Unsaturated iridium pyridinedicarboxylate pincer complexes with catalytic activity in borylation of arenes

Article abstract of DOI:10.1039/c1dt11046b

Unsaturated σ,π-cyclooctenyl and hydrido Ir(iii) complexes bearing an unusual tridentate dianionic ONO pincer-type ligand have been straightforwardly obtained from 2,6-pyridinedicarboxylic acid and standard Ir(i) starting materials. These complexes efficiently catalyzed the arene C-H borylation under thermal conditions. The Royal Society of Chemistry 2011.

Full text of DOI:10.1039/c1dt11046b

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PAPER
Unsaturated iridium pyridinedicarboxylate pincer complexes with catalytic
activity in borylation of arenes†
Duc Hanh Nguyen,a Jesu´s J. Pe´rez-Torrente,*a Laura Lomba,a M. Victoria Jime´nez,a Fernando J. Lahoza and
Luis A. Oro*a,b
Received 6th April 2011, Accepted 3rd June 2011
DOI: 10.1039/c1dt11046b
Unsaturated s,p-cyclooctenyl and hydrido Ir(III) complexes bearing an unusual tridentate dianionic
ONO pincer-type ligand have been straightforwardly obtained from 2,6-pyridinedicarboxylic acid and
standard Ir(I) starting materials. These complexes efficiently catalyzed the arene C–H borylation under
thermal conditions.
On the other hand, Periana et al. have shown that Ir(III)
Introduction
complexes [Ir(acac)2(R)(py)] (R = CH3, Ph) are efficient cat-
Catalyst design for the selective functionalization of unreactive
alysts in several processes based on C–H activation, such
C–H bonds is one of the major challenges in transition metal
as hydroarylation of olefins and H/D exchange, operating
chemistry.1 The efficient generation of coordinatively unsaturated
metal species is generally required for C–H bond activation,
high catalytic activity and a broad substrate scope. Metal-
catalyzed borylation of aryl C–H bonds has become a conve-
nient methodology for the preparation of synthetically useful
aromatic boron compounds.2 The most active catalyst, operating
under mild conditions, is generated from [Ir(m-OMe)(cod)2]2 and
dtbpy (dtbpy = 4,4¢-di-tert-butyl-2,2¢-bipyridine).3 Mechanistic
and computational studies have evidenced the involvement of
the 16-electron trisboryl complex [Ir(dtbpy)(Bpin)3] as the key
intermediate that undergoes oxidative addition of the aryl C–H
bond, in a turnover-limiting step, to form the arylboronate ester
through a catalytic cycle involving Ir(III) and Ir(V) species.4 In
spite of the versatility and high performance of this system, only
a few well-defined iridium catalysts have been reported up to date.
also through Ir(V) intermediates.10 O-donor ligands in these
systems play an important role, stabilizing the complexes in
the required reaction conditions and facilitating access to
higher oxidation states, modulating the electron density at
the metal centers via a hard/hard interaction or p-donating
effects.11
Inspired by the structural features of Periana’s catalysts and
the versatility of tridentate pincer ligands, which impart to
metal complexes an evenness of stability and reactivity ap-
propriate for catalytic activity,12 we envisaged the potential
of tridentate dianionic ONO pincer-type ligands for the de-
sign of Ir(III) compounds with applications in catalytic C–H
activation/functionalization processes. In particular, we have
focused on the 2,6-pyridinedicarboxylate ligand because of its
dianionic character with hard and electronegative coordination
atoms and rigid tridentate pincer structure that requires only
three coordination positions allowing for available coordination
sites.
5
[Ir(Cp*)H(Bpin)(PMe3)] and [Ir(h -indenyl)(cod)]/diphosphine
were early representative examples of catalytic systems containing
phosphine ligands.5 Tris(pyrazolyl)borate and biscarbene iridium
complexes, [Ir(Tp)(cod)] (Tp = hydridotris(pyrazolyl)borate) and
[Ir(cod)(NHC)2]+ (NHC = N-heterocyclic carbene), were reported
in 2006 by Murata6 and Herrmann7 and co-workers, respectively,
to catalyse the borylation of arenes with HBpin. Later on, the
catalytic activity of iridium(I) salicylaldiminato-cyclooctadiene
complexes in the presence of several P- and N-donor ligands,8
and iridium(III) pincer N-heterocyclic carbene complexes in com-
bination with a base have been reported.9
Results and discussion
Synthesis of unsaturated iridium(III) pincer complexes
The reaction of 2,6-pyridinedicarboxylic acid (H2pydc) with [Ir(m-
OMe)(cod)]2 in CH2Cl2/MeOH gave a yellow solution of the
3
unsaturated Ir(III) compound [Ir(k -pydc)(1-k-4,5-h-C8H13)] (1)
which was isolated as a yellow solid in 90% yield after chromato-
graphic purification. Compound 1 is insoluble in chlorinated sol-
vents but, interestingly, is soluble in a dichloromethane/methanol
aDepartamento de Qu´ımica Inorga´nica, Instituto de S´ıntesis Qu´ımica y
Cata´lisis Homoge´nea - ICQCH, Universidad de Zaragoza-C.S.I.C., 50009-
Zaragoza, Spain; Fax: 34 976 761187; Tel: 34 976 762286
1
mixture. 1H and 13C{ H} NMR spectra were fully consistent
bKing Fahd University of Petroleum and Minerals, KFUPM visiting Profes-
sor, Dhahran 31261, Saudi Arabia. E-mail: perez@unizar.es, oro@unizar.es
with the presence of a s–p cyclooctenyl ligand coordinated as
1-k-4,5-h-C8H13 which was further confirmed by a single crystal
X-ray diffraction study of the methanol solvate. Compound 1-
MeOH is octahedral with a meridional 2,6-pyridinedicarboxylate
† Electronic supplementary information (ESI) available: Determination
of the kinetic parameters for the pyridine exchange in 1-py. See DOI:
10.1039/c1dt11046b
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3
ligand k -O,N,O coordinated,13 a 1-k-4,5-h-C8H13 ligand with
the double bond trans to the pyridinic nitrogen atom, and a
methanol molecule linked trans to the Ir–C bond (Fig. 1). The
most relevant structural parameter of this complex is the lengthy
Ir–O(5) distance of the coordinated methanol ligand, 2.263(3)
˚
A, significantly longer than the carboxylate Ir–O(1) or Ir–O(3)
˚
bonds, 2.073(3) A, most likely as a consequence of the high
structural trans-effect of the alkylic Ir–C(11) bond; this structural
feature supports the observed lability of the methanol molecule
in its chemical behaviour. This crystal structure is stabilized by
the presence of two classical intermolecular hydrogen bonds,
one involving the coordinated methanol molecule (O(5) . . . O(4)¢
◦
˚
2.649(4) A, O(5)–H(5) . . . O(4)¢ 170(5) ) and the second one
involving the solvate methanol moiety (O(1S) . . . O(1) 2.867(5)
◦
˚
A, O(1S)–H(1S) . . . O(1) 173(8) ).
Scheme 1
pyridine exchange with py-d5 (py*) to give 1-py* was observed at
room temperature (Scheme 2).
Fig. 1 Molecular structure of 1-MeOH. Selected geometrical data
◦
˚
(bond lengths [A] and angles [ ]): Ir–O(1) 2.073(3), Ir–O(3) 2.073(3),
Ir–O(5) 2.263(3), Ir–N(1) 1.977(3), Ir–C(11) 2.069(4), Ir–C(14) 2.171(4),
Ir–C(15) 2.181(4), C(1)–O(1) 1.315(5), C(1)–O(2) 1.211 (5), C(7)–O(3)
1.294(5), C(7)–O(4) 1.231(5), C(11)–C(12) 1.555(7), C(11)–C(18) 1.523(6),
C(13)–C(14) 1.510(7), C(14)–C(15) 1.381(7), C(15)–C(16) 1.507(7),
C(19)–O(5) 1.439(5); O(1)–Ir–O(3) 157.31(11), O(5)–Ir–C(11) 175.71(16),
N(1)–Ir–M(1)* 177.65(13) (M(1)* midpoint C(14)/C(15)).
Scheme 2
The exchange process was investigated by 1H NMR in CD2Cl2
by measuring the decay of [1-py] with time at different [py-
d5] and temperatures under pseudo first-order conditions. The
concentrations of 1-py and free py with time were determined
by integration of the corresponding o-H resonances. The ln[1-
py] vs t representations provided a linear fit that is representative
of a first-order kinetic transformation with the slope of the line
corresponding to the observed first-order rate constant k (s-1).
The influence of the [py-d5] on the reaction rate was investigated
in the concentration range 136–407 mM at [1-py]0 = 3.66 mM and
263.15 K. It has been found that the reaction rate is not affected
by [py-d5] which is in agreement with a dissociative process. The
influence of the temperature on the reaction rate was investigated
in the temperature range 248.15–268.15 K at [1-py]0 = 3.66 mM
and [py*] = 0.136 M. The rate constant was determined at five
different temperatures and the activation parameters, DH# and
DS#, were determined using the logarithmic form of the Eyring
equation (Fig. 2). The activation parameters were estimated to
be DH# = 94 2 kJ mol-1 and DS# = 26 8 J K-1 mol-1 (DG# =
86 4 kJ mol-1, 293.15 K). These values compare well with those
reported for exchange processes in related labile octahedral Ir(III)
complexes.11
The mechanism for the formation of 1 was investigated by
NMR. Monitoring the reaction at low temperature showed the
immediate formation of the fluxional square planar Ir(I) complex
2
2
[Ir(k -Hpydc)(cod)], with a monodeprotonated ligand k -O,N
coordinated, as the only detectable intermediate species in the
2
route to 1. The protonation of the iridium center in [Ir(k -
Hpydc)(cod)] by the free -COOH arm of the tridentate ligand to
3
give an Ir(III) hydride intermediate [IrH(k -pydc)(cod)], formally
an oxidative addition, followed by subsequent migratory insertion
could be a reasonable pathway.
The unsaturated iridium(III)-hydride complex [Ir(H)(k -pydc)
3
(coe)] (2) has been obtained as a yellow air-stable solid in
excellent yield by reaction of H2pydc with [Ir(m-OH)(coe)2]2 in
CH2Cl2/MeOH. The high-field resonance at d = -34.48 ppm in
1
the H NMR spectrum suggests a 16-electron square-pyramidal
Cs structure with the hydrido ligand at the apical position
(Scheme 1).14 Interestingly, the formation of 2 further supports
the hydride/insertion mechanism for the formation of 1.
3
Reaction of 1 with pyridine gave the octahedral complex [Ir(k -
pydc)(1-k-4,5-h-C8H13)(py)] (1-py). The py ligand in 1-py is labile,
as expected from the trans-effect exerted by the alkyl ligand, and
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using HBpin giving a 24% conversion to PhBpin in 20 h at
100 ◦C (entry 1). However, a conversion of 77% was attained
with 1-py under the same conditions (entry 2). Interestingly, good
conversion was achieved when using B2pin2 (72%) indicating that
both boryl groups participate in the reaction (entry 3). In the same
way, compound 2-py is more active than 2 giving conversions
of 63% and 39%, respectively, in 20 h at 90 ◦C using HBpin as
the borylation reagent (entries 4 and 5). However, in the case
of 2-py the use of B2pin2 requires a higher temperature to get
acceptable conversions, 82% at 110 ◦C (entry 6). We have observed
that the catalytic activity of 2-py decreases in the presence of
added pyridine which is in agreement with the slightly inferior
catalytic activity of 3 (entry 7). The removal of the cyclooctenyl
ligand in 1 should be a prerequisite for catalytic activity and, in
agreement with its outstanding thermal stability, harsh conditions
are generally required compared to 2 that bear reactive and labile
hydride and cyclooctene ligands, respectively. However, the high
temperature required to maintain an acceptable catalytic activity
points to the formation of the same active species, probably an
unsaturated boryl-Ir(III) complex which could be stabilized by an
additional pyridine ligand.
Fig. 2 Eyring plot for the py/py-d5 exchange in 1-py.
Similarly, reaction of 2 with pyridine gave the octahedral
3
complex [Ir(H)(k -pydc)(coe)(py)] (2-py) which was isolated as a
yellow solid in 91% yield. The hydride ligand in 2-py was observed
at d = -26.66 ppm, down-field shifted by 7.8 ppm compared to 2
due to the coordination of the py ligand in trans. In fact, the 1H–1H
NOESY spectrum showed cross-peaks between the hydride ligand
and the nearest >CH2 protons of the coe ligand, and between the
ortho-protons of pyridine ligand and the CH protons of the coe
ligand, which support the proposed stereochemistry.
The pyridinedicarboxylate-based catalyst 1-py is also suitable
for the borylation of monosubstituted arenes Ph–R (R = Me,
CF3, OMe, Cl). In general, the reactions resulted in a mixture
of meta and para disubstituted products with meta/para ratios
of 1.9 (R = Me), 2.4 (R = CF3) and 2.6 (R = Cl), slightly over
the statistical ratio (entries 8–10). Interestingly, the activation of
benzylic C–H bonds in toluene was not observed. The lack of
ortho disubstituted products can be ascribed to the steric effect of
the substituent. However, the borylation of anisole gave 6% of the
ortho product with a meta/para ratio of 2.7 (entry 11) probably by
the directing effect of the methoxo moiety. In agreement with this,
the borylation of 1,3-dimethoxybenzene was unselective and gave
12% of the unusual pinacol (2,4-dimethoxyphenyl)boronate ester.
The attempt to purify crude 2-py by chromatography on
3
alumina gave [Ir(H)(k -pydc)(py)2] (3) as a result of the replace-
1
ment of the cyclooctene ligand by pyridine (Scheme 1). The H
NMR of 3 in CD2Cl2 showed no equivalent pyridine ligands,
supporting their relative cis disposition, and a hydride ligand at d =
-23.69 ppm. The hydride ligand in 2 undergoes fast H/D exchange
3
in MeOH-d4 to give [Ir(D)(k -pydc)(coe)] (2-d1). H/D exchange
also takes place in 2-py at a lower rate (50% in 20 h) but not in 3,
suggesting a progressive reduction of the hydride acid character.
Catalytic borylation of arenes
The new pincer complexes were evaluated as catalysts for the
borylation of arenes using HBpin or B2pin2 with iridium catalyst
loadings of 5.0 mol% (for HBpin) and 2.5 mol% (for B2pin2) in
order to maintain the boron/iridium ratio. Representative results
of the activity of the complexes are summarized in Table 1.
Compound 1 was moderately active in the borylation of benzene
Influence of electronic effects on the pincer ligand
In order to investigate the influence of the electronic effects
in the pincer ligand on the catalytic activity-related com-
plexes with electronically different 4-substituted X-pydc2- lig-
Table 1 Aromatic C–H borylation catalyzed by iridium pyridinedicar-
3
ands were prepared. Complex [Ir(k -pydc-Cl)(1-k-4,5-h-C8H13)]
boxylate pincer complexesa
(4) was straightforwardly obtained from 4-chloropyridine-2,6-
dicarboxylic acid following the established synthetic protocol.
Further reaction with pyridine gave 4-py that was isolated as
3
a yellow solid in good yield. Complex [Ir(k -pydc-OMe)(1-k-
Entry Catalyst Arene
Boron reagent T/◦C Yield (%)b (o : m : p)
4,5-h-C8H13)(py)] (5-py), containing the 4-methoxo-pyridine-2,6-
dicarboxylate ligand, was obtained in moderate yield from 4-py
and sodium methoxide. However, the reaction of 4-nitropyridine-
2,6-dicarboxylic acid with [Ir(m-OMe)(cod)]2 gave the unexpected
dinuclear complex [Ir{m-pydc-NO2}(1-k-4,5-h-C8H12–OMe)]2 (6)
that was isolated as a red-brown solid in excellent yield. The
presence of cyclooctenylmethoxy15 ligands in 6 has been unam-
1
2
3
4
5
6
7
8
1
R = H
HBpin
HBpin
B2pin2
HBpin
HBpin
B2pin2
B2pin2
100
100
100
90
24
77
72
39
63
82
79
1-py
1-py
2
2-py
2-py
3
1-py
1-py
1-py
1-py
90
110
110
120
120
120
120
1
biguously determined by H and 13C NMR and the dinuclear
R = Me B2pin2
72 (0 : 66 : 34)
85 (0 : 71 : 29)
75 (0 : 72 : 28)
68 (6 : 69 : 25)
9
10
11
R = CF3 B2pin2
formulation is based on the HRMS spectra that showed a peak
for 6 + Na+. The proposed dinuclear structure, based on molecular
models, consists of two octahedral iridium centers bridged by
two carboxylate fragments forming a central four-membered Ir2O2
ring.16 The two pydc-NO22- ligands adopt a mutual anti disposition
in order to avoid the steric interference between both cyclooctenyl
R = Cl
B2pin2
R = OMe B2pin2
a Reaction conditions: arene (22 mmol), HBpin (0.146 mmol) or B2pin2
(0.073 mmol), catalyst (0.0037 mmol) without solvent for 20 h. b Yields,
based on boron atom, and isomer ratios were determined by 1H NMR.
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Table 2 Effect of temperature on the catalytic borylation of benzene with
B2pin2 by iridium 4-X-pyridinedicarboxylate pincer complexesa
Yield (%)
Entry
Catalyst
X
90 ◦
C
100 ◦
C
120 ◦
C
1
2
3
4
1-py
H
Cl
OMe
NO2
60
68
2
72
75
71
—
80
82
77
65
4-py
5-py
Fig. 3 Numbering scheme for NMR data
6 + pyb
—
Miocroflex mass spectrometer using DCTB (trans-2-[3-(4-tert-
butylphenyl)-2-methyl-2-propenylidene]malononitrile) or dithra-
nol as the matrix. FT-IR spectra were collected on a Nicolet
Nexus 5700 FT spectrophotometer equipped with a Nicolet Smart
Collector diffuse reflectance accessory.
a See Table 1 for reaction conditions. b Two equiv. of py were added.
ligands, resulting in an unsymmetrical structure (Scheme 1). We
do not have evidence on the formation of a mononuclear species
from 6 and pyridine which suggests a robust dinuclear structure.
The effect of the temperature on the catalytic activity of the
mononuclear complexes 1-py, 4-py, 5-py, and the dinuclear 6 in
the presence of py is shown in Table 2.
Standard literature procedures were used to prepare the starting
materials [Ir(m-OMe)(cod)]2 and [Ir(m-OH)(coe)2]2.19 Pyridine-
18
2,6-dicarboxylic acid (H2pydc) was obtained from Fluka and used
as received. 4-chloropyridine-2,6-dicarboxylic acid (H2pydc-Cl)
and 4-nitropyridine-2,6-dicarboxylic acid (H2pydc-NO2) were pre-
pared from chelidamic acid (4-hydroxypyridine-2,6-dicarboxylic
acid, Fluka) following the procedures described in the literature.20
Pinacolborane (HBpin) and bis(pinacolato)diboron (B2pin2) were
obtained from AldrichꢀC and used as received.
Compound 4-py, having a –Cl substituent with an electron-
withdrawing role, is slightly more active than 1-py in the tem-
◦
perature range of 90–120 C (entry 2). In contrast, 5-py with an
electron-donating –OMe substituent is somewhat less active (entry
3).17 Nevertheless, the dinuclear compound 6 having ligands with
a strong electron-withdrawing –NO2 substituent is far less active
(entry 4) and shows no activity up to 120 ◦C, probably as a result
of the remarkable stability of the dinuclear framework rather than
an electronic effect.
[Ir(j3-pydc)(1-j-4,5-g-C8H13)] (1)
[Ir(m-OMe)(cod)]2 (250 mg, 0.377 mmol) and H2pydc (126 mg,
0.754 mmol) were reacted in a CH2Cl2/MeOH mixture (3/1,
40 mL) at room temperature for 14 h. The resulting yellow solution
was filtered and then concentrated to dryness in vacuo. The crude
compound was dissolved in a CH2Cl2/MeOH (20 : 1) mixture
(3 mL) and then eluted through an alumina column (7 ¥ 1.5 cm) to
give a yellow solution. Concentration of the solution to ca. 1 mL
and slow addition of diethyl ether gave the compound as a yellow
solid which was filtered, washed with diethyl ether (2 ¥ 3 mL) and
dried in vacuo (335 mg, 90%; found: C, 38.46; H, 3.95; N, 2.78.
C15H16IrNO4·CH3OH requires C, 38.54; H, 4.04; N, 2.81). dH
(400.16 MHz, 298 K, CD2Cl2/CD3OD, Me4Si): 8.30 (1H, t, J 8.06,
4-H), 8.12 (1H, dd, J 1.5 and 8.1, 3-H or 5-H), 8.08 (1H, dd, 1.5
and 8.1, 3-H or 5-H) (pydc), 5.77 (1H, td, J 3.6 and 8.8, 4-H), 5.55
(1H, dd, J 3.6 and 9.5, 5-H), 3.09 (1H, d, J 16.0, 1H, 6-H), 2.30
(1H, m, 3-H), 2.20 (1H, m, 6-H), 2.15 (1H, m, 3-H), 1.94 (1H, m, 2-
H), 1.90 (1H, m, 1-H), 1.89 (1H, m, J 10.0 and 19.0 Hz, 7-H), 1.57
(1H, d, J 12.4, 7-H), 0.92 (1H, tt, J 2.2 and 13.9, 8-H), 0.35 (1H,
dd, J 3.6 and 12.4, 2-H), -0.013 (1H, ddd, J 3.6, 7.3 and 13.9 Hz,
8-H) (1-k-4,5-h -C8H13); dC (75.48 MHz; 298 K; CD2Cl2/CH3OD;
Me4Si): 175.54, 175.21 (CO), 148.30, 147.16 (C-2 and C-6),
141.30 (C-4), 131.16, 130.89 (C-3 and C-5) (pydc), 89.50 (C-4),
85.12 (C-5), 40.71 (C-2), 35.12 (C-8), 27.84 (C-6), 26.39 (C-3),
25.17 (C-7), 15.12 (C-1) (C8H13); nmax(CH2Cl2/MeOH)/cm-1 1660
(CO); nmax(solid)/cm-1 1678 (CO); MS (MALDI-Tof, DCTB,
CH2Cl2/MeOH) m/z: 467.8 (M+).
Conclusions
In summary, we have described a new synthetic methodology
for the preparation of unsaturated Ir(III) complexes having an
unusual O-donor-based dianionic pincer-type ligand that are
active catalysts for arene C–H borylation. Further work on
synthesis, reactivity studies and catalytic applications are currently
in progress.
Experimental
All experiments were carried out under an atmosphere of argon
using Schlenk techniques or a glovebox. Solvents were obtained
from a Solvent Purification System (Innovative Technologies).
CD2Cl2, benzene-d6, toluene-d8 (Euriso-top) were dried using
activated molecular sieves. Methanol-d4 (<0.02% D2O, Euriso-
top) was used as received. Elemental analyses were carried out
in a Perkin-Elmer 2400 CHNS/O analyzer. NMR spectra were
recorded on Bruker AV-400 and AV-300 spectrometers. Chemical
shifts are reported in ppm relative to tetramethylsilane and
referenced to partially deuterated solvent resonances. Coupling
constants (J) are given in Hertz. Spectral assignments were
achieved by combination of H–1H C O S Y, N O E S Y, 13C DEPT
1
1
1
and APT, H–13C HSQC and H–13C HMBC experiments. The
numbering scheme used in the NMR data of the compounds
is shown in Fig. 3. Electrospray mass spectra (ESI-MS) were
recorded on a Bruker MicroTof-Q using sodium formiate as
reference. High resolution electrospray mass spectra were recorded
on a LTQ-FT Ultra (Thermo Scientific) under NanoSI conditions
at the Institute for Research in Biomedicine (PCB-Universitat de
Barcelona). MALDI-Tof mass spectra were obtained on a Bruker
[Ir(j3-pydc)(1-j-4,5-g-C8H13)(py)] (1-py)
3
A suspension of [Ir(k -pydc)(1-k-4,5-h-C8H13)] (0.1 g, 0.2 mmol)
in pyridine (4 mL) was heated to gentle reflux with stirring for 4
h. The resulting yellow solution was concentrated to dryness in
vacuo and the crude compound dissolved in CH2Cl2 (3 mL) and
then eluted through an alumina column (7 ¥ 1.5 cm) to give a
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yellow solution. Concentration of the solution to ca. 1 mL and
slow addition of diethyl ether gave the compound as a yellow
solid which was filtered, washed with diethyl ether (2 ¥ 3 mL)
and dried in vacuo (92 mg, 85%; found: C, 44.16; H, 4.01; N,
5.13. C20H21IrN2O4 requires C, 44.03; H, 3.88; N, 5.13); 1H NMR
(400.16 MHz, CD3OD/CD2Cl2, RT): dH 1H NMR (400.16 MHz,
CD3OD/CD2Cl2, RT): d 8.24 (2H, dd, J 1.5 and 6.6, o-H, py),
8.06 (1H, t, J 7.6, 4-H), 7.98 (1H, dd, J 1.4 and 8.0, 3-H or 5-H),
7.93 (1H, dd, J 1.4 and 8.0, 3-H or 5-H) (pydc), 7.68 (1H, tt, J 1.5
and 7.3, p-H, py), 7.30 (2H, m, J 1.5 and 6.6, m-H, py), 5.58 (1H,
td, J 3.0, 8.8, 4-H), 5.09 (1H, dd, J 8.8 and 2.2, 5-H), 3.02 (1H, d,
J 16.8, 6-H), 2.39 (1H, m, 3-H), 2.22 (2H, m, 3-H and 6-H), 2.01
(1H, m, 2-H), 1.83–1.73 (1H, qt, J 4.4 and 13.9, 7-H), 1.71 (1H, br
t, J 2.9, 1-H), 1.58 (1H, br d, J 13.9, 7-H), 1.08 (1H, td, J 1.6 and
13.9, 8-H), 0.67 (1H, dd, J 8.2 and 13.2, 2-H), 0.34 (1H, dq, J 2.9
and 13.9, 8-H) (C8H13); dC (75.48 MHz; 298 K; CD2Cl2/CH3OD;
Me4Si): 175.01, 174.68 (CO), 149.45 (2C, o-C, py), 147.03, 139.62
(C-2 and C-6, pydc), 140.09 (p-C, py), 139.62 (C-4, pydc), 130.95,
130.63 (C-3 and C-5, pydc), 127.25 (2C, m-C, py), 90.06 (C-4),
86.20 (C-5), 39.80 (C-2), 34.41 (C-8), 27.44 (C-6), 27.29 (C-3),
24.60 (C-7), 17.17 (C-1) (C8H13); nmax(solid)/cm-1 1662 (CO); MS
(MALDI-Tof, DCTB, CH2Cl2) m/z: 467.8 (M+-py); MS (ESI+,
CH3CN) m/z: 545.0 (M+ - H), 466.0 (M+ - py - H).
room temperature for 8 h afforded a yellow solution. The volatiles
were removed under vacuum to give a yellow residue that was
washed several times with diethyl ether. The solid was dissolved
in the minimum volume of CH2Cl2 and then diethyl ether was
added to give the compound as a yellow solid which was filtered,
washed several times with diethyl ether and dried under vacuum.
(0.250 g, 91%; found: C, 43.52; H, 4.35; N, 5.25. C20H23IrN2O4
requires C, 43.87; H, 4.23; N, 5.12); 1H NMR (400.16 MHz,
CD2Cl2, RT): dH 8.39 (2H, dd, J 1.5 and 6.6, o-H, py), 8.05 (1H, dd,
J 6.6 and 8.8, 4-H), 7.97 (2H, m, 3-H or 5-H) (pydc), 7.77 (1H, tt, J
1.5 and 7.7, p-H), 7.40 (2H, t, J 6.6, m-H) (py), 5.09 (2H, m, = CH,
coe), 2.35–2.11 (4H, m), 1.94–1.82 (2H, m), 1.65 (2H, m), 1.53–
1.39 (4H, m), (>CH2, coe), -26.66 (1H, s, Ir–H). dC (75.48 MHz;
298 K; Me4Si): 173.38 (2C, CO, pydc), 147.98 (2C, o-C, py), 146.59
(C-2 and C-6), 138.67 (C-4) (pydc), 138.57 (p-C, py), 128.82 (C-3
and C-5, pydc), 126.05 (2C, m-C, py), 85.03 (2C, CH), 31.89,
29.35, 26.76 (2 C each, >CH2) (coe). nmax(solid)/cm-1 2170 (Ir–H),
1666 (CO); MS (MALDI-Tof, DCTB, CH2Cl2) m/z: 467.9 (M+ -
py).
[Ir(H)(j3-pydc)(py)2] (3)
3
A dichloromethane solution of complex [Ir(H)(k -pydc)(coe)(py)]
3
(4), obtained in situ by reaction of [Ir(H)(k -pydc)(coe)] (103 mg,
[Ir(j2-Hpydc)(cod)]
0.200 mmol) with an excess of pyridine, was eluted through an
alumina column (7 ¥ 1.5 cm) with a MeOH/CH2Cl2 mixture
(20/80) to give a yellow solution. Concentration of solution
and slow addition of diethyl ether gave the compound as a
yellow solid that was filtered, washed with diethyl ether and dried
under vacuum. (0.093 g, 90%; found: C, 39.26; H, 2.85; N, 8.05.
C17H14IrN3O4 requires C, 39.53; H, 2.73; N, 8.13); 1H NMR
(400.16 MHz, CD2Cl2, RT): dH 8.87 (2H, dd, J 1.4 and 6.6, o-
H, trans-py), 8.45 (2H, m, J 1.48 and 5.14 Hz, o-H, cis-py), 7.90
(1H, dd, J 7.25 and 8.65, 4-H, pydc), 7.87 (1H, tt, J 1.5 and 8.0,
p-H, trans-py), 7.83 (2H, m, 3-H and 5-H, pydc), 7.73 (1H, tt, J
1.5 and 8.0, p-H, cis-py), 7.38–7.32 (4H, m, m-H of trans and cis-
py), -23.69 (1H, s, Ir–H); dC (75.48 MHz; 298 K; CD2Cl2; Me4Si):
175.02, (2C, CO, pydc), 153.62, 153.52 (2 C each, o-C, trans-py),
150.08 (2C, C-2 and C-6, pydc), 148.09 (2C, o-C, cis-py), 137.87
(p-C, cis-py), 137.28 (p-C, trans-py), 136.10 (C-4, pydc), 127.98
(2C, C-3 and C-5, pydc), 125.69 and 125.59 (4C, m-C, cis and
trans-py); nmax(solid)/cm-1 2153 (Ir–H), 1651 (CO); MS (ESI+,
CH3CN) m/z: 518.0 (M+ + H), 439.0 (M+ + H - py).
An NMR tube was charged with [Ir(m-OMe)(cod)]2 (17 mg,
0.025 mmol), H2pydc (8.4 mg, 0.05 mmol) and MeOH-d4/CD2Cl2
(1/1, 0.6 mL). The tube was shaken at room temperature for
1
15 min and then cooled at 198 K and monitored by H NMR
at low temperature. dH (300.13 MHz, 208 K, CD2Cl2/CD3OD,
Me4Si): 8.05–7.95 (3H, br), 7.45 (1H, br) (Hpydc), 4.26 (2H, br,
CH), 3.77 (2H, br, CH), 2.09 (m, 4H, >CH2), 1.28 (m, 4H,
>CH2) (cod); dH (300.13 MHz, 263 K, CD2Cl2/CD3OD, Me4Si):
8.08–7.86 (4H, bm, Hpydc), 4.24 (4H, m, CH), 2.24 (4H, m,
>CH2), 1.56 (4H, m, >CH2) (cod).
[Ir(H)(j3-pydc)(coe)] (2)
[Ir(m-OH)(coe)2]2 (430 mg, 0.500 mmol) and H2pydc (167 mg,
1.00 mmol) were reacted in a CH2Cl2/MeOH mixture (3/1,
40 mL) at room temperature for 14 h to give a bright yellow solu-
tion. The solution was filtered and then concentrated under vac-
uum to ca. 2 mL. Slow addition of diethyl ether gave the compound
as a yellow solid which was filtered, washed with diethyl ether (2 ¥
3 mL) and dried in vacuo (410 mg, 87%; found: C, 38.40; H, 3.95;
N, 2.91. C15H18IrNO4 requires C, 38.45; H, 3.87; N, 2.99); 1H NMR
(400.16 MHz, CD3OD/CD2Cl2, RT): dH 8.22 (1H, t, J 7.3, 4-H),
8.04 (2H, d, J 7.3, 3-H and 5-H) (pydc), 5.35 (2H, m, CH), 2.10
(4H, m, >CH2), 1.82 (2H, m, >CH2), 1.69 (2H, m, >CH2), 1.46
(4H, m, >CH2) (coe), -34.48 (1H, s, Ir–H); dC (75.48 MHz; 298 K;
CD2Cl2/CD3OD; Me4Si): 175.54, (2C, CO), 148.03 (2C, C-2 and
C-6), 140.90 (C-4), 130.01 (2C, C-3 and C-5) (pydc), 86.49 (2C,
CH), 32.51 (2C, >CH2), 29.41 (2C, >CH2), 27.62 (2C, >CH2),
(coe). nmax(solid)/cm-1 2258 (Ir–H), 1675, 1625, 1607, 1586 (CO);
MS (MALDI-Tof, DCTB, CH2Cl2) m/z: 468.1 (M+ - H).
[Ir(j3-pydc-Cl)(1-j-4,5-g-C8H13)] (4)
H2pydc-Cl (0.211 g, 1.047 mmol) and [Ir(m-OMe)(cod)]2 (0.335 g,
0.505 mmol) were reacted in CH2Cl2/MeOH (40 mL, 5 : 1) for 14 h
at room temperature. The resulting red solution was dried in vac-
uum and the residue dissolved in CH2Cl2 (5 mL) and then eluted
through an alumina column (14 ¥ 1.5 cm) with CH2Cl2/MeOH
(20 : 1) to give a red solution. The solvent was removed under
vacuum to give the compound as a red solid (0.470 g, 87%; found:
C, 33.61; H, 3.21; N, 2.58. C15H15ClIrNO4·2H2O requires C, 33.55;
H, 3.3.56; N, 2.60); dH (400.16 MHz, 298 K, CD2Cl2/CD3OD,
Me4Si): 8.12 (1H, s), 8.08 (1H, s) (3-H and 5-H, pydc-Cl), 5.88
(1H, td, J 3.3 and 9.1, 4-H), 5.65 (1H, d, J 7.3, 5-H), 3.17 (1H, d,
J 15.9, 6-H), 2.38 (1H, m, J 3.5 and 9.4, 3-H), 2.26–2.11 (2H, m,
3-H and 6-H), 2.00 (1H, s, 1- H), 1.95 (1H, d, J 11.4, 2-H), 1.85
(1H, m, J 4.6 and 14.1, 7-H), 1.64 (1H, d, J 13.4, 7-H), 0.94 (1H,
[Ir(H)(j3-pydc)(coe)(py)] (2-py)
3
To a suspension of [Ir(H)(k -pydc)(coe)] (234 mg, 0.500 mmol) in
CH2Cl2 (40 mL) was added pyridine in excess (1 mL). Stirring at
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Dalton Trans., 2011, 40, 8429–8435 | 8433
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t, J 13.9, 8-H), 0.40 (1H, dd, J 9.0 and 12.9, 2-H), 0.03 (1H, m,
8-H) (C8H13); dC (75.48 MHz; 298 K; CD2Cl2/CH3OD; Me4Si):
172.9, 172.7 (CO), 148.0, 147.4, 146.9 (C-2, C-4 and C-6), 130.0,
129.8 (C-3 and C-5) (pydc-Cl), 88.9 (C-4), 84.5 (C-5), 39.6 (C-2),
34.1 (C-8), 26.8 (C-6), 25.2 (C-3), 23.9 (C-7), 14.6 (C-1) (C8H13);
172.7, 172.3 (CO), 168.4 (C-4) (pydc-OMe), 148.6 (2C, o-C, py),
147.6, 146.6 (C-2 and C-6) (pydc-OMe), 138.3 (p-C), 126.1 (2C,
m-C) (py), 115.1, 114.8 (C-3 and C-5) (pydc-OMe), 87.5 (C-4),
83.3 (C-5) (C8H13), 57.3 (-OMe), 39.2 (C-2), 33.7 (C-8), 26.7 (C-6),
26.6 (C-3), 23.9 (C-7), 16.4 (C-1), (C8H13); nmax(solid)/cm-1 1662,
1608 (CO); MS (ESI+, CH3CN) m/z: 577 (M++ H).
n
max(solid)/cm-1 1634 (CO); MS (ESI+, CH3CN) m/z: 502.1 (M+-
H).
[Ir{l-pydc-NO2}(1-j-4,5-g-C8H12-OMe)]2 (6)
[Ir(j3-pydc-Cl)(1-j-4,5-g-C8H13)(py)] (4-py)
H2pydc-NO2 (0.051 g, 0.240 mmol) and [Ir(m-OMe)(cod)]2
(0.080 g, 0.120 mmol) were reacted in CH2Cl2/MeOH (3 mL, 5 : 1)
to give a dark brown solution that was stirred for 3 h at room tem-
perature. The solvent was removed under vacuum to give the com-
pound as a red brown solid (0.122 g, 94%; found: C, 35.22; H, 3.05;
N, 5.37. C32H34Ir2N4O14 requires C, 35.49; H, 3.16; N, 5.17); dH
(500.13 MHz, 298 K, CD2Cl2/CD3OD, Me4Si): 8.79 (1H, s), 8.75
(1H, s), 7.40 (1H, s), 7.36 (1H, s) (3-H and 5-H pydc-NO2), 5.99
(1H, m, 4-H), 5.66 (1H, m, 4-H¢), 5.60 (1H, m, 5-H), 5.33 (1H,
m, 5-H¢), 3.27 (6H, s, OMe), 3.25 (1H, H-6), 3.14 (1H, m, 6-H¢),
2.82 (2H, m, 8-H and 8-H¢), 2.31–2.21 (2H, m, 6-H and 3-H),
2.18–2.13 (4H, m, 1-H, 3-H, 3-H¢ and 6-H¢), 2.12–2.04 (2H, m,
1-H¢ and 3-H¢), 1.77–1.63 (4H, m, 7-H and 7-H¢), 1.64 (1H, m,
2-H), 1.55 (1H, m, 2-H¢), 0.81 (1H, dd, J 9.5 and 14.0, 2-H), 0.69
(1H, dd, J 8.5 and 13.5, 2-H¢) (C8H12–OMe); dC (125.77 MHz; 298
K; CD2Cl2/CH3OD; Me4Si): 175.21, 172.81, 172.33 (2C) (CO),
160.14, 155.52 (C-4), 149.68, 149.01, 146.8, 146.0 (C-2 and C-
6), 124.56, 124.20 (C-3 and C-5), 110.17, 109.93 (C-3¢ and C-5¢)
(pydc-NO2), 92.06 (C-4), 88.05 (C-4¢), 87.13 (C-5), 83.14 (C-5¢),
82.89 (C-8¢), 82.32 (C-8), 49.97 (OMe), 33.82 (C-2¢), 33.48 (C-2),
29.81 (C-7¢), 29.51 (C-7), 25.83 (C-3¢), 25.73 (C-6 and C-6¢), 25.42
(C-3), 14.70 (C-1), 11.41 (C-1¢) (C8H12–OMe). nmax(solid)/cm-1
1634 (CO); HRMS (ESI+, MeOH) calc’d for C32H34Ir2N4O14Na+
(6 + Na+) 1105.11989, found 1105.11996.
Pyridine (1 mL, 0.012 mol) was added to a red solution
of [Ir(k -pydc-Cl)(1-k-4,5-h-C8H13)] (0.470 g, 0.939 mmol) in
3
CH2Cl2/MeOH (40 mL, 5 : 1) to give a yellow solution that was
stirred for 14 h at RT. The volatiles were removed under vacuum
to give a yellow residue that was dissolved in CH2Cl2 (5 ml)
and then filtered through celite. Slow diffusion of diethyl ether
(15 mL) at 258 K for 24 h gave the compound as a yellow solid
that was filtered off, washed with diethyl ether and dried under
vacuum (0.338 g, 62%; found: C, 41.71; H, 3.36; N, N, 4.79.
C20H20ClIrN2O4 requires C, 41.41; H, 3.47; N, 4.83); dH (400.16
MHz, 298 K, CD2Cl2/CD3OD, Me4Si): 8.40 (2H, dt, J 1.5 and
4.8, o-H, py), 8.02 (1H, d, J 2.0), 7.98 (1H, d, J 2.0) (pydc-Cl),
7.76 (1H, tt, J 1.5 and 7.8, p-H, py), 7.38 (2H, m, m-H, py), 5.66
(1H, td, J 3.5 and 9.3, 4- H), 5.17 (1H, d, J 9.6, 5-H), 3.12 (1H, d,
J 16.9, 6-H), 2.50 (1H, m, 3-H), 2.40-2.25 (m, 2H, 3-H and 6-H)
2.13 (m, 1H, 2-H), 1.93 (1H, ct, J 4.3 and 14.1 Hz, 7-H), 1.87
(1H, m, 1-H), 1.70 (1H, d, J 13.1, 7-H), 1.18 (1H, m, 8-H), 0.78
(1H, dd, J 8.8 and 13.4, 2-H), 0.46 (1H, m, J 3.8 and 13.9, 8-H)
(C8H13); dC (75.48 MHz; 298 K; CD2Cl2/CH3OD; Me4Si): 171.6,
171.2 (CO) (pydc-Cl), 148.6 (2C, o-C, py), 147.1, 146.4, 146.0 (C-
2, C-4 and C-6) (pydc-Cl), 138.4 (p-C, py), 129.68, 129.40 (C-3
and C-5) (pydc-Cl), 126.1 (2C, m-C, py), 88.8 (C-4) 84.8 (C-5),
39.9 (C-2), 33.5 (C-8), 26.6 (C-6), 26.5 (C-3), 23.7 (C-7), 16.2 (C-1)
(C8H13); nmax(solid)/cm-1 1661 (CO); MS (ESI+, CH3CN) m/z:
502.1 (M+-py).
General procedure for the catalytic borylation reactions
The catalytic borylation of aromatic compounds were carried out
under an argon atmosphere in a glass reaction tube fitted with a
greaseless high-vacuum stopcock (KontesꢀC tube). The reactions
were conducted in the aromatic substrate as solvent, using HBpin
or B2pin2 as the boron source with iridium catalyst loadings of
2.5 mol% (for HBpin) or 5.0 mol% (for B2pin2) in order to maintain
the boron/iridium ratio. In a typical experiment, the reactor was
charged with the catalyst (0.0037 mmol), the corresponding arene
(22 mmol) and HBpin (21.2 mL, 0.146 mmol) or B2pin2 (18.62 mg,
0.073 mmol) and the solution stirred and heated at the required
temperature for 20 h. The solvent was removed under vacuum at
room temperature and the residue analysed by 1H NMR in order
to determine the conversion and selectivity. Identification of the
products was done by comparison of the spectroscopic data with
those reported in the literature.
[Ir(j3-pydc-OMe)(1-j-4,5-g-C8H13)(py)] (5-py)
3
A suspension of [Ir(k -pydc-Cl)(1-k-4,5-h-C8H13)(py)] (0.153 mg,
0.264 mmol) and NaOCH3 (0.059 mg, 1.100 mmol) in MeOH
(10 mL) was stirred for 3 days at room temperature to give a
yellow solution. The volatiles were removed under vacuum and
the yellow residue dissolved in MeOH (5 mL) and then eluted
with MeOH/CH2Cl2 through an alumina column (Grade III, 7 ¥
1.5 cm). The resulting yellow solution was concentrated under
vacuum to ca. 2 mL and the slow diffusion of diethyl ether
(15 mL) at 258 K for 24 h gave the compound as a yellow solid that
was filtered off, washed with diethyl ether and dried under vacuum
(0.050 g, 33%; found: C, 42.98; H, 4.54; N, N, 5.00. C21H23IrN2O5
requires C, 43.82; H, 4.03; N, 4.87). dH (300.13 MHz, 298 K,
CD2Cl2/CD3OD, Me4Si): 8.40 (2H, dt, J 1.5 and 4.8, o-H, py),
7.74 (1H, tt, J 1.8 and 7.6, p-H, py), 7.57 (1H, d, J 2.5), 7.53 (1H,
d, J 2.5) (pydc-OMe), 7.37 (2H, m, m-H, py), 5.56 (1H, td, J 3.3
and 9.1, 4-H), 5.09 (1H, d, J 9.6, 5-H), 4.01 (3H, s, -OMe), 3.10
(1H, d, J 15.9, 6-H), 2.46 (1H, m, 3-H), 2.31–2.27 (m, 2H, 3-H and
6-H), 2.13 (m, 1H, 2-H), 1.91 (1H, qt, J 4.3 and 13.5 Hz, 7-H),
1.87 (1H, m, 1-H), 1.71 (1H, d, J 13.6, 7-H), 1.25 (1H, m, 8-H),
0.75 (1H, dd, J 8.8 and 15.1, 2-H), 0.43 (1H, m, J 3.8 and 13.9,
8-H) (C8H13); dC (75.48 MHz; 298 K; CD2Cl2/CH3OD; Me4Si):
Determination of the kinetic parameters for pyridine exchange in
compound 1-py
The kinetic parameters for the pyridine exchange in compound
3
[Ir(k -pydc)(1-k-4,5-h-C8H13) (py)] (1-py) were determined by
NMR spectroscopy. A 5 mm NMR tube containing a CD2Cl2
solution of 1-py (3.66 mM) and py-d5 (py*, 136–407 mM)
was introduced into the NMR probe precooled to the desired
8434 | Dalton Trans., 2011, 40, 8429–8435
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temperature (248–268 K). After allowing for thermal equilibration
and experiment setup periodic NMR spectra (typically each 2–10
min) with identical acquisition parameters were recorded over
several hours. The relative concentrations of 1-py and free py
with time were determined by integration of the corresponding
o-H resonances using automatic integration software. The relative
concentrations were converted to absolute concentrations by
assuming that [1-py] + [py] = 3.66 mM. Rate constants at five
different temperatures were obtained from linear least-square
regression analysis. The activation parameters, DH# and DS#,
were calculated from a linear least-squares fit of ln(k/T) versus
1/T (Eyring equation).
Notes and references
1 (a) Activation and Functionalization of C-H Bonds, ed. K. I. Goldberg
and A. S. Goldman, ACS Symposium Series, Vol. 885, Washington
DC, 2004; (b) R. G. Bergman, Nature, 2007, 446, 391; (c) K. Godula
and D. Sames, Science, 2006, 312, 67.
2 I. A. I. Mkhalid, J. H. Barnard, T. B. Marder, J. M. Murphy and J. F.
Hartwig, Chem. Rev., 2010, 110, 890.
3 (a) T. Ishiyama, J. Takagi, K. Ishida, N. Miyaura, N. Anastasi and J. F.
Hartwig, J. Am. Chem. Soc., 2002, 124, 390; (b) T. Ishiyama, J. Takagi,
F. J. Hartwig and N. Miyaura, Angew. Chem., Int. Ed., 2002, 41, 3056.
4 (a) T. M. Boller, J. M. Murphy, M. Hapke, T. Ishiyama, N. Miyaura
and J. F. Hartwig, J. Am. Chem. Soc., 2005, 127, 14263; (b) H. Tamura,
H. Yamazaki, H. Sato and S. Sakaki, J. Am. Chem. Soc., 2003, 125,
16114.
5 (a) J.-Y. Cho, M. K. Tse, D. Holmes, R. E. Maleczka Jr. and M. R.
Smith III., Science, 2002, 295, 305; (b) J.-Y. Cho, C. N. Iverson and M.
R. Smith, J. Am. Chem. Soc., 2000, 122, 12868; (c) C. N. Iverson and
M. R. Smith III., J. Am. Chem. Soc., 1999, 121, 7696.
Crystal structure determination
Suitable yellow crystals for X-ray diffraction of 1-MeOH were
obtained by slow evaporation of a solution of 1 in CH2Cl2/MeOH.
Data collection was performed at low temperature (100(2)K) on
a Bruker SMART APEX CCD diffractometer equipped with
6 M. Murata, H. Odajima, S. Watanabe and Y. Masuda, Bull. Chem. Soc.
Jpn., 2006, 79, 1980.
7 (a) G. D. Frey, C. F. Rentzsch, D. von Preysing, T. Scherg, M.
Mu¨hlhofer, E. Herdtweck and W. A. Herrmann, J. Organomet. Chem.,
2006, 691, 5725; (b) C. F. Rentzsch, E. Tosh, W. A. Herrmann and F.
E. Ku¨hn, Green Chem., 2009, 11, 1610.
˚
graphite-monochromated Mo-Ka radiation (l = 0.71073 A) using
narrow frames (0.3◦ in w). Cell parameters were refined from the
observed setting angles and detector positions of strong reflections
(4797 refl., 2q < 57.0◦). Data were corrected for Lorentz and
polarization effects, and a semi empirical absorption correction
was applied using SADABS program.21 The structure was solved
by Patterson method and completed by successive difference
Fourier syntheses (SHELXS-86). Refinement was carried out
by full-matrix least-squares on F2 with SHELXL97,22 including
isotropic and subsequent anisotropic displacement parameters for
all non-hydrogen atoms. All hydrogen atoms were included from
calculated positions and refined with only riding displacement
8 Z. Yinghuai, K. C. Yan, L. Jizhong, C. S. Hwei, Y. C. Hon, A. Emi, S.
Zhenshun, M Winata, N. S. Hosmane and J. A. Maguire, J. Organomet.
Chem., 2007, 692, 4244.
9 A. R. Chianese, A. Mo, N. L. Lampland, R. L. Swartz and P. T. Bremer,
Organometallics, 2010, 29, 3019.
10 (a) J. Oxgaard, R. P. Muller, W. A. Goddard III. and R. A. Periana,
J. Am. Chem. Soc., 2004, 126, 352; (b) J. Oxgaard, R. A. Periana and
W. A. Goddard III., J. Am. Chem. Soc., 2004, 126, 11658; (c) A. G.
Wong-Foy, G. Bhalla, X. Y. Liu and R. A. Periana, J. Am. Chem. Soc.,
2003, 125, 14292; (d) T. Matsumoto, D. J. Taube, R. A. Periana, H.
Taube and H. Yoshida, J. Am. Chem. Soc., 2000, 122, 7414.
11 G. Bhalla, X. Y. Liu, J. Oxgaard, W. A. Goddard III and R. A. Periana,
J. Am. Chem. Soc., 2005, 127, 11372.
12 The Chemistry of Pincer Compounds, ed. D. Morales-Morales and C.
M. Jensen, Elsevier, Amsterdam, 2007.
-3
˚
parameters. All the highest electronic residuals above 1.0 e A
13 For 18-electron Ir(III) compounds containing carboxyl picolinato
derivatives see: (a) S. K. Sengupta, S. K. Sahni and R. N. Kapoor,
Polyhedron, 1983, 2, 317; (b) Z. Ning, Q. Zhang, W. Wu and H. Tian,
J. Organomet. Chem., 2009, 694, 2705.
14 E. Ben-Ari, M. Gandelman, H. Rozenberg, L. J. W. Shimon and D.
Milstein, J. Am. Chem. Soc., 2003, 125, 4714.
15 A. Macchioni, G. Bellachioma, G. Cardaci, M. Travaglia and C.
Zuccaccia, Organometallics, 1999, 18, 3061.
16 Related precedents of this coordination mode: (a) M. Ranjbar, H.
Aghabozorga and A. Moghimi, Acta Crystallogr., Sect. E: Struct. Rep.
Online, 2002, 58, m304; (b) E. Yang, Z.-J. Li, J. Zhang, Y.-B. Chen and
Y. - G. Ya o , Acta Crystallogr., Sect. C: Cryst. Struct. Commun., 2004,
60, m457.
were observed in close proximity of the Ir metal and have no
chemical sense.
Crystal Data for 1-MeOH: C16H20IrNO5·CH3OH (CCDC
819913), M = 530.57, yellow prism, 0.18 ¥ 0.16 ¥ 0.15 mm3,
˚
monoclinic, P21/c, a = 12.5949(7), b = 13.7791(8), c = 11.4521(7) A,
◦
3
-3
˚
b = 116.4180(10) ; V = 1779.92(18) A , Dc = 1.980 g cm , T = 100
K, Z = 4, m(Mo-Ka) = 7.534 mm-1, min. and max. transmission
factors 0.343 and 0.400; 2qmax = 57.66◦, 11 737 measured ref.,
4273 independent ref. (Rint = 0.026), 292 refined parameters, R1 =
0.0268 and wR2 = 0.0607 for all data, goodness-of-fit on F2
=
17 (a) H. Wang, H. Wang, P. Liu, H. Yang, J. Xiao and C. Li, J. Mol.
Catal. A: Chem., 2008, 199, 128; (b) C. Hansch, A. Leo and R. W. Taft,
Chem. Rev., 1999, 97, 165.
18 R. Uso´n, L. A. Oro and J. A. Cabeza, Inorg. Synth., 1985, 23, 126.
19 D. A. Ortmann and H. Werner, Z. Anorg. Allg. Chem., 2002, 628, 1373.
20 (a) H. Nishiyama, M. Yamaguchi, M. Kondo and K. Itoh, J. Org.
Chem., 1992, 57, 4306; (b) J. B. Lamture, Z. H. Zhou, A. S. Kumar and
T. G. Wensel, Inorg. Chem., 1995, 34, 864.
1.051. Full crystallographic details have been deposited with the
Cambridge Crystallographic Data Centre with CCDC reference
number 819913.
Acknowledgements
Financial support from Ministerio de Ciencia
e Inno-
21 G. M. Sheldrick, SADABS (v.2.03), Empirical Absorption and Correc-
tion Software, University of Go¨ttingen, Germany, 1999.
22 G. M. Sheldrick, Acta Crystallogr., Sect. A, 2008, 64, 112.
vacio´n (MICINN/FEDER) is gratefully acknowledged (Projects:
CTQ2010-15221, CSD2006-0015 and CSD2009-00050).
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 8429–8435 | 8435
©