Synthesis, structure, and reactivity of hydridoiridium complexes bearing a pincer-type PSiP ligand

Article abstract of DOI:10.1002/asia.201100085

A series of iridium tetrahydride complexes [Ir(H)₄(PSiP-R)] bearing a tridentate pincer-type bis(phosphino)silyl ligand ([{2-(R ₂P)C₆H₄}₂MeSi]^-, PSiP-R, R=Cy, iPr, or tBu) were synthesized by the reduction of [IrCl(H)(PSiP-R)] with Me₄N·BH₄ under argon. The same reaction under a nitrogen atmosphere afforded a rare example of thermally stable iridium(III)-dinitrogen complexes, [Ir(H)₂(N₂)(PSiP-R)]. Two isomeric dinitrogen complexes were produced, in which the PSiP ligand coordinated to the iridium center in meridional and facial orientations, respectively. Attempted substitution of the dinitrogen ligand in [Ir(H) ₂(N₂)(PSiP-Cy)] with PMe₃ required heating at 150 °C to give the expected [Ir(H)₂(PMe₃)(PSiP-Cy)] and a trigonal bipyramidal iridium(I)-dinitrogen complex, [Ir(N ₂)(PMe₃)(PSiP-Cy)]. The reaction of [Ir(H) ₄(PSiP-Cy)] with three equivalents of 2-norbornene (nbe) in benzene afforded [Ir^I(nbe)(PSiP-Cy)] in a high yield, while a similar reaction of [Ir(H)₄(PSiP-R)] with an excess of 3,3-dimethylbutene (tbe) in benzene gave the C-H bond activation product, [Ir^III(H)(Ph) (PSiP-R)], in high yield. The oxidative addition of benzene is reversible; heating [Ir^III(H)(Ph)(PSiP-Cy)] in the presence of PPh₃ in benzene resulted in reductive elimination of benzene, coordination of PPh ₃, and activation of the C-H bond of one aromatic ring in PPh ₃. [Ir^III(H)(Ph)(PSiP-R)] catalyzed a direct borylation reaction of the benzene C-H bond with bis(pinacolato)diboron. Molecular structures of most of the new complexes in this study were determined by a single-crystal X-ray analysis. Copyright

Full text of DOI:10.1002/asia.201100085

FULL PAPERS
DOI: 10.1002/asia.201100085
Synthesis, Structure, and Reactivity of Hydridoiridium Complexes Bearing a
Pincer-Type PSiP Ligand
Hongyun Fang,[a] Yoong-Kee Choe,[b] Yonghua Li,[a] and Shigeru Shimada*[a]
À
Abstract: A series of iridium tetrahy-
dride complexes [Ir(H)4A(PSiP-R)] bear-
ing a tridentate pincer-type bis(phos-
dinitrogen ligand in [Ir(H)2(N2)
Cy)] with PMe3 required heating at
1508C to give the expected [Ir(H)2
(PSiP-
the C H bond activation product,
E
[IrIII(H)(Ph)
(PSiP-R)], in high yield.
The oxidative addition of benzene is
phino)silyl
ligand
([{2-
A
R
reversible; heating [IrIII(H)(Ph)
ACHTUNGTRENNUNG
(R2P)C6H4}2MeSi]À, PSiP-R, R=Cy,
iPr, or tBu) were synthesized by the re-
Cy)] in the presence of PPh3 in ben-
zene resulted in reductive elimination
of benzene, coordination of PPh3, and
A
ACHTUNGTRENNUNG
duction of [IrCl(H)
N
CHTUNGTRENNUNG
À
Me4N·BH4 under argon. The same re-
action under a nitrogen atmosphere af-
forded a rare example of thermally
activation of the C H bond of one aro-
G
E
matic ring in PPh3. [IrIII(H)(Ph)
(PSiP-
R)] catalyzed a direct borylation reac-
À
stable iridium
plexes, [Ir(H)2(N2)
G
G
tion of the benzene C H bond with
G
bis(pinacolato)diboron.
Molecular
meric dinitrogen complexes were pro-
duced, in which the PSiP ligand coordi-
nated to the iridium center in meri-
dional and facial orientations, respec-
tively. Attempted substitution of the
structures of most of the new com-
plexes in this study were determined
by a single-crystal X-ray analysis.
À
Keywords: C H activation · dini-
trogen complexes
·
iridium
·
ligands · silicon
Introduction
electron-rich metal center and coordinatively unsaturated
species by its strong trans-labilizing effect. We have been
working on the reaction of chelating disilyl and trisilyl com-
pounds with Group 10 transition-metal complexes and re-
ported a number of unusual complexes bearing chelating
silyl ligands.[2] We believe that the above-mentioned unique
character of the silyl ligands strongly affected the formation
of such complexes. Therefore, “ancillary” silyl ligands would
provide transition-metal complexes with unique reactivities
useful for catalysis. However, simple silyl ligands usually
have high reactivity and cannot stay on transition metals as
“ancillary” ligands. Incorporation of a silyl group in a multi-
dentate ligand framework would be a useful strategy to
make “ancillary” silyl ligands. There are two types of ap-
proaches for this kind of silyl ligand: 1) incorporation of one
silyl group at the center of the multidentate framework and
2) attachment of two silyl groups in a rigid multidentate
framework. The second approach is so far rather limited
and the xanthsil ligand by Tobita and co-workers is a repre-
sentative example.[3] The first approach was initiated by Sto-
bart and co-workers, who reported tridentate [(Ph2P-
Silyl ligands have strong s-donating characters and show a
stronger trans influence than do commonly used ligands in
transition-metal chemistry.[1] Silyl ligands would make an
[a] Dr. H. Fang, Dr. Y. Li,+ Dr. S. Shimada
Research Institute for Innovation in Sustainable Chemistry
National Institute of Advanced Industrial Science and
Technology (AIST), Central 5, 1-1-1 Higashi
Tsukuba, Ibaraki 305-8565 (Japan)
Fax : (+81)29-861-4588
E-mail: s-shimada@aist.go.jp
[b] Dr. Y.-K. Choe
Nanosystem Research Institute
National Institute of Advanced Industrial Science and
Technology (AIST), Centeral-2, 1-1-1 Umezono
Tsukuba 305-8578 (Japan)
[+] Present address:
College of Chemistry and Chemical Engineering
Southeast University
Nanjing 211189 (Peopleꢀs Republic of China)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.201100085.
AHCTUNGTRENNUNG
(CH2)n)2MeSi]À (n=2 or 3) and [(2-(Ph2P)C6H4CH2)2MeSi]À
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Chem. Asian J. 2011, 6, 2512 – 2521

and
tetradentate
[(Ph2PCH2CH2)3Si]À
and
[(2-
did not isomerize into their syn isomers, which reflects a
more rigid nature of k3-P, P’,Si-Si(Me){(C6H4)2PR2}2 than k3-
P, P’,Si-Si(Me){(CH2)3PPh2}2.
(Ph2P)C6H4CH2)3Si]À ligands and their Group 8–10 transi-
tion-metal complexes.[4] Recently, transition-metal com-
plexes bearing other tridentate P2Si, N2Si,[5] and S2Si[6]-type
ligands and tetradentate P3Si[7] and S3Si[8]-type ligands have
been reported. We are interested in [{2-(R2P)C6H4}2MeSi]À
ligands (=PSiP-R, R=Cy (cyclohexyl), iPr, or tBu), which
would have high electron-donating properties and higher ri-
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
Reduction of iridium chlorides 2a–c (Scheme 2) was ex-
[14]
amined by using nBu4N·BH4 and Me4N·BH4 as reducing
gidity than do [(Ph2PACTHNUTRGNEUNG
(CH2)n)2MeSi]À ligands.[9] Recently, the
research groups of Turculet,[10] Iwasawa,[11] and Milstein[12]
have reported Group 8–10 transition-metal complexes bear-
ing [{2-(R2P)C6H4}2R’Si]À ligands (R=aryl or alkyl) and
their unique reactivities. In this paper, we report on the syn-
thesis and unique properties of hydridoiridium complexes
bearing PSiP-R ligands.
Results and Discussion
Treatment of 1a–c with 0.5 equivalents of [IrClACTHUNRGTNEUNG(cod)]2
(cod=1,4-cyclooctadiene) in toluene at 708C resulted in oxi-
À
dative addition of the Si H bond to the iridium(I) center to
give the 16-electron complexes 2a–c in high yields
1
À
(Scheme 1). H NMR spectroscopy of 2a–c showed the Ir
Scheme 2. Preparation of iridium–tetrahydride and dinitrogen dihydride
complexes.
agents. Me4N·BH4 proved to be more suitable in this case;
the reaction took place smoothly with two equivalents of
Me4N·BH4 in EtOH/C6H6 under argon to give iridium tetra-
1
hydride complexes 3a–c in high yields. H NMR spectra of
Scheme 1. Preparation of iridium complexes 2a–c.
À
3a and 3b showed single broad signals corresponding to Ir
H with 4H integration at around d=À10 ppm, whereas that
of 3c showed two separated broad signals at d=À9.5 (3H)
and À11.5 ppm (1H). IR spectra of 3a–c showed two in-
tense Ir–H absorptions at 1969 and 1911 cmÀ1, respectively,
for 3a, 1983 and 1905 cmÀ1 for 3b, and 2026 and 1888 cmÀ1
for 3c.[15] Molecular structures of 3a and 3c were established
by X-ray diffraction. Figure 1 shows the molecular structure
2
H signals as triplets with small J
(P,H) values of 14 Hz at
around d=À23 ppm, which suggests a cis relationship of the
H and the two P atoms. Complex 2a has already been re-
ported by Turculet and co-workers and its molecular struc-
ture was established by X-ray analysis.[10b] Based on the sim-
1
ilarity of the H NMR spectra, stereochemistry of 2b and 2c
is probably the same as that of 2a as shown in Scheme 1.
NMR spectroscopic analysis of the crude mixture suggested
a possible existence of stereoisomers for at least 2a and 2c;
of 3c. Recently, the molecular structure of [IrH4ACHTUNGTRENNUNG(PCP)]
(PCP= k3-1,3-(CH2PtBu2)2C6H3) in the solid state was de-
termined by neutron diffraction, and the positions of four Ir-
bonded hydrogen atoms were unambiguously established.[15]
1
À
small triplet signals in the H NMR spectra in the Ir H
region (d=À29.63 ppm (2J
G
For 3c, four Ir H atoms could be located in the difference
À
À41.20 ppm (2J
G
map by the X-ray analysis and their positions agree well
nals in 31P NMR spectra (d=49.0 for 2a and 72.0 ppm for
2c) were observed, although the structure of the minor spe-
cies could not be established. Recently, Sola and co-workers
reported a detailed study on related complexes [IrX(H)-
with those of [Ir(H)4ACHTUNGETRN(UNG PCP)]. Furthermore, we performed
DFT calculations on the structure of 3c and could repro-
duce the structure determined by X-ray analysis including
the position of the iridium-bonded hydrogen atoms reasona-
bly. Complexes 3a and 3b are thermally stable; for example,
no change was observed upon heating a [D8]toluene solution
of 3a under argon at 1008C for three days. On the other
hand, 3c gradually changes into a new complex in solution
even at room temperature.[16]
ACHTUNGTRENNUNG ACHUTNTGREN{NUNG (CH2)3PPh2}2; X=Cl, Br,
(biPSi)] (biPSi=k3-P, P’,Si-Si(Me)
I), which showed equilibrium between anti/syn isomers (rel-
À
ative stereochemistry of the methyl group (Si Me) and the
À
hydrido group (Ir H): anti/syn 93:7 in C6D6 for [IrCl(H)-
(biPSi)]).[13] On the other hand, isolated 2a–c (anti isomers)
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S. Shimada et al.
FULL PAPERS
mer-4a was obtained in high yield if the reduction of 2a was
performed by using only one equivalent of Me4N·BH4 under
À
N2. Two Ir H signals at d=À13.40 and À10.09 ppm in the
1H NMR spectrum appeared as doublets of triplets (2J-
2
G
N
gests that each hydrogen atom is in a cis position with re-
spect to the two phosphorus atoms. Therefore, the structure
of mer-4a in solution seems to be the same to that in the
solid state.
The same dinitrogen complex mer-4a was also formed on
heating the tetrahydride complex 3a at 658C under a nitro-
gen atmosphere in a sealed NMR tube, although conversion
was low (ca. 10%). On the other hand, the reduction of 2a
with Me4N·BH4 under nitrogen or argon with small nitrogen
contamination sometimes afforded another complex
(31P NMR: d=43.0 ppm) in addition to 3a (31P NMR: d=
50.4 ppm) and mer-4a (31P NMR: d=53.2 ppm) in varying
quantities. Although the amount of the third complex was
very small in most cases, it was formed in a similar quantity
to that of mer-4a in a few cases. Fortunately, we could get a
small amount of single crystals of the third product from the
mixtures. To our surprise, the third product proved to be
also an iridium dihydride dinitrogen complex, fac-4a, by X-
ray diffraction, in which the PSiP ligand coordinated to the
iridium in a facial orientation as shown in Figure 2b. This
result suggests good flexibility of the PSiP ligand. At the
moment, we are unable to clarify the factor that affects the
Figure 1. Thermal ellipsoid plots (50% probability level for Ir, P, Si, and
C atoms) of 3c. Hydrogen atoms bonded to carbon atoms are omitted
À
for clarity. Selected bond lengths [ꢂ] and angles [8]: Ir1 P1: 2.3203(6),
À
À
À
À
Ir1 P2: 2.3207(6), Ir1 Si1: 2.3413(6), Ir1 H48: 1.59(3), Ir1 H49: 1.43(4),
À
À
Ir1 H50: 1.60(3), Ir1 H51: 1.49(3); P1-Ir1-P2: 166.13(2), P1-Ir1-Si1:
86.29(2), P2-Ir1-Si1: 86.56(2), Si1-Ir1-H50: 65.4(12), Si1-Ir1-H51:
63.7(14), H48-Ir1-H49: 79(2), H48-Ir1-H50: 80.5(16), H49-Ir1-H51: 72(2).
When the same reduction of 2a with Me4N·BH4 was con-
ducted under nitrogen instead of argon, a new complex was
1
obtained in addition to 3a. The H NMR spectrum of the
À
new complex showed two Ir H signals 1H integration, re-
1
spectively, which suggests it is an iridium dihydride complex.
X-ray structural analysis revealed that the new complex is
an iridium dihydride dinitrogen complex mer-4a. As shown
in Figure 2a, the PSiP ligand coordinates to the iridium
center in a meridional orientation. The dinitrogen complex
ratio of mer/fac isomers. The H NMR spectrum of fac-4a
À
showed one Ir H signal with 2H integration at d=
À11.80 ppm as a doublet of doublets (2J
ACHTUNGTRENUN(NG P,H)=19 and
102 Hz), which suggests that the hydrogen atom is in a cis
position with respect to one phosphorus atom and in a trans
position with respect to the
other phosphorus atom. There-
fore, the structure of fac-4a in
solution seems to be similar to
that in the solid state. Similar
dinitrogen complexes mer-4b
(31P NMR: d=63.4 ppm) and
fac-4b
(31P NMR:
d=
50.1 ppm) were also formed
from 2b or 3b, although fac-4b
could not be isolated and only
identified from the similarity
of its NMR spectra (1H NMR:
d=À11.94 ppm (dd, 2H, 2J-
À
AHCTUNGERTG(NNUN P,H)=20, 102 Hz; Ir H)) to
those of fac-4a. On the other
hand, we did not observe the
formation of a dinitrogen com-
plex for the tBu derivative.
Complexes 4a and 4b are
rare examples of stable IrIII–di-
nitrogen complexes. It is
known that IrIII complexes
Figure 2. Thermal ellipsoid plots (50% probability level for Ir, P, Si, and C atoms) of a) mer-4a and b) fac-4a.
For mer-4a, one of two independent molecules in the unit cell is shown. Hydrogen atoms bonded to carbon
atoms are omitted for clarity. Terminal nitrogen atom (N2) in each isomer disordered in two positions and
only one of the disordered atoms is shown for clarity. Selected bond lengths [ꢂ] and angles [8]: For mer-4a:
À
À
À
À
À
À
À
À
Ir1 P1: 2.2903(9), Ir1 P2: 2.2915(9), Ir1 Si1: 2.3736(7), Ir1 N1: 1.910(3); P1 Ir1 P2: 155.94(2), P1 Ir1 Si1:
À
À
À
À
À
À
À
À
À
84.81(3), P1 Ir1 N1: 101.66(12), P2 Ir1- Si1: 84.65(2), P2 Ir1 N1: 101.60(12), Si1 Ir1 N1: 101.40(10), H56
À
À
À
À
À
À
À
Ir1 H57: 82(2); for fac-4a: Ir1 P1: 2.3366(7), Ir1 P2: 2.3430(7), Ir1 Si1: 2.3574(6), Ir1 N1: 1.937(3); P1 Ir1
bearing
a
tripyrazolylborate
À
À
À
À
À
À
À
P2: 104.98(2), P1 Ir1 Si1: 85.49(2), P1 Ir1 N1: 102.34(8), P2 Ir1 Si1: 83.61(2), P2-Ir1-N1: 102.86(8), Si1
À
Ir1 N1: 167.95(8).
ligand form stable IrIII–dinitro-
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Chem. Asian J. 2011, 6, 2512 – 2521

Hydridoiridium Complexes
1
gen complexes,[17] whereas other examples are usually unsta-
ble.[18] For iridium complexes bearing pincer-type ligands,
IrI–dinitrogen complexes are well known,[19] whereas no
IrIII–dinitrogen complex is reported. As shown in Figure 2a,
in mer-4a a weakly coordinating dinitrogen ligand occupies
the position trans to the hydride ligand but not the silyl
ligand. Silyl ligands generally have a stronger trans influence
than hydride ligands and, therefore, the dinitrogen ligand is
usually expected to occupy the position trans to the silyl
ligand as in fac-4a. Complex mer-4a is very stable; after
heating a [D8]toluene solution of mer-4a at 1508C under
argon for one day, approximately 80% of mer-4a remained
with the formation of several uncharacterized complexes as
dride ligand judging from the H NMR spectrum of the re-
2
action mixture and showed two signals at d=À67.1 (t, J-
2
(P,P)=104 Hz; PMe3) and 44.2 ppm (d, J
E
an 1:2 ratio in the 31P NMR spectrum, the J
2
which is much larger than that of 5 (18 Hz). The 2J
ACHTUNGTRENNUNG
value of 104 Hz is similar to those of trigonal bipyramidal
[Ir(CO)(H)L3] (L=phosphine ligands), in which three phos-
phine ligands occupy the equatorial positions.[20] Although
the other product could not be isolated in pure form, crys-
tallization of a mixture of two products from pentane af-
forded a mixture of single crystals of the two compounds. X-
ray structure analysis of several crystals revealed the molec-
ular structure of the minor product to be 6 as shown in
Scheme 3. Complex 6 is an iridium(I)–dinitrogen complex
1
judged from H and 31P NMR spectra.
Replacement of the dinitrogen ligand of mer-4a with a
phosphine ligand was examined. Treatment of mer-4a with
an excess of PMe3 in [D8]toluene in an evacuated sealed
NMR tube at 1008C for two days resulted in partial conver-
sion of mer-4a (ca. 30%) to two new complexes. Further
heating at 1508C for 1.5 days was required for the complete
conversion. The same reaction under a N2 atmosphere at
1508C for two days on a larger scale afforded the new com-
plexes in an approximately 2:1 ratio by 31P NMR spectro-
scopic integration. The major product was isolated and its
structure was identified to be the expected iridium dihydride
Scheme 3. Reaction of mer-4a with PMe3.
À
phosphine complex 5. It shows two Ir H signals at d=
with PMe3 instead of two hydride ligands in the starting
complex. As shown in Figure 4, 6 has a trigonal bipyramidal
orientation with three phosphorus atoms at equatorial posi-
tions, which is consistent with the 31P NMR spectrum de-
À15.44 (dt, 2J
ACHTUNGTRENNUNG
1
ACHTUNGTRENNUNG(P,H)=27, 14 Hz) in the H NMR spectrum and two signals
2
2
at d=À65.1 (t, J
ACHTUNGTRENNUNG(P,P)=18 Hz; PMe3) and 48.4 ppm (d, J-
N
scribed above. Recently, [IrI
free complex of 6, was reported.[10d] Interestingly, [IrI
(PSiP-Cy)] was obtained in a high yield by the reaction of
ACHUTGTNERNNUG(PMe3)ACHTUNGTRENNUNG
vealed that complex 5 has a similar configuration to mer-4a
with PMe3 occupying the same position as N2 (Figure 3).
The above NMR spectroscopic data are consistent with the
solid-state structure. The minor product does not have a hy-
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
2a with Me3SiCH2Li and subsequent treatment with PMe3
under a nitrogen atmosphere. There is no description in the
paper regarding possible formation of complex 6. These re-
Figure 4. Thermal ellipsoid plots (40% probability level for Ir, P, Si, N,
and C atoms) of complex 6. Hydrogen atoms are omitted for clarity. Se-
À
À
Figure 3. Thermal ellipsoid plots (50% probability level for Ir, P, Si, and
C atoms) of complex 5. Hydrogen atoms bonded to carbon atoms are
lected bond lengths [ꢂ] and angles [8]: Ir1 P1: 2.3251(9), Ir1 P2:
À
À
À
À
2.3245(9), Ir1 P3: 2.2806(10), Ir1 Si1: 2.4081(9), Ir1 N1: 1.907(4), N1
À
À
À
À
À
À
À
omitted for clarity. Selected bond lengths [ꢂ] and angles [8]: Ir1 P1:
N2: 1.150(4); P1 Ir1 P2: 122.73(3), P1 Ir1 P3: 118.00(3), P1 Ir1 Si1:
81.90(3), P1 Ir1 N1: 93.99(12), P2-Ir1-P3: 117.61(3), P2 Ir1 Si1:
81.41(3), P2 Ir1 N1: 95.83(12), P3 Ir1 Si1: 94.39(3), P3 Ir1 N1:
92.95(12), Si1 Ir1 N1: 172.62(12), Ir1 N1 N2: 179.2(3).
À
À
À
À
À
À
À
À
2.2943(4), Ir1 P2: 2.2901(4), Ir1 P3: 2.3252(5), Ir1 Si1: 2.3675(6); P1
À
À
À
À
À
À
À
À
À
À
À
Ir1 P2: 150.273(17), P1 Ir1 P3: 104.695(16), P2 Ir1 P3: 104.813(16),
P1 Ir1 Si1: 83.700(15), P2 Ir1 Si1: 83.610(18), P3 Ir1 Si1: 108.65(2).
À
À
À
À
À
À
À
À
À
À
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S. Shimada et al.
FULL PAPERS
sults probably suggest that 6 was produced from mer-4a
without dissociation of the dinitrogen ligand.
Complex 6 has a similar structure to a iridium–dinitrogen
complex bearing a tetradentate tris(phosphino)silyl ligand,
[Ir(N2)k4-P,P’,P’’,Si-{Si(o-C6H4PiPr2)3}] (7).[7b] The similarity
of complexes 6 and 7 suggests that the connection of the
third phosphorus moiety to the silicon atom as in the k4-
P, P’,P’’,Si-{Si(o-C6H4PiPr2)3}À ligand is not essential for the
formation of trigonal bipyramidal iridium–dinitrogen com-
À À
plexes. The sum of the three P Ir P angles in 6 (358.38) is
À À
nearer to 3608 than that in 7 (354.98), whereas the Si Ir N
angle in 6 (172.68) is less straight than that in 7 (177.18).
Marked differences in the structural parameters of 6 and 7
À
were found in some bond lengths; the Ir Si bond length in 6
(2.4081(9) ꢂ) is much longer than that in 7 (2.304(2) ꢂ),
À
whereas the Ir N bond length in 6 (1.907(4) ꢂ) is much
shorter than that in 7 (2.033(4) ꢂ). These differences are re-
Scheme 4. Reaction of complexes 3a–c with nbe or tbe/benzene and 9a
with PPh3.
À
flected in the N N bond lengths, which in 6 (1.150(4) ꢂ) is
longer than that in 7 (1.094(4) ꢂ).
Reaction of mer-4a with PPh3 in [D8]toluene proceeded
when the mixture was heated up to 1008C (ca. 20% conver-
sion) in a sealed evacuated NMR tube to probably give a
similar complex to 5 judging from the 1H and 31P NMR
spectra of the reaction mixture (1H NMR: d=À15.75 (dt,
1H, 2J
A
(P,H)=112, 21 Hz; Ir H), À10.26 ppm (dt, 1H, 2J-
À
(P,H)=24, 15 Hz; Ir H); 31P NMR: d=12.0 (t, 2J
E
À
2
15 Hz; PPh3), 42.1 ppm (d, J
N
heating at 1508C for two days decreased the amount of the
PPh3-bound complex to approximately 5%, and unexpected-
ly formed fac-4a as a main product (ca. 60%). On the other
hand, when the same reaction at 1508C (toluene, 3 days)
was conducted under a N2 atmosphere, mainly a 1:1:1 mix-
ture of mer-4a, fac-4a, and a new complex was obtained.
The new complex is probably a trigonal bipyramidal IrI–di-
nitrogen complex similar to 6, judging from its 31P NMR
spectroscopic signals (d=3.8 (t, 2J
N
2
40.1 ppm (d, J
N
Complexes 3a–c can be used as precursors of IrI species
by the reaction with alkenes, such as norbornene (nbe) and
3,3-dimethylbutene (tbe). In the case of nbe, the reaction of
3a with three equivalents of nbe took place at room temper-
ature to afford the IrI–nbe adduct 8 in nearly quantitative
yield as an orange powder (Scheme 4). Recently, a related
ethylene complex was prepared by the reaction of 2a with
Me3SiCH2Li and subsequent treatment with ethylene,
whereas its molecular structure was not determined.[10d] As
shown in Figure 5, the Ir center of 8 considerably distorted
from the square-planar configuration as observed for a relat-
À
Figure 5. Thermal ellipsoid plots (50% probability level for Ir, P, Si, and
C atoms) of complex 8. Hydrogen atoms are omitted for clarity. Selected
À
À
bond lengths [ꢂ] and angles [8]: Ir1 P1: 2.2824(6), Ir1 P2: 2.2775(7),
À
À
À
À
Ir1 Si1: 2.3201(8), Ir1 C38: 2.181(3), Ir1 C39: 2.191(3), C38 C39:
À
À
À
À
1.433(4); P1-Ir1-P2: 137.21(3), P1 Ir1 Si1: 80.55(3), P1 Ir1 C38:
À
À
À
À
À
À
89.27(7), P1 Ir1 C39: 126.61(8), P2 Ir1 Si1: 80.51(3), P2 Ir1 C38:
À
À
À
À
125.77(7), P2 Ir1 C39: 88.46(8), Si1 Ir1 C38: 145.91(8), Si11-Ir1-C39:
À
À
À
À
145.40(8), Ir1-C38-C43: 120.0(2), Ir1 C38 H38: 109(3), Ir1 C39 C40:
À
À
À
À
À
À
120.1(2), Ir1 C39 H39: 112.5(19), C39 C38 C43: 105.4(2), C39 C38
À
À
À
À
À
H38: 122.9(18), C43 C38 H38: 119(2), C38 C39 C40: 105.7(3), C38
C39 H39: 119.6(17), C40 C39 H39: 119.1(17).
À
À
À
ed complex [RhI (PSiP-Cy)].[10d] The nbe C C double
ACHTUNGTRENNUNG(PMe3)ACHTUNGTRENNUGN
bond was significantly elongated (1.433(4) ꢂ) compared to
that of uncoordinated nbe (1.334(1) ꢂ), which suggests a
strong p-back donation.[21] On the other hand, 1H and
31P NMR spectra of complex 8 in C6D6 solution showed the
presence of two species in an approximately 3:2 ratio (in the
31P NMR spectrum at d=62.8 (s) and 61.1 ppm (brs)). The
ratio did not change depending on the samples (crude mix-
ture or recrystallized sample). These observations probably
suggest that complex 8 exists as an equilibrium mixture of
two isomeric forms in solution.
The reaction of 3a–c with an excess of tbe did not afford
isolable IrI–tbe complexes, probably because tbe is too
bulky to form a stable olefin complex. When the reaction
À
was performed in benzene, a facile C H bond activation
took place at room temperature for 3a and 3b or at 508C
for 3c to give [Ir(H)Ph
ACHTUNGTRENNUNG
2516
www.chemasianj.org
ꢁ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Asian J. 2011, 6, 2512 – 2521

Hydridoiridium Complexes
quantitatively (Scheme 4). The same complex 9a has already
been reported by Turculet and co-workers by the reaction of
2a with MeLi in benzene.[10b] Because the molecular struc-
ture of 9a has not been determined by X-ray diffraction, we
tried to obtain single crystals of these complexes and suc-
ceeded to determine the molecular structure of 9c
(Figure 6). Although the position of the hydride ligand
could not be determined, the configuration of the Ir center
would be distorted square-based pyramidal with the Si atom
at the apical position or distorted trigonal bipyramidal with
Si, C, and H atoms at the equatorial positions.[22]
Figure 7. Thermal ellipsoid plots (50% probability level for Ir, P, Si, and
C atoms) of complex 10. One of two independent molecules in the unit
cell is shown. Hydrogen atoms are omitted for clarity. Selected bond
lengths [ꢂ] and angles [8] (two values for both independent molecules
À
À
are shown): Ir1 P1: 2.3343(14), 2.3326(13), Ir1 P2: 2.3706(12),
À
À
2.3885(12), Ir1 P3: 2.4512(15), 2.4402(14), Ir1 Si1: 2.3031(16),
À
À
À
2.3033(14), Ir1 C39: 2.104(6), 2.112(5); P1 Ir1 P2: 103.25(4), 105.53(4),
P1 Ir1 P3: 111.76(5), 110.29(5), P2 Ir1 P3: 110.50(4), 108.93(4), P1
Ir1 Si1: 85.10(5), 85.23(5), P2-Ir1-Si1: 84.02(5), 83.07(4), P3 Ir1 Si1:
153.25(5), 155.92(5), P3 Ir1 C39: 66.19(17), 66.87(16), Ir1 P3 C38:
83.5(2), 83.49(19), P3 C38 C39: 101.8(4), 102.6(4), Ir1 C39 C38:
108.5(4), 107.0(3).
À
À
À
À
À
À
À
À
À
À
À À
À
À
À
À
À
Table 1. C H borylation of benzene with bis(pinacolato)diboron cata-
lyzed by complexes 9a–c.[a]
Figure 6. Thermal ellipsoid plots (50% probability level for Ir, P, Si, and
C atoms) of complex 9c. One of three independent molecules in the unit
cell is shown. Hydrogen atoms bonded to carbon atoms are omitted for
À
À
clarity. Selected bond lengths [ꢂ] and angles [8]: Ir1 P1: 2.3249(14), Ir1
Entry
Catalyst
Amount [mol%]
Yield [%][b]
À
À
P2: 2.3267(13), Ir1 Si1: 2.2656(14), Ir1 C30: 2.135(5); P1-Ir1-P2:
1
2
3
4
9a
9b
9c
9c
5
5
5
1
65
20
88
82
À
À
À
À
À
À
159.70(5), P1 Ir1 Si1: 85.19(5), P1 Ir1 C30: 100.97(14), P2 Ir1 Si1:
85.80(5), P2 Ir1 C30: 99.04(14), Si1 Ir1 C30: 126.04(14).
À
À
À
À
[a] Reaction conditions: diboron (0.40 mmol), benzene (2 mL), 1208C,
24 h in a sealed tube. [b] Determined by 1H NMR spectroscopic analysis
of the crude mixture by using 1,4-dioxane as an internal standard.
Complex 9a reacted with triphenylphosphane with an
elimination of benzene to form an ortho-metalated triphe-
nylphosphane complex 10 (Scheme 4). The reaction slowly
took place even at room temperature and heating at 608C
resulted in the complete conversion of 3a to give 10 as a
main product (61% isolated yield). As shown in Figure 7,
complex 10 has a distorted octahedral Ir center with the
Conclusions
À
PSiP ligand in a facial orientation. The Ir1 P3 length (2.44–
The study described here clearly showed some unique char-
À
2.45 ꢂ) is considerably longer than the Ir1 P1 (2.33 ꢂ) and
acter of the tridentate pincer-type bis(phosphino)silyl ligand
À
À
À
Ir1 P2 (2.37–2.39 ꢂ) lengths. Also the former is much
([{2-(R2P)C6H4}2MeSi] , PSiP R, R=Cy, iPr, or tBu) in the
À
longer than the Ir P lengths in related iridaphosphacyclobu-
chemistry of hydridoiridium complexes. Hydridoiridium
tene rings (2.25–2.39 ꢂ).[23] This is apparently attributed to
complexes bearing the PSiP R ligand were synthesized by
À
the strong trans influence of the silyl ligand.
the reduction of [IrCl(H)
A
À
Because a facile C H bond activation of benzene took
The reduction of 2a–c with two equivalents of Me4N·BH4
under an argon atmosphere afforded tetrahydride complexes
3a–c, whereas that of 2a–b with one equivalent of
Me4N·BH4 under a nitrogen atmosphere gave dinitrogen di-
hydride complexes 4a–b. Complexes 4a–b are a rare exam-
ple of stable IrIII–dinitrogen complexes and the first example
of IrIII–dinitrogen complexes bearing a pincer-type ligand.
place, a catalytic borylation reaction of benzene with bis(pi-
nacolato)diboron was examined by using complexes 9a–c as
a catalyst.[24] As shown in Table 1, catalytic benzene boryla-
tion took place at 1208C. Among 9a–c, 9c is most efficient
and only 1 mol% of 9c afforded 2-phenyl-4,4,5,5-tetrameth-
yl-1,3,2-dioxaborolane (11) in high yield (Table 1, entry 4).
Chem. Asian J. 2011, 6, 2512 – 2521
ꢁ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemasianj.org
2517

S. Shimada et al.
FULL PAPERS
afford a white solid, which was recrystallized from hexane to give 1a in
80% yield (2.69 g). 1H and 31P{1H} NMR spectroscopic data were identi-
cal to those in the literature;[10b] 29Si{1H} NMR (C6D6, 99.1 MHz): d=
ACHTUNGTREN(NUNG P,Si)=20 Hz); elemental analysis calcd (%) for
C37H56P2Si: C 75.21, H 9.55; found: C 74.76, H 9.56.
Complexes 4a–b were proved to exist in two isomeric forms,
in which the PSiP ligand coordinated to the Ir center in
meridional and facial orientations, respectively; this showed
good flexibility of the PSiP ligand. These dinitrogen com-
plexes are unusually stable and did not decompose consider-
ably by heating even at 1508C. The stability of the dinitoro-
gen complexes also reflected in the attempted replacement
of the dinitrogen ligand of mer-4a with PMe3, which re-
quired heating at 1508C for the complete conversion to give
the expected replacement product 5 and an unexpected IrI–
dinitrogen complex 6. PSiP–IrI complexes can be readily
generated from the tetrahydride complexes 3a–c by treat-
ment with alkenes and are active for the cleavage of ben-
À23.6 ppm (t, 3J
Product (2-iPr2PC6H4)2SiHMe (1b)
Compound 1b was prepared from 2-iPr2PC6H4Br[26] (1.42 g, 5.20 mmol)
and MeHSiCl2 (267 mL, 2.6 mmol) by a similar procedure to that de-
scribed above for 1a. The crude product was almost quantitatively (1.1 g)
obtained as a viscous, air-sensitive colorless liquid, which was used for
the preparation of 2b without further purification. 1H NMR (C6D6,
499.1 MHz): d=0.85–0.90 (m, 12H), 0.94 (d, 3H, J=4 Hz), 1.08–1.13 (m,
12H), 1.86–2.03 (m, 4H), 6.28 (quasi octet, 1H, J=3, 1J
ACHTNUTRGNEUNG(Si,H)=208 Hz),
7.13–7.20 (m, 4H), 7.37 (d, 2H, J=7 Hz), 7.73 ppm (d, 2H, J=7 Hz);
31P{1H} NMR (C6D6, 202.0 MHz): d=0.6 ppm (s); 29Si{1H} NMR (C6D6,
À
99.1 MHz): d=À24.0 ppm (t, 3J
(P,Si)=19 Hz); 29Si NMR (C6D6,
ACHTUNGTRENNUNG
ACHTUNGTREN(NGNU H,Si)=209 Hz).
zene C H bond; treatment of 3a with three equivalents of
nbe afforded a stable IrI–nbe complex 8, whereas that of
3a–c with two or more equivalents of tbe gave benzene ad-
99.1 MHz): d=À24.0 ppm (brd, J
1
Product (2-tBu2PC6H4)2SiHMe (1c)
dition products [Ir(H)PhACTHNURGTNE(UNG PSiP-R)] 9a–c. A preliminary
Compound 1c was prepared from 2-tBu2PC6H4Br (4.89 g, 16.2 mmol) and
MeHSiCl2 (0.834 mL, 8.12 mmol) by the similar procedure to that de-
scribed above for 1a. The crude product was almost quantitatively
(3.95 g) obtained as a viscous, air-sensitive colorless liquid, which was
used for the preparation of 2c without further purification. 1H NMR
(C6D6, 499.1 MHz): d=0.92 (d, 3H, J=4 Hz), 1.17 (d, 18H, J=3 Hz),
study on the catalytic application of these complexes
showed complexes 9a–c had good catalytic activity for the
borylation reaction of benzene with bis(pinacolato)diboron,
which suggests a high potential for the PSiP ligand in cataly-
sis.
1.19 (d, 18H, J=3 Hz), 6.44 (quasi octet, 1H, 1J
ACTHNUTRGNEUNG(H,Si)=216 Hz), 7.14–
7.18 (m, 4H), 7.73–7.78 ppm (m, 4H); 31P{1H} NMR (C6D6, 202.0 MHz):
d=23.2 ppm (s); 29Si{1H} NMR (C6D6, 99.1 MHz): d=À24.0 ppm (t, 3J-
A
Experimental Section
AHCTUNGTRENNUNG
General Procedures
AHCTUNGTREG(NNUN PSiP-Cy)] (2a)
All manipulations of air-sensitive materials were carried out under an
argon or nitrogen atmosphere by using standard Schlenk techniques or in
a glovebox. C6D6, [D8]toluene, and [D8]THF were distilled from Na/ben-
zophenone ketyl. All other anhydrous solvents were purchased from
Kanto Chemicals or Aldrich and vacuum-transferred prior to use. 1H,
29Si, and 31P NMR spectra were recorded on Jeol LA500 spectrometer.
Chemical shifts are given in ppm by using external references (tetrame-
thylsilane (d=0 ppm) for 1H and 29Si, and 85% H3PO4 (d=0 ppm) for
31P) and coupling constants were reported in hertz. Unless otherwise
noted, NMR spectra were measured at room temperature.
AHCTUNGTRENNUNG
uene solution (30 mL) of 1a (4.1 g, 6.95 mmol). The mixture was heated
at 708C for 24 h. Volatiles were removed under vacuum and the residue
was washed with hexane (3ꢃ5 mL) to give 2a as a yellow powder (5.13 g,
90%). NMR spectroscopic data were identical to those in the literatur-
e.[10b]
Product [IrCl(H)
ACHTUNGTREN(NGNU PSiP-iPr)] (2b)
Compound 2b was prepared from 1b (2.28 g, 5.42 mmol) and [IrClACHTUNGTRENNUNG(cod)]2
(1.83 g, 2.71 mmol) by a similar procedure to that described above for 2a
in 90% yield (3.21 g). IR (KBr): n˜ =2221 cmÀ1 (s, IrH); 1H NMR (C6D6,
Product (2-BrC6H4)tBu2P
499.1 MHz): d=À23.89 (t, 1H, 2J
ACHTUNGTRNE(NUNG P,H)=14 Hz), 0.75 (s, 3H), 0.84 (q,
This compound was prepared by a similar procedure to that reported for
6H, J=7 Hz), 1.06 (q, 6H, J=7 Hz), 1.25–1.38 (m, 12H), 2.59–2.69 (m,
2H), 3.00–3.10 (m, 2H), 7.08 (t, 2H, J=7 Hz), 7.19 (t, 2H, J=7 Hz),
7.25–7.30 (m, 2H), 7.96 ppm (d, 2H, J=7 Hz); 31P{1H} NMR (C6D6,
202.0 MHz): d=69.0 ppm (s); 29Si{1H} NMR (C6D6, 99.1 MHz): d=
8.8 ppm (s); elemental analysis calcd (%) for C25H40SiP2IrCl: C 45.61, H
6.14; found: C 45.94, H 6.08.
the preparation of (2-BrC6H4)Cy2P. [25] A mixture of Pd
ACHTUNGTRENNUNG
0.02 mmol),
0.024 mmol), and Cs2CO3 (393 mg, 1.2 mmol) in 1,4-dioxane (3 mL) was
stirred for 1 h at room temperature under N2. Then 2-bromoiodobenzene
(284 mg, 1.0 mmol) and tBu2PH (146 mg, 1.0 mmol) were added by sy-
ringe. The mixture was stirred at 808C for 3 days and then allowed to
cool to room temperature, filtered, and concentrated. The crude product
was purified by flash column chromatography on silica gel to afford the
title compound as a colorless solid (150 mg, 50%). 1H NMR (C6D6,
499.1 MHz): d=1.15 (d, 18H, J=11 Hz), 6.73 (t, 1H, J=7 Hz), 6.91 (t,
1H, J=7 Hz), 7.53 (dd, 1H, J=8, J=4 Hz), 7.64 ppm (d, 1H, J=7 Hz);
31P{1H} NMR (C6D6, 202.0 MHz): d=32.29 ppm (s); elemental analysis
calcd (%) for C14H22PBr: C 55.83, H 7.36; found: C 56.02, H 7.44.
Product [IrCl(H)
ACHTUNGTREN(NGNU PSiP-tBu)] (2c)
Compound 2c was prepared from 1c (3.65 g, 7.50 mmol) and [IrClACHTUNGTRENNUNG(cod)]2
(2.53 g, 3.75 mmol) by a similar procedure to that described above for 2a
in 90% yield (4.82 g) as an isomeric mixture (2c/isomer 1:0.2) as a
yellow solid. 1H NMR (C6D6, 499.1 MHz): for the major isomer d=
2
À23.69 (t, 1H, J
ACHUTGTNRNEUG(N P,H)=14 Hz), 0.86 (s, 3H), 1.39 (t, 18H, JACHTUNTGREN(NUNG P,H)=7 Hz),
1.55 (t, 18H, JACTHNUGRTNEUNG(P,H)=7 Hz), 7.03 (t, 2H, J=8 Hz), 7.16 (t, 2H, J=8 Hz),
Product {2-(c-C6H11)2PC6H4}2SiHMe (1a)
7.67 (brd, 2H, J=8 Hz), 8.00 ppm (d, 2H, J=8 Hz); characteristic signals
for the minor isomer d=À41.20 (t, 1H, 2J
ACHTUNGERTN(NUNG P,H)=13 Hz; IrH), 0.26 (s;
nBuLi (7.2 mL, 1.59m in hexane, 11.3 mmol) was added dropwise to an
Et2O solution (30 mL) of 2-Cy2PC6H4Br (4.00 g, 11.3 mmol) at À788C.
The mixture was allowed to warm to room temperature over the course
of 1 h. Then the mixture was cooled to À788C and MeHSiCl2 (0.58 mL,
5.7 mmol) was added by syringe. The resulting pale-yellow solution was
allowed to warm to room temperature and stirred for 14 h. Volatiles
were removed under vacuum and the residue was extracted with benzene
(15 mL) and filtered. The filtrate was concentrated under vacuum to
SiCH3), 7.78 (brd, J=8 Hz), 8.21 ppm (d, J=7 Hz); 31P{1H} NMR (C6D6,
202.0 MHz): d=78.5 (s, major), 72.0 ppm (s, minor); 29Si{1H} NMR
(C6D6, 99.1 MHz, inept): d=7.5 ppm (s; SiMe, major); IR (KBr): n˜ =
2224 cmÀ1 (s, IrH); elemental analysis calcd (%) for C29H48SiP2IrCl: C
48.76, H 6.77; found: C 48.97, H 6.69.
2518
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ꢁ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Asian J. 2011, 6, 2512 – 2521

Hydridoiridium Complexes
Product [Ir(H)
G
7 Hz); 31P{1H} NMR (C6D6, 202.0 MHz): d=63.4 ppm (s); 29Si{1H} NMR
(C6D6, 99.1 MHz): d=34.8 ppm (s).
Complex 2a (3.0 g, 3.6 mmol) and (NMe4)BH4 (640 mg, 7.2 mmol) in a
mixture of ethanol (15 mL) and benzene (30 mL) were stirred at room
temperature under Ar for 6 h and then at 658C for 10 h. Volatiles were
removed under vacuum and the residue was extracted with benzene
(30 mL). The benzene extracts were filtered and concentrated under
vacuum to afford a light-yellow solid. The solid was washed with ethanol
(3ꢃ10 mL) and hexane (3ꢃ10 mL) and dried under vacuum to give 3a
(2.54 g, 90%) as a white solid. IR (KBr): n˜ =1969 (s, IrH), 1911 cmÀ1 (s,
IrH); 1H NMR (C6D6, 499.1 MHz): d=À10.40 (brs, 4H), 1.13 (s, 3H),
0.81–1.87 (m, 38H), 2.04–2.18 (m, 4H), 2.41 (brd, 2H), 7.10 (t, 2H, J=
7 Hz), 7.25 (t, 2H, J=7 Hz), 7.40–7.44 (m, 2H), 8.15 ppm (d, 2H, J=
7 Hz); 31P{1H} NMR (C6D6, 202.0 MHz): d=50.4 ppm (s); 29Si{1H} NMR
([D8]THF, 99.1 MHz): d=28.4 ppm (s); elemental analysis calcd (%) for
C37H59SiP2Ir: C 56.52, H 7.58; found: C 56.91, H 7.55.
Product [Ir(H)2ACTHNUGTRENNUG(PMe3)ACHTUNGTRNEN(UGN PSiP-Cy)] (5)
PMe3 (76 mL, 0.74 mmol) was added to a solution of mer-4a (400 mg,
0.493 mmol) in toluene (10 mL). The mixture was heated at 1508C for
2 days under nitrogen to give a mixture of 5 and 6 in an approximately
2:1 ratio by 31P NMR spectroscopic integration. Volatiles were removed
under vacuum and the residue was washed with pentane (3ꢃ5 mL) af-
fording 5 as a white solid in 50% yield (211 mg). IR (KBr): n˜ =2072 (s,
IrH), 1856 cmÀ1 (s, IrH); 1H NMR (C6D6, 499.1 MHz): d=À15.44 (dt,
1H, 2J
A
ACHTUNGERTN(NUNG P,H)=27, 14 Hz), 0.51 (q,
2H, J=12 Hz), 0.70–0.82 (m, 2H), 1.17 (s, 3H; SiMe), 1.58 (d, 9H, J=
7 Hz; PMe3), 1.07–1.87 (m, 28H), 1.92–2.05 (m, 6H), 2.16 (brd, 2H, J=
12 Hz), 2.32 (t, 2H, J=11 Hz), 2.45 (q, 2H, J=12 Hz), 7.09 (t, 2H, J=
7 Hz), 7.26 (t, 2H, J=7 Hz), 7.37 (brd, 2H), 8.36 ppm (d, 2H, J=7 Hz);
31P{1H} NMR (C6D6, 202.0 MHz): d=À65.1 (t, J=18 Hz), 48.4 ppm (d,
J=18 Hz); elemental analysis calcd (%) for C40H66SiP3Ir: C 55.84, H
7.75; found: C 55.92, H 7.64.
Product [Ir(H)4ACHTUNGTRENNUNG(PSiP-iPr)] (3b)
Complex 3b was prepared by a similar procedure to that for 3a by using
2b (2.4 g, 3.65 mmol) and (NMe4)BH4 (650 mg, 7.29 mmol). Yield: 1.5 g
(70%); IR (KBr): n˜ =1983 (s, IrH), 1905 cmÀ1 (s, IrH); 1H NMR (C6D6,
499.1 MHz): d=À10.71 (brs, 4H), 0.76 (q, 6H, J=7 Hz), 0.85 (q, 6H,
J=7 Hz), 1.03 (s, 3H), 1.10 (q, 6H, J=7 Hz), 1.22 (q, 6H, J=7 Hz),
1.74–1.84 (m, 2H), 2.05–2.15 (m, 2H), 7.08 (t, 2H, J=7 Hz), 7.22 (t, 2H,
J=7 Hz), 7.21–7.31 (m, 2H), 8.09 ppm (d, 2H, J=7 Hz); 31P{1H} NMR
(C6D6, 202.0 MHz): d=61.2 ppm (s); 29Si{1H} NMR ([D8]THF,
99.1 MHz): d=28.1 ppm (s); elemental analysis calcd (%) for
C25H41SiP2Ir: C 47.97, H 6.94; found: C 47.97, H 6.99.
Product [Ir(N2)ACTHNUGTRENNUG(PMe3)ACHTUNGTRNEN(UGN PSiP-Cy)] (6)
Complex 6 could not be isolated in a pure form. The following spectro-
scopic data were collected by the analysis of a mixture of 5 and 6 ob-
tained from the above reaction. IR (KBr): n˜ =1926 cmÀ1 (s, NꢀN);
31P{1H} NMR (C6D6, 202.0 MHz): d=À67.1 (t, J=104 Hz), 44.2 ppm (d,
J=104 Hz).
Product [IrACTHUNTGRENNUG(nbe)ACHTUNGTREN(NGUN PSiP-Cy)] (8)
Product [Ir(H)4ACHTUNGTRENNUNG(PSiP-tBu)] (3c)
2-Norbornene (144 mg, 1.53 mmol) was added to a solution of complex
3a (400 mg, 0.51 mmol) in benzene (20 mL). The mixture was stirred at
room temperature for 1 day. Volatiles were removed under vacuum, af-
fording 8 as an orange powder quantitatively (445 mg). 1H NMR (C6D6,
499.1 MHz): d=À0.48 (d, 0.4H, J=9 Hz), 0.35 (s, 1.2H; SiCH3), 0.96 (s,
1.8H; SiH3), 0.70–2.45 (m, 47.6H), 2.74 (brs, 1H), 2.95 (brt, 2H, J=
11 Hz), 3.15 (brs, 1H), 3.38 (brs, 1.2H), 3.64 (brs, 0.8H), 7.00–7.20 (m,
2.8H), 7.33 (t, 1.2H, J=7 Hz), 7.50 (d, 1.2H, J=7 Hz), 7.56–7.64 (m,
1.6H), 8.26 ppm (d, 1.2H, J=7 Hz); 31P{1H} NMR (C6D6, 202.0 MHz):
d=61.1 (brs), 62.8 ppm (s); elemental analysis calcd (%) for
C44H65SiP2Ir: C 60.44, H 7.51; found: C 60.63, H 7.52.
Complex 3c was prepared by a similar procedure to that for 3a by using
2c (4.1 g, 5.74 mmol) and (NMe4)BH4 (1.02 g, 11.5 mmol). Yield: 3.9 g
(90%); IR (KBr): n˜ =2026 (m, IrH), 1888 cmÀ1 (m, IrH); 1H NMR
(C6D6, 499.1 MHz): d=À11.50 (brs, 1H), À9.50 (brs, 3H), 0.82 (s, 3H),
1.37 (brs, 18H), 1.45 (t, 18H, J=7 Hz), 7.07 (t, 2H, J=7 Hz), 7.21 (t,
2H, J=7 Hz), 7.85 (brd, 2H, J=7 Hz), 8.10 ppm (d, 2H, J=7 Hz);
31P{1H} NMR (C6D6, 202.0 MHz): d=81.7 ppm (brs); 29Si{1H} NMR
([D8]THF, 99.1 MHz, À708C): d=17.6 ppm (s); elemental analysis calcd
(%) for C29H49SiP2Ir: C 51.22, H 7.28; found: C 51.73, H 7.33.
Product [Ir(H)2(N2)mer-(PSiP-Cy)] (mer-4a)
[Ir(H)(Ph)ACTHNUTRGNE(UNG PSiP-Cy)] (9a)
Complex 2a (320 mg, 0.39 mmol) and (NMe4)BH4 (34 mg, 0.39 mmol) in
a mixture of ethanol (5 mL) and benzene (10 mL) were vigorously stirred
under a nitrogen atmosphere at room temperature for 6 h and then at
658C for 10 h. Volatiles were removed under vacuum and the residue
was washed with ethanol (3ꢃ5 mL) and hexane (3ꢃ3 mL) and dried
under vacuum to give mer-4a as a white powder (270 mg, 85%). IR
tbe (25 mL, 0.19 mmol) was added to a solution of complex 3a (50 mg,
0.06 mmol) in benzene (5 mL). The mixture was stirred at room tempera-
ture for 4 h. Volatiles were removed under vacuum, affording complex
9a as an orange/red solid quantitatively (55 mg). NMR spectroscopic
data were identical to those in the literature.[10b]
1
(KBr): n˜ =2091 (s), 1944 (s), 1886 cmÀ1 (s); H NMR (C6D6, 499.1 MHz):
[Ir(H)(Ph)ACTHNUTRGNE(NUG PSiP-iPr)] (9b)
d=À13.40 (dt, 1H, 2J
G
G
ACHTUNGTRENNUNG ACHTUNGTRENNUNG(P,H)=14 Hz), 1.10 (s, 3H), 0.77–1.93 (m, 36H), 2.15 (q,
(H,H)=3, 2J
Complex 9b was produced as a red solid by a similar procedure to that
for 9a by using 3b (50 mg, 0.080 mmol) and tbe (31 mL, 0.24 mmol).
Yield: 55 mg (quantitative); IR (KBr): n˜ =1944 cmÀ1 (m, IrH); 1H NMR
4H, J=12 Hz), 2.35 (q, 2H, J=12 Hz), 2.43 (brd, 2H, J=12 Hz), 7.10 (t,
2H, J=7 Hz), 7.26 (t, 2H, J=7 Hz), 7.36–7.40 (m, 2H), 8.23 ppm (d, 2H,
J=7 Hz); 31P{1H} NMR (C6D6, 202.0 MHz): d=53.3 ppm (s);
29Si{1H} NMR (C6D6, 99.1 MHz): d=36.5 ppm (s). Both complexes mer-
4a and mer-4b did not give satisfactory elemental analysis results. A re-
lated dinitrogen–iridium complex also gave an unsatisfactory result.[7b]
(C6D6, 499.1 MHz): d=À11.67 (t, 1H, 2J
ACHTUNGERTN(NUNG P,H)=17 Hz), 0.84 (s, 3H),
0.86–1.04 (m, 18H), 1.26 (q, 6H, J=7 Hz), 2.30–2.40 (m, 2H), 2.54–2.65
(m, 2H), 7.01 (t, 1H, J=7 Hz), 7.10 (t, 2H, J=7 Hz), 7.18 (t, 2H, J=
7 Hz), 7.27–7.31 (m, 2H), 7.48 (t, 2H, J=7 Hz), 7.67 (d, 2H, J=7 Hz),
7.96 ppm (d, 2H, J=7 Hz); 31P{1H} NMR (C6D6, 202.0 MHz): d=
65.3 ppm (s); 29Si{1H} NMR (C6D6, 99.1 MHz, inept): d=6.6 ppm (s).
Product [Ir(H)2(N2)ACHTUNGTRENNUNG(PSiP-iPr)] (mer-4b)
Complex 2b (300 mg, 0.46 mmol) and (NMe4)BH4 (40 mg, 0.46 mmol) in
a mixture of ethanol (5 mL) and benzene (10 mL) were vigorously stirred
at room temperature for 6 h and then at 658C for 10 h. Volatiles were re-
moved under vacuum and the residue was extracted with pentane
(40 mL). The pentane extracts were filtered and concentrated under
vacuum to afford mer-4b as a light-yellow solid (270 mg, 90%). IR
Product [Ir(H)(Ph)ACTHNUGRTNEUNG(PSiP-tBu)] (9c)
tbe (114 mL, 0.89 mmol) was added to a solution of complex 3c (200 mg,
0.29 mmol) in benzene (10 mL). The mixture was heated at 508C for
7 days. Volatiles were removed under vacuum affording 9c as a red solid
quantitatively (222 mg). IR (KBr): n˜ =2027 cmÀ1 (m, IrH); 1H NMR
1
2
(KBr): n˜ =2091 (s), 1948 (s), 1874 cmÀ1 (s); H NMR (C6D6, 499.1 MHz):
(C6D6, 499.1 MHz): d=À12.34 (t, 1H, J
ACHTUNGTNER(NUNG P,H)=17 Hz), 0.96 (s, 3H), 1.09
d=À13.71 (dt, 1H, 2J
G
E
(t, 18H, J=7 Hz), 1.43 (t, 18H, J=7 Hz), 7.05 (t, 3H, J=7 Hz), 7.16 (t,
2H, J=7 Hz), 7.42–7.48 (m, 2H), 7.67 (brd, 2H), 7.71 (d, 1H, J=7 Hz),
7.95 (d, 1H, J=8 Hz), 8.03 ppm (d, 2H, J=7 Hz); 31P{1H} NMR (C6D6,
202.0 MHz): d=78.3 ppm (s); 29Si{1H} NMR (C6D6, 99.1 MHz, inept):
2
(H,H)=4, J
N
1.04 (s, 3H), 1.07 (q, 6H, J=7 Hz), 1.26 (q, 6H, J=7 Hz), 2.09–2.19 (m,
4H), 7.07 (t, 2H, J=7 Hz), 7.20–7.25 (m, 4H), 8.17 ppm (d, 2H, J=
Chem. Asian J. 2011, 6, 2512 – 2521
ꢁ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemasianj.org
2519

S. Shimada et al.
FULL PAPERS
Table 2. Crystallographic data for 3a, 3c, mer-4a, fac-4a, 5, 6, 8, 9c, and 10.
3a
3c·C6H6
mer-4a
fac-4a
5·0.5C5H12
6
8·3.5C6H6
9c
10
Shelxl
Crystals
Crystals
Shelxl
Shelxl
Shelxl
Shelxl
Shelxl
Shelxl
formula
Fw
C37H59IrP2Si
786.13
C35H57IrP2Si
760.09
C37H57IrN2P2Si C37H57IrN2P2Si C42.5H72IrP3Si
812.12 812.12 896.26
C40H64IrN2P3Si C65H86IrP2Si
886.19 1149.65
C35H53IrP2Si
756.06
C58H73IrP3Si
1083.44
crystal size
[mm]
0.24ꢃ0.06ꢃ0.04 0.20ꢃ0.15ꢃ0.14 0.24ꢃ0.16ꢃ0.10 0.25ꢃ0.20ꢃ0.16 0.25ꢃ0.17ꢃ0.13 0.22ꢃ0.06ꢃ0.05 0.21ꢃ0.12ꢃ0.12 0.21ꢃ0.16ꢃ0.05 0.39ꢃ0.06ꢃ0.03
crystal system
space group
a [ꢂ]
b [ꢂ]
c [ꢂ]
triclinic
PÀ1
monoclinic
P21/c
11.0921(6)
10.9825(6)
28.6024(15)
90
90.808(1)
90
3484.0(3)
4
monoclinic
P21/c
24.2600(11)
15.5571(7)
20.9815(10)
90
111.695(1)
90
7357.8(6)
8
orthorhombic
Pbca
19.3344(11)
17.4179(10)
21.5692(12)
90
monoclinic
P21/c
9.5285(3)
22.4192(8)
20.2549(7)
90
93.932(1)
90
4316.7(3)
4
monoclinic
P21/n
11.8160(8)
17.7185(12)
19.2063(13)
90
96.722(1)
90
3993.4(5)
4
triclinic
PÀ1
orthorhombic
P212121
10.3159(5)
30.4106(14)
32.7094(15)
90
monoclinic
P21/c
10.2262(5)
48.604(3)
20.6904(10)
90
97.521(1)
90
10195.4(9)
8
9.7221(5)
23.4765(13)
24.0799(13)
103.948(1)
91.658(1)
92.491(1)
5324.5(5)
6
10.0489(5)
13.1478(8)
22.5246(11)
83.964(1)
85.769(1)
74.465(1)
2848.1(3)
2
a [8]
b [8]
g [8]
90
90
90
90
V [ꢂ3]
Z
7263.7(7)
8
1.485
10261.4(8)
12
1.468
Dcalcd [MgmÀ3
]
1.471
1.449
1.466
1.379
1.474
1.340
1.412
FG
2412
1552
3312
3312
1852
1816
1194
4608
4456
m
G
]
3.920
3.991
3.786
3.835
3.268
3.533
2.466
4.065
2.781
T [K]
no. of rflns
measd
153(2)
31564
153(2)
20485
153(2)
43946
153(2)
41850
153(2)
24132
153(2)
21825
153(2)
16748
153(2)
61208
153(2)
59835
no. of unique
rflns
22471
7777
16401
8281
9762
8868
11966
22647
22712
no. of variables 1095
R1(Io>2.0s(Io)) 0.052
421
0.020
899
0.023
396
0.025
427
0.019
425
0.030
620
0.024
1024
0.027
1136
0.053
G
wR2 (all data)
GOF
0.104
1.168
0.044
1.025
0.055
1.084
0.052
1.270
0.050
1.049
0.076
1.043
0.066
1.093
0.064
0.97
0.105
1.128
max./min. resid- 1.54/À0.82
0.70/À0.46
1.21/À0.86
1.23/À1.01
1.13/À0.58
2.93/À0.89
1.38/À0.84
1.69/À0.48
1.95/À3.39
ual electron
density [eꢂÀ3
]
d=5.0 ppm (s); elemental analysis calcd (%) for C35H53SiP2Ir: C 55.59, H
7.08; found: C 54.60, H 7.09.
bridge Crystallographic Data Centre at www.ccdc.cam.ac.uk/data_
request/cif.
Computational details
Product [Ir(H)ACHTUNGTRENNUNG(PPh2C6H4)ACHUTNGTRENN(UGN PSiP-Cy)] (10)
Geometry optimizations were performed by using density functional
theory[29–31] with B3LYP functionals.[32,33] As for the basis sets, we used 6-
3,3-Dimethyl-1-butene (99 mL, 0.77 mmol) was added to a solution of
complex 3a (300 mg, 0.38 mmmol) in benzene (10 mL). The mixture was
stirred for 4 h at room temperature giving 9a almost quantitatively. Then
PPh3 (100 mg, 0.38 mmol) was added. The mixture was stirred at 608C
for 1 day. Volatiles were removed under vacuum and the resulting crude
product was purified by recrystallization from a mixture of THF and
hexane affording 10 as a white solid (243 mg, 61%). IR (KBr): n˜ =
2071 cmÀ1 (m, IrH); 1H NMR (C6D6, 499.1 MHz): d=À9.36 (dt, 1H, 2J-
31GACHTNUTGRNEUNG
(d,p) sets for C and H.[34] For Si and P, we used LANL2DZ basis
sets,[35] the core parts of which were represented by effective core poten-
tials (ECP). Because of their hypervalent nature, we added a polarization
function for the standard LANL2DZ sets.[36] For Ir, we used ECP devel-
oped by Dolg and Stoll[37] in conjunction with the valence basis sets of
Rappoport et al.,[38] the combination of which are denoted as def2-SVPD
in the EMLS basis exchange database.[39,40] Cartesian coordinates and en-
ergetics of 3c are shown in the Supporting information.
(P,H)=119, 20 Hz), À0.26 (brq, 1H, J=12 Hz), 0.30 (brq, 1H, J=
12 Hz), 1.35 (s, 3H, SiCH3), 0.60–1.82 (m, 37H), 1.98 (brq, 1H, J=
12 Hz), 2.08 (brd, 1H, J=12 Hz), 2.55 (brd, 1H, J=12 Hz), 2.65 (brq,
1H, J=12 Hz), 3.10 (brt, 1H, J=10 Hz), 6.82–6.95 (m, 6H), 7.04 (t, 1H,
J=7 Hz), 7.08–7.23 (m, 4H), 7.27 (t, 2H, J=7 Hz), 7.33–7.42 (m, 2H),
7.51 (t, 2H, J=8 Hz), 7.63–7.68 (m, 1H), 7.90 (d, 1H, J=7 Hz), 8.20–
8.26 ppm (m, 3H); 31P{1H} NMR (C6D6, 202.0 MHz): d=À84.6 (dd, 2J-
Acknowledgements
ACHTUNGTRENNUNG
(P,P)=16, 28 Hz), 17.1 (brs), 46.3 ppm (brs); 29Si{1H} NMR (C6D6,
99.1 MHz, inept): d=30.2 ppm (d, J=132 Hz); elemental analysis calcd
(%) for C55H70SiP3Ir: C 63.24, H 6.77; found: C 63.23, H 6.85.
This work was supported by a Grant-in-Aid for Scientific Research (no.
19350035) from the Ministry of Education, Science, Sports and Culture,
Japan.
X-ray crystallography
Data collection was performed on a Bruker Smart Apex CCD diffrac-
tometer (MoKa radiation, graphite monochromator). Data were corrected
for absorption. The structures were solved by the Patterson method.
Structure refinement was carried out by full-matrix least-squares on F2.
Structure solution and refinement were performed by using a Crystal
Structure software package[27] with the SHELX-97 program.[28] Crystallo-
graphic data are summarized in Table 2. CCDC 809498, 809499, 809500,
809501, 809502, 809503, 809504, 809505, and 809506 contain the supple-
mentary crystallographic data for complexes 3a, 3c, mer-4a, fac-4a, 5, 6,
8, 9c, and 10. These data can be obtained free of charge from The Cam-
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Received: January 30, 2011
Published online: June 15, 2011
Chem. Asian J. 2011, 6, 2512 – 2521
ꢁ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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