Aurophilicity in gold(I) thiosemicarbazone clusters

Article abstract of DOI:10.1039/c1dt11680k

The reaction of the phosphine thiosemicarbazone ligands HLPH and HLPMe with Au(i) ions yields the gold complexes [Au₃(HLPH)₂Cl ₂]Cl·2MeOH (1·2MeOH) and [Au₂(HLPMe)Cl ₂] (2). The structures determined by X Ray diffraction, [Au ₃(HLPH)₂Cl₂]Cl·4MeOH (1·4MeOH) and [Au₂(HLPMe)Cl₂]₂ (2), are the first examples of gold(i) thiosemicarbazone clusters showing aurophilicity. The structure of the trinuclear cation 1 contains the Au(1) atom located in an inversion centre, being connected to another gold(i) atom, Au(2), through a phosphino thiosemicarbazone molecule which acts as a S,P-bridging ligand. Additionally, every gold(i) atom in the trinuclear cation 1 assembles into trinuclear linear cluster units by means of close gold-gold interactions, being connected through the crystal cell in a 2D zigzag mode. The crystal structure of [Au₂(HLPMe)Cl₂]₂ (2) contains one discrete molecule [(AuCl)₂(HLPMe)] in the asymmetric unit, which is further assembled into tetranuclear [(AuCl)₂(HLPMe)]₂ units by means of close gold-gold interactions. Both clusters are highly luminescent in solution.

Full text of DOI:10.1039/c1dt11680k

View Article Online / Journal Homepage / Table of Contents for this issue
Dynamic Article Links
Dalton
Transactions
Cite this: Dalton Trans., 2012, 41, 1363
www.rsc.org/dalton
PAPER
Aurophilicity in gold(I) thiosemicarbazone clusters†
Alfonso Castin˜eiras and Rosa Pedrido*
Received 5th September 2011, Accepted 19th October 2011
DOI: 10.1039/c1dt11680k
The reaction of the phosphine thiosemicarbazone ligands HLPH and HLPMe with Au(I) ions yields
the gold complexes [Au3(HLPH)2Cl2]Cl·2MeOH (1·2MeOH) and [Au2(HLPMe)Cl2] (2). The structures
determined by X Ray diffraction, [Au3(HLPH)2Cl2]Cl·4MeOH (1·4MeOH) and [Au2(HLPMe)Cl2]2 (2),
are the first examples of gold(I) thiosemicarbazone clusters showing aurophilicity. The structure of the
trinuclear cation 1 contains the Au(1) atom located in an inversion centre, being connected to another
gold(I) atom, Au(2), through a phosphino thiosemicarbazone molecule which acts as a S,P-bridging
ligand. Additionally, every gold(I) atom in the trinuclear cation 1 assembles into trinuclear linear cluster
units by means of close gold–gold interactions, being connected through the crystal cell in a 2D zigzag
mode. The crystal structure of [Au2(HLPMe)Cl2]2 (2) contains one discrete molecule [(AuCl)2(HLPMe)]
in the asymmetric unit, which is further assembled into tetranuclear [(AuCl)2(HLPMe)]2 units by means
of close gold–gold interactions. Both clusters are highly luminescent in solution.
1b).10 More recently, another S2-dimer gold(I) complex has been
reported, [Au(H2Plhexim)]2Cl2·S8·6H2O, but this complex was
isolated after reduction of the expected gold(III) complex by the
thiosemicarbazone thione group (Scheme 1c).11
Introduction
Polynuclear gold(I) complexes have received much interest
in recent decades mainly due to their intriguing structural
dispositions,1 their rich photoluminescent properties2 or even
their potential applications in very different fields such as
pharmaceutics,3 optical sensors,4 chemosensing,5 etc. Heteroleptic
phosphine thiolato gold(I) complexes can be considered an
important class of polynuclear compounds, because the presence
of several P–Au–S structural units in their structures facilitates
the formation of Au ◊ ◊ ◊ Au interactions. These contacts, which
are comparable in strength with hydrogen bonding,6 have been
recognized as a major motif for the design of functional molecular
and supramolecular arrangements, both in the solid state and in
solution.7 While playing a significant role in the supramolecular
aggregation pattern of gold(I) compounds, the existence of au-
rophilic interactions is not a requirement for luminescence, though
they may influence the emission of phosphino gold(I) thiolates.8
The use of thiosemicarbazone ligands as thiolate scaffolds to
stabilize gold(I) ions in the presence of phosphines is a quite
recent event. Thus in 2006, Casas et al. published a [P,S]-monomer
gold(I) compound derived from K3 vitamin-thiosemicarbazone
ligand and triphenylphosphine as co-ligand (Scheme 1a).9 In
2006 Lobana et al. reported a S2-monomer gold(I) complex
exclusively derived from 3-nitrobenzaldehyde thiosemicarbazone,
which was isolated as a homoleptic thiosemicarbazonate complex,
despite its synthesis in the presence of triphenylphosphine (Scheme
Recently, we have started to use phosphino thiosemicarbazone
ligands in order to achieve M(I) (M = Cu, Ag, Au) homoleptic
calcogenide compounds. These ligands were previously employed
to obtain Ni(II),12 Au(III)13 and Pt(II)14 complexes only. Func-
tionalization of a thiosemicarbazide skeleton with a phosphine
head by means of a simple iminic condensation allowed us to
isolate different Ag(I) clusters,15 Cu(I) monomers,16 and two Au(I)
dinuclear complexes, the cation [Au(HLPPh)]2 (Scheme 1d),17
2+
and the chloro-cation [Au2(HLPEt)4Cl]+ (Scheme 1e).16 None of
these gold(I) compounds exhibit aurophilicity,6 since they do not
display any Au–Au interaction.
Owing to the scantiness of reports on thiosemicarbazone
Au(I) complexes and with the aim of exploring if the terminal
substituents of the thiosemicarbazone branch play any role in the
stoichiometry, the nuclearity and the photophysical properties of
the resultant compounds, we decide to further explore the coordi-
native behaviour of phosphino thiosemicarbazone ligands towards
gold(I) ions. In this occasion we have studied the interaction
of the 4-N unsubstituted and 4-N-methyl substituted phosphino
thiosemicarbazone ligands (Scheme 2). As a result of our studies,
we report herein the first cases of Au(I) thiosemicarbazone cluster
compounds showing aurophilicity.
Results and discussion
Departamento de Qu´ımica Inorga´nica, Facultade de Farmacia, Campus
Vida, Universidade de Santiago de Compostela, Santiago de Compostela,
15782, Spain. E-mail: rosa.pedrido@usc.es
Chemistry
† Electronic supplementary information (ESI) available. CCDC reference
numbers 808092–808095. For ESI and crystallographic data in CIF or
other electronic format see DOI: 10.1039/c1dt11680k
The ligands HLPH and HLPMe (Scheme 2) were synthe-
sized by condensation of 2-diphenylphosphinebenzaldehyde with
This journal is
The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 1363–1372 | 1363
©

View Article Online
Scheme 1 Gold(I) complexes with thiosemicarbazone ligands.
electrolyte.18 The maintenance of the structure of the complexes
in solution is further supported by ESI+ mass spectrometry. The
mass spectrum of 1·2MeOH exhibits the fragments [Au(HLPH)]+,
[Au2(HLPH)2]2+ and [Au3(HLPH)2]3+, thus confirming the pro-
posed stoichiometry in solution. For 2 we have identified the
[Au(HLPMe)]+, [Au2(HLPMe)2]2+ and [Au3(HLPH)2]3+ fragments.
The latter could correspond to species polymerized by means of
Au ◊ ◊ ◊ Au interactions.
The 1H NMR spectra for the gold(I) complexes 1·2MeOH
and 2 show the characteristic NH thiosemicarbazone signals, but
shifted downfield with respect to the free ligands, which points
towards a neutral character of the ligands in these complexes.
The displacement experienced by these signals (ca. 0.7 ppm
in 1·2MeOH and 0.2 ppm in 2) could be attributed to the
establishment of hydrogen-bond interactions in solution.19 The
imine signal hardly changes position in the spectra, which rules
out the coordination of the imine nitrogen to the soft gold(I)
centres. The 31P spectra exhibit single signals at 29.7 (1·2MeOH)
and 29.9 (2) ppm respectively, depicting the equivalence of the
phosphine groups in these complexes. These signals are very
significantly shifted downfield compared with the corresponding
free ligands (~40 ppm), being indicative of coordination through
to the phosphorus atom. These values compare well with those
found in polynuclear gold(I) complexes having [PCl] linear kernels
and showing aurophilic interactions.20
Scheme 2 Ligands HLPR (R = H, Me).
thiosemicarbazide and 4-N-methylthiosemicarbazide respectively,
following the published procedure.15–17 Crystallization of the
ethanolic mother-liquors gave rise to good quality crystals of both
phosphino thiosemicarbazone ligands.
The synthesis of the gold(I) complexes was performed by
treatment of a solution of Au(tdg)Cl (tdg = thiodiglycol = 2,2¢-
thiobis(ethanol) with the ligands HLPH and HLPMe. The two
complexes were readily characterized by elemental analysis, IR,
mass spectrometry (ESI+), 1H and31P NMR spectroscopy, the pro-
posed formulae being [Au3(HLPH)2Cl2]Cl·2MeOH (1·2MeOH)
and [Au2(HLPMe)Cl2] (2). The complexes are air- and light-
stable and soluble in common organic solvents. Partial evap-
oration of the solvent afforded the crystalline products
[Au3(HLPH)2Cl2]Cl·4MeOH (1·4MeOH) and [Au2(HLPMe)Cl2]
(2).
Structural studies
The presence of n(NH) bands in the range 3400–3200 cm-1
confirms the coordination of the neutral ligands HLPH and
HLPMe to the Au(I) centres. The IR absorptions attributable to
the C S group have undergone low energy shifts with respect to
the free ligands, this being indicative of the C S bond weakening
after coordination. We also have observed that the n(C–N + C–
C) bands have experienced some displacement in all complexes,
probably due to the establishment of hydrogen-bond interactions,
because coordination through the nitrogen atoms is unlikely.
The molar conductance value of 62.2 mS cm-1, measured for
the gold(I) complex 1·2MeOH is in agreement with a 1 : 1 elec-
trolyte compound. For complex 2, the low value of conductance
experimentally measured of 13.2 mS cm-1, corresponds to a non-
Crystal structures of HLPH and HLPMe. The molecular
structures of the ligands HLPH and HLPMe are shown in Fig. 1
and 2 respectively, while selected geometric parameters are given
in Table 2.
The ligands HLPH and HLPMe crystallize in the triclinic
¯
P1 space group as two independent molecules in the asymmetric
unit (denoted as I and II for each ligand). In both compounds
all the molecules are E isomers in terms of the phosphorus-
azomethine nitrogen positions, but in HLPH the two molecules
have the same conformation, while in HLPMe they show opposite
arrangements. In the molecule I these atoms are located cis, while
in the molecule II they appear trans for the two molecules in
HLPH.21 These different orientations could be attributed to the
1364 | Dalton Trans., 2012, 41, 1363–1372
This journal is
The Royal Society of Chemistry 2012
©

View Article Online
In HLPMe, molecule II displays a similar hydrogen bonding pat-
tern than that in HLPH (Table S1, ESI†) while molecule I exhibits
a different conformation, due to the absence of the intramolecular
hydrogen bonds N(14)–H(14A) ◊ ◊ ◊ N(12) and C(17)–H(17) ◊ ◊ ◊ P(1)
(Fig. S2, ESI†), together with the existence of weak p–p stacking
˚
[Cg{C(61)/C(66)}–Cg{C(61)/C(66)}, 2 - x, -y, 1 - z; 3.970 A,
◦
a = 0.0 ]23 and p-ring interactions [ 2.951–3.182 A for H ◊ ◊ ◊ Cg,
˚
131.0–161.0◦ for a and 14.1–15.6◦ for b].
All the bond distances and angles are in the usual range found
for phosphine,24 and thiosemicarbazone ligands,19 and does not
merit further analysis.
Crystal structure of [Au3(HLPH)2Cl2]Cl·4MeOH (1·4MeOH).
The compound 1·4MeOH crystallizes in the monoclinic space
group P21/c with half a molecule in the asymmetric unit. The
gold(I) atom Au(1) is located in the inversion centre at a special
position, being connected to another gold(I) atom, Au(2), through
a phosphino thiosemicarbazone molecule, which acts as a S,P-
bridging ligand. Consequently, the complex is composed of a
trinuclear gold(I) cation (Fig. 3), a chloride anion with a 50%
occupation and four methanol solvate molecules. Thus, every
external Au(I) in the cation exhibits a distorted linear kernel by
coordination to the phosphorus and the chloride atoms, with a
P(1)–Au(2)–Cl(1) angle of 177.99(5)◦. The deviation from linearity
could be attributed to the establishment of short intermolecular
Au ◊ ◊ ◊ Au interactions (vide infra).6,25 The central gold of the cation
exhibits a perfect linear geometry (S–Au–S angle is 180◦). This
angle is notably higher than those in gold thiosemicarbazone
complexes exhibiting an S–Au–S mode.10
Fig. 1 Molecular structure and numbering scheme for the two indepen-
dent molecules in the HPLH asymmetric unit.
packing resulting from different hydrogen-bond patterns and/or
p-stacking interactions.
In HLPH, both molecules feature the typical intramolecular
N–H ◊ ◊ ◊ N hydrogen bond of thiosemicarbazone moeities, which
involves the thioamide nitrogen [N(14), N(24)] and the imine
nitrogen atom [N(12), N(22)] (Table S1, ESI†), together with
a non-classical C–H ◊ ◊ ◊ P interaction established between the
imine carbon and the phosphorus atoms. Both conformers are
linked in the asymmetric unit by an intermolecular hydrogen
bond engaging the thioamide N(24)-hydrogen atom of II and
the thioamide sulfur atom S(1) of I (Fig. S1, ESI†). In addition,
molecule I features intermolecular N–H ◊ ◊ ◊ S hydrogen bonds
involving the hydrazide and the thiomide nitrogen atoms and the
thioamide sulfur, while molecule II exhibits those involving the
hydrazide nitrogen atom only. The arrangement of the molecules
is additionally influenced by the existence of a weak C–H ◊ ◊ ◊ p
interaction [C(35)–H(35) ◊ ◊ ◊ Cg{C(51)/C(56)}; H ◊ ◊ ◊ Cg = 3.078
The Au–P and Au–Cl bond lengths of 2.228(1) and 2.303(2)
˚
A, respectively, are well within range reported for other Cl–Au–
P complexes.26 The Au(2)–S(1) bond lengths of 2.297(2) A are
˚
˚
shorter than that of 2.319(1) A found in [AuCl(HL)(PEt3)] (HL =
Vit K3 thiosemicarbazone),9 but within the range observed for
˚
gold(I) thiolate complexes (2.276–2.292 A), as a result of the
perfect S–Au–S alignment.27
Moreover the structure of 1·4MeOH exhibits two short dis-
˚
tances, Au1 ◊ ◊ ◊ H14B (2.88 A) that could be considered weak
agnostic interactions (Fig. 4).28 The AuS2H2 skeleton is almost
◦
◦
22
˚
A, a = 151.9 and b = 15.0 ] (Cg = ring centroid).
planar [the deviation of Au(1) from the least-squares plane is
Fig. 2 Molecular structure and numbering scheme for the two independent molecules in the HPLMe asymmetric unit.
The Royal Society of Chemistry 2012 Dalton Trans., 2012, 41, 1363–1372 | 1365
This journal is
©

View Article Online
Table 1 Crystal data and structure refinement for the compounds HLPH, HLPMe, 1·4MeOH and 2
HLPH
HLPMe
1·4MeOH
2
Empirical formula
Mr
C20H18N3PS
363.40
C21H20N3PS
377.43
C44H52Au3Cl3N6O4P2S2
1552.23
Monoclinic
C21H20Au2Cl2N3PS
842.26
Crystal system
Triclinic
Triclinic
Triclinic
¯
¯
¯
Space group
P1
P1
P21/n
P1
˚
a/A
8.6649(6)
8.3820(9)
10.769(3)
10.466(2)
23.213(5)
90
9.1233(8)
10.3094(8)
13.3409(11)
100.296(4)
105.008(4)
96.479(4)
1175.64(17)
2
˚
b/A
13.2989(10)
16.2517(11)
84.183(4)
88.693(4)
89.976(4)
1862.6(2)
4
1.296
0.267
13.9983(15)
18.2378(18)
72.072(6)
82.970(5)
78.154(5)
1988.6(4)
4
1.261
0.252
˚
c/A
a/◦
b/◦
g /◦
92.877(4)
90
2613.0(10)
2
1.973
8.741
3
˚
V/A
Z
Dc/Mg m-3
2.379
12.863
780
0.22 ¥ 0.14 ¥ 0.05
1.62–34.97
-14/14, -16/16, 0/21
48953/10345
m/mm-1
F(000)
760
792
1480
Crystal size/mm
0.24 ¥ 0.09 ¥ 0.04
1.26–26.55
-10/10, -16/16, 0/20
33453/7639
0.050
26.55 (98.6%)
0.9894/0.9388
7639/451
1.067
R1 = 0.0891
wR2 = 0.2345
R1 = 0.1387
wR2 = 0.2598
2.691/-0.502
0.37 ¥ 0.05 ¥ 0.04
1.55–26.54
-10/10, -16/17, 0/22
37195/8169
0.0739
26.54 (98.6%)
0.9900/0.9124
8169/469
0.944
R1 = 0.0734
wR2 = 0.1704
R1 = 0.1308
wR2 = 0.1935
1.215/-0.688
0.20 ¥ 0.07 ¥ 0.05
1.76–26.37
-13/13, 0/13, 0/29
29302/5341
0.0479
26.37 (100%)
0.6690/0.2738
5341/279
1.081
R1 = 0.0235
wR2 = 0.0432
R1 = 0.0626
wR2 = 0.0988
3.395/-3.451
q range/◦
Limiting indices hkl
Refl. collect/unique
Rint
Completeness q/◦
Max./min. transm.
Data/parameters
Goodness-of-fit on F2
Final R indices
34.97 (99.9%)
0.5656/0.1641
10345/271
1.084
R1 = 0.0263
wR2 = 0.0557
R1 = 0.0354
wR2 = 0.0581
4.123/-2.774
R indices (all data)
-3
˚
Drmax/min/e A
◦
˚
Table 2 Selected bond lengths (A) and angles ( ) for HLPH and HLPMe
HLPH-I
HLPMe-I
HLPH-II
HLPMe-II
S(1)–C(18)
1.682(5)
1.331(6)
1.383(5)
1.280(6)
1.689(4)
1.325(5)
1.368(4)
1.289(5)
S(2)–C(28)
1.688(5)
1.314(6)
1.383(5)
1.270(6)
1.683(4)
1.330(5)
1.382(4)
1.273(5)
C(18)–N(14)
N(13)–N(12)
N(12)–C(17)
C(28)–N(24)
N(23)–N(22)
N(22)–C(27)
S(1)–C(18)–N(14)
S(1)–C(18)–N(13)
N(14)–C(18)–N(13)
C(18)–N(13)–N(12)
N(13)–N(12)–C(17)
N(12)–C(17)–C(16)
122.2(4)
119.9(4)
117.9(4)
120.3(4)
115.9(4)
121.1(4)
124.7(3)
119.5(3)
115.8(4)
119.7(3)
115.2(3)
122.1(4)
S(2)–C(28)–N(24)
S(2)–C(28)–N(23)
N(24)–C(28)–N(23)
C(28)–N(23)–N(22)
N(23)–N(22)–C(27)
N(22)–C(27)–C(26)
122.4(4)
119.6(4)
118.0(4)
119.8(4)
115.6(4)
120.5(4)
124.0(3)
119.6(3)
116.4(3)
119.6(3)
117.0(3)
120.4(3)
Fig. 3 View of the cation in 1·4MeOH, showing the numbering scheme of the atoms in the molecule. Symmetry codes are given in Table 3.
1366 | Dalton Trans., 2012, 41, 1363–1372
This journal is
The Royal Society of Chemistry 2012
©

View Article Online
Fig. 4 View of the associated molecules of cation 1 as present in the crystal, showing the linear gold(I) trimers. The dotted lines indicate the aurophilic
and weak agostic interactions.
◦
˚
Table 3 Selected bond lengths (A) and angles ( ) for 1·4MeOH and 2
As a result of the establishment of the gold–gold interactions
the different linear trimers are connected through the crystal cell
in a 2D zigzag mode (Fig. S3, ESI†).
1·4MeOH
2
The existence of linearity in trinuclear Au(I) clusters is not
frequent31 and contrasts with most of the reported cases, for
which bent32 or triangular33 arrangements have been observed.
The bending degree in Au(I) cluster chains is closely related with
the strength of the Au ◊ ◊ ◊ Au interactions whiting the cluster. Thus,
a larger bending angle has been attributed to strong Au ◊ ◊ ◊ Au
interactions, which could be enhanced by the coordination of
halide ligands at the end of the chain.34
Au(1)–S(1)
2.2972(15)
2.2972(15)
3.1480(5)
3.1480(5)
2.2278(13)
2.3026(16)
3.1480(5)
Au(2)–S(1)
2.2659(8)
2.3020(8)
3.0492(3)
3.5034(7)
2.2341(7)
2.3172(7)
4.5659(4)
Au(1)–S(1)1
Au(1)–Au(2)2
Au(1)–Au(2)3
Au(2)–P(1)
Au(2)–Cl(2)
Au(1)–Au(2)1
Au(1)–Cl(1)1
Au(1)–P(1)
Au(1)–Cl(1)
Au(1)–Au(1)1
Au(2)–Cl(1)
Au(2)–Au(1)4
S(1)1–Au(1)–S(1)
P(1)–Au(2)–Cl(1)
Au(2)2–Au(1)–Au(2)3
180.00
177.99(5)
180.00
S(1)–Au(2)–Cl(2)
P(1)–Au(1)–Cl(1)
P(1)–Au(1)–Cl(1)1
Cl(1)–Au(1)–Cl(1)1
169.80(3)
173.01(3)
95.06(2)
78.62(2)
An additional point of interest in the structure of 1·4MeOH
lies in its crystal packing (Fig. S4, ESI†). As expected, the
thioamide and the hydrazine hydrogen atoms of the thiosemicar-
bazone, together with the hydroxyl hydrogen atoms of methanol
molecules are involved in hydrogen-bond formation (Table 4),
with N(14), N(13), O(2) and O(3) acting as the H-donors and
the chloride counter-anions, Cl(2), and the oxygen atoms of
methanol molecules, O(2) and (O3), as acceptors. These inter-
actions give rise to the rings Cl(2)/O(3), Cl(2)/O(3)/N(14) and
Cl(2)/O(3)/N(14) of graph sets R2 (4), R2 (4), and R4 (8),
Symmetry transformations: for 1·4MeOH: 1: -x, -y - 1, -z + 1; 2: -x, -y,
-z + 1; 3: x, y - 1, z; 4: x, y + 1, z; for 2: 1: -x + 1, -y + 1, -z.
◦
˚
0.792(3) A] and forms a dihedral angle of 17.4(2) with the
thiosemicarbazone moiety.
More interestingly, every gold(I) atom in cation 1 assembles
into trinuclear linear gold(I) units by means of close aurophililic
interactions (Fig. 4), and therefore this complex is a cluster
compound. Thus, every central S,S-coordinated Au(1) atoms
occupies the central site of the cluster. The other two gold(I)
atoms (Au(2)), which belong to different trimer complexes,
are located at the sides of the aggregate. The Au(1) ◊ ◊ ◊ Au(2)
distances of 3.1480(5) A fall within the aurophilic range, being
indicative of a significant interaction between the two pairs of gold
centres.29,30
4
3
6
respectively.35 The chloride ions Cl(2) and the oxygen atoms O(2)
and O(3) establish further hydrogen bonds with the hydrogen
atoms of methanol and the thioamide/hydrazide N–H groups,
resulting in an alternating cation–methanol–anion–methanol–
cation chain [N(13)/O(2)/C(l2)/O(3)/N(14)]. Within the chain,
˚
the hydrogen bonds combine to yield the graph set C4 (8)
4
(Table 4).
Of particular interest is the perfect linear arrangement adopted
by the trinuclear core in the [Au3(HPLH)2Cl2]+ cation, which arises
from the Au(1) atom position in the inversion centre of the trimer.
The S(1)–Au(1)–S(1a) (a: -x, -y - 1, -z + 1), Cl(1b)–Au(2b)–P(1b)
(b: -x, -y, -z + 1) and Cl(c)–Au(2c)–P(1c) (c: x, y - 1, z) vectors are
not parallel, but are twisted by 77.20(5) and -91.2(1)◦, respectively.
Crystal structure of [Au2(HLPMe)Cl2]2 (2). compound 2 crys-
tallizes in the triclinic space group P1, with one discrete molecule
[(AuCl)2(HLPMe)] in the asymmetric unit (Fig. 5). Each phos-
phino thiosemicarbazone ligand is bound to two different gold(I)
atoms, one of them, Au(1), through the phosphorus atom [Au(1)–
¯
˚
P(1) = 2.2341(7) A], whereas the second gold(I) ion, Au(2), is
This journal is
The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 1363–1372 | 1367
©

View Article Online
Table 4 Hydrogen bond parameters [A, ◦] for 1·4MeOH and 2
˚
D–H ◊ ◊ ◊ A
D–H
H ◊ ◊ ◊ A
D ◊ ◊ ◊ A
∠DHA
1·4MeOH
N(13)–H(13A) ◊ ◊ ◊ O(2)1
N(14)–H(14A) ◊ ◊ ◊ O(3)1
N(14)–H(14A) ◊ ◊ ◊ Cl(2)3
N(14)–H(14B) ◊ ◊ ◊ Cl(1)2
O(2)–H(2) ◊ ◊ ◊ Cl(2)
O(3)–H(3) ◊ ◊ ◊ Cl(2)4
O(3)–H(3) ◊ ◊ ◊ Cl(2)5
N(14)–H(14B) ◊ ◊ ◊ Au(1)
0.88
0.88
0.88
0.88
0.84
0.85
0.85
0.88
1.88
2.14
2.67
2.55
2.05
1.73
2.44
2.89
2.749(11)
2.89(2)
3.379(9)
3.328(8)
2.862(9)
2.45(2)
171.2
142.9
138.8
147.6
162.2
141.5
132.4
120.4
3.08(3)
3.421(7)
2
N(13)–H(13A) ◊ ◊ ◊ Cl(1)1
N(14)–H(14A) ◊ ◊ ◊ N(12)
N(14)–H(14A) ◊ ◊ ◊ Cl(2)2
C(17)–H(17) ◊ ◊ ◊ Cl(1)1
C(23)–H(23) ◊ ◊ ◊ Cl(1)3
N(13)–H(13A) ◊ ◊ ◊ Au(2)
C(17)–H(17) ◊ ◊ ◊ Au(1)
0.83
0.76
0.76
0.98
0.92
0.83
0.98
2.55
2.18
2.83
2.77
2.83
2.84
2.86
3.325(3)
2.606(3)
3.393(3)
3.5464()
3.5854
3.327(2)
3.389(3)
158.0
115.7
132.9
136.53
140.73
119.4
115.1
Symmetry transformations: for 1·4MeOH: 1: -x + 1, -y + 1, -z; 2: -x +
1, -y, -z; 3: 1 + x, y, z; for 2: 1: x + 1/2, y - 1/2, -z + 1/2; 2: -x, -y, -z +
1; 3: x - 1/2, -y + 1/2, z + 1/2; 4: -x + 1, -y + 1, -z; 5: x - 1, y, z.
Fig. 6 Intermolecular association of 2 through aurophilic interactions
(symmetry operation, a: -x + 1, -y + 1, -z).
steric interactions of the bulky phosphine that could prevent the
dimerization of the complex through Au ◊ ◊ ◊ Au interactions.36
The establishment of aurophilic contacts permits the formation
of a twenty-membered metallacycle, which features a couple of
Au ◊ ◊ ◊ Au pairs (Fig. 7). The central part of the metallacycle
˚
ring is essentially a parallelogram with sides of 4.318(1) A
a
˚
for P(1) ◊ ◊ ◊ Cl(1 ) (a: -x + 1, -y + 1, -z) and 4.543(1) A for
P(1) ◊ ◊ ◊ Cl(1), and an angle of 129.290(2)◦. The thiosemicarbazone
moieties are twisted by 85.65(5)◦ as a result of the need to bring the
two gold atoms into close proximity and maximize the aurophilic
attractions. The conformation of the auromacrocycle is achieved
Fig. 5 Molecular structure of complex 2.
coordinated to the thioamide sulfur atom [Au(2)–S(1) = 2.2659(8)
˚
A]. The gold(I) atoms complete their coordination sphere with
˚
a chlorine atom [Au–Cl = av. 2.3096(8) A], therefore generating
distorted linear kernels [173.01(3)◦ for P(1)–Au(1)–Cl(1) and of
169.80(3)◦ for S(1)–Au(2)–Cl(2)]. The P–Au, S–Au and Cl–Au
bond lengths fall within the range expected for linear phosphine
gold(I)-chloride systems.26
The dinuclear gold monomer [(AuCl)2(P,S-HLPMe)] is further
assembled into tetranuclear [(AuCl)2(HLPMe)]2 units by means
of close gold–gold interactions [Au(1) ◊ ◊ ◊ Au(2a) (a: -x + 1, -y
˚
+ 1, -z) of 3.0492(3) A], therefore explaining the deviation from
linearity. (Fig. 6). The dinuclear units show torsion angles Cl(1)–
Au(1)–Au(2)–Cl(2) of -81.53◦, which are close to the value of
90◦ estimated for X(1)–Au(1)–Au(2)–X(2) torsion angles in those
cases where the gold–gold separation falls in the range 3.00–
32c
˚
3.25 A.
Fig. 7 Perspective view of the Au4S2P2 central core in 2, illustrating the
metallacycle structure and the endocycle weak interactions (symmetry
operation, a: -x + 1, -y + 1, -z).
The phosphino thiosemicarbazone strands are disposed with
an anti arrangement in complex 2 probably to avoid unfavourable
1368 | Dalton Trans., 2012, 41, 1363–1372
This journal is
The Royal Society of Chemistry 2012
©

View Article Online
by means of weak agostic interactions between Au(2) and one
below 300 nm could be attributed to intraligand (IL) transitions
of the phosphino thiosemicarbazone moieties, while the lowest
energy bands are characteristic of thiolato gold(I) phosphine
systems.37
˚
proton of the hydrazine nitrogen atom [H(13A) ◊ ◊ ◊ Au(2), 2.84 A;
˚
N(13) ◊ ◊ ◊ Au(2), 3.327(2) A] and also between Au(1) and a proton
˚
of a methyl carbon atom [H(17) ◊ ◊ ◊ Au(1), 2.86 A; C(17) ◊ ◊ ◊ Au(1),
3.389(3) A] (Table 4).28 It is noteworthy that there are also classical
The emission spectra of the ligands HLPH and HLPMe
and their corresponding Au(I) complexes 1·4MeOH and 2 were
recorded at room temperature in methanol (Fig. 9). These spectra
exhibit intense bands, with maxima at ca. 359 (HLPH), 353
(HLPMe), 415 (1·4MeOH) and 378 (2) nm (excitation at 320
(HLPH, HLPMe) or 340 nm (1·4MeOH and 2). As it can be
seen from the data, the emissions in the complexes are slightly red-
shifted by 56 (1·4MeOH) and 38 (2) cm-1, respectively, compared
with the emissions in the parent ligands. It has been reported that
the luminescence properties in most phosphine gold(I) thiolates
are determined mainly by the nature of the thiolate ligand.
Although the phosphine ligand often contains a chromophore, the
optical processes predominantly occur via the excitation of sulfur
with subsequent charge transfer to gold.1f Another factor to be
considered in halo phosphine Au(I) complexes is the contribution
of halide ligands to the energy levels.20a Whereas the existence of
Au–Au interactions, either intermolecularly or intramolecularly,
is not mandatory for emission in thiolates, if present, they could
influence the emission energy and the excitation maxima of the
metal complexes.2,8b,c
˚
and non-classical hydrogen-bonding interactions within the ring.
Specifically, the metallacycle exhibits two hydrogen bonds, N(13)
and C(17) acting as proton donors and Cl(1) as acceptor. The
˚
metallo-ring, with approximate dimensions of the 8.20 ¥ 8.01 A,
features a distorted square cavity through the crystal cell, the
˚
chloride ions Cl1 and Cl1a being oriented ca. 1.6 A above and
below the cavity, respectively (Fig. 7).
In the crystal packing two-dimensional layers run approxi-
mately parallel to the plane (111) (Fig. S5, ESI†) This assembly
arises from new inter- and intramolecular hydrogen bonds involv-
ing the thioamide nitrogen atom N(14) and the C(23) atom acting
as proton donors, and the imine nitrogen atom, N(12), and the
chlorine atoms of neighbouring tetramers as acceptors (Table 4).
Photophysical studies
Electronic absorption spectroscopy. The electronic absorption
spectra of the ligands HLPH and HLPMe are very similar (Fig.
8), showing high-energy absorption shoulders at ca. 232 and
272 nm and a strong low-energy absorption band at ca. 320 nm.
The close resemblance of their UV-visible absorption spectra is
understandable since a variation in the size of the substituents
located at the terminal 4-N position of the thiosemicarbazone
should have very little influence on the spectroscopic properties
of the ligands. However, the absorption spectra of the crystalline
gold(I) complexes 1·4MeOH and 2 are notably different. Thus, UV
spectrum of complex 1·4MeOH shows a notable displacement on
the high energy absorptions with respect to the corresponding
ligand HLPH, with bands appearing at 267, 338 and 373 nm. The
spectrum of complex 2 is similar to its precursor ligand HLPMe,
but the low energy absorption band (~320 nm) is split in three
bands at 313, 325 and 340 nm. In these complexes the absorptions
Fig. 9 Emission spectra of the ligands HLPH and HLPMe and the Au(I)
complexes 1·4MeOH and 2 in methanol (1 ¥ 10-5 M).
The fact that the ligands HLPH and HLPMe and its corre-
sponding Au(I) complexes 1·4MeOH and 2 exhibit bands at similar
energy values suggests that the emissions probably arise from the
same electronic states, and therefore they could be assignable to
intraligand (IL) or S-to-Au LMCT transitions. However some
influence from aurophilic contacts and a certain degree of charge
transfer from chloride to gold can not be discounted.38
The introduction of different substituents in the 4-N-terminal
position of the thiosemicarbazone chain affects mainly the struc-
ture of the complexes,16,17 but does not significantly their emission
properties. Thus, we must indicate that all Au(I) complexes
of the series HLPR (R = H, Me, Et, Ph) exhibit different
structures despite that they were synthesised by using the same
Fig. 8 Absorption spectra of the ligands HLPH and HLPMe and the
Au(I) complexes 1·4MeOH and 2 in methanol (1 ¥ 10-5 M).
This journal is
The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 1363–1372 | 1369
©

View Article Online
chemical procedure and crystallised under similar conditions.
Previous works covering the structural chemistry of different N-
substituted ligands indicated that the 4-N-terminal group of the
thiosemicarbazones does not exert a great influence in the structure
of the assembled complex. The Au(I) HLPR (R = H, Me, Et,
Ph) collection of complexes breaks that prediction: the ethyl and
phenyl derivates are Au(I) dimers with metal–metal interactions
(Schemes 1d and e),16,17 while the herein presented unsubstituted
and methyl derived Au(I) complexes are trinuclear and dinuclear
complexes, further assembled by means of aurophilic interactions
(vide supra). Regarding the emissive properties, the ethyl and
phenyl derived complexes displayed enhanced luminescence, but
at similar wavelengths as their precursor ligands.16,17 In the
herein studied unsubstituted and the methyl substituted gold(I)
derivatives the emission is slightly red-shifted with respect to the
corresponding ligands. Hence, in these cases the presence of gold–
gold contacts could be a factor influencing the slight displacement
of the emission maxima.
Synthesis of the ligands
The ligands 2-(2-(diphenylphosphino)benzylidene) thiosemicar-
bazone (HLPH) and 2-(2-(diphenylphosphino)benzylidene)-N-
methylthiosemicarbazone (HLPMe) were prepared following the
procedure reported before,15–17 which is detailed in ESI†. In both
cases good quality crystals were obtained from ethanol solutions
(vide supra).
Synthesis of the complexes
The Au(I) complexes were synthesized by reaction of reduced
H[AuCl4] with the ligands HLPH and HLPMe, respectively.
The experimental procedures and the characterization data are
summarized below.
[Au3(HLPH)2Cl2]Cl·2MeOH (1·2MeOH). 46.55 mg (0.381
mmol) of 2,2¢-thiodiethanol were added to 50.29 mg (0.127
mmol) of H[AuCl4] previously dissolved in water (~2 mL). The
colourless solution formed was added to 50 mg of the ligand
HLPH (0.127 mmol) dissolved in methanol (30 mL). The clear
solution was refluxed for 2 h and then left stirring overnight
at room temperature. After that, the solution was concentrated
to a small volume (15 mL) and allowed to crystallize at room
temperature for 24 h. After that time the crystalline solid obtained
was filtered off and finally dried in vacuo. Yield: 0.15 g (79%);
mp >221 ◦C; C42H44Au3Cl3N6O2P2S2 (1488.18): calc.: C, 33.9;
H, 3.0; N, 5.6; S, 4.3; found: C, 33.7; H, 3.1; N, 5.6; S,
4.4%; ESI(+) 560.1 [Au(HLPH)]+; 757.6 [Au2(HLPH)]2+, 1119.2
Conclusions
In summary, tuning a thiosemicarbazone ligand with a phos-
phine group not only allows the isolation of homoleptic Au(I)
thiosemicarbazone complexes, but also leads to the first cases of
thiosemicarbazone clusters showing aurophilicity. These clusters
are luminescent at room temperature with the emission maxima
possibly influenced by the presence of multiple aurophilic contacts.
These clusters perfectly exemplify that the synergistic combination
of the attractive forces from hydrogen bonds and Au ◊ ◊ ◊ Au
interactions contributes to the stabilization of gold(I) polymeric
arrays.
[Au2(HLPH)2]2+, 1315.1 [Au3(HLPH)2]3+; H NMR (DMSO-d6,
1
ppm): d 6.77 (m, 1H), 7.48–7.69 (m, 12H), 8.43 (m, 2H), 8.82
(s, 1H), 8.79 (s, 1H), 12.28 (s, 1H); 31P NMR (DMSO-d6, ppm):
d 29.7; IR (KBr, cm-1): 3485, 3332 n(OH) + n(NH), 1553–1436
n(C N) + n(C–N), 1080 n(N–N), 751 n(C S); 370, 308 n(Au–
Cl); UV/Vis (MeOH): lmax = 267, 338, 373 nm. KM = 62.2 mS
cm-1. Well-shaped colourless needles of 1·4MeOH were studied by
X-ray diffraction. The same complex 1·2MeOH was obtained by
using a 3 : 2 metal : ligand ratio in the reaction.
Experimental section
Materials
All solvents, thiosemicarbazide, 4-N-methylthiosemicarbazide
and 2-diphenylphosphinobenzaldehyde are commercially avail-
able and were used without further purification. Commercial
H[AuCl4] was reduced with 2,2¢-thio-bis(ethanol) in a 1 : 1
methanol : water mixture.
[Au2(HLPMe)Cl2] 2. 93.11 mg (0.762 mmol) of 2,2¢-
thiodiethanol were added to 92.27 mg (0.254 mmol) of H[AuCl4]
previously dissolved in water (~2 mL). The colourless solution
formed was added to 100 mg of the ligand HLPMe (0.254
mmol) dissolved in methanol (30 mL). The white suspension
formed was refluxed for 2 h and then left stirring overnight at
room temperature. After that, the suspended white solid was
filtered off and finally dried under vacuo. Yield 71% (0.15 g);
mp >245 ◦C; C21H20Au2Cl2N3P1S1 (842.28): calc.: C, 29.9; H,
2.4; N, 5.0; S, 3.8; found: C, 29.8; H, 2.2; N, 5.1; S, 3.9%;
ESI(+) 574.1 [Au(HLPMe)]+; 1147.1 [Au2(HLPMe)2]2+; 1343.1
Methods
Elemental analysis of C, H, N and S were performed on a
FISONS EA 1108 analyzer. 1H, 13C and 31P NMR studies (H3PO4
was used as internal reference) in a VARIAN MERCURY 300
spectrometer. Infrared spectra were measured from KBr pellets on
a BRUKER IFS-66V spectrophotometer in the ranges 4000–100
or 500–100 cm-1. Electrospray ionisation (ESI) mass spectra were
recorded on an API4000 Applied Biosystems mass spectrometer
with Triple Cuadrupole analyser. Conductivity was measured at
1
[Au3(HLPMe)2]3+; H NMR (DMSO-d6, ppm): d 2.98 (d, 3H),
6.75 (m, 1H), 7.70–7.43 (m, 9H), 8.39 (m, 4H), 8.69 (m, 2H), 11.88
(s, 1H); 31P NMR (DMSO-d6, ppm): d 29.93; IR (KBr, cm-1):
3334 n(NH), 1574–1436 n(C N) + n(C–N), 1098 n(N–N), 749
n(C S) 408, 335 n(Au–Cl); UV/Vis (MeOH): lmax = 267, 313,
325, 340 nm. KM = 13.2 mS cm-1. Recrystallization of solid 2 in
methanol at room temperature yielded the same compound as
colourless prismatic crystals.
◦
25 C from 10-3 M solutions in DMF on a Crison Micro CM
2200 conductivimeter. UV-vis spectra were measured in a Hewlett
Packard 8452A spectrophotometer using 1 ¥ 10-5 M solutions in
methanol. Luminescence was recorded at room temperature in a
Jovin Yvon-Spex Fluoromax-2 spectrophotometer using 1 ¥ 10-5
M solutions in methanol.
1370 | Dalton Trans., 2012, 41, 1363–1372
This journal is
The Royal Society of Chemistry 2012
©

View Article Online
Crystal structure determinations
Bardaj´ı, M. J. Calhorda, P. J. Costa, P. G. Jones, A. Laguna, M. R.
Pe´rez and M. D. Villacampa, Inorg. Chem., 2006, 45, 1059; (i) S.-Y. Yu,
Q.-F. Sun, T. K.-M. Lee, E. C.-C. Cheng, Y.-Z. Li and V. W.-W. Yam,
Angew. Chem., Int. Ed., 2008, 47, 4551; (j) T. K.-Ming Lee, N. Zhu and
V. W. - W Ya m , J. Am. Chem. Soc., 2010, 132, 17646; (k) I. O. Koshevoy,
C.-L. Lin, A. J. Karttunen, M. Haukka, C.-W. Shih, P.-T. Chou, S. P.
Tunik and T. A. Pakkanen, Chem. Commun., 2011, 47, 5533.
3 S. Y. Ho, E. R. T. Tiekink, in Metallotherapeutic Drugs and Metal-
Based Diagnostic Agents: The Use of Metals in Medicine, ed. M. Gielen
and E. R. T. Tiekink, John Wiley & Sons Ltd, Chichester, UK, 2005,
ch. 26, p. 507.
Colourless crystals of HLPH and HLPMe, [Au3(HLPH)2Cl2]-
Cl·4MeOH (1·4MeOH) and [Au(HLPMe)2Cl]2 2 were mounted
on glass fibers and used for data collection. Crystal data were
collected at 100.0(1) K (HLPLH, 2) or 110(2) K (HLPMe) using a
Bruker X8 Kappa APEXII diffractometer or at 110(2) K using a
Bruker Smart CCD 1000 diffractometer (1·4MeOH). Graphite-
˚
monochromated Mo-Ka radiation (l = 0.71073 A) was used
4 M. A. Mansour, W. B. Connick, R. J. Lachicotte, H. J. Gysling and R.
Eisenberg, J. Am. Chem. Soc., 1998, 120, 1329.
5 (a) V. W.-W. Yam, C. K. Li and C. L. Chan, Angew. Chem., Int. Ed.,
1998, 37, 2857; (b) V. W.-W. Yam, C. L. Chan, C. K. Li and K. M. C.
Wong, Coord. Chem. Rev., 2001, 216–217, 173; (c) X. He, F. Herranz,
E. C.-C. Cheng, R. Vilar and V. W.-W. Yam, Chem.–Eur. J., 2010, 16,
9123.
throughout. The data for HLPH, HLPMe and 2 were processed
withAPEX239 orSAINT (1·4MeOH)andcorrectedfor absorption
using SADABS.40 The structures were solved by direct methods
using SHELXS-9741 and refined by full-matrix least-squares tech-
niques against F2 using SHELXL-97.41 Positional and anisotropic
atomic displacement parameters were refined for all non-hydrogen
atoms. Hydrogen atoms for HLPH and 1·4MeOH were included
in geometrically idealized positions and for HLPMe and 2 were
located in difference maps. The N–H hydrogen atoms were located
unambiguously from difference Fourier maps for all compounds.
In all compounds, the hydrogen atoms were included in refinement
as fixed contributions riding on attached atoms with isotropic
displacement parameters constrained to 1.2Ueq of their carrier
atoms. The lowest and highest peaks in the final difference Fourier
map were located close to the phosphorus atoms in the ligands
and close to the gold atoms in complex. Criteria of a satisfactory
complete analysis were the ratios of rms shift to standard deviation
less than 0.001 and no significant features in final difference maps.
Atomic scattering factors were obtained from International Tables
for Crystallography.42 Molecular graphics were prepared with
6 (a) F. Scherbaum, A. Grohmann, B. Huber, C. Kruger and H.
Schmidbaur, Angew. Chem., Int. Ed. Engl., 1988, 27, 1544; (b) H.
Schmidbaur, S. Cronje, B. Djordjevic and O. Schuster, Chem. Phys.,
2005, 311, 151; (c) H. Schmidbaur, A. Grohmann and M. E. Olmos,
Gold: Progress in Chemistry Biochemistry and Technology, ed. H.
Schmidbaur, Wiley, Chichester, 1999, p. 648; (d) W. Schneider, A. Bauer
and H. Schmidbaur, Organometallics, 1996, 15, 5445; (e) C. Hollatz, A.
Schier and H. Schmidbaur, J. Am. Chem. Soc., 1997, 119, 8115; (f) H.
Schmidbaur, Gold Bull., 2000, 33, 3; (g) H. Schmidbaur and A. Schier,
Chem. Soc. Rev., 2008, 37, 1931.
7 (a) D. Braga, F. Grepioni and G. R. Desiraju, Chem. Rev., 1998, 98,
1375; (b) S. R. Pathaneni and G. R. Desiraju, J. Chem. Soc., Dalton
Trans., 1993, 319; (c) M. A. Bennett, L. L. Welling and A. C. Willis,
Inorg. Chem., 1997, 36, 5670; (d) P. M. Van Calcar, M. M. Olmstead
and A. L. Balch, J. Chem. Soc., Chem. Commun., 1995, 1773; (e) P.
M. Van Calcar, M. M. Olmstead and A. L. Balch, Inorg. Chem., 1997,
36, 5231; (f) D. M. P. Mingos, J. Yau, S. Menzer and D. J. Williams,
Angew. Chem., 1995, 107, 2045; (g) C. P. McArdle, M. J. Irwin, M. C.
Jennings and R. J. Puddephatt, Angew. Chem., 1999, 111, 3571; (h) B.-
Chiau Tzeng, A. Schier and H. Schmidbaur, Inorg. Chem., 1999, 38,
3978.
ORTEP, implemented in PLATON,43 and with DIAMOND.44
A
summary of the crystal data, experimental details and refinement
results are listed in Table 1.
8 (a) V. W.-W. Yam and E. C.-C. Cheng, Gold Bull., 2001, 34, 20; (b) S.
Y. Ho, E. C.-Chin Cheng, E. R. T. Tiekink and V. W.-W. Yam, Inorg.
Chem., 2006, 45, 8165; (c) I. O. Koshevoy, E. S. Smirnova, M. Haukka,
A. Laguna, J. C. Chueca, T. A Pakkanen, S. P. Tunik, I. Ospino and O.
Crespo, Dalton Trans., 2011, 40, 7412.
Acknowledgements
9 J. S. Casas, E. E. Castellano, M. D. Couce, J. Ellena, A. Sa´nchez, J.
Sordo and C. Taboada, J. Inorg. Biochem., 2006, 100, 1858.
10 T. S. Lobana, S. Khanna and R. J. Butcher, Inorg. Chem. Commun.,
2008, 11, 1433.
Financial support from Xunta de Galicia (INCITE08PXIB-
203128PR).
11 A. Castin˜eiras, S. Dehnen, A. Fuchs, I. Garc´ıa-Santos and P. Sevillano,
Dalton Trans., 2009, 2731.
References
12 V. M. Leovac, B. Riba´r, G. Argay, A. Ka´lma´n and I. Brcˇeski, J. Coord.
Chem., 1996, 39, 11.
13 U. Abram, K. Ortner, R. Gust and K. Sommer, J. Chem. Soc., Dalton
Trans., 2000, 735.
14 D. You, S. O. Kang, J. Ko and M. Choi, Bull. Korean Chem. Soc., 1997,
18, 305.
15 (a) A. Castin˜eiras and R. Pedrido, Inorg. Chem., 2008, 47, 5534; (b) A.
Castin˜eiras and R. Pedrido, Inorg. Chem., 2009, 48, 4847.
16 A. Castin˜eiras and R. Pedrido, Dalton Trans., 2010, 39, 3572.
17 A. Castin˜eiras, R. Pedrido and G. Pe´rez-Alonso, Eur. J. Inorg. Chem.,
2008, 5106.
1 (a) M. C. Gimeno and A. Laguna, Silver and Gold. Comprehensive
Coordination Chemistry II, ed, J. A. MacCleverty and T. J. Meyer,
Elsevier, Pergamon, New York, 2003, vol. 6, p. 911; (b) Modern
Supramolecular Gold Chemistry, ed. A. Laguna, Wiley-WCH, 2008;
(c) H. E. Abdou, A. A. Mohamed, J. P. Fackler Jr, Gold Chemistry:
Applications and Future Directions in the Life Sciences, ed. F. Mohr,
Wiley-WCH, 2009; (d) R. J. Puddephatt, Chem. Soc. Rev., 2008, 37,
2012; (e) M. C. Gimeno and A. Laguna, Chem. Soc. Rev., 2008, 37,
1952; (f) E. R. T. Tiekink and J.-G. Kang, Coord. Chem. Rev., 2009, 253,
1627; (g) T. N. Hooper, M. Green and C. A. Russell, Chem. Commun.,
2010, 46, 2313; (h) A. Himmelspach, M. Finze and S. Raub, Angew.
Chem., Int. Ed., 2011, 50, 2628; (i) I. O. Koshevoy, M. Haukka, S. I.
Selivanov, S. P. Tunik and T. A. Pakkanen, Chem. Commun., 2010, 46,
8926.
2 (a) J. M. Forward, D. Bohmann, J. P. R. Fackler Jr. and J. Staples, Inorg.
Chem., 1995, 34, 6330; (b) V. W.-W. Yam and K. K.-W. Lo, Chem. Soc.
Rev., 1999, 28, 323; (c) V. W.-W. Yam, E. C. C. Cheng and Z. Y. Zhou,
Angew. Chem., Int. Ed., 2000, 39, 1683; (d) Y. Lee and R. Eisenberg,
J. Am. Chem. Soc., 2003, 125, 7778; (e) A. Pintado-Alba, H. De la
Riva, M. Niewenhuyzen, D. Bautista, P. R. Raithby, H. A. Sparkes, S.
J. Teat, J. M. Lo´pez-de-Luzuriaga and M. C. Lagunas, Dalton Trans.,
2004, 3459; (f) S.-K. Yip, E. C.-C. Cheng, L.-H. Yuan, N. Zhu and V.
W. - W. Ya m , Angew. Chem., Int. Ed., 2004, 43, 4954; (g) J. Chen, A.
A. Mohamed, H. E. Abdou, J. A. Krause Bauer, J. P. Fackler Jr., A.
E. Bruce and M. R. M. Bruce, Chem. Commun., 2005, 1575; (h) M.
18 W. J. Geary, Coord. Chem. Rev., 1971, 7, 81.
19 R. Pedrido, A. M. Gonza´lez-Noya, M. J. Romero, M. Mart´ınez-
Calvo, M. Va´zquez Lo´pez, E. Go´mez-Fo´rneas, G. Zaragoza and M.
R. Bermejo, Dalton Trans., 2008, 6776.
20 (a) D. Ferna´ndez, M. I. Garc´ıa-Seijo, M. Bardaj´ı, A. Laguna and M. E.
Garc´ıa-Ferna´ndez, Dalton Trans., 2008, 2633; (b) U. Monkowius, M.
Zabel and H. Yersin, Inorg. Chem. Commun., 2008, 11, 409.
21 (a) J. Easmon, G. Heinisch and W. Holzer, Heterocycles, 1989, 29,
1399; (b) D. X. West, C. S. Carlson, K. J. Bouck and A. E. Liberta,
Transition Met. Chem., 1991, 16, 271; (c) D. X. West, B. L. Mokijewski,
H. Gebremedhin and T. J. Romack, Transition Met. Chem., 1992, 17,
384.
22 G. A. Bogdamonic, A. Spasojevic´-de Bire´ and S. D. Zaric, Eur. J. Inorg.
Chem., 2002, 1599.
This journal is
The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 1363–1372 | 1371
©

View Article Online
23 C. Janiak, J. Chem. Soc., Dalton Trans., 2000, 3885.
24 I. Schranz, G. R. Lief, S. J. Midstokke and L. Stahl, Inorg. Chem., 2002,
41, 6919.
25 M. B. Smith, S. H. Dale, S. J. Coles, T. Gelbrich, M. B. Hursthouse and
M. E. Light, CrystEngComm, 2006, 8, 140.
26 (a) M. R. J. Elsegood, M. B. Smith and S. H. Dale, Acta Crystallogr.,
Sect. E: Struct. Rep. Online, 2006, 62, m1850; (b) R. C. Bott, P. C. Healy
and G. Smith, Polyhedron, 2007, 26, 2803.
27 (a) K. Nunokawa, S. Onaka, Y. Mizuno, K. Okazaki, T. Sunahara,
M. Ito, M. Yaguchi, H. Imai, K. Inoue, T. Ozeki, H. Chiba and T. J.
Yoshida, J. Organomet. Chem., 2005, 690, 48; (b) S. Onaka, M. Yaguchi,
R. Yamauchi, T. Ozeki, M. Ito, T. Sunahara, Y. Sugiura, M. Shiotsuka,
K. Nunokawa, M. Horibe, K. Okazaki, A. Iida, H. Chiba, K. Inoue, H.
Imai and K. Sako, J. Organomet. Chem., 2005, 690, 57, and references
therein.
28 (a) M. J. Calhorda, Chem. Commun., 2000, 801; (b) G. R. Desiraju, J.
Chem. Soc., Dalton Trans., 2000, 3745; (c) M. Lein, Coord. Chem. Rev.,
2009, 253, 625.
29 A. Bondi, J. Phys. Chem., 1964, 68, 441.
30 H. Schmidbauer, Gold Bull., 1990, 23, 11.
31 (a) W. Schuh, H. Kopacka, K. Wurst and P. Peringer, Chem. Commun.,
2001, 2186; (b) S. D. Hanna, S. I. Khan and J. I. Zink, Inorg. Chem.,
1996, 35, 5813.
33 (a) E. C. Constable, C. E. Housecroft, M. Mneuburger, S. Schaffner and
E. J. Shardlow;, Acta Crystallogr., Sect. E: Struct. Rep. Online, 2007,
63, m1698; (b) C.-M. Che, H.-K. Yip, V. W.-W. Yam, P.-Y. Cheung, T.-
F. Lai, S.-J. Shieh and S.-M. Peng, J. Chem. Soc., Dalton Trans., 1992,
427.
34 P. Pyykko¨, J. Li and N. Runeberg, Chem. Phys. Lett., 1994, 218,
133.
35 J. Bernstein, R. E. Davis, L. Shimoni and N.-L. Chang, Angew. Chem.,
Int. Ed. Engl., 1995, 34, 1555.
36 K. Angermaier, E. Zeller and H. Schmidbaur, J. Organomet. Chem.,
1994, 472, 371.
37 C.-K. Li, X.-X. Lu, K. M.-C. Wong, C.-L. Chan, N. Zhu and V. W.-W.
Yam, Inorg. Chem., 2004, 43, 7421.
38 (a) E. J. Ferna´ndez, A. Laguna, J. M. Lo´pez-de-Luzuriaga, M. Monge,
M. Montiel, M. E. Olmos, R. C. Puelles and E. Sa´nchez- Forcada,
Eur. J. Inorg. Chem., 2007, 4001; (b) Y. Zhou, W. Chen and D.
Wang, Dalton Trans., 2008, 1444; (c) M. Bardaj´ı, M. J. Calhorda,
P. J. Costa, E. J. Ferna´ndez, A. Laguna, J. M. Lo´pez-de-Luzuriaga,
M. Monge and E. Sa´nchez-Forcada, Dalton Trans., 2011, 40,
3287.
39 Bruker APEX2 Software, Bruker AXS Inc V2.0-1, Madison, WI, USA,
2005.
40 G. M. Sheldrick, SADABS. Program, for Empirical Absorption Correc-
tion of Area Detector Data, University of Gottingen, Germany, 1997.
41 G. M. Sheldrick, Acta Crystallogr., Sect. A: Found. Crystallogr., 2007,
64, 112.
42 A. J. C. Wilson, International Tables for Crystallography, Vol. C, Kluwer
Academic Publishers, Dordrecht, 1992.
43 A. L. Spek, J. Appl. Crystallogr., 2003, 36, 7.
32 (a) D. Li, C.-M. Che, S.-M. Peng, S.-T. Liu, Z.-Y. Zhou and T. C.
W. M a k , J. Chem. Soc., Dalton Trans., 1993, 189; (b) H. Xiao, Y.-X.
Weng, W.-T. Wong, T. C. W. Mak and C.-M. Che, J. Chem. Soc., Dalton
Trans., 1997, 221; (c) D. V. Toronto, B. Weissbart, D. S. Tinti and A. L.
Balch, Inorg. Chem., 1996, 35, 2484; (d) A. Hamel, N. W. Mitzel and H.
Schmidbaur, J. Am. Chem. Soc., 2001, 123, 5106; (e) T.-L. Zhang, Y.
Qina and X.-G. Meng, Acta Crystallogr., Sect. E: Struct. Rep. Online,
2005, 61, m2588.
44 K. Brandenburg, DIAMOND, ver. 3.2; Crystal Impact GbR, Bonn,
Germany, 2009.
1372 | Dalton Trans., 2012, 41, 1363–1372
This journal is
The Royal Society of Chemistry 2012
©