Cationic iridium(III) complexes bearing phosphaalkene and 2-pyridylphenyl ligands

Article abstract of DOI:10.1021/om700275s

The reactions of [Ir(ppy)₂(H₂O)₂](OTf) (ppy = 2-pyridylphenyl) with 1,2-diaryl-3,4-bis[(2,4,6-tri-tert-butylphenyl) phosphinidene]cyclobutenes (DPCB-Y) afford [Ir(ppy)₂(DPCB-Y)](OTf) (Y = CF₃ (1), H (2), and OMe (3)) in high yields. The 2-(2-pyridyl)phosphaethene (PN) analogue [Ir(ppy)₂(PN)](OTf) (4) is prepared in a similar manner. Complexes 1-4 are characterized by elemental analysis, NMR and electronic spectroscopy, cyclic voltammetry, and/or X-ray structural analysis.

Full text of DOI:10.1021/om700275s

3708
Organometallics 2007, 26, 3708-3712
Cationic Iridium(III) Complexes Bearing Phosphaalkene and
2-Pyridylphenyl Ligands
Akito Hayashi, Takeshi Ishiyama, Masaaki Okazaki, and Fumiyuki Ozawa*
International Research Center for Elements Science (IRCELS), Institute for Chemical Research,
Kyoto UniVersity, Uji, Kyoto 611-0011, Japan
ReceiVed March 22, 2007
The reactions of [Ir(ppy)2(H2O)2](OTf) (ppy ) 2-pyridylphenyl) with 1,2-diaryl-3,4-bis[(2,4,6-tri-tert-
butylphenyl)phosphinidene]cyclobutenes (DPCB-Y) afford [Ir(ppy)2(DPCB-Y)](OTf) (Y ) CF3 (1), H
(2), and OMe (3)) in high yields. The 2-(2-pyridyl)phosphaethene (P∧N) analogue [Ir(ppy)2(P∧N)](OTf)
(4) is prepared in a similar manner. Complexes 1-4 are characterized by elemental analysis, NMR and
electronic spectroscopy, cyclic voltammetry, and/or X-ray structural analysis.
and yellow emission, respectively.13 The marked variation in
the emission color is mainly due to the difference in the metal
t2g orbital levels dependent on ancillary ligands. In this study,
we examined the π-accepting ability of DPCB-Y ligands in [Ir-
(ppy)2(DPCB-Y)]+ complexes. It was found that the oxidation
potential is rather sensitive to the substituents of DPCB-Y
ligands. The synthesis of a related 2-(2-pyridyl)phosphaethene
complex is also reported.
Introduction
The appropriate choice of ancillary ligands is essential to gain
desirable functions of transition metal complexes. From the
electronic point of view, ancillary ligands are classified as
σ-donors and π-acceptors. The former includes nitrogen bases
such as dimines and bipyridines, phosphines, N-heterocyclic
carbenes, and cyclopentadienyl derivatives; their properties may
be finely tuned by chemical modifications. On the other hand,
ancillary ligands that are strong π-acceptors are limited. Al-
though carbon monoxide is a typical π-acceptor, this molecule
is generally reactive toward organometallic compounds and its
chemical modification is infeasible. This situation has urged us
to examine a new type of π-accepting ligand 1,2-diaryl-3,4-
bis-[(2,4,6-tri-tert-butylphenyl)phosphinidene]cyclobutenes
(DPCB-Y), whose electronic and steric properties can be con-
trolled by introducing a variety of substituents to the backbone.1,2
The most striking feature of DPCB-Y is the extremely low-
lying π*-orbitals spread over the diphosphinidenecyclobutene
skeleton to induce strong π-back-donation from transition
metals.3
This paper reports the synthesis, structures, and properties
of cationic iridium(III) complexes bearing 2-pyridylphenyl (ppy)
and DPCB-Y ligands. Over the past years, a number of studies
have been carried out on the photophysical properties of
octahedral d6 Ru(II), Os(II), Rh(III), and Ir(III) complexes,4-6
because of their potential applications to photoreductants,7
emissive materials,8-11 and chemical sensors.12 In 2003, Nazeer-
uddin et al. reported a new series of Ir(III) complexes (NBu4)-
[Ir(ppy)2(CN)2], (NBu4)[Ir(ppy)2(NCS)2], and (NBu4)[Ir(ppy)2-
(NCO)2] (ppy ) 2-pyridylphenyl), which exhibit blue, green,
Results and Discussion
Synthesis. A variety of iridium(III) complexes bearing
2-pyridylphenyl (ppy) ligands have been synthesized from [Ir-
(8) (a) Baldo, M. A.; O’Brien, D. F.; You, Y.; Shoustikov, A.; Sibley,
S.; Thompson, M. E.; Forrest, S. R. Nature 1998, 395, 151. (b) Baldo, M.
A.; Lamansky, S.; Burrows, P. E.; Thompson, M. E.; Forrest, S. R. Appl.
Phys. Lett. 1999, 75, 4. (c) Thompson, M. E.; Burrows, P. E.; Forrest, S.
R. Curr. Opin. Solid State Mater. Sci. 1999, 4, 369. (d) Baldo, M. A.;
Thompson, M. E.; Forrest, S. R. Nature 2000, 403, 750. (e) Adachi, C.;
Kwong, R. C.; Djurovich, P.; Adamovich, V.; Baldo, M. A.; Thompson,
M. E.; Forrest, S. R. Appl. Phys. Lett. 2001, 79, 2082. (f) Lamansky, S.;
Djurovich, P. I.; Abdel-Razzaq, F.; Garon, S.; Murphy, D. L.; Thompson,
M. E. J. Appl. Phys. 2002, 92, 1570. (g) Chen, F.-C.; Yang, Y.; Thompson,
M. E.; Kido, J. Appl. Phys. Lett. 2002, 80, 2308.
(9) (a) Wang, Y.; Herron, N.; Grushin, V. V.; LeCloux, D.; Petrov, V.;
Appl. Phys. Lett. 2001, 79, 449. (b) Watanabe, T.; Nakamura, K.; Kawami,
S.; Fukuda, Y.; Tsuji, T.; Wakimoto, T.; Miyaguchi, S.; Yahiro, M.; Yang,
M.-J.; Tsutsui, T. Synth. Met. 2001, 122, 203. (c) Xie, H. Z.; Liu, M. W.;
Wang, O. Y.; Zhang, X. H.; Lee, C. S.; Hung, L. S.; Lee, S. T.; Teng, P.
F.; Kwong, H. L.; Zheng, H.; Che, C. M. AdV. Mater. 2001, 13, 1245. (d)
Ostrowski, J. C.; Robinson, M. R.; Heeger, A. J.; Bazan, G. C. Chem.
Commun. 2002, 784. (e) Zhu, W.; Mo, Y.; Yuan, M.; Yang, W.; Cao, Y.
Appl. Phys. Lett. 2002, 80, 2045. (f) Markham, J. P. J.; Lo, S.-C.; Magennis,
S. W.; Burn, P. L.; Samuel, I. D. W. Appl. Phys. Lett. 2002, 80, 2645. (g)
Duan, J.-P.; Sun, P.-P.; Cheng, C.-H. AdV. Mater. 2003, 15, 224. (h) Houjou,
H.; Shimizu, Y.; Koshizaki, N.; Kanesato, M. AdV. Mater. 2003, 15, 1458.
(i) Laskar, I. R.; Chen, T.-M. Chem. Mater. 2004, 16, 111. (j) Slinker, J.
D.; Gorodetsky, A. A.; Lowry, M. S.; Wang, J.; Parker, S.; Rohl, R.;
Bernhard, S.; Malliaras, G. G. J. Am. Chem. Soc. 2004, 126, 2763.
(10) (a) Tsuboyama, A.; Iwasaki, H.; Furugori, M.; Mukaide, T.;
Kamatani, J.; Igawa, S.; Moriyama, T.; Miura, S.; Takiguchi, T.; Okada,
S.; Hoshino, M.; Ueno, K. J. Am. Chem. Soc. 2003, 125, 12971. (b)
Tsuboyama, A.; Takiguchi, T.; Okada, S.; Osawa, M.; Hoshino, M.; Ueno,
K. Dalton Trans. 2004, 1115.
* To whom correspondence should be addressed. E-mail: ozawa@
scl.kyoto-u.ac.jp.
(1) (a) Ozawa, F.; Yoshifuji, M. C. R. Chimie 2004, 7, 747. (b) Ozawa,
F.; Yoshifuji, M. Dalton Trans. 2006, 4987.
(2) For reviews of related studies, see: (a) Le Floch, P. Coord. Chem.
ReV. 2006, 250, 627. (b) Yoshifuji, M. Pure Appl. Chem. 2005, 77, 2011.
(c) Mathey, F. Angew. Chem., Int. Ed. 2003, 42, 1578. (d) Weber, L. Angew.
Chem., Int. Ed. 2002, 41, 563.
(3) Ozawa, F.; Kawagishi, S.; Ishiyama, T.; Yoshifuji, M. Organome-
tallics 2004, 23, 1325.
(4) Juris, A.; Balzani, V.; Barigelletti, F.; Campagna, S.; Belser, P.; von
Zelewsky, A. Coord. Chem. ReV. 1988, 84, 85.
(5) Meyer, T. J. Acc. Chem. Res. 1989, 22, 163.
(6) Kalyanasundaram, K.; Gra¨tzel, M. Coord. Chem. ReV. 1977, 77, 347.
(7) (a) Belmore, K. A.; Venderpool, R. A.; Tsai, J.-C.; Khan, M. A.;
Nicholas, K. M. J. Am. Chem. Soc. 1988, 110, 2004. (b) Silaware, N. D.;
Goldman, A. S.; Ritter, R.; Tyler, D. R. Inorg. Chem. 1989, 28, 1231.
(11) (a) Gao, F. G.; Bard, A. J. Chem. Mater. 2002, 14, 3465. (b) Gao,
F. G.; Bard, A. J. J. Am. Chem. Soc. 2000, 122, 7426. (c) Handy, E. S.;
Pal, A. J.; Rubner, M. F. J. Am. Chem. Soc. 1999, 121, 3525.
(12) (a) Amao, Y.; Ishikawa, Y.; Okura, I. Anal. Chim. Acta 2001, 445,
177. (b) Zakeeruddin, S. M.; Fraser, D. M.; Nazeeruddin, M. K.; Gra¨tzel,
M. J. Electroanal. Chem. 1992, 337, 253.
(13) Nazeeruddin, M. K.; Humphry-Baker, R.; Berner, D.; Rivier, S.;
Zuppiroli, L.; Graetzel, M. J. Am. Chem. Soc. 2003, 125, 8790.
10.1021/om700275s CCC: $37.00 © 2007 American Chemical Society
Publication on Web 06/08/2007

Cationic Iridium(III) Complexes
Scheme 1
Organometallics, Vol. 26, No. 15, 2007 3709
(ppy)2(µ-Cl)]2.14-18 Accordingly, we first examined the reaction
of this complex with DPCB-Y. However, no coordination of
DPCB-Y took place. We therefore introduced a more labile
complex, [Ir(ppy)2(H2O)2](OTf),19 which smoothly underwent
substitution of H2O ligands with DPCB-Y to give 1-3 (Scheme
1). The reaction cleanly proceeded in CH2Cl2 at room temper-
ature, and analytically pure compounds were obtained simply
by evaporating the solvent, followed by washing the resulting
solids with Et2O (84-92% yields). The 2-(2-pyridyl)phospha-
ethene (P∧N) complex 4 was synthesized in a similar manner
Figure 1. ORTEP drawing of 2‚(2THF) with thermal ellipsoids
at the 50% probability level. Hydrogen atoms, counteranion, and
two molecules of THF are omitted for clarity.
(86% yield). To our knowledge, complexes 1-4 are the first
examples of iridium(III) complexes bearing sp2-hybridized
phosphorus ligands. Complexes 1-3 are stable in the solid
state as well as in poorly coordinating solvents such as
CH2Cl2, CHCl3, and THF, but easily dissociate the DPCB-Y
ligands in MeCN. On the other hand, complex 4 was stable
even in MeCN.
Characterization. Complexes 1-4 were identified by elemen-
tal analysis and NMR spectroscopy. As a representative exam-
ple, complex 1 exhibited aromatic proton signals assignable to
ppy ligands in a range typical for Ir(III) ppy complexes (δ 5.75-
9.88).20 The tert-butyl protons of 2,4,6-tri-tert-butylphenyl
groups (Mes*) were observed as three sets of singlets at δ 0.77
(18H), 1.26 (18H), and 1.75 (18H), showing hindered rotation
around the C(Mes*)-P bonds, making the two ortho tert-butyl
groups nonequivalent. The 31P{1H} NMR chemical shift (δ
130.6) was considerably higher than that of free DPCB-CF3 (δ
180.7). Complexes 2 and 3 showed similar spectroscopic
features.
Crystal Structure of 2. The X-ray diffraction analysis
of 2 was performed for single crystals grown by slow diffusion
of a THF solution into Et2O at room temperature. Figure 1
illustrates the molecular structure, which adopts a typical
octahedral geometry around iridium, taking the cis-C,C and
trans-N,N disposition of the ppy ligands. Selected bond
distances and angles are listed in Table 1. The Ir-C (2.045(5),
2.042(5) Å) and Ir-N (2.078(4), 2.072(4) Å) lengths are with-
in the range reported for bipyridine and diphosphine ana-
logues (1.99-2.06 Å for Ir-C, 1.98-2.08 Å for Ir-N).15f,17,18
On the other hand, the N-Ir-N (165.56(16)°) angle is
significantly smaller than that of the related complexes, pro-
bably due to steric repulsion between the pyridine rings and
the Mes* groups (C, D); the interatomic distances between the
carbons C25‚‚‚C57 (3.216(7) Å) and C52‚‚‚C68 (3.221(7) Å)
are much shorter than the sum (3.7 Å) of the effective van der
Waals radii of methyl groups (2.0 Å) and the half-thickness of
the π-electron cloud of aromatic rings (1.7 Å). The coordi-
nation plane A consisting of Ir, P1, C1, C4, and P2 atoms
is coplanar to the cyclobutene ring B, but almost perpen-
dicular to the Mes* rings (C and D) on the phosphorus
atoms.
(14) (a) Sprouse, S.; King, K. A.; Spellane, P. J.; Watts, R. J. J. Am.
Chem. Soc. 1984, 106, 6647. (b) King, K. A.; Spellane, P. J.; Watts, R. J.
J. Am. Chem. Soc. 1985, 107, 1431. (c) King, K. A.; Watts, R. J. J. Am.
Chem. Soc. 1987, 109, 1589. (d) Osawa, Y.; Sprouse, S.; King, K. A.;
DeArmond, M. K.; Hanck, K. W.; Watts, R. J. J. Phys. Chem. 1987, 91,
1047. (e) Garces, F. O.; King, K. A.; Watts, R. J. Inorg. Chem. 1988, 27,
3464. (f) Dedeian, K.; Djurovich, P. I.; Garces, F. O.; Carlson, G.; Watts,
R. J. Inorg. Chem. 1991, 30, 1685. (g) Wilde, A. P.; Watts, R. J. J. Phys.
Chem. 1991, 95, 622. (h) Wilde, A. P.; King, K. A.; Watts, R. J. J. Phys.
Chem. 1991, 95, 629.
(15) (a) Lamansky, S.; Djurovich, P.; Murphy, D.; Abdel-Razzaq, F.;
Lee, H.-E.; Adachi, C.; Burrows, P. E.; Forrest, S. R.; Thompson, M. E. J.
Am. Chem. Soc. 2001, 123, 4304. (b) Lamansky, S.; Djurovich, P.; Murphy,
D.; Abdel-Razzaq, F.; Kwong, R.; Tsyba, I.; Bortz, M.; Mui, B.; Bau, R.;
Thompson, M. E. Inorg. Chem. 2001, 40, 1704. (c) Gao, R.; Ho, D. G.;
Hernandez, B.; Selke, M.; Murphy, D.; Djurovich, P. I.; Thompson, M. E.
J. Am. Chem. Soc. 2002, 124, 14828. (d) Tamayo, A. B.; Alleyne, B. D.;
Djurovich, P. I.; Lamansky, S.; Tsyba, I.; Ho, N. N.; Bau, R.; Thompson,
M. E. J. Am. Chem. Soc. 2003, 125, 7377. (e) Li, J.; Djurovich, P. I.;
Alleyne, B. D.; Tsyba, I.; Ho, N. N.; Bau, R.; Thompson, M. E. Polyhedron
2004, 23, 419. (f) Li, J.; Djurovich, P. I.; Alleyne, B. D.; Yousufuddin, M.;
Ho, N. N.; Christopher Thomas, J.; Peters, J. C.; Bau, R.; Thompson, M.
E. Inorg. Chem. 2005, 44, 1713.
(16) (a) Colombo, M. G.; Hauser, A.; Gu¨del, H. U. Inorg. Chem. 1993,
32, 3088. (b) Calogero, G.; Giuffrida, G.; Serroni, S.; Ricevuto, V.;
Campagna, S. Inorg. Chem. 1995, 34, 541. (c) Mamo, A.; Stefio, I.; Parisi,
M. F.; Credi, A.; Venturi, M.; Pietro, C. D.; Campagna, S. Inorg. Chem.
1997, 36, 5947. (d) Griffiths, P. M.; Loiseau, F.; Puntoriero, F.; Serroni,
S.; Campagna, S. Chem. Commun. 2000, 2297. (e) Plummer, E. A.;
Hofstraat, J. W.; De Cola, L. Dalton Trans. 2003, 2080.
(17) (a) Neve, F.; Crispini, A.; Campagna, S.; Serroni, S. Inorg. Chem.
1999, 38, 2250. (b) Neve, F.; Crispini, A.; Loiseau, F.; Campagna, S. J.
Chem. Soc., Dalton Trans. 2000, 1399. (c) Neve, F.; Crispini, A. Eur. J.
Inorg. Chem. 2000, 1039. (d) Neve, F.; Crispini, A.; Serroni, S.; Loiseau,
F.; Campagna, S. Inorg. Chem. 2001, 40, 1093. (e) Neve, F.; La Deda, M.;
Crispini, A.; Bellusci, A.; Puntoriero, F.; Campagna, S. Organometallics
2004, 23, 5856.
(18) (a) Lo, K. K.-W.; Ng, D. C.-M.; Chung, C.-K. Organometallics
2001, 20, 4999. (b) Lo, K. K.-W.; Chung, C.-K.; Ng, D. C.-M.; Zhu, N.
New J. Chem. 2002, 26, 81. (c) Lo, K. K.-W.; Chung, C.-K.; Zhu, N.
Chem.-Eur. J. 2003, 9, 475. (d) Lo, K. K.-W.; Chung, C.-K.; Lee, T. K.-
W.; Lui, L.-H.; Tsang, K. H.-K.; Zhu, N. Inorg. Chem. 2003, 42, 6886. (e)
Lo, K. K.-W.; Chan, J. S.-W.; Lui, L.-H.; Chung, C.-K. Organometallics
2004, 23, 3108. (f) Lo, K. K.-W.; Chan, J. S.-W.; Chung, C.-K.; Tsang, V.
W.-H.; Zhu, N. Inorg. Chim. Acta 2004, 357, 3109. (g) Lepeltier, M.; Lee,
T. K.-M.; Lo, K. K.-W.; Toupet, L.; Le Bozec, H.; Guerchais, V. Eur. J.
Inorg. Chem. 2005, 110.
(19) Schmid, B.; Garces, F. O.; Watts, R. J. Inorg. Chem. 1994, 33, 9.
(20) Garces, F. O.; Watts, R. J. Magn. Reson. Chem. 1993, 31, 529.

3710 Organometallics, Vol. 26, No. 15, 2007
Hayashi et al.
Table 1. Selected Bond Distances (Å) and Angles (deg) for
2‚(2THF)
Ir-P1
2.5281(13)
2.5228(16)
2.045(5)
2.042(5)
1.494(7)
1.498(7)
1.475(7)
Ir-N1
2.078(4)
2.072(4)
1.682(5)
1.674(5)
1.388(7)
1.464(6)
1.472(7)
Ir-P2
Ir-N2
Ir-C63
Ir-C74
C1-C4
C1-C2
C3-C4
P1-C1
P2-C4
C2-C3
C2-C5
C3-C11
P1-Ir-P2
N1-Ir-N2
C63-Ir-C74
81.85(5)
165.56(16)
85.54(19)
C1-P1-C17
C4-P2-C35
106.9(2)
104.7(2)
A-B
A-C
A-D
0.74(35)
85.53(11)
88.44(13)
B-E
B-F
58.40(19)
23.48(32)
Figure 2. Absorption spectra of phosphaalkene ligands.
Table 2. Electrochemical Data for 1-4a
redox
E
pa (V) vs Fc/Fc+
[1]/[1]+
[2]/[2]+
[3]/[3]+
[4]/[4]+
+1.37
+1.30
+0.92
+1.15
a In CH2Cl2 (0.1 M nBu4NBF4) at room temperature, sweep rate
50 mV s-1
.
The 1,2-diphenyl-3,4-diphosphinidenecyclobutene skeleton of
the DPCB-H ligand notably changed bond distances upon the
coordination, involving elongation of the C2-C3 bond (+0.5%)
and shortening of the C1-C4 (-2.7%), C2-C5 (-0.5%), and
C3-C11 (-1.0%) bonds as compared with free DPCB-H.21 As
previously pointed out for PtMe2(DPCB-H),3 these structural
variations are attributable to the occurrence of π-back-donation
from the t2g orbitals of iridium to the π*-orbitals of the DPCB-H
ligand, while the magnitude of variation is somewhat smaller
than that of the platinum complex.
Electrochemical Analysis. The cyclic voltammograms of
1-4 showed one irreversible one-electron oxidation wave in
the region 0.92-1.37 V vs Fc/Fc+. As seen from Table 2, the
oxidation potentials are sensitive to the substituent Y on the
DPCB-Y ligands. Thus, the CF3 group in 1 causes a positive
shift, whereas the OMe group in 3 causes a negative shift. The
large cathodic shift by 450 mV in 1 compared with 3 is
ascribable to the strong electron-withdrawing nature of the CF3
group, which induces π-back-donation from the iridium center
through the π-conjugation system spread over the 1,2-diphenyl-
3,4-diphosphinidenecyclobutene skeleton. On the basis of the
oxidation potentials, the t2g orbital levels are estimated to be in
the order 3 > 4 > 2 > 1.
Electronic Spectra. Figure 2 shows the absorption spectra
of DPCB-Y and P∧N ligands. The DPCB-Y ligands displayed
strong absorptions with a shoulder in the UV and visible regions.
The absorption bands at around 330 nm are assigned to π-π*
transitions.22 As expected for π-conjugated molecules, DPCB-
OMe exhibited the absorption maximum at the longest wave-
length (λmax ) 335 (OMe), 328 (H), 329 nm (CF3)). The P∧N
ligand showed two absorption bands at the maxima of 283 and
328 nm, which are tentatively assigned to π-π* transitions of
the pyridine and phosphaalkene parts, respectively. The longer
wavelength for the phosphaalkene part is consistent with the
previous MO calculation for phosphaethene showing an ex-
tremely low-lying π*-orbital and a moderately high-lying
π-orbital across the PdC bond.3
Figure 3. Absorption spectra of iridium(III) complexes 1-4.
Figure 3 compares the UV-vis spectra of 1-4. All complexes
showed strong absorptions at 250-300 nm due to the spin-
allowed π-π* transitions of the ppy ligands.9j,14,16-19 The other
π-π* transitions arising from the phosphaalkene parts were
observed in the region 356-382 nm with a broad shoulder band
at 400-550 nm. The latter absorptions are significantly red-
shifted as compared with the corresponding free ligands,
showing the occurrence of extended π-conjugation through
π-back-bonding between iridium and the phosphaalkenes. Since
the π-back-donation should stabilize the metal t2g orbitals, a
blue-shift of the MLCT band of the Ir(ppy)2 moiety was also
expected. However, the corresponding absorption was not clearly
observed due to the overlap with much stronger π-π* transition
bands.
Emission spectra of 1-4 were measured in a degassed
chloroform solution at room temperature. No notable emission
was observed for 2 and 3. On the other hand, 1 and 4, bearing
DPCB-CF3 and P∧N ligands, exhibited bluish-green (λem ) 492
nm, Φem ) 0.02) and green (λem ) 513 nm, Φem ) 0.03)
luminescence, respectively. The emission maxima were in
significantly shorter wavelength regions than that of [Ir(ppy)2-
(bpy)]+ (λem ) 600 nm),14g and comparable to that of
[Ir(ppy)2(CN)2]- (λem ) 470, 502 nm) and [Ir(ppy)2(NCS)2]-
(λem ) 506, 520 nm), having electron-withdrawing ligands.13
Conclusion
We have synthesized a new series of cationic iridium(III)
complexes bearing phophaalkene and 2-pyridylphenyl ligands
and examined their electrochemical and photophysical proper-
ties. It has been confirmed that the metal t2g levels can be tuned
by chemical modification of the phosphaalkene ligands. The
(21) Appel, R.; Winkhaus, V.; Knoch, F. Chem. Ber. 1987, 120, 243.
(22) Nakamura, A.; Kawasaki, S.; Toyota, K.; Yoshifuji, M. Chem. Lett.
2004, 33, 1570.

Cationic Iridium(III) Complexes
Organometallics, Vol. 26, No. 15, 2007 3711
Table 3. Crystallographic Data for 2‚(2THF)
DPCB-CF3 ligand in 1 serves as a particularly effective
π-acceptor to cause bluish-green luminescence at 492 nm.
color
habit
red
block
cryst size (mm)
formula
fw
0.10 × 0.06 × 0.06
C83H100F3IrN2O5P2S
1548.85
Experimental Section
General Considerations. All manipulations were carried out
under a dry nitrogen atmosphere using standard Schlenk techniques
unless otherwise noted. NMR spectra were recorded on a Varian
Mercury 300 spectrometer at room temperature. Chemical shifts
a (Å)
b (Å)
c (Å)
14.266(6)
24.292(9)
21.352(8)
92.193(3)
7394(5)
monoclinic
P21/c
4
3.03-27.48
57 524
16 695 [Rint ) 0.0882]
98.4%
1.112
R1 ) 0.0604, wR2 ) 0.1052
R1 ) 0.0907, wR2 ) 0.1165
â (deg)
V (Å3)
1
are reported in δ, referenced to H (of residual protons) and 13C
cryst syst
space group
Z
θ range (deg)
no. of reflns collected
no. of indep reflns
completeness to θ
goodness-of-fit on F2
final R indices [I >2σ(I)]
R indices (all data)
signals of deuterated solvents as internal standards or to the 31P
signal of 85% H3PO4 as an external standard. Elemental analysis
was performed on a Perkin-Elmer 2400 II CHN analyzer. UV-vis
absorption and emission spectra were recorded on JASCO V-560
and Hitachi F-2500 spectrometers, respectively. Dichloromethane
was dried over CaH2 and distilled prior to use. Diethyl ether and
THF were distilled from sodium benzophenone ketyl before use.
The compounds [Ir(ppy)2(H2O)2](OTf),19 DPCB-Y (Y ) CF3, H,
OMe)3 and 2-(2-pyridyl)phosphaethene (P∧N)23 were synthesized
by published procedures. Other chemicals were purchased and used
as received.
Synthesis of [Ir(ppy)2(DPCB-CF3)](OTf) (1). To a solution of
[Ir(ppy)2(H2O)2](OTf) (50.3 mg, 0.0734 mmol) in CH2Cl2 (2.0 mL)
was added DPCB-CF3 (65.5 mg, 0.0745 mmol) with constant
stirring. The yellow solution immediately turned red. After stirring
at room temperature for 2 h, volatiles were removed under reduced
pressure. The residue was washed with Et2O and hexane at 0 °C
and was dried under reduced pressure to give an orange powder of
1. Yield: 104 mg (92%). Mp: 195 °C. 1H NMR (CDCl3): δ 0.77
(s, 18H, o-tBu), 1.26 (s, 18H, p-tBu), 1.75 (s, 18H, o-tBu), 5.75
(d, JHH ) 7.3 Hz, 2H, ppy), 6.55 (d, JHH ) 8.2 Hz, 4H, ppy), 6.76
(t, JHH ) 7.0 Hz, 2H, ppy), 6.85 (t, JHH ) 7.1 Hz, 2H, ppy), 7.13
(s, 2H, Mes*), 7.20 (d, JHH ) 8.6 Hz, 4H, ppy), 7.47 (d, JHH ) 7.0
Hz, 2H, ppy), 7.50 (s, 2H, Mes*), 7.60 (t, JHH ) 5.9 Hz, 2H, ppy),
8.01 (d, JHH ) 7.5 Hz, 2H, ppy), 8.22 (t, JHH ) 7.7 Hz, 2H, ppy),
9.88 (d, JHH ) 5.5 Hz, 2H, ppy). 13C{1H} NMR (CDCl3): δ 31.0
(p-CMe3), 32.7 (o-CMe3), 33.5 (o-CMe3), 35.1 (p-CMe3), 37.3
(o-CMe3), 38.3 (o-CMe3), 120.8, 121.0 (q, JFC ) 321 Hz, OTf),
122.7, 123.2, 123.3 (q, JFC ) 273 Hz, CF3), 123.5, 124.3, 125.4,
125.5, 126.1 (m), 127.7, 130.1, 131.1, 131.6, 131.9, 140.3, 142.8
Hz), 184.1 (t, JPC ) 21 Hz, PdC). 31P{1H} NMR (CDCl3): δ 119.7
(s). Anal. Calcd for C75H84F3IrN2O3P2S: C, 64.13; H, 6.03; N, 1.99.
Found: C, 64.48; H, 5.99; N, 2.04.
Synthesis of [Ir(ppy)2(DPCB-OMe)](OTf) (3). Compound 3
was synthesized as a red powder similarly to 1, using [Ir(ppy)2-
(H2O)2](OTf) (50.2 mg, 0.0732 mmol), CH2Cl2 (2 mL), and
DPCB-OMe (59.6 mg, 0.0731 mmol). Yield: 89.9 mg (84%).
Mp: 197 °C. H NMR (CDCl3): δ 0.79 (s, 18H, o-tBu), 1.30
1
(s, 18H, p-tBu), 1.72 (s, 18H, o-tBu), 3.72 (s, 6H, OMe), 5.76
(dd, JHH ) 5.1 Hz, 2H, ppy), 6.34 (d, JHH ) 9.0 Hz, 4H, ppy),
6.42 (d, JHH ) 9.0 Hz, 4H, ppy), 6.73 (t, JHH ) 6.9 Hz, 2H, ppy),
6.82 (t, JHH ) 7.5 Hz, 2H, ppy), 7.19 (s, 2H, Mes*), 7.44 (d, JHH
) 7.5 Hz, 2H, ppy), 7.47 (s, 2H, Mes*), 7.50 (t, JHH ) 6.0 Hz,
2H, ppy), 7.97 (d, JHH ) 7.7 Hz, 2H, ppy), 8.15 (t, JHH ) 7.4 Hz,
2H, ppy), 9.94 (d, JHH ) 5.1 Hz, 2H, ppy). 13C{1H} NMR
(CDCl3): δ 31.2 (p-CMe3), 32.6 (o-CMe3), 33.5 (o-CMe3), 35.1
(p-CMe3), 37.3 (o-CMe3), 38.3 (o-CMe3), 55.2 (OMe), 114.0, 120.4,
121.0 (q, JFC ) 321 Hz, OTf), 121.2, 122.5, 122.7, 123.5, 123.9,
124.1, 126.8, 129.5, 129.9, 131.2, 139.7, 143.7, 143.8 (dd, JPC
)
106 and 8.6 Hz, PdCC), 153.1, 156.1, 156.3 (dd, JPC ) 54, 34
Hz), 157.3 (t, JPC ) 4.3 Hz), 157.6, 160.7, 167.8 (t, JPC ) 2.9 Hz),
184.5 (t, JPC ) 20 Hz, PdC). 31P{1H} NMR (CDCl3): δ 110.8 (s).
Anal. Calcd for C77H88F3IrN2O5P2S: C, 63.14; H, 6.06; N, 1.91.
Found: C, 63.15; H, 6.01; N, 1.67.
Synthesis of [Ir(ppy)2(P∧N)](OTf) (4). Compound 4 was
synthesized as a bright ocher power similarly to 1, using [Ir(ppy)2-
(H2O)2](OTf) (74.7 mg, 0.109 mmol), CH2Cl2 (3 mL), and P∧N
(dd, JPC ) 107, 9.8 Hz, PdCC), 143.6, 153.7, 155.5 (dd, JPC
)
56, 36 Hz), 156.1, 157.0, 157.7, 167.5, 182.6 (t, JPC ) 21 Hz, Pd
C). 31P{1H} NMR (CDCl3): δ 130.6 (s). Anal. Calcd for C77H82F9-
IrN2O3P2S: C, 60.03; H, 5.36; N, 1.82. Found: C, 59.76; H, 5.22;
N 1.83.
Synthesis of [Ir(ppy)2(DPCB-H)](OTf) (2). Compound 2 was
synthesized as an orange powder similarly to 1, using [Ir(ppy)2-
(H2O)2](OTf) (50.0 mg, 0.0729 mmol), CH2Cl2 (2 mL), and
DPCB-H (55.3 mg, 0.0732 mmol). Yield: 88.5 mg (86%). Mp:
1
(41.3 mg, 0.112 mmol). Yield: 95.6 mg (86%). Mp: 184 °C. H
NMR (THF-d8): δ 0.90 (s, 9H, o-tBu), 1.33 (s, 9H, p-tBu), 1.69
(s, 9H, o-tBu), 5.73 (t, JHH ) 6.8 Hz, 1H), 6.34 (d, JHH ) 7.6 Hz,
1H), 6.74 (t, JHH ) 7.1 Hz, 1H), 6.82 (t, JHH ) 7.8 Hz, 1H), 6.89
(t, JHH ) 7.6 Hz, 1H), 7.01 (t, JHH ) 7.4 Hz, 1H), 7.13-7.19
(m, 1H), 7.35 (t, JHH ) 6.1 Hz, 1H), 7.42 (t, JHH ) 6.5 Hz, 1H),
7.47 (s, 1H), 7.56 (s, 1H), 7.65 (d, JHH ) 7.1 Hz, 1H), 7.80 (d, JHH
) 8.0 Hz, 1H), 7.92-8.08 (m, 5H), 8.16 (d, JHH ) 3.9 Hz, 1H),
8.18 (d, JHH ) 4.1 Hz, 1H), 8.22 (d, JHH ) 5.3 Hz, 1H), 8.81
(d, JPH ) 22 Hz, 1H, PdCH), 9.11 (d, JHH ) 5.3 Hz, 1H). 13C-
{1H} NMR (CDCl3): δ 30.9 (p-CMe3), 33.1 (o-CMe3), 33.7
(o-CMe3), 35.0 (p-CMe3), 36.8 (o-CMe3), 37.7 (o-CMe3), 118.6,
119.3 (d, J ) 2.9 Hz), 120.1, 120.7 (q, JFC ) 320 Hz, OTf), 120.7,
122.4 (d, J ) 6.3 Hz), 122.6, 122.8, 123.0, 123.3 (d, J ) 5.8 Hz),
123.6, 123.8, 123.9, 124.2, 124.6, 124.9 (d, J ) 5.2 Hz), 125.4 (d,
J ) 3.5 Hz), 125.6, 125.7, 126.4, 126.6, 128.2, 129.9, 129.9, 130.3,
1
256 °C. H NMR (CDCl3): δ 0.78 (s, 18H, o-tBu), 1.27 (s, 18H,
p-tBu), 1.73 (s, 18H, o-tBu), 5.76 (dd, JHH ) 7.7, 2.9 Hz, 2H, ppy),
6.44 (d, JHH ) 7.7 Hz, 4H, ppy), 6.74 (t, JHH ) 7.7 Hz, 2H, ppy),
6.82 (t, JHH ) 7.2 Hz, 2H, ppy), 6.91 (t, JHH ) 7.9 Hz, 4H, ppy),
7.13 (d, JHH ) 2.6 Hz, 2H, Mes*), 7.15 (t, JHH ) 8.1 Hz, 2H,
ppy), 7.44 (d, JHH ) 6.8 Hz, 2H, ppy), 7.46 (s, 2H, Mes*), 7.54
(t, JHH ) 6.1 Hz, 2H, ppy), 7.99 (d, JHH ) 7.1 Hz, 2H, ppy), 8.20
(t, JHH ) 7.5 Hz, 2H, ppy), 9.93 (d, JHH ) 4.9 Hz, 2H, ppy). 13C-
{1H} NMR (CDCl3): δ 31.1 (p-CMe3), 32.6 (o-CMe3), 33.5
(o-CMe3), 35.1 (p-CMe3), 37.2 (o-CMe3), 38.2 (o-CMe3), 120.6,
121.0 (q, JFC ) 321 Hz, OTf), 122.4, 122.8, 123.4, 124.0, 124.1,
126.3 (m), 127.4, 128.4, 128.7, 129.9, 129.9, 131.2, 139.9, 143.4
(dd, JPC ) 107, 9.2 Hz, PdCC), 143.7, 153.1, 155.9, 157.1 (t, JPC
) 4.3 Hz), 157.2 (dd, JPC ) 55, 35 Hz), 157.4, 167.6 (t, JPC ) 2.6
(24) Beurskens, P. T.; Beuskens, G.; de Gelder, R.; Garc´ıa-Grana, S.;
Gould, R. O.; Israel, R.; Smits, J. M. M. The DIRDIF99 Program System;
University of Nijmegen: The Netherlands, 1999.
(25) Sheldrick, G. M. SHELXL-97; University of Go¨ttingen: Germany,
1997.
(23) (a) Jouaiti, A.; Geoffroy, M.; Bernardinelli, G. Tetrahedron Lett.
1992, 33, 5071. (b) van der Sluis, M.; Beverwijk, V.; Termaten, A.;
Gavrilova, E.; Bickelhaupt, F.; Kooijman, H.; Veldman, N.; Spek, A. L.
Organometallics 1997, 16, 1144.

3712 Organometallics, Vol. 26, No. 15, 2007
Hayashi et al.
131.3, 131.4 (d, J ) 6.9 Hz), 132.6, 133.3, 134.9, 138.4, 138.7,
138.8, 139.1, 139.3, 139.9, 140.5 (d, J ) 2.9 Hz), 142.0 (d, J )
5.8 Hz), 142.7, 143.1, 143.5, 144.3, 145.4, 149.0, 149.5, 150.4,
151.1, 151.8, 151.9, 152.8, 153.3, 154.3, 154.4, 155.8, 156.4, 160.5
(d, J ) 4.6 Hz), 165.8, 166.6 (d, J ) 6.3 Hz), 167.9, 168.5, 168.9,
204.3. 31P{1H} NMR (CDCl3): δ 244.3 (s). Anal. Calcd for
C47H50F3IrN3O3PS: C, 55.50; H, 4.95; N, 4.13. Found: C, 55.31;
H, 5.21; N, 4.03.
X-ray Crystal Structure Determination of 2. The intensity data
were collected on a Rigaku Mercury CCD diffractometer at 173 K
with graphite-monochromated Mo KR radiation (λ ) 0.71070 Å).
The structure was solved by DIRDIF9924 and refined by full-matrix
least-squares procedures on F2 for all reflections (SHELXL-97).25
All hydrogen atoms were placed using AFIX instructions, while
other atoms were refined anisotropically. Crystallographic data for
the structural analysis have been deposited with the Cambridge
Crystallographic Center (CCDC No. 638281). Crystallographic data
for 2‚(2THF) are summarized in Table 3.
Acknowledgment. This work was supported by Grants-in-
Aid for Scientific Research on Priority Areas (No. 18064010,
“Synergy of Elements”) from the Ministry of Education, Culture,
Sports, Science, and Technology, Japan.
Supporting Information Available: Crystallographic data for
2 in cif format. This material is available free of charge via the
Internet at http://pubs.acs.org.
OM700275S