Preparation and crystal structure of bis(isocyanide)gold(I) bis(phenylene-1,2-dithiolato)aurates(III)

Article abstract of DOI:10.1515/znb-2002-0808

The reaction of (isocyanide)gold(I) chlorides [(RNC)AuCl, R = ^tBu, ^cHex] with phenylene-1,2-dithiol and sodium methoxide (molar ratio 2:1:2) in methanol / dichloromethane leads to the formation of deep green mixed-valent salts [(RNC)₂Au]⁺[Au(S₂C₆H ₄)₂]^- in ca. 35% yield. As determined by single crystal X-ray diffraction methods, the two compounds have entirely different supramolecular structures. For R = ^tBu stacked planar anions and rod-like cations form alternating layers, while for R = ^cHex alternating cations and anions are arranged in chains with long S- -Au contacts [3.422 ?].

Full text of DOI:10.1515/znb-2002-0808

Preparation and Crystal Structure of Bis(isocyanide)gold(I)
Bis(phenylene-1,2-dithiolato)aurates(III)
Hendrik Ehlich, Annette Schier, and Hubert Schmidbaur
Anorganisch-chemisches Institut der Technischen Universita¨t Mu¨nchen,
Lichtenbergstrasse 4, D-85747 Garching, Germany
Reprint requests to Prof. Dr. Schmidbaur. E-mail: H.Schmidbaur@lrz.tum.de
Z. Naturforsch. 57 b, 890–894 (2002); received June 10, 2002
Gold Complexes, Isocyanide Complexes, Phenylene-dithiolate Complexes
The reaction of (isocyanide)gold(I) chlorides [(RNC)AuCl, R = tBu, cHex] with phenylene-
1,2-dithiol and sodium methoxide (molar ratio 2:1:2) in methanol / dichloromethane leads to
the formation of deep green mixed-valent salts [(RNC)2Au]+[Au(S2C6H4)2] in ca. 35% yield.
As determined by single crystal X-ray diffraction methods, the two compounds have entirely
different supramolecular structures. For R = tBu stacked planar anions and rod-like cations form
alternating layers, while for R = cHex alternating cations and anions are arranged in chains with
˚
long S- -Au contacts [3.422 A].
Introduction
In an attempt to probe this unusual reaction with
complexes in which the tertiary phosphine is re-
placed by an isocyanide ligand, very similar results
have now been obtained [8]. The products have very
interesting supramolecular structures as illustrated
in the present report.
The reaction of (phosphine)gold(I) or (iso-
cyanide)gold(I) halides [(R3P)AuX / (RNC)AuX;
X = Cl, Br, I; R = alkyl, aryl] with simple thiols
RSH in the presence of an auxiliary base affords
high yields of the corresponding thiolates LAuSR.
Many of these compounds have interesting struc-
tural properties and are key substrates for many ap-
plications ranging from “liquid golds” for gilding
to preparations for chemotherapy [1]. Difunctional
thiols HS-Q-SH with the -SH groups well separated
by an organic spacer -Q- (an alkanediyl, alkenediyl,
alkynediyl, or arenediyl) give the same type of din-
uclear thiolates LAu-S-Q-S-AuL [2 - 5].
By contrast, related reactions with phenylene-
1,2-dithiol (dithiocatechol) with (phosphine)gold(I)
halides are reported to lead to an unexpected
redox process in which gold(III) complexes
of a deep green colour are produced [6, 7].
In a typical example, (Et3P)AuCl and 1,2-C6-
H4(SH)2 are converted to a significant extent
(together with several by-products, not all of
which have been identified) into a salt with
the colourless bis(triethylphosphine)gold(I) cation
[(Et3P)2Au]+ and the green bis(phenylene-1,2-di-
thiolato)gold(III) anion [Au(S2C6H4)2] [6]. With
iPro3P similar results were obtained, but smaller
amounts of the green by-product were observed [8].
Reaction Products
tButyl- and chexyl-isocyanide were chosen as the
ligands RNC because they were expected to exert
similar electronic, but different steric effects. Their
gold(I) complexes are readily prepared from (dime-
thylsulfide)- or (tetrahydrothiophene)gold(I) chlo-
ride and the free isocyanide, and the products can
be dissolved in dichloromethane [9, 10]. These so-
lutions are then treated at room temperature with
a methanol solution of disodium phenylene-1,2-di-
thiolate, prepared in situ from 1,2-C6H4 (SH)2 and
two equivalents of MeONa. After evaporation of
the solvents the products can be extracted from the
residue with dichloromethane. Crystallization from
dichloromethane / pentane gives deep green nee-
dles in yields of ca. 35%. There is a mixture of by-
t
c
products in the mother liquors (R = Bu, Hex) of
which two can be separated (R = cHex). They have
been identified as a co-crystallisate of a tetranuclear
cluster [(cHexNC)Au2(S2C6H4)]2 and a carbene
complexe (cHexNC)Au[C(NHcHex)2] Cl [8].
c
¨
¨
0932–0776/02/0800–0890 $ 06.00
2002 Verlag der Zeitschrift fur Naturforschung, Tubingen www.znaturforsch.com
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H. Ehlich et al. · Bis(isocyanide)gold(I) Bis(phenylene-1,2-dithiolato)aurates(III)
891
Fig. 1. Cation and anion of the cyclohexylisocyanide complex 2. [ORTEP drawing with 50% probability ellipsoids].
˚
Selected distances [A] and angles [ ]: Au1-S1 2.308(1), Au1-S2 2.305(1), Au2-C1 1.968(6), C1-N1 1.146(8), N1-
C223 1.443(7); S1-Au1-S2 89.78(5), S1-Au1-S2' 90.22(5), S1-Au1-S1' 180.0, S2-Au1-S2' 180.0, C1-Au2-C1' 180.0,
Au2-C1-N1 175.2(6), C1-N1-C223 177.1(6).
2 (RNC)AuCl + 1,2-C6H4(SNa)2
[(RNC)2Au]+[Au(1,2-S2C6H4)2] + by-products
1: R = tBu, 2: R = cHex
Compounds 1 and 2 have been identified by their el-
emental analyses, and FAB mass spectra have con-
firmed both the cation and the anion of compound
2. The NMR spectra (in CDCl3 solution at 20 C)
1
gave the expected signals for the H and 13C nu-
clei (Experimental Part). The chemical shifts of the
anion resonances are almost identical for both com-
pounds. The compounds are stable in air and not
sensitive to light. The crystals can be dissolved in
dichloromethane, trichloromethane and tetrahydro-
furan, but they are insoluble in pentane and diethyl
ether.
Crystal Structures
Crystals of the cyclohexylisocyanide complex 2
¯
are triclinic, space group P1, with one formula unit
Fig. 2. Stacking of cations and anions of compound 2 in
the unit cell. View parallel to the b axis.
in the unit cell. The asymmetric unit contains one
half of the cation and one half of the anion, the
remainder of the two ions being generated by inver-
sion symmetry (Fig. 1).
The cation is a rod-like entity with a quasi-linear
array of no less than seven atoms. The cyclohexyl
rings are in a chair conformation. In the anion, the
against the AuS4 unit, which is planar by symmetry.
The geometry of this anion is known from previous
investigations on salts containing different cations
[11, 12].
Thecationsandanionsofcompound 2 arestacked
atoms of each dithiolate ligand are planar with the alternatingly in columns parallel to the b axis of
two planes parallel to each other, but slightly tilted the crystal (Fig. 2). The main axis of the cation is
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892
H. Ehlich et al. · Bis(isocyanide)gold(I) Bis(phenylene-1,2-dithiolato)aurates(III)
t
Fig. 3. Cation and anion of the butylisocyanide com-
plex 1. [ORTEP drawing with 50% probability ellipsoids].
˚
Selected distances [A] and angles [ ]: Au1-S1 2.307(1),
Au1-S2 2.305(1), Au2-C1 1.966(5), C1-N1 1.143(6), N1-
C2 1.461(6); S1-Au1-S2 89.75(4), S1-Au1-S2' 90.25(4),
S1-Au1-S1' 180.0, S2-Au1-S2' 180.0, C1-Au2-C1' 169.9
(3), Au2-C1-N1 176.7 (4), C1-N1-C2 175.2(5).
Fig. 5. Orientation of the cations of complex 1 in the unit
cell.
Fig. 4. Orientation of the anions of complex 1 in the unit
cell.
Fig. 6. Complete population of the unit cell of complex 1.
roughly parallel to one of the two S-Au-S axes of
the anion. The gold atoms of a given column are on
a common straight line with an Au- -Au distance of
the cation and the anion. The remainder of the ions is
generated by twofold axes passing through the gold
atoms (Fig. 3). The structure of the anion resembles
that of compound 1 and of other salts recorded in the
literature. The cations have a quasi-linear chain of
seven atoms terminated at both ends by branching
methyl groups, but surprisingly there is a significant
bending at the gold atom: C1-Au2-C1' 169.9(3) .
The cations thus may be referred to as slightly bent
long-bar dumb-bells (a weight-lifting gear).
˚
as much as 3.881 A. Because of the tilt of the ions
against this metal axis, the closest contact between
the ions is between a sulfur and a gold atom at
˚
3.422 A. Therefore, the stacking of the columns
is not based on aurophilic interactions, which are
known to be most significant for contacts between
gold atoms in the oxidation state (+I).
Crystals of compound 1 are monoclinic, space
group C2/c, with Z = 4 formula units in the unit
The packing of cations and anions in the struc-
cell. The asymmetric unit contains one half of both ture is rather complex and shows no close contacts
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H. Ehlich et al. · Bis(isocyanide)gold(I) Bis(phenylene-1,2-dithiolato)aurates(III)
893
Table 1. Crystal data, data collection, and
structure refinement.
1
2
Crystal data
Formula
Mr
[a]
2
2
2
1 2
wR2 = [Σ w(Fo – Fc )2] Σ [w(Fo )2]
;
C22H26Au2N2S4
840.62
monoclinic
C2/c
16.8619(2)
13.1972(2)
13.6019(2)
90
122.517(1)
90
C26H30Au2N2S4
892.69
w = 1/[ 2(Fo ) + (ap)2 + bp]; p = (Fo + 2Fc )/3;
a = 0.0149 (1), 0.0000 (2); b = 25.01 (1),
0.00 (2).
2
2
2
Crystal system
Space group
triclinic
¯
P1
˚
a (A)
6.8936(3)
7.7610(3)
13.1656(7)
76.949(2)
86.711(2)
83.584(2)
681.5(1)
2.175
˚
b (A)
˚
c (A)
( )
( )
( )
3
˚
V (A )
2552.3(1)
2.188
3
calc (g cm
Z
F(000)
)
4
1
422
110.08
1576
1
(Mo-K ) (cm
Data collection
T( C)
Measured reflections
Unique reflections
Absorption correction
Tmin/Tmax
)
118.22
–130
44955
–130
21114
2808 [Rint = 0.047] 2874 [Rint = 0.068]
DELABS
0.304/0.742
DELABS
0.082/0.536
Refinement
Refined parameters
190
157
Final R values [I 2 (I)]
R1
0.0267
0.0332
wR2[a]
0.0583
0.0845
(shift/error)max
fin
< 0.001
< 0.001
3
˚
(max/min) (eA
)
1.107/–3.452
1.878/–1.609
between the components. It is obvious that the plate- General procedure for the preparation
like anions and the long-bar dumb-bell cations are
The dithiol 1,2-C6H4(SH)2 is treated with two equiva-
difficult to accommodate together to give an effi-
cient space-filling arrangement. There is neither an
alternating stacking of cations and anions nor a sep-
arate close stacking of the anion platelets. Neigh-
bouring anion platelets are strongly tilted against
each other (roof-like) and the large space between
lents of MeONa in 2 ml of anhydrous methanol. This so-
lution is added to a solution of two equivalents of the com-
plex (RNC)AuCl in 2 ml of dichloromethane with stirring
at r. t. After 1 h the solvents are removed in a vacuum and
the residue is extracted with 4 ml of dichloromethane.
Careful layering of the green solution with pentane and
these scales is filled with the long-bar dumb-bell cooling to –20 C (or diffusion of pentane vapour into the
solution in a closed system kept at this temperature) in-
duces the crystallization of the products. Green crystals,
stable in air and light.
cations. Figs. 4 and 5 show the orientation of anions
and cations separately, while Fig. 6 gives a super-
position representing the complete population.
t
Compound 1: BuNCAuCl (100 mg, 0.317 mmol);
MeONa (17 mg, 0.317 mmol); C6H4(SH)2 (23 mg,
0.159 mmol); yield 45 mg (34%). C22H26Au2N2S4
(840.65) calcd. C 31.43, H 3.12, N 3.33; found C 30.07,
H 3.10, N 3.30. NMR (CDCl3, 20 C) 1H: 1.52 (s, 18H,
Experimental Part
All experiments were routinely carried out in an at-
mosphere of dry nitrogen. Glassware was oven-dried and
filled with nitrogen and solvents were distilled, degassed
and saturated with nitrogen. Standard equipment was used
throughout. The dithiol and isocyanides were commer-
cially available, the gold complexes were prepared fol-
lowing published procedures [9, 10].
Me); 6.86 and 7.19 (AA'BB', 8H, C6H4). 13
C
1H : 29.5
(s, Me); 59.6 (s, CC3); 133.6 (br. s, CAu); 123.5, 128.3
and 142.4 (all s, C6H4).
c
Compound 2: HexNCAuCl (100 mg, 0.293 mmol),
MeONa (16 mg, 0.293 mmol), C6H4(SH)2 (21 mg,
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894
H. Ehlich et al. · Bis(isocyanide)gold(I) Bis(phenylene-1,2-dithiolato)aurates(III)
0.147 mmol); yield 41 mg (31%). C26H30Au2N2S4 treated anisotropically for all non-hydrogen atoms. All
(892.73) calcd. C 34.98, H 3.39, N 3.14; found C hydrogen atoms were placed in idealized calculated po-
33.10, H 3.46, N 3.63. MS (FAB+/-): m/z = 415.6 sitions and allowed to ride on their corresponding carbon
(100%) [(RNC)2Au]+; 477.2 (4.4%) [Au(S2C6H4)2] . atoms with fixed isotropic contributions. Further informa-
NMR (CDCl3, 20 C) 1H. 1.38, 1.68, 1.91, and 3.84 tion on crystal data, data collection and structure refine-
c
(all m, 22H, Hex); 6.81 and 7.16 (AA'BB', 8H, C6H4). ment are summarized in Table 1. Important interatomic
13C 1H : 23.1, 24.9, 31.90, and 55.2 (all s, cHex); 140.0 distances and angles are shown in the corresponding Fig-
(br. s, CAu); 124.4, 128.4 and 142.5 (all s, C6H4).
ure Captions. Displacement parameters and tables of in-
teratomic distances and angles have been deposited with
the Cambridge Crystallographic Data Centre, 12 Union
Road, Cambridge CB2 1EZ, UK. The data are available
on request on quoting CCDS 186714, 186715.
Crystal structure determination
Specimens of suitable quality and size were mounted
on the ends of quartz fibers in F06206R oil and used for
intensity data collection on a Nonius DIP2020 diffrac-
tometer, employing graphite-monochromated Mo-K ra-
diation. The structures were solved by a combination
of direct methods (SHELXS-97) and difference-Fourier
syntheses and refined by full matrix least-squares calcu-
lations on F2 (SHELXL-97). The thermal motion was
Acknowledgements
This work was supported by Deutsche Forschungsge-
meinschaft, Fonds der Chemischen Industrie, Volkswa-
genstiftung, and Degussa AG and Heraeus GmbH.
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