Selective synthesis of U-shaped terpyridines. Versatile ligands for the preparation of platinum complexes

Article abstract of DOI:10.1039/b316633c

The development of a simple and highly selective method for the preparation of substituted U-shaped terpyridines is described. The treatment of imine 5 with ternary iminium salts 2 leads to the terpyridines 4. A possible mechanism is discussed. The terpyridine derivatives are used for the preparation of several platinum(II) complexes 14. Complex 14e is characterized by single-crystal X-ray analysis.

Full text of DOI:10.1039/b316633c

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Selective synthesis of U-shaped terpyridines.
Versatile ligands for the preparation of platinum complexes
Dirk Sielemann, Andreas Winter, Ulrich Flörke and Nikolaus Risch*
Universität Paderborn, Fakultät für Naturwissenschaften, Department Chemie,
Warburger Str. 100, 33098 Paderborn, Germany. E-mail: nr@chemie.upb.de;
Fax: ϩ49 5251 603245; Tel: ϩ49 5252 602176
Received 12th December 2003, Accepted 3rd February 2004
First published as an Advance Article on the web 16th February 2004
The development of a simple and highly selective method for the preparation of substituted U-shaped terpyridines is
described. The treatment of imine 5 with ternary iminium salts 2 leads to the terpyridines 4. A possible mechanism is
discussed. The terpyridine derivatives are used for the preparation of several platinum() complexes 14. Complex 14e
is characterized by single-crystal X-ray analysis.
of a mixture of S- and U-shaped substituted terpyridines
Introduction
(Scheme 1).31 The two isomers are formed via different reaction
The design of oligopyridines and related compounds has
pathways. So far, we assumed them to be comparable with
recently been the subject of intensive investigations. Ligands
an aldol-type and a Michael-type reaction. Yet, it has not been
bearing 2,2Ј-bipyridine, 2,2Ј:6Ј,2Љ-terpyridine or 1,10-phenan-
possible to influence the ratio in which the two isomers are
throline subunits are extremely versatile building blocks for the
formed. Therefore, our efforts concentrated on mechanistic
construction of metallo-supramolecular systems.1–3 In recent
studies. Our main goal was to develop a new method, that
years, interest has focused on polypyridine derivatives, which
allows us to synthesize the U-shaped terpyridines selectively in
can be used for the synthesis of luminescent and redox-
good yields.
active polynuclear ruthenium complexes where energy- and/or
electron-transfer processes can be induced by light.4–7 A variety
of potential applications such as artificial photosynthesis,8
photocatalysis,9 molecular photovoltaic cells,10 molecular
informatics11 and opto-electronic devices12,13 are beginning to
emerge from this new field of research. Fused polypyridine
compounds also constitute an effective route to preorganised
clefts and cavities for the complexation of metals14–16 and
organic guests.17,18 Previously, several toroidal macrocycles
having potentially useful metal binding properties15 have been
synthesized.19
Lippard’s findings that (2,2Ј:6Ј,2Љ-terpyridine)-platinum()
complexes bind to double-stranded DNA by intercalation
have led to new approaches in cancer therapy.20 Recently, Lowe
et al. have shown that terpyridine–platinum() complexes also
exhibit cytotoxity against a number of ovarian tumour cell
lines.21–25 Several of these compounds showed even greater
activities than carboplatin, a therapeutic agent widely used for
the treatment of human ovarian cancers.
In view of these attractive applications, we were interested in
simple synthetic methods for the preparation of oligopyridines
bearing either 2,2Ј-bipyridine, 2,2Ј:6Ј,2Љ-terpyridine or 1,10-
phenanthroline subunits.
Scheme 1 Synthesis of U- and S-shaped terpyridines 3 and 4 in a
domino reaction.
Different methologies26–30 have been developed for these
heterocycles, but due to their great importance, the develop-
ment of novel and more flexible synthetic methods still remains
an active area of research. Our studies in the field of ternary
iminium salts have led to the development of highly efficient
one-pot domino-type reactions yielding a wide range of sub-
stituted pyridines, bipyridines or terpyridines.31–36 Domino
reactions offer many advantages compared to traditional
syntheses, such as minimization of waste and the consumption
of solvents, reagents, adsorbents and energy.
The method we used in the past was a one-pot reaction in
which ketone 1 and iminium salt 2 are reacted in the presence of
a large excess of ammonium acetate (3 eq.). These conditions
result in the formation of rather large quantities of the
S-shaped isomer 3 whereas the U-isomers 4 often can only be
isolated in low yields (Table 1, Method A). We presume,
that imine 5 is initially formed by the reaction of ammonium
acetate with ketone 1 as similar conditions are often used in the
literature for the preparation of imines.37 The nucleophilic
addition of 5 to the iminium salt 2 affords 6. Previously,
intermediates such as 6 have been isolated in our research
group.38 The reaction sequence is expected to be initiated by
the formation of imine 5, as NMR experiments showed that
ternary iminium salts do not react with ketone 1. Consecutive
deprotonation of the iminium salt and reprotonation at the
secondary amino group affords hydrochlorides 7. It is well
Results and discussion
As shown earlier, the reaction of one equivalent of an iminium
salt and two equivalents of 5,6,7,8-tetrahydroquinolinone in
the presence of ammonium acetate leads to the formation
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4
O r g . B i o m o l . C h e m . , 2 0 0 4 , 2, 8 6 3 – 8 6 8
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Table 1 Product distribution using the one-pot method (method A) and the sequential method (method B)
Iminium salt 2
R1
Method
Solvent
Product
Ratio S : U isomer
Yield (%)b
2a
A
B
CHCl3
DMSO
3a
4a
72 : 0
5 : 65
72
70
2b
2c
2da
2e
2f
A
B
CHCl3
DMSO
3b
4b
52 : 8
7 : 66
71
73
A
B
CH3CN
DMSO
3c
4c
45 : 39
0 : 64
84
64
A
B
CHCl3
DMSO
3d
4d
46 : 49
0 : 44
95
44
A
B
DMF
DMSO
3e
4e
31 : 29
0 : 61
60
61
A
B
CH3CN
DMSO
3f
4f
5 : 19
0 : 73
24
73
a Perchlorate. b Isolated yield after column chromatography on neutral Al2O3.
known, that Mannich bases easily undergo thermal elimination
of amine yielding α,β-unsaturated ketones.32,39 Here, the reac-
tion leads to the Michael acceptor 8. The S-shaped terpyridines
3 result from a condensation of 5 with β-amino imine 9, which
is formed by Michael-addition of ammonia to 8 (Scheme 2).
A very similar mechanism has been discussed by Bell et al.,
who have applied this method successfully to the synthesis of
heptacyclic terpyridyl clefts.15 Both studies let us conclude, that
the large excess of ammonia present in the reaction mixture
strongly favours the formation of 9 which in consequence leads
to the S-shaped terpyridine 3.
Scheme 3 Synthesis of U-shaped terpyridines 4.
mediate 8. The Michael acceptor 8 is efficiently trapped by the
ketone 1 (and not by ammonia) to afford the Michael-addition
product 10. Subsequent cyclization to 11 and oxidation of this
dihydropyridine then leads to the U-shaped terpyridines 4.
Since the iminium salts 2d–f are hydrolyzed very easily, the
imine 5 should be prepared in the presence of molecular sieves,
trapping the water formed during the condensation reaction.
The hydrolysis of the iminium salts can be prevented increasing
the yield of the U-shaped terpyridine. In conclusion, this new
method allows synthesizing U-shaped terpyridines in very good
yields, selectively.
Another of our interests was to investigate, if these terpyridine
derivatives 4 could be used for the preparation of platinum()
complexes. On the preparative basis of the reaction described
above, we employed a procedure developed by Lowe and
Vilaivan.25 Pt(COD)I2 (12) is treated with silver tetrafluoro-
borate in acetone followed by the addition of the U-shaped
terpyridine 4 in acetonitrile to give an acetonitrile terpyridine–
platinum() bis(tetrafluoroborate) complex 13. The aceto-
nitrile ligand can be displaced easily by donor-ligands, such
as 4-picoline, to yield the platinum complexes 14 (Scheme 4).
This protocol was applied to several differently substituted
terpyridines to give the products in very good yields (Table 2).
The crystal structure of 14e shows distorted square planar
coordination geometry of the Pt atom (Fig. 1).
Scheme 2 Postulated mechanism for the formation of the S-shaped
isomer 3.
As a result of these considerations, a new method (Table 1,
method B) was evolved in which imine 5 is synthesized
separately by preheating ketone 1 with one equivalent of
ammonium acetate in DMSO. Thereafter, the iminium salt 2
(1 eq.) and further ketone 1 (1 eq.) are added to the solution of
5. Actually, the formation of the S-isomer is suppressed while
the yield of the U-isomer is strongly increased. The postulated
mechanism is shown in Scheme 3. Just like in case of the
S-shaped isomer 3 the reaction sequence proceeds via inter-
Since the terpyridine ligand does not have an ideal tridentate
bite, the bond length Pt–N(2) (1.926(7) Å) is significantly
shorter than the Pt–N(1) and Pt–N(3) bonds (2.043(8) Å,
O r g . B i o m o l . C h e m . , 2 0 0 4 , 2, 8 6 3 – 8 6 8
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Fig. 1 Molecular structure of the cation of 14e. Selected bond lengths (Å) and angles (Њ): Pt–N1 2.043(8), Pt–N2 1.926(7), Pt–N3 2.048(8), Pt–N4
2.021(7), N2–Pt–N4 178.6(3), N2–Pt–N1 79.6(3), N4–Pt–N1 99.6(3), N2–Pt–N3 80.4(3), N4–Pt–N3 100.4(3), N1–Pt–N3 160.0(3). The Pt atom lies
0.016 Å above the N4-plane.
ovarian tumour cell lines is likely to be a result of this
property.21,40
So far, only derivatives with ethylene bridges have been syn-
thesized. Since this new method should allow the preparation
of terpyridines with varying tridentate bite angles, a large
number of complexes with high chemical diversity can be
envisioned. The direct modulation of the Pt–N(2) bond length
should be possible thereby determining the activity of platinum
complexes.
Experimental
General
All reagents were purchased from commercial sources and
used without further purification unless specified. All solvents
were dried and distilled according to standard procedures
and stored under argon. Chromatographic separation was per-
formed on aluminum oxide (neutral, Akt. III, Fa. Macherey &
Nagel, 0.063–0.200 mm). Melting points were obtained on a
Büchi SMP-20 mp apparatus and are uncorrected. IR spectra
were measured on a Nicolet 510 P FT-IR spectrometer. All
NMR spectra were recorded on a Bruker ARX 200 instrument
(200 bzw, 50 MHz). Mass spectrometry was carried out using a
Finigan MAT 8200 (EI MS, 70 eV) or a Finnigan MAT 8230
apparatus (FAB MS, m-nitrobenzyl alcohol matrix). Elemental
analyses were obtained on a Perkin-Elmer M240 analyzer. UV
spectra were measured on a Shimadzu UV-2101 PC spectro-
meter. Ketone 1 and iminium chlorides 2 were prepared by
procedures described in the literature.41–45
Scheme 4 Preparation of terpyridine platinum() complexes 14.
Table 2 Synthesis of terpyridine platinum() complexes 14
P()-complex 14
U-terpyridine 4
Yield (%)a
14a
14b
14c
14d
14e
14f
4a
4b
4c
4d
4e
4f
66
63
72
50
60
51
General procedure for the synthesis of substituted U-shaped
terpyridines 4a–c
a Isolated yield after crystallization from CH3CN–E2O.
A
solution of 5,6,7,8-tetrahydroquinolinone 1 (150 mg,
1.01 mmol) and ammonium acetate (85 mg, 1.1 mmol) in dry
DMSO (10 ml) was heated at 85 ЊC for 5 min. In a second
flask 5,6,7,8-tetrahydroquinolinone 1 (150 mg, 1.01 mmol) and
iminium salt 2 (291 mg, 1.01 mmol) were dissolved in dry
DMSO (10 ml). The solution of the iminium salt and the
ketone was then added to the solution of the freshly prepared
imine 5 and heated for 16 h at 120 ЊC. The reaction mixture was
cooled to room temperature and water (40 ml) was added.
The solution was then extracted with CH2Cl2 (3 × 30 ml). The
combined organic layers were washed with water (3 × 20 ml)
2.048(8) Å respectively). Observations for similar complexes
made by Lowe et al. suggest that this distortion results in a
trans-effect which in consequence should weaken the Pt–N(4)
(2.021(7) Å) bond.24 Therefore, the substitution of the 4-pico-
line ligand by an associative mechanism is strongly favoured.
Obviously, the trans-effect is responsible for the unusual ease
of substitution of the 4-picoline ligand by a nucleobase.
The high activity of terpyridine–platinum() complexes against
O r g . B i o m o l . C h e m . , 2 0 0 4 , 2, 8 6 3 – 8 6 8
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and dried over MgSO4. After removal of the solvent, the
of the solvent, the residue was purified by chromatography
residue was purified by chromatography on Al2O3.46
on Al2O3.46
5,6,8,9-Tetrahydro-7-(3Ј-bromophenyl)quino[8,7-b][1,10]-
phenanthroline (4a). Prepared from 1 (600 mg, 4.02 mmol),
3-brombenzylidenemorpholinium chloride 2a (580 mg, 2.01
mmol) and ammonium acetate (170 mg, 2.20 mmol). Yield:
573 mg (65%), yellow powder, after chromatography on Al2O3,
CH2Cl2; CH2Cl2–MeOH, 25 : 1, mp >270 ЊC46 (Found: C,
68.23; H, 4.05; N 9.41. C25H18BrN3 requires C, 68.19; H, 4.12;
N, 9.54%); νmax(KBr)/cmϪ1 3934, 2945, 2836, 1553, 1440, 1393,
1222, 1114, 928, 906, 793, 726; δH(200 MHz; CDCl3; SiMe4)
2.72 (mc, 4 H, CH2), 2.89 (mc, 4 H, CH2), 7.24 (mc, 3 H), 7.41
(mc, 2 H), 7.58 (mc, 3 H), 8.71 (d, 3J = 4.7 Hz, 2 H); δC(50 MHz,
CDCl3, SiMe4) 25.9 (t), 27.8 (t), 123.3 (s), 123.7 (d), 127.8 (d),
130.8 (d), 131.9 (d), 132.3 (s), 133.4 (s), 135.5 (d), 139.8 (s),
146.4 (s), 149.6 (d), 151.4 (s), 152.6 (s); m/z (EI MS): 441
([M(81Br)ϩ], 77), 440 ([M(81Br)ϩ] Ϫ H, 91), 439 ([M(79Br)ϩ],
100), 438 ([M(79Br)ϩ] Ϫ H, 85), 360 (17), 358 (21), 284 (10), 282
(15), 220 (6), 180 (39), 178 (41).
5,6,8,9-Tetrahydro-7-(4Ј-N,N-diethylaminophenyl)quino-
[8,7-b][1,10]phenanthroline (4d). Prepared from 1 (294 mg, 2.0
mmol), N,N-dimethyl-4Ј-(diethylamino)benzylidene ammon-
ium chloride 2d (205 mg, 1.0 mmol) and ammonium acetate
(80 mg, 1.0 mmol). Yield: 190 mg (44%), brown powder, after
chromatography on Al2O3, CH2Cl2–MeOH, 50 : 1, mp >300 ЊC
(lit.,31 yield: 37%, mp >300 ЊC) (Found C, 80.62; H, 6.52; N,
12.95. C29H28N4 requires C, 80.52; H, 6.52; N, 12.95%);
νmax(KBr)/cmϪ1 2100, 2009, 1981, 1945, 1923, 1894, 1462, 1365,
3
1190; δH(200 MHz, CDCl3, SiMe4) 1.19 (t, J = 6.50 Hz, 6 H),
2.68–2.98 (m, 8 H), 3.40 (mc, 4 H), 6.75 (mc, 2 H), 7.00 (mc,
2 H), 7.19 (mc, 2 H), 7.52 (mc, 2 H), 8.67 (mc, 2 H); δC(50 MHz,
CDCl3, SiMe4) 11.9 (q), 24.8 (t), 26.7 (t), 43.5 (t), 110.5 (t), 11.4
(d), 122.1 (s), 122.7 (d), 129.1 (d), 129.3 (d), 132.5 (s), 132.9 (s),
134.9 (d), 146.6 (s), 147.4 (d), 147.7 (s), 149.3 (s), 151.6 (s).
5,6,8,9-Tetrahydro-7-(4Ј-methoxyphenyl)chino[8,7-b][1,10]-
phenanthroline (4e). Prepared from 1 (294 mg, 2.0 mmol),
N,N-dimethyl-4Ј-(methoxy)benzylidene ammonium chloride 2e
(199 mg, 1.0 mmol) and ammonium acetate (80 mg, 1.0 mmol).
Yield: 241 mg (61%), brown powder, after chromatography on
Al2O3, CH2Cl2–MeOH, 50 : 1, mp >300 ЊC (lit.,31 yield: 28%,
mp >300 ЊC) (Found C, 80.02; H, 5.51; N, 10.56. C26H21N3O
requires C, 79.77; H, 5.41; N, 10.73%); νmax(KBr)/cmϪ1 3050,
2930, 2835, 1605, 1570, 1505, 1450, 1430, 1400, 1385, 1285,
1240, 1170, 1110, 1025, 845; δH(200 MHz, CDCl3, SiMe4)
2.70–2.75 (m, 4 H, CH2), 2.83–2.89 (m, 4 H, CH2), 3.89 (s, 3 H,
OCH3), 7.04 (mc, 2 H), 7.14 (mc, 2 H), 7.21 (dd, 3J = 7.6, 4.8 Hz,
5,6,8,9-Tetrahydro-7-(4Ј-bromophenyl)quino[8,7-b][1,10]-
phenanthroline (4b). Prepared from 1 (600 mg, 4.02 mmol),
4-brombenzylidenemorpholinium chloride 2b (580 mg, 2.01
mmol) and ammonium acetate (180 mg, 2.20 mmol). Yield:
582 mg (66%), yellow powder, after chromatography on Al2O3,
CH2Cl2; CH2Cl2–MeOH, 25 : 1, mp 290 ЊC (dec.) (lit.,47 yield:
8%, mp 291 ЊC) (Found: C, 68.06; H, 4.13; N 9.33. C25H18BrN3
requires C, 68.19; H, 4.12; N, 9.54%); νmax(KBr)/cmϪ1 3062,
3003, 2942, 2885, 2844, 1678, 1579, 1540, 1490, 1457, 1452,
1401, 1222, 1201, 1113, 1067, 1011, 847; δH(200 MHz, CDCl3,
SiMe4) 2.75 (mc, 4 H, CH2), 2.94 (mc, 4 H CH2), 7.34 (mc, 4 H),
7.75 (mc, 4 H), 8.66 (mc, 2 H); δC(50 MHz, CDCl3, SiMe4) 25.6
(t), 27.6 (t), 122.7 (s), 124.1 (d), 130.7 (d), 132.6 (d), 132.6 (s),
133.8 (s), 136.3 (d), 147.2 (s), 148.9 (d), 150.6 (s), 152.2 (s);
m/z (EI MS): 441 ([M(81Br)ϩ], 81), 440 ([M(81Br)ϩ] Ϫ H, 97), 439
([M(79Br)ϩ], 100), 438 ([M(79Br)ϩ] Ϫ H, 89), 360 (28), 358 (33),
284 (12), 282 (18), 220 (6), 180 (37), 178 (36).
3
4
3
2 H), 7.52 (dd, J = 7.6 Hz, J = 1.6 Hz, 2 H), 8.75 (dd, J =
4
4.8 Hz, J = 1.6 Hz, 2 H); δC(50 MHz, CDCl3, SiMe4) 25.5 (t),
27.5 (t), 55.4 (q), 114.2 (d), 123.2 (d), 129.3 (s), 129.9 (d), 132.7
(s), 132.2 (s9, 135.2 (d), 147.5 (s), 148.9 (d), 150.5 (s), 152.4 (s),
159.3 (s).
5,6,8,9-Tetrahydro-7-(1-furfuryl)quino[8,7-b][1,10]phen-
anthroline (4f ). Prepared from 1 (294 mg, 2.0 mmol), 2-furfuryl-
piperidinium chloride 2f (199 mg, 1.00 mmol) and ammonium
acetate (80 mg, 1.0 mmol). Yield: 255 mg (73%), brown powder,
after chromatography on Al2O3, CH2Cl2–MeOH, 50 : 1, mp
>300 ЊC (lit.,31 yield: 75%, mp >300 ЊC) (Found C, 78.44;
H, 5.02; N, 12.05. C23H17N3O requires C, 78.61; H, 4.88; N,
11.96%); νmax(KBr)/cmϪ1 3292, 3051, 2934, 2838, 1698, 1576,
1547, 1456, 1370, 1208, 1113, 1013, 884, 818; δH(200 MHz,
CDCl3, SiMe4) 2.89 (mc, 8 H, CH2), 6.48 (mc, 1 H), 6.56 (mc,
1 H), 7.19 (mc, 2 H), 7.51 (mc, 2 H), 7.59 (s, 1 H), 8.72 (mc, 2 H);
δC(50 MHz, CDCl3, SiMe4) 25.8 (t), 27.6 (t), 11.3 (d), 112.5 (d),
123.6 (d), 133.6 (s), 135.6 (s), 135.5 (d), 137.1 (s), 143.3 (d),
148.4 (s), 149.3 (d), 151.3 (s), 152.5 (s), 197.1 (s); m/z (EI MS):
351 ([Mϩ], 97), 350 (100), 349 (88), 320 (57), 282 (85), 255 (10),
175 (7), 160 (22).
5,6,8,9-Tetrahydro-7-phenylquino[8,7-b][1,10]phenanthroline
(4c). Prepared from 1 (600 mg, 4.02 mmol), benzylidene-
morpholinium chloride 2c (422 mg, 2.01 mmol) and ammo-
nium acetate (180 mg, 2.20 mmol). Yield: 467 mg (65%),
yellow crystals, after chromatography on Al2O3, CH2Cl2–
MeOH, 25 : 1, mp 254 ЊC (dec.) (lit.,31 yield: 45%, mp 254 ЊC).
The compound is isolated as the mono hydrate (Found C,
77.75; H, 5.53; N, 11.17. C25H21N3O requires C, 79.13; H, 5.58;
N, 11.07%); νmax(KBr)/cmϪ1 3650, 3040, 2972, 2828, 1564, 1540,
1433, 1382, 1217, 1110, 810; δH(200 MHz, CDCl3, SiMe4) 2.70
(mc, 4 H, CH2), 2.88 (mc, 4 H, CH2), 7.19 Ϫ 7.24 (m, 4 H), 7.45
Ϫ 7.56 (m, 5 H), 8.75 (dd, 3J = 4.8 Hz, 4J = 1.6 Hz, 2 H); δC(50
MHz, CDCl3, SiMe4) 25.4 (t), 27.4 (t), 123.5 (d), 128.0 (d),
128.6 (d), 128.9 (d), 132.4 (s), 133.4 (s), 135.6 (d), 137.3 (s),
147.9 (s), 148.7 (d), 150.4 (s), 152.2 (s); m/z (EI MS): 361 ([Mϩ],
100), 360 (66), 359 (16), 358 (21), 356 (10), 180 (11), 179 (11),
178 (15).
Preparation of terpyridine-platinum complexes 14a–f
To a suspension of diiodo(cycloocta-1,5-diene)platinum 12
(55 mg, 0.10 mmol) in acetone (1 ml) was added silver tetra-
fluoroborate (40 mg, 0.21 mmol). The resulting mixture was
stirred at room temperature until a colorless solution was
obtained (20–30 min). The AgI precipitate was then removed
by filtration. The solution was added to a suspension of ter-
pyridine 4 (0.08 mmol) in acetonitrile (0.5 ml) and the reaction
mixture was stirred at room temperature for another 30 min.
The acetonitrile complex precipitating was collected by centri-
fugation, suspended in acetonitrile (1 ml) and treated with
4-picoline (20 µl) for 30 min to give a clear solution. The
picoline complex was precipitated by addition of diethyl ether
to give the crude complex, which was recrystallized from
acetonitrile by slow diffusion of diethyl ether vapour.46
General procedure for the synthesis of substituted terpyridines
4d–f
A suspension of 1 (150 mg, 1.01 mmol), ammonium acetate
(85 mg, 1.1 mmol) and ground molecular sieves (4 Å, 200 mg)
in dry DMSO (10 ml) was heated at 85 ЊC for 5 min. Iminium
salt 2 (291 mg, 1.01 mmol) dissolved in dry DMSO (5 ml)
was then added; finally, after another 5 min at 85 ЊC, 1 (150 mg,
1.01 mmol) was added. The resulting mixture was heated for
16 h at 120 ЊC and then cooled to room temperature. Water
(40 ml) was added and the resulting mixture was extracted with
CH2Cl2 (3 × 30 ml). The combined organic layers were washed
with water (3 × 20 ml) and dried over MgSO4. After removal
O r g . B i o m o l . C h e m . , 2 0 0 4 , 2, 8 6 3 – 8 6 8
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Complex 14a: [Pt(L)4-picoline][BF4]2 (L ؍ 4a). Prepared
from PtCODI2 (55 mg, 0.10 mmol), AgBF4 (40 mg, 0.20 mmol),
4a (35 mg, 0.04 mmol) and 4-picoline (25 µl). Yield 47 mg
(66%), yellow crystals, after crystallization from CH3CN–Et2O,
mp >250 ЊC;46 νmax(KBr)/cmϪ1 3048, 1631, 1610, 1439, 1418,
1067; δH(200 MHz, CD3CN, SiMe4) 2.68 (s, 3 H, CH3), 2.99
(mc, 4 H, CH2), 3.31 (mc, 4 H, CH2), 7.41 (mc, 1 H), 7.54–7.87
(m, 19 H), 8.16 (mc, 2 H), 8.87 (mc, 1 H); δC(50 MHz, CD3CN,
SiMe4) 21.0 (q), 24.0 (t), 26.0 (t), 123.0 (s), 127.5 (d), 129.2 (d),
129.3 (d), 131.0 (d), 131.6 (d), 132.9 (d), 135.6 (s), 137.1 (s),
137.4 (s), 138.9 (s), 139.3 (s), 142.9 (d), 149.5 (s), 150.3 (d), 152.1
(d), 155.3 (s), 155.5 (s); m/z (FABϩ): 815 ([M Ϫ BF4]ϩ, 20), 728
([M Ϫ 2 BF4]ϩ, 19), 635 ([M Ϫ 2 BF4 Ϫ picoline]ϩ, 41).
CH3), 7.18–7.38 (m, 4 H), 7.52–7.88 (m, 6 H), 8.13–8.27 (m,
2 H), 8.55–8.97 (m, 2 H); δC(50 MHz, CD3CN, SiMe4) 21.0 (q),
24.1 (t), 24.32 (t), 26 (13 (t), 26.5 (t), 55.7 (q), 55.8 (t), 114.9 (d),
115.0 (d), 125.2 (d), 129.0 (d), 129.3 (d), 129.4 (d), 129.5 (d),
130.1 (d), 131.4 (d), 137.2 (s), 138.9 (s), 142.8 (d), 150.2 (d),
152.1 (d), 155.2 (s), 155.8 (s), 161.0 (s).
X-Ray structure analysis of 14e48. [C32H28N4OPt][BF4]2*2
CH3CN, Mr = 935.4 g molϪ1, crystal size 0.60 × 0.12 ×
0.08 mm3, T = 193(2) K, monoclinic, space group P21/n,
a = 19.275(4), b = 8.415(3), c = 23.953(5) Å, β = 111.90(1)Њ, V =
3605(1) Å3, Z = 4, Dc = 1.724 g cmϪ3, µ = 3.974 mmϪ1, F(000) =
1840. Data collection was performed on a Bruker AXS P4
diffractometer using graphite monochromated Mo-Kα radi-
ation, ω-scan, 2.5 < θ< 25.0Њ, index ranges h: Ϫ1/22, k: Ϫ10/1,
l: Ϫ28/26; 7818 reflections collected, 6263 unique reflections,
LP correction, gaussian absorption correction. Structure
solved by direct and conventional Fourier synthesis, full-matrix
least-squares refinement based on F 2 and 489 parameters,
all but H atoms refined anisotropically, H atoms refined with
riding model. Refinement converged at R1 (I > 2σ(I )) = 0.053,
wR2 (all data) = 0.136, S = 1.025, min./max. height in final
∆F map Ϫ0.88/0.93 e ÅϪ3. The structure consists of one cation,
two tetrafluoroborate anions and two acetonitrile solvent
molecules per asymmetric unit.† Programs used: SHELXTL.49
Complex 14b: [Pt(L)4-picoline][BF4]2 (L ؍ 4b). Prepared
from PtCODI2 (55 mg, 0.10 mmol), AgBF4 (40 mg, 0.20 mmol),
4b (35 mg, 0.04 mmol) and 4-picoline (25 µl). Yield: 45 mg
(63%), yellow crystals, after crystallization from CH3CN–Et2O,
mp >250 ЊC;46 νmax(KBr)/cmϪ1 2913, 2365, 1610, 1403, 1051;
δH (200 MHz, CD3CN, SiMe4) 2.68 (s, 3 H, CH3), 2.99 (mc, 4 H,
CH2), 3.30 (mc, 4 H, CH2), 7.32 (mc, 2 H), 7.60–7.87 (m, 8 H),
8.14 (d, 3J = 7.8 Hz, 2 H), 8.84 (mc, 2 H); δC(50 MHz, CD3CN,
SiMe4) 21.0 (q), 24.0 (t), 26.0 (t), 123.8 (s), 129.1 (d), 129.3 (d),
130.5 (d), 132.5 (d), 132.8 (d), 137.0 (s), 138.9 (s), 142.9 (d),
149.5 (s), 150.3 (d), 152.1 (d), 152.7 (s), 155.3 (s), 155.5 (s);
m/z(FABϩ): 815 ([MϪBF4]ϩ, 23), 728 ([M Ϫ 2 BF4]ϩ, 22), 635
([M Ϫ 2 BF4 Ϫ picoline]ϩ, 31).
Complex 14f: [Pt(L)4-picoline][BF4]2 (L ؍4f ). Prepared form
PtCODI2 (55 mg, 0.10 mmol), AgBF4 (40 mg, 0.20 mmol), 4f
(29 mg, 0.08 mmol) and 4-picoline (25 µl). Yield: 33 mg (51%),
yellow crystals, after crystallization from CH3CN–Et2O, mp
>250 ЊC;46 νmax(KBr)/cmϪ1 2919, 2852, 1600, 1435, 1057; δH(200
MHz, CD3CN, SiMe4) 2.68 (s, 3 H, CH3), 3.39 (mc, 8 H, CH2),
Complex 14c: [Pt(L)4-picoline][BF4]2 (L ؍ 4c). Prepared
from PtCODI2 (55 mg, 0.10 mmol), AgBF4 (40 mg, 0.20 mmol),
4c (29 mg, 0.08 mmol) and 4-picoline (25 µl). Yield: 47 mg
(72%), yellow crystals, after crystallization from CH3CN–Et2O,
mp >250 ЊC;46 νmax(KBr)/cmϪ1 3058, 1624, 1608, 1411, 1429,
1035, 803; δH(200 MHz, CD3CN, SiMe4) 2.68 (s, 3 H, CH3),
2.99 (m, 4 H, CH2), 3.30 (m, 4 H, CH2), 7.41 (mc, 2 H), 7.52–
3
3
3
6.85 (dd, J = 3.5 Hz, J = 1.8 Hz, 1 H), 7.35 (d, J = 3.5 Hz,
1 H), 7.60–7.77 (m, 7 H), 7.93 (d 3J = 1.8 Hz, 1 H), 8.17
3
4
3
(dd, J = 7.5 Hz, J = 1.4 Hz, 2 H), 8.84 (d, J = 7.2 Hz, 2 H);
δC(50 MHz, CD3CN, SiMe4) 21.0 (q), 24.8 (t), 26.1 (t), 112.7
(d), 117.3 (d), 129.1 (d), 129.3 (d), 136.0 (s), 138.9 (s), 141.4 (s),
142.8 (d), 146.0 (s), 146.2 (d), 149.7 (s), 150.1 (d), 152.1 (d),
155.3 (s), 155.6 (s).
3
3
7.87 (m, 9 H), 8.15 (d, J = 7.7 Hz, 2 H), 8.86 (d, J = 5.4 Hz,
2 H); δC(50 MHz, CD3CN, SiMe4) 21.0 (q), 24.0 (t), 26.1 (t),
128.3 (d), 129.1 (d), 129.3 (d), 129.3 (d), 130.0 (d), 133.4 (s),
137.0 (s), 138.9 (s), 142.9 (d), 149.5 (s), 150.3 (d), 152.1 (d),
154.0 (s), 155.3 (s), 155.7 (s); m/z (FABϩ): 734 ([ M Ϫ BF4]ϩ, 8),
648 ([M Ϫ 2 BF4]ϩ, 10), 576 ([M Ϫ 2 BF4 Ϫ picoline ϩ F]ϩ, 29),
555 ([M Ϫ 2 BF4]ϩ, 30); λmax(CH3CN): 419 (ε/dm3 molϪ1 cmϪ1
6000), 398 (4100), 317 (17700), 2667 (5900), 239 (4900).
† CCDC reference number 152310. See http://www.rsc.org/suppdata/
ob/b3/b316633c/ for crystallographic data in.cif or other electronic
format.
Complex 14d: [Pt(L)4-picoline][BF4]2 (L ؍ 4d). Prepared
from PtCODI2 (55 mg, 0.10 mmol), AgBF4 (40 mg, 0.20 mmol),
4d (35 mg, 0.08 mmol) and 4-picoline (25 µl). The solvent was
removed in vacuo as the acetonitrile complex did not precipi-
tate. The desired complex can be prepared following the pro-
cedure described for the other complexes. Yield: 32 mg (50%),
violet crystals, after crystallization from CH3CN–Et2O, mp
>250 ЊC;46 νmax(KBr)/cmϪ1 2919, 1610, 1408, 1057; δH(200
MHz, CD3CN, SiMe4) 1.24 (t, 3J = 6.9 Hz, –CH2CH3), 2.57 (s,
3 H, CH3), 3.07 (mc, 4 H, CH2), 3.30 (mc, 4 H, CH2), 3.51 (q,
3J = 6.9 Hz, 4 H, –CH2CH3), 6.91 (d, 3J = 8.8 Hz, 2 H), 7.23 (d,
3J = 8.8 Hz, 2 H), 7.58–7.77 (m, 6 H), 8.14 (d, 3J = 7.7 Hz, 2 H),
8.86 (d, 3J = 6.4 Hz, 2 H); δC(50 MHz, CD3CN, SiMe4) 12.2 (q),
21.0 (q), 24.4 (t), 26.3 (t), 44.5 (t), 111.5 (d), 118.6 (s), 128.9 (d),
129.3 (d), 130.2 (d), 136.9 (s), 138.8 (s), 142.7 (d), 149.0 (s),
149.2 (s), 150.1 (d), 152.1 (d), 154.8 (s), 155.2 (s), 156.0 (s);
λmax(CH3CN): 496 (ε/dm3 molϪ1 cmϪ1 4500), 419 (4000), 349
(3300), 316 (14100), 300 (13700), 282 (13600), 244 (800).
Acknowledgments
We thank the Fonds der Chemischen Industrie, the Deutsche
Forschungsgemeinschaft and the Grünenthal GmbH for the
financial support of this work.
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