Iridium-assisted C≡C bond cleavage of 1-alkyne by water: Preparation of new alkyl derivatives

Article abstract of DOI:10.1039/b303635a

Alkyl complexes IrCl₂(η¹-CH₂Ar)(CO) (PPh₃)₂ (1) [Ar = Ph (a), p-tolyl (b)] were prepared by allowing the hydride mer- or fac-IrHCl₂(PPh₃)₃ to react with terminal alkynes ArC≡CH in the presence of water. The complexes were characterized spectroscopically (IR and ¹H, ³¹P, ¹³C NMR) and by the X-ray crystal structure determination of 1b. The acyl complex IrCl₂{C(O)CH₂ C(CH₃)₃}(PPh₃)₂ (2) was also prepared by reacting mer-IrHCl₂(PPh₃)₃ with tert-butylacetylene HC≡CC(CH₃)₃ in the presence of H₂O. A reaction path for the hydration of terminal alkyne in the presence of the Ir(III) complex leading to the cleavage of the C≡C bond, with the formation of the complexes 1 or 2 is also proposed. Acetylide complexes IrHCl(C≡CAr) (PPh₃)₃ (3), IrHCl(C≡CAr) (AsPh₃)₃ (4) [Ar = Ph (a), p-tolyl (b)] and IrHCl(C≡CPh){PPh(OEt)₂}(PPh₃)₂ (5) were prepared by reacting IrHCl₂L₃ (L = PPh₃, AsPh₃) or IrHCl₂ {PPh(OEt)₂}(PPh₃)₂ with lithium acetylide. Protonation reaction with Bronsted acids of the acetylide 3 was also studied and led to unstable vinyl derivatives. The stable vinyl [IrCl{η²-CH=C(H)COOMe}L₂]BPh₄ (6,7) [L = PPh₃ (6), AsPh₃ (7)] complexes, instead, were prepared by allowing IrHCl₂L₃ to react first with AgCF₃SO₃ and then with methyl propiolate.

Full text of DOI:10.1039/b303635a

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᎐
Iridium-assisted C᎐C bond cleavage of 1-alkyne by water:
᎐
preparation of new alkyl derivatives
Gabriele Albertin,*a Stefano Antoniutti,a Alessia Bacchi,b Giancarlo Pelizzib
and Francesca Piasentea
a Dipartimento di Chimica, Università Ca’ Foscari di Venezia, Dorsoduro 2137, 30123 Venezia,
Italy
b Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica,
Università di Parma, Parco Area delle Scienze 17/A, 43100 Parma, Italy
Received 1st April 2003, Accepted 23rd May 2003
First published as an Advance Article on the web 18th June 2003
Alkyl complexes IrCl2(η1-CH2Ar)(CO)(PPh3)2 (1) [Ar = Ph (a), p-tolyl (b)] were prepared by allowing the hydride
᎐
mer- or fac-IrHCl (PPh ) to react with terminal alkynes ArC᎐CH in the presence of water. The complexes were
᎐
2
3 3
characterized spectroscopically (IR and 1H, 31P, 13C NMR) and by the X-ray crystal structure determination of 1b.
The acyl complex IrCl2{C(O)CH2C(CH3)3}(PPh3)2 (2) was also prepared by reacting mer-IrHCl2(PPh3)3 with tert-
᎐
butylacetylene HC᎐CC(CH ) in the presence of H O. A reaction path for the hydration of terminal alkyne in the
᎐
3
3
2
᎐
presence of the Ir() complex leading to the cleavage of the C᎐C bond, with the formation of the complexes 1 or 2 is
also proposed. Acetylide complexes IrHCl(C᎐CAr)(PPh ) (3), IrHCl(C᎐CAr)(AsPh ) (4) [Ar = Ph (a), p-tolyl (b)]
and IrHCl(C᎐CPh){PPh(OEt) }(PPh ) (5) were prepared by reacting IrHCl L (L = PPh , AsPh ) or IrHCl -
᎐
᎐
᎐
᎐
᎐
3
3
3 3
᎐
᎐
2
3
2
2
3
3
3
2
{PPh(OEt)2}(PPh3)2 with lithium acetylide. Protonation reaction with Brønsted acids of the acetylide 3 was also
studied and led to unstable vinyl derivatives. The stable vinyl [IrCl{η2-CH᎐C(H)COOMe}L ]BPh (6,7) [L = PPh (6),
᎐
2
4
3
AsPh3 (7)] complexes, instead, were prepared by allowing IrHCl2L3 to react first with AgCF3SO3 and then with
methyl propiolate.
Atmosphere dry-box. Once isolated, the complexes turned out
to be quite air-stable and were stored at Ϫ25 ЊC. All solvents
used were dried over appropriate drying agents, degassed on a
vacuum line, and distilled into vacuum-tight storage flasks.
Introduction
Transition metal complexes are known to promote hydration of
unactivated alkyne affording species such as aldehydes, ketones,
or vinyl alcohol complexes.1 In some cases the metal-assisted
reaction of 1-alkynes with water has been reported to give a
C–C triple bond cleavage with the formation of CO and a
saturated hydrocarbon with one fewer carbon atom. They are
generally present as a carbonyl and η1-alkyl ligand.2–4 Among
the metal centres, a prominent role is played by those of the
iron-group. A mechanistic study on the stoichiometric Ru()-
assisted C–C fission of phenylacetylene by water involving the
participation of a Ru()–vinylidene intermediate has also been
recently reported.3a Less is known for other metal centres and,
for the iridium, the formation of an acyl [Ir]C(CO)CH2Ph
derivative by hydrolysis of phenylacetylene was reported in one
Phosphine PPh(OEt)2 was prepared by the method of Rabino-
t
witz and Pellon.6 Alkynes RC᎐CH (R = Ph, p-tolyl, Bu or
᎐
᎐
Prn, Si(CH3)3, COOMe) were Aldrich products, used without
further purification. Lithium acetylide Li [ArC᎐C] (Ar = Ph,
ϩ
Ϫ
᎐
᎐
p-tolyl) was prepared by reacting a slight excess of 1-alkyne (22
mmol) with lithium (20 mmol, 0.14 g) in 10 cm3 of tetrahydro-
furan (THF). Oxygen-18-labelled water (95 atom% 18O) was an
Aldrich product. Other reagents were purchased from com-
mercial sources in the highest available purity and used as
received. Infrared spectra were recorded on Digilab Bio-Rad
FTS-40 or Nicolet Magna 750 FT-IR spectrophotometers.
NMR spectra (1H, 13C, 31P) were obtained on Bruker AC200 or
AVANCE 300 spectrometer at temperatures between Ϫ90 and
ϩ30 ЊC, unless otherwise stated. 1H and 13C{1H} (Table 2)
spectra are referred to internal tetramethylsilane; 31P{1H}
chemical shifts are reported with respect to 85% H3PO4, with
downfield shifts considered positive. The COSY and HMQC
NMR experiments were obtained on the Bruker AVANCE 300
instrument using its standard programs. The SwaN-MR soft-
ware package7 was used to treat NMR data. The conductivity
of 10Ϫ3 mol dmϪ3 solutions of the complexes in MeNO2 at 25 ЊC
was measured with a Radiometer CDM 83 instrument.
case with a binuclear complex,4b while a carbonyl complex was
᎐
obtained in the reaction of PhC᎐CH with both a metallacyclo
᎐
complex4a and, very recently, with a water-soluble iridium
derivative.4c However, what is known of the hydrolysis of alkyne
is still rather limited and further studies on the influence of the
metal centre, the ancillary ligands and the nature of the alkyne
on the reaction course and the nature of the final product
should therefore be desirable.
We have previously reported some studies on the reactivity of
metal complexes of the iron triad and of cobalt with 1-alkynes,
which allows the synthesis of the acetylide, vinyl and vinylidene
derivatives.5 We have now extended these investigations to
include iridium as a metal centre and found a new example of
hydration of terminal alkyne promoted by a transition metal
complex which yields both alkyl-carbonyl and acyl derivatives.
The results of these studies, which also include the synthesis of
both alkynyl and vinyl complexes of Ir() and a detailed study
on the hydrolysis of the alkyne, are reported here.
Synthesis of the complexes
The hydrides mer- and fac-IrHCl2(PPh3)3, mer-IrHCl2(AsPh3)3
and IrHCl2{PPh(OEt)2}(PPh3)2 were prepared following the
reported methods.8
IrCl2(ꢀ1-CH2Ar)(CO)(PPh3)2 (1) [Ar ؍ Ph (a), p-tolyl (b)]
An excess of the appropriate alkyne (0.2 mmol) was added to a
solution of mer-IrHCl2(PPh3)3 (0.100 g, 0.095 mmol) in 10 cm3
of THF and the reaction mixture was refluxed for 1 h. The
solvent was removed under reduced pressurre giving an oil
which was triturated with ethanol (5 cm3). An orange–yellow
solid slowly separated out from the resulting solution, which
Experimental
General
All synthetic work was carried out under an inert atmosphere
(argon) using standard Schlenk techniques or a Vacuum
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
D a l t o n T r a n s . , 2 0 0 3 , 2 8 8 1 – 2 8 8 8
2881

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was filtered and recrystallized by cooling to Ϫ25 ЊC a saturated
solution prepared at room temperature by treating the solid
with 10 cm3 of ethanol and enough CH2Cl2 to dissolve it. It can
be noted that the addition of an excess of H2O (0.2 mmol, 36
µL) to the reaction mixture does not change the yield in the
Reaction of mer- or fac-IrHCl2(PPh3)3 with phenylacetylene in
NMR tube
In a vacuum-atmosphere dry box a sample of mer- or fac-IrH-
Cl2(PPh3)3 (20 mg, 0.019 mmol) was placed in a screw-cap
5-mm NMR tube and 1 cm3 of the appropriate deuterated sol-
vent (THF-d8, CD2Cl2 or C6D6) was added. An excess of phenyl-
acetylene (0.04 mmol, 4.5 µL) was added by syringe to the
resulting suspension and the NMR tube was transferred into
the probe of the spectrometer. Owing to the low solubility of
IrHCl2(PPh3)3 complex in THF-d8 and C6D6, the reaction was
carried out at 40 ЊC preheating the probe to this temperature.
To the reaction mixture in the NMR tube was also added in
some cases an excess of H2O, D2O or H218O and the reaction
was monitored by recording successive spectra.
products; yield ≥80% (Found: C, 58.45; H, 4.06; Cl, 7.70%.
—
C44H37Cl2IrOP2 (1a) requires C, 58.28; H, 4.11; Cl, 7.82%); νmax
/
cmϪ1 (CO) 2048s (KBr); δH (CD2Cl2, 293 K) 7.95–6.06 (35H, m,
Ph) and 3.55 (2H, t, CH2, JPH = 6 Hz); δP (CD2Cl2, 293 K)
Ϫ15.41 (s). (Found: C, 58.85; H, 4.19; Cl, 7.88%. C45H39Cl2-
—
IrOP2 (1b) requires C, 58.69; H, 4.27; Cl, 7.70%); νmax/cmϪ1
(CO) 2048s (KBr); δH (CD2Cl2, 293 K) 7.95–5.80 (m), 6.69, 5.95
(d) (34H, Ph), 3.52 (2H, t, CH2, JPH = 6 Hz) and 2.23 (3H, s,
CH3); δP (CD2Cl2, 293 K) Ϫ15.68 (s).
IrCl2(ꢀ1-CD2Ph)(CO)(PPh3)2 (1a-d2)
᎐
IrHCl(C᎐CAr)(PPh ) (3) [Ar ؍ Ph (a), p-tolyl (b)]
᎐
3
3
This complex was prepared in the same manner as the related
To a solution of mer-IrHCl2(PPh3)3 (0.100 g, 0.095 mmol) in
᎐
10 cm3 of THF was added an excess of the appropriate
1a by adding first an excess of PhC᎐CH (0.2 mmol, 22 µL) and
᎐
ϩ
Ϫ
3
then an excess of D2O (0.4 mmol, 7.2 µL) to a solution of
mer-IrHCl2(PPh3)3 (0.100 g, 0.095 mmol) in 10 cm3 of THF.
After 1 h of reflux of the resulting solution and the evaporation
of the solvent at reduced pressure, the addition of EtOD
allowed to separate the solid. Proton and 13C NMR spectra
confirm the selective replacement of the methylenic hydrogen
atoms of the benzylic group by deuterium.
᎐
Li [ArC᎐C] (0.38 mmol, 0.19 cm of a 2.0 M solution in THF)
᎐
and the reaction mixture refluxed for about 1 h. The solvent was
removed by evaporation under reduced pressure to give a red–
brown oil which was treated with ethanol (5 cm3). By vigorous
stirring of the resulting solution, a red–brown solid slowly
separated out, which was filtered and recrystallized from tolu-
ene–ethanol; yield ≥75% (Found: C, 66.52; H, 4.68; Cl, 3.35%.
C62H51ClIrP3 (3a) requires C, 66.69; H, 4.60; Cl, 3.17%);
—
νmax/cmϪ1 (IrH) 2168w and (C᎐C) 2098m (KBr); δ (C6D6,
IrCl2(ꢀ1-CH2Ph)(C18O)(PPh3)2 (1a-18O)
᎐
᎐
H
293 K) 7.70–6.85 (50H, m, Ph) and Ϫ11.62 (1H, dt, HϪ, 2JPHcis
=
This complex was prepared in the same manner as the related
2
18 Hz, JPHtrans = 140 Hz); δP (C6D6, 293 K) spin syst A2B, δA
—
1a-d2 using H218O (95 atom% 18O) instead of D2O. νmax/cmϪ1
Ϫ4.92, δB Ϫ22.36, JAB = 15 Hz. (Found: C, 66.78; H, 4.68; Cl,
18
᎐
(C᎐ O) 2005 (KBr).
᎐
3.01%. C63H53ClIrP3 (3b) requires C, 66.92; H, 4.72; Cl, 3.14%);
—
νmax/cmϪ1 (IrH) 2162w and (C᎐C) 2099m (KBr); δ (C6D6,
᎐
᎐
H
IrCl2{ꢀ1-C(O)CH2C(CH3)3}(PPh3)2 (2)
293 K) 7.70–6.80 (49H, m, Ph), 2.18 (3H, s, CH3) and Ϫ11.61
(1H, dt, HϪ, 2JPHcis = 18 Hz, 2JPHtrans = 140 Hz); δP (C6D6, 293 K)
spin syst A2B, δA Ϫ5.02, δB Ϫ22.41, JAB = 15 Hz.
t
᎐
An excess of Bu C᎐CH (0.3 mmol, 38 µL) was added to a
᎐
solution of mer-IrHCl2(PPh3)3 (0.100 g, 0.095 mmol) in 10 cm3
of CH2Cl2 and the reaction mixture was stirred at room
temperature for 40 h. The solvent was removed under reduced
pressure to give a red–brown oil which was triturated with
ethanol (5 cm3). A yellow solid separated out from the resulting
solution, which was filtered and recrystallized from CH2Cl2–
ethanol. It can be noted that the addition of an excess of H2O
(0.3 mmol, 5.4 µL) to the reaction mixture does not change
either the reaction course, or the yield in the final product;
yield ≥70% (Found: C, 56.61; H, 4.78; Cl, 8.18%. C42H41Cl2-
᎐
IrHCl(C᎐CAr)(AsPh ) (4) [Ar ؍ Ph (a), p-tolyl (b)]
᎐
3
3
These complexes were prepared exactly in the same manner as
the related complexes 3 by reacting mer-IrHCl2(AsPh3)3 with an
ϩ
Ϫ
᎐
excess of Li [ArC᎐C] in THF at reflux for 3 h; yield ≥70%
᎐
(Found: C, 59.81; H, 4.05; Cl, 2.65%. C62H51As3ClIr (4a)
—
requires C, 59.65; H, 4.12; Cl, 2.84%); νmax/cmϪ1 (IrH) 2166w
᎐
and (C᎐C) 2095m (KBr); δH (C6D6, 293 K) 7.74–6.80 (50H, m,
᎐
Ph) and Ϫ14.18 (1H, s, HϪ). (Found: C, 59.70; H, 4.32; Cl,
—
IrOP2 requires C, 56.88; H, 4.66; Cl, 8.00%); νmax/cmϪ1
3.02%. C63H53As3ClIr (4b) requires C, 59.93; H, 4.23; Cl,
—
2.81%); νmax/cmϪ1 (IrH) 2156w and (C᎐C) 2098m (KBr); δ
(C᎐O) 1681s (KBr); δ (CD Cl , 293 K) 7.70–6.90 (30H, m, Ph),
᎐
H
2
2
᎐
᎐
H
2.76 (2H, s, CH2) and 0.69 (9H, s, CH3); δP (CD2Cl2, 293 K)
8.25 (s).
(CD2Cl2, 293 K) 7.60–6.50 (49H, m, Ph), 2.27 (3H, s, CH3) and
Ϫ14.73 (1H, s, HϪ).
IrCl2{ꢀ1-C(O)CD2C(CH3)3}(PPh3)2 (2-d2)
᎐
IrHCl(C᎐CPh){PPh(OEt) }(PPh ) (5)
᎐
2
3 2
This complex was prepared in the same manner as the related 2,
This complex was prepared in the same manner as the related
compounds 3 and 4 by refluxing a 10 cm3 THF solution of
IrHCl2{PPh(OEt)2}(PPh3)2 (0.100 g, 0.101 mmol) containing
t
᎐
by adding first an excess of Bu C᎐CH (0.3 mmol, 38 µL) and
᎐
then an excess of D2O (0.4 mmol, 7.2 µL) to a solution of
mer-IrHCl2(PPh3)3 (0.100 g, 0.095 mmol) in 10 cm3 of THF.
The reaction mixture was stirred for 40 h and, after evaporation
of the solvent, the solid complex was recovered by stirring the
oil obtained with EtOD. The 1H NMR spectra confirm
the selective replacement of the methylenic hydrogen atom of
the neopentyl group by deuterium.
ϩ
Ϫ
an excess of Li [PhC᎐C] (0.4 mmol, 0.2 cm3 of a 2.0 M
᎐
᎐
solution in THF) for about 18 h; yield ≥30% (Found: C, 61.85;
H, 4.81; Cl, 3.21%. C54H51ClIrO2P3 requires C, 61.62; H, 4.88;
—
Cl, 3.37%); νmax/cmϪ1 (IrH) 2166w and (C᎐C) 2099s (KBr);
᎐
᎐
δH (CD2Cl2, 293 K) 7.60–6.67 (40H, m, Ph), 3.80, 3.61 (4H, m,
2
CH2), 1.09 (6H, t, CH3) and Ϫ11.78 (1H, dt, HϪ, JPH = 4 Hz,
2JPH = 18 Hz); δP (CD2Cl2, 293 K) spin syst AB2, δA 100.23,
δB Ϫ1.97, JAB = 18 Hz.
IrCl2{ꢀ1-C(18O)CH2C(CH3)3}(PPh3)2 (2-18O)
This complex was prepared in the same manner as 2 by adding
[IrCl{ꢀ2-CH᎐C(H)COOMe}(PPh ) ]BPh (6)
᎐
t
3
2
4
᎐
first an excess of Bu C᎐CH (0.3 mmol, 38 µL) and then an
᎐
excess of H218O (95 atom% 18O) (0.3 mmol, 5.4 µL) to a solution
In a 25-cm3 three-necked round-bottomed flask were placed a
solid sample of mer-IrHCl2(PPh3)3 (0.150 g, 0.143 mmol) and
an equimolar amount of AgCF3SO3 (0.143 mmol, 0.037 g).
Dichlorometane (10 cm3) was added and the reaction mixture
of mer-IrHCl2(PPh3)3 in 10 cm3 of CH2Cl2. After 40 h of
stirring of the reaction mixture and work-up, a yellow solid was
—
obtained. νmax/cmϪ1 (C᎐18O) 1649 (KBr).
᎐
D a l t o n T r a n s . , 2 0 0 3 , 2 8 8 1 – 2 8 8 8
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Table 1 Crystal data and structure refinement for IrCl2(η1-CH2-
stirred for about 24 h in the dark. After filtration to remove
(p-tolyl))(CO)(PPh3)2ؒ3H2O (1bؒ3H2O)
the solid AgCl, an equimolar amount of methyl propiolate
᎐
HC᎐CCOOMe was added (0.143 mmol, 13 µL) and the
᎐
Empirical formula
Formula weight
Temperature/K
C45H45Cl2IrO4P2
974.85
293(2)
reaction mixture stirred for 24 h. The solvent was removed by
evaporation under reduced pressure to give an oil which was
treated with ethanol (3 cm3). The addition of an excess of
NaBPh4 (0.3 mmol, 0.103 g) in 2 cm3 of ethanol to the resulting
solution caused the separation of a pale-yellow solid which was
filtered and crystallized by slow cooling to Ϫ25 ЊC of its satur-
ated solution prepared at room temperature using a mixture of
ethanol and CH2Cl2 as solvent; yield ≥55% (Found: C, 66.22; H,
4.69; Cl, 3.24%. C64H55BClIrO2P2 requires C, 66.46; H, 4.79; Cl,
Wavelength/Å
0.71069
Crystal system
Space group
Orthorhombic
P21ab
Unit cell dimensions
a/Å
b/Å
17.814(3)
25.489(5)
c/Å
10.209(2)
4635(1)
V/Å3
—
3.07%); νmax/cmϪ1 (CO) 1570m (KBr); δH (CD2Cl2, 293 K) 7.80–
Z
4
Dc/Mg mϪ3
1.397
3.102
1952
6.80 (50H, m, Ph), 9.47 (1H, dt, CαH, JHH = 15 Hz, JPH = 9 Hz),
6.11 (1H, d, CβH, JHH = 15 Hz) and 3.71 (3H, s, CH3);
Absorption coefficient/mmϪ1
F(000)
δP (CD2Cl2, 293 K) spin syst AB, δA Ϫ15.2, δB Ϫ17.8, JAB
=
Crystal size/mm
Theta range for data collection/Њ
Index ranges
0.4 × 0.4 × 0.6
3–22
0 ≤ h ≤ 18, 0 ≤ k ≤ 26, 0 ≤ l ≤ 10
2958
2958
1872
13.8 Hz.
[IrCl{ꢀ2-CH᎐C(H)COOMe}(AsPh ) ]BPh (7)
Reflections collected
Independent reflections
Observed independent
reflections [I > 2σ(I )]
Refinement method
Data/restraints/parameters
Goodness-of-fit on F 2
Final R indices [I > 2σ(I )]
R indices (all data)
Absolute structure parameter
Extinction coefficient
Largest ∆F max., min./e ÅϪ3
᎐
3
2
4
This complex was prepared exactly in the same manner as the
related complex 6 starting from mer-IrHCl2(AsPh3)3; yield
≥45% (Found: C, 61.60; H, 4.38; Cl, 3.02%. C64H55As2BClIrO2
Full-matrix least-squares on F 2
2958/1/175
1.041
R1 = 0.0842, wR2 = 0.2056
R1 = 0.1416, wR2 = 0.2466
Ϫ0.01(4)
—
requires C, 61.77; H, 4.45; Cl, 2.85%); νmax/cmϪ1 (CO) 1580m
(KBr); (CD2Cl2, 293 K) 8.00–7.80 (50H, m, Ph), 9.66, 6.02 (2H,
d, CαH and CβH, JHH = 16 Hz) and 3.64 (3H, s, CH3).
0.0009(5)
2.181, Ϫ2.998
X-Ray crystal structure determination of IrCl2(ꢀ1-CH2( p-tolyl))-
(CO)(PPh3)2ؒ3H2O (1bؒ3H2O).
Suitable crystals were obtained by slow cooling to Ϫ20 ЊC of a
saturated solution of the complex in an ethanol–dichloro-
methane mixture (10 : 1 ratio). The crystals were analysed as
obtained and contained three water molecules per iridium
atom. A yellow irregular prism single crystal was mounted on a
glass fiber and X-ray diffraction data were collected on a Philips
PW1100 diffractometer, using graphite monochromated Mo-
Kα radiation (λ = 0.71069 Å). Crystal decay resulted negligible.
The phase problem was solved by direct methods9 and refined
by full-matrix least squares on all F 2,10 with the support of
the WinGX package.11 Exctinction effects were accounted for
by refining an exctinction parameter as implemented in
SHELXL97.10 Anisotropic displacement parameters were
refined for all non carbon atoms, while carbon atoms and
carbonyl oxygen were located from Fourier maps and refined
isotropically. Hydrogens were introduced in calculated
positions. All aromatic rings were constrained to behave as rigid
bodies. Three water molecules were found in the asymmetric
unit, but the relative hydrogens were not located in the final
map. Use of the Cambridge Crystallographic Database12
facilities was made for structure discussion. The final map was
featureless, except for large residues close to the iridium. Data
collection and refinement results are summarized in Table 1.
CCDC reference number 207370.
᎐
The reaction entails the hydrolysis of 1-alkyne with a C᎐C
᎐
bond cleavage and the formation of 1, in agreement with the
reaction shown in Scheme 1. The stoichiometry of this reaction
is confirmed by the separation of both complex 1 and free PPh3
from the reaction mixture carried out in “anhydrous” THF or
CH2Cl2 as a solvent in about quantitative yield (≥90%). The
addition of H2O, in fact, is not necessary for the progress of the
reaction, because the traces of H2O present even in highly
anhydrous solvents is shown to be enough to afford the final
complex 1. However, that H2O is involved in the metal-
mediated hydrolysis of the alkyne, yielding the alkyl-carbonyl
derivative 1, is unambiguously confirmed by the addition of
D2O or H218O to the reaction mixture, which yield either
the labelled IrCl2(η1-CD2Ph)(CO)(PPh3)2 (1a-d2) or the
IrCl2(η1-CH2Ph)(C18O)(PPh3)2 (1a-18O) complexes, respectively.
In the reaction mixture, the presence of free H2 (singlet at 4.6
ppm in CD2Cl2)13 was also detected by 1H NMR so confirming
the proposed stoichiometry for the reaction (Scheme 1).
The alkyl-carbonyl complexes 1 are orange–yellow solids
which are stable in the air, diamagnetic, soluble in the more
common organic solvents and non-electrolytes. Their formul-
ation is confirmed by analytical and spectroscopic data (Table
2) and by the X-ray crystal structure determination of the
IrCl2(η1-CH2(p-tolyl))(CO)(PPh3)2ؒ3H2O (1bؒ3H2O) complex.
Its molecular structure is shown in Fig. 1 along with the label-
ing scheme. The most relevant geometric parameters are listed
in Table 3. The metal coordination is octahedral, with the two
triphenylphosphine ligands trans to each other, while the
CH2(p-tolyl) and CO molecules are cis to each other. The co-
ordination is completed by two chlorine atoms, and the Ir–Cl
bond length is significantly affected by the different trans
influence of the carbonyl and CH2(p-tolyl) groups, the latter
inducing a certain weakening of the Ir–Cl2 bond (2.506(9) Å)
relative to the Ir–Cl1 one (2.42(1) Å). The geometry of the CO
ligand (Ir–C 1.75(6), C–O 1.24(5) Å) apparently deviates from
the average values found in literature for hexa-coordinated
Ir–CO systems (1.88 and 1.14 Å, respectively), but the observed
bond lengths are probably affected by a thermal motion bias.
The bonds relating to the coordination of the CH2(p-tolyl)
group (Ir–C 2.24(5), CH2–C(Ar) 1.62(5) Å) are apparently
See http://www.rsc.org/suppdata/dt/b3/b303635a/ for crystal-
lographic data in CIF or other electronic format.
Results and discussion
Both mer- and fac-iridium() complexes IrHCl2(PPh3)3 react
᎐
with terminal alkynes HC᎐CAr in THF or CH Cl to give the
᎐
2
2
alkyl-carbonyl derivatives IrCl2(η1-CH2Ar)(CO)(PPh3)2 (1),
which were then isolated and characterized (Scheme 1).
Scheme 1 Ar = Ph (a), p-tolyl (b)
D a l t o n T r a n s . , 2 0 0 3 , 2 8 8 1 – 2 8 8 8
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Table 2 13C{1H} NMR Data for selected iridium complexes
13C{1H} NMRa, b
δ/ppm J/Hz
Complex
Assignment
IrCl2(η1-CH2Ph)(CO)(PPh3)2 c 1a
160.8 t
C᎐O
᎐
J(13C31P) = 7.5
12.8 t
CH2
J(13C31P) = 2
160.9 t
IrCl2(η1-CH2(p-tolyl))(CO)(PPh3)2 1b
C᎐O
᎐
J(13C31P) = 7.5
21.0 s
CH3
CH2
12.7 t
J(13C31P) = 2
176.7 t
IrCl2{C(O)CH2C(CH3)3}(PPh3)2 2
C᎐O
᎐
J(13C31P) = 3
65.9 s
CH2
C(CH3)3
CH3
Cβ
33.7 s
28.6 s
᎐
IrHCl(C᎐CPh)(PPh3)3 3a
110.8 br
96.1 dt
᎐
Cα
J(13C31P)cis = 11
J(13C31P)trans = 14
113.2 s
᎐
IrHCl(C᎐CPh)(AsPh3)3 4a
Cβ
Cα
Cβ
Cα
CH2
CH3
᎐
88.2 s
114.6 s
92.4 m, br
66.2 d
16.4 s
164.5 s
135.9 s, br
128.5 s
᎐
IrHCl(C᎐CPh){PPh(OEt)2}(PPh3)2 5
᎐
[IrCl{η2-CH᎐C(H)COOMe}(PPh3)2]BPh4 6
C᎐O
᎐
᎐
Cα
Cβ
51.3 s
163.9 s
136.1 s
CH3
[IrCl{η2-CH᎐C(H)COOMe}(AsPh3)2]BPh4 7
C᎐O
᎐
᎐
Cα
128.1 s
51.0 s
Cβ
CH3
a In CD2Cl2 at 25 ЊC, unless otherwise noted. b Phenyl carbon resonances are omitted. c In C6D6.
Table 3 Selected bond lengths (Å) and angles (Њ) for IrCl2(η1-CH2-
(p-tolyl))(CO)(PPh3)2 (1b)
Ir–C44
Ir–C43
Ir–P1
Ir–P2
Ir–Cl1
1.75(6)
2.24(5)
2.37(1)
2.42(1)
2.42(1)
2.506(9)
1.62(5)
1.24(5)
1.58(6)
C44–Ir–C43
C44–Ir–P1
C43–Ir–P1
C44–Ir–P2
C43–Ir–P2
P1–Ir–P2
C44–Ir–Cl1
C43–Ir–Cl1
P1–Ir–Cl1
P2–Ir–Cl1
C44–Ir–Cl2
C43–Ir–Cl2
P1–Ir–Cl2
P2–Ir–Cl2
Cl1–Ir–Cl2
C25–C43–Ir
O1–C44–Ir
102(2)
83(2)
94(1)
99(2)
88(1)
177.0(4)
168(2)
87(1)
88.5(4)
89.7(4)
77(2)
176(1)
89.4(4)
88.4(4)
94.2(4)
113(3)
169(5)
Ir–Cl2
C43–C25
O1–C44
C28–C46
Fig. 1 Perspective view and labeling of the molecular structure of
IrCl2(η1-CH2(p-tolyl))(CO)(PPh3)2 (1b). Phenyl groups of triphenyl-
phosphine are omitted for clarity. Thermal ellipsoids and spheres are
represented at the 50% probability level.
weaker with respect to those observed for
Ir()–CH2Ar complex: Ir–C 2.102(3)–2.125(3) Å, CH2–C(Ar)
1.496(5) Å, in pentacoordinated dibenzyl(bis(diphenyl-
a related
two triphenylphosphine ligands eclipse each other (torsion
C31–P2–P1–C7 6.6Њ).
a
phosphinomethyl(dimethyl)silyl)amino-P,PЈ,N)iridium deriv-
ative14 (structure determined at Ϫ40 ЊC). The intramolecular
geometry for IrCl2(η1-CH2(p-tolyl))(CO)(PPh3)2 is character-
ized by a syn orientation of the CH2(p-tolyl) group with respect
to the carbonyl ligand (C44–Ir–C43–C25 21Њ, C25 ؒ ؒ ؒ C44 3.21
Å), with the C43–C25 bond almost eclipsed with respect to the
Ir–C44–O1 vector. The CH2(p-tolyl) ligand is in fact sterically
confined between the bulky triphenylphosphine groups and the
equatorial orientation of the aryl ring on the carbonyl side is
the least hindered by intramolecular non-bonded interactions.
Accordingly, the carbonyl is displaced from the CH2(p-tolyl)
group, causing the widening of the C43–Ir–C44 angles (102(2)Њ)
and the compression of the C44–Ir–Cl2 (77(2)Њ) angles. The
The IR spectra of compounds 1 show a strong band at 2048
cmϪ1, attributed to the νCO of the carbonyl ligand. In the
1
18
labelled compound IrCl (η -CH Ph)(C᎐ O)(PPh ) (1a-18O)
᎐
᎐
2
2
3 2
the νC O falls at 2006 cmϪ1 with ∆ν of 42 cmϪ1, which is in good
agreement with the value calculated15 (∆ν = 47 cmϪ1) from the
change in reduced mass.
18
The NMR data of IrCl2(η1-CH2Ar)(CO)(PPh3)2 1 derivatives
agree with their formulation and with the presence in solution
1
of a geometry I like those of the solid state. In fact, the H
NMR spectra show, beside the signals of the phenyl protons of
the PPh3 ligands, a triplet at 3.55 ppm for 1a and at 3.52 ppm
for 1b attributed to the methylene protons of the alkyl CH2Ar
ligand. In the spectra of 1b a singlet at 2.18 ppm of the p-tolyl
D a l t o n T r a n s . , 2 0 0 3 , 2 8 8 1 – 2 8 8 8
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substituent was also observed. The 13C spectra of complexes 1
(Table 2) confirm the presence of CO and CH2Ar ligands, show-
ing a triplet at 160.8 (1a) and 160.9 (1b) ppm of the carbonyl
carbon atom and a triplet at 12.8 (1a) and 12.7 (1b) ppm of the
methylene CH2Ar group. A 1H, 13C HMQC experiment clearly
correlates this latter signal with the proton triplet at 3.55 ppm
of the Ir–CH2–Ar group, in agreement with the proposed
assignment. In the temperature range between ϩ20 and Ϫ80 ЊC,
the 31P{1H} NMR spectra of 1 appear as a sharp singlet
suggesting the magnetic equivalence of the two phosphine
ligands. On the basis of these data a cis–trans structure I
(Fig. 2) can be proposed.
A complex containing an acyl C(O)R ligand may be con-
sidered as a precursor of the derivative containing both the
carbonyl and the alkyl ligand as in the IrCl2(CO)(η1-CH2Ar)-
(PPh3)2 (1) complexes obtained in the reaction of IrHCl2(PPh3)3
with arylalkynes. We have therefore studied the behaviour of
complex 2 in solution by NMR spectra and observed that while
at room temperature it is very stable, at 60 ЊC it slowly reacts
to give a new species whose spectra indicate it to be the alkyl-
carbonyl IrCl2{η1-CH2C(CH3)3}(CO)(PPh3)2 (1c) derivative
formed by CO deinsertion of the acyl ligand (Scheme 3).
Scheme 3
The proton NMR spectra of a solution of 2 in THF-d8 show
the disappearance of the two singlets at 2.76 and at 0.69 ppm of
the C(O)CH2C(CH3)3 group and the appearance of one triplet
at 2.49 ppm and one singlet at 0.46 ppm attributable to the
η1-CH2C(CH3)3 ligand of the alkyl compound 1c. Also in the
31P{1H} NMR spectra a new singlet at Ϫ13.00 ppm appears,
concurrent with the disappearance of the signal of 2.
Unfortunately, this reaction is too slow as compared with the
decomposition that takes place at 60 ЊC to allow the carbonyl
IrCl2{η1-CH2C(CH3)3}(CO)(PPh3)2 (1c) to be prepared in pure
form. However, a comparison of its 1H and 31P NMR data with
those of the related complexes 1a and 1b strongly supports the
proposed formulation for this species.
Fig. 2
The iridium complex mer- or fac-IrHCl2(PPh3)3 also reacts
᎐
with tert-butylacetylene, HC᎐CC(CH ) to give a yellow solid
᎐
3
3
which does not result to be the expected carbonyl-alkyl
derivative like 1, but an acyl complex of the IrCl2{η1-C(O)-
CH2C(CH3)3}(PPh3)2 type (2), as shown in Scheme 2.
We have also tested other acetylenes such as CH3CH2-
᎐
᎐
᎐
CH C᎐CH, (CH ) SiC᎐CH and HC᎐CCO R in the reaction
᎐
᎐
᎐
2
3
3
2
with IrHCl2(PPh3)3, but neither alkyl- nor acyl-derivatives were
obtained. The reaction seems to proceed with color change of
the reaction mixture, but the NMR spectra do not reveal the
presence of the hypothesized species and only intractable oils
were separated from the reaction.
Scheme 2
The reaction with tert-butylacetylene involves also in this
case the hydrolysis of the alkyne promoted by the traces of
water present in the solvent to give the acyl complex 2. This is
confirmed by the red shift of the νCO observed in the labelled
IrCl2{η1-C(18O)CH2C(CH3)3}(PPh3)2 (2-18O) complex, pre-
pared by adding H218O to the reaction mixture, and by the
preparation of IrCl2{η1-C(O)CD2C(CH3)3}(PPh3)2 (2-d2) in the
reaction with D2O. The formulation of 2 as an acyl complex
is supported by IR and NMR spectroscopic data. The IR spec-
trum shows a medium intensity band at 1681 cmϪ1 attributed to
the νCO of the C(O)CH2C(CH3)3 group. This band shifts to 1649
cmϪ1 in the labelled 2-18O complex (∆ν = 32 cmϪ1), according to
the proposed attribution. The 1H NMR spectra of 2 exhibits a
singlet at 2.76 ppm, attributed to the CH2 protons and a singlet
at 0.69 of the CH3 protons of the neopentyl CH2C(CH3)3
moiety. However, strong support for the presence of the acyl
ligand comes from the 13C spectrum, which shows a triplet at
176.7 ppm due to the carbonyl carbon atom and three singlets
at 65.9, 33.7 and 28.6 ppm attributed to the CH2, C(CH3)3 and
CH3 carbon atoms of the neopentyl group, respectively. APT
NMR studies confirmed the proposed attribution, whereas a
1H, 13C HMQC NMR experiment clearly correlates the proton
singlets at 2.76 and at 0.69 ppm with the 13C{1H} signals at 65.9
and at 28.6 ppm of the CH2 and CH3 groups of the neopentyl,
in agreement with the proposed formulation.
Although the number of tested acetylenes is limited, these
results seem to indicate that the hydratation of alkynes con-
taining aryl substituents proceeds with a complete cleavage of
᎐
the C᎐C bond affording both CO and the alkyl CH Ar groups,
᎐
2
each behaving as a ligand. With alkyl- or silyl-substituents,
᎐
instead, the hydratation of RC᎐CH acetylenes does not give
᎐
isolable products, except with the tert-butyl substituent which
has the property to stabilize an acyl–iridium derivative of the
type IrCl2{C(O)CH2C(CH3)3}(PPh3)2 2.
The hydrolysis of terminal alkynes yielding 1 and 2 was
studied extensively in order to obtain information useful to
propose a mechanism for the reaction. Treating both mer- and
fac-IrHCl2(PPh3)3 in CD2Cl2 or THF-d8 solution with phenyl-
acetylene in a NMR tube one can observe the slow formation
of 1a and free PPh3. The addition of H2O increases the reaction
rate but does not change the profile of the spectra of the
reaction mixture which shows the appearance of the signal of
᎐
free PPh immediately after the addition of PhC᎐CH whose
᎐
3
signal slowly disappears. The lability of the PPh3 ligand in
IrHCl2(PPh3)3, which was observed also in other reactions,8f,16
may suggest that the first step of the reaction is the substitution
2
᎐
of PPh with the alkyne giving an η -PhC᎐CH intermediate [A]
᎐
3
(Scheme 4). A tautomerization of the π-coordinate alkyne on
the iridium centre could then take place giving a vinylidene
derivative [B]. This tautomerization is expected on the basis
In the temperature range between ϩ20 and Ϫ80 ЊC the 31P
spectrum appears as a sharp singlet suggesting the magnetic
equivalence of the two phosphine ligands. The spectroscopic
data, however, do not give conclusive information on the
geometry of the complexes, which contain five ligands, but may
reach the octahedral structure through an agostic interaction
between the iridium centre and a C–H bond of a methyl
substituent of the acyl ligand, or of the phenyl groups of the
PPh3 ligands.
Scheme 4
D a l t o n T r a n s . , 2 0 0 3 , 2 8 8 1 – 2 8 8 8
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of the large number of precedents17,18 involving d6 metal com-
plexes and should occur via a 1,2-hydrogen shift mechanism.
We therefore attempted to detect this intermediate by monitor-
ing the reaction course by NMR spectra (1H, 13C, 31P), but did
not observe any signal attributable to a vinylidene ligand. In
fact, the absence of the characteristic carbene carbon signal17
between 350 and 280 ppm in the 13C NMR spectrum seems to
exclude the presence of any vinylidene species, at least in
detectable amounts. Therefore, the only new signals that appear
in the spectrum of the reaction mixture, i.e. a singlet at 3.64
comes from the proton spectra which show, in the case of the
phosphine complexes 3 and 5, one doublet of triplets in the
characteristic low-frequency region at Ϫ11.62 (3a), at Ϫ11.61
(3b) and at Ϫ11.78 (5) ppm. Taking into account that the 31P
spectra are A2B or AB2 multiplets, the hydride pattern can be
easily simulated using the appropriate A2BX or AB2X (X = H)
model, with the parameters reported in the Experimental
section. The high value of 140 Hz found for one of the two JPH
in complexes 3a and 3b also suggest that the hydride ligand is in
a mutually trans position with one phosphine and in cis with the
other two, as in a type-II geometry (Fig. 3). The presence of the
acetylide ligand in the complexes is also confirmed by the 13C
1
ppm for H and a singlet at 114.1 ppm for 13C, may be tenta-
tively attributed to the CH resonances (APT NMR experiment)
2
᎐
of an η -PhC᎐CH ligand formed in the initial step of the
spectra (Table 2) which show the Cα and Cβ carbon atoms of the
᎐
᎐
reaction. However, the failure to detect the vinylidene inter-
C᎐CPh group of 3a at 96.1 and at 110.6 ppm, respectively. The
᎐
mediate does not mean that [Ir]᎐C᎐C(H)Ph species can be ruled
Cα appears as one doublet of triplets due to the coupling with
the phosphorus nuclei of the phosphine and the comparable
values observed for the two J(13C31P) of 11 and 14 Hz, respect-
ively, agrees with a type-II geometry for the complex.
᎐ ᎐
out, because its further reaction with H2O to give the final
product can be faster than its formation, making its concen-
tration undetectable.
Stable and isolable vinylidene complexes of iridium are well
known17a,19 but are generally tetracoordinate complexes of Ir(),
with stable species of Ir() still unknown. This agrees with our
difficulty to detect a Ir() vinylidene intermediate. Neverthe-
less, our results with D2O and H218O which give 2-d2 and 2-18O,
᎐
respectively, and the isolation, with HC᎐CC(CH ) , of acyl-
᎐
3
3
complex 2 prompt us to propose a pathway similar to those
recently proposed by Bianchini et al.3a for the hydrolysis of
terminal alkyne giving 1, which involves a [Ir]–vinylidene
complex [B] as the key intermediate.20 This mechanism involves
the attack of H2O on the vinylidene [B] Cα carbon atom to give
an hydroxycarbene21,22 IrHCl2P2[C(OH)CH2Ar] intermediate
[C], which can eliminate H2 yielding the unsaturated acyl deriv-
ative IrCl2P2[C(O)CH2Ar] [D]. From this acyl intermediate, the
formation of the final alkyl-carbonyl complex 1 can be readily
explained by CO deinsertion of the acyl ligand.
Fig. 3
In the related mixed-ligand compound 5 the values of the two
JPH suggest a mutually cis position of the hydride with all the
phosphines. Unfortunately, the broad multiplet that appears at
92.4 ppm in the 13C NMR spectrum for the Cα carbon atom
2
13
᎐
of the C᎐CPh ligand does not allow to determine the J( CP)
᎐
value and this prevents the unambiguous assignment of a
geometry for the complex.
The 1H NMR spectra of the arsino-complexes IrHCl-
᎐
Vinyl and acetylide complexes
(ArC᎐C)(AsPh ) (4) show the hydride signal as a singlet
᎐
3
3
at Ϫ14.18 (4a) and at Ϫ14.73 (4b) ppm, whereas in the 13C
spectrum of 4a the Cα and Cβ carbon resonances of the acetyl-
ide ligand appear at 82.2 and at 113.2 ppm, respectively. These
data support the proposed formulation but, also in this case, do
not allow structural information to be obtained in solution.
Studies on the properties of the acetylide complexes 3–5
indicate that they are robust complexes, whose substitution
reactions with several ligands (phosphine, CO, ClϪ, etc.) are
slow even in reflux conditions. Protonation reactions with
Brønsted acids were also studied in order to test whether the
In parallel to the studies with terminal alkynes, we have
also tested the behaviour of mer-IrHCl2(PPh3)3 towards
ϩ
Ϫ
᎐
Li [ArC᎐C] and found that the reaction proceeds to give the
᎐
᎐
alkynyl IrHCl(ArC᎐C)(PPh ) (3) derivatives (Scheme 5). The
᎐
3
3
related mixed-ligand IrHCl2{PPh(OEt)2}(PPh3)2 compound,
as well as the arsino IrHCl2(AsPh3)3 complex also react with
ϩ
Ϫ
᎐
᎐
Li [ArC᎐C] to give the alkynyl IrHCl(ArC᎐C){PPh(OEt) }-
᎐
᎐
2
᎐
(PPh ) (5) and IrHCl(ArC᎐C)(AsPh ) (4) derivatives which
᎐
3
2
3 3
were isolated and characterized.
proton attack takes place on the acetylide ligand to yield a [Ir]᎐
᎐
C᎐C(H)Ar vinylidene complex, or on the hydride to give a
᎐
dihydrogen [Ir]–(η2-H2) derivative. The reaction was studied at
different temperatures in a NMR tube by adding progressive
amounts of HBF4ؒEt2O to 3a in CD2Cl2 and the spectra show
that the disappearance of the hydride ligand was already
observed at Ϫ80 ЊC. However, neither signals attributable to an
η2-H2 complex formed by the protonation of the hydride, nor
due to free H2 were detected in the spectra of the protonated
solution. Furthermore, even after the addition of an excess of
HBF4ؒEt2O, the formation of a vinylidene complex was not
detected by 1H and 13C spectra. Instead, two doublets of
multiplets at 8.38 and 5.53 ppm, respectively, appear in the
proton spectra, which strongly suggest the formation of a vinyl
complex.24 The protonation reaction seems therefore to take
place on the acetylide ligand, giving a coordinated terminal
alkyne which can react with the hydride to yield the final vinyl
complex (Scheme 6).
Scheme 5
The complexes 3–5 are red–brown solids which are stable in
the air, diamagnetic, moderately soluble in the more common
organic solvents and non-electrolytes. The analytical and
spectroscopic data support the proposed formulation. The IR
spectra show a medium-intensity band at 2095–2099 cmϪ1
attributed to the νC᎐C of the acetylide ligand.23 In the spectra a
weak absorption at ᎐2168–2156 cmϪ1 also appears due to the νIrH
of the hydride ligand. Support for the presence of the hydride
This vinyl complex is, unfortunately, thermally unstable and
decomposed already at Ϫ10 ЊC, preventing its separation to the
solid state.
These results prompted us to attempt a different method to
prepare stable vinyl complexes and the reactions sequence
reported in Scheme 7 does allow this synthesis to be achieved.
D a l t o n T r a n s . , 2 0 0 3 , 2 8 8 1 – 2 8 8 8
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51.3 ppm of the methyl group, while the Cα and Cβ vinyl carb-
ons appear at 135.9 and 128.5 ppm, respectively. A 1H,13C
HMQC experiment allowed us to correlate the vinyl Cα and Cβ
carbon signals to the proton multiplets at 9.47 and 6.11 ppm, in
agreement with the proposed formulation. In the temperature
range between ϩ30 and Ϫ80 ЊC the 31P{1H} NMR spectrum
of 6 appears as an AB multiplet indicating the magnetic
inequivalence of the two phosphine ligands. On the basis of the
spectroscopic data alone we cannot unambiguously assign a
geometry to our derivative 6, although type III is plausible and
can be proposed.
Scheme 6
The proton NMR spectra of the arsino complex [IrCl-
{η2-CH᎐C(H)COOMe}(AsPh ) ]BPh (7) show two doublets at
᎐
3
2
4
3
9.66 and 6.02 ppm with JHH of 16 Hz attributed to the two
vinyl protons Hα and Hβ, respectively, of the vinyl group. The
13C spectra confirm the presence of the η2-ligand showing the
characteristic signals of the Cα and Cβ vinyl carbon atoms at
136.1 and at 128.1 ppm and those of the carbonyl and of the
methyl group at 163.9 and 51.0 ppm, respectively. These data,
therefore, support the proposed formulation for the arsino-
vinyl derivative.
Scheme 7
Conclusions
Because the reaction of mer-IrHCl2(PPh3)3 with terminal
alkyne does not give the insertion into the Ir–H bond yielding
In this contribution we have reported a new example of
hydrolysis of terminal alkynes promoted by Ir() hydride
complexes which gives, depending on the nature of the alkyne,
an alkyl-carbonyl IrCl2(η1-CH2Ar)(CO)(PPh3)2 or an acyl
IrCl2{η1-C(O)CH2C(CH3)3}(PPh3)2 derivative. The structural
characterization of an alkyl-carbonyl iridium complex is also
described. Furthermore, the synthesis of new alkynyl
᎐
the vinyl species, but the hydrolysis of the ArC᎐CH group
᎐
giving 1, we prepared the new hydride [E] by reacting
IrHCl2(PPh3)3 with AgCF3SO3. This complex (tentatively
formulated as [IrHCl(PPh3)3]ϩCF3SO3Ϫ) was not isolated, but
was treated in solution with terminal alkyne and, while with
phenylacetylene only intractable products were obtained, with
methyl propiolate a yellow solid was isolated after precipitation
with NaBPh4 and work-up, whose analytical and spectroscopic
data indicated to be the chelate vinyl complex 6. The related
IrHCl(ArC᎐C)L and chelate [IrCl{η2-CH᎐C(H)COOMe}-
᎐
᎐
᎐
3
L2]BPh4 (L = PPh3, AsPh3) vinyl derivatives was achieved using
mer-IrHCl2L3 as a precursor.
arsino derivative [IrCl{η2-CH᎐C(H)COOMe}(AsPh ) ]BPh
References and notes
᎐
3
2
4
(7) was also obtained by reacting IrHCl2(AsPh3)3 first with
1 (a) J. Halpern, B. R. James and A. L. W. Kemp, J. Am. Chem. Soc.,
1966, 88, 5142; (b) N. X. Hu, Y. Aso, T. Otsubo and F. Ogura,
Tetrahedron Lett., 1986, 27, 6099; (c) W. D. Harman, J. C. Dobson
and H. Taube, J. Am. Chem. Soc., 1989, 111, 3061; (d ) T. M. M.
Khan, S. B. Halligudi and S. Shukla, J. Mol. Catal., 1990, 58, 299;
(e) W. Hiscox and P. W. Jennings, Organometallics, 1990, 9, 1997; ( f )
Y. Fukuda and K. Utimoto, J. Org. Chem., 1991, 56, 3729; (g)
J. Blum, H. Huminer and H. Alper, J. Mol. Catal., 1992, 75, 153;
(h) I. K. Meier and J. A. Marsella, J. Mol. Catal., 1993, 78, 31; (i)
M. Tokunaga, T. Suzuki, N. Koga, T. Fukushima, A. Horiuchi and
Y. Wakatsuki, J. Am. Chem. Soc., 2001, 123, 11917.
2 (a) O. M. Abu Salah and M. I. Bruce, J. Chem. Soc., Dalton Trans.,
1974, 2302; (b) M. I. Bruce and A. G. Swincer, Aust. J. Chem., 1980,
33, 1471; (c) B. P. Sullivan, R. S. Smythe, E. M. Kober and
T. J. Meyer, J. Am. Chem. Soc., 1982, 104, 4701; (d ) C. Mountassir,
T. Ben Hadda and H. Le Bozec, J. Organomet. Chem., 1990, 388,
C13; (e) S. Davies, J. P. McNally and A. J. Smallbridge, Adv.
Organomet. Chem., 1990, 30, 30; ( f ) W. Knaup and H. Werner,
J. Organomet. Chem., 1991, 411, 471.
3 (a) C. Bianchini, J. A. Casares, M. Peruzzini, A. Romerosa and
F. Zanobini, J. Am. Chem. Soc., 1996, 118, 4585; (b) M. L. Buil,
M. A. Esteruelas, A. M. López and E. Oñate, Organometallics, 1997,
16, 3169.
4 (a) J. M. O’Connor and L. Pu, J. Am. Chem. Soc., 1990, 112, 9013;
(b) M. V. Jiménez, E. Sola, A. P. Martínez, F. J. Lahoz and
L. A. Oro, Organometallics, 1999, 18, 1125; (c) C. S. Chin, D. Chong,
B. Maeng, J. Ryu, H. Kim, L. Kim and H. Lee, Organometallics,
2002, 21, 1739.
5 (a) G. Albertin, P. Amendola, S. Antoniutti, S. Iannelli, G. Pelizzi
and E. Bordignon, Organometallics, 1991, 10, 2876; (b) G. Albertin,
S. Antoniutti, E. Del Ministro and E. Bordignon, J. Chem. Soc.,
Dalton Trans., 1992, 3203; (c) G. Albertin, S. Antoniutti and
E. Bordignon, J. Chem. Soc., Dalton Trans., 1995, 719; (d )
G. Albertin, S. Antoniutti, E. Bordignon, F. Cazzaro, S. Iannelli
and G. Pelizzi, Organometallics, 1995, 4, 4114; (e) G. Albertin,
S. Antoniutti, A. Bacchi, E. Bordignon and G. Pelizzi,
Organometallics, 1995, 14, 4126; ( f ) G. Albertin, S. Antoniutti,
M. Bettiol, E. Bordignon and F. Busatto, Organometallics, 1997, 16,
4959; (g) G. Albertin, S. Antoniutti, E. Bordignon and D. Bresolin,
J. Organomet. Chem., 2000, 609, 10.
᎐
AgCF3SO3 and then with HC᎐CCOOMe. These vinyl com-
᎐
plexes 6, 7 were formed through the insertion of methyl pro-
piolate into the Ir–H bond of the hydride [E] and probably
involved an initial coordination of the alkyne on the metal. The
O-coordination of the carbonyl group to give the chelate vinyl
ligand is followed by the dissociation of one PPh3 ligand
yielding a final pentacoordinate species.
Complexes 6 and 7 are yellow solids which are stable in the
air and in solution of polar organic solvents, where they behave
as 1 : 1 electrolytes.25 Support for the presence of a chelate
O-bonded vinyl ligand comes from the IR spectra which show
the νCO as a medium-intensity band at a relatively low fre-
1
quency26 of 1570–1580 cmϪ1. The H NMR spectrum of the
phosphine complex 6 shows, beside the signals of the phenyl
protons, one doublet of triplets at 9.47 ppm attributed to the Hα
proton and a doublet at 6.11 ppm due to the Hβ proton of the
C H ᎐C (H )COOMe vinyl ligand. A singlet at 3.71 ppm of
᎐
α
α
β
β
the methyl protons was also observed. Homodecoupling
experiments and a 1H COSY spectrum confirmed the proposed
3
attribution. A value of 15 Hz for JHH was also observed and,
although it is somewhat high for a cis arrangement of the two
vinyl protons,26,27 the IR spectra support the presence of the
chelate (III) vinyl ligand (Fig. 4). The 13C spectra of 6 confirm
the presence of the CH᎐C(H)COOCH ligand showing a
᎐
3
singlet at 164.5 ppm of the carbonyl carbon atom, a singlet at
Fig. 4
D a l t o n T r a n s . , 2 0 0 3 , 2 8 8 1 – 2 8 8 8
2887

View Article Online
6 R. Rabinowitz and J. Pellon, J. Org. Chem., 1961, 26, 4623.
7 G. Balacco, J. Chem. Inf. Comput. Sci., 1994, 34, 1235.
8 (a) S. Park, A. J. Lough and R. H. Morris, Inorg. Chem., 1996,
35, 3001; (b) L. Vaska, J. Am. Chem. Soc., 1961, 83, 751; (c)
R. G. Hayter, J. Am. Chem. Soc., 1961, 83, 1259; (d ) N. Ahmad,
S. D. Robinson and M. F. Uttley, J. Chem. Soc., Dalton Trans.,
1972, 843; (e) G. L. Geoffroy and R. Pierantozzi, J. Am. Chem.
Soc., 1976, 98, 8054; ( f ) G. Albertin, S. Antoniutti,
E. Bordignon and F. Menegazzo, J. Chem. Soc., Dalton Trans.,
2000, 1181.
9 SIR97: A New Program for Solving and Refining Crystal Structures:
A. Altomare, M. C. Burla, M. Camalli, G. Cascarano,
C. Giacovazzo, A. Guagliardi, A. G. Moliterni, G. Polidori and
R. Spagna, J. Appl. Crystallogr., 1999, 32, 115.
10 G. M. Sheldrick, SHELXL97: Program for Structure Refinement;
University of Goettingen, Germany, 1997.
11 L. J. Farrugia, J. Appl. Crystallogr., 1999, 32, 837.
12 F. H. Allen, O. Kennard and R. Taylor, Acc. Chem. Res., 1983, 16,
146.
13 R. H. Crabtree, M. Lavin and L. Bonneviot, J. Am. Chem. Soc.,
1986, 108, 4032.
852; (c) H. Werner, A. Höhn and M. Schulz, J. Chem. Soc., Dalton
Trans., 1991, 777; (d ) H. Werner, R. W. Lass, O. Gevert and J. Wolf,
Organometallics, 1997, 16, 4077; (e) K. Ilg and H. Werner,
Organometallics, 2001, 20, 3782.
20 A cationic vinylidene intermediate may also be formed by
2
᎐
protonation of the coordinate alkyne in IrHCl2(η -PhC᎐CH)(PPh3)2
᎐
[A] to give a formal Ir() cationic vinyl species [IrHCl2{CH᎐
᎐
C(H)Ph}(PPh3)2]ϩ which can undergo the Caulton-type20a reaction
to give the vinylidene [IrCl2{᎐᎐C᎐C(H)Ph}(PPh3)2]ϩ and H2.
᎐
Reaction of this intermediate with OHϪ or with H2O followed by
deprotonation can then give the acyl complex [D]: (a) M. Olivan,
E. Clot, O. Eisenstein and K. G. Caulton, Organometallics, 1998, 17,
3091.
21 Hydroxycarbene metal complexes are generally unstable and
thermally degrade to give acyl derivatives via HCl-elimination when
chloride ligands are present in the complex framework.21a
Deprotonation of hydroxycarbene complexes with weak bases,
giving formyl derivatives, was also observed.21b (a) K. R. Grundy
and J. Jenkins, J. Organomet. Chem., 1984, 265, 77; (b) M. A. Lilga
and J. A. Ibers, Organometallics, 1985, 4, 590.
22 For hydroxycarbene metal complexes, see: (a) R. A. M. Robertson,
A. D. Poole, M. J. Payne and D. J. Cole-Hamilton, J. Chem. Soc.,
Dalton Trans., 2000, 1817; (b) C. P. Casey, C. J. Czerwinski and
R. K. Hayashi, J. Am. Chem. Soc., 1995, 117, 4189; (c) D. S. Barrett,
C. Glidewell and D. J. Cole-Hamilton, J. Chem. Soc., Chem.
Commun., 1988, 1079; (d ) V. Guerchais and C. Lapinte, J. Chem.
Soc., Chem. Commun., 1986, 663; (e) D. S. Barrett and D. J.
Cole-Hamilton, J. Organomet. Chem., 1986, 306, C41; ( f ) W. E.
Buhro, A. Wong, J. H. Merrifield, G.-Y. Lin, A. C. Constable and
J. A. Gladysz, Organometallics, 1983, 2, 1852; (g) E. O. Fischer
and A. Riedel, Chem. Ber., 1968, 101, 156.
14 M. D. Fryzuk, P. A. MacNeil, R. L. Massey and R. G. Ball,
J. Organomet. Chem., 1989, 368, 231.
15 D. M. P. Mingos, in Comprehensive Organometallic Chemistry, ed.
E. W. Abel, F. G. A. Stone and G. Wilkinson, Pergamon Press,
Oxford, UK, 1982, vol. 3, p. 1.
16 G. Albertin et al. manuscript in preparation.
17 (a) M. I. Bruce, Chem. Rev., 1991, 91, 197; (b) C. Bianchini,
M. Peruzzini, A. Vacca and F. Zanobini, Organometallics, 1991, 10,
3697; (c) M. D. Fryzuk, L. Huang, N. T. McManus, P. Paglia,
S. J. Rettig and G. S. White, Organometallics, 1992, 11, 2979; (d )
J. R. Lumprey and J. P. Selegue, J. Am. Chem. Soc., 1992, 114, 5518;
(e) I. de los Rios, M. Jimenez-Tenorio, M. C. Puerta and P. Valerga,
J. Am. Chem. Soc., 1997, 119, 6529; ( f ) M. I. Bruce, B. C. Hall,
N. N. Zaitseva, B. W. Skeldon and A. H. White, J. Chem. Soc.,
Dalton Trans., 1998, 1793; (g) C. Bruneau and P. H. Dixneuf, Acc.
Chem. Res., 1999, 32, 311.
23 J. Manna, K. D. John and M. D. Hopkins, Adv. Organomet. Chem.,
1995, 38, 79.
24 For vinyl complexes see: refs. 5a,c and (a) C. Bianchini, P. Barbaro,
A. Meli, M. Peruzzini, A. Vacca and F. Vizza, Organometallics,
1993, 12, 2505; (b) C. Bohanna, M. A. Esteruelas, F. J. Lahoz,
E. Oñate and L. A. Oro, Organometallics, 1995, 14, 4685.
25 W. J. Geary, Coord. Chem. Rev., 1971, 7, 81.
18 (a) J. Silvestre and R. Hoffmann, Helv. Chim. Acta, 1985, 68, 1461;
(b) Y. Wakatsuki, N. Koga, H. Yamazaki and K. Morokuma, J. Am.
Chem. Soc., 1994, 116, 8105.
26 G. Albertin, S. Antoniutti and E. Bordignon, J. Chem. Soc., Dalton
Trans., 1995, 719 and references therein.
19 (a) F. J. Garcia Alonso, A. Höhn, J. Wolf, H. Otto and H. Werner,
Angew. Chem., Int. Ed. Engl., 1985, 24, 406; (b) A. Höhn, H. Otto,
M. Dziallas and H. Werner, J. Chem. Soc., Chem. Commun., 1987,
27 (a) B. Chamberlain and R. J. Mawby, J. Chem. Soc., Dalton Trans.,
1991, 2067; (b) J. M. Bray and R. J. Mawby, J. Chem. Soc., Dalton
Trans., 1989, 589.
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