[PF6]2 As catalyst for the meyer-schuster rearrangement of arylpropargylic alcohols under mild conditions

Article abstract of DOI:10.1002/ejic.201402882

The novel iridium complex [IrCpNCMe₂PPh₂Me][PF₆]₂ I efficiently catalyzed the Meyer-Schuster rearrangement of selected arylpropargylic alcohols into α,β-unsaturated aldehydes under mild conditions and without the need of a co-catalyst. A mechanism involving a hydroxy alkenylcarbene intermediate is proposed. [IrCpNCMe₂PPh₂Me][PF₆]₂ efficiently catalyzes the rearrangement of propargylic alcohols into α,β-unsaturated aldehydes under mild conditions and without the need of a co-catalyst.

Full text of DOI:10.1002/ejic.201402882

FULL PAPER
DOI:10.1002/ejic.201402882
[IrCp*(NCMe)2(PPh2Me)][PF6]2 as Catalyst for the
Meyer–Schuster Rearrangement of Arylpropargylic
Alcohols under Mild Conditions
María Talavera,[a] Jorge Bravo,[a] Luca Gonsalvi,[b]
Maurizio Peruzzini,[b] Cristiano Zuccaccia,[c] and Sandra Bolaño*[a]
Keywords: Homogeneous catalysis / Iridium / Carbene ligands / Isomerization / Tautomerization / Alcohols / Aldehydes
The novel iridium complex [IrCp*(NCMe)2(PPh2Me)][PF6]2
(I) efficiently catalyzed the Meyer–Schuster rearrangement
of selected arylpropargylic alcohols into α,β-unsaturated al-
dehydes under mild conditions and without the need of a co-
catalyst. A mechanism involving a (hydroxy)alkenylcarbene
intermediate is proposed.
synthesis of α,β-unsaturated carbonyl compounds, for ex-
ample, by aldol-like condensation reactions, are generally
multistep sequences that lack atom economy. Thus, the
quest for catalytic atom-efficient protocols running at lower
temperature and under generally milder conditions are of
interest for both academia and industry. A possible answer
to these requirements is the Meyer–Schuster rearrangement
of propargylic alcohols, which has been reported to be
efficiently catalyzed by different systems, for example, rheni-
um(I) and silver(I) complexes containing iminophos-
phorane-phosphane ligands, copper(I) diaryliodonium
salts, rhodium(I) complexes with bidentate phosphane li-
gands (rac-BINAP, dppe, or dcpe), and allyl–ruthenium(II)
and rhenium(V)–oxo complexes.[4] A drawback of this
catalytic method is, however, the need for relatively high
temperatures (323–433 K) and/or the use of an acid me-
dium.[4]
Introduction
Propargylic alcohols are organic substrates with a wide
range of applications from synthesis to catalytic reactions,[1]
which makes them very attractive as organic synthons.[2]
The isomerization of propargylic alcohols into α,β-unsat-
urated carbonyl compounds is a typical example of atom-
economic processes in which no secondary products are
generated: the process formally involves the 1,3-shift of the
hydroxy moiety followed by tautomerization (Meyer–
Schuster rearrangement, Scheme 1).
Scheme 1. Meyer–Schuster rearrangement of propargylic alcohols.
We have recently reported on the reactions of
[IrCp*Cl(NCMe)(L)][PF6] (L = PMe3, PPh2Me) with prop-
argylic alcohols.[5,6] The (methoxy)alkenylcarbene com-
plexes obtained undergo a cyclometalation reaction to yield
iridacycles containing different numbers of atoms.[6] Con-
tinuing our interest in the organometallic reactivity of these
species and to understand the mechanism of these reac-
tions, we synthesized the complex [IrCp*(NCMe)2-
(PPh2Me)][PF6]2 (I) and studied its reactivity with different
propargylic alcohols. Unexpectedly, complex I turned out
to be a good catalyst for propargylic alcohol isomerization
by Meyer–Schuster rearrangement. The scope of the cata-
lyst reaction was studied by using a small library of prop-
argylic alcohols. Interestingly, it was possible to perform the
catalytic reactions under very mild temperature conditions
with good-to-excellent conversions. A mechanistic in-
terpretation is also proposed based on NMR studies of stoi-
chiometric reactions.
α,β-Unsaturated carbonyl compounds represent an inter-
esting class of organic molecules because they undergo typi-
cal reactions of alkenes and carbonyl compounds, are valu-
able building blocks in organic synthesis, and are important
intermediates in the production of natural products of bio-
logical and pharmaceutical importance.[3] The traditional
[a] Departamento de Química Inorgánica, Facultad de Química,
Universidad de Vigo,
36310 Vigo, Spain
E-mail: bgs@uvigo.es
http://webs.uvigo.es/webc09/inorganica.php?mod=qi2
[b] Consiglio Nazionale delle Ricerche, Istituto di Chimica dei
Composti Orgnometallici (ICCOM-CNR),
Via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze,
Italy
[c] Dipartimento di Chimica, Università di Perugia,
Via Elce di Sotto 8, 06123 Perugia, Italy
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Table 1. Meyer–Schuster rearrangement of a small library of prop-
Results and Discussion
argylic alcohols catalyzed by [IrCp*(NCMe)2(PPh2Me)][PF6]2 (I).[a]
[IrCp*(NCMe)2(PPh2Me)][PF6]2 (I) as Propargylic Alcohol
Isomerization Catalyst
Complex I was easily synthesized as shown in Equa-
tion (1). The experimental conditions and characterization
data for I are reported in the Exp. Sect.
(1)
First, we studied the stoichiometric reaction of I with
1,1-diphenyl-2-propyn-1-ol (1a) in dichloromethane at
room temperature. To our surprise, instead of the expected
formation of a well-defined organometallic derivative, 3,3-
diphenylpropenal (1b) was obtained quantitatively together
with I [Equation (2)].
(2)
To determine whether this reaction could occur under
catalytic conditions, 1a and I (5 mol-%) were dissolved in
CD2Cl2 (0.6 mL) and transferred into an NMR tube. After
2 hours at room temperature, total conversion into 1b was
observed (Table 1, entry 1). Lowering the catalyst loading
to 1 mol-% and performing the reaction for 24 h gave a
maximum conversion of around 70%.
1
[a] All isomerization reactions were monitored by H NMR spec-
troscopy. The reactions were performed in an NMR tube at room
temp. in CD2Cl2 and with a ratio of [substrate]/[I] = 20. [b] [Sub-
strate]/[I] = 10. [c] Yields were determined by 1H NMR spec-
troscopy. The yields of the isolated products (after purification) are
given in parentheses.
The scope of the reaction was extended to a series of
differently substituted propargylic alcohols (2a–5a). The
corresponding aldehydes (2b–5b) were obtained in good
yields under very mild conditions (r.t., 5 mol-% of I;
Table 1). Higher conversions could be obtained in most of
the cases by increasing the amount of catalyst to 10 mol-%.
It is important to note that 1) all the reactions shown in
Table 1 took place at room temperature and in the absence
of any co-catalyst, unlike other reported examples,[4] 2) ana-
lytically pure aldehydes could be isolated from the reaction
mixture by simple extraction with diethyl ether from the
oily residue obtained after removal of the reaction solvent
under vacuum and purification through a silica column.
Different behavior was observed for the propargylic
alcohols 1-phenyl-2-propyn-1-ol (6a), 1-(4-nitrophenyl)-1-
phenyl-2-propyn-1-ol (7a), and 3-butyn-1-ol (8a). Instead of
the corresponding α,β-unsaturated aldehyde, the treatment
of 6a with I (5 mol-%) in CD2Cl2 at moderate temperature
(308 K) gave a diastereomeric mixture of the dipropargyl
ether 6b [Equation (3)] in low conversion (ca. 25%, esti-
mated by NMR).
(3)
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Interestingly, in the case of the reaction of 7a with I occurred. The reaction was repeated under stoichiometric
[Equation (4)], the isomerization reaction occurred to give conditions, and in this case it was possible to obtain the
a mixture of aldehyde 7b as the E and Z isomers (ca. 1.2:1 oxacyclocarbenecomplexes[IrCp*{=C1O(CH2)2C4H2(C1–C4)}(NCMe)-
mol ratio, estimated by NMR) in low conversion (27% of (PPh2Me)][PF6]2 (III) and [IrCp*{=C1O(CH2)2C4H2(C1–
the isolated isomers) together with the carbonyl complex C4)}2(PPh2Me)][PF6]2 (IV) in an approximately 3:1 mol ra-
[IrCp*{CH=C(p-NO2-C6H4)(Ph)}(CO)(PPh2Me)][PF6] (II, tio [estimated by NMR, Equation (5)].
ca. 1:1 mol ratio of the cis and trans isomers of Cα–Cβ,
The formation of the cyclic carbene ligand in III and IV
estimated by NMR). The formation of compound II from 3-butyn-1-ol (8a) can be explained through the
can be explained by the decarbonylation of the “acyl inter- formation of hydroxyvinylidene intermediate A, in which
mediate” D (see Scheme 2). Aldehyde 7b and II were sepa- the metal-coordinated vinylidene carbon atom undergoes
rated from the reaction mixture, isolated, and fully charac- intramolecular nucleophilic attack by the alcohol function-
terized.
ality. The formation of hydroxyvinylidene intermediates
Finally, when 8a was treated with I under the standard from propargylic alcohols is well reported in the litera-
conditions described above (Table 1) no catalytic reaction ture.[7]
(4)
(5)
(6)
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Slightly different behavior was observed by repeating this idene ligand gives the (hydroxy)alkenylcarbene complex C.
last reaction with the monoacetonitrile complex analogue Upon tautomerization, C transforms into the acyl complex
of I, [IrCp*Cl(NCMe)(PPh2Me)][PF6] (V). In this case, the D. The corresponding aldehyde is eliminated through a de-
oxacyclocarbene complex [IrCp*Cl{=C1O(CH2)2C4H2(C1– metalation process to regenerate the catalyst I.
C4)}(PPh2Me)][PF6] (VI) was formed, and upon treatment
This mechanism differs to that suggested by Gimeno and
with AgPF6 and 8a, the aforementioned complex IV was co-workers,[4g] which is based on the formation of an allen-
obtained [Equation (6)]. Compounds III, IV, and VI were ylidene intermediate by dehydration of the (hydroxy)-
fully characterized.
vinylidene complex with the subsequent re-addition of
To establish further the scope of this method, the reac- water at the α carbon of the allenylidene ligand to give the
tion was performed with the alkylpropargylic alcohols 2- (hydroxy)alkenylcarbene.
methyl-3-butyn-2-ol, 3-methyl-1-pentyn-3-ol, 3-ethyl-1-
To further validate our working hypothesis, our catalytic
pentyn-3-ol, 1-ethynyl-1-cyclopentanol, and 1-ethynyl-1-cy- reactions were carried out in the presence of molecular
clohexanol as substrates under the conditions described sieves as drying agent to ensure that water is not involved in
above (Table 1). In all cases only decomposition products our reactions. The Meyer–Schuster rearrangement products
were observed, so the Meyer–Schuster rearrangement does were formed in the same yields as in the original experi-
not occur with alkylpropargylic alcohols under these condi- ments (Table 1). This indicates the absence of an allenylid-
tions.
ene intermediate in our reactions because the presence of
the drying agent precludes the formation of the (hydroxy)-
alkenylcarbene through the addition of water (to the allen-
ylidene moiety).
Proposed Mechanism for the Meyer–Schuster
Rearrangement Catalyzed by I
Indirect proof of the conversion of B into C is the forma-
Based on the experimental results and the formation of tion of the oxacyclocarbene III, which was obtained by in-
complexes II and III, the mechanism presented in Scheme 2 tramolecular attack of the hydroxy group at the α carbon
can be proposed.
[Equation (5)], whereas the formation of the acyl complex
The first step involves the decoordination of one aceto- D is compatible with the reaction to give product II. The
nitrile ligand followed by coordination of the substrate to formation of an Ir–carbonyl complex (e.g., II) via an acyl
give vinylidene intermediate B. Then intramolecular nucleo- complex, which we have previously observed,[5] is probably
philic attack of the OH group at the α carbon of the vinyl- linked to the deactivation of the catalyst, which prevents
Scheme 2. Proposed mechanism for the Meyer–Schuster rearrangement catalyzed by I.
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solution. The solvent was removed under vacuum and the solid
obtained was redissolved in dichloromethane. The solution was fil-
tered through Celite® and the solvent removed under vacuum to
yield a yellow solid that was washed with diethyl ether (3ϫ 5 mL)
the regeneration of I, thereby lowering the reaction yield,
as in the case of the catalytic reaction with 7a. This reaction
may be due to the electron-withdrawing effect of the NO2
substituent on the phenyl group because when a π donor
(OMe) or a weak electron donor (Me) are the substituents
on the phenyl group, the Ir–carbonyl complex was not
formed.
and vacuum-dried, yield 450 mg (60%). IR: ν = (CN) 2329 and
˜
2301 (w); (PF6) 837 (s) cm–1. 1H NMR (CD2Cl2): δ = 7.65–7.60 (m,
5
6 H, PPh2CH3), 7.55–7.47 (m, 4 H, PPh2CH3), 2.59 (d, JHP
=
2
1.1 Hz, 6 H, NCCH3), 2.47 (d, JHP = 10.6 Hz, 3 H, PPh2CH3),
1.66 [d, JHP = 2.5 Hz, 15 H, C5(CH3)5] ppm. 31P{1H} NMR
4
1
(CD2Cl2): δ = –8.85 (s, PPh2CH3), –144.13 (sept, JPF = 710.7 Hz,
PF6) ppm. 13C{1H} NMR (CD2Cl2): δ = 133.1 (s, 1 C, PPh2Me),
Conclusions
3
2
132.3 (d, JCP = 9.9 Hz, 2 C, PPh2Me), 129.9 (d, JCP = 11.1 Hz,
2 C, PPh2Me), 127.5 (d, JCP = 58.2 Hz, 2 C, Cipso), 98.1 [s,
C5(CH3)5], 124.5 (s, NCCH3), 12.5 (d, JCP = 40.3 Hz, PPh2CH3),
1
In this work we have synthesized the new iridium com-
plex [IrCp*(NCMe)2(PPh2Me)][PF6]2 (I), which was used
as a homogeneous catalyst for the Meyer–Schuster re-
arrangement of propargylic alcohols without the need of a
co-catalyst to give the corresponding aldehydes in good
yields at room temperature. Although the catalytic protocol
is efficient for aryl substrates, in the case of
HCϵCCR1R2OH, in which neither R is a phenyl group, no
activity was observed.
A mechanism for the rearrangement reaction has been
proposed involving the formation of a (hydroxy)alkenyl-
carbene intermediate arising from the intramolecular attack
of the OH group at the α carbon of the vinylidene formed
in the first step of the catalytic cycle. The (hydroxy)alkenyl-
carbene evolves to an acyl complex that finally releases the
α,β-unsaturated aldehyde.
1
8.8 [s, C5(CH3)5], 4.0 (s, NCCH3) ppm.
General Procedure for the Catalytic Isomerization of Propargylic
Alcohols into α,β-Unsaturated Aldehydes: In an NMR tube the cata-
lyst (5 mg, 0.006 mmol) was dissolved under argon in CD2Cl2
(0.6 mL). Then the corresponding propargylic alcohol (0.12 mmol)
was added and the reaction mixture was left at room temperature
for the chosen time (see Table 1). The solvent was removed under
vacuum and the corresponding aldehyde was extracted from the
obtained oil with diethyl ether and purified through a silica column
using hexane/AcOEt (4:1) as eluent.
3,3-Di-p-tolylacrylaldehyde (3b): IR: ν = (CO) 1661 (s) cm–1. 1H
˜
3
NMR (CD3Cl): δ = 9.50 (d, JHH = 8.0 Hz, 1 H, CHO), 7.28–7.21
(m, 4 H, Ph), 7.21–7.14 (m, 4 H, Ph), 6.45 (d, JHH = 7.9 Hz, 1 H,
3
=CH), 2.42 (s, 3 H, CH3), 2.37 (s, 3 H, CH3) ppm. 13C{1H} NMR
(CD3Cl): δ = 193.9 (s, CHO), 162.7 (s, =C), 141.1 (s, C-CH3), 139.8
(s, C-CH3), 137.3 (s, Cipso), 134.1 (s, Cipso), 131.0 (s, 2 C, Ph), 129.5
(s, 2 C, Ph), 129.1 (s, 2 C, Ph), 128.9 (s, 2 C, Ph), 126.6 (s, =CH),
21.5 (s, 2 C, CH3) ppm. MS (m/z, referred to the most abundant
isotopes): m/z = 237.1239 [M + 1]+, 236.1202 [M]+, 221.10 [M –
CH3]+.
Experimental Section
General: All experiments were carried out under argon using
Schlenk techniques. Solvents were dried by the usual procedures[8]
and distilled under argon prior to use. The starting materials
[IrCp*Cl2(PPh2Me)][9] and [IrCp*Cl(NCMe)(PPh2Me)]PF6 (V)[5]
were prepared as described in the literature. All reagents were ob-
tained from commercial sources except for propargylic alcohols 3–
5a and 7a, which were synthesized following the method described
by Mantovani et al.[10] Aldehydes 1b,[4g] 2b,[11] 5b,[12] and diprop-
argyl ether 6b[13] were identified by comparison with the spectro-
scopic data reported in the literature. Unless stated otherwise,
NMR spectra were recorded at room temperature with a Bruker
ARX-400 spectrometer at 400 (1H), 161 (31P{1H}), and 100 MHz
(Z,E)-3-Phenyl-3-(p-tolyl)acrylaldehyde (4b): IR: ν = (CO) 1666
˜
(s) cm–1. MS (m/z, referred to the most abundant isotopes): m/z =
223.1076 [M + 1]+, 222.1042 [M]+, 207.06 [M – CH3]+, 178.06 [M –
CH3 – CHO]+.
3
Z Isomer: 1H NMR (CD3Cl): δ = 9.55 (d, JHH = 7.9 Hz, 1 H,
CHO), 7.39–7.34 (m, 4 H, Ph), 7.34–7.29 (m, 1 H, Ph), 7.23–7.16
3
(m, 4 H, Ph-CH3), 6.57 (d, JHH = 7.9 Hz, 1 H, =CH), 2.39 (s, 3
H, CH3) ppm. 13C{1H} NMR (CD3Cl): δ = 193.8 (s, CHO), 162.4
(s, =C), 139.9 (s, C-CH3), 137.0 (s, Cipso-Ph-CH3), 133.9 (s, Cipso
-
Ph), 131.0–128.4 (all s, Ph, Ph-CH3), 127.3 (s, =CH), 21.5 (s,
CH3) ppm.
1
(13C{1H}) using the solvent as the internal lock. H and 13C{1H}
signals are referenced to internal TMS and those of 31P{1H} to
85% H3PO4; downfield shifts (expressed in ppm) are considered
positive. 1H and 13C{1H} NMR (or JMOD) signal assignments
were confirmed by {1H,1H}-COSY, {1H,1H}-NOESY, {1H,13C}-
HSQC, {1H,13C}-HMBC and DEPT experiments. Coupling con-
stants are given in Hz. IR spectra were recorded with a Jasco FT/
IR–6100 spectrometer using KBr pellets. CHN analyses were car-
ried out with a Carlo–Erba 1108 analyzer. Mass spectra were ac-
quired with an Apex-Qe spectrometer by using the high-resolution
electrospray technique for organometallic complexes and the high-
and low-resolution electron impact techniques for organic com-
pounds.
3
E Isomer: 1H NMR (CD3Cl): δ = 9.51 (d, JHH = 8.0 Hz, 1 H,
CHO), 7.51–7.39 (m, 4 H, Ph), 7.34–7.29 (m, 1 H, Ph), 7.29–7.23
3
(m, 4 H, Ph-CH3), 6.60 (d, JHH = 8.0 Hz, 1 H, =CH), 2.44 (s, 3
H, CH3) ppm. 13C{1H} NMR (CD3Cl): δ = 193.8 (s, CHO), 162.6
(s, =C), 141.2 (s, C-CH3), 137.0 (s, Cipso-Ph-CH3), 137.0 (s, Cipso
-
Ph), 131.0–128.4 (all s, Ph, Ph-CH3), 126.7 (s, =CH), 21.5 (s,
CH3) ppm.
(Z,E)-3-Phenyl-3-(p-nitrophenyl)acrylaldehyde (7b): After 2 d at
room temperature, the solvent was removed under vacuum and the
organic fraction was extracted from the obtained oil with diethyl
ether, a mixture of 7a and 7b was obtained (ca. 70:30 mol ratio,
estimated by NMR). They were separated and purified through a
silica column using, in this case, hexane/AcOEt (9:1) as eluent. A
mixture of E and Z isomers of 7b was obtained in a ca. 1.2:1 mol
[IrCp*(NCMe)2(PPh2Me)][PF6]2 (I): An orange solution of
[IrCp*Cl2(PPh2Me)] (500 mg, 0.83 mmol) in acetonitrile (35 mL)
was treated with silver(I) hexafluorophosphate (465 mg, ratio (estimated by NMR), yield (isolated isomeric mixture):
1.84 mmol). The reaction mixture was stirred for 5 min at room
temperature, and then was decanted and filtered to obtain a yellow
16.3 mg (27%). IR: ν = (CO) 1663 (s); (NO ) 1518 (s) and 1347
˜
2
(s) cm–1.
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3
1
Z Isomer: 1H NMR (CD3Cl): δ = 9.49 (d, JHH = 8.0 Hz, 1 H,
PPh2CH3), –144.11 (sept, JPF = 711.1 Hz, PF6) ppm. 13C{1H}
2
CHO), 8.26–8.20 (m, 2 H, 3-H), 7.56–7.48 (m, 2 H, 2-H), 7.48– NMR (CD2Cl2): δ = 271.6 (d, JCP = 10.4 Hz, Ir=C), 133.6–130.0
3
1
1
7.44 (m, 1 H, Ph), 7.34–7.27 (m, 4 H, Ph), 6.69 (d, JHH = 8.0 Hz, (PPh2Me), 128.9 (d, JCP = 60.9 Hz, Cipso), 127.7 (d, JCP
=
1 H, =CH) ppm. 13C{1H} NMR (CD3Cl): δ = 192.1 (s, CHO), 59.2 Hz, Cipso), 124.9 (s, NCCH3), 102.1 [d, 2JCP = 1.6 Hz, C5(CH3)5],
159.4 (s, =C), 148.5 (s, C-4), 143.4 (s, C-1), 138.5 (s, Cipso-Ph), 92.6 (s, O-CH2), 57.0 (s, =C-CH2), 21.0 (s, CH2CH2CH2), 12.2 (d,
131.6–128.2 (all s, Ph, C-2), 129.1 (s, =CH), 124.0 (s, C-3) ppm.
1JCP = 42.6 Hz, PPh2CH3), 8.9 [s, C5(CH3)5], 4.5 (s, NCCH3) ppm.
3
E Isomer: 1H NMR (CD3Cl): δ = 9.59 (d, JHH = 7.7 Hz, 1 H,
[IrCp*{=C1O(CH2)2C4H2(C1–C4)}2(PPh2Me)][PF6]2 (IV): 3-Butyn-
1-ol (8a; 18 μL, 0.23 mmol) was added to a yellow solution of VI
(150 mg, 0.19 mmol) in dichloromethane (10 mL) and the mixture
was stirred for 5 min. Silver(I) hexafluorophosphate (59 mg,
0.23 mmol) was then added. The mixture was stirred for 2 h and
then the clear brown solution obtained was filtered through Celite®
and the solvent removed under vacuum to yield a brown solid that
was washed with diethyl ether (3ϫ 4 mL) and dried in vacuo, yield
CHO), 8.37–8.31 (m, 2 H, 3-H), 7.56–7.48 (m, 2 H, 2-H, Ph), 7.44–
3
7.37 (m, 2 H, Ph), 6.62 (d, JHH = 7.7 Hz, 1 H, =CH) ppm.
13C{1H} NMR (CD3Cl): δ = 192.9 (s, CHO), 159.4 (s, =C), 148.8
(s, C-4), 146.1 (s, C-1), 135.6 (s, Cipso-Ph), 131.6–128.2 (all s, Ph,
C-2), 130.3 (s, =CH), 123.8 (s, C-3) ppm.
[IrCp*{CH=C(p-NO2-C6H4)(Ph)}(CO)(PPh2Me)]PF6 (II): From
the previous experiment, the remaining solid after the extraction of
7a and 7b was washed with pentane (2 mL) and dried in vacuo to
yield a mixture of the cis and trans isomers (ca. 1:1 mol ratio of the
cis and trans isomers at Cα–Cβ, estimated by NMR), yield (isolated
(isolated product): 182 mg (73%). IR: ν = (PF ) 838 (s) cm–1. 1H
˜
6
NMR (CD2Cl2): δ = 7.67–7.54 (m, 6 H, PPh2CH3), 7.17–7.07 (m,
4 H, PPh2CH3), 5.33–5.25 (m, 2 H, O-CH2), 5.07–4.96 (m, 2 H, O-
2
2
CH2), 3.14 (t, JHP = 7.5 Hz, 4 H, =C-CH2), 2.34 (d, JHP
=
isomeric mixture): 5.3 mg (95%). IR: ν = (CO) 2029 (s); (PF ) 841
˜
6
10.5 Hz, 3 H, PPh2CH3), 2.25–2.15 (m, 2 H, CH2CH2CH2),
(s) cm–1. MS (m/z, referred to the most abundant isotopes): m/z =
780 [M]+. C38H39F6IrNO3P2 (925.89): calcd. C 49.30, H 4.25, N
1.51; found C 49.51, H 4.33, N 1.60.
4
2.07–1.98 (m, 2 H, CH2CH2CH2), 1.77 [d, JHP = 2.0 Hz, 15 H,
C5(CH3)5] ppm. 31P{1H} NMR (CD2Cl2): δ = –10.27 (s, PPh2CH3),
1
–144.14 (sept, JPF
=
711.4 Hz, PF6) ppm. 13C{1H} NMR
1
3
2
4
cis Isomer: H NMR (CD2Cl2): δ = 8.07 (d, JHH = 8.7 Hz, 2 H,
3-H), 7.61–7.74 (m, 2 H, PPh2CH3), 7.39–7.56 (m, 5 H, PPh2CH3),
(CD2Cl2): δ = 266.2 (d, JCP = 9.4 Hz, Ir=C), 133.4 (d, JCP
=
3
2.6 Hz, PPh2Me), 132.1 (d, JCP = 10.4 Hz, PPh2Me), 130.0 (d,
3
2JCP = 11.5 Hz, PPh2Me), 128.0 (d, JCP = 61.8 Hz, Cipso), 106.3
1
7.20–7.34 (m, 6 H, Ph, PPh2CH3), 7.18 (d, JHP = 8.6 Hz, 1 H, α-
H), 7.07 (d, JHH = 8.4 Hz, 2 H, Ph), 6.57 (d, JHH = 8.5 Hz, 2 H,
3
3
[s, C5(CH3)5], 90.6 (s, 2 C, O-CH2), 58.3 (s, 2 C, =C-CH2), 21.9 (s,
2
4
1
2-H), 2.37 (d, JHP = 10.5 Hz, 3 H, PPh2CH3), 1.86 [d, JHP
=
2 C, CH2CH2CH2), 15.5 (d, JCP = 43.6 Hz, PPh2CH3), 9.3 [s,
2.8 Hz, 15 H, C5(CH3)5] ppm. 31P{1H} NMR (CD2Cl2): δ = –14.92
C5(CH3)5] ppm. MS (m/z, referred to the most abundant isotopes):
m/z = 667.23287 [M]+. C31H40F12IrO2P3 (957.78): calcd. C 38.88,
H 4.21; found C 39.21, H 4.29.
(s, PPh2CH3), –144.49 (sept, JPF = 710.7 Hz, PF6) ppm. 13C{1H}
1
2
NMR (CD2Cl2): δ = 166.5 (d, JCP = 13.7 Hz, CO), 152.7 (s, C-
β), 150.6 (s, C-1), 147.5 (s, C-4), 143.3 (s, Cipso), 126.6–133.6 (Ph,
[IrCp*Cl{=CO(CH2)2CH2}(PPh2Me)]PF6 (VI): 3-Butyn-1-ol (8a;
17.5 μL, 0.22 mmol) was added to a yellow solution of V (150 mg,
0.20 mmol) in methanol (15 mL), and the mixture was stirred for
20 min. The yellow solution obtained was concentrated under vac-
uum to around 2 mL and a yellow solid precipitated. This product
was separated by decantation, washed with diethyl ether (3ϫ
2
PPh2Me), 131.0 (s, 2 C, C-2), 124.0 (s, 2 C, C-3), 116.2 (d, JCP
13.7 Hz, C-α), 104.2 [s, C5(CH3)5], 12.4 (d, JCP = 43.8 Hz,
PPh2CH3), 9.0 [s, C5(CH3)5] ppm.
=
1
1
3
trans Isomer: H NMR (CD2Cl2): δ = 8.10 (d, JHH = 8.7 Hz, 2 H,
3
3-H), 7.63–7.74 (m, 4 H, PPh2CH3), 7.45 (d, JHP = 7.8 Hz, 1 H,
α-H), 7.39–7.55 (m, 6 H, PPh2CH3), 7.22–7.34 (m, 5 H, Ph, 2-H),
3 mL), and dried in vacuo, yield (isolated product): 91 mg (58%).
3
2
1
IR: ν = (PF ) 838 (s) cm–1. H NMR (CD Cl ): δ = 7.62–7.41 (m,
6.46 (d, JHH = 6.5 Hz, 2 H, Ph), 2.40 (d, JHP = 10.5 Hz, 3 H,
˜
6
2
2
4
PPh2CH3), 1.85 [d, JHP = 2.3 Hz, 15 H, C5(CH3)5] ppm. 31P{1H}
10 H, PPh2CH3), 5.26–5.18 (m, 1 H, O-CH2), 5.03–4.95 (m, 1 H,
1
2
NMR (CD2Cl2): δ = –14.51 (s, PPh2CH3), –144.49 (sept, JPF
=
O-CH2), 2.49–2.37 (m, 1 H, =C-CH2), 2.34 (d, JHP = 10.6 Hz, 3
710.7 Hz, PF6) ppm. 13C{1H} NMR (CD2Cl2): δ = 165.2 (d, JCP
= 12.9 Hz, CO), 150.4 (s, C-β), 149.6 (s, C-1), 146.6 (s, C-4), 144.8
(s, Cipso), 126.6–133.6 (Ph, PPh2Me, C-2), 124.0 (s, 2 C, C-3), 122.4
2
H, PPh2CH3), 2.25–2.13 (m, 1 H, =C-CH2), 1.97–1.85 (m, 1 H,
4
CH2CH2CH2), 1.62 [d, JHP = 2.2 Hz, 15 H, C5(CH3)5], 1.50–1.38
(m, 1 H, CH2CH2CH2) ppm. 31P{1H} NMR (CD2Cl2): δ = –17.30
2
1
1
(s, PPh2CH3), –144.16 (sept, JPF = 710.6 Hz, PF6) ppm. 13C{1H}
(d, JCP = 13.6 Hz, C-α), 104.0 [s, C5(CH3)5], 13.3 (d, JCP
43.4 Hz, PPh2CH3), 9.0 [s, C5(CH3)5] ppm.
=
NMR (CD2Cl2): δ = 275.8 (d, 2JCP = 11.7 Hz, Ir=C), 132.7 (d, 2JCP
2
= 9.9 Hz, PPh2Me), 132.3 (d, JCP = 9.6 Hz, PPh2Me), 132.25 (d,
Synthesis of [IrCp*{=C1O(CH2)2C4H2(C1–C4)}(NCMe)(PPh2Me)]-
[PF6]2 (III): 3-Butyn-1-ol (8a; 31 μL, 0.39 mmol) was added to a
yellow solution of I (150 mg, 0.18 mmol) in dichloromethane
(10 mL), and the mixture was stirred for 18 h at room temperature.
The brown solution obtained was concentrated under vacuum and
a brown solid precipitated. This product was washed with diethyl
ether (3ϫ 3 mL) and dried in vacuo. A mixture of complexes III
and IV was obtained in an approximately 3:1 mol ratio (estimated
by NMR), yield (isolated mixture): 105 mg (ca. 67% for III).
4
4JCP = 3.7 Hz, PPh2Me), 132.2 (d, JCP = 2.8 Hz, PPh2Me), 130.9
1
1
(d, JCP = 59.6 Hz, Cipso), 130.4 (d, JCP = 57.8 Hz, Cipso), 129.2
3
3
(d, JCP = 4.0 Hz, PPh2Me), 129.1 (d, JCP = 4.1 Hz, PPh2Me),
2
3
99.7 [d, JCP = 2.0 Hz, C5(CH3)5], 90.2 (s, O-CH2), 56.7 (d, JCP
=
1
1.8 Hz, =C-CH2), 21.0 (s, CH2CH2CH2), 12.9 (d, JCP = 42.3 Hz,
PPh2CH3), 8.8 [s, C5(CH3)5] ppm. MS (m/z, referred to the most
abundant isotopes): m/z = 633.16309 [M]+. C27H34ClF6IrOP2
(778.18): calcd. C 41.67, H 4.40; found C 41.68, H 4.41.
1
III: IR: ν = (CN) 2292 and 2328 (w); (PF ) 837 (s) cm–1. H NMR
˜
6
Acknowledgments
(CD2Cl2): δ = 7.67–7.56 (m, 6 H, PPh2CH3), 7.51–7.42 (m, 2 H,
PPh2CH3), 7.35–7.27 (m, 2 H, PPh2CH3), 5.49–5.46 (m, 1 H, O-
CH2), 5.18–5.08 (m, 1 H, O-CH2), 3.01–2.86 (m, 1 H, =C-CH2), The authors thank the University of Vigo CACTI services for re-
2
2.83 (s, 3 H, NCCH3), 2.46 (d, JHP = 10.7 Hz, 3 H, PPh2CH3), cording the NMR and mass spectra and carrying out the elemental
2.16–2.09 (m, 1 H, CH2CH2CH2), 1.89–1.76 (m, 1 H, =C-CH2), analyses. M. T. thanks the University of Vigo for funding through
4
1.72 [d, JHP = 2.1 Hz, 15 H, C5(CH3)5], 1.72–1.60 (m, 1 H, a Predoctoral Fellowship and the Spanish Ministry of Education
CH2CH2CH2) ppm. 31P{1H} NMR (CD2Cl2): δ = –14.05 (s,
(MINECO) for a mobility grant.
Eur. J. Inorg. Chem. 2014, 6268–6274
6273
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
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Received: September 17, 2014
Published Online: November 25, 2014
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© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim