The synthesis and characterization of rhenium nitrosyl complexes. The X-ray crystal structures of [ReBr2(NO)(NCMe)3], [Re(NO)(N 5)] (BPh4)2] and [ReBr2(NO)(NCMe) {py-CH2-NH～CH<su

Article abstract of DOI:10.1016/j.ica.2013.01.017

Reactions of low oxidation state rhenium-nitrosyl complexes with polyamine ligands have been examined. Rhenium(II)-nitrosyl complexes gave an array of unstable products that were difficult to isolate cleanly. The rhenium(I)-nitrosyl complex [ReBr₂

Full text of DOI:10.1016/j.ica.2013.01.017

Inorganica Chimica Acta 405 (2013) 455–460
Contents lists available at SciVerse ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
The synthesis and characterization of rhenium nitrosyl complexes.
The X-ray crystal structures of [ReBr (NO)(NCMe) ], [Re(NO)(N )]
2
3
5
(
BPh ) ] and [ReBr (NO)(NCMe) {py-CH -NHꢀCH CH -N(CH -py) }]
4
2
2
2
2
2
2
2
a
a
a
b
c
c
Ashfaq Mahmood , Zeynep Akgun , Yijie Peng , Peter Müller , Yanfeng Jiang , Heinz Berke ,
Alun G. Jones , Terrence Nicholson
a
a,
⇑
a
The Department of Radiology, Harvard Medical School and Brigham & Women’s Hospital, Boston, MA 02215, USA
The Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Anorganisch-Chemisches Inst., University of Zurich, Winterthurerstrasse, 190 CH-8057 Zurich, Switzerland
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
Reactions of low oxidation state rhenium–nitrosyl complexes with polyamine ligands have been exam-
ined. Rhenium(II)–nitrosyl complexes gave an array of unstable products that were difficult to isolate
Received 1 November 2012
Received in revised form 10 January 2013
Accepted 20 January 2013
Available online 6 February 2013
cleanly. The rhenium(I)–nitrosyl complex [ReBr
easily isolated.
2
(NO)(NCMe)
3
] gave multiple products which were more
The major product from the reaction of [ReBr
,N ,N
-tris(2-pyridinylmethyl)-1,2 ethanediamine was the dicationic species [Re(NO)(N5)]2
which was isolated as the bis-tetraphenylborate salt. The other major product [ReBr
py-CH CH N(CH -py)
raphy. This species contains the same potentially pentadentate ligand, only here it is coordinated through
only two of its amine functional groups. Left dangling is the secondary amine and both of its pyridyl
groups.
2
(NO)(NCMe) ] with the potentially pentadentate ligand
3
+
N
1
1
2
,
Keywords:
Rhenium
Nitrosyl
Polyamine
Pentadentate
2
(NO)(NCMe)
{
2
NHꢀCH
2
2
2
2
}], was separated from a number of other neutral species via chromatog-
Both amine complexes are diamagnetic and both display their respective parent ions in the ESI(+)
2
+
mass spectra. The dication [Re(NO)(N5)]
ReBr (NO)(NCMe){py-CH CH N(CH
NHꢀCH
spectrum of [ReBr (NO)(NCMe){py-CH
And the infrared spectrum of [Re(NO)(N5)](BPh
shows its half mass parent peak at 275 m/z while
[
2
2
2
2
2
-py)
2
}] shows its parent peak at 751 m/z. The infrared
ꢁ1
2
2
NHꢀCH
2
CH
2
N(CH
2
-py)
2
}] displays its
(N@O) at 1714 cm
Ó 2013 Elsevier B.V. All rights reserved.
m(N@O) at 1676 cm .
ꢁ1
4
)
2
displays its
m
.
1
. Introduction
Here we report similar difficulties employing the dianionic
Re(II) nitrosyl complex (Me N) [ReNOBr ] [5]. Multiple products
4
2
5
We recently reported on the difficulties encountered when
were obtained as determined chromatographically, many with
limited solution stability when this precursor was reacted with
the same set of polyamine ligands used in the technetium reac-
examining the coordination chemistry of technetium–nitrosyl
complexes with polyamine and phosphine-amine ligands [1,2].
The starting material initially used in these reactions was the
2 3
tions. The rhenium(I) nitrosyl complex [ReBr (NO)(NCMe) ] [6]
anionic Tc(II) complex (Bu
4
N)[TcNOCl
4
] [3]. This highly reactive
gave more easily isolable products with these polyamine ligands,
but simple substitution reactions again gave a surprisingly large
number of products under ambient reaction conditions.
species was shown to be easily reduced to Tc(I) under ambient
reaction conditions, generating a host of products as determined
by infrared spectroscopy, greatly complicating even simple
substitution reactions. However, when the Tc(I) nitrosyl complex
[
TcCl
2
(NO)(HOMe)(PPh
)
3 2
] [4] was employed as starting material,
2. Experimental
the number of by-products was greatly diminished, allowing the
major products to be more easily isolated and fully characterized.
Reagents and solvents were used as received unless otherwise
stated. Routine infrared spectra were obtained on a Perkin Elmer
Spectrum One FTIR Spectrometer. H NMR spectra were collected
1
on a Bruker (600 mHz) spectrometer. Mass spectra were obtained
on a Bruker Daltonics APEXII 3 Tesla Fourier Transform Mass
Spectrometer (Ion Cyclo-tron Resonance Mass Spectrometer).
⇑
Corresponding author. Tel.: +1 6173508942.
E-mail addresses: tnichlsn@yahoo.com, terrence_nicholson@hms.harvard.edu
(
T. Nicholson).
0
020-1693/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ica.2013.01.017

4
56
A. Mahmood et al. / Inorganica Chimica Acta 405 (2013) 455–460
concentrated and purified by a silica gel chromatography using
–6% methanolic NH (7 M NH in methanol)/97–94% CH Cl as
eluent, to yield the desired product, as a yellow oil (60%).
NMR (CDCl , 600 MHz): 8.49 (dd, 2H, Ar), 7.59 (m, 2H, Ar), 7.27
d, 2H, Ar), 7.11 (m, 2H, Ar), 3.87 (s, 4H, CH ), 3.78 (s, 4H, CH ).
3
3
3
2
2
1
H
3
(
2
2
1 1 2
4.2. (N ,N ,N -Tris(2-pyridinylmethyl)-1,2-ethanediamine) [B]
(A)
(B)
[
B] was synthesized following a modified literature procedure
11]. A solution of 3.8 g (15.9 mmol) of [A] and 1.7 g (15.9 mmol)
of 2-pyridinecarboxaldehyde in 10 mL Et O was stirred at room
Scheme 1. Addition of a pyridyl arm to the linear tetradentate ligand.
[
3
. X-ray crystal structure determination
Low-temperature diffraction data (/-and
2
2
temperature with CaCl protection for 16 h. The resulting white
x
-scans) were col-
precipitate was isolated by filtration and washed with Et O to af-
2
0
lected on a Siemens Platform three-circle diffractometer coupled
to a Bruker-AXS Smart Apex CCD detector with graphite-mono-
chromated Mo Ka radiation (k = 0.71073 Å).
ford the intermediate compound (2,2 -((2-pyridin-2-yl)imidazolli-
dine-1,3-diyl)bis(methylene)))dipyridine) (4.5 g, 13.8 mmol, 86%
yield). To a solution of 1.0 g (3.04 mmol) of this intermediate in
The structures were solved by direct methods using SHELXS [7]
50 mL MeOH was added 0.19 g (3.02 mmol) of NaBH CN and
3
2
and refined against F on all data by full-matrix least squares with
0.46 mL (5.98 mmol) of CF CO H. The solution was stirred at room
3
2
SHELXL-97 [8] following established refinement strategies [9]. All
non-hydrogen atoms were refined anisotropically. All hydrogen
atoms were included into the model at geometrically calculated
positions and refined using a riding model. The isotropic displace-
ment parameters of all hydrogen atoms were fixed to 1.2 times the
U value of the atoms they are linked to (1.5 times for methyl
groups and hydroxyl hydrogen atoms).
temperature with CaCl2 protection for 18 h. A 15% NaOH solution
(30 mL) was added and after stirring for 3 h, the solution was
extracted three times with 50 mL of CH Cl and the combined or-
2
2
ganic layers were dried (Na SO ). Evaporation of the solvent affor-
2
4
ded 0.70 g (2.13 mmol) of [B]. See Scheme 1 below (70% yield) as a
1
yellow oil. H NMR (CDCl , 600 MHz) d: 8.45 (dd, 1H, Ar), 8.43 (dd,
3
2H, Ar), 7.58–7.54 (overlapped m, 3H, Ar), 7.43 (d, 2H, Ar), 7.28 (d,
1
4
H, Ar), 7.09 (m, 1H, Ar), 7.06 (m, 2H, Ar), 3.82 (s, 2H, CH
H, CH ), 2.78 (m, 4H, CH ) [11].
2
), 3.79 (s,
2
2
4
. Synthesis
4
.1. N ,N -Bis(2-pyridinyl-methyl)-1,2-ethanediamine [A]
1
2
4.3. [ReBr
2
(NO)(NCMe)
3
]
The procedure was adapted from published literature [10]. A
solution of ethane-1,2-diamine (1.2 g, 20 mmol) in dry EtOH
30 mL) was added dropwise to a solution of pyridine-2-carbalde-
hyde (4.28 g, 40 mmol) in dry EtOH (100 mL). The mixture was re-
fluxed for 12 h and after cooling to room temperature the solvent
was removed. The resulting residue was redissolved in methanol,
[ReBr
2
(NO)(NCMe) ] was prepared as described in [12] and
3
purified with column chromatography, eluting with 5% methanol
in dichloromethane. The only mobile component was an orange
band which was collected, concentrated via rotary evaporation
and recrystallized by slow evaporation at room temperature to
(
ꢁ1
yield large, dark orange crystals. IR(neat): m(N@O) at 1686 cm .
followed by addition of NaBH
night. The solvent was evaporated, following extraction with
dichloromethane and water. The dichloromethane extract was
4
(1.5 g, 40 mmol) and stirred over-
The X-ray crystallography has been reported previously, however
a second unit cell/crystallographic solution was discovered and is
reported here. See Table 3.
Scheme 2. Synthetic approach to synthesizing the 2 complexes which incorporate the potentially pentadentate ligand. Complex 1 only utilizes 2 of the 5 available amine
groups while complex 2 is fully encapsulated by the pentadentate ligand.

A. Mahmood et al. / Inorganica Chimica Acta 405 (2013) 455–460
457
Table 1
Selected bond lengths and angles for complex 1,
ReBr (NO)(NCMe){py-CH CH N(CH -py) }].
NHꢀCH
[
2
2
2
2
2
2
Re1–Br1
Re1–Br2
Re1–N6
Re1–N1
Re1–N3
Re1–N4
N6–O1
2.564(1)
2.558(1)
1.737(8)
2.060(7)
2.127(6)
2.220(7)
1.21(1)
N6–Re1–N1
N6–Re1–N3
N1–Re1–N3
N6–Re1–N4
N1–Re1–N4
N3–Re1–N4
N6–Re1–Br2
N1–Re1–Br2
N3–Re1–Br2
N4–Re1–Br2
N6 Re1 Br1
N1–Re1–Br1
N3–Re1–Br1
N4–Re1–Br1
Br2–Re1–Br1
O1–N6–Re1
95.4(3)
95.3(3)
169.2(3)
171.2(3)
93.4(3)
75.9(3)
96.3(3)
89.3(3)
89.2(2)
84.5(2)
93.3(3)
88.2(2)
91.5(2)
86.2(2)
170.24(3)
174.4(7)
residue chromatographed on a silica preparatory plate, eluting
with 3% methanol in dichloromethane. The major mobile band
was bright orange and was isolated, concentrated via rotary
evaporation and recrystallized by slow evaporation of a metha-
nol–dichloromethane mixture. See Scheme 2 below for a diagram
depicting the synthesis of complex 1. The infrared spectrum of this
Fig. 1. An ORTEP diagram of [ReBr
labeled. Hydrogen atoms have been omitted for clarity.
2 3
(NO)(NCMe) ], showing non-carbon atoms
2
4.4. [ReBr (NO)(NCMe){py-CH
2
NHꢀCH
2 2 2 2
CH N(CH -py) }], complex 1
ꢁ1
product displays a
m(N@O) at 1676 cm . ESI(+) mass spectrum:
+
1
A 49 mg sample of [ReBr
3 mg of N5 ligand [B] and 45 mL of dichloromethane and stirred
2
(NO)(NCMe) ] was combined with
3
751 m/z = [ReBr (NO)(NCMe)(N5)] . H NMR (CDCl , 600 MHz) d:
2
3
3
8.41 (d, 2H, Ar), 8.13 (d, 1H, Ar), 7.56 (m, 2H, Ar), 7.43 (d, 2H,
Ar), 7.17–7.09 (overlapped m, 4H, Ar), 6.95 (d, 1H, Ar), 5.40
(m(br), 1H, NH), 5.24 (d, 1H, CH), 4.22 (dd, 1H, CH), 3.89
at RT. The golden colored solution darkened to golden-brown
overnight. After 72 h at RT, the solvent was removed and the
Fig. 2. An ORTEP diagram of complex 1, [ReBr
2
(NO)(NCMe){py-NHꢀN(py)
2
}], showing only non-carbon atoms labeled. Hydrogen atoms have been omitted for clarity.

4
58
A. Mahmood et al. / Inorganica Chimica Acta 405 (2013) 455–460
Fig. 3. An ORTEP diagram of complex 2, the dication [Re(NO){py-NHꢀN(py)
}]2+, showing only non-carbon atoms labeled. Hydrogen atoms have been omitted for clarity.
2
(
(
overlapped d, 2H, CH
m, 1H, CH), 2.99 (s, 3H, CH
2
), 3.69 (d, 2H, CH
2
), 3.45 (m, 1H, CH), 2.97
new imaging agents is the technetium(I)-tricarbonyl core. This
lipophilic core has only three facial coordination sites available
for ligand incorporation, seriously restricting the scope of poten-
tial coligands. The Tc(I)–nitrosyl core is less lipophilic than the
3
), 2.86 (m, 1H, CH), 2.65 (m, 1H, CH).
4
4 2
.5. [Re(NO)(N5)](BPh ) , complex 2
{
3
Tc(I)-(CO) } core and it has five coordination sites available to
A 81 mg sample of [ReBr
5 mg of the N5 ligand [B] in 50 mL of methanol. After 72 h at
2 3
(NO)(NCMe) ] was combined with
accommodate coligands. When this new species is more fully
developed, it may prove very useful in radiopharmaceutical
development.
Rhenium–nitrosyl complexes are under increased scrutiny in
organometallic chemistry as hydrogenation catalysts and transfer
agents [11]. In that regard, substitution reactions of Re–nitrosyl
complexes such as (Me N) [Re(NO)Cl ] are being examined [6].
4 2 5
Preliminary results of reactions of our polyamine ligands with this
Re(II)–nitrosyl complex give similar results to those we obtained
5
RT, the methanol was removed via rotary evaporation. The result-
ing brown residue was washed with dichloromethane, causing the
formation of a brown oil, which was dissolved with the addition of
a few mL of methanol. Excess sodium tetraphenylborate was
added, which caused the formation of a dark colored precipitate.
The precipitate was removed via vacuum filtration and the filtrate
set aside to evaporate at RT. After 12 h, methanol was added,
allowing isolation of deep red-purple crystals after 24 hours at
RT. See Scheme 2 below for a diagram depicting the synthesis of
4 4
with the technetium(II) complex (Bu N)[TcNOCl ] [1]. These reac-
tions are greatly complicated by redox reactions competing with
the intended ligand substitution reactions. Reactions with the rhe-
ꢁ1
complex 2. IR(KBr) m(N@O) at 1714 cm . ESI(+) mass spectrum:
2
+ 1
2
1
1
7
3
75 m/z = [Re(NO)(N5)] . H NMR (CDCl , 600 MHz) d: 8.54 (d,
2 3
nium(I) complex [ReBr (NO)(NCMe) ] proved less problematic in
H, Ar), 8.45 (d, 1H, Ar), 8.19 (m, 1H, Ar), 7.89 (s, 1H, Ar), 7.82 (d,
H, Ar), 7.63 (m, 1H, Ar), 7.59–7.54 (overlapped m, 2H, Ar), 7.49–
.44 (overlapped m, 3H, Ar), 7.291 (m(br), Ar(TPB)), 7.014 (m,
this regard, however a number of products were formed as deter-
mined by thin layer chromatography and infrared spectroscopy. An
X-ray crystallographic study of this deep red-orange complex was
performed to confirm its identity. The neutral Re(I) complex dis-
plays the three acetonitrile ligands coordinated in a meridional
manner, with the nitrosyl and two bromines coordinated similarly.
Bonding parameters for the nitrosyl ligand are typical for linearly
coordinated nitrosyl ligands of this type, {Re–N 1.823(6) Å and
N–O 1.173(7) Å and Re–N–O of 179.6(9)°} with multiple bonding
throughout the Re–N–O moiety. The Re–N bond lengths to the
three acetonitrile ligands are similar and in the expected range.
The Re–Br bond lengths too are unexceptional. The infrared spec-
Ar(TPB)), 6.86 (m, Ar(TPB)), 6.57 (m(br), 1H, NH), 4.91 (d, 1H, CH),
.82 (m, 2H, CH ), 4.73 (m, 2H, CH ), 3.97 (d, 1H, CH), 3.49 (m, 1H,
CH), 3.44 (m, 1H, CH), 3.36 (m, 1H, CH), 2.74 (m, 1H, CH).
4
2
2
5
. Discussion
The technetium(I)–nitrosyl core presents interesting chemical
properties that might be found useful in radiopharmaceutical de-
sign. Of the cores currently employed in established radiophar-
maceuticals, the technetium(V)-oxo core is the most versatile. It
has the capacity to accommodate ligation at its available five
coordination sites. This versatility is reflected in the number of
established imaging agents that incorporate this core, including
ꢁ1
trum of this complex displays the
Fig. 1 for an ORTEP diagram of complex 1. For a complete list of
bonding parameters see Ref. [11].
m(N@O) at 1686 cm . See
This neutral Re(I) complex [ReBr (NO)(NCMe) ] was reacted
2
3
9
9m
TcO-HMPAO, 99mTcO-ECD, 99mTcO-MAG
99m
3
, and
TcO-TRODAT.
1 1 2
with the neutral pentadentate amine ligand N ,N ,N -tris(2-pyrid-
The core currently receiving the most attention in the search for
inylmethyl)-1,2-ethanediamine [2] in dichloromethane at room
temperature. The resulting crude product mixture was chromato-
graphed in silica, with the major brownish product remaining
immobile at the baseline. The most prominent mobile component
1
The missing ligand proton signal is buried under the tetraphenylborate aromatic
signal d 7.29. This was confirmed by a 2-D NMR spectroscopic analysis.

A. Mahmood et al. / Inorganica Chimica Acta 405 (2013) 455–460
459
Table 2
the ambient reaction conditions employed and in the non-polar
solvent, the rhenium precursor is more strongly bonded to the
bromide ligands and the acetonitrile ligand cis to the nitrosyl
core than was anticipated. A similar result was reported by Berke
Selected bond lengths and angles for complex 2,
4 2
[Re(NO)(N5)](BPh ) .
Re1–N6
Re1–N1
Re1–N2
Re1–N3
Re1–N4
Re1–N5
N6–O1
1.758(1)
2.080(1)
2.103(1)
2.130(1)
2.166(1)
2.179(1)
1.190(2)
et al. with their synthesis of [ReCl
2
(NO)(NCMe)(PR
] and the phosphine in acetonitrile at 70°
12]. The rhenium–nitrogen bond length to the nitrosyl nitrogen
3 2
) ] from
[
[
2 3
ReCl (NO)(NCMe)
is 1.737(8) Å with the N–O bond length of the nitrosyl group at
1
.210(10) Å. The Re–N–O bond angle is 174.4(7)°. The bromide
N6–Re1–N1
N6–Re1–N2
N1–Re1–N2
N6–Re1–N3
N1–Re1–N3
N2–Re1–N3
N6–Re1–N4
N1–Re1–N4
N2–Re1–N4
N3–Re1–N4
N6–Re1–N5
N1–Re1–N5
N2–Re1–N5
N3–Re1–N5
N4–Re1–N5
O1–N6–Re1
98.24(6)
94.81(6)
89.05(6)
95.68(7)
94.42(6)
168.36(6)
102.30(7)
158.86(6)
94.15(6)
78.70(6)
172.62(6)
77.86(6)
78.97(5)
90.89(6)
82.25(6)
173.8(1)
ligands are in a cis orientation in the precursor and are mutually
trans in this reaction product. The bidentate ligand coordination
results in a very contracted bite angle of only 75.9(3)°. This large
distortion from octahedral results in the remaining bond angles
within the coordination sphere being somewhat distorted as well.
Fig. 2 displays an ORTEP diagram from complex 1 and Table 1 lists
selected bond lengths and angles.
The major product from the analogous reaction in methanol is
4 2
the fully chelated dication [Re(NO)(N5)](BPh ) complex 2. This
species is precipitated from the reaction mixture by addition of so-
dium tetraphenylborate, which causes a dark colored precipitate to
form. The infrared spectrum of this complex displays the
m
(N@O) at
ꢁ1
1
714 cm . The ESI(+) mass spectrum displays the half-parent
peak at 275 m/z, which corresponds to [Re(NO)(N5)] /2. The 1
2+
H
NMR data for this diamagnetic species are listed in Section 2 (vide
supra).
was a bright orange species, complex 1, that was isolated and
crystallized by slow evaporation of the eluting solvent mixture of
methanol and dichloromethane. The infrared spectrum of this
The X-ray crystallographic analysis of this dication shows the
Re–N and N–O bond lengths to be 1.7587(16) Å and 1.190(2) Å
respectively, reflecting the multiple bonding throughout the nitro-
syl unit. The Re–N–O bond angle is 173.83(15)°, somewhat dis-
torted from linear. The Re–N bond lengths to the amines are
such that the aliphatic amine bond lengths are longer than those
to the pyridyl termini. The Re–N5 bond length is the longest of
all at 2.1792(15) Å, which is a result of the trans-influence of the
multiply-bonded nitrosyl unit pulling electrons away from the
trans-amine ligand and lengthening its bond. Steric constraints im-
posed by the chelated ligand cause significant deviations from
octahedral geometry. Fig. 3 displays an ORTEP diagram for complex
ꢁ1
complex displays a strong absorption at 1676 cm which corre-
sponds to the (N@O). The ESI(+) mass spectrum displays the par-
ent peak [ReBr
diamagnetic, with the H NMR spectrum data listed in Section 2
m
+
2
(NO)(NCMe)(N5)] at 751 m/z. Complex 1 is
1
(vide supra).
The X-ray crystallographic structural analysis of these
crystals proved them to be the neutral Re(I) complex
ReBr (NO)(NCMe){py-CH CH N(CH -py) }], which con-
NHꢀCH
tains the pentadentate polyamine ligand coordinated in
[
2
2
2
2
2
2
a
bidentate manner, with the three remaining amine moieties
dangling in a pendant manner. This result suggests that under
2
and Table 2 lists selected bond lengths and angles.
Table 3
X-ray Crystallographic Data Collection Parameters.
[
ReBr
2
(NO)(NCMe)
3
]
Complex 1
26Br
Complex 2
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
C
6
9
H Br
2
N
4
ORe
C
22
H
2
7
N ORe
74 75 2 6
C H B N O2.50Re
499.19
100(2)
0.71073
monoclinic
P2(1)/c
782.56
100(2)
0.71073
1296.22
100(2)
0.71073
monoclinic
P2(1)/n
monoclinic
P2
1
8.0641(9)
10.0173(12)
15.5094(18)
97.120(2)
1243.2(2)
4
2.667
16.179
904
7.3668(12)
27.048(4)
13.123(2)
94.214(4)
2607.8(7)
4
1.993
7.759
1512
15.7874(13)
22.2079(18)
18.3931(15)
107.466(2)
6151.4(9)
4
1.400
2.029
2664
b (Å)
c (Å)
b (°)
Volume (Å )
3
Z
3
Density (calculated) (Mg/m )
Absorption coefficient (mm 1)
F(000)
ꢁ
3
Crystal size (mm )
0.10 ꢂ 0.04 ꢂ 0.01
2.43–31.51°
56304
0.44 ꢂ 0.41 ꢂ 0.04
0.17 ꢂ 0.15 ꢂ 0.15
H
range for data collection
1.51–31.51°
2.17–31.57°
Reflections collected
166395
310040
Independent reflections
Absorption correction
Max. and min. transmission
Data/restraints/param.
4138 [Rint = 0.0413]
multi scan
0.8314 and 0.4474
4138/66/143
1.098
16555 [Rint = 0.0467]
multi scan
0.7466 and 0.1315
17363/609/657
1.120
17671 [Rint = 0.0409]
multi scan
0.7506 and 0.7242
20470/459/876
1.058
2
Goodness-of-fit on F
Final R indices [I > 2
R indices (all data)
r(I)]
R
R
1
= 0.0343, wR
= 0.0409, wR
2
= 0.0802
= 0.0842
R
R
1
= 0.0195, wR
= 0.1402, wR
2
= 0.0439
= 0.1422
R
R
1
= 0.0248, wR
= 0.0600, wR
2
= 0.0330
= 0.0649
1
2
1
2
1
2

4
60
A. Mahmood et al. / Inorganica Chimica Acta 405 (2013) 455–460
6
. Conclusion
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[
[
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1
The authors would like to thank L. Li of the Massachusetts Insti-
tute of Technology Spectrometry Laboratory for the mass spec-
trum. The X-ray diffractometer and associated instrumentation
was purchased with the help of funding from the National Science
Foundation (NSF) under Grant Number CHE-0946721.
[
7