Cleavage of hydrazine N-N bonds by RuMo3S4 cubane-type clusters

Article abstract of DOI:10.1021/ic0500560

The mixed-metal cubane-type clusters [(Cp*Mo) ₃(μ₂-S)₄RuH₂(PR ₃)]-[PF₆] [Cp* = η⁵-C ₅Me₅; R = Ph (2), Cy (5)] were effective for the N-N bond cleavage of hydrazine and phenylhydrazine via a disproportionation reaction. The ammonia cluster [(Cp*Mo)₃(μ₃-S) ₄Ru(NH₃)(PPh₃)][PF₆] (3) and/or the unprecedented double-cubane-type cluster with bridging nitrogenous ligands [{(Cp*Mo)₃-(μ₃-S)₄Ru} ₂(μ₂-NH₂)(μ₂-NHNH ₂)][PF₆]₂ (4) were isolated from the reaction mixtures, and their structures were determined by X-ray diffraction studies.

Full text of DOI:10.1021/ic0500560

Inorg. Chem. 2005, 44, 3768−3770
Cleavage of Hydrazine N−N Bonds by RuMo S Cubane-Type Clusters
3
4
Izuru Takei,† Keita Dohki,† Koji Kobayashi,† Toshiaki Suzuki,‡ and Masanobu Hidai*,†
Department of Materials Science and Technology, Faculty of Industrial Science and Technology,
Tokyo UniVersity of Science, Noda, Chiba 278-8510, Japan, and RIKEN Institute,
Wako, Saitama 351-0198, Japan
Received January 14, 2005
4
2
The mixed-metal cubane-type clusters [(Cp*Mo)
3
(
µ
3
-S)
Ph (2), Cy (5)] were effective for the
−N bond cleavage of hydrazine and phenylhydrazine via a
4
RuH
2
(PR
3
)]-
acids. In these reactions, the substrates are activated via η -
] [Cp* ) η5-C
coordination to the unique Pd or Ni atom embedded in the
[
PF
6
Me ; R )
5 5
Mo
aniline is observed when MePhNNH
proton and electron sources in the presence of Mo
3
S
4
aggregate. Further, catalytic formation of N-methyl-
is treated with certain
(M
Rh, Ir) clusters. During our continuous study of the
catalysis of cubane-type clusters, we have now found that
RuMo clusters are effective for the N-N bond cleavage
of hydrazines, and cubane-type clusters containing nitro-
genous ligands such as NH , NH , and NHNH are obtained
from the reaction mixtures.
Previously, we reported that the incomplete cubane-type
N
2
disproportionation reaction. The ammonia cluster [(Cp*Mo)
S) Ru(NH )(PPh )][PF ] (3) and/or the unprecedented double-
cubane-type cluster with bridging nitrogenous ligands [ (Cp*Mo)
-S) Ru -NH )( -NHNH )][PF (4) were isolated from the
3 3
(µ -
2 2 4
M S
4
3
3
6
5
)
{
3
-
(
µ
3
4
}
2
(µ
2
2
µ
2
2
6
]
2
3 4
S
reaction mixtures, and their structures were determined by X-ray
diffraction studies.
3
2
2
5
cluster [(Cp*Mo)
serves as a versatile precursor for the synthesis of hetero-
bimetallic MMo S (M ) Ru, Ni, and Pd) cubane-type
clusters. Thus, a heterobimetallic RuMo
a phosphine and two hydrides on the ruthenium center,
(Cp*Mo) (µ -S) RuH (PPh )][PF ] (2), is readily available
from the reaction of 1 and [RuH (PPh ] (eq 1).
3
(µ
2
-S)
3
(µ
3
-S)][PF
6
5 5
] (1, Cp* ) η -C Me )
The chemistry of cubane-type metal sulfido complexes has
been receiving much attention in relation to the active sites
of metalloenzymes such as ferredoxins and nitrogenases as
3 4
6
3 4
S cluster bearing
1
well as hydrodesulfurization catalysts. Coucouvanis et al.
[
3
3
4
2
3
6
reported that MoFe
S
3 4
and VFe
S
3 4
clusters catalytically
2
4
3 3
)
reduce hydrazine with certain proton and electron sources.
We have developed several rational synthetic routes to
various cubane-type complexes with desired metal composi-
tions, some of which show intriguing reactivities toward
3
small molecules. Clusters with a PdMo
S
3 4
or NiMo S
3 4
core
exhibit remarkable catalytic activity for some reactions of
alkynes including intramolecular cyclization of alkynoic
*
To whom correspondence should be addressed. E-mail:
hidai@rs.noda.tus.ac.jp.
†
Tokyo University of Science.
RIKEN Institute.
‡
(
(
(
1) (a) Transition Metal Sulfur Chemistry; Stiefel, E. I., Matsumoto, K.,
Eds.; American Chemical Society: Washington, DC, 1996. (b)
Shibahara, T. Coord. Chem. ReV. 1993, 123, 73. (c) Beinert, H.; Holm,
R. H.; M u¨ nck, E. Science 1997, 277, 653. (d) Hernandez-Molina, R.;
Sokolov, M. N.; Sykes, A. G. Acc. Chem. Res. 2001, 34, 223.
2) (a) Malinak, S. M.; Demadis, K. D.; Coucouvanis, D. J. Am. Chem.
Soc. 1995, 117, 3126. (b) Coucouvanis, D.; Demadis, K. D.; Malinak,
S. K.; Mosier, P. E.; Tyson, M. A.; Laughlin, L. J. J. Mol. Catal. A:
Chem. 1996, 107, 123. (c) Demadis, K. D.; Malinak, S. M.;
Coucouvanis, D. Inorg. Chem. 1996, 35, 4038 and references therein.
3) (a) Hidai, M.; Kuwata, S.; Mizobe, Y. Acc. Chem. Res. 2000, 33, 46.
Reaction of cluster 2 with 20 equiv (1 equiv ) 1 mol per
mole of cluster 2) of anhydrous hydrazine in THF at room
(4) (a) Murata, T.; Mizobe, Y.; Gao, H.; Ishii, Y.; Wakabayashi, T.;
Nakano, F.; Tanase, T.; Yano, S.; Hidai, M.; Echizen, I.; Nanikawa,
H.; Motomura, S. J. Am. Chem. Soc. 1994, 116, 3389. (b) Wakaba-
yashi, T.; Ishii, Y.; Murata, T.; Mizobe, Y.; Hidai, M. Tetrahedron
Lett. 1995, 36, 5585. (c) Wakabayashi, T.; Ishii, Y.; Ishikawa, K.;
Hidai, M. Angew. Chem., Int. Ed. Engl. 1996, 35, 2123. (d) Takei, I.;
Wakebe, Y.; Suzuki, K.; Enta, Y.; Suzuki, T.; Mizobe, Y.; Hidai, M.
Organometallics 2003, 22, 4639.
(b) Hidai, M.; Ishii, Y.; Kuwata, S. In Modern Coordination Chemistry;
Leigh, G. J., Winterton, N., Eds.; Royal Society of Chemistry:
Cambridge, U.K., 2002; pp 208-216. (c) Hidai, M. In PerspectiVes
in Organometallic Chemistry, Screttas, C. G., Steele, B. R., Eds.; Royal
Society of Chemistry: Cambridge, U.K., 2003; pp 62-73.
(5) Seino, H.; Masumori, T.; Hidai, M.; Mizobe, Y. Organometallics 2003,
22, 3424.
(6) Takei, I.; Suzuki, K.; Enta, Y.; Dohki, K.; Suzuki, T.; Mizobe, Y.;
Hidai, M. Organometallics 2003, 22, 1790.
3768 Inorganic Chemistry, Vol. 44, No. 11, 2005
10.1021/ic0500560 CCC: $30.25
© 2005 American Chemical Society
Published on Web 04/27/2005

COMMUNICATION
Figure 2. Structure of [{(Cp*Mo)3(µ3-S)4Ru}2(µ2-NH2)(µ2-NHNH2)][PF6]2
(
4) showing 30% thermal ellipsoids. Hydrogen atoms and a PF6 anion are
Figure 1. Structure of [(Cp*Mo)3(µ3-S)4Ru(NH3)(PPh3)][PF6] (3) showing
0% thermal ellipsoids. Hydrogen atoms and a PF6 anion are omitted for
clarity. Selected bond lengths (Å): Ru1-Moav, 2.869(2); Mo-Moav,
.877(2); Ru1-N1, 2.30(2); Ru1-P1, 2.366(5).
omitted for clarity. Selected bond lengths (Å): Ru1-Ru2, 2.690(2); Ru1-
Moav, 2.800(2); Ru2-Moav, 2.803(2); Mo-Moav, 2.825(2); Ru1-N1,
2.124(14); Ru2-N1, 2.085(13); Ru1-N3, 2.084(12); Ru2-N3, 2.082(13);
N1-N2, 1.46(2).
3
2
temperature for 3 h gave ammonia (1.2 equiv) and N
2
(0.45
-S)
are bridged by both a µ
hydrazido(1-) ligand (Figure 2).
2
-NH
2
2 2
amido ligand and a µ -NHNH
7
,8
equiv). Further, the ammonia cluster [(Cp*Mo)
Ru(NH )(PPh )][PF
crystals by addition of hexanes to the filtered and concen-
3
(µ
3
4
-
10
3
3
6
] (3) (0.50 equiv) was isolated as brown
The Ru-Ru distance is 2.690(2) Å, which is slightly
shorter than that of the typical Ru-Ru single bond, probably
because of the presence of bridging µ-amido and µ-hydrazido
ligands. The Ru-Mo distances [2.801(2) Å, average] and
the Mo-Mo distances [2.825(2) Å, average] in cluster 4 are
consistent with M-M single bonds, which are slightly shorter
than the corresponding Ru-Mo bonds in clusters 2 and 3.
1
trated THF solution. The H NMR spectrum of 3 (THF-d
exhibits a signal at δ 2.45 (br s, 3H) due to the NH ligand,
and the IR spectrum of 3 shows weak absorptions at 3279,
8
)
3
-
1
3
304, and 3371 cm assignable to νN-H. The molecular
structure of 3 was determined by an X-ray diffraction study,
and an ORTEP drawing of the cationic part is given in Figure
The N-N bond length of 1.46(2) Å in the µ
2
-NHNH
indicates a single bond, and the N-N axis is nearly
perpendicular to the Ru-Ru vector. The Ru face is folded
2
ligand
9
1
. The Ru-N bond distance [2.30(2) Å] is compatible with
11
conventional Ru-NH
3
bond distances. As predicted by the
2 2
N
effective atomic number (EAN) rule, the 60-electron RuMo S
3 4
with a dihedral angle of 106.6(7)° around the Ru-Ru axis.
A balanced equation for the above transformation of
hydrazine into ammonia and N
is described by eq 2.
cluster has three Ru-Mo bonds [2.869(2) Å, average] and
three Mo-Mo bonds [2.877(2) Å, average], which are
slightly longer than those in cluster 2 [Ru-Mo, 2.861(1) Å;
Mo-Mo, 2.848(1) Å, average]. The Ru-P bond distance
2
in the presence of cluster 2
[2.366(5) Å] is also longer than that in cluster 2 [2.328(1)
3NH NH f 4NH + N
2
(2)
2
2
3
Å]. On the other hand, the THF-insoluble precipitate
separated from the reaction mixture was recrystallized from
The effects of the reaction conditions on the transformation
of hydrazine with cluster 2 were investigated, and the typical
results are summarized in Table 1. When the reaction was
carried out in THF at 60 °C, the disproportionation reaction
proceeded catalytically. However, during the reaction, a part
of cluster 2 was transformed into the THF-insoluble double-
CH
type cluster [{(Cp*Mo)
PF (4) (0.041 equiv) as dark green crystals. The H NMR
spectrum of 4 (CD Cl ) exhibits bands at δ 4.13 (m, 2H,
NH ) and 5.07 (m, 1H, NH), indicating the presence of a
hydrazido(1-) ligand. A signal at δ 5.70 (br s, 2H) might
be due to the NH ligand. The IR spectrum of 4 shows
characteristic νN-H bands at 3290 and 3380 cm . X-ray
analysis revealed that the two RuMo cubane-type cores
2 2
Cl -hexanes to afford the unprecedented double-cubane-
3
(µ -S) Ru} (µ -NH )(µ -NHNH )]-
3
4
2
2
2
2
2
1
[
6 2
]
2
2
2
cubane-type cluster 4. The RuMo
) cyclo-C 11), [(Cp*Mo) (µ -S) RuH
prepared by the reaction of cluster 1 with [RuH
3
S
4
cluster with PCy
(PCy )][PF ] (5), was
(H
3 2
(PCy ) ]. The catalytic activity of cluster 5 for the dispro-
3
(Cy
6
H
3
3
4
2
3
6
2
-
1
2
2 2
) -
1
2
S
3 4
portionation reaction of hydrazine was higher than that of
cluster 2. In contrast to the reaction with cluster 2, the double-
cubane-type cluster 4 was obtained in moderate yield from
the reaction with cluster 5, but the corresponding ammonia
cluster was not isolated. It should be noted that ammonia
(
7) The formation of ammonia was quantitatively analyzed by the
indophenol method, and the amount of the unreacted hydrazine was
determined by the p-dimethylaminobenzaldehyde method. See: (a)
Weatherburn, M. W. Anal. Chem. 1967, 39, 971. (b) Watt, G. W.;
Chrisp, J. D. Anal. Chem. 1952, 24, 2006. (c) Takahashi, T.; Mizobe,
Y.; Sato, M.; Uchida, Y.; Hidai, M. J. Am. Chem. Soc. 1980, 102,
7
461.
(
8) The evolution of H2 (0.10 equiv) was also observed, which probably
(10) Crystallographic data for [{(Cp*Mo)3(µ3-S)4Ru}2(µ2-NH2)(µ2-NHNH2)]-
[PF6]2 (4): orthorhombic, Pban (No. 50), a ) 29.4581(9) Å, b )
arises from the reductive elimination of the two hydrides in cluster
2
9) Crystallographic data for [(Cp*Mo)3(µ3-S)4Ru(NH3)(PPh3)][PF6]
6
3
.
29.3083(11) Å, c ) 19.9652(7) Å, V ) 17237(1) Å , Z ) 12, Dcalcd
-
3
-1
(
) 2.459 g cm ; µ ) 21.997 cm , R1 ) 0.067 and wR2 ) 0.189 for
6257 unique reflections [I > 3.00σ(I)], GOF ) 1.115.
(11) (a) Heaton, B. T.; Jacob, C.; Page, P. Coord. Chem. ReV. 1996, 154,
193 and references therein. (b) Jahncke, M.; Neels, A.; Stoeckli-Evans,
H.; S u¨ ss-Fink, G. J. Organomet. Chem. 1998, 565, 97.
(12) See Supporting Information.
(
3): monoclinic, P21/c (No. 14), a ) 11.1350(7) Å, b ) 23.9955(15)
3
Å, c ) 19.7074(13) Å, â ) 95.005(3)°, V ) 5245.5(6) Å , Z ) 4,
-
3
-1
Dcalcd ) 1.706 g cm ; µ ) 12.576 cm , R1 ) 0.065 and wR2 )
.165 for 3816 unique reflections [I > 3.00σ(I)], GOF ) 1.078. All
0
2
structures were refined by least-squares methods against F .
Inorganic Chemistry, Vol. 44, No. 11, 2005 3769

COMMUNICATION
Table 1. Catalytic Disproportionation of Hydrazinea
nuclear and dinuclear complexes with sulfur ligands as well
as cubane-type metal sulfido clusters (vide supra). Mono-
yield of products (equiv)d
temp time
conv of
NH2NH2
1
4
b,c
NH3c
N2e
nuclear molybdenum thiolate complexes and a dinuclear
cluster
(°C)
(h)
3
4
15
f
ruthenium complex with bridging thiolate ligands promote
the catalytic disproportionation reaction of hydrazine to form
2
2
2
2
5
5
3
6
rt
3
18
18
48
18
18
18
18
1.7
3.4
5.9
11.5
3.6
15.2
6.0
1.2
3.1
6.6
12.1
4.0
20.0
6.9
0.45
0.88
1.6
3.0
1.2
0.50 0.041
0.56 0.070
0.38 0.15
0.39 0.14
f
rt
60
60
ammonia and N
2
. Furthermore, a sulfido-bridged dinuclear
f
molybdenum complex is also effective for the catalytic
rt
-
-
0.19
0.23
1
6
60
60
60
4.7
2.0
reduction of hydrazine, and a sulfido-bridged diiron(II)
0.54 0.12
0
17
compound cleaves the N-N bond of phenylhydrazine. The
<0.5
<0.1 <0.1
0
catalytic activities of clusters 2, 3, and 5 for hydrazine
disproportionation were lower than those of the mononuclear
molybdenum and dinuclear ruthenium thiolate complexes
described above.
a
Reaction conditions: cluster, 0.050 mmol; NH2NH2, 1.00 mmol; THF,
b
c
2
0 mL; under Ar. Moles of NH2NH2 consumed per mole of cluster. See
ref 7. 1 equiv ) 1 mol per mole of cluster. Determined by GLC. Room
temperature.
d
e
f
In summary, we have demonstrated the N-N bond
cluster 3 was effective for the disproportionation reaction,
cleavage of hydrazines by using RuMo
clusters and succeeded in the isolation of the ammonia cluster
and the double-cubane-type cluster with bridging NH and
NHNH ligands 4. Further investigations are now in progress
to elucidate the reaction mechanisms for the disproportion-
ation of hydrazines catalyzed by RuMo clusters.
3 4
S cubane-type
whereas the CO cluster [(Cp*Mo)
3
(µ
3 4 3
-S) Ru(CO)(PPh )]-
13
[
PF ] (6) exhibited no catalytic activity, presumably because
6
3
2
of the difficulty of substituting hydrazine for the CO ligand.
Treatment of cluster 2 with 20 equiv of phenylhydrazine
2
in THF at 60 °C for 18 h produced aniline (2.3 equiv), N
1.6 equiv), benzene (2.1 equiv), and ammonia (1.2 equiv),
2
3 4
S
(
Acknowledgment. This work was supported by the
Ministry of Education, Culture, Sports, Science and Technol-
ogy, Japan, including the “Open Research Center” Project.
and ammonia cluster 3 (0.35 equiv) was isolated from the
reaction mixture. A similar transformation of phenylhydra-
zine proceeded when cluster 5 was employed. A balanced
equation for the transformation of phenylhydrazine may be
shown in eq 3.
Supporting Information Available: Experimental details and
crystallographic data for 3 and 4. This material is available free of
charge via the Internet at http://pubs.acs.org.
2
PhNHNH f PhNH + N + PhH + NH
(3)
2
2
2
3
IC0500560
(
14) Hitchcock, P. B.; Hughes, D. L.; Maguire, M. J.; Marjani, K.; Richards,
Cleavage of hydrazine N-N bonds in relation to biological
nitrogen fixation has previously been reported for mono-
R. L. J. Chem. Soc., Dalton Trans. 1997, 4747.
(
(
15) Kuwata, S.; Mizobe, Y.; Hidai, M. Inorg. Chem. 1994, 33, 3619.
16) Block, E.; Gabriel, O.-O.; Kang, H.; Zubieta, J. J. Am. Chem. Soc.
1992, 114, 758.
(
13) The RuMo3S4 carbonyl cluster [(Cp*Mo)3(µ3-S)4Ru(CO)(PPh3)][PF6]
(
6) was prepared from the reaction of 2 with CO gas in THF (see
(17) Vela, J.; Stoian, S.; Flaschenriem, C. J.; M u¨ nck, E.; Holland, P. L. J.
Am. Chem. Soc. 2004, 126, 4522.
Supporting Information).
3770 Inorganic Chemistry, Vol. 44, No. 11, 2005