Molecular and spectroscopic properties of hydridecarbonyl ruthenium complexes with pyrazine carboxylic acid ligands

Article abstract of DOI:10.1016/j.poly.2011.09.032

The hydride carbonyl ruthenium(II) [RuH(CO)(pyzCOO)(PPh₃) ₂] (1), [RuH(CO)(pyz-2,3-COO[CH₃])(PPh₃) ₂]·H₂O (2) and dinuclear Ru(II)/Ru(III) [RuH(CO)(PPh₃)(pyz-2,3-COO)Ru(CO)Cl₂(PPh₃) ₂] (3) complexes were synthesized and characterized by IR, ¹H, ³¹P NMR, UV-Vis spectroscopy and X-ray crystallography. The experimental studies were complemented by quantum chemical calculations, which were used to identify the nature of the interactions between the ligands and the central ion, and the orbital composition in the frontier electronic structure. Based on a molecular orbital scheme, the calculated results allowed the interpretation of the UV-Vis spectra obtained at an experimental level. The luminescence property of the complex 2 was determined. The ac magnetic susceptibility measurements showed a residual magnetism evidenced by the small values of the molar susceptibility, not exceeding 0.5 emu/mol at 2 K, a lack of a Curie-Weiss region and weak magnetic interactions below 20 K.

Full text of DOI:10.1016/j.poly.2011.09.032

Polyhedron 31 (2012) 319–331
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Molecular and spectroscopic properties of hydridecarbonyl ruthenium
complexes with pyrazine carboxylic acid ligands
b
b
J.G. Małecki a, , T. Gron , H. Duda
⇑
´
a Department of Crystallography, Institute of Chemistry, University of Silesia, ul. Szkolna 9, 40-006 Katowice, Poland
b Institute of Physics, University of Silesia, ul. Uniwersytecka 4, 40-007 Katowice, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 30 July 2011
Accepted 17 September 2011
Available online 4 October 2011
The hydride carbonyl ruthenium(II) [RuH(CO)(pyzCOO)(PPh3)2] (1), [RuH(CO)(pyz-2,3-COO[CH3])(P-
Ph3)2]ꢀH2O (2) and dinuclear Ru(II)/Ru(III) [RuH(CO)(PPh3)(pyz-2,3-COO)Ru(CO)Cl2(PPh3)2] (3) complexes
were synthesized and characterized by IR, 1H, 31P NMR, UV–Vis spectroscopy and X-ray crystallography.
The experimental studies were complemented by quantum chemical calculations, which were used to
identify the nature of the interactions between the ligands and the central ion, and the orbital composi-
tion in the frontier electronic structure. Based on a molecular orbital scheme, the calculated results
allowed the interpretation of the UV–Vis spectra obtained at an experimental level. The luminescence
property of the complex 2 was determined. The ac magnetic susceptibility measurements showed a
residual magnetism evidenced by the small values of the molar susceptibility, not exceeding 0.5 emu/
mol at 2 K, a lack of a Curie-Weiss region and weak magnetic interactions below 20 K.
Keywords:
Ruthenium hydridocarbonyl complexes
Pyrazine carboxylic acid
Ruthenium(III)/ruthenium(II) dinuclear
complexes
Absorptions and emissions electronic
spectra
Ó 2011 Elsevier Ltd. All rights reserved.
DFT
Dynamic magnetic susceptibility
1. Introduction
stability of these complexes [11], which are interesting due to
theirs properties. Pyrazine derivatives can act as exo-bidentate
Ruthenium hydride complexes containing carbonyl and triaryl-
phosphine ligands are interesting due to their reactivity and effi-
ciency as catalysts in a wide spectrum of reactions [1–6]. On the
ligands. This feature makes pyrazine and its derivatives intriguing
ligands for the study of dinuclear or multinuclear mixed-valence
and mixed-metal complexes [12–14].
other hand, complexes of ruthenium containing
p
-acceptor nitro-
Here an experimental and quantum chemical study of ruthenium
hydridocarbonyl complexes with pyrazine carboxylic acid ligands is
reported. The quantum chemical study includes characterization of
the molecular and electronic structures of the complexes by analysis
of the optimized molecular geometries and electronic populations
using the natural bond orbitals scheme. The latter was used to iden-
tify the nature of the interactions between the ligands and the cen-
tral ion. The calculated density of states shows the interactions and
influences the orbital composition in the frontier electronic struc-
ture. Time dependent density functional theory (TD-DFT) was finally
used to calculate the electronic absorption spectra. Based on a
molecular orbital scheme, these results allow the interpretation of
the UV–Vis spectra obtained at an experimental level. The com-
plexes reported in this paper combine the interest in ruthenium hy-
dride carbonyl coordination compounds and complexes containing
N-heterocyclic ligands [15–23]. Additionally the magnetic proper-
ties of a dinuclear complex were measured.
gen-bearing ligands, especially N-heteroaromatic ligands, have
been widely studied as systems for the conversion of energy. Stud-
ies on the synthesis and characterization of ruthenium complexes
containing N-heteroaromatic ligands have received considerable
recent attention, owing to their interesting photophysical and pho-
tochemical properties. The azine ligands have energetically low
lying p-antibonding orbitals, which can accept electrons from filled
metal d orbitals. As a consequence, they can exhibit charge transfer
bands with interesting spectroscopic properties in the visible re-
gion [7]. Ligands containing a pyrazine ring are widely studied
and their
p-donor properties are interesting. Their combination
with other donor atoms should in principle afford complexes with
tunable spectroscopic properties [8–10]. The hydride ligand – a
powerful
r-donor – is found to be very efficient at compensating
for electron deficiency at a metal central ion in complexes. The
‘‘trans effect’’ of the Hꢁ ligand and the interaction between car-
bonyl and donor ligands (such as carboxyl or chloride) in trans
positions to one another are stabilizing factors which explain the
2. Experimental
⇑
All reagents used for the synthesis of the complexes are commer-
cially available and have been used without further purification. The
Corresponding author.
E-mail address: gmalecki@us.edu.pl (J.G. Małecki).
0277-5387/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2011.09.032

320
J.G. Małecki et al. / Polyhedron 31 (2012) 319–331
[RuHCl(CO)(PPh3)3] complex was synthesized according to the liter-
ature method [24].
3: Yield 73%. IR (KBr, cmꢁ1): 3045
(Ru–H); 1593 (C@N; C@C); 1559 as(COO); 1480 d(C–CH in the plane); 1433
Ph(P–Ph); 1359 s(COO); 1219, 1155 (pyz ring); 998 d(CHpyz out the plane)
plane); 749 d(Ru–pyz plane); 695
mArH; 1947, 1943 m(CO); 1923
m
m
m
m
m
m
;
843 d(Ru–pyz
COO in the
COO out of the
d(pyz ring out of the plane); 516
(log
m(N–Ru). UV–Vis (dichloromethane, nm
2.1. Synthesis of [RuH(CO)(pyzCOO)(PPh3)2] (1), [RuH(CO)(pyz-2,3-
COO[CH3])(PPh3)2]ꢀH2O (2) and [RuH(CO)(PPh3)(pyz-2,3-
COO)Ru(CO)Cl2(PPh3)2] (3)
e
): 603.0 (1.41), 570.0 (1.69), 515.0 (1.67), 450.2 (1.22), 371.5
(1.19), 298.4 (2.13), 212.6 (4.97). 1H NMR (400 MHz, CDCl3) d
(ppm): 7.75 (dd, J = 17.5, 7.1 Hz, Hpyz), 7.72–7.21 (m, PPh3),
ꢁ9.529 (tRu–H, J = 19.3 Hz). 31P NMR (CDCl3) d (ppm): 47.12 (s),
43.16 (s, PPh3), 26.17 (s, (Ru(2)PPh3).
The complexes 1 and 2 were synthesized in the reaction
between [RuHCl(CO)(PPh3)3] (0.1 g, 1 ꢂ 10ꢁ4 mol) and pyrazine-
2-carboxylic acid (pyzCOO) or pyrazine-2,3-dicarboxylic acid
(pyz-2,3-COO) in methanol solution (100 cmꢁ3). The reaction with
pyrazine-2,3-dicarboxylic acid was also performed in acetone and
complex 3 was obtained. A mixture of the compounds was refluxed
in methanol or acetone for 4 h. After this time, it was cooled and
filtered. Crystals suitable for X-ray crystal analysis were obtained
by slow evaporation of the reaction mixtures.
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 Lab Alliance UV–Vis 8500
spectrophotometer in the range of 900–180 nm in methanol solu-
tion. The 1H and 31P NMR spectra were obtained at room tempera-
ture in CDCl3 using a Bruker 400 MHz spectrometer. Luminescence
measurements were made on methanolic solutions with an F-2500
FL spectrophotometer at room temperature. Dynamic (ac) magnetic
susceptibility was measured with the aid of a Quantum Design Sys-
tem (MPMS XL) and recorded in the temperature range 2–300 K and
at an internal oscillating magnetic field Hac = 3.9 Oe with an internal
frequency f = 300 Hz.
1: Yield 62%. IR (KBr, cmꢁ1): 3048
1655 m(C C@C); 1580 as(COO); 1479 d(C–CH
m
ArH; 1973
m(CO); 1928 m(Ru–H)
plane); 1434
in the
;
@
N;
m
mPh(P–Ph); 1334
ms(COO); 1092 d(C–CH in the plane); 745 d(C–C out of the plane)
;
694 d
; 517 (P–Ph+P–Ru). UV–Vis (methanol, nm (log ): 361.5
m
e
(C–C in the plane)
(1.17), 316.2 (1.90), 273.1 (2.86), 224.2 (sh), 210.6 (4.82). 1H NMR
(400 MHz, CDCl3) d (ppm): 8.39 (s, Hpyz), 7.90 (d, J = 2.9 Hz, 2Hpyz),
7.83–7.49 (m, PPh3), ꢁ9.51 (tRu–H, J = 19.6 Hz). 31P NMR (CDCl3) d
(ppm): 43.85 (s, PPh3).
2: Yield 73%. IR (KBr, cmꢁ1): 3447
1922
d(C–CH
d(C–CH
m
OH; 3055
(Ru–H); 1749 (H2O); 1644 m(C@N; C@C); 1569
plane); 1437 Ph(P–Ph); 1339 s(COO); 1299
plane); 795 d(C–C plane); 693 d(C–C
m
ArH; 1958 m(CO)
;
m
m
as(COO); 1479
2.3. Computational methods
m
m
ms(COO); 1093
in the
;
The calculations were carried out using the GAUSSIAN09 [25] pro-
gram. Molecular geometries of the singlet ground state of com-
plexes 1 and 2, and the doublet state of the dimeric complex 3
were fully optimized in the gas phase at the B3LYP/DZVP level of
theory. [26,27] For each compound a frequency calculation was car-
ried out, verifying that the optimized molecular structure obtained
in the
out of the
in the plane)
519 m(P–Ph+P–Ru). UV–Vis (methanol, nm (loge): 360.0 (1.26), 310.2
(1.79), 274.0 (2.32), 267.0 (2.41), 232.0 (sh), 211.8 (4.92). 1H
NMR (400 MHz, CDCl3) d (ppm): 7.88 (d, 2Hpyz), 7.76–7.23 (m,
PPh3), 3.83 (s, CH3), 1.56 (s, H2O), ꢁ9.57 (tRu–H, J = 19.4 Hz). 31P
NMR (CDCl3) d (ppm): 44.04 (s, PPh3).
Table 1
Crystal data and structure refinement details of the complexes [RuH(CO)(pyzCOOH)(PPh3)2] (1), [RuH(CO)(pyz-2,3-COO[CH3])(PPh3)2]ꢀH2O (2) and [Ru2HCl2(PPh3)3(pyz-2,3-
COO)] (3).
1
2
3
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
Unit cell dimensions
a (Å)
C
42H34N2O3P2Ru
C44H36N2O5P2Ru, H2O
853.77
295.0 (2)
monoclinic
P21/n
C62H48Cl2N2O6P3Ru2
1282.97
295.0 (2)
777.72
295.0 (2)
monoclinic
P21/n
triclinic
ꢀ
P1
10.196(2)
15.426(3)
22.871(5)
90
97.51(3)
90
3566.3(12)
4
1.448
0.572
1592
14.8922(5)
15.5794(5)
17.6954(7)
90
93.385(3)
90
4098.4(2)
4
1.384
12.4781(6)
13.8575(7)
17.7429(8)
69.534(4)
87.090(5)
83.246(4)
2854.3(2)
2
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
Volume (Å3)
Z
Calculated density (mg/m3)
Absorption coefficient (mmꢁ1
F (000)
1.493
0.760
1298
)
0.513
1752
Crystal dimensions (mm)
h range for data collection (°)
Index ranges
0.09 ꢂ 0.07 ꢂ 0.03
3.32 to 25.05
ꢁ12 6 h 6 12
ꢁ15 6 k 6 18
ꢁ27 6 l 6 27
19891
0.37 ꢂ 0.32 ꢂ 0.06
3.65 to 25.05
ꢁ17 6 h 6 17
ꢁ18 6 k 6 18
ꢁ21 6 l 6 20
38929
0.18 ꢂ 0.12 ꢂ 0.05
3.40 to 25.05
ꢁ14 6 h 6 14
ꢁ16 6 k 6 16
ꢁ21 6 l 6 21
28425
Reflections collected
Independent reflections (Rint
Data/restraints/parameters
Goodness-of-fit on F2
)
6294 (0.0488)
6294/0/455
0.970
7237 (0.0331)
7237/0/514
1.058
10056 (0.0684)
10056/0/698
0.938
Final R indices [I > 2
r
(I)]
R1 = 0.0374
wR2 = 0.0720
R1 = 0.0697
wR2 = 0.0784
0.742 and ꢁ0.536
R1 = 0.0320
wR2 = 0.0772
R1 = 0.0446
wR2 = 0.0830
0.514 and ꢁ0.408
R1 = 0.0715
wR2 = 0.1364
R1 = 0.1404
wR2 = 0.1594
1.007 and ꢁ1.010
R indices (all data)
Largest difference in peak and hole (e Åꢁ3
)

J.G. Małecki et al. / Polyhedron 31 (2012) 319–331
321
Fig. 1. ORTEP drawings of the complexes [RuH(CO)(pyzCOOH)(PPh3)2] (1), [RuH(CO)(pyz-2,3-COO[CH3])(PPh3)2]ꢀH2O (2) and [Ru2HCl2(PPh3)3(pyz-2,3-COO)] (3) with 50%
probability displacement ellipsoids. Hydrogen atoms (except Ru–H) and the water molecule in complex (2) are omitted for clarity.

322
J.G. Małecki et al. / Polyhedron 31 (2012) 319–331
Fig. 1 (continued)
corresponds to an energy minimum, thus only positive frequencies
were expected. The DZVP basis set [28] with f functions and with
exponents of 1.94722036 and 0.748930908 was used to describe
the ruthenium atom, and the basis set used for the lighter atoms
(C, N, O, P, H, Cl) was 6-31G with a set of ‘‘d’’ and ‘‘p’’ polarization
functions. The TD-DFT (time dependent density functional theory)
method [29] was employed to calculate the electronic absorption
spectra of the complexes in the solvent PCM (Polarizable Continuum
Model) model. In this work 90 singlet excited states were calculated
as vertical transitions for the complexes. A natural bond orbital
(NBO) analysis was also made for all the complexes using the NBO
5.0 package [30] included in GAUSSIAN09. Natural bond orbitals are
orbitals localized on one or two atomic centers that describe molec-
ular bonding in a manner similar to a Lewis electron pair structure,
and they correspond to an orthonormal set of localized orbitals of
maximum occupancy. NBO analysis provides the contribution of
2h = 50.10°. The unit cell parameters were determined from
least-squares refinement of the setting angles of 7523, 12218 and
10395 strongest reflections for complexes 1, 2 and 3, respectively.
Details concerning crystal data and refinement are gathered in
Table 1. Lorentz, polarization and empirical absorption corrections
using spherical harmonics implemented in SCALE3 ABSPACK scal-
ing algorithm [32] were applied. The structure was solved by the
Patterson method and subsequently completed by difference Fou-
rier recycling. All the non-hydrogen atoms were refined anisotrop-
ically using the full-matrix, least-squares technique. The hydrogen
atoms were found from the difference Fourier synthesis after four
cycles of anisotropic refinement, and were refined as ‘‘riding’’ on
the adjacent carbon atom with individual isotropic temperature
factor equal 1.2 times the value of equivalent temperature factor
of the parent atom. The Olex2 [33] and SHELXS97, SHELXL97 [34] pro-
grams were used for all the calculations. Atomic scattering factors
were those incorporated in the computer programs.
atomic orbitals (s, p, d) to the NBO
r and p hybrid orbitals for
bonded atom pairs. In this scheme, three NBO hybrid orbitals are
defined, bonding orbital (BD), lone pair (LP) and core (CR), which
were analyzed on the atoms directly bonded to or presenting some
kind of interaction with the ruthenium atom. The contribution of a
group (ligands, central ion) to a molecular orbital was calculated
using Mulliken population analysis. GaussSum 2.2 [31] 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 Maxi-
mum) of 0.3 eV.
3. Results and discussion
3.1. Spectroscopic characterization of the complexes
The 31P NMR spectra of the complexes [RuH(CO)(pyz-
COOH)(PPh3)2] (1) and [RuH(CO)(pyz-2,3-COO[CH3])(PPh3)2]ꢀH2O
(2) show singlets at 43.848 and 44.038 ppm. The broadening of
the signals suggests that the triphenyphosphine ligands are not in
perfect trans positions. In the case of complex 3, the 31P NMR spec-
trum presents three signals at 47.122, 43.158 and 26.166 ppm. The
low field signals indicate PPh3 ligands at a ruthenium(II) central ion
and the high field signal is attributed to a triphenylphosphine mol-
ecule at the Ru(III) centre. The 1H NMR spectra of the complexes
show a set of signals corresponding to the PPh3 ligands. The pyra-
zine aromatic protons in the spectra of complexes 1 and 2 are visible
as a singlet at 8.386 ppm (H(3)) and doublets due to the magnetic
ortho coupling of the H(4) and H(5) protons at 7.896 ppm in 1 and
7.882 ppm in 2. The signals are shifted compared with free pyrazine
carboxylic acid (9.24, 8.91, 8.85 ppm) due to the shielding effect of
the ruthenium central ion. The spectrum of complex 2 presents sig-
nals at 3.827 and 1.557 ppm that are attributed to the ester CH3
2.4. Crystal structure determination and refinement
The crystals of [RuH(CO)(pyzCOO)(PPh3)2] (1), [RuH(CO)(pyz-
2,3-COO[CH3])(PPh3)2]ꢀH2O (2) and [RuH(CO)(PPh3)(pyz-2,3-CO-
O)Ru(CO)Cl2(PPh3)2] (3) were mounted in turn on an Xcalibur,
Atlas, Gemini Ultra Oxford Diffraction automatic diffractometer
equipped with a CCD detector, and were used for data collection.
X-ray intensity data were collected with graphite monochromated
MoKa
radiation (k = 0.71073 Å) at temperature of 295.0(2) K, with
the
x
scan mode. Ewald sphere reflections were collected up to

J.G. Małecki et al. / Polyhedron 31 (2012) 319–331
323
Table 2
Table 3
Selected bond lengths (Å) and angles (°) for the complexes [RuH(CO)(pyz-
Hydrogen bonds for the complexes [RuH(CO)(pyzCOOH)(PPh3)2] (1), [RuH(CO)(pyz-
2,3-COO[CH3])(PPh3)2]ꢀH2O (2) and [Ru2HCl2(PPh3)3(pyz-2,3-COO)] (3) (Å and °).
COOH)(PPh3)2]
[Ru2HCl2(PPh3)3(pyz-2,3-COO)] (3).
(1),
[RuH(CO)(pyz-2,3-COO[CH3])(PPh3)2]ꢀH2O
(2)
and
D–Hꢀ ꢀ ꢀA
d(D–H)
d(Hꢀ ꢀ ꢀA)
d(Dꢀ ꢀ ꢀA)
<(DHA)
1
Exp
2
1
Calc
Exp
Calc
C(26)–H(26)ꢀ ꢀ ꢀO(2)
0.93
0.93
2.41
2.51
3.123(4)
3.021(4)
133.3
114.8
C(18)–H(18)ꢀ ꢀ ꢀO(2)
Bond lengths (Å)
2
Ru(1)–C(1)
Ru(1)–N(1)
Ru(1)–O(2)
Ru(1)–P(1)
Ru(1)–P(2)
Ru–H1(Ru)
C(1)–O(1)
1.814(3)
2.167(2)
2.113(2)
2.3554(10)
2.3487(10)
1.56(3)
1.856
2.237
2.160
2.433
2.433
1.620
1.165
1.822(5)
2.151(3)
2.146(3)
2.3461(11)
2.3554(11)
1.73(4)
1.854
2.240
2.160
2.434
2.438
1.620
1.165
C(8)–H(8A)ꢀ ꢀ ꢀO(1) #1
C(31)–H(31)ꢀ ꢀ ꢀO(4) #2
C(35)–H(35)ꢀ ꢀ ꢀO(6) #3
C(38)–H(38)ꢀ ꢀ ꢀO(2)
0.96
0.93
0.93
0.93
2.39
2.60
2.58
2.51
3.252(9)
3.303(7)
3.490(8)
3.157(6)
149.1
133.0
167.6
128.0
3
1.153(4)
1.151(6)
C(5)–H(5)ꢀ ꢀ ꢀO(2) #4
C(16)–H(16)ꢀ ꢀ ꢀO(3)
C(44)–H(44)ꢀ ꢀ ꢀCl(1)
C(60)–H(60)ꢀ ꢀ ꢀCl(2)
0.93
0.93
0.93
0.93
2.57
2.42
2.74
2.77
3.173(9)
3.196(8)
3.181(7)
3.604(8)
122.9
140.6
109.7
149.2
Angles (°)
C(1)–Ru(1)–O(2)
C(1)–Ru(1)–N(2)
O(2)–Ru(1)–N(1)
C(1)–Ru(1)–P(2)
O(2)–Ru(1)–P(2)
P(2)–Ru(1)–N(1)
P(1)–Ru(1)–C(1)
P(1)–Ru(1)–O(2)
P(1)–Ru(1)–N(1)
P(1)–Ru(1)–P(2)
C(1)–Ru(1)–H(1)
O(2)–Ru(1)–H(1)
N(1)–Ru(1)–H(1)
P(2)–Ru(1)–H(1)
P(1)–Ru(1)–H(1)
Ru(1)–C(1)–O(1)
178.52(11)
103.68(12)
76.41(9)
89.53(10)
88.99(6)
94.68(6)
88.07(10)
93.41(6)
92.25(6)
173.03(3)
84.4(12)
95.5(12)
171.5(12)
87.8(10)
85.5(11)
178.7(3)
173.40
98.52
74.93
93.95
86.06
96.34
88.92
92.56
95.96
166.81
91.00
95.00
170.00
84.00
83.00
174.66
175.76(18)
100.08(19)
75.74(12)
94.32(15)
87.24(8)
94.72(9)
92.32(15)
86.86(8)
93.92(9)
168.02(4)
84.7(13)
99.4(13)
173.5(13)
89.2(13)
81.5(13)
177.8(5)
173.73
99.18
74.65
94.04
93.36
96.07
88.39
85.50
95.17
167.97
91.00
96.00
170.00
85.00
83.00
174.93
Symmetry transformations used to generate equivalent atoms: #1 1/2 ꢁ x, ꢁ1/2 + y,
1/2 ꢁ z; #2, ꢁ1/2 + x,3/2 ꢁ y, ꢁ1/2 + z; #3 1 ꢁ x, 1 ꢁ y, ꢁz; #4 1 ꢁ x, 1 ꢁ y, 1 ꢁ z.
3
Exp
Calc
Exp
Calc
Bond lengths
(Å)
Ru(1)–C(1)
Ru(1)–N(1)
Ru(1)–O(3)
Ru(1)–P(1)
Ru(1)–P(2)
Ru–H(1)
1.816(7)
2.162(4)
2.140(4)
2.3782(18) 2.451
2.3648(17) 2.427
1.72(5)
1.851
2.232
2.179
Ru(2)–C(2)
Ru(2)–N(2)
Ru(2)–O(6)
Ru(2)–P(3)
Ru(2)–Cl(1)
Ru(2)–Cl(2)
C(2)–O(2)
1.800(8)
2.123(5)
2.127(4)
2.3316(17) 2.406
2.380(2) 2.454
2.3887(19) 2.457
1.843
2.140
2.181
1.610
1.163
C(1)–O(1)
1.160(8)
1.145(8)
1.162
Angles (°)
C(1)–Ru(1)–
O(3)
C(1)–Ru(1)–
N(1)
O(3)–Ru(1)–
N(1)
C(1)–Ru(1)–
P(2)
O(3)–Ru(1)–
P(2)
N(1)–Ru(1)–
P(2)
C(1)–Ru(1)–
P(1)
O(3)–Ru(1)–
P(1)
N(1)–Ru(1)–
P(1)
P(2)–Ru(1)–
P(1)
C(1)–Ru(1)–
H(1)
O(3)–Ru(1)–
H(1)
N(1)–Ru(1)–
H(1)
P(2)–Ru(1)–
H(1)
P(1)–Ru(1)–
H(1)
Ru(1)–C(1)–
O(1)
174.8(2)
101.4(2)
73.90(16)
88.5(2)
174.19 C(2)–Ru(2)–
99.0(2)
97.17
172.15
75.02
91.57
N(2)
100.95 C(2)–Ru(2)–
O(6)
174.0(2)
75.06(17)
90.6(2)
73.31
89.10
92.07
93.22
94.30
85.52
95.64
N(2)–Ru(2)–
O(6)
C(2)–Ru(2)–
P(3)
N(2)–Ru(2)–
P(3)
O(6)–Ru(2)–
P(3)
C(2)–Ru(2)–
Cl(1)
N(2)–Ru(2)–
Cl(1)
O(6)–Ru(2)–
Cl(1)
Fig. 2. The
p-stacking interaction in the [RuH(CO)(pyzCOOH)(PPh3)2] (1) complex
molecule.
93.84(12)
92.14(13)
93.0(2)
170.44(15) 171.10
group and water molecule respectively. The 1H NMR spectra of the
complexes present signals at high field (ꢁ9.514, ꢁ9.568 and
ꢁ9.529 ppm) which indicate the presence of a hydride coordinated
with the metal. The shifts of the signals are due to the shielding ef-
fect of the metal and to the charge of the hydrogen atom. The Ru–H
signals are triplets due to coupling with the two trans equivalent
phosphorus atoms (JHP ꢃ 19.4 Hz).
95.40(11)
89.7(2)
96.26
90.70
86.39
88.04
95.22
94.83
86.72
85.63
90.89
171.65
174.74
85.45(12)
95.63(13)
171.68(6)
89.6(17)
95.4(17)
166.6(18)
80.5(17)
91.3(17)
177.0(6)
84.06(14)
89.06(14)
96.71(6)
95.7(2)
The IR spectra of complexes 1 and 2 display strong C„O bands
at 1973 and 1958 cmꢁ1. In the IR spectrum of complex (3) two m(CO)
stretching bands are present at 1947 and 1943 cmꢁ1. The differ-
ences in the vibration frequencies between the carbonyl groups
bonded to the Ru(III) and Ru(II) ions are connected to the differ-
ence in bond orders in the carbonyl groups. The bond length in
the carbonyl group bonded to ruthenium(II) is longer compared
with the one at Ru(III). Moreover the inclusion of electron-acceptor
ligands, such as chlorine, in the coordination sphere should pro-
duce an effect decreasing the electron density on the metal, and
therefore increasing the bond order of the CO bond and increasing
the vibration frequency. The electron–donor hydride ligand at the
Ru(II) ion delivers electron density via backbonding to the
169.73 P(3)–Ru(2)–
Cl(1)
89.00
C(2)–Ru(2)–
Cl(2)
97.00
N(2)–Ru(2)–
Cl(2)
86.87(14)
84.63(13)
91.55(7)
170.05(7)
175.0(7)
170.00 O(6)–Ru(2)–
Cl(2)
84.00
P(3)–Ru(2)–
Cl(2)
87.00
Cl(1)–Ru(2)–
Cl(2)
176.32 Ru(2)–C(2)–
O(2)

324
J.G. Małecki et al. / Polyhedron 31 (2012) 319–331
Fig. 3. IR spectra of the complexes [RuH(CO)(pyz-2,3-COO[CH3])(PPh3)2]ꢀH2O (2) and [Ru2HCl2(PPh3)3(pyz-2,3-COO)] (3).
anti-bonding orbitals of the CO ligand and produces a decrease of
about 4 cmꢁ1 in the vibration frequency of the CO bond [35]. The
electronic effect is supported by theoretically determined charge
values which indicate a more negatively charged Ru(II) central
ion (ꢁ0.72) than Ru(III) (ꢁ0.26). The charge on the hydride ion is
close to zero, (0.06) with a positive sign. Additionally the decrease
of the CO vibration frequencies from 1973 to 1958 cmꢁ1 in com-
plexes 1 and 2 respectively indicates differences in the acceptor
properties of pyrazine-2-carboxylic acid and pyrazine-2,3-dicar-
boxylic acid. In fact, by reducing the electron density on the metal
interaction, which would increase the bond order, and in turn
increase the vibration frequency of the CO bond. So it can be said
that the dicarboxylic ligand behaves as a stronger acceptor with
respect to the monocarboxylic derivative.
The mCO and mRu–H stretching bands in the parent [RuHCl
(CO)(PPh3)3] complex are at 2020 and 1922 cmꢁ1 respectively
and the decrease of the carbonyl stretches are clearly visible in
the studied complexes. The Ru–H stretching bands are displayed
at 1928, 1922 and 1923 cmꢁ1 in the spectra of complexes 1, 2
and 3, respectively. Stretching vibrations for C@C and C@N are
observed in the 1593–1655 cmꢁ1 range. The asymmetric and
carbonyl ligand, it will receive electron density via a dp ?
p⁄

J.G. Małecki et al. / Polyhedron 31 (2012) 319–331
325
Table 4
The occupancies and hybridization of the calculated R–H, Ru–C and C„O natural bond orbitals (NBOs) of the complexes [RuH(CO)(pyzCOOH)(PPh3)2] (1), [RuH(CO)(pyz-2,3-
COO[CH3])(PPh3)2] (2) and [Ru2HCl2(PPh3)3(pyz-2,3-COO)] (3).
BD (2-center bond)
Occupancy
Hybridization of NBO
Wiberg bond indices
Ru–H
1
2
3
1.844 (0.121)
1.843 (0.121)
1.854 (0.112)
0.723(sp0.64d2.39
0.725(sp0.63d2.39
0.727(sp0.61d2.48
)Ru + 0.690(s)H
)Ru + 0.689(s)H
)Ru + 0.686(s)H
0.77
0.78
Ru–C
1.945 (0.062)
1.944 (0.144)
1
2
0.581(sp0.82d2.60
0.581(sp0.87d2.63
)
)
Ru + 0.814(sp0.50
Ru + 0.814(sp0.50
)
)
1.35
1.35
C
C
3
Ru(1)
Ru(2)
1.946 (0.136)
1.949 (0.132)
0.581(sp0.82d2.60
0.576(sp0.68d2.33
)
)
Ru + 0.813(sp0.52
Ru + 0.817(sp0.52
)
)
1.34
1.33
C
C
C„O
1
2
1.996 (0.216)
1.995 (0.219)
1.992 (0.048)
1.996 (0.217)
1.995 (0.223)
1.992 (0.047)
0.496(sp27.42
0.496(sp)C + 0.868(p)O
0.545(sp2.67 C + 0.838(sp1.57
0.497(sp25.54
0.494(sp)C + 0.869(sp33.33
)
C + 0.868(sp22.13
)
2.01
2.01
O
)
)
O
)
C + 0.868(sp20.68
)
O
)
O
0.546(sp2.63
)
C + 0.838(sp1.54
)
O
3
Ru(1)
1.996 (0.216)
1.994 (0.208)
1.992 (0.054)
1.996 (0.212)
1.996 (0.194)
1.995 (0.043)
0.499(sp31.13
0.502(sp22.38
)
)
C + 0.866(sp24.52
C + 0.865(sp18.14
)
)
2.03
2.04
O
O
0.545(sp2.80
)
C + 0.838(sp1.65
)
O
Ru(2)
0.491(p)C + 0.871(p)O
0.504(sp16.72 C + 0.871(sp13.08
0.547(sp2.55 C + 0.837(sp1.57
)
)
)
O
O
)
Fig. 4. Interactions between ruthenium atoms and carbonyl and chloride ligands in the complex [Ru2HCl2(PPh3)3(pyz-2,3-COO)] (3).
symmetric stretches of the COO groups gave bands with maxima in
the ranges 1580–1559 and 1359–1339 cmꢁ1 respectively.
bond distances and angles are collected in Table 2. The structures
of the complexes can be considered as distorted octahedral with
the largest deviation from the expected 90° bond angles coming
from the bite angle of the pyrazine carboxylic acid. It equals
76.41(9), 75.74(12) and 73.90(16), 75.06(17)° for the N–Ru–O
angles in complexes 1, 2 and 3 respectively. The P–Ru–P angles
are lower than 180°, being in the 168.02(4)–173.03(3)° range.
The trans effect of the Hꢁ ligand is visible in an elongation of the
Ru(1)–N(1) bond by about 0.04 Å compared to the Ru(2)–N(2)
bond distance in the dinuclear complex 3. Some differences in
the bond lengths of the carbonyl group have been mentioned
3.2. Molecular structures
Crystals of the complexes suitable for single crystal X-ray anal-
yses were obtained by slow evaporation of the reaction mixtures.
The complexes 1 and 2 crystallize in the monoclinic P21/n space
ꢀ
group, and the dinuclear complex 3 in the triclinic P1 space group.
Complex 2 crystallizes as a solvate with one water molecule. Fig. 1
presents the molecular structures of the complexes and selected

326
J.G. Małecki et al. / Polyhedron 31 (2012) 319–331
Fig. 5. The density of states (DOS) diagrams for complexes 1 and 2.
earlier. As shown in Fig. 1, the CO groups are in trans positions to
the carboxyl groups of pyrazine in the complexes. This configura-
tion is preferred because of the donor/acceptor properties of the
carboxyl and carbonyl groups. In the [RuHCl(CO)(pyz)(PPh3)2]
complex, the pyrazine occupies the trans position to the carbonyl
ligand [36], which indicates an electronic reason for the configura-
tion of the ligands about the ruthenium central ions in the
complexes.
in Table 3. Additionally, in the structure of the complexes some
electronic interactions ( stacking) between the PPh3 phenyl
and pyrazine rings are visible. Fig. 2 presents the alignment of
the centroids formed by the pyrazine and phosphine phenyl rings.
The plane-to-plane distance between the #P2 centroid, determined
by C(31) to C(36) carbons, and pyrazine ring is equal to 3.63 Å,
p–p
indicating a p–p stacking interaction. The angle between the nor-
mal to #P2 and #pyz is 20.36°. It follows that the interaction
between #P2 and #pyz is very weak. A similar arrangement of
the phosphine phenyl and pyrazine rings occurs in the structures
In the molecular structures of the complexes several weak
inter- and intramolecular hydrogen bonds [37] exist, as collected

J.G. Małecki et al. / Polyhedron 31 (2012) 319–331
327
Fig. 6. The overlap partial density of states diagrams for the complex [Ru2HCl2(PPh3)3(pyz-2,3-COO)] (3).
of other complexes. In the molecule of complex 2, the distances
between #P1 (C(21)–C(26)), #P2 (C(39)–C(44)) and the #pyz cen-
troid are 3.79 and 3.70 Å and the angles are 21.08 and 18.30°,
respectively. In the structure of the dinuclear complex 3 a similar
arrangement occurs in the coordination sphere of ruthenium(II),
with distances #P1–#pyz 3.81, #P2–#pyz 3.68 Å and angles equal
N,O–donor ligands do not show covalent bonding with ruthenium.
Coulomb-type interactions between the ruthenium central ions
and the pyrazine derivatives ligands are clearly visible in the calcu-
lated Wiberg bond indices, whose values are considerably lower
than one. The Ru–N and Ru–O bond indices are similar and are
close to 0.37 and 0.39 in complexes 1 and 2, and are 0.37 and
0.36 (Ru2+), 0.43 and 0.34 (Ru3+) in 3. The Ru–P bond orders are
also smaller than 1 (0.7).
For the carbonyl groups of the investigated complexes, three
natural bond orbitals were detected for the C–O bond, and one
for the Ru–C bond. The Ru–C bond orbitals are polarized towards
the carbon atom, and the C–O bond orbitals are polarized towards
the oxygen end. The oxygen atom of the carbonyl ligand has one
lone pair (LP) orbital. The occupancies and hybridization of the
Ru–H, Ru–C and CO bonds are gathered in Table 4 (anti-bonding
NBOs are given in round brackets). The charges of the CO ligands
can be easily calculated by summing the individual charges on
the carbon and oxygen atoms, and have values of 0.18 in com-
plexes 1 and 2, and 0.20 (Ru2+) and 0.23 (Ru3+) in 3. These values
show that there is some charge transfer between CO and the Ru
fragment. The Wiberg indexes of the CO bonds in the complexes
are reduced (by about 0.22) with respect to free CO (WCO = 2.23).
These weak values are in agreement with the elongation of the
C–O bond in the complexes and the charge distribution in the ter-
minal bonding carbonyl group to the ruthenium central ion. The
bonding can be described as the result of two electron transfers.
to 14.33 and 15.37°. These intramolecular
p–p interactions may
explain the presence of singlet signals in the 31P NMR spectra of
compmlexes 1 and 2. The P(1)–Ru(1)–P(2) angle of about 170° in
the crystal structures changes to about 180° in solution by increas-
ing the strength of the p–p interactions.
3.3. Optimized geometries, hybrid and molecular orbitals description
The ground states geometries of the studied complexes were
optimized in singlet states in the case of complexes 1 and 2, and
in the doublet state for complex 3 using the DFT method with
the B3LYP functional. The calculations were carried out for gas
phase molecules and in general the predicted bond lengths and
angles are in agreement with the values based on the X-ray crystal
structure data. The general trends observed in the experimental
data are well reproduced in the calculations. The calculated IR fre-
quencies of complexes 2 and 3, shown in Fig. 3, confirm the calcu-
lated structures with the experimental ones, and the differences in
the calculated and experimental spectra mainly result from the
negligence of intermolecular interactions for the gas phase. From
the data collected in Table 2, one may see that the majority of dif-
ferences between the experimental and calculated geometries are
found in the Ru–P distances (ꢃ0.09 Å) and the angle differences
do not exceed 6.5°. The C„O bond lengths do not undergo impor-
tant changes and maximally a slight increase of ꢃ0.017 Å is seen
for the carbonyl group at Ru(2) in complex 3.
First this binding mode involves a
r-donation from the CO lone
pair orbital to the LUMO orbital of complex. On the other hand,
the highest occupied orbitals of the metallic fragment, mainly
4dRu orbitals, are involved in a
p back-bonding from the metal to
the CO p⁄ orbitals. Additionally the charge on the carbonyl group
bonded to the ruthenium(III) central ion in complex 3 has the high-
est positive value, which indicates the smallest charge transfer
from metal to CO. This is consistent with crystallographic data in
Table 2, where the C„O bond length is only 1.145(8) Å. Fig. 4
shows the interaction between the ruthenium atoms and the
carbonyl and chloride ligands in the complex [Ru2HCl2(PPh3)3
The NBO analyses were performed for the complexes, which
allowed the nature of the coordination between ruthenium and
the atoms of the ligands directly interacting with it to be known.
This methodology also gave a better understanding of the opti-
mized molecular structures. In the analysis it was found that the

328
J.G. Małecki et al. / Polyhedron 31 (2012) 319–331
Fig. 7. Experimental and calculated UV–Vis spectra of the complexes [RuH(CO)(pyz-2,3-COO[CH3])(PPh3)2]ꢀH2O (2) and [Ru2HCl2(PPh3)3(pyz-2,3-COO)] (3).
(pyz-2,3-COO)] (3). As one can see, the
p
-acceptor interaction be-
composition of their coordination spheres. The densities of states
(DOS) in terms of Mulliken population analysis were calculated
using the GAUSSSUM program, and Fig. 5 presents the composition
of the fragment orbitals contributing to the molecular orbitals for
complex 2. The HOMOs are mainly localized on the ruthenium
tween the carbonyl groups and ruthenium(III) is very small com-
pared with the Ru(II)–CO interaction. However, a small transfer
of electron density to the acceptor p⁄ carbonyl orbitals is compen-
sated by the presence of the acceptor chloride ligands.
Analysis of the frontier molecular orbitals is useful for under-
standing spectroscopic properties, such as electronic absorption
and emission spectra of organometallic complexes. The electronic
structures of complexes 1 and 2 are similar because of the similar
atoms (ꢃ53%) with
a contribution from triphenylphosphine
(ꢃ30%) and the pyrazine derivative ligands (ꢃ15%). The LUMOs
are basically located in the pyrazine ligands. The d orbitals of the
ruthenium central ions contribute in LUMO+2 (dz2) and LUMO+9/

J.G. Małecki et al. / Polyhedron 31 (2012) 319–331
329
Table 5
The calculated electronic transitions for the complex [Ru2HCl2(PPh3)3(pyz-2,3-COO)] (3).
[nm]
f
Transitions
Charter
dRu(III)
691.14
684.39
673.75
660.65
606.42
558.99
557.48
536.75
501.29
490.91
482.71
480.91
478.20
450.57
429.80
396.65
392.23
387.401
379.80
366.52
364.11
363.79
0.0022
0.0
H-7(b) ? LUMO(b) (32%), H-3(b) ? LUMO(b) (25%)
/
p
Cl ? dRu
/
ppyz
HOMO(
a
) ? LUMO(
a
) (51%), HOMO(b) ? L+1(b) (45%)
dRu
dRu
dRu
/
/
/
p
p
p
Cl ? dRu
PPh3 ? dRu
PPh3 ? dRu
/ppyz
/
/
0.0023
0.0011
0.0677
0.0385
0.0031
0.0020
0.0020
0.0069
0.0437
0.0596
0.0080
0.0176
0.0994
0.0081
0.0723
0.0036
0.0269
0.001
H-12(b) ? LUMO(b) (19%), H-4(b) ? LUMO(b) (37%)
H-6(b) ? LUMO(b) (18%), H-5(b) ? LUMO(b) (33%)
ppyz
ppyz
HOMO(
a
) ? LUMO(
a) (39%), HOMO(b) ? L+1(b) (45%)
dRu(III)
dRu(III)
/
/
p
p
Cl ? dRu
Cl ? dRu/
/ppyz
H-1(
H-2(
a
) ? LUMO(
a
a
) (32%), H-1(b) ? L+1(b) (47%)
) (35%), H-2(b) ? L+1(b) (31%)
ppyz
a) ? LUMO(
dRu(II)
dRu(III)
dRu(III)
dRu(III)
dRu(III)
/pPPh3 ? dRu/ppyz
HOMO(b) ? L+2(b) (89%)
H-23(b) ? LUMO(b) (77%)
/
/
/
/
pCl ? ppyz
p
p
pCl
Cl ? dRu
Cl ? dRu
/
/
ppyz
ppyz
H-1(
H-1(b) ? L+2(b) (66%)
H-2( ) ? LUMO( ) (36%), H-2(b) ? L+1(b) (37%)
H-24(b) ? LUMO(b) (76%)
H-2( ) ? L+1( ) (20%), H-2(b) ? L+2(b) (63%)
H-29(b) ? LUMO(b) (61%), H-28(b) ? LUMO(b) (38%)
H-12( ) ? LUMO( ) (10%), H-12(b) ? L+1(b) (14%)
a) ? L+1(a) (91%)
? ppyz
a
a
dRu(II)
PPh3 ? dRu
dRu(II) PPh3 ? dRu
pyz ? dRu
PPh3 ? dRu
/
p
PPh3 ? dRu
/
/
ppyz
ppyz
p
/ppyz
a
a
/p
p
p
/
ppyz
ppyz
a
a
/
H-31(b) ? LUMO(b) (47%), H-29(b) ? LUMO(b) (11%)
H-4(b) ? L+1(b) (40%), H-3(b) ? L+1(b) (19%)
dRu(II)
/
p
/
pPPh3
/
p
pyz ? dRu
Cl ? dRu
PPh3 ? dRu
/ppyz
pPPh3
/
/
ppyz
ppyz
H-11(
H-15(
a
) ? LUMO(
a
a
) (14%), H-11(b) ? L+1(b) (11%)
) (21%)
dRu(II)
p
/
a) ? LUMO(
pPPh3 ? dRu/ppyz
0.0039
0.0053
H-15(b) ? L+1(b) (19%)
H-3( ) ? L+1( ) (12%)
pPPh3
pPPh3
/
/
p
p
Cl ? dRu
Cl ? dRu
/
/
ppyz
ppyz
a
a
Fig. 8. The fluorescence spectrum of the complex [RuH(CO)(pyz-2,3-COO[CH3])(PPh3)2]ꢀH2O (2) in methanolic solution (c = 5 ꢂ 10ꢁ4 mol/dm3).
2
+10 (dx ꢁ y2) in complexes 1 and 2. The carbonyl ligands play a
Based on the pseudooctahedral geometry of the complexes and
taking into account d–d transitions assigned to 1A1 ? 1T1 and
1A1 ? 1T2 in an octahedral environment (or 1A1 ? 1A2/B1/E in low-
er symmetry fields), the ligand field parameter 10Dq can be esti-
mated as 28469 and 28660 cmꢁ1 for the complexes 1 and 2,
respectively. Racah’s parameters are B = 248 and 279 cmꢁ1, and
the nepheloauxetic parameters have values b55 = 0.34 and 0.39.
The bands observed in the vicinity of 40 000 cmꢁ1 (250 nm) have
been attributed to intra- and interligand (pbC6H6 ? 3dphosphorus
significant role in the HOMOꢁ1 and HOMOꢁ2 orbitals. In the case
of complex 3, the LUMO is also localized on the pyrazine dicarbox-
ylic ligand, with a contribution from the ruthenium(II) and (III)
2
2
dx ꢁ y orbitals, indicating a weak interaction between the two
ruthenium centers in the complex. The interaction is visible in
Fig. 6 and, as one can see, the values of the Ru(II)–Ru(III) interac-
tion in the energy range adequate for occupied and virtual molec-
ular orbitals is small but positive, indicating some stabilizing
interaction through the bridging pyrazine ligand.
and
Charge Transfer transitions (dRu
highest experimental bands, close to 210.0 nm, may result from
transitions in the PPh3 ligands and from
p⁄ excitations in the
p
?
p
C@C) transitions with an admixture of Metal–Ligand
?
p⁄
and dRu
?
p⁄Ph). The
N–ligand
3.4. Experimental and theoretical electronic spectra
p
?
The UV–Vis spectra of the monomeric complexes 1 and 2 are
N-heteroaromatic ligands. Fig. 7 presents the experimental and
similar and maxima close to 360, 316 and 273 nm were measured.
calculated UV–Vis spectra of the complex [RuH(CO)

330
J.G. Małecki et al. / Polyhedron 31 (2012) 319–331
solutions (with concentrations of 5 ꢂ 10ꢁ4 mol/dm3) at room tem-
0
80
160
240
320
0.4
0.3
0.2
0.1
0.0
perature. The excitations of complexes 1 and 2 were executed at a
wavelength near to the maximum of the first electronic absorption.
The excitation and emission spectra of complex 2 are presented in
Fig. 8, and as can be seen, the excitation at 355 nm gave fluores-
cence with a maximum at 439 nm. The red shifts of the emission
maximum of about 90 nm is typical for ruthenium(II) complexes
and emissions originating from the lowest energy metal to ligand
charge transfer (MLCT) state, derived from the excitation involving
Hac = 3.9 Oe
f = 300 Hz
a d
? pligand transition, are observed. The assignment is supported
p
by the analysis of the frontier orbitals of the corresponding com-
plexes, showing a contribution of ligand nature.
The excitation of complex 1 does not give any measurable emis-
sion, which confirms the MLCT nature of the fluorescence for com-
plex 2. As shown in the DOS diagrams presented in Fig. 5, the
LUMO and LUMO+1 orbitals in complex 2 are localized mainly on
the pyrazine ligand, in contrast to complex 1 where the ruthenium
orbitals play a role in LUMO+1. The dichloromethane solution of
complex 3 was excited in the range between 350 and 700 nm,
and no emissions were observed, which is not surprising consider-
ing the electronic structure of the complex.
[RuH(CO)(PPh3)(pyz-2,3-COO)Ru(CO)Cl2(PPh3)2] (3)
0.05
0.00
-0.05
0
80
240
320
T 1(6K0)
3.5. Magnetic properties
The ac magnetic susceptibility measurements for the complex
[RuH(CO)(PPh3)(pyz-2,3-COO)Ru(CO)Cl2(PPh3)2] (3), displayed in
Fig. 9, showed small values of the molar susceptibility, not exceed-
ing 0.5 emu/mol at 2 K, a lack of a Curie-Weiss region and a weak
magnetic interactions below 20 K, characteristic for a residual
magnetism. In paramagnets, the Curie-Weiss law is obeyed, show-
ing a hyperbolic temperature dependence of the susceptibility (cf.
Fig. 9. In phase v0 and out of phase v00 components of the dynamic susceptibility vs.
temperature T for the complex [RuH(CO)(PPh3)(pyz-2,3-COO)Ru(CO)Cl2(PPh3)2] (3)
recorded at an internal oscillating magnetic field Hac = 3.9 Oe with an internal
frequency f = 300 Hz.
(pyz-2,3-COO[CH3])(PPh3)2] (2). The first band in the spectra of
complexes 1 and 2 have HOMO/HOMOꢁ1 ? LUMO (98%/94%)
character. As the frontier HOMOs are localized on the d ruthenium
v
(T) in Ni [38] and Mn [39] complexes). The in-phase component
v0(T) is already fluctuating around zero above 20 K. It suggests that
all the ions are diamagnetic. A fact that the energy is not being
wasted for ordering and/or the reorientation of spins is also attest-
ing to it, since the out of phase component, v00(T) in Fig. 9 also fluc-
tuates around zero. A small increase in v0(T) below 20 K is probably
connected with different electron density localized on the ruthe-
nium ions.
orbitals with an admixture of p–PPh3, and the LUMOs are localised
on the pyrazine derivative ligands, Metal–Ligand Charge Transfer
transitions are associated with these orbital transitions. Higher
energy bands (316, 273 nm) have been attributed to Metal–Ligand
Charge Transfer transitions (d ? p⁄PPh3/pyz). In this energy region,
the transitions between HOMOꢁ3 ? LUMO (93%), HOMOꢁ1 ?
LUMO+2 (53%) and HOMO ? LUMO+5 (56%) were calculated.
The UV–Vis spectrum of complex 3 displays a broad band in the
wavelengths range 700–400 nm. Analysis of this spectrum on the
basis of terms due to two ruthenium central atoms with different
oxidation states is difficult. It can be assumed that 2T2g ? 4T1g and
2T2g ? 4T2g transitions occur at longer wavelengths, and in the
500–400 nm range the 2T2g ? /2A1g, 2T1g transitions play a role with
4. Conclusion
Three new hydride-carbonyl complexes of ruthenium were syn-
thesized and characterized by infra red, proton and phosphorus nu-
clear magnetic resonance, electronic absorption and emission
spectroscopy and X-ray crystallography. The experimental studies
were completed by theoretical calculations. The NBO calculations
show that the donor properties of the carbonyl group predominate
the MLCT (d ? p⁄quin) and LMCT (
pquin ? d) transitions. The UV–Vis
spectrumof thecomplexwas predictedbytheTDDFT methodand 90
electronic transitions are calculated. The experimental and calcu-
lated electronic spectra of the complex are presented in Fig. 7. The
UV–Vis spectrum was calculated to only 355 nm, so the shortest
wavelength experimental bands are not assigned to calculated tran-
sitions. Generally in the energy range considered, transitions were
calculated between H-11(b), H-12(b), H-7(b), H-6(b) and HOMO(b)
the
p-acceptor ability in the ruthenium(III) complexes. The small
transfer of electron density to the acceptor p⁄ carbonyl orbitals is
compensated by the presence of acceptor ligands such as chloride.
The theoretical results are in accordance with the experimental IR
spectra and structural data. The donations from the ligands to the
Ru(III) central ion in the [Ru2HCl2(PPh3)3(pyz-2,3-COO)] complex
result in the final diamagnetism of the complex, as the ac magnetic
susceptibility as well as the NMR studies have shown. The elec-
tronic structures of these complexes, presented in particular by
the density of states diagrams, have been correlated with their abil-
ity to fluoresce and have been used to analyze the UV–Vis spectra.
to LUMO(b) and at the shorter energies the H-1(
(490 nm) and H-2( ) ? LUMO( ) (36%) (480 nm) transitions are
visible. The transitions have d ? d character with an admixture of
pyrazine and chloride orbitals. The participation of d ruthenium
a) ? L+1(a) (91%)
a
a
p
orbitals is shown in the DOS diagram in the inset of Fig. 7. Some cal-
culated electronic transitions are presented in Table 5, and as can be
seen, in most of the transitions the excitation of ruthenium(III) is in-
volved. This is consistent with more electron density being localized
on the Ru(III) atom as compared to Ru(II), associated with the weak
donor interaction with the carbonyl group.
Acknowledgement
The emission characteristics of the complexes have been exam-
ined in methanol (for 1 and 2) and dichloromethane (for 3)
Calculations have been carried out in Wroclaw Centre for Net-
working and Supercomputing (http://www.wcss.wroc.pl).

J.G. Małecki et al. / Polyhedron 31 (2012) 319–331
331
[20] J.G. Małecki, R. Kruszyn´ ski, D. Tabak, J. Kusz, Polyhedron 26 (2007)
5120.
Appendix A. Supplementary data
[21] J.G. Małecki, R. Kruszynski, Z. Mazurak, Polyhedron 26 (2007) 4201.
[22] J.G. Małecki, R. Kruszyn´ ski, Polyhedron 26 (2007) 2686.
[23] J.G. Małecki, R. Kruszyn´ ski, J. Coord. Chem 60 (2007) 2085.
[24] N. Ahmad, J.J. Levinson, S.D. Robinson, M.F. Uttely, Inorg. Synth. 15 (1974)
48.
CCDC 828260, 828261 and 829183 contains the supplementary
crystallographic data for the complexes [RuH(CO)(pyzCOO)(PPh3)2]
(1), [RuH(CO)(pyz-2,3-COO[CH3])(PPh3)2]ꢀH2O (2) and [Ru2HCl2
(CO)(pyz-2,3-COO)(PPh3)3] (3). These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
[25] 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.
References
[1] L. Salvi, A. Salvini, F. Micoli, C. Bianchini, W. Oberhauser, J. Organomet. Chem.
692 (2007) 1442.
[2] C. Po Lau, S. Man Ng, G. Jia, Z. Lin, Coord. Chem. Rev. 251 (2007) 2223.
[3] C. Jun Yue, Y. Liu, R. He, J. Mol. Catal. A: Chem. 259 (2006) 17.
[4] F. Nipa Haque, A.J. Lough, R.H. Morris, Inorg. Chim. Acta 361 (2008) 3149.
[5] P. Buskens, D. Giunta, W. Leitner, Inorg. Chim. Acta 357 (2004) 1969.
[6] J. Bravo, J. Castro, S. Garcia-Fontana, M.C. Rodriguez-Martinez, G. Albertin, S.
Antoniutti, A. Manera, J. Organomet. Chem. 692 (2007) 5481.
[7] M. Chandra, A.N. Sahay, D.S. Pandey, M.C. Puerta, P. Valerga, J. Organomet.
Chem. 648 (2002) 39.
[26] A.D. Becke, J. Chem. Phys. 98 (1993) 5648.
[27] C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785.
[28] K. Eichkorn, F. Weigend, O. Treutler, R. Ahlrichs, Theor. Chim. Acc. 97 (1997)
119.
[29] 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.
[8] A.K. Singh, P. Kumar, M. Yadav, D.S. Pandey, J. Organomet. Chem. 695 (2010) 567.
[9] M. Arias, J. Concepción, I. Crivelli, A. Delgadillo, R. Díaz, A. Francois, F. Gajardo,
R. López, A.M. Leiva, L. Loeb, Chem. Phys. 326 (2006) 54.
[10] W. Henry, W.R. Browne, K.L. Ronayne, N.M. O’Boyle, J.G. Vos, J.J. McGarvey, J.
Mol. Struct. 735–736 (2005) 123.
[30] E.D. Glendening, A. E. Reed, J. E. Carpenter, F. Weinhold, NBO (version 3.1).
[31] N.M. O’Boyle, A.L. Tenderholt, K.M. Langner, J. Comp. Chem. 29 (2008) 839.
[32] CrysAlis RED, Oxford Diffraction Ltd., Version 1.171.29.2.
[33] O.V. Dolomanov, L.J. Bourhis, R.J. Gildea, J.A.K. Howard, H. Puschmann, J. Appl.
Cryst. 42 (2009) 339.
[11] B.J. Coe, S.J. Glenwright, Coord. Chem. Rev. 203 (2000) 5.
[12] C.R. Samanamú, A.F. Richards, Polyhedron 26 (2007) 923.
[13] R. Lalrempuia, P. Govindaswamy, Yurij A. Mozharivskyj, M. Rao Kollipara,
Polyhedron 23 (2004) 1069.
[34] G.M. Sheldrick, Acta Cryst. A64 (2008) 112.
[35] J.G. Małecki, R. Kruszynski, J. Coord. Chem. 60 (2007) 2085.
[36] M. Yánez, J. Guerrero, P. Aguirre, S.A. Moya, G. Cárdenas-Jirón, J. Organomet.
Chem. 694 (2009) 3781.
_
[14] A. Skarzyn´ ska, M. Siczek, Polyhedron 27 (2008) 1930.
[37] G.R. Desiraju, T. Steiner, The Weak Hydrogen Bond in Structural Chemistry and
´
[15] J.G. Małecki, A. Maron, Polyhedron 30 (2011) 1225.
Biology, Oxford University Press, 1999.
´
[16] J.G. Małecki, Polyhedron 30 (2011) 79.
[17] J.G. Małecki, Polyhedron 29 (2010) 2489.
[18] J.G. Małecki, R. Kruszyn´ ski, Z. Mazurak, Polyhedron 28 (2009) 3891.
[19] J.G. Małecki, R. Kruszyn´ ski, Z. Mazurak, J. Coord. Chem. 61 (2008) 2186.
[38] J.G. Małecki, A. Switlicka, T. Gron´ , M. Bałanda, Polyhedron 29 (2010) 3198.
´
[39] J.G. Małecki, B. Machura, A. Switlicka, T. Gron´ , M. Bałanda, Polyhedron 30
(2011) 746.