Synthesis, characterization, and crystal structure analysis of the first terdentate [C,N,S] thiosemicarbazone complex with a six-membered palladacycle: Influence of steric effects on ring size

Article abstract of DOI:10.1002/ejic.200501100

The reaction of the thiosemicarbazone ligands 1-(COMe)-3-[C(H)=NN(H)C(=S) NHR]C₈H₅N, (R = H a, Me b, Et c) with potassium tetrachloropalladate in an ethanol/water mixture led to the new tetranuclear palladium(II) compounds [Pd{1-(COMe)-3-[C(H)=NN=C(S)NHR]C₈H ₄N-k³C5,N,S}]₄ (R = H 1a, Me 1b, Et 1c) which contain six-membered metallacycles. The thiosemicarbazone ligands in these complexes are terdentate through the C, N, and S atoms and are deprotonated at the NH group. The Pd-S bond formed is sufficiently strong to undergo reactions with nucleophiles without bond cleavage. Reaction of 1a and 1b with 1,2-bis(diphenylphosphanyl)ethane (dppe) gave the dinuclear species [{Pd[1-(COMe)-3-{C(H)=NN=C(S)NHR}C₈H₄N]} ₂(μ-Ph₂P(CH₂)₂PPh₂)] (R = H 2a, Me 2b). The molecular structure of complex 1b has been determined by X-ray diffraction analysis. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.

Full text of DOI:10.1002/ejic.200501100

FULL PAPER
DOI: 10.1002/ejic.200501100
Synthesis, Characterization, and Crystal Structure Analysis of the First
Terdentate [C,N,S] Thiosemicarbazone Complex with a Six-Membered
Palladacycle: Influence of Steric Effects on Ring Size
Adriana Amoedo,[a] Luis A. Adrio,[a] José M. Antelo,[a] Javier Martínez,[a]
M. Teresa Pereira,[a] Alberto Fernández,[b] and José M. Vila*[a]
Dedicated to Professor Victor Riera on the occasion of his 70th birthday
Keywords: Thiosemicarbazones / Cyclometalation / Palladium / Indole / Crystal structure
The reaction of the thiosemicarbazone ligands 1-(COMe)-3-
[C(H)=NN(H)C(=S)NHR]C8H5N, (R = H a, Me b, Et c) with
potassium tetrachloropalladate in an ethanol/water mixture
led to the new tetranuclear palladium(II) compounds [Pd{1-
(COMe)-3-[C(H)=NN=C(S)NHR]C8H4N-k3C5,N,S}]4 (R = H
1a, Me 1b, Et 1c) which contain six-membered metallacycles.
The thiosemicarbazone ligands in these complexes are terd-
entate through the C, N, and S atoms and are deprotonated
at the NH group. The Pd–S bond formed is sufficiently strong
to undergo reactions with nucleophiles without bond cleav-
age. Reaction of 1a and 1b with 1,2-bis(diphenylphos-
phanyl)ethane (dppe) gave the dinuclear species [{Pd[1-
(COMe)-3-{C(H)=NN=C(S)NHR}C8H4N]}2(µ-Ph2P(CH2)2-
PPh2)] (R = H 2a, Me 2b). The molecular structure of complex
1b has been determined by X-ray diffraction analysis.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
Schelate bond, which hinders opening of the metalated and
coordination rings at the metal center, thus making the li-
gands excellent pincer species that powerfully occupy three
of the four coordination positions of the metal, thereby al-
lowing only the fourth coordination site to undergo further
reaction with nucleophiles.
Introduction
Cyclometalated compounds, which make up a fair por-
tion of species pertaining to the organometallic family, are
quite numerous and have been studied to a great degree,
among other reasons owing to the great number of organic
substrates that can undergo a cyclometalation reaction to
form a stable five-membered ring.[1–7] In particular, thio-
semicarbazone ligands are prominent in this process in view
of the donor atoms they display, which is not only limited
to the nitrogen and sulfur atoms of the thiosemicarbazide
chain, or to additional donors set on the parent aldehyde
or ketone, but also because metal–carbon bonding makes
them appropriate terdentate [C,N,S] ligands. This makes
them reminiscent of the related terdentate [C,N,N] Schiff
bases[8–10] and [C,N,O] semicarbazones[11] in that com-
pounds with two fused rings at the metal center are formed;
recently, a further example of [C,N,N] pincer complexes has
been reported.[12]
Another interesting issue related to these ligands is that
upon treatment with the corresponding palladium or plati-
num salt, tetrameric compounds bearing a central Pd4S4 or
Pt4S4 central core are obtained, an outcome which, in the
majority of cases, seems to be an inevitable consequence of
their chemistry. In view of our previous results, and in ef-
forts to progress further into the chemistry of cyclomet-
alated thiosemicarbazones, we were interested in establish-
ing if tetrameric compounds could also be obtained in the
case of six-membered palladacycles, for which purpose we
chose ligands derived from condensed systems where five-
or six-membered metalated rings may be formed. It has
been reported that in ligands with condensed rings, the site
and/or the electronic properties of the substituents may
force the formation of six-membered metalated rings as op-
posed to the more stable five-membered ones.[13,14] Further-
more, previous studies have also shown that bulky groups
close to the potential metalation site impede metal–carbon
bond formation by hindering approach of the metal to the
carbon atom.[15] With this in mind we chose the thiosemi-
carbazones derived from the condensation of 1-acetyl-3-in-
That thiosemicarbazone derivatives exhibit an altogether
different chemical behavior is due to the strength of the Pd–
[a] Departamento de Química Inorgánica, Universidad de Santi-
ago de Compostela,
15782 Santiago de Compostela, Spain
Fax: +34-981-595-012
E-mail: qideport@usc.es
[b] Departamento de Química Fundamental, Universidad de A
Coruña,
15071 A Coruña, Spain
3016
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Thiosemicarbazone Complex with a Six-Membered Palladacycle
FULL PAPER
dolecarboxaldehyde and the corresponding thiosemicarb- clometalated compounds were obtained from the ligands,
azide, where, although metalation could, in principle, be as shown in Scheme 1. In a typical experiment, a suspension
achieved through the pyrrole (C2) or the phenyl (C5) car- of K2PdCl4 in ethanol/water was treated with the corre-
bon atoms to give a five- or a six-membered metalated ring, sponding thiosemicarbazone ligand to give complexes
respectively, the acetyl group on the pyrrole nitrogen atom [Pd{1-(COMe)-3-[C(H)=NN=C(S)NHR]C8H4N-k3C5,N,S}]4
should sufficiently hinder approach of the palladium atom (R = H 1a, Me 1b, Et 1c) as air-stable solids, which
to the C(2) carbon, in which case metalation of the ligand were fully characterized, with the ligand in the
should occur at the C(5) carbon. This paper describes the (E,Z) configuration. The mass spectrum (FAB) shows
results of this endeavor.
peaks at m/z 1458 (1a), 1515 (1b), and 1571 (1c) for the
molecular ion, and the isotopic composition suggests a tet-
ranuclear complex of formula C48H40N16O4Pd4S4 (1a),
C52H48N16O4Pd4S4 (1b), and C56H56N16O4Pd4S4 (1c).
The IR data are in agreement with deprotonation of the
Results and Discussion
The ligands a–c were prepared by reaction of 1-acetyl-3-
indolecarboxaldehyde with thiosemicarbazide, 4-methyl- ligand at the hydrazine nitrogen upon complex forma-
thiosemicarbazide, or 4-ethylthiosemicarbazide, respectively tion[16–19] (vide supra). The ν(C=N) band is shifted to lower
(see Exp. Sect.). The bands at around 3380 and 3140 cm–1 wavenumbers,[20] contrary to the trend observed for other
in the IR spectra of these compounds are due to ν(N–H) thiosemicarbazone complexes, which show a shift to higher
absorption of the NH2 and NH groups, respectively; the wavenumbers.[15] The ν(C=S) band disappears, in agree-
latter is not present in the spectra of the complexes.[15] The ment with loss of double-bond character upon deproton-
ligands also show characteristic ν(C=N) and ν(C=S) ation of the NH group. Although these data are in good
stretches in their IR spectra at around 1615 and 830 cm–1, accordance with metalation of the thiosemicarbazone, they
respectively. In the 1H NMR spectra the resonances at give little insight as to the metalated carbon atom, for which
around δ = 11.5 and 8.30 ppm were assigned to the NH definite proof was obtained from the 1H NMR spectra,
and HC=N protons, respectively (see Exp. Sect.). New cy- whose data are fully consistent with metalation of the C(1)
Scheme 1. (i) K2PdCl4/EtOH; (ii) Ph2P(CH2)2PPh2/Me2CO, 1:2.
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J. M. Vila et al.
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carbon atom. Thus, a singlet at δ = 7.41 (1a), 7.41 (1b) and i.e., the one involving Pd(1A); the structural data for the
7.68 ppm (1c) was assigned to the pyrrole C(2)H proton other three molecular units are very similar. The palladium
resonance, which is shifted to lower frequency with respect atom exhibits a slightly distorted square-planar geometry
to its position in the spectra of the free ligands (δ Ϸ with a central nucleus comprised of an eight-membered ring
8.3 ppm). The complex ABCD spin system due to the H(5)– of alternating palladium and sulfur atoms, which adopts a
H(8) protons that is seen for the ligands is absent in the boat conformation. Each palladium atom is bonded to four
spectra of the complexes, where it gives way to a simple different donor atoms: three pertaining to a terdentate thio-
three-proton first-order spectrum that can be unambigu- semicarbazone, namely the aryl C(1) carbon, the imine N(2)
ously assigned and clearly indicates loss of the H5 proton nitrogen, and the thioamide S(1) sulfur atom, with a fourth
upon metalation. Thus, two doublets at around δ = 8.6 and donor being a sulfur atom S(1B) from a neighboring ligand.
8.4–8.0 ppm were ascribed to the H6 and H8 protons, The plane formed by the ligating atoms at palladium
respectively, whereas a triplet at around δ = 7.1 ppm was [C(1A), N(2A), S(1A), S(1B): plane 1] is essentially planar
assigned to the H7 resonance (see Exp. Sect.). Also relevant (rms = 0.0132), with slight displacement of the metal atom
is the absence of the signal for the NH group and the high- by 0.0395 Å. The remaining planes at palladium: the
field shift of the HC=N resonance by about 0.4– metallacycle [Pd(1A), C(1A), C(6A), C(10A), C(11A),
0.9 ppm.[21,22] Only one set of signals was detected in the 1H N(2A): plane 2], the coordination ring [Pd(1A), N(2A),
NMR spectra, thereby precluding mixtures of compounds N(3A), C(12A), S(1A): plane 3], and the metalated phenyl
bearing different metalated carbons and confirming the ring [C(1A), C(2A), C(3A), C(4A), C(5A), C(6A): plane 4]
strong steric hindrance exerted by the C(O)Me group, are nearly coplanar [angles between planes 1 and 2 =
which selectively directs the palladium atom towards the 1.60(0.08)°, 1 and 3 = 1.13(0.08)°, 1 and 4 = 1.35(0.10)°, 2
phenyl C5 atom.
and 3 = 2.70(0.08)°, 2 and 4 = 2.80(0.12)°, and 3 and 4 =
1.23(0.11)°]. All bond lengths are in their typical ranges,
and the S(1A)–C(12A) [1.765(8) Å] and N(3A)–C(12A)
bond lengths [1.299(7) Å] are consistent with increased sin-
Crystal and Molecular Structure of 1b
Suitable crystals of complex 1b were grown by slowly gle- and double-bond character, respectively. The Pd(1A)–
evaporating a DMSO solution. Crystal data are given in S(1A) bond [2.3380(14) Å] is longer than the Pd(1A)–S(1B)
the Exp. Sect. An ORTEP illustration of the structure, with bond [2.3208(13) Å], thus confirming the greater trans in-
selected interatomic distances and angles, is shown in Fig- fluence of the phenyl carbon as compared to the imine ni-
ure 1.
trogen atom. The Pd(1A)–C(1A) bond [2.021(5) Å] is
The asymmetric unit of 1b consists of two molecules of shorter than the expected value of 2.081 Å,[23] probably due
compound 1b and eight DMSO solvent molecules. Al- to partial multiple-bond character.[11,24] The Pd(1)–N(1)
though the overall structure for each molecule is only ap- bond [2.064(4) Å] is longer than previous values found in
proximately S4-symmetric, the four cyclometalated moieties related complexes (sum of the covalent radii for palladium
are not symmetry-related. Nevertheless, discussion shall be and nitrogen: 2.01 Å[10]), due not only to the trans influence
limited to the data pertaining to one fourth of the molecule, of the sulfur atom but also to the greater size of the met-
Figure 1. Molecular structure of 1b, with labelling scheme. Hydrogen atoms have been omitted for clarity. Selected bond lengths and
angles: Pd(1A)–C(1A) 2.021(5), Pd(1A)–N(2A) 2.064(4), Pd(1A)–S(1B) 2.3208(13), Pd(1A)–S(1A) 2.3380(14), S(1A)–C(12A) 1.749(6),
N(3A)–C(12A) 1.299(7), N(3A)–N(2A) 1.439(5), N(2A)–C(11A) 1.292(6), C(1A)–C(6A) 1.390(6), C(11A)–C(10A) 1.410(7), C(10A)–
C(6A) 1.457(6); C(1A)–Pd(1A)–N(2A) 94.27(18), C(1A)–Pd(1A)–N(2A) 94.27(18), N(2A)–Pd(1A)–S(1B) 173.23(12), C(1A)–Pd(1A)–
S(1A) 176.29(14), N(2A)–Pd(1A)–S(1A) 83.45(12), S(1B)–Pd(1A)–S(1A) 89.92(5), C(6A)–C(1A)–Pd(1A) 118.7(4), C(1A)–C(6A)–C(10A)
130.4(5), C(11A)–C(10A)–C(6A) 125.2(4), N(2A)–C(11A)–C(10A) 123.5(5), C(11A)–N(2A)–N(3A) 112.1(4), C(11A)–N(2A)–Pd(1A)
128.0(4), N(3A)–N(2A)–Pd(1A) 119.9(3), C(12A)–N(3A)–N(2A) 113.6(4), N(3A)–C(12A)–S(1A) 127.2(4), C(12A)–S(1A)–Pd(1A) 95.4(2).
3018
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Thiosemicarbazone Complex with a Six-Membered Palladacycle
FULL PAPER
Figure 2. Packing diagram of compound 1b showing the parallel arrangement of the cyclometalated units.
alated ring in the present compound. The angles between with a phosphorus trans to nitrogen. The 31P NMR reso-
adjacent atoms in the coordination sphere are close to the nance is a singlet at δ = 70.41 (2a) and 70.34 ppm (2b),
expected value of 90°. However, as opposed to previous re- thus showing the equivalence of the two 31P nuclei. The 31
P
sults where the C–Pd–N bite angle was less than 90°, due chemical shift values are also consistent with a phosphorus
to formation of a five-membered metallacycle,[25,26] the six- trans to nitrogen.[27–30]
membered ring in the present case allows a larger bite of
the C,N chelate, thereby relieving strain on the angle at the
metal; consequently, the C(1A)–Pd(1A)–N(1A) angle is
94.27°. On the other hand, inspection of the N(2A)–
Pd(1A)–S(1A) bite angle of the five-membered Pd–N–N–
C–S ring shows a similar value to that observed earlier in
Conclusions
We have shown that thiosemicarbazones derived from
condensed systems, such as indole, may behave as terdent-
ate [C,N,S] pincer ligands in a cyclometalation reaction with
related complexes, with a value of 83.45°. The Pd–Pd bond
palladium salts to give new tetranuclear species, which have
lengths across parallel sets of cyclometalated moieties,
been fully characterized in solution, as has one compound
which are in the range 3.8–4.1 Å, preclude any interaction
in the solid state. From a structural point of view they are
between the metal atoms.
closely related to similar systems reported by us previously,
Two noteworthy observations regarding the structure are
although in the present case the condensed rings seem to
that pairs of metalated units are fixed in a nearly co-planar
favor π stacking of the molecules in the unit cell. An added
parallel mode (angle between planes of about 3.2°, with
novelty to these compounds is the formation of a six-mem-
bered metallacycle, the first example with thiosemicarb-
azones, which is induced by the presence of bulky groups
groups of parallel units separated by about 3.6 Å), and at
an angle of 43° to the a axis (see Figure 2), thus indicating
a possible weak π-stacking with the pyrrole rings set in an
that hinder formation of the more common, and stable,
alternating disposition (see Figure 2).
five-membered metalated ring.
Reactivity of the Complexes
Experimental Section
General Remarks: Solvents were purified by standard methods.[31]
Reactions of 1a and 1b with Ph2P(CH2)2PPh2 (dppe)
were tested in order to corroborate the behavior observed
All chemicals were reagent grade. K2PdCl4 was purchased from
by us in related compounds. Thus, treatment of 1a and 1b
Alfa Products and 1,2-bis(diphenylphosphanyl)ethane (dppe) from
with Ph2P(CH2)2PPh2 in a 1:2 molar ratio gave compounds
Aldrich-Chemie. Microanalyses were carried out at the Servicio de
Análisis Elemental at the Universidad de Santiago using a Carlo
Erba Elemental Analyzer (model 1108). IR spectra were recorded
[{Pd[1-(COMe)-3-[C(H)=NN=C(S)NHR]C8H4N]}2(µ-
Ph2P(CH2)2PPh2)] (R = H 2a, Me 2b) as pure, air-stable
1
solids, which were fully characterized (Scheme 1). The H
as Nujol mulls or KBr discs with a Perkin–Elmer 1330 or a Matt-
NMR spectra show a signal at δ = 8.79 (2a) and 8.32 ppm
(2b), shifted to higher frequency with respect to the corre-
sponding tetramers, which was assigned to the HC=N reso-
nance. It appears as a doublet owing to coupling to the
phosphorus nucleus. The H6 resonance [δ = 6.11 (2a) and
6.11 ppm (2b)] is shifted to lower frequency by about
1.5 ppm with respect to the parent complexes owing to
son spectrophotometer. NMR spectra were obtained for solutions
in [D6]DMSO with Bruker WM-250 and AMX-300 spectrometers
and are referenced to SiMe4 (1H) or 85% H3PO4 (31P{1H}). All
chemical shifts are reported downfield from standards. The FAB
mass spectra were recorded with a Fisons Quatro mass spectrome-
ter with a Cs ion gun; 3-nitrobenzyl alcohol was used as the matrix.
Synthesis of 1-(COMe)-3-[C(H)=NN(H)C(=S)NH2]C8H5N (a): 1-
shielding by the phosphane phenyl rings, in accordance Acetyl-3-indolecarboxaldehyde (411 mg, 0.002 mol) and hydrochlo-
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J. M. Vila et al.
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ric acid (35%, 0.6 mL) were added to a suspension of thiosemicarb-
azide (200 mg, 0.002 mol) in water (25 mL) to give a clear solution,
which was stirred at room temperature for 4 h. The white solid that
precipitated was filtered off, washed with cold water, and dried in
0.014 mmol) in acetone (15 mL). The mixture was stirred for 3 h
and the resulting orange solid filtered off and dried. Yield: 23.5 mg
(76%). C50H44N8O2P2Pd2S2 (1127.9): calcd. C 53.3, H 3.9, N 9.9,
S 5.7; found C 53.1, H 4.0, N 9.8, S 5.8. IR: ν(N–H) 3344 m cm–1;
1
vacuo. Yield: 497 mg (87%). C12H12N4OS (260.32): calcd. C 55.4, ν(C=O) 1714 s; ν(C=N) 1607 m. H NMR ([D6]DMSO): δ = 8.96
3
H 4.7, N 21.5, S 12.3; found C 55.5, H 4.7, N 21.6, S 12.4. IR:
(s, 1 H, H2), 8.79 (d, JH,P = 2.7 Hz, 1 H, HC=N), 8.25 (d, JH7,H8
ν(N–H) 3388 m, 3132 m cm–1; ν(C=O) 1709 s; ν(C=N) 1617 s; = 8.4 Hz, 1 H, H8), 7.09 (t, 1 H, H7), 6.11 (d, JH7,H6 = 8.4 Hz, 1
3
ν(C=S) 838 m. 1H NMR ([D6]DMSO): δ = 11.48 (s, 1 H, NH),
8.35 (s, 1 H, H2), 8.34 (m, 2 H, H5,H8), 8.30 (s, 1 H, HC=N), 8.24,
7.61 (br., 2 H, NH2), 7.36 (m, 2 H, H6, H7), 2.68 ppm (s, 3 H,
COMe).
H, H6), 2.66 ppm (s, 3 H, COMe). 31P{1H} NMR ([D6]DMSO): δ
= 70.41 ppm (s). FAB-MS: m/z 1128 [M]+.
Compound 2b was synthesized following a similar procedure.
2b: Yield: 23.8 mg (78%). C52H48N8O2P2Pd2S2 (1155.9): calcd. C
54.0, H 4.2, N 9.7, S 5.6; found C 53.8, H 4.1, N 9.8, S 5.5. IR:
ν(N–H) 3375 m cm–1; ν(C=O) 1710 s; ν(C=N) 1599 m. 1H NMR
([D6]DMSO): δ = 8.90 (s, 1 H, H2), 8.32 (d, JH,P = 2.7 Hz, 1 H,
Thiosemicarbazones b and c were prepared following a similar pro-
cedure.
1-(COMe)-3-[C(H)=NN(H)C(=S)NHMe]C8H5N
(b):
Yield:
3
480 mg (92%). C13H14N4OS (274.35): calcd. C 56.9, H 5.1, N 20.4,
S 11.7; found C 56.7, H 5.0, N 20.6, S 11.8. IR: ν(N–H) 3289 m,
3129 m cm–1; ν(C=O) 1715 s; ν(C=N) 1612 s; ν(C=S) 823 m. 1H
NMR ([D6]DMSO): δ = 11.50 (s, 1 H, NH), 8.37 (m, 2 H, H5,H8),
8.33 (s, 1 H, H2), 8.30 (s, 1 H, HC=N), 8.06 (br., 1 H, NHMe),
HC=N), 8.25 (d, JH7,H8 = 8.8 Hz, 1 H, H8), 6.83 (t, 1 H, H7),
3
6.21 (br., 2 H, NHMe), 6.11 (d, JH7,H6 = 8.8 Hz, 1 H, H6), 2.74
3
(s, 3 H, COMe), 2.50 ppm (d, JH,H = 4.4 Hz, 3 H, NHMe).
31P{1H} NMR ([D6]DMSO): δ = 70.34 ppm (s). FAB-MS: m/z
1156 [M]+.
3
7.39 (m, 2 H, H6, H7), 3.08 (d, JH,H = 4.4 Hz, 3 H, NHMe),
X-ray Crystallographic Study: A single crystal of complex 1b was
mounted on a glass fiber and transferred to the diffractometer.
Three-dimensional, room temperature X-ray data were collected on
a Bruker SMART CCD diffractometer by the ω-scan method using
graphite-monochromated Mo-Kα radiation (see Table 1 for details).
All the measured reflections were corrected for Lorentz and polar-
ization effects and for absorption by semi-empirical methods based
2.68 ppm (s, 3 H, COMe).
1-(COMe)-3-[C(H)=NN(H)C(=S)NHEt]C8H5N (c): Yield: 431 mg
(89%). C14H16N4OS (288.37): calcd. C 55.8, H 5.6, N 19.4, S 11.1;
found C 55.6, H 5.5, N 19.3, S 11.0. IR: ν(N–H) 3372 m, 3140 m
cm–1; ν(C=O) 1719 s; ν(C=N) 1615 s; ν(C=S) 831 m. 1H NMR
([D6]DMSO): δ = 11.45 (s, 1 H, NH), 8.36 (m, 2 H, H5, H8), 8.33
(s, 1 H, H2), 8.30 (s, 1 H, HC=N), 8.10 (br., 1 H, NHEt), 7.40 (m,
2 H, H6, H7), 3.65 (m, 2 H, NHCH2CH3), 2.67 (s, 3 H, COMe),
on symmetry-equivalent and repeated reflections (Tmax./Tmin.
=
0.816/0.587). The structure was solved by direct methods and re-
fined by full-matrix least-squares on F2. Hydrogen atoms were in-
cluded in calculated positions and refined in a riding mode. The
structure contains eight symmetry-related voids of 37 Å3 contain-
ing unresolvable solven; this was treated using the squeeze method,
which lowered the R1 value by about 25%.[32] Refinement con-
verged at a final R = 0.0827 (observed data, F) and wR2 = 0.1128
3
1.19 ppm (t, JH,H = 7.1 Hz, 3 H, NH CH2CH3).
Preparation of 1a: Ethanol (40 mL) was added to a stirred solution
of K2PdCl4 (100 mg, 0.306 mmol) in water (6 mL) and the fine yel-
low suspension obtained was treated with a (80 mg, 0.306 mmol).
The mixture was stirred for 24 h at room temperature. The brown
precipitate was filtered off, washed with ethanol, and dried in
vacuo. Yield: 264 mg (59%). C48H40N16O4Pd4S4 (1458.9): calcd. C
39.5, H 2.8, N 15.4, S 8.8; found C 39.8, H 2.8, N 15.2, S 8.7. IR:
ν(N–H) 3331 m cm–1; ν(C=O) 1709 s; ν(C=N) 1604 m. 1H NMR
([D6]DMSO): δ = 8.66 (br., 1 H, H6), 8.41 (s, 1 H, H2), 8.24 and
Table 1. Crystal data and structure refinement for compound 1b.
Empirical formula
Formula weight
Temperature
C208H176N64O16Pd16S16
6043.49
293(2) K
7.61 (br., 2 H, NH2), 7.98 (br., 1 H, H8), 7.44 (s, 1 H, HC=N),
3
7.13 (t, JH7,H6
=
3JH7,H8 = 7.8 Hz, 1 H, H7), 2.72 ppm (s, 3 H,
Wavelength
0.71073 Å
COMe). FAB-MS: m/z 1458 [M]+.
Crystal system
Space group
Unit cell dimensions
triclinic
P1
¯
Compounds 1b and 1c were synthesized following a similar pro-
cedure.
a = 13.018(3) Å, α = 86.517(4)°
b = 21.501(5) Å, β = 88.051(4)°
c = 26.225(6) Å, γ = 86.305(4)°
7308(3) Å3
1b: Yield: 342 mg (62%). C52H48N16O4Pd4S4 (1515.0): calcd. C
41.2, H 3.2, N 15.0, S 8.5; found C 40.9, H 3.2, N 15.2, S 8.6. IR:
ν(N–H) 3394 m cm–1; ν(C=O) 1710 s; ν(C=N) 1600 m. 1H NMR
Volume
Z
1
1.373 Mgm–3
3
Calculated density
Absorption coefficient
F(000)
([D6]DMSO): δ = 8.58 (d, JH7,H6 = 8.0 Hz, 1 H, H6), 7.98 (d,
1.130 mm–1
3JH7,H8 = 8.0 Hz, 1 H, H8), 7.86 (s, 1 H, HC=N); 7.41 (s, 1 H, H2),
2992
3
7.05 (t, JH7,H6
=
3JH7,H8 = 8.0 Hz, 1 H, H7), 6.20 (br., 2 H,
Crystal size
0.65×0.40×0.18 mm3
3
NHMe), 2.85 (d, JH,H = 4.4 Hz, 3 H, NHMe), 2.55 ppm (s, 3 H,
Theta range for data collection 0.95 to 26.43°
COMe). FAB-MS: m/z 1515 [M]+.
Limiting indices
–16 Յ h Յ 16,
–26 Յ k Յ 26,
0 Յ l Յ 32
83071/29736 [R(int) = 0.0447]
98.9% (26.43°)
1c: Yield: 300 mg (55%). C56H56N16O4Pd4S4 (1571.10): calcd. C
42.8, H 3.6, N 14.3, S 8.2; found C 43.0, H 3.6, N 14.2, S 8.1. IR:
ν(N–H) 3359 m cm–1; ν(C=O) 1716 s; ν(C=N) 1603 m. 1H NMR
Reflections collected/unique
Completeness to θ
Absorption correction
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I Ͼ 2σ(I)]
R indices (all data)
3
3
(CDCl3): δ = 8.63 (d, JH7,H6 = 8.1 Hz, 1 H, H6), 8.41 (d, JH7,H8
Multi-scan
3
3
= 8.1 Hz, 1 H, H8), 7.68 (s, 1 H, H2), 6.79 (t, JH7,H6 = JH7,H8
=
Full-matrix least-squares on F2
29736/0/1457
8.1 Hz, 1 H, H7), 6.33 (s, 1 H, HC=N), 4.83 (br., 2 H, NHEt), 3.39
3
(m, 2 H, NHCH2CH3), 2.76 (s, 3 H, COMe), 0.88 ppm (t, JH,H
6.7 Hz, 3 H, NH CH2CH3). FAB-MS: m/z 1571 [M]+.
=
1.016
R1 = 0.0404, wR2 = 0.1005
R1 = 0.0827, wR2 = 0.1128
0.900 and –0.681 eÅ–3
Complex
2a:
1,2-Bis(diphenylphosphanyl)ethane
(11 mg,
Largest diff. peak and hole
0.028 mmol) was added to a suspension of complex 1a (20 mg,
3020
www.eurjic.org
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2006, 3016–3021

Thiosemicarbazone Complex with a Six-Membered Palladacycle
FULL PAPER
(all unique data, F2), with allowance for thermal anisotropy of all
non-hydrogen atoms. Minimum and maximum final electron den-
sity –0.681 and 0.900 eÅ–3. The structure solution and refinement
were carried out using the program package SHELX-97.[33]
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CCDC-291523 contains the supplementary crystallographic data
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Acknowledgments
We
thank
the
Xunta
de
Galicia,
Spain
(project
PGIDT99PXI20907B) and the DGES (grant no. PB98-0638-C02-
01/02) for financial support.
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Received: December 7, 2005
Published Online: June 6, 2006
Eur. J. Inorg. Chem. 2006, 3016–3021
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3021