Triply cyclometalated trinuclear iridium(iii) and trinuclear palladium(ii) complexes with a tri-mesoionic carbene ligand

Article abstract of DOI:10.1039/c5cc05506g

The first example of a triply cyclometalated homopolynuclear tri-Ir^III complex with additional carbene donors is presented. Cooperative catalysis and the interplay between homogenous and heterogeneous catalyses are discussed for the tri-Ir^III complex and a related non-cyclometalated tri-Pd^II complex.

Full text of DOI:10.1039/c5cc05506g

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COMMUNICATION
Triply cyclometalated trinuclear iridium(III) and trinuclear
palladium(II) complexes with a tri-mesoionic carbene ligand†
Ramananda Maity, Amel Mekic, Margarethe van der Meer, Amit Verma and Biprajit Sarkar*
Received (in XXX, XXX) Xth XXXXXXXXX 2014, Accepted Xth XXXXXXXXX 20XX
5
DOI: 10.1039/b000000x
1,3,5-tri substituted benzene derived tristriazolium salt was
unsuccessful.13c We believed that steric effects might render the
formation of cyclometalated complexes with this ligand system
difficult. Hence, we decided to introduce additional phenyl rings
45 on the ligand backbone to reduce steric crowding and synthesized
the tris-triazolium salt 2 (Scheme 1). We present here the first
triply cyclometalated trinuclear IrIII complex from a 1,3,5-
triphenylbenzene derived tri-MIC ligand, where the coordinated
MIC moieties are further removed from each other and allow the
50 IrIII centers to undergo cyclometalation. In addition, a trinuclear
PEPPSI type PdII complex has also been synthesized using the
same tri-MIC ligand platform. Apart from synthetic and structural
aspects, we also present catalytic results for transfer
hydrogenation and C–C coupling reactions with the IrIII and PdII
55 complexes, respectively, discussing catalytic cooperativity and
homogeneous versus heterogeneous catalysis.
The first example of a triply cyclometalated homopolynuclear
tri-IrIII complex with additional carbene donors is presented.
Cooperative catalysis and the interplay between homogenous
and heterogeneous catalysis is discussed for the tri-IrIII
10 complex and a related non-cyclometalated tri-PdII complex.
N-Heterocyclic carbenes (NHCs) have emerged as a useful class
of ligands in organometallic chemistry.1 Although the majority of
these ligands are based on imidazol-2-ylidenes2 or 1,2,4-triazol-5-
ylidenes3 (normal NHCs), their mesoionic counterparts 1,2,3-
15 triazol-5-ylidenes4 are currently gaining immense popularity. The
mesoionic carbenes (MIC) have been postulated as even better
sigma donors compared to their classical counterparts.4a
A
number of complexes bearing 1,2,3-triazol-5-ylidenes have
emerged in the literature with the complexes being often tested
20 for their potency in various homogeneous catalytic processes.5
Recently, we have reported on such type of complexes as
catalysts for various organic transformations such as Suzuki–
Miyaura cross-coupling reactions,6 “click” reactions,7 reduction
of aromatic nitro compounds8 and for oxidation reactions.9 Most
25 of the reported complexes possessing 1,2,3-triazol-5-ylidene
ligands are of mononuclear type.4,5,10 Only a few dinuclear
complexes possessing a MIC donor at each metal center have
been reported in the literature recently.11 Even though
polynuclear metal complexes have become popular in recent
30 years owing to their augmented catalytic activity12 compared to
their mononuclear counterparts, examples of such complexes
with higher nuclearity containing MIC donors remain rare.13
Recently, we showed that a di-substituted phenylene bridged
bistriazolium salt after deprotonation reacts to yield a dinuclear
35 IrIII complex with additional cyclometalation of the central phenyl
ring (Fig. 1).13a For PdII that prefers a square planar coordination
geometry, reaction with either di- or 1,3,5-tri substituted benzene
derived triazolium salts in the presence of K2CO3 and pyridine
yielded the PEPPSI type complexes (Fig. 1).13b However, the
40 intended synthesis of triply cyclometalated IrIII complex with
Fig.
60 ligands.13
1
Dinuclear IrIII and trinuclear PdII Complexes with MIC
The reaction of the tris-triazolium salt 2 with Ag2O followed
by the addition of [Ir(Cl)2Cp*]2 in the presence of sodium acetate
resulted in the formation of a triply cyclometalated trinuclear IrIII
65 complex [3] in 84% yield. The complex [3] is stable under air and
moisture and well soluble in solvents like chloroform and
dichloromethane. The complex [3] is characterized by 1H,
13C{1H} NMR spectroscopy and ESI mass spectrometry. The
1
formation of complex [3] was easily monitored by the H NMR
70 spectroscopy, which shows the disappearance of the triazolium
C–H protons signal ( = 9.31 ppm) for the original tris-triazolium
1
salt 2. Both the H and 13C{1H} NMR spectra of complex [3]
Institut für Chemie und Biochemie, Anorganische Chemie, Freie
Universität Berlin, Fabeckstraße 34-36, D-14195, Berlin, Germany. E-
mail: biprajit.sarkar@fu-berlin.de; Fax: +49-30-838-53310.
† Electronic supplementary information (ESI) available: Preparation and
spectroscopic properties of complexes [3] and [4]. Details of the crystal
structure determinations for [4]·2.75CH2Cl2 (CCDC 1062049). See
http://www.rsc.org/suppdata/xx/b0/b00000x/
show more than one set of signals in solution which implies the
presence of different rotational isomers of the complex in
75 solution. The rotamers are caused due to the free rotation of the
[IrIII(Cl)Cp*(CMIC^CAr)] moieties around the Caryl–Caryl bonds. On
This journal is © The Royal Society of Chemistry [year]
[journal], [year], [vol], 00–00 | 1

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Page 2 of 5
heating the sample to 90°C, the signals of the rotamers merge to a
the C5H resonance of the precursor triazolium salt 2 (δ = 129.2
single set of signal (Fig. S11). The resonances for four chemically
40 ppm).
different aryl C–H protons appeared as four sets in the range of 
Single crystals suitable for an X-ray difDfrOacI:ti1o0n.10a3n9Vai/leCyw5sAiCsrtCiwc0lee5O5re0nl6inGe
obtained for complex [4] by slow diffussion of pentane into a
saturated dichloromethane solution of complex [4] at ambient
temperature. The molecular structure analysis confirmed the
45 formation of trinuclear palladium complex depicted in Scheme 1.
The asymmetric unit contains ⅓ formula unit of the complex [4]
and disordered dichloromethane molecules. The ⅓ unit is related
to the rest ⅔ unit by a crystallographic inversion center. In
complex [4] each palladium atom is coordinated to one strongly
50 bound MIC donor and a weakly coordinated pyridine donor trans
to it. The remaining coordination sites of each palladium center
are occupied by iodido ligands. The C1–Pd1–N4 (Fig. 2) bond
angle measures 177.4(3)°. This value, like the Pd1–C1 (1.954(6)
Å) and Pd1–N4 (2.096(6) Å) bond lengths, fall in the range
55 previously described for palladium MIC complexes.13b,16 The
MIC donor planes are almost coplanar to the central aryl ring
plane, however, they are rotated out of the nearest aryl ring plane
to coordinate with palladium centers. The torsion angle of the
MIC donor plane to the nearest aryl ring plane measures 35.26°.
60 The two central phenyl rings of the tri-mesoionic carbene ligands
of neighboring molecules are oriented in a coplanar fashion with
a centroid to centroid separation of 3.498 Å indicating π···π
interactions between these rings.
=
8.17−8.29, 7.908.02, 7.497.52, 7.277.43 ppm. The
5
cyclometalation of the aryl ring was confirmed by 2D correlation
NMR spectroscopy which shows a resonance (broad) at  =
159.6 ppm, attributed to the cyclometalated aryl carbon atom.
The resonance for the characteristic carbene carbon atoms was
observesd at  = 153.1 ppm also as a broad signal. These
10 resonances fall in the range reported for cyclometalated
complexes bearing MIC donor ligands.13,14 The resonance for the
carbene carbon atom in complex [3] is more upfield shifted
compared to their corresponding resonance in complexes
possessing cyclometalated classical NHC ligands.15 The ESI mass
15 (positive ions) spectrum of complex [3] shows the peaks at m/z =
1884.4968 (calcd for [[3]Cl]+ 1884.4863) and 823.7659 (calcd
for [[3]2Cl]2+ 823.7583) as strongest signals, also confirming the
formation of complex [3].
65
Fig. 2 ORTEP plot of [4]·2.75CH2Cl2 (left). Ellipsoids are drawn at
50 % probability. Hydrogen atoms and solvent molecules have been
omitted for clarity. Intermolecular π-π stacking (right).
20 Scheme 1 Preparation of complexes [3] and [4].
70
The catalytic transfer hydrogenation is a widely used method
for reducing multiple bonds. Conversion of aldehydes and
ketones to the corresponding alcohols represents the most
prominent examples. Iridium and ruthenium complexes bearing
NHC ligands have been widely used as catalysts for transfer
The treatment of the tristriazolium salt 2 with PdCl2 in the
presence of K2CO3 as an external base in pyridine yielded a
trinuclear PEPPSI type PdII complex [4]. The complex [4] is
25 stable under air and moisture for long time and also has a good
solubility in chlorinated solvents like chloroform and
dichloromethane. The formation of complex [4] was monitored
75 hydrogenation.17 However, similar catalytic conversions using
complexes bearing MIC ligands have been rare.8,13a,18 In this
context, catalytic transfer hydrogenation studies have been
carried out with the triply cyclometalated IrIII complex [3]. The
catalytic conversions for the trinuclear complex have also been
80 compared with a related cyclometalated mononuclear complex C
(Fig. 3).
1
by H NMR spectroscopy, which shows only one set of signals
along with the disappearance of the triazolium C–H proton
30 resonance ( = 9.31 ppm) for the precursor triazolium salt 2. The
resonances for the C–H protons of pyridine rings appeared as
multiplets at δ = 8.99, 7.75–7.78 and 7.33–7.36 ppm. Upon
complexation the resonance for α-hydrogen atoms of the pyridine
ring (δ = 8.99 ppm) appeared more downfield shifted compared
35 to their corresponding resonance in free pyridine (δ = 8.62). The
characteristic resonance for the Ctrz–Pd carbon atoms was
observed at δ = 133.1 ppm in the 13C{1H} NMR spectrum of
complex [4]. This resonance is slightly downfield shifted from
N
N
N
N
N
N
I
Ir
Pd
I
Cl
N
C
D
Fig. 3 Mononuclear IrIII and PdII Complexes.
2
| Journal Name, [year], [vol], 00–00
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Page 3 of 5
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Table 1 Catalytic transfer hydrogenation of aldehyde and ketones.[a]
40
Entry
Ar
Catalyst
Conversion
Isolated
(%)D1O6I:h10.1039Vi/eCYw5iACertClidc0le5(%O50n)l6inGe
1
2
3
4
5
6
Ph
[4]
D
80
60
91
63
81
65
71
45
85
59
70
46
Entry
R
R
Catalyst
Conversion
Conversion
1
2
Ph
(%) 1 h
80
(%) 3 h
99
4-Me(Ph)
4-Me(Ph)
[4]
D
1
Ph
H
[3]
C
2
Ph
H
40
99
4-OMe(Ph) [4]
4-OMe(Ph)
3
4-Br(Ph)
4-Br(Ph)
Ph
H
[3]
C
50
99
D
4
H
35
99
5
CH
CH
Ph
Ph
[3]
C
40
65
3
3
On performing the reactions with 5.0 mol% of the
mononuclear complex D or 1.67 mol% (same amount of
palladium for both types of complexes) of the trinuclear complex
6
Ph
24
40
7
Ph
[3]
C
42
80
8
Ph
13
29
45 [4], almost 1.5 times more conversion of 5 to 6 was achieved for
the trinuclear complex (Table 2, 71%; isolated yield, see ESI)
when compared with the mononuclear complex (45%; isolated
yield, see ESI). The active palladium catalyst was unaffected by
the addition of excess Hg(0) to the reaction mixture and leads to
50 similar yield for the α-arylation product even after addition of
Hg(0). This is strong indication of the homogeneous nature of our
catalysts for the α-arylation reaction. We also tested the
efficiency of [4] and D as catalysts for the Suzuki-Miyaura cross-
coupling reaction. For that reaction, no further conversion to the
55 coupling product was observed any more after Hg(0) addition.
Addition of mercury after 1 h (13% conversion) inhibited further
catalytic coupling and no biaryl aldehyde product (phenylboronic
acid and 4-bromobenzaldehyde as substrates) was formed during
the subsequent 5 h time. This observation suggests the possibility
60 that Pd(0) nanoparticles (NP) are the active catalyst in Suzuki–
Miyaura cross-coupling reactions under the mentioned reaction
conditions, as has been previously observed for related systems.10
9
Ph
4-Br(Ph)
4-Br(Ph)
4-Me(Ph)
4-Me(Ph)
[3]
C
30
61
10
11
12
Ph
11
40
4-Me(Ph)
4-Me(Ph)
[3]
C
20
62
8
38
[a]
Reactions conditions: 0.5 mol % catalyst (0.167 mol % for the
trinuclear complex and 0.5 mol % for the mononuclear complex),
20 mol % KOH, isopropanol, 100 °C.
5
Isopropanol was used as a hydrogen source for the transfer
hydrogenation reactions. KOH (20 mol%) was used as a base and
10 the reactions were performed at 100 °C. The reaction was carried
out with 0.5 mol% of the mononuclear complex or 0.167 mol%
(same amount of iridium for both complexes) of the trinuclear
complex. Both complexes show
a
full conversion of
benzaldehyde 4-bromo-benzaldehyde to the corresponding
15 benzylalcohol after 3 h. Decrease in reaction time to 1 h shows a
higher conversion (80 or 50%) for the trinuclear complex
compared with mononuclear IrIII complex (40 or 35%). The
trinuclear complex is also a more active precatalyst for more
challenging substrates like acetophenone, benzophenone and
20 substituted benzophenone (Table 1).
Table 3 Suzuki–Miyaura cross-coupling reaction.[a]
65
The palladium-catalyzed C–C bond formation process
between an aryl ring and the α-position of a carbonyl compound
has been widely explored as a mild catalytic method.19 However,
α-arylation of amides (particularly the intermolecular version) is
25 comparatively less common and rarely explored with
palladium(II) NHC complexes.20 This is an important catalytic
reaction for synthesizing valuable chemicals. The trinuclear
palladium(II) complex [4] has been tested as a catalyst for both α-
arylation and Suzuki–Miyaura cross-coupling reactions. The
30 catalytic efficiency of the trinuclear complex [4] has also been
compared to the efficiency of a similar mononuclear counterpart
D (Fig. 3). The α-arylation reactions were typically carried out in
toluene in the presence of NaOtBu (2.5 equiv.) as a base and the
reactions were performed at 120 °C for 16 h.
Entry
Ar
Ph
Ph
4-Me(Ph)
4-Me(Ph)
Catalyst Conversion
(%) 5 h
Conversion
(%) 12 h
1
2
3
4
[4]
D
58
52
60
64
85
90
87
92
[4]
D
[a]
Reactions conditions: 0.5 mol % catalyst (0.167 mol % for the
trinuclear complex), 1.4 mol% K2CO3, water, rt, 5 h.
70
As is to be expected, for the Suzuki-Miyaura coupling where
Pd-NPs are the active species, both D and [4] delivered similar
conversions. (Table 3).
Summarizing, we have presented here the synthesis of a
novel tris-triazolium salt 2 based on an extended phenylene
75 platform. 2 was used to synthesize a trinuclear complex [3] where
each IrIII center is coordinated by a MIC unit and additionally
cyclometalates the aryl rings of the ligand. 2 was also used to
synthesize the trinuclear PEPPSI type complex [4] upon reaction
with PdCl2 in the presence of pyridine and K2CO3. The complex
35
Table 2 α-Arylation reaction using PdII complexes.
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 3

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Page 4 of 5
[3] is the first example of a triply cyclometalated trinuclear IrIII
complex containing additional carbene donors. The tri-iridium
complex [3] is an active pre-catalyst for the conversion of
aldehyde and ketones to the corresponding alcohols and shows
possible signs of cooperative effects in catalysis. The trinuclear
PEPPSI type complex [4] is an active catalyst for both α-arylation
of amides and the Suzuki–Miyaura cross-coupling reaction. [4]
displays possible signs of cooperative effects for the α-arylation
reaction which proceeds homogeneously. The same complex also
10 catalyzes the Suzuki-Miyaura cross-coupling reaction, albeit
through the formation of Pd(0)-NPs in a heterogenous medium,
and thus no cooperativity is observed. The new ligand platform
presented here opens up new avenues for generating multi-
cyclometalated complexes and investigating potentially
15 cooperative catalysis. The results on α-arylation of amides shows
the potential of Pd-MIC complexes as potent pre-catalysts for that
important reaction. Furthermore, our results on the Suzuki-
Miyaura cross-coupling reaction shows that for such reactions
that are carried out in water even under mild conditions (room
20 temperature), Pd-NPs are often likely to be the real active
catalyst.
65
70
75
Bolje and J. Kosmrlj, Org. Lett. 2013, 15, 5084.
S. Hohloch, W. Frey, C.-Y. Su and B. Sarkar, Dalton Trans.,
2013, 42, 11355.
6
7
View Article Online
(a) S. Hohloch, C.-Y. Su and B. Sarkar, Eur. J. Inorg. Chem.,
DOI: 10.1039/C5CC05506G
2011, 3067; (b) S. Hohloch, D. Scheiffele and B. Sarkar, Eur. J.
Inorg. Chem., 2013, 3956; (c) S. Hohloch, B. Sarkar, L. Nauton,
F. Cisnetti and A. Gautier, Tetrahedron Lett., 2013, 54, 1808.
(a) S. Hohloch, L. Suntrup and B. Sarkar, Organometallics, 2013,
32, 7376.
(a) S. Hohloch, L. Hettmanczyk and B. Sarkar, Eur. J. Inorg.
Chem., 2014, 3164; (b) A. Bolje, S. Hohloch, D. Urankar, A.
Pevec, M. Gazvoda, B. Sarkar and J. Košmrlj, Organometallics,
2014, 33, 2588; (c) S. Hohloch, S. Kaiser, F. L. Duecker, Al.
Bolje, R. Maity, J. Košmrljb and B. Sarkar, Dalton Trans., 2015,
44, 686.
5
8
9
80 10 D. Canseco-Gonzalez, A. Gniewek, M. Szulmanowicz, H.
Müller-Bunz, A. M. Trzeciak and M. Albrecht, Chem. –Eur. J.,
2012, 18, 6055.
11 (a) M. T. Zamora, M. J. Farguson and M. Cowie,
Organometallics, 2012, 31, 5384; (b) J. Cai, X. Yang, K.
85
Arumugam, C. W. Bielawski and J. L. Sessler, Organometallics,
2011, 30, 5033; (c) E. C. Keske, O. V. Zenkina, R. Wang and C.
M. Crudden, Organometallics, 2012, 31, 456; (d) K. J. Kilpin, U.
S. D. Paul, A.-L. Lee and J. D. Crowley, Chem. Commun., 2011,
47, 328.
90 12 M. Weiss and R. Peters, Bimetallic Catalysis: Cooperation of
Carbophilic Metal Centers in: Cooperative Catalysis – Designing
Efficient Catalysts for Synthesis, R. Peters (Ed.), Wiley-VCH,
Weinheim, 2015.
The authors thank the Fonds der Chemischen Industrie (FCI)
and the Freie Universität Berlin for financial support. The
25 ERASMUS-MUNDUS program is acknowledged for providing a
post-doctoral fellowship to AV.
13 (a) R. Maity, S. Hohloch, M. van der Meer and B. Sarkar, Chem.
95
100
105
110
−Eur. J., 2014, 20, 9952; (b) R. Maity, M. van der Meer and B.
Sarkar, Dalton trans. 2015, 44, 46. (c) R. Maity, M. van der
Meer, S. Hohloch and B. Sarkar, Organometallics, 2015, 34,
3090.
Notes and references
14 K. F. Donnelly, R. Lalrempuia, H. Müller-Bunz and M. Albrecht,
Organometallics, 2012, 31, 8414.
1
for selected reviews see: (a) P. de Frémont, N. Marion and S. P.
Nolan, Coord. Chem. Rev., 2009, 253, 862; (b) M. Melaimi, M.
Soleilhavoup and G. Bertrand, Angew. Chem., Int. Ed., 2010, 49,
8810; (c) F. E. Hahn and M. C. Jahnke, Angew. Chem., Int. Ed.,
2008, 47, 3122; (c) M. Melaimi, M. Soleilhavoup and G.
Bertrand, Angew. Chem., Int. Ed., 2010, 49, 8810; (d) C. C. Loh
and D. Enders, Chem. –Eur. J. 2012, 18, 10212; (e) J. D. Egbert,
C. S. J. Cazin and S. P. Nolan, Catal. Sci. Technol., 2013, 3, 912.
(a) M. C. Jahnke and F. E. Hahn, Top. Organomet. Chem., 2010,
30, 95; (b) W. A. Herrmann, Angew. Chem., Int. Ed., 2002, 41,
1290.
(a) A. Zanardi, R. Corberán, J. A. Mata and E. Peris,
Organometallics, 2008, 27, 3570; (b) H. Braband, O. Blatt and U.
Abram, Z. Anorg. Allg. Chem., 2006, 632, 2251; (c) D. Enders
and T. Balensiefer, Acc. Chem. Res., 2004, 37, 534; (d) D.
Enders, O. Niemeier and A. Henseler, Chem. Rev., 2007, 107,
5606; (e) M. He and J. W. Bode, J. Am. Chem. Soc. 2008, 130,
418.
15 (a) R. Maity, H. Koppetz, A. Hepp and F. E. Hahn, J. Am. Chem.
Soc., 2013, 135, 4966: (b) R. Maity, A. Rit, C. Schulte to Brinke,
J. Kösters and F. E. Hahn, Organometallics, 2013, 32, 6174; (c)
R. Maity, A. Rit, C. Schulte to Brinke, C. G. Daniliuc and F. E.
Hahn, Chem. Commun., 2013, 49, 1011.
30
35
16 E. C. Keske, O. V. Zenkina, R. Wang and C. M. Crudden,
Organometallics, 2012, 31, 6215.
2
3
17 For selected examples, see: (a) S. Horn and M. Albrecht, Chem.
Commun., 2011, 47, 8802; (b) D. Gnanamgari, E. L. O. Sauer, N.
D. Schley, C. Butler, C. D. Incarvito and R. H. Crabtree,
Organometallics, 2009, 28, 321; (c) N. Gürbüz, E. O. Özcan, I.
Özdemir, B. Cetinkaya, O. Sahin and O. Büyükgüngör, Dalton
Trans. 2012, 41, 2330; (d) A. C. Hillier, H. M. Lee, E. D. Stevens
and S. P. Nolan, Organometallics 2001, 20, 4246.
40
45
50
55
60
115 18 A. Bolje, S. Hohloch, M. van der Meer, J. Košmrlj and B. Sarkar,
Chem. −Eur. J., 2015, 21, 6756.
19 for selected examples see: (a) D. A Culkin and J. F. Hartwig,
Acc. Chem. Res., 2003, 36, 234; (b) B. C. Hamann and J. F.
Hartwig, J. Am. Chem. Soc., 1997, 119, 12382; (c) A. Verma, N.
Prajapati, S. Salecha, R. Giridhar and M. R. Yadav, Tetrahedron
Lett., 2013, 54, 2029.
20 for selected examples see: (a) X. Luan, R. Mariz, C. Robert, M.
Gatti, S. Blumentritt, A. Linden and Reto Dorta, Org. Lett., 2008,
24, 5569; (b) Y.-X. Jia, D. Katayev, G. Bernardinelli, T. M.
4
(a) P. Mathew, A. Neels and M. Albrecht, J. Am. Chem. Soc.,
2008, 130, 13534; (b) K. F. Donnelly, A. Petronilho and M.
Albrecht, Chem. Commun., 2013, 49, 1145; (c) R. H. Crabtree,
Coord. Chem. Rev., 2013, 257, 755; (d) J. M. Aizpurua, R. M. 120
Fratila, Z. Monasterio, N. Perez-Esnaola, E. Andreieff, A.
Irastorza and M. Sagartzazu-Aizpurua, New J. Chem., 2014, 38,
474; (e) D. Schweinfurth, N. Deibel, F. Weisser and B. Sarkar,
Nach. der Chem., 2011, 59, 937; (f) G. Guisado-Barrios, J.
Bouffard, B. Donnadieu and G. Bertrand, Angew. Chem., Int. Ed.,
2010, 49, 4759; (g) J. D. Crowley, A. Lee and K. J. Kilpin, Aust.
J. Chem., 2011, 64, 1118.
125
130
135
Seidel and E. P. Kündig, Chem. −Eur. J., 2010, 16, 6300; (c) X.
Luan, L. Wu, E. Drinkel, R. Mariz, M. Gatti and R. Dorta, Org.
Lett., 2010, 12, 1912; (d) B. Zheng, T. Jia and P. J. Walsh, Adv.
Synth. Cat. 2014, 356, 165; (e) A. M. Taylor, R. A. Altman and
S. L. Buchwald, J. Am. Chem. Soc. 2009, 131, 9900; (f) B.
Zheng, T. Jia and P. J. Wlash, Org. Lett. 2013, 15, 4190; (g) E.
Koch, R. Takise, A. Studer, J. Yamaguchi and K. Itami, Chem.
Commun, 2015, 51, 855.
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for selected examples see: (a) R. Saravanakumar, V. Ramkumar
and S. Sankararaman, Organometallics, 2011, 30, 1689; (b) R.
Lalrempuia, H. Müller-Bunz, S. Bernhard and M. Albrecht,
Angew. Chem., Int. Ed., 2010, 49, 9765; (c) T. Nakamura, T.
Terashima, K. Ogata and S. Fukuzawa, Org. Lett. 2011, 13, 620;
(d) J. R. Wright, P. C. Young, N. T. Lucas, A.-L. Lee and J. D.
Crowley, Organometallics, 2013, 32, 7065; (e) J. Huang, J.-T.
Hong and S. H. Hong, Eur. J. Org. Chem. 2012, 6630; (f) A.
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DOI: 10.1039/C5CC05506G
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A tri-cyclometalated IrIII MIC complex and a tri-PdII MIC
complex are presented. The complexes show potential
cooperative catalytic behavior.
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