Cluster core expansion through incorporation of transition-metal fragments or an alkyne molecule into an incomplete cubane-type Fe2RuS 4 cluster

Article abstract of DOI:10.1246/cl.2004.1130

Treatment of Cp^S2₂Fe₂S₄ (Cp^S2 = 1,3-C₅H₃(SiMe₃)₂) with [CpRu(MeCN)₃]⁺ in acetonitrile at room temperature led to the formation of an i

Full text of DOI:10.1246/cl.2004.1130

1130
Chemistry Letters Vol.33, No.9 (2004)
Cluster Core Expansion through Incorporation of Transition-metal Fragments or an Alkyne
Molecule into an Incomplete Cubane-type Fe2RuS4 Cluster
Masaaki Okazaki,ꢀ Atsushi Sakuma, Hiromi Tobita,ꢀ and Hiroshi Oginoy
Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578
yMiyagi Study Center, University of the Air, Sendai 980-8577
(Received June 9, 2004; CL-040659)
Treatment of CpS22Fe2S4 (CpS2 = 1,3-C5H3(SiMe3)2) with
[CpRu(MeCN)3]þ in acetonitrile at room temperature led to the
formation of an incomplete cubane-type cluster [(CpS2Fe)2-
(CpRu)S4]þ (1). Further treatment of 1 with [Cp0Ru(MeCN)3]þ
.
Cluster 1 reacted with DMAD to give the 1:1 adduct through for-
mation of three sulfur–carbon bonds.
bane-type cluster through incorporation of one metal fragment.7
The thermal reaction of 1 with [CpRu(MeCN)3](TFPB) in ace-
tonitrile was carried out at 70 ꢂC for 6 h (Scheme 1). Volatiles
were removed under reduced pressure and recrystallization of
the residue from CH2Cl2/hexane at ꢁ10 ꢂC afforded a dark
brown solid of [(CpS2Fe)2(CpRu)2S4](TFPB)2 (2) in 65% yield.8
The results of the elemental analysis and mass spectrum are in
good agreement with the formula of 2. We have not been able
to make single crystals of 2 suitable for X-ray diffraction study.
Thermolysis of 1 and bulkier [CpꢀRu(MeCN)3](PF6) under
the slightly severer conditions (75 ꢂC, 7 h), followed by treat-
ment with NH4PF6, gave [(CpS2Fe)2(CpRu)(CpꢀRu)S4](PF6)2
(3) in 25% yield (Scheme 1).9 Recrystallization of the evaporat-
ed reaction mixture residue from acetonitrile/diethyl ether gave
single crystals suitable for X-ray diffraction study. An ORTEP
drawing of the cationic part in 3 is depicted in Figure 1.5 Com-
plex 3 has an Fe2Ru2S4 cubane-type core with Cp, Cpꢀ, and two
CpS2 ligands. The Fe2Ru2 core is distorted from the ideal tetra-
(Cp0 = Cp, Cpꢀ) produced [(CpS2Fe)2(CpRu)(Cp0Ru)S4]2þ
Dinuclear transition-metal sulfido complexes of the type
Cp02M2S4 (Cp0 = Cp and substituted Cp) have been recognized
as useful building blocks for the rational synthesis of transition
metal sulfido clusters,1 which are important because of their po-
tential use for the biological and industrial catalytic processes.2
Our research has focused on the cluster construction starting
from Cp02Fe2S4.3 Reactions of Cpꢀ2Fe2S4 with iron and rutheni-
um carbonyls gave closo-(CpꢀFe)2M(CO)3(ꢀ3-S)2 clusters.3a
In the reaction with [CpꢀRu(MeCN)3](PF6), cubane-type
[Cpꢀ4Fe2Ru2S4](PF6)2 was formed. Introduction of bulkier
CpS2 ligands (CpS2 = 1,3-C5H3(SiMe3)2) onto the iron centers
allowed the isolation of the intermediate, [(CpS2Fe)2-
(CpꢀRu)S4](PF6).3b Existence of three bulky substituted Cp li-
gands, however, led to the poor reactivity of the cluster. This pa-
per describes the synthesis and structure of sterically less crowd-
ed [(CpS2Fe)2(CpRu)S4]þ, and the reactions of this trinuclear
cluster with [Cp0Ru(MeCN)3]þ (Cp0 = Cp, Cpꢀ) or an alkyne
molecule resulting in cluster core expansion.
An acetonitrile solution of CpS22Fe2S4 and 1 equiv. of
[CpRu(MeCN)3](TFPB) (TFPB = tetrakis{3,5-bis(trifluorome-
thyl)phenyl}borate) was stirred for 2 h at room temperature
(Scheme 1). Volatiles were removed under reduced pressure
and recrystallization of the residue from CH2Cl2/hexane at
ꢁ10 ꢂC gave dark brown crystals of [(CpS2Fe)2(CpRu)S4]-
(TFPB) (1) in 74% yield.4 ORTEP drawing of the cationic part
in 1 is depicted in Figure 1.5 The structural feature of 1 resembles
that of [(CpS2Fe)2(CpꢀRu)S4](PF6) we previously reported.3b
Thus, the cluster possesses an Fe2Ru core with ꢀ3-ꢁ1:ꢁ2:ꢁ2
and ꢀ3-ꢁ1:ꢁ1:ꢁ2 disulfido groups. The bond lengths of Ru–
ꢀ
hedral structure. The distances of Ru1–Ru2 (2.8206(11) A),
ꢀ
Ru1–Fe1 (2.7313(16) A), and Ru2–Fe2 (2.7452(17) A) indicate
ꢀ
the presence of each metal–metal single bond, while the dis-
ꢀ
ꢀ
tances of Ru1–Fe2 (3.3889(17) A), Ru2–Fe1 (3.3884(16) A),
ꢀ
and Fe1–Fe2 (3.4154(19) A) indicate no bond between them. As-
suming that one ꢀ3-sulfido ligand donates four electrons to the
core, cluster 3 can be recognized as a 66e species. This electron
count is consistent with the existence of three metal–metal bonds
as an electron-precise cluster. Compound 3 is the first Fe2Ru2S4
cubane-type cluster that is X-ray characterized.
We succeeded in the synthesis of the transition-metal sulfido
cubane-type cluster 3 having three different metal fragments, by
means of the stepwise incorporation of two different metal frag-
ments into CpS22Fe2S4. Such a synthetic methodology has not
been well established.10 In 1995, Kunchen and his co-workers
succeeded for the first time in the stepwise construction of the
Mo2WCuS4 cubane-type clusters by reacting Mo2S4(R2PS2)2
with W(CO)3(MeCN)3 and then with CuI.10a Hidai et al. nicely
developed this method and synthesized a variety of cubane-type
heterometallic sulfido clusters.10b
Heating an acetonitrile solution of 2 with dimethyl acety-
lenedicarboxylate (DMAD) at 75 ꢂC for 5 h led to quantitative
formation of 4 (Eq 1). Recrystallization of the evaporated
reaction mixture residue from diethyl ether/hexane at ꢁ10 ꢂC
afforded dark brown crystals of 4 in 88% yield.11 The results
of elemental analysis and mass spectrum indicate that cluster 4
makes the adduct with DMAD in the ratio of 1:1.
ꢀ
ꢀ
Fe1 (2.7627(6) A) and Ru–Fe2 (2.7791(6) A) are in the normal
range expected for the ruthenium–iron single bonds. The dis-
tance between two iron atoms is 3.4814(7), indicating the ab-
sence of a direct bond between them. Cluster 1 can be best de-
scribed as
a
‘‘CpRu’’-fragment-capped ‘‘CpS22Fe2S4’’, in
which the ‘‘CpS22Fe2S4’’ fragment is bound to the ruthenium
center in ꢂ5(Fe1,Fe2,S1,S3,S4) fashion. Rauchfuss et al. report-
ed formation of [Cpꢀ3Ru3S4](PF6) by the reaction of Cpꢀ2Ru2S4
with [CpꢀRu(MeCN)3](PF6), of which the SO2 adduct has been
characterized by X-ray diffraction study.6
Shibahara et al. reported the reaction of an incomplete cu-
bane-type cluster [Mo3(ꢀ3-S)(ꢀ-S)3(H2O)9]4þ with acetylene
to form the adduct [Mo3(ꢀ3-S)(ꢀ-S)(ꢀ3-S2C2H2)]4þ 12 The al-
.
kenedithiolate ligand bridges over two molybdenum atoms sym-
metrically, in which the two molybdenum centers and the pro-
Cluster 1 can be considered as an incomplete cubane-type
Fe2RuS4 cluster, which could provide a direct route to the cu-
Copyright Ó 2004 The Chemical Society of Japan

Chemistry Letters Vol.33, No.9 (2004)
1131
Me3Si
Fe
2+
SiMe3 Me3Si
S
+
SiMe3
S
SiMe3 Me3Si
+
[Cp'Ru(MeCN) ]
3
SiMe3
+
[CpRu(MeCN) ]
S
S
3
Me3Si
Fe
Ru
S
S
Me3Si
Fe
Fe
SiMe3
S
Me3Si
Fe
Fe
SiMe3
70 °C, 6 h (Cp)
rt, 2h
S
S
75 °C, 7 h (Cp*)
S
S
R
Ru
Ru
S
R
R
2 (R = H)
3 (R = Me)
R
1
R
Scheme 1.
C6
O4
C4
O1
Ru
S1
S4
O2
S3
C5
C2
C3
S2
Fe2
S2
O3
S4
C1
Fe1
S3
Ru1
S1
S2
Fe2
Fe1
Fe2
S4
Ru2
Ru
S1
Fe1
S3
1
3
4
Figure 1. ORTEP drawings of 1, 3, and 4. Thermal ellipsoids are shown at the 30% probability level. The counter anion and hydrogen
atoms were omitted for clarity. In 4, CpS2 and Cp ligands were also omitted.
tons of the alkenedithiolate ligand are both chemically equiva-
1
incomplete cubane-type cluster 1 with [CpꢀRu(MeCN)3]þ gave
a cubane-type cluster 3 with three different metal fragments. One
molecule of DMAD was incorporated into 1 to form 4 with an
unprecedented core.
lent. However, this is not the case for cluster 4. The H signals
of the SiMe3 groups on the CpS2 ligands were observed at ꢃ
0.41, 0.46, 0.53, and 0.58, indicating the presence of two chemi-
1
cally inequivalent, chiral iron centers. Accordingly, the H sig-
nals of two methyl groups on the DMAD fragment were ob-
References and Notes
1
2
J. Wachter, Angew. Chem., Int. Ed. Engl., 28, 1613 (1989).
a) R. Holm, Adv. Inorg. Chem., 38, 1 (1992). b) B. C. Wiegand
and C. M. Friend, Chem. Rev., 92, 491 (1992).
served independently at ꢃ 3.30 and 3.89.
MeO2C
3
a) T. Mitsui, S. Inomata, and H. Ogino, Inorg. Chem., 33, 4934
(1994). b) M. Yuki, K. Kuge, M. Okazaki, T. Mitsui, S. Inomata,
H. Tobita, and H. Ogino, Inorg. Chim. Acta, 291, 395 (1999). c)
M. Okazaki, M. Yuki, K. Kuge, and H. Ogino, Coord. Chem.
Rev., 198, 367 (2000).
CO2Me
C
Ru
C
S
S
75 °C, 5 h
S
1
+
DMAD
Me3Si
SiMe3
(1)
S
Fe
Me3Si
Fe
SiMe3
4
5
1: Anal. Found: C, 42.14; H, 3.65%. Calcd for C59H59B-
24Fe2RuS4Si4: C, 41.97; H, 3.52%. MS (FAB) m=z 825 (Mþ,
4
F
100).
The structure of 4 was unequivocally determined by X-ray
The crystallographic data can be obtained free of charge from the
Cambridge Crystallographic Data Centre (CCDC240682-
240684).
E. J. Houser, H. Krautscheid, T. B. Rauchfuss, and S. R. Wilson,
J. Chem. Soc., Chem. Commun., 1994, 1283.
a) T. Shibahara, Adv. Inorg. Chem., 37, 143 (1991). b) M. Hidai,
S. Kuwata, and Y. Mizobe, Acc. Chem. Res., 33, 46 (2000). c) R.
Llusar and S. Uriel, Eur. J. Inorg. Chem., 2003, 1271, and
references cited therein.
diffraction study (Figure 1).5 Cluster 1 makes an adduct with
one molecule of DMAD which bridges over Ru, S1, S2, and
S4 atoms, in which two sulfur–sulfur bonds and two rutheni-
um–iron bonds were cleaved as a result of the incorporation of
DMAD: The distances of S1–C2, S2–C1, and S4–C2 are
6
7
ꢀ
1.883(10), 1.692(7), and 1.971(9) A, respectively, indicating
the formation of three carbon–sulfur bonds. The formation of
the ruthenium–carbon bond is evident from the distance of
ꢀ
Ru–C1 (2.091(8) A). The distance of Fe1–Fe2 (2.6524(11) A)
is in the normal range expected for the single iron–iron bonds,
ꢀ
whereas the distances of Ru–Fe1 (3.5005(10) A) and Ru–Fe2
ꢀ
(3.4597(10) A) indicate the absence of the ruthenium–iron bond.
The carbon–carbon distance in the alkenedithiolate ligand is
ꢀ
1.460(10), which is closer to that of ethane (1.54 A) than to that
8
9
2: Anal. Found: C, 42.44; H, 2.75%. Calcd for C96H76B2F48
-
ꢀ
Fe2Ru2S4Si4: C, 42.43; H, 2.82%. MS (FAB) m=z 992 (Mþ, 100).
3: Anal. Found: C, 32.85; H, 4.50%. Calcd for C37H62F12
-
Fe2P2Ru2S4Si4: C, 32.89; H, 4.62%. MS (FAB) m=z 1062 (Mþ,
100).
10 a) H. Diller, H. Keck, H. Wunderlich, and W. Kuchen, J. Organo-
met. Chem., 489, 123 (1995). b) H. Seino, T. Kaneko, S. Fujii, M.
Hidai, and Y. Mizobe, Inorg. Chem., 42, 4585 (2003).
ꢀ
of ethene (1.33 A).
11 4: Anal. Found: C, 42.60; H, 3.70%. Calcd for C65H65BF24
-
Fe2O4RuS4Si4: C, 42.65; H, 3.58%. MS (FAB) m=z 968 (Mþ, 91).
12 T. Shibahara, G. Sakane, and S. Mochida, J. Am. Chem. Soc., 115,
10408 (1993).
In conclusion, we achieved the stepwise construction of
Fe2RuS4 (1) and Fe2Ru2S4 (2) clusters by the reaction of
CpS22Fe2S4 with [CpRu(MeCN)3]þ. Further treatment of the
Published on the web (Advance View) August 7, 2004; DOI 10.1246/cl.2004.1130