P-Tolylimido rhenium(V) complexes - Synthesis, X-ray studies, spectroscopic characterization and DFT calculations

Article abstract of DOI:10.1016/j.poly.2010.05.011

The p-tolylimido rhenium(V) complexes [Re(p-NC₆H ₄CH₃)X₃(EPh₃)₂] (X = Cl, Br; E = As, P) and [Re(p-NC₆H₄CH₃)Cl ₂(hmpbta)(PPh₃)]·MeCN h

Full text of DOI:10.1016/j.poly.2010.05.011

Polyhedron 29 (2010) 2381–2392
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
p-Tolylimido rhenium(V) complexes – Synthesis, X-ray studies, spectroscopic
characterization and DFT calculations
*
´
B. Machura , M. Wolff, A. Switlicka, I. Gryca
Department of Crystallography, Institute of Chemistry, University of Silesia, 9th Szkolna St., 40-006 Katowice, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
The p-tolylimido rhenium(V) complexes [Re(p-NC6H4CH3)X3(EPh3)2] (X = Cl, Br; E = As, P) and
[Re(p-NC6H4CH3)Cl2(hmpbta)(PPh3)]ꢀMeCN have been synthesized and characterized spectroscopically
and structurally. The electronic spectra of [Re(p-NC6H4CH3)Cl3(PPh3)2] and [Re(p-NC6H4CH3)Cl2-
(hmpbta)(PPh3)](Hhmpbta-2-(20-hydroxy-50-methylphenyl)benzotriazole) were investigated at the
TDDFT level employing B3LYP functional in combination with LANL2DZ. Additional information about
bonding between the rhenium atom and p-tolylimido ligand in the complexes [Re(p-NC6H4CH3)Cl3-
(PPh3)2] and [Re(p-NC6H4CH3)Cl2(hmpbta)(PPh3)] was obtained by NBO analysis.
Received 20 March 2010
Accepted 7 May 2010
Available online 23 May 2010
Keywords:
Rhenium imido complexes
X-ray structure
DFT calculations
NBO analysis
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
rating specific targeting molecules on the substituents at the nitro-
gen site. Although kit preparations for the imaging of almost all
Imido complexes are known for the majority of the d-block
metals, and they are in the center of scientific interest in context
of basic research and employment of them in catalysis. These com-
pounds have been successfully employed in the catalytic hydroam-
ination of alkynes, the synthesis of various nitrogen heterocycles,
alkene metathesis, activation of hydrocarbons including methane,
and in cycloaddition reactions with unsaturated organic substrates
[1–6].
The properties of the metal–nitrogen bond can vary greatly
with differences in the steric and electronic environment, and
the coordinated imido ligand can adopt a variety of geometries:
terminal linear (A), terminal bent (B), doubly bridging (C) and tri-
ply bridging (D) [1–6].
main organs and organ systems exist and there is some experience
in the labeling of biomolecules, there is still a need for new ap-
proaches and new labeling procedures. It is obvious that promising
contributions are expected from the coordination chemistry and
organometallic chemistry which plays an important role in the
development of novel rhenium and technetium radiopharmaceuti-
cals. It is a challenge for synthetic chemists to supply novel meth-
ods and compound for the radiopharmaceutical community [7].
In this context, the design, synthesis and reactivity of novel imi-
do rhenium complexes has become the aim of several laboratories,
including ours.
The first arylimido rhenium complexes were synthesized by
Chatt and Rowe in 1962 using aniline as the source of the imido
ligand. The analogous [Re(NAr)X3(PPh3)2] compounds were subse-
quently reported [8–22], but surprisingly, only few of them were
structurally examined, namely [Re(NC6H5)Cl3(PPh3)2]ꢀCH2Cl2 [12]
[Re(NC6H5)Cl3(PPh3)2]ꢀCHCl3 [13], [Re(NC6H5)Cl2(OMe)(PPh3)2]ꢀ
CH2Cl2 [14], [Re(o-NC6H4NHCH3)Br2Cl(PPh3)2] [15], [Re(o,o-
NC6H4(OH)(NH2)Cl3(PPh3)2] [16], [Re(o-NC6H4NHPh)Cl3(PPh3)2]ꢀ
CH2Cl2 [17], [Re(p-NC6H4COONC4H4O2)Cl3(PPh3)2]ꢀCH2Cl2ꢀEtOH
[18], [Re(m-NC6H4COCH3)Cl3(PPh3)2]ꢀ(CH3)2CO [19], [Re(o-NC6-
M
M
M
N
R
M
N
B
N
R
N
C
M
R
R
M
M
D
A
A thorough understanding of bonding between transition metals
and imido ligands is of great theoretical and commercial interest.
Recently, high-valent imido complexes of Tc and Re have been
also proposed as potential radiopharmaceuticals as alternatives
to oxo and nitrido compounds owing to the possibility of incorpo-
H4NH2)Cl3(PPh3)2]
[20],
[Re(p-NC6H4(CH2)3COOEt)Cl3(PPh3)2]
[21], [Re(p-NC6H4NH2)Cl3(PPh3)2]ꢀPPh3 [22]. Although the complex
[Re(p-NC6H4CH3)Cl3(PPh3)2] has been known and used as starting
material in the synthesis of arylimido rhenium complexes, its crys-
tal and molecular structure has not been determined so far.
In the first step of our studies we have structurally character-
ized the imido Re(V) complexes [Re(p-NC6H4CH3)X3(PPh3)2]
* Corresponding author.
E-mail address: basia@ich.us.edu.pl (B. Machura).
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.05.011

2382
B. Machura et al. / Polyhedron 29 (2010) 2381–2392
2.3. [Re(p-NC6H4CH3)Br3(PPh3)2] (2)
/cmꢁ1): 3016 (m), 1591 (m), 1481 (m), 1434 (s), 1389
HO
N
N
IR (KBr;
m
N
(w), 1340 (w), 1306 (w), 1196 (w), 1174 (w), 1096 (m), 1029 (w),
824 (m), 744 (m), 709 (sh), 693 (s), 564 (w), 522 (s), 512 (sh),
500 (sh), 449 (w).
CH3
UV–Vis (CH3CN; kmax [nm] (e
; [dm3 molꢁ1 cmꢁ1])): 712.6 (250),
Scheme 1. Structure of Hhmpbta ligand.
344.3 (14450), 255.3 (38650), 222.2 (179100).
Anal. Calc. for C43H37Br3P2NRe: C, 48.93; H, 3.53; N, 1.33. Found:
C, 48.85; H, 3.55; N, 1.48%.
(X = Cl, Br), as well as we have synthesized and examined their ar-
sine analogues [Re(p-NC6H4CH3)X3(AsPh3)2] for the first time.
The second step of our study has concerned the reactivity of
[Re(p-NC6H4CH3)Cl3(PPh3)2] towards 2-(20-hydroxy-50-methyl-
phenyl)benzotriazole (Hhmpbta, see Scheme 1).
2.4. Preparation of [Re(p-NC6H4CH3)Cl3(AsPh3)2] (3)
trans-[ReOCl3(AsPh3)2] (0.5 g, 0.54 mmol) and p-toluidine
(0.85 g, 0.79 mmol) in benzene (100 ml) was refluxed for 6 h under
argon atmosphere. The resulting solution was reduced in volume
to ꢃ10 ml, and green crystalline precipitate of 3 was filtered off
and dried in the air. X-ray quality crystals were obtained by recrys-
tallization from acetonitrile. Yield 60%.
Recently some oxo rhenium complexes incorporating this
ligand have been synthesized and characterized [23], but imido
transition metal compounds of 2-(20-hydroxy-50-methyl-
phenyl)benzotriazole are unknown. Furthermore, to our best
knowledge only two other transition metal complexes with
hmpbtaꢁ ion are structurally characterized so far – [MoO2(a-
IR (KBr; m
/cmꢁ1): 3056 (m), 1590 (m), 1571 (sh), 1483 (m), 1435
cac)(hmpbta)] and [{VO(acac)2}(l-L)] (acac – acetylacetonate). In
the Mo complex the 2-(20-hydroxy-50-methylphenyl)benzotriazo-
late ion is coordinated in a bidentate mode, whereas in the V oxo-
complex – as bridging ligand [24].
(s), 1338 (w), 1310 (w), 1189 (w), 1169 (w), 1076 (m), 1025 (w),
823 (m), 738 (m), 692 (s), 559 (w), 472 (s) and 457(sh), 444(w).
UV–Vis (CH3CN; kmax [nm] (e
; [dm3 molꢁ1 cmꢁ1])): 759.4 (130),
342.0 (16530), 245.0 (64800), 220.4 (120790).
Anal. Calc. for C43H37Cl3As2NRe: C, 51.13; H, 3.69; N, 1.39.
Found: C, 51.63; H, 3.57; N, 1.43%.
The experimental studies on the imido rhenium complexes
have been accompanied computationally by the density functional
theory (DFT) and time-dependent DFT calculations. Currently den-
sity functional theory (DFT) is commonly used to examine the elec-
tronic structure of transition metal complexes. It meets with the
requirements of being accurate, easy to use and fast enough to al-
low the study of relatively large molecules of transition metal com-
plexes [25,26].
2.5. Preparation of [Re(p-NC6H4CH3)Br3(AsPh3)2] (4)
A procedure similar to that for 3 was used with trans-[ReO-
Br3(AsPh3)2] (0.50 g, 0.47 mmol) and p-toluidine (0.80, 0.75 mmol).
Yield 55%.
Additional information about bonding between the rhenium
atom and imido ligand in [Re(p-NC6H4CH3)Cl3(PPh3)2] and [Re(p-
NC6H4CH3)Cl2(hmpbta)(PPh3)] has been obtained by NBO analysis.
IR (KBr; m
/cmꢁ1): 3054 (w), 1591 (m), 1572 (sh), 1482 (m), 1434
(s), 1361 (w) 1337 (w), 1301 (w), 1186 (m), 1169 (m), 1114 (m),
1074 (m), 1024 (w), 821 (s), 736 (s), 692 (s), 648 (w), 616 (w),
561 (m), 475 (s) and 453(m), 444(w).
2. Experimental
UV–Vis (CH3CN; kmax [nm] (e
; [dm3 molꢁ1 cmꢁ1])): 632.3 (375),
344.6 (24760), 240.0 (84620), 220.7 (180590).
Anal. Calc. for C43H37Br3As2NRe: C, 45.16; H, 3.26; N, 1.22.
Found: C, 45.40; H, 3.36; N, 1.29%.
2.1. General procedure
The syntheses of [Re(p-NC6H4CH3)X3(AsPh3)2] were carried out
under argon atmosphere. The solvents were of reagent grade and
used as received. Ammonium perrhenate, triphenylphosphine, tri-
phenylarsine and p-toluidine were purchased from Aldrich. The
complexes [ReOX3(EPh3)2] (X = Cl, Br; E = As, P) and [Re(p-
NC6H4CH3)X3(PPh3)2] were prepared according to the literature
methods [27,9].
Infrared spectra were recorded on a Nicolet Magna 560 spectro-
photometer in the spectral range 4000 ꢂ 400 cmꢁ1 with the sam-
ples in the form of potassium bromide pellets. Electronic spectra
were measured on a spectrophotometer Lab Alliance UV–Vis
8500 in the range 1100 ꢂ 180 nm in deoxygenated acetonitrile
solution. 1H NMR spectrum was obtained in CDCl3 using Bruker
Avance 400 spectrometer. Elemental analysis (C H N) was per-
formed on a Perkin-Elmer CHN-2400 analyzer.
2.6. Preparation of [Re(p-NC6H4CH3)Cl2(hmpbta)(PPh3)2]ꢀMeCN
(5ꢀMeCN)
[Re(p-NC6H4CH3)Cl3(PPh3)2] (0.50 g, 0.54 mmol) was added to
2-(20-hydroxy-50-methylphenyl)benzotriazole (0.14 g, 0.62 mmol)
in acetonitrile (50 ml) and the reaction mixture was refluxed for
5 h. The resulting solution was reduced in volume to ꢃ10 ml and al-
lowed to cool to room temperature. A green crystalline precipitate
of 5ꢀMeCN was filtered off and dried in the air. X-ray quality crystals
were obtained by recrystallization from acetonitrile Yield 80%.
IR (KBr; m
/cmꢁ1): 3049 (w), 1590 (m), 1570 (w), 1482 (m), 1433
(s), 1355 (w), 1317 (w), 1187 (m), 1169 (m), 1089 (m), 1017 (m),
819 (m), 744 (s), 694 (s), 619(w), 561 (m), 520 (s), 497 (s), 453
(m) and 418(w).
1H NMR (CDCl3, ppm): d = 7.94 (d,1H), 7.88 (d,1H), 7.54 (t,1H),
7.32–7.20 (m,10H), 7.12–7.05 (m,6H), 7.16 (t,1H), 6.96 (d,2H),
6.88 (d,1H), 6.81 (d,3H), 2.28 (s,3H), 2.03 (s,3H).
Anal. Calc. for C40H35PCl2N5ORe: C, 53.99; H, 3.96; N, 7.87.
Found: C, 54.25; H, 3.89; N, 7.98%.
2.2. [Re(p-NC6H4CH3)Cl3(PPh3)2] (1)
IR (KBr; m
/cmꢁ1): 3060 (m), 1590 (m), 1572 (w), 1483 (m), 1434
(s), 1338 (w), 1310 (w), 1198 (w), 1170 (w), 1089 (m), 1016 (w),
822 (m), 745 (m), 694 (s), 561 (w), 521 (s), 509 (s), 494(m), 458
(w) and 444(w).
2.7. Crystal structures determination and refinement
1H NMR (CDCl3, ppm): d = 7.96–7.88 (m, 10H), 7.26–7.21 (m,
20H), 6.69 (t, 2H) 6.48 (t, 2H) 2.11 (s, 3H).
The X-ray intensity data of 1–5 were collected on a Gemini A Ul-
Anal. Calc. for C43H37Cl3P2NRe: C, 56.00; H, 4.04; N, 1.52. Found:
C, 50.64; H, 3.97; N, 1.63%.
tra diffractometer equipped with Atlas CCD detector and graphite
monochromated Mo K
a
radiation (k = 0.71073 Å) at room

B. Machura et al. / Polyhedron 29 (2010) 2381–2392
2383
temperature. Details concerning crystal data and refinement are gi-
ven in Table 1. Lorentz, polarization and empirical absorption cor-
rection using spherical harmonics implemented in SCALE3
ABSPACK scaling algorithm [28] were applied. The structures 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 hydrogen atoms were treated as ‘‘riding” on their parent car-
bon atoms and assigned isotropic temperature factors equal 1.2
(non-methyl) and 1.5 (methyl) times the value of equivalent tem-
perature factor of the parent atom. The methyl groups were al-
lowed to rotate about their local threefold axis. SHELXS 97 and
SHELXL 97 [29] programs were used for all the calculations. Atomic
scattering factors were those incorporated in the computer
programs.
equation formalism (IEF-PCM) [37]. For complexes 1 and 5, 120
and 110 singlet–singlet spin-allowed excitations in solution were
taken into account, respectively.
Natural bond orbital (NBO) calculations were performed with
the NBO code [38] included in GAUSSIAN 03.
3. Results and discussion
3.1. Synthesis
The diamagnetic complexes [Re(p-NC6H4CH3)X3(EPh3)2] (X = Cl,
Br; E = As, P) have been prepared in good yield by a standard meth-
od – in the reactions of trans-[ReOX3(EPh3)2] with an excess of p-
toluidine in benzene
[ReOX3(EPh3)2] + p-H2N-C6H4-CH3 ? [Re(p-
NC6H4CH3)X3(EPh3)2] + H2O (X = Cl, Br; E = P, As).
2.8. Computational details
Since the complexes [ReOX3(AsPh3)2] easily transform into [Re-
OX3(AsPh3)(OAsPh3)] in solution in air [39], the syntheses of [Re(p-
NC6H4CH3)X3(AsPh3)2] were carried out under argon atmosphere.
The substitution reaction of [Re(p-NC6H4CH3)Cl3(PPh3)2] with
2-(20-hydroxy-50-methylphenyl)benzotriazole (Hhmpbta) leads to
the formation of the neutral imido compound [Re(p-
NC6H4CH3)Cl2(hmpbta)(PPh3)]ꢀMeCN.
The gas phase geometries of 1 and 5 were optimised without
any symmetry restrictions in singlet ground-states with the DFT
method using the hybrid B3LYP functional of GAUSSIAN 03 [30–32].
The calculations were performed using ECP LANL2DZ basis set
[33] with an additional d and f function with the exponent
a
= 0.3811 and 2.033 [34] for the rhenium and the standard 6-
All the complexes 1–5 are formally rhenium(V) compounds
with the p-tolylimido unit as a dianionic NR2ꢁ ligand. Since the
imido core NR2ꢁ is isoelectronic to the core O2ꢁ and tends to form
analogous complexes with rhenium, a short comparison with the
Re(V) oxocompounds deserves comment.
31G basis set for the other atoms. For chlorine, oxygen, nitrogen
and phosphorous atoms, diffuse and polarization functions were
added [35]. All vibrations in the calculated vibrational spectrum
of 1 and 5 were real, thus the both geometries correspond to true
energy minimum.
The electronic spectra of 1 and 5 were calculated with the
TDDFT method [36], and the solvent effect (acetonitrile) was sim-
ulated using the polarizable continuum model with the integral
The [ReOX3(EPh3)2] (X = Cl, Br; E = P, As) complexes are conve-
nient starting materials. In the reactions with uninegative N,O-do-
nor chelate ligand they form mono- and di-substituted compounds
of [ReOX2(N–O)(EPh3)] and [ReOX(N–O)2] type [23,40–46]. The
Table 1
Crystal data and structure refinement for 1, 2, 3, 4 and 5ꢀMeCN.
1
2
3
4
5ꢀMeCN
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
C
43H37Cl3P2NRe
C43H37Br3P2NRe
1055.61
293(2)
0.71073
monoclinic
P21/n
C43H37Cl3As2NRe
1010.13
293(2)
0.71073
monoclinic
P21/c
C43H37Br3As2NRe
1143.51
293.0(2)
0.71073
monoclinic
P21/n
C40H35Cl2N5OPRe
889.80
293(2)
922.23
293(2)
0.71073
monoclinic
P21/c
0.71073
triclinic
ꢀ
P1
14.4134(2)
10.8466(17)
24.3129(4)
–
97.106(17)
–
3771.8(6)
4
1.624
12.5079(2)
14.0679(2)
22.5556(3)
–
101.786(2)
–
3885.21(10)
4
1.805
14.3802(2)
10.9126(2)
24.7596(3)
–
96.239(2)
–
3862.4(10)
4
1.737
12.650(3)
14.089(3)
22.661(5)
90
100.77(3)
90
3967.6(14)
4
1.914
10.610(2)
12.830(3)
14.498(3)
92.07(3)
104.89(3)
103.04(3)
1848.8(6)
2
b (Å)
c (Å)
a
(°)
b (°)
(°)
c
Volume (Å3)
Z
Dcalc (Mg mꢁ3
)
1.598
3.513
884
Absorption coefficient (mmꢁ1
F(0 0 0)
)
3.552
1832
6.327
2048
5.086
1976
7.771
2192
Crystal size (mm)
h Range for data collection (°)
Index ranges
0.166 ꢄ 0.120 ꢄ 0.070
3.38–25.00
ꢁ17 6 h 6 16
ꢁ12 6 k 6 12
ꢁ28 6 l 6 28
35 792
0.158 ꢄ 0.157 ꢄ 0.007
3.33–25.00
ꢁ14 6 h 6 14
ꢁ16 6 k 6 16
ꢁ26 6 l 6 26
37 667
0.225 ꢄ 0.106 ꢄ 0.101
3.43–25.00
ꢁ17 6 h 6 17
ꢁ12 6 k 6 12
ꢁ29 6 l 6 29
37 903
0.228 ꢄ 0.201 ꢄ 0.114
3.44–25.00
ꢁ15 6 h 6 15
ꢁ16 6 k 6 16
ꢁ26 6 l 6 26
37 152
0.102 ꢄ 0.118 ꢄ 0.08
3.39–25.00
ꢁ12 6 h 6 12
ꢁ15 6 k 6 15
ꢁ17 6 l 6 17
34 860
Reflections collected
Independent reflections (Rint
)
6622 (0.0323)
99.8
0.635–1.000
6622/0/452
0.966
6828 (0.0271)
99.8
0.475–1.000
6828/0/452
0.942
6785 (0.0270)
99.8
0.522–1.000
6785/0/452
1.011
6966 (0.0407)
99.7
0.387–1.000
6966/0/452
1.027
6510 (0.0255)
99.8
0.853–1.000
6510/0/454
1.011
Completeness to 2h = 25° (%)
Minimum and maximum transmission
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
Final R indices [I > 2
r
(I)]
R1 = 0.0176
wR2 = 0.0377
R1 = 0.0244
wR2 = 0.0386
0.488 and ꢁ0.426
R1 = 0.0183
wR2 = 0.0398
R1 = 0.0292
wR2 = 0.041
0.504 and ꢁ0.556
R1 = 0.0210
wR2 = 0.0452
R1 = 0.0291
wR2 = 0.0464
0.732 and ꢁ0.473
R1 = 0.0256
wR2 = 0.0559
R1 = 0.0457
wR2 = 0.0591
0.623 and ꢁ0.766
R1 = 0.0180
wR2 = 0.0426
R1 = 0.0224
wR2 = 0.0432
0.735 and ꢁ0.331
R indices (all data)
Largest difference peak and hole [e Åꢁ3
]

2384
B. Machura et al. / Polyhedron 29 (2010) 2381–2392
course of these reactions depends on many factors, including type
of the ligand and reaction conditions. The title 2-(20-hydroxy-50-
methylphenyl)benzotriazole (Hhmpbta) reacts with [ReOX3-
(EPh3)2] complexes to give monosubstituted [ReOX2(hmpb-
ta)(EPh3)]ꢀMeCN stereoisomers with cis halide arrangement [23].
The imido rhenium complexes incorporating uninegative N,O-
donor chelate ligands have been studied relatively rarely [47,48].
The [Re(p-NC6H4CH3)X3(EPh3)2] complexes are supposed to react
in similar way to the analogous [ReOX3(EPh3)2]. The examined
reaction of [Re(p-NC6H4CH3)Cl3(PPh3)2] with 2-(20-hydroxy-
50-methylphenyl)benzotriazole (Hhmpbta) seems to support
this hypothesis. Likewise as [ReOCl3(PPh3)2], the [Re(p-
NC6H4CH3)Cl3(PPh3)2] complex reacts with Hhmpbta to give cis-
the methyl groups of the hmpbtaꢁ and imido ligands as singlets
at 2.28 and 2.03 ppm. The aromatic region of the 1H NMR spectrum
is more difficult to identify, owing to some overlapping of the sig-
nals of the aromatic protons of phosphine, organoimido and
hmpbtaꢁ ligands. However, the phenyl proton of the coordinated
PPh3 molecule appear as two multiplets in the ranges 7.32–7.20
and 7.12–7.05 ppm. The benzotriazole protons appear in the range
7.12–7.05 and downfield as three singlets at 7.94, 7.88, 7.54 ppm.
The protons of the phenyl-imido and phenyl-subsituent of benzo-
triazole ring (in hmpbtaꢁ ligand) fall upfield as doublets and trip-
lets in the range 7.16 –6.80 ppm. In the both spectra of 1 and 5
there is no evidence of paramagnetic broadening, confirming that
complexes [Re(p-NC6H4NH2)Cl3(PPh3)2] and [Re(p-NC6H4CH3)Cl2-
(hmpbta)(PPh3)]ꢀMeCN are diamagnetic.
[Re(p-NC6H4CH3)Cl2(hmpbta)(PPh3)]ꢀMeCN.
Surprisingly,
the
cis-X,X arrangement in the [Re(NAr)X2(N-O)(PPh3)] complexes
has not been confirmed so far [47], whereas the majority of the
known [ReOX2(O–N)(PPh3)] structures has halide ligands in cis
geometry [23,40–46].
3.2. X-ray studies
The crystallographic data of 1–4 and 5ꢀMeCN are summarized in
Table 1. The short intra- and intermolecular contacts detected in
the imido complexes are gathered in Table 2. In the structures
[Re(p-NC6H4CH3)X3(EPh3)2] (X = Cl, Br; E = As, P) and [Re(p-
NC6H4CH3)Cl2(hmpbta)(PPh3)]ꢀMeCN the classical hydrogen bonds
can not be found, only some C–Hꢀ ꢀ ꢀX, C–Hꢀ ꢀ ꢀO and C–Hꢀ ꢀ ꢀN weak
inter- and intramolecular hydrogen bonds exist [49,50].
Similar to the related imido complexes it is extremely difficult
to identify the Re-NC6H4CH3 stretches in the IR spectra of 1–5, as
they may be mixed with mC
@
N
and mP–C modes of PPh3 and
hmpbtaꢁ ligands [8–22]. The experimental vibrational spectra of
1 and 5 are compared to the calculated (non-scaled) ones (Figs. 1
and 2). For both complexes the calculated
m(Re-NC6H4CH3) fre-
quencies appear at ꢃ1425 and 1050 cmꢁ1
.
In the 1H NMR spectra of 1 and 5 the aromatic region containing
signals from protons of the phenyl groups of the imido and tri-
phenylphosphine molecules (8.00–6.40 ppm) is accompanied by
distinctive signals corresponding the alkyl protons of p-methylph-
enylimido and hmpbtaꢁ ligands (2.30–2.00 ppm). The 1H NMR
spectrum of 1 measured in CDCl3 shows the phenyl-imido reso-
nances as a two triplets at 6.69 and 6.48 ppm, methyl-imido reso-
3.3. [Re(p-NC6H4CH3)X3(EPh3)2] complexes
All the complexes [Re(p-NC6H4CH3)X3(EPh3)2] show octahedral
geometry about the central rhenium atom defined by the p-meth-
ylphenylimido group, three halide ions in meridional geometry and
the two mutually trans-triphenylphosphine or triphenylarsine
molecules. The ligands cis to the p-methylphenylimido group are
all bowed slightly away from p-NC6H4CH3 moiety to minimize ste-
ric congestion around the rhenium atom.
nances as
a singlet at 2.11 ppm and phenyl proton of the
coordinated PPh3 molecules as two multiplets in the ranges
7.96–7.88 and 7.26–7.21 ppm. The 1H NMR spectrum of 5 shows
Fig. 1. The experimental and calculated (non-scaled) vibrational spectra of 1.

B. Machura et al. / Polyhedron 29 (2010) 2381–2392
2385
Fig. 2. The experimental and calculated (non-scaled) vibrational spectra of 5.
Table 2
Short intra- and intermolecular contacts detected in 1–4 and 5ꢀMeCN.
D–Hꢀ ꢀ ꢀA
D–H
Hꢀ ꢀ ꢀA
Dꢀ ꢀ ꢀA
D–Hꢀ ꢀ ꢀA
1
C5–H5ꢀ ꢀ ꢀCl1_#1
C14–H14ꢀ ꢀ ꢀCl2
C20–H20ꢀ ꢀ ꢀCl2
C30–H30ꢀ ꢀ ꢀCl2
C30–H30ꢀ ꢀ ꢀCl3
0.93
0.93
0.93
0.93
0.93
2.71
2.58
2.80
2.72
2.66
3.513(3)
3.394(3)
3.628(3)
3.339(3)
3.380(3)
144.8
146.1
148.9
124.5
135.0
2
C8–H8ꢀ ꢀ ꢀBr2
C14–H14ꢀ ꢀ ꢀBr2
C20–H20ꢀ ꢀ ꢀBr2
0.93
0.93
0.93
2.88
2.88
2.82
3.679(3)
3.751(3)
3.562(3)
144.7
155.7
138.1
3
C8–H8ꢀ ꢀ ꢀCl2
C8–H8ꢀ ꢀ ꢀCl3
C20–H20ꢀ ꢀ ꢀCl2
C28–H28ꢀ ꢀ ꢀCl2_#2
C33–H33ꢀ ꢀ ꢀCl1_#3
0.93
0.93
0.93
0.93
0.93
2.81
2.71
2.67
2.82
2.71
3.435(4)
3.448(4)
3.493(4)
3.592(4)
3.512(4)
125.9
137.0
148.1
141.2
144.7
4
C26–H26ꢀ ꢀ ꢀBr2
0.93
2.89
3.679(5)
142.9
5ꢀMeCN
C6–H6ꢀ ꢀ ꢀO1
0.93
0.93
0.93
0.93
2.44
2.61
2.78
2.43
3.237(4)
3.168(3)
3.631(3)
2.746(4)
143.2
118.7
152.2
99.7
C27–H27ꢀ ꢀ ꢀN1
C30–H30ꢀ ꢀ ꢀCl2_#2
C37–H37ꢀ ꢀ ꢀN4
#1: ꢁx, 1ꢁy, 1ꢁz; #2: 1ꢁx, 2ꢁy, 1ꢁz; #3: ꢁx, 1ꢁy, 1ꢁz.
Fig. 3. The molecular structure of 1. Displacement ellipsoids are drawn at 50%
probability.
The molecular structure of 1 is presented in Fig. 3, the molecular
structures of 2, 3 and 4 are analogous. The selected bond lengths
and angles of 1–4 are collected in Tables 3 and 4.
The Re(1)–N(1)–C(37) bond angles in the structures [Re(p-
NC6H4CH3)X3(EPh3)2] [170.32(17)° for 1, 176.87(19)° for 2 and
169.4(2)° for 3 and 176.8(3)° for 4] agree with the linear coordina-
tion mode of the arylimido ligands. The Re–N(1) bond lengths of
[Re(p-NC6H4CH3)X3(EPh3)2] [1.7113(19) Å for 1, 1.710(2) Å for 2
and 1.726(3) Å for 3 and 1.707(3) Å for 4] fall in the range 1.67–
1.74 Å, typical of mononuclear complexes of rhenium(V) having
[Re„NR]3+ core, and indicate the presence of a triple bond Re„N
[8–22]. These values are in good agreement with those for mer,-
trans-[Re(NPh)Cl3(PPh3)2] (1.726(6) Å and 172.6(6)°) and [Re(4-
NC6H4NH2)Cl3(PPh3)2] (1.719(4) Å and 177.2(4)°) [12,22].

2386
B. Machura et al. / Polyhedron 29 (2010) 2381–2392
Table 3
The experimental and optimised bond lengths (Å) and angles (°) for 1.
Bond lengths
Experimental
Optimised
Bond angles
Experimental
Optimised
Re(1)–N(1)
Re(1)–Cl(1)
Re(1)–Cl(2)
Re(1)–Cl(3)
Re(1)–P(1)
Re(1)–P(2)
1.7173(19)
2.3973(7)
2.4102(6)
2.4398(7)
2.4936(6)
2.4871(6)
1.713
2.489
2.477
2.515
2.558
2.545
N(1)–Re(1)–Cl(1)
N(1)–Re(1)–Cl(2)
Cl(1)–Re(1)–Cl(2)
N(1)–Re(1)–Cl(3)
Cl(1)–Re(1)–Cl(3)
Cl(2)–Re(1)–Cl(3)
N(1)–Re(1)–P(1)
Cl(1)–Re(1)–P(1)
Cl(2)–Re(1)–P(1)
Cl(3)–Re(1)–P(1)
N(1)–Re(1)–P(2)
Cl(1)–Re(1)–P(2)
Cl(2)–Re(1)–P(2)
Cl(3)–Re(1)–P(2)
P(1)–Re(1)–P(2)
Re(1)–N(1)–C(37)
96.17(6)
174.04(6)
89.79(2)
87.82(6)
176.00(2)
86.22(2)
97.11(6)
87.40(2)
83.14(3)
92.41(2)
94.13(6)
89.25(2)
85.90(3)
90.17(2)
168.55(2)
90.59
176.35
90.59
89.28
177.48
87.25
96.04
90.19
84.99
88.31
95.98
89.07
83.01
91.97
167.97
175.34
Table 4
The experimental bond lengths (Å) and angles (°) for 2, 3, 4 complexes.
Bond lengths
2
3
4
Bond angles
2
3
4
X = Br
X = Cl; E = As
X = Br; E = As
X = Br
X = Cl; E = As
X = Br; E = As
Re(1)–N(1)
Re(1)–X(1)
Re(1)–X(2)
Re(1)–X(3)
Re(1)–E(1)
Re(1)–E(2)
1.710(2)
1.726(3)
1.707(3)
N(1)–Re(1)–X(1)
N(1)–Re(1)–X(2)
X(1)–Re(1)–X(2)
N(1)–Re(1)–X(3)
X(3)–Re(1)–X(1)
X(3)–Re(1)–X(2)
N(1)–Re(1)–E(1)
E(1)–Re(1)–X(1)
E(1)–Re(1)–X(2)
E(1)–Re(1)–X(3)
N(1)–Re(1)–E(2)
E(2)–Re(1)–X(1)
E(2)–Re(1)–X(2)
E(2)–Re(1)–X(3)
E(1)–Re(1)–E(2)
Re(1)–N(1)–C(37)
92.26(6)
96.20(8)
175.18(8)
88.47(3)
88.78(8)
174.95(3)
86.57(3)
93.52(8)
90.20(2)
85.25(2)
90.30(2)
97.32(8)
87.21(2)
84.07(2)
91.37(2)
169.065(11)
169.4(2)
91.41(10)
177.68(10)
86.883(14)
92.30(10)
176.242(15)
89.420(15)
90.45(10)
89.507(13)
91.10(2)
89.892(13)
91.11(10)
92.541(13)
87.40(2)
2.5595(3)
2.5832(3)
2.5730(3)
2.5005(7)
2.4859(7)
2.3920(8)
2.4080(8)
2.4327(8)
2.5569(3)
2.5612(3)
2.5681(7)
2.5755(8)
2.5582(6
2.5546(10)
2.5551(10)
176.01(7)
90.617(9)
90.69(6)
176.769(10)
86.500(9)
90.82(7)
89.271(17)
91.99(2)
89.371(17)
90.94(7)
88.353(16)
86.376(18)
92.916(17)
177.10(2)
176.87(19)
87.960(13)
177.392(14)
176.8(3)
The Re–P and Re–Cl bond distances fall within the normal range
in six-coordinate rhenium complexes [12–22].
rous atoms (plane A), 0.0401(8) Å from the plane formed by the
two nitrogen, one halogen and oxygen atoms (plane B) and
0.0065(7) Å from the plane formed by nitrogen, oxygen, halogen
and phosphorous atoms (plane C). Least squares plane A is inclined
at 89.25(5)° to plane B and at 88.90(5)° to plane C; planes B and C
are inclined at 87.49(5)°, respectively.
The interatomic distance between the rhenium atom and the
oxygen atom of hmpbtaꢁ ligand is shorter than an ideal single
Re–O bond length (ca. 2.04 Å) [51], indicating small delocalization
in the N(1)–Re(1)–O(1) moiety. The Re–N(1) bond length of [Re(p-
NC6H4CH3)Cl2(hmpbta)(PPh3)]ꢀMeCN [1.720(2) Å] falls in the range
1.67–1.74 Å, typical of mononuclear complexes of rhenium(V) hav-
ing [Re„NR]3+ core, and indicate the presence of a triple bond
Re„N [8–22]. The Re(1)–N(1)–C(19) bond angle in the structure
[Re(p-NC6H4CH3)Cl3(PPh3)2] [175.99(18)°] agrees with the linear
coordination mode of the p-NC6H4CH3 ligand [52–54].
3.4. cis-[Re(p-NC6H4CH3)Cl2(hmpbta)(PPh3)]ꢀMeCN complex
The
perspective
drawing
of
[Re(p-NC6H4CH3)Cl2-
(hmpbta)(PPh3)]ꢀMeCN is presented in Fig. 4, and the selected bond
distances and angles of 5ꢀMeCN are collected in Table 5. The rhe-
nium atom is coordinated by p-methylphenylimido group, two
chloride ions, the phosphorus atom of PPh3 molecule and the
bidentate N,O donor of the 2-(20-hydroxy-50-methylphenyl)ben-
zotriazolato ligand. The oxygen atom of 2-(20-hydroxy-50-methyl-
phenyl)benzotriazolato ligand occupies trans position to the 4-
methylphenylimido ion and triphenylphosphine molecule with
their
p-acidity adopts cis position with respect to the RN„Re–O
unit. Consequently, the RN„Re–O core with multiply bonded imi-
The elongation of the Re(1)–Cl(2) distance trans to the phospho-
rus atom of PPh3 molecule in comparison with Re(1)–Cl(1) bond
trans to the nitrogen atom of the 2-(20-hydroxy-50-methyl-
phenyl)benzotriazolato ligand in 5ꢀMeCN is a consequence of struc-
tural trans effect of the PPh3 ligand.
do ligand is stabilized to some extent due to accessible
from rhenium to triphenylphosphine molecule.
p-donation
The chloride ions of 5ꢀMeCN are arranged in cis geometry, sim-
ilar as in the related [ReOCl2(hmpbta)(PPh3)]ꢀMeCN. The majority
of the known [ReOX2(O–N)(PPh3)] structures has halide ligands
in cis geometry [23,40–46], whereas the cis-X,X arrangement in
the [Re(NAr)X2(N–O)(PPh3)] complexes has been confirmed for
the first time. The chloride ions of the known [Re(p-NC6H4CH3)
Cl2(RN=CHC6H4O)(PPh3)] (R = Ph, Me) occupy trans positions to
each other [47].
3.5. Geometry optimisation, charge distribution, electronic structure
and NBO analysis
The geometries of the complexes 1 and 5 were optimised in sin-
glet states using the DFT method with the B3LYP functional. The
optimised geometric parameters are gathered in Tables 3 and 5.
The Re(1) atom of 5ꢀMeCN is displaced 0.1569(6) Å from the
plane formed by the two halogen, one nitrogen and one phospho-

B. Machura et al. / Polyhedron 29 (2010) 2381–2392
2387
Table 6
Atomic charges from the Natural Population Analysis (NPA) for [Re(p-
NC6H4CH3)Cl3(PPh3)2] (1) and [Re(p-NC6H4CH3)Cl2(hmpbta)(PPh3)] (5).
Atom
1
5
Re(1)
Cl(1)
Cl(2)
Cl(3)
P(1)
ꢁ0.554
ꢁ0.315
ꢁ0.292
ꢁ0.337
1.528
0.773
ꢁ0.429
ꢁ0.464
1.384
P(2)
1.535
N(1)
O(1)
N(2)
ꢁ0.161
ꢁ0.315
ꢁ0.689
ꢁ0.278
and 6, respectively. In discussion of the orbital character the local
symmetry of the rhenium center has been considered; for complex
1: z-axis goes along the N(1)–Re–Cl(2) linkage, and x-axis – through
the P(1)–Re–P(2) bonds; for complex 5: z-axis goes along the N(1)–
Re–O(1) linkage, and x-axis – through the P(1)–Re–Cl(2) bonds.
The highest occupied MO of 1 is of rhenium dxy type with an
antibonding contribution from p chloride orbitals. The dyz, dxy
,
p
dz2 and dx2
orbitals of the central atom constitute mainly the
ꢁy2
LUMO, LUMO+1, LUMO+2 and LUMO+3, respectively. The dyz and
dxy rhenium orbitals bear antibonding character towards the p
p
nitrogen orbitals of the imido ligand; the LUMO, LUMO+1 can be
considered as NR orbitals. The value of the energy separation
p
* „
Re
Fig. 4. The molecular structure of 5ꢀMeCN. Displacement ellipsoids are drawn at
between the highest occupied molecular orbital (HOMO) and the
lowest unoccupied molecular orbital (LUMO) equals to 2.99 eV.
The HOMO and HOMO-1 of 5 are of dxy type with some contri-
50% probability.
The calculated 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.
Table 6 presents the atomic charges from the Natural Popula-
tion Analysis (NPA) for 1 and 5. The calculated charge on the rhe-
nium atom in 5 is larger in comparison with the starting compound
[Re(p-NC6H4CH3)Cl3(PPh3)2] (1). However, the both values are con-
siderably lower than the formal charge +5. The populations of the
butions from p chloride and hmpbtaꢁ orbitals. The LUMO and
p
LUMO+1 can be ascribed as
p-antibonding rhenium–imido molec-
ular orbitals. The dx2 and dz2 rhenium orbital contributes to the
ꢁy2
LUMO+3 and LUMO+8, respectively. The value of the energy sepa-
ration between the highest occupied molecular orbital (HOMO)
and the lowest unoccupied molecular orbital (LUMO) of 5 equals
to 3.13 eV. This value is considerable higher in comparison with
the HOMO–LUMO gap of 1 being the starting material in the syn-
thesis of [Re(p-NC6H4CH3)Cl2(hmpbta)(PPh3)]. The bigger absolute
value of the energy gap means better stability, and explains easily
formation of 5 in the reaction of 1 with 2-(20-hydroxy-50-methyl-
phenyl)benzotriazole. On the other hand the complex 5 seems to
be only more stable than the related oxocompound [ReOCl2(hmpb-
ta)(AsPh3)] with HOMO–LUMO gap equal to 3.10 eV [23].
The nature of the rhenium–imido ligand interaction in 1 and 5
has been studied by NBO analysis. The occupancy and composition
of the calculated Re–NR natural bond orbitals (NBOs) are given in
Table 7.
d
xy, dxz, dyz, dx2ꢁy2 and dz2 rhenium orbitals are following: 1.078,
1.949, 0.911, 1.146 and 1.046 for 1 and 1.004, 1.036, 1.050, 1.223
and 1.485 for 5. It confirms significant charge donation from the
NR2ꢁ and hmpbtaꢁ ligands, chloride ions and triphenylphosphine
molecule.
The [Re(p-NC6H4CH3)Cl3(PPh3)2] and [Re(p-NC6H4CH3)Cl2-
(hmpbta)(PPh3)] are closed-shell structures. Their partial molecu-
lar orbital diagrams with the several highest occupied and lowest
unoccupied molecular orbital contours are presented in Figs. 5
Table 5
The experimental and optimised bond lengths [Å] and angles [°] for 5ꢀMeCN.
Bond lengths
Experimental
Optimised
Bond angles
Experimental
Optimised
Re(1)–N(1)
Re(1)–O(1)
Re(1)–N(2)
Re(1)–Cl(1)
Re(1)–P(1)
Re(1)–Cl(2)
1.720(2)
1.9881(17)
2.140(2)
2.3744(9)
2.4560(13)
2.4319(13)
1.724
2.022
2.151
2.452
2.529
2.471
N(1)–Re(1)–O(1)
N(1)–Re(1)–N(2)
O(1)–Re(1)–N(2)
N(1)–Re(1)–Cl(1)
O(1)–Re(1)–Cl(1)
N(2)–Re(1)–Cl(1)
N(1)–Re(1)–P(1)
O(1)–Re(1)–P(1)
N(2)–Re(1)–P(1)
Cl(1)–Re(1)–P(1)
N(1)–Re(1)–Cl(2)
O(1)–Re(1)–Cl(2)
N(2)–Re(1)–Cl(2)
Cl(1)–Re(1)–Cl(2)
Cl(2)–Re(1)–P(1)
Re(1)–N(1)–C(19)
172.58(8)
93.14(9)
80.68(7)
97.28(7)
89.36(6)
167.56(6)
90.36(7)
86.52(6)
98.47(6)
88.28(3)
95.24(7)
88.37(6)
85.27(6)
87.01(4)
173.09(2)
175.99(18)
173.49
97.30
80.95
94.13
88.41
166.70
90.64
83.41
97.62
89.00
94.13
89.39
83.49
88.48
172.44
173.30

2388
B. Machura et al. / Polyhedron 29 (2010) 2381–2392
π*(PPh3)
π*(PPh3)
L+6
L+5
dz2, π*(PPh3)
L+3
-1.00
-2.00
-3.00
-4.00
-5.00
-6.00
-7.00
L+4
dx 2, π*(PPh3)
2
L+2
-y
dyz, π*(p-tol), π(Cl)
dxz, π*(p-tol), π(Cl)
L+1
LUMO
d
xy, π(Cl)
HOMO
H-1
n(P), π(PPh3), π(Cl)
H-2
H-3
H-4
π(p-tol), dxz, π(Cl)
π(PPh3)
Fig. 5. The energy (eV), character and some contours of the unoccupied molecular orbitals of [Re(p-NC6H4CH3)Cl3(PPh3)2] (1). 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 legend, the reader is referred to the web
version of this article.)
In the both imido complexes, three Re–NR natural bond orbitals
were detected. The Re–N bond orbital of -character is strongly
of the spectrum, only transitions with oscillator strengths larger
than 0.030 are listed in Tables 8 and 9.
r
polarized towards the nitrogen atom, and the s and p nitrogen
orbitals and s and d rhenium orbitals take part in the bond forma-
The investigated complexes are of large size; the numbers of ba-
sis functions are equal to 838 for 1 and 786 for 6. The calculated
electron transitions do not comprise all the experimental absorp-
tion bands. Thus the shortest wavelength experimental bands of
the examined complexes are not assigned to the calculated transi-
tions or the assignment is not complete.
tion. The Re–N bond orbitals of
p-character are result of overlap-
ping of the empty dxy and dyz rhenium orbitals with the occupied
px and pz orbitals of the deprotonated nitrogen of the imido ligand.
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 occupied and unoccupied orbitals in-
volved in the electronic transitions.
3.6. Electronic spectra
The experimental and calculated electronic spectra of 1 and 5
are presented in Figs. 7 and 8, respectively. The positions of absorp-
tion bands for the other [Re(p-NC6H4CH3)X3(EPh3)2] complexes are
3.7. Electronic spectrum of 1
given in the experimental part. Each calculated transition for 1 and
2
5 is represented by a gaussian function y ¼ ceꢁbx with the height
The low-energy absorption band of 1 originates from the
HOMO ? LUMO and HOMO ? LUMO+1 transitions. As it can be
(c) equal to the oscillator strength and b equal to 0.04 nmꢁ2
.
Tables 8 and 9 present the most important electronic transi-
tions calculated with the TDDFT method assigned to the observed
absorption bands of 1 and 5, respectively. For the high energy part
seen from the Fig. 5, the HOMO is composed of p chloride orbitals
and dxy rhenium atomic orbital, the LUMO and LUMO+1 are delo-
p
calized on central ion and
p-antibonding orbitals of the p-meth-

B. Machura et al. / Polyhedron 29 (2010) 2381–2392
2389
π*(p-tol), π*(PPh3)
L+6
π*(PPh3)
π*(PPh3)
L+5
L+4
-1.00
-2.00
-3.00
-4.00
-5.00
-6.00
-7.00
dx 2, π*(PPh3)
2
-y
L+3
L+2
π*(hmpbta), π*(p-tol), dyz
dyz, π*(hmpbta), π*(p-tol)
dxz, π*(p-tol)
L+1
LUMO
dxy, π(hmpbta), π(Cl)
dxy, π(hmpbta), π(Cl)
HOMO
H-1
π(p-tol), π(hmpbta), dyz
π(p-tol), π(hmpbta), dyz
π(PPh3)
H-2
H-3
H-4
Fig. 6. The energy (eV), character and some contours of the unoccupied molecular orbitals of [Re(p-NC6H4CH3)Cl2(hmpbta)(PPh3)] (5). 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 legend, the reader is referred to the
web version of this article.)
Table 7
The occupancy and composition of the calculated natural bond orbitals (NBOs) between the rhenium and the p-tolylimido ligand for [Re(p-NC6H4CH3)Cl3(PPh3)2] (1) and [Re(p-
NC6H4CH3)Cl2(hmpbta)(PPh3)] (5).
BD
Occupancy
Composition of NBO
BD*
Occupancy
1
Re–N
Re–N
Re–N
1.94
1.97
1.90
0.520 (sp0.33d2.50 Re + 0.854 (sp0.74
0.627 (d)Re + 0.779 (p)N
0.664 (d)Re + 0.748 (p)N
)
)
N
0.854 (sp0.33d2.50
0.779 (d)Re ꢁ 0.627 (p)N
0.748 (d)Re ꢁ 0.664 (p)N
)
Re ꢁ 0.520 (sp0.74
)
0.23
0.18
0.25
N
5
Re–N
Re–N
Re–N
1.96
1.97
1.92
0.486 (sp0.01d2.90
0.629 (d)Re + 0.777 (p)N
0.656 (d)Re + 0.755 (p)N
)
Re + 0.874(sp0.83
)
N
0.874 (sp0.01d2.90) ꢁ 0.486 (sp0.83
0.777 (d)Re ꢁ 0.629 (p)N
)
N
0.30
0.22
0.35
0.755 (d)Re ꢁ 0.656 (p)N
BD denotes 2-center bond; * denotes antibond NBO.
ylphenylimido ligand. Accordingly, the transition at 716.1 nm can
be seen as a delocalized MLLCT (Metal–Ligand-to-Ligand CT) transi-
tion. However, considering that the molecular orbitals, involved in
the electronic transitions assigned to the longest wavelength
experimental band, comprise mainly rhenium 5d atomic orbitals
(Fig. 3), the HOMO ? LUMO and HOMO ? LUMO+1 transitions
may be ascribed as transitions of d ? d character.
The transitions assigned to the experimental bands at 344.3
and 253.0 nm can be seen as mixed (Cl)/ (p-tol)/ (PPh3) ?
Re ( Ligand–Metal Charge Transfer; LMCT) and (Cl)/ (p-tol)/
(PPh3) ? *(p-tol) ( Ligand–Ligand Charge Transfer; LLCT)
transitions.
p
p
p
p
p
p
p
The absorption band at 221.5 nm results mainly from Ligand–Li-
gand Charge Transfer and interligand (IL) transitions.

2390
B. Machura et al. / Polyhedron 29 (2010) 2381–2392
2.00
1.60
1.20
0.80
0.40
Fig. 7. The experimental (black) and calculated (red) electronic absorption spectra
of [Re(p-NC6H4CH3)Cl3(PPh3)2] (1). (For interpretation of the references to colour in
this figure legend, the reader is referred to the web version of this article.)
0.00
400.00
800.00
[nm]
3.8. Electronic spectrum of 5
Fig. 8. The experimental (black) and calculated (red) electronic absorption spectra
of [Re(p-NC6H4CH3)Cl2(hmpbta)(PPh3)] (5). (For interpretation of the references to
colour in this figure legend, the reader is referred to the web version of this article.)
Likewise for 1, the longest wavelength experimental band of 5
may be attributed to the transition of d ? d character or may be
Table 8
The energy and molar absorption coefficients of experimental absorption bands and the electronic transitions calculated with the TDDFT method for [Re(p-NC6H4CH3)Cl3(PPh3)2]
(1).
The most important orbital excitations
Character
k (nm)
E (eV)
f
Experimental
K (nm) (E (eV)) e
H ? L
H ? L+1
d/
d/
p
(Cl) ? d/
p
*(p-tol)
*(p-tol)
684.0
648.3
1.81
1.91
0.0001
0.0011
716.1 (1.73) 200
p(Cl) ? d/
p
H-2 ? L
H-7 ? L
H-8 ? L
H-10 ? L
H-11 ? L
H-6 ? L
H-16 ? L
H-13 ? L+1
H-12 ? L+1
p
p
p
p
p
p
p
p
p
(p-tol)/d/
(PPh3) ? d/
(PPh3)/ (p-tol) ? d/
(PPh3) ? d/ *(p-tol)
(Cl)/ (p-tol)/
(PPh3) ? d/
(Cl)/
(PPh3) ? d/
p
(Cl) ? d/
p
*(p-tol)
366.7
354.7
347.2
345.9
332.5
3.38
3.50
3.57
3.58
3.73
0.0906
0.0830
0.0326
0.0300
0.0329
344.1 (3.60) 13 600
p*(p-tol)
p
p*(p-tol)
p
p
p(PPh3) ? d/
p
*(p-tol)
p*(p-tol)
p
(p-tol) ? d/
*(p-tol)
(p-tol)/ (PPh3) ? d/
p*(p-tol)
306.4
302.4
4.05
4.10
0.0425
0.0596
p
(Cl)/
p
p
p
*(p-tol)
H ? L+5
d/
p(Cl) ?
p*(PPh3)
291.4
4.26
0.0405
253.0 (4.90) 28 100
H-15 ? L+1
H-1 ? L+2
H-17 ? L+1
H-18 ? L+1
H-19 ? L
H-1 ? L+3
H-4 ? L+2
H-1 ? L+4
H-11 ? L+2
H-1 ? L+7
H ? L+13
H-1 ? L+7
H-1 ? L+6
p
p
p
p
p
p
p
p
p
p
(Cl)/
(Cl)/n(P)/
(PPh3)/
p
(PPh3) ? d/
p
*(p-tol)
p
(PPh3) ? d/
p*(PPh3)
288.9
283.0
279.0
268.2
262.9
257.4
255.7
242.1
4.29
4.38
4.44
4.62
4.72
4.82
4.85
5.12
0.2812
0.0703
0.0605
0.0403
0.0821
0.0363
0.0459
0.0421
p
(Cl) ? d/
*(p-tol)
*(p-tol)
(PPh3) ? d/
(PPh3) ? d/ *(PPh3)
(Cl)/n(P)/ (PPh3) ?
(Cl)/ (p-tol)/ (PPh3) ? d/
(Cl)/n(P)/ (PPh3) ?
(Cl) ? *(PPh3)
p*(p-tol)
(Cl) ? d/
p
(Cl) ? d/
p
(Cl)/n(P)/
p
p*(PPh3)
p
p
p*(PPh3)
p
p
p
*(PPh3)
p
p*(p-tol)/
p
*(PPh3)
*(PPh3)
d/
p
p
p
p
241.9
5.13
0.0459
(Cl)/n(P)/
p
(PPh3) ?
(PPh3) ?
p
p
*(p-tol)/
*(PPh3)
p
(Cl)/n(P)/
p
H-2 ? L+4
H-22 ? L
p
r
p
p
p
p
(p-tol)/
(N) ? d/
(p-tol) ? d/
(PPh3)/ (Cl) ?
p
(Cl)/d ?
*(p-tol)
*(PPh3)
*(PPh3)
(PPh3) ? *(p-tol)/
*(PPh3)
*(p-tol)/d
*(PPh3)
p
*(PPh3)
233.9
232.7
232.2
5.30
5.33
5.34
0.0306
0.0368
0.0407
221.5 (5.60) 59 040
p
H-14 ? L+2
H-5 ? L+5
H-1 ? L+8
H-4 ? L+5
H ? L+17
H-10 ? L+4
H-11 ? L+4
H-11 ? L+3
p
p
p
(Cl)/n(P)/
p
p
p*(PPh3)
(PPh3) ?
p
228.3
224.5
5.43
5.52
0.0376
0.0354
d/
p(Cl) ?
p
p
p
p
(PPh3) ? p
(Cl)/
(Cl)/
p
p
(p-tol)/
(p-tol)/
p
(PPh3) ?
p*(PPh3)
p(PPh3) ? d/
p
*(PPh3)
e
– molar absorption coefficient [dm3 molꢁ1 cmꢁ1]; f – oscillator strength; H – highest occupied molecular orbital; L – lowest unoccupied molecular orbital.

B. Machura et al. / Polyhedron 29 (2010) 2381–2392
2391
Table 9
The energy and molar absorption coefficients of experimental absorption bands and the electronic transitions calculated with the TDDFT method for [Re(p-
NC6H4CH3)Cl2(hmpbta)(PPh3)] (5).
The most important orbital excitations
Character
k (nm)
E (eV)
f
Experimental
K (nm) (E(eV)) e
H ? L
H ? L+1
H ? L+1
H-1 ? L
H ? L+1
H ? L+2
H-1 ? L+2
H-2 ? L
H-4 ? L
d/
d/
d/
d/
d/
d/
d/
p
p
p
p
p
p
p
(hmpbta)/
(hmpbta)/
(hmpbta)/
(hmpbta)/
(hmpbta)/
(hmpbta)/
(hmpbta)/
p
p
p
p
p
p
p
(Cl) ? d/
(Cl) ? d/
(Cl) ? d/
(Cl) ? d/
(Cl) ? d/
(Cl) ? d/
(Cl) ? d/
p
p
p
p
p
p
p
*(p-tol)
621.9
601.2
482.1
470.1
1.99
2.06
2.57
2.64
0.0055
0.0004
0.0426
0.1082
582.5 (2.13) 300
*(hmpbta)/
*(hmpbta)/
*(p-tol)
*(hmpbta)/
*(hmpbta)/
*(hmpbta)/
p
p
*(p-tol)
*(p-tol)
401.3 (3.10) 14 700
320.0 (3.87) 23 150
p*(p-tol)
p*(p-tol)
p*(p-tol)
415.7
391.2
365.6
354.5
348.0
340.8
337.4
2.98
3.17
3.39
3.50
3.56
3.64
3.67
0.1624
0.0801
0.0458
0.0543
0.0442
0.1997
0.0697
p
p
p
p
p
p
p
p
p
p
p
p
p
(p-tol)/
(PPh3) ? d/
(p-tol)/ (hmpbta)/d ? d/
(hmpbta)/d ? d/ *(p-tol)
(PPh3) ? d/ *(hmpbta)/ *(p-tol)
(p-tol)/ (hmpbta)/d ? d/ *(hmpbta)/
(PPh3) ? d/ *(p-tol)
p(hmpbta)/d ? d/
p
*(p-tol)
p
*(p-tol)
H-3 ? L
H-5 ? L
p
p
*(p-tol)
p
H-4 ? L+1
H-3 ? L+1
H-7 ? L
H-5 ? L+1
H-5 ? L+1
H-7 ? L
p
p
p
p
p*(p-tol)
p
333.0
332.4
3.72
3.73
0.0666
0.0333
(hmpbta)/d ? d/
(hmpbta)/d ? d/
p
p
*(hmpbta)/
*(hmpbta)/
p
p
*(p-tol)
*(p-tol)
(PPh3) ? d/
(p-tol)/ (hmpbta)/d ? d/
(Cl)/ (p-tol)/ (O) ? d/ *(p-tol)
(PPh3) ? d/ *(hmpbta)/ *(p-tol)
(hmpbta)/ (Cl) ? *(PPh3)/d
p*(p-tol)
H-2 ? L+2
H-13 ? L
H-9 ? L+1
H-1 ? L+4
H-13 ? L+1
H-14 ? L
H-8 ? L+2
H-14 ? L+1
H-4 ? L+3
H-17 ? L+1
H-6 ? L+3
H-8 ? L+3
H-1 ? L+10
H-15 ? L+2
H-15 ? L+2
H-1 ? L+13
H ? L+12
H-18 ? L+1
H-3 ? L+5
H-4 ? L+5
H-19 ? L+1
H-12 ? L+3
H-19 ? L+1
H-1 ? L+13
H-8 ? L+4
H-6 ? L+5
p
p
*(hmpbta)/
p*(p-tol)
315.2
308.6
304.4
284.3
280.9
279.6
279.4
273.2
254.5
252.3
246.6
244.0
239.1
3.93
4.02
4.07
4.36
4.41
4.43
4.44
4.54
4.87
4.91
5.03
5.08
5.19
0.0802
0.0407
0.0399
0.0304
0.1174
0.0349
0.0311
0.0302
0.0371
0.0654
0.0361
0.0563
0.0423
p
p
p
p
p
p
d/
p
p
260.2 (4.76) 24 180
255.7 (4.85) 51 980
p
p
p
p
p
p
p
p
(Cl)/
(Cl)/
p
p
(p-tol)/
(p-tol)/
p
p
(O) ? d/
(O) ? d/
p
p
*(hmpbta)/
*(p-tol)
p*(p-tol)
(PPh3)/
(Cl)/ (p-tol)/
(PPh3) ? d/
(Cl)/ (hmpbta)/
(PPh3) ? d/ *(PPh3)
(PPh3)/ (Cl) ? d/
(hmpbta)/
p
(Cl) ? d/
(O) ? d/
*(PPh3)
(N) ? d/p*(hmpbta)/p*(p-tol)
p*(hmpbta)/
p
*(p-tol)
p
p
p
*(hmpbta)/p
*(p-tol)
p
p
p
p
p
p*(PPh3)
d/
p
p
(Cl) ?
p*(PPh3)/d
p(hmpbta)/d ? d/
p*(hmpbta)/
p
p
*(p-tol)
*(p-tol)
p(hmpbta)/d ? d/
p*(hmpbta)/
238.6
5.20
0.0609
d/
d/
p
p
(hmpbta)/
p
(Cl) ?
(Cl) ?
p
p
*(hmpbta)
*(PPh3)/ *(hmpbta)/d
*(hmpbta)/ *(p-tol)
*(PPh3)/d
(hmpbta)/
p
p
p
p
p
p
p
p
d/
p
p
(Cl)/
(p-tol)/
(PPh3) ?
(hmpbta) ? d/
(Cl) ? d/ *(PPh3)
(hmpbta) ? d/ *(hmpbta)/
(hmpbta)/ (Cl) ?
(PPh3)/ (Cl) ? *(PPh3)/d
(PPh3) ? *(PPh3)/d
p
(hmpbta)/
(hmpbta)/d ?
*(PPh3)/d
*(hmpbta)/
p
(N)/d ? d/
p
p
231.6
229.8
5.35
5.39
0.0640
0.0305
p
p
p
p
p
*(p-tol)
*(p-tol)
228.9
228.4
5.42
5.43
0.0405
0.0347
p
p
p
p
p
p*(hmpbta)
227.2
226.1
5.46
5.48
0.0434
0.0313
p
p
p
e
– Molar absorption coefficient [dm3 molꢁ1 cmꢁ1]; f – oscillator strength; H – highest occupied molecular orbital; L – lowest unoccupied molecular orbital.
seen as a delocalized MLLCT (Metal–Ligand-to-Ligand CT) transi-
tions. The same character can be assigned to the experimental
absorption at 401.3 nm.
The PPh3 molecule is cis-located in relation to the Re„N moiety,
which forces the metal nonbonding d electrons to lie in the plane
perpendicular to the M„N bond axis.
The transitions assigned to the experimental bands at 320.0,
260.2 and 255.7 nm can be seen as mixed Ligand–Metal Charge
Transfer (LMCT),Metal–Ligand Charge Transfer (LMCT) andLigand–Li-
gand Charge Transfer (LLCT) transitions.
Supplementary data
CCDC 770324–770328 contain the supplementary crystallo-
graphic data for
C43H37Cl3P2NRe, C43H37Br3P2NRe, C43H37Cl3-
4. Conclusions
As2NRe, C43H37Br3As2NRe and C40H35Cl2N5OPRe. These data can
be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/
retrieving.html, or from the Cambridge Crystallographic Data Cen-
tre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-
033; or e-mail: deposit@ccdc.cam.ac.uk.
The complexes [Re(p-NC6H4CH3)X3(EPh3)2] (X = Cl, Br; E = As, P)
have been characterized structurally and spectroscopically. Like-
wise as the analogous oxocomplexes [ReOX3(EPh3)2] (X = Cl, Br;
E = As, P), they seem to be convenient starting materials in the
reactions with uninegative N,O-donor chelate ligand. [Re(p-
NC6H4CH3)Cl3(PPh3)2] reacts with 2-(20-hydroxy-50-methyl-
phenyl)benzotriazole (Hhmpbta) forming [Re(p-NC6H4CH3)
Cl2(hmpbta)(PPh3)]ꢀMeCN. It is the first imido rhenium(V) com-
pound of [Re(NAr)X2(NꢁO)(PPh3)] type with cis-Cl,Cl arrangement.
For all the examined complexes, the structural studies and NBO
analysis confirm a linear coordination mode of the p-NC6H4CH3 li-
gand and triple bond between the rhenium and the imido ligand.
Acknowledgements
The GAUSSIAN 03 calculations were carried out in the Wrocław
Centre for Networking and Supercomputing, WCSS, Wrocław, Po-
land, http://www.wcss.wroc.pl, under calculational Grant No. 51/
96.

2392
B. Machura et al. / Polyhedron 29 (2010) 2381–2392
H.P. Hratchian, J.B. Cross, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann, O.
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