Cyclo-ruthenated and -platinated complexes bearing phosphonate substituents

Article abstract of DOI:10.1016/j.ica.2009.12.008

Two new, potentially cyclometalating terdentate ligands bearing phosphonate substituents, Et₂O₃P-N^C(H)^N (5) and Et₂O₃P-C(H)^N^N (7), have been prepared. The corresponding ruthenium complexes, [1]⁺ and [2]⁺, respectively, were obtained by reaction with [RuCl₃(tpy)]. Complexes [1]⁺ and [2]⁺ display electronic properties characteristic for cyclometalated ruthenium complexes. The platinum complex [3], of N^C(H)^N ligand 5, was also prepared and is highly phosphorescent in solution. In general, the phosphonate group electronically behaves equivalent to a carboxylate moiety.

Full text of DOI:10.1016/j.ica.2009.12.008

Inorganica Chimica Acta 363 (2010) 1701–1706
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Cyclo-ruthenated and -platinated complexes bearing phosphonate substituents
Sipke H. Wadman a, Duncan M. Tooke b, Anthony L. Spek b, Gerard P.M. van Klink a,1, Gerard van Koten a,
*
a Chemical Biology and Organic Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
b Crystal and Structural Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
a r t i c l e i n f o
a b s t r a c t
Article history:
Two new, potentially cyclometalating terdentate ligands bearing phosphonate substituents, Et2O3P-
N^C(H)^N (5) and Et2O3P-C(H)^N^N (7), have been prepared. The corresponding ruthenium complexes,
[1]+ and [2]+, respectively, were obtained by reaction with [RuCl3(tpy)]. Complexes [1]+ and [2]+ display
electronic properties characteristic for cyclometalated ruthenium complexes. The platinum complex [3],
of N^C(H)^N ligand 5, was also prepared and is highly phosphorescent in solution. In general, the phos-
phonate group electronically behaves equivalent to a carboxylate moiety.
Received 17 July 2009
Accepted 4 December 2009
Available online 6 January 2010
Keywords:
Cyclometalated
Ruthenium
Ó 2009 Elsevier B.V. All rights reserved.
Spectroscopy
Phosphonate
1. Introduction
and C,N,N0-bonding [18,19] motif are known to be very efficient
emitters, we also prepared the platinum complex of the
Polypyridine complexes of ruthenium have been the focus of
spectroscopic studies for decades [1–4]. The combination of a me-
tal based oxidation in combination with ligand based reductions
results in diverse and interesting properties such as emission from
a charge transfer triplet state. These complexes are widely applied
as pigments for dye sensitized solar cells (DSSCs) [5,6]. Replacing
one of the coordinating nitrogen atoms for a carbon atom results
in the corresponding cyclometalated [7] complex and this change
has a tremendous effect on the electronic properties of the com-
plex [8,9]. Recently we demonstrated that cycloruthenated com-
plexes, anchored via carboxylate groups to TiO2, can act as
efficient sensitizers for DSSCs [10], and more recently this has been
confirmed by others [11]. We then became interested in the corre-
sponding phosphonate functionalized complexes for two reasons.
Firstly, although the Hammett [12] parameter for the phosphonate
N^C(H)^N ligand.
2. Results and discussion
2.1. Synthesis
For the preparation of the phosphonate bearing complexes
[1](PF6) and [2](PF6) the synthetic procedure as depicted in
Scheme 1 was followed. The C2v-symmetrical cyclometalated com-
plex [1]+ was prepared by reaction of [RuCl3(tpy)], activated with
AgBF4 in acetone, with ligand 5 in n-BuOH, and isolated as the
PFꢀ6 salt by anion exchange. Ligand 5 was obtained from bromo
compound 4 by applying palladium mediated coupling with
diethyl phosphite. Compound 4 was obtained from 1,3,5-tribromo-
benzene using Suzuki C–C coupling methodology. Compound 4 has
previously been prepared utilizing Stille [20] or Negishi [21] meth-
odology, however, the procedure described here is higher yielding
and circumvents the use of toxic stannane intermediates. In this
procedure, CuI is added to prevent coordination of the product, a
potential ligand, to the palladium catalyst [22]. Complex [2]+ was
prepared by reacting [RuCl3(tpy)] with ligand 7 in aqueous MeOH
in the presence of N-methylmorpholine as sacrificial reductant.
Ligand 7 was obtained using Kröhnke’s method for pyridine con-
densation [23]. Chalcone 6 was reacted with (2-pyridinylcarbon-
yl)pyridinium iodide in the presence of NH4OAc as nitrogen
source. Compound 6 was prepared from acetophenone by conden-
sation with ethyl formate, chlorination using SOCl2, followed
by Michaelis–Arbuzov condensation with triethylphosphite.
Complexes [1]+ and [2]+ were obtained as dark red and purple
moiety is close to that of the carboxylate group (rpðPO
= 0.60,
3Et2
Þ
rpðCO = 0.45) the free phosphonate acts as a stronger anchoring
2EtÞ
moiety for attachment to solid inorganic substrates such as TiO2
[13–15]. Secondly, organometallic phosphonates can also be used
to produce irreversible inhibited semi-synthetic metallo-enzymes
[16].
We have prepared ligands with either N,C,N0- or C,N,N0-binding
motif bearing a diethylphosphonate moiety on the central ring. The
cycloruthenated complexes were prepared and spectroscopically
investigated. Because cycloplatinated complexes with N,C,N0-[17]
* Corresponding author.
E-mail address: g.vankoten@uu.nl (G. van Koten).
Present address: DelftChemTech, Faculty of Applied Sciences, Delft University of
1
Technology, Julianalaan 136, 2628 BL Delft, The Netherlands.
0020-1693/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2009.12.008

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S.H. Wadman et al. / Inorganica Chimica Acta 363 (2010) 1701–1706
PF6
D
B
C
N
N
N
N
N
Br
Br
N
N
i
ii
iii
A
Br
Et2O3P
Et2O3P
Ru
Br
N
N
4
5
[1](PF6)
PF6
E
C
D
N
PO3Et2
v
N
N
iv
vi
Et2O3P
N
Et2O3P
B
N
Ru
N
O
O
N
A
6
7
[2](PF6)
Scheme 1. Synthesis of [1]+ and [2]+, and NMR numbering scheme. (i) Dimethylpyridin-2-boronate, CuI, Pd(PPh3)4, KOH, DME, reflux 20 h, (ii) HPO3Et2, Pd(PPh3)4, NEt3, reflux
5 h, (iii) [RuCl3(tpy)], AgBF4, acetone, n-BuOH, (iv) (1) NaH, ethyl formate, 3 h, (2) aqueous H2SO4, C6H6, (3) SOCl2, C6H6, reflux, 12 h, (4) (EtO)3P, 145 °C, 0.5 h, (v) (2-
pyridinylcarbonyl)pyridinium iodide, NH4OAc, MeOH, reflux, 3 h, (vi) [RuCl3(tpy)], N-methylmorpholine, aqueous MeOH, reflux, 18 h.
microcrystalline solids, respectively. Deprotection of the phospho-
nate ester to the phosphoric acid was attempted with refluxing
hydrochloric acid, treatment with bromotrimethylsilane, or boron
tribromide, all of which resulted in fast decomposition of the com-
plexes. The complexes are stable in refluxing strongly alkaline
solutions, but even with extended reaction times only partial
N(1)
saponification could be achieved, which unfortunately prohibited
solar cell testing of these compounds.
N(3)
The platinum complex [PtCl(Et2O3P-N^C^N)], [3], could be pre-
pared by heating a solution of 5 with K2PtCl6 in aqueous MeCN.
C(1)
Additionally, the ester-functionalized ruthenium complexes [Ru(-
N(4)
MeO2C-N^C^N)(tpy)], and [Ru(EtO2C-C^N^N)(tpy)], were available
from previous studies [9,10], and selected parameters are pre-
sented here for comparative purposes.
N(5)
N(2)
The NMR spectroscopic data obtained for the NMR active nuclei
agreed with the structures proposed for the complexes. All reso-
nances in the 1H and 13C{1H} spectra were unequivocally assigned
using two-dimensional correlation experiments. J-coupling to the
31P nucleus was observed for the adjacent 1H nuclei, as well as to
all 13C nuclei in the central ring, except for the formally anionic
Fig. 1. View of the molecular structure of [Ru(Et2O3P-N^C^N)(tpy)](PF6) ([1](PF6)).
Displacement ellipsoids are drawn at the 50% probability level. The PF6 anion has
been omitted for clarity.
13
C
ipso
in [1]+. The J-coupling constant in [1]+ and [2]+ for the A4
and B4 13C nucleus, respectively, agreed with the observed cou-
pling between the carbon satellites in the 31P NMR spectra, corrob-
orating the assignment. In the platinum complex, [3], 195Pt
satellites are observed for the proximal B6 proton nuclei. Again,
the 13C resonances assigned to the central ring are split by J-cou-
pling to the phosphorus nucleus, and the coupling constant of A4
agrees with the observed satellites in the 31P NMR spectrum.
Table 1
Selected bond lengths (Å), angles (°) for [1]+.
C1–Ru
N1–Ru
N2–Ru
N1–Ru–N2
N3–Ru–N5
1.931 (4)
2.093 (4)
2.079 (4)
157.2 (2)
155.7 (2)
N3–Ru
N4–Ru
N5–Ru
C1–Ru–N4
2.073 (4)
2.029 (4)
2.069 (4)
178.4 (2)
2.2. Crystal structure determination of [1](PF6)
[1]+ and the ester-functionalized analogue, [Ru(MeO2C-
Single crystals of [Ru(Et2O3P-N^C^N)(tpy)](PF6), [1](PF6) suit-
able for X-ray diffraction analyses were obtained by slow evapora-
tion of an MeCN solution. The tpy and N,C,N0-binding ligands adopt
a rather flat geometry and are mutual perpendicularly coordinated
to the ruthenium center in [1]+, see Fig. 1 and Table 1 for the
molecular geometry and relevant data of the cation [1]+. The con-
strained geometry of the ligands results in an overall distorted
octahedral geometry, as is usually observed in comparable crystal
structures [24,25]. As can be expected for the non-uniform donor
set, the bond lengths span a wide range from 1.93 Å for the car-
bon-to-ruthenium bond to 2.09 Å for the peripheral pyridine nitro-
gen-to-ruthenium bonds on the same ligand. As a matter of fact,
N^C^N)(tpy)], are virtually isostructural.
2.3. Electronic properties
The electrochemical data for the complexes are presented in
Table 2. In general in polypyridine ruthenium complexes, the
oxidation process is metal based, while the reduction processes
are ligand based [1,2]. The cyclometalation results in a negative
shift of 700 and 730 mV for [1]+ and [2]+, respectively, compared
ox
1=2
to the non-cyclometalated [Ru(Et2O3P-tpy)(tpy)]2+ (E = 0.94 V)
[26]. Since it has been previously established that the level of the

S.H. Wadman et al. / Inorganica Chimica Acta 363 (2010) 1701–1706
1703
Table 2
Table 3
Spectroscopic properties.
Cyclic voltammetry data.a.
RuII/RuIII
L1L2/L1Å–L2
L1Å–L2/L1Å–L2ꢂ–
Complex
Absorptiona kmax (nm)
(103 Mꢀ1 cmꢀ1))
Emissionb
kmax (nm)
uem
c
(
e
E1/2 (V) (
1.34b
DEp (mV))
[1]+
[2]+
[3]+c
0.24 (62)
0.21 (59)
0.58b,d
ꢀ1.91 (67)
ꢀ1.85 (61)
ꢀ2.03 (72)
[1]+
495 (14.6), 315 (40.5),
278 (69.4), 240 (47.5)
492 (13.8)
744
743
783
780
482
1.5 ꢁ 10ꢀ5
1.5 ꢁ 10ꢀ5
1.1 ꢁ 10ꢀ5
1.3 ꢁ 10ꢀ5
0.22
0.94b
ꢀ2.18 (87)
[Ru(MeO2C-N^C^N)-
(tpy)](PF6)
a
[2]+
517 (17.0), 318 (37.8),
276 (48.1), 237 (46.5)
523 (18.8)
Data collected in MeCN with n-Bu4NPF6 as supporting electrolyte at 100 mV/s;
potentials reported relative vs. ferrocene/ferrocenium (Fc/Fc+) used as internal
standard.
[Ru(EtO2C-C^N^N)-
(tpy)](PF6)
b
Irreversible, Ep,a given.
Data collected at 1 V/s.
c
d
[3]+
478 (0.15), 398 (5.8),
378 (7.6), 289 (19.2),
256 (41.2)
d
Pt based.
a
b
c
In MeCN at rt.
lowest unoccupied molecular orbital (LUMO) for the cyclometalat-
ed ligand is expected to be higher in energy than that of an isoelec-
tronic but neutral polypyridine ligand [27,28]. It thus seems logical
to assign the first reduction processes as tpy based, although in the
case of [2]+ it might well be associated with the cyclometalating li-
gand [9]. In [2]+ one additional reduction process is observed in the
available electrochemical window, assigned as based on the cyclo-
metalated ligand. Due to the electron rich metal center, the ligand
In argon deaerated MeCN solution at rt.
Emission quantum yield, relative to [Ru(bpy)3](PF6)2 as a standard in deaerated
MeCN; uem = 0.062 [34].
d
In argon deaerated CH2Cl2 solution at rt.
[10], while the Hammett parameter for the phosphonate moiety
r
(
p = 0.60) is slightly larger than that of the carboxylate group
based reductions are also negatively shifted compared to [Ru(E-
(
rpðCO
= 0.45) [12]. The platinum complex [3] also displays in-
2MeÞ
red
t2O3P-tpy)(tpy)]2+ (E = –1.60 V) [26], but to a lesser extent as
tense bands below 300 nm, assigned as
tion, a low energy feature is observed, composed of several
transitions, previously assigned to a mixture of * and charge
p–p* transitions. In addi-
1=2
the oxidation process. The N^C(H)^N ligand in platinum complex
[3] is reduced at increased negative potential, while the platinum
based oxidation is observed as an irreversible wave, with a signif-
icant larger gap between the oxidation and reduction processes.
The absorption spectra of [1]+ and [2]+ see Fig. 2 and Table 3,
p–p
transfer transitions [17]. The very weak features around 475 nm
are assigned to platinum assisted direct population of the 3p
–p*
states [17,18].
As a result of the distorted octahedral geometry in [Ru(tpy)2]2+
type complexes a relatively weak ligand field is apparent [1–4]. As
a consequence, the 3MLCT state is provided with an efficient, non-
radiative, decay path via low lying metal centered (3MC) states,
and the complexes are non-emissive at room temperature. Intro-
duction of electron accepting moieties on one of the ligands is a
feasible way to stabilize the 3MLCT compared to the 3MC as well
as the GS and hence promote room temperature emission [29]. In-
deed, room temperature phosphorescence is observed for [Ru(E-
t2O3P-tpy)(tpy)]2+ (kmax = 650 nm) [26] and [Ru(EtO2C-tpy)-
(tpy)]2+ (kmax = 667, /em = 2.7 ꢁ 10–4) [30]. Cyclometalation has
been established as another effective way to increase room tem-
perature emission by destabilizing the 3MC state [27,28,31]. As also
the metal based GS is affected, the increase in room temperature
efficiency comes at the expense of the emission energy. Indeed,
emission is observed for [1]+ and [2]+, see Table 3, at longer wave-
lengths compared to that of the non-cyclometalated complex, and,
in line with the energy gap law [2,32], with lower efficiency. The
platinum complex [3] is a much more efficient emitter with a
quantum yield of 22%. The emission profile is highly structured,
with a vibronic progression of 1300 cmꢀ1, typical for coupling with
display strong ligand-centered
p–p* transitions in the UV part of
the spectrum assigned to both ligands. The visible region is domi-
nated by strong metal-to-ligand charge transfer (1MLCT) transi-
tions characteristic for ruthenium polypyridine complexes [1,2].
Compared to [Ru(Et2O3P-tpy)(tpy)]2+ (kmax = 482 nm) the 1MLCT
features are bathochromically shifted, in line with the decrease
in the gap between the oxidation and reduction processes in [1]+
and [2]+. The strong
r-donating anionic carbon destabilizes the
mostly metal based ground state more than the 1MLCT excited
state. The absorption spectra of complexes [1]+ and [2]+ are almost
identical to that obtained for the carboxylate functionalized com-
plexes [Ru(MeO2C-N^C^N)(tpy)] and [Ru(EtO2C-C^N^N)(tpy)]
70
60
50
40
30
20
10
0
aromatic C@C vibrations and characteristic of
p–p* ligand-cen-
tered emission with little involvement of the metal [33]. Compared
to the native complex [PtCl(N^C^N)] (kmax = 491, /em = 0.60) and
the ester-functionalized [PtCl(EtO2C-N^C^N)] (kmax = 481, /em
0.58) the quantum efficiency of 3 is somewhat decreased [17].
=
3. Conclusions
We have prepared two new, phosphonate functionalized, cyclo-
metalating terdentate ligands with N,C,N0- and C,N,N0-binding
mode, and the corresponding ruthenium complexes. The single
crystal X-ray structure displayed the expected mutual perpendicu-
lar coordination of the ligands. Cations [1]+ and [2]+ displayed elec-
tronic properties characteristic for cyclometalated ruthenium
complexes. All NMR resonances could be unequivocally assigned
200
400
600
800
1000
Wavelength (nm)
Fig. 2. Electronic absorption spectrum and normalized emission of [1]+ (black,
solid) and [2]+ (red, dash) in MeCN and [3]+ (blue, dot) in CH2Cl2 at rt. (For
interpretation of the references to color in this figure legend, the reader is referred
to the web version of this article.)

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S.H. Wadman et al. / Inorganica Chimica Acta 363 (2010) 1701–1706
using two-dimensional correlation experiments and J-coupling
considerations. The oxidation and reduction processes are nega-
tively shifted as a result of the increased electron density at the
metal center. The 1MLCT absorption features are significantly
bathochromically shifted. As a result of the destabilization of the
3MC states, room temperature emission is observed. The emission
energy is rather low, and as a consequence the efficiency is de-
creased. The platinum complex [3] displays electronic properties
very similar to its unsubstituted and ester-functionalized ana-
logues. Its intense room temperature emission is highly structured,
but somewhat decreased in quantum yield. The strong binding of
phosphonates to semiconductor surfaces renders these complexes
interesting candidates as pigments for dye sensitized solar cells.
bined organic layers were dried over MgSO4, filtered and concen-
trated in vacuo. The product was purified by column
chromatography on SiO2 (ethyl acetate:pentane:NEt3 = 1:1:3%,
v/v) yielding 4 as a off-white solid (2.76 g, 70%).
0
1H NMR (300 MHz, CDCl3): d 8.72 (d, 2H, 3J = 5.1 Hz, Ar6 H), 8.56
(s, 1H, Ar4H), 8.23 (s, 2H, Ar2,6H), 7.86–7.74 (m, 4H, 3J = 5.6 Hz,
0
0
0
Ar3 H + Ar4 H), 7.29 (d, 2H, 3J = 6.9 Hz, 3J = 5.1 Hz, Ar5 H). 13C NMR
(75 MHz, CDCl3): d 155.9, 150.0, 141.9, 137.1, 130.5, 124.3, 123.8,
123.0, 121.0.
4.3. Diethyl 3,5-di(2-pyridyl)phenylphosphonate (5)
A solution of 4 (0.6 g, 2 mmol), HPO3Et2 (0.60 mL, 4.6 mmol),
and Pd(PPh3)4 (0.11 g, 0.1 mmol) in NEt3 (5 mL) was heated under
reflux for 5 h. The volatiles were removed in vacuo, and the residue
taken up in MeOH and filtered over SiO2 with MeOH and CH2Cl2.
The product was purified by column chromatography on SiO2 (eth-
ylacetate:NEt3 = 95:5, v/v), yielding Et2O3P-N^C^N as a colorless oil
(0.175 g, 25%).
4. Experimental
4.1. General
All air-sensitive reactions were performed under a dry nitrogen
atmosphere using standard Schlenk techniques. Absolute solvents
were dried over appropriate drying agents and distilled before
use. All other solvents and reagents were purchased and used as
received. 1H, 13C{1H}, 31P, and 195Pt NMR spectra were recorded
at 298 K on a Varian 300 MHz Inova spectrometer and/or on a Var-
ian 400 MHz NMR system. NMR spectra were referenced to the sol-
vent residual signal [35], except for the 195Pt spectra, which were
externally referenced to a 1 M solution of Na2PtCl6 in D2O [36].
1H spectral assignments were based on chemical shift and integral
considerations as well as COSY and NOESY two-dimensional exper-
iments. The 13C{1H} resonances are assigned on the basis of gHSQC,
gHMBC experiments and J-coupling considerations. Solution UV–
Vis spectra were recorded on a Cary 50 Scan UV–Vis spectropho-
tometer. Steady-state emission spectra were obtained on a SPEX
fluorolog spectrometer. The emission quantum yield was mea-
sured by the method of Crosby and Demas [37] with [Ru(b-
py)3](PF6)2 in argon deaerated MeCN as standard (/r = 0.062) and
calculated by /s = /r(Br/Bs)(ns/nr)2(Ds/Dr), in which n is the refrac-
tive index of the solvents, D is the integrated intensity and the sub-
scripts s and r refer to sample and reference standard solution,
respectively. The quantity B is calculated by B = 1–10ꢀAL, where A
is the absorbance and L is the optical path length. Cyclic voltammo-
grams were recorded in a single compartment cell under a dry
nitrogen atmosphere. The cell was equipped with a Pt microdisk
working electrode, Pt wire auxiliary electrode and a Ag/AgCl wire
reference electrode. The working electrode was polished with Alu-
mina nano powder between scans. All redox potentials are re-
ported against the ferrocene–ferrocenium (Fc/Fc+) redox couple
used as an internal standard [38,39]. The potential control was
achieved with a PAR Model 263A potentiostat. All electrochemical
samples were 10ꢀ1 M in Bu4NPF6 as the supporting electrolyte in
CH3CN distilled over KMnO4 and Na2CO3. Elemental analyses were
carried out by Kolbe Mikroanalytisches Laboratorium (Mülheim an
der Ruhr, Germany). (2-Pyridinylcarbonyl)pyridinium iodide [40]
and [RuCl3(tpy)] [41] were prepared following literature
procedure.
1H NMR (300 MHz, CDCl3): d 8.90–8.88 (m, 1H, A4), 8.70 (d,
2
3J = 4.5 Hz, 2H, B6), 8.72 (dd, J31P–1H = 13.5 Hz, 4J = 1.5 Hz, 2H,
A2,6), 7.86 (d, 3J = 7.8 Hz, 2H, B3), 7.76 (dd, 3J = 7.8 Hz, 3J = 7.5 Hz,
2H, B4), 7.25 (dd, 3J = 7.5 Hz, 3J = 4.5 Hz, 2H, B5), 4.2–4.1 (m, 4H,
CH2CH3), 1.4–1.3 (m, 6H, CH2CH3). 13C NMR (100 MHz, CDCl3):
d 156.0, 149.8, 140.2 (2J31P–13C = 15 Hz), 137.0, 130.4 (1J31P–13C
=
11 Hz), 129.5 (3J31P–13C = 188 Hz), 129.4, 122.8, 120.9, 62.3
(2J31P–13C = 5 Hz), 16.4. 31P NMR (162 MHz, CD3CN):
d 14.2
(1J31P–13C = 188 Hz). Anal. Calc. for C20H21N2O3P: C, 65.21; H, 5.75;
N, 7.60. Found: C, 65.00; H, 5.65; N, 7.43%.
4.4. Diethyl 3-oxo-3-phenylpropenylphosphonate (6)
Compound 6 was prepared following adapted literature proce-
dures [42–44]. To a suspension of NaH (5.25 g, 220 mmol) in THF
(200 mL) was added at 0 °C ethyl formate (18.0 mL, 220 mmol)
and acetophenone (17.0 mL, 146 mmol). The cooling bath was re-
moved and the resulting mixture was stirred for 3 h. The formed
precipitate was isolated by centrifugation and washed with Et2O
(2 ꢁ 80 mL), suspended in benzene (80 mL), and decomposed with
H2O (40 mL) and 10% aqueous H2SO4 (40 mL). The benzene layer
was separated and dried over CaCl2. To this solution SOCl2
(12.0 mL, 166 mmol) was added, and the mixture heated under re-
flux for 12 h. The compound was isolated by distillation, yielding
phenyl-2-chlorovinylketone as colorless oil. A mixture of phenyl-
2-chlorovinylketone (1.87 g, 11 mmol) and triethylphosphite
(2.0 mL, 11 mmol) was placed in a oil bath heated to 100 °C, and
gradually heated to 145 °C during which the evolution of gas was
observed. The product was isolated by column chromatography
on SiO2 (ethylacetate:CH2Cl2 = 1:1, v/v), yielding the product as a
colorless oil (0.738 g, 27%).
1H NMR (300 MHz, CDCl3): d 7.98 (d, 2H, 3J = 8.0 Hz, Ar2H), 7.79
2
(dd, 1H, 3J = 17.0 Hz, J31P–1H = 21.3 Hz, CHCHPO3Et2), 7.60 (t, 1H,
3J = 7.0 Hz, Ar4H), 7.49 (dd, 2H, 3J = 8.0 Hz, 3J = 7.0 Hz, Ar3H), 6.91
3
(dd, 1H, 3J = 17.0 Hz, J31P–1H = 19.2 Hz, CHCHPO3Et2), 4.2–4.1 (m,
4H, CH2CH3), 1.3–1.4 (m, 6H, CH2CH3).
4.5. Diethyl 6-phenyl-2,20-bipyridin-4-ylphosphonate (7)
4.2. Bromo-3,5-di(2-pyridyl)benzene (4)
A suspension of 6 (0.74 g, 2.75 mmol), NH4OAc (2.3 g, 30 mmol),
and (2-pyridinylcarbonyl)pyridinium iodide (1.02 g, 3.1 mmol) in
MeOH (20 mL) was heated under reflux for 3 h. The resulting sus-
pension was filtered over SiO2 (ethyl acetate + 2% NEt3) and evap-
orated to dryness. The resulting oil was heated in vacuo to 75 °C for
2 h, and purified by column chromatography on SiO2 (ethyl ace-
tate:pentane = 1:1, v/v), yielding the product as a colorless oil
(0.63 g, 63%).
Freshly prepared dimethylboropyridine [22] (starting from 2-
bromopyridine (3.7 mL, 38 mmol) was dissolved in DME and added
to 1,3,5-tribromobenzene (3.5 g, 11 mmol), CuI (2.5 g, 13 mmol),
Pd(PPh3)4 (0.7 g, 0.6 mmol), and crushed KOH (3.6 g, 64 mmol).
The resulting mixture was heated under reflux for 20 h. After cool-
ing down to rt, H2O (100 mL) was added, the phases separated and
the aqueous phase extracted with Et2O (3 ꢁ 200 mL). The com-

S.H. Wadman et al. / Inorganica Chimica Acta 363 (2010) 1701–1706
1705
3
1H NMR (400 MHz, CDCl3): d 8.66 (d, 1H, 3J31P–1H = 14.0 Hz, B5),
8.59 (d, 1H, 3J = 4.4 Hz, C6), 8.51 (d, 1H, 3J = 8.0 Hz, C3), 8.10 (d, 2H,
(100 MHz, CDCl3): d 185.0 (A1), 165.0 (B2, J31P–13C = 14 Hz),
3
157.8 (D2), 156.8 (C2), 155.2 (B6, J31P–13C = 15 Hz), 153.9 (E2,6),
151.8 (C6), 151.7 (D6), 147.4 (A2), 138.4 (C4),135.9 (D4), 135.7
(B4, J31P–13C = 187 Hz),135.7 (A6), 130.4 (E4), 130.1 (A5), 127.3
(C5), 127.0 (D5), 126.1 (A3), 124.7 (C3), 124.0 (D3), 123.1 (E3,5),
3
3J = 7.6 Hz, A2), 8.09 (d, 1H, J31P–1H = 14.4 Hz, B3), 7.71 (dd, 1H,
3J = 8.0 Hz, 3J = 7.6 Hz, C4), 7.40 (dd, 2H, 3J = 7.6 Hz, 3J = 7.2 Hz,
A3), 7.33 (t, 1H, 3J = 7.2 Hz, A4), 7.20 (dd, 1H, 3J = 7.2 Hz,
3J = 4.4 Hz, C5), 4.12 (m, 4H, CH2CH3), 1.12 (m, 6H, CH2CH3).
13C NMR (100 MHz, CDCl3): d 156.6 (2J31P–13C = 13 Hz), 156.1
(2J31P–13C = 13 Hz), 155.2, 149.0, 139.1 (1J31P–13C = 185 Hz), 138.1,
136.7, 129.4, 128.6, 126.8, 124.0, 121.7 (3J31P–13C = 10 Hz), 121.2,
120.5 (3J31P–13C = 10 Hz), 62.5 (2J31P–13C = 6 Hz), 16.2. 31P NMR
1
2
2
122.4 (A4), 121.0 (B5, J31P–13C = 10 Hz), 120.0 (B3, J31P–13C
=
10 Hz), 64.1 (2J31P–13C = 6 Hz), 16.9. 31P NMR (162 MHz, CD3CN):
d 15.8 (1J31P–13C = 187 Hz), ꢀ143.5 (1J31P–19F = 706 Hz). Anal. Calc.
for C35H31F6N5O3P2Ru: C, 49.65; H, 3.69; N, 8.27. Found: C, 49.78;
H, 3.62; N, 8.22%. MALDI-TOF-MS (DHB Matrix): m/z = 702.11
[M+] (calcd for C35H31N5O3PRu, 702.12).
(162 MHz, CDCl3):
d
16.5 (1J31P–13C = 185 Hz). Anal. Calc. for
C20H21N2O3P: C, 65.21; H, 5.75; N, 7.60. Found: C, 65.29; H, 5.81;
N, 7.53%.
4.8. [PtCl(Et2O3P-N^C^N)], [3]
4.6. [Ru(Et2O3P-N^C^N)(tpy)](PF6), [1]+
A
solution of 5 (28 mg, 0.08 mmol) and K2PtCl6 (33 mg,
0.08 mmol) in aqueous MeCN (1:3, v/v, 8 mL) was heated under re-
flux for 3 days. After cooling the red solution down to rt, the result-
ing yellow solution was dried in vacuo. The dark solid was
dissolved in DMSO (0.5 mL), and precipitated with water (30 mL).
The yellow solid was washed with Et2O (50 mL), yielding the prod-
uct as a yellow solid (15 mg, 72%).
A suspension of [RuCl3(tpy)] (140 mg, 0.31 mmol) and AgBF4
(195 mg, 0.99 mmol) in acetone (40 mL) was heated under reflux
for 2 h. The resulting suspension was filtered, and the purple solu-
tion concentrated in vacuo. The solid was dissolved in n-BuOH
(40 mL), 5 (175 mg, 0.47 mmol) was added, and the mixture heated
under reflux for 20 h. After cooling down, the solution was filtered
over Celite, the product precipitated by addition of an excess of
aqueous KPF6 solution, and collected by filtration. The product
was collected through the filter with acetone, and purified by col-
umn chromatography on SiO2 (MeCN:H2O:1 M NaNO3 = 18:1:1,
v/v), yielding the product as a red solid (180 mg, 68%).
3
1H NMR (400 MHz, DMSO-d6): d 9.14 (d, 2H, 3J = 4.8 Hz, J195Pt–
1H = 38 Hz, B6), 8.32 (d, 2H, 3J = 7.6 Hz, B3), 8.23 (dd, 2H, 3J = 7.6 Hz,
3
3J = 7.6 Hz, B4), 8.02 (d, 2H, J31P–1H = 13.2 Hz, A3,5), 7.61 (dd, 2H,
3J = 7.6 Hz, 3J = 4.8 Hz, B5), 4.00–4.10 (m, 4H, CH2CH3), 1.25–1.35
(m, 6H, CH2CH3). 13C NMR (100 MHz, DMSO-d6): d 166.1, 165.4,
151.4, 140.9 (2J31P–13C = 17 Hz), 140.7, 127.5 (3J31P–13C = 12 Hz),
124.8, 122.7 (1J31P–13C = 190 Hz), 121.3, 61.7 (2J31P–13C = 5 Hz),
16.2. 31P NMR (162 MHz, DMSO-d6): d 20.6 (1J31P–13C = 190 Hz).
195Pt NMR (64 MHz, DMSO-d6): d 3574. MALDI-TOF-MS (DHB
Matrix): m/z = 562.44 [M+ꢀCl] (calcd for C20H20N2O3PPt, 562.09).
1H NMR (400 MHz, CD3CN): d 8.77 (d, 2H, 3J = 8.0 Hz, D3,5), 8.56
(d, 2H, 3J31P–1H = 13.2 Hz, A3,5), 8.44 (d, 2H, 3J = 8.0 Hz, C3), 8.32 (t,
1H, 3J = 8.0 Hz, D4), 8.28 (d, 2H, 3J = 8.0 Hz, B3), 7.72 (dd, 2H,
3J = 8.0 Hz, 3J = 7.6 Hz, C4), 7.67 (dd, 2H, 3J = 8.0 Hz, 3J = 7.6 Hz,
B4), 7.13 (d, 2H, 3J = 5.6 Hz, B6), 7.08 (d, 2H, 3J = 5.6 Hz, C6), 6.95
(dd, 2H, 3J = 7.6 Hz, 3J = 5.6 Hz, C5), 6.74 (dd, 2H, 3J = 7.6 Hz,
3J = 5.6 Hz, B5), 4.29 (m, 4H, CH2CH3), 1.46 (t, 6H, 3J = 7.0 Hz,
CH2CH3). 13C NMR (100 MHz, CD3CN): d 230.8 (A1), 168.5 (B2),
159.8 (C2), 155.6 (C6), 153.5 (D2,6), 152.9 (B6), 143.8 (A2,6,
3J31P–13C = 17 Hz), 136.6 (B4), 136.4 (C4), 134.1 (D4), 127.3 (C5),
4.9. X-ray structure determination of [1](PF6)
X-ray data were collected on a Nonius KappaCCD diffractometer
0
2
(Rotating anode, graphite monochromator, Mo Ka, k = 0.71073 ÅA,
126.2 (A3,5, J31P–13C = 11 Hz), 124.6 (C3), 123.5 (D3,5), 123.2
1
h(max) = 25°, 150 K). Dark red plate, orthorhombic, P212121,
a = 9.0085(4), b = 17.427(2), c = 21.7456(18) Å, V = 3413.9(5) Å3,
Z = 4, d(calc) = 1.647 g/cm3. The structure is incommensurate with
a Q-vector of 0.43 along (0 0 1). The reported structure was solved
with DIRDIF99 [45] using the main reflections only. Refinement with
SHELXL-97 [46] converged at R = 0.0454 for 5073 reflections with
(B5), 121.0 (B3), 120.2 (A4, J31P–13C = 193 Hz), 63.2 (CH2CH3
2J31P–13C = 5 Hz), 16.9 (CH2CH3). 31P NMR (162 MHz, CD3CN): d
22.5 (1J31P–13C = 193 Hz), ꢀ143.4 (1J31P–19F = 707 Hz). MALDI-TOF-
MS (DHB Matrix): m/z = 702.10 [M+] (calcd for C35H31N5O3PRu,
702.12).
4.7. [Ru(Et2O3P-C^N^N)(tpy)](PF6), [2]+
I > 2r(I), wR2 = 0.1091 for all 6011 reflections, S = 1.036, 528
parameters. Both the PF6 anion and the chains on P1 were included
in the refinement with a disorder model (0.56:0.44 and 0.56:0.48,
respectively). Hydrogen atoms were taken into account at calcu-
lated positions and refined riding on their carrier atoms. The ORTEP
illustration and structure checking were done with PLATON [47].
A suspension of [RuCl3(tpy)] (152 mg, 0.34 mmol), 7 (150 mg,
0.41 mmol), and N-methylmorpholine (10 drops) in aqueous
MeOH (1:1, v/v, 60 mL) was heated under reflux for 18 h. After
cooling down, the solution was filtered over Celite. The product
was precipitated by the addition of an excess aqueous KPF6 and re-
moval of acetone in vacuo. The product was isolated by filtration
and collected through the filter with acetone. The product was
purified by column chromatography on SiO2 (MeCN:H2O:1 M
NaNO3 = 18:1:1, v/v) and Al2O3 (CH2Cl2:MeCN = 1:1, v/v), yielding
the product as a purple solid (134 mg, 46%).
Acknowledgements
The authors gratefully acknowledge the support from the Euro-
pean Commission through the funding of the project FULLSPEC-
TRUM within the Sixth Framework Program under number SES6-
CT-2003-502620. This work was partially supported (DMT and
ALS) by the Council for Chemical Sciences of the Netherlands Orga-
nization for Scientific Research (NWO/CW).
1H NMR (400 MHz, CD3CN): d 8.62 (d, 2H, 3J = 8.0 Hz, E3,5), 8.60
3
(d, 1H, J31P–1H = 13.2. Hz, B5), 8.58 (d, 1H, 3J = 8.0 Hz, C3), 8.42 (d,
3
1H, J31P–1H = 13.2 Hz, B3), 8.40 (d, 2H, 3J = 8.0 Hz, D3), 8.10 (t, 1H,
3J = 8.0 Hz, E4), 7.93 (d, 1H, 3J = 7.6 Hz, A3), 7.87 (dd, 1H,
3J = 8.0 Hz, 3J = 7.6 Hz, C4), 7.74 (dd, 2H, 3J = 8.0 Hz, 3J = 7.6 Hz,
D4), 7.51 (d, 1H, 3J = 5.2 Hz, C6), 7.36 (d, 2H, 3J = 5.6 Hz, D6), 7.11
(dd, 1H, 3J = 7.6 Hz, 3J = 5.2 Hz, C5), 7.01 (dd, 2H, 3J = 7.6 Hz,
3J = 5.6 Hz, D5), 6.77 (dd, 1H, 3J = 7.6 Hz, 3J = 6.8 Hz, A4), 6.57 (dd,
1H, 3J = 7.6 Hz, 3J = 6.8 Hz, A5), 5.79 (d, 1H, 3J = 7.6 Hz, A6), 4.35
(m, 4H, CH2CH3), 1.48 (t, 6H, 3J = 7.0 Hz, CH2CH3) 13C NMR
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.ica.2009.12.008.

1706
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