Synthesis, crystal, molecular and electronic structures of thiocyanate hydrido-carbonyl ruthenium(II) complexes with imidazole derivatives ligands

Article abstract of DOI:10.1016/j.poly.2010.05.019

[RuH(CO)(SCN)(PPh₃)₃] and [RuH(CO){SCN}(PPh ₃)₂(L)]{SCN} complexes (where L = benzimidazole, 2-(2-pyridyl)benzimidazole and 2,2′-bis(4,5-dimethylimidazolyl)) have been prepared and studied by IR, NMR, UV-Vis spe

Full text of DOI:10.1016/j.poly.2010.05.019

Polyhedron 29 (2010) 2489–2497
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis, crystal, molecular and electronic structures of thiocyanate
hydrido-carbonyl ruthenium(II) complexes with imidazole derivatives ligands
J.G. Małecki
Department of Crystallography, Institute of Chemistry, University of Silesia, 9th Szkolna St., 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:
[RuH(CO)(SCN)(PPh3)3] and [RuH(CO){SCN}(PPh3)2(L)]{SCN} complexes (where L = benzimidazole,
2-(2-pyridyl)benzimidazole and 2,20-bis(4,5-dimethylimidazolyl)) have been prepared and studied by
IR, NMR, UV–Vis spectroscopy and X-ray crystallography. Electronic structures and bonding of the
obtained complexes were defined on the basis of DFT method. Values of the ligand field parameter
10Dq and Racah’s parameters were estimated for the studied compounds, and the luminescence proper-
ties were determined.
Received 17 April 2010
Accepted 21 May 2010
Available online 26 May 2010
Keywords:
Ruthenium hydridocarbonyl complexes
Ruthenium thiocyanate complexes
Benzimidazole
Ó 2010 Elsevier Ltd. All rights reserved.
2-(2-Pyridyl)benzimidazole
2,20-Bis(4,5-dimethylimidazolyl)
X-ray structure
UV–Vis
Luminescence
DFT
TD-DFT
1. Introduction
2. Experimental
The chemistry of ruthenium complexes with nitrogen-contain-
ing ligands has been attracting continuous attention due to their
variety of structures, reactivities and photophysical and photo-
chemical properties [1]. Especially the ruthenium analog of Vaska
and Diluzio’s complex [2] – [RuHCl(CO)(PPh3)3] – is the most stud-
ied compound of the series of ruthenium(II) hydridecarbonyl com-
plexes. Additionally, the azine, especially polyazine ligands have
All reagents used for the synthesis of the complex are commer-
cially available and have been used without further purification.
The [RuHCl(CO)(SCN)(PPh3)3] complex was synthesized according
to the literature method [7].
2.1. Synthesis of [RuH(CO)(SCN)(PPh3)3] (1)
energetically low lying
p-antibonding orbitals, which can accept
The complex was synthesized in a reaction between [RuHCl(CO)
(SCN)(PPh3)3] (1 ꢁ 10ꢀ4 mol) and NH4SCN (1 ꢁ 10ꢀ4 mol) in meth-
anol solution (50 cmꢀ3). The mixture of the compounds was re-
fluxed in methanol by 3 h. After this time, it was cooled and
filtered. The crystals suitable for X-ray crystal analysis were ob-
tained by slow evaporation of the reaction mixture.
electrons from filled metal d orbitals. In consequence, they can ex-
hibit charge transfer bands with interesting spectroscopic proper-
ties in the visible region [3]. Ligands containing imidazole ring are
relatively less studied but their moderate
interesting. Its combination with other donor atoms should in
p-donor properties are
principle afford complexes with tunable spectroscopic properties
[4,5]. The hydride ligand – a powerful
Yield 81%. Anal. Calc. for C56H46NOP3RuS: C, 68.98; H, 4.76; N,
r-donor – is found to be
1.44. Found: C, 69.14; H, 4.69; N, 1.39%. IR (KBr): 3056
SCN); 2019 (Ru–H); 1947 (CO); 1479, 1311 d(C–CH
Ph(P–Ph); 1089 d(C–CH
m
ArH; 2089
;
in the plane)
very efficient at compensating the electron deficiency at the metal
central ion in complexes. The ‘‘trans effect” of Hꢀ ligand and the
interaction between CO and N-donor ligands in trans positions to
one another are stabilizing factors which explain stability of these
complexes [6], are interesting due to their properties.
m(CN
1433
m
m
from
m
plane); 999 d(C–H
;
in the
out of the plane)
828
m(SC from SCN), 743 d(C–C out of the plane); 695 d(C–C in the plane); 520
m(P–Ph P–Ru), 494 d(NCS), UV–Vis (methanol; log e): 371.1 (1.21),
+
323.4 (3.90), 246.8 (4.86), 213.3 (5.12). 1H NMR (d, CDCl3):
7.642–6.940 (m, PPh3), ꢀ7.045, ꢀ7.295 (dt, HRu). 13C NMR (d,
CDCl3): 203.897 (CO), 148.435 (NCS), 127.918, 129.540, 134.134,
134.871, 138.501 (PPh3). 31P NMR (d, CDCl3): 39.400 (d, PPh3).
E-mail address: gmalecki@us.edu.pl
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.05.019

2490
J.G. Małecki / Polyhedron 29 (2010) 2489–2497
2.2. Synthesis of [RuH(CO){SCN}(PPh3)2(L)]{SCN}
2.5. [RuH(CO)(PPh3)2(DMIM)](SCN) (4)
This complex was synthesized in the reaction between
[RuHCl(CO)(PPh3)3] (1 ꢁ 10ꢀ4 mol), NH4SCN (1 ꢁ 10ꢀ4 mol), benz-
imidazole, 2-(2-pyridyl)benzimidazole and 2,20-bis(4,5-dimethy-
limidazolyl) in methanol solution (50 cmꢀ3). The mixture of the
compounds was refluxed in methanol by 3 h. After this time, it
was cooled and filtered. The crystals suitable for X-ray crystal
analysis were obtained by slow evaporation of the reaction
mixture.
Yield 58%. Anal. Calc. for C48H45N5OP2RuS: C, 63.85; H, 5.02; N,
7.76. Found: C, 63.82; H, 5.07; N, 7.79%. IR (KBr): 3004
CH; 2044 (Ru–H); 1927 (CO); 1663 mCN C@C; 1479, 1310 d(C–CH in the plane)
1433 Ph(P–Ph); 1092 d(C–CH in the plane); 998 d(C–H out of the plane); 746
d(C–C out of the plane); 695 d(C–C in the plane); 519 (P–Ph + P–Ru). UV–Vis
mArH; 2798
m
m
m
,
m
;
m
m
(methanol; log e): 399.7 (1.19), 300.2 (2.51), 254.7 (3.27), 212.8
(4.84). 1H NMR (d, CDCl3): 11.725 (s, NH), 7.701–7.284 (m, PPh3),
2.266 (s, CH3), ꢀ11.974 (t, HRu). 31P NMR (d, CDCl3): 45.474 (s,
PPh3).
2.3. [RuH(CO)(SCN)(PPh3)2(BIm)]ꢂH2O (2)
2.5.1. Physical measurements
Yield 60%. Anal. Calc. for C45H39N3O2P2RuS: C, 63.67; H, 4.63; N,
Infrared spectra were recorded on a Nicolet Magna 560 spectro-
photometer in the spectral range 4000–400 cmꢀ1 with the sample
in the form of a KBr pellet. Electronic spectra were measured on a
Lab Alliance UV–Vis 8500 spectrophotometer in the range of 500–
180 nm in acetonitrile solution. The 1H, 13C and 31P NMR spectra
were obtained at room temperature in CDCl3 using Bruker 400
spectrometer. Luminescence measurements were made on a F-
2500 FL spectrophotometer at room temperature. Elemental anal-
yses (C, H, N) were performed on a Perkin–Elmer CHN-2400
analyzer.
4.95. Found: C, 63.64; H, 4.60; N, 5.01%. IR (KBr): 3099
SCN); 1969 (Ru–H); 1926 (CO); 1620 mCN
plane); 1434 P–Ph; 1090 d(C–CH
mArH; 2075
C@C; 1481,
plane); 959
m(CN
1269 d(C–CH
m
m
,
m
from
m
in the
in the
d(C–H out of the plane); 863
m(SC from SCN), 740 d(C–C out of the plane); 695
d(C–C plane); 517 m(P–Ph P–Ru), 421 d(NCS). UV–Vis (methanol;
in the
+
log e
): 398.9 (1.12), 328.7 (1.29), 267.0 (3.05), 212.9 (4.84). 1H
NMR (d, CDCl3): 8.222 (s, H), 7.400–7.104 (m, PPh3), 1.584 (H2O),
ꢀ6.945, ꢀ7.185 (dt, HRu). 31P NMR (d, CDCl3): 40.194 (s, PPh3).
2.4. [RuH(CO)(PPh3)2(PyBIm)](SCN) (3)
2.5.2. DFT calculations
Yield 74%. Anal. Calc. for C50H40N4OP2RuS: C, 66.14; H, 4.44; N,
6.17. Found: C, 66.12; H, 4.47; N, 6.14%. IR (KBr): 3050 mArH; 2833,
The calculations were carried out using GAUSSIAN09 [8] program.
The DFT/B3LYP [9] method was used for the geometry optimiza-
tion and electronic structure determination, and electronic spectra
were calculated by TD-DFT [10] method. The calculations were
performed using the DZVP basis set [11] with f functions with
exponents 1.94722036 and 0.748930908 on ruthenium atom,
and polarization functions for all other atoms: 6-31g(2d,p) – sulfur,
6-31g** – carbon, nitrogen and 6-31g(d,p) – hydrogen. The PCM
(Polarizable Continuum Model) solvent model was used in the
2594
d(C–CH
d(C–H
m
(SCN), 2062
m
(Ru–H); 1950
m
(CO); 1606 mCN
,
m
C@C; 1479, 1327
plane); 1433
plane); 741 d(C–C
mPh(P–Ph); 1093 d(C–CH
plane); 999
;
in the plane)
in the
in the
plane); 697 d(C–C
out of the
out of the
519 m(P–Ph P–Ru). UV–Vis (methanol; log e): 434.7 (1.13), 324.4
+
(2.35), 255.5 (3.14), 215.2 (4.27). 1H NMR (d, CDCl3): 14.410 (s,
NH), 8.605 (s, H6(py)), 7.799–6.766 (m, PPh3, PyBIm), ꢀ11.432 (t,
H
Ru). 31P NMR (d, CDCl3): 44.488 (s, PPh3).
Table 1
Crystal data and structure refinement details of [RuH(CO)(SCN)(PPh3)3] (1), [RuH(SCN)(CO)(PPh3)2(BIm)]ꢂH2O (2), [RuH(CO)(PPh3)2(PyBIm)](SCN) (3) and [RuH(CO)(PPh3)2(D-
MIM)](SCN) (4) complexes.
1
2
3
4
Empirical formula
Formula weight
C
56H46NOP3RuS
C45H37N3OP2RuS, H2O
848.87
C50H40N4OP2RuS
907.93
C48H45N5OP2RuS
902.96
974.98
Temperature (K)
Crystal system
Space group
298.0(2)
monoclinic
P21/n
298.0(2)
monoclinic
P21/n
298.0(2)
monoclinic
P21/n
298.0(2)
monoclinic
P21/n
Unit cell dimensions
a (Å)
b (Å)
c (Å)
12.9891(2)
17.6236(3)
20.8544(4)
91.5622(17)
4772.11(16)
4
1.357
0.514
2008
12.0924(4)
11.0550(3)
30.0455(9)
90.855(3)
4016.1(2)
4
1.404
0.563
1744
14.0299(2)
21.8552(4)
14.3385(3)
91.3354(16)
4395.36(13)
4
1.372
0.519
1864
13.9207(4)
17.1242(3)
18.5967(5)
99.044(2)
4378.00(18)
4
b
V (Å3)
Z
Calculated density (mg m3)
Absorption coefficient (mmꢀ1
F(0 0 0)
1.370
)
1864
Crystal dimensions (mm)
h Range for data collection (°)
Index ranges
0.38 ꢁ 0.12 ꢁ 0.07
3.34–25.05
ꢀ15 6 h 6 15
ꢀ20 6 k 6 20
ꢀ24 6 l 6 24
40684
0.16 ꢁ 0.15 ꢁ 0.05
3.36–25.05
ꢀ14 6 h 6 10
ꢀ12 6 k 6 13
ꢀ35 6 l 6 35
12420
0.16 ꢁ 0.15 ꢁ 0.12
3.35–25.05
ꢀ16 6 h 6 16
ꢀ26 6 k 6 26
ꢀ17 6 l 6 17
39328
0.39 ꢁ 0.27 ꢁ 0.12
3.52–25.05
ꢀ16 6 h 6 16
ꢀ20 6 k 6 20
ꢀ22 6 l 6 22
41364
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness-of-fit on F2
8435 [Rint = 0.0287]
8435/0/572
1.211
6902 [Rint = 0.0298]
6902/0/497
0.970
7741 [Rint = 0.0353]
7741/0/536
0.990
7656 [Rint = 0.0345]
7656/0/531
1.039
Final R indices [I > 2
r
(I)]
R1 = 0.0267
wR2 = 0.0648
R1 = 0.0403
wR2 = 0.0670
0.454 and ꢀ0.288
R1 = 0.0334
wR2 = 0.0653
R1 = 0.0519
wR2 = 0.0685
0.402 and ꢀ0.476
R1 = 0.0349
wR2 = 0.0726
R1 = 0.0535
wR2 = 0.0765
0.451 and ꢀ0.491
R1 = 0.0404
wR2 = 0.0979
R1 = 0.0635
wR2 = 0.1070
0.632 and ꢀ0.543
R indices (all data)
Largest difference in peak and hole

J.G. Małecki / Polyhedron 29 (2010) 2489–2497
2491
Gaussian calculations with methanol as the solvent. Natural bond
orbital (NBO) calculations were performed with the NBO code
[12] included in GAUSSIAN09. The contribution of a group to a molec-
ular orbital was calculated using Mulliken population analysis.
GAUSSSUM 2.2 [13] was used to calculate group contributions to the
molecular orbitals and to prepare the partial density of states
(PDOS) and overlap population density of states (OPDOS) spectra.
The PDOS and OPDOS spectra were created by convoluting the
molecular orbital information with Gaussian curves of unit height
and FWHM (Full Width at Half Maximum) of 0.3 eV. Mayer bond
orders were calculated with use of QMFORGE program [14]. The
ADF single point calculations were performed for the B3LYP/GAUSS-
IAN09 optimized geometries with use of ADF program (Release 2008)
[15].
In the case of [RuH(CO)(SCN)(PPh3)3] (1) complex, a doublet in
the 31P NMR spectrum is visible at 39.400 ppm in accordance with
the structure confirmed by X-ray. In the 13C NMR spectrum of com-
plex 1, apart from signals attributed to PPh3 and CO ligands, a sig-
nal at 148.435 ppm ascribed to thiocyanate carbon was shown.
Infrared spectra of the obtained complexes have characteristic
bands due to ligands vibrations. The intense bands around
2000 cmꢀ1 and above 1900 cmꢀ1 in IR spectra indicate the pres-
ence of hydrido and carbonyl ligands in the complexes. The
stretching modes of the Ar–H present maxima at 3056, 3099,
3050 and 3004 cmꢀ1, for complexes 1–4, respectively. The methyl
groups (DMIM) C–H stretching and bend modes have the maxima
at 2798 and 1092 cmꢀ1, respectively. The twist modes of benzene
C–H are at 999 cmꢀ1 for complexes 1 and 3 and 959 and
998 cmꢀ1 for compounds 2 and 4. N-heteroaromatic ligands in
complexes 2, 3 and 4 present stretching mode of CN groups bands
at 1620, 1606, 1663 cmꢀ1, respectively. The intense band with
maximum at 1433 (1434) cmꢀ1 is characteristic to stretching of
phenyl C–H bonds in triphenylphosphine complexes. The coordi-
nation mode of thiocyanate ligand in the complexes 1 and 2 are
indeterminable from the IR spectral data of these compounds.
Three characteristic bands are observed at 2089, 828, 494 cmꢀ1
in IR spectrum of 1 and 2075, 863, 421 cmꢀ1 for 2 ascribed, respec-
2.6. Crystal structures determination and refinement
Crystals of [RuH(CO)(SCN)(PPh3)3] (1), [RuH(SCN)(CO)(PPh3)2-
(BIm)]ꢂH2O (2), [RuH(CO)(PPh3)2(PyBIm)](SCN) (3) and [RuH-
(CO)(PPh3)2(DMIM)](SCN) (4) were mounted in turn on an
Xcalibur, Atlas, Gemini ultra Oxford Diffraction automatic diffrac-
tometer equipped with a CCD detector, and used for data collec-
tion. X-ray intensity data were collected with graphite
tively to m(CN), m(CS) and d(NCS). For N-bonded complexes, generally
monochromated Mo Ka radiation (k = 0.71073 Å) at temperature
the C–N stretching band is in a lower region around 2050 cmꢀ1
than that of 2100 cmꢀ1 for S-bonded complexes. However, the fre-
quencies of the bands are sensitive to other factors like coexisting
ligands and the structure of the compounds were determined using
X-ray analysis. While the M–S–C angles of S-bonded thiocyanato li-
gand in complexes are bent around 110°, the M–N–C angles of N-
bonded isothiocyanato ligands are close to linear. The Ru(1)–N(1)–
C(1) angles in complexes 1 and 2 are 163.32(17) and 170.1(2),
respectively indicating the isothiocyanato ligands. The more bent
structure of Ru(1)–N(1)–C(1) in complex 1 is connected with the
298.0(2) K, with scan mode. Ewald sphere reflections were col-
x
lected up to 2h = 50.10. The unit cell parameters were determined
from least-squares refinement of the setting angles of 24824, 7175,
23700 and 23887 strongest reflections for complexes 1–4, respec-
tively. Details concerning crystal data and refinement are gathered
in Table 1. During the data reduction, the decay correction coeffi-
cient was taken into account. Lorentz, polarization and numerical
absorption corrections were applied. The structures were solved
by Patterson method. All the non-hydrogen atoms were refined
anisotropically using full-matrix, least-squares technique on F2.
The Ru–H hydrogen atoms were found from difference Fourier syn-
thesis after four cycles of anisotropic refinement, and refined as
‘‘riding” on the adjacent atom with individual isotropic tempera-
ture factor equal 1.2 times the value of equivalent temperature fac-
tor of the parent atom, with geometry idealization after each cycle.
OLEX2 [16] program was used for all the calculations. Atomic scat-
tering factors were those incorporated in the computer programs.
presence of a strong
p-acceptor CO ligand in trans position. The
trans effect of the Hꢀ ligand results in an elongation of the Ru(1)–
N(1) bond in complex 2 by about 0.06 Å. In cationic complexes 3
and 4, under the influence of trans hydrido ligands the bond dis-
tances Ru(1)–N(3) are longer than Ru(1)–N(1) by about 0.1 Å. In
the case of [RuH(CO)(PPh3)2(DMIM)](SCN) (4) complex, the bond
distances in thiocyanate anion are longer due to hydrogen bonds
occurring between sulfur and imidazole NH group, and intra- and
intermolecular hydrogen bonds connected nitrogen atom and
methyl group of DMIM ligand and phenyl phosphine. The hydro-
gen bonds present in the structures of all studied compounds, were
collected in Table 3, and these bonds in compounds 2, 3 and 4 were
depicted in Fig. 2.
3. Results and discussion
The reactions of the [RuHCl(CO)(PPh3)3] complex with benz-
imidazole (BIm), 2-(2-pyridyl)benzimidazole (PyBIm) or 2,20-
bis(4,5-dimethylimidazolyl) (DMIM) and ammonium thiocyanate
have been carried out. Refluxing the starting ruthenium(II) com-
plex with ammonium thiocyanate in methanol leads to [RuH(-
CO)(SCN)(PPh3)3] complex (1) with good yield, and in the
reactions between [RuHCl(CO)(PPh3)3] complex with stoichiome-
tric quantity of NH4SCN and N-donor ligands as benzimidazole,
2-(2-pyridyl)benzimidazole or 2,20-bis(4,5-dimethylimidazolyl),
neutral [RuH(CO)(SCN)(PPh3)2(BIm)]ꢂH2O (2) and cationic [RuH(-
CO)(PPh3)2(PyBIm)](SCN) (3), [RuH(CO)(PPh3)2(DMIM)](SCN) (4)
complexes form. Elemental analysis of the complexes is in a good
agreement with their formulas. The 1H NMR spectra of the com-
plexes displayed sets of signals, given in Section 2, that where as-
cribed to N-heteroaromatic and triphenylphosphine ligands. The
doublet of triplets at ꢀ7.045, ꢀ7.295, ꢀ6.945, ꢀ7.185 ppm and
triplets at ꢀ11.432, ꢀ11.974 ppm indicated the hydride ligand in
neutral 1, 2 and cationic 3, 4 complexes, respectively. The singlets
in 31P NMR spectra of complexes 2, 3 and 4 at 40.194, 44.488 and
45.474 ppm indicated both the triphenylphosphine ligands in the
compounds are equivalent and they are mutually trans disposed.
All studied complexes crystallize in the monoclinic space group
P21/n. The molecular structures with the structural drawings of the
compounds are shown in Fig. 1. The selected bond lengths and an-
gles are listed in Table 2. In the studied complexes, the ruthenium
atom has an octahedral environment and the distortions from
octahedra are visible in the angles between PPh3 ligands with value
152.26(2)° for complex 1 (caused by steric hindrance), 3.8° for 2,
6.3° in complex 3 and 15.6° for 4. The C–N and C–S bond lengths
values in the neutral complexes 1 and 2 fall in the 1.158(3) Å,
1.151(3)(3) Å and 1.619(2) Å, 1.647(3) Å ranges respectively, simi-
lar to those observed for isothiocyanate complexes.
The complex 1 is an analog of well known [RuHCl(CO)(PPh3)3]
in which chloride ligand was replaced by isothiocyanate anion. In
the structure of complex 2, hydride ligand is in trans position to-
wards NCSꢀ ligand and this configuration results from stronger
p
-acceptor properties of NCSꢀ ligand than those of benzimidazole,
and thus the favored position of Hꢀ relative to isothiocyanate li-
gand. In the complexes 3, 4 with bidendate N-heteroaromatic li-
gands, the isothiocyanate ligand was substituted during the

2492
J.G. Małecki / Polyhedron 29 (2010) 2489–2497
Fig. 1. ORTEP drawing of [RuH(CO)(SCN)(PPh3)3] (1), [RuH(SCN)(CO)(PPh3)2(BIm)]ꢂH2O (2), [RuH(CO)(PPh3)2(PyBIm)](SCN) (3) and [RuH(CO)(PPh3)2(DMIM)](SCN) (4) with
50% probability displacement ellipsoids. Hydrogen atoms (except Ru–H) are omitted for clarity.

J.G. Małecki / Polyhedron 29 (2010) 2489–2497
2493
3.1. Electronic structure
To get an insight in the electronic structures and bonding prop-
erties of the studied complexes, the calculations in the DFT method
were carried out. Before the calculations of electronic structures of
the studied compounds, their geometries were optimized in singlet
states using the DFT method with the B3LYP functional. In general,
the predicted bond lengths and angles are in a good agreement
with the values based on the X-ray crystal structure data, and
the general trends observed in the experimental data are well
reproduced in the calculations. The maximum differences between
optimized and experimental geometry of the studied compounds
are visible in the Ru–H(Ru) distance (ꢃ0.201 Å) for complex 3
and the angle differences do not exceed 3°. The stabilization ener-
gies calculated in NBO analyses have shown that the lone pairs
localized on the N atom of isothiocyanate ligand in complex 1 do-
nate the charge to ruthenium, and the stabilization energy (DEij) is
54.98 kcal/mol. In the complex 2, the same interaction is equal to
202.77 kcal/mol. The back donations to isothiocyanate ligands are
equal to 40.38 and 37.84 kcal/mol for 1 and 2, respectively. The sta-
bilization energy connected to interaction between N-heteroaro-
matic ligands and ruthenium central ions are 171.79, 321.94 and
315.38 kcal/mol in compounds 2, 3 and 4, respectively. The back
donations from ruthenium to N-heteroaromatic ligands have val-
ues 24.20 kcal/mol to benzimidazole ligand, 40.36 kcal/mol to 2-
(2-pyridil)benzimidazole and 41.00 kcal/mol to 2,20-bis(4,5-dime-
thylimidazolyl) ligand, respectively. The data suggest that the
donation from ligands to dRu orbitals plays a role in the electronic
structure of the complexes which can be seen in the occupancies of
the ruthenium d orbitals and on the other hand in the charge of
ruthenium central ion. The occupancies of dRu, obtained from
NBO analysis, are as follows 1: dxy – 0.94; dxz – 1.83; dyz – 1.86;
2
2
2
2
2
dx
– 1.86; dz – 0.83, 2: dxy – 0.99; dxz – 1.85; dyz – 1.85; dx
ꢀy
ꢀy
– 1.83; dz2 – 0.82, 3: dxy – 0.99; dxz – 1.87; dyz – 1.85; dx 2 – 1.81;
2
ꢀy
2
2
2
2
dz – 0.80, 4: dxy – 1.22; dxz – 1.53; dyz – 1.16; dx
– 1.70; dz –
ꢀy
1.31. The natural atomic charges on the ruthenium central ion in
the studied complexes with N-heteroaromatic ligands are: ꢀ0.85
in 2 and ꢀ0.80 in complexes 3 and 4.
In the HOMO orbitals of the studied neutral complexes 1 and 2,
the thiocyanate ligands play a significant role with 81% share, and
the contribution of dRu orbitals is equal to 11% and 18% in com-
plexes 1 and 2, respectively. The HOMO orbitals of the cationic
complexes 3 and 4 are localized on dRu (50% in 3; 34% in 4) and
PPh3 in complex 3 (43%) or DMIM (54%) ligand in 4 which is impor-
tant referred to luminescence properties of this complex. In the
electronic structure of [RuH(CO)(SCN)(PPh3)3] (1) complex, dRu
orbitals are diffused in the HOMO-2 to HOMO-7 energy range with
participation between 59% and 43%. The molecular orbitals with
significant contribution of d ruthenium orbitals in the other stud-
ied complexes are HOMO-2/3/4 (59%, 49%, 62%) in 2, HOMO-1/2/
3 (53%, 77%, 25%) in 3 and HOMO-1/2/3/4 (28%, 47%, 77%, 31%) in
4. The LUMO orbitals of the neutral complexes 1 and 2 are localized
on the triphenylphosphine ligands (78%) with antibonding partici-
pation of 16% and 18% dRu orbitals. In complexes 3 and 4, LUMO are
p* N-heteroaromatic ligands (96%, 95%) orbitals. Virtual molecular
orbitals with large contribution of dRu are, moreover mentioned
LUMO in neutral complexes, diffused in energy scope correspond-
ing to energy range between ꢀ2.8 and ꢀ2.2 eV, i.e. LUMO + 15 to
LUMO + 20 (15–24% in 1; 11–31% in 2; 10–21% in 3; 14–22% in
4). The dRu orbitals take part in the LUMO + 2 and LUMO + 3 of
the cationic complex 3 and LUMO + 1, LUMO + 2 in 4 with contri-
butions of 21%, 10% and 21%, 16%, respectively.
Fig. 2. Hydrogen bonds in complexes 2, 3 and 4.
In the frontier region, neighboring orbitals may be a quasi-
degeneracy of the energetic levels, and taking into consideration
only the HOMO and LUMO may not yield a realistic description
of the frontier orbitals. For this reason, the density of states
formation reactions, resulting in formation of a very stable system
with trans PPh3 ligands.

2494
J.G. Małecki / Polyhedron 29 (2010) 2489–2497
Table 2
Selected bond lengths (Å) and angles (°) for [RuH(CO)(SCN)(PPh3)3] (1), [RuH(SCN)(CO)(PPh3)2(BIm)]ꢂH2O (2), [RuH(CO)(PPh3)2(PyBIm)](SCN) (3) and [RuH(CO)(PPh3)2(D-
MIM)](SCN) (4) complexes.
1
2
3
4
Bond lengths (Å)
Ru(1)–C(2)
Ru(1)–N(1)
Ru(1)–P(1)
Ru(1)–P(2)
Ru(1)–P(3)
Ru–H1(Ru)
N(1)–C(1)
1.829(2)
2.098(17)
2.363(5)
2.383(5)
2.479(5)
1.53(2)
1.158(3)
1.619(2)
1.155(3)
Ru(1)–C(2)
Ru(1)–N(1)
Ru(1)–N(2)
Ru(1)–P(1)
Ru(1)–P(2)
Ru–H1(Ru)
N(1)–C(1)
S(1)–C(1)
1.829(3)
2.159(2)
2.157(2)
2.334(6)
2.371(6)
1.597(19)
1.151(3)
1.647(3)
1.156(3)
Ru(1)–C(1)
Ru(1)–N(1)
Ru(1)–N(3)
Ru(1)–P(1)
Ru(1)–P(2)
Ru–H1(Ru)
N(99)–C(99)
S(99)–C(99)
C(1)–O(1)
1.840(3)
2.114(2)
2.219(2)
2.3576(7)
2.3682(7)
1.39(3)
1.132(4)
1.595(3)
1.147(4)
Ru(1)–C(1)
Ru(1)–N(1)
Ru(1)–N(3)
Ru(1)–P(1)
Ru(1)–P(2)
Ru–H1(Ru)
N(5)–C(5)
S(1)–C(48)
C(1)–O(1)
1.839(4)
2.142(3)
2.240(3)
2.3620(9)
2.3537(9)
1.600(3)
1.630(2)
2.017(16)
1.145(4)
S(1)–C(1)
C(2)–O(1)
C(2)–O(1)
Angles (°)
P(1)–Ru(1)–P(2)
P(1)–Ru(1)–P(3)
P(1)–Ru(1)–N(1)
P(1)–Ru(1)–C(2)
P(2)–Ru(1)–P(3)
P(2)–Ru(1)–N(1)
P(2)–Ru(1)–C(2)
P(3)–Ru(1)–N(1)
P(3)–Ru(1)–C(2)
N(1)–Ru(1)–C(2)
P(2)–Ru(1)–H(1)
P(3)–Ru(1)–H(1)
N(1)–Ru(1)–H(1)
C(2)–Ru(1)–H(1)
P(1)–Ru(1)–H(1)
Ru(1)–N(1)–C(1)
Ru(1)–C(2)–O(1)
S(1)–C(1)–N(1)
152.26(2)
102.01(2)
84.31(5)
91.83(7)
103.62(2)
82.15(4)
97.88(7)
97.18(5)
91.55(7)
171.01(8)
76.5(8)
P(1)–Ru(1)–P(2)
P(1)–Ru(1)–N(1)
P(1)–Ru(1)–N(2)
P(1)–Ru(1)–C(2)
P(2)–Ru(1)–N(1)
P(2)–Ru(1)–N(2)
P(2)–Ru(1)–C(2)
N(1)–Ru(1)–N(2)
N(1)–Ru(1)–C(2)
N(2)–Ru(1)–C(2)
C(2)–Ru(1)–H(1)
P(2)–Ru(1)–H(1)
N(1)–Ru(1)–H(1)
P(1)–Ru(1)–H(1)
N(2)–Ru(1)–H(1)
Ru(1)–N(1)–C(1)
Ru(1)–C(2)–O(1)
S(1)–C(1)–N(1)
176.21(2)
92.87(6)
90.12(5)
88.20(8)
90.86(6)
89.33(5)
91.55(8)
88.77(8)
103.35(9)
167.83(9)
80.0(7)
P(1)–Ru(1)–P(2)
P(1)–Ru(1)–N(1)
P(1)–Ru(1)–N(3)
P(1)–Ru(1)–C(1)
P(2)–Ru(1)–N(1)
P(2)–Ru(1)–N(3)
P(2)–Ru(1)–C(1)
N(1)–Ru(1)–N(3)
N(1)–Ru(1)–C(1)
N(3)–Ru(1)–C(1)
C(1)–Ru(1)–H(1)
P(2)–Ru(1)–H(1)
N(1)–Ru(1)–H(1)
P(1)–Ru(1)–H(1)
N(3)–Ru(1)–H(1)
173.73(2)
93.08(6)
93.48(5)
87.60(8)
88.20(6)
92.78(5)
90.84(8)
74.83(8)
177.21(10)
107.84(10)
85.5(12)
90.2(11)
91.8(12)
83.6(11)
166.2(12)
P(1)–Ru(1)–P(2)
P(1)–Ru(1)–N(1)
P(1)–Ru(1)–N(3)
P(1)–Ru(1)–C(1)
P(2)–Ru(1)–N(1)
P(2)–Ru(1)–N(3)
P(2)–Ru(1)–C(1)
N(1)–Ru(1)–N(3)
N(1)–Ru(1)–C(1)
N(3)–Ru(1)–C(1)
C(1)–Ru(1)–H(1)
P(2)–Ru(1)–H(1)
N(1)–Ru(1)–H(1)
P(1)–Ru(1)–H(1)
N(3)–Ru(1)–H(1)
164.46(3)
90.92(7)
98.55(8)
87.33(11)
90.97(7)
96.86(8)
91.13(11)
75.51(11)
177.63(13)
103.16(14)
91.50(11)
80.70(12)
89.80(11)
83.90(12)
165.20(11)
176.3(8)
86.5(8)
84.7(8)
88.4(7)
176.6(7)
87.9(7)
78.6(8)
87.9(7)
163.32(17)
175.29(19)
178.35(19)
170.1(2)
172.6(2)
179.9(3)
Ru(1)–C(1)–O(1)
S(99)–C(99)–N(99)
175.8(3)
179.1(3)
Ru(1)–C(1)–O(1)
S(1)–C(48)–N(5)
178.7(4)
161.4(10)
Table 3
From the DOS plot of complex 1 one can see that the isothiocyanate
ligand play significant role in frontier HOMO orbitals of neutral
complexes (especially in the absence of N-heteroaromatic donor li-
gands). On the OPDOS plots of the neutral complexes 1 and 2, the
antibonding interaction between isothiocyanate ligands and ruthe-
nium(II) central ion in the HOMO and HOMO-1 orbitals is visible.
In all studied complexes, the influence of carbonyl and hydride li-
gands on ruthenium d orbitals in frontier HOMO orbitals has posi-
tive values indicating a bonding character of these interactions. In
the case of cationic complexes 3 and 4, the N-heteroaromatic li-
gands participate in the frontier HOMO orbitals with antibonding
character.
Hydrogen bonds for [RuH(CO)(SCN)(PPh3)3] (1), [RuH(SCN)(CO)(PPh3)2(BIm)]ꢂH2O (2),
[RuH(CO)(PPh3)2(PyBIm)](SCN) (3) and [RuH(CO)(PPh3)2(DMIM)](SCN) (4) complexes
(Å and °).
D–Hꢂ ꢂ ꢂA
1
C(16)–H(16)ꢂ ꢂ ꢂN(1)
2
O(1)–H(2A)ꢂ ꢂ ꢂS(1) #1
O(2)–H(2B)ꢂ ꢂ ꢂS(1) #2
C(6)–H(6)ꢂ ꢂ ꢂO(1) #2
N(3)–H(3)ꢂ ꢂ ꢂO(2)
d(D–H)
d(Hꢂ ꢂ ꢂA)
d(Dꢂ ꢂ ꢂA)
<(DHA)
0.93
2.44
3.237(3)
143.6
0.824(19)
0.864(19)
0.93
2.52(2)
2.64(2)
2.50
3.336(3)
3.494(3)
3.304(4)
2.831(3)
168(4)
169(4)
145.2
161.5
0.86
2.00
3
N(2)–H(2)ꢂ ꢂ ꢂN(99) #3
C(10)–H(10)ꢂ ꢂ ꢂN(99) #3
C(34)–H(34)ꢂ ꢂ ꢂN(99) #4
C(13)–H(13)ꢂ ꢂ ꢂS(99)
0.86
0.93
0.93
0.93
1.96
2.48
2.51
2.86
2.814(4)
3.365(5)
3.322(5)
3.565(3)
174.0
159.8
146.8
133.5
In the frontier occupied and virtual molecular orbitals, the val-
ues of the interaction between ruthenium ions and imidazole
derivatives indicate the benzimidazole as weakest
p-acceptor
among the studied ligands. This conclusion is confirmed addition-
ally by the mentioned earlier stabilization energy and bonds
orders.
4
N(2)–H(2)ꢂ ꢂ ꢂS(1)
N(4)–H(4)ꢂ ꢂ ꢂS(1)
C(11)–H(11C)ꢂ ꢂ ꢂN(5)
C(14)–H(14)ꢂ ꢂ ꢂN(5) #5
0.86
0.86
0.96
0.93
2.27
2.85
2.19
2.57
3.110(10)
3.616(12)
2.83(3)
167.1
149.2
124.0
117.6
Mayer bond orders of Ru–P bonds in complex 1 are close to 1.5
for Ru–P(1), Ru–P(2) and 1.05 for Ru–P(3), which is connected with
the trans effect of hydrido ligand. In the other complexes, Ru–P
bonds orders are similar and close to 1.4. The Ru–CO and Ru–H
bonds orders also are much alike in all studied complexes with val-
ues close to 2.6 and 1.7, respectively. The values of bond orders be-
tween ruthenium central ions and N-donor ligands lower than 1
(0.7 – BIm; 0.7 and 0.5N trans to Ru–H – PyBim, DMIM) indicate a par-
ticipation of ionic character in the bonds. In order to determine the
bonding energy between ruthenium and N-heteroaromatic ligands
in the studied complexes 2, 3 and 4, the energy decomposition
analysis of the studied complexes based on the work of Morokuma
[17] and the extended transition state (ETS) partitioning scheme of
Ziegler [18] have been carried out using ADF program at the level
of B3LYP/TZP have been performed. The binding energy of the com-
pound was calculated as the difference between the energy of com-
plexes with the optimized geometry and the energies of the
3.11(2)
Symmetry transformations used to generate equivalent atoms: #1 1 ꢀ x, ꢀy, 2 ꢀ z;
#2 x, ꢀ1 + y, z; #3 1/2 + x, 3/2 ꢀ y, ꢀ1/2 + z; #4 1/2 ꢀ x, 1/2 + y, 1/2 ꢀ z; #5 ꢀ1/2 + x,
1/2 ꢀ y, 1/2 + z.
(DOS) and overlap population density-of-states (OPDOS) in terms
of Mulliken population analysis were calculated using the GAUSSSUM
program. They provide a pictorial representation of MOs composi-
tions and their contributions to chemical bonding. The DOS (for
complexes 1 and 4 for example) and OPDOS diagrams are shown
in Fig. 3, and they may enable us to ascertain the bonding, non-
bonding and antibonding characteristics with respect to the partic-
ular fragments. A positive value in OPDOS plots means a bonding
interaction; while a negative value represents antibonding interac-
tion, and a near zero value indicates a non-bonding interaction.

J.G. Małecki / Polyhedron 29 (2010) 2489–2497
2495
Fig. 3. The density of states (DOS) and overlap partial density of states (OPDOS) diagrams for studied complexes.
optimized ligands benzimidazole, 2-(2-pyridyl)benzimidazole,
2,20-bis(4,5-dimethylimidazolyl) and [RuH(CO){SCN}(PPh3)2]{+}
fragment. General theoretical background on the bond energy
decomposition scheme can be found in the review paper [19]. Ta-
ble 4 gathers the results of energy decomposition analysis calcu-
lated for the complexes in methanol solvent as more realistic

2496
J.G. Małecki / Polyhedron 29 (2010) 2489–2497
Table 4
Energy decomposition analysis (in CH3OH solvent) for complexes [RuH(SCN)-
(CO)(PPh3)2(BIm)] (2), [RuH(CO)(PPh3)2(PyBIm)]+ (3) and [RuH(CO)(PPh3)2(DMIM)]+
(4) in the [RuH{SCN}(CO)(PPh3)2]{+} fragment and the BIm, PyBIm and DMIM ligands
(energies in kcal molꢀ1).
2
3
4
Energy [kcal/mol]
D
D
D
D
D
D
Eelstat
Ekinetic
ECoulomb
EXC
Esolvation
E
ꢀ76.55
ꢀ51.08
163.99
ꢀ54.43
ꢀ24.00
ꢀ42.06
ꢀ174.61
ꢀ652.80
805.64
ꢀ94.30
ꢀ51.72
ꢀ167.79
ꢀ144.23
ꢀ659.54
765.46
ꢀ77.04
ꢀ52.41
ꢀ167.75
(Steric+OrbInt)
than the calculation in gas phase. As it could be seen, the Coulomb
energies in complexes 2–4 play an important role for the-
[RuH(CO){SCN}(PPh3)2]{+} – L binding in solution. Additionally,
the energies in the complexes 3 and 4 are very similar which indi-
cates the ligands are close each other in respect of their
properties.
p-acceptor
3.2. Electronic spectra
In the UV–Vis spectrum of the complex 1, one may notice a
small inflection at 26967 cmꢀ1 in the unsymmetrical band with a
maximum at 30921 cmꢀ1. Based on the pseudooctahedral geome-
try of the studied complexes and taking into account the d–d tran-
sitions assigned to 1A1 ? 1T1 and 1A1 ? 1T2 in octahedron (or
1A1 ? 1A2/B1/E in lower symmetry fields), the ligand field parame-
ter 10Dq can be estimated to 27920 cmꢀ1 for the complex. Ade-
quately Racah’s parameters are B = 249 cmꢀ1; C = 991 cmꢀ1 and
the nepheloauxetic parameter has value b55 = 0.35. In case of the
complexes 2, 3 and 4, the bands in the UV–Vis spectra are better
visible and the values of the ligand field parameter 10Dq, calcu-
lated on the basis of the positions and molar extinction coefficients
of electronic bands for the investigated complexes, are equal to
26 387 cmꢀ1 for 2, 24 931 cmꢀ1 for complex 3 and 27 062 cmꢀ1
Fig. 4. The emissions spectra of the complexes 1, 2 and 4 in the methanolic
solutions (c = 5 ꢁ 10ꢀ4 mol/dm3). (A) Excitation at 370 (1) and 399 nm (2, 4). (B)
Excitation at 323 (1), 329 (2) and 300 nm (4).
for compound 4. Racah’s parameters are equal to B = 335 cmꢀ1
,
489 cmꢀ1, 518 cmꢀ1, C = 1333 cmꢀ1, 1946 cmꢀ1, 2063 cmꢀ1 and
the nepheloauxetic parameters are b55 = 0.46, 0.68 and 0.72 for
compounds 2, 3 and 4, respectively. The bands observed in the
vicinity of 40 000 cmꢀ1 (250 nm) have been attributed to intra-
Summarizing, four new carbonyl ruthenium(II) complexes with
thiocyanate and N-heteroaromatic ligands are synthesized. The
molecular structures of the compounds are determined by X-ray
and the spectroscopic properties as infrared, 1H, 31P NMR spectra
were studied. Based on the crystal structures, the computational
researches were made in order to determine the electronic struc-
tures of the studied compounds. The obtained results were used
and interligand (pbC6H6 ? 3dphosphorus and
p
?
p
C@C) transitions
with admixture of Metal–Ligand Charge Transfer transitions
(dRu and dRu Ph). The highest experimental bands
close to 210.0 nm may result from transitions in the PPh3 ligands
and from * excitations in the N-heteroaromatic ligands.
?
p*
N-ligand
? p*
p
? p
Emission properties of the complexes 1, 2 and 4 have been
examined in the methanol solutions (with concentration of
5 ꢁ 10ꢀ4 mol/dm3) at room temperature. The excitations were exe-
cuted at two wavelengths corresponding to maximum of first elec-
tronic absorption, it means at 370, 323 nm in 1, 399, 329 in 2 and
399, 300 nm in complex 4. In all complexes, the emissions with
maxima at 442, 397 – 1, 465, 399 – 2, 465, 427 nm – 4 originating
from the lowest energy metal to ligand charge transfer (MLCT)
to compare
p-acceptor properties of imidazole type ligands. The
acceptor properties of N-donor ligands explained the differences
(replacing Hꢀ or NCSꢀ ligands) in the structure of studied com-
plexes. On the basis of a pseudooctahedral configuration of the
studied complexes and their electronic spectra, the values of the li-
gand field parameter 10Dq and Racah’s parameters were esti-
mated. Emission properties of the complexes have been
examined. The emissions originating from the lowest energy metal
to ligand charge transfer (MLCT) state, derived from the excitation
state, derived from the excitation involving a d
? pligand transition
p
are observed. The assignment is also supported by the analysis of
the frontier orbitals of the corresponding complexes showing a
partial contribution of ligands nature. In the case of neutral com-
plexes 1 and 2, the excitations at shorter wavelengths gave stron-
ger emission peaks. The emission of complex 4 is very intense
compared to neutral complexes which is connected with the signif-
icant contribution of DMIM ligand in the frontier HOMO and LUMO
orbitals. In Fig. 4 the luminescence spectra of the complexes are
presented, and in the spectrum of complex 4 (excited at 399 nm)
a broadening is visible, which suggests that more than one state
is involved in luminescence process.
involving a d
? pligand transition are observed. The assignment is
p
supported by the analysis of the frontier orbitals of the correspond-
ing complexes showing a partial contribution of ligands nature.
4. Supplementary data
CCDC 762976, CCDC 765981, CCDC 763072 and CCDC 770163
contains the supplementary crystallographic data for [RuH(CO)-
(SCN)(PPh3)3], [RuH(SCN)(CO)(PPh3)2(BIm)]ꢂH2O, [RuH(CO)(PPh3)2-
(PyBIm)](SCN) and [RuH(CO)(PPh3)2(DMIM)](SCN) complexes.

J.G. Małecki / Polyhedron 29 (2010) 2489–2497
2497
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, Inc.,
Wallingford, CT, 2009.
These data can be obtained free of charge via http://www.ccdc.ca-
m.ac.uk/conts/retrieving.html, or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK;
fax: (+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
[9] A.D. Becke, J. Chem. Phys. 98 (1993) 5648;
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