A novel rhenium(III) complex with bis(pyrazol-1-yl)methane: X-ray structure and DFT calculations for [ReCl3(bpzm)(PPh3)]

Article abstract of DOI:10.1016/j.poly.2007.06.040

The [ReCl₃(MeCN)(PPh₃)₂] complex reacts with bis(pyrazol-1-yl)methane (bpzm) to give [ReCl₃(bpzm)(PPh₃)]. This compound has been studied by IR, UV-Vis spectroscopy, magnetic measurement and X-ray crystallography. The molecular orbital diagram of [ReCl₃(bpzm)(PPh₃)] has been calculated with the density functional theory (DFT) method. The spin-allowed triplet-triplet electronic transitions of [ReCl₃(bpzm)(PPh₃)] have been calculated with the time-dependent DFT method, and the UV-Vis spectrum of the title compound has been discussed on this basis. The magnetic behavior is characteristic of a mononuclear d⁴ low-spin octahedral Re(III) complex (³T_1g ground state) and arises because of the large spin-orbit coupling (ζ = 2500 cm^-1), which gives a diamagnetic ground state.

Full text of DOI:10.1016/j.poly.2007.06.040

Polyhedron 26 (2007) 4833–4840
www.elsevier.com/locate/poly
A novel rhenium(III) complex with bis(pyrazol-1-yl)methane:
X-ray structure and DFT calculations for [ReCl3(bpzm)(PPh3)]
a,
a
b
c
c
d
*
´
B. Machura , R. Penczek , R. Kruszynski , J. Kłak , J. Mrozinski , J. Kusz
a
Department of Crystallography, Institute of Chemistry, University of Silesia, 9th Szkolna Street, 40-006 Katowice, Poland
b
Department of X-ray Crystallography and Crystal Chemistry, Institute of General and Ecological Chemistry,
_
Lodz University of Technology, 116 Zeromski Street, 90-924 Ło´dz´, Poland
c
Faculty of Chemistry, Wroclaw University, F. Joliot-Curie 14 Street, 50-383 Wrocław, Poland
Institute of Physics, University of Silesia, 4th Uniwersytecka Street, 40-006 Katowice, Poland
d
Received 21 March 2007; accepted 1 June 2007
Available online 10 September 2007
Abstract
The [ReCl3(MeCN)(PPh3)2] complex reacts with bis(pyrazol-1-yl)methane (bpzm) to give [ReCl3(bpzm)(PPh3)]. This compound has
been studied by IR, UV–Vis spectroscopy, magnetic measurement and X-ray crystallography. The molecular orbital diagram of
[ReCl3(bpzm)(PPh3)] has been calculated with the density functional theory (DFT) method. The spin-allowed triplet–triplet electronic
transitions of [ReCl3(bpzm)(PPh3)] have been calculated with the time-dependent DFT method, and the UV–Vis spectrum of the title
compound has been discussed on this basis. The magnetic behavior is characteristic of a mononuclear d4 low-spin octahedral Re(III)
complex (3T1g ground state) and arises because of the large spin–orbit coupling (f = 2500 cmꢀ1), which gives a diamagnetic ground state.
ꢀ 2007 Elsevier Ltd. All rights reserved.
Keywords: Rhenium(III) complexes; Bis(pyrazol-1-yl)methane ligand; X-ray structure; DFT calculations; Magnetic measurement
1. Introduction
These molecules form a variety of coordination
compounds with main group and transition metals [1–9].
However, the rhenium complexes with bis(pyrazol-1-yl)alk-
ane ligands have been studied relatively little [10,11]. It
prompted us to explore the reactivity of [ReCl3(MeCN)-
(PPh3)2] towards bis(pyrazol-1-yl)methane (bpzm). The
[ReCl3(MeCN)(PPh3)2] complex has proven to be a useful
precursor in the synthesis of Re(III) compounds. It easily
reacts with mono- and bidentate ligands to give [ReCl3L3],
[ReCl3L2(PPh3)] and [ReCl3(L–L)(PPh3)] compounds
[12–14].
Bis(pyrazol-1-yl)alkanes (R2C)n(pzx)2 constitute a fam-
ily of stable and flexible bidentate ligands, isoelectronic
and isosteric with the well-known bis(pyrazolyl)borates.
The coordination properties of bis(pyrazol-1-yl)alkanes
may be varied in a rather wide range by introducing sub-
stituents into the pyrazole rings. Hence, the donor ability
of the ligands is determined by the presence of electron-
withdrawing or electron-donating functional groups, and
steric factors altered by the introduction of bulky alkyl
groups into the rings and the alkane bridge between them
[1].
Here, we present the synthesis, spectroscopic data, crys-
tal, molecular and electronic structure of the [ReCl3(bpzm)-
(PPh3)] complex. The electronic structure has been
determined with the density functional theory (DFT)
method,
and
the
electronic
spectrum
of
*
Corresponding author.
E-mail addresses: basia@ich.us.edu.pl (B. Machura), rafal.kruszynski@
[ReCl3(bpzm)(PPh3)] has been calculated with the time-
dependent DFT method. Currently density functional the-
ory (DFT) is commonly used to examine the electronic
p.lodz.pl (R. Kruszynski), jmroz@wchuwr.chem.uni.wroc.pl (J. Mro-
´
zinski).
0277-5387/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2007.06.040

4834
B. Machura et al. / Polyhedron 26 (2007) 4833–4840
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 transition
metal complexes [15]. Recent studies have also supported
the TD-DFT method to be applicable for open- and
closed-shell 5d-metal complexes, giving good assignment
of experimental spectra [16–18].
Anal. Calc. for C26H25Cl5N4PRe: C, 39.63; H, 3.20; N,
7.11. Found: C, 39.75; H, 3.30; N, 7.29%.
2.4. X-ray diffraction studies
A brown crystal of [ReCl3(bpzm)(PPh3)] Æ CH2Cl2 was
mounted on a KM-4-CCD automatic diffractometer
equipped with a CCD detector, and used for data collec-
tion. X-ray intensity data were collected with graphite
2. Experimental
˚
monochromated MoKa radiation (k = 0.71073 A) at
2.1. General procedure
295(1) K. Details concerning crystal data and refinement
are given in Table 1. Lorentz, polarization and numerical
absorption corrections [20] were applied. The structure
was solved by the Patterson method and subsequently com-
pleted by difference Fourier recycling. All the non-hydro-
gen atoms were refined anisotropically using the full-
matrix, least-squares technique. The hydrogen atoms were
treated as ‘‘riding’’ on their parent carbon atoms and
assigned isotropic temperature factors equal to 1.2 times
the value of the equivalent temperature factor of the parent
atom. SHELXS97 [21], SHELXL97 [22] and SHELXTL [23] pro-
grams were used for all the calculations. Atomic scattering
factors were those incorporated in the computer programs.
All the reagents used for the syntheses were commer-
cially available and were used without further purification.
The [ReCl3(MeCN)(PPh3)2] complex was prepared as
reported previously [12], and bis(pyrazol-1-yl)methane
was synthesised according to the modified literature
method [19].
The IR spectrum were recorded on a Nicolet Magna 560
spectrophotometer in the spectral range 4000–400 cmꢀ1
with the sample in the form of KBr pellets. The electronic
spectrum was measured on a spectrophotometer Lab Alli-
ance UV–Vis 8500 in the range 1000–200 nm in dichloro-
methane solution. Elemental analyses (C H N) were
performed on a Perkin–Elmer CHN-2400 analyzer.
2.5. Computational details
2.2. Preparation of bis(pyrazol-1-yl)methane (bpzm)
The GAUSSIAN03 program [24] was used in the calcula-
tions. The geometry optimisation of the [ReCl3(bpzm)-
(PPh3)] complex was carried out with the DFT method
Pyrazole (9.6 g, 0.1 mol), Bu4N+HSO4 (1.7 g, 0.005
ꢀ
mol), potassium carbonate (13.8 g, 0.1 mol), powdered
KOH (5,6 g, 0.1 mol), and an excess of dry methylene chlo-
ride (300 cm3) were intensively stirred and refluxed in a
water bath for 6 h. After this time, aꢀsecond portion of
KOH (5.6 g, 0.1 mol) and Bu4N+HSO4 (1.7 g, 0.005 mol)
was added and the mixture was intensively stirred and
refluxed for an additional 6 h. The liquid layer was removed
and the residue was washed three times with 100 cm3 of
methylene chloride. The combined organic layers were
dried with anhydrous magnesium sulfate and methylene
chloride was removed on a rotary evaporator. The pale yel-
low residue was purified by vacuum sublimation as previ-
ously described [19] (isolated yield 87%, 8.9 g).
Table 1
Crystal data and structure refinement for [ReCl3(bpzm)(PPh3)] Æ CH2Cl2
Empirical formula
C26H25Cl5N4PRe
Formula weight
Temperature (K)
Wavelength (A)
Crystal system
Space group
787.92
295(1)
0.71073
monoclinic
P21/n
˚
Unit cell dimensions
˚
a (A)
10.2233(3)
19.7599(6)
15.1285(2)
101.411(2)
2995.72(13)
4
1.747
4.579
1536
˚
b (A)
˚
c (A)
b (ꢁ)
Volume (A )
3
˚
Z
Dcalc (Mg/m3)
2.3. Preparation of [ReCl3(bpzm)(PPh3)] Æ CH2 Cl2
Absorption coefficient (mmꢀ1
F(000)
)
[Re(MeCN)Cl3(PPh3)2] (0.50 g, 0.58 mmol) and bpzm
(0.1 g, 0.67 mmol) in dichloromethane (40 cm3) were
refluxed for 4 h. The starting material gradually dissolved
and the colour of the reaction solution became dark brown.
The volume was condensed to 10 cm3, diethyl ether
(50 cm3) was added and a brown microcrystalline solid
was filtered. The product was washed with EtOH and cold
ether, and dried in vacuo (yield 90%). The crystals suitable
for X-ray investigation were obtained by recrystallization
from a mixture of dichloromethane/methanol.
Crystal size (mm)
h range for data collection (ꢁ)
0.06 · 0.12 · 0.24
2.86–25.00
Index ranges
ꢀ9 6 h 6 12
ꢀ23 6 k 6 23
ꢀ17 6 l 6 17
18,634/5267 [Rint = 0.0294]
96.6%
0.749 and 0.518
5267/0/334
1.037
R1 = 0.0214 wR2 = 0.0518
R1 = 0.0300 wR2 = 0.0518
0.863 and ꢀ0.832
Reflections collected/independent
Completeness to 2h = 50.2ꢁ
Maximum and minimum transmission
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R indices (all data)
Largest difference peak and hole (e A
IR (KBr; m/cmꢀ1): 1587(w), 1574(w), 1518(m) and 1510
ꢀ3
˚
)
(w) mCN and mC@C
;

B. Machura et al. / Polyhedron 26 (2007) 4833–4840
4835
with the use of the B3LYP functional [25,26]. The elec-
tronic spectrum of the [ReCl3(bpzm)(PPh3)] complex was
calculated with the TDDFT method [27]. The calculations
were performed by using an ECP basis set on the rhenium
contribution vD estimated from the Pascal constants [29]
and equal
–
363 · 10ꢀ6 cm3 molꢀ1 for complex
[ReCl3(bpzm)(PPh3)]. The effective magnetic moment was
calculated from the equation, leff = 2.83(vMT)1/2 (B.M.).
atom, the standard 6-31+g basis for chlorine, phospho-
**
rus and nitrogen, 6-31g basis for carbon and 6-31G basis
3. Results and discussion
*
for hydrogen atoms. The Xe core electrons of Re were
replaced by an effective core potential and a DZ quality
Hay and Wadt Los Alamos ECP basis set (LANL2DZ)
[28] was used for the valence electrons. An additional d
function with exponent a = 0.3811 and f function with
exponent a = 2.033 on the rhenium atom were added.
The [ReCl3(bzpm)(PPh3)] complex was prepared in
good yield by a ligand exchange reaction starting from
[ReCl3(MeCN)(PPh3)2] and bis(pyrazol-1-yl)methane
(bpzm):
½ReCl3ðMeCNÞðPPh3Þ2ꢁ þ bpzm
! ½ReCl3ðbzpmÞðPPh3Þꢁ þ MeCN þ PPh3
2.6. Magnetic measurement
It was isolated as a brown microcrystalline solid, soluble in
common organic solvents. The elemental analysis of the
complex is in good agreement with its formulation. The
characteristic bands corresponding to the m(CN) and
m(C@C) modes of the bpzm ligand appear at 1600–
1500 cmꢀ1 in the IR spectrum of [ReCl3(bzpm)(PPh3)] [30].
Magnetic measurements in the temperature range 1.8–
300 K were performed using a Quantum Design SQUID-
based MPMSXL-5-type magnetometer. The SQUID mag-
netometer was calibrated with the palladium rod sample
(Materials Research Corporation, measured purity
99.9985%). The superconducting magnet was generally
operated at a field strength ranging from 0 to 5 T. Mea-
surements were made at a magnetic field of 0.5 T. Correc-
tions are based on subtracting the sample-holder signal and
3.1. Crystal structure
[ReCl3(bzpm)(PPh3)] crystallises as the dichloromethane
solvate, and the dichloromethane molecule is not bonded
to any atom of the Re(III) complex. No intermolecular
interactions with enough strength to govern crystal packing
or molecule conformation were found in the structure of
[ReCl3(bzpm)(PPh3)], only some weak intramolecular
hydrogen bonds [31,32] were detected in the [ReCl3(bzpm)-
(PPh3)] molecule and they are gathered in Table 2.
Table 2
Hydrogen bonds for [ReCl3(bpzm)(PPh3)]
˚
˚
D
A
H ꢂ ꢂ ꢂ A (A)
D ꢂ ꢂ ꢂ A (A)
D—H ꢂ ꢂ ꢂ A (ꢁ)
C(12)
C(18)
C(18)
C(22)
Cl(3)
Cl(3)
N(3)
Cl(3)
2.60
2.79
2.59
2.49
3.433(4)
3.497(4)
3.248(5)
3.249(4)
148.8
133.9
128.5
134.7
Fig. 1. The molecular structure of [ReCl3(bpzm)(PPh3)] (50% probability ellipsoids). The hydrogen atoms of the phenyl and pyrazole rings are omitted for
clarity.

4836
B. Machura et al. / Polyhedron 26 (2007) 4833–4840
The molecular structure of [ReCl3(bpzm)(PPh3)] is given
The chloride ions of [ReCl3(bpzm)(PPh3)] are arranged
in a meridional fashion, and the nitrogen atom of the bpzm
ligand occupies the trans position to the Cl(1) ion. The mer
geometry of the ReX3 fragment has been confirmed for the
[ReCl3(pzH)2(PPh3)] and [ReCl3(3,5-Me2pzH)2(PPh3)]
complexes [14], but in the [ReX3(L–L)(PPh3)] compounds
with bipy-like ligands the mer geometry is definitely rarer
than the fac arrangement [33]. It seems that electronic fac-
tors favour the meridional configuration in [ReCl3(bpzm)-
(PPh3)]. The facial disposition of halide ions in the
[ReCl3(L–L)(PPh3)] complexes is preferred by the strong
p acceptor L–L ligand, as it maximizes the back-bonding
effect. It is significant that the Re–N distances in
in Fig. 1. The pseudooctahedral environment of the Re
center in [ReCl3(bpzm)(PPh3)] shows clear distortions,
induced by the bite angle of the chelating bpzm ligand.
Upon coordination of bis(pyrazol-1-yl)methane to the rhe-
nium centre, a six-membered cycle (made by the four nitro-
gen atoms, the rhenium atom and the carbon atom) is
formed, and the formed ring shows a boat distorted toward
sofa conformation with the rhenium and the carbon atoms
off the plane defined by the four nitrogen atoms (with devi-
ations from the least squares plane of 0.624(5) and
˚
0.640(5) A, respectively). The planar, in the range of exper-
imental error, pyrazole rings are inclined at 57.1(2)ꢁ.
Table 3
The experimental and optimized bond lengths (A) and angles (ꢁ) for [ReCl3(bpzm)(PPh3)]
˚
Bond lengths
Experimental
Optimized
Bond angles
Experimental
Optimized
Re(1)–N(1)
Re(1)–N(3)
Re(1)–Cl(1)
Re(1)–Cl(2)
Re(1)–Cl(3)
Re(1)–P(1)
2.146(3)
2.122(3)
2.3983(9)
2.3552(9)
2.3718(9)
2.4199(9)
2.165
2.158
2.450
2.405
2.446
2.492
N(3)–Re(1)–N(1)
N(3)–Re(1)–Cl(2)
N(1)–Re(1)–Cl(2)
N(3)–Re(1)–Cl(3)
N(1)–Re(1)–Cl(3)
Cl(2)–Re(1)–Cl(3)
N(3)–Re(1)–Cl(1)
N(1)–Re(1)–Cl(1)
Cl(2)–Re(1)–Cl(1)
Cl(3)–Re(1)–Cl(1)
N(3)–Re(1)–P(1)
N(1)–Re(1)–P(1)
Cl(2)–Re(1)–P(1)
Cl(3)–Re(1)–P(1)
Cl(1)–Re(1)–P(1)
84.97(11)
86.43(8)
87.90(9)
92.89(8)
88.87(9)
176.75(3)
170.69(8)
86.98(8)
88.62(3)
91.61(3)
95.88(8)
177.66(9)
94.32(3)
88.91(3)
92.34(3)
85.76
84.34
86.96
90.53
89.04
173.71
171.84
87.30
91.00
93.65
97.89
176.08
94.79
89.51
89.16
Table 4
The energy and character of the selected molecular orbitals with a and b spins for [ReCl3(bpzm)(PPh3)]
MOs with a spin
E (eV)
MOs with b spin
Character
E (eV)
Character
HOMO ꢀ 10
HOMO ꢀ 9
HOMO ꢀ 8
HOMO ꢀ 7
HOMO ꢀ 6
HOMO ꢀ 5
HOMO ꢀ 4
HOMO ꢀ 3
HOMO ꢀ 2
HOMO ꢀ 1
HOMO
ꢀ7.188
ꢀ6.988
ꢀ6.899
ꢀ6.745
ꢀ6.654
ꢀ6.568
ꢀ6.431
ꢀ6.307
ꢀ5.559
ꢀ5.304
ꢀ5.198
ꢀ1.064
ꢀ0.790
ꢀ0.700
ꢀ0.541
ꢀ0.378
ꢀ0.269
ꢀ0.080
0.038
p(Cl), p(PPh3), n(P), n(N)
p(PPh3), p(Cl)
p(PPh3), p(Cl)
p(PPh3), p(Cl)
p(PPh3), p(Cl)
ꢀ7.262
ꢀ7.178
ꢀ7.074
ꢀ6.939
ꢀ6.868
ꢀ6.686
ꢀ6.607
ꢀ6.450
ꢀ6.381
ꢀ6.227
ꢀ4.770
ꢀ2.550
ꢀ2.162
ꢀ0.888
ꢀ0.750
ꢀ0.548
ꢀ0.431
ꢀ0.320
ꢀ0.106
0.036
p(Cl), p(PPh3), p(bpzm)
p(Cl), p(PPh3)
p(Cl), p(PPh3)
p(PPh3), p(Cl)
p(PPh3), p(Cl)
p(PPh3), p(Cl), n(P)
p(PPh3), p(Cl)
p(Cl), p(PPh3)
p(PPh3), p(Cl), n(P)
p(Cl), p(PPh3)
dxz(Re), p(Cl)
dyz(Re), p(Cl), p*(bpzm)
dxy(Re), p(Cl), p*(bpzm)
p*(bpzm)
p(Cl), p(PPh3)
p(PPh3), n(P) p(Cl)
p(PPh3), n(P) p(Cl)
dyz(Re), p(Cl)
dxz(Re), p(Cl)
dxy(Re), p(Cl)
p*(bpzm)
p*(bpzm), p*(PPh3)
p*(bpzm), p*(PPh3), dz2(Re)
p*(PPh3), dz2(Re)
p*(PPh3), dx2ꢀy2(Re)
LUMO
LUMO + 1
LUMO + 2
LUMO + 3
LUMO + 4
LUMO + 5
LUMO + 6
LUMO + 7
LUMO + 8
LUMO + 9
LUMO + 10
p*(PPh3), p*(bpzm)
p*(bpzm)
d
x2ꢀy2(Re), p (PPh3)
p*(PPh3), dz2(Re)
p*(PPh3)
*
p*(PPh3)
p*(PPh3)
p*(bpzm)
p*(PPh3)
p*(PPh3)
0.062
0.346
0.516
p*(PPh3)
0.064
0.147
p*(bpzm)
p (bpzm)
*
d
x2ꢀy2(Re), p*(PPh3)

B. Machura et al. / Polyhedron 26 (2007) 4833–4840
4837
Fig. 2. The selected HOMO and LUMO orbitals with a spin for [ReCl3(bpzm)(PPh3)]. Positive values of the orbital contour are represented in blue
(0.04 au) and negative values – in yellow (ꢀ0.04 au). (For interpretation of the references to colour in this figure, the reader is referred to the web version of
this article.)
˚
[ReCl3(bpzm)(PPh3)] (2.146(3) and 2.122(3) A) are longer
3.00
than those in [ReX3(bipy)(PPh3)] (2.099(8) and 2.094(8)
˚
A), with the facial disposition of the halide ions [34]. On
the other hand, these values are shorter than comparable
distances for saturated amine complexes where metal-to-
ligand p-back bonding is not possible, for instance, the
2.00
Re–NH2 distance in the compound [Re(N2)(ampy)-
˚
(tbpy)(PPh3)]PF6 is 2.197(7) A [35]. Some differences are
observed between the Re(1)–N(1) and Re(1)–N(3) bond
lengths as the Re(1)–N(3) distance is affected by the trans
influence of the triphenylphosphine ligand. The presence
of Re–PPh3 back-bonding diminishes the demand on
1.00
p (bpzm) orbitals. The most important experimental bond
*
lengths and angles of [ReCl3(bzpm)(PPh3)] are reported in
Table 3.
0.00
200.00
3.2. Geometry optimisation
400.00
600.00
800.00
The geometry of [ReCl3(bpzm)(PPh3)] was optimized in
the triplet and singlet states using the DFT method with
Fig. 3. The experimental (—-) and calculated (---) electronic absorption
spectra of [ReCl3(bpzm)(PPh3)].

4838
B. Machura et al. / Polyhedron 26 (2007) 4833–4840
the B3LYP functional. The energy of the singlet state is
12.7 kcal higher. The optimized geometric parameters of
the triplet state are gathered in Table 3. In general, the pre-
dicted 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 experimental data are
well reproduced in the calculations.
MOs of [ReCl3(bpzm)(PPh3)], the largest numbers consti-
tute p orbitals of the phenyl rings of PPh3 and pCl orbitals.
The H-2, H-1 and HOMO orbitals with a-spin and HOMO
orbital with b-spin have pReꢀCl character. The lowest unoc-
cupied molecular orbital with a-spin is localised on the
p-antibonding orbitals of the bpzm ligand. The LUMO
and L+1 orbitals with b-spin can be represented as a com-
bination of pReꢀCl, and pbpzm, with predominant involve-
ment of the former component.
3.3. Molecular orbitals
The energies and characters of several highest occupied
and lowest unoccupied molecular orbitals of [ReCl3-
(bpzm)(PPh3)] are presented in Table 4. The selected
HOMO and LUMO orbitals of [ReCl3(bpzm)(PPh3)] with
a spin are depicted in Fig. 2. Among the highest occupied
3.4. Electronic spectrum
The experimental and calculated electronic spectra of
[ReCl3(bpzm)(PPh3)] are presented in Fig. 3. Each calcu-
lated transition is represented by a gaussian function
Table 5
The spin-allowed triplet–triplet electronic transitions calculated with the TDDFT method and the assignments of the calculated transitions to the
experimental absorption bands for [ReCl3(bpzm)(PPh3)]
The most important
orbital excitations
Character
k (nm)
E (eV)
f
Experimental K
(nm) (E (eV)) e
H-1(b) ! L(b)
H(b) ! L + 2(b)
H(a) ! L(a)
p(Cl)/p(PPh3) ! d
d ! p*(bzpm)
451.2
444.3
421.4
2.75
2.79
2.94
0.0004
0.0015
0.0011
435.0 (2.85) 320
d ! p*(bzpm)
H(a) ! L(a)
d ! d/p*(PPh3)
d ! p*(bzpm)
H(b) ! L + 2(b)
H-2(b) ! L(b)
H-3(b) ! L(b)
415.6
413.2
406.4
2.98
3.00
3.05
0.0034
0.0064
0.0009
p(PPh3)/n(P)/p(Cl) ! d
p(Cl)/p(PPh3) ! d
H(b) ! L + 2(b)
H(b) ! L + 4(b)
H-1(b) ! L + 1(b)
H(b) ! L + 3(b)
H(a) ! L(a)
d ! p*(bzpm)
397.2
3.12
0.0068
p(Cl)/p(PPh3) ! d
d ! p*(PPh3)/p*(bpzm)
d ! p*(bpzm)
387.1
377.0
3.20
3.29
0.0102
0.0066
H(b) ! L + 3(b)
H(a) ! L(a)
d ! p*(PPh3)/p*(bpzm)
d ! p*(bpzm)
376.3
373.0
366.5
3.29
3.32
3.38
0.0045
0.0196
0.0066
H-5(b) ! L(b)
H-1(a) ! L(a)
H-1(a) ! L(a)
H(b) ! L + 3(b)
H(b) ! L + 10(b)
H(b) ! L + 6(b)
p(PPh3)/n(P)/p(Cl) ! d
d ! p*(bpzm)
356.8 (3.47) 2700
d ! p*(bpzm)
d ! p*(PPh3)/p*(bpzm)
d ! d
345.0
332.1
3.59
3.73
0.0025
0.0062
d ! p*(PPh3)
H(b) ! L + 5(b)
H-8(b) ! L + 1(b)
H-9(b) ! L + 1(b)
H-10(b) ! L(b)
p(Cl)/p(PPh3) ! d
315.7
3.93
0.0188
p(Cl)/p(PPh3)/p(bpzm) ! d
d ! p*(PPh3)/p*(bpzm)
p(Cl)/p(bpzm) ! d
d ! p*(PPh3)/p*(bpzm)
p(Cl)/p(PPh3) ! d
314.4
312.1
304.8
301.9
295.3
292.8
284.4
3.94
3.97
4.07
4.11
4.20
4.23
4.36
0.0150
0.0065
0.0122
0.0123
0.0127
0.0057
0.0120
H-1(a) ! L + 2(a)
H-11(b) ! L(b)
269.4 (4.60) 13400
H-2(a) ! L + 1(a)
H-9(b) ! L + 1(b)
H-13(b) ! L(b)
p(Cl)/p(bpzm) ! d
p(Cl)/p(bpzm) ! d
p(Cl)/p(PPh3)/p(bpzm) ! d
p(Cl) ! d
H-11(b) ! L + 1(b)
H-10(b) ! L + 1(b)
H-15(b) ! L(b)
282.7
255.5
4.39
4.85
0.0082
0.0065
H-17(b) ! L(b)
p(Cl)/p(PPh3)/n(P)/n(N) ! d
H-15(b) ! L + 1(b)
H-1(b) ! L + 3(b)
H-2(a) ! L + 7(a)
H-18(b) ! L(b)
p(Cl) ! d
p(Cl)/p(PPh3) ! p*(bpzm)/p*(PPh3)
d ! p*(PPh3)
254.9
249.9
4.86
4.96
0.0082
0.0062
226.8 (5.47) 13780
215.2 (5.76) 14370
n(P) ! d
H-2(b) ! L + 2(b)
H-2(a) ! L + 7(a)
p(PPh3)/n(P)/p(Cl) ! p*(bpzm)
d ! p*(PPh3)
249.5
248.4
4.97
4.99
0.0063
0.0061

B. Machura et al. / Polyhedron 26 (2007) 4833–4840
4839
2
y ¼ ceꢀbx with the height (c) equal to the oscillator
2.0
strength and b equal to 0.04 nmꢀ2
.
1.8
1.6
1.4
1.2
1.0
The spin-allowed triplet–triplet electronic transitions
calculated with the TDDFT method for [ReCl3(bpzm)-
(PPh3)] are gathered in Table 5. For the high energy part
of the spectrum, only transitions with oscillator strengths
larger than 0.0050 are listed in Table 5.
The investigated complex is of large size, the number of
basis functions is equal to 605. A hundred electron transi-
tions calculated by the TDDFT method do not comprise
all the experimental absorption bands. The UV–Vis spec-
trum of [ReCl3(bpzm)(PPh3)] was calculated only to
240 nm, so the shortest wavelength experimental band can-
not be assigned to the calculated transitions, and the
assignment of the band at 226.8 nm is not complete. Some
additional intraligand and interligand transitions are
expected to be found at higher energies in the calculation
for [ReCl3(bzpm)(PPh3)].
0.0
0
100
150
200
250
300
T [K]
Fig. 4. Plots of the experimental effective magnetic moment leff (d) vs.
temperature for the complex [ReCl3(bpzm)(PPh3)].
The electronic absorption spectrum of [ReCl3(bpzm)-
(PPh3)] is similar to those observed for [ReCl3(pzH)2-
(PPh3)] and [ReCl3(3,5-Me2pzH)2(PPh3)] [14]. Some
intense bands are observed below 300 nm and two consid-
erably weaker absorptions exist in the low energy range. In
contrast, the solution spectra of fac-[ReCl3(L–L)(PPh3)]
display multiple transitions of moderate intensity in the
form of peaks and shoulders in the visible region (400–
1000 nm) [34,36].
0.016
0.014
0.012
0.010
0.008
0.006
0.004
0.002
0.000
The experimental bands of [ReCl3(bpzm)(PPh3)] at
435.0, 356.8 and 269.4 nm are attributed to Ligand–Metal
Charge Transfer (p(Cl) ! d and p(PPh3) ! d) and Metal–
Ligand Charge Transfer (d ! p (PPh ) and d !
*
3
p (bpzm)) transitions.
*
The absorption band at 226.8 nm results mainly from
Ligand–Ligand Charge Transfer and intraligand (IL)
transitions.
0
10000
20000
30000
40000
50000
H [Oe]
Fig. 5. Field dependence of the magnetization for the complex
[ReCl3(bpzm)(PPh3)] at 2 K.
3.5. Magnetic properties
2 K is shown in Fig. 5. The M versus H curve for the
complex very slowly increases and indicates a value of
the magnetization near to zero (0.015 B.M.) at 5 T. The
magnetization of the sample confirms that the ground state
is diamagnetic.
The magnetic properties of [ReCl3(bpzm)(PPh3)] under
the form leff versus T (leff the effective magnetic moment)
is shown in Fig. 4. The chloro-derivative of rhenium(III),
shows
a
room temperature magnetic moment of
1.74 B.M. (0.379 cm3molꢀ1K). The magnetic moment of
the solid is temperature dependent between 300 and
60 K. Only a slight magnetic anomaly is observed in the
temperature range 55–14 K, and below 14 K the value of
the vMT product decreases with temperature lowering. This
behavior is characteristic of mononuclear d4 low-spin octa-
hedral Re(III) complexes (3T1g ground state) [37–45] and
arises because of the large spin–orbit coupling (f =
2500 cmꢀ1 [46]), which gives a diamagnetic ground state.
It seems that at room temperature, in accordance with
Boltzmann’s distribution, the higher magnetic state is pop-
ulated, and it is depopulated with temperature lowering
and a decrease of the magnetic moment is observed.
The variation of the magnetization M versus the mag-
netic field H for the complex [ReCl3(OPPh3)(dppt)] at
4. Supplementary material
CCDC 640910 contains the supplementary crystallo-
graphic data for C26H25Cl5N4PRe. These data can be
obtained free of charge via http://www.ccdc.cam.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 deposit@ccdc.
cam.ac.uk.
Acknowledgements
The GAUSSIAN03 calculations were carried out in the
Wrocław Centre for Networking and Supercomputing,

4840
B. Machura et al. / Polyhedron 26 (2007) 4833–4840
Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X.
Li, J.E. Knox, H.P. Hratchian, J.B. Cross, C. Adamo, J. Jaramillo, R.
Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C.
Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma, G.A. Voth, P.
Salvador, J.J. Dannenberg, V.G. Zakrzewski, S. Dapprich, A.D.
Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K.
Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S.
Clifford, J. Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P.
Piskorz, I. Komaromi, R.L. Martin, D.J. Fox, T. Keith, M.A. Al-
Laham, C.Y. Peng, A. Nanayakkara, M. Challacombe, P.M.W. Gill,
B. Johnson, W. Chen, M.W. Wong, C. Gonzalez, J.A. Pople, GAUSS-
IAN03, Revision B.03, Gaussian, Inc., Pittsburgh PA, 2003.
[25] A.D. Becke, J. Chem. Phys. 98 (1993) 5648.
WCSS, Wrocław, Poland under calculational Grant No.
51/96. The work was supported by the Polish Ministry of
Science and Higher Education Grant No. 1T09A12430.
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