A novel heteroditopic terpyridine-pincer ligand as building block for mono- and heterometallic Pd(II) and Ru(II) complexes

Article abstract of DOI:10.1021/ic051967c

A palladium-catalyzed Stille coupling reaction was employed as a versatile method for the synthesis of a novel terpyridine-pincer (3, TPBr) bridging ligand, 4′-{4-BrC₆H₂(CH₂NMe ₂)₂-3,5}-2,2′:6′,2″-terpyridine. Mononuclear species [PdX(TP)] (X = Br, Cl), [Ru(TPBr)(tpy)](PF₆) ₂, and [Ru(TPBr)₂](PF₆)₂, synthesized by selective metalation of the NCNBr-pincer moiety or complexation of the terpyridine of the bifunctional ligand TPBr, were used as building blocks for the preparation of heterodi- and trimetallic complexes [Ru(TPPdCl)(tpy)] (PF₆)₂ (7) and [Ru(TPPdCl)₂]-(PF ₆)₂ (8). The molecular structures in the solid state of [PdBr(TP)] (4a) and [Ru(TPBr)₂](PF₆)₂ (6) have been determined by single-crystal X-ray analysis. Electrochemical behavior and photophysical properties of the mono-and heterometallic complexes are described. All the above di- and trimetallic Ru complexes exhibit absorption bands attributable to ¹MLCT (Ru → tpy) transitions. For the heteroleptic complexes, the transitions involving the unsubstituted tpy ligand are at a lower energy than the tpy moiety of the TPBr ligand. The absorption bands observed in the electronic spectra for TPBr and [PdCl(TP)] have been assigned with the aid of TD-DFT calculations. All complexes display weak emission both at room temperature and in a butyronitrile glass at 77 K. The considerable red shift of the emission maxima relative to the signal of the reference compound [Ru(tpy)₂]²⁺ indicates stabilization of the luminescent ³MLCT state. For the mono- and heterometallic complexes, electrochemical and spectroscopic studies (electronic absorption and emission spectra and luminescence lifetimes recorded at room temperature and 77 K in nitrile solvents), together with the information gained from IR spectroelectrochemical studies of the dimetallic complex [Ru(TPPdSCN)(tpy)] (PF₆)₂, are indicative of charge redistribution through the bridging ligand TPBr. The results are in line with a weak coupling between the {Ru(tpy)₂} chromophoric unit and the (non)metalated NCN-pincer moiety.

Full text of DOI:10.1021/ic051967c

Inorg. Chem. 2006, 45, 2143−2155
A Novel Heteroditopic Terpyridine-Pincer Ligand as Building Block for
Mono- and Heterometallic Pd(II) and Ru(II) Complexes
,§
Marcella Gagliardo,† Gema Rodr´ıguez,† Henk H. Dam,† Martin Lutz,| Anthony L. Spek,|
,
Remco W. A. Havenith,#,‡ Paolo Coppo,+ Luisa De Cola,+ Frantisˇek Hartl,+
Gerard P. M. van Klink,† and Gerard van Koten*,†
Debye Institute, Organic Chemistry and Catalysis, Padualaan 8,
3584 CH Utrecht, The Netherlands, BijVoet Center for Biomolecular Research, Crystal and
Structural Chemistry, Padualaan 8, 3584 CH Utrecht, The Netherlands, Debye Institute,
Theoretical Chemistry Group, Padualaan 8, 3584 CH Utrecht, The Netherlands, and Van’t Hoff
Institute for Molecular Sciences, Molecular Photonic Materials, UniVersity of Amsterdam,
Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands
Received November 14, 2005
A palladium-catalyzed Stille coupling reaction was employed as a versatile method for the synthesis of a novel
terpyridine-pincer (3, TPBr) bridging ligand, 4 4-BrC6H2(CH2NMe2)2-3,5 -2,2 :6 ,2′′-terpyridine. Mononuclear species
[PdX(TP)] (X Br, Cl), [Ru(TPBr)(tpy)](PF6)2, and [Ru(TPBr)2](PF6)2, synthesized by selective metalation of the
′
-{
}
′ ′
)
NCNBr-pincer moiety or complexation of the terpyridine of the bifunctional ligand TPBr, were used as building
blocks for the preparation of heterodi- and trimetallic complexes [Ru(TPPdCl)(tpy)](PF6)2 (7) and [Ru(TPPdCl)2]-
(PF6)2 (8). The molecular structures in the solid state of [PdBr(TP)] (4a) and [Ru(TPBr)2](PF6)2 (6) have been
determined by single-crystal X-ray analysis. Electrochemical behavior and photophysical properties of the mono-
and heterometallic complexes are described. All the above di- and trimetallic Ru complexes exhibit absorption
bands attributable to 1MLCT (Ru
f tpy) transitions. For the heteroleptic complexes, the transitions involving the
unsubstituted tpy ligand are at a lower energy than the tpy moiety of the TPBr ligand. The absorption bands
observed in the electronic spectra for TPBr and [PdCl(TP)] have been assigned with the aid of TD-DFT calculations.
All complexes display weak emission both at room temperature and in a butyronitrile glass at 77 K. The considerable
red shift of the emission maxima relative to the signal of the reference compound [Ru(tpy)2]2+ indicates stabilization
of the luminescent 3MLCT state. For the mono- and heterometallic complexes, electrochemical and spectroscopic
studies (electronic absorption and emission spectra and luminescence lifetimes recorded at room temperature and
77 K in nitrile solvents), together with the information gained from IR spectroelectrochemical studies of the dimetallic
complex [Ru(TPPdSCN)(tpy)](PF6)2, are indicative of charge redistribution through the bridging ligand TPBr. The
results are in line with a weak coupling between the
pincer moiety.
{Ru(tpy)2} chromophoric unit and the (non)metalated NCN-
Introduction
multimetallic complexes between Ru- and Os-polypyridine
chromophores communicating through a wide range of linear
bridging ligands.1 Recent developments have highlighted
many possibilities resulting from the incorporation of transi-
tion metals in multifunctional assemblies covalently attached
to soft chromophoric centers.2 A fascinating field of study
is emerging on molecular architectures with unique photo-
chemical and electrochemical properties aimed at energy
conversion, photonic and electronic devices, and biomedical
applications.3 Metallosupramolecular structures based on
(hetero)ditopic linear bridging ligands, prepared via the
introduction of functionalities at the 4′-position of a terpy-
ridine moiety, play a major role in this field. The possibility
of building systems assembled in a topologically controlled
In the past decade, attention has been focused considerably
on photoinduced electron- and energy-transfer processes in
* To whom correspondence should be addressed. E-mail:
g.vankoten@chem.uu.nl. Fax: 31-30-252-3615. Tel: 31-30-253-3120.
† Debye Institute, Organic Chemistry and Catalysis.
| Bijvoet Center for Biomolecular Research, Crystal and Structural
Chemistry.
§ To whom crystallographic inquiries may be directed. E-mail:
a.l.spek@chem.uu.nl.
# Debye Institute, Theoretical Chemistry Group. (This group is affiliated
with Organic Chemistry and Catalysis.)
‡ Address correspondence pertaining to theoretical calculations to this
author. E-mail: r.w.a.havenith@chem.uu.nl.
+ Van’t Hoff Institute for Molecular Sciences.
Present address: Physikalisches Institut, Westfa¨lische Wilhelmss
Universita¨t Mu¨nster, Mendelstrasse 7, 48149 Mu¨nster, Germany.
10.1021/ic051967c CCC: $33.50
Published on Web 02/09/2006
© 2006 American Chemical Society
Inorganic Chemistry, Vol. 45, No. 5, 2006 2143

Gagliardo et al.
Scheme 1. Synthesis of TPBr Ligand (3)a
a Reagents and conditions: (i) (a) two equivalents of tBuLi, Et2O, -100 °C, 0.5 h; (b) Me3SnCl, Et2O, -100 °C f RT, 15 h. (ii) LiCl, [PdCl2(PPh3)2],
toluene, reflux, 20 h.
fashion, in which donor and acceptor components are situated
in opposite directions, makes the use of terpyridine units
attractive.4 The structural advantages of terpyridine-type
complexes are, however, offset by their less-favorable
photophysical properties.1 For example, [Ru(tpy2)]2+ com-
pounds have short-lived excited states and thus display a very
weak emission at room temperature.5 A significant increase
in the luminescence lifetime can be achieved by a proper
functionalization of terpyridine ligands at the 4′-position.1b,i,6
However, insertion of organometallic subunits containing
a metal-carbon σ-bond in such species is still relatively
unexplored.7 Organometallic components incorporated into
supramolecular architectures, with the influence of other tun-
able building blocks, are expected to exhibit reactivity pat-
terns quite different from those of their mononuclear coun-
terparts.7 For example, recent results published by Inagaki
and co-workers demonstrated that dinuclear Ru-Pd species
[(bpy)2Ru(µ-bmp)Pd(Me)(Me2CO)]3+ and [(bpy)2Ru(µ-bmp-
)Pd(Me)(MeCN)]3+ (bmp ) 2,2′-bipyrimidine), containing
a photosensitizing RuII unit and a reactive Pd center,
catalyzed selective dimerization of R-methylstyrene to give
2,4-diphenyl-4-methyl-1-pentene under irradiation with vis-
ible light.8
(1) (a) Sauvage, J.-P.; Collin, J.-P.; Chambron, J.-C.; Guillerez, S.;
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The ability of the monoanionic, terdentate-coordinating
pincer ligands to give stable cyclometalated complexes,
which can be applied as catalysts in various organic
transformations9 or in the construction of materials10 (e.g.,
liquid crystalline materials and optical and electrooptical
devices), prompted us to investigate molecular assemblies
on the basis of the novel heteroditopic terpyridine-pincer
ligand 4′-{4-BrC6H2(CH2NMe2)2-3,5}-2,2′:6′,2′′-terpyridine
(TPBr (3); Scheme 1). In light of the rich coordination
chemistry of both the terpyridine1-3 and the NCN-aryl
pincer moieties11 the TPBr ligand is envisaged as a valuable
building block for construction of metallo-supramolecular
polymers12 and decoration of dendritic wedges13 that incor-
porate catalytically active fragments and photosensitizing
RuII-tpy moieties.
Here, the synthesis of the novel ligand TPBr and the first
examples of its coordination chemistry are presented. The
dual reactivity of TPBr permits the synthesis of monometallic
complexes bearing externally directed vacant binding sites.
These species can further be used as building blocks for the
preparation of heterometallic complexes via stepwise syn-
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5486.
2144 Inorganic Chemistry, Vol. 45, No. 5, 2006

NoWel Heteroditopic Terpyridine-Pincer Ligand
Scheme 2. Synthesis of Homometallic Complexes 4b, 5, and 6a
a Reagents and conditions: (i) (a) 0.5 equiv of [Pd2(dba)3]‚CHCl3, C6H6, reflux, 2 h; (b) Me3SiOTf, CH2Cl2; (c) NaCl, acetone. (ii) (a) [RuCl3(tpy)],
N-ethylmorpholine, MeOH, reflux, 1 h; (b) NaPF6, MeOH. (iii) (a) 0.5 equiv of RuCl3‚3H2O, Et3N, EtOH, reflux, 1 h; (b) NaPF6, MeOH.
theses, using the “complex-as-ligand” approach.2a In addition,
for a deeper understanding of the nature of the intercompo-
nent electronic coupling between the metal centers through
the bridging ligand in the synthesized heterodi- and trime-
tallic species, we have applied electrochemical, spectroelec-
trochemical, and photophysical methods.
Synthesis of Monometallic Pd and Ru Complexes.
Monometalated complexes 4a ([PdBr(TP)]), 5 ([Ru(TPBr)-
(tpy)](PF6)2), and 6 ([Ru(TPBr)2](PF6)2) were synthesized
by a selective reaction of the NCNBr-pincer or tpy moiety
of the heteroditopic ligand 3 with the appropriate metal
precursor complex. Thus, 4a was prepared by the oxidative
addition of palladium to the Caryl-Br bond of the NCNBr-
pincer terminus of 3 in refluxing benzene using the Pd0
precursor [Pd2(dba)3]‚CHCl317 (dba ) dibenzylideneacetone)
(Scheme 2). Scrambling of the bromide anion in solution in
the presence of chloride is expected when applying 4a as a
building block in the synthesis of heterometallic complexes.
Thus, 4a was converted to the chloride analogue 4b
[TPPdCl] by bromide abstraction with Me3SiOTf, followed
Results and Discussion
Synthesis of the Heteroditopic Ligand [TPBr]. Attempts
to prepare the heteroditopic ligand 4′-{BrC6H2(CH2NMe2)2-
2,6}-2,2′:6′,2′′-terpyridine (TPBr, (3), Scheme 1) by applying
the Kro¨hnke methodology14 gave a mixture of different
compounds, from which the desired product could not be
isolated by standard procedures. Application of a Pd-
catalyzed Stille cross-coupling15 proved to be a facile one-
step synthetic pathway toward 3. The formation of 3 was
achieved by reaction of the stannane pincer compound 4′-
{BrC6H2(CH2NMe2)2-2,6}SnMe3 (2) with 4′-(CF3SO3)-2,2′:
6′,2′′-terpyridine16 (Scheme 1).
(11) (a) Rodr´ıguez, G.; Albrecht, M.; Schoenmaker, J.; Lutz, M.; Spek, A.
L.; van Koten, G. J. Am. Chem. Soc. 2002, 124, 5127. (b) Albrecht,
M.; Lutz, M.; Spek, A. L.; van Koten, G. Nature 2000, 406, 970. (c)
Slagt, M. Q.; Stiriba, S.-E.; Kautz, H.; Klein Gebbink, R. J. M.; Frey,
H.; van Koten, G. Organometallics 2004, 23, 1525.
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41, 3825. (b) Lohmeijer, B. G. G.; Schubert, U. S. J. Polym. Sci.,
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318.
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Gagliardo et al.
Figure 1. Displacement ellipsoid plot of complex 4a (50% probability level). Hydrogen atoms have been omitted for clarity.
by treatment with an excess of NaCl. The structural config-
uration of solid 4a was obtained from a single-crystal X-ray
diffraction analysis. A molecular plot of complex 4a is shown
in Figure 1, and a selection of bond lengths, angles, and
torsion angles is reported in Table 1. The PdII center is in a
presence of the reducing agent N-ethylmorpholine. Treatment
of the intensely red-colored solution with NaPF6 resulted in
the precipitation of 5 as a purple-red powder. Because of
the low symmetry of the compounds, assignments of the
1
aromatic fingerprint region of the H NMR spectrum were
1
aided by 2D H-1H COSY NMR spectroscopy. The most
Table 1. Selected Bond Lengths (Å), Bond Angles (deg), and Torsion
Angles (deg) of Complex 4a
relevant features in the 1H NMR spectrum are the singlet at
8.24 ppm for the aromatic protons of the NCN-pincer moiety,
the doublet at 9.08 ppm for H(3′)A of the coordinated tpy,
and the singlet at 9.35 ppm for H(3′)B of the coordinated
tpy moiety of ligand 3.
Bond Lengths (Å)
Pd1-Br1
Pd1-C1
Pd1-N1
2.5406(3)
1.924(2)
2.1234(19)
Pd1-N2
C4-C15
C13-C23
C17-C18
2.1183(19)
1.485(3)
1.485(3)
1.494(3)
The reaction of equimolar amounts of ligand 3 and RuCl3‚
3H2O in EtOH produced the intermediate building block
[RuCl3(TPBr)], which was isolated and subsequently treated
with a second equivalent of ligand 3 in refluxing MeOH in
the presence of the reducing agent N-ethylmorpholine. The
resulting red methanolic solution was reacted with NaPF6
to give the ruthenium complex [Ru(TPBr)2](PF6)2 (6, Scheme
2). Protonation of the NMe2 groups of the NCN-pincer
moieties by the acid formed during the reaction was
circumvented by the addition of Et3N to the reaction mixture.
Because of the symmetry of the molecule, only eight
resonances are observed in the 1H NMR spectrum of complex
6. In the aliphatic region, two singlets are present for the
NMe2 protons (2.39 ppm) and the benzylic CH2 groups (3.76
ppm) of the NCN-pincer moieties. In the aromatic region,
only six peaks are observed; five of them are attributed to
the tpy and the remaining one is assigned to the aromatic
protons of the NCN-pincer moiety.
Bond Angles (deg)
Br1-Pd1-C1
N1-Pd1-N2
Br1-Pd-N1
176.48(6)
161.98(7)
96.97(5)
Br1-Pd1-N2
C1-Pd1-N1
C1-Pd1-N2
100.91(5)
81.17(8)
80.86(8)
Torsion Angles (deg)
23.7(3) C16-C17-C18-N4
C3-C4-C15-C14
C3-C4-C15-C16
C14-C13-C23-N5
-2.6(3)
-152.6(2) C16-C17-C18-C19 177.6(2)
-2.2(3) C1-C2-C7-N1
-30.4(2)
-17.1(3)
C14-C13-C23-C24 -179.9(2) C1-C6-C10-N2
distorted square-planar environment and embedded in the
terdentate coordination pocket of the NCN framework. The
bond lengths in 4a are consistent with the values reported
for other neutral NCN-PdII complexes. The three pyridine
rings of the tpy moiety adopt a planar conformation, with
the nitrogen atoms in adjacent rings trans with respect to
each other, thereby minimizing the electrostatic repulsion
between the nitrogen lone pairs and the molecular dipoles.
A torsion angle of 23.7(3)° for C3-C4-C15-C14 indicates
twisting of the NCN and tpy moieties about the interannular
C4-C15 bond, which is in the expected 20-40° range of
ortho-H biphenyl compounds.
Single crystals of complex 6 suitable for X-ray diffraction
analysis were obtained by the slow diffusion of Et2O into a
MeCN solution of 6. Figure 2 depicts a molecular plot of 6.
A selection of bond lengths, bond angles, and torsion angles
is given in Table 2. The crystal structure of 6 shows the
The monometallic complex 5 was prepared by the direct
reaction of [RuCl3(tpy)] with 3 in refluxing MeOH in the
2146 Inorganic Chemistry, Vol. 45, No. 5, 2006

NoWel Heteroditopic Terpyridine-Pincer Ligand
Figure 2. Displacement ellipsoid plot of cationic complex 6 (50% probability level). Hydrogen atoms, PF6 counterions, and partially occupied acetonitrile
solvent molecules have been omitted for clarity. Only one conformation of the disordered pincer arm at C292 is shown.
Table 2. Selected Bond Lengths (Å), Bond Angles (deg), and Torsion
Angles (deg) of the First Independent Molecule of Complex 6
Bond Lengths (Å)
Ru-N11
Ru-N12
Ru-N71
Ru-N72
1.965(5)
1.970(5)
2.065(6)
2.078(6)
Ru-N131
Ru-N132
C192-C42
C191-C41
2.060(5)
2.056(6)
1.484(9)
1.491(9)
Bond Angles (deg)
N11-Ru-N12
N11-Ru-N71
N11-Ru-N131
179.4(2)
79.2(2)
79.1(2)
N71-Ru-N131
N11-Ru-N132
N11-Ru-N72
158.1(2)
101.2(2)
100.9(2)
Torsion Angles (deg)
C31-C21-C81-C91
N11-C21-C81-N71
2.5(14) C242-C192-C42-C32 138.6(8)
1.0(10) C242-C192-C42-C52 -39.6(12)
C51-C61-C141-C151 2.1(13) C201-C191-C41-C51 150.7(7)
N11-C61-C141-N131 1.2(9) C201-C191-C41-C31 -30.5(11)
C32-C22-C82-C92
N12-C22-C82-N72
C52-C62-C142-C152 1.6(13)
N12-C62-C142-N132 1.9(9)
-0.8(13)
-3.2(9)
ruthenium center in a distorted octahedral environment with
both tpy moieties of each ligand 3 meridionally coordinated.
All Ru-N distances and internal pyridine angles are similar
to those obtained for other Ru(II)-tpy derivatives.1h,18 The
tpy units are approximately planar, forming torsion angles
in the range -3.2(9) to 2.5(14)°. The torsion angles C242-
C192-C42-C52 and C201-C191-C41-C31 (-39.6(12)
and -30.5(11)°, respectively) illustrate twisting of the
interannular C41-C191 and C42-C192 bonds, respectively.
The edge-to-edge length of this rigid rodlike 6 is 21.735(2)
Å for Br1‚‚‚Br2.
Synthesis of Heterometallic Complexes. Heterometallic
complexes 7 ([Ru(TPPdCl)(tpy)](PF6)2) and 8 ([Ru(TPPdCl)2]-
(PF6)2) were prepared from the mononuclear organometallic
complex 4b. The Pd-C bond in 4b proved to be stable under
the reaction conditions applied in the following synthetic
steps. This stability qualifies 4b as an inert and versatile
building block in the complex-as-ligand approach.2a The
reaction of [RuCl3(tpy)] with 1 equiv of 4b in MeOH in the
Figure 3. UV-vis absorption spectra of ligand 3 (s) and complex 4b
(- - -) measured in CH2Cl2 at 298 K. Inset: UV-vis absorption spectra
of 2,2′:6′,2′′-terpyridine (s) and the pincer ligand [BrC6H3(CH2NMe2)2-
2,6] (- - -) measured in CH2Cl2 at 298 K.
presence of the reducing agent N-ethylmorpholine yielded
7 (Scheme 3). The synthesis of 8 was accomplished in a
similar two-step procedure. First, 4b was reacted with RuCl3‚
3H2O in refluxing EtOH to give the intermediate building
block [RuCl3(TPPdCl)] (Scheme 3). Subsequently, this
intermediate was treated with a second equivalent of 4b in
refluxing MeOH in the presence of N-ethylmorpholine.
Coordination of the palladium center to the NCNBr-pincer
moiety prevents the protonation of the NMe2 groups by the
acid formed during the reaction, thereby circumventing the
1
need for Et3N addition. H NMR studies have shown that
both 7 and 8 can also be prepared by the oxidative addition
of palladium to the Caryl-Br bond in 5 and 6, respectively,
by using the Pd0 precursor [Pd2(dba)3]‚CHCl3 in refluxing
benzene (Scheme 3). However, the extensive washing
procedures required to remove liberated dba lowers the yield
of this route considerably.
(18) (a) Beley, M.; Collin, J.-P.; Louis, R.; Metz, B.; Sauvage, J.-P. J. Am.
Chem. Soc. 1991, 113, 8521. (b) Constable, E. C.; Cargill Thompson,
A. M. W. New J. Chem. 1992, 16, 855.
Inorganic Chemistry, Vol. 45, No. 5, 2006 2147

Gagliardo et al.
Table 3. Electronic Absorption and Emission Data
λ
max (nm)a
λ
em (nm)b
(τ (µs))
compd
(ꢀmax × 104 (M-1 cm-1))
[PdCl(NCN)] (9)
255 (4.02), 279 (1.95), 286 (1.96), ndc
307 (1.30)
307 (5.2), 475 (1.26)
255 (3.46), 280 (4.30),
320 sh (0.63)
293 (3.70), 330 sh (1.65)
308 (5.9), 483 (1.80)
318 (6.2), 490 (2.50)
[Ru(tpy)2]2+ d
598 (11)
nd
[TPBr] (3)e
[PdCl(TP)] (4b)e
nd
[Ru(TPBr)(tpy)]2+ (5)
[Ru(TPBr)2]2+ (6)
624 (14)
629 (13)
624 (15)
630 (13)
nd
[Ru(TPPdCl)(tpy)]2+ (7)
[Ru(TPPdCl)]2+ (8)
271 (3.50), 308 (5.0), 485 (2.04)
283 (3.75), 308 (4.9) 496 (1.8)
[Ru(TPPdSCN)(tpy)]2+ (10) 272 (3.27), 309 (3.43),
487 (2.94)
a Measured at 298 K in MeCN. b Measured at 77 K in a butyronitrile
glass (λex ) 480 nm). c n.d. ) not determined. d See ref 3d. e Measured at
298 K in CH2Cl2.
Electronic Absorption Spectra. Table 3 reports the
absorption maxima (λmax) and molar absorption extinction
coefficients (ꢀmax) for 3 and 4b in CH2Cl2 and for 5-8 in
MeCN (elelctronic spectra in Figures 3 and 4, respectively).
Data for the pincer complex [PdCl{C6H3(CH2NMe2)2-2,6}]
(9)17 and the reference compound [Ru(tpy)2](PF6)23d have also
been included for comparison.
Figure 4. UV-vis absorption spectra of complexes 5 (- ‚‚ -), 7
(- ‚ -), 6 (s), and 8 (- - -) in MeCN at 298 K. The inset shows the
emission spectrum of complex 8 in butyronitrile at 77 K (λex ) 480 nm).
Scheme 3. Synthesis of Heterodi- and Trimetallic Complexes 7 and 8a
a Reagents and conditions: (i) (a) [RuCl3(tpy)], N-ethylmorpholine, MeOH, reflux, 1 h; (b) NaPF6, MeOH. (ii) (a) RuCl3‚3H2O (1 equiv), EtOH, reflux,
1 h; (b) 4b (1 equiv) and N-ethylmorpholine, MeOH, reflux, 1.5 h; (c) NaPF6, MeOH. (iii) [Pd2(dba)3]‚CHCl3 (0.5 equiv), C6H6, reflux, 2 h. (iv) (a)
[Pd2(dba)3]‚CHCl3 (2 equiv), reflux, 2 h; (b) Me3SiOTf (2 equiv), CH2Cl2; (c) NaCl, acetone.
2148 Inorganic Chemistry, Vol. 45, No. 5, 2006

NoWel Heteroditopic Terpyridine-Pincer Ligand
Figure 5. Contour plot of HOMOs and LUMOs of 3 and 4b calculated at the B3LYP/LANL2-DZ level, involved in the electronic transitions presented
in Table 5.
Table 4. TD-DFT Excitation Energies (E) and Non-Vanishing
The electronic spectrum of 3 (Figure 3) is not the simple
Oscillator Strengths (f > 0.02) Calculated for 3 and 4b
sum of the spectra of the unsubstituted tpy (λmax ) 280 nm;
wavelength
(nm)
log ꢀmax ) 4.3) and the pincer ligand [BrC6H3(CH2NMe2)2-
state
composition
E (eV)
f
2,6] (NCNBr) (λmax ) 269 nm; log ꢀmax ) 1.) (Figure 3,
inset). This suggests that the tpy and NCNBr-pincer moieties
in ligand 3 are not fully electronically independent but rather
weakly coupled.
The electronic absorption spectrum of complex 4b shows
in the UV region a band pattern similar to that of ligand 8
but slightly shifted to a lower energy. The main difference
is an intense shoulder dominating the 300-350 nm region
and tailing down to 450 nm.
To understand the changes in the spectrum of the free
ligand caused by coordination of the Pd-Cl moiety and to
elucidate the origin of the new low-lying transitions, we
decided to calculate the electronic spectra of both compounds
using the time-dependent DFT (TD-DFT) approach (at the
B3LYP/LANL2-DZ level). Table 4 presents the low-lying
3
7A 62% (H - 2 f L + 1); 34% (H - 3 f L) 3.89
11A 92% (H - 2 f L) 4.07
16A 56% (H - 3 f L); 36% (H - 2 f L + 1) 4.21
319
305
294
283
366
0.030
0.367
0.223
0.272
0.020
21A 87% (H - 3 f L + 1)
3A 95% (Hf L)
4.39
3.39
4b
11A 41% (H - 3 f L + 1); 29%
4.00
310
0.051
(H - 5 f L); 9% (H - 6 f L)
14A 73% (H - 3 f L); 16% (H f L + 2)
16A 81% (H f L + 2); 15% (H - 3f L)
17A 30% (H - 5 f L); 16% (H - 8 f L + 1) 4.24
21A 59% (H - 4 f L + 1); 22% 4.35
(H - 5 f L + 1); 9% (H f L + 5)
4.13
4.17
300
297
292
285
0.105
0.190
0.182
0.320
electronic transitions in 3 and 4b with oscillator strengths
larger than 0.02. The calculated TD-DFT values are in
reasonable agreement with the experimental absorption
maxima of both compounds.
Inorganic Chemistry, Vol. 45, No. 5, 2006 2149

Gagliardo et al.
The occupied and virtual molecular orbitals involved in
the electronic transitions of 3 and 4b are depicted in Figure
5. The (HOMO - 3) and (LUMO + 1) of 3 and the (HOMO
- 5 )and (LUMO + 1) of 4b have the same π character and
are localized exclusively on the tpy subunit (π(tpy) and π*-
(tpy), respectively). The π*(tpy) character can also be
attributed to the LUMO of these compounds, which is,
however, partly localized on the ring π-system of the NCN-
pincer subunit. The (HOMO - 2) of 3 and the (HOMO -
3) of 4b are mainly localized on the NCN-pincer ring and,
to a minor extent, on the central pyridine ring of the tpy
subunit. No equivalent high-lying occupied molecular orbitals
of 3 are found for the HOMO and (HOMO - 4) of 4b, as
these orbitals show dominant contributions from the Pd-Cl
moiety, with a partial involvement of the NCN-pincer ring:
π*(Pd-Cl) and π*(Cl-Pd-C), respectively.
Taking into account the close correspondence between the
orbitals, we conclude that the intraligand (IL) transitions to
the 7A, 11A, and 16A states of 3 (Table 4) have natures
similar to those of the 11A, 14A, and 17A states of 4b,
respectively. However, we must not forget the major
contribution of the Pd-Cl moiety to the (HOMO - 3) of
4b, which also attributes to the 11A and 14A states a
significant metal-to-ligand, MLCT, and ligand-to-ligand,
LLCT, charge-transfer, character, respectively.
Upon coordination of the Cl-Pd fragment to ligand 3,
two new excitations appear in the near-UV region spectrum
of 4b: to the 3A state (calculated at 365 nm, HOMO f
LUMO) and to the 16A state (calculated at 297 nm, HOMO
f (LUMO + 2) and (HOMO - 3) f LUMO), both having
a mixed LLCT/MLCT character with a dominant π*(Pd-
Cl) f π*(tpy) component. Comparison of the experimental
electronic absorption spectra with the calculated transitions
leads to the following assignments. The intense experimental
band at 280 nm in the spectrum of 3 can be attributed to the
close-lying transitions 11A and 16A calculated at 305 and
294 nm, with large oscillator strengths and combined π*-
(Br-NCN) f π* (tpy) and π(tpy)f π* (tpy) character. The
band at 255 nm probably arises because of the π(tpy)f π*-
(tpy) transition to the 21A state, calculated at 283 nm. The
weak shoulder at 320 nm then corresponds to the much less
intense transition 7A with a prevailing π*(Br-NCN) f π*-
(tpy) character.
The transitions calculated for 4b at 285, 292, 297, and
300 nm contribute to the overall shape of the intense
experimental absorption band of the complex at 293 nm.
Considering the large contribution of the dπ(Pd) and pπ(Cl)
orbitals to the HOMO and (HOMO - 3), it can be concluded
that the intense band at 293 nm (encompassing the excitations
to the 14A, 16A, and 17A states) has a mixed π(tpy) f π*-
(tpy) (IL) and π*(Cl-Pd-NCN) f π*(tpy) (LLCT/MLCT)
character. The shoulder at 330 nm in the spectrum of 9b
has more than double the intensity of ligand 3 at 320 nm.
This comparison facilitates its assignment to the electronic
transition 11A calculated at 309 nm and the signal has nearly
double the oscillator strength of that of the 7A transition of
ligand 3. This difference is probably caused by the coordina-
tion of the Pd-Cl moiety, which again attributes the 11A
transition to a partial π(Cl-Pd)/π(NCN) f π* (tpy) (L′LCT/
MLCT) character. This absorption feature is also apparent
in the electronic absorption spectra of the heterometallic
complexes 7 and 8 (see below). The new HOMO f LUMO
transition of complex 4b (3A), with a mixed π*(Cl-Pd-
NCN) f π* (tpy) (LLCT/MLCT) character and a low
oscillator strength, was calculated at 366 nm. It is probably
partly hidden under the intense shoulder at 330 nm and
corresponds to the tailing observable down to 420 nm (Figure
3).
The electronic absorption spectra of the Ru-containing
complexes 5-8 (Figure 4) display features that can be
interpreted by comparison with the literature data1 and on
grounds of the TD-DFT analysis (vide supra). The intense
absorption bands in the UV region between 250 and 320
nm (Table 3) belong to the spin-allowed π f π*(tpy) and
π* f π*(tpy) (IL/LLCT/MLCT) transitions that are derived
from the Pd-Cl, NCN-pincer, and tpy moieties, as discussed
above for ligand 3 (7A, 11A, 16A, 21A) and complex 4b
(11A, 14A, 16A, 17A). Electronic spectra of complexes 7
and 8 also display a shoulder at ca. 360 nm, which is absent
in the spectra of the mononuclear Ru complexes 5 and 6.
For complex 8 with two Pd-Cl moieties bound to the NCN-
pincer termini, the shoulder has nearly double the intensity
of that in complex 7 with a single TPPd-Cl chromophore.
On the basis of these observations, we determine that the
corresponding electronic transition probably has the same
π*(Cl-Pd-NCN) f π*(tpy) (LLCT/MLCT) origin as the
HOMO f LUMO transition (3A) of complex 4b, which is
calculated and observed at the same energy (vide supra).
For all Ru-containing complexes 5-8, less-intense com-
posed absorption bands fall in the visible spectral region (λmax
) 483-500 nm; log ꢀmax ) 4.3-4.4). They can be
straightforwardly assigned to electronic transitions with a
predominant dπ(Ru)fπ*(tpy) charge-transfer (MLCT) char-
acter1 involving both the tpy moiety of ligand 3 and the
peripheral tpy ligand. Comparison of the mononuclear Ru
unsymmetric complexes 5 and 7 with the reference com-
3d
pound [Ru(tpy)2](PF6)2 (λmax ) 475 nm; log ꢀmax ) 4.1)
reveals that their MLCT maxima are slightly red-shifted (and
gain extra intensity) with the increasing substitution at the
4′-position of the peripheral tpy ligands with the NCNBr-
pincer moiety. We have attributed the red shift (see also
emission spectra) to the lowest excited state that is localized
on the unsubstituted tpy because of the electron-donating
character of the tpy moiety of ligand 3. The bathochromic
shift becomes slightly larger for the symmetric complexes 6
and 8, most likely because of an extension of the π-system
and stabilization of the lowest MLCT state(s). Coordination
of the Pd-Cl fragments to the NCN-pincer termini in the
heterometallic complexes 7 and 8 does not result in
significant changes in the spectra compared to the spectra
of the palladium-free species, indicating a weak intercom-
ponent coupling.1a
Electrochemistry. Cyclic and square wave voltammetries
in MeCN solutions were applied to study the redox properties
of the PdII-based complexes 4b and [PdCl{C6H3(CH2NMe2)2-
2,6}] ([PdCl(NCN)] (9) and the RuII-based complexes 5-8.
2150 Inorganic Chemistry, Vol. 45, No. 5, 2006

NoWel Heteroditopic Terpyridine-Pincer Ligand
Table 5. Electrochemical Data for Complexes 4b, 5-8, 10, and the
are slightly lower than that for the parent compound [Ru-
(tpy)2](PF6)2 (Table 5). In particular, the presence of the PdII
ion contributes clearly to a slight decrease in the reduction
potentials by ∼100 mV in the heterodi- and trimetallic
complexes 7 and 8. Thus, the functionalization of the NCN-
pincer moiety with the Pd-Cl fragment renders the bridging
ligand more difficult to reduce.
Reference Compounda
Ep,a(ox)
E1/2(ox)
compd
Pd-based Ru-based
E1/2(red)
[PdCl(NCN)] (9)
0.69d
0.98
0.82
0.87
0.81
0.82
0.85
[Ru(tpy)2]2+c
-1.58 -1.86
-1.62 -1.89
-1.63 -1.90
-1.67 -1.92
-1.68 -1.98
-1.65 -1.92
[Ru(TPBr)(tpy)]2+ (5)
[Ru(TPBr)2]2+ (6)
[Ru(TPPdCl)(tpy)]2+ (7)
[Ru(TPPdCl)2]2+ (8)
[Ru(TPPdSCN)(tpy)]2+ (10)d
In the cathodic potential region of all the complexes,
additional irreversible processes occur at -2.29 and -2.38
V vs Fc/Fc+ that possibly involve the reduction of the pincer
moiety. This hypothesis is supported by the results reported
by Connick and co-workers,23 according to which no
organometallic complexes containing NCN-pincer ligands
undergo reduction at potentials less negative then -1.8 V.
IR and UV-Vis Spectroelectrochemistry. To collect
more evidence for a weak electronic communication between
the metal centers in the heterodinuclear species through the
bridging ligand 3, we performed a cyclic voltammetric and
IR/UV-vis spectroelectrochemical study of complex 10
([Ru(TPPdSCN)(tpy)](PF6)2). Complex 10 contains SCN-
as a spectator ligand, i.e., a ligand that can easily be probed
and does not affect the overall properties of the complex.
The infrared spectrum of solid 10 displays a sharp ν(SCN)
absorption band at 2080 cm-1, characteristic of an S-bonded
thiocyanate group.24 On the basis of the infrared spectrum,
it can be concluded that the S-bonded species is the only
product obtained by exchanging the chloride in 7 for SCN-
in reaction with AgSCN. The exclusive S-bonding of the
SCN- ligand is expected on the basis of the poor π-acceptor
properties of the monoanionic NCN-pincer ligand, which
enhances the relative tendency of the “soft” donor sulfur atom
to participate in π-bonding.
a Measured at 298 K in MeCN. (0.1 M TBAH; scan rate ) 100 mV
s-1). Potentials reported in volts vs Fc/Fc+. b Measured at 298 K in CH2Cl2.
c See ref 3d. d Measured at 298 K in butyronitrile.
Table 5 presents redox potentials for all the studied com-
plexes and the reference compound [Ru(tpy)2](PF6)2.3d
The cyclic voltammogram of 9 exhibits an irreversible
oxidation at 0.69 V, similar to that of related monoanionic
NCN-pincer ligands reported elsewhere.19,20 This suggests
that upon oxidation, reorganization takes place. Para func-
tionalization of 9 with a tpy ligand (i.e., construction of 4b)
results in a considerable change of the redox properties of
the palladium center. For 4b ([PdCl(TP)]), no PdII-based
oxidation process could be detected within the potential limits
of the electrolyte. An inductive electronic effect of the tpy
of the bridging ligand 3 might account for the shift of the
formally PdII-based oxidation to potentials higher than those
of 9 (Mulliken21 populations: tpy/[NCNPdCl] ) 138.9/121.1
electrons instead of the ideal of 139.0/121.0).
The anodic potential region of the voltammograms of the
studied RuII-based complexes 5-8 exhibits a reversible one-
electron wave for the RuII/RuIII redox couple, which is 100-
160 mV less positive than the oxidation potential of
3d
[Ru(tpy)2](PF6)2 (see Table 3). Previously reported DFT
The cyclic voltammogram of 10, recorded in butyronitrile
at room temperature, exhibits features similar to those
observed for the related system 7: a reversible RuII/RuIII
anodic wave and two reversible one-electron tpy-centered
cathodic processes (Table 5). Importantly, replacement of
the Cl- ligand by the π-acceptor SCN- ligand clearly renders
the PdII center less electron-rich. This leads to a weaker back
π-bonding interaction with the bridging ligand in 10 than in
7, which results in less-negative centered ligand reductions
and a higher redox potential for the RuII/RuIII couple (Table
3).
The IR absorption spectrum of 10 in butyronitrile contain-
ing 0.1 M TBAH displays again the sharp ν(SCN) band of
the thiocyanato ligand at 2080 cm-1. This stretching mode
forms a convenient probe for spectroelectrochemical moni-
toring of subtle changes in electron density at the palladium
center caused by the tpy reduction.
calculations on [Ru(tpy)2]2+ and the analogous system [Ru-
(t-Bu-phtpy)2]2+ are in line with the observed behavior.22
From the HOMO energies of [Ru(tpy)2]2+ and [Ru(t-Bu-
phtpy)2]2+, it follows that the latter complex is more prone
to oxidation.22 The data reported in Table 3 reveal that the
RuII/RuIII oxidation potentials of the monometallic species
(5 and 6) fall in the same anodic region as those obtained
for the heterodi- and trimetallic complexes (7 and 8). This
result points to a limited electronic communication between
the RuII and PdII centers in the ground state, weakly mediated
by the bridging ligand 3. It is interesting to note that for
complexes 7 and 8, no PdII-based oxidation process could
be detected within the anodic potential limits of the
electrolyte.
Two reversible one-electron cathodic waves belong to the
reduction of the substituted and unsubstituted tpy moieties.1
For both heteroleptic (5 and 7) and homoleptic (6 and 8)
complexes, the initial reduction is shifted to potentials that
One-electron reduction of 10 within an optically transpar-
ent thin-layer electrochemical (OTTLE) cell25 in butyronitrile
(19) (a) Hershel, J.; Krause Bauer, J. A.; Connick, W. B. Inorg. Chem.
2004, 43, 725.
(20) (a) Back, S.; Lutz, M.; Spek, A. L.; Lang, H.; van Koten, G. J.
Organomet. Chem. 2001, 620, 227. (b) Back, S.; Gossage, R. A.; Lutz,
M.; del Rio, I.; Spek, A. L.; Lang, H.; van Koten, G. Organometallics
2000, 19, 3296.
(23) Jude, H.; Krause Bauer, J. A.; Connick, W. B. J. Am. Chem. Soc.
2003, 125, 3446.
(24) Nakamoto, K. In Infrared and Raman Spectra of Inorganic and
Coordination Compounds, 4th ed.; Wiley-Interscience: New York,
1997; p 117, part B.
(21) Mulliken, R. S. J. Chem. Phys. 1955, 23, 1833.
(22) Zhou, X.; Ren, A.-M.; Feng, J.-K. J. Organomet. Chem. 2005, 690,
338.
(25) (a) Krejc´ık, M.; Danek, M.; Hartl, F. J. Electroanal. Chem., Interfacial
Electrochem. 1991, 317, 179. (b) Hartl, F.; Luyten, H.; Nieuwenhuis,
H. A.; Schoemaker, G. C. Appl. Spectrosc. 1994, 48, 1522.
Inorganic Chemistry, Vol. 45, No. 5, 2006 2151

Gagliardo et al.
electron reduced species 10- completely regenerated the
spectrum of 10, whereas the reoxidation of 102- did not fully
recover the UV-vis spectrum of 10- and 10. In particular,
the absorption bands in the UV region of the spectrum were
lower in intensity. This behavior agrees with the conclusions
from the IR spectroelectrochemical studies: two-electron
reduced species 102- undergoes some transformation of the
NCN-Pd fragment while the redox-active {Ru(tpy)2}n (n
) 2+, 1+, 0) core remains intact. The reactivity of the
NCN-Pd-SCN fragment documents the weak, but not
negligible, tpy-NCN(Pd-X) communication, as the second
cathodic process is most likely localized on the tpy-NCN
moiety.
Luminescence Properties. The luminescence of the RuII-
based complexes (5-8) was investigated upon excitation with
480 nm light in deaerated acetonitrile at room temperature
and in a frozen butyronitrile matrix at 77 K. The lumines-
cence band maxima and lifetimes are listed in Table 3. At
room temperature, all complexes show a weak emission
profile centered at 640 nm, with lifetimes around 0.9 ns.
These values are very similar to those reported for reference
compound [Ru(tpy)2](PF6)2 (λmax ) 640 nm; τ ) 0.2 ns).3d
It is recognized that for [Ru(tpy)2]2+ and its derivatives,
the room-temperature luminescence from the lowest 3MLCT
(Ru f tpy) excited state is thermally quenched because of
the population of low-lying 3MC states that decay nonradia-
tively.1a,5 However, in a glass matrix at 77 K, the lumines-
cence quantum yield can be high because of the lack of
thermal activation.1a
Figure 6. UV-vis spectra of [Ru(TPPdSCN)(tpy)]2+ (10) (s), [Ru-
(TPPdSCN)(tpy)]+ (10-) (- - -), and [Ru(TPPdSCN)(tpy)] (102-
)
(- ‚ -), recorded in an OTTLE cell at 293 K. The solvent was butyronitrile
containing 0.1 M TBAH.
at 293 K smoothly produced the stable cation [Ru(TPPd-
SCN)(tpy)]+ (10-), as was documented by the thin-layer
cyclic voltammogram recorded in the course of the experi-
ment. The shape, position, and intensity of the ν(SCN) band
remained unchanged. This observation is consistent with the
first reduction step being localized at the peripheral (unsub-
stituted) tpy ligand. The addition of a second electron resulted
in a shift of the ν(SCN) band from 2080 to 2050 cm-1. This
shift to smaller wavenumbers could reflect an increased
electron density at the PdII center and increased π-back-
donation to the thiocyanate ligand. However, reoxidation of
the two-electron-reduced species 10-2 did not completely
recover the 2080 cm-1 band of 10-, indicating that 10-2
underwent a secondary chemical reaction on the time scale
of the electrolysis, most likely involving only the TPPd-
SCN fragment. The reduced Ru-tpy moiety remained
unaffected, as evidenced by the complete reversibility of the
thin-layer voltammetric response. The inherent stability of
the {Ru(tpy)2}2+ core in the reduced complexes 10- and 10-2
was further confirmed by a parallel UV-vis spectroelectro-
chemical experiment using the OTTLE cell and a less-
concentrated solution. The UV-vis absorption spectra of 10
and its one- and two-electron reduced species, 10- and 10-2,
are depicted in Figure 6. The spectrum of 10 displays
characteristic features also observed for 7 (vide supra) and
the reference compound [Ru(tpy)2](PF6)23d: intense IL/
LLCT/MLCT ligand-centered transitions in the UV region
(λmax ) 272-310 nm with log ꢀmax ) 3.27-3.43) and a dπ-
(Ru) f π*(tpy) metal-to-ligand-charge-transfer (MLCT)
band at λmax ) 487 nm (log ꢀmax ) 2.94) (Table 4).3d One-
and two-electron reduction of 10 caused a red shift of the
MLCT band at 487 nm to 524 and 554 nm, respectively
(Figure 6). Importantly, similar spectral changes were
observed in the visible spectral region of the stepwise
electrochemical reduction of the reference compound [Ru-
(tpy)2]2+.26 At higher energy, the intense bands between 272
and 310 nm, attributed to IL/LLCT/MLCT transitions, which
involve the tpy moieties of the bridging ligand (vide infra),
decrease considerably in intensity. Reoxidation of the one-
Although no detailed analysis has been carried out, we
expect the same kind of photophysical properties for the
complexes 5-8. In the butyronitrile matrixes at 77 K, all
the complexes indeed show bright red 3MLCT emission. The
emission spectra (see inset of Figure 4) resemble that of [Ru-
(tpy)2]2+, although the maxima are red-shifted by about 30
nm because of the electron-donating substituents at the 4′-
position of the tpy ligand (Table 3).1b
Homoleptic complexes 6 and 8 emit at a slightly lower
energy (λmax ) 630 nm) than the heteroleptic species 5 and
7 (λmax ) 624 nm) (Table 3). This minor shift may reflect,
as already discussed for the absorption, the different terpy-
ridine units involved in the lowest excited state. The emission
lifetimes, determined with a streak camera interfaced to a
nanosecond laser source set at 480 nm, show similar
differences as the emission maxima. The homoleptic com-
plexes 6 and 8 exhibit identical emission lifetimes of 13 µs,
whereas the heteroleptic complexes 5 and 7 live slightly
longer: 14 µs and 15 µs, respectively. The emission lifetimes
of complexes 5-8 are anyway longer than that of the
reference compound [Ru(tpy)2]2+ (10.6 µs),1a consistent with
the previous reports on RuII-complexes with terpyridine
ligands bearing electron-donating groups at the 4′-position.1b
The small differences can be attributed to a higher degree
of vibronic coupling to the ground state for those complexes
emitting at a lower energy (6 and 8), with consequent
shortening of the excited-state lifetime. The presence or
absence of the Pd-Cl moiety does not have a significant
influence on the emission properties of the ruthenium-tpy
(26) Berger, R. M.; McMillin, D. R. Inorg. Chem. 1988, 27, 4245.
2152 Inorganic Chemistry, Vol. 45, No. 5, 2006

NoWel Heteroditopic Terpyridine-Pincer Ligand
or 85% H3PO4 as an external reference (31P NMR spectra).
Elemental analyses were performed by Dornis und Kolbe, Mik-
roanalytisches Laboratorium, Mu¨llheim ad Ruhr, Germany. High-
resolution electron spray ionization (ESI) mass spectra were
recorded with a Micromass LC-TOF mass spectrometer at the
Department of Biomolecular Mass Spectrometry, Utrecht Univer-
sity.
chromophores. Thus, the 3MLCT excited state is ap-
proximately the same for all the complexes, confirming that
the energies of the unsubstituted and substituted tpy are very
similar. Furthermore, coordination of the palladium to the
NCNBr-pincer moieties has no detectable effect on the
electronic properties of the chromophoric units, as already
concluded from the electrochemical and electronic absorption
data.
Electronic Spectroscopic Measurements. UV-vis absorption
spectra were obtained with a Varian Cary 1 spectrophotometer.
Steady-state luminescence was measured in freshly distilled buty-
ronitrile at 77 K, using a Spex Fluorolog 1681 spectrofluorimeter
equipped with a Xe arc light source, a Hamamatsu R928 photo-
multiplier tube detector, and double excitation and emission
monochromators. Emission spectra were corrected for source
intensity and detector response using standard correction curves.
Deaerated solutions were prepared by the freeze-pump-thaw
technique on a high-vacuum line. For nanosecond time-resolved
emission measurements, a continuously tuned Coherent Infinity
XPO laser (set at 480 nm) working at 10 Hz, with a pulse of 2 ns
fwhm, was used as an excitation source. Full spectra and decays
were recorded using a Hamamatsu C5680-21 streak camera
equipped with an M 5677 sweep unit. The time resolution of this
setup is about 200 ps, as limited by laser width. Estimated errors
are as follows: band maxima, (2 nm; relative luminescence
intensity, (20%; lifetimes, (10%.
Conclusions
A novel heteroditopic ligand TPBr was synthesized in
which properties of 2,2′:6′,2′′-terpyridine and NCNBr-pincer
([BrC6H3(CH2NMe2)2-2,6]) ligands are combined. Like other
bridging heteroditopic ligands based on terpyridine substi-
tuted at the 4′-position, TPBr can be regarded as an appealing
rigid and linear bridging building block for the construction
of one-dimensional nanostructures based on metal complexes.
Selective metalation or coordination of the NCNBr-pincer
or tpy moieties with an appropriate transition-metal precursor
affords mononuclear species that can be further used for the
stepwise syntheses of nanometer-scale rigid rodlike heterodi-
and trimetallic species with a length up to 21.735(2) Å.
For all relevant complexes, oxidation of the ruthenium
centers occurs at nearly identical anodic potentials. This
observation indicates that in the ground state, the HOMOs
are almost unaffected by the presence of covalently attached
(non)metalated NCN-pincer units at the 4′-position of the
tpy ligand. Nevertheless, minor differences in reduction
potentials and the results of spectroscopic and spectroelec-
trochemical studies are consistent with a weak electronic
interaction between the tpy and NCN-pincer subunits. It is
important to point out that the large twist (dihedral) angle
between these subunits, as observed for complexes 4b (23.7
(3)°) and 6 (-39.6(12) and -30.5(11)°) with X-ray structural
analysis, probably makes them almost electronically inde-
pendent (geometric decoupling).1b,k,27 Combined with the
high intensity of the MLCT transitions in the visible region
(ꢀ ≈ 2 × 104 M-1 cm-1) and the possibility to bind a wide
range of transition metals at the NCN-pincer moieties, the
design features of the presented building blocks open the
possibility of exploring syntheses of organometallic polymers
with interesting redox and photophysical properties.
Electrochemical Experiments. Cyclic and square-wave volta-
mmetric scans were performed with a gastight single-compartment
cell under an atmosphere of dry nitrogen. The cell was equipped
with a Pt microdisk working (apparent surface area of 0.42 mm2),
Pt wire auxiliary, and Ag wire pseudoreference electrodes. The
working electrode was carefully polished with a 0.25 µm grain
diamond paste between scans. The potential control was achieved
with a PAR Model 283 potentiostat. All redox potentials are
reported against the ferrocene-ferrocenium (Fc/Fc+) redox couple
used as an internal standard (E1/2 ) +0.63 V vs NHE28);29 10-1
M
Bu4NPF6 was used as a supporting electrolyte. All electrochemical
samples were 5 × 10-4 M in the studied complexes.
IR Spectroelectrochemistry. Experiments were performed with
an optically transparent thin-layer electrochemical (OTTLE) cell25
equipped with a Pt minigrid working electrode and CaF2 optical
windows. The controlled-potential electrolyses were carried out with
a PA4 potentiostat (EKOM, Czech Republic). All the electrochemi-
cal samples were 5 × 10-2 in the studied complex and contained
3 × 10-1 M Bu4NPF6. IR spectra were recorded with a Bio-Rad
FTS-7 spectrometer at 2 cm-1 resolution (16 scans).
Computational Details. Geometries of 3 and 4b (C1 symmetry)
were optimized at the B3LYP level using GAMESS-UK.30 TD-
DFT calculations were performed using the B3LYP exchange/
correlation functional with DALTON.31 The LANL2-DZ32 basis
set was used Pd calculations, and the SV Dunning33 basis set as
built in GAMESS-UK was used for all other atoms.
Experimental Section
General. All the experiments were carried out under a dry
nitrogen atmosphere, using standard Schlenk techniques. Benzene,
toluene, pentane, hexane, and diethyl ether (Et2O) were distilled
from sodium/benzophenone. Dichloromethane was dried over CaH2.
Methanol was dried over magnesium and used freshly distilled.
The complexes [Pd2(dba)3]‚CHCl3,17 [Ru(tpy)Cl3], and18b 4′-triflato-
2,2′:6′,2′′-terpyridine16 and compounds 111a and 917 were synthesized
according to literature procedures. All other reagents were used as
(28) Gritzner, G.; Kuta, J. Pure Appl. Chem. 1984, 56, 461.
(29) Pavlishchuk, V. V.; Addison, A. W. Inorg. Chim. Acta 2002, 298,
97.
(30) Guest, M. F.; Bush, L. J.; van Dam, H. J.; Sherwood, P.; Thomas, J.
M. H.; van Lenthe, J. H.; Havenith, R. W. A.; Kendrick, J. J. Mol.
Phys. 2005, 103, 719.
(31) DALTON, a molecular electronic structure program, Release 2.0; 2005,
see http://www.kjemi.uio.no/software/dalton/dalton.html.
(32) a) Dunning, T. H., Jr.; Hay, P. J. In Modern Theoretical Chemistry;
Schaefer, H. F., III, Ed.; Plenum Press: New York, 1977; Vol. 3. b)
Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 299.
(33) Dunning, T. H., Jr.; Hay, P. J. In Methods of Electronic Structure
Theory; Schaefer, H. F., III, Ed.; Plenum Press: New York, 1977;
Vol. 2.
1
purchased. H (200.1 or 300.1 MHz), 13C (75 MHz), and 31P (81
MHz) NMR spectra were recorded at 298 K on a Varian AC200
or Varian INOVA 300 spectrometers. Chemical shifts are given in
ppm relative to the residual solvent signal (1H and 13C NMR spectra)
(27) Laine´, P.; Bedioui, F.; Ochsenbein, P.; Marvaud, V.; Bonin, M.;
Amouyal, E. J. Am. Chem. Soc. 2002, 124, 1364.
Inorganic Chemistry, Vol. 45, No. 5, 2006 2153

Gagliardo et al.
Hz, ArH), 137.6 (2JSnC ) 45 Hz), 140.3 (1JSnC ) 430 and 451 Hz).
Anal. Calcd for C15H27BrN2Sn: C, 41.51; H, 6.27. Found: C, 41.15;
H, 6.00.
Table 6. Crystallographic Details
4a
6
formula
C27H28BrN5Pd
[C54H56Br2N10Ru](PF6)2‚
0.4C2H3N
1412.34
4′-{4-BrC6H2(CH2NMe2)2-3,5}-2,2′:6′,2"-tpy [TPBr] (3). 4′-
Triflato-2,2′:6′,2′′-terpyridine (1.50 g, 3.93 mmol), 2 (2.15 g, 4.96
mmol), [PdCl2(PPh3)2] (0.11 g, 0.16 mmol), and dried LiCl (0.53
g, 12.59 mmol) were refluxed in dry toluene (50 mL) for 20 h in
a 100 mL round-bottom flask under a nitrogen atmosphere.
Subsequently, the solvent was removed in vacuo, and the residue
was redissolved in CH2Cl2. The CH2Cl2 solution was washed with
water, filtered over Celite, and dried over MgSO4. After removal
of the solvent, the residue was purified via silica gel chromatography
using ethyl acetate-hexane (1:1 v/v) as the eluent to afford pure 3
fw
608.85
cryst color
cryst size (mm3)
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
yellow
red
0.48 × 0.30 × 0.06
monoclinic
P21/c (No. 14)
14.6370(1)
9.1587(1)
19.1888(2)
90
108.0173(3)
90
2446.23(4)
4
0.30 × 0.18 × 0.06
triclinic
P1h (No. 2)
11.1057(2)
14.4557(2)
20.2558(4)
88.9444(6)
84.7470(5)
68.7656(6)
3017.99(9)
2
1.554
1.720
0.53
30377
1
as a light yellow solid (yield 0.71, g 45%), mp 157 °C. H NMR
Z
(300 MHz, CDCl3): δ 2.37 (s, 12H, NCH3), 3.70 (s, 4H, NCH2),
7.35 (dd, JHH ) 12.0, 0,9 Hz, 2H, PyrH(5, 5′′)), 7.85 (s, 2H, ArH),
Dx (g/cm3)
1.653
2.418
0.65
µ (mm-1
)
7.88 (td, JHH ) 7.51, 1.61 Hz, 2H, PyrH(4, 4′′)), 8.66 (d, JHH
)
(sin θ/λ)max (Å-1
)
7.9 Hz, 2H, PyrH(3, 3′′)), 8.70 (s, 2H, PyrH(3′, 5′)), 8.73 (d, JHH
) 4.3 Hz, 2H, PyrH(6, 6′′)).13C NMR (75 MHz, CDCl3): δ 45.5
(NCH3), 63.8 (NCH2), 119.1, 121.5, 123.8, 128.2, 128.7, 136.9,
137.5, 139.1, 149.1, 149.7, 156.0, 156.2. Anal. Calcd for C27H28-
BrN5: C, 64.54; H, 5.62; N, 13.94. Found: C, 64.46; H, 5.58; N,
13.91.
no. of maesured reflns 47360
abs corr
PLATON (DELABS) PLATON (ABST)
abs corr range
no. of unique reflns
params/restraints
R1/wR2 [I > 2σ(I)]
R1/wR2 (all reflns)
S
0.46-0.83
0.61-0.91
7622
5619
311/0
895/1679
0.0626/0.1736
0.0770/0.1847
1.052
0.0270/0.0704
0.0334/0.0731
1.059
[PdBr(TP)] (4a). A mixture of 3 (0.34 g, 0.68 mmol) and [Pd2-
(dba)3]‚CHCl3 (0.35 g, 0.34 mmol) was refluxed in dry benzene
(20 mL) for 2 h. The solvent was evaporated in vacuo, and the
obtained residue was dissolved in CH2Cl2. Addition of Et2O caused
the precipitation of a yellow powder that was collected by
centrifugation, washed several times with Et2O, and dried in vacuo.
Yellow crystals suitable for X-ray analysis were grown by slow
diffusion of Et2O into a CH2Cl2 solution of 3a (yield 0.28 g, 68%).
1H NMR (300 MHz, CDCl3): δ 3.02 (s, 12H, NCH3), 4.09 (s, 4H,
NCH2), 7.34 (s, 2H, ArH), 7.36 (ddd, JHH ) 7.5, 4.8, 1.2 Hz, 2H,
Pyr(5, 5′′), 7.87 (td, JHH ) 7.8, 1.8 Hz, 2H, Pyr(4, 4′′)), 8.64 (s,
2H, Pyr(3′, 5′)), 8.06 (d, JHH ) 7.8 Hz, 2H, Pyr(3, 3′′)), 8.71 (d,
JHH ) 4.8 Hz, 2H, Pyr(6, 6′′)), 13C NMR (75 MHz, CDCl3) δ 53.8
(NCH3), 74.5 (NCH2), 118.5, 119.0, 121.4, 123.9, 135.4, 136.9,
145.6, 149.1, 150.6, 155.7, 156.2, 159.4; Anal. Calcd for C27H28-
BrN5Pd: C, 53.26; H, 4.64; N, 11.50. Found: C, 53.20; H, 4.73;
N, 11.38.
F
min/max (e/Å3)
-0.84/0.44
-1.30/1.25
X-ray Structure Determinations. X-ray intensities were mea-
sured on a Nonius KappaCCD diffractometer with rotating anode
and graphite monochromator (λ ) 0.71073 Å) at a temperature of
150(2) K. The structures were solved with automated Patterson
methods34 and refined with SHELXL-9735 on F2 of all reflections.
Non-hydrogen atoms were refined freely with anisotropic displace-
ment parameters. In 4a, all hydrogen atoms were located in the
difference Fourier map; in 6, hydrogen atoms were introduced in
geometrically idealized positions. In both structures, H atoms were
refined with a riding model. In 6, the PF6 anions and one of the
pincer arms were heavily disordered and the acetonitrile solvent
molecule was refined with only partial occupation. Geometry
calculations, drawings, and checks for higher symmetry were
performed with the PLATON package.36 Further crystallographic
details are given in Table 6.
[TPPdCl] (4b). A solution of 4a (0.230 g, 0.38 mmol) and Me3-
SiOTf (0.088 g, 0.45 mmol) in CH2Cl2 was stirred at room
temperature for 30 min. The solvent was evaporated in vacuo, and
the solid residue obtained was redissolved in acetone. An excess
of NaCl was added, and the resulting suspension was stirred
overnight at room temperature. The solvent was removed in vacuo,
and the collected solid residue was dissolved in CHCl3. The organic
layer was washed with water and acetone and then dried in vacuo,
yielding 4b as a yellow solid that was separated by centrifugation,
washed with water and Et2O, and dried in vacuo (yield 0.120 g,
71%). The NMR data of complex 4b are identical to those reported
for complex 4a.
Synthesis of Ligands and Complexes. 4′-{BrC6H2(CH2NMe2)2-
2,6}-trimethyltin [Me3SnNCNBr] (2). A solution of tBuLi (6.38
mL, 1.5 M in pentane) was added dropwise to a solution of 1 (2.00
g, 5.04 mmol) in Et2O (50 mL) at -100 °C under vigorous stirring.
After 15 min, a solution of Me3SnCl (1.5 g, 7.56 mmol) in 25 mL
of Et2O was added. The resulting suspension was allowed to warm
to room temperature and stirred overnight. Subsequently, water was
added, and the obtained mixture was treated with 10-1 M NaOH
(0.5 mL). The Et2O layer was separated, and the water layer was
washed twice with 50 mL of Et2O. The organic layers were
combined, washed with brine, dried over MgSO4, filtered, and
1
concentrated to afford 2 as a colorless oil (yield 2.1 g, 92%). H
[Ru(TPBr)(tpy)](PF6)2 (5). The brown suspension obtained by
adding together 3 (50 mg, 0.10 mmol), [RuCl3(tpy)] (44 mg, 0.10
mmol), and 4 drops of N-ethylmorpholine in MeOH (15 mL) was
degassed on a Schlenk line and subsequently refluxed for 75 min.
The resulting deep red mixture was filtered over Celite, and the
solvent was removed in vacuo. The residue obtained was washed
with acetone and CH2Cl2 and dissolved in MeOH (5 mL). A
saturated solution of NaPF6 in MeOH was added, resulting in the
precipitation of 5 as a red powder that was collected by filtration,
washed with cold acetone, and dried in vacuo (yield 65 mg, 61%).
1H NMR (300 MHz, CD3COCD3): δ 2.39 (s, 12H, NCH3), 3.76
NMR (200 MHz, CDCl3): δ 0.29 (s, JSn-H ) 27.2 Hz, 9H, Sn-
(CH3)3), 2.31 (s, 12H, NCH3), 3.54 (s, 4H, NCH2), 7.39 (s, 2H,
ArH). 13C NMR (75 MHz, CDCl3): δ -9.3 (1JSnC ) 337 and 352
Hz, Sn(CH3)3), 45.5 (NCH3), 63.9 (CH2), 128.1, 136.8 (2JSnC ) 40
(34) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.; Garcia-
Granda, S.; Gould, R. O.; Smits, J. M. M.; Smykalla, C. The DIRDIF99
Program System; Technical Report of the Crystallography Laboratory,
University of Nijmegen: Nijmegen, The Netherlands, 1999.
(35) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure Refine-
ment; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(36) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7.
2154 Inorganic Chemistry, Vol. 45, No. 5, 2006

NoWel Heteroditopic Terpyridine-Pincer Ligand
(s, 4H, NCH2), 7.31-7.37 (m, 4H, PyrA(5, 5′′), PyrB(5, 5′′)), 7.73
(d, JHH ) 4.9 Hz, 2H, PyrB(6, 6′′)), 7.82 (d, JHH ) 5.5 Hz, 2H,
PyrA(6, 6′′)), 8.09 (t, JHH ) 7.9 Hz, 4H, PyrA(4, 4′′) and PyrB(4,
4′′)), 8.24 (s, 2H, ArH), 8.59 (t, JHH ) 8.1 Hz, 1H, PyrA(4′)), 8.82
(d, JHH ) 7.2 Hz, 2H, PyrB(3, 3′′)), 8.95 (d, JHH ) 7.8 Hz, 2H,
PyrA(3, 3′′)), 9.08 (d, JHH ) 8.1 Hz, 2H, PyrA(3′, 5′)), 9.35 (s,
2H, PyrB(3′, 5′)). 13C NMR (75 MHz, CD3COCD3) δ 46.0 (NCH3),
64.5 (NCH2), 122.8, 125.0, 125.6, 125.8, 128.7, 128.8, 129.5, 129.7,
137.0, 137.2, 139.2, 139.3, 141.6, 149.0, 153.6, 153.7, 156.6, 156.8,
159.3, 159.4. Anal. Calcd for C42H39BrF12N8P2Ru: C, 44.77; H,
3.49; N, 9.94. Found: C, 44.58; H, 3.34; N, 9.76.
[Ru(TPPdCl)2](PF6)2 (8). A solution of 4b (54 mg, 0.10 mmol)
and [RuCl3‚3H2O] (20 mg, 0.10 mmol) in EtOH (10 mL) was
degassed in a Schlenk line and subsequently refluxed for 1 h. The
solvent was then removed in vacuo. The resulting brown-red residue
was collected by filtration; washed with EtOH, water, and Et2O;
and dried in air. Subsequently, the brown solid was refluxed with
a second equivalent of 4b (54 mg, 0.10 mmol) and a few drops of
N-ethylmorpholine in MeOH (10 mL) for 1.5 h. The brown solution
turned red upon heating. The solvent was removed in vacuo. The
red solid obtained was collected by filtration and washed with
acetone and CH2Cl2. The resulting chlorine complex was then
dissolved in MeOH (20 mL). Next, an excess of methanolic NaPF6
was added, yielding 8 as a red solid that was collected by filtration,
washed with cold acetone and CH2Cl2, and dried in vacuo (yield
99 mg, 70%).1H NMR (300 MHz, CD3OD): δ 3.01 (s, 12H, NCH3),
4.32 (s, 4H, NCH2), 7.28 (t, JHH ) 6.3 Hz, 2H, Pyr(5, 5′′)), 7.53
(d, JHH ) 5.2 Hz, 2H, Pyr(6, 6′′)), 7.80 (t, JHH ) 7.9 Hz, 2H, Pyr-
(4, 4′′)), 8.24 (s, 2H, ArH), 8.88 (d, JHH ) 7.3 Hz, 2H, Pyr(3, 3′′)),
9.21 (s, 2H, Pyr(3′, 5′)). 13C NMR (75 MHz, CD3COCD3): δ 53.4
(NCH3), 75.0 (NCH2), 120.4, 122.1, 125.4, 128.4, 129.3, 139.0,
148.5, 153.4, 156.4, 159.3, 163.25, 169.28. ESI-MS: m/z 615.04
([M - 2PF6]2+).
[Ru(TPBr)2](PF6)2 (6). The solution obtained by adding together
3 (120 mg, 0.24 mmol), RuCl3‚3H2O (50 mg, 0.24 mmol), and a
few drops of Et3N in EtOH (15 mL) was degassed on a Schlenk
line. The resulting mixture, which rapidly turned brown-red upon
heating, was stirred at reflux temperature for 1 h. After the hot
mixture was filtered, the solvent was removed in vacuo. The brown
solid obtained was washed with water and CH2Cl2 until the eluent
remained colorless. Subsequently, the brown solid was refluxed in
MeOH (15 mL) with a second equivalent of 3 (120 mg, 0.24 mmol)
and a few drops of N-ethylmorpholine in MeOH for 1.5 h. The
brown solution turned to red upon heating. The solvent was
evaporated in vacuo, and the obtained red residue was washed with
acetone and dissolved in MeOH. Addition of a saturated aqueous
solution of NaPF6 resulted in the precipitation of 6 as a red powder
that was collected by filtration, washed with cold acetone, and dried
in vacuo (yield 212 mg, 63%). 1H NMR (300 MHz, CD3COCD3):
δ 2.39 (s, 24H, NCH3), 3.76 (s, 8H, NCH2), 7.34 (ddd, JHH ) 7.5,
5.4, 1.5 Hz, 4H, Pyr(5, 5′′)), 7.83 (d, JHH ) 5.4 Hz, 4H, Pyr(6,
6′′)), 8.10 (td, JHH ) 7.5, 1.5 Hz, 4H, Pyr(4, 4′′)), 8.24 (s, 4H,
ArH), 8.96 (d, JHH ) 8.1 Hz, 4H, Pyr(3, 3′′)), 9.35 (s, 4H, Pyr(3′,
5′′)). 13C NMR (75 MHz, CD3COCD3): δ 46.0 (NCH3), 64.5
(NCH2), 122.9, 125.8, 128.8, 129.6, 129.7, 137.0, 139.2, 141.6,
149.0, 153.7, 156.8, 159.4. Anal. Calcd for C54H56Br2F12N10P2Ru:
C, 46.46; H, 4.04; N, 10.03. Found: C, 46.40; H, 3.94; N,
9.97.
[Ru(TPPdSCN)(tpy)](PF6)2 (10). A solution of 7 (57 mg, 0.05
mmol) in dry CH2Cl2 (20 mL) was added under nitrogen and
exclusion of light to a Schlenk vessel containing AgSCN (8.3 mg,
0.05 mmol) dissolved in dry CH2Cl2 (5 mL). The mixture was
stirred at room temperature for 5 h. Subsequently, AgCl was filtered
off over Celite, and all volatiles were removed in vacuo to afford
15 as a red powder (yield 58 mg, 95%). 1H NMR (300 MHz, CD3-
COCD3): δ 3.03 (s, 12H, NCH3), 4.37 (s, 4H, NCH2), 7.35-7.29
(m, 4H, PyrA(5, 5′′), PyrB(5, 5′′)), 7.69 (d, JHH ) 4.5 Hz, 2H,
PyrB(6, 6′′)), 7.77 (d, JHH ) 4.8 Hz, 2H, PyrA(6, 6′′)), 7.84 (s,
2H, ArH), 8.10-8.02 (m, 4H, PyrA(4, 4′′), PyrB(4, 4′′)), 8.57 (t,
JHH ) 8.1 Hz, 1H, PyrA(4′)), 8.81 (d, JHH ) 8.1 Hz, 2H, PyrB(3,
3′′)), 8.95 (d, JHH ) 8.1 Hz, 2H, PyrA(3, 3′′)), 8.76 (d, JHH ) 8.1
Hz, 2H, PyrA(3′, 5′)), 9.07 (s, 2H, PyrB(3′, 5′)). 13C NMR (75
MHz, CD3COCD3): δ 52.6 (NCH3), 74.4 (NCH2), 120.2, 122.0,
124.8, 125.5 (2×), 128.6, 128.7, 134.7, 136.9, 138.0, 139.0, 148.3,
149.5, 150.0, 153.4, 156.5, 156.9, 159.4. IR (Nujol, PrCN): ν-
(SCN) ) 2080 cm-1. ESI-MS: m/z 460.07 ([M - 2PF6]2+); 1066.19
([M - PF6]+).
[Ru(TPPdCl)(tpy)](PF6)2 (7). A brown suspension of 3 (111
mg, 0.19 mmol), [RuCl3(tpy)] (86 mg, 0.19 mmol) and 4 drops of
N-ethylmorpholine in MeOH (15 mL) was degassed on a Schlenk
line and subsequently refluxed for 1 h. The mixture, which turned
deep red upon heating, was then filtered over Celite, and all volatiles
were removed in vacuo. The residue obtained was washed with
acetone and dissolved in MeOH (5 mL). A saturated aqueous
solution of NaPF6 was added, resulting in the precipitation of 7 as
a red powder; it was collected by filtration, washed with cold
Acknowledgment. The authors kindly acknowledge A.
D’Aleo for his assistance during lifetime measurements
performed at room temperature. This work was supported
by the Council for Chemical Sciences from the Dutch
Organization of Scientific Research (NWO). The authors
thank NWO/NCF for the use of supercomputer time on
TERAS/ASTER, SARA (The Netherlands, Project SG-032).
R.W.A.H. acknowledges financial support from the NWO
Grant 700.53.401.
1
acetone, and dried in vacuo (yield 100 mg, 39%). H NMR (300
MHz, CD3CN): δ 3.00 (s, 12H, NCH3), 4.30 (s, 4H, NCH2), 7.15-
7.20 (m, 4H, PyrA(5, 5′′), PyrB(5, 5′′)), 7.35 (d, JHH ) 4.9 Hz,
2H, PyrB(6, 6′′)), 7.42 (d, JHH ) 4.9 Hz, 2H, PyrA(6, 6′′)), 7.70
(s, 2H, ArH), 7.90-7.97 (m, 4H, PyrA(4, 4′′), PyrB(4, 4′′)), 8.42
(t, JHH ) 8.1 Hz, 1H, PyrA(4′)), 8.50 (d, JHH ) 8.1 Hz, 2H, PyrB-
(3, 3′′)), 8.61 (d, JHH ) 8.1 Hz, 2H, PyrA(3, 3′′)), 8.76 (d, JHH
)
Supporting Information Available: Cif files of crystal data
collection and refinement parameters, atomic coordinates, bond
lengths and angles, anisotropic displacement parameters for com-
plexes 4a and 6. This material is available free of charge via Internet
at http://pubs.acs.org.
8.1 Hz, 2H, PyrA(3′, 5′)), 9.35 (s, 2H, PyrB(3′, 5′)). 13C NMR (75
MHz, CD3CN): δ 53.1 (NCH3), 74.5 (NCH2), 120.2, 121.9, 124.4,
125.1 (2×), 128.1, 128.2, 134.5, 136.4, 138.7, 138.8, 148.3, 149.5,
153.0, 153.2, 156.0, 156.2, 158.8, 158.9. Anal. Calcd for C42H39-
ClF12N8P2PdRu: C, 42.44; H, 3.31; N, 9.43. Found: C, 42.59; H,
3.46; N, 9.29.
IC051967C
Inorganic Chemistry, Vol. 45, No. 5, 2006 2155