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T.L. Nicholson et al. / Inorganica Chimica Acta 362 (2009) 3637–3640
to reflux yielding a yellow–brown solution. The solution was al-
lowed to evaporate at room temperature, yielding first a dull peach
colored precipitate. This solid contained exclusively the fac isomer
as determined by infrared spectroscopy. The both isomers are
however present in the mother liquor and the recrystallized prod-
uct, as determined by infrared spectroscopy.
Anal. Calc. Results* for TcCl2P2ON2C32H37: C, 55.12; H, 5.31; N,
Fig. 1. Nitrosyl bonding conformations, linear on the left, bent in the middle and
bridging on right.
4.02. Found: C, 54.19[10]; H, 5.38; N, 3.88%. IR(neat):
m(N@O),
1789 cmÀ1. ESI(+) Mass spectrum: 647 m/z, [TcCl2(NO)(PNPpr)].
*(PNPbu ligand employed for analytical preparation).
Table 1
X-ray data collection parameters.
3.2. mer-[TcCl2(NO)(PNPpr)]
Complex (1)
Complex (2)
A sample of H[TcNOCl4] was dissolved in 50 mL MeCN. To this
was added 42 mg, (1 equivalent) of PNPpr, which rapidly dissolved
yielding a yellow–orange solution. The solution was stirred at
room temperature for 90 min and then refluxed with no further
color change. The solution was reduced in volume to 5 mL, and
then allowed to evaporate slowly at room temperature, yielding
rod shaped, orange crystals. The mother liquor contains both struc-
tural isomers as determined by infrared spectroscopy.
Empirical formula
Formula weight
Crystal system
Space Group
a (Å)
C31.25H35.50Cl2.50N2OP2Tc
702.718
orthorhombic
Pna2(1)
11.5189
23.6427
12.7998
3485.87(10)
4
C34H39.50Cl2N3.50OP2Tc
743.064
orthorhombic
Pna2(1)
19.1840
17.0729
21.2377
6955.91
8
b (Å)
c (Å)
V (Å3)
Z
Dcalc (Mg/m3)
T (°C)
1.339
1.419
IR(neat): m
(N@O), 1689 cmÀ1. ESI(+) Mass spectrum: 647 m/z,
À173
À173
[TcCl2(NO)(PNPpr)], 1331 m/z, [TcCl2(NO)(PNPpr)]/[TcCl3(NO)-
(PNPpr)].
R, Rw
0.056, 0.166
1.162
0.028, 0.060
1.049
Goodness of fit (GOF)
4. Discussion
data set collected at À173 °C. The scan mode used was 2
maximum 2h of 60°. A total of 13 679 reflections were collected of
which 9756 were of I > 2 (I) and were used in the final refinement.
The technetium atom was located using the direct methods. Neu-
tral atomic scattering factors were used throughout the analysis.
Extinction effects were not observed. Final hydrogen atom posi-
tions were calculated. All non-hydrogen atoms were refined
anisotropically.
x, with a
The search for new coordination complexes of technetium, and
to a lesser extent rhenium, for evaluation as diagnostic imaging
and therapeutic agents in nuclear medicine continues, albeit at a
significantly diminished pace with technetium, due to licensing
and regulatory hurdles now in place for the long-lived isotope99
Tc. Reports of Group 7 coordination complexes incorporating the
nitrosyl ligand have been few and far between [7,11–18], which
is due to the lack of easily prepared synthetic precursors. We re-
cently reported the facile synthesis of H[TcNOCl4] in a ‘one-pot’
preparation from pertechnetate [19], making the second row nitro-
syl chemistry more accessible.
r
2.1.2. mer-[TcCl2(NO)(PNPpr)]Á(3/2CH3CN)
The crystal data and some experimental details of the structure
determination are given in Table 1. An orange needle shaped crys-
tal of mer-[TcCl2(NO)(PNPpr)] was isolated from the acetonitrile
mixture as described below. The crystals dimensions were
0.25 Â 0.05 Â 0.05 mm. The diffractometer employed was a Sie-
mens three-circle diffractometer/Bruker APEX CCD with the data
A representation of the tridentate bis-phosphine-amine ligand
PNPpr is shown in Fig. 2 [20].
The reaction of HTcNOCl4 with one equivalent of PNPpr in
refluxing methanol yields predominantly the facial complex
[TcCl2(NO)(PNPpr)]. This dull yellow colored species crystallizes
from the slow evaporation of this solution. The sterically hindered,
tridentate ligand occupies three facial coordination sites with the
amine nitrogen coordinated trans to the nitrosyl ligand, in a dis-
torted octahedral geometry. The Tc–N bond to the nitrosyl nitrogen
atom is 1.751(5) Å and the N–O bond length is 1.163(6) Å, both of
which are within the expected range for this type of multiply
bonded species. The Tc–N–O bond angle is 177.9(4)° which con-
firms the linear nature of the nitrosyl core. The Tc–Cl bond lengths
are somewhat elongated, with (Tc–Cl1) at 2.4695(11) Å and
set collected at À173 °C. The scan mode used was 2
imum 2h of 58°. A total of 18 728 reflections were collected of
which 17 420 were of I > 2 (I) and were used in the final refine-
x, with a max-
r
ment. The technetium atom was located using the direct methods.
Neutral atomic scattering factors were used throughout the analy-
sis. Extinction effects were not observed. Final hydrogen atom
positions were calculated. All non-hydrogen atoms were refined
anisotropically. The two crystallographically independent mole-
cules of the mer structure are almost related by an inversion center,
making the pseudo space group Pbcn (after a unit cell transforma-
tion). This inversion center is only fulfilled by about 90% of all
ordered atoms and refinement in the centrosymmetric space group
is not stable. Two of the three CH3CN solvent molecules are
disordered.
3. Synthesis
3.1. fac-[TcCl2(NO)(PNPpr)]
A sample of H[TcNOCl4] was dissolved in 50 mL MeOH. To this
was added 40 mg, (1 equivalent) of PNPpr. The reaction mixture
was stirred at room temperature for 90 min, which failed to
completely dissolve the ligand. This suspension was then brought
Fig. 2. Representation of the tridentate ligand bis[(2-diphenylphosphino)pro-
pyl]amine (PNPpr) where R = n-propyl.
Nicholson
