Chemistry of polynuclear cationic gold(I) thiolates of formula [Au 2(StBu)(L2)][BF4]

Article abstract of DOI:10.1002/ejic.200800918

The reactivity of the gold(I) cationic complexes [Au₂(StBu)- (L₂)][BF₄] {L = PMe₃, PEt₃, PtBu₃; L₂ = dppe [dppe = 1,2-bis(diphenylphosphanyl) ethane]} was studied. These complexe

Full text of DOI:10.1002/ejic.200800918

FULL PAPER
DOI: 10.1002/ejic.200800918
Chemistry of Polynuclear Cationic Gold(I) Thiolates of Formula
[Au2(StBu)(L2)][BF4]
Pietro Diversi,*[a] Angela Cuzzola,[a] and Fabio Ghiotto[b]
Keywords: Gold / Thiolates / Aurophilicity / Phosphanes / Mass spectrometry (ESI)
The reactivity of the gold(I) cationic complexes [Au2(StBu)-
(L2)][BF4] {L = PMe3, PEt3, PtBu3; L2 = dppe [dppe = 1,2-
bis(diphenylphosphanyl)ethane]} was studied. These com-
plexes undergo cleavage of the Au–Au bonds by reaction
with phosphanes to give quantitative yields of [Au(StBu)-
(L)n] and [Au(L)n][BF4] (n = 2 or 3) in the case of monodentate
phosphanes, and [Au2(StBu)2(dppe)] and [Au(dppe)2][BF4] in
the case of the dppe derivative. These compounds also react
with [Au(StBu)(L)] and exchange the neutral moiety bonded
to the [Au(L)]+ cation. In both cases some indication of the
nature of the intermediates was reached by mass spectrome-
try (ESI) and NMR spectroscopy.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
Introduction
Gold(I) complexes in the solid state often adopt struc-
tures, in which polynuclear cores of gold centres are bound
together by weak bonding interactions (aurophilicity).[1] In
particular, the cationic (phosphane)gold(I) thiolate com-
plexes [Au2(SR)(L2)][BF4], studied by the Bruce and
Schmidbaur groups, are usually arranged in the solid state
as dimeric structures, with a core of four gold atoms bound
together by aurophilic interactions.[2]
In recent papers we reported the preparation of the com-
plexes [Au2(StBu)(L2)][BF4] [L = PMe3 (2a), PEt3 (2b),
PtBu3 (2c); L2 = dppm, dppe (2d)] from the corresponding
[Au(StBu)(L)] (1) complex using Bruce’s method, and we
showed by mass spectrometry and NMR spectroscopy that,
depending on the nature of the phosphane ligand and the
solvent, some of them maintain, in part at least, the tetra-
nuclear structure in solution (Figure 1).[3,4] In particular,
the aurophilic interactions between neighbouring Au atoms
survive in solution when the phosphane ligand has a small
steric hindrance (PMe3) or is bidentate, then in the follow-
ing discussion 2a and 2d are better described as tetranuclear
dications (Figure 1).
Figure 1. Monomeric (left) and dimeric (right) structures of cations
2.
philic interactions. It is of some relevance in this context to
remember that Schmidbaur has prepared the first proto-
typical complex of the series, [Au2(SMe)(PMe3)2][BF4], just
by the reaction of [Au(SMe)(PMe3)] with [Au(PMe3)]+.[2b]
On the basis of these considerations we studied the be-
haviour of 2 in the presence of variable amounts of free
phosphane or 1. In the case of the reaction with phospha-
nes we expected that some exchange should take place since
many mononuclear (phosphane)gold(I) derivatives have
been reported to rapidly exchange with free phosphane.[5]
Actually, we observed that phosphanes are able to cleave
the thiolato-bridged gold–gold interaction, giving the corre-
sponding neutral phosphane thiolato derivatives and cat-
ionic phosphane complexes, and that [Au(StBu)(L)] ex-
changes with [Au2(StBu)(L2)][BF4] or inserts into the Au–
Au bond of 2 to give large cyclic cores of Au and S atoms.
Here we describe the results of this investigation together
with a combined mass spectrometric and NMR spectro-
scopic study of the reactions.
The basic unit of these gold(I) complexes can be consid-
ered formally as resulting from the interaction of complex
1 with [Au(PR3)]+, with the thiolato group bridging two
gold centres, which are additionally bonded through auro-
[a] Dipartimento di Chimica e Chimica Industriale dell’Università
di Pisa
Via Risorgimento 35, 56126 Pisa, Italy
Fax: +39-050-2219410,
E-mail: div@dcci.unipi.it
[b] Scuola Normale Superiore
Piazza dei Cavalieri 7, 56126 Pisa, Italy
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
Eur. J. Inorg. Chem. 2009, 545–553
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
545

P. Diversi, A. Cuzzola, F. Ghiotto
FULL PAPER
same conditions shows not only the same peaks in the posi-
tive-ion mode but also the signal corresponding to [BF4]–
in the negative-ion mode.
Results and Discussion
Reactivity of Gold(I) Cationic Thiolates with Phosphanes
The NMR spectra in CD2Cl2 of the mixture, recorded
before the separation of the products by precipitation with
pentane, indicates that a dynamic situation is proceeding,
since the 1H NMR spectrum shows two large resonances at
δ = 1.48 and 1.61 ppm, and the 31P NMR spectrum one
large peak centred at δ = 4.64 ppm. These peaks are roughly
the average values of the corresponding signals in the re-
acting species. It is possible that the equilibrium according
to Equation (1) is present {possibly by the formation of the
addition intermediate [Au2(StBu)(PMe3)3]+}.
Precipitation of 4a with pentane should cause the shift-
ing of the equilibrium to the right and leave 1a as the solu-
ble product. Obviously, this fact implies that mixing
[Au(PMe3)2][BF4] and [Au(StBu)(PMe3)] in CD2Cl2 in a 1:1
ratio should give the same equilibrium mixture; actually,
the spectrum of this mixture is basically identical to that
obtained from the reaction of 2a with trimethylphosphane
(signals at δ = 1.46 and 1.59 ppm in the 1H NMR spectrum;
one large signal at δ = 5.01 ppm in the 31P NMR spectrum).
A complex of formula [Au2(SR)(PPh3)3]+, similar to the
above proposed gold intermediate, is reported in the litera-
ture,[7] and the phosphane ligands were found to compete
for the coordination sites at the two gold centres, exhibiting
a fluxional behaviour on the NMR scale.
Reaction of [Au4(StBu)2(PMe3)4][BF4]2 (2a) with
Phosphanes
The first reaction studied was between 2a and PMe3,
chosen because of the spectral simplicity of the species in-
volved (Scheme 1). Compound 2a and trimethylphosphane
in a 1:2 ratio were allowed to react in a dichloromethane
solution at room temperature. The reaction was almost im-
mediate. The resulting mixture was added dropwise whilst
stirring into a large excess of pentane immediately giving
an off-white precipitate. The solid was collected by filtration
and dried, while the solvent of the filtrate was removed in
vacuo to afford a beige solid. The insoluble product was
identified as [Au(PMe3)2][BF4] (3a) by comparison of the
1H and 31P NMR spectra with those reported in the litera-
ture for [Au(PMe3)2]+[6] and by the presence in the mass
spectrum of a positive ion peak at m/z = 349. Compound
3a was also prepared from [AuCl(PMe3)2] and Ag[BF4] ac-
cording to a published procedure in order to compare the
spectroscopic properties of the insoluble product with those
of an authentic sample.[6a]
The product obtained from the pentane solution was
identified as [Au(StBu)(PMe3)] (1a). The 1H NMR spec-
trum in CD2Cl2 consists of a singlet at δ = 1.46 ppm from
the StBu group and a doublet at δ = 1.55 ppm (JP,H
=
Quite interestingly it turned out that, by using a 2a/phos-
9.9 Hz) from the PMe3 group; the 31P NMR spectrum phane stoichiometric ratio of 1:4, the neutral product was
(CD2Cl2) shows a singlet at δ = 1.40 ppm. Interestingly, the 1a as in the previous case, but the ionic product turned out
mass spectrum (ESI; methanol) in the positive ion mode to be spectroscopically different from the expected
1
presents, in addition to the peak at m/z
=
363 [Au(PMe3)2][BF4] (3a). In fact, the H NMR spectrum in
{[Au(StBu)(PMe3) + H]+}, peaks at m/z = 349 {[Au- CD2Cl2 of the ionic product, dried under reduced pressure
(PMe3)2]+}, 635 {[Au4(StBu)2(PMe3)4]2+} and 921 {[Au6- (20 Torr), shows a doublet at δ = 1.47 ppm (JH,P = 7.7 Hz),
(StBu)4(PMe3)4]2+}. As already noted,[4] the peak at m/z = and the 31P NMR spectrum presents a singlet at δ =
635 arises from the oxidation of the neutral thiolato group –15.40 ppm. In CDCl3 the resonances are similar [1H
during the ionisation process (as confirmed by the absence NMR: δ = 1.50 ppm (d, JH,P = 7.2 Hz); 31P NMR: δ =
of [BF4]– in the negative-mode analysis). This compound –15.86 ppm (s)]. The NMR parameters are different from
gives a fragment peak at m/z = 349 and an adduct peak at those reported in the literature for some of the salts of
m/z = 921. Of course the mass spectrum of 2a under the [Au(PMe3)2]+ (Table 1).
Scheme 1. Reaction of 2a with PMe3.
(1)
546
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 545–553

Chemistry of Polynuclear Cationic Gold(I) Thiolates
1
Table 1. H and 31P NMR spectroscopic data for [Au(PMe3)2]X.
X–
Solvent
δ(1H) [ppm]
δ(31P) [ppm]
Ref.
[6a]
[6b]
[6b]
[6c]
[6c]
Cl–
CDCl3
D2O/H2O
D2O/H2O
CDCl3
CD3OD
CDCl3
1.6 (s)
1.6 (br. s)
1.6 (br. s)
3.4 (s)
Cl–, Br–, I–
[NO3]–, [BF4]–
[Au{P(O)(OMe)2}2]–
[Au{P(O)(OMe)2}2]–
[BF4]–
1.69 (d, JH,P = 8.5 Hz)
1.58 (d, JH,P = 8.6 Hz)
1.66 (t, JH,P = 4.0 Hz)
1.61 (t, JH,P = 4.0 Hz)
4.3 (s)
7.2 (s)
8.79 (s)
8.70 (s)
this work
this work
[BF4]–
CD2Cl2
Moreover, the integrated area of the phosphane signal in
the 1H NMR spectrum evaluated with respect to an internal
standard (ferrocene, hexamethylbenzene) is consistent with
the presence of three phosphane ligands per gold centre.
The product was found to be converted into [Au(PMe3)2]-
[BF4] after being kept at 10–4 bar overnight, and this ex-
plains the contradictory results of the NMR and MS (ESI)
data {m/z = 349 corresponding to [Au(PMe3)2]+}, because,
under the high-vacuum conditions such as those operating
in the mass spectrometer, it is most likely that the product
loses a phosphane ligand to give the stable [Au(PMe3)2]+.
All the [Au(PMe3)n]+ (n = 1–4) cations are reported in
the literature:[6,8,9] [Au(PMe3)2]+ and [Au(PMe3)4]+ have
been isolated, whereas the existence of [Au(PMe3)3][BF4] is
questioned. Actually, on the basis of evidence from IR spec-
tra some authors conclude that [Au(PMe3)3][BF4] does not
exist at all, being a 1:1 mixture of [Au(PMe3)2][BF4] and
[Au(PMe3)4][BF4].[6a]
equimolar amount of dppm because of its ability to stabi-
lize two tricoordinate gold atoms bonded together by auro-
philic interactions.[10] Unfortunately, the NMR spectra at
room temperature were poorly informative, showing a dy-
namic behaviour, and the 31P NMR at –70 °C was quite
complex, showing i.a. a singlet from trimethylphosphane at
δ = 1.88 ppm and two singlets at δ = 31.78 and 30.56 ppm
from dppm. On the other hand the mass spectrum (ESI)
seems to confirm the hypothesis of the above proposed gold
intermediate, showing, in addition to the peaks correspond-
ing to [Au(PMe3)2]+, [Au2(dppm)2]2+ and [Au4(StBu)2-
(PMe3)4]2+, a peak at m/z = 1019 from the dinuclear com-
plex [Au2(StBu)(PMe3)2(dppm)]+. Unfortunately, any at-
tempt to isolate the product has been unsuccessful.
We also added 1 equiv. of phosphane to a CDCl3 solu-
tion of [Au(PMe3)2]+ in order to achieve the stoichiometric
requirements for the formation of [Au(PMe3)3]+; however,
1
the H NMR spectrum shows a doublet at δ = 1.59 ppm
(JH,P = 8.8 Hz) and the 31P NMR a signal at δ = –6.96 ppm,
which are different from the values found above for the
ionic products of the reaction between 2a and PMe3. Ad-
dition of further amounts of PMe3 shifts the 31P NMR sig-
nal progressively to high fields (up to δ = –24.44 ppm),
Reaction of [Au2(StBu)(PEt3)2][BF4] (2b) with
Triethylphosphane
[Au2(StBu)(PEt3)2][BF4] (2b) was treated with triethyl-
whereas the proton doublet broadens into a large signal. phosphane by using a 2b/phosphane molar ratio of 1:1. Af-
Since these parameters seem to be typical of an exchange ter the usual workup, the ionic and neutral fractions were
between coordinated and free phosphane, and different separated and it was found that the insoluble fraction con-
from those of “[Au(PMe3)3][BF4]”, the question of whether tained about half of the starting material 2b (unreacted) in
the ionic product is indeed the [Au(PMe3)3][BF4] salt is still addition to the expected [Au(PEt3)2][BF4] complex. Moni-
open.
toring by NMR spectroscopy showed that a 1:2 ratio was
The reaction of 2a with PMe3 in a 1:4 ratio is peculiar in strictly necessary for the reaction to reach completeness.
another sense: the reacting mixture, before separation of the [Au(PEt3)2][BF4] (3b) was identified by NMR spectroscopy
products, showed unexpectedly quite narrow NMR signals in CD2Cl2 (1H NMR: two complex resonances, centred at
(a different situation from the one found for the reaction δ = 1.97 and 1.21 ppm for the CH2 and CH3 protons,
with equimolar amounts) suggesting that a precise species respectively; 31P NMR: singlet at δ = 47.3 ppm) and mass
1
was obtained. In particular the H NMR [singlet at δ = spectrometry (ESI) {m/z = 433 corresponding to [Au-
1.47 ppm and a doublet at δ = 1.54 ppm (JH,P = 9.2 Hz) in (PEt3)2]+}. Compounds of the formula [Au(PEt3)n][PF6] (n
a 1:4 ratio] and the 31P NMR spectra (one singlet at δ = = 2, 3, 4) are reported in the literature, but only the dicoor-
–3.90 ppm) could be indicative of a species, in which the dinated cation has been isolated,[11] and the 31P NMR spec-
PMe3 ligands are all equivalent or fluxional. We tentatively trum of an authentic sample of 3b prepared according to a
proposed structure A for this intermediate.
Interestingly, this behaviour is strictly peculiar to this zation.[5a,11]
stoichiometry since for a higher and lower 2a/phosphane As for the soluble fraction, the H NMR spectrum in
ratio the resonances are again large and unresolved. In or- C6D6 presents a singlet at δ = 1.89 ppm for the thiolato
der to detect an addition product, 2a was treated with an group, a double quartet at δ = 1.15 ppm (JH,P = 8, JH,H
literature procedure gives further support for the characteri-
1
=
Eur. J. Inorg. Chem. 2009, 545–553
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
547

P. Diversi, A. Cuzzola, F. Ghiotto
FULL PAPER
7.7 Hz) and a double triplet at δ = 0.75 ppm (JH,P = 17.6, vacuum conditions [Au(StBu)(PEt3)2] could lose a phos-
JH,H = 7.7 Hz) for the triethylphosphane. The 31P NMR phane ligand to give the more stable [Au(StBu)(PEt3)]. In
spectrum shows one signal at δ = 38.22 ppm, which is fairly fact the product, when kept at 10–3 Torr pressure for some
consistent with that found for [Au(StBu)(PEt3)] (δ = hours, changed into [Au(StBu)(PEt3)], preventing elemental
1
38.36 ppm, C6D6). The H NMR spectrum presents some analysis.
differences: the StBu chemical shift of δ = 1.89 ppm is quite
There are several literature papers on related tricoordin-
close to the value found in [Au(StBu)(PEt3)] (δ = 1.93 ppm), ate gold(I) complexes. For example, the triphenylphosphane
but the phosphane resonances are different (δ = 0.63 and derivatives [Au(SR)(PPh3)2] (R = S2COCH2CH3, SC6F5,
0.90 ppm). In particular, the 1:2 thiolato/phosphane ratio C5Me5CS2, etc.)[12] in the solid state exhibit longer Au–P
of the integrated areas are consistent with the formula distances than in the corresponding phosphanyl–gold dico-
[Au(StBu)(PEt3)2] (Scheme 2). This was supported by the ordinated complexes.
reaction of a C6D6 solution of [Au(StBu)(PEt3)] with trieth-
In an effort to understand some mechanistic aspects the
ylphosphane in a 1:1 ratio in an NMR tube that gave the reaction was monitored by NMR spectroscopy in CD2Cl2
same spectroscopic parameters observed in the case of the solution. The 31P NMR spectrum of the reaction mixture
soluble fraction.
before separation of the products presented one sharp sing-
let at δ = 39.48 ppm, and the 1H NMR showed well-re-
solved signals: a singlet at δ = 1.51 ppm for the thiolato
group, a double quartet at δ = 1.9 ppm (JH,P = 8, JH,H
=
7.7 Hz) and a structured signal centred at δ = 1.18 ppm for
the phosphane CH2 and CH3 groups. The spectrum is quite
similar to that of the starting cation 2b [apart from the fact
that the presence of some benzene (the phosphane was
added as a benzene solution) caused a small change
(0.07 ppm) of the chemical shifts compared to those ob-
served in pure CD2Cl2]. A structure like B, which derives
from the addition of a triethylphosphane ligand to each
gold atom, could explain the above results provided that the
phosphane ligands are all equivalent.
Scheme 2. Reaction of 2b with PEt3.
Alternatively, the neutral compound could consist of
[Au(StBu)(PEt3)] containing PEt3, trapped in the crystals of
the solid, so that dissolving the complex could cause the
phosphane to be lost and rapidly exchange with coordi-
nated phosphane. In order to clarify this point some vari-
able-temperature NMR experiments were performed in
deuterated toluene. Whereas the signals in the 1H NMR
spectrum broadened from –10 to –80 °C, the 31P NMR
spectrum (δ = 39.93 ppm at 25 °C) was more informative.
Between –10 and –30 °C the signal shifts gradually to δ =
37.95 ppm. A second peak appears below –30 °C and at
–80 °C in addition to the major peak (δ = 37.04 ppm), and
a second singlet arises at δ = 41.90 ppm (Figure S1 in the
Supporting Information). No signal corresponding to free
phosphane was found. The resonance at δ = 41.90 ppm is
not far (considering the different solvent and anionic li-
gand) from the value reported for [Au(PEt3)2]PF6 (δ =
43.3 ppm, CD2Cl2).[5a]
The formation of a tricoordinate gold thiolate seems to
be peculiar to triethylphosphane. This product was also ob-
tained when treating 2a with triethylphosphane by using 2a/
phosphane in a 1:4 ratio. After the usual workup, roughly
equal amounts of 3a and [Au(StBu)(PEt3)2] were formed
together with minor amounts of 3b and [Au(PMe3)(PEt3)]+
(Scheme 3).
Then, since no evidence for the presence of free exchang-
ing phosphane was found, we are inclined to propose the
equilibrium according to Equation (2) to explain these data.
(2)
The mass spectrum analysis is not clear-cut showing a
peak at m/z = 405 {[Au(StBu)(PEt3) + H]+} in addition to
other minor signals from secondary reactions. There are in
fact peaks at m/z
=
433 {[Au(PEt3)2]+}, 719
{[Au2(StBu)(PEt3)2]+} and at higher m/z values arising from
adducts of 2b with [Au(StBu)(PEt3)] (1b) formed in the gas
phase during MS (ESI) analysis (m/z = 1005 {[Au3(StBu)2-
(PEt3)2]+} and m/z = 1123 {[Au3(StBu)2(PEt3)3]+}). The
[Au(PEt3)2]+ ion derives from the fragmentation of 2b,
which is formed by electrochemical oxidation of the neutral
compound during the ionization process by electrospray.
Scheme 3. Reaction of 2a with PEt3.
1
In fact, the H NMR spectrum of the insoluble fraction
However, these results do not invalidate the hypothesis of a in CD2Cl2 presents a triplet at δ = 1.61 ppm (JH,P = 4.0 Hz)
tricoordinate complex, since in the gas phase under high- (PMe3) as the major signal, which together with the 31P
548
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 545–553

Chemistry of Polynuclear Cationic Gold(I) Thiolates
NMR major singlet at δ = 8.73 ppm is indicative of the
presence of [Au(PMe3)2][BF4] (3a). A double triplet at δ =
1.23 ppm (JH,H = 8, JH,P = 18.7 Hz) and a large structured
1
signal at δ = 1.94 ppm for PEt3 are also present in the H
NMR spectrum as minor peaks. The 31P NMR spectrum
shows minor signals, a singlet at δ = 47.20 ppm (s) for [Au-
(PEt3)2][BF4] (3b) and two doublets at δ = 44.93 (d, JP,P
=
335.5 Hz) and 11.01 ppm (d, JP,P = 335.5 Hz) for [Au(PMe3)-
(PEt3)][BF4]. The mass spectrum (ESI) confirms this assign-
ment by showing peaks at m/z = 349 {[Au(PMe3)2]+}, m/z
= 391 {[Au(PMe3)(PEt3)]+} and m/z = 433 {[Au(PEt3)2]+}.
In contrast, only one pentane-soluble product was de-
tected and isolated, which was characterized as [Au(StBu)-
(PEt3)2] by NMR spectroscopy in C6D6 and MS (ESI) (see
above for discussion).
Scheme 4. Proposed mechanisms for the reaction of 2c with dppe.
A point that remains to be explained is the apparent
selectivity of this reaction since [Au(StBu)(PEt3)2] is the
only neutral product and 3a is largely predominant with
The two cationic species were easily identified on the ba-
only small amounts of the other possible (phosphane)gold sis of their spectroscopic behaviour by comparison with the
cations. This is particularly remarkable since it is well above reported data and the literature.[13,14] In particular
known that gold(I) compounds are often involved in phos- the 31P NMR spectrum in CD2Cl2 shows the two phos-
phane exchange reactions;[5] this happens, for instance, for phane resonances at δ = 97.09 and 21.93 ppm, assigned to
compounds like [Au(PR3)n]+.
3c and [Au(dppe)2]+, respectively. Accordingly, mass spec-
trometry (ESI) shows peaks at m/z = 601 {[Au(PtBu3)2]+}
and 993 {[Au(dppe)2]+} (positive-ion mode) and at m/z =
87 ([BF4]–) (negative-ion mode).
Reaction of [Au2(StBu)(PtBu3)2][BF4] (2c) with
Phosphanes
The reaction between [Au2(StBu)(PtBu3)2][BF4] (2c) and
The pentane-soluble neutral compound was identified as
PtBu3 gives [Au(PtBu3)2][BF4] (5c) and [Au(StBu3)(PtBu3)] [Au(StBu)(PtBu3)] (1c) from 1H NMR [singlet at δ =
(1c) in roughly equal amounts.
1.93 ppm and a doublet at δ = 1.06 ppm (JH,P = 13.2 Hz)]
The 31P NMR spectrum of the ionic product (one singlet and 31P NMR (δ = 91.48 ppm) spectroscopy in C6D6. The
at δ = 97.00 ppm) is quite close to the value of δ = 97.4 ppm mass spectrum (ESI) of the positive ions confirmed the
in CDCl3 reported by Schmidbaur et al. for 3c.[13] The mass structure by showing
a
peak at m/z
=
489
spectrum (ESI) confirmed this formulation: m/z = 601 {[Au(StBu)(PtBu3) + H]+}, in addition to other peaks de-
{[Au(PtBu3)2]+}. The 1H NMR spectrum in CD2Cl2 (which riving from in situ oxidation during the ionization process
was not previously reported, as far as we know) presents as discussed elsewhere.[4]
the phosphane resonance as a double doublet centred at δ
Interestingly, dppe does not give any neutral derivative,
= 1.55 ppm (JH,P = 7 Hz); in principle this would be consis- being completely consumed to afford [Au(dppe)2][BF4].
tent with the presence of two nonequivalent PtBu3 ligands,
Two rational mechanisms are depicted in Scheme 4. The
but the X-ray structure reported in the literature shows a trapping by the diphosphane of the [Au(PtBu3)]+ species,
linear coordination around the gold centre with the two formed after the displacement of the neutral
tert-butyl groups staggered and equivalent.[13b] At the mo- [Au(StBu)(PtBu3)], could result in two possible intermedi-
ment we have no satisfactory explanation for this observa- ates: a dinuclear dicoordinated (phosphane)gold cation (C)
tion.
or a tricoordinated gold cation (D). In both cases dispro-
The NMR parameters in C6D6 of the pentane-soluble portionation of one of these intermediates gives the final
fraction are consistent with those found for 1c, prepared by cationic products [Au(dppe)2][BF4] and 3c.
a different route, and the mass spectrum (ESI), as expected,
Both intermediates have some support in the literature:
presents a peak at m/z = 489 assigned to [Au(StBu)(PtBu3) for instance several examples of tricoordinate gold(I) com-
+ H]+ and the oxidation product at m/z = 601 {[Au- pounds containing a di- and a monophosphane ligand of
(PtBu3)2]+} and m/z = 887 {[Au2(StBu)(PtBu3)2]2+} (no the type [Au(PPh3)(dppe)][Co(CO)4],[15] [Au(PPh3)(dppe)]-
–
BF4 is present, see discussion above).
[X] (X = Cl, CN),[16] and [AuCl(PPh3)(dppe)][17] have been
Since 2c has been shown to exist in solution only as a reported.
monocationic dinuclear species,[4] it appeared interesting to
study the feasibility of the addition of dppe to the thiolato-
bridged gold–gold moiety. The reaction, carried out by
using equimolar amounts of 2c and dppe, proceeded in an
Reaction of [Au4(StBu)2(dppe)2][BF4]2 (2d) with
Bis(1,2-diphenylphosphanyl)ethane
When equimolar amounts of dppe and 2d were used the
unexpected way to give [Au(StBu)(PtBu3)] (1c) and a mix- reaction did not run to completeness, as shown by the pres-
ture of [Au(dppe)2][BF4] and [Au(PtBu3)2][BF4] in a 1:1 ra- ence of the starting complex in the insoluble pentane frac-
tio as shown in Scheme 4.
tion. However, in the same fraction [Au(dppe)2][BF4] was
Eur. J. Inorg. Chem. 2009, 545–553
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
549

P. Diversi, A. Cuzzola, F. Ghiotto
FULL PAPER
isolated and identified by comparison of the spectroscopic creases with the amount of 1a added indicates that the ex-
data. MS analysis showed positive ion peaks at m/z = 993 change is in the “slow-exchange” regime. Variable-tempera-
1
{[Au(dppe)2]+}, 881 {[Au4(StBu)2(dppe)2]2+} and 1168 ture H NMR experiments showed that the signals become
–
{[Au3(StBu)2(dppe)]+} and 87 [BF4 ] as the negative ion.
resolved starting from –20 °C; below –40 °C a singlet at δ
1H NMR spectra recorded in C6D6 of the pentane-solu- = 1.48 ppm {close to the corresponding signal at δ =
ble fraction show a singlet at δ = 1.88 ppm for the thiolato 1.46 ppm in [Au(StBu)(PMe3)]} and a doublet at δ =
ligand, a signal centred at δ = 2.62 ppm for the dppe CH2 1.65 ppm (JH,P = 11.0 Hz) for PMe3 are observed. The 31P
group and two large signals between δ = 6.8 and 7.6 ppm NMR spectrum shows a sharp resonance at δ = –3.07 ppm,
for the aromatic protons. The 31P NMR spectrum shows a which remained as the only signal even at –70 °C. This is a
signal at δ = 37.90 ppm. This compound was identified as result that is difficult to rationalize unless suggesting (at
[Au2(StBu)2(dppe)] by comparison of its spectroscopic data high temperature) a slow scrambling of free and coordi-
with those of a pure sample prepared by an alternative nated [Au(StBu)(PMe3)], and (at low temperature) a sym-
route.[3,4] The MS (ESI) analysis confirms the attribution, metric or quasi-symmetric stabilized intermediate.
showing the diagnostic peak at m/z = 993 {[Au2(StBu)2-
The mass spectrum (ESI) of this solution gives some sup-
(dppe) + Na]+} in addition to peaks at m/z = 881 port for a trinuclear intermediate, because it shows an ion
{[Au4(StBu)2(dppe)2]2+}, 1024 {[Au5(StBu)3(dppe)2]2+} and peak at m/z (%) = 997 {[Au3(StBu)2(PMe3)3]+ (52)}, in ad-
1168 {[Au3(StBu)2(dppe)]+} deriving from the electrospray dition to the ion peaks at m/z (%) = 349 {[Au(PMe3)2]+
process (see above for discussion).
(83)}, 363 {[Au(StBu)(PMe3) + H]+ (40)}, 635 {[Au4(StBu)2-
The presence of unreacted [Au4(StBu)2(dppe)2][BF4]2 in- (PMe3)4]2+ (100)} and 921 {[Au6(StBu)4(PMe3)4]2+ (72)}.
dicates that in this case a different stoichiometry with re- The intensity of the peak at m/z = 997 and its persistence
spect to that used in the above reactions is required in order under different experimental conditions should rule out in-
to drive the reaction to completeness. Indeed, by using the strumental artefacts. It is perhaps of some relevance to re-
right stoichiometry {3 equiv. of dppe per equiv. of member that the trinuclear complex [(CH2S)2(AuPPh3)3]+
[Au4(StBu)2(dppe)2](BF4)2}[Au(dppe)2][BF4]and[Au2(StBu)2- prepared by Schmidbaur and coworkers presents a similar
(dppe)] were obtained in almost quantitative yields accord- NMR behaviour showing even at –60 °C the equivalence of
ing to Equation (3).
the phosphane groups.[2b] In this case the authors propose
a low-energy mechanism that exchanges the three Au(PPh3)
groups for the two sulfur donors. Then it is possible that a
similar situation may arise in our case.
Interestingly, by using a 1:4 [Au4(StBu)2(PMe3)4][BF4]2/
(3)
1
[Au(StBu)(PMe3)] ratio, the H and 31P NMR spectra are
well resolved even at room temperature, indicating that a
rapid exchange occurs. The NMR parameters are not very
different from those reported above for the precedent ex-
Reactivity of Gold(I) Cationic Thiolates in the Presence of
Neutral Precursors
periment [1H NMR: δ = 1.46 ppm (s) and 1.61 ppm (d); 31
NMR: δ = –0.09 ppm].
P
As a further aspect of the chemistry of the [Au2(StBu)(L)2]-
[BF4] systems, the reaction of the cationic complexes 2a
with neutral phosphane thiolates [Au(StBu)(L)] was investi-
gated. This mixture resembles the situation that occurs dur-
ing the preparation of 2, when [FeCp2]+ is gradually added
to a solution of [Au(StBu)(L)] in dichloromethane.
However, any attempt to isolate some ionic intermediates
by adding pentane to the CH2Cl2 solution resulted only in
the recovery of 2a leaving the neutral thiolate in solution.
[Au4(StBu)2(PMe3)4][BF4]2 (2a) + [Au(StBu)(PEt3)]
(1b)
[Au4(StBu)2(PMe3)4][BF4]2 (2a) + [Au(StBu)(PMe3)]
(1a)
The reaction between [Au4(StBu)2(PMe3)4][BF4]2 and
[Au(StBu)(PEt3)] in CD2Cl2 in a 1:1, 1:2 and 1:4 ratio was
1
The H NMR spectrum of 2a in CD2Cl2 shows a singlet studied. After addition of the neutral compound to the
at δ = 1.58 ppm and a doublet at δ = 1.67 ppm (JP,H
11.4 Hz) and the 31P NMR spectrum a singlet at δ = (in particular the resonance from the PMe3 protons) until
–1.91 ppm. the signals appeared well resolved when the 1:4 ratio was
=
ionic one, all the NMR signals became increasingly broad
After addition of even small amounts of reached; the 1H NMR spectrum shows a singlet at δ =
[Au(StBu)(PMe3)] (1a) to this solution, partial coalescence 1.53 ppm for the thiolato group, a doublet at δ = 1.64 ppm
of the trimethylphosphane doublet and broadening of the (JH,H = 11.0 Hz) for PMe3, a double quartet at δ =
31P NMR resonance (without significant changes in the 1.95 ppm (JH,P = 9.9, JH,H = 7.7 Hz) and a double triplet
chemical shifts) occurs. Further broadening in the 1H NMR at δ = 1.25 ppm (JH,P = 9.9, JH,H = 18.7 Hz) for PEt3. In
spectrum is observed upon addition of more 1a. When the 31P NMR spectrum two signals are present at δ = 38.26
2 equiv. of the neutral thiolate per equiv. of 2a were added, and –0.09 ppm, which were assigned to PEt3 and PMe3,
the phosphane appeared as quite a broad signal. Accord- respectively, by comparison with the spectra of other (phos-
ingly, the 31P resonance at δ = –1.99 ppm resulted in quite phane)gold derivatives. The chemical shifts are about the
a broad signal (ca. 80 Hz). The fact that broadening in- same as those of 2a and 2b, and the behaviour is quite sim-
550
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 545–553

Chemistry of Polynuclear Cationic Gold(I) Thiolates
Scheme 5. Reaction of 2a with 1b.
ilar to that observed for the 2a/1a reaction, supporting the ported by [Au(SR)(phosphane)] (1). The phosphane traps
idea that
a
rapid exchange between coordinated the [Au(phosphane)]+ moiety cleaving a gold–thiolato bond
[Au(StBu)(PMe3)] and [Au(StBu)(PEt3)] takes place.
with concurrent loss of neutral 1, while free and coordi-
The MS (ESI) data of the solutions (Table S1 in the Sup- nated [Au(SR)(phosphane)] exchange. However, the dif-
porting Information) show the presence of gold species of ferent combinations of 2 and phosphane may produce gold
various nuclearity and in particular 2a, 2b and complexes that have different coordination numbers, as
[Au2(StBu)(PMe3)(PEt3)]+. The attribution of the ion shown in Scheme 6 in the case of the monophosphane de-
[Au2(StBu)(PMe3)(PEt3)]+ was confirmed by comparison rivatives.
with an authentic sample, prepared from [Au(PMe3)]BF4
by reaction with [Au(StBu)(PEt3)] according to a procedure
described by Bruce et al.[2f] [Au(PMe3)]BF4 was generated
by the reaction of [Au(Cl)(PMe3)] with Ag[BF4] in CH2Cl2
and used without isolating it. The mass spectrum of the
mixture shows a peak at m/z = 635 corresponding to the
Scheme 6. General scheme for the reaction of 2 with monophos-
phanes.
tetranuclear species [Au4(StBu)2(PMe3)4]2+ and peaks at
m/z = 677 and 719 relative to the dinuclear monocationic
species [Au2(StBu)(PMe3)(PEt3)]+ and [Au2(StBu)(PEt3)2]+,
The exchange reactions of 1 with complexes 2 may have
respectively. Recalling that the tetranuclear core is main-
tained in solution only when the phosphane is relatively
small,[3,4] it seems that the presence of one PEt3 ligand in
the [Au2(StBu)(PMe3)(PEt3)]+ is sufficient to cause the
compound to exist in the dinuclear form.
By increasing the amounts of [Au(StBu)(PEt3)], the in-
tensity of the peaks corresponding to [Au2(StBu)(PMe3)-
(PEt3)]+ and [Au2(StBu)(PEt3)2]+ increases and, as a conse-
quence, the intensity of the signal relative to [Au4(StBu)2-
(PMe3)4]2+ decreases (Table S1).
in principle useful synthetic applications for the preparation
of new derivatives 2, by using [Au(SR)(phosphane)] sys-
tems, different from the corresponding coordinated moiety
in 1.
Finally the reactivity does not seem to be influenced by
the aggregation state of 2 in solution since, as we have
shown in a previous paper, 2a, 2b and 2c exist in solution
as a dimer, a mixture of a dimer and monomer and a mono-
mer, respectively.[4]
In addition to these peaks there are signals at m/z = 997,
1039 and 1081 corresponding to phosphane trinuclear clus-
ters of AuI, already proposed for the reaction of 2a with 1a.
The presence of these species, although in principle could
be formed during the ionization process (see above), could
be of some support for the involvement of such intermedi-
ates for all the reactions between 2 and 1.
The spectroscopic behaviour is consistent with a dynamic
situation involving 2a, 2b and the corresponding derivative
containing two different phosphanes (at least in the hypo-
thesis that the PEt3 protons of the different species resonate
at roughly the same frequency and that the PMe3 signals
are more sensitive to the environment) (Scheme 5).
Experimental Section
Chemicals: All manipulations and reactions were carried out under
dinitrogen or argon by using standard techniques. All solvents were
used without any further purifications. The following compounds
were prepared according to literature procedures: [Au(StBu)(L)] (L
= PMe3, PEt3, PtBu3; 1a, 1b, 1c),[3] [Au2(StBu)2(L2)] (L2 = dppe;
1d),[4] [Au2(StBu)(L2)][BF4] (L = PMe3, PEt3, PtBu3; 2a, 2b, 2c; L2
= dppe; 2d)[4] and [Au(Cl)(L)] (L = PMe3, PEt3, PtBu3).[18]
Physical Measurements: 1H and 31P NMR spectra were recorded
with a Varian Gemini 200 instrument, working at 200 MHz. Car-
bon and hydrogen elemental analyses were performed in the micro-
analysis laboratory of the Dipartimento di Scienze Farmaceutiche
dell’Università di Pisa. Mass spectra were obtained from an Ap-
plied Biosystems-MDS Sciex API 4000 triple quadrupole mass
spectrometer (Concord, Ont., Canada), equipped with a Turbo-V
ionspray (TIS) source. The operative parameters used were as fol-
lows: ionspray voltage (IS), 5.0 kV; gas source 1 (GS1), 25; gas
source 2 (GS2), 25; turbo temperature (TEM), 0 °C; entrance po-
tential (EP), 10 V; declustering potential (DP), 20 V; scan range,
m/z = 300–1500. Each sample for MS (ESI) was prepared by a
1:100 dilution of a dichloromethane solution (5 mg/mL) of the tar-
By raising further the [Au(StBu)(PEt3)]/2a ratio there is
no significant change in the NMR and mass spectra of the
solution, thus supporting the idea that the molar ratio 2 has
a special meaning in terms of the mechanistic requirements.
Conclusions
The results of this study show that the complexes 2 in-
deed react as a sort of [Au(phosphane)]+ fragment sup- get compound with methanol, and it was infused by a syringe
Eur. J. Inorg. Chem. 2009, 545–553
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
551

P. Diversi, A. Cuzzola, F. Ghiotto
FULL PAPER
pump Harvard Mod. 22 (Harvard Apparatus, Holliston, MA,
USA).
Reaction of [Au2(StBu)(PEt3)2][BF4] (2b) with PEt3: [Au2(StBu)-
(PEt3)2][BF4] (2b) (0.086 g, 0.107 mmol) was treated with PEt3 in
CH2Cl2 (0.89 , 0.23 mL, 0.21 mmol) to give:
Reaction of [Au(Cl)(L)] with L (L = PMe3, PEt3, PtBu3). Formation
of [Au(Cl)(L)2]: The complexes were prepared according to the pro-
cedure described in the literature.[5a,6b] [Au(Cl)(PtBu3)2] has not
been reported before.
[Au(PEt3)2][BF4] (3b): Off white crystals. Yield: 0.045 g (80%).
1
[Au(StBu)(PEt3)2]: Colourless oil. Yield: 0.045 g (79%). H NMR
(C6D6): δ = 1.89 (s, 9 H, StBu), 1.15 (dq, JP,H = 8, JH,H = 7.7 Hz,
12 H, PCH2), 0.75 (dt, JP,H = 17.6, JH,H = 7.7 Hz, 18 H, PCMe)
ppm. 31P NMR (C6D6): δ = 38.22 ppm. MS (ESI+): m/z (%) =
405 (17) [Au(StBu)(PEt3) + H]+, 433 (92) [Au(PEt3)2]+, 718 (100)
[Au2(StBu)(PEt3)2]+, 1005 (37) [Au3(StBu)2(PEt3)2]+.
[Au(Cl)(PtBu3)2]: White microcrystals were obtained from a dichlo-
romethane solution. Yield: 0.370 g (85%). C24H54AuClP2 (637.06):
calcd. C 45.3, H 8.5; found C 45.7, H 8.6. 1H NMR (200 MHz,
3
CDCl3, 25 °C): δ = 1.60 (dd, JP,H = 7 Hz, PtBu3) ppm. 31P NMR
Reaction of [Au2(StBu)(PtBu3)2][BF4] (2c) with PtBu3: [Au2(StBu)-
(PtBu3)2][BF4] (2c) (0.165 g, 0.17 mmol) was treated in CH2Cl2
with PtBu3 (0.082 mL, 0.34 mmol) to give:
(200 MHz, CDCl3, 25 °C): δ = 98.89 (s) ppm.
Reaction of [Au(Cl)(L)2] (L = PMe3, PEt3, PtBu3) with Ag[BF4].
Formation of [Au(L)2][BF4] (L = 3a, 3b, 3c): All the complexes were
prepared according to the same procedure adopted for the reaction
of [Au(Cl)(PMe3)2] with Ag[BF4], which is reported as an example.
[Au(PtBu3)2][BF4] (3c): White crystals. Yield: 0.114 g (100%).
[Au(StBu)(PtBu3)] (1c): Colourless oil. Yield: 0.081 g (98%). 1H
NMR (C6D6): δ = 1.88 (s, 9 H, StBu), 1.09 (d, JP,H = 13.2 Hz, 27
H, PtBu), 1–1.4 (br. m) ppm. 31P NMR (C6D6): δ = 91.44 (s), 96.13
(s), 63.22 (s), 62.55 (s), 61.57 (s) ppm. MS (ESI+): m/z (%) = 489
(24) [Au(StBu)(PtBu3) + H]+, 601 (68) [Au(PtBu3)2]+, 887 (100)
[Au2(StBu)(PtBu3)2]+.
Ag[BF4] (0.097 g, 0.5 mmol) was added to
a solution of
[Au(Cl)(PMe3)2] (0.100 g, 0.276 mmol) in dichloromethane
(10 mL), and the mixture was stirred in the dark for 2 h. The pre-
cipitate of AgCl was removed by filtration. The solvent was then
evaporated, and the solid residue was washed with pentane
(2ϫ10 mL), dried in vacuo and crystallized from dichloromethane
as white microcrystals. Yield: 0.214 g (98%). C6H18AuBF4P2
(435.93): calcd. C 16.5, H 4.2; found C 16.7, H 4.1. 1H NMR
Reaction of [Au2(StBu)(dppe)][BF4] (2d) with dppe: [Au2(StBu)-
(dppe)][BF4] (2d) (0.065 g, 0.067 mmol) was treated with dppe
(40.1 mg, 0.10 mmol) to give:
[Au(dppe)2][BF4]: White crystals. Yield: 0.070 g (97%). 1H NMR
(CD2Cl2): δ = 2.44 (br. s, 8 H, PCH2), 7.0–7.4 (br. m, 40 H, PPh)
ppm. 31P NMR (CD2Cl2): δ = 21.96 ppm. MS (ESI+): m/z (%) =
993 (100) [Au(dppe)2]+.
[Au2(StBu)2(dppe)] (1d): Colourless oil. Yield: 0.063 g (97%). 1H
NMR (C6D6): δ = 1.91 (s, 18 H, StBu), 2.51 (br. s, 4 H, PCH2),
6.8–7.5 (br. m, 20 H, PPh2) ppm. 31P NMR (C6D6): δ = 30.29 ppm.
MS (ESI+): m/z (%) = 881 (100) [Au4(StBu)2(dppe)2]2+, 993 (25)
[Au2(StBu)2(dppe) + Na]+, 1024 (58) [Au5(StBu)3(dppe)2]2+, 1167
(25) [Au3(StBu)2(dppe)]+.
2
(200 MHz, CDCl3, 25 °C): δ = 1.66 (t, JP,H = 4.0 Hz, PMe3) ppm.
31P NMR (200 MHz, CDCl3, 25 °C): δ = 8.79 (s) ppm. MS (ESI+):
m/z = 349 [Au(PMe3)2]+.
Complex 3b: Light-grey microcrystals were obtained from a dichlo-
romethane solution. Yield: 0.253 g (97%). C12H30AuBF4P2
(520.09): calcd. C 27.7, H 5.8; found C 27.6, H 5.6. 1H NMR
(200 MHz, CD2Cl2, 25 °C): δ = 1.21 (br. m, 18 H, Me), 1.97 (br.
m, 12 H, CH2) ppm. 31P NMR (200 MHz, CD2Cl2, 25 °C): δ =
47.30 (s) ppm. MS (ESI+): m/z = 433 [Au(PEt3)2]+.
Complex 3c: Light-grey microcrystals were obtained from a dichlo-
romethane solution. Yield: 0.340 g (99%). C24H54AuBF4P2
(688.41): calcd. C 41.9, H 7.9; found C 41.2, H 7.7. 1H NMR
(200 MHz, CD2Cl2, 25 °C): δ = 1.55 (dd, 3JP,H = 7.0 Hz, Me) ppm.
31P NMR (200 MHz, CD2Cl2, 25 °C): δ = 97.00 (s) ppm. MS
(ESI+): m/z = 601 [Au(PtBu3)2]+.
Reaction of [Au2(StBu)(L2)][BF4] (L = PMe3, PEt3, PtBu3, PPh3)
with [Au(StBu)(L)]: The reaction of [Au4(StBu)2(PMe3)4][BF4]2 (2a)
with [Au(StBu)(PMe3)] (1a) is reported as an example. A solution
of 2a (0.008 g, 11.0ϫ10–3 mmol) in CD2Cl2 (1 mL) was placed in
an NMR tube and 1H NMR, 31P NMR and mass spectra were
recorded. The desired amount of [Au(StBu)(PMe3)] (1a) was then
added, and, after dissolution of the solid, the resulting solution was
left for 1 h to reach equilibrium. This solution was then re-exam-
Reaction of [Au2(StBu)(L2)][BF4] (L = PMe3, PEt3, PtBu3, PPh3;
L2 = dppe) with Phosphanes: The reaction of [Au4(StBu)2(PMe3)4]-
[BF4]2 (2a) with PMe3 is described as an example. [Au4(StBu)2-
(PMe3)4][BF4]2 (0.122 g, 0.168 mmol) was dissolved in dichloro-
methane (5 mL) and added to a toluene solution of trimethylphos-
phane (1 , 0.17 mL, 0.17 mmol). After being stirred for ca. 1 h,
the solution was added dropwise whilst stirring to pentane
(100 mL), immediately giving a white solid. After stirring for
15 min, the solid was collected by filtration and dried. This was
washed with pentane (2ϫ5 mL), dried and identified as [Au-
(PMe3)2][BF4] (3a). Yield: 70 mg (96%). 1H NMR (CDCl3): δ =
1
ined by H NMR and 31P NMR spectroscopic and MS analyses.
Preparation of [Au2(StBu)(PMe3)(PEt3)][BF4]:
A solution of
Ag[BF4] (0.097 g, 0.50 mmol) in ethanol (5 mL) was added slowly
at 0 °C in the darkness to [Au(Cl)(PMe3)] (0.145 g, 0.50 mmol) in
CH2Cl2 (5 mL). The solution was stirred in the darkness for a fur-
ther 30 min and was then filtered through Celite and dried. The
residue was dissolved in CH2Cl2 (5 mL), and the solution was
added dropwise into a solution of CH2Cl2 (5 mL) containing
1.66 (br. s, 18 H, PMe3) ppm. 31P NMR (CDCl3): δ = 8.96 ppm. [Au(StBu)(PEt3)] (1b) (0.202 g, 0.50 mmol) in the darkness whilst
MS (ESI+): m/z (%) = 349 (100) [Au(PMe3)2]+. The pentane solu-
tion obtained after separation of 3a was concentrated to dryness
in vacuo leaving a white solid. This was dissolved in pentane and
crystallized by cooling the solution to –20 °C. White crystals of
[Au(StBu)(PMe3)] (1a) were obtained. Yield: 50 mg (82%). 1H
NMR (C6D6): δ = 1.91 (s, 9 H, StBu), 0.54 (d, JP,H = 9.9 Hz, 9 H,
PMe) ppm. 31P NMR (C6D6): δ = 0.72 ppm. MS (ESI+): m/z (%)
stirring. The stirring was continued for 30 min, after which the
solution was concentrated to ca. 3 mL, and pentane was added,
layer on layer. A light sensitive solid was obtained, which was
washed with pentane (3ϫ3 mL), and the solvent was removed in
vacuo. Yield: 0.29 g (72%). H NMR (200 MHz, CD2Cl2, 25 °C):
δ = 1.58 (s, 18 H, StBu), 1.66 (d, JP,H = 11.0 Hz, 18 H, PMe3), 1.95
1
(dq, JP,H = 9.5, JH,H = 7.7 Hz, 12 H, PCH2Me), 1.23 (dt, JP,H
=
= 349 (45) [Au(PMe3)2]+, 363 (15) [Au(StBu)(PMe3) + H]+, 635 19.0, JH,H = 7.7 Hz, 18 H, PCH2Me) ppm. 31P NMR (CD2Cl2,
(100) [Au4(StBu)2(PMe3)4]2+, 761 (15 not assigned), 921 (29) 25 °C): δ = 38.07 (s), –1.96 (s) ppm. MS (ESI+): m/z (%) = 349
[Au6(StBu)4(PMe3)4]2+
.
(71) [Au(PMe3)2]+, 391 (50) [Au(PMe3)(PEt3)]+, 433 (26) [Au-
552
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 545–553

Chemistry of Polynuclear Cationic Gold(I) Thiolates
(PEt3)2]+, 635 (58) [Au4(StBu)2(PMe3)4]2+, 677 (100) [Au2(StBu)-
(PMe3)(PEt3)]+, 719 (71) [Au(StBu)(PEt3)2]+. C13H33Au2BF4P2S
(764.15): calcd. C 20.4, H 4.4; found C 20.1, H 4.1.
S. Al Baker, W. E. Hill, J. Chem. Soc., Dalton Trans. 1986,
1297–1300.
[6] a) H. Schmidbaur, R. Franke, Chem. Ber. 1972, 105, 2985–
2997; b) K. Angermaier, E. Zeller, H. Schmidbaur, J. Or-
ganomet. Chem. 1994, 472, 371–376; c) C. Hollatz, A. Schier,
H. Schmidbaur, Chem. Ber./Recueil 1997, 130, 1333–1338.
[7] J. M. Lopez-de-Luzuriaga, A. Sladek, H. Schmidbaur, J. Chem.
Soc., Dalton Trans. 1996, 4511–4512.
Supporting Information (see footnote on the first page of this arti-
cle): Additional figure showing the VT NMR spectra for the reac-
tion between [Au(PEt3)2][StBu] and [Au(StBu)(PEt3)2] and table re-
porting the MS (ESI) data of the solutions containing [Au4(StBu)2-
(PMe3)4][BF4]2 and [Au(StBu)(PEt3)].
[8] A. Bayler, A. Bauer, H. Schmidbaur, Chem. Ber./Recueil 1997,
130, 115–118.
[9] M. Preisenberger, A. Schier, H. Schmidbaur, J. Chem. Soc.,
Dalton Trans. 1999, 1645–1650.
[10] a) W. Bensch, M. Prelati, W. Ludwig, J. Chem. Soc., Chem.
Commun. 1986, 1762–1763; b) C. M. Che, H. L. Kwong, C. K.
Poon, V. W. W. Yam, J. Chem. Soc., Dalton Trans. 1990, 3215–
3219; c) A. Burini, R. Galassi, B. R. Pietrosi, G. Rafaiani, J.
Organomet. Chem. 1996, 519, 161–167.
Acknowledgments
We thank Ceramvetro (Florence) for the generous gift of gold.
[1] a) F. Scherbaum, A. Grohmann, B. Huber, C. Krüger, H.
Schmidbaur, Angew. Chem. Int. Ed. Engl. 1988, 27, 1544–1546;
b) H. Schmidbaur, Gold Bull. 1990, 23, 11–21; c) H. Schmid-
baur, Chem. Soc. Rev. (London) 1995, 24, 391–400; d) H.
Schmidbaur, Gold Bull. 2000, 33, 3–10; e) H. Schmidbaur, Na-
ture 2001, 413, 31–32; f) R. J. Puddephatt, Coord. Chem. Rev.
2001, 216, 313–332; g) P. Pyykkö, Angew. Chem. Int. Ed. 2004,
43, 4412–4456.
[2] a) A. Sladek, H. Schmidbaur, Chem. Ber. 1995, 128, 907–909;
b) A. Sladek, K. Angermaier, H. Schmidbaur, Chem. Commun.
1996, 1959–1960; c) J. Chen, T. Jiang, G. Wei, A. A. Mohamed,
C. Homrighausen, J. A. Krause Bauer, A. E. Bruce, M. R. M.
Bruce, J. Am. Chem. Soc. 1999, 121, 9225–9226; d) A. A. Mo-
hamed, A. E. Bruce, M. R. M. Bruce, Met.-Based Drugs 1999,
6, 233–238; e) A. A. Mohamed, H. E. Abdou, J. Chen, A. E.
Bruce, M. R. M. Bruce, Commun. Inorg. Chem. 2002, 23, 321–
334; f) A. A. Mohamed, J. Chen, A. E. Bruce, M. R. M. Bruce,
J. A. Krause Bauer, D. T. Hill, Inorg. Chem. 2003, 42, 2203–
2205; g) J. Chen, A. A. Mohamed, H. E. Abdou, J. A.
Krause Bauer, J. P. Fackler Jr, A. E. Bruce, M. R. M. Bruce,
Chem. Commun. 2005, 1575–1577.
[3] a) P. Diversi, F. Balzano, A. Cuzzola, F. Ghiotto, G. Uccello-
Barretta, P. Salvadori, Atti del XXII Convegno SCI 2006, INO-
P-91, Firenze, Settembre 2006; b) A. Battisti, O. Bellina, P. Di-
versi, S. Losi, F. Marchetti, P. Zanello, Eur. J. Inorg. Chem.
2007, 865–875.
[4] a) A. Cuzzola, P. Diversi, F. Ghiotto, P. Salvadori, MASSA
2007, Italian annual meeting on mass spectrometry, Lucca, 2–5
settembre 2007, OR-3, p. 35; b) F. Balzano, A. Cuzzola, P. Di-
versi, F. Ghiotto, G. Uccello-Barretta, Eur. J. Inorg. Chem.
2007, 5556–5562.
[11] a) C. Kowala, J. M. Swan, Aust. J. Chem. 1966, 19, 547–554;
b) A. A. Isab, A. L. Hormann, D. T. Hill, D. E. Griswold, M. J.
DiMartino, C. F. Shaw III, Inorg. Chem. 1989, 28, 1321–1326;
c) M. M. El-Etri, W. M. Scovell, Inorg. Chem. 1990, 29, 480–
484; d) M. C. Gimeno, A. Laguna, Chem. Rev. 1997, 97, 511–
522.
[12] a) W. Beck, S. Tadros, Z. Anorg. Allg. Chem. 1970, 375, 231–
237; b) H. Otto, H. Werner, Chem. Ber. 1987, 120, 97–104; c)
H. M. Sakhawat, H. M. Latif, A. A. Abderehman, Transition.
Met. Chem. 1990, 15, 120–125; d) Z. Assefa, R. J. Staples, J. P.
Fackler, Inorg. Chem. 1994, 33, 2790–2798; e) . S. Zeltner, S.
Jelonek, J. Sieler, R. M. Olk, Eur. J. Inorg. Chem. 2001, 1535–
1541.
[13] a) E. Zeller, A. Schier, H. Schmidbaur, Z. Naturforsch., Teil B
1994, 49, 1243–1245; b) A. Sladek, H. Schmidbaur, Z. Natur-
forsch., Teil B 1995, 50, 859–863.
[14] a) S. J. Berners-Price, M. A. Mazid, P. J. Sadler, J. Chem. Soc.,
Dalton Trans. 1984, 969–974; b) S. J. Berners-Price, P. J. Sadler,
Inorg. Chem. 1986, 25, 3822–3827; c) J. L. Davidson, W. E.
Lindsell, K. J. McCullough, C. H. McIntosh, Organometallics
1995, 14, 3497–3506; d) R. C. Bott, The electrochemical oxi-
dation of metallic gold and application to the synthesis of gold(I)
tertiary phosphine complexes 1998, chapter 4 (Ph. D. Degree
Thesis, Griffith University, Brisbane).
[15] R. T. Sane, P. R. Kulkarni, Curr. Sci. 1974, 43, 42.
[16] a) R. Colton, K. L. Harrison, Y. A. Mah, J. C. Traeger, Inorg.
Chim. Acta 1995, 231, 65–71; b) F. Caruso, M. Rossi, C.
Opazo, C. Pettinari, J. Argent. Chem. Soc. 2004, 92, 119–124.
[17] F. Caruso, M. Rossi, J. Tanski, C. Pettinari, F. Marchetti, J.
Med. Chem. 2003, 46, 1737–1742.
[18] A. K. Al-Sa’ady, C. A. McAuliffe, R. V. Parish, J. A. Sand-
bank, Inorg. Synth. 1985, 23, 191.
[5] a) M. J. Mays, P. A. Vergnano, J. Chem. Soc., Dalton Trans.
1979, 1112–1115; b) C. B. Colburn, W. E. Hill, C. A. McAuliffe,
R. V. Parish, J. Chem. Soc., Chem. Commun. 1979, 218–219; c)
Received: September 15, 2008
Published Online: January 7, 2009
Eur. J. Inorg. Chem. 2009, 545–553
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
553