Synthesis, structure and catalytic activity of the first iridium(I) siloxide versus chloride complexes with 1,3-mesitylimidazolin-2-ylidene ligand

Article abstract of DOI:10.1016/j.jorganchem.2007.11.013

The first iridium(I) complex containing siloxyl and N-heterocyclic carbene ligand such as [Ir(cod)(IMes)(OSiMe₃)] (1) and [Ir(CO)₂(IMes)(OSiMe₃)] (3) have been synthesized and their structures solved by spectroscopy and X-ray methods as well as catalytic properties in selected hydrogenation reactions have been presented in comparison to their chloride analogues, i.e. [Ir(Cl)(cod)(IMes)] (2) and [Ir(Cl)(CO)₂(IMes)] (4). The attempts at synthesis of iridium(I) complex with tert-butoxyl ligand has failed as leading instead to the iridium hydroxide complex [Ir(cod)(OH)(IMes)] (5) whose X-ray structure has also been solved. All complexes (1)-(5) show square planar geometry typical of the four-coordinated iridium complexes. Catalytic activity of complexes 1 and 2 was tested in transfer hydrogenation of acetophenone and hydrogenation of olefins.

Full text of DOI:10.1016/j.jorganchem.2007.11.013

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 693 (2008) 321–328
www.elsevier.com/locate/jorganchem
Synthesis, structure and catalytic activity of the first iridium(I) siloxide
versus chloride complexes with 1,3-mesitylimidazolin-2-ylidene ligand
Ireneusz Kownacki, Maciej Kubicki, Karol Szubert, Bogdan Marciniec *
Department of Organometallic Chemistry, Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznan, Poland
Received 28 September 2007; received in revised form 6 November 2007; accepted 7 November 2007
Available online 17 November 2007
Abstract
The first iridium(I) complex containing siloxyl and N-heterocyclic carbene ligand such as [Ir(cod)(IMes)(OSiMe
3
)] (1) and
[
Ir(CO) (IMes)(OSiMe )] (3) have been synthesized and their structures solved by spectroscopy and X-ray methods as well as catalytic
2
3
properties in selected hydrogenation reactions have been presented in comparison to their chloride analogues, i.e. [Ir(Cl)(cod)(IMes)] (2)
and [Ir(Cl)(CO) (IMes)] (4). The attempts at synthesis of iridium(I) complex with tert-butoxyl ligand has failed as leading instead to the
2
iridium hydroxide complex [Ir(cod)(OH)(IMes)] (5) whose X-ray structure has also been solved. All complexes (1)–(5) show square pla-
nar geometry typical of the four-coordinated iridium complexes. Catalytic activity of complexes 1 and 2 was tested in transfer hydroge-
nation of acetophenone and hydrogenation of olefins.
Ó 2007 Published by Elsevier B.V.
Keywords: Iridium siloxide complexes; Imidazolin-2-ylidene ligand; Catalysis; Hydrogenation reactions
1
. Introduction
and papers [5]. In the last decade, numerous reports on syn-
thesis of neutral and cationic iridium complexes with vari-
ous monodentate and polydentate carbene ligands have
been published [6]. Iridium-carbene complexes have been
proved very attractive and efficient catalysts of organic
transformations including: hydrogenation [6j,6w,7], trans-
fer hydrogenation [6h,6l,8], hydroamination [6r], Oppe-
nauer-type oxidation [6s], hydrosilylation of olefins [6k]
and ketones [6o]. Molecular compounds containing a
TM–O–Si moiety are regarded as models of metal com-
plexes immobilized on silica and silicate surfaces known
to catalyze a variety of organic transformations [9–11].
Since 1982 more than 100 new TM–siloxide complexes
including terminal and/or also bridging siloxy ligands have
been synthesized and characterized by X-ray and spectro-
scopic methods to determine their molecular structure
(for a review see [9a,9b] and references therein). The
properties of siloxide as an ancillary ligand in the system
TM–O–SiR3 have been effectively utilized in molecular
catalysis but predominantly by early transition metal
complexes. We have reported previously the synthetic
methods and crystal structures of binuclear and
N-heterocyclic carbenes have recently attracted consid-
erable attention in homogeneous catalysis because they
can be used instead of sterically demanding tertiary phos-
phine ligands [1] which control the reactivity and selectivity
of transition metal complexes as reaction catalysts [2,3].
The phosphorus based ligands are air sensitive and at high
temperatures the P–C bond in these ligands undergoes deg-
radation [2b]. On the other hand, strongly nucleophilic
(
electron-rich) bulky ligands and resistant to oxidation
agents such as carbenes, formed from N and C substituted
imidazolium salts, can be considered as alternatives to
phosphines [4]. The complexes with stable carbenes are
known to be formed by almost all metals of the periodic
table. Synthetic methods and properties of various
carbenes and their TM-complexes (where TM = transition
metal) have been recently described in a number of reviews
*
Corresponding author. Tel.: +48 618291366; fax: +48 618291508.
E-mail address: marcinb@amu.edu.pl (B. Marciniec).
0
022-328X/$ - see front matter Ó 2007 Published by Elsevier B.V.
doi:10.1016/j.jorganchem.2007.11.013

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I. Kownacki et al. / Journal of Organometallic Chemistry 693 (2008) 321–328
phosphine-containing mononuclear rhodium(I) [12] and
iridium(I) [13] siloxide complexes, as well as the application
of those complexes in catalytic transformations of organo-
silicon compounds, i.e. silylative coupling of olefins with
vinylsilanes [13a,14], curing of polysiloxanes via hydrosily-
lation [15] as well as hydroformylation [16] and silylcarb-
onylation [17] of vinylsilanes.
In this paper, we present the synthesis of the first irid-
ium(I) complexes containing siloxyl and carbene ligands
as well as their structure and catalytic properties in selected
reactions in comparison to those of their chloride
analogues.
2
. Results and discussion
Fig. 1. Anisotropic ellipsoid representation of complex 1. The ellipsoids
are drawn at 50% probability level, hydrogen atoms are omitted for
clarity. X1 and X2 are the middlepoints of C@C bonds.
2.1. Synthesis of carbene iridium(I) complexes and
structural studies
The 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene
ligand was synthesized from bis(2,4,6-trimethylphenyl)imi-
dazolium chloride according to a well known method [5]
and was used for the reaction in the pure form. Treatment
of imidazolin-2-ylidene ligand with binuclear complexes
[
{Ir(l-X)(cod)} ] (where X = Cl, OSiMe ) in benzene solu-
2 3
tion gave mononuclear complexes. Their formation occurs
via a cleavage of bridging bonds in the dimeric form,
according to the equation presented in Scheme 1, similarly
to the procedure observed for nucleophilic ligands, e.g.
PCy [13b].
3
1
13
Both H and C NMR support the complexation of the
iridium atom with the carbene ligand. The H NMR spec-
Fig. 2. Anisotropic ellipsoid representation of complex 2. The ellipsoids
are drawn at 50% probability level, hydrogen atoms are omitted for
clarity. X1 and X2 are the middlepoints of C@C bonds.
1
tra show resonance lines coming from 1,3-bis(2,4,6-tri-
methylphenyl)imidazolin-2-ylidene ligand at 6.92; 6.80
(
2
6
2,4,6-Me C H ); 6.15 (@CHN); 2.59, 2.19, 1.90 (–CH ,
tert-butoxyl ligand, which is a structural analogue to irid-
ium siloxide complex 1. Unfortunately, treatment of 2 with
3
6
2
3
,4,6-Me C H ) for 1 and 6.78; 6.81 (2,4,6-Me C H );
3 6 2 3 6 2
t
t
.15 (@CHN); 2.59, 2.15, 2.05 (–CH , 2,4,6-Me C H )
typical reagents e.g. NaOBu or KOBu have not given the
expected iridium tert-butoxide derivative, but instead, the
iridium(I) hydroxide carbene complex 5 was obtained.
Reaction of 1 and 2 complexes with carbon monoxide
affords iridium derivatives containing two carbonyl
ligands, according to Scheme 2.
3
3
6
2
for 2. For compound 1 the singlet at 0.40 ppm corresponds
1
3
to the protons from the siloxyl ligand. In the C NMR
spectrum the ligating carbon atom of carbene ligand was
found at 185.4 ppm for 1 and at 182.11 ppm for 2. Single
crystals of 1 and 2 suitable for an X-ray diffraction study
were grown from a toluene solution at ꢀ15 °C. The solid-
state structure is shown in Figs. 1 and 2. Moreover, we
have tried to synthesize iridium(I) complex containing
Due to a strong donor capability of carbene ligands,
the cyclooctadiene ligand can be totally substituted by a
N
OC
N
C6H6
1
or 2
+
2 CO
Ir
N
N
X
C6H6
-cod, r.t. OC
X
Ir
Ir
+
Ir
N
-
cod, r.t.
X
N
X
X = OSiMe (3), Yield = 82%
3
X = OSiMe3 (1), Yield = 86%
X = Cl (2), Yield = 93%
X = Cl
(4), Yield = 75%
Scheme 2. Formation of iridium(I) carbonyl derivatives with bonded
IMes ligand.
Scheme 1. Formation of iridium(I) mononuclear carbene complexes.

I. Kownacki et al. / Journal of Organometallic Chemistry 693 (2008) 321–328
323
previously [17]. In that case, both complexes were isolated
and fully characterized by spectroscopic techniques. The
1
H NMR spectra of compounds 3 and 4 confirmed the
presence of 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-yli-
dene ligand in the coordination sphere of iridium,
evidenced by the appearance of characteristic lines, corre-
sponding to IMes ligand: 6.77 (2,4,6-Me C H ); 6.02
3
6
2
(
@CHN); 2.05, 2.23 (–CH , 2,4,6-Me C H ) for 3 and
3
3
6
2
6
.75; 7.74 (2,4,6-Me C H ); 6.06 (@CHN); 2.04, 2.24
3
6
2
(
–CH , 2,4,6-Me C H ) for 4. For compound 3 the singlet
3 3 6 2
at 0.26 ppm was assigned to the protons from the siloxyl
1
3
ligand. In the C NMR spectra the ligating carbon atom
of carbene ligand was found at 182.89 ppm for 3 and at
1
80.76 ppm for 4. Additionally, single crystals of complex
Fig. 3. Anisotropic ellipsoid representation of complex 3. The ellipsoids
are drawn at 50% probability level, hydrogen atoms are omitted for
clarity.
3 suitable for an X-ray diffraction study were grown from
a toluene solution at ꢀ20 °C. Figs. 1–4 show the perspec-
tive views of the structure of complexes 1–3 and 5; Table
1
presents some selected geometrical parameters. The
coordination of iridium is square-planar, as in the major-
ity of the four-coordinated iridium complexes. In the
Cambridge Crystallographic Database [18] there are 193
iridium complexes with the coordination number four
(Version 5.27, November 2005, May 2006 update); of those
almost 90% are close to square planar. Fig. 5 shows the
distribution of the sum of valence angles around the Ir
atom in these structures; for the typical cases, the ideal val-
ues are 720° (square-planar), 660° (tetrahedral) and 630°
(trigonal pyramid). However, the degree of distortion of
the ideal square is different in the four complexes analyzed.
In 1 and 5 the deviations from the plane calculated for the
four coordination centers (including the middle points of
the double bonds of cyclooctadiene moiety) are as large
as 0.15 Aꢀ, and the sum of valence angles is relatively far
from the ideal value: 703.8° in 1 and 704.3° and 702.9°
in the two symmetry-independent molecules of 5. In con-
trast, in the other two complexes, the distortions are signif-
icantly less important: the maximum deviations from the
Fig. 4. Anisotropic ellipsoid representation of complex 5. The ellipsoids
are drawn at 50% probability level, hydrogen atoms are omitted for
clarity. X1 and X2 are the middlepoints of C@C bonds.
stronger acceptor ligand, carbon monoxide [6f]. Similar
replacement of cyclooctadiene ligand by CO was observed
in the case of [Ir(cod)(PCy )(OSiMe )] which we reported
3
3
Table 1
Selected geometrical parameters (distances in Aꢀand dihedral angles in °)
1
2
3
5A
2.047 (6)
2.003(7)
2.064(6)
2.007(5)
5B
2.042(6)
1.986(7)
2.056(6)
1.998(5)
Ir–C(IMes)
Ir–X(cod)
2.050(5)
1.996(5)
2
2.082(13)
1.998(12)
2.098(12)
2.055(9)
.055(5)
Ir–O
2.020(4)
1.993(5)
Ir–Cl
2.361(3)
Ir–C(O)
1.756(11)
1
.827(11)
O–Si
C@O
1.612(4)
1.872
74.0(2)
86.0(2)
77.4(2)
36.3(2)
1.600(6)
1.199(10)
.156(10)
1
hSi–Ci
(
(
(
(
coord)/(Im)
Im)/(PhA)
Im)/(Ph2)
Ph1)/(Ph2)
67.5(4)
80.2(5)
79.4(5)
33.3(3)
74.4(3)
83.2(3)
77.5(3)
31.0(4)
57.2(3)
69.7(3)
72.1(3)
46.0(3)
55.3(3)
68.7(3)
70.5(3)
48.0(3)
X is the middlepoint of the double bond in the cyclooctadiene fragment; the planes are denoted as follows: (coord): the plane by Ir and four coordination
centers; (Im): carbene plane and (Ph1) and (Ph2): phenyl rings.

324
I. Kownacki et al. / Journal of Organometallic Chemistry 693 (2008) 321–328
cationic complexes with bonded carbene ligand and pyri-
dine, [Ir(cod)(py)(L)]PF (where L = IMes, IPr, ICy), were
6
applied in the transfer hydrogenation reaction [8a]. Struc-
0
turally similar complexes [Ir(cod)(L)(L )]PF (where L =
6
0
n
IMe, IMes; L = P( Bu) , PCy , PPh ) containing simulta-
3
3
3
neously carbene and phosphine ligands [7c] were also used
as catalyst precursors in hydrogenation of olefins. Neutral
iridium-carbene complexes [Ir(Cl)(cod)(L)] (where L = chiral
carbene ligand) were successfully applied to asymmetric
hydrogenation of N-acetylalanine methyl ester [6w] and
transfer hydrogenation of acetophenone [8b].
Our neutral iridium(I) complexes 1 and 2 with bonded
1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene ligand
(IMes) were tested for catalytic activity in two reactions:
transfer hydrogenation of acetophenone and hydrogena-
tion of olefins. Selected results are presented in Table 2.
The complexes appeared very active in reduction of aceto-
phenone to the corresponding alcohol via hydrogen trans-
i
fer from PrOH with KOH as a promoter. In both cases full
conversion was observed, however in the presence of silox-
ide precursor 1 a higher value of TOF was noted. Com-
plexes 1 and 2 show high activity also in homogenous
hydrogenation reaction. Under mild conditions full conver-
sion of cis-cyclooctene was observed after 2 h. In the
hydrogenation of trans-stilbene, both precursors demon-
strated good activity and 72% yield was determined for
complex 2.
Fig. 5. The scattergram of the sum of valence angles around the Ir atom
for all four-coordinated Ir found in Cambridge Crystallographic
Database.
least-squares plane by four points are 0.009 Aꢀ (2) and
0
7
.029 Aꢀ (3), and the sums of the valence angles are
11.5° (2) and 713.4°(3). It should be noted, however, that
regardless of the degree of the square folding, the iridium
atom always lies almost exactly in the least-squares plane.
The other geometrical features of the molecules are similar
in all four complexes and close to the typical values (for
some examples, cf. Table 1). The cyclooctadiene fragments
in 1, 2 and 5 are close to a boat conformation (two torsion
3. Experimental
3.1. General methods and chemicals
All syntheses and manipulations were carried out under
argon using standard Schlenk’s and vacuum techniques.
The imidazolin-2-ylidene ligand was synthesized according
to a well-known method [5]. The binuclear complexes
[{Ir(l-Cl)(cod)} ] [19] and [{Ir(l-OSiMe )(cod)} ] [13a] were
angles along the ring close to 0°, C approximate symme-
2
try). The overall conformations of the complexes are sim-
ilar as can be shown by the dihedral angles between the
planar fragments (Table 1).
2
3
2
1
synthesized according to methods described previously. H,
C and Si NMR spectra were recorded on a Varian Gem-
1
3
29
The carbene plane is significantly twisted with respect to
the iridium coordination plane and both phenyl rings are
almost perpendicular to the carbene plane, certainly due
to the steric stress caused by the substituents at ortho-posi-
tions. Only in two molecules of 5 these twists are smaller
but still large. In the crystal structures of 2 and 5 there
are toluene (solvent) molecules: two toluene molecules
per one complex molecule in 2 and one toluene molecule
per two complexes in 5. The role of the solvent molecule
is to stabilise the crystal structure, but there are no signif-
icant specific interactions; probably they just fill the voids
thanks to the appropriate shape.
ini 300 VT spectrometer and Varian Mercury 300 VT in
C D . The chemicals were obtained from the following
6
6
sources: sodium trimethylsilanolate, potassium tert-butano-
late, paraformaldehyde, glyoxal, 2,4,6-trimethylaniline,
hydrochloric acid diethyl ether solution, cis-cyclooctene,
trans-stilbene, acetophenone and C D from Aldrich Chem-
6
6
ical Co., toluene, hexane, 2-propanol, and acetone from
POCH Gliwice (Poland), hydrogen from Messer Co. All sol-
vents were dried and distilled under argon prior to use.
3.2. Synthesis of [Ir(cod)(IMes)(OSiMe )] (1)
3
2.2. Catalytic properties of selected Ir-complexes in
hydrogenation type reactions
Portions of 0.2 g [{Ir(l-OSiMe )(cod)} ] (0.257 mmol)
3
2
and 0.16 g of 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-
ylidene (IMes) (0.526 mmol) were placed in a Schlenk’s
flask equipped with a magnetic bar in argon atmosphere.
Then 5 mL of dried and deoxygenated benzene was added.
The reaction was carried out for 24 h at room temperature.
As mentioned above, the synthesis of iridium complexes
with monodentate carbene ligands and their application in
catalysis were described previously [6–8]. Square-planar

I. Kownacki et al. / Journal of Organometallic Chemistry 693 (2008) 321–328
325
Table 2
Selected results of the catalytic activity of complex 1 vs. 2
ꢀ
1
Complex
Time (h)
Yield (%)
TOF (h )
Transfer hydrogenation
O
OH
OH
O
cat.
+
+
Ph
Ph
a
1
2
8
12
99
99
125 (222 )
a
83 (143 )
Hydrogenation
cat.
+
H2
1
2
2
2
100
100
50
50
Ph
Ph
cat.
+
H2
Ph
Ph
1
2
2
2
51
72
25.5
36
ꢀ
3
ꢀ2
i
Conditions of transfer hydrogenation: [ketone]:[Ir] = 1:10 , [acetophenone]:[KOH] = 1:10 , 80 °C, 20 mL PrOH. Conversion and yield were determined
by H NMR.
1
ꢀ
2
2 2 2
Conditions of hydrogenation reaction: [olefin]:[Ir] = 1:10 , CH Cl , 5 bars of H , 2 h.
ꢀ1
TOF (h ) – total average turnover frequency.
a
Turnover frequency at 50% conversion.
After that time solution was filtered off by a cannula system
and benzene was evaporated to dryness. To the crude prod-
uct, 10 mL of dried and deoxygenated pentane was added.
At the next step, the contents were cooled to ꢀ35 to
equipped with magnetic bar in argon atmosphere. Then
10 mL of dried and deoxygenated benzene was added and
the mixture was stirred with a magnetic stirrer. The reaction
was continued for 2 h and then benzene was evaporated to
1/5 of the initial volume and 5 mL of dried and deoxygen-
ated pentane was added. The precipitate was three times
washed with pentane by decantation. The complex was
dried under vacuum for about 4 h (yield: 0.714 g (93%)).
Anal. Calc. for C H N ClIr (640.28): C, 54.40; H,
ꢀ
30 °C for crystallization. After this, time the solution
was decanted and the precipitate was three times washed
with pentane by decantation at ꢀ60 °C, than dried under
vacuum (yield: 0.306 g (86%)).
Anal. Cacl. for C H N OSiIr (694.1): C, 55.38; H,
3
2
45
2
29 36
2
6
.54; N, 4.04. Found: C, 55.59; H, 6.93; N, 3.85%.
5.67; N, 4.38. Found: C, 54.55; H, 5.91; N, 4.25%.
1
1
H NMR (300 MHz, C D , 300 K) d (ppm) = 6.92
H NMR (300 MHz, C D , 300 K) d (ppm) = 6.78 (s,
6
6
6
6
(
4
s, 2H, Mes); 6.80 (s, 2H, Mes); 6.15 (s, 2H, =CHN);
.45 (m, 2H, cod); 2.85 (m, 2H, cod); 2.59 (s, 6H, CH3
Mes); 2.19 (s, 6H, CH Mes); 1.90 (s, 6H, CH Mes); 1.80
2H, Mes); 6.81 (s, 2H, Mes); 6.15 (s, 2H, @CHN); 4.70
(m, 2H, cod); 3.19 (m, 2H, cod); 2.59 (s, 6H, CH ); 2.15
3
(s, 6H, CH ); 2.05 (s, 6H, CH ); 1.80 (m, 4H, cod); 1.35
3
3
3
3
(
m, 4H, –CH –); 1.40 (m, 4H, –CH –); 0.40 (s, 9H,
(m, 4H, cod).
2
2
1
3
OSiMe ).
C NMR (75.42 MHz, C D , 300 K) d (ppm) = 182.11
3
6
6
1
3
C NMR (75.42 MHz, C D , 300 K) d (ppm) = 185.40
(CN ); 138.65; 137.96; 136.77; 134.40; 130.13 (Mes); 123.12
6
6
2
(
(
(
(
:CN ); 138.50; 138.10; 136.80; 134.10 (Mes); 122.38
@CHN–); 79.47; 44.56 (@CH–, cod); 34.10; 29.75
(@CHN–); 83.38; 50.77 (@CH–, cod); 34.07; 29.3 (–CH –,
2
2
cod); 21.0; 20.13; 18.24 (–CH , Mes).
3
–CH –, cod); 21.06; 19.94; 18.126 (–CH , Mes); 5.95
2
3
s, –OSiMe3).
3.4. Synthesis of complex [Ir(CO) (IMes)(OSiMe )] (3)
2
3
3
.3. Synthesis of [Ir(Cl)(cod)(IMes)] (2)
Portions of 0.380 g (1.25 mmol) of 1,3-bis(2,4,6-trimeth-
To the complex [Ir(cod)(IMes)(OSiMe3)] (0.2 g,
.288 mmol) a portion of 3 mL of dried and deoxygenated
benzene in the Schlenk’s tube was added. Then to a vigor-
ously stirred solution, 20 mL of carbon monoxide was
introduced. The reaction was carried out for 0.5 h at room
0
ylphenyl)imidazolin-2-ylidene (IMes) and 0.403 g (0.6
mmol) of [{Ir(l-Cl)(cod)} ] were placed in a Schlenk’s flask
2

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I. Kownacki et al. / Journal of Organometallic Chemistry 693 (2008) 321–328
1
temperature. After that time, the mixture was filtered off by
a cannula system, and then the solvent and cyclooctadiene
were evaporated. To the crude product (yellow solid) 4 mL
of dried and deoxygenated pentane was added. The
obtained solution was allowed at ꢀ35 to ꢀ30 °C for crys-
tallization. The crystals obtained was washed by two small
portions of pentane at ꢀ60 °C and dried under vacuum
H NMR (300 MHz, C D , 300 K) d (ppm) = 6.81 (m,
6 6
4H, Mes); 6.10 (s, 2H, @CHN); 4.71 (m, 2H, cod); 3.18
(m, 2H, cod); 2.60 (s, 6H, CH Mes); 2.11 (s, 6H, CH
Mes); 2.05 (s, 6H, CH Mes); 1.84 (m, 4H, –CH –); 1.36
3
3
3
2
(m, 4H, –CH –).
2
1
3
C NMR (75.42 MHz, C D , 300 K) d (ppm) = 181.95
6
6
(:CN ); 138.63; 137.93; 136.73; 134.36 (Mes); 123.06
(@CHN–); 83.40; 50.78 (@CH–, cod); 34.09; 29.35
2
(
yield: 0.151 g (82%)).
Anal. Calc. for C H N O SiIr (641.85): C, 48.65; H,
(–CH –, cod); 21.05; 20.17; 18.28 (–CH , Mes).
2
6
33
2
3
2
3
5
4
.18; N, 4.36. Found: C, 48.90; H, 5.63; N, 4.18%.
1
H NMR (300 MHz, C D , 300 K) d (ppm) = 6.77 (s,
3.7. Catalytic tests
6
6
H, Mes); 6.02 (s, 2H, @CHN–); 2.05 (s, 12H, –Me), 2.23
(
s, 6H, –Me); 0.26 (s, 9H, –OSiMe ).
Catalytic tests were performed according to the follow-
ing procedures.
3
1
3
C NMR (75.42 MHz, C D , 300 K) d (ppm) = 182.89
6
6
(
(
:CN ); 173.30 (CO); 139.72, 135.78, 129.69 (Mes); 122.77
2
@CHN–); 21.36, 18.77 (–Me, Mes); 4.73 (–OSiMe ).
3.7.1. Hydrogen transfer reactions
3
2
9
Si NMR (59.59 MHz, C D , 300 K) d (ppm) = 9.37
In a 25 mL round-bottomed flask equipped with reflux
condenser, gas inlet, bubbler and a stir bar 10 mL of 2-pro-
panol was placed via syringe under argon, then potassium
6
6
(
–OSiMe3).
ꢀ
3
3
.5. Synthesis of complex [Ir(Cl)(CO) (IMes)] (4)
2
hydroxide (1.12 mg, 0.02 mmol) and 10 mmol of iridium
complex were added. After the mixture was stirred at room
temperature for 15 min, then acetophenone (240 mg,
2.0 mmol) was added. The reaction mixture was stirred at
80 °C to completed conversion (reaction progress was con-
A
portion of complex [Ir(Cl)(cod)(IMes)] (0.2 g,
0
.31 mmol) was dissolved in 3 mL of dried and deoxygen-
ated benzene in the Schlenk’s tube. Then to a vigorously
stirred solution, 20 mL of carbon monoxide was intro-
duced. The reaction was carried out for 0.5 h at room tem-
perature, and then the solvent and cyclooctadiene were
evaporated. To the crude product (pale yellow solid)
1
trolled by H NMR). The solvent was removed under
1
vacuum, and the residue was analyzed by H NMR
spectroscopy.
2
mL of dried and deoxygenated pentane was added, and
3.7.2. Hydrogenation of olefins
In a Schlenk’s tube 10 mL of dried and oxygen-free
CH Cl was placed then 8.0 mmol of cis-cyclooctene and
0.08 mmol of iridium precursor or 5.0 mmol of trans-stil-
bene and 0.05 mmol of iridium precursors were added.
The obtained solution was transferred by a cannula system
into the pressure reactor, which was flushed with argon
then the solution was filtered off by a cannula system.
The filtrate was allowed at ꢀ35 to ꢀ30 °C for crystalliza-
tion. The crystals obtained was washed by two small por-
tions of pentane at ꢀ60 °C and dried under vacuum
2
2
(
yield: 0.137 g (75%)).
Anal. Calc. for C H N O ClIr (588.12): C, 46.97; H,
2
3
24
2
2
4
.11; N, 4.76. Found: C, 47.21; H, 4.53; N, 4.58%.
prior to use. Then the reactor was pressurized with H up
2
1
H NMR (300 MHz, C D , 300 K) d (ppm) = 6.75 (s,
to 5 bars. The reaction mixture was magnetically stirred
at 40 °C for 2 h. After this time the reactor was allowed
to cool to room temperature. The solvent was removed
from the reaction mixture under vacuum, and the residue
6
6
2
H, Mes); 7.74 (s, 2H, Mes); 6.06 (s, 2H, @CHN); 2.04
(
(
s, 12H, CH ); 2.24 (s, 6H, CH ).
3 3
1
3
C NMR (75.42 MHz, C D , 300 K) d (ppm) = 180.76
6
6
1
:CN ); 139.56; 135.33; 129.58 (Mes); 123.22 (@CHN–);
was analyzed by H NMR spectroscopy.
2
2
1.03; 18.66 (–CH , Mes).
3
3.8. X-ray structure determination
3
.6. Synthesis of complex [Ir(cod)(OH)(IMes)] (5)
X-ray data were collected at room temperature (com-
Portions of 0.1 g (0.156 mmol) [Ir(Cl)(cod)(IMes)] and
6.21 mg g (0.243 mmol) BuOK were placed in a Schlenk’s
pounds 1 and 3) and at 100 K (2 and 5) by the x-scan
technique, on a KUMA KM4CCD diffractometer [20]
with graphite-monochromatized Mo Ka radiation (k =
0.71073 Aꢀ). The data were corrected for Lorentz-polariza-
tion effects [21] as well as for absorption by SORTAV [22].
Accurate unit-cell parameters were determined by the
least-squares fit of 8202 (1), 7139 (2), 3199 (3) and 5462
(5) reflections of highest intensity, chosen from the whole
experiment. The structures were solved with SHELXS97 [23]
and refined with the full-matrix least-squares procedure
t
2
flask in argon atmosphere. Then 4 mL of dried and deoxy-
genated benzene were added. The reaction was conducted
for 24 h at room temperature. After this time benzene
was evaporated and 10 mL of dried and deoxidized pen-
tane were added. The entire mixture was filtered of by a
cannula system. From the obtained filtrate the solvent
was evaporated leaving yellow-orange solid (yield:
0
.0863 g (89%)).
2
Anal. Calc. C H N OIr (621.83): C, 56.01; H, 6.00; N,
on F by SHELXL97 [24]. Scattering factors incorporated in
2
9
37
2
4
.50. Found: C, 56.11; H, 6.43; N, 4.23%.
SHELXL97 were used. All non-hydrogen atoms were refined

I. Kownacki et al. / Journal of Organometallic Chemistry 693 (2008) 321–328
327
Table 3
Crystal data, data collection and structure refinement
Compound
1
2
3
5
Formula
C
32
H
45
N
2
OSiIr
C
29
H
36ClN
2
Ir ꢁ 2(C
7
H
8
)
C
26
H
33
N
2
O
3
SiIr
C
667.87
Triclinic
29
H
37
N
2
7 8
OIr ꢁ 1/2(C H )
Formula weight
Crystal system
Space group
694.01
Monoclinic
P2 /c
9.7545(5)
17.7272(8)
18.1858(9)
90
92.596(3)
90
3141.5(3)
4
824.54
Orthorhombic
P2
11.5383(14)
17.068(2)
18.8499(13)
90
90
90
3712.2(7)
4
1.475
641.85
Monoclinic
P2 /n
9.1157(7)
14.9832(10)
21.2079(13)
90
98.749(6)
90
2862.9(3)
4
ꢁ
1
1
2
1
2
1
1
P1
˚
a (A)
14.171(1)
14.706(1)
15.499(1)
68.73(1)
69.94(1)
89.56(1)
2802.4(4)
4
˚
b (A)
˚
c (A)
a (°)
b (°)
c (°)
˚
3
V (A )
Z
ꢀ3
D
x
(g cm
)
1.467
1.489
1.583
F(000)
l (mm
1400
4.314
1672
3.701
1272
4.732
1340
4.79
ꢀ1
)
Crystal size (mm)
T (K)
0.35 ꢂ 0.2 ꢂ 0.1
0.4 ꢂ 0.1 ꢂ 0.07
0.15 ꢂ 0.1 ꢂ 0.1
0.2 ꢂ 0.1 ꢂ 0.1
293(2)
100(1)
293(2)
100(1)
H Range (°)
hkl Range
3.63–27.00
ꢀ12 6 h 6 12,
2.97–25.00
ꢀ13 6 h 6 7,
ꢀ20 6 k 6 20,
ꢀ22 6 l 6 22
24531
3.41–25.00
ꢀ10 6 h 6 10,
ꢀ13 6 k 6 17,
ꢀ25 6 l 6 25
14170
5.23–29.91
ꢀ17 6 h 6 19,
ꢀ19 6 k 6 19,
ꢀ21 6 l 6 21
28537
ꢀ
ꢀ
14 6 k 6 23,
23 6 l 6 23
Reflections collected
17573
Reflections unique (Rint
)
6698 (0.045)
5646
343
0.0396
0.0775
0.0513
0.0824
1.075
6522 (0.083)
4952
430
0.0706
0.164
0.0841
0.174
0.985
4975 (0.066)
2831
298
0.0506
0.1074
0.0927
0.0782
0.933
14317 (0.054)
9229
671
0.0513
0.1013
0.0892
0.1069
1.115
Reflections with I > 2r(I)
Number of parameters
R(F) [I > 2r(I)]
2
wR(F ) [I > 2r(I)]
R(F) [all data]
2
wR(F ) [all data]
Goodness-of-fit
Maximum/minimum Dq
1.58/ꢀ1.24
4.84/ꢀ3.23
0.861/ꢀ0.940
2.74/ꢀ2.85
˚
ꢀ3
)
(e A
CCDC deposition number
296879
296880
296881
296882
anisotropically, hydrogen atoms were placed geometrically,
in idealized positions, and refined as rigid groups, Uiso of
hydrogen atoms were set as 1.2 (1.3 for methyl groups)
times Ueq of the appropriate carrier atom. Relevant crystal
data are listed in Table 3, together with refinement details.
(b) J. Schwarz, V.P.W. B o¨ hm, M.G. Gardiner, M. Grosche, W. A
Herrmann, W. Hieringer, G. Raudaschl-Sieber, Chem. Eur. J. 6
(
(
2000) 1773;
c) E. Peris, J.A. Loch, J. Mata, R.H. Crabtree, Chem. Commun.
(2001) 201.
[2] (a) L.H. Pignolet, Homogeneous Catalysis with Metal Phosphine
Complexes, Plenum, New York, 1983;
(
b) J.P. Collman, L.S. Hegedus, J.R. Norton, R.G. Finke, Principles
4
. Supplementary material
and Application of Organotransition Metal Chemistry, second ed.,
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3] (a) G.J. Kubas, Acc. Chem. Res. 21 (1988) 120;
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(
(
(
(
CCDC 296879, 296880, 296881 and 296882 contain the
[
supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
c) S.T. Nguyen, R.H. Grubbs, J.W. Ziller, J. Am. Chem. Soc. 115
1993) 9858;
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Acknowledgements
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(
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248) from the Ministry of Science and Higher Education,
and postdoctoral fellowship from Foundation for Polish
Science (I. Kownacki).
[
5] (a) W.A. Herrmann, C. K o¨ cher, Angew. Chem., Int. Ed. Engl. 36
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