B. Kuhn, U. Abram
ARTICLE
Na2mnt[23] were prepared following literature procedures. The synthe-
sis of [Re(NPh-4-NH2)Cl3(PPh3)2] was slightly modified to improve
the yield and the purity of the product. Infrared spectra were measured
as KBr pellets with a Shimadzu FT IR spectrometer between 400 and
4000 cm–1. Elemental analyses were determined with a Heraeus vario
EL elemental analyzer. NMR spectra were taken with a JEOL
400 MHz multinuclear spectrometer.
It is noteworthy, that, in contrast to previous reports on imido-
rhenium(V) compounds,[3,4] no hydrolytic decomposition has
been observed for the phenylimido complexes reported in this
paper. This recommends them for considerations with respect to
nuclear medical applications. Thus, we prepared an analogous
complex to compound 4b, which carries an additional amino
group at the phenyl ring of the imido ligand. With this modifi-
cation, coupling reactions with biorelevant molecules such as
peptides are possible. An appropriate starting material,
[Re(NC6H4-4-NH2)Cl3(PPh3)2], has previously been published
by Machura and co-workers.[20]
Syntheses
[Re(NC6H4-4-NH2)Cl3(PPh3)2]:
[ReOCl3(PPh3)2]
(450 mg,
The reaction of [Re(NC6H4-4-NH2)Cl3(PPh3)2] with Na2mnt
in methanol results in a rapid dissolution of the green solid
and the formation of a red solution. Addition of (AsPh4)Cl
results in a red solid of (AsPh4)[Re(NC6H4-4-NH2)(mnt)2] (5).
Recrystallization from CH2Cl2/isopropanol gives long, red
needles. The IR spectrum of the compound is similar to that of
4b with an intense νC≡N vibration at 2200 cm–1. Additionally,
medium bands at 3450 and 3360 cm–1 can be assigned to the
NH frequencies of the amino group.
Figure 2 shows a structural plot of the complex anion of
compound 5, which has also been studied by X-ray diffraction.
The compound crystallizes in the orthorhombic space group
Pna21 with a unit cell of the dimensions a = 25.881(2) Å, b =
6.492(1) Å and c = 22.589(2) Å. The obtained data set with
wR2 = 0.1062 was not of sufficient quality to justify a compre-
0.54 mmol) was suspended in acetone (15 mL). PPh3 (2.5 g,
9.54 mmol) and 4-NH2-aniline (100 mg, 0.92 mmol) were added in
acetone (5 mL). The mixture was heated under reflux for 3 h. The
resulting olive green precipitate was filtered off and washed with ethyl
ether. Yield 350 mg (75 %). Elemental analysis calcd.
C42H36Cl3N2P4Re: C 54.7; H 3.9; N 3.0 %; found: C 54.8; H 3.9; N
2.8 %. IR (KBr): ν = 3460 (m), 3335 (st), 3195 (w), 3055 (w), 1615
˜
(st), 1585 (st), 1480 (m), 1435 (m), 1370 (st), 1325 (m), 1190 (w),
1165 (st), 1090 (m), 1030 (w), 1005 (w), 925 (w), 845 (w), 745 (m),
695 (st), 600 (w), 565 (w), 520 (st), 515 (st), 450 (w), 425 (w) cm–1.
4a: A suspension of [Tc(NPh)Cl3(PPh3)2] (82 mg, 0.1 mmol) and
Na2mnt (51 mg, 0.4 mmol) in methanol (15 mL) was heated under
reflux for 1 hour. After cooling to room temperature, (AsPh4)Cl·2H2O
(42 mg, 0.1 mmol) in methanol (1 mL) was added. The solvent was
removed in vacuo and the resulting red-brown residue was washed
hensive discussion of the crystallographic data. The results of with ethyl ether and recrystallized from methanol. Yield 45 mg (55 %).
IR (KBr): ν = 3060 (w), 2960 (w), 2915 (w), 2205 (st), 1500 (m),
˜
the study, however, unambiguously confirm the composition
of the complex cation and all main structural features of com-
pound 4b do also apply for 5.
1480 (m), 1465 (m), 1440 (st), 1310 (m), 1185 (w), 1150 (m), 1110
(w), 1080 (m), 1020 (m), 995 (m), 940 (w), 900 (w), 840 (w), 740
(st), 685 (st), 505 (m), 465 (st) cm–1.
4b: [Re(NPh)Cl3(PPh3)2] (91 mg, 0.1 mmol) was suspended in metha-
nol (30 mL) and treated with Na2mnt (43 mg, 0.23 mmol). After heat-
ing to reflux for 10 min,
a clear red solution was obtained.
(AsPh4)Cl·2H2O (42 mg, 0.1 mmol) was added. Deep red crystals de-
posited upon slow evaporation. Yield 54 mg (57 %). Elemental analy-
sis: C38H25AsN5ReS4: calcd. C 48.5; H 2.7; N 7.4; S 13.6 %; found:
C 48.4; H 2.4; N 7.4; S 13.6 %. IR (KBr): ν = 3060 (w), 2205 (st),
˜
1580 (w), 1510 (st), 1475 (st), 1440 (st), 1355 (st), 1185 (w), 1155
(m), 1080 (m), 1030 (w), 995 (m), 740 (st), 685 (st), 505 (m), 465 (m)
1
cm–1. H NMR (CDCl3): δ = 7.9–7.6 (m, 20 H, As-Ph), 7.3–6.9 ppm
(m, 5 H, N-Ph). FAB–-MS: m/z 558 M–, 482 M– - (C–CN)2, 374
[Re(NPh)S3]–.
Figure 2. Space-filling representation of the complex anion of 5 with
a terminal NH2 group being far away from the coordination sphere.
5: [Re(NC6H4-4-NH2)Cl3(PPh3)2] (93 mg, 0.1 mmol) was suspended
in methanol (50 mL) and treated with Na2mnt (51 mg, 0.40 mmol).
After heating to reflux for 10 min, a clear red solution was obtained.
(AsPh4)Cl·2H2O (42 mg, 0.1 mmol) was added and the solvent was
removed in vacuo. The residue was washed with water and ethyl ether.
Recrystallization from CH2Cl2/isopropanol gave long, red needles.
Yield 22 mg (23 %). Elemental analysis: calcd. C38H26AsN6ReS4: C
47.7; H 2.7; N 8.8; S 13.4 %; found: C 48.4; H 2.3; N 8.5; S 13.1 %.
The phenyl ring of the imido ligand in complex 5 acts as a
spacer and, thus, the terminal NH2 group is readily accessible
for coupling reactions with activated peptides and proteins.
This holds also true for phenylimido complexes with other,
more bulky, chelating ligands, which might be more appropri-
ate for biological applications than maleonitriledithiolate.
IR (KBr): ν = 3450 (st), 3360 (st), 3060 (w), 2270 (w), 2200 (st), 1615
˜
(st), 1590 (st), 1505 (m), 1490 (st), 1440 (st), 1340 (w), 1290 (m),
1185 (w), 1165 (m), 1150 (m), 1115 (m), 1080 (m), 1020 (m), 995
(m), 920 (w), 820 (m), 745 (st), 685 (st), 600 (w), 505 (m), 465 (m)
cm–1.1H NMR (CDCl3): δ = 7.8–7.6 (m, 20 H, As–Ph), 6.6–6.4 ppm
Experimental Section
Materials and Measurements
The
starting
complexes
[Re(NC6H4-4-NH2)Cl3(PPh3)2],[20]
[Tc(NPh)Cl3(PPh3)2],[21] (m, 5 H, N–Ph). FAB–-MS: m/z 573 M–, 481 M– - (C–CN)2 -NH2, 389
[Re(NPh)Cl3(PPh3)2],[22]
and [Re{NPh(p-NH2)}S3]–.
244
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2011, 242–245