Polynuclear Gold(I) Complexes of Mercaptocarboxylic Acids

Article abstract of DOI:10.1515/znb-1996-0602

In a search for air-stable and water-soluble mercapto compounds of gold with a high gold content, benzylthiol, α-mercapto-acetic acid, β-mercapto-propionic acid, and thiosalicylic acid were converted into aurated sulfonium salts by treatment with reagents of the type [(R₃P)Au]₃O⁺ BF₄^- or [(R₃P)Au]⁺ BF₄^-. - BzSH served as a mono-functional model thiol, which was converted into BzS[Au(PMe₃)]₂⁺ BF₄^- (1). The small tertiary phosphine was chosen in order to minimize steric effects. In the crystal the cations are associated into centrosymmetrical climers through short Au-Au contacts (auriophilicity). - The two carboxylic acids with thiol functions, HSCH₂COOH and HSCH₂CH₂COOH, gave triply aurated species of the type {[(Ph₃P)Au]₂S(CH₂)_nCOOAu(PPh ₃)}⁺ BF₄^- (2: n = 2, 3: n = 3). The crystal structure analysis of the representative compound 2 showed again the presence of centrosymmetrical cation dimers with geometrical details of the sulfonium part of the molecules very similar to those of the reference compound 1. In addition, the carboxyl groups in 2 and 3 bear a (phosphine)gold unit mono-hapto bound at one of the oxygen atoms. - 2-HS-C₆H₄-COOH was converted into a sulfonium salt {[(Ph₃P)Au]₂S-C₆H₄-COOH}⁺ BF₄^- (4), which crystallizes free of solvent from dry dichloromethane, and as a monohydrate with one mole of dichloromethane (4a = 4·H₂O·CH₂Cl₂) from hydrous CH₂Cl₂. In the solvent-free crystalline phase (4) the cations are associated into dimers with the usual intermolecular double Au-Au contacts, but in 4a there are monomeric cations with the water molecule hydrogen-bonded to the carboxylic acid function.

Full text of DOI:10.1515/znb-1996-0602

Polynuclear Gold(I) Complexes of Mercaptocarboxylic Acids
A lexander Sladek, W olfgang Schneider, Klaus A ngerm aier, A ndreas Bauer,
H ubert Schm idbaur*
Anorganisch-chemisches Institut der Technischen Universität München,
Lichtenbergstrasse 4, D-85747 Garching, Germany
Dedicated to Professor Kurt Dehnicke on the occasion o f his 65th birthday
Z. Naturforsch. 51 b, 765-772 (1996); received January 17, 1996
Gold(I) Thiolates, (Benzylthiolato)gold(I) Complexes, Gold(I) Mercaptocarboxylates, Polynu-
clear Gold(I) Complexes
In a search for air-stable and water-soluble mercapto compounds of gold with a high gold
content, benzylthiol, a-mercapto-acetic acid, /3-mercapto-propionic acid, and thiosalicylic acid
were converted into aurated sulfonium salts by treatment with reagents of the type [(R^PjAufiO*
BF4~ or [(R}P)Au]+ BF4~. - BzSH served as a mono-functional model thiol, which was
converted into BzS[Au(PMe3)]2+ BF4- (1). The small tertiary phosphine was chosen in or-
der to minimize steric effects. In the crystal the cations are associated into centrosymmetri-
cal dimers through short Au-Au contacts (auriophilicity). - The two carboxylic acids with
thiol functions, HSCFbCOOH and HSCH2CH2COOH, gave triply aurated species of the type
{[(Ph3P)Au]2S(CH2)nCOOAu(PPh3)}+ BF4~ (2: n = 2, 3; n = 3). The crystal structure analy-
sis of the representative compound 2 showed again the presence of centrosymmetrical cation
dimers with geometrical details of the sulfonium part of the molecules very similar to those of
the reference compound 1. In addition, the carboxyl groups in 2 and 3 bear a (phosphine)gold
unit mono-hapto bound at one of the oxygen atoms. - 2-HS-C6H4-COOH was converted into
a sulfonium salt {[(Ph3P)Au]2S-C6H4-COOH}+ BF4~ (4), which crystallizes free of solvent
from dry dichloromethane, and as a monohydrate with one mole of dichloromethane (4a =
4 H2O CH2CI2) from hydrous CH2CI2. In the solvent-free crystalline phase (4) the cations are
associated into dimers with the usual intermolecular double Au-Au contacts, but in 4a there are
monomeric cations with the water molecule hydrogen-bonded to the carboxylic acid function.
Introduction
formulations like e. g. anionic species derived from
thiomalonic [19] or thiosalicylic acid [20].
Gold metal surfaces [1] and gold cations (Au+
or LAu+) have a high affinity for thioether (RSR),
thiol (RSH) and thiolate (RS_ ) functions [2]. Gold
complexes based on these functions are the most
important classes of compounds for all aspects of
gold usage [3]. Gold thiolates in particular have
been the main ingredients of all gold pastes (liquid
golds) for gilding in arts, handicraft and technology,
and of virtually all drugs that appeared in the long
history of gold therapy in medicine [4, 5].
Most of these compounds are neutral gold(I) thi-
olates (LAuSR) with or without an auxiliary lig-
and L [6-18]. Both L and R may carry functional
groups, however, and recent interest has focused
on the potential offered by such variations, e. g. for
improved solubility or resorption properties, respec-
tively. Current studies also include phosphine-free
In an important extension of this chemistry, work
carried out in the 1970ies has shown that the sul-
fur atoms in thiol(ate)s can accept more than one
LAu+ group with the formation of thiolato-bridged
dinuclear cations [21 - 26] of the type [RS(AuL)2]+.
The structures of salts of such cations have been
determined [14, 25, 26] and were found to show in-
teresting intramolecular A u-A u interactions and in-
termolecular association phenomena. The individ-
ual cations feature extremely small Au-S-Au angles
(ca. 85°) and, correspondingly, short A u-A u con-
tacts (of ca. 3.1 A), and two of these cations un-
dergo aggregation through generation of an almost
perfect square of gold atoms (A). This structural
pattern is similar to the findings for the [S(AuL)3]+
cations (B).
A dvanced theoretical calculations of the bonding
situation in the com pounds of the type [S(A uL)3]+
have dem onstrated that relativistic and correlation
* Reprint requests to Prof. Dr. H. Schmidbaur.
0939-5075/96/0600-0765 $ 06.00
©
1996 Verlag der Zeitschrift für Naturforschung. All rights reserved.
K
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A. Sladek et al. ■Polynuclear Gold(I) Complexes of Mercaptocarboxylic Acids
766
L
L
L
A
L
B
effects are essential for a description of the elec-
tronic situation in the new clusters [27].
2-HS-C6H4-COOH. These compounds were ex-
pected to be water-soluble gold thiolates with a high
gold content, as required for a number of applica-
tions in advanced technology and medicine.
Digold(organo)sulfonium salts [RS(AuL)2]+ X~
may also be involved in the in vivo degradation and
metabolism of gold drugs. Spectroscopic evidence
has been accumulated which justifies this assump-
tion [5].
Results
S,S-Bis[(trim ethylphosphine)gold(I)]-
benzylsulfonium tetrafluoroborate ( \ )
Following earlier contributions from this labo-
ratory [21,26] we now present the results of syn-
thetic and structural work on another example of
type A with the smallest tertiary phosphine (PM e3),
Benzylthiol is readily converted into the digold-
sulfonium salt (1) by reaction with two equiva-
and on related compounds derived from mercapto- lents of (trimethylphosphine)gold(I) tetrafluorobo-
rate [28] in dichloromethane/tetrahydrofuran. The
product is obtained (in 74% yield) as an air-stable,
colourless, crystalline solid, m.p. 179°C, which is
easily characterized by its analytical and spectro-
scopic data.
carboxylic acids HS(CH2)„COOH (n = 1, 2) and
BzSH + 2 [(Me3P)Au]+ BF4~
-> [HBF4] + B zS[A u(PM e3)]2+ BF4~
1
(1)
Compound 1 crystallizes in the monoclinic space
group P2]/n with four formula units in the unit
cell (Table I). The lattice contains tetrafluoroborate
anions and dimeric cations {[(Me3P)Au]2SBz}22+
(Fig. 1). In the monomeric unit, the benzyl sulfur
atom is bridging the two gold atoms with a sharp
angle A ul-S-A u2 of only 8 1.7(1)° and a short Au 1-
Au2 contact of 3.060(1) A. The two C-S-Au angles
are much larger [101.0(4) and 101.5(1)°] and may
be taken as standard angles at sulfonium centers.
Fig. 1. Molecular structure of the cation dimer of com-
pound 1 with atomic numbering. The monomer com-
ponents are related by a center of inversion. (ORTEP.
50% probability ellipsoids; hydrogen atoms omitted for
clarity.) - Selected distances [A] and angles [°]: Au l -
Au2 3.060(1 ).A ul-A u2’3.078(1 ),Aul-S 2.331(3), Au2-
S 2.345(3), Aul-Pl 2.262(3), Au2-P2 2.258(4), S-Cl
1.85(1); Aul-S-Au2 81.7(1), Aul-S-Cl 110.6(4), Au2-
S-Cl 101.0(5), A u2-Aul-Au2'78.5(1).
The dimers are formed through an approach of
two monomers in a head-to-tail fashion with A u l-
Au2'/Au 1-A u2 distances of 3.078( 1) Ä as the clos-
est intermolecular contacts. The dimers have a crys-
tallographic center of inversion in the center of the
square of gold atoms formed in the association pro-
cess. The structure is analogous to literature data
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767
A. Sladek et al. • Polynuclear Gold(I) Complexes of Mercaptocarboxylic Acids
Table I. Crystallographic data for compounds 1, 2 CH2CI2, 4 and 4a.
1
4
4a
2C H 2C12
Empirical formula
C56H47AU3BF4O2P3S
C44H39AU2BCI2F4O3P2S
C,3H25AU2BF4P2S
C43H35AU2BF402? 2S
CH,C12
1639.54
triclinic
Formula weight
Crystal system
756.03
monoclinic
1158.45
triclinic
1261.46
monoclinic
P2i/n (14)
12.375 (1)
9.259(1)
18.763 (3)
90
96.63 (1)
90
2135.6 (5)
2.35
Space group (No.)
P2, (4)
12.517(1)
12.530(1)
14.264(1)
90
102.63(1)
90
2183.0(2)
1.76
Pi (2)
11.321(1)
13.400(1)
14.578(1)
71.03(1)
88.64(1)
72.67(1)
1989.9(3)
1.93
Pi (2)
13.157(1)
a [A]
b [A]
c [A]
a [ ° ]
ß[°]
7 [°J
V [A3]
Pcalc [gem-3]
Z
14.378 (2)
15.325 (2)
80.67(1)
80.50(1)
79.17(1)
2782.3 (6)
1.96
4
2
2
2
/x(Mo-Ka ) [cm-1]
T [°C]
70.1
-68
140.00
-59
81.6
-68
75.5
-62
Radiation
Scan
Mo-Kq
G -6
Mo-Kq
0 - 0
Mo-Kq
U)
Mo-Kq
6-6
hkl Range
Measured /
unique reflections
± 16/ ± 17/ + 18
10888/10228
± 2 3 / + 15/ + 11
5152/4210
±
1 3 / ± 1 6 / + 17
± 1 5 / ± 15/ + 17
8560/8401
7800 / 7794
Observed reflections 3583
9082
6779
8072
[with F0 > 4cr(F0)]
Refined parameters
R*
wR2** / Rw***
ptin(max/min) [eA~3] + 4.4 9 /-3 .9 0
Absorption corr.:
209
0.0520
- / 0.0730
652
0.0299
- / 0.0339
+ 1.36/- 1.57
empirical
0.7321/0.9998
537
0.0254
-/0.0388
+ 2.17/-0.98
empirical
0.6308 / 0.9990
500
0.0213
0.0580/-
+ 0 .9 6 /-0 .7 3
empirical
0.5738 / 0.9990
no
Tmin / Tmax
Weighting scheme
(a / b)****
or (Ilk)*****
1= 1.0000 /
k = 0.006289
/ = 1.0000 /
k = 0.000176
/ = 1.0000 /
k = 0.005947
a = 0.0191 /
b = 2.5950
*R = £(IFoMFcI)/£IFoI; **w/?2=[£(Fo2-Fc2)2 /£ [w (F 02 ) 2]1/2; **“/?v,=[w(IF0l-IFcl)2 /£wF<>2],/2;
****w=q/[a2(Fo)2+(ap)2+bp];p=[Max(Fo2,0)+2Fc2]/3;* ^ ^ H ’=l/[(72(Fo)+k(Fo)2].
recorded for other RS[A u(PR '3)]2+ salts: R = Bz, R'
= Ph [14]; R = 'B u, R' = Ph [26]. Except for cases
w ith severe steric hindrance, the structure shown in
Fig. 1 should thus be taken as the com m on config-
uration of this type of cations.
0,S,S-Tris[(triphenylphosphine)gold(l)]-a-
m ercaptoacetate and -ß-m ercaptopropionate
tetrafluoroborate (2, 3)
Treatm ent o f m ercaptoacetic acid w ith equim o-
lar quantities o f tris[(triphenylphosphine)gold(I)]-
oxonium tetrafluoroborate [30] in dichlorom ethane
at room tem perature gives high yields of the triply
Sim ilar results were also obtained w ith a , u;-
dithiols, which can give rise to one-dim ensional
aggregates through contacts between the bifurcated
groups at either end of the m olecules [29]. Tri- and
polythiols behave accordingly [26, 29].
aurated m ercaptocarboxylate tetrafluoroborates
2
and 3. C om pound 2 is an air-stable, colourless,
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768
A. Sladek et al. ■Polynuclear Gold(I) Complexes of Mercaptocarboxylic Acids
crystalline material, m.p. 168°C with decomposi-
tion, while compound 3 is an off-white powder,
difficult to purify, which could not be crystallized.
Both compounds are not soluble in acidic or alcaline
water, but are stable under these conditions.
tetrafluoroborate anions, and dimeric cations which
are shown in Fig. 2. The sulfur atom of each
monomeric unit is doubly aurated and thus con-
verted into a sulfonium center, while the carboxy-
late group is mono-aurated at one of the oxygen
atoms. As in the model compound 1, the pyramid
with the sulfur apex is very steep, with an A ul-S-
Au2 angle of only 81.1(1)° and a distance Au 1-A u2
of 3.042(1) A. The remaining two angles at sul-
fur [A ul-S-C l 103.6(2)°, Au2-S-Cl 105.4(2)°] are
larger and closer to a pseudo-tetrahedral standard.
The third gold atom (Au3) is attached to one car-
HS(CH2)nCOOH + [(Ph3P)Au]30 + BF4~
-> [HzO] +
{[(Ph3P)Au]2S(CH2)nC (0)0A u(PPh3)}+ BF4-
2 {n = 1)
3 (n = 2)
(2)
Analytical and spectroscopic data of both com- boxylate oxygen atom [Au3-01 2.057(4) A], with
the usual linear coordination at the metal atom.
pounds are in full agreement with the proposed
composition and structure (Experimental Part).
The aggregation of the cation into dimers occurs
via the bifurcated sulfonium end groups and af-
fords an almost regular square of gold atoms (with
the crystallographic center of inversion in its cen-
ter) with distances A ul-A u2'/A u2-A ul' 3.079(1)
A. The structural similarity of compounds 1 and 2
is immediately obvious from Figures 1 and 2.
T h e31P{1H} NMR spectra (in CDC13) show only
one broad singlet at room temperature, but at -60°C
these signals are split consistently into two peaks
of relative intensity 1:2. This result rules out an
isomeric structure with triply aurated sulfur centers
and free carboxylate groups, instead of the 0,S,S-
aurated alternative formulated in Eq. (2), or the less
likely S,0,0-aurated isomer.
It is interesting to note that no further aggrega-
tion (into chains or larger rings) takes place through
intermolecular contacts between the carboxylate-
bound gold atoms. This may have steric reasons.
Crystals of compound 2, grown from CH 2C12 by
layering with diethyl ether, are triclinic, space group
P i, with two formula units and two dichloromethane
solvent molecules in the unit cell (Table I). The
lattice contains independent solvent molecules,
Compound 3 is believed to have a structure simi-
lar to that of the lighter homologue 2, but except for
the analogies in the spectral data, there is no proof
for this suggestion.
S, S-Bis[(triphenylphosphine )gold(I)]-
hydrogenthiosalicylate tetrafluoroborate (4)
Thiosalicylic acid is aurated regioselectively at
its sulfur atom on treatment of the compound with
two equivalents of [(Ph3P)Au]BF4 in tetrahydrofu-
ran at 0°C. The product 4 is obtained as a colourless,
air- and water-stable solid in 75 % yield, m.p. 220°C
with decomposition. The behaviour in acidic or al-
caline water is analogous to compounds 2 and 3.
Fig. 2. Molecular structure of the cation dimer of com-
pound 2 with atomic numbering. The monomer com-
ponents are related by a center of inversion. (OR-
TEP. 50% probability ellipsoids; hydrogen atoms omit-
ted for clarity.) - Selected distances [A] and angles [°]:
Au 1-Au2 3.042( 1), Au 1-Au2' 3.079( 1), Au 1-S 2.337( 1),
Au2-S 2.341(1), Aul-Pl 2.269(1), Au2-P2 2.259(1), S-
C1 1.846(7), Au3-0 2.057(4), Au3-P3 2.215(2), 01-
C2 1.277(7), 02-C2 1.213(7), C1-C2 1.516(7); Aul-
S-Au2 81.1(1), Aul-S-Cl 103.6(2), Au2-S-Cl 105.4(2),
Au2-Aul-Au2' 93.5(1), Pl-Aul-S 172.0(1), P2-Au2-S
173.4(1). P3-Au3-0 172.6(1).
2-HS-C6H4-COOH + 2 [(Ph3P)Au]+ BF4~
[HBF4] + [2-{[(Ph3P)Au]2S}C6H4COOH]+ BF4~
4
(3)
The analytical data and the NMR spectra of the
compound are in good agreement with the proposed
formula (Experimental Section).
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A. Sladek et al. ■Polynuclear Gold(I) Complexes of Mercaptocarboxylic Acids
Fig. 4. Molecular structure of the monomeric cation in
phase 4a (4 H2O CH2CI2) with atomic numbering. (OR-
TEP, 50% probability ellipsoids, arene hydrogen atoms
omitted for clarity; the water molecule is hydrogen-
bonded to the carboxylic acid function and to the
BF4- anion.) - Selected distances [A] and angles [°]:
A ul-A u2 3.107(1), Aul-S 2.332(1), Au2-S 2.340(1),
Aul-Pl 2.269(1), Au2-P2 2.258(1), A u2-02 3.079, S-
C1 1.793(7), 0 1 -C7 1.19(1), 02-C7 1.302(9), C7-C2
1.520(9), 02-H 0.950, H -03 2.612, 0 3 -0 2 2.612, 03-
H1 1.045, H I-FI 1.721, 03-F1 2.766; Aul-S-Au2
83.4(1), Aul-S-Cl 109.6(2), Au2-S-Cl 104.8(2), Pl-
Aul-S 177.2( 1), P2-Au2-S 168.8(1), 0 1 -C7-02 124.5(6),
01-C7-C2 120.6(7), 02-C7-C2 114.8(6), 02-H -03
164.0, 03-H1-F1 167.1. Symmetry positions of 03: x,
y, z; FI: x, y, z+1.
Fig. 3. Molecular structure of compound 4 with atomic
numbering. The dication has a crystallographic center
of inversion. (ORTEP, 50% probability ellipsoids; arene
hydrogen atoms omitted for clarity; the carboxylic acid
functions are hydrogen-bonded to the BF4~ anions.) - Se-
lected distances [A] and angles [°]: Aul-Au2 3.1270(5),
Au 1-S 2.348( 1), Au2-S 2.352( 1), Au 1-P 1 2.273( 1), Au2-
P2 2.260(3), A u 2 -0 1 2.778, S-Cl 1.803(3), 02-C7
1.326(4), 01-C7 1.208(4), C7-C2 1.482(5), 02-F1 2.721,
H-Fl 1.885, 02-H 0.836; Aul-S-Au2 83.44(3), Aul-S-
C1 107.2(1), Au2-S-Cl 111.7(1), Pl-Aul-S 178.22(3),
P2-Au2-S 174.14(3), 01-C 7-02 121.7(3), 02-C7-C2
112.6(3), 01-C7-C2 125.7(3), 02-H-F1 161.3. Symme-
try position of F I: x, y, z.
Single crystals obtained from
anhydrous
dichlorom ethane/pentane (triclinic, space group P I ,
Z = 2) are free of solvent (Table I). The lattice con-
tains centrosym m etrical dim eric cations w ith the
same basic skeleton [CS(A uL)2]2 as present in com -
pounds 1 and 2 (Fig. 3). The distorted square of
gold atom s form ed in the dim erisation has edges
A u l-A u 2 = 3.1270(5) A and A u l-A u 2 7 A u l'-A u 2
3.1628(4) A, with A u -A u -A u angles of 91.84(1)°
at Au 1 and 88.16( 1)° at Au2. The Au 1-S-A u2 angle
is sm all [83.44(3)°], w hile the A u l-S -C l and A u2-
S-C l angles are larger at 107.2(1)° and 111.7(1)°,
The structure of com pound 4 is thus an unprece-
dented exam ple where auriophilic bonding (A u -
Au) is overruling hydrogen bonding (betw een car-
boxylic acid groups). It is unlikely that steric ef-
fects are responsible for this preference, since the
thiosalicylic acid group of the m onom eric cations
in particular would be free to be rotated in positions
suitable for hydrogen bonding of the type present
e. g. in acetic acid. The com pensation of the loss
of packing energy through hydrogen bonding to the
BF4“ anions helps to save the cation dim erization
via A u-A u contacts.
respectively.
There is a sub-van der W aals contact betw een
one of the gold atom s and one of the carboxylate
oxygen atom s (A u 2 -0 1 2.778 A), but very surpris-
ingly there are no hydrogen bonds betw een the two
carboxylic acid functions. The distance betw een a
fluorine atom of the anion and the hydroxyl oxy-
gen atom , as well as the angle at the hydrogen atom
[02-F 1 2.721 A, 0 2 -H -F 1 161.3°] can be taken as
indicative of a hydrogen bond betw een these units,
however.
Single crystals obtained from hydrous dichloro-
m ethane upon layering w ith pentane contain one
m ole of C H 2CI2 and one m ole of H 2O per for-
m ula unit (4a). The m onoclinic unit cell, space
group P 2 1, com prises
Z = 2 of these form ula
units and two solvent m olecules (Table I). The lat-
tice is built from independent tetrafluoroborate an-
ions, dichlorom ethane m olecules, and m onom eric
cations w hich form a hydrogen bond w ith the w ater
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770
A. Sladek et al. ■Polynuclear Gold(I) Complexes of Mercaptocarboxylic Acids
molecule through their carboxylic acid function
(Fig. 4).
C h h ^A u^BFj PtS (756.03)
Calcd C 20.64, H 3.33, S 4.24%,
Found C 20.11, H 3.09, S 4.18%.
In the cation, the two gold atoms are attached to
the mercaptide sulfur atom converting it into a pyra-
midal sulfonium center. The Au-S-Au angle of only
83.4(1)° is associated with a short A u-Au contact
of 3.107(1) Ä. Together with the angles C l-S-A ul
[109.6(2)°] and C l-S-A u2 [104.8(2)°], these data
of the monomeric cations are very similar to those
in the dimeric cations in crystals of compound 4
(above). It appears that the dimerization is associ-
ated with only very minor structural changes. The
crystal structures of compounds 4 and 4a, which
were obtained serendipitously by using hydrous
and anhydrous solvents, respectively, have offered
a unique chance to compare monomers and dimers
of the same species of this type in virtually strain-
free lattices. It is very important to know that the
formation of supramolecular structures through au-
riophilic bonding is not associated with significant
changes in the basic structures of the components.
O.S,S-Tris[(triphenylphosphine)gold(I)]-a-
mercaptoacetate tetrafluoroborate (2)
A solution of [(Ph3P)Au]30+ BF4- (0.43 g, 0.29
mmol) in dichloromethane (10 mL) is treated with o-
mercaptoacetic acid (0.02 mL. 0.29 mmol) at RT. After
4 h the reaction mixture is filtered and the product is
precipitated from the filtrate by addition of diethyl ether;
colourless, crystalline solid; 76 % yield (0.34 g), m.p.
168°C with decomposition, soluble in CH2CI2, CHCI3and
tetrahydrofuran, insoluble in pentane and diethyl ether,
air- and moisture-stable in solution and as a solid.
'H NMR (CDCI3, -60°C): b = 7.00 - 7.50, m, 45H, Ph:
3.83, s, 2H, CH2. ,3C{'H} NMR (CDCI3, -60°C): b =
36.5, s, CH2; 126.9, br d, J(P,C) = 65.3 Hz, and 127.4.
br d, J(P,C) = 58.8 Hz, C(ipso); 129.2, br s, C(meta);
132.2, br s, C(para); 133.7, br s, C(ortho); 175.8, s, C 0 2.
3IP{'H} NMR (CDCI3, -60°C): b = 27.0, s, IP, PAuO;
34.1, s, 2P, PAuS.
C56H47AU3BF4O2P3S O.9 CH2CI2 (1635.38)
Calcd C 41.83, H3.01, Au 36.13, Cl 4.12%,
Found C 41.38, H 3.05, Au 35.80, Cl 4.12%.
Experimental Part
General: All experiments were routinely carried out
under an atmosphere of dry, purified nitrogen. Glassware
was dried and filled with nitrogen, solvents were distilled
and kept under nitrogen. NMR: Jeol GX 400, TMS as in-
ternal standard, phosphoric acid as external standard. MS:
Finnigan MAT 90. Starting materials were either commer-
cially available or were prepared following literature pro-
cedures: [(Ph?P)Au]30 + BF4- [30], [(Me3P)Au]+BF4~
[28], (Me3P)AuCl [31],
0,S,S-Tris[(triphenylphosphine)gold(I)]-ß-
mercaptopropionate tetrafluoroborate (3)
The preparative method was the same as described for
2, with 0.02 mL (0.23 mmol) of /3-mercaptopropionic
acid. The product (0.27 g, 75% yield) is a stable, off-
white powder. 1H NMR (here and in the following as for
2): b = 2.73, s, 2H, CH2S; 3.50, s, 2H, CH2; 7.05 - 7.45.
m, 45H, Ph. ,3C{'H} NMR: b = 29.0, s, CH2S; 43.2, s.
CH2; 127.1, d, J(P,C) = 60.7 Hz, and 127.1, d, J(P,C) =
65.3 Hz, C(ipso); 129.0, d. J(P,C) = 11.9 Hz, and 129.4, d.
J(P,C)= 12.9 Hz, C(meta); 132.0, s, and 132.3, s, C(para);
133.6, d,J(P,C)= 13.8 Hz, and 133.7, d, J(P,C) = 12.9 Hz.
C(ortho); 175.5, s, C 0 2. 3iP{'H} NMR: b = 27.3, s, IP.
PAuO; 34.3, s, 2P, PAuS.
S,S-Bis[(trimethylphosphine)gold(I)]-benzylsulfonium
tetrafluoroborate (1)
(Trimethylphosphine)gold(I) tetrafluoroborate (0.25 g,
0.5 mmol) was freshly prepared from the chloride and
AgBF4 in tetrahydrofuran (20 mL) at 0°C and treated with
thiobenzylalcohol BzSH (0.03 mL, 0.25 mmol) for 4 h.
The volume of the reaction mixture is reduced to 10 mL
in a vacuum and mixed with diethyl ether (10 mL). The
colourless, crystalline precipitate is recrystallized from
dichloromethane/ diethyl ether; 74 % yield (0.19 g), m.p.
179°C, soluble in CH2CI2 and CHCI3, insoluble in pen-
tane and diethyl ether, air- and moisture-stable both in
solution and as a solid.
C57H49AU3BF4O2P3SO.8 CH2CI2 (1636.67)
Calcd C 42.42, H3.12, Au 36.10, Cl 3.47%,
Found C 41.81. H 3.20, Au 35.80, Cl 3.39%.
S,S-Bis[(triphenylphosphine)gold(I)]-
(hydrogen)thiosalicylate tetrafluoroborate (4, 4a)
(Ph3P)AuCl (0.122 g, 0.247 mmol) is treated with
AgBF4 (0.048 g, 0.247 mmol) in tetrahydrofuran (20 mL)
at 0°C to give a solution of [(Ph3P)Au]BF4. To the filtrate
is added a solution of thiosalicylic acid (0.019 g, 0.123
mmol) in 5 mL of THF and allowed to react for 30 min
at 0°C with stirring. The solvent is removed in a vacuum
'H NMR (CDCI3, 23°C): b = 1.60 ppm, d. J(P.H) = 9.9
Hz. 18H, Me; 4.30, s, 2H, CH2; 7.2 - 7.5, m, 5H, Ph.
31P{ 1H} NMR (CDCI3): b = -3.2, s. MS (FAB. nitroben-
zylalcohol): m/z = 669. M+ (17 %).
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A. Sladek et al. ■Polynuclear Gold(I) Complexes of Mercaptocarboxylic Acids
771
and the oily residue taken up in dichloromethane. Lay-
ering of the solution with pentane gives a small amount
of colourless crystals (5 mg, 4) and a violet oil, which
is again taken up in CH2CI2, filtered to remove colloidal
gold particles, and reprecipitated, now as a colourless
solid, with pentane. This crop (4a, 0.117 g, 75 % yield)
contains dichloromethane and water. The crystals loose
solvent at 129°C and decompose above 220°C.
Crystal Structure Determination
Suitable crystals of compounds 1, 2, 4 and 4a were
sealed under argon at dry ice temperature into glass
capillaries and examined directly on the diffractometer.
Data were corrected for Lorentz, polarisation and absorp-
tion effects. Structures were solved by direct methods
and refined by full-matrix least-squares calculations. The
thermal motion was treated anisotropically for all non-
hydrogen atoms, and isotropically for all hydrogen atoms.
Details of the X-ray structure determinations have been
deposited at Fachinformationszentrum Karlsruhe GmbH,
D-76344 Eggenstein-Leopoldshafen, Germany, and may
be obtained by quoting the CSD number 59244.
'H NMR (4a, CHCI3, 23°C): 6 = 5.24, s, CH2C12; 5.37,
br s, H30 +; 7.26 - 7.46, m, C6H5/4 ; 7.85, d, J(H,H) = 7.3
Hz, H(ortho-S); 7.90, d, J(H,H) = 8.5 Hz, H(ortho-C02).
13C {'H } NMR (CDCI3, 23°C): 6 = 127.6, d, J(P,C) =
61 Hz, C(ipso)Ph; 129.6, d, J(P,C) = 12 Hz, C(meta)Ph;
132.5, d, J(P,C) = 2 Hz, C(para)Ph; 133.8, d, J(P,C) = 14
Hz, C(ortho)Ph; 128.5, 130.0, 132.0, 132.9, 134.0, 136.6,
not assigned (C6H4); 168.4, s, COOH. 31P {'H } NMR
(CDCI3, -60°C): 6 = 33.1, s.
Acknowledgement
This work was supported by Deutsche Forschungsge-
meinschaft and by Fonds der Chemischen Industrie. The
authors are grateful to Mr. J. Riede for establishing the
X-ray data sets.
4a: C43H35AuoBF40 ,P .S H.O CH,CL (1261.46)
Calcd C 41.89, H3.12% ,
Found C 41.92, H 3.04%.
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