Synthesis, crystal, molecular and electronic structure of the [ReCl 4(pzH)(PPh3)] and [ReCl4(pyz)(PPh3)] complexes

Article abstract of DOI:10.1016/j.poly.2005.09.022

The reactions of the [ReCl₄(PPh₃)₂] complex with pyrazole (pzH) and pyrazine (pyz) have been examined and two novel Re(IV) compounds - [ReCl₄(pzH)(PPh₃)] (1) and [ReCl ₄(pyz)(PPh₃)] (2) - have been obtained. The compounds have been studied by IR, UV-Vis spectroscopy and X-ray crystallography. The electronic structures of 1 and 2 have been calculated with the density functional theory (DFT) method. The spin-allowed quartet-quartet electronic transitions of 1 and 2 have been calculated with the time-dependent DFT method, and the UV-Vis spectra of the title compounds have been discussed on this basis. From magnetic studies a small, negative value of J obtained confirms the occurrence of weak antiferromagnetic interactions between the rhenium centers in the crystal lattice.

Full text of DOI:10.1016/j.poly.2005.09.022

Polyhedron 25 (2006) 1348–1358
www.elsevier.com/locate/poly
Synthesis, crystal, molecular and electronic structure of
the [ReCl4(pzH)(PPh3)] and [ReCl4(pyz)(PPh3)] complexes
a,
a
b
c
c
*
´
B. Machura , A. Jankowska , R. Kruszynski , J. Kłak , J. Mrozinski
a
Department of Inorganic and Radiation Chemistry, 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
Faculty of Chemistry, Wroclaw University, F. Joliot-Curie 14 Street, 50-383 Wrocław, Poland
c
Received 7 September 2005; accepted 22 September 2005
Available online 24 February 2006
Abstract
The reactions of the [ReCl4(PPh3)2] complex with pyrazole (pzH) and pyrazine (pyz) have been examined and two novel Re(IV) com-
pounds – [ReCl4(pzH)(PPh3)] (1) and [ReCl4(pyz)(PPh3)] (2) – have been obtained. The compounds have been studied by IR, UV–Vis
spectroscopy and X-ray crystallography. The electronic structures of 1 and 2 have been calculated with the density functional theory
(DFT) method. The spin-allowed quartet–quartet electronic transitions of 1 and 2 have been calculated with the time-dependent
DFT method, and the UV–Vis spectra of the title compounds have been discussed on this basis. From magnetic studies a small, negative
value of J obtained confirms the occurrence of weak antiferromagnetic interactions between the rhenium centers in the crystal lattice.
ꢀ 2005 Elsevier Ltd. All rights reserved.
Keywords: Rhenium(IV) complexes; Pyrazole and pyrazine; X-ray structure; Electronic structure; DFT calculations
1. Introduction
OX3(AsPh3)(OAsPh3)] complexes (X = Cl or Br) with pyr-
azole (pzH) or pyrazine (pyz). The products of these
syntheses include (i) mononuclear [Re(NO)Br3(pzH)
(AsPh3)], [Re(NO)Cl3(OPPh3)(pyz)], [ReCl3(pzH)2(PPh3)],
[ReCl3(pzH)3] [ReOX2{g2-N2C3H3C(CH3)2O}(PPh3)], [Re
Recent interest in the coordination chemistry of
rhenium arises mainly from the introduction of bꢀ emitting
isotopes 188Re and 186Re in radiotherapy and its similarity
with technetium, whose metastable c-emitting isotope
99mTc plays important role in diagnostic nuclear medicine.
The success of the 186Re(Sn)HEDP radiopharmaceutical as
a palliative of bone pain has particularly reawakened
interest in the coordination chemistry of rhenium in order
to develop new 186/188Re radiopharmaceuticals which could
be used for the treatment of cancer [1–6].
OBr3(OAsPh3)(pzH)],
[ReOCl2(pzH)2(OAsPh3)](ReO4)
complexes and (ii) dinuclear compounds of [{Re(O)-
X(PPh3)}2(l-O)(l-pz)2] and [{ReOBr2(pyz)2}2(l-O)] com-
position [7–12].
These findings prompted us to explore the reactions of
[ReCl4(PPh3)2] with pyrazole and pyrazine. Here, we
present spectroscopic investigation, crystal, molecular and
electronic structures of [ReCl4(pzH)(PPh3)] (1) and [Re-
Cl4(pyz)(PPh3)] (2). The electronic structures of 1 and 2
have been calculated with the density functional theory
(DFT) method. The spectroscopic investigation of 1 and
2 comprises IR and UV–Vis studies. The UV–Vis spectra
have been discussed on the basis of the spin-allowed quar-
tet–quartet electronic transitions calculated for 1 and 2
complexes with the time-dependent DFT (TD-DFT)
Previously, we investigated the reactions of the [Re(NO)
Br3(AsPh3)2], [Re(NO)Cl3(OPPh3)(PPh3)], [ReCl3(MeCN)
(PPh3)2], [ReO(OEt)X2(PPh3)2], [ReOX3(PPh3)2] and [Re-
*
Corresponding author.
E-mail addresses: bmachura@poczta.onet.pl, basia@ich.us.edu.pl (B.
Machura), kruszyna@p.lodz.pl (R. Kruszynski), jmroz@wchuwr.chem.
uni.wroc.pl (J. Mrozinski).
´
0277-5387/$ - see front matter ꢀ 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2005.09.022

B. Machura et al. / Polyhedron 25 (2006) 1348–1358
1349
method. The recent calculations with the TD-DFT method
2.4. Crystal structures determination and refinement
for open- and closed-shell of 5d-metal complexes (including
rhenium complexes) have supported the TD-DFT method
to be applicable for such systems giving good assignment
of experimental spectra [13–19].
The X-ray intensity data of 1 and 2 were collected on a
KM-4-CCD automatic diffractometer equipped with CCD
detector, 20 and 29 s exposure time was used receptively
and all reflections of Ewald sphere was collected up to
2h = 50ꢁ. The unit cell parameters were determined from
least-squares refinement of the setting angles of 7903 and
12323 strongest reflections, respectively, for 1 and 2. De-
tails concerning crystal data and refinement are given in
Table 1. Lorentz, polarization and numerical absorption
corrections [21] were applied. The structure were solved
by the Patterson method and subsequently completed by
the difference Fourier recycling. All the non-hydrogen
atoms were refined anisotropically using full-matrix,
least-squares technique. The carbon bonded hydrogen
atoms were founded on difference Fourier synthesis and
they were refined as ‘‘riding’’ on their parent carbon atoms
2. Experimental
2.1. General procedure
The reactions were carried out under argon atmosphere.
All solvents were of reagent grade and were used as re-
ceived. Ammonium perrhenate, Ph3P, pzH and pyz were
purchased from Aldrich and used as received.
[ReCl4(PPh3)2] was prepared according to the literature
method [20].
IR spectra were recorded on a Nicolet Magna 560
spectrophotometer in the spectral range 4000–400 cmꢀ1
with the samples in the form of KBr pellets. Electronic
spectra were measured on a spectrophotometer Lab
Alliance UV–VIS 8500 in the range 900–200 nm in deoxy-
genated dichloromethane solution. Elemental analyses (C
H N) were performed on a Perkin–Elmer CHN-2400
analyzer.
˚
[d(C–H) = 0.96 A] and assigned isotropic temperature fac-
tors equal 1.2 times the value of equivalent temperature
Table 1
Crystal data and structure refinement for 1 and 2
1
2
Empirical formula
Formula weight
Temperature (K)
C21 H19Cl4N2PRe
658.35
293(2)
C22H19Cl4N2PRe
670.36
293(2)
2.2. Preparation of [ReCl4(pzH)(PPh3)] (1)
˚
Wavelength (A)
0.71073
0.71073
[ReCl4(PPh3)2] (1 g, 1.15 mmol) and pzH (0.30 g,
4.4 mmol) in chloroform (100 cm3) were refluxed over-
night. The colour of the reaction mixture changed slowly
from dark red to brown. The volume was condensed to
10 cm3 and orange microcrystalline solid was formed by
an addition of 100 cm3 of ethanol. The product was
washed with EtOH and cold ether, and dried in vacuo.
The crystals of 1 suitable for X-ray investigation were
obtained by recrystallization from CHCl3–EtOH. Yield
80%.
Crystal system
Space group
Unit cell dimensions
triclinic
monoclinic
P21/c
ꢀ
P1
˚
a (A)
10.5796(7)
11.0495(7)
11.3454(8)
78.276(6)
86.039(5)
65.089(6)
1177.58(14)
2
17.5845(5)
9.05250(10)
15.7452(6)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
109.002(2)
c (ꢁ)
Volume (A3)
Z
2369.80(12)
4
1.879
IR (KBr, cmꢀ1) 3342 (s), 3140 (m) 3062 (w), 1580 (w)
1517 (m) 1486 (s), 1444 (s), 1405 (m), 1350 (s), 1268 (m),
1150 (m), 1128 (s) 1093 (s), 1058 (s), 1008 (w), 778 (s),
755 (s), 700 (s), 582 (m), 531 (s), 494 (s).
Density (calculated)
(Mg/m3)
1.857
Absorption coefficient
5.692
5.659
(mmꢀ1
)
F(0 0 0)
634
1292
Crystal size (mm)
h Range for data collection 3.53–25.10ꢁ
Index ranges
0.55 · 0.45 · 0.35
0.39 · 0.30 · 0.09
3.09–25.11ꢁ
ꢀ20 6 h 6 20
ꢀ10 6 k 6 10
ꢀ13 6 l 6 18
23594
Anal. Calc. for C9H15N6Cl4ORe: C, 38.31; H, 2.91; N,
4.25. Found: C, 38.53; H, 3.0; N, 4.30%.
ꢀ12 6 h 6 12
ꢀ13 6 k 6 13
ꢀ13 6 l 6 11
11470
2.3. Preparation of [ReCl4(pyz)(PPh3)] (2)
Reflections collected
Independent reflections
Completeness to 2h (%)
Maximum and minimum
transmission
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
4172 (Rint = 0.0291) 4222 (Rint = 0.0190)
A procedure similar to that for 1 was used with
[ReCl4(PPh3)2] (1 g, 1.15 mmol) and pyz (0.3 g, 3.7 mmol).
An orange crystalline precipitate of 2 was collected in 80%
yield.
99.5
99.8
0.198 and 0.083
0.639 and 0.217
4172/0/262
1.096
4222/0/271
1.143
IR (KBr, cmꢀ1) 3093 (w) 3059 (w), 1581 (w) 1512 (w)
1481 (s), 1434 (s), 1414 (m), 1339 (w), 1318 (w), 1188 (w),
1149 (s) 1120 (s), 1090 (s), 1053 (s), 1028 (w), 807 (s), 746
(s), 691 (vs), 524 (s), 502 (s), 465 (m), 450 (sh).
Anal. Calc. for C9H15N6Cl4ORe: C, 39.42; H, 2.86; N,
4.18. Found: C, 39.63; H, 2.92; N, 4.31%.
R1 = 0.0240
wR2 = 0.0602
R1 = 0.0247
R1 = 0.0607
0.981 and ꢀ1.183
R1 = 0.0176
wR2 = 0.0350
R1 = 0.0194
wR2 = 0.0355
0.751 and ꢀ0.701
R indices (all data)
Largest difference peak
and hole (e Aꢀ3
)

1350
B. Machura et al. / Polyhedron 25 (2006) 1348–1358
factor of the parent carbon atom. SHELXS97 [22], SHELXL97
[23] and SHELXTL [24] programs were used for all the calcu-
lations. Atomic scattering factors were those incorporated
in the computer programs.
3.1. X-ray structures
Perspective drawings of 1 and 2 are given in Figs. 1 and
2, respectively. The rhenium atom of the both complexes is
in a distorted octahedral environment with four chlorine
2.5. Computational details
GAUSSIAN03 program [25] was used in the calculations.
The geometry optimization was carried out with the DFT
method with the use of B3LYP functional [26,27]. The elec-
tronic spectra were calculated with the TDDFT method
[28]. The calculations were performed by using ECP basis
set on the rhenium atom, the standard 6-31+g
basis
**
for chlorine, oxygen and nitrogen, 6-31+g for carbon
*
and 6-31G basis for hydrogen atoms. The Xe core electrons
of Re were replaced by an effective core potential and DZ
quality Hay and Wadt Los Alamos ECP basis set
(LANL2DZ) [29] was used for the valence electrons. Addi-
tional d function with exponent a = 0.3811 and f function
with exponent a = 2.033 on the rhenium atom were added.
2.6. Magnetic measurement
The magnetic measurements of the powdered samples
was measured over the temperature range 1.8–300 K using
a Quantum Design SQUID – based MPMSXL – 5-type
magnetometer. The superconducting magnet was generally
operated at a field strength ranging from 0 to 5 T measure-
ments. Measurements sample of compounds were made at
magnetic field 0.5 T.
Fig. 1. The molecular structure of 1. The hydrogen atoms of the phenyl
rings are omitted for clarity.
The SQUID magnetometer was calibrated with the palla-
dium rod sample. Corrections are based on subtracting the
sample – holder signal and contribution vD estimated from
the Pascal constants [37] and equal ꢀ257 · 10ꢀ6 cm3 molꢀ1
for complex [ReCl4(pzH)(PPh3)] (1) and ꢀ263 · 10ꢀ6
cm3 molꢀ1 for complex [ReCl4(pyz)(PPh3)] (2). The t.i.p.
per Re4+ center was assumed to be 70 · 10ꢀ6 cm3 molꢀ1
.
The effective magnetic moment was calculated from the
1=2
equation, leff ¼ 2:83ðvMTÞ ðB.M.Þ.
3. Results and discussion
The [ReCl4(pzH)(PPh3)] (1) and [ReCl4(pyz)(PPh3)] (2)
complexes have been obtained in high yield in the reactions
of [ReCl4(PPh3)2] with pyrazole and pyrazine, respectively
½ReCl4ðPPh3Þ ꢁ þ pzH ! ½ReCl4ðpzHÞðPPh3Þꢁ þ PPh3 ðR:1Þ
½ReCl4ðPPh3Þ2ꢁ þ pyz ! ½ReCl4ðpyzÞðPPh3Þꢁ þ PPh3 ðR:2Þ
2
The excess of pzH and pyz ensures the maximum yield of
the products.
The elemental analysis of the complexes is in good agree-
ment with their formulation. The presence of the strong band
intherangeassignabletoN–Hvibrationsinthespectrumof1
confirms the coordination of pyrazole in a neutral monoden-
tate form. The absorption bands at ꢂ1580 and ꢂ1515 cmꢀ1
are typical of mono-coordinated diaza ligands [30].
Fig. 2. The molecular structure of 2. The hydrogen atoms of the phenyl
rings are omitted for clarity.

B. Machura et al. / Polyhedron 25 (2006) 1348–1358
1351
ions in the equatorial plane, and N-donor ligand and PPh3
molecule in axial positions. Table 1 presents crystal data
and structural refinement for 1 and 2. The most important
experimental bond lengths and angles for 1 and 2 are re-
ported in Tables 2 and 3, respectively. The Re–N, Re–Cl
and Re–P bond lengths are unexceptional, they agree well
with appropriate values found previously in similar rhe-
nium compounds [7–12]. The weak C–Hꢃ ꢃ ꢃCl and medium
strength N–Hꢃ ꢃ ꢃCl intra- and intermolecular hydrogen
bonds [31,32] of 1 and 2 are presented in Table 4. Via these
interactions a hydrogen bonded dimer (in 1) and infinite
hydrogen bonded chains along crystallographic b axis (in
2) are created. The shortest Reꢃ ꢃ ꢃRe distance is 6.670 and
as 2.06, 2.46 and 2.23 [35], respectively, and b was taken
as 0.37 [33]. The computed bond valences of rhenium
are mReꢀN = 0.761; mReꢀP = 0.840; mReꢀCl = 0.775, 0.758,
0.730, 0.764 v.u. (valence units) for 1 and ReꢀN = 0.666;
m
ReꢀP = 0.871; mReꢀCl = 0.758, 0.763, 0.784, 0.751 v.u.
(valence units) for 2. These means that the triphenylphos-
phine groups are strongest bonded substituents, the
strength of Re–Cl bonds are comparable to the strength
of Re–N(pyrazole) bond, and the pyrazine is the weakest
bonded substituent (the bond is about 15% weaker in
comparison to Re–N(pyrazole)).
3.2. Optimized geometries
˚
7.753 A, respectively, for 1 and 2.
The bond valences were computed as mij =
exp[(Rij ꢀ dij)/b] [33–36], where Rij is the bond-valence
parameter (in the formal sense the Rij parameter value
can be considered as an idealized single-bond length be-
tween i and j atoms). The RReꢀN, RReꢀP, RReꢀCl were taken
The geometries of 1 and 2 were optimized in quartet and
doublet states using the DFT method with the B3LYP
functional. The energies of the doublet states are of 15.8
and 16.3 kcal higher for 1 and 2, respectively. The
optimized geometric parameters of the quartet states are
Table 2
˚
The experimental and optimized bond lengths (A) and angles (ꢁ) for 1
Bond lengths
Bond angles
Experimental
Optimized
Experimental
Optimized
Re(1)–Cl(1)
Re(1)–Cl(2)
Re(1)–Cl(3)
Re(1)–Cl(4)
Re(1)–N(1)
Re(1)–P(1)
2.3245(11)
2.3323(10)
2.3464(11)
2.3296(11)
2.161(3)
2.383
3.371
2.369
2.405
2.173
2.586
N(1)–Re(1)–Cl(3)
N(1)–Re(1)–Cl(2)
Cl(3)–Re(1)–Cl(2)
N(1)–Re(1)–Cl(1)
Cl(3)–Re(1)–Cl(1)
Cl(2)–Re(1)–Cl(1)
N(1)–Re(1)–Cl(4)
Cl(3)–Re(1)–Cl(4)
Cl(2)–Re(1)–Cl(4)
Cl(1)–Re(1)–Cl(4)
N(1)–Re(1)–P(1)
Cl(3)–Re(1)–P(1)
Cl(2)–Re(1)–P(1)
Cl(1)–Re(1)–P(1)
Cl(4)–Re(1)–P(1)
88.10(9)
88.62(9)
88.48(4)
88.41(9)
176.30(4)
92.67(4)
89.29(9)
88.96(5)
176.74(4)
89.77(5)
175.87(9)
95.02(4)
88.76(3)
88.52(4)
93.46(4)
87.69
90.17
89.35
88.84
176.00
92.73
88.10
88.18
176.96
89.73
178.56
93.74
89.67
89.74
92.12
2.5245(9)
Table 3
˚
The experimental and optimized bond lengths (A) and angles (ꢁ) for 2
Bond lengths
Bond angles
Experimental
Experimental
Optimized
Optimized
Re(1)–Cl(1)
Re(1)–Cl(2)
Re(1)–Cl(3)
Re(1)–Cl(4)
Re(1)–N(1)
Re(1)–P(1)
2.3323(7)
2.3300(8)
2.3202(7)
2.3359(7)
2.2106(19)
2.5111(6)
2.386
2.368
2.368
2.380
2.2265
2.577
N(1)–Re(1)–Cl(3)
N(1)–Re(1)–Cl(2)
Cl(3)–Re(1)–Cl(2)
N(1)–Re(1)–Cl(1)
Cl(3)–Re(1)–Cl(1)
Cl(2)–Re(1)–Cl(1)
N(1)–Re(1)–Cl(4)
Cl(3)–Re(1)–Cl(4)
Cl(2)–Re(1)–Cl(4)
Cl(1)–Re(1)–Cl(4)
N(1)–Re(1)–P(1)
Cl(3)–Re(1)–P(1)
Cl(2)–Re(1)–P(1)
Cl(1)–Re(1)–P(1)
Cl(4)–Re(1)–P(1)
89.74(6)
86.59(6)
88.45(3)
89.00(6)
90.78(3)
175.53(2)
88.76(6)
177.25(3)
89.16(3)
91.49(3)
178.47(5)
91.70(2)
92.93(2)
91.50(2)
89.78(2)
88.81
87.53
88.96
87.99
90.16
175.46
88.79
176.74
88.74
91.96
178.38
92.16
93.78
90.71
90.29

1352
B. Machura et al. / Polyhedron 25 (2006) 1348–1358
Table 5
gathered in Tables 2 and 3 for 1 and 2, respectively. In gen-
eral, the predicted bond lengths and angles are in good
agreement with the values based upon the X-ray crystal
structure data.
Atomic charges from the natural population analysis (NPA) for 1 and 2
Atom
1
2
Re(1)
Cl(1)
Cl(2)
Cl(3)
Cl(4)
P(1)
0.558
0.535
ꢀ0.345
ꢀ0.323
ꢀ0.320
ꢀ0.371
1.395
ꢀ0.352
ꢀ0.317
ꢀ0.323
ꢀ0.339
1.408
3.3. Charge distribution
Table 5 presents the atomic charges from the natural
population analysis (NPA) for 1 and 2 complexes. The cal-
culated charges on the rhenium atoms are considerable
lower than the formal charge +4. It results from charge
donation from the chloride ions and triphenylphosphine li-
gand. There is large positive charge on the P atom, and the
charges on the chloride ions are significantly smaller than
ꢀ1. The populations of the dxy, dxz, dyz, dx2ꢀy2 and d2z orbi-
N(1)
N(2)
ꢀ0.343
ꢀ0.474
ꢀ0.340
ꢀ0.412
tals of the central atoms in 1 and 2 are following: complex 1
– 1.235, 1.239, 1.046, 1.130 and 1.228; complex 2 – 1.246,
1.233, 1.116, 1.124 and 1.186.
3.4. Molecular orbitals
Table 4
Hydrogen bonds for 1 and 2
The energies and characters of the selected MOs for 1
and 2 are presented in Tables 6 and 7, respectively. The
D
A
Hꢃ ꢃ ꢃA
Dꢃ ꢃ ꢃA
D–Hꢃ ꢃ ꢃA
rhenium atoms in
1
and
2
compounds possess
1
(dxz)1(dyz)1(dxy)1 configuration. For 1 and 2 complexes,
the rhenium dxz, dyz and dxy orbitals make main contribu-
tions into the HOMO ꢀ 2, HOMO ꢀ 1 and HOMO 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 antibonding character towards the pp orbitals
of the chloride ligands. For complex 1, the LUMO with a
N(2)
N(2)
C(2)
C(4)
C(21)
Cl(4)
Cl(4)a
Cl(2)
Cl(3)
Cl(2)
2.75
2.63
2.66
2.75
2.62
3.212(5)
3.340(5)
3.497(4)
3.300(4)
3.149(5)
115.2
140.1
149.7
118.7
116.5
2
C(2)
C(2)
C(19)
C(20)
Cl(1)
Cl(4)
Cl(2)
Cl(4)b
2.78
2.72
2.73
2.72
3.456(3)
3.389(3)
3.188(3)
3.580(3)
130.7
129.1
111.1
153.3
spin and the LUMO + 9 with b spin are of d2-rCl-rP char-
z
acter. The dx2ꢀy2 rhenium orbital has a significant contribu-
tion in the LUMO + 1 with a spin and the LUMO + 6 with
b spin.
a
ꢀx, 1 ꢀ y, 1 ꢀ z.
b
ꢀx, y + 0.5, ꢀz ꢀ 0.5.
Table 6
The energies and characters of the selected molecular orbitals with a and b spins for 1
a MO
b MO
E (eV)
E (eV)
Character
Character
HOMO ꢀ 12
HOMO ꢀ 11
HOMO ꢀ 10
HOMO ꢀ 9
HOMO ꢀ 8
HOMO ꢀ 7
HOMO ꢀ 6
HOMO ꢀ 5
HOMO ꢀ 4
HOMO ꢀ 3
HOMO ꢀ 2
HOMO ꢀ 1
HOMO
ꢀ7.849
ꢀ7.771
ꢀ7.662
ꢀ7.401
ꢀ7.323
ꢀ7.113
ꢀ7.093
ꢀ6.985
ꢀ6.944
ꢀ6.908
ꢀ6.696
ꢀ6.455
ꢀ6.275
ꢀ1.556
ꢀ1.358
ꢀ1.020
ꢀ0.825
ꢀ0.625
ꢀ0.455
ꢀ0.436
ꢀ0.170
ꢀ0.113
0.351
p(Cl), p(pzH)
p(Cl)
p(pzH), p(Cl)
p(Ph)
ꢀ7.990
ꢀ7.898
ꢀ7.735
ꢀ7.637
ꢀ7.581
ꢀ7.572
ꢀ7.371
ꢀ7.133
ꢀ7.073
ꢀ7.007
ꢀ6.936
ꢀ6.894
ꢀ6.788
ꢀ3.500
ꢀ3.349
ꢀ2.914
ꢀ1.103
ꢀ1.011
ꢀ0.793
ꢀ0.690
ꢀ0.543
ꢀ0.441
ꢀ0.254
p(pzH), p(Cl)
p(pzH), p(Cl)
p(Cl)
p(Cl), n(P), n(N)
p(pzH), p(Cl)
p(Cl)
p(Ph)
p(Cl), p(Ph)
p(Ph)
p(Cl), p(Ph)
p(Ph)
p(Ph), p(Cl)
p(Ph), n(P)
p(Cl)
p(Ph), dxz(Re)
p(Ph), p(Cl), dyz(Re)
p(Ph), dyz
p(Ph), n(P)
p(Ph), p(Cl), dxz
dyz(Re), p(Cl), p(Ph)
dxz(Re), p(Cl)
dxy(Re), p(Cl)
LUMO
dz2 ðReÞ-rðPÞ-rðNÞ
dx2ꢀy2 ðReÞ-rðClÞ
p*(Ph), r*(P–C)
p*(Ph), r*(P–C)
p*(pzH)
dyz(Re), p(Cl)
dxz(Re), p(Cl)
dxy(Re), p(Cl)
p*(Ph), r*(P–C), dz2 ðReÞ
p*(Ph), r*(P–C), dz2 ðReÞ
p*(Ph), r*(P–C)
dx2ꢀy2 ðReÞ-rðClÞ
p*(pzH)
LUMO + 1
LUMO + 2
LUMO + 3
LUMO + 4
LUMO + 5
LUMO + 6
LUMO + 7
LUMO + 8
p*(Ph)
p*(Ph), dz2 ðReÞ
p*(Ph)
p*(Ph)
p*(Ph)
dz2 ðReÞ, p*(Ph)

B. Machura et al. / Polyhedron 25 (2006) 1348–1358
1353
Table 7
The energies and characters of the selected molecular orbitals with a and b spins for 2
a MO
b MO
E (eV)
E (eV)
Character
Character
HOMO ꢀ 12
HOMO ꢀ 11
HOMO ꢀ 10
HOMO ꢀ 9
HOMO ꢀ 8
HOMO ꢀ 7
HOMO ꢀ 6
HOMO ꢀ 5
HOMO ꢀ 4
HOMO ꢀ 3
HOMO ꢀ 2
HOMO ꢀ 1
HOMO
ꢀ7.988
ꢀ7.986
ꢀ7.905
ꢀ7.507
ꢀ7.438
ꢀ 7.223
ꢀ7.195
ꢀ7.080
ꢀ7.029
ꢀ6.964
ꢀ6.734
ꢀ6.698
ꢀ6.392
ꢀ2.471
ꢀ1.736
ꢀ1.454
ꢀ1.351
ꢀ1.147
ꢀ0.882
ꢀ0.587
ꢀ0.506
ꢀ0.298
ꢀ0.168
p(Cl)
p(Cl), n(P), n(N)
p(Cl)
p(Ph)
p(Cl)
p(Ph), dyz
p(Ph)
p(Ph), dxz
p(Ph), n(P)
p(Ph), dxz, n(P), n(N)
ꢀ8.409
ꢀ8.072
ꢀ7.874
ꢀ7.817
ꢀ7.793
ꢀ7.722
ꢀ7.467
ꢀ7.244
ꢀ7.171
ꢀ7.132
ꢀ7.027
ꢀ6.978
ꢀ6.885
ꢀ3.727
ꢀ3.538
ꢀ3.040
ꢀ2.276
ꢀ1.354
ꢀ1.264
ꢀ1.128
ꢀ0.840
ꢀ0.757
ꢀ0.508
p(pyz), p(Cl)
n(N)
p(Cl), p(pyz)
p(Cl), n(P), n(N)
p(Cl)
p(Cl)
p(Ph), p(Cl)
p(Cl), p(Ph)
p(Ph)
p(Cl), p(Ph)
p(Ph)
dyz(Re), p(Cl)
dxz(Re), p(Cl)
dxy(Re), p(Cl)
p*(pyz)
p(Ph), p(Cl)
p(Ph), n(P)
LUMO
dyz(Re), p(Cl), p*(pyz)
dxz(Re), p(Cl)
LUMO + 1
LUMO + 2
LUMO + 3
LUMO + 4
LUMO + 5
LUMO + 6
LUMO + 7
LUMO + 8
LUMO + 9
dz2 ðReÞ-rðPÞ-rðNÞ
dx2ꢀy2 ðReÞ-rðClÞ, p*(pyz)
p*(pyz), dx2ꢀy2 -rðClÞ
p*(Ph), r*(P–C)
p*(Ph), r*(P–C)
p*(Ph), r*(P–C), dz2 ðReÞ
p*(Ph)
dxy(Re), p(Cl)
p*(pyz), dxz
p*(pyz)
dz2 ðReÞ-rðPÞ-rðNÞ, p*(Ph)
p*(Ph), r*(P–C), dz2 ðReÞ
p*(Ph), r*(P–C), dxz(Re)
dx2ꢀy2 ðReÞ-rðClÞ
p*(Ph)
p*(Ph)
p*(Ph)
For complex 2, the LUMO orbital with a-spin has pre-
dominantly p* (pyz) character. The d2z rhenium orbital has
a significant contribution in the LUMO + 1 with a spin
and the LUMO + 5 with b spin, whereas the LUMO + 2
with a spin and the LUMO + 8 with b have predominantly
dx2ꢀy2 -rCl character. A contribution of r* (P–C) phosphine
orbitals is visible in several unoccupied molecular orbitals
with a and b spins of 1 and 2 compounds. These orbitals
are involved in the p-back bonding between metal center
and phosphine ligand. In classical concepts empty phos-
phorous 3d orbitals are used for this purpose. Now, it is
generally recognized that the d orbitals, which are very
high in energy play only a minor role in the pMꢀPR3 bond
formation [33].
The investigated complexes are of large size; the number
of basis functions is equal 532 and 546 for 1 and 2, respec-
tively. Ninety electron transitions calculated by the
TDDFT method do not comprise all the experimental
absorption bands. The shortest wavelength experimental
band of 2 is not assigned to the calculated transitions,
and the assignment for the complex 1 is not complete. As
the solution spectra of PPh3, pyrazole and pyrazine exhibit
intense absorption bands in 270–200 nm region, some addi-
tional intraligand and interligand transitions are expected
to be found at higher energies in the calculations for
1 and 2.
The longest wavelength weak experimental bands at
752 nm for 1 and 761 nm for 2 correspond to the spin-for-
4
2
bidden transitions A1g ! Eg.
For 1 and 2 complexes, the experimental absorption
bands between 500 and 250 nm result from d–d and
ligand–metal charge transfer (LMCT) transitions. The last
ones occur from chloride, phosphine and pyrazole or pyr-
azine ligand orbitals to the d rhenium orbitals. The
d ! d transitions calculated in this range have small oscil-
lator strengths. Consequently, they do not contribute sig-
nificantly to the overall shape of these bands.
3.5. Electronic spectrum from the TDDFT calculations
The electronic spectra of 1 and 2 exhibit two intense
absorption bands below 300 nm and some weaker absorp-
tions in the low energy range. The experimental and calcu-
lated electronic spectra of 1 and 2 are presented in Figs. 3
and 4, respectively. Each calculated transition was repre-
sented by a gaussian function with the height equal to
the oscillator strength and width equal to 0.04.
3.6. Magnetic properties
Tables 8 and 9 show the energies and molar absorption
coefficients of the experimental absorption bands and the
spin-allowed quartet–quartet electronic transitions calcu-
lated with the TDDFT method for 1 and 2, respectively.
The assignment of the calculated transitions to the experi-
mental absorption bands was based on the criterion of the
energy and oscillator strength of the calculated transition.
The magnetic properties of [ReCl4(pzH)(PPh3)] (1) com-
plex under the form vM versus T and vMT versus T (vM
being the molar magnetic susceptibilities) are shown in
Fig. 5. The effective magnetic moment of 3.40 B.M.
(vMT = 1.44 cm3 molꢀ1 K) at 300 K corresponding three

1354
B. Machura et al. / Polyhedron 25 (2006) 1348–1358
Fig. 3. The experimental (a) and calculated (b) electronic absorption spectrum of 1.
unpaired electrons. The reduction of magnetic moments in
comparison with the spin-only value (3.87 B.M.) can be ex-
plained on the basis of depopulation of spin–orbit coupled
excited states and/or zero-field effects. The magnetic sus-
ceptibilities of other rhenium(IV) salts have been reported
elsewhere [38–42]. The value of vMT product decreases only
slightly with temperature lowering. In the low-temperature
range (below 50 K), a more evident decrease of the value of
vMT is observed with continuous decrease of the tempera-
ture to 0.04 cm3 molꢀ1 K (0.57 B.M.) at 1.8 K.
80–300 K are equal to 1.50 cm3 molꢀ1 and ꢀ10.1 K,
respectively. A negative value of Weiss constant suggests
the antiferromagnetic coupling of the rhenium(IV) centers
in the crystal lattice.
To interpret quantitatively the susceptibility data, we
used the approaches in which we considered that magnetic
susceptibility of this complex might be described by the
4
susceptibility of A2g term with the zero-field splitting [43].
Zero-field splitting and ligand field of symmetry lower
than cubic lead to the anisotropy of magnetic properties
of an ion. The relevant spin Hamiltonian is defined by
the following equation:
The susceptibility curves exhibit the maximum at 8 K,
indicating the presence the antiferromagnetic 3D ordering
in the crystal lattice with the ratio of the Curie–Weiss H
to the NeelÕs temperature H/TN ꢄ 1.
ꢀ
ꢁ
1
H ¼ D S2z ꢀ SðS þ 1Þ þ gIIbHzSz þ g?bðHxSx þ HySyÞ;
3
The values of the Curie and Weiss constants determined
from the relation 1/vM = f(T) over temperature range
ð1Þ

B. Machura et al. / Polyhedron 25 (2006) 1348–1358
1355
Fig. 4. The experimental (a) and calculated (b) electronic absorption spectrum of 2.
where DS2z represents the splitting into two Kramers dou-
Since our data concern powdered sample, the average
magnetic susceptibility is equal to vav = 1/3vII + 2/3v^.
The least-squares fit of the experimental data using this
equation was limited to the 9–300 K range and leads to
blets in the absence of magnetic field. The parallel and per-
3
2
pendicular zero field susceptibilities for S ¼ (Eqs. (2) and
(3)) were corrected by the factor predicted from the molec-
ular field (Eq. (4)) [42,44]:
D = 20.8 cmꢀ1
,
gII = 1.10, g^ = 2.03 and zJ0 = ꢀ4.18
cmꢀ1
.
The agreement factor
R
defined as R ¼
ꢂ
ꢃ
Nb2g2ReII
4kT
2D
1 þ 9 exp ꢀ kT
ꢂ
ꢃ
ꢂ
ꢃ
2
2
Rni¼1 vemxp ꢀ vmcalc =Rin¼1 vemxp is 2.93 · 10ꢀ5
.
ꢂ
ꢃ
vII ¼
v? ¼
ꢃ
;
ð2Þ
ð3Þ
2D
1 þ exp ꢀ kT
The magnetic properties of [ReCl4(pyz)(PPh3)] (2) com-
plex under the form vM versus T and vMT versus T (vM
being the molar magnetic susceptibilities) are plotted in
Fig. 6. The effective magnetic moment of 3.35 B.M.
(vMT = 1.40 cm3 molꢀ1 K) at 300 K corresponding three
unpaired electrons. The magnetic curve show that the
vMT values remain nearly constant in a wide range and
smoothly decrease at low temperatures. The slight decrease
of vMT at low temperatures could be attributed to zero-
field splitting effect [45].
ꢄ
ꢂ
ꢃꢅ
Nb2g2
kT
2D
2D
4 þ 6
1 ꢀ exp ꢀ kT
Re? ꢃ
;
ꢂ
ꢃ
2D
4kT
1 þ exp ꢀ kT
where D is the zero-field splitting parameter, N is the Avo-
gadroÕs number, g is the spectroscopic splitting factor, b is
the Bohr magneton, k is the Boltzmann constant and T is
the absolute temperature.
vav
ꢆ
ꢇ
vav
¼
;
ð4Þ
2zJ0
1 ꢀ
vav
Ng2avb2
Generally, the complex 2 shows linear vꢀM1 vs. T behavior
in the 80–300 K interval, with C = 1.44 cm3 molꢀ1 and
H = ꢀ7.9 K.
wherezJ0 istheexchangeparameterandwasappliedtocalcu-
late magnetic exchange effect by means of a molecular field.

1356
B. Machura et al. / Polyhedron 25 (2006) 1348–1358
Table 8
The energy and molar absorption coefficients of absorption bands and the electronic transitions calculated with the TDDFT method for 1
The most important orbital excitations
Character
k (nm)
E (eV)
f
Experimental k (nm) (E [eV]) e
H ꢀ 5(b) ! L(b)
H(b) ! L(b)
p(Cl)/p(Ph) ! d
p(Ph)/n(P) ! d
p(Ph)/n(P) ! d
p(Cl)/p(Ph) ! d
p(Ph)/n(P) ! d
p(Ph)/p(Cl) ! d
513.0
2.42
0.0011
470.0(2.64)780
H(b) ! L(b)
501.6
2.47
0.0025
H ꢀ 5(b) ! L(b)
H(b) ! L + 1(b)
H ꢀ 1(b) ! L(b)
471.1
459.3
2.63
2.70
0.0052
0.0017
H ꢀ 1(b) ! L + 1(b)
p(Ph)/p(Cl) ! d
p(Ph) ! d
p(Ph) ! d
p(Cl) ! d
p(Cl)/p(Ph) ! d
p(Cl) ! d
d ! d
435.6
423.7
419.6
415.9
2.85
2.93
2.95
2.98
0.0054
0.0013
0.0063
0.0032
409.0(3.03)2420
H ꢀ 4(b) ! L(b)
H ꢀ 2(b) ! L + 1(b)
H ꢀ 7(b) ! L + 1(b)
H ꢀ 5(b) ! L + 1(b)
H ꢀ 10(b) ! L(b)
H(a) ! L + 1(a)
406.2
402.9
401.1
3.05
3.08
3.09
0.0015
0.0005
0.0007
H(a) ! L + 1(a)
d ! d
H ꢀ 7(b) ! L + 1(b)
H ꢀ 10(b) ! L + 1(b)
H ꢀ 8(b) ! L + 1(b)
H ꢀ 9(b) ! L(b)
p(Cl) ! d
397.1
379.3
3.12
3.27
0.0024
0.0068
370.0(3.35)4560
p(Cl) ! d
p(pzH)/p(Cl) ! d
p(Cl), n(P), n(N) ! d
d ! d
377.4
362.8
3.28
3.42
0.0028
0.0008
H ꢀ 1(a) ! L(a)
H ꢀ 1(a) ! L + 1(a)
H ꢀ 11(b) ! L(b)
p(pzH)/p(pCl) ! d
p(Cl) ! d
359.5
358.6
3.45
3.46
0.0045
0.0091
H ꢀ 10(b) ! L + 1(b)
H ꢀ 8(b) ! L + 1(b)
H ꢀ 8(b) ! L + 1(b)
H ꢀ 4(b) ! L+2(b)
p(pzH)/p(Cl) ! d
p(pzH)/p(Cl) ! d
p(Ph) ! d
357.1
350.9
3.47
3.53
0.0058
0.0005
H ꢀ 2(a) ! L(a)
d ! d
338.0(3.67)6850
H ꢀ 1(a) ! L + 1(a)
H ꢀ 4(b) ! L+2(b)
H ꢀ 2(a) ! L(a)
p(Ph) ! d
349.5
350.0
334.8
331.2
3.55
3.56
3.71
3.74
0.0040
0.0002
0.0277
0.0298
d ! d
H ꢀ 7(b) ! L+2(b)
H ꢀ 9(b) ! L+2(b)
H ꢀ 8(b) ! L+2(b)
H ꢀ 12(b) ! L + 1(b)
H ꢀ 10(b) ! L+2(b)
H ꢀ 8(b) ! L+2(b)
H ꢀ 2(a) ! L + 1(a)
p(Cl) ! d
p(Cl), n(P), n(N) ! d
p(pzH)/p(Cl) ! d
p(pzH)/p(Cl) ! d
p(Cl) ! d
330.1
319.3
3.76
3.88
0.0230
0.0152
p(pzH)/p(Cl) ! d
d ! d
314.2
3.95
0.0004
H ꢀ 13(b) ! L + 1(b)
H ꢀ 14(b) ! L(b)
H ꢀ 4(a) ! L(a)
p(Cl) ! d
297.5
291.6
276.5
4.17
4.25
4.48
0.0187
0.0134
0.0133
293.2(4.23)18,515
p(Cl) ! d
p(Ph), n(P) ! d
p(Ph)/p(Cl) ! d
p(Cl) ! d
H ꢀ 3(a) ! L(a)
H ꢀ 8(a) ! L(a)
267.2
4.64
0.0285
H ꢀ 16(b) ! L + 1(b)
H ꢀ 16(b) ! L + 1(b)
H ꢀ 8(a) ! L + 1(a)
H ꢀ 4(a) ! L(a)
p(Cl)/r(Cl) ! d
p(Cl)/r(Cl) ! d
p(Cl) ! d
266.4
257.2
4.65
4.82
0.0217
0.0170
p(Ph), n(P) ! d
H ꢀ 1(a) ! L(a)
d ! p*(Ph)
d ! p*(Ph)
247.7
246.5
5.01
5.03
0.0294
0.0114
231.6(5.35)54,400
H(b) ! L+4(b)
H ꢀ 2(a) ! L+2(a)
(
ꢀ
ꢁꢀ
ꢈ
ꢉꢁꢀ1
Nb2g2?
kT
2D
kT
The experimental magnetic data of complex 2 were fitted
to the empirical relations proposed earlier [46]. The parallel
and perpendicular zero field susceptibilities (Eqs. (5) and
(6)) were corrected by the factor predicted from the molec-
ular field (Eq. (4)) [42,44]:
vI?
¼
1 þ 9 exp
ꢀ
,
)
ꢈ
ꢉ
D
kT
þ 3Nb2g2? tanh
4D
(
, )
ꢈ
ꢉ
ꢈ
ꢉ
ꢀ
ꢈ
ꢉꢁ
ꢂ
ꢃ
ꢂ ꢃ
Nb2g2II
4kT
2D
J
kT
J
J
J
2kT
1 þ 9 exp ꢀ kT exp
þ sec h2
2
ð6Þ
kT
ꢅ
tanh
ꢂ
ꢃ
vII ¼
ꢃ
ð5Þ
2D
2kT
1 þ exp ꢀ kT

B. Machura et al. / Polyhedron 25 (2006) 1348–1358
1357
Table 9
The energy and molar absorption coefficients of absorption bands and the electronic transitions calculated with the TDDFT method for 2
The most important orbital excitations
Character
k (nm)
E (eV)
f
Experimental k (nm) (E [eV]) e
H ꢀ 5(b) ! L(b)
H(b) ! L(b)
p(Cl)/p(Ph) ! d
p(Ph)/n(P) ! d
p(Ph)/n(P) ! d
p(Ph)/n(P) ! d
p(Ph)/p(Cl) ! d
p(Ph) ! d
527.1
2.35
0.0005
490.0(2.53)1650
H(b) ! L(b)
513.6
486.4
473.0
456.1
2.41
2.55
2.62
2.72
0.0028
0.0037
0.0022
0.0043
H(b) ! L + 1(b)
H ꢀ 1(b) ! L(b)
H ꢀ 2(b) ! L(b)
H ꢀ 1(b) ! L + 1(b)
p(Ph)/p(Cl) ! d
447.5
438.3
432.1
420.1
2.77
2.83
2.87
2.95
0.0025
0.0015
0.0042
0.0014
408.4(3.04)2180
H ꢀ 4(b) ! L(b)
p(Ph) ! d
H ꢀ 2(b) ! L + 1(b)
H ꢀ 7(b) ! L + 1(b)
H ꢀ 5(b) ! L + 1(b)
H ꢀ 8(b) ! L(b)
p(Ph) ! d
p(Cl) ! d
p(Cl)/p(Ph) ! d
p(Cl) ! d
413.6
3.00
0.0014
H(a) ! L+2(a)
d ! d
393.6
393.1
390.1
383.5
374.2
3.15
3.15
3.18
3.23
3.31
0.0002
0.0030
0.0031
0.0003
0.0023
382.0(3.25)2715
339.0(3.66)6150
H ꢀ 8(b) ! L + 1(b)
H ꢀ 9(b) ! L(b)
H(a) ! L + 1(a)
H ꢀ 10(b) ! L(b)
p(Cl) ! d
p(Cl), n(P), n(N) ! d
d ! d
p(Cl)/p(pyz) ! d
H ꢀ 1(a) ! L + 1(a)
H ꢀ 2(a) ! L + 1(a)
H ꢀ 2(a) ! L(a)
d ! d
361.4
358.5
352.4
336.2
334.9
329.9
3.43
3.46
3.52
3.69
3.70
3.70
0.0003
0.0004
0.0218
0.0379
0.0131
0.0194
d ! d
D ! p*(pyz)
p(Cl) ! d
p(Cl) ! d
p(Cl)/p(pyz) ! d
p(Ph)/p(Cl) ! d
d ! d
H ꢀ 7(b) ! L+2(b)
H ꢀ 8(b) ! L+2(b)
H ꢀ 10(b) ! L+2(b)
H ꢀ 6(b) ! L+2(b)
H ꢀ 1(a) ! L+2(a)
H ꢀ 2(a) ! L+2(a)
H ꢀ 14(b) ! L + 1(b)
H ꢀ 15(b) ! L(b)
328.8
326.1
308.5
297.8
279.6
3.77
3.80
4.02
4.16
4.43
0.0046
0.0054
0.0119
0.0126
0.0261
d ! d
p(Cl)/d ! d
p(Cl)/r(Cl) ! d
p(Ph) ! d
275.2(4.51)22,715
230.2(5.39)58,225
H ꢀ 3(a) ! L + 1(a)
Since our data concern powdered sample, the experi-
mental magnetic susceptibility is equal vav = 1/3vII +
2/3v^. The least-squares fit of the experimental data using
this equation was limited to the whole temperature range
and leads to D = ꢀ21.3 cmꢀ1, J = ꢀ1.19 cmꢀ1, zJ0 =
ꢀ0.58 cmꢀ1 and gav = 1.72. The agreement factor R de-
A negative value of the exchange parameter suggests the
presence of weak antiferromagnetic interactions between
ReIV ions at crystal lattice.
The occurrence of a bulky ligands result in the diamag-
netic dilution due to increasing distance between the para-
magnetic ReIV centers, the magnetic interaction might be
transmitted by hydrogen bonds.
2
2
fined as R ¼ Rni¼1ðvmexp ꢀ vmcalcÞ =Rni¼1ðvemxp
Þ
is 1.14 · 10ꢀ4
.
0.06
0.05
0.04
0.03
0.02
0.01
0.00
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0.30
0.25
0.20
0.15
0.10
0.05
0.00
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0
50
100
150
200
250
300
0
50
100
150
200
250
300
T [K]
T [K]
Fig. 5. Thermal dependence of vM (d) and vMT (s) for [ReCl4(pzH)-
(PPh3)] (1) vM (d). The solid line is the calculated curve.
Fig. 6. Thermal dependence of vM (d) and vMT (s) for [ReCl4(pyz)-
(PPh3)] (2). The solid line is the calculated curve.

1358
B. Machura et al. / Polyhedron 25 (2006) 1348–1358
[17] C.E. Powell, M.P. Cifuentes, A.M. McDonagh, S.K. Hurst, N.T.
4. Conclusions
Lucas, C.D. Delfs, R. Stranger, M.G. Humphrey, S. Houbrechts, I.
Asselberghs, A. Persoons, D.C.R. Hockless, Inorg. Chim. Acta 352
(2003) 9.
Two novel Re(IV) compounds – [ReCl4(pzH)(PPh3)] (1)
and [ReCl4(pyz)(PPh3)] (2) – have been prepared and struc-
turally as well as spectroscopically characterized. The
geometries of 1 and 2 were optimized in quartet and
doublet states using the DFT method with the B3LYP
functional. The energies of the doublet states of 1 and 2
complexes are higher, which is consistent with the results
of magnetic measurements. The values of effective magnetic
moments of 1 and 2 complexes at 300 K correspond to
three unpaired electrons and confirm (dxz)1(dyz)1(dxy)1
configuration of the rhenium atoms in 1 and 2.
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5. Supplementary data
Supplementary data for C21H19Cl4N2PRe and
C22H19Cl4N2PRe are available from the CCDC, 12 Union
Road, Cambridge CB2 1EZ, UK on request, quoting the
deposition numbers: 276935 for 1 and 276936 for 2.
Acknowledgments
The GAUSSIAN03 calculations were carried out in the
Wrocław Centre for Networking and Supercomputing,
WCSS, Wrocław, Poland. Crystallographic part was
financed by funds allocated by the Ministry of Scientific
Research and Information Technology to the Institute of
General and Ecological Chemistry, Technical University
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