A practical synthetic method for dodecacarbonyltrimthenium, Ru3(CO)12, using ruthenium dioxide hydrate

Article abstract of DOI:10.1016/S0022-328X(99)00139-4

Ruthenium dioxide hydrate (RuO₂·xH₂O) reacts with carbon monoxide at 5-20 atm to give dodecacarbonyltriruthenium, Ru₃(CO)₁₂, in an excellent yield. Ruthenium carboxylate complexes [Ru₂(OCOR)₂(CO)₄]_n (R = H or CH₃) are almost quantitatively obtainable from the same reaction in the presence of formic or acetic acid. These isolable Ru complexes and the Ru dioxide hydrate efficiently effect a reductive carbonylation of nitrobenzene in aniline to produce N,N′-diphenylurea.

Full text of DOI:10.1016/S0022-328X(99)00139-4

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Journal of Organometallic Chemistry 584 (1999) 197–199
A practical synthetic method for dodecacarbonyltriruthenium,
Ru (CO) , using ruthenium dioxide hydrate
3
12
a,
a
a
Izumi Shimoyama *, Tetsuo Hachiya , Masatsugu Mizuguchi ,
a
a
b
Tomomichi Nakamura , Mikio Kaihara , Takao Ikariya
a
Materials and Processing Research Center, NKK Corporation, 1 Kokan-cho, Fukuyama, Hiroshima 721-8510, Japan
Faculty of Engineering, Tokyo Institute of Technology, 2-12-1, O-okayama, Meguro-ku, Tokyo 152-8552, Japan
b
Received 2 February 1999; accepted 3 March 1999
Abstract
Ruthenium dioxide hydrate (RuO ·xH O) reacts with carbon monoxide at 5–20 atm to give dodecacarbonyltriruthenium,
2
2
Ru (CO) , in an excellent yield. Ruthenium carboxylate complexes [Ru (OCOR) (CO) ] (R=H or CH ) are almost quantita-
3
12
2
2
4 n
3
tively obtainable from the same reaction in the presence of formic or acetic acid. These isolable Ru complexes and the Ru dioxide
hydrate efficiently effect a reductive carbonylation of nitrobenzene in aniline to produce N,N%-diphenylurea. © 1999 Elsevier
Science S.A. All rights reserved.
Keywords: Ruthenium oxide; Ruthenium carbonyl; Carboxylate; Carbonylation
1. Introduction
2. Results and discussion
Dodecacarbonyltriruthenium, Ru (CO)
(1), is
Complex 1 can be easily obtained in an 80% isolated
yield from the reaction of compound 2 and 20 atm of
CO at 160°C in toluene [6]. The reaction proceeds
rapidly to give a clear orange solution containing com-
plex 1 from the black suspension. On cooling the
reaction mixture, an orange crystalline compound pre-
cipitates. In aniline, the reaction gave the complex 1 in
a good yield under mild condition (5 atm of CO).
Compound 2 reacts readily with CO in aqueous formic
acid or acetic acid to give carboxylate complexes
[Ru (OCOR) (CO) ] (R=H or CH ) [7] in almost
quantitative yields. High CO pressure is required for
the reaction to take place smoothly, otherwise the
atmospheric pressure of CO in refluxing mesitylene,
acetic acid, or acetic anhydride gave the corresponding
products in poor yields. An addition of triphenylphos-
phine under the standard conditions mentioned above
resulted in several unidentified carbonyl triphenylphos-
phine complexes. Table 1 summarizes the representative
results. In contrast to the reactivity of 2, a commer-
cially available anhydrous ruthenium(IV) dioxide,
3
12
widely used as a highly efficient catalyst for many kinds
of homogeneous catalyses [1] and serves as an impor-
tant trinuclear framework in Ru cluster chemistry
[
1a,2]. For example, we have recently achieved the
complex 1 catalyzed reductive carbonylation of ni-
trobenzene to N,N%-diphenylurea [3], which is a key
intermediate of aromatic isocyanates [4]. Although the
catalyst 1 has a satisfactory activity for this carbonyla-
tion in a practical sense, it is not easily obtainable at a
reasonable cost because the known synthetic procedure
requires very high CO pressure conditions and a com-
plicated workup procedure [5]. An efficient synthetic
method is highly desirable for the further development
of the carbonylation reaction catalyzed by complex 1.
This paper discloses a practical preparative method of
complex 1 from reacting a commercially available
ruthenium dioxide hydrate (RuO ·xH O) 2 with CO
2
2
4 n
3
2
2
under mild reaction conditions and the application of 2
to a catalyst precursor for the reductive carbonylation
of nitrobenzene.
RuO , is completely inert under identical reaction con-
2
*
Corresponding author. Fax: +818-49-453840.
ditions. X-ray diffraction analyses of these two Ru
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00139-4

198
I. Shimoyama et al. / Journal of Organometallic Chemistry 584 (1999) 196–199
Table 1
Reaction of ruthenium dioxide hydrate, RuO ·xH O and CO
2
2
Solvent
CO (atm)
Temperature (°C)
Time (h)
Product
Yielda (%)
C H CH
20
5
3
160
160
145
160
2
2
1
1
Ru (CO)
80
70
96
95
6
5
3
3
12
C H NH
Ru (CO)
6
5
2
3
12
HCOOH (aq)
[Ru (OCOH) (CO) ]
2 2 4 n
CH COOH
10
[Ru (OCOCH ) (CO) ]
2 3 2 4 n
3
a
Isolated yield.
oxides show that 2 has an amorphous structure while
anhydrous RuO2 has a crystalline structure, which
might be responsible for the difference in the reactiv-
ity under mild conditions [8].
High-pressure IR spectroscopic studies [9] on the
reaction of 2 with CO in aniline under 50 atm of CO
at 160°C clearly indicate that a mononuclear pen-
In conclusion, we found that a commercially avail-
able compound 2 is a useful starting material for syn-
thesis of carbonyl cluster 1 as well as an excellent
catalyst precursor for the catalytic carbonylation of
nitrobenzene to N,N%-diphenylurea which is a key in-
termediate of aromatic isocyanates [12].
tacarbonyl ruthenium complex, Ru(CO) (wCO=1995
5
−
1
3
. Experimental
.1. Synthesis of Ru (CO) and [Ru (OCOH) (CO) ]
4 n
and 2030 cm ), is the initial product of the reaction
10]. The mononuclear carbonyl complex is then con-
[
3
verted into 1. Although the detailed mechanism of
the formation of 1 from 2 is not yet clear, CO works
as a reducing agent [1b,e] of the ruthenium oxide.
3
12
2
2
RuO ·xH O (Ru content 47 wt. %) purchased from
2
2
Nippon Engelhard was used as a starting material
without further purification. A 200 ml stainless steel
autoclave, charged with 1 g of RuO ·xH O and 50 ml
A rapid and quantitative formation of Ru(CO) or
5
complex 1 from 2 mentioned above should allow the
utilization of compound 2 as an efficient catalyst pre-
cursor for the reductive carbonylation of nitrobenzene
to N,N%-diphenylurea in aniline. As expected, the re-
action of nitrobenzene (40 mmol) in aniline (40 g)
under 50 atm of CO at 160°C with RuO ·xH O (50
2
2
of toluene, was pressurized with approximately 20
atm of CO at room temperature. The mixture was
then heated to 160°C and stirred for 2 h. On cooling
and releasing the pressure, orange compound crystal-
lized was filtered and washed with cold toluene. Iso-
lated yield; 80% (0.76 g) as the first crop. Orange
crystalline compound was identical to authentic
product, Ru (CO) : IR (KBr) 2062, 2026, 2004
2
2
mg) proceeds rapidly to give N,N%-diphenylurea in ex-
cellent yields as shown in Scheme 1. The catalytic
activity estimated by turnover frequency (TOF) is al-
most identical to that accessible with complex 1, sug-
gesting that transformation of compound 2 to the
catalytically active species via pentacarbonylruthenium
is almost quantitative during the carbonylation reac-
tion (Table 2). The Ru formate complex,
3
12
−
1
cm . Similarly, the reaction of RuO ·xH O in the
2
2
presence of aqueous formic acid or acetic acid was
carried out to form the carbonyl formate or carbonyl
acetate complex in a 96 or 95% yield, respectively. IR
analysis of these complexes indicates that they are
identical to the authentic compounds. [Ru (OCOH) -
[
Ru (OCOH) (CO) ] , obtained above, also effects the
2 2 4 n
2
2
carbonylation reaction with a similar activity to those
of 1 and 2. The formate complex decomposes possi-
bly by releasing H and CO to lead an catalytically
−1
(
CO) ] : IR (KBr) 2040, 1998, 1957 cm
.
4
n
[Ru (OCOCH ) (CO) ] : IR (KBr) 2049, 1996, 1969,
2
3 2
4 n
−1
2
2
1
952 cm
.
active ruthenium complex under the reaction condi-
tion. In fact, the high-pressure IR spectra of the car-
bonylation reaction with 1, 2 and the formate
complex showed that an identical but unidentified
−
1
carbonyl complex (wCO=1980 and 2040 cm ) can be
detected [9] at the initial stage of the reaction in all
cases. The product, N,N%-diphenylurea, quantitatively
reacts with alcohols to provide phenyl carbamic es-
ters. The same aromatic carbamates are also obtain-
able from the carbonylation of nitrobenzene catalyzed
by Ru or Pd complexes in alcohols solvents [1b,11].
Scheme 1.

I. Shimoyama et al. / Journal of Organometallic Chemistry 584 (1999) 196–199
199
Table 2
(d) Y. Tsuji, T. Ohsumi, T. Kondo Y. Watanabe, J. Organomet.
Chem. 309 (1986) 333. (e) J.F. Knifton, J. Am. Chem. Soc. 103
(1981) 3959. (f) Recent review article: T. Naota, H. Takaya, S.-I.
Murahashi, Chem. Rev. 98 (1998) 2599.
Ru complexes catalyzed reductive carbonylation of nitrobenzene to
N,N%-diphenylurea
Catalyst
Ru (mmol)
TOFa
[2] M.I. Bruce, in: G. Wilkinson, F.G.A. Stone, E.W. Abel (Eds.),
Comprehensive Organometallic Chemistry, vol. 4, Pergamon,
Oxford, 1982, p. 661, 889.
[3] (a) T. Ikariya, Shokubai Catal. 31 (1989) 271. (b) Japan Patent
Kokai 62-59251, 62-59262, 62-59253, 62-111960, 62-111958; US
Patent 4678856.
Ru (CO)
0.047
0.047
0.054
0.75
120
130
110
0
3
12
RuO ·xH O
2
2
[
Ru (OCOH) (CO) ]
2 2 4 n
RuO2
Ru black
0.99
0
[4] (a) S. Cenini, F. Ragaini, Reductive Carbonylation of Organic
Nitroaromatic Compounds, Kluwer, Dordrecht, The Nether-
lands, 1997. (b) G.W. Parshall, S.D. Ittel, Homogeneous Cataly-
sis, 2nd ed., Wiley, New York, 1992.
a
TOF, mol of N,N%-diphenylurea/mol of Ru·h.
[
5] (a) C.R. Eady, P.F. Jackson, B.F.G. Johnson, J. Lewis, M.C.
Malatesta, M. McPartlin, W.J.H. Nelson, J. Chem. Soc. Dalton
Trans. (1980) 383. (b) M.I. Bruce, C.M. Jensen, N.L. Jones,
Inorg. Syn. 26 (1989) 259.
3
.2. Measurement of TOF of reducti6e carbonylation of
nitrobenzene
In a typical experiment 0.047 mmol of RuO ·xH O,
0 mmol of nitrobenzene and 40 ml of aniline were
[6] E.A. Seddon, K.R. Seddon, The Chemistry of Ruthenium, El-
sevier, Amsterdam, 1984, p. 981.
2
2
4
[
7] (a) E.A. Seddon, K.R. Seddon, The Chemistry of Ruthenium,
Elsevier, Amsterdam, 1984, pp. 894. (b) G.R. Crooks, B.F.G.
Johnson, J. Lewis, I.G. Williams, G. Gamlen, J. Chem. Soc. A
placed in a 100-ml stainless steel autoclave. The reactor
was flushed with CO and pressured to 50 atm with CO.
The mixture was heated to 160°C with agitation, held
at this temperature for 2 h. On cooling of the reactor
and releasing the CO pressure, the reaction mixture was
analyzed by LC. In some cases the reaction mixture was
filtered to obtain N,N%-diphenylurea as a solid. The
initial rate (TOF=mol of N,N%-diphenylurea/mol of
Ru h) was determined at the initial 30% conversion of
nitrobenzene, where the selectivity of N,N%-diphenyl-
urea was over 95%.
(
1969) 2761.
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[
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(
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[12] The authors gratefully acknowledge collaborative work with
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.