Solid state packing of [Rh(β-diketonato)(CO)2] complexes. Crystal structure of [Rh(PhCOCHCOC4H3S)(CO)2]

Article abstract of DOI:10.1016/j.molstruc.2013.07.046

A neutral columnar stacking of [Rh(PhCOCHCOC₄H ₃S)(CO)₂] molecules was obtained in the crystalline solid state, i.e. the complex forms molecular wires in the solid state. The metal-metal interactions of [Rh(PhCOCHCOC₄H₃S)(CO) ₂] and related [Rh(β-diketonato)(CO)₂] complexes show, that [Rh(β-diketonato)(CO)₂] complexes generally form a dimer-like arrangement, with a Rh^IRh^I distance of 3.18-3.54 A?. The dimeric units either stack in infinite chains, or interact with each other via weak Rhπ, or weak hydrogen bond interactions.

Full text of DOI:10.1016/j.molstruc.2013.07.046

Journal of Molecular Structure 1051 (2013) 137–143
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Solid state packing of [Rh(b-diketonato)(CO)2] complexes. Crystal
structure of [Rh(PhCOCHCOC4H3S)(CO)2]
⇑
Marrigje Marianne Conradie, Jeanet Conradie
Department of Chemistry, University of the Free State, P.O. Box 339, Bloemfontein 9300, South Africa
g r a p h i c a l a b s t r a c t
h i g h l i g h t s
The structure and solid state packing of complex [Rh(PhCOCHCOC4H3S)(CO)2] are compared with those of
related [Rh(b-diketonato)(CO)2] complexes.
ꢀ
ꢀ
ꢀ
Crystal structure of
[Rh(PhCOCHCOC4H3S)(CO)2].
Typical structural parameters of
[Rh(b-diketonato)(CO)2] complexes.
Metal–metal interactions in [Rh(b-
diketonato)(CO)2] complexes.
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 18 June 2013
Received in revised form 25 July 2013
Accepted 25 July 2013
Available online 8 August 2013
A neutral columnar stacking of [Rh(PhCOCHCOC4H3S)(CO)2] molecules was obtained in the crystalline
solid state, i.e. the complex forms ‘‘molecular wires’’ in the solid state. The metal–metal interactions of
[Rh(PhCOCHCOC4H3S)(CO)2] and related [Rh(b-diketonato)(CO)2] complexes show, that [Rh(b-diketo-
nato)(CO)2] complexes generally form a dimer-like arrangement, with a RhIARhI distance of 3.18–
3.54 Å. The dimeric units either stack in infinite chains, or interact with each other via weak RhAp, or
weak hydrogen bond interactions.
Keywords:
Ó 2013 Elsevier B.V. All rights reserved.
Rhodium
b-Diketone
Dicarbonyl
Metal–metal interaction
1. Introduction
[Rh(acac)(CO)2] (where acac = acetylacetonato), are catalytic pre-
cursors for the hydrogenation and for hydroformylation of unsatu-
rated alcohols [7], for the hydrogenation of alkenes [8] and for the
hydroformylation of 1-hexene [9]. Square planar 16-electron d8
rhodium(I) complexes are electron deficient and coordinatively
unsaturated, causing these systems to be prone to stacking by
allowing the formation of metal–metal bonds [10] and chains
[11,12] with weak metal–metal interactions between the rhodium
atoms [13,14]. The extended interactions are the result of metal–
The first square planar [Rh(b-diketonato)(CO)2] complex was
reported by Bonati and Wilkinson [1]. Rhodium-dicarbonyl com-
plexes are known for their application in catalysis and catalytic
precursors, for example the square planar rhodium(I) [Rh(CO)2(-
I)2]ꢁ complex, which is used for the manufacture of acetic acid,
by catalytic carbonylation of methanol [2–6]. Rhodium-dicarbonyl
complexes containing
a
b-diketonato ligand, such as
metal
r
-bonding between the square planar d8 transitional metal
complexes [15]. Examples of metal chains with strong metal–metal
bonds are known, which are catalytically active in processes, such
⇑
Corresponding author. Tel.: +27 51 4012194; fax: +27 51 4446384.
E-mail address: conradj@ufs.ac.za (J. Conradie).
0022-2860/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2013.07.046

138
M.M. Conradie, J. Conradie / Journal of Molecular Structure 1051 (2013) 137–143
as the water gas shift reaction and CO2 reduction [16]. One-dimen-
sional stacking of metal centres has led to materials with interest-
ing properties in the crystal phase, such as magnetism and
one-dimensional conductivity [15,17]. In this paper we discuss
the packing of [Rh(b-diketonato)(CO)2] complexes.
mation of the salt [NH2(CH3)2]+[Rh(CO)2Cl2]ꢁ [27]. Addition of the
b-diketone PhCOCH2COC4H3S to the reaction mixture, with an ex-
cess of water, resulted in the precipitation of the red [Rh(b-diketo-
nato)(CO)2] complex.
3.2. Structure of [Rh(PhCOCHCOC4H3S)(CO)2]
2. Experimental
The atom labelling of [Rh(PhCOCHCOC4H3S)(CO)2] is shown in
Fig. 1. Crystal data of the structure of [Rh(PhCOCHCOC4H3S)(CO)2]
is summarized in Table 1, while selected bond lengths, angles and
torsion angles can be found in Table 2. The [Rh(PhCOCHCOC4H3S)
(CO)2] molecules pack in the P212121 space group, with Z = 4. The
2.1. Synthesis
[Rh(PhCOCHCOC4H3S)(CO)2] was synthesized as described pre-
viously [18].
Rh(I) atom has
a square planar coordination sphere. The
C(1)AO(2) and C(3)AO(1) bonds in the b-diketonato skeleton of
the [Rh(b-diketonato)(CO)2] complex are 1.250(9) Å and
1.265(10) Å respectively, and is shorter than the corresponding
bonds in the free b-diketone, which are 1.268(3) Å and 1.330(3) Å
respectively. The CAO and CAC bonds of intermediate order, indi-
cate a conjugation which forms a pseudo-aromatic system. The 2-
thienyl (C4H3S) and phenyl (Ph) groups bonded to the b-diketone
backbone are both rotated out of the plane formed by the rest of
the molecule, by 2° and 15° respectively. The orientation of the
2-thienyl group bonded to a b-diketonato backbone is often flat
relative to the plane through the b-diketonato backbone
[19,30,28], while the orientation of a Ph group bonded to a b-dike-
tonato backbone is often rotated [29,30]. Although both the side
groups phenyl and 2-thienyl are aromatic, the larger angle of the
phenyl relative to the plane, compared to the angle between 2-thi-
enyl and the plane, implies that the conjugation between the pseu-
do-aromatic b-diketonato ring and the 2-thienyl is stronger than
the conjugation with the phenyl.
2.2. Crystallography
Crystals of the [Rh(PhCOCHCOC4H3S)(CO)2] complex (where
PhCOCH2COC4H3S = benzoylthienylacetone or 1-phenyl-3-(2-thie-
nyl)-1,3-propanedione [19]) were obtained with difficulty by
recrystallization from hexane. Only one crystal of [Rh(PhCOCH-
COC4H3S)(CO)2] produced an X-ray diffraction pattern that was
deemed suitable for data collection. The red crystal was mounted
on a glass fibre and used for the X-ray crystallographic analysis.
The X-ray intensity data was measured on a Bruker X8 Apex II
4K Kappa CCD diffractometer area detector system, equipped with
a graphite monochromator and a Mo K fine-focus sealed tube
a
(k = 0.71073 Å), operated at 1.5 kW power (50 kV, 30 mA). The
detector was placed at a distance of 3.75 cm from the crystal.
The crystal temperature during the data collection was kept con-
stant at 100(2) K, using an Oxford 700 series cryostream cooler.
The initial unit cell and data collection was achieved by the
Apex2 software [20], utilizing COSMO [21] for optimum collection
of more than a hemisphere of reciprocal space. A total of 1778
3.3. RhAL bonds and LARhAL0 angles in [Rh(b-diketonato)(CO)2]
complexes
frames were collected, with a scan width of 0.5° in
u and x, and
an exposure time of 40 s frameꢁ1. The frames were integrated
using a narrow-frame integration algorithm and reduced with
the Bruker SAINT-Plus [22] and XPREP [22] software packages,
respectively. The integration of the data, using a monoclinic cell,
yielded a total of 25,770 reflections to a maximum h angle of
28.5°, of which 3596 were independent, with a Rint = 0.152. Analy-
sis of the data showed no significant decay during the data
collection. Data was corrected for absorption effects, using the
multi-scan technique SADABS [23], with minimum and maximum
transmission coefficients of 0.620 and 0.937 respectively.
Selected geometric data of [Rh(PhCOCHCOC4H3S)(CO)2] is com-
pared with data of the structurally similar [Rh(b-diketonato)(CO)2]
complexes, where b-diketonato = CH3COCHCOCH3 [13], PhCOCHC-
OCH3 [31], PhCOCHCOCH2CH3 [32], PhCOCHCOCH2CH2CH3 [33],
FcCOCHCOCF3 [34] (Fc = ferrocenyl = (C5H5)Fe(C5H4)) and CF3-
COCHCOCH3 [35] in Table 2. For all these [Rh(b-diketonato)(CO)2]
complexes, the RhAO bonds of a specific complex is the same with-
in 0.01 Å, except for [Rh(FcCOCHCOCF3)(CO)2], where the RhAO
bond nearest to the ferrocenyl group is 0.03 Å longer, than the
RhAO bond nearest to the CF3 group. The difference in RhAO bonds
in the latter complex is expected, because of the strong electron
The structure was solved by the direct methods package SHEL-
XS [24] and refined using the X-Seed software package [25] incor-
porating SHELXL [24]. The final anisotropic full-matrix least-
squares refinement on F2 with 235 variables, converged at
R1 = 0.075 for the observed data and wR2 = 0.2076 for all data.
The GOF was 1.06. The largest peak on the final difference electron
density synthesis was 3.49 e Åꢁ3, at 0.5 Å from Rh1, and the deep-
est hole was ꢁ1.60 e Åꢁ3, at 0.77 Å from Rh1.
donating property of the ferrocenyl group (
vFc = 1.87 [36]), com-
pared to that of CF3 group ( CF3 = 3.01 [36]) on the b-diketonato li-
v
gand (FcCOCHCOCF3)ꢁ. This electronic trans influence of the
ferrocenyl group, should also lead to a shorter RhAC0 bond, trans
to the longer RhAO bond, but the inaccuracy of the bonds
RhAC = 1.83(2) and RhAC0 = 1.84(1) Å, prevented clear identifica-
tion of this effect in [Rh(FcCOCHCOCF3)(CO)2]. The observed short-
er RhAC0 bond, trans to the RhAO bond nearest to the electron
donating phenyl group in [Rh(PhCOCHCOCF3)(CO)2], can be due
The aromatic H atoms were placed in geometrically idealized
positions (CAH = 0.95 Å) and were constrained to ride on their par-
ent atoms with Uiso(H) = 1.2Ueq(C). Non-hydrogen atoms were re-
fined with anisotropic displacement parameters. Atomic
scattering factors were taken from the International Tables for
Crystallography, Volume C [26]. The molecular plot was drawn,
using the X-Seed programme [25].
O
O
S
-
O
O
CO
CO
Cl
Cl
CO
CO
DMF
Rh
3. Results and discussion
Rh
RhCl3.nH2O
3.1. Synthesis
S
[Rh(PhCOCHCOC4H3S)(CO)2] was synthesized as shown in
Scheme 1. Heating a DMF solution of RhCl3.nH2O, leads to the for-
Scheme 1. Synthetic route for the synthesis of [Rh(PhCOCHCOC4H3S)(CO)2] from
RhCl3.nH2O.

M.M. Conradie, J. Conradie / Journal of Molecular Structure 1051 (2013) 137–143
139
Table 1
Crystal data and structure refinement of [Rh(PhCOCHCOC4H3S)(CO)2].
Empirical
formula
Formula
weight
C15H9O4RhS
Theta range for
data collection
Index ranges
3.5–40.5°
388.19 g molꢁ1
ꢁ8 6 h 6 8
ꢁ15 6 k 6 15
ꢁ26 6 l 6 26
25770
Temperature
Wavelength
100(2) K
Reflections
collected
Independent
reflections
0.71073 Å
3596
[Rint = 0.152]
Crystal system Orthorhombic
Theta maximum
Absorption
correction
28.5°
Multi-scan
Space group
P212121
Unit cell
dimensions b = 11.4245(18) Å
c = 19.557(3) Å
a = 6.4610(9) Å
Max. and min.
transmission
0.937 and 0.620
a
= 90°
b = 90°
= 90°
c
Volume
Z
1443.6(4) Å3
Refinement
method
Data/restraints/
parameters
Goodness-of-fit
on F2
Full-matrix least-
squares on F2
3596/26/185
4
Fig. 1. Molecular plot of [Rh(PhCOCHCOC4H3S)(CO)2], showing atom labelling.
Density
(calculated)
Absorption
coefficient
(l)
1.786 Mg mꢁ3
1.34 mmꢁ1
1.06
to the electronic trans influence of the phenyl group (
vPh = 2.21
[36]), compared to that of the CF3 gꢁroup (
v
CF3 = 3.01 [36]) on the
Final R indices
[I > 2sigma(I)]
R1 = 0.075
b-diketonato ligand (PhCOCHCOCF3) . The OARhAO0 and CARhAC0
angles of the [Rh(RCOCHCO0R0)(CO)2] complexes, are the same
within 1° and 2° respectively. In summary, the bonds around the
rhodium centre of the [Rh(PhCOCHCOC4H3S)(CO)2] molecule and
the other [Rh(b-diketonato)(CO)2] molecules, are very similar
(Table 2).
F(000)
768
R indices (all
data)
R1 = 0.0747
wR2 = 0.2076
Crystal size
–
0.40 ꢃ 0.09 ꢃ 0.05
Largest diff. peak 3.49 and
mm3
–
and hole
Absolute
structure
parameter
ꢁ1.60 e Åꢁ3
0.45(10)
3.4. Packing of [Rh(b-diketonato)(CO)2] complexes
The packing diagram of the [Rh(PhCOCHCOC4H3S)(CO)2] mole-
cules, are given in Fig. 2. The main point of interest here, is that
the [Rh(PhCOCHCOC4H3S)(CO)2] molecules stack in an infinite
chain of rhodium atoms along the a-axis, with a RhꢂꢂꢂRh distance
of 3.250 Å. Neighbouring units are oriented with an angle of 180°
in the opposite direction, due to an inversion symmetry operation
(Fig. 2(a)). The rhodium atoms that form the core of a column, are
stacked in a zigzag fashion with an angle between RhꢂꢂꢂRh vectors
of 167.4°. Typical RhARh single bonds are 2.35–2.45 Å [37]. The
typical RhIARhI bond length in a dimer with true covalent bonds,
and in which there are no supporting bridge ligands between met-
als, varies from 2.82 to 3.24 Å [11,38]. However, the 3.250 Å dis-
tance between the Rh atoms in [Rh(PhCOCHCOC4H3S)(CO)2], fall
well within the typical distance between two rhodium(I) mole-
cules in extended metal chains, which have no covalent metal–me-
tal bonds, but still contain meaningful weak metal–metal
metal–metal bond, but does indicate clearly that interactions be-
tween metal atoms do exist.
Similar RhꢂꢂꢂRh interactions resulting in extended metal chains,
were also observed for [Rh(b-diketonato)(CO)2] molecules with the
b-diketonato ligand = (CH3COCHCOCH3)ꢁ, (PhCOCHCOCF3)ꢁ and
(PhCOCHCOCH3)ꢁ.
The [Rh(CH3COCHCOCH3)(CO)2] molecules consist of weak
dinuclear units, with a RhꢂꢂꢂRh distance of 3.253 Å. These [Rh(CH3-
COCHCOCH3)(CO)2] dimers are stacked along the a-axis, with a dis-
tance of 3.271 Å between the dimers, in a similar linear fashion
than the [Rh(PhCOCHCOC4H3S)(CO)2] dimers. The neighbouring
atoms in a dinuclear unit are oriented with an angle of 180° in
the opposite direction, due to an inversion symmetry operation.
A stereo view of this stacking arrangement is given in Fig. 3. The
rhodium atoms which form the core of a column, are not perfectly
aligned on top of one another, with an angle between Rhꢂ ꢂ ꢂRh vec-
tors of 175.28°.
interactions, which is
a distance between 3.25 and 3.68 Å
[11,13,14]. The 3.250 Å distance between Rh atoms in [Rh(PhC-
OCHCOC4H3S)(CO)2], is therefore too long to be considered a true
Table 2
Selected geometric and crystallographic data of square planar complexes [Rh(b-diketonato)(CO)2], where b-diketonato = (RCOCHC0O0R0)ꢁ, with R and R0 groups as indicated.
R
R0
RhAO (Å)
RhAO0 (Å)
RhAC (Å) RhAC0a/Å
OARhAO0 (°) CARhAC0 (°) Space group Stack in
Rhꢂ ꢂ ꢂRh (Å)
3.250
3.253, 3.271 [13]
3.308, 3.461 [31]
Reference
This study
Ph
C4H3S
2.028(6)
2.040(4)
2.050(1)
2.041(5)
2.044(4)
2.035(1)
1.866(9)
1.831(7)
1.854(2)
1.846(9)
1.831(7)
1.848(2)
1.852(2)
90.4(2)
90.8(2)
90.61(5)
90.36(6)
88.1(3)
88.9(3)
87.98(7)
89.14(9)
89.14(8)
89.1(6)
87(1)
P212121
P1
Long chain
Long chain
Long chain
Dinuclear units 3.175
Dinuclear units 3.179
ꢀ
CH3 CH3
Ph
CH3
CH2CH3
P21/c
P21/n
Phb
Phb
Fcc
Phb
2.0288(13) 2.0285(14) 1.849(2)
[32]
[33]
[34]
[35]
ꢀ
CH2CH2CH3 2.0300(12) 2.0295(13) 1.851(2)
CF3
CF3
1.8446(19) 90.72(5)
P1
2.049(8)
2.02(2)
2.016(9)
2.02(2)
1.83(2)
1.82(3)
1.84(1)
1.79(3)
90.2(3)
89.8(7)
C2/c
Pbca
Long chain
Dinuclear units 3.346
3.537
a
b
c
RhAC0 bond is on the side of O0, trans to RhAO.
Ph = phenyl.
Fc = ferrocenyl.

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M.M. Conradie, J. Conradie / Journal of Molecular Structure 1051 (2013) 137–143
Fig. 2. (a) Orientation of the dinuclear [Rh(PhCOCHCOC4H3S)(CO)2] molecules, viewed perpendicularly to the coordination plane. (b) Packing of the [Rh(PhCOCHCOC4H3-
S)(CO)2] molecules, resulting in a ‘‘molecular wire’’ along the a-axis. (c) Packing accentuated by the blue spheres around the rhodium centre. (For interpretation of the
references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 3. (a) Orientation of three different dinuclear [Rh(b-diketonato)(CO)2] molecules, viewed perpendicularly to the coordination plane. (b) Packing of the three [Rh(b-
diketonato)(CO)2] molecules, resulting in an infinite chain. (c) Packing accentuated by the blue spheres around the rhodium centre. The three b-diketonato ligands pictured
are: (CH3COCHCOCH3)ꢁ (top), (PhCOCHCOCH3)ꢁ (middle) and (PhCOCHCOCF3)ꢁ (bottom). (For interpretation of the references to colour in this figure legend, the reader is
referred to the web version of this article.)

M.M. Conradie, J. Conradie / Journal of Molecular Structure 1051 (2013) 137–143
141
Fig. 4. (a) Orientation of the dinuclear [Rh(FcCOCHCOCF3)(CO)2] units, viewed perpendicularly to the coordination plane. (b) Packing of the dinuclear [Rh(FcCOCHCOCF3)(-
CO)2] units, with weak RhA interactions shown and (c) accentuated by the blue spheres around the rhodium centres. (For interpretation of the references to colour in this
p
figure legend, the reader is referred to the web version of this article.)
Fig. 5. Orientation of the following two dinuclear units, viewed perpendicularly to the coordination plane: (a) [Rh(PhCOCHCOCH2CH3)(CO)2] and (b) [Rh(PhCOCHCOCH2-
CH2CH3)(CO)2]. (c) Packing of the first dinuclear [Rh(PhCOCHCOCH2CH3)(CO)2] units, comprising of weak RhꢂꢂꢂH interactions and (d) the same [Rh(PhCOCHCOCH2CH3)(CO)2]
packing, accentuated by the blue spheres around the rhodium centre. (e) Packing of the second dinuclear [Rh(PhCOCHCOCH2CH2CH3)(CO)2] units, comprising of weak
CAHꢂ ꢂ ꢂO@C interactions and (f) the same [Rh(PhCOCHCOCH2CH2CH3)(CO)2] packing, accentuated by the blue spheres around the rhodium centre. (For interpretation of the
references to colour in this figure legend, the reader is referred to the web version of this article.)
The [Rh(PhCOCHCOCH3)(CO)2] molecules also form dinuclear
units, which are oriented with an angle of 180° in the opposite
direction, due to an inversion symmetry operation. The Rhꢂ ꢂ ꢂRh
distance between the rhodium atoms within the dinuclear unit is
3.308 Å, and slightly longer (3.461 Å) between the different
dinuclear units. The [Rh(PhCOCHCOCH3)(CO)2]2 dinuclear units
stack in infinite arrays along the b-axis, see Fig. 3.
The [Rh(PhCOCHCOCF3)(CO)2] molecules stack in infinite arrays
along the c-axis, with a Rhꢂ ꢂ ꢂRh distance of 3.537 Å between the
molecules. Different from the [Rh(PhCOCHCOC4H3S)(CO)2] and

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M.M. Conradie, J. Conradie / Journal of Molecular Structure 1051 (2013) 137–143
[Rh(CH3COCHCOCH3)(CO)2] complexes, the neighbouring [Rh(PhC-
OCHCOCF3)(CO)2] molecules in a dinuclear unit are staggered with
an OARhꢂ ꢂ ꢂRhAO torsion angle of 114.2° between them. The b-
diketonato ligands in neighbouring molecules of this dinuclear
unit, are orientated in opposite directions, i.e. the neighbouring
molecules are anti-eclipsed. The angle between the RhꢂꢂꢂRh vectors
forming the core of a column, is 170.0°. The phenyl (Ph) group
bonded to the b-diketonato backbone in [Rh(PhCOCHCOCF3)(CO)2],
is rotated out of the plane, formed by the rest of the molecule by
22°, which is slightly more than the 15° rotation of the phenyl
group in the [Rh(PhCOCHCOC4H3S)(CO)2] complex.
In the case of the [Rh(b-diketonato)(CO)2] molecules with the
b-diketonato ligands = (PhCOCHCOCH2CH3)ꢁ, (PhCOCHCOCH2CH2
CH3)ꢁ and (FcCOCHCOCF3)ꢁ, no extended metal chains were
observed in the solid state, however, the packing of the
[Rh(b-diketonato)(CO)2] molecules does result in dinuclear units.
The [Rh(FcCOCHCOCF3)(CO)2] molecules form weak dinuclear
units, with a Rhꢂ ꢂ ꢂRh distance of 3.346 Å. As with [Rh(PhCOCH-
COCF3)(CO)2], the two units of a [Rh(FcCOCHCOCF3)(CO)2] dimer
are staggered, with an OARhꢂ ꢂ ꢂRhAO torsion angle of 96.2° be-
tween the units (Fig. 4(a)), and with the orientation of the neigh-
bouring molecules again being anti-eclipsed. The dinuclear units
[43,44]. The short Rhꢂ ꢂ ꢂRh distance observed in [Rh(PhCOCHC-
OCH2CH3)(CO)2] and [Rh(PhCOCHCOCH2CH2CH3)(CO)2] (3.175 Å
and 3.179 Å), is thus shorter than generally observed in dinuclear
units, and falls within the range of the typical RhIARhI bond length
of a dimer with true covalent bonds, 2.82–3.24 Å [11,38].
4. Conclusions
We have presented here the comparative study of the packing
of [Rh(b-diketonato)(CO)2] dinuclear units. The rhodium(I) metal
ion in [(Rh(PhCOCHCOC4H3S)(CO)2] forms RhꢂꢂꢂRh interactions in
the solid state, resulting in the formation of molecular wires. Sim-
ilar RhꢂꢂꢂRh interactions are observed for [Rh(CH3COCHCOCH3)
(CO)2], [Rh(PhCOCHCOCF3)(CO)2] and [Rh(PhCOCHCOCH3)(CO)2].
The [Rh(PhCOCHCOCH2CH3)(CO)2], [Rh(PhCOCHCOCH2CH2CH3)
(CO)2] and [Rh(FcCOCHCOCF3)(CO)2] complexes, however, do not
form infinite metal–metal chains, but form dinuclear [Rh(b-diketo-
nato)(CO)2] units in the solid state.
Supplementary material
CCDC 943069 contains the supplementary crystallographic data
for this paper.
are further supported by
p–p interactions, which exist between
the neighbouring cyclopentadienyl rings of the ferrocenyl (Fc)
groups. The cyclopentadienyl rings are displaced from each other,
in a slipped or offset alignment [39], with a centroid–centroid sep-
aration of 3.585 Å. One main difference between [Rh(FcCOCH-
COCF3)(CO)2] and the [Rh(b-diketonato)(CO)2] complexes with
b-diketonato = (CH3COCHCOCH3)ꢁ, (PhCOCHCOCF3)ꢁ and (PhC-
OCHCOCH3)ꢁ, which are illustrated in Fig. 3, is that the dinuclear
units do not stack with the rhodium as a central axis. In this case,
the dinuclear unit additionally rotates a further 180°, so that the
rhodium centre of the one pair stacks on the b-diketonato back-
Acknowledgements
Financial assistance by the South African National Research
Foundation and the Central Research Fund of the University of
the Free State, is gratefully acknowledged.
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