Luminescent gold-silver complexes derived from neutral bis(perfluoroaryl) diphosphine gold(i) precursors

Article abstract of DOI:10.1039/c2dt32973e

Complex [Au{4-C₆F₄(4-C₆BrF ₄)}(tht)] reacts with diphosphines (L-L) such as bis(diphenylphosphino)methane (dppm) or 1,2-bis(diphenylphosphino)benzene (dppb) in a 2:1 molar ratio in dichloromethane, leading to neutral products of stoichiometry [(Au{4-C₆F₄(4-C₆BrF ₄)})₂(μ-L-L)] (L-L = dppm (1), dppb (2)). In the crystal structure of complex 2 short Au...Au interactions of 2.9367(5) and 2.9521(5) A appear. This complex displays an orange emission, which is assigned to arise from a charge transfer transition from a metal centered Au-Au orbital to an orbital located at the diphosphine ligand. Addition of silver trifluoroacetate to these complexes in a 1:1 or a 2:1 molar ratio generates polymeric heterometallic gold-silver compounds of stoichiometry [Ag ₂Au₂{4-C₆F₄(4-C₆BrF ₄)}₂(CF₃CO₂)₂(μ-L-L)] _n (L-L = dppm (3), dppb (4)), which confirms the capability of the neutral [(Au{4-C₆F₄(4-C₆BrF₄)}) ₂(μ-diphosphine)] units to act as electron density donors when treated with a Lewis acid substrate. These heterometallic derivatives show blue emissions indicating large HOMO-LUMO band gaps, due to the stabilization that the gold-based HOMO orbitals suffer when the electron withdrawing silver trifluoroacetate fragments interact with them.

Full text of DOI:10.1039/c2dt32973e

Dalton
Transactions
View Article Online
View Journal | View Issue
PAPER
Luminescent gold–silver complexes derived from
neutral bis(perfluoroaryl)diphosphine gold(I)
precursors†
Cite this: Dalton Trans., 2013, 42, 4267
R. Vilma Bojan,a Rafal Czerwieniec,*b Antonio Laguna,c Tania Lasanta,a
José M. López-de-Luzuriaga,*a Miguel Monge,a M. Elena Olmosa and Harmut Yersin*b
Complex [Au{4-C6F4(4-C6BrF4)}(tht)] reacts with diphosphines (L–L) such as bis(diphenylphosphino)-
methane (dppm) or 1,2-bis(diphenylphosphino)benzene (dppb) in a 2 : 1 molar ratio in dichloromethane,
leading to neutral products of stoichiometry [(Au{4-C6F4(4-C6BrF4)})2(μ-L–L)] (L–L = dppm (1), dppb (2)).
In the crystal structure of complex 2 short Au⋯Au interactions of 2.9367(5) and 2.9521(5) Å appear. This
complex displays an orange emission, which is assigned to arise from a charge transfer transition from a
metal centered Au–Au orbital to an orbital located at the diphosphine ligand. Addition of silver trifluoro-
acetate to these complexes in a 1 : 1 or a 2 : 1 molar ratio generates polymeric heterometallic gold–silver
compounds of stoichiometry [Ag2Au2{4-C6F4(4-C6BrF4)}2(CF3CO2)2(μ-L–L)]n (L–L = dppm (3), dppb (4)),
which confirms the capability of the neutral [(Au{4-C6F4(4-C6BrF4)})2(μ-diphosphine)] units to act as elec-
tron density donors when treated with a Lewis acid substrate. These heterometallic derivatives show blue
emissions indicating large HOMO–LUMO band gaps, due to the stabilization that the gold-based HOMO
orbitals suffer when the electron withdrawing silver trifluoroacetate fragments interact with them.
Received 20th July 2012,
Accepted 18th December 2012
DOI: 10.1039/c2dt32973e
www.rsc.org/dalton
charge transfer (LMCT), metal-to-ligand charge transfer
(MLCT), metal-to-metal charge transfer (MMCT), ligand-to-
Introduction
Aurophilic Au(I)⋯Au(I) interactions have traditionally been the ligand charge transfer (LLCT) and intraligand charge transfer
most studied nonbonding contacts between closed-shell metal (IL) types.5 Nevertheless, the use of phosphines as ligands
ions.1 However, over the past few years, complexes with metallo- allows the interaction of metal pπ and phosphine π-acceptor
philic interactions between gold(I) centres and other closed- orbitals generating low-energy empty π orbitals in the ligands,
shell metal atoms (Au⋯M) have attracted great interest due to which are available as acceptor orbitals for MLCT transitions,
their theoretical interest,2 photophysical properties3 or poten- although a mixed MLCT/MC excited state cannot either be
tial applications.4 In this sense, the presence of a heavy gold excluded.
atom (Au) in these complexes enhances the spin orbit coupling
Additionally in these systems, a strategy that permits the
of the systems, which in turn facilitates the access to triplet tuning of the emission is to incorporate electron donating
excited states via intersystem crossing. In addition, the possibi- or accepting groups, which modify the relative energy of the
lities of electronic transitions are numerous, thus the lowest frontier orbitals in the coordination sphere of the gold centres.
excited states may be of metal-centred (MC), ligand-to-metal In that sense, our group has contributed a number of
examples in which heteronuclear complexes are formed by
Lewis acid–base reactions between basic gold complexes and
aDepartamento de Química, Universidad de La Rioja, Centro de Investigación en
metallic acid salts. Usually, the stability of these complexes is
Síntesis Química (CISQ), Complejo Científico-Tecnológico, 26004-Logroño, Spain.
enhanced by an appreciable ionic component because the met-
E-mail: josemaria.lopez@unirioja.es
allic fragments are of opposite charge. In those examples, the
main ionic character of the interaction makes the excited
states to arise from MMCT transitions and, therefore, the
direct comparison of the energies of the transitions with those
observed for the precursor gold complexes is not possible.
Also, a recent strategy consists of the synthesis of hetero-
nuclear complexes starting from neutral precursors. In this
bInstitut für Physikalische und Theoretische Chemie, Universität Regensburg,
Universitätstr. 31, D-93040 Regensburg, Germany.
E-mail: rafal.czerwieniec@chemie.uni-regensburg.de,
harmut.yersin@chemie.uni-regensburg.de
cDepartamento de Química Inorgánica, Instituto de Ciencia de Materiales de Aragón,
Universidad de Zaragoza-CSIC, 50009-Zaragoza, Spain
†CCDC 891443–891445. For crystallographic data in CIF or other electronic
format see DOI: 10.1039/c2dt32973e
This journal is © The Royal Society of Chemistry 2013
Dalton Trans., 2013, 42, 4267–4277 | 4267

View Article Online
Paper
Dalton Transactions
way, the metal–metal interactions are formed by weaker van
der Waals forces and the charge transfer component that
dominated the excited state in the former is diminished.
On the other hand, as it is well known, the neutral deriva-
tives [Au(C6X5)(tht)] (X = halogen, tht = tetrahydrothiophene)
are important starting materials for the synthesis of gold(I)
complexes through displacement reactions of the weakly co-
ordinated tht ligand by other neutral or anionic ligands, result-
ing in the formation of mononuclear [Au(C6X5)L] or [Au(C6X5)-
X′]− (L, X′ = monodentate ligands) or polynuclear compounds
−
[{Au(C6X5)}nL]n or [{Au(C6X5)}nX′]n (L, X′
= polydentate
ligands) that often display aurophilic interactions.6 With
these precedents, we wondered if the neutral diaryl derivative
[Au{4-C6F4(4-C6BrF4)}(tht)] could react with diphosphines, in
order to obtain basic gold(I) compounds where the presence of
intramolecular interactions is favoured by the bidentate
ligand. The choice of this diaryl precursor is based on
the experience acquired by our group in reactions with bis-
(perhalophenyl)aurate(I) derivatives and acid metallic salts, in
which the basicity of the gold precursor is strongly influenced
by the type of aryl groups.4b,c,7,8 In addition, phosphines are
well known to stabilize electron-rich transition metals in low
oxidation states due to the important π back bonding.
ð1Þ
As Lewis acid we have chosen the dinuclear silver(I)
trifluoroacetate, whose acid capability is very high as we have
shown in previous papers.7–9
Taking into account all above, we studied the behaviour
of the new diaryldiphosphine gold(I) derivatives [Au{4-C6F4-
(4-C6BrF4)}(L)] (L = dppm, dppb) as electron density donors by
treating them with the Lewis acid silver(I) trifluoroacetate. The
crystal structures of the resulting complexes have been deter-
mined by X-ray diffraction methods, and their optical proper-
ties have been experimentally and theoretically studied in
order to rationalize the results.
Fig. 1 Identification of the four inequivalent fluorine atoms in compounds 1
and 2.
at 548–461 cm−1 due to the bidentate diphosphine ligands.
Mass spectra (MALDI-TOF(−)) show signals corresponding to
[Au{4-C6F4(4-C6BrF4)}2]− at m/z = 949 (100%).
Results and discussion
Synthesis and characterization
The 1H NMR spectra of complexes 1 and 2 recorded in
Compounds [(Au{4-C6F4(4-C6BrF4)})2(μ-L–L)] (L–L
= bis(di-
phenylphosphino)methane (dppm) (1) or 1,2-bis(diphenyl- CDCl3 show signals at 7.80–7.28 ppm (1) and 7.62–7.26 ppm
(2), corresponding to the aromatic hydrogen atoms. Besides,
in the spectrum of 1 a triplet at 3.65 ppm is present (2J(H–P)
phosphino)benzene (dppb) (2)) were obtained by reactions of
[Au{4-C6F4(4-C6BrF4)}(tht)] and the selected diphosphines in a
=
2 : 1 molar ratio, using dichloromethane as a solvent. As 9.2 Hz) due to the methylenic hydrogens, which are coupled
with both equivalent phosphorus atoms of the dppm ligand.
The 19F NMR spectra of complexes 1 and 2 show four multi-
plets corresponding to the four inequivalent fluorine atoms in
the 4-C6F4(4-C6BrF4) ligand at −116.5, −133.9, −137.1 and
−140.5 ppm (1) or −114.7, −133.5, −137.2 and −141.0 ppm (2)
expected, the reactions occur with displacement of the weakly
bound tetrahydrothiophene as a free ligand and in almost
quantitative yields (see eqn (1)).
Complexes 1 and 2 are isolated as white solids, stable to air
and moisture at room temperature. They are soluble in
dichloromethane, tetrahydrofuran, acetone and diethyl ether, for F1–F4, respectively (see Fig. 1). The positions for the signals
observed in the 19F NMR spectrum for complex 1 are similar to
and insoluble in n-hexane.
those described for the starting material [Au{4-C6F4(4-C6BrF4)}-
agree well with the stoichiometries (see the Experimental (tht)].10 However, the signal for F1 in complex 2 is shifted to
Analytical and spectroscopic data of complexes 1 and 2
down field.
The 31P{1H} NMR spectra of these complexes display a
section). Their IR spectra show, among others, absorptions at
∼1630, ∼1600, ∼1570, ∼1100 and ∼855 cm−1 arising from the
presence of the 4-C6F4(4-C6BrF4) group bonded to gold(I), and singlet at 32.3 (1) and 34.1 ppm (2), which confirms the
4268 | Dalton Trans., 2013, 42, 4267–4277
This journal is © The Royal Society of Chemistry 2013

View Article Online
Dalton Transactions
Paper
equivalence of the phosphorus atoms in the molecule and
their coordination to the gold centres.
Treatment of [(Au{4-C6F4(4-C6BrF4)})2(μ-L–L)] (L–L = bis-
(diphenylphosphino)methane (dppm) (1) or 1,2-bis(diphenyl-
phosphino)benzene (dppb) (2)) with silver trifluoroacetate
in dichloromethane, in a 1 : 1 or a 1 : 2 molar ratio, leads to the
formation of heterometallic gold silver compounds [Ag2Au2-
{4-C6F4(4-C6BrF4)}2(CF3CO2)2(μ-L–L)]n (L–L = dppm (3), dppb
(4)) (see eqn (2)).
n½Au2f4-C6F4ð4-C6BrF4Þg fμ-PPh2RPPh2gꢀ þ 2n AgCF3CO2
ðR ¼ CH2ð1Þ; C62H4ð2ÞÞ
! n½Au2Ag2f4-C6F4ð4-C6BrF4Þg2ðCF3CO2Þ2fμ-PPh2RPPh2gꢀ
ðR ¼ CH2ð3Þ; C6H4ð4ÞÞ
ð2Þ
Reactions of these precursors with the silver salt in
different molar ratios lead in all cases to a mixture of com-
plexes 3 or 4 and the metal complex added in excess.
Complexes 3 and 4 are isolated as pale yellow solids, stable
to air and moisture at room temperature. They are soluble in
dichloromethane, tetrahydrofuran, acetone and diethyl ether,
and insoluble in n-hexane.
Analytical and spectroscopic data of these complexes agree
with the proposed stoichiometries (see the Experimental
section). Their IR spectra show, among others, absorptions
at 1571, ∼1100 and 856 cm−1 arising from the presence of the
{4-C6F4(4-C6BrF4)} group bonded to gold(I), at 547–459 cm−1
corresponding to the phosphine ligands, and at ∼1645 and
∼1180 cm−1 due to C–O and C–F stretching modes, which con-
firms the presence of trifluoroacetate anions in the molecule.
Fig. 2 Crystal structure of one molecule (up) and packing of molecules in the
crystal (bottom) for compound 2. Hydrogen atoms are omitted for clarity.
1
The H NMR spectra in CDCl3 of complexes 3 and 4 show
the signals corresponding to the methylenic (3) and aromatic
hydrogen atoms (3, 4) at similar shifts to those described for
compounds 1 and 2, respectively.
(4-C6BrF4)}2{μ-1,2-C6H4(PPh2)2}] in the asymmetric unit, where
the diphosphine ligand acts as a bridge between the two gold
centres. A perspective view of the [Au2{4-C6F4(4-C6BrF4)}2{μ-1,2-
C6H4(PPh2)2}] molecule and the packing in the crystal of 2 are
shown in Fig. 2.
In this complex the Au–Au distances are 2.9367(5)
and 2.9521(5) Å, which are considered Au⋯Au intramolecular
interactions (see Table 2). The shortest intermolecular Au–Au
distance is 8.323 Å, which excludes any considerable metal–
metal intermolecular interaction. Thus, the [Au2{4-C6F4-
(4-C6BrF4)}2{μ-1,2-C6H4(PPh2)2}] molecules in the crystal of 2
can be regarded as isolated molecules in a rigid crystalline
environment.
Each gold atom is coordinated to the ipso carbon of the
bis(perhalophenyl) ligand, with normal Au–C and Au–P
bond distances between 2.045(10) and 2.063(9) Å, and between
2.272(2) and 2.295(3) Å, respectively, the longer ones
being similar to those found in related complexes of the type
[Au2(aryl)2(μ-L–L)].11
The 19F NMR spectra of complexes 3 and 4 show four multi-
plets corresponding to the four inequivalent fluorine atoms in
the aromatic ligand 4-C6F4(4-C6BrF4) at −115.6, −133.7, −137.0
and −140.0 ppm (3) or −114.2, −133.4, −137.2 and −140.7 ppm
(4) for F1–F4, respectively. In addition, the CF3 group of the tri-
fluoroacetate ligands appears at −73.1 (3) and −73.3 ppm (4).
Finally, the 31P{1H} NMR spectra of these complexes display
a singlet at 32.4 (3) and 33.9 ppm (4), which confirms the
equivalence of the phosphorus atoms in the molecule and
their coordination to the gold centres.
The resemblance between the spectroscopic data of com-
plexes 3 and 4 with those of their precursor complexes would
be in agreement with the loss of the intermetallic interactions
in solution.
X-ray structural determination of derivatives 2, 3 and 4
The environment of the gold centres shows a deviation
from the linearity, with C–Au–P angles in the range 173.8(3)–
169.3(3)°, probably due to the presence of aurophilic intramole-
cular interactions aided by the rigidity generated by the
Single crystals suitable for X ray diffraction studies of complex
2 were obtained by slow diffusion of n-hexane into a saturated
solution of the complex in dichloromethane. The crystal struc-
ture for 2 shows two dinuclear molecules of [Au2{4-C6F4-
This journal is © The Royal Society of Chemistry 2013
Dalton Trans., 2013, 42, 4267–4277 | 4269

View Article Online
Paper
Dalton Transactions
Table 1 Data collection and structure refinement details for 1–3
Compound
2
3·0.5C6H14·H2O
4·0.5CH2Cl2
Chemical formula
Crystal habit
Crystal size/mm
Crystal system
C54H24Au2Br2F16P2
Colourless prism
0.3 × 0.28 × 0.2
Monoclinic
P21/n
C53H22Ag2Au2Br2F22O4P2·0.5C6H14·H2O
Colourless prism
0.25 × 0.25 × 0.2
Triclinic
ˉ
P1
C58H24Ag2Au2Br2F22O4P2·0.5CH2Cl2
Colourless plate
0.35 × 0.3 × 0.15
Triclinic
ˉ
P1
Space group
a/Å
b/Å
c/Å
α/°
15.3232(3)
17.5150(5)
37.5226(9)
90
99.901(1)
90
9920.5(4)
8
2.132
13.0125(6)
14.8392(5)
17.5999(7)
91.369(2)
110.783(2)
92.024(2)
3172.9(2)
2
12.1335(3)
15.0322(6)
18.1077(7)
102.664(1)
91.933(2)
107.338(2)
3058.51(19)
2
β/°
γ/°
V/Å3
Z
Dc/g cm−3
2.126
2.255
M
F(000)
1592.43
6000
2031.22
1910
2076.67
1950
T/°C
2θmax/°
−150
−173
−150
56
56
56
μ(Mo-Kα)/mm−1
No. refl. measured
No. unique refl.
Rint
7.683
124 465
23 182
0.0701
0.0637
0.1259
23 182
1369
332
6.637
6.929
47 997
14 985
0.0627
0.0576
0.1558
14 985
798
33
1.043
4.815
49 615
14 674
0.0549
0.0675
0.2387
14 674
856
190
1.125
3.430
R [F > 2σ(F)]a
wR [F2, all refl]b
No. of refl. used
No. of parameters
No. of restraints
Sc
1.197
4.599
Max. residual electron density/e Å−3
2
a R(F) = Σ||Fo| − |Fc||/Σ|Fo|. b wR(F2) = [Σ{w(Fo2 − Fc2)2}/Σ{w(Fo2)2}]0.5; w−1 = σ2(Fo2) + (aP)2 + bP, where P = [Fo + 2Fc2]/3 and a and b are constants
adjusted by the program. c S = [Σ{w(Fo2 − Fc2)2}/(n − p)]0.5, where n is the number of data and p the number of parameters.
Table 2 Selected bond lengths [Å] and angles [°] for complex 2
Au(1)–C(1)
Au(2)–C(21)
Au(1)–P(1)
2.058(9)
2.045(10)
2.277(3)
2.295(3)
2.9367(5)
173.8(3)
169.8(3)
Au(3)–C(101)
Au(4)–C(121)
Au(3)–P(3)
Au(4)–P(4)
Au(3)–Au(4)
C(101)–Au(3)–P(3)
C(121)–Au(4)–P(4)
2.063(9)
2.053(10)
2.272(2)
2.278(3)
2.9521(5)
173.5(3)
169.3(3)
Au(2)–P(2)
Au(1)–Au(2)
C(1)–Au(1)–P(1)
C(21)–Au(2)–P(2)
1,2-C6H4(PPh2)2 ligand. The aromatic rings in the 4-C6F4-
(4-C6BrF4) ligands display dihedral angles of 52.12(29)° and
58.80(30)°, lower than the value described for the free ligand:
60.2(1)°.12
Single crystals suitable for X-ray diffraction studies of com-
plexes 3·0.5C6H14·H2O and 4·0.5CH2Cl2 were obtained by
slow diffusion of n-hexane into a saturated solution of the
complexes in dichloromethane, both of them crystallizing
with the solvent. Crystal structures of 3·0.5C6H14·H2O and
4·0.5CH2Cl2 are formed by the repetition of alternating dinuc-
lear [Au2{4-C6F4(4-C6BrF4)}2(μ-L–L)] (L–L = dppm, dppb) and
[Ag2(CF3CO2)2] units, which are connected by short un-
supported Au⋯Ag contacts, generating polymeric chains (see
Fig. 3 and 4).
Fig. 3 Expansion of the crystal structure for compound 3. Hydrogen atoms are
omitted for clarity. Colour code: gold: yellow; silver: blue; phosphorous: orange;
carbon: grey; oxygen: red; fluorine: light green; bromine: dark red.
other polymeric Au/Ag species, such as [AuAgR(CF3CO2)(tht)]n
(R = C6F5, C6Cl5), [AuAg2(C6Cl2F3)(CF3CO2)2(tht)]n,8 [AuAg4-
(mes)(RCO2)4(tht)x]n (x = 1, R = CF3, CF2CF3; x = 3, R = CF2CF3;
mes = mesityl, 2,4,6-C6Me3H2), {[AuAg4(mes)(CF3CO2)4(tht)-
(H2O)]·H2O·CH2Cl2}n,7a (NBu4)2[AuAg4(C6Cl2F3)2 (CF3CO2)5]7b
or [AuAg3(C6F5)(CF3CO2)3(CH2PPh3)]n,9 where the Au–Ag dis-
tances lie in the range of 2.8135(5)–3.1347(7) Å (average value
of 2.9054 Å) (see Table 3 and 4).
These Au⋯Ag interactions, of 2.8377(7) and 2.7984(8) Å
in 3·0.5C6H14·H2O, and 2.9106(10) and 2.8532(9)
Å in
4·0.5CH2Cl2, are in general shorter than those described for
4270 | Dalton Trans., 2013, 42, 4267–4277
This journal is © The Royal Society of Chemistry 2013

View Article Online
Dalton Transactions
Paper
The gold atoms are linearly coordinated to the Cipso of the
perhalobiphenyl ligand and to one of the phosphorus of the
diphosphine, with normal Au–C (2.044(9)–2.079(13) Å) and
Au–P distances (2.268(3)–2.287(2) Å). The aromatic rings in the
4-C6F4(4-C6BrF4) ligand form dihedral angles between 54.52(15)
and 73.90(51)°.
Regarding the silver atoms, it is worth mentioning the pres-
ence of a rather unusual Ag⋯C contact of 2.666(12) Å between
one of the silver atoms of each unit and the meta carbon of a
phenyl group of the diphosphine in the crystal structure of
3·0.5C6H14·H2O. Similarly, one of the silver atoms of each
[Ag2(CF3CO2)2] interacts with one ipso carbon of the perhalobi-
phenyl ligand, with a Ag–C distance of 2.698(12) Å in the case
of complex 4·0.5CH2Cl2.
Fig. 4 Expansion of the crystal structure for compound 4. Hydrogen atoms are
omitted for clarity. Colour code: gold: yellow; silver: blue; phosphorous: orange;
carbon: grey; oxygen: red; fluorine: light green; bromine: dark red.
Photophysical properties
The absorption spectra of the precursor gold complexes 1 and
2 in dichloromethane solutions (≈10−6 mol L−1) display
similar features with strong absorptions starting at 225 nm
with tails extending to 325 nm. Thus, both show intense
maxima at 233 (ε = 11 × 104 (1), 9 × 103 mol−1 L cm−1 (2)) and
254 nm (ε = 13 × 104 (1), 9.4 × 103 mol−1 L cm−1 (2)). These
bands can arise from transitions located in the bis(perhalo-
phenyl) ligand, probably between π–π* orbitals, and from σ →
aπ transitions associated with coordinated phosphines. In fact,
the perhalophenyl precursor gold complex [Au{4-C6F4(4-
C6BrF4)}(tht)] displays one absorption at 259 nm, which is red
shifted from the corresponding free perhalophenyl (248 nm)
and, on the other hand, free phosphines display bands
assigned to l → aπ transitions at higher wavelengths.13
Additionally, for both complexes a broadening can be observed
in the less energetic region that can be related to the presence
of intramolecular gold–gold interactions.
Table 3 Selected bond lengths [Å] and angles [°] for complex 3·0.5C6H14·H2O
Au(1)–C(1)
Au(2)–C(21)
Au(1)–P(1)
Au(2)–P(2)
Au(1)–Au(2)
Au(1)–Ag(1)
Au(2)–Ag(2)
C(1)–Au(1)–P(1)
C(21)–Au(2)–P(2)
Ag(1)–Au(1)–Au(2)
Ag(2)–Au(2)–Au(1)
2.052(8)
2.047(9)
2.287(2)
2.275(2)
2.9830(5)
2.8377(7)
2.7984(8)
174.8(2)
173.9(3)
149.85(2)
139.90(2)
Ag(1)–O(1)
Ag(1)–O(2)#1
Ag(2)–O(3)
Ag(2)–O(4)#2
Ag(2)–C(75)#2
Ag(1)–Ag(1)#1
Ag(2)–Ag(2)#2
O(2)#1–Ag(1)–O(1)
O(3)–Ag(2)–O(4)#2
Ag(1)#1–Ag(1)–Au(1)
Au(2)–Ag(2)–Ag(2)#2
2.184(8)
2.181(7)
2.204(8)
2.233(9)
2.666(12)
2.8214(14)
2.8860(16)
157.7(2)
160.3(3)
123.30(4)
122.49(4)
Symmetry transformations used to generate equivalent atoms: #1 −x +
1, −y + 2, −z + 1 #2 −x + 2, −y + 1, −z + 1.
Table 4 Selected bond lengths [Å] and angles [°] for complex 4·0.5CH2Cl2
Au(1)–C(1)
Au(2)–C(21)
Au(1)–P(1)
Au(2)–P(2)
Au(1)–Ag(2)
Au(2)–Ag(1)
Au(1)–Au(2)
C(1)–Au(1)–P(1)
C(21)–Au(2)–P(2)
Ag(2)–Au(1)–Au(2)
Ag(1)–Au(2)–Au(1)
2.079(13)
2.044(9)
2.268(3)
2.285(2)
2.9106(10)
2.8532(9)
2.9884(5)
173.0(3)
175.6(3)
149.66(3)
145.08(3)
Ag(1)–Ag(1)#1
Ag(2)–Ag(2)#2
Ag(1)–O(2)
Ag(1)–O(1)
Ag(2)–O(3)
Ag(2)–O(4)
Ag(2)–C(1)
O(2)–Ag(1)–O(1)
O(3)–Ag(2)–O(4)
Au(2)–Ag(1)–Ag(1)#1
Au(1)–Ag(2)–Ag(2)#2
2.8605(16)
2.9293(19)
2.202(9)
2.207(10)
2.213(12)
2.226(12)
2.698(12)
163.6(3)
In the case of the heterometallic gold–silver complexes 3
and 4, the absorption spectra display almost identical features.
Thus, complex 3 shows bands at 234 (ε = 7 × 103 mol−1 L cm−1
)
and 254 nm (ε = 8.3 × 103 mol−1 L cm−1) and complex 4 at 238
(ε = 8.7 × 103 mol−1 L cm−1) and 251 nm (ε = 9 × 103 mol−1
L
cm−1), respectively. Consequently, we assign these bands to
similar origins to that in the precursors. In addition, both
show weak non-well resolved bands at 295 nm (ε = 2.6 × 103
mol−1 L cm−1 (3)) and 310 nm (ε = 1.5 × 103 mol−1 L cm−1 (4)).
These bands are not present in the spectra of the phosphines
or perhalophenyl ligands. Therefore, we can tentatively assign
them to the presence of intermetallic interactions (Au⋯Au or
Au⋯Ag) (see Fig. 5).
157.0(4)
133.47(5)
114.05(5)
Symmetry transformations used to generate equivalent atoms: #1 −x +
1, −y + 1, −z + 1 #2 −x + 1, −y, −z.
In addition to these metal–metal contacts, there are Ag⋯Ag
intramolecular interactions within the silver trifluoroacetate
dimers of 2.8214(14) and 2.8860(16) Å in 3·0.5C6H14·H2O, and
2.8605(16) and 2.9293(19) Å in 4·0.5CH2Cl2, obviously favoured
by the presence of bridging ligands. Finally, also the gold
centres of each dinuclear unit maintain an intermetallic
contact of 2.9830(5) Å in 3·0.5C6H14·H2O and 2.9884(5) Å in
4·0.5CH2Cl2. It is worth noting that the Au–Au distances are of
the same order in both structures, about 0.04 Å longer than in
complex 2. Therefore, this shortening seems to be a conse-
quence of the incorporation of the [Ag2(CF3CO2)2] units.
Both Au(I) complexes 1 and 2 as well as the hybrid Au–Ag
crystals 3·0.5C6H14·H2O and 4·0.5CH2Cl2 are brightly lumines-
cent. The emission spectra together with the excitation profiles
recorded for solid samples at room temperature are repro-
duced in Fig. 6. Emission maxima, quantum yields and decay
times are listed in Table 5.
Crystalline samples of the studied Au(I) complexes show
intense green (1) and orange (2) luminescence with high
quantum yields ϕPL of 58 and 14% for 1 and 2, respectively.
They show broad and unstructured emission bands centered
This journal is © The Royal Society of Chemistry 2013
Dalton Trans., 2013, 42, 4267–4277 | 4271

View Article Online
Paper
Dalton Transactions
Table 5 Summary of the photophysical properties of Au(I) complexes 1 and 2
and hybrid Au–Ag compounds 3·0.5C6H14·H2O and 4·0.5CH2Cl2 determined for
solid samples at ambient temperature. Respective emission spectra are drawn in
Fig. 6. All measurements were carried out under an inert N2 atmosphere
a
RT λem
[nm]
Emission decay
time τem [μs]
Photoluminescence quantum
yield ϕPL d [%]
1
2
3
4
496
593
439
436
1.5b
6.2b
2.5b
0.3b
1.0c
58
14
24
<3e
a Experimental error 1 nm. b Experimental error 0.2 μs. c The decay
is distinctly non-monoexponential. The measured decay profile could
Fig. 5 UV-Vis spectra of complexes 1–4 in dichloromethane.
be successfully fitted only by using a biexponential decay function.
e
d Experimental error
3%. ϕPL of this material lies below the
resolution threshold of our setup, which is about 3%.
largely forbidden transitions. Therefore, they are assigned as
phosphorescence from the lowest excited triplet state T1 to the
ground state S0. Intensive T1 → S0 emissions with ϕPL of tens
of percent and radiative decay times of several microseconds
are frequently found for organometallic compounds of tran-
sition metal ions (mostly 3-rd row, e.g. Pt, Ir, Au),14 in which
strong spin–orbit coupling (SOC) induced by the heavy metal
atom leads to effective mixing of the triplet and singlet wave-
functions.14a,15 In particular, the lowest triplet state can get
certain contributions from higher lying singlet states and, as a
result, the formally spin-forbidden T1 → S0 transition becomes
partly allowed. Compounds with distinctly strong SOC, like
Ir-tris(2-phenylpyridine), Ir(ppy), may show ϕPL values of
almost 100% with an emission decay time τem in the order of
1 microsecond.14b,16
The large difference between the energy of the emissions in
complexes 1 and 2 suggests that, in this case, a metal centred
Au–Au transition is not likely, since as it is expected, small
differences in metal–metal distances in the complexes should
not lead to important changes in the energy of the emissions.
On the other hand, an intraligand (IL) ππ* transition located in
the diaryl groups or in the phosphine ligand can be excluded
because more energetic emissions should be expected. Also
metal (gold) to ligand (bis(perfluoroaryl)) charge transfer
(MLCT) transitions can also be ruled out, since in such cases
similar emissions should be expected for both complexes.
What it seems likely is that the photophysical properties of 1
and 2 strongly depend on the bridging diphosphine ligand.
However, the exact role of the dppm and dppb ligands is
difficult to assess. Among the possibilities, reasonable
assumptions are, for example, that the emissions can arise
from a metal (gold) to ligand (phosphine) charge transfer
(MLCT), or from a ligand (bis(perfluoroaryl)) to ligand (phos-
phine) charge transfer. Especially in the case of complex 1, an
ILCT associated with the σ → aπ transition in the phosphine
cannot be ruled out, since its emission appears at similar ener-
gies than those reported for other gold–diphosphine com-
plexes in which the emissions were assigned to have that
origin.13
Fig. 6 Room-temperature excitation and luminescence spectra of solid Au(I)
complexes 1 and 2 and Au–Ag hybrid crystals 3·0.5C6H14·H2O and 4·0.5CH2Cl2.
Emission spectra were recorded upon excitation at λexc = 380 nm. Excitation
spectrum of each sample was recorded at a detection wavelength λdet corre-
sponding to the respective emission maximum. Luminescent intensity is in arbi-
trary units. Energy scale (in cm−1) is given for orientation.
at λmax of 496 (1) and 593 nm (2), respectively. The emission
spectra are considerably red-shifted relative to the lowest-
energy absorptions manifested in the excitation spectra
(Fig. 6). For instance, for complex 1, emission maximum (λmax
= 496 nm) and the lowest absorption band maximum (λabs
365 nm) are separated by ca. 7000 cm−1
≈
.
On the other hand, the decay times τem of luminescence
determined for 1 and 2 are τem = 1.5 and 6.2 μs, respectively.
Such high τem values show that these emissions represent
4272 | Dalton Trans., 2013, 42, 4267–4277
This journal is © The Royal Society of Chemistry 2013

View Article Online
Dalton Transactions
Paper
Interestingly, the reaction between the gold complexes 1
and
2 and silver trifluoroacetate with the subsequent
formation of heterometallic Au–Ag structures leads to con-
siderable changes in the photophysical behaviour. Both
mixed-metal Au–Ag crystals of 3 and 4 display blue lumine-
scence, with λmax = 439 and 436 nm, respectively. Interestingly,
compound 3 displays a high luminescence quantum yield of
24% while the decay time is determined to be τem = 2.5 μs. As
in the precursor complexes, they do not show emissive proper-
ties in solution and the lifetimes suggest phosphorescent pro-
cesses (see Table 5). In principle, the origins of the electronic
transitions that give rise to the luminescence can be similar to
the precursor gold complexes (see above), nevertheless a
curious blue shift, which is larger in the case of complex 2, is
observed when silver trifluoroacetate is incorporated into the
structure.
Taking into account the molecular structures of complexes
2 and 4, the Au–Au distance in [Ag2Au2{4-C6F4(4-C6BrF4)}2-
(CF3CO2)2(μ-dppb)]n is only 0.04 Å longer than that found for
complex 2. This small variation seems not to be responsible
for a blue shift of more than 6500 cm−1. Consequently, the
interacting gold centres seem not to be the only responsible
for the transitions, although the blue shift suggests the stabil-
ization of the HOMO orbitals, probably due to the electron
withdrawing silver trifluoroacetate fragments interacting with
them. Therefore, what it seems likely is that the emissions
arise from transitions between the electron rich bis(perhalo-
phenyl) groups to empty antibonding orbitals of the phos-
phines and that the introduction of the electron withdrawing
silver trifluoroacetate diminishes the electron density in those
ligands through the gold centres, stabilizing the HOMO orbi-
tals and shifting the emissions to higher energies. In order to
get more insight into the orbital nature of the emitting state
DFT computational studies on models of the complexes were
performed (see below).
Fig. 7 Theoretical excitation energy (red line) compared to the excitation spec-
trum for complex 2 (up). Frontier molecular orbitals involved in the lowest triplet
excitation for model [Au2(C6F4-C6F4Br)2(dppb)] representing complex
(bottom).
2
First, the nature of the frontier orbitals has been analysed
from the results obtained in single-point DFT-B3LYP calcu-
lations (see Fig. 7 and 8). For the dinuclear gold(I) model
[Au2{4-C6F4(4-C6BrF4)}2(μ-dppb)] (2), the highest occupied
molecular orbital HOMO is mostly located at the metal centres
DFT calculations
In view of the different photophysical properties observed showing a 5dz2σ* antibonding character (51% of contribution
experimentally for the dinuclear diphosphinogold(I) precur- obtained from the population analysis), with some contri-
sors and the corresponding gold(I)–silver(I) heteronuclear bution from the perhalophenyl ligands (38%) and the diphos-
derivatives, we have carried out single point DFT and TD-DFT phine (11%). The population analysis of other highly occupied
calculations on model systems of complexes 2 and 4. In the molecular orbitals (HOMO − 1 to HOMO − 5) shows a main
case of model 2, it consists of the [Au2{4-C6F4(4-C6BrF4)}2- contribution from the perhalophenyl ligands. By contrast, the
(μ-dppb)] structure obtained through X ray diffraction studies, lowest unoccupied molecular orbital LUMO is mainly centered
whereas in the case of model 4 we have built up a model at the phosphine ligand (89%) with a smaller contribution
system using the X-ray diffraction results that is based on the from the gold(I) centres (7%). A similar assignment of the
dinuclear gold(I) moiety of model 2 with two dinuclear LUMO orbital was recently proposed for dinuclear diphos-
[Ag2(CF3CO2)2] units, each one interacting with one gold(I) phine gold(I) thiolate complexes.17 Other unoccupied mole-
centre. We have also made an analysis of the electron density cular orbitals such as LUMO + 1 to LUMO + 3 are also mainly
from the total SCF density mapped with electrostatic potential located at the phosphine ligand, although some small contri-
(ESPs) on these models in order to check which are the donor- butions from perhalophenyl groups and gold centres are also
and the electron-acceptor parts of the molecule. Finally, the noticeable (see population analysis in Table 6).
use of TD-DFT has allowed us to estimate the energy of the
In the case of model [Au2Ag4{4-C6F4(4-C6BrF4)}2(CF3CO2)4-
first triplet excitation that could be related to the phosphores- (μ-dppb)], representing complex 4, the character of the frontier
cent emissions observed experimentally for both compounds.
orbitals shows significant differences with respect to that of
This journal is © The Royal Society of Chemistry 2013
Dalton Trans., 2013, 42, 4267–4277 | 4273

View Article Online
Paper
Dalton Transactions
Table 7 Population analysis showing the contribution of the different mole-
cular parts for [Au2Ag4{4-C6F4(4-C6BrF4)}2(CF3CO2)4(μ-dppb)]
%4-C6F4-
(4-C6BrF4)
Model (orbital)
%Au
%Ag
%dppb
%CF3CO2
(LUMO)
(HOMO)
(HOMO − 1)
(HOMO − 2)
23
2
38
1
10
0
14
2
16
97
32
95
48
0
12
1
3
1
4
1
Fig. 8 Theoretical excitation energy (red line) compared to the excitation spec-
trum for complex 4 (up). Frontier molecular orbitals involved in the lowest triplet
excitation for model [Au2Ag4(C6F4-C6F4Br)2(CF3CO2)4(dppb)] representing
complex 4 (bottom).
Fig. 9 Electron densities from the total SCF density mapped with electrostatic
potentials (ESPs) for models of complexes 2 (up) and 4 (bottom).
Table 6 Population analysis showing the contribution of the different mole-
cular parts for [Au2{4-C6F4(4-C6BrF4)}2(μ-dppb)]
In Fig. 9 we show the electron densities from the total SCF
density mapped with electrostatic potentials (ESPs) for models
2 and 4. In the case of model 2, we observe that most of the
electron density is located at the bis(perhalophenyl) groups
and, to a less extent, at gold centres. It is worth mentioning
that the electron-deficient part of the molecule is the phos-
phine ligand, what, together with the observed experimental
results and the molecular orbital analysis, would suggest that
the luminescence observed for this complex would arise from
Model (orbital)
%Au
%4-C6F4(4-C6BrF4)
%dppb
(LUMO + 3)
(LUMO + 2)
(LUMO + 1)
(LUMO)
9
10
10
7
23
12
5
4
38
68
78
85
89
11
(HOMO)
51
model 2. Thus, the HOMO orbital is mostly located (97%) at a mixed triplet ligand to ligand transition between the bis-
the bis(perhalophenyl) ligands bonded to gold(I), while the (perhalophenyl) ligand and the diphosphine (3LLCT) and a
occupied orbital showing a 5dz2σ* antibonding character in metal (gold centres) to ligand (diphosphine) charge transfer
the Au(I) metal centres (38%), with some contribution of the transition (3MLCT). In the case of model 4, the colour contrast
bis(perhalophenyl) ligands (32%), is now the HOMO − 1 is not very clear but it seems that the electron-rich part of the
orbital. Again, HOMO − 2 is placed at the bis(perhalophenyl) molecule is mainly the anionic bis(perhalophenyl) ligands
ligands. Another interesting difference is found for the charac- and, to a lesser extent, the gold(I) centres, whereas the diphos-
ter of the LUMO orbital, in which a larger metal-character is phine ligand and the silver centres are the electron-deficient
developed (23% at Au and 10% at Ag) if compared to model 2, part of the molecule. Again, this result would be in agreement
although the diphosphine is still the largest contribution to with the experimental observations and the molecular orbital
this orbital (48%) (see Fig. 8 and Table 7).
structure, which suggests that the emission in these
4274 | Dalton Trans., 2013, 42, 4267–4277
This journal is © The Royal Society of Chemistry 2013

View Article Online
Dalton Transactions
Paper
heteronuclear compounds would arise from a ligand to ligand Instrumentation
charge transfer transition from the perhalophenyl groups to
the diphosphine, although a small contribution from a tran-
sition among the metals could not be ruled out.
Infrared spectra were recorded in the 4000–200 cm−1 range on
a Nicolet Nexus FT-IR using Nujol mulls between polyethylene
sheets. C, H analyses were carried out with a Perkin-Elmer
240C microanalyzer. Mass spectra were recorded on a Bruker
Microflex MALDI-TOF, using dithranol (DIT) as a matrix. 1H,
19F and 31P{1H} NMR spectra were recorded on a Bruker ARX
300 in CDCl3 solutions. Chemical shifts are quoted relative to
SiMe4 (1H, external), CFCl3 (19F, external) and H3PO4 (85%)
(31P{1H}, external). Luminescence spectra were recorded for
solid samples with a Horiba Jobin Yvon Fluorolog 3 steady-
state fluorescence spectrometer. This spectrometer was modi-
fied to allow for measurements of emission decay times. As
excitation source a pulsed diode laser (PicoQuant GmbH
As we have commented above, complexes 2 and 4 display
phosphorescent emissions at different energies. The use of the
TD-DFT approach allows us to estimate the energy and mole-
cular orbitals involved in the lowest triplet electronic excitation,
which can be related to the observed emissions. The calculated
triplet excitation energy for model 2 is 388 nm and it is com-
parable with the experimental excitation spectrum of complex
2 in solid state at room temperature (see Fig. 7). This triplet
excitation arises from the occupied HOMO and arrives
mainly to LUMO with some contributions from LUMO + 1 to
LUMO + 3. Taking into account the above mentioned character
for these orbitals, we can confirm the experimental and
the theoretically predicted phosphorescent emission for
complex 2, based on the MO calculations and the electrostatic
potentials as an admixture of a 3LLCT and a 3MLCT transition.
A similar TD-DFT analysis has been carried out for model
system [Au2Ag4{4-C6F4(4-C6BrF4)}2(CF3CO2)4(μ-dppb)] repre-
senting complex 4. The theoretically predicted triplet exci-
tation energy of 393 nm fits fairly well with the experimental
excitation maximum at 375 nm (see Fig. 8). In this case, the
molecular orbitals involved in this electronic transition are the
occupied HOMO to HOMO − 2 and the empty LUMO. This
Model LDH-P-C-375) with the excitation wavelength λexc
=
372 nm and a pulse width of 100 ps was used. The emission
was detected with a photomultiplier attached to a FAST
ComTec multichannel scaler PCI card with a time resolution
of 250 ps. Photoluminescence (PL) quantum yields were deter-
mined using a Hamamatsu system for absolute PL quantum
yield measurements (type C9920-02) equipped with an inte-
grating sphere with the Spectralon® inner surface coating.
Synthesis
Synthesis of [Au2{4-C6F4(4-C6BrF4)}2{µ-PPh2CH2PPh2}] (1)
MO’s combination would indicate that the experimentally and [Au2{4-C6F4(4-C6BrF4)}2{µ-1,2-(C6H4)(PPh2)2}] (2). To a solu-
observed phosphorescence would arise from a 3LLCT tran- tion of [Au{4-C6F4(4-C6BrF4)}(tht)]11 (0.227 mmol, 150.0 mg) in
sition, involving MOs located at the bis(perhalophenyl) units dichloromethane was added PPh2CH2PPh2 (0.113 mmol,
as the starting orbitals and arriving to an orbital placed mainly 44.0 mg) or 1,2-C6H4(PPh2)2 (0.113 mmol, 51.0 mg). After 1 h
at the diphosphine, although a contribution from the metals, of stirring, the solution was concentrated under vacuum.
both in the starting and the arriving orbitals, could not be Finally, the addition of n-hexane (5 mL) led to the precipitation
neglected.
of products 1 or 2 as white solids.
(1) Yield: 90%. Elemental analysis (%) calcd for
1
(C49H22Au2Br2F16P2): C 38.46, H 1.45. Found: C 39.04, H 1.48.
1H NMR (300 MHz, CDCl3, ppm): δ 7.80–7.28 (20H, C6H5) and
Conclusions
2
3.65 (t, 2H, CH2, J(H–P) = 9.2 Hz). 19F NMR (283 MHz, CDCl3,
The use of different diphosphines, such as dppm or dppb, ppm): δ −116.5 (m, 4F, F1), −133.9 (m, 4F, F2), −137.1 (m, 4F,
leads to the synthesis of a new class of bisaryldiphosphinegold(I) F3), −140.5 (m, 4F, F4). 31P{1H} NMR (121 MHz, CDCl3, ppm): δ
orange emitters. The addition of silver trifluoroacetate to the 32.3 (s). MALDI-TOF(−) m/z (%): 949 [Au{4-C6F4(4-C6BrF4)}2]−
complexes [(Au{4-C6F4(4-C6BrF4)})2(μ-L–L)] (L–L = dppm (1), (100). FT-IR (Nujol): ν(4-C6F4(4-C6BrF4)) at 1629, 1597, 1571,
dppb (2)) generates a very large shift of their emission maxima 1097 and 858 cm−1, ν(CH2(PPh2)2) at 524, 509, 479 and
to the blue region.
461 cm−1
(2) Yield: 95%. Elemental analysis (%) calcd for
.
Experimental results and DFT and TD-DFT calculations on
2
3
the model system of 2 reveal an admixture of a LLCT and a (C54H24Au2Br2F16P2): C 40.73, H 1.52. Found: C 40.85, H 1.50.
3MLCT transition as the origin for its phosphorescent behav- 1H NMR (300 MHz, CDCl3, ppm): δ 7.62–7.26 (m, 24H). 19F
iour, whereas on the model system of complex 4 phosphor- NMR (283 MHz, CDCl3, ppm): δ −114.7 (m, 4F, F1), −133.5 (m,
escence would mainly arise from a 3LLCT transition.
4F, F2), −137.2 (m, 4F, F3), −141.0 (m, 4F, F4). 31P{1H} NMR
(121 MHz, CDCl3, ppm): δ 34.1 (s). MALDI-TOF(−) m/z (%):
949 [Au{4-C6F4(4-C6BrF4)}2]− (100). FT-IR (Nujol): ν(4-C6F4-
(4-C6BrF4)) at 1630, 1598, 1570, 1096 and 854 cm−1, ν(1,2-
Experimental
General
C6H4(PPh2)2) at 548, 536, 516 and 501 cm−1
Synthesis of [Ag2Au2{4-C6F4(4-C6BrF4)}2(CF3CO2)2{µ-
.
Silver trifluoroacetate, bis(diphenylphosphino)methane and PPh2CH2PPh2}]n (3) and [Ag2Au2{4-C6F4(4-C6BrF4)}2(CF3CO2)2-
1,2-bis(diphenylphosphino)benzene are commercially available {µ-1,2-C6H4(PPh2)2}]n (4). To solution of [Au2{4-C6F4-
a
and were purchased from Aldrich.
(4-C6BrF4)}2{µ-PPh2CH2PPh2}] (1) (0.068 mmol, 105.0 mg) or
This journal is © The Royal Society of Chemistry 2013
Dalton Trans., 2013, 42, 4267–4277 | 4275

View Article Online
Paper
Dalton Transactions
[Au2{4-C6F4(4-C6BrF4)}2{µ-1,2-(C6H4)(PPh2)2}] (2) (0.068 mmol, were performed. The B3LYP functional19 as implemented in
108.0 mg) in dichloromethane (20 mL) was added AgCF3CO2 GAUSSIAN0920 was used. In all calculations, the Karlsruhe
(0.136 mmol, 30.0 mg). After 1 h of stirring, the solution was split-valence quality basis sets21 augmented with polarization
concentrated under vacuum. Finally, the addition of n-hexane functions22 were used (SVP). The Stuttgart effective core poten-
(5 mL) led to the precipitation of products 3 or 4 as pale yellow tials of Andrae augmented with two f-type polarization func-
solids.
(3) Yield: 65%. Elemental analysis (%) calcd for
tions were used for Au and Ag.23 The population analysis has
been carried out using the GaussSum 2.2 program.24 We have
3
(C53H22Au2Ag2Br2F22O4P2): C 32.32, H 1.12. Found: C 32.40, H also carried out an analysis of the electron densities from the
1.15. 1H NMR (300 MHz, CDCl3, ppm): δ 7.79–7.28 (20H, C6H5) total SCF density mapped with electrostatic potentials (ESPs)
2
and 3.80 (t, 2H, CH2, J(H–P) = 11.0 Hz). 19F NMR (283 MHz, for model systems [Au2{4-C6F4(4-C6BrF4)}2(μ-dppb)] and
CDCl3, ppm): δ −73.1 (s, 3F, –CF3), −115.6 (m, 4F, F1), −133.7 [Au2Ag4{4-C6F4(4-C6BrF4)}2(CF3CO2)4(μ-dppb)].
(m, 4F, F2), −137.0 (m, 4F, F3), −140.0 (m, 4F, F4). 31P{1H}
NMR (121 MHz, CDCl3, ppm): δ 32.4 (s). MALDI-TOF(+) m/z
(%): 1065 [AgAu{4-C6F4(4-C6BrF4)}{μ-PPh2CH2PPh2}]+ (50),
1639 [AgAu2{4-C6F4(4-C6BrF4)}2{μ-PPh2CH2PPh2}]+ (25). FT-IR
Acknowledgements
(Nujol): ν(4-C6F4(4-C6BrF4)) at 1571, 1102 and 856 cm−1
ν(CF3CO2) at 1648 and 1174 cm−1, ν(CH2(PPh2)2) at 524, 508,
479 and 459 cm−1
,
The German Federal Ministry of Education and Research
(BMBF) and D.G.I.(MEC)/FEDER (project number CTQ2010-
20500-C02-02) are acknowledged for the funding of our
research. T. L. thanks MICINN for a grant. J. M. L-de-L and
H. Y. acknowledge the receipt of an MICINN-DAAD joint project
(HD2008-0022). The authors thank to the Centro de Super-
computación de Galicia (CESGA) for computational resources.
.
(4) Yield: 65%. Elemental analysis (%) calcd for
4 (C58H24Au2Ag2Br2F22O4P2): C 34.23, H 1.18. Found: C 34.45,
H 1.19. 1H NMR (300 MHz, CDCl3, ppm): δ 7.61–7.28 (24H,
C6H5). 19F NMR (283 MHz, CDCl3, ppm): δ −73.1 (s, 3F, –CF3),
−114.2 (m, 4F, F1), −133.4 (m, 4F, F2), −137.2 (m, 4F, F3),
−141.0 (m, 4F, F4). 31P{1H} NMR (121 MHz, CDCl3, ppm):
δ 33.9 (s). MALDI-TOF(−) m/z (%): 333 [Ag(CF3CO2)2]− (100),
555 [Ag2(CF3CO2)3]− (25). FT-IR (Nujol): ν(4-C6F4(4-C6BrF4)) at
Notes and references
1098 and 856 cm−1, ν(CF3CO2) at 1645 and 1197 cm−1
,
ν(CH2(PPh2)2) at 547, 534, 518 and 501 cm−1
.
1 (a) H. Schmidbaur, in Gold: Progress in Chemistry, Biochem-
istry and Technology, John Wiley & Sons, New York, 1999;
Crystallography
(b)
H.
Schmidbaur,
Nature,
2001,
413,
31;
Crystals were mounted in inert oil on glass fibers and trans-
ferred to the cold gas stream of a Nonius Kappa CCD diffracto-
meter equipped with an Oxford Instruments low-temperature
attachment. Data were collected using monochromated Mo Kα
radiation (λ = 0.71073 Å). Scan type ω and ϕ. Absorption correc-
tions: semiempirical (based on multiple scans). The structures
were solved by direct methods and refined on F2 using the
program SHELXL-97.18 All non-hydrogen atoms were refined
anisotropically. Hydrogen atoms were included using a riding
model. Further details of the data collection and refinement
are given in Table 1. Selected bond lengths and angles are col-
lected in Tables 2–4 and crystal structures of complexes 2–4 in
Fig. 2–4. In spite of absorption corrections have been carried
out, the low quality of the crystals and the high absorption
coefficients have given rise to the presence of slightly high
residual density peaks. Similarly, due to the same reasons, the
value of S parameter in complex 4 is slightly larger than
usually. CCDC-891443–891445 contains the supplementary
crystallographic data for this paper.
(c) H. Schmidbaur, Gold Bull., 1990, 23, 11.
2 (a) P. Pyykkö, Chem. Rev., 1997, 97, 597; (b) P. Pyykkö,
Angew. Chem., Int. Ed., 2004, 43, 4412; (c) P. Pyykkö, Inorg.
Chim. Acta, 2005, 358, 4113; (d) P. Pyykkö, Chem. Soc. Rev.,
2008, 37, 1967.
3 (a) J. M. Forward, J. P. Fackler Jr. and Z. Assefa, in Opto-
electronic Properties of Inorganic Compounds, ed.
D. M. Roundhill and J. P. Fackler Jr., Plenum, New York,
1999, pp. 195–226; (b) J. M. López-de-Luzuriaga, in Modern
Supramolecular Gold Chemistry, ed. A. Laguna, Wiley-VCH,
Weinheim, 2008, p. 347.
4 (a) E. J. Fernández, A. Laguna, J. M. López-de-Luzuriaga
and M. Monge, Spanish Patent, P200001391, 2003;
(b) E. J. Fernández, J. M. López-de-Luzuriaga, M. Monge,
M. E. Olmos, J. Pérez, A. Laguna, A. A. Mohammed and
J. P. Fackler Jr., J. Am. Chem. Soc., 2003, 125, 2022;
(c) E. J. Fernández, J. M. López-de-Luzuriaga, M. Monge,
M. Montiel, M. E. Olmos, J. Pérez, A. Laguna,
F. Mendizábal, A. A. Mohamed and J. P. Fackler Jr., Inorg.
Chem., 2004, 43, 3573; (d) E. J. Fernández, J. M. López-de-
Luzuriaga, M. Monge, M. E. Olmos, R. C. Puelles,
A. Laguna, A. A. Mohamed and J. P. Fackler Jr., Inorg.
Chem., 2008, 47, 8069.
Computational details
The model systems used in the theoretical studies of [Au2-
{4-C6F4(4-C6BrF4)}2(μ-dppb)] and [Au2Ag4{4-C6F4(4-C6BrF4)}2-
(CF3CO2)4(μ-dppb)] were taken from the X ray diffraction data
for complexes 2 and 4. Keeping all distances, angles and dihe-
dral angles frozen, single-point DFT or TD-DFT calculations
5 (a) A. Vogler and H. Kunkely, Coord. Chem. Rev., 2001, 489,
219; (b) E. J. Fernández, A. Laguna and M. E. Olmos, Adv.
Organomet. Chem., 2005, 52, 77.
4276 | Dalton Trans., 2013, 42, 4267–4277
This journal is © The Royal Society of Chemistry 2013

View Article Online
Dalton Transactions
Paper
6 (a) E. J. Fernández, A. Laguna, J. M. López-de-Luzuriaga,
M. Monge, M. Montiel and M. E. Olmos, Inorg. Chem.,
2007, 46, 2953; (b) E. J. Fernández, A. Laguna, J. M. López-
de-Luzuriaga, M. Montiel, M. E. Olmos and J. Pérez, Organo-
metallics, 2005, 24, 1631; (c) E. J. Fernández, A. Laguna,
J. M. López de Luzuriaga, F. Mendizabal, M. Monge,
M. E. Olmos and J. Pérez, Chem.–Eur. J., 2003, 9, 456;
(d) E. J. Fernández, J. M. López-de-Luzuriaga, M. Monge,
M. E. Olmos, J. Pérez and A. Laguna, J. Am. Chem. Soc.,
2002, 124, 5942; (e) E. J. Fernández, P. G. Jones, A. Laguna,
J. M. López-de-Luzuriaga, M. Monge, J. Pérez and
M. E. Olmos, Inorg. Chem., 2002, 41, 1056; (f) O. Crespo,
E. J. Fernández, P. G. Jones, A. Laguna, J. M. López-de-
Luzuriaga, A. Mendía, M. Monge and M. E. Olmos, Chem.
Commun., 1998, 2233; (g) P. G. Jones and C. Thöne, Acta
T. Fischer, M. Zabel and H. Yersin, Inorg. Chem., 2009, 48,
4179; (d) S. Jamali, R. Czerwieniec, R. Kia, Z. Jamshidi and
M. Zabel, Dalton Trans., 2011, 40, 9123; (e) R. Czerwieniec,
T. Hofbeck, O. Crespo, A. Laguna, M. C. Gimeno and
H.
Yersin,
Inorg.
Chem.,
2010,
49,
3764;
(f) V. N. Kozhevnikov, M. C. Durrant and J. A. G. Williams,
Inorg. Chem., 2011, 50, 6304; (g) A. F. Rausch, L. Murphy,
J. A. G. Williams and H. Yersin, Inorg. Chem., 2012, 51, 312;
(h) M. Panigati, M. Mauro, D. Donghi, P. Mercandelli,
P. Mussini, L. De Cola and G. D’Alfonso, Coord. Chem. Rev.,
2012, 256, 1621; (i) L. Murphy, P. Brulatti, V. Fattori,
M. Cocchi and J. A. G. Williams, Chem. Commun., 2012, 48,
5817; ( j) C.-W. Hsu, C.-C. Lin, M.-W. Chung, G.-H. Lee,
P. T. Chou, C.-H. Chang and P. Y. Chen, J. Am. Chem. Soc.,
2011, 133, 12085.
Crystallogr., Sect. C: Cryst. Struct. Commun., 1992, 48, 1312; 15 A. F. Rausch, H. H. H. Homeier and H. Yersin, Top. Curr.
(h) M. A. Bennet, D. C. R. Hockless, A. D. Rae, L. L. Welling Chem., 2010, 29, 193.
and A. C. Willis, Organometallics, 2001, 20, 79; 16 A. Kapturkiewicz and G. Angulo, Dalton Trans., 2003, 3907.
(i) M. Bardají, P. G. Jones, A. Laguna, M. D. Villacampa and 17 P. J. Costa and M. J. Calhorda, Inorg. Chim. Acta, 2006, 359,
N. Valverde, Dalton Trans., 2003, 4529; ( j) R. Usón,
A. Laguna, M. Laguna, I. Colera and E. De Jesús, J. Organo- 18 G. M. Sheldrick, SHELXL-97, Program for Crystal Structure
met. Chem., 1984, 263, 121. Refinement, University of Göttingen, Germany, 1997.
7 (a) E. J. Fernández, A. Laguna, J. M. López-de-Luzuriaga, 19 (a) A. D. Becke, J. Chem. Phys., 1992, 96, 215;
3617.
M. Montiel, M. E. Olmos, J. Pérez and R. C. Puelles, Organo-
metallics, 2006, 25, 4307; (b) E. J. Fernández, A. Laguna,
(b) A. D. Becke, J. Chem. Phys., 1993, 98, 5648; (c) C. Lee,
W. Yang and R. G. Parr, Phys. Rev. Lett., 1998, 37, 785.
J. M. López-de-Luzuriaga, M. Monge, M. Montiel, 20 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. E. Olmos, J. Pérez, R. C. Puelles and J. C. Sáenz,
J. Chem. Soc., Dalton Trans., 2005, 1162.
8 E. J. Fernández, P. G. Jones, A. Laguna, J. M. López-de-
Luzuriaga, M. Monge, M. E. Olmos and R. C. Puelles,
Organometallics, 2007, 26, 5931.
9 E. J. Fernández, C. Hardacre, A. Laguna, M. C. Lagunas,
J. M. López-de-Luzuriaga, M. Monge, M. Montiel,
M. E. Olmos, R. C. Puelles and E. Sánchez-Forcada, Chem.–
Eur. J., 2009, 16, 6222.
10 R. Usón, A. Laguna, M. Laguna, I. Colera and E. De Jesús,
J. Organomet. Chem., 1984, 263, 121.
11 (a) X. Honk, K. K. Cheung, C. X. Guo and C.-M. Che,
J. Chem. Soc., Dalton Trans., 1994, 1867; (b) M. Bardají,
P. G. Jones, A. Laguna, A. Moracho and A. K. Fischer,
J. Organomet. Chem., 2002, 648, 1.
12 T. Pilati, P. Metrangolo and G. Resnati, Acta Crystallogr.,
2001, 57, 113.
M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone,
B. Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato,
X. Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng,
J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda,
J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao,
H. Nakai, T. Vreven, J. A. Montgomery Jr., J. E. Peralta,
F. Ogliaro, M. Bearpark, J. J. Heyd, E. Brothers,
K. N. Kudin, V. N. Staroverov, R. Kobayashi, J. Normand,
K. Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar,
J. Tomasi, M. Cossi, N. Rega, N. J. Millam, M. Klene,
J. E. Knox, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo,
R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin,
R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Martin,
K. Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador,
J. J. Dannenberg, S. Dapprich, A. D. Daniels, Ö. Farkas,
J. B. Foresman, J. V. Ortiz, J. Cioslowski, D. J. Fox,
GAUSSIAN 09 (Revision A.1), Gaussian, Inc., Wallingford CT,
2009.
13 A. Pintado-Alba, H. de la Riva, M. Niewhuyzen, D. Bautista,
P. R. Raithby, H. A. Sparkes, S. J. Teat, J. M. López-de- 21 A. Schäfer, H. Horn and R. Ahlrichs, J. Chem. Phys., 1992,
Luzuriaga and M. C. Lagunas, Dalton Trans., 2004, 3459. 97, 2571.
14 (a) H. Yersin, A. F. Rausch, R. Czerwieniec, T. Hofbeck and 22 T. H. Dunning Jr., J. Chem. Phys., 1994, 100, 5829.
T. Fischer, Coord. Chem. Rev., 2011, 255, 2622; 23 D. Andrae, U. Haeussermann, M. Dolg, H. Stoll and
(b) T. Hofbeck and H. Yersin, Inorg. Chem., 2010, 49, 9290;
H. Preuss, Theor. Chim. Acta, 1990, 77, 123.
(c) D. N. Kozhevnikov, V. N. Kozhevnikov, M. M. Ustinova, 24 N. M. Boyle, A. L. Tenderholt and K. M. Langner, J. Comput.
A. Santoro, D. W. Bruce, B. Koenig, R. Czerwieniec,
Chem., 2008, 29, 839.
This journal is © The Royal Society of Chemistry 2013
Dalton Trans., 2013, 42, 4267–4277 | 4277