Synthesis and structural analysis of new palladium(II) thiosaccharinates with triphenylphosphane or diphosphanes

Article abstract of DOI:10.1002/zaac.200900099

A series of palladium(II) thiosaccharinates with triphenylphosphane (PPh₃), bis(diphenylphosphanyl)methane (dppm), and bis(diphenylphosphanyl)ethane (dppe) have been prepared and characterized. From mixtures of thiosaccharin, Htsac, and palladium(II) acetylacetonate, Pd(acac)₂, the palladium(II) thiosaccharinate, Pd(tsac)₂ (tsac: thiosaccharinate anion) (1) was prepared. The reaction of 1 with PPh ₃, dppm, and dppe leads to the mononuclear species Pd(tsac) ₂(PPh₃)₂MeCN (2), [Pd(tsac)₂(dppm)] (3), Pd(tsac)₂(dppm)₂ (4), and [Pd(tsac) ₂(dppe)].M.eCN (5). Compounds 2, 4, and 5 have been, prepared also by the reaction, of Pd(acac)₂ with the corresponding phosphane and Htsac. All the new complexes have been characterized by chemical analysis, UV/Vis, IR, and Raman spectroscopy. Some of them, have been, also characterized by NMR spectroscopy. The crystalline structures of complexes 3, and 5 have been studied by X-ray diffraction techniques. Complex 3 crystallizes in the monoclinic space group P2₁/n with a = 16.3537(2), b = 13.3981(3), c = 35.2277(7) A, ss = 91.284(1)°, and Z = 8 molecules per unit cell, and complex 5 in Pl₁/n with a = 10.6445(8), b = 26.412(3), c = 15.781(2) A, β = 107.996(7)°, and Z = 4. In compounds 3 and 5, the palladium ions are in a distorted square planar environment. They are closely related, having two sulfur atoms of two thiosaccharinate anions, and two phosphorus atoms of one molecule of dppm or dppe, respectively, bonded to the Pd^II atom. The molecular structure of complex 3 is the first reported for a mononuclear Pd^II dppm-thionate system.

Full text of DOI:10.1002/zaac.200900099

ARTICLE
DOI: 10.1002/zaac.200900099
Synthesis and Structural Analysis of New Palladium(II) Thiosaccharinates
with Triphenylphosphane or Diphosphanes
Susana H. Tarulli,[a] Oscar V. Quinzani,*[a] Sandra D. Mandolesi,[a] Jorge A. Guida,[b]
Gustavo A. Echeverría,[c] Oscar E. Piro,[c] and Eduardo E. Castellano[d]
Keywords: Palladium; Thiosaccharin; Diphosphanes; Xꢀray diffraction; Coordination chemistry
Abstract. A series of palladium(II) thiosaccharinates with triphenylꢀ them have been also characterized by NMR spectroscopy. The crystalꢀ
phosphane (PPh3), bis(diphenylphosphanyl)methane (dppm), and line structures of complexes 3, and 5 have been studied by Xꢀray difꢀ
bis(diphenylphosphanyl)ethane (dppe) have been prepared and characꢀ fraction techniques. Complex 3 crystallizes in the monoclinic space
terized. From mixtures of thiosaccharin, Htsac, and palladium(II) acetꢀ group P21/n with a = 16.3537(2), b = 13.3981(3), c = 35.2277(7) Å,
ylacetonate, Pd(acac)2, the palladium(II) thiosaccharinate, Pd(tsac)2 β = 91.284(1)°, and Z = 8 molecules per unit cell, and complex 5 in
(tsac: thiosaccharinate anion) (1) was prepared. The reaction of 1 with P21/n with a = 10.6445(8), b = 26.412(3), c = 15.781(2) Å, β =
PPh3, dppm, and dppe leads to the mononuclear species 107.996(7)°, and Z = 4. In compounds 3 and 5, the palladium ions are
Pd(tsac)2(PPh3)2·MeCN (2), [Pd(tsac)2(dppm)] (3), Pd(tsac)2(dppm)2 in a distorted square planar environment. They are closely related, havꢀ
(4), and [Pd(tsac)2(dppe)]·MeCN (5). Compounds 2, 4, and 5 have ing two sulfur atoms of two thiosaccharinate anions, and two phosphoꢀ
been prepared also by the reaction of Pd(acac)2 with the corresponding rus atoms of one molecule of dppm or dppe, respectively, bonded to
phosphane and Htsac. All the new complexes have been characterized the PdII atom. The molecular structure of complex 3 is the first reported
by chemical analysis, UV/Vis, IR, and Raman spectroscopy. Some of for a mononuclear PdIIꢀdppmꢀthionate system.
coupling reactions [4]. In the last years several works on PdII
Introduction
and PtII polynuclear complexes with a variety of anionic or
Metalꢀheterocyclic thioamides systems received much attenꢀ
neutral ligands were published and, in part, reviewed recently
tion in the last decades because they are present in biological
[5].
systems [1], they were also applied in the pharmaceutical inꢀ
The heterocyclic thioamides (thiones) show thioneꢀthiol tauꢀ
dustry [2]. Molecules containing nitrogen and sulfur donor atꢀ
tomeric equilibria [6], a fact that makes them versatile chelatꢀ
oms coordinated to platinum and gold, have been recognized
ing agents, especially for heavy metals [7]. Due to the large
for their antiꢀtumoral activity [3]. Moreover, a great number
size of the sulfur atom and the proximity of the imine nitrogen
of PdII and PtII inorganic or organometallic complexes, speꢀ
atom, considerable bridging capabilities are also found for hetꢀ
cially with monoꢀ and diphosphanes, were prepared and charꢀ
erocyclic thionates, the deprotonated forms of thiones. η1ꢀS
acterized as catalyst for a variety of oxidation, reduction or
and η1ꢀN monodentating, η2ꢀS,N chelating, µ2ꢀS, µ2ꢀS,N, µ3ꢀ
S,N (η2ꢀS, η1ꢀN) and µ4ꢀS,N (η3ꢀS, η1ꢀN) bridging behaviors
* Prof. Dr. O. V. Quinzani
were observed, yielding from oligoꢀ to polymeric species [7].
In contrast with the rich chemistry of thiones and thionates
with metal cations as CuI, RuII, AgI, PtII or HgII, fewer pallaꢀ
diumꢀthione compounds were studied and only the crystal
structure of a small fraction of them were reported in the literaꢀ
ture. Simple PdIIꢀthionates (PdL2) were generally prepared as
almost insoluble compounds [8]. When L was benzothiazoleꢀ
2ꢀthionate, benzisothiazoleꢀ2ꢀthionate, or pyridineꢀ2ꢀthionate,
Pd2L4 molecular arrangements were observed, with the thionꢀ
ates acting as µ2ꢀS,N bridging ligands [8a, 8e, 8f]. Many terꢀ
nary complexes prepared from the reaction of PdL2 complexes
or other PdII salts with mono or diphosphanes were also reꢀ
ported. In fact, cisꢀ and transꢀ[PdL2(PR3)2], [Pd(η1ꢀL)(η2ꢀ
L)(PR3)], [Pd(η2ꢀL)(PR3)2]X, [Pd(η2ꢀL)(PR3)X], and [Pd2(µꢀ
L)2(PR3)2X2] (X: second anion) complexes with different types
of thionates were synthesized [8c, 8d, 9]. Employing diphosꢀ
phanes as coꢀligands, several compounds with [PdL2(PP)] or
Fax: +54ꢀ291ꢀ4595160
EꢀMail: quinzani@criba.edu.ar
[a] INQUISUR, Departamento de Química
Universidad Nacional del Sur
Avda. Alem 1253
B8000CPB, Bahía Blanca, Argentina
[b] CEQUINOR, Facultad de Ciencias Exactas
Universidad Nacional de La Plata
C.C. 962
1900 La Plata, Argentina
and Departamento de Ciencias Básicas
Universidad Nacional de Luján
Rutas 5 y 7
Luján, Argentina
[c] Departamento de Física and Instituto IFLP
(Conicet, CCT La Plata)
Facultad de Ciencias Exactas, Universidad Nacional de La Plata
C.C. 67
1900 La Plata, Argentina
[d] Instituto de Física de São Carlos
Universidade de São Paulo
CP. 369
13560 São Carlos (SP), Brazil
1604
© 2009 WileyꢀVCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2009, 635, 1604–1612

Palladium(II) Thiosaccharinates with Triphenylphosphane or Diphosphanes
[Pd(η2ꢀL)(PP)]X stoichiometries, with PP = dppm [3b, 8b, 9a,
10], dppe [9e, 10], dppp and dppb [8b, 10] were reported. Curiꢀ
ously, no crystal structure of the [PdL2(dppm)]ꢀtype compound
is currently found in the CCDC database and only two
[PdL2(dppe)]ꢀtype complexes are deposited there [9a, 10]. La
guna and coꢀworkers prepared dinuclear PdII complexes with
pyridineꢀ2ꢀthionate and dppm having the structures [Pd2(µ2ꢀ
S,NꢀC5H4SN)(µ2ꢀκ2ꢀSꢀC5H4SN)(µ2ꢀdppm)(κ1SꢀC5H4SN)2] and
[Pd2(µ2ꢀS,NꢀC5H4SN)3(µ2ꢀdppm)]Cl [11].
With the aim to further explore the coordination behavior of
thiosaccharin, C6H4S(O)2NHC(S) (Htsac) (see Scheme 1), the
thione form of saccharin, we studied new palladium thiosacꢀ
charinates. In the last years, we reported monoꢀ and polyꢀnuꢀ
clear structures of AgI, PbII, CuI, and CdII thiosaccharinates
[12]. As was already reported, the thiosaccharinate anion can
coordinate metal atoms through the endocyclic nitrogen and/
or the hexocyclic sulfur atoms, therefore acting with a great
variety of coordination modes [12d].
formed with a Carlo Erba EA1108 instrument at INQUIMAE (FCEyN,
UBA, Argentine). Conductivity measurements of dichloromethane
(CH2Cl2) solutions of the compounds were performed with an OAKꢀ
TON digital conductimeter calibrated against aqueous solutions of
twice recrystallized KCl (744.7 ppm, 1413 µS).
Spectroscopic Measurements
The IR spectra of the substances as KBr pellets and Nujol mulls were
recorded in the 4000 to 400 cm–1 range with a Nicolet Nexus FTIR
spectrometer. The Raman spectra of the solids, run in the region beꢀ
tween 3500 to 100 cm–1, were obtained with a FRA 106 accessory
mounted on a Bruker IFS 66 FTIR instrument, using the 1064 nm
excitation line from an NdꢀYAG laser. The UV/Vis spectra of the soluꢀ
tions and the KBr dispersed solids were registered using a Cecil 2021
spectrophotometer. The 1H, 13C and 31P{1H} NMR spectra of the comꢀ
pounds in [D6]DMSO and CDCl3 solutions, at 300 K, were recorded
with multiꢀnuclear Bruker ARXꢀ300 or Bruker AVANCEꢀ300 instruꢀ
ments. The chemical shift data were measured employing the replaceꢀ
ment methods and are given relative to external H3PO4 and TMS.
Synthesis
Palladium(II) Thiosaccharinate Pd(tsac)2 (1): The yellowishꢀorange
solid was obtained after dropwise addition of a solution of thiosacchaꢀ
rin (68.5 mg, 0.344 mmol) in acetonitrile (MeCN) (3 mL) to a solution
of Pd(acac)2 (52.4 mg, 0.172 mmol) in MeCN (5 mL), kept under conꢀ
stant stirring at room temperature, on dry air. The microcrystalline
solid was collected by filtration, washed with small portions of MeCN
and diethyl ether and afterwards dried on air. Yield: 66 mg (76 %). It
shows almost the same spectroscopic features of the hydrated product
obtained by Vieytes et al. [16]. All the procedures performed to obtain
good crystals of the substance were unsuccessful. Analytical percent
composition calculated for C14H8N2O4PdS4: C 33.4; H 1.6; N 5.6 and
S 25.5 %; Found: C 33.8; H 1.9; N 5.9, and S 25.9 %. Molar conductꢀ
ance (Ω–1·mol–1·cm2): 4 (1.0 × 10–5 m solutions in CH2Cl2). IR (KBr):
Scheme 1. Tautomeric and deprotonation equilibria of thiosaccharin.
ν = 1468s, 1422s, 1344s, 1241vs, 1182vs, 1131m, 1022s, 1011s, 803s,
598m, 555s cm–1. Raman (pure solid) bands: 378m, 349s, 268m, 195w
cm–1. UV/Vis (CH2Cl2) λmax (ε): 255 (28718), 294 (23821), 375 (sh)
nm; (DMSO) λmax (ε): 279 (36360), 339 (29920), 420 (sh) nm; (KBr
disks) λmax (ε): (240) (vs), 300 (w), 360 (w) nm.
˜
In this work, we present the synthesis, Xꢀray structural
analysis and spectroscopic characterization of two new pallaꢀ
diumꢀthiosaccharinate complexes, namely bis(η1ꢀSꢀthiosacchaꢀ
rinato)ꢀη2ꢀ{bis(diphenylphosphanyl)methane)}palladium(II),
[Pd(tsac)2(dppm)], and bis(η1ꢀSꢀthiosaccharinato)ꢀη2ꢀ{bisꢀ
(diphenylphosphanyl)ethane)}ꢀpalladium(II), [Pd(tsac)2ꢀ
(dppe)]·MeCN. Palladium(II) thiosaccharinate, Pd(tsac)2, and
the two mononuclear species Pd(tsac)2(PPh3)2·MeCN, and
Pd(tsac)2(dppm)2 were also prepared and characterized.
Bis(thiosaccharinato)bis(triphenylphosphane)palladium(II) Monoꢀ
acetonitrile Pd(tsac)2(PPh3)2.CH3CN (2): Method 1: PPh3 (10.5 mg,
0.040 mmol) was added to an orange suspension of 1 (10.1 mg,
0.020 mmol) in MeCN (5 mL). After two hours of continuous stirring
at 40 °C, the suspension became pale yellow. The solid was collected
by filtration, washed with small portions of MeCN and diethyl ether
and afterwards dried on air. Yield: 15 mg (70 %). All attempts to obꢀ
tain single crystal samples of the substance suitable for Xꢀray diffracꢀ
tion analyses were unsuccessful, due to the extremely low solubility
of the compound in common solvents. Analytical percent composition
calculated for C52H41N3O4P2PdS4: C 58.5; H 3.9; N 3.9 and S 12.0 %;
Experimental Section
General Remarks
Palladium(II) acetylacetonate, triphenylphosphane, bis(diphenylphosꢀ
phine)methane (dppm) and bis(diphenylphosphine)ethane (dppe), were
purchased from Aldrich and used without further purification. Thiosacꢀ
charin (Htsac) in its αꢀform was prepared following the technique pubꢀ
lished by Schibye et al. [13] and characterized by melting point and
IR spectroscopic analysis [14a]. Potassium thiosaccharinate, K(tsac),
was prepared according to the procedure reported by M. Penavic et al.
Found: C 58.4; H 3.2; N 4.0, and S 12.4 %. IR (KBr): ν = 2220vw,
˜
1466s, 1435s, 1422m, 1316vs, 1229s, 1164vs, 1124m, 1096m, 999s,
800s, 693s, 588m, 512s cm–1. Raman (pure solid) bands: 375m, 257s,
219m, 201m cm–1. UV/Vis (KBr disks) λmax (ε): 220 (vs), 276 (w),
318 (w), 365 (m) nm.
[14b]. Water was biꢀdestillated prior to use and the other solvents were Method 2: Solid PPh3 (31.6 mg, 0.120 mmol) was added to a MeCN
of analytical reagent grade and dried by commonly used techniques solution (4 mL) of 18.3 mg (0.060 mmol) of Pd(acac)2. The yellow
[15]. The elemental composition analysis of C, N, H and S were perꢀ solution was stirred for one hour at 40 °C. After that, a MeCN solution
Z. Anorg. Allg. Chem. 2009, 1604–1612
© 2009 WileyꢀVCH Verlag GmbH & Co. KGaA, Weinheim
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O. V. Quinzani et al.
ARTICLE
(3 mL) containing thiosaccharin (23.9 mg, 0.120 mmol) was dropped in MeCN (8 mL). The yellow solution was stirred for one hour at
on and a clear yellow solid immediately appeared. The suspension was 50 °C. Afterwards, a solution of thiosaccharin (15.9 mg, 0.080 mmol)
stirred also for one hour and then filtered off. The solid was washed in MeCN (3 mL) was added. After about twenty minutes a yellow solid
with small portions of MeCN and diethyl ether, and then air dried. appears that was filtered off, washed with small portions of MeCN and
Yield 30 mg (47 %).
diethyl ether, and afterwards dried on air. Yield 11 mg (22 %).
Bis(thiosaccharinato){bis(diphenylphosphanyl)ethane}palladium(II)
Monoacetonitrile Pd(tsac)2(dppe)·MeCN (5): Method 1: Dppe
(15.9 mg, 0.040 mmol) was added to a suspension containing
Pd(tsac)2 (20.1 mg, 0.040 mmol) in MeCN (7 mL). The initially bright
yellow reaction mixture was stirred for three hours at room temperaꢀ
ture, until its color gradually turned to pale yellow. The solid was
filtered, washed with small portions of MeCN and diethyl ether and
afterwards dried on air. Yield 29.1 mg (81 %). Analytical percent comꢀ
position calculated for C42H35N3O4P2PdS4: C 53.5; H 3.7; N 4.5 and
S 13.6 %; Found: C 53.5; H 4.0; N 4.1; and S 14.0 %. Molar conductꢀ
ance (Ω–1 mol–1 cm–1): 2 (1.0 × 10–3 m solutions in CH2Cl2). IR
Bis(thiosaccharinato){bis(diphenylphosphanyl)methane}pallaꢀ
dium(II) Pd(tsac)2(dppm) (3):
A solution of dppm (11.5 mg,
0.030 mmol) in MeCN (3 mL) was added to a suspension of 1
(15.1 mg, 0.030 mmol) in MeCN (5 mL) at 30 °C with continuous
stirring. After one hour, the suspension became a clear yellow solution.
The solution was warmed and evaporated until it reached a third of its
original volume. It was kept at 10 °C for one day after which pale
yellow crystals, suitable for Xꢀray diffraction analysis, formed. Yield
14.2 mg (53 %). Analytical percent composition calculated for
C39H30N2O4P2PdS4: C 52.8; H 3.4; N 3.2 and S 14.5 %; Found: C
52.8; H 3.7; N 3.2, and S 14.6 %. Molar conductance (Ω–1·mol–1·cm2):
2 (6.0 × 10–4 m solutions in CH Cl ). IR (KBr): ν = 1460s, 1436s,
˜
(KBr): ν = 1463s, 1437s, 1416s, 1309vs, 1232s, 1155vs, 1123s, 1106m,
˜
2
2
1002s, 887m, 807s, 754m, 691s, 555s, 535s cm–1. Raman (pure solid)
bands: 368m, 257s, 233m, 158s cm–1. UV/Vis (CH2Cl2) λmax (ε): 265
(41200), 334 (6240) nm; (KBr disks) λmax (ε): (210) (vs), 286 (w), 375
(w) nm. 1H NMR ([D6]DMSO): δ = 8.25–8.09 (m, 8 H, Hβ dppe);
8.08–8.01 (m, 2 H, H6 tsac); 7.97–7.88 (m, 2 H, H3 tsac); 7.88–7.79
(m, 4 H, H4/H5 tsac); 7.79–7.62 (m, 12 H, Cγ/Cδ dppe); 2.92 (m, 4
H, CH2). 13C NMR ([D6]DMSO): tsac: δ = 184.92 (C1); 137.74 (C7);
133.54 (C5); 132.73 (C4); 124.66 (C6); 120.57 (C3); dppe: δ =
133.79(d, Cβ, 2J(13C, 31P), 12.3 Hz) 132.45 (Cδ); 129.28 (d, Cγ, 3J(13C,
1407m, 1308vs, 1229s, 1153vs, 1123s, 1105m, 1000s, 809s, 738s,
689m, 588m cm–1. Raman (pure solid) bands: 370s, 257s, 228m, 168s
cm–1. UV/Vis (CH2Cl2) λmax (ε): 265 (35000), 350 (6200) nm; (KBr
1
disks) λmax (ε): (200) (vs), 230 (sh), 295 (w), 360 (w) nm. H NMR
(CDCl3): δ = 7.93–7.77 (m, 10 H, H6 tsac and Hβ dppm); 7.70–7.62
(m, 2 H, H3 tsac); 7.58–7.49 (m, 4 H, H4/H5 tsac); 7.49–7.35 (m, 12
H, Cδ/Cγ dppm); 4.22 (t, 2 H, CH2, J2
/
31P: 9.9 Hz). 13C NMR
(CDCl3): tsac: δ = 184.53 (C1); 138.19 (C7); 134.21 (C2); 132.63
(C5); 131.65 (C4); 125.04 (C6); 120.26 (C3); dppm: δ = 133.44 (d,
1
31P), 11.7 Hz); 127.34 (d, Cα, J(13C, 31P), 41.9 Hz); 27.76 (dd, CH2,
2
Cβ, 3J(13C, 31P), 6.0 Hz); 133.36 (d, Cβ’, J(13C, 31P), 6.0 Hz); 132.34
2J(13C, 31P), 12.9 Hz); 1J(13C, 31P), 32.8 Hz). 31P{1H} NMR
([D6]DMSO): δ = 120.44 (s).
(Cδ); 129.44 (d, Cγ, 3J(13C, 31P),6.0 Hz); 129.36 (d, Cγ’, 3J(13C,
31P),6.0 Hz); 127.01 (d, Cα, 1J(13C, 31P),24.9 Hz); 126.73 (d, Cα’,
1
1J(13C, 31P), 25.0 Hz); 42.60 (t, CH2, J(13C, 31P), 24.8 Hz). 31P{1H}
Upon slow evaporation of saturated solutions of the complex in acetoꢀ
nitrile, well formed yellow crystals of compound 5 were collected.
These crystals were employed in the structural Xꢀray diffraction study
reported herewith.
NMR (CDCl3): δ = 10.42 (s). The atom numbering for the NMR specꢀ
troscopic data is shown in Scheme 2.
Method 2: To a solution containing Pd(acac)2 (12,2 mg, 0.040 mmol)
and dppe (32.0 mg, 0.080 mmol) in MeCN (8 mL), another MeCN
solution (2 mL) containing thiosaccharin (16.0 mg, 0.080 mmol) was
added under constant stirring at 50 °C. The small amount of a pale
yellow solid formed was filtered off and the clear solution was slowly
evaporated, at room temperature. After three days, a mixture of yellow
and small orange crystals appeared. The yellow solid correspond to
compound 5 and the orange solid seemed to be a PdI complex similar
to the dinuclear Pd2(dppm)2(tsac)2 compound (6) (see below) [17].
Scheme 2. Atoms numbering for tsac, dppm and dppe molecules.
Bis(thiosaccharinato)bis{bis(diphenylphosphanyl)methane}ꢀ
palladium(II) Pd(tsac)2(dppm)2 (4): Method 1: A solution of dppm
(23.1 mg, 0.060 mmol) in MeCN (2 mL) was added to a suspension
of 1 (15.1 mg, 0.030 mmol) in MeCN (2 mL). The mixture was stirred
for two hours at 40 °C. The initial bright yellow suspension gradually
faded and the residual solid was filtered off, washed with small porꢀ
tions of MeCN and diethyl ether, and afterwards dried on air. Yield
17.3 mg (45 %). Analytical percent composition calculated for
C64H52N2O4P4PdS4: C 60.5; H 4.1; N 2.2 and S 10.1 %; Found: C
59.7; H 4.0; N 2.4, and S 10.0 %. Molar conductance (Ω–1·mol–1·cm2):
Xꢀray Diffraction Data
Crystal data, data collection procedure, structure determination methꢀ
ods and refinement results for complexes 3 and 5 are summarized in
Table 1 [18–24].
The hydrogen atoms were positioned stereoꢀchemically and refined
with the riding model. The methyl hydrogen atoms of the crystallizaꢀ
tion acetonitrile molecule in 5 were optimized by treating them as a
rigid groups that were allowed to rotate around the corresponding C–
C bond. ORTEP [25] molecular drawings of the complexes are shown
in Figure 2 and Figure 3. CIF files containing details of the crystal
structures reported in the paper have been deposited with the Camꢀ
bridge Structural Data Base and are available free of charge upon reꢀ
quest from The Director, Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK. (Fax: +44ꢀ1233ꢀ336033; Eꢀ
5 (1.0 × 10–3 m solutions in CH Cl ). IR (KBr): ν = 1464s, 1434s,
˜
2
2
1421m, 1315s, 1229s, 1163vs, 1123m, 1099m, 1000s, 801s, 737m,
695s, 588m, 555s cm–1. Raman (pure solid) bands: 371m, 255m,
166m cm–1. UV/Vis (CH2Cl2) λmax (ε): 255 (70000), 285 (36000), 325
(6000) nm; (KBr disks) λmax (ε): (200) (vs), 290 (w), 356 (w) nm.
Method 2: A solution of dppm (30.8 mg, 0.080 mmol) in MeCN Mail: deposit@ccdc.cam.ac.uk; WEB: http://www.csdc.cam.ac.uk),
(2 mL) was added to a solution of Pd(acac)2 (12.2 mg, 0.040 mmol) reference numbers CCDCꢀ718963 (3), and CCDCꢀ718964 (5).
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© 2009 WileyꢀVCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2009, 1604–1612

Palladium(II) Thiosaccharinates with Triphenylphosphane or Diphosphanes
Table 1. Crystal data and refinement results for [Pd(tsac)2(dppm)] (3), and [Pd(tsac)2(dppe)]·MeCN (5).
3
5
Empirical formula
Formula weight
Temperature /K
Crystal system
Space group
C39H30N2O4P2PdS4
887.23
C42H35N3O4P2PdS4
942.31
150(2)
293(2)
monoclinic
P21/n
monoclinic
P21/n
Unit cell dimensionsa)
a /Å
16.3537(2)
10.6445(8)
b /Å
13.3981(3)
26.412(3)
c /Å
35. 2277(7)
15.781(2)
β /°
91.284(1)
107.996(7)
Volume /Å3
7716,8(2)
4219.7(8)
Z, calculated density /Mg·m–3
Absorption coefficient /mm–1
F(000)
8, 1.527
4, 1.483
0.824
6.481
3600
1920
Crystal size /mm
Crystal color / shape
Diffractometer / scan
Radiation
ζ range data collection /°
Index ranges
0.12 × 0.03 × 0.02
yellow / plate
0.24 × 0.24 × 0.10
yellow / plate
Enraf–Nonius CAD4 / ω–2J
CuꢀKα, λ = 1.54184 Å
3.35 to 68.03
–12 ≤ h ≤ 12, –1 ≤ k ≤ 30, –18 ≤ l ≤ 0
98.0 (to J = 68.03°)
6129
KappaCCD / φ and ω
MoꢀKα, λ = 0.71073 Å
3.04 to 26.00
–20 ≤ h ≤ 12, –16 ≤ k ≤ 16, –43 ≤ l ≤ 43
99.7 (to J = 26.00°)
10394
Completeness /%
Observed reflections [I > 2σ(I)]
Data collection
Data reductionb)
Absorption correction
Structure solutionc)
Refinementd)
COLLECT [18]
DENZOꢀSCALEPACK [20]
Numerical [22]
SHELXSꢀ97 [23]
SHELXLꢀ97 [24]
Full matrix leastꢀsquares on F2
EXPRESS [19]
XCAD4 [21]
Refinement method
Weights /w
[σ2(Fo )+(0.051P)2]–1
[σ2(Fo )+(0.069P)2+4.79P]–1
2
2
2
2
2
2
P = [Max(Fo ,0)+2Fc ]/3
1.014
P = [Max(Fo ,0)+2Fc ]/3
1.051
Goodnessꢀofꢀfit on F2
Reflections collected/unique
R(int)
57765/15144
0.0792
8158/7522
0.0452
Data / restraints / parameters
15144 / 0 / 937
0.0452, 0.0949
0.0795, 0.1040
0.863 and –0.814
7522 / 0 / 508
0.0443, 0.0571
0.1187, 0.1324
0.651 and –1.443
R1(obs,), R1(all)e)
wR2(obs,), wR2(all)e)
Largest peak and hole /e.A–3
a) Leastꢀsquares refinement of the angular settings for 57765 reflections in the 3.04<J<26.00° range for 3 and 24 reflections in the 16.48 < J <
34.36° range for 5. b) Corrections by Lorentz and polarization effects. c) Neutral scattering factors and anomalous dispersion corrections. d)
Structure solved by direct and Fourier methods. The final molecular model obtained by anisotropic fullꢀmatrix leastꢀsquares refinement of the
2
2 2
2 2 1/2
nonꢀhydrogen atoms. e) R indices defined as: R1 = Σ||Fo| – |Fc||/Σ|Fo|, wR2 = [Σw(Fo –Fc ) /Σw(Fo ) ]
.
Supporting Information: Listings of fractional atomic coordinates and
equivalent isotropic displacement parameters (Tables S7–8), full intraꢀ
molecular bond lengths and angles (Tables S9–10), atomic anisotropic
displacement parameters (Tables S11–12) and hydrogen atoms posiꢀ
tions (Tables S13–14), along with tables of full IRꢀRaman data for
complexes 1 to 5 (Table S15) can be obtained from the authors upon
request.
can act as a good coordinating agent for soft metals, hence
giving rise to mononuclear and polyꢀnuclear structures with or
without the presence of other ligands.
The yellowishꢀorange little soluble palladium(II) thiosacchaꢀ
rinate (1) was obtained by the direct reaction of palladium(II)
salts (nitrate or acetylacetonate) with thiosaccharin in water,
light alcohols or MeCN. When PPh3 is added to suspensions
of 1 in MeCN, a very insoluble ternary palladium(II) thiosacꢀ
charinate (2) was obtained (Scheme 3).
Results and Discussion
When 1:1 molar relations between 1 and diphosphanes
(dppm or dppe) are mixed in MeCN, pure solids are obtained
(3 and 5). The singleꢀcrystal Xꢀray diffraction analysis of both
Chemistry of Palladium(II) and Palladium(I) Thiosacchariꢀ
nates
As it is wellꢀknown for other heterocyclic thiones, thiosacꢀ compounds showed the presence of mononuclear complexes,
charin shows a tautomeric equilibrium in solution (see with S2P2 square coordination spheres around the metal. Comꢀ
Scheme 1). It is present in its thiol form in dimethylsulfoxide plexes 3 and 5 are insoluble in water, moderately soluble in
solutions and in the thione form in nonꢀcoordinating solvents, MeCN or CHCl3, and soluble in DMSO. They are indefinitely
as was observed by NMR spectroscopy [26]. In the solid state air and light stable. Using a 1:2 molar relationship between 1
it shows only the thione form [14a]. Its thiolate (thionate) form and dppm, in MeCN, a new solid compound (4) is obtained.
Z. Anorg. Allg. Chem. 2009, 1604–1612
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1607

O. V. Quinzani et al.
ARTICLE
Scheme 3. Synthesis of the PdIIꢀthiosaccharinate complexes.
The spectroscopic data of complex 4 show that the PdII atoms the presence of oxygen, the yellow complex 3 slowly forms
are surrounded by two sulfur atoms of thiosaccharinate anions and can be recovered in crystalline form upon evaporation.
and two phosphorus atoms of two different monocoordinated
dppm molecules.
Structural and Spectroscopic Analysis of Palladium(II) Thiꢀ
osaccharinates
Reducing a suspension of [Pd(tsac)2(dppm)] in MeCN with
NaBH4, the orange dipalladium(I) complex [Pd2(dppm)2ꢀ
(tsac)2] (6) is obtained. Its crystal Xꢀray diffraction analysis
showed a sideꢀbyꢀside “Pd2(µꢀdppm)2” framework with the
thiosaccharinate ligands coordinated to the metal centers
Spectroscopic Analysis of Pd(tsac)2 (1)
As discussed in our previous reports the most detachable viꢀ
through their exocyclic sulfur atoms [17]. Complex 6 is indefiꢀ brational bands useful for structural analysis, correspond to the
nitely stable to moisture in its solid form. In solution, and in vibrations of the five membered isothiazol and the thiocarbonꢀ
Table 2. Selected infrared (IR) and Raman (R) bands (in cm–1) for Pd(tsac)2 (1), Pd(tsac)2(PPh3)2·MeCN (2), [Pd(tsac)2(dppm)] (3),
Pd(tsac)2(dppm)2 (4), and [Pd(tsac)2(dppe)]·MeCN (5)a).
1
2
3
4
5
Assignment
IRb)
R
IR
R
IR
R
IR
R
IR
R
2220vw
1435s
2245vw
1437s
1416s
1309s
1232s
1155vs
1123s
1106m
1002s
ν(CN) MeCN
ν(CC) PPhn
ν(CN) ν(CC)
νas(SO2)
1436s
1434w
1408s
1434s
1421m
1315s
1229s
1163vs
1123m
1099m
1000s
1440w
1416s
1422s
1344s
1241vs
1182vs
1129s
1392s
1422m
1316vs
1229s
1422s
1408m
1308vs
1229s
1421s
1312vw
1230vs
1157m
1128vw
1099m
1239vs
1179s
1234vs
1154s
1229vs
1153s
1233vs
1159s
ν(φC)δ = (CCC)
νs(SO2)
1163vs
1124m
1096m
999 s
1153vs
1123s
1105m
1000vs
ν(φS) ν(CS)
δ(CH) PPhn
ν(CS)δ = (CNS)
ν(CC) PPhn
ν(NS)
1093s
999vs
1106s
998vs
1104s
999vs
695m
1022/1011s 1015s
805s
998vs
800s
693 s
588m
809s
689m
588m
801s
695s
588m
808s
691s
589m
699m
592w
375m
331w
698m
588w
370 s
323m
696m
589vw
371m
333w
νas(PPhn)
598 s
596m
378m
349s
γ(CCC) δ(SO2)
γ(isoindol)
ν(PdS) ν(NS)
ν(PdN)
368m
324m
268m
257 s
219m
257s
228m
255m
217w
257s
233m
δs(PCn)
νas(PPdP)
δ(isoindol)
νs(PPdP)
166m
168m
166m
179m
a) tsac = thiosaccarinate anion. b) vs: very strong, s: strong, m: medium, w: weak, vw: very weak, br: broad.
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Z. Anorg. Allg. Chem. 2009, 1604–1612

Palladium(II) Thiosaccharinates with Triphenylphosphane or Diphosphanes
Figure 1. Electronic spectra of 2.0 × 10–5 m solutions of Pd(tsac)2
(1): ——— in DMSO; ꢀ ꢀ ꢀ ꢀ in CH2Cl2.
Figure 3. Molecular plot of [Pd(tsac)2(dppe)]·MeCN (5).
assignable to stretching motions of Pd–S and Pd–N bonds (349
and 268 cm–1, respectively) [28].
There are three possible molecular structures for the binary
compound 1: a) a square planar mononuclear Pd(tsac)2 form,
with two S,Nꢀchelating tsac ligands, b) a dinuclear Pd2(tsac)4
form, with four S,Nꢀbridging tsac ligands between the two PdII
atoms, or c) a polynuclear Pdn(tsac)n form, with the tsac liꢀ
gands acting as µ3ꢀS,N bridges between the PdII atoms. The
first structure is the less possible because it needs two strained
four membered rings formed by S,Nꢀchelating heterocyclic thiꢀ
onates [9e]. As was already pointed out, binary PdII thionates
with dinuclear arrangements are known [8]. For the complex
[Pd(py2S)2]2·2CHCl3 (py2S = pyridineꢀ2ꢀthionate), K. Umako
shi et al. reported the existence of an inversion center with a
short Pd–Pd distance of 2.622 Ǻ and PdS2N2 cisꢀsquare arꢀ
rangements for the two PdII atoms [8f]. They reported also a
medium intensity band in the UV/Vis spectra in solution, cenꢀ
tered at 430 nm, indicative of the existence of a “Pd–Pd” bond
in the complex [8f]. In the electronic spectra of complex 1 in
Figure 2. Molecular plot of [Pd(tsac)2(dppm)] (3) showing the labeling
of the nonꢀhydrogen atoms and their displacement ellipsoids at the
30 % probability level.
ilic groups [12]. These characteristic bands are assigned in Taꢀ the solid state and in diluted CH2Cl2 solutions, no such bands
ble 2 considering our previous works and also published theoꢀ were observed (Figure 1) and the type b) molecular arrangeꢀ
retical vibration analysis of other authors [27]. For the “free” ment is discarded. So, some kind of polynuclear molecular
nonꢀcoordinating anion in the ionic bis(tryphenylphosꢀ structure is expected for the palladium(II)ꢀthiosaccharinate
phine)iminium thiosaccharinate, PNP(tsac), the bands owing to complex. The electronic spectra of 1 show differences between
the stretching vibrations of the C–N and C–Sexo bonds are loꢀ the CH2Cl2 and DMSO solutions (Figure 1). In the former solꢀ
cated at 1365 and 1010 cm–1, respectively [26].
vent a low energy band at 294 nm appeared, which can be
Three observations on the vibrational spectroscopic data of assigned to the π→π* transition of the C=S bond in the tsac
the solid complex 1 indicate that the tsac anions are acting as anions [12f, 29]. The solid substance dispersed in KBr shows
S,Nꢀbridges or S,Nꢀchelates: a) the difference in wavenumbers a similar low energy band at 300 nm. In the spectra of 1 in
between the IR and Raman bands assignable to the stretching DMSO, this band is shifted to 339 nm, too much to be asꢀ
motions of the C–N bonds [1422 (IR) and 1392 (R) cm–1] and signed to a solvent effect. Probably a dissociation process ocꢀ
the C–Sexo bonds [1022/1011 (IR) and 1015 (R) cm–1], b) the curs and mononuclear species of the type Pd(tsac)2(DMSO)2
relatively high energy of the stretching vibrations of the C–Sexo appear [12f]. This behavior agrees with the NMR spectroꢀ
bonds, and c) the existence of low energy Raman dispersions scopic data in [D6]DMSO. The thiocarbonilic carbon atoms
Z. Anorg. Allg. Chem. 2009, 1604–1612
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O. V. Quinzani et al.
ARTICLE
(C1) show a unique 13C NMR signal (189 ppm) lowꢀfield thiocyanate ligands [30]. The average Pd–P (2.258 Å) and Pd–
shifted against to Htsac (161 ppm) and slightly shifted upꢀfield S (2.391 Å) distances of complex 3 are a little shorter and
against the free thiosaccharinate anion (191 ppm) [16]. In longer, respectively, than in [Pd(dppm)(SCN)2] (2.273 and
weak coordinating solvents like CH2Cl2, the polyꢀnuclear 2.364 Å, respectively), maybe because of steric effects of the
structure of the solid complex 1 could be retained.
bulky tsac anions. The structural parameters of the dppm liꢀ
gand are almost the same as those observed in other diphosꢀ
phane complexes [11, 30].
Crystal Structure of [Pd(tsac)2(dppm)] (3)
There are two closely related complexes per asymmetric
unit. Figure 2 shows a drawing of one of these molecules.
Bond lengths and angles around the palladium(II) ions are
listed in Table 3.
Crystal Structure of [Pd(tsac)2(dppe)]·MeCN (5)
Figure 3 shows a molecular drawing of the complex. Bond
lengths and angles around the palladium atom are included in
Table 3.
Table 3. Selected bond lengths /Å and angles /° around PdII ion in
[Pd(tsac)2(dppm)] (3) and [Pd(tsac)2(dppe)]·MeCN (5) complexes.
The conformation of Pd(tsac)2(dppe) complex is closely reꢀ
lated to Pd(tsac)2(dppm) (see Figure 1 and Figure 2). The PdII
ion is in a less distorted environment [Pd–P bond lengths of
2.251(1) and 2.256(1) Å and bite P–Pd–P angle of 84.90(4)°;
Pd–S bond lengths of 2.380(1) and 2.383(1) Å and (S–Pd–
S) = 94.72(4)°], as expected for the more flexible chelating P–
CH2–CH2–P group of dppe ligand as compared with the P–
CH2–P group of dppm.
[Pd(tsac)2(dppm)]
[Pd(tsac)2(dppe)]
Bond lengths
Pd(1)–P(1)
Pd(1)–P(3)
Pd(2)–P(2)
Pd(2)–P(4)
Pd(1)–S(11)
Pd(1)–S(31)
Pd(2)–S(21)
Pd(2)–S(41)
2.2696(10) Pd–P(1)
2.2510(14)
2.2566(14)
2.2479(10) Pd–P(2)
2.2383(10)
2.2762(10)
2.4017(10) Pd–S(11)
2.3905(10) Pd–S(21)
2.3702(10)
2.3806(14)
2.3834(14)
Several molecular structures of square planar [Pd(dppe)T2]
(T: thiolate anion) compounds were reported in literature [31].
Lobana et al. reported the crystalline structures of the comꢀ
plexes [Pd(pym2S)2(dppe)] (pym2S = 2ꢀmercaptopyrimidine)
and [Pd(py2S)2(dppe)], as part of the study of mononuclear
PdII thionates with several diphosphanes: dppm, dppe, dppp,
dppmS and dppmSe ligands [9a, 10]. As far as we know, those
complexes are the only two mononuclear PdIIꢀthionateꢀdppe
complexes previously reported. The averaged Pd–P (2.254 Å)
and Pd–S (2.382 Å) distances of complex 5 are slightly differꢀ
ent from corresponding values reported for [Pd(pym2S)2ꢀ
(dppe)] (2.2770 and 2.3808 Å, respectively) [9a], and
[Pd(py2S)2(dppe)] (2.280 and 2.358 Å, respectively) [10],
hence suggesting the presence of steric hindrance between the
tsac ligands. This effect is also observed in the value of the
S–Pd–S angle between thionates [94.71(5)°], greater than in
the [Pd(pym2S)2(dppe)] and [Pd(py2S)2(dppe)] complexes
(89.13 and 83.90°, respectively). The structural parameters of
the dppe ligand are almost the same in the three complexes.
The similar complex [Pd(dppe)(SCN)(NCS)] was prepared
and its molecular structure was reported by Palenik et al. [30].
The most important difference in comparison to complex 5 is
the composition of the squareꢀplanar coordination sphere of
the PdII atoms in both complexes: a P2S2 environment in comꢀ
plex 5 and a P2SN sphere in the Palenik et al. compound. The
latter shows longer Pd–P distances [2.252(2) and 2.264(2) Å]
and shorter Pd–S bond length [2.252(2) Å] than complex 5.
The conformation and structural parameters of the dppe liꢀ
gands in both complexes are almost the same.
2.4012(10)
Angles
P(1)–Pd(1)–P(3)
P(1)ꢀPd(19ꢀS(11)
P(3)–Pd(1)–S(11)
P(1)–Pd(1)–S(31)
P(3)–Pd(1)–S(31)
S(11)–Pd(1)–S(31)
P(2)–Pd(2)–P(4)
P(2)–Pd(2)–S(21)
P(4)–Pd(2)–S(21)
P(2)–Pd(2)–S(41)
P(4)–Pd(2)–S(41)
S(21)–Pd(2)–S(41)
73.23(4)
102.03(4)
174.13(4)
166.79(4)
93.98(4)
90.93(4)
72.84(4)
91.65(4)
162.60(4)
174.53(4)
102.75(4)
93.15(4)
P(1)–Pd–P(2)
84.86(5)
89.59(5)
173.49(5)
175.18(5)
90.97(5)
94.71(5)
P(1)–Pd–S(11)
P(2)–Pd–S(11)
P(1)–Pd–S(21)
P(2)–Pd–S(21)
S(11)–Pd–S(21)
In both complexes, the PdII atom is in a distorted square
environment, cisꢀcoordinated to a dppm molecule acting as a
bidentate ligand through its phosphorus atoms [Pd1–P bond
lengths of 2.248(1) and 2.260(1) Å and bite P1–Pd1–P3 angle
of 73.24(4)°; Pd2–P bond lengths of 2.238(1) and 2.276(1) Å
and (P2–Pd2–P4) = 72.84(4)°] and to the exocyclic sulfur
atom of two thiosaccharinate anions [Pd1–S distances of
2.391(1) and 2.401(1) Å and (S11–Pd1–S31) = 90.92(3)°;
Pd2–S lengths of 2.371(1) and 2.401(1) Å and (S21–Pd2–
S41) = 93.15(4)°]. Trans P–Pd–S angles are 166.80(4) and
174.13(4)° for complex 1 and 162.60(4) and 174.58(4)° for
complex 2.
As far as we know, complex 3 is the first PdIIꢀthionate strucꢀ
ture with a chelating dppm molecule reported. Other PdIIꢀthiꢀ
onateꢀdppm mixtures yield dinuclear complexes with the diꢀ
phosphane acting as bridges (see as an example the work of
A. Mendía et al. [11]). G. L. Palenik et al. prepared the monoꢀ
nuclear complex [Pd(dppm)(SCN)2], which has also a square
planar metal environment built by two phosphorus atoms of a
Spectroscopic Analysis of the Complexes [Pd(tsac)2(PPh3)2]
(2), [Pd(tsac)2(dppm)] (3), [Pd(tsac)2(dppm)2] (4) and
[Pd(tsac)2(dppe)] (5)
For the ternary complexes 2 to 5 the vibration bands assigned
chelating dppm molecule and two sulfur atoms of two η1ꢀSꢀ to the stretching motions of C–N and C–Sexo bonds (Table 2)
1610
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Z. Anorg. Allg. Chem. 2009, 1604–1612

Palladium(II) Thiosaccharinates with Triphenylphosphane or Diphosphanes
confirm the presence of the tightly bonded thiosaccharinate liꢀ mined the influence of several factors over those structural reꢀ
gands [12, 32]. The positions of the two bands are slightly arrangements, such as the temperature or the number of phosꢀ
different to the values observed for other coordination forms phine ligands and their structures, by using NMR spectroscopy
of the thiosaccharinate anion, like 1419/1003 cm–1 for η2ꢀN,S [12f, 36]. There were several reports of pyridineꢀ2ꢀthionate
[12h] or 1411/997 cm–1 for µ2ꢀS [12f]. The Raman bands of complexes of the type [Pd(µ2ꢀN,Sꢀpy2S)(Cl)(L)]2 [L = PMe3,
medium intensity appearing at ca. 320 and 230 cm–1 were asꢀ PMe2Ph, PMe(Ph)2], which exhibit dynamic behavior in soluꢀ
signed to stretching vibrations of the Pd–S and Pd–P bonds, tion in contrast to the closely related compounds [Pd(µ2ꢀN,Sꢀ
according to the theoretical vibrational calculations performed py2S)(Cl)(PPh3)]2 and [Pd(η2ꢀN,Sꢀpy2S)(Cl)(PPh3)] whose 1H
for the complex [Pd2(dppm)2(tsac)2] [17]. The stretching vibraꢀ NMR spectrum shows a stereochemically rigid structure in soꢀ
1
tions of the SO2 groups, principally the antiꢀsymmetric mode, lution [9e, 9f]. The room temperature H and 31P{1H} NMR
show that the oxygen atoms are not involved in hydrogen spectra of concentrated solutions of the complexes 3 and 5 in
bridges. The assignments of the phosphine internal movements [D6]DMSO were obtained and compared with the data of the
were made according to vibrational studies of other authors corresponding free ligand. The presence of only one set of
[33]. The Raman bands assignable to the stretching of the Pd– signals for both complexes confirms the existence of only one
P bonds in complex 2 suggest a cis arrangement of the PPh3 molecular species in solution without any mononuclear/dinuꢀ
ligands. Several PdIIꢀthionateꢀPPh3 complexes with the phosꢀ clear rearrangements equilibrium. The chemical shifts of the
phane ligands in cis positions have been reported by other reꢀ 31P{1H} NMR signals also indicate that the dppm or dppe molꢀ
search groups, with different coordination forms for the thionꢀ ecules are still coordinated in solution. Unfortunately, because
ate ligands: chelating in [Pd(η2ꢀN,Sꢀpym2S)(PPh3)2](ClO4) of the very low solubility of complex 2 in common organic
[9e] or [Pd(η2ꢀN,Sꢀpy2S)(Cl)(PPh3)] [9e, 9g]; bridging in solvents, its NMR spectra were of low quality and are not
[Pd(µ2ꢀN,Sꢀpy2S)(Cl)(PPh3)]2 [9d].
The UV/Vis spectra of complexes 2–5 as solid dispersed in
reported here.
Complex 4 is a little surprising compound. The chemical
KBr disks result very similar to each other. They show a weak analysis and the vibration and electronic spectroscopic data are
broad band around 365 nm because of the π→π* transitions of in agreement with a PdII complex with two thiosaccharinate
the C–Sexo thiocarbonilic bond [29]. Other intense bands in the ligands and two dppm molecules. The existence of one set of
range 200–220 nm were assigned to the π→π* transitions of signals for the anions indicates that they are equivalent and
the benzene rings of the diphosphane ligands [34]. The spectra tightly bonded to the metal atoms. The NMR analyses of the
of CH2Cl2 solutions of compounds 3–5 show band displaceꢀ compound were necessary to understand the type of coordinaꢀ
ments that can be attributed to solvent effects (Figure 4). Moꢀ tion of the dppm molecules. The 31P{1H} NMR spectra show
lar conductance of the complexes in CH2Cl2 solutions shows two signals centered at 34 and 15 ppm, corresponding to one
that they behave as molecular moieties. As a reference standꢀ coordinated and one uncoordinated phosphorus atom, respecꢀ
ard, we employed the ionic K(tsac) salt dissolved in MeCN. tively. Therefore, a cisꢀPd(tsac)2(η1ꢀdppm)2 square planar
The solution showed a conductance of 120 Ω–1·mol–1·cm–1, structure is proposed for complex 4.
which corresponds to a 1:1 electrolyte [35].
Conclusions
The thiosaccharinate anion in its thiolate form strongly bond
palladium atoms in +2 or +1 oxidation states. The structurally
resolved palladium thiosaccharinates, [Pd(tsac)2(dppm)] and
[Pd(tsac)2(dppe)], show a preferred η1ꢀS monocoordination
form for the anions. In the presence of the strong soft bases
PPh3, dppm or dppe, the palladium(II) thiosaccharinate produꢀ
ces little soluble squareꢀplanar complexes with S2P2 coordinaꢀ
tion spheres.
Acknowledgement
We thank financial support from SGCyT UNS (Projects M24/Q010 and
Q025), CONICET of Argentina, and FAPESP of Brazil. Part of the Xꢀ
ray diffraction data were collected at LANADI (CONICET). J.A.G,
G.A.E. and O.E.P. are Research Fellows of CONICET. We thank Dr.
M. Gonzalez Sierra (IQUIRꢀCONICET/UNR, Rosario, Argentina) for
kindly supplying us with the NMR spectroscopic data of complex 3.
Figure 4. Electronic spectra of 2.0 × 10–5
m
solutions in
CH2Cl2: ——— Pd(tsac)2dppm (3); ꢀ ꢀ ꢀ ꢀ Pd(tsac)2(dppm)2 (4);
▬▬▬ Pd(tsac)2dppe (5).
One of the characteristics of the monophosphaneꢀ and diꢀ
phosphaneꢀpalladium chemistry is the existence of mononuꢀ
clear/dinuclear rearrangement equilibria or dinuclear/dinuclear
fluxional equilibria in solution. Several research groups deterꢀ
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O. V. Quinzani et al.
ARTICLE
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