Heteroleptic κ2(N,C2)-2-phenylpyridine platinum complexes: The use of bis(pyrazolyl)borates as ancillary ligands

Article abstract of DOI:10.1016/j.ica.2007.02.001

Luminescent platinum(II) bis(pyrazolyl)borate complexes bearing orthometalated phenylpyridines (based on 2-phenylpyridine, 3-hexyloxy-2-phenylpyridine and (4-(pyridine-2-yl)-phenyl)methanol) and bis(pyrazolyl)borate ligands (employed as potassium dihydridobis(pyrazolyl)borate and potassium dihydridobis(3,5-dimethylpyrazolyl)borate) have been synthesized and characterized. By reaction of K₂PtCl₄ with phenylpyridine ligands a precursor has been obtained which was further converted to the corresponding heteroleptic complexes. All platinum(II) bis(pyrazolyl)borate complexes have been investigated by nuclear magnetic resonance, Fourier transform infrared spectroscopy, thermal analysis and UV-Vis absorption spectroscopy. Luminescence as well as lifetime measurements in solution and in the solid state have been performed to establish a qualitative relationship between structure and luminescence properties. The absorption and emission properties of these complexes are governed by the nature of the orthometalating ligand with emission maxima ranging from 488 to 551 nm. Emission spectra at room temperature show well-resolved vibronic fine structures and a strong spin-orbit coupling. For the compounds under investigation the mixing of the excited states leads to apparent lifetimes in the microsecond regime (5.7-8.6 μs), rendering these materials phosphorescent.

Full text of DOI:10.1016/j.ica.2007.02.001

Inorganica Chimica Acta 360 (2007) 2767–2777
www.elsevier.com/locate/ica
Heteroleptic j2(N,C2)-2-phenylpyridine platinum complexes: The use
of bis(pyrazolyl)borates as ancillary ligands
a
b
a
b
Fabian Niedermair , Kerstin Waich , Stefan Kappaun , Torsten Mayr ,
a
c
a,
*
Gregor Trimmel , Kurt Mereiter , Christian Slugovc
a
Institute for Chemistry and Technology of Organic Materials (ICTOS), Graz University of Technology, Stremayrgasse 16, A-8010 Graz, Austria
Institute of Analytical Chemistry – Workgroup Chemo- and Biosensors, Graz University of Technology, Stremayrgasse 16, A-8010 Graz, Austria
b
c
Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9/164, A-1060 Vienna, Austria
Received 7 November 2006; received in revised form 29 January 2007; accepted 5 February 2007
Available online 11 February 2007
Abstract
Luminescent platinum(II) bis(pyrazolyl)borate complexes bearing orthometalated phenylpyridines (based on 2-phenylpyridine, 3-hex-
yloxy-2-phenylpyridine and (4-(pyridine-2-yl)-phenyl)methanol) and bis(pyrazolyl)borate ligands (employed as potassium dihydrido-
bis(pyrazolyl)borate and potassium dihydridobis(3,5-dimethylpyrazolyl)borate) have been synthesized and characterized. By reaction
of K2PtCl4 with phenylpyridine ligands a precursor has been obtained which was further converted to the corresponding heteroleptic
complexes. All platinum(II) bis(pyrazolyl)borate complexes have been investigated by nuclear magnetic resonance, Fourier transform
infrared spectroscopy, thermal analysis and UV–Vis absorption spectroscopy. Luminescence as well as lifetime measurements in solution
and in the solid state have been performed to establish a qualitative relationship between structure and luminescence properties. The
absorption and emission properties of these complexes are governed by the nature of the orthometalating ligand with emission maxima
ranging from 488 to 551 nm. Emission spectra at room temperature show well-resolved vibronic fine structures and a strong spin-orbit
coupling. For the compounds under investigation the mixing of the excited states leads to apparent lifetimes in the microsecond regime
(5.7–8.6 ls), rendering these materials phosphorescent.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Platinum; Bis(pyrazolyl)borate; Luminescence
1. Introduction
sitions comprise either metal–metal-to-ligand charge trans-
fer (MMLCT) or excimeric ligand-to-ligand charge
transfer with MMLCT excited states strongly decreasing
with a decreasing Pt–Pt distance [5].
Research on luminescent square-planar platinum(II)
complexes focused on their potential applications in differ-
ent fields such as chemical sensors [1], organic light emit-
ting diodes (OLEDs) [2], or photovoltaic devices [3].
Emission from Pt(II) complexes is typically assigned to
ligand centred (LC) or metal-to-ligand charge transfer
(MLCT) states. Among this class of materials many Pt(II)
complexes tend to form aggregates which exhibit rich exci-
mer photophysics causing marked red shifts relative to the
mononuclear emission spectra [4]. The corresponding tran-
In terms of emitting LC or MLCT excited states it is
important that the metal centred (MC) states lie distinctly
higher in energy or otherwise, the excited states tend to
equilibrate thermally through the MC states and quench-
ing of the emission through a fast radiationless decay
occurs. An increase of the energy gap of the MC excited
states can be achieved by imposing a strong ligand field to
the platinum centre, e.g. by metalated aromatic carbon
atoms coordinated to the platinum atom [6]. This design
principle is typically realized by using 2-arylpyridine or
2-(20-thienyl)pyridine derivatives as the cyclometalated
ligands. The resulting homoleptic [7] and heteroleptic
*
Corresponding author. Tel.: +43 316 873 8454; fax: +43 316 873 8951.
E-mail address: slugovc@tugraz.at (C. Slugovc).
0020-1693/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2007.02.001

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F. Niedermair et al. / Inorganica Chimica Acta 360 (2007) 2767–2777
complexes bearing either two cyclometalated ligands [8] or
a single cyclometalating ligand and a noncyclometalating
ancillary ligand [9] have been reported to be emissive in
solution and in the solid state with luminescence lifetimes
in the microsecond range indicating emission from the
triplet excited states [9a,9b,9c,15a]. Although the homo-
leptic Pt(II) complexes exhibit desirable photo physical
properties for different applications, heteroleptic Pt(II)
complexes offer several distinct advantages such as an
easy tuning of the solubility, absorption and emission
characteristics as well as radiative lifetimes by a proper
choice of ancillary ligands. Consequently, a plenitude of
chemical sensors for biomolecules [1c,10–13], gases or
organic vapours [1b,14] has been realized utilizing these
materials.
dimer [Pt(j2(N,C2)-2-phenylpyridine)Cl]2. The reaction
was accomplished in a solvent mixture of 3:1 of 2-ethoxy-
ethanol and water at a temperature of 80 ꢁC within 16 h
(cf. Scheme 1). After removal of the solvent by evapora-
tion, a yellow residue was obtained which was further puri-
fied by repeated washing with hot methanol followed by
washing with n-pentane giving a yellow microcrystalline
powder in 86% yield. The obtained material was character-
1
ized by H and 13C NMR spectroscopy.
1
Integration of the H NMR spectrum gave 17 proton
signals (cf. Fig. 1) with characteristic signals for the pro-
tons in position 6 of the pyridine rings at 9.62 and
9.24 ppm pointing to the presence of two individual phe-
nyl–pyridine moieties. Both signals exhibited platinum sat-
ellites evidencing coordination of both molecules to the
platinum centre. However, from the corresponding spectra
only one indicative resonance for metalation of phenylpyri-
dine could be observed, which was characterized by plati-
num satellites and its resonance at high field at 6.19 ppm.
From these data, the product was identified as j2(N,C2)-
(2-phenylpyridine)-j1(N)-(2-phenylpyridine)chloro plati-
num(II) (2a) which is in accordance with the work of Ford
and co-workers who described 2a as a minor by-product in
the synthesis of Bu4N[j2(N,C2)-(2-phenylpyridine)PtCl2]
by adding 4 equiv. of 1a to a solution of (Bu4N)2[PtCl4]
[9a]. By this group the corresponding dimer [j2(N,C2)-(2-
phenylpyridine)PtCl]2 was obtained upon the addition of
1.1 equiv 1a to a solution of (Bu4N)2[PtCl4]. Also Cho
et al. reported the preparation of 2a using a similar proce-
dure as described in this work [19]. It is worth noting that
in our hands no evidence for the dimer [Pt(j2(N,C2)-2-phe-
nylpyridine)Cl]2 could be retrieved, although the formation
of such a dimer was initially anticipated based on the liter-
ature stating the preparation of Pt(II) l-dichloro-bridged
dimers using similar reaction conditions [15a,20].
Among heteroleptic j2(N,C2)-2-phenylpyridine plati-
num complexes acetyl acetonate (acac) or dipivolylmethane
(dpm) are the most common ancillary ligands [15].
Although several studies on these materials have been
reported in recent times [15], investigations on correspond-
ing bis(pyrazolyl)borates are still rare [16,17]. In this con-
tribution, we wish to report our results on using
dihydridobis(pyrazolyl)borate (bp) and dihydridobis(3,5-
dimethylpyrazolyl)borate (bp*) as ancillary ligands in het-
eroleptic j2(N,C2)-2-phenylpyridine Pt(II) derivatives, both
of which are isoelectronic to the commonly used acac
ligand. Synthesis, structure, thermal as well as absorption
and emission characteristics of the corresponding com-
plexes will be discussed and a qualitative relationship
between structure and luminescence properties will be
established. The results presented herein line up with very
recent reports on Pt(II) complexes [1a,17,20,15b], and pro-
vide an amenable and versatile tool for tuning material
properties of phosphorescent Pt(II) complexes towards
particular needs.
The precursor compounds 2b and 2c were prepared
analogously to 2a using (4-(pyridin-2-yl)phenyl)methanol
(1b) and 3-hexyloxy-2-phenylpyridine (1c) as starting mate-
rials. Compounds 1b and 1c were prepared according to the
literature procedures by the reduction of 4-pyridin-2-yl-
benzaldehyde with LiAlH4 in dry THF [27] or via Suzuki
cross-coupling reactions [32]. Compounds 2b and 2c were
isolated in yields of 41–47% after product purification by
washing with methanol and n-pentane. NMR data of 2c
2. Results and discussion
2.1. Synthesis and characterization
For the preparation of the cyclometalated Pt(II) com-
plexes, K2PtCl4 was reacted according to the method of
Lewis et al. [10a,18,20] in the presence of 2–2.5 equiv.
2-phenylpyridine in order to obtain the l-dichloro bridged
R1
R2
EtOCH2CH2OH : H2O = 3 : 1
Cl
80˚C, 16h, Argon
N
K2PtCl4
+
Pt
R2
N
N
R2
R1
R1
1a: R1 = H, R2 = H
1b: R1 = CH2OH, R2 = H
1c: R1 = H, R2 = OHex
2a: R1 = H, R2 = H
2b: R1 = CH2OH, R2 = H
2c: R1 = H, R2 = OHex
Scheme 1.

F. Niedermair et al. / Inorganica Chimica Acta 360 (2007) 2767–2777
2769
Fig. 1. 1H NMR spectrum of 2a.
revealed similar features as the NMR spectra of precursor
2a. Orthometalation of the precursor derivative 2c was evi-
dent due to the characteristic upfield shift of the Ph3 proton
compared to the free ligand. This upfield shift is presum-
ably a result of a shielding effect as described in the work
of Ford and co-workers [9a]. Furthermore, the proton
Py6 of the orthometalated ligand in 2c revealed a significant
downfield shift giving a signal at 9.35 ppm. Attempts to
characterize 2b by NMR-spectroscopy were unsuccessful
due to low solubility in all common organic solvents. The
identity of 2b was assured by elemental analysis and full
characterization of the corresponding follow-up products
(vide infra).
Starting from the precursor materials 2a–2c and the cor-
responding bis(pyrazolyl)borate ligands 3a and 3b, a series
of platinum(II) bis(pyrazolyl)borate complexes 4a–4f was
prepared by reacting both educts in CH2Cl2 at room tem-
perature under an inert atmosphere of argon (cf. Scheme
2) [15]. Compounds 4a–4f were obtained analytically pure
by column chromatography on silica using CH2Cl2 or
CHCl3/MeOH = 20/1 as solvent yielding 10–80% of the
corresponding compounds (cf. Section 4).
NMR-spectra of the platinum(II) bis(pyrazolyl)borate
complexes showed characteristic features concerning the
downfield shifts of the protons Ph3 in the range from
7.29 to 7.14 ppm and Ph6 from 8.41 to 8.34 ppm. The pro-
ton Py6 next to the orthometalated centre was shifted to
higher fields when compared to the corresponding precur-
sor complexes. Signals were observed in the range of
8.62–8.21 ppm. Concerning compounds 4c and 4d, signals
for protons Ph2 and Ph6 were shifted to higher fields when
compared to the free ligand [27].
Fourier transform infrared measurements of 4a–4f
exhibited characteristic signals for the B–H bond at
2412 cmꢀ1 (4a), 2418 cmꢀ1 (4c) and 2417 cmꢀ1 (4e). The
bp derivatives 4a, 4c and 4e displayed typically fine struc-
tured signals in the BH2 stretch region as described by Tro-
fimenko [25]. In contrast, the corresponding IR spectra of
the bp* derivatives gave two distinct signals for the axial
and the equatorial B–H bond at 2453 and 2363 cmꢀ1
R
3H
R3
R1
R3
B
R3
N
H
N
N
N
N
N
Cl
CH2Cl2, RT, Argon
N
N
H
H
N
+
Pt
Pt
K
B
R3
R2
N
R2
N
R2
R3
R3
R1
R3
R1
2a: R1 = H, R2 = H
2b: R1 = CH2OH, R2 = H
2c: R1 = H, R2 = OHex
4a: R1 = H, R2 = H, R3 = H
3a: R3 = H
3b: R3 = Me
4b: R1 = H, R2 = H, R3 = Me
4c: R1 = CH2OH, R2 = H, R3 = H
4d: R1 = CH2OH, R2 = H, R3 = Me
4e: R1 = H, R2 = OHex, R3 = H
4f: R1 = H, R2 = OHex, R3 = Me
Scheme 2.

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F. Niedermair et al. / Inorganica Chimica Acta 360 (2007) 2767–2777
(4b), 2455 and 2369 cmꢀ1 (4d), as well as 2453 and
2370 cmꢀ1 (4f).
To further confirm the structural identities of the pre-
pared platinum(II) bis(pyrazolyl)borate complexes, single
crystals were grown from a representative complex by ether
diffusion into saturated CH2Cl2 solutions of 4b.
where the boron bonded hydrogen, syn-oriented to Pt, is
substituted by a third 1H-pyrazole moiety, pronounced
agnostic interactions between the N-bound hydrogen and
tetracoordinated Pt with Ptꢁ ꢁ ꢁH distances of about 2.3–
˚
2.4 A have been observed [21,22] (see Fig. 3).
The crystal structure of complex 4b shows an approxi-
mately planar arrangement of the phenylpyridine ligand
and the folded bis(pyrazolyl)borate ligand (cf. Fig. 2). Plat-
inum is in a slightly twisted square planar coordination, the
r.m.s. aplanarity of the PtN3C coordination figure is
2.2. Thermal properties
To determine the thermal stability of compounds 4a –4f,
heat flux DSC/TGA measurements were performed. The
peak maxima of the melting points are significantly lower
in the case of the bp derivatives, i.e. 175.6 ꢁC for 4a and
149.3 ꢁC for 4e compared to their bp* counterparts with
212.5 ꢁC for 4b and 191.4 ꢁC for 4f. Compounds 4c and
4d show slight uncharacteristic exothermal signals at 153
and 161 ꢁC which are accompanied with approx. 4% weight
loss as determined by TGA measurements (cf. below). No
melting point was observed for 4c and 4d. Both results
point to an ongoing condensation reaction starting above
150 ꢁC. For practical applications, materials with good
thermal stability are favoured because of improved device
lifetimes [23]. The thermal stability of compounds 4a–4f
was evaluated by TGA measurements under a nitrogen
atmosphere. As shown in Fig. 4, all materials exhibit ther-
mal stabilities up to 140 ꢁC. While compounds 4a, 4b and
4f decompose immediately after melting, compound 4e
exhibits thermal stability above its melting point. The tem-
perature at a weight loss of 5% acts as an indicator for ther-
mal stability of the compounds under investigation. From
the corresponding temperature values (cf. Table 1), an
increased thermal stability of the bp* derivatives (4b and
4f) compared to the bp complexes (4a and 4e) becomes evi-
dent. Concerning the methylol substituted derivatives (4c
and 4d) the bp complex 4c shows higher thermal stability
(5% weight loss at 232 ꢁC) compared to the bp* derivative
4d (5% weight loss at 208 ꢁC). Although the complexes
reported herein display lower thermal stabilities than anal-
ogous acac complexes which show values around 370 ꢁC
[15], a sufficient thermal stability for thermal evaporation
processes is found.
˚
0.045 A. The phenylpyridine ligand is distinctly twisted
showing an interplanar angle between the two planar rings
of 10.4(1)ꢁ. The coordinating carbon C(11) exerts a distinct
˚
trans effect on the Pt–N(4) bond, which is longer by 0.08 A
than the Pt–N(3) bond trans to the pyridine nitrogen N(5).
These geometric features are in good accord with the
related complex (diethyl-bis(pyrazolyl)borato)-(2-(2,4-
difluorophenyl)pyridine)- platinum(II), reported recently
by Ma et al. [17]. It appears worthy of mention that com-
plex 4b bears a good precondition for a disordered distribu-
tion of phenyl and pyridine rings in the solid state.
Surprisingly, this is not the case, as could be shown during
the structure refinement by population parameter analysis
of C(11) and N(5) and is also proved by the asymmetry
in Pt–C and Pt–N bond lengths which would vanish in case
of a disordered arrangement of the complexes in the lattice.
One reason for this is likely that in the solid state of 4b the
benzene ring shows a pronounced p–p stacking interaction
with a neighbouring complex (shortest C–C distances ca.
˚
3.40 A), whereas the pyridine ring does not. It is further
noteworthy that there is no backbiting of the hydrogen
atom of the B–H bond to the platinum centre, the distance
˚
Ptꢁ ꢁ ꢁH(2) being 2.915 A. This is essentially a result of the
unsuitable geometry of the complex, which would require
serious distortions to bring H(2) close enough for typical
˚
agostic Ptꢁ ꢁ ꢁH interactions with Pt–H < 2.5 A. In cases
Fig. 2. ORTEP plot of 4b (displacement ellipsoids at 40% probability level).
˚
Selected bond lengths (A) and angles (ꢁ): Pt–N(2) 2.030(2), Pt–N(4)
2.109(2), Pt–C(11) 1.997(2), Pt–N(5) 2.013(2), Ptꢁ ꢁ ꢁH(2) 2.916 (non-
bonding); N(2)–Pt–N(4) 84.1(1), N(2)–Pt–C(11) 96.6(1), N(4)–Pt–N(5)
98.7(1), C(11)–Pt–N(5) 80.6(1).
Fig. 3. Thermogravimetric analysis of compounds 4a–4f.

F. Niedermair et al. / Inorganica Chimica Acta 360 (2007) 2767–2777
2771
at room temperature under ambient conditions and under
an inert atmosphere of nitrogen. Data are given in Table
2, spectra for the bp derivatives 4a, 4c and 4f as well as
for the bp* derivatives 4b, 4d and 4e are shown in Figs. 5
and 6.
2.4. Absorption properties
Absorption spectra of the platinum(II) bis(pyraz-
olyl)borate complexes are characterized by low energy
transitions in the range of 350–420 nm with coefficients of
extinction (e) between 1500 and 7600 Mꢀ1 cmꢀ1 that can
be assigned to metal-to-ligand charge transfer (MLCT)
transitions. The absorption bands between 330 and
350 nm are attributed to the bis(pyrazolyl)borate ligands,
while the more intense absorption bands in the high energy
region result from p–p* ligand-centred (LC) transitions
[15]. Substitution on the pyridine ring with an electron
Fig. 4. Heat flux DSC of 4a–4f. No endothermic heat flow indicative for a
melting point could be observed for 4c and 4d.
Table 1
Thermal data for complexes 4a–4f
Complex
Mp (ꢁC)a
5% Weight loss at T (ꢁC)
4a
4b
4c
4d
4e
4f
a
176
213
b
186
214
232
208
214
225
b
149
191
Peak maxima.
b
No melting point observed.
2.3. Electronic spectroscopy
To establish a qualitative relationship between structure
and luminescence characteristics, the photo physical prop-
erties of the platinum(II) complexes were investigated.
Absorption and emission spectroscopies were carried out
Fig. 5. Absorption and emission spectra of 4a, 4c and 4e measured in
CHCl3.
Table 2
Absorption and emission properties of the platinum(II) complexes at room temperature
Complex
Absorption, kmax
Emission
kmax (nm)
N2
sN (ls)c
a
b
c
I
Iair
s
N2
2
k (nm) (e (10ꢀ3 cmꢀ1 Mꢀ1))
sair
4a
4b
4c
4d
4e
4f
a
331 (7.2), 350 (5.9), 401 (1.5)
488/520a
488/521b
491/523a
491/524b
492/525a
493/528b
496/529a
496/528b
513/548a
514/547b
517/551a
516/549b
1.19
1.47
1.46
1.44
1.25
1.53
1.34
1.46
1.48
1.57
1.31
1.49
5.7
7.0
8.6
7.7
6.0
7.1
333 (8.1), 363 (7.2), 411 (2.1)
333 (8.0), 350 (5.8), 401 (1.7)
335 (8.1), 365 (5.9), 411 (1.9)
328 (10.2), 341 (15.4), 356 (7.0), 412 (2.5)
330 (12.0), 345 (15.3), 370 (7.6), 421 (3.0)
CHCl3 solutions; energy (eV) is calculated according to the following equation: energy (eV) = 1240/k.
Dispersion in polystyrene (2 wt% complex in polystyrene (10% in CHCl3)).
Apparent lifetimes measured at a modulation frequency of 20 kHz for the embedded complex in polystyrene. Deviations between the intensity ratios
b
c
and lifetimes ratios under nitrogen are attributed to a non ideal (multi-exponential) decay.

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F. Niedermair et al. / Inorganica Chimica Acta 360 (2007) 2767–2777
matrix using a modulation frequency of 20 kHz at room
temperature under an inert atmosphere of nitrogen (cf. Sec-
tion 4) gave apparent lifetimes significantly higher than
those of corresponding acac complexes. While the bis(pyr-
azolyl)borate complexes exhibited apparent lifetimes
between 5.7 and 8.6 ls, typical apparent lifetimes between
1.4 and 2.6 ls are reported for e.g. analogous acac or
dpm derivatives [1a,15a].
PL quantum yields for complexes 4a, 4b, 4e and 4f gave
values lower than 1% in aerated solution. Compounds 4c
and 4d bearing the hexyloxy group in position 3 on the pyr-
idine ring showed quantum yields of approximately 1%. For
comparison, quantum yields of acac complexes and deriva-
tives at room temperature in solution revealed values in the
range between 1% and 25% in the case of sterically demand-
ing acac derivatives [1a,15a]. The low quantum yields
obtained for the bis(pyrazolyl)borate complexes are presum-
ably a consequence of the luminescence quenching mecha-
nisms as described by Thompson and co-workers [15a].
Fig. 6. Absorption and emission spectra of 4b, 4d and 4f measured in
CHCl3.
donating hexyloxy group in position 3 leads to a significant
overall increase of absorbance and to additional character-
istic and strong absorption feature peaking at 341 (4e) and
345 nm (4f). Comparing the absorption spectra of com-
plexes 4a and 4b with those for ppyPt(dpm) [15a], the influ-
ence of the ancillary ligand is revealed. The
bis(pyrazolyl)borate ligands cause a blue shift of approx.
20–30 nm of the absorption features attributed to MLCT
transitions (in the range of 350–430 nm).
3. Conclusion
Herein we reported an efficient synthetic route for the
preparation of novel luminescent platinum(II) bis(pyraz-
olyl)borate complexes by the reaction of a precursor mate-
rial with the anionic bidentate bis(pyrazolyl)borates acting
as coligands. The described compounds can be easily pre-
pared, are uncharged and thermally stable in air making
them candidates for use in e.g. optoelectronic devices. Both
ancillary ligands, dihydridobis(pyrazolyl)borate and dihy-
dridobis(3,5-dimethylpyrazolyl)borate, do hardly effect
important photophysical properties like the emission max-
imum or the maxima of transition bands at lowest energy
of the complexes. These properties are mainly determined
by the nature of the phenylpyridine ligand. Changing the
electron density of the phenylpyridine ligand by introduc-
tion of a hexyloxy-substituent in 3-position of the pyridine
moiety leads to an increase of the molar extinction coeffi-
cient of all absorption features and a bathochromic shift
of the emission maximum of about 25 nm compared to
compounds featuring the parent phenylpyridine or the
methylol substituted phenylpyridine ligand. All bis(pyraz-
olyl)borate complexes are emissive in solution and in the
solid state with apparent lifetimes in the microsecond
regime (5.7–8.6 ls). The results presented herein provide
a versatile and convenient tool for the preparation of phos-
phorescent platinum(II) complexes towards particular
needs, further systematic studies on the influences of ligand
modifications on the photo physical properties are cur-
rently in progress.
2.5. Emission properties
All complexes exhibited a greenish photoluminescence
(PL) in solution at room temperature under ambient condi-
tions. The data are given in Table 2 and spectra are shown
in Figs. 5 and 6. The structured luminescence and micro-
second apparent radiative lifetimes at 298 K in the range
of 4.0 (4a) to 8.6 ls (4c) (determined under an inert atmo-
sphere of nitrogen) are consistent with emission properties
governed by the nature of the phenylpyridine ligand and
with emission characteristics originating from a mixed
3LC-MLCT excited state [15]. The obtained luminescence
maxima of complexes 4a and 4b are in accordance with
data from the literature. For example, ppyPt(dpm) exhib-
ited structured emission bands with emission maxima at
485 and 520 nm [1a]. While substitution by the methylol
moiety on the phenyl ring of the phenylpyridine ligand
exerts little influence on the emission maxima peaking at
492 4 nm and 524 4 nm, a significant shift of the emis-
sion maxima is observed for the hexyloxy substituted deriv-
atives resulting in emission maxima of 515 2 and
549 2 nm. Solid state emission spectra showed similar
values concerning emission wavelengths compared to the
emission maxima in solution. Out of that no evidence for
aggregation and excimer formation could be retrieved.
Further it has to be noted that changes on the bis(pyraz-
olyl)borate ligand revealed no impact on the luminescence
maxima of the Pt(II) complexes.
4. Experimental
4.1. Materials and measurements
Apparent lifetime measurements of the platinum(II)
bis(pyrazolyl)borate complexes measured in a polystyrene
Manipulations were performed under an inert atmo-
sphere of purified nitrogen or argon using Schlenk tech-

F. Niedermair et al. / Inorganica Chimica Acta 360 (2007) 2767–2777
2773
niques and/or a glovebox. Unless otherwise noted, materi-
als were obtained from commercial sources (Aldrich, Fluka
or Lancaster) and were used without further purification.
The solvents were purified according to standard proce-
dures [24]. Potassium dihydridobis(pyrazolyl)borate [25],
potassium dihydridobis(3,5-dimethylpyrazolyl)borate [25],
2-bromo-3-hexyloxypyridine [26], and (4-pyridine-2-yl-
phenyl)methanol [27] were prepared according to the liter-
X-ray data for 4b were collected on a Bruker Smart
APEX CCD diffractometer using graphite-monochro-
˚
mated Mo Ka radiation (k = 0.71073 A) and 0.3ꢁ x-scan
frames covering a complete sphere of the reciprocal space
with hmax = 30ꢁ. After data integration with program
SAINT corrections for absorption, k/2 effects, and crystal
decay were applied with program SADABS [30]. The structure
was solved by direct methods, expanded with Fourier syn-
theses, and refined on F2 with the program suite SHELX97
[31]. All non-hydrogen atoms were refined anisotropically.
H atoms were placed in calculated positions and thereafter
treated as riding. Crystal data: C21H24BN5Pt, Mr = 552.35,
monoclinic, space group P21/c (no. 14), T = 173(2) K,
1
ature procedures. H NMR spectra were recorded on a
Varian INOVA 500 MHz Spectrometer at 500 MHz,
13C{1H} NMR spectra were recorded at 125 MHz. Assign-
ment of the peaks was done by DEPT and COSY NMR
spectroscopy. Solvent residual peaks were used for refer-
encing the NMR-spectra to the corresponding values given
in the literature [28]. FT-IR spectra were obtained from
films on KBr windows with a Perkin–Elmer Spectrum
One and a DTGS-detector. UV–Vis absorption spectra
were recorded on a Cary 50 Bio UV–Visible Spectropho-
tometer, luminescence spectra on a Perkin–Elmer Lumines-
cence Spectrometer LS50B. Lifetime measurements
involved the preparation of coated capillaries. The coated
capillaries were prepared using cocktails consisting of
2 mg of the corresponding Pt(II) complex and 100 mg of
polystyrene dissolved in 1 mL chloroform. The polymer
solutions were sucked into a Pasteur pipette and the excess
of the solution was blown out with compressed air. The
resulting films were dried in a drying chamber at 70 ꢁC
for 12 h. Luminescence excitation and emission spectra
were acquired in air and while flushing the capillaries with
nitrogen with a Fluorescence Spectrometer Perkin–Elmer
LS50B. Phase angle measurements were performed using
a system recently described [29]. A dual-phase lock-in
amplifier (DSP 830; Stanford Research Inc.) was used for
sine-wave modulation of the LED at a frequency of
20 kHz and for detection. The optical system consisted of
a UV LED (1.4 mW at 20 mA; kmax = 365 nm; 5 mm;
Roithner Lasertechnik, Vienna, Austria), a bifurcated glass
fiber bundle of a 2 mm diameter and a red-sensitive PMT
module (H5701-02; Hamamatsu; Herrsching, Germany)
equipped with a long-pass filter (OG515; Schott; Mainz,
Germany). The measurements were carried out in air and
in a nitrogen atmosphere. The apparent lifetimes were
recorded according to the equation tanD/ = 2pms, where
D/ indicates the phase shift, m the modulation frequency
and s the luminescence lifetime. Photoluminescence (PL)
˚
a = 14.9305(6), b = 10.0845(4), c = 14.5314(6) A, b =
3
ꢀ1
˚
113.515(1)ꢁ, V = 2006.25(14) A , Z = 4, l = 7.010 mm
.
Of 21555 reflections collected, 5835 were independent
(Rint = 0.025); final R indices: R1 = 0.025 (all data),
wR1 = 0.043 (all data). A structural view of 4b with selected
geometric data is shown in Fig. 2.
4.2. Synthesis of 3-hexyloxy-2-phenylpyridine (1b)
Compound 1b was prepared adopting a published pro-
tocol [32]. Phenyl boronic acid (168.0 mg, 1.38 mmol), 2-
bromo-3-hexyloxypyridine (146.5 mg, 0.57 mmol) and
Na2CO3 were suspended in a degassed solution of tolu-
ene/EtOH/H2O = 1/1/1 (12 mL). The catalyst tetrakis(tri-
phenylphosphine)palladium(0) (25 mg, 4 mol%) was
added under an inert atmosphere of argon and the mixture
was stirred at 95 ꢁC for 24 h. After cooling to room temper-
ature, H2O (8 mL) was added to the reaction mixture. The
reaction mixture was extracted with CH2Cl2 (4 · 50 mL)
and the organic phase was separated, dried over Na2SO4
and the solvent was removed under reduced pressure.
The resulting orange oil was purified by column chroma-
tography (SiO2, eluent Cy/EE = 15/1) sampling the band
at Rfꢂ 0.5 (Cy/EE = 15/1). Yield: 126.4 mg (87.2%).
Anal. Calc. for C17H21NO: C, 79.96; H 8.29. Found: C,
1
80.04; H, 8.44%. H NMR (d, 20 ꢁC, CDCl3, 500 MHz):
3
4
8.30 (dd, 1H, JHH = 4.9 Hz, JHH = 1.5 Hz, Py6), 7.94
(d, 2H, JHH = 7.3 Hz, Ph2,6), 7.44 (m, 2H, Ph3,5), 7.37
3
(m, 1H, Ph4), 7.27 (dd, 1H, 3JHH = 8.3 Hz, 4JHH = 1.5 Hz,
Py4), 7.21 (m, 1H, Py5), 4.00 (t, 2H, JHH = 6.8 Hz,
3
OHex1), 1.79 (p, 2H, OHex2), 1.45 (m, 2H, OHex5), 1.32–
1.30 (m, 4H, OHex3,4), 0.89 (m, 3H, OHex6). 13C{1H}
NMR (d, 20 ꢁC, CDCl3, 125 MHz): 153.3 (1C, Py3),
148.3 (1C, Py2), 141.3 (1C, Py6), 137.9 (1C, Ph1), 129.6
(2C, Ph3,5), 128.4 (1C, Ph4), 128.0 (2C, Ph2,6), 123.1 (1C,
Py5), 119.8 (1C, Py4), 68.8 (1C, OHex1), 31.7 (1C, OHex4),
29.2 (1C, OHex2), 26.0 (1C, OHex3), 22.8 (1C, OHex5),
14.2 (1C, OHex6).
quantum yields were measured on
a
Shimadzu
RF-5301PC spectrofluorometer calibrated using a tung-
sten–halogen light source (Ocean Optics LS-1-CAL) and
a Perkin–Elmer Lambda 9 UV–Vis–near-infrared spectro-
photometer using quinine sulphate dehydrate in 0.1 N
H2SO4 as the standard. Combined differential scanning cal-
orimetry (DSC)/thermogravimetric analysis (TGA) mea-
surements were performed with a Polymer Laboratories
simultaneous thermal analyzer STA 625 (crucibles: alumi-
num from Rheometric Scientific). Thermal properties were
determined with a heat rate of 10 ꢁC/min in a nitrogen flow
o approximately 35 mL/min.
4.3. Synthesis of j2(N,C2)-(2-phenylpyridine)-j1(N)-(2-
phenylpyridine)chloroplatinum(II) (2a)
A 3:1 mixture of degassed ethoxyethanol and water
(12 mL) was added to K2PtCl4 (215.5 mg, 0.519 mmol).

2774
F. Niedermair et al. / Inorganica Chimica Acta 360 (2007) 2767–2777
After stirring for 10 min 2-phenylpyridine (178.1 mg,
1.148 mmol) was added. The reaction mixture was heated
at 80 ꢁC and stirred for 16 h under an inert atmosphere
of argon. The solvent was then removed under reduced
pressure and methanol (5 mL) was added to the yellow res-
idue. The reaction mixture was stirred for 10 min at room
temperature and the yellow precipitate was filtered off. The
residue was washed with methanol (2 · 2 mL) and n-pen-
tane (2 · 5 mL) and was dried in vacuo. Yield: 241.5 mg
(86.2%).
4.6. Synthesis of j2(N,C2)-(2-phenylpyridine)-j2(N,N)-
dihydridobis(pyrazolyl)borate platinum(II) (4a)
Degassed CH2Cl2 (7 mL) was added to a mixture of 2a
(100.1 mg, 0.185 mmol) and 3a (60.9 mg, 0.327 mmol) con-
tained in an oven dried Schlenk tube. The reaction mixture
was stirred at room temperature for 5 h. The solvent was
then removed under reduced pressure and the residue was
purified by column chromatography (SiO2, eluent CH2Cl2)
sampling the first yellow band (Rf ꢂ0.9 in CH2Cl2). Yield:
64.6 mg (70.2%) yellow crystals.
Anal. Calc. for C22H17ClN2Pt: C, 48.94; H, 3.17. Found:
C, 49.30; H, 2.96%. 1H NMR (d, 20 ꢁC, CDCl3, 500 MHz):
Anal. Calc. for C17H16BN5Pt: C, 41.15; H, 3.25. Found:
C, 41.17; H, 3.44%. 1H NMR (d, 20 ꢁC, CDCl3, 500 MHz):
3
9.62 (d, 1H, JHH = 5.9 Hz, Py6), 9.24 (d, 1H,
0
0
0
3JHH = 5.9 Hz, Py6 ), 8.08 (m, 2H, Ph2 ,6 ), 7.94 (t, 1H,
8.62 (d, 1H, JHH = 5.9 Hz, Py6), 7.88 (t, 1H,
3
0
3JHH = 7.3 Hz, Py4 ), 7.73 (t, 1H, JHH = 78 Hz, Py4),
3JHH = 7.3 Hz Py4), 7.75 (d, 1H, JHH = 7.8 Hz, Ph60),
3
3
0
7.63 (d, 1H, JHH = 7.3 Hz, Py3 ), 7.51 (d, 1H,
7.72, 7.69 (d, 2H, JHH = 2.2 Hz, JHH = 2.2 Hz, Pz3,30),
3
3
3
0
3JHH = 7.8 Hz, Py3), 7.37 0 (t, 1H, JHH = 7.3 Hz, Ph4 ),
7.63, 7.59 (d, 2H, JHH = 2.2 Hz, JHH = 2.0 Hz, Pz5,5 ),
3 3
3
0
0
7.32 (m, 4H, Ph6, Py5 , Ph3 , Ph5 ), 7.06 (t, 1H,
7.55 (dd, 1H, JHH = 7.1 Hz, JHH = 2.0 Hz, Py3), 7.29
3
4
3JHH = 7.3 Hz, Py5), 6.99 (t, 1H, JHH = 7.3 Hz, Ph5),
(dd, 1H, JHH = 7.0 Hz, JHH = 1.7 Hz, Ph3), 7.17 (m,
3
3
4
6.87 (t, 1H, JHH = 7.3 Hz, Ph4), 6.19 (d, 1H,
2H, Ph4,5), 7.10 (vt, 1H, JHH = 6.3 Hz, Py5), 6.32, 6.27
3
3
0
3JHH = 7.3 Hz, Ph3). 13C{1H} NMR (d, 20 ꢁC, CDCl3,
(vt, 2H, JHH = 2.2 Hz, JHH = 2.2 Hz, Pz4,4 ). 13C{1H}
NMR (d, 20 ꢁC, CDCl3, 125 MHz): 168.2 (1C, Ph2),
149.5 (1C, Py6), 145.4 (1C, Py2), 143.2 (1C, Ph1), 141.9
3
3
0
125 MHz): 167.3 (1C, Py2), 162.4 (1C, Py2 ), 154.5 (1C,
0
0
Py6), 151.3 (1C, Py6 ), 144.3 (1C, Ph1), 141.1 (1C, Ph1 ),
0
139.9 (1C, Py4), 138.5 (1C, Py4 ), 137.8 (1C, Ph5), 130.9
(1C, Ph3), 139.9 (1C, Py4), 138.7 (1C, Ph6), 136.3, 136.2
0
0
0
(1C, Ph5 ), 129.9 (1C, 0 Ph3), 129.7 (2C, Ph6,6 ), 129.4 (1C,
(2C, Pz3,3 ), 134.2 (1C, Ph5), 129.9 (1C, Ph4), 124.1, 123.7
0
0
0
Ph3 ), 128.0 (2C, Ph4,4 ), 127.4 (1C, Ph2), 124.0 (1C, Ph2 ),
(2C, Pz5,5 ), 122.0 (1C, Py3), 119.0 (1C, Py5), 105.65,
0
0
0
123.3, 123.2 (2C, Py3,3 ), 121.8 (1C, Py5), 118.1 (1C, Py5 ).
105.64 (2C, Pz4,4 ). IR (film on a KBr-window cast from
CH2Cl2-solution, cmꢀ1): 3115 (w), 3044 (w), 2918 (w),
2846 (w), 2412 (m), 1609 (m), 1583 (w), 1501 (w), 1484
(m), 1438 (w), 1412 (m), 1306 (m), 1268 (w), 1240 (w),
1204 (w), 1174 (w), 1145 (s), 1097 (w), 1072 (w), 1059 (s),
1032 (w), 985 (w), 881 (m), 752 (s), 732 (m).
4.4. Synthesis of j2(N,C3)-((4-(pyridin-2-yl)phenyl)-
methanol)-j1(N)-((4-(pyridin-2- yl)phenyl)-
methanol)chloroplatinum(II) (2b)
Compound 2b was prepared similarly to 2a using (4-
(pyridin-2-yl)phenyl)methanol (245.7 mg, 1.326 mmol) as
the starting material. Yield: 151.4 mg (41.4%).
Anal. Calc. for C24H21ClN2O2Pt: C, 48.05; H, 3.53.
Found: C, 48.29; H, 3.74%.
4.7. Synthesis of j2(N,C2)-(2-phenylpyridine)-j2(N,N)-
dihydridobis(3,5-dimethylpyrazolyl) borate platinum(II)
(4b)
Compound 4b was prepared similarly to 4a, using 2a
(100.9 mg, 0.187 mmol) and 3b (68.1 mg, 0.281 mmol) as
the starting materials (Rf ꢂ 0.9 in CH2Cl2). Yield:
59.9 mg (58.0%).
4.5. Synthesis of j2(N,C2)-(3-hexyloxy-2-phenylpyridine)-
j1(N)-(3-hexyloxy-2-phenylpyridine)chloroplatinum(II)
(2c)
Anal. Calc. for C21H24BN5Pt: C, 45.66; H 4.38. Found:
C, 45.58; H, 4,61%. 1H NMR (d, 20 ꢁC, CDCl3, 500 MHz):
Compound 2c was prepared similarly to 2a using 3-hex-
yloxy-2-phenylpyridine (334.6 mg, 1.310 mmol) as the
starting material. Yield: 210.8 mg (47.0%).
3
8.48 (d, 1H, JHH = 5.9 Hz, Py6), 7.82 (t, 1H,
3
3JHH = 7.3 Hz, Py4), 7.68 (d, 1H, JHH = 8.0 Hz, Ph6),
3
Anal. Calc. for C34H41ClN2O2Pt: C, 55.17; H, 5.58%.
7.48 (d, 1H, JHH = 8.0 Hz, Py3), 7.16 (d, 1H,
1
Found C, 54.93; H, 5.77%. H NMR (d, 20 ꢁC, CDCl3,
3JHH = 6.8 Hz, Ph3), 7.08 (m, 2H, Ph4,5), 7.00 (t, 1H,
0
500 MHz): 9.35 (d, 01H, JHH = 5.6 Hz, Py6), 8.80 (d, 1H,
3JHH = 6.1 Hz, Py5), 5.82 (s, 2H, Pz4,4 ), 2.34, 2.32, 2.28,
3
0
0
0
3JHH = 5.6 Hz, Py6 ), 8.20 (d, 1H, JHH = 7.8 Hz, Py4 ),
2.27 (s, 12H, CH33;3 ;5;5 ). 13C{1H} NMR (d, 20 ꢁC, CDCl3,
3
0
0
7.79 (m, 2H, Ph2 ,6 ), 7.43 0 (d, 10H, JHH = 8.3 Hz, Py4),
125 MHz): 168.5 (1C, Ph2), 150.5 (1C, Py6), 147.8, 146.8
3
0
0
0
0
7.30–7.26 (m, 5H, Ph6, Py5 , Ph3 ,4 ,5 ), 7.00–6.93 (m, 2H,
(2C, Pz3,3 ), 145.4, 145.2, 144.9 (3C, Py2, Pz5,5 ), 143.8
(1C, Ph1), 138.4 (1C, Ph3), 135.8 (1C, Ph6), 129.5 (1C,
Ph4,5), 6.86 (t, 1H, JHH = 7.3 Hz, Py5), 6.30 (d, 1H,
3
0
3JHH = 7.3 Hz,0 Ph3), 4.08–3.90 (m, 4H, OHex1,1 ), 1.90
Py4), 123.5, 123.4 (2C, Ph4,5), 121.5 (1C, Py3), 118.7 (1C,
0
(p, 2H, OHex2 ), 1.64 (p, 2H, OHe0x2), 1.55–1.49 (m, 4H,
Py5), 0105.9, 105.7 (2C, Pz4,4 ), 15.6, 14.2, 13.3, 12.9 (4C,
0
0
0
OHex5,5 ), 1.35 (m, 4H, OHex3 ,4 ), 1.28–1.20 (m, 4H,
CH33;3 ;5;5 ). IR (film on KBr-window cast from CH2Cl2-
solution, cmꢀ1): 3044 (w), 2956 (w), 2923 (m), 2852 (w),
2453 (s), 2363 (s), 2258 (w), 1608 (s), 1583 (m), 1538 (s),
0
OHex3,4), 0.91 (t, 3H, JHH = 6.8 Hz, OHex6 ), 0.84 (t,
3
3
3H, JHH = 6.6 Hz, OHex6).

F. Niedermair et al. / Inorganica Chimica Acta 360 (2007) 2767–2777
2775
0
1483 (s), 1438 (m), 1420 (s), 1385 (m), 1309 (w), 1268 (w),
1161 (s), 1107 (s), 1067 (w), 1034 (w), 979 (w), 889 (m),
782 (m), 755 (s), 734 (m).
Py2, Pz5,5 ), 144.1 (1C, Ph4), 142.1 (1C, Ph1), 138.4 (1C,
Ph2), 134.2 (1C, Py4), 123.6, 122.3 (2C, Ph5,6), 121.6 (1C,
0
Py3), 118.8 (1C, Py5), 106.1, 105.8 (2C, Pz4,4 ), 65.9 (1C,
0
0
PhCH2OH), 15.6, 14.2, 13.3, 12.9 (4C, CH3;3 ;5;5 ). IR (film
3
4.8. Synthesis of j2(N,C3)-((4-(pyridin-2-yl)phenyl)-
methanol)-j2(N,N)-dihydridobis(pyrazolyl)borate-
platinum(II) (4c)
on KBr-window cast from CH2Cl2-solution, cmꢀ1): 3406
(m), 3127 (w), 3084 (w), 3038 (w), 2956 (m), 2924 (s),
2856 (m), 2455 (s), 2369 (m), 2263 (w), 2212 (w), 1736
(w), 1609 (s), 1592 (s), 1538 (s), 1566 (m), 1539 (s), 1482
(s), 1435 (m), 1420 (s), 1389 (s), 1311 (w), 1265 (w), 1239
(w), 1161 (s), 1107 (s), 1056 (m), 979 (w), 889 (m), 823
(w), 782 (m), 776 (s), 751 (m), 735 (m), 697 (w), 686 (w).
Compound 4c was prepared similarly to 4a, using 2b
(78.7 mg, 0.131 mmol) and 3a (36.8 mg, 0.198 mmol) as
the starting materials. Purification was accomplished by fil-
tration over Na2SO4 and column chromatography (SiO2,
elution with CHCl3 and then with CHCl3/MeOH = 20/1)
sampling the yellow band at (Rf ꢂ 0.5 in CHCl3/
MeOH = 20/1). The yellow residue was washed with n-pen-
tane. Filtering off of the residue gave 4c as a yellow pow-
der. Yield: 37.0 mg (53.6%).
4.10. Synthesis of j2(N,C2)-(3-hexyloxy-2-phenylpyridine)-
j2(N,N)-dihydridobis (pyrazolyl)borateplatinum(II) (4e)
Compound 4e was prepared similarly to 4a, using 2c
(49.2 mg, 0.066 mmol) and 3a (20.0 mg, 0.107 mmol) as
the starting materials (Rf ꢂ 0.4 in Cy/EE = 1/1). Yield:
30.2 mg (76.3%).
Anal. Calc. for C18H18BN5OPt: C, 41.08; H 3.45.
1
Found: C, 40.86; H, 3.21%. H NMR (d, 20 ꢁC, CDCl3,
3
500 MHz: 8.62 (d, 1H, JHH = 5.4 Hz, Py6), 7.89 (t, 1H,
Anal. Calc. for C23H28BN5OPt: C, 46.32; H, 4.73. Found:
C, 46.17; H, 4.75%. 1H NMR (d, 20 ꢁC, CDCl3, 500 MHz):
3
3JHH = 7.3 Hz, Py4), 7.76 (d, 1H, JHH = 7.8 Hz, Ph50),
7.72, 7.69 (d, 2H, JHH = 1.2 Hz, JHH = 1.5 Hz, Pz3,30),
8.41 (m, 1H, Ph6), 8.29 (d, 1H, JHH = 5.6Hz, Py6), 7.70–
3
3
3
0
0
7.64, 7.59 (d, 2H, JHH = 1.7 Hz, JHH = 1.5 Hz, Pz5,5 ),
7.68 (m, 2H, Pz3,3 ), 7.63, 7.54 (m, 2H, Pz5,5 ), 7.40 (d, 1H,
3
3
7.55 (d, 1H, JHH = 8.0 Hz, Py3), 7.26 (s, 1H, Ph2), 7.19
3JHH = 8.5 Hz, Py4), 7.25 (m, 1H, Ph3), 7.13 (m, 2H,
3
(d, 1H, JHH = 8.3 Hz, Ph6), 0 7.12 (t, 1H, JHH = 6.6 Hz,
Py5), 6.33, 6.28 (t, 2H, Pz4,4 ), 4.67 (s, 2H, PhCH2OH).
13C{1H} NMR (d, 20 ꢁC, CDCl3, 125 MHz): 167.8 (1C,
Ph3), 149.6 (1C, Py6), 145.0 (1C, Py2), 143.5 (1C, Ph4),
Ph4,5), 7.01 (t, 1H, JHH = 7.3 Hz, Py5), 6.30, 6.25 (t, 2H,
3
3
3
0
Pz4,4 ), 4.15 (t, 2H, JHH = 6.1 Hz, OHex1), 1.97 (p, 2H,
3
OHex2), 1.56 (m, 2H, OHex5), 1.39 (m, 4H, OHex3,4), 0.93
(t, 3H, JHH = 7.3 Hz, OHex6). 13C{1H} NMR (d, 20 ꢁC,
3
142.5 (1C, Ph1), 141.8 (1C, Ph2), 139.9 (1C, Ph5), 138.8
CDCl3, 125 MHz): 157.4 (1C, Ph2), 153.8 (1C, Py3), 146.3
0
(1C, Py4), 136.4, 136.2 (2C, Pz3,3 ), 132.6 (1C, Ph6), 123.9,
(1C, Py2), 143.2 (1C, Ph1), 142.0, 141.8 (2C, Py6, Ph6),
0
0
122.8 (2C, Pz5,5 ), 122.0 (1C, Py3), 119.1 (1C, Py5), 105.9,
140.0 (1C, Ph3), 136.2, 136.0 (2C, Pz3,3 ), 133.6 (1C, Ph5),
0
0
105.7 (2C, Pz4,4 ), 66.0 (1C, PhCH2OH). IR (film on
KBr-window cast from CH2Cl2-solution, cmꢀ1): 3357 (w),
3121 (w), 3049 (w), 2923 (w), 2867 (w), 2418 (m), 1728
(w), 1608 (m), 1592 (m), 1566 (w), 1500 (w), 1483 (s),
1436 (w), 1411 (s), 1307 (m), 1268 (w), 1240 (w), 1203
(w), 1175 (w), 1146 (s), 1100 (w), 1072 (m), 1059 (s), 985
(w), 879 (m), 823 (w), 762 (s), 718 (m), 639 (w), 626 (w).
128.8, 128.5 (2C, Pz5,5 ), 123.8 (1C, Ph4), 121.7, 121.5 (2C,
0
Py4,5), 105.54, 105.51 (2C, Pz4,4 ), 69.6 (1C, OHex1), 31.6
(1C, OHex4), 29.0 (1C, OHex2), 25.9 (1C, OHex3), 22.7
(1C, OHex5), 14.2 (1C, OHex6). IR (film on KBr-window
cast from CH2Cl2-solution, cmꢀ1): 3118 (w), 3048 (w),
2953 (m), 2930 (m), 2870 (m), 2417 (s), 1572 (s), 1556 (w),
1500 (m), 1459 (m), 1428 (s), 1412 (s), 1306 (s), 1278 (s),
1240 (w), 1236 (m), 1204 (m), 1174 (m), 1145 (s), 1097 (w),
1071 (m), 1059 (s), 1021 (w), 1001 (w), 946 (w), 878 (m),
796 (m), 754 (s), 736 (s), 719 (m), 636 (w), 626 (w).
4.9. Synthesis of j2(N,C3)-((4-(pyridin-2-yl)phenyl)-
methanol)-j2(N,N)-dihydridobis(3,5-dimethylpyrazolyl)-
borate platinum(II) (4d)
4.11. Synthesis of j2(N,C2)-(3-hexyloxy-2-phenylpyridine)-
j2(N,N)-dihydridobis(3,5-dimethylpyrazolyl)borate
platinum(II) (4f)
Compound 4d was prepared similarly to 4c, using 2b
(99.0 mg, 0.165 mmol) and 3b (59.9 mg, 0.247 mmol) as
the starting materials (Rf ꢂ 0.5 in CHCl3/MeOH = 20/1).
Yield: 10.2 mg (10.6%).
Compound 4f was prepared similarly to 4a, using 2c
(101.1 mg, 0.137 mmol) and 3b (49.3 mg, 0.204 mmol) as
the starting materials (Rfꢂ 0.9 in CH2Cl2, Rf ꢂ 0.6 in Cy/
EE = 3/1). Yield: 60.6 mg (68.0%).
Anal. Calc. for C22H26BN5OPt: C, 45.37; H, 4.50.
1
Found: C, 45.32; H, 4.77%. H NMR (d, 20 ꢁC, CDCl3,
3
500 MHz): 8.48 (d, 1H, JHH = 5.6 Hz, Py6), 7.83 (t, 1H,
3
3JHH = 7.6 Hz, Py4), 7.69 (d, 1H, JHH = 8.1 Hz, Ph5),
Anal. Calc. for C27H36BN5OPt: C, 49.70; H, 5.56.
3
1
7.49 (d, 1H, JHH = 7.6 Hz, Py3), 7.26 (s, 1H, Ph2), 7.12
Found: C, 49.61; H, 5.32%. H NMR (d, 20 ꢁC, CDCl3,
(d, 1H, JHH = 8.3 Hz, 0Ph6), 7.02 (t, 1H, JHH = 6.1 Hz,
500 MHz): 8.34 (d, 1H, JHH = 7.8 Hz, Ph6), 8.21 (d,
3
3
3
Py5), 5.82 (s, 2H, Pz4,4 ), 4.61 (s, 2H, PhCH2OH), 2.34,
1H, JHH = 5.6 Hz, Py6), 7.35 (d, 1H, JHH = 8.5 Hz,
3
3
0
0
2.32, 2.28, 2.26 (s, 12H, CH33;3 ;5;5 ). 13C{1H} NMR (d,
Py4), 7.14 (d, 1H, JHH = 7.3 Hz, Ph3), 7.08–7.01 (m,
3
20 ꢁC, CDCl3, 125 MHz): 168.1 (1C, Ph3), 150.5 (1C,
2H, Ph4,5), 6.91 (t, 1H, JHH = 5.9 Hz, Py5), 5.80 (s, 2H,
3
0
0
Py6), 147.8, 146.8 (2C, Pz3,3 ), 145.3, 145.07, 145.05 (3C,
Pz4,4 ), 4.13 (t, 2H, JHH = 6.3 Hz, OHex1), 2.34, 2.31,
3

2776
F. Niedermair et al. / Inorganica Chimica Acta 360 (2007) 2767–2777
0
0
2.24 (m, 12H, CH33;3 ;5;5 ), 1.96–1.94 (m, 2H, OHex2), 1.56
(m, 2H, OHex5), 1.38 (m, 4H, OHex3,4), 0.93 (t, 3H,
3JHH = 7.1 Hz, OHex6). 13C{1H} NMR (d, 20 ꢁC, CDCl3,
125 MHz)0: 157.9 (1C, Ph2), 153.6 (1C, Py3), 147.8, 1460.8
(2C, Pz3,3 ), 146.3 (1C, Py2), 145.1, 144.8 (2C, Pz5,5 ),
143.8 (1C, Ph1), 142.7 (1C, Py6), 135.0 (1C, Ph6), 128.6,
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(1C, OHex4), 29.1 (1C, OHex2), 26.0 (1C, OHex3), 22.7
3;30;5;50
(1C, OHex5), 15.7, 14.2, 14.1, 13.3, 12.9 (5C, CH3
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(m), 2453 (s), 2370 (m), 2261 (w), 1734(w), 1570 (s), 1556
(m), 1538 (s), 1455 (s), 1426 (s), 1388 (m), 1305 (m), 1276
(s), 1234 (m), 1207 (m), 1160 (s), 1107 (s), 1058 (w), 1021
(w), 945 (w), 889 (m), 797 (m), 779 (m), 755 (s), 736 (s).
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Acknowledgements
Financial support by the Austrian Science Fund (FWF)
in the framework of the Austrian Nano Initiative (Re-
search Project Cluster 0700 – Integrated Organic Sensor
and Optoelectronics Technologies – Research Project
0701) is gratefully acknowledged.
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Appendix A. Supplementary material
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(1997) 1451.
CCDC 625970 contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free
of charge via http://www.ccdc.cam.ac.uk/conts/retriev-
ing.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/
j.ica.2007.02.001.
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