The effect of hard and soft donors on structural motifs in (isocyanide)gold(I) complexes

Article abstract of DOI:10.1002/1522-2675(20011017)84:10<3216::AID-HLCA3216>3.0.CO;2-7

Treatment of the (isocyanide)gold(I) species LAuCl (L =′BuNC, 2,6-Me₂C₆H₃NC) with 4-mercaptobenzoic acid in the presence of NaOMe yields the complexes [Au(4-SC₆H₄CO₂H)L] in good yield. Reaction of LAuCl with 2-HSQn (Qn = quinoline) and 2-HSPy (Py = pyridine) under the same conditions provides the thiolato compounds [Au(2-SQn)L] and [Au(2-SPy)L], respectively. A structural investigation of the pyridylthiolato compound revealed chains of molecules with alternating medium and long Au-Au interactions. Treatment of this compound with HBF₄ results in the cationic species [Au(2-HSPy)(2,6-Me₂C₆H₃NC)]⁺ as the BF₄^- salt. The same product is obtained on reaction of [AuCl(2,6-Me₂C₆H₃NC)] with AgOTf followed by HSPy. Treatment of the gold(I) halide compounds LAuCl (L =′BuNC, 2,6-Me₂C₆H₃NC) with potassium 1,3,4-thiadiazole-2,5-dithiolate (KSSSK) leads to the isolation of dinuclear thiolatogold complexes [(AuL)₂(SSS)]. These products go on to form insoluble polymers through loss of isocyanide on standing in solution. A single crystal of [{Au(′BuNC)}₂(SSS)] was obtained and the subsequent structural analysis revealed one of the most complicated networks known based solely on aurophilic interactions. A good comparison to the 'soft' S-donation of the thiolato ligands was provided by the synthesis of a number of nitratogold(I)complexes with the anion bound through the 'hard' O-donor. Reaction of ⁱPrNC and CyNC with Au(tht)Cl provided the complexes [AuCl(ⁱPrNC)] and [AuCl(CyNC)], respectively. These compounds were found to yield the respective nitrato species [Au(NO₃)ⁱPrNC)] and [(Au(NO₃)(CyNC)] on treatment with AgNO₃. The nitrato complexes yielded single crystals enabling a structural investigation to be carried out. While [Au(NO₃)(CyNC)] has a more conventional structure with dimers aligned into strings with alternating short and long aurophilic bonding, [Au(NO₃)(ⁱPrNC)] has a unique structure based on strings of alternating, corner-sharing Au₆ and Au₈ units with short Au-Au contacts in edge-sharing Au₃ triangles.

Full text of DOI:10.1002/1522-2675(20011017)84:10<3216::AID-HLCA3216>3.0.CO;2-7

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Helvetica Chimica Acta ± Vol. 84 (2001)
The Effect of Hard and Soft Donors on Structural Motifs in
(Isocyanide)gold(I) Complexes
by James D. E. T. Wilton-Ely, Hendrik Ehlich, Annette Schier, and Hubert Schmidbaur*
Anorganisch-chemisches Institut der Technischen Universität München, Lichtenbergstrasse 4,
D-85747 Garching
In memoriam Luigi M. Venanzi
Treatment of the (isocyanide)gold(I) species LAuCl (L ˆ tBuNC, 2,6-Me2C6H3NC) with 4-mercaptoben-
zoic acid in the presence of NaOMe yields the complexes [Au(4-SC6H4CO2H)L] in good yield. Reaction of
LAuCl with 2-HSQn (Qn ˆ quinoline) and 2-HSPy (Py ˆ pyridine) under the same conditions provides the
thiolato compounds [Au(2-SQn)L] and [Au(2-SPy)L], respectively.
A structural investigation of the
pyridylthiolato compound revealed chains of molecules with alternating medium and long Au Au interactions.
‡
Treatment of this compound with HBF4 results in the cationic species [Au(2-HSPy)(2,6-Me2C6H3NC)] as the
BF4 salt. The same product is obtained on reaction of [AuCl(2,6-Me2C6H3NC)] with AgOTf followed by HSPy.
Treatment of the gold(I) halide compounds LAuCl (L ˆ tBuNC, 2,6-Me2C6H3NC) with potassium 1,3,4-
thiadiazole-2,5-dithiolate (KSSSK) leads to the isolation of dinuclear thiolatogold complexes [(AuL)2(SSS)].
These products go on to form insoluble polymers through loss of isocyanide on standing in solution. A single
crystal of [{Au(tBuNC)}2(SSS)] was obtained and the subsequent structural analysis revealed one of the most
complicated networks known based solely on aurophilic interactions. A good comparison to the ꢀsoftꢁ S-
donation of the thiolato ligands was provided by the synthesis of a number of nitratogold(I)complexes with the
anion bound through the ꢀhardꢁ O-donor. Reaction of iPrNC and CyNC with Au(tht)Cl provided the complexes
[AuCl(iPrNC)] and [AuCl(CyNC)], respectively. These compounds were found to yield the respective nitrato
species [Au(NO3)iPrNC)] and [(Au(NO3)(CyNC)] on treatment with AgNO3. The nitrato complexes yielded
single crystals enabling a structural investigation to be carried out. While [Au(NO3)(CyNC)] has a more
conventional structure with dimers aligned into strings with alternating short and long aurophilic bonding,
[Au(NO3)(iPrNC)] has a unique structure based on strings of alternating, corner-sharing Au6 and Au8 units with
short Au Au contacts in edge-sharing Au3 triangles.
Introduction. ± Isocyanidegold compounds have attracted increasing attention over
the last decade due to their potential in a number of applications. Their use as MOCVD
precursors for the deposition of Au films was first explored by Puddephatt and co-
workers [1] in 1987. Since then, it has been shown that isocyanide gold alkynyls and
halides have an important role to play in recent advances in the field of liquid crystal
applications [2]. The observation that (isocyanide)gold(I) halides are able to form
liquid crystalline phases is thought to arise from the presence of weak Au Au
interactions. Such interactions are facilitated by the low steric bulk of the isocyanide
ligand which allows ꢀrod-likeꢁ molecules to be designed, as illustrated in the structures
of examples such as [Au(CꢀCSiMe3)(tBuNC)] [3] and [Au(MeNC)2]CF3SO3 [4].
Much research has been centered on the preparation and investigation of the properties
of (acetylide)(isocyanide)gold complexes [5]. For example, complexes of the general
formula [Au(4-RC6H4CꢀC)(tBuNC)] (R ˆ NO2, C6H4NO2, etc.) [6] have been
investigated in reference to their nonlinear optical properties. The possibility of

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combining the isocyanide and acetylide functionalities was elegantly demonstrated by
Puddephatt with a series of acetylide (alkynyl)(isocyanoaryl)gold(I) complexes of the
form [Au(CꢀCtBu)(CNC6H4CꢀCH)] [7].
The linear, sterically unencumbered nature of the isocyanide ligand leads to the
observation of short Au Au contacts in the solid state, as displayed in the cyano
isocyanide example [AuCN(MeNC)] [8] as well as the complexes mentioned above.
The related binuclear cyano species [Au2(CN)2(dmb)] (dmb ˆ 1,8-diisocyano-p-
menthane) shows surprisingly short Au Au interactions in addition to interesting
luminescence behavior [9]. More recently, the isocyanide ligand has been employed to
stabilize AuI complexes with weakly coordinating anions such as [AuNO3(RNC)] (R ˆ
t
tBu, 2,6-Me2C6H3) [10]. The Bu derivative was found to be an effective precursor for
the deposition of Au on iron oxide in order to form a catalytically active surface for the
low temperature oxidation of CO [11].
‡
If one considers the enormously rich chemistry accessible from the [Au(PR3)]
‡
synthon, it is reasonable to expect that the analogous [Au(RNC)] fragment should
also lead to a similarly fascinating range of compounds. Due to the planar geometry of
‡
species such as [Au(PhNC)] , markedly different structures can be expected for these
complexes. As mentioned above, in acetylide gold chemistry, the difference in steric
requirements of the donor ligand (isocyanide vs. phosphine) has been exploited in the
design of ꢀrod-likeꢁ molecules which are able to pack in different ways to those
observed for phosphinogold complexes.
The application of gold thiolate species in fields as diverse as medicine [12], thin-
film technology [13], and ceramics [14] has led to great interest in complexes of the
general type [Au(SR)(PR3)] (R ˆ alkyl, aryl) whether in mono- or polymetallic
systems. As yet, relatively little effort has been expended in the field of (isocyanide)-
gold(I) thiolate chemistry [15]. A recent report from Bachman et al. [16] concentrated
on compounds of the form [Au(SPh)(RNC)] which were found to be unstable with
respect to isocyanide loss and formation of a highly luminescent modification of
[Au(PhS)]n. This is in direct contrast to the behavior of the complexes [Au(SR')(PR3)]
(R, R' ˆ alkyl, aryl) which show a greater stability [17].
Following recent work in this group on isocyanide thiocyanate complexes of AuI
[18], we have turned our attention to the coordination and structural chemistry of
‡
thiolates with the [Au(RNC)] fragment. In a past report [15], we detailed the
preparation and structural characterization of the thiosalicylate complexes [Au(2-
SC6H4CO2H)(RNC)] (R ˆ tBu, 2,6-Me2C6H3) which exhibited both Au Au contacts
and H-bonding interactions. These complexes are soluble in THF and show no
tendency toward decomposition through loss of the isocyanide ligand. This is also in
direct contrast to the observation by Bachman et al. [16] mentioned above. In order to
probe the factors governing this differing reactivity, we decided to generate a number of
novel (isocyanide)gold(I) thiolate examples by reaction of a range of thiols with
(isocyanide)gold halide precursors. This report expands upon preliminary work
detailed in a communication [19].
As mentioned above, recent work performed both in this group [10a] and by others
[10b] has explored the area of gold nitrate chemistry. The (isocyanide)gold(I) nitrates
included here serve to explore the effect of strongly electronegative substituents on the
stability and structure of such species.

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Results and Discussion. ± Thiolato Complexes. Addition of one mole equivalent of
4-sulfanylbenzoic acid to the (isocyanide)gold(I) halide compounds [AuCl(RNC)]
(R ˆ tBu, 2,6-Me2C6H3) in the presence of NaOMe results in clean formation of the
complexes [Au(4-SC6H4CO2H)(RNC)] [R ˆ tBu, 1; 2,6-Me2C6H3, 2] (Scheme 1). The
presence of the isocyanide ligand was indicated by strong nÄ(CN) absorptions at
2220 cm 1 (1) and 2207 cm 1 (2). Further confirmation was provided by the resonances
in the 1H-NMR spectrum. The H-atoms of the Me groups in 1 give rise to a sharp singlet
at 1.58 ppm, whereas the isocyanide ligand in 2 displays resonances at 2.48 (s), 7.24 (d)
and 7.38 (t) ppm with J(H,H) ˆ 7.7 Hz. Similar patterns were found for all complexes
discussed hereafter. In addition to these, resonances for the C6H4 unit were observed at
7.44, 7.65 (AB, J(H,H) ˆ 8.4 Hz) and 10.96 (CO2H) ppm. We have reported the
preparation of the analogous complexes with carboxyl substitution at C(2). In view of
recent work from these laboratories [15] demonstrating the radical structural changes
brought about by changes in the substitution pattern of this ligand, it was unfortunate
that no single crystals of 1 and 2 of suitable quality could be obtained.
Scheme 1
OH
O
RNC Au
S
R = tBu, 2,6-Me2C6H3
1
2
i)
[AuCl(RNC)]
ii)
iii)
N
N
RNC Au
S
RNC Au
S
R = tBu, 2,6-Me2C6H3
R = tBu, 2,6-Me2C6H3
5
6
3
4
i) 2-HSC6H4CO2H, NaOMe: ii) 2-HSQn, NaOMe. iii) 2-HSPy, NaOMe.
The ligands quinoline-2-thiol (2-HSQn) [20] and pyridine-2-thiol (2-HSPy) [21]
have been shown to coordinate well to (phosphino)gold(I) fragments and such
compounds with 2-HSPy have been investigated in the context of anti-tumor activity
[22]. This made them attractive ligands with which to examine the coordination ability
of the (isocyanide)gold(I) fragment. The planar, sterically undemanding nature of
these isocyanides also makes their compounds suited to the formation of Au Au

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contacts. The reactions of these ligands with the isocyanide complexes [AuCl(RNC)]
(R ˆ tBu, 2,6-Me2C6H3) proceed smoothly to provide [Au(2-SQn)(RNC)] (R ˆ tBu, 3;
2,6-Me2C6H3, 4) and [Au(2-SPy)(RNC)] (R ˆ tBu, 5; 2,6-Me2C6H3, 6) as pale yellow
microcrystalline solids (Scheme 1). Characteristic spectroscopic data were observed for
the isocyanide ligands. The thiolate groups gave rise to a number of resonances in the
1H-NMR spectrum. For 5, two doublets are observed at 7.54 and 7.74 ppm (J(H,H) ˆ
8.7 Hz) for the H-atoms in the 3- and 6-position of the Py ring whereas the H C(5) and
H
C(4) protons give rise to triplets at 7.32 and 7.61 ppm (J(H,H) ˆ 7.7 Hz ) . The
resonances arising from the quinoline-2-thiolate ligand proved more difficult to assign
individually.
Treatment of the complex [Au(2-SPy)(2,6-Me2C6H3NC)] (6) with HBF4 leads to
the protonation of the Py group at the N-atom to provide [Au(2-HSPy)(2,6-
Me2C6H3NC)]OTf (7). The same product is accessible from the direct reaction of
[AuCl(2,6-Me2C6H3NC)] with pyridine-2-thiol in the presence of AgOTf (Scheme 2).
This second route actually leads more cleanly and in higher yields to complex 7. The
1H-NMR spectrum of 7 reveals a new broad resonance for the protonated Py group at
1
12.50 ppm. A shift to lower frequency (2213 to 2217 cm ) is observed in the nÄ(CN)
absorption in the solid-state IR spectrum consistent with the assumption that the
positive charge is delocalized throughout the molecule and not isolated on the Py N-
atom. The presence of the TfO counterion is confirmed by microanalytical data.
Scheme 2. Preparation of Complex 7 through Direct Reaction with Thiol or via Protonation
H
N
HSPy
2,6-Me2C6H3NC Au Cl
2,6-Me2C6H3NC Au
S
AgOTf
[7]OTf/BF4
N
HBF4
2,6-Me2C6H3NC Au
S
6
Treatment of a solution of 2 mol-equiv. of [AuCl(RNC)] (R ˆ tBu, 2,6-Me2C6H3) in
CH2Cl2 with one mole equivalent of potassium 1,3,4-thiadiazole-2,5-dithiolate,
(KSSSK) in MeOH affords the colorless products [{Au(tBuNC)}2(SSS)] (R ˆ tBu, 8;
2,6-Me2C6H3, 9) along with an insoluble, yellow material (Scheme 3). 8 and 9 are
soluble in CH2Cl2 and CHCl3, but insoluble in pentane. The 13C-NMR spectra show the
Scheme 3. Preparation of Bimetallic Examples 8 and 9
RNC Au
S
SK
S
2 [AuCl(RNC)]
- 2 KCl
N
N
S
KS
N
N
RNC Au
S
R = tBu, 2,6-Me2C6H3
8
9

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expected resonances for the isocyanide ligand along with a singlet at 166.2 ppm
attributable to the SSS unit. A strong nÄ(CN) absorption for the isocyanide ligand in 8 is
1
observed in the IR spectrum at 2232 cm , whereas two bands (due to solid-state
1
splitting effects) are seen at 2213 and 2207 cm for 9. In the FAB-MS, the parent ions
‡
M are detected at m/z ˆ 710 for 8 and m/z ˆ 804 for 9.
The compounds are stable when stored at low temperature, however, in contrast to
the other results reported here, even microcrystalline powders of 8 and 9 show loss of
tBuNC, a fact clearly indicated by the distinct isocyanide odor of the samples. Clear
solutions in chlorocarbon solvents gradually form a yellow precipitate which cannot
then be redissolved. Some of this yellow insoluble material was also observed in the
t
initial stage of the preparation of the BuNC complex. Microanalytical data1) for the
product indicate partial loss of the isocyanide ligand after several weeks at 208 leading
to formation of the polymeric disulfide [Au2(SSS)]n. This process (shown in Scheme 4)
can be accelerated by heating compound 8 under reflux in anaerobic conditions for 3 h
in toluene or by heating the solid under vacuum. This is a similar degradation to that
noticed recently by Bachman et al. [16]. Intensifying the thermal conditions further
results in an even deposition of Au metal.
Scheme 4. Polymerization and Decomposition Pathway for 8
N
N
HEAT
Au0
[Au2C2N2S3]n
KS
SK
S
- 2 tBuNC
2 [AuCl(tBuNC)]
HEAT
- 2 KCl
N
N
CNR
Au
CNR
CNR
Au
CNR
Au
S
S
S
Au
CNR
Au
S
Au
CNR
S
S
S
S
S
R = tBu
N
N
N
N
8
Nitrato Complexes. Direct reaction of the free isocyanide ligands with (tetrahy-
drothiophene)gold(I) chloride results in the isolation of the new isocyanide complexes
[AuCl(iPrNC)] (10) and [AuCl(CyNC)] (11) in good yield (Scheme 5). Strong
1
1
absorptions in the solid state IR spectrum (2257 cm , 10; 2259 cm , 11) confirm
coordination of the isocyanide ligands. The FAB-MS of complexes 10 and 11 failed to
‡
display molecular ions but did show abundant fragmentations for [2M Cl] ions. Such
di(gold)chloronium cations bound by phosphino ligands have been shown to exist in
the corresponding BF4 , ClO4 , and AsF6 salts [23].
1
)
Almost total elimination of the isocyanide ligand was observed. The conditions necessary to remove the
remaining approx. 0.1 mole of tBuNC resulted in sample decomposition and the appearance of metallic Au.
Anal. calc. for [C2Au2N2S3]n ´ 0.1 C5H9N: C 5.45, H 0.16, N 5.34; found: C 5.62, H 0.20, N 5.27.

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Scheme 5. Preparation of Nitrato Complexes and Their Precursors
RNC
RNC Au Cl
R = C3H7
C6H11
Cl
Au
S
10
11
- tht
AgNO3
- AgCl
ONO2 R = C3H7
C6H11
RNC Au
12
13
Treatment of 10 and 11 with AgNO3 in MeOH yields the complexes
[Au(NO3)(iPrNC)] (12) and [Au(NO3)(CyNC)] (13), respectively (Scheme 5). Solid
1
state IR spectroscopic data confirm the retention of the isocyanide ligand (2263 cm ,
1
12; 2267 cm , 13), the shift to higher frequency reflecting the electronic change
brought about by the replacement of chloro for nitrato ligand. Microanalytical data
confirm the empirical composition, as does the observation of molecular ions in the MS
(CI) at m/z ˆ 328 (12) and 369 (13). After even relatively short periods (few hours) in
solution, deposition of elemental Au is observed. This is not noted for the precursors 10
and 11 and is in accordance with the weaker coordination ability of NO3 relative to
that of Cl .
Together, the nitrato complexes 12 and 13 and the species detailed above permit a
comparison of the effects related to the contrasting ꢀhardꢁ (NO3 ) and ꢀsoftꢁ (thiolate)
donors to be drawn. Single crystals of both complexes 12 and 13 were obtained enabling
this comparison to be extended to a structural investigation.
Structural Discussion. ± Crystals of 6 (obtained from CH2Cl2/pentane) are triclinic,
Å
of space group P1, with Z ˆ 2 formula units in the unit cell. The asymmetric unit
consists of one molecule with a slightly bent main axis comprising the atoms
C(11) N(1) C(1) Au(1) S(1) (Fig. 1). The xylyl and the Py rings are virtually
coplanar. The N-atom of the Py group (N(2)) is in a Z-shaped orientation regarding the
Au(1) S(1) C(21) N(2) conformation, i.e., it is directed away from the Au-atom.
Two molecules are arranged in pairs parallel and head-to-tail with the Au(1) Au(1')
distance of 3.589(1) Š representing the shortest contact between the two molecules
which are related by a center of inversion (Fig. 2). These dimers form strings of
molecules with longer intermolecular Au(1) Au(1'') contacts of 4.037(1) Š, in which
all Au-atoms lie on a line with alternating distances and only slight puckering. No arene
stacking is discernible either within each chain or between chains as shown in Fig. 3.
This arrangement is not uncommon in the structural chemistry of (isocyanide)gold
complexes. The literature has several examples of related organizational principles
[4][10][16][18b]. It should be noted that the soft donor character of the thiolato ligand
does not induce a significant shortening of the aurophilic contacts [24]. As with most
‡
other [Au(RNC)] complexes, the Au Au contacts remain around the upper limit of
the range accepted for aurophilic bonding (2.9 ± 3.6 Š). The contact between dimers is
beyond the sum of the Van der Waals radii. Therefore metal metal interactions should
not be considered the determining structural factor in the shape of the string-like
arrangement of molecules.

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Fig. 1. Molecular structure of 6 (ORTEP, 50% probability ellipsoid). Selected bond lengths [Š] and angles [8]:
Au(1) C(1) 1.970(9), Au(1) S(1) 2.267(2), C(1) N(1) 1.13(1), N(1) C(11) 1.41(1), S(1) C(21) 1.740(8);
C(1) Au(1) S(1) 174.0(2), Au(1) S(1) C(21) 108.9(3), N(1) C(1) Au(1) 175.5(8), C(1) N(1) C(11)
175.7(9).
Fig. 2. Chain of dimeric molecules in the structure of 6 with intra-dimer distance Au(1) Au(1B) 3.589(1) Š and
inter-dimer contacts Au(1) Au(1A) 4.037(1) Š
Crystals of 8 are monoclinic, of space group P21/n, with Z ˆ 12 molecular
(dinuclear) units in the unit cell. The asymmetric unit contains three independent
molecules of similar geometry, one of which is shown in Fig. 4 as a representative
example. Both the molecular geometry and the packing (Fig. 5) have been described in

Helvetica Chimica Acta ± Vol. 84 (2001)
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Fig. 3. Projection along the chains of molecules in the crystal of 6. There is no arene stacking discernible.
a preliminary publication [19], and so the discussion will not be duplicated here. The
structure, however, is included and will be referred to later as a reference for the three
new structures. It is important to note that the structure of 8 displays double-strings of
Au-atoms running parallel within the layers of the structure held together by relatively
short Au Au contacts (3.0447(3) ± 3.3476(4) Š). All Au Au distances of neighboring
metal atoms are thus well within the range for appreciable Au Au interactions. The
dinuclear character of the building blocks and the closely interwoven structure seem to
support aurophilic bonding even for molecules with isocyanide ligands which are
classified as strong s-donors, but poor p-acceptors.
Crystals of [Au(NO3)(CyNC)] (13) are monoclinic, space group P21/n, with Z ˆ 4
formula units in the unit cell. The isocyanide ligand has the expected structure with a
chair conformation for the six-membered ring. The individual complex molecules
display a slightly bent five-atom axis C(11) N(1) C(1) Au(1) O(1) of standard
bond lengths which are organized in centrosymmetrical dimers in which two monomers
are coupled parallel and head-to-tail through a short Au Au contact of 3.1839(4) Š
(Fig. 6). The dimers are arranged in strings with long Au Au distances of 3.9432(4) Š
between them. The resulting chain of Au-atoms with alternating distances exhibits a
zig-zag puckering. The NO3 groups are slightly twisted away from the center of the
dimer to which they are attached. This brings one of the terminal O-atoms (O(2)) closer
to a Au-atom of the neighboring dimer (at 3.4991(7) Š). Due to the long distance,

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Fig. 4. One of the three independent molecules in the structure of the dinuclear compound 8. The remaining two
complexes have similar dimensions and conformations. Selected data were included in a preliminary
communication [19].
Fig. 5. Arrangement of the dinuclear complex molecules of 8 (Fig. 4) in a layer structure
however, the interactions will probably contribute very little to the lattice energy. The
structure of 13 is of considerable interest because it shows that the introduction of an
anionic ligand with a hard O donor atom causes the aurophilic bonds in the dimers to

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Fig. 6. Chain of dimeric molecules in the structure of 13 with intra-dimer distances Au Au' 3.1839(4) Š and
inter-dimer contacts Au Au'' 3.9432(4) Š. Selected bond lengths [Š] and angles [8]: Au C(1) 1.874(7),
Au O(1) 2.005(5), N(1) C(1) 1.111(9), N(1) C(11) 1.410(7), N(2) O(1) 1.243(8); C(1) Au O(1)
172.3(2), C(1) N(1) C(11) 178.0(7), N(2) O(1) Au 114.0(4), N(1) C(1) Au 177.7(6).
become shorter compared to those in 6, where the soft donor atom of the thiolate anion
leads to a much larger Au Au separation. It should also be noted that there is no steric
influence imposed by the Cy groups which appear to be accommodated strain-free at
the periphery of the chains (Fig. 6).
i
Å
Crystals of [Au(NO3)( PrNC)] (12) are triclinic, of space group P1, with Z ˆ 12
formula units in the unit cell. The asymmetric unit contains six independent molecules
with similar dimensions, one of which is shown in Fig. 7. The axes C
N C Au O are
almost perfectly linear with the usual bond lengths. These molecules are assembled into
exceedingly complex chains, in which the Au-atoms form two different types of planar
units sharing corners: In a suitable projection (Fig. 8), centrosymmetric units of six Au-
atoms are discernible in which two atom triples Au(1) Au(2) Au(3) sit next to each
other (head-to-tail, Au(1) Au(2) Au(3) 173.53(1)8) to form a set of four edge-
sharing triangles. This set of Au-atoms is found to share its terminal Au-atoms Au(3)
with another set of eight Au-atoms with two chains Au(3) Au(4) Au(5) Au(6) also
paired head-to-tail to form six edge-sharing Au triangles. The angles Au(3) Au(4)-
Au(5) (177.97(1)8) and Au(4) Au(5) Au(6) (175.1(1)8) are both close to linear.
The ꢀraft-likeꢁ Au6 and Au8 platforms are virtually planar as shown in the three
projections provided in Figs. 8a ± f.
The edges of all Au triangles are well within the range of aurophilic bonding;
between 3.0578(5) Š for Au(5) Au(5') and 3.4672(4) Š for Au(5) Au(6). The atoms

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Fig. 7. Molecular structure of one of the six independent molecules of 12 (ORTEP, 50% probability ellipsoids, H-
atoms omitted). Selected bond lengths [Š] and angles [8]: Au(1) C(1) 1.92(1), Au(1) O(11) 2.048(6),
C(1) N(11) 1.12(1), N(11) C(11) 1.49(1); O(11) Au(1) C(1) 174.1(3), Au(1) C(1) N(11) 176.6(9),
C(1) N(11) C(11) 175(1), Au(1) O(11) N(12) 114.9(4).
Au(1) and Au(6) maintain three close Au contacts, while Au(2), Au(3), Au(4), and
Au(5) entertain their four closest Au neighbors.
The molecular axes of neighboring [Au(NO3)(iPrNC)] complexes in a given unit
are roughly parallel but, through the tilting of the units against each other, the ligands
point in different directions. Because of this variation in orientation of the isocyanide
and NO3 groups, the Au core of one chain is shielded on all sides and well separated
from neighboring strings (Fig. 9). The lattice contains no solvent molecules.
i
The complicated structure of the PrNC complex 12 comes as a surprise after the
relatively simple pattern found for the CyNC complex 13, and even more so since both
complexes have the same NO3 ligand. It should be noted that if one were to ꢀtrimꢁ the
C-atoms C(3) C(5) of the Cy substituent, one would, in effect, have an iPr group. The
i
steric requirements of an Pr group in the coordination environment of the Au-atoms
are therefore comparable to that of the Cy group. The changes in steric bulk should
have a major effect only in the periphery of the molecular chains, and yet the packing of
the molecules 12 and 13 is entirely different. It appears that the efficient packing of the
molecular chains (i.e., the space-filling accommodation of the iPr/Cy and NO3 groups)
is perhaps more significant than commonly expected. The pattern of the weak
aurophilic interactions is therefore influenced significantly by these packing forces.
Conclusion. ± The structures of a number of new (isocyanide)gold(I) complexes
with both hard and soft co-ligands have been determined. The range of supramolecular
structural motifs encountered demonstrates the fascinating and unpredictable nature of
structures determined by aurophilic interactions. Two of the structures reported here (8
and 12) can be considered among the most complicated observed for molecules bound
exclusively through intermetallic contacts. The (isocyanide)gold thiolate and nitrate
‡
compounds demonstrate the versatility of the (AuRNC) fragment which, compared to
‡
the ubiquitous (AuPR3) species, has been much neglected in the field of (iso-
cyanide)gold(I) chemistry.

Helvetica Chimica Acta ± Vol. 84 (2001)
3227
f
c
b
e
a
d

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Helvetica Chimica Acta ± Vol. 84 (2001)

Helvetica Chimica Acta ± Vol. 84 (2001)
3229
Experimental Part
General. The experiments were carried out routinely in air. Potassium 1,3,4-thiadiazole-2,5-dithiolate
(KSSSK), 4-sulfanylbenzoic acid, pyridine-2-thiol and quinoline-2-thiol were obtained commercially. The
compounds [AuCl(tBuNC)] [25], [AuCl(2,6-Me2C6H3NC)] [26], Au(tht)Cl (tht ˆ tetrahydrothiophene) [26],
isopropylisocyanide [27], and cyclohexylisocyanide [27] were prepared following literature procedures. IR
Spectra: Perkin-Elmer 1600 Series FT-IR Spectrometer; in KBr/Nujol; in cm 1. NMR: JEOL GX-400
spectrometer using deuterated solvents with the usual standards at 258; d in ppm, J(H,H) in Hz. MS: Varian
MAT311A instrument (FAB, 4-nitrophenylmethanol); m/z (rel. %).
[Au(4-SC6H4CO2H)(tBuNC)] (1). A soln. of [AuCl(tBuNC)] (120 mg, 0.38 mmol) in CH2Cl2 (10 ml) was
treated dropwise with a soln. of 4-sulfanylbenzoic acid (60 mg, 0.39 mmol) and NaOMe (23 mg, 0.43 mmol) in
MeOH (5 ml). The mixture was stirred for 1 h, and solvent was removed. The crude product was triturated in
H2O (20 ml) to remove NaCl and excess NaOMe. A colorless product was collected, washed with H2O (10 ml)
and pentane (10 ml), and dried. Yield: 100 mg (61%). IR: 2220 (nÄ(CN)). 1H-NMR ((D8)THF): 1.58 (s, 3 Me);
‡
‡
7.44, 7.65 (AB, J ˆ 8.4, C6H4); 10.96 (br. s, CO2H). FAB-MS: 714 (33, [M ‡ tBuNC] ), 434 (100, M ), 377 (100,
[M tBu] ), 363 (30, [Au(tBuNC)2] ). Anal. calc. for C12H14AuNO2S: C 33.27, H 3.26, N 3.23; found: C 32.75,
‡
‡
H 3.00, N 2.77.
[Au(4-SC6H4CO2H)(2,6-Me2C6H3NC)] (2). As for 1, with [AuCl(2,6-Me2C6H3NC)] (90 mg, 0.25 mmol),
4-sulfanylbenzoic acid (38 mg, 0.25 mmol), and NaOMe (15 mg, 0.28 mmol). Yield: 82 mg (69%). IR: 2207
(nÄ(CN)). 1H-NMR ((D8)THF): 2.48 (s, 2 Me); 7.24 (d, J ˆ 7.7, H C(3), H C(5) of C6H3); 7.38 (t, J ˆ 7.7,
‡
H
C(4) of C6H3); 7.49, 7.68 (AB, J ˆ 8.4, C6H4), 10.90 (br. s, CO2H). FAB-MS: 482 (6, M ). Anal. calc. for
C16H14AuNO2S: C 39.93, H 2.93, N 2.91; found: C 39.44, H 2.88, N 2.84.
[Au(2-SQn)(tBuNC)] (3). A soln. of [AuCl(tBuNC)] (50 mg, 0.16 mmol) in CH2Cl2 (10 ml) was treated
dropwise with a soln. of quinoline-2-thiol (26 mg, 0.16 mmol) and NaOMe (10 mg, 0.19 mmol) in MeOH (5 ml).
The mixture was stirred for 1 h, and solvent was removed. The crude solid was dissolved in CH2Cl2 (10 ml) and
filtered through diatomaceous earth. Et2O (15 ml) was added to the filtrate to precipitate a pale yellow product
which was washed with Et2O (10 ml) and dried. The product was found to become only sparingly soluble in
chlorinated solvents after precipitation from CH2Cl2/pentane. Yield: 43 mg (62%). IR: 2222 (nÄ(CN)). 1H-NMR
(CD2Cl2): 1.56 (s, 3 Me); 7.33 (t, J ˆ 8.0, 1 H of SQn); 7.53 (d, J ˆ 8.0, 1 H of SQn); 7.63 (d, J ˆ 8.5, 1 H of SQn);
‡
‡
‡
7.75 (d, J ˆ 8.5, 1 H of SQn). FAB-MS: 720 (28, [2M SQn] ), 441 (44, M ), 385 (100, [M tBu] ). Anal. calc.
for C14H15AuN2S: C 38.19, H 3.43, N 6.36; found: C 38.70, H 3.50, N 6.21.
[Au(2-SQn)(2,6-Me2C6H3NC)] (4). As for 3, with [AuCl(2,6-Me2C6H3NC)] (50 mg, 0.14 mmol), quino-
line-2-thiol (22 mg, 0.14 mmol) and NaOMe (8 mg, 0.15 mmol). Yield: 48 mg (72%). IR: 2205 (nÄ(CN)).
1H-NMR (CD2Cl2): 2.46 (s, 2 Me); 7.15 (d, J ˆ 7.4, H C(3), H C(5) of Ph); 7.38 (t, J ˆ 7.4, 1 H of SQn); 7.40
(t, J ˆ 7.4, H C(4) of Ph); 7.54 (d, J ˆ 8.7, 1 H of SQn); 7.59 (d, J ˆ 7.5, 1 H of SQn); 7.66 (d, J ˆ 7.5, 1 H of SQn);
‡
‡
‡
7.82 (d, J ˆ 8.7, 1 H of SQn). FAB-MS: 816 (33, [2M SQn] ), 490 (100, M ), 358 (60, [M C9H9N] ). Anal.
calc. for C18H15AuN2S: C 44.27, H 3.10, N 5.74; found: C 44.50, H 3.23, N 6.01.
[Au(2-SPy)(tBuNC)] (5). A soln. of [AuCl(tBuNC)] (50 mg, 0.16 mmol) in CH2Cl2 (10 ml) was treated
dropwise with a soln. of pyridine-2-thiol (18 mg, 0.16 mmol) and NaOMe (10 mg, 0.19 mmol) in MeOH (5 ml).
After stirring for 1 h, solvent was removed and the crude solid dissolved in CH2Cl2 (10 ml) and filtered through
diatomaceous earth. Et2O (15 ml) was added to the filtrate to precipitate a colorless product which was washed
with Et2O (10 ml) and dried. The product was found to become only sparingly soluble in chlorinated solvents
after precipitation from CH2Cl2/pentane. Yield: 31 mg (50%). IR: 2247, 2228 (nÄ(CN)). 1H-NMR (CD2Cl2): 1.56
(s, 2 Me); 7.32 (t, J ˆ 7.7, H C(5) of Py); 7.54 (d, J ˆ 8.7, H C(3) of Py); 7.61 (t, J ˆ 7.7, H C(4) of Py); 7.74
‡
‡
‡
(d, J ˆ 8.7, H C(6) of Py). FAB-MS: 391 (20, M ), 335 (16, [M tBu] ), 308 (8, [M tBuNC] ). Anal. calc. for
C10H13AuN2S: C 29.14, H 3.26, N 6.47; found: C 28.74, H 3.00, N 6.74.
[Au(2-SPy)(2,6-Me2C6H3NC)] (6). As for 5, with [AuCl(2,6-Me2C6H3NC)] (50 mg, 0.14 mmol), pyridine-
2-thiol (15 mg, 0.14 mmol) and NaOMe (8 mg, 0.15 mmol). Yield: 52 mg (86%). IR: 2213 (nÄ(CN)). 1H-NMR
(CD2Cl2): 2.43 (s, 2 Me); 6.91 (t, J ˆ 7.1, H C(5) of Py); 7.15 (d, J ˆ 7.6, H C(4), H C(5) of Ph); 7.32 (t, J ˆ 7.6,
H
C(4) of Ph); 7.41 (d, J ˆ 6.0, H C(3) of Py); 7.44 (t, J ˆ 7.1, H C(4) of Py). FAB-MS: 766 (20, [2M
‡ ‡ ‡ ‡
SPy] ), 438 (100, M ), 328 (9, [M SPy] ), 308 (28, [M CNX] ). Anal. calc. for C14H13AuN2S ´ 1.5 CH2Cl2:
C 36.23, H 2.94, N 5.83; found: C 36.18, H 3.18, N 5.84.
[Au(2-HSPy)(2,6-Me2C6H3NC)]OTf (7). a) (50 mg, 0.19 mmol) was added to a stirred soln. of [AuCl(2,6-
Me2C6H3NC)] (70 mg, 0.19 mmol) in THF (20 ml) at 08. After 5 min stirring, during which the formation of Au
colloid was observed, pyridine-2-thiol (21 mg, 0.19 mmol) was added and the mixture stirred for a further
25 min. Solvent was removed and the crude product was dissolved in CH2Cl2 (10 ml) and filtered through

3230
Helvetica Chimica Acta ± Vol. 84 (2001)
diatomaceous earth. Et2O (15 ml) was added to the filtrate to precipitate a pale yellow product which was
washed with Et2O (10 ml) and dried. Yield: 81 mg (72%).
b) A soln. of HBF4 in Et2O (4 drops) was added to a stirred soln. of [Au(2-SPy)(2,6-Me2C6H3NC)] (50 mg,
0.114 mmol) in CH2Cl2/MeOH (20 ml, 1:1). After stirring for 20 min, solvent was removed, and the product
extracted into CH2Cl2 (2 Â 10 ml). The volume of the extracts was reduced to ca. 5 ml and Et2O (20 ml) added to
precipitate the pale yellow product. Yield: 38 mg (65%). IR: 2217 (nÄ(CN)). 1H-NMR (CD2Cl2): 2.50 (s, 2Me);
7.21 (d, J ˆ 7.7, H C(3), H C(5) of Ph); 7.31 (t, J ˆ 6.9, H C(5) of Py); 7.38 (t, J ˆ 7.7, H C(4) of Ph); 7.78
(d, J ˆ 7.4, H C(3) of Py); 7.86 (t, J ˆ 6.9, H C(4) of Py); 8.42 (d, J ˆ 7.4, H C(6) of Py); 12.50 (br., NH).
‡
‡
‡
FAB-MS: 765 (2, [2M SPy] ), 439 (100, M ), 328 (4, [M SPy] ). Anal. calc. for C15H14AuF 3N2O3S2: C 30.62,
H 2.40, N 4.76; found: C 30.61, H 2.22, N 4.56.
[{Au(tBuNC)}2(SSS)] (8). A soln. of KSSSK (36 mg, 0.16 mmol) in MeOH (5 ml) was added dropwise to a
stirred soln. of [AuCl(tBuNC)] (100 mg, 0.32 mmol) in CH2Cl2 (15 ml). After stirring for 2 h, a fine yellow
precipitate was present. Solvent was removed, and the crude product dissolved in CH2Cl2 (20 ml) and filtered
through diatomaceous earth to remove the yellow solid. After concentration of the soln. to ca. 10 ml, pentane
(20 ml) was carefully added to precipitate a colorless solid. This was washed with pentane (20 ml) and dried.
Yield: 79 mg (70%). IR: 2232 (nÄ(CN)). 1H-NMR (CDCl3): 1.58 (s, Me). 13C-NMR (CD2Cl2): 166.2 (s, C2N2S3);
‡
140.7 (br. s, tBuNC); 59.0 (s, CMe3); 29.5 (s, Me). FAB-MS: 710 (6, M ). Anal. calc. for C12H18Au2N4S3: C 20.34,
H 2.56, N 7.91; found: C 20.15, H 2.37, N 7.84.
[{Au(2,6-Me2C6H3NC)}2(SSS)] (9). A soln. of KSSSK (31 mg, 0.14 mmol) in MeOH (5 ml) was added
dropwise to a stirred soln. of [AuCl(2,6-Me2C6H3NC)] (100 mg, 0.28 mmol) in CH2Cl2 (15 ml). After stirring for
2 h, a substantial amount of a fine, yellow precipitate was present. Solvent was removed and the crude product
dissolved in CH2Cl2 (20 ml) and filtered through diatomaceous earth to remove the yellow solid. After
concentration of the soln. to ca. 10 ml, pentane (20 ml) was carefully added to precipitate a colorless solid. This
was washed with pentane (20 ml) and dried. Yield: 43 mg (39%). IR: 2213, 2207 (nÄ(CN)). 1H-NMR
((D8)THF): 2.44 (s, 2 Me); 7.17 (d, J ˆ 7.5, H C(3), H C(5) of Ph); 7.34 (t, J ˆ 7.6, H C(4) of Ph). FAB-MS:
‡
804 (5, M ). Anal. calc. for C20H18Au2N4S3: C 29.86, H 2.26, N 6.96; found: C 29.43, H 2.38, N 7.21.
[AuCl(iPrNC)] (10). A suspension of Au(tht)Cl (2.20 g, 6.86 mmol) in CH2Cl2 (20 ml) was treated with
iPrNC (1 ml, 10.10 mmol) to give a clear soln. After stirring for 1 h, solvent and other volatiles were removed
under vacuum. The residue was redissolved in 5 ml of CH2Cl2. Colorless crystals of the product were obtained by
the diffusion of pentane vapor into the soln. in a closed system at 208. Yield: 1.76 g (85%). IR: 2257 (nÄ(CN)).
1H-NMR (CDCl3): 4.10 (sept., J ˆ 7.0, CHMe2), 1.50 (d, J ˆ 7.0, 2 Me). 13C-NMR (CDCl3): 132.8 (br. s, CN);
‡
‡
‡
49.5 (s, CHMe2); 22.2 (s, Me). FAB-MS: 799 (3, [3M Cl] ), 567 (100, [2M Cl] ), 335 (7, [Au(iPrNC)2] ),
‡
266 (4, [M Cl] ). Anal. calc. for C4H7AuClN: C 15.92, H 2.34, N 4.65; found: C 15.77, H 2.49, N 4.64.
[AuCl(CyNC)] (11). As for 10, with Au(tht)Cl (2.00 g, 6.24 mmol) and CyNC (1 ml, 8.00 mmol) in 20 ml of
CH2Cl2. Yield: 1.85 g (87%). Colorless microcrystals. IR: 2259 (nÄ(CN)). 1H-NMR (CDCl3): 3.88, 1.98, 1.76, 1.43,
(4m, 1 :2 :4 :4 H of Cy). 13C-NMR (CDCl3): 55.0, 31.7, 24.5, 22.5 (4s, Cy) (CN resonance not observed). FAB-
‡
‡
MS: 647 (70, [2M Cl] ), 415 (22, [Au(CyNC)2] ). Anal. calc. for C7H11AuClN: C 24.61, H 3.25, N 4.10; found:
C 24.61, H 3.17, N 4.06.
[Au(NO3)(iPrNC)] (12). (Isopropylisocyanide)gold(I) chloride (10; 1.00 g, 3.32 mmol) was dissolved in
CH2Cl2 (30 ml) and added slowly to a stirred soln. of AgNO3 (0.70 g, 4.12 mmol) in MeOH (30 ml) at 788.
After 1 h, the solvent was removed under vacuum, and the residue dissolved in CH2Cl2 (10 ml). Crystallization
as for 10. Yield: 0.60 g (55%). IR: 2263 (nÄ(CN)). 1H-NMR (CDCl3): 4.16 (sept., J ˆ 7.0, CHMe2); 1.49 (d, J ˆ 7.0,
‡
2 Me). 13C-NMR (CDCl3): 122.2 (br. s, CN); 50.2 (s, CHMe2); 21.9 (s, Me). CI-MS: 328 (23, M ). Anal. calc. for
C4H7AuN2O3: C 14.64, H 2.15, N 8.54; found: C 14.63, H 2.04, N 8.60.
[Au(NO3)(CyNC)] (13). As for 12, with (cyclohexylisocyanide)gold(I) chloride (11; 0.50 g, 1.46 mmol)
and AgNO3 (0.30 g, 1.77 mmol) in CH2Cl2/MeOH (10 ml :15 ml). Yield: 0.33 g (61%). Colorless crystals. IR:
2267 (nÄ(CN)). 1H-NMR (CDCl3): 3.96, 1.95, 1.70, 1.36 (4m, 1:2 :4 :4 H of Cy). 13C-NMR (CDCl3): 122.2 (br. s,
‡
CN); 55.7, 31.2, 24.3, 22.6 (4s, Cy). CI-MS: 369 (2M ). Anal. calc. for C7H11AuN2O3: C 22.84, H 3.01, N 7.61;
found: C 23.23, H 2.90, N 7.66.
Crystallography. Specimens of suitable quality and size were mounted on the ends of quartz fibers in
F 06206R oil and used for intensity data collection on a Nonius DIP2020 diffractometer, employing graphite-
monochromated MoKa radiation. Intensity data for all compounds were corrected for absorption effects
(DELABS). The structures were solved by a combination of direct methods (SHELXS-97) and difference-
Fourier syntheses and refined by full matrix least-squares calculations on F2 (SHELXL-97). The thermal motion
was treated anisotropically for all non-H-atoms. All H-atoms were calculated and allowed to ride on their parent
atoms with fixed isotropic contributions (Uiso(fix) ˆ 1.5  Ueq of the attached C-atom). Further information on

Helvetica Chimica Acta ± Vol. 84 (2001)
3231
crystal data, data collection and structure refinement are summarized in the Table2). Important interatomic
distances and angles are given in the corresponding figure captions.
Table 1. Crystal Data, Data Collection, and Structure Refinement for 6, 8, 12 and 13.
[Au(SPy)(2,6-Me2C6H3NC)] [{Au(tBuNC)}2(SSS)] [Au(NO3)(iPrNC)] [Au(NO3)(CyNC)]
(6)
(8)
(12)
(13)
Crystal data
Formula
Mr
C14H13AuN2S
438.29
C12H18Au2N4S3
708.42
C4H7AuN2O3
328.08
C7H11AuN2O3
368.14
Crystal system
Space group
a [Š]
b [Š]
c [Š]
triclinic
P1
monoclinic
P21/n
13.9440(1)
18.4157(2)
21.9061(2)
90
95.244(1)
90
5601.7(1)
2.520
triclinic
P1
monoclinic
P21/n
6.1624(1)
23.4436(4)
6.2240(1)
90
101.581(1)
90
880.9(1)
2.776
Å
Å
7.5855(3)
7.9758(3)
12.6376(7)
101.812(2)
90.751(3)
116.418(3)
665.5(1)
2.187
10.9194(1)
12.3663(1)
18.0092(3)
77.739(1)
85.929(1)
71.342(1)
2251.5(1)
2.904
a [8]
b [8]
g [8]
V [Š3]
1calc [g cm
Z
3
]
2
12
12
4
F(000)
m(MoKa) [cm
412
111.92
3888
160.29
1776
195.54
680
166.68
1
]
Data collection
T [8]
130
130
130
130
Measured reflections
Unique reflections
25633
2370 [Rint ˆ 0.040)
161073
12224 [Rint ˆ 0.060]
77449
37734
9135 [Rint ˆ 0.048] 2063 [Rint ˆ 0.063]
Refinement
Refined parameters
Final R values [I ˆ 2s(I)]
R1
163
568
541
118
0.0490
0.0357
0.0333
0.0396
wR2
0.1464
0.0801
0.0824
0.1089
Weighting schemea)
a ˆ 0.1165
a ˆ 0.00
a ˆ 0.00
a ˆ 0.0654
b ˆ 0.81
b ˆ 34.60
b ˆ 7.55
b ˆ 5.50
a) wR2 ˆ {[Sw(Fo2 Fc2)2]/S[w(Fo2)2]}1/2; w ˆ 1/[s2(Fo2) ‡ (ap)2 ‡ bp]; p ˆ (Fo2 ‡ 2Fc2)/3.
Support of this work by the Deutsche Forschungsgemeinschaft, the Volkswagenstiftung, the Alexander von
Humboldt Stiftung (J. D. E. T. W.-E.), and by the Fonds der Chemischen Industrie is gratefully acknowledged.
The authors are also indebted to Degussa AG and Heraeus GmbH for the donation of chemicals.
REFERENCES
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2
)
Crystallographic data (excluding structure factors) for the structures reported in this paper have been
deposited with the Cambridge Crystallographic Data Centre as deposition No. CCDC 172317 ± 172320.
Copies of the data can be obtained, free of charge, on application to the CCDC, 12 Union Road, Cambridge
CB2 1EZ (fax: ‡ 44(1223)336 033; e-mail: deposit@ccdc.cam.ac.uk).

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Helvetica Chimica Acta ± Vol. 84 (2001)
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Received June 15, 2001