On rhodium(III) chloride complexes with N,N-dimethylformamide

Article abstract of DOI:10.1134/S1070328407030074

A prolonged storage of a solution of RhCl₃?nH₂O in N,N-dimethylformamide (DMF) at room temperature is attended by the consecutive formation of two precipitates, which mainly contain the [(CH ₃)₂NH₂][RhCl₅(DMF)] complex (I) and the complex [RhCl₃(DMF)₃] (II) liberates. The addition of PPh₄Cl to an aqueous solution of complex I brings about the precipitation of [PPh₄][RhCl₄(H₂O)₂] (III). Complex II (a mixture of mer-and fac-isomers) can be obtained also by treatment of [RhCl₃(CH₃CN)₃] with DMF. In the course of the latter reaction, the formation of intermediate complex [RhCl ₃(CH₃CN)₂(DMF)] (IV) is observed. Complexes I-IV are characterized by elemental analysis; complexes I, II, and IV are characterized by the IR and ¹H and ¹³C NMR spectra. The structures of III and IV are determined by X-ray diffraction analysis. Nauka/Interperiodica 2007.

Full text of DOI:10.1134/S1070328407030074

ISSN 1070-3284, Russian Journal of Coordination Chemistry, 2007, Vol. 33, No. 3, pp. 194–202. © Pleiades Publishing, Ltd., 2007.
Original Russian Text © Yu.S. Varshavskii, T.G. Cherkasova, V.N. Khrustalev, I.S. Podkorytov, A.B. Nikol’skii, 2007, published in Koordinatsionnaya Khimiya, 2007, Vol. 33,
No. 3, pp. 202–210.
On Rhodium(III) Chloride Complexes
with N,N-Dimethylformamide
Yu. S. Varshavskiia, T. G. Cherkasovaa, V. N. Khrustalevb, I. S. Podkorytovc,
and A. B. Nikol’skiia
a Research Institute of Chemistry, St. Petersburg State University,
Universitetskii pr. 26, Petrodvorets, St. Petersburg, 198504 Russia
b Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
ul. Vavilova 28, Moscow, 119991 Russia
c Lebedev Research Institute of Synthetic Rubber, ul. Gapsal’skaya 1, St. Petersburg, 198035 Russia
Received February 16, 2006
Abstract—A prolonged storage of a solution of RhCl3 · nH2O in N,N-dimethylformamide (DMF) at room tem-
perature is attended by the consecutive formation of two precipitates, which mainly contain the
[(CH3)2NH2][RhCl5(DMF)] complex (I) and the complex [RhCl3(DMF)3] (II) liberates. The addition of PPh4Cl
to an aqueous solution of complex I brings about the precipitation of [PPh4][RhCl4(H2O)2] (III). Complex II
(a mixture of mer- and fac-isomers) can be obtained also by treatment of [RhCl3(CH3CN)3] with DMF. In the
course of the latter reaction, the formation of intermediate complex [RhCl3(CH3CN)2(DMF)] (IV) is observed.
Complexes I–IV are characterized by elemental analysis; complexes I, II, and IV are characterized by the IR
and 1H and 13C NMR spectra. The structures of III and IV are determined by X-ray diffraction analysis.
DOI: 10.1134/S1070328407030074
N,N-dimethylformamide (DMF) has been widely [(CH3)2NH2]2[RhCl5(DMF)] (I). The filtrate was
used within the latter four decades as carbonylating
agent in the synthesis of Rh(I) carbonyl complexes [1–8].
The authors of [9, 10] returned to the studies of these
reactions and, at the same time, characterized some
Rh(III) complexes formed on interaction of Rh(III)
chloride with DMF. In this publication, we report new
data on Rh(III) chloride complexes containing coordi-
nated DMF molecules.
retained for further storage. Twenty days after the
beginning of the experiment, a new light brown precip-
itate (product 2) was separated from the solution and
identified as [RhCl3(DMF)3] (II). The compositions of
both precipitates varied slightly from experiment to
experiment. Although the elemental analyses of prod-
ucts 1 and 2, which precipitated from a solution of
RhCl3 · nH2O in DMF can be considered satisfactory,
the detailed comparison of the IR and 1H NMR spectra
with the analytical data shows that each product con-
tains small quantities of another product as an impurity
and also contains admixtures of the other related com-
pounds, for example, [(CH3)2NH2][RhCl4(DMF)(H2O)],
[(CH3)2NH2][RhCl4(DMF)2], etc. (Obviously, the pre-
cipitate with the molar ratio Cl : Rh = 4.2, which
formed in small quantity and was filtered off 15 days
after the beginning of the experiment, also belongs to
this type of salts.) In 40 days, one more portion of the
precipitate was filtered off; its composition and spec-
trum coincided with those of salt I, separated at the
beginning of the process. The dimethylammonium cat-
ion, contained in the above salt products, is likely to be
resulted from the of known reaction of gradual decom-
position of DMF [11] under the action of the acid
agents present in the solution (excess hydrochloric
acid, the acidity of hydrated Rh chloride itself):
Since the commercial samples of Rh(III) chloride
significantly differ in the content of water of crystalli-
zation and free HCl, we made an attempt to standardize
them to some extent by repeated (two to three times)
evaporation of an aqueous solution of commercial
grade sample on a water bath. According to the analyt-
ical data, the molar ratio Cl : Rh in the samples we used
decreased in this case from ~3.6 to 3.1; at the same
time, the acidity of their aqueous solutions decreased
(from pH ~1.60 to pH ~1.75). The results cited below
refer particularly to such standardized samples.
On prolonged storage of Rh(III) chloride solutions
in DMF, successive formation of crystalline precipi-
tates with different compositions is observed. Com-
monly, at sufficient solution concentration (near
0.4 mmol/ml), the precipitate is formed already after
2−3 days, and then its quantity gradually increases. Ten
days later, we filtered cherry red precipitate (product 1)
and identified it as a demethylammonium salt
(CH3)2N(CO)H + H+
(CH3)2NH+2 + CO.
194

ON RHODIUM(III) CHLORIDE COMPLEXES
195
The observations presented in this article should be DMF (3.01, 2.85; a signal at 7.92 ppm is overlapped by
regarded not as the recommended procedure of the syn- the signal of the coordinated DMF), and the signal from
thesis of individual complexes I and II, but only as the the methyl protons of the dimethylammonium cation in
characteristics of the main products formed as a result salt admixtures, which, as was indicated above, are
of slow processes spontaneously occurring at room always present in product 2. Close to the signals from
temperature in solutions of Rh(III) chloride hydrate in the coordinated DMF protons (both methyl and
DMF.
formyl), the additional signals are commonly recorded
with δ1ç, which slightly differ (by 0.01–0.03 ppm)
from the above signals. We assumed that these signals
are due to the DMF molecules in the products of the
complex aquation. The significant and increasing with
the storage time degree of aquation of [RhCl3(DMF)3]
is confirmed by the signals in the spectra of these solu-
tions corresponding to a free DMF and by the intensity
of these signals increasing with time.
The 13C NMR spectrum of an aqueous solution of
product 2 fully agrees with such interpretation of its
proton spectrum. The highest intensities are shown by
singlets from the coordinated DMF molecules at 34.0,
39.5 ppm (the methyl carbon) and 170.1 ppm (the
formyl carbon); the splitting of the signal from the
formyl C as a result of interaction 13ë–103Rh was not
detected.
1
The H NMR spectrum of product 1 (a solution in
D2O) contains singlet signals from methyl protons of
the dimethylammonium cation (2.72 ppm), from the
methyl (2.85 and 3.01 ppm) and formyl (7.93 ppm) pro-
tons of DMF. On the basis of the spectrum of a solution
of DMF in D2O we measured and the literature data
[12], we assigned these signals to a free DMF and,
hence, can conclude that on dissolution of the complex,
the DMF molecules contained in the anion almost
quantitatively pass into the solution and are replaced by
water molecules. In addition to the indicated intense
singlets, the spectrum contains some close but weak
signals, which are likely to be due to the above admix-
tures contained in product 1.
The 13C NMR spectrum of product 1 exhibits sin-
glets from the methyl carbons of dimethylammonium
(35.4 ppm), methyl (32.0 and 37.6 ppm) and formyl
(165.5 ppm) carbons of a DMF molecule. As in the case
with the proton spectrum, the chemical shifts of DMF
almost coincide with their values in the spectrum of
DMF in D2O we measured and with the data of [12].
As with the proton spectra of product 2, these
intense singlets lie close to the additional weak signals,
which probably correspond to the DMF molecules in
the other isomeric form of the complex or the products
of its partial aquation. The spectrum also contains weak
signals that we assigned to a free DMF and the dimeth-
ylammonium cation.
Salt I was previously characterized in [10], and the
values of the chemical shifts we established for the 1H
and 13C signals in its NMR spectra satisfactorily agree
We obtained complex II free from the admixtures
with the data reported in [10]. Note that although these by interaction of DMF with the known acetonitrile
shifts correspond to free molecules [12], the authors of Rh(III) complex [RhCl3(CH3CN)3] [14–17]. Judging
[10] discovered the doublet splitting of a signal of
from the number and position of the absorption maxima
formyl C at δ13C 165.2 ppm with the spin-spin coupling ν(CN) in the IR spectra of several compounds
constant 2J(CRh) 17 Hz.
[RhCl3(CH3CN)3], we synthesized following the proce-
dures [15, 17], they were the mixtures of the mer- and
fac-isomers in the quantitative ratio that changed from
experiment to experiment. As noted in [17], the relative
content of the isomers in a particular compound
[RhCl3(CH3CN)3] depends on peculiarities of the com-
position of the initial Rh(III) chloride and on details in
the synthesis procedures. As was expected, the heating
of a solution of this complex in DMF gives the
[RhCl3(DMF)3] complex in a good yield as a mixture of
the mer- and fac-isomers. We believe that the relative
content of the isomers in the reaction product depends
on the isomeric composition of the initial acetonitrile
The addition of [PPh4]ël to an aqueous solution of
product 1 gives cherry red crystalline precipitate
[PPh4][RhCl4(H2O)2] · H2O (III). This fact suggests that
the aquation of the [RhCl5(DMF)]2– anion is attended
by removal from its coordination sphere of a portion of
chloride ions, in addition to the DMF molecule. The pH
value of an aqueous solution of a salt (~4.0) indicates
the high degree of acid dissociation of the coordinated
water molecules. The results of X-ray diffraction anal-
ysis of complex III revealed that in its anion, the coor-
dinated water molecules are cis to one another. Previ-
ously [13], the trans-diaqua anion [RhCl4(H2O)2]– in the
composition of the salt [NMe4][RhCl4(H2O)2] was
described.
1
complex. Typical examples of the H and 13C NMR
spectra of the complex thus obtained are presented in
Fig. 1. The 1H spectrum consists of three groups of sig-
nals: one group in the region of resonances of the
formyl proton and two groups in the region of the meth-
1
The H NMR spectrum of product 2 (a solution in
D2O) contains intense signals from the methyl (3.08
and 3.18 ppm) and formyl (7.92 ppm) protons of the ylprotons, each groups containing three singlets with
coordinated DMF. In addition to these signals, the spec- different intensities (Fig. 1a). We assigned the signals
trum exhibits also the signals from the protons of a free as follows. In each group, the most intense singlet cor-
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 33 No. 3 2007

196
VARSHAVSKII et al.
1
1
1
(‡)
2
2
2
3
3
3
8.05 8.00 7.95 7.90 7.85 7.80 7.75
(b)
3.20
3.15
3.10
3.05
1
2
3
171.5
171.0
170.5
170.0
169.5 δ, ppm
Fig. 1. The NMR spectra of the complex [RhCl (DMF) ] (II) obtained from [RhCl (CH CN) ] (D O solvent): (1) fac-isomer,
3
3
3
3
3
2
1
(2) mer-isomer (DMF trans-DMF), (3) mer-isomer (DMF trans-Cl). (a) 500 MHz H (fourfold increase in the vertical scale of the
formyl protons 8.05–7.75 ppm as compared with the methyl region 3.20-3.05 ppm); (b) 125 mHz C; the signals of the formyl
13
carbon nuclei.
responds to three equivalent DMF molecules in the fac- (IV). The results of the study of its molecular structure
isomer; the second (in intensity) singlet corresponds to
two equivalent DMF molecules that are trans to one
another in the mer-isomer; finally, the weakest singlet
corresponds to the DMF molecule in the mer-isomer in
the trans-position to the chloride ligand. The 13C NMR
spectrum of this complex in a region of the formyl car-
bon has the same shape (Fig. 1b). The signals from the
methyl carbons appear as singlets, most likely, due to
the fact that the chemical shifts corresponding to differ-
ent positions of the DMF molecules in the isomeric
are given below. Compound IV is insoluble in common
organic solvents; its IR spectrum contains the absorp-
tion bands due to the coordinated molecules CH3CN
and DMF. The 1H NMR spectrum of an aqueous solu-
tion of complex IV contains signals from a free and
coordinated DMF, coordinated CH3CN, and a number
of signals that are likely to be assigned to the products
of transformation of the coordinated acetonitrile [18]
that we did not identify. Note that complex IV can be
forms of [RhCl3(DMF)3] isomers are very close. Note obtained also at room temperature. Its crystals precipi-
that in this spectrum, we did not observe the splitting of tate on storage of a solution of [RhCl3(CH3CN)3] in
the signals from the formyl carbon due to the interac-
tion 13ë–103Rh either, although in this case, all the sig-
nals under consideration correspond to the coordinated
DMF molecules.
DMF already in 1–2 h.
We performed X-ray diffraction analysis of com-
plexes III and IV. In the anionic complex III, the coor-
dinated water molecules are in the cis-position to one
another (Fig. 2).The anions form infinite chains due to
hydrogen bonds involving the coordinated and solvate
water molecules and the chloride ligands (Fig. 3). The
bond lengths and bond angles in complex III are listed
in Tables 1, 2. The Rh–Cl and Rh–O bond lengths are
in a good agreement with the values found previously
in [13, 19, 20] for the anions trans-[RhCl4(H2O)2]– and
On the basis of the above data one can conclude that
product 2 spontaneously precipitated from the solutions
of Rh chloride in DMF consists almost fully of the fac-
[RhCl3(DMF)3].
Commonly, at the initial stage of the heating of a
solution of [RhCl3(CH3CN)3] in DMF, an intermediate
salmon red precipitate is formed that is dissolved on
further heating and transforms to the final product, i.e.,
[RhCl5(H2O)]2– and reflect the same geometric trans-
a
mixture of the mer- and fac-isomers of
[RhCl3(DMF)3]. According to the elemental analysis effect of the ligands: the bonds Rh–Cl and Rh–O in the
data, the composition of the intermediate precipitate trans-position to the chloride ligands are longer than
corresponds to the formula [RhCl3(CH3CN)2(DMF)]
those in the trans-position to the water molecules:
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 33 No. 3 2007

ON RHODIUM(III) CHLORIDE COMPLEXES
197
cis-[RhCl4(H2O)2]–
trans-[RhCl4(H2O)2]– [13]
[RhCl5(H2O)]2– [20]
r(Rh–Cl)av.-trans-Cl
r(Rh–Cl)-trans-O
r(Rh–O)-trans-Cl
r(Rh–O)-trans-O
2.336
2.329
2.347
2.304
2.090
2.300 (av.)
2.080 (av.)
2.032
The structure of complex IV is presented in Fig. 4.
The bond lengths and bond angles are given in Table 3.
The comparison of the values r(Rh–Cl) and r(Rh–O) in
For [(CH3)2NH2]2[RhCl5(DMF)] (C7H23N3ORhCl5)
anal. calcd. (%): Rh, 23.10; Cl, 39.79; C, 18.87; H, 5.16; N, 9.42.
Found (%): Rh, 23.46; Cl, 39.82; C, 19.58; H, 5.25; N, 9.47.
IV
and
in
the
related
complex
cis-
[RhCl3(DMSO)2(DMF)] [21] also indicated that these
bond lengths depend on the nature of the trans-ligand:
The IR spectrum (mineral oil mull), ν cm–1: 1640–
1644 vw, 1580, 1564, 1490, ~1450, 1438, 1428, 1366,
1262, 1250 sh, 1114, 1062, 1014, 890, 823, 812, 708.
Underlined wave numbers of the absorption maxima
trans-O
r(Rh–Cl) 2.2868 (IV) 2.3204 (IV);
2.336 (Ò‰Ì.) [21]
2.060 (IV)
trans-Cl
trans-S
2.366 [21]
are supposed to be due to the cation (CH3)2NH+2 . The
r(Rh–O)
2.112 [21]
1H NMR (D2O), δ, ppm: 2.72(12H) ((CH3)2NH+2 ),
3.01(3H), and 2.85 (3H) ((CH3)2NCOH), 7.93(1H)
((CH3)2NCOH). The 13C NMR (D2O), δ, ppm: 35.4
EXPERIMENTAL
((CH3)2NH+2 ), 37.6 and 32.0 ((CH3)2NCOH), 165.5
((CH3)2NCOH). The complex is soluble in water and
insoluble in organic solvents.
All the reactions were carried out in the atmosphere
of dry argon using traditional Schlenk technique. DMF
was used as received. Special purity grade acetonitrile
was distilled over calcium hydride. Diethyl ether was
kept over potassium hydroxide and then over calcium
hydride and was distilled over calcium hydride. The 1H
and 13C NMR spectra were recorded on a Bruker AM-
500 spectrometer at 500 and 125 Mhz, respectively.
The signals of the 1H and 13C nuclei of the DMF methyl
group at 2.85 and 32.0 ppm, respectively, were used as
internal standards [12]. The IR spectra (mineral oil
mulls, solutions in CHCl3) were measured on a Specord
75IR spectrometer. The pH of the solutions was mea-
sured using galvanic cell consisting of the pH-metric
electrode (a ESL-63 glass hydrogen electrode) and a
EVL-M3 silver chloride reference electrode. The emf
was measured with a pH-120.1 high-resistance voltme-
ter.
Cl(4)
O(2)
O(1)
Rh(1)
Interaction of Rh(III) chloride with DMF at
room temperature. The commercial sample of Rh(III)
chloride hydrate was dissolved in water and evaporated
on a water bath to dryness; this procedure was repeated
2–3 times. In Rh(III) chloride (standardized in this
way), the ratio Cl : Rh = 3.10 (Rh 40.26%, Cl 42.8%).
Such standardized sample (5.0 g) was dissolved in
commercial DMF (45 ml). The solution obtained (cRh =
0.44 mmol/ml) was stored in the atmosphere of argon
for 3 months. Several days later, the formation of a pre-
cipitate was observed.
Cl(2)
Cl(1)
Cl(3)
In 10 days, crystals of red color were filtered,
washed with acetone, and dried in a vacuum (the mass
of product 1was 0.68 g).
–
Fig. 2. The structure of the [RhCl (H O) ] anion in the
4
2
2
composition of III (50% probability ellipsoids).
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 33 No. 3 2007

198
VARSHAVSKII et al.
y
0
x
–
Fig. 3. H-bonded chains along the x-axis of the[RhCl (H O) ] anions and solvate water molecules (hydrogen bonds are shown in
4
2
2
the dashed lines).
In 20 days, fine crystalline precipitate of a light nals at 37.5, 32.0 and 165.5 ppm (free DMF) and
brown color was filtered off, washed with acetone, and
dried in a vacuum (the mass of product 2 was 1.24 g).
35.4 ppm (the dimethylammonium cation). The com-
pound is soluble in water, DMF, chloroform and is
insoluble in benzene, diethyl ether, hexane. The disso-
lution of the compound in chloroform, filtration of the
obtained solution, and the treatment of a residue with
For [RhCl3(DMF)3] (C9H21N3O3RhCl3)
anal. calcd. (%): Rh, 24.01; Cl, 24.81; C, 25.22; H, 4.90; N, 9.80.
Found (%):
Rh, 24.23; Cl, 25.23; C, 24.82; H, 4.91; N, 9.91.
1
benzene give the product, whose H NMR spectrum
does not contain the signal from (CH3)2NH+2 .
The IR spectrum (mineral oil mull), ν cm–1:
1635 vw, br, 1490, ~1450, 1438, 1364, 1256, 1118,
1062, 706. The spectrum contains very weak maxima at
Interaction of [(CH3)2NH2]2[RhCl5(DMF)] with
[PPh4]Cl. A solution of [PPh4]Cl (0.37 g, 0.99 mmol)
in water (3 ml) was added to a solution of product 1
(0.4 g, 0.9 mmol) in water (3 ml) and the mixture was
allowed to stand. In 4 h, the obtained crystals of red
color were washed with water and acetone. The yield
was 0.48 g (85%).
1013, 890, 822, 819 cm–1 (the cation (CH3)2NH+2 ). The
1H NMR (D2O), δ, ppm: 3.18(3H) and 3.08(3H)
((CH3)2NCOH), 7.92(1H) ((CH3)2NCOH). In addition
to these signals, the spectrum contains the signals from
the protons of a free DMF (3.01, 2.85, 7.92 ppm),
sometime the signals at ~3.17, 3.09, 7.97 ppm from the
isomeric and/or aquated forms of the complex, and a
weak signal at 2.72 ppm (the (CH3)2NH+2 cation in the
For [PPh4][RhCl4(H2O)2] · H2O (C24H26O3PRhCl4)
salt admixtures). The 13ë NMR, (D2O), δ, ppm: 39.5,
34.0 ((CH3)2NCOH), 170.1 ((CH3)2NCOH); weak sig-
anal. calcd. (%): Rh, 16.12; Cl, 22.22; C, 45.16; H, 4.07.
Found (%):
Rh, 16.29; Cl, 22.48; C, 44.92; H, 3.97.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 33 No. 3 2007

ON RHODIUM(III) CHLORIDE COMPLEXES
199
Table 1. Selected bond lengths and bond angles in the [RhCl4(H2O)2]– anion of complex III
Bond
d, Å
Angle
ω, deg
Angle
ω, deg
Rh(1)–O(2)
Rh(1)–O(1)
Rh(1)–Cl(1)
2.074(4)
2.086(4)
2.2980(14)
O(2)Rh(1)O(1)
O(2)Rh(1)Cl(1)
86.85(15)
91.36(11)
Cl(1)Rh(1)Cl(4)
Cl(2)Rh(1)Cl(4)
93.91(5)
90.04(5)
O(1)Rh(1)Cl(1)
O(2)Rh(1)Cl(2)
177.12(11)
175.74(11)
O(2)Rh(1)Cl(3)
O(1)Rh(1)Cl(3)
88.69(11)
89.48(11)
Rh(1)–Cl(2)
Rh(1)–Cl(4)
Rh(1)–Cl(3)
2.3025(14)
2.3314(14)
2.3407(14)
O(1)Rh(1)Cl(2)
Cl(1)Rh(1)Cl(2)
O(2)Rh(1)Cl(4)
O(1)Rh(1)Cl(4)
90.17(11)
91.74(5)
Cl(1)Rh(1)Cl(3)
Cl(2)Rh(1)Cl(3)
Cl(4)Rh(1)Cl(3)
88.23(5)
94.33(5)
175.08(5)
86.83(11)
88.24(11)
Table 2. Hydrogen bonds in the structure of [PPh4][RhCl4(H2O)2] · H2O (III)
Distance, Å
Symmetry
transformation
D–H···A
DHA angle, deg
D–H
H···A
D···A
O(1)–H(1OA)···Cl(3)
O(1)–H(1OB)···Cl(2)
O(2)–H(2OA)···Cl(1)
O(2)–H(2OB)···O(3)
O(3)–H(3OA)···Cl(4)
O(3)–H(3OB)···Cl(3)
0.91
0.98
0.93
0.90
0.89
0.97
2.26
2.22
2.12
1.73
2.24
2.32
3.116(5)
3.126(5)
3.026(5)
2.632(6)
3.130(5)
3.257(5)
157
153
162
176
177
163
[–x + 1, –y, –z + 1]
[–x + 1, –y, –z + 1]
[–x + 2, –y, –z + 1]
[–x + 2, –y, –z + 1]
The compound has a limited solubility in DMF; it is powdered light brown solid was filtered off, washed
with acetone, and dried in a vacuum for 5 h. The yield
was 1.34 g (80%). The compound is soluble is water,
DMF and insoluble in benzene, diethyl ether, hexane.
insoluble in water, acetone and the other organic sol-
vents.
Synthesis of complex II. A suspension of the com-
plex [RhCl3(CH3CN)3] [15, 17] (1.3 g, 3.9 mmol) in
DMF (13 ml) was stirred at 80°C. The initial complex
dissolved quickly to form a brown-red solution. In ~10
min, the precipitate of a salmon-red color was formed
that was identified as [RhCl3(CH3CN)2(DMF)] (IV). On
further heating of the reaction mixture, the precipitate
For [RhCl3(DMF)3](C9H21N3O3RhCl3)
anal. calcd. (%): Rh, 24.01; Cl, 24.82; C, 25.22; H, 4.90; N, 9.80.
Found (%):
Rh, 24.11; Cl, 24.75; C, 25.25; H, 4.91; N, 9.64.
The IR spectrum (mineral oil mull), ν cm–1:
1635 vw, br, 1486, 1430, 1364, 1255, 1154 vw, 1116,
1060 w, 704. The 1H NMR (freshly prepared solution in
D2O), δ, ppm: 3.18, 3.08 ((CH3)2NCOH), 7.92
((CH3)2NCOH) (presumably the fac-isomer); 3.20, 3.11
((CH3)2NCOH), 7.88 ((CH3)2NCOH) (presumably DMF
trans-Cl in the mer-isomer); 3.17, 3.05 ((CH3)2NCOH),
7.84 ((CH3)2NCOH) (presumably DMF trans-DMF in
the mer-isomer). In addition to these signals, the spec-
trum contains also the signals from the protons of a free
DMF (3.01, 2.85, a signal at 7.92 ppm is overlapped by
a signal from the coordinated DMF). The 13C NMR
(freshly prepared solution in D2O), δ, ppm: 170.2
1
dissolved fully. The solvent was removed in a vacuum
at 60°C. Then, DMF (4 ml) was added to an oily residue
and heated at 100°C for 10 min. The solvent was again
removed in a vacuum at 60°C; evacuation was contin-
ued for 3–4 h, the product was separated by trituration
of an oily residue with some portions of benzene. The
1
The duration of this stage depends on the ratio of the mer- and
fac-isomers in the initial acetonitrile complex; if the precipitate
did not dissolv fully in 1 h, the reaction mixture was heated again
for another 10 min at 100°C. In the case of pure fac-
[RhCl (CH CN) ], no precipitate can be observed.
3
3
3
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 33 No. 3 2007

200
VARSHAVSKII et al.
C(5A)
C(4A)
C(2A)
C(3)
N(1A)
N(2A)
C(1A)
Cl(2A)
O(1)
N(1)
C(3A)
Rh(1)
C(1)
O(1A)
C(2)
Cl(1)
Cl(2)
N(2)
C(4)
C(5)
Fig. 4. The structure of complex IV (40% probability ellipsoids, the alternative position of the DMF molecule is shown in the dot-
and-dash line).
For [RhCl3(CH3CN)2(DMF)] (C7H13N3ORhCl3)
((CH3)2NCOH) (the fac-isomer) 169.7, 171.5,
((CH3)2NCOH) (the mer-isomer). The 13C nuclei of all
methyl groups are presented in the spectrum by two sin-
glets at 39.6 and 34.1 ppm.
anal. calcd. (%): Rh, 28.23; Cl, 29.18; C, 23.07; H, 3.57; N, 11.52.
Found (%):
Cl, 29.29; C, 23.24; H, 3.58; N, 11.62.
Rh, 28.30;
Synthesis of complex IV. In some experiments, the
above reaction between [RhCl3(CH3CN)3] and DMF
was terminated at the stage of formation of an interme-
diate precipitate, which was isolated and studied.A sus-
pension of [RhCl3(CH3CN)3] (0.5 g, 1.5 mmol) in DMF
The IR spectrum (mineral oil mull), ν cm–1: 2310 w,
1634 w, 1496, 1438, 1428 sh, 1416 sh, 1364, 1244,
1126, 1062, 1032, 1010, 708.
X-ray
diffraction
analysis
H2O (III)
of
and
5 ml) was stirred at 80°C. The initial complex dissolved [PPh4][RhCl4(H2O)2]
·
quickly and in 10–15 min, the precipitate of a salmon- [RhCl3(CH3CN)2(DMF)] (IV). The unit cell parame-
red color appeared. The precipitate was filtered, washed ters and reflection intensities for compounds III and IV
with acetone, and dried in a vacuum. The yield of the were measured on automated Bruker SMART 1000
precipitate varies within wide limits (up to 70%). The CCD diffractometer (λMoKα radiation, graphite mono-
compound is insoluble in common organic solvents.
chromator, ϕ and ω scan mode). The absorption correc-
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 33 No. 3 2007

ON RHODIUM(III) CHLORIDE COMPLEXES
201
Table 3. Selected bond lengths and bond angles in the struc- Table 4. The main crystallographic parameters for complex
ture of [RhCl3(CH3(CN)2(DMF)] (IV) III and IV
Value
Bond
d, Å
Bond
d, Å
Parameter
III
IV
Rh(1)–N(2)
Rh(1)–O(1)
Rh(1)–Cl(1)
Rh(1)–Cl(2)
O(1)–C(1)
1.983(3)
2.060(4)
N(1)–C(1)
N(1)–C(2)
1.351(7)
1.470(7)
1.470(7)
1.127(4)
1.446(5)
M
638.13
100(2)
P21/n
364.46
290(2)
C2/c
Temperature, K
Space group
Crystal size, mm
a, Å
2.2868(11) N(1)–C(3)
2.3204(10) N(2)–C(4)
0.32 × 0.24 × 0.18 0.12 × 0.10 × 0.08
10.7960(19)
16.420(3)
14.865(3)
90
99.705(4)
90
2597.4(8)
4
1.632
1288
11.55
0.819; 0.709
1.86–27.04
7.2079(8)
16.6545(19)
11.4052(13)
90
100.650(2)
90
1345.5(3)
4
1.799
720
18.44
0.866; 0.809
2.45–28.02
1.260(7)
C(4)–C(5)
b, Å
c, Å
Angle
ω, deg
Angle
ω, deg
α, deg
N(2)Rh(1)N(2A) 178.67(12) Cl(2)Rh(1)Cl(2A) 178.08(6)
β, deg
γ, deg
N(2)Rh(1)O(1)
N(2)Rh(1)Cl(1)
97.19(16) C(1)O(1)Rh(1) 120.6(2)
V, Å3
Z
89.34(6) C(1)N(1)C(2)
120.57(13)
120.55(12)
118.9(2)
ρ(calcd.), g cm–3
F(000)
O(1)Rh(1)Cl(1) 168.41(9) C(1)N(1)C(3)
Cl(2)Rh(1)N(2A) 89.43(8) C(2)N(1)C(3)
µ
Mo cm–1
N(2)Rh(1)Cl(2)
O(1)Rh(1)Cl(2)
90.59(8) C(4)N(2)Rh(1) 175.9(2)
Tmax; Tmin
Scan interval on 2θ,
98.50(14) O(1)C(1)N(1)
123.30(14)
179.2(3)
deg
Cl(1)Rh(1)Cl(2) 90.96(3) N(2)C(4)C(5)
Total number of re-
flections
23037
6645
Number of indepen- 5615 (Rint = 0.035) 1600 (Rint = 0.030)
dent reflections (Rint)
tion was applied for the data obtained using the SADABS
program [22]. The main crystallographic characteris-
tics and summary of data collection and refinement are
given in Table 4. The structures were solved by the
direct method and refined by the full-matrix least-
squares method in anisotropic approximation for non-
hydrogen atoms. Crystal III contains one solvate water
molecule in a unit cell. Complex IV in crystal occupies
partial position on axis 2, while DMF molecule is dis-
ordered over two positions with respect to this axis. The
hydrogen atoms of water molecules in structure III and
of acetonitrile molecules in structure IV were localized
objectively in the Fourier difference syntheses and
refined with the fixed positional and thermal parame-
ters. The positions of the remaining H atoms in struc-
tures III and IV were calculated geometrically and
refined in isotropic approximation with the fixed posi-
tional (rider model) and thermal (Uiso(H) = 1.2Ueq(C))
parameters. All the calculations were performed with
the SHELXTL PLUS program package (version 5.10)
[23]. The coordinates of the atoms, bond lengths, bond
angles, and anisotropic thermal parameters for com-
pounds III and IV are deposited with the Cambridge
Structural Database.
Number of reflec-
4916
1342
tions with I > 2σ(I)
Number of refined
parameters
298
93
R1 (for reflections
with I > 2σ(I))
0.0621
0.1544
0.0301
0.0757
wR2 (for all reflec-
tions)
GOOF
ρ
1.040
2.051/–0.867
1.041
1.050/–0.606
max/ρmin, eÅ–3
of the RF President Program for support of scientific
schools (project NSh-1060.2003.03).
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