Aurophilicity at sulfur centers. Synthesis and reactivity of the complex [S(Au2dppf)]; formation of polynuclear sulfur-centered complexes. Crystal structures of [S(Au2dppf)]·2CHCl3, [(μ-Au2dppf){S(Au2dppf)}2](OTf) 2· 8CHCl3, and [S(AuPPh2Me) 2(Au2dppf)]

Article abstract of DOI:10.1021/ja9517678

Treatment of [Au₂Cl₂(μ-dppf)] (dppf =1,1′-bis(diphenylphosphino)ferrocene) with Li₂S (molar ratio 1:1) in ethanol gives a yellow solid [S(Au₂dppf)] (1). The sulfur atom in complex 1 can coordinate several neutral or cationic gold(I) fragments giving the trinuclear neutral [S{Au(C₆F₅)}(Au₂dppf)] (2) or cationic derivatives [S(AuL)(Au₂dppf)]ClO₄ [L = CH₂PPh₃ (3), PPh₃ (4), PPh₂Me (5)]. A pentanuclear complex [Au{S(Au₂dppf)₂}]ClO₄ (6) is obtained by reaction of 2 equiv of complex 1 with 1 equiv of [Au(tht)₂]ClO₄, in which the central gold atom is bonded to two sulfur atoms. Treatment of compound 1 with [Au₂(OTf)₂(μ-dppf)] (OTf = trifluoromethylsulfonate) in a molar ratio 2:1 affords the hexanuclear complex [(μ-Au₂dppf){S(Au₂dppf)}₂](OTf)₂ (7), in which two SAu₃ units are joined through the dppf ligand. The reaction of 1 with 2 equiv of [Au(OClO₃)PR₃] leads to the quadruply bridging derivatives [S(AuPR₃)₂(Au₂dppf)](ClO₄) ₂ [PR₃ = PPh₃ (8), PPh₂Me (9)]. Crystal structure determinations were performed for complexes 1, 7, and 9. [S(Au₂dppf)] (1) crystallizes in the monoclinic space group P2/n, with a = 12.571(4) A?, b = 10.579(4) A?, c = 15.212(4) A?, β = 107.84(3)°, Z = 2, T = -130 °C. [(μ-Au₂dppf){S(Au₂dppf)}₂](OTf)₂ (7) is triclinic, P1, with a = 15.177(3), b = 18.408(4), c = 27.894(8) A?, α = 88.83(2), β = 84.46(2), γ = 67.78(2), Z = 2, T = -100 °C. [S(AuPPh₂Me)₂(Au₂dppf)](ClO₄) ₂ (9) is triclinic, P1, with a = 13.727(2) A?, b = 15.952(3) A?, c = 17.763(2) A?, α = 71.738(12)°, β= 73.264(14)°, γ= 75.96(2)°, Z = 2, T = -100 °C. All three complexes display short gold(I)-gold(I) interactions.

Full text of DOI:10.1021/ja9517678

J. Am. Chem. Soc. 1996, 118, 4839-4845
4839
Aurophilicity at Sulfur Centers. Synthesis and Reactivity of the
Complex [S(Au2dppf)]; Formation of Polynuclear
Sulfur-Centered Complexes. Crystal Structures of
[S(Au2dppf)]‚2CHCl3, [(µ-Au2dppf){S(Au2dppf)}2](OTf)2‚
8CHCl3, and [S(AuPPh2Me)2(Au2dppf)](ClO4)2‚3CH2Cl2
Fernando Canales,† M. Concepcio´n Gimeno,† Antonio Laguna,*,† and
Peter G. Jones‡
Contribution from the Departamento de Qu´ımica Inorga´nica, Instituto de Ciencia de Materiales
de Arago´n, UniVersidad de Zaragoza-C.S.I.C., 50009 Zaragoza, Spain, and Institut fu¨r
Anorganische und Analytische Chemie der Technischen UniVersita¨t, Postfach 3329, D-38023,
Braunschweig, Germany
ReceiVed May 31, 1995. ReVised Manuscript ReceiVed September 13, 1995X
Abstract: Treatment of [Au2Cl2(µ-dppf)] (dppf ) 1,1′-bis(diphenylphosphino)ferrocene) with Li2S (molar ratio 1:1)
in ethanol gives a yellow solid [S(Au2dppf)] (1). The sulfur atom in complex 1 can coordinate several neutral or
cationic gold(I) fragments giving the trinuclear neutral [S{Au(C6F5)}(Au2dppf)] (2) or cationic derivatives [S(AuL)-
(Au2dppf)]ClO4 [L ) CH2PPh3 (3), PPh3 (4), PPh2Me (5)]. A pentanuclear complex [Au{S(Au2dppf)2}]ClO4 (6) is
obtained by reaction of 2 equiv of complex 1 with 1 equiv of [Au(tht)2]ClO4, in which the central gold atom is
bonded to two sulfur atoms. Treatment of compound 1 with [Au2(OTf)2(µ-dppf)] (OTf ) trifluoromethylsulfonate)
in a molar ratio 2:1 affords the hexanuclear complex [(µ-Au2dppf){S(Au2dppf)}2](OTf)2 (7), in which two SAu3
units are joined through the dppf ligand. The reaction of 1 with 2 equiv of [Au(OClO3)PR3] leads to the quadruply
bridging derivatives [S(AuPR3)2(Au2dppf)](ClO4)2 [PR3 ) PPh3 (8), PPh2Me (9)]. Crystal structure determinations
were performed for complexes 1, 7, and 9. [S(Au2dppf)] (1) crystallizes in the monoclinic space group P2/n, with
a ) 12.571(4) Å, b ) 10.579(4) Å, c ) 15.212(4) Å, â ) 107.84(3)°, Z ) 2, T ) -130 °C. [(µ-Au2dppf){S(Au2-
dppf)}2](OTf)2 (7) is triclinic, P1h, with a ) 15.177(3), b ) 18.408(4), c ) 27.894(8) Å, R ) 88.83(2), â ) 84.46(2),
γ ) 67.78(2), Z ) 2, T ) -100 °C. [S(AuPPh2Me)2(Au2dppf)](ClO4)2 (9) is triclinic, P1h, with a ) 13.727(2) Å,
b ) 15.952(3) Å, c ) 17.763(2) Å, R ) 71.738(12)°, â ) 73.264(14)°, γ ) 75.96(2)°, Z ) 2, T ) -100 °C. All
three complexes display short gold(I)-gold(I) interactions.
Introduction
contribution to their stability. It is probable that relativistic
effects play a role in this type of bonding.7-9 The gold-gold
interactions of ca. 3.0 Å are associated with bond energies of
ca. 33 kJ/mol;10-13 their strength is obviously influenced by the
electronic effects of the ligand bonded to gold, but it is becoming
more and more clear that steric effects are also very important.
To illustrate this fact, species of the type C(AuPR3)4 could only
be isolated when sufficient bulky ligands such as tricyclohexyl-
phosphine were used,14 otherwise penta- and hexanuclear
compounds were obtained.
In the last few years a great deal of interest has focussed on
species where (phosphine)gold fragments coordinate around a
central heteroatom.1 Thus interesting hypercooordinated
compounds2-6 of the type [C(AuPPh3)5]+, [C(AuPPh3)6]2+
,
[N(AuPPh3)5]2+, [P(AuPPh3)5]2+, and [P(AuPPh3)6]3+ have been
described, apart from other complexes with more conventional
stoichiometry. Their structures are fascinating from the theo-
retical point of view. Usually, the chemistry of the first row
elements of the p-block is known to follow classical rules of
bonding, and only in cases of extreme electron-deficiency had
the traditional electron count to be reconsidered to account for
special types of molecular or solid state structures. Many of
the heteroatom-centered complexes presented here are electron
deficient and the gold-gold interactions provide a significant
We are interested in such complexes where sulfur is the
central heteroatom. The chemistry of this type of gold(I)
complexes was originally limited15-19 to the triply bridging
species [S(AuPR3)3]+, but we have since reported the crystal
(7) Pyykko¨, P.; Desclaux, J. P. Acc. Chem. Res. 1979, 12, 276.
(8) Pitzer, K. S. Acc.Chem. Res. 1979, 12, 271.
(9) Pyykko¨, P. Chem. ReV. 1988, 88, 563.
(10) Dziwok, K.; Lachmann, J.; Wilkinson, D. L.; Mu¨ller, G.; Schmid-
baur, H. Chem. Ber. 1990, 123, 423.
(11) Schmidbaur, H.; Dziwok, K.; Grohmann, A.; Mu¨ller, G. Chem. Ber.
1989, 122, 893.
(12) Schmidbaur, H.; Graf, W.; Mu¨ller, G. Angew. Chem., Int. Ed. Engl.
1988, 27, 417.
(13) Narayanaswamy, R.; Young, M. A.; Parkhurst, E.; Ouellette, M.;
Kerr, M. E.; Ho, D. M.; Elder, R. C.; Bruce, A. E.; Bruce, M. R. M. Inorg.
Chem. 1993, 32, 2506.
(14) Schmidbaur, H.; Steigelmann, O. Z. Naturforsch. 1992, 47, 1721.
(15) Kowala, C.; Swan, J. M. Aust. J. Chem. 1966, 19, 547.
(16) Abel, E. W.; Jenkins, C. R. J. Organomet. Chem. 1968, 14, 285.
(17) Jones, P. G.; Sheldrick, G. M.; Ha¨dicke, E. Acta Crystallogr., Sect.
B 1980, 36, 2777.
† Instituto de Ciencia de Materiales de Arago´n.
‡ Institut fu¨r Anorganische und Analytische Chemie der Technischen
Universita¨t.
X Abstract published in AdVance ACS Abstracts, May 1, 1996.
(1) Schmidbaur, H. Pure Appl. Chem. 1993, 65, 691 and references cited
therein.
(2) Scherbaum, F.; Grohmann, A.; Mu¨ller, G.; Schmidbaur, H. Angew.
Chem., Int. Ed. Engl. 1989, 28, 463.
(3) Scherbaum, F.; Grohmann, A.; Huber, B.; Kru¨ger, C.; Schmidbaur,
H. Angew. Chem., Int. Ed. Engl. 1988, 27, 1544.
(4) Grohmann, A.; Riede, J.; Schmidbaur, H. Nature 1990, 345, 140.
(5) Schmidbaur, H.; Weidenhiller, G.; Steigelmann, O. Angew. Chem.,
Int. Ed. Engl. 1991, 30, 433.
(6) Zeller, E.; Schmidbaur, H. J. Chem. Soc., Chem. Commun. 1993,
69.
S0002-7863(95)01767-7 CCC: $12.00 © 1996 American Chemical Society

4840 J. Am. Chem. Soc., Vol. 118, No. 20, 1996
Canales et al.
Scheme 1
Table 1. Analitical Data and Other Properties for the Complexes 1-9
Anal. (%)a
H
b
complex
[S(Au2dppf)] (1)
yield (%)
90
C
S
ΛM
ν(Au-S)c
41.81
(41.65)
36.06
(35.74)
40.52
(40.99)
40.15
(40.58)
37.92
(38.22)
35.73
(36.18)
38.84
(38.95)
40.06
(40.08)
36.79
3.05
(2.88)
1.97
(2.10)
2.63
(2.92)
2.53
(2.82)
2.49
(2.80)
2.33
(2.50)
2.61
(2.64)
2.61
(2.79)
2.71
3.09
(3.27)
1.92
(2.38)
1.86
(2.06)
1.74
(2.08)
1.91
(2.17)
2.60
(2.84)
3.61
(4.00)
1.31
(1.53)
1.80
d
377 (m)
301 (m)
[S{Au(C6F5)}(Au2dppf)] (2)
89
97
91
91
97
95
90
85
12.2
137.6
137.7
142.9
d
[S{Au(CH2PPh3)}(Au2dppf)](ClO4) (3)
[S(AuPPh3)(Au2dppf)](ClO4) (4)
[S(AuPPh2Me)(Au2dppf)](ClO4) (5)
[Au{S(Au2dppf)}2](ClO4) (6)
356 (br,w)
335 (br,w)
282 (w)
[(µ-Au2dppf){S(Au2dppf)}2](OTf)2 (7)
[S(AuPPh3)2(Au2dppf)](ClO4)2 (8)
[S(AuPPh2Me)2(Au2dppf)](ClO4)2 (9)
224.5
254.1
255.6
(36.51)
(2.76)
(1.62)
a Calculated values are given in parentheses b In acetone, values in Ω-1 cm2 mol-1 c Values in cm-1 d Not enough soluble.
. .
structure20 of the electron-deficient derivative [S(AuPPh3)4]2+
.
the square pyramidal form found in [S(AuPPh3)4]2+; it can be
regarded as distorted trigonal bipyramidal at sulfur, with one
position occupied by the lone pair of electrons.
Here we report a similar type of complex, with the difference
that an [Au2(µ-PP)]2+ fragment around the sulfur atom serves
as a building block. It can react with several gold(I) derivatives
affording tri- and tetranuclear complexes, some of them with
unprecedented structural frameworks. Thus we describe the
structure of [S(AuPPh2Me)2(Au2dppf)]2+ (dppf ) 1,1′-bis-
(diphenylphosphino)ferrocene), which does not correspond to
Results and Discussion
The reaction of [Au2Cl2(µ-dppf)] (dppf ) 1,1′-bis(diphe-
nylphosphino)ferrocene) with 1 equiv of Li2S in ethanol affords
the dinuclear complex [S(Au2dppf)] (1), in which the two gold
atoms are bridged by the 1,1′-bis(diphenylphosphino)ferrocene
ligand and the sulfur atom (see Scheme 1). Complex 1 is an
orange air- and moisture-stable solid.
(18) Schmidbaur, H.; Kolb, A.; Zeller, E.; Schier, A.; Beruda, H. Z.
Anorg. Allg. Chem. 1993, 619, 1575.
(19) Angermaier, K.; Schmidbaur, H. Chem. Ber. 1994, 127, 2387.
(20) Canales, F.; Gimeno, M. C.; Jones, P. G.; Laguna, A. Angew. Chem.,
Int. Ed. Engl. 1994, 33, 769.

Aurophilicity at Sulfur Centers
J. Am. Chem. Soc., Vol. 118, No. 20, 1996 4841
Table 2. NMR Data for Complexes 1-9
NMRa
31P
1H
Hâ Cp
4.6 (s, br)
complex
dppf
L
HR Cp
3.9 (s, br)
CH3
CH2
2JHP
[S(Au2dppf)] (1)
[S{Au(C6F5)}(Au2dppf)] (2)
30.0 (s)
25.3 (s)
26.1 (s)
27.4 (s)
27.0 (s)
25.5 (br)
28.5 (s)
25.1 (s)
23.0 (s)
26.4 (s)
25.9 (s)
3.9 (s, br)
4.0 (s, br)
4.10 (s, br)
4.10 (s, br)
(4.5-3.8) (m, br)
(4.7, 4.5, 4.4, 4.1, 4.0, 3.2, 3.0) (m)
4.6 (s, br)
4.5 (s, br)
4.46 (s, br)
4.50 (s, br)
[S{Au(CH2PPh3)}(Au2dppf)](ClO4) (3)
[S(AuPPh3)(Au2dppf)](ClO4) (4)
[S(AuPPh2Me)(Au2dppf)](ClO4) (5)
[Au{S(Au2dppf)}2](ClO4) (6)
[(µ-Au2dppf){S(Au2dppf)}2](OTf)2 (7)
30.8 (s)
34.1 (s)
18.9 (s)
2.14 (d)
12.69
9.76
2.12 (d)
[S(AuPPh3)2(Au2dppf)](ClO4)2 (8)
[S(AuPPh2Me)2(Au2dppf)](ClO4)2 (9)
32.9 (s)
18.6 (s, br)
4.18 (s)
4.14 (s, br)
4.59 (s)
4.59 (s, br)
2.07 (d)
10.74
a Recorded in CDCl3, coupling constants in hertz; s ) singlet, d ) doublet, m ) multiplet, br ) broad.
the gold-gold interaction. The Au-S distance is 2.300(2) Å
and is longer than in the latter complex, 2.157(5) and 2.161(5)
Å; however, it falls in the same range as found in [S(AuP-
Ph3)3]+ 17,18 or [Au{S(AuPPh3)2}2]+;22 where the sulfur atom is
surrounded by three gold atoms. Also, the Au-P bond length
of 2.247(2) Å is longer than in [S(AuPPh3)2], although similar
to the Au-P distances in bis(diphenylphosphino)ferrocene-
gold complexes.23 The coordination at the gold centers is
slightly distorted from linear, with a P-Au-S angle of
173.78(6)°. There is a contact of 3.535 Å between a dichlo-
romethane chlorine and the gold atom. This is the first example
of a digold-diphosphine unit coordinated to a sulfur center,
and shows the great flexibility of the dppf ligand to adapt to
different geometries at the metal center.
Figure 1. The structure of complex 1 in the crystal. Displacement
parameter ellipsoids represent 50% probability surfaces. The H atoms
are omitted for clarity. The crystallographic 2-fold axis passes through
the atoms S and Fe.
Complex 1 can serve as a building block for preparing
polynuclear sulfur-centered complexes. We have studied the
reactions of 1 with several gold(I) derivatives. Thus the
treatment of 1 with 1 equiv of [Au(C6F5)tht] affords the neutral
derivative [S(AuC6F5)(Au2dppf)] (2), and with [Au(CH2PPh3)-
tht]ClO4 or [Au(OClO3)PR3] the cationic complexes [S(AuL)(Au2-
dppf)]ClO4 [L ) CH2PPh3 (3), PPh3 (4), PPh2Me (5)] are
obtained. They behave as nonconducting (2) or as 1:1
electrolytes (3-5) in an acetone solution. In the IR spectra the
most significant absorptions are weak bands arising from the
ν(Au-S) vibrations, in complex 2 bands of the pentafluorophe-
nyl group bonded to gold(I) at 1499 s and 953 m cm-1, and in
compound 3 the ν(Au-C) band of the ylide ligand at 575 m
Table 3. Selected Bond Lengths (Å) and Angles (deg) for 1a
Au-P
2.247(2)
2.8820(10)
2.035(7)
2.041(7)
Au-S
2.300(2)
2.025(7)
2.039(7)
2.056(7)
Au-Au#1a
Fe-C(5)
Fe-C(2)
Fe-C(4)
Fe-C(1)
Fe-C(3)
P-Au-S
173.78(6)
51.21(4)
113.9(2)
77.57(9)
P-Au-Au#1a
C(1)-P-Au
C(11)-P-Au
122.66(5)
110.4(2)
116.0(2)
S-Au-Au#1a
C(21)-P-Au
Au-S-Au#1a
a Symmetry transformations used to generate equivalent atomss#1:
1
3
-x + /2, y, -z + /2.
cm-1
.
In the IR spectrum the absorptions arising from ν(Au-Cl)
in the starting material are replaced by two bands from ν(Au-
S). The NMR data are consistent with the formulation and only
one signal is observed in the 31P{1H} NMR spectrum, because
The 1H NMR spectra show in all the cases two broad singlets
for the cyclopentadienyl protons; the resonances of the meth-
ylene and methyl groups of the ylide and the methyl of the
phosphine ligand appear as doublets. The 31P{1H} NMR spectra
show two signals because of the two different phosphorus
environments, with the exception of complex 2 where only one
resonance appears. An upfield displacement (∆ ≈ 3 ppm) is
observed compared to the starting material for the signal of the
diphosphine phosphorus. This upfield shift has also been
reported in the conversion of (phosphine)gold(I) compounds to
homoleptic hypercoordinated species such as [C(AuL)5]+ and
1
of the equivalence of both phosphorus atoms; in the H NMR
spectrum, apart from the multiplets for the phenyl protons, two
broad singlets appear for the R and â protons of the cyclopen-
tadienyl rings (Table 2).
The FAB+ mass spectrum shows the molecular peak plus a
proton at m/z ) 981 (MH+, 42%). The most intense peak
corresponds to the species Au(dppf)+ at m/z 751 and higher
peaks appear at m/z 1177 [(M + Au)+, 8%] and 2158 [(2M +
Au)+, 57%].
[C(AuL)6]2+
.
The FAB+ mass spectra of complexes 3-5 show the
molecular cation peak as the most intense at m/z 1453 (3), 1439
(4), and 1377 (5). Other fragments are [AuL]+, and [AuL2]+,
The crystal structure of complex 1 has been confirmed by
X-ray diffraction and the molecule is shown in Figure 1.
Selected bond lengths and angles are collected in Table 3. The
molecule has crystallographic 2-fold symmetry. The two gold
atoms are bridged by the sulfur atom and there is a short
intramolecular Au‚‚‚Aui contact of 2.8820(10) Å, much shorter
than that found in the complex [S(AuPPh3)2] [3.018(1) Å].21
The Au-S-Aui (i ) -x + 1/2, y, -z + 3/2) angle is very narrow
[77.57(9)°] compared to [S(AuPPh3)2] [88.77(1)°], thus favoring
(21) Lensch, C.; Jones, P. G.; Sheldrick, G. M. Z. Naturforsch. 1982,
37b, 944.
(22) Jones, P. G.; Lensch, C.; Sheldrick, G. M. Z. Naturforsch. 1982,
37b, 141.
(23) Hill, D. T.; Girard, G. R.; McCabe, F. L.; Johnson, R. K.; Stupik,
P. D.; Zhang, J. H.; Reifj, W. M.; Eggleston, D. S. Inorg. Chem. 1989, 28,
3529.

4842 J. Am. Chem. Soc., Vol. 118, No. 20, 1996
Canales et al.
Table 4. Selected Bond Lengths (Å) and Angles (deg) for 7
Au(1)-P(1)
Au(1)-Au(4)
Au(1)-Au(3)
Au(2)-S(1)
Au(3)-P(3)
Au(3)-Au(6)
Au(4)-S(2)
Au(4)-Au(6)
Au(5)-S(2)
Au(6)-P(6)
2.250(10)
2.905(2)
3.247(2)
2.328(8)
2.262(10)
3.283(2)
2.368(9)
3.272(2)
2.324(9)
2.270(10)
Au(1)-S(1)
Au(1)-Au(2)
Au(2)-P(2)
Au(2)-Au(3)
Au(3)-S(1)
Au(4)-P(4)
Au(4)-Au(5)
Au(5)-P(5)
Au(5)-Au(6)
Au(6)-S(2)
2.337(9)
2.922(2)
2.266(9)
3.246(2)
2.338(9)
2.282(10)
2.920(2)
2.269(9)
3.247(2)
2.328(9)
P(1)-Au(1)-S(1)
S(1)-Au(1)-Au(4)
S(1)-Au(1)-Au(2)
P(1)-Au(1)-Au(3)
173.1(3) P(1)-Au(1)-Au(4)
84.5(2) P(1)-Au(1)-Au(2)
101.6(3)
122.3(2)
51.1(2) Au(4)-Au(1)-Au(2) 134.83(6)
135.4(3) S(1)-Au(1)-Au(3)
46.0(2)
Au(4)-Au(1)-Au(3) 93.59(5) Au(2)-Au(1)-Au(3) 63.23(5)
P(2)-Au(2)-S(1)
S(1)-Au(2)-Au(1)
S(1)-Au(2)-Au(3)
P(3)-Au(3)-S(1)
S(1)-Au(3)-Au(2)
S(1)-Au(3)-Au(1)
P(3)-Au(3)-Au(6)
174.2(3) P(2)-Au(2)-Au(1)
51.4(2) P(2)-Au(2)-Au(3)
122.8(3)
133.8(3)
46.0(2) Au(1)-Au(2)-Au(3) 63.27(5)
Figure 2. The cation of complex 7 in the crystal. Displacement
parameter ellipsoids represent 50% probability surfaces. Carbon atoms
are spheres of arbitrary radius. H atoms are omitted for clarity.
169.6(3) P(3)-Au(3)-Au(2)
45.8(2) P(3)-Au(3)-Au(1)
125.4(2)
137.1(3)
46.0(2) Au(2)-Au(3)-Au(1) 53.49(4)
101.0(2) S(1)-Au(3)-Au(6)
87.8(2)
and at m/z 2157 the peak assigned to the cation [Au{S(Au2-
dppf)}2]+ appears.
Although these complexes have not been characterized by
X-ray diffraction, we assume they have a similar structural
framework to that found in the complexes [S(AuPR3)3]+, with
short contacts among the gold(I) centers.
Au(2)-Au(3)-Au(6) 131.38(6) Au(1)-Au(3)-Au(6) 85.69(5)
P(4)-Au(4)-S(2)
S(2)-Au(4)-Au(1)
S(2)-Au(4)-Au(5)
P(4)-Au(4)-Au(6)
171.6(3) P(4)-Au(4)-Au(1)
85.8(2) P(4)-Au(4)-Au(5)
102.5(2)
120.8(2)
50.8(2) Au(1)-Au(4)-Au(5) 136.38(7)
133.3(3) S(2)-Au(4)-Au(6)
45.3(2)
Au(1)-Au(4)-Au(6) 91.74(6) Au(5)-Au(4)-Au(6) 62.96(5)
P(5)-Au(5)-S(2)
S(2)-Au(5)-Au(4)
S(2)-Au(5)-Au(6)
P(6)-Au(6)-S(2)
S(2)-Au(6)-Au(5)
S(2)-Au(6)-Au(4)
P(6)-Au(6)-Au(3)
173.7(3) P(5)-Au(5)-Au(4)
52.2(2) P(5)-Au(5)-Au(6)
122.8(2)
137.8(3)
As we have remarked before, all the positive-ion FAB
experiments for these complexes reveal with high intensity a
peak that corresponds to the species [Au{S(Au2dppf)}2]+. This
indicates the stability of this derivative, and for this reason we
have synthesized it by treatment of 1 with [Au(tht)2]ClO4 in a
2:1 molar ratio. The reaction affords the complex [Au{S(Au2-
dppf)}2]ClO4 (6) as an orange solid, scarcely soluble in common
45.8(2) Au(4)-Au(5)-Au(6) 63.82(5)
167.6(3) P(6)-Au(6)-Au(5)
45.7(2) P(6)-Au(6)-Au(4)
125.5(2)
139.9(3)
46.3(2) Au(5)-Au(6)-Au(4) 53.22(4)
99.8(2) S(2)-Au(6)-Au(3)
90.9(2)
Au(5)-Au(6)-Au(3) 133.50(6) Au(4)-Au(6)-Au(3) 86.49(5)
Au(2)-S(1)-Au(3)
Au(3)-S(1)-Au(1)
Au(5)-S(2)-Au(4)
C(11)-P(1)-Au(1)
C(21)-P(1)-Au(1)
C(31)-P(2)-Au(2)
C(61)-P(3)-Au(3)
C(51)-P(3)-Au(3)
C(81)-P(4)-Au(4)
88.2(3) Au(2)-S(1)-Au(1)
88.0(3) Au(5)-S(2)-Au(6)
77.0(3) Au(6)-S(2)-Au(4)
77.6(2)
88.5(3)
88.3(3)
1
solvents. The H NMR spectrum shows broad bands for the
cyclopentadienyl protons, and also a broad singlet is observed
for the phosphorus atoms of the diphosphine in the 31P{1H}
spectrum. We believe that the solid state structure corresponds
to that found in [Au{S(AuPPh3)2][SnMe3Cl2],22 with a gold(I)
atom bonded to two [S(AuPPh3)2] units in such a manner that
the gold and sulfur atoms adopt a boat configuration.
We have also synthesized a hexanuclear derivative which
contains two SAu3 cores connected through a bridging dppf
ligand. The reaction of complex 1 with a freshly prepared
solution of [Au2(OTf)2(µ-dppf)] in dichloromethane (molar ratio
2:1) leads to [(µ-Au2dppf){S(Au2dppf)}2](OTf)2 (7). Compound
7 is an orange solid stable to moisture and air and behaves as
a 2:1 electrolyte in an acetone solution.
The room temperature NMR spectra show broad bands that
sharpen when the experiments are carried out at -55 °C. The
31P{1H} NMR spectrum presents three singlets assigned to the
three different phosphorus environments (in each SAu3P3 unit).
The 1H NMR spectrum is rather complex in the cyclopentadienyl
proton region, and shows five multiplets with a 1:6:3:1:1 ratio
that makes difficult the assignment to particular protons.
The structure of complex 7 has been confirmed by an X-ray
diffraction study and the cation is shown in Figure 2. Selected
bond lengths and angles are given in Table 4. The complex
crystallizes with an idealized composition that includes eight
molecules of chloroform. The structure consists of an S2Au6
core that shows short intramolecular Au-Au interactions. These
distances vary from 2.905(2) to 3.272(2) Å. The shortest
contacts, Au(1)-Au(4) ) 2.905(2) Å, Au(1)-Au(2) ) 2.922(2),
and Au(4)-Au(5) ) 2.920(2) Å, involve gold atoms of the Au2-
dppf2+ fragment that are bonded to the same sulfur atom. The
shortest contact between gold and iron is 4.284 Å. The
116.1(11) C(131)-P(1)-Au(1) 107.9(9)
116.5(9) C(136)-P(2)-Au(2) 110.9(9)
114.2(9) C(41)-P(2)-Au(2)
113.7(9)
116.5(11) C(151)-P(3)-Au(3) 113.1(10)
107.3(9) C(71)-P(4)-Au(4) 112.5(10)
115.4(9) C(141)-P(4)-Au(4) 110.1(9)
111.8(9)
C(146)-P(5)-Au(5) 112.1(9) C(91)-P(5)-Au(5)
C(101)-P(5)-Au(5) 116.7(9) C(156)-P(6)-Au(6) 112.2(11)
C(111)-P(6)-Au(6) 118.1(9) C(121)-P(6)-Au(6) 107.3(9)
sulfur atoms lie 1.465 and 1.466 Å out of the planes formed by
their three gold neighbors.
The Au-S-Au angles are very different. There are two very
narrow angles, Au(2)-S(1)-Au(1) ) 77.6(2)° and Au(5)-
S(2)-Au(4) ) 77.0(3)°, involving the gold atoms linked to the
same sulfur atom, and these angles are very similar to those in
complex 1; the other Au-S-Au angles have values of ca. 88°
and are similar to those found in [S(AuP)3]+ complexes with
bulky tertiary phosphines. The geometry around the gold atoms
is slightly distorted from linear, with the major deviations for
Au(3) and Au(6) being 169.6(3) and 167.6(3)°, respectively.
Finally, we have studied reactions where further auration of
the sulfur atom takes place. Thus, the treatment of 1 with 2
equiv of [Au(OClO3)PPh3] or [Au(OClO3)PPh2Me] leads to the
quadruply bridged species [S(AuPR3)2(Au2dppf)2](ClO4)2 [PR3
) PPh3 (8), PPh2Me (9)]. These complexes have similar IR
spectra to compounds 4 and 5, with the exception of the ν-
(Au-S) bands, which are too weak to be observed. We have
previously observed this pattern of medium, weak, or unob-
served ν(Au-S) bands when changing from doubly to triply
and to quadruply bridging sulfido ligands. The conductivity

Aurophilicity at Sulfur Centers
J. Am. Chem. Soc., Vol. 118, No. 20, 1996 4843
Figure 4. Perspective view of the gold and sulfur atoms in complex
9 showing the coordination geometry of the sulfur atom.
Figure 3. The cation of complex 9 in the crystal. Displacement
parameter ellipsoids represent 50% probability surfaces. Carbon atoms
are spheres of arbitrary radius. H atoms are omitted for clarity.
Table 5. Selected Bond Lengths (Å) and Angles (deg) for
Complex 9
Au(1)-P(1)
Au(1)-Au(2)
Au(2)-P(2)
Au(3)-Au(3)
Au(3)-P(3)
Au(4)-P(4)
2.265(6)
2.9047(13)
2.263(5)
2.9210(12)
2.270(5)
2.256(6)
Au(1)-S
2.404(6)
2.9520(12)
2.416(5)
2.9775(14)
2.367(5)
2.309(5)
Au(1)-Au(3)#1a
Au(2)-S
Au(2)-Au(4)
Au(3)-S
Au(4)-S
P(1)-Au(1)-S
172.9(2)
P(1)-Au(1)-Au(2)
120.9(2)
S-Au(1)-Au(2)
S-Au(1)-Au(3)#1a
P(2)-Au(2)-S
53.14(12) P(1)-Au(1)-Au(3)#1a 106.0(2)
78.46(13) Au(2)-Au(1)-Au(3)#1a 129.49(4)
175.7(2)
52.74(13) P(2)-Au(2)-Au(3)
51.60(12) Au(1)-Au(2)-Au(3)
P(2)-Au(2)-Au(1)
123.0(2)
130.69(14)
83.06(3)
49.35(12)
80.88(3)
117.72(14)
S-Au(2)-Au(1)
S-Au(2)-Au(3)
Figure 5. Association of two cations of 9 in the crystal. Phenyl rings
and H atoms are omitted for clarity.
P(2)-Au(2)-Au(4) 132.8(2)
S-Au(2)-Au(4)
Au(1)-Au(2)-Au(4) 90.27(4) Au(3)-Au(2)-Au(4)
atom and the other by the gold atom Au(2) (Figure 4). The
complex is then electron-deficient, since only three bonding
molecular orbitals are occupied, as has been proposed for the
P(3)-Au(3)-S
170.8(2)
P(3)-Au(3)-Au(2)
S-Au(3)-Au(2)
S-Au(3)-Au(1)#1a
P(4)-Au(4)-S
53.13(13) P(3)-Au(3)-Au(1)#1a 101.58(13)
87.57(13) Au(2)-Au(3)-Au(1)#1a 139.70(4)
171.3(2)
P(4)-Au(4)-Au(2)
134.9(2)
109.8(2)
108.1(2)
75.27(14)
110.1(6)
116.4(7)
109.7(6)
111.8(6)
115.9(8)
111.5(9)
complexes [As(AuPPh3)4]+ 24 and [S(AuPPh3)4]2+ 20
.
S-Au(4)-Au(2)
Au(4)-S-Au(1)
Au(4)-S-Au(2)
Au(1)-S-Au(2)
C(21)-P(1)-Au(1)
C(41)-P(2)-Au(2)
C(31)-P(2)-Au(2)
C(81)-P(3)-Au(3)
C(61)-P(4)-Au(4)
C(51)-P(4)-Au(4)
52.56(13) Au(4)-S-Au(3)
124.4(2)
78.1(2)
There are intramolecular gold-gold contacts, the shortest
being between the equatorial gold atoms and the gold atom
perpendicular to them, with values of 2.9047(12), 2.9210(12),
and 2.9775(14) Å. These distances are of the same order as
those found in [S(AuPPh3)4]2+ [2.883(2)-2.938(2) Å]. In the
crystal the cations of 9 are paired across symmetry centers
(Figure 5); the intermolecular interactions, Au(1)-Au(3i) )
2.9520(12) Å (i ) 1 - x, 1 - y, 1 - z), are much shorter than
in [S(AuPPh3)4]2+ (3.202 Å).
Au(3)-S-Au(1)
Au(3)-S-Au(2)
74.1(2)
C(1)-P(1)-Au(1)
C(11)-P(1)-Au(1)
C(6)-P(2)-Au(2)
C(71)-P(3)-Au(3)
C(101)-P(3)-Au(3)
C(100)-P(4)-Au(4)
112.7(6)
111.9(6)
115.4(7)
107.6(7)
110.8(7)
114.3(6)
a Symmetry transformations used to generate equivalent atomss#1:
-x + 1, -y + 1, -z + 1.
The Au-S-Au angles for the three gold atoms located in
the equatorial plane are 124.4(2), 109.8(2) and 108.1(2)°; these
values differ from the ideal 120°, which may be a consequence
of the interaction with the other gold atom. These angles are
big enough to prevent further contacts between the equatorial
gold atoms, Au(1)-Au(3) ) 3.863 Å, Au(1)-Au(4) ) 4.170
Å, and Au(3)-Au(4) ) 3.826 Å. The Au-S-Au angles
between the gold atom in the apical position and the gold atoms
in the plane are very narrow, 74.1(2)-78.1(2)°, because of the
gold-gold contacts. These values are similar to those found
of complexes 4 and 5 in acetone solutions corresponds to that
of 2:1 electrolytes.
1
The H NMR spectra show in both cases, apart from the
phenyl protons, two multiplets associated with the R and â
protons of the cyclopentadienyl groups, and in the spectrum of
complex 9 a doublet for the methyl group appears. The 31P
NMR spectra show two singlets of similar intensity for the two
types of phosphorus enviroments. An upfield displacement of
ca. 1 ppm is observed for the two resonances compared to those
in complexes 4 and 5.
The structure of complex 9 has been confirmed by X-ray
diffraction anaysis (Figure 3). Selected bond lengths and angles
are given in Table 5. The complex crystallizes with three
molecules of dichloromethane per asymmetric unit. The
structure reveals a new type of structural framework, because
it can be regarded as a trigonal bipyramid with one of the apical
positions occupied by the lone pair of electrons at the sulfur
in complex 1 and in [S(AuPPh3)4]2+
.
The sulfur atom lies 0.57 Å out of the plane formed by Au(1),
Au(3), and Au(4), whereas Au(2) lies 1.84 Å below that plane.
The Au-S bond lengths are different, the longest corresponds
to the gold atom in the apical position, Au(2)-S ) 2.416(5)
Å, and the shortest, Au(3)-S
)
2.367(5)
Å
and
(24) Zeller, E.; Beruda, H.; Kolb, A.; Bissinger, P.; Riede, J.; Schmidbaur,
H. Nature 1991, 352, 141.

4844 J. Am. Chem. Soc., Vol. 118, No. 20, 1996
Canales et al.
Table 6. Details of Data Collection and Structure Refinement for the Complexes 1, 7, and 9
compound
chemical formula
crystal habit
crystal size/mm
space group
a/Å
1.2CHCl3
7.8CHCl3
C112H92Au6Cl24F6Fe3O6P6S4
yellow plate
0.45 × 0.25 × 0.10
P1h
15.177(3)
18.408(4)
27.894(8)
88.83(2)
84.46(2)
67.78(2)
7180(3)
2
1.925
4162.08
3960
-100
43
7.03
0.18-0.60
15950
9.3CH2Cl2
C36H32Au2Cl6FeP2S
orange prism
0.65 × 0.35 × 0.25
P2/n
12.571(4)
10.579(4)
C63H60Au4Cl8FeO8P4S
orange plate
0.70 × 0.45 × 0.03
P1h
13.727(2)
15.952(3)
17.763(2)
71.738(12)
73.264(14)
75.96(2)
3487.5(9)
2
2.122
2228.37
2112
-100
50
9.07
0.19-0.72
11617
11512
0.106
0.077
0.194
b/Å
c/Å
15.212(4)
R/deg
â/deg
107.84(3)
γ/deg
U/Å3
1925.7(11)
2
2.106
1221.10
1160
-130
50
Z
Dc/Mg m-3
M
F(000)
T/°C
2θmax/deg
µ(Mo KR)/mm-1
transmission
no. of reflcns measd
no. of unique reflcns
Rint
8.55
0.24-0.55
3617
3415
0.042
0.040
0.114
218
158
1.072
2.32
15877
0.180
0.078
0.218
556
403
0.865
1.88
Ra (F, F > 4σ(F))
wRb (F2, all reflcns)
no. of parameters
no. of restraints
Sc
797
1096
1.086
2.93
max ∆F/e Å-3
2
2
a R(F) ) ∑||Fo| - |Fc||/∑|Fo|. b wR(F2) ) [∑{w(Fo2 - Fc2)2}/∑{w(Fo )2}]0.5; w-1 ) σ2(Fo ) + (aP)2 + bP, where P ) [Fo2 + 2Fc2]/3 and a and
b are constants adjusted by the program. c S ) [∑{w(Fo - Fc2)2}/(n - p)]0.5, where n is the number of data and p the number of parameters.
2
pared by published procedures. [Au(OClO3)PR3] was prepared from
Au(4)-S ) 2.309(5) belong to the gold atoms bonded to PPh2-
[AuCl(PR3)]29 and AgClO4.
Me; it is well-known that axial bonds tend to be longer than
Synthesis of [S(Au2dppf)] (1). To a solution of Li2S (0.046 g, 1
equatorial in trigonal bipyramidal systems. The Au-P distances
mmol) in ethanol (50 mL) was added [Au2Cl2(µ-dppf)] (1.019 g, 1
fall in the range 2.256(6)-2.265(6) Å and are longer than those
mmol). The orange suspension was stirred for 2 h, and then the solid
found in complex 1 or [S(AuPPh2Me)3]+, but slightly shorter
was filtered off to yield complex 1.
than those in the complex [S(AuPPh3)4]2+
.
Synthesis of [S(AuC6F5)(Au2dppf)] (2). To a solution of [S(Au2-
dppf)] (0.098 g, 0.1 mmol) in dichloromethane (20 mL) was added
[Au(C6F5)tht] (0.045 g, 0.1 mmol) and then the mixture was stirred
for 30 min. The solution was concentrated to ca. 5 mL and addition
of hexane (15 mL) gave a yellow solution of complex 2.
Synthesis of [S(AuL)(Au2dppf)]ClO4 (L ) CH2PPh3 (3), PPh3
(4), PPh2Me (5)). To a solution of [S(Au2dppf)] (0.098 g, 0.1 mmol)
in 20 mL of dichloromethane was added [Au(CH2PPh3)tht]ClO4 (0.066
g, 0.1 mmol) or [Au(OClO3)PPh3] (0.1 mmol) or [Au(OClO3)PPh2-
Me] (0.1 mmol) and then the mixture was stirred for 30 min. Solvent
was evaporated to ca. 5 mL and addition of diethyl ether (15 mL) gave
complexes 3-5.
Studies carried out with the sulfur-centered cations [S(Au-
PR3)3]+ have shown the influence of the size and electronic/
inductive effects of the phosphine ligand;19 thus with PMe3 the
[S(AuPMe3)3]+ pyramids are grouped in pairs through Au-Au
contacts, which are further linked by other Au-Au interactions
to give strings. The cations [S(AuPPh2Me)3]+ are paired across
symmetry centers, while [S(AuPiPr)3]+ are monomers. We have
shown that the ligand attached to gold may also influence the
structure of the monomers [S(AuL)4]2+
.
Experimental Section
Synthesis of [(µ-Au){S(Au2dppf)}2]ClO4 (6). To a dichlo-
romethane solution (20 mL) of [S(Au2dppf)] (0.196 g, 0.2 mmol) was
added [Au(tht)2]ClO4 (0.047 g, 0.1 mmol). The solution was stirred
for 5 min and the solvent was evaporated to ca. 5 mL. Addition of
diethyl ether (15 mL) gave complex 6.
Synthesis of [(µ-Au2dppf){S(Au2dppf)}2](OTf)2 (7). To a dichlo-
romethane (20 mL) solution of [Au2Cl2(µ-dppf)] (0.102 g, 0,1 mmol)
was added AgOTf (0.051 g, 0.2 mmol) and then the mixture was stirred
for 2 h. The precipitated AgCl was filtered off and to the resulting
solution containing [Au2(OTf)2(µ-dppf)] was added [S(Au2dppf)] (0.196
g, 0.2 mmol), and then the mixture was stirred for 5 min. Evaporation
of the solvent to ca. 5 mL and addition of hexane (10 mL) gave a
yellow solid of complex 7.
Synthesis of [S(AuPR3)2(Au2dppf)](ClO4)2 (L ) PPh3 (8), PPh2Me
(9)). To a solution of [S(Au2dppf)] (0.098 g, 0.1 mmol) in 20 mL of
dichloromethane was added [Au(OClO3)PR3] (0.2 mmol) and the
mixture was stirred for 5 min. Evaporation of solvent to ca. 5 mL and
addition of n-hexane (15 mL) gave complexes 8 or 9.
X-ray Structure Determinations. Crystals were mounted in inert
oil on glass fibres. Data were colleted using monochromated Mo KR
General Procedures. Infrared spectra were recorded in the range
4000-200 cm-1 on a Perkin-Elmer 883 spectrophotometer using Nujol
mulls between polyethylene sheets. Conductivities were measured in
ca. 5 × 10-4 mol dm-3 solutions with a Philips 9509 conductimeter
and ΛM is given in Ω-1 cm2 mol-1. C, H, S analyses were carried out
with a Perkin-Elmer 240C microanalyzer. NMR spectra were recorded
on Varian 300 Unity and Bruker 300 spectrometers in CDCl3. Chemical
shifts are relative to SiMe4 (1H, external), 85% H3PO4 (31P, external),
and CFCl3 (19F, external). Mass spectra were recorded on a VG
Autospec using FAB techniques and nitrobenzyl alcohol as the matrix.
The yields, analysis, conductivities, and infrared ν(Au-S) band are
collected in Table 1. The starting materials [Au2Cl2(µ-dppf)],23,25 [Au-
28
(C6F5)tht],26 [Au(CH2PPh3)tht]ClO4,27 and [Au(tht)2]ClO4 were pre-
(25) Gimeno, M. C.; Laguna, A.; Sarroca, C.; Jones, P. G. Inorg. Chem.
1993, 32, 5926.
(26) Uso´n, R.; Laguna, A. Organomet. Synth. 1989, 3, 322.
(27) Aguirre, C. J.; Gimeno, M. C.; Laguna, A.; Laguna, M.; Lo´pez de
Luzuriaga, J. M.; Puente, F. Inorg. Chim. Acta 1993, 208, 31.
(28) Uso´n, R.; Laguna, A.; Laguna, M.; Jime´nez, J.; Go´mez, M. P.; Sainz,
A.; Jones, P. G. J. Chem. Soc., Dalton Trans. 1990, 3457.
(29) Uso´n, R.; Laguna, A. Inorg. Synth. 1982, 21, 71.

Aurophilicity at Sulfur Centers
J. Am. Chem. Soc., Vol. 118, No. 20, 1996 4845
radiation (λ ) 0.71073). Difractometer type: Stoe-STADI-4 (1),
Siemens P4 (7, 9), both with a Siemens low-temperature attachment.
Scan type ω/θ (1), ω (7, 9). Cell constants were refined from (ω
angles (1) or setting angles (7, 9) of ca. 60 reflections in the range 2θ
20-22°. Absorption corrections were applied on the basis of Ψ-scans
(9) or with the program SHELXA (1, 7).30
Structures were solved by direct methods (1, 9) or by the heavy-
atom method (7) and refined on F2 using the program SHELXL-93.31
All non-hydrogen atoms were refined anisotropically for complexes 1
and 9, and for compound 7 only Au, Fe, S, and P atoms, with the
others refined isotropically. Hydrogen atoms were included using a
riding model. Because of the moderate quality of the X-ray data, the
refinements were stabilized by an extensive system of restraints to light
atom temperature factors and ring symmetry. Special refinement details
were the following: Complex 7 contains eight identifiable chloroform
sites, but the high displacement parameters indicate partial occupation.
All calculations, however, assume the idealized composition. Complex
9 contains three CH2Cl2 sites; for two of these molecules, the two
chlorine atoms are disordered over three positions. However, the true
disorder is probably more complicated. The precision of the structures
of 7 and 9 necessarily suffers from the presence of solvent of
crystallization with high displacement parameters. Other data are
collected in Table 6.
Acknowledgment. We thank the Direccio´n General de
Investigacio´n Cient´ıfica y Te´cnica (No. PB94-0079) and the
Fonds der Chemischen Industrie for financial support. M.C.G.
thanks the C.O.N.A.I. for financial support for a stay in
Braunschweig.
Supporting Information Available: Tables of crystal data,
data collection, and solution and refinement parameters, hy-
drogen atomic coordinates and thermal parameters, bond
distances and angles, and anisotropic thermal parameters for 1,
7, and 9 (27 pages). This material is contained in libraries on
microfiche, immediately follows this article in the microfilm
version of the journal, can be ordered from the ACS, and can
be downloaded from the Internet; see any current masthead page
for ordering information and Internet access instructions.
(30) Sheldrick, G. M. SHELXA. A Program for Absorption Corrections
(unpublished).
(31) Sheldrick, G. M. SHELXL-93. A Program for Crystal Structure
Refinement; University of Go¨ttingen, 1993.
JA9517678