Synthesis and characterisation of two novel Rh(I) carbene complexes: Crystal structure of [Rh(acac)(CO)(L1)]

Article abstract of DOI:10.1016/j.jorganchem.2005.04.046

The [Rh(acac)(CO)(L)] (acac = acetylacetonato; L₁ = 1,3-bis-(2,6-diisopropylphenyl)imidazolinylidene and L₂ = 1,3-bis-(2,4,6-trimethylphenyl)imidazolinylidene) complexes were prepared by the action of the parent carbene on [Rh(acac)(CO)₂] in THF. The crystal structure characterisation of [Rh(acac)(CO)(L₁)] revealed a slightly distorted square planar geometry with the carbene ligand orientated almost perpendicular to the equatorial plane; an elongated trans Rh-O bond of 2.0806(18) ? reflecting the considerable trans-influence of the carbene ligand. By measuring the CO stretching frequencies in a range of [Rh(acac)(CO)(L)] complexes (L = CO, L₁, L₂, PPh ₃, PⁿBu₃, P(O-2,4-^tBu ₂-Ph)₃) the following electron donating ability series was established: L₁ ～ L₂ ～ PⁿBu ₃ > PPh₃ > P(O-2,4-^tBu ₂-Ph)₃ > CO; indicating the carbenes investigated in this study to have a similar electronic cis-influence as trialkyl phosphines. Both complexes do not display hydroformylation activity towards 1-hexene in the absence of added phosphine or phosphite ligands under the conditions investigated (P = 60; T = 85 °C). In the presence of a phosphine or phosphite ligand the resulting hydroformylation catalysis was identical to that observed for [Rh(acac)(CO)₂] and the corresponding ligand and subsequent high-pressure ³¹P NMR studies confirmed substitution of the carbene ligand under these conditions.

Full text of DOI:10.1016/j.jorganchem.2005.04.046

Journal of Organometallic Chemistry 690 (2005) 3422–3426
www.elsevier.com/locate/jorganchem
Synthesis and characterisation of two novel Rh(I) carbene
complexes: Crystal structure of [Rh(acac)(CO)(L1)]
Michael S. Datt, Jerald J. Nair, Stefanus Otto *
Sasol Technology Research & Development, P.O. Box 1, Sasolburg 1947, South Africa
Received 7 March 2005; revised 15 April 2005; accepted 15 April 2005
Available online 15 June 2005
Abstract
The [Rh(acac)(CO)(L)] (acac = acetylacetonato; L
trimethylphenyl)imidazolinylidene) complexes were prepared by the action of the parent carbene on [Rh(acac)(CO) ] in THF.
1 2
= 1,3-bis-(2,6-diisopropylphenyl)imidazolinylidene and L = 1,3-bis-(2,4,6-
2
1
The crystal structure characterisation of [Rh(acac)(CO)(L )] revealed a slightly distorted square planar geometry with the carbene
˚
ligand orientated almost perpendicular to the equatorial plane; an elongated trans Rh–O bond of 2.0806(18) A reflecting the con-
siderable trans-influence of the carbene ligand. By measuring the CO stretching frequencies in a range of [Rh(acac)(CO)(L)] com-
n
, P Bu
t
, P(O–2,4- Bu
plexes (L = CO, L
n
1
, L
2
, PPh
3
3
2 3
–Ph) ) the following electron donating ability series was established:
t
> P(O–2,4- Bu
L
1
ꢀ L
2
ꢀ P Bu
3
> PPh
3
2
–Ph) > CO; indicating the carbenes investigated in this study to have a similar electronic
3
cis-influence as trialkyl phosphines. Both complexes do not display hydroformylation activity towards 1-hexene in the absence of
added phosphine or phosphite ligands under the conditions investigated (P = 60; T = 85 ꢀC). In the presence of a phosphine or phos-
phite ligand the resulting hydroformylation catalysis was identical to that observed for [Rh(acac)(CO)
2
] and the corresponding
ligand and subsequent high-pressure P NMR studies confirmed substitution of the carbene ligand under these conditions.
2005 Elsevier B.V. All rights reserved.
3
1
ꢁ
Keywords: Rhodium(I); Carbene; Crystallography; Hydroformylation
1
. Introduction
attractive ligand class for possible application in homo-
geneous catalysis.
The behaviour of organometallic complexes is criti-
As part of an extensive investigation [8–10] into the
catalytic properties of organometallic complexes in the
field of homogeneous catalysis, two [Rh(acac)(CO)(L)]
cally linked to the ligand system to which they are co-
ordinated. Ligand properties can be tuned to produce
complexes displaying very specific characteristics in
terms of chemical reactivity and selectivity in catalytic
processes as well as to exhibit desirable physical proper-
ties such as solubility in certain media. In this regard
metal carbene complexes [1–5] have attracted much
attention in the last decade since they provide an extra
handle for functionalisation on the catalyst. N-heterocy-
clic carbenes are considered to be better electron donat-
ing ligands than phosphines [6,7] making them an
complexes (L = 1,3-bis-(2,6-diisopropylphenyl)imidazo-
1
linylidene and L = 1,3-bis-(2,4,6-trimethylphenyl)imi-
2
dazolinylidene) were synthesised as catalyst precursors.
In this paper, we report the crystal structure of [Rh-
3
(acac)(CO)(L )] and high-pressure P NMR evidence
1
1
that the rhodium–carbene bond is cleaved under hydro-
formylation reaction conditions.
2
. Experimental
*
All solvents used were purified by standard proce-
dures and air sensitive preparations were carried out
Corresponding author. Tel.: +27 16 9604456; fax: +27 11 5223218.
E-mail address: Fanie.Otto@sasol.com (S. Otto).
0
022-328X/$ - see front matter ꢁ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.04.046

M.S. Datt et al. / Journal of Organometallic Chemistry 690 (2005) 3422–3426
3423
under a positive nitrogen pressure. The carbene li-
gands were prepared according to a literature proce-
dure [11].
were calculated as riding on the parent C atoms (alkyl =
˚
˚
0.96 A, aryl = 0.93 A) and refined with an overall
temperature factor, all non-H atoms were refined aniso-
tropically. The graphics were done using the Diamond
Visual Crystal Structure Information System software
2
.1. Synthesis of [Rh(acac)(CO)(L)] complexes
[
17].
Deprotonation of the respective imidazolinium chlo-
rides was performed as described in the literature [11];
addition of a stoichiometric amount of [Rh(acac)(CO)2]
to this solution resulted in the formation of the desired
2.3. Catalysis
A 300 ml Parr autoclave was charged with the respec-
tive rhodium–carbene complex (0.25 mM) and 1-hexene
(3 M) in toluene. The autoclave was then heated to
85 ꢀC and pressurised with 60 bar synthesis gas
complexes in good yields.
[
À1
Rh(acac)(CO)(L )]: (m(CO)/CH Cl /cm ) 1963;
1
2
2
1
3
H (CDCl ): 1.26 (d, 4· CH , JH–H = 6.9 Hz, L1),
3
3
3
1
.33 (d, 4· CH3,
J
= 6.9 Hz, L ), 1.78 (s, CH ,
(H :CO, 1:1) for 2 h. End of run catalytic performance
H–H
1
3
2
acac), 1.79 (s, CH , acac), 3.41 (sept, 4· CH(CH ) ,
was derived from ballast vessel pressure drops and GC
analysis.
3
3 2
3
J
= 6.9 Hz, L ), 3.99 (s, 2· CH , L ), 5.17 (s, CH,
H–H
1
2
1
acac), 7.23 (d, 4· m-CH, L ), 7.37 (t, 2· p-CH, L );
1
1
1
3
C: 23.74 (s, 4· CH , L ), 26.40 (s, 4· CH , L ),
2.4. Spectroscopy
3
1
3
1
2
(
4
7.50 (s, 1· CH , acac), 27.78 (s, 1· CH , acac), 28.52
3
3
s, 4· CH(CH ) , L ), 53.92 (s, 2· CH , L ), 124.40 (s,
All IR spectra were recorded as CH Cl solutions in a
2
3
2
1
2
1
2
· m-C, L ), 128.80 (s, 4· o-C, L ), 136.98 (s, 2· ipso-
variable length solution cell on a Bruker Equinox 55
FTIR instrument equipped with a KBr beamsplitter
and controlled by an external computer using OPUS
software for acquisition, analysis and manipulation of
data. Signal detection was done with a DTGS detector
and 32 scans per spectrum were performed using a
10 kHz scanner velocity with no optical filtering.
1
1
C, L ), 147.15 (s, 2· p-C, L ), 184.55 (s, 1· C, acac),
1
1
1
1
8
86.40 (s, 1· C, acac), 190.44 (d, 1· C„O, J
=
Rh–C
1
2.5 Hz), 210.75 (d, 1· C-carbene, J
= 53.6 Hz).
Anal. calc. for C H N O Rh: C, 63.86; H, 7.31; N,
Rh–C
3
3
45
2
3
4
.51. Found: C, 64.18; H, 7.40; N, 4.57%.
Rh(acac)(CO)(L )]: (m(CO)/CH Cl /cm ) 1958;
À1
[
H (CDCl ): 1.74 (s, CH , acac), 1.80 (s, CH , acac),
2
2
2
1
1
13
31
The H, C and P NMR spectra were recorded on
a 400 MHz Varian Unity Inova spectrometer using
standard pulse sequences at 303 K unless otherwise sta-
3
3
3
2
2
.29(s, 2· p-CH , L ), 2.39 (s, 4· o-CH , L ), 3.92 (s,
3
2
3
2
· CH , L ), 5.16 (s, CH, acac), 6.92 (s, 4· m-CH,
2
2
1
3
1
L2); C: 18.49 (s, 4· o-CH , L ), 21.09 (s, 2· p-CH ,
ted. Chemical shifts are reported in ppm (d). H NMR
spectra were calibrated on the residual CHCl peak at
3
2
3
L ), 26.36 (s, 1· CH , acac), 27.62 (s, 1· CH , acac),
2
3
3
3
1
3
5
0.97 (s, 2· CH , L ), 100.08 (s, 1· CH, acac), 129.33
7.25 ppm, C NMR spectra on the CDCl carbon at
3
2
2
3
1
(
s, 4· m-C, L ), 136.43 (s, 4· o-C, L ), 136.71 (s, 2·
77.0 ppm and the P NMR spectra relative to an
external standard of 85% H PO at 0 ppm. All high-
pressure experiments were performed in a 10 mm
high-pressure Roe cell without spinning. The samples
were prepared by transferring a mixture of [Rh(acac)-
(CO)(L)] and the phosphine/ phosphite in toluene
2
2
ipso-C, L ), 137.55 (s, 2· p-C, L ), 184.15 (s, 1· C, acac),
1
2
2
3
4
1
86.73 (s, 1· C, acac), 190.31 (d, 1· C„O, J
2.0 Hz), 207.29 (d, 1· C-carbene, J
=
= 53.3 Hz).
Rh–C
1
8
Anal. calc. for C H N O Rh: C, 60.44; H, 6.20; N,
Rh–C
2
7
33
2
3
5
.22. Found: C, 60.35; H, 6.53; N, 5.46%.
(1.5 ml toluene + 1.0 ml toluene-d ) to the HP-NMR
8
2
.2. Crystallography
cell. The cell was flushed with argon, closed and pres-
surised to 20 bar at room temperature with syngas
(H :CO = 1:1). Before recording the spectra, the HP-
Intensity data for [Rh(acac)(CO)(L )] were collected
1
2
at 293(2) K on a Siemens SMART CCD diffractometer
˚
NMR cell was shaken for 10 min in a mechanical vor-
tex shaker in order to maximise the amount of syngas
dissolved in the mixture and to allow the mixture to
equilibrate.
using Mo Ka (0.71073 A) radiation [12]. Individual
frames were collected using the x-scan technique and
the first 50 frames were recollected after completion to
correct for decay of which none was observed. All reflec-
tions were merged and integrated using SAINT [13] and
corrected for Lorentz, polarisation and absorption ef-
fects using SADABS [14]. The structure was solved by
the direct method and the positions of the non-H atoms
determined from consecutive Fourier maps and refined
through full-matrix least-squares cycles using the
SHELXS97 [15] and SHELXL97 [16] software package with
3. Results and discussion
3.1. Synthesis and characterisation
The carbene ligands were synthesised according to
established procedures and Rh–carbene complexes were
synthesised without significant problems as detailed in
P
2
(
|F | À |F |) being minimised. The hydrogen atoms
o
c

3424
M.S. Datt et al. / Journal of Organometallic Chemistry 690 (2005) 3422–3426
1
Section 2. The H NMR spectra of the compounds are
very diagnostic with all signals well resolved.
Two methyl groups of the iso-propyl substituents on
C(25)
C(24)
C(23)
C(26)
the phenyl rings of the [Rh(acac)(CO)(L )] complex are
1
C(29)
diastereotopic and appear as two sets of doublets that
1
couple to the neighbouring CH in the H NMR spec-
C(33)
O(2)
C(27)
C(31)
1
trum. In the corresponding C NMR spectrum, two
3
C(22)
O(1)
N(2)
C(2)
C(3)
singlets are observed for the iso-propyl methyl groups
1
which are consistent with this observation. The H and
C(1)
C(28)
C(30)
C(4)
C(6)
Rh
1
3
C NMR spectroscopic assignments are consistent with
those previously reported for the uncoordinated carbene
ligand [11]. The methyl groups of the acac ligand are in
different environments as shown by their magnetic
unequivalency. Two sets of doublets centred at 190.44
C(32)
C(5)
C(9)
O(3)
C(7)
N(1)
C(8)
C(19)
C(20)
1
1
( JRh–C = 82.5 Hz) and 210.75 ppm ( JRh–C = 53.6 Hz)
were attributed to the carbonyl and carbene carbons,
respectively.
C(10)
C(18) C(16)
C(11)
C(19)
C(15)
1
In the H NMR spectrum of [Rh(acac)(CO)(L )] all
C(21)
2
C(17)
C(12)
four ortho methyl substituents on the phenyl rings reso-
nate as a single signal indicating magnetic equivalence
associated with free rotation around the N-phenyl
C(14)
1
bonds. Two sets of doublets centred at 190.31 ( J
C(13)
Fig. 1. Numbering scheme and thermal ellipsoids (30% probability)
Rh–C
1
82.0 Hz) and 207.29 ppm ( J
=
= 53.3 Hz) were
Rh–C
attributed to the carbonyl and carbene carbons, respec-
tively. Both Rh–carbene coupling constants compare
well with those in previously reported systems [5].
for [Rh(acac)(CO)(L )]. Hydrogen atoms were omitted for clarity.
1
the CO ligand, respectively. As indicated by the N(2)–
C(7)–Rh–C(1) torsion angle of 76.5(3)ꢀ the imidazolium
ring of the carbene ligand is orientated almost perpen-
dicular to the coordination plane in accordance with
the preferred coordination mode for these molecules.
Even though a significant steric demand is expected
from the carbene ligand both the C(1)–Rh–C(7) and
the C(7)–Rh–O(3) angles of 90.52(12)ꢀ and 90.57(9)ꢀ
indicate only a moderate distortion from the ideal 90ꢀ.
This observations seems to suggest that the bulky
parts of the carbene ligand, i.e., the bis(1,6-diisopropyl-
phenyl) substituents, are removed from the inner Rh
3
.2. Crystallography
The numbering scheme and thermal displacement
ellipsoids are shown in Fig. 1 and selected geometrical
parameters are given in Table 1.
The structure of [Rh(acac)(CO)(L )] shows the com-
plex to exhibit a slightly distorted square planar geome-
try with the carbene, L , coordinated through the
1
1
carbene carbon as expected. The Rh–O bonds of
˚
2.0806(18) and 2.058(2) A clearly reflect the larger
trans-influence of the carbene as compared to that of
Table 1
Selected geometrical parameters for [Rh(acac)(CO)(L
1
)]
˚
Bond (A)
Angle (ꢀ)
Torsion angle (ꢀ)
Rh–O2
Rh–O3
Rh–C1
Rh–C7
C1–O1
O2–C3
O3–C5
C3–C4
C5–C4
N1–C7
N1–C8
N1–C10
N2–C7
N2–C9
N2–C22
2.0806(18)
2.058(2)
1.780(3)
1.975(3)
1.160(4)
1.269(3)
1.282(4)
1.379(4)
1.392(4)
1.353(3)
1.471(3)
1.446(3)
1.348(3)
1.475(3)
1.444(3)
C1–Rh–O2
C1–Rh–O3
C1–Rh–C7
O2–Rh–O3
C7–Rh–O2
C7–Rh–O3
O1–C1–Rh
N1–C7–Rh
N1–C7–N2
N2–C7–Rh
90.96(11)
174.31(12)
90.52(12)
88.45(8)
N2–C7–Rh–C1
76.5(3)
82.0(3)
79.9(3)
C9–N2–C22–C23
C8–N1–C10–C11
C17–C16–C11–C12
C18–C16–C11–C12
C20–C19–C15–C14
C21–C19–C15–C14
C29–C28–C23–C24
C30–C28–C23–C24
C32–C31–C27–C26
C33–C31–C27–C26
68.5(4)
À54.3(4)
41.4(4)
174.71(9)
90.57(9)
177.6(3)
À84.3(4)
À45.8(4)
76.4(4)
124.04(17)
106.4(2)
129.47(19)
À78.0(4)
45.1(4)

M.S. Datt et al. / Journal of Organometallic Chemistry 690 (2005) 3422–3426
3425
Ref.
Table 2
Comparison of geometrical parameters and CO stretching frequencies in [Rh(acac)(CO)(L)] complexes
L
Rh–L
Rh–CO
1.780(3)
Rh–OCO
2.058(2)
Rh–O
L
3
m(CO) (CHCl )
L
L
1
1.975(3)
2.0806(18)
1963
1958
1961
2012
2084
1984
1980
TW
TW
TW
[19]
2
n
P Bu
3
CO
1.75(2)
1
2.06(2)
2.05(2)
.76(2)
PPh
PPh
3
2.244(2)
2.2331(11)
1.801(8)
1.799(4)
1.800(4)
1.826(3)
1.817(2)
1.823(3)
2.029(5)
2.027(3)
2.038(3)
2.016(2)
2.033(2)
2.040(2)
2.087(4)
2.072(3)
2.068(3)
2.054(2)
2.078(2)
2.063(2)
[20]
[21]
a
2
Fc
2
.2375(13)
P(NC
P(NC
4
H
H
4
)
3
2.166(1)
2.223(1)
2.170(1)
2012 (KBr)
1990
2006
[22]
[23]
[23]
TW
4
4
)Ph
2
P(OPh)
t
P(O–2,4- Bu
3
2
–Ph)
3
2007
a
Two independent molecules in the unit cell.
coordination sphere to such an extent as not to influence
it significantly. This concept is supported by the C(9)–
N(2)–C(22)–C(23) and C(8)–N(1)–C(10)–C(11) torsion
angles of 82.0(3)ꢀ and 79.9(3)ꢀ, respectively, indicate
that both phenyl rings are orientated almost perpendic-
ular with respect to the imidazolium ring of the carbene.
Furthermore the iso-propyl groups are orientated in
such a way that the hydrogen atoms are pointing to-
wards the equatorial plane describe by the ligands
around the rhodium atom minimising the steric demand
of the carbene ligand. The iso-propyl substituents are all
orientated very similar with respect to the phenyl rings,
see appropriate torsion angles in Table 1, with a stag-
gered conformation exhibited.
In order to elucidate the behaviour of the compounds
in the presence of a phosphorous donor ligand high-pres-
sure P NMR spectroscopic studies were conducted.
These experiments indicated that the rhodium–carbene
complexes described in this paper are not stable under
hydroformylation reaction conditions and appear to be
3
1
liberated. Reaction of [Rh(acac)(CO)(L )] with an excess
2
of PPh3 results in the formation of a [Rh(acac)-
(L )(PPh )] complex as suggested by the appearance of
2
3
1
a doublet at 34.5 ppm ( J
31
= 123 Hz) in the
P
NMR spectrum. In the presence of 20 bar synthesis
Rh–P
gas (H /CO, 1:1) the signal at 34.5 ppm disappeared
2
with the appearance of two doublets at 36.9 ppm
1
( J
1
= 140 Hz) and 44.3 ppm ( J
= 151 Hz),
Rh–P
Rh–P
Based on the comparative structural data in Table 2
all bonds are within normal ranges for this class of com-
pound. The Rh–O bond trans to the carbene is very sim-
ilar to that found trans to phosphine ligands confirming
the large trans-influence of these ligands. In accordance
with known literature [18] the CO stretching frequencies
seem to indicate that the electron donating capability of
the carbene ligands is larger than for a triaryl phosphine
and comparable to that of a trialkyl phosphine.
respectively. The doublet at 36.9 ppm corresponds to
the formation of the well known hydroformylation rho-
dium–phosphine precursor [HRh(CO) (PPh ) ] [24].
2
3 2
The resonance at 44.3 ppm is thought to be a non-
hydride rhodium–carbene complex tentatively assigned
+
as [Rh(CO) (L )(PPh )] . On increasing the temperature
3
2
3
from 30 to 100 ꢀC the intensity of the signal correspond-
ing to the rhodium–carbene complexes decreased and fi-
nally disappeared. The displacement of the carbene
appears to be irreversible as upon cooling and re-acquir-
ing the spectrum the signal at 44.3 ppm did not reap-
3
.3. Catalysis
pear. Similarly, reaction of [Rh(acac)(CO)(L )] with
2
t
P(O–2,4- Bu –Ph) in the presence of syngas results in
The activity towards hydroformylation of 1-hexene
has been evaluated using [Rh(acac)(CO)(L )] as catalyst
precursor with and without added PPh3 and
2
3
3
the formation of three doublets in the P NMR spec-
1
2
1
trum at 154.2 ppm ( J
1
= 264 Hz), 137.3 ppm ( J
Rh–P
Rh–P
t
P(O–2,4- Bu –Ph) as auxiliary ligands. No catalyst
1
= 223 Hz) and 134.7 ppm ( J
= 249 Hz), respec-
Rh–P
2
3
activity towards the hydroformylation of 1-hexene was
observed using [Rh(acac)(CO)(L)] (L = L and L ) in
the absence of an additional ligand. It was found though
that the catalytic activity observed in the presence of the
auxiliary ligand corresponds to that of using [Rh(acac)-
tively. The latter two doublets correspond to the
formation of complexes of the type [HRh(CO) (P(O–
1
2
3
t
t
2,4- Bu –Ph) )] and [HRh(CO) (P(O–2,4- Bu –Ph) ) ]
2 3 2 2 3 2
as described in the literature [9]. Rhodium-hydride
1
signals were observed in the H NMR spectrum which
(
CO) ] as catalyst precursor with the respective ligand.
2
corresponded to the non-carbene ligated rhodium–
phosphite complexes. The signal at 154.2 ppm is thought
All autoclave experiments thus indicate that no addi-
tional beneficial effect was derived from the presence
of the carbene in the catalyst precursor.
t
to be a complex of the type [Rh(CO) (P(O–2,4- Bu –
3
2
+
Ph) ) (L )] . In accordance with the behaviour in the
3
2

3426
M.S. Datt et al. / Journal of Organometallic Chemistry 690 (2005) 3422–3426
corresponding PPh study the intensity of the signal at
3
[6] J. Huang, H.-J. Schanz, E.D. Stevens, S.P. Nolan, Organomet-
allics 18 (1999) 2370.
1
54.2 ppm decreased and disappeared irreversibly with
[7] J. Huang, E.D. Stevens, S.P. Nolan, J.L. Petersen, J. Am. Chem.
Soc. 121 (1999) 2674.
increasing temperature. No rhodium–carbene-hydride
complexes were observed. The cleavage of the rho-
dium–carbene bond is currently attributed to hydride-
transfer to the coordinated carbene but would required
additional studies to prove unambiguously.
[
8] C. Crause, L. Bennie, L. Damoense, C.L. Dwyer, C. Grove, N.
Grimmer, W. Janse van Rensburg, M.M. Kirk, K.M. Mokheseng,
S. Otto, P.J. Steynberg, Dalton Trans. (2003) 2036.
[9] M.S. Datt, D. Foster, L. Bennie, C. Steenkamp, J.J. Huyser, L.
Kirsten, G. Steyl, A. Roodt, R. Crous, Dalton Trans. (2005) 1108.
The observations made during the current study were
surprising since it have been shown previously that Rh–
carbene complexes do display hydroformylation activity
in the absence of phosphines and phosphites [25,26]. In
all of these systems though the catalyst precursor also
contained either chloride or bromide ligands that might
influence the final composition/stability of the activated
catalytic species and in such a way account for the differ-
ence in catalytic behaviour.
[
10] A. Bollmann, K. Blann, J.T. Dixon, F.M. Hess, E. Killian, H.
Maumela, D.S. McGuiness, D.H. Morgan, A. Neveling, S. Otto,
M.J. Overett, A.M.Z. Slawin, P. Wassercheid, S. Kuhlmann, J.
Am. Chem. Soc. 126 (2004) 14712.
[
[
11] A.J. Arduengo III, R. Krafczyk, R. Schmutzler, H.A. Craig, J.R.
Goerlich, W.J. Marchall, M. Unverzagt, Tetrahedron 55 (1999)
1
4523.
12] Empirical formula: RhC33
Monoclinic; Space group: P2 /n; a = 12.3484(17) A; b = 21.096(3)
45 2 3
H N O ; FW: 620.62; Crystal system:
˚
1
˚
˚
˚
3
A; c = 13.2520(18) A; b = 109.812(3)ꢀ ; V = 3247.9(8) A ; Z = 4;
À1
l = 0.558 mm
;
T
max/Tmin
,
0.967/ 0.912; Crystal size:
0
.29 · 0.23 · 0.18 mm; h limit: 2.53 to 28.28; Index ranges:
À15 6 h 6 16, À28 6 k 6 27, À17 6 l 6 16; Collected reflections:
7330; Independent reflections: 8058; Rint: 0.0925; Observed
4
. Supplementary material
2
reflections [I > 2rI]: 5160; Data/ restraints/parameters: 8058/0/
363; GoF: 0.937; R/wR (I > 2rI): 0.0400/0.0827; R/wR (all data):
Full crystallographic details for [Rh(acac)(CO)(L1)]
have been deposited with the Cambridge Crystallo-
graphic Data Centre, CCDC 264388.
˚
À3
.
0
.0804/0.0932; Dqmax/Dqmin: 0.306/À0.615 e A
[
13] SAINT, Siemens Analytical X-ray Instruments Inc., Madison, WI,
USA, 1995.
[
14] G.M. Sheldrick, SADABS, University of G o¨ ttingen, Germany.
15] G.M. Sheldrick, SHELXS97, Program for Solving Crystal Struc-
tures, University of G o¨ ttingen, Germany.
[
Acknowledgements
[
[
[
16] G.M. Sheldrick, SHELXL97, Program for Refining Crystal Struc-
tures, University of G o¨ ttingen, Germany.
Financial support from Sasol Technology is grate-
fully acknowledged. Megan Kirk of Sasol Technology
R&D is thanked for recording the P NMR spectra
while Prof. Andreas Roodt and Dr. Alfred Muller of
the Rand Afrikaans University are thanked for their
assistance with the crystallography.
17] K. Brandenburg, M. Berndt, DIAMOND, Version 2.1a, Crystal
Impact GbR, Bonn, Germany, 1999.
3
1
18] H.C. Martin, N.H. James, J. Aitken, J.A. Gaunt, H. Adams, A.
Haynes, Organometallics 22 (2003) 4451.
[19] N.A. Bailey, E. Coates, G.B. Robertson, F. Bonati, R. Ugo,
Chem. Commun. (1967) 1041.
[
[
[
20] J.G. Leipoldt, S.S. Basson, L.D.C. Bok, T.I.A. Gerber, Inorg.
Chim. Acta 26 (1978) L35.
21] S. Otto, A. Roodt, J.J.C. Erasmus, J.C. Swarts, Polyhedron 17
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