Variable coordination of amine functionalised N-heterocyclic carbene ligands to Ru, Rh and Ir: C-H and N-H activation and catalytic transfer hydrogenation

Article abstract of DOI:10.1039/c1dt10753d

Chelating amine and amido complexes of late transition metals are highly valuable bifunctional catalysts in organic synthesis, but complexes of bidentate amine-NHC and amido-NHC ligands are scarce. Hence, we report the reactions of a secondary-amine funct

Full text of DOI:10.1039/c1dt10753d

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PAPER
Variable coordination of amine functionalised N-heterocyclic carbene ligands
to Ru, Rh and Ir: C–H and N–H activation and catalytic transfer
hydrogenation†
Warren B. Cross,* Christopher G. Daly, Youcef Boutadla and Kuldip Singh
Received 25th April 2011, Accepted 14th July 2011
DOI: 10.1039/c1dt10753d
Chelating amine and amido complexes of late transition metals are highly valuable bifunctional
catalysts in organic synthesis, but complexes of bidentate amine–NHC and amido–NHC ligands are
scarce. Hence, we report the reactions of a secondary-amine functionalised imidazolium salt 2a and a
primary-amine functionalised imidazolium salt 2b with [(p-cymene)RuCl
Ir). Treating 2a with [Cp*MCl and NaOAc gave the cyclometallated compounds Cp*M(C,C)I (M =
Rh, 3; M = Ir, 4), resulting from aromatic C–H activation. In contrast, treating 2b with
2
]
2
and [Cp*MCl
2
]
2
(M = Rh,
]
2 2
[
(p-cymene)RuCl
2
]
2
, Ag
2
O and KI gave the amine–NHC complex [(p-cymene)Ru(C,NH
2
)I]I (5). The
t
reaction of 2b with [Cp*MCl
Cp*Rh(NH
complex could be accessed: treating 7 with trifluoroacetic acid gave the amine–NHC complex
Cp*Ir(C,NH )I][CF CO ] (8). These are the first primary amine– or amido–NHC complexes of Rh
2
]
2
(M = Rh, Ir), NaO Bu and KI gave the amine–NHC complex
[
2
)I]I (6) or the amido–NHC complex Cp*Ir(C,NH)I (7); both protonation states of the Ir
[
2
3
2
and Ir. Solid-state structures of the complexes 3–8 have been determined by single crystal X-ray
diffraction. Complexes 5, 6 and 7 are pre-catalysts for the catalytic transfer hydrogenation of
acetophenone to 1-phenylethanol, with ruthenium complex 5 demonstrating especially high reactivity.
Introduction
In addition to the commonly employed sulfonamide donor,
10
11–13
other chelating groups such as aryl, phosphine
and
Late transition metal amine and amido complexes are important
compounds that have found valuable applications in bifunctional
14
thiol/thioether have also been used to tether the reactive nitrogen
to the metal in transfer hydrogenation. However, despite the
recent dominance of N-heterocyclic carbene ligands in catalysis,
there are very few examples of NHC donor groups tethering a
nucleophilic amido ligand to an electrophilic metal in bifunctional
catalysis, a consequence of the scarcity of efficient routes to
these catalysts. The coordination of secondary amine- and amido-
functionalised NHC ligands to Rh(I) has been described, but
these complexes showed poor activity for the hydrogenation
of cyclohexene and no activity was observed for the transfer
1–3
catalysis. In organic synthesis, chelating amine and amido com-
plexes have come to prominence in reactions such as hydrogenation
4
5,6
under H , transfer hydrogenation and isomerisation of allylic
2
7
alcohols.
Of these reactions, the asymmetric transfer hydrogenation
between alcohols and carbonyl compounds, catalysed by half-
sandwich complexes of Ru, Ir or Rh with a chiral diamine ligand
such as N-tosyl-1,2-diphenylethylenediamine, has been the most
fully investigated. Elucidation of the mechanism has revealed
that deprotonation of the primary amine group gives a metal
amido complex that catalyses the transfer of an acidic and a basic
hydrogen from i-PrOH to the carbonyl substrate. The second
donor of the chelating amine ligand is crucial, as it increases the
resistance to undesirable M–N bond cleavage.
15
hydrogenation of ketones and imines. More closely related to this
work, Morris has recently reported the coordination of a primary
benzylamine functionalised NHC ligand to (p-cymene)Ru(II) and
Cp*Ru(II): reaction of a benzonitrile functionalised imidazolium
salt with nickel(II) chloride and in situ reduction of the nitrile
8
9
group with NaBH
4
gave a nickel complex [Ni(C,NH
2
)][PF ] .
6
2
Subsequent transmetallation of the amine–NHC ligand from
nickel to ruthenium gave the complexes A and B (Fig. 1), which
were shown to catalyse transfer hydrogenation and hydrogenation
Department of Chemistry, University of Leicester, University Road, Leices-
ter, LE1 7RH, UK. E-mail: wbc2@le.ac.uk; Fax: +44 (0)116 252 3789;
Tel: +44(0)116 252 2126
16–18
under H .
2
1
13
1
†
Electronic supplementary information (ESI) H and C{ H} NMR
Previously, we have reported tridentate amido-bis(NHC) (CNC)
complexes of palladium and platinum and a bidentate amido–
spectra for all new compounds; X-ray crystallographic data (CIF) for
compounds 3 to 8. CCDC reference numbers 823381–823386. For ESI
and crystallographic data in CIF or other electronic format see DOI:
19
NHC (C,N-dipp) complex of palladium. These complexes were
prepared from secondary amine functionalised imidazolium salts,
1
0.1039/c1dt10753d
9
722 | Dalton Trans., 2011, 40, 9722–9730
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Synthesis and structure of rhodium and iridium (C,C) complexes
Reacting the secondary amine functionalised imidazolium salt 2a
t
with [(p-cymene)RuCl
2
◦
]
2
and either Ag
2
O, NaOAc or NaO Bu in
dichloromethane at 33 C gave an intractable mixture of products.
In contrast, performing the reaction of 2a with [Cp*RhCl and
]
2 2
NaOAc for 5 days at room temperature gave a 40% yield of a
single product: the cyclometallated compound Cp*Rh(C,C)I (3),
resulting from the activation of an aromatic C–H bond, Scheme
16–18
t
Fig. 1 Ruthenium (C,NH
2
) complexes reported by Morris.
2. With Ag O as the base there was no reaction, whereas NaO Bu
2
1
gave a lower conversion to 3, as judged by H NMR spectroscopy.
which were obtained using an efficient cross-coupling/alkylation
strategy. Herein, we report that the same efficient strategy can
be used for the synthesis of primary amine functionalised imida-
zolium salts. Subsequently, we describe methods for the coordina-
tion of both primary- and secondary-amine functionalised NHC
ligands to half-sandwich complexes of Ru(II), Ir(III) and Rh(III)
and our observations of C–H and N–H activation. In doing so, we
disclose the first primary amine- and amido- functionalised NHC
complexes of rhodium and iridium. In addition, we evaluate the
catalytic activity of these complexes for the transfer hydrogenation
of acetophenone.
The identity of 3 is clear from its spectroscopic data and was
confirmed by X-ray crystallography, vide infra. The observation
of a nOe between the amine NH resonance at 4.78 ppm and the
signals for the protons on the NHC ring confirmed that the amine
group was not bound to the metal; it was clear, therefore, that
the amine remained protonated and was not bound to the metal
in a bidentate (C,NR) or (C,NHR) complex. Further evidence
that 3 contained a cyclometallated (C,C) ligand was provided by
the presence of only three signals for the aromatic ring linking
the NHC to the amine nitrogen. The C{ H} NMR spectrum
recorded for 3 also verifies the cyclometallated structure, with a
doublet at 158.3 ppm (JRh–C = 40 Hz) for the aryl carbon and
another at 163.6 ppm (JRh–C = 63 Hz) for the NHC carbon bonded
to rhodium.
1
3
1
Results and discussion
The imidazolium pro-ligand 2a, functionalised with a secondary
19
amine, has been previously reported by our group. The same
strategy was also used to prepare the primary amine functionalised
imidazolium salt 2b, but with two modifications in the Ullman-
type coupling of 2-bromoaniline with imidazole: changing the
solvent from DMF to acetonitrile and changing the catalyst from
CuI to Cu
Scheme 1).
2
O enabled a more facile isolation of intermediate 1
(
Scheme 2 Cyclometallation of secondary amine functionalised NHC
ligands on Rh and Ir.
The same cyclometallation reaction was also observed with
iridium: stirring pro-ligand 2a with [Cp*IrCl
overnight at room temperature, followed by stirring with KI for
h, gave the cyclometallated complex Cp*Ir(C,C)I (4) in 61%
2
]
2
and NaOAc
3
yield. As has been observed in other studies, it was clear that
the cyclometallation reaction proceeded much faster and more
Scheme 1 Synthesis of primary amine functionalised imidazolium salt
a
2
b.
35,36
t
efficiently for Ir than Rh.
Using NaO Bu as the base in place of
NaOAc gave an intractable mixture of products, with no evidence
To prepare half-sandwich complexes of Ru and Ir containing
for the formation of 4. However, unlike with Rh the reaction did
NHC ligands, several bases have been employed for the depro-
tonation of an appropriate imidazolium salt: most prominently
proceed with Ag O as the base, but the reaction was much slower.
The H NMR spectrum for 4 is almost identical to that recorded
for the Rh analogue 3, with only small differences in the chemical
2
1
20–27
22,23,28,29
silver(I) oxide,
sodium acetate
and sodium/potassium t-
30,31
32
33
butoxide,
but also sodium hydride, cesium carbonate and n-
shifts for the signals in each spectrum. Hence, the NH singlet at
2
3
4
butyl lithium. We chose to investigate the reactions of pro-ligands
4.85 ppm showed a nOe with the two protons on the NHC ring
and there are only three signals for the aromatic ring linking the
t
2a and 2b with Ag
2
O, NaOAc and NaO Bu in the presence of the
1
3
1
metal half-sandwich dimers [(p-cymene)RuCl
Cp*IrCl
2
]
2
, [Cp*RhCl
2
]
2
and
NHC to the amine nitrogen. In the C{ H} NMR spectrum for
4, the signal for the carbene was found at 163.6 ppm.
[
2
2
] .
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◦
Table 1 Selected bond lengths ( A˚ ) and angles ( ) for 3 and 4
Cp*Rh(C,C)I (3)
Cp*Ir(C,C)I (4)
M–C(1) (NHC)
M–C(5) (aryl)
M–I(1)
1.993(6)
2.048(6)
2.6756(9)
2.161(6)
1.978(8)
2.048(7)
2.6693(8)
2.169(7)
2.198(7)
2.253(8)
2.264(7)
2.280(7)
78.1(3)
M–C(Cp*)
2
2
2
2
.188(6)
.231(6)
.271(6)
.276(5)
C(1)–M(1)–C(5)
78.2(2)
In complexes 3 and 4, C–H activation is preferred over coor-
dination of the amine to the metal. Indeed, no reaction occurred
upon treating the dimers [Cp*MCl
2
2
] (M = Rh and Ir) with pro-
ligand 2a in the absence of base, and there was no evidence of
amine coordination to cleave the chloride bridged dimers, even at
elevated temperatures. Computational and experimental studies
of the mechanism of cyclometallation at Cp*Ir(III) have suggested
that acetate acts as an intramolecular base in an ambiphilic
37,38
reaction.
Cyclometallation of NHC ligands coordinated to
Cp*Ir has been observed previously, involving activation of both
22,23,28,39
3
21,40
aromatic C–H
and C(sp )–H bonds.
These complexes
have also found applications in catalysis: Albrecht and Crabtree
have independently reported Cp*Ir(C,C) complexes that are pre-
3
9,41
catalysts for water oxidation,
and Peris has demonstrated
23,28
diboration of alkenes and catalytic H/D exchange.
The solid-state structures of 3 and 4 were determined by X-ray
crystallography, the structures are shown in Fig. 2 and selected
bond lengths and angles are presented in Table 1. The racemic
complexes 3 and 4 contain stereogenic metal centres and both
crystallise in the centrosymmetric, monoclinic space group P2 /c
1
with both enantiomers in the unit cell. Moreover, 3 and 4 have very
similar structures and almost identical unit cell dimensions. The
complexes adopt a piano stool geometry, with ligand bite angles
◦
(
ca. 78 ) that are consistent with those previously reported for 5-
membered rings resulting from the cyclometallation of an NHC
2
1,39,40
ligand on Cp*Ir.
˚
In 4, the Ir–NHC bond length (1.978(8)
˚
A) and Ir–aryl bond length (2.048(7) A) are also consistent
22,23,28,39
with related Cp*Ir(C,C)X complexes.
In 3, the Rh–NHC
1.993(6) A) and Rh–aryl (2.048(6) A) bond lengths are almost
identical to those in 4, reflecting the almost identical ionic radii
˚
˚
(
4
2
of Rh(III) and Ir(III). In both complexes there is a tilt in the
Cp* ring relative to the metal centre, which reflects the relative
trans influence of the other three ligands. Hence, in each complex
the two M–C(Cp*) bonds opposite the iodide ligand are the
Fig. 2 Solid-state structures of (a) Cp*Rh(C,C)I (3) and (b) Cp*Ir(C,C)I
(4) (ellipsoids drawn at 50% probability). Hydrogen atoms except N–H
have been omitted for clarity.
˚
shortest (2.161(6) to 2.198(7) A), whilst the three M–C(Cp*) bonds
opposite to the NHC and aryl ligands are longest (2.231(6) to
Whereas we were unable to isolate an identifiable product from the
◦
˚
reaction of imidazolium salt 2a with [(p-cymene)RuCl ] and Ag O,
2
.280(7) A). There is a twist of ca. 11.5 between the mean plane
2
2
of NHC ring and the mean plane of the aryl ring in both 3 and 4,
most likely as a consequence of the ortho-amine substituent.
the same reaction with 2b gave the amine–NHC complex [(p-
cymene)Ru(C,NH )I]I (5) in 51% yield after column chromatogra-
phy, Scheme 3. The salt 5 was clearly identified from its H NMR
spectrum: four doublets for the aromatic p-cymene protons are
2
1
Synthesis and structure of ruthenium, rhodium and iridium
consistent with the coordination of a bidentate (C,NH ) ligand
2
(
C,NH ) and (C,NH) complexes
2
and a monodentate (iodide) ligand. Further evidence for the
coordination of the amine to ruthenium was obtained from the
On the basis that the bulky 2,6-diisopropylphenyl substituent may
prevent the amine nitrogen binding to the metal in a half-sandwich
complex, we next investigated the reactions of the primary amine
2
two NH doublets at 4.17 and 8.52 ppm ( JHH = 10.8 Hz). In the
1
3
1
C{ H} NMR spectrum recorded for 5, the carbene resonance is
functionalised imidazolium salt 2b with [(arene)MCl
2
]
2
and base.
found at 175.9 ppm, very similar to the carbene resonance reported
9
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be more acidic when coordinated to Ir(III) than when coordinated
43
to Rh(III). Reactions with either Ag O or NaOAc as the base
2
instead gave a complex mixture of products, and we were unable
to isolate a pure compound on a preparative scale. As expected
1
for a (C,NH) coordination complex, the H NMR spectrum for 7
contains four signals for the aromatic ring linking the NHC ring
to the nitrogen and an NH singlet resonance that integrates to
1
3
1
1
H. In the C{ H} NMR spectrum recorded for 7, the carbene
Scheme 3 Synthesis of the ruthenium amine–NHC complex 5.
resonance appears at 154.6 ppm. The solid-state structure of 7 was
determined by X-ray crystallography, vide infra.
16
for the related complex A (175.1 ppm). The solid-state structure
of 5 was confirmed by single crystal X-ray diffraction, vide infra.
Using either NaOAc or NaO Bu in place of silver(I) oxide also
Considering the base employed in the reactions of imidazolium
salts with Ru(II), Rh(III) and Ir(III) halides, we found sodium
acetate to be the optimum choice for the preparation of the Rh
and Ir cyclometallated-NHC complexes 3 and 4, whilst sodium
t-butoxide was the optimum choice for preparing the Rh and Ir
amine– and –NHC complexes 6 and 7. For the preparation of the
Ru amine–NHC complex 5, silver oxide was the optimum base.
Importantly, our investigations do not suggest that the outcome
of the reactions were necessarily dictated by the nature of the base:
as described above, for most of the reactions an alternative base
gave the same major product but in lower yield.
With a view to applications in bifunctional catalysis, we were
keen to access both protonation states of a nitrogen donor atom
for the same metal–ligand scaffold. We were pleased to find that
treating the iridium amido–NHC complex 7 with one equivalent
of trifluoroacetic acid gave quantitative conversion to the amine–
t
gave 5, but in each case the conversion was lower than that with
1
Ag
2
O, as judged from the H NMR spectrum of the crude product.
As for ruthenium, the reaction of imidazolium salt 2b and
Cp*RhCl also gave the amine–NHC complex, this time
Cp*Rh(C,NH )I]I (6), in 45% yield after column chromatography
Scheme 4). For Cp*Rh, sodium t-butoxide proved to be the
optimum base, using Ag O or NaOAc gave byproducts that could
[
[
]
2 2
2
(
2
not be separated from 6. Coordination of the amine to the metal
was again apparent from the two NH signals (4.76 and 7.32 ppm)
1
13
1
present in the H NMR spectrum recorded for 6. In the C{ H}
NMR spectrum for 6, the carbene signal is a doublet (JRhC = 54
Hz) at 169.5 ppm.
NHC salt [Cp*Ir(C,NH
of 8 was evident from its H NMR spectrum, which contained the
familiar pair of NH doublets at 5.87 and 6.78 ppm. In the C{ H}
NMR spectrum recorded for 8, the carbene resonance was evident
at 156.4 ppm. The solid-state structure of 8 was also determined
by X-ray crystallography, vide infra.
2
1
)I][CF
3
CO
2
] (8), Scheme 4. The identity
1
3
1
The solid-state structures of the amine– and amido–NHC
complexes 5 to 8 were confirmed by single crystal X-ray diffraction
(Fig. 3 and 4, selected bond lengths and angles in Table 2).
The complexes adopt the expected piano stool geometry, with a
stereogenic metal centre; they crystallise in centrosymmetric space
¯
groups (P1 for 5 to 7; P2
1
/n for 8) with both enantiomers in the
unit cell. The ligand bite angles in the six-membered chelate rings
Scheme 4 Synthesis of the Rh and Ir (C,NH
to 8.
2
) and (C,NH) complexes 6
t
Whereas the reaction of 2b with [Cp*RhCl
2
]
2
and NaO Bu
gave the amine–NHC salt 6, in the analogous reaction with
Cp*IrCl the amine was also deprotonated to give the neutral
NHC complex Cp*Ir(C,NH)I (7) in 65% yield, Scheme 4; the
[
–
]
2 2
Fig.
3
Solid-state structure of one of the unique molecules of
)I]I (5) (ellipsoids drawn at 50% probability).
[
(p-cymene)Ru(C,NH
2
different outcome for Ir is consistent with a mechanism involving
deprotonation of the amine group upon coordination to the metal:
since Ir(III) has a greater charge density than Rh(III) the amine will
Hydrogen atoms except N–H have been omitted for clarity. There is
intermolecular hydrogen-bonding between the anion and cation d(H··I2) =
2.730 A˚ .
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In each of the amine–NHC complexes 5, 6 and 8, there is
intermolecular hydrogen bonding between one of the amine N–
H protons and the non-coordinated anion (iodide for 5 and 6,
trifluoroacetate for 8). The M–N bond lengths vary only by ca.
˚ ˚
.05 A for the series of complexes 5 to 8 (2.101(7) A for the amido
0
˚
complex 7 and 2.114(9) to 2.154(8) A for the amine complexes
, 6 and 8). The M–C(NHC) bond lengths in 5 to 8 are also
5
˚
very similar, lying within ca. 0.1 A of each other (1.978(9) to
˚
.082(13) A). Looking more closely at ruthenium complex 5, the
2
˚
˚
Ru–C distance (2.054(11) A) and Ru–N distance (2.154(8) A) are
similar to those reported for the related complex A (d(Ru–C) =
1
6
˚
2
.092(5); d(Ru–N) = 2.146(4) A). In contrast, the ligand bite
◦
angle is much smaller in the 6-membered chelate ring of 5 (ca. 80 )
than in the 7-membered chelate ring of A (91.98(17) ).
◦
16
Catalytic transfer hydrogenation
The Ru and Rh amine–NHC complexes 5 and 6 and the Ir amido–
NHC complex 7 were investigated for their ability to act as pre-
catalysts for the transfer hydrogenation of acetophenone to 1-
phenylethanol. The reactions were performed in isopropanol in
the presence of sodium t-butoxide, with a catalyst/base/substrate
ratio of 1 : 8 : 200, Table 3.
The ruthenium complex 5 demonstrated excellent catalytic
◦
activity, with a conversion >90% after only 0.5 h at 80 C (Table
◦
3
, entry 1). Lowering the temperature to 20 C, however, gave
no detectable conversion, even after 72 h (entry 3). The rhodium
amine–NHC complex 5 also gave high conversion (>95%), but
only after 72 h (entry 4); adding AgPF to eliminate the iodide
6
anion did not aid the reaction (entry 5). The iridium amido–
NHC complex 7 showed a similar catalytic activity to the rhodium
amine–NHC complex 6 (entry 6), but including the AgPF additive
6
had a detrimental effect on the rate of the reaction (entry 7). For an
otherwise similar inner coordination sphere, the higher reactivity
of (arene)Ru compared with Cp*Rh and Cp*Ir pre-catalysts has
44
been observed previously in transfer hydrogenation reactions.
Noyori and co-workers showed that the ruthenium amido com-
plex [(p-cymene)Ru(TsNCHPhCHPhNH)] catalyses the transfer
8
hydrogenation of acetophenone in the absence of base. Hence,
we also attempted the reaction involving iridium amido complex
7
in the absence of base: the reaction did proceed, but the
conversion over the same time period was significantly reduced
entry 8). When AgPF was added to the reaction, with the aim of
forming the 16-electron complex [Cp*Ir(C,NH)][PF ] in situ, the
(
6
6
Fig.
molecules of [Cp*Rh(C,NH
Cp*Ir(C,NH )I][CF CO ] (8) (ellipsoids drawn at 50% probability).
4
Solid-state structures of (a) one of the unique
conversion was even lower (entry 9). This poor activity for 7 in the
2
)I]I (6), (b) Cp*Ir(C,NH)I (7), (c)
absence of base suggests that the reaction may not proceed by the
8
[
2
3
2
outer-sphere bifunctional mechanism. Indeed for pre-catalyst A,
Hydrogen atoms except N–H have been omitted for clarity. There is
an alternative inner-sphere mechanism has been proposed for the
intermolecular hydrogen-bonding for 6 d(H··I2A) = 2.680 A˚ and 8
H
2
-hydrogenation of ketones, in which the H–H bond is cleaved
d(H··O2) = 1.989 A˚ .
18
by a metal-alkoxide.
Conclusions
in 5 to 8 are only slightly larger than those in the five-membered
◦
cyclometallated chelate rings of 3 and 4 (79.9(4) to 81.1(3) for
We have investigated the coordination of bidentate amine func-
tionalised N-heterocyclic carbene ligands to (p-cymene)Ru(II) and
Cp*M(III) (M = Rh,Ir) scaffolds. Reacting the secondary-amine
◦
5
to 8, cf. 78.2(2) and 78.1(3) for 3 and 4). However, the angle
between the mean plane of the NHC ring and the mean plane of
the aryl ring is much larger in 5 to 8 than it is in 3 and 4 (36.3 and
functionalised imidazolium salt 2a with [Cp*MCl
gave the cyclometallated NHC complexes Cp*M(C,C)I (M = Rh,
3; M = Ir, 4), via activation of an aromatic C–H bond. In these
2
] and NaOAc
2
◦
◦
◦
◦
3
1.4 in 5, 32.6 and 32.8 in 6, 36.8 in 7, 34.5 in 8, compared
◦
with ca. 11.5 in 3 and 4).
9
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◦
Table 2 Selected bond lengths ( A˚ ) and angles ( ) for 5, 6, 7 and 8
[
(p-cymene)Ru(C,NH
2
)I]I (5)
[Cp*Rh(C,NH
molecule 1
2
)I]I (6)
molecule 2
Cp*Ir(C,NH)I (7)
2 3 2
[Cp*Ir(C,NH )I][CF CO ] (8)
molecule 1
molecule 2
M–C(1)
M–N(1)
M–I(1)
2.054(11)
2.154(8)
2.7116(16)
2.163(12)
2.082(13)
2.114(9)
2.7177(17)
2.175(13)
-2.342(19)
79.9(4)
2.041(12)
2.121(9)
2.6985(16)
2.143(12)
-2.231(13)
80.4(5)
2.060(11)
2.118(10)
2.7034(16)
2.136(13)
-2.227(12)
80.7(4)
1.978(9)
2.101(7)
2.6843(11)
2.129(8)
-2.228(9)
81.1(3)
2.026(9)
2.153(7)
2.7082(9)
2.172(10)
-2.256(9)
80.0(3)
M–C(arene)
-
2.275(11)
80.4(4)
C(1)–M(1)–N(1)
a
Table 3 Catalytic transfer hydrogenation of acetophenone to 1-phenylethanol
Conversion/% (determined by GC)
◦
Entry
Cat.
Base
Additive
—
Temp./ C
0.5 h
1 h
24 h
72 h
t
1
2
3
4
5
6
7
8
9
5
5
5
6
6
7
7
7
7
NaO Bu
NaO Bu
NaO Bu
NaO Bu
NaO Bu
NaO Bu
NaO Bu
—
—
80
80
20
80
80
80
80
80
80
91
93
0
—
—
—
—
—
—
95
93
0
7
3
7
9
0
0
—
—
0
86
75
78
46
11
2
—
—
0
99
96
96
68
24
3
t
AgPF
—
6
t
t
—
t
AgPF
—
AgPF
—
6
6
6
t
t
AgPF
a
All reactions were performed in i-PrOH, with a cat.:base:substrate ratio of 1 : 8 : 200
complexes, the bulky 2,6-diisopropylphenyl substituent appears to
prevent the amine nitrogen from coordinating to the metal. Unlike
for 2a, reactions of the primary-amine functionalised imidazolium
salt 2b gave nitrogen-bound products. Hence, the reaction of 2b
were prepared as reported in the literature. All other reagents were
obtained from Sigma-Aldrich, Johnson Matthey or Alfa Aesar
and used as supplied. NMR spectra were recorded on a Bruker
DPX300, DRX400 or AV500 spectrometer; chemical shifts have
been referenced to the residual protonated solvent peak and J
with [(p-cymene)RuCl
complex: [(p-cymene)Ru(C,NH
Cp*MCl
2
]
2
, Ag O and KI gave the amine–NHC
2
1
2
)I]I (5). For the reaction of 2b with
values are given in Hz. For some compounds, assignments for H
t
13
1
1
1
1
1
[
2
]
2
(M = Rh or Ir) and NaO Bu, the outcome depended
and C{ H} NMR spectra were aided by H- H COSY, H- H
1 13
upon the nature of the metal: for rhodium the product was the
amine–NHC complex [Cp*Rh(C,NH )I]I (6), whereas for iridium
the product was the amido–NHC complex Cp*Ir(C,NH)I (7).
Hence we have described an efficient route to (C,NH ) and (C,NH)
NOESY and H- C HMQC 2D NMR experiments. ESI mass
spectra were recorded on a micromass Quattra LC spectrometer
in MeCN/MeOH with a cone voltage of +25 V; FAB mass spectra
were obtained on a Kratos concept spectrometer using NBA
as the matrix. Elemental analyses were performed at London
Metropolitan University.
2
2
complexes, involving only 3 steps from commercial materials.
Protonation of the amido donor in 7 with trifluoroacetic acid gave
the amine–NHC complex [Cp*Ir(C,NH
2
)I][CF
3
CO ] (8). These
2
are the first primary amine– or primary amido–NHC complexes
of Rh and Ir. There are very few reports of the application
of functionalised NHC ligands in bifunctional catalysis; hence,
complexes 5, 6 and 7 were tested for the catalytic transfer
2
-(1H-Imidazol-1-yl)phenylamine (1)
2-Bromoaniline (1.000 g, 5.952 mmol), imidazole (0.607 g,
8.92 mmol), Cu O (0.043 g, 0.30 mmol), Cs CO (3.881 g,
11.90 mmol) and 8-hydroxyquinoline (0.173 g, 1.19 mmol) were
suspended in MeCN (10 mL) in a pre-dried sealable tube under an
atmosphere of air. The tube was sealed and heated at 100 C with
2
2
3
◦
hydrogenation of acetophenone to 1-phenylethanol at 80 C. The
Rh and Ir pre-catalysts 6 and 7 showed high conversion (>95%)
but over a relatively long time period of 72 h. In contrast, the
Ru pre-catalyst 5 was significantly more active, giving >90%
conversion after only 0.5 h.
◦
stirring for 3 days. The volatiles were then removed in vacuo and the
product extracted into CH
with H O (3 ¥ 150 mL) and brine (100 mL), dried (MgSO
the solvent removed in vacuo to give 1 (0.791 g, 86%) as a brown
2
Cl
2
(70 mL). The solution was washed
2
4
) and
◦
◦
46
solid m.p. 103–104 C (lit. 103–106 C).
Experimental
All manipulations were performed under dry, oxygen free nitrogen
using standard Schlenk techniques unless otherwise stated. THF
was dried over and distilled from sodium-benzophenone prior to
2
-(3-iso-Propyl-1H-imidazolium)phenylamine iodide (2b)
In a sealable tube under an atmosphere of air, iso-propyl iodide
(0.77 mL, 7.6 mmol) was added to a suspension of 1 (1.07 g,
6.93 mmol) in MeCN (10 mL). The tube was sealed and heated at
use, CH
2
Cl
2
was distilled from CaH and i-PrOH was distilled
2
from Mg turnings. N-(2-(3-isopropyl-1H -imidazolium)phenyl)-
19
45
◦
2
,6-diisopropylaniline iodide (2a) and [Cp*MCl
2
]
2
(M = Rh, Ir)
90 C for 3 days. The mixture was then allowed to cool to room
This journal is © The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 9722–9730 | 9727

View Article Online
temperature and the volatiles removed in vacuo. Recrystallisation
from hot MeOH/Et O three times gave analytically pure 2b
6.9, CHCH
3
), 4.85 (2H, m, NCHCH
3
+ NH), 6.00 (1H, d, J = 7.9,
2
ArH), 6.68 (1H, t, J = 7.7, ArH), 7.08 (1H, d, J = 2.2, NCHCHN),
7.23–7.15 (3H, m, 2,6- PrC
◦
1
i
(
(
1.480 g, 65%) as pale green crystals m.p. 190–191 C. H NMR
400 MHz, d -MeOH) d 1.66 (6H, d, J = 6.7, CHCH ),4.79 (1H,
), 6.79 (1H, t, J = 7.7, ArH), 6.97 (1H, d, J =
6
H ), 7.27 (1H, d, J = 7.5, ArH), 8.39
3
13 1
4
3
(1H, d, J = 2.2, NCHCHN); C{ H} NMR (125 MHz, CD
2
2
Cl )
5
sept, J = 6.7, CHCH
3
d 10.3 (h -C
5
Me
5
), 22.9, 23.3, 23.8, 24.5, 24.9, 25.1(CHCH ),
3
5
8
7
.2, ArH), 7.25 (1H, d, J = 7.7, ArH), 7.30 (1H, t, J = 8.2, ArH),
.71 (1H, s, NCHCHN), 7.92 (1H, s, NCHCHN), 9.27 (1H, s,
28.3, 28.4 (2,6-C
Me
124.1, 124.2, 125.0, 125.3, 132.6, 134.3 (ArCH), 137.8, 138.9,
142.3, 143.5, 144.4 (ArC), 163.6 (N C–Ir); m/z (ESI) 727 (20%,
6
H
3
–(CH(CH
3
)
2
)
2
), 52.3 (NCH(CH ) ), 92.1 (h -
3
2
C
5
5
), 115.0 (ArCH), 115.3 (NHC–CH), 119.4 (NHC–CH),
1
3
1
N
2
CH); C{ H} NMR (100 MHz, d
), 118.4, 118.6 (ArCH), 121.9 (ArC), 122.4, 25.4
NCHCHN), 128.1, 132.7 (ArCH), 137.2 (N CH), 144.8 (ArC);
m/z (ESI) 202 (100%, [M-I] ); Anal. Calcd. for C12 : C,
3.78; H, 4.90; N, 12.77. Found C, 43.69; H, 4.82; N, 12.60%.
4
-MeOH) d 23.0 (CHCH
3
),
55.0 (CHCH
3
2
+
+
+
(
2
[M-I+MeCN] ), 686 (15%, [M-I] ), 362 (100%, [(C,C)+2H] );
Anal. Calcd. for C34 : C, 50.11; H, 5.57; N, 5.16. Found C,
50.20; H, 5.48; N, 5.08%.
+
H
16IN
3
H
45IIrN
3
4
Cp*Rh(C,C)I (3)
[(p-cymene)Ru(C,NH )I]I (5)
2
A suspension of [Cp*RhCl
2
]
2
(0.100 g, 0.178 mmol) and NaOAc
Cl (5 mL) were stirred at room
A suspension of [(p-cymene)RuCl
zolium salt 2b (0.099 g, 0.30 mmol) and Ag
in CH Cl
solvent was removed in vacuo, and then the crude mixture was
dissolved in acetone (20 mL). KI (0.498 g, 3.00 mmol) was added
to the solution, which was then heated at reflux for 1 h. The solvent
2
] (0.090 g, 0.15 mmol), imida-
2
(
0.052 g, 0.63 mmol) in CH
2
2
2
O (0.036 g, 0.16 mmol)
(20 ml) was stirred for 32 h at 33 C in the dark. The
◦
temperature for 10 min. Imidazolium salt 2a (0.158 g, 0.324 mmol)
was then added and the mixture stirred for 5 days. The mixture was
then filtered through Celite and evaporated to dryness. Purification
by flash column chromatography (CH
as a yellow-orange solid m.p. 230 C (dec.), R
2
2
2
Cl
2
) gave 3 (0.091 g, 40%)
0.60 (CH Cl ).
◦
f
2
2
was removed in vacuo and the crude solid redissolved in CH
2
Cl
2
Crystals suitable for structure determination by X-ray diffraction
(20 mL) filtered through Celite, and then concentrated under
vacuum. Purification by flash column chromatography (gradient
1
were obtained from CH
2
Cl
2
/hexane. H NMR (400 MHz, CDCl )
3
d 0.99 (3H, d, J = 6.9, CHCH
3
), 1.10 (3H, d, J = 6.8, CHCH
3
3
3
),
),
),
of CH
2
Cl
2
to 50% acetone/CH
2
Cl ) gave 5 (0.105 g, 51%) as a dark
2
◦
1
1
1
.16 (3H, d, J = 6.8, CHCH
.56 (3H, d, J = 6.9, NCHCH
3
), 1.17 (3H, d, J = 6.9, CHCH
), 1.67 (3H, d, J = 6.9, NCHCH
green/blue solid m.p. 200 C (dec.). Crystals suitable for structure
determination by X-ray diffraction were obtained by diffusion of
3
5
1
.82 (15H, s, h -C
5
Me
5
), 3.04 (1H, sept, J = 6.9, CHCH
), 4.78 (1H, s, NH), 4.88 (1H, sept, J =
), 6.07 (1H, d, J = 7.8, ArH), 6.73 (1H, t, J = 7.7,
ArH), 7.04 (1H, d, J = 2.1, NCHCHN), 7.18 (3H, m, ArH), 7.35
3
), 3.13
Et
CD
d, J = 6.9, p-cymene CHCH
1.58 (3H, d, J = 6.7, NCHCH
(1H, sept, J = 6.9, p-cymene CHCH
NH), 4.99 (1H, sept, J = 6.7, NCHCH
2
O into a saturated CHCl
3
solution of 5. H NMR (500 MHz,
(
1H, sept, J = 6.8, CHCH
.9, NCHCH
3
2
Cl
2
) d 0.90 (3H, d, J = 6.9, p-cymene CHCH
), 1.56 (3H, d, J = 6.7, NCHCH
), 2.06 (3H, s, p-cymene CH ), 2.10
), 4.17 (1H, d, JHH = 10.8,
), 5.21 (2H, m, p-cymene
3
), 0.92 (3H,
6
3
3
3
),
3
3
1
3
1
2
(
1H, d, J = 7.4, ArH), 8.40 (1H, d, J = 2.2, NCHCHN); C{ H}
3
5
NMR (125 MHz, CDCl
3
) d 10.5 (h -C
5
Me
5
), 22.7, 23.3, 23.8,
3
2
4.3, 24.8, 24.9 (CHCH
3
), 27.9, 28.1 (2,6-C
6
H
3
-(CH(CH
3
)
2
)
2
), 52.1
ArH), 5.76 (1H, d, J = 6.2, p-cymene ArH), 6.22 (1H, d, J = 6.2,
5
(
(
NCH(CH ), 98.0 (d, JRh–C = 6, h -C
NHC–CH), 119.3 (NHC–CH), 123.8, 123.9, 124.5, 124.9, 133.1,
3
)
2
5
Me
5
), 115.2 (ArCH), 115.6
p-cymene ArH), 7.31–7.38 (3H, m, ArH), 7.39 (1H, d, J = 2.3,
2
NCHCHN), 7.71 (1H, d, J = 2.3, NCHCHN), 8.52 (1H, d, JHH
=
1
3
1
1
4
34.1, 136.5 (ArCH), 138.2, 142.7, 144.1, (ArC), 158.3 (d, JRh–C
0, ArC–Rh), 163.6 (d, JRh–C = 63, N C–Rh); m/z (ESI) 726 (80%,
Rh: C,
6.28; H, 6.25; N, 5.79. Found C, 56.39; H, 6.19; N, 5.88%.
=
10.8, NH), 8.63 (1H, d, J = 7.7 ArH); C{ H} NMR (125 MHz,
2
CD
2
Cl
2
) d 20.2 (p-cymene CH
3
), 21.0, 23.9 (p-cymene CHCH
), 55.4 (NCHCH
3
),
),
+
+
[
M+H] ), 598 (100%, [M-I] ); Anal. Calcd. for C34
H
45IN
3
24.0, 24.8 (NCHCH
3
), 31.9 (p-cymene CHCH
3
3
5
83.0, 83.2, 84.1, 89.5 (p-cymene ArCH), 103.0, 110.6 (p-cymene
ArC), 121.08, 121.13, 121.9, 122.9, 127.7, 128.8 (ArCH), 133.0,
+
1
36.3 (ArC), 175.9 (N
2
C–Ru); m/z (ESI) 564 (100%, [M-I] , 202
Cp*Ir(C,C)I (4)
+
(100% [(C,NH
2
)+H] ); Anal. Calcd. for C22
H
29
I
2
N
3
Ru: C, 38.27;
A suspension of [Cp*IrCl
2
]
2
(0.040 g, 0.050 mmol) and NaOAc
Cl (3 mL) were stirred at room
H, 4.23; N, 6.09. Found C, 38.07; H, 4.02; N, 5.91%.
(
0.016 g, 0.20 mmol) in CH
2
2
temperature for 10 min. Imidazolium salt 2a (0.048 g, 0.10 mmol)
was then added and the mixture stirred for a further 15 h.
After this time, a saturated solution of aq. KI (3 mL) was
added, and the mixture stirred vigorously for 3 h. The organic
[
Cp*Rh(C,NH
2
)I]I (6)
t
A suspension of [Cp*RhCl
(0.012 g, 0.13 mmol), imidazolium salt 2b (0.021 g, 0.064 mmol)
and KI (0.054 g, 0.32 mmol) in CH Cl (5 mL) was stirred
2
]
2
(0.020 g, 0.032 mmol), NaO Bu
layer was separated, dried (MgSO
4
) and concentrated in vacuo.
2
2
Purification by flash column chromatography (CH
2
Cl
2
) gave 4
at room temperature for 4 days. The mixture was then filtered
through Celite and evaporated to dryness. The crude residue
was re-dissolved in acetone (3 mL) and stirred vigorously for
2 h with a saturated solution of aq. KI (3 mL). The organic
◦
(
0.050 g, 61%) as a yellow-orange solid m.p. 218–220 C, R
f
0
.67 (CH
2
Cl
2
). Crystals suitable for structure determination by
O/pentane solution
Cl ) d 0.96 (3H, d,
), 1.13 (3H, d, J = 6.9, CHCH
), 1.17 (3H, d, J = 6.9, CHCH
X-ray diffraction were obtained from an Et
of 4 at 3 C. H NMR (400 MHz, CD
J = 6.9, CHCH
J = 6.9, CHCH
2
◦
1
2
2
layer was separated, dried (MgSO
4
) and the volatiles removed
3
3
3
), 1.15 (3H, d,
), 1.53 (3H, d,
in vacuo. Purification by flash column chromatography (10%
3
acetone/CH
m.p. 95 C, R
2
Cl
2
) gave 6 (0.020 g, 45%) as a dark red solid
0.6 (10% acetone/CH Cl ). Crystals suitable for
◦
J = 6.9, NCHCH
3
), 1.66 (3H, d, J = 6.9, NCHCH
3
), 1.86 (15H, s,
f
2
2
5
h -C
5
Me
5
), 3.04 (1H, sept, J = 6.9, CHCH ), 3.18 (1H, sept, J =
3
structure determination by X-ray diffraction were obtained from
9
728 | Dalton Trans., 2011, 40, 9722–9730
This journal is © The Royal Society of Chemistry 2011

View Article Online
1
CH
2
Cl
2
/hexane. H NMR (400 MHz, CDCl
), 1.59 (3H, d, J = 6.7, CHCH
), 4.69 (1H, sept, J = 6.7, CHCH ), 4.76 (1H, br, NH),
.32 (3H, m, ArH, NH), 7.54 (2H, m, ArH, NCHCHN), 7.97
3
) d 1.53 (3H, d,
X-ray crystallographic studies
J = 6.7, CHCH
3
3
), 1.62 (15H, s,
5
All single crystal diffraction data were collected using graphite-
monochromated Mo-Ka X-radiation (l = 0.71073 A) on a Bruker
h -C
5
Me
5
3
˚
7
APEX 2000 CCD diffractometer at 150 K. The data were corrected
for Lorentz and polarisation effects and empirical absorption
corrections applied. Structures were solved by Patterson methods
and structures refined by least-squares full-matrix refinement
(
1H, d, J = 2.2, NCHCHN), 8.31 (1H, dd, J = 7.0, 1.2, ArH);
1
3
1
5
C{ H} NMR (125 MHz, CDCl
3
) d 10.3 (h -C
5
Me
5
), 23.8, 25.8
5
(
CHCH
3
), 54.5 (CH(CH
3
)
2
), 98.1 (d, JRh–C = 6, h -C
5
Me ), 121.5
5
(
1
NCHCHN), 122.2 (ArCH), 122.3 (NCHCHN), 123.0, 127.2,
28.0 (ArCH), 132.5, 134.7 (ArC), 169.5 (d, JRh–C = 54, N
m/z (FAB) 566 (100%, [M-I] ); Anal. Calcd. for C22
C, 38.12; H, 4.36; N, 6.06. Found C, 38.05; H, 4.26; N, 5.87%.
2
47
against F employing SHELXTL version 6.10. Hydrogen atoms
2
C–Rh);
Rh:
˚
+
were included in calculated positions (d(C–H) = 0.95 to 0.99 A)
H
30
N
3 2
I
riding on the bonded atom with isotropic displacement parameters
set to 1.5 Ueq(C) for methyl H atoms and 1.2 Ueq(C) for all
other C atoms. All non-H atoms were refined with anisotropic
displacement parameters. For complexes 5, 6 and 8, disordered
Cp*Ir(C,NH)I (7)
4
8
solvent was removed using the SQUEEZE option of PLATON.
[
Cp*IrCl
2
]
2
(0.040 g, 0.050 mmol), imidazolium salt 2b (0.033 g,
.10 mmol) and NaO Bu (0.019 g, 0.20 mmol) were suspended in
THF (5 mL) and stirred for 15 h at room temperature. After this
time, the solvent was removed in vacuo and the solid redissolved
t
0
Crystal data for 3. C H IN Rh, M = 725.54, monoclinic,
3
4
45
3
W
space group P2 /c, a = 13.277(5), b = 8.466(3), c = 28.869(11)
3
1
◦
A˚ , a = 90, b = 95.710(8), c = 90 , V = 3229(2) A˚ , Z = 4,
1
-
-1
in CH
then removed in vacuo to give a crude solid that was extracted with
boiling Et O (5 ¥ 15 mL). The Et O washings were combined, hot
filtered through Celite and the filter pad washed with hot Et
2
Cl
2
(10 mL) and filtered through Celite. The volatiles were
rcalcd = 1.493 Mg m 3, m = 1.511 mm , F(000) = 1472, crystal
3
size 0.16 ¥ 0.12 ¥ 0.08 mm , 24670 reflections collected, 6361
◦
2
2
unique [R(int) = 0.1738] (completeness to q = 26.00 = 99.9%).
Empirical absorption correction made, Tmax and Tmin 0.831 and
2
O
(
6
2 ¥ 5 mL). Removal of the solvent in vacuo gave 7 (0.043 g,
5%) as a red-orange solid m.p. 160 C (dec.). Crystals suitable
0.521 respectively. GOF = 0.922, final R indices > 2 s I] R =
1
◦
0.0599, wR = 0.1103, R indices (all data) R = 0.0907, wR =
2
1
2
-
3
for structure determination by X-ray diffraction were obtained
0.1242. Largest diff. peak and hole 2.034 and -1.294 eA˚
.
◦
1
from an Et
CDCl ) d 1.59 (6H, d, J = 6.8, CHCH
.39–2.59 (0.8H, br s, NH), 5.02 (1H, sept, J = 6.8, CHCH
1H, t, J = 7.6, ArH), 6.67 (1H, d, J = 7.6, ArH), 6.85 (1H, t, J =
2
O/pentane solution of 7 at 3 C. H NMR (500 MHz,
Crystal data for 4.
C
34
H
45IIrN
3
, M
W
= 814.83, monoclinic,
5
3
3
), 1.62 (15H, s, h -C
5
Me
5
),
space group P2
A, a = 90, b = 95.654(5), g = 90 , V = 3223.7(16) A , Z = 4,
1
/c, a = 13.219(4), b = 8.444(3), c = 29.021(9)
2
(
7
3
), 6.38
◦
3
˚
˚
-
3
-1
r
calcd = 1.679 Mgm , m = 5.126 mm , F(000) = 1600, crystal
.6, ArH), 7.02–7.05 (2H, m, ArH + NCHCHN), 7.46 (1H, d,
3
size 0.23 ¥ 0.19 ¥ 0.13 mm , 24406 reflections collected, 6341
1
3
1
5
J = 2.2, NCHCHN); C{ H} NMR (125 MHz, CDCl
3
) d 9.6 (h -
◦
unique [R(int) = 0.0652] (completeness to q = 26.00 99.9%).
5
C
1
1
(
5
Me ), 23.2–26.4 (br, CHCH ), 53.5 (CHCH
5
3
3
), 88.8 (h -C
5
Me ),
5
Empirical absorption correction made, Tmax and Tmin 0.831 and
14.4 (ArCH), 118.2, 118.3, 119.2, 119.7 (ArCH/NCHCHN),
0
0
0
.587 respectively. GOF = 1.049, final R indices > 2 s I] R
.0487, wR = 0.1305, R indices (all data) R = 0.0615, wR
.1370. Largest diff. peak and hole 2.542 and -2.850 eA .
1
=
=
26.4 (ArCH), 128.2, 151.4 (ArC), 154.6 (N C–Ir); m/z (ESI) 656
2
+
+
2
1
2
100%, [M+H] ), 528 (10%, [M-I] ); Anal. Calcd. for C22
H
29IIrN :
3
-
3
˚
C, 40.37; H, 4.47; N, 6.42. Found C, 40.48; H, 4.52; N, 6.31%.
Crystal data for 5·(0.5CHCl
3
)·(Et
2
O).
C
¯
26.50
H
39.50Cl1.50I -
2
N
3
ORu, M
W
= 824.16, triclinic, space group P1, a = 11.772(6),
[
Cp*Ir(C,NH
2
)I][CF
3
CO
2
] (8)
˚
b = 14.552(7), c = 16.056(8) A, a = 77.716(9), b = 88.809(9), g =
◦
3
-1
Trifluoroacetic acid (6 mL, 0.009 g, 0.08 mmol) was added to a
stirred solution of 7 (0.050 g, 0.076 mmol) in CH Cl (10 mL)
at room temperature, resulting in an immediate colour change
from dark orange to yellow. After stirring for 1 h, the solvent
was removed in vacuo to give 8 (0.058 g, 99%) as a yellow solid
m.p. 100 C (dec.). Crystals suitable for structure determination
by X-ray diffraction were obtained by diffusion of pentane into
a saturated CHCl
d 1.57 (15H, s, h -C
85.046(10) , V = 2678(2) A˚ , Z = 4, r = 2.044 Mg m 3, m = 3.068
mm , F(000) = 1612, crystal size 0.15 ¥ 0.10 ¥ 0.04 mm , 21113
reflections collected, 10398 unique [R(int) = 0.1013] (completeness
calcd
-
1
3
2
2
◦
to q = 26.00 98.7%). Empirical absorption correction made, T
max
and Tmin 0.831 and 0.574 respectively. GOF = 0.869, final R indices
> 2 s I] R = 0.0684, wR = 0.1444, R indices (all data) R = 0.1308,
◦
1
2
1
-
3
wR = 0.1635. Largest diff. peak and hole 1.183 and -1.139 eA˚
2
.
1
3
5
solution of 8. H NMR (500 MHz, CDCl
3
)
Crystal data for 6·(5CH
2
Cl
2
).
C
27.50
H
41Cl11
I
2
N
3
Rh, M
W
=
5
Me
5
), 1.60 (6H, d, J = 6.8, CHCH
3
), 4.78
¯
1
160.29, triclinic, space group P1, a = 9.430(3), b = 11.745(4),
(
(
(
1H, sept, J = 6.8, CHCH
1H, d, J = 11.9, NH), 7.30 (1H, d, J = 2.2, NCHCHN), 7.33
1H, t, J = 7.7, ArH), 7.38 (1H, t, J = 7.7, ArH), 7.45 (1H, d,
3
), 5.87 (1H, d, J = 11.9, NH), 6.78
◦
˚
c = 29.671(10) A, a = 89.104(8), b = 86.111(8), g = 75.463(7) ,
3
-3
-1
˚
V = 3173.7(19) A , Z = 4, r = 2.428 Mg m , m = 3.442 mm ,
c
3
F(000) = 2260, crystal size 0.23 ¥ 0.13 ¥ 0.08 mm , 25014 reflections
J = 7.7, ArH), 7.48 (1H, d, J = 7.7, ArH), 7.67 (1H, d, J = 2.2,
collected, 12332 unique [R(int) = 0.1037] (completeness to q =
1
3
1
5
NCHCHN); C{ H} NMR (125 MHz, CDCl
3
5
) d 9.4 (h -C
5
Me ),
5
◦
2
T
2
6.00 98.7%). Empirical absorption correction made, Tmax and
2
3.5, 26.0 (CHCH
3
), 54.3 (CHCH
), 120.5, 120.6 (NCHCHN), 121.6, 121.9, 128.0,
C–Ir), 160.1 (q, J =
3
), 91.1 (h -C
5
Me
5
), 115.5 (q,
min 0.831 and 0.535 respectively. GOF = 0.937, final R indices >
s I] R = 0.0840, wR = 0.2165, R indices (all data) R = 0.1193,
= 0.2301. Largest diff. peak and hole 2.920 and -1.356 e.A .
J = 287.4, CF
3
1
2
1
1
3
28.2 (ArCH), 132.9, 135.3 (ArC), 156.4 (N
9.9, CF CO ); m/z (ESI) 656 (100%, [M-CF
CO
H, 3.93; N, 5.47. Found C, 37.58; H, 3.87; N, 5.38%.
2
-
3
˚
wR
2
+
3
2
3
CO
IIrN
2
] ), 528 (20%,
+
[M-HI-CF
3
2
] ); Anal. Calcd. for: C24
H
30
F
3
3
O
2
: C, 37.50;
Crystal data for 7.
group P1, a = 9.218(3), b = 10.812(3), c = 11.389(4) A, a = 75.863(5),
C
22
H
29IIrN
3
, M
W
= 654.58, triclinic, space
¯
˚
This journal is © The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 9722–9730 | 9729

View Article Online
◦
˚
b = 78.648(5), g = 86.600(5) , V = 1079.1(6) A3, Z = 2, rcalcd
=
11 M. Ito, A. Sakaguchi, C. Kobayashi and T. Ikariya, J. Am. Chem. Soc.,
2007, 129, 290–291.
-
1
-1
2
0
0
.015 Mg m 3, m = 7.628 mm , F(000) = 624, crystal size 0.13 ¥
.11 ¥ 0.05 mm3, 8383 reflections collected, 4177 unique [R(int) =
.0537] (completeness to q = 26.00 98.5%). Empirical absorption
1
2 M. Ito, M. Hirakawa, A. Osaku and T. Ikariya, Organometallics, 2003,
2
2, 4190–4192.
◦
13 M. Ito, Pure Appl. Chem., 2008, 80, 1047–1053.
correction made, Tmax and Tmin 0.862 and 0.586 respectively.
GOF = 1.012, final R indices > 2 s I] R = 0.0471, wR = 0.0963,
= 0.1008. Largest diff. peak
14 M. Ito, Y. Shibata, A. Watanabe and T. Ikariya, Synlett, 2009, 10,
1
621–1626.
1
2
1
5 H. Jong, B. O. Patrick and M. D. Fryzuk, Can. J. Chem., 2008, 86,
03–810.
16 W. W. N. O, A. J. Lough and R. H. Morris, Organometallics, 2009, 28,
755–6761.
R indices (all data) R
1
= 0.0612, wR
2
8
-
3
˚
and hole 2.294 and -1.647 e.A .
6
Crystal data for 8·(5C
5
H
12).
C
49
H
90
F
3
IIrN
3
O
2
, M = 1129.34,
W
1
7 W. W. N. O, A. J. Lough and R. H. Morris, Chem. Commun., 2010, 46,
8240–8242.
monoclinic, space group P2
1
/n, a = 16.957(3), b = 10.360(2), c =
1.186(4) A, a = 90, b = 110.741(4), g = 90 , V = 3480.6(12) A ,
◦
3
18 W. W. N. O, A. J. Lough and R. H. Morris, Organometallics, 2011, 30,
˚
˚
2
1
236–1252.
-
3
-1
Z = 4, r = 2.155 Mg m , m = 4.795 mm , F(000) = 2312, crystal
3
c
1
2
2
9 W. B. Cross, C. G. Daly, R. L. Ackerman, I. R. George and K. Singh,
Dalton Trans., 2011, 40, 495–505.
size 0.15 ¥ 0.13 ¥ 0.03 mm , 26753 reflections collected, 6829
◦
0 F. Hanasaka, K.-i. Fujita and R. Yamaguchi, Organometallics, 2006,
unique [R(int) = 0.1501] (completeness to theta = 26.00 100.0%).
Empirical absorption correction made, Tmax and Tmin 0.862 and
.539 respectively. GOF = 0.795, final R indices > 2 s I] R
.0541, wR = 0.1052, R indices (all data) R = 0.0949, wR
.1136. Largest diff. peak and hole 0.991 and -1.925 e.A .
2
5, 4643–4647.
1 Y. Tanabe, F. Hanasaka, K.-i. Fujita and R. Yamaguchi,
0
0
0
1
=
=
Organometallics, 2007, 26, 4618–4626.
22 R. Corberan, M. Sanau and E. Peris, Organometallics, 2006, 25, 4002–
2
1
2
-
3
4008.
˚
2
2
3 R. Corberan, M. Sanau and E. Peris, J. Am. Chem. Soc., 2006, 128,
3
974–3979.
Catalytic transfer hydrogenation
4 M. Viciano, M. Feliz, R. Corberan, J. A. Mata, E. Clot and E. Peris,
Organometallics, 2007, 26, 5304–5314.
General procedure. In a Schlenk flask under an atmosphere
25 R. Corberan, M. Sanau and E. Peris, Organometallics, 2007, 26, 3492–
of nitrogen, a solution of acetophenone (0.200 g, 1.70 mmol)
3498.
◦
26 A. Prades, R. Corber a´ n, M. Poyatos and E. Peris, Chem. Eur. J., 2008,
in iso-propanol (6 mL) was preheated to 80 C with stirring.
1
4, 11474–11479.
The appropriate pre-catalyst (5, 6 or 7, 0.0085 mmol), sodium
2
2
2
7 A. Prades, M. Poyatos and E. Peris, Adv. Synth. Catal., 2010, 352,
t-butoxide (6 mg, 0.062 mmol) and AgPF (0.003 g, 0.01 mmol)
6
1155–1162.
8 R. Corberan, V. Lillo, J. A. Mata, E. Fernandez and E. Peris,
Organometallics, 2007, 26, 4350–4353.
9 M. Poyatos, W. McNamara, C. Incarvito, E. Clot, E. Peris and R. H.
Crabtree, Organometallics, 2008, 27, 2128–2136.
30 F. Hanasaka, K.-I. Fujita and R. Yamaguchi, Organometallics, 2005,
were then added as appropriate. Periodically, aliquots were
removed from the reaction mixture by syringe. The aliquots
were immediately quenched by dilution with EtOAc and then
analysed by gas chromatography using a Perkin-Elmer Clarus 500
chromatograph equipped with a Perkin-Elmer Elite 5 column (PE5
2
4, 3422–3433.
¨
3
1 I. Ozdemir, S. Demir, N. Gurbuz, B. Cetinkaya, L. Toupet, C. Bruneau
3
0 m ¥ 0.25 mm). Helium was used as a mobile phase with a flow
and P. H. Dixneuf, Eur. J. Inorg. Chem., 2009, 1942–1949.
-
1
-1
rate of 1 mL min and a split rate of 50 mL min . The injector
32 A. Zanardi, R. Corberan, J. A. Mata and E. Peris, Organometallics,
◦
◦
2
008, 27, 3570–3576.
temperature was 250 C, the oven temperature was 130 C and the
FID temperature was 280 C. Retention times (t min ) were:
◦
-1
33 N. G u¨ rb u¨ , S. Ya s¸ ar, E. O. Ozean, I. Ozdemir and B. C¸ etinkaya, Eur. J.
R
Inorg. Chem., 2010, 3051–3056.
acetophenone, 3.54; (R/S)-1-phenylethanol, 3.45. All reported
conversions are an average of two reactions.
3
3
4 R. Cariou, C. Fischmeister, L. Toupet and P. H. Dixneuf,
Organometallics, 2006, 25, 2126–2128.
5 L. Li, W. W. Brennessel and W. D. Jones, Organometallics, 2009, 28,
3
492–3500.
Acknowledgements
36 Y. Boutadla, D. L. Davies, R. C. Jones and K. Singh, Chem. Eur. J.,
2
011, 17, 3438–3448.
We thank the University of Leicester for a graduate studentship
CGD), the EPSRC (EP/H028323/1) for financial support and
Johnson Matthey for a loan of Ru, Rh and Ir salts.
37 D. L. Davies, S. M. A. Donald, O. Al-Duaij, S. A. Macgregor and M.
P o¨ lleth, J. Am. Chem. Soc., 2006, 128, 4210–4211.
8 Y. Boutadla, D. L. Davies, S. A. Macgregor and A. I. Poblador-
Bahamonde, Dalton Trans., 2009, 5887–5893.
(
3
3
9 T. P. Brewster, J. D. Blakemore, N. D. Schley, C. D. Incarvito, N. Hazari,
G. W. Brudvig and R. H. Crabtree, Organometallics, 2011, 30, 965–
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730 | Dalton Trans., 2011, 40, 9722–9730
This journal is © The Royal Society of Chemistry 2011