Synthesis of a novel class of trigonal bipyramidal nitrido Tc(V) complexes with phosphino-thiol ligands. Crystal structure of [99gTc(N)(L1)2] [L1 = 2-(diphenylphosphino)ethanethiolato] and [99gTc(N)(L5)2] [L5 = 2-(ditolylphosphino)propanethiolato]

Article abstract of DOI:10.1021/ic9903477

Reactions of the precursor complexes [^99gTc(N)Cl₂(PPh₃)₂] and [^99gTc(N)Cl₄]^- with phosphine-thiol ligands (HLⁿ) of the type R₂PCH₂CH₂SH (R = phenyl, methoxypropyl), R₂′PCH₂CH₂CH₂SH (R′ = phenyl, tolyl), and R₂″P-o-C₆H₄SH (R″ = phenyl) afforded the five-coordinated, disubstituted nitrido technetium(V) complexes [^99gTc-(N)(Lⁿ)₂]. The complexes were characterized by elemental analysis, ¹H and ³¹P NMR spectroscopy, FT IR, and positive FAB MS spectra. Structural characterization of [^99gTc(N)(L¹)₂] (1) [HL¹ = (C₆H₅)₂PCH₂CH₂SH] and [^99gTc(N)(L⁵)₂] (5) [HL⁵ = (o-CH₃C₆H₄)₂PCH₂CH ₂CH₂SH] showed that the bidentate phosphino-thiol ligands are coordinated to the technetium center through the neutral phosphorus atom and the deprotonated thiol sulfur atom. These complexes possess an uncommon trigonal bipyramidal geometry with the two phosphorus atoms occupying the two transaxial positions and the two sulfur atoms on the equatorial plane along with the nitrido nitrogen atom. Compound 1 crystallizes in the monoclinic space group C2/c, a = 24.84(2) ?, b = 7.327(6) ?, c = 31.52(2) ?, β = 111.06(10)°, and Z = 8. Compound 5 crystallizes in the monoclinic space group P2₁/n, a = 11.090(1) ?, b= 14.387(2) ?, c = 11.087(1) ?, β= 113.62(1)°, and Z = 2.

Full text of DOI:10.1021/ic9903477

Inorg. Chem. 1999, 38, 4473-4479
4473
Synthesis of a Novel Class of Trigonal Bipyramidal Nitrido Tc(V) Complexes with
Phosphino-Thiol Ligands. Crystal Structure of [99gTc(N)(L1)2] [L1 )
2-(Diphenylphosphino)ethanethiolato] and [99gTc(N)(L5)2] [L5 )
2-(Ditolylphosphino)propanethiolato]
Cristina Bolzati,1 Alessandra Boschi,1 Licia Uccelli,1 Erica Malago`,1 Giuliano Bandoli,2
Francesco Tisato,3 Fiorenzo Refosco,3 Roberto Pasqualini,4 and Adriano Duatti*,1
Laboratorio di Medicina Nucleare, Dipartimento di Medicina Clinica e Sperimentale, Universita` di
Ferrara, Via L. Borsari, 46, 44100 Ferrrara, Italy, ICTIMA CNR, Area della Ricerca, Corso Stati Uniti,
4, 35020 Padova, Italy, Dipartimento di Scienze Farmaceutiche, Universita` di Padova, Via Marzolo, 5,
35131 Padova, Italy, and CIS bio international, 91192 Gif-sur-Yvette, France
ReceiVed March 30, 1999
Reactions of the precursor complexes [99gTc(N)Cl2(PPh3)2] and [99gTc(N)Cl4]- with phosphine-thiol ligands (HLn)
of the type R2PCH2CH2SH (R ) phenyl, methoxypropyl), R2′PCH2CH2CH2SH (R′ ) phenyl, tolyl), and R2′′P-
o-C6H4SH (R′′ ) phenyl) afforded the five-coordinated, disubstituted nitrido technetium(V) complexes [99gTc-
1
(N)(Ln)2]. The complexes were characterized by elemental analysis, H and 31P NMR spectroscopy, FT IR, and
positive FAB MS spectra. Structural characterization of [99gTc(N)(L1)2] (1) [HL1 ) (C6H5)2PCH2CH2SH] and
[
99gTc(N)(L5)2] (5) [HL5 ) (o-CH3C6H4)2PCH2CH2CH2SH] showed that the bidentate phosphino-thiol ligands
are coordinated to the technetium center through the neutral phosphorus atom and the deprotonated thiol sulfur
atom. These complexes possess an uncommon trigonal bipyramidal geometry with the two phosphorus atoms
occupying the two transaxial positions and the two sulfur atoms on the equatorial plane along with the nitrido
nitrogen atom. Compound 1 crystallizes in the monoclinic space group C2/c, a ) 24.84(2) Å, b ) 7.327(6) Å,
c ) 31.52(2) Å, â ) 111.06(10)°, and Z ) 8. Compound 5 crystallizes in the monoclinic space group P21/n, a
) 11.090(1) Å, b ) 14.387(2) Å, c ) 11.087(1) Å, â ) 113.62(1)°, and Z ) 2.
Introduction
Some years ago, Baldas and co-workers first explored nitrido
technetium chemistry.9-13 Following these pioneering investiga-
Radiopharmaceuticals containing the γ-emitting isotope 99mTc
still continue to occupy a prominent position in diagnostic
nuclear medicine due to the favorable nuclear properties (Eγ )
142 keV, t1/2 ) 6.02 h) and availability of this radionuclide. In
the last two decades, dramatic advancements of the studies of
the basic chemistry of technetium complexes have led to the
introduction into clinical application of useful tracers for heart,
brain, and kidneys.5
tions, our research group and others have further studied the
coordination chemistry and biological properties of technetium
complexes characterized by the presence of the terminal Tct
N multiple bond.14-20 Extensive studies have been carried out
on the synthesis and biological evaluation of square pyramidal
nitrido technetium(V) complexes with dithiocarbamate,21,22
(9) Baldas, J.; Bonnyman, J.; Pojer, P.; M.; Williams, G. A. J. Chem.
Soc., Dalton Trans. 1981, 1798-1801.
A considerable number of these tracers belong to the class
of complexes containing the monoxo, [TcdO]3+, and trans
dioxo, [OdTcdO]+, cores. The recent introduction of an
efficient method for the preparation of nitrido technetium(V)
species at the “carrier free” level6-8 has made this class of
compounds more attractive for the development of 99mTc
radiopharmaceuticals, whose production has been focused in
the past primarily on oxo-technetium complexes.
(10) Baldas, J. Pure Appl. Chem. 1990, 1079-1080.
(11) Baldas, J.; Boas, J. F.; Bonnyman, J.; Colmanet, S. F.; Williams, G.
A. Inorg. Chim. Acta 1991, 179, 151-154.
(12) Baldas, J.; Bonnyman, J. Int. J. Appl. Radiat. Isot. 1985, 36, 3-139.
(13) Dehnicke, K.; Stra¨hle, J. Angew. Chem., Int. Ed. Engl. 1992, 31, 955-
978.
(14) Duatti, A.; Uccelli, L. Trends Inorg. Chem. 1996, 4, 27-41.
(15) Duatti, A.; Bolzati, C.; Uccelli, L.; Zucchini, G.-L. Transition Met.
Chem. 1997, 22, 313-314.
(16) Abram, U.; Schulz Lang, E.; Abram, S.; Wegmann, J.; Dilworth, J.
R.; Kirmse, R.; Woollins, J. D. J. Chem. Soc., Dalton Trans. 1997,
623-630.
(1) University of Ferrara.
(2) University of Padova.
(3) ICTIMA, CNR, Padova.
(4) CIS bio international, Gif-sur-Yvette, France.
(5) Jurisson, S.; Berning, D.; Jia, W.; Ma, D. Chem. ReV. 1993, 93, 1137-
1156.
(17) de Vries, N.; Costello, C. E.; Jones, A. G.; Davison, A. Inorg. Chem.
1990, 29, 1348-1352.
(18) Marchi, A.; Rossi, R.; Marvelli, L.; Bertolasi, V. Inorg. Chem. 1993,
32, 4673-4674.
(19) Refosco, F.; Tisato, F.; Moresco, A.; Bandoli, G. J. Chem. Soc., Dalton
Trans. 1995, 3475-3482.
(6) Duatti, A.; Marchi, A.; Pasqualini, R. J. Chem. Soc., Dalton Trans.
1990, 3729-3733.
(20) Tisato, F.; Refosco, F.; Bandoli, G. Coord. Chem. ReV. 1994, 135/
136, 325-397.
(7) Pasqualini, R.; Comazzi, V.; Bellande, E.; Duatti, A.; Marchi, A. Appl.
Radiat. Isot. 1992, 43, 1329-1333.
(21) Pasqualini, R.; Duatti, A.; Bellande, E.; Comazzi, V.; Brucato, V.;
Hoffschir, D.; Fagret, D.; Comet, M. J. Nucl. Med. 1994, 35, 334-
341.
(8) Marchi, A.; Uccelli, L.; Marvelli, L.; Rossi, R.; Giganti, M.; Bertolasi,
V.; Ferretti, V. J. Chem. Soc., Dalton Trans. 1996, 3105-3109.
10.1021/ic9903477 CCC: $18.00 © 1999 American Chemical Society
Published on Web 09/08/1999

4474 Inorganic Chemistry, Vol. 38, No. 20, 1999
Bolzati et al.
dithiocarboxylate,23,24 and dithiophosphinate ligands,25 and with
ONS-type Schiff base ligands.26,27 Five- and six-coordinated
nitrido technetium(V) complexes have been also prepared with
N2S2-type ligands,28,29 diphosphines, and polyphosphines,30,31
and cyclic and acyclic polydentate amine ligands.32-34
Chart 1
In spite of the well-developed technetium chemistry with
thiolate and phosphine ligands, studies on the reactivity of mixed
polydentate phosphine-thiol ligands toward technetium,35-38
and more generally toward other transition metals,39-42 have
appeared in the literature only recently. Examples are repre-
sented by the five-coordinate and six-coordinate technetium-
(III) species of the type [99gTc{P(C6H4S-o)3}(CNPri)n] (n ) 1
or 2),38 prepared by reduction-substitution reactions of the
potentially tridentate ligand P(C6H4SH-o)3 onto [99gTcO4]- in
the presence of isonitriles. In addition, a few more technetium-
(III) complexes, such as octahedral mer-[99gTc(L2)3] and trigonal
bipyramidal [99gTc(Ln)2(S-LndO)] (n ) 1, 4), have been
prepared by our group.35,38 The paucity of investigations in this
area probably reflects the lack of commercially available
functionalized phosphines, the syntheses of which require a
multistep approach and tedious procedures.43-45
In this study we report an extensive investigation on the
synthesis and structural characterization of novel, five-
coordinate, disubstituted nitrido technetium(V) complexes of
the type [99gTc(N)(Ln)2], where HLn (n ) 1-5) is a mixed,
bidentate phosphine-thiol ligand [HL1 ) 2-(diphenylphos-
phino)ethanethiol; HL2 ) 2-(diphenylphosphino)thiophenol; HL3
) 2-(dimethoxypropylphosphino)ethanethiol; HL4 ) 2-(di-
phenylphosphino)propanethiol; HL5 ) 2-(ditolylphosphino)-
propanethiol] (Chart 1). Biodistribution studies in rats and
primates have demonstrated that this new category of agents
accumulate selectively in myocardium tissue and that washout
from blood, lung, and liver is extremely fast.46 A detailed
description of these biological results will be reported else-
where.47 The compound [99gTc(N)(L2)2] has been briefly
described previously by Dilworth and co-workers.48 A prelimi-
nary report on this chemistry has been communicated.49
(22) Pasqualini, R.; Duatti, A. J. Chem. Soc., Chem. Commun. 1992, 1354-
1355.
(23) Bolzati, C.; Uccelli, L.; Duatti, A.; Venturini, M.; Morin, C.;
Che`radame, S.; Refosco, F.; Ossola, F.; Tisato, F. Inorg. Chem. 1997,
36, 3582-3585.
(24) Uccelli, L.; Bolzati, C.; Boschi, A.; Duatti, A.; Morin, C.; Pasqualini,
R.; Giganti, M.; Piffanelli, A. Nucl. Med. Biol. 1999, 26, 63-67.
(25) Bellande, E.; Comazzi, V.; Laine, J.; Lecayon, M.; Pasqualini, R.;
Duatti, A.; Hoffschir, D. Nucl. Med. Biol. 1995, 22, 315-320.
(26) Tisato, F.; Mazzi, U.; Bandoli, G.; Cros, G.; Darbieu, M.-H.; Coulais,
Y.; Guiraud, R. J. Chem. Soc., Dalton Trans. 1991, 1301-1307.
(27) Marchi, A.; Duatti, A.; Rossi, R.; Magon, L.; Pasqualini, R.; Bertolasi,
V.; Ferretti, V.; Gilli, G. J. Chem. Soc., Dalton Trans. 1988, 1743-
1749.
(28) Cros, G.; Tahar, H. B.; de Montauzon, D.; Gleizes, A.; Coulais, Y.;
Guiraud, R.; Bellande, E.; Pasqualini, R. Inorg. Chim. Acta 1994, 227,
25-31.
(29) Marchi, A.; Marvelli, L.; Rossi, R.; Magon, L.; Bertolasi, V.; Ferretti,
V.; Gilli, P. J. Chem. Soc., Dalton Trans. 1992, 1485-1490.
(30) Marchi, A.; Marvelli, L.; Rossi, R.; Magon, L.; Uccelli, L.; Bertolasi,
V.; Ferretti, V.; Zanobini, F. J. Chem. Soc., Dalton Trans. 1993, 1281-
1286.
(31) Archer, C. M.; Dilworth, J. R.; Griffiths, D. V.; McPartlin, M.; Kelly,
J. D. J. Chem. Soc., Dalton Trans. 1992, 183-189.
(32) Marchi, A.; Garuti, P.; Duatti, A.; Magon, L.; Rossi, R.; Ferretti, V.;
Bertolasi, V. Inorg. Chem. 1990, 29, 2091-2096.
(33) Marchi, A.; Rossi, R.; Magon, L.; Duatti, A.; Casellato, U.; Graziani,
R.; Vidal, M.; Riche, F. J. Chem. Soc., Dalton Trans. 1990, 1935-
1940.
Experimental Section
CAUTION! 99gTc is a weak â-emitter (Eâ ) 0.292 MeV, t1/2
)
2.12 × 105 years). All manipulations were carried out in laboratories
approved for low-level radioactivity using monitored hoods and
gloveboxes. When handled in milligram amounts, 99gTc does not present
a serious health hazard since common laboratory glassware provides
adequate shielding. Bremsstrahlung is not a significant problem due to
the low energy of the â-particles. However, normal radiation safety
procedures must be used at all times, especially with solid samples, to
prevent contamination and inhalation.
Materials. Technetium-99g as [NH4][99gTcO4] was obtained from
Oak Ridge National Laboratory. Samples were dissolved in water and
treated with excess aqueous ammonia and H2O2 (30%) at 80 °C prior
to use to eliminate residual TcO2. Solid samples of purified ammonium
pertechnetate were obtained by slow evaporation of the solvent under
heating at 40 °C. General literature methods were applied to the
preparation of the precursor complexes [As(C6H5)4][99gTc(N)Cl4]50 and
(34) Duatti, A.; Marchi, A.; Bertolasi, V.; Ferretti, V. J. Am. Chem. Soc.
1991, 113, 9680-9682.
(35) Bolzati, C.; Refosco, F.; Tisato, F.; Bandoli, G.; Dolmella, A. Inorg.
Chim. Acta 1992, 201, 7-10.
(36) Tisato, F.; Refosco, F.; Bandoli, G.; Bolzati, C.; Moresco, A. J. Chem.
Soc., Dalton Trans. 1994, 1453-1461.
(37) Maina, T.; Pecorale, A.; Dolmella, A.; Bandoli, G.; Mazzi, U. J. Chem.
Soc., Dalton Trans. 1994, 2437-2443.
(38) de Vries, N.; Cook, J.; Jones, A.; Davison, A. Inorg. Chem. 1991, 30,
2662-2665.
(46) Bolzati, C.; Uccelli, L.; Refosco, F.; Tisato, F.; Duatti, A.; Pasqualini,
R.; Piffanelli, A. Q. J. Nucl. Med. 1997, 41 (Suppl.), 1.
(47) C. Bolzati, A. Boschi, L. Uccelli, E. Malago`, A. Duatti, A. Piffanelli,
R. Pasqualini, F. Refosco, F. Tisato. Manuscript in preparation.
(48) Dilworth, J. R.; Hutson, A. J.; Morton, S.; Harman, M.; Hursthouse,
M. B.; Zubieta, J.; Archer, C. M.; Kelly, J. D. Polyhedron 1992, 11,
2151-2155.
(49) Tisato, F.; Refosco, F.; Bandoli, G.; Bolzati, C.; Uccelli, L.; Duatti,
A.; Piffanelli, A. In Technetium and Rhenium in Chemistry and
Nuclear Medicine 4; SGEditoriali: Padova, Italy, 1995; pp 167-172.
(50) Baldas, J.; Bonnyman, J.; Williams, G. A. Inorg. Chem. 1986, 25,
150-153.
(39) Stephen, D. W. Inorg. Chem. 1984, 23, 2207-2210.
(40) Dilworth, J. R.; Zheng, Y.; Lu, S.; Wu, Q. Transition Met. Chem.
1992, 17, 364-368.
(41) Dilworth, J. R.; Zheng, Y.; Miller, R. J. Chem. Soc., Dalton Trans.
1992, 1757-1762.
(42) Blower, P. J.; Dilworth, J. R. Coord. Chem. ReV. 1987, 76, 121-185.
(43) Hoots, J.; Rauchfuss, T.; Wroblesky, D. Inorg. Synth. 1982, 21, 175-
179.
(44) Rauchfuss, T. Inorg. Chem. 1977, 16, 2966-2971.
(45) Yardley, J.; Fletcher, H. Synthesis 1976, 244-247.

Novel Trigonal Bipyramidal Nitrido Tc(V) Complexes
99gTc(N)Cl2(PPh3)2].51 Common laboratory solvents were reagent grade
Inorganic Chemistry, Vol. 38, No. 20, 1999 4475
[
Table 1. 31P NMR Spectral Parameters of Five-Coordinate
Phosphino-Thiolato 99gTc Complexes
and used as purchased.
Physical Measurements. Elemental analyses (C, H, N, S) were
performed on a Carlo Erba 1106 elemental analyzer. Analysis of
radioactive technetium was performed as previously described25 by
dissolving weighed samples in HNO3/H2O2 mixtures and counting the
resulting radioactivity in a Packard TRICARB 3000 scintillation
counter. FT IR spectra were recorded on a Nicolet 510P Fourier
transform spectrometer, in the range 4000-200 cm-1 and in KBr
mixtures, using a Spectra-Tech diffuse-reflectance collector accessory.
Proton and 31P NMR spectra were collected on a Bruker AC-200
instrument, using SiMe4 as internal reference (1H) and 85% aqueous
H3PO4 as external reference (31P). Positive ion fast atom bombardment
mass spectra (FAB+) of selected complexes in an NBA matrix were
recorded on a VG 30-250 spectrometer (VG Instrument) at the probe
temperature. Xe was used as the primary beam gas, and the ion gun
was operated at 8 keV (ca. 1.28 × 10-15 J) and 100 µA. Chromato-
graphic separations were accomplished on a SiO2 column (45 × 2 cm,
70-230 mesh, Aldrich).
δ
31P,
ppm
δ
31P (free ligand),
ppm
complex
[TcV(N)(L1)2] (1)
∆γ1/2, Hza
250
140 (273 K)
110 (250 K)
65 (235 K)
170
66.2
-20.0
[TcIII(L1)2(S-L1)]
71.8
-20.0
-20.0
-5.9b 50
[TcIII(L1)2(S-L1dO)]
69.9
240
27.7c 40
[TcV(N)(L2)2] (2)
[TcV(N)(L3)2] (3)
[TcV(N)(L4)2] (4)
63.5
65.6
22.3
280
220
260
155 (273 K)
90 (250 K)
55 (235 K)
200
-14.7
-32.8
-19.0
[TcIII(L4)2(S-L4dO)]d
22.4
-19.0
31.4c 40
Synthesis of the Ligands. HL1 and HL4 were synthesized according
to the method reported by Blower et al.52 (for HL4, ethylene sulfide
was replaced by propylene sulfide), while HL2 was prepared as
described elsewhere.53,54 HL3 and HL5 were purchased from Argus
Chemicals. Since all mixed phosphino-thiol ligands discussed here
are air sensitive, they were stored under an inert atmosphere and all
reactions and manipulations were routinely performed under a nitrogen
atmosphere using standard Schlenk techniques.
[TcV(N)(L5)2] (5)
21.1
33.1
240
300
-21.0
-7.4
[TcV(N)Cl2(PPh3)2]e
a Measured at 298 K unless otherwise noted. b Uncoordinated P(III)
of the S-L1 ligand. c OdP(V) of the S-L1dO ligand. d Taken from ref
10b. e Trace amounts of free PPh3 (δ ) -7.4 ppm) and oxidized
OdPPh3 (δ ) 27.5 ppm) are present.
Syntheses of 99gTc Complexes. All of the complexes [99gTc(N)-
(Ln)2] (n ) 1-5) were prepared according to the same general
procedure. [99gTc(N)Cl2(PPh3)2] (0.045 g, 0.065 mmol) was suspended
in 10 mL of dichloromethane, and an excess (1:10) of the appropriate
ligand HLn (n ) 1, 2, 4, 5) was added with stirring (with the ligand
HL2 a 1:3 ratio was used). The mixture was refluxed for 1 h, and the
initial pink-orange color turned yellow. After cooling, the solvent was
removed by passing an argon stream through the reaction solution thus
causing the precipitation of a yellow solid. The crude material was
washed with ethanol and diethyl ether and dried under vacuum. The
resulting pale-yellow solid was recrystallized by slow evaporation from
a dichloromethane/methanol mixture.
[
99gTc(N)(L3)2] (3). The same procedure described above was applied
to the reaction of [99gTc(N)Cl2(PPh3)2] with the ligand HL3. The final
product was isolated as a yellow oily residue after evaporation of the
reaction solvent. This oil was found to dissolve in all common solvents,
and any attempt to convert it into a solid material was unsuccessful.
The compound was purified by column chromatography on silica gel
using ethanol/chloroform/benzene (0.1:2.0:1.5) as the mobile phase,
and collected as a yellow band. Characterization was carried out only
through NMR and FAB mass spectroscopy. FAB MS: m/z 588 [MH+].
1H NMR (CDCl3, ppm): 1.96 (m, 20H), 2.82 (m, 4H), 3.28 (s, 12H),
3.36 (m, 8H).
31P NMR spectral data for complexes 1-5 are collected in Table 1.
Alternatively, the complexes [99gTc(N)(Ln)2] could be prepared
starting from the tetrachloro nitrido Tc(VI) complex [As(C6H5)4][99gTc-
(N)Cl4]. However, in these preparations, a careful selection of the
experimental conditions was required to achieve final yields comparable
with those obtained with the precursor complex [99gTc(N)Cl2(PPh3)2].
A typical preparation was carried out as described below.
A 10-fold molar excess of the appropriate ligand HLn (n ) 1, 2, 4,
5) (with HL2 the metal-to-ligand ratio was 1:3) was dissolved in 5.0
mL of ethanol. To this solution was added 50 µL (0.65 mmol) of
trifluoroacetic acid (TFA), previously diluted with water (1:10),
followed by the addition of 5.0 mL of an ethanolic solution containing
0.05 g (0.08 mmol) of [As(C6H5)4][99gTc(N)Cl4]. The mixture was
refluxed for 1 h, and the initial red-orange color turned quickly to
yellow. After cooling to room temperature, a yellow precipitate formed,
which was collected by filtration, washed with ethanol and diethyl ether,
and dried under vacuum. Recrystallization was carried out as described
above. The final yields ranged between 70% and 83%.
It should be noted that the presence of TFA was found to be essential
for obtaining the final complexes starting from [As(C6H5)4][99gTc(N)-
Cl4]. When the synthesis was conducted without addition of a proton
source, the yields of the compounds [99gTc(N)(Ln)2] were always lower
than 40% because of the concomitant formation of a series of secondary
Tc(III) byproducts, which were studied in detail only with the ligand
HL1 (see Results and Discussion). The synthesis and characterization
of the Tc(III) complex [99gTc(L1)2(S-L1)], where S-L1 represents a
monodentate, deprotonated L1 ligand, is reported below.
[
99gTc(N)(L1)2] (1). Yield: 94% (based on 99gTc). FT IR (cm-1):
1053 [ν(TctN)]. FAB MS: m/z 604 [MH+]. 1H NMR (CDCl3, ppm):
2.75 (m, 8H), 8.10-7.20 (20H, aromatic). Anal. Calcd for C28H28P2S2-
NTc: C, 55.72; H, 4.64; N, 2.32; S, 10.61; Tc, 16.42. Found: C, 55.68;
H, 4.60; N, 2.34; S, 10.14; Tc, 17.01.
[
99gTc(N)(L2)2] (2). Yield: 93% (based on 99gTc). FT IR (cm-1):
1041 [ν(TctN)]. FAB MS: m/z 700 [MH+]. 1H NMR (CDCl3, ppm):
8.10-6.60 (aromatic). Anal. Calcd for C36H28P2S2NTc: C, 61.80; H,
4.01; N, 2.00; S, 9.16; Tc, 14.16. Found: C, 61.67; H, 2.06; N, 1.95;
S, 9.03; Tc, 14.09.
[
99gTc(N)(L4)2] (4). Yield: 92% (based on 99gTc). FT IR (cm-1):
1045 [ν(TctN)]. FAB MS: m/z 632 [MH+]. 1H NMR (CDCl3, ppm):
2.26 (m, 8H), 2.57 (m, 4H), 8.00-7.25 (20H, aromatic). Anal. Calcd
for C30H32P2S2NTc: C, 57.05; H, 5.07; N, 2.22; S, 10.14; Tc, 15.69.
Found: C, 57.08; H, 5.12; N, 2.20; S, 9.65; Tc, 15.22.
[
99gTc(N)(L5)2] (5). Yield: 90% (based on 99gTc). FT IR (cm-1):
1039 [ν(TctN)]. FAB MS: m/z 688 [MH+]. 1H NMR (CDCl3, ppm):
2.24 (m, 4H), 2.34 (s, 12H), 2.57 (m, 8H), 7.90-7.10 (16H, aromatic).
Anal. Calcd for C34H40P2S2NTc: C, 59.39; H, 5.82; N, 2.04; S, 9.32;
Tc, 14.41. Found: C, 58.92; H, 5.82; N, 2.00; S, 8.95; Tc, 14.37.
Compounds 1, 2, 4, and 5 are soluble in chlorinated solvents,
benzene, and toluene and insoluble in alcohols, acetonitrile, and diethyl
ether.
(51) Abram, U.; Lorenz, B.; Kaden, L.; Scheller, D. Polyhedron 1988, 7,
285-289.
(52) Blower, P. J.; Dilworth, J. R.; Leigh, G. J.; Neaves, B. D.; Normanton,
[
99gTc(L1)2(S-L1)]. [As(C6H5)4][99gTc(N)Cl4] (0.05 g, 0.08 mmol) was
dissolved in 5.0 mL of dichloromethane, and to the resulting solution
was added a 10-fold molar excess of the ligands HL1 [HL1
2-(diphenylphosphino)ethanethiolato (Ph2PCH2CH2SH)]. The color of
the mixture turned from orange to fuchsia. A small drop of the reaction
solution was placed on a silica gel plate (60 F254, Merck) through a
F. B.; Hutchinson, J.; Zubieta, J. A.. J. Chem. Soc., Dalton Trans.
1985, 2647-2653.
)
(53) Block, E.; Ofori-Okai, G.; Zubieta, J. J. Am. Chem. Soc. 1989, 111,
2327-2332.
(54) Figuly, G.; Loop, C.; Martin, J. C. J. Am. Chem. Soc. 1989, 111, 654-
657.

4476 Inorganic Chemistry, Vol. 38, No. 20, 1999
Bolzati et al.
Table 2. Crystal Data and Details of Data Collection for
Complexes 1 and 5
compd
formula
space group
cryst syst
fw, g mol-1
a, Å
b, Å
c, Å
â, deg
T, °C
1
5
C28H28NP2S2Tc
C2/c
monoclinic
602.6
24.84(2)
7.327(6)
31.52(2)
111.06(10)
21
C34H40NP2S2Tc
P21/n
monoclinic
686.7
11.090(1)
14.387(2)
11.087(1)
113.62(1)
21
λ, Å
Z
0.710 73
8
0.710 73
2
F(000)
2464
5353(7)
1.495
8.31
5.2-40.1
2057
0.057
0.140
1.060
1.33-0.72
712
1620.9(3)
1.407
6.96
4.9-46.1
1778
0.060
0.165
1.066
0.51-0.81
V, Å3
F
calc, g cm-1
µ, cm-1
2ϑ range, deg
obs reflns
R1a
Figure 1. ORTEP representation of complex 1 showing thermal
ellipsoids at the 40% probability level.
wR2a
GOFa
∆Fmax, ∆Fmin, e Å-3
2 2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|; wR2 ) [∑[w(Fo2 - Fc2)2]/∑[w(Fo ) ]]1/2
;
GOF ) [∑[w(Fo2 - Fc2)2]/(n - p)]1/2 (n ) number of reflections, p )
number of parameters).
syringe. Thin-layer chromatography (TLC) was performed using
ethanol/chloroform/benzene (0.1:2:1.5) showing the presence of three
colored spots (fuchsia, Rf ) 0.22, yellow, Rf ) 0.78, pink, Rf ) 0.95).
These products were separated through column chromatography on SiO2
using the same mobile phase given above for TLC. Elution yields a
first pink band followed by a yellow one, the fuchsia component being
retained on the column. Evaporation of the solvent led to isolation of
the corresponding pink and yellow solids. The yellow compound was
identified as the nitrido Tc(V) complex [99gTc(N)(L1)2]. The pink
product was found to convert slowly into the fuchsia Tc(III) complex
[
99gTc(L1)2(S-L1dO)] when it was dissolved in chloroform and the
resulting solution was allowed to evaporate under air. The crystal
structure of the complex [99gTc(L1)2(S-L1dO)] has been reported
previously.35,36 It comprises two bidentate L1 ligands and an oxidized
form of L1 (S-L1dO) acting as a monodentate ligand through the
deprotonated thiol sulfur atom, and carrying the oxo-phosphorus(V)
group. On the basis of these findings, we speculated that the structure
of the pink complex could be formulated as [99gTc(L1)2(S-L1)] where
S-L1 represents the ligand L1 that is coordinated to the metal center
only through the negative sulfur atom. Yield: 28% (based on 99gTc).
FAB MS: m/z, 835 [MH+]. 1H NMR (CDCl3, ppm): 7.65-7.10 (30H,
aromatic), 3.10-1.8 (12H, aliphatic). Anal. Calcd for C42H42P3S3Tc:
C, 60.43; H, 5.04; S, 11.51; Tc, 11.87. Found: C, 60.28; H, 5.02; S,
11.29; Tc, 11.37. The 31P NMR spectrum showed a peak at δ ) 71.8
ppm assigned to the two phosphorus atoms of the two bidentate L1
ligands, and one peak at δ ) -5.9 ppm assigned to the phosphorus
atom of the monodentate ligand S-L1.
Figure 2. ORTEP representation of complex 5 showing thermal
ellipsoids at the 40% probability level.
Crystallographic Data Collection and Refinement. The intensity
data were measured on a Siemens Nicolet R3m/V four-circle diffrac-
tometer using Mo KR radiation and the ω-2ϑ scan mode at 294 K.
Absorption corrections were made according to ψ curves of four
reflections at ø ca. 90°. The crystal parameters and the other
experimental details of data collection and refinement procedures are
summarized in Table 2. The structures were solved by standard
Patterson methods and refined by full-matrix least-squares methods on
F2, using the SHELXTL/PC55 and SHELXL-9356 programs.
Figure 3. The double image of complex 5 derived by Fourier synthesis.
2Θmax ) 40°. In spite of this, all non-hydrogen atoms were refined
anisotropically and refinement resulted satisfactorily. For compound 5
(Figure 2) the solution of the structure was rather difficult due to the
siting of the Tc atom at 0, 0, 1/2. The metal, P(1), S(1), and S(1′) atoms
were located from a Patterson synthesis, and subsequent observed
Fourier synthesis showed the positions of the C(1A)-(7A) atoms, along
with a double image of the molecule from which the C(1B)-(7B) and
C(1B′)-(7B′) atoms were identified (Figure 3). After five cycles of
refinement of the parameters of these atoms, a difference Fourier
synthesis gave reliable coordinates for the six carbons of the two
propylene groups. The heavy atoms were assigned anisotropic thermal
The diffracting ability of sample 1 (Figure 1) fell off rapidly with
increasing Bragg angle, and much of the higher angle data were flagged
as weak. As a consequence, the data collection for 1 was restricted to
(55) Sheldrick, G. M. SHELXTL/PC Version 5.3; Siemens Analytical X-ray
Instruments Inc.: Madison, WI, USA, 1994.
(56) Sheldrick, G. M. SHELXL-93 Program for Crystal Structure Refine-
ment; University of Go¨ttingen: Go¨ttingen, Germany, 1993.

Novel Trigonal Bipyramidal Nitrido Tc(V) Complexes
Inorganic Chemistry, Vol. 38, No. 20, 1999 4477
Table 3. Selected Bond Lengths (Å) and Angles (deg) for
Complex 1
Scheme 1
Tc-P(1)
Tc-P(2)
Tc-S(1)
Tc-S(2)
Tc-N(1)
S(1)-C(2)
S(2)-C(4)
2.415(3)
2.399(3)
2.342(4)
2.353(4)
1.638(9)
1.83(1)
P(1)-C(1)
P(1)-C(1A)
P(1)-C(1B)
P(2)-C(3)
P(2)-C(1C)
P(2)-C(1D)
C(1)-C(2)
C(3)-C(4)
1.83(1)
1.82(1)
1.81(1)
1.81(1)
1.81(1)
1.82(1)
1.50(2)
1.50(2)
1.87(1)
P(1)-Tc-P(2)
P(1)-Tc-S(1)
P(1)-Tc-S(2)
P(1)-Tc-N(1)
P(2)-Tc-S(1)
P(2)-Tc-S(2)
P(2)-Tc-N(1)
S(1)-Tc-S(2)
S(1)-Tc-N(1)
165.5(1)
83.3(1)
92.1(1)
97.2(3)
90.7(1)
82.8(1)
97.3(3)
135.0(1)
112.5(3)
S(2)-Tc-N(1)
Tc-P(1)-C(1)
Tc-P(2)-C(3)
Tc-S(1)-C(2)
Tc-S(2)-C(4)
P(1)-C(1)-C(2)
P(2)-C(3)-C(4)
S(1)-C(2)-C(1)
S(2)-C(4)-C(3)
112.5(3)
104.0(4)
105.6(3)
108.8(4)
108.8(4)
110.1(9)
111.1(7)
113.6(9)
113.3(8)
hedral, tris-substituted complex [99gTc(L1)3] (Scheme 1). In
99gTcIII(L1)2(S-L1)], S-L1 represents a monodentate L1 ligand
[
coordinated to the metal ion through the deprotonated sulfur
atom, while in [99gTcIII(L1)2(S-L1dO)], S-L1dO indicates the
oxo phosphorus(V) form of the same phosphine-thiol ligand
still coordinated through the sulfur atom. The influence of acidic
conditions on the outcome of the reactions of ligands HLn with
[
99gTc(N)Cl4]- can be easily explained by assuming that high
Table 4. Selected Bond Lengths (Å) and Angles (deg) for
Complex 5
proton concentrations should keep the thiol group of the ligands
protonated, thus reducing its donor affinity toward the metal
center. Consequently, the phosphorus atom of the phosphine-
thiol ligand may react first by substituting a chlorine atom and,
in turn, stabilizing the +5 metal oxidation state in the resulting
[TctN]2+ group, in much the same way as it is commonly
observed when [99gTc(N)Cl4]- reacts with simple monophos-
phine ligands.50 Under more basic conditions, deprotonation of
the thiol group would be enhanced and competitive displacement
of the nitrido group with the concomitant formation of Tc(III)
species would occur. Nucleophilic attack of the thiolate sulfur
atom of the phosphine-thiol ligand at the nitrido nitrogen atom
is most likely responsible of the removal of the TctN multiple
bond. These reactions constitute rare examples of displacement
of a terminal nitrido group from a technetium complex, which
have been previously observed only with simple bidentate thiol
ligands.57 It is worthy to note here that complex 1 is converted
into the related Tc(III) complexes only through prolonged
heating in solution and in the presence of a large excess of the
ligand HL1. Thus, the sudden formation of the complex [99gTcIII-
(L1)2(S-L1)] must involve the first removal of the TctN bond
from [99gTc(N)Cl4]- and not from 1.
Tc-P(1)
Tc-S(1)
Tc-S(1′)
Tc-N(1)
P(1)-C(1)
P(1A)-C(1′)
2.407(2)
2.336(4)
2.337(4)
1.65(1)
2.12(2)
2.11(2)
C(1)-C(2)
C(1′)-C(2′)
C(2)-C(3)
C(2′)-C(3′)
S(1)-C(3)
S(1′)-C(3′)
1.55(2)
1.55(2)
1.53(2)
1.53(3)
1.83(2)
1.82(2)
S(1)-Tc-P(1)
S(1′)-Tc-P(1A)
S(1)-Tc-S(1′)
S(1)-Tc-N(1)
S(1′)-Tc-N(1)
P(1)-Tc-N(1)
P(1A)-Tc-N(1)
Tc-P(1)-C(1)
91.7(1)
91.7(1)
131.5(2)
114.5(5)
113.9(5)
90.1(4)
89.9(4)
99.9(4)
P(1)-C(1)-C(2)
P(1A)-C(1′)-C(2′)
C(1)-C(2)-C(3)
C(1′)-C(2′)-C(3′)
S(1)-C(3)-C(2)
S(1′)-C(3′)-C(2′)
Tc-S(1)-C(3)
111(1)
111(1)
119(2)
119(2)
116(1)
116(1)
112.4(6)
112.1(6)
Tc-S(1′)-C(3′)
parameters, the phenyl rings were treated as “rigid body”, and the atoms
with the same y value were satisfactorily refined with a fixed occupancy
of 0.5. The maximum and minimum peaks on the final Fourier-
difference map corresponded to 0.51, and -0.81 e Å-3, in the vicinity
of the Tc atom. Refinement in the two alternative space groups of higher
symmetry (Cmca or Aba2) resulted in unacceptable R factor values
(0.11 and 0.12, respectively), with some high peaks (up to 4.2 e Å-3
in the proximity of phosphorus and sulfur atoms, and unrealistic metrical
parameters.
Selected bond distances and angles are summarized in Tables 3 and
4 for 1 and 5, respectively.
)
Elemental analyses of complexes 1, 2, 4, and 5 were in
excellent agreement with the proposed formulation. FT IR
spectra exhibited the characteristic ν(TctN) stretching vibration
in the range 1030-1053 cm-1. FAB+ mass spectra of 1-5
showed the presence of the parent molecule with no detectable
fragmentation.
Results and Discussion
Synthesis and Characterization. The nitrido Tc(V) com-
plexes 1-5 were easily prepared by treating the precursor
complex [99gTc(N)Cl2(PPh3)2] with an excess of the appropriate
phosphino-thiol ligand in dichloromethane solutions, and
isolated as yellow crystals (except for the complex with the
ligand L3, see Experimental section) from dichloromethane/
methanol mixtures in almost quantitative yields.
All [99gTc(N)(Ln)2] (n ) 1-5) are diamagnetic as expected
for d2 complexes containing the [TcVtN]2+ core. Proton NMR
spectra exhibited multiplet signals in the aromatic and aliphatic
regions consistent with the presence of methylene and/or phenyl
groups, with the correct integration ratio. At the opposite, 31P
NMR spectra showed very broad signals at ambient temperature
(Table 1). On lowering the temperature, lines became narrower,
with half line width decreasing from 250 Hz at room temperature
to 60 Hz at 235 K. This behavior parallels that found by Abram
and co-workers in six-coordinate [99gTc(N)X2(PMe2Ph)3] (X )
Cl, Br) complexes.51 In these latter compounds, line broadening
has been attributed to the coupling of the 31P nuclei with the
quadrupolar 99gTc nucleus. As summarized in Table 1, 31P NMR
spectra of [99gTc(N)(Ln)2] complexes exhibited a remarkable
downfield shift of the phosphorus signal upon phosphino-
thiolato coordination. The position of this peak in the spectral
Starting from the precursor Tc(VI) complex [99gTc(N)Cl4]-,
the reactions with phosphine-thiol ligands HLn (n ) 1, 2, 4,
5), in acidic media, afforded the same symmetric, bis-substituted
nitrido Tc(V) complexes 1, 2, 4, and 5, which were collected
in high yield. However, when these reactions were conducted
without addition of a proton source, a more pronounced
reduction of the metal oxidation state, with the concomitant
removal of the TctN terminal group, was observed. Under these
conditions, a series of chemically related Tc(III) derivatives were
obtained, which were fully characterized only with the ligand
HL1. This series comprised both the five-coordinated complexes
(57) Colmanet, S. F.; Williams, G. A.; Mackay, M. F. J. Chem. Soc., Dalton
Trans. 1987, 2305-2310.
[
99gTcIII(L1)2(S-L1)] and [99gTcIII(L1)2(S-L1dO)] and the octa-

4478 Inorganic Chemistry, Vol. 38, No. 20, 1999
Bolzati et al.
the boat (C2V) conformation with P(1) and C(3) atoms above
the TcS(1)C(2)C(1) mean plane by 1.18 and 0.74 Å, respectively
(Figure 2).
The bond lengths and angles in the coordination sphere are
similar to those observed in the other five-coordinate Tc(V)
nitrido complexes listed in Table 5 and need no comment. In
crystals of both 1 and 5, the molecules are packed individually
and interact via normal van der Waals contacts.
Using the structural index parameter τ58 [τ ) (â - R)/60,
where R and â are the two largest angles around Tc], its value
is 0.50 and 0.81 for 1 and 5, respectively. This suggests that
the trigonal bipyramidal geometry has to be preferred for 5 (τ
) 1 for ideal trigonal bipyramidal geometry, and τ ) 0 for
ideal square pyramidal geometry), while for 1 the geometry has
to be considered as intermediate between the two ideal limits.
Table 5 reports τ values for a number of monomeric five-
coordinate nitrido Tc(V) complexes. These data indicate that
the situation encountered here with phosphino-thiol Tc(V)
nitrido complexes is quite uncommon since the preferred
coordination geometry is usually square pyramidal, while
complexes 1 and 5 exhibit the highest values of τ index.
Examination of Table 5 shows that only six complexes have a
τ value greater than 0.35. The structures of these complexes
are characterized by two distinct features: (i) only donor atoms
of group 15 lie in the two apical positions, and (ii) only donor
atoms of group 16 and/or 17 span the positions in the equatorial
plane along with the nitrido ligand. This observation may
suggest a possible way to account for the change from square
pyramidal to trigonal bipyramidal geometry by carefully con-
sidering the effect of varying the chemical nature of the set of
atoms placed on the remaining four positions of a five-
coordinated arrangement where one position is always occupied
by the TctN group. Crystal data (Table 5) clearly show that,
in complexes where the TctN group is coordinated to ligands
through four π-donor atoms such as S- and X- (X ) halogen),
the resulting geometry is invariably square pyramidal with four,
Figure 4. Alternative ORTEP representation of complex 1 showing
thermal ellipsoids at the 40% probability level.
Figure 5. Alternative ORTEP representation of complex 5 showing
thermal ellipsoids at the 40% probability level.
window appears to be dependent on the length of the carbon
chain between P and S atoms. Specifically, phosphinoethanethi-
olato ligands generating a five-membered chelate ring gave rise
to larger deshielding effects than the corresponding phosphi-
nopropanethiolato ligands (six-membered chelate ring). This
behavior was observed also in diamagnetic five-coordinated
Tc(III) derivatives of the type [99gTc(Ln)2(S-LndO) (n ) 1,
4).35,38
(58) Addison, A. W.; Rao, T. N.; Reedijk, J.; van Rijn, J.; Verschoor, G.
C. J. Chem. Soc., Dalton Trans. 1984, 1349-1356.
(59) Colmanet, S. F.; Mackay, M. F. Inorg. Chim. Acta 1988, 147, 173-
178.
(60) Rossi, R.; Marchi, A.; Casellato, U.; Graziani, R. J. Chem. Soc., Dalton
Trans. 1990, 2923-2925.
(61) Williams, G. A.; Baldas, J. Aust. J. Chem. 1989, 42, 875-884.
(62) Abram, U.; Mu¨nze, R.; Kirmse, P.; Ko¨hler, K.; Dietzsch, W.; Golicˇ,
L. Inorg. Chim. Acta 1990, 169, 49-53.
Structure. In complexes 1 and 5 the [TctN]2+ core is
coordinated by two phosphino-thiol ligands and the P(1)- - -
P(2) line has the appearance of the axis in an approximate
trigonal bipyramidal structure (Figures 1 and 2), in which the
equatorial positions are occupied by N(1), S(1), and S(2) atoms.
Alternatively, the coordination geometry can be described as a
distorted rectangular pyramid, with the P2S2 donor atom set in
the basal positions, identical atoms being diametrically opposed,
and the nitrido ligand occupying the apical position (Figures 4
and 5). In the square pyramidal description, the P and S donor
atoms lie out of the P2S2 plane on opposite sides by (0.30 Å
in 1 and (0.48 Å in 5, while the Tc atom is above this plane
by 0.60 Å in 1 and 0.48 Å in 5 toward the nitrido ligand. The
P- - -S bite distance of 3.15 Å in 1 lengthens to 3.40 Å in 5,
and accordingly, the P-Tc-S angle of 83.3° in 1 enlarges to
91.7° in 5. In 1, the two five-membered TcSC2P rings assume
the envelope (Cs) conformation with C(1) and C(3) atoms out
of the pertinent TcSCP mean plane by 0.67 and 0.64 Å,
respectively. These TcSCP mean planes are roughly perpen-
dicular to the S(1)N(1)S(2) plane, both dihedral angles being
93.2° (Figure 1). In 5, the two six-membered TcSC3P rings adopt
(63) Ritter, S.; Abram, U.; Dilworth, J. R. Z. Anorg. Allg. Chem. 1996,
622, 1975-1978.
(64) Cros, G.; Belhadj, T. H.; de Montauzun, D.; Gleizes, A.; Coulais, Y.;
Guiraud, R.; Bellande, E.; Pasqualini, R. Inorg. Chim. Acta 1994, 227,
25-31.
(65) Pietzsch, H.-J.; Spies, H.; Leibnitz, P.; Rech, G. Polyhedron 1993,
12, 2995-3002.
(66) Abram, U.; Abram, S.; Dilworth, J. R. Z. Anorg. Allg. Chem. 1996,
622, 1257-1262.
(67) Dilworth, J. R.; Hu¨bener, R.; Abram, U. Z. Anorg. Allg. Chem. 1997,
623, 880-882.
(68) Baldas, J.; Boas, J. F.; Colmanet, S. F.; Williams, G. A. J. Chem.
Soc., Dalton Trans. 1992, 2845-2853.
(69) Abram, U.; Lang, E. S.; Abram, S.; Wegmann, J.; Dilworth, J. R.;
Kirmse, R.; Woollins, J. D. J. Chem. Soc., Dalton Trans. 1997, 623-
630.
(70) Abram, U.; Abram, S.; Stach, J.; Dietzsch, W.; Hiller, W. Z.
Naturforsch. 1991, 46b, 1183-1187.
(71) Abram, U.; Abram, S.; Mu¨nze, R.; Ja¨ger, E.-G.; Stach, J.; Kirmse,
R.; Amiraal, G.; Beurskens, P. T. Inorg. Chim. Acta 1991, 182, 233-
238.
(72) Abrams, M. J.; Larsen, S. K.; Shaikh, S. N.; Zubieta, J. Inorg. Chim.
Acta 1991, 185, 7-15.
(73) Baldas, J.; Boas, J. F.; Colmanet, S. F.; Williams, G. A. J. Chem.
Soc., Dalton Trans. 1991, 2441-2447.
(74) Rossi, R.; Marchi, A.; Aggio, S.; Magon, L.; Duatti, A.; Casellato,
U.; Graziani, R. J. Chem. Soc., Dalton Trans. 1990, 447-451.

Novel Trigonal Bipyramidal Nitrido Tc(V) Complexes
Inorganic Chemistry, Vol. 38, No. 20, 1999 4479
Table 5. τ Values in Monomeric, Five-Coordinate Nitrido Tc(V) Complexesa
complex
τ
ref
complex
τ
ref
[Tc(N)(SCOCOS)2]2-
[Tc(N)(SCOS)2]2-
0.00
0.00
0.00
0.01
0.02
0.02
0.02
0.03
0.05
0.06
0.07
0.08
0.08
0.08
59
60
61
62
9
63
64
65
65
65
66
67
68
69
[Tc(N)(i-mns)2]2-
0.09
0.10
0.10
0.18
0.20
0.26
0.28
0.36
0.38
0.39
0.42
0.43
0.47
70
30
26
71
18
17
27
72
73[
74
27
30
50
[Tc(N)Cl2(PP1)]
[Tc(N)(mnt)2]2-
[Tc(N)(S2N2)]
[Tc(N)(SCOCOS)2]2-b
[Tc(N)(S2CNEt2)2]
[Tc(N)(mnt)(PMe2Ph)]
[Tc(N)(SNNS)]
[Tc(N)(ecbap)(PPh3)]
[Tc(N)Cl(cys)(PPh3)]
[Tc(N)(SC6HMe4)2{NHC(NMe2)2}2]
[Tc(N)(SB1)(PPh3)]
[Tc(N)Cl2(PPh3)2]
[Tc(N)Cl2(AsPh3)2]
[Tc(N)Cl{PhNC(OEt)S}]
[Tc(N)(SB2)2]
[Tc(N)Cl(14S4)]+c
[Tc(N)Cl(18S6)]+c
Tc(N)Cl{16S4-(OH)2}]+c
[Tc(N)(HEt2tcb)2]
[Tc(N)(dmit)2]2-
[Tc(N)Cl2(PP2)
[Tc(N)(quin)2]
[Tc(N)(S2CNEt2](SCOCOS)]-
[Tc(N){N(SPPh2)2}2]
a Abbreviations: mnt ) 1,2-dicyanoethenedithiolato(1-); SNNS ) N,N′-ethylenebis(methyl-2-aminocyclopentene-1-dithiocarboxylato)(2-); HEt2tcb
) N,N-diethylthiocarbamoylbenzaminidato(1-); dmit ) isotrithionedithiolato(1-); i-mns ) 1,1-dicyanoethene-2,2-diselenolato(1-); PP1
)
bis(diphenylphosphinoethyl)propylamine; S2N2 ) N,N′-ethylenebis(thioacetylacetarylideneiminato(2-); ecbap ) N-(2-ethoxycarbonyl-3-oxo-but-
1-en(1)yl-2-aminophenolato(2-); cys ) O-ethyl-L-cysteinato(1-); SB1 ) S-methyl-3-(2-hydroxyphenylmethylene)dithiocarbazato(2-); SB2 )
S-methyl-3-isopropylidenedithiocarbazato(1-); PP2 ) 1,8-bis(diphenylphosphino)-3,6-dioxaoctane; quin ) 8-quinolinethiolato(1-). b Monoclinic
modification of ref 59. c Thiacrown ether.
almost equivalent, basal bonds resulting in an approximate C4V
symmetry. Since the phosphine-thiol ligands utilized in this
study comprise a mixed set of coordinating atoms, including
one π-donor, negative sulfur and one π-acceptor, neutral
phosphorus atom, it is straightforward to assume that, on
changing the coordinating set of four equivalent π-donor atoms
to a mixed P2S2 set, the almost regular C4V symmetry cannot
longer be maintained. In particular, the crystallographic results
shown here seem to indicate that the two π-acceptor phosphorus
atoms prefer to occupy a reciprocal trans position of the five-
coordinated arrangement, the two π-donor sulfur atoms still
keeping a relative cis position. Obviously, only a trigonal
bipyramidal arrangement can accommodate such a distribution
of coordinating atoms around the TctN group, thus forcing
the system to achieve this final geometry. As predicted for
trigonal bipyramidal compounds, the transaxial π-acceptor
phosphorus atoms should be bound to the [TctN]2+ core using
a set of equivalent orbitals that is different from that utilized
by the two equatorial π-donor sulfur atoms.
possess an uncommon trigonal bipyramidal geometry in contrast
with most nitrido Tc(V) complexes, which exhibit a square-
pyramidal geometry. The stability of the trigonal bipyramidal
arrangement appears to be related to the specific set of
coordinating atoms composed of two π-donor sulfur atoms and
two π-acceptor phosphorus atoms. P atoms were found to
occupy the two transaxial positions while S atoms span two
positions on the equatorial plane along with the N3- nitrogen
atom. A more extended survey of the relationships between
geometry and specific sets of coordinating atoms in nitrido
Tc(V) complexes may contribute to elucidate both electronic
and steric factors favoring each type of five-coordinated
arrangement.
Acknowledgment. We are grateful to Mr. M. Fratta for
elemental analyses. Financial support for this work was provided
by CIS bio international, Gif-sur-Yvette, France.
Supporting Information Available: Listings, from the Cambridge
Crystallographic Data Centre, the crystallographic methods, fractional
atomic coordinates and the equivalent thermal parameters for all atoms,
anisotropic thermal parameters, and bond lengths and angles for 1 and
5 and description of the synthesis of [99gTc(L1)2(S-L1)]. This material
is available free of charge via the Internet at http://pubs.acs.org.
Conclusions
A novel series of five-coordinated, nitrido technetium(V)
complexes with phosphine-thiol ligands has been described.
Structural characterization of these complexes showed that they
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