Synthesis of a library of iridium-containing dinuclear complexes with bridging PNNN and PNNP ligands (BL), [LM(μ-BL)M′L′]BF 4. 1. Specific synthesis of isomeric heterodinuclear complexes with switched metal arrangements

Article abstract of DOI:10.1021/om050896m

Specific synthesis of a series of Ir-containing homo- and heterodinuclear complexes with the PNNP (3,5-bis((diphenylphosphino)methyl)pyrazolato) and PNNN ligands (3-(diphenylphosphino)methyl-5-pyridylpyrazolato) is reported. Reaction of the PNNX-H precursors (X = P, N) with [Ir(cod)₂]BF₄ gives pale yellow precipitates, which are characterized as the cyclic dimers of the 1:1 adduct, [μ-K¹(P): κ²(AyO-PNNX-H)Ir(cod)] ₂(BF₄)₂ (X = P, N). In the case of the PNNN system, subsequent sequential treatment of the 1:1 adduct with NEt₃ and a second metal reagent ([M(L)(cod)]BF₄: M(L) = Rh(cod), Pd(allyl)) (reaction 1) gives [(cod)Ir(PNNN)M(L)]BF4, whereas the reversed addition of the reagents (reaction 2) furnishes [(L)M(PNNN)Ir(cod)]BF ₄, the regioisomer with the switched metal arrangement. Selective preparation of the heterodinuclear PNNP complexes [(cod)Ir(PNNP)M(L)]BF ₄ requires the addition according to reaction 1. In reaction 1 of the 1:1 dinuclear adduct of the PNNN system, deprotonation of the N-H part triggers interligand migration of the Ir(cod) fragment from the N,N site of one ligand to the P,N site of the other ligand to give [(cod)Ir(PNNN)]BF₄, which reacts with the second metal fragment at the N,N site to furnish [(cod)Ir(PNNN)M(L)]BF4. On the other hand, reaction 2 involves dissociation of the dinuclear species into the mononuclear N,N-coordinated one, [(PNNN-H)Ir(cod)]BF₄, and subsequent interaction at the free P moiety followed by deprotonation and coordination gives the other regioisomer. These intriguing transformations result from the unique coordination properties of Ir (cationic vs neutral, hard vs soft, 5- vs 4-coordination, N,N vs P,N chelation), which are controlled by the deprotonation-protonation procedure. As a result of the present study, a library for Ir-containing homo- and heterodinuclear Ir(I) complexes with the PNNP and PNNN ligands has been constructed.

Full text of DOI:10.1021/om050896m

1344
Organometallics 2006, 25, 1344-1358
Articles
Synthesis of a Library of Iridium-Containing Dinuclear Complexes
with Bridging PNNN and PNNP Ligands (BL), [LM(µ-BL)M′L′]BF4.
1. Specific Synthesis of Isomeric Heterodinuclear Complexes with
Switched Metal Arrangements
Christian Dubs, Toshiki Yamamoto, Akiko Inagaki, and Munetaka Akita*
Chemical Resources Laboratory, Tokyo Institute of Technology, R1-27, 4259 Nagatsuta, Midori-ku,
Yokohama 226-8503, Japan
ReceiVed October 18, 2005
Specific synthesis of a series of Ir-containing homo- and heterodinuclear complexes with the PNNP
(3,5-bis((diphenylphosphino)methyl)pyrazolato) and PNNN ligands (3-(diphenylphosphino)methyl-5-
pyridylpyrazolato) is reported. Reaction of the PNNX-H precursors (X ) P, N) with [Ir(cod)2]BF4 gives
pale yellow precipitates, which are characterized as the cyclic dimers of the 1:1 adduct, [(µ-κ1(P):
κ2(N,X)-PNNX-H)Ir(cod)]2(BF4)2 (X ) P, N). In the case of the PNNN system, subsequent sequential
treatment of the 1:1 adduct with NEt3 and a second metal reagent ([M(L)(cod)]BF4: M(L) ) Rh(cod),
Pd(allyl)) (reaction 1) gives [(cod)Ir(PNNN)M(L)]BF4, whereas the reversed addition of the reagents
(reaction 2) furnishes [(L)M(PNNN)Ir(cod)]BF4, the regioisomer with the switched metal arrangement.
Selective preparation of the heterodinuclear PNNP complexes [(cod)Ir(PNNP)M(L)]BF4 requires the
addition according to reaction 1. In reaction 1 of the 1:1 dinuclear adduct of the PNNN system, depro-
tonation of the N-H part triggers interligand migration of the Ir(cod) fragment from the N,N site of one
ligand to the P,N site of the other ligand to give [(cod)Ir(PNNN)]BF4, which reacts with the second
metal fragment at the N,N site to furnish [(cod)Ir(PNNN)M(L)]BF4. On the other hand, reaction 2 involves
dissociation of the dinuclear species into the mononuclear N,N-coordinated one, [(PNNN-H)Ir(cod)]BF4,
and subsequent interaction at the free P moiety followed by deprotonation and coordination gives the
other regioisomer. These intriguing transformations result from the unique coordination properties of Ir
(cationic vs neutral, hard vs soft, 5- vs 4-coordination, N,N vs P,N chelation), which are controlled by
the deprotonation-protonation procedure. As a result of the present study, a library for Ir-containing
homo- and heterodinuclear Ir(I) complexes with the PNNP and PNNN ligands has been constructed.
systems2 and polyoxometalates.3 In the former systems, multiple
metal centers are integrated by a well-designed bridging poly-
dentate ligand mimicing the active site of the target metalloen-
zyme. To shed light on the non-metal-metal-bonded organo-
metallic systems, we have been studying polynuclear complexes
based on the PNNP ligand 1 (3,5-bis((diphenylphosphino)meth-
yl)pyrazolato),4 which separates the two metal centers beyond
the metal-metal bonding interaction but is flexible enough to
fit substrates of various sizes (Scheme 1). In previous papers,
we reported that the dirhodium tetracarbonyl complex [(PNNP)-
Rh2(CO)4]BF4 was labile enough to release the two inner CO
ligands trans to the P atoms and generated a coordinately
unsaturated species (A) with cis-divacant coordination sites,
which could bind a substrate with up to four donating electrons.5
Introduction
Polynuclear complexes are expected to display unique chemi-
cal behavior through cooperative interaction of the metal centers,
which cannot be realized by mononuclear species.1 Furthermore,
heteropolynuclear complexes consisting of metals of different
kinds may realize more sophisticated functions through sharing
the required functions by the metal centers of different
characters, but selective synthesis of heteronuclear complexes
is not always facile and frequently encounters problems such
as formation of homonuclear complexes as byproducts.
When attention is turned to the structural motifs of poly-
nuclear complexes, metal-metal-bonded cluster systems have
been the major research subject of polynuclear organometallic
chemistry, and little attention has been paid to the non-metal-
metal-bonded systems.1 This situation is in marked contrast to
the relevant inorganic systems such as bioinorganic model
(2) See for example, the special issue for biomimetic inorganic chem-
istry: Chem. ReV. 2004, 104, 347-1200.
(3) (a) See, for example, the special issue for polyoxometalates: Chem.
ReV. 1998, 98, 1-388. (b) Yamase, T: Pope, M. T. Polyoxometalate
Chemistry for Nano-Composite Design (Nanostructure Science and Tech-
nology); Kluwer Academic: New York; 2002.
(4) (a) Schenk, T. G.; Downs, J. M.; Milne, C. R. C.; Mackenzie, P. B.;
Boucher, H.; Whelan, J.; Bosnich, B. Inorg. Chem. 1985, 24, 2334. (b)
Schenk, T. G.; Milne, C. R. C.; Sawyer, J. F.; Bosnich, B. Inorg. Chem.
1985, 24, 2338. (c) Bosnich, B. Inorg. Chem. 1999, 38, 2554.
(1) Braunstein, P.; Oro, L. A.; Raithby, P. R. Metal Clusters in Chemistry;
Wiley-VCH: Weinheim, 1999; Vols. 1-3. Dyson, P. J.; McIndoe, J. S.
Transition Metal Carbonyl Cluster Chemistry; Gordon and Breach Sci-
ence: Amsterdam, 2000. Shriver, D. F.; Kaesz, H. D.; Adams, R. D. The
Chemistry of Metal Cluster Complexes; VCH: New York, 1990. Abel, E.
W.; Stone, F. G. A.; Wilkinson, G. ComprehensiVe Organometallic
Chemistry II; Pergamon: Oxford, U.K., 1995; Vols. 3-10.
10.1021/om050896m CCC: $33.50 © 2006 American Chemical Society
Publication on Web 02/03/2006

Ir Complexes with Bridging PNNN and PNNP Ligands
Organometallics, Vol. 25, No. 6, 2006 1345
Scheme 1
and 2 equiv of the metal reagent. Selective preparation of
heterodinuclear complexes, however, usually requires effort;
otherwise, a mixture of homo- and heteronuclear complexes may
be formed. In any event, for selective synthesis of a heterodi-
nuclear complex, selective preparation of a mononuclear 1:1
adduct precursor is essential, and the 1:1 adduct can be
accessible by addition of a first metal reagent to an excess
amount of a dinucleating ligand. Subsequent treatment with a
second metal reagent will furnish the heterodinuclear complex,
as exemplified for a pyrazolato-based ligand system (B) leading
to the heterodinuclear complex D (Scheme 2; addition of
cationic fragments is shown, where addition of a base is needed).
Simply changing the addition order of the metal reagents should
form the regioisomer D′ with the switched metal arrangement.
This procedure, in principle, can be applicable to any system
but is not always successful. For example, coordination of B to
a cationic metal fragment causes labilization of the N-H proton
(a decrease of its pKa value), in part, to result in spontaneous
deprotonation without addition of a base to give the neutral
species E, which further reacts with the mononuclear reagent
present in the reaction mixture to give the homodinuclear
product F as a byproduct. If the deprotonation process, however,
can be controlled by any method, the reaction sequence serves
as an efficient synthetic method for a variety of dinuclear
complexes.
Our study on the symmetrical homodinuclear PNNP system
has been extended to a heterodinuclear one. As a first attempt,
we have designed and synthesized a novel P,N-coordinating
dinucleating ligand, PNNN (2; 3-((diphenylphosphino)methyl)-
5-pyridylpyrazolato), having a P,N and an N,N coordination
site, and studied its conversion to homo- and heterodinuclear
complexes (Scheme 1). While pyrazolato-based bridging ligands
with two coordinating tethers at the 3- and 5-positions of the
ring such as 1 have been studied as dinucleating ligands for
bioinorganic studies to a considerable extent,6 unsymmetrical
ligands such as 2 remain rare.7
Described herein are the results of our systematic synthetic
study of homo- and heterodinuclear complexes with the PNNN
ligand and relevant PNNP complexes as well.8 We have found
that a simple change of the experimental procedure leads to
specific formation of regioisomeric pairs of heterometallic
PNNN complexes. As a result of the present study, we have
succeeded in construction of a library of homo- and heterodi-
nuclear PNNN and PNNP complexes.
As for the synthesis of dinuclear complexes, homonuclear
species can be readily obtained by simply mixing the ligand
Results and Discussion
Preparation and Isolation of the Dinucleating Ligands
PNNP-H (1-H) and PNNN-H (2-H). Preparation of the
PNNP-H ligand (1-H) was first reported 20 years ago by
Bosnich.4a Because of its sensitivity to air, 1-H is stored as the
nickel adduct, [(PNNP)2Ni2](ClO4)2, and before use the free
ligand 1-H is liberated by treatment with KCN and used as a
benzene solution. This procedure, however, cannot be applied
to the preparation of heterodinuclear complexes, because an
exact 1:1 reaction is essential for selective preparation of a 1:1
adduct intermediate and the exact concentration of a benzene
solution of 1-H prepared as described above cannot be deter-
mined. Instead of trapping 1-H as the Ni adduct, the crude
product is subjected to column chromatographic purification
(silica gel) under argon, and a spectroscopically pure sample
of 1-H is successfully obtained as a waxy solid.
(5) (a) Tanaka, S.; Inagaki, A.; Akita, M. Angew. Chem., Int, Ed. 2001,
40, 2865. (b), Tanaka, S.; Dubs, C.; Inagaki, A.; Akita, M. Organometallics
2004, 23, 317. (c) Tanaka, S.; Dubs, C.; Inagaki, A.; Akita, M. Organo-
metallics 2005, 24, 163. (d) Dubs, C.; Inagaki, A.; Akita, M. Chem.
Commun. 2004, 2760.
(6) Demshko, S.; Leibling, G.; Maringgele, W.; Meyer, F.; Mennerich,
C.; Christopher, K.; Klauss, H. H.; Pritzkow, H. Inorg. Chem. 2005, 44,
519. Ackermann, J.; Meyer, F.; Pritzkow, H. Inorg. Chim. Acta 2004, 357,
3703. Leibling, G.; Demeshko, S.; Bauer-Siebenlist, B.; Meyer, F.; Pritzkow,
H. Eur. J. Inorg. Chem. 2004, 12, 2413. Bauer-Siebenlist, B.; Meyer, F.;
Farkas, E.; Vidovic, D.; Cuestas-Seijo, J. A.; Herbst-Imer, R.; Pritzkow,
H. Inorg. Chem. 2004, 43, 4189. Kryatov, S, V.; Rybak-Akimova, E. V.;
Meyer, F.; Pritzkow, H. Eur. J. Inorg. Chem. 2003, 8, 1581. Ackermann,
J.; Meyer, F.; Kaifer, E.; Pritzkow, H. Chem. Eur. J. 2002, 8, 247. Meyer,
F.; Pritzkow, H. Inorg. Chem. Commun. 2001, 4, 305. Meyer, F.; Konrad,
M.; Kaifer, E. Eur. J. Inorg. Chem. 1999, 11, 1851. Konrad, M.; Meyer,
F.; Jacobi, A.; Kircher, P.; Rutsch, P.; Zsolnai, L. Inorg, Chem. 1999, 38,
4559. Meyer, F.; Kaifer, F.; Kircher, P.; Katja, H.; Pritzkow. H. Chem.
Eur. J. 1999, 5, 1617. Meyer, F.; Jacobi, A.; Nuber, B.; Rutsch, P.; Zsolnai,
L. Inorg. Chem. 1998, 37, 1213. Konrad, M.; Meyer, F.; Heinze, K.; Zsolnai,
L. J. Chem. Soc., Dalton Trans. 1998, 199. Roeder, J. C.; Meyer, F.;
Pritzkow, H. Organometallics 2001, 20, 811. Roeder, J. C.; Meyer, F.;
Kaifer, E. Angew. Chem., Int. Ed. 2002, 41, 2304. Roeder, J. C.; Meyer,
F.; Pritzkow, H. Chem. Commun. 2001, 2176. Sens, C.; Romero, I.;
Rodriguez, M.; Llobet, A.; Parella, T.; Benet-Buchholz, J. J. Am. Chem.
Soc. 2004, 126, 7798. Nakano, K.; Kawata, S.; Yoneda, K.; Fuyuhiro, A.;
Yagi, T.; Nasu, S.; Morimoto, S.; Kaizaki, S. Chem. Commun. 2004, 2892.
Nakano, K.; Suemura, N.; Kawata, S.; Fuyuhiro, A.; Yagi, T.; Nasu, S.;
Morimoto, S.; Kaizaki, S. Dalton Trans. 2004, 982. Catalano, V. J.; Craig,
T. J. Inorg. Chem. 2003, 42, 321. Catalano, V.; Craig, T. J. Polyhedron
2000, 19, 475. Baitalik, S.; Floerke, U.; Nag, K. Inorg. Chem. 1999, 38,
3296. Baitalik, S.; Floerke, U.; Nag, K. J. Chem. Soc., Dalton Trans. 1999,
719. Mernari, B.; Abraham, F.; Lagrenee, M.; Drillon, M.; Legoll, P. J.
Chem. Soc., Dalton Trans. 1993, 1707. Bayon, J. C.; Net, G.; Esteban, P.;
Rasmussen, P. G.; Bergstrom, D. F. Inorg. Chem. 1991, 30, 4771. Bayon,
J. C.; Esteban, P.; Net, G.; Rasmussen, P. G.; Baker, K. N.; Hahn, C. W.
Inorg. Chem. 1991, 30, 2572.
(7) Pons, J.; Lopez, X.; Benet, E.; Casabo, J.; Teixidor, F.; Sanchez, F.
J. Polyhedron 1990, 9, 2839. Pons, J.; Sanchez, F. J.; Labarta, A.; Casabo,
J.; Teixidor, F.; Caubet, A. Inorg. Chim. Acta 1993, 208, 167. Konrad, M.;
Wuthe, S.; Meyer, F.; Kaifer, E. Eur. J. Inorg. Chem. 2001, 9, 2233. Ni-
Iya, K.; Fuyuhiro, A.; Yagi, T.; Nasu, S.; Kuzushita, K.; Morimoto, S.;
Kaizaki, S. Bull. Chem. Soc. Jpn. 2001, 74, 1891. Buchler, S.; Myer, F.;
Kaifer, E.; Pritzkow, H. Inorg. Chim. Acta 2002, 337, 371. Roeder, R. C.;
Meyer, F.; Winter, R. F.; Kaifer, E. J. Organomet. Chem. 2002, 541, 113.
Baitalik, S.; Bag, P.; Nag, K. Polyhedron 2002, 21, 2481. Baitalik, S.;
Florke, U.; Nag, K. Inorg. Chim. Acta 2002, 337, 439. Sens, C.; Rodriguez,
M.; Romero, I.; Llobet, A.; Parella, T.; Sullivan, B. P.; Benet-Buchholz, J.
Inorg. Chem. 2003, 42, 2040. Kawahata, R.; Tsukuda, T.; Yagi, T.; Subhan,
A.; Nakata, H.; Fuyuhiro, A.; Kaizaki, S. Chem. Lett. 2003, 32, 1084.
Roeder, J. C.; Meyer, F.; Kaifer, E.; Pritzkow, H. Eur. J. Inorg. Chem.
2004, 8, 1646. Baitalik, S.; Bag, P.; Florke, U.; Nag, K. Inorg. Chim. Acta
2004, 357, 699. Sheng, T.; Dechert, S.; Hyla-Kryspin, I.; Winter, R. F.;
Meyer, F. Inorg. Chem. 2005, 44, 3863. Nakano, K.; Suemura, Naohiko,
Y.; Kawat, S.; Kaizaki, S. Dalton Trans. 2005, 4, 740.

1346 Organometallics, Vol. 25, No. 6, 2006
Dubs et al.
Scheme 2
The PNNN ligand 2-H is prepared in a manner analogous to
the synthetic route reported for 1-H and can be isolated as a
waxy solid after chromatographic separation under an inert
atmosphere. Synthetic details are described in the Experimental
Section (Scheme 11).
treatment of 1-H with appropriate metal reagents 3 (2 equiv) in
the presence of NEt3, as reported by Bosnich,4a but better yields
are obtained by the use of the isolated ligand (1-H) (Scheme
3). The corresponding PNNN complexes 5 are also readily
obtained by similar procedures and have been characterized on
the basis of their spectroscopic data: in particular, the presence
of two sets of NMR signals for the two M(L) moieties
Preparation of Homodinuclear Complexes. Homodinuclear
complexes with the PNNP ligand (4) are readily prepared by
Figure 1. ORTEP views of the cationic parts of the cationic homo- and heterodinuclear complexes (a) 5c, (b) 7a, (c) 7b, and (d) 8b and
of (e) the mononuclear neutral complex 12, all drawn with thermal ellipsoids at the 30% probability level.

Ir Complexes with Bridging PNNN and PNNP Ligands
Organometallics, Vol. 25, No. 6, 2006 1347
Scheme 3
the solvent, and a single species is observed in DMSO-d6. A
single crystal obtained from CH2Cl2-Et2O contains the isomers
in the ratio 0.53 (supine):0.43 (prone). An ORTEP view of the
major species and selected structural parameters of 5c are shown
in Figure 1 and Table 1, respectively, and its structural features
will be discussed later together with related compounds.
Specific Preparation of Isomeric Pairs of Heterodinuclear
PNNN Complexes. Treatment of 2-H with [Ir(cod)2]BF4 (3a;
1 equiv) in CH2Cl2 gives the pale yellow precipitate 6 in an
almost quantitative yield (Scheme 4). Formation of a 1:1 adduct
(6) has been confirmed by the relative intensities of the 1H NMR
signals for the PNNN and cod ligands. The low solubility and
rather featureless NMR data of 6, however, hamper its detailed
spectroscopic characterization (e.g. 13C NMR). A 31P NMR
spectrum contains a singlet signal (δP -5.5), which falls out of
the range of the 31P NMR signals for related compounds such
incorporated into the P,N and N,N sites. NMR spectra reveal
that the Pd(η3-allyl) complex 5c consists of two isomers, which
turn out to be the supine and prone isomers9 of the allyl ligand
attached to the Pd(N,N) site, as characterized by X-ray crystal-
lography. The envelope conformation of the five-membered
metallacycle renders the two configurations diastereomeric, and
1
1
as 4, 5, 7, and 8. Comparison of the structures and H NMR
the interconversion of the two isomers is slower than the H
NMR coalescence time scale. The isomer ratio is dependent on
data of the compounds reported herein reveals that the charac-
Table 1. Selected Structural Parameters for [LM(PNNN)M′L′]BF4 (5c, 7a,b, and 8b) and (cod)Ir(PNNN) (12)a
5c
7a
Ir(cod)
Rh(cod)
7bc
8b
12
Ir(cod)
ML
M′L′
Pd(allyl)
Pd(allyl)b
Ir(cod)
Pd(allyl)
Pd(allyl)
Ir(cod)
M‚‚‚M′
M-P1
M-N1
M′-N2
M′-N3
M-L
4.566(1)
2.280(2)
2.132(8)
2.120(6)
4.444(1)
2.297(3)
2.095(9)
2.10(1)
4.300(2)
2.290(6)
2.05(2)
2.10(2)
4.292(2)
2.292(6)
2.07(2)
2.11(2)
2.09(2)
2.14(2) (C01)
2.22(2) (C02)
2.09(3) (C05)
2.18(2) (C06)
2.12(3) (C1)
2.10(5) (C2)
2.10(4) (C3)
4.639(1)
2.290(3)
2.17(1)
2.13(1)
2.289(3)
2.07(1)
2.104(8)
2.129(8)
2.06(2)
2.13(1)
2.217(8) (C1)
2.14(1) (C2)
2.09(1) (C3)
2.14(1) (C01B)
2.17(1) (C02B)
2.19(1) (C05B)
2.24(2) (C06B)
2.14(1) (C01A)
2.17(1) (C02A)
2.13(1) (C05A)
2.16(2) (C06A)
2.12(3) (C01)
2.21(2) (C02)
2.10(3) (C05)
2.13(2) (C06)
2.11(2) (C1)
2.09(3) (C2)
2.12(3) (C3)
2.27(1) (C1)
2.17(2) (C2)
2.09(2) (C3)
2.14(1) (C06)
2.11(2) (C01)
2.15(2) (C02)
2.15(2) (C05)
2.10(1) (C06)
2.20(1) (C01)
2.17(1) (C02)
2.16(1) (C05)
M′-L′
2.26(4) (C4)b
2.16(2) (C5)b
2.13(1) (C6)b
P1-M-N1
82.0(2)
79.8(3)
162.0(6)
178.2(5)
19(1)
78.2(3)
77.4(4)
149.1(8)
139.7(9)
71(1)
77.3(5)
79.3(7)
168(1)
172(2)
50(2)
79.2(5)
77.0(8)
139(2)
149(2)
41(3)
83.0(3)
79.8(5)
166(1)
177(1)
17(2)
79.1(3)
N2-M′-N3
M-N1-N2-C13
M′-N2-N1-C11
M-N1-N2-M′
178.2(8)
a Interatomic distances in Å and bond angles and dihedral angles in deg. b The Pd2(allyl) part was disordered.12 c With two independent molecules.
Scheme 4

1348 Organometallics, Vol. 25, No. 6, 2006
Dubs et al.
Scheme 5
teristic doublet H6 signal of the pyridyl moiety (Scheme 4; the
H6 atom is denoted as H10 in the Experimental Section (Chart
2)) serves as a diagnostic for determination of the coordination
site of the M(cod) fragment; the H6 signals for the N,N-coor-
dinated species ([X(PNNN)M(cod)+] (X ) none or a metal
fragment: δH ∼8) appear at higher field compared to those of
the P,N-coordinated regioisomers ([(cod)M(PNNN)X]+; δH
>8.5). On the basis of these diagnostics, the 1:1 adduct
(δH(H6) 7.98) was tentatively assigned as the N,N-coordinated
species 6′. It is notable, however, that an ESI-MS spectrum
contains signals attributed to a dimeric species (m/z 1285.0
([(PNNN-H)(PNNN)Ir2(cod)2]+), and 1373.0 ([(PNNN)2Ir2-
(cod)2(BF4)]+) in addition to the signal for a monomeric species
(m/z 642.6 ([(PNNN)Ir(cod)]+)). Although 6 cannot be char-
acterized by the spectroscopic data mentioned above, compari-
son with the PNNP system described below leads to the
conclusion that the 1:1 adduct is not the monomeric species 6′
but the dimeric species 6.
Then the 1:1 adduct 6 is converted into heterodinuclear
complexes by treatment with a second metal fragment. Sequen-
tial treatment of 6 with a base (NEt3) and [M(L)(cod)]BF4
(3; M(L) ) Rh(cod), Pd(allyl)) (reaction 1) results in selec-
tive formation of heterodinuclear complexes 7a,b, where the
Ir fragment sits on the P,N site and the second metal frag-
ment is introduced to the N,N site. To our surprise, simple
switching of the order of the addition of the second metal
fragment and the base (reaction 2) leads to the formation of the
regioisomeric heterodinuclear complexes 8a,b with the switched
metal arrangement. The selectivity is perfect, and neither the
other isomeric species nor homodinuclear species can be
detected. It is also remarkable that, in reaction 1, the Ir(cod)
fragment is shifted from the N,N chelating site (6) to the P,N
chelating site (7).
The formation of the heterodinuclear complexes [LM(µ-
PNNN)M′L′]+ is readily confirmed by the 1H NMR data
containing the signals for the two metal fragments (L and L′ in
a 1:1 ratio) and the ESI-MS data, and the coordination sites of
the metal fragments have been determined by spectroscopic
analysis and verified by crystallography. For the Ir-Rh pair
7a-8a, the 31P NMR signal of 8a appears as a doublet signal
(δP (JRh-P ) 155 Hz)) due to coupling with the Rh nucleus,
while a singlet signal is observed for 7a. On the other hand,
for the Ir-Pd pair 7b-8b, the allyl carbon signals of 8b appear
as doublet signals owing to coupling with the P nucleus
indicating P,N coordination of the Pd(allyl) fragment, while 7b
shows the deshielded H6 signal of the pyridyl moiety (δH 8.53)
indicative of coordination of the Ir(cod) fragment to the P,N
site according to the diagnostics mentioned above. The metal
arrangements of the Ir-Rh complex 7a and the Ir-Pd pair
7b-8b have been verified by X-ray crystallography (Figure
1b-d).
complexes prompted us to extend the preparation to the PNNP
system. Formation of regioisomers is not applicable, because
of the symmetric structure of PNNP. In this case, too, the
addition order of the reagents turns out to be crucial for selective
reactions.
Treatment of 1-H with [Ir(cod)2]BF4 (3a) gives the 1:1 adduct
9 as a pale yellow precipitate in a manner similar to that for 6
(Scheme 5). While 9 is also sparingly soluble in most organic
solvents, the following spectroscopic data consistent with a
dimeric structure have been obtained. 1H and 31P NMR spectra
of 9 observed in DMSO-d6 are shown in Figure 2a. Character-
istic spectroscopic features are as follows. (1) The 31P NMR
spectrum contains a pair of doublet signals coupled with each
other (δP -16.11, 4.37 (JP-P ) 42 Hz)), indicating coordination
of two inequivalent phosphorus atoms to a single metal (Ir)
center. This indicates that 9 is an oligomeric species, because
the two P atoms in 1-H separated by >4 Å cannot be chelated
1
to a single metal center. (2) The sharp single H NMR signals
for the hydrogen atom for the 4-position of the pyrazolate ring
(HA; δH 5.10) and the N-H proton (δH 11.60) are in a 1:1
ratio, indicating formation of a symmetrical oligomer and
retention of the protonated form. (3) The 13C NMR data com-
parable to those of the reference compounds, 1-H and the P,N-
chelated species 10b (Chart 1), support κ1 and κ2 coordination
of the PNNP ligand, which bridges two metal centers. (4) An
ESI-MS spectrum containing peaks at m/z 765.4 ([(PNNP-H)-
Ir(cod)]+), 1529.1 ([(PNNP)(PNNP-H)Ir2(cod)2]+), and 1615.0
([(PNNP-H)2Ir2(cod)2(BF4)]+) is consistent with a dimeric
structure. On the basis of these results the yellow precipitate 9
can be characterized as a cyclic, dimeric species with five-
coordinate Ir centers, as shown in Scheme 5. The notable
differences in the δP values observed for 9 vs other complexes
(δP ∼30; 4, 5, 7, and 8) mentioned above can be ascribed to
the difference in the coordination number: 5 for 9 vs 4 for the
others. Analogous 1:1 reactions of 1-H with 3b,c give mixtures
of products, as noted for 2-H (see above).
Upon subsequent introduction of the Rh fragment, treatment
of 9 with NEt3 followed by addition of 3b (reaction 1) furnishes
the heterodinuclear complex 10a in an excellent yield, while
the reversed addition of the two reagents (reaction 2) affords a
mixture of the desired product 10a and the homodinuclear
complexes 4a,b. In the case of the Ir-Pd complex 10b, the
desired product is obtained irrespective of the addition order.
The new heterodinuclear complexes 10a,b are readily char-
acterized by spectroscopic data, being consistent with a 1:1:1
adduct of the Ir and Rh/Pd fragments and the PNNP ligand.
It should be noted that this type of specific formation of
regioisomeric species is observed only when the Ir(cod) frag-
ment is introduced as the first metal fragment. For example,
1:1 reactions of 2-H with the Rh (3b) and Pd reagents (3c) give
mixtures of mono- and dinuclear complexes, presumably
following the process discussed in Scheme 2. This result
indicates that the specific reactions observed for the Ir system
are thanks to the unique coordination properties of Ir.
Specific Preparation of Heterodinuclear PNNP Com-
plexes. The successful preparation of the heterodinuclear PNNN
(8) Some of the results have already been reported as a communication.5d
(9) Yasuda, H.; Tatsumi, K.; Okamoto, T.; Mashima, K.; Lee, K.;
Nakamura, A.; Kai, Y.; Kanehisa, N.; Kasai, N. J. Am. Chem. Soc. 1985,
107, 2410

Ir Complexes with Bridging PNNN and PNNP Ligands
Organometallics, Vol. 25, No. 6, 2006 1349
Figure 2. 1H (400 MHz) and 31P NMR spectra (81 MHz) for (a) 9 (in DMSO-d6), (b) 13 (in CD2Cl2), and (c) 14b (in CD2Cl2). Residual
solvents (CH2Cl2, CHDCl2, hexane) and impurities are denoted by asterisks.
Chart 1
No homonuclear complex has been detected for the products
obtained from reaction 1.
Scheme 6
Mechanism of the Metal Switching Process. (i) 1:1 Ad-
ducts 6 and 9. The key intermediates of the present unique
transformations are the 1:1 adducts 6 and 9. The low solubility
of 6 and 9 hampers detailed spectroscopic characterization and
recrystallization. However, for the PNNP adduct 9, the dimeric
structure is consistent with the spectroscopic data as discussed
above. The single set of NMR signals suggests a cyclic oligo-
meric structure, and the dimeric structure is supported by the
ESI-MS data. The PNNN adduct 6 has also been characterized
as the dimeric species on the basis of (1) the ESI-MS data and
(2) the δP signals different from those of the 4-coordinate square-
planar species.
A dynamic feature is noted for the PNNN system (Scheme
6). The 1:1 reaction of 1-H with 3a gives 6 as described above,
but a 2:1 reaction affords the 2:1 adduct 11, which is converted
to the 1:1 adduct 6 upon further addition of 1 equiv of 3a.
Furthermore, treatment of 6 with 2 equiv of 1-H reverts the
reaction to give 11. Although the Ir/PNNP-H system is dynamic,
the selective formation of the dimeric species is ascribed to the

1350 Organometallics, Vol. 25, No. 6, 2006
Dubs et al.
Scheme 7
low solubility of 6 in organic solvents. A 1:1 mixing of 1-H
and 3a may form a mixture containing 11 and 6, but precipita-
tion of the dimer 6 finally drives the reaction to the selective
formation (precipitation) of the 1:1 adduct 6. The 2:1 adduct
11 with the unsymmetrical coordination of two PNNN ligands
is characterized on the basis of (1) a pair of doublet 31P NMR
dimeric adduct I, which may be equilibrated with the four-
coordinate species J, and subsequent switching of the coordina-
tion site followed by proton transfer and repetition of similar
processes regenerates 6. Thus, the formation mechanism of the
heterodinuclear complexes is in sharp contrast to the anticipated
one described in Scheme 2 and involves the supramolecular
dimeric intermediates G-J. The acidity of the N-H protons
in the monomeric (6′) and dimeric structures (6), however, may
not be significantly different, and therefore, deprotonation of
the labilized N-H protons discussed in the Introduction (Scheme
2) may be hindered by the supramolecular structure. For
consideration of the spatial arrangement of the dimeric structure
6, structural optimization has been performed by means of
MM2,10 and the obtained optimized structure is shown in Figure
3, where the result of the PNNP species 9 showing essentially
signals coupled with each other (δP -19.6 (d), 8.9 (d) (JP-P
)
11.7 Hz)) being very similar to that of 9 with a similar metal
coordination structure, (2) two sets of 1H and 13C NMR signals
for the PNNN ligands, and (3) a deshielded H6 signal for the
pyridyl moieties (δH 8.73, 8.99), indicating no N,N coordination
of the Ir(cod) fragment. Although intra- or interligand N-H-N
hydrogen-bonding interactions are possible, they cannot be
defined by the obtained spectroscopic data alone.
(ii) Reaction 1 Initiated by Deprotonation of 6 and 9. To
get information on reaction 1 the 1:1 adducts are treated with
NEt3.
(a) PNNN System Involving Switching of Metal Coordina-
tion Site. Reaction of the PNNN complex 6 with NEt3 gives
the neutral red complex 12, which reverts to 6 upon acidification
with HBF4‚OEt2 (Scheme 7). The pH-dependent interconversion
is quantitative. The characterization of 12 is based on (1) the
31P NMR data (δP 31.2) comparable to those of P,N-chelated
species such as 7, 8, and 10 and (2) the diagnostic H6 signal of
the pyridyl part (δH 8.50), and its molecular structure has been
determined by X-ray crystallography (Figure 1e).
The mechanism of the pH-dependent interconversion sum-
marized in Scheme 7 deserves comment. The deprotonation of
6 should form the monoprotonated, monocationic species G and
then the neutral species H. Although these intermediates cannot
be detected, a PNNP intermediate (13) corresponding to G is
observed, as described in the next section (ii(b)). At the stage
of G-H, the change of the charge of the complexes (+1 f 0)
causes reorganization of the coordination structure associated
with the changes of (i) the coordination number (5 f 4) and
(ii) the chelation parts (N,N f P,N), and it is remarkable that
the Ir(cod) fragment is mutually shifted from one PNNN ligand
to the other PNNN ligand to complete the neutralization process.
On the other hand, protonation of 12 should initially form the
Figure 3. Structures of 6 and 9 obtained by MM2 optimization
(with space-filling and wire frame expressions; for the wire frame
expressions the Ph and cod groups are omitted for clarity).
the same feature is also included. The most significant feature
is that the N-H part is surrounded by the cod and phenyl groups
(10) The MM2 optimization was carried out with the software included
in the CS ChemBats3D Pro package (version 5.0).

Ir Complexes with Bridging PNNN and PNNP Ligands
Organometallics, Vol. 25, No. 6, 2006 1351
Scheme 8
to hinder approach of a base. A similar feature is noted for 9.
Thus, it is concluded that the N-H proton embedded in the
ligand pocket is so kinetically stabilized as to be sluggish with
respect to deprotonation.
P,N-chelated neutral mononuclear species 12, which further
reacts with the second metal reagent to give the 7-type products
(Scheme 7).
(b) PNNP System. The PNNP complex 9 is also susceptible
to deprotonation, but a different type of product is obtained,
owing to the different properties of the bridging ligands PNNP
(1) and PNNN (2) (Scheme 8). The deprotonation does not
afford a neutral product like 12 but is terminated at the stage of
the monodeprotonated, monocationic species 13, even in the
presence of an excess amount of NEt3. 1H and 31P NMR spectra
of an isolated sample of 13 are shown in Figure 2b. The 31P
NMR spectrum (a pair of doublets coupled with each other;
δP -19.3 (d), 6.9 (d) (JP-P ) 29.4 Hz)), which is very similar
to that of 9, indicates a dimeric structure, which is also sup-
ported by the ESI-MS data (m/z 1527.1 ([(PNNP-H)(PNNP)-
Ir2(cod)2]+). The most characteristic feature is the sharp singlet
1H NMR signal at low field (δH 13.38) assignable to N-H,
and its intensity (1H) as well as a single set of 1H NMR signals
for the PNNP parts is in accord with the symmetrical structure,
in which the two noncoordinating N atoms are bridged by the
proton.
The driving force for the present unique interconversion can
be explained in terms of the favored coordination number and
chelate set, which depend on the charge of the Ir center. The
electron-rich neutral species 12 should prefer the softer P,N
chelate to form a four-coordinate structure peculiar to 16e
species of d8 metals, whereas the cationic hard species 6 prefers
a five-coordinate structure with the hard N,N chelate. At the
stage of H and I, where the two coordination modes are
exchangeable, the Ir center chooses the coordination site (NN
vs PN), which fits the properties of the Ir center (cationic hard
Ir(I)/N,N-chelate/5-coordinate vs neutral soft Ir(0)/P,N-chelate/
4-coordinate). These coordination features are characteristic of
Ir, and therefore, similar reactions of the Rh and Pd species do
not result in the selective formation of the 1:1 adducts cor-
responding to 6 but afford mixtures of products.
A related metal migration process was reported for µ-pyra-
zolato complexes, L2Ir(µ-pz)2IrL′2, by Oro.11 The mechanism
proposed (σ-1,2-metallotropic shift) involves a shift of the metal
center via a π-coordinated µ-η1:η2-intermediate and is totally
different from our system.
Accordingly, the mechanisms of the subsequent steps are
different from those of the PNNN system described above, and
a proposed mechanism is also included in Scheme 8. To verify
the proposed mechanism, the intermediate 13 is subjected to
reactions with 3b (Rh) and 3c (Pd). Although both reactions
afford the heterodinuclear complexes 10 in the presence of NEt3
(Scheme 5), intermediates can be characterized spectroscopically
for the Ir-Pd system 14b as described below.
Thus in reaction 1 of the PNNN system, deprotonation of 6
with NEt3 causes the interligand metal migration to furnish the
(11) Yuan, Y.; Jime´nez, M. V.; Sola, E.; Lahoz, F. J.; Oro, L. A. J. Am.
Chem. Soc. 2002, 124, 752. Tejel, C.; Villoro, C. C.; Ciriano, M. A.; Lo´pez,
J. A.; Eguiza´bal, E.; Lahoz, F. J.; Bakhmutov, V. I.; Oro, L. A.
Organometallics 1996, 15, 2967.

1352 Organometallics, Vol. 25, No. 6, 2006
Dubs et al.
Figure 4. 31P NMR spectrum for a 1:2 reaction mixture of 13 and
3c (observed at 81 MHz in CDCl3).
A 1:2 reaction between 13 and 3c gives a mixture of the
heterodinuclear complex 10b and a trinuclear species 14b
(Scheme 8a), as can be seen from the 31P NMR chart (Figure
4). The trinuclear complex 14b can be alternatively prepared
in a selective manner by a 1:1 reaction between 9 and 3c
Figure 5. Reaction of 14b and 3c in the presence of NEt3
monitored by 31P NMR (at 81 MHz in CD2Cl2): (a) a mixture of
14b and 3c (before addition of NEt3); (b) after addition of 0.6 equiv
of NEt3; (c) after further addition of an excess amount of NEt3.
1
(Scheme 8b), and H and 31P NMR spectra of 14b obtained
from the reaction of Scheme 8b are shown in Figure 2c. The
intensities of the allyl and cod signals and a single set of the
PNNP signals reveal a 1:2 incorporation of the Pd and Ir
fragments and a symmetrical structure as well. The signals for
the allyl ligand are located at δH 5.6, 4.05, and 3.27, being
typical for η3 coordination. The 13C NMR data for the PNNP
ligand of 14b are comparable to those of 12, and comparison
with the reference compounds in Chart 1 suggests a µ-κ1:κ2-
bridging coordination mode for the PNNN ligand. In accord
with this mode, the 31P NMR signal at 27.9 ppm is assigned to
the phosphorus atom in the P,N chelate and the other signal to
the κ1-coordinating phosphorus atom. The lack of P-P coupling
supports coordination of the phosphorus atoms to different metal
centers. The composition of the trinuclear structure is supported
by the ESI-MS data (m/z 1849.8 ({[(PNNP-H)2Ir2(cod)2Pd-
(allyl)](BF4)2}+)).
Scheme 9
Then reaction of the Pd-Ir adduct 14b with NEt3 has been
examined. An equimolar amount of 3c is added to 14b so that
the stoichiometry becomes comparable to reaction 1 (Ir:Pd )
1:1), because 14b is a 2 (Ir):1 (Pd) adduct (Scheme 8c). Fig-
ure 5a shows a 31P NMR spectrum for a 1:1 mixture of 14b
and 3c. When 0.6 equiv of NEt3 is added to the mixture, a
part of 14b is converted into 10b (Figure 5b) and further addi-
tion of NEt3 causes quantitative conversion of 14b into 10b
(Figure 5c).
On the basis of the above-mentioned results, a plausible
mechanism for reaction 1 of the PNNP system is proposed, as
summarized in Scheme 8. The first event occurring in this
system is reaction of the dinuclear 1:1 adduct 9 with NEt3, which
causes monodeprotonation of 9 to give the monocationic
intermediate 13. The resultant 13 then interacts with the second
metal reagent 3 to give a mixture of the heterodinuclear product
10 and the trinuclear 1:2 adduct 14, and the latter species 14 is
deprotonated by NEt3 present in excess in the reaction mixture
to give the monocationic species K, which separates into 10
and the neutral mononuclear species L. L is converted to 10
upon interaction with 3 in the reaction mixture to accomplish
the selective transformation.
processes, and a plausible mechanism is summarized in Scheme
9. Dissociation of the dimeric species 6 into the monomeric
N,N-coordinated intermediate [(PNNN-H)Ir(cod)]+ followed by
coordination of the free P atom to 3 gives the trinuclear inter-
mediate M analogous to 14. Subsequent deprotonation (N) and
chelation afford the cationic heterodinuclear product 8 and the
neutral N,N-chelated mononuclear species O, which is also
converted to 8 via coordination of 3 to the free P,N site. ESI-
MS signals for M (M(L) ) Pd(allyl)) support the proposed
mechanism, while attempted reaction between 6 and 3 results
in a mixture of products and no intermediate can be character-
ized by other spectroscopic methods, including NMR.
(b) PNNP System. The reaction of 9 with 3c gives the
trinuclear adduct 14b as described above (Scheme 8b), and
subsequent steps should be analogous to those described in
Scheme 8 to lead to 10 in a selective manner. In contrast to the
Pd system, the reaction of 8 with the Rh reagent 3b gives a
mixture of products and, accordingly, subsequent treatment with
NEt3 also results in a mixture, being consistent with the results
of the preparative reaction (Scheme 5). The difference can be
attributed to the instability of 14a (M(L) ) Rh(cod)) compared
to 14b (M(L) ) Pd(allyl). In the presence of NEt3 (reaction 1),
as soon as 14a is formed, immediate deprotonation leads to K
(iii) Reaction 2 Involving a Second Metal Reagent-Base
Addition Sequence. (a) PNNN System. Comparison of the
structures of the intermediate 6 and the product 8 suggests that
reaction 2 can be apparently explained in terms of a simple
combination of dissociation, coordination, and deprotonation

Ir Complexes with Bridging PNNN and PNNP Ligands
Organometallics, Vol. 25, No. 6, 2006 1353
Scheme 10
etc. eventually to give 10a in a selective manner. However, in
reaction 2, where the reaction mixture is stirred for a while
before addition of NEt3, the intermediate 14a gradually degrades
to mono- and dinuclear species, which lead to the mixture of
products.
Molecular Structures of PNNN and PNNP Complexes. The
cationic dinuclear PNNN complexes 5c, 7a, 7b, and 8b and
the mononuclear neutral complex 12 have been characterized
by X-ray crystallography. Their ORTEP views are shown in
Figure 1, and their selected structural parameters are compared
in Table 1.
deprotonation, leading to the formation of homodinuclear
byproducts as noted in Scheme 2. The dimeric structures result
from the coordination properties of the cationic Ir centers, which
prefer five-coordinate structures. It is also noteworthy that the
coordination properties of the Ir center can be switched by the
protonation-deprotonation process. Deprotonation changes the
cationic Lewis acidic hard Ir center into the neutral soft one
and, as a result, (1) the coordination number decreases from 5
to 4 and (2) the Ir center is transferred from the hard N,N site
to the soft P,N site. Thus, it is concluded that the present unique
transformations are based on the peculiar coordination properties
of Ir.
No metal-metal interaction is present, judging from the
intermetallic distances (>4.2 Å). All metal centers adopt square-
planar coordination geometries, as usually observed for four-
coordinate d8-metal complexes with 16 valence electrons, and
coordination of the allyl ligand to the N,N-chelated metal is
virtually symmetrical, in contrast to that of the P,N-chelated
metal, owing to the trans effect of the phosphorus atom. The
most significant difference noted is the M-N1-N2-M′
dihedral angle, which apparently results from the steric repulsion
between the ML and M′L′ moieties. An envelope-type confor-
mation is observed for the five-membered P,N chelate, but the
N,N counterpart is much less folded. In the five-membered P,N
chelate, the most bulky fragment (M(cod) > PPh2 > Pd(allyl))
is folded up from the plane defined by the other four vertices
to form an envelope conformation. It is notable that, in the case
of 7b with the two bulky M(cod) fragments, the two fragments
are folded up and down as can be seen from the M-N1-
N2-C13 and M′-N2-N1-C11 dihedral angles. The cod
ligands on the two different metal centers are close enough to
distort the backbone, suggesting the possibility of interaction
between the two ligands on the different metal centers. Such a
ligand arrangement would lead to a new mode of dimetallic
activation and interaction of two different substrates on the two
metal centers.
Conclusions. In this article we present a novel synthetic
method for a series of homo- and heterodinuclear complexes
with the dinucleating PNNN and PNNP ligands. It is remarkable
that, in the case of the PNNN system, a simple change of the
experimental procedure (addition order of the reagents) brings
about formation of pairs of heterodinuclear complexes with the
switched metal arrangements and the method can be applied to
the synthesis of the heterodinuclear PNNP complexes. The
present unique transformations are realized by a combination
of the following unique features (Scheme 10; the squares and
the pentagons stand for four- and five-coordinate structures,
respectively). The key intermediates are 6 and 9, having the
supramolecular dimeric structures, which prevent spontaneous
In the following paper, the reactivity of the obtained
complexes will be discussed and, in combination with the
present results, a library of homo- and heterodinuclear PNNP
and PNNN complexes has been established.
Experimental Section
General Methods. All manipulations were carried out under an
inert atmosphere by using standard Schlenk tube techniques. THF
and ether (Na-K alloy), CH2Cl2 (P2O5), and EtOH (Mg(OEt)2) were
treated with appropriate drying agents, distilled, and stored under
argon. 1H and 13C NMR spectra were recorded on Bruker AC-200
(1H, 200 MHz; 31P, 81 MHz) and JEOL EX-400 spectrometers (1H
(VT, 2D), 400 MHz; 13C, 100 MHz). Chemical shifts (downfield
from TMS (1H and 13C) and H3PO4 (31P)) and coupling constants
are reported in ppm and in Hz, respectively. Ph, py, and pz stand
for the phenyl, pyridyl, and pyrazolyl parts, respectively, and the
numbering schemes for the PNNP and PNNN ligands are shown
in Chart 2. Solvents for NMR measurements containing 0.5% TMS
were dried over molecular sieves, degassed, distilled under reduced
pressure, and stored under Ar. IR spectra were obtained on a FT/
IR 5300 spectrometer. ESI-MS and FD-MS spectra were recorded
on a ThermoQuest Finnigan LCQ Duo mass spectrometer and a
JEOL JMS-700 mass spectrometer, respectively.13 The metal
14b
reagents 3a,14a 3b,14a and 3c
were prepared according to the
published procedures. Other chemicals were purchased and used
as received. Chromatography was performed on silica gel.
Chart 2

1354 Organometallics, Vol. 25, No. 6, 2006
Dubs et al.
Scheme 11
Preparation of PNNP-H (1-H). PPh3 (3.1 g, 12 mmol) was
dissolved in dry THF (25 mL). Finely cut lithium (0.18 g, 26 mmol)
was added, and the red solution was stirred for 4 h at ambient
temperature. To the resultant solution cooled to -75 °C was added
3,5-bis(chloromethyl)pyrazole (0.60 g, 3.0 mmol) in one portion.
The mixture was stirred for 10 min at -75 °C and for 2 h at 0 °C.
After addition of deoxygenated water (25 mL), the products were
extracted with ether (20 mL × 4). The combined organic phases
were dried over MgSO4, filtered, and concentrated to 7 mL under
reduced pressure. The mixture was separated by silica gel column
chromatography with ether-hexane (1:1) and then with ether as
eluent. PNNP-H (1-H) was obtained as a sticky white solid from
the second fraction after removal of the volatiles under reduced
pressure. 1-H (1.39 g, 2.34 mmol, 78% yield): δH (CDCl3) 3.32
(s, 4H, H6,7), 5.71 (s, 1H, H4), 7.27-7.40 (m, 20H, Ph); δP (CDCl3)
-22.07 (s); δC (CDCl3) 26.9 (dt, JC-H ) 130, JC-P ) 15, C6,7),
104.8 (dd, JC-H ) 178, JC-P ) 6, C4), 128.4-132.8 (Ph), 137.9
(d, JC-P ) 15, Ph), 144.44 (s, C3,5); IR (KBr) 3195, 3069, 1953,
1562, 1432, 1096, 1024, 740, 694 cm-1; FD-MS m/z 464 (M+).15
Preparation of PNNN-H (2-H). The reaction sequence for 2-H
is summarized in Scheme 11.16
(i) Preparation of 2C. Sodium (2.5 g, 0.11 mol) was dissolved
in dry ethanol (150 mL) at room temperature under argon. (Caution!
Because hydrogen is released from the reaction, sodium cut in small
pieces should be added carefully so that that the reaction does not
become vigorous.) To the resultant NaOEt solution was added
diethyl oxalate (14.0 mL, 0.10 mol) followed by 2-acetylpyridine
(2A; 11.5 mL, 0.10 mol). After the solution was stirred for 18 h,
the volatiles were evaporated, and the resultant dark-colored paste
was dissolved in water (100 mL). The aqueous solution was
neutralized with acetic acid and extracted with diethyl ether (100
mL; four times). The combined organic phases were dried over
MgSO4 and filtered, and the solvent was evaporated to yield 2B
(20.19 g, 0.097 mol; crude yield: 97%) as a brownish white solid.
2B was used as obtained without further purification.
salt of 3-(ethoxycarbonyl)-5-(pyridin-2-yl)pyrazole (2C). A second
crop was recovered from the filtrate by concentration and cooling
of the filtrate. Combined yield of 2C: 71% (22.0 g, 0.071 mol;
with 1 mol of EtOH solvate). 2C: δH (DMSO-d6) 1.32 (3H, t, J )
6.8, CH3), 4.34 (4H, q, J ) 7.2, CH2), 7.77-7.86 (2H, m, pz +
py-H5), 8.39 (2H, m, py), 8.73 (1H, d, J ) 5.2, py-H6); IR (KBr)
3106 (νCH; py), 2974, 2859 (νCH), 1725 cm-1 (νCdO); ESI-MS m/z
218.2 (M - Cl). Anal. Calcd for C11H14N3O2Cl: C, 48.62; H, 5.19;
N, 15.47; O, 17.67; Cl, 12.88. Found: C, 48.23; H, 5.20; N, 15.48;
O, 17.67; Cl, 13.04.
(ii) Preparation of 2D. An 11.14 g portion (44 mmol) of 2C
was dissolved in H2O (30 mL). The pH was adjusted to 8 by
addition of saturated aqueous Na2HPO4 solution. The aqueous phase
was extracted with ether (three times). The combined organic phases
were dried over MgSO4, filtered, and evaporated to leave a slightly
brown solid, which was dissolved in dry ether (300 mL). The
ethereal solution was slowly added to LiAlH4 (5 g) suspended in
50 mL of dry ether, and the mixture was refluxed for 10 h. The
flask was immersed in an ice-water bath, and the reaction mixture
was hydrolyzed with water carefully. The volatiles were removed
under reduced pressure, and the obtained white cake was suspended
in methanol (350 mL). CO2 gas was bubbled through the solution
for 10 min, and the mixture was refluxed for 8 h. Filtration and
evaporation under reduced pressure gave a white solid. Water in
this residue was removed by azeotropic distillation with ethanol
(three times). The resultant solid was dissolved in EtOH, and
concentrated aqueous HCl (5 mL) was added. Addition of ether
caused precipitation of 2D, which was purified by crystallization
from MeOH-ether. 2D (8.22 g, 39 mmol, 89% yield): δH (DMSO-
d6) 4.57 (2H, s, CH2OH), 7.27 (1H, s, pz), 7.82 (1H, t, J ) 5.9,
py-H4), 8.39 (1H, d, J ) 8.4, py-H3), 8.48 (1H, t, J ) 7.6, py-H5),
8.70 (1H, d, J ) 5.2, py-H6); IR (KBr) 3292, 3129, 3003, 2768,
1608 cm-1; ESI-MS: m/z 176.1 (M - Cl).
(iii) Preparation of 2E. 2D (6.02 g, 28.6 mmol) was dissolved
in SOCl2 (50 mL) and refluxed for 30 min. The excess SOCl2 was
removed under reduced pressure, the residue was dissolved in
ethanol, and the solution was filtered. The product 2E (5.95 g, 26.0
mmol, 91% yield) was obtained as a brownish solid by slow
addition of ether. 2E: δH (DMSO-d6) 4.89 (2H, s, CH2Cl), 7.40
(1H, s, pz), 7.79 (1H, t, J ) 6.6, py-H4), 8.35 (1H, d, J ) 7.6,
py-H3), 8.43 (1H, t, J ) 7.6, py-H5), 8.71 (1H, d, J ) 5.6, py-H6);
The crude solid sample of 2B (20.19 g, 0.097 mol) was dissolved
in dehydrated ethanol, and then NH2NH2‚H2O (4.26 mL, 1 equiv)
was added dropwise to the solution. After the mixture was refluxed
for 3 h, the volatiles were removed under reduced pressure. The
resultant brownish paste was dissolved in ether (100 mL), and the
organic phase was washed with water (40 mL × 2). The combined
aqueous phases were extracted again with ether (100 mL). The
combined organic phases were dried over MgSO4, filtered, and
evaporated to leave a sticky white solid. The solid was dissolved
in ethanol (50 mL), and concentrated HCl (4 mL) was added to
form a HCl salt. Slow addition of ether gave the hydrochloride
IR (KBr) 3122, 3067, 2953, 1631, 1616, 785 cm-1
.
(iv) Preparation of 2-H. To a dry THF solution of PPh3 (2.82
g) was added lithium wire (186 mg) cut in small pieces. Stirring
the mixture for 3 h at ambient temperature gave LiPPh2 as a dark
red solution. The mixture was cooled with a dry ice-MeOH bath,
and 2E (1.31 g, 5.7 mmol) was added in one portion. After the
mixture was stirred for 10 min at the same temperature, the mixture
was further stirred for 2 h at 0 °C and then for 30 min at room
temperature. Addition of deoxygenated water was followed by
extraction with deoxygenated ether (three times). The ether extract
was dried over MgSO4, filtered, and concentrated to 10 mL.
Products were separated by silica gel column chromatography under
argon using dry and deoxygenated solvents. Elution with Et2O-
(12) The unsymmetrical coordination of the Pd2(allyl) moiety in 5c is
an artifact due to the disorder of the allyl ligand (supine vs prone).
(13) For cationic complexes, M+ stands for the molecular weight of the
cationic part.
(14) (a) Reference 4a. (b) White, D. A. Inorg. Synth. 1972, 13, 61.
(15) Despite several attempts an analytically pure sample could not be
obtained.
(16) The wrong structure of 2B in the Supporting Information of ref 5d
has been corrected.

Ir Complexes with Bridging PNNN and PNNP Ligands
Organometallics, Vol. 25, No. 6, 2006 1355
hexane (1:1) was followed by elution with ether. From the second
ether eluent, 2-H (1.33 g, 3.9 mmol, 68% yield) was isolated as a
white solid after removal of the volatiles under reduced pressure.
2-H: δH (CDCl3) 3.47 (2H, s, H12), 6.43 (1H, s, H4), 7.11 (1H,m,
H9), 7.33-7.35 (6H, m, Ph), 7.46-7.50 (4H, m, Ph), 7.52 (1H, d,
J ) 7.8, H7), 7.61 (1H, dt, J ) 8.0 and 1.6, H8), 8.54 (1H, d, J )
H7 + Ph), 8.03 (1H, t, J ) 6.5 Hz, H8), 8.53 (1H, d, J ) 5.1,
H10); δP (DMSO-d6) 36.7 (s); δP (CD2Cl2) 33.2 (s), 32.7 (s) (5:6;
two diastereomers); δC (could not be analyzed owing to the presence
of two isomers). IR (KBr) 3062, 1603, 1453, 1052 cm-1; ESI-MS:
13 m/z 638.1 (M+), 611.9 (M+ - allyl + OH), 597.2 (M+ - allyl),
571.8 (M+ - 2allyl + OH), 556.2 (M+ - 2allyl). Anal. Calcd for
C27H27N3PPd2BF4: C, 44.53; H, 3.77; N, 5.56. Found: C, 44.78;
H, 3.76; N, 5.80.
4.8, H10), 11.01 (1H, bs, N-H); δC (CDCl3) 27.7 (dd, JC-H
)
132, JP-H ) 15, C11), 104.0 (dd, JC-H ) 174, JP-H ) 6, C4), 120.0
(d, JC-H ) 163, C7), 122.6 (d, JC-H ) 164, C9), 128.4 (dd, JC-H
) 162, JC-P ) 7, C14), 128.78 (d, JC-H ) 160, C15), 132.7 (dd,
JC-H ) 162, JC-P ) 21, C13), 136.8 (d, JC-H ) 163, C8), 138.2
(d, JC-P ) 15, C12), 144.6 (s), 147.8 (s), 149.2 (s, C3/5/6), 149.3
(d, JC-H ) 177, C10); FD-MS m/z 343 (M+). Anal. Calcd for
C21H18N3P: C, 73.44; H, 5.38; N, 12.24. Found: C, 73.01; H, 5.51;
N, 11.67.
[Ir(PNNN-H)(cod)]2(BF4)2 (6). Slow addition of 3a (170 mg,
0.34 mmol) to 2-H (130 mg, 0.38 mmol) dissolved in 20 mL of
CH2Cl2 gave a yellow solution, out of which a white solid
precipitated. After 1 h the volatiles were removed under reduced
pressure. The resultant residue was washed with THF (twice) and
ether (once) and dried in vacuo to give 6 as a white solid (241 mg,
0.17 mmol, 96% yield). 6: δH (CD2Cl2) 1.8-2.0 (4H, br, cod), 2.4-
2.6 (2H, br, cod), 2.6-2.8 (2H, br, cod), 3.2-3.4 (3H, m, 3H, H11
+ cod), 3.7-3.8 (1H, m, cod), 5.10 (1H, s, H4), 6.88 (2H, br, cod),
7.29-7.55 (8H, m, Ph + H7,9), 7.7-7.8 (4H, m, Ph), 7.88 (1H, t,
J ) 7.6 Hz, H8), 7.98 (1H, d, J ) 5.1 Hz, H10); δP (DMSO-d6)
-5.5; δP (solid) 0.59; IR (KBr) 2962 (m), 1261 (m), 1084 (s), 1028
cm-1 (s); ESI-MS:13 m/z 644.6 (M+/2), 942.5 (M+ - PNNN -
2H), 1285.0 (M+ - H), 1373.0 (M+ + BF4). Anal. Calcd for
C59H32N6P2Cl2Ir2B2F8 (6‚CH2Cl2): C, 45.83; H, 4.04; N, 5.44.
Found: C, 45.43; H, 4.22; N, 5.60.
[(cod)Ir(PNNN)Ir(cod)]BF4 (5a). To 2-H (180 mg, 0.52 mmol)
dissolved in CH2Cl2 (20 mL) was added 3a (520 mg, 1.04 mmol).
After 2 min Et3N (74 µL, 0.52 mmol) was added and the solution
was stirred for 30 min. Evaporation of the solvent gave a dark red
solid, which was dissolved in methanol and the resultant solution
was filtered through a Celite pad to give an orange solution. The
methanol solution was concentrated to 7 mL at 60 °C. Cooling to
-12 °C gave 5a (332 mg, 0.32 mmol, 62% yield). 5a: δH (CDCl3)
1.43-2.64 (16H, m, cod), 2.97 (1H, br, cod), 3.29 (1H, br, cod),
3.92-3.99 (2H, m, cod), 4.26-4.41 (2H, m, H11), 4.69-4.82 (3H,
m, cod), 5.34 (1H, br, cod), 7.15 (1H, s, H4), 7.38-7.63 (11H, m,
py + Ph), 7.84 (1H, d, J ) 5.9, H10), 8.01-8.11 (2H, m, H7,8);
δP (CDCl3) 34.9 (s); δC (CDCl3) 26.1, 28.5, 29.8, 31.6 (cod), 33.9
(td, JC-H ) 134, JC-P ) 58, C11), 35.0, 38.3 (cod), 61.4 (d, JC-H
) 157, cod), 64.2 (d, JC-H ) 160, cod), 66.3, 67.4, 67.7 (cod),
75.4 (d, JC-H ) 154, cod), 85.6 (d, JC-H ) 159, cod), 94.8 (d,
JC-H ) 154, cod), 101.7 (dd, JC-H ) 180, JC-P ) 9, C4), 121.5 (d,
JC-H ) 165, C7), 124.5 (d, JC-H ) 168, C9), 129.2-135.2 (Ph),
141.0 (d, JC-H ) 172, C8), 147.5 (d, JC-H ) 181, C10), 153.1,
156.3, 158.3 (s, C3/5/6); IR (KBr) 2916, 2882, 2833, 1611, 1454,
1083 cm-1; ESI-MS13 m/z 942.5 (M+), 832.5 (M+ - cod). Anal.
Calcd for C37H31Ir2BF4: C, 43.15; H, 4.01; N, 4.08. Found: C,
42.98; H, 4.07; N, 3.96.
[(cod)Ir(PNNN)Rh(cod)]BF4 (7a). To 6 (157 mg, 0.11 mmol)
suspended in CH2Cl2 (20 mL) was added NEt3 (34 µL, 0.24 mmol,
1.1 equiv), and the resultant mixture was stirred for 1 h. The
suspension turned into an orange solution, which was slowly added
to a CH2Cl2 solution of 3b (96 mg, 0.24 mmol, 1.1 equiv). The
mixture turned dark red, and after 15 min, the solution was washed
with deoxygenated water (20 mL) two times to remove HNEt3‚
BF4. The organic layer was dried over MgSO4, filtered through a
Celite pad, and concentrated to 3 mL under reduced pressure. Slow
addition of ether led to the precipitation of 7a as a bright orange
solid (171 mg, 0.18 mmol, 83% yield). 7a: δH (CD2Cl2) 1.35-3.2
(16H, br, cod), 3.30-5.7 (10H, br, cod + H11), 6.80 (1H, s, H4),
7.33 (1H, t, J ) 6, H9), 7.40-7.80 (12H, m, py + Ph), 7.96 (1H,
t, J ) 7.8, H8); δP (CD2Cl2) 38.1 (s); δC (CD2Cl2) 26.0 (t, JC-H
132, cod), 28.8 (t, JC-H ) 136, cod), 31.3 (td, JC-H ) 131, JC-P
)
)
[(cod)Rh(PNNN)Rh(cod)]BF4 (5b). 5b (bright orange solid;
62% yield) was prepared as described for 5a. 5b: δH (CDCl3) 1.6-
2.9 (16H, m, cod), 3.4-5.9 (8H, br, cod), 3.99 (2H, d, J ) 8.4,
H11), 6.84 (1H, s, H4), 7.28 (1H, t, J ) 6.0, H9), 7.50-7.30 (10H,
m, Ph), 7.68 (1H, d, J ) 5.2, H10), 7.75 (1H, d, J ) 7.6, H7), 7.92
(1H, t, J ) 7.6, H8); δP (CDCl3) 37.2 (d, JP-Rh ) 154.6); δC
(CD2Cl2) 31.0 (td, JC-H ) 133, JC-P ) 27, C11), 47.7 (s, cod),
33, C11), 32.7 (t, JC-H ) 133 Hz, cod), 34.8 (t, JC-H ) 133 Hz,
cod), 38.1 (t, JC-H ) 132, cod), 64.0 (d, JC-H ) 153, cod), 65.6
(d, JC-H ) 160, cod), 79.0 (d, JC-H ) 153, cod), 83.08 (d, JC-H
)
144, cod), 85.2 (d, JC-H ) 148, cod), 94.9 (d, JC-H ) 153, cod),
101.1 (dd, JC-P ) 9, JC-H ) 177, C4), 121.3 (d, JC-H ) 166, C7),
123.7 (d, JC-H ) 170, C9), 129.0-134.9 (Ph), 140.1 (d, JC-H
)
78.9 (dd, JC-H ) 162, JC-P ) 12, (cod)Rh(P)), 101.0 (dd, JC-H
176, JC-P ) 9, C4), 120.8 (d, JC-H ) 163, C7), 123.4 (d, JC-H
)
)
165, C8), 147.4 (d, JC-H ) 183, C10), 152.6 (s, C5/6), 156.0 (d,
JC-P ) 6, C3), 156.3 (s, C5/6); IR (KBr) 2916 (m), 2879 (m), 2831
(m), 1608 (m), 1449 (m), 1060 (s) cm-1; ESI-MS13 m/z 854.3 (M+
- cod). Anal. Calcd for C37H41N3BF4PRhIr: C, 47.24; H, 4.39; N,
4.46. Found: C, 47.05; H, 4.63; N, 4.01.
171, C9), 129.1-131.4 (Ph), 140.02 (d, JC-H ) 171, C8), 147.3
(d, JC-H ) 188, C10), 152.9, 153.1, 156.2 (s, C3/5/6); IR (KBr)
2932, 2878, 2831, 1608, 1450, 1083 cm-1; ESI-MS:13 m/z 764.2
(M+), 654.3 (M+ - cod). Anal. Calcd for C38H35OBF4Rh2 (5b‚
MeOH): C, 51.66; H, 5.13; N, 4.76. Found: C, 51.20; H, 4.92; N,
4.83.
[(cod)Ir(PNNN)Pd(allyl)]BF4 (7b). (i) From 6. 7b was obtained
in 89% yield as described for 7a. (ii) From 12. To a mixture of 12
(56 mg, 0.087 mmol) and NEt3 (5 µL) dissolved in CH2Cl2 (5 mL)
was slowly added a CH2Cl2 solution (5 mL) of 3c (30 mg, 0.088
mmol) and Et3N (5 µL). The solution was stirred for 15 min and
concentrated to 4 mL under reduced pressure, and addition of
diethyl ether gave 7b as a beige solid (74 mg, 0.084 mmol, 97%
yield). 7b: δH (CD2Cl2) 1.73-2.50 (8H, m, cod), 3.24 (2H, t, J )
10.7, allyl), 3.38 (1H, s, cod), 3.92-4.01 (3H, m, H11 + cod),
4.11 (1H, d, J ) 5.9, allyl), 4.58 (1H, d, J ) 5.1, allyl), 5.22 (2H,
s, cod), 5.81 (1H, m, allyl), 6.83 (1H, s, H4), 7.38 (1H, t, J ) 6.1,
H9), 7.45-7.70 (10H, m, Ph), 7.77 (1H, d, J ) 8.0, H7), 7.99 (1H,
t, J ) 7.8, H8), 8.53 (1H, d, J ) 4.9, H10); δP (CD2Cl2) 37.70 (s);
δC (CD2Cl2) 28.7 (t, JC-H ) 127, cod), 30.4 (td, JC-H ) 134, JC-P
) 32.2, C11), 31.4 (t, JC-H ) 125, cod), 31.6 (t, JC-H ) 128, cod),
34.9 (t, JC-H ) 124, cod), 60.5 (t, JC-H ) 159, allyl), 62.7 (d, JC-H
) 161, cod), 63.0 (d, JC-H ) 154, cod), 63.0 (t, JC-H ) 157, allyl),
[(allyl)Pd(PNNN)Pd(allyl)]BF4 (5c). Et3N (35 µL, 0.25 mmol)
was added to a mixture of 2-H (87 mg, 0.25 mmol) and 3c (173
mg, 0.50 mmol) dissolved in 10 mL of CH2Cl2. The solution was
stirred for 30 min, and the volatiles were removed in vacuo. The
residue was washed twice with cold methanol and ether, extracted
with CH2Cl2, and filtered through a Celite pad to give a colorless
solution. Concentration of the solution under reduced pressure to
3 mL and slow addition of ether gave 5c (a mixture of diastereo-
mers; 156 mg, 0.22 mmol, 86% yield) as a colorless solid. 5c: δH
(CD2Cl2) 2.76 (1H, t, J ) 14.8, allyl), 3.15 (1H, d, J ) 12.7, allyl),
3.33 (0.6H, d, J ) 12.1, allyl), 3.46 (0.4H, d, J ) 12.3, allyl),
3.72-4.15 (6H, m, H11 + allyl), 4.89 (0.6H, t, J ) 5.2, allyl),
5.09 (0.4H, t, J ) 5.5, allyl), 5.65-5.88 (2H, m, allyl), 6.78 and
6.77 (1H, s, H4), 7.31 (1H, t, J ) 6.7, H9), 7.45-7.78 (11H, m,

1356 Organometallics, Vol. 25, No. 6, 2006
Dubs et al.
89.8 (dd, JC-H ) 149, JC-P ) 12, cod), 93.2 (dd, JC-H ) 155, JC-P
) 10, cod), 101.7 (dd, JC-H ) 177, JC-P ) 10, C4), 115.3 (d, JC-H
) 163, allyl), 121.5 (d, JC-H ) 168, C7), 124.3 (d, JC-H ) 168,
C9), 129.2 (d, JC-H ) 163, Ph), 129.3-133.8 (Ph), 140.2 (d, JC-H
) 164, C8), 152.3 (s, C5/6), 152.9 (d, JC-H ) 183, C10), 155.9 (d,
JC-P ) 7, C3), 156.53 (s, C5/6); IR (KBr) 2915, 2880, 2834, 1606,
1449, 1054 cm-1; ESI-MS13 m/z 790.3 (M+), 746.4 (M+ - allyl).
Anal. Calcd for C32.5H35N3 BF4PClPdIr (7b‚0.5CH2Cl2): C, 42.45;
H, 3.83; N, 4.57. Found: C, 42.05; H, 3.86; N, 4.57.
times with deoxygenated water (15 mL), and the CH2Cl2 layer was
dried over MgSO4. The solution was filtered through a Celite pad
and concentrated to 3 mL under reduced pressure. Slow addition
of hexane led to the precipitation of 10a as an orange solid (675
mg, 0.635 mmol, 93% yield). 10a: δH (CDCl3) 1.3-3.2 (18H, br,
cod), 3.6-4.3 (4H, m, H6,7), 4.3-4.7 (4H, br, cod), 6.27 (2H, bt,
J ) 6.6, cod), 6.37 (1H, s, H4), 7.3-7.8 (20H, m, Ph); δP (CDCl3)
31.9 (s), 35.0 (d, JRh-P ) 154 Hz); δC (CD2Cl2) 25.7 (td, JC-H
)
125, JC-Rh ) 3, cod), 25.8 (td, JC-H ) 138, JC-Rh ) 3, cod), 28.5
(t, JC-H ) 121, cod), 30.6 (td, JC-H ) 138, JC-P ) 27, C6/7-Rh),
30.5 (td, JC-H ) 133, JC-P ) 33, C6/7-Ir), 32.3 (m, cod), 34.0 (t,
[(cod)Rh(PNNN)Ir(cod)]BF4 (8a). Addition of NEt3 (68 µL,
0.49 mmol) to a mixture of 6 (327 mg, 0.22 mmol) and 3b (200
mg, 0.49 mmol) dissolved in CH2Cl2 (20 mL) caused a color change
to red. After 20 min the solution was washed twice with deoxy-
genated water, and the CH2Cl2 layer was dried over MgSO4.
Filtration through a Celite pad, concentration to 5 mL under reduced
pressure, and slow addition of diethyl ether gave 8a as a bright red
precipitate (368 mg, 0.39 mmol, 87% yield). 8a: δH (CD2Cl2) 1.5-
2.6 (16H, m, cod), 3.7-5.3 (8H, br, cod), 4.03 (2H, d, J ) 8.0,
H11), 6.71 (1H, s, H4), 7.3-7.6 (11H, m, Ph + H9), 7.74 (1H, d,
J ) 7.0, H7), 7.87 (1H, d, J ) 5.3, H10), 8.01 (1H, t, J ) 7.8,
H8); δP (CD2Cl2) 38.8 (d, JP-Rh ) 155 Hz); δC (CD2Cl2) 31.2 (td,
JC-H ) 131, cod), 37.0 (m, cod), 38.3 (m, cod), 61.7 (d, JC-H
)
149, (cod)Ir), 61.8 (d, JC-H ) 149, (cod)Ir), 75.3 (dd, JC-H ) 150,
JC-Rh ) 12, (cod)Rh), 77.4 (dd, JC-H ) 155, JC-Rh ) 12, (cod)-
Rh), 86.6 (dd, JC-H ) 158, JC-P ) 17, (cod)Ir), 94.6 (dd, JC-H
)
158, JC-P ) 8, (cod)Ir), 100.9 (ddd, JC-H ) 151, JC-Rh,C-P ) 14
and 7, (cod)Rh), 101.9 (dt, JC-H ) 182, JC-P ) 10, C4), 105.8 (dt,
JC-H ) 158, JC-P,C-Rh ) 7, (cod)Rh), 128-135 (Ph), 153.7 (dd,
JC-P,C-Rh ) 8 and 3, C3), 156.2 (d, JC-P ) 6, C5); IR (KBr) 2920,
1434, 1084 cm-1; ESI-MS13 m/z 975.3 (M+), 865.6 (M+ - cod).
Anal. Calcd for C45H49N2BF4P2RhIr: C, 50.90; H, 4.65; N, 2.63.
Found: C, 51.08; H, 4.75; N, 2.58.
JC-H ) 134, JC-P ) 28, C11), 27-32 (m, cod), 79.0 (dd, JC-H
)
159, JC-Rh ) 12, C16), 101.7 (dd, JC-H ) 178, JC-P ) 10, C4),
121.0 (d, JC-H ) 167, C7), 124.2 (d, JC-H ) 169, C9), 129.2-
131.5 (Ph), 141.0 (d, JC-H ) 166, C8), 147.5 (d, JC-H ) 178, C10),
153.5, 153.7, 158.3 (s, C3/5/6); IR (KBr) 2915, 2878, 2830, 1611,
1453, 1083 cm-1; ESI-MS13 m/z 854.2 (M+), 744.4 (M+ - allyl).
Anal. Calcd for C37H41N3BF4PRhIr: C, 47.24; H, 4.39; N, 4.46.
Found: C, 46.85; H, 4.36; N, 4.31.
[(cod)Ir(PNNP)Pd(allyl)]BF4 (10b). 10b (yellow solid; 90%
yield) was prepared as described for 10a. 10b: δH (CD2Cl2) 1.4-
3.9 (9H, m, cod + allyl), 2.96 (1H, br, cod), 3.7-3.9 (3H, m, H6,7
or cod or allyl), 3.9-4.1 (3H, m, H6,7 or cod or allyl), 4.14 (1H,
br, cod), 4.94 (1H, br, cod), 5.31-5.34 (2H, m, allyl), 5.7-5.8
(1H, m, allyl), 6.36 (1H, s, H4), 7.4-7.8 (20H, m, Ph); δP
(CD2Cl2) 28.1 (s), 33.7 (s); δC (CD2Cl2) 27.3 (t, JC-H ) 125,
cod), 29.7 (t, JC-H ) 122, cod), 30.2 (td, JC-H ) 134, JC-P ) 32,
C7-Ir), 31.0 (td, JC-H ) 135, JC-P ) 27, C6-Rh), 32.7 (t, JC-H
) 129, cod), 36.3 (t, JC-H ) 122, cod), 51.6 (td, JC-H ) 152, JC-P
) 4, allyl), 60.4 (d, JC-H ) 151, cod), 61.4 (d, JC-H ) 155, cod),
81.2 (td, JC-H ) 159, JC-P ) 29, allyl), 87.9 (dd, JC-H ) 149,
JC-P ) 16, cod), 93.7 (dd, JC-H ) 154, JC-P ) 10, cod), 102.1 (dt,
JC-H ) 177, JC-P ) 9, C4), 118.5 (dd, JC-H ) 160, JC-P ) 6,
allyl), 129. 1-134.6 (Ph), 154.8 (d, JC-P ) 6, C3/5), 156.1 (d,
JC-P ) 7, C3/5); IR (KBr) 3052, 2914, 2877, 2830, 1434, 1058
cm-1; ESI-MS13 m/z 911.2 (M+), 869.4 (M+ - allyl). Anal. Calcd
for C40H42N2BF4P2PdIr: C, 48.13; H, 4.24; N, 2.80. Found: C,
48.26; H, 4.42; N, 2.80.
[(allyl)Pd(PNNN)Ir(cod)]BF4 (8b). 8b (red powder; 82% yield)
was prepared as described for 5a. 8b: δH (CD2Cl2) 1.71 (2H, br,
cod), 1.92 (2H, br, cod), 2.28 (4H, br, cod), 2.68 (1H, br, allyl),
3.70-4.20 (8H, m, H11 + cod + allyl), 5.24 (1H, t, J ) 6.8, allyl),
5.69 (1H, m, allyl), 6.76 (1H, s, H4), 7.37 (1H, td, JC-H ) 6.6 and
1.2, H9), 7.40-7.7 (10H, m, Ph), 7.76 (1H, d, J ) 7.6, H7), 7.89
(1H, d, J ) 5.6, H10), 8.00 (1H, td, JC-H ) 8.0 and 1.2, H8); δP
(CD2Cl2) 34.0; δC {1H}17 (CD2Cl2) 30.3 (br, cod), 30.4 (d, JC-P
)
22), 32.2 (br, cod), 51.0 (d, JC-P ) 5, allyl), 65.0 (br, cod), 84.1
(d, JC-P ) 31, allyl), 102.7 (d, JC-P ) 8, C4), 118.6 (d, JC-P ) 3,
allyl), 120.7 (s, C7), 124.3 (s, C9), 129.1-132.7 (Ph), 141.2 (s,
C8), 147.2 (s, C10), 153.7 (d, JC-P ) 5, C3), 155.0, 158.5 (s, C5/
6); IR (KBr) 1608, 1464, 1084, 1053 cm-1; ESI-MS13 m/z 790.3
(M+), 748.4 (M+ - allyl). Anal. Calcd for C32H34N3PIrPdBF4: C,
43.82; H, 3.90; N, 4.88. Found: C, 43.75; H, 3.81; N, 4.79.
[Ir(PNNP-H)(cod)]2(BF4)2 (9). Slow addition of 3a (500 mg,
1.00 mmol) to 1-H (592 mg, 1.12 mmol) dissolved in 5 mL of
CH2Cl2 caused precipitation of a white solid. After 30 min the
volatiles were removed under reduced pressure. The resultant
residue was washed with THF and ether and dried in vacuo to give
9 as a white solid (835 mg, 0.49 mmol, 98% yield). 9: δH (DMSO-
d6) 1.0-4.6 (32H, m, H6,7 + cod), 5.1 (2H, s, H4), 5.7-8.3 (40H,
m, Ph), 11.60 (2H, s, N-H); δP (DMSO-d6) 4.4 (d, JPP ) 42),
[Ir(PNNN-H)2(cod)]BF4 (11). 2-H (49 mg, 0.014 mmol) and
3a (30 mg, 0.006 mmol, 0.42 equiv) were dissolved in CH2Cl2
(3 mL). After the mixture was stirred for 10 min, ether was
added to precipitate the product. Removal of the solvent by a
cannula and washing twice with diethyl ether gave 11 as a white
solid (65 mg, 0.006 mmol, 100% yield). 11: δH (CD2Cl2) 1.4-1.8
(6H, br, cod), 2.10 (2H, br, cod), 3.40 (2H, br, cod), 3.85 (4H, br,
cod + H11), 4.3-4.6 (2H, m, H11), 6.65 (1H, s, H4), 6.8-7.9
(27H, m, aromatic), 8.73 (1H, d, J ) 3.8, H10), 8.99 (1H, d, J )
4.4, H10); δH (-80 °C) 12.93 (1H, bs, NH), 16.41 (1H, bs,
NH); δP (CD2Cl2) -19.6 (d, JP-P ) 12, P in the P,N chelate), 8.9
(d, JP-P ) 12, κ1(P)); δC {1H}17 (CD2Cl2) 30.8 (t, JC-H ) 129
cod), 32.1 (d, JC-P ) 26, C11), 32.2 (d, JC-P ) 25, C11), 32.9
(t, JC-H ) 131, cod), 63.4 (br. d, JC-H ) 150, cod), 64.5 (dd,
JC-H ) 160, JC-P ) 7, cod), 101.9 (dd, JC-H ) 177, JC-P ) 12,
-16.1 (d, JPP ) 42); δC (DMSO-d6) 27.2 (td, JC-H ) 131, JC-P
21, C6), 30.1 (d, JC-H ) 132, cod), 32.3 (td, JC-H ) 128, JC-P
)
)
27, C7), 67.1 (overlapped, cod), 101.5 (dd, JC-H ) 183, JC-P ) 9,
C4), 128.6-138.3 (Ph), 142.1 (s, C3), 156.8 (d, JC-P ) 9, C5); IR
(KBr) 3053 (m), 2944 (m), 1560 (m), 1434 (s), 1084 (s), 1032 (s)
cm-1; ESI-MS13 m/z 765.4 (M+/2), 1529.1 (M+ - H), 1615.0 (M+
- H + BF4). Anal. Calcd for C74H76N4P4Ir2B2F8: C, 52.18; H,
4.49; N, 3.29. Found: C, 51.81; H, 4.72; N, 3.11.
[(cod)Ir(PNNP)Rh(cod)]BF4 (10a). NEt3 (107 µL, 1.1 equiv)
was added to 9 (584 mg, 0.34 mmol) suspended in CH2Cl2 (20
mL), and the resultant mixture was stirred for 12 h to give an orange
solution. Upon slow addition of 3b (278 mg, 0.686 mmol) the color
changed to dark red. After 15 min the solution was washed two
C4), 104.3 (dd, JC-H ) 179, JC-P ) 7, C4), 120.4 (d, JC-H
163, C7), 120.8 (d, JC-H ) 163, C7), 123.8 (d, JC-H ) 164, C9),
124.2 (d, JC-H ) 163, C9), 127.6-133.4 (Ph), 137.4 (d, JC-H
164, C8), 137.8 (d, JC-H ) 163, C8), 142.7, 146.1, 146.2, 147.1,
)
)
147.3 (s, C3,5,6), 149.8 (d, JC-H ) 179, C10), 156.4 (d, JC-P
)
13, C3); IR (KBr) 2962, 1625, 1261, 1083 (BF4) cm-1; ESI-MS13
m/z 877.5 (M+ - cod), 644.4 (M+ - PNNN-H). Anal. Calcd for
C50H48N6BF4P2Ir: C, 55.92; H, 4.51; N, 7.83. Found: C, 56.33;
H, 4.87; N, 7.20.
(cod)Ir(PNNN) (12). A mixture of 6 (303 mg, 0.21 mmol) and
NEt3 (57 µL, 0.41 mmol) dissolved in 10 mL of CH2Cl2 was stirred
(17) JC-H coupling constants could not be determined, owing to the low
solubility in organic solvents or instability.

Ir Complexes with Bridging PNNN and PNNP Ligands
Organometallics, Vol. 25, No. 6, 2006 1357
Table 2. Crystallographic Data for 5c and 7a
for 30 min. The volatiles were removed under reduced pressure,
and the resultant residue was dissolved in hot MeOH (30 mL).
Filtration through a Celite pad and concentration to 10 mL under
reduced pressure followed by slow cooling to -30 °C gave a red
powder. The supernatant was removed by a cannula and the red
powder washed once with cold MeOH and twice with cold ether
to give 12 as a red solid (164 mg, 0.25 mmol, 62% yield). From
the combined organic phases a second crop of 12 (34 mg, 0.05
mmol) was obtained: overall yield 198 mg, 0.31 mmol, 75%). 12:
δH (CD2Cl2) 2.10 (4H, br, cod), 2.28 (4H, br, cod), 3.33 (2H, br,
cod), 3.59 (2H, d, J ) 10.4, H11), 5.79 (2H, br, cod), 6.73 (1H, s,
H4), 7.07 (1H, dd, J ) 7.4 and 1.4, H9), 7.42-7.73 (11H, m, Ph
+ py), 8.00 (1H, d, J ) 8.0, H7), 8.50 (1H, d, J ) 4.7, H10); δH
(DMSO-d6) 1.6-2.0 (8H, br, cod), 3.62 (2H, d, J ) 10.2, H11),
3.87 (4H, br, cod), 6.65 (1H, s, H4), 7.11 (1H, t, J ) 6.1, H9),
7.4-7.6 (10H, br, Ph), 7.67 (1H, td, J ) 7.4 and 1.4, H8), 7.85
(1H, d, J ) 8.0, H7), 8.43 (1H, d, J ) 4.1, H10); δP (CD2Cl2)
5c
7a
solvate
formula
formula wt
cryst syst
space group
a/Å
2CH2Cl2
C27H27N3BF4PPd2
724.11
triclinic
P1h
10.638(4)
11.351(3)
12.251(4)
97.89(2)
110.574(8)
91.28(2)
1367.9(8)
2
C39H45N3BF4PCl4RhIr
1110.52
triclinic
P1h
12.795(3)
13.033(4)
14.044(5)
99.43(1)
103.25(2)
91.89(2)
2242(1)
2
b/Å
c/Å
R/deg
â/deg
γ/deg
V/Å3
Z
d
calcd/g cm-3
1.758
1.423
10 296
1.644
3.660
15 787
µ/mm-1
no. of diffractions
collected
no. of variables
R1 for data with
I > 2σ(I)
361
469
31.21; δC (CD2Cl2) 29.4 (t, JC-H ) 126, cod), 32.3 (td, JC-H
131, JC-P ) 33, C11), 33.4 (t, JC-H ) 125.6, cod), 58.2 (d, JC-H
)
)
0.0658 (for
3082 data)
0.1746 (for all
5648 data)
0.0907 (for
7162 data)
0.2660 (for all
9062 data)
150, cod), 94.3 (dd, JC-H ) 155, JC-P ) 11, cod), 99.8 (dd,
JC-H ) 176, JC-P ) 10, C4), 119.4 (d, JC-H ) 161, C7), 121.0 (d,
JC-H ) 158, C9), 128.7-132.9 (Ph), 135.7 (d, JC-H ) 160, C8),
148.8 (d, JC-H ) 164, C10), 154.1, 154.6, 155.2 (s, C3/5/6); IR
(KBr) 2910, 2876, 2828, 1610, 1591, 1452, 1433, 1083 cm-1; ESI-
MS m/z 642.5 (M+ + H). Anal. Calcd for C30H33N3OPIr (12‚
MeCN): C, 53.39; H, 4.93; N, 6.23. Found: C, 53.13; H, 4.59; N,
6.19.
wR2
radiation (λ ) 0.710 69 Å) at -60 °C. Indexing was performed
from three oscillation images, which were exposed for 3 min. The
crystal-to-detector distance was 110 mm (2θmax ) 55°). In the
reduction of data, Lorentz and polarization corrections and empirical
absorption corrections were made.18 The data collection of 5c was
made on a Rigaku AFC7R automated four-circle diffractometer by
using graphite-monochromated Mo KR radiation (λ ) 0.710 69 Å)
at room temperature. The unit cell was determined and refined by
a least-squares method using 20 independent reflections (2θ ≈ 20°).
Data were collected with ω-2θ scan techniques. If σ(F)/F was
more than 0.1, a scan was repeated up to three times and the results
were added to the first scan. Three standard reflections were
monitored at every 150 measurements. Absorption correction was
made with the Ψ-scan technique. Data collections were performed
with a VENTURIS FX 5133 computer. The crystallographic data
for 5c and 7a are summarized in Table 2. The crystallographic data
and CIF files for the other compounds, which appeared in ref 5d
and therefore are not included in the Supporting Information, are
available from the CSD (7b, CCDC 243414; 8b, CCDC 243413;
12, CCDC 243415).
{[Ir(PNNP)(COD)]2H}BF4 (13). To 9 (190 mg, 0.11 mmol)
suspended in CH2Cl2 (20 mL) was added NEt3 (34 µL, 1.1 equiv),
and the mixture was stirred for 12 h. The solution was washed
twice with H2O and then dried over MgSO4. Filtration and re-
moval of the volatiles under reduced pressure gave 13 as a white
solid (93 mg, 0.058 mmol, 53% yield). 13: δH (CD2Cl2) 1.5-2.3
(16H, br, cod), 2.99 (4H, br, cod), 3.1-4.0 (8H, m, H6), 4.4
(4H, br, cod), 5.61 (2H, s, H4), 6.6-7.5 (40H, m, Ph), 13.28 (1H,
s, N-H); δP (CD2Cl2) 6.9 (d, JP-P ) 29), -19.3 (d, JP-P
29); 13C NMR data could not be obtained due to the low solubility
in organic solvents; IR (KBr) 3053, 1561, 1434, 1084, 694 cm-1
)
;
ESI-MS13 m/z 765.4 ((M+ + H)/2), 1063.4 (M+ - PNNP-H),
1527.1 (M+). Anal. Calcd for C74.75H76.5N4BF4P4Cl1.5Ir2 (13‚
0.75CH2Cl2): C, 53.46; H, 4.59; N, 3.33. Found: C, 53.28; H,
4.97; N, 3.38.
The structural analysis was performed on an IRIS O2 computer
using the teXsan structure solving program system obtained from
the Rigaku Corp., Tokyo, Japan.19 Neutral scattering factors were
obtained from the standard source.20
The structures were solved by a combination of direct methods
(SHELXS-86)21 and Fourier synthesis (DIRDIF94).22 Least-squares
refinements were carried out using SHELXL-97 21 (refined on F2)
linked to teXsan. Unless otherwise stated, all non-hydrogen atoms
were refined anisotropically, methyl hydrogen atoms were refined
using riding models, and other hydrogen atoms were fixed at the
calculated positions. For 5c, one of the two allyl groups was found
to be disordered and refined with two components (C4-C5:C4A-
C5A ) 0.53:0.47). Hydrogen atoms attached to the disordered parts
[(allyl)Pd{(PNNP-H)Ir(cod)}2](BF4)3 (14b). To 9 (20 mg, 0.012
mmol) suspended in CH2Cl2 (5 mL) was added 3c (4.0 mg, 0.012
mmol), and the suspension was stirred until a red solution was
obtained. Then the volatiles were removed under reduced pressure,
and the resultant red solid was washed twice with ether to give
14b (21 mg, 0.011 mmol, 90% yield). 14b: δH (CD2Cl2) 2.0-2.4
(16H, br, cod), 3.27 (2H, m, allyl), 3.44 (4H, br, cod), 3.59 (2H, d,
JC-P ) 10.2, H6 or H7), 3.73 (2H, t, J ) 3.92, H6 or H7), 4.05
(2H, d, J ) 5.1, allyl), 5.25 (4H, br, cod), 5.6-5.7 (3H, m, H4 +
allyl), 7.1-7.6 (40H, m, Ph), 11.42 (2H, s, N-H); δP (CD2Cl2)
12.2 (s), 27.9 (s); δC (CD2Cl2) 26.8 (td, JC-H ) 136, JC-P ) 19,
C7-Pd), 29.7 (t, JC-H ) 127, cod), 30.7 (td, JC-H ) 134, JC-P
)
31, C6-Ir), 32.6 (t, JC-H ) 127, cod), 62.2 (dd, JC-H ) 157, JC-P
) 8, cod), 74.7 (tt, JC-H ) 151, JC-P ) 13, allyl), 93.4 (dd, JC-H
) 155, JC-P ) 12, cod), 105 (d, JC-H ) 181, C4), 122.9 (dd, JC-H
) 132, JC-P ) 7, allyl), 122.9-133.0 (Ph), 142.92 (s), 159.1 (d,
(18) Higashi, T. Program for Absorption Correction; Rigaku Corp.,
Tokyo, Japan, 1995.
(19) teXsan; Crystal Structure Analysis Package, version 1.11; Rigaku
Corp., Tokyo, Japan, 2000.
(20) International Tables for X-ray Crystallography; Kynoch Press:
Birmingham, U.K., 1975; Vol. 4.
(21) (a) Sheldrick, G. M. SHELXS-86: Program for Crystal Structure
Determination; University of Go¨ttingen, Go¨ttingen, Germany, 1986. (b)
Sheldrick, G. M. SHELXL-97: Program for Crystal Structure Refinement;
University of Go¨ttingen, Go¨ttingen, Germany, 1997.
(22) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garcia-Granda, S.; Gould, R. O.; Smits, J. M. M.; Smykalla, C. The DIRDIF
Program System; Technical Report of the Crystallography Laboratory;
University of Nijmegen, Nijmegen, The Netherlands, 1992.
JC-P ) 7, C3/5); IR (KBr) 2920, 1561, 1435, 1083 (s), 694 cm-1
;
ESI-MS13 m/z 1849.8 (M+), 1617.0 ({[(PNNP-H)Ir(cod)2](BF4)}+),
911.3 [(PNNP)Ir(cod)Pd(allyl)]+), 765.5 [(cod)Ir(PNNP)Ir(cod)]+).
Anal. Calcd for C79H85N4B3F12P4Cl2Ir2 (14b‚CH2Cl2): C, 45.02;
H, 4.07; N, 2.73. Found: C, 45.34; H, 4.11; N, 2.73.
X-ray Crystallography. Single crystals of 5c, 7a‚2CH2Cl2,
7b‚0.5CH2Cl2, 8b, and 12 were obtained by recrystallization from
CH2Cl2-ether. Diffraction measurements, except for 5c, were made
on a Rigaku RAXIS IV imaging plate area detector with Mo KR

1358 Organometallics, Vol. 25, No. 6, 2006
Dubs et al.
were not included in the refinement. For 7a, the two CH2Cl2
molecules were refined isotropically, and hydrogen atoms attached
to CH2Cl2 were not included in the refinement. One of the two
CH2Cl2 molecules, being found to be disordered, was refined by
taking into account two components (Cl3-C52-Cl4:ClA-C52A-
Cl4A ) 0.60:0.40).
Science and Technology for financial support of this research.
A Monbukagakusho scholarship for C.D. from the Japanese
Government is gratefully acknowledged.
Supporting Information Available: Tables and figures giving
crystallographic results (12 pages); data are also available as CIF
files. This material is available free of charge via the Internet at
http://pubs.acs.org.
Acknowledgment. We are grateful to the Ministry of
Education, Culture, Sports, Science and Technology of the
Japanese Government and the Japan Society for Promotion of
OM050896M