Dinuclear rhodium(II) pivalate complexes with N-donor ligands

Article abstract of DOI:10.1007/s11172-005-0293-5

Eight dinuclear rhodium(II) complexes containing various, (primarily, polyfunctional) N-donor ligands in the trans position with respect to the Rh-Rh bond were synthesized and characterized by X-ray diffraction. In the Chinese-lantern dinuclear rhodium(II) pivalates, Rh^II ₂ (μ-OOCCMe₃)₄(L)₂ (L is 2,3-diaminopyridine (2), 7,8-benzoquinoline (4), 2,2′:6′,2″-terpyridine (5), N-phenyl-o-phenylenediamine (7)), and Rh^II ₂ (μ-OOCCMe₃)₄L¹L² (3, L ¹ is 2-phenylpyridine, L² = MeCN), the steric effects of the axial ligands are most strongly reflected in the Rh-N(L) and Rh-Rh bond lengths. The introduction of chelating ligands containing a conformationally rigid chelate ring leads to the cleavage of two carboxylate bridges to form the dinuclear double-bridged structure Rh^II ₂ (μ- OOCCMe₃)₂(OCCMe₃)₂(η ²-L³)₂, where L³ is 8-amino-2,4-dimethylquinoline (6). The reaction of complex 7 containing coordinated N-phenyl-o-phenylenediamine with pyrrole-2,5-dialdehyde afforded the new Rh^II ₂(μ-OOCCMe₃)₄(L ⁴)₂ complex (8) containing 5-(1-phenyl-1-H-benzimidazol-2- yl)-1H-pyrrole-2-carbaldehyde (L⁴) in the axial positions of the dirhodium tetracarboxylate fragment. The coordinated diamine differs in reactivity from the free diamine. The reaction of the former with the above dialdehyde affords the [1+1]-condensation product, viz., 5-{(E)-[(2- anilinophenyl)imino]methyl}-1-H-pyrrole-2-carbaldehyde, whereas the reaction of unsubstituted o-phenylenediamine gives 5-{(E)-[(2-aminophenyl)imino]methyl}-1-H- pyrrole-2-carbaldehyde (L⁵) . The reaction of the latter with Rh ^II ₂(μ-OOCCMe₃)₄(H ₂O)₂ affords the dinuclear complex Rh^II ₂(μ-OOCCMe₃)₂(OOCCMe₃) ₂(η²-L⁵)₂ (9), which is an analog of complex 6 containing only two bridging carboxylate groups.

Full text of DOI:10.1007/s11172-005-0293-5

588
Russian Chemical Bulletin, International Edition, Vol. 54, No. 3, pp. 588—599, March, 2005
Dinuclear rhodium(II) pivalate complexes with Nꢀdonor ligands
A. A. Sidorov,ꢀ G. G. Aleksandrov, E. V. Pakhmutova, A. Yu. Chernyad´ev, I. L. Eremenko, and I. I. Moiseev
N. S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences,
31 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (095) 955 4835. Eꢀmail: sidorov@igic.ras.ru
Eight dinuclear rhodium(II) complexes containing various, (primarily, polyfunctional)
Nꢀdonor ligands in the trans position with respect to the Rh—Rh bond were synthesized and
characterized by Xꢀray diffraction. In the Chineseꢀlantern dinuclear rhodium(II) pivalates,
RhII2(µꢀOOCCMe3)4(L)2 (L is 2,3ꢀdiaminopyridine (2), 7,8ꢀbenzoquinoline (4), 2,2´:6´,2″ꢀterꢀ
pyridine (5), Nꢀphenylꢀoꢀphenylenediamine (7)), and RhII2(µꢀOOCCMe3)4L1L2 (3, L1 is
2ꢀphenylpyridine, L2 = MeCN), the steric effects of the axial ligands are most strongly reflected
in the Rh—N(L) and Rh—Rh bond lengths. The introduction of chelating ligands containing
a conformationally rigid chelate ring leads to the cleavage of two carboxylate bridges to form
2
the dinuclear doubleꢀbridged structure RhII2(µꢀOOCCMe3)2(OOCCMe3)2(η ꢀL3)2, where
L3 is 8ꢀaminoꢀ2,4ꢀdimethylquinoline (6). The reaction of complex 7 containing coorꢀ
dinated Nꢀphenylꢀoꢀphenylenediamine with pyrroleꢀ2,5ꢀdialdehyde afforded the new
RhII2(µꢀOOCCMe3)4(L4)2 complex (8) containing 5ꢀ(1ꢀphenylꢀ1Hꢀbenzimidazolꢀ2ꢀyl)ꢀ1Hꢀ
pyrroleꢀ2ꢀcarbaldehyde (L4) in the axial positions of the dirhodium tetracarboxylate fragment.
The coordinated diamine differs in reactivity from the free diamine. The reaction of the former
with the above dialdehyde affords the [1+1]ꢀcondensation product, viz., 5ꢀ{(E)ꢀ[(2ꢀanilinoꢀ
phenyl)imino]methyl}ꢀ1Hꢀpyrroleꢀ2ꢀcarbaldehyde, whereas the reaction of unsubstituted
oꢀphenylenediamine gives 5ꢀ{(E)ꢀ[(2ꢀaminophenyl)imino]methyl}ꢀ1Hꢀpyrroleꢀ2ꢀcarbaldeꢀ
hyde (L5). The reaction of the latter with RhII2(µꢀOOCCMe3)4(H2O)2 affords the dinuclear
2
complex RhII2(µꢀOOCCMe3)2(OOCCMe3)2(η ꢀL5)2 (9), which is an analog of complex 6
containing only two bridging carboxylate groups.
Key words: rhodium(II), dinuclear complexes, pivalate, Xꢀray diffraction study,
metal—metal bond, Nꢀdonor ligands.
The behavior of dinuclear RhII complexes with four
also contain the bulky donor tertꢀbutyl groups. In addiꢀ
tion, we examined the possibility of using the axial posiꢀ
tions in dinuclear rhodium(II) pivalates to perform conꢀ
densation of arenediamine with pyrroledialdehyde.
carboxylate bridges (soꢀcalled "lantern dimers") is charꢀ
acterized by the retention of the bimetallic tetracarboxylate
fragment in the reactions with the majority of Nꢀdonor
ligands due, in part, to stability of the Rh—Rh bond.1,2
Even the use of chelating ligands rather often leads
to monodentate coordination with retention of the
Rh2(µꢀOOCCR)4 fragment.1 This fact allows one to study
the influence of the nature of donor ligands axially coorꢀ
dinated to metal atoms on the characteristics of the
metal—metal and metal—carboxylate bonds. This, in turn,
helps in predicting ways of activation of the dinuclear
metal carboxylate fragment. In addition, the presence of a
stable metal fragment with delocalized metal—carboxyꢀ
late—metal bonds shows promise in using the axial posiꢀ
tion in complexes to perform various chemical transforꢀ
mations of a coordinated organic donor, including redox
reactions.2
Results and Discussion
The known dinuclear rhodium(II) acetate
Rh2(MeCO2)4py2 containing pyridine molecules in
the axial positions has the strong metal—metal bond
(2.3963(2) Å) combined with the strong bonds between
the rhodium atoms and the pyridine nitrogen atoms
(2.247(2) Å).3 The similar geometric parameters were obꢀ
served in the Rh2(MeCO2)4(4ꢀCN—Py)2 complex with
4ꢀpyridinecarbonitrile4 (Table 1). The presence of two
methyl groups in the α positions of the pyridine ring leads
to substantial changes in the geometric parameters. In the
Rh2(MeCO2)4(2,6ꢀMe2C5H3N)2 complex, the Rh—Rh
bond is slightly elongated (2.4137(5) Å) and the Rh—N
bond is substantially elongated (2.403(4) Å).5 In diꢀ
rhodium pivalate complexes, these effects can be more
In the present study, we used various αꢀsubstituted
pyridine derivatives as axial Nꢀdonor ligands, thus introꢀ
ducing particular disturbances in the step of formation of
dinuclear metal fragments with pivalate bridges, which
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 581—591, March, 2005.
1066ꢀ5285/05/5403ꢀ0588 © 2005 Springer Science+Business Media, Inc.

Dinuclear RhII pivalate complexes
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 3, March, 2005
589
Table 1. Selected dinuclear rhodium carboxylates with pyridine
ligands
monodentateꢀcoordinated at the pyridine nitrogen atom
to form the very strong Rh—N(py) bond (2.270(2) Å;
Fig. 1, Table 2). The metal—metal bond in the
Rh2(µꢀOOCCMe3)4 fragment of complex 2 (Rh—Rh,
2.4072(7) Å) is slightly longer than that observed in the
starting complex 1 (see Table 1), but it is shorter than that
in the known acetate complex containing the 2,6ꢀdiꢀ
methylpyridine ligands.5 In this case, the N—Rh—Rh—N
fragment remains linear (see Table 2). It should be noted
that there are intraꢀ and intermolecular hydrogen bonds
between the protons of the amino group N(2)H2, on the
one hand, and the oxygen atoms of the pivalate anion
and the nitrogen atom of the acetonitrile solvate molꢀ
ecule (N(2)—H...O(3)(OOCR), 2.966(6) and 2.21 Å;
N—H—O, 144°; N(2)—H...N(1s), 3.103(6) and 2.29 Å;
N—H—N, 155°), on the other hand, in the structure of
complex 2.
An increase in steric strain in the dinuclear system was
achieved by introducing the bulky Ph substituent at the
α position of the pyridine molecule. It appeared that
2ꢀphenylpyridine reacts with complex 1 in an acetonitrile
solution to form the unsymmetrical dinuclear "lantern
complex" (MeCN)Rh(µꢀOOCCMe3)4Rh(PhC5H4N) (3)
containing different terminal ligands, viz., acetonitrile and
phenylpyridine (see Scheme 1).
In molecule 3, the N—Rh—Rh—N fragment is nonꢀ
linear (see Table 2, Fig. 2), which is untypical of dinuclear
rhodium(II) carboxylates. The Rh—Rh—N(phenylpyriꢀ
dine) group is also nonlinear, and the Rh—N(py) bond in
this group is elongated to 2.338(3) Å (see Table 2). By
contrast, the opposite Rh—N(NCMe) bond in the linear
N—Rh—Rh fragment is rather short (2.251(3) Å; see
Table 2). The formation of this unusual unsymmetrical
"lantern dimer" is apparently attributable to competition
for the axial positions in the dinuclear tetracarboxylate
fragment between the small but weakly basic acetonitrile
molecules and the sterically unfavorable but strongly baꢀ
sic phenylpyridine molecules. As a result, intermediate
unsymmetrical complex 3 is generated, which is the most
stable compound under the reaction conditions.
Compound
Bond/Å
Rh—Rh Rh—N(L)
Referꢀ
ence
Rh2(MeCO2)4py2
Rh2(MeCO2)4(4ꢀCN—Py)2
2.3963(2) 2.247(2)
1, 3
1, 4
2.393(1)
2.243(4),
2.244(4)
Rh2(MeCO2)4(Me2py)2
Rh2(µꢀOOCCМе3)4(Et3N)2
Rh2(µꢀOOCCМе3)4(γ,γ´ꢀbpy)* 2.395(1)
2.4137(5) 2.403(4)
5
6
6
2.413(1)
2.391(2)
2.264(2),
2.224(2)
2.123(3),
2.361(3)
2.295(2)
Rh2(Me3CCO2)4Nic2
2.371(1)
2.371(5)
7
8
Rh2(Me3CCO2)4(H2O)2
* The compound is
a polymer in which the dinuclear
{Rh2(µꢀOOCCMe3)4} fragments are linked by the bridging
γ,γ´ꢀdipyridyl molecules.
pronounced due to the presence of the bulky tertꢀbutyl
substituents in the carboxylate anions. However, the
known series of rhodium(II) pivalate complexes with
Nꢀdonor ligands is limited to dinuclear complexes with
the axial triethylamine,6 γ,γ´ꢀdipyridyl,6 and 2ꢀnitroxyꢀ
ethynylnicotinamide (Nicorandil, Nic) molecules,7
among which Rh2(µꢀOOCCMe3)4(Et3N)2 is characterꢀ
ized by the largest steric strain and, correspondingly, the
longest metal—metal and metal—nitrogen bonds6 (see
Table 1).
The reactions with the use of trimethylacetate comꢀ
plexes and 2,3ꢀdiaminopyridine containing the donor NH2
group as the α substituent, afford products with similar
structures. The reaction of Rh2(µꢀOOCCMe3)4(H2O)2
(1)8 with 2,3ꢀdiaminopyridine in acetonitrile produces
the Rh2(µꢀOOCCMe3)4L2 complex (2, L is 2,3ꢀdiꢀ
aminopyridine, Scheme 1).
In spite of the fact that at least two nitrogen atoms of
2,3ꢀdiaminopyridine can be formally involved in binding
to the metal center in molecule 2, the ligand L is
Scheme 1
L is 2,3ꢀdiaminopyridine (2), 7,8ꢀbenzoquinoline (4), terpyridine (5)
i. Ar, MeCN, 20 °C.

590
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 3, March, 2005
Sidorov et al.
C(1SA)
C(2SA)
N(1SA)
C(14)
C(15)
C(6A)
C(13)
O(4A)
C(2A)
O(3A)
O(2A)
C(12)
N(1)
C(1A)
O(1A)
N(2A)
C(11)
O(1)
Rh(1)
N(3)
C(5)
Rh(1A)
N(3A)
C(11A)
N(2)
C(1)
O(2)
N(1A)
O(4)
C(15A)
C(12A)
C(13A)
C(2)
C(4)
O(3)
C(6)
N(1S)
C(2S)
C(3)
C(7)
C(8)
C(14A)
C(9)
C(1S)
C(10)
Fig. 1. Structure of complex 2.
Table 2. Selected geometric characteristics of dinuclear rhodium(II) pivalates
Comꢀ
pound
Distance/Å
Angle/deg
Rh—Rh
Rh—N
Rh—O
O—Rh—N
Rh—Rh—N
Rh—N—C
2
3
2.4072(7) 2.270(2)
2.033(2)—2.053(2)
89.09(7), 89.57(7), 176.30(5)
94.91(7), 95.17(7)
125.7(2), 115.7(2)
2.3997(6) 2.338(3) N(py)
2.251(3) N(MeCN)
2.030(3)—2.044(3)
83.9(1), 89.2(1),
94.6(1), 100.7(1)
171.36(9) Rh(py),
130.9(3), 109.7(3)
Rh(py), 175.5(4),
Rh(MeCN)
177.19(9)
Rh(MeCN)
174.1(1)
4
5
6
2.4131(8) 2.403(4)
2.4046(9) 2.343(4)
2.037(3)—2.046(3)
2.028(3)—2.040(3)
85.9(1), 98.1(1),
91.3(1), 92.8(1)
87.0(1), 93.2(1),
91.1(1), 97.1(1)
104.1(3), 131.3(3)
174.77(9)
132.2(3), 107.1(3)
2.486 (1) 2.243(7)a, 2.250(8)a 2.015(6)—2.067(6)c, 95.5(3)e, 85.1(3)f, 169.0(2)a, 169.0(2)a, 131.9(6)a, 107.9(6)a,
2.024(7)b, 2.027(7)b 2.040(6)d
101.8(3)g
93.47(8)—90.41(8) 178.85(7)
89.6(1), 95.0(1) 175.81(8)
95.2(2)b, 96.2(2)b
113.5(5)b
115.8(2)
117.6(2), 136.8(2)
137.6(4)o, 102.3(3)p
108.2(3)q
7
8
9
2.3893(6) 2.281(3)
2.4056(7) 2.301(3)
2.032(2)—2.041(2)
2.037(3)—2.054(3)
2.4651(7) 2.288(4)h, 2.048(4)i 2.042(3)—2.077(3)c, 91.6(1)j, 101.6(2)k, 173.1(1)m, 96.5(1)n
2.040(4)d
91.6(1)l
a N(py).
f O(4)—Rh(2)—N(3).
g O(2)—Rh(2)—N(3).
h Rh(1)—N(2).
j O(2)—Rh(1)—N(2).
k O(4)—Rh(1)—N(2).
l O(5)—Rh(1)—N(2).
m N(2)—Rh(1)—Rh(2).
n N(3)—Rh(1)—Rh(2).
o C(26)—N(2)—Rh(1).
p C(27)—N(2)—Rh(1).
q C(32)—N(3)—Rh(1).
b N(NH2).
c Rh—O(µꢀOOCCMe3).
d Rh—O(η ꢀOOCCMe3)aver
.
i Rh(1)—N(3).
1
e O(7)—Rh(2)—N(3).

Dinuclear RhII pivalate complexes
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 3, March, 2005
591
C(9)
C(8)
C(7)
C(6)
C(10)
C(4)
C(3)
O(3)
C(2)
O(4)
C(23)
C(1)
C(22)
C(224)
C(27)
O(2)
O(1)
C(21)
C(33)
N(2)
Rh(2)
C(28)
C(25)
C(26)
C(32)
N(1)
Rh(1)
O(6)
C(29)
C(11)
C(31)
O(5)
C(30)
C(13)
O(7)
O(8)
C(14)
C(12)
C(16)
C(19)
C(17)
C(15)
C(18)
C(20)
Fig. 2. Structure of complex 3.
It should be noted that bulkier 7,8ꢀbenzoquinoline
remains uncoordinated in an acetonitrile solution under
these conditions. However, this situation can be changed
by using a noncoordinating hydrocarbon solvent (for exꢀ
ample, toluene) instead of acetonitrile. In toluene,
the Rh2(µꢀOOCCMe3)4(bquin)2 complex (4, bquin is
7,8ꢀbenzoquinoline) (see Scheme 1) is formed in nearly
100% yield. Xꢀray diffraction study (see Table 2 and Fig. 3)
demonstrated that the Rh—Rh bond (2.4131(8) Å) in
complex 4 is substantially longer than the metal—metal
distances in dinuclear rhodium carboxylates with apical
ligands, whose coordination is sterically hindered.1—6,8 In
addition, the Rh—N bond length is as large as 2.403(4) Å,
although the N—Rh—Rh—N fragment remains nearly
linear (N—Rh—Rh, 174.1(1)°).
Formally, the geometric characteristics of the termiꢀ
nal pyridine rings in 2,2´:6´,2″ꢀterpyridine are similar to
those observed in the analogous fragment of 2ꢀphenylꢀ
pyridine. However, terpyridine contains three pyridine
rings and serves as the ligand possessing a high chelating
ability. At room temperature, terpyridine readily reacts
with complex 1 in acetonitrile to form the dinuclear
[Rh2(OOCCMe3)4terpy2] compound (5). The structure
of the latter is analogous to that of the known9 acetate
[Rh2(MeCOO)4terpy2]. In trimethylacetate complex 5
(see Scheme 1, Fig. 4), terpyridine is also monodentateꢀ
coordinated through one nitrogen atom of the termiꢀ
nal ring.
Xꢀray diffraction study demonstrated that the main
geometric parameters of complex 5 (see Table 2) are simiꢀ
lar to the characteristics of the known acetate analog,9 the
steric effects of the apical ligand in complex 5 being reꢀ
flected primarily in elongation of the Rh—N bonds
(2.343(4) Å). The formation of symmetrical dinuclear
complex 5 in acetonitrile is, apparently, attributable to
high basicity of the nitrogen atoms in the terpyridine molꢀ
ecule, which, in fact, diminishes the probability of comꢀ
petition with the nitrogen atoms of MeCN observed in
the reaction with phenylpyridine.
Therefore, the use of aminopyridine and terpyridine
in reactions with complex 1, in spite of the formal possiꢀ
bility of the formation of chelate rings with rhodium
atoms and partial cleavage of the tetrabridged carboxyꢀ
late system, did not lead to the transformation of the
{Rh2(OOCCMe3)4} fragment. In this respect, 8ꢀaminoꢀ
2,4ꢀdimethylquinoline is, apparently, more promisꢀ
ing because it contains, on the one hand, the αꢀmethyl
substituent in the pyridine ring and, on the other hand,
the amino group in the position convenient for the
formation of a stable fiveꢀmembered chelate metalloꢀ
cycle. We found that the reaction of 8ꢀaminoꢀ2,4ꢀdiꢀ
methylquinoline with Rh2(µꢀOOCCMe3)4(H2O)2 afꢀ

592
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 3, March, 2005
Sidorov et al.
C(19)
C(20)
C(18)
C(21)
C(1A)
O(1A)
O(2A)
C(17)
C(6A)
C(22)
C(11A)
O(3A)
O(4A)
C(16)
C(23)
Rh(1A)
N(1A)
N(1)
C(15)
Rh(1)
C(11)
C(23A)
O(4)
C(8)
C(14)
C(13)
O(3)
C(10)
C(6)
O(1)
C(7)
C(12)
O(2)
C(1)
C(9)
C(3)
C(2)
C(5)
C(4)
Fig. 3. Structure of complex 4.
C(7A)
C(7)
C(8)
C(6)
C(12A) C(5)
O(2A)
C(12)
O(2)
C(10)
O(3)
C(18A)
C(18)
C(17A)
C(19A)
C(17)
C(19)
C(20)
O(3A)
C(9)
C(20A)
Rh(1)
O(4)
C(11)
N(1A)
Rh(1A)
O(4A)
C(21A)
N(2A)
N(1)
C(21)
N(2)
C(13)
C(14)
C(15)
C(22)
C(28)
O(1A)
O(1)
C(29)
C(30)
C(1)
C(4)
C(23)
C(27)
C(26)
C(16)
C(3)
C(2)
C(24)
N(3A)
C(25)
C(3A)
C(31)
N(3)
Fig. 4. Structure of complex 5.
forded the dinuclear Rh2(η2ꢀ{Me2(C9H4N)NH2})2(µꢀ
OOCCMe3)2(OOCCMe3)2 complex (6) containing only
two bridging pivalate ligands (Scheme 2, Fig. 5). In comꢀ
plex 6, the metal—metal bond is substantially elongated
(Rh—Rh, 2.486(1) Å).
The fiveꢀmembered metallocycles adopt an envelope
conformation.10 The N(2) and N(4) atoms deviate from
the planes passing through the other four atoms of the
corresponding metallocycles by 0.47 and 0.55 Å, respecꢀ
tively. The Rh—N(py)aver bond length (2.246(8) Å) has a

Dinuclear RhII pivalate complexes
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 3, March, 2005
593
C(2)
C(7)
C(6)
C(1)
C(23)
C(24)
C(22)
O(1)
C(21)
O(3)
O(2)
O(4)
N(3)
C(25)
C(26)
N(1)
Rh(1)
C(29)
C(33)
C(34)
C(32)
C(27)
Rh(2)
C(28)
C(40)
C(35)
C(37)
C(36)
N(2)
O(6)
O(5)
C(11)
C(39)
N(4)
O(7)
C(38)
C(16)
C(12)
O(8)
C(17)
Fig. 5. Structure of complex 6.
Scheme 2
late with 8ꢀaminoꢀ2,4ꢀdimethylquinoline begins with the
binding of the rhodium atoms to the nitrogen atom of the
heterocycle and, due to planarity of the bicyclic 8ꢀaminoꢀ
2,4ꢀdimethylquinoline molecule, leads finally to the forꢀ
mation of the chelate ring and the transformation into the
doubleꢀbridged metal carboxylate fragment.
For RhII carboxylates, coordination of the primary
amino groups bound to the aromatic ring can occur in the
absence of competition with the more basic pyridine niꢀ
trogen atom. However, the reaction with oꢀphenylenediꢀ
amine (containing no pyridine fragments) affords a gelꢀ
like product, which has, apparently, a polymeric structure
due to bridging coordination of the diamine that links the
Rh2(µꢀOOCCMe3)4 fragments.11 A dinuclear molecular
system can be formed using Nꢀphenylꢀoꢀphenylenediꢀ
amine containing the nonequivalent amino groups. The
NH2 group is more reactive. Earlier, it has been found
that this group is easily bound to the dinuclear nickel(II)
tetrapivalate fragment.12 It appeared that the reaction of 1
with Nꢀphenylꢀoꢀphenylenediamine in toluene afforded
the Rh2(µꢀOOCCMe3)4(PhHN(C6H4)NH2)2 complex (7,
Scheme 3, Fig. 6) in high yield. Xꢀray diffraction study
demonstrated that molecule 7 retains the dinuclear
tetracarboxylate metal fragment (Rh—Rh, 2.3893(6) Å),
and the diamine is coordinated to the rhodium atom as a
monodentate ligand through the primary amino group
(Rh—N, 2.281(3) Å). Since the diphenylamino fragment
of the ligand has no short contacts with the dinuclear
metal carboxylate fragment, the geometric characteristics
i. Ar, C6H6, Rhat : L = 1 : 1.
typical value, whereas the average distance to the amino
groups, whose lone pairs are more accessible (compared
to the lone pair of the pyridine fragment) for the interacꢀ
tion with metal, is substantially shorter (Rh—N(NH2)aver
2.025(7) Å). Taking into account the above results, it can
,
be hypothesized that the reaction of the starting carboxyꢀ

594
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 3, March, 2005
Sidorov et al.
C(43)
C(4)
C(42)
C(21)
C(41)
H(11)
C(3)
O(3)
C(6)
C(7)
O(4)
C(23)
N(2A)
C(1)
O(1)
C(2)
O(2A)
C(22)
N(1)
C(8)
C(5)
Rh(1)
O(2)
H(12)
C(9)
Rh(1A)
C(10)
N(2)
C(11)
N(1A)
O(1A)
H(21)
O(3A)
O(4A)
C(16)
C(12)
C(15)
C(14)
C(13)
Fig. 6. Structure of complex 7.
Scheme 4
of the latter (see Table 2) are similar to the usual characꢀ
teristics of the known lanternꢀtype rhodium carboxylates
with sterically unhindered apical ligands.1
Scheme 3
R = H, Rh
involves condensation of the free secondary amino group
and the coordinated primary amino group with the
dialdehyde molecule to give the fiveꢀmembered ring. Unꢀ
der the reaction conditions, the latter is oxidized to the
imidazole ring in the resulting Rh2(µꢀOOCCMe3)4(L4)2
complex (8, L4 is 5ꢀ(1ꢀphenylꢀ1Hꢀbenzimidazolꢀ2ꢀyl)ꢀ
1Hꢀpyrroleꢀ2ꢀcarbaldehyde, Scheme 5, Fig. 7).
In spite of the formation of the rather bulky Nꢀdonor
axial ligand by condensation of the coordinated diamine
molecule with dialdehyde, the tetracarboxylate fragment
Rh2(µꢀOOCCMe3)4 in complex 8 is retained. In the
dimeric fragment of the latter, the metal—metal bond is
substantially longer (Rh—Rh, 2.4056(7) Å) than that in
the starting complex 7. The Rh—N bonds are also elonꢀ
gated, the N—Rh—Rh—N fragment remaining linear (see
i. Toluene, 110 °C.
The stable dirhodium tetracarboxylate fragment is reꢀ
tained upon condensation of the coordinated Nꢀphenylꢀ
oꢀphenylenediamine molecules with pyrroleꢀ2,5ꢀdialdeꢀ
hyde. It should be noted that the free diamine reacts with
this dialdehyde to give only the [1+1]ꢀcondensation prodꢀ
uct, viz., 5ꢀ{(E)ꢀ[(2ꢀanilinophenyl)imino]methyl}ꢀ1Hꢀ
pyrroleꢀ2ꢀcarbaldehyde (Scheme 4).13
The reaction of pyrroleꢀ2,5ꢀdialdehyde with the
Rh2(µꢀOOCCMe3)4(PhHN(C6H4)NH2)2 complex (7)

Dinuclear RhII pivalate complexes
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 3, March, 2005
595
Scheme 5
the absence of the contracting effect of hydrogen bonding
between the protons of the NH group of the new ligand
and the oxygen atoms of the bridging carboxylate groups
(N(3)—H...O(1)(OOCR): N...O, 2.859 Å; H...O, 1.98 Å;
N—H—O, 166°). Apparently, condensation is determined
to a large extent by the electronic and geometric features
of the amino groups in the coordinated diamine molecule
of the starting complex 7.
The reaction of pivalate 1 with the [1+1]ꢀcondensaꢀ
tion product of pyrroleꢀ2,5ꢀdialdehyde with oꢀphenyleneꢀ
diamine (5ꢀ{(E)ꢀ[(2ꢀaminophenyl)imino]methyl}ꢀ1Hꢀ
pyrroleꢀ2ꢀcarbaldehyde14) (see Scheme 4) did not lead
to the further transformation of the [1+1]ꢀN donor.
This reaction produced the Rh2(OOCCMe3)4[NH2—
(C6H4)N(H)=C(H)—C4H2N—CHO]2 complex (9) conꢀ
taining the chelateꢀcoordinated starting ligand as the maꢀ
jor product (Scheme 6).
Chelation of the Nꢀdonor ligand causes cleavage of
two bridging pivalate groups, the terminal coordination of
the latter being stabilized by hydrogen bonding between
one proton of the NH2 groups and the uncoordinated
oxygen atoms of the monodentateꢀcoordinated carbꢀ
oxylate ligands (N(3)—H...O(6), 1.98 and 2.688 Å;
N—H—O, 148°; N(6)—H...O(8), 1.94 and 2.656 Å). In
addition, there are hydrogen bonds between the H atom
of the pyrrole ring and the O atoms of the bridging carbꢀ
oxylate ligands (N(1)—H...O(4), 2.03 and 2.888 Å;
N—H—O, 160°; N(4)—H...O(1), 1.99 and 2.872 Å;
N—H—O, 167°) (Fig. 8). In the doublyꢀbridged diꢀ
rhodium tetracarboxylate fragment, the metal—metal
bond is substantially elongated (2.4651(7) Å) compared
to that observed in the starting compound 1. The Rh—N
distances (Rh—NH2, 2.037(4) and 2.048(4) Å; Rh—N=C,
Table 2). These effects are not surprising, because the
environment of the nitrogen atom in the fiveꢀmembered
ring involved in binding to the metal atom is analogous to
the environment of the pyridine ligand containing two α
substituents. Moreover, a larger increase in the distance
between the metal atoms would, evidently, be expected in
O(5)
C(28)
C(26)
C(27)
O(4A)
N(3)
C(25)
C(3)
C(2)
O(1)
O(3A)
Rh(1A)
C(4)
C(24)
O(2)
N(1A)
O(1A)
C(1)
C(22)
C(17)
N(2)
C(23)
C(21)
Rh(1)
C(11)
O(3)
N(1)
O(2A)
C(18)
C(20)
O(4)
C(19)
C(16)
C(15)
C(6)
C(9)
C(12)
C(7)
C(14)
C(10)
C(13)
C(8)
Fig. 7. Structure of complex 8.

596
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 3, March, 2005
Sidorov et al.
Scheme 6
2,2´:6´,2″ꢀterpyridine, 8ꢀaminoꢀ2,4ꢀdimethylquinoline, and
Nꢀphenylꢀoꢀphenylenediamine (Fluka). Pyrroleꢀ2,5ꢀdialdehyde
and 5ꢀ(1ꢀphenylꢀ1Hꢀbenzimidazolꢀ2ꢀyl)ꢀ1Hꢀpyrroleꢀ2ꢀcarbꢀ
aldehyde were prepared according to a procedure described earꢀ
lier.14 The IR spectra of the complexes were recorded on a
Specord Mꢀ80 instrument in KBr pellets.
Bis(2,3ꢀdiaminopyridino)tetra(µ ꢀpivalato)dirhodium(II)
2
acetonitrile disolvate, Rh2(µꢀOOCCMe3)4((NH2)2C5H3N)2•
•2MeCN (2). Acetonitrile (10 mL) was added to a mixture
of complex 1 (0.21 g, 0.32 mmol) and 2,3ꢀdiaminopyridine
(0.07 mg, 0.64 mmol). The reaction mixture was stirred at 80 °C
for 1 h until the reagents were completely dissolved. The soluꢀ
tion was filtered off from the portion remained undissolved,
concentrated at 0.1 Torr (20 °C) to 2 mL, cooled to –5 °C, and
kept for 24 h. The red crystals that precipitated were separated
by decantation, washed with cold hexane, and dried under arꢀ
gon. The yield of 2•2MeCN was 0.11 g (38% based on rhodium).
Found (%): C, 44.5; H, 6.6; N, 12.1. C34H56N8O8Rh2. Calcuꢀ
lated (%): C, 44.84; H, 6.21; N, 12.31. IR (KBr), ν/cm–1: 3434 s,
2960 s, 2928 m, 2856 m, 1624 m, 1576 v.s, 1520 w, 1484 s,
1472 s, 1456 m, 1412 v.s, 1376 m, 1376 m, 1364 m, 1298 w,
1260 v.s, 1244 m, 1220 s, 1096 s, 1024 s, 925 w, 804 v.s, 748 w,
636 m, 460 m. The crystals were suitable for Xꢀray diffraction
analysis.
Acetonitrilo(2ꢀphenylpyridino)tetra(µ ꢀpivalato)dirhodium(II)
2
acetonitrile disolvate, Rh2(µꢀOOCCMe3)4(C5H4NC6H5)ꢀ
(MeCN)•2MeCN (3). Complex 1 (0.1 g, 0.15 mmol) was disꢀ
solved in MeCN (10 mL) and then 2ꢀphenylpyridine (0.05 mL,
0.3 mmol) was added. The reaction mixture was stirred at 20 °C
for 5 min until the reagents were completely dissolved. The
solution was filtered off from the portion remained undissolved,
concentrated at 0.1 Torr (20 °C) to 2 mL, cooled to –5 °C, and
kept for 24 h. The redꢀviolet crystals that precipitated were
separated by decantation, washed with cold hexane, and dried
under argon. The yield of 5•2MeCN was 0.1 g (71% based on
rhodium). Found (%): C, 50.4; H, 6.6; N, 6.2. C37H54N4O8Rh2.
2.288(4) and 2.285(4) Å) in the chelate metallocycle are
similar to those found in analogous complex 6 (see
Table 2).
Calculated (%): C, 50.00; H, 6.14; N, 6.31. IR (KBr), ν/cm–1
:
Investigation of the influence of the nature of the axial
Nꢀdonor ligands on the stability of the dirhodium tetraꢀ
carboxylate structure demonstrated that an increase in
the size of the α substituents leads primarily to an elongaꢀ
tion of the Rh—N bond (axial ligand) and an increase in
the deviation of this bond from the symmetry axis of the
heterocycle passing through the nitrogen atom and the
carbon atom in the para position. The presence of a donor
solvent (MeCN) can hinder the formation of symmetrical
dinuclear complexes (2ꢀphenylpyridine) or prevent coorꢀ
dination of the pyridine derivative (7,8ꢀbenzoquinoline).
The axial positions in the dinuclear dirhodium pivalate
fragment can be used to perform transformations of the
coordinated Nꢀdonors, in particular, of amines (for exꢀ
ample, in condensation with aldehyde molecules).
3434 s, 3075 w, 2958 s, 2927 s, 2856 m, 1741 w, 1584 v.s,
1483 v.s, 1457 m, 1413 v.s, 1375 s, 1361 s, 1298 w, 1222 v.s,
1160 w, 1075 w, 1022 w, 992 w, 925 w, 894 m, 802 m, 780 m,
763 s, 745 m, 701 m, 634 s, 462 s. The crystals were suitable for
Xꢀray diffraction analysis.
Di(7,8ꢀbenzoquinolino)tetra(µ ꢀpivalato)dirhodium(II),
2
Rh2(µꢀOOCCMe3)4(C13H9N)2 (4). A mixture of complex 1
(0.21 g, 0.32 mol) and benzoquinoline (0.115 g, 0.64 mmol) was
dissolved in toluene (50 mL). The reaction solution was kept at
80 °C for 0.5 h, concentrated at 0.1 Torr (~60 °C) to 2 mL, and
kept for one day. The green crystals that precipitated were sepaꢀ
rated by decantation, washed with cold hexane, and dried under
argon. The yield of 4 was 0.29 g (93%). Found (%): C, 56.8;
H, 5.3; N, 2.7. C46H54N2O8Rh2. Calculated (%): C, 57.02;
H, 5.58; N, 2.89. IR (KBr), ν/cm–1: 3108 w, 3048 w, 3004 w,
2924 s, 2904 m, 2868 w, 1716 w, 1700 w, 1664 w, 1636 m,
1616 m, 1580 v.s, 1516 w, 1480 s, 1452 m, 1412 s, 1396 m,
1356 m, 1324 m, 1288 m, 1260 v.s, 1220 s, 1156 w, 1092 v.s,
1024 v.s, 940 w, 896 w, 876 w, 828 m, 804 v.s, 724 m, 716 w,
708 w, 660 w, 632 s, 596 w, 460 m, 440 w, 400 s. The crystals
were suitable for Xꢀray diffraction analysis.
Experimental
The synthesis of the complexes was performed with the
use of commercial waterꢀfree solvents. The starting
Rh2(µꢀOOCCMe3)4(H2O)2 complex (1) was prepared accordꢀ
ing to a known procedure.8 New compounds were syntheꢀ
sized with the use of 2,3ꢀdiaminopyridine, 2ꢀphenylpyridine,
Bis(2,2´:6´,2″ꢀterpyridino)tetra(µ ꢀpivalato)dirhodium(II),
2
Rh2(µꢀOOCCMe3)4((C5H4N)2C5H3N)2 (5). Acetonitrile
(10 mL) was added to a mixture of complex 1 (0.14 g, 0.21 mmol)

Dinuclear RhII pivalate complexes
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 3, March, 2005
597
C(4)
C(2)
C(5)
C(3)
H(37A)
O(10)
C(37)
H(30A)
H(29A)
C(30)
H(35A)
C(35)
C(36)
H(4A)
N(4)
C(1)
O(1)
C(29)
C(31)
O(2)
H(31A)
C(32)
C(34)
H(34A)
H(28A)
C(9)
C(28)
C(33)
H(3E)
C(27)
N(2)
O(3)
C(7)
C(6)
C(8)
Rh(1)
C(38)
H(38A)
N(3)
N(5)
C(39)
Rh(2)
H(26A)
O(7)
H(40A)
C(40)
C(41)
H(3A)
H(1A)
O(4)
C(17)
O(5)
C(26)
C(20)
C(10)
C(44)
N(6)
C(16)
O(8)
H(6A)
O(6)
C(21)
C(22)
N(1)
H(41A)
C(19)
H(6B)
C(11)
H(22A)
C(42)
C(43)
H(43A)
C(25)
O(9)
C(23)
H(23A)
C(24)
H(42A)
C(12)
C(13)
C(15)
C(14)
H(25A)
Fig. 8. Structure of complex 9.
and terpyridine (0.05 g, 0.21 mmol). The reaction mixture was
stirred at 20 °C for 5 min until the reagents were completely
dissolved. The solution was filtered off from the portion reꢀ
mained undissolved, concentrated at 0.1 Torr (20 °C) to 2 mL,
and kept at room temperature for 24 h. The violet crystals that
precipitated were separated by decantation, washed with cold
hexane, and dried under argon. The yield of 5 was 0.09 g (39%
based on rhodium). Found (%): C, 55.5; H, 5.8; N, 7.5.
C50H58N6O8Rh2. Calculated (%): C, 55.72; H, 5.44; N, 7.81.
IR (KBr), ν/cm–1: 2960 s, 2928 s, 2858 m, 1664 m, 1584 v.s,
1560 s, 1484 s, 1460 m, 1412 v.s, 1372 s, 1360 m, 1298 w,
1260 w, 1220 v.s, 1156 w, 1075 w, 1022 w, 988 w, 896 m, 796 m,
768 v.s, 656 m, 632 s, 464 m.
1636 m, 1616 s, 1576 w, 1548 m, 1484 m, 1456 m, 1420 m,
1396 s, 1352 m, 1260 w, 1220 m, 1092 m, 1022 w, 925 w, 802 s,
768 m, 624 s, 472 m. The crystals suitable for Xꢀray diffraction
analysis were obtained by recrystallization from MeCN.
Bis(Nꢀphenylꢀoꢀphenylenediamino)tetra(µ ꢀpivalato)diꢀ
2
rhodium(II) toluene monosolvate, Rh2(µꢀOOCCMe3)4ꢀ
[N(H2)C6H4N(H)Ph]2•C6H5Me (7). A mixture of complex 1
(0.28 g, 0.43 mol) and Nꢀphenylꢀoꢀphenylenediamine (0.16 g,
0.86 mol) was dissolved in toluene (40 mL) under argon at
50—80 °C, concentrated to 5 mL at 50 °C (0.1 Torr), and cooled
to 5 °C. Large brightꢀpink prismatic crystals that precipiꢀ
tated were separated by decantation, washed with toluene, and
dried in air. The yield was 98%. Found (%): C, 58.5; H, 6.3;
N, 2.9. C51H68N2O8Rh2. Calculated (%): C, 58.74; H, 6.57;
N, 2.69. IR (KBr), ν/cm–1: 3345 v.s, 3278 v.s, 2980 v.s,
2965 v.s, 2930 s, 2870 m, 2857 m, 1590 s, 1565 v.s, 1555 s,
1505 m, 1472 v.s, 1455 m, 1400 v.s, 1368 m, 1350 m, 1330 w,
1295 s, 1262 m, 1230 w, 1210 w, 1150 w, 1075 w, 1035 w,
954 s, 900 w, 885 m, 805 m, 725 s, 695 w, 625 s, 590 w, 570 m,
455 m, 440 m. The crystals were suitable for Xꢀray diffraction
analysis.
The crystals were suitable for Xꢀray diffraction analysis.
2
Bis(η ꢀ8ꢀaminoꢀ2,4ꢀdimethylquinolino)di(µ ꢀpivalato)dipivaꢀ
2
latodirhodium(II), Rh2(µꢀOOCCMe3)4(Me2(C9H4N)NH2)2 (6).
Benzene (10 mL) was added to a mixture of complex 1 (0.1 g,
0.15 mmol) and 8ꢀaminoꢀ2,4ꢀdimethylquinoline (0.05 g
0.3 mol). The mixture was stirred at 20 °C for 5 min until the
reagents were completely dissolved. The solution was concenꢀ
trated at 0.1 Torr (20 °C) to 2 mL and kept at room temperature
for 24 h. The finelyꢀcrystalline crimson compound that precipiꢀ
tated was separated by decantation, washed with cold hexane,
and dried under argon. The yield of 6 was 0.1 g (67% based on
rhodium). Found (%): C, 52.7; H, 6.2; N, 5.5. C42H60N4O8Rh2.
Di(5ꢀ(1ꢀphenylꢀ1Hꢀbenzimidazolꢀ2ꢀyl)ꢀ1Hꢀpyrroleꢀ2ꢀcarbꢀ
aldehydo)ꢀtetra(µ ꢀpivalato)dirhodium(II) benzene pentasolvate,
2
Rh2(µ ꢀOOCCMe3)4(L4)2•5C6H6 (8) (L4 is 5ꢀ(1ꢀphenylꢀ1Hꢀ
2
benzimidazolꢀ2ꢀyl)ꢀ1Hꢀpyrroleꢀ2ꢀcarbaldehyde). Complex 7
(0.196 g, 0.2 mol) was dissolved in benzene (50 mL) under argon
and then pyrroleꢀ2,5ꢀdialdehyde (0.049 g, 0.4 mol) was added.
Calculated (%): C, 52.83; H, 6.35; N, 5.87. IR (KBr), ν/cm–1
3552 m, 3476 s, 3416 v.s, 3279 w, 2964 m, 2930 m, 2866 w,
:

598
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 3, March, 2005
Sidorov et al.
Table 3. Crystallographic parameters of the compounds under study
Parameter*
2•2MeCN 3•2MeCN
4
5
6
7•0.5MeC6H5 8•5C6H6 9•2C6H4Me2
–
–
Space group
a/Å
b/Å
P21/n
10.821(3)
12.643(4)
15.817(4)
90
94.268(5)
90
2157.9(10)
2
P21/n
P21/n
Pnma
22.317(3)
19.501(3)
11.364(2)
90
P21/n
17.901(6)
18.925(6)
13.411(5)
90
P1
C2/c
P1
13.182(4)
16.940(5)
18.529(6)
12.317(3)
11.496(2)
15.122(3)
9.404(3)
12.032(3)
12.640(3)
92.64(2)
35.844(10) 12.677(3)
12.755(4)
22.174(6)
90
13.669(3)
17.905(4)
85.940(5)
c/Å
α/deg
β/deg
γ/deg
V/Å3
Z
92.272(6)
91.654(5)
90
90
92.810(10) 107.51(2) 127.996(5) 70.917(5)
90
4538(3)
4
1.398
0.779
108.07(2)
1281.2(6)
1
1.388
0.698
90
7989(4)
4
1.308
0.474
70.917(5)
2914.3(11)
2
1.425
0.629
4134(2)
4
1.428
0.849
2140.3(8) 4945.6(15)
2
4
ρ
calc/g cm–3
1.402
0.818
1.503
0.826
1.446
0.725
µ/mm–1
Radiation
Number of
measured
reflections
Number of
nonequivalent
с I > 2σ
MoꢀKα (λ = 0.71073 Å)
16549
25080
5168
20141
7577
10118
15871
4838
4532
13806
7698
14221
7756
3017
3054
4011
R1
wR2
0.0477
0.1267
0.0558
0.1289
0.0627
0.1387
0.0552
0.1239
0.0702
0.1505
0.0276
0.0773
0.0563
0.1606
0.0595
0.1268
* The molecular formulas: 2•2MeCN, C34H56N8O8Rh2; 3•2MeCN, C37H54N4O8Rh2; 4, C46H54N2O8Rh2; 5, C50H58N6O8Rh2;
6, C42H60N4O8Rh2; 7•0.5MeC6H5, C51H68N4O8Rh2; 8•5C6H6, C86H90N6O10Rh2; 9•2C6H4Me2, C60H79N6O10Rh2.
The reaction solution was kept at ~80 °C for 20 min. Then the
darkꢀviolet solution was concentrated to 10 mL and cooled
to 20 °C. After 48 h, large red crystals were filtered off, washed
with cold hexane, and dried in vacuo. The yield was 0.161 g
(65%). Found (%): C, 56.82; H, 5.08; N, 7.14. C86H90N6O10Rh2.
procedure.15 The semiempirical absorption correction was
applied.16
The structures of all complexes were solved by direct methꢀ
ods and refined by the fullꢀmatrix leastꢀsquares method with
anisotropic displacement parameters for all nonhydrogen atoms.
The hydrogen atoms in the complexes were revealed from differꢀ
ence electron density syntheses and refined isotropically with a
common temperature factor. All calculations were carried out
using the SHELX97 program package.17
Xꢀray diffraction data for complex 7 were collected on an auꢀ
tomated fourꢀcircle Siemens P3/PC diffractometer (λ(MoꢀKα),
λ = 0.71074 Å, T = –120 °C). The unit cell parameters were
determined using 24 equivalent reflections with 2θ < 24—28°.
Three strong reflections with 0 < χ < 65° were used as the check
reflections and were measured after each 100 reflections. For
complex 7, the intensities of the check reflections showed no
decrease in the course of data collection, and therefore, special
corrections were not applied.
The structure of complex 7 was solved by direct methods
and refined by the fullꢀmatrix leastꢀsquares method with anisoꢀ
tropic displacement parameters for all nonhydrogen atoms. The
hydrogen atoms were revealed from difference Fourier syntheses
and refined isotropically. Selected geometric parameters of the
compounds are given in Table 2. The crystallographic paramꢀ
eters of the compounds are listed in Table 3. Compounds 2, 4,
and 6—8 have the crystallographic Ci symmetry, and compound 5
has the crystallographic Cs symmetry.
Calculated (%): C, 56.76; H, 5.24; N, 7.09. IR (KBr), ν/cm–1
:
3248 m, 2960 m, 2928 m, 2872 w, 1664 s, 1576 s, 1480 m,
1456 w, 1416 m, 1384 m, 1328 w, 1304 w, 1288 w, 1224 m,
1152 w, 896 w, 792 m, 768 m, 744 m, 688 m, 632 w, 464 w.
Crystals were suitable for Xꢀray diffraciton analysis.
2
Di(η ꢀ5ꢀ{(E)ꢀ[(2ꢀaminophenyl)imino]methyl}ꢀ1Hꢀpyrroleꢀ
2ꢀcarbaldehydo)di(µ ꢀpivalato)dipivalatodirhodium(II ),
2
Rh2(OOCCMe3)4(NH2—(C6H4)N=C(H)—C4H2N—CHO)2 (9).
A solution of 5ꢀ{(E)ꢀ[(2ꢀaminophenyl)imino]methyl}ꢀ1Hꢀpyrꢀ
roleꢀ2ꢀcarbaldehyde (0.045 g, 0.211 mol) in chloroform (15 mL
was added to Rh2(OOCCMe3)4•2H2O (0.072 g, 0.105 mol) disꢀ
solved in oꢀxylene (20 mL). The reaction solution was concenꢀ
trated to 15 mL (40 °C, 0.1 Torr). A red crystalline product
precipitated during slow evaporation of the solvent at room temꢀ
perature. The mother liquor was filtered off. The crystals
were washed with cold hexane and dried in vacuo. The yield
was 0.109 g (88%). Found (%): C, 57.4; H, 6.4; N, 6.8.
C60H79N6O10Rh2. Calculated (%): C, 57.69; H, 6.25; N, 6.73.
IR (KBr), ν/cm–1: 3440 m, 3280 m, 2952 m, 2928 m, 2864 w,
1672 s, 1608 m, 1584 s, 1536 s, 1480 m, 1456 s, 1416 w, 1392 m,
1352 m, 1264 m, 1216 m, 1168 m, 1120 m, 1088 w, 1048 w,
1008 w, 944 w, 904 w, 880 w, 840 w, 792 m, 776 m, 752 w, 672 w,
632 w, 568 w, 504 w, 456 w.
Xꢀray diffraction study. Xꢀray diffraction data sets for comꢀ
plexes 2—6, 8, and 9 were collected on an automated Bruker
AXS SMART diffractometer equipped with a CCD detector
(graphite monochromator, 110 K, ω scanning technique with a
step of 0.3°, exposure time per frame was 30 s) using a standard
We thank S. E. Nefedov for providing us with Xꢀray
diffraction data for compound 7.
This study was financially supported by the Russian
Foundation for Basic Research (Project Nos 04ꢀ03ꢀ32883,

Dinuclear RhII pivalate complexes
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 3, March, 2005
599
Zh. Neorg. Khim., 1996, 41, 2029 [Russ. J. Inorg. Chem.,
1996, 41, 2029 (Engl. Transl.)].
8. F. A. Cotton and T. R. Felthouse, Inorg. Chem., 1980,
19, 323.
9. N. Hirashima, S. Nusebye, Y. Muto, and M. Kato, Acta
Chem. Scand., 1990, 44, 984.
10. C. J. Hawkins, Absolute Configuration of Metal Complexes,
WileyꢀInterscience, New York—London—Sydney—Toronto,
1971, 430 pp..
11. E. V. Pakhmutova, Ph. D. (Chem.) Thesis, N. S. Kurnakov
Institute of General and Inorganic Chemistry of the Russian
Academy of Sciences, Moscow, 2003 (in Russian).
12. A. A. Sidorov, I. G. Fomina, A. E. Malkov, A. V.
Reshetnikov, G. G. Aleksandrov, V. M. Novotortsev, S. E.
Nefedov, and I. L. Eremenko, Izv. Akad. Nauk, Ser. Khim.,
2000, 1915 [Russ. Chem. Bull., Int. Ed., 2000, 49, 1887].
13. A. Yu. Chernyad´ev, Yu. A. Ustynyuk, G. G. Aleksandrov,
A. A. Sidorov, V. M. Novotortsev, V. N. Ikorskii, S. E.
Nefedov, I. L. Eremenko, and I. I. Moiseev, Izv. Akad.
Nauk, Ser. Khim., 2002, 1448 [Russ. Chem. Bull., Int. Ed.,
2002, 51, 1575].
14. A. Yu. Chernyad´ev, Yu. A. Ustynyuk, O. V. Yazev, E. A.
Kataev, M. D. Reshetova, A. A. Sidorov, G. G. Aleksandrov,
V. M. Novotortsev, V. N. Ikorskii, S. E. Nefedov, I. L.
Eremenko, and I. I. Moiseev, Izv. Akad. Nauk, Ser. Khim.,
2001, 2334 [Russ. Chem. Bull., Int. Ed., 2001, 50, 2445].
15. SMART (Control) and SAINT (Integration) Software, Verꢀ
sion 5.0, Bruker AXS Inc., Madison (WI), 1997.
16. G. M. Sheldrick, SADABS, Program for Scanning and Correcꢀ
tion of Area Detector Data, Göttingen University, Göttingen
(Germany), 1997.
02ꢀ03ꢀ33075, and 00ꢀ03ꢀ40104), the Russian Academy of
Sciences (Target Program for Basic Research of the Chemꢀ
istry and Materials Science Division of the Russian Acadꢀ
emy of Sciences "Chemistry and Physical Chemistry of
Supramolecular Systems and Atomic Clusters"), the Preꢀ
sidium of the Russian Academy of Sciences (Program for
Basic Research "Directed Synthesis of Compounds with
Desired Properties and Construction of Functional Maꢀ
terials on Their Basis," the Project "Development of Proꢀ
cedures for the Directed Design of New Molecules and
Ligands in the Inner Sphere of Monoꢀ and Polynuclear
Transition Metal Complexes"), and the Grant of the Govꢀ
ernment of Moscow ("Infrastructure and Addressed Supꢀ
port of Science").
References
1. F. A. Cotton and R. A. Walton, Multiple Bonds Between
Metal Atoms, Clarendon Press, Oxford, 1993, p. 432.
2. F. A. Cotton, G. Wilkinson, C. A. Murillo, and
M. Bochmann, Advanced Inorganic Chemistry, J. Wiley and
Sons, Inc., New York, 1999, p. 1054.
3. Y.ꢀB. Koh and G. G. Christoph, Inorg. Chem., 1978,
17, 2920.
4. F. A. Cotton and T. R. Felthouse, Acta Crystallogr., 1984,
C40, 42.
5. M. Morooka, S. Ohba, M. Nakashima, T. Tokaii, Y. Muto,
M. Kato, and O. W. Steward, Acta Crystallogr., 1992,
C48, 1888.
6. M. Handa, M. Watanabe, D. Yosioka, S. Kawabata,
R. Nukada, M. Mikuriya, H. Azuma, and K. Kasuga, Bull.
Chem. Soc. Jpn, 1999, 72, 2681.
17. G. M. Sheldrick, SHELX97, Program for the Solution of
Crystal Structures, Göttingen University, Göttingen (Gerꢀ
many), 1997.
7. I. L. Eremenko, M. A. Golubnichaya,S. E. Nefedov, I. B.
Baranovskii,I. A. Ol´tshnitskaya, O. G. Ellert, V. M.
Novotortsev, L. T. Eremenko, and D. A. Nesterenko,
Received December 15, 2004;
in revised form January 20, 2005