMR spectra were acquired on Bruker
DPX300 spectrometer at ambient temperature.
General Synthetic Procedure:
Solid KBr (720 mg, 6 mmol) was added to a solution (R = Cy) or a suspension (R = Xyl)
of [PdCl2(CNR)2] (0.20 mmol) in acetone (20 mL) at 20–25 ºC, and the reaction mixture was
stirred at RT for ca. 4 d. The formed yellow suspension was evaporated at 40–45 ºC and the
product was extracted with three (R = Cy) or ten (R = Xyl) 5-mL portions of CH2Cl2. The
resulting bright yellow solution was filtered off remove some insoluble material; the filtrate was
evaporated at room temperature to dryness, washed with two 5-mL portions of cold (5 °C) Et2O,
and then dried in vacuo at 20–25 °C.
trans-[PdBr2(CNCy)2] (3), 90%. Anal. Calcd. for C14H22N2Br2Pd: C, 34.70; H, 4.58; N,
5.78. Found: C, 34.75; H, 4.57; N, 5.82. ESI+-MS, m/z: calcd. for C14H22N2Br2NaPd+ 506.9058,
found 506.9089 [M + Na]+. IR (KBr, selected bands, cm–1): ν(C–H) 2938–2853 (m), ν(C≡N)
2231 (s), ν(Pd–Br) 262 (s). IR (CHCl3, selected bands, cm–1): ν(C≡N) 2233 (s). 1H NMR (300.13
MHz, CDCl3, δ): 1.38–1.54 (m, 8Н, CH2), 1.72–2.04 (m, 12H, CH2), 3.93–4.07 (m, 2H, CH).
13C{1H} NMR (75.47 MHz, CDCl3, δ): 22.6 (4C, CH2), 25.1 (2C, CH2), 32.0 (4C, CH2), 55.5
(2C, CH, 1JC,N = 4.8 Hz), 120.5 (2C, C≡N, 1JC,N = 22.0 Hz).
4

trans-[PdBr2(CNXyl)2] (4), 85%. Anal. Calcd. for C18H18N2Br2Pd: C, 40.90; H, 3.43; N,
5.30. Found: C, 44.94; H, 3.47; N, 5.27. ESI+-MS, m/z: calcd. for C18H18N2Br2NaPd+ 550.8743,
found 550.8739 [M + Na]+, calcd. for C18H18N2Br2KPd+ 566.8483, found 566.8498 [M + K]+. IR
(KBr, selected bands, cm–1): ν(C≡N) 2207 (s), δ(C–H from Ar) 780 (m), ν(Pd–Br) 239 (s). IR
1
(CHCl3, selected bands, cm–1): ν(C≡N) 2209 (s). H NMR (300.13 MHz, CDCl3, δ): 2.53 (s,
3
3
12Н, CH3), 7.16 (d, JH,H = 7.6 Hz, 4Н, C3–H and C5–H from Xyl), 7.30 (t, JH,H = 8.0 Hz, 2Н,
C4–H from Xyl). 13C{1H} NMR (75.47 MHz, CDCl3, δ): 19.1 (4C, CH3), 125.5 (2C, C≡N, 1JC,N
= 10.8 Hz), 128.6 (4C, C3 and C5 from Xyl), 131.0 (2C, C4 from Xyl), 132.4 (2C, C1 from Xyl,
1JC,N = 23.8 Hz), 137.0 (4C, C2 and C6 from Xyl).
2.2. X-ray structural analysis
Crystals of 3 and 4 suitable for X-ray diffraction were obtained by a slow evaporation of
a solution of respective compound in a CH2Cl2/Et2O mixture in air at room temperature. Crystals
were fixed on a micro mount and placed on an Agilent Technologies SuperNova Atlas
Diffractometer and measured at a temperature of 100 K for 4 and 293 K for 3 using micro
focused monochromated CuKα radiation. The crystals of 3 were very small and, moreover, were
destroyed as under cooling with liquid nitrogen and without cooling. The unit cell parameters
were refined by least square techniques using 8012 for 4 and 1438 for 3 reflections in the 2θ
range of 3.62–76.46º for 4 and 4.41–48.21º for 3. The structures were solved by the direct
methods and refined for 4 (R1 = 0.028) and for 3 (R1 = 0.030) by means of the SHELXL-97
program [19] (Table 2) incorporated in the OLEX2 program package [20]. Positions of H atoms
in both structures were modeled using the ‘riding’ model. Analytical numeric absorption
correction was applied in CrysAlisPro [21] program complex using a spherical harmonics,
implemented in SCALE3 ABSPACK scaling algorithm for 4 and a multifaceted crystal model
based on expressions derived by R.C. Clark & J.S. Reid [22] for 3.
5

The X-ray powder diffraction data were obtained at room temperature using a Rigaku Miniflex II
Desktop X-ray diffractometer equipped with a Cu-Kα source. Data were scanned over the
angular range 5–60°(2θ) with a step size of 0.02°(2θ) and scan rate 5º2θ/min.
2.3. Computational details
All computations has been carried out at the DFT/HF hybrid level of theory using
Becke’s three-parameter hybrid exchange functional in combination with the gradient-corrected
correlation functional of Lee, Yang, and Parr (B3LYP) [23-26] by using GAUSSIAN 2003 [27]
and GAUSSIAN 2009 [28] program packages.
The optimization of the 1-4 cis-/trans-isomer geometries was performed using the 6-
31+G(d,p) basis set for nonmetal atoms and effective core potential model with triple-z basis sets
CEP121G for Pd(II). Solvent effects were taken into account at full geometries optimization
calculations using the polarizable continuum mode (PCM) with CH3CN taken as a solvent. The
Hessian matrix was calculated analytically for the optimized structures in order to prove the
location of correct minima (no imaginary frequencies) and to estimate the thermodynamic
parameters. Gibbs free energies (G) were calculated for 25°С.
3. Results and discussion
The trans-[PdBr2(CNR)2] (R = Cy, Xyl) were synthesized employing readily accessible
complexes cis-[PdCl2(CNR)2] and excess KBr in acetone at RT for ca. 4 d (Scheme 3).
Scheme 3. Synthesis of trans-dibromo-bis-isocyanide Pd(II) complexes 3 and 4.
6

Complexes 3 and 4 are well soluble in dichromethane, chloroform, alcohols (methanol,
ethanol) and sparingly soluble in diethyl ether.
Complexes 3 and 4 were characterized by elemental analyses (C, H, N), high resolution
ESI+-MS, IR, 1H and 13C{1H} NMR spectroscopies. These species give satisfactory
microanalyses that are consistent with the proposed formulations. In the ESI+-MS, the typical
ions that detected were [M + Na]+ and/or [M + K]+ with the characteristic isotopic distribution.
The IR spectra in KBr pellets / CHCl3 solutions of 3 and 4 display one stretching vibration due to
ν(C≡N) at 2231/2233 cm–1 (for 3) and at 2207/2209 cm–1 (for 4), suggesting the trans-position of
the two isocyanide ligands, while cis-[PdCl2(CNR)2] complexes 1 and 2 show two overlapped
ν(C≡N) bands at 2248/2247 and 2230/2231 cm–1 for 1 [17] and at 2216 and 2190 cm–1 for 2 [14].
This assumption is also confirmed upon comparison of the IR data for 3 with those for
different cis- and trans- dihalogeno-bis-(cyclohexylisocyanide) palladium complexes (Table 1).
Table 1. The stretching vibrations due to ν(C≡N) for cis- and trans- dihalogeno-bis-
(cyclohexylisocyanide) palladium complexes (cm–1).
Solvent cis-[PdCl2(CNR)2] trans-[PdCl2(CNR)2]
complex 3
trans-[PdI2(CNR)2]
2248 and 2230 [17]
KBr
–
2231 (this work)
2224 [16]
2261 and 2244 [16]
2247 and 2231 [17]
2253 and 2235 [16]
CHCl3
2233 [16]
2233 (this work)
–
The 1H NMR spectrum of 3 displays the characteristic signal of the CH protons from the
cyclohexyl rings at ca. 4 ppm, while in the 13C{1H} NMR spectrum, the corresponding CH
1
carbon signal emerges at 55.5 ppm. The H NMR spectrum of 4 exhibits a singlet resonance
from the CH3 protons at 2.53 ppm and doublet (δ = 7.16 ppm) and triplet (δ = 7.30 ppm) from
H
H
the aromatic hydrogen atoms, while in the 13C{1H} NMR resonances appear at 19.1 ppm (CH3).
The 13C{1H} NMR spectra of both 3 and 4 display a weak signals at 120.5 (for 3) or 125.5 ppm
(for 4) assigned to the isocyanide C atom. Signals from the C atom, which linked to the
7

isocyanide N atom have a fine structure and composed of three lines equal intensity, because of
the 14N–C coupling [29].
X-ray Structures. The crystallographic data and processing parameters for 3, and 4 are
listed in Table S1 (Supplementary Information), the plots for the structures can be found in
Figure 1 and 2 and bond lengths and angles are given in the legend to the corresponding plots.
In 3 and 4, the bromides are in the trans-position [Br1–Pd1–Br2 179.40(3)° for 3; Br1–Pd1–
Br1# 180.000(6) for 4] and two carbons from the isocyanide ligands complete the slightly
distorted square planar environment around the metal center.
In both structures, the isocyanide ligands are exclusively in the trans-position, while in
starting complexes 1 and 2 the isocyanide ligands are in the cis-position [13, 14]. The fragments
C–N–C–Pd in both complexes are almost linear: the angles Pd1–C1–N1 and Pd1–C2–N2 found
for 3 is 174.6(7)° and 176.2(8)°, respectively and Pd1–C1–N1 found for 4 is 177.0(2)°. The
angles C1–N1–C9 and C2–N2–C3 are 178.8(8)° and 175.4(8)°, respectively in 3 and C1–N1–
C2 is 175.8(3)° in 4. The metal–carbon bonds (Pd1–C1 1.955(9) Å and Pd1–C2 1.964(9) Å for
3; Pd1–C1 1.963(3) Å for 4) are slightly longer then the values in corresponding cis-
[PdCl2(CNR)2] (1.932(7) and 1.933(7) Å in 1 [13] and 1.906(7) and 1.915(6) Å in 2 [14]),
presumably, due to the greater trans influence of the CNR ligands than that of Cl [12, 30, 31].
Simultaneously two CN triple bonds of the isocyanide moieties have an equal bond lengths in
each compound (1.146(8) Å for 3 and 1.149(4) Å for 4), while the corresponding
cis-[PdCl2(CNR)2] have the different CN bond lengths (1.142(9) and 1.127(9) Å for 3 [13] and
1.145(8) and 1.157(9) Å for 4 [14]). Both cyclohexyl rings of 3 in the crystal are in a chair
conformation, and both of the NC groups are equatorial.
In the crystal structure of 3, the packing exhibits a pseudo-bedding parallel to the plane
YZ (Figure 3). However, the shortest distance is observed between molecules of the adjacent
layers (Table 2). Their parameters indicate the presence of a very weak hydrogen bonding, C–
H···Br, leading to the formation of infinite chains of molecules parallel to the X axis (Figure 4).
8

In the crystal structure of 4, bromine atoms form a molecular chain C18H18N2Br2Pd along the X
axis through hydrogen bond interaction with the methyl groups (atoms C8 and C9) of the
adjacent molecules. Similar contacts with a benzene ring (C6 atom) of neighboring chains give a
three-dimensional crystal structure (Table 2, Figure 4).
The X-ray powder diffraction data for 3 and 4 fully agree with the powder diffraction
data calculated by the single-crystal structure suggesting homogeneity of the sample.
Figure 1. View of 3 with the atomic numbering schemes. Thermal ellipsoids are drawn
with the 50% probability. Hydrogen labels are omitted for simplicity. Selected bond lengths (Å)
Pd1–Br1 2.4158(8); Pd1–Br2 2.4178(8); Pd1–C1 1.955(9); Pd1–C2 1.964(9); C1–N1 1.146(8);
C2–N2 1.146(8); N2–C3 1.453(10); N1–C9 1.467(10) and bond angles C1–Pd1–C2 178.0(3);
C1–Pd1–Br1 88.7(2); C1–Pd1–Br2 91.4(2); N1–C1–Pd1 174.6(7); N2–C2–Pd1 176.2(8); C2–
N2–C3 175.4(8); C1–N1–C(9) 178.8(8).
9

Figure 2. View of 4 with the atomic numbering schemes. Thermal ellipsoids are drawn
with the 50% probability. Hydrogen labels are omitted for simplicity. Selected bond lengths (Å)
Pd1–Br1 2.4179(3); Pd1–C1 1.963(3); C1–N1 1.149(4); N1–C2 1.399(3) and bond angles N1–
C1–Pd1 177.0(2); C1#1–Pd1–C1 180.0001; C1–Pd1–Br1#1 91.08(8); C1–Pd1–Br1 88.92(8);
C1–N1–C2 175.8(3)
10

Figure 3
11

Figure 4.
Table 2. Selected hydrogen bond lengths [Å] and angles [°] for 3 and 4
D–H···A
d(H···A)
3.06(5)
3.08(5)
3.09(5)
2.95(5)
2.99(5)
d(D···A)
3.758(5)
3.807(5)
4.022(5)
3.714(5)
3.862(5)
<(DHA)
129(1)
131(1)
165(1)
139(1)
159(1)
C3–H3···Br2 #1
C9–Н9···Br1 #2
C8–H8C···Br1#1
3*
4** C9–Н9B···Br1#2
C6–Н6···Br1#3
*Symmetry transformations used to generate equivalent atoms: #1 1+x, y, z; #2 x–1, y, z
**Symmetry transformations used to generate equivalent atoms: #1 1-x, y, z; #2 –x, 1–y, 1–z; #3
x–1.5, 1.5–y, 0.5+z
Theoretical calculations.
Experimental results clearly demonstrate that geometry of the complex depends strongly
on the type of halogen ligand present in 1–4. From X-ray studies, it can be concluded that in
solid state the dichloride species 1 and 2 exist as cis isomers, while dibromide 3 and 4 as trans
species. In order to shed light on this situation, we attempted to rationalize their structure using
quantum chemistry calculations at DFT level.
DFT optimizations demonstrated that in the absence of any intermolecular interactions
(i.e. in the gas phase) trans-forms are more stable for all 1–4 independently on type of the
halogen ligands (Table 3). The differences (Gcis–Gtrans) at 25 °C are of 25–26 kJ/mole for each of
12

dichloro palladium complexes 1 and 2 and are slightly higher for the dibromides [(Gcis–Gtrans) at
25 °C = 29 are 34 kJ/mole for 3 and 4, respectively).
25 °С
Table 3. µgas and (Gcis–Gtrans
)
for complexes 1−4 calculated by DFT
(Gcis–Gtrans), kJ/mole
μ
gas
Complex
(D)
gas
MeCN
cis-form
trans-form
cis-form
14.1
0.3
1
2
3
4
25.2
−3.6
12.5
0.0
25.8
29.0
33.8
−5.6
4.1
trans-form
cis-form
13.8
0.3
trans-form
cis-form
12.2
0.0
2.4
trans-form
On going from the gas phase to solution, the situation is changing. Indeed, for 1 and 2 in
acetonitrile the cis-forms become more stable by ca. 4−6 kJ/mole (Table 3). The plausible
reason of this variation is due to the high dipole moment of this forms (μ = 14.1 D for 1 and μ
cis
cis
= 12.5 D for 2) when compared with the trans-form (μ = 0.3 D and 0 D, respectively) (Table
cis
3). Naturally, in the solid phase where the role of intermolecular interactions is further increased,
the dichloro palladium complexes 1[13] and 2[32] crystallize exclusively in the cis-form. It is
also consistent with the data obtained earlier for complex 1 indicating that in chloroform solution
(which is less polar than MeCN, and which therefore occupies an intermediate position between
the gas phase and the MeCN) an equilibrium between both cis and trans occurs [16]. In contrast,
dibromo species 3 and 4, increasing of the dipole moment is not sufficient to reverse the
stability, and the trans-form is more stable in acetonitrile solution, although the energy
difference is greatly reduced (Table 3). Such reduction in the importance of intermolecular
13

interactions can be explained in the framework of the continuum solvation models [33] taking
into account the larger dibromo complexes 3 and 4 compared to dichloro species 1 and 2.
4. Conclusion
Concluding, complexes trans-[PdBr2(CNR)2] (R = Cy, Xyl) were prepared by the metathetical
reaction between the corresponding cis-dichloro derivatives with excess KBr in acetone and
fully characterized by several spectroscopic techniques including X-ray crystallography.
Experimental and theoretical data are in agreement that trans coordination modes are preferable
for dibromo species as in gas phase or in solution (based on calculations) and in a solid state
(based on X-ray studies). In contrast, the dichloro complex [PdCl2(CNCy)2], was found to be
more stable as trans-form in gas phase and cis-form in solution as well as in solid state,
presumably due to the differences of µ for these forms.
Supporting Information
Electronic Supplementary Information (ESI) available: Table of X-rays methods (Table
S1) and optimized geometries for cis- and trans-1–4 in gas phase and MeCN solution. Full
crystallographic data for compounds 3 and 4 have been deposited with the Cambridge
Crystallographic Data Centre, deposition numbers CCDC 934144 for 3 and 934145 for 4. Copy
may be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif or from the Director
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: +44 1223 336 033; e-mail:
deposit@ccdc.cam.ac.uk).
Acknowledgements
This research was supported by joint award of Russian Foundation for Basic Research
(Grants 14-03-00297-a, 14-03-31204 мол_а, and 14-03-01005-a), St. Petersburg State
University (Grant 12.38.195.2014), and FCT Portugal (project PTDC/QUI-QUI/109846/2009).
14

Studies were performed at Center for Magnetic Resonance, Center for X-ray Diffraction
Studies, Educational Center of Chemistry, and Center for Chemical Analysis and Materials
Research of Saint Petersburg State University.
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18

Graphical Abstract
19

Highlights
•
•
•
Dibromo-bis-isocyanide palladium complexes are prepared via metathetical reaction from
corresponding chlorides
Geometry of complexes in solution and solid-state is established on basis of spectroscopic
data
trans coordination modes are preferable for dibromo species in solution (based on DFT
calculations) and in a solid state (based on X-ray studies)
20