Applications of PC(sp3)P iridium complexes in transfer dehydrogenation of alkanes

Article abstract of DOI:10.1021/cs500892p

Iridium ethylene complexes based on the PC(sp³)P pincer-type triptycene ligand have been synthesized. Complexes bearing various substituents on the phosphines have been investigated as catalysts in transfer dehydrogenation of alkanes. The complex 8a, which bears isopropyl groups, has demonstrated high stability and activity when used as a catalyst in the disproportionation of 1-hexene at 180 °C and in the transfer dehydrogenation of linear and cyclic alkanes with tert-butylethylene as a hydrogen acceptor at 200°C. A similar complex bearing a CH₂NMe₂ group, 33, allowed support of the catalyst on γ-alumina for operation in a heterogeneous mode.

Full text of DOI:10.1021/cs500892p

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Article
Applications of PC(sp3)P Iridium Complexes
in Transfer Dehydrogenation of Alkanes
David Bézier, and Maurice Brookhart
ACS Catal., Just Accepted Manuscript • DOI: 10.1021/cs500892p • Publication Date (Web): 21 Aug 2014
Downloaded from http://pubs.acs.org on September 2, 2014
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ACS Catalysis
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Applications of PC(sp3)P Iridium Complexes in Transfer
Dehydrogenation of Alkanes
David Bézier and Maurice Brookhart*
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Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599ꢀ3290, United
States
Many of these modifications provided improvement of the
stability and the activity of the catalysts for the dehydrogenation
of linear and cyclic alkanes.11 These pincer complexes allowed
the development of other significant applications such as alkane
metathesis,8c, 12 alkane dehydroaromatization8a and the synthesis
of pꢀxylene from ethylene.8b New pincer complexes such as
metalloceneꢀbased (PCP)Ir complexes,13 (CCC)Ir carbene
ABSTRACT: Iridium ethylene complexes based on the
PC(sp3)P pincerꢀtype triptycene ligand have been synthesized.
Complexes bearing various substituents on the phosphines have
been investigated as catalysts in transfer dehydrogenation of
alkanes. The complex 8a bearing isopropyl groups has demonꢀ
strated high stability and activity when used as a catalyst in the
disproportionation of 1ꢀhexene at 180 °C and in the transfer dehyꢀ
drogenation of linear and cyclic alkanes with tertꢀbutylethylene as
a hydrogen acceptor at 200 °C. A similar complex bearing a
CH2NMe2 group, 33, allowed support of the catalyst on γꢀalumina
for operation in a heterogeneous mode.
complexes,14
(
CF3PCP)Ru complexes15 and 7–6–7 ringꢀbased
iridium complexes16 have also demonstrated catalytic activity for
alkane dehydrogenation.
The immobilization on solid supports of PCP and POCOP
iridium complexes was reported by our group in collaboration
with the Goldman group. Catalysts bearing basic functional
groups (1g, 2c and 2d) were successfully supported on alumina.
The 2c/Al2O3 system showed particularly high activity and
recyclability for alkane dehydrogenation17 and alkane
metathesis.12b
KEYWORDS: pincer complexes, iridium, CꢀH activation, deꢀ
hydrogenation, alkanes, supported catalyst
In the quest for developing highly thermally stable catalysts for
alkane dehydrogenation, we have been interested by the
development of the PC(sp3)PꢀIr complexes.18 The synthesis and
applications of aliphatic C(sp3)ꢀmetalated pincer complexes are
far less common than their C(sp2) analogs. These types of
complexes often suffer from instability due to the presence of
INTRODUCTION
The selective cleavage and functionalization of CꢀH bonds has
been a widely studied topic in organometallic chemistry in recent
years.1 The dehydrogenation of alkanes transforms inexpensive
hydrocarbon feedstocks into olefins, which are valuable
intermediates in the synthesis of fine chemicals and polymers.
Industrially, catalytic alkane dehydrogenation is carried out on
large scales using heterogeneous systems at high temperatures
which results in low product selectivities.2
The first use of homogeneous catalysts for transfer
dehydrogenation of alkanes was reported independently by
Crabtree and Felkin.3 Turnover numbers (TONs) were limited due
to catalyst decomposition at high temperatures. A major advance
was the discovery of the robust and effective iridium pincer
catalyst (tBuPCP)IrH2 1a (Figure 1) initially reported by Kaska and
Jensen and later studied extensively by Goldman.4 Derivatives of
easily
abstractable
αꢀ
and
βꢀhydrogens.
Recently,
dibenzobarreleneꢀbased PC(sp3)PꢀM pincer complexes (M = Ir,19
Ru,19b, 19h Pt,19b, 20 Ni,20a Pd,20 Rh19g) were described by Gelman
and coworkers. In this family, iridium complexes based on the
PC(sp3)P triptycene ligand (Figure 2)19aꢀd showed interesting
properties. The strong σꢀdonation of the metalated bridgehead sp3
hybridized carbon combined with the lack of labile αꢀ and βꢀ
hydrogens allowed robustness and stability of these complexes.
The complexes 5c and 5e were found highly active when used as
catalysts for the transfer hydrogenation of ketones in
isopropanol.19a, b The transfer dehydrogenation of alcohols to form
ketones was also demonstrated by using complex 5e as a
catalyst.19c
this complex were further developed by modifying substituents on
the phosphine (1bꢀ1d),4e,
adding functional groups to the
5
aromatic backbone (1eꢀ1g),6 replacing the phosphines by
phosphinite groups (2aꢀ2d),7 creating hybrid complexes (3a,8 3b9)
and incorporating an anthracenyl group in the backbone (4a,
4b).8a, b, 10
Particularly interested by this family of complexes and the
possibility that they will exhibit high stabilities and turnover
numbers, we decided to investigate their use as catalysts for
alkane transfer dehydrogenation.
Figure 1. Examples of active PCP iridium pincer complexes for
alkane dehydrogenation.
Figure 2. Iridium triptyceneꢀbased pincer complexes developed
by Gelman.
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We report here the synthesis of a variety of iridium triptycene
similar conditions, the catalytic system (tBuPOCOP)IrHCl /
NaOtBu is reported to yield a maximum TON of 1880.9
1
2
3
4
bis(phosphine) ethylene complexes bearing different alkyl
substituents on the phosphine atoms and their use as catalysts in
transfer dehydrogenation of alkanes. We also report synthesis of
complexes bearing basic functional groups which allowed their
support on γꢀalumina for operation in a heterogeneous mode.
Table 1. TONs for the transfer dehydrogenation of COA
and TBE catalyzed by complexes 8a, 8b and 8c.[a]
5
6
7
RESULTS AND DISCUSSION
Synthesis of iridium triptycene bis(phosphine) ethylene
complexes. Following the procedure developed by Gelman,21 we
synthesized 1,8ꢀbis(phosphino)triptycene ligands by varying the
group R carried on the phosphine (R = iPr (6a), Cy (6b), Cp (6c),
Scheme 1). These bis(phosphines) were treated with
[Ir(COE)2Cl]2 at reflux in toluene to generate the corresponding
hydridochloride iridium complexes 7aꢀ7c. The structure of the
complex 7a has been confirmed by Xꢀray crystallography (see
Supporting Information). Deprotonation with NaOtBu followed
by addition of ethylene yielded the ethylene complexes (R = iPr
(8a), R = Cy (8b), R = Cp (8c)).
Entry
t [h]
0.5
1
8a
8b
ꢀ
8c
ꢀ
8
9
1
2
3
4
5
6
910
1410
2250
2590
2650
2820
ꢀ
ꢀ
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2
ꢀ
ꢀ
4
ꢀ
ꢀ
6
ꢀ
ꢀ
24
35
40
[a] TONs were calculated based on conversion of TBE determined by GC analysis.
COA (15.2 mmol), TBE (15.2 mmol), [Ir] (0.005 mmol).
We also tested complexes 8b and 8c in similar conditions.
Surprisingly, they demonstrated extremely low activities (TONs ≈
40 after 24 h, entry 6).22
Scheme 1. Synthesis of iridium triptycene bis(phosphine)
ethylene complexes.
By monitoring the in situ reaction employing 8a, the initially
observed species was the IrꢀTBE complex, 12 (31P{1H} NMR: δ =
50.25 (d, JPP = 320 Hz), 46.35 (d, JPP = 320 Hz)) (Scheme 3). As
the reaction proceeds and product COE accumulates, the IrꢀCOE
complex 13 begins to appear (31P{1H} NMR: δ = 57.06 (s)).
Thus, like the (POCOP)Ir catalyst 2a, the resting state(s) of the
catalyst are the olefin complexes. It is noteworthy that the Ir(III)
vinyl hydride, Ir(H)[CH=CHC(CH3)3], generated from the
oxidative addition of the TBE vinylic CꢀH bond, has never been
detected in this system.23 By carrying out competition
experiments, we determined that the binding affinities of TBE and
COE are the same (Scheme 3). In the case of Ir(POCOP) catalyst
2a, the binding affinity of COE is much greater than TBE and
thus catalysis is significantly inhibited as the concentration of
COE builds.7b This is not the case here since TBE and COE
exhibit similar binding affinities.
The ethylene complex 8a (31P{1H} NMR: δ = 62.54 (s)) can be
reversibly transformed to the tetrahydride iridium complex 9
(31P{1H} NMR: δ = 56.70 (s); 1H NMR: ꢀ9.34 (t, J = 9.8 Hz, 4H))
by addition of H2 (Scheme 2). The addition of CO to the complex
8a allowed the in situ observation of the dicarbonyl complex 10
which was converted to the monocarbonyl complex 11 (31P{1H}
NMR: δ = 56.70 (s); IR ν(CO) = 1946 cmꢀ1) under vacuum.
Scheme 2. Transformation of the iridium ethylene complex 8a
to the tetrahydride and carbonyl complexes.
Scheme 3. Resting states of the transfer dehydrogenation of COA
and TBE catalyzed by 8a.
Next, we investigated the catalytic activity of 8a for the transfer
dehydrogenation of linear alkanes (Table 2). A solution of nꢀ
octane containing 8a (1.0 mM, 3 ꢁmol) and TBE (6.0 M, 18
mmol) was heated at 200 °C under argon (entry 1). After 5 min,
62 TONs were obtained in which 1ꢀoctene represented 16% of the
total of octenes. The catalytic system has shown high activity
(TOF up to 40 minꢀ1) and stability (TON = 6000 after 10 h) at 200
°C. By decreasing the reaction temperature to 100 °C with 0.5 M
of TBE, the 1ꢀoctene represented up to 27% of the octenes after 1
h of reaction (TON = 34). Under these conditions, full conversion
of TBE to TBA (TON = 500) was obtained after 29 h. From data
in Table 2 it is clear that olefin isomerization occurs readily under
these conditions. Since higher fractions of 1ꢀoctene are observed
at lower TONs it seems likely this olefin is the initially formed
product and internal olefin isomers follow from rapid
isomerization.24
Use of iridium bis(phosphine) triptycene ethylene
complexes as catalysts for transfer dehydrogenation of
alkanes. The complexes 8a, 8b, 8c, were first tested as catalysts
for transfer dehydrogenation of cyclooctane (COA) with tertꢀ
butylethylene (TBE) as the hydrogen acceptor. Results are
summarized in Table 1. A system containing 1.3 mM (5 ꢁmol,
0.03 mol%) of iridium catalyst (8a, 8b or 8c), COA (3.9 M, 15.2
mmol, 3030 equivalents relative to Ir), and TBE (3.9 M, 15.2
mmol), was heated at 200 °C under argon in a sealed vessel. We
found that the catalyst 8a was highly active for the COA/TBE
dehydrogenation. TONs of 910 and 2590 have been obtained after
30 min and 4 h, respectively (entry 1, 4). A total of 93% of the
TBE was converted to TBA after 24 h (2820 turnovers with a
ratio of COE/1,3ꢀcyclooctadiene = 3:1). By comparison under
The olefin isomerization mechanism by iridium pincer catalysts
has been recently shown to proceed via a πꢀallyl mechanism
involving a η3ꢀallyl iridium hydride intermediate.25 In a previous
study, the (POCOP)Ir system was shown to thermodynamically
favor the η2ꢀolefin complex over the η3ꢀallyl hydride complex.
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After formation of the (tBuPOCOP)Ir(η3ꢀpropenyl)(H) at ꢀ88 °C,
Synthesis of iridium bis(phosphine) triptycene complexes
this complex rapidly converts to the (tBuPOCOP)Ir(η2ꢀpropene) at
ꢀ58 °C. An important difference was observed when using the
PC(sp3)PꢀIr system (Scheme 4). By exposing the PC(sp3)PꢀIrH4 9
to 1 atm of propylene at room temperature, we observed the
favored formation of the complex Ir(η3ꢀpropenyl)(H) 14 (31P{1H}
1
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4
5
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7
8
bearing a basic functional group for support on alumina.
Encouraged by the high activity and stability of the PC(sp3)PꢀIr
complex 8a as a catalyst for transfer dehydrogenation of alkanes,
the synthesis of similar complexes bearing a basic functional
group on the backbone of the triptycene has been investigated. We
previously reported the highly active and recyclable
heterogeneous system (OKꢀPOCOP)IrH2 (2c)/Al2O3 as a catalyst
for alkane metathesis12b and transfer dehydrogenation of
cyclooctane.17
1
NMR: δ 38.12 (d, JPP = 338 Hz), 35.82 (d, JPP = 338 Hz); H
NMR: ꢀ13.58 (dd, J = 22.4 Hz, J = 16.7 Hz, 1H)) over the Ir(η2ꢀ
propene) 15 (31P{1H} NMR: δ 57.69 (d, JPP = 300 Hz), 53.61 (d,
JPP = 300 Hz)) with a ratio 14/15 = 6:1 after 20 min and 19:1 after
2 h.26
9
Figure 3. 1ꢀHexene disproportionation profile with 8a.
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Table 2. Transfer dehydrogenation of nꢀoctane with TBE
8a (0.04 mol%)
catalyzed by 8a.[a]
2
+
180 °C
29.7 mmol
isomers
8a
(1.0 mM)
n-octane
+
TBE
octenes
+
TBA
200 or 100 °C
(6 or 0.5 M)
1ꢀ
1ꢀOctene
fraction
[%][b]
transꢀ2ꢀ
Octene
[mM]
cisꢀ2ꢀ
Octene
[mM]
t
Entry
1[c]
TON Octene
[mM]
[min]
5
62
10
10
27
6
16
7
36
57
11
28
10
135
30 1205
2
302
487
41
600 6000
0.1
163
Figure 4. Product distribution after 29 h from disproportionation
of 1ꢀhexene with 8a.
2[d]
60
120
34
91
9
18
6
27
19
1
13
46
8
13
55
1740
500
192
[a] TONs were calculated based on conversion of TBE determined by GC analysis.
[b] The fraction of 1ꢀoctene relative to the total of octenes. [c] Ir (1.0 mM), TBE (6
M), 200 °C. [d] Ir (1.0 mM), TBE (0.5 M), 100 °C.
Scheme 4. Formation of Ir(η3ꢀpropenyl)(H) 14 and Ir(η2ꢀpropene)
15
C6D6
(iPr)2P
+
+
Ir
H4
P(iPr)2
(iPr)2P
(iPr)2P
Ir
P(iPr)2
P(iPr)2
Ir
rt
H
1 atm
Inspired by these results, we targeted the synthesis of the
alkoxide PC(sp3)PꢀIr 24 (Scheme 5). Deprotonation of the 1,8ꢀ
dibromoanthrone 16 with CsF in acetonitrile formed the 1,8ꢀ
dibromoanthracene alkoxide 17 which reacted with benzyne
(generated in situ from the reaction between the 2ꢀ
(trimethylsilyl)phenyl trifluoromethanesulfonate and excess CsF)
to form the dibromotriptycene alkoxide 18. After protonation and
protection with Et3SiH/B(C6F5)3, the dibromotriptycene
triethylsilylether 20 was isolated. Lithium halogen exchange and
addition of the diisopropylchlorophosphine generated the bisꢀ
(diisopropylphosphine) derivative 21 which was successfully
converted to the iridium hydridochloride complex 22. After
addition of ethylene and NaOtBu, the ethylene complex 23
(31P{1H} NMR: δ = 62.30 ppm (s)) was isolated. However, all
attempts to deprotect the triethylsilyl ether group to generate the
alkoxide compound 24 have been unsuccessful, thwarting the
ability to support the complex on alumina.
9
14
15
20 min: 14/15 = 6:1
2 h: 14 15
/
= 19:1
Recently we reported the synthesis of paraꢀxylene using
ethylene as the sole feedstock. The important step of this reaction
is the conversion of 1ꢀhexene to 2,4ꢀhexadiene by catalytic
disproportionation. The catalytic activity of PC(sp3)PꢀIr 8a in this
reaction has been explored. The kinetic profile of 1ꢀhexene
disproportionation catalyzed by 8a (0.04 mol %, 180 °C) was
followed by GC (Figure 3). Under these conditions, 1ꢀhexene is
rapidly converted to a mixture of hexenes prior to significant
hydrogen transfer and the hexadienes produced appear as the
thermodynamic ratio of dienes. The reaction reaches equilibrium
after 10 h under these conditions. The product distribution after 29
h is reported in Figure 4 and shows the formation of the (2E, 4E),
(2Zꢀ4E)ꢀhexadienes and hexane as major products. In our
previous report,8b we found that using catalysts (iPrPOCCP)Ir 3a
and anthraphos iridium complex 4b under similar conditions,
equilibrium was achieved after ca. 13 and 3.5 h, respectively. The
catalysts (tBuPCP)Ir 1a and (tBuPOCOP)Ir 2a have shown very low
activity for this reaction. Complex PC(sp3)PꢀIr 8a is a little less
active than complex 4b but demonstrates similar activity to
complex 3a in the disproportionation of 1ꢀhexene.
Noting our previous report showing that Me2NꢀPCPꢀIr 1g could
be supported on alumina,17 we decided to explore an alternate
strategy and incorporate a –NMe2 group on the triptycene
backbone. The synthesis of the complex Me2NCH2ꢀPC(sp3)PꢀIr,
33, is outlined in Scheme 6. Starting from the dibromoanthracene
25, the reaction with the methylbenzyne (generated in situ from
the
reaction
between
the
2ꢀaminoꢀ5ꢀmethylbenzoic
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Scheme 5. Attempt of the synthesis of the alkoxide PC(sp3)PꢀIr complex 24
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Scheme 6. Synthesis of the Me2NCH2ꢀPC(sp3)PꢀIr complex 33
acid 26 and the oxidant) formed the two isomers of
dibromo(methyl)triptycene 27a and 27b in 1:1 ratio.
retained the orange color. After addition of TBE, the reaction was
heated at 200 °C and monitored by GC (Table 3).
a
Bromination, followed by nucleophilic substitution with
dimethylamine yielded the two amines, 29 and 30, which were
separated by chromatography on silica gel. NOESY experiments
allowed easy distinction between the two amines by the
observation of an NOE enhancement between the protons HaꢀHd
and HbꢀHc in 29 and 30. The amine 30 was transformed to the
corresponding bisꢀ(diisopropylphosphine)triptycene 31 which was
further converted to the iridium ethylene complex 33 (31P{1H}
NMR: δ = 62.59 ppm (s)).
Table 3. Transfer dehydrogenation of COA and TBE cataꢀ
lyzed by 33/Al2O3.[a]
TON
PC(sp3)PꢀIr
NMe2CH2ꢀ
Entry
γꢀAl2O3
PC(sp3)PꢀIr 33
8a
Supported iridium bis(phosphine) triptycene 33 as a catalyst
for the transfer dehydrogenation of alkanes. Various types of
γꢀaluminas (basic, Na2CO3 modified, acidic, neutral, low soda)
were screened as the supports for the iridium catalyst. We used
our previously reported conditions17 to support in situ the iridium
complex 33 on γꢀAl2O3. By mixing the iridium complex (5 ꢁmol)
33 in cyclooctane, an orange solution was obtained. When 250
mg of γꢀAl2O3 was added, the solution was completely
decolorized and the alumina acquired the orange color of the
iridium complex. In contrast, a similarly treated solution of 8a
1
2
ꢀ
2040
2800
Basic
185
235
20
ꢀ
Na2CO3
modified
3
4
5
6
Neutral
Low soda
Acidic
1230
1250
70
ꢀ
20
ꢀ
[a] TONs were calculated based on conversion of TBE determined by GC analysis.
COA (15.2 mmol), TBE (15.2 mmol), Ir (0.005 mmol).
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By first comparing the activity of the catalyst 33 with the
ºC, hold for 20 min. Calibration curves were prepared using
1
2
3
4
5
6
7
8
catalyst 8a in a homogeneous mode (without γꢀAl2O3), we
observed similar activities for the two catalysts (TONs = 2040
and 2800, respectively, entry 1). The supported systems (33/γꢀ
Al2O3) were investigated and modest catalytic activities were
obtained due to the fast decomposition of the catalytic systems.
Best results were achieved with TONs of 1230 and 1250 by using
neutral and low soda γꢀAl2O3, respectively (entry 4, 5). Very low
TONs were obtained when other types of γꢀAl2O3 were used. Test
reactions were conducted by mixing the complex 8a with basic
and low soda γꢀAl2O3. TONs of 20 have been achieved in both
cases demonstrating direct inhibition of the catalytic activity in
presence of γꢀAl2O3. Consequently, by supporting the complex 33
on γꢀAl2O3 (neutral and low soda), we stabilized the catalytic
system by limiting direct interaction between the alumina and the
iridium center. However, the stabilization was not sufficient to
achieve a highly stable, recyclable heterogeneous catalytic
system.
standard samples. Products were confirmed using authentic
samples and calibrated with an internal standard (mesitylene).
High resolution mass spectrometer (HRMS) analyses were carried
out by the Mass Spectrometry Facility at UNC. Elemental
analyses were carried out by Atlantic Microlab, Inc. of Norcross,
GA. Xꢀray diffraction studies were conducted on a BrukerꢀAXS
SMART APEXII diffractometer. Crystals were selected and
mounted using Paratone oil on a MiteGen Mylar tip. Complexes
7b, 7c, 8b, 8c and 32 are highly soluble in hydrocarbon solvents,
unable to be crystallized and are not stable to column
chromatography, so inevitably they contain some solvent as an
impurity and do not pass elemental analysis. However, all of these
complexes show a single 31P resonance for symmetrical structures
and only two 31P signals in one case where two isomers are
present (7c).
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General
procedure
for
the
synthesis
of
1,8ꢀ
bis(phosphino)triptycene 6aꢀ6c. The bis(phosphines) were
synthesized following the procedure reported by Gelman.21 To a
cold stirred solution (ꢀ78 °C) of 1,8ꢀdibromotriptycene (1.5 g,
3.64 mmol) and TMEDA (2.8 mL, 18.2 mmol) in dry THF (18
mL) was added nꢀBuLi (1.6 M, 4.6 mL, 7.28 mmol) over a period
of 30ꢀ35 min. The solution was stirred for an additional 15 min,
and the chlorophosphine (7.28 mmol) solution in THF (1 mL) was
added dropwise. The solution was allowed to reach room
temperature and then refluxed for 1 h. After cooling to room
temperature, ethyl acetate (20 mL) was added under air; the
organic phase was successively washed with sodium bicarbonate
and water, dried on Na2SO4 and evaporated. The white solid was
washed 3 times with MeOH, affording the product as a white
powder.
CONCLUSIONS
Syntheses of new PC(sp3)PꢀIr(ethylene) pincer complexes based
on the triptycene ligand have been achieved. The iridium ethylene
complex 8a bearing isopropyl substituents on phosphorus shows
exceptionally high activity and stability as a catalyst for the
transfer dehydrogenation of linear and cyclic alkanes at 200 °C
and for the disproportionation of 1ꢀhexene at 180 °C. The
synthesis of similar complexes bearing basic functionalities in the
backbone has been described. The complex bearing a NMe2CH2ꢀ
substituent, 33, has been successfully supported on γꢀalumina.
Modest catalytic activity has been observed for the transfer
dehydrogenation of alkanes when using this supported catalyst,
but the catalyst lifetime is limited due to degradation by reaction
with the alumina support. Other types of supports are now under
investigation in our laboratories in an effort to circumvent this
problem.
1,8ꢀbis(diisopropylphosphino)triptycene 6a: Following the
general procedure, 1.06 g (2.18 mmol, 60%) of compound 6a
was
obtained
from
1.2
mL
(7.28
mmol)
of
diisopropylchlorophosphine. The product was obtained as
described previously.21
EXPERIMENTAL SECTION
1,8ꢀbis(dicyclohexylphosphino)triptycene 6b: Following the
general procedure, 1.70 g (2.62 mmol, 72%) of compound 6b
General Considerations
was
obtained
from
1.6
mL
(7.28
mmol)
of
All manipulations were carried out under an argon atmosphere
using standard Schlenk, highꢀvacuum, and glovebox techniques.
Argon was purified by passing through columns of BASF R3ꢀ11
catalyst (Chemalog) and 4 Å molecular sieves. Benzeneꢀd6,
tolueneꢀd8, pꢀxyleneꢀd10, CD2Cl2 and CDCl3 (Cambridge Isotope
Laboratories) were used without purification. THF, nꢀhexane, nꢀ
pentane and toluene were distilled from sodium, then degassed by
three freezeꢀpumpꢀthaw cycles and stored in an argon atmosphere
glovebox. Cyclooctane (COA) (99%), tertꢀbutylethylene (TBE)
(98.5%), nꢀoctane (99%) and 1ꢀhexene were purchased from
Aldrich and dried over Na overnight, then distilled under vacuum
and stored in an argon atmosphere glovebox prior to use. Acidic,
neutral, low soda and basic γꢀAl2O3, were purchased from Strem,
calcined at 400 °C under a flow of oxygen for 16 h and stored
under argon. 1,8ꢀdibromoanthracene,21 1,8ꢀdibromotriptycene21
dicyclohexylchlorophosphine. 31P{1H} NMR (CDCl3, 162 MHz):
1
δ ꢀ16.67 (s). H NMR (CDCl3, 400 MHz): δ 7.50 (t, J = 6.3 Hz,
1H), 7.37ꢀ7.33 (m, 4H), 7.11 (d, J = 7.7 Hz, 2H), 6.97ꢀ6.93 (m,
4H), 5.37 (s, 1H), 2.05ꢀ1.99 (m, 6H), 1.83ꢀ1.80 (m, 4H), 1.65ꢀ
1.49 (m, 11H), 1.43.1.05 (m, 19H), 0.95ꢀ0.83 (m, 6H). HRMS
(C44H56P2): calc. [M + H]+: 647.3936, found [M + H]+: 647.3926.
1,8ꢀbis(dicyclopentylphosphino)triptycene 6c: Following the
general procedure, 0.97 g (1.64 mmol, 45%) of compound 6c was
obtained
from
1.4
mL
(7.28
mmol)
of
dicyclopentylchlorophosphine. 31P{1H} NMR (CDCl3, 162 MHz):
1
δ ꢀ17.80 (s). H NMR (CDCl3, 400 MHz): δ 7.53ꢀ7.51 (m, 1H),
7.39ꢀ7.34 (m, 4H), 7.16 (m, 2H), 6.99ꢀ6.96 (m, 4H), 5.37 (s, 1H),
2.28 (m, 2H), 1.98 (m, 6H), 1.71 (m, 6H), 1.58ꢀ1.40 (m, 18H),
1.28 (m, 4H). HRMS (C40H48P2): calc. [M + H]+: 591.3310, found
[M + H]+: 591.3293.
27
and [Ir(COE)2Cl]2 were prepared according to previously
reported procedures. All other reagents and solvents mentioned in
this text were purchased from commercial sources and used as
received. NMR spectra were recorded on Bruker spectrometers
(DRXꢀ400, AVANCEꢀ400, AVANCEꢀ500 and AVANCEꢀ600).
1H and 13C NMR spectra were referenced to residual solvent
peaks. 31P NMR chemical shifts were referenced to an external
H3PO4 standard. Gas chromatographic analysis of reactions was
conducted on an Agilent Technologies 6850 GC instrument fitted
with a fused silica capillary column (100 m length × 0.25 mm ID
× 0.50 ꢁm film thickness) using the following parameters: FID
detector: temperature = 300 ºC, initial temperature: 40 ºC, final
temperature: 250 ºC, oven program: 40 ºC, hold for 20 min, ramp
1: 85 ºC/min to 150 ºC, hold for 5 min, ramp 2: 10 ºC/min to 250
General procedure for the synthesis of PC(sp3)PꢀIr(H)(Cl)
27
7aꢀ7c. [IrCl(COE)2]2 (0.255 g, 0.28 mmol) was added to a
solution of 1,8ꢀbis(phosphino)triptycene 6aꢀ6c (0.59 mmol) in 10
ml of toluene. The contents were stirred at reflux overnight. After
evaporation of the solvent, the orange residue was washed 6 times
with 15 mL of cold pentane and dried under vacuum to afford the
product as an orange solid.
iPrPC(sp3)PꢀIr(H)(Cl) 7a. Following the general procedure,
0.180 g (0.252 mmol, 45%) of compound 7a was obtained from
0.286 g (0.59 mmol) of 1,8ꢀbis(diisopropylphosphino)triptycene
1
6a. 31P{1H NMR (C6D6, 162 MHz): δ 63.93 (s). H NMR (C6D6,
600 MHz): δ 7.83 (d, J = 7.0 Hz, 1H), 7.14ꢀ7.10 (m, 2H), 6.94
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ACS Catalysis
Page 6 of 11
(dd, J = 7.3 Hz, J = 1.3 Hz, 1H), 6.85ꢀ6.84 (m, 4H), 6.78 (td, J =
2H), 2.21 (d, J = 12.7 Hz, 2H), 2.10ꢀ2.08 (m, 2H), 1.67 (t, J =
1
2
3
4
5
6
7
8
7.5 Hz, J = 1.3 Hz, 1H), 6.62 (td, J = 7.5 Hz, J = 1.2 Hz, 1H),
5.18 (s, 1H), 2.67ꢀ2.63 (m, 2H), 2.48ꢀ2.45 (m, 2H), 1.48 (q, J =
7.5 Hz, 6H), 1.11 (q, J = 7.8 Hz, 6H), 1.00 (q, J = 7.4 Hz, 6H),
0.88 (q, J = 7.2 Hz, 6H), ꢀ35.12 (t, J = 15.1 Hz, 1H). 13C NMR
(C6D6, 151 MHz): δ 168.8 (t, J = 15.8 Hz, 2C), 153.4, 146.8,
145.3 (t, J = 6.6 Hz, 2C), 134.8 (t, J = 23.0 Hz, 2C), 126.2 (2C),
125.8, 125.1 (t, J = 3.2 Hz, 2C), 124.7, 124.6 (2C), 123.8, 122.5,
54.7, 33.7 (d, J = 5.5 Hz, 1C), 28.8 (t, J = 12.1 Hz, 2C), 25.5 (t, J
= 16.2 Hz, 2C), 20.5 (2C), 19.6 (t, J = 2.6 Hz, 2C), 19.5 (t, J = 2.6
Hz, 2C), 19.1 (2C). Anal. Calcd for C32H40ClIrP2: C 53.81, H
5.64; found: C 53.95, H 5.75.
CyPC(sp3)PꢀIr(H)(Cl) 7b. Following the general procedure,
0.210 g (0.241 mmol, 43%) of compound 7b was obtained from
0.381 g (0.59 mmol) of 1,8ꢀbis(dicyclohexylphosphino)triptycene
6b. The product was washed one time with cold pentane. 31P{1H}
NMR (C6D6, 162 MHz): δ 56.76 (s). 1H NMR (C6D6, 400 MHz): δ
7.90 (d, J = 7.3 Hz, 1H), 7.12ꢀ7.01 (m, 2H), 6.97ꢀ6.88 (m, 5H),
6.79ꢀ6.76 (t, J = 7.4 Hz, 1H), 6.68ꢀ6.64 (t, J = 7.4 Hz, 1H), 5.20
(s, 1H), 2.65 (m, 2H), 2.50ꢀ2.46 (m, 2H), 2.36ꢀ2.33 (m, 4H), 2.18ꢀ
2.07 (m, 3H), 1.83 (m, 2H), 1.62ꢀ1.49 (m, 6H), 1.45ꢀ1.37 (m, 4H),
1.32ꢀ1.09 (m, 14H), 1.00ꢀ0.76 (m, 7H), ꢀ34.64 (t, J = 15 Hz, 1H).
12.2 Hz, 4H), 1.59 (m, 3H), 1.55ꢀ1.52 (m, 4H), 1.48ꢀ1.36 (m,
15H), 1.08ꢀ1.05 (m, 6H), 0.76ꢀ0.62 (m, 4H). NMR (C6D6, 151
MHz): δ 168.8 (t, J = 20.2 Hz, 2C), 158.2, 148.3, 147.1 (t, J = 7.6
Hz, 2C), 135.6 (t, J = 20.0 Hz, 2C), 130.4, 126.2 (2C), 124.9
(2C), 124.7 (2C), 123.5, 123.1, 123.0, 67.8 (t, J = 6.0 Hz, 1C),
55.0, 39.7 (t, J = 11.4 Hz, 2C), 36.1 (t, J = 17.3 Hz, 2C), 31.4
(2C), 30.8 (2C), 30.2 (2C), 29.6 (4C), 29.4 (2C), 27.8 (t, J = 6.4
Hz, 2C), 27.7 (t, J = 5.2 Hz, 2C), 27.6 (2C), 27.4 (t, J = 6.2 Hz,
2C), 27.0 (2C), 26.5 (2C).
CpPC(sp3)PꢀIrꢀethylene 8c. Following the general procedure,
0.127 g (0.157 mmol, 83%) of compound 8c was obtained from
0.156 g (0.189 mmol) of the mixture of the two compounds 7c'
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1
and 7c''. 31P{1He NMR (C6D6, 162 MHz): δ 50.80 (s). H NMR
(C6D6, 400 MHz): δ 7.82 (d, J = 7.2 Hz, 1H), 7.31 (d, J = 7.0 Hz,
2H), 7.16ꢀ7.12 (m, 3H, overlapping the residual C6D5H peak),
6.98 (t, J = 7.3 Hz, 2H), 6.88 (t, J = 7.5 Hz, 1H), 6.73 (t, J = 7.4
Hz, 1H), 5.32 (s, 1H), 2.81 (t, J = 2.4 Hz, 4H), 2.71ꢀ2.66 (m, 4H),
1.88ꢀ1.85 (m, 4H), 1.80ꢀ1.78 (m, 3H), 1.70ꢀ1.59 (m, 6H), 1.54ꢀ
1.50 (m, 8H), 1.44ꢀ1.42 (m, 5H), 1.31ꢀ1.24 (m, 6H). 13C NMR
(C6D6, 151 MHz): δ 167.9 (t, J = 19.9 Hz, 2C), 158.3, 148.1,
146.8 (t, J = 7.9 Hz, 2C), 137.3 (t, J = 21.0 Hz, 2C), 130.0, 126.0
(2C), 125.1 (t, J = 2.9 Hz, 2C), 124.7 (2C), 123.8, 123.2, 123.0,
67.7 (t, J = 5.5 Hz, 1C), 54.9, 43.1 (t, J = 12.7 Hz, 2C), 38.6 (t, J
= 18.7 Hz, 2C), 32.5, 30.4 (t, J = 2.9, 4C), 30.1, 29.9 (2C), 29.9
(2C), 29.3, 28.1, 26.8 (t, J = 4.6 Hz, 2C), 26.3 (t, J = 4.6 Hz, 2C),
25.9 (t, J = 4.9 Hz, 2C), 25.7 (t, J = 4.8 Hz, 2C).
In situ generation of iPrPC(sp3)PꢀIrH4 9. To a C6D6 solution of
5 mg of iPrPC(sp3)PꢀIrꢀethylene 8a (7.1 ꢁmol) in a JꢀYoung tube
was added 1 atm of H2. An immediate color change from orange
to colorless was observed. The resulting complex 9 was
quantitatively generated and characterized by NMR. 31P{1H}
NMR (C6D6, 162 MHz): δ 56.70 (s). 1H NMR (C6D6, 400 MHz): δ
8.10 (d, J = 7.6 Hz, 1H), 7.22 (d, J = 7.0 Hz, 2H), 7.16ꢀ7.14 (m,
1H, overlapping the residual C6D5H peak), 6.95 (t, J = 7.4 Hz,
1H), 6.87 (t, J = 7.3 Hz, 2H), 6.83ꢀ6.80 (m, 2H), 6.77 (t, J = 7.3
Hz, 1H), 5.31 (s, 1H), 2.08ꢀ2.06 (m, 2H), 1.58ꢀ1.55 (m, 2H), 1.18
(q, J = 7.5 Hz, 6H), 0.89 (q, J = 7.2 Hz, 6H), 0.83 (q, J = 7.5 Hz,
6H), 0.73 (q, J = 7.2 Hz, 6H), ꢀ9.34 (t, J = 9.8 Hz, 4H).
CpPC(sp3)PꢀIr(H)(Cl) 7c. Following the general procedure,
0.325 g (0.241 mmol, 71%) of compounds were obtained as a
mixture of two isomers 7c' and 7c'' with a ratio 1:1 from 0.349 g
(0.59 mmol) of 1,8ꢀbis(dicyclopentylphosphino)triptycene 6c.
The products were not washed with cold pentane due to their high
solubility in this solvent. Characteristic signals: 7c': 31P{1H} NMR
1
(C6D6, 162 MHz): δ 54.10 (s). H NMR (C6D6, 400 MHz): δ ꢀ
34.64 (t, J = 15.5 Hz, 1H). 7c'': 31P{1H} NMR (C6D6, 162 MHz):
1
δ 31.90 (s). H NMR (C6D6, 400 MHz): δ ꢀ28.56 (t, J = 15.6 Hz,
1H).
General procedure for the synthesis of PC(sp3)PꢀIrꢀethylene
8aꢀ8c. One equivalent (0.189 mmol) of the respective PC(sp3)Pꢀ
Ir(H)(Cl) (7aꢀ7c) and 2.3 equiv of NaOtBu (0.042 g, 0.435 mmol)
were dissolved in toluene (10 mL) in a Kontes Flask, filled with 1
atm of ethylene and stirred at 60 °C for 48 h. The solvent was
evaporated under high vacuum and the Kontes flask was
transferred to the glovebox, pentane was added, and the solution
was filtered through a 0.2 ꢁm pore size syringe filter (Nalgene
199ꢀ2020) into another Schlenk flask. The solvent was removed
in vacuo to afford the corresponding PC(sp3)PꢀIrꢀethylene
complexes 8aꢀ8c as orange powders.
In situ generation of iPrPC(sp3)PꢀIr(CO)2 10 and synthesis of
iPrPC(sp3)PꢀIr(CO) 11. To a C6D6 solution of 10 mg of
iPrPC(sp3)PꢀIrꢀethylene 8a (14.2 ꢁmol) in a JꢀYoung tube was
added 1 atm of CO. An immediate color change from orange to
pale yellow was observed. The resulting complex iPrPC(sp3)Pꢀ
Ir(CO)2 10 was quantitatively generated and characterized by
NMR. This complex cannot be isolated as a solid due to loss of
CO. 31P{1H} NMR (C6D6, 162 MHz): δ 57.93 (s). 1H NMR
(C6D6, 400 MHz): δ 8.63 (d, J = 7.6 Hz, 1H), 7.16ꢀ7.12 (m, 3H,
overlapping the residual C6D5H peak), 6.99 (t, J = 7.6 Hz, 1H),
6.85ꢀ6.76 (m, 5H), 5.18 (s, 1H), 2.42ꢀ2.40 (m, 2H), 1.89ꢀ1.87 (m,
2H), 1.13ꢀ1.07 (m, 12H), 0.91ꢀ0.88 (m, 6H), 0.65ꢀ0.63 (m, 6H).
13C NMR (C6D6, 151 MHz): δ 184.4 (t, J = 11.2 Hz, CO), 184.0
(CO), 167.5 (t, J = 18.1 Hz, 2C), 154.9, 146.9 (t, J = 8.2 Hz, 2C),
145.9, 134.2 (t, J = 20.9 Hz, 2C), 130.0, 125.3 (t, J = 3.0 Hz, 2C),
124.9 (3C), 124.8 (2C), 124.7, 123.2, 62.2 (t, J = 3.4 Hz, 1C),
55.4, 30.6 (t, J = 17.0 Hz, 2C), 28.1 (t, J = 11.7 Hz, 2C), 19.7
(2C), 19.6 (t, J = 2.2 Hz, 2C), 19.4 (t, J = 3.1 Hz, 2C), 18.4 (2C).
The solvent was removed under vacuum and the resulting
complex iPrPC(sp3)PꢀIr(CO) 11 was isolated and characterized
by NMR and IR (9 mg, 13.5 ꢁmol, 95%). 31P{1H} NMR (C6D6,
iPrPC(sp3)PꢀIrꢀethylene 8a. Following the general procedure,
0.124 g (0.176 mmol, 93%) of compound 8a was obtained from
0.135 g (0.189 mmol) of iprPC(sp3)PꢀIr(H)(Cl) 7a. 31P{1H} NMR
1
(C6D6, 162 MHz): δ 62.54 (s). H NMR (C6D6, 400 MHz): δ 7.78
(d, J = 7.3 Hz, 1H), 7.30 (d, J = 6.9 Hz, 2H), 7.13 (m, 1H,
overlapping the residual C6D5H peak), 7.04ꢀ7.01 (m, 2H), 6.94 (t,
J = 7.3 Hz, 2H), 6.85 (d, J = 7.3 Hz, 1H), 6.71 (t, J = 7.3 Hz, 1H),
5.30 (s, 1H), 2.77 (t, J = 2.5 Hz, 4H), 2.61ꢀ2.56 (m, 2H), 2.42ꢀ
2.38 (m, 2H), 1.12 (q, J = 7.0 Hz, 6H), 0.90ꢀ0.82 (m, 18H). 13C
NMR (C6D6, 151 MHz): δ 168.4 (t, J = 19.6 Hz, 2C), 158.1,
148.2, 147.0 (t, J = 7.9 Hz, 2C), 135.4 (t, J = 20.1 Hz, 2C), 130.4,
125.9 (2C), 124.8 (t, J = 2.8 Hz, 2C), 124.8 (2C), 123.6, 123.0,
122.8, 67.9 (t, J = 5.3 Hz, 1C), 54.9, 34.4, 29.8 (t, J = 11.7 Hz,
2C), 28.8 (t, J = 1.7 Hz, 4C), 25.9 (t, J = 17.6 Hz, 2C), 22.7 , 20.4
(t, J = 3.3 Hz, 1C), 19.6, 18.8, 18.8 (2C), 14.2. Anal. Calcd for
C34H43IrP2: C 57.85, H 6.14; found: C 58.05, H 6.25.
CyPC(sp3)PꢀIrꢀethylene 8b. Following the general procedure,
0.150 g (0.174 mmol, 92%) of compound 8b was obtained from
0.165 g (0.189 mmol) of CyPC(sp3)PꢀIr(H)(Cl) 7b. 31P{1H} NMR
1
162 MHz): δ 74.21 (s). H NMR (C6D6, 600 MHz): δ 7.82 (d, J =
7.3 Hz, 1H), 7.29ꢀ7.28 (m, 2H), 7.12 (d, J = 7.2 Hz, 1H), 6.91ꢀ
6.89 (m, 5H), 6.69 (t, J = 7.4 Hz, 1H), 5.21 (s, 1H), 2.59ꢀ2.55 (m,
2H), 2.08ꢀ2.06 (m, 2H), 1.35 (q, J = 7.5 Hz, 6H), 1.08ꢀ1.03 (m,
12H), 0.81 (q, J = 7.3 Hz, 6H). 13C NMR (C6D6, 151 MHz): δ
193.7 (t, J = 7.9 Hz, CO), 166.5 (t, J = 18.2 Hz, 2C), 158.9, 149.8,
148.1 (t, J = 7.1 Hz, 2C), 134.4 (t, J = 22.3 Hz, 2C), 129.8, 126.5
1
(C6D6, 202 MHz): δ 57.55 (s). H NMR (C6D6, 600 MHz): δ 7.77
(d, J = 7.4 Hz, 1H), 7.34 (d, J = 7.0 Hz, 2H), 7.17ꢀ7.13 (m, 3H,
overlapping the residual C6D5H peak), 7.01 (t, J = 7.4 Hz, 2H),
6.84 (t, J = 7.5 Hz, 1H), 6.73 (t, J = 7.3 Hz, 1H), 5.33 (s, 1H),
2.82 (t. J = 2.4 Hz, 4H), 2.55ꢀ2.53 (m, 2H), 2.35 (t, J = 12.5 Hz,
ACS Paragon Plus Environment

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ACS Catalysis
(2C), 125.9 (2C), 125.3 (t, J = 3.2 Hz, 2C), 124.2, 123.5, 123.4,
residual CHCl3 peak), 7.16ꢀ7.08 (m, 2H), 6.96 (t, J = 7.7 Hz, 2H),
6.40 (s, 1H), 3.30 (s, 1H). 13C NMR (CDCl3, 101 MHz): δ 148.5
(2C), 145.4, 142.5 (2C), 141.9, 129.5 (2C), 126.9 (2C), 126.2,
125.9, 124.4 (2C), 119.5, 119.3, 118.4 (2C), 81.1, 50.9. HRMS
(C20H12Br2O): calc. [M + H]+: 426.9333, found [M + H]+:
426.9325.
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75.2 (t, J = 3.6 Hz, 1C), 55.0, 30.3 (t, J = 11.9 Hz, 2C), 26.2 (t, J
= 17.5 Hz, 2C), 20.6 (t, J = 3.2 Hz, 2C), 19.9 (2C), 19.7 (2C),
19.1 (2C). IR (hexanes, cmꢀ1): 1946 ν(CO).
In situ generation of iPrPC(sp3)PꢀIr(TBE) 12. To a C6D6
solution of 5 mg of iPrPC(sp3)PꢀIrꢀethylene 8a (7.1 ꢁmol) in a Jꢀ
Young tube was added 1 atm of H2. After 5 minutes of stirring,
TBE (9 ꢁL, 73 ꢁmol) was added. An immediate color change
from colorless to orange was observed. The resulting complex 12
was quantitatively generated and characterized by NMR. 31P{1H}
NMR (C6D6, 162 MHz): δ 50.25 (d, J = 320 Hz, 1P), 46.35 (d, J =
Synthesis of 1,8ꢀdibromotriptyceneꢀOSiEt3 20. To a solution
of dichloromethane (15 mL) containing 1,8ꢀdibromotriptyceneꢀ
OH 19 (1.23 g, 2.87 mmol) and B(C6F5)3 (0.103 g, 0.20 mmol)
was added Et3SiH (1.40 mL, 8.61 mmol) at room temperature and
mixed for 16 h. After evaporation of volatiles compounds, the
crude product was purified by chromatography on silica gel
(hexaneꢀEtOAc, 10:0.2) affording 20 as a white powder (1.32 g,
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320 Hz, 1P). H NMR (C6D6, 400 MHz): δ 8.15 (d, J = 7.2 Hz,
1H), 7.30 (d, J = 6.7 Hz, 2H), 7.19ꢀ7.16 (m, 1H, overlapping the
residual C6D5H peak), 6.98ꢀ6.90 (m, 5H), 6.74 (t, J = 7.4 Hz, 1H),
5.28 (s, 1H), 4.77ꢀ4.66 (m, 1H), 3.46 (t, J = 11.4 Hz, 1H), 3.00
(m, 1H), 2.69 (m, 1H), 2.54 (m, 1H), 2.22 (m, 1H), 1.96 (d, J =
7.9 Hz, 1H), isopropyl and tꢀbutyl protons are overlapped with the
excess of TBE and 2,2ꢀdimethylbutane.
In situ generation of iPrPC(sp3)PꢀIr(COE) 13. To a C6D6
solution of 5 mg of iPrPC(sp3)PꢀIrꢀethylene 8a (7.1 ꢁmol) in a Jꢀ
Young tube was added 1 atm of H2. After 5 minutes of stirring,
COE (9 ꢁL, 73 ꢁmol) was added. An immediate color change
from colorless to orange was observed. The resulting complex 13
was quantitatively generated and characterized by NMR. 31P{1H}
NMR (C6D6, 162 MHz): δ 57.06 (s). 1H NMR (C6D6, 400 MHz): δ
7.95 (d, J = 7.3 Hz, 1H), 7.29 (d, J = 6.9 Hz, 2H), 7.20ꢀ7.16 (m,
1H, overlapping the residual C6D5H peak), 7.02ꢀ6.98 (m, 3H),
6.92 (t, J = 7.3 Hz, 2H), 6.78 (t, J = 7.3 Hz, 1H), 5.31 (s, 1H),
3.81ꢀ3.79 (m, 2H), 2.65ꢀ2.58 (m, 6H), 1.99ꢀ1.84 (m, 6H), 1.67ꢀ
1.64 (m, 2H), 1.25ꢀ1.20 (q, J = 7.6 Hz, 6H), 1.01ꢀ0.97 (m, 6H),
0.92ꢀ0.85 (m, 8H), 0.67 (q, J = 7.8 Hz, 6H).
1
85%). H NMR (CDCl3, 600 MHz): δ 7.54 (d, J = 7.5 Hz, 1H),
7.50 (d, J = 7.2 Hz, 1H), 7.46 (d, J = 7.5 Hz, 2H), 7.23 (d, J = 8.1
Hz, 2H), 7.12 (t, J = 7.5 Hz, 1H), 7.08 (t, J = 7.4 Hz, 1H), 6.93 (t,
J = 7.8 Hz, 2H), 6.37 (s, 1H), 1.17 (t, J = 7.9 Hz, 9H), 1.06ꢀ1.02
(m, 6H). 13C NMR (CDCl3, 151 MHz): δ 149.6 (2C), 146.4, 142.2
(2C), 141.6, 129.2 (2C), 126.6 (2C), 125.9, 125.6, 124.2 (2C),
120.7, 119.6 (2C), 119.4, 85.3, 50.8, 8.5 (3C), 7.8 (3C).
Synthesis of 1,8ꢀbis(diisopropylphosphino)triptyceneꢀOSiEt3
21. Following the same procedure as for 6a, 1.06 g (1.72 mmol,
65%) of coumpond 21 was obtained as a white powder from 1,8ꢀ
dibromotriptyceneꢀOSiEt3 20
(1.16
g,
2.13
mmol),
diisopropylchlorophosphine (0.68 mL, 4.26 mmol), nꢀBuLi (2.7
mL, 4.26 mmol) and TMEDA (1.61 mL, 10.66 mmol) in 11 mL
1
of THF. 31P{1H} NMR (CDCl3, 162 MHz): δ ꢀ9.00 (s). H NMR
(CDCl3, 600 MHz): δ 7.54 (d, J = 7.4 Hz, 2H), 7.51 (d, J = 7.5 Hz,
1H), 7.46 (t, J = 5.1 Hz, 1H), 7.37 (d, J = 7.3 Hz, 1H), 7.11 (d, J
= 7.6 Hz, 1H), 7.04ꢀ7.00 (m, 3H), 6.95 (t, J = 7.0 Hz, 1H), 2.21ꢀ
2.17 (m, 2H), 2.08ꢀ2.04 (m, 2H), 1.22ꢀ1.19 (m, 15H), 1.09ꢀ1.05
(m, 6H), 1.02ꢀ0.99 (m, 6H), 0.91ꢀ0.88 (m, 6H), 0.78ꢀ0.75 (m,
6H). HRMS (C38H54OP2Si): calc. [M + H]+: 617.3497, found [M
+ H]+: 617.3511.
Synthesis of (OSiEt3)ꢀiPrPC(sp3)PꢀIr(H)(Cl) 22. Following the
same procedure as for 7a, 0.149 g (0.176 mmol, 51%) of
compound 22 was obtained from 0.213 g (0.345 mmol) of 1,8ꢀ
In situ generation of Ir(η3ꢀpropenyl)(H) 14 and Ir(η2ꢀ
propene) 15. To a C6D6 solution of 5 mg of iPrPC(sp3)PꢀIrꢀ
ethylene 8a (7.1 ꢁmol) in a JꢀYoung tube was added 1 atm of H2.
After 5 minutes of stirring, 1 atm of propylene was added. After
20 min, we observed a ratio 14/15 = 6:1 and 19:1 after 2 h. The
resulting complexes 14 and 15 were quantitatively generated and
characterized by NMR. 14: 31P{1H} NMR (C6D6, 162 MHz): δ
bis(diisopropylphosphino)triptyceneꢀOSiEt3 21 and 0.154
g
1
38.12 (d, J = 338 Hz, 1P), 35.82 (d, J = 338 Hz, 1P). H NMR
(0.173 mmol) of [IrCl(COE)2]21in 10 mL of toluene. 31P{1H NMR
(C6D6, 243 MHz): δ 64.19 (s). H NMR (C6D6, 600 MHz): δ 7.83
(d, J = 7.3 Hz, 1H), 7.67 (d, J = 7.3 Hz, 2H), 7.48 (d, J = 7.3 Hz,
1H), 6.97 (t, J = 7.5 Hz, 2H), 6.87ꢀ6.85 (m, 2H), 6.79 (t, J = 7.4
Hz, 1H), 6.75 (t, J = 7.4 Hz, 1H), 2.68ꢀ2.65 (m, 2H), 2.47ꢀ2.45
(m, 2H), 1.49 (q, J = 7.6 Hz, 6H), 1.16 (t, J = 7.9 Hz, 9H), 1.10
(q, J = 7.9 Hz, 6H), 1.05ꢀ0.89 (m, 12H), 0.89 (q, J = 7.0 Hz, 6H),
ꢀ35.34 (t, J = 14.9 Hz, 1H). 13C NMR (C6D6, 151 MHz): δ 167.4
(t, J = 15.7 Hz, 2C), 151.4, 149.0, 146.8 (t, J = 6.0 Hz, 2C), 134.5
(t, J = 22.9 Hz, 2C), 126.5 (2C), 125.3, 124.9 (2C), 124.8, 123.6,
121.5 (2C), 119.3, 85.9, 32.4, 28.9 (t, J = 12.0 Hz, 2C), 25.6 (t, J
= 16.3 Hz, 2C), 20.5 (2C), 19.6 (2C), 19.5 (2C), 19.2 (2C), 8.8
(3C), 7.9 (3C). Anal. Calcd for C38H54ClIrOP2Si: C 54.04, H 6.44;
found: C 54.13, H 6.49.
(C6D6, 600 MHz): δ 8.54 (d, J = 7.5 Hz, 1H), 7.23ꢀ7.21 (m, 1H),
7.19 (d, J = 7.2 Hz, 1H), 7.16ꢀ7.13 (m, 1H, overlapping the
residual C6D5H peak), 7.01 (td, J = 7.5 Hz, J = 1.2 Hz, 1H), 6.90ꢀ
6.88 (m, 1H), 6.86 (td, J = 7.3 Hz, J = 1.8 Hz, 1H), 6.81 (td, J =
7.4 Hz, J = 1.2 Hz, 1H), 6.78ꢀ6.76 (m, 1H), 5.29 (s, 1H), 4.65ꢀ
4.58 (m, 1H, H2), 3.48 (d, J = 6.4 Hz, 1H, Hsyn), 2.85 (d, J = 6.0
Hz, 1H, Hsyn), 2.56ꢀ2.47 (m, 2H), 2.16ꢀ2.14 (m, 1H, Hanti), 1.89ꢀ
1.85 (m, 1H), 1.83 (t, J = 9.7 Hz, 1H, Hanti), 1.73ꢀ1.70 (m, 1H),
1.14ꢀ1.11 (m, 3H), 1.00ꢀ0.97 (m, 3H), 0.92ꢀ0.88 (m, 6H), 0.78ꢀ
0.74 (m, 6H), 0.64ꢀ0.61 (m, 3H), 0.44ꢀ0.40 (m, 3H), ꢀ13.58 (dd, J
= 22.4 Hz, J = 16.7 Hz, 1H). 15: 31P{1H} NMR (C6D6, 162 MHz):
δ 57.69 (d, J = 300 Hz, 1P), 53.61 (d, J = 300 Hz, 1P).
Synthesis
of
1,8ꢀdibromotriptyceneꢀOH
19.
1,8ꢀ
dibromoanthrone 1621, 28 (2 g, 5.68 mmol) and CsF (4.32 g, 28.4
mmol) were mixed in 80 mL of acetonitrile at room temperature
for 30 min. A fast color change from yellow to red was observed.
Synthesis of (OSiEt3)ꢀ iPrPC(sp3)PꢀIrꢀethylene 23. Following
the same procedure as for 8a, 0.124 g (0.176 mmol, 93%) of
compound 23 was obtained from 0.100 g (0.118 mmol) of
(OSiEt3)ꢀiPrPC(sp3)PꢀIr(H)(Cl) 22 and 0.026 g (0.272 mmol) of
NaOtBu in 6 mL of toluene. 31P{1H} NMR (C6D6, 162 MHz): δ
A
solution
containing
2ꢀ(trimethylsilyl)phenyl
trifluoromethanesulfonate (2.72 mL, 11.36 mmol) in 16 mL of
acetonitrile was slowly added for 1 h to the reaction mixture and
stirred another 2 h. 40 mL of aqueous HCl (2M) were added
dropwise followed by 150 mL of ethyl acetate. The organic layer
was separated and the aqueous layer was extracted with EtOAc (2
x 80 mL). The combined organic layers were washed with H2O (2
x 60 mL), dried on MgSO4 and the solvent was evaporated. The
crude product was purified by chromatography on silica gel
(hexaneꢀEtOAc, 10:1 to 10:3) affording 19 as a white powder
(1.35 g, 55%). 1H NMR (CDCl3, 400 MHz): δ 7.53 (d, J = 7.1 Hz,
2H), 7.47 (d, J = 7.4 Hz, 2H), 7.26ꢀ7.24 (m, 2H, overlapping the
1
62.30 (s). H NMR (C6D6, 400 MHz): δ 7.83ꢀ7.79 (m, 3H), 7.65
(d, J = 6.3 Hz, 1H), 7.08ꢀ7.01 (m, 4H), 6.88ꢀ6.81 (m, 2H), 2.67 (t,
J = 2.5 Hz, 4H), 2.61ꢀ2.55 (m, 2H), 2.42ꢀ2.36 (m, 2H), 1.20 (t, J =
7.6 Hz, 9H), 1.14ꢀ1.05 (m, 15H), 0.90ꢀ0.81 (m, 15H). 13C NMR
(C6D6, 151 MHz): δ 167.0 (t, J = 19.8 Hz, 2C), 156.2, 150.1,
148.3 (t, J = 7.7 Hz, 2C), 135.2 (t, J = 20.4 Hz, 2C), 130.0, 126.3
(2C), 124.7 (t, J = 2.8 Hz, 2C), 123.7, 122.9, 121.6 (2C), 119.6,
85.9, 66.5, 31.3, 29.9 (t, J = 11.8 Hz, 2C), 29.0 (t, J = 1.7 Hz, 4C),
26.0 (t, J = 17.7 Hz, 2C), 22.8 , 20.4 (t, J = 3.3 Hz, 1C), 19.7,
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ACS Catalysis
Page 8 of 11
18.9, 18.9 (2C), 14.3, 9.0 (3C), 8.0 (3C). Anal. Calcd for
C34H43IrP2: C 57.46, H 6.87; found: C 57.12, H 7.07.
127.0 (2C), 126.4, 124.6, 124.3, 122.9 (2C), 119.6 (2C), 64.3,
54.9, 52.2, 45.6 (2C). HRMS (C23H19Br2N): calc. [M + H]+:
467.9963, found [M + H]+: 467.9965.
1
2
3
4
5
6
7
8
9
Synthesis of 1,8ꢀdibromotriptyceneꢀCH3 27a and 27b. The
protocol developed by Gelman29 was modified as followed: 1,8ꢀ
dibromoanthracene (1.12 g, 3.33 mmol) in 12 mL of 1,2ꢀ
dimethoxyethane and isopentyl nitrite (0.76 mL, 5.66 mmol) were
placed in a 100 mL threeꢀnecked roundꢀbottomed flask fitted with
a reflux condenser and a mechanical stirrer. The mixture was
heated to reflux and the solution of 2ꢀAminoꢀ5ꢀmethylbenzoic
acid (1.01 g, 6.66 mmol) in 7 mL of 1,2ꢀdimethoxyethane was
added slowly over 40 min by means of a syringe pump. The
mixture was cooled down to room temperature and an additional
portion of isopentyl nitrite (0.76 mL, 5.66 mmol) was added at
once. After resuming reflux, another portion of 2ꢀAminoꢀ5ꢀ
methylbenzoic acid (1.01 g, 6.66 mmol) in 7 mL of 1,2ꢀ
dimethoxyethane was added over 30 min. The mixture was cooled
down to room temperature and 3 mL of methanol along with 50
mL of 10% sodium hydroxide were added. The solution was
cooled to ca. 0 °C, mixed 10 min. and filtered. The residue was
washed with 3 portions of chilled methanol/water (4/1) and the
powder was air dried overnight. The products 27a and 27b were
obtained as a mixture of two isomers with a ratio 1:1 and a
conversion of 86%. The crude material was used without further
purification.
Synthesis
of
1,8ꢀbis(diisopropylphosphino)triptyceneꢀ
CH2NMe2 31. Following the same procedure as for 6a, 0.85 g
(1.56 mmol, 73%) of compound 31 was obtained as a white
powder from 1,8ꢀdibromotriptyceneꢀCH2NMe2 30 (1.00 g, 2.13
mmol), diisopropylchlorophosphine (0.68 mL, 4.26 mmol), nꢀ
BuLi (2.7 mL, 4.26 mmol) and TMEDA (1.6 mL, 10.66 mmol) in
10 mL of THF. 31P{1H} NMR (CDCl3, 162 MHz): δ ꢀ8.59 (s). 1H
NMR (CDCl3, 400 MHz): δ 7.45 (t, J = 4.8 Hz, 1H), 7.34ꢀ7.30 (m,
4H), 7.10ꢀ7.08 (m, 2H), 6.96 (t, J = 7.5 Hz, 2H), 6.83 (dd, J = 7.4
Hz, J = 1.6 Hz, 1H), 5.34 (s, 1H), 3.29 (s, 2H), 2.20ꢀ2.17 (m, 8H),
2.10ꢀ2.01 (m, 2H), 1.24ꢀ1.19 (m, 6H), 1.03ꢀ0.98 (m, 6H), 0.92ꢀ
0.87 (m, 6H), 0.78ꢀ0.74 (m, 6H). HRMS (C35H47NP2): calc. [M +
H]+: 544.3262, found [M + H]+: 544.3292.
Synthesis of (NMe2CH2)ꢀiPrPC(sp3)PꢀIr(H)(Cl) 32. Following
the same procedure as for 7a, 0.160 g (0.207 mmol, 38%) of
compound 32 was obtained from 0.300 g (0.551 mmol) of 1,8ꢀ
bis(diisopropylphosphino)triptyceneꢀCH2NMe2 31 and 0.247 g
(0.276 mmol) of [IrCl(COE)2]2 in 12 mL of toluene. 31P{1H}
NMR (C6D6, 243 MHz): δ 63.68 (s). 1H NMR (C6D6, 600 MHz): δ
7.79 (d, J = 7.5 Hz, 1H), 7.22 (m, 1H), 7.13ꢀ7.11 (m, 3H), 6.85ꢀ
6.81 (m, 4H), 5.23 (s, 1H), 3.10 (s, 2H), 2.67 (m, 2H), 2.48ꢀ2.46
(m, 2H), 1.94 (s, 6H), 1.50ꢀ1.49 (m, 6H), 1.15ꢀ1.11 (m, 6H), 1.02ꢀ
0.99 (m, 6H), 0.92ꢀ0.90 (m, 6H), ꢀ35.09 (t, J = 14.9 Hz, 1H).
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Synthesis of 1,8ꢀdibromotriptyceneꢀCH2Br 28a and 28b. The
crude material 27aꢀb (3.9 g, 86% pure, 6.24 mmol), Nꢀ
Bromosuccinimide (1.55 g, 8.74 mmol) and AIBN (0.031 g, 0.187
mmol) were dissolved in 300 mL of benzene and heated at reflux
for 3 hours. The solution was cooled to room temperature, filtered
and the organic layer was separated. The aqueous layer was
extracted with CH2Cl2 (50 mL), the combined organic layers were
dried over MgSO4 and the solvent was evaporated. After addition
of CCl4 (60 mL), the solution was heated at reflux and cooled to ꢀ
15 °C. The solution was filtered to separate the succinimide. The
solvent was evaporated and the white powder was air dried
overnight. 3.33 g of crude materials 28a and 28b were obtained
as a mixture of two isomers with a ratio 1:1 with full conversion
of the starting material 27aꢀb. The crude material was used
without further purification.
Synthesis
of
(NMe2CH2)ꢀiPrPC(sp3)PꢀIrꢀethylene
33.
Following the same procedure as for 8a, 0.142 g (0.186 mmol,
90%) of compound 33 was obtained from 0.160 g (0.207 mmol)
of (NMe2CH2)ꢀiPrPC(sp3)PꢀIr(H)(Cl) 32 and 0.040 g (0.415
mmol) of NaOtBu in 12 mL of toluene. 31P{1H} NMR (C6D6, 162
1
MHz): δ 62.59 (s). H NMR (C6D6, 600 MHz): δ 7.73 (d, J = 7.5
Hz, 1H), 7.34 (d, J = 1.6 Hz, 1H), 7.30ꢀ7.28 (m, 2H), 7.04ꢀ7.01
(m, 2H), 6.94ꢀ6.91 (m, 3H), 5.33 (s, 1H), 3.20 (s, 2H), 2.77 (t, J =
2.4 Hz, 4H), 2.60ꢀ2.58 (m, 2H), 2.43ꢀ2.41 (m, 2H), 1.99 (s, 6H),
1.13 (q, J = 7.0 Hz, 6H), 0.91ꢀ0.85 (m, 18H). 13C NMR (C6D6,
151 MHz): δ 168.6 (t, J = 19.7 Hz, 2C), 156.8, 148.3, 147.1 (t, J =
7.9 Hz, 2C), 135.4 (t, J = 20.2 Hz, 2C), 134.3, 129.9, 125.9 (2C),
124.9 (t, J = 2.9 Hz, 2C), 124.9 (2C), 123.9, 123.4, 67.8 (t, J =
5.2 Hz, 1C), 64.6, 55.1, 45.1, 34.5, 29.8 (t, J = 11.6 Hz, 2C), 28.8
(t, J = 1.8 Hz, 4C), 25.9 (t, J = 17.6 Hz, 2C), 22.7 , 20.5 (t, J = 3.2
Hz, 1C), 19.7, 18.9, 18.9 (2C), 14.3. Anal. Calcd for C37H50IrNP2:
C 58.25, H 6.61, N 1.84; found: C 57.32, H 7.10, N 1.64.
Synthesis of 1,8ꢀdibromotriptyceneꢀCH2NMe2 29, 30. The
crude material 28aꢀb (3.33 g, 6.59 mmol) and dimethylamine (40
wt. % in H2O, 12.5 mL, 99 mmol) were dissolved in 13 mL of
toluene and the solution was heated at reflux for 3 h. After
cooling to room temperature, 60 mL of HCl 2N was added. The
organic layer was washed with Et2O (3x50 mL) and 120 mL of
NaOH (2N) was added dropwise. The aqueous layer was
extracted with CH2Cl2 (4x50 mL), the combined organic layers
were dried on MgSO4 and the solvent was evaporated. The crude
product was purified by chromatography on silica gel (EtOAcꢀ
NEt3, 10:0.5) affording 29 (0.97 g, 2.06 mmol, 32%) and 30 (1.00
g, 2.12 mmol, 33%) as white powders. NOESY experiments
allowed easy distinction between the two amines by observation
of an NOE enhancement between the protons HaꢀHd and HbꢀHc.
General procedure for transfer dehydrogenation of COA
with TBE catalyzed by 8a. In an argon filled glovebox, a 4 mL
Kontes vial equipped with a Teflon screwꢀcap was charged with
the complex 8a (3.5 mg, 5.0 ꢁmol) and dissolved in a solution of
COA (1.7 g, 15.15 mmol) and TBE (1.278 g, 15.15 mmol), sealed
and heated in a preheated oilꢀbath at 200 °C. At regular intervals,
the tube was cooled to room temperature and a sample was
analyzed by gas chromatography.
General procedure for transfer dehydrogenation of nꢀoctane
with TBE catalyzed by 8a. In an argon filled glovebox, a 4 mL
Kontes vial equipped with a Teflon screwꢀcap was charged with
the complex 8a (2.1 mg, 3.0 ꢁmol, 1mM) and dissolved in a
solution of nꢀoctane (2.113 g, 3 mL, 18.5 mmol) and TBE (1.515
g, 18 mmol, 6M), sealed and heated in a preheated oilꢀbath at 200
°C. At regular intervals, the tube was cooled to room temperature
and a sample was analyzed by gas chromatography.
1
29: H NMR (CDCl3, 600 MHz): δ 7.50 (d, J = 1.6 Hz, 1H, Hd),
7.34 (d, J = 7.5 Hz, 1H, Hc), 7.30 (d, J = 7.3 Hz, 2H), 7.20 (dd, J
= 8.0 Hz, J = 1.0 Hz, 2H), 6.97 (dd, J = 7.5 Hz, J = 1.6 Hz, 1H),
6.86 (dd, J = 8.1 Hz, J = 7.3 Hz, 2H), 6.39 (s, 1H, Ha), 5.41 (s,
1H, Hb), 3.35 (s, 2H), 2.21 (s, 6H). 13C NMR (CDCl3, 151 MHz):
δ 147.8 (2C), 144.3 (2C), 143.7, 143.5, 136.9, 129.2 (2C), 127.0
(2C), 126.5, 125.4, 123.5, 122.7 (2C), 119.7 (2C), 64.3, 54.6,
52.4, 45.7 (2C). HRMS (C23H19Br2N): calc. [M + H]+: 467.9963,
General procedure for the disproportionation of 1ꢀhexene
catalyzed by 8a. In an argon filled glovebox, a 4 mL Kontes vial
equipped with a Teflon screwꢀcap was charged with the complex
8a (9.5 mg, 13.5 ꢁmol) and dissolved in nꢀhexane (2.5 g, 29.7
mmol), sealed and heated in a preheated oilꢀbath at 180 °C. At
regular intervals, the tube was cooled to room temperature and a
sample was analyzed by gas chromatography. An aliquot of 90 ꢁL
1
found [M + H]+: 467.9965. 30: H NMR (CDCl3, 600 MHz): δ
7.45 (d, J = 7.4 Hz, 1H, Hd), 7.41 (d, J = 1.6 Hz, 1H, Hc), 7.28 (d,
J = 7.3 Hz, 2H), 7.20 (dd, J = 8.1 Hz, J = 1.0 Hz, 2H), 6.98ꢀ6.93
(m, 1H), 6.86 (dd, J = 8.1 Hz, J = 7.3 Hz, 2H), 6.39 (s, 1H, Ha),
5.40 (s, 1H, Hb), 3.33 (s, 2H), 2.19 (s, 6H). 13C NMR (CDCl3, 151
MHz): δ 147.7 (2C), 145.1, 144.2 (2C), 142.1, 137.0, 129.1 (2C),
ACS Paragon Plus Environment

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ACS Catalysis
of solution was combined with 10 ꢁL of mesitylene as an internal
(7) (a) GoettkerꢀSchnetmann, I.; White, P.; Brookhart, M. J. Am.
1
2
3
4
5
6
7
8
standard.
Chem. Soc. 2004, 126, 1804ꢀ1811; (b) GottkerꢀSchnetmann, I.;
Brookhart, M. J. Am. Chem. Soc. 2004, 126, 9330ꢀ9338; (c)
GöttkerꢀSchnetmann, I.; White, P. S.; Brookhart, M.
Organometallics 2004, 23, 1766ꢀ1776; (d) MoralesꢀMorales, D.;
Redón, R. o.; Yung, C.; Jensen, C. M. Inorg. Chim. Acta 2004,
357, 2953ꢀ2956.
(8) (a) Ahuja, R.; Punji, B.; Findlater, M.; Supplee, C.; Schinski,
W.; Brookhart, M.; Goldman, A. S. Nat. Chem. 2011, 3, 167ꢀ171;
(b) Lyons, T. W.; Guironnet, D.; Findlater, M.; Brookhart, M. J.
Am. Chem. Soc. 2012, 134, 15708ꢀ15711; (c) NawaraꢀHultzsch,
A. J.; Hackenberg, J. D.; Punji, B.; Supplee, C.; Emge, T. J.;
Bailey, B. C.; Schrock, R. R.; Brookhart, M.; Goldman, A. S.
ACS Catal. 2013, 3, 2505ꢀ2514.
(9) Yao, W.; Zhang, Y.; Jia, X.; Huang, Z. Angew. Chem. Int. Ed.
2014, 53, 1390ꢀ1394.
(10) Haenel, M. W.; Oevers, S.; Angermund, K.; Kaska, W. C.;
Fan, H.ꢀJ.; Hall, M. B. Angew. Chem. Int. Ed. 2001, 40, 3596ꢀ
3600.
(11) (a) Choi, J.; MacArthur, A. H. R.; Brookhart, M.; Goldman,
A. S. Chem. Rev. 2011, 111, 1761ꢀ1779; (b) Choi, J.; Goldman,
A., IrꢀCatalyzed Functionalization of C–H Bonds. In Iridium
Catalysis, Andersson, P. G., Ed. Springer Berlin Heidelberg:
2011; Vol. 34, 139ꢀ167; (c) Haibach, M. C.; Kundu, S.;
Brookhart, M.; Goldman, A. S. Acc. Chem. Res. 2012, 45, 947ꢀ
958.
(12) (a) Goldman, A. S.; Roy, A. H.; Huang, Z.; Ahuja, R.;
Schinski, W.; Brookhart, M. Science 2006, 312, 257ꢀ261; (b)
Huang, Z.; Rolfe, E.; Carson, E. C.; Brookhart, M.; Goldman, A.
S.; ElꢀKhalafy, S. H.; MacArthur, A. H. R. Adv. Synth. Catal.
2010, 352, 125ꢀ135.
General procedure for transfer dehydrogenation of COA
with TBE catalyzed by γꢀAl2O3ꢀsupported complex 33. In an
argon filled glovebox, a 4 mL Kontes vial equipped with a Teflon
screwꢀcap was charged with the complex 33 (3.9 mg, 5.0 ꢁmol)
and dissolved in a solution of COA (1.7 g, 15.15 mmol). γꢀAl2O3
(250 mg) was added to the solution and the suspension was stirred
at room temperature for 2ꢀ4 h. After few seconds of stirring, the
solution was completely decolorized and the alumina acquired the
orange color of the pincer complex. TBE (1.278 g, 15.15 mmol)
was added to the suspension and the vial was sealed and heated in
a preheated oilꢀbath at 200 °C. At regular intervals, the tube was
cooled to room temperature and a sample was analyzed by gas
chromatography.
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ASSOCIATED CONTENT
Supporting Information
Images of NMR spectra for all new compounds and Xꢀray crystalꢀ
lographic file in CIF format of the complex 7a. This material is
available free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*Eꢀmail: mbrookhart@unc.edu
Notes
The authors declare no competing financial interests.
ACKNOWLEDGMENT
(13) Kuklin, S. A.; Sheloumov, A. M.; Dolgushin, F. M.;
Ezernitskaya, M. G.; Peregudov, A. S.; Petrovskii, P. V.; Koridze,
A. A. Organometallics 2006, 25, 5466ꢀ5476.
(14) (a) Chianese, A. R.; Mo, A.; Lampland, N. L.; Swartz, R. L.;
Bremer, P. T. Organometallics 2010, 29, 3019ꢀ3026; (b) Zuo, W.;
Braunstein, P. Organometallics 2011, 31, 2606ꢀ2615; (c)
Chianese, A. R.; Drance, M. J.; Jensen, K. H.; McCollom, S. P.;
Yusufova, N.; Shaner, S. E.; Shopov, D. Y.; Tendler, J. A.
Organometallics 2014, 33, 457ꢀ464.
We gratefully acknowledge the financial support of the National
Science Foundation as part of the Center for Enabling New Techꢀ
nologies through Catalysis (CENTC, CHEꢀ1205189).
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