Aryldiazenido ruthenium(II) complexes. Structure and characterization of p-tolyldiazenido ruthenium(II) complexes with pyrazole and imidazole ligands

Article abstract of DOI:10.1016/j.poly.2012.12.012

The p-tolyldiazenido ruthenium(II) complexes [RuCl₃(PPh ₃)₂(N₂PhCH₃)]·CH ₃OH (1), [RuCl₃(PPh₃)(N₂PhCH ₃)(HPz)] (2) and [RuCl₃(PPh

Full text of DOI:10.1016/j.poly.2012.12.012

Polyhedron 51 (2013) 102–110
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Aryldiazenido ruthenium(II) complexes. Structure and characterization of
p-tolyldiazenido ruthenium(II) complexes with pyrazole and imidazole ligands
⇑
J.G. Małecki , I. Gryca, M. Penkala
Department of Crystallography, Institute of Chemistry, University of Silesia, ul. Szkolna 9, 40-006 Katowice, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
The p-tolyldiazenido ruthenium(II) complexes [RuCl3(PPh3)2(N2PhCH3)]ꢀCH3OH (1), [RuCl3(PPh3)
(N2PhCH3)(HPz)] (2) and [RuCl3(PPh3)(N2PhCH3)(Im)]ꢀCH3OH (3) were synthesized and characterized
by IR, 1H, 13C, 31P NMR, electronic absorption and emission spectroscopy, and X-ray crystallography. In
Received 7 November 2012
Accepted 4 December 2012
Available online 2 January 2013
the molecular structure of complex (1) some
p–p stacking interactions are observed, whereas in the
structure of the imidazole complex (3) graph set analysis shows intermolecular hydrogen bonded rings.
The electronic structures of the complexes were calculated by DFT based on their crystal structures. The
spin-allowed singlet–singlet electronic transitions of the complexes were calculated by time-dependent
DFT and the UV–Vis spectra have been discussed on this basis. The emission properties of the complexes
were also studied.
Keywords:
Ruthenium p-tolyldiazenido complexes
Pyrazole
Imidazole
X-ray
Electronic structure
Ó 2012 Elsevier Ltd. All rights reserved.
Absorption and emission electronic spectra
DFT
1. Introduction
spectroscopic characterization (IR, 1H NMR). Indeed, the Cam-
bridge Structural Database (CSD; ConQuest v. 1.14; 2012) presents
Research involving ruthenium coordination chemistry incorpo-
rating various kinds of ligands has upsurged in recent years due to
the fascinating reactivities exhibited by the resultant complexes
[1]. Althoughmostof the ligandscontainingazo nitrogen are multid-
entate (bi- or tridentate), the coordination mode of azo nitrogen to
transition or non-transition metal ions is well documented [2–14].
Studies on the chemistry of ruthenium complexes with azo ligands
have been ongoing and several interesting results related to electron
transfer reactions, formation of metal–carbon bonds, aromatic ring
amination, isomerism, cytotoxicity toward cancer cells, application
in catalytic transformations and complexes with azo ligands that
can act as a molecular switch, have been reported [15–23]. A signif-
icant property of the azo type ligands, due to the presence of the –
N@N– group, is that it may lead to the stabilization of low valent
only one structure of a ruthenium(II) phosphine complex with a
p-tolylazo ligand, published in 1973 [41].
Research on p-tolyldiazo complexes, especially ruthenium ones,
concern the coordination geometries of the diazo ligand and its
similarity to the nitrosyl group. The isoelectronic nature of NO+
+
and the ArN2 moiety allows the assumption that the coordinated
aryldiazonium cation may also exhibit a duality of bonding modes.
It can be characterized as either linear or bent M–N–N structural
units, as shown in scheme below:
metal oxidation states. This is caused by its
p acidity and the
presence of low lying azo-centered p⁄-molecular orbitals [24,25].
However most of the studied complexes containing the
R–N@N–R0 type azo compounds as well as the aryldiazenido com-
plexes have been overlooked in the literature. Nevertheless, some
papers referred to aryldiazenido complexes of selected metals of
groups 17, 18 and 19, i.e. Mn, Re and Ir [26–34]. Several reports
on ruthenium aryldiazenido complexes have been released in the
1970s [35–40]. These studies concerned the synthesis and primary
Based on crystallographic evidence, it can be concluded that for
describing the linear mode of bonding, the Ib unit is clearly more
important than unit Ia. Similar studies extended by the dynamic
behavior of aryldiazenido ligands in half sandwich ruthenium(II)
complexes have been published in 2000 [42].
Nevertheless the reactivity of ruthenium aryldiazenido com-
plexes has not been investigated yet. Moreover their electronic
structures, bonding properties as well as absorption and emission
electronic spectra have not been determined by density functional
⇑
Corresponding author.
E-mail address: gmalecki@us.edu.pl (J.G. Małecki).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.12.012

J.G. Małecki et al. / Polyhedron 51 (2013) 102–110
103
theory (DFT). Hence in this paper we report an experimental and
quantum chemical study of ruthenium(II) p-tolyldiazenido
complexes. Starting from the known [RuCl3(PPh3)2(N2PhCH3)]
compound, reactions with pyrazole and imidazole, leading to the
new complexes [RuCl3(PPh3)(N2PhCH3)(HPz)] and [RuCl3(PPh3)
(N2PhCH3)(HIm)]ꢀCH3OH, have been performed. Quantum chemi-
cal studies, which include characterization of the molecular and
electronic structures of the complexes by analyzing the optimized
molecular geometries and electronic populations using the natural
bond orbitals scheme, have been conducted. NBO analysis was also
used to identify nature of the interactions between the azo ligand
and the metal. The calculated density of states showed the interac-
tions and influences of the orbital compositions in the frontier
electronic structures. Finally, time dependent density functional
theory (TD-DFT) was used to calculate and interpret the electronic
absorption spectra.
128.62 (s, PPh3), 128.00 (d, J = 10.5 Hz, p-toluidine), 120.20 (s, p-
toluidine), 106.75 (d, J = 3.5 Hz HPz, p-toluidine), 21.63 (s, p-tolui-
dine). UV–Vis (methanol, loge): 421 (1.21), 304 (2.36), 275 (3.61),
267 (3.92), 261 (3.90), 212 (4.81). Fluorescence (c = 1 ꢂ 10ꢁ4 mol/
cm3, methanol): exc: 244 nm; em: 291, 385 nm.
Complex (3): Yield: 68%. IR (KBr, cmꢁ1): 3430, 3340
m
NH; 3056
(C@C)PPh3; 1576 m(C@N/C@C)HIm
Ph(P–Ph); 1183 d(C–C toluidine); 1091,
1066 d(CH3); 815, 748 d(C–C out of the plane); 695 d(C–C in the plane); 520
d(ring)
1H NMR (400 MHz, CDCl3) d: 10.38 (s, HIm), 8.24 (s, p-tolu-
m
ArH; 2961
mCH3; 1841
m
(N@N); 1622
m
;
1483 d(C–CH
plane); 1434
m
in the
.
idine), 7.98 (dd, J = 10.7, 8.0 Hz, PPh3), 7.29 (d, J = 7.6 Hz, PPh3),
7.10 (dt, J = 37.7, 12.9 Hz, HIm), 6.89 (s, HIm), 3.51 (s, CH3OH),
2.42 (d, J = 8.3 Hz, p-toluidine), 2.19 (s, CH3OH). 31P NMR
(162 MHz, CDCl3) d: 23.39 (s). 13C NMR (101 MHz, CDCl3) d:
144.72 (s, p-toluidine), 134.52 (d, J = 9.1 Hz, HIm), 131.05 (s, p-
toluidine), 130.77 (s, PPh3), 130.28 (s, PPh3), 128.53 (s, p-toluidine),
127.78 (s, HIm), 21.60 (s, p-toluidine). UV–Vis (methanol, loge):
424 (1.24), 308 (2.34), 272 (3.67), 266 (3.97), 261 (4.01), 214
(4.78). Fluorescence (c = 1 ꢂ 10ꢁ4 mol/cm3, methanol): exc:
243 nm; em: 293, 389 nm.
2. Experimental
All reagents, except p-tolyldiazenido tetrafluoroborate, used for
the syntheses of the complexes were commercially available and
were used without further purification. The p-tolyldiazenido
tetrafluoroborate was synthesized by standard diazotization of
p-toluidine.
2.2. Physical measurements
Infrared spectra were recorded on a Nicolet Magna 560 spectro-
photometer in the spectral range 4000–400 cmꢁ1 using KBr pellets.
Electronic spectra were measured on a Jasco V-600 spectropho-
tometer in the range 600–180 nm in methanol solutions. The 1H,
13C and 31P NMR spectra were obtained at room temperature in
CDCl3 using a Bruker 400 MHz spectrometer. Luminescence mea-
surements were made in methanolic solutions on an F-2500 FL
spectrophotometer at room temperature.
2.1. Synthesis of the complexes [RuCl3(PPh3)2(N2PhCH3)]ꢀCH3OH (1),
[RuCl3(PPh3)(N2PhCH3)(HPz)] (2) and
[RuCl3(PPh3)(N2PhCH3)(Im)]ꢀCH3OH (3)
Complex (1) was prepared according to the literature method
[41] using CsCl instead of LiCl and has been obtained in almost
quantitative yield. Complexes (2) and (3) have been synthesized
as follows:
2.3. Computational methods
To a suspension of a 0.18 g sample of [RuCl3(PPh3)2(N2PhCH3)]-
ꢀCH3OH in a 1:1 solution of methanol:acetone, 0.02 g of pyrazole or
imidazole was added. In both cases, the mixture was refluxed for
3 h and then cooled down and filtered (the same products were ob-
tained by stirring the reaction mixtures overnight). After standing
overnight at room temperature, crystals suitable for X-ray crystal
analysis were formed.
The calculations were carried out using the GAUSSIAN09 [43] pro-
gram. Molecular geometries of the singlet ground state of the com-
plexes were fully optimized in the gas phase at the B3LYP/DZVP
level of theory [44,45]. For each complex frequency calculations
were carried out, verifying that the obtained optimized molecular
structures correspond to energy minimum; thus only positive fre-
quencies were found. The DZVP basis set [46] with f functions with
exponents 1.94722036 and 0.748930908 was used to describe the
ruthenium atom and the basis set used for the lighter atoms (C, N,
Cl, P, H) was 6-31G with a set of ‘‘d’’ and ‘‘p’’ polarization functions.
The TD-DFT method [47] was employed to calculate the electronic
absorption spectra of the complexes using the solvent Polarizable
Continuum Model (PCM). In this work 100 singlet excited states
were calculated as vertical transitions for the complexes. Natural
bond orbital (NBO) analysis was also made for all the complexes
using the NBO 5.0 package [48] included in GAUSSIAN09. Natural bond
orbitals are orbitals localized on one or two atomic centers which
describe molecular bonding in a manner similar to a Lewis electron
pair structure. They correspond to an orthonormal set of localized
orbitals of maximum occupancy. NBO analysis provides the contri-
Complex (1): IR (KBr, cmꢁ1): 3056
(C@C); 1482 d(C–CH in the plane); 1434 Ph(P–Ph); 1294 d(C–C toluidine); 1052
d(CH3); 816, 747 d(C–C out of the plane); 695 d(C–C in the plane); 520 d(ring)
mArH; 1889, 1868 m(N@N); 1573
m
m
.
1H NMR (400 MHz, CDCl3) d: 8.43–7.50 (m, p-toluidine, PPh3), 7.47
(t, J = 14.5 Hz, p-toluidine, PPh3), 7.43 (s, p-toluidine, PPh3), 6.89
(d, J = 8.1 Hz, p-toluidine), 6.70 (d, J = 8.2 Hz, p-toluidine), 3.51 (s,
methanol), 2.36 (s, p-toluidine), 1.42 (d, J = 104.1 Hz, methanol).
31P NMR (162 MHz, CDCl3) d: 11.21 (s). 13C NMR (101 MHz, CDCl3)
d: 134.87 (t, J = 5.1 Hz, p-toluidine), 130.47–129.82 (m, PPh3,
p-toluidine), 128.50 (s, PPh3), 127.78 (t, J = 4.9 Hz, p-toluidine),
21.47 (s, p-toluidine). UV–Vis (methanol, loge): 437 (1.29), 374
(2.31), 277 (3.77), 271 (3.98), 266 (3.76), 228 (4.34), 211 (4.88).
Fluorescence (c = 1 ꢂ 10ꢁ4 mol/cm3, methanol): exc: 258 nm; em:
288, 399 nm
bution of atomic orbitals (s, p, d) to the NBO
r and p hybrid orbitals
Complex (2): Yield: 72%. IR (KBr, cmꢁ1): 3446, 3331
m
NH; 3058
(C@N/C@C)HPz; 1482
Ph(P–Ph); 1183 d(C–C toluidine); 1124, 1045
d(CH3); 813, 777, 749 d(C–C out of the plane); 695 d(C–C in the plane); 520
d(ring)
1H NMR (400 MHz, CDCl3) d: 12.06 (s, NH), 8.26 (s, p-tolui-
for bonded atom pairs. In this scheme, three NBO hybrid orbitals
are defined, namely bonding orbital (BD), lone pair (LP), and core
(CR). They were analyzed for the atoms directly bonded to the
ruthenium atom or presenting some kind of interaction with it.
The contribution of particular groups (ligands, metal center) to a
molecular orbital was calculated using Mulliken population analy-
sis. GaussSum 2.2 [49] was used to calculate group contributions to
the molecular orbitals and to prepare the partial density of states
(DOS) spectra. The DOS spectra were created by convoluting the
molecular orbital information with Gaussian curves of unit height
and a FWHM (Full Width at Half Maximum) of 0.3 eV.
m
ArH; 1876, 1858
m(N@N); 1637m(C@C)PPh3; 1577, 1571 m
d(C–CH plane); 1432
m
in the
.
dine), 8.09–7.92 (m, PPh3), 7.67 (s, PPh3), 7.30 (dd, J = 9.4, 4.5 Hz,
HPz), 7.11 (dd, J = 23.9, 8.4 Hz, HPz), 6.43 (s, p-toluidine), 2.36 (d,
J = 44.7 Hz, CH3(toluidine)), 2.19 (s, CH3OH). 31P NMR (162 MHz,
CDCl3) d: 24.43 (s, PPh3). 13C NMR (101 MHz, CDCl3) d: 143.27 (s,
p-toluidine), 139.80 (s, HPz), 134.48 (d, J = 9.2 Hz, PPh3), 131.08
(s, HPz), 130.45 (d, J = 2.6 Hz, PPh3), 129.97 (s, p-toluidine),

104
J.G. Małecki et al. / Polyhedron 51 (2013) 102–110
Table 1
Crystal data and structure refinement details of complexes [RuCl3(PPh3)2(N2PhCH3)]ꢀCH3OH (1), [RuCl3(PPh3)(N2PhCH3)(HPz)] (2) and [RuCl3(PPh3)(N2PhCH3)(Im)]ꢀCH3OH (3).
1
2
3
Empirical formula
Formula weight
C
43H37Cl3N2P2Ru,CH3OH
C28H26Cl3N4PRu
656.92
C28H26Cl3N4PRu,CH3OH
688.96
883.15
T [K]
Crystal system
Space group
295.0(2)
monoclinic
P21/c
295.0(2)
monoclinic
C2/c
295.0(2)
monoclinic
P21/n
Unit cell dimensions
a (Å)
b (Å)
c (Å)
12.4604(6)
18.4627(9)
18.5702(8)
92.577(4)
4267.8(3)
4
1.374
0.665
1808
17.9994(4)
18.0599(3)
17.3058(4)
91.953(2)
5622.3(2)
8
1.552
0.925
2656
9.9120(3)
15.2795(4)
20.9555(7)
96.075(3)
3155.90(17)
4
1.450
0.830
1400
b (°)
V (Å3)
Z
Dcalc (Mg/m3)
Absorption coefficient (mmꢁ1
F(000)
)
Crystal dimensions (mm)
h range for data collection (°)
Index ranges
0.15 ꢂ 0.06 ꢂ 0.04
3.27–25.05
ꢁ14 6 h 6 14
ꢁ21 6 k 6 21
ꢁ22 6 l 6 22
39482
0.23 ꢂ 0.09 ꢂ 0.03
3.38–25.05
ꢁ21 6 h 6 21
ꢁ21 6 k 6 21
ꢁ20 6 l 6 20
25724
0.20 ꢂ 0.11 ꢂ 0.03
3.31–25.05
ꢁ11 6 h 6 11
ꢁ18 6 k 6 18
ꢁ24 6 l 6 24
27220
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2s(I)]
7528 [Rint = 0.0552]
7528/0/481
1.041
R1 = 0.0421
wR2 = 0.1010
R1 = 0.0572
wR2 = 0.1101
0.748/ꢁ0.401
4975 [Rint = 0.0252]
4975/0/339
1.035
R1 = 0.0267
wR2 = 0.0618
R1 = 0.0378
wR2 = 0.0657
0.703/ꢁ0.356
5571 [Rint = 0.0494]
5571/0/362
1.029
R1 = 0.0417
wR2 = 0.0758
R1 = 0.0671
wR2 = 0.0812
0.335/ꢁ0.363
R indices (all data)
Largest difference in peak and hole (e Åꢁ3
)
2.4. Crystal structure determination and refinement
parent complex (1) to 1841 cmꢁ1 in the imidazole one (3) suggests
increasing population of the diazenido p⁄ orbital in the row of
complexes (1), (2) and (3).
The crystals of [RuCl3(PPh3)2(N2PhCH3)]ꢀCH3OH (1), [RuCl3
(PPh3)(N2PhCH3)(HPz)] (2) and [RuCl3(PPh3)(N2PhCH3)(Im)]ꢀCH3OH
(3) were mounted in turn on an Xcalibur, Atlas, Gemini Ultra Ox-
ford Diffraction automatic diffractometer equipped with a CCD
detector, and used for data collection. X-ray intensity data were
The 1H, 13C and 31P NMR spectra of the complexes are given in
Section 2. The signals in the proton and carbon NMR spectra are as-
signed to the p-tolyldiazenido, triphenylphosphine and diazole li-
gands, as seen in Section 2.1. In the phosphorus spectrum of the
parent complex [RuCl3(PPh3)2(N2PhCH3)]ꢀCH3OH (1), one signal
(11.21 ppm) for the magnetically equivalent phosphorus atoms sug-
gests the presence of two triphenylphosphine groups in perfect trans
positions relative to each other. Incorporating the diazine ligands
into the coordination sphere of the parent diazenido complex (1)
gave monophosphine complexes for which the 31P NMR signals
are shifted to lower fields, 24.43 and 23.39 ppm in the complexes
withthepyrazole and imidazole ligands, respectively. Thedifference
of approximately 1 ppm between d(31P) in complexes (2) and (3)
collected with graphite monochromated MoK
(k = 0.71073 Å) at temperature 295.0(2) K, with the
radiation
scan mode.
a
x
Ewald sphere reflections were collected up to a 2h value of 50.10.
The unit cell parameters were determined from least-squares
refinements of the setting angles of 11429, 9025 and 6984 stron-
gest reflections. Details concerning crystal data and refinement
are gathered in Table 1. Lorentz, polarization and empirical absorp-
tion corrections using spherical harmonics implemented in SCALE3
ABSPACK scaling algorithm [50] were applied. The structures were
solved by the Patterson method and subsequently completed by
difference Fourier recycling. All the non-hydrogen atoms were re-
fined anisotropically using the full-matrix, least-squares tech-
nique. The OLEX2 [51] and SHELXS97, SHELXL97 [52] programs were
used for all the calculations. Atomic scattering factors were incor-
porated in the computer programs.
could be explained by the stronger
p acceptor ability of 1,2- com-
pared to 1,3-diazole occupying a trans position to the PPh3 ligand.
Hence a slightly greater deshielding effect is observed for pyrazole
complex (2). Of course, at the same time, these data indicate a stron-
ger
r donor property of the imidazole in the trans position.
3.2. Molecular structures
3. Results and discussion
Crystals suitable for single crystal X-ray analysis were obtained
by slow evaporation of the reaction mixtures. The complexes crys-
tallize in the monoclinic system, P21/c, C2/c and P21/n space groups
as solvates with one methanol molecule (1 and 3) and without sol-
vent as complex (2). The molecular structures of the complexes are
displayed as ORTEP representations in Fig. 1, and selected bond dis-
tances and angles are collected in Table 2. The crystal structure of
complex (1) has been published earlier as an acetone solvate [41]
and our results agree with those published earlier. The differences
between the structures are visible in the N@N bond length (that re-
ported earlier is shorter by 0.012 Å); moreover the Ru–N–N and N–
N–Ar angles differ by about 1°. The structures of the complexes can
3.1. Spectroscopic characterization of the complexes
The p-tolyldiazenido ligands are characterized in the infrared
spectra by strong bands with maxima in the range 1850–
1900 cmꢁ1. The IR spectra of the starting complex (1), (2) and (3)
present bands at (1889, 1868), (1876, 1858) and 1841 cmꢁ1
,
respectively. These frequencies are remarkable similar to the val-
ues of (NO) found for the analogous nitrosyl complexes. For com-
m
parison, in the IR spectrum of [RuCl3(NO)(PPh3)(HPz)] the nitrosyl
stretching band is observed at 1879 cmꢁ1 [53]. However, some
decreasing of the stretching frequencies from 1889 cmꢁ1 in the

J.G. Małecki et al. / Polyhedron 51 (2013) 102–110
105
Fig. 1. ORTEP drawings of complexes [RuCl3(PPh3)2(N2PhCH3)]ꢀCH3OH (1), [RuCl3(PPh3)(N2PhCH3)(HPz)] (2) and [RuCl3(PPh3)(N2PhCH3)(Im)]ꢀCH3OH (3) with 50% probability
displacement ellipsoids. Hydrogen atoms and methanol solvent molecules in complexes (1) and (3) are omitted for clarity.
be considered as distorted octahedral and the deviations from the
expected bond angles do not exceed 5° (Table 2). The Ru–P dis-
tances in the p-tolyldiazenido complex (1), equal to 2.4378(11)
and 2.4407(11) Å, fall in the range 2.41–2.44 Å observed for six-
coordinate ruthenium(II) complexes containing mutually trans
PPh3 ligands. The ruthenium–PPh3 bond distances have similar val-
ues in the complexes (2) and (3), but they are shorter by about
0.06 Å than those in (1). The enhancement of the Ru–P bond is
probably due to weaker Ru–N(HPz/Im) backbonding than for the
ruthenium–phosphine one. The Ru(1)–Cl(2) distances are notice-
ably shorter compared to Ru(1)–Cl(1)/(3) as a result of its trans po-
sition relative to the diazenido ligand. The trans effect of the
aryldiazenido ligand resembles the effect caused by a linear nitro-
syl moiety, but the shortening of the Ru(1)–Cl(2) bond presented in
the pyrazole nitrosyl ruthenium(II) complex is larger than that ob-
the case of r- and p-donor ligands, such as chloride. Moreover,
the electronic properties of other ligands have an impact on the
trans effect of the diazenido ligand, as can be seen in the data col-
lected in Table 2. The Ru(1)–Cl(2) distance in complex (2) is shorter
due to the stronger
p-acceptor properties of the pyrazole ligand
compared to the imidazole ligand. Thereby the Ru(1)–N(1) dis-
tance in the pyrazole complex (2) is slightly shorter by 0.004 Å.
In the pyrazole complex (2) the N(1)–N(2) bond length is elongated
compared with the parent complex (1) by about 0.013 Å, while in
the imidazole complex (3) the elongation of the diazenido bond
is negligible. The lengthening of the N–N bond and decrease of
the Ru–N–N angle in the pyrazole complex (2) confirm a weaker
backbonding interaction in complex (2) than in complex (3). How-
ever the comparison between complex (2) and its nitrosyl analog
shows some elongation of the Ru–N2PhCH distance compared to
Ru–NO; 1.731(2) Å in [RuCl3(NO)(PPh3)(HPz)] and 1.784(2) Å in
[RuCl3(N2PhCH3)(PPh3)(HPz)]. In both the nitrosyl and diazenido
complexes the coordination modes are not perfectly linear. In
served in the complex (2). The
and nitrosyl groups enhances the
gands in the trans position which results in bond shortening in
p-acceptor nature of both diazenido
p-donation character of the li-

106
J.G. Małecki et al. / Polyhedron 51 (2013) 102–110
Table 2
Selected bond lengths [Å] and angles [°] of complexes [RuCl3(PPh3)2(N2PhCH3)]ꢀCH3OH (1), [RuCl3(PPh3)(N2PhCH3)(HPz)] (2) and [RuCl3(PPh3)(N2PhCH3)(Im)]ꢀCH3OH (3).
1
2
3
Exp
Calc
Exp
Calc
Exp
Calc
Bond lengths [Å]
Ru(1)–N(1)
Ru(1)–N(3)
Ru(1)–Cl(1)
Ru(1)–Cl(2)
Ru(1)–Cl(3)
Ru(1)–P(1)
Ru(1)–P(2)
N(1)–N(2)
1.788(3)
1.80
1.784(2)
2.144(2)
2.3760(7)
2.3492(6)
2.4031(7)
2.3689(7)
1.80
1.787(3)
2.126(3)
2.3689(9)
2.3619(9)
2.3998(10)
2.3667(10)
1.80
2.18
2.41
2.38
2.50
2.43
2.19
2.39
2.44
2.47
2.43
2.3926(11)
2.3896(11)
2.3867(10)
2.4378(11)
2.4407(11)
1.152(4)
2.49
2.43
2.42
2.51
2.51
1.17
1.165(3)
1.17
1.157(4)
1.18
Angles [°]
N(1)–Ru(1)–Cl(1)
N(1)–Ru(1)–Cl(2)
N(1)–Ru(1)–Cl(3)
N(3)–Ru(1)–Cl(1)
N(3)–Ru(1)–Cl(2)
N(3)–Ru(1)–Cl(3)
N(1)–Ru(1)–N(3)
Cl(1)–Ru(1)–Cl(2)
Cl(1)–Ru(1)–Cl(3)
Cl(2)–Ru(1)–Cl(3)
N(1)–Ru(1)–P(1)
N(3)–Ru(1)–P(1)
N(1)–Ru(1)–P(2)
Cl(1)–Ru(1)–P(1)
Cl(1)–Ru(1)–P(2)
Cl(2)–Ru(1)–P(1)
Cl(2)–Ru(1)–P(2)
Cl(3)–Ru(1)–P(1)
Cl(3)–Ru(1)–P(2)
P(1)–Ru(1)–P(2)
Ru(1)–N(1)–N(2)
N(1)–N(2)–C(1)
89.39(10)
175.87(11)
88.33(10)
91.8
175.7
86.3
87.15(7)
177.24(7)
91.94(7)
87.84(6)
86.79(6)
87.52(6)
91.39(9)
90.71(2)
175.25(2)
90.05(3)
92.98(7)
175.55(6)
88.6
89.69(9)
175.11(10)
90.25(9)
88.97(9)
86.27(9)
89.84(9)
88.91(13)
91.10(3)
178.81(4)
88.86(3)
93.64(10)
177.16(9)
88.9
174.5
91.8
88.7
85.5
87.5
90.1
91.4
176.3
87.9
93.0
176.7
175.2
91.1
89.3
85.4
89.1
90.0
90.5
178.4
89.3
93.3
176.6
94.56(4)
176.87(4)
87.75(4)
90.34(10)
92.5
178.2
89.4
91.6
90.34(10)
86.71(4)
87.10(4)
88.71(4)
91.04(4)
95.45(4)
90.77(4)
173.76(4)
172.0(3)
136.7(4)
91.6
88.4
88.4
88.6
88.6
91.7
91.7
175.5
178.1
136.6
93.23(2)
88.87(2)
91.48(2)
93.7
90.1
91.4
89.79(4)
91.19(3)
91.40(4)
90.2
91.2
91.3
169.4(2)
133.5(3)
174.4
134.6
172.6(3)
132.9(3)
174.3
133.4
the nitrosyl complex the Ru–N–O angle is 176.6(3)° and the
p-tolyldiazo ligand is more bent with values of 169.4(2)° and
172.6(3)° in the complexes with pyrazole and imidazole, respec-
tively. A comparison of the metric parameters of the nitrosyl and
p-tolyldiazo pyrazole ruthenium(II) complexes shows both ligands
solvent molecules in (1) and (3) and, in general, the predicted bond
lengths are over-estimated by about 0.1 Å and the angles are al-
most unchanged. Nevertheless the general trends observed in the
experimental data are reproduced in the calculations, as can be
seen in the data collected in Table 2.
as good
p
-acceptors, but the diazenido ligand is seems to be
Based on the optimized geometries of the complexes, NBO
analyses were performed in order to reveal the nature of the
coordination mode between ruthenium and the donor atoms of
weaker than NO, which is clearly visible in Fig. 3. Generally this
fact comes from differences in the shortening of the ruthenium–
chloride distance in the trans arrangement to the nitrosyl and
diazenido ligands.
In the molecular structures of the complexes several inter- and
intra-molecular hydrogen bonds [54] exist and details of these are
collected in Table 3. In the crystal structure of the imidazole com-
plex (3) graph set analysis [55] shows the dimeric form (R44ð16Þ) of
the complex linked through methanol molecules, as is presented in
Fig. 2. In the molecular structure of the parent complex (1) some
Table 3
Hydrogen bonds for complexes [RuCl3(PPh3)2(N2PhCH3)]ꢀCH3OH (1),[RuCl3(PPh3)
(N2PhCH3)(HPz)] (2) and [RuCl3(PPh3)(N2PhCH3)(Im)]ꢀCH3OH (3) (Å and °).
D–Hꢀ ꢀ ꢀA
1
C(3)–H(3). . .Cl(1) #1
C(6)–H(6). . .Cl(2) #2
C(15)–H(15). . .Cl(1)
C(15)–H(15). . .Cl(2)
C(27)–H(27). . .Cl(2)
d(D–H)
d(Hꢀ ꢀ ꢀA)
d(Dꢀ ꢀ ꢀA)
h(DHA)
0.93
0.93
0.93
0.93
0.93
2.82
2.82
2.71
2.68
2.67
3.533(5)
3.562(5)
3.309(5)
3.358(5)
3.447(5)
134.3
137.4
123.1
130.3
141.1
p–p stacking between a PPh3 phenyl and the phenyl ring of the
p-tolyldiazenido ligand is also observable. The plane-to-plane dis-
tance between the phosphine phenyl centroid, determined by
C(38)–C(43), and the C(1)–C(6) carbons of the N2PhCH3 ligand is
equal to 3.933 Å, with the angle between the normal and the cen-
troids being 9.75° and with a shift distance 2.22 Å. The P(1)–Ru(1)–
P(2) angle in the complex of 173.76(4)°, lower than that for a linear
arrangement, indicates geometrically non-equivalent phosphine
2
N(4)–H(4). . .Cl(3)
N(4)–H(4). . .Cl(3) #3
C(18)–H(18). . .Cl(1)
C(24)–H(24). . .Cl(2)
0.84(3)
0.84(3)
0.93
2.66(3)
2.72(3)
2.59
3.157(3)
3.375(3)
3.336(3)
3.544(3)
119(3)
136(3)
137.9
146.9
0.93
2.73
moieties, though the presented p-stacking interaction may explain
3
the singlet signal in the 31P NMR spectrum.
O(1)–H(1). . .Cl(3)
N(4)–H(4). . .O(1) #1
C(8)–H(8). . .Cl(1)
C(22)–H(22). . .Cl(2)
C(24)–H(24). . .Cl(1)
C(24)–H(24). . .Cl(2)
1.02(9)
1.01(6)
0.93
0.93
0.93
2.16(9)
1.87(6)
2.81
2.68
2.77
3.161(4)
2.833(6)
3.247(5)
3.519(4)
3.285(4)
3.427(4)
166(8)
159(5)
110.0
150.2
116.2
140.4
3.3. Quantum calculations
0.93
2.66
The ground states geometries of the complexes were optimized
in singlet states using the DFT method with the B3LYP functional.
The calculations were carried out for gas phase molecules without
Symmetry transformations used to generate equivalent atoms: #1 1 ꢁ x, 1 ꢁ y,
1 ꢁ z; #2 1 ꢁ x, 1/2 + y, 3/2 ꢁ z; #3 1/2 ꢁ x, 1/2 ꢁ y, 1 ꢁ z.

J.G. Małecki et al. / Polyhedron 51 (2013) 102–110
107
Fig. 2. The R44ð16Þ motif in the crystal structure of complex (3).
Table 4
The occupancies and hybridization of the calculated R–N and N–N natural bond
orbitals (NBOs) of complexes [RuCl3(PPh3)2(N2PhCH3)] (1), [RuCl3(PPh3)(N2PhCH3)(-
HPz)] (2) and [RuCl3(PPh3)(N2PhCH3)(Im)] (3).
BD (2-
center
bond)
Occupancy
Hybridization of NBO
Wiberg
bond
indices
Ru–N(Ntolyl)
1
2
3
1.902 (0.218)
0.468
1.27
(sp2.50d2.99 Ru + 0.884(sp0.61
) )
N
1.887 (0.511)
1.905 (0.231)
0.744 (p7.33d66.81
0.470
)Ru + 0.668(p)N
0.42
1.28
(sp3.02d3.55 Ru + 0.883(sp0.61
) )
N
1.884 (0.500)
1.907 (0.228)
1.893 (0.478)
0.732 (p7.96d65.16
0.468 (p3.07d3.56 Ru + 0.884(sp0.78
0.733 (p7.26d64.32
)Ru + 0.681(p)N
0.42
1.30
0.42
)
)
N
)Ru + 0.681(p)N
N–N
1
1.985 (0.068)
1.963 (0.409)
1.984 (0.087)
1.962 (0.399)
1.986 (0.016)
1.961 (0.401)
0.696(sp1.86
0.674(p)N(1) + 0.738(p)N(2)
0.693(sp1.87 N(1) + 0.721(sp1.11
0.675(p)N(1) + 0.738(p)N(2)
0.707(sp1.63 N(1) + 0.707(sp1.64
0.674(p)N(1) + 0.734(p)N(2)
)
N(1) + 0.718(sp1.14
)
)
)
2.01
1.99
1.98
N(2)
N(2)
N(2)
2
3
)
Fig. 3. The overlap partial density of states (OPDOS) diagram for the complex
[RuCl3(PPh3)(N2PhCH3)(HPz)] (2) with the ruthenium–nitrosyl ligand interaction in
[RuCl3(PPh3)(NO)(HPz)] (dash-dot line).
)
the ligands. These analyses showed that the bonding between the
p-tolyldiazenido ligands and ruthenium is covalent; the calculated
Wiberg bond’s indices have values from 1.27 to 1.30 (Table 4). The
highest value in the imidazole complex (3) suggests the strongest
The natural population of the valence dRu orbitals in complex (1)
2
(dxy 1.71, dxz 1.92, dyz 1.15, dx2
1.14 and dz 1.20) corresponds
ꢁy2
rather to ruthenium(0). The sum of the n(dz2) and n(dx2 ) values
ꢁy2
delocalization of p-electron density over the linear fragment –N@N–.
reflect the
r-donor properties of the ligands, and these are 2.34
For the diazenido group two natural bond orbitals for N–N, and
two for the Ru–N bonds were detected. However participation of
the p orbital in the hybrid describing the second Ru–N2 bond is
highest in the imidazole complex (3), as presented in Table 4. The
Wiberg indices of ruthenium(II) and the pyrazole or imidazole nitro-
gen donor atom bonds are 0.436 and 0.431, respectively. These val-
ues indicate Coulomb-type interactions and confirm the higher
donor properties of 1,3- (Im) than 1,2-diazole (HPz) ligands. The dif-
ferences in the donor–acceptor properties of pyrazole and imidazole
are stated in the natural charges on the ruthenium, being equal to
ꢁ0.36 in (1), ꢁ0.11 in (2) and ꢁ0.41 in (3). The low charge in complex
in (1), 2.75 in (2) and 2.76 in (3), while the d occupancies (dxz
p
and dyz) of 3.07 in (1) and (3) and 3.10 in (2), significantly lower
than 4, suggest rather strong
p-acceptor properties of the ligands
surrounding the central ruthenium ion. The interaction of the li-
gands with the ruthenium atom in complex (1), presented in
Fig. 3, clearly shows that the
r-donor property of the diazenido li-
gand is noticeable smaller than that of the chloride ligands, but it is
similar to that of the triphenylphosphine ligand. The
p-acceptor
ability of N2PhCH is emphasized in LUMO, LUMO+1 (d
) and
x2ꢁy2
LUMO+3 (dz2). Fig. 4 presents the density of states (DOS) diagram
for the parent complex (1) with contours of the molecular orbitals,
and with the main contributions of Ru–N2PhCH3. As can be seen,
the py component of the diazenido group is mostly engaged in
the Ru–N2(PhCH3) bond (HOMOꢁ3). The HOMOꢁ2 contour shows
electron density transfer (connected with coordination to the
ruthenium metal) to the N(2) atom, which manifests in natural va-
lence populations of the N(1) and N(2) atoms being equal to 4.76
and 5.034, respectively, as well as in natural charges (N(1) 0.211;
N(2) ꢁ0.066). The electron density transfer is correlated with,
(2) confirms the strong p-acceptor property of pyrazole and at the
same coincides with the weaker Ru–N(HPz) backbonding interaction
in complex (2) than in complex (3). Hence the natural charges on the
–N@N– part of the diazenido ligand decrease from 0.15 in (1)
through 0.12 in (2) to 0.11 in (3). The Wiberg indices, equal to 0.8
for chloride in a trans position to the p-tolyldiazenido ligand and
0.7 for two mutually trans chloride ligands, also indicate the cova-
lent character of the interaction between chloride and ruthenium
in these complexes.

108
J.G. Małecki et al. / Polyhedron 51 (2013) 102–110
enabled by symmetry, interactions between ruthenium d and the
p
Cl(2) and Cl(3) ligands (the chloride ligands lie on the y and z axes).
The participation of ruthenium d orbitals in the frontier HOMOs
and LUMOs in complex (1) are in the range from 16% to 34% for
HOMOꢁ3 to HOMO and from 31 to 53% for LUMO to LUMO+3.
The presence of the pyrazole or imidazole ligand in the coordina-
tion sphere of complexes (2) and (3) slightly increases the partici-
pation of the dRu orbitals in the HOMOs (19–38%) and decreases the
participation in the LUMOs (15–51%). Moreover the HOMO–LUMO
energy gap increases from 3.17 eV in (1), to 3.22 eV in (3) and then
to 3.29 eV in complex (2). This change influences the luminescent
properties of the complexes. Figs. 3 and 4 show that the HOMOs
are composed of ruthenium d orbitals, with an antibonding contri-
bution of chloride
p orbitals. In turn, the p-tolyldiazenido ligand
orbitals take part in HOMOꢁ2 and HOMOꢁ3 in complex (1) and
HOMOꢁ2/ꢁ1 in the pyrazole and imidazole complexes (2) and
(3). Interestingly, the non-bonding ruthenium–diazenido ligand
interaction in the parent complex (1) changes to bonding character
in the complexes (2) and (3) with the diazole ligands (Fig. 3). The
1,2- and 1,3-diazole ligands play a meaningful role in HOMOꢁ6,
localized over the whole complex molecules with percentage par-
ticipations of ruthenium and the ligands as follows: dRu (10%),
PPh3 (52–54%), Cl (7–10%), N2PhCH3 (8%) and pyrazole (17%) or
imidazole (23%) in complexes (2) or (3), respectively. The LUMO
and LUMO+1 in these complexes are localized on the ruthenium
Fig. 4. The overlap partial density of states (OPDOS) diagram for the complex
[RuCl3(PPh3)2(N2PhCH3)] (2).
d orbitals (32%) and p⁄
(63%) orbitals. The triphenylphos-
N2PhCH3
phine ligands play a role in the formation of LUMO+2, while
the diazole (HPz, HIm) ligands participate in the formation of
higher virtual orbitals (LUMO+10). LUMO+3 consist of the ruthe-
nium dz orbital as well as p⁄ orbitals of chloride, phosphine and
2
p-tolyldiazenido ligands (see Fig. 5).
3.4. Experimental and theoretical electronic spectra
The UV–Vis spectra of the complexes are similar and present
maxima in the visible part of the spectrum, in the range 437–
421 nm. In the near ultraviolet region complex (1) presents a max-
imum at 374 nm, which is shifted to higher energy (304 and
308 nm) for complexes (2) and (3), of lower symmetry. In these re-
gions, the transitions from HOMO, HOMOꢁ2 and HOMOꢁ7/8 to
LUMO and LUMO+1 were calculated. These bands have LF (ligand
field) character, but based on the participation of the ligands in
Fig. 5. The density of states (DOS) diagram for complex (1) with contours of the
molecular orbitals describing the ruthenium p-tolyldiazenido ligand interaction.
Fig. 6. UV–Vis spectrum of a methanolic solution of complex (1).

J.G. Małecki et al. / Polyhedron 51 (2013) 102–110
109
in the IR band positions of the complexes. The donor–acceptor
properties of p-tolyldiazenido and nitrosyl ligands were compared
using the density-of-state method. The electronic structures of the
complexes were characterized in particular by density-of-state
diagrams. Solutions of the complexes excited in the UV spectral re-
gion gave two fluorescence maxima at 280 nm and close to 400 nm
(385–399 nm).
Acknowledgement
Calculations have been carried out in Wroclaw Centre for Net-
working and Supercomputing (http://www.wcss.wroc.pl).
References
[1] J.L. Pratihar, N. Maiti, P. Pattanayak, S. Chattopadhyay, Polyhedron 24 (2005)
1953.
[2] D. Banerjee, U. Ray, S. Jasimuddin, J.-C. Liou, T.-H. Lu, C. Sinha, Polyhedron 25
(2006) 1299.
[3] D. Patra, J.L. Pratihar, B. Shee, P. Pattanayak, S. Chattopadhyay, Polyhedron 25
(2006) 2637.
Fig. 7. The fluorescence spectra of complexes (1), (2) and (3) in methanol solutions
(c = 1 ꢂ 10ꢁ4 mol/dm3).
[4] P. Pratihar, A.K. Dasmahapatra, C. Sinha, Polyhedron 26 (2007) 1217.
[5] T. Ren, Chem. Rev. 108 (2008) 4185.
[6] T.K. Mondal, S.K. Sarker, P. Raghavaiah, C. Sinha, Polyhedron 27 (2008) 3020.
[7] P. Pattanayak, J.L. Pratihar, D. Patra, V.G. Puranik, S. Chattopadhyay, Polyhedron
27 (2008) 2209.
[8] J.L. Pratihar, P. Pattanayak, J.H. Huang, S. Chattopadhyay, Inorg. Chim. Acta 362
(2009) 5170.
[9] D. Sardar, P. Datta, P. Mitra, C. Sinha, Polyhedron 29 (2010) 3170.
[10] P. Pattanayak, D. Patra, J.L. Pratihar, A. Burrows, M. Mohan, S. Chattopadhyay,
Inorg. Chim. Acta 363 (2010) 2865.
these molecular orbitals MLCT (Metal–Ligand Charge Transfer)
transitions also occur in the bands. The insertion of diazole ligands
in complexes (2) and (3) resulted in increasing the energy of the
second band associated with the participation of pyrazole and
imidazole in orbitals involved in the transitions (Hꢁ7/ꢁ8 ? L+1
63%; 53%). Moreover, as mentioned above, in the diazole com-
plexes the energies of the occupied molecular orbitals decrease
with the increasing energy of the unoccupied MOs, which also ex-
plains the changes in the second band positions in the UV
spectrum.
[11] A.K. Sharma, S. Biswas, S.K. Barman, R. Mukherjee, Inorg. Chim. Acta 363
(2010) 2720.
[12] J.L. Pratihar, P. Pattanayak, D. Patra, R. Rathore, S. Chattopadhyay, Inorg. Chim.
Acta 367 (2011) 182.
[13] J.L. Pratihar, P. Pattanayak, D. Patra, Chia-Her Lin, S. Chattopadhyay,
Polyhedron 33 (2012) 67.
[14] D. Mallick, A. Nandi, K.K. Sarker, P. Datta, T.K. Mondal, C. Sinha, Inorg. Chim.
Acta 387 (2012) 352.
[15] A.C.G. Hotze, M. Bacac, A.H. Velders, B.A.J. Jansen, H. Kooijman, A.L. Spek, J.G.
Haasnoot, J. Reedijk, J. Med. Chem. 46 (2003) 1743.
[16] A.C.G. Hotze, E.P.L. van der Geer, S.E. Caspers, H. Kooijman, A.L. Spek, J.G.
Haasnoot, J. Reedijk, Inorg. Chem. 43 (2004) 4935.
[17] S. Halder, R. Acharyya, S.-M. Peng, G.-H. Lee, M.G.B. Drew, S. Bhattacharya,
Inorg. Chem. 45 (2006) 9654.
[18] S.J. Dougan, M.M.A. Habtemariam, S. Parsons, P.J. Sadler, Inorg. Chem. 45
(2006) 10882.
[19] H.-Y. Ye, F.-R. Dai, L.-Y. Zhang, Z.-N. Chen, Inorg. Chem. 46 (2007) 6129.
[20] S. Kannan, R. Ramesh, Y. Liu, J. Organomet. Chem. 692 (2007) 3380.
[21] S. Samanta, P. Singh, J. Fiedler, S. Záliš, W. Kaim, S. Goswami, Inorg. Chem. 47
(2008) 1625.
[22] C. Renner, L. Moroder, Chem. Biol. Chem. 7 (2006) 868.
[23] J. Otsuki, T. Akasaka, K. Araki, Coord. Chem. Rev. 252 (2008) 32.
[24] M. Kurihara, A. Hirooka, S. Kume, M. Sugimoto, H. Nishihara, J. Am. Chem. Soc.
124 (2002) 8800.
[25] K. Yamaguchi, S. Kume, K. Namiki, M. Murata, N. Tamai, H. Nishihara, Inorg.
Chem. 44 (2005) 9056.
In the UV region (277–261 nm) three close together bands are
visible, as shown in Fig. 6. The frontier orbitals HOMO plus
LUMO+4 and LUMO+5 are engaged in transitions that correspond
to two bands, whilst a third band comes from the HOMOꢁ9 ? LU-
MO+3 transition. Based on the compositions of these orbitals, the
bands have a mixed nature which can be specified by MLCT, LMCT
and LLCT transitions types. Solutions of the complexes that have
been excited at 258, 244 and 243 nm for complexes (1), (2) and
(3), respectively, gave two emissions peaks one with a maxima
close to 280 nm and a much stronger peak at 399, 385 and
389 nm, respectively. Fig. 7 presents the fluorescence spectra.
The relative intensities of the emission bands are about 1.5 for
(1), 4 for (2) and 5 for complex (3), thus the imidazole complex
(3) gave a very intense emission. The complicated structure of
the luminescence spectra suggests that more than one state is in-
volved in the luminescence process. Hence the luminescence is of
IL/MLCT origin in these systems. Probably excited molecules of
these complexes undergo intersystem crossing and/or internal
conversions between states and these can be luminescent. Similar
emissions have been reported for a half-sandwich ruthenium com-
plex with the 2-(20-hydroxyphenyl)–benzoxazole ligand [56].
[26] C.F. Barrientos-Penna, A.H. Klahn-Oliva, D. Sutton, Organometallics 4 (1985)
367.
[27] A. Garcia-Minsal, D. Sutton, Organometallics 15 (1996) 332.
[28] A. Cusanelli, D. Sutton, Organometallics 14 (1995) 4651.
[29] A. Cusanelli, R.J. Batchelor, F.W.B. Einstein, D. Sutton, Organometallics 13
(1994) 5096.
[30] C.F. Barrientos-Penna, F.W.B. Einstein, D. Sutton, A.C. Willis, Inorg. Chem. 19
(1980) 2740.
[31] X. Yan, R.J. Batchelor, F.W.B. Einstein, X. Zhang, R. Nagelkerke, D. Sutton, Inorg.
Chem. 36 (1997) 1237.
4. Conclusion
In summary the p-tolyldiazenido ruthenium(II) complex
[RuCl3(PPh3)2(N2PhCH3)], as well as new pyrazole and imidazole
complexes [RuCl3(PPh3)(N2PhCH3)(L)] were synthesized and char-
acterized by spectroscopy and X-ray crystallography. The crystal
structure of complex (1) reveals non-covalent interactions be-
tween the aromatic rings and in the molecular structure of the
imidazole [RuCl3(PPh3)(N2PhCH3)(Im)]ꢀCH3OH complex (3) an
intermolecular hydrogen bonded ring is observed. The theoretical
results obtained from NBO and analysis of the interactions be-
tween ruthenium and the diazenido and diazole ligands were used
to explain the differences in bond lengths as well as the differences
[32] X. Yan, R.J. Batchelor, F.W.B. Einstein, D. Sutton, Inorg. Chem. 35 (1996) 7818.
[33] X. Yan, F.W.B. Einstein, D. Sutton, Can. J. Chem. 73 (1995) 939.
[34] G.C.-Y. Kim, R.J. Batchelor, X. Yan, F.W.B. Einstein, D. Sutton, Inorg. Chem. 34
(1995) 6163.
[35] J.A. McCleverty, R.N. Whiteley, J. Chem. Soc., Chem. Commun. (1971) 1159.
[36] J.A. McCleverty, D. Seddon, D.R.N. Whiteley, J. Chem. Soc., Dalton Trans. (1975)
839.
[37] B.L. Haymore, J.A. Ibers, Inorg. Chem. 14 (1975) 3060.
[38] B.L. Haymore, J.A. Ibers, Inorg. Chem. 14 (1975) 2784.
[39] K.R. Laing, S.D. Robinson, M.F. Uttley, J. Chem. Soc., Chem. Commun. (1973)
176.
[40] K.R. Laing, S.D. Robinson, M.F. Uttley, J. Chem. Soc., Dalton Trans. (1973) 2713.
[41] J.V. McArdle, A.J. Schultz, B.J. Corden, R. Eisenbergi, Inorg. Chem. 12 (1973)
1676.

110
J.G. Małecki et al. / Polyhedron 51 (2013) 102–110
[42] L. Fan, F.W.B. Einstein, D. Sutton, Organometallics 19 (2000) 684.
[43] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
G. Scalmani, V. Barone, B. Mennucci, G.A. Petersson, H. Nakatsuji, M. Caricato,
X. Li, H.P. Hratchian, A.F. Izmaylov, J. Bloino, G. Zheng, J.L. Sonnenberg, M.
Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y.
Honda, O. Kitao, H. Nakai, T. Vreven, J.A. Montgomery Jr., J.E. Peralta, F. Ogliaro,
M. Bearpark, J.J. Heyd, E. Brothers, K.N. Kudin, V.N. Staroverov, R. Kobayashi, J.
Normand, K. Raghavachari, A. Rendell, J.C. Burant, S.S. Iyengar, J. Tomasi, M.
Cossi, N. Rega, J.M. Millam, M. Klene, J.E. Knox, J.B. Cross, V. Bakken, C. Adamo,
J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C.
Pomelli, J.W. Ochterski, R.L. Martin, K. Morokuma, V.G. Zakrzewski, G.A. Voth,
P. Salvador, J.J. Dannenberg, S. Dapprich, A.D. Daniels, O. Farkas, J.B. Foresman,
J.V. Ortiz, J. Cioslowski, D.J. Fox, Gaussian 09, Revision A.1, Gaussian, Inc.,
Wallingford, CT, 2009.
[47] M.E. Casida, in: J.M. Seminario (Ed.), Recent Developments and Applications of
Modern Density Functional Theory, Theoretical and Computational Chemistry,
vol. 4, Elsevier, Amsterdam, 1996, p. 391.
[48] E.D. Glendening, A.E. Reed, J.E. Carpenter, F. Weinhold, NBO (version 3.1), 2004.
[49] N.M. O’Boyle, A.L. Tenderholt, K.M. Langner, J. Comput. Chem. 29 (2008) 839.
[50] CrysAlis RED, Oxford Diffraction Ltd., Version 1.171.35.21, 2012.
[51] O.V. Dolomanov, L.J. Bourhis, R.J. Gildea, J.A.K. Howard, H. Puschmann, J. Appl.
Crystallogr. 42 (2009) 339.
[52] G.M. Sheldrick, Acta Crystallogr., Sect A 64 (2008) 112.
[53] J.G. Małecki, M. Jaworska, R. Kruszynki, Polyhedron 24 (2005) 359.
[54] G.R. Desiraju, T. Steiner, The Weak Hydrogen Bond in Structural Chemistry and
Biology, Oxford University Press, 1999.
[55] M.C. Etter, J.C. MacDonald, J. Bersnstein, Acta Crystallogr., Sect. B 46 (1990)
256.
[44] A.D. Becke, J. Chem. Phys. 98 (1993) 5648.
[45] C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785.
[56] J.G. Małecki, R. Kruszynski, M. Jaworska, P. Lodowski, Z. Mazurak, J.
Organomet. Chem. 693 (2008) 1096.
[46] K. Eichkorn, F. Weigend, O. Treutler, R. Ahlrichs, Theor. Chem. Acc. 97 (1997)
119.