Thione complexes of Rh(I): A first comparison with the bonding and catalytic activity of related carbene and imine compounds

Article abstract of DOI:10.1039/b414040k

Heterocyclic mono(thione), trans-bis(thione), cis-bis(thione), trans-(carbene-thione), cis-(carbene-thione), trans-(phosphine-thione) and mono(imine) complexes of rhodium(I) have been prepared and fully characterised. Chloro(η⁴-1,5-cyclooctadiene)(L)rhodium(I) (1a, L = 1,3-diisopropyl-4,5-dimethyl-2,3-dihydro-1H-imidazol-2-thione; 1b, L = 1,3,4,5-tetramethyl-2,3-dihydro-1H-imidazol-2-thione) appear as isomers at room temperature due to slow coordination exchange on the S-donor atom. In the three structures determined, the substituent on the sulfur appears syn to Cl. Hindered rotation about the Rh-carbene bond is revealed in the NMR spectra of seven new complexes with isopropyl substituents on the heterocyclic carbene ligands. The trans influence of the thione ligands is smaller than that of carbenes but larger than that shown by imines and chloride. Thione complexes are better catalyst precursors than the carbene complexes for the hydroformylation of 1-hexene under the chosen reaction conditions: 80°C, 8 MPa CO-H₂ (1 : 1), 16 h, 1 : 1000 catalyst to 1-hexene ratio.

Full text of DOI:10.1039/b414040k

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F U L L P A P E R
Thione complexes of Rh(I): a first comparison with the bonding and
catalytic activity of related carbene and imine compounds†
Arno Neveling, Gerrit R. Julius, Stephanie Cronje, Catharine Esterhuysen and
Helgard G. Raubenheimer*
Department of Chemistry, University of Stellenbosch, Private Bag X1, Matieland, 7602,
Stellenbosch, South Africa. E-mail: hgr@sun.ac.za; Fax: +27 21 808 3849;
Tel: +27 21 808 3850
Received 15th September 2004, Accepted 3rd November 2004
First published as an Advance Article on the web 26th November 2004
Heterocyclic mono(thione), trans-bis(thione), cis-bis(thione), trans-(carbene–thione), cis-(carbene–thione),
trans-(phosphine-thione) and mono(imine) complexes of rhodium(I) have been prepared and fully characterised.
4
Chloro(g -1,5-cyclooctadiene)(L)rhodium(I) (1a, L = 1,3-diisopropyl-4,5-dimethyl-2,3-dihydro-1H-imidazol-
2-thione; 1b, L = 1,3,4,5-tetramethyl-2,3-dihydro-1H-imidazol-2-thione) appear as isomers at room temperature due
to slow coordination exchange on the S-donor atom. In the three structures determined, the substituent on the sulfur
appears syn to Cl. Hindered rotation about the Rh–carbene bond is revealed in the NMR spectra of seven new
complexes with isopropyl substituents on the heterocyclic carbene ligands. The trans influence of the thione ligands is
smaller than that of carbenes but larger than that shown by imines and chloride. Thione complexes are better catalyst
precursors than the carbene complexes for the hydroformylation of 1-hexene under the chosen reaction conditions:
80 ◦C, 8 MPa CO–H2 (1 : 1), 16 h, 1 : 1000 catalyst to 1-hexene ratio.
Introduction
Thione complexes of organometallic Rh(I) are rare. Cauzzi and
co-workers used rhodium(I)-anchored thiourea-functionalised
silica xerogels 1 and later silesquioxanes 2 in the hydroformyla-
tion of styrene. Certain carbonyl complexes that contain these
ligands are unstable but crystal structures of cyclooctadiene-
(cod)-stabilised products have been determined. Later, Breuzard
et al. employed chiral thioureas in an attempted asymmetric
hydroformylation of styrene.3
The striking similarities between phosphines and N-heterocy-
clic carbenes both from viewpoints of complex synthetic metho-
dologies and chemical bonding, have been noted by many
authors and are probably eventually best described by Herrmann
et al.4,5 The advantages of the latter ligand-types in homogene-
ous catalysis are also well established.6 However, few complexes
with rhodium(I) have been made. Crudden and co-workers pre-
pared and characterised two carbene analogues of Wilkinson’s
catalyst, and studied their application in the hydroformylation of
styrene.7 Mata et al.8 recently reported that [RhCl(cod)]2 favours
bidentate coordination with bis(carbene) ligands that contain
Scheme 1
long (CH2)n linkers, whereas linkers with n = 1 or 2 afford
dinuclear, monodentately-coordinated compounds (Scheme 1).
Building on the work of Oro et al.9 we reported new rhodium
complexes coordinated by anionic and neutral bidentate imine
ligands.10
Here we describe the synthesis of a series of thione complexes
derived from [RhCl(cod)]2 and [RhCl(CO)2]2. A new group of
neutral and cationic heterocyclic carbene complexes as well
as neutral imine compounds are also discussed. Finally, the
effectivity and activity of the former two series of compounds
as precatalysts in the hydroformylation of 1-hexene under mild
conditions, are compared.
Results and discussion
Synthetic aspects
All compounds were prepared according to the reactions
in Scheme 2 via the addition of a ligand, L (L = thione,
† Electronic supplementary information (ESI) available: Overlay of com-
plexes 6 and 9. See http://www.rsc.org/suppdata/dt/b4/b414040k/
Scheme 2
T h i s j o u r n a l i s T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
D a l t o n T r a n s . , 2 0 0 5 , 1 8 1 – 1 9 2
1 8 1
©

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carbene or imine), to Cl-bridged [RhCl(cod)]2. The carbonyl
complexes, RhCl(CO)2L, were obtained by substitution of the
cyclooctadiene ligand with CO. Replacement of the halide is
also possible, leading to the formation of cationic complexes.
Complexes 1a, 1b and 2 formed in high yields while complexes
3a, 3b and 4 were only obtained in very low yields. However,
the use of [RhCl(CO)2]2 as starting material with the thione
ligands which were added in stoichiometric amounts at room
temperature, produced the carbonyl complexes 3 and 4 in almost
quantitative yields.
The binuclear rhodium complexes [RhCl(cod)]2 and
[RhCl(CO)2]2 are also readily cleaved by N-donor ligands.11–13
The imines 4-methylthiazole and 4,5-dimethylthiazole afforded
the neutral monorhodium complexes 11a and 11b, whereas the
addition of 4-methylthiazole to [RhCl(CO)2]2 furnished complex
12 at room temperature.
Reaction of an excess thione (1,3-diisopropyl-4,5-dimethyl-
2,3-dihydro-1H-imidazol-2-thione) with complex 3a gave the
trans-bis(thione) complex 13, but only in a low yield. The
addition of trimethylamine oxide (to oxidise and remove CO)
to the reaction mixture, led to the desired complex 13 in a
reasonable yield. Complex 14 was obtained similarly from 7.
A cyclooctadiene rhodium(I) carbene complex (5) related to
1a was isolated and the addition of two mole quantities of
carbene ligand per mole of rhodium atom, led to the formation
of the cationic species (6). Bubbling carbon monoxide through
THF solutions of the cyclooctadiene complexes 5 and 6, yielded
the monocarbene complex 7 as well as the trans-bis(carbene)
complex 8.
The addition of two mole quantities of thione per mole
rhodium in [RhCl(cod)]2 only furnished the mononuclear thione
complex 1a again. However, addition of AgBF4 to the reaction
mixture precipitated the chloride leading to the formation of
the desired ionic complex 15. Complex 16, a cis-bis(thione)
compound, formed in the presence of CO. The assignment of a
cis-configuration to this complex was based on IR and NMR
data. Complexes 17 and 18 that each contain a carbene ligand
as well as a thione ligand, were prepared in similar fashion to 15
and 16.
The phosphine-containing compounds 19–20b resulted from
the addition of the chosen phosphine to complexes 3a or 7.
Spectroscopic characterisation
The NMR signals of the thione complex 1a exhibit broadening
and coalescence in its 1H NMR spectrum, a phenomenon also
observed by Mu¨ller and Stock during the characterisation of
cyclooctadiene(imine)rhodium(I) complexes.13
Interestingly, two broad signals appeared for all the protons
of the two methyl groups, on the imidazole ring, in 1a and
1b. For the N–CH(CH3)2 protons of the thione ligand in 1a,
however, only one broad peak was observed, similar to the
NMR spectrum of the free ligand. Each of the carbon atoms of
the thione ligand gave rise to two signals at room temperature,
whereas none of the cyclooctadiene carbon atoms exhibited this
phenomenon. At higher temperatures, the signals in both the
proton and 13C NMR spectra (in toluene-d8) coalesce but still
remain somewhat broad (Fig. 1).
A cationic cyclooctadiene rhodium complex with a bidentate
carbene ligand (9) was prepared according to Scheme 2 (2L
replaced by LˆL) by deprotonation of the imidazolium salt
precursor with KOtBu. The corresponding cationic carbonyl
complex (10) formed readily in the presence of CO. Our method
differs somewhat from that of Mata et al. mentioned before (see
Scheme 1).8
The room-temperature NMR information suggests the pres-
ence of isomers (Fig. 2) caused by slow inversion about the
rhodium sulfur bond. Abel et al. reported the occurrence of
a ring-flipping process in rhodium complexes with sulfur-donor
ligands due to possible sulfur inversions as indicated by variable-
temperature NMR studies.14
1 8 2
D a l t o n T r a n s . , 2 0 0 5 , 1 8 1 – 1 9 2

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No indication of inversion was found for the thione complexes
2 and 4. The protons and carbons of both methyl groups of
1
2 were observed as two separate multiplets in the H NMR
spectrum due to restricted rotation about the N–C(S) bond.
These signals were similar to the corresponding ones in free
N,N-dimethylthioformamide (d 3.22 and 3.15).
Broadening and coalescence of resonances occurs in both the
proton and 13C NMR spectra of the cyclooctadiene(thiazole)
complexes 11a and 11b during temperature variation but in the
dicarbonyl complex 12, free rotation occurs around the Rh–N
bond.
The most significant changes are observed for the signals of
the one methyl group of the thiazole ligand upon complexation
of the ligand in 11b. The two methyl groups of the free ligand are
observed at d 2.34 and 2.33 in the 1H NMR spectrum, whereas
they occur at d 2.89 and 2.33 (S–C–CH3) in the complex.
The appearance of diastereotopic methyl signals for the
isopropyl substituents in the carbene complexes 5, 7, 14, 17, 18,
20a and 20b indicate hindered rotation around the Rh–Ccarbene
bond.15
Rh–C and Rh–P coupling constants are used to determine
the relative trans influences exhibited by ligands.16 By com-
paring the Rh–P coupling constants in the 31P NMR spectra
of 20a (116.3Hz), 19 (158.5Hz) as well as in trans-[RhCl-
(CO)(LEt)(PPh3)] (112 Hz) (LEt is 1,3-diethyl-2,3,4,5-tetrahy-
dro-1H-imidazol-2-ylidene), trans-[RhCl(CO)(PPh3)2] (129 Hz),
trans-[Rh(CO)(LEt)2(PPh3)]Cl (117 Hz) and trans-[Rh(CO)-
(LEt)(PPh3)2]Cl (132 Hz),16 it is clear that the heterocyclic
carbenes effect a larger trans influence than phosphines and
phosphines larger than thiones. This order is substantiated by
the data in Table 1. Although some exceptions occur (group a), it
can be stated with certainty that the trans ligand is statically more
influenced by thiones than by imines or chlorides (in that order).
An unusual coupling of the phosphorous atom in 20b to the
proton in the 4-position of the thiazole ring via the sulfur atom,
was confirmed by selective homonuclear proton decoupling as
well as selective heteronuclear phosphorus decoupling (Fig. 3).
However, sharp signals were observed in the room temper-
ature NMR spectra of the carbonyl complexes 3a, 3b, 16, 18,
the carbene-containing complex 14, the triphenylphosphine-
containingcomplex 19 as wellas inthe cyclooctadiene complexes
15 and 17. In the cyclooctadiene complexes this is probably due
to the presence of only one isomer as a result of steric reasons,
whereas the carbonyl complexes most probably undergo very
fast sulfur inversions.
Fig. 1 1H NMR spectra of complex 1a in toluene-d8.
Fig. 3 The signal of the proton in the 4-position of the thiazole ring
observed in the 1H NMR spectrum of 20b (A); after selective homonu-
clear proton proton decoupling (B), and after selective heteronuclear
phosphorus decoupling (C).
Fig. 2 Two possible isomers of 1a.
D a l t o n T r a n s . , 2 0 0 5 , 1 8 1 – 1 9 2
1 8 3

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Table 1 31C NMR chemical shifts and coupling constants of selected complexes
Chemical shifts and coupling
constants trans to the ligand
Group
a
Complex
Ligands
Ligand in trans position
d/ppm
JRh
–
C
1a
5
11b
6
15
thione, Cl
carbene, Cl
imine, Cl
bis(carbene)
bis(thione)
bis(imine)
thione, carbene
thione, Cl
carbene, Cl
imine, Cl
bis(carbene)
bis(thione)
bis(imine)
thione, carbene
thione
cod
cod
cod
cod
cod
cod
cod
CO
CO
CO
CO
CO
CO
CO
carbene
carbene
83.7, 74.4
97.4, 68.1
85.1, 76.3
89.3
81.2
85.3
75.4, 92.7
182.9, 182.9
187.7, 184.4
184.1, 180.8
189.9
184.3
182.7
11.6, 14.5
7.4, 14.7
8.4, 11.1
7.3
11.6
12.1
12.1, 7.4
66.9, 66.9
54.3, 75.4
70.1, 72.9
57.6
69.8
70.1
b
[Rh(cod)(Hbbtm)][BF4]10,a
c
d
17
3b
7
12
e
10
16
[Rh(CO)2(Hbbtm)][BF4]10,a
f
g
18
14
20a
183.6, 189.2
175.1
177.2
70.6, 56.7
54.8
45.4
PPh3
a Hbbtm = bis{benzothiazol-2-yl}methane.
Table 2 Catalytic hydroformylation of 1-hexene (80 ◦C, 8 MPa CO–H2 (1 : 1), reaction time of 16 h and a catalyst : substrate ratio of 1 : 1000)
Catalyst precursor
Conversion (%)
Yield of aldehydes (%)
l : b Ratioa
2-Ethylpentanalb (%)
1a
3a
5
100
100
100
29
100
20
100
100
100
21
100
16
1 : 1
1 : 1
9
9
6
0
9
0
10
0
7
11
8
11
11
5
0
5
0
8
7
10
1 : 0.9
1 : 0.6
1 : 1.1
1 : 0.6
1 : 1
1 : 0.6
1 : 1
6
7
8
9
100
64
100
53
10
12
15
17
16
18
19
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
1 : 1.3
1 : 1
1 : 1.3
1 : 1.1
1 : 0.7
1 : 0.4
1 : 0.7
1 : 0.6
1 : 0.9
1 : 0.8
1 : 1.2
c
19 + 4PPh3
19 + 4 thioned
20a
c
20a + 4PPh3
Rh(PPh3)3Cl
10
[Rh(CO)2(Hbbtm)]BF4
a l : b = n-aldehyde: all other aldehydes. b Amount of all 2-ethylpentanal/amount of all aldehydes × 100. c 4 denotes four mole equivalents; d thione =
1,3-diisopropyl-4,5-dimethyl-2,3-dihydro-1H-imidazol-2-thione.
From the observed vibrational frequencies of the dicarbonyl
complexes 3a, 3b and 4 it is clear that the heterocyclic thiones
donate more electron density to the metal centre than thio-
formamide. The carbene complex 7 exhibits m(CO) vibration
frequencies similar to those of the thione complexes 3a and 3b.
The IR data also suggest that the two thione ligands in the
cationic cis-bis(thione) complex, 16, donate only slightly more
electron density to the Rh centre than the carbene and thione
ligands of the cis-carbene(thione) complex, 18.
The mass spectra of thione complexes other than 3a and 4,
could not be determined by electron impact probably because
of the easy dissociation of the thione ligand. Electron spray
ionisation mass spectrometry (in acetonitrile) was used for all
the other thione complexes. In many such instances acetonitrile
remained coordinated to the complexes, often after thione
dissociation had occurred.
precursors for the conversion of 1-hexene into aldehydes in
toluene. First experiments were carried out under a set of
conditions (8 MPa, 80 ◦C, CO–H2 (1 : 1)), chosen to comply
with the safety features of the reactor system used. The results
are summarised in Table 2. Conversion of the alkene to aldehydes
is quantitative in almost all the experiments. No measurable
hydrogenation occurs.
Incomplete reactions (after 16 h) are only found for three
of the precursor catalysts, the cis-bis(carbene) compounds
6 and 10, and the trans-bis(carbene) complex 8. This is
in contrast to the quantitative conversion by the chelated
bis(carbene)cyclooctadiene 9. Unreacted 1-hexene as well as 2-
hexene and 3-hexene (8, 4 and 11%, respectively, for complexes
6, 8 and 10) are present in the three incompletely hydrofomylated
reaction mixtures.
All the thione and imine complexes afford all three possible
aldehydes, whereas the carbene complexes 6, 8, 10 (mentioned
above) and 20a yield only 1-heptanal and 2-methylhexanal, with
20a giving a 100% conversion. With added phosphine the thione
complex 19 also affords no formation of 2-ethylpentanal. A
product l : b ratio of close to 1 : 1 is found for most of the
complexes. The two complexes with two thione ligands (15 and
Hydroformylation results
In a series of preliminary experiments to probe and compare the
use of thione, carbene and imine ligands in hydroformylation, a
number of the new rhodium compounds were used as catalyst
1 8 4
D a l t o n T r a n s . , 2 0 0 5 , 1 8 1 – 1 9 2

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Table 3 Catalytic hydroformylation of 1-hexene under varied conditions
Catalyst
precursor
Isomerised hexene
present (%)
Conditionsa
Conversion (%)
Yield of aldehydes (%)
l : b Ratio
2-Ethylpentanal (%)
3a
A
A
A
A
B
B
B
B
B
C
C
C
C
D
D
D
D
E
E
E
E
0
0
100
100
100
91
100
100
0
100
100
100
100
31
3
0
0
100
71
14
30
—
—
—
—
0
0
0
17
0
0
—
0
38
0
44
9
0
—
—
0
9
0
0
—
—
1 : 0.5
1 : 0.4
1 : 1
1 : 0.6
1 : 1
—
—
0
0
8
0
8
2
—
12
2
3
0
0
0
—
—
9
7
19
100
100
100
74
100
100
—
100
62
100
56
20a
3a
7
19
20a
1 : 0.5
—
Rh(PPh3)3Cl
3a
7
1 : 1.6
1 : 0.5
1 : 0.5
1 : 0.4
1 : 0.6
1 : 0.5
—
—
1 : 1
1 : 0.6
1 : 0.4
1 : 0.4
19
20a
3a
7
19
20a
3a
7
22
3
—
—
100
62
14
30
0
0
0
19
20a
a Conditions: A: 80 ◦C, 8 MPa, 16h, catalyst : substrate 1 : 1000, [BMIM]BF4 as solvent; B: 80 ◦C, 8 MPa, 16h, catalyst : substrate 1 : 1000, dodecane
as solvent; C: 80 ◦C, 4 MPa, 16h, catalyst : substrate 1 : 1000, toluene as solvent; D: 80 ◦C, 8 MPa, 3h, catalyst : substrate 1 : 1000, toluene as solvent;
E: 80 ◦C, 8 MPa, 6h, catalyst : substrate 1 : 1000, toluene as solvent. b TOF = (mol aldehydes formed/mol catalyst) h−1
.
16) effect the worst l : b ratios (1 : 1.3), whereas the phosphine-
containing complexes 19 and 20a, and the three complexes that
give incomplete reactions, exhibit l : b ratios much better than
1 : 1. The addition of phosphine to the carbene complex 20a
(Table 2) leads to a worse l : b ratio and the formation of 2-
ethylpentanal, while the opposite effect occurs with the thione
complex 19. Added free thione has no measureable effect.
Hydroformylation reactions were carried out in the ionic
liquid [BMIM]BF4 (BMIM = 1-butyl-3-methyl-1H-imidazol-
3-ium) followed by extraction with ether after 16 h, (Table 3, A).
The carbonyl(thione) complex, 3a, and the carbene(carbonyl)
complex, 7, are inactive in the ionic liquid, while the trans-
phosphine(thione) complex, 19, and the trans-carbene(phos-
phine) complex, 20a, unfortunately leach into the organic
phase.
X-Ray structure determinations
The molecular structures of the three thione complexes (1b,
2 and 19) are shown in Figs. 4–6 and selected bond lengths
◦
˚
(A) and angles ( ) are given in Table 4 while the two carbene
complexes (6 and 9) are shown in Figs. 7 and 8 with selected bond
lengths and angles given in Table 5. The molecular structures of
these complexes exhibit square planar configurations around
the central Rh atoms. These configurations are distorted in all
examples except 19 since two of the coordination points are at
the centers of the double bonds in the cod ligands. In 1b, 2 and
19 the substituent on the sulfur is syn to the Cl.
Reactions in dodecane (Table 3, B) indicate that the catalyst
activity is solvent dependent. Wilkinson’s catalyst is completely
inactive in dodecane and complex 7 is less active than in toluene.
At a lower pressure of 4 MPa (Table 3, C) the catalytic activity
of the carbene complexes, 7 and 20a, are less than at 8 MPa,
whereas the thione complexes, 3a and 19, still yield a 100%
conversion to aldehydes. At the lower pressure, the l : b ratio
for 19 improves somewhat while this ratio is lowered with 3a.
A large amount of isomerised hexene is present in the reaction
mixtures of 7 and 20a.
Variation of the total reaction time (Table 3, D and E) indi-
cates that the active catalytic species forms only after a period
of time under hydroformylation conditions. With a reaction
time of 3 h only 3a and 7 are active, whereas all four chosen
complexes, as well as Wilkinson’s catalyst, are active after 6 h.
The l : b ratio of thealdehydes formed is higher for the incomplete
hydroformylation reactions than for the completed reactions.
In addition, the amount of isomerised hexene observed after
a certain time differs for the four complexes used, indicating
that the rate of isomerisation of the substrate again depends on
the nature of the catalyst. Complex 3a is by far the most active
catalyst (TOF > 167 h−1 after 6 h) allthough the l : b ratio is low.
Complex 20a produces a 100% conversion to aldehydes after a
reaction time of 9 h (TOF > 111 h−1). The hydroformylation of
styrene carried out by Tiripicchio et al. using a thiourea complex
of rhodium, also yields a 100% conversion to aldehyde, but only
after reaction times of 10–12 h.1
Fig. 4 The molecular structure of 1b showing the numbering scheme.
Hydrogen atoms have been omitted for clarity. Displacement ellipsoids
are shown at the 50% probability level.
Fig. 5 The molecular structure of 2 showing the numbering scheme.
Hydrogen atoms have been omitted for clarity. Displacement ellipsoids
are shown at the 50% probability level.
D a l t o n T r a n s . , 2 0 0 5 , 1 8 1 – 1 9 2
1 8 5

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Fig. 8 The molecular structure of the cation of 9 showing the
numbering scheme. Hydrogen atoms, solvent molecules, counter ions
and one of the independent molecules in the asymmetric unit have
been omitted for clarity. Displacement ellipsoids are shown at the 50%
probability level.
Fig. 6 The molecular structure of 19 showing the numbering scheme.
Hydrogen atoms have been omitted for clarity. Displacement ellipsoids
are shown at the 50% probability level.
◦
˚
Table 4 Selected bond lengths (A) and angles ( ) for the thione
complexes 1b, 2 and 19
◦
˚
Table 5 Selected bond lengths (A) and angles ( ) for carbene complexes
6 and 9. Values for both independent molecules in the asymmetric unit
of 9 are listed
1b
2
19
Rh(1)–Cl(1)
Rh(1)–S(1)
S(1)–C(11)
2.3783(9)
2.3602(7)
1.725(2)
2.3808(9)
2.3665(8)
1.688(3)
2.3700(6)
2.4067(6)
1.723(2)
6
9
Rh(1)–C(11)
Rh(1)–C(21)
Rh(2)–C(41)
Rh(2)–C(51)
2.059(4)
2.051(4)
2.038(4)
2.020(4)
2.028(4)
2.023(4)
Cl(1)–Rh(1)–S(1)
C(11)–S(1)–Rh(1)
92.95(2)
108.81(7)
95.05(3)
110.87(12)
90.25(2)
106.85(7)
C(11)–Rh(1)–C(21)
C(41)–Rh(2)–C(51)
88.43(13)
83.77(15)
83.79(15)
The presence of a bridge between the two imidazole rings in 9,
surprisingly, does not play as large a role in the orientation of the
imidazole rings as might be expected, and an overlay of 6 and
9 indicates that there is very little difference in their structures
despite the two imidazole rings being linked in 9 and not in 6
(see ESI†). The greatest difference is in the C–Rh–C bond angles,
which are 88.43(13) and 83.73(15)◦, respectively.
The molecular structures of 1b, 2, 6, 9 and 19 show that
complex 2, followed by 1b and 19, exhibits the least steric
hindrance around the central Rh atom.
Only complex 19 exhibits any intermolecular interactions,
where phenyl face-to-edge interactions between triphenylphos-
phine groups on neighbouring molecules result in alternating
layers of triphenylphosphine and thione ligands. A similar
packing arrangement is observed for 1b, but since there are
no intermolecular interactions driving the packing, the cod
and thione layers are more loosely defined. Layered structures
are also observed for 6 and 9, where the anions and solvents
form layers between the complexes. In 6 the disordered water
and dichloromethane solvent molecules form hydrogen bonded
chains within the layer structure.
Fig. 7 The molecular structure of the cation of 6 showing the
numbering scheme. Hydrogen atoms, solvent molecules and counter
ion have been omitted for clarity. Displacement ellipsoids are shown at
the 50% probability level.
˚
The relatively long Rh–S bond distance (2.4067(6) A) in 19 can
be attributed to the trans influence of phosphine, as discussed
above. The C–S distance in 2 is somewhat shorter than in the
other thiones 1b and 19 indicating that the C–S bond is also
strengthend by the high neighbouring double bond character.
The imidazole rings in molecular structures 1b, 6, 9 and
19 are oriented approximately perpendicular to the molecular
square plane (89.24(7)◦; 83.9(1) and 82.5(1)◦; 82.6(2), 81.6(2),
83.7(2) and 80.3(2)◦; 77.51(5)◦ respectively), with the greatest
deviation from 90◦ seen for 19 due to the presence of the sulfur.
A view along S(1)–Rh(1)–P(1) (thus also along one of the axes
of the molecular plane) shows that the thione ligand is staggered
with respect to the triphenylphosphine ligand (torsion angle
C(11)–S(1)–P(1)–C(31) 166.7(1)◦). The isopropyl groups also
have different orientations leading to the imidazole ring being
twisted asymmetrically away from the molecular plane. In 2
however, the plane through the N,N-dimethylthioformamide
ligand is almost co-planar with the molecular plane.
Concluding remarks
Our results demonstrate that thione and imine complexes of
Rh(I) are as readily prepared and characterised as comparable
carbene (or phosphine) complexes. Thione ligands may also be
combined with carbene ligands in forming stable complexes.
More spesifically, mono(thione), trans-bis(thione), cis-bis-
(thione), trans-(carbene–thione), cis-(carbene–thione), trans-
(phosphine–thione) and mono(imine) complex-types of
rhodium(I) are now known. The thione complexes under selected
conditions are more active catalyst precursors than the carbenes
for hydroformylation of 1-hexene although their selectivity is
low.
Questions to be answered are whether the role played by the
thione (or carbene or imine) ligand(s) is kinetically or thermody-
namically important and, furthermore, whether thiones might
1 8 6
D a l t o n T r a n s . , 2 0 0 5 , 1 8 1 – 1 9 2

View Article Online
become more useful in hydroformylation or other processes as
catalyst-ligands by effective design and tailoring.
0.49 mmol) and 1,3,4,5-tetramethyl-2,3-dihydro-1H-imidazol-
2-thione (0.11 g, 0.72 mmol). A yellow microcrystalline solid
1
(0.36 g, 90%) was obtained. H NMR (300 MHz, CD2Cl2): d
4.28 (m, 2H, cod olefinic trans to thione ligand), 3.87 (m, 2H,
cod olefinic cis to thione ligand), 3.62 (m, 6H, N–CH3), 2.35
(m, 4H, cod aliphatic equatorial), 2.09 (m, 6H, N–C–CH3), 1.72
Experimental
General procedures and analytical equipment
1
(m, 4H, cod aliphatic axial); 13C{ H} NMR (75 MHz, CD2Cl2):
All reactions and manipulations were carried out under a dry
argon atmosphere using standard Schlenk and vacuum-line
techniques. All solvents were dried and purified by conventional
methods and freshly distilled under nitrogen shortly before
use. Flash column chromatography was performed with “flash
grade” SiO2 (SDS 230–400 mesh). All the common reagents,
including N,N-dimethylthioformamide and KOtBu, were used
as obtained from commercial suppliers without further purifica-
tion. The two easily accessible starting materials, [RhCl(cod)]2
and [RhCl(CO)2]2, were prepared by literature procedures17 as
were 1,3-diisopropyl-4,5-dimethyl-2,3-dihydro-1H-imidazol-2-
thione,1,3-diisopropyl-4,5-dimethyl-2,3-dihydro-1H-imidazol-2-
ylidene, 1,3,4,5-tetramethyl-2,3-dihydro-1H-imidazol-2-thione
and 1,3,4,5-tetramethyl-2,3-dihydro-1H-imidazol-2-ylidene.18
All compounds prepared are stable in air and in solution unless
otherwise stated. The rhodium complexes are soluble in polar
organic solvents and insoluble in non-polar organic solvents in
general while some are also insoluble in diethyl ether.
1
=
=
d 156.3 (s, C S), 124.4 (s, N–C C–N), 83.6 (d, J(C,Rh) =
11.9 Hz, cod olefinic trans to thione ligand), 74.8 (d, 1J(C,Rh) =
13.8 Hz, cod olefinic cis to thione ligand), 33.6 (s, N–CH3), 32.4
(s, cod aliphatic trans to thione ligand), 31.3 (s, cod aliphatic
cis to thione ligand), 9.7 (s, N–C–CH3); MS (ESI): m/z 523
([M+ − Cl + thione ligand], 87), 408 ([M+ − Cl + CH3CN],
100), 402 ([M+], 3), 367 ([M+ − Cl], 82), 212 ([thione ligand+],
◦
30), 180 ([carbene ligand+], 16%); mp 199–200 C. Anal. Calc.
for C15H24ClN2SRh: C, 44.73; H, 6.01; N, 6.95. Found: C, 44.62;
H, 6.03; N, 7.13%.
Chloro(g4 -1,5-cyclooctadiene)(N,N-dimethylthioformamide)-
rhodium(I) (2). N,N-dimethylthioformamide (0.07 cm3,
0.75 mmol) was added to a solution of [RhCl(cod)]2 (0.19 g,
0.38 mmol) in THF (30 cm3). A yellow suspension formed
within 2 min. Stirring was continued for another hour after
which the solvent was removed. The microcrystalline yellow
solid was washed three times with ether (50 cm3) and dried in
1
Melting points were determined on an Electrothermal 9100
apparatus and are uncorrected. Mass spectra were recorded on
an AMD 604 (EI, 70 eV), VG Quattro (ESI, 70 eV, solvent
acetonitrile) or VGA 70-70E (FAB, 70 eV, Xe gas as bombard-
ment gas and 3-nitrobenzyl alcohol as matrix) instrument, the
IR spectra on a Perkin-Elmer 1600 Series FTIR spectrometer
and NMR spectra on a Varian 300 FT or INOVA 600MHz
vacuo (0.25 g, 97%). H NMR (300 MHz, CD2Cl2): d 9.75 (s,
=
1H, S CH), 4.61 (m, 2H, cod olefinic trans to thione ligand),
3.85 (m, 2H, cod olefinic cis to thione ligand), 3.33 (m, 3H,
N–CH3), 3.23 (m, 3H, N–CH3), 2.38 (m, 4H, cod aliphatic
1
equatorial), 1.83 (m, 4H, cod aliphatic axial); 13C{ H} NMR
=
(75 MHz, CD2Cl2): d 191.6 (s, C S), 87.1 (m, cod olefinic trans
to thione ligand), 75.5 (m, cod olefinic cis to thione ligand),
47.5 (s, N–CH3), 40.1 (s, N–CH3), 32.2 (s, cod aliphatic trans to
thione ligand), 31.2 (s, cod aliphatic cis to thione ligand); MS
(ESI): m/z 389 ([M+ + thione ligand], 58), 341 ([M+ − Cl +
CH3CN], 9), 335 ([M+], 1), 300 ([M+ − Cl], 100%); mp 209 ◦C
(decomp.). Anal. Calc. for C11H19ClNSRh: C, 39.36; H, 5.70;
N, 4.17. Found: C, 40.01; H, 5.64; N,4.24%.
spectrometer (1H NMR at 300/600 MHz, 13C{ H} NMR at
1
75/150 MHz and 31P{ H} NMR at 121/243 MHz, d reported
1
relative to the solvent resonance or external reference 85%
H3PO4). Elemental analyses were carried out by the Department
of Chemistry, University of Cape Town, South Africa.
Chloro(g4-1,5-cyclooctadiene)(1,3-diisopropyl-4,5-dimethyl-2,3-
dihydro-1H-imidazol-2-thione)rhodium(I) (1a). 1,3-Diisopropyl-
4,5-dimethyl-2,3-dihydro-1H-imidazol-2-thione (0.18 g,
0.84 mmol) and [RhCl(cod)]2 (0.21 g, 0.42 mmol) were mixed
together in THF (25 cm3). A precipitate formed within seconds
of combining the starting materials. Stirring was continued for
90 min and then the solvent was stripped in vacuo. Complex
1a was purified by flash chromatography on a short column
(2 cm diameter) of silica (2 cm). The excess [RhCl(cod)]2 that
remained after the reaction was removed from the column with
CH2Cl2, after which yellow complex 1a (0.34 g, 88% after drying
in vacuo) was obtained upon washing with ether. 1H NMR
(300 MHz, CD2Cl2): d 5.63 (broad signal, 2H, N–CH), 4.33 (m,
2H, cod olefinic trans to thione ligand), 3.82 (m, 2H, cod olefinic
cis to thione ligand), 2.35 (m, 4H, cod aliphatic equatorial),
2.20 (m, 3H, N–C–CH3), 2.14 (m, 3H, N–C–CH3), 1.75 (m,
4H, cod aliphatic axial), 1.53 (m, 3H, N–CH–(CH3)2), 1.40
Chloro(dicarbonyl)(1,3-diisopropyl-4,5-dimethyl-2,3-dihydro-
1H-imidazol-2-thione)rhodium(I) (3a). A solution of [RhCl-
(CO)2]2 (0.18 g, 0.46 mmol) in THF (10 cm3) was treated
with
1,3-diisopropyl-4,5-dimethyl-2,3-dihydro-1H-imidazol-
2-thione (0.20 g, 0.92 mmol). The orange solution turned
light yellow. After stirring the reaction mixture for 1 h the
solvent was removed in vacuo. The remaining solid was washed
three times with pentane (10 cm3) to yield 3a as a pale yellow
microcrystalline solid (0.15 g, 85%). 1H NMR (300 MHz,
CD2Cl2): d 5.52 (broad signal, 2H, N–CH), 2.23 (m, 6H,
3
N–C–CH3), 1.49 (d, J(H,H) = 7.2 Hz, 12H, N–CH–(CH3)2);
1
13C{ H} NMR (75 MHz, CD2Cl2): d 184.2, 183.2 (two doublets,
1
=
J(C,Rh) = 67.5 Hz, CO-ligands), 151.6 (s, C S), 126.4 (s,
=
N–C C–N), 52.4 (s, N–CH), 21.2 (s, N–CH–CH3), 10.9 (s,
N–C–CH3); MS (EI): m/z 406 ([M+], 3), 378 ([M+ − CO], 2),
314 ([M+ − 2CO − Cl], 5), 212 ([thione ligand+], 87%); IR
(CH2Cl2): m(CO) 2069, 1994 cm−1; mp 88–90 ◦C. Anal. Calc. for
C13H20ClN2O2SRh: C, 38.39; H, 4.96; N, 6.89. Found: C, 38.10;
H, 5.05; N, 6.98%.
1
(m, 3H, N–CH–(CH3)2); 13C{ H} NMR (75 MHz, CD2Cl2): d
=
=
=
155.6 (s, C S), 155.4 (s, C S), 125.3 (s, N–C C–N), 122.3 (s,
N–C C–N), 83.7 (d, J(C,Rh) = 11.6 Hz, cod olefinic trans
1
=
to thione ligand), 74.4 (d, 1J(C,Rh) = 14.5 Hz, cod olefinic cis
to thione ligand), 51.9 (s, N–CH), 49.9 (s, N–CH), 32.5 (s, cod
aliphatic trans to thione ligand), 31.4 (s, cod aliphatic cis to
thione ligand), 21.4 (s, N–CH–CH3), 21.1 (s, N–CH–CH3), 11.0
(s, N–C–CH3), 10.8 (s, N–C–CH3); MS (ESI): m/z 635 ([M+ −
Cl + thione ligand], 100), 458 ([M+], 1), 423 ([M+ − Cl], 100),
212 ([thione ligand+], 14), 180 ([carbene ligand+], 20%); mp
140–141 ◦C. Anal. Calc. for C19H32ClN2SRh: C, 49.73; H, 7.03;
N, 6.10. Found: C, 49.58; H, 6.81; N, 6.26%.
Chloro( dicarbonyl )( 1, 3, 4, 5 - tetramethyl-2, 3 -dihydro-1H-
imidazol-2-thione)rhodium(I) (3b). The same procedure as for
3a was followed for the preparation of 3b from [RhCl(CO)2]2
(0.10 g, 0.24 mmol) and 1,3,4,5-tetramethyl-2,3-dihydro-
1H-imidazol-2-thione (0.07 g, 0.47 mmol). Complex 3b is a
1
yellow–brown microcrystalline solid (0.15 g, 85%). H NMR
(300 MHz, CD2Cl2): d 3.65 (s, 6H, N–CH3), 2.23 (s, 6H,
1
N–C–CH3); 13C{ H} NMR (75 MHz, CD2Cl2): d 182.9 (d,
1
=
J(C, Rh) = 66.9 Hz, CO-ligands), 152.3 (s, C S), 125.6 (s,
Chloro(g4-1,5-cyclooctadiene)(1,3,4,5-tetramethyl-2,3-dihydro-
1H-imidazol-2-thione)rhodium(I) (1b). Complex 1b was pre-
pared in the same way as 1a, using [RhCl(cod)]2 (0.18 g,
N–C C–N), 34.0 (s, N–CH3), 9.8 (s, N–C–CH3); MS (ESI):
=
m/z 471 ([M+ − Cl + thione ligand], 100), 443 ([M+ − CO–Cl +
thione ligand], 30), 415 ([M+ − 2CO − Cl + thione ligand],
D a l t o n T r a n s . , 2 0 0 5 , 1 8 1 – 1 9 2
1 8 7

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35), 156 ([thione ligand+], 43), 156 ([thione ligand+ − S], 26%);
IR (CH2Cl2): m(CO) 2071, 1998 cm−1; mp 88–89 ◦C (decomp.).
Anal. Calc. for C9H12ClN2O2SRh: C, 30.83; H, 3.45; N, 7.99.
Found: C, 31.08; H, 3.28; N, 7.83%.
within moments. After 5 min the reaction mixture was dried
in vacuo and washed with pentane (10 cm3). The remaining
yellow powder was again dissolved in CH2Cl2 (20 cm3) after
which carbon monoxide was bubbled through the solution for
10 min. The mixture was again reduced to dryness and washed
with pentane. Complex 7 is a light yellow microcrystalline solid
Chloro(dicarbonyl)(N,N -dimethylthioformamide)rhodium(I)
(4). Complex 4 was prepared in the same way as 3a from
[RhCl(CO)2]2 (0.22 g, 0.58 mmol) and N,N-dimethylthio-
formamide (0.10 cm3, 1.17 mmol). The product was washed
with pentane (20 cm3) and with two portions of ether
(20 cm3). Complex 4 is a slightly hygroscopic brown–yellow
microcrystalline solid (0.27 g, 83%) and cannot be stored
indefinitely. 1H NMR (300 MHz, CD2Cl2): d 9.66 (m, 1H,
1
(0.20 g, 93%). H NMR (300 MHz, CD2Cl2): d 5.32 (septet,
3J(H,H) = 7.1 Hz, 2H, N–CH), 2.16 (s, 6H, N–C–CH3), 1.51
(d, 3J(H,H) = 7.1 Hz, 6H, N–CH–(CH3)2), 1.49 (d, 3J(H,H) =
1
7.1 Hz, 6H, N–CH–(CH3)2); 13C{ H} NMR (75 MHz, CD2Cl2):
d 187.7 (d, 1J(C,Rh) = 54.3 Hz, CO trans to the carbene
1
ligand), 184.4 (d, J(C,Rh) = 75.4 Hz, CO cis to the carbene
ligand), 170.7 (d, 1J(C,Rh) = 43.0 Hz, N–C–N), 127.2 (s,
=
S CH), 3.43 (m, 3H, N–CH3), 3.35 (d, J(H,H) = 0.08 Hz,
=
N–C C–N), 54.7 (s, N–CH), 22.7 (s, N–CH–CH3), 22.2 (s,
13
1
=
N–CH–CH3), 10.6 (s, N–C–CH3); MS (EI): m/z 374 ([M+],
6), 346 ([M+ − CO], 14), 282 ([M+ − 2CO − Cl], 100%); IR
(CH2Cl2): m(CO) 2076, 1996 cm−1; mp 150 ◦C (decomp.). Anal.
Calc. for C13H20ClN2O2Rh: C, 41.67; H, 5.38; N, 7.48. Found:
C, 42.03; H, 5.22; N, 7.31%.
N–CH3); C{ H} NMR (75 MHz, CD2Cl2): d 189.1 (s, S C),
1
182.5 (d, J(C, Rh) = 70.4 Hz, CO-ligands), 48.4 (s, N–CH3),
40.7 (s, N–CH3); MS (EI): m/z 283 ([M+], 1), 103 ([Rh+], 14), 89
([thione ligand+], 100%); IR (CH2Cl2): m(CO) 2081, 2009 cm−1;
◦
mp 52 C. Anal. Calc. for C5H7ClNO2SRh: C, 21.18; H, 2.49;
N, 4.94. Found: C, 21.33; H, 2.51; N, 4.82%.
Chloro(carbonyl)-trans-bis(1,3,4,5-tetramethyl-2,3-dihydro-
1H-imidazol-2-ylidene)rhodium(I) (8). Carbon monoxide was
bubbled through a yellow solution of 6 (0.16 g, 0.32 mmol) in
25 cm3 of CH2Cl2 for 30 min. The reaction mixture was dried
in vacuo and washed twice with pentane (50 cm3) and twice
with ether (50 cm3). The yellow microcrystalline solid (0.12 g,
90%) was dried in vacuo. 1H NMR (300 MHz, CD2Cl2): d
Chloro(g4 -1,5-cyclooctadiene)(1,3-diisopropyl-4,5-dimethyl-
2,3-dihydro-1H-imidazol-2-ylidene)rhodium(I) (5). The reac-
tion of 0.84 g (4.68 mmol) 1,3-diisopropyl-4,5-dimethyl-
2,3-dihydro-1H-imidazol-2-ylidene with 1.21 g (2.45 mmol)
[RhCl(cod)]2 in THF (40 cm3) yielded the monocarbene
complex 5 as a yellow solid. An excess of [RhCl(cod)]2 was used
to prevent the formation of a biscarbene complex. Complex
5 was purified by flash chromatography on a short column.
The excess [RhCl(cod)]2 that remained after the reaction was
removed from the column with CH2Cl2. Complex 5 was isolated
from the column with ether and dried in vacuo to yield a yellow
microcrystalline solid (1.74 g, 85%). 1H NMR (300 MHz,
1
3.91 (s, 12H, N–CH3), 2.11 (s, 12H, C–CH3); 13C{ H} NMR
(75 MHz, CD2Cl2): d 188.4 (d, 1J(C,Rh) = 82.8 Hz, CO ligand),
1
=
182.9 (d, J(C,Rh) = 40.6 Hz, N–C–N), 125.3 (s, N–C C–N),
36.0 (s, N–CH3), 9.7 (s, C–CH3); MS (EI): m/z 414 ([M+], 6),
386 ([M+ − CO], 41), 351 ([M+ − CO − Cl], 2), 124 [carbene
ligand+]; IR (CH2Cl2): m(CO) 1934 cm−1; mp 219 ◦C (decomp.).
Anal. Calc. for C15H24ClN4ORh: C, 43.44; H, 5.83; N, 13.51.
Found: C, 43.72; H, 5.77; N, 13.36%.
3
CD2Cl2): d 6.10 (septet, J(H,H) = 7.2 Hz, 2H, N–CH), 4.81
(m, 2H, cod olefinic trans to carbene ligand), 3.31 (m, 2H,
cod olefinic cis to carbene ligand), 2.32 (m, 4H, cod aliphatic
equatorial), 2.10 (s, 6H, N–C–CH3), 1.87 (m, 4H, cod aliphatic
[(g4 -1,5-Cyclooctadiene)-cis-(1,1ꢀ -propylene-3,3ꢀ -dimethyl-
2,3,2ꢀ,3ꢀ-tetrahydro-1,1ꢀH-diimidazol-2,2ꢀ -diylidene)rhodium(I)]
hexafluorophosphate (9). [RhCl(cod)]2 (0.17 g, 0.35 mmol) was
added to a suspension of [1,1ꢀ-propylene-3,3ꢀ-dimethyl-1,1ꢀH-
diimidazole][dihexafluorophosphate]19 (0.16 g, 0.38 mmol) in
15 cm3 THF. The addition of KOtBu (0.130 g, 1.14 mmol)
yielded a dark yellow solution. This solution was stirred for
4 h before the solvent was removed in vacuo. The remaining
yellow powder was washed with 5 portions of 30 cm3 of
ether. Complex 9 was extracted with THF (five portions,
30 cm3) and filtered through anhydrous MgSO4. Complex 9
was isolated using THF from a short column after removal of
the last traces of [RhCl(cod)]2 with CH2Cl2. Complex 9 is a
1
axial), 1.55 (d, 3J(H,H) = 7.2 Hz, 6H, N–CH–(CH3)2); 13C{ H}
NMR (75 MHz, CD2Cl2): d 180.7 (d, 1J(C,Rh) = 51.5 Hz,
1
=
N–C–N), 126.1 (s, N–C C–N), 97.4 (d, J(C,Rh) = 7.4 Hz,
cod olefinic trans to carbene ligand), 68.1 (d, 1J(C,Rh) =
14.7 Hz, cod olefinic cis to carbene ligand), 54.4 (s, N–CH),
33.5 (s, cod aliphatic trans to carbene ligand), 29.5 (s, cod
aliphatic cis to carbene ligand), 22.6 (s, N–CH–CH3), 22.3 (s,
N–CH–CH3), 10.7 (s, N–C–CH3); MS (EI): m/z 426 ([M+], 26),
282 ([M+–cod–Cl], 24), 180 ([carbene ligand+], 86); mp 193 ◦C
(decomp.). Anal. Calc. for C19H32ClN2Rh: C, 53.47; H, 7.56; N,
6.56. Found: C, 53.31; H, 7.62; N, 6.66%.
Cis-[(g4-1,5-cyclooctadiene)bis(1,3,4,5-tetramethyl-2,3-dihydro-
1H-imidazol-2-ylidene)rhodium(I)]chloride (6). [RhCl(cod)]2
(0.22 g, 0.44 mmol) dissolved in 5 cm3 of THF was treated
with a freshly prepared solution of the carbene ligand in THF
(10 cm3, 9.0 mmol). A yellow precipitate formed immediately.
Stirring was continued for 2 h. The suspension was filtered
and the light yellow precipitate was then washed with ether
(20 cm3). Complex 6 (0.12 g, 56%) was recrystallised from
CH2Cl2 and pentane. 1H NMR (300 MHz, CD2Cl2): d 4.19
(m, 4H, cod olefinic), 3.84 (s, 12H, N–CH3), 2.39 (m, 4H, cod
aliphatic equatorial), 2.13 (m, 4H, cod aliphatic axial), 2.00 (m,
yellow microcrystalline solid (0.12 g, 56%). 1H NMR (300 MHz,
2
=
acetone-d6): d 7.21 (d, J(H,H) = 1.8 Hz, 2H, N–CH CH), 7.11
2
3
=
(d, J(H,H) = 1.8 Hz, 2H, N–CH CH), 5.09 (dd, J(H,H) =
11.3 Hz, 2J(H,H) = 14.4 Hz, 2H, N–CH2 equatorial), 4.63 (m,
2H, cod olefinic), 4.08 (m, 2H, cod olefinic), 4.45 (dd, 3J(H,H) =
2
6.4 Hz, J(H,H) = 14.4 Hz, 2H, N–CH2 axial), 4.06 (s, 6H,
N–CH3), 2.81 (m, 2H, N–CH2–CH2–CH2–N), 2.55 (m, 4H, cod
aliphatic equatorial), 2.26 (m, 4H, cod aliphatic axial); 13C{ H}
1
1
NMR (75 MHz, acetone-d6): d 183.8 (d, J(C,Rh) = 52.5 Hz,
1
=
N–C–N), 124.6 (s, N–C C–N), 91.2 (d, J(C,Rh) = 7.9 Hz,
1
cod olefinic), 90.1 (d, J(C,Rh) = 7.9 Hz, cod olefinic), 54.2
1
12H, C–CH3); 13C{ H} NMR (75 MHz, CD2Cl2): d 178.7 (d,
(s, N–CH3), 39.3 (s, N–CH2), 34.8 (s, N–CH2–CH2–CH2–N),
32.3 (s, cod aliphatic), 32.1 (s, cod aliphatic); MS (FAB): m/z
1
=
J(C,Rh) = 53.2 Hz, N–C–N), 126.7 (s, N–C C–N), 89.3 (d,
1J(C,Rh) = 7.3 Hz, cod olefinic), 36.7 (s, N–CH3), 31.6 (s, cod
aliphatic), 9.6 (s, C–CH3); MS (ESI): m/z 459 ([M+], 100%); mp
159 ◦C (decomp.). Anal. Calc. for C22H36ClN4Rh: C, 53.39; H,
7.33; N, 11.32. Found: C, 53.02; H, 7.69; N, 11.08%.
◦
415 ([M+], 55), 307 ([M+ − cod], 32%); mp 215–217 C. Anal.
Calc. for C19H28F6N4PRh: C, 40.73; H, 5.04; N, 10.00. Found:
C, 40.88; H, 5.33; N, 9.86%.
[Dicarbonyl(cis-(1,1ꢀ -propylene-3,3ꢀ -dimethyl-2,3,2ꢀ,3ꢀ -tetra-
hydro-1,1ꢀH-diimidazol-2,2ꢀ -diylidene)rhodium(I)] hexafluoro-
phosphate (10). Complex 10, a light yellow microcrystalline
solid (0.05 g, 88%), was prepared in the same way as 7, using
9 (0.07 g, 0.12 mmol). 1H NMR (300 MHz, acetone-d6):
Chloro(dicarbonyl)(1,3-diisopropyl-4,5-dimethyl-2,3-dihydro-
1H-imidazol-2-ylidene)rhodium(I) (7). Carbon monoxide was
bubbled through a yellow solution of 5 (0.27 g, 0.63 mmol)
in 20 cm3 of CH2Cl2. The reaction mixture turned orange
1 8 8
D a l t o n T r a n s . , 2 0 0 5 , 1 8 1 – 1 9 2

View Article Online
2
=
d 7.38 (d, J(H,H) = 1.9 Hz, 2H, N–CH CH), 7.31 (d,
C, 24.55; H, 1.72; N, 4.77. Found: C, 24.49; H, 1.81; N,
4.64%.
J(H,H) = 1.9 Hz, 2H, N–CH CH), 4.78 (dd, 3J(H,H) =
2
=
11.6 Hz, 2J(H,H) = 14.4 Hz, 2H, N–CH2 equatorial), 4.50 (dd,
Chloro(carbonyl)-trans-bis(1,3-diisopropyl-4,5-dimethyl-2,3-
dihydro-1H-imidazol-2-thione)rhodium(I) (13). Complex 3a
(0.16 g, 0.40 mmol) was added to a suspension of trimethylamine
oxide (0.03 g, 0.40 mmol) in 30 cm3 of THF. After stirring for
30 min, 1,3-diisopropyl-4,5-dimethyl-2,3-dihydro-1H-imidazol-
2-thione (0.08 g, 0.40 mmol) was added to the orange solution.
The reaction mixture was stirred for two weeks and then
dried in vacuo. The solid was washed five times with pentane
(20 cm3), dissolved in ether (100 cm3), filtered over anhydrous
MgSO4 (2 cm) and dried in vacuo as an orange microcrystalline
solid (0.10 g, 43%). 1H NMR (300 MHz, CD2Cl2): d 5.91
(broad signal, 4H, N–CH), 2.18 (m, 12H, N–C–CH3), 1.49
3J(H,H) = 5.9 Hz, 2J(H,H) = 14.4 Hz, 2H, N–CH2 axial), 3.98
(s, 6H, N–CH3), 2.82 (m, 2H, N–CH2–CH2–CH2–N); 13C{ H}
1
1
NMR (75 MHz, acetone-d6): d 189.9 (d, J(C,Rh) = 57.6 Hz,
1
CO ligands), 173.9 (d, J(C,Rh) = 44.6 Hz, N–C–N), 125.9
=
=
(s, N–C C–N), 125.7 (s, N–C C–N), 54.5 (s, N–CH3), 39.7
(s, N–CH2), 33.6 (s, N–CH2–CH2–CH2–N); MS (FAB): m/z
363 ([M+], 100), 335 ([M+ − CO], 12), 307 ([M+ − 2CO], 52);
IR (CH2Cl2): m(CO) 2085, 2028 cm−1; mp 174 ◦C (decomp.).
Anal. Calc. for C13H16F6N4O2PRh: C, 30.73; H, 3.17; N, 11.03.
Found: C, 30.90; H, 3.08; N, 11.17%.
Chloro(g4 -1,5-cyclooctadiene)(4-methylthiazole)rhodium(I)
(11a). 4-Methylthiazole (0.09 cm3, 0.77 mmol) was added to a
solution of [RhCl(cod)]2 (0.20 g, 0.40 mmol) in THF (10 cm3).
A yellow suspension was observed after 30 min. Stirring was
continued for another 3 days. Complex 11a was isolated from a
short SiO2 flash chromatography column with CH2Cl2 as eluant
1
(m, 24H, N–CH–(CH3)2); 13C{ H} NMR (75 MHz, CD2Cl2):
1
=
d 187.1 (d, J(C,Rh) = 75.3 Hz, CO), 153.5 (m, C S), 125.9
=
(m, N–C C–N), 51.9 (m, N–CH), 21.7 (m, N–CH–CH3),
11.1 (m, N–C–CH3); MS (ESI): m/z 808 ([M+ − Cl + thione
ligand + CH3CN], 53), 596 ([M+ − Cl + CH3CN], 10), 212
([thione ligand+], 22), 156 ([thione ligand+ − S], 100%); IR
(CH2Cl2): m(CO) 1931 cm−1; mp 131–132 ◦C. Anal. Calc. for
C23H40ClN4OS2Rh: C, 46.74; H, 6.82; N, 9.48. Found: C, 46.53;
H, 6.79; N, 9.55%.
and dried in vacuo as a yellow microcrystalline solid (0.20 g,
72%). H NMR (300 MHz, CD2Cl2): d 8.85 (s, 1H, N CH–S),
1
=
7.06 (s, 1H, S–CH2), 4.57 (m, 2H, cod olefinic trans to thiazole
ligand), 3.49 (m, 2H, cod olefinic cis to thiazole ligand), 2.93 (s,
3H, N–CH–CH3), 2.46 (m, 4H, cod aliphatic equatorial), 1.78
Chloro(carbonyl)-trans-(1,3-diisopropyl-4,5-dimethyl-2,3-di-
hydro-1H-imidazol-2-thione)(1,3-diisopropyl-4,5-dimethyl-2,3-di-
hydro-1H-imidazol-2-ylidene)rhodium(I) (14). Complex 14 was
prepared in a similar fashion than 13 using complex 7 (0.16 g,
0.44 mmol), trimethylamine oxide (0.03 g, 0.44 mmol) and 1,3-
diisopropyl-4,5-dimethyl-2,3-dihydro-1H-imidazol-2-thione
(0.09 g, 0.43 mmol). Complex 14 was purified by flash
chromatography on a short column. Excess 7 was separated
from 14 by elution with ether, and 14 was then isolated from
the column with THF. The yellow solution was dried in vacuo
to yield a yellow microcrystalline solid (0.14 g, 56%). 1H NMR
(m, 4H, cod aliphatic axial); 13C{ H} NMR (75 MHz, CD2Cl2):
1
=
=
=
d 154.3 (s, N C–S), 153.4 (s, N–C C), 115.5 (s, S–C C), 85.3
(m, cod olefinic trans to thiazole ligand), 76.4 (m, cod olefinic
cis to thiazole ligand), 32.0 (m, cod aliphatic trans to thiazole
ligand), 31.3 (m, cod aliphatic cis to thiazole ligand), 18.5 (m,
N–C–CH3); MS (FAB): m/z 346 ([M+], 7), 310 ([M+ − Cl],
10), 211 ([M+ − Cl − thiazole ligand], 16%); mp 232–233 ◦C
(decomp.). Anal. Calc. for C12H17ClNSRh: C, 41.69; H, 4.96;
N, 4.05. Found: C, 41.81; H, 4.88; N, 4.16%.
Chloro(g4-1,5-cyclooctadiene)(4,5-dimethylthiazole)rhodium(I)
(11b). The procedure followed for 11a was used to prepare 11b
from [RhCl(cod)]2 (0.19 g, 0.39 mmol) and 4,5-dimethylthiazole
(0.09 cm3, 0.80 mmol). Complex 11b is a yellow microcrystalline
solid (0.19 g, 67%) with the same solubility properties as 11a.
H NMR (300 MHz, CD2Cl2): d 8.63 (s, 1H, N CH–S), 4.56
3
(300 MHz, CD2Cl2): d 6.21 (septet, J(H,H) = 7.2 Hz, 2H,
N–CH carbene ligand), 5.96 (broad signal, 2H, N–CH thione
ligand), 2.21 (s, 6H, N–C–CH3), 2.16 (s, 6H, N–C–CH3), 1.53 (d,
3J(H,H) = 7.2 Hz, 12H, N–CH–(CH3)2 thione ligand), 1.48 (d,
3J(H,H) = 7.2 Hz, 6H, N–CH–(CH3)2 carbene ligand), 1.45 (d,
1
=
1
3J(H,H) = 7.2 Hz, 6H, N–CH–(CH3)2 carbene ligand); 13C{ H}
(m, 2H, cod olefinic trans to thiazole ligand), 3.49 (m, 2H, cod
olefinic cis to thiazole ligand), 2.89 (s, 3H, N–CH–CH3), 2.46
(m, 4H, cod aliphatic equatorial), 2.33 (d, J(H,H) = 0.8 Hz, 3H,
NMR (75 MHz, CD2Cl2): d 187.5 (d, 1J(C,Rh) = 80.8 Hz, CO),
1
175.1 (d, J(C,Rh) = 54.8 Hz, N–C–N carbene ligand), 157.2
=
=
=
(s, C S), 125.6 (s, N–C C–N), 124.5 (s, N–C C–N), 54.3
(s, N–CH carbene ligand), 51.5 (s, N–CH thione ligand), 22.1
(s, N–CH–CH3 carbene ligand), 22.0 (s, N–CH–CH3 carbene
ligand), 21.2 (s, N–CH–CH3 thione ligand), 10.9 (s, N–C–CH3),
10.9 (s, N–C–CH3); MS (ESI): m/z 735 ([M+ − Cl + thione
ligand, 4), 564 ([M+ − Cl + CH3CN], 4), 523 ([M+ − Cl], 62),
495 ([M+ − Cl − CO], 15), 352 ([M+ − Cl − thione ligand +
CH3CN], 14), 324 ([M+ − Cl − thione ligand − CO + CH3CN],
100), 311 ([M+ − Cl − thione ligand], 7), 283 ([M+ − Cl −
thione ligand − CO], 41%); IR (CH2Cl2): m(CO) 1934 cm−1; mp
172–173 ◦C. Anal. Calc. for C23H40ClN4OSRh: C, 49.42; H,
7.21; N, 10.02. Found: C, 49.11; H, 7.13; N, 10.33%.
S–CH–CH3), 1.79 (m, 4H, cod aliphatic axial); 13C{ H} NMR
1
=
=
(75 MHz, CD2Cl2): d 150.0 (s, N C–S), 149.7 (s, N–C C),
1
=
128.5 (s, S–C C), 85.1 (d, J(C,Rh) = 8.4 Hz, cod olefinic trans
1
to thiazole ligand), 76.3 (d, J(C,Rh) = 11.1 Hz, cod olefinic
cis to thiazole ligand), 32.2 (s, cod aliphatic trans to thiazole
ligand), 31.1 (s, cod aliphatic cis to thiazole ligand), 16.9 (m,
N–C–CH3), 12.1 (m, S–C–CH3); MS (FAB): m/z 359 ([M+],
11), 323 ([M+ − Cl − H], 53), 211 ([M+ − Cl − thiazole ligand],
38%); mp 226 ◦C (decomp.). Anal. Calc. for C12H19ClNSRh:
C, 43.41; H, 5.32; N, 3.89. Found: C, 43.23; H, 5.44; N,
3.80%.
Chloro(dicarbonyl)(4-methylthiazole)rhodium(I) (12). Fol-
lowing the same procedure as for 3a, 12 was prepared
from [RhCl(CO)2]2 (0.10 g, 0.24 mmol) and 4-methylthiazole
(0.04 cm3, 0.44 mmol) in THF (5 cm3) as a yellow–brown
[(g4-1,5-Cyclooctadiene)bis(1,3-diisopropyl-4,5-dimethyl-2,3-
dihydro-1H-imidazol-2-thione)rhodium(I) tetrafluoroborate (15).
A solution of [RhCl(cod)]2 (0.19 g, 0.39 mmol) and 1,3-di-
isopropyl-4,5-dimethyl-2,3-dihydro-1H-imidazol-2-imidazole-
2(3H)-thione (0.33 g, 1.56 mmol) in THF (5 cm3) was added
to a suspension of AgBF4 (0.16 g, 0.79 mmol) in THF (5 cm3).
The precipitation of AgCl was observed almost immediately.
Stirring was continued for 2 h. The reaction mixture was
filtered over Celite (2 cm) and the filtrate dried in vacuo.
The yellow microcrystalline solid (0.46 g, 83%) was washed
microcrystalline solid (0.08 g, 64%). 1H NMR (300 MHz,
4
=
CD2Cl2): d 9.05 (d, J(H,H) = 2.5 Hz, 1H, N CH–S), 7.21
4
4
(dq, J(H,H) = 1.0 Hz, J(H,H) = 2.5 Hz, 1H, S–CH2), 2.69
(s, 3H, N–CH–CH3); 13C{ H} NMR (75 MHz, CD2Cl2): d
1
1
184.1 (d, J(Rh,C) = 70.1 Hz, CO ligand trans to the thiazole
1
ligand), 180.8 (d, J(Rh,C) = 72.9 Hz, CO ligand cis to the
1
thiazole ligand), 157.8 (s, N C–S), 153.8 (s, N–C C), 116.3 (s,
three times with ether (20 cm3) and dried in vacuo. H NMR
=
=
+
=
S–C C), 19.0 (m, N–C–CH3); MS (FAB): m/z 293 ([M ], 1), 99
(300 MHz, CD2Cl2): d 5.44 (broad signal, 4H, N–CH), 3.76
(m, 4H, cod olefinic), 2.30 (m, 4H, cod aliphatic equatorial),
2.21 (s, 12H, N–C–CH3), 1.80 (m, 4H, cod aliphatic axial), 1.49
([thiazole ligand+], 100%); IR (CH2Cl2): m(CO) 2088, 2014 cm−1;
mp 57–58 ◦C (decomp.). Anal. Calc. for C6H5ClNO2SRh:
D a l t o n T r a n s . , 2 0 0 5 , 1 8 1 – 1 9 2
1 8 9

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3
1
(d, J(H,H) = 7.2 Hz, 24H, N–CH–(CH3)2); 13C{ H} NMR
Complex 18 was purified using short column chromatography.
It was isolated with THF after removal of all the other products
from the column with CH2Cl2. Complex 18 was dried in vacuo
and washed with pentane (10 cm3) and ether (10 cm3) leaving a
yellow microcrystalline solid (0.07 g, 74%). 1H NMR (300 MHz,
CD2Cl2): d 5.36 (broad signal, 2H, N–CH thione ligand), 5.30
(septet, 3J(H,H) = 7.2 Hz, 2H, N–CH carbene ligand), 2.29 (s,
=
=
(75 MHz, CD2Cl2): d 152.2 (s, C S), 126.8 (s, N–C C–N),
81.2 (d, 1J(C,Rh) = 11.6 Hz, cod olefinic), 52.1 (s, N–CH), 31.7
(s, cod aliphatic), 21.5 (s, N–CH–CH3), 11.0 (s, N–C–CH3);
MS (ESI): m/z 635 ([M+], 74), 464 ([M+ − thione ligand +
CH3CN], 81), 423 ([M+ − thione ligand], 100), 212 ([thione
ligand+], 17), 180 ([thione ligand+ − S], 21%); mp 182 ◦C. Anal.
Calc. for C30H52BF4N4S2Rh: C, 49.87; H, 7.25; N, 7.75. Found:
C, 49.71; H, 7.24; N, 7.85%.
3
6H, N–C–CH3), 2.22 (s, 6H, N–C–CH3), 1.58 (d, J(H,H) =
7.2 Hz, 6H, N–CH–(CH3)2 carbene ligand), 1.56 (d, 3J(H,H) =
7.2 Hz, 6H, N–CH–(CH3)2 carbene ligand), 1.57 (d, 3J(H,H) =
[(Dicarbonyl)-cis-bis(1,3-diisopropyl-4,5-dimethyl-2,3-dihydro-
1H-imidazol-2-thione)rhodium(I)] tetrafluoroborate (16). The
same procedure as used to prepare 7 was employed to prepare
complex 16 from 15 (0.24 g, 0.33 mmol). Complex 16 is a slightly
hygroscopic yellow–orange microcrystalline product (0.21 g,
1
7.2 Hz, 12H, N–CH–(CH3)2 thione ligand); 13C{ H} NMR
1
(75 MHz, CD2Cl2): d 189.2 (d, J(C,Rh) = 56.7 Hz, CO trans
1
to carbene ligand), 183.6 (d, J(C,Rh) = 70.6 Hz, CO trans
to thione ligand), 164.9 (d, 1J(C,Rh) = 40.9 Hz, N–C–N
=
=
carbene ligand), 152.2 (s, C S), 128.6 (s, N–C C–N), 127.1
(s, N–C C–N), 55.3 (s, N–CH carbene ligand), 52.4 (s, N–CH
1
95%) and cannot be stored indefinitely. H NMR (300 MHz,
CD2Cl2): d 5.45 (broad signal, 4H, N–CH), 2.27 (s, 12H,
=
thione ligand), 22.6 (s, N–CH–CH3 carbene ligand), 22.1
(s, N–CH–CH3 carbene ligand), 21.1 (s, N–CH–CH3 thione
ligand), 10.9 (s, N–C–CH3), 10.8 (s, N–C–CH3); MS (ESI):
m/z 551 ([M+], 81), 523 ([M+ − CO], 67), 495 ([M+ − 2CO],
17), 352 ([M+ − CO − thione ligand + CH3CN], 10), 324
3
N–C–CH3), 1.52 (d, J(H,H) = 7.2 Hz, 24H, N–CH–(CH3)2);
1
13C{ H} NMR (75 MHz, CD2Cl2): d 184.3 (d, 1J(C,Rh) =
=
=
69.8 Hz, CO ligands), 149.9 (s, C S), 127.5 (s, N–C C–N),
52.6 (s, N–CH), 21.2 (s, N–CH–CH3), 10.9 (s, N–C–CH3);
MS (ESI): m/z 767 ([M+ − CO + thione ligand], 6), 596
([M+ − CO + CH3CN], 4), 583 ([M+], 100), 555 ([M+ − CO],
39), 527 ([M+ − 2CO], 18), 212 ([thione ligand+], 63%); IR
(CH2Cl2): m(CO) 2066, 2001 cm−1; mp 65 ◦C. Anal. Calc. for
C24H40BF4N4O2S2Rh: C, 43.00; H, 6.01; N, 8.36. Found: C,
42.89; H, 6.14; N, 8.29%.
([M+ − 2CO − thione ligand + CH3CN], 100), 311 ([M+
−
CO − thione ligand], 7), 283 ([M+ − 2CO − thione ligand],
53), 212 ([thione ligand+], 11), 180 ([carbene ligand+], 22%); IR
(CH2Cl2): m(CO) 2071, 2009 cm−1; mp 123–124 ◦C. Anal. Calc.
for C24H40BF4N4O2SRh: C, 45.15; H, 6.32; N, 8.78. Found: C,
45.27; H, 6.28; N, 8.81%.
[(g4-1,5-Cyclooctadiene)(1,3-diisopropyl-4,5-dimethyl-2,3-di-
hydro-1H-imidazol-2-thione)(1,3-diisopropyl-4,5-dimethyl-2,3-
Chloro(carbonyl)-trans-(triphenylphosphine)(1,3-diisopropyl-4,
5-dimethyl-2,3-dihydro-1H-imidazol-2-thione)rhodium(I) (19).
Triphenylphosphine (0.26 g, 1.00 mmol) was added to a solution
of 3a (0.41 g, 1.00 mmol) in THF (10 cm3). Carbon monoxide
evolution was observed as the mixture was stirred at room
temperature. After 30 min, the reaction mixture was dried in
vacuo and washed four times with 20 cm3 of ether. Complex
dihydro-1H-imidazol-2-ylidene)rhodium(I)]
tetrafluoroborate
(17). A solution of 5 (0.19 g, 0.44 mmol) and 1,3-diisopropyl-
4,5-dimethyl-2,3-dihydro-1H-imidazol-2-thione (0.09 g,
0.44 mmol) in 5 cm3 of THF was added to a suspension of
AgBF4 (0.10 g, 0.51 mmol) in THF (5 cm3). A white precipitate,
AgCl, was observed almost immediately. Stirring was continued
for 1 h. Yellow microcrystalline complex 17 (0.28 g, 91%)
1
19 is a yellow microcrystalline solid (0.52 g, 82%). H NMR
(300 MHz, CD2Cl2): d 7.68 (m, 6H, aromatic protons), 7.37
(m, 9H, aromatic protons), 5.87 (broad signal, 2H, N–CH),
2.19 (s, 6H, N–C–CH3), 1.52 (d, 3J(H,H) = 7.2 Hz, 6H,
1
was isolated in the same manner as 15. H NMR (300 MHz,
CD2Cl2): d 5.97 (septet, 3J(H,H) = 7.2 Hz, 2H, N–CH carbene
ligand), 5.32 (broad signal, 2H, N–CH thione ligand), 3.92
(m, 2H, cod olefinic trans to carbene ligand), 3.75 (m, 2H,
cod olefinic trans to thione ligand), 2.33 (m, 4H, cod aliphatic
equatorial), 2.24 (s, 6H, N–C–CH3), 2.17 (s, 6H, N–C–CH3),
1
N–CH–(CH3)2); 13C{ H} NMR (75 MHz, CD2Cl2): d 188.5
1
2
(dd, J(C,Rh) = 75.5 Hz, J(C,P) = 16.2 Hz, CO), 155.3 (s,
C S), 135.6 (d, 1J(C,P) = 46.5 Hz, Ph–C ipso), 135.5 (d,
=
2J(C,P) = 11.6 Hz, Ph–C ortho), 130.8 (d, J(C,P) = 1.8 Hz,
3
3
4
1.95 (m, 4H, cod aliphatic axial), 1.61 (d, J(H,H) = 7.2 Hz,
Ph–C meta), 128.8 (d, J(C,P) = 9.8 Hz, Ph–C para), 125.4
6H, N–CH–(CH3)2 carbene ligand), 1.56 (d, 3J(H,H) =
7.2 Hz, 6H, N–CH–(CH3)2 carbene ligand), 1.51 (d, 3J(H,H) =
=
(s, N–C C–N), 51.9 (s, N–CH), 21.2 (s, N–CH–CH3), 10.9
(s, N–C–CH3); 31P{ H} NMR (121 MHz, CD2Cl2): d 32.5 (d,
1
1
7.2 Hz, 12H, N–CH–(CH3)2 thione ligand); 13C{ H} NMR
1J(C,P) = 158.5 Hz); MS (ESI): m/z 817 ([M+ − Cl + thione
ligand], 100), 605 ([M+ − Cl], 17), 180 ([thione ligand+], 7); IR
(CH2Cl2): m(CO) 1959 cm−1; mp 177–180 ◦C. Anal. Calc. for
C30H35ClN2OPSRh: C, 56.21; H, 5.50; N, 4.37. Found: C, 56.41;
H, 5.43; N, 4.44%.
1
(75 MHz, CD2Cl2): d 176.5 (d, J(C,Rh) = 50.2 Hz, N–C–N
=
=
carbene ligand), 152.9 (s, C S), 127.2 (s, N–C C–N), 126.8
(s, N–C C–N), 92.7 (d, J(C,Rh) = 7.4 Hz, cod olefinic trans
1
=
1
to carbene ligand), 75.4 (d, J(C,Rh) = 12.1 Hz, cod olefinic
trans to thione ligand), 54.8 (s, N–CH carbene ligand), 52.2 (s,
N–CH thione ligand), 32.8 (s, cod aliphatic trans to carbene
ligand), 30.0 (s, cod aliphatic trans to thione ligand), 22.5 (s,
N–CH–CH3 carbene ligand), 22.1 (s, N–CH–CH3 carbene
ligand), 21.6 (s, N–CH–CH3 thione ligand), 11.1 (s, N–C–CH3),
10.8 (s, N–C–CH3); MS (ESI): m/z 603 ([M+], 45), 432 ([M+ −
thione ligand + CH3CN], 15), 391 ([M+ − thione ligand], 100),
Chloro(carbonyl)-trans-(triphenylphosphine)(1,3-diisopropyl-4,
5-dimethyl-2,3-dihydro-1H-imidazol-2-ylidene)rhodium(I) (20a).
Complex 20a was preapared in the same manner as 19
using triphenylphosphine (0.09 g, 0.34 mmol) and 7 (0.13 g,
0.34 mmol). Complex 20a is a light yellow microcrystalline
solid (0.20 g, 97%). 1H NMR (300 MHz, CD2Cl2): d 7.55
3
(m, 15H, aromatic protons), 5.84 (septet, J(H,H) = 7.2 Hz,
i
349 ([M+ − thione ligand − Pr], 93), 212 ([thione ligand+], 46),
2H, N–CH), 2.19 (s, 6H, N–C–CH3), 1.57 (d, 3J(H,H) =
180 ([carbene ligand+], 40%); mp 141 ◦C (decomp.). Anal. Calc.
for C30H52BF4N4SRh: C, 52.18; H, 7.59; N, 8.11. Found: C,
52.39; H, 7.64; N, 7.98%.
3
7.2 Hz, 6H, N–CH–(CH3)2), 1.55 (d, J(H,H) = 7.2 Hz, 6H,
1
N–CH–(CH3)2); 13C{ H} NMR (75 MHz, CD2Cl2): d 188.4
1
2
(dd, J(C,Rh) = 78.7 Hz, J(C,P) = 15.6 Hz, CO), 177.2 (dd,
2
[(Dicarbonyl)-cis-(1,3-diisopropyl-4,5-dimethyl-2,3-dihydro-1H-
imidazol-2-thione)(1,3-diisopropyl-4,5-dimethyl-2,3-dihydro-1H-
imidazol-2-ylidene)rhodium(I)] tetrafluoroborate (18). Carbon
monoxide was bubbled through a solution of 17 (0.10 g,
0.15 mmol) in CH2Cl2, (30 cm3) for 30 min. The reaction
mixture was dried in vacuo to yield a green microcrystalline
solid. The product was dissolved in CH2Cl2 (15 cm3) and filtered
over Celite, dried in vacuo and washed with pentane (20 cm3).
1J(C,Rh) = 45.4 Hz, J(C,P) = 123.2 Hz, N–C–N), 135.7 (d,
1J(C,P) = 39.1 Hz, Ph–C ipso), 135.6 (d, J(C,P) = 11.9 Hz,
2
3
Ph–C ortho), 130.7 (d, J(C,P) = 1.8 Hz, Ph–C meta), 128.9
4
4
(d, J(C,P) = 9.5 Hz, Ph–C para), 126.3 (d, J(C,P) = 3.1 Hz,
=
N–C C–N), 54.4 (s, N–CH), 22.7 (s, N–CH–CH3), 22.3 (s,
N–CH–CH3), 10.7 (s, N–C–CH3); 31P{ H} NMR (121 MHz,
1
CD2Cl2): d 32.8 (d, 1J(C,P) = 116.3 Hz); MS (ESI): m/z
614 ([M+], 100), 573 ([M+ − Cl], 57%); IR (CH2Cl2): m(CO)
1 9 0
D a l t o n T r a n s . , 2 0 0 5 , 1 8 1 – 1 9 2

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Table 6 Crystallographic data for thione complexes 1a, 2 and 19, and complexes 6 and 9
1a
2
19
Chemical formula
C15H24N2SRhCl
C11H19NSRhCl
C30H35N2OPSRhCl
2(C19H28N4Rh+)·
2(PF6−)·CH2Cl2
1205.59
C22H36N4Rh+Cl−·CH2Cl2·
0.5H2O
Mr/g mol−1
402.78
335.69
640.99
588.84
Crystal system
Space group
Monoclinic
P21/c
Monoclinic
P21/n
Monoclinic
P21/c
Orthorhombic
P212121
15.8475(2)
17.4778 (2)
17.5446(2)
90
4859.5(1)
4
1.648
203(2)
0.940
1.02–27.48
0.23 × 0.12 × 0.1
−19 to 19 −21 to
21 −21 to 19
35432
Monoclinic
C2/c
˚
a/A
14.389(3)
7.7020(15)
14.993(3)
100.79 (3)
1632.2(6)
4
1.639
173(2)
1.330
1.4–27.5
7.2603(1)
15.2871(2)
11.6752(1)
90.018(1)
1295.82(3)
4
1.721
193(2)
1.654
1.02–29.58
9.0467(1)
10.5875(1)
30.4334(3)
94.147(1)
2907.34(5)
4
1.464
193(2)
0.832
1.02–28.7
26.8149(4)
13.2815(3)
18.8678(5)
126.851(1)
5377.0(2)
8
1.455
173 (2)
0.953
1.02–27.48
0.22 × 0.21 × 0.17
−31 to 33 −16 to −15 −20
to 23
˚
b/A
˚
c/A
b/◦
3
˚
V/A
Z
Dc/g cm−3
T/K
l/cm−1
h/◦
Crystal size/mm
Index ranges, hkl
0.19 × 0.12 × 0.10 0.11 × 0.09 × 0.08 0.22 × 0.21 × 0.17
−18 to 18, −9 to
10, −19 to 19
−9 to 9, −19 to
19, −14 to 14
9994
−11 to 11 −13 to
13 −38 to 38
12308
No. of reflections collected 11509
11822
No. of reflections used
Parameters
R1 (Fo > 2rFo)
wR2 (all data)
3740
197
0.0247
0.0514
5983
141
0.0267
0.0788
7915
340
0.0271
0.0670
22001
641
0.0325
0.0632
5231
311
0.0419
0.1053
1958 cm−1; mp 168 ◦C. Anal. Calc. for C30H35ClN2OPRh: C,
59.17; H, 5.79; N, 4.60. Found: C, 59.31; H, 5.73; N, 4.48%.
Crystallography
The crystal data collection and refinement details for com-
plexes 1b, 2, 6, 9 and 19 are summarised in Table 6. X-
Ray quality single crystals of the complexes were obtained by
crystallisation from concentrated CH2Cl2 solutions layered with
pentane. Data were collected on an Enraf-Nonius KappaCCD
diffractometer20 using graphite-monochromated Mo-Ka radia-
Chloro(carbonyl)-trans-(tri{2ꢀH-thiazol}phosphine)(1,3-diiso-
propyl-4,5-dimethyl-2,3-dihydro-1H-imidazol-2-ylidene)rhodium-
(I) (20b). Complex 20b was prepared in the same way
as 20a, starting from 7 (0.08 g, 0.21 mmol) and tri{2ꢀH-
thiazol}phosphine (0.06 g, 0.20 mmol). Complex 20b was
isolated as a cream microcrystalline solid (0.11 g, 82%). 1H
˚
tion (k = 0.71073 A) and scaled and reduced using DENZO-
SMN21 the structures were solved by the heavy atom method
and refined anisotropically for all the non-hydrogen atoms by
full-matrix least squares calculations on F2 using SHELXL-9722
within the X-Seed environment.23 In 6 a difference Fourier map
showed the presence of disorder in the water and CH2Cl2 solvent
molecules, as well as the chloride anion. The positions of the
disordered atoms (only one Cl of the CH2Cl2 was disordered
over two sites, in the ratio 0.8:0.2) could be identified from
the difference Fourier map and refined anisotropically. The
Cl− and H2O were both disordered over two sites with 50%
occupancy each. Four of the F atoms in one of the PF6 ions in
9 were also found to be disordered over a number of sites. Nine
different disorder positions were identified from the difference
Fourier map, and refined anisotropically, with the sum of the
site occupancies being 4. Elongated anisotropic displacement
parameters suggest that more disorder sites are possible, but
these were not further modelled. ORTEP-III for Windows24as
used to generate the various figures of the five complexes at the
50% probability level.
3
NMR (300 MHz, CD2Cl2): d 8.10 (d, J(H,H) = 3.1 Hz, 3H,
3
4
N–CH–CH), 7.71 (dd, J(H,H) = 3.1 Hz, J(H,H) = 1.7 Hz,
3
3H, S–CH–CH), 5.77 (septet, J(H,H) = 7.2 Hz, 2H, N–CH),
3
2.22 (s, 6H, N–C–CH3), 1.60 (d, J(H,H) = 7.2 Hz, 6H, N–
3
CH–(CH3)2), 1.57 (d, J(H,H) = 7.2 Hz, 6H, N–CH–(CH3)2);
13C{ H} NMR (75 MHz, CD2Cl2): d 186.5 (dd, J(C,Rh) =
1
1
77.1 Hz, 2J(C,P) = 15.6 Hz, CO), 173.6 (dd, 1J(C,Rh) =
2
1
46.1 Hz, J(C,P) = 137.4 Hz, N–C–N), 163.7 (d, J(C,P) =
3
60.0 Hz, P–C), 145.9 (d, J(C,P) = 17.7 Hz, P–C–N–C), 126.5
3
=
(d, J(C,P) = 3.8 Hz, P–C–S–C), 126.4 (s, N–C C–N), 54.8
(s, N–CH), 22.9 (s, N–CH–CH3), 22.5 (s, N–CH–CH3), 10.9
(s, N–C–CH3); 31P{ H} NMR (121 MHz, CD2Cl2): d 15.6 (d,
1
1J(C,P) = 122.5 Hz); MS (EI): m/z 602 ([M+ − CO], 2), 421
([M+ − CO − carbene ligand], 17), 283 ([M+ − CO − Cl −
phosphine ligand], 19%); IR (CH2Cl2): m(CO) 1981 cm−1; mp
◦
168–171 C. Anal. Calc. for C21H26ClN5OPS3Rh: C, 40.08; H,
4.27; N, 11.41. Found: C, 40.32; H, 4.11; N, 11.24%.
General procedure for hydroformylation reactions
CCDC reference numbers 250303–250307.
The catalyst precursor and a magnetic stirrer bar were placed
inside a 300 cm3 stainless steel autoclave. The apparatus was
sealed, all the air was removed by vacuum and the autoclave
filled with argon. The solvent and substrate were then added
and the autoclave charged with a 1 : 1 hydrogen–carbon
monoxide mixture. The vessel was placed in an oil bath set
at a certain temperature. After the chosen reaction time the
apparatus was cooled, opened and the solution removed. A
sample was taken to determine the conversion and n : l ratio
using gas chromatography on a non-polar column (PS 255,
FS 66, 1.2 mm × 40 m × 0.32 mm). For the standard set
of conditions 0.016 mmol precursor catalyst, 2 cm3 substrate
(1-hexene) and 10 cm3 solvent (toluene) was used. When the
ionic liquids were used instead of toluene, the solvent was added
before sealing the autoclave. Isolation of the product was done
by extraction of the organic product with ether.
See http://www.rsc.org/suppdata/dt/b4/b414040k/ for cry-
stallographic data in CIF or other electronic format.
Acknowledgements
We thank Sasol Technology for the funding of this research
as well as Johnson Matthey, PLC for their generous loan of
RhCl3·xH2O.
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1 9 2
D a l t o n T r a n s . , 2 0 0 5 , 1 8 1 – 1 9 2