Synthesis of soluble, linear bisphenanthrolines for the construction of heteroleptic nanoGrids and nanoboxes

Article abstract of DOI:10.1055/s-2001-16093

The preparation of several new and soluble bisphenanthrolines that are important building blocks for various supramolecular structures based on heteroleptic copper(I) complexes is described.

Full text of DOI:10.1055/s-2001-16093

PAPER
1561
Synthesis of Soluble, Linear Bisphenanthrolines for the Construction of
Heteroleptic NanoGrids and Nanoboxes
Synthesisof Soluble,
L
i
inear
B
c
isphenanth
h
r
olines ael Schmittel,* Christoph Michel, Andreas Wiegrefe, Venkateshwarlu Kalsani
FB 8-OC1 (Chemie und Biologie), Universität Siegen, Adolf-Reichwein-Strasse, 57068 Siegen, Germany
Fax +(49)2713270; E-mail: schmittel@chemie.uni-siegen.de
Received 12 March 2001; revised 10 April 2001
acterized by bulky ortho-aryl substituents at the bisimine
binding sites is warranted.
For systematic studies of the coordination chemisty,5 we
first chose to synthesize a small series of bisphenanthro-
Abstract: The preparation of several new and soluble bisphenan-
throlines that are important building blocks for various supramolec-
ular structures based on heteroleptic copper(I) complexes is
described.
Key words: palladium, cross-coupling, nucleophilic substitution, line ligands 1 bearing sterically encumbered groups
phenanthrolines
(Scheme 1). The mesityl or duryl groups not only serve to
control the heteroleptic complex formation but should
also help to raise the solubility, which is a notorious prob-
lem for longer linear polytopic bisimines.13 As rigid linear
Currently, there is enormous interest in the design and
spacers between the phenanthroline, we chose to test
butadiyne 1,4-diethynylbenzene and diethynylbiphenyl.
preparation of polydentate ligands capable of self-assem-
bly processes.1 Among the polydentate ligands, oligo-
2,2 -bipyridines2 and oligophenanthrolines3 have assumed
a particular standing because in presence of numerous
metal cations they form strong complexes with a predict-
able spatial arrangement, an advantage used extensively
for the preparation of various supramolecular architec-
tures, e.g., ladders, grids, rotaxanes, helicates, and oth-
ers.1,2
spacer
N
N
N
N
1
Multi-ion nanometer-sized lattice or grid structures may
open interesting perspectives for the creation of molecu-
lar-level devices.4 As the leading pioneer in this field,
Lehn et al. have elaborated numerous single-ligand [n n]
grids (mostly n = 2,3) on the basis of bipyridine sub-
units.5,6 Defects in [5 5] grids caused by one lacking
ligand have recently led to a single example of a [4 5]
grid,4 while filling of interstitial spaces in [2 2] grids
driven by , -stacking have formally resulted in [3 3]
bisbipyridine grids.7
= mesityl or 4-bromo-duryl
spacer
= different bisalkynes
Y
Y
Scheme 1
The starting point of our synthetic strategy was 3-bro-
mophenanthroline (2),14 which, following a protocol of
Sonogashira,15 was coupled with trimethylsilylacetylene
in the presence of [PdCl2(PPh3)2] and CuI to provide 3 in
92% yield (Scheme 2). The arene groups were then added
in positions 2 and 9 by nucleophilic substitution according
to Sauvage.16 After some optimization, we realized that
the stepwise addition of both aryl groups was superior to
the one-pot procedure. Interestingly, upon addition of 1.5
equivalents of the aryl lithium compound (prepared by
halogen-metal exchange after analysis by GC) to 3, a
highly regioselective addition in position 2 occurred. Only
in one case, the 9-addition product was detected in traces.
The addition products were isolated (in the mesityl case as
bright yellow crystals) and oxidized with activated man-
ganese dioxide to afford the monosubstituted phenanthro-
lines 4a,b.
While the above examples were based on homoleptic
complexes ( = single-ligand systems), a spectacular ex-
ample of a [nA mB] grid (ligand A with n binding sites +
ligand B with m binding sites), i.e. a [2 3] grid8 has been
described recently. Its thermodynamically controlled for-
mation, however, was accompanied by small amounts of
the [2 2] and [3 3] grids. Hence, we now propose to de-
velop a general and quantitative route to heteroleptic
[nA mB] grids by making use of our concept for the clean
formation of heteroleptic copper(I)9 and silver(I)10
bisphenanthroline complexes. The performance of our
concept has already been demonstrated for simple and
nanosize structures.11 As it critically depends on a fine
balance of steric shielding and of , -interactions,9,10 the
preparation of a series of linear bisphenanthrolines12 char-
In the second substitution step, a mesityl group was intro-
duced in position 9 following the same protocol as men-
tioned above. Again, the halogen-metal exchange had to
be controlled carefully. In one case, the butylsubstituted
phenanthroline 7 (9%) was furnished when we used an
Synthesis 2001, No. 10, 30 07 2001. Article Identifier:
1437-210X,E;2001,0,10,1561,1567,ftx,en;T02201SS.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0039-7881

1562
M. Schmittel et al.
PAPER
i)
SiMe3
Br
SiMe3
N
N
N
N
N
N
2
3
7
ii), iii)
iv), v), vi)
SiMe3
N
N
Ar
4a Ar = mesityl (69%)
4b Ar = bromoduryl (73%)
SiMe3
N
N
SiMe3
vii)
N
N
Ar
8
5a Ar = mesityl (68%)
5b Ar = bromoduryl (83%)
I
N
N
H
N
N
Ar
9
6a Ar = mesityl (95%)
6b Ar = bromoduryl (95%)
Figure
Scheme 2 Reagents
and
conditions:
i)
HC C(TMS),
[PdCl2(PPh3)2], CuI, benzene, Et3N, 80–90 °C, 1 d; ii) ArBr, n-BuLi,
Et2O; iii) MnO2, CH2Cl2; iv) MesBr, n-BuLi, Et2O; v) H2O; vi)
MnO2; vii) KOH (aq)
of 6a with 4,4 -dibromobiphenyl under Pd-catalysis
failed; the starting material was recovered. Isolation of the
pure bisphenanthrolines was readily achieved by column
chromatography and subsequent recrystallization from
cyclohexane.
excess of n-butyllithium (Figure). On the other side, the
use of a large excess of mesityllithium led to double sub-
stitution resulting in the formation of phenanthroline 8.
Such a double substitution has been observed for
phenanthroline17 and pyridines,18 though only in few cas-
es.
As a reference, we also synthesized the unsymmetrical
bisphenanthroline 14 that combines a steric encumbered
phenanthroline with an unhindered one. It was prepared
via Sonogashira coupling by the reaction of 6a with
phenanthroline 13 (Scheme 5).22
After deprotection of 5 with aqueous KOH, we obtained
the free acetylene 6 constituting a useful precursor for the
bisphenanthrolines.
In summary, a method for the convergent preparation of
linear bisphenanthrolines with bulky groups at the bi-
simine site has been developed. As a key step, the cou-
pling of various diiodo compounds with substituted
ethynylphenanthrolines was used.
The bisphenanthrolines 10–12 were obtained employing
two different methods. Various attempts to synthesize the
desired bisphenanthroline 10 using Hay oxidation
conditions19 failed, while coupling of 6a under Pd-
catalyzed20 conditions readily afforded 10a in 51% yield
(Scheme 3). The product could be purified by column
chromatography.
PdCl2(PPh3)2, CuI,
Et3N, 80 °C, 16 h, O2
(benzene)
6a,b
Pd/Cu-catalyzed Sonogashira coupling15,21 of 6a,b with
1,4-diiodobenzene and 4,4 -diiodobiphenyl, respectively
afforded the corresponding bisphenanthrolines 11a,b and
12a,b in yields from 31–92% (Scheme 4). For best yields,
the reaction was conveniently monitored by ESI-MS
spectroscopy. As a side product, linear phenanthrolines
10a or 10b were found in traces. Coupling at room tem-
perature under the same conditions led to the
monophenanthroline 9 (Figure) in very low yield. Alter-
natively, attempts to synthesize 12a through the coupling
N
N
N
N
Ar
Ar
10a Ar = mesityl (51%)
10b Ar = bromoduryl
Scheme 3
Synthesis 2001, No. 10, 1561–1567 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Synthesis of Soluble, Linear Bisphenanthrolines
1563
were carried out with a Carlo Erba Elemental Analyzer 1106. Elec-
trospray mass spectra (ESI-MS) were recorded using a Thermo-
Quest LCQ Deca. TLC was done on SiO2 (silica gel 60 F254, Merck).
The degree of lithiation can readily be monitored by GC, while
progress of substitution at phenanthroline is best controlled by ESI-
MS.
2
H
I
I
N
N
n
Ar
PdCl2(PPh3)2, CuI,
Et3N, 80 °C, 2 d,
(benzene)
6a Ar = mesityl
6b Ar = bromoduryl
2-(2,4,6-Trimethylphenyl)-3-(trimethylsilanylethynyl)-1,2-
dihydro-[1,10]phenanthroline
A solution of 1-bromo-2,4,6-trimethylbenzene (3.69 g, 18.5 mmol)
in anhyd Et2O (45 mL) was treated dropwise with n-BuLi (2.5 M in
hexane, 12.4 mL, 31.0 mmol) and stirred for 14 h at 0 °C. After ad-
dition of 3-trimethylsilanylethynyl-[1,10]phenanthroline22 (1.80 g,
6.52 mmol), the resulting purple solution was stirred for 22 h at r.t.
After hydrolysis with aqueous NH4Cl (50 mL) and separation of the
phases, the aqueous layer was extracted with CH2Cl2 (3 30 mL).
The combined organic layers were dried (MgSO4) and the solvents
were removed to give a bright yellow oil. After adding pentane (20
mL), yellow crystals of 2-(2,4,6-trimethylphenyl)-3-(trimethylsila-
nylethynyl)-1,2-dihydro-[1,10]phenanthroline precipitated (1.99 g,
69%).
N
N
N
N
n
Ar
Ar
11a n = 1, Ar = mesityl (75%)
11b n = 1, Ar = bromoduryl (92%)
12a n = 2, Ar = mesityl (31%)
12b n = 2, Ar = bromoduryl (71%)
Scheme 4
Mp 188–190 °C.
The ability of the obtained ligands to form supramolecular
coordination compounds is now under investigation in our
laboratories.23 Incidentally, their use has already led to the
clean preparation of novel nanoboxes based on heterolep-
tic copper(I) and silver(I) complex formation,11,24 the re-
dox properties25 of which are currently being investigated.
Additionally, the ligands also open new perspectives due
to their potential as tuneable fluorophores26 and photoac-
tive wires.27,28
IR (KBr): = 3395 (N-H), 2954 (C-H), 2137 (C C), 1598 (C=C),
1558, 1513, 1481, 1387, 1248, 1108, 1001, 920, 846 (Mes-H), 791,
758 (Ph-H), 682 cm–1.
1H NMR (250 MHz, CDCl3): = 0.02 (s, 9H, 3’-H), 2.27 (s, 3H,
8”-H), 2.31 (br s*, 6H, 7”-, 9”-H), 5.88 (s, 1H, N-H), 6.53 (d, 1H,
J = 2.1 Hz, 2-H), 6.71 (d, 1H, J = 2.1 Hz, 4-H), 6.80–6.90 (br s*,
2H, 3”-H, 5”-H), 6.84 (d, 1H, J = 8.3 Hz, 6-H), 7.01 (d, 1H,
J = 8.3 Hz, 5-H), 7.24 (dd, 1H, J = 8.0, 4.3 Hz, 8-H), 7.92 (dd, 1H,
J = 8.0, 1.8 Hz, 7-H), 9.15 (dd, 1H, J = 4.3, 1.8 Hz, 9-H); *coales-
cence.
Anal. Calcd for C26H28N2Si: C, 78.74; H, 7.12; N, 7.06. Found: C,
78.51; H, 6.98; N, 6.73.
All reagents were commercially available and used without further
purification. The solvents were dried with appropriate desiccants
and distilled prior to use (CH2Cl2 from P2O5, MeCN from P2O5 and
NaH, DMSO from CaSO4 under reduced pressure). 1H NMR spec-
tra were recorded on either Bruker AC 200 (200 MHz) or Bruker
AC 250 (250 MHz) spectrometers (using the deuterated solvent as
the lock and residual solvent as the internal reference). IR spectra
were recorded on a Perkin–Elmer (1605 FT-IR). Microanalyses
2-(2,4,6-Trimethylphenyl)-3-(trimethylsilanylethynyl)-
[1,10]phenanthroline (4a)
Activated MnO2 (5.00 g, 5.75 mmol) was added in two portions to
a solution of 2-(2,4,6-trimethylphenyl)-3-(trimethylsilanylethynyl)-
1,2-dihydro-[1,10]phenanthroline (3.08 g, 7.77 mmol) in CH2Cl2
(50 mL), and the mixture was stirred for 2 h at r.t. After drying
(MgSO4), the solvent was removed and the resulting solid was pu-
rified by column chromatography (SiO2, CHCl3, Rf = 0.35) to pro-
vide 4a as a white solid. Yield: 2.76 g (90%); mp 276 °C.
H
IR (KBr): = 2956, 2918, 2845, 2156 (C C), 1614, 1584, 1547,
1467, 1396, 1299, 1249, 1179, 1156, 1104, 996, 846, 696, 636cm–1.
N
N
+
1H NMR (250 MHz, CDCl3): = 0.02 (s, 9H, 3’-H), 2.00 (s, 6H,
7”-, 9”-H), 2.31 (s, 3H, 8”-H), 6.87 (s, 2H, 3”-H, 5”-H), 7.60 (dd,
1H, J = 8.0, 4.2 Hz, 8-H), 7.76 (d, 1H, J = 8.5 Hz, 6-H), 7.80 (d,
1H, J = 8.5 Hz, 5-H), 8.23 (dd, 1H, J = 8.0, 1.5 Hz, 7-H), 8.37 (s,
1H, 4-H), 9.20 (dd, 1H, J = 4.2, 1.5 Hz, 9-H).
6a
I
N
N
13C NMR (53 MHz, CDCl3): = –0.6 (C-3’), 19.9 (C-7”, -9”), 21.1
(C-8”), 101.0 (C-1’), 101.9 (C-2’), 120.1 (C-3), 123.0 (C-8), 125.9
(C-3”), 126.5 (C-4a), 126.8 (C-6a), 127.7 (C-5), 129.2 (C-6), 135.7
(C-4”), 135.9 (C-7), 137.0 (C-2”), 137.1 (C-1”), 138.6 (C-4), 144.9
(C-10a), 146.1 (C-1a), 150.6 (C-9), 163.3 (C-2).
13
PdCl2(PPh3)2, CuI,
Et3N, 90 °C, 3 d,
(benzene)
38%
Anal. Calcd for C26H26N2Si: C, 79.14; H, 6.64; N, 7.10. Found: C,
78.80; H, 6.76; N, 6.89.
N
N
N
N
2-(4-Bromo-2,3,5,6-tetramethylphenyl)-3-(trimethylsilanyl-
ethynyl)-[1,10]phenanthroline (4b)
1,4-Dibromo-2,3,5,6-tetramethylbenzene29 (17.5 g, 60.0 mmol)
was dissolved in Et2O (100 mL) before adding n-BuLi (2.5 M, 24.0
mL, 60.0 mmol, solution in hexane) dropwise over 30 min at 0°C.
14
Scheme 5
Synthesis 2001, No. 10, 1561–1567 ISSN 0039-7881 © Thieme Stuttgart · New York

1564
M. Schmittel et al.
PAPER
The lithiation was completed after 3 h and phenanthroline 3 (8.50 g,
30.7 mmol) was added slowly over 15 min under a N2 atm. The so-
lution, which turned to a dark violet color, was then stirred for 24 h
at r.t. After neutralization with sat. NH4Cl (250 mL) and extraction
with CH2Cl2 (3 100 mL), the organic layer was dried (MgSO4).
The concentrated reaction mixture (volume: 50 mL) was subse-
quently oxidized with MnO2 (15.6 g, 180 mmol) for 12 h, and fil-
tered through a pad of Celite. After concentration of the filtrate, the
crude product was purified by column chromatography (CH2Cl2,
then Et2O) to afford a light yellow solid, which on washing with cy-
clohexane furnished a white solid. Yield: 10.9 g (22.4 mmol, 73%);
mp 238 °C.
IR (KBr): = 2956, 2918, 2845, 2156 (C C), 1614, 1584, 1547,
1467, 1396, 1299, 1249, 1179, 1156, 1104, 996, 846, 696, 636 cm–1.
1H NMR (250 MHz, CDCl3): = 0.04 (s, 9H, 3’-H), 2.05 (s, 6H,
7”-, 9”-H), 2.11 (s, 6H, 7”’-, 9”’-H), 2.29 (s, 3H, 8”-H), 2.30 (s, 3H,
8”’-H), 6.86 (s, 2H, 3”-, 5”-H), 6.92 (s, 2H, 3”’-, 5”’-H), 7.56 (d,
1H, J = 8.2 Hz, 8-H), 7.78 (d, 1H, J = 8.9 Hz, 6-H), 7.85 (d, 1H,
J = 8.9 Hz, 5-H), 8.26 (d, 1H, J = 8.2 Hz, 7-H), 8.39 (s, 1H, 4-H).
13C NMR (63 MHz, CDCl3): = –0.6 (C-3’), 20.0 (C-7”, -9”), 20.5
(C-7”’, -9”’), 21.1 (C-8”), 21.2 (C-8”’), 100.7 (C-1’), 102.2 (C-2'),
119.9 (C-3), 125.1 (C-8), 125.6 (C-3”), 126.3 (C-3”’), 126.8 (C-4a),
127.5 (C-6a), 127.8 (C-5), 128.5 (C-6), 135.8 (C-4”’), 136.0 (C-4”),
136.1 (C-2”), 136.8 (C-2”’), 137.1 (C-1”’), 137.5 (C-1”), 137.9 (C-
7), 138.8 (C-4), 144.8 (C-10a), 145.9 (C-1a), 160.4 (C-9), 162.6 (C-
2).
IR (KBr): = 3037, 2956, 2154 (C C), 1585 (C =C), 1550, 1490,
1469, 1391, 1248, 1187, 863, 843, 759, 695, 637 cm–1.
1H NMR (200 MHz, CDCl3): = 0.00 (s, 9H, 3’-H), 1.95 (s, 6H,
2”-H, 6”-H), 2.43 (s, 6H, 3”H, 5”H), 7.60 (dd, 1H, J = 8.0, 4.3 Hz,
8-H), 7.77 (d, 1H, J = 8.8 Hz, 6-H), 7.80 (d, 1H, J = 8.8 Hz, 5-H),
8.23 (dd, 1H, J = 8.0, 1.8 Hz, 7-H), 8.38 (s, 1H, 4-H), 9.19 (dd, 1H,
J = 4.3, 1.8 Hz, 9-H).
13C NMR (CDCl3, 53 MHz): = –0.6 (C-3’), 19.5 (C-7”, -10”),
20.9 (C-8”, -9”), 101.0 (C-1’), 101.9 (C-2’), 120.1 (C-3), 123.0 (C-
8), 125.9 (C-3”), 126.7 (C-4a), 126.8 (C-6a), 127.7 (C-5), 129.4 (C-
6), 136.1 (C-4”), 135.9 (C-7), 137.2 (C-2”), 137.3 (C-1”), 138.4 (C-
4), 144.9 (C-10a), 146.0 (C-1a), 150.6 (C-9), 163.8 (C-2).
Anal. Calcd for C35H36N2Si: C, 81.98; H, 7.08; N, 5.46. Found: C,
81.88; H, 7.35; N, 5.16.
2-(4-Bromo-2,3,5,6-tetramethylphenyl)-3-(trimethlysilyl-
ethynyl)-9-(2,4,6-trimethylphenyl)-[1,10]phenanthroline (5b)
n-BuLi (2.5 M in hexane, 8.00 mL, 20.0 mmol) was added slowly
at 0 °C to a solution of anhyd Et2O (25 mL) containing bromomes-
itylene (3.90 g, 3.00 mL, 20.0 mmol) and the mixture was stirred for
3 h at r.t. To this solution was added 4b (5.00 g, 10.2 mmol) over
15 min and the resulting violet solution was stirred for 24 h at r.t.
The reaction mixture was neutralized with sat. NH4Cl and extracted
with CH2Cl2. The organic layer was concentrated (volume: 50 mL)
and oxidized with MnO2 (5.20 g, 60.0 mmol) for 16 h. The reaction
mixture was filtered through a pad of Celite and the solvent was re-
moved under reduced pressure. The crude product obtained was
purified by column chromatography (EtOAc–hexane, 5:95;
Rf = 0.5230) affording a light brown solid which on washing with
cyclohexane furnished a white solid. Yield: 5.20 g (8.50 mmol,
83%); mp 243–245 °C.
MS (ESI): m/z (%) = 488.5 (100) [M + H]+.
Anal. Calcd for: C27H27BrN2Si: C, 66.52; H, 5.58; N, 5.75. Found:
C, 66.63; H, 5.59; N, 5.79.
9-Butyl-2-(2,4,6-trimethylphenyl)-3-(trimethylsilanylethynyl)-
[1,10]phenanthroline (7)
Obtained as side product in the preparation of 5a.
Yield: 280 mg (9%); mp 188–190 °C; Rf = 0.45 (CHCl3).
IR (KBr): = 2953, 29517, 2144 (C=C), 1618, 1580, 1537, 1506
1461, 1418, 1357, 1248, 1196, 1146, 1103, 1016, 988, 897, 864,
848, 759, 698, 640, 581 cm–1.
1H NMR (200 MHz, CDCl3): = –0.01 (s, 9H, 3’-H), 1.96 (s, 6H,
2”-, 6”-H), 2.09 (s, 6H, 2”’-, 6”’-H), 2.30 (s, 3H, 4”’-H), 2.42 (s,
6H, 3”-, 5”’-H), 6,90 (s, 2H, 5”’-, 3”’-H) 7.54 (dd, 1H, J = 8.0, 4.3
Hz, 8-H), 7.81 (dd, 2H, J = 9.8, 2.1 Hz, 5-, 6-H), 8.24 (d, 1H,
J = 8.0 Hz, 7-H), 8.39 (s, 1H, 4-H).
IR (KBr): = 2947, 2866, 2155 (C C), 1616, 1584, 1541, 1463,
1394, 1366, 1249, 912, 864, 845, 758, 641cm–1.
1H NMR (250 MHz, CDCl3): = 0.04 (s, 9H, 3’-H), 0.94 (t, 3H,
J = 7.3 Hz, -CH3), 1.43 (m, 2H, -CH2), 1.81 (m, 2H, -CH2), 1.89 (s,
6H, 7”-, 9”-H), 2.34 (s, 3H, 8”-H), 3.13 (t, 2H, J = 8.0 Hz, Ar-
CH2), 6.92 (s, 2H, 3”-, 5”-H), 7.49 (d, 1H, J = 8.3 Hz, 8-H), 7.69
(d, 1H, J = 8.6 Hz, 5-H), 7.76 (d, 1H, J = 8.6 Hz, 6-H), 8.13 (d,
1H, J = 8.3 Hz, 7-H), 8.35 (s, 1H, 4-H).
13C NMR (53 MHz, CDCl3): = –0.5 (C-3’), 20.0 (C-7”, -10”),
20.4 (C-7”’, -9”’), 20.9 (C-8”, -9”), 21.2 (C-8”’), 100.9 (C-1’),
102.0 (C-2’), 119.2 (C-3), 125.0 (C-8), 125.6 (C-3”), 126.0 (C-3”’),
126.8 (C-4a), 127.2 (C-6a), 127.6 (C-5), 128.3 (C-6), 134.9 (C-4”’),
135.2 (C-4”) 135.4 (C-2”), 136.0 (C-2”’), 137.0 (C-1”’), 137.5 (C-
1”), 137.8 (C-7), 138.4 (C-4), 144.2 (C-10a), 145.7 (C-1a), 160.0
(C-9), 162.1 (C-2).
13C NMR (53 MHz, CDCl3): = 0.6 (Si-CH3), 14.0, 20.0, 21.1,
22.6, 32.3, 38.9, 100.6 (C C), 102.2 (C C), 119.7, 123.0, 124.8,
126.6, 126.8, 127.3, 127.5, 127.9, 136.0, 136.1, 136.9, 138.8, 144.6,
145.6, 162.3, 163.7.
Anal. Calcd for C30H34N2Si·0.5 H2O: C, 78.38; H, 7.67; N, 6.09.
Found: C, 78.62; H, 7.36; N, 6.06.
MS (ESI): m/z (%) = 606.6 (100) [M + H]+.
2,9-Bis(2,4,6-trimethylphenyl)-3-trimethylsilanylethynyl-
[1,10]phenanthroline (5a)
Anal. Calcd for: C36H37BrN2Si: C, 71.39; H, 6.16; N, 4.63. Found:
C, 71.40; H, 6.15; N, 4.65.
A solution of n-BuLi in pentane (2.5 M, 12.4 mL, 31.1 mmol) was
slowly added to a solution of 1-bromo-2,4,6-trimethylbenzene (3.69
g, 18.6 mmol) in anhyd Et2O (100 mL) at 0 °C. The resulting mix-
ture was stirred for 7 h at 0 °C. After addition of 2-(2,4,6-trimeth-
ylphenyl)-3-trimethylsilanylethynyl-[1,10]phenanthroline (4a, 1.82
g, 5.62 mmol), the solution assumed first a yellow and then a dark
violet color, and the mixture was stirred for 24 h at r.t. After addi-
tion of aq NH4Cl (50 mL), the layers were separated and the aque-
ous layer was extracted with CH2Cl2 (3 30 mL). The combined
organic extracts were stirred with activated MnO2 (5 g) for 3 h. The
mixture was dried (MgSO4) and filtered. After evaporation of the
filtrate, the resulting brown oil was purified by column chromatog-
raphy (SiO2, CHCl3, Rf = 0.51) yielding a colorless solid. Yield:
68%; mp 276 °C.
2,9-Bis(2,4,6-trimethylphenyl)-3-ethynyl-[1,10]phenanthroline
(6a)
2,9-Bis(2,4,6-trimethylphenyl)-3-trimethylsilanylethynyl-
[1,10]phenanthroline (5a, 170 mg, 330 mol) was dissolved in THF
(10 mL), and aq KOH (1 N, 10 mL) was added. After stirring for 2
h, the solution was diluted with aq NH4Cl (20 mL) and extracted
with CH2Cl2 (3 5 mL). The combined organic phases were dried
(MgSO4), and the solvents were removed yielding a colorless solid.
Yield: 138 mg (95%); mp 248 °C.
IR (KBr): = 3274 ( C-H), 2955, 2915, 2849, 2091 (C C), 1615,
1582, 1536, 1458, 1105, 848, 637, 614 cm–1.
Synthesis 2001, No. 10, 1561–1567 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Synthesis of Soluble, Linear Bisphenanthrolines
1565
1H NMR (200 MHz, CDCl3): = 2.08 (s, 6H, 7”-, 9”-H), 2.13 (s,
6H, 7’”-, 9’”-H), 2.31 (s, 6H, 8”-, 8’”-H), 3.13 (s, 1H, 3’-H), 6.90
(s, 2H, 3”-, 5”-H), 6.92 (s, 2H, 3’”-, 5’”-H), 7.58 (d, 1H, J = 8.3 Hz,
8-H), 7.80 (d, 1H, J = 8.8 Hz, 5-H), 7.87 (d, 1H, J = 8.8 Hz, 6-H),
8.28 (d, 1H, J = 8.3 Hz, 7-H), 8.48 (s, 1H, 4-H).
13C NMR (53 MHz, CDCl3): = 20.0 (C-7”, -9”), 20.5 (C-7’”, -
9’”), 21.1 (C-8”), 21.2 (C-8’”), 80.8 (C-2’), 82.2 (C-1’), 118.7 (C-
3), 125.3 (C-8), 125.4 (C-3''), 126.5 (C-3'''), 127.0 (C-4a), 127.6 (C-
6a), 128.0 (C-5), 128.5 (C-6), 135.8 (C-4’”), 136.1 (C-4”), 136.6
(C-2”), 136.7 (C-2’”), 137.4 (C-1”), 137.5 (C-1’”), 137.9 (C-4),
140.3 (C-7), 145.2 (C-10a), 145.8 (C-1a), 160.4 (C-9), 161.8 (C-2).
13C NMR (53 MHz, CDCl3): = 20.0 (C-7”, -9”), 20.5 (C-7”’, -
9”’), 21.1 (C-8”), 21.2 (C-8”’), 87.0 (C-1’), 94.9 (C-2’), 120.0 (C-
3), 125.1 (C-8), 125.7 (C-3”), 126.8 (C-3”’), 128.0 (C-4a), 128.3
(C-6a), 128.5 (C-5), 131.6 (C-6), 135.8 (C-4”’), 136.1 (C-4”), 136.2
(C-2”), 136.8 (C–2”’), 137.3 (C-1”), 137.5 (C-1”’), 137.8 (C-4),
138.4 (C-7), 144.7 (C-10a), 145.9 (C-1a), 160.5 (C-9), 162.0 (C-2).
MS (ESI): m/z (%) = 879.4 (100) [M + H]+, 440.2 (40) [M + 2H]2+.
Anal. Calcd for C64H54N4·H2O: C, 85.68; H, 6.29; N, 6.24. Found:
C, 85.42; H, 6.31; N, 6.00.
1,4-Bis[3-(2,9-di(2,4,6-trimethylphenyl)-[1,10]phenanthro-
linyl)ethynyl]benzene11 (11a)
Anal. Calcd for C32H28N2 0.25H2O: C, 86.35; H, 6.45; N, 6.43.
Found: C, 86.18; H, 6.38; N, 6.27.
2,9-Bis(2,4,6-trimethylphenyl)-3-ethynyl-[1,10]phenanthroline
(6a, 149 mg, 338 mol), 1,4-diiodobenzene (55.8 mg, 169 mol), CuI
(25 mg, 132 mol) and [PdCl2(PPh3)2] (11.8 mg, 16.9 mol) were
stirred in anhyd benzene (5 mL) and Et3N (5 mL) under Ar for 3 d
at 80 °C. The solvents were removed and the residue was dissolved
in CH2Cl2 (30 mL). The resulting solution was washed with aq KCN
(2%, 10 mL) and the organic phase was dried (MgSO4). After re-
moval of the solvent, the residue was purified by column chroma-
tography (SiO2, CHCl3, Rf = 0.20), and recrystallized from
cyclohexane to yield a yellow solid. Yield: 80 mg (75%); mp
280 °C.
2-(4-Bromo-2,3,5,6-tetramethylphenyl)-9-(2,4,6-trimethyl-
phenyl)-3-ethynyl-[1,10]phenanthroline (6b)
2-(4-Bromo-2,3,5,6-tetramethylphenyl)-3-(trimethlysilanylethy-
nyl)-9-(2,4,6-trimethylphenyl)-[1,10]phenanthroline (5b, 2.50 g,
4.10 mmol) was dissolved in a mixture of MeOH (120 mL) and
THF (100 mL), and KOH (1 N, 150 mL) was added slowly. After
stirring for 12 h at r.t., the solution was neutralized with sat. NH4Cl
and extracted with CH2Cl2 (200 mL). The combined organic layers
were dried (MgSO4). Evaporation of the solvent provided a yellow
solid, which was purified by column chromatography (EtOAc–hex-
ane, 5:95, Rf = 0.4230). The resultant light yellow solid upon wash-
ing with cyclohexane afforded a white solid. Yield: 2.10 g (3.90
mmol, 95%); mp 227–235 °C.
IR (KBr): = 2923, 2854, 2207 (C C), 1698, 1613, 1580, 15363,
1503, 1457, 1400, 1293,1144, 1106, 1065, 1031, 991, 913, 846,
774, 637 cm–1.
1H NMR (250 MHz, CDCl3): = 2.07 (s, 12H, 7”-, 9”-H), 2.11 (s,
12H, 7”’-, 9”’-H), 2.31 (s, 6H, 8”-H), 2.35 (s, 6H, 8”’-H), 6.93 (s,
8H, 3”-, 5”-, 3”’-, 5”’-H), 7.03 (s, 4H, 4’-Ph-H), 7.58 (d, 2H,
J = 8.3 Hz, 8-H), 7.83 (d, 2H, J = 8.8 Hz, 5-H), 7.88 (d, 2H,
J = 8.8 Hz, 6-H), 8.29 (d, 2H, J = 8.3 Hz, 7-H), 8.46 (s, 2H, 4-H).
13C NMR (53 MHz, CDCl3): = 20.0 (C-7”, -9”), 20.5 (C-7”’, -
9”’), 21.1 (C-8”), 21.2 (C-8”’), 89.1 (C-2'), 94.6 (C-1’), 119.7 (C-
3), 122.8 (C-3'), 125.1 (C-8), 125.6 (C-3”), 126.8 (C-3”’), 126.9 (C-
4a), 127.5 (C-6a), 127.9 (C-5), 128.5 (C-6), 131.4 (C-4’), 135.9 (C-
2”), 136.1 (C–2”’), 136.2 (C-4”), 136.8 (C-1”), 137.3 (C-4), 137.6
(C-7), 137.8 (C-4”’), 138.4 (C-1”’), 144.8 (C-10a), 145.8 (C-1a),
160.5 (C-9), 162.0 (C-2).
IR (KBr): = 3271 ( C-H), 3000, 2923, 2850 (C C), 1615, 1579,
1537, 1504, 1488, 1460, 1450 1416, 1383, 1358 1288, 1186, 1146,
1102, 1014, 983, 931, 896, 849, 761, 674, 639, 582 cm–1.
1H NMR (200 MHz, CDCl3): = 1.98 (s, 6H, 2”-, 6”-H), 2.11 (s,
6H, 2”’-, 6”’-H), 2.30 (s, 3H, 4”’-H), 2.42 (s, 6H, 3”-, 5”-H), 3.11
(s, 1H, 7’-H), 6,91 (s, 2H, 3”’-, 5”’-H) 7.55 (d, 1H, J = 8.0 Hz, 8-
H), 7.78 (dd, 2H, J = 9.8, 2.0 Hz, 5-, 6-H), 8.26 (d, 1H, J = 8.0 Hz,
7-H), 8.48 (s, 1H, 4-H).
13C NMR (53 MHz, CDCl3):
= 19.8 (C-7”, -10”), 20.2 (C-
7”’, -9”’), 20.7 (C-8”, -9”), 21,0 (C-8”’), 82.4 (C-2’), 85.7 (C-1’),
119.4 (C-3), 124.7 (C-8), 125.0 (C-3''), 126.1 (C-3”’), 126.7 (C-4a),
127.1 (C-6a), 127.7 (C-5), 128.3 (C-6), 134.8 (C-4”’), 135.2 (C-4”)
135.4 (C-2”), 136.2 (C-2”’), 136.9 (C-1”), 137.2 (C-1”’), 137.8 (C-
4), 138.4 (C-7), 144.4 (C-10a), 145.7 (C-1a), 160.4 (C-9), 162.4 (C-
2).
MS (ESI): m/z (%) = 955.8 (100) [M + H]+, 478.5 (20) [M + 2H]2+.
MS (CI) (70–100 eV): m/z (%) = 955 (100) [M+], 427 (5) [M], 279
(16), 143 (12), 114 (21), 93 (9), 85 (6).
MS (ESI): m/z (%) = 533.5 (100) [M + H]+.
Anal. Calcd for C70H58N4·1.5H2O: C, 85.59; H, 6.26; N, 5.70.
Found: C, 85.47; H, 6.26; N, 5.59.
Anal. Calcd for: C33H29BrN2: C, 74.29; H, 5.48; N, 5.25. Found: C,
74.40; H, 5.75; N, 5.65.
1,4-Bis[3-(2-(4-bromo-2,3,5,6-tetramethylphenyl)-9-(2,4,6-
trimethylphenyl)-[1,10]phenanthroline)-ethynyl]-benzene
(11b)
1,4-Bis[3-(2,9-di(2,4,6-trimethylphenyl)-[1,10]phenanthro-
linyl)]butadiyne (10a)
2-(4-Bromo-2,3,5,6-tetramethylphenyl)-3-(ethynyl)-9-(2,4,6-tri-
methylphenyl)-1,10-phenanthroline (6b, 300 mg, 0.56 mmol), di-
iodobenzene (92.7 mg, 0.28 mmol), [Pd(PPh3)2Cl2] (9.70 mg, 0.03
mmol), and CuI (41.0 mg, 0.22 mmol) were dissolved in benzene
(10 mL) and Et3N (10 mL) under N2. The reaction mixture was re-
fluxed at 90 °C for 24 h and monitored by ESI. It was diluted with
CH2Cl2 (60 mL) and washed twice with aq KCN (400 mg in 10 mL
H2O) and finally with H2O. The organic layer was dried (MgSO4).
Solvent evaporation yielded a light brown solid, which was purified
by column chromatography (EtOAc–hexane, 5:95, Rf = 0.3030) to
give the linear ligand as a light yellow solid. Upon washing with cy-
clohexane a white solid was furnished. Yield: 299 mg (0.26 mmol,
92%), mp 285 °C.
2,9-Bis(2,4,6-trimethylphenyl)-3-ethynyl-[1,10]phenanthroline
(6a, 73.0 mg, 166 mol), CuI (16.0 mg, 84.2 mol) and
[PdCl2(PPh3)2] (22.0 mg, 34.0 mol) were stirred in anhyd benzene
(20 mL) and Et3N (5 mL) under Ar for 16 h at 80 °C. After removal
of the solvents, the remaining solid was dissolved in CH2Cl2 and
washed with aq KCN (2%, 20 mL). The residue was purified by col-
umn chromatography (SiO2, CH2Cl2, Rf = 0.23) to furnish a white
crystalline product. Yield: 37.0 mg (51%); mp 279 °C.
IR (KBr): = 3024, 2918, 1854, 2210 (C C), 1614, 1578, 1535,
1457, 1392, 1292, 1156, 1107, 1030, 913, 886, 847, 774, 719, 613
cm–1.
1H NMR (250 MHz, CDCl3): = 2.03 (s, 12H, 7”-, 9”-H), 2.10 (s,
12H, 7”’-, 9”’-H), 2.30 (s, 6H, 8”-H), 2.34 (s, 6H, 8”’-H), 6.92 (s,
8H, 3”-, 5”-, 3”’-, 5”’-H), 7.58 (d, 2H, J = 8.3 Hz, 8-H), 7.79 (d,
2H, J = 8.8 Hz, 5-H), 7.87 (d, 2H, J = 8.8 Hz, 6-H), 8.27 (d, 2H,
J = 8.3 Hz, 7-H), 8.45 (s, 2H, 4-H).
IR (KBr): = 3437 ( C-H), 2949, 2857 (C C), 2209, 1614, 1584,
1532, 1504, 1458, 1416, 1383, 1261, 1162, 1141, 1100, 1016,
986,848, 771, 720, 639, 583, 544 cm–1.
Synthesis 2001, No. 10, 1561–1567 ISSN 0039-7881 © Thieme Stuttgart · New York

1566
M. Schmittel et al.
PAPER
1H NMR (200 MHz, CDCl3): = 2.01 (s, 12H, 2”-,6”-H), 2.11 (s,
12H, 2”’-, 6”’-H), 2.3 (s, 6H, 4”’H), 2.46 (s, 12H, 3”’-, 5”’-H), 6,93
(s, 4H, 5’-, 3’-H), 6.98 (s, 4H, 4’-Ph-H) 7.56 (d, 2H, J = 8.0 Hz, 8-
H), 7.81 (dd, 4H, J = 9.8, 2.1 Hz, 5-, 6-H), 8.28 (d, 2H, J = 8.0 Hz,
7-H), 8.47 (s, 2H, 4-H).
J = 8.7 Hz, 3’-, 5’-H) 7.57 (d, 2H, J = 8.0 Hz, 8-H), 7.82 (dd, 4H,
J = 9.8, 2.1 Hz, 5-, 6-H), 8.29 (d, 2H, J = 8.0 Hz, 7-H), 8.49 (s, 2H,
4-H).
13C NMR (53 MHz, CDCl3,): = 20.5 (C-7”, -10”), 20.9 (C-7”’,
-9”’), 21.0 (C-8”,-9”), 21.1 (C-8”’), 89.0 (C-2'), 95.0 (C-1'), 119.7
(C-3), 122.7 (C-3'), 125.2 (C-8), 125.6 (C-3''), 126.8 (C-3”’), 127.1
(C-4a), 127.5 (C-6a), 128.0 (C-5’) 128.4 (C-5), 128.7 (C-6), 129.1
(C-4’), 131.9 (C-2”), 133.5 (C-2”’), 133.5 (C-4”), 134.5 (C-1”),
135.9 (C-4), 137.5 (C-7), 137.9 (C-4”’), 138.9 (C-1”’), 140.4 (C-
6’), 144.7 (C-10a), 145.7 (C-1a), 160.5 (C-9), 162.4 (C-2).
13C NMR (53 MHz, CDCl3):
= 20.5 (C-7”, -10”), 20.9 (C-
7”’, -9”’), 21.0 (C-8”, -9”), 21.1 (C-8”’), 89.0 (C-2’), 95.0 (C-1’),
119.7 (C-3), 122.7 (C-3’), 125.2 (C-8), 125.6 (C-3”), 126.8 (C-3”’),
127.1 (C-4a), 127.6 (C-6a), 128.4 (C-5), 128.5 (C-6), 129.2 (C-4’),
131.3 (C-2”), 133.5 (C-2”’), 133.6 (C-4”), 134.5 (C-1”), 136.0 (C-
4), 137.5 (C-7), 137.8 (C-4”’), 138.9 (C-1”’), 144.7 (C-10a), 145.8
(C-1a), 160.6 (C-9), 162.4 (C-2).
MS (ESI): m/z (%) = 1217.2 (100) [M + H]+.
Anal. Calcd for: C78H64Br2N4: C, 76.97; H, 5.30; N, 4.60. Found: C,
77.24; H, 5.65; N, 4.48.
MS (ESI): m/z (%) = 1142.1 (100) [M + H]+.
Anal. Calcd for: C72H60Br2N4: C, 75.79; H, 5.30; N, 4.91. Found: C,
76.02; H, 5.12; N, 4.75.
3-(4-[1,10]Phenanthrolin-3-yl-ethynyl-phenylethynyl)-2,9-
bis(2,4,6-trimethylphenyl)-[1,10]phenanthroline (14)
2,9-Bis(2,4,6-trimethylphenyl)-3-ethynyl-[1,10]phenanthroline
(6a, 106 mg, 240 mol), 3-(4-iodo-phenylethynyl)-[1,10]phenan-
throline (13, 98.0 mg, 240 mol), CuI (20.0 mg, 105 mol), and
[PdCl2(PPh3)2] (10.0 mg, 12.0 mol) in anhyd benzene (10 mL) and
anhyd Et3N (10 mL) were stirred under Ar for 3 d at 85 °C. Workup
was analogous to that for 11a (Rf = 0.21) providing a yellow solid.
Yield: 66.0 mg (38%); mp > 300 °C.
4,4’-Bis[3-(2,9-di(2,4,6-trimethylphenyl)-[1,10]phenanthro-
linyl)ethynyl]-biphenyl (12a)
2,9-Bis(2,4,6-trimethylphenyl)-3-ethynyl-[1,10]phenanthroline
(150 mg, 340 mol), 4,4'-diiodobiphenyl (60 mg, 150 mol), CuI
(20.0 mg, 105 mol), and [PdCl2(PPh3)2] (23.8 mg, 34.0 mol) in
anhyd benzene (10 mL) and Et3N (2 mL) were stirred for 2 dat
85 °C. Workup was analogous to that for 11a (Rf = 0.17) and pro-
vided a yellow solid. Yield: 87 mg (31%); mp 293 °C.
IR (KBr): = 3205 (s, C-H), 2202 (w, C C), 1590 (m, C =C), 1477
(s, C= C), 1415 (s), 1261 (m), 1095 (m), 1053 (m), 1202 (s), 940
(m), 818 (s, Ar-H), 729 (s, Ar-H) cm–1.
IR (KBr): = 2919, 2860, 2202 (C C), 1611, 1456, 1378, 1269,
1109, 1067, 1025, 848, 820 cm–1.
1H NMR (250 MHz, CDCl3): = 2.10 (s, 12H, 7”-, 9”-H), 2.12 (s,
12H, 7”’-, 9”’-H), 2.31 (s, 6H, 8”-H), 2.35 (s, 6H, 8”’-H), 6.93 (br
s, 8H, 3”-, 5”-, 3”’-, 5”’-H), 7.22 (d, 4H, J = 8.5 Hz, Ar-H), 7.48
(d, 4H, J = 8.5 Hz, Ar-H), 7.58 (d, 2H, J = 8.2 Hz, 8-H), 7.83 (d,
2H, J = 9.0 Hz, 5-H), 7.89 (d, 2H, J = 9.0 Hz, 6-H), 8.29 (d, 2H,
J = 8.2 Hz, 7-H), 8.48 (s, 2H, 4-H).
13C NMR (53 MHz, CDCl3): = 20.1 (C-7”, -9”), 20.5 (C-7”’, -
9”’), 21.1 (C-8”), 21.2 (C-8”’), 88.1 (C-2’), 94.7 (C-1’), 120.0 (C-
3), 122.2 (C-3’), 125.1 (C-8), 125.7 (C-3”), 126.7 (C-3”’), 126.8 (C-
4a), 127.5 (C-6a), 127.6 (C-5’) 128.0 (C-5), 128.5 (C-6), 132.1 (C-
4’), 135.9 (C-2”), 136.1 (C-2”’), 136.2 (C-4”), 136.9 (C-1”), 137.3
(C-4), 137.6 (C-7), 137.9 (C-4”’), 138.4 (C-1”’), 140.2 (C-6’),
144.9 (C-10a), 145.9 (C-1a), 156.7 (C-9), 160.5 (C-2).
1H NMR (250 MHz, CDCl3): = 2.09 (s, 6H, 7”’-, 9”’-H), 2.10 (s,
6H, 7””-, 9””-H), 2.28 (s, 3H, 8”’-H), 2.33 (s, 3H, 8””-H), 6.90 (s,
2H, 3””-H), 6.92 (s, 2H, 3”’-H), 7.17 (d, 2H, J = 8.6 Hz, 4’-H),
7.52 (d, 2H, J = 8.6 Hz, 5’-H), 7.52 (d, 1H, J = 8.3 Hz, 8”-H), 7.65
(dd, 1H, J = 8.0, 4.4 Hz, 8-H), 7.77 (d, 2H, J = 8.4 Hz, 6-, 6”-H),
7.84 (d, 2H, J = 8.4 Hz, 5-, 5”-H), 8.26 (dd, 1H, J = 8.0, 1.8 Hz,
7-H), 8.29 (d, 1H, J = 8.3 Hz, 7”-H), 8.38 (d, 1H, J = 1.9 Hz, 4-
H), 8.48 (s, 1H, 4”-H), 9.21 (dd, 1H, J = 4.4, 1.8 Hz, 9-H), 9.26 (d,
1H, J = 1.9 Hz, 2-H).
13C NMR (53 MHz, CDCl3):
= 20.0 (C-7”’, -9”’), 20.5 (C-
7””, -9””), 21.0 (C-8”’), 21.1 (C-8””), 87.7 (C-2’), 88.3 (C-7’), 94.4
(C-1’), 95.0 (C-8’), 119.2 (C-3), 119.6 (C-3”), 122.4 (C-3’), 123.2
(C-8”), 125.1 (C-8), 125.6 (C-3”’), 125.9 (C-6’), 126.8 (C-4a),
126.9 (C-3””), 127.3 (C-4a”), 127.4 (C-6a), 127.6 (C-6a”), 127.9
(C-5”), 128.3 (C-5), 128.5 (C-6''), 128.9 (C-6), 131.5 (C-4'), 131.9
(C-5’), 135.8 (C-2”’), 135.9 (C–2””), 136.2 (C-4”’), 136.8 (C-1”’),
137.2 (C-4”), 137.4 (C-7”), 137.6 (C-4), 137.8 (C-7), 138.0 (C-4””),
138.5 (C-1””), 144.8 (C-10a”), 144.9 (C-1a”), 145.8 (C-10a), 145.9
(C-1a), 150.5 (C-9), 151.9 (C-2), 160.4 (C-9”), 161.9 (C-2”).
MS (ESI): m/z (%) = 1031.6 (100) [M + H]+, 515.7 (40) [M + 2H]2+.
Anal. Calcd for C76H62N4·CH2Cl2: C, 82.85; H, 5.78; N, 5.02.
Found: C, 82.45; H, 5.42; N, 5.11.
4,4’-Bis[3-(2-(4-bromo-2,3,5,6-tetramethylphenyl)-9-(2,4,6-
trimethylphenyl)-[1,10]phenanthrolinyl)-ethynyl]-biphenyl
(12b)
MS (ESI): m/z (%) = 719.4 (100) [M + H]+, 360.3 (20) [M + 2H]2+.
Phenanthroline (6b, 300 mg, 0.56 mmol), 4,4'-diiodobiphenyl (114
mg, 0.28 mmol), [Pd(Ph3P)2Cl2] (19.7 mg, 0.03 mmol), and CuI
(41.0 mg, 0.22 mmol) were dissolved in anhyd benzene (10 mL) and
anhyd Et3N (10 mL). The mixture was refluxed at 90°C for 28 h.
After cooling to r.t., it was diluted with CH2Cl2 (60 mL) and washed
with aq KCN (400 mg in 10 mL H2O) and finally with H2O. The or-
ganic layer was dried (MgSO4) and solvent evaporation yielded a
light orange solid. Purification by column chromatography
(EtOAc–hexane, 1:5, Rf = 0.33) and washing with cyclohexane af-
forded the linear ligand 12b as a yellow solid. Yield: 243 mg (0.20
mmol, 71%); mp 296 °C.
Acknowledgement
We are grateful to the DFG and the Fonds der Chemischen Industrie
for continued financial support.
References
(1) Swiegers, G. F.; Malefeste, T. J. Chem. Rev. 2000, 100,
3483.
(2) (a) Constable, E. C. Pure Appl. Chem. 1996, 68, 253.
(b) Kaes, C.; Katz, A.; Hosseini, M. W. Chem. Rev. 2000,
100, 3553.
(3) (a) Blanco, M. J.; Jimenez, M. C.; Chambron, J. C.; Heitz,
V.; Linke, M.; Sauvage, J.-P. Chem. Soc. Rev. 1999, 28,
293. (b) Sauvage, J.-P. Acc. Chem. Res. 1998, 31, 611.
(c) Sammes, P. G.; Yahioglu, G. Chem. Soc. Rev. 1994, 23,
327.
IR (KBr): = 3434 ( C-H), 2920, 2855, 2207 (C C), 1719, 1613,
1583, 1534, 1493, 1458, 1417, 1382, 1292, 1161, 1141, 1004, 985,
912, 849, 822, 771, 755, 720, 689, 540 cm–1.
1H NMR (200 MHz, CDCl3): = 2.04 (s, 12H, 2’’-, 6’’-H), 2.12 (s,
12H, 2’’’-, 6’’’-H), 2.31 (s, 6H, 4’’’-H), 2.46 (s, 12H, 3’’-, 5’’-H), 6,92
(s, 4H, 3’’’-, 5’’’-H), 7.13 (d, 4H, J = 8.7 Hz, 2’-, 6’-H), 7.49 (d, 4H,
Synthesis 2001, No. 10, 1561–1567 ISSN 0039-7881 © Thieme Stuttgart · New York

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Synthesis 2001, No. 10, 1561–1567 ISSN 0039-7881 © Thieme Stuttgart · New York