Coordination of bidentate aroylhydrazone-based N,N-Donor ligands to the fac-[re(co)3]+ core

Article abstract of DOI:10.1007/s10870-014-0524-4

The reaction of the potentially bidentate aroylhydrazone-based N,N-donor ligands N-(di(pyridin-2-yl)-methylene)benzohydrazide (Hdpmb) and 3-((pyridin-2-yl)methyleneamino)-2,3-dihydro-2-(pyridin-2-yl)quinazolin-4-(1H) one (Hppq) with [Re(CO)₅Cl]

Full text of DOI:10.1007/s10870-014-0524-4

J Chem Crystallogr (2014) 44:368–375
DOI 10.1007/s10870-014-0524-4
ORIGINAL PAPER
Coordination of Bidentate Aroylhydrazone-Based N,N-Donor
Ligands to the fac-[Re(CO) ] Core
+
3
Janvier Mukiza
Eric C. Hosten
•
Thomas I. A. Gerber
•
Received: 9 April 2014 / Accepted: 12 June 2014 / Published online: 24 June 2014
Springer Science+Business Media New York 2014
ꢀ
?
the fac-[Re(CO)3] core allows flexibility [1] and conse-
Abstract The reaction of the potentially bidentate aro-
ylhydrazone-based N,N-donor ligands N-(di(pyridin-2-yl)-
methylene)benzohydrazide (Hdpmb) and 3-((pyridin-2-yl)
methyleneamino)-2,3-dihydro-2-(pyridin-2-yl)quinazolin-
quently it is most promising for labelling a variety of low
molecular weight biomolecules [3]. In addition the fac-
?
[M(CO) ] (M = Tc and Re) core shows a high stability in
3
4
-(1H)one (Hppq) with [Re(CO) Cl] in alcohol led to
5
water compared to the radiopharmaceuticals based on the
3
[ReO] core which is prone to oxidation to perrhenate
?
the isolation of the neutral complexes fac-[Re(CO)3
-
[ReO ] in water [3].
Cl(Hdpmb)] (1) and fac-[Re(CO) Cl(Hppq)] (2) respec-
3
4
tively. Spectroscopic data and the X-ray crystal structures
of the complexes are reported. The cell parameters of the
Acyl and aroyl hydrazone-based ligands (Scheme 1)
are of interest due to the variety of biological and
chemical activities of these molecules [4]. Hydrazones
exhibit physiological and biological activities in the
treatment of several diseases such as tuberculosis [5], iron
over-load [6, 7], and also as inhibitors for many enzymes
[8]. Hydrazone metal complexes have also found appli-
cations in various physical and chemical process such as
non-linear optics, sensors and medicine [9], and they can
effectively act as catalysts towards alkene epoxidation
[10]. Metal complexes with acyl and aroylhydrazone
ligands are also of interest in the field of electrochromism
in which a change in the oxidation state of the metal is
possible [11].
˚
complexes are 1: monoclinic, P2 /c, a = 13.7393(9) A,
1
˚
3
˚
b = 12.0512(8) A, c = 13.3543(9) A, b = 107.105(2)ꢁ,
˚
V = 2113.4(2) A , R = 0.0317, wR = 0.0699; and 2.‘
1
2
˚
a = 17.607(1) A,
ethanol:monoclinic,
P2 /c,
b =
1
˚
˚
2
4
0.826(1) A, c = 13.5887(8) A, b = 101.875(2)ꢁ, V =
3
876.0(5) A , R = 0.0228, wR = 0.0503.
˚
1
2
Keywords Rhenium(I) ꢀ Bidentate ꢀ Aroylhydrazone-
based ꢀ Crystal structures
Introduction
Acyl and aroylhydrazone ligands are characterised by
the trigonal N- and O-donor atoms that can coordinate to
transition metal ions [12], acting as bidentate [13], triden-
tate, tetradentate [14] or even pentadentate chelates [15]
depending on the heterocyclic ring-substituents attached to
the hydrazone moiety. Aroylhydrazone derivatives may
exhibit keto-enol tautomerization (Scheme 1) which can
model the coordination of the ligand to the metal as neutral
(keto form) or mononegative (in the deprotonated enol
form) [4].
6
Due to its low-spin d electron configuration, rhe-
?
nium(I) complexes containing the fac-[Re(CO) ] core are
3
of interest since they exhibit a high kinetic and thermo-
dynamic stability [1]. In this core the three CO ligands are
facially arranged with three vacant coordination sites, and
it can coordinate to a variety of mono- and multidentate
ligands, including amines, amides, thioethers, imines, thi-
ols, carboxylates and phosphines [1, 2]. The small size of
In this report the coordination mode of the two
aroylhydrazone-based ligands 3-((pyridin-2yl)methylene-
amino)-2,3-dihydro-2-(pyridin-2-yl)quinazolin-4-(1H)one
(Hppq) and N-(di(pyridin-2-yl)methylene)benzohydrazide
J. Mukiza ꢀ T. I. A. Gerber (&) ꢀ E. C. Hosten
Department of Chemistry, Nelson Mandela Metropolitan
University, Port Elizabeth 6031, South Africa
e-mail: thomas.gerber@nmmu.ac.za
1
23

J Chem Crystallogr (2014) 44:368–375
369
?
Hdpmb) to the fac-[Re(CO)3] core is presented and
(
O
OH
discussed.
N
R2
R1
N
N
R2
H
R1
N
Experimental
R
3
R3
Materials and Instrumentation
Scheme 1 Keto-enol tautomerization of acyl and aroylhydrazone
ligands
All materials were commercially available and used as
received. [Re(CO) Cl] was obtained from Aldrich.
5
Infrared (IR) spectra were recorded on a Digilab
FTS3100 Excalibur HE spectrophotometer and were run as
Yield = 74 %, m.p. = 285 ꢁC. Anal. Calc.: C, 41.9; H,
1
KBr pellets. H NMR spectra were recorded on a Bruker
2
.7; N, 9.2. Found: C, 41.5; H, 2.5; N, 10.0 %. IR (mmax/
-
1
cm ): m(C:O, fac) 1897, 1928, 2025; m(C=O) 1674;
Avance 300 MHz spectrometer as solutions in DMSO-d at
6
1
m(C=N) 1614, 1650; m(Re - N) 453, 482. H NMR (295 K,
ppm): 7.75 (d, 4H, H(132), H(112), H(212), H(232)), 7.10
2
5 ꢁC, using TMS as internal standard. Electronic spectra
were obtained with a Shimadzu UV-3100 spectrophotom-
eter. Microanalyses were obtained on a Carlo Erba EA1108
elemental analyser, and melting points were determined on
an Electrothermal IA-900 apparatus. Conductivity mea-
(d, 4H, H(215), H(235), H(135), H(115)), 7.35 (t, 4H,
H(213), H(233), H(133), H(113)), 7.30 (t, 4H, H(214),
H(234), H(114), H(134)), 7.00 (d, 2H, H(123), H(233)),
-
1
2
-1
7
.25 (d, 2H, H(226), H(126)), 7.50 (m, 4H, H(224),
H(225), H(125), H(124)), 6.91 (s, 2H, H(24), H(14)), 7.65
s, 2H, H(21), H(11)), 7.20 (s, 2H, H(23), H(13)). Elec-
surements (in the unit ohm cm mol ) were carried out
-
3
with 10 M solutions at 298 K with a Phillips PW9509
conductometer.
(
-
1
-1
tronic spectrum (methanol, k (e, M cm )): 319 (46500),
94 nm (5600).
3
Synthesis of [Re(CO) Cl(Hdpmb)] (1)
3
3
Re(CO) Cl] (50 mg, 0.14 mmol) in 10 cm of methanol
X-ray Crystallography
[
5
3
was added to 0.28 mmol (85 mg) of Hdpmb in 5 cm of
methanol. The mixture was heated under reflux for 4 h,
resulting in a clear yellow-green solution, which was fil-
tered after being cooled to room temperature. No precipi-
tate was obtained from filtration. Yellow-green crystals
suitable for X-ray crystallography were grown in 1 week
by the slow evaporation of the filtrate at room temperature.
Yield = 65 %, m.p. = 225 ꢁC. Anal. Calc.: C, 41.5; H,
Single crystal X-ray crystallography studies were per-
formed at 200 K using a Bruker Kappa Apex II diffrac-
tometer with graphite monochromated Mo Ka radiation
˚
(
k = 0.71069 A). For data collection, APEX-II was used
while for cell refinement and data reduction, SAINT was
used [16]. The structures were solved by direct methods
applying SHELXS-2013 [17] and refined by least-squares
procedures using SHELXL-2013 [17], with SHELXLE
2
.3; N, 9.2. Found: C, 41.5; H, 2.1; N, 9.6 %. IR (mmax/
-
1
[
18] as a graphical interface.
cm ): m(C:O, fac) 1895, 2011, 2030; m(C=O) 1654;
1
All non-hydrogen atoms were anisotropically refined.
m(C=N) 1579; m(Re–N) 482. H NMR (295 K, ppm): 8.77
Carbon and oxygen bound hydrogen atoms were calculated
in idealised geometrical positions. Nitrogen-bound H
atoms were located on a difference Fourier map and
(
d, 2H, H(12), H(22)), 7.48 (t, 2H, H(14), H(24)), 8.18 (d,
2
2
H, H(15), H(25)), 7.89 (t, 2H, H(13), H(23)), 6.68 (dd,
H, H(32), H(36)), 7.40 (s, H, H(34)), 7.93 (d, 2H, H(33),
˚
restrained to 0.88 A bond length. Structure 2 contains an
H(35)). Electronic spectrum (dichloromethane, k, (e,
M
-
1
-1
cm )): 320 nm (92100).
ethanol solvent molecule disordered over two positions in a
ratio of 0.40:0.60. The corresponding atoms’ anisotropic
displacement parameters and bond lengths were restraint to
the same values (Fig. 1).
Synthesis of [Re(CO) Cl(Hppq)] (2)
3
3
Data were corrected for absorption effects with the
numerical method using SADABS [16].
[
Re(CO) Cl] (101 mg, 0.28 mmol) in 10 cm of ethanol
5
3
was added to 0.56 mmol (185 mg) of Hppq in 10 cm of
ethanol. The mixture was heated under refluxed for 6 h
under nitrogen, resulting in an orange-red solution, which
was cooled to room temperature. An orange-red precipitate
was removed by filtration. Orange-red crystals suitable for
X-ray measurement were grown within 5 days by the slow
evaporation of the mother liquor at room temperature.
Results and Discussion
The Hppq ligand was prepared by the heating under reflux
of two molar equivalents of 2-picolinaldehyde with
123

3
70
J Chem Crystallogr (2014) 44:368–375
Fig. 1 Aroylhydrazone based-
ligands derivatives used in this
study
H
N
H
N
N
N
O
N
N
N
O
N
N
Hppq
Hdpmb
O
H
N
NH2
N
N
O
N
H
MeOH
+
2
N
N
Reflux 6 h
N
NH2
O
Hppq
O
O
H
N
NH2
N
N
+
H
MeOH
Reflux 6 h
N
N
O
N
N
Hdpmb
Scheme 2 Synthesis of Hppq and Hdpmb ligands
two equivalents of Hdpmb with [Re(CO) Cl] in methanol
5
H
N
for 4 h. The complex is air-stable, yellow-green in colour,
not soluble in water but soluble in methanol, ethanol,
dichloromethane, acetone, dimethylformamide and
dimethylsulfoxide.
N
O
Cl
The infrared spectrum is characterised by intense
N
N
-
absorption bands at 1,895, 2,011 and 2,030 cm . These
1
Re
OC
?
CO
bands are assigned to m(C:O) of the fac-[Re(CO) ] unit
CO
3
-
1
[
19]. The band of medium intensity at 1,654 cm
is
3
Fig. 2 Line structure of [Re(CO) Cl(Hdpmb)] (1)
ascribed to the stretching vibration of the non-coordinated
-
1
ketonic CO group. The absorption at 1,579 cm
is
assigned to m(C=N) of the coordinated ligand, and the
-
1
2
-aminobenzohydrazide, while Hdpmb was obtained by the
medium intensity band at 482 cm is ascribed to m(Re–N).
The UV–Vis spectrum in dichloromethane shows only one
intense absorption peak at 322 nm which is assigned to the
intraligand p ? p* transition.
reaction of equimolar ratios of benzohydrazide with di-2-
pyridylketone [4]. The syntheses are described in
Scheme 2.
The proton NMR spectrum of 1 consists of sharp well-
defined peaks. The fact that the two pyridyl rings are
magnetically equivalent is shown by the fact that only four
two-proton signals are observed for the eight pyridyl pro-
tons at 8.77 (d, 2H, H(12), H(22)), 7.48 (t, 2H, H(14),
H(24)), 8.18 (d, 2H, H(15), H(25)) and 7.89 (t, 2H, H(13),
H(33)). The five protons on the benzoyl phenyl ring give
[
Re(CO) Cl(Hdpmb)] (1)
3
The compound [Re(CO) Cl] provides a convenient route to
5
the preparation of rhenium(I) complexes containing the
?
fac-[Re(CO)3] core. The complex [Re(CO) Cl(Hdpmb)]
3
(
1) (Fig. 2) was synthesised by the heating under reflux of
1
23

J Chem Crystallogr (2014) 44:368–375
371
C23
O5
C24
C22
C34
C25
C33
C5
N2
C21
C32
C35
C1
N3
Cl1
C36
C3
Re1
O3
C31
N4
C2
C4
C11
N1
O4
C15
O1
C12
C14
C13
Fig. 3 ORTEP view of complex 1 showing 50 % probability displacement ellipsoids and atom labelling
The distortion from an ideal octahedron results in the
trans angles [Cl(1)–Re(1)–C(3) = 174.9(2)ꢁ, N(1)–Re(1)–
C(5) = 175.8(2)ꢁ, N(2)–Re(1)–C(4) = 176.6(2)ꢁ] being
non-linear. These distortions are also the result of the
constraints imposed by the bidentate coordination mode of
Hdpmb, which forms a six-membered ring metallocycle
with a bite angle N(1)–Re(1)–N(2) of 83.5(1)ꢁ. The bond
angles C(4)–Re(1)–C(5) [87.6(2)ꢁ], Cl(1)–Re(1)–N(2)
H
N
N
OC
CO
Re
Cl
CO
N
N
N
O
[
84.1(1)ꢁ] and Cl(1)–Re(1)–N(1) [83.8(1)ꢁ] also show
significant deviations from orthogonality. The bond dis-
˚
tance Re(1)–Cl(1) = 2.447(1) A is close to the average
3
Fig. 4 Line structure of [Re(CO) Cl(Hppq)]
˚
Re–Cl distance of 2.479(1) A observed in similar com-
rise to three peaks at 6.68 (dd, 2H, H(32), H(36)), 7.40 (s,
H, H(34)) and at 7.93 ppm (d, 2H, H(33), H(35)) (see
Fig. 3 for labelling).
plexes [24, 25].
The average C–O bond distance (for the three carbonyls
˚
coordinated to rhenium) is 1.150(8) A, and the O(1)–C(2)
˚
bond distance 1.226(5) A illustrates that it is a double bond
The ORTEP diagram of 1 is shown in Fig. 3. The rhenium
atom is coordinated in a distorted octahedral geometry to
three carbonyls in a facial orientation, two pyridyl nitrogens
N(1) and N(2) and a chloride ion. The average Re–CO bond
[25]. The average Re–C–O bond angle is 178.93(5)ꢁ.
The C(1), N(3), N(4), C(2), O(1) ligand backbone is
˚
essentially planar (r.m.s. of all fitted atoms = 0.0758 A)
˚
distance of 1.905(5) A falls in the range observed [1.900(2)–
indicating extended amide-type resonance (Tables 1
and 2).
˚
1
.928(2) A] for similar complexes [19–21].
The Re(1)–N(1) bond distance of 2.176(3) A is slightly
˚
There is one intramolecular C–HꢀꢀꢀN hydrogen bond
(see Table 3 for the metrics). Adjacent molecules have N–
HꢀꢀꢀO intramolecular hydrogen bonds between the ketone
˚
shorter than the Re(1)–N(2) bond distance [2.206(4) A],
and these values are close to those previously reported for
rhenium(I)–N(imines) bond which typically fall in the
and amide groups which in terms of graph-set analysis the
2
2
˚
range 2.15–2.22 A [19, 22, 23] (Fig. 4).
can be described by means of a R
(8) descriptor on the
123

3
72
J Chem Crystallogr (2014) 44:368–375
˚
Table 1 Crystal and structure refinement data for complexes 1 and 2
Table 2 Selected bond lengths (A) and angles (ꢁ) for the complexes
1
2
1
Formula
C
21
H
14ClN
4
4
O Re
5 4 2 6
2(C22H15ClN O Re).C H O
Re(1)–N(1)
2.176(3)
2.447(1)
1.912(5)
1.226(5)
1.368(6)
174.9(2)
176.6(2)
83.5(1)
Re(1)–N(2)
Re(1)–C(3)
2.206(4)
1.901(5)
1.903(5)
1.145(6)
1.296(5)
175.8(2)
87.6(2)
Formula weight 608.01
1316.15
Monoclinic
P21/c
Re(1)–Cl(1)
Crystal system
Space group
Monoclinic
Re(1)–C(4)
Re(1)–C(5)
P21/c
O(1)–C(2)
O(3)–C(3)
˚
a (A)
13.7393(9)
12.0513(8)
13.3543(9)
107.105(2)
2113.4(2)
4
17.607(1)
20.826(1)
13.5887(8)
101.875(2)
4876.0(5)
4
N(3)–N(4)
N(3)–C(1)
˚
b (A)
Cl(1)–Re(1)–C(3)
N(2)–Re(1)–C(4)
N(1)–Re(1)–N(2)
N(1)–Re(1)–C(4)
Cl(1)–Re(1)–N(1)
N(3)–N(4)–C(2)
N(1)–Re(1)–C(5)
C(4)–Re(1)–C(5)
N(2)–Re(1)–C(5)
Cl(1)–Re(1)–N(2)
Re(1)–C(3)–O(3)
N(4)–C(2)–C(31)
˚
c (A)
b (ꢁ)
Volume (A )
92.5(2)
3
˚
96.3(2)
84.1(1)
Z
83.8(1)
179.7(5)
120.4(4)
Density
(
1.911
1.793
119.7(4)
-
g cm )
3
2
Absorption
coefficient
5.912
5.135
-
1
Re(1)–Cl(1)
2.4899(8)
2.160(2)
1.400(3)
1.380(4)
2.179(3)
2.485(1)
176.43(9)
172.3(1)
74.16(9)
73.73(9)
Re(1)–N(11)
Re(1)–C(14)
2.184(2)
1.913(3)
1.467(4)
1.438(4)
2.168(2)
1.917(4)
172.2(1)
98.6(1)
(
mm
F(000)
Crystal size
mm)
Temperature
K)
)
Re(1)–N(12)
1168
2552
N(12)–N(13)
N(13)–C(13)
0.41 9 0.42 9 0.48 0.08 9 0.31 9 0.52
N(13)–C(12)
N(14)–C(13)
(
Re(2)–N(21)
Re(2)–N(22)
200
200
(
Re(2)–Cl(2)
Re(2)–C(24)
h range (ꢁ)
Index ranges h
2.3–28.4
-18/18
-13/16
-17/17
43,787
1.8–8.4
-23/23
-27/27
-18/18
189,997
Cl(1)–Re(1)–C(15)
N(12)–Re(1)–C(16)
N(11)–Re(1)–N(12)
N(21)–Re(2)–N(22)
N(11)–Re(1)–C(14)
N(11)–Re(1)–C(16)
N(13)–N(12)–C(11)
N(13)–C(13)–N(14)
k
l
118.1(2)
107.4(2)
Reflection
measured
Independent/
observed
reflections
5,228/4,580
5,228/284
12,169/10,805
Data/
parameters
12,169/642
1.17
Table 3 Hydrogen-bond geometry ( A˚ , 8)
D–HꢀꢀꢀA
D–H
HꢀꢀꢀA
DꢀꢀꢀA
D–HꢀꢀꢀA
Goodness-of-fit 1.29
2
on F
a
1
Final R indices 0.0317
I [ 2r(I)]
0.0228
i
N4–H4ꢀꢀꢀO1
0.87(4)
0.95
2.00(4)
2.53
2.847(5)
3.215(6)
3.497(5)
2.878(5)
163(5)
129
[
ii
C13–H13ꢀꢀꢀO3
C25–H25ꢀꢀꢀCl1
C32–H32ꢀꢀꢀN3
b
(
wR
2
= 0.0699)
(wR
2
= 0.0503)
iii
0.95
2.81
130
Largest diff.
peak/hole
2.35/-2.06
1.67/-1.08
0.95
2.46
106
-
3
˚
e A )
2
(
i
N14–H14ꢀꢀꢀO21
0.86(3)
0.86(3)
0.95
2.08(3)
2.49(3)
2.59
2.796(4)
3.346(3)
3.464(3)
3.510(3)
3.066(4)
3.311(4)
2.904(5)
3.138(6)
3.172(5)
141(3)
176(3)
153
ii
N24–H24ꢀꢀꢀCl2
unary level. There is also one hydrogen bond to a chloride.
The structure is also stabilised by pꢀꢀꢀp bonding between
adjacent N(2), C(21), C(22), C(23), C(24), C(25) rings with
iii
C11–H11ꢀꢀꢀCl1
C13–H13ꢀꢀꢀCl1
C112–H112…O11
1.00
2.63
146
i
˚
an inter-centroid distance of 3.578(3) A. There is also a
0.95
2.41
126
iv
C113–H113ꢀꢀꢀO14
C135–H135ꢀꢀꢀN14
C224–H224…O16
C225–H225…O16
0.95
2.59
133
carbonyl p ring interaction between C(2) and O(1) and the
ring N(1), C(11), C(12), C(13), C(14), C(15) with a length
0.95
2.59
100
iv
iv
˚
.427(4) A to the ring centroid.
0.95
2.51
123
3
0.95
2.59
120
[
Re(CO) Cl(Hppq)] (2)
3
a
Symmetry codes: (i) 1 - x, 1 - y, -z; (ii) 1 - x, -1/2 ? y,
/2 - z; (iii) x, 1/2 - y, -1/2 ? z
1
b
The complex [Re(CO) Cl(Hppq)] (2) was prepared by the
3
Symmetry codes: (i) x, 1/2 - y, -1/2 ? z; (ii) 1 - x, -y, 1 - z;
iii) x, 1/2 - y, 1/2 ? z; (iv) -x, -1/2 ? y, 1/2 - z
(
reaction of [Re(CO) Cl] with two equivalents of Hppq in
5
1
23

J Chem Crystallogr (2014) 44:368–375
373
C225
O16
C224
C113
C112
C226
C235
C16
Re1
N11
O15
C114
C223
C234
C15
C233
C115
C222
C111
C14
C221
C231
Cl1
C22
N24
O14
N12
C11
C232
C23
O21
N25
O11
C12
N13
N23
N22
O25
N15
C13
C25
C21
C121
N14
O26
C132
C131
C126
C124
C26
C122
C211
Cl2
C215
Re2
C135
C125
C123
N21
C133
C134
C24
C214
O24
C212
C213
Fig. 5 ORTEP view of complex 2 showing 50 % probability displacement ellipsoids and atom labelling. Hydrogen atoms and the ethanol
solvent of crystallisation have been omitted for clarity
ethanol under reflux conditions and nitrogen for 6 h. It is
air stable, red–orange in colour, not soluble in water but
soluble in a variety of solvents including methanol, etha-
nol, dichloromethane, acetone, dimethylformamide and
dimethylsulfoxide. A racemic mixture of ligand was used
as a starting material. In the crystal analysed the two
ligands in the asymmetric unit has a chirality of R at C(13)
and C(23).
of the coordinated ligand, and the absorption at 394 nm is
assigned to a metal-to-ligand charge transfer (MLCT).
The proton NMR spectrum of 2 consists of sharp well-
defined peaks. The corresponding signals of each pyridyl
ring of the Hppq ligand in the complex are magnetically
equivalent, giving the expected doublet-triplet-doublet-tri-
plet set of signals at 7.75 (4H, H(132), H(112), H(212),
H(232)), 7.30 (4H, H(214), H(234), H(114), H(134)), 7.10
(4H, H(215), H(235), H(135), H(115)) and 7.35 ppm (4H,
H(213), H(233), H(133), H(113)) respectively. The ten
protons on both benzoyl phenyl ring give rise to three
peaks at 7.01 (d, 2H, H(123), H(223)), 7.25 (d, 2H, H(226),
H(121)) and 7.55 ppm (m, 4H, H(224), H(225), H(124),
H(125)). The presence of two NH protons is supported by
singlet peak at 6.95 ppm (H(24), H(14)) (see Fig. 5 for
labelling).
The infrared spectrum is characterised by intense bands
-
at 1897 and 2,025 cm , and a medium intense band at
1
-
1
1
,928 cm . These bands are ascribed to m(C:O) of the
fac-[Re(CO) ] unit [36]. The band of medium intensity at
?
3
-
1
1
,674 cm is assigned to the non-coordinated m(C=O).
The absorptions at 1,614 and 1,650 cm are ascribed to
-
1
m(C=N) of the coordinated ligand, and the bands of med-
-
1
ium intensity at 453 and 482 cm are assigned to m(Re–
N).
The ORTEP diagram of 2 (Fig. 5) shows two similar
rhenium(I) complexes in the asymmetric unit. Both contain
?
the fac-[Re(CO)3] core in a distorted octahedral geome-
The UV–Vis spectrum in methanol illustrates an intense
absorption at 319 nm and a less intense peak at 394 nm.
The former is ascribed to an intraligand p ? p* transition
try. Each rhenium atom is coordinated to three carbonyl
123

3
74
J Chem Crystallogr (2014) 44:368–375
donors in a facial orientation, one imino nitrogen, one
the Re coordinated carbonyls have a p ring interaction less
˚
˚
pyridyl nitrogen atom and a chloride ion.
˚
The average Re–CO bond distances [1.9253 A] fall in
˚
the range observed [1.900(2)–1.928(2) A] for similar
than 4 A to the ring centroid. The shortest is 3.410(3) A
between C(16)–O(16) and the ring Re(1), N(11), C(111),
C(11), N(12).
complexes [19–21]. The Re(1)–N(11) bond distance of
˚
The reaction of [Re(CO) X] (X = Cl, Br) with bidentate
5
2
.184(2) A is slightly longer than the Re(1)–N(12) bond
nitrogen-donor ligands L has been well studied. Octahedral
˚
length of 2.160(2) A. This may be due to the coordination
requirements of the Hppq ligand which forms a five-
membered ring metallocycle. The bond distances Re(2)–
complexes of the type fac-[Re(CO) X(L)] have been iso-
3
0
lated in all these cases with 2,2 -pyridine [27], 1,10-phe-
nanthroline [28] and piperazine [29] as ligands. However,
with tridentate benzimidazole and quinoline derivatives,
˚
˚
N(21) [2.179(3) A] and Re(2)–N(22) [2.168(2) A] in the
second complex are closer to each other. The distortion
from an ideal octahedron is the result of the non-linear
trans angles Cl(1)–Re(1)–C(15) = 176.43(9)ꢁ, N(11)–
Re(1)–C(14) = 172.18(1)ꢁ,
72.31(1)ꢁ, N(21)–Re(2)–C(25) = 173.7(1)ꢁ, N(22)–
complex salts of the type [Re(CO) (L)]X were obtained
3
[30].
N(12)–Re(1)–C(16) =
Supplementary Data
1
Re(2)–C(24) = 170.3(1)ꢁ
79.9(1)ꢁ. These distortions may be the result of the con-
and
Cl(2)–Re(2)–C(26) =
CCDC 995063 and 995104 contain the supplementary
crystallographic data for complexes 1 and 2 respectively.
These data can be obtained free of charge via http://www.
ccdc.cam.ac.uk/conts/retrieving.html, or from the Cam-
bridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; Fax:(?44)1223-336-033; or
Mail:deposit@ccdc.cam.ac.uk.
1
straints imposed by the bidentate coordination of Hppq
which forms a five-membered ring metallocycle. The dis-
tortion from an ideal octahedral is also shown by the bite
angle N(11)–Re(1) - N(12) of 74.16(9)ꢁ.
The Re(1)–Cl(1) and Re(2)–Cl(2) bond lengths of
˚
.4899(8) and 2.485(1) A respectively are close to that
2
observed in complex 1, and are close to the average Re–Cl
˚
distance of 2.479(1) A which is observed in similar com-
plexes [24, 26]. The bond angles Cl(1)–Re(1)–C(14)
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