Insertion of nitrene and chalcogenolate groups into the Ir-C σ bond in a cyclometalated iridium(III) complex

Article abstract of DOI:10.1016/j.jorganchem.2010.02.002

Treatment of [Cp*Ir(ppy)Cl] (Cp* = η⁵-C₅Me₅, ppyH = 2-(2-pyridyl)phenyl) with Ag(OTf) (OTf^- = triflate) in MeOH and MeCN gave the solvento complexes [Cp*Ir(ppy)(solv)][OTf] (solv = MeOH (1) and MeCN (2)). Complex 1 is capable of catalyzing oxidation and azirdination of styrene with PhIO and PhINTs (Ts = tosyl), respectively. Treatment of 2 with a stoichiometric amount of PhINTs resulted in the insertion of the NTs group into the Ir-C(ppy) bond and formation of [Cp*Ir(η²-ppy-NTs)(MeCN)][OTf] (3). Treatment of 1 with R₂E₂ afforded [Cp*Ir(ppy)(η¹-R₂E₂)][OTf] (E = S (4), Se (5), Te (6)). Reactions of 4 and 5 with Ag(OTf) resulted in cleavage of the E-E bond and insertion of an ER group into the Ir-C(ppy) bond. The crystal structures of complexes 2-6 and [Cp*Ir(η²-ppy-S-p-tol)(H₂O)][OTf]₂ have been determined.

Full text of DOI:10.1016/j.jorganchem.2010.02.002

Journal of Organometallic Chemistry 695 (2010) 1399–1404
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Insertion of nitrene and chalcogenolate groups into the Ir–C
cyclometalated iridium(III) complex
r
bond in a
*
Yiu-Keung Sau, Xiao-Yi Yi, Ka-Wang Chan, Chun-Sing Lai, Ian D. Williams, Wa-Hung Leung
Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 5 January 2010
Received in revised form 2 February 2010
Accepted 2 February 2010
Available online 10 February 2010
Treatment of [Cp*Ir(ppy)Cl] (Cp* =
g
5-C5Me5, ppyH = 2-(2-pyridyl)phenyl) with Ag(OTf) (OTfꢀ = triflate)
*
in MeOH and MeCN gave the solvento complexes [Cp Ir(ppy)(solv)][OTf] (solv = MeOH (1) and MeCN
(2)). Complex 1 is capable of catalyzing oxidation and azirdination of styrene with PhIO and PhINTs
(Ts = tosyl), respectively. Treatment of 2 with a stoichiometric amount of PhINTs resulted in the insertion
*
of the NTs group into the Ir–C(ppy) bond and formation of [Cp Ir(
1-R2E2)][OTf] (E = S (4), Se (5), Te (6)). Reactions of 4 and 5
*
ment of 1 with R2E2 afforded [Cp Ir(ppy)(g
g
2-ppy-NTs)(MeCN)][OTf] (3). Treat-
Keywords:
Iridium
Cyclometalated
Insertion
with Ag(OTf) resulted in cleavage of the E–E bond and insertion of an ER group into the Ir–C(ppy) bond.
The crystal structures of complexes 2–6 and [Cp*Ir(
g
2-ppy-S-p-tol)(H2O)][OTf]2 have been determined.
Ó 2010 Elsevier B.V. All rights reserved.
Nitrene
1. Introduction
complexes with terminal oxo and imido ligands are unknown. This
prompted us to explore the atom transfer chemistry of Cp*Ir(ppy)
*
Half-sandwich iridium cyclopentadienyl complexes have
received considerable attention due to their applications in C–H
activation and functionalization [1–3]. Of note is cationic
complexes. In this work, we describe the reactions of [Cp Ir(ppy)
(solv)]+ with oxo and nitrene donors. We found that reaction of
+
*
[Cp Ir(ppy)(MeCN)] with PhINTs (Ts = tosyl) resulted in insertion
of the nitrene group into the Ir–C(ppy) bond. Also, the treatment
of Cp Ir(ppy)(g
1-R2E2) (E = S, Se) with AgI led to E–E cleavage
*
[Cp*Ir(PMe3)Me(solv)]+ (Cp* =
g
5-C5Me5) that can activate alkane
C–H bonds under mild conditions [3]. One possible mechanism
for the Cp*Ir(III)-mediated C–H activation involves an oxidative
addition-reductive elimination pathway [3–7]. Therefore, in order
to develop efficient Ir-based catalysts for C–H activation, knowl-
and insertion of an ER group into the Ir–C(ppy) bond. The crystal
structures of [Cp Ir(g2-ppy-NTs)(MeCN)][OTf] and [Cp Ir(
S-p-tol)(H2O)][OTf]2 will be reported.
2-ppy-
*
*
g
*
edge of the organometallic chemistry of higher valent Cp Ir com-
plexes is essential.
2. Experimental
In an attempt to synthesize high-valent Ir complexes, we sought
to investigate the oxidation reactions of Cp*Ir complexes stabilized
by bidentate, cyclometalated 2-(2-pyridyl)phenyl (ppy) ligands.
Our interest in high valent cyclometalated iridium complexes is
stimulated by recent reports that Ir–ppy complexes are capable
of catalyzing oxidation of water using CeIV as the primary oxidant
[8,9]. A theoretical study showed that the electronic structure of an
electrophilic Ir-oxo species, namely [Cp*Ir(O)(ppy)]+, is consistent
with this complex being the reactive intermediate for the Ir-med-
iated water oxidation [8]. High-valent Ir complexes containing
metal-ligand multiple bonds are rare. The only structurally charac-
terized Ir terminal oxo complex is tetrahedral [IrV(O)(mes)3]
2.1. General
All manipulations were carried out under nitrogen by standard
Schlenk techniques. Solvents were purified, distilled and degassed
prior to use. NMR spectra were recorded on a Varian Mercury 300
spectrometer operating at 300 and 282.4 MHz for 1H and 19F,
respectively. Chemical shifts (d, ppm) were reported with reference
to SiMe4 (1H and 13C) and C6H5CF3 19F). Elemental analyses were
(
*
performed by Medac Ltd., Surrey, UK. The compound [Cp Ir(ppy)Cl]
was synthesized as described elsewhere [14]. Atom labeling
schemes for the ppyH ligand is shown in Scheme 1.
(mes = mesityl) [10]. The IrIII complexes [Cp Ir(NR)] [11],
*
[Cp*2Ir2(l-O)2(PPh3)] [12] and [Cp*2Ir2(l l-O)] [13] have
-NBut)(
V
*
been isolated by Bergman and coworkers. Nevertheless, Cp Ir
*
2.2. Preparation of [Cp Ir(ppy)(H2O)][OTf] (1)
*
To a suspension of [Cp Ir(ppy)Cl] (50 mg, 0.096 mmol) in meth-
* Corresponding author. Tel.: +852 2358 7360; fax: +852 2358 1594.
E-mail address: chleung@ust.hk (W.-H. Leung).
anol (10 mL) was added AgOTf (25 mg, 0.097 mmol). The color of
0022-328X/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.02.002

1400
Y.-K. Sau et al. / Journal of Organometallic Chemistry 695 (2010) 1399–1404
2H, H2 and H7), 7.77 (m, 2H, H3 and H6), 7.96 (d, J = 7.5 Hz, 1H,
3
1
4
5
6
H4), 8.11 (d, J = 8.4 Hz, 1H, H5), 9.26 (d, J = 5.1 Hz, 1H, H8) ppm.
19F{1H} NMR (CDCl3): d = ꢀ77.8 ppm. Anal. Calc. for C31H33N3O5F3-
S2Ir: C, 44.28; H, 3.96; N, 5.00. Found: C, 44.09; H, 3.93; N, 4.90%.
7
2
N
9
8
2.7. Preparation of [Cp*Ir(ppy)(g
1-E2R2)][OTf] (E = S, R = p-tol (4);
Scheme 1. Atom labeling scheme for the ppyH ligand.
E = Se, R = Ph (5); E = Te, R = Ph (6))
the mixture changed from orange to yellow and a white precipitate
was formed. The mixture was stirred at room temperature for 1 h
and filtered. Recrystallization from CH2Cl2–hexane gave a yellow
crystalline solid. Yield: 50 mg (83%). 1H NMR (300 MHz, CDCl3):
d = 1.73 (s, 15H, C5Me5), 2.63 (s, 2H, H2O), 7.16 (dt, J1 = 1.2 Hz, J2
=7.2 Hz, 1H, H1), 7.23 (dt, J1 = 1.2 Hz, J2 = 7.2 Hz, 1H, H2), 7.34 (dt,
J1 = 1.2 Hz, J2 = 5.4 Hz, 1H, H7), 7.65 (d, J = 1.2 Hz, 1H, H3), 7.72 (d,
J = 2.4 Hz, 1H, H6), 7.80 (d, J = 1.2 Hz, 1H, H4), 7.86 (d, J = 2.4 Hz,
1H, H5), 8.95 (dt, J1 = 1.2 Hz, J2 = 5.4 Hz, 1H, H8) ppm. 19F{1H}
NMR (CDCl3): d = ꢀ77.8 ppm. Anal. Calc. for C22H25O4NF3SIr: C,
40.73; H, 3.88; N, 2.16. Found: C, 41.12; H, 3.91; N, 2.11%.
To a solution of complex 1 (50 mg, 0.074 mmol) in CH2Cl2
(10 mL) at 0 °C was added E2R2 (0.075 mmol). The resulting red
mixture was stirred at room temperature overnight and a yellow
solution was formed. The volatiles were removed in vacuo and
the residue was recrystallized from CH2Cl2–hexane to give yellow
crystals which were suitable for X-ray diffraction analysis.
Complex 4: Yield: 54 mg (84%). 1H NMR (300 MHz, CDCl3):
d = 1.80 (s, 15H, C5Me5), 2.20 (s, 3H, C6H4CH3), 2.26 (s, 3H,
C6H4CH3), 6.45 (d, J = 8.1 Hz, 2H, C6H4CH3), 6.70 (d, J = 8.1 Hz, 2H,
C6H4CH3), 7.00 (d, J = 7.5 Hz, 2H, C6H4CH3), 7.05 (d, J = 7.5 Hz, 2H,
C6H4CH3), 7.20–7.26 (m, 3H, H1, H2, H7), 7.55 (d, J = 7.8 Hz, 2H,
H4, H5), 7.68 (t, J = 9.9 Hz, 2H, H3, H6), 8.32 (s, 1H, H8) ppm.
19F{1H} NMR (CDCl3): d = ꢀ77.6 ppm. Anal. Calc. for C36H37O3N-
F3S3Ir: C, 49.30; H, 4.25; N, 1.60. Found: C, 49.35; H, 4.35; N, 1.79%.
Complex 5: Yield: 50 mg (78%). 1H NMR (300 MHz, CDCl3):
d = 1.84 (s, 15H, C5Me5), 6.40 (d, J = 8.1 Hz, 2H, Ph), 6.65 (d,
J = 8.1 Hz, 2H, Ph), 7.05 (t, J = 7.5 Hz, 3H, Ph), 7.13 (t, J = 7.5 Hz,
3H, Ph), 7.22–7.29 (m, 3H, H1, H2, H7), 7.62 (d, J = 7.8 Hz, 2H, H4,
H5), 7.74 (t, J = 9.9 Hz, 2H, H3, H6), 8.45 (s, 1H, H8) ppm. 19F{1H}
NMR (CDCl3): d = ꢀ76.5 ppm. Anal. Calc. for C34H33O3NF3SSe2Ir:
C, 43.31; H, 3.53; N, 1.49. Found: C, 43.19; H, 3.60; N, 1.61%.
Complex 6: Yield: 54 mg, 73%. 1H NMR (300 MHz, CDCl3):
d = 1.78 (s, 15H, C5Me5), 6.42 (d, J = 8.1 Hz, 2H, Ph), 6.56 (d,
J = 8.1 Hz, 2H, Ph), 6.89 (t, J = 7.5 Hz, 3H, Ph), 7.08 (t, J = 7.5 Hz,
3H, Ph), 7.18–7.26 (m, 3H, H1, H2, H7), 7.54 (d, J = 7.8 Hz, 2H, H4,
H5), 7.68 (t, J = 9.9 Hz, 2H, H3, H6), 8.36 (s, 1H, H8) ppm. 19F{1H}
NMR (CDCl3): d = ꢀ77.6 ppm. Anal. Calc. for C34H33O3NF3STe2Ir:
C, 39.26; H, 3.20; N, 1.35. Found: C, 40.17; H, 3.22; N, 1.37%.
*
2.3. Preparation of [Cp Ir(ppy)(MeCN)][OTf] (2)
*
To a suspension of [Cp Ir(ppy)Cl] (50 mg, 0.096 mmol) in MeCN
(10 mL) was added AgOTf (25 mg, 0.097 mmol). The mixture was
stirred for 1 h and filtered. Recrystallization from MeCN–Et2O gave
yellow crystals which were suitable for X-ray diffraction analysis.
Yield: 56 mg (87%). Alternatively, complex 2 could be obtained in
good yield by recrystallization of complex 1 from MeCN–Et2O. 1H
NMR (300 MHz, CDCl3): d = 1.73 (s, 15H, C5Me5), 2.41 (s, 3H,
NCMe), 7.18 (dt, J1 = 1.2 Hz, J2 = 7.2 Hz, 1H, H1), 7.26 (dt,
J1 = 1.2 Hz, J2 = 7.2 Hz, 1H, H2), 7.39 (dt, J1 = 1.2 Hz, J2 = 5.4 Hz, 1H,
H7), 7.68 (d, J = 1.2 Hz, 1H, H3), 7.78 (d, J = 2.4 Hz, 1H, H6), 7.85
(d, J = 1.2 Hz, 1H, H4), 7.87 (d, J = 2.4 Hz, 1H, H5), 8.93 (dt,
J1 = 1.2 Hz, J2 = 5.4 Hz, 1H, H8) ppm. 19F{1H} NMR (CDCl3):
d = ꢀ77.8 ppm. Anal. Calc. for C24H26O3N2F3SIr: C, 42.91; H, 3.90;
N, 4.17. Found: C, 42.88; H, 3.91; N, 4.11%.
2-ppy-ER)(H2O)][OTf]2 (E = S, R = p-tol (7);
2.4. Ir-catalyzed oxidation of styrene with PhIO
*
2.8. Preparation of [Cp Ir(
g
E = Se, R = Ph (8))
To a suspension solution of PhIO (220 mg, 1 mmol) and styrene
(460 lL, 4 mmol) in CH2Cl2 (2.5 mL) at 0 °C was added complex 1
To a solution of complex 4 or 5 (0.059 mmol) in CH2Cl2 (10 mL)
was added AgOTf (26 mg, 0.10 mmol), the mixture was stirred at
room temperature for 4 h. The volatiles were removed in vacuo
and the residue was recrystallized from acetone–Et2O to give yel-
low crystals which were suitable for X-ray diffraction analysis.
Complex 7: Yield: 35 mg (65%). 1H NMR (300 MHz, acetone-d6):
d = 1.56 (s, 15H, C5Me5), 2.20 (s, 3H, C6H4CH3), 2.87 (s, 2H, H2O),
6.98 (d, J = 8.1 Hz, 2H, C6H4CH3), 7.05 (d, J = 8.1 Hz, 2H, C6H4CH3),
7.59 (d, J = 17.1 Hz, 1H, H1), 7.83 (t, J = 7.8 Hz, 2H, H2, H7), 8.23–
8.29 (m, 2H, H3, H6), 8.43 (d, J = 5.4 Hz, 2H, H4, H5), 9.03 (s, 1H,
H8) ppm. 19F{1H} NMR (CDCl3): d = ꢀ78.5 ppm. Anal. Calc. for
C30H32O7NF6S3Ir: C, 39.13; H, 3.50; N, 1.52. Found: C, 38.98; H,
3.54; N, 1.33%.
(0.01 mmol) in CH2Cl2 (2.5 mL).The mixture was stirred at 0 °C un-
til all PhIO dissolved completely. The organic products were ana-
lyzed by GLC using an HP-1 column and quantified by internal
standard method.
2.5. Ir-catalyzed aziridination of styrene with PhINTs
To a suspension solution of PhINTs (373 mg, 1 mmol) and sty-
rene (460 lL, 4 mmol) in CH2Cl2 (2.5 mL) at 0 °C was added com-
plex 1 (0.01 mmol) in CH2Cl2 (2.5 mL). The mixture was stirred at
0 °C until all PhINTs dissolved completely. The organic products
were analyzed by GLC using an HP-1 column and quantified by
internal standard method.
Complex 8: Yield: 32 mg (53%). 1H NMR (300 MHz, acetone-d6):
d = 1.54 (s, 15H, C5Me5), 3.12 (s, 2H, H2O), 7.12 (d, J = 8.1 Hz, 2H,
Ph), 7.27 (t, J = 8.1 Hz, 3H, Ph), 7.78 (d, J = 21.4 Hz, 1H, H1), 8.10
(t, J = 8.2 Hz, 2H, H2, H7), 8.18–8.29 (m, 2H, H3, H6), 8.39 (d,
J = 7.7 Hz, 2H, H4, H5), 8.97 (s, 1H, H8) ppm. 19F{1H} NMR (CDCl3):
d = ꢀ78.5 ppm. Anal. Calc. for C29H30O7NF6S2SeIr: C, 36.52; H,
3.17; N, 1.49. Found: C, 36.33; H, 3.14; N, 1.33%.
2.6. Preparation of [Cp*Ir(g
2-ppy-NTs)(MeCN)][OTf] (3)
To a solution of complex 2 (50 mg, 0.074 mmol) in dichloro-
methane (10 mL) at 0 °C was added PhINTs (27 mg, 0.075 mmol).
The green mixture was slowly warmed to room temperature and
stirred overnight to give a yellow solution. The volatiles were re-
moved in vacuo and the residue was recrystallized from CH2Cl2–
hexane to give yellow crystals suitable for X-ray diffraction analy-
sis. Yield: 48 mg (85%). 1H NMR (300 MHz, CDCl3): d = 1.48 (s, 15H,
C5Me5), 2.22 (s, 3H, C6H4CH3), 2.44 (s, 3H, NCMe), 6.87 (d,
J = 7.8 Hz, 2H, C6H4CH3), 7.08 (m, 3H, C6H4CH3 and H1), 7.40 (m,
2.9. X-ray crystallography
Crystal data and experimental details for complexes 2–7 are
summarized in Table 1. Preliminary examinations and intensity
data collection were carried out on a Bruker SMART-APEX 1000

Y.-K. Sau et al. / Journal of Organometallic Chemistry 695 (2010) 1399–1404
1401
Table 1
Crystallographic data and experimental details for complexes 2–7.
2
3
4
5
6
7
Formula
Formula weight
a (Å)
b (Å)
c (Å)
C24H26F3IrN2O3S
671.73
12.129(8)
13.151(9)
15.612(1)
90
C31H33F3IrN3O5S2
840.92
15.734(2)
14.689(2)
14.266(2)
90
C36H37F3IrNO3S3
877.05
12.2352(10)
15.5541(13)
19.1033(16)
90
C34H33F3IrNO3SSe2
942.79
11.5234(7)
15.2084(9)
19.5704(11)
90
C34H33F3IrNO3STe2
1040.07
11.3662(6)
15.6741(9)
19.7157(11)
90
C30H32F6IrNO7S3
920.95
16.5553(14)
12.3006(11)
32.598(3)
90
a
(°)
b (°)
102.519(1)
90
2431.1(3)
4
95.342(2)
90
3282.8(7)
4
104.838(2)
90
3514.3(5)
4
101.877(1)
90
3356.3(3)
4
101.891(1)
90
3437.1(3)
4
90
90
c
(°)
V (Å3)
6638.2(10)
8
Z
Crystal system
Space group
Monoclinic
P21/c
1.835
100(2)
5.630
Monoclinic
P21/c
1.701
298(2)
4.255
Monoclinic
P21/c
1.658
173(2)
4.030
Monoclinic
P21/c
1.866
173(2)
6.261
Monoclinic
P21/c
2.010
173(2)
5.660
Orthorhombic
Pbca
1.843
173(2)
4.292
qcalc (g cmꢀ3
T (K)
)
l
(mmꢀ1
)
F(0 0 0)
1312
1664
1744
1824
1968
3632
Number of reflections
12 554
23 116
18 155
22 959
16 365
37 897
Number of independent reflections
4188
5734
5600
5826
5498
5578
Rint
0.0480
0.0877
0.0599
0.0242
0.0559
0.1012
R1, wR2 (I > 2
R1, wR2 (all data)
GOF
r
(I))
0.0418, 0.0759
0.0539, 0.0792
1.080
0.0556, 0.0774
0.1000, 0.0842
0.975
0.0492, 0.0894
0.0705, 0.0959
1.013
0.0210, 0.0493
0.0267, 0.0508
1.034
0.0644, 0.1244
0.0835, 0.1320
1.034
0.0335, 0.0494
0.0746, 0.0541
0.964
Table 2
area-detector diffractometer using graphite-monochromated Mo
radiation (k = 0.70173 Å). The collected frames were processed
Selected bond lengths (Å) and angles (°) for [Cp*Ir(ppy)(MeCN)][OTf] (2).
Ka
with the software SAINT and the data was corrected for absorption
using the program SADABS [15]. Structures were solved by direct
methods and refined by full-matrix least-squares on F2 using the
SHELXTL software package [16]. Unless stated otherwise, non-hydro-
gen atoms were refined with anisotropic displacement parameters.
Carbon-bonded hydrogen atoms were included in calculated posi-
tions and refined in the riding mode using SHELXL97 default
parameters.
Ir(1)–N(1)
Ir(1)–C(1)
Ir(1)–C(3)
Ir(1)–C(5)
C(22)–N(2)–Ir(1)
C(21)–Ir(1)–N(1)
2.103(5)
2.144(6)
2.153(7)
2.237(6)
173.2(5)
78.3(2)
Ir(1)–N(2)
Ir(1)–C(2)
Ir(1)–C(4)
Ir(1)–C(21)
N(2)–Ir(1)–N(1)
N(2)–Ir(1)–C(21)
2.039(5)
2.159(7)
2.225(6)
2.047(6)
86.0(2)
89.2(2)
[OTf] (solv = H2O (1), MeCN (2)). Complex 2 also could be prepared
by recrystallization of 1 from MeCN–Et2O. Fig. 1 shows the struc-
ture of the complex cation in 2; selected bond lengths and angles
3. Results and discussion
*
are listed in Table 2. The Ir–C(Cp ) (av. 2.184(7) Å), Ir–C(ppy)
3.1. Reaction of [Cp*Ir(ppy)(solv)]+ with oxo donors
(2.047(6) Å), and Ir–N(ppy) (2.103(5) Å) distances are similar to
*
those in [Cp Ir(ppy)Cl] [9]. The Ir–NCMe distance of 2.039(5) Å
Treatment of [Cp*Ir(ppy)Cl] with Ag(OTf) (OTf- = triflate) in
compares well with that of [Cp*Ir(PPh3)(NCMe)2]+ (2.086(8) and
2.066(8) Å) [17].
*
MeOH and MeCN gave the solvento complexes [Cp Ir(ppy)(solv)]
In an attempt to synthesize Ir-oxo species, reactions of 1 with
oxo donors have been investigated. Addition of 1 equivalent of
PhIO to 1 in CH2Cl2 at ꢀ10 °C resulted in dissolution of PhIO and
formation reactive green species and PhI. The green species was
thermally unstable and decomposed to 1 above 0 °C. Despite many
attempts, we have not been able to isolate or characterize this
green species. The decomposition of PhIO was found to be catalytic
with respect to Ir. For example, treatment of PhIO with 1 mol% of 1
afforded PhI in 56% yield. In the presence of excess styrene, this
reaction afforded a ca. 7:1 mixture of styrene oxide and benzalde-
hyde with a total turnover number (TON) of 46 (Scheme 2), sug-
gesting that the green species is possibly an Ir-oxo species that
can transfer the oxo group to styrene. An alternative candidate of
the green species is an Ir–I(O)Ph adduct [18], in which the IIII = O
group is activated by the Lewis acidic Ir center. Complex 1 can also
catalyze the oxidation of styrene with tert-butylhydroperoxide,
PhIO
1 mol% 1
O
+ PhCHO + PhI
6%
CH2Cl2
RT, 12h
Ph
Ph
40%
Fig. 1. Molecular structure of the complex cation in 2. Hydrogen atoms are omitted
for clarity. The ellipsoids are drawn at a 50% probability level.
Scheme 2. Ir-catalyzed oxidation of styrene with PhIO.

1402
Y.-K. Sau et al. / Journal of Organometallic Chemistry 695 (2010) 1399–1404
+
*
albeit with a smaller TON (16) and lower selectivity (styrene oxide/
benzaldehyde ratio of ca. 1.5:1). Additional studies are required to
elucidate the mechanism of the Ir-catalyzed epoxidation.
3.3. Reaction of [Cp Ir(ppy)(solv)] with R2E2
Oxidative addition of R2E2 (E = S or Se) is a convenient synthetic
route of transition metal thiolate complexes. Of particular interest
are PdIV and PtIV bis(chalcogenolate) complexes, which are in-
volved in metal-catalyzed selective addition of E–E bonds to al-
kynes [21]. Recently, we reported that reaction of IrIII alkyl
complexes with R2S2 led to formation of IrIII bis(thiolate) com-
plexes, possibly via oxidative addition of the S–S bond to IrIII and
subsequent C–S bond elimination [22]. Thus, in an attempt to pre-
+
*
3.2. Reaction of [Cp Ir(ppy)(solv)] with PhINTs
We next turned our attention to the reaction of 1 with nitrene
donors. Treatment of 1 with PhINTs at ꢀ10 °C resulted in a green
solution that turned yellow upon warming to ca. 0 °C. We have
not been able to trap or characterize the green or yellow species.
Nevertheless, for the reaction of 2 with PhINTs afforded, a yellow
crystalline product characterized as the ppy–tosylamido complex
*
pare higher valent Cp Ir chalcogenolate complexes, reactions of 1
with R2E2 (E = S, Se, Te) were attempted. However, instead of oxi-
dative addition of the E-E bond, reaction of 1 with R2E2 led to iso-
[Cp*Ir(
The presence of the tosyl group in 3 was evidenced by 1H NMR
(d = 2.22 ppm) and IR (1063 cmꢀ1
(S@O)) spectroscopies. Treat-
ment of PhINTs with styrene in the presence of 1 mol% of 1 affor-
ded styrene tosylaziridine with TON of 15 (Scheme 4),
g
2-ppy-NTs)(MeCN)][OTf] (3) was isolated (Scheme 3).
lation of the IrIII g1-dichalcogenide complexes [Cp
*Ir(ppy)(g1
-
E2R2)][OTf] (E = S, R = p-tol (4); E = Se, R = Ph (5); E = Te, R = Ph
(6)) (Scheme 5). The 1H NMR spectrum of 4 displayed two singlets
at d 2.20 and 2.26 ppm due to the p-Me protons of the tolyl groups,
,
m
a
consistent with the
should be noted that R2E2 usually binds to metal in a
ion, e.g. [CpMn(CO)2]2( -RE-ER) [23]. Metal complexes containing
1-RE-ER ligands, which have been suggested to be an intermedi-
g
1-binding mode of the disulfide ligand. It
suggesting that the green intermediate (possibly an Ir-nitrene spe-
cies) can act as a nitrene transfer agent. Compound 3 could also be
synthesized by reaction of 2 with TsN3 that is a typical nitrene pre-
cursor, lending further support for the nitrene transfer from PhINTs
to Ir. A possible mechanism for the formation of compound 3 is
l- ,g
g1 1 fash-
l
g
ate in oxidative addition of R2E2 with Pd(0), are less common [24].
The crystal structures of the complex cations in 4–6 are shown
in Figs. 3–5, respectively; selected bond lengths and angles are
compiled in Table 4. The Ir–C(Cp*), Ir–C(ppy) (2.053(7), 2.052(2)
and 2.053(12) Å, respectively), and Ir–N(ppy) (2.095(6), 2.087(2)
and 2.087(10) Å, respectively) distances for 4–6 are similar to those
of 2. The corresponding Ir–E (2.335(18), 2.451(3) and 2.593(9) Å)
and E–E (2.091(3), 2.370(5) and 2.593(9) Å) distances are consis-
tent with the trend of covalent radii of the chalcogens.
Interestingly, treatment of 4 and 5 with excess Ag(OTf) led to
cleavage of the E–E bond. Migratory insertion of one of the ER
groups into the Ir–C(ppy) bond afforded the
*
olate complexes [Cp Ir{g
2-ppy-ER)(H2O)][OTf]2 (E = S, R = p-tolyl
shown in Scheme 3. Reaction of PhINTs with 1 initially gives a tran-
+
*
sient Ir = NTs species, possibly [Cp Ir(ppy)(NTs)] , that transfers
the NTs group to styrene. In the absence of olefin, the nitrene group
inserts into the Ir–C(ppy) bond to yield 3. It should be noted that
insertion of nitrene group into the Pd–C bond of a palladacycle
has been reported recently. A stepwise mechanism involving a PdIV
nitrene intermediate and migratory insertion of the nitrene group
into the Pd–C bond has been proposed [19].
The molecular structure of the cation [Cp*Ir(g
2-ppy-NTs)
(MeCN)]+ in 3 is shown in Fig. 2; selected bond lengths and angles
are listed in Table 3. The Ir–C(Cp*) and Ir–N(ppy) distances
(2.158(9) and 2.133(6) Å, respectively) are similar to those in 2.
The ppy moiety is twisted with the dihedral angle between the
pyridyl and phenyl rings of 37.1° apparently due to insertion of
the NTs group. The Ir–N(amide) distance of 2.112(6) Å is similar
g
2-pyridyl-chalcogen-
(7); E = Se, R = Ph (8)) (Scheme 5). The fate of the remaining ER
group has not been studied. The 1H NMR spectrum of 7 shows only
one methyl resonance signal at d = 2.20 ppm, indicating that the
loss of one p-tolS group in the disulfide ligand. In addition, a singlet
at d = 3.12 ppm assignable to the H2O ligand was observed.
*
to that in [Cp Ir(PMe3)Ph(NH2)] (2.105(8) Å) [20].
+
+
Cp*
Cp*
Ir
PhINTs or
TsN3
(2)
Ir
N
MeCN
MeCN
N
CH2Cl2
0oC to RT
NTs
2
3
nitrene
insertion
PhINTs
-PhI
-MeCN
MeCN
Cp*
+
Ir
N
NTs
Scheme 3. Synthesis of complex 3.

Y.-K. Sau et al. / Journal of Organometallic Chemistry 695 (2010) 1399–1404
1403
Ts
N
1 mol% 1
+ PhINTs
+ PhI
Ph
CH2Cl2
RT, 12 h
Ph
15%
Scheme 4. Ir-catalyzed aziridination of styrene with PhINTs.
Fig. 3. Molecular structure of the complex cation in 4. Hydrogen atoms are omitted
for clarity. The ellipsoids are drawn at a 50% probability level.
Fig. 2. Molecular structure of the complex cation in 3. Hydrogen atoms are omitted
for clarity. The ellipsoids are drawn at a 50% probability level.
Table 3
2-ppy-NTs)(MeCN)][OTf] (3).
*
Selected bond lengths (Å) and angles (°) for [Cp Ir(
g
Ir(1)–N(1)
Ir(1)–N(3)
Ir(1)–C(2)
Ir(1)–C(4)
N(2)–Ir(1)–N(1)
N(3)–Ir(1)–N(2)
S(1)–N(2)–Ir(1)
2.133(6)
2.025(8)
2.149(9)
2.177(9)
80.5(2)
Ir(1)–N(2)
Ir(1)–C(1)
Ir(1)–C(3)
Ir(1)–C(5)
N(3)–Ir(1)–N(1)
C(21)–N(2)–Ir(1)
C(30)–N(3)–Ir(1)
2.112(6)
2.167(8)
2.163(9)
2.136(8)
84.4(2)
91.2(3)
125.7(4)
113.2(5)
171.8(8)
The molecular structure of the complex cation in 7 is shown in
Fig. 6; selected bond lengths and angles are listed in Table 5. The
Ir–C(Cp*) (av. 2.170(5) Å) and Ir–S (2.3639(12) Å) distances for 7
are similar to those in 4. However, the Ir–N(ppy) (2.127(4)) Å dis-
tance is longer than that in 4, presumably due to the formation of
the six-membered metallacycle. The torsion angle between the
Fig. 4. Molecular structure of the complex cation in 5. Hydrogen atoms are omitted
for clarity. The ellipsoids are drawn at a 50% probability level.
pyridine and phenyl rings in the ppy moiety is determined to be
43.5°.
+
2+
Cp*
Ir
Cp*
Ag(OTf)
- "ER"
R2E2
CH2Cl2
E
R
1
H2O
Ir
N
N
E
ER
R
E = S, R = p-tol (4)
E = Se, R = Ph (5)
E = Te, R = Ph ( 6)
E = S, R = p-tol (7)
E = Se, R = Ph (8)
Scheme 5. Synthesis of complexes 4–8.

1404
Y.-K. Sau et al. / Journal of Organometallic Chemistry 695 (2010) 1399–1404
Table 5
Selected bond lengths (Å) and angles (°) for [Cp*Ir(g
2-ppy-Stol)(H2O)][OTf]2 (7).
Ir(1)–N(11)
Ir(1)–S(1)
Ir(1)–C(2)
Ir(1)–C(4)
N(11)–Ir(1)–O(10)
N(11)–Ir(1)–S(1)
O(10)–Ir(1)–S(1)
2.127(4)
2.3639(12)
2.141(5)
2.179(5)
83.23(13)
85.77(12)
89.51(9)
Ir(1)–O(10)
Ir(1)–C(1)
Ir(1)–C(3)
Ir(1)–C(5)
C(22)–S(1)–Ir(1)
C(23)–S(1)–Ir(1)
2.153(3)
2.181(5)
2.175(5)
2.172(6)
98.49(17)
118.35(17)
4. Conclusions
*
In summary, we have studied the reactions of [Cp Ir(ppy)
(H2O)]+ with oxo and nitrene donors. We found that [Cp*Ir(ppy)
(H2O)]+ can catalyze the epoxidation of styrene with PhIO, possibly
via a high-valent Ir-oxo active species. Reaction of [Cp*Ir(ppy)
(MeCN)]+ with PhINTs led to migratory insertion of the nitrene into
the Ir–C(ppy) bond and formation of [Cp*Ir(g
2-ppy-NTs)(MeCN)]+.
+
*
Reaction of [Cp Ir(ppy)(H2O)] with R2E2 led to the formation of
Fig. 5. Molecular structure of the complex cation in 6. Hydrogen atoms are omitted
for clarity. The ellipsoids are drawn at a 50% probability level.
the adducts [Cp*Ir(ppy)(
2-ppy-ER)(H2O)]2+
*
give [Cp Ir(g .
g
1-E2R2)]+ that reacted with Ag(OTf) to
Table 4
5. Supplementary material
1-R2E2)][OTf] (RE = p-tolS,
*
Selected bond lengths (Å) and angles (°) for [Cp Ir(ppy)(
g
PhSe, PhTe).
CCDC 609384, 609385 and 619389–609392 contain the supple-
mentary crystallographic data complexes 2–7. These data can be
obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
RE = p-tolS (4)
RE = PhSe (5)
RE = PhTe (6)
Ir–Cp*
2.168(8)
2.173(6)
2.189(7)
2.245(7)
2.263(8)
2.053(7)
2.095(6)
2.3350(18)
89.60(19)
77.9(3)
2.173(3)
2.183(3)
2.204(3)
2.260(3)
2.261(3)
2.052(3)
2.087(2)
2.4508(3)
89.63(8)
78.00(10)
89.67(7)
106.120(16)
108.34(9)
2.157(12)
2.192(11)
2.212(13)
2.220(16)
2.225(14)
2.053(12)
2.087(10)
2.5930(9)
77.5(5)
89.4(3)
89.5(3)
102.56(3)
105.0(3)
Acknowledgment
Ir–C(ppy)
Ir–N
Ir–E
C(ppy)–Ir(1)–E
C(ppy)–Ir(1)–N
E–Ir(1)–N
Ir–E–E0
We thank Dr. Herman H.Y. Sung for solving the crystal struc-
tures. The financial support from the Hong Kong Research Grants
Council (Project No. 601708) is gratefully acknowledged.
90.13(7)
109.44(9)
111.0(2)
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Fig. 6. Structure of the complex cation in 7. Hydrogen atoms are omitted for clarity.
The ellipsoids are drawn at a 50% probability level.