Two-point cooperative binding of ketones by a metal and by a neighboring pendant NH group

Article abstract of DOI:10.1021/om000115b

An iridium complex having a 2-aminoquinolinate ligand can bind both lone pairs of ketones such as acetone and 2-hexanone in a two-point fashion via a coordinate Ir-O bond and an N-H?O hydrogen bond. This two-point binding orients the ketone so that the fluxional exchange of the two distinct methyl groups in the acetone complex is strongly slowed relative to the situation where the pendant NH₂ group is absent. In addition, certain substrates, such as 3-hexanone, can form complexes only when the H-bonding group is absent. We propose that H-bonding orients the substrate in the mirror plane of the molecule in such a way that the Et group of the substrate causes steric repulsion with the Ir-H group. In unsymmetrical cases such as PhCHO, the orientation occurs so that the aldehyde proton is located near the Ir-H group.

Full text of DOI:10.1021/om000115b

2228
Organometallics 2000, 19, 2228-2232
Tw o-P oin t Coop er a tive Bin d in g of Keton es by a Meta l
a n d by a Neigh bor in g P en d a n t NH Gr ou p
Karin Gruet and Robert H. Crabtree*,†
Chemistry Department, Yale University, 225 Prospect Street,
New Haven, Connecticut 06520-8107
Dong-Heon Lee*,‡
Department of Chemistry, Chonbuk National University, Chonju, 561-756, Korea
Louise Liable-Sands and Arnold L. Rheingold*,§
Chemistry Department, University of Delaware, Newark, Delaware, 19716
Received February 8, 2000
An iridium complex having a 2-aminoquinolinate ligand can bind both lone pairs of ketones
such as acetone and 2-hexanone in a two-point fashion via a coordinate Ir-O bond and an
N-H‚‚‚O hydrogen bond. This two-point binding orients the ketone so that the fluxional
exchange of the two distinct methyl groups in the acetone complex is strongly slowed relative
to the situation where the pendant NH2 group is absent. In addition, certain substrates,
such as 3-hexanone, can form complexes only when the H-bonding group is absent. We
propose that H-bonding orients the substrate in the mirror plane of the molecule in such a
way that the Et group of the substrate causes steric repulsion with the Ir-H group. In
unsymmetrical cases such as PhCHO, the orientation occurs so that the aldehyde proton is
located near the Ir-H group.
In tr od u ction
The pendant group must be rigidly held to prevent
direct binding to the metal, and so a chelate system was
preferred. An amino group seemed appropriate in being
both a base and a hydrogen bond proton donor. 2-Ami-
nobenzoquinoline seemed most suitable for our first
efforts since it can very readily be synthesized from
NaNH2 and benzoquinoline and also readily cyclometa-
lates with a number of metal centers. Related work has
appeared.7
In prior work,8 we have shown how such a complex
(1), conveniently formed by cyclometalation of 2-ami-
nobenzoquinoline (Scheme 1), allows us to observe the
reversible heterolytic cleavage of H2 and the stabiliza-
tion of an HF complex by protonation of a fluoro
complex.
There is growing interest in the effects of hydrogen
bonding in coordination and organometallic chemistry,
including crystal engineering and supramolecular
architecture.1-3
Multifunctional complexes in which the ligands have
reactive groups not involved in metal-ligand binding
may give rise to useful new properties not otherwise
obtainable. With the ultimate aim of combining molec-
ular recognition4 with catalysis5 to obtain high selectiv-
ity, we have looked at the effect of appending reactive
groups to suitable organometallic ligands. This is done
in such a way that these groups cannot bind directly to
the metal but only bind tosor react withsan exogenous
ligand that is bound to the metal. A simple example is
shown as 1 below, where a pendant amino group hy-
drogen bonds to a water ligand. In this way two-point
binding is obtained, which should in principle allow the
ligands to be oriented. The pendant groups are neither
inner sphere,6 directly bound to the metal, nor outer
sphere, freely diffusing, so we consider these groups as
being in the intermediate sphere.
Resu lts a n d Discu ssion
In growing a crystal of 1 from CH2Cl2/hexane for
structural characterization, we were surprised to find
that the product was not the expected aqua complex, 1,
but proved to be the 2-hexanone complex, 2. Subsequent
investigation showed that the n-hexane used was au-
toxidized9 and contained both 2- and 3-hexanone in
† E-mail: robert.crabtree@yale.edu.
‡E-mail: dhl@moak.chonbuk.ac.kr.
§E-mail: ARNRHEIN@UDEL.EDU.
(1) Braga, D.; Grepioni, F.; Desiraju, G. R. Chem. Rev. 1998, 98 (4),
1375.
(2) Braga, D.; Grepioni, F.; Desiraju, G. R. J . Organomet. Chem.
1997, 548 (1), 33.
(3) Brammer, L.; Zhao, D.; Ladipo, F. T.; Braddockwilking, J . Acta
Crystalogr. Sect. B: Struct. Sci. 1995, B51, 632.
(4) Lehn, J . M. Angew. Chem., Int. Ed. Engl. 1990, 29, 1304.
(5) Reetz, M. T. J . Heterocyclic Chem. 1998, 35, 1065.
(6) Poulopoulou, V. G.; Taube, H. Inorg. Chem. 1997, 36, 4782.
(7) (a) Chu, H. S.; Lau, C. P.; Wong, K. Y. Wong Organometallics
1998, 17, 2768. (b) Ayllon, J . A.; Sabo-Etienne, S.; Chaudret, B. Inorg.
Chim. Acta 1997, 259, 1.
(8) (a) Lee, D.-H.; Patel, B. P.; Clot, E.; Eisenstein, O.; Crabtree, R.
H. Chem. Commun. 1999, 297. (b) Patel, B. P.; Crabtree, R. H. J . Am.
Chem. Soc. 1996, 118, 13105. (c) Lee, D.-H.; Patel, B. P.; Rheingold,
A. L.;Crabtree, R. H. Organometallics 1999, 18, 1615.
(9) Crabtree, R. H.; Habib, A. In Comprehensive Organic Chemistry;
Trost, B. M., Ed.; Pergamon: Oxford, 1991; Chapter 1.1.
10.1021/om000115b CCC: $19.00 © 2000 American Chemical Society
Publication on Web 05/05/2000

Two-Point Cooperative Binding of Ketones
Organometallics, Vol. 19, No. 11, 2000 2229
F igu r e 2. Details of the hydrogen-bonding interaction in
2, omitting the PPh3 ligands. The H atoms are normalized
(d(NH) ) 1.03 Å) in calculated positions assuming a planar
-NH2 group. Further selected bond distances (Å) and
angles (deg): N(2)‚‚‚O(1), 2.897(7); C(82)-O(1)-H(2A),
140.5; C(82)-O(1)‚‚‚N(2), 145.6(9); C(82)-O(1)-Ir, 130.2-
(9).
F igu r e 1. Overall structure of the cation of 2 with 30%
probability ellipsoids and omitting the anion and all H
atoms except Ir-H (calcd position) for clarity.
Ta ble 1. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
for 2‚CH2Cl2
Sch em e 1
empirical formula
C56H54Cl2F6IrN2OP3
fw
1241.02
temp (K)
173(2)
wavelength (Å)
cryst syst
space group
unit cell dimensions
a (Å)
0.71073
monoclinic
P21/c
13.5162(2)
17.9411(2)
21.8105(3)
90
100.1738(5)
90
5205.80(14), 4
1.583
2.823
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
volume (Å3), Z
density (calcd) (g/cm3)
abs coeff (mm-1
)
F(000)
2488
cryst dimens (mm)
θ range for data collection (deg) 1.48-28.23
limitig indices
0.50 × 0.40 × 0.40
-17 e h e 17, 0 e k e 20,
0 e l e 28
20 479
10899 (Rint ) 0.0597)
0.3980 and 0.3326
full-matrix least-squares on F2
10899/9/680
approximately equimolar amounts, so the reaction
proceeds as shown in eq 1. Confirmation was obtained
by use of stoichiometric quantities of 2-hexanone, which
allows 2 to be prepared on a large scale in good yield.
no. of reflns collected
no. of ind reflns
transmission factors
refinement method
no. of data/restraints/params
goodness-of-fit on F2
final R indices [I > 2σ(I)]
R indices (all data)
0.939
R1 ) 0.0459, wR2 ) 0.0922
R1 ) 0.0794, wR2 ) 0.1033
1.051 and -1.265
largest diff peak and
hole (e Å-3
)
Ir-O(1) distance of 2.251(4) Å in 2 is consistent with a
normal coordinate bond.
X-r a y Cr ysta llogr a p h y of 2. The results of a single-
crystal X-ray study of 2 are given in Figures 1 and 2
and Tables 1 and 2. The structure has the usual octa-
hedral arrangement around Ir(III), with an essentially
planar aminobenzoquinolate ligand. The 2-hexanone is
clearly resolved. Although the NH2 hydrogens are not
observed in the crystal structure, the N‚‚‚O distance of
2.897(7) Å is in the range expected for N-H‚‚‚OdC
hydrogen bonding.10 Comparison with the structure of
[IrH2(Me2CO)2(PPh3)2]BF4, where the acetone is also η1-
bound11 and where Ir-O is 2.235(5) Å, shows that the
Sp ectr oscop y of 2. Spectroscopic data are also
consistent with hydrogen bonding.10 The thin-film IR
spectroscopic study shows two distinctive ν(NH) stretch-
ing bands at 3427 and 3364 cm-1, both shifted from the
single band observed at 3411 cm-1 for the free ligand.
In the 1H NMR spectrum, at room temperature, the
signal at 4.84 ppm of the free ligand is shifted toward
the aromatic region (6-8 ppm) once bonded to the
metal, and at low temperature the hydrogen-bonded NH
is observed at 7.70 ppm, whereas the non-hydrogen-
bonded NH is observed at 5.89 ppm.
(10) J effrey, G. A.; Saenger, W. Hydrogen Bonding in Biological
Structures; Springer: Berlin, 1994.
(11) Crabtree, R. H.; Hlatky, G. G.; Parnell, C. A.; Segmuller, B. E.;
Uriarte, R. J . Inorg. Chem. 1984, 23, 354

2230 Organometallics, Vol. 19, No. 11, 2000
Gruet et al.
Ta ble 2. Selected Bon d Len gth s a n d An gles for
the solution leads to observation of a distinct peak for
free acetone at 2.08 ppm, showing that free and bound
acetone do not exchange at a significant rate at the
decoalescence temperature.
Com p lex 2‚CH2Cl2
bond distances (Å)
bond angles (deg)
Ir(1)-P(1)
2.3395(14)
2.3516(14)
2.251(4)
2.196(5)
2.024(5)
C(14)-Ir(1)-N(1)
79.8(2)
97.6(14)
117.38(17)
84.1(13)
93.04(12)
91.0(13)
91.59(12)
91.59(12)
172.85(5)
176.3(14)
83.8(14)
98.63(17)
90.64(11)
88.13(14)
Ir(1)-P(2)
Ir(1)-O(1)
Ir(1)-N(1)
Ir(1)-C(14)
C(82)-O(1)
C(14)-Ir(1)-H(1)
C(14)-Ir(1)-O(1)
H(1)-Ir(1)-P(1)
N(1)-Ir(1)-P(1)
H(1)-Ir(1)-P(2)
N(1)-Ir(1)-P(2)
N(1)-Ir(1)-P(2)
P(1)-Ir(1)-P(2)
H(1)-Ir(1)-N(1)
H(1)-Ir(1)-O(1)
N(1)- Ir(1)-O(1)
O(1)-Ir(1)-P(1)
O(1)-Ir(1)-P(2)
1.283(10)
In contrast, in 4H when the pendant -NH2 group is
replaced by an -H, above -80 °C the acetone shows
one Me resonance, indicating that the rotation is faster
than for 4 and the pendant group is responsible for the
slow rotation in 4, and shows incipient decoalescence
at -90 °C. In other words the two-point binding does
indeed favor the oriented mode of acetone binding.
This can best be interpreted in terms of a model12 in
which the N-H‚‚‚O hydrogen bond is broken on C-N
bond rotation by 90° to give the proposed transition
state, 5, where the lone pair that was H-bonded to the
NH2 group in 4 is now pointing away from the pendant
NH bond. Fast exchange with free acetone is prevented
by maintenance of the relatively strong Ir-O bond in
4, and the observed barrier can therefore be interpreted
as the sum of the intrinsic barrier for rotation about
the Ir-O bond and the N-H‚‚‚O H-bond.
Con sequ en ces of Liga n d Or ien ta tion by Tw o-
P oin t Bin d in g. The ketone in 2 is held in a two-point
binding mode. Because both keto lone pairs lie in the
Me(CdO)R plane, this plane is forced to be coincident
with the plane of the bq ligand. The ketone is therefore
oriented by the hydrogen bonding so that the methyl
group is close to the adjacent Ir-H group. If the methyl
group of 2-hexanone is replaced by the ethyl group of
3-hexanone, as in 3, steric interference might be ex-
pected to disfavor binding. The fact that the 2-hexanone
complex was formed from an equimolar mixture of 2-
and 3-hexanone suggests that there is indeed selectivity
for binding the 2-isomer. Unsuccessful attempts were
made to prepare the 3-hexanone derivative, 3, under
several different conditions, including ones that gave
the 2-hexanone complex.
Control studies are possible with the unsubstituted
derivatives lacking the 2-NH2 group and therefore being
incapable of significant hydrogen bonding and ligand
orientation. We refer to these compounds using the
same numbering scheme as before but with a postscript
H, as in 3H. These controls are not perfect because the
-NH2 and -H groups are expected to have different
electronic effects, but they are expected to be satisfac-
tory for the purposes for which they have been used.
We found that with the unsubstituted benzoquinoline,
3-hexanone complex, 3H, could readily be made. Be-
cause of the absence of hydrogen bonding, the ketone
may be able to rotate in such a way as to avoid
prohibitive steric repulsions.
As we have previously discussed,12 we can learn about
the N-H‚‚‚O H-bond strength by looking at the ex-
change between Ha and Hb in the amino group. The two
hydrogens decoalesce on cooling and give separate
resonances at -90 °C. Once again, at the transition
state for -NH2 rotation, the N-H‚‚‚O H-bond is broken
and the observed barrier can be interpreted as the
sum of the intrinsic C-NH2 rotation barrier and the
N-H‚‚‚O H-bond. We have previously estimated12 the
intrinsic barrier at 5.8 kcal/mol, and so the observed
barrier of 8.9 kcal/mol, obtained by conventional line
shape analysis,13 implies that the N-H‚‚‚O H-bond
strength is ca. 3.1 kcal/mol. Since the observed barrier
for acetone rotation in 4 (Me/Me* exchange) is 9.9 kcal/
mol, we can estimate an intrinsic barrier for rotation
about the Ir-O bond of 6.8 kcal/mol. This is too low for
decoalescence in 4H, the corresponding complex lacking
the pendant NH2 group, as indeed is found experimen-
tally: an incipient decoalescence is seen for 4H down
to -90 °C, the limit set by the solvent.
If binding to 1 really does orient the ketone, this ought
to have consequences on the dynamic NMR spectrum.
We therefore prepared the acetone complex 4 via the
route of eq 2. Although 4 has two distinct Me groups,
labeled Me and Me* in the diagram, at room tempera-
ture the NMR spectrum shows only one methyl group
at 1.57 ppm. On cooling, the signal decoalesces to give
two peaks at 1.36 and 1.45 ppm in a 1:1 ratio as the
acetone rotation is frozen. Addition of free acetone to
Oth er Su bstr a tes. Other organic molecules can also
be bound in a two-point manner by the system. Of most
interest is the urea present in complex 6H, where the
steric effect of the NMe group is close to that of the Et
(12) Peris, E.; Lee., J . C., J r.; Rambo, J . R.; Eisenstein, O.; Crabtree,
R. H. J . Am. Chem. Soc. 1995, 117, 3845
(13) Sandstrom, J . Dynamic NMR Spectroscopy; Academic Press:
New York, 1982.

Two-Point Cooperative Binding of Ketones
Organometallics, Vol. 19, No. 11, 2000 2231
(2-Am in o-7,8-ben zoqu in olin a to)h yd r id o(2-h exa n on e)-
b is(t r ip h en ylp h osp h in e)ir id iu m (III) H exa flu or op h os-
p h a te (2H). [Ir(cod)(PPh3)2]PF6 (263 mg, 0.27 mmol) and 7,8-
benzoquinoline (48 mg, 0.27 mmol) were dissolved in freshly
distilled dichloromethane (10 mL). The resulting red solution
was allowed to cool to 0 °C. 2-Hexanone was added (335 µL,
2.7 mmol). Dihydrogen gas was bubbled for 15 min with
constant stirring to give a yellow solution. The ice bath was
removed, and dihydrogen gas was allowed to bubble for an
additional 15 min. Then, heptane (100 mL) was added drop-
wise. The solution was filtered in vacuo to give a pale yellow
precipitate, which was dried in vacuo to yield 238 mg of 2H
group in 3-hexanone. While 6H is readily formed,
attempts to prepare 6 led to failure; this is reminiscent
of the situation for 3 versus 3H.
Con clu sion
Complex 1 allows ketone ligands to be oriented so that
the complex is selective for binding 2-hexanone over
3-hexanone. The fluxional exchange of Me and Me* in
the acetone complex is also significantly slowed. Com-
parisons with the complex lacking the pendant NH2
were made. This two-point binding approach offers
possibilities for future development.
1
as a powder (80%). H NMR (CD2Cl2, 500 MHz, 293 K, ppm):
δ -16.18 (t, 1H, 2J H-P ) 14.65 Hz, Ir-H), 1.27-1.89 (m, 12H),
6.70-9.33 (m, 38H). 1H NMR (CD2Cl2, 500 MHz, 183 K,
2
ppm): δ -16.01 (t, 1H, J H-P ) 14.65 Hz, Ir-H), 1.34-2.00
(m, 12H), 6.60-9.07 (m, 38H). 31P{1H} NMR (CD2Cl2, 125
MHz, 293 K, ppm): δ 18.11 (s). IR (thin-film, cm-1): η, 1640.6
(CdO), 2232.9 (Ir-H). Anal. Calcd for C55H51F6IrNOP3‚0.5(CH2-
Cl2): C, 56.32, H, 4.43, N, 1.18. Found: C, 56.34, H, 4.35, N,
0.95.
Exp er im en ta l Section
All operations were carried out under argon atmosphere
using standard Schenk techniques. Solvents were dried over
calcium hydride (CH2Cl2) or sodium/benzophenone (Et2O).
1
Hexane was degassed prior use. H NMR and 31P{1H} NMR
(7,8-Ben zoq u in olin a t o)h yd r id o(3-h exa n on e)b is(t r i-
ph en ylph osph in e)ir idiu m (III) Hexaflu or oph osph ate (3H).
[Ir(cod)(PPh3)2]PF6 (192 mg, 0.20 mmol) and 7,8-benzoquino-
line (35 mg, 0.20 mmol) were dissolved in freshly distilled
dichloromethane (10 mL). The resulting red solution was
allowed to cool to 0 °C. 3-Hexanone was added (25 mL, 0.20
mmol). Dihydrogen gas was bubbled for 5 min with constant
stirring. The yellow solution was allowed to warm to room
temperature. Then, dry diethyl ether (100 mL) was added
dropwise. The solution was filtered in vacuo to give a yellow
precipitate, which was dried in vacuo to yield 67 mg of 3H as
spectra were recorded on either GE Omega 300 or GE Omega
500 spectrometers. Chemical shifts were measured with refer-
ence to the residual solvent resonance. IR spectra were
recorded on a Midac M1200 FT-IR spectrometer. Microanyly-
ses were carried out by Robertson Microlit Laboratories.
Cr ysta l Da ta for 2‚CH2Cl2: C56H54Cl2F6IrN2OP3, fw )
1241.02, monoclinic, space P21/c, a ) 13.5162(2) Å, b )
17.9411(2) Å, c ) 21.8105(3) Å, R ) 90°, â ) 100.1738(5)°, γ )
90°, V ) 5205.80(14) Å3, Z ) 4, Dc )1.583 g cm-3, F(000) )
2488, µ ) 2.823 mm-1, T )173 K, R(int) ) 0.0597, Mo KR(λ )
0.71073 Å), ω and æ scans, 20 479 reflections collected, 10 899
independent reflections, R(F) ) 4.59% for 7255 observed
independent reflections (4° e 2θ e 57°). Data were collected
on a Siemens P4 diffractometer with a SMART/CCD detector.
An empirical absorption correction was applied, based on a
Fourier series in the polar angles of the incident and diffracted
rays, and was used to model an absorption surface for the
difference between the observed and calculated structure
factors.14 Four equatorial F atoms on the PF6- counterion are
equally disordered over two positions, and the distances were
constrained to an average P-F distance of 1.54 Å. A molecule
of CH2Cl2 is cocrystallized in the asymmetric unit. The hydride
H was located from the difference map, and its distance was
constrained to Ir-H ) 1.60 Å. All non-hydrogen atoms were
refined with anisotropic thermal parameters, and all other
hydrogen atoms were treated as idealized contributions. Final
R indices are R1 ) 0.0459, wR2 ) 0.0922. Further details may
be obtained from the Cambridge Crystallographic Data Centre.
1
a powder (29%). H NMR (CD2Cl2, 500 MHz, 293 K, ppm): δ
-16.07 (m, 1H, Ir-H), 0.80-2.20 (m, 12H), 6.70-9.40 (m,
1
38H). H NMR (CD2Cl2, 500 MHz, 183 K, ppm): δ -16.71 (t,
2
1H, J H-P ) 14.99 Hz, Ir-H), 0.40-2.00 (m, 12H), 6.50-9.00
(m, 38H). 31P{1H} NMR (CD2Cl2, 125 MHz, 293 K, ppm): δ
18.46 (s). IR (thin-film, cm-1): ν, 1630.3 (CdO), 2222.6 (Ir-
H). Anal. Calcd for C55H51NOP3F6Ir‚1.4(CH2Cl2): C, 53.76, H,
4.30, N, 1.11. Found: C, 54.11, H, 3.80, N, 1.36.
(2-Am in o-7,8-ben zoqu in olin a to)h yd r id o(a ceton e)bis-
(tr ip h en ylp h osp h in e)ir id iu m (III) Hexa flu or op h osp h a te
(4). [Ir(cod)(PPh3)2]PF6 (417 mg, 0.43 mmol) and 2-amino-7,8-
benzoquinoline (83 mg, 0.43 mmol) were dissolved in acetone
(10 mL). The resulting red solution was allowed to cool to 0
°C. Dihydrogen gas was bubbled for 30 min with constant
stirring. The beige solution was allowed to warm to room
temperature. Then, heptane (100 mL) was added dropwise.
The solution was filtered in vacuo to give a beige precipitate,
which was dried in vacuo to yield 404 mg of 3 as a powder
1
(2-Am in o-7,8-ben zoqu in olin a to)h yd r id o(2-h exa n on e)-
b is(t r ip h en ylp h osp h in e)ir id iu m (III) H exa flu or op h os-
p h a te (2). The PF6 salt of 1 (200 g, 0.20 mmol)5c was dissolved
in degassed CH2Cl2 (10 mL), and distilled 2-hexanone (100 mg,
1 mmol) was added. The resulting solution was stirred for 30
min. To the yellow solution was added hexane (ca. 20 mL) until
the solution became cloudy. The solution was then filtered
through a medium-porosity frit, and addition of more hexane
(50 mL) gave a light yellow precipitate, which was washed with
ether (30 mL) and dried in vacuo to directly yield 160 mg (70%)
(84%). H NMR (CD2Cl2, 300 MHz, 293 K, ppm): δ -16.70 (t,
2
1H, J H-P ) 14.65 Hz, Ir-H), 1.57 (br s, 12H, coord + free
CH3-CO-CH3), 6.65-7.58 (m, 39H, NH2 + bq + Ph). 1H NMR
(CD2Cl2, 300 MHz, 183 K, ppm): δ -16.57 (t, 1H, 2J H-P ) 14.65
Hz, Ir-H), 1.36 (s, 3H, CO-CH3), 1.45 (s, 3H, CO-CH3), 2.08
(s, 6H, CH3-CO-CH3), 6.19 (s, 1H, NHa), 6.55-7.48 (m, 37H,
bq + Ph), 7.86 (s, 1H, NHb). 31P{1H} NMR (CD2Cl2, 121 MHz,
293 K, ppm): δ 20.54 (s). IR (thin-film, cm-1): ν, 1650.9 (Cd
O), 2207.3 (Ir-H), 3366.4 (NH), 3479.6 (NH). Anal. Calcd for
C
52H46F6IrN2OP3: C, 56.02, H, 4.16, N, 2.51. Found: C, 56.23,
1
of pure powder. H NMR (CD2Cl2, 500 MHz, 293 K, ppm): δ
H, 4.41, N, 2.46.
2
-16.60 (t, 1H, J H-P ) 14.80 Hz, Ir-H), 1.28-2.00 (m, 12H),
(7,8-Ben zoq u in olin a t o)h yd r id o(a cet on e)b is(t r ip h en -
ylp h osp h in e)ir id iu m (III) Hexa flu or op h osp h a te (4H). [Ir-
(cod)(PPh3)2]PF6 (334 mg, 0.34 mmol) and 7,8-benzoquinoline
(61 mg, 0.34 mmol) were dissolved in acetone (10 mL). The
resulting red solution was allowed to cool to 0 °C. Dihydrogen
gas was bubbled for 15 min with constant stirring to lead to a
milky yellow solution. The ice bath was removed, and dihy-
drogen gas was allowed to bubble for an additional 15 min.
Then, heptane (100 mL) was added dropwise. The solution was
filtered in vacuo to give a pale yellow precipitate, which was
6.70-8.10 (m, 39H). 1H NMR (CD2Cl2, 500 MHz, 183 K,
2
ppm): δ -16.35 (t, 1H, J H-P ) 14.80 Hz, Ir-H), 1.34-2.41
(m, 12H), 5.89 (s, 1H, NHa) 6.62-7.80 (m, 37H), 7.70 (s, 1H,
NHb). 31P{1H} NMR (CD2Cl2, 125 MHz, 293 K, ppm): δ 19.41
(s). IR (thin film, cm-1): ν 1564 (CdO), 2176 (IrH), 3364 (NH),
3427 (NH). Anal. Calcd for C55H52F6IrN2OP3: C, 57.13, H, 4.53,
N, 2.42. Found: C, 56.89, H, 4.45, N, 2.22.
(14) Walker, N.; Stewart, D. Acta Crystallogr. 1983, A39, 158.

2232 Organometallics, Vol. 19, No. 11, 2000
Gruet et al.
2
dried in vacuo to yield 273 mg of 4H as a powder (74%). 1H
NMR (CD2Cl2, 300 MHz, 293 K, ppm): δ -16.20 (t, 1H,2J H-P
) 14.65 Hz, Ir-H), 1.57 (br s, 12H, coord + free CH3-CO-
CH3), 6.80-9.15 (m, 38H, bq + Ph). 1H NMR (CD2Cl2, 300
MHz, 183 K, ppm): δ -16.09 (t, 1H, 2J H-P ) 14.65 Hz, Ir-H),
1.26 (v br s, 3H, CO-CH3), 1.64 (v br s, 3H, CO-CH3), 2.09
(s, 6H, CH3-CO-CH3), 6.78-9.36 (m, 38H, bq + Ph). 31P{1H}
NMR (CD2Cl2, 121 MHz, 293 K, ppm): δ 17.97 (s). IR (thin-
film, cm-1): ν, 1655.9 (CdO), 2176.2 (Ir-H). Anal. Calcd for
NMR (CD2Cl2, 500 MHz, 183 K, ppm): δ -15.86 (t, 1H, J H-P
) 13.92 Hz, Ir-H), 0.22 (s, 9H, coord CH3), 0.97 (s, 9H, free
CH3), 6.00-9.40 (m, 38H), 8.78 (s, 1H, coord CH), 9.42 (s, 1H,
free CH). 31P{1H} NMR (CD2Cl2, 125 MHz, 293 K, ppm): δ
18.03 (s). IR (thin-film, cm-1): ν, 1645.9 (CdO), 2171.1 (Ir-
H). Anal. Calcd for C54H49NOP3F6Ir‚2.75(CH2Cl2): C, 50.06,
H, 4.03, N, 1.03. Found: C, 50.15, H, 3.84, N, 1.36.
(2-Am in o-7,8-b e n zoq u in olin a t o)h yd r id o(d im e t h yl-
for m am ide)bis(tr iph en ylph osph in e)ir idiu m (III) Hexaflu o-
r op h osp h a te (8). [Ir(cod)(PPh3)2]PF6 (291 mg, 0.30 mmol) and
2-amino-7,8-benzoquinoline (58 mg, 0.30 mmol) were dissolved
in freshly distilled dichloromethane (10 mL). The resulting red
solution was allowed to cool to 0 °C. Dimethylformamide was
added (233 µL, 3.0 mmol). Dihydrogen gas was bubbled for 15
min with constant stirring to give a brown-yellowish solution.
The ice bath was removed, and dihydrogen gas was allowed
to bubble for an additional 15 min.Then, degassed heptane
(100 mL) was added dropwise. After 30 min, a brown oil was
decanted under an atmosphere of argon, which was dried in
C
52H45F6IrNOP3: C, 56.78, H, 4.12, N, 1.27. Found: C, 56.46,
H, 4.06, N, 1.08.
(7,8-Be n zoq u in olin a t o)h yd r id o(1,3-d im e t h yl-2-im i-
d a zolid in on e)bis(tr ip h en ylp h osp h in e)ir id iu m (III) Hexa -
flu or op h osp h a te (6H). [Ir(cod)(PPh3)2]PF6 (258 mg, 0.27
mmol) and 7,8-benzoquinoline (47 mg, 0.27 mmol) were dis-
solved in freshly distilled dichloromethane (10 mL). The re-
sulting red solution was allowed to cool to 0 °C. 1,3-Dimethyl-
2-imidazolidinone was added (291 µL, 2.7 mmol). Dihydrogen
gas was bubbled for 15 min with constant stirring to give a
yellow solution. The ice bath was removed, and dihydrogen
gas was allowed to bubble for an additional 15 min. Then,
degassed heptane (100 mL) was added dropwise. The solution
was filtered in vacuo to give a pale yellow precipitate, which
was dried in vacuo to yield 130 mg of 6H as a powder (42%).
1H NMR (CD2Cl2, 500 MHz, 293 K, ppm): δ -15.97 (t, 1H,
2J H-P ) 14.65 Hz, Ir-H), 2.62-3.29 (m, 10H), 6.75-9.19 (m,
1
vacuo to yield 124 mg of 8 as a powder (37%). H NMR (CD2-
Cl2, 500 MHz, 293 K, ppm): δ -16.59 (t, 1H, J H-P ) 14.65
2
Hz, Ir-H), 2.30 (s, 3H, coord CH3), 2.35 (s, 3H, coord CH3),
2.85 (s, 3H, free CH3), 2.94 (s, 3H, free CH3), 6.50 (s, 1H, coord
CH), 6.60-7.90 (m, 39H), 8.00 (s, 1H, free CH). 1H NMR (CD2-
2
Cl2, 500 MHz, 183 K, ppm): δ -16.43 (t, 1H, J H-P ) 14.65
Hz, Ir-H), 2.17 (s, 3H, coord CH3), 2.23 (s, 3H, coord CH3),
2.81 (s, 3H, free CH3), 2.91 (s, 3H, free CH3), 6.21 (s, 1H, NHb),
6.31 (s, 1H, coord CH), 6.50-7.40 (m, 39H), 7.51 (s, 1H, NHa),
7.95 (s, 1H, free CH). 31P{1H} NMR (CD2Cl2, 125 MHz, 293 K,
ppm): δ 20.23 (s). IR (thin-film, cm-1): ν, 1640.6 (CdO), 2182.2
(Ir-H), 3345.7 (NH), 3479.6 (NH). Anal. Calcd for C52H47N3-
OP3F6Ir‚0.5(CH2Cl2): C, 53.82, H, 3.96, N, 3.57. Found: C,
54.20, H, 3.97, N, 3.74.
1
38H). H NMR (CD2Cl2, 500 MHz, 183 K, ppm): δ -15.71 (t,
2
1H, J H-P ) 14.99 Hz, Ir-H), 2.13-3.21 (m, 10H), 6.58-8.90
(m, 38H). 31P{1H} NMR (CD2Cl2, 125 MHz, 293 K, ppm): δ
18.19 (s). IR (thin-film, cm-1): ν, 1649 (CdO), 2136 (Ir-H).
Anal. Calcd for C54H49N3OP3F6Ir‚0.5(CH2Cl2): C, 53.27, H,
4.14, N, 3.39. Found: C, 53.48, H, 4.32, N, 3.07.
(2-Am in o -7,8-b e n zo q u in o lin a t o )h y d r id o (t r im e t h -
ylacetaldehyde)bis(triphenylphosphine)iridium(III) Hexa-
flu or op h osp h a te (7). [Ir(cod)(PPh3)2]PF6 (304 mg, 0.31 mmol)
and 2-amino-7,8-benzoquinoline (60 mg, 0.31 mmol) were
dissolved in freshly distilled dichloromethane (10 mL). The
resulting red solution was allowed to cool to 0 °C. Trimeth-
ylacetaldehyde was added (34 µL, 0.31 mmol). Dihydrogen gas
was bubbled for 5 min with constant stirring to give a yellow
solution. The solution was allowed to warm to room temper-
ature and gave an orange solution. Then, dry diethyl ether
(100 mL) was added dropwise. The solution was filtered in
vacuo to give a pink precipitate, which was dried in vacuo to
yield 72 mg of 7 as a powder (20%). 1H NMR (CD2Cl2, 500 MHz,
293 K, ppm): δ -16.23 (m 1H, Ir-H), 0.60 (br s, 18H, coord +
free CH3), 6.40-8.00 (m, 39H), 9.18 (s, 2H, coord + free CH).
1H NMR (CD2Cl2, 500 MHz, 183 K, ppm): δ -15.89 (m, 1H,
Ir-H), 0.10 (s, 9H, coord CH3), 0.97 (s, 9H, free CH3), 6.08-
8.50 (m, 39H), 8.81 (s, 1H, coord CH), 9.36 (s, 1H, free CH).
31P{1H} NMR (CD2Cl2, 125 MHz, 293 K, ppm): δ 20.94 (s). IR
(thin-film, cm-1): ν, 1635.3 (CdO), 2197.0 (Ir-H), 3376.7 (NH),
3479.6 (NH). Anal. Calcd for C54H50N2OP3F6Ir‚0.75(CH2Cl2):
C, 54.50, H, 4.30, N, 2.32. Found: C, 54.49, H, 3.89, N, 2.44.
(7,8-Be n zoq u in olin a t o)h yd r id o(t r im e t h yla ce t a ld e -
h yd e)bis(tr ip h en ylp h osp h in e)ir id iu m (III) Hexa flu or o-
p h osp h a te (7H). [Ir(cod)(PPh3)2]PF6 (322 mg, 0.33 mmol) and
7,8-benzoquinoline (60 mg, 0.33 mmol) were dissolved in
freshly distilled dichloromethane (10 mL). The resulting red
solution was allowed to cool to 0 °C. Trimethylacetaldehyde
was added (36 µL, 0.33 mmol). Dihydrogen gas was bubbled
for 5 min with constant stirring to give a yellow solution. The
solution was allowed to warm to room temperature and gave
a pale orange solution. Then, dry diethyl ether (100 mL) was
added dropwise. The solution was filtered in vacuo to give a
yellow precipitate, which was dried in vacuo to yield 84 mg of
7H as a powder (22%). 1H NMR (CD2Cl2, 500 MHz, 293 K,
ppm): δ -16.05 (m 1H, Ir-H), 0.66 (br s, 18H, coord + free
CH3), 6.75-9.40 (m, 38H), 9.20 (s, 2H, coord + free CH). 1H
(7,8-Ben zoqu in olin a to)h yd r id o(d im eth ylfor m a m id e)-
b is(t r ip h en ylp h osp h in e)ir id iu m (III) H exa flu or op h os-
p h a te (8H). [Ir(cod)(PPh3)2]PF6 (313 mg, 0.32 mmol) and 7,8-
benzoquinoline (57 mg, 0.32 mmol) were dissolved in freshly
distilled dichloromethane (10 mL). The resulting red solution
was allowed to cool to 0 °C. Dimethylformamide was added
(250 mL, 3.2 mmol). Dihydrogen gas was bubbled for 15 min
with constant stirring to give a yellow solution. The ice bath
was removed, and dihydrogen gas was allowed to bubble for
an additional 15 min.Then, degassed heptane (100 mL) was
added dropwise. The solution was filtered in vacuo to give a
yellow precipitate, which was dried in vacuo to yield 244 mg
1
of 8H as a powder (67%). H NMR (CD2Cl2, 500 MHz, 293 K,
2
ppm): δ -16.21 (t, 1H, J H-P ) 15.87 Hz, Ir-H), 2.27 (s, 3H,
coord CH3), 2.55 (s, 3H, coord CH3), 2.82 (s, 3H, free CH3), 2.92
(s, 3H, free CH3), 6.43 (s, 1H, coord CH), 6.65-9.17 (m, 38H),
7.97 (s, 1H, free CH). 1H NMR (CD2Cl2, 500 MHz, 183 K,
2
ppm): δ -16.13 (t, 1H, J H-P ) 15.87 Hz, Ir-H), 2.15 (s, 3H,
coord CH3), 2.54 (s, 3H, coord CH3), 2.78 (s, 3H, free CH3), 2.88
(s, 3H, free CH3), 6.16 (s, 1H, coord CH), 6.60-9.14 (m, 38H),
7.91 (s, 1H, free CH). 31P{1H} NMR (CD2Cl2, 125 MHz, 293 K,
ppm): δ 17.14 (s). IR (thin-film, cm-1): ν, 1656.1 (CdO), 2140.1
(Ir-H). Anal. Calcd for C52H46N2OP3F6Ir‚0.5(CH2Cl2): C, 54.52,
H, 4.09, N, 2.42. Found: C, 54.44, H, 4.04, N, 2.23.
Ack n ow led gm en t. We thank the NSF and the
Chonbuk National University for support.
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates, bond distances, bond angles, anisotropic displace-
ment coefficients, and hydrogen atom coordinates for the
structural analyses of compound 2‚CH2Cl2. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM000115B