Unexpected structural preference for aggregates with metallophilic Ag- - -Au contacts in (trimethylphosphine)silver(I) and -gold(I) phenylethynyl complexes. An experimental and theoretical study

Article abstract of DOI:10.1021/om050985z

(Me₃P)AuC≡CPh is a molecular compound associated into chains through aurophilic contacts, while ≡ its silver analogue exists as the ionic isomer [(Me₃P)₂Ag]⁺[Ag(C≡CPh) ₂]^-. Equivalent mixtures of the two compounds (Au:Ag = 1:1) in dichloromethane yield the ionic mixed-metal compound [(Me ₃P)₂Ag]⁺[Au(C≡CPh)₂] ^-, which is stable in solution only in the presence of an excess of the Me₃P ligand. Under these conditions it can be crystallized, and in the crystals the cations and the anions (with idealized D_3d and D_2h symmetry, respectively) are aggregated via heterometallophilic bonding, generating linear -Ag-Au-Ag-Au- chains. The solid was found to be also unstable at room temperature, owing to a rapid loss of four out of six tertiary phosphines, which leads to a product of the composition [(Me₃P) ₂Ag]⁺[Ag₂Au₃(C≡CPh) ₆]^-. By crystal structure analysis, the anion was shown to have three [PhC≡CAuC≡CPh]^- anions associated via two Ag⁺ cations to give a Ag₂Au₃ core unit of quasi-D_3h symmetry. Structure and bonding in this anion have been analyzed through density functional calculations of the [Ag₂Au ₃(C≡CH)₆]^- model and shown to be largely ionic in nature. Deviations of the experimental and calculated geometrical details could be traced to the electrostatic field in the crystal. In the unit cell, the cluster anions are associated with the [(Me₃P) ₂Ag]⁺ cations (of idealized D_3h symmetry) via heterometallophilic contacts in which two of the three gold atoms are involved.

Full text of DOI:10.1021/om050985z

1004
Organometallics 2006, 25, 1004-1011
Unexpected Structural Preference for Aggregates with Metallophilic
Ag- - -Au Contacts in (Trimethylphosphine)silver(I) and -gold(I)
Phenylethynyl Complexes. An Experimental and Theoretical Study
Oliver Schuster, Uwe Monkowius, Hubert Schmidbaur,* R. Shyama Ray, Sven Kru¨ger, and
Notker Ro¨sch*
Department Chemie, Technische UniVersita¨t Mu¨nchen, Lichtenbergstrasse 4, 85747 Garching, Germany
ReceiVed NoVember 16, 2005
(Me3P)AuCtCPh is a molecular compound associated into chains through aurophilic contacts, while
its silver analogue exists as the ionic isomer [(Me3P)2Ag]+[Ag(CtCPh)2]-. Equivalent mixtures of the
two compounds (Au:Ag ) 1:1) in dichloromethane yield the ionic mixed-metal compound
[(Me3P)2Ag]+[Au(CtCPh)2]-, which is stable in solution only in the presence of an excess of the Me3P
ligand. Under these conditions it can be crystallized, and in the crystals the cations and the anions (with
idealized D3d and D2h symmetry, respectively) are aggregated via heterometallophilic bonding, generating
linear -Ag-Au-Ag-Au- chains. The solid was found to be also unstable at room temperature, owing
to a rapid loss of four out of six tertiary phosphines, which leads to a product of the composition
[(Me3P)2Ag]+[Ag2Au3(CtCPh)6]-. By crystal structure analysis, the anion was shown to have three
[PhCtCAuCtCPh]- anions associated via two Ag+ cations to give a Ag2Au3 core unit of quasi-D3h
symmetry. Structure and bonding in this anion have been analyzed through density functional calculations
of the [Ag2Au3(CtCH)6]- model and shown to be largely ionic in nature. Deviations of the experimental
and calculated geometrical details could be traced to the electrostatic field in the crystal. In the unit cell,
the cluster anions are associated with the [(Me3P)2Ag]+ cations (of idealized D3h symmetry) via
heterometallophilic contacts in which two of the three gold atoms are involved.
only limited experimental data) appears to be lower than for
Au- - -Au contacts, the effect may yet be significant in many
condensed systems.11
Introduction
Most solid-state structures and many molecular configurations
and conformations of two-coordinated gold(I) complexes are
strongly influenced or even determined by aurophilic inter-
actions.1-3 The gain in energy resulting from an intra- or
intermolecular mutual approach of two formally “closed-shell”
gold centers is known to be on the order of 5-10 kcal/contact
and thus is in the same range as for conventional hydrogen
bonds.4 This phenomenon has attracted considerable interest,
and the number of reports on experimental observations and
theoretical treatments has increased very rapidly because Au- - -
Au interactions are associated with novel mesogenic, nonlinear
optical, and in particular photoemissive properties of the
molecules and their aggregates.5
In the past few years empirical evidence has finally also been
accumulated for mixed-metal Au- - -Ag interactions, addressed
very generally as metallophilic bonding between 5d10 and 4d10
centers.12-20 In the course of our own recent studies of gold(I)
and silver(I) ethynyl complexes we have become confronted
with a few particularly striking examples of apparently metallo-
philicity-induced reaction patterns and structural motifs which
were then followed up by complementary preparative experi-
ments, structural studies, and theoretical calculations. One set
(9) Siemeling, U.; Vorfeld, U.; Neumann, B.; Stammler, H.-G. J. Chem.
Soc., Chem. Commun. 1997, 1723.
(10) Poblet, J.-M.; Benard, M. J. Chem. Soc., Chem. Commun. 1998,
1179.
(11) Zhang, J.-P.; Wang, Y.-B.; Huang, X.-C.; Lin, Y.-Y.; Chen, X.-M.
Chem. Eur. J. 2005, 11, 552.
(12) Uso´n, R.; Laguna, A.; Laguna, M.; Jones, P. G.; Sheldrick, G. M.
J. Chem. Soc., Chem. Commun. 1981, 1097.
(13) Uso´n, R.; Laguna, A.; Laguna, M.; Manzano, B. R.; Jones, P. G.;
Sheldrick, G. M. J. Chem. Soc., Dalton Trans. 1984, 285.
(14) Uso´n, R.; Laguna, A.; Laguna, M.; Manzano, B. R.; Tapia, A. Inorg.
Chim. Acta 1985, 101, 151.
Similar observations have also been made with related
silver(I) compounds, and argentophilic interactions are consid-
ered in all recent, more detailed discussions of molecular and
solid-state structures of silver(I) complexes.6-10 Although the
energy associated with Ag- - -Ag contacts (for which there are
(1) Schmidbaur, H.; Cronje, S.; Djordjevic, B.; Schuster, O. Chem. Phys.
2005, 311, 151.
(2) Schmidbaur, H.; Grohmann, A.; Olmos, M. E. In Gold: Progress in
Chemistry, Biochemistry and Technology; Schmidbaur, H., Ed.; Wiley:
Chichester, U.K., 1999; p 647.
(3) Pyykko¨, P. Angew. Chem. Int. Ed. 2004, 43, 441.
(4) Mingos, D. M. P. J. Chem. Soc., Dalton Trans. 1996, 5, 561.
(5) Parish, R. V. Gold Bull. 1998, 1, 14.
(6) Djordjevic, B.; Schuster, O.; Schmidbaur, H. Inorg. Chem. 2005, 3,
673.
(7) Fernandez, E. J.; Lopez-de-Luzuriaga, J. M.; Monge, M.; Rodriguez,
M. A.; Crespo, O.; Gimeno, M. C.; Laguna, A.; Jones, P. G. Inorg. Chem.
1998, 23, 6002.
(15) Uso´n, R.; Laguna, A.; Laguna, M.; Uson, A.; Jones, P. G.; Freire
Erdbru¨gger, C. Organometallics 1987, 8, 1778.
(16) Rawashdeh-Omary, M. A.; Omary, M. A.; Fackler, J. P. Inorg. Chim.
Acta 2002, 334, 376.
(17) (a) Abu-Salah, O. M.; Knobler, C. B. J. Organomet. Chem. 1986,
302, C10. (b) Abu-Salah, U. M.; Al-Ohaly, A. R.; Knobler, C. B. J. Chem.
Soc., Chem. Commun. 1985, 1502.
(18) Mazhar Ul, H.; Horne, W.; Abu-Salah, O. M. J. Crystallogr.
Spectrosc. Res. 1992, 4, 421.
(19) Hussain, M. S.; Ul-Haque, M.; Abu-Salah, O. M. J. Cluster Sci.
1996, 2, 167.
(8) El-Bahraoui, J.; Molina, J. M.; Olea, D. P. J. Phys. Chem. 1998,
102, 2443.
(20) Abu-Salah, O. M. J. Organomet. Chem. 1998, 565, 211 and
references therein.
10.1021/om050985z CCC: $33.50 © 2006 American Chemical Society
Publication on Web 01/21/2006

Aggregates with Metallophilic Ag- - -Au Contacts
Organometallics, Vol. 25, No. 4, 2006 1005
Scheme 1
of results on phenylethynylgold(I) and -silver(I) complexes is
summarized in the present account.
There is extensive literature on gold(I) and silver(I) ethynyls
which has been reviewed several times in the secondary and
tertiary literature,2,21-24 and a comprehensive treatment is again
in preparation. For background information, the reader is referred
to these coverages. References of the most recent work25,26 can
also serve as key citations.
Preparative Results
suggest the coexistence of homo- and heteroleptic species, as
shown in Scheme 1. Even at -85 °C no complete resolution
can be achieved. For the solid (in KBr), the IR absorption
for ν(CtC) appears at 2097 cm-1, similar to the absorptions
As described in an earlier account, (trimethylphosphine)-
phenylethynylgold(I) is obtained from the reaction of equimolar
quantities of (Me3P)AuCl and LiCtCPh in THF at -78 °C.
The structure and spectroscopic properties have been reported.27
In this context it should be emphasized that the NMR spectra
of solutions of (Me3P)AuCtCPh in dichloromethane are not
temperature-dependent. The 1H and 13C resonances of the PMe3
ligands are clean first-order doublets, indicating that no ligand
redistribution takes place in solution to give, for example, the
homoleptic ions [(Me3P)2Au]+ and [Au(CtCPh)2]-, the former
of which would give rise to A9XX′A′9 and AXX′ spin systems,
respectively.
PhenylethynylsilVer(I) was first described by Glaser as early
as 1870.28 It is obtained as the brown, insoluble polymer [AgCt
CPh]n from PhCtCH and silver salts and has a variable
analytical composition, depending on the reagents and reaction
conditions. It can be dissolved in dichloromethane upon addition
of a solution of an equimolar amount of Me3P (in toluene), and
the product crystallizes from dichloromethane/pentane (85%
yield, mp 173 °C with decomposition). The temperature
dependence of the NMR data collected in this work for solutions
in dichloromethane suggests a dynamic behavior, the compound
partly undergoing ligand redistribution to the homoleptic, ionic
complex [(Me3P)2Ag]+[Ag(CtCPh)2]-. This result confirms an
early crystal structure analysis by Corfield and Shearer.29
Surprisingly, the reaction of [(Me3P)2Ag]+[Ag(CtCPh)2]-
with 2 equiv of (Me3P)Au(CtCPh) (ratio Ag:Au ) 1:1) in
dichloromethane at 20 °C was found to give crystalline products
which have a variable composition depending on the reaction
and workup times. It was only upon addition of an excess of
free Me3P to the reaction mixture that a crystalline product of
the expected composition with a ratio Me3P:Ag:Au:CtCPh )
2:1:1:2 could be isolated in high yield (87%). Upon heating
this colorless crystalline solid melts with decomposition at 153-
155 °C. However, the samples always are distinctly malodorous
and appear to lose Me3P.
for the salts [Ph3PMe]+[Au(CtCPh)2]- (2099 cm-1 30
and
)
[nBu4N]+[Au(CtCPh)2]- (2098 cm-1),31 in which the anion is
not subjected to any specific influence of the large “innocent”
phosphonium or ammonium cations. In contrast to the results
in solution, in the solid state only the ionic form is present.
The same compound has also been obtained from several
other reactions, including treatment of (Me3P)Au(CtCPh)3 with
silver nitrate or (AgCtCPh)n in dichloromethane, indicating
selective transfer of ligands between the two metal cations. In
all cases it was found to be advantageous if an excess of Me3P
was present in the reaction mixture.
To obtain information on the nature of the product generated
in the absence of excess Me3P, solutions of (Me3P)AuCtCPh
and [(Me3P)2Ag]+[Au(CtCPh)2]- in dichloromethane were left
at room temperature for some time before workup, allowing
Me3P and solvent vapors to escape. Subsequent workup afforded
colorless and yellow crystals. The former were again identified
as [(Me3P)2Ag]+[Au(CtCPh)2]-, while the latter (mp 195 °C
with decomposition) were shown to have the phosphine-deficient
composition [(Me3P)2Ag3Au3(CtCPh)6]. A crystal structure
determination revealed the presence of [(Me3P)2Ag]+ cations
and [Ag2Au3(CtCPh)6]- anions associated into strings with an
alternating sequence of ions.
In dichloromethane solution rapid ligand exchange is observed
in NMR experiments, analogous to the behavior described for
[(Me3P)2Ag]+[Au(CtCPh)2]-. In the IR spectrum of the solid
(KBr) the ν(CtC) band is only slightly shifted, to 2079 cm-1
,
as compared to the signal for the Me3P-rich starting material
(2097 cm-1), suggesting that the new environment of the
[Au(CtCPh)2]- anions has only a marginal influence on the
bonding in the phenylethynyl groups. The electronic absorption
spectrum of the compound in dichloromethane solution at 20
°C is very similar to that of (Me3P)Au(CtCPh), suggesting that
the bands have to be assigned to intraligand transitions of the
Au-CtCPh units. Solutions cooled to 77 K show yellow-green
emission with a maximum at 534 nm, not very different from
the emission of the solid at 556 nm (Figure 1). This result
suggests that the cluster does not disintegrate in solution at low
temperature.
By analytical, spectroscopic, and structural data it has
been confirmed that the compound has the ionic structure
[(Me3P)2Ag]+[Au(CtCPh)2]-. The NMR spectra of solutions
in dichloromethane are again temperature dependent and
(21) Schmidbaur, H.; Schier, A. Sci. Synth. 2004, 691.
(22) Schmidbaur, H. Organogold Compounds; Slawisch, A., Ed.; Springer-
Verlag: Berlin, 1980.
(23) Fackler, J. P., Jr.; Liu, C. W. Sci. Synth. 2004, 663.
(24) Gimeno, M. C.; Laguna, A. In ComprehensiVe Coordination
Chemistry II; McCleverty, J. A., Meyer, T. J., Eds.; Elsevier: Oxford, U.K.,
2004; p 911.
(25) Wei, Q.-H.; Zhang, L.;-Y.; Yin, G.-Q.; Shi, L.-X.; Chen, Z.-N. J.
Am. Chem. Soc. 2004, 126, 9940.
(26) Vicente, J.; Chicote, M.-T.; Alvarez-Falcon, M. M. Organometallics
2005, 24, 4666.
(27) Schuster, O.; Liau, R.-Y.; Schier, A.; Schmidbaur, H. Inorg. Chim.
Acta 2005, 358, 1429.
Structural Results
Bis(trimethylphosphine)silVer(I) bis(phenylethynyl)gold(I) crys-
tallizes in orthorhombic needles of space group Pbcm with four
formula units in the unit cell. In the crystals, the components
are disordered in equal distribution over two sets of atomic sites,
which were found to account for all atoms except for the
hydrogen atoms of two methyl groups (C102, C202). The two
(28) Glaser, C. Liebigs Ann. Chem. 1870, 154, 137.
(29) Corfield, P. W. R.; Shearer, H. M. M. Acta Crystallogr., Sect. C:
Cryst. Struct. Commun. 1966, 4, 502.
(30) Schuster, O.; Schmidbaur, H. Organometallics 2005, 24, 2289.
(31) Schuster, O.; Schmidbaur, H. Inorg. Chim. Acta, in press.

1006 Organometallics, Vol. 25, No. 4, 2006
Schuster et al.
Figure 1. Absorption spectra of (a) (Me3P)Au(CtCPh) and of
(b) [(Me3P)2Ag3Au3(CtCPh)6] in CH2Cl2 at room temperature and
emission spectra of [(Me3P)2Ag3Au3(CtCPh)6] (c) in solution
(CH2Cl2, λexc 390 nm) and (d) in the solid state (λexc 400 nm) at
room temperature.
Figure 2. Chain of alternating cations and anions in the crystal
structure of [(Me3P)2Ag]+[Au(CtCPh)2]- forming a linear axis of
metal atoms connected by metallophilic bonding (ORTEP, 50%
probability ellipsoids, hydrogen atoms omitted). Selected bond
lengths (Å) and angles (deg): Ag1-P1 ) 2.419(5), Ag1-P2 )
2.368(5), Au1-C11 ) 1.99(2), Au1-C21 ) 2.02(2), C11-C12
) 1.27(3), C21-C22 ) 1.16(3); P1-Ag1-P2 ) 175.8(2), C11-
Au1-C21 ) 176.3(9), Ag1-Au1-Ag1′ ) 179.53(4), Au1-Ag1-
Au1′ ) 179.53(4).
Me3P ligands at the silver atom are not related by symmetry,
but their conformation approaches quite closely the point group
D3d. The Ag-P distances of 2.419(5) and 2.368(5) Å (average
2.393 Å) are longer than the Au-P distances in [(Me3P)2Au]+
cations (e.g. 2.304(6) Å for the cation of [(Me3P)2Au]+Cl-), as
expected on the basis of new data on atomic radii.32,33
The axis P1-Ag1-P2 is approximately linear (angle 175.8(2)
Å). Each cation is attached to two anions through Ag-Au
metallophilic bonding with distances Au1-Ag1 ) 3.206(2) Å
and Ag1-Au1′ ) 3.224(2) Å. The resulting chain of alternating
Ag and Au atoms is quasi-linear, with angles Au1-Ag1-Au1′
and Ag1-Au1-Ag1′ both at 179.53(4)° (Figure 2).
In the anions, the angle C11-Au1-C21 is 176.3(9)° with
distances Au1-C11 ) 1.99(2) Å and Au1-C21 ) 2.02(2) Å.
The two phenyl rings within each anion are roughly coplanar.
Each C11-Au1-C21 axis is tilted against the two neighboring
P1-Ag1-P2 axes by 69° (average). The Ag-Au-Ag-Au
chains run parallel to the a axis of the unit cell. The projection
shown in Figure 3 suggests that the tilting of the axes of the
cations away from the axes of the anions is due to crystal
packing. Note that the structure of the heterobimetallic
[(Me3P)2Ag]+[Au(CtCPh)2]- differs severely from that of the
homobimetallic analogue [(Me3P)2Ag]+[Ag(CtCPh)2]- with its
strongly bent cations and anions.29
Figure 3. Packing of the chains shown in Figure 2 in the unit cell
of [(Me3P)2Ag]+[Au(CtCPh)2]- projected parallel to the chain of
metal atoms along the a axis (arbitrary radii for all atoms).
[Bis(trimethylphosphine)silVer(I)(+)]{bis[µ3-silVer(I)]tris-
[µ2,η2:η2-bis(phenylethynyl)gold(I)](-)} forms yellow mono-
clinic crystals of space group Cc with four formula units in the
unit cell. The cations have conformations different from those
in the precursor salt [(Me3P)2Ag]+[Au(CtCPh)2]-, with their
symmetry approaching quite closely point group D3h (instead
of D3d). The angle P1-Ag1-P2 is 177.1(1)°, and the torsional
angle C11-P1-P2-C21 is 5.6°, with the Ag-P bonds equi-
distant at 2.392(3) Å.
allow for interactions with six carbon atoms for each of them
(Figure 4). In these positions, the silver atoms are also in close
contact with the gold atoms, with distances ranging from
2.854(2) to 3.0390(9) Å, which clearly represent metallophilic
bonding. The metal core Ag2Au3 thus has a trigonal-bipyramidal
structure with six axial-equatorial Ag-Au bonds, but with the
equatorial-equatorial Au-Au contacts (3.95 Å average) too
long for significant metallophilic contributions.
The pentanuclear anion (Ag2Au3) can be described in various
approaches. Its idealized symmetry is D3h, with the gold atoms
of three collinear PhCtCAuCtCPh anions forming an equi-
lateral triangle. The two silver cations are inserted into this anion
triple on the 3-fold axis and on the levels of the triple bonds to
The structure type of the pentanuclear anion is known from
previous work by Abu-Salah,17-20 who prepared and character-
ized several species [M2M′3(CtCR)6]- featuring various com-
binations of M, M′ ) Cu, Ag, Au, with [nBu4N]+ or [(Ph3P)2N]+
counterions. The present case is special in that the anionic cluster
is associated with the [(Me3P)2Ag]+ cation into chains of
alternating cationic and anionic components, which are linked
through Ag- - -Au metallophilic bonding. Two of the three gold
atoms of the anion entertain such Ag-Au contacts, while the
(32) Bayler, A.; Schier, A.; Bowmaker, G. A.; Schmidbaur, H. J. Am.
Chem. Soc. 1996, 118, 7006.
(33) Tripathi, U. M.; Bauer, A.; Schmidbaur, H. J. Chem. Soc., Dalton
Trans. 1997, 2865.

Aggregates with Metallophilic Ag- - -Au Contacts
Organometallics, Vol. 25, No. 4, 2006 1007
Figure 4. Structure of the anion in crystals of [(Me3P)2Ag]+[Ag2Au3-
(CtCPh)6]-. (ORTEP, 50% probability ellipsoids, hydrogen atoms
omitted). Selected bond lengths (Å) and angles (deg): Au1-C111
) 1.99(3), Au1-C121 ) 2.00(2), Au2-C211 ) 2.02(2), Au2-
C221 ) 2.01(1), Au3-C311 ) 2.01(2), Au3-C321 ) 1.99(1),
C111-C112 ) 1.22(2), C121-C122 ) 1.25(2), C211-C212 )
1.23(2), C221-C222 ) 1.21(2), C311-C312 ) 1.20(2), C321-
C322 ) 1.23(2); C111-Au1-C121 ) 174.3(5), C211-Au2-C221
) 173.8(5), C311-Au1-C321 ) 178.5(5). For intermetallic
distances, see Figure 5.
Figure 6. Optimized structure of the model cluster [Ag2Au3-
(CtCH)6]-. (The atomic numbering is different from that used in
the crystallographic part.)
Table 1. Crystal Data and Data Collection and Structure
Refinement Details
[(Me3P)2Ag]+
[(Me3P)2Ag]+
[Ag(CtCPh)2]-
[Ag2Au3(CtCPh)6]-
empirical formula
Mr
cryst syst
space group
a/Å
C22H22AgAuP2
653.17
orthorhombic
Pbcm
6.4292 (2)
18.6655 (4)
19.2969 (5)
90
C54H48Ag3Au3P2
1673.37
monoclinic
Cc
33.0696 (4)
9.9668 (2)
18.6939 (3)
90
123.9803(6)
90
5109.27(15)
2.175
b/Å
c/Å
R/deg
â/deg
90
90
γ/deg
V/Å3
2315.71(11)
1.873
4
F
calcd/g cm-3
Z
4
Figure 5. Aggregation of cations and anions of the compound
[(Me3P)2Ag]+[Ag2Au3(CtCPh)6]- into chains: (a) core unit of
metal atoms (ORTEP); (b) chain including the ligands (arbitrary
radii, hydrogen atoms omitted). Selected bond lengths (Å) and
angles (deg): Ag1-P1 ) 2.392(3), Ag1-P2 ) 2.392(3), Au1-
Ag1′′ ) 2.9996(8), Au1-Ag2 ) 2.9397(9), Au1-Ag3 ) 3.0390(9),
Au2-Ag1 ) 2.9945(8), Au2-Ag2 ) 2.9676(9), Au2-Ag3 )
2.854(2), Au3-Ag2 ) 3.001(1), Au3-Ag3 ) 3.004(1); P1-Ag1-
P2 ) 177.1(1), Au1′-Ag1-Au2 ) 171.26(3), Au1-Ag2-Au2 )
85.10(3), Au1-Ag2-Au3 ) 79.99(2), Au2-Ag2-Au3 ) 85.29(3),
Au1-Ag3-Au2 ) 85.31(3), Au1-Ag3-Au3 ) 78.39(3), Au2-
Ag3-Au3 ) 87.23(3).
F(000)
1240
73.15
143
56 468
2161 (Rint ) 0.054)
229/0
3120
98.06
143
67 806
59 586 (Rint ) 0.075)
565/2
µ(Mo KR) (cm-1
T/K
)
no. of reflns measd
no. of unique rflns
no. of refined params/
restraints
R1 (I g 2σ(I))
0.0523
0.1061
0.0371
0.0959
0.080(5)
wR2a
Flack parameter
weighting scheme
a
0.0000
36.4130
0.967/-1.210
0.0470
31.3640
2.295/-2.518
b
σ
fin(max/min)/e Å-3
third one (Au3) is not involved (Figure 5). The distances Ag1-
Au2 and Ag1-Au1′ of 2.9945(8) and 2.9996(8) Å, respectively,
are short and very similar to the intraanionic interactions,
suggesting rather strong interionic linkages.
2
2
2
2
a wR2) {∑[w(Fo - Fc )2]/∑[w(Fo )2]}1/2; w ) 1/[σ2(Fo ) + (ap)2
bp], p ) (Fo + 2Fc )/3.
+
2
2
efforts toward elucidating the structure and bonding in the
anionic cluster complex [Ag2Au3(CtCPh)6]-. To this end, we
carried out model calculations applying a scalar-relativistic
density functional approach. We modeled this complex as an
isolated moiety in idealized D3h symmetry. Also, we replaced
the phenylethynyl by ethynyl ligands to simplify the calculations
(Figure 6).
As a check of our model strategy, we compare in Table 2
pertinent bond lengths of [Au(CtCR)2]- for R ) H, CH3 to
the crystal structure30 of [nBu4N]+[Au(CtCPh)2]-. The largest
deviation, 0.004 Å, between diethynylgold and dipropynylgold
anions is found for the Au-C bond lengths, supporting
ethynylide as the model ligand. Deviations from the experi-
mental data for the bis(phenylethynyl)gold anion are somewhat
Computational Studies
From the preceding discussion, it is clear that, besides the
metallophilic interactions, electrostatic interactions play an im-
portant role in the extended structures characterized. Metallo-
philic interactions are mainly of dispersive character34 and thus
are not amenable to a quantitative description by density
functional methods based on current (semi-) local exchange-
correlation potentials.35 We therefore focused our computational
(34) Pyykko¨, P. Chem. ReV. 1997, 97, 597.
(35) Koch, W.; Holthausen, M. C. A Chemist’s Guide to Density
Functional Theory, 2nd ed.; Wiley-VCH: Weinheim, Germany, 2002; Sect.
12.4.

1008 Organometallics, Vol. 25, No. 4, 2006
Schuster et al.
Table 2. Pertinent Structure Parametersa of the Moiety
metal distances that are somewhat shorter than those obtained
in the crystal structure analysis: Au-Au distances are 0.04 Å
shorter and Au-Ag distances 0.07 Å shorter than the corre-
sponding values in the crystal structure. The distance between
Ag atoms and the ethynyl ligands, as measured by the distance
Ag-C1, compare reasonably well with experiment: 2.30 Å.
Calculated distances Ag-C1 are 0.05 Å shorter than the
experimental values. In the cluster compound, the [Au(CtCH)2]-
units stay almost linear; the angle C1-Au-C1′ is calculated to
be bent 2° from the main axis of the cluster.
[Au(CtCR)2]- from Calculation and Experiment
R
b
Hb
CH3
Phc
Au-C1
1.953
1.227
180
1.957
1.228
180
1.992
1.205
175
C1-C2
C1′-Au-C1
a Bond lengths are given in Å and angles in deg. b Calculation, this work.
c Experiment, [nBu4N]+[Au(CtCPh)2]-.28
Table 3. Pertinent Structure Parameters Calculated for the
Model Complex [Ag2Au3(CtCH)6]- and Related Modelsa
Including Point Charges (PC) in Comparison with Averaged
Experimental Results for [Ag2Au3(CtCPh)6]-
One may advance two major arguments to rationalize the
general tendency of the model calculations of underestimating
interatomic bond distances, leaving aside the limited accuracy
of the computational methods applied. One expects crystal-
packing effects to elongate interatomic distances due to steric
stress; on the other hand, the crystal field of the surrounding
ions, missing in the model calculations, also may influence the
geometry. To inspect qualitatively this latter effect, we consid-
ered a neutral model of D3h symmetry where we placed three
systemb
[Ag2Au3L6]- [Ag2Au3L6]PC3 [PC2Au3L6]- exptlc
Au-Au
Au-Ag
Au-C1
Ag-C1
C1-C2
3.912
2.904
1.960
2.295
1.229
178
3.950
2.946
1.957
2.304
1.229
179
2.888
2.472
1.962
1.841
1.223
170
3.952
2.968
1.998
2.353
1.223
176
C1′-Au-C1
1
point charges of /3 e in the plane of the Au triangle at radial
a For details of computational models see text. Bond lengths are given
distances of 2.997 Å from the Au atoms (model [Ag2(AuL)3]-
PC3, Table 3); that distance is the average of Au-Ag dis-
tances involving Ag atoms of nearest-neighbor counterions in
the crystal structure. As the charge of the cluster ion
[Ag2Au3(CtCH)6]- is neutralized in this complex, it may serve
as a rough qualitative model to probe crystal field effects.
in Å and angles in deg. b L ) CtCH. c Reference 28.
larger. The Au-C distance calculated for the diethynylgold
anion is ∼0.04 Å shorter while the CtC bond is ∼0.02 Å longer
than the corresponding experimental values. These deviations
are not easily attributed to a single source; they may mainly
reflect deviations due to crystal-packing effects. Such packing
effects are obviously responsible for the angle C-Au-C′:
calculated at 180° for the isolated anion but determined to be
175° in the crystal structure (Table 2). The calculated CtC bond
length of 1.23 Å in the ethynyl ligands of [Au(CtCH)2]- falls
between the corresponding values calculated for an isolated
ethynyl radical (1.21 Å) and an ethynylide anion (1.25 Å).
Potential derived charges36 confirm this situation to be inter-
mediate between ionic and covalent. They amount to 0.23 e
for Au and -0.62 e for the CtCH ligands of [Au(CtCH)2]-.
The metal-ligand bond of this moiety is mainly due to σ
Indeed, the largest changes resulting in this model in
comparison to the isolated cluster ion are elongations of metal-
metal distances. The Au-Au distance increases by 0.04 Å to
3.95 Å; this exact reproduction of the experimental average is
likely due to fortuitous error compensation. The Au-Ag
contacts are also elongated by 0.04 Å to 2.95 Å, now also in
very satisfactory accord with experiment (2.97 Å). All other
pertinent structure characteristics are hardly altered: bond
distances change by less than 0.01 Å, and the angle C1-Au-
C1′ changes by about 1°.
All metal centers of the cluster ion [Ag2Au3(CtCPh)6]-
exhibit formal oxidation state +I. For the Au atoms, this is
qualitatively confirmed by the results calculated for our model
compound [Ag2Au3(CtCH)6]-, as revealed by inspecting the
CtC bond lengths. As for [Au(CtCH)2]-, the calculated C-C
distance of 1.23 Å (Table 3) indicates a partially ionic character
of the Au-ethynylide bond (see above). To probe the character
of metal-metal interactions and, in particular, the oxidation state
of the Ag atoms in the model compounds, we invoked a third
model system, [PC2(AuL)3]-, where we replaced the Ag atoms
of the cluster by point charges of 1 e (Table 3). We optimized
the structure of this model, keeping the point charges at fixed
locations to represent the effect of the crystal environment. As
the main result, we determined a very large reduction of the
Au-Au distances, by about 1 Å. Surprisingly, this strong
“contraction” of the complex has only a marginal effect on other
structural parameters. The Au-C1 bonds increase by 0.002 Å,
and the CtC bonds contract by 0.006 Å. The bending of
diethynylgold units, as measured by the angle C1-Au-C1′,
increases from 2 to 10°. We observe hardly any geometry
relaxation when the Ag atoms are replaced by point charges.
This finding suggests marginal orbital interactions between silver
and diethynylgold units and thus points to a strongly ionic nature
of the Ag centers as well as to a mainly ionic interaction between
these Ag(I) ions and diethynylgold units. A possible covalent
interaction of the Ag centers with the ethynyl π systems has to
be classified as weak, as the CtC bond lengths elongate only
slightly (by 0.002 Å) in the presence of Ag ions. Potential-
2
bonding between Au(dz ) and σ orbitals of the ligands. In fact,
2
a three-orbital interaction between the dz and s orbitals of Au
and the symmetric linear combination of the σ frontier orbitals
of the two ligands occurs, leading to a high-lying nonbonding
sd hybrid orbital on Au (HOMO-1). The π system of the ethynyl
ligands forms the HOMO of the anion [Au(CtCH)2]-, with
some Au(d) contribution, and the HOMO-2.
Optimization of the isolated anion [Ag2Au3(CtCH)6]- yields
a structure which closely agrees with experimental findings for
Ag2Au3(CtCPh)6]-, averaged according to the approximate D3h
symmetry (Table 3). As for the isolated moiety [Au(CtCH)2]-,
the Au-C distance of 1.96 Å is ∼0.04 Å shorter than the
experimental value. The CtC bond is calculated at 1.23 Å,
slightly longer (0.01 Å) than found in experiment, just as
obtained for the diethynylgold anion. Comparing experimental
results, one notes that the average value of CtC bonds in the
crystal structure of the cluster anion [Ag2Au3(CtCPh)6]- is 0.02
Å longer than for the single anion30 [Au(CtCPh)2]-, while our
calculations yield identical values for diethynylgold and the
cluster anion (Tables 2 and 3). In the crystal structure, CtC
bond lengths scatter by the same amount (0.02 Å), which is
comparable to the experimental uncertainty (see the Supporting
Information); thus, experimental and calculated results are
compatible. Our computational models also result in metal-
(36) Besler, B. H.; Merz, K. M.; Kollman, P. A. J. Comput. Chem. 1990,
11, 431.

Aggregates with Metallophilic Ag- - -Au Contacts
Organometallics, Vol. 25, No. 4, 2006 1009
we conclude that the ethynyl groups in the cluster compound
have a distance close to optimal for an interaction between Ag
and the π systems of the ethynyl ligands. With 1.22 Å, the CtC
bonds of the ligands are shorter than in the cluster compound,
reflecting the formally neutral nature of these ligands compared
to their more anionic character in the diethynylgold moieties.
In model 1, the binding energy per acetylene ligand is
calculated at 25 kcal/mol. Due to the similar diameters of the
two complexes compared, model 2 yields almost the same ligand
binding energy (Table 4). Stronger effects have been determined
for model 3, where the Ag cation is shifted from the plane
through the centers of the CtC bonds to a plane defined by
the three corresponding C atoms of the ligands. Then the Ag-C
distance shrinks from 2.39 to 2.30 Å for the closer C atoms.
Interestingly, the shift of the Ag cations has only a negligible
effect on the length of the CtC bond (Table 4). Also the binding
energy of the ligands decreases by only 1.5 kcal/mol compared
to that in model 1. Replacing the Ag cation in model 3 by a
point charge of 1 e results in a further slight decrease of the
binding energy per ligand to about 19 kcal/mol. This last result
corroborates that most of the binding between the acetylene
ligands and the Ag+ centers is due to electrostatic effects. In
model 3, only about 15% of this interaction (4 kcal/mol per
ligand) can be ascribed to orbital interactions.
Figure 7. Optimized structure of the model complex [Ag(HCt
CH)3]+.
Table 4. Characteristics of the Complex [Ag(HCtCH)3]+
Calculated with Different Constraints and Approximations
(Models 1-4)a
′
C1-C2
Ag-C1
C1-C1
C2-C1-Ag
BE
model 1b
model 2c
model 3d
model 4e
1.217
1.217
1.216
1.216
2.385
2.370
2.295
2.295
3.994
3.967
3.967
3.967
75
75
93
93
25.0
24.8
23.5
19.4
a Bond lengths are given in Å, angles in deg, and binding energies per
HCtCH ligand (BE) in kcal/mol. b Geometry optimized in D3h symmetry.
c As for model 1, but C-C′ fixed at the value 3.967 Å calculated for the
complex [Ag2Au3(CtCH)6]-. d As for model 2, but symmetry constraints
reduced to C3V and height of Ag fixed as calculated for the complex
[Ag2Au3(CtCH)6]- (Ag-C ) 2.295 Å). e As for model 3 (including
geometry), but Ag cations replaced by point charge of 1 e.
In summary, in agreement with our analysis of the properties
of the cluster [Ag2Au3(CtCH)6]-, our model study of
[Ag(HCtCH)3]+ points toward a mainly electrostatic interac-
tion. If anything, orbital interactions play only a minor role. In
view of the closed-shell d10 electronic structure of Ag+ these
results appear plausible.
derived charges of the cluster ion [Ag2Au3(CtCH)6]-, which
probe the long-range electrostatic field,36 confirm our geometry-
based analysis. While Ag centers are assigned a charge of 0.51
e, Au centers are characterized by only 0.14 e, while the ethynyl
ligands carry a charge of 0.41 e, in line with the intermediate
bond length of the ethynyl ligands between radicals and anions
and with the molecular orbital analysis of the [Au(CtCH)2]-
moieties described above.
Conclusions
In the present account a particularly striking example is
presented of the self-assembly of bis(phenylethynyl)gold(I)
anions with silver cations to produce the pentanuclear mixed-
metal aggregate [Ag2(PhCtCAuCtCPh)3]- with an Ag2Au3
core of D3h symmetry (Figure 5): in dichloromethane solutions
containing [PhCtCAuCtCPh]- anions, [(Me3P)2Ag]+ cations
are stripped of their tertiary phosphine ligands and the bare Ag+
cations are trapped between three rodlike bis(phenylethynyl)-
gold anions. The compound [(Me3P)2Ag]+[Au(CtCPh)2]-,
therefore, is only stable in the presence of excess trimethylphos-
phine, which counteracts the dissociation of the cation. Other-
wise, loss of Me3P is observed in both solution and the solid
state. With excess Me3P present in the mother liquor, colorless
[(Me3P)2Ag]+[Au(CtCPh)2]- can be crystallized. In the crys-
tals, the cations and anions are associated to chains with
alternating components through mixed-metal metallophilic
bonding along linear -Ag-Au-Ag-Au- axes (Figure 2). In
the absence of Me3P, from the same solutions yellow crystals
of [(Me3P)2Ag]+[Ag2Au3(CtCPh)6]- are obtained. This com-
pound is strongly photoluminescent as a solid and in solution
at room temperature (Figure 1). The absorption and emission
profiles are very similar, suggesting undissociated clusters in
solution. In the crystal, the cluster anions are associated with
the cations via Ag-Au metallophilic bonding in which only
two of the three equatorial gold atoms of the Ag2Au3 bipyramid
are involved (Figures 5 and 6).
To quantify the interaction in the cluster compounds between
the cationic Ag centers and the ethynyl π systems, we examined
a series of models of the complex [Ag(HCtCH)3]+ (Figure 7).
In comparison to the cluster compound [Ag2Au3(CtCH)6]- this
complex allows for an easier inspection of effects of π orbital
interactions of Ag; in addition, an energy analysis of this
interaction is possible, which is hampered by the strong ionic
contributions in the gold-silver cluster. First, we optimized this
complex in D3h symmetry (model 1), allowing optimal bonding
to the acetylene π orbitals. In model 2, we fixed the C-C
distances between different acetylene ligands at 3.967 Å, which
corresponds to the C1-C1′ distance in [Ag2Au3(CtCH)6]-, to
account for the proper size of the cluster compound. In a third
step toward the structure of [Ag2Au3(CtCH)6]-, we lowered
the symmetry of our model complex to C3V and shifted the Ag
ion from the plane defined by the centers of the CtC bonds to
the position obtained by optimizing [Ag2Au3(CtCH)6]-, to
yield Ag-C1 distances identical with those in the latter cluster.
This model, model 3, mimics the structural characteristics of
[Ag2Au3(CtCH)6]-, but the diethynylgold ligands are replaced
by acetylene. In a last step (model 4), we substituted a point
charge of 1 e for the silver cation, without further relaxation of
the geometry.
The optimized structure of [Ag(HCtCH)3]+ in the D3h
symmetry (model 1) yields an Ag-C distance of 2.39 Å (Table
4), about 0.1 Å longer than the value for Ag-C1 in the cluster
[Ag2Au3(CtCH)6]-. The diameter of the complex, as judged
by the distance C-C′ of 3.99 Å between corresponding C atoms
of different acetylene ligands, is very similar to the value
calculated for C1-C1′ in [Ag2Au3(CtCH)6]- (3.97 Å). Thus,
Complexes of the type [M2M′3(CtCR)6]- have been obtained
previously with various combinations of coinage metals M/M′,
including [Cu2Au3(CtCPh)6]-, for which the unusual structure
has first been determined.17,20 The structural details of known
examples are not very different, except for distances depending
on the change in ionic radii of the coinage metals.

1010 Organometallics, Vol. 25, No. 4, 2006
Schuster et al.
CPh) (29 mg, 0.1 mmol) and (Me3P)Au(CtCPh) (37 mg, 0.1
mmol) in 20 mL of CH2Cl2, but no PMe3 was added before
crystallization. Colorless needles and yellow plates were obtained.
Washing the product mixture with three 1 mL portions of CH2Cl2
yielded 30 mg (54% yield) of yellow plates. Mp: 195-196 °C
dec. IR (KBr, cm-1): 2079 (m, ν(CtC)). MS (FABpos, m/z): 615
(64.0%) [(PhCtC)2Ag2Au]+, 481 (37.0%) [(PhCtC)AgAu-
(PMe3)]+, 349 (100%) [(Me3P)2Au]+. Anal. Calcd for C54H48-
Ag3Au3P2 (1673.37): C, 38.76; H, 2.89. Found: C, 39.19; H, 2.89.
Crystal Structure Determinations. The single crystals were
placed in inert oil on the top of a glass pin and transferred to the
cold gas stream of the diffractometer. Crystal data were collected
using a Nonius DIP2020 system with monochromated Mo KR (λ
) 0.710 73 Å) radiation at -130 °C. The structures were solved
by direct methods (SHELXS-97) and refined by full-matrix least-
squares calculations on F2 (SHELXL-97).37 Non-hydrogen atoms
were refined with anisotropic displacement parameters. Hydrogen
atoms were placed in idealized positions and refined using a riding
model with fixed isotropic contributions if possible. Crystals of
[(Me3P)2Ag][Au(CtCPh)2] were found to be disordered (sof ) 0.5).
Due to this fact, hydrogen atoms of methyl groups on special
positions (C102, C202) could be neither calculated nor found in
the Fourier map. Residual peaks/holes in the electron density maps
are all very close to the heavy-metal atoms. Further information
on crystal data, data collection, and structure refinement is
summarized in Table 1. Important interatomic distances and angles
are given in the figure captions. Complete lists of displacement
parameters and tables of interatomic distances and angles have been
deposited with the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, U.K.. The data are available
on request on quoting CCDS files 292086 and 292087.
Computational Section. In calculations, we applied the all-
electron LCGTO-FF-DF approach (linear combination of Gaussian-
type orbitals fitting function density functional),38 as implemented
in the parallel program ParaGauss.39,40 To account for relativistic
effects, we chose the scalar-relativistic variant of the Douglas-
Kroll-Hess approach to relativistic density functional theory.41
Spin-orbit effects were neglected, because all heavy-element
species examined have a closed-shell electronic structure. Structures
have been optimized with an LDA exchange-correlation func-
tional,42 while energies were calculated self-consistently with a more
accurate GGA functional,43,44 employing LDA geometries. This
strategy is motivated by the well-known tendency of GGA
functionals to overestimate bond lengths of heavy-element com-
pounds, whereas LDA functionals overestimate binding energies
but yield accurate geometries.45,46 To represent the Kohn-Sham
To shed light on the nature of bonding in these clusters,
density functional calculations of the model complex [Ag2Au3-
(CtCH)6]-, imposing D3h symmetry constraints, have been
carried out, which resulted in satisfactory agreement with
suitably averaged experimental structure data for [Ag2Au3-
(CtCPh)6]-. Deviations could partially be traced to the packing
of the ions in the crystal and to effects of the resulting
electrostatic field. Comparison with a model where Ag+ ions
are replaced by positive point charges as well as structural and
energetic analyses of the model complex [Ag(HCtCH)3]+ have
pointed toward a mainly ionic binding situation within the cluster
ions [Ag2Au3(CtCH)6]-, between the building blocks Ag+ and
[Au(CtCH)2]-.
Experimental Section
General Procedure. All organometallic syntheses were per-
formed in a dry deoxygenated dinitrogen atmosphere using standard
Schlenk techniques. All solvents were distilled from an appropriate
drying agent and stored over molecular sieves (4 Å) and under
nitrogen. Solutions were handled at -78 °C unless otherwise stated
and protected against light. All standard chemicals were purchased
from Aldrich or Fluka and used without further purification.
28
[Ag(CtCPh)]n and (Me3P)Au(CtCPh)27 were prepared as de-
scribed in the literature. Mass spectra were recorded on a Finnigan
MAT 90 spectrometer using FAB as an ionization method. NMR
spectra were obtained at various temperatures on JEOL-400 and
JEOL-270 spectrometers. Chemical shifts are reported in δ values
relative to the residual solvent resonances converted to TMS (1H).
31P{1H} NMR spectra are referenced to external aqueous H3PO4
(85%). The single-crystal X-ray diffraction measurements were
performed at -130 °C on a Nonius DIP 2020 diffractometer using
graphite-monochromated Mo KR radiation.
(Phenylethynyl)(trimethylphosphine)silver(I), (Me3P)AgCt
CPh. To a stirred suspension of 418 mg of [Ag(CtCPh)]n (2.0
mmol) in 40 mL of CH2Cl2 was added 2.0 mmol of PMe3 dissolved
in 2 mL of toluene. The resulting clear solution was protected
against light and stirred for 1/2 h before the solvents were removed
in vacuo. Recrystallization from dichloromethane/pentane at -30
°C gave 485 mg (85% yield) of a colorless solid. Mp: 173 °C dec.
2
1H NMR (CD2Cl2, room temperature): δ 1.22 (d, JHP ) 9.5 Hz,
9H, P(CH3)), 7.26-7.47 (m, 5 H, C6H5). 13C{1H} NMR (CD2Cl2,
room temperature): δ 15.5 (d, 1JCP ) 17.7 Hz, P(CH3)), 102.9 (s,
Ag-CtCPh), 118.8 (s, Ag-CtCPh), 124.0 (s, i-(C6H5)), 127.8
(s, p-(C6H5)), 128.1 (s, o-(C6H5)), 132.1 (s, m-(C6H5)). 31P{1H}
NMR (CD2Cl2, room temperature): δ -38.7 (s, P(CH3)). Anal.
Calcd for C11H14AgP (285.07): C, 46.35; H, 4.95. Found: C, 45.88;
H, 4.80.
(37) Sheldrick, G. M., SHELXL-97: Programs for Crystal Structure
Analysis; University of Go¨ttingen, Go¨ttingen, Germany, 1997.
(38) Dunlap, B. I.; Ro¨sch, N. AdV. Quantum Chem. 1990, 21, 317.
(39) Belling, T.; Grauschopf, T.; Kru¨ger, S.; Mayer, M.; No¨rtemann,
F.; Staufer, M.; Zenger, C.; Ro¨sch N. In High Performance Scientific and
Engineering Computing; Bungartz, H.-J., Durst, F., Zenger, C., Eds.; Lecture
Notes in Computational Science and Engineering 8; Springer: Heidelberg,
Germany, 1999; pp 439-453.
(40) Belling, T.; Grauschopf, T.; Kru¨ger, S.; No¨rtemann, F.; Staufer, M.;
Mayer, M.; Nasluzov, V. A.; Birkenheuer, U.; Hu, A.; Matveev, A. V.;
Fuchs-Rohr, M. S. K.; Shor, A. M.; Neyman, K. M.; Ganyushin, D. I.;
Kerdcharoen, T.; Woiterski, A.; Gordienko, A. B.; Majumder, S.; Ro¨sch,
N. ParaGauss Version 3.0; Technische Universita¨t Mu¨nchen, Mu¨nchen,
Germany, 2004.
[Bis(trimethylphosphine)silver(I)][bis(phenylethynyl)-
aurate(I)], [(Me3P)2Ag][Au(CtCPh)2]. A sample of (Me3P)Ag-
(CtCPh) (29 mg, 0.1 mmol) was dissolved in 20 mL of CH2Cl2,
and 1 equiv of (Me3P)Au(CtCPh) (37 mg, 0.1 mmol) was added.
Stirring was continued for 10 min at room temperature. After
addition of 0.5 mL of PMe3 (0.5 mmol, 1.0 M in toluene), pentane
was diffused slowly into the clear reaction mixture at -30 °C. A
total of 57 mg (87% yield) of colorless needles was collected. Mp:
153-155 °C dec. IR (KBr, cm-1): 2097 (m, ν(CtC)). MS
(FABpos, m/z): 615 (40.2%) [(PhCtC)2Ag2Au]+, 481 (21.1%)
[(PhC2)AgAu(PMe3)]+, 349 (100%) [(Me3P)2Au]+, 317 (93.3%)
[(PhCtC)Ag2]+, 273 (20.1%) [(Me3P)Au]+, 261 (34.5%) [(Me3P)2-
Ag]+, 185 (45,8%) [(Me3P)Ag]+. MS (FABneg, m/z): 399 (18.1%)
[(PhCtC)2Au]-, 153 (100%) [(MeP)Ag]-. Anal. Calcd for
C22H28AgAuP2 (659.17): C, 40.19; H, 4.28. Found: C, 40.33; H,
4.35.
(41) Ro¨sch, N.; Kru¨ger, S.; Mayer, M.; Nasluzov, V. A. In Recent
DeVelopments and Applications of Modern Density Functional Theory;
Seminario, J., Ed.; Theoretical and Computational Chemistry Series 4,
Elsevier: Amsterdam, 1996; p 497.
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[Bis(trimethylphosphine)silver(I)][hexakis(µ2,η2-phenyleth-
ynyl)trigold(I)disilver(I)], [(Me3P)2Ag][Ag2Au3(C≡CPh)6]. The
reaction was carried out as described above, using (Me3P)Ag(Ct
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Aggregates with Metallophilic Ag- - -Au Contacts
Organometallics, Vol. 25, No. 4, 2006 1011
orbitals, we used very flexible Gaussian-type basis sets, contracted
in generalized fashion. For Au, a set of 21s, 17p, 11d, and 7f
exponents was contracted to [11s, 10p, 7d, 3f].47 The basis set for
Ag was (18s, 13p, 9d) contracted to [7s, 6p, 4d].48 For C and H,
we used standard basis sets of sizes (9s, 5p, 1d)/[5s, 4p, 1d] and
(6s, 1p)/[4s, 1p], respectively.49 The auxiliary basis set, used in
the LCGTO-FF-DF approach to represent the electronic charge
density when evaluating the Hartree contribution, was constructed
according to a standard procedure.38 The atomic basis sets were
augmented by sets of five p-type polarization exponents on all
atoms, five d-type exponents on all centers but H, and five f-type
exponents on the metal centers. Each set of these “polarization”
exponents was constructed as a geometric series with a progression
of 2.5, starting with 0.1, 0.2, and 0.3 au for p, d, and f types,
respectively.
Acknowledgment. This work was supported by the Deutsche
Forschungsgemeinschaft, Fonds der Chemischen Industrie,
Volkswagenstiftung, and Heraeus GmbH.
Supporting Information Available: CIF files giving details
of crystal data, data collection and structure refinement details,
atomic coordinates, isotropic and anisotropic thermal parameters,
and all bond lengths and angles. This material is available free of
charge via the Internet at http://pubs.acs.org.
OM050985Z
(49) (a) Van Duijneveldt, F. B. IBM Res. Rep. 1971, RJ 945. (b)
Huzinaga, S.; Andzelm, J.; Klobukowski, M.; Radzio-Andzelm, E.; Sakai,
Y.; Tatewaki, H. Gaussian Basis Sets for Molecular Calculations;
Elsevier: Amsterdam, 1984 (C: d exponent 0.60). (c) Frisch, M. J.;
Pople, J. A.; Binkley, J. S. J. Chem. Phys. 1984, 80, 3265 (H: p exponent
1.0).
(47) Ha¨berlen, O. D.; Ro¨sch, N. Chem. Phys. Lett. 1992, 199, 491.
(48) Matveev, A. V.; Neyman, K. M.; Yudanov, I. V., Ro¨sch, N. Surf.
Sci. 1999, 426, 123.