(η5-Cp)Rh(III)/Ir(III) complexes with bis(chalcogenoethers) (E, E′ Ligands: E = S/Se; E′ = S/Se): Synthesis, structure, and applications in catalytic oppenauer-type oxidation and transfer hydrogenation

Article abstract of DOI:10.1021/om401150s

The air- and moisture-insensitive half-sandwich complexes [(η⁵-Cp)Rh(L)Cl][PF₆] (1-3) and [(η⁵- Cp)Ir(L)Cl][PF₆] (4-6) have been prepared by reacting L = L1-L3 (1,2-bis(phenylthio)ethane (L1), 1-(phenylseleno)-2-(phenylthio)ethane (L2) and 1,2-bis(phenylseleno)ethane (L3)) with [(η⁵-Cp)RhCl(μ-Cl)] ₂ and [(η⁵-Cp)IrCl(μ-Cl)]₂, respectively, at room temperature followed by treatment with NH ₄PF₆. Their HR-MS and ¹H, ¹³C{ ¹H}, and ⁷⁷Se{¹H} NMR spectra have authenticated them. The single-crystal structures of 1-6 have been established by X-ray crystallography. Complexes 1-6 have been explored for catalytic Oppenauer-type oxidation of alcohols and transfer hydrogenation of ketones with 2-propanol. 3 and 6 were the most efficient in the two catalytic reactions (TON values up to 9.9 × 10² and 9.8 × 10³, respectively) and were therefore investigated in detail. 3 is the first example of a Rh(III) species explored for Oppenauer-type oxidation. The catalysis appears to be homogeneous. In transfer hydrogenation it appears that one of the catalytic species is without a Cp* ring. DFT calculations indicate higher reactivity for Rh complexes in comparison to Ir complexes. This order has also been found for the two catalytic reactions experimentally. The calculated bond lengths/angles by DFT are generally consistent with the experimental values.

Full text of DOI:10.1021/om401150s

Article
pubs.acs.org/Organometallics
(η5‑Cp*)Rh(III)/Ir(III) Complexes with Bis(chalcogenoethers) (E, E′
Ligands: E = S/Se; E′ = S/Se): Synthesis, Structure, and Applications in
Catalytic Oppenauer-Type Oxidation and Transfer Hydrogenation
Om Prakash, Kamal Nayan Sharma, Hemant Joshi, Pancham L. Gupta, and Ajai K. Singh*
Department of Chemistry, Indian Institute of Technology Delhi, New Delhi 110016, India
S
* Supporting Information
ABSTRACT: The air- and moisture-insensitive half-sandwich complexes [(η5-
Cp*)Rh(L)Cl][PF6] (1−3) and [(η5-Cp*)Ir(L)Cl][PF6] (4−6) have been
prepared by reacting L = L1−L3 (1,2-bis(phenylthio)ethane (L1), 1-(phenyl-
seleno)-2-(phenylthio)ethane (L2) and 1,2-bis(phenylseleno)ethane (L3)) with
[(η5-Cp*)RhCl(μ-Cl)]2 and [(η5-Cp*)IrCl(μ-Cl)]2, respectively, at room temper-
1
ature followed by treatment with NH4PF6. Their HR-MS and H, 13C{1H}, and
77Se{1H} NMR spectra have authenticated them. The single-crystal structures of 1−
6 have been established by X-ray crystallography. Complexes 1−6 have been
explored for catalytic Oppenauer-type oxidation of alcohols and transfer hydro-
genation of ketones with 2-propanol. 3 and 6 were the most efficient in the two
catalytic reactions (TON values up to 9.9 × 102 and 9.8 × 103, respectively) and
were therefore investigated in detail. 3 is the first example of a Rh(III) species
explored for Oppenauer-type oxidation. The catalysis appears to be homogeneous.
In transfer hydrogenation it appears that one of the catalytic species is without a Cp* ring. DFT calculations indicate higher
reactivity for Rh complexes in comparison to Ir complexes. This order has also been found for the two catalytic reactions
experimentally. The calculated bond lengths/angles by DFT are generally consistent with the experimental values.
reactions invariably require catalysts, which therefore have
received significant attention.7 In the transition-metal-catalyzed
oxidations of alcohols, oxidizing agents such as N-methyl-
morpholine N-oxide (NMO), tert-butyl hydroperoxide
(tBuOOH), sodium oxychloride (NaOCl), sodium periodate
(NaIO4), oxygen, and hydrogen peroxide are commonly used.8
However, the byproducts are not always environmentally
friendly. In the Oppenauer-type oxidation of alcohols using
acetone as solvent cum oxidant, 2-propanol is a byproduct,
which is appealing from both an environmental and an
economical point of view. In fact, both acetone and 2-propanol
are environmentally friendly9 and therefore make Oppenauer-
type oxidation somewhat green. Some transition-metal
complexes have been reported to catalyze Oppenauer-type
oxidation.10 The Ru(II) complexes are efficient catalysts11 for
this purpose, especially bimetallic complexes11g with Rh(I), at
high temperature and under an inert atmosphere. Some N-
heterocyclic carbene (NHC) based (η5-Cp*)Ir(III) complexes
have also been found to be suitable for the Oppenauer-type
oxidation of alcohols.12
INTRODUCTION
■
The diverse applications of chalcogenoethers have been
reported in the literature.1 The transition-metal complexes of
mono- and bis(thio-/selenoether) ligands have acquired
importance due to their potential applications as models for
biological activity,2a building blocks for supramolecular frame-
work,2b single-source precursors for metal chalcogenide
materials,2c and catalysts.2d The supramolecular chemistry of
complexes of chalcogenoethers with all s-, p-, and d-block
elements has received much attention.3 However, bidentate
chalcogenoethers explored to design half-sandwich complexes
of Rh(III)/Ir(III) suitable for Oppenauer-type oxidation of
alcohols and transfer hydrogenation of ketones have not been
studied our knowledge. There are few reports known to us in
which bis(chalcogenoether) ligands have been reacted with (η5-
Cp*)Rh(III)/Ir(III) to prepare new complexes.4 The sources
of rhodium and iridium for these half-sandwich complexes are
the dimers [(η5-Cp*)RhCl(μ-Cl)]2 and [(η5-Cp*)IrCl(μ-Cl)]2,
respectively, which undergo a rich variety of chemistry via an
intermediary chloro bridge cleavage reaction, leading to the
formation of a series of interesting neutral and cationic
mononuclear complexes.5
Transfer hydrogenation has emerged as a convenient and
versatile method for the reduction of carbonyl compounds;13 it
is an attractive alternative to hydrogenation because it is easy to
execute due to the absence of hazardous hydrogen gas and
The Oppenauer-type oxidation of alcohols is interesting, as it
does not require a separate oxidant, since non-noxious acetone
is used as both an oxidant and a solvent. In the transfer
hydrogenation of ketones, 2-propanol is used as the source of
hydrogen, which eliminates flammable hydrogen gas.6 These
Received: November 26, 2013
© XXXX American Chemical Society
A
dx.doi.org/10.1021/om401150s | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
pressure vessels to handle it.6 Transfer hydrogenation of
ketones has been catalyzed by a number of ruthenium species,
including half-sandwich complexes.14 However, Rh and Ir
complexes, particularly half-sandwich types containing organo-
chalcogen ligands, have scarcely been explored.15 Herein, we
report the synthesis and single-crystal structural aspects of
complexes 1−6 of (η5-Cp*)Rh(III)/Ir(III) with bis(thio-/
selenoether) ligands (L1−L3; Chart 1). Their applications in
(both catalysis and structural aspects). It appears that a Rh/Ir
species without a Cp* ring also contributes to catalysis of
transfer hydrogenation.
RESULTS AND DISCUSSION
■
The syntheses of L1−L3 and their complexes are summarized
in Scheme 1. Complexes 1−6 all appear to be formed by chloro
bridge cleavages of [(η5-Cp*)RhCl(μ-Cl)]2/[(η5-Cp*)IrCl(μ-
Cl)]2 followed by reaction with bis(thio-/selenoether) ligands
L1−L3 at room temperature, facilitated due to chloride
extraction with NH4PF6. The ligand L2 has been synthesized
for the first time. The procedures used for the synthesis of L1
and L3 are simpler than those used earlier2,16 and give a
relatively higher yield, ∼95%. Ligands L1−L3 have good
solubility in the common organic solvents CHCl3, CH2Cl2,
CH3OH, and CH3CN. Complexes 1−6 are moderately soluble
in solvents such as CHCl3, CH2Cl2, and CH3OH but have good
solubility in CH3CN. The pale yellow liquids L1−L3 are stable
under ambient conditions and can be stored at room
temperature for several months. The solutions of complexes
1−6 made in CH3CN are also stable for several months under
ambient conditions. The elemental analyses and multinuclear
NMR, IR, and mass spectral data of 1−6 are consistent with
single-crystal structures deduced from X-ray diffraction and
given below.
Chart 1
catalyzing the Oppenauer-type oxidation of alcohols with
acetone and transfer hydrogenation of ketones with 2-PrOH
have been explored. Reactions of half-sandwich complexes of
both Rh(III) and Ir(III) with the Se,Se ligand L3 have been
found to show the highest catalytic efficiency among the
present six complexes. All of these results are given in the
present paper. Density functional theory (DFT) calculations
have been carried out and support the experimental results
Scheme 1. Synthesis of Ligands L1−L3 and Complexes 1−6
B
dx.doi.org/10.1021/om401150s | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Crystal Structures. Crystals of 1−6 of suitable quality for
X-ray diffraction were obtained by vapor diffusion of diethyl
ether into concentrated solutions of these complexes made in a
methanol/acetonitrile mixture (1/4 v/v). The crystallographic
and refinement data for 1−6 are summarized in the Supporting
Information (Tables S1 and S2). The crystal system for both
the complexes 1 and 4 is orthorhombic. The presence of
pseudosymmetry in the structure suggests the higher symmetry
space group Pbca, but attempts to refine the structure in this
space group resulted in unacceptably high R and Rw values.
Thus, the structures were solved in space group Pn21a.
Consequently, a “B” level pseudosymmetry error appears in
their CIFs. Such an observation is not uncommon in the case of
an orthorhombic system and was also reported earlier.17 L1−
L3 exhibit identical bonding modes in all of the complexes 1−
6: i.e., a five-membered ring is formed on their coordination
with both the metal centers. The molecular structure diagrams
of the cations of 1−6 are given in Figures 1−6, respectively,
Figure 3. Structure of the cation of 3. Bond lengths (Å): Rh(1)−Se(1)
2.4579(13), Rh(1)−Se(2) 2.4864(12), Rh(1)−Cl(1) 2.408(2), Rh−C
2.148(9)−2.189(9). Bond angles (deg): Se(1)−Rh(1)−Se(2)
84.25(4), Se(1)−Rh(1)−Cl(1) 94.25(8), Se(2)−Rh(1)−C1(1)
80.98(6).
Figure 4. Structure of the cation of 4. Bond lengths (Å): Ir(1)−S(1)
2.3559(18), Ir(1)−S(2) 2.3422(18), Ir(1)−Cl(1) 2.3712(9), Ir−C
2.183(7)−2.191(6). Bond angles (deg): S(1)−Ir(1)−S(2) 86.83(4),
S(1)−Ir(1)−Cl(1) 89.89(7), S(2)−Ir(1)−C1(1) 92.71(7).
Figure 1. Structure of the cation of 1. Bond lengths (Å): Rh(1)−S(1)
2.380(2), Rh(1)−S(2) 2.386(2), Rh(1)−Cl(1) 2.3702(14), Rh−C
2.140(6)−2.203(7). Bond angles (deg): S(1)−Rh(1)−S(2) 86.52(5),
S(1)−Rh(1)−Cl(1) 90.35(7), S(2)−Rh(1)−C1(1) 93.71(7).
Figure 5. Structure of the cation of 5 .Bond lengths (Å): Ir(1)−Se(1)
2.4892(9), Ir(1)−S(1) 2.3553(17), Ir(1)−Cl(1) 2.4101(18), Ir−C
2.144(9)−2.185(10). Bond angles (deg): S(1)− Ir(1)−Se(1)
84.97(5), S(1)−Ir(1)−Cl(1) 93.26(7), Se(1)−Ir(1)−C1(1) 80.19(6).
their cations there is a pseudo-octahedral half-sandwich “piano-
stool” disposition of donor atoms around Rh/Ir. The centroid
of the η5-Cp* ring occupies nearly the center of a triangular
face of an octahedron. A chelate ring with the metal center is
formed through chalcogen atoms, and a chlorine atom
completes the coordination sphere. This results in an overall
three-legged piano-stool conformation.
The Rh−S bond distances in 1 (2.380(2) and 2.386(2) Å)
and 2 (2.3692(19) Å) are of the same order and are consistent
with the values reported for [(η5-Cp*)RhCl(1,1′-(1,2-
Figure 2. Structure of the cation of 2. Bond lengths (Å): Rh(1)−Se(1)
2.5037(10), Rh(1)−S(1) 2.3692(19), Rh(1)−Cl(1) 2.4090(19), Rh−
C 2.144(8)−2.136(9). Bond angles (deg): S(1)−Rh(1)−Se(1)
84.47(6), S(1)−Rh(1)−Cl(1) 94.15(7), Se(1)−Rh(1)−C1(1)
81.02(6).
−
with selected bond lengths and angles. The H atoms and PF6
anions have been omitted for clarity, and ellipsoids are given at
the 30% probability level (carbon atoms are in stick forms). In
C
dx.doi.org/10.1021/om401150s | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
ported. The Ir−Se distances in 5 (2.4892(9) Å) and 6
(2.4863(8) and 2.4455(8) Å) are somewhat longer than the
values reported for [η5-Cp*Ir{Se2C2(CO2Me)2}] (2.3494(7)
and 2.3520(7) Å).25 The Ir−Se bond lengths of [η5-Cp*IrCl(μ-
SeCOC6H5)(κ2-SeCOC6H4−)Ir(η5-Cp*)] (2.445(2)−
2.495(1) Å)26 and [η5-Cp*Ir(μ3-Se)2{PtTol(PPh3)}2]
(2.416(1)−2.422(1) Å)21 are consistent with those of 5 and
6. The Ir−η5-Cp*(centroid) distances in 4−6 (1.814−1.820 Å)
are consistent with the reported values for complexes [(η5-
Cp*)Ir(phpy)Cl] (1.863 Å).27 The PF6− anion has been found
to be involved in C−H···F secondary interactions in each of the
complexes 1−6, resulting in chains and sometimes a helical
pattern (Figure 7). The secondary interactions and H···F
distances for other complexes are given in the Supporting
Information (Figures S1−S6 and Table S5).
Figure 6. Structure of the cation of 6. Bond lengths (Å): Ir(1)−Se(1)
2.4863(8), Ir(1)−Se(1) 2.4455(8), Cl(1)−Ir(1) 2.4059(16), Ir−C
2.187(8)−2.186(7). Bond angles (deg): Se(1)−Ir(1)−Se(2) 85.77(3),
Se(1)− Ir(1)−Cl(1) 80.12(5), Se(2)−Ir(1)−C1(1) 92.86(5).
Spectral Data. The signals in 77Se{1H} NMR spectra of 2,
3 and 5, 6 appear shifted to a higher frequency by ∼65 ppm
(Supporting Information, Figures S13−S18) in comparison to
these of free L2 and L3, due to their coordination with Rh/Ir
through Se. Two signals observed in the 77Se{1H} NMR
ethanediyl)bis(3-methylimidazole-2-thione)]Cl (2.3967(11)
Å)18 and [(η5-Cp*)RhCl{2-(phenylthiomethyl)pyridine}]PF6
(2.383(2) Å).15 The Rh−Se bond lengths of 2 (2.5037(10)
Å) and 3 (2.4579(13) and 2.4864(12) Å) are shorter than that
of [η5-Cp*RhCl{η2-(SePPh2)2N}]BF4 (2.5266(8) Å)19 but
consistent with the value 2.487(1) Å reported for a half-
sandwich complex of Rh(III) with 2-(phenylselenomethyl)-
pyridine.15 The Rh−C(Cp* centroid) distances (1.794−1.809
Å) of complexes 1−3 are normal.20
1
spectra of 3 and 6 are due to diastereomers. In the H and
13C{1H} NMR spectra of 1−6 signals of protons and carbon
atoms generally appear at higher frequencies relative to those of
free ligands which coordinate with Rh and Ir in a bidentate
mode. The magnitude of shift to higher frequency is large for
(E)CH2CH2(E′) (E = E′ = S, Se; E/E′ = S/Se): up to 10.1
ppm in 13C{1H) NMR and, for protons attached to them, up to
The Ir−S bond distances for 4 (2.3559(18) and 2.3422(18)
Å) and 5 (2.3553(17) Å) are similar and fall in the range
2.318(1)−2.3872(10) Å, in which Ir−S bond lengths of [η5-
Cp*Ir(CO)(μ-STol)Pt(STol)(PPh3)],21 [η5-Cp*Ir(η2-ppy-S-p-
tol)(H2O)][OTf]2,22 [η5-Cp*Ir(4,6-di-tert-butyl-(2-methylthio-
1
0.82 ppm. In the H and 13C{1H} NMR spectra of 1−3 the
1
signals of the η5-Cp* group (two singlets in H NMR) were
found shifted to lower frequency (maximum shifts ∼0.3 and 2.1
ppm, respectively) with respect to those of [(η5-Cp*)RhCl(μ-
Cl)]2. The substitution of Cl with less electronegative S and Se
appears to be the reason for it. Similar shifting of Cp* signals of
23
phenylimino)-o-benzoquinone](PF6)·CH2Cl2 and [η5-Cp*Ir-
(nBuPPh2)({7-(S)PPh2}-8-S-7,8-C2B9H10)]24 have been re-
Figure 7. (a) Noncovalent C−H···F interactions in 1. (b) Helical chain formed in the crystal of 1 by noncovalent interactions.
D
dx.doi.org/10.1021/om401150s | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
4−6 with respect to those of [(η5-Cp*)IrCl(μ-Cl)]2 were
Table 2. Effect of Catalyst Loading on TON and TOF for
1
observed in their H and 13C{1H} NMR spectra.
Transfer Hydrogenation of Acetophenone Catalyzed by 3
a
HRMS spectra of complexes 1−6 indicate that chloride in all
of them is considerably labile, and consequently a molecular ion
peak is not observed in any case. The peak of the species [M −
Cl]+ has been observed in the spectra of all complexes 1−6
(Supporting Information, Figures S7−S12). In some spectra
the peak of the fragment [(η5-Cp*)MCl]+ (M = Rh, Ir) has
also been observed.
and 6
amt of catalyst
(mol %)
time
(h)
conversion
TOF
(h−1
b
entry
(%)
TON
19.8
)
c
1
5
0.50
0.50
0.75
1.5
1.5
2
99
92
99
96
85
95
98
88
98
98
90
98
95
85
94
40
37
d
2
5
18.4
19.8
96
d
3
5
26
c
4
1
64
Catalytic Studies. Transfer Hydrogenation of Ketones.
Transfer hydrogenation of ketones (Scheme 2) using 2-
d
5
1
85
57
d
6
1
95
48
c
7
0.1
0.1
0.1
0.01
0.01
0.01
0.001
0.001
0.001
3
980
327
293
245
1960
1800
1634
9500
8500
6267
Scheme 2. Transfer Hydrogenation of Ketones
d
8
3
880
980
d
9
4
c
10
5
9800
9000
9800
95000
85000
94000
d
10
5
d
11
6
c
12
10
10
15
d
13
d
14
a
Conditions: 1 mmol of acetophenone, 10 mol % of KOH, 15 mL of
b
c
d
2-propanol, 80 °C, in air. Determined by NMR. Rh complex 3. Ir
complex 6.
propanol as the hydrogen donor catalyzed with present
complexes 1−6 (0.01 mol %) (5 h with 1−3 and 6 h with
4−6) at the moderate temperature of 80 °C has been explored.
The reduction of ketones to the corresponding alcohols occurs
in the presence of KOH, which was reported earlier to be the
best inorganic base for such reactions.28 The most efficient
conversions (up to 98%) were found in the case of
acetophenone with all of the complex catalysts, while in the
case of aliphatic ketones the conversions were up to 93%. The
complexes of the Se,Se ligand were found to be somewhat more
efficient as catalysts than the corresponding S,S/S,Se analogues,
as for the substrate cyclopropanone TON values were found to
be 8000, 8500, 9300, 8000, 8400, and 9000, respectively, for
complexes 1−6. Thus, detailed investigations were carried out
for complexes 3 and 6. The percent conversions and TONs are
given in Table 1. Using 5 mol % of catalyst 3, 99% conversion
may be achieved in 30 min (Table 2). The conversions do not
significantly improve when the reaction time is increased from
5−6 to 10 h with 0.01 mol % loading of catalyst. In comparison
to the amounts of most other Rh and Ir species reported for
transfer hydrogenation (TH), the mole percent loading
required in the case of 3 and 6 is only one tenth or lower.29
When the transfer hydrogenation reactions catalyzed with 3
and 6 are monitored with 77Se{1H} NMR spectroscopy, it is
observed that the signals in the spectra shift to higher frequency
(20−25 ppm), indicating that probably the M−Cl bond is
cleaved or weakened very significantly to make a coordination
site on metal center available so that formation of an
intermediate having a M−H bond can take place.30 The
transfer hydrogenation reactions catalyzed with 3 and 6 were
also monitored with 1H NMR spectra. After 1 h a broad singlet
was noticed around δ −9.8 and −13.1 ppm, respectively. These
signals are characteristic of hydrides and indicate the formation
Table 1. Catalytic Applications of Complexes 3 and 6
a
c
transfer hydrogenation of ketones
Oppenauer-type oxidation of alcohols
b
b
TON (conversion (%))
TON (conversion (%))
substrate
3
6
substrate
cyclopentanol
3
6
cyclopentanone
cyclohexanone
acetophenone
9300 (93)
9200 (92)
9800 (98)
9600 (96)
9600 (96)
9400 (94)
9600 (96)
8600 (86)
8800 (88)
9000 (90)
9200 (92)
9800 (98)
9600 (96)
9600 (96)
9400 (94)
9500 (95)
8500(85)
8800 (88)
900 (90)
910 (961)
920 (92)
980 (98)
900 (90)
820 (82)
980 (98)
900 (96)
910 (91)
920 (92)
850 (85)
900 (90)
990 (99)
880 (88)
900 (90)
920 (92)
980 (98)
880 (88)
800 (80)
950 (95)
900 (90)
920 (92)
940 (94)
800 (80)
910 (91)
990 (99)
cyclohexanol
benzyl alcohol
propiophenone
benzophenone
4-methylacetophenone
4-chloroacetophenone
2-octanone
4-methoxybenzyl alcohol
4-methylbenzyl alcohol
4-chlorobenzyl alcohol
1-phenylethanol
benzhydrol
2-pentanone
1-phenylpropanol
1-(4-methylphenyl)ethanol
1-(4-chlorophenyl)ethanol
2-octanol
2-pentanol
a
Conditions: 1 mmol of substrate (ketone), 10 mol % of KOH, catalyst 0.01 mol %, 15 mL of 2-propanol, 80 °C, time 5 h for 3 and 6 h for 6, in air.
b
c
Conversion determined by NMR. Conditions: 1 mmol of substrate (alcohol), 15 mL of acetone (0.1% water), catalyst 0.1 mol %, 1.5 mmol of
K2CO3, 80 °C, time 5 h for 3 and 7 h for 6, in air.
E
dx.doi.org/10.1021/om401150s | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
of a M−H bond.12 Thus, catalytic reactions with the present
Table 3. Effect of Catalyst Loading on TON and TOF for
Oxidation of 1-Phenylethanol Catalyzed by 3 and 6
a
complexes probably proceed via formation of a metal hydride
1
complex intermediate. In H NMR spectra recorded while
amt of catalyst
(mol %)
time
(h)
conversion
TOF
(h−1
transfer hydrogen is progressing in the presence of any of 1−6
b
entry
(%)
TON
)
a small signal appears around 1.91 ppm, which is possibly due
c
1
5
0.25
0.25
0.50
1
99
88
98
99
85
96
98
88
95
92
76
88
95
85
94
19.8
17.6
19.6
99
79
70
1
to free Cp*, as it is not observed in the H NMR spectrum of
d
2
5
any of these complexes. This indicates that probably a species
generated with the loss of Cp* (most likely as [(Solv)nML]3+)
is also present during catalysis.31 In the case of transfer
hydrogenation catalyzed with the Ru(II)−arene system the loss
of arene and participation of ringless species in catalysis has
been recently proposed.32 It is possible that a similar thing is
happening in the present case, as some role of [(Solv)nML]3+ in
catalysis cannot be ruled out. However, the formation of its
dimer and its role in catalysis is ruled out, as the TOF increases
with lower amounts of catalyst.
d
3
5
39
c
4
1
99
d
5
1
1
85
85
d
6
1
1.5
5
96
64
c
7
0.1
0.1
0.1
0.01
0.01
0.01
0.001
0.001
0.001
980
327
293
238
920
760
733
317
283
269
d
8
5
880
d
9
7
950
c
10
10
10
12
30
30
35
9200
7600
8800
9500
8500
9400
d
10
d
11
The catalytic efficiency varies with chalcogen donor sites in
the ligand. It varies in the order Se,Se > Se,S > S,S when the
other coligands are the same and may be tailored by a stronger
electron-donating tendency of Se toward the metal center, thus
promoting the formation of hydride with it. The formation of
an M−H-containing intermediate and the absence of NH group
(essential for the Noyori mechanism6) in the ligand system
suggest that transfer hydrogenation by 1−6 is catalyzed by a
conventional mechanism:13i i.e., via alkoxide formation. The
Rh(III) species appear to be better catalysts than those of
Ir(III) (Table 2), as in the case of Ir complexes for conversions
comparable with those of Rh analogues with the same catalyst
loading, the reaction time needed is somewhat longer.
c
12
d
13
d
14
a
Conditions: 1 mmol of 1-phenylethanol, 15 mL of acetone (0.1%
b
c
water), 1.5 equiv of K2CO3, 80 °C, in air. Determined by NMR. Rh
complex 3. Ir complex 6.
d
Scheme 4. Proposed Mechanism of Oppenauer-Type
Oxidation of Alcohols
Oppenauer-Type Oxidation of Alcohols. The Oppenauer-
type oxidation of alcohols in the presence of 1−6 (0.1 mol %)
(Scheme 3) using acetone as an oxidant at 80 °C in the
Scheme 3. Oppenauer-Type Oxidation of Alcohols
presence of K2CO3 has been studied. Maximum conversions
were reached in 5 h with catalysts 1−3 and in 7 h with catalysts
4−6 (Scheme 3). As for transfer hydrogenation, the catalytic
efficiency follows the order Se,Se > Se,S > S,S when the other
coligands are the same. For example, TON values for oxidation
of 1-phenylethanol are 840, 900, 980, 750, 800, and 880,
respectively, for 1−6. Thus, detailed investigations were carried
out with 3 and 6. The percent conversions and TON values
have been summarized in Table 1. A conversion of 99% is
obtained in 15 min if a catalyst loading of 5 mol % is used
(Table 3). The representative catalytic reactions in the presence
electron-donating tendency of Se toward the metal center, thus
promoting the formation of hydride with it. Similarly, Rh(III)
species are somewhat better catalysts than Ir(III) species. This
has been corroborated by the fact that more time is needed in
the case of Ir complexes to get conversions comparable to those
of Rh species (Table 3).
3 is the first example of an Rh(III) species explored for
Oppenauer-type oxidation. In comparison to other Ir and Ru
species the required mole percent loading of 6 (for an almost
similar reaction time) is lower or comparable.11,12
1
of 3 and 6 have been monitored by 77Se{1H} and H NMR.
The signals in 77Se{1H} NMR spectra have been found to be
shifted to higher frequency (21−28 ppm) in the course of the
1
reaction. In H NMR spectra new signals at δ −9.1 and −12.5
ppm have been found to appear in the course of catalysis with 3
and 6, respectively. These signals may be ascribed to the
formation of metal hydride species.12 Therefore, the oxidation
of alcohols appears to be catalyzed by 1−6 via the pathway
suggested in Scheme 4. The greater catalytic efficiency of 3 and
6 relative to other complexes may be tailored by a stronger
Homogeneous vs Heterogeneous Transfer Hydrogenation
Catalysis. It has been reported that transfer hydrogenation in
glycerol catalyzed with iridium complexes under microwave
F
dx.doi.org/10.1021/om401150s | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
conditions results in the formation of Ir NPs which have a
negative effect on the catalytic process.33 It is possible that such
metal NPs are formed with the present complexes also and
make some contribution to catalysis. Thus, it is important to
understand whether the present transfer hydrogenation
catalysis is homogeneous or heterogeneous, and a mercury
poisoning test34 has been executed for this purpose. The
mercury poisoning test with acetophenone in 2-propanol using
catalysts 3 and 6 showed no significant inhibition of conversion
to products (Table 4). Thus, the present catalysis appears to be
more intimately in the catalytic process (probably in an
associative manner) and may cause reactivity differences. The
HOMO−LUMO energy gaps of Rh complexes are smaller than
those of Ir complexes (see Table 7), and their variation is
contributed more by the LUMO, which suggests that this
energy gap may be correlated to catalytic activity: that is, a
small gap in Rh complexes relative to Ir analogues may result in
higher reactivity for the former. As the LUMO is antibonding
between Cp* and metal, an increase of its electron density may
be responsible for dissociation of Cp*. The DFT calculations
have placed more negative natural bond orbital atomic charge
on Rh (see Figures S20 and S21 (Supporting Information) and
Table 7), which may facilitate hydride formation. The M−H
formation is generally considered as the rate-determining step,
and therefore charge may be a controlling influence. This
observation is consistent with the higher activity of Rh species
in comparison to Ir species.
Table 4. Mercury Test for Catalytic Transfer
a
Hydrogenation
b
entry
catalyst/Hg
time (h)
conversion (%)
c
1
1/0
3
3
3
3
98
88
90
82
d
2
1/0
c
3
1/400
1/400
d
4
CONCLUSION
■
a
Conditions: 1 mmol of acetophenone, 10 mol % of KOH, 15 mL of
The half-sandwich “piano-stool” complexes [(η5-Cp*)Rh(L)-
Cl][PF6] and [(η5-Cp*)Ir(L)Cl][PF6] (1−6) of bis(thio-/
selenoether) ligands (L = L1−L3) have been synthesized and
characterized by multinuclear NMR, HR-MS, and X-ray
crystallography . The complexes are the first examples of half-
sandwich complexes of rhodium(III)/iridium(III) with S,S,
S,Se, and Se,Se ligands explored for the transfer hydrogenation
of ketones and Oppenauer-type oxidation of alcohols. They
show promising TON values (transfer hydrogenation reactions
of ketones of up to 9.8 × 103, oxidation of alcohols of up to 9.9
× 102). Further, 3 is the first example of a Rh(III) species
explored for Oppenauer-type oxidation. Their air and moisture
stability is an additional advantage. The catalytic efficiencies
follow the orders Rh > Ir and Se,Se > Se,S > S,S. The higher
catalytic efficiency of Rh species appears to be consistent with
DFT calculations.
b
2-propanol, catalyst 0.1 mol %, 80 °C, in air. Determined by NMR.
c
d
Rh complex 3. Ir complex 6.
homogeneous in nature. The PPh3 poisoning test has also been
used.35 In the presence of 5 equiv of PPh3 the reaction occurs
with only a 6% decrease in percent conversion (Table 5). This
supports the homogeneous nature of catalysis, as inferred from
the Hg test. There was also no visible sign of formation of NPs.
Table 5. PPh3 Poisoning Test for Catalytic Transfer
a
Hydrogenation
b
entry
catalyst/PPh3
time (h)
conversion (%)
c
1
1/0
1/0
1/5
1/5
3
3
3
3
98
88
92
85
d
2
c
3
d
4
a
EXPERIMENTAL SECTION
Conditions: 1 mmol of acetophenone, 10 mol % of KOH, 15 mL of
■
b
Physical Measurements. IR spectra in the range 4000−400 cm−1
2-propanol, catalyst 0.1 mol %, 80 °C, in air. Determined by NMR.
c
d
Rh complex 3. Ir complex 6.
were recorded on a Nicolet Proteg
́
e 460 FT−IR spectrometer as KBr
pellets. The C, H, and N analyses were carried out with a Perkin-Elmer
2400 Series II C, H, and N analyzer. High-resolution mass spectral
measurements were performed with electron spray ionization (10 eV,
180 °C source temperature, sodium formate as reference compound)
on a Bruker MIcroTOF-Q II instrument, the sample being taken in
CH3CN. The 1H, 13C{1H}, and 77Se{1H} NMR spectra were recorded
on a Bruker Spectrospin DPX-300 NMR spectrometer at 300.13,
75.47, and 57.24 MHz, respectively. The chemical shifts are given in
ppm relative to known standards. Yields refer to isolated yields of
DFT Calculations. Density functional theory (DFT)
calculations (see the Experimental Section for details) were
performed on all six complexes 1−6. The HOMOs (highest
occupied molecular orbitals) of all complexes are essentially
similar and are positioned primarily over the Rh or Ir and the
Cp* ring, with some contribution of S or Se and Cl donor
atoms. The d orbitals of Rh(III)/Ir(III) interacting with π
orbitals of the η5-Cp* ring and the p orbital of chlorine and
chalcogen atoms constitute these HOMOs (see the Supporting
Information Figures S19 and S20). The calculated bond
lengths/angles are given in Table 6. The agreement between
the experimentally observed bonding parameters and the
calculated values is better for M−Cl and M−Cp*(centroid).
The difference between calculated and observed M−E (E = S,
Se) bond distances in some cases is ∼0.03 Å. The calculated
and experimentally found bond angles are generally close
(Table 6), except in a few cases: e.g., S1−Rh−S2 and S1−Ir−
S2.
1
compounds which have purity ≥95% (established by H NMR). All
reactions have been carried out in glassware dried in an oven, under
ambient conditions, except for the synthesis of L1−L3. A nitrogen
atmosphere, if required, was created using Schlenk techniques. The
commercial nitrogen gas was used after passing it successively through
traps containing solutions of alkaline anthraquinone, sodium
dithionite, alkaline pyrogallol, concentrated H2SO4, and KOH pellets.
For single-crystal structures the data were collected on a Bruker AXS
SMART Apex CCD diffractometer using Mo Kα (0.71073 Å)
radiation at 298(2) K. The software SADABS37 was used for
absorption correction (if needed) and SHELXTL for space group,
structure determination, and refinements.38 Hydrogen atoms were
included in idealized positions with isotropic thermal parameters set at
1.2 times that of the carbon atom to which they are attached in all
cases.
The HOMO/LUMO energies of a complex may be
correlated to some extent to its chemical reactivity.36 The
LUMO has a higher energy than the HOMO in 1−6 and also
varies more with the complex. Therefore, it may be involved
Chemical and Reagents. Diphenyl diselenide, thiophenol,
NaBH4, chloroethanol, and ammonium hexafluorophosphate procured
G
dx.doi.org/10.1021/om401150s | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
́
Table 6. Comparison of Selected Bond Lengths (Å) and Angles (deg) of 1−6 Determined Experimentally and Calculated by
DFT
1
2
3
bond angle/
length
optimized
value
bond angle/
length
optimized
value
bond angle/
length
optimized
value
Rh−S(1)
Rh−Cl(1)
Rh−S(2)
2.380(2)
2.3702(14)
2.3702(14)
1.809(0)
86.52(5)
90.35(7)
93.71(7)
4
2.558
2.425
2.524
1.807
78.54
93.78
92.03
Rh−Se(1)
Rh−Cl(1)
Rh−S(1)
2.5037(10)
2.4090(19)
2.3692(19)
1.806(1)
84.47(6)
81.02(6)
94.15(7)
5
2.585
2.440
2.515
1.821
83.24
79.81
92.40
Rh−Se(1)
Rh−Cl(1)
Rh−Se(2)
2.4579(13)
2.408(2)
2.4864(12)
1.794(3)
84.25(4)
94.25(8)
80.98(6)
6
2.564
2.442
2.587
1.827
83.58
93.36
80.72
a
a
a
Rh−C
Rh−C
Rh−C
S1−Rh−S2
S1−Rh−Cl
Cl−Rh−S2
Se1−Rh−S1
Se1−Rh−Cl
Cl−Rh−S1
Se1−Rh−Se2
Se1−Rh−Cl
Cl−Rh−Se2
bond angle/
length
optimized
value
bond angle/
length
optimized
value
bond angle/
length
optimized
value
Ir−S(1)
Ir−Cl(1)
Ir−S(2)
2.3559(18)
2.3712(9)
2.3422(18)
1.818(0)
2.524
2.426
2.562
1.797
79.15
91.60
89.58
Ir−Se(1)
Ir−Cl(1)
Ir−S(1)
2.4892(9)
2.4101(18)
2.3553(17)
1.814(0)
2.595
2.449
2.514
1.807
81.93
80.20
90.98
Ir−Se(1)
Ir−Cl(1)
Ir−Se(2)
Ir−Ca
Se1−Ir−Se2
Se1−Ir−Cl
Cl−Ir−Se2
2.4863(8)
2.4059(16)
2.4455(8)
1.820(1)
85.77(3)
80.12(5)
92.86(5)
2.591
2.451
2.568
1.814
83.32
79.84
92.07
a
Ir−C
Ir−Ca
S1−Ir−S2
S1−Ir−Cl
Cl−Ir−S2
86.83(4)
Se1−Ir−S1
Se1−Ir−Cl
Cl−Ir−S1
84.97(5)
89.89(7)
80.19(6)
92.71(7)
93.26(7)
a
C = centroid of Cp*.
was added dropwise, and the refluxing of the mixture was continued
further for 3 h. After it was cooled to room temperature, the mixture
was poured into 100 cm3 of distilled water, neutralized with dilute
sodium hydrochloride, and extracted with 100 cm3 of chloroform. The
extract was washed with water (3 × 50 cm3) and dried over anhydrous
sodium sulfate. Its solvent was evaporated off under reduced pressure
on a rotary evaporator, resulting in L1/L2 as a pale yellow oil.
Ligand L1. Yield: 1.15 g, ∼95%. 1H NMR (CDCl3, 25 °C vs
Table 7. HOMO−LUMO Energy Gap of 1−6 and Natural
Bond Orbital (NBO) Analysis of Atomic Charge
NBO atomic charge
energy gap
complex
(eV)
metal
chalcogen E chalcogen E′
Cl
1
2
3
4
5
6
3.7552
3.8254
3.7644
4.4333
4.4632
4.4148
−0.197
−0.288
−0.376
−0.114
−0.220
−0.324
+0.437
+0.457
+0.738
+0.478
+0.478
+0.816
+0.463
+0.795
+0.798
+0.469
+0.810
+0.757
−0.401
−0.394
−0.398
−0.380
−0.380
−0.377
Me4Si): δ (ppm) 3.08 (s, 4H, H5, H6), 7.22−7.30 (m, 6H, H1−2
,
H9−10), 7.49−7.65 (m, 4H, H3, H8). 13C{1H} NMR (CDCl3, 25 °C vs
Me4Si): δ (ppm) 33.4 (C5, C6), 126.0 (C1, C10), 127.9 (C4, C7), 129.1
(C2, C9), 132.9 (C3, C8). IR (KBr, cm−1): 3038 (m; νC−H(aromatic)),
2952 (s; νC−H(aliphatic)), 1490 (m; νCC(aromatic)), 764 (m; νC−H(aromatic)).
Ligand L2. Yield: 1.30 g, 91%. 1H NMR (CDCl3, 25 °C vs Me4Si):
δ (ppm) 3.01−3.08 (m, 2H, H6), 3.12−3.19 (m, 2H, H5), 7.16−7.26
(m, 6H, H1−2, H9−10), 7.44−7.61 (m, 4H, H3, H8). 13C{1H} NMR
(CDCl3, 25 °C vs Me4Si): δ (ppm) 26.5 (C6), 34.2 (C5), 126.5 (C1),
127.3 (C10), 129.0 (C2), 129.2 (C9), 130.0 (C2), 131.6 (C7), 133.2
(C8), 135.1 (C7). 77Se{1H}NMR (CD3CN, 25 °C vs Me2Se): δ (ppm)
321.73. IR (KBr, cm−1): 3076 (m; νC−H(aromatic)), 2992 (s;
νC−H(aliphatic)), 1483 (m; νCC(aromatic)), 775 (m; νC−H(aromatic)).
from Sigma−Aldrich (USA) were used as received. (2-
Chloroethylthio)benzene,39 (2-chloroethylseleno)benzene,40 [(η5-
42
Cp*)RhCl(μ-Cl)]2,41 and [(η5-Cp*)IrCl(μ-Cl)]2 were prepared
according to literature methods. All of the solvents were dried and
distilled before use by standard procedures.43 Common reagents and
chemicals available locally were used.
DFT Calculations. All DFT calculations were carried out at the
Department of Chemistry, Supercomputing Facility for Bioinformatics
and Computational Biology, IIT Delhi, with the GAUSSIAN-09
program,44 with an immediate objective of understanding the present
complexes. The geometry of complexes 1−6 was optimized at the
M0645 level using a LANL2DZ46 basis set for metal and chalcogen
atoms and 6-31G* basis sets for C, H, and Cl. Natural bond orbital
(NBO) analysis of atomic charges was carried out for all compounds
1−6 by using the M06 functional.45 All calculations were carried out in
the gas phase and at 298.15 K. Geometry optimizations were carried
out without any symmetry restriction with X-ray coordinates of the
molecule. Harmonic force constants were computed at the optimized
geometries to characterize the stationary points as minima. The
molecular orbital plots were made using the Chemcraft program
package (http://www.chemcraftprog.com). Cartesian coordinates and
associated energies are given in the Supporting Information (Table
S6).
Synthesis of L3. Diphenyl diselenide (0.6245, 2.0 mmol) dissolved
in 30 cm3 of ethanol was treated with a solution (made in 5% NaOH)
of NaBH4 (0.149 g, 4.0 mmol; added dropwise) under an N2
atmosphere until it become colorless due to the formation of PhSeNa.
(2-Chloroethylseleno)benzene (0.878 g, 4.0 mmol) dissolved in 5 cm3
of ethanol was added to the colorless solution with constant stirring.
The reaction mixture was stirred further for 3−4 h and poured into
100 cm3 of ice-cold distilled water and extracted with CHCl3 (5 × 40
cm3). The extract was washed with water (3 × 50 cm3) and dried over
anhydrous sodium sulfate. Its solvent was evaporated off under
reduced pressure on a rotary evaporator, resulting in L3 as a pale
1
yellow oil. Yield: 1.25 g, 92%. H NMR (CDCl3, 25 °C vs Me4Si): δ
(ppm) 3.16 (s, 4H, H5, H6), 7.26−7.28 (m, 4H, H2, H9), 7.44−7.45
(m, 4H, H3, H8), 7.62−7.65 (m, 2H, H1, H10). 13C{1H} NMR (CDCl3,
25 °C vs Me4Si): δ (ppm) 27.2 (C5, C6), 127.2 (C1, C10), 127.7 (C4,
C7), 129.2 (C2, C9), 133.1 (C3, C8). 77Se{1H} NMR (CDCl3, 25 °C vs
Me2Se): δ (ppm) 339.9. IR (KBr, cm−1): 3067 (m; νC−H(aromatic)), 2982
(s; νC−H(aliphatic)), 1485 (m; νCC(aromatic)), 753 (m; νC−H(aromatic)).
Synthesis of Complexes 1−3. The solid [(η5-Cp*)RhCl(μ-Cl)]2
(0.05 g, 0.1 mmol) and appropriate ligand L1−L3 (0.2 mmol)
dissolved in CH3OH (15 cm3) were mixed, and the mixture was stirred
Synthesis of Ligands L1 and L2. Sodium hydroxide (0.224 g, 6
mmol) dissolved in 5 cm3 of water was added dropwise to thiophenol
(0.5 mL, ∼5 mmol) taken up in 50 cm3 of dry ethanol and refluxed for
0.5 h under an N2 atmosphere. (2-Chloroethylthio)benzene/(2-
chloroethylseleno)benzene (5 mmol) dissolved in 20 cm3 of ethanol
H
dx.doi.org/10.1021/om401150s | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
for 8 h at room temperature. The resulting orange solution was
filtered, and the volume of the filtrate was reduced (∼7 cm3) with a
rotary evaporator. It was mixed with solid NH4PF6 (0.032 g, 0.2
mmol), and the resulting orange microcrystalline solid was filtered,
washed with 10 cm3 of ice-cold CH3OH, and dried in vacuo. Single
crystals of 1−3 were obtained by diffusion of diethyl ether into their
solutions (1 cm3) made in a mixture (1/4) of CH3OH and CH3CN.
Complex 1. Yield: 0.106 g, ∼85%. Anal. Calcd for
C24H29ClRhS2[PF6]: C, 43.35; H, 4.40. Found: C, 43.59; H, 4.19.
(CDCl3, 25 °C vs Me2Se): δ (ppm) 357.52. HR-MS (m/z, CH3CN):
[M]+ 657.0483; calculated value for C24H29ClIrSSe 657.0457 (δ −4.0
ppm). IR (KBr, cm−1): 3175 (m; νC−H (aromatic)), 2922 (s;
νC−H(aliphatic)), 1576 (m; νCC(aromatic)), 841 (s; νP−F), 749(m;
νC−H(aromatic)).
Complex 6. Yield: 0.145 g, ∼85%. Anal. Calcd for
C24H29ClIrSe2[PF6]2: C, 33.99; H, 3.45. Found: C, 33.80; H, 3.69.
1
Mp: 265 °C. H NMR (CD3CN, 25 °C vs Me4Si): δ (ppm) 1.43 (s,
15H, H of Me(Cp*)), 3.25−3.58 (m, 2H, H5), 3.61−3.76 (m, 2H,
H6), 7.21−7.27 (m, 4H, H2, H9), 7.32−7.4. (m, 4H, H3, H8), 7.44−
7.47 (m, 2H, H1, H10). 13C{1H}NMR (CD3CN, 25 °C vs Me4Si): δ
(ppm) 8.3 (C of Me(Cp*), 32.3 (C5), 37.2 (C6), 94.4 (C of Cp*),
129.4 (C1), 129.6 (C10), 130.2 (C4), 130.5 (C7), 131.4 (C2), 131.7
(C9), 131.8 (C3), 133.6 (C8). 77Se{1H} NMR (CD3CN, 25 °C vs
Me2Se): δ (ppm) 397.2 (Se1), 405.0 (Se2). HR-MS (m/z, CH3CN):
[M]+ 704.9928; calculated value for C22H29ClIrSe2 704.9904 (δ −3.3
ppm). IR (KBr, cm−1): 3154 (m; νC−H(aromatic)), 2993 (s; νC−H(aliphatic)),
1576 (m; νCC(aromatic)), 840 (s; νP−F), 746 (m; νC−H(aromatic)).
1
Mp: 260 °C. H NMR (CD3CN, 25 °C vs Me4Si): δ (ppm) 1.57 (s,
15H, H of Me(Cp)), 3.43−3.68 (m, 4H, H6, H5), 7.33−7.58 (m, 6H,
H1−2, H9−10), 7.73 (m, 4H, H3, H8). 13C{1H} NMR (CD3CN, 25 °C vs
Me4Si): δ (ppm) 8.4 (C of Me(Cp*)), 39.9 (C5, C6), 96.3 (C of Cp*),
129.3 (C1, C10), 131.3 (C4, C7), 131.8 (C2, C9), 133.4 (C3, C8). HR-
MS (m/z, CH3CN)” [M]+ 519.0449, calculated value for
C24H29ClRhS2 519.0450 (δ −0.3 ppm). IR (KBr, cm−1): 3142 (m;
νC−H(aromatic)), 2920 (s; νC−H(aliphatic)), 1578 (m; νCC(aromatic)), 839 (s;
νP−F),749 (m; νC−H(aromatic)).
Complex 2. Yield: 0.112 g, ∼80%. Anal. Calcd for C24H29ClRhSeS-
Procedure for Catalytic Oppenauer-Type Oxidation of
Alcohols. The appropriate complex 1−6 (0.1 mol %) dissolved in
15 cm3 of acetone (containing ∼0.1% water) was mixed with the
alcohol substrate (1 mmol) and K2CO3 (1.5 mmol). The mixture was
refluxed at 80 °C for 5 h (1−3) or 7 h (4−6). The reaction was
followed by 1H NMR spectroscopy. On completion of the reaction the
reaction mixture was cooled to room temperature and the solvent was
evaporated off using a rotary evaporator. The residue having an
oxidized product was extracted with 20 cm3 of petroleum ether (40−
60 °C). The solvent from the petroleum ether extract was evaporated
off, and the oxidized product present in the residue was analyzed by its
1H NMR spectrum. The products were authenticated by comparing
1
[PF6]: C, 40.49; H, 4.11. Found: C, 40.65; H, 4.08. Mp: 242 °C. H
NMR (CD3CN, 25 °C vs Me4Si): δ (ppm) 1.49 (s, 15H, H of
Me(Cp*)), 3.26−3.65 (m, 2H, H5), 3.68−4.01 (m, 2H, H6), 7.46−
7.69 (m, 8H, H2−3, H8−9), 8.05−8.07 (m, 2H, H1, H10). 13C{1H} NMR
(CD3CN, 25 °C vs Me4Si): δ (ppm) 8.41 (C of Me(Cp*), 33.0 (C5),
39.1 (C6), 100.9 (C of Cp*), 129.5 (C1), 130.0 (C10), 130.9 (C2),
131.6 (C9), 131.8 (C3), 132.0 (C7), 132.5 (C8), 132.6 (C4) . 77Se{1H}
NMR (CDCl3, 25 °C vs Me2Se): δ (ppm) 389.8. HR-MS (m/z,
CH3CN): [M]+ 566.9897; calculated value for C24H29RhSSe 566.9891
(δ −1.0 ppm). IR (KBr, cm−1): 3158 (m; νC−H(aromatic)), 2991 (s;
νC−H(aliphatic)), 1586 (m; νCC(aromatic)), 844 (s; νP−F), 745 (m;
νC−H(aromatic)).
their NMR spectra with those of standard samples.
Complex 3. Yield: 0.128 g, ∼85%. Anal. Calcd for
Procedure for Catalytic Transfer Hydrogenation of Ketones.
A solution of a ketone (1 mmol) made in 2-propanol (15 cm3), KOH
(10 mol %), and the appropriate complex from 1−6 (0.01 mol %
dissolved in CH3CN) was mixed and heated at 80 °C for 5 h in the
C24H29ClRhSe2[PF6]2: C, 37.99; H, 3.85. Found: C, 37.50; H, 3.92.
1
Mp: 240 °C. H NMR (CD3CN, 25 °C vs Me4Si): δ (ppm) 1.54 (s,
15H, H of Me(Cp*)), 3.31−3.63 (m, 2H, H5), 3.65−3.89 (m, 2H,
H6), 7.45−7.67 (m, 8H, H2−3, H8−9), 7.85−7.88 (m, 2H, H1, H10).
13C{1H}NMR (CD3CN, 25 °C vs Me4Si): δ (ppm) 8.7 (C of
Me(Cp*)), 33.0 (C5), 36.1 (C6), 100.1 (C of Cp*), 126.5 (C1), 129.8
(C10), 130.3 (C4), 130.9 (C7), 131.4 (C2), 131.5 (C9), 132.6 (C3),
133.6 (C8). 77Se{1H} NMR (CD3CN, 25 °C vs Me2Se): δ (ppm)
403.8 (Se1), 413.8 (Se2). HR-MS (m/z, CH3CN): [M]+ 614.9337;
calculated value for C24H29ClRhSe2 614.9337 (δ 0.1 ppm). IR (KBr,
cm−1): 3150 (m; νC−H(aromatic)), 2972 (s; νC−H(aliphatic)), 1574 (m;
νCC(aromatic)), 849 (s; νP−F), 743 (m; νC−H(aromatic)).
1
case of 3 and 6 h in the case of 6. The reaction was followed by H
NMR spectroscopy. After completion of the reaction, the reaction
mixture was cooled to room temperature. The solvent was removed on
a rotary evaporator, and the resulting semisolid was extracted with
diethyl ether (3 × 20 cm3). The extract was passed through a short
column (∼8 cm3 in length) of silica gel. The column was washed with
∼50 cm3 of diethyl ether. All the eluates from the column were mixed,
and the solvent from the mixture was evaporated off on a rotary
evaporator. The resulting residue was subjected to 1H NMR. The final
conversions are reported as an average of two runs of each catalytic
reaction.
Hg Poisoning Test. An excess of Hg (Hg/(Rh,Ir) 400/1) was
placed in the reaction flask. Thereafter the transfer hydrogenation
reaction of acetophenone (1.0 mmol) with 2-propanol (15 mL) using
3 or 6 (0.1 mol %) as catalyst was carried out in the flask under
optimum conditions. A conversion of ∼90% was observed after 3 h of
reaction.
Synthesis of Complexes 4−6. The solid [(η5-Cp*)IrCl(μ-Cl)]2
(0.05 g, 0.1 mmol) and appropriate ligand L1−L3 (0.2 mmol)
dissolved in CH3OH (15 cm3) were mixed, and the mixture was stirred
for 10 h at room temperature. The resulting yellow solution was
filtered. After workup as described for 1−3, single crystals of 4−6 were
obtained by diffusion of diethyl ether into their solution (1 cm3) made
in a mixture (1/4) of CH3OH and CH3CN.
Complex 4. Yield: 0.124 g, ∼82%. Anal. Calcd for
C24H29ClIrS2[PF6]: C, 38.22; H, 3.88. Found: C, 38.37; H, 3.57.
1
PPh3 Poisoning Test. To the transfer hydrogenation reaction
mixture of acetophenone with 2-propanol (15 mL) was added PPh3
(0.5 mol %) under the optimum conditions after addition of catalyst 3
or 6 (0.1 mol %). After 3 h of reaction ∼92% of the product was
obtained.
Mp: 282 °C. H NMR (CD3CN, 25 °C vs Me4Si): δ (ppm) 1.79 (s,
15H, H of Me(Cp*)), 3.39−3.78 (m, 4H, H6, H5), 7.33−7.50 (m, 6H,
H1−2, H9−10), 7.61−7.73 (m, 4H, H3, H8). 13C{1H} NMR (CD3CN, 25
°C vs Me4Si): δ (ppm) 7.9 (C of Me(Cp*)), 38.4 (C5, C6), 95.1 (C of
Cp*), 129.2 (C1, C10), 130.0 (C4, C7), 130.4 (C2, C9), 133.0 (C3, C8).
HR-MS (m/z, CH3CN): [M]+ 609.1021; calculated value for
C24H29ClIrS2 609.1013 (δ −1.4 ppm). IR (KBr, cm−1): 3192 (m;
νC−H(aromatic)), 2922 (s; νC−H(aliphatic)), 1578 (m; νCC(aromatic)), 838 (s;
νP−F), 749 (m; νC−H(aromatic)).
ASSOCIATED CONTENT
■
S
* Supporting Information
Complex 5. Yield: 0.135 g, ∼85%. Anal. Calcd for C24H29ClIrSeS-
Figures, tables, and CIF files giving crystal and refinement data,
bond lengths and angles, secondary interaction distances,
structures, NMR and mass spectra, crystallographic data
(CCDC nos. 926183, 926184, 926185, 926186, 926187, and
926188, respectively, for 1−6), and HOMO−LUMO energy
gaps and partial charges. This material is available free of charge
via the Internet at http://pubs.acs.org.
1
[PF6]: C, 35.98; H, 3.65. Found: C, 35.64; H, 3.92. Mp: 270 °C. H
NMR (CD3CN, 25 °C vs Me4Si): δ (ppm) 1.48 (s, 15H, H of
Me(Cp*)), 3.28−3.57 (m, 2H, H5), 3.69−3.75 (m, 2H, H6), 7.47−
7.65 (m, 8H, H2−3, H8−9), 7.96−7.98 (m, 2H, H1, H10). 13C{1H} NMR
(CD3CN, 25 °C vs Me4Si): δ (ppm) 8.20 (C of Me(Cp*), 34.4 (C5),
39.7 (C6), 94.4 (C of Cp*), 128.0 (C1), 129.4 (C10), 129.8 (C2), 130.0
(C9), 130.2 (C3), 131.6 (C7), 132.4 (C8), 132.9 (C4). 77Se{1H} NMR
I
dx.doi.org/10.1021/om401150s | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(d) Malacea, R.; Poli, R.; Manoury, E. Coord. Chem. Rev. 2010, 254,
AUTHOR INFORMATION
Corresponding Author
*A.K.S.: e-mail, aksingh@chemistry.iitd.ac.in, ajai57@hotmail.
com; fax, +91 11 26581102; tel, +91 11 26591379.
■
́
729. (e) Bartok, M. Chem. Rev. 2010, 110, 1663. (f) Wu, X.; Xiao, J.
Chem. Commun. 2007, 2449. (g) Touge, T.; Hakamata, T.; Nara, H.;
Kobayashi, T.; Sayo, N.; Saito, T.; Kayaki, Y.; Ikariya, T. J. Am. Chem.
Soc. 2011, 133, 14960. (h) Lagaditis, P. O.; Lough, A. J.; Morris, R. H.
́
J. Am. Chem. Soc. 2011, 133, 9662. (i) Vazquez-Villa, H.; Reber, S.;
Notes
Ariger, M. A.; Carreira, E. M. Angew. Chem., Int. Ed. 2011, 50, 8979.
(j) Soni, R.; Collinson, J.; Clarkson, G. C.; Wills, M. Org. Lett. 2011,
13, 4304. (k) Wang, C.; Li, C.; Wu, X.; Pettman, A.; Xiao, J. Angew.
Chem. 2009, 121, 6646; Angew. Chem., Int. Ed. 2009, 48, 6524.
(8) (a) Marko, I. E.; Giles, P. R.; Tsukazaki, M.; Brown, S. M.; Urch,
C. J. Science 1996, 274, 2044. (b) Sato, K.; Aoki, M.; Takagi, J.; Noyori,
R. J. Am. Chem. Soc. 1997, 119, 12386. (c) Nishimura, T.; Onoue, T.;
Ohe, K.; Uemura, S. Tetrahedron Lett. 1998, 39, 6011. (d) Peterson, K.
P.; Larock, R. C. J. Org. Chem. 1998, 63, 3185. (e) Hanyu, A.;
Takezawa, E.; Sakaguchi, S.; Ishii, Y. Tetrahedron Lett. 1998, 39, 5557.
(f) Marko, I. E.; Giles, P. R.; Tsukazaki, M.; Chelle-Regnaut, I.;
Gautier, A.; Brown, S. M.; Urch, C. J. J. Org. Chem. 1999, 64, 2433.
(g) Nishimura, T.; Onoue, T.; Ohe, K.; Uemura, S. J. Org. Chem. 1999,
64, 6750. (h) ten Brink, G.-J.; Arends, I. W. C. E.; Sheldon, R. A.
Science 2000, 287, 1636. (i) Kakiuchi, N.; Maeda, Y.; Nishimura, T.;
Uemura, S. J. Org. Chem. 2001, 66, 6620. (j) Mori, K.; Yamaguchi, K.;
Hara, T.; Mizugaki, T.; Ebitani, K.; Kaneda, K. J. Am. Chem. Soc. 2002,
124, 11572. (k) Jensen, D. R.; Schultz, M. J.; Mueller, J. A.; Sigman, M.
S. Angew. Chem., Int. Ed. 2003, 42, 3810. (l) Das, S.; Punniyamurthy,
T. Tetrahedron Lett. 2003, 44, 6033. (m) Iwasawa, T.; Tokunaga, M.;
Obora, Y.; Tsuji, Y. J. Am. Chem. Soc. 2004, 126, 6554. (n) Mueller, J.
A.; Goller, C. P.; Sigman, M. S. J. Am. Chem. Soc. 2004, 126, 9724.
(o) Mori, K.; Hara, T.; Mizugaki, T.; Ebitani, K.; Kaneda, K. J. Am.
Chem. Soc. 2004, 126, 10657.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
The authors acknowledge Professor B. Jayaram for computa-
tional facilities and thank the Department of Science and
Technology, New Delhi (India) for the following: research
project no. SR/S1/IC-40/2010, partial financial assistance
(under the FIST programme) for the single-crystal X-ray
diffractometer, and mass spectral facilities at IIT Delhi.
Financial support from the Council of Scientific and Industrial
Research (India), research project no. 01(2421)10/EMR-II,
and the award of a Junior/Senior Research Fellowship to K.N.S.
are gratefully acknowledged. O.P. and H.J. thank the University
Grants Commission (India) for Junior/Senior Research
Fellowships.
REFERENCES
■
(1) (a) Cremlyn, R. J. An Introduction to Organosulfur Chemistry;
Wiley: Chichester, U.K., 1996. (b) Devillanova, F. A. Handbook of
Chalcogen Chemistry: New Perspectives in Sulfur, Selenium and
Tellurium; Royal Society of Chemistry: London, 2007. (c) Murray,
S. G.; Hartley, F. R. Chem. Rev. 1981, 81, 365. (d) Freudendahl, D. M.;
Shahzad, S. A.; Wirth, T. Eur. J. Org. Chem. 2009, 11, 1649.
(9) Alfonsi, K.; Colberg, J.; Dunn, P. J.; Fevig, T.; Jennings, S.;
Johnson, T. A.; Kleine, H. P.; Knight, C.; Nagy, M. A.; Perry, D. A.;
Stefaniak, M. Green Chem. 2008, 10, 31.
(10) (a) Namy, J. L.; Souppe, J.; Collin, J.; Kagan, H. B. J. Org. Chem.
1984, 49, 2045. (b) Ishii, Y.; Nakano, T.; Inada, A.; Kishigami, Y.;
Sakurai, K.; Ogawa, M. J. Org. Chem. 1986, 51, 240. (c) Krohn, K.;
(2) (a) Kermagoret, A.; Morgant, G.; d’Angelo, J.; Tomas, A.;
Roussel, P.; Bastian, G.; Collery, P.; Desmaele, D. Polyhedron 2011, 30,
̈
347. (b) Awaleh, M. O.; Badia, A.; Brisse, F.; Bu, X.-H. Inorg. Chem.
2006, 45, 1560. (c) Boadi, N. O.; Malik, M. A.; O’Brien, P.; Awudza, J.
A. M. Dalton Trans. 2012, 41, 10497. (d) Henderson, W. H.; Check,
C. T.; Proust, N.; Stambuli, J. P. Org. Lett. 2010, 12, 824.
Knauer, B.; Kupke, J.; Seebach, D.; Beck, A. K.; Hayakawa, M. Synthesis
̈
1996, 1341. (d) da Silva, A. C.; Piotrowski, H.; Mayer, P.; Polborn, K.;
(3) (a) Levason, W.; Reid, G.; Zhang, W. Dalton Trans. 2011, 40,
8491. (b) Levason, W.; Orchard, S. D.; Reid, G. Coord. Chem. Rev.
2002, 225, 159. (c) Levason, W.; Maheshwari, S.; Ratnani, R.; Reid,
G.; Webster, M.; Zhang, W. Inorg. Chem. 2010, 49, 9036. (d) Farina,
P.; Levason, W.; Reid, G. Dalton Trans. 2013, 42, 89. (e) Black, J. R.;
Champness, N. R.; Levason, W.; Reid, G. J. Chem. Soc., Dalton Trans.
1995, 1, 3439.
(4) (a) Levason, W.; Orchard, S. D.; Reid, G.; Street, J. M. J. Chem.
Soc., Dalton Trans. 2000, 2537. (b) Barton, A. J.; Levason, W.; Reid,
G.; Ward, A. J. Organometallics 2001, 20, 3644. (c) Miranda-Soto, V.;
Parra-Hake, M.; Morales-Morales, D.; Toscano, R. A.; Boldt, G.; Koch,
A.; Grotjahn, D. B. Organometallics 2005, 24, 5569. (d) Xu, C.; Goh, L.
Y.; Pullarkat, S. A. Organometallics 2011, 30, 6499.
Severin, K. Eur. J. Inorg. Chem. 2001, 685.
(11) (a) Almeida, M. L. S.; Beller, M.; Wang, G.-Z.; Backvall, J.-E.
̈
Chem. Eur. J. 1996, 2, 1533. (b) Wang, G.-Z.; Backvall, J.-E. J. Chem.
̈
Soc., Chem. Commun. 1992, 337. (c) Terashima, T.; Kamigaito, M.;
Baek, K.-Y.; Ando, T.; Sawa-moto, M. J. Am. Chem. Soc. 2003, 125,
5288. (d) Nishibayashi, Y.; Yamauchi, A.; Onodera, G.; Uemura, S. J.
Org. Chem. 2003, 68, 5875. (e) Nishibayashi, Y.; Takei, I.; Uemura, S.;
Hidai, M. Organometallics 1999, 18, 2291. (f) Wang, G.-Z.;
Andreasson, U.; Backvall, J.-E. J. Chem. Soc., Chem. Commun. 1994,
̈
1037. (g) Gauthier, S.; Scopelliti, R.; Severin, K. Organometallics 2004,
23, 3769.
(12) (a) Hanasaka, F.; Fujita, K.-i.; Yamaguchi, R. Organometallics
2004, 23, 1490. (b) Suzuki, T.; Morita, K.; Tsuchida, M.; Hiroi, K. J.
Org. Chem. 2003, 68, 1601. (c) Fujita, K.; Furukawa, S.; Yamaguchi, R.
J. Organomet. Chem. 2002, 649, 289. (d) Fujita, K.; Yamamoto, K.;
Yamaguchi, R. Org. Lett. 2002, 4, 2691. (e) Hanasaka, F.; Fujita, K.-i.;
Yamaguchi, R. Organometallics 2005, 24, 3422.
(13) (a) Zassinovich, G.; Mestroniand, G.; Gladiali, S. Chem. Rev.
1992, 92, 1051. (b) Noyori, R.; Hashiguchi, S. Acc. Chem. Res. 1997,
30, 97. (c) Everaere, K.; Mortreux, A.; Carpentier, J. F. Adv. Synth.
Catal. 2003, 345, 67. (d) Clapham, S. E.; Hadzovic, A.; Morris, R. H.
Coord. Chem. Rev. 2004, 248, 2201. (e) Gladiali, S.; Alberico, E. Chem.
Soc. Rev. 2006, 35, 226. (f) Samec, J. S. M.; Backvall, J. E.; Andersson,
P. G.; Brandt, P. Chem. Soc. Rev. 2006, 35, 237. (g) Ikariya, T.; Blacker,
A. J. Acc. Chem. Res. 2007, 40, 1300. (h) Wang, C.; Wu, X.; Xiao, J.
Chem. Asian J. 2008, 3, 1750. (i) Noyori, R.; Yamakawa, M.;
Hashiguchi, S. J. Org. Chem. 2001, 66, 7931.
(5) (a) Grutzmacher, H. Angew. Chem., Int. Ed. 2008, 47, 1814.
̈
(b) Liu, J.; Wu, X.; Iggo, J. A.; Xiao, J. Coord. Chem. Rev. 2008, 252,
782. (c) Severin, K. Chem. Commun. 2006, 31, 3859. (d) Carmona, E.;
Cingolani, A.; Marchetti, F.; Pettinari, C.; Pettinari, R.; Skelton, B. W.;
White, A. H. Organometallics 2003, 22, 2820. (e) Steinke, T.; Gemel,
C.; Cokoja, M.; Winter, M. A.; Fischer, R. Chem. Commun. 2003, 9,
1066.
(6) (a) Hashiguchi, S.; Fujii, A.; Takehara, J.; Ikariya, T.; Noyori, R. J.
Am. Chem. Soc. 1995, 117, 7562. (b) Uematsu, N.; Fujii, A.;
Hashiguchi, S.; Ikariya, T.; Noyori, R. J. Am. Chem. Soc. 1996, 118,
4916. (c) Fujii, A.; Hashiguchi, S.; Uematsu, N.; Ikariya, T.; Noyori, R.
J. Am. Chem. Soc. 1996, 118, 2521. (d) Ikariya, T.; Murata, K.; Noyori,
R. Org. Biomol. Chem. 2006, 4, 393. (e) Haack, K. J.; Hashiguchi, S.;
Fujii, A.; Ikariya, T.; Noyori, R. Angew. Chem., Int. Ed. 1997, 36, 285.
(f) Hashiguchi, S.; Fujii, A.; Haack, K. J.; Matsumura, K.; Ikariya, T.;
Noyori, R. Angew. Chem., Int. Ed. 1997, 36, 288.
(14) (a) Singh, P.; Singh, A. K. Organometallics 2010, 29, 6433.
(b) Nieto, I.; Livings, M. S.; Sacci, J. B.; Reuther, L. E.; Zeller, M.;
Papish, E. T. Organometallics 2011, 30, 6339−6342. (c) Hounjet, L. J.;
Ferguson, M. J.; Cowie, M. Organometallics 2011, 30, 4108. (d) Wylie,
(7) (a) Zheng, C.; You, S. Chem. Soc. Rev. 2012, 41, 2498. (b) Zhang,
W.; Chien, S.; Hor, T. S. A. Coord. Chem. Rev. 2011, 255, 1991.
(c) Alonso, F.; Riente, P.; Yus, M. Acc. Chem. Res. 2011, 44, 379.
J
dx.doi.org/10.1021/om401150s | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
W. N. O.; Lough, A. J.; Morris, R. H. Organometallics 2012, 31, 2137.
(e) Wu, X.; Liu, J.; Tommaso, D. D.; Iggo, J. A.; Catlow, C. R. A.;
Bacsa, J.; Xiao, J. Chem. Eur. J. 2008, 14, 7699. (f) Singh, P.; Singh, M.;
Sing, A. K. J. Organomet. Chem. 2009, 694, 3872. (g) Das, D.; Singh,
P.; Prakash, O.; Singh, A. K. Inorg. Chem. Commun. 2010, 13, 1370.
(15) Prakash, O.; Singh, P.; Mukherjee, G.; Singh, A. K.
Organometallics 2012, 31, 3379.
(16) (a) Hartley, F. R.; Murray, S. G.; Levason, W.; Soutter, H. E.;
McAuliffe, C. A. Inorg. Chim. Acta 1979, 35, 265. (b) Reimer, K. J.;
Shaver, A. Inorg. Synth. 1979, 19, 159. (C) Gulliver, D. J.; Hope, E. G.;
Levason, W.; Murray, S. G.; Potter, D. M.; Marshall, G. L. J. Chem.
Soc., Perkin Trans. 2 1984, , 429.
(17) (a) Wang, Q.; Chen, D.-F. Acta Crystallogr., Sect. E: Struct. Rep.
Online 2007, 63, o4018. (b) Fun, H.-K.; Yeap, C. S.; Sujith, K. V.;
Kalluraya, B. Acta Crystallogr., Sect. E: Struct. Rep. Online 2009, 65,
o1196.
(18) Jia, W.-G.; Huang, Y.-B.; Lin, Y.-J.; Jin, G.-X. Dalton Trans.
2008, 5612.
(37) Sheldrick, G. M. SADABS, Version 2.10; University of Gottingen,
̈
Gottingen, Germany, 2003.
̈
(38) (a) Sheldrick, G. M. Acta Crystallogr., Sect. A: Found. Crystallogr.
1990, A46, 467. (b) Sheldrick, G. M. SHELXL-NT, Version 6.12;
University of Gottingen, Gottingen, Germany, 2000.
̈
̈
(39) Brace, N. O. J. Org. Chem. 1993, 58, 4506.
(40) McManus, S. P.; Lam, D. H. J. Org. Chem. 1978, 43, 650.
(41) Kang, W.; Moseley, K.; Maitlis, P. M. J. Am. Chem. Soc. 1969, 91,
5970.
(42) White, C.; Yates, A.; Maitlis, P. M. Inorg. Synth. 1992, 29, 228.
(43) Furniss, B. S.; Hannaford, A. J.; Smith, P. W. G.; Tatchell, A. R.
Vogel’s Textbook of Practical Organic Chemistry, 5th ed.; ELBS,
Longman Group: London, 1989.
(44) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci,
B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H.
P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.;
Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima,
T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.;
Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin,
K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.;
Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega,
N.; Millam, N. J.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.;
Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.;
Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.;
Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.;
(19) Valderrama, M.; Contreras, R.; Lamata, M. P.; Viguri, F.;
Carmona, D.; Lahoz, F. J.; Elipe, S.; Oro, L. A. J. Organomet. Chem.
2000, 607, 3.
́
(20) Simοn-Manso, E.; Valderrama, M.; Gantzel, P.; Kubiak, C. P. J.
Organomet. Chem. 2002, 651, 90.
(21) Nakagawa, T.; Seino, H.; Mizobe, Y. Organometallics 2010, 24,
2254.
(22) Sau, Y. K.; Yi, X. Y.; Chan, K. W.; Lai, C. S.; Williams, I. D.;
Leung, W. H. J. Organomet. Chem. 2010, 695, 1399.
̈
Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, J. O.;
Foresman, B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09,
Revision D.01; Gaussian, Inc., Wallingford, CT, 2009.
(23) Hubner, R.; Weber, S.; Strobel, S.; Sarkar, B.; Zal
Organometallics 2011, 30, 1414.
́
is,
̌
S.; Kaim, W.
̈
́
(45) Wei, M.-M.; Garcıa-Melchor, M.; Daran, J.-C.; Audin, C.;
Lledos, A.; Poli, R.; Deydier, E.; Manoury, E. Organometallics 2012, 31,
6669.
(24) Huo, X. K.; Su, G.; Jin, G. X. Chem. Eur. J. 2010, 16, 12017.
(25) Nagao, S.; Seino, H.; Okada, T.; Mizobe, Y.; Hidai, M. Dalton
Trans. 2000, 3546.
(26) Kumbhare, L. B.; Wadawale, A. P.; Jain, V. K.; Sieger, M.; Kaim,
W. Inorg. Chem. Commun. 2010, 13, 475.
́
(46) (a) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 270.
(b) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 299.
(27) Liu, Z.; Salassa, L.; Habtemariam, A.; Pizarro, A. M.; Clarkson,
G. J.; Sadler, P. J. Inorg. Chem. 2011, 50, 5777.
(28) Turkmen, H.; Pape, T.; Hahn, F. E.; C
metallics 2008, 27, 571.
̧
etinkaya, B. Organo-
̈
(29) (a) Yang, L.; Kruger, A.; Neels, A.; Albrecht, M. Organometallics
̈
2008, 27, 3161. (b) Guo, X.-Q.; Wang, Y.-N.; Wang, D.; Cai, L.-H.;
Chen, Z.-X.; Hou, X.-F. Dalton Trans. 2012, 41, 14557. (c) Canivet, J.;
Suss-Fink, G.; Stepnicka, P. Eur. J. Inorg. Chem. 2007, 4736.
̈
(d) Binobaid, A.; Iglesias, M.; Beetstra, D.; Dervisi, A.; Fallis, I.;
Cavell, K. J. Eur. J. Inorg. Chem. 2010, 5426.
(30) Bacchi, A.; Balordi, M.; Cammi, R.; Elviri, L.; Pelizzi, C.;
Picchioni, F.; Verdolino, V.; Goubitz, K.; Peschar, R.; Pelagatti, P. Eur.
J. Inorg. Chem. 2008, 4462.
(31) Hintermair, U.; Sheehan, S. W.; Parent, A. R.; Ess, D. H.;
Richens, D. T.; Vaccaro, P. H.; Brudvig, G. W.; Crabtree, R. H. J. Am.
Chem. Soc. 2013, 135, 10837.
(32) DePasquale, J.; Kumar, M.; Zeller, M.; Papish, E. T.
Organometallics 2013, 32, 966.
(33) Azua, A.; Mata, J. A.; Peris, E.; Lamaty, F.; Martinez, J.;
Colacino, E. Organometallics 2012, 31, 3911.
(34) (a) Foley, P.; DiCosimo, R.; Whitesides, G. M. J. Am. Chem. Soc.
1980, 102, 6713. (b) Anton, D. R.; Crabtree, R. H. Organometallics
1983, 2, 855. (c) Eberhard, M. R. Org. Lett. 2004, 6, 2125.
(d) Widegren, J. A.; Finke, R. G. J. Mol. Catal. A: Chem. 2003, 198,
317.
(35) (a) Bayram, E.; Linehan, J. C.; Fulton, J. L.; Roberts, J. A. S.;
Szymczak, N. K.; Smurthwaite, T. D.; Ozkar, S.; Balasubramanian, M.;
Finke, R. G. J. Am. Chem. Soc. 2011, 133, 18889. (b) Bayram, E.; Finke,
R. G. ACS Catal. 2012, 2, 1967.
(36) (a) Mebi, C. A. J. Chem. Sci. 2011, 123, 727. (b) Chattaraj, P. K.;
Maiti, B. J. Am. Chem. Soc. 2003, 125, 2705. (c) Pearson, R. G. Acc.
Chem. Res. 1993, 26, 250. (d) Parr, P. G.; Pearson, R. G. J. Am. Chem.
Soc. 1983, 105, 7512. (e) Parr, R. G.; Szentpaly, L.; Liu, S. J. Am. Chem.
Soc. 1999, 121, 1922. (f) Liu, S. J. Chem. Sci. 2005, 117, 477.
K
dx.doi.org/10.1021/om401150s | Organometallics XXXX, XXX, XXX−XXX