Unsymmetrical pnp-pincer type phosphaalkene ligands protected by a fused-ring bulky eind group: Synthesis and applications to rh(i) and ir(i) complexes

Article abstract of DOI:10.1021/acs.organomet.6b00113

We recently reported that 2-(phospholanylmethyl)-6-(2-phosphaethenyl)pyridine (PPEP) with a 2,4,6-tri-tert-butylphenyl group (Mes?) as steric protection of the PC bond serves as a noninnocent ligand on Ir(I), leading to extremely high reactivity toward metal-ligand cooperative activation of ammonia and acetonitrile. The high reactivity is largely due to the strong accepting properties of the PC bond. However, PPEP had a stability problem that provokes the loss of the PC bond on other transition metals, including Rh(I), and restricts its utilization. This paper describes the synthesis of Eind-PPEP protected by an octaethyl-s-hydrindacen-4-yl group (Eind) instead of Mes?. The fused-ring bulky Eind group successfully prevents the loss of the PC bond and enables us to compare the reactivity of Rh(I) and Ir(I) complexes toward ammonia. The complex K[RhCl(Eind-PPEP?)], bearing a dearomatized Eind-PPEP? ligand, undergoes simple ligand displacement to give [Rh(NH₃)(Eind-PPEP?)], whereas the iridium analogue K[IrCl(Eind-PPEP?)] causes N-H bond cleavage to form [Ir(NH₂)(Eind-PPEP)]. DFT calculations indicate a thermodynamic cause of the metal-dependent product change.

Full text of DOI:10.1021/acs.organomet.6b00113

Article
pubs.acs.org/Organometallics
Unsymmetrical PNP-Pincer Type Phosphaalkene Ligands Protected
by a Fused-Ring Bulky Eind Group: Synthesis and Applications to
Rh(I) and Ir(I) Complexes
Hiro-omi Taguchi,† Daichi Sasaki,† Katsuhiko Takeuchi,† Shota Tsujimoto,‡ Tsukasa Matsuo,‡
Hiromasa Tanaka,§ Kazunari Yoshizawa,§ and Fumiyuki Ozawa*,†
†International Research Center for Elements Science (IRCELS), Institute for Chemical Research, Kyoto University, Uji, Kyoto
611-0011, Japan
‡Department of Applied Chemistry, Faculty of Science and Engineering, Kinki University, Higashi-Osaka, Osaka 577-8502, Japan
§Institute for Materials Chemistry and Engineering, International Research Center for Molecular Systems, Kyushu University,
Nishi-ku, Fukuoka 819-0395, Japan
S
* Supporting Information
ABSTRACT: We recently reported that 2-(phospholanylmethyl)-6-(2-
phosphaethenyl)pyridine (PPEP) with a 2,4,6-tri-tert-butylphenyl group
(Mes*) as steric protection of the PC bond serves as a noninnocent
ligand on Ir(I), leading to extremely high reactivity toward metal−ligand
cooperative activation of ammonia and acetonitrile. The high reactivity is
largely due to the strong π-accepting properties of the PC bond.
However, PPEP had a stability problem that provokes the loss of the PC
bond on other transition metals, including Rh(I), and restricts its
utilization. This paper describes the synthesis of Eind-PPEP protected by
an octaethyl-s-hydrindacen-4-yl group (Eind) instead of Mes*. The fused-
ring bulky Eind group successfully prevents the loss of the PC bond and enables us to compare the reactivity of Rh(I) and
Ir(I) complexes toward ammonia. The complex K[RhCl(Eind-PPEP*)], bearing a dearomatized Eind-PPEP* ligand, undergoes
simple ligand displacement to give [Rh(NH3)(Eind-PPEP*)], whereas the iridium analogue K[IrCl(Eind-PPEP*)] causes N−H
bond cleavage to form [Ir(NH2)(Eind-PPEP)]. DFT calculations indicate a thermodynamic cause of the metal-dependent
product change.
complex K[3b] in Scheme 1 bearing a dearomatized PNP-
pincer type phosphaalkene ligand (PPEP*) causes instant
cleavage of the N−H bond of ammonia (1 atm) at room
temperature.3d DFT calculations have revealed that the
reactivity is effectively enhanced by strong π back-donation
from the metal to the phosphaalkene unit.
Complex K[3b] is prepared from 1b bearing a 2,6-
bis(phosphaethenyl)pyridine ligand (BPEP), as illustrated in
Scheme 1.3d While the Mes* substituent is commonly used for
steric protection of PC bonds, the Mes*-PCH group has
been known to undergo C−H addition/cyclization on
transition metals to form a phospholanylmethyl group in
some instances.6 The conversion of BPEP into the unsym-
metrical PNP-pincer ligand PPEP in Scheme 1 (1b → 2b)
proceeds via this process. A crucial requirement is that BPEP
undergoes C−H addition/cyclization exclusively at one of the
Mes*-PCH groups. The reaction of Ir(I) complex 1b
proceeded in perfect selectivity, and the resulting 2b was
INTRODUCTION
■
Phosphaalkenes with a PC double bond are an interesting
class of phosphorus compounds, which possess an extremely
low lying π* orbital and thus serve as strong π acceptors toward
transition metals.1 We are currently interested in the
application of this particular ligand property in organometallic
chemistry.2−4 This paper describes the synthesis of a novel
pyridine-based PNP-pincer type phosphaalkene ligand that
exhibits noninnocent behavior on group 9 metals.
Metal−ligand cooperative activation of chemical bonds aided
by noninnocent behavior of pyridine-based pincer ligands has
found wide application in catalytic transformations.5 PNP- and
PNN-pincer complexes with a phosphanylmethyl group on the
pyridine core undergo deprotonation at the benzylic position to
cause dearomatization of the pyridine ring. The dearomatized
complex cleaves chemical bonds in a heterolytic manner, along
with regeneration of the aromatic pyridine ring, where the
metal center and the dearomatized ligand serve as a Lewis acid
and a Brønsted base, respectively.
We recently found that the reactivity of dearomatized PNP-
pincer complexes of Ir(I) toward metal−ligand cooperation
could be remarkably enhanced by incorporating a phosphaal-
kene unit into the PNP-pincer scaffold.3d−g For example,
Special Issue: Organometallics in Asia
Received: February 10, 2016
© XXXX American Chemical Society
A
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the phospha-Peterson reagent Eind-P(SiMe3)Li. The first step
is the treatment of 5 with Eind-PPMe3, generated in situ
from Eind-PCl2,10 PMe3, and zinc dust in THF. The phospha-
Wittig reaction took place selectively at one of the formyl
groups, and the desired compound 6 was isolated as a pale
yellow powder in 74% yield by column chromatography.
Compound 6 was then treated with Mes*-PPMe3 in THF,
and Eind-BPEP (7) was obtained in 97% yield. This product
was contaminated with a small amount of Mes*-PH2, which
could not be removed by repeated chromatographic
purifications. Accordingly, compound 7 was identified by
NMR spectroscopy and mass spectrometry and used for
complex formation without further purification. The 31P{1H}
NMR spectrum displayed two singlet signals at δP 285.8 and
275.2, consistent with the unsymmetrical structure of 7 having
different substituents on phosphorus atoms.
Scheme 1
Synthesis of Eind-BPEP Complexes 8 and 9. Eind-BPEP
(7) was coordinated with rhodium and iridium chlorides by the
reactions with [Rh(μ-Cl)(η2-C2H4)2]2 and [Ir(μ-Cl)(η2-
coe)2]2, respectively (Scheme 3). Both reactions took place
instantly at room temperature to give [RhCl(Eind-BPEP)] (8)
and [IrCl(Eind-BPEP)] (9) quantitatively, as confirmed by
NMR spectroscopy.
Scheme 3
totally stable to further C−H addition/cyclization. On the
other hand, attempts at other transition-metal complexes,
including Rh(I) complex 1a, were unsuccessful due to the
occurrence of successive C−H addition/cyclization at both
Mes*-PCH groups, giving rise to complete loss of PC
bonds.3f
We therefore attempted to synthesize a novel BPEP ligand
that can be selectively converted to PPEP on various metals. In
this case, the most reliable way is the introduction of a steric
protecting group that is stable to C−H addition/cyclization
into one of the phosphaalkene units. We found that the
1,1,3,3,5,5,7,7-octaethyl-s-hydrindacen-4-yl group (Eind),7 hav-
ing a fused-ring bulky structure, effectively prevents undesirable
loss of the PC bond. Using the newly synthesized
phosphaalkene ligand Eind-PPEP, we could observe a distinct
change in the reaction products of K[M(Cl)(Eind-PPEP*)] (M
= Rh, Ir) and ammonia depending on the metals.
RESULTS AND DISCUSSION
■
Synthesis of Eind-BPEP (7). Compound 7, having Mes*-
PCH and Eind-PCH groups at the 2,6-positions of
pyridine, was synthesized by a two-step procedure starting from
2,6-pyridinedicarboxaldehyde (5) (Scheme 2). While phos-
phaalkene units may be constructed either by a phospha-
Peterson reaction8 or by a phospha-Wittig reaction,9 we chose
the phospha-Wittig reaction due to the difficulty in preparing
The 31P{1H} NMR spectrum of rhodium complex 8
displayed two sets of doublets of doublets at δP 239.2 (2JPP
=
=
1
1
519 Hz, JRhP = 207 Hz) and δP 231.2 (2JPP = 519 Hz, JRhP
204 Hz), which were assigned to Mes*-PCH and Eind-P
CH groups, respectively, referring to the chemical shifts of
[RhCl(BPEP)] (δP 242.4)11 and [RhCl(Eind-PPEP)] (10; δP
230.5). Similarly, complex 9 showed two sets of doublets at δP
249.3 and 237.2 (2JPP = 560 Hz), assignable to Mes*-PCH
and Eind-PCH groups, respectively. The large 2JPP couplings
are consistent with the trans arrangement of two phosphorus
Scheme 2
1
atoms. Moreover, the JRhP values of 8 are reasonable for a
Rh(I) complex.
Complexes 8 and 9 were isolated as crystalline solids, suitable
for X-ray diffraction analysis, in 60 and 84% yields, respectively.
Figure 1 shows the crystal structures, which are superimposable
with one another. Both complexes adopt a square-planar
geometry around the metal: ∑(Rh) = 360.1°, ∑(Ir) = 360.0°.
The Eind-BPEP ligand adopts meridional coordination, and the
chlorido ligand occupies the fourth coordination site. The
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complex 11 displayed two sets of doublets at δP 232.7 and
25.4 (2JPP = 480 Hz) in the 31P{1H} NMR spectrum.
The occurrence of C−H addition/cyclization giving a
phospholanylmethyl group was supported by the appearance
1
of benzylic proton and carbon signals in the H and 13C{1H}
NMR spectra: complex 10, δH 4.32 (dd, 2JHH = 18.4 Hz, 2JPH
=
9.6 Hz, 1H), 4.10 (dd, 2JHH = 18.4 Hz, 2JPH = 9.7 Hz, 1H) and
δC 50.6 (s, 1JPC = 18 Hz); complex 11, δH 4.02 (dd, 2JHH = 18.8
2
2
2
Hz, JPH = 9.9 Hz, 1H), 4.01 (dd, JHH = 18.8 Hz, JPH = 10.2
1
Hz, 1H) and δC 51.1 (s, JPC = 26 Hz). Two benzylic protons
are diastereotopic with each other, showing two sets of signals
2
with a large JHH coupling (ca. 18 Hz). This signal pattern is
consistent with the structure of Eind-PPEP having a chiral
phospholanylmethyl group.
Synthesis of Dearomatized Eind-PPEP* Complexes 12
and 13. Treatment of Eind-PPEP complexes 10 and 11 with
K[N(SiMe3)2] (1 equiv) in THF at room temperature resulted
in deprotonation at the benzylic position to give the
dearomatized complexes K[RhCl(Eind-PPEP*)] (K[12]) and
K[IrCl(Eind-PPEP*)] (K[13]), respectively. Similarly, com-
plexes 10 and 11 reacted with tBuOK in THF in the presence
of 18-crown-6 (18C6) to form [K(18C6)][12] and [K-
(18C6)][13], respectively. The anionic parts showed the
same NMR spectrum irrespective of the kind of counterion.
Since the crown ether adducts were easily crystallized in high
yields (both 80%), [K(18C6)][12] and [K(18C6)][13] were
characterized by NMR and X-ray analysis in detail.
Figure 1. Molecular structures of [RhCl(Eind-BPEP)] (8) and
[IrCl(Eind-BPEP)] (9) with 50% probability ellipsoids. Hydrogen
atoms are omitted for clarity. Selected bond distances (Å) and angles
(deg): complex 8, Rh−P1 2.243(3), Rh−P2 2.205(3), Rh−N
2.061(9), Rh−Cl 2.318(3), P1−C1 1.646(10), P2−C2 1.668(10),
C1−C3 1.465(13), C2−C7 1.436(13), P1−Rh−P2 161.83(10), N−
Rh−Cl 178.3(2), C1−P1−C8 112.8(5), C2−P2−C26 113.5(5);
complex 9, Ir−P1 2.2349(9), Ir−P2 2.2128(8), Ir−N 2.047(3), Ir−
Cl 2.3099(9), P1−C1 1.671(3), P2−C2 1.673(3), C1−C3 1.446(5),
C2−C7 1.441(4), P1−Ir−P2 161.32(3), N−Ir−Cl 177.73(8), C1−
P1−C8 113.37(16), C2−P2−C26 114.40(16).
The 31P{1H} NMR signals of 12 appeared at δP 211.3 (2JPP
=
433 Hz, 1JRhP = 182 Hz) and δP 19.2 (2JPP = 433 Hz, 1JRhP = 169
Hz) as two sets of doublets of doublets. These signals were
clearly shifted upfield in comparison with the parent complex
10. Similarly, the signals of iridium complex 13 (δP 218.8 and
2
18.9, JPP = 458 Hz) appeared at a higher magnetic field in
comparison to those of 11. The presence of a dearomatized
pyridine unit in complex 12 was indicated by three character-
istic signals of ring protons at δH 6.03, 5.92, and 5.49. While the
vinylic proton signal of Eind-PPEP* overlapped with a residual
proton signal of the solvent (THF-d8) as confirmed by HMQC
experiments, the vinylic carbon signal was observed at δC 74.7
Mes* and Eind groups are oriented nearly perpendicular to the
coordination plane. The C2−P2−C26(Eind) and C1−P1−
C8(Mes*) bond angles are comparable to each other for both
complexes. The P1−C1 and P2−C2 bond lengths in 8
(1.646(10) and 1.668(10) Å) and in 9 (1.671(3) and
1.673(3) Å) are typical of PC double bonds. The Rh−P1,
Rh−P2, Rh−N, and Rh−Cl lengths of 8 are comparable to
those of [RhCl(BPEP)].11 Moreover, the Ir−P1, Ir−P2, Ir−N,
and Ir−Cl lengths of 9 are nearly the same as those of
[IrCl(BPEP)].3c
Synthesis of Eind-PPEP Complexes 10 and 11.
Complexes 8 and 9 were converted to [RhCl(Eind-PPEP)]
(10) and [IrCl(Eind-PPEP)] (11) by C−H addition/
cyclization of the Mes*-PCH group, respectively (Scheme
3). Although 8 and 9 have very similar structures, their
reactivities were significantly different from each other. Heating
iridium complex 9 in toluene at 70 °C overnight led to
quantitative formation of 11; the reactivity was comparable to
that of [IrCl(BPEP)] (1) in Scheme 1.3d In contrast, rhodium
complex 8 was stable at this temperature and converted to 10
by heating at 140 °C for 2 days in a sealed tube.
1
(d, JPC = 51 Hz). On the other hand, the vinylic proton and
carbon signals of iridium complex 13 appeared at δH 3.89
(virtual triplet, Japp = 3.8 Hz) and δC 73.1 (1JPC = 64 Hz),
respectively.
Figure 2 shows the X-ray structures of [K(18C6)][12] and
[K(18C6)][13], adopting a square-planar configuration around
the metals: ∑(Rh) = 360.5°, ∑(Ir) = 360.3°. The Rh−Cl bond
length in 12 (2.3382(7) Å) and Ir−Cl bond length in 13
(2.3557(16) Å) are consistent with dative bonding, whereas the
Cl and K atoms are significantly distant from each other
(2.9570(10) and 2.994(2) Å). Thus, the rhodium and iridium
complexes may be described as anionic species bearing
electrostatic interactions with the [K(18C6)] cation.
The P1−C1 bonds in 12 (1.751(3) Å) and 13 (1.750(6) Å)
are clearly shorter than normal P−C single bonds, whereas the
C1−C3 bond lengths (1.383(4) and 1.379(9) Å) are between
those expected for single and double bonds. These variations
are characteristic of dearomatized PNP-pincer ligands.5 On the
other hand, the P2−C2 bond lengths (1.673(3) and 1.675(6)
Å) are typical of PC double bonds.
Complexes 10 and 11 were isolated in quantitative yields and
identified by NMR spectroscopy and elemental analysis. The
31P{1H} NMR spectrum of 10 exhibited two sets of doublets of
1
doublets at δP 230.5 (2JPP = 461 Hz, JRhP = 183 Hz) and δP
Reactions of Dearomatized Eind-PPEP* Complexes
with Ammonia. The rhodium and iridium complexes
coordinated with Eind-PPEP* were subjected to the reactions
with ammonia (1 atm) in THF-d8 at room temperature
1
26.0 (2JPP = 461 Hz, JRhP = 168 Hz); the chemical shifts are
consistent with the unsymmetrical structure of PPEP bearing
phosphaethenyl and phospholanylmethyl groups. Likewise,
C
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respectively, and characterized by NMR spectroscopy and
elemental analysis.
The reaction of the rhodium complex K[12] with ammonia
was instantly completed, to form the ammine complex 14 in
almost quantitative yield. Thus, simple displacement of the Cl−
ligand with ammonia took place. The dearomatized pyridine
unit was preserved, as indicated by three characteristic signals of
ring protons at δH 6.04, 5.91, and 5.49 and of a vinylic proton at
1
δH 3.48 in the H NMR spectrum. A broad signal arising from
the ammine ligand was observed at δH 2.13. Complex 14 was
also examined by X-ray diffraction analysis: see the Supporting
Information. While the data quality was insufficient for a
detailed discussion of structural parameters (R1 = 0.1458), the
existence of a dearomatized pyridine ring with a phosphola-
nylmethylidene substituent was evidenced by characteristic
P1−C1 (1.74(1) Å) and C1−C3 bond lengths (1.38 Å), which
were comparable to those of [K(18C6)][12] (1.751(3) and
1.383(4) Å) in Figure 2. Moreover, the P2−C2 bond length
(1.65(1) Å) was appropriate for a phosphaalkene unit.
On the other hand, the iridium complex K[13] led to metal−
ligand cooperative activation of the N−H bond of ammonia, to
afford a quantitative yield of parent amido complex 15 bearing
an aromatized pyridine ring. The 1H NMR spectrum showed a
broad signal assignable to the amido ligand at δH 3.95; the
chemical shift was similar to that observed for the PPEP amido
complex 4 (δH 3.82).3d The benzylic proton signals appeared at
δH 4.15 and 4.14 as two sets of doublet of doublets with a large
geminal coupling (2JHH = 20.3 Hz).
Thus, we could observe a dramatic change in the reaction
courses depending on the metals. Since both reactions in
Scheme 4 were completed instantly at room temperature, it
would be reasonable that the distinct change would be mainly
due to thermodynamic reasons. We therefore compared the
relative stabilities of ammine and amido complexes by DFT
calculations. The calculations were performed with the B3LYP-
D functional and triple-ζ quality basis sets for the whole
molecules without omission of any substituents. Solvent effects
(THF) were included by PCM calculations: see the Supporting
Information for computational details.
Figure 2. Molecular structures of [K(18-crown-6)][RhCl(Eind-
PPEP*)] ([K(18C6)][12]) and [K(18-crown-6)][IrCl(Eind-
PPEP*)] ([K(18C6)][13]) with 50% probability ellipsoids. Hydrogen
atoms are omitted for clarity. Selected bond distances (Å) and angles
(deg): complex [K(18C6)][12], Rh−P1 2.2800(7), Rh−P2
2.2192(7), Rh−N1 2.067(2), Rh−Cl 2.3382(7), P1−C1 1.751(3),
P2−C2 1.673(3), C1−C3 1.383(4), C2−C7 1.437(4), Cl−K
2.9570(10), P1−Rh−P2 162.61(3), N−Rh−Cl 171.32(6); complex
[K(18C6)][13], Ir−P1 2.2869(16), Ir−P2 2.2174(17), Ir−N
2.068(5), Ir−Cl 2.3557(16), P1−C1 1.750(6), P2−C2 1.675(6),
C1−C3 1.379(9), C2−C7 1.434(8), Cl−K 2.994(2), P1−Ir−P2
162.59(6), N−Ir−Cl 172.36(15).
As a result, it was found that the rhodium ammine complex
14 (RhNH3) is more stable than the amido complex [Rh-
(NH2)(Eind-PPEP)] (RhNH2) (eq 1); in contrast, the iridium
ammine complex [Ir(NH3)(Eind-PPEP*)] (IrNH3) is less stable
than the amido complex 15 (IrNH2) (eq 2). The energy
differences between two species (ΔG298 = −2.4 and +2.2 kcal/
(Scheme 4). Due to the difficulty in separating reaction
products from [K(18C6)]Cl, the reactions were conducted
with K[MCl(Eind-PPEP*)] (M = Rh, Ir), generated in situ
from 10 and 11 by treatment with K[N(SiMe3)2]. The resulting
complexes 14 and 15 were isolated in 98 and 99% yields,
mol) correspond to the ratios RhNH3/RhNH2 = 58/1 and IrNH3
/
IrNH2 = 1/41, respectively. Thus, while the energy differences
are somewhat smaller than those expected for the experimental
observations showing selective formation of either complex, the
tendencies were reproduced by DFT calculations.
Scheme 4
*
[Rh(NH3)(Eind‐PPEP )] > [Rh(NH2)(Eind‐PPEP)]
ΔG298([RhNH3 ]−[RhNH2]) = −2.4 kcal/mol
(1)
(2)
*
[Ir(NH3)(Eind‐PPEP )] < [Ir(NH2)(Eind‐PPEP)]
ΔG298([IrNH3 ]−[IrNH2]) = +2.2 kcal/mol
CONCLUSION
In this study, we could synthesize a novel PNP-pincer type
phosphaalkene ligand (Eind-PPEP) that functions as a
■
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dryness under reduced pressure to afford Eind-BPEP (7) as a yellow
solid (259 mg, 0.32 mmol, 97%). The crude product was purified by
column chromatography using deactivated neutral alumina and hexane
as the eluent to remove a small amount of Mes*PH2 formed by
decomposition of the phospha-Wittig reagent (Mes*PPMe3).
Data for 7 are as follows. 1H NMR (CD2Cl2, 25 °C): δ 8.86 (d, 2JPH
noninnocent ligand on transition metals. Unlike PPEP, bearing
Mes* as a steric protecting group of the PC bond, Eind-
PPEP protected by a fused-ring bulky Eind group was
sufficiently stable against C−H addition/cyclization even on a
Rh(I) center. Therefore, we could compare the reactivity of
K[MCl(Eind-PPEP*)] (M = Rh, Ir) toward ammonia and
found a dramatic change in the reaction courses depending on
the metals. It is worth noting that the reactivity of the iridium
complex K[13] toward N−H bond cleavage of ammonia is
comparable to that of the PPEP* complex K[3b]. This
observation indicates that, while the Eind group seems sterically
more demanding than the Mes* group, the highly reactive
nature of the dearomatized phosphaalkene complex toward
metal−ligand cooperative activation is successfully preserved
after structural modification using Eind. At present, we are
synthesizing various late-transition-metal complexes with Eind-
PPEP and Eind-PPEP* ligands. Those results, including their
reaction chemistry, will be reported in due course.
2
= 25.6 Hz, 1H, EindPCH), 8.13 (d, JPH = 25.3 Hz, 1H, Mes*P
CH), 7.58 (t, 3JHH = 7.8 Hz, 1H, Py), 7.55 (d, 3JHH = 7.8 Hz, 1H, Py),
7.45 (s, 2H, m-Mes*), 7.39 (d, 3JHH = 7.8 Hz, 1H, Py), 6.73 (s, 1H, p-
Eind), 1.91−1.76 (m, 8H, 4 × CH2CH3), 1.81 (s, 4H, 2 × CH2),
1.74−1.55 (m, 8H, 4 × CH2CH3), 1.53 (s, 18H, o-tBu), 1.36 (s, 9H,
p-tBu), 0.85 (t, 3JHH = 7.4 Hz, 12H, 4 × CH2CH3), 0.77 (t, 3JHH = 7.4
Hz, 12H, 4 × CH2CH3). 13C{1H} NMR (CD2Cl2, 25 °C): δ 181.8 (d,
1
1JPC = 34 Hz, EindPCH), 175.9 (d, JPC = 35 Hz, Mes*PCH),
158.7 (d, JPC = 28 Hz), 158.6 (d, JPC = 27 Hz), 154.7 (s), 150.6 (s),
150.4 (s), 150.0 (s), 139.6 (d, 1JPC = 54 Hz, ipso-Ar), 137.3 (s), 136.3
(d, 1JPC = 48 Hz, ipso-Ar), 122.6 (s, m-Mes*), 121.3 (s, p-Eind), 119.8
(t, JPC = 18 Hz), 119.7 (t, JPC = 17 Hz), 53.6 (s), 48.8 (s), 42.7 (s,
4
CH2), 38.8 (s), 35.6 (s), 34.4 (d, JPC = 7 Hz, o-C(CH3)3), 34.1 (br,
CH2CH3), 33.5 (br, CH2CH3), 31.8 (s, p-C(CH3)3), 10.0 (s,
CH2CH3), 9.6 (s, CH2CH3). 31P{1H} NMR (CD2Cl2, 25 °C): δ
285.8 (s), 275.2 (s). HRMS (APCI): calcd for C53H79NP2, 792.5761
([M + H]+); found, 792.5774.
EXPERIMENTAL SECTION
■
General Considerations. All manipulations were performed
under a nitrogen atmosphere using a glovebox and Schlenk techniques.
Eind-PCl2 was prepared as previously reported.10 The other chemicals
were obtained from commercial sources. NMR spectra were recorded
on a 400 MHz spectrometer. Chemical shifts are reported in δ (ppm),
Synthesis of Eind-BPEP Complexes 8 and 9. A typical synthetic
procedure is described for [RhCl(Eind-BPEP)] (8). The complex
[Rh(μ-Cl)(C2H4)2]2 (26 mg, 0.067 mmol) was suspended in THF (2
mL), and a solution (1 mL) of Eind-BPEP (122 mg, 0.15 mmol) in
THF (1 mL) was added at room temperature. The mixture instantly
changed into a greenish brown solution. The solution was stirred for
30 min and concentrated under reduced pressure. Addition of Et2O
(0.5 mL) led to the formation of a dark green crystalline solid of 8,
which was collected by filtration, washed with Et2O (0.3 mL × 5), and
dried under vacuum (75 mg, 0.080 mmol, 60%). The complex
[IrCl(Eind-BPEP)] (9) was similarly prepared from [Ir(μ-Cl)(coe)2]2
and isolated as a greenish brown crystalline solid (84%).
1
referenced to H (residual) and 13C signals of deuterated solvents as
internal standards or to the 31P signal of 85% H3PO4 as an external
standard. The assignments of 13C signals are based on HMQC
experiments. Elemental analysis was performed by ICR Analytical
Laboratory, Kyoto University.
Synthesis of Eind-BPEP (7). Synthesis of 6. To a mixture of zinc
dust (348 mg, 5.3 mmol) and Eind-PCl2 (300 mg, 0.62 mmol) in THF
(4 mL) was added a 1.0 M THF solution of PMe3 (1.5 mL, 1.5 mmol)
at room temperature. After it was stirred for 1 h, the reaction mixture
was added dropwise to a THF solution (6 mL) of 5 (86 mg, 0.64
mmol) by a cannula at 0 °C over 10 min. The mixture was stirred at
room temperature for 6 h, and solvent was removed under reduced
pressure. The residue was suspended in hexane (600 mL) and the
suspension filtered through a Celite pad to remove zinc dust, ZnCl2,
and Me3PO. The filtrate was concentrated to half volume and purified
by gel filtration using 1,2-dihydroxy-3-propoxypropyl-modified silica
gel with hexane as the eluent to afford 6 as a pale yellow powder (241
mg, 0.45 mmol, 74%).
1
Data for 8 are as follows. H NMR (CD2Cl2, 25 °C): δ 7.66 (dd,
3
4
2JPH = 17.5 Hz, JRhH = 3.6 Hz, 1H, EindPCH), 7.59 (d, JPH = 2.5
2
Hz, 2H, m-Mes*), 7.28−7.23 (m, 1H, Py), 7.19 (dd, JPH = 18.1 Hz,
3JRhH = 3.6 Hz, 1H, Mes*PCH), 6.91 (d, 5JPH = 3.3 Hz, 1H, p-Eind),
6.72−6.68 (m, 2H, Py), 2.39−2.24 (m, 4H, 2 × CH2CH3), 2.18−2.11
(m, 2H, CH2CH3), 1.97−1.88 (m, 2H, CH2CH3), 1.93 (d, 2JHH = 14.0
2
Hz, 2H, CH2), 1.84 (d, JHH = 14.0 Hz, 2H, CH2), 1.74 (s, 18H,
o-tBu), 1.72−1.52 (m, 8H, 4 × CH2CH3), 1.38 (s, 9H, p-tBu), 0.90 (t,
3JHH = 7.4 Hz, 6H, 2 × CH2CH3), 0.85 (t, JHH = 7.4 Hz, 6H, 2 ×
3
3
3
CH2CH3), 0.83 (t, JHH = 7.6 Hz, 6H, 2 × CH2CH3), 0.77 (t, JHH
=
7.3 Hz, 6H, 2 × CH2CH3). 13C{1H} NMR (CD2Cl2, 25 °C): δ 168.5
(d, JPC = 8 Hz), 157.2 (s), 153.7 (d, JPC = 2 Hz), 153.3 (s), 151.0 (s),
1
Data for 6 are as follows. H NMR (C6D6, 25 °C): δ 10.05 (s, 1H,
CHO), 9.21 (d, 2JPH = 25.5 Hz, 1H, EindPCH), 7.48 (d, 3JHH = 7.7
1
2
3
3
150.9 (s), 149.3 (dd, JPC = 36 Hz, JRhC = 4 Hz, EindPCH), 148.1
(dd, 1JPC = 36 Hz, 2JRhC = 4 Hz, Mes*PCH), 134.4 (s), 126.8−126.4
(m, ipso-Ar), 124.3−123.9 (m, ipso-Ar), 123.7 (d, 4JPC = 2 Hz, p-Eind),
Hz, 1H, Py), 7.31 (d, JHH = 7.7 Hz, 1H, Py), 6.88 (t, JHH = 7.7 Hz,
1H, Py), 6.86 (s, 1H, p-Eind), 2.11−2.02 (m, 4H, 2 × CH2CH3),
1.98−1.89 (m, 4H, 2 × CH2CH3), 1.78 (s, 4H, 2 × CH2), 1.76−1.58
3
3
123.4 (d, JPC = 7 Hz, m-Mes*), 114.6 (t, JPC = 8 Hz, JRhC = 8 Hz),
(m, 8H, 4 × CH2CH3), 0.90 (t, JHH = 7.4 Hz, 12H, 4 × CH2CH3),
0.86 (t, 3JHH = 7.4 Hz, 12H, 4 × CH2CH3). 13C{1H} NMR (C6D6, 25
114.3 (t, JPC = 8 Hz, JRhC = 8 Hz), 54.2 (s), 48.8 (s), 43.0 (s, CH2),
39.5 (s), 35.9(s), 35.0 (d, 4JPC = 2 Hz, CH2CH3), 34.8 (d, 4JPC = 2 Hz,
o-C(CH3)3), 34.4 (s, CH2CH3), 33.7 (s, CH2CH3), 33.5 (s, CH2CH3),
31.6 (s, p-C(CH3)3), 10.5 (s, CH2CH3), 10.4 (s, CH2CH3), 9.6 (s, 2 ×
1
°C): δ 193.3 (s, CHO), 180.3 (d, JPC = 36 Hz, EindPCH), 158.8
(d, JPC = 15 Hz), 153.9 (s), 150.7 (d, JPC = 3 Hz), 150.2 (s), 137.8 (s),
136.3 (d, 1JPC = 48 Hz, ipso-Eind), 124.3 (d, JPC = 18 Hz), 121.5 (s, p-
Eind), 120.1 (d, JPC = 6 Hz), 53.7 (s), 49.0 (s), 42.9 (s, CH2), 34.4 (br
s, CH2CH3), 33.7 (br s, CH2CH3), 10.1 (s, CH2CH3), 9.8 (s,
CH2CH3). 31P{1H} NMR (C6D6, 25 °C): δ 284.2 (s). Anal. Calcd for
C35H50NOP: C, 79.05; H, 9.48; N, 2.63. Found: C, 79.10; H, 9.62; N,
2.65.
2
CH2CH3). 31P{1H} NMR (CD2Cl2, 25 °C): δ 239.2 (dd, JPP = 519
Hz, 1JRhP = 207 Hz), 231.2 (dd, 2JPP = 519 Hz, 1JRhP = 204 Hz). Anal.
Calcd for C53H79ClNP2Rh: C, 68.41; H, 8.56; N, 1.51. Found: C,
68.32; H, 8.65; N, 1.65.
1
Data for 9 are as follows. H NMR (CD2Cl2, 25 °C): δ 8.96 (dd,
2JPH = 13.3 Hz, 4JPH = 5.4 Hz, 1H, EindPCH), 8.50 (dd, 2JPH = 14.1
Hz, 4JPH = 5.1 Hz, 1H, Mes*PCH), 7.79−7.74 (m, 1H, Py), 7.65 (d,
4JPH = 2.9 Hz, 2H, m-Mes*), 7.05−7.03 (m, 1H, Py), 7.00−6.98 (m,
Synthesis of 7. To a mixture of zinc dust (235 mg, 3.6 mmol) and
Mes*-PCl2 (119 mg, 0.33 mmol) in THF (3.5 mL) was added a 1.0 M
THF solution of PMe3 (0.9 mL, 0.9 mmol) at room temperature. After
it was stirred for 3 h, the reaction mixture was added dropwise to a
THF solution (7 mL) of 6 (174 mg, 0.33 mmol) by a cannula at 0 °C.
The mixture was stirred at room temperature for 6 h, and volatiles
were removed under reduced pressure. The residue was suspended in
hexane (30 mL) and the suspension filtered through a Celite pad to
remove zinc dust, ZnCl2, and Me3PO. The filtrate was concentrated to
5
1H, Py), 6.95 (d, JPH = 1.7 Hz, 1H, p-Eind), 2.35−2.24 (m. 4H, 2 ×
CH2CH3), 2.14−2.06 (m, 2H, CH2CH3), 1.94 (d, 2JHH = 14.0 Hz, 2H,
2
CH2), 1.94−1.81 (m, 2H, CH2CH3), 1.85 (d, JHH = 14.0 Hz, 2H,
CH2), 1.79−1.58 (m, 8H, 4 × CH2CH3), 1.72 (s, 18H, o-tBu), 1.41 (s,
9H, p-tBu), 0.92 (t, 3JHH = 7.4 Hz, 6H, 2 × CH2CH3), 0.862 (t, 3JHH
=
7.2 Hz, 6H, 2 × CH2CH3), 0.857 (t, 3JHH = 7.2 Hz, 6H, 2 × CH2CH3),
E
DOI: 10.1021/acs.organomet.6b00113
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
0.71 (t, 3JHH = 7.3 Hz, 6H, 2 × CH2CH3). 13C{1H} NMR (CD2Cl2, 25
°C): δ 174.6 (dd, JPC = 9 and 4 Hz), 157.4 (vt, Japp = 2 Hz), 154.0 (d,
JPC = 2 Hz), 153.3 (s), 151.2 (s), 151.1 (s), 143.2 (d, JPC = 53 Hz,
(s, 3H, CH3), 1.42 (s, 9H, tBu), 1.36 (s, 9H, tBu), 0.95−0.76 (m, 24H,
8 × CH2CH3). 13C{1H} NMR (THF-d8, 25 °C): δ 168.0 (d, JPC = 7
Hz), 167.3 (dd, JPC = 6 and 3 Hz), 160.4 (dd, JPC = 14 and 5 Hz),
154.9 (d, JPC = 2 Hz), 154.8 (d, JPC = 10 Hz), 152.7 (d, JPC = 2 Hz),
152.5 (s), 150.9 (d, JPC = 7 Hz), 150.8 (d, JPC = 10 Hz), 143.9 (d, 1JPC
= 47 Hz, EindPCH), 130.9 (s), 128.9 (dd, JPC = 20 and 4 Hz), 126.9
(dd, 37 and 6 Hz), 124.0 (d, 3JPC = 9 Hz, Ar), 123.4 (d, 4JPC = 2 Hz, p-
1
Mes*PCH), 142.6 (d, 1JPC = 53 Hz, EindPCH), 135.8 (vt, Japp
=
1
1
3 Hz, Py), 127.3 (d, JPC = 21 Hz, ipso-Ar), 124.5 (dd, JPC = 21 Hz,
3JPC = 5 Hz, ipso-Ar), 124.0 (d, 4JPC = 3 Hz, p-Eind), 123.5 (d, 3JPC = 8
Hz, m-Mes*), 108.0 (dd, JPC = 7 and 6 Hz), 107.8 (dd, JPC = 7 and 6
Hz), 54.3 (s), 48.7 (s), 43.0 (s, CH2), 39.5 (s), 36.0 (s), 34.6 (s,
CH2CH3), 34.4 (d, 4JPC = 1 Hz, o- C(CH3)3), 33.9 (s, CH2CH3), 33.6
(s, 2 × CH2CH3), 31.6 (s, p-C(CH3)3), 10.5 (s, CH2CH3), 10.3 (s,
CH2CH3), 9.6 (s, 2 × CH2CH3). 31P{1H} NMR (CD2Cl2, 25 °C): δ
3
Eind), 121.6 (d, JPC = 25 Hz), 119.6 (d, JPC = 9 Hz, Ar), 118.2 (dd,
JPC = 12 and 8 Hz), 54.8 (s), 54.7 (s), 51.1 (d, 1JPC = 26 Hz, PyCH2P),
49.0 (s), 48.9 (s), 44.5 (vt, Japp = 4 Hz), 43.7 (s, CH2), 43.6 (s, CH2),
1
40.8 (d, JPC = 34 Hz, PCH2), 38.1 (s), 36.0 (s), 34.8 (s, CH2CH3),
2
2
34.6 (s, CH2CH3), 34.52 (s, CH2CH3), 34.47 (s, CH2CH3), 34.4 (s,
249.3 (d, JPP = 560 Hz), 237.2 (d, JPP = 560 Hz). Anal. Calcd for
C53H79ClNP2Ir: C, 62.42; H, 7.81; N, 1.37. Found: C, 62.28; H, 7.88;
N, 1.32.
4
CH2CH3), 34.1 (s, CH2CH3), 33.7 (s, CH3), 33.6 (d, JPC = 2 Hz,
C(CH3)3), 33.4 (s, CH2CH3), 33.3 (s, CH2CH3), 31.9 (s, CH3), 31.8
(s, C(CH3)3), 10.90 (s, CH2CH3), 10.86 (s, CH2CH3), 10.6 (s,
CH2CH3), 10.5 (s, CH2CH3), 9.8 (s, 2 × CH2CH3), 9.7 (s, 2 ×
Synthesis of Eind-PPEP Complexes 10 and 11. The complex
[RhCl(Eind-BPEP)] (8; 14 mg, 0.015 mmol) was dissolved in
toluene-d8 (0.6 mL) and heated at 140 °C for 2 days in a sealed NMR
sample tube. The solution gradually changed from dark green to dark
2
CH2CH3). 31P{1H} NMR (THF-d8, 25 °C): δ 232.7 (d, JPP = 480
Hz), 25.4 (d, 2JPP = 480 Hz). Anal. Calcd for C53H79ClNP2Ir: C, 62.42;
H, 7.81; N, 1.37. Found: C, 62.23; H, 7.86; N, 1.24.
1
red. H and 31P{1H} NMR analysis revealed the complete conversion
Synthesis of Eind-PPEP* Complexes 12 and 13. A solution of
tBuOK (6.7 mg, 0.060 mmol) and 18-crown-6 (16 mg, 0.060 mmol) in
THF (1 mL) was added to a THF solution (1 mL) of 10 (56 mg,
0.060 mmol). The solution instantly changed from dark red to dark
greenish brown. After 20 min at room temperature, the complete
conversion of 10 was confirmed by 31P{1H} NMR analysis. The
solvent was removed under reduced pressure, and Et2O (0.3 mL) was
added to the residue, affording dark brown crystals of [K(18C6)]-
[RhCl(Eind-PPEP*)] ([K(18C6)][12]). The supernatant was
removed by decantation, and the crystalline soild was washed with
Et2O (0.3 mL × 5) and dried under vacuum (59 mg, 0.048 mmol,
80%). The complex [K(18C6)][IrCl(Eind-PPEP*)] ([K(18C6)]-
[13]) was similarly prepared from 11 as dark green crystals (80%).
Data for [K(18C6)][12] are as follows. 1H NMR (THF-d8, 25 °C):
δ 7.52 (dd, 2JPH = 16.3 Hz, 3JRhH = 2.7 Hz, 1H, EindPCH), 7.27 (dd,
4JPH = 3.8 Hz, 4JHH = 1.4 Hz, 1H, Ar), 7.08 (d, 4JHH = 1.4 Hz, 1H, Ar),
of 8 to 10. The solution was filtered through a Celite pad to remove a
small amount of black solids and concentrated to dryness to give a
dark red crystalline solid of 10 (14 mg, 100%), which was analytically
pure. The iridium Eind-PPEP complex 11 was prepared by heating a
toluene solution of 9 at 70 °C for 10 h and isolated as a pure brown
crystalline solid in quantitative yield.
1
Data for 10 are as follows. H NMR (THF-d8, 25 °C): δ 8.06 (dd,
2JPH = 17.0 Hz, 3JRhH = 3.6 Hz, 1H, EindPCH), 7.58 (br t, 3JHH = 7.7
Hz, 1H, Py), 7.46 (dd, 4JPH = 4.8 Hz, 4JHH = 1.7 Hz, 1H, Ar), 7.27 (d,
4JHH = 1.7 Hz, 1H, Ar), 7.13−7.10 (m, 1H, Py), 7.02 (br d, 3JHH = 6.4
Hz, 1H, Py), 6.92 (s, 1H, p-Eind), 4.32 (dd, 2JHH = 18.4 Hz, 2JPH = 9.6
2
2
Hz, 1H, PyCH2P), 4.10 (dd, JHH = 18.4 Hz, JPH = 9.7 Hz, 1H,
PyCH2P), 2.83−2.71 (m, 2H, PCH2 + CH2CH3), 2.57−2.47 (m, 1H,
CH2CH3), 2.36 (dd, 2JHH = 14.8 Hz, 2JPH = 2.1 Hz, 1H, PCH2), 2.25−
2.14 (m, 3H, CH2CH3), 2.06−1.93 (m, 4H, CH2CH3 + CH2), 1.89−
1.83 (m, 3H, CH2CH3 + CH2), 1.79−1.58 (m, 8H, 4 × CH2CH3),
6.74 (s, 1H, p-Eind), 6.03 (m, 1H, Py), 5.92 (dd, 3JHH = 8.4 Hz, 4JPH
=
t
1.53 (s, 9H, Bu), 1.51 (s, 3H, CH3), 1.46 (s, 3H, CH3), 1.35 (s, 9H,
2.8 Hz, 1H, Py), 5.49 (dd, 3JHH = 6.5 Hz, 4JPH = 3.9 Hz, 1H, Py), 3.56
(vt, 1H, PyCHP), 3.53 (s, 24H, 18-crown-6), 3.11−3.03 (m, 1H,
tBu), 0.93 (t, 3JHH = 6.8 Hz, 6H, 2 × CH2CH3), 0.90−0.82 (m, 12H, 4
× CH2CH3), 0.82−0.75 (m, 6H, 2 × CH2CH3). 13C{1H} NMR
(THF-d8, 25 °C): δ 166.3 (d, JPC = 10 Hz), 164.0 (d, JPC = 10 Hz),
2
CH2CH3), 2.74−2.70 (m, 1H, CH2CH3), 2.46 (dd, JHH = 13.5 Hz,
3JPH = 4.0 Hz, 1H, PCH2), 2.33−2.19 (m, 4H, 2 × CH2CH3), 2.10−
160.1 (dd, JPC = 11 and 5 Hz), 154.9 (d, JPC = 2 Hz), 154.7 (d, JPC
=
2
1.94 (m, 2H, CH2CH3), 1.88 (d, JHH = 13.6 Hz, 2H, CH2), 1.82 (d,
11 Hz), 153.3 (d, JPC = 2 Hz), 153.0 (s), 150.8 (d, JPC = 6 Hz), 150.7
2JHH = 13.6 Hz, 1H, CH2), 1.80 (d, 2JHH = 13.6 Hz, 1H, CH2), 1.71 (s,
1
2
(d, JPC = 6 Hz), 149.0 (dd, JPC = 32 Hz, JRhC = 3 Hz, EindPCH),
132.5 (s), 129.3−129.0 (m), 128.6 (dt, JRhC = 19 Hz, JPC = 19 and 7
t
9H, Bu), 1.71−1.54 (m, 9H, 4 × CH2CH3 + PCH2), 1.42 (s, 3H,
3
Hz), 123.9 (d, JPC = 8 Hz, Ar), 123.2 (s, p-Eind), 120.8 (d, JPC = 25
CH3), 1.38 (s, 3H, CH3), 1.31 (s, 9H, tBu), 0.91 (t, 3JHH = 7.3 Hz, 6H,
2 × CH2CH3), 0.87−0.77 (m, 18H, 6 × CH2CH3). The coupling
constant for the vinylic proton at δ 3.56 was obscured due to the
overlap with a residual signal of THF-d8. 13C{1H} NMR (THF-d8, 25
°C): δ 173.5 (dd, JPC = 25 Hz, JRhC = 3 Hz), 163.6 (d, JPC = 10 Hz),
158.6 (dd, JPC = 10 and 5 Hz), 153.8 (d, JPC = 10 Hz), 152.45 (s),
3
Hz), 119.6 (d, JPC = 8 Hz, Ar), 118.9 (dd, JPC = 13 and 8 Hz), 54.9
1
(s), 54.7 (s), 50.6 (d, JPC = 18 Hz, PyCH2P), 49.21 (s), 43.18 (s),
1
45.4−45.2 (m), 43.7 (s, CH2), 43.6 (s, CH2), 42.3 (d, JPC = 27 Hz,
PCH2), 38.3 (s), 36.1 (s), 35.5 (s, CH2CH3), 35.3 (s, CH2CH3), 35.1
(d, 4JPC = 3 Hz, CH2CH3), 34.8 (s, CH2CH3), 34.7 (s, CH2CH3), 34.6
4
4
1
(d, JPC = 2 Hz, CH2CH3), 33.8 (d, JPC = 3 Hz, C(CH3)3), 33.7 (s,
152.41 (s), 150.5 (d, JPC = 2 Hz), 149.7 (d, JPC = 33 Hz, EindP
3
CH3), 33.3 (s, CH2CH3), 33.2 (s, CH2CH3), 32.1 (d, JPC = 9 Hz,
CH), 149.4 (d, JPC = 4 Hz), 149.1 (d, JPC = 5 Hz), 136.7−136.5 (br d,
JPC = 25 Hz), 132.8 (ddd, JPC = 29 and 20 Hz, JRhC = 7 Hz), 129.4 (vt,
CH3), 31.9 (s, C(CH3)3), 11.02 (s, CH2CH3), 10.99 (s, CH2CH3),
3
10.7 (s, CH2CH3), 10.6 (s, CH2CH3), 9.8 (s, 4 × CH2CH3). 31P{1H}
Japp = 3 Hz), 121.1 (d, JPC = 7 Hz, Ar), 120.8 (s, p-Eind), 117.6 (d,
2
1
NMR (THF-d8, 25 °C): δ 230.5 (dd, JPP = 461 Hz, JRhP = 183 Hz),
3JPC = 7 Hz, Ar), 109.3 (dd, JPC = 21 and 10 Hz), 100.4 (d, JPC = 28
Hz), 74.7 (d, 1JPC = 51 Hz, PyCHP), 71.0 (s, 18-crwon-6), 54.4 (s),
54.2 (s), 48.34 (s), 48.30 (s), 43.7 (d, 1JPC = 27 Hz, PCH2), 43.8−43.7
(m), 43.6 (s, CH2), 43.5 (s, CH2), 38.6 (s), 35.3 (s), 34.7 (s,
CH2CH3), 34.6 (s, CH2CH3), 34.5 (s, CH2CH3), 34.4 (s, CH2CH3),
34.03 (s, C(CH3)3), 34.00 (s, CH3), 33.97 (s, CH2CH3), 33.7 (d, 4JPC
= 3 Hz, CH2CH3), 32.9 (s, CH2CH3), 32.8 (s, CH2CH3), 32.3 (d, 3JPC
= 8 Hz, CH3), 31.8 (s, C(CH3)3), 11.0 (s, CH2CH3), 10.9 (s,
CH2CH3), 10.4 (s, CH2CH3), 10.3 (s, CH2CH3), 9.5 (s, 2 ×
CH2CH3), 9.4 (s, 2 × CH2CH3). 31P{1H} NMR (THF-d8, 25 °C): δ
2
1
26.0 (dd, JPP = 461 Hz, JRhP = 168 Hz). Anal. Calcd for
C53H79ClNP2Rh: C, 68.41; H, 8.56; N, 1.51. Found: C, 68.68; H,
8.83; N, 1.73.
1
Data for 11 are as follows. H NMR (THF-d8, 25 °C): δ 8.94 (dd,
2JPH = 12.7 Hz, JPH = 4.1 Hz, 1H, EindPCH), 7.99 (td, JHH = 7.6
4
3
5
4
4
Hz, JPH = 1.7 Hz, 1 H, Py), 7.47 (dd, JPH = 4.8 Hz, JHH = 1.7 Hz,
4
3
1H, Ar), 7.30 (d, JHH = 1.7 Hz, 1H, Ar), 6.96 (br d, JHH = 7.2 Hz,
1H, Py), 6.95 (s, 1H, p-Eind), 6.90 (br d, 3JHH = 7.6 Hz, 1H, Py), 4.02
2
2
2
(dd, JHH = 18.8 Hz, JPH = 9.9 Hz, 1H, PyCH2P), 4.01 (dd, JHH
=
2
2
1
2
18.8 Hz, JPH = 10.2 Hz, 1H, PyCH2P), 2.81−2.69 (m, 2H, PCH2 +
211.3 (dd, JPP = 433 Hz, JRhP = 182 Hz), 19.2 (dd, JPP = 433 Hz,
1JRhP = 169 Hz). Anal. Calcd for C65H102ClKNO6P2Rh: C, 63.32; H,
8.34; N, 1.14. Found: C, 63.04; H, 8.54; N, 1.08.
2
CH2CH3), 2.63−2.51 (m, 1H, CH2CH3), 2.38 (dd, JHH = 14.8 Hz,
2JPH = 3.1 Hz, 1H, PCH2), 2.32−2.18 (m, 3H, CH2CH3), 2.16−2.09
(m, 1H, CH2CH3), 2.07−2.00 (m, 1H, CH2CH3), 1.95 (d, 2JHH = 13.9
Hz, 2H, CH2), 1.86 (d, 2JHH = 13.9 Hz, 1H, CH2), 1.85 (d, 2JHH = 13.9
Hz, 1H, CH2), 1.91−1.63 (m, 9H, CH2CH3), 1.51 (s, 3H, CH3), 1.50
Data for [K(18C6)][13] are as follows. 1H NMR (THF-d8, 25 °C):
δ 8.90 (dd, 2JPH = 11.7 Hz, 4JPH = 3.6 Hz, 1H, EindPCH), 7.27 (dd,
4JPH = 3.8 Hz, 4JHH = 1.7 Hz, 1H, Ar), 7.12 (d, 4JHH = 1.7 Hz, 1H, Ar),
F
DOI: 10.1021/acs.organomet.6b00113
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
6.76 (s, 1H, p-Eind), 6.13 (dd, 3JHH = 8.1 and 6.8 Hz, 1H, Py), 6.06−
6.03 (m, 2H, Py), 3.89 (vt, Japp = 3.8 Hz, PyCHP), 3.53 (s, 24H, 18-
crown-6), 3.23−3.14 (m, 1H, CH2CH3), 2.90−2.81 (m, 1H,
(s), 44.2−44.1 (m), 43.4 (s, CH2), 43.3 (d, 1JPC = 28 Hz, PCH2), 43.2
(s, CH2), 38.5 (s), 35.5 (s), 35.0 (s, CH2CH3), 34.7 (s, CH2CH3), 34.1
4
4
(s, 2 × CH2CH3), 33.9 (d, JPC = 4 Hz, CH2CH3), 33.7 (d, JPC = 3
1
2
Hz, C(CH3)3), 33.5 (d, 4JPC = 4 Hz, CH2CH3), 33.4 (s, CH3), 33.18 (s,
CH2CH3), 2.37 (br dd, JHH = 13.6 Hz, JPH = 7.2 Hz, 1H, PCH2),
2.32−2.17 (m, 4H, 2 × CH2CH3), 2.03−1.93 (m, 2H, CH2CH3), 1.88
(d, 2JHH = 13.8 Hz, 2H, CH2), 1.81 (d, 2JHH = 13.8 Hz, 1H, CH2), 1.80
(d, 2JHH = 13.8 Hz, 1H, CH2), 1.71−1.57 (m, 9H, CH2CH3 + PCH2),
3
CH2CH3), 33.15 (s, CH2CH3), 32.1 (d, JPC = 8 Hz, CH3), 31.7 (s,
C(CH3)3), 10.7 (s, CH2CH3), 10.31 (s, CH2CH3), 10.25 (s, CH2CH3),
10.2 (s, CH2CH3), 9.5 (s, 2 × CH2CH3), 9.4 (s, 2 × CH2CH3).
t
1.55 (s, 9H, Bu), 1.47 (s, 3H, CH3), 1.37 (s, 3H, CH3), 1.32 (s, 9H,
2
1
31P{1H} NMR (THF-d8, 25 °C): δ 215.2 (dd, JPP = 368 Hz, JRhP
=
tBu), 0.92−0.77 (m, 24H, 8 × CH2CH3). 13C{1H} NMR (THF-d8, 25
°C): δ 177.4 (d, JPC = 20 Hz), 167.4 (dd, JPC = 8 and 3 Hz), 159.0 (dd,
JPC = 13 and 5 Hz), 154.0 (d, JPC = 9 Hz), 152.5 (s), 150.71 (s),
150.69 (s), 149.7 (d, JPC = 5 Hz), 149.4 (d, JPC = 6 Hz), 141.9 (d, 1JPC
= 48 Hz, EindPCH), 135.8 (dd, JPC = 34 and 5 Hz), 133.8 (dd, JPC
177 Hz), 16.4 (dd, 2JPP = 368 Hz, 1JRhP = 167 Hz). HRMS (ESI): calcd
for C53H81N2P2Rh, 910.4925 ([M]+); found, 910.4936.
1
Data for 15 are as follows. H NMR (THF-d8, 25 °C): δ 8.72 (dd,
2JPH = 7.5 Hz, 4JPH = 3.4 Hz, 1H, EindPCH), 7.63 (ddd, 3JHH = 8.0
3
5
4
3
Hz, JHH = 6.8 Hz, JPH = 3.0 Hz, 1H, Py), 7.45 (dd, JPH = 4.5 Hz,
4JHH = 1.6 Hz, 1H, Ar), 7.30 (d, 4JHH = 1.6 Hz, 1H, Ar), 6.95 (s, 1H, p-
= 22 and 17 Hz), 130.7 (s), 122.3 (d, JPC = 7 Hz, Ar), 121.2 (s, p-
Eind), 117.8 (d, 3JPC = 8 Hz, Ar), 105.9 (dd, JPC = 18 and 8 Hz), 98.6
(d, JPC = 26 Hz), 73.1 (d, 1JPC = 64 Hz, PyCHP), 71.1 (s, 18-crown-
6), 54.5 (s), 54.3 (s), 48.3 (s), 48.2 (s), 43.9 (s, CH2), 43.7 (s, CH2),
43.3 (br s), 43.1 (d, 1JPC = 29 Hz, PCH2), 38.5 (s), 35.4 (s), 34.44 (s,
CH2CH3), 34.43 (s, CH2CH3), 34.35 (s, CH2CH3), 34.34 (s,
3
3
Eind), 6.88 (br d, JHH = 8.0 Hz, 1H, Py), 6.69 (br d, JHH = 6.8 Hz,
1H, Py), 4.15 (dd, 2JHH = 20.3 Hz, 2JPH = 10.7 Hz, 1H, PyCH2P), 4.14
2
2
(dd, JHH = 20.3 Hz, JPH = 10.2 Hz, 1H, PyCH2P), 3.95 (br, 2H,
NH2), 2.98−2.89 (m, 1H, CH2CH3), 2.77−2.68 (m, 1H, CH2CH3),
4
2
2
2
CH2CH3), 34.2 (d, JPC = 2 Hz, C(CH3)3), 34.1 (s, CH3), 33.9 (br
2.63 (dd, JHH = 15.1 Hz, JPH = 4.0 Hz, 1H, PCH2), 2.40 (dt, JHH
=
15.1 Hz, 2JPH = 3.7 Hz, 1H, PCH2), 2.24−1.93 (m, 6H, 3 × CH2CH3),
1.90−1.88 (m, 4H, 2 × CH2), 1.86−1.60 (m, 8H, 4 × CH2CH3), 1.53
s, CH2CH3), 33.2 (br s, CH2CH3), 33.1 (s, CH2CH3), 32.9 (s,
3
CH2CH3), 32.4 (d, JPC = 9 Hz, CH3), 31.8 (s, C(CH3)3), 11.02 (s,
CH2CH3), 10.98 (s, CH2CH3), 10.5 (s, CH2CH3), 10.4 (s, CH2CH3),
t
t
(s, 3H, CH3), 1.52 (s, 3H, CH3), 1.38 (s, 9H, Bu), 1.36 (s, 9H, Bu),
0.95−0.67 (m, 24H, 8 × CH2CH3). 13C{1H} NMR (THF-d8, 25 °C):
δ 163.5 (dd, JPC = 6 and 2 Hz), 161.0 (dd, JPC = 7 and 3 Hz), 159.8
(dd, JPC = 14 and 5 Hz), 155.2 (d, JPC = 10 Hz), 154.3 (d, JPC = 2 Hz),
151.0 (s), 150.9 (s), 150.3 (d, JPC = 7 Hz), 150.1 (d, JPC = 7 Hz), 135.1
(d, 1JPC = 43 Hz, EindPCH), 131.1 (d, JPC = 18 Hz), 125.5 (dd, JPC
9.6 (s, 2 × CH2CH3), 9.5 (s, 2 × CH2CH3). 31P{1H} NMR (THF-d8,
2
2
25 °C): δ 218.8 (d, JPP = 458 Hz), 18.9 (d, JPP = 458 Hz). Anal.
Calcd for C65H102ClIrKNO6P2: C, 59.04; H, 7.78; N, 1.06. Found: C,
58.64; H, 8.00; N, 1.22.
Reactions of Eind-PPEP* Complexes with Ammonia. A THF-
d8 solution (0.3 mL) of K[N(SiMe3)2] (2.0 mg, 0.010 mmol) was
added to a THF-d8 solution (0.3 mL) of 10 (9.3 mg, 0.010 mmol) at
room temperature in an NMR sample tube. The solution instantly
changed from dark red to dark greenish brown. After 30 min at room
temperature, the complete conversion of 10 to K[12] was confirmed
by 1H and 31P{1H} NMR analysis. The resulting solution was degassed
by freeze−pump−thaw cycles (three times) and charged with an
anhydrous NH3 gas (1 atm). The solution turned reddish brown.
Volatile materials were removed under reduced pressure, and the
residue was dissolved in hexane (1 mL) and filtered through a glass
fiber filter to remove KCl. The filtrate was concentrated to dryness
under reduced pressure to give a reddish brown crystalline solid of
[Rh(NH3)(Eind-PPEP*)] (14; 9.0 mg, 98%). Complex 14 was
gradually degraded upon drying under reduced pressure, probably due
to dissociation of the ammine ligand. Therefore, the complex did not
give a satisfactory elemental analysis, and its composition was
confirmed by HRMS analysis and NMR spectroscopy.
3
= 32 and 5 Hz), 123.7 (d, JPC = 8 Hz, Ar), 123.2 (vt, Japp = 3 Hz),
122.8 (d, JPC = 25 Hz), 122.6 (d, 4JPC = 2 Hz, p-Eind), 119.1 (d, 3JPC
=
8 Hz, Ar), 113.3 (dd, JPC = 13 and 4 Hz), 54.7 (s), 54.6 (s), 50.0 (d,
1JPC = 29 Hz, PyCH2P), 48.35 (s), 48.34 (s), 44.0 (t, JPC = 4 Hz), 43.6
1
(s, CH2), 43.4 (s, CH2), 43.2 (d, JPC = 34 Hz, PCH2), 38.2 (s), 35.7
(s), 34.3 (s, CH2CH3), 34.23 (s, CH2CH3), 34.15 (s, CH2CH3), 34.07
(s, CH2CH3), 33.7 (s, CH3), 33.2 (s, CH2CH3), 33.14 (s, CH2CH3),
4
33.06 (d, JPC = 2 Hz, C(CH3)3), 32.3 (s, CH2CH3), 32.2 (s,
CH2CH3), 31.6 (s, C(CH3)3), 31.5 (s, CH3), 10.5 (s, CH2CH3), 10.43
(s, CH2CH3), 10.37 (s, CH2CH3), 10.3 (s, CH2CH3), 9.52 (s, 2 ×
CH2CH3), 9.49 (s, 2 × CH2CH3). 31P{1H} NMR (THF-d8, 25 °C): δ
2
2
173.6 (d, JPP = 468 Hz), 26.4 (d, JPP = 468 Hz). Anal. Calcd for
C53H81N2P2Ir: C, 63.63; H, 8.16; N, 2.80. Found: C, 63.35; H, 8.24; N,
2.55.
X-ray Crystal Structure Determination. The intensity data were
collected at 103 K on a Rigaku Saturn70 CCD diffractometer with the
VariMax Optic, using Mo Kα radiation (λ = 0.71075 Å). The intensity
data were corrected for Lorentz and polarization effects and for
absorption (multiscan12). The structures were solved by direct
methods (SHELXS-97)13 and refined by least-squares calculations
on F2 for all reflections (SHELXL-97),13 using Yadokari-XG 2009.14
Non-hydrogen atoms were refined anisotropically. Hydrogen atoms
were placed at calculated positions and included in calculations
without refinement of their parameters. The crystallographic data and
a summary of solution and refinement are given in Tables S1 and S2 in
the Supporting Information.
Computational Details. DFT calculations were carried out by
using the Gaussian 09 program.15 We adopted the B3LYP-D
functional, which is the B3LYP hybrid functional16 combined with
an empirical dispersion correction developed by Grimme.17 For
optimization, we chose SDD for Ir and Rh and 6-31G(d) for the other
atoms as basis sets.18 Systematic vibrational analyses were carried out
for all complexes to characterize stationary-point structures. To
determine the energy differences, we performed single-point
calculations at the optimized geometries using the 6-311+G(d,p)
basis set instead of the 6-31G(d) basis set. Solvation effects (THF)
were taken into account by using the polarizable continuum model
(PCM).19 Thermal corrections at 298.15 K were applied for evaluating
the free energy changes (ΔG298).
Complex K[13] was similarly prepared from 11 and K[N(SiMe3)2]
in THF-d8; this solution was treated with NH3 (1 atm) at room
temperature. The reaction was instantly completed, and [Ir(NH2)-
(Eind-PPEP)] (15) was isolated as a dark green crystalline solid
(99%).
1
Data for 14 are as follows. H NMR (THF-d8, 25 °C): δ 7.64 (dd,
2JPH = 17.4 Hz, 3JRhH = 2.9 Hz, 1H, EindPCH), 7.38 (dd, 4JPH = 4.1
4
4
Hz, JHH = 1.8 Hz, 1H, Ar), 7.18 (d, JHH = 1.8 Hz, 1H, Ar), 6.85 (s,
1H, p-Eind), 6.04 (m, 1H, Py), 5.91 (dd, 3JHH = 8.2 Hz, 4JPH = 4.7 Hz,
1H, Py), 5.49 (t, 3JHH = 5.7 Hz, 4JPH = 5.7 Hz, 1H, Py), 3.48 (br d, 2JPH
= 3.9 Hz, 1H, PyCHP), 2.89−2.80 (m, 1H, CH2CH3), 2.68−2.58
(m, 1H, CH2CH3), 2.34−2.23 (m, 4H, 2 × CH2CH3), 2.13 (br, 3H,
NH3), 2.09−2.01 (m, 3H, PCH2 + CH2CH3), 1.89 (br s, 4H, 2 ×
1
CH2), 1.79 (s, 9H, tBu), 1.78 (dd, JHH = 13.8 Hz, 2JPH = 4.6 Hz, 1H,
PCH2), 1.70−1.49 (m, 8H, 4 × CH2CH3), 1.42 (s, 3H, CH3), 1.39 (s,
3H, CH3), 1.32 (s, 9H, tBu), 0.91 (t, 3JHH = 7.2 Hz, 6H, 2 × CH2CH3),
3
0.85 (t, JHH = 7.2 Hz, 12H, 4 × CH2CH3), 0.81−0.75 (m, 6H, 2 ×
CH2CH3). 13C{1H} NMR (THF-d8, 25 °C): δ 173.6 (dd, JPC = 24 Hz,
JRhC = 3 Hz), 162.8 (br d, JPC = 10 Hz), 159.5 (dd, JPC = 12 and 4 Hz),
1
156.3 (d, JPC = 37 Hz, EindPCH), 154.0 (d, JPC = 10 Hz), 152.7
(s), 152.3 (d, JPC = 1 Hz), 152.0 (s), 150.6 (d, JPC = 5 Hz), 150.5 (d,
JPC = 5 Hz), 134.4 (br d, JPC = 30 Hz), 130.9 (vt, Japp = 5 Hz), 130.2−
129.8 (m), 123.0 (d, 3JPC = 7 Hz, Ar), 122.2 (s, p-Eind), 118.7 (d, 3JPC
= 7 Hz, Ar), 113.4 (dd, JPC = 21 and 12 Hz), 103.5 (d, JPC = 33 Hz),
1
74.0 (d, JPC = 54 Hz, PyCHP), 54.4 (s), 54.3 (s), 48.59 (s), 48.57
G
DOI: 10.1021/acs.organomet.6b00113
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(6) (a) Tsang, C.; Rohrick, C. A.; Saini, T. S.; Patrick, B. O.; Gates,
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.6b00113.
■
D. P. Organometallics 2002, 21, 1008−1010. (b) Houdard, R.;
S
́
Mezailles, N.; Le Goff, X.-F.; Le Floch, P. Organometallics 2009, 28,
5952−5959.
(7) (a) Matsuo, T.; Tamao, K. C. R. Chim. 2010, 13, 1104−1110.
(b) Matsuo, T.; Tamao, K. Bull. Chem. Soc. Jpn. 2015, 88, 1201−1220.
(c) Matsuo, T.; Suzuki, K.; Fukawa, T.; Li, B.; Ito, M.; Shoji, Y.; Otani,
T.; Li, L.; Kobayashi, M.; Hachiya, M.; Tahara, Y.; Hashizume, D.;
Fukunaga, T.; Fukazawa, A.; Li, Y.; Tsuji, H.; Tamao, K. Bull. Chem.
Soc. Jpn. 2011, 84, 1178−1191.
Characterization and crystal data of 8, 9, [K(18C6)][12],
and [K(18C6)][13] and the X-ray structure of 14 (PDF)
Crystallographic data for 8, 9, [K(18C6)][12], [K-
(18C6)][13], and 14 (CIF)
(8) (a) Jouaiti, A.; Geoffroy, M.; Bernardinelli, G. Tetrahedron Lett.
1992, 33, 5071−5074. (b) Yam, M.; Chong, J. H.; Tsang, C.-W.;
Patrick, B. O.; Lam, A. E.; Gates, D. P. Inorg. Chem. 2006, 45, 5225−
5234.
Cartesian coordinates of the optimized structures (XYZ)
AUTHOR INFORMATION
Corresponding Author
*E-mail for F.O.: ozawa@scl.kyoto-u.ac.jp.
Notes
■
(9) Shah, S.; Protasiewicz, J. D. Chem. Commun. 1998, 3, 1585−1586.
(10) Li, B.; Tsujimoto, S.; Li, Y.; Tsuji, H.; Tamao, K.; Hashizume,
D.; Matsuo, T. Heteroat. Chem. 2014, 25, 612−618.
(11) Hayashi, A.; Okazaki, M.; Ozawa, F.; Tanaka, R. Organometallics
2007, 26, 5246−5249.
The authors declare no competing financial interest.
(12) Blessing, R. H. Acta Crystallogr., Sect. A: Found. Crystallogr. 1995,
51, 33−38.
ACKNOWLEDGMENTS
■
(13) Sheldrick, G. M. SHELXL-97; University of Gottingen,
̈
This work was supported by KAKENHI (26288050 (F.O.))
from the JSPS and by a MEXT Grant-in-Aid for Scientific
Research on Innovative Areas “Stimuli-responsive Chemical
Species” (24109003 (T.M.), 24109014 (K.Y.), and 24109010
(F.O.)). We thank the Collaborative Research Program of
Institute for Chemical Research, Kyoto University (grant
#2015-21), and the MEXT Project of “Integrated Research
on Chemical Synthesis” for partial support.
Gottingen, Germany, 1997.
̈
(14) Kabuto, C.; Akine, S.; Kwon, E. Nippon Kessho Gakkaishi 2009,
51, 218−224.
(15) 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, J. M.; 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.;
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DOI: 10.1021/acs.organomet.6b00113
Organometallics XXXX, XXX, XXX−XXX