Reactions of coinage metal salts with a mixed sulfonic/carboxylic acid anhydride

Article abstract of DOI:10.1002/zaac.200700336

The synthesis and structures of four new compounds are reported. [Cu ₂(2-sba)(dppm)₂] (1), [Ag₄(2-sba) ₂(PPh₃)₄] (2), [Ag₂(2-sbaH) ₂(PPh₃)₄] (3),

Full text of DOI:10.1002/zaac.200700336

DOI: 10.1002/zaac.200700336
Reactions of Coinage Metal Salts with a Mixed Sulfonic/Carboxylic Acid
Anhydride
Weifeng Shia, Le Zhanga, Maryam Shafaei-Fallaha, and Alexander Rothenbergera,b,
*
Karlsruhe, a Institut für Anorganische Chemie der Universität (TH) and b Forschungszentrum Karlsruhe GmbH, Institut für
Nanotechnologie
Received July 5th, 2007.
Dedicated to Professor Dieter Fenske on the Occasion of his 65th Birthday
Abstract. The synthesis and structures of four new compounds
are reported. [Cu2(2-sba)(dppm)2] (1), [Ag4(2-sba)2(PPh3)4] (2),
acid anhydride with metal salts under anhydrous conditions (1, 2)
and in the presence of water (3, 4).
[Ag2(2-sbaH)2(PPh3)4] (3), [Ag(2-sbaH)(PPh3)3] (4) (2-sbaH2
2-sulfobenzoic acid) were prepared by treatment of 2-sulfobenzoic
ϭ
Keywords: Copper; Silver; Metal carboxylates; Metal alkoxides;
Crystal structures; Mixed anhydrides
Introduction
Mixed sulfonic/carboxylic acid derivatives have received a
lot of attention as ingredients for microemulsions contain-
ing micelles as novel reaction containers [1, 2]. It has been
demonstrated, that in these micelles, nanoscale particles can
be formed with favourable size distribution [1, 2]. Recently,
sulfonated carboxylic acids have also been used in an effort
to generate porous coordination polymers [3Ϫ5]. In ad-
dition to metal phosphonateϪbased metalorganic frame-
works, similar compounds containing metal sulfonates as
building blocks are likely to emerge [6]. More commonly,
sulfonic/carboxylic acid derivatives, e.g., 2-sulfobenzoic acid
anhydride are used as reagents in stereoselective synthesis
[7, 8] and only recently the 1-step dichlorination of
2-sulfobenzoic acid anhydride by PCl5 has been reported
[9]. To the best of our knowledge, however, no reactions
between metal salts and compounds containing the struc-
tural fragment ϪSO2-O-C(O)Ϫ have been reported. The
investigation to be presented here adds on to previously re-
ported work of reactions between perthio- and perseleno-
phosphonic acid anhydrides [10Ϫ16] and describes reac-
tions of 2-sulfobenzoic acid anhydride with coinage metal
salts.
Scheme 1 Synthesis of 1-4 (MX ϭ CuOtBu, AgO2CMe; 2-sbaH2 ϭ
2-sulfobenzoic acid; dppm ϭ 1,2-Bis-diphenylphospinomethane).
Possibly, traces of water were present in reactions leading to the
formation of 3 and 4.
As a common theme of the reactions, the ring-opening of
the acid anhydride was observed producing coinage metal
complexes of the [2-sba]2Ϫ and [2-sbaH]Ϫ anions (2-sbaH2 ϭ
2-sulfobenzoic acid). In the case of 1, the complex formed
consists of the [2-sba]2Ϫ anion which coordinates two Cuϩ
ions. In the presence of the auxiliary ligand dppm crystals
of 1 were obtained (Fig. 1, scheme 1). In the solid state
Cu(1) is four-coordinated by the [2-sbaH]Ϫ anion in chelat-
ing mode via O atoms of the sulfonato/carboxylato group
and P(1,3) of two bridging dppm ligands. Cu(2) is sur-
rounded by P(2,3) and µ-O(4).
The reaction bears a remarkable resemblance to earlier
investigations where di-tert-butylether was identified un-
equivocally as the leaving group in reactions of CuOtBu
with the perthiophosphonic acid anhydride [ArP(S)(µ-S)]2
(Ar ϭ 4-anisyl) [12]. 1 represents the first mixed sulfonate/
carboxylate salt obtained under anhydrous conditions. The
new reaction presented here may offer a very convenient
route to novel metal complexes and it is currently probed if
solvent can be excluded entirely.
Results and Discussion
When the late transition metal salts CuOtBu and
AgO2CMe are treated with 2-sulfobenzoic acid anhydride
and tertiary phosphines the complexes 1-4 were obtained.
* Dr. A. Rothenberger
Institut für Anorganische Chemie
der Universität Karlsruhe
Engesserstraße 15
76131 Karlsruhe
Fax: 0721-6088440
In order to probe the broader applicability of the concept
to open up mixed sulfonic/carboxylic acid anhydrides by
generating volatile leaving groups, a number of metal car-
boxylates were treated with 2-sulfobenzoic acid anhydride.
In the case of AgO2CMe this resulted in the formation of
E-mail: ar252@chemie.uni-karlsruhe.de
Z. Anorg. Allg. Chem. 2007, 633, 2431Ϫ2434
 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
2431

W. Shi, L. Zhang, M. Shafaei-Fallah, A. Rothenberger
Figure 1 Molecular structure of 1 in the solid state.
Figure 2 Molecular structure of 2 (phenyl groups of triphenyl-
phosphine ligands are omitted; symmetry operation (A) Ϫxϩ1,
Ϫyϩ1, Ϫzϩ1).
˚
Selected bond lengths /A and angles /°: S(1)-O(1) 1.447(3), S(1)-O(2)
1.450(3), S(1)-O(3) 1.463(3), Cu(1)-O(3) 2.085(3), Cu(1)-O(4) 2.130(3),
Cu(1)-P(1) 2.2251(12), Cu(1)-P(3) 2.2457(13), Cu(2)-P(2) 2.2359(13), Cu(2)-
P(4) 2.2263(13), Cu(2)-O(4) 2.025(3), O(3)-Cu(1)-O(4) 91.84(11), O(3)-Cu(1)-
P(1) 116.36(9), O(4)-Cu(1)-P(1) 102.33(10), O(3)-Cu(1)-P(3) 103.49(9), O(4)-
Cu(1)-P(3) 110.15(9), P(1)-Cu(1)-P(3) 126.98(5), O(4)-Cu(2)-P(4) 105.52(10),
O(4)-Cu(2)-P(2) 107.84(10), P(4)-Cu(2)-P(2) 145.56(5).
˚
Selected bond lengths /A and angles /°: S(1)-O(1) 1.493(3), S(1)-O(2)
1.445(2), S(1)-O(3) 1.451(3), Ag(1)-O(1) 2.444(2), Ag(1)-O(4) 2.268(3),
Ag(1)-O(1A) 2.580(3), Ag(2)-O(4A) 2.167(2), Ag(2)-O(1) 2.491(3), Ag(1)-
P(1) 2.3518(12), Ag(2)-P(2) 2.3390(11), O(4)-Ag(1)-P(1) 143.02(7), O(4)-
Ag(1)-O(1) 80.99(9), P(1)-Ag(1)-O(1) 126.37(7), O(4)-Ag(1)-O(1A) 71.95(9),
P(1)-Ag(1)-O(1A) 130.80(7), O(1)-Ag(1)-O(1A) 80.46(9), O(4A)-Ag(2)-P(2)
155.17(6), O(4A)-Ag(2)-O(1) 75.39(9), P(2)-Ag(2)-O(1) 126.64(6).
2 (Fig. 2, scheme 1). As volatile leaving group acetic acid
anhydride was formed (verified by 13C NMR of the mother
liquor; scheme 2).
ditions gave rise to 3 and 4. In the solid state 3 exists as a
dimer of two [Ag(2-sbaH)(PPh3)2] units (Fig. 3). The two
units are connected by two moderate hydrogen bonds be-
tween O(5) and O(2A) and between symmetry-related O
atoms (distance O(5)···O(2A) 2.624(3) A) [23]. In the 1H
˚
NMR spectrum a resonance for hydrogen-bonded protons
was observed at 14 ppm and in the crystal structure hydro-
gen atoms were fixed in calculated positions.
Scheme 2 Detailed synthesis of 2 (2-sbaH2 ϭ 2-sulfobenzoic
acid).
In the solid state 2 exists as a centrosymmetric dimer of
[Ag2(2-sba)(PPh3)2] units held together by µ2-O(4) and µ3-
O(1). AgϪO and AgϪP distances found in 2 are similar to
distances found in related phosphine-stabilised AgI sulfon-
ates [17Ϫ22]. Despite the clear-cut synthesis of 2 correct
elemental analysis could not be obtained indicating that
there are several metal complexes formed with different ra-
tios phosphine:Ag. Only 2, however, could be characterized
by X-ray crystallography. The multidentate nature of the
[2-sba]2Ϫ anion promises a rich coordination chemistry of
mixed sulfonate/carbolxylate ligands in future. Here the
preparation of 1 and 2 illustrates a new synthetic route to
these species. The fact that a metal alkoxide or a metal car-
boxylate can generate a volatile leaving group (ether or an-
hydride), when treated with a mixed sulfonic/carboxylic
acid anhydride, indicates a potentially broader applicability
of the synthetic concept (the formation of di-tert-butylether
or acetic anhydride is believed to represent the thermo-
dynamic driving force for the reactions).
Figure 3 Molecular structure of 3 (phenyl groups of triphenyl-
phosphine ligands are omitted; symmetry operation (A) Ϫxϩ1,
Ϫyϩ1, Ϫzϩ1).
˚
Selected bond lengths /A and angles /°: S(1)-O(1) 1.466(2), S(1)-O(2)
1.467(2), S(1)-O(3) 1.447(2), Ag(1)-O(1) 2.373(2), Ag(1)-O(4) 2.524(2),
Ag(1)-P(1) 2.4464(7), Ag(1)-P(2) 2.4387(7), O(5)···O(2A) 2.624(3), O(1)-
Ag(1)-P(2) 125.17(6), O(1)-Ag(1)-P(1) 95.20(5), P(2)-Ag(1)-P(1) 127.45(2),
O(1)-Ag(1)-O(4) 88.84(7), P(2)-Ag(1)-O(4) 93.33(5), P(1)-Ag(1)-O(4)
122.51(6).
Hydrolysis of 2-sulfobenzoic acid anhydride, treatment
with AgO2CMe and crystallization under different con-
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Z. Anorg. Allg. Chem. 2007, 2431Ϫ2434

Reactions of Coinage Metal Salts with a Mixed Sulfonic/Carboxylic Acid Anhydride
toluene (the experiment was also performed using D6-benzene in
order to confirm the formation of acetic anhydride). The cloudy
solution was stirred for 3 hours, and then 524 mg (2.0 mmol) PPh3
was added. The resulted colorless solution was stirred for overnight
and D6-Benzene was removed. Addition of CH2Cl2 (8 mL) and
pentane (13 mL) at room temperature for one week produced col-
orless crystal 2. 0.28 g, yield 60 %; mp 218 °C; despite repeated
attempts, correct elemental analysis could not be obtained indicat-
ing that possibly byproducts with different phosphine:Ag ratio
are formed.
IR (KBr): ν(CH) 3055 s, ν(CO) 1662 s, 1477 s, ν(C-H of PPh) 1434 s, ν(S-O)
1327 s, ν(S-O) 1158 s, 973 s, 844 m, 745 s cmϪ1
.
3: A mixture of 184 mg (1.00 mmol) 2-sulfobenzoic acid cyclic
anhydride and 167 mg (1.00 mmol) AgO2CMe was dissolved in
8 mL THF and 1 mL of a standard solution of water in THF
(1 mol/L). The cloudy solution was stirred for 5 hours, and then
524 mg (2.00 mmol) PPh3 was added. The colorless solution was
stirred 12 h. Storage of the solution at room temperature for one
week produced colorless crystals of 3. 0.51 g, yield 61 %; mp
120 °C; Found: C, 62.01; H, 4.55 %. C43H35AgO5P2S requires C,
61.95; H, 4.23 %.
Figure 4 Molecular structure of 4 (phenyl groups of triphenyl-
phosphine ligands are omitted).
˚
Selected bond lengths /A and angles /°: S(1)-O(3) 1.473(10), S(1)-O(4)
1.443(10), S(1)-O(5) 1.447(9), Ag(1)-P(1) 2.543(2), Ag(1)-P(2) 2.563(2),
Ag(1)-P(3) 2.546(3), Ag(1)-O(1) 2.559(11), O(3)···O(2) 2.491(13), P(1)-Ag(1)-
P(3) 115.46(9), P(1)-Ag(1)-O(1) 99.4(2), P(1)-Ag(1)-P(2) 117.25(6), P(3)-
Ag(1)-O(1) 117.5(2), P(3)-Ag(1)-P(2) 113.63(9), O(1)-Ag(1)-P(2) 90.3(2).
IR (KBr): ν(CH) 3059 s, 2981 s, ν(OH) 2623 m, ν(CO) 1705 s, 1478 s, ν(C-H
The Ag atom in 3 is chelated by an O atom of the sulfon-
ato and carboxyl group. Coordination of two PPh3 ligands
completes the distorted tetrahedral coordination sphere of
Ag(1). A slightly modified work-up produced 4 in moderate
yield. In contrast to 3 intramolecular strong hydrogen-
of PPh) 1438 s, ν(S-O) 1367 s, ν(S-O) 1167 s, 1017 s, 899 s, 749 s cmϪ1 1H
;
NMR (400 MHz, CDCl3, 25 °C) δ ϭ 14.16 (1H, s, br, OH), 7.98-7.82 (4H,
m, ArH), 7.3ϳ7.5 (30H, m, ArH), 5.33 (2H, s, CH2Cl2); 31P NMR
(162 MHz, CDCl3, 25 °C, 65 % H3PO4) δ ϭ 11.6.
4: The preparation follows the procedure described for 3. Addition
of CH2Cl2 (5 mL) and pentane (9 mL) at room temperature fol-
lowed by storage of the reaction mixture for three days produced
colorless crystals of 4. 0.53 g, yield 67 %; mp 130 °C; Found: C,
62.93; H, 4.23 %. C61H50AgO5P3S·CH2Cl2 requires C, 63.03; H,
4.44 %.
˚
bonding is observed in 4 (distance O(3)···O(2) 2.491(13) A).
O(1) of the carboxylato ligand and P atoms of three PPh3
ligands are coordinated to Ag(1) in distorted tetrahedral
arrangement.
Future work will attempt to extend the investigations to
other metals and in particular to make use of mixed
sulfonic/carboxylic acid anhydrides as novel building blocks
for coordination polymers.
IR (KBr): ν(ArH) 3056 s, ν(OH) 2604 m, ν(CO) 1702 s, 1658 s, 1481 s,
ν(C-H of PPh) 1434 s, ν(S-O) 1376 s, ν(S-O) 1163 s, 1001 s, 746 s cmϪ1 1H
;
NMR (400 MHz, CDCl3, 25 °C) δ ϭ 14.40 (1H, s, OH), 8.00-7.85 (4H, m,
ArH), 7.3ϳ7.4 (45H, m, ArH), 5.33 (2H, s, CH2Cl2); 31P NMR (162 MHz,
CDCl3, 25 °C, 65 % H3PO4) δ ϭ 10.9.
Experimental Section
X-ray Crystallographic Study
All operations were carried out in an atmosphere of purified dini-
trogen. Solvents were dried over appropriate drying agents and
freshly distilled. CuOtBu was synthesized according to a published
procedure [24].
Data for 1-4 were collected on S (I II and S IV) dif-
fractometers using graphite-monochromated Mo-Kα radiation (λ ϭ
˚
0.71073 A). The structures were solved by direct methods and re-
fined by full-matrix least-squares on F2 (all data) using the S
program package [25]. Hydrogen atoms were placed in calculated
positions, non-hydrogen atoms were assigned anisotropic thermal
parameters. Disordered components were refined with isotropic
thermal parameters. A summary of crystal data and refinement
parameters is given in table 1.
1: A mixture of 184 mg (1.00 mmol) 2-sulfobenzoic acid cyclic an-
hydride and 136 mg (1.00 mmol) CuOtBu was dissolved in 12 mL
toluene (or DME). The yellow solution was heated for 5 minutes
under reflux. A solution of 385 mg (1.0 mmol) dppm in 5 mL tolu-
ene was added and the mixture stirred for 2 h. Toluene (or DME)
was removed under reduced pressure. Addition of CH2Cl2 (4 mL)
and pentane (5 mL) at room temperature and storage of the solu-
tion for four days produced colorless crystals of 1. 0.3 g, yield 53 %;
mp 160 °C (decomposition); Found: C, 60.79; H, 4.27 %.
2C57H48Cu2O5P4S·CH2Cl2 requires C, 60.66; H, 4.34 %.
CCDC nos. 649058-649061 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge at www.ccdc.cam.ac.uk/conts/retrieving.html [or from the
Cambridge Crystallographic Data Centre, 12, Union Road, Cam-
bridge CB2 1EZ, UK; fax: (internat.) ϩ44-1223/336-033; E-mail:
deposit@ccdc.cam.ac.uk].
IR (KBr): ν(CH) 3051 s, 2917 m, ν(COO) 1615 s, 1486 s, ν(C-H of PPh)
1434 s, ν(S-O) 1360 s, ν(S-O) 1167 s, 1008 s, 848 s, 608 s cmϪ1 1H NMR
;
(400 MHz, CDCl3, 25 °C) δ ϭ 8.36-7.77 (4H, m, ArH), 7.1ϳ7.5 (40H, m,
ArH), 5.34 (s, CH2Cl2), 3.16 (4H, br, CH2); 31P NMR (162 MHz, CDCl3,
25 °C, 65 % H3PO4) δ ϭ Ϫ9.8.
Acknowledgment. The work was funded by the DFG Center for
Functional Nanostructures (fellowship W. S.) and the Forschungsz-
entrum Karlsruhe. A. R. thanks Prof. Dieter Fenske for his support.
2: A mixture of 184 mg (1.0 mmol) 2-sulfobenzoic acid cyclic anhy-
dride and 167 mg (1.0 mmol) AgO2CMe was dissolved in 4 mL
Z. Anorg. Allg. Chem. 2007, 2431Ϫ2434
 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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2433

W. Shi, L. Zhang, M. Shafaei-Fallah, A. Rothenberger
Table 1 Details of the X-ray data collection and refinements.
Compound
1
2
3
4
Formula
Formula weight
T/K
C60H54Cl6Cu2O5P4S
1350.75
200(2)
C86H68Ag4O10P4S2
1880.88
150(2)
C47H43AgO6P2S
905.68
100(2)
C61H50AgO5P3S
1095.85
150(2)
Crystal system
Space group
monoclinic
P21/c
12.861(3)
20.043(4)
23.815(5)
triclinic
P1
triclinic
P1
orthorhombic
Pbca
19.729(4)
20.415(4)
24.949(5)
¯
¯
˚
a/A
12.064(2)
13.310(3)
13.901(3)
69.52(3)
69.15(3)
66.99(3)
1861.5(6)
1
12.4353(6)
13.0267(7)
14.4157(8)
81.829(4)
87.077(4)
61.620(4)
2033.33(19)
2
˚
b/A
˚
c/A
Ͱ/°
β/°
γ/°
100.65(3)
3
˚
V/A
6033(2)
4
1.159
2760
10049(3)
8
0.591
4512
Z
µ/mmϪ1
1.241
944
0.676
932
F(000)
Reflections collected
Unique data
Rint
Parameters
wR2 (all data)
R1 [I>2σ(I)]
12873
10218
0.0188
703
0.1766
0.0514
13046
7555
0.0666
478
0.1374
0.0477
16183
8248
0.0389
515
0.1166
0.0382
12962
6343
0.0738
227
0.2138
0.0723
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Dalton Trans. 2005, 3909.
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