Preparation and crystal structure of (2,2′-bibenzimidazole) dihalobis(triphenylphospine)rhenium(III) halides

Article abstract of DOI:10.1016/j.poly.2004.01.012

The reaction of ReOX₃(PPh₃)₂ (where X=Cl, Br) with 2,2^′-bibenzimidazole (bibzimH₂) in the presence of excess PPh₃ yields the rhenium(III) cationic complexes [ReX₂(PPh₃)₂(bibzimH₂)]X, in which the phosphines are trans to one another, whereas the plane perpendicular to this direction includes the chelating bidentate bibzimH₂ and two cis halogen ligands. The third halogen is a halide counter-ion, attached to the complex cation via a pair of N-H?X^- hydrogen bonds involving the two N-H groups of bibzimH₂. Crystallographic work on the chloro compound indicates that the departure from octahedral geometry is controlled by the bite of the bibzimH₂ ligand and that the presence of the phenylene groups does not introduce substantial steric hindrance. Despite the fact that the species is paramagnetic, the ¹H NMR spectra were fully assigned.

Full text of DOI:10.1016/j.poly.2004.01.012

Polyhedron 23 (2004) 1139–1144
www.elsevier.com/locate/poly
Preparation and crystal structure of
(2,20-bibenzimidazole)dihalobis(triphenylphospine)rhenium(III)
halides
*
ꢀ
Franßcois Baril-Robert, Andre L. Beauchamp
Dꢀepartement de chimie, Universitꢀe de Montrꢀeal, C.P. 6128, Succursale Centre-ville, Montrꢀeal, QC, Canada H3C 3J7
Received 3 September 2003; accepted 18 January 2004
Abstract
The reaction of ReOX3(PPh3)2 (where X ¼ Cl, Br) with 2,20-bibenzimidazole (bibzimH2) in the presence of excess PPh3 yields the
rhenium(III) cationic complexes [ReX2(PPh3)2(bibzimH2)]X, in which the phosphines are trans to one another, whereas the plane
perpendicular to this direction includes the chelating bidentate bibzimH2 and two cis halogen ligands. The third halogen is a halide
counter-ion, attached to the complex cation via a pair of N–Hꢀ ꢀ ꢀXꢁ hydrogen bonds involving the two N–H groups of bibzimH2.
Crystallographic work on the chloro compound indicates that the departure from octahedral geometry is controlled by the bite of
the bibzimH2 ligand and that the presence of the phenylene groups does not introduce substantial steric hindrance. Despite the fact
1
that the species is paramagnetic, the H NMR spectra were fully assigned.
Ó 2004 Elsevier Ltd. All rights reserved.
Keywords: Rhenium; Benzimidazole; Bibenzimidazole; Crystal structure; Paramagnetic NMR
1. Introduction
and the other is not. Hydrogen bonding then takes place
with donors, acceptors, or more interestingly, with units
containing one of each, including monodeprotonated
biimidazolate itself, which gives access to an enlarged
variety of patterns for crystal engineering. This versa-
tility is well illustrated by the series of compounds re-
ported by Takodoro et al. [4–7]. Finally, fully
deprotonated dianionic biimidazolate can behave as a
bis-bidentate/chelating unit like the oxalate dianion and
link two metal centers into larger building blocks [8–10]
that could be considered in the development of molec-
ular devices [11,12].
In our previous contributions [13,14], we reported
that the Re(V) precursors ReOX3(PPh3)2 and Re-
O(OEt)X2(PPh3)2 are reduced cleanly by PPh3 in the
presence of biimH2, giving good yields of the rhenium(III)
cationic complexes cis,trans-[ReX2(PPh3)2(biimH2)]X
with X ¼ Cl, Br and I. The residual N–H protons of co-
ordinated biimH2 were found to be moderately acidic
and to participate in strong hydrogen-bonding interac-
tions, leading to tight ion pairs with halide or carbox-
ylate counter-ions. By using the smaller phosphine
PMe3, neutral complexes containing monodeprotonated
In the recent years, our laboratory has become in-
terested in the complexation of 2,20-biimidazole (bi-
imH2, Scheme 1) to various metal centers. In the
formally neutral form, two nitrogen donors in coplanar
rings can adopt a syn orientation leading to chelates
similar to those of bipyridine. However, biimH2 differs
from bipyridine by the presence of five-membered rings,
which change the bite angle for chelate formation and
allow for more conformational freedom about the con-
necting C2–C20 bond, thereby leading to oligomeric or
polymeric structures [1–3]. In both cases, the residual N–
H bonds generate in the crystal particular hydrogen-
bond patterns from which supramolecular assemblies
can be constructed. Extra structural features appear
when biimidazole coordinates in the monoanionic form,
since one of the uncoordinated nitrogens is protonated
* Corresponding author. Tel.: +514-343-6446; fax: +514-343-7586.
E-mail address: andre.beauchamp@umontreal.ca (A.L. Beau-
champ).
0277-5387/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2004.01.012

1140
F. Baril-Robert, A.L. Beauchamp / Polyhedron 23 (2004) 1139–1144
H
efficient and an extra purification step was introduced.
The yellow solid was dissolved in boiling NaOH, 0.25
M, and refluxed for 2 days. Some insoluble material was
filtered off and the dark-brown solution was neutralized
with concentrated HCl. The light-violet solid was fil-
tered, transferred into water and refluxed for 1 h to re-
move any ionic form of the molecule. Finally, the solid
was filtered, washed with water, ethanol and diethyl
ether, and dried in air. Yield: 24%.
H
N
N1
5
4
2
2'
N
N3
Scheme 1.
H
N
H
N1
8
5
7
6
2
2'
2.3. Preparation of [ReX2(PPh3)2(bibzimH2)]X
N3
N
A suspension of PPh3 (0.238 g; 0.91 mmol) and
bibzimiH2 (0.123 g; 0.52 mmol) in 40 mL CHCl3 is
heated to the boiling point, and ReOCl3(PPh3)2 (0.354
g; 0.42 mmol) is added. The lime-green solution darkens
quickly and the mixture is refluxed for 2.5 h. It is filtered
hot and evaporation of the resulting dark-red solution
yields a sticky dark-red material. Upon dropwise addi-
tion of diethyl ether, a red powder is obtained, which is
filtered and washed with diethyl ether. Crystals of the
solvent-free material are obtained by slow diffusion of
diethyl ether into a CH2Cl2 solution.
Scheme 2.
biimidazole could be isolated as dimers assembled by a
pair of complementary N–Hꢀ ꢀ ꢀN hydrogen bonds. This
study is being extended here to 2,2-bibenzimidazole
(bibzimH2, Scheme 2), in which the presence of phenylene
units opens a number of possibilities for ligand tuning via
substitution on the ring. We wish to report the prepara-
tion and structural characterization of the compounds
[ReX2(PPh3)2(bibzimH2)]X, which show that the extra
phenylene rings do not introduce appreciable steric
or other undesirable effects and that the chemistry of
the Re(III)-biimH2 systems is applicable to the bulkier
bibzimH2 system.
2.3.1. [ReCl2(PPh3)2(bibzimH2)]Cl
1
Yield: 77%. H NMR (CDCl3): see text. MS FABþ
(m/z): 1014 [M]þ, 752 [M ) PPh3]þ, 717 [M )
PPh3 ) Cl]þ. UV–Vis (k (nm) (e (Mꢁ1 cmꢁ1)): 558 (670),
522 (675), 469 (1350), 434 (1400), 404 (1200), 360 (8700),
341 (8750), 330 (6500). Composition was determined by
X-ray diffraction on a crystal picked up in the mor-
phologically homogeneous sample.
2. Experimental
2.1. Reactants and methods
2.3.2. [ReBr2(PPh3)2(bibzimH2)]Br
KReO4 and all other reactants were obtained from
Aldrich and used without further purification. Re-
OCl3(PPh3)2 [15] and ReOBr3(PPh3)2 [16] were prepared
by literature methods. Deuterated solvents were pur-
chased from Aldrich or CDN Isotopes.
Same as above, from ReOBr3(PPh3)2. Yield: 72%.
Anal. Calc. for C50H40Br3N4P2Re: C, 50.69; H, 3.40; N,
4.73. Found: C, 50.94; H, 3.42; N, 4.72%. 1H NMR
(CDCl3): see text. MS FABþ (m/z): 1102 [M]þ, 843
[M ) PPh3]þ, 762 [M ) PPh3-Br]þ.
The NMR spectra were measured with Bruker ARX-
400 or AMX-300 spectrometers. For the 1H spectra, the
residual solvent signals (DMSO-d6, 2.50 ppm; CDCl3,
7.26 ppm) were used as internal references and the
chemical shifts are expressed in ppm versus SiMe4.
Electronic spectra were recorded as CHCl3 solutions in
quartz cells with a UV–Vis–NIR Cary 5E spectrometer.
FABþ mass spectra in NBA were measured at the
2.4. X-ray diffraction study
To grow the crystals used for X-ray work, the powder
was placed in a vial and covered with acetone, the vial
was closed tightly and left at room temperature for a few
days. The powder dissolved slowly and reprecipitated as
less soluble red blocks of the solvate cis-[ReCl2(PPh3)2-
(bibzimH2)]Cl ꢀ 3(CH3)2CO. The X-ray data were col-
lected with a Bruker Smart 2K CCD diffractometer using
the graphite-monochromatized Cu Ka radiation, as
described elsewhere [18]. The data were interpreted with
the SHELXTL software [19]. The XPREP procedure [20]
was used to apply an absorption correction based on
crystal morphology. The non-hydrogen atoms were
generally refined anisotropically. The hydrogens were
first placed at idealized positions and allowed to ride
ꢀ
ꢀ
Centre de Spectrometrie de Masse de lÕUniversite de
ꢀ
Montreal. Elemental analyses were run at the Labora-
ꢀ
ꢀ
ꢀ
ꢀ
toire dÕAnalyse Elementaire de lÕUniversite de Montreal.
2.2. Preparation of the ligand
2,20-Bibenzimidazole was prepared as described by
Fieselmann et al. [17]. In our hands, the purification by
recrystallization from ethylene glycol was not totally

F. Baril-Robert, A.L. Beauchamp / Polyhedron 23 (2004) 1139–1144
1141
Table 1
Crystal data for [ReCl2(PPh3)2(bibzimH2)]Cl ꢀ 3(CH3)2CO
cycles. The final R factor of 0.055 is considered to be
satisfactory, considering the severe disorder present in
the structure. The crystal data are collected in Table 1.
A data set was also collected on red plates of the
solvent-free complex salt, grown by slow diffusion of
diethyl ether into a saturated CH2Cl2 solution of the
raw material. These crystals belong to space group Pbca,
Formula
Formula weight
T (K)
C59H58Cl3N4O3P2Re
1225.58
220(2)
Diffractometer
Crystal system
Space group
Bruker Smart CCD 2K
monoclinic
P21=n (no. 14)
14.4209(2)
23.6633(4)
16.7633(2)
94.860(1)
ꢁ
ꢁ
a (A)
with a ¼ 11:199, b ¼ 23:455, c ¼ 34:567 A and Z ¼ 8
ꢁ
b (A)
molecules per cell. The complex showed the same
structure as the Tris–acetone solvate, except for a two-
fold orientation disorder around the Re–P bond for one
of the PPh3 ligands. Because of disorder and poor
crystal quality, the R factor could not be reduced below
of 0.12. No further efforts were devoted to this material,
since better crystals of the solvate had become available
in the meantime.
ꢁ
c (A)
b (deg)
Volume (A )
3
ꢁ
5699.8(1)
Z
4
1.428
50 312
dcalc (g/cm3)
Reflection cell parameters
Crystal dimensions (mm)
ꢁ
0.16 ꢂ 0.26 ꢂ 0.38
Cu Ka (1.54178)
63.60
Radiation (k, A)
l (cmꢁ1
)
Transmission range
Reflections measured
Reflections independent
Reflections observed (I > 2r)
Rꢃ ðI > 2rÞ
0.185–0.361
68 215
11 165 (Rint ¼ 0:07)
9843
0.0555
3. Results and discussion
ꢃ
wR2 (I > 2r)
0.1582
1.076
Good yields of the bromo and chloro complexes
[ReX2(PPh3)2(bibzimH2)]X are obtained by heating
ReOX3(PPh3)2 and bibenzimidazole in CHCl3 in the
presence of excess PPh3 (Scheme 3). Infrared spectra
confirm the presence of PPh3 and bibzimH2 in the
compounds. A definite proof for the structure is pro-
vided by the X-ray diffraction results discussed below.
The presence of the [ReX2(PPh3)2(bibzimH2)]þ ion in
the solid is consistent with the FABþ spectra showing
the parent-ion pattern with the expected isotopic dis-
tribution, together with fragments resulting from the
loss of PPh3 and X. The good solubility in solvents like
CH2Cl2 and CHCl3 agrees with the presence of tight ion
pairs, as noted for the biimidazole complexes [13]. The
Sꢃ (I > 2r)
P
P
P
P
2
2 1=2
* R ¼ kFoj ꢁ jFck= jFoj, wR2 ¼ f ½wðFo2 ꢁ Fc2Þ ꢄ= wðFo2Þ g
,
P
2
1=2
S ¼ f ½wðFo2 ꢁ Fc2Þ ꢄ=ðNobs ꢁ NparamÞg
.
on the supporting atom. No disorder was detected in
the [ReCl2(PPh3)2(bibzimH2)]þ unit, but the chloride
counter-ion and the three acetone molecules of the
asymmetric unit were disordered. Each of these acetone
sites was modeled with three different sets of positions.
The FLAT option was used to keep the molecule planar,
whereas constraints were applied on interatomic dis-
tances, based on the average data for solvate acetone in
the Cambridge Crystallographic Database [21] [C@O,
1
ꢁ
ꢁ
ꢁ
1.21 A; C–CH3, 1.47 A; Oꢀ ꢀ ꢀCH3, 2.33 A; CH3ꢀ ꢀ ꢀCH3,
compounds were fully characterized by H NMR.
ꢁ
2.51 A]. A very small tolerance on the distances had to
In the free ligand, the two benzimidazole units con-
nected via the C2–C20 bond are symmetry equivalent
(Scheme 2). In addition, the N–H protons are involved
in a fast tautomeric exchange between the ring N atoms,
which renders the H5/H8 pair (and H6/H7 pair) chemi-
cally, but not magnetically, equivalent. Accordingly,
only two signals are observed (AA0BB0 system, Fig. 1),
but they are not first order. The chemical shifts and
coupling constants (Table 2) were determined from the
method described by Sohar [22].
be applied to stabilize the refinement. The occupancies
were first refined with a constraint applied to normalize
their sum to unity, then they were rounded off to the
nearest 0.05 and fixed (0.60/0.20/0.20) for the rest of the
refinement. The chloride ion was described by means of
two positions located on each side of the plane through
bibzimH2. These positions were initially refined sepa-
rately, then simultaneously. The occupancies were refined
as above and fixed (0.60/0.40) in the last least-squares
PPh3
O
X
PPh3
X
X
X
N
N
NH
NH
bibzimH2/PPh3
Re
X
Re
X
CHCl3/∆
Ph3P
PPh3
Scheme 3.

1142
F. Baril-Robert, A.L. Beauchamp / Polyhedron 23 (2004) 1139–1144
CH2Cl2
H7
H6
H8
H5
NH
Η6/7
H5/8
7.70
7.60
7.50
7.40
7.30
7.20
7.0
6.5
6.0
5.5
(ppm)
5.0
4.5
4.0
(ppm)
Fig. 2. Signals of the coordinated bibenzimidazole protons in the 1H
NMR spectrum (CDCl3) of [ReCl2(PPh3)2(bibzimH2)]Cl]. The
CH2Cl2 signal results from residual traces of the recrystallization
solvent.
Fig. 1. 1H NMR signals (DMSO-d6) of the aromatic protons of free
bibenzimidazole.
Table 2
1H NMR chemical shifts (ppm) and coupling constants (Hz) of bib-
zimH2 (DMSO-d6)
orbitals containing the unpaired electrons are more
concentrated on H6 than on any other proton, whereas
its neighbor H7 is predicted to be the least affected by the
unpaired electrons. Accordingly, the higher-field triplet
(3.76 (Cl); 4.25 (Br) ppm) is assigned to H6, whereas the
other triplet (7.03 (Cl); 6.71 (Br) ppm) must correspond
to H7. A COSY 2D experiment for [ReBr2(PPh3)2(bib-
zimH2)]Br indicates proximity for the protons appearing
at 6.22 and 4.25 ppm, respectively. This allows us to
assign the doublet at 6.22 ppm to H5 and the other
doublet at 6.01 ppm to H8. The acidic N–H protons give
a broad peak at 4.44 (Cl) or 4.89 (Br) ppm.
d, H5=8
d, H6=7
3J56 ¼ 3J78
3J67
7.66 ppm (m)
7.29 ppm (m)
7.9 Hz
6.5 Hz
1.3 Hz
0.0 Hz
4J57 ¼ 4J68
5J58
The low-spin d4 center in rhenium(III) monomers is
1
paramagnetic. Despite this fact, the H NMR spectra
are relatively clean, integrations are reliable and cou-
plings are often observed. The data for the bibzimH2
complexes are collected in Table 3. The PPh3 signals
appear at the same positions as for the related com-
plexes of biimidazole [13] and they are readily identified
from multiplicities and integrations. The ortho protons,
close to the metal center, undergo a considerable shift
(13.3 ppm) downfield from their normal position (7–8
ppm). Since the Re–N bonds are non-labile, bibzimH2
gives four C–H signals between ꢅ7 and ꢅ3.7 ppm
(Fig. 2). In contrast with those of PPh3, they are shifted
upfield by paramagnetism. The second-order effects
noted for the free ligand have now disappeared, since
the signals have been shifted considerably. H5 and H8
appear as doublets and can be distinguished from H6
and H7, which give pseudo-triplets because of couplings
with two adjacent protons. One of the latter protons
appears at much higher field (ꢅ4 ppm) than the other.
Semi-empirical PM3 calculations [23] suggest that the
3.1. Crystal structures
The [ReCl2(PPh3)2(bibzimH2)]Cl unit is shown in
Fig. 3. The octahedral environment of rhenium(III) in-
cludes one non-deprotonated bidentate bibzimH2 ligand,
two phosphines trans to one another and two chlorines.
The third chlorine is actually the counter ion forming two
N–Hꢀ ꢀ ꢀClꢁ hydrogen bonds with bibzimH2. Selected
interatomic distances and bond angles are compared with
those of the biimidazole analog [13] in Table 4.
Most of the departure from octahedral coordination
originates from the small bite angle (76.7(2)°) of bib-
zimH2, which allows the opposite Re–Cl bonds to move
away from each other (Cl(1)–Re–Cl(2) ¼ 96.97(5)° ). The
Re–P bonds, perpendicular to the ReCl2N2 plane, are
not exactly collinear (P(1)–Re–P(2) ¼ 175.21(4)°), but
Table 3
1H NMR data for the [ReX2(PPh3)2(bibzimH2)]X complexes (in CDCl3)
[ReCl2(PPh3)2(bibzimH2)]Cl
[ReBr2(PPh3)2(bibzimH2)]Br
PPh3, Ho
PPh3, Hp
PPh3, Hm
13.31 (d, 12H), 3J ¼ 7:0 Hz
13.32 (d, 12H), 3J ¼ 7:1 Hz
8.38 (t, 6H), 3J ¼ 7:4 Hz
8.11 (t, 12H), 3J ¼ 7:6 Hz
6.71 (t, 2H), 3J ¼ 8:1 Hz
6.22 (d, 2H), 3J ¼ 8:4 Hz
6.01 (d, 2H), 3J ¼ 8:3 Hz
4.89 (s broad, 2H)
8.42 (t, 6H), 3J ¼ 7:1 Hz
8.18 (t, 12H), 3J ¼ 7:5 Hz
7.03 (t, 2H), 3J ¼ 8:0 Hz
6.60 (d, 2H), 3J ¼ 8:2 Hz
6.38 (d,2H), 3J ¼ 8:6 Hz
4.44 (s broad, 2H)
bibzimH2, H7
bibzimH2, H5
bibzimH2, H8
bibzimH2, (N)H
bibzimH2, H6
3.76 (t, 2H), 3J ¼ 7:7 Hz
4.25 (t, 2H), 3J ¼ 7:7 Hz

F. Baril-Robert, A.L. Beauchamp / Polyhedron 23 (2004) 1139–1144
1143
because the extra phenylene rings leave less space for the
phosphine phenyl rings.
The two benzimidazole halves of the coordinated li-
gand are coplanar (dihedral angle ¼ 1.7(3)°). As de-
picted in Fig. 4, ring closure induces in-plane distortions
to improve the overlap between the metal orbitals and
the ligand r lone pairs, leading to a large difference
0
0
between the N3–C2–C2 and N1–C2–C2 angles. In the
present bibzimH2 complex, this difference is somewhat
smaller (ꢅ117° versus ꢅ130°) than for the biimH2
complexes (ꢅ116° versus ꢅ133°). Thus, the phenylene
rings act as bulky a substituents counteracting ligand
distortion, which explains that the Cl–Re–Cl angle is
smaller here (ꢅ97°) than in the biimH2 analog (ꢅ99°).
The N–H groups form hydrogen bonds with the
chloride counter-ion (Fig. 3 and Table 5). The Nꢀ ꢀ ꢀCl
ꢁ
distances of ꢅ3.06 A and the N–Hꢀ ꢀ ꢀCl angles (ꢅ154°)
close to linearity correspond to moderately strong in-
teractions [24]. The reduction of ligand distortion is a
favorable factor, since it allows the Nꢀ ꢀ ꢀCl distance and
the N–Hꢀ ꢀ ꢀCl angle to be greater than for the biimH2
Fig. 3. ORTEP drawing of the [ReCl2(PPh3)2(bibzimH2)]Cl ion pair.
For simplicity, the carbon-bonded hydrogens are omitted.
Table 4
Selected distances (A) and angles (deg) in the [ReCl2(PPh3)2(LH2)]Cl
compounds
ꢁ
complexes (ꢅ3.16 A and ꢅ147°, respectively) [13].
ꢁ
The phosphines are related by an approximate mirror
plane. Two phenyl groups of each phosphine are posi-
tioned above (or below) the bibzimH2 ligand, whereas
the third phenyl ring is roughly parallel to the Re–P
bond and the ortho hydrogen is nested between the two
chloro ligands. A similar conformation has been ob-
served for [ReCl2(PPh3)2(biimH2)]Cl [13]. However, in
contrast with the latter case, there are no appreciable p
interactions between the phosphine phenyl rings and
those of the bibzimH2, since these rings are not parallel
(dihedral angle of 20.5° and 25.0°) and the inter-ring
LH2
bibzimH2
biimH2 [13]
Bond lengths
Re–N(13)
Re–N(23)
Re–P(1)
2.127(4)
2.145(4)
2.496(1)
2.494(1)
2.360(1)
2.369(1)
2.114(3)
2.129(3)
2.476(1)
2.466(1)
2.381(1)
2.354(1)
Re–P(2)
Re–Cl(1)
Re–Cl(2)
Bond angles
N(13)–Re–N(23)
P(1)–Re–P(2)
76.7(2)
175.21(4)
96.97(5)
89.4(1)
76.0(1)
177.24(3)
99.38(4)
90.8(1)
ꢁ
distances are relatively large (3.49 and 3.65 A).
Cl(1)–Re–Cl(2)
P(1)–Re–N(13)
P(1)–Re–N(23)
P(1)–Re–Cl(1)
The ion pairs form columns along the unit cell b di-
rection and the acetone solvent molecules occupy
channels between these columns.
92.3(1)
90.0(1)
91.51(5)
88.15(5)
88.9(1)
89.98(4)
90.22(4)
91.0(1)
P(1)–Re–Cl(2)
P(2)–Re–N(13)
P(2)–Re–N(23)
P(2)–Re–Cl(1)
91.7(1)
88.5(1)
90.96(5)
87.48(5)
169.0(1)
92.3(1)
87.93(4)
91.91(4)
173.2(1)
97.3(1)
HN
HN
N
N
P(2)–Re–Cl(2)
2'
2
2'
2
Cl(1)–Re–N(13)
Cl(1)–Re–N(23)
Cl(2)–Re–N(13)
Cl(2)–Re–N(23)
N(11)–C(12)–C(22)
N(13)–C(12)–C(22)
N(21)–C(22)–C(12)
N(23)–C(22)–C(12)
C(12)–N(13)–Re
C(14)–N(13)–Re
C(22)–N(23)–Re
C(24)–N(23)–Re
Re
N3
HN1
N3
HN1
94.0(1)
87.3(1)
170.7(1)
130.7(5)
117.0(4)
128.8(5)
117.5(4)
114.4(3)
140.1(4)
114.3(3)
140.8(3)
163.3(1)
133.9(4)
115.4(4)
132.5(4)
117.0(4)
116.5(3)
137.3(3)
115.1(3)
138.8(3)
Fig. 4. Undistorted biimidazole molecule (left) and distorted coordi-
nated ligand (right).
Table 5
Geometry of the hydrogen bonds in [ReCl2(PPh3)2(bibzimH2)]Cl
ꢁ
D–A (A)
ꢁ
H–A (A)
D–Hꢀ ꢀ ꢀA
D–H–A (°)
N(11)–H(11)ꢀ ꢀ ꢀCl(31)a
N(21)–H(21)ꢀ ꢀ ꢀCl(31)a
N(11)–H(11)ꢀ ꢀ ꢀCl(32)a
N(21)–H(21)ꢀ ꢀ ꢀCl(32)a
3.000(9)
3.078(8)
3.128(9)
3.018(8)
2.18
2.27
2.33
2.21
155.8
154.3
152.2
155.0
the deviation is small. The Re–N and Re–Cl bond
lengths compare well with those of the biimH2 complex,
but the Re–P bonds are ꢅ0.02 longer here, probably
a Occupancies: Cl(31), 0.60; Cl(32), 0.40.

1144
F. Baril-Robert, A.L. Beauchamp / Polyhedron 23 (2004) 1139–1144
[3] C.A. Hester, R.G. Baughman, H.L. Collier, Polyhedron 16 (1997)
2893.
4. Conclusion
[4] M. Tadokoro, H. Kanno, T. Kitajima, H. Shimada-Umemoto, N.
Nakanishi, K. Isobe, K. Nakasuji, Proc. Natl. Acad. Sci. USA 99
(2002) 4950.
This work shows that the extra aromatic rings in
bibzimH2 do not preclude the formation of the [Re-
X2(PPh3)2(LH2)]X complexes observed with biimidazole
and that they introduce only small structural differences
due to steric effect. Therefore, this system, with the extra
advantage of tunability by substitution on the phenylene
unit, could provide a valuable starting point to prepare
bimetallic compounds by coordination of an extra me-
tallic center to the external N donors.
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Enoki, K. Nakasuji, Chem. Lett. (1995) 613.
€
€
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M. Duati, S. Fanni, J.G. Vos, Inorg. Chem. 39 (2000) 1621.
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(1987) 4148.
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5. Supplementary material available
[11] A.P. de Silva, H.Q.N. Gunaratne, T. Gunnlaugsson, A.J.M.
Huxley, C.P. McCoy, J.T. Rademacher, T.E. Rice, Chem. Rev. 97
(1997) 1515.
Crystallographic information as a CIF file has been
deposited with the Cambridge Crystallographic Data
Centre (CCDC No. 215000). Copies of the data can be
obtained free of charge via www.ccdc.cam.ac.uk/conts/
retrieving.html or from the Cambridge Crystallographic
Data Centre, 12, Union Road, Cambridge CB2 1EZ,
UK; fax: +44 1233 336033; or e-mail: deposit@
ccdc.cam.ca.uk.
[12] M.D. Ward, Chem. Soc. Rev. (1995) 121.
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(2002) 6527.
Acknowledgements
[19] G.M. Sheldrick, SHELXTL, The Complete Software Package for
Single Crystal Structure Determination, Release 5.10., Bruker
AXS Inc., Madison, WI, 1997.
We thank the Natural Sciences and Engineering Re-
search Council of Canada for financial support, and Dr.
[20] XPREP, X-ray Data Preparation and Reciprocal Space Explora-
tion Program, Release 5.10, Bruker AXS Inc., Madison, WI,
1997.
ꢀ
M. Simard and F. Belanger-Gariepy for assistance in the
interpretation of the X-ray diffraction data.
ꢀ
[21] Cambridge Structural Database, Version 5.4, November 2002
release with February 2003 updates, Cambridge Crystallographic
Data Centre, Cambridge, UK.
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[2] C.A. Hester, H.L. Collier, R.G. Baughman, Polyhedron 15 (1996)
4255.