Helical complexes containing diamide-bridged benzene-o-dithiolato/ catecholato ligands

Article abstract of DOI:10.1002/chem.200601167

The benzene-o-dithiol/catechol ligands H₄-2 and H₄-3 react with [TiO(acac)₂] to give the dinuclear, double-stranded anionic complexes [Ti₂(L)₂(μ-OCH₃) ₂]^2- ([22]^2-, L = 2^4-; [23] ^2-, L = 3^4-). NMR spectroscopic investigations reveal that the complex anion [Ti₂(2)₂(μ-OCH₃) ₂]^2- is formed as a mixture of three of four possible isomers/pairs of enantiomers, whereas only one isomer of the complex anion [Ti₂(3)₂(μ-OCH₃)₂]^2- is obtained. The crystal structure analysis of (PNP)_2- [Ti ₂(3)₂(μ-OCH₃)₂] shows a parallel orientation of the ligand strands, whereas the structure determination for (AsPh₄)₂[Ti₂(2)₂(μ-OCH ₃)₂] does not yield conclusive results about the orientation of the ligand strands due the presence of different isomers in solution, the possible co-crystallisation of different isomers and severe disorder in the crystal. NMR spectroscopy shows that ligand H₄-3 reacts at elevated temperature with [TiO(acac)₂] to give the triple-stranded helicate (PNP)₄ [Ti₂(3)₃] ((PNP)₄[24]) as a mixture of two isomers, one with a parallel orientation of the ligand strands and one with an antiparallel orientation. Exclusively the triple-stranded helicates [Ti₂(L)₃] ^4- ([25]^4-, L = 1^4-; [26]^2-, L = 4^4-) are formed in the reaction of ligands H₄-1 and H ₄-4 with [TiO-(acac)₂]. The molecular structures of Na(PNP)₃[Ti₂(1)₃]·CH ₃OH·H₂O·Et₂O (Na(PNP) ₃[25]·CH₃OH·H₂O·Et ₂O) and Na_1.5(PNP)_6.5[Ti₂(4) ₃]₂·3 DMF (Na_1.5(PNP) _6.5[26]₂·3DMF) reveal a parallel orientation of the ligand strands in both complexes, which is retained in solution. The sodium cations present in the crystal structures lead to two different kinds of aggregation in the solid state. Na-[25]-Na-[25]-Na polymeric chains are formed from compound Na-(PNP)₃[25], with the sodium cations coordinated by the carbonyl groups of two ligand strands from two different [Ti ₂(1)₃]^4- ions in addition to solvent molecules. In contrast to this, two [Ti₂(4)₃]^4- ions are connected by a sodium cation that is coordinated by the three meta oxygen atoms of the catecholato groups of each complex tetraanion to form a central (NaO ₆) octahedron in the anionic pentanuclear complex {[26]-Na-[26]} ^7-.

Full text of DOI:10.1002/chem.200601167

DOI: 10.1002/chem.200601167
Helical Complexes Containing Diamide-Bridged Benzene-o-dithiolato/
Catecholato Ligands
Christian Schulze Isfort,[a] Thorsten Kreickmann,[a] Tania Pape,[a] Roland Frçhlich,[b] and
F. Ekkehardt Hahn*[a]
Abstract: The benzene-o-dithiol/cate-
chol ligands H4-2 and H4-3 react with
different isomers and severe disorder
in the crystal. NMRspectroscopy
shows that ligand H4-3 reacts at elevat-
Na1.5
(PNP)6.5
U
(Na1.5-
AHCTREUNG
[TiO
double-stranded anionic complexes
[Ti2(L)2
(m-OCH3)2]2À ([22]2À, L=24À
[23]2À, L=34À). NMRspectroscopic in-
vestigations reveal that the complex
anion [Ti2(2)2
(m-OCH3)2]2À is formed as
A
orientation of the ligand strands in
both complexes, which is retained in
solution. The sodium cations present in
the crystal structures lead to two differ-
ent kinds of aggregation in the solid
state. Na-[25]-Na-[25]-Na polymeric
chains are formed from compound Na-
ed temperature with [TiO
give the triple-stranded helicate
(PNP)4[Ti2(3)3] ((PNP)4[24]) as a mix-
A
A
;
AHCTREUNG
ture of two isomers, one with a parallel
orientation of the ligand strands and
one with an antiparallel orientation.
Exclusively the triple-stranded heli-
cates [Ti2(L)3]4À ([25]4À, L=14À; [26]2À,
L=44À) are formed in the reaction of
ligands H4-1 and H4-4 with [TiO-
ACHTREUNG
a mixture of three of four possible iso-
mers/pairs of enantiomers, whereas
only one isomer of the complex anion
A
coordinated by the carbonyl groups of
two ligand strands from two different
[Ti2(1)3]4À ions in addition to solvent
molecules. In contrast to this, two
[Ti2(3)2
crystal structure analysis of (PNP)2-
[Ti2(3)2(m-OCH3)2] shows a parallel ori-
entation of the ligand strands, whereas
the structure determination for
(AsPh4)2[Ti2(2)2(m-OCH3)2] does not
A
A
N
ACHTREUNG
A
N
[Ti2(4)3]4À ions are connected by
a
T
sodium cation that is coordinated by
the three meta oxygen atoms of the
catecholato groups of each complex
tetraanion to form a central {NaO6} oc-
tahedron in the anionic pentanuclear
complex {[26]-Na-[26]}7À.
A
ACHTREUNG
yield conclusive results about the ori-
entation of the ligand strands due the
presence of different isomers in solu-
tion, the possible co-crystallisation of
Keywords: directional ligands · hel-
ical structures · O,S donor ligands ·
self-assembly · titanium
Introduction
pared by transition-metal-directed self-assembly reactions.[2]
Among these, metallohelicates have attracted special inter-
est due to their presence in nature.[3] Raymond et al. isolat-
ed the first triple-stranded helicate [Fe2(RA)3] (H2RA=rho-
dothorulic acid) that contains exclusively oxygen donor
functions from hydroxamato groups.[4]
The spontaneous self-assembly of supramolecular coordina-
tion compounds has attracted much interest over the last
few decades,[1] and several structural motifs have been pre-
The first structurally characterised metallohelicate con-
tains two tris(bipyridine) ligands and three CuI ions and was
reported by Lehn et al. in 1987.[5] In the following years, hel-
icate chemistry was dominated by ligands with nitrogen
donors like oligopyrimidines. Later, the groups of Ray-
mond,[6] Stack[7] and Albrecht[8] prepared a series of dicate-
chol ligands that have been used to prepare dinuclear,
triple-stranded helicates. Besides helicates, tetranuclear clus-
ters of the type [M4L6]nÀ have been prepared from dicate-
chol ligands and selected metal ions, and these clusters have
been used as host molecules in host–guest chemistry.[9]
[a] Dr. C. Schulze Isfort, Dr. T. Kreickmann, T. Pape,
Prof. Dr. F. E. Hahn
Institut für Anorganische und Analytische Chemie
Westfälische Wilhelms-Universität Münster
Corrensstrasse 36, 48149 Münster (Germany)
Fax : (+49)251-833-3108
E-mail: fehahn@uni-muenster.de
[b] Dr. R. Frçhlich
Organisch-Chemisches Institut
Westfälische Wilhelms-Universität Münster
Corrensstrasse 40, 48149 Münster (Germany)
2344
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Chem. Eur. J. 2007, 13, 2344 – 2357

FULL PAPER
Sulfur donor groups remain comparatively rare in supra-
molecular chemistry. In 1995, we described a method for the
ortho functionalisation of benzene-1,2-dithiol that led to the
preparation of the first bis- and tris(benzene-o-dithiol) li-
gands.[10] Some dinuclear, non-helical nickel complexes[11]
and a tetranuclear metallacycle[12] have since been described
with this type of ligand, and the first triple-stranded heli-
cates with bis(benzene-o-dithiolato) ligands have been de-
scribed recently.[13]
Triple-stranded helicates built from ligands containing dif-
ferent donor units (a type of directional ligand) are rare.
The orientation of a directional ligand in a dinuclear com-
plex is of special interest since both complexes with stereo-
isomeric metal centres (L, D isomers) and regioisomeric
complexes (parallel or antiparallel orientation of the li-
gands) can be formed. Several directional ligands have been
used successfully for the preparation of dinuclear helical
complexes. For instance, Albrecht et al. have described
triple-stranded helicates build from the catechol/aminophe-
nol ligand A.[14] A homodinuclear complex with an antipar-
allel orientation of the ligands was obtained from the reac-
tion of A with GaIII or TiIV, whereas the reaction of A with a
mixture of GaIII and TiIV gave a heterodinuclear complex
with a parallel orientation of the ligand strands. In addition,
1,2-dithiolato dianion; M=Mo,[18] W[19]) can adopt a pseudo-
octahedral ([MoV
A
N
prismatic ([MoVI
N
N
ometry. Incorporation of molybdenum or tungsten into di-
nuclear, triple-stranded complexes with ligands like H4-1
could lead to a helicate with two octahedral metal centres
or to a non-helical complex containing at least one trigonal-
prismatic {MVIS6} (M=WVI or MoVI) metal centre. This,
however, would require the parallel orientation of the
ligand strands in the dinuclear, triple-stranded complex. In a
first study we have demonstrated that ligand H4-1 reacts
with TiIV to form a triple-stranded, dinuclear helicate with a
parallel orientation of the ligand strands.[17] However, since
H4-1 is directional with respect to the donor groups and the
spacer unit, the reasons for the parallel orientation of the
ligand strands remained speculative. With this contribution
we expand our study of the coordination chemistry of mixed
benzene-o-dithiolato/catecholato ligands and report on the
TiIV coordination chemistry of the ligands H4-2–H4-4, which
contain a non-directional, symmetrical diamide bridge be-
tween the donor groups.
Results and Discussion
directional ligands that have identical donor groups but an
asymmetric spacer between them (B[15] and C[16]) are known.
An antiparallel orientation of the ligand strands was ob-
served in homodinuclear double-stranded silver complexes
with ligand B, which was attributed mainly to the geometric
situation within the ligand,[15] and Albrecht et al. have de-
scribed a series of unsymmetrical, amino-acid-bridged dica-
techol ligands of type C that form only dinuclear double-
stranded complexes with TiIV; no dinuclear, triple-stranded
helicates were observed.[16]
Ligand synthesis: Scheme 1 depicts, as an example, the prep-
aration of ligand H4-2 using a procedure which is similar to
the method developed by Albrecht et al. for the synthesis of
ligands of type C.[20] The synthesis starts from 2,3-di(isopro-
pylmercapto)benzoic acid chloride (5), which we have re-
ported previously.[10] Reaction of 5 with the single tert-
butyloxycarbonyl
(Boc)-protected ethylenediamine 6[21] in
A
the presence of NEt3 yields compound 7. Removal of the
Boc group by treatment with trifluoroacetic acid liberates
the free amine 8. Compounds of type 8 with aliphatic
spacers between the nitrogen atoms have been isolated in
their deprotonated form, while the compounds with aromat-
ic spacers are normally isolated as hydrochlorides. Com-
pound 8 reacts with 2,3-di(benzyloxy)benzoic acid chlo-
ride[22] to give the S- and O-alkylated ligand precursor 9.
Both the benzyl and the isopropyl protection groups can be
removed simultaneously by treatment with sodium/naphtha-
lene in THF to give H4-2 after hydrolysis with HCl/H2O. Li-
We recently reported the synthesis of the first mixed ben-
zene-o-dithiol/catechol ligand H4-1,[17] which is a new type of
directional ligand that contains two different donor groups
with an unsymmetrical spacer between them. Our interest in
the coordination chemistry of ligands containing the ben-
zene-o-dithiolato donor unit was triggered by the unique
features of tris(benzene-1,2-dithiolato) complexes. For ex-
ample, complexes of the type [M
(bdt)3]nÀ (bdt=benzene-
A
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2345

F. E. Hahn et al.
iour of the analogous dicate-
cholato and bis(benzene-o-di-
thiolato) ligands with the same
topology as H4-1, which both
form dinuclear, triple-stranded
helicates of type [M2L3]nÀ
when reacted in a metal/ligand
ratio of 2:3 (M=FeIII, dicate-
cholato ligand;[7a] M=TiIV,
bis(benzene-o-dithiolato
A
able to isolate Na2[22] in an
analytically pure form or to
crystallise the compound. Re-
crystallisation of Na2[22] in the
presence of (AsPh4)Cl from a
methanol/diethyl ether solution
gave, after cation exchange,
analytically pure (AsPh4)2[22]
as a red powder which was
fully characterised by elemen-
tal analysis, mass spectrometry
and NMRspectroscopy.
Scheme 1. Preparation of ligand H4-2.
Owing to the directionality
gands of type H4-2 are only soluble in DMF and are there-
fore easily purified by washing with water and diethyl ether.
Ligands H4-1,[17] H4-3 and H4-4 were synthesised following
the same procedure, the only difference being the use of the
singly Boc-protected amines 10 (for H4-1), 14 (for H4-3) and
18 (for H4-4) (Scheme 1) instead of 6 for the initial coupling
with the acid chloride 5.
of the ligand 24À two regioisomeric complexes [22]2À can be
formed, one with an antiparallel orientation of the ligand
strands and one with a parallel orientation (Scheme 2).
Apart from these parallel and antiparallel regioisomers, a
total of seven stereoisomers of the complex dianion [22]2À
are possible due to the chirality of the (distorted) octahedral
titanium centres. Three stereoisomers result from the anti-
parallel orientation of the ligand strands, while the parallel
orientation leads to another four stereoisomers (Figure 1).
Six of these seven stereoisomers form three pairs of enantio-
mers, while no enantiomer exists for the D,L complex with
an antiparallel orientation of the ligand strands (Figure 1).
If all isomers coexist in solution, a maximum of four sets
of resonances will be observed in the NMRspectra (one for
each isomer/pair of enantiomers). A similar situation has
been described by Albrecht, who reported a complex anion
composed of two TiIV ions coordinated by two phenylala-
nine-bridged (directional) dicatecholato ligands and two
bridging methoxy co-ligands.[16]
Synthesis of the dinuclear, double-stranded complex
(AsPh4)2
three equivalents of ligand H4-2 with two equivalents of
[TiO(acac)2] and Na2CO3 in methanol gave a brownish solu-
tion containing the double-stranded, dinuclear complex Na2-
[Ti2(2)2(m-OCH3)2] (Na2[22]) rather than the hoped-for
triple-stranded, dinuclear helical complex Na4[Ti2(2)3]
(Scheme 2). No evidence for the formation of the triple-
stranded helicate Na4[Ti2(2)3] was found even after increas-
ing the ligand:metal ratio. This is in contrast to the behav-
A
G
ACHTREUNG
A
ACHTREUNG
AHCTREUNG
AHCTREUNG
The 1H NMRspectrum of
(AsPh4)2[22] shows two singlets
for the protons of the methoxy
groups
at
d=4.38
and
4.52 ppm, 12 doublets and six
triplets for the aromatic pro-
tons of the benzene-o-dithiola-
to and catecholato groups
(Figure 2), and six signals for
the aliphatic CH2 protons of
the ethylene bridge. This clear-
ly shows that three of the four
possible isomers (or pairs of
Scheme 2. Preparation of (AsPh4)2
G
N
A
enantiomers)
are
formed
2346
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Chem. Eur. J. 2007, 13, 2344 – 2357

Helical Complexes Containing Diamide-Bridged Ligands
FULL PAPER
ence of three isomers (or pairs of enantiomers) of
(AsPh4)[22] in solution. However, the expected six NH reso-
nances are detected at low temperature (Figure 3).
Figure 3. Variable temperature 1H NMRspectra of (AsPh 4)2[22] (in
[D7]DMF) showing four NH resonances at ambient temperature (303 K)
and six NH resonances at low temperature (223 K).
Figure 1. Schematic representation of the possible stereoisomers of com-
plex anion [22]2À
.
It has been demonstrated that the amide proton reso-
1
nance in the H NMRspectrum is a sensitive probe for the
detection of hydrogen bonds between it and the donor
groups (O and S) of the adjacent benzene-o-dithiolato and
catecholato groups.[17] Strong N H···O/S hydrogen bonds
À
give rise to a downfield shift of the NH resonances relative
to the uncoordinated, protonated ligand. The NH resonan-
ces of ligand H4-2 appear as singlets at d=9.10 (catechol
amide) and 8.83 ppm (benzene-o-dithiol amide) in the
1H NMRspectrum. We have not been able to assign the six
NH resonances at d=10.06, 9.82, 9.53, 9.00, 8.33 and
8.10 ppm that are observed in the 1H NMRspectrum of
(AsPh4)2[22] at low temperature (Figure 3), therefore it re-
mains open to speculation which kind of hydrogen bonds
À
À
(N H···O or N H···S) are formed in the complex anion
Figure 2. Part of the 1H NMRspectrum of (AsPh 4)2[22] (in [D7]DMF)
showing 12 doublets and six triplets for the aromatic protons of the
ligand strands.
[22]2À.
The NMRspectra of (AsPh )2[22] do not become simpler
4
upon heating or extended standing of solutions of the com-
plex at room temperature, thus indicating that the isomers
do not differ significantly in their energy. Red single crystals
of (AsPh4)2[22]·2CH3OH were obtained by slow diffusion of
diethyl ether into a methanolic solution of (AsPh4)2[22].
Compound (AsPh4)2[22]·2CH3OH crystallises in the centro-
during the preparation of (AsPh4)2[22] and coexist in solu-
tion. Each of these isomers (or pairs of enantiomers) gives
rise to four doublets and two triplets for the aromatic pro-
tons of the ligand strands and two signals for the methylene
protons of the bridging ethylene group. The mixture of
three isomers must contain at least one complex with a par-
allel and one complex with an antiparallel orientation of the
ligand strands.
¯
symmetric space group P1 with Z=1. The complex dianion
[22]2À resides on a crystallographic inversion centre. Provid-
ed that there is no crystallographic disorder, the complex
dianions [22]2À with a parallel orientation of the ligand
strands, which are present in solution, cannot lie on an in-
version centre. The detection of [22]2À on a crystallographic
inversion centre could therefore indicate that only complex
anions with an antiparallel orientation of the ligand strands
are present in the crystals of (AsPh4)2[22]·2CH3OH. Alter-
natively, all three isomers present in solution could co-crys-
tallise in a disordered lattice. Unfortunately, the latter situa-
tion was observed with crystals of (AsPh4)2[22]·2CH3OH.
The dianion [22]2À is severely disordered in the solid state.
All donor atoms (S and O) coordinated to the titanium
atoms are disordered. As a consequence, each benzene-o-di-
thiolato group can be replaced with a catecholato group,
and vice versa, therefore no unambiguous assignment can
1
Integration of the signal intensities in the H NMRspec-
trum of (AsPh4)2[22] shows that two main isomers (46 and
35%) and one minor isomer (19%) are present in solution.
Unfortunately, we have not been able to assign the stereo-
isomers based on the NMRspectra. The formation of three
isomers (or pairs of enantiomers) is also corroborated by
the observation of 36 signals for the aromatic carbon atoms
of the benzene-o-dithiolato and catecholato groups (12 for
each isomer or pair of enantiomers) in the 13C NMRspec-
trum of (AsPh4)2[22].
Only four resonances for the amide NH protons of [22]2À
are observed at ambient temperature (two for each isomer
or pair of enantiomers). This appears to contradict the pres-
Chem. Eur. J. 2007, 13, 2344 – 2357
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2347

F. E. Hahn et al.
be made regarding the donor atoms for each titanium atom
in [22]2À and thus the orientation of the ligand strands
cannot be determined. In addition, no reliable bond distan-
ces or angles can be determined. Since anion [22]2À possess-
es a crystallographic inversion centre in the middle of the
[Ti2(m-OCH3)2] ring in the crystal lattice, it can be assumed
A
that only anions with opposite configurations at the two
metal centres (meso complexes) crystallise. However, such
meso complex dianions can form with both a parallel or an-
tiparallel orientation of the ligand strands. Thus, the crystal
structure determination only confirms the chemical compo-
sition of the dianion to be [Ti2(2)2
(m-OCH3)2]2À. One of the
A
isomers of [22]2À present in the crystal structure of (As-
Ph4)2[22]·2CH3OH is depicted in Figure 4. This is the isomer
with the antiparallel orientation of the ligand strands and
opposite configurations at the metal centres that corre-
sponds best to the crystallographically observed site symme-
try.
Figure 5. 1H NMRspectrum of (PNP) [23] (in [D7]DMF).
2
the observation of only two amide NH resonances at d=
10.19 and 9.30 ppm. These resonances are shifted downfield
to a different extent (Dd=0.31 and 1.11 ppm) compared to
the free ligand H4-3 (NH resonances at d=10.50 and
10.41 ppm). We take this difference as an indication that
only one NH proton of each ligand strand is engaged in a
À
strong N H···X (X=O, S) hydrogen bond. Owing to the dif-
ferences in electronegativity and local charges at the donor
À
atoms, it is reasonable to assume that N H···O hydrogen
bonds have been formed to the catecholato oxygen atoms.[17]
The NMRspectra of (PNP) [23] are consistent with both
2
a parallel and an antiparallel orientation of the ligand
strands. We therefore attempted to determine the molecular
structure of (PNP)2[23]. Single crystals of (PNP)2[23] suita-
ble for an X-ray diffraction analysis were grown by slow dif-
fusion of diethyl ether into a solution of (PNP)2[23] in ace-
tone. (PNP)2[23] crystallises in the triclinic space group P1
with Z=1. The molecular structure of the dianion [23]2À is
depicted in Figure 6. The ligand strands in [23]2À are orient-
ed in a parallel fashion. One titanium atom (Ti2) is coordi-
nated by six oxygen atoms in a distorted octahedral fashion,
whereas the other titanium atom (Ti1) is coordinated by two
oxygen atoms and four sulfur atoms, also in a distorted octa-
hedral fashion, with the oxygen atoms in a cis arrangement.
Figure 4. ORTEP drawing of the centrosymmetric [22]2À anion present in
the crystal structure of (AsPh4)2[22]·2CH3OH. The labelling of the donor
groups (S and O) is arbitrary since all donor atoms are disordered. Hy-
drogen atoms have been omitted for clarity.
Synthesis of the dinuclear complexes (PNP)
OCH3)2] ((PNP)2[23]) and (PNP)4[Ti2(3)3] ((PNP)4[24]):
Only the brown, double-stranded complex Na2[Ti2(3)2(m-
OCH3)2] (Na2[23]) was obtained upon treatment of three
equivalents of H4-3 with two equivalents of [TiO(acac)2] and
A
G
AHCTREUNG
A
ACHTREUNG
AHCTREUNG
Na2CO3 in methanol at 258C. Addition of two equivalents
of (PNP)Cl (PNP+ =bis(triphenylphosphoranylidene)am-
monium) to a methanolic solution of Na2[23] gave (PNP)2-
A
N
crystallised from acetone/diethyl ether to yield analytically
pure, crystalline (PNP)2[23].
The complex dianion [23]2À can exist as the same mixture
of isomers as described for [22]2À (Figure 1). However, the
1H NMRspectrum of (PNP) [23] (Figure 5) shows only one
2
set of signals for the aromatic protons of the ligand strands
(four doublets and two triplets for the aromatic donor
groups and two doublets of triplets and two doublets for the
bridging phenylene group), thereby indicating that only one
of the possible isomers is formed. This is corroborated by
Figure 6. ORTEP plot of the anion [23]2À with the amide hydrogen atoms
shown at calculated positions. The dotted lines indicate hydrogen bonds.
2348
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Chem. Eur. J. 2007, 13, 2344 – 2357

Helical Complexes Containing Diamide-Bridged Ligands
FULL PAPER
The two titanium atoms and the methoxy ligands form the
central [Ti2(m-OCH3)2] ring with a Ti···Ti separation of
A
3.180(2) Š (Table 1), which is similar to the value found in
[22]2À and in other complexes with a similar structure.[7a,16]
Table 1. Selected bond lengths [Š] and angles [8] in (PNP)2[23].
Parameter
Parameter
Ti1···Ti2
3.180(2)
2.381(2)
2.364(3)
2.377(2)
2.422(3)
1.990(5)
1.929(5)
1.975(5)
1.921(6)
2.010(5)
À
À
Ti1 S1
Ti1 O42
2.009(5)
2.008(5)
1.996(5)
81.37(8)
81.87(8)
75.0(2)
79.8(2)
79.9(2)
75.3(2)
À
À
Ti1 S2
Ti2 O41
À
À
Ti1 S3
Ti2 O42
À
Ti1 S4
S1-Ti1-S2
À
Ti2 O1
S3-Ti1-S4
À
Ti2 O2
O41-Ti1-O42
O1-Ti2-O2
O3-Ti2-O4
O41-Ti2-O42
À
Ti2 O3
À
Ti2 O4
Figure 7. 1H NMRspectrum of (PNP) [24] (in [D7]DMF).
À
4
Ti1 O41
1
all peaks in the H NMRspectrum can be assigned unam-
biguously. However, six triplets are observed between d=
6.73 and 6.39 ppm, which can be assigned to the protons Ha–
Hf that are attached in the meta positions of the benzene-o-
dithiolato and catecholato rings (Figure 8). This observation
suggests that at least two isomers of [24]4À are formed,
namely the complex anions with a parallel and the one with
an antiparallel orientation of the ligand strands.
À
Strong N H···O hydrogen bonds are formed in the solid
state, as indicated by the H NMRspectrum. This leads to
1
À
À À À
nearly planar N H···O C C C rings and short, non-bond-
ing N···O distances (N2···O1 2.779(8) and N4···O3
2.731(8) Š). Partly due to these strong N H···O hydrogen
bonds, the Ti O bonds to the oxygen donors in the ortho
position to the amide group are elongated (Ti2 O1 1.990(5)
and Ti2 O3 1.975(5) Š), while
the bonds to the oxygen atoms
À
À
À
À
in the meta position are short-
À
À
er (Ti2 O2 1.929(5) and Ti2
O4 1.921(6) Š). Contrary to
this, the benzene-o-dithiolato
amide subunits are not planar
and exhibit long intramolecu-
lar N···S separations (N1···S1
2.948(6)
and
N3···S3
3.106(7) Š), which are indica-
À
tive of weak or no N H···S hy-
drogen bonds.
Figure 8. Possible regioisomers of the anion [24]4À
.
The reaction of three equiv-
alents of H4-3 with two equiva-
lents of [TiO(acac)2] and
G
Na2CO3 in methanol at an elevated temperature of 508C ini-
tially leads to the formation of the double-stranded complex
Only five of the six expected signals for the amide protons
(Figure 7, assuming the presence of anions [24]4À with paral-
lel and antiparallel orientations of the ligand strands; see
Figure 8) are observed between d=12.03 and 10.70 ppm. All
signals for the amide protons are shifted downfield relative
to those of the free ligand H4-3, although to a different
extent (Dd=0.19–1.52 ppm). We therefore assume that
Na2
plex is quantitatively converted into the triple-stranded heli-
cate Na4[Ti2(3)3] (Na4[24]) within 12 h at 508C. We assume
A
G
ACHTREUNG
that complex Na4[24] is formed by a reaction between
Na2[23] and the deprotonated ligand 34À. This suggestion is
corroborated by the observation that Na2[23] does not form
the triple-stranded helicate Na4[24] at an elevated tempera-
ture in the absence of 34À.
À
À
strong N H···O and weak N H···S hydrogen bonds exist in
the complex anion [24]4À similar to those in the complex
anion [23]2À.
The salt (PNP)
A
An evaluation of the signal intensities shows that the
triple-stranded helicate with a parallel orientation of the
ligand strands is the major product (65%), while the heli-
cate with the antiparallel orientation is obtained as the
minor product (35%). We assume that the elevated reaction
temperature employed for the preparation of (PNP)4[24] is
precipitate after addition of four equivalents of (PNP)Cl to
a methanolic solution of Na4[24]. The H NMRspectrum of
(PNP)4[24] shows more than one set of signals for the ligand
strands, thus indicating that a mixture of isomers is present
in solution (Figure 7). Due to an overlap of the signals, not
Chem. Eur. J. 2007, 13, 2344 – 2357
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2349

F. E. Hahn et al.
4À
À
responsible for the formation of the two isomeric complex
mation of a strong N H···O hydrogen bond in [25] . Con-
trary to this, the resonance for the amide proton of the ben-
zene-o-dithiolato amide subunit in [25]4À (He at d=
8.14 ppm) is shifted slightly to high field (Dd=À0.11 ppm)
anions [24]4À.
Synthesis of the triple-stranded helicates Na
(Na(PNP)3[25]) and Na(PNP)3[Ti2(4)3] (Na(PNP)3[26]): Li-
gands H4-1 and H4-4 exclusively form dinuclear, triple-
stranded helicates Na4[Ti2(1)3] (Na4[25]) and Na4[Ti2(4)3]
(Na4[26]) when treated with [TiO(acac)2] in a 3:2 stoichiom-
etry in the presence of Na2CO3. Attempts to obtain a dinu-
clear double-stranded complex Na2[Ti2(1)2(m-OCH3)2] relat-
A
G
A
N
G
N
compared to the free ligand. This indicates that no or only
weak N H···S hydrogen bonds exist in [25] . The NMR
4À
À
A
N
spectroscopic data indicate the presence of the parallel re-
gioisomer and only one pair of stereoisomers in solution.
However, they do not allow the determination of which pair
of stereoisomers (L,D/D,L or L,L/D,D complexes) is pres-
ent.
AHCTREUNG
A
ACHTREUNG
ed to Na4[22] failed, even though H4-1 and H4-2 possess sim-
ilar ligand backbones. Surprisingly, only three of the four
sodium cations in Na4[25] and Na4[26] can be exchanged for
PNP+ cations upon addition of up to 10 equivalents of
(PNP)Cl to methanolic solutions of Na4[25] and Na4[26].
Single crystals of Na
ble for an X-ray diffraction analysis were grown by slow dif-
fusion of diethyl ether into a solution of Na(PNP)3[25] in
(PNP)3[25]·CH3OH·H2O·Et2O suita-
AHCTREUNG
wet methanol. The complex crystallises in the triclinic space
group P1 with Z=1. The molecular structure of the anion
[25]4À is depicted in Figure 10. It confirms the parallel orien-
Compounds Na
N
N
as analytically pure red powders after recrystallisation from
methanol/diethyl ether.
1
The H NMRspectrum of Na
A
set of signals for the ligand strands, which is indicative of
the formation of only one geometrical isomer of [25]4À with
a parallel orientation of the ligand strands in solution. The
aromatic protons of the benzene-o-dithiolato and catechola-
to groups appear as one triplet (d=6.65 (Hg) and 6.32 (Hc)
ppm) and two doublets (d=7.08 (Hf), 6.98 (Hh) and d=7.15
(Hb), 6.21 ppm (Hd)) for each ring (Figure 9). The triplet at
d=9.80 ppm was assigned to the catechoyl amide NH
proton (Ha) based on the observed coupling with the neigh-
bouring CH2 group of the bridging unit. The downfield shift
(Dd=0.70 ppm) of this NH signal (Figure 9, bottom) rela-
tive to the free ligand H4-1 (Figure 9, top) indicates the for-
Figure 10. ORTEP diagram of the anion [25]4À with amide hydrogen
atoms at calculated positions. The dotted lines indicate hydrogen bonds.
tation of the ligand strands that was concluded from the
NMRspectroscopic data. Each of the titanium atoms is co-
ordinated by six identical donor atoms (O or S) in a distort-
À
ed octahedral fashion. The Ti O bond lengths (Table 2) fall
in the range reported for other TiIV tris(catecholato) com-
plexes.[23] The Ti S bond lengths vary only slightly and are
À
comparable to bond lengths reported for tris(o-benzenedi-
thiolato) complexes of TiIV.[24] A helical twist of 65.68 has
been calculated. Both titanium atoms in the studied crystal
of Na(PNP)3[25] assume the same configuration, namely L.
G
Since it crystallises in the acentric space group P1, the D,D
stereoisomer must also have formed during the reaction. A
similar spontaneous resolution of stereoisomers upon crys-
tallisation was first described for triple-stranded NiII com-
plexes with oligobipyridine ligands.[25] At ambient tempera-
ture we observed the formation of only one pair of helical
stereoisomers. However, the formation of meso helicates of
the L,D and D,L type might be possible by a dynamic pro-
cess, for example at elevated temperature.
Figure 9. 1H NMRspectra (in [D 7]DMF, *=DMF resonances) of H4-1
(top) and Na(PNP)3[25] (bottom).
A
2350
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ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 2344 – 2357

Helical Complexes Containing Diamide-Bridged Ligands
FULL PAPER
Table 2. Selected bond lengths [Š] and angles [8] in complexes Na-
A
ACHTREUNG
[a]
G
Na1.5(PNP)6.5[26]2
N
À
Ti1 Ti2
9.795(2)
2.392(3)
2.381(3)
2.387(3)
2.416(3)
2.436(3)
2.430(3)
1.992(6)
2.010(6)
1.977(6)
1.941(6)
1.915(6)
1.904(6)
81.94(9)
81.64(9)
81.68(9)
79.8(2)
12.460/12.514
2.369(5)/2.390(4)
À
Ti1 S1a
(S12)
À
Ti1 S1b
À
Ti1 S1c
À
Ti1 S2a
(S11)
2.427(5)/2.427(4)
À
Ti1 S2b
À
Ti1 S2c
Figure 11. Part of the crystal structure of Na(PNP)3[25]·H3OH·Et2O·H2O.
H
À
Ti2 O3a
(O34)
2.007(9)/1.988(10)
2.016(10)/1.960(11)
81.83(15)/81.61(12)
80.4(4)/79.7(4)
7À
The PNP+ ions and the disordered diethyl ether molecule have been
omitted. Only the oxygen donor atoms of the water and methanol mole-
cules coordinated to the bridging sodium cation are depicted.
À
Ti2 O3b
À
Ti2 O3c
À
Ti2 O4a
A
À
Ti2 O4b
À
Ti2 O4c
containing parallel oriented ligand strands. With the related
directional ligand containing catechol/aminophenol donor
groups reported by Albrecht et al., only the antiparallel
ligand orientation, which leads to a minimal charge separa-
tion in the complex, was observed for homobinuclear com-
plexes.[14] The directional ligand H4-1 was expected to
behave similarly. However, H4-1 is a directional ligand with
regards to both the donor groups and the spacer between
them. Upon formation of the triple-stranded helicate [25]4À
a distorted {TiS6} octahedron and a smaller {TiO6} octahe-
dron are obtained. It is reasonable to expect that the steri-
cally more demanding part of the unsymmetrical -C(Me)2-
CH2- spacer is oriented towards the larger {TiS6} octahe-
dron, thereby causing the parallel orientation of the ligand
strands. This orientation allows the formation of three stable
S1a
A
U
S1b-Ti1-S2b
S1c-Ti1-S2c
O3a
A
O3b-Ti2-O4b
O3c-Ti2-O4c
78.9(2)
80.0(3)
[a] The asymmetric unit contains 1/3 of the anion {[26]4À-Na+-[26]4À
} ;
the titanium and sodium atoms reside on special positions on a threefold
axis (Wyckoff position c, site symmetry 3).
1
As was seen in the H NMRspectrum for solutions of Na-
À
A
the solid state. This leads to nearly planar N H···O C C C
rings and short intramolecular nonbonding N···O distances
(2.664(10)–2.673(10) Š). In contrast, the benzene-o-dithiola-
À
À À À
À
to amide subunits exhibit non-planar N H···S C C C rings
(Figure 10) and longer intramolecular nonbonding N···S dis-
tances (3.051(8)–3.193(7) Š), which indicates that only weak
intramolecular N H···O hydrogen bonds and of three
À
À À À
almost planar N H···O C C C(O) rings within the cate-
choyl amide groups at the {TiO6} octahedron (Figure 10).
This type of intramolecular hydrogen bond has been ob-
served for other helicates with amide- bridged catecholato
donor groups[6c,7b] and for other catechoyl amide com-
plexes,[26] and has often been shown to determine the molec-
À
or no N H···S hydrogen bonds exist in the solid state.
The Ti O bonds to the oxygen donors in the ortho posi-
tion to the amide function are slightly longer (1.977(6)–
2.010(6) Š) than those to the oxygen donors in the meta po-
sition (1.904(6)–1.941(6) Š, Table 2). A similar effect is ob-
À
ular structure.[27] Similarly strong N H···S hydrogen bonds
À
were not observed in [25]4À, and the benzenedithiolato
groups are not coplanar with the attached amide groups. We
therefore propose a structure-determining influence of the
unsymmetrical -C(Me)2-CH2- spacer on the formation of the
parallel regioisomer of [25]4À. This postulate is corroborated
by the observation that ligand H4-2, which contains a sym-
metrical CH2-CH2 spacer, forms, among others, the dinu-
À
served for the benzene-o-dithiolato groups, where the Ti S
bonds to the sulfur donors in the ortho position are slightly
longer (2.416(3)–2.436(3) Š) than those to the sulfur donor
atoms in the meta position to the amide function (2.381(3)–
2.392(3) Š). While the effect is smaller for the Ti S bonds
than for the Ti O bonds, it cannot be attributed exclusively
to the existence of intramolecular hydrogen bonds, as such
interactions only exist in the catechoyl amide part of the
complex anion.
À
À
clear TiIV complex [Ti2(2)2(OMe)2]2À, which has an antiparal-
lel orientation of the ligand strands.
A
The unit cell contains one [25]4À ion, three PNP cations,
one sodium cation and one molecule each of water, metha-
nol and (disordered) diethyl ether. The PNP cations main-
tain no remarkable contacts with the anion whereas the Na+
cation acts as a bridge between the [25]4À anions by coordi-
nating to the amide carbonyl functions of two different
anions, which leads to the formation of infinite chains in the
crystal lattice (Figure 11). The Na+ ions complete their coor-
dination sphere by coordinating to one molecule each of
methanol and water.
The reaction of three equivalents of H4-4, two equivalents
of [TiO
ACHTREUNG
ture under argon yields a deep red solution of Na
ACHTREUNG
(Na4[26]). As was observed with Na
ACHTREUNG
of the four sodium cations can be substituted with PNP+
cations, even when a large excess of (PNP)Cl (up to
10 equiv) is added to a methanolic solution of Na4(26). The
1H NMRspectrum of Na
(PNP)3[26] consists of only one set
R
of signals, which is in accordance with the presence of only
one regioisomer with a parallel orientation of the ligand
strands. Two signals are been observed for the amide pro-
tons, at d=12.01 and 10.68 ppm. The strong downfield shift
We can only speculate about the driving force for the for-
mation of the triple-stranded helical complex anion [25]4À
Chem. Eur. J. 2007, 13, 2344 – 2357
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2351

F. E. Hahn et al.
for the protons of the catechoyl amide group in [26]4À (Dd=
1.5 ppm) relative to the signal in the free ligand H4-4 is
Bridging of related triple-stranded helicates containing di-
catecholato ligands by alkali cations, which leads to linear
polymeric chains, has been described.[3b] The formation of
the linear polymeric chain Na+-[26]4À-Na+-[26]4À-Na+ is,
however, not possible, since the coordination of the soft
sulfur donors to the hard sodium cations is unfavourable.
À
caused by the formation of strong N H···O hydrogen bonds.
The signal for the benzene-o-dithiolato-bound amide pro-
tons is shifted only slightly downfield (Dd=0.17 ppm), thus
À
indicating that no, or only weak, N H···S hydrogen bonds
exist in the anion [26]4À.
Attempts to crystallise Na
of diethyl ether into a solution of Na
to the formation of single crystals of Na1.5-
(PNP)6.5[26]2·3DMF suitable for an X-ray analysis. The com-
ACHTREUNG
A
Conclusion
G
We have reported the synthesis of a series of mixed ben-
zene-o-dithiol/catechol ligands and their coordination
chemistry with titanium(iv). Dinuclear, triple-stranded heli-
cates [Ti2(L)3]4À and dinuclear, double-stranded complexes
¯
plex crystallises in the hexagonal space group R3c (Z=12).
The titanium atoms and the sodium atoms of the {[26]-Na-
[26]}7À unit reside on a threefold crystallographic axis.
Nearly identical structural parameters are observed for the
two [26]4À anions in each {[26]-Na-[26]}7À unit (Table 2), in-
cluding identical configurations at all titanium centres. The
crystal structure of one of the [26]4À anions with a L,L con-
figuration is depicted in Figure 12 and confirms the parallel
orientation of the ligand strands. Both titanium atoms are
coordinated in a slightly distorted octahedral fashion by six
identical donor atoms (O or S).
[Ti2(L)2
(m-OCH3)2]2À are formed depending on the ligand
G
backbone and the reaction conditions. The directionality of
the ligand strands in 24À leads to the formation of up to
three of four possible isomers/pairs of stereoisomers in solu-
tion. For most of the complexes that have been investigated,
a parallel orientation of the ligand strands is observed. We
are currently investigating the preparation and properties of
heterodinuclear complexes with mixed benzene-o-dithiolato/
catecholato ligands. In particular, the formation of triple-
stranded helicates containing both {Ti(catecholato)3}2À and
{M
[M
ACHTREUNG
AHCTREUNG
nal-prismatic (n=0) or octahedral (n=1) coordination ge-
ometry. Redox reactions at heterodinuclear (Mo,W/Ti),
triple-stranded helicates could be used to change the coordi-
nation geometry at one of the metal centres (MoS6, WS6),
while the geometry at the other metal centre (TiO6) remains
unchanged. This would, in principle, allow the switching on
or off of the helicity of the triple-stranded, heterodinuclear
helicate by a redox reaction.
Experimental Section
All operations were carried out under an atmosphere of dry argon by
using Schlenk and vacuum techniques. Solvents were dried by standard
methods and freshly distilled prior to use. NMRspectra were recorded at
258C with a Bruker AC 200 (200 MHz), Bruker AMX 400 (400 MHz) or
Varian Inova (600 MHz) spectrometer and are reported relative to TMS
as an internal standard or to the solvent signal. IRspectra were recorded
with a Bruker Vector 22 IRspectrometer. Mass spectra were measured
with a Varian MAT 212 (EI), a Micromass Quattro LC-Z (ESI) or a
Bruker Reflex IV (MALDI) spectrometer. Elemental analyses were per-
formed with a Vario EL III CHNS analyzer. Commercially available
Figure 12. ORTEP diagram of one [26]4À anion (left) and the aggregate
{[26]-Na-[26]}7À (right). The asymmetric unit contains 1/3 of the anion
{[26]4À-Na+-[26]4À 7À; the titanium and sodium atoms reside on a special
}
position on a threefold axis.
[TiO(acac)2] (Aldrich) was used without further purification. 2,3-Di(iso-
C
Although nearly planar catechoyl amide subunits, and
À
À
therefore strong N H···O hydrogen bonds (N O nonbond-
ing distances of 2.68(2)–2.73(2) Š), are formed in the solid
1,2-Diamino-N-(tert-butyloxycarbonyl)ethane (6): A solution of di-tert-
butyl dicarbonate (3.84 g, 17.6 mmol) in chloroform (50 mL) was added
at 08C to a solution of ethylenediamine (6 mL, 88 mmol) in chloroform
(400 mL) and the mixture was stirred for 12 h at ambient temperature.
The solvent was removed in vacuo and the remaining solid was dissolved
in ethyl acetate. The organic phase was washed with NaCl solution
(10 mL, 35%), dried with Na2SO4 and the solvent removed in vacuo.
Compound 6 was obtained as a colourless oil after distillation in vacuo.
Yield: 2.4 g (15.0 mmol, 85%). 1H NMR(200 MHz, CDCl 3): d=5.28 (s,
À
state, the Ti O bonds to the two different oxygen donor
atoms are nearly uniform (2.007(9) and 2.016(10)/1.988(10)
and 1.960(11) Š, Table 2). We assume that the coordination
of the sodium cation to the three oxygen donor atoms in the
meta position to the amide group has a similar effect as the
À
N H···O hydrogen bonds and leads to a similar elongation
À
of the Ti O bonds.
2352
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ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 2344 – 2357

Helical Complexes Containing Diamide-Bridged Ligands
FULL PAPER
1H; C(O)NH), 3.02 (q, 3J=6.1 Hz, 2H; NHCH2), 2.66 (t, 3J=6.1 Hz,
2H; NH2CH2), 1.31 (s, 9H; CH3), 1.12 ppm (s, 2H; NH2); 13C NMR
C
N
G
(50 MHz, CDCl3): d=156.1 (C(O)NH), 78.7 (OC(CH3)3), 43.2 (NHCH2),
G
41.6 (NH2CH2), 28.2 ppm (CH3); elemental analysis calcd (%) for
C7H16N2O2: C 52.48, H 10.07, N 17.48; found: C 52.24, H 10.12, N 17.32.
1-(tert-Butylcarbamido)-2-[2,3-di(isopropylmercapto)benzamido]benzene
(15): A solution of 5 (1.07 g, 3.7 mmol) in THF (10 mL) was added to a
solution of NEt3 (560 mL, 3.85 mmol) and N-(tert-butyloxycarbonyl)-1,2-
diaminobenzene (14; 772 mg, 3.7 mmol) in THF (30 mL). The solution
was stirred for 12 h at ambient temperature and NEt3·HCl was then fil-
tered off. The solvent was removed in vacuo and the solid obtained was
washed with water and diethyl ether. Compound 15 was obtained as
white powder. Yield: 1.48 g (3.21 mmol, 87%). 1H NMR(300 MHz,
CDCl3): d=8.58 (br.s, 1H; NH), 7.82 (d, 1H; Ar-H), 7.56–7.17 (m, 6H;
1,2-Diamino-N-(tert-butyloxycarbonyl)-1,1’-dimethylethane (10): Com-
pound 10 was prepared as described for 6 from di-tert-butyl dicarbonate
(3.84 g, 17.6 mmol) and (1,1’-dimethylethylenediamine (7.75 g, 88 mmol).
Yield: 2.5 g (13.5 mmol, 77%) of a colourless oil. 1H NMR(200 MHz,
CDCl3): d=5.12 (br.s, 1H; C(O)NH), 3.96 (s, 1H; C(O)NH-CHH), 2.94
(s, 1H; C(O)NH-CHH), 1.77 (s, 2H; NH2), 1.38 (s, 9H; CH3), 1.04 ppm
(s, 6H; CH3); 13C NMR(50 MHz, CDCl 3): d=156.8 (C(O)NH), 79.4
(OC
A
G
(CH3)2CH2), 28.9 (OC-
Ar-H), 6.73 (s, 1H; NH), 3.66–3.52 (m, 2H; CH(CH3)2), 1.56 (s, 9H; OC-
N
A
G
(CH3)3), 1.47 (d, 6H; CH
N
N
C9H20N2O2: C 57.42, H 10.71, N 14.88; found: C 57.37, H 10.51, N 14.34.
131.7, 129.5, 128.7, 128.4, 127.4, 125.9, 125.7, 124.9, 123.9 (Ar-C), 81.0
1,2-Diamino-N-(tert-butyloxycarbonyl)benzene (14): 1,2-Diaminobenzene
(2.5 g, 25 mmol) and Boc-ON (6.15 g, 25 mmol) were dissolved in DMF
(50 mL) and heated to 558C for 3 h. The solvent was removed in vacuo
and the residue dissolved in toluene (60 mL). The organic layer was
washed with aqueous NaOH (10%, 2”50 mL) and NaCl (10%, 2”
50 mL) and dried with MgSO4. Recrystallisation from chloroform/hexane
(OC
A
G
N
23.1 ppm (CH
AHCTREUNG
62.58, H 7.00, N 6.08; found: C 62.60, H 6.95, N 6.06.
1-(tert-Butylcarbamido)-4-[2,3-di(isopropylmercapto)benzamido]benzene
(19): Compound 19 was prepared as described for 15 from a solution of 5
(1.07 g, 3.7 mmol) in THF (10 mL), NEt3 (560 mL, 3.85 mmol) and N-
(tert-butyloxycarbonyl)-1,4-diaminobenzene (18; 772 mg, 3.7 mmol) in
THF (30 mL). Yield: 1.54 g (3.34 mmol, 89%) of a colourless powder.
1H NMR(300 MHz, CDCl 3): d=8.85 (br.s, 1H; NH), 7.56–7.29 (m, 7H;
gave
a
colourless powder. Yield: 3.0 g (15.8 mmol, 63%). 1H NMR
(300 MHz, CDCl3): d=7.43 (dd, 1H; Ar-H), 7.15 (td, 1H; Ar-H), 6.93
(td, 1H; Ar-H), 6.89 (dd, 1H; Ar-H), 6.61 (s, 1H; C(O)NH), 3.88 (s, 2H;
NH2), 1.69 ppm (s, 9H; CH3); 13C NMR(75 MHz, CDCl 3): d=153.8
(C(O)NH), 139.9, 125.9, 124.7, 124.6, 119.3, 117.3 (Ar-C), 80.3 (OC-
Ar-H), 6.57 (br.s, 1H; NH), 3.45 (sept, 1H; CH
CH(CH3)2), 1.47 (s, 9H; OC(CH3)3), 1.35 (d, 6H; CH
(d, 6H; CH
(CH3)2); 13C NMR(75 MHz, CDCl 3): d=166.9, 153.3 (CO),
146.2, 142.5, 135.4, 133.7, 129.5, 128.9, 126.7, 121.1, 119.8 (Ar-C), 80.9
(OC(CH3)3), 41.7 (SCH), 36.6 (SCH), 28.7 (OC(CH3)3), 23.5 (CH(CH3)2),
23.0 ppm (CH
ACHTREUNG
A
G
A
N
ACHTREUNG
(99) [M+ÀtBu], 135 (38) [M+ÀOtBu], 108 (100) [M+ÀBoc]; elemental
analysis calcd (%) for C11H16N2O2: C 63.44, H 7.74, N 13.45; found: C
63.30, H 7.61, N 13.34.
ACHTREUNG
A
N
ACHTREUNG
A
1,4-Diamino-N-(tert-butyloxycarbonyl)benzene (18): Compound 18 was
prepared as described for 14 from 1,4-diaminobenzene (2.5 g, 25 mmol)
and Boc-ON (6.15 g, 25 mmol). Yield: 4.6 g (22.3 mmol, 89%) of a col-
ourless powder. 1H NMR(300 MHz, CDCl 3): d=7.36 (d, 2H; Ar-H),
6.86 (br.d, 2H; Ar-H), 6.70 (br.s, 1H; C(O)NH), 3.73 (s, 2H; NH2),
[M+ÀBoc], 317 (18) [M+ÀBocÀiPr], 253 (64) [M+ÀNH
211 (67) [M+ÀNH(C6H4)NHBocÀiPr]+, 152 (100); elemental analysis
calcd (%) for C24H32N2O3S2: C 62.58, H 7.00, N 6.08; found: C 62.59, H
6.90, N 5.96.
1.76 ppm (s, 9H; CH3); 13C NMR(75 MHz, CDCl ): d=153.3 (C(O)NH),
1-Amino-2-[2,3-di(isopropylmercapto)benzamido]ethane (8): A sample
of compound 7 (1.55 g, 3.75 mmol) was dissolved in chloroform (15 mL)
and trifluoroacetic acid (3 mL, 15.2 mmol) was added carefully. The solu-
tion was stirred for 24 h at ambient temperature and the solvent was re-
moved in vacuo. Hydrochloric acid (20 mL, 5m) was added and the aque-
ous phase was washed with diethyl ether (2”20 mL). NaOH was then
added to the aqueous phase and this phase was extracted at pH 14 with
dichloromethane (3”20 mL). The combined organic layers were dried
with MgSO4 and the solvent was removed in vacuo to give 8. Yield:
0.99 g (3.2 mmol, 84%) of a white powder. 1H NMR(200 MHz, CDCl 3):
3
142.4, 129.6, 121.0, 115.4 (Ar-C), 79.8 (OC
U
G
1-(tert-Butyloxycarbamido)-2-[2,3-di(isopropylmercapto)benzamido]-
ethane (7): A solution of 2,3-di(isopropylmercapto)benzoic acid chloride
(5; 1.27 g, 4.4 mmol) in THF (10 mL) was added to a solution of NEt3
(700 mL, 4.84 mmol) and N-(tert-butyloxycarbonyl)-1,2-diaminoethane (6;
700 mg, 4.4 mmol) in THF (50 mL). The solution was stirred for 12 h and
the NEt3·HCl formed was filtered off. The solvent was removed in vacuo
and the residue was washed with water and dichloromethane to give 7 as
a white powder. Yield: 1.55 g (3.78 mmol, 86%). 1H NMR(200 MHz,
CDCl3): d=7.24 (m, 3H; Ar-H), 6.82 (s, 1H; NH), 5.22 (s, 1H; NH), 3.41
d=7.25 (m, 3H; Ar-H), 6.89 (br.s, 1H; NH), 3.43 (sept, 2H; CH
3.40 (q, 2H; C(O)NHCH2), 2.86 (t, 2H; CH2NH2), 1.37 (s, 2H; NH2),
1.33 (d, 6H; CH(CH3)2), 1.15 ppm (d, 6H; CH
(CH3)2); 13C NMR
(CH3)2),
A
ACHTREUNG
(50 MHz, CDCl3): d=168.9 (CO), 149.2, 145.5, 143.6, 128.7, 127.5, 124.7
(Ar-C), 42.8 (C(O)NHCH2), 41.3 (NH2CH2), 40.4 (SCH), 36.0 (SCH),
(m, 6H; S-CH
6H; CH(CH3)2), 1.17 ppm (d, 6H; CH
CDCl3): d=169.2, 156.2 (NHC(O)), 145.7, 143.5, 128.9, 128.5, 127.4,
124.5 (Ar-C), 79.3 (OC(CH3)3), 40.4 (SCH), 40.2 (CH2), 39.6 (CH2), 35.9
(SCH), 28.3 (OC(CH3)3), 23.1 (CH(CH3)2), 22.5 ppm (CH(CH3)2); ele-
A
N
22.9 (CH
N
N
A
ACHTREUNG
C15H24N2OS2: C 57.65, H 7.74, N 8.96; found: C 57.13, H 7.60, N 8.72.
G
1-Amino-2-[2,3-di(isopropylmercapto)benzamido]-2-(2,2’-dimethyl)-
ethane (12): Compound 12 was prepared as described for 8 from 11
A
N
ACHTREUNG
mental analysis calcd (%) for C20H32N2O3S2: C 58.22, H 7.82, N 6.79;
found: C 58.16, H 8.01, N 6.56.
(1.67 g, 3.75 mmol) and trifluoroacetic acid (3 mL, 15.2 mmol). Yield
1
0.83 g (2.43 mmol, 64%) of a white powder. H NMR(300 MHz, CDCl ):
3
d=7.53–7.44 (m, 3H; Ar-H), 6.60 (br.s, 1H; NH), 3.78–3.65 (m, 2H; CH-
1-(tert-Butyloxycarbamido)-2-[2,3-di(isopropylmercapto)benzamido]-2,2’-
dimethylethane (11): Compound 11 was prepared as described for 7 from
AHCTREUNG
A
N
ACHTREUNG
a
solution of 5 (1.27 g, 4.4 mmol) in THF (10 mL), NEt3 (700 mL,
4.84 mmol) and N-(tert-butyloxycarbonyl)-1,1’-dimethyl-1,2-diamino-
ethane (10; 828 mg, 4.4 mmol) in THF (50 mL). Yield: 1.56 g (3.56 mmol,
81%) of a colourless powder. 1H NMR(300 MHz, CDCl 3): d=7.37–7.48
A
ACHTREUNG
G
ACHTREUNG
tal analysis calcd (%) for C17H28N2OS2: C 59.96, H 8.29, N 8.23, S 18.83;
found: C 59.67, H 8.09, N 8.09, S 18.44.
(m, 3H; Ar-H), 6.31 (br.s, 1H; NHC
3.60–3.74 (m, 4H; SCH(CH3)2, NHCH2), 1.60 (s, 9H; OC
(d, 6H; CH(CH3)2), 1.55 (s, 6H; C(CH3)2CH2), 1.40 ppm (d, 6H; CH-
(CH3)2); 13C NMR(75 MHz, CDCl 3): d=169.0, 157.1 (CO), 146.1, 145.2,
129.4, 128.8, 127.7, 124.5 (Ar-C), 79.5 (OC(CH3)3), 59.3 (C(CH3)2CH2),
56.0 (CH2), 40.4 (SCH), 36.4 (SCH), 28.8 (OC(CH3)3), 25.4 (C-
ACHTREUNG
A
ACHTREUNG
A
N
1-(Ammonium
chlorido)-2-[2,3-di(isopropylmercapto)benzamido]ben-
R
zene (16): Compound 15 (1.0 g, 2.17 mmol) was dissolved in chloroform
(20 mL) and trifluoroacetic acid (1.67 mL, 21.7 mmol) was added drop-
wise. The solution was stirred for 24 h at ambient temperature and the
A
ACHTREUNG
AHCTREUNG
Chem. Eur. J. 2007, 13, 2344 – 2357
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2353

F. E. Hahn et al.
solvent was removed in vacuo. The residue was dissolved in hydrochloric
acid (40 mL, 5m) and diethyl ether was added dropwise. The precipitate
was filtered off, washed with diethyl ether and dried in vacuo to give 16
17 as
a
yellow powder. Yield: 1.31 g (1.94 mmol, 98%). 1H NMR
(300 MHz, CDCl3): d=9.89 (s, 1H; NH), 8.31 (s, 1H; NH), 7.74–7.01 (m,
20H; Ar-H), 5.10 (s, 2H; OCH2), 5.08 (s, 2H; OCH2), 3.46–3.27 (m, 2H;
as
(300 MHz, CDCl3): d=10.67 (s, 1H; NH), 7.55–7.41 (m, 7H; Ar-H), 4.86
(s, 3H; NH2·HCl), 3.66–3.44 (m, 2H; CH(CH3)2), 1.34 (d, 6H; CH-
(CH3)2), 1.15 ppm (d, 6H; CH
(CH3)2); 13C NMR(75 MHz, CDCl 3): d=
190.3 (CO), 177.6, 171.6, 147.6, 145.2, 133.3, 130.8, 130.4, 129.4, 127.4,
127.2, 125.9, 125.5 (Ar-C), 41.3 (SCH), 37.5 (SCH), 23.9 (CH(CH3)2),
23.6 ppm (CH(CH3)2); elemental analysis calcd (%) for C19H25ClN2OS2:
C 57.48, H 6.35, N 7.06; found: C 57.41, H 6.21, N 6.99.
1-(Ammonium chlorido)-2-[2,3-di(isopropylmercapto)benzamido]ben-
a
colourless powder. Yield: 0.79 g (1.98 mmol, 91%). 1H NMR
CH
A
A
N
13C NMR(75 MHz, CDCl 3): d=180.1, 167.9 (CO), 164.5, 152.2, 150.5,
149.3, 147.3, 146.0, 142.6, 136.8, 133.3, 131.3, 130.9, 130.7, 129.5, 129.2,
129.1, 128.7, 128.1, 127.6, 126.6, 126.3, 125.4, 125.2, 124.9, 124.3, 124.1,
AHCTREUNG
A
ACHTREUNG
118.4 (Ar-C), 77.3 (OCH2), 71.9 (OCH2), 40.8 (CH
A
U
A
ACHTREUNG
AHCTREUNG
calcd (%) for C40H40N2O4S2: C 70.98, H 5.96, N 4.14; found: C 70.57, H
5.88, N 3.76.
ACHTREUNG
1-[2,3-Di(benzyloxy)benzamido]-4-[2,3-di(isopropylmercapto)benzami-
do]benzene (21): Compound 21 was prepared as described for 17 from
2,3-di(benzyloxy)benzoic acid chloride (726 mg, 1.98 mmol), NEt3
(0.72 mL, 4.95 mmol) and compound 20 (786 mg, 1.98 mmol). Yield:
zene (20): Compound 20 was prepared as described for 16 from 19 (1.0 g,
2.17 mmol) and trifluoroacetic acid (1.67 mL, 21.7 mmol). Yield: 0.78 g
1
(1.96 mmol, 90%) of a colourless powder. H NMR(300 MHz, CD 3OD):
1.27 g (1.88 mmol, 95%) of
a
yellow powder. 1H NMR(400 MHz,
d=8.01–7.96 (m, 2H; Ar-H), 7.63–7.53 (m, 4H; Ar-H), 7.39 (dd, 1H; Ar-
CDCl3): d=10.28 (s, 1H; NH), 9.18 (s, 1H; NH), 8.07 (dd, 1H; Ar-H),
H), 4.94 (br.s, 3H; NH2 ·HCl), 3.76 (sept, 1H; CH
ACHTREUNG
7.85–7.34 (m, 19H; Ar-H), 5.43 (s, 2H; OCH2), 5.40 (s, 2H; OCH2), 3.73
1H; CH
C
G
ACHTREUNG
(sept, 1H; CH
A
T
A
ACHTREUNG
130.8, 130.2, 129.5, 127.4, 124.7, 122.5 (Ar-C), 40.7 (SCH), 36.9 (SCH),
166.1, 162.9 (CO), 151.7, 145.7, 138.7, 138.3, 136.2, 135.7, 129.4, 129.3,
129.0, 128.8, 128.7, 128.6, 128.3, 128.2, 127.6, 126.7, 125.8, 124.6, 123.5,
117.5, 115.8, 115.6, 114.3, 111.2 (Ar-C), 76.7 (OCH2), 71.4 (OCH2), 41.1
23.6 (CH
A
N
C19H25N2ClOS2: C 57.48, H 6.35, N 7.06; found: C 57.50, H 6.23, N 6.91.
1-[2,3-Di(benzyloxy)benzamido]-2-[2,3-di(isopropylmercapto)benzami-
do]ethane (9):
(CH
A
(CH3)2), 23.0 (CH
G
N
elemental analysis calcd (%) for C40H40N2O4S2: C 70.98, H 5.96, N 4.14;
found: C 70.36, H 5.89, N 3.82.
(457 mg, 1.37 mmol) was dissolved in THF (20 mL) and this solution was
added dropwise to a solution of NEt3 (207 mL, 1.51 mmol) and compound
8 (430 mg, 1.37 mmol) in THF (30 mL). The reaction mixture was stirred
for 12 h at ambient temperature and the NEt3·HCl formed was then fil-
tered off. The solvent was removed in vacuo and the crude product was
purified by column chromatography (SiO2; CH2Cl2 then ethyl acetate) to
give compound 9 as a yellow powder. Yield: 698 mg (1.11 mmol, 81%).
1H NMR(300 MHz, CDCl 3): d=8.39 (t, 1H; NH), 7.92–7.36 (m, 16H;
Ar-H), 6.87 (t, 1H; NH), 5.42 (s, 2H; OCH2), 5.37 (s, 2H; OCH2), 3.77–
3.70 (m, 6H; CH
1.40 ppm (d, 6H; CH
166.1 (CO), 151.6, 146.9, 145.6, 143.5, 139.4, 136.4, 132.7, 129.0, 128.7,
126.8, 128.5, 128.1, 127.7, 127.6, 127.5, 127.2, 124.6, 124.3, 123.2, 117.3
(Ar-C), 76.4 (OCH2), 71.3 (OCH2), 40.4 (CH
General procedure for the preparation of the ligands H4-1–H4-4: The
ligand precursors 9, 13, 17 and 21 and naphthalene (1.25 equiv per pro-
tecting group) were dissolved in THF. Pieces of sodium (2.5 equiv per
protecting group) were added and the solutions were stirred for 12 h at
ambient temperature. Methanol (5 mL) was added and the stirring was
continued for 15 min. The solvents were then removed in vacuo and the
residue was dissolved in degassed water (50 mL). The aqueous phase was
washed with diethyl ether (3”20 mL) and filtered. Hydrochloric acid was
added and the precipitate obtained was isolated by filtration, washed
with water and diethyl ether, and dried in vacuo.
G
C
ACHTREUNG
1-(2,3-Dihydroxybenzamido)-2-(2,3-dimercaptobenzamido)-2,2’-dimethyl-
ethane (H4-1): Prepared from 2 mmol of compound 13. Yield: 96%.
1H NMR(300 MHz, [D 7]DMF): d=10.44 (br.s, 2H; OH), 9.10 (t, 1H;
NH), 8.25 (s, 1H; NH), 7.60 (d, J=7.8 Hz, 1H; Ar-H), 7.49 (d, J=
8.2 Hz, 1H; Ar-H), 7.35 (d, J=7.8 Hz, 1H; Ar-H), 7.12 (t, J=7.8 Hz,
1H; Ar-H), 7.05 (d, J=8.2 Hz, 1H; Ar-H), 6.78 (t, J=8.2 Hz, 1H; Ar-
ACHTREUNG
(CH2CH2), 35.9 (CH(CH3)2), 22.9 (CH(CH3)2), 22.6 ppm (CH
emental analysis calcd (%) for C36H40N2O4S2: C 68.76, H 6.41, N 4.45;
found: C 68.14, H 6.04, N 4.76.
G
G
ACHTREUNG
1-[2,3-Di(benzyloxy)benzamido]-2-[2,3-di(isopropylmercapto)benzami-
do]-2,2’-dimethylethane (13): Compound 13 was prepared as described
for 9 from 2,3-di(benzyloxy)benzoic acid chloride (457 mg, 1.37 mmol),
NEt3 (207 mL, 1.51 mmol) and compound 12 (467 mg, 1.37 mmol) in THF
(30 mL). Yield: 827 mg (1.26 mmol, 92%) of a yellow powder. 1H NMR
(300 MHz, CDCl3): d=8.29 (br.t, 1H; NH), 7.73 (dd, 1H; Ar-H), 7.62–
7.25 (m, 15H; Ar-H), 6.67 (br.s, 1H; NH), 5.30 (s, 2H; OCH2), 5.26 (s,
H), 5.59 (br.s, 2H; SH), 3.82 (d, 2H; C
(CH3)2); 13C NMR(75 MHz, [D 7]DMF): d=171.4, 169.9 (CO), 150.6,
147.5, 137.6, 134.0, 131.6, 130.6, 126.1, 125.6, 119.5, 118.8, 118.0, 116.1
(Ar-C), 56.1 (CH2C(CH3)2), 48.4 (CH2C(CH3)2), 24.9 ppm (CH2C(CH3)2);
A
AHCTREUNG
A
N
ACHTREUNG
IR(KBr): n˜ =3307 (s, OH), 3064 (m, Ar-H), 2973 (m, CH), 2534 (w, SH),
1641 (s, C=O), 1588, 1523 cmÀ1 (s, NH); elemental analysis calcd (%)
for C18H20N2O4S2: C 55.08, H 5.14, N 7.14; found: C 54.78, H 5.06, N
6.87.
2H; OCH2), 3.73 (d, 2H; CH2C
1.50 (d, 6H; CH(CH3)2), 1.40 (s, 6H; C
(CH3)2); 13C NMR(75 MHz, CDCl 3): d=169.9, 167.0 (CO), 152.1, 147.1,
U
N
ACHTREUNG
ACHTREUNG
1-(2,3-Dihydroxybenzamido)-2-(2,3-dimercaptobenzamido)ethane (H4-2):
Prepared from 2 mmol of compound 9. Yield: 91%. 1H NMR(400 MHz,
[D7]DMF): d=13.00 (br.s, 2H; OH), 9.10 (s, 1H; NH), 8.83 (s, 1H; NH),
7.59 (d, J=7.8 Hz, 1H; Ar-H), 7.47 (d, J=7.8 Hz, 1H; Ar-H), 7.45 (d,
J=8.0 Hz, 1H; Ar-H), 7.08 (t, J=7.8 Hz, 1H; Ar-H), 7.00 (d, J=8.0 Hz,
1H; Ar-H), 6.71 (t, J=8.0 Hz, 1H; Ar-H), 5.93 (br.s, 2H; SH), 3.63 ppm
145.1, 145.0, 136.7, 129.5, 129.2, 129.1, 129.0, 128.9, 128.7, 128.6, 128.3,
128.2, 128.0, 127.9, 124.9, 124.7, 123.7, 117.7 (Ar-C), 76.7 (OCH2), 71.9
(OCH2), 56.0 (CH2C
(CH(CH3)2), 24.9 (CH2C
(CH3)2); elemental analysis calcd (%) for C38H44N2O4S2: C 69.48, H 6.75,
N
G
N
A
A
ACHTREUNG
ACHTREUNG
(s, 4H; CH2CH2); 13C NMR(100 MHz, [D ]DMF): d=170.7, 169.3 (CO),
N 4.26; found: C 69.27, H 6.69, N 4.04.
7
150.2, 146.7, 134.5, 133.2, 131.6, 131.3, 125.6, 124.6, 118.7, 117.9, 117.2,
115.0 (Ar-C), 39.1 ppm (CH2CH2); IR(KBr): n˜ =3363 (s, OH), 3057 (m,
Ar-H), 2935 (w, C-H), 2528 (m, SH), 1639 (s, C=O), 1588 (s, NH), 1458,
1-[2,3-Di(benzyloxy)benzamido]-2-[2,3-di(isopropylmercapto)benzami-
do]benzene (17): A sample of 2,3-di(benzyloxy)benzoic acid chloride
(726 mg, 1.98 mmol) was dissolved in THF (20 mL) and added dropwise
to a solution of NEt3 (0.720 mL, 4.95 mmol) and compound 16 (786 mg,
1.98 mmol) in THF (30 mL). The solution was stirred for 12 h and the
NEt3·HCl formed was then filtered off. The solvent was removed in
vacuo. The residue was dissolved in CH2Cl2 (30 mL) and the organic
layer was washed with aqueous solutions of NaOH (20 mL, 10%), hydro-
chloric acid (20 mL, 2m) and NaCl (20 mL, 35%). The organic phase was
dried with MgSO4, the solvent was removed in vacuo and the crude prod-
uct was purified by column chromatography (SiO2, ethyl acetate) to give
1328, 1263, 1173, 742 cmÀ1
;
elemental analysis calcd (%) for
C16H16N2O4S2: C 52.73, H 4.43, N 7.69; found: C 51.70, H 4.49, N 6.48.
1-(2,3-Dihydroxybenzamido)-2-(2,3-dimercaptobenzamido)benzene (H4-
3): Prepared from 2 mmol of compound 17. Yield: 90%. 1H NMR
(300 MHz, [D7]DMF): d=11.34 (s, 2H; OH), 10.50 (s, 1H; NH), 10.41 (s,
1H; NH), 8.10–6.81 (m, 10H; Ar-H), 5.86 ppm (s, 2H; SH); 13C NMR
(75 MHz, [D7]DMF): d=168.9, 168.8 (CO), 150.0, 147.5, 136.5, 134.8,
132.3, 132.2, 131.9, 130.4, 128.5, 126.9, 126.5, 126.4, 126.3, 125.9, 119.9,
2354
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 2344 – 2357

Helical Complexes Containing Diamide-Bridged Ligands
FULL PAPER
119.2, 119.0, 117.2 ppm (Ar-C); IR(KBr): n˜ =3270 (s, OH), 3063 (m, Ar-
H), 2532 (w, SH), 1645 (s, C=O), 1596, 1523 cmÀ1 (s, NH); elemental
analysis calcd (%) for C20H16N2O4S2: C 58.24, H 3.91, N 6.79; found: C
57.64, H 4.40, N 6.50.
rical isomers of [24]4À (parallel and antiparallel) lead to overlapping sig-
nals, which could not be resolved in the 1H NMRspectrum; 13C NMR
(150 MHz, [D7]DMF): d=171.4, 171.2, 171.1, 169.5, 169.4, 169.2 (CO),
165.5, 165.4, 165.3, 165.1, 158.5, 158.4, 158.3, 156.0, 140.4, 140.1, 139.4,
138.2, 137.8, 136.9, 134.1, 133.1, 132.3, 131.5, 128.4, 126.4, 124.4, 124.3,
124.2, 123.9, 123.8, 123.7, 122.1, 120.6, 120.3, 120.2, 117.2, 117.1 ppm (Ar-
C). The two geometrical isomers of [24]4À (parallel and antiparallel)
should give rise to a total of 54 resonances in the 13C NMRspectrum;
these could not all be resolved; MS (ESI, negative ions): m/z 1198.7
1-(2,3-Dihydroxybenzamido)-4-(2,3-dimercaptobenzamido)benzene (H4-
4): Prepared from 2 mmol of compound 21. Yield: 95%. 1H NMR
(300 MHz, [D7]DMF): d=11.94 (br.s, 2H; OH), 10.53 (s, 1H; NH), 10.51
(s, 1H; NH), 7.96–7.86 (m, 4H; Ar-H), 7.71–7.67 (m, 2H; Ar-H), 7.53 (d,
1H; Ar-H), 7.21 (t, 1H; Ar-H), 7.13 (d, 1H; Ar-H), 6.83 (t, 1H; Ar-H),
6.07 ppm (br.s, 2H; SH); 13C NMR(75 MHz, [D 7]DMF): d=169.1, 167.9
(CO), 150.2, 147.5, 137.3, 136.5, 135.1, 134.6, 132.0, 130.7, 126.2, 125.9,
122.4, 120.9, 119.9, 119.0, 118.8, 117.1 ppm (Ar-C); IR(KBr): n˜ =3290 (s,
OH), 3008 (m, Ar-H), 2551 (w, SH), 1644 (s, C=O) 1448, 1522 cmÀ1 (s,
NH); elemental analysis calcd (%) for C20H16N2O4S2: C 58.24, H 3.91, N
6.79; found: C 58.21, H 4.03, N 6.53.
[(PNP)
A
G
N
tal analysis calcd (%) for C204H156N10O12P8S6Ti2: C 70.50, H 4.52, N 4.03;
found: C 70.31, H 4.42, N 3.89.
Na
A
G
N
[TiO
AHCTREUNG
dissolved in degassed methanol (20 mL). The solution was stirred for
12 h at ambient temperature and (PNP)Cl (98 mg, 0.17 mmol) was then
added. The solution was filtered and the solvent was removed in vacuo.
The crude product was recrystallised from methanol/diethyl ether to give
A
G
ACHTREUNG
ACHTREUNG
0.19 mmol) were dissolved in methanol (20 mL) and the solution was stir-
red for 12 h at ambient temperature. Ph4AsCl (81 mg, 0.19 mmol) was
then added to the reaction mixture and the red solution was filtered. Dif-
fusion of diethyl ether into the filtrate at room temperature gave
(AsPh4)2[22] as a dark red powder. Yield: 25 mg (0.015 mmol). 1H NMR
(600 MHz, [D7]DMF): d=10.26 (s; NH), 10.08 (s; NH), 9.19 (s; NH),
8.49 (s; NH), 7.98–7.84 (m, 40H; AsPh4-H), 7.11, 7.06, 6.93, 6.92, 6.91,
6.81, 6.80, 6.73 (d; Ar-H), 6.72 (t; Ar-H), 6.70 (d; Ar-H), 6.50, 6.49, 6.42
(t; Ar-H), 6.25 (d; Ar-H), 6.21, 6.19 (t; Ar-H), 6.10, 6.05 (d; Ar-H), 4.52
(s, 3H; OCH3), 4.38 (s, 3H; OCH3), 3.90–3.17 ppm (m, 8H; CH2CH2);
13C NMR(150 MHz, [D 7]DMF): d=170.7, 170.2, 168.2, 168.1, 167.8,
166.9 (CO), 162.2, 161.8, 160.2, 160.0, 157.4, 155.7, 147.9, 147.6, 136.5 (9”
Ar-C), 135.1 (AsPh4-C), 134.9 (Ar-C), 134.2, 131.7 (2”AsPh4-C), 128.5,
127.5, 127.1, 126.7, 122.4, 122.1, 121.4, 121.3, 121.1, 120.6, 120.3, 120.1,
119.8, 119.7, 119.2, 119.1, 117.9, 117.7, 117.0, 116.4, 115.8, 115.7, 115.4,
115.3, 111.9, 111.6 (26”Ar-C), 64.4, 61.3 (CH3), 39.9, 39.8, 39.5, 38.9,
38.6, 38.3 ppm (CH2); only three of the expected four AsPh4 carbon reso-
nances were detected in the 13C NMRspectrum; MS (MALDI, negative
60 mg (0.02 mmol, 23%) of Na
A
G
1H NMR(500 MHz, [D 7]DMF, solvent-free compound): d=9.80 (br.t,
3H; NH), 8.14 (br.s, 3H; NH), 7.80–7.60 (m, 90H; PNP Ar-H), 7.15 (d,
3J=7.8 Hz, 3H; Ar-H), 7.08 (d, 3J=7.5 Hz, 3H; Ar-H), 6.98 (d, 3J=
7.5 Hz, 3H; Ar-H), 6.65 (t, 3J=7.5 Hz, 3H; Ar-H), 6.32 (t, 3J=7.8 Hz,
3H; Ar-H), 6.21 (d, 3J=7.8 Hz, 3H; Ar-H), 4.81 (br.s, 6H; CH2),
1.38 ppm (br.s, 18H; CH3); 13C NMR(125 MHz, [D 7]DMF, solvent-free
compound): d=169.41, 167.44 (CO), 161.81, 161.40, 155.24, 152.05,
135.63 (5”Ar-C), 134.34, 133.08, 133.03, 132.98, 130.24, 130.19, 130.11,
128.48, 128.46, 127.62 (Ar-C and PNP-C), 128.22, 123.03, 121.85, 117.86,
116.47, 115.56, 112.29 (Ar-C), 54.980 (CH2C
25.16 ppm (br; CH2C(CH3)2); MS (ESI, negative ions): m/z 630.7
[Ti2(1)3 +2H]2À
elemental analysis calcd (%) for solvent-free Na-
(PNP)3[25] C162H138N9NaO12P6S6Ti2: C 67.10, H 4.80, N 4.35; found: C
66.67, H 4.95, N 4.10.
Na(PNP)3[Ti2(4)3] Na
[TiO(acac)2] (45 mg, 0.17 mmol) and Na2CO3 (18 mg, 0.17 mol) were dis-
U
G
AHCTREUNG
;
AHCTREUNG
A
G
A
AHCTREUNG
ions): m/z 1260 [(AsPh4)Ti2(1)2
A
solved in degassed methanol (20 mL) and the solution was stirred for
16 h at ambient temperature. (PNP)Cl (98 mg, 0.17 mmol) was then
added and the solution was filtered. Removal of the solvent gave a red
solid. Recrystallisation from methanol/diethyl ether gave 95 mg
3055 (w, Ar-H), 2922, 2817 (w, C-H), 1641 cmÀ1 (C=O); elemental analy-
sis calcd (%) for C82H70As2N4O10S4Ti2: C 59.86, H 4.29, N 3.41; found: C
59.16, H 4.42, N 3.89.
(0.032 mmol, 38%) of Na
(PNP)3[26] as a red solid. 1H NMR(500 MHz,
G
A
G
A
[D7]DMF): d=12.01 (t, 3H; NH), 10.68 (s, 3H; NH), 7.90–7.60 (m, 90H;
PNP Ar-H), 7.32 (d, 3J=8.6 Hz, 3H; Ar-H), 7.22 (d, 3J=7.5 Hz, 3H; Ar-
H), 7.06 (d, 3J=8.6 Hz, 3H; Ar-H), 6.74 (t, 3J=8.6 Hz, 3H; Ar-H), 6.41
(t, 3J=7.5 Hz, 3H; Ar-H), 6.30 (d, 3J=7.5 Hz, 3H; Ar-H), 7.95 ppm (m,
12H; Ar-H); 13C NMR(125 MHz, [D 7]DMF): d=167.9, 166.3 (CO),
162.2, 161.9, 155.1, 152.7, 136.8, 136.2 (Ar-C), 135.0 (PNP Ar-C), 134.6
(Ar-C), 133.7 (PNP Ar-C), 133.6 (PNP Ar-C), 130.9 (PNP Ar-C), 130.8
(PNP Ar-C), 130.7 (PNP Ar-C), 129.8, 129.1, 128.2, 125.1, 123.1, 121.1,
120.7, 118.8, 116.9 ppm (Ar-C); six instead of the expected four resonan-
ces for the PNP cations were observed; MS (MALDI, negative ions): m/z
ACHTREUNG
dissolved in methanol and the solution was stirred for 12 h at ambient
temperature. (PNP)Cl (69 mg, 0.17 mmol) was then added and the red
precipitate that formed was isolated by filtration, washed with methanol
and dried in vacuo. The crude product was purified by recrystallisation
from acetone/diethyl ether to give 61 mg (0.03 mmol) of (PNP)2[23] as
red crystals. 1H NMR(600 MHz, [D 7]DMF): d=10.19 (s, 1H; NH), 9.30
(s, 1H; NH), 8.73 (d, 1H; Ar-H), 8.00–7.87 (m, 60H; PNP-H), 7.50 (d,
1H; Ar-H), 7.35 (dt, 1H; Ar-H), 7.26 (d, 1H; Ar-H), 7.16 (dt, 1H; Ar-
H), 7.13 (d, 1H; Ar-H), 6.91 (d, 1H; Ar-H), 6.87 (t, 1H; Ar-H), 6.54 (t,
1H; Ar-H), 6.44 (d, 1H; Ar-H), 4.48 ppm (s, 6H; OCH3); 13C NMR
(150 MHz, [D7]DMF): d=167.9, 166.7 (CO), 160.9, 160.6, 156.1, 144.8,
136.4, 135.3, 135.1, 134.2, 131.7, 131.3, 128.7, 127.8, 127.3, 124.5, 124.3,
123.3, 122.1, 120.7, 119.7, 117.9, 116.7, 113.7 (PNP-C and Ar-C), 65.6 ppm
2936 [(PNP)3
A
G
N
calcd (%) for C168H126N9NaO12P6S6Ti2: C 68.17, H 4.29, N 4.26; found: C
69.10, H 4.41, N 4.14.
X-ray crystallography: (AsPh4)2[22] was crystallised as its methanol sol-
vate (AsPh4)2[22]·2CH3OH by slow diffusion of diethyl ether into a
methanolic solution of (AsPh4)2[22] at room temperature. Crystals of
compound (PNP)2[23] were obtained by recrystallisation from acetone/di-
(OCH3); MS (ESI, negative ions): m/z 487.1 [Ti2(3)2
(OCH3)2]2À; elemen-
tal analysis calcd (%) for C114H90N6O10P4S4Ti2: C 66.73, H 4.42, N 4.10;
found: C 67.30, H 4.10, N 3.88.
N
ethyl ether. The solvate Na
by diffusion of diethyl ether into a methanolic solution of Na
at room temperature. Crystals of Na1.5(PNP)6.5[26]2·3DMF were obtained
ACHTREUNG
A
[Ti2(3)3] (PNP)4[24]: Ligand H4-3 (104 mg, 0.25 mmol), [TiO-
ACHTREUNG
ACHTREUNG
AHCTREUNG
in methanol (20 mL) and the solution was stirred for 12 h at 508C.
(PNP)Cl (69 mg, 0.17 mmol) was then added and the solvent was re-
moved in vacuo. Recrystallisation from methanol/diethyl ether gave
76 mg (0.022 mmol) of (PNP)4[24] as a red solid. 1H NMR(600 MHz,
[D7]DMF): d=12.03 (s; NH), 11.87 (s; NH), 11.04 (br.s; NH), 10.99 (s;
NH), 10.70 (s; NH), 7.96–7.82 (m; Ar-H), 7.75–7.56 (m; Ar-H), 7.34–7.20
(m; Ar-H), 7.05 (dd; Ar-H), 7.01 (dd; Ar-H), 6.93 (dd; Ar-H), 6.73 (t;
Ar-H), 6.69 (t; Ar-H), 6.63 (t; Ar-H), 6.57–6.54 (m; Ar-H), 6.53 (t; Ar-
H), 6.46 (t; Ar-H), 6.39 (t; Ar-H), 6.28 ppm (dd; Ar-H); the two geomet-
by diffusion of diethyl ether into a DMF solution of Na
room temperature.
A
X-ray diffraction data were collected at À758C ((AsPh4)2[22] and Na1.5
-
(PNP)6.5[26]2·3DMF) on an Enraf–Nonius Kappa CCD diffractometer or
at À1208C ((PNP)2[23] and Na
C
a
Chem. Eur. J. 2007, 13, 2344 – 2357
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2355

F. E. Hahn et al.
(AsPh4)2[22]·2CH3OH (0.84ꢀTꢀ0.92) and Na1.5
(PNP)6.5[26]2·3DMF
[1] J.-M. Lehn, Supramolecular Chemistry: Concepts andPerspectives ,
VCH, Weinheim, 1995.
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2005–2062; b) M. Albrecht, Chem. Rev. 2001, 101, 3457–3497.
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5371–5374; b) C. J. Carrano, S. R. Cooper, K. N. Raymond, J. Am.
Chem. Soc. 1979, 101, 599–604; c) R. C. Scarrow, D. L. White, K. N.
Raymond, J. Am. Chem. Soc. 1985, 107, 6540–6546.
(PNP)3[25]·CH3OH·H2O·Et2O (0.97ꢀTꢀ0.99). Structure solutions were
performed with SHELXS[30] in all cases and the refinement was carried
out with SHELXL[31] using anisotropic thermal parameters for all non-
hydrogen atoms (for exceptions see below). Hydrogen atoms were added
to the structure models at calculated positions and refined as riding
atoms. Owing to the cell dimensions, data collection was done with a
crystal to detector distance of 130 mm for Na1.5(PNP)6.5[26]2·3DMF. As a
U
result, the number of observed reflections is limited. The positional pa-
rameters of the carbon atoms of the cations and the solvent molecule in
the asymmetric unit were refined with isotropic thermal parameters. One
nitrogen atom of one PNP cation was refined with split positions. Due to
the limited number of observed intensities we could not clearly localize
one half PNP cation. Alternatively, there could be one disordered half
sodium cation in the asymmetric unit. The exact composition of the crys-
[5] a) J.-M. Lehn, A. Rigault, J. Siegel, J. Harrowfield, B. Chevrier, D.
Moras, Proc. Natl. Acad. Sci. USA 1987, 84, 2565–2569; b) R.
Krämer, J.-M. Lehn, A. Marquis-Rigault, Proc. Natl. Acad. Sci.
USA 1993, 90, 5394–5398; c) B. Hasenknopf, J.-M. Lehn, G. Baum,
D. Fenske, Proc. Natl. Acad. Sci. USA 1996, 93, 1397–1400.
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Chem. Soc. 1996, 118, 7221–7222; b) D. L. Caulder, K. N. Raymond,
Angew. Chem. 1997, 109, 1508–1510; Angew. Chem. Int. Ed. Engl.
1997, 36, 1440–1442; c) M. Meyer, B. Kersting, R. E. Powers, K. N.
Raymond, Inorg. Chem. 1997, 36, 5179–5191.
talline compound Na
therefore not be determined unambiguously and the average value Na1.5
(PNP)6.5[26]2·3DMF was taken as the correct composition of the crystal-
A
G
-
ACHTREUNG
line material. Additional crystal, data collection and refinement details
are summarised in Table 3.
[7] a) E. J. Enemark, T. D. P. Stack, Inorg. Chem. 1996, 35, 2719–2720;
b) E. J. Enemark, T. D. P. Stack, Angew. Chem. 1995, 107, 1082–
1084; Angew. Chem. Int. Ed. Engl. 1995, 34, 996–998.
CCDC-226389 ((AsPh4)2[22]·2CH3OH), CCDC-616878 ((PNP)2[23]),
CCDC-234748 (Na
G
[8] a) M. Albrecht, S. Kotila, Angew. Chem. 1995, 107, 2285–2287;
Angew. Chem. Int. Ed. Engl. 1995, 34, 2134–2137; b) M. Albrecht,
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8923–8938; c) D. H. Leung, D. Fiedler, R. G. Bergman, K. N. Ray-
(Na1.5(PNP)6.5[26]2·3DMF) contain the supplementary crystallographic
ACHTREUNG
data for this paper. These data can be obtained free of charge from the
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
This work was financially supported by the Deutsche Forschungsgemein-
schaft (GRK 673) and the NRW Graduate School of Chemistry Münster
(predoctoral grant to TK). We thank Dr Klaus Bergander and Dr.
Alexander Hepp for measuring the NMRspectra.
Table 3. Crystallographic data for (AsPh4)2[22]·2CH3OH, (PNP)2[23], Na
(AsPh4)2[22]·2CH3OH (PNP)2[23]
A
ACHTREUNG
N
G
G
ACHTREUNG
chem. formula
cryst. size [mm]
colour
Fw
space group
a [Š]
b [Š]
c [Š]
a [8]
b [8]
C84H78As2N4O12S4Ti2
0.15”0.15”0.05
red
C114H90N6O10P4S4Ti2
0.15”0.06”0.02
red
C167H154N9NaO15P6S6Ti2
0.10”0.07”0.04
red
C363H288N21.5Na1.5O27P13S12Ti4
0.50”0.45”0.15
red
1709.38
2051.84
3023.96
6396.56
¯
¯
P1 (no. 2)
P1 (no. 1)
13.186(2)
14.528(2)
14.556(2)
73.040(3)
73.040(3)
68.401(3)
24.33.8(5)
1
P1 (no. 1)
13.594(3)
17.190(4)
18.900(4)
66.722(4)
79.188(4)
82.523(4)
3977.6(15)
1
R3c (no. 167)
11.493(1)
12.771(1)
15.029(1)
67.69(1)
83.54(1)
75.44(1)
1974.9(3)
1
24.236(1)
24.236(1)
225.276(6)
90
90
120
g [8]
V [Š3]
Z
114595(7)
12
l [Š]
0.71073
198(2)
1.437
0.71073
123(2)
1.400
0.71073
123(2)
1.262
0.71073
198(2)
1.112
T [K]
1 calcd [gcmÀ3
]
refl. collected/2Vmax
unique reflns
10456/50.0
6936
5068
574/0
1.204
19327/50.0
16293
10465
1280/16293
0.382
24856/45.2
20191
13406
1932/3
0.306
115369/45.0
16319
6684
744/0
0.262
refl. obs. (I>2s(I))
no. of parameters/restr
m [mmÀ1
]
R1 (I>2s(I))
wR2 (all data)
GOF
0.068
0.153
1.058
+0.709/À0.909
0.070
0.144
0.990
+0.690/À0.389
0.077
0.188
0.994
+1.297/À0.342
0.187
0.464
2.258
+1.474/À0.739
À3
residual density [eŠ
]
2356
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 2344 – 2357

Helical Complexes Containing Diamide-Bridged Ligands
FULL PAPER
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Received: August 11, 2006
Published online: December 14, 2006
Chem. Eur. J. 2007, 13, 2344 – 2357
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2357