Coordination chemistry of di-2-pyridylketone. Synthesis, spectroscopic investigations, X-ray studies and DFT calculations of Re(III) and Re(V) complexes

Article abstract of DOI:10.1016/j.poly.2009.06.048

The paper presents a combined experimental and computational study of Re(III) and Re(V) complexes containing di-2-pyridylketone and its gem-diol form - [ReCl₃(dpk-N,O)(PPh₃)] (1), [ReCl₃(dpk-N,N′)(OPPh₃)] (2) an

Full text of DOI:10.1016/j.poly.2009.06.048

Polyhedron 28 (2009) 2821–2830
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Coordination chemistry of di-2-pyridylketone. Synthesis, spectroscopic
investigations, X-ray studies and DFT calculations of Re(III) and Re(V) complexes
b
c
d
B. Machura a, , J. Mrozinski , R. Kruszynski , J. Kusz
*
´
a Department of Crystallography, Institute of Chemistry, University of Silesia, 9th Szkolna St., 40-006 Katowice, Poland
b Faculty of Chemistry, Wroclaw University, F. Joliot-Curie 14 St., 50-383 Wrocław, Poland
Department of X-ray Crystallography and Crystal Chemistry, Institute of General and Ecological Chemistry, Lodz University of Technology, 116 Zeromski St., 90-924 Łódz, Poland
d Institute of Physics, University of Silesia, 4th Uniwersytecka St., 40-006 Katowice, Poland
c
_
´
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 14 May 2009
Accepted 7 June 2009
The paper presents a combined experimental and computational study of Re(III) and Re(V) complexes
containing di-2-pyridylketone and its gem-diol ꢁform
– [ReCl3(dpk-N,O)(PPh3)] (1), [ReCl3(dpk-
N,N0)(OPPh3)] (2) and [ReOBr3(dpk-OH)]ꢀ2(dpkH+Br ) (3). All the complexes have been characterized
spectroscopically and structurally (by single-crystal X-ray diffraction). The complex 2 has been addition-
ally studied by magnetic measurement. The magnetic behavior of 2 is characteristic of mononuclear octa-
hedral Re(III) complex with d4 low-spin (3T1g ground state) and arise because of the large spin–orbit
coupling (f = 2500 cmꢁ1), which gives diamagnetic ground state. DFT and time-dependent (TD)DFT calcu-
lations have been carried out for [ReCl3(dpk-N,N0)(OPPh3)] and [ReOBr3(dpk-OH), and their UV–vis spec-
tra have been discussed on this basis.
Keywords:
Rhenium complexes
Di-2-pyridylketone
X-ray
Electronic structure
DFT and TDDFT calculations
Magnetic measurement
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
In this context, the design, synthesis and reactivity of novel rhe-
nium complexes has become the aim of several laboratories,
The coordination chemistry of rhenium is a field of current
growing interest from various viewpoints. The attention of scien-
tists concentrates on synthetic aspects, structural, physicochemical
properties and reactivity, as well as on topics with an applied char-
acter such as the development of radiotherapeutic cancer agents,
nitrogen fixation and catalysis [1].
including ours.
Here, we present synthesis, spectroscopic investigation, crystal
and molecular structure of three rhenium complexes with di-2-
pyridylketone (dpk) and its gem-diol. Investigation into the proper-
ties of the ligand di-2-pyridyl ketone was first reported in 1967 by
Osborne and McWhinnie and numerous reactions of di-2-pyridyl
ketone with transition metals have been studied to date. The dpk
can act as a bidentate, tridentate or bridging ligand. As a chelate
di-2-pyridylketone can bind to the metal center ion via one of
two modes: either through the two nitrogen atoms located in the
pyridine rings or through one pyridyl nitrogen and the carbonyl
oxygen [11]. The majority of metal complexes with dpk are coordi-
nated in the N,N-mode. The N,O-coordination mode of dpk has been
confirmed in [RuCl2(DMSO)(dpk-N,O)] [12] and [Ru(Cp)(dpk-N,O)]
[13].
After the initial coordination with the metal ion, the carbonyl
oxygen atom of the dpk ligand can become subject to nucleophilic
attack by water or alcohols, and the formation of (2-py)2C(OH)2 or
(2-py)2C(OR)(OH) has been frequently observed. The deprotonated
gem-diol or hemiacetal form of (2-py)2CO coordinates to the metal
centers as N,N0,O chelates or as bridging ligands. The monoanionic
form usually bridge two or three metal ions, while the dianionic
form can bridge as many as five metal sites [11].
The 186Re (1.07 MeV b-emitter, t1/2 90 h) and 188Re (2.12 MeV b-
emitter, t1/2 17 h) are among the most attractive isotopes for appli-
cations in targeted radionuclide therapy [2,3]. The diazenido and
dinitrogen rhenium complexes are important in view of their sig-
nificance in the field of nitrogen fixation [4–6]. Methyltrioxorhe-
nium is one of the most versatile catalysts for olefin oxidation
reactions, aldehyde olefination and olefin metathesis [7,8]. The
mer,trans-[ReOCl3(PPh3)2] and its derivatives catalyze the
oxidation of sulfides to sulfoxides, thiols to disulfides and catalyze
oxygen-transfer from sulfoxides to phosphines [8]. The
[ReOCl2(O–N)(PPh3)] chelates with pyridinecarboxylate ligands
exhibit a remarkable catalytic activity for the carboxylation of eth-
ane by CO in the presence of K2S2O8 to a mixture of propionic and
acetic acids in a single-pot process [9]. The [CH3ReO(pic)2] complex
is an active precursor in olefin oxidation and forms epoxides in a
two-phase H2O2–H2O/CH2Cl2 system [10].
* Corresponding author.
E-mail addresses: basia@ich.us.edu.pl (B. Machura), jmroz@wchuwr.chem.uni.
wroc.pl (J. Mrozin´ ski), rafal.kruszynski@p.lodz.pl (R. Kruszynski).
The rhenium complexes with di-2-pyridylketone have been
studied relatively little [14,15]. It prompts us to explore the
0277-5387/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2009.06.048

2822
B. Machura et al. / Polyhedron 28 (2009) 2821–2830
reactivity of [ReCl3(MeCN)(PPh3)2] towards the dpk ligand. The
[ReCl3(MeCN)(PPh3)2] complex has proven to be useful precursor
in the synthesis of Re(III) compounds [16–18]. The [ReCl3(MeCN)-
(PPh3)2] also easily reacts with di-2-pyridylketone to give
[ReCl3(dpk-N,O)(PPh3)] (1) with rarer N,O-coordination of dpk
ligand. The solid [ReCl3(dpk-N,O)(PPh3)] can be handled in air
without significant degradation, but rapid isomerisation with
oxidation of coordinated PPh3 occurs in organic solvents at room
temperature in the presence of atmospheric oxygen. In fact, the
starting purple solution of [ReCl3(dpk-N,O)(PPh3)] in chloroform
turns to dark red and crystals of [ReCl3(dpk-N,N0)(OPPh3)] (2) with
N,N-coordination of dpk ligand are deposited.
IR (KBr;
and 1542(w) mCN and
Anal. Calc. for C29H23Cl3N2O2PRe: C, 46.13; H, 3.07; N, 3.71.
Found: C, 46.79; H, 3.30; N, 3.45%.
m
/cmꢁ1): 1649(vs)
C@C; 1135(vs) and 1119(vs) mRe@O
mC@O; 1609(m), 1591(m), 1575(m)
m
.
2.4. Preparation of [ReOBr3(dpk-OH)]ꢀ2(dpkH+Brꢁ) (3)
A mixture of [ReOBr3(PPh3)2] (0.50 g, 0.52 mmol), di-2-pyridyl-
ketone (0.28 g, 1.52 mmol) and acetone (100 ml) was stirred at
room temperature for 12 h. Half of the solvent was removed and
diethyl ether (50 ml) was added to precipitate the product as green
solid, which was filtered off and dried. Yield 85%. Crystals suitable
for X-ray investigation were obtained by recrystallization from
acetonitrile.
N,N0,O coordination mode of monoanionic form of (2-py)2CO
has been confirmed in the [ReOBr3(dpk-OH)]ꢀ2(dpkH+Brꢁ) (3),
isolated from the reaction of [ReOBr3(PPh3)2] with excess of
di-2-pyridylketone in acetone in air.
IR (KBr;
mCN and C@C; 958(s) mRe@O
m mC@O; 1599(s), 1579(s) and 1520(s)
/cmꢁ1): 1683(vs)
m
.
The structures of all the complexes [ReCl3(dpk-N,O)(PPh3)] (1),
[ReCl3(dpk-N,N0)(OPPh3)] (2) and [ReOBr3(dpk-OH)]ꢀ2(dpkH+Brꢁ)
(3) have been proven by X-ray diffraction. The complexes
[ReCl3(dpk-N,N0)(OPPh3)] and [ReOBr3(dpk-OH)], which are stable
in solution, have been also studied by UV–vis spectroscopy. The
electronic spectra of [ReCl3(dpk-N,N0)(OPPh3)] and [ReOBr3(dpk-
OH)] have been discussed in detail using the density functional
theory (DFT) and time-dependent DFT (TDDFT) calculations.
Currently the density functional theory (DFT) is commonly used
to examine the electronic structure of transition metal complexes.
It meets with the requirements of being accurate, easy to use and
fast enough to allow the study of relatively large molecules of tran-
sition metal complexes [19]. Recent studies have also supported
the TDDFT method to be applicable for open- and closed-shell of
5d-metal complexes giving good assignment of experimental spec-
tra [20–22].
Anal. Calc. for C33H27Br4N6O5Re: C, 36.25; H, 2.49; N, 7.69.
Found: C, 36.89; H, 2.37; N, 7.39%.
2.5. Crystal structures determination and refinement
The X-ray intensity data of 1, 2 and 3 were collected on a KM-4-
CCD automatic diffractometer equipped with CCD detector and
graphite monochromated Mo Ka radiation (k = 0.71073 Å). Details
concerning crystal data and refinement are given in Table 1. Lor-
entz, polarization and absorption correction [24] were applied.
The structures were solved by the Patterson method and subse-
quently completed by the difference Fourier recycling. All the
non-hydrogen atoms were refined anisotropically using full-ma-
trix, least-squares technique. The hydrogen atoms were treated
as ‘‘riding” on their adjacent atoms and assigned isotropic temper-
ature factors equal 1.2 times the value of equivalent temperature
factor of the aromatic parent atoms and equal 1.5 times the value
of equivalent temperature factor of the oxygen atom (OH). SHELXS97
[25], SHELXL97 [26] and SHELXTL [27] programs were used for all the
calculations. Atomic scattering factors were those incorporated in
the computer programs.
2. Experimental
2.1. General procedure
The reagents used to the synthesis were commercially available
and were used without further purification. The [Re(MeCN)Cl3-
(PPh3)2] [16] and [ReOBr3(PPh3)2] [23] complexes were prepared
according to the literature methods.
IR spectra were recorded on a Nicolet Magna 560 spectropho-
tometer in the spectral range 4000–400 cmꢁ1 with the samples
in the form of KBr pellets. Electronic spectra were measured on a
spectrophotometer Lab Alliance UV–vis 8500 in the range 1000–
180 nm in acetonitrile solution. Elemental analyses (CHN) were
performed on a Perkin–Elmer CHN-2400 analyzer.
2.6. Computational details
The ground states geometries of [ReCl3(dpk-N,N0)(OPPh3)] and
[ReOBr3(dpk-OH)] were optimized without any symmetry restric-
tions with the DFT method using the hybrid B3LYP functional of
GAUSSIAN-03 [28–30].
The calculations were performed using ECP basis set LANL2DZ
[31] with an additional d and f function with the exponent
a
= 0.3811 and a = 2.033 [32] for rhenium and the standard 6-
31G basis set for other atoms. For chloride, bromide, oxygen, nitro-
gen and phosphorous atoms, diffuse and polarization functions
were added [33–38]. Vibrational frequencies of [ReCl3(dpk-
N,N0)(OPPh3)] and [ReOBr3(dpk-OH)] were calculated to ensure
that optimized geometries represented minima.
2.2. Preparation of [ReCl3(dpk-N,O)(PPh3)] (1)
[Re(MeCN)Cl3(PPh3)2] (0.5 g, 0.58 mmol) and di-2-pyridylke-
tone (0.11 g, 0.60 mmol) in CH2Cl2 (80 cm3) were heated under ar-
gon atmosphere for 5 h. The starting material gradually dissolved
and the color of the reaction solution became blue-purple. The
volume of the reaction solution was condensed to 10 cm3 and
allowed to cool to room temperature. Dark pink microcrystalline
precipitate was formed and filtered off.
The electronic spectra of [ReCl3(dpk-N,N0)(OPPh3)] and [ReOBr3
(dpk-OH)] were calculated with the TDDFT method, and the solvent
effect (acetonitrile) was simulated using the polarizable continuum
model with the integral equation formalism (IEF-PCM) [39–42].
Natural bond orbital (NBO) calculations for [ReOBr3(dpk-OH)]
were performed with the NBO code [43] included in GAUSSIAN-03.
IR (KBr;
1538(w) mCN and mC@C
m mC@O; 1608(w), 1590(m), 1572(m) and
/cmꢁ1): 1646(s)
.
Anal. Calc. for C29H23Cl3N2OPRe: C, 47.13; H, 3.14; N, 3.79.
Found: C, 47.61; H, 3.42; N, 3.62%.
2.7. Magnetic measurement
Magnetization measurements of polycrystalline samples were
2.3. Preparation of [ReCl3(dpk-N,N0)(OPPh3)] (2)
carried out with
a Quantum Design SQUID magnetometer
(MPMSXL-5-type) at a magnetic field of 0.5 T over the temperature
range 1.8–300 K. Magnetization measurements versus magnetic
field (0–5 T) were made at 2 K.
A solution of [ReCl3(dpk-N,O)(PPh3)] in chloroform was stood
for several days in air and dark red crystals were deposited.

B. Machura et al. / Polyhedron 28 (2009) 2821–2830
2823
Table 1
Crystal data and structure refinement for 1, 2 and 3 complexes.
1
2
3
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
C29H23Cl3N2OPRe
739.01
293(2)
0.71073
monoclinic
P21/n
C29H23Cl3N2O2PRe
755.01
293(2)
0.71073
orthorhombic
P212121
C33H27Br4N6O5Re
1093.45
120(1)
0.71073
triclinic
ꢀ
P1
Unit cell dimensions (Å, °)
a = 11.621(2)
b = 12.505(3)
c = 18.938(4)
a = 9.9643(3)
b = 13.9694(5)
c = 19.7787(6)
a = 8.98070(10)
b = 13.0557(2)
c = 16.2930(2)
a
= 69.0060(10)
b = 81.8530(10)
= 79.3880(10)
b = 90.12(3)
c
Volume (Å3)
2752.1(10)
4
1.784
4.791
2753.10(15)
4
1.822
4.794
1472
1747.05(4)
2
2.079
8.102
1044
Z
Dcalc (mg/m3)
Absorption coefficient (mmꢁ1
F(0 0 0)
)
1440
Crystal size (mm)
h Range for data collection (°)
Index ranges
0.05 ꢂ 0.08 ꢂ 0.19
3.22–25.00
ꢁ13 6 h 6 13
ꢁ10 6 k 6 14
ꢁ22 6 l 6 22
15 206
0.04 ꢂ 0.18 ꢂ 0.20
2.90–25.00
ꢁ9 6 h 6 11
ꢁ15 6 k 6 16
ꢁ23 6 l 6 23
17 510
0.183 ꢂ 0.181 ꢂ 0.176
1.76–25.05
ꢁ10 6 h 6 10
ꢁ15 6 k 6 15
ꢁ19 6 l 6 19
Reflections collected
17 564
Independent reflections
Completeness to 2h (%)
4710 (Rint = 0.0471)
98.6
4852 (Rint = 0.0556)
99.8
6200 (Rint = 0.0272)
99.9
Maximum and minimum transmission
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
0.792 and 0.641
4710/0/334
0.857
0.822 and 0.405
4852/0/343
1.083
0.259 and 0.241
6200/0/443
1.050
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0294, wR2 = 0.0506
R1 = 0.0681, wR2 = 0.0554
1.210 and ꢁ0.739
R1 = 0.0260, wR2 = 0.0722
R1 = 0.0303, wR2 = 0.0731
0.927 and ꢁ0.985
R1 = 0.0217, wR2 = 0.0533
R1 = 0.0264, wR2 = 0.0550
0.593 and ꢁ1.432
Largest difference in peak and hole (e Åꢁ3
)
Corrections are based on subtracting the sample – holder signal
and contribution vD estimated from the Pascal constants [44] and
equal – 376 ꢂ 10ꢁ6 for complex Re(III). The effective magnetic mo-
m
(Re@O) stretching band of 3 is found at 958 cmꢁ1. The medium
intensity band at 3045 cmꢁ1 assignable to
(OH) vibrations con-
m
firms the monoanionic gem-diol form of dpk in the coordination
sphere of 3. The strong bands at 1135 and 1119 cmꢁ1 in the IR
spectrum of 2 confirm the presence of the coordinated OPPh3 mol-
ecule [45].
ment was calculated from the equation,
l
eff = 2.83(vcMorr ꢂ T)1/2 B.M.
3. Results and discussion
3.1. Preparation and infrared data
3.2. Crystal structures
The [ReCl3(dpk-N,O)(PPh3)] (1) complex was prepared in good
yield by ligand exchange reaction starting from [ReCl3(MeCN)-
(PPh3)] and di-2-pyridylketone (dpk):
[ReCl3(MeCN)(PPh3)2] + dpk ? [ReCl3(dpk-N,O)(PPh3)] + PPh3 +
MeCN
The solid [ReCl3(dpk-N,O)(PPh3)] can be handled in air without
significant degradation, but rapid isomerisation with oxidation of
coordinated PPh3 occurs in organic solvents at room temperature
in the presence of atmospheric oxygen. The [ReCl3(dpk-N,N0)-
(OPPh3)] (2) compound has been isolated during crystallization
of [ReCl3(dpk-N,O)(PPh3)] from chloroform in air.
The crystallographic data of the 1, 2 and 3 complexes are sum-
marized in Table 1. The short intra- and intermolecular contacts
[46,47] detected in the 1, 2 and 3 are gathered in Table 2. The per-
spective drawings of 1, 2 and 3 are presented in Figs. 1–3, and the
selected bond distances and angles of 1, 2 and 3 are collected in Ta-
bles 3–5, respectively.
The overall structure of 1 can be considered as a distorted octa-
hedral with the largest deviation from the expected 90° bond an-
gles coming from the bite angle di-2-pyridylketone coordinated
in N,O-mode. It equals to 76.08(14)°, and it is similar to that re-
ported for the related [Ru(Cp)(dpk-N,O)] (78.38(7)°) [13]. The bite
The [ReOBr3(dpk-OH)]ꢀ2(dpkH+Brꢁ) (3) compound has been ob-
tained in the reaction of [ReOBr3(PPh3)2] with excess of di-2-pyri-
dylketone in acetone in a system open to the atmosphere. In this
case the carbonyl oxygen atom of the di-2-pyridylketone is subject
to nucleophilic attack by water and gem-diol form of dpk is formed.
The elemental analyses of the 1, 2 and 3 complexes are in good
agreement with their formulation. The selected frequencies observed
in the IR spectra of 1, 2 and 3 complexes are given in Section 2.
angles O–M–N in the structures with a-iminoketo chelate ligands
bounded to transition metals depend mainly on the size of the me-
tal center, the smallest values (down to 67°) were found for AgI
complexes and the largest angles (up to 85°) were observed for
compounds with CuII [48].
The electron rich central ion of 1 shows larger affinity towards
the less basic but strongly
p accepting carbonyl oxo atom, and the
Re–O(1) is slightly shorter than the Re–N(1) bond (Table 3). The
pyridyl rings of dpk ligand are planar in the range of experimental
error and they are inclined at 5.9(3)°.
The chloride ions of 1 are arranged in a facial fashion, typical of
the [ReX3(L–L)(PPh3)] compounds with bipy-like ligands [49]. In
A band due to the
1649 and 1683 cmꢁ1 for 1, 2 and 3, respectively. In the case of 3
this band is consequence of (C@O) vibration of the protonated
ligand present in the outer coordination sphere. The characteristic
bands corresponding to the (CN), (C@C) modes of dpk and dpk-
OH are observed in the range 1610–1500 cmꢁ1
The strong
m(C@O) vibration of dpk appears at 1646,
m
m
m
the [ReX3(L–L)(PPh3)] complexes with two excellent
p acceptor li-
.
gands coordinated to -donor rhenium(III) center the back-bonding
p

2824
B. Machura et al. / Polyhedron 28 (2009) 2821–2830
Table 2
two carbon atoms. The planar in the range of experimental error
pyridyl rings are inclined at 51.3(2)°. By forming a six-membered
Hydrogen bonds for 1, 2 and 3 complexes.
chelate ring dpk allows Re(III) center to achieve a geometry that
D
A
Hꢀ ꢀ ꢀA
Dꢀ ꢀ ꢀA
D—Hꢀ ꢀ ꢀA
is closer to octahedral than is possible for
five-membered chelate.
a-iminoketo which form
1
C(8)
C(8)
C(18)
C(26)
C(29)
Cl(2)
O(1)
Cl(2)
N(2)
Cl(1)
2.69
2.59
2.73
2.29
2.69
3.444(5)
3.150(6)
3.539(6)
2.899(7)
3.286(7)
138.2
119.5
146.2
122.3
123.0
The asymmetric unit of 3 contains one complex molecule [Re-
OBr3(dpk-OH)], two bromide anions and two 2-pyridyl-2-pyryd-
iniumketone cations. In complex molecule of 3 monoanionic
gem-diol form (2-py)2C(OH)Oꢁ coordinates to the Re(V) center
through the deprotonated hydroxy group and two pyridyl nitro-
gen atoms. The coordination sphere of [ReOBr3(dpk-OH)] is com-
pleted by two bromide and terminal oxo ligands, and the
geometry about Re(V) can be described as a very distorted
octahedral.
The oxygen atom of dpk-OH is coordinated in trans position to
the terminal oxo ligand. The high concentration of electronic den-
sity along the Re–O axis strongly influences the positions of the
adjacent halogen atoms, which are pushed away. The planar in
the range of experimental error pyridyl rings of the diol are in-
clined at 72.72(10)°. Aromatic rings of cations are inclined at dis-
tinctly smaller angles: 24.8(2)° and 22.4(2)°. The pyridine ring is
in trans arrangement to the pyrydinium ring in one of cations
and cis in second one.
2
C(9)
C(15)
C(27)
C(18)
Cl(2)#1
Cl(3)#2
O(1)#3
Cl(2)
2.68
2.73
2.48
2.77
3.506(8)
3.474(7)
2.886(8)
3.683(7)
148.5
137.6
106.7
166.8
3
O(3)
Br(99)
Br(98)
O(21)
N(41)
2.36
2.39
2.25
2.08
2.30
2.68
2.90
2.91
2.46
3.175(2)
3.153(3)
2.620(4)
2.685(4)
2.919(5)
3.377(3)
3.787(4)
3.715(4)
3.316(4)
171.5
148.6
106.0
126.5
123.3
138.8
159.4
145.7
153.7
N(22)
N(22)
N(42)
C(28)
N(42)
C(11)
C(29)
C(51)
N(21)
Br(99)#4
Br(2)#5
Br(98)#6
O(2)#4
#1: 0.5 + x, 1.5 ꢁ y, 1 ꢁ z; #2: 0.5 ꢁ x, 2 ꢁ y, ꢁ0.5 + z; #3: ꢁ0.5 + x, 2.5 ꢁ y, 1 ꢁ z;
#4: 1 ꢁ x, 1 ꢁ y, 1 ꢁ z; #5: 2 ꢁ x, ꢁy, ꢁz; and #6: 3 ꢁ1 + x, y, z.
The Re–N bond lengths of 1 and 2 are similar to those found for
the rhenium(III) polypyridyl compounds ([ReCl2(bipy)2]PF6
–
2.094(5) and 2.096(5) Å [50] and in the [ReL(terpy)2]2+ (L = Cl,
OH, NCS) complexes – about 2.10 Å [51]) and significantly shorter
effect is maximized in the facial disposition, which ensures mini-
mum competition between the two ligands for identical metal
orbitals.
than comparable distances of 3, where metal-to-ligand
bonding is not possible.
p-back
The Re–Cl(3) distance of 1 is affected by trans influence of tri-
phenylphospine and is longer than the Re—Cl(1) and Re—Cl(2)
bond lengths located in trans positions to the dpk ligand.
The Re–Ot bond length of 3 falls in the range 1.639–1.76 Å,
which is typical of mononuclear complexes of rhenium(V) having
[ReO]3+ core, and indicates the presence of a triple bond Re„O
[52]. The interatomic distance between the rhenium atom and
the oxygen atom of dpk-OH ligand is somewhat shorter in compar-
ison with an ideal single Re–O bond length (ca. 2.04 Å) [53], and
indicates small delocalization in the O(2)–Re(1)–O(1) moiety. In
keeping with that, the O(1)–Re(1)–O(2) angle is equal 157.10(11),
notably less than 180°.
The fac geometry of chloride ions are also confirmed in complex
2. However, in this case facial arrangement seems to be sustained
by steric advantages. Phosphine oxides are purely donor in charac-
ter, and lack acceptor properties favor the meridional configuration
of chloride ligands in the complexes [ReX3(L–L)(OPPh3)] with
approximately planar L–L ligands. The di-2-pyridylketone is coor-
dinated to the Re(III) center of 2 in a nonplanar N,N-mode, and
nonplanarity seems to be responsible for fac Chloride arrangement
in 2. Upon coordination of di-2-pyridylketone to the rhenium via
two nitrogen atoms, a six-membered cycle is formed, and the
formed ring shows a boat conformation with the rhenium and
the carbonyl group off the plane defined by the two nitrogen and
Fig. 1. The molecular structure of 1.

B. Machura et al. / Polyhedron 28 (2009) 2821–2830
2825
Table 3
The experimental bond lengths (Å) and angles (°) for 1.
Bond lengths
Experimental
Bond angles
Experimental
Re(1)–O(1)
Re(1)–N(1)
Re(1)–Cl(1)
Re(1)–Cl(2)
Re(1)–Cl(3)
Re(1)–P(1)
1.997(3)
2.091(4)
2.3314(15)
2.3524(15)
2.3979(15)
2.4469(15)
O(1)–Re(1)–N(1)
N(1)–Re(1)–Cl(1)
N(1)–Re(1)–Cl(2)
N(1)–Re(1)–Cl(3)
O(1)–Re(1)–Cl(1)
O(1)–Re(1)–Cl(2)
O(1)–Re(1)–Cl(3)
Cl(1)–Re(1)–Cl(2)
Cl(3)–Re(1)–Cl(2)
Cl(3)–Re(1)–Cl(1)
O(1)–Re(1)–P(1)
N(1)–Re(1)–P(1)
Cl(1)–Re(1)–P(1)
Cl(2)–Re(1)–P(1)
Cl(3)–Re(1)–P(1)
76.08(14)
93.88(12)
168.94(12)
86.62(12)
169.79(10)
93.77(10)
89.52(10)
96.38(5)
88.95(6)
91.74(6)
90.43(10)
95.04(12)
88.61(5)
89.33(5)
178.28(5)
from the large spin–orbit coupling (f = 2500 cmꢁ1 [63]),which
gives diamagnetic ground state. It seems that in room temperature,
in accordance Boltzmann’s distribution, it is populated higher mag-
netic state, which is depopulated with temperature lowering and
decreasing of the magnetic moment is observed.
The variation of the magnetization M versus the magnetic field
H for complex 2 at 2 K is shown in Fig. 5.
Fig. 2. The molecular structure of 2.
The magnetization versus magnetic field curve for complex very
slowly increases and indicates value of the magnetization 0.36 B.M
at 5 T, confirms that the ground state of the complex is
diamagnetic.
In all the compounds the molecules (and ions in 3) are con-
nected via intermolecular interaction to the three-dimensional
nets, however, in compounds 1 and 2 the intermolecular bonds
are weak due to absence of strong hydrogen bond donors. In 3
the medium strength hydrogen bonds link molecules and ions to
the [ReOBr3(dpk-OH)]ꢀ ꢀ ꢀBrꢁꢀ ꢀ ꢀHdpk+ trimers and Brꢁꢀ ꢀ ꢀHdpk+ di-
mers and these clusters are connected via weak C–Hꢀ ꢀ ꢀA hydrogen
bonds to the three-dimensional net.
3.4. Geometry optimization
The geometries of [ReCl3(dpk-N,N0)(OPPh3)] and [ReOBr3(dpk-
OH)] complexes were optimized by the DFT method with the
B3LYP functional. The geometry of [ReCl3(dpk-N,N0)(OPPh3)] was
optimized in triplet and singlet states, and geometry of [Re-
3.3. Magnetic properties
OBr3(dpk-OH)]
– in singlet state. For complex [ReCl3(dpk-
N,N0)(OPPh3)] the energy of the triplet state is of 22.12 kcal/mol
smaller in comparison with the singlet state. It is in good agree-
ment with the magnetic measurements. The effective magnetic
moment of [ReCl3(dpk-N,N0)(OPPh3)] is equal to 2.59 B.M. at
300 K and decreases with temperature lowering (to 0.91 B.M. at
1.8 K). This behavior is characteristic of mononuclear octahedral
Re(III) complex with d4 low-spin (3T1g ground state). The optimized
geometric parameters of [ReCl3(dpk-N,N0)(OPPh3)] (triplet state)
The magnetic properties of 2 under the form molar magnetic
susceptibility (vM) and vMT = f(T) are shown in Fig. 4.
The complex 2 shows in the whole temperature range lowering
of the magnetic moment from 2.59 B.M. at 300 K up to 0.91 B.M. at
1.8 K.
This behavior is characteristic of mononuclear Re(III) complexes
(3T1g ground state) with d4 low-spin octahedral [54–62] and arise
Fig. 3. The molecular structure of 3.

2826
B. Machura et al. / Polyhedron 28 (2009) 2821–2830
Table 4
The experimental and optimized bond lengths (Å) and angles (°) for 2.
Bond lengths
Experimental
Optimized
Bond angles
Experimental
Optimized
Re(1)–O(2)
Re(1)–N(2)
Re(1)–N(1)
Re(1)–Cl(1)
Re(1)–Cl(2)
Re(1)–Cl(3)
O(2)–P(1)
2.061(4)
2.055(5)
2.079(6)
2.3831(15)
2.3792(17)
2.3315(17)
1.513(5)
2.080
2.082
2.080
2.442
2.441
2.383
1.537
N(2)–Re(1)–N(1)
O(2)–Re(1)–N(1)
N(1)–Re(1)–Cl(1)
N(1)–Re(1)–Cl(2)
N(1)–Re(1)–Cl(3)
N(2)–Re(1)–Cl(1)
N(2)–Re(1)–Cl(2)
N(2)–Re(1)–Cl(3)
O(2)–Re(1)–Cl(1)
O(2)–Re(1)–Cl(2)
O(2)–Re(1)–Cl(3)
Cl(2)–Re(1)–Cl(1)
Cl(3)–Re(1)–Cl(1)
Cl(3)–Re(1)–Cl(2)
N(2)–Re(1)–O(2)
P(1)–O(2)–Re(1)
87.3(2)
87.8(2)
86.93
87.57
174.95
89.97
90.78
90.07
176.02
90.23
89.45
89.73
176.48
92.84
93.30
92.33
87.57
150.54
175.85(15)
90.55(15)
89.35(17)
88.69(17)
172.67(17)
92.18(17)
90.82(13)
87.78(13)
176.17(13)
93.30(6)
91.86(6)
94.80(6)
85.1(2)
158.8(3)
Table 5
The experimental and optimized bond lengths (Å) and angles (°) for 3.
Bond lengths
Experimental
Optimized
Bond angles
Experimental
Optimized
Re(1)–O(1)
Re(1)–O(2)
Re(1)–N(1)
Re(1)–N(2)
Re(1)–Br(1)
Re(1)–Br(2)
1.681(2)
1.961(2)
2.144(3)
2.151(3)
2.4858(4)
2.4796(4)
1.680
2.022
2.196
2.197
2.536
2.536
O(1)–Re(1)–O(2)
O(1)–Re(1)–N(1)
O(2)–Re(1)–N(1)
O(1)–Re(1)–N(2)
O(2)–Re(1)–N(2)
N(1)–Re(1)–N(2)
O(1)–Re(1)–Br(2)
O(2)–Re(1)–Br(2)
N(1)–Re(1)–Br(2)
N(2)–Re(1)–Br(2)
O(1)–Re(1)–Br(1)
O(2)–Re(1)–Br(1)
N(1)–Re(1)–Br(1)
N(2)–Re(1)–Br(1)
Br(2)–Re(1)–Br(1)
157.10(11)
88.21(11)
74.38(9)
89.88(11)
74.16(9)
85.02(10)
103.30(9)
93.65(6)
168.02(7)
91.62(7)
102.69(8)
92.47(6)
90.71(7)
166.61(7)
89.967(13)
154.81
88.66
72.99
88.72
72.98
85.14
103.37
94.11
167.08
90.35
103.39
94.04
90.35
167.00
91.41
0.4
0.3
0.2
0.1
0.06
0.05
0.04
0.03
0.02
0.01
0.00
0.8
0.6
0.4
0.2
0.0
0.0
0
0
50
100
150
T(K)
200
250
300
1
2
3
4
5
H (Tesla)
Fig. 4. Experimental magnetic plotted as
vM (d) and vMT (s) versus T for complex
Fig. 5. Field dependence of the magnetization for complex 2.
2.
and [ReOBr3(dpk-OH)] (singlet state) are gathered in Tables 4 and
5, respectively. Generally, the predicted bond lengths and angles
are in agreement with the values based upon the X-ray crystal
structure data, and the general trends observed in the experimen-
tal data are well reproduced in the calculations.
and [ReOBr3(dpk-OH)] are presented in Tables 6 and 7, respec-
tively. The selected contours of frontier orbitals of [ReCl3(dpk-
N,N0)(OPPh3)] and [ReOBr3(dpk-OH)] are presented in Figs. 6 and
7, respectively.
Among the highest occupied MOs of [ReCl3(dpk-N,N0)(OPPh3)]
the largest numbers constitute
p orbitals of the phenyl rings with
3.5. Molecular orbitals
a contribution from Cl atoms. The rhenium dxz, dyz and dxy orbitals
make main contributions into the HOMOꢁ2, HOMOꢁ1 and HOMO
The energies and characters of several highest occupied and
lowest unoccupied molecular orbitals of [ReCl3(dpk-N,N0)(OPPh3)]
with a spin and HOMO, LUMO and LUMO+1 with b spin. In all
these molecular orbitals, the rhenium dxz, dyz and dxy orbitals bear

B. Machura et al. / Polyhedron 28 (2009) 2821–2830
2827
Table 6
antibonding character towards the p orbitals of the chloride ions
p
and oxygen donor. The d2z rhenium orbital has a significant contri-
The energy and character of the selected molecular orbitals with
[ReCl3(dpk-N,N0)(OPPh3)].
a and b spins for
bution in the LUMO+7 with
whereas the LUMO+10 with
a
a
spin and the LUMO+11 with b spin,
spin and the LUMO+13 with b have
MOs with
a
spin
MOs with b spin
predominantly dx2
character. Among the lowest unoccupied
ꢁy2
E (eV)
Character
E (eV)
Character
MOs of[ReCl3(dpk-N,N0)(OPPh3)], the largest numbers constitute
orbitals of the dpk ligand. The phenyl ring orbitals of the tri-
HOMOꢁ5
HOMOꢁ4
HOMOꢁ3
HOMOꢁ2
HOMOꢁ1
HOMO
ꢁ7.256
ꢁ7.113
ꢁ7.062
ꢁ6.388
ꢁ6.230
ꢁ5.853
ꢁ2.856
ꢁ1.667
ꢁ1.438
ꢁ1.308
ꢁ1.194
ꢁ0.876
ꢁ0.792
ꢁ0.735
p(Ph)
p(Ph)
p(Ph)
ꢁ7.366
ꢁ7.282
ꢁ7.248
ꢁ7.106
ꢁ7.045
ꢁ5.081
ꢁ2.997
ꢁ2.978
ꢁ2.734
ꢁ1.552
ꢁ1.355
ꢁ1.236
ꢁ1.178
ꢁ0.862
p(Ph)
p(Ph)
p(Ph)
p(Ph)
p(Ph),
p
p
phenylphosphine oxide ligand participate in the higher unoccupied
orbitals.
The HOMO of [ReOBr3(dpk-OH)] is mainly localized on the dxy
rhenium orbital and p chloride orbitals. The LUMO and LUMO+1
are also to a large extent formed by rhenium d
(dxz and dyz orbitals) with some contribution of p oxygen orbitals.
The LUMO+4 is of dx2
utes to the LUMO+7.
dxz(Re),
dyz(Re),
dyz(Re),
p
p
p
(Cl),
(Cl),
(Cl),
p
p
p
(OOPPh
(OOPPh
(dpk)
)
)
3
p
(Cl)
3
dxy
,
p
(dpk), p(Cl)
p
LUMO
p*(dpk), dxy
p*(dpk)
dxz(Re), p*(dpk)
dyz(Re), p*(dpk)
p*(dpk), dyz
p
atomic orbital
LUMO +1
LUMO+2
LUMO+3
LUMO+4
LUMO+5
LUMO+6
LUMO+7
p*(OPPh3), p*(dpk), d2z
p*(dpk), dz2, p*(OPPh3)
p*(OPPh3)
p
p*(dpk), dxz
character, and d2z rhenium orbital contrib-
ꢁy2
p*(dpk), p*(OPPh3)
p*(dpk), p*(OPPh3)
p*(OPPh3)
p*(OPPh3)
p*(dpk), d2z
dz2
p*(OPPh3)
3.6. NBO analysis
The nature of rhenium–terminal oxygen interaction in [Re-
OBr3(dpk-OH)] has been studied by NBO analysis. The occupancy
and composition of the calculated Re–Ot natural bond orbitals
(NBOs) are given in Table 8. Each natural bond orbital (NBO) rAB
can be written in terms of two directed valence hybrids (NHOs)
hA and hB on atoms A and B:
Table 7
The energy and character of the selected molecular orbitals for [ReOBr3(dpk-OH)].
E (eV)
Character
HOMOꢁ5
HOMOꢁ4
HOMOꢁ3
HOMOꢁ2
HOMOꢁ1
HOMO
ꢁ8.123
ꢁ7.932
ꢁ7.648
ꢁ7.550
ꢁ7.291
ꢁ6.264
ꢁ3.066
ꢁ2.860
ꢁ1.903
ꢁ1.532
ꢁ1.378
ꢁ1.349
ꢁ0.673
ꢁ0.270
p
p
p
p
p
(dpk-OH),
(Br), (Ot)
(dpk-OH),
p
(Br),
(Br),
p
(Ot)
(Ot)
p
ð1ÞrAB ¼ cAhA þ cBhB;
where cA and cB are polarization coefficients. Each valence bonding
NBO must in turn be paired with a corresponding valence anti-
bonding NBO:
ð2ÞrꢃAB ¼ cBhA ꢁ cAhB
to complete the span of the valence space. The Lewis-type (donor)
NBOs are thereby complemented by the non-Lewis-type (acceptor)
NBOs that are formally empty in an idealized Lewis picture. The
interactions between ‘filled’ Lewis-type NBOs and ‘empty’ non-Le-
p
p
(Br),
(Br)
p(dpk-OH)
dyz(Re),
p(Br)
LUMO
dyz
dyz
,
,
p
p
(O)
(O)
LUMO+1
LUMO+2
LUMO+3
LUMO+4
LUMO+5
LUMO+6
LUMO+7
p*(dpk-OH), dyz
p*(dpk-OH), dx2
ꢁy2
dx2
ꢁy2
p*(dpk-OH)
p*(dpk-OH)
dz2
Fig. 6. The selected HOMO and LUMO orbitals with
a
and b spin for [ReCl3(dpk-N,N0)(OPPh3)].

2828
B. Machura et al. / Polyhedron 28 (2009) 2821–2830
Fig. 7. The selected HOMO and LUMO orbitals for [ReOBr3(dpk-OH)].
Table 8
The occupancy of the calculated natural bond orbitals (NBOs) between the rhenium and the oxo ligand for [ReOBr3(dpk-OH)].
BD
Occupancy
Composition of NBO
BD*
Occupancy
Re–Ot
Re–Ot
1.994
1.984
0.566(d)Re + 0.825(p)O
0.566(d)Re + 0.824(p)O
0.825(d)Re ꢁ 0.566(p)O
0.824(d)Re ꢁ 0.566(p)O
0.255
0.307
*Denotes antibond NBO.
BD: denotes two-center bond.
wis NBOs lead to loss of occupancy from the localized NBOs of the
idealized Lewis structure into the empty non-Lewis orbitals, and
they are referred to as ‘delocalization’ corrections to the zeroth-or-
der natural Lewis structure [43].
of predominant Coulomb-type interactions between the central
ion and ligands [64]. The terminal oxo ligand of 1 has two lone pair
orbitals, and electron density from one of them is strongly delocal-
ized into non-Lewis rhenium orbital. Accordingly, NBO analysis
confirms a triple bond between the rhenium and the terminal oxy-
gen ligand.
The detected natural Re–Ot bond orbitals of 3 are
p orbitals –
the px and py oxygen orbitals and dxz and dyz rhenium orbitals are
involved in their formation. Not detected rRe—O bond has character
t
1.60
1.20
0.80
0.40
0.00
2.00
1.50
1.00
0.50
0.00
200.00
400.00
600.00
800.00
1000.00
400.00
800.00
Fig. 8. The experimental (black) and calculated (red) electronic absorption spectra
of the solution of 2 in acetronitrile. (For interpretation of the references to color in
this figure legend, the reader is referred to the web version of this article.)
Fig. 9. The experimental (black) and calculated (red) electronic absorption spectra
of the solution of 3 in acetronitrile. (For interpretation of the references to color in
this figure legend, the reader is referred to the web version of this article.)

B. Machura et al. / Polyhedron 28 (2009) 2821–2830
2829
3.7. Electronic spectra
N,N0)(OPPh3)] and [ReOBr3(dpk-OH)] in terms of the energy of
the experimental bands and calculated transitions.
The experimental and calculated electronic spectra of
[ReCl3(dpk-N,N0)(OPPh3)] and [ReOBr3(dpk-OH)] are presented in
3.8. [ReCl3(dpk-N,N0)(OPPh3)]
Figs. 8 and 9, respectively. Each calculated transition is represented
2
by a gaussian function y ¼ ceꢁbx with the height (c) equal to the
The low-energy absorption band at 761.0 nm originates from
the transition between HOMO and LUMO+2 with b spins. As can
be seen from the Fig. 6, the b HOMO is delocalized on central
oscillator strength and b equal to 0.04 nmꢁ2
.
Tables 9 and 10 present the most important electronic transi-
tions calculated with the TDDFT method assigned to the observed
absorption bands of [ReCl3(dpk-N,N0)(OPPh3)] and [ReOBr3(dpk-
OH)]. For the high energy part of the spectrum, only transitions
with oscillator strengths larger than 0.020 are listed in Tables 9
and 10. The assignment of the calculated orbital excitations to
the experimental bands was based on an overview of the contour
plots and relative energy to the orbitals HOMO and LUMO involved
in the electronic transitions. As seen in Figs. 8 and 9, TDDFT/PCM
calculations well reproduce the absorption spectra of [ReCl3(dpk-
ion, chloride ions and dpk ligand, whereas the b LUMO+2 are
*
formed of dRe orbitals and
p
-bonding orbitals of dpk ligand.
Accordingly, the transition can be seen as a delocalized MLLCT (Me-
tal–Ligand-to-Ligand CT) transition. The same character can be as-
signed to the experimental absorptions at 487.1, 372.7 and
266.9 nm.
The investigated complex is of large size; the numbers of basis
functions are equal to 646. The calculated electron transitions
(100) do not comprise all the experimental absorption bands; the
Table 9
The energy and molar absorption coefficients of experimental absorption bands and the electronic transitions calculated with the TDDFT method for [ReCl3(dpk-N,N0)(OPPh3)].
The most important orbital excitations
Character
k (nm)
E (eV)
f
Experimental
K
[nm] (E [eV])
e
H(b) ? L+2(b)
d/p
(Cl)/
p
(dpk) ? p*(dpk)/d
969.6
1.28
0.0184
897.2 (1.38) 200
761.0 (1.63) 1050
487.1 (2.55) 1750
H(
H(b) ? L+3(b)
H( ) ? L+1(
Hꢁ8(b) ? L+1(b)
a
) ? L(
a
)
d/
d/
d/
p
p
p
(Cl)/
(Cl)/
(Cl)/
p
(Cl)/
(Cl)/
p
p
p
(dpk) ? p*(dpk)/d
(dpk) ? p*(dpk)/d
(dpk) ? p*(dpk)
526.7
476.6
374.4
333.7
331.6
300.9
2.35
2.60
3.31
3.72
3.74
4.12
0.0753
0.0394
0.0525
0.0339
0.0241
0.0511
a
a)
372.7 (3.33) 1580
266.9 (4.65) 42 700
p(Cl)/
(dpk) ? d/p*(dpk)
Hꢁ1(
a
a
) ? L+1(
) ? L+3(
a
a
)
)
d/
d/
p
p
p
p
(OOPPh ) ? p*(dpk)
3
Hꢁ1(
(OOPPh ) ? p*(dpk)/p*(OPPh3)/d
Hꢁ12(b) ? L+1(b)
p
p
p
p
(dpk)/
(Cl)/
(Cl)/
p
(Cl)/p(3OOPPh ) ? d/p*(dpk)
3
Hꢁ12(
Hꢁ10(b) ? L+2(b)
Hꢁ14( ) ? L(
H(b) ? L+15(b)
Hꢁ13(b) ? L+2(b)
a
) ? L(
a
)
p
p
(dpk) ? p*(dpk)/d
(dpk)/
286.0
4.34
0.0229
p
p
(OOPPh ) ? p*(dpk)/d
3
a
a
)
(dpk)/
p
(Cl)/
(OOPPh ) ? p*(dpk)/d
277.8
269.4
4.46
4.60
0.0301
0.0205
3
d/p
(dpk)/
p
(Cl) ? p*(dpk)
p(dpk)/
p
(Cl) ? p*(dpk)/d
202.0 (6.14) 131 600
e
– molar absorption coefficient [dm3 molꢁ1 cmꢁ1]; f – oscillator strength; H – highest occupied molecular orbital; and L – lowest unoccupied molecular orbital.
Table 10
The energy and molar absorption coefficients of experimental absorption bands and the electronic transitions calculated with the TDDFT method for [ReOBr3(dpk-OH)].
The most important orbital excitations
Character
k (nm)
721.7
640.0
339.2
E (eV)
1.72
f
Experimental
K
[nm] (E [eV])
e
H ? L
d/
d/
d/
p
p
p
(Br) ? d
0.0014
0.0003
0.0781
794.1 (1.56) 50
623.6 (1.99) 230
H ? L+1
(Br) ? d
(Br) ? pꢃ(dpk-OH)/d
1.94
H ? L+2
3.66
367.4 (3.37) 7300
278.1 (4.46) 82 000
204.0 (6.08) 105 300
Hꢁ2 ? L
Hꢁ2 ? L+1
Hꢁ4 ? L
p
p
p
(Br)/
(Br)/
(Br)/
p(dpk-OH) ? d
p(dpk-OH) ? d
p(Ot) ? d
330.3
318.5
3.75
3.89
0.0127
0.0248
H ? L+3
d/
(Br)/
d/
(Br) ? pꢃ(dpk-OH)
p
(Br) ? pꢃ(dpk-OH)/d
(Ot) ? d
308.3
296.6
293.8
243.0
4.02
4.18
4.22
5.10
0.0430
0.0147
0.0531
0.0707
Hꢁ4 ? L
p
p
H ? L+5
p
Hꢁ3 ? L+2
p
(Br)/
p(dpk-OH)/
p
(Ot) ? pꢃ(dpk-OH)/d
Hꢁ4 ? L+2
Hꢁ3 ? L+5
Hꢁ7 ? L+2
Hꢁ5 ? L+3
Hꢁ1 ? L+7
Hꢁ8 ? L+2
Hꢁ10 ? L+3
Hꢁ2 ? L+6
Hꢁ7 ? L+5
Hꢁ10 ? L+2
Hꢁ16 ? L+1
Hꢁ9 ? L+4
Hꢁ10 ? L+3
Hꢁ3 ? L+7
Hꢁ11 ? L+2
Hꢁ4 ? +6
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
p
(Br)/
(Br)/
(Br)/
p
p
p
(Ot) ? pꢃ(dpk-OH)/d
(dpk-OH)/
(dpk-OH)/
229.5
216.4
214.0
209.8
202.4
198.1
197.6
5.40
5.73
5.79
5.91
6.13
6.26
6.27
0.0229
0.0283
0.0507
0.0376
0.1187
0.1226
0.0552
p
p
p
(O) ? pꢃ(dpk-OH)
(O) ? pꢃ(dpk-OH)/d
(dpk-OH)/
p
(O)/
(Br) ? pꢃ(dpk-OH)/d
(Br) ? d
(dpk-OH) ? pꢃ(dpk-OH)/d
(Br)/
(Br)/
(Br)/
(Br)/
(Ot)/
(Br)/
(Br)/
(Br)/
(Br)/
(Br)/
(Br)/
p
p
p
p
p
p
p
p
p
p
p
(dpk-OH)/p
(Ot) ? pꢃ(dpk-OH)/d
(dpk-OH) ? pꢃ(dpk-OH)
(dpk-OH)/
(dpk-OH)/
(dpk-OH) ? d
(dph-OH)/
p
p
(Ot) ? pꢃ(dpk-OH)
195.1
192.6
189.5
189.2
187.7
186.3
185.5
185.4
184.7
184.4
6.35
6.44
6.54
6.55
6.60
6.66
6.68
6.69
6.71
6.72
0.0625
0.0258
0.0625
0.3537
0.0656
0.0440
0.0322
0.0234
0.0281
0.0559
(O) ? pꢃ(dpk-OH)/d
p
p
p
(Ot) ? d
(dpk-OH)/
(dpk-OH)/
(Ot) ? pꢃ(dpk-OH)/d
(Ot) ? d
(dpk-OH) ? pꢃ(dpk-OH)/d
(Ot) ? pꢃ(dpk-OH)
Hꢁ13 ? L+2
(dpk-OH) ? pꢃ(dpk-OH)/d
Hꢁ8 ? L+5
(dpk-OH) ? pꢃ(dpk-OH)
e
– molar absorption coefficient [dm3 molꢁ1 cmꢁ1]; f – oscillator strength; H – highest occupied molecular orbital; and L – lowest unoccupied molecular orbital.

2830
B. Machura et al. / Polyhedron 28 (2009) 2821–2830
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wavelength experimental band of 2 is not assigned to the calcu-
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expected to be found at higher energies in the calculations for 2.
3.9. [ReOBr3(dpk-OH)]
The two longest wavelength experimental bands of 3 originate
in the HOMOꢁLUMO and HOMOꢁLUMO+1 transitions, respec-
tively. As can be seen from the Fig. 7, the LUMO and LUMO+1 orbi-
tals are mainly formed from rhenium d atomic orbitals, the HOMO
orbital is delocalized among rhenium ion and bromide orbitals.
Accordingly, the transitions assigned to the experimental bands at
794.1 and 623.6 nm can be seen as mixed bromide ? Re (Ligand-
Metal Charge Transfer; LMCT) and d ? d (Ligand Field; LF) transitions.
The experimental absorption band at 367.4 nm can be assigned
to Ligand-Metal Charge Transfer transitions occurring from the bro-
mide, oxo, and dpk-OH ligands to d rhenium orbitals.
The absorption bands at 278.1 and 204.0 nm result mainly from
Ligand-Ligand Charge Transfer and interligand (IL) transitions, but
participation of Ligand-Metal Charge Transfer into this band is also
confirmed by the calculations.
Supplementary data
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CCDC 731661, 731662 and 731663 contain the supplementary
crystallographic data for C29H23Cl3N2OPRe, C29H23Cl3N2O2PRe and
C33H27Br4N6O5Re. These data can be obtained free of charge via
http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Center, 12 Union Road, Cam-
bridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
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Acknowledgements
The GAUSSIAN-03 calculations were carried out in the Wrocław
Center for Networking and Supercomputing, WCSS, Wrocław, Po-
land, http://www.wcss.wroc.pl, under calculational Grant No. 51/
96.
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