C-H activation of methyl vinyl ketone in Ir(acac){η2-CH2=CHC(O)CH3}(PCy3)

Article abstract of DOI:10.1016/S0022-328X(98)00690-1

The cyclooctene complex Ir(acac)(cyclooctene)(PCy₃) (1) reacts with methyl vinyl ketone to give Ir(acac){η²-CH₂=CHC(O)CH₃}(PCy₃) (2) and cyclooctene. In benzene at 70°C, complex 2 affords by means of an intramolecular C-H activation process the thermodynamically favored alkenyl derivative Ir(acac)H{(Z)-CH=CHC(O)CH₃}(PCy₃) (3), which was isolated as a mixture of the isomers 3a (PCy₃ trans to carbonyl group of alkenyl ligand) and 3b (PCy₃ trans to acac). Isomers 3a and 3b do not react with tricyclohexylphosphine. However, the complex Ir(acac)H{(E)-CH=CHC(O)CH₃}(PCy₃)₂ (4) can be obtained by treatment of 2 with the phosphine in benzene at 70°C. Complex 2 also reacts with HBF₄ at -78°C, to give the five-coordinate hydrido derivative [Ir(acac)H{η²-CH₂=CHC(O)CH₃}(PCy₃)]BF₄ (5). In solution, complex 5 is only stable at temperatures lower than -40°C. At room temperature and in the presence of acetonitrile, it evolves into the alkyl compound [Ir(acac){CH₂CH₂C(O)CH₃}(NCCH₃)(PCy₃)]BF₄ (6), as a result from the selective anti-Markovnikov insertion of the carbon-carbon bond of the activated olefin into the Ir-H bond of the 5.

Full text of DOI:10.1016/S0022-328X(98)00690-1

Journal of Organometallic Chemistry 564 (1998) 241–247
CꢀH activation of methyl vinyl ketone in
Ir(acac){p2-CH2ꢁCHC(O)CH3}(PCy3)
Ricardo Castarlenas, Miguel A. Esteruelas *, Marta Mart´ın, Luis A. Oro
Departamento de Qu´ımica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n, Uni6ersidad de Zaragoza-CSIC, 50009 Zaragoza, Spain
Received 30 March 1998
Abstract
The cyclooctene complex Ir(acac)(cyclooctene)(PCy3) (1) reacts with methyl vinyl ketone to give Ir(acac){p2-
CH2ꢁCHC(O)CH3}(PCy3) (2) and cyclooctene. In benzene at 70°C, complex 2 affords by means of an intramolecular CꢀH
activation process the thermodynamically favored alkenyl derivative Ir¸(a¹c¹ac¹)H¹¹{(¹Z¹)-¹C¹H¹ꢁ¹C¹H¹C¹(ºO)CH3}(Pcy3) (3), which was
isolated as a mixture of the isomers 3a (PCy3 trans to carbonyl group of alkenyl ligand) and 3b (PCy3 trans to acac). Isomers 3a
and 3b do not react with tricyclohexylphosphine. However, the complex Ir(acac)H{(E)-CHꢁCHC(O)CH3}(PCy3)2 (4) can be
obtained by treatment of 2 with the phosphine in benzene at 70°C. Complex 2 also reacts with HBF4 at -78°C, to give the
five-coordinate hydrido derivative [Ir(acac)H{p2-CH2ꢁCHC(O)CH3}(PCy3)]BF4 (5). In solution, complex 5 is only stable at
temperatures lower than −40°C. At room temperature and in the presence of acetonitrile, it evolves into the alkyl compound
¸¹¹¹¹¹¹¹¹¹¹¹º
[Ir(acac){CH2CH2C(O)CH3}(NCCH3)(PCy3)]BF4 (6), as a result from the selective anti-Markovnikov insertion of the car-
bonꢀcarbon bond of the activated olefin into the IrꢀH bond of the 5. © 1998 Elsevier Science S.A. All rights reserved.
Keywords: CꢀH activation; Methyl vinyl ketone complexes; Iridium complexes; Hydrido complexes
1. Introduction
of ethylene with the coordinatively unsaturated frag-
ment Ir(p5-C5Me5)(PMe3) leads not only to coordina-
M(p2-olefin) complexes, which are key intermediates
in catalytic processes involving olefins, can be formed
by direct y-complexation and by vinylic oxidative addi-
tion followed by intramolecular reductive elimination
(Scheme 1). Thus, it has been observed that the reaction
tion but also to oxidative addition to give a
hydrido–vinyl metal complex, which isomerizes into
the thermodynamically favored y-olefin metal com-
pound [1].
The majority of hydrido–alkenyl metal complexes
are thermodynamically unstable with respect to the
corresponding M(p2-olefin) species [2–8]. However, in
the iridium chemistry, there are a few notable excep-
tions in which the relative stabilities are reversed. In
1988, Werner et al. [9] found that a number of activated
olefins reacted with [Ir(v-Cl)(PiPr3)2]2 to form octahe-
dral alkenyl-hydrido derivatives, via less stable Ir(p2-
olefin) intermediates. Subsequently, it was observed
that in cyclohexane at 100°C the four-coordinate com-
plex Ir(p2-TpMe, CF )(CO)(p -C2H4) completely isomer-
2
3
Scheme 1.
ized into the hydrido-vinyl Ir(p3-TpMe, CF )H-
3
* Corresponding author. Fax: +34 97 61761187.
(CHꢁCH2)(CO) [10], and that the reaction of
0022-328X/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00690-1

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R. Castarlenas et al. / Journal of Organometallic Chemistry 564 (1998) 241–247
singlets at 1.74 and 1.63 ppm for the protons of the
methyl groups of the i-diketonato ligand. The olefinic
protons of the activated olefin give rise to a doublet of
doublets of doublets (ꢁCH) at 3.95 ppm with HꢀH
coupling constants of 11.1 and 7.2 Hz and a HꢀP
coupling constant of 3.7 Hz, a doublet of doublets
[ꢁCH cis to ꢀC(CO)CH3] at 3.28 ppm with HꢀH cou-
pling constants of 11.1 and 1.6 Hz, and a doublet of
doublets of doublets [ꢁCH trans to ꢀC(O)CH3] at 2.42
ppm with HꢀH coupling constants of 7.2 and 1.6 Hz
and a HꢀP coupling constant also of 1.6 Hz. The low
value (11.1 Hz) of the Jtrans HꢀH should be noted, which
is reduced by 6.3 Hz with regard to the coupling
constant between the hydrogen protons mutually trans
disposed in the free methyl vinyl ketone (17.4 Hz). This
suggests that the coordination of the carbonꢀcarbon
double bond of the h,i-unsaturated ketone to the
iridium center of 2 produces a weaker intraligand car-
bonꢀcarbon double bond than that expected, as a result
of an unusually strong y-donor power of the metallic
center, which is comparable to that of the metal-based
half-sandwich complexes of type (C5R5)ML2 [17,18].
This is also revealed by the 13C{1H}-NMR spectrum,
which shows the resonances of the olefinic carbon
atoms at 39.2 and 22.3 ppm, shifted toward high field
by about 100 ppm in comparison with the resonances
of the free ligand (137.4 and 128.7 ppm). The 13C{1H}-
NMR spectrum of 2 also supports the square planar
coordination of the iridium atom. Thus, it shows a
singlet at 29.8 ppm and a doublet at 28.5 (JPꢀC=5.4
Hz) ppm, assigned to the inequivalent methyl groups of
the acetylacetonato ligand. The chemical shift, and the
multiplicity of these resonances as well as the value of
the PꢀC coupling constant agree well with those previ-
ously found in the related complexes Rh(acac)(p2-
RCꢂCR)(PCy3) (R=Ph, CO2CH3) [19]. Furthermore,
the spectroscopic data indicated that only one of the
two possible stereoisomers is formed.
[Ir(v-Cl)(cyclooctene)2]2
with
Na[HB(pz)3]
gave
IrH[HB(pz)3](|-C8H13)(C8H14) [11]. Recently, Carmona
et al. [12–14] have reported that IrTpMe (C2H4)2 ther-
2
mally rearranges into IrTpMe H(CHꢁCH2)(p -CH2ꢁ
CH2), which undergoes intramolecular coupling of the
vinyl and ethylene ligands with formation of the allylic
2
2
complex IrTpMe H(p -CH2CHCHMe), and is capable
of regioselectively activating the two CꢀH bond of the
O-bearing methylene groups of cyclic ethers with for-
mation of Fischer-type carbene derivatives, which also
contain an IrꢀH and Irꢀbutyl functionality.
3
2
In the search for transition–metal complexes which
are catalytically active in the hydrogenation, hydrosily-
lation and hydrostannylation of unsaturated organic
substrates, we have recently reported on the reactivity
of the acetylacetonato iridium compound Ir(a-
cac)(cyclooctene)(PCy3) [15]. As a continuation of this
work, we became interested to know whether complex
Ir(acac)(cyclooctene)(PCy3) can also be used as starting
material for the preparation of hydrido–alkenyl com-
pounds by oxidative addition of methyl vinyl ketone. In
this paper, we report on the synthesis of new alkenyl
and alkyl complexes, starting from Ir(acac)(cyclo-
octene)(PCy3) and methyl vinyl ketone.
2. Results and discussion
2.1. Synthesis and characterization of alkenyl
complexes
The
cyclooctene
ligand
of
Ir(acac)(cyclo-
octene)(PCy3) (1) is easily displaced by methyl vinyl
ketone. The addition of one equiv. of this activated
olefin to pentane suspensions of 1 affords Ir(acac){p2-
CH2ꢁCHC(O)CH3}(PCy3) (2) after 5 min. The reaction
proceeds at room temperature and the new compound
is isolated as an orange solid in 81% yield (Eq. 1).
The nucleophilic character of the metallic center of 2 is
also revealed by means of the oxidative addition of the
olefin CꢀH bond, disposed cis to the ꢀC(O)CH3 group of
the coordinated methyl vinyl ketone molecule. Thus, after
9 days at 70°C, benzene solutions of 2 afford mixtures of
the¸i¹so¹m¹e¹rs¹3¹a¹a¹n¹d¹3¹b¹o¹f ¹thºe hydrido–alkenyl complex
Ir(acac)H{(Z)-CHꢁCHC(O)CH3}(PCy3) (Scheme 2)
and 2 in a molar ratio of about 50:25:25. The isomeriza-
tion was followed by 1H- and 31P{1H}-NMR spec-
troscopy and the formation of products resulting from
the CꢀH activation of benzene was not observed. Be-
cause, in general, the CꢀH activation of benzene is
kinetically more favored than that of a vinylic group [20],
this observation suggests that the isomerization of 2 into
3 is an intramolecular process. This is confirmed by the
fact that neither reaction rate nor the above mentioned
The IR spectrum of 2 in KBr shows at 1578 and 1521
cm−1 two strong w(CO) absorptions for the carbonyl
groups of the acetylacetonato ligand, indicating that
this ligand is coordinated in a s2-oxygen bonding mode
[16]. The presence of the h,i-unsaturated ketone in 2 is
also supported by the IR spectrum which shows an-
other w(CO) band at 1657 cm−1. This value is lower
than the frequency for free methyl vinyl ketone ob-
served at 1681 cm−1. In agreement with the square-pla-
nar coordination of the iridium atom, at room
1
temperature, the H-NMR spectrum of 2 displays two

R. Castarlenas et al. / Journal of Organometallic Chemistry 564 (1998) 241–247
243
1
compound in Scheme 2. In the H-NMR spectrum, the
resonance due to the hydrido ligand is observed at
−24.03 ppm as a doublet with a HꢀP coupling con-
stant of 23.7 Hz, while those corresponding to the ꢁCH
protons of the alkenyl ligand appear at 11.56 and 7.31
ppm as doublets with a HꢀH coupling constants of 7.5
Hz. In the 13C{1H}-NMR spectrum, the resonance of
the carbon atom of the carbonyl group of the alkenyl
ligand, in contrast to that of 3a, appears as a singlet at
207.0 ppm. The resonances corresponding to the h- and
i-carbon atoms of the alkenyl ligand are observed at
199.6 and 137.9 ppm as doublets with PꢀC coupling
constants of 15.0 and 3.2 Hz, respectively. In addition it
should be mentioned a doublet (JPꢀC=6.1) at 27.5
ppm, due to a methyl group of the i-diketonato ligand,
which supports the trans disposition of the tricyclo-
hexylphosphine and a carbonyl group of the acetylacet-
onate. The 31P{1H}-NMR spectrum contains a singlet
at 13.0 ppm, which under off-resonance conditions due
to the PꢀH coupling is split into a doublet.
Scheme 2.
The structures of 3a and 3b were confirmed by NOE
experiments. Irradiating the hydrido resonance of 3a
gave an increase in the intensities of the both signals of
the vinylic protons of the alkenyl ligand, whereas irra-
diating the hydrido resonance of 3b gave an increase in
the intensities of the h-vinylic proton of the alkenyl
group and the ꢀCHꢀ proton of the acetylacetonato
ligand, and the signal of the i-vinyl proton of the
alkenyl group showed a negative NOE.
Isomers 3a and 3b do not regenerate the y-olefin
complex 2 even after 2 months, suggesting that the
hydrido-alkenyl-iridium moiety is thermodynamically
more stable than the Ir{p2-CH2ꢁCHC(O)CH3} unit.
The stabilization of the hydrido-alkenyl-iridium moiety
caused by the chelate formation also manifests itself in
isomers 3a and 3b being inert towards tricyclo-
hexylphosphine. So, the addition of this phosphine to
toluene solutions of 3a and 3b does not open the
chelate ring by breaking of the IrꢀO bond, even under
reflux conditions. However, a new compound contain-
ing a monodentate alkenyl ligand is obtained from the
reaction of 2 with tricyclohexylphosphine. Thus, the
treatment of 2 in benzene with one equiv. of tricyclo-
hexylphosphine at 70°C affords after 7 days the hy-
drido–alkenyl complex Ir(acac)H{(E)ꢀCHꢁCHC(O)-
CH3}(PCy3)2 (4), which was isolated as a white solid in
78% yield (Scheme 2).
molar ratio are affected by the presence of an equiva-
lent of methyl vinyl ketone in the solutions of 2.
Isomers 3a and 3b were separated from the mixture
by column chromatography (Al2O3 neutral, activity
grade V) and characterized by MS, IR and 1H,
13C{1H} and 31P{1H}-NMR spectroscopy.
In agreement with the structure shown in Scheme 2,
in high field region of the 1H-NMR spectrum, the
isomer 3a displays at −24.47 ppm a doublet with a
HꢀP coupling constant of 24.0 Hz, which strongly
supports the cis disposition of the hydrido and phos-
phine ligands. In low field region, the most noticeable
resonances appear at 11.34 and 6.98 ppm as doublets of
doublets with a HꢀH coupling constant of 7.5 Hz and
HꢀP coupling constants of 1.8 and 1.4 Hz, respectively,
and were assigned to the vinylic hydrogen atoms of the
alkenyl ligand. With regard to the value of the HꢀH
coupling constant there is no doubt about the mutually
cis disposition of these atoms. The coordination of the
carbonyl group of the alkenyl ligand and its disposition
trans in relation to the phosphine ligand is strongly
supported by the 13C{1H}-NMR spectrum, which
shows at 208.4 ppm a doublet with a PꢀC coupling
constant of 3.2 Hz. The resonances of the h- and
i-carbon atoms of the alkenyl ligand are observed at
201.9 and 135.2 ppm, respectively. In agreement with
the mutually cis disposition of the h-carbon and the
tricyclohexylphosphine ligand, the first of them appears
as a doublet with a PꢀC coupling constant of 6.8 Hz,
and the second one as a singlet. The 31P{1H}-NMR
spectrum shows a singlet at 15.8 ppm, which under
off-resonance conditions due to the PꢀH coupling is
split into a doublet.
The behavior of 2 is similar to that of the related
ethylene derivative Ir(acac)(p2-CH2ꢁCH2)(PiPr3) which
evolves in benzene at 60°C, in the presence of triiso-
propylphosphine, into the hydrido–vinyl compound
Ir(acac)H(CHꢁCH2)(PiPr3)2 [21].
Previously, we have observed that in the presence of
tricyclohexylphosphine, the complex Ir(acac)(cyclo-
octene)(PCy3) reacts with molecular hydrogen, pheny-
lacetylene, silanes and HSnPh3 to afford six-coordinate
1
The H, 13C{1H} and 31P{1H}-NMR spectra of 3b
also agree well with the structure proposed for this

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R. Castarlenas et al. / Journal of Organometallic Chemistry 564 (1998) 241–247
iridium(III) derivatives Ir(acac)HX(PCy3)2 (X=H,
C2Ph, SiR3, SnPh3). Because, the related five-coordinate
complexes Ir(acac)HX(PCy3) do not react with tricyclo-
hexylphosphine to give Ir(acac)HX(PCy3)2, we have
suggested that the formation of the six-coordinate iridi-
um(III) compounds proceeds via four-coordinate iridi-
um(I) intermediates containing the acetylacetonate
coordinated in a p1-C3-fashion [15]. The formation of 4
according to Scheme 2 and the inertia of 3a and 3b
towards tricyclohexylphosphine are new evidences in
favor of this proposal.
at 1686 cm−1, and an absorption due to the [BF4]−
anion with Td symmetry centered at 1061 cm−1, indi-
cating that, although the metallic center of 5 is coordi-
natively unsaturated, the anion is not coordinated to
the iridium atom.
The presence of the hydrido ligand in 5 is also
supported by the 1H- and 31P{1H}-NMR spectra in
1
dichloromethane-d2 at 213 K. Thus, the H-NMR spec-
trum shows a hydrido resonance at −17.19 ppm,
which appears as a doublet with a HꢀP coupling con-
stant of 18.0 Hz, and the 31P{1H}-NMR spectrum
contains a singlet at 7.4 ppm, which under off-reso-
nance conditions due to the PꢀH coupling is split into a
In addition, it should be mentioned the high stability
of the hydrido-alkenyl-iridium moiety of 4 toward the
reductive elimination of methyl vinyl ketone. In this
case, it can be related to the cis constraint imposed by
the chelating acetylacetonato ligand and the fact that in
a concerted reductive elimination the ligands trans to
the leaving groups move into mutually trans positions
in the resulting four-coordinate complex [22–24].
Complex 4 was characterized by elemental analysis,
MS, IR and 1H-, 13C{1H}- and 31P{1H}-NMR spec-
troscopy. In the IR spectrum of 4 in KBr, the most
prominent feature is a w(IrꢀH) band at 2243 cm−1. In
1
doublet. In the H-NMR spectrum, the olefinic protons
of the methyl vinyl ketone give rise to a doublet of
doublets (ꢁCH) at 4.54 ppm with HꢀH coupling con-
stants of 12.1 and 6.0 Hz, another doublet of doublets
[ꢁCH cis to ꢀC(O)CH3] at 4.10 ppm with HꢀH and
HꢀP coupling constants of 12.1 and 2.7 Hz, respec-
tively, and a doublet [ꢁCH trans to ꢀC(O)CH3] at 3.63
ppm with a HꢀH coupling constant of 6.0 Hz. In
addition, it should be noted that the value of the
Jtrans HꢀH of 5 is 1.0 Hz higher than that of 2, in
agreement with the expected decrease of the nucle-
ophilic character of the metallic center of 2 as a result
from the protonation. This is also revealed by the
13C{1H}-NMR spectrum of 5 in dichloromethane-d2 at
1
the H-NMR spectrum the resonance due to the hy-
drido ligand is observed at −24.46 ppm, as a triplet
with a HꢀP coupling constant of 16.2 Hz. The reso-
nances corresponding to the vinylic hydrogen atoms of
the alkenyl group appear at 10.91 (IrꢀCHꢁ) and 6.48
(ꢁCHꢀ) ppm as doublets with a HꢀH coupling constant
of 16.5 Hz. This value strongly supports the trans
stereochemistry at the carbon–carbon double bond
[25]. In the 13C{1H}-NMR spectrum the resonances due
to the IrꢀCHꢁ and ꢁCHꢀ alkenyl carbon atoms are
observed at 160.5 and 141.1 ppm, respectively. The
31P{1H}-NMR spectrum shows a singlet at 14.0 ppm,
which under off-resonance conditions due to the PꢀH
coupling is split into a doublet.
2.2. Synthesis and characterization of alkyl complexes
The nucleophilic character of the metallic center of 2
is not only revealed by the reactions shown in Scheme
2 but also by the reaction of this complex with HBF4
(Scheme 3). Treatment of diethyl ether suspensions of 2
with 1 equiv. of HBF4.OEt2 at −78°C affords the
hydrido-y-olefin complex [Ir(acac)H{p2-CH2ꢁCHC(O)-
CH3}(PCy3)]BF4 (5), which was isolated as a white
solid in 71% yield.
The IR spectrum of 5 in KBr strongly supports the
presence of the hydrido ligand, showing the IrꢀH
stretching frequency at 2232 cm−1. This spectrum also
contains two w(CO) bands at 1583 and 1523 cm−1 in
agreement with the s2-oxygen coordination bonding
mode of the acetylacetonato group. Furthermore, the
spectrum shows the w(CO) band corresponding to the
carbonyl group of the coordinated methyl vinyl ketone
Scheme 3.

R. Castarlenas et al. / Journal of Organometallic Chemistry 564 (1998) 241–247
245
methyl vinyl ketone yields the derivative Ir(acac){p2-
CH2ꢁCHC(O)CH3}(PCy3), where the iridium atom
shows a strong y-donor power. The nucleophilic char-
acter of the metallic center of this complex is evident in
the intramolecular oxidative addition of a CꢀH olefinic
bond of the coordinated h,i-unsaturated ketone to give
th¸e¹¹t¹he¹r¹m¹o¹dy¹n¹a¹m¹ic¹al¹ly¹ºfavored alkenyl complex
Ir(acac)H{(Z)ꢀCHꢁCHC(O)CH3}(PCy3), and in the re-
action with HBF4 to afford the five-coordinate hydrido
compound [Ir(acac)H{p2-CH2ꢁCHC(O)CH3}(PCy3)]-
BF4.
213 K, which shows the resonances of the olefinic
carbon atoms as singlets at 52.9 and 24.8 ppm. The first
of them shifted 13.7 ppm to lower field in comparison
with related resonance of 2. Furthermore, it must be
mentioned that, in agreement with the structure pro-
posed for 5 in Scheme 3, the resonances corresponding
to the carbonyl group of the methyl vinyl ketone and
the methyl groups of the acetylacetonato ligand appear
as singlets at 214.0, 29.6 and 27.9 ppm, respectively.
In the solid state, complex 5 is stable for a week if
kept under argon at −20°C. Under argon and at
temperatures lower than −40°C, the dichloromethane
solutions of 5 are also stable. However at higher tem-
peratures, these solutions rapidly evolve to a mixture of
eight products, according to the 31P{1H}-NMR spectra,
which could not be identified.
The high stability of the hydrido-alkenyl-iridium
moiety of Ir¸(a¹c¹ac¹)H¹¹{(¹Z¹)ꢀ¹C¹H¹ꢁ¹C¹H¹C¹(ºO)CH3}(PCy3),
caused by the chelated formation, is also manifes-
ted by its inertia towards PCy3. Although this
complex does not react with the phosphine, an
¸¹¹¹¹¹¹¹¹¹¹¹¹¹¹º
Ir(acac)H{(E)ꢀCHꢁCHC(O)CH3}(PCy3)2 derivative is
obtained by treatment of Ir(acac){p2-CH2ꢁCHC(O)-
CH3}(PCy3) with PCy3. This complex is also very sta-
ble, and its stability can be related to the cis constraint
imposed by chelating acetylacetonato ligand, and the
fact that in a concerted reductive elimination the lig-
ands trans to the leaving groups move into mutually
trans positions in the resulting four-coordinate com-
plex.
The five coordinate hydrido complex [Ir(acac)-
H{p2-CH2ꢁCHC(O)CH3}(PCy3)]BF4 is only stable at
very low temperature. Attempts to stabilize it by
ad¸d¹it¹io¹n¹¹of¹¹a¹ce¹to¹n¹iºtrile lead to the alkyl derivative
[Ir(acac){CH2CH2C(O)CH3}(NCCH3)(PCy3)]BF4, as a
result from the selective anti-Markovnikov insertion of
the carbon–carbon double bond of the activated olefin
into the IrꢀH bond.
Attempts to stabilize 5 by addition of acetonitrile
lead to a white solid in 92% yield. According to the
elemental analysis, the composition corresponds to a
1
1:1 adduct of 5 and acetonitrile. The H-NMR spec-
trum of this new compound does not contain a signal in
the hydrido region, which suggests that an insertion
reaction of the activated olefin into the IrꢀH bond of 5
has taken place.
1
With regard to the IR and H- and 13C{1H}-NMR
spectra, there is no doubt that an anti-Markovnikov
type of insertion has taken place and the alkyl complex
[Ir¸(a¹c¹ac¹)¹{C¹H¹¹2C¹H¹¹2C¹(ºO)CH3}(NCCH3)(PCy3)] BF4 (6 in
Scheme 3) has been formed.
The IR spectrum in KBr shows together with the
w(CO) bands of the acetylacetonato ligand at 1587 and
1514 cm−1, a CꢁO stretching frequency at 1630 cm−1
corresponding to a coordinated ketonic CꢁO group (for
In conclusion, we report the synthesis of a new olefin
complex with a very remarkable nucleophilic character,
which allows the preparation of new alkenyl and alkyl
compounds by means of oxidative addition reactions.
1
comparison, see Refs. [26–28]). In the H-NMR spec-
trum, besides the signals of the phosphine, acetylaceto-
nato and acetonitrile protons three absorptions are
observed at 2.95, 2.65 and 2.43 ppm, which are assigned
to the IrCH2, ꢀCH2ꢀ and ꢀCH3 protons of the metalla-
cycle. The resonances of IrCH2 and ꢀCH2ꢀ carbon
atoms of metallacycle appear in the 13C{1H}-NMR
spectrum at −8.9 and 52.5 ppm, respectively, the first
one is observed as a doublet with a PꢀC coupling
constant of 5.6 Hz, while the second one is observed as
a singlet. Furthermore, the spectrum contains at 236.2
ppm a doublet with a PꢀC coupling constant of 3.2 Hz,
for the ketonic carbon atom of alkyl ligand, which
supports its coordination and its trans disposition in
relation to the phosphine ligand. The 31P{1H}-NMR
spectrum shows a singlet at −4.3 ppm.
4. Experimental section
All reactions were carried out under argon atmo-
sphere using Schlenk tube techniques. Solvents were
dried by known procedures and distilled under argon
prior to use. The starting complex Ir(acac)(coe)(PCy3)
(1) was prepared by the published method [29]. IR
spectra were recorded on a Perkin Elmer 883 spectrom-
eter, and the NMR spectra on Varian UNITY 300,
Varian GEMINI 2000 (300 MHz) and Bruker ARX
300 instruments. The 13C-NMR signals were assigned
by DEPT experiments. C, H and N analyses were
carried out with a Perkin Elmer 2400 CHNS/O micro-
analyzer. MS data were recorded on a VG Auto Spec
instrument. The ions were produced, FAB+ mode,
with the standard Cs+ gun at ca. 30 kV, and 3-ni-
trobenzyl alcohol (NBA) was used as the matrix.
3. Concluding remarks
This study has revealed that the reaction of the
cyclooctene complex Ir(acac)(cyclooctene)(PCy3) with

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R. Castarlenas et al. / Journal of Organometallic Chemistry 564 (1998) 241–247
4.1. Preparation of Ir¸(a¹c¹ac¹)¹{p¹2¹-¹C¹H¹2¹ꢁ¹C¹H¹C¹(ºO)CH3}-
(PCy3) (2)
onance). Data for 3b: IR (CH2Cl2, cm−1): w(IrꢀH)
2219; w(CO)acac 1585 and 1521; w(CO)mvk overlapped by
w(CO)acac. H-NMR (300 MHz, C6D6): l 11.56 (d, 1H,
1
J
cis HꢀH=7.5 Hz, IrCH
6 ꢁCH); 7.31 (d, 1H, Jcis HꢀH=7.5
A suspension of 1 (1009 mg, 1.48 mmol) in 25 ml of
n-pentane was treated with methyl vinyl ketone (121 ml,
1.48 mmol). A spontaneous color change from yellow
to orange occurred, and the mixture was stirred for 5
min at room temperature. Then the solution was con-
centrated in vacuo for about 5 ml yielding an orange
precipitate. The solvent was decanted, and the solid was
washed with n-pentane (3×1 ml) and dried in vacuo.
Yield 775 mg (81%). Anal. Calcd. for C27H46IrO3P: C,
50.53; H, 7.22. Found: C, 50.55; H, 7.53. IR (KBr,
Hz, IrCHꢁCH); 5.22 (s, 1H, CH of acac); 2.10 (s, 3H,
6
CH3 of mvk); 1.83 and 1.75 (both s, 6H, CH3 of acac);
2.2–1.0 (m, 33H, PCy3); −24.03 (d, 1H, JPꢀH=23.7
Hz, IrH). 13C{1H}-NMR (75.4 MHz, C6D6): l 207.0 (s,
CO of mvk); 199.6 (d, JPꢀC=15.0 Hz, IrC
184.4 and 184.1 (both s, CO of acac); 137.9 (d, JPꢀC
3.2 Hz, IrCHꢁCH); 100.7 (d, JPꢀC=1.4 Hz, CH of
acac); 33.7 (d, JPꢀC=31.8 Hz, CH of PCy3); 27.5 (d,
PꢀC=6.1 Hz, CH3 of acac); 25.4 (s, CH3 of acac); 23.7
6 HꢁCH);
=
6
J
(s, CH3 of mvk); 28.9, 27.9, 27.8 and 26.9 (all s, CH2 of
PCy3). 31P{1H}-NMR (121.4 MHz, C6D6): l 13.0 (s; d
off-resonance). MS (FAB+): m/z=641 (M+ −1).
1
cm−1): w(CO)mvk 1657; w(CO)acac 1578 and 1521. H-
NMR (300 MHz, C6D6): l 5.19 (s, 1H, CH of acac);
3.95 (ddd, 1H, Jtrans HꢀH=11.1 Hz, Jcis HꢀH=7.2 Hz,
4.3. Preparation of Ir¸(a¹c¹ac¹)¹H¹{¹(E¹)¹(C¹H¹ꢁ¹C¹H¹¹Cº(O)CH3}-
(PCy3)2 (4)
J
J
PꢀH=3.7 Hz, ꢁCH); 3.28 (dd, 1H, Jtrans HꢀH=11.1 Hz,
gem HꢀH=1.6 Hz, ꢁCH2); 2.42 (ddd, 1H, Jcis HꢀH=7.2
Hz, Jgem HꢀH=JPꢀH=1.6 Hz, ꢁCH2); 2.34 (s, 3H, CH3
of mvk); 1.74 and 1.63 (both s, 6H, CH3 of acac);
2.2–1.1 (m, 33H, PCy3). 13C{1H}-NMR (75.4 MHz,
C6D6): l 206.7 (s, CO of mvk); 187.4 and 180.9 (both s,
CO of acac); 101.4 (s, CH of acac); 39.2 (s, ꢁCH); 31.6
(d, JPꢀC=29.8 Hz, CH of PCy3); 30.4 and 30.2 (both s,
CH2 of PCy3); 29.8 (s, CH3 of acac); 28.5 (d, JPꢀC=5.4
Hz, CH3 of acac); 28.1, 28.0 and 27.0 (all s, CH2 of
PCy3); 26.2 (s, CH3 of mvk); 22.3 (s, ꢁCH2). 31P{1H}-
NMR (121.4 MHz, C6D6): l 0.1(s).
A solution of 2 (300 mg, 0.47 mmol) in 15 ml of
benzene was treated with PCy3 (143 mg, 0.51 mmol)
and stirred for 7 days at 70°C. During this time the
color turned from orange to brown. The solution was
concentrated to ca. 1 ml and chromatographed on
alumina neutral (activity grade V). THF eluted a brown
fraction from which the solvent was removed in vacuo
affording a brown solid. The precipitate was washed
twice with 2 ml of methanol yielding a white solid.
Yield: 340 mg (78%). Anal. Calcd. for C45H79IrO3P2: C,
58.60; H, 8.63. Found: C, 58.51; H, 8.25. IR (KBr,
cm−1): w(IrꢀH) 2243; w(CO)mvk 1639; w(CO)acac 1590
4.2. Preparation of Ir¸(a¹ca¹c¹)H¹{¹(¹Z¹)ꢀ¹C¹H¹ꢁ¹C¹H¹C¹(ºO)-
CH3}(PCy3) (3a,b)
1
and 1517. H-NMR (300 MHz, C6D6): l 10.91 (d, 1H,
J
J
trans HꢀH=16.5 Hz, IrCH
trans HꢀH=16.5 Hz, IrCHꢁCH
6
ꢁCH); 6.48 (d, 1H,
A solution of 2 (300 mg, 0.47 mmol) in 15 ml of
benzene was stirred for 9 days at 70°C and the color
turned from orange to brown. The solution was con-
centrated to ca. 1 ml and chromatographed on alumina
neutral (activity grade V). A diethyl ether/n-pentane
(7/3) mixture eluted a yellow fraction from which the
solvent was removed in vacuo affording a yellow oil
that contained both isomers a,b (2/1). Data for 3a: IR
(CH2Cl2, cm−1): w(IrꢀH) 2219; w(CO)acac 1585 and
1521; w(CO)mvk overlapped by w(CO)acac. 1H-NMR (300
6
); 5.23 (s, 1H, CH of
acac); 2.33 (s, 3H, CH3 of mvk); 1.84 and 1.68 (both s,
6H, CH3 of acac); 2.1–1.1 (m, 66H, PCy3); −24.46 (t,
1H, JPꢀH=16.2 Hz, IrH). 13C{1H}-NMR (75.4 MHz,
C6D6): l 193.1 (s, CO of mvk); 186.5 and 184.0 (both s,
CO of acac); 160.5 (t, JPꢀC=7.4 Hz, IrC
(s, IrCHꢁCH); 103.2 (s, CH of acac); 32.8 (vt, N=24.4
Hz, CH of PCy3); 29.9 and 28.5 (both s, CH3 of acac);
29.0 and 28.8 (both s, CH2 of PCy3); 28.2–28.0 (CH2 of
PCy3); 25.4 (s, CH3 of mvk). 31P{1H}-NMR (121.4
MHz, C6D6): l 14.0 (s; d off-resonance). MS (FAB+):
m/z=923 (M+ +1).
6 HꢁCH); 141.1
6
MHz, C6D6): l 11.34 (dd, 1H, Jcis HꢀH=7.5 Hz, JPꢀH
1.8 Hz, IrCHꢁCH); 6.98 (dd, 1H, Jcis HꢀH=7.5 Hz,
PꢀH=1.4 Hz, IrCHꢁCH); 5.31 (s, 1H, CH of acac);
=
6
J
6
4.4. Preparation of [Ir¸(a¹ca¹c¹)H¹{¹p¹2¹-C¹H¹2¹ꢁ¹C¹H¹C¹(Oº)CH3}-
(PCy3)]BF4 (5)
2.06 (s, 3H, CH3 of mvk); 1.89 and 1.79 (both s, 6H,
CH3 of acac); 2.2–1.0 (m, 33H, PCy3); −24.47 (d,
J
PꢀH=24.0 Hz, IrH). 13C{1H}-NMR (75.4 MHz,
C6D6): l 208.4 (d, JPꢀC=3.2 Hz, CO of mvk); 201.9 (d,
PꢀC=6.8 Hz, IrCHꢁCH); 185.5 and 185.2 (both s, CO
of acac); 135.2 (s, IrCHꢁCH); 100.8 (d, JPꢀC=1.9 Hz,
CH of acac); 33.7 (d, JPꢀC=31.8 Hz, CH of PCy3);
28.9, 27.9, 27.8 and 26.8 (all s, CH2 of PCy3); 28.2 and
27.6 (both s, CH3 of acac); 23.8 (s, CH3 of mvk).
31P{1H}-NMR (121.4 MHz, C6D6): l 15.8 (s; d off-res-
A suspension of 2 (160 mg, 0.25 mmol) in diethyl
ether (15 ml) was cooled to −78°C and treated with
HBF4 (34 ml, 0.25 mmol). The suspension was stirred
for 30 min and the color changed from orange to
brown. The solid was washed three times with 2 ml of
cold diethyl ether and dried in vacuo to obtain 4 as a
white solid. Yield 130 mg (71%). Anal. Calcd. for
J
6
6

R. Castarlenas et al. / Journal of Organometallic Chemistry 564 (1998) 241–247
247
thanks the Ministerio de Educacio´n y Ciencia of Spain
for a grant.
C27H47BF4IrO3P: C, 44.44; H, 6.49. Found: C 44.33; H,
6.98. IR (KBr, cm−1): w(IrꢀH) 2232; w(CO)mvk 1686;
1
w(CO)acac 1583 and 1523; w(BF4) 1061. H-NMR (300
MHz, CD2Cl2, 213 K): l 5.63 (s, 1H, CH of acac); 4.54
(dd, 1H, Jtrans HꢀH=12.1 Hz, Jcis HꢀH=6.0 Hz, ꢁCH);
4.10 (dd, 1H, Jtrans HꢀH=12.1 Hz, JPꢀH=2.7 Hz,
ꢁCH2); 3.63 (d, 1H, Jcis HꢀH=6.0 Hz, ꢁCH2); 2.44 (s,
3H, CH3 of mvk); 2.05 and 2.01 (both s, 6H, CH3 of
References
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acac); 2.5–1.1 (m, 33H, PCy3); −17.19 (d, 1H, JPꢀH
=
18.0 Hz, IrH). 13C{1H}-NMR (75.4 MHz, CD2Cl2, 213
K): l 214.0 (s, CO of mvk); 187.7 and 185.3 (both s,
CO of acac); 102.1 (s, CH of acac); 52.9 (s, ꢁCH); 36.2
(s, CH3 of mvk); 34.5 (d, JPꢀC = 34.7 Hz, CH of
PCy3); 30.5–26.7(CH2 of PCy3); 29.6 and 27.9 (both s,
CH3 of acac); 24.8 (s, ꢁCH2). 31P{1H}-NMR (121.4
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4.5. Preparation of [Ir¸(a¹c¹ac¹)¹{C¹H¹¹2C¹H¹2¹C¹(ºO)CH3}-
(NCCH3)(PCy3)]BF4 (6)
[9] H. Werner, T. Dirnberger, M. Schulz, Angew. Chem. Int. Ed.
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A suspension of 5 (100 mg, 0.14 mmol) in 15 ml of
diethyl ether was cooled to −78°C and treated with
acetonitrile (9 ml, 0.15 mmol). After 5 min at low
temperature the suspension was allowed to warm to
room temperature and stirred 40 min. The color was
clearer and the white precipitate was decanted, washed
with diethyl ether (4×2 ml) and dried in vacuo. Yield
98 mg (91%). Anal. Calcd. for C29H50NBF4IrO3P: C,
45.19; H, 6.54. Found: C 45.15; H, 6.83. IR (KBr,
cm−1): w(CN) 2239; w(CO)mvk 1630; w(CO)acac 1587 and
1514; w(BF4) 1060. 1H-NMR (300 MHz, CD2Cl2): l
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Cano, J. Organomet. Chem. 307 (1986) 83.
5.48 (s, 1H, CH of acac); 2.95 (m, 2H, IrCH2
6 CH2); 2.73
[17] H. Werner, Angew. Chem. Int. Ed. Engl. 22 (1983) 927.
[18] M.A. Esteruelas, A.M. Lo´pez, N. Ruiz, J.I. Tolosa,
Organometallics 16 (1997) 4657.
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P. Steinert, H. Werner, Organometallics 15 (1996) 3436.
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4244.
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2297.
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2295.
(s, 3H, NCCH3); 2.65 (m, 2H, IrCH2CH2) 2.43 (s, 3H,
6
6
CH3 of mvk); 2.07 and 1.81 (both s, 6H, CH3 of acac);
2.0–1.1 (m, 33H, PCy3). 13C{1H}-NMR (75.4 MHz,
CD2Cl2): l 236.2 (d, JPꢀC=3.2 Hz, CO of mvk); 189.7
and 184.7 (both s, CO of acac); 120.3 (s, NC
102.0 (d, JPꢀC=3.2 Hz, CH acac); 52.5 (s, IrCH2C
34.9 (d, JPꢀC=31.3 Hz, CH of PCy3); 28.7, 28.1, 27.8
and 26.5 (all s, CH2 of PCy3); 28.6 and 28.0 (both s,
6
CH3);
H2);
6
CH3 of acac); 26.9 (s, CH3 of mvk); 4.3 (s, NCC
6 H3);
−8.9 (d, JPꢀC=5.6 Hz, IrC
(121.4 MHz, CD2Cl2): l −4.3 (s).
6
H2CH2). 31P{1H}-NMR
[26] H. Werner, R. Weinand, H. Otto, J. Organomet. Chem. 307
(1986) 49.
[27] H. Werner, U. Meyer, K. Peters, H.G. von Schnering, Chem.
Ber. 122 (1989) 2097.
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Schu¨lnken, C. Valero, H. Werner, Organometallics 11 (1992)
2034.
Acknowledgements
We thank the DGICYT (Projects PB 94-1186 and PB
95-0806, Programa de Promocio´n General del
Conocimiento) for financial support and R. Castarlenas
[29] M.A. Esteruelas, F.J. Lahoz, E. On˜ate, L.A. Oro, L. Rodriguez,
Organometallics 14 (1995) 263.
.