New pathways to compact tetragold(I) bis(phenylene-1,2-dithiolate) complexes with tertiary phosphine and isonitrile ligands

Article abstract of DOI:10.1021/om020149e

Treatment of phenylene-1,2-dithiol (or its 4-methyl derivative) with equimolar quantities of tris[(triisopropylphosphine)gold]oxonium tetrafluoroborate under mild conditions (in dichloromethane, -20 to +20 °C) yields the trinuclear complex salts {[(ⁱPr₃P)Au]₃[S₂C₆H_{4 /3}-(Me)]}BF₄ (1, 3). From concentrated solutions warmed above 20 °C the neutral tetranuclear complexes {(_iPr₃P)₂Au₄S₂C₆ H_4/3(Me)]₂} (2, 4) are crystallized in good yields. [(ⁱPr₃P)₂Au]BF₄ (6) was identified as the byproduct of the ligand redistribution reaction which converts the tri- into the tetranuclear clusters. With {[(Ph₃P)Au]₃O}BF₄ no such ligand scrambling occurs and only the trinuclear complex salt {[(Ph₃P)Au]₃(S₂C₆H₄)}BF ₄ (5) is formed. The structures of 2 and 4 have been determined by single-crystal X-ray diffraction studies. Although the crystals are not isomorphous, the molecules are almost superimposable. In the ligand framework, the four gold atoms form two edge-sharing, almost equilateral triangles which allow for tight aurophilic bonding. A similar tetranuclear cluster, [(RNC)₂Au₄(S₂C₆H₄)₂ ] (7; R = cyclohexyl), is generated in low yield in the reaction of (RNC)AuCl with C₆H₄(SNa)₂. It has been isolated as a cocrystallizate with the (isocyanide)(carbene)gold(I) complex salt {(RNC)Au[C(NHR)₂]}Cl (8) present in the reaction mixture, and the structure of the dichloromethane solvate has been determined. The components are aggregated in strings via aurophilic contacts following the sequence ...(7)(8)(8)(7)(8)(8)... The deep green gold(I)/ gold(III) salt [(RNC)₂Au] [AuS₂C₆H₄)₂] is the main product of the reaction.

Full text of DOI:10.1021/om020149e

2400
Organometallics 2002, 21, 2400-2406
New P a th w a ys to Com p a ct Tetr a gold (I)
Bis(p h en ylen e-1,2-d ith iola te) Com p lexes w ith Ter tia r y
P h osp h in e a n d Ison itr ile Liga n d s
Hendrik Ehlich, Annette Schier, and Hubert Schmidbaur*
Anorganisch-chemisches Institut der Technischen Universita¨t Mu¨nchen,
Lichtenbergstrasse 4, D-85747 Garching, Germany
Received February 21, 2002
Treatment of phenylene-1,2-dithiol (or its 4-methyl derivative) with equimolar quantities
of tris[(triisopropylphosphine)gold]oxonium tetrafluoroborate under mild conditions (in
dichloromethane, -20 to +20 °C) yields the trinuclear complex salts {[(iPr3P)Au]3[S2C6H4/3
-
(Me)]}BF4 (1, 3). From concentrated solutions warmed above 20 °C the neutral tetranuclear
complexes {(iPr3P)2Au4[S2C6H4/3(Me)]2} (2, 4) are crystallized in good yields. [(iPr3P)2Au]BF4
(6) was identified as the byproduct of the ligand redistribution reaction which converts the
tri- into the tetranuclear clusters. With {[(Ph3P)Au]3O}BF4 no such ligand scrambling occurs
and only the trinuclear complex salt {[(Ph3P)Au]3(S2C6H4)}BF4 (5) is formed. The structures
of 2 and 4 have been determined by single-crystal X-ray diffraction studies. Although the
crystals are not isomorphous, the molecules are almost superimposable. In the ligand
framework, the four gold atoms form two edge-sharing, almost equilateral triangles which
allow for tight aurophilic bonding. A similar tetranuclear cluster, [(RNC)2Au4(S2C6H4)2] (7;
R ) cyclohexyl), is generated in low yield in the reaction of (RNC)AuCl with C6H4(SNa)2. It
has been isolated as a cocrystallizate with the (isocyanide)(carbene)gold(I) complex salt
{(RNC)Au[C(NHR)2]}Cl (8) present in the reaction mixture, and the structure of the
dichloromethane solvate has been determined. The components are aggregated in strings
via aurophilic contacts following the sequence ...(7)(8)(8)(7)(8)(8)... The deep green gold(I)/
gold(III) salt [(RNC)2Au][Au(S2C6H4)2] is the main product of the reaction.
In tr od u ction
gives free access to the gold atoms for metal-metal
interactions.
Gold thiolates and their complexes with donor ligands
are the most widely used compounds in gold chemistry.1
The commercial products include, inter alia, “liquid
golds” for gilding in classical handicraft2 and in modern
surface technology,3 self-assembled monolayers on sur-
faces,4 and liquid crystal precursor molecules,5 as well
as gold drugs for chemotherapy.6
Many compounds of the gold(I) thiolate series show
a surprisingly rich supramolecular chemistry owing to
the aurophilicity phenomenon,7-9 observed for all ex-
amples where a sufficiently open molecular structure
For the design of multidimensional gold(I) thiolate
complexes based on this novel type of intermolecular
interaction, the introduction of polyfunctional thiols
with template character is particularly promising. Phe-
nylene-1,3-dithiol and phenylene-1,4-dithiol have re-
cently been probed successfully for the construction of
one-dimensional polymers.10 Di-, tri-, and tetraauration
leads to gold(I) thiolates, bis[gold(I)]sulfonium salts, or
a combination of both bridged by the phenylene units.
These end groups were found to be “sticky” at their
metal atoms and to act like a metal solder for connecting
the individual units into chains.
In previous work with the corresponding phenylene-
1,2-dithiols or related dithiols it has been demonstrated
that polyauration of these substrates leads to conven-
tional di- and trinuclear complexes (A and B) if tri-
arylphosphines are employed as ligands (Chart 1).11-14
In the trinuclear complexes, the neighboring gold thi-
(1) Gold: Progress in Chemistry, Biochemistry and Technology;
Schmidbaur, H., Ed.; Wiley: Chichester, U.K., 1999.
(2) Landgraf, G. In ref 1, p 146.
(3) Puddephatt, R. J . In ref 1, p 239.
(4) Puddephatt, R. J . In ref 1, p 250.
(5) (a) Espinet, P. Gold Bull. 1999, 32, 127. (b) Adams, H.; Bailey,
N. A.; Bruce, D. W.; Dhillon, R.; Dunmur, D. A.; Hunt, S. E.; Lalinde,
E.; Maggs, A. A.; Orr, R.; Styring, P.; Wragg, M. S.; Maitlis, P. M.
Polyhedron 1988, 7, 1861. (c) Maitlis, P. M.; Bruce, D. W.; Dhillon, R.;
Dunmur, D. A.; Fanizzi, F. P.; Hunt, S. E.; LeLaguedec, R.; Lalinde,
E.; Orr, R.; Rourke, J . P.; Salt, N. J . S.; Stacey, J . P.; Styring, P. New
J . Chem. 1990, 14, 549. (d) Adams, H.; Albe´niz, A. C.; Bailey, N. A.;
Bruce, D. W.; Cherodian, A. S.; Dhillon, R.; Dunmur, D. A.; Espinet,
P.; Feijoo, J . L.; Lalinde, E.; Maitlis, P. M.; Richardson, R. M.; Ungar,
G. J . Mater. Chem. 1991, 1, 843.
(9) Narayanaswamy, R.; Young, M. A.; Parkhurst, E.; Ouelette, M.;
Kerr, M. E.; Ho, D. M.; Elder, R. C.; Bruce, A. E.; Bruce, M. R. M.
Inorg. Chem. 1993, 32, 2506.
(10) Ehlich, H.; Schier, A.; Schmidbaur, H. Inorg. Chem., submitted
for publication.
(6) Shaw, C. F., III. In ref 1, p 267.
(7) Scherbaum, F.; Grohmann, A.; Huber, B.; Kru¨ger, C.; Schmid-
baur, H. Angew. Chem., Int. Ed. Engl. 1988, 27, 1544.
(8) (a) Nakamoto, M.; Hiller, W.; Schmidbaur, H. Chem. Ber. 1993,
126, 605. (b) Fackler, J . P., J r.; Staples, R. J .; Elduque, A.; Grant, T.
Acta Crystallogr. 1994, C50, 520. (c) Sladek, A.; Angermaier, K.;
Schmidbaur, H. J . Chem. Soc., Chem. Commun. 1996, 1959.
(11) (a) Gimeno, M. C.; J ones, P. G.; Laguna, A.; Laguna, M.;
Terroba, R. Inorg. Chem. 1994, 33, 3932. (b) Sladek, A.; Schmidbaur,
H. Chem. Ber. 1995, 128, 907. (c) Sladek, A.; Schmidbaur, H. Inorg.
Chem. 1996, 35, 3268.
(12) Nakamoto, M.; Koijman, H.; Paul, M.; Hiller, W.; Schmidbaur,
H. Z. Anorg. Allg. Chem. 1993, 619, 1341.
10.1021/om020149e CCC: $22.00 © 2002 American Chemical Society
Publication on Web 05/07/2002

Tetragold(I) Bis(phenylene-1,2-dithiolate) Complexes
Organometallics, Vol. 21, No. 12, 2002 2401
Ch a r t 1. Gold (I) Com p lexes of P h en ylen e-1,2-d ith iols
Sch em e 1. P r ep a r a tion of Com p lexes 1 a n d 3
olate and bis(gold)sulfonium groups are intimately
aggregated to give V-shaped triatomic gold units of high
stability (B; Chart 1). The same observation is made
when the dinuclear complexes derived from phenylene-
1,2-dithiol are reacted with rhodium or iridium com-
plexes to afford heterotrinuclear compounds containing
the (Au2M) cores (M ) Rh, Ir).14b With triethylphos-
phine, however, the reactions are accompanied by an
unprecedented partial loss of ligands, which leads to
vacancies in the coordination sphere of the metal for
more compact clustering.13a,15 Tetranuclear dimers are
obtained in which the metal atoms form rhombic units
(C; Chart 1).
These investigations have now been extended to
include other tertiary phosphines, as well as isonitriles,
as auxiliary ligands, which were expected to enhance
cluster formation owing to their smaller size. In par-
ticular, the opening of a “direct route” to the compounds
(from only two components in the right stoichiometry)
was desirable in order to test the ligand-dependent
stability of the products. Previously employed multi-
component syntheses, even if carried out in the absence
of oxidative agents, have the distinct disadvantage of
the unexpected formation of gold(III) compounds, with
salts of the bis(phenylene-1,2-dithiolato)gold(III) anion
as the most common byproducts.11a,12,16 This phenom-
enon is immediately obvious from the appearance of the
deep green color of this anion.
trinuclear gold(I) phenylene-1,2-dithiolate tetrafluorobo-
rate {[(i-Pr3P)Au]3S2C6H4}+BF4 (1) in 83% yield as a
-
colorless microcrystalline solid (Scheme 1) with only a
few larger crystals of the byproduct 2. This compound
2 crystallizes in almost 63% yield within 2 h if the
reaction mixture is concentrated under vacuum to a
small volume at 20 °C (Scheme 2). It has been identified
as a tetranuclear bis(phenylene-1,2-dithiolate) in which
only two of the four phosphine ligands remain: [(iPr3P)2-
Au4(S2C6H4)2] (2).
The same results were obtained in experiments with
4-methylphenylene-1,2-dithiol and the oxonium salt
bearing the triisopropylphosphine ligand. The analogous
compounds 3 and 4 were isolated in 79 and 67% yields,
respectively (Schemes 1 and 2).
In contrast, the reaction of {[(Ph3P)Au]3O}BF4 with
phenylene-1,2-dithiol gave only one product without loss
of phosphine: {[(Ph3P)Au]3S2C6H4}BF4 (5), in 90% yield
(Scheme 3).
Regarding the mechanism of formation of 1/3 or 2/4,
it appears that compounds 1 and 3 are first formed, as
suggested by the stoichiometry of the reactants. The two
initial products then undergo cleavage into the salt
P r ep a r a tive Resu lts
The reaction of phenylene-1,2-dithiol with an equimo-
lar quantity of tris[(triisopropylphosphine)gold(I)]oxonium
tetrafluoroborate in dichloromethane at ambient tem-
perature was found to give two different products,
depending on the workup procedure employed. Precipi-
tation of the product directly from the reaction mixture
by cooling to -20 °C and adding pentane gives the
(13) (a) Davila, R. M.; Elduque, A.; Grant, T.; Staples, R. J .; Fackler,
J . P., J r. Inorg. Chem. 1993, 32, 1749. (b) Davila, R. M.; Staples, R. J .;
Elduque, A.; Harlass, M. M.; Kyle, L.; Fackler, J . P., J r. Inorg. Chem.
1994, 33, 5940.
(14) (a) Terroba, R.; Fernandez, E. J .; Hursthouse, M. B.; Laguna,
M. Polyhedron 1998, 17, 2433. (b) del Rio, I.; Terroba, R.; Cerrada, E.;
Hursthouse, M. B.; Laguna, M.; Light, M. E.; Ruiz, A. Eur. J . Inorg.
Chem. 2001, 2013.
(15) Nakamoto, M.; Schier, A.; Schmidbaur, H. J . Chem. Soc., Dalton
Trans. 1993, 1347.
(16) Davila, R. M.; Staples, R. J .; Fackler, J . P., J r. Acta Crystallogr.
1994, C50, 1898.

2402 Organometallics, Vol. 21, No. 12, 2002
Ehlich et al.
the structure of the latter has been determined.11 Sim-
ilar characteristics are assumed for 5 on the basis of,
for example, almost identical 31P NMR spectroscopic
data.
Sch em e 2. P r ep a r a tion of Com p lexes 2 a n d 4
Compounds 2 and 4 are very different from complexes
1, 3, and 5 in that they are completely insoluble in
both polar and nonpolar organic solvents. Therefore, no
characterization by solution spectroscopy was pos-
sible, but the molecular structures were determined by
single-crystal X-ray diffraction studies (below). Note
that the low solubility of 2 and 4 may also be a driving
force for the ligand redistribution of the precursor
products 1 and 3.
A cluster of the type 2/4 with cyclohexyl isocyanide
as the ligand instead of triisopropylphosphine was
obtained as one of several products of the reaction
between (cyclohexyl isocyanide)gold(I) chloride and di-
sodium phenylene-1,2-dithiolate in the molar ratio 2:1
in methanol. This product (7; Scheme 4) was detected
in the reaction mixture by monitoring its spectroscopic
data (Experimental Section). It could finally be cocrys-
tallized serendipitously with [bis(cyclohexylamino)car-
bene](cyclohexyl isocyanide)gold(I) chloride (8; Scheme
4) and dichloromethane in the molar ratio 1:2:2 (see
below). For this crystalline phase spectroscopic and
elemental analysis data were also obtained.
Sch em e 3. P r ep a r a tion of Com p lex 5
The main product of the reaction in Scheme 4 is the
deep green bis(cyclohexyl isocyanide)gold(I) bis(phen-
ylene-1,2-dithiolato)aurate(III) (9), which will be pre-
sented in a more appropriate context.17
Str u ctu r a l Stu d ies
Crystals of the compounds 2 and 4 are not isomor-
phous. The former are orthorhombic, space group Pbca,
with Z ) 4 formula units, while the latter are mono-
clinic, space group P21/n, with Z ) 2 formula units in
the unit cell. However, the structures of the individual
molecules are very similar, as illustrated by the super-
position shown in Figure 1. Note that the molecules
differ only by the presence/absence of the 4-methyl
group in the phenylene-1,2-dithiolate ligands.
In both 2 and 4 the atoms are related by a center of
inversion located in the middle of the parallelogram
formed by the four gold atoms (Figures 2 and 3). The
two edges of these units are very similar: The distances
Au1-Au2 and Au1-Au2A are 3.0398(3) and 3.0384(3)
Å for 2 and 3.0667(7) and 3.0855(7) Å for 4. Because of
the acute angles Au1-Au2-Au1A of 63.653(8)° (2) and
62.54(2)° (4) the transannular distances Au1-Au1A are
also short, at 3.2053(4) Å for 2 and at 3.193(1) Å for 4,
and thus are still in the range for significant aurophilic
bonding. The parallelogram can be described as formed
by two edge-sharing, almost equilateral triangles with
the four peripheral edges bridged on different sides by
the thiolate sulfur atoms. The gold atoms Au1 are
linearly two-coordinated (S1A-Au1-S2 ) 175.87(5)° in
2 and 175.4(1)° in 4), while the gold atoms Au2 are
planar three-coordinate (with sums of the angles at
359.7 and 359.9°). The alkylphosphine and dithiolate
ligands show no anomalies. The structures of 2 and 4
will not be discussed any further, because there are
-
[(iPr3P)2Au]+BF4 (6) (Scheme 2) and the secondary
products 2 and 4, respectively. Compound 6 could be
detected in the mother liquor of the precipitates by 31P
(s, 74.4 ppm) and 1H (dd, 1.34 ppm; dsep, 2.51 ppm)
NMR spectroscopy. In the reaction with {[(Ph3P)Au]3O}-
BF4 no cleavage of the primary product (5) occurs
which would give [(Ph3P)2Au]BF4. Ph3P may be classi-
fied as a poorer leaving group and may meet more or
less ideal steric conditions in 5, which make rearrange-
ments thermodynamically unfavorable. It is probably
no coincidence that the analogous reaction with 4-
methylphenylene-1,2-dithiol also gives the analogous
product only.
Two analogues of compounds 1 and 3 (with different
dithiols and phosphines) have been structurally char-
acterized.11b,c The analytical and spectroscopic data of
the new compounds show no anomalies and suggest sim-
ilar structural characteristics. The perchlorate salt of
the cation present in compound 5 and the corresponding
4-methyl derivative have previously been reported, and
(17) Ehlich, H.; Schier, A.; Schmidbaur, H. To be submitted for
publication.

Tetragold(I) Bis(phenylene-1,2-dithiolate) Complexes
Organometallics, Vol. 21, No. 12, 2002 2403
Sch em e 4. P r ep a r a tion of Com p lexes 7-9
when pentane is allowed to diffuse slowly into a dichlo-
romethane solution of the products formed according to
Scheme 4 and were separated mechanically. The struc-
ture consists of infinite chains of the components with
the sequence ...7,8,8,7,8,8..., as shown in Figure 4. The
tetranuclear cluster 7 and the pairs of the carbene
complex salts 8 reside around centers of inversion. The
chloride counterion is associated with the carbene part
and with the dichloromethane solvate molecules via
hydrogen bonding.
The components 7 and 8 (and 8 with 8) are associated
through aurophilic bonding which extends along the
chain axis with a slight puckering as shown by the
following intermolecular bond lengths and angles:
Au1-Au3 ) 3.2925(6) Å, Au1-Au1B ) 3.466(1) Å,
Au1B-Au1-Au3 ) 162.2(1)°, Au1-Au3-Au2 ) 163.46-
(2)°. Note that the aurophilic contact Au1-Au1B con-
nects two cations and is thus maintained against
Coulomb repulsion.
The cluster 7 with the composition [(cHexNC)2Au4-
F igu r e 1. Superposition of the structures of compounds
2 and 4.
(S2C6H4)2] has
a core structure similar to that
known from previous examples with trialkylphosphine
ligands,13a,15 including the compounds 2 and 4 (see
above). The four gold atoms form a parallelogram
(planar by crystallographic inversion symmetry) with
the edges Au2-Au3 ) 3.0466(6) Å and Au2-Au3′ )
3.0984(6) Å. Together with the shorter of the two
diagonals, Au2-Au2′ ) 3.1588(7) Å, these data show
that the tetranuclear unit is again formed from two
many similarities with examples described pre-
viously.13a,15
Crystals of the composition (7)(8)2(CH2Cl2)2 are tri-
clinic, space group P1h, with one cluster unit 7, two
carbene complex salts 8, and two dichloromethane
molecules in the unit cell. They appear as colorless
needles together with the green needles of compound 9

2404 Organometallics, Vol. 21, No. 12, 2002
Ehlich et al.
F igu r e 4. Infinite chains in the structure of crystals of
the composition (7)(8)2(CH2Cl2)2 (ORTEP drawing with 50%
probability ellipsoids). Selected distances (Å) and angles
(deg): Au1-Au3 ) 3.2965(6), Au1-Au1B ) 3.466(1), Au3-
Au2 ) 3.0466(6), Au3-Au2A ) 3.0984(6), Au2-Au2A )
3.1588(7), Au1-C1 ) 2.03(1), Au1-C2 ) 1.98(1), Au2-S1
) 2.312(3), Au2-S2A ) 2.303(3), Au3-C3 ) 1.95(1), Au3-
S1 ) 2.528(3), Au3-S2 ) 2.421(3); Au1B-Au1-Au3 )
162.2(1), Au1-Au3-Au2 ) 163.46(2), Au1-Au3-Au2A )
F igu r e 2. Structure of compound 2 (ORTEP drawing with
50% probability ellipsoids, H atoms omitted for clarity).
Selected distances (Å) and angles (deg): Au1-S1 ) 2.318-
(2), Au1-S2A ) 2.320(2), Au1-Au2 ) 3.0398(3), Au1-
Au1A ) 3.2053(4), Au1-Au2A ) 3.0384(3); S1-Au1-S2A
) 175.87(5), Au2-Au1-Au2A ) 116.347(8), Au2A-Au1-
Au1A ) 58.194(8), Au2-Au1-Au1A ) 58.153(8).
119.60(2), C1-Au1-C2
) 177.9(4) S1-Au2-S2A )
175.0(1).
atoms Au3/Au3′ are three-coordinated with the atoms
C3, Au3, S1, and S2 all in one plane (sum of the valence
angles at Au3 359.7(1)°). The small angle S1-Au3-S2
(85.49(9)°) imposed by the ligand span of the phenylene-
1,2-dithiolate unit, and by the optimization of the
aurophilic Au2-Au2′ contacts, means an unusually
large distortion away from the ideal 120°. This is
probably the reason why the two bond lengths Au3-S1
) 2.528(3) Å and Au3-S2 ) 2.421(3) Å and the two
angles C3-Au3-S1/S2 (130.2(3)/144.0(3)°) are signifi-
cantly different. The isocyanide ligand is “leaning over”
toward S1 in order to somewhat straighten the axis N3-
C3-Au3-S2. A similar distortion has also been ob-
served for 2 and 4 (P1 closer to S1 than to S2 in Figures
2 and 3).
The carbene complex unit 8 has linearly two-coordi-
nated gold atoms (Au1) with conventional isocyanide
bonding (N1-C2-Au1) and “Fischer carbene” coordina-
tion (N11/N12-C1-Au1). The C1 atom is in a trigonal-
planar environment (sum of the angles 359.9°). Since
there is precedent for this type of coordination, the
structure of component 8 is not discussed in detail.18
The dimensions of the hydrogen bonding of the chloride
anion are summarized in Table 1.
F igu r e 3. Structure of compound 4 (ORTEP drawing with
50% probability ellipsoids, H atoms omitted for clarity).
Selected distances (Å) and angles (deg): Au1-S2 ) 2.305-
(3), Au1-S1A ) 2.306(3), Au1-Au2 ) 3.0667(7) Au1-
Au1A ) 3.193(1), Au1-Au2A ) 3.0857(7); S2-Au1-S1A
) 175.4(1), Au2-Au1-Au2A ) 117.47(2), Au2A-Au1-
Au1A ) 58.44(2), Au2-Au1-Au1A ) 59.02(2).
Discu ssion a n d Con clu sion
The present work has shown that the reaction of
equimolar quantities of tris[(trialkylphosphine)gold(I)]-
oxonium tetrafluoroborates and phenylene-1,2-dithiols
is a convenient, high-yield, one-step route to compact
bis(phosphine)tetragold bis(phenylene-1,2-dithiolate) clus-
ters (2 and 4; Scheme 2). These tetranuclear compounds
are formed in a ligand redistribution process from tris-
(phosphine)(phenylene-1,2-dithiolato)trigold tetrafluo-
roborate intermediates, with bis(phosphine)gold tet-
edge-sharing, almost equilateral triangles. The three
endocyclic Au-Au-Au angles are all close to 60°: Au2′-
Au2-Au3′ ) 58.26(1)°, Au2-Au3-Au2′ ) 61.86(1)°,
Au2-Au2′-Au3 ) 59.88(1)°. With these dimensions of
the Au4 unit, compound 7 is another classical example
for tight aurophilic bonding. The short Au-Au contacts
are associated with small Au-S-Au angles of only
77.89(8)° at S1 and 81.93(8)° at S2.
(18) Raubenheimer, H. G.; Cronje, S. In Gold: Progress in Chem-
istry, Biochemistry and Technology; Schmidbaur, H., Ed.; Wiley:
Chichester, U.K., 1999; p 608 ff.
While the cluster atoms Au2/Au2′ are linearly two-
coordinated (S1′-Au2-S2 ) 175.0(1)°), the cluster

Tetragold(I) Bis(phenylene-1,2-dithiolate) Complexes
Organometallics, Vol. 21, No. 12, 2002 2405
Ta ble 1. Cr ysta l Da ta a n d Da ta Collection a n d Str u ctu r e Refin em en t Deta ils
2
4
7(8)2(CH2Cl2)2
Crystal Data
formula
Mr
cryst syst
space group
a (Å)
C
30H50Au4P2S4
C32H54Au4P2S4
1416.80
monoclinic
P21/n
11.3630(4)
14.6980(6)
12.4590(4)
90
110.982(2)
90
1942.9(1)
2.422
C68H104Au6Cl6N8S4
2556.33
triclinic
P1h
12.2612(4)
12.3935(3)
14.2413(5)
78.193(1)
87.988(1)
72.019(1)
2013.9(1)
2.103
1388.75
orthorhombic
Pbca
13.5964(1)
15.3692(2)
17.7202(2)
90
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
90
90
3702.9(1)
2.491
4
F
calcd (g cm-3
Z
)
2
1
F(000)
2560
161.30
1312
153.37
1208
112.32
µ(Mo KR) (cm-1
)
Data Collection
T (°C)
-130
-130
-130
no. of measd rflns
no. of unique rflns
abs cor
98 026
87 126
72 102
4098 (Rint ) 0.059)
DELABS
4288 (Rint ) 0.050)
DELABS
8400 (Rint ) 0.096)
DELABS
T
min/Tmax
0.195/0.665
0.131/0.602
0.143/0.615
Refinement
no. of refined params
181
190
421
final R values (I g 2σ(I))
R1
wR2a
a/b
0.0308
0.0803
0.0000/17.72
0.0596
0.1157
0.0007/44.48
0.0546
0.1266
0.0000/0.000
wR2) {[∑w(Fo - Fc2)2]/∑[w(Fo2)2]}1/2; w ) 1/[σ2(Fo2) + (ap)2 + bp]; p ) (Fo + 2Fc2)/3.
a
2
2
rafluoroborates as the byproducts (Scheme 2). With
lateral triangles. There is precedent for this type of
aggregation, which appears to be one of the most
favorable supramolecular aggregation modes in gold(I)
chemistry.1
oxonium salts bearing triarylphosphine ligands, no such
ligand redistribution occurs and the trinuclear salts are
the sole products (5; Scheme 3).
Tetranuclear clusters of the type obtained with tri-
alkylphosphines are also generated in the reaction of
(isocyanide)gold(I) chlorides (RNC)AuCl with alkali-
metal phenylene-1,2-dithiolates. However, the resulting
bis(isocyanide)tetragold bis(phenylene-1,2-dithiolate) (7;
Scheme 4) is only a minor byproduct in this reaction
and was isolated as a cocrystallizate with (isocya-
nide)(diaminocarbene)gold(I) chloride in a dichloro-
methane solvate, (7)(8)2(CH2Cl2)2. Component 8 of the
type (RNC)Au[C(NHR)2]+Cl- (Scheme 4) is probably
formed from the bis(isocyanide)gold chloride byproduct
[(RNC)2Au]+Cl- upon addition of the alkylamine RNH2
present in the reaction mixture owing to trace hydrolysis
of the isocyanide (R ) cyclohexyl).
The main product of the reaction between (RNC)AuCl
and C6H4(SNa)2 is a deep green salt of the composition
[(RNC)2Au]+[Au(S2C6H4)]- containing gold in two oxida-
tion states (Au(I) in the cation and Au(III) in the anion)
(Scheme 4). Similar redox products have been observed
in analogous reactions with (R3P)AuCl compounds in
several laboratories and are not fully understood,
because the oxidizing agent (and its reduction product)
have not yet been identified.11a,12,16 Further work is
necessary to clarify this point.
Exp er im en ta l Section
All experiments were carried out under an atmosphere of
dry, pure nitrogen. Solvents were dried and saturated with
nitrogen, and glassware was oven-dried and filled with nitro-
gen. Standard equipment was used throughout. The tris(gold)-
oxonium salts (LAu)3O+BF4- (L ) iPr3P, Ph3P) and (cyclohexyl
isocyanide)gold chloride were prepared by following estab-
lished procedures.19,20 The phenylenedithiols and all other
reagents are commercially available.
Tr is[(tr iisopr opylph osph in e)gold](ph en ylen e-1,2-dith i-
ola te) Tetr a flu or obor a te (1) a n d Its 4-Meth yl An a logu e
(3). A solution of {[(iPr3P)Au]3O}BF4 (150 mg, 0.13 mmol, for
1; 100 mg, 0.085 mmol, for 3) in dichloromethane (5 mL) is
treated with a solution of 1,2-C6H4(SH)2 (18 mg, 0.13 mmol)
or 1,2,4-C6H3(SH)2(Me) (13 mg, 0.085 mmol) in 2 mL of the
same solvent and a small quantity of NaBF4 for 1 h at 0 °C
with stirring. The precipitate is filtered off and the product
precipitated from the filtrate by layering with pentane at -20
°C. Colorless solids were obtained (1, 140 mg, 83% yield; 3, 88
mg, 79% yield). A few large crystals of 2/4 may also be formed,
which should be separated in order to obtain pure products.
Anal. Calcd for 1, C33H67Au3BF4P3S2: C, 30.52; H, 5.20.
Found: C, 31.07; H, 5.36. Anal. Calcd for 3, C34H69Au3-
BF4P3S2: C, 31.11; H, 5.30. Found: C, 32.30; H, 5.73. 31P{1H}
NMR (CD2Cl2, 20 °C; δ): 1, 69.0 (s); 3, 68.5 (s). 1H NMR (CD2-
Cl2, 20 °C; δ): 1, 1.26 (dd, J ) 7.0 and 16.1 Hz, 54 H, Me),
2.28 (dsep, J ) 7.0 and 7.3 Hz, 9 H, CH(Me)2), 7.01 and 7.86
The structures of the new tetranuclear compounds (2,
4, and 7) are very similar and have been shown to
contain the neutral cluster [Au4(S2C6H3R)2] (R ) H, Me)
stabilized by either two trialkylphosphine or two iso-
cyanide ligands. The cluster geometry is indicative of
intimate aurophilic bonding which supports the exceed-
ingly compact arrangement of the four metal atoms at
the corners of two coplanar, edge-sharing, almost equi-
(19) (a) Nesmeyanov, A. N.; Perevalova, E. G.; Struchkov, Y. T.;
Antipin, M. Y.; Grandberg, K. I.; Dyadchenko, V. P. J . Organomet.
Chem. 1980, 201, 343. (b) Yang, Y.; Ramamoorthy, V.; Sharp, P. R.
Inorg. Chem. 1993, 32, 1946.
(20) Wilton-Ely, J . D. E. T.; Ehlich, H.; Schier, A.; Schmidbaur, H.
Helv. Chim. Acta 2001, 84, 3216.

2406 Organometallics, Vol. 21, No. 12, 2002
Ehlich et al.
(dd, J ) 5.9 and 3.3 Hz, 4 H, C6H4); 3, 1.25 (dd, J ) 7.2 and
16.1 Hz, 54 H, (Me)2CH), 2.27 (dsep, J ) 7.2 and 6.9 Hz, 9 H,
CH(Me)2), 2.25 (s, 3 H, Me(Ph)), 7.69, 7.70, and 6.82 (m, 3 × 1
H, C6H3). 13C{1H} NMR (CD2Cl2, 20 °C; δ): 1, 20.65 (d, J )
6.9 Hz, Me), 24.9 (d, J ) 29.2 Hz, CH), 125.8, 135.1, and 138.9
(s, C6H4); 3, 20.47 (d, J ) 1.6 Hz, (Me)2CH), 24.40 (d, J ) 28.5
Hz, CH(Me)2), 20.58 (s, Me(Ph)), 126.8, 134.6, 134.8, 135.3,
135.8, and 138.7 (all s, C6H3(Me)).
Bis(tr iisop r op ylp h osp h in e)tetr a gold Bis(p h en ylen e-
1,2-d ith iola te) (2) a n d Its 4-Meth yl An a logu e (4). The
reactions described for the preparation of 1/3 give a reaction
mixture which upon a different workup yields products 2 and
4 instead. To this end, the filtrate is concentrated under
vacuum at room temperature to a volume of 1 mL and the
residue kept at this temperature for prolonged time. After 2 h
the products begin to separate as large crystals, which cannot
be redissolved in dichloromethane: 2, 112 mg, 63% yield; 4,
81 mg, 67% yield.
chanical separation). MS (FAB): cations, m/z 415.6 (99%)
[(cHexNC)2Au]+; anions, m/z 477.2 (4.4%) [Au(S2C6H4)2]-. The
crystal structure has been determined.17
The colorless needles separated from the green needles were
subjected to a single-crystal X-ray diffraction study and shown
to have the composition (7)(8)2(CH2Cl2)2 (Scheme 4, Figure 4).
Anal. Calcd for C66H100Au6Cl2N8S4 + C5H12: C, 34.68; H,
4.59; N, 4.56. Found: C, 35.63; H, 4.38; N, 4.60. The cocrys-
tallizate is soluble in chloroform (at 20 °C) and shows the
1
following NMR signals. H NMR (δ): 7 + 8, 1.38, 1.68, 1.91,
and 3.84/3.57 (m, rel intens 4:4:2:1 H, C6H11), 7.33 and 7.65
(dd, J ) 1.5 and 4.7 Hz, rel int.ens 2:2 H, C6H4); 8, 9.12 (br s,
NH). 13C{1H} NMR (δ): 7 + 8, 23.1, 24.5/24.9, 31.3/31.9, and
51.6/55.2 (s, C6H11); 8, 195.5 (s, CN2), CN-cHex not observed;
7, 126.0, 129.4, 142.3 (s, C6H4).
Cr ysta l Str u ctu r e Deter m in a tion s. Specimens of suit-
able quality and size of compounds 2, 4, and 7(8)2(CH2Cl2)2
were mounted on the ends of quartz fibers in F06206R oil and
Anal. Calcd for 2, C30H50Au4P2S4: C, 25.95; H, 3.63; Au,
used for intensity data collection on a Nonius DIP2020
56.73. Found: C, 26.23; H, 3.77; Au, 55.60. Calcd for 4, C32H54
Au4P2S4: C, 27.13; H, 3.84; Au, 55.61. Found: C, 25.56; H,
3.73; Au, 54.60.
-
diffractometer, employing graphite-monochromated Mo KR
radiation. The structures were solved by a combination of
direct methods (SHELXS-97) and difference Fourier syntheses
and refined by full-matrix least-squares calculations on F2
(SHELXL-97). The thermal motion was treated anisotropically
for all non-hydrogen atoms. All hydrogen atoms were calcu-
lated and allowed to ride on their parent atoms with fixed
isotropic contributions. Important interatomic distances and
angles are given in the corresponding figure captions. Aniso-
tropic thermal parameters and complete lists 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
CCDC-184333-184335.
Tr is[(t r ip h en ylp h osp h in e)gold ](p h en ylen e-1,2-d it h i-
ola te) Tetr a flu or obor a te (5). A 281 g amount (0.19 mmol)
of {[(Ph3P)Au]3O}BF4 dissolved in 5 mL of CH2Cl2 is reacted
for 1 h at 20 °C with a small amount of NaBF4 and a solution
of 1,2-C6H4(SH)2 (27 mg, 0.19 mmol) in 2 mL of the same
solvent with stirring. After filtration the product is precipitated
by careful layering with pentane at -20 °C. The colorless solid
(270 mg, 89% yield) is soluble in di- and trichloromethane but
insoluble in pentane and diethyl ether. Anal. Calcd for C60H49
-
Au3BF4P3S2: C, 44.91; H, 3.08; Au, 36.82. Found: C, 44.73;
H, 2.76; Au, 37.04. The NMR data are in agreement with those
reported for the perchlorate salt, including the temperature
dependence of the 31P resonance (δ); 20 °C, 35.41; -50 °C, 44.9
(1 P), 34.1 (2 P).
Rea ction of (Cycloh exyl isocya n id e)gold Ch lor id e
w ith Disod iu m P h en ylen e-1,2-d ith iola te. (cHexNC)AuCl
(100 mg, 0.293 mmol) is reacted with NaOMe (16 mg, 0.293
mmol) and C6H4(SH)2 (21 mg, 0.147 mmol) in a mixture of
methanol (2 mL) and dichloromethane (2 mL) at 20 °C for 1 h
with stirring. The reaction mixture is evaporated to dry-
ness under vacuum, and the residue is extracted with 4 mL
of CH2Cl2. Upon careful layering with pentane a mixture
of crystals is formed, consisting mainly of the green needles
of [(cHexNC)2Au][Au(S2C6H4)2] (41 mg, 31% yield after me-
Ack n ow led gm en t. This work was generously sup-
ported by the Deutsche Forschungsgemeinschaft, the
Fonds der Chemischen Industrie, the Volkswagenstif-
tung, Degussa AG, and Heraeus GmbH.
Su p p or tin g In for m a tion Ava ila ble: Tables giving de-
tails of crystal data, data collection, and structure refinement,
atomic coordinates, isotropic and anisotropic thermal param-
eters, and all bond lengths and angles. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM020149E