Syntheses and X-ray structures of mixed-metal gold phosphine clusters including an example having a highly asymmetric Re2Au2 skeleton

Article abstract of DOI:10.1016/S0020-1693(99)00209-1

This study describes the synthesis and single crystal X-ray characterization of three new heteronuclear gold clusters, i.e. (OC)₅Re-Re(CO)₄Au₂dppfe (1), Au₄Co₂(CO)₇(PPh₃)₃ (2), and [Au-Co(CO)₄]₂(cis-dpen) (3). They were synthesized from reaction of (AuCl)₂dppfe with NaRe(CO)₅ at room temperature, reaction of (PPh₃)AuCl with NaCo(CO)₄, and reaction of (AuCl)₂-(cis-dpen) with NaCo(CO)₄, respectively. Compound 1 crystallizes in the monoclinic space group P2₁/n with a = 15.331(7), b = 23.427(9), c = 13.621(6) A, β = 112.53(3)° and Z = 4. Compound 2 crystallizes in the triclinic space group P1 with a = 12.838(4), b = 22.406(6),_c = 11.759(4) A, a = 103.15(2), β = 117.06(2), γ = 82.78(2)°, and Z = 2. Compound 3 crystallizes in the triclinic space group P1 with a = 10.704(2), b = 17.437(3), c = 10.597(2) A, α = 96.73(2), β = 108.02(2), γ = 99.53(2)°, and Z = 2. In 1, two gold atoms in the Au₂dppfe group are bound to one Re atom in the Re₂(CO)₉ group. Thus, the total skeleton is highly asymmetric. The metal skeleton of 2 is composed from a butterfly-like Au₄ backbone with a capping Co(CO)₃ group and the terminal Co(CO)₄ group coordinated to one Au atom. Two gold atoms come close in 3 to cause intramolecular aurophilic interaction. Terminal Co(CO)₄ groups in 2 make an intermolecular pair in a head-to-tail manner in the crystal.

Full text of DOI:10.1016/S0020-1693(99)00209-1

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Inorganica Chimica Acta 294 (1999) 255–265
Syntheses and X-ray structures of mixed-metal gold phosphine
clusters including an example having a highly asymmetric Re2Au2
skeleton
Yoshitaka Katsukawa a, Satoru Onaka b,*, Yasuhiro Yamada b, Masahiro Yamashita a
a Di6ision of Informatics for Science, Graduate School of Human Informatics and PRESTO(JST), Nagoya Uni6ersity, Chikusa-ku,
Nagoya 464-8601, Japan
b Department of En6ironmental Technology, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showaku,
Nagoya 466-8555, Japan
Received 14 January 1999; accepted 2 April 1999
Abstract
This study describes the synthesis and single crystal X-ray characterization of three new heteronuclear gold clusters, i.e.
(OC)5Re–Re(CO)4Au2dppfe (1), Au4Co2(CO)7(PPh3)3 (2), and [Au–Co(CO)4]2(cis-dpen) (3). They were synthesized from reaction
of (AuCl)2dppfe with NaRe(CO)5 at room temperature, reaction of (PPh3)AuCl with NaCo(CO)4, and reaction of (AuCl)2-(cis-
dpen) with NaCo(CO)4, respectively. Compound 1 crystallizes in the monoclinic space group P21/n with a=15.331(7),
,
(
b=23.427(9), c=13.621(6) A, i=112.53(3)° and Z=4. Compound 2 crystallizes in the triclinic space group P1 with
,
a=12.838(4), b=22.406(6), c=11.759(4) A, h=103.15(2), i=117.06(2), k=82.78(2)°, and Z=2. Compound 3 crystallizes in
(
,
the triclinic space group P1 with a=10.704(2), b=17.437(3), c=10.597(2) A, h=96.73(2), i=108.02(2), k=99.53(2)°, and
Z=2. In 1, two gold atoms in the Au2dppfe group are bound to one Re atom in the Re2(CO)9 group. Thus, the total skeleton
is highly asymmetric. The metal skeleton of 2 is composed from a butterfly-like Au4 backbone with a capping Co(CO)3 group and
the terminal Co(CO)4 group coordinated to one Au atom. Two gold atoms come close in 3 to cause intramolecular aurophilic
interaction. Terminal Co(CO)4 groups in 2 make an intermolecular pair in a head-to-tail manner in the crystal. © 1999 Elsevier
Science S.A. All rights reserved.
Keywords: Gold complexes; Cluster complexes; Phosphine complexes; Crystal structures
We have been interested in the synthesis of nanometer-
sized metal clusters by assembling small metal clusters
1. Introduction
into a suitable spacer and/or a linker [31]; spacer and/or
linker molecules employed in these studies were aro-
There has been increasing interest in the preparation
of mixed-metal clusters that contain gold [1–18], not
matic molecules or phosphine derivatives. In regard to
only because of their potential as bimetallic catalysts
this idea, our attention has recently been directed to the
[19–21], but also because of their intriguing chemical
and physical properties [1,22]. Recently, gold complexes
use of gold(I) complexes as a spacer and/or a linker to
connect metal clusters in order to construct supra-
have made another development in the field of
molecules and/or multidimensional arrays of metal
supramolecular chemistry where they serve as a build-
ing block and/or a linker of component blocks to
construct supramolecules [23–29]; in these studies, the
clusters in crystals with the aid of aurophilic inter-
action using the technique of crystal engineering. In-
deed we have succeeded to yield a multidimensional
role of aurophilic interaction is quite important [30].
array in the single crystal of (PhS–Au)2(m-trans-dpen)
(dpen=1,2-bis(diphenylphosphino)ethylene) by the
* Corresponding author. Tel.: +81-52-735 5160; fax: +81-52-735
5160.
E-mail address: onklustr@ks.kyy.nitech.ac.jp (S. Onaka)
dual use of Au···Au and p–p interactions [32]. Our next
target is to incorporate metal clusters into a Au(I)–
0020-1693/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(99)00209-1

256
Y. Katsukawa et al. / Inorganica Chimica Acta 294 (1999) 255–265
phosphine complex to construct a multidimensional
array of metal clusters. Therefore, we first have at-
tempted to make a heteronuclear metal–metal bond on
a Au(I)–phosphine complex. This paper reports on the
syntheses and the crystal structure analyses of three
new mixed-metal clusters which contain Au–Re and
Au–Co bonds, respectively.
2.2. Synthesis of complexes
2.2.1. (OC)5Re–Re(CO)4Au2dppfe (1)
To a THF filtrate (15 ml) of NaRe(CO)5 prepared
from 0.10 g (0.14 mmol) of Re2(CO)10 and Na amalgam
was added a THF solution (8 ml) of (AuCl)2(m-dppfe)
(100 mg, 0.10 mmol) for 10 min and the mixture was
stirred for 28 h at room temperature. The solvent was
vacuum-stripped to leave orange–red solid. This solid
was washed with a small amount of hexane and the
residue was extracted with each 10 ml of benzene five
times. The benzene was distilled off from the combined
extracts to leave an orange–red solid. This solid was
recrystallized from CH2Cl2-hexane to give orange crys-
tals. Yield 50 mg (32%). IR (KBr): w(CO) 2086(w),
2. Experimental
2.1. General comments
All solvents were purified by standard methods. All
reactions were done under argon atmosphere. 1,1%-bis-
(diphenylphosphino)ferrocene (dppfe) and cis-1,2-bis-
(diphenylphosphino)ethylene (cis-dpen) were purchased
from Strem Chemicals, Re2(CO)10 and Co2(CO)8 were
also purchased from Strem Chemicals. (AuCl)2(m-
dppfe) [33], (AuCl)2(m-cis-dpen) [34], and (PPh3)AuCl
[35] were prepared according to the literature. IR spec-
tra were recorded on a JASCO Valor-III FT-IR spec-
trometer. Absorption spectra were measured using a
JASCO Ubest V-570DS spectrometer. 31P NMR spec-
tra were recorded on a Varian XL-200 spectrometer,
the chemical shifts of which were referenced to H3PO4.
2018(m), 1997(s), 1928(s), 1874(s) cm−1
(CDCl3, 298 K): 52.7 (s).
.
31P NMR
2.2.2. Au4Co2(CO)7(PPh3)3 (2)
A THF solution (40 ml) of Co2(CO)8 (420 mg, 1.2
mmol) was treated with Na amalgam for 2 h. After the
solution was filtered, the THF solution of NaCo(CO)4
was added slowly to an ice-cooled THF solution (80
ml) of AuCl(PPh3) (888 mg, 1.8 mmol) for 1 h and the
mixture was stirred at this temperature for 19 h. The
solution changed from yellow to orange–red. The sol-
vent was distilled off at reduced pressure. The residue
Table 1
Crystal data a
Compound
(OC)5Re–Re(CO)4Au2dppfe (1)
Au4Co2(CO)7(PPh3)3 (2)
[AuꢀCo(CO)4]2(m-cis-dpen) (3)
Formula
C43H28Au2FeO9P2Re2
C61H45Co2O7P3
1888.6
triclinic
C34H22Au2Co2O8P2
1132.3
triclinic
Formula weight
Crystal system
Space group
1572.8
monoclinic
P21/n
15.331(7)
23.427(9)
13.621(6)
90
112.53(3)
90
4519(3)
4
(
(
P1
P1
,
a (A)
12.838(4)
22.406(6)
11.759(4)
103.15(2)
117.06(2)
82.78(2)
2932(2)
2
10.704(2)
17.437(3)
10.597(2)
96.73(2)
108.02(2)
99.53(2)
1824.7(6)
2
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
Dcalc. (g cm−3
)
2.313
0.25×0.20×0.05
55.19
2.140
0.45×0.25×0.20
51.34
2.062
0.45×0.40×0.20
45.23
Crystal dimensions (mm3)
v (Mo Ka) (cm−1
Scan type
)
ꢀ
ꢀ
ꢀ–2q
Scan range
1.45+0.35 tanq
5.0
45.0
1.50+0.35 tanq
5.0
45.0
1.45+0.35 tanq
5.0
55.0
Scan speed (° min−1
2qmax (°)
)
Temperature (K)
Unique reflections
298
5916
3430
538
298
7664
5871
700
298
8372
Reflections with ꢀFoꢀ\3|(ꢀFoꢀ)
4820 b
Number of parameters refined
439
R
0.084
0.051
0.121
Rw
0.098
0.039
0.148
a
2
2 1/2
Mo Ka radiation (u=0.71073 A); R=ꢁꢀꢀFoꢀ−ꢀFcꢀꢀ/ꢀFoꢀ; Rw=[ꢁ(ꢀFoꢀ−ꢀFcꢀ) /ꢁw(Fo) ] where w=1/|2(F).
,
b
ꢀFoꢀ\6|(ꢀFoꢀ).

Y. Katsukawa et al. / Inorganica Chimica Acta 294 (1999) 255–265
257
Fig. 1. The ORTEP drawing of (OC)5Re–Re(CO)4Au2dppfe (1).
Fig. 3. The ORTEP drawing of [Au–Co(CO)4]2(m-cis-dpen) (3).
2.2.3. [Au–Co(CO)4]2(v-cis-dpen) (3)
A THF solution (25 ml) of Co2(CO)8 (150 mg, 0.445
mmol) was treated with Na amalgam for 2 h. The THF
solution of NaCo(CO)4 thus obtained was transferred
to another flask by use of a syringe and to this was
added a THF solution (40 ml) of (AuCl)2(m-cis-dpen)
(370 mg, 0.43 mmol). The mixture was stirred at room
temperature overnight by covering the reaction vessel
with a black cloth. The resulting pale yellow solution
was filtered and the solvent was distilled off at reduced
pressure. The residue was washed with a small amount
of hexane and the brown solid left was recrystallized
from hexane–dichloromethane to afford pale yellow
single crystals. Yield, 70 mg (14%) in a form of single
crystals. IR (Nujol): w(CO) 2051(s), 1981(s,sh),
1965(vs,sh), and 1945(vs) cm−1 31P NMR: 17.4.
.
2.3. X-ray data collection and crystal structure
determination
Fig. 2. The ORTEP drawing of Au4Co2(CO)7(PPh3)3 (2).
All X-ray data were collected by use of a MAC
MXC3 diffractometer equipped with
a
graphite
was dissolved in a minimum amount of benzene and
the solution was loaded to a Yamazen medium-pressure
liquid chromatograph, YFLC 700 (Waco-gel C-200).
The first fraction eluted with benzene was collected.
The solvent was vacuum-stripped. The residue was
washed with pentane and the dark red residue was
extracted with ether. Orange–red crystals were grown
from ether to afford 130 mg of 2 (yield, 15%). The main
product of this reaction was Ph3P–Au–Co(CO)4 as was
reported by Nyholm and coworkers [36]. IR (Nujol
mull): w(CO) 2054(w), 2042(m), 2033(m,sh), 1984(m),
,
monochromated Mo Ka radiation (u=0.71073 A).
Crystal data for 1, 2, and 3 are collected in Table 1.
The structures were solved by direct methods (SIR 92
for 1 and 2 and DIRDIF for 3 in the Crystan-GM
program package provided by MAC Science). The
structures were refined by a full-matrix least-squares
method. All non-hydrogen atoms were refined with
anisotropic thermal parameters. The analytical absorp-
tion correction was applied at the final stage of refine-
ments [37]. The crystal of 3 showed broad reflections
and this property seems responsible for rather high R
factor. The molecular structures of 1, 2, and 3 are
shown in Figs. 1–3, respectively. The atomic coordi-
1960(vs), 1952(vs), 1929(m), 1910(s), 1902(s) cm−1
.
31P
NMR (CDCl3, 298 K): 39.5(s).

258
Y. Katsukawa et al. / Inorganica Chimica Acta 294 (1999) 255–265
Table 2
Table 3
2
2
,
The atomic coordinates and isotropic thermal parameters, Beq (A )
for 1
,
The atomic coordinates and isotropic thermal parameters, Beq (A )
for 2
Atom
x
y
z
Beq
Atom
x
y
z
Beq
Aul
Au2
Rel
Re2
Fel
P1
P2
C1
C2
C3
C4
C5
C6
C7
C8
C9
−0.3385(1)
−0.2061(1)
−0.3459(1)
−0.1770(1)
−0.4293(4)
−0.4613(6)
−0.2026(7)
−0.495(2)
−0.463(3)
−0.512(3)
−0.566(4)
−0.560(3)
−0.292(2)
−0.312(3)
−0.386(3)
−0.402(5)
−0.346(3)
−0.426(3)
−0.444(3)
−0.298(4)
−0.231(3)
−0.372(3)
−0.238(3)
−0.149(2)
−0.110(3)
−0.070(3)
−0.467(4)
−0.500(3)
−0.283(3)
−0.170(2)
−0.398(3)
−0.283(2)
−0.133(2)
−0.065(2)
−0.004(2)
−0.575(2)
−0.594(3)
−0.670(2)
−0.729(3)
−0.712(3)
−0.630(2)
−0.430(2)
−0.493(3)
−0.466(3)
−0.379(4)
−0.308(4)
−0.335(2)
−0.234(3)
−0.210(3)
−0.237(4)
−0.282(3)
−0.312(4)
−0.290(4)
−0.085(3)
−0.019(3)
0.075(6)
−0.10852(7)
−0.12999(7)
−0.00309(7)
−0.04487(6)
−0.2325(2)
−0.1751(4)
−0.1838(4)
−0.182(2)
−0.141(2)
−0.166(3)
−0.223(3)
−0.229(2)
−0.241(2)
−0.271(2)
−0.314(2)
−0.307(2)
−0.262(1)
0.033(2)
−0.006(1)
0.072(2)
−0.002(2)
−0.077(2)
0.002(1)
−0.103(1)
0.023(2)
−0.060(2)
0.053(1)
−0.2673(1)
−0.3500(1)
−0.1385(1)
−0.2010(1)
−0.5530(4)
−0.3329(8)
−0.4879(8)
−0.478(3)
−0.535(4)
−0.646(3)
−0.656(3)
−0.538(4)
−0.524(2)
−0.445(4)
−0.509(6)
−0.617(5)
−0.626(4)
−0.079(5)
−0.292(4)
−0.181(4)
−0.007(3)
−0.088(3)
−0.332(3)
−0.093(3)
−0.116(4)
−0.227(3)
−0.045(4)
−0.378(4)
−0.204(3)
0.072(3)
−0.057(3)
−0.406(2)
−0.021(2)
−0.071(3)
−0.238(2)
−0.324(3)
−0.229(4)
−0.216(3)
−0.281(4)
−0.377(5)
−0.388(4)
−0.269(3)
−0.287(3)
−0.255(5)
−0.176(4)
−0.144(4)
−0.192(3)
−0.610(3)
−0.690(4)
−0.782(6)
−0.796(4)
−0.714(4)
−0.620(5)
−0.467(3)
−0.467(5)
−0.464(8)
−0.438(5)
−0.426(4)
−0.442(3)
3.77(5)
Au1
Au2
Au3
Au4
Co1
Co2
P1
P2
P3
C1
C2
C3
C4
C5
C6
C7
O1
O2
O3
0.86988(5)
0.63675(5)
0.68880(6)
0.82977(6)
0.7699(2)
0.8722(2)
0.9955(4)
0.4803(4)
0.6071(4)
0.868(2)
0.824(2)
0.633(2)
0.817(1)
0.774(1)
1.018(2)
0.893(2)
0.928(1)
0.854(1)
0.541(1)
0.777(1)
0.711(1)
1.113(1)
0.907(1)
0.966(1)
1.003(1)
0.984(2)
0.931(2)
0.897(2)
0.912(1)
1.144(1)
1.238(1)
1.356(1)
1.368(1)
1.275(2)
1.161(2)
1.001(1)
1.084(1)
1.088(2)
1.008(2)
0.926(1)
0.921(1)
0.422(1)
0.504(1)
0.460(2)
0.342(2)
0.262(1)
0.299(1)
0.357(1)
0.343(1)
0.247(2)
0.166(2)
0.183(1)
0.281(1)
0.504(1)
0.595(1)
0.611(2)
0.542(2)
0.459(2)
0.439(2)
0.596(1)
0.633(1)
0.26427(3)
0.23205(3)
0.35730(3)
0.18304(3)
0.30180(9)
0.07210(9)
0.2516(2)
0.1794(2)
0.4187(2)
0.3606(8)
0.2692(8)
0.3288(8)
0.0640(8)
0.1002(8)
0.0993(8)
0.92061(6)
0.85559(6)
0.88665(6)
1.04529(6)
1.0770(2)
1.0720(2)
0.8252(4)
0.6878(4)
0.7371(4)
1.141(2)
1.216(2)
1.065(2)
0.905(2)
1.140(2)
1.161(2)
1.086(2)
1.196(1)
1.317(1)
1.061(1)
0.790(1)
1.189(1)
1.220(1)
1.095(1)
0.687(1)
0.590(2)
0.492(2)
0.495(2)
0.591(2)
0.688(2)
0.938(1)
0.913(1)
0.996(2)
1.100(2)
1.121(2)
1.045(2)
0.763(2)
0.851(2)
0.805(2)
0.677(2)
0.596(2)
0.638(2)
0.746(1)
0.852(1)
0.907(2)
0.851(2)
0.743(2)
0.687(2)
0.610(1)
0.691(2)
0.635(2)
0.501(2)
0.425(2)
0.477(2)
0.556(1)
0.536(2)
0.423(2)
0.341(2)
0.365(2)
0.473(2)
0.579(1)
0.506(1)
4.07(2)
3.72(2)
4.04(2)
4.52(3)
4.07(8)
4.65(9)
4.2(2)
3.7(1)
3.9(2)
5.9(8)
6.6(8)
5.3(7)
5.7(7)
5.4(7)
6.0(8)
7.5(9)
9.4(7)
9.1(6)
7.2(6)
7.7(6)
8.0(6)
9.3(7)
9.8(7)
4.2(6)
5.5(7)
5.7(7)
6.0(8)
6.3(8)
5.8(7)
4.4(6)
5.1(7)
5.4(7)
6.1(8)
7.7(9)
6.0(7)
4.6(6)
5.9(7)
7.6(9)
6.6(9)
6.2(8)
5.2(7)
4.1(6)
4.9(6)
6.3(8)
5.5(7)
5.8(7)
5.4(7)
3.8(6)
4.7(6)
6.8(8)
6.3(8)
6.5(8)
5.5(7)
3.9(6)
5.8(7)
7.2(9)
8(1)
4.09(5)
4.53(5)
3.45(5)
4.0(2)
3.6(3)
3.9(3)
5(1)
6(2)
7(2)
8(2)
7(2)
4(1)
6(1)
8(2)
11(3)
6(2)
7(2)
5(1)
6(2)
5(1)
−0.0042(8)
0.4034(7)
0.2571(6)
0.3468(6)
0.0554(6)
0.1150(6)
0.1138(7)
−0.0558(6)
0.1870(7)
0.1871(8)
0.1322(9)
0.0825(8)
0.0841(8)
0.1371(8)
0.2344(6)
0.2407(7)
0.2221(8)
0.1951(8)
0.1905(9)
0.2086(8)
0.3176(7)
0.3648(8)
0.4188(8)
0.4235(8)
0.3813(8)
0.3259(7)
0.1285(6)
0.1027(7)
0.0667(7)
0.0541(7)
0.0797(7)
0.1162(7)
0.2310(6)
0.2848(7)
0.3241(8)
0.3101(8)
0.2570(9)
0.2152(8)
0.1336(7)
0.1535(8)
0.1227(9)
0.073(1)
C10
C11
C12
C13
C14
C15
C16
C17
C18
C19
O11
O12
O13
O14
O15
O16
O17
O18
O19
C21
C22
C23
C24
C25
C26
C31
C32
C33
C34
C35
C36
C41
C42
C43
C44
C45
C46
C51
C52
C53
C54
C55
C56
O4
O5
O6
O7
5(2)
5(1)
4(1)
6(2)
C11
C12
C13
C14
C15
C16
C17
C18
C19
C20
C21
C22
C23
C24
C25
C26
C27
C28
C31
C32
C33
C34
C35
C36
C37
C38
C39
C40
C41
C42
C43
C44
C45
C46
C47
C48
C51
C52
4(1)
11(2)
11(2)
9(2)
9(2)
8(1)
7(1)
6(1)
6(1)
6(1)
3(1)
6(2)
9(2)
6(2)
7(2)
6(2)
4(1)
7(2)
7(2)
6(2)
8(2)
4(1)
5(1)
6(2)
8(2)
7(2)
−0.007(2)
0.114(2)
−0.003(2)
−0.115(2)
0.024(1)
−0.133(1)
0.059(1)
−0.067(1)
−0.157(1)
−0.168(2)
−0.149(4)
−0.113(2)
−0.104(2)
−0.116(2)
−0.244(1)
−0.295(3)
−0.343(2)
−0.352(2)
−0.299(2)
−0.258(2)
−0.143(2)
−0.159(2)
−0.125(2)
−0.084(2)
−0.060(3)
−0.092(3)
−0.213(2)
−0.181(2)
−0.196(3)
−0.238(5)
−0.292(3)
−0.271(2)
10(2)
10(3)
5(1)
7(2)
11(3)
14(4)
9(2)
0.081(4)
0.029(4)
−0.076(3)
0.0514(8)
0.0820(7)
0.3775(7)
0.4024(7)
8(1)
5.6(7)
3.8(6)
4.2(6)
6(2)

Y. Katsukawa et al. / Inorganica Chimica Acta 294 (1999) 255–265
259
Table 3 (Continued)
Table 4
2
,
The atomic coordinates and isotropic thermal parameters, Beq (A )
for 3
Atom
x
y
z
Beq
C53
C54
C55
C56
C57
C58
C59
C60
C61
C62
C63
C64
C65
C66
C67
C68
0.625(1)
0.577(2)
0.532(2)
0.546(2)
0.460(1)
0.374(1)
0.260(2)
0.239(2)
0.330(2)
0.439(2)
0.691(2)
0.634(1)
0.699(2)
0.818(2)
0.878(2)
0.810(2)
0.3648(8)
0.3084(8)
0.2867(8)
0.3188(8)
0.4476(6)
0.4475(7)
0.4757(8)
0.5011(8)
0.4989(8)
0.4706(8)
0.4875(7)
0.5447(7)
0.5947(8)
0.5877(8)
0.5306(8)
0.4809(8)
0.387(2)
0.339(2)
0.413(2)
0.534(2)
0.708(2)
0.582(2)
0.564(2)
0.670(2)
0.801(2)
0.817(2)
0.776(1)
0.756(2)
0.778(2)
0.820(2)
0.846(2)
0.822(2)
5.3(7)
6.4(8)
7.9(9)
6.5(8)
4.4(6)
5.0(7)
7.0(9)
6.4(8)
7.1(9)
6.1(8)
4.6(6)
4.9(7)
5.9(8)
6.0(8)
6.7(8)
5.6(7)
Atom
x
y
z
Beq
Au1
Au2
Co1
Co2
P1
P2
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
C14
C15
C16
C17
C18
C19
C20
C21
C22
C31
C32
C33
C34
C35
C36
C37
C38
C39
C40
C41
C42
O3
0.1310(2)
0.2238(1)
0.2667(1)
0.3207(4)
0.2579(4)
0.1212(6)
0.2907(6)
0.138(2)
0.205(3)
0.309(3)
0.377(4)
0.243(4)
0.390(4)
0.198(3)
0.226(3)
0.359(4)
0.246(3)
0.051(2)
0.081(3)
0.026(3)
−0.051(3)
−0.080(3)
−0.034(3)
0.067(2)
0.036(2)
−0.016(3)
−0.039(3)
−0.015(3)
0.042(3)
0.367(2)
0.360(3)
0.421(3)
0.491(3)
0.498(3)
0.436(3)
0.325(3)
0.379(3)
0.405(3)
0.369(3)
0.311(3)
0.294(3)
0.309(2)
0.404(2)
0.185(2)
0.429(2)
0.162(2)
0.209(2)
0.427(2)
0.238(2)
0.2300(2)
0.2805(1)
0.1278(6)
0.0668(5)
0.320(1)
0.4934(9)
0.486(4)
0.563(4)
0.278(5)
0.149(5)
0.007(6)
0.059(5)
0.160(5)
0.004(4)
0.119(6)
4.9(1)
−0.1373(2)
0.2480(6)
−0.3291(6)
0.053(1)
−0.001(1)
0.059(5)
4.9(1)
5.0(2)
5.2(2)
3.7(3)
4.4(3)
7(2)
5(1)
6(2)
8(2)
8(2)
8(2)
5(1)
5(1)
13(4)
8(2)
4(1)
6(2)
5(2)
6(2)
8(2)
7(2)
6(2)
8(2)
6(2)
7(2)
7(2)
6(2)
6(2)
6(2)
7(2)
8(2)
6(2)
6(2)
5(1)
4(1)
6(2)
8(2)
6(2)
9(2)
7(1)
6(1)
9(2)
9(1)
6(1)
7(1)
7(1)
7(1)
0.058(4)
0.383(4)
0.087(5)
0.210(5)
0.341(5)
−0.409(4)
−0.226(4)
−0.30(1)
−0.470(6)
0.176(4)
−0.085(5)
0.327(3)
0.358(4)
0.359(4)
0.335(5)
0.315(4)
0.302(4)
0.251(4)
0.315(4)
0.258(5)
0.119(5)
0.046(4)
0.108(4)
0.534(4)
0.608(4)
0.653(5)
0.583(5)
0.509(5)
0.480(4)
0.615(4)
0.725(4)
0.823(4)
0.777(4)
0.657(4)
0.577(4)
0.366(3)
0.142(4)
−0.102(3)
0.010(3)
0.222(3)
−0.046(3)
0.159(3)
−0.187(3)
nates are listed in Tables 2–4 and selected bond lengths
and angles are tabulated in Tables 5–7.
0.318(5)
0.393(5)
0.346(5)
0.229(7)
0.104(6)
3. Results and discussion
−0.085(5)
−0.192(6)
−0.310(4)
−0.374(5)
−0.300(6)
−0.146(5)
0.160(6)
3.1. Synthesis and structure of (OC)5Re–Re(CO)4Au2-
dppfe (1)
The reaction of (AuCl)2(m-dppfe) with NaRe(CO)5
was first reported by Hor and coworkers several years
ago; the product which they isolated from the reaction
mixture at −78°C and was characterized by spectro-
scopic data is [Au–Re(CO)5]2(m-dppfe) (4) [38]. The
product which we obtained in this study from the
similar reaction mixture at room temperature exhibits
an entirely different IR spectrum in w(CO) region from
that of 4. Therefore, single crystal X-ray analysis has
been made; 1 possesses the molecular structure with an
unusual asymmetric Re2Au2 skeleton as is shown in
Fig. 1. One plausible explanation why the product
obtained by us is different from that by Hor and
coworkers is that 4 produced at low temperature is
converted to (OC)5Re–Re(CO)4Au2dppfe (1) by heat
(room temperature). Therefore, we are now planning to
synthesize Hor’s product at low temperature and to
heat the product in solutions.
0.284(5)
0.415(5)
0.365(7)
0.256(6)
0.136(5)
−0.047(4)
−0.013(4)
−0.052(5)
−0.214(6)
−0.301(5)
−0.211(7)
0.467(3)
O4
O5
O6
O7
O8
O9
O10
0.014(3)
0.134(4)
0.395(4)
−0.447(3)
−0.132(4)
−0.267(4)
−0.552(3)
The molecular structure of 1 is akin to those of
[Au2Fe2(CO)8(m-dppm)] (5) [39], [Ru4H(CO)12B-
{Au2dppfe}] (6) [40], and [RhRu3HCp*(CO)9B(Au2-
dppfe)(AuCl)](7) [41] but is unusual in that two
gold atoms are coordinated to only one Re atom. Two
gold atoms make bonds with different Fe atoms and do
not bridge two Fe atoms in 5, two gold atoms are
bonded to two different Ru atoms in 6, and they bridge
two Ru atoms in 7. They all possess intramolecular
Au–Au bond(s) and the conformations of Au2dppfe
moieties in 6 and 7 are quite close to that of 1.
,
The Au1–Au2 distance in 1 is 2.719(2) A, which is
,
shorter than those in aforementioned 5 (2.915(1) A),
,
6 (2.818(2)), 7 (2.850(1) A), [Au4(PPh3)4Re(H)4{P-
(p-tol)3}2](BPh4) (8) (2.709–2.829 A), and (PhMe2P)3-
ReH2(AuPPh3)3 (9) (2.787(2)–2.812(2) A). The Re2–
Au distances are almost equal (Au1–Re2=2.730(2),
Au2–Re2=2.757(2) A). These distances are close to
those in 8 (2.709–2.741 A) [2] and slightly longer than
those in 9 (2.688(2)–2.730(2) A) [9]. The distance be-
,
,
,
,
,

260
Y. Katsukawa et al. / Inorganica Chimica Acta 294 (1999) 255–265
Table 5
,
Selected bond lengths (A) and angles (°) with e.s.d.s in parentheses for 1
,
Bond lengths (A)
Au1–Re2
Au1–P1
Re1–C11
Re1–C14
Re2–C17
C11–O11
C14–O14
C17–O17
P1–C1
2.730(2)
2.342(9)
1.90(6)
1.97(4)
1.93(4)
1.03(9)
1.12(5)
1.15(5)
1.85(4)
Au2–Re2
Au2–P2
2.757(2)
2.28(1)
2.06(4)
1.97(4)
2.00(5)
1.15(6)
1.12(6)
1.11(5)
1.85(4)
Au1–Au2
Re1–Re2
Re1–C13
Re2–C16
Re2–C19
C13–O13
C16–O16
C19–O19
2.719(2)
3.175(3)
2.07(5)
1.99(4)
1.85(4)
1.10(6)
1.11(5)
1.22(6)
Re1–C12
Re1–C15
Re2–C18
C12–O12
C15–O15
C18–O18
P2–C6
Bond angles (°)
Au1–Re2–Re1
Au2–Au1–P1
Au1–Au2–Re2
Au1–P1–C1
Au1–Re2–C17
Au2–Re2–C16
Au2–Re2–C19
Re1–Re2–C18
Re2–Re1–C12
Re2–Re1–C15
61.83(6)
109.7(3)
59.80(6)
109(1)
77(1)
81(1)
67(1)
84(2)
94(1)
Au2–Re2–Re1
P1–Au1–Re2
Au2–Au1–Re2
Au2–P2–C6
Au1–Re2–C18
Au2–Re2–C17
Re1–Re2–C16
Re1–Re2–C19
Re2–Re1–C13
120.14(6)
169.8(3)
60.80(6)
112(1)
145(2)
89(1)
85(2)
172(1)
77(2)
Au1–Au2–P2
P2–Au2–Re2
Au1–Re2–Au2
Au1–Re2–C16
Au1–Re2–C19
Au2–Re2–C18
Re1–Re2–C17
Re2–Re1–C11
Re2–Re1–C14
134.5(3)
163.4(3)
59.40(6)
87(1)
126(1)
154(2)
89(1)
167(1)
73(2)
97(2)
Table 6
,
Selected bond lengths (A) and angles (°) with e.s.d.s in parentheses for 2
,
Bond lengths (A)
Au1–Au2
Au2–Au3
Au2–Co1
Au4–Co2
Au3–P3
2.876(1)
2.870(1)
2.629(2)
2.536(2)
2.269(4)
1.73(2)
Au1–Au3
Au2–Au4
Au3–Co1
Au1–P1
Co1–C1
Co2–C4
Co2–C7
2.8672(9)
2.7798(8)
2.543(2)
2.306(6)
1.73(2)
Au1–Au4
Au1–Co1
Au4–Co1
Au2–P2
Co1–C2
Co2–C5
2.805(1)
2.626(3)
2.665(2)
2.292(3)
1.76(2)
Co1–C3
Co2–C6
1.73(2)
1.73(2)
1.76(2)
1.79(2)
Bond angles (°)
Au1–Au2–Au3
Au1–Au4–Au2
Au3–Au1–Au4
Co1–Au1–Au3
Co1–Au2–Au3
Co1–Au3–Au2
Au1–Co1–Au2
Au2–Co1–Au3
Co2–Au4–Co1
P1–Au1–Au2
P1–Au1–Co1
P2–Au2–Au4
P3–Au3–Au2
59.86(2)
62.00(2)
105.83(3)
54.93(5)
54.86(5)
57.73(4)
66.36(5)
67.40(5)
162.72(9)
138.93(9)
163.8(1)
126.7(1)
127.72(9)
Au1–Au3–Au2
Au2–Au1–Au3
Au3–Au2–Au4
Co1–Au1–Au4
Co1–Au2–Au4
Co1–Au4–Au1
Au1–Co1–Au3
Au2–Co1–Au4
Co2–Au4–Au1
P1–Au1–Au3
P2–Au2–Au1
P2–Au2–Co1
P3–Au3–Co1
60.17(2)
59.97(2)
106.41(2)
58.66(5)
58.96(4)
57.33(6)
67.36(7)
63.34(4)
139.55(8)
124.7(1)
140.5(1)
162.6(1)
170.8(1)
Au1–Au2–Au4
Au2–Au1–Au4
Co1–Au1–Au2
Co1–Au2–Au1
Co1–Au3–Au1
Co1–Au4–Au2
Au1–Co1–Au4
Au3–Co1–Au4
Co2–Au4–Au2
P1–Au1–Au4
P2–Au2–Au3
P3–Au3–Au1
59.43(2)
58.58(2)
56.86(4)
56.78(6)
57.72(6)
57.70(4)
64.01(6)
120.64(8)
128.26(5)
128.4(1)
126.2(1)
130.7(1)
,
The Au–P bond lengths are 2.28(1)–2.342(9) A. These
,
tween Re1 and Au1 is 3.058(2) A. This distance is
significantly longer than the usual Au–Re bond. In
addition, 18-electron rule does not request a covalent
bond between Re1 and Au1 atoms. Therefore, we sug-
gest that there is not a strong interaction between Re1
and Au1 atoms. Thus, the Au2Re skeleton is close to a
regular triangle; this is supported from the relevant
angles described below. The flexibility of dppfe for
coordination to transition metals should make it possi-
ble to take such an unusual and crowded structure [42].
distances are longer than those of [Au–Co(CO)4]2(m-
,
dppfe) (10) (2.258(3)–2.262(2) A) and of [Au–
Mn(CO)5]2(m-dppfe) (11) (2.27(5)–2.28(5) A) [31e]. The
,
Au1–Re2–Au2 angle and the Au1–Re2–Re1 angle are
close to those of the regular triangles of 59.40(6) and
61.83(6)°, respectively. The Re2–Au1–Au2 and Re2–
Au2–Au1 angles are 60.80(6) and 59.80(6)°, respec-
tively. The Au2–Re2–Re1 angle is 120.14(6)°. The
P1–Au1–Au2 and the P2–Au2–Au1 angles are
109.7(3) and 134.5(3)°, respectively.

Y. Katsukawa et al. / Inorganica Chimica Acta 294 (1999) 255–265
261
Table 7
Selected bond lengths (A) and angles (°) with e.s.d.s in parentheses for 3
,
,
Bond lengths (A)
Au1···Au2
Au2–Co2
Co1–C3
Co1–C6
Co2–C9
C4–O4
3.265(3)
2.511(5)
1.84(4)
1.80(6)
1.73(6)
0.96(8)
1.08(6)
1.13(6)
Au1–Co1
Au2–P2
Co1–C4
Co2–C7
Co2–C10
C5–O5
2.482(7)
2.222(9)
2.17(7)
1.80(5)
1.80(5)
1.38(6)
1.33(6)
1.73(5)
Au1–P1
C1–C2
Co1–C5
Co2–C8
C3–O3
C6–O6
C9–O9
P2–C2
2.28(1)
1.35(6)
1.65(6)
1.59(5)
1.08(5)
1.10(8)
1.18(7)
1.85(5)
C7–O7
C10–O10
C8–O8
P1–C1
Bond angles (°)
P1–Au1–Co1
Au2–P2–C2
Au1–Co1–C5
Au2–Co2–C8
169.0(4)
117(1)
82(2)
P2–Au2–Co2
Au1–Co1–C3
Au1–Co1–C6
Au2–Co2–C9
164.9(4)
76(2)
177(2)
84(2)
Au1–P1–C1
119(1)
79(2)
78(1)
Au1–Co1–C4
Au2–Co2–C7
Au2–Co2–C10
81(1)
177(1)
,
length is longer than those of 12 (2.50(1) A) [36], 10
3.2. Synthesis and structure of Au4Co2(CO)7(PPh3)3 (2)
,
,
(2.492(1)–2.499(1) A) [31e], and 13 (2.46(2) A) [8]. The
The reaction of AuCl(PPh3) with Co(CO)−4 was first
reported by Nyholm and coworkers in 1964 [36]. The
product they isolated was the targeted Ph3PAu–
Co(CO)4 (12) and the isolation of Au4Co2(CO)7(PPh3)3
(2) was not reported. They produced Co(CO)−4 anion
by reacting Co2(CO)8 with pyridine in THF and we
prepared this anion by reduction of Co2(CO)8 with Na
amalgam. Thus, the cation for Nyholm’s synthesis is
[Copy5]2+ and the cation in our synthesis is Na+. This
difference in the cation for producing Co(CO)−4 anion
should be responsible for the formation of our cluster.
The molecular structure of 2 is composed of a but-
terfly-like Au4 skeleton and triphenyl phosphines and/
or a Co(CO)4 group are coordinated to each gold atom
as a terminal ligand [8]. The Co(CO)3 group caps the
Au4 skeleton. The skeletal structure looks like a frag-
ment of Au6(PPh3)4[Co(CO)4]2 (13) reported by Velden
et al. except the existence of the capping Co(CO)3
group [8] and/or looks like (dppe)2Au3In3Cl6(thf)3 (14)
and [(dppe)2Au3In3Br7(thf)]− (15) reported by Schmid-
baur et al. [43]. The Au–Au distances are categorized
into two groups, that is, rather long Au–Au distances
Au–P bond lengths (2.269(4)–2.306(6) A) are almost in
,
,
the same range as those of 13 (2.28(4)–2.37(2) A) [8].
The Au3–Au1–Au4 angle is 105.83(3)° and the Au3–
Au2–Au4 angle is 106.41(2)°. The Au–Au–Co(cap-
ping) angles are classified into three groups, that is, the
groups around the 59° (Co1–Au1–Au4 and Co1–
Au2–Au4), the groups around 55° (Co1–Au1–Au3
and Co1–Au2–Au3), and the groups around 57°
(Co1–Au1–Au2, Co1–Au2–Au1, Co1–Au3–Au1,
Co1–Au3–Au2, Co1–Au4–Au1, and Co1–Au4–
Au2). The fact that the capping Co(CO)3 group is
slightly leaned to the Au3 atom is substantiated by
comparisons of these bond angles and the Co1–Au
bond lengths mentioned above. The Co(CO)4 group has
the similar slightly distorted trigonal bipyramidal coor-
dination as those of 10, 12 and 13. In order to assimi-
late these core structural features, two propositions are
presented; firstly the 18-electron rule suggests that the
Co(CO)4 group is an anion and the capped Co(CO)3
group should be a cation if four Co1–Au bonds are
assumed. Thus the cationic charge on Co1 is cancelled
by the anionic charge on the terminal Co(CO)4 group
to make the cluster neutral. Second proposition is that
the capping Co(CO)3 group makes three Au–Co bonds
between Co1 and Au1, Au2, and Au3, respectively, but
there is no bond between Co1 and Au4. In addition the
terminal Co(CO)4 is an anion and Au4 is a cation to
make the cluster neutral. The latter interpretation is
based on the facts that (1) the Co1–Au4 bond is the
longest among the four Co1–Au bonds and the Au4–
Au1 and Au4–Au2 bonds are shorter than Au3–Au1
and Au3–Au2 bonds and (2) the 197Au Mo¨ssbauer
spectrum and a LCGTO-DF method calculation on the
Mulliken charge of Au atoms for 14 and 15 which have
quite similar core structures to the present cluster have
shown that the Au atom in a similar corner position
,
(2.8672(9)–2.876(1) A) and short Au–Au distances
,
(2.7798(8)–2.805(1) A). The latter bonds are concerned
with the Au4 atom to which the terminal Co(CO)4
,
group is bonded. The Au4–Co2 bond (2.536(2) A) is
the shortest among the five Au–Co bonds and the
Au3–Co1 bond, which is located at the opposite side to
the Au4–Co2 bond, is the next short Au–Co bond
,
(2.543(2) A). Among four Co1–Au bond lengths, the
,
Co1–Au3 bond length is the shortest (2.543(2) A) and
,
the Co1–Au4 is the longest (2.665(2) A). Among five
Au–Au bond lengths, those concerned with Au4 atom,
that is, Au4–Au1 and Au4–Au2 bond lengths are
significantly shorter than those of Au1–Au2, Au1–
Au3, and Au2–Au3 bond lengths. The Au4–Co2 bond

262
Y. Katsukawa et al. / Inorganica Chimica Acta 294 (1999) 255–265
can be assigned oxidation state +1 and other Au
atoms are assigned oxidation state 0 [43]. However, the
Co1–Au4 bond is not longer enough than Co1–Au1
of the splitting of each peak and such a pair formation
in a head-to-tail manner is responsible for w(CO) split-
ting by intermolecular dipole–dipole interaction in
solid states. The IR spectrum of a Nujol mull sample of
2 is shown in Fig. 5a and that of a benzene solution
sample is shown in Fig. 5b; the KBr disk sample shows
a similar IR spectrum as that of a Nujol mull sample.
Apparently the peak at 2032 cm−1 for the solution
sample splits into two peaks (2042 and 2033 cm−1) for
the Nujol mull sample. Similar splitting is observed for
the peaks at 1955 cm−1 (1960 and 1952 cm−1) and
1916 cm−1 (1910 and 1902 cm−1). The peaks observed
for the solution sample at 2054 and 1984 cm−1 are
,
and Co1–Au2 bond (only 0.04 A longer) to neglect the
bond between Co1 and Au4 atoms. Therefore, this
issue must wait for future spectroscopic study such as
XPS and/or 197Au Mo¨ssbauer measurements.
3.3. Synthesis and structure of
[Au-Co(CO)4]2(v-cis-dpen) (3)
The title compound was obtained as was aimed by
reacting NaCo(CO)4 with (AuCl)2(m-cis-dpen) in THF
with 2:1 mole ratio. The maintenance of the cis-
configuration in 3 is amazing, because (Au–X)2(m-cis-
dpen) (X=Cl, Br, I, and p-SC6H4CH3) is isomerized
easily to (Au-X)2(m-trans-dpen) in solutions [45]. Thus,
the two Au atoms come close in the molecule (the
observed as a single peak at 2054 and 1984 cm−1
,
respectively for the Nujol mull sample. The weak peak
at 1929 cm−1 observed for the Nujol mull sample
should be hidden behind the shoulder of the main peak
at 1955 cm−1 for the solution sample. Thus, the w(CO)
peaks are classified into two groups, that is, the group
of 2032(w), 1955(vs), and 1916(m) cm−1 and the group
of 2054(s), 1984(s), and perhaps 1929 cm−1 (read from
the spectrum of the solid sample). The terminal
Co(CO)4 group has a C36 local symmetry and the
capping Co(CO)3 group has a Cs local symmetry.
Therefore, the Co(CO)3 group is also expected to show
three (2A%+A¦) IR-active vibrations. The assignment
that the CO vibrations in the terminal Co(CO)4 group
contribute mainly to the former peaks is rationalized if
the same reasoning for the splitting is applicable to the
IR spectrum of the solid sample of 2. Under this
,
Au–Au distance is 3.265(3) A) to suggest an in-
tramolecular aurophilic interaction [32]. The in-
tramolecular Au–Au distance in (AuCl)2(m-cis-dpen) is
,
3.05(1) A [44]. Thus, the aurophilic interaction is re-
duced by replacing the Cl anions with Co(CO)4 groups.
,
The Au–Co bond lengths are 2.482(7) and 2.511(5) A,
which are in the same range of Au–Co bonds in 10
[31e]. The cis-dpen group is concluded to afford almost
the same electronic effect on the Au–Co bond as that
of dppfe. The P–Au–Co bonds are slightly distorted
from linearity (169.0(4) and 164.9(4)°). The steric repul-
sion that resulted from the cis configuration may be
responsible for the distortion from the linearity. Al-
though two Co atoms are not in the close proximity
,
(the intramolecular Co–Co distance is 5.04(1) A), some
CO groups coordinated to these cobalt atoms come
,
close in the molecule (3.3(1)–3.47(7) A), but they are
not parallel in the molecule.
3.4. Crystal structures of 1, 2, and 3
As described in the introduction, we are very much
interested in the crystal packing of these clusters for
possible unveiling of the intermolecular Au–Au inter-
action. Although drawings of crystal packings for these
clusters do not indicate such an aurophilic interaction
in the crystals, an interesting intermolecular pair forma-
tion in a head-to-tail manner is detected for the termi-
nal Co(CO)4 groups of 2. Fig. 4 displays the crystal
packing of the cluster 2 along the c axis and the pair
formation is indicated by circles. The nearest contact in
,
this pair is 3.46(3) A (C6···O7). In the previous paper,
we have found that similar pairs are formed in the
crystal among the neighboring Co(CO)4 groups in [Au–
Co(CO)4]2(m-dppfe) (10) and the peaks observed for
solid samples are doubled with expected numbers of
peaks (2A1+E) under a C36 local symmetry for 10
[31e]. We have concluded that the doubling is the result
Fig. 4. A projection of the crystal of 2 along the c axis. The
indicates Co2 atom and
(13) indicates Au atoms.

Y. Katsukawa et al. / Inorganica Chimica Acta 294 (1999) 255–265
263
Fig. 5. (a) IR spectrum of 2 in the w(CO) region for a Nujol mull sample. (b) IR spectrum of 2 in the w(CO) region for a benzene solution.
Fig. 6. Absorption spectra of 1 (—), 2 (----), and 3 (--·--·) in a CH2Cl2 solution at room temperature. Inserted Figure: absorption spectra for
expanded scale of absorbance in the 350–450 nm region.
assignment, these vibrations (2032, 1955, and 1916
cm−1) are just in-between for those of 12 (2045, 1975,
and 1945 cm−1) and 13 (2010, 1940, and 1885 cm−1).
Thus, the electron density on the metal skeleton of 2 is
deduced to be lower than that of 13 and higher than
that of 12 [8].
clei of 1 resonate in significantly lower field compared
with that of 10 (32.36) where Au atoms are bonded to
Co atoms [31e], but is close to those of 4 (53.58), 8
(55.3), and 9 (57.3) where Au atoms are bonded to Re
atoms. The 31P NMR spectrum of 2 shows a sharp
signal at l 39.5 at room temperature. This is peculiar if
the solid-state core structure is maintained in a solu-
tion. A rational interpretation is that the Co1–Au4
bond is cleaved in a solution to produce a pseudo C36
symmetry species with the CoAu3(PPh3)3 core. The 31P
NMR spectrum of 3 shows a peak at l 17.4, which is
significantly shifted to a higher field compared with that
3.5. Spectroscopic data of 1, 2, and 3
The 31P NMR spectrum shows a single resonance at
l 52.7 for 1 in CDCl3, which suggests that the molecu-
lar structure of 1 is maintained in solutions. The 31P-nu-

264
Y. Katsukawa et al. / Inorganica Chimica Acta 294 (1999) 255–265
Chem. Soc., Dalton Trans. (1995) 2639. J.R. Galsworthy, C.E.
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of 2 and 10. Intramolecular Au···Au interaction may be
responsible for this high field shift.
All the clusters synthesized in this work are
light-yellow to orange–red. The absorption spectra of
these new clusters at wavelengths greater than 260 nm
are displayed in Fig. 6. The orange–red complex 1
displays a weak absorption at 390 and the orange–red
complex 2 shows weak peaks at 300 and 400 nm, while
the pale-yellow complex 3 shows a weak absorption at
335 nm. These absorptions are assigned tentatively due
to gold(I)–gold(I) interaction(s) based on the recent
interpretation for [Au3(dppm)2X2]X complexes by Che
and coworkers [46], because all these compounds
possess gold(I)–gold(I) interactions.
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Acknowledgements
This work was supported by Iketani Science and
Technology Foundation and Grant-in Aids for Scien-
tific Research on Priority Areas (No. 10149221 ‘Metal-
assembled Complexes’) from Ministry of Education,
Science, Sports, and Culture, Japan.
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