Metallosupramolecular chemistry with bis(benzene-o-dithiolato) ligands

Article abstract of DOI:10.1021/ja063655u

The bis(benzene-o-dithiol) ligands H₄-1, H₄-2, and H₄-3 react with [Ti(OC₂H₅)₄] to give dinuclear triple-stranded helicates [Ti₂L₃]^4- (L = 1⁴, 2<

Full text of DOI:10.1021/ja063655u

Published on Web 08/19/2006
Metallosupramolecular Chemistry with
Bis(benzene-o-dithiolato) Ligands
Thorsten Kreickmann,† Christian Diedrich,‡ Tania Pape,† Han Vinh Huynh,†
Stefan Grimme,‡ and F. Ekkehardt Hahn*,†
Contribution from the Institut fu¨r Anorganische und Analytische Chemie, UniVersita¨t Mu¨nster,
Wilhelm Klemm Strasse 8, 48149 Mu¨nster, Germany, and Organisch-Chemisches Institut,
UniVersita¨t Mu¨nster, Corrensstrasse 40, 48149 Mu¨nster, Germany
Received May 25, 2006; E-mail: fehahn@uni-muenster.de
Abstract: The bis(benzene-o-dithiol) ligands H4-1, H4-2, and H4-3 react with [Ti(OC2H5)4] to give dinuclear
triple-stranded helicates [Ti2L3]4- (L ) 14-, 24-, 34-). NMR spectroscopic investigations revealed that the
complex anions possess C3 symmetry in solution. A crystal structure analysis for (PNP)4[Ti2(2)3] ((PNP)4-
[14]) confirmed the C3 symmetry for the complex anion in the solid state. The complex anion in Li(PNP)3-
[Ti2(1)3] (Li(PNP)3[13]) does not exhibit C3 symmetry in the solid state due to the formation of polymeric
chains of lithium bridged complex anions. Complexes [13]4- and [14] 4- were obtained as racemic mixtures
of the ∆,∆ and Λ,Λ isomers. In contrast to that, complex (PNP)4[Ti2(3)3] ((PNP)4[15]) with the enantiomerically
pure chiral ligand 34- shows a strong Cotton effect in the CD spectrum, indicating that the chirality of the
ligands leads to the formation of chiral metal centers. The o-phenylene diamine bridged bis(benzene-o-
dithiol) ligand H4-4 reacts with Ti4+ to give the dinuclear double-stranded complex Li2[Ti2(4)2(µ-OCH3)2]
containing two bridging methoxy ligands between the metal centers. The crystal structure analysis and the
1H NMR spectrum of (Ph4As)2[Ti2(4)2(µ-OCH3)2] ((Ph4As)2[(16]) reveal C2 symmetry for the anion [Ti2(4)2-
(µ-OCH3)2]2-. For a comparative study the dicatechol ligand H4-5, containing the same o-phenylene diamine
bridging group as the bis(benzene-o-dithiol) ligands H4-4, was prepared and reacted with [TiO(acac)2] to
give the dinuclear complex anion [Ti2(5)2(µ-OCH3)2]2-. The molecular structure of (PNP)2[Ti2(5)2(µ-OCH3)2]
((PNP)2[17]) contains a complex anion which is similar to [16]2-, with the exception that strong N-H‚‚‚O
hydrogen bonds are formed in complex anion [17]2-, while N-H‚‚‚S hydrogen bonds are absent in complex
anion [16]2-
.
Introduction
(bipyridine) ligands and three Cu(I) ions. During the following
decade, the helicate chemistry was dominated by ligands with
nitrogene donors such as oligopyrimidines. Later, Raymond,6
Stack,7 and Albrecht8 prepared a series of dicatechol ligands
with different bridging groups that have been used for the
preparation of dinuclear triple-stranded helicates.
Similar ligands with sulfur donors, e.g., with benzene-o-
dithiolate donor groups, remained rare in supramolecular
chemistry most likely owing to the difficulties encountered
during the preparation of bis(benzene-o-dithiol) ligands. In 1995
we described a method for the ortho-functionalization of
The metal directed self-assembly of supramolecular coordina-
tion compounds has attracted much interest during the past two
decades.1 Several different structural motifs have been prepared
in transition metal directed self-assembly reactions.2 Among
those, metallohelicates have attracted special interest owing to
their presence in nature.3 Raymond et al. isolated the first triple-
stranded helicate [Fe2(RA)3] (H2RA ) rhodothorulic acid) that
contains exclusively oxygen donors from hydroxamato groups.4
The first metallohelicate analyzed by X-ray diffraction was
described by Lehn et al. in 1987.5 It consists of two tris-
(6) (a) Kersting, B.; Meyer, M.; Powers, R. E.; Raymond, K. N. J. Am. Chem.
Soc. 1996, 118, 7221-7222. (b) Caulder, D. L.; Raymond, K. N. Angew.
Chem. 1997, 109, 1508-1510; Angew. Chem., Int. Ed. Engl. 1997, 36,
1440-1442. (c) Meyer, M.; Kersting, B.; Powers, R. E.; Raymond, K. N.
Inorg. Chem. 1997, 36, 5179-5191.
† Institut fu¨r Anorganische und Analytische Chemie.
‡ Organisch-Chemisches Institut.
(1) Lehn, J.-M. Supramolecular Chemistry: Concepts and PerspectiVes;
VCH: Weinheim, 1995.
(7) (a) Enemark, E. J.; Stack, T. D. P. Inorg. Chem. 1996, 35, 2719-2720.
(b) Enemark, E. J.; Stack, T. D. P. Angew. Chem. 1995, 107, 1082-1084;
Angew. Chem., Int. Ed. Engl. 1995, 34, 996-998.
(2) Swiegers, G. F.; Malefetse, T. J. Chem. ReV. 2000, 100, 3483-3537.
(3) (a) Piguet, C.; Bernardinelli, G.; Hopfgartner, G. Chem. ReV. 1997, 97,
2005-2062. (b) Albrecht, M. Chem. ReV. 2001, 101, 3457-3497.
(4) (a) Carrano, C. J.; Raymond, K. N. J. Am. Chem. Soc. 1978, 100, 5371-
5374. (b) Carrano, C. J.; Cooper, S. R.; Raymond, K. N. J. Am. Chem.
Soc. 1979, 101, 599-604. (c) Scarrow, R. C.; White, D. L.; Raymond, K.
N. J. Am. Chem. Soc. 1985, 107, 6540-6546.
(8) (a) Albrecht, M.; Kotila, S. Angew. Chem. 1995, 107, 2285-2287; Angew.
Chem., Int. Ed. Engl. 1995, 34, 2134-2137. (b) Albrecht, M.; Kotila, S.
Chem. Commun. 1996, 2309-2310. (c) Albrecht, M.; Kotila, S. Angew.
Chem. 1996, 108, 1299-1300; Angew. Chem., Int. Ed. Engl. 1996, 35,
1208-1210. (d) Albrecht, M.; Schneider, M.; Ro¨ttele, H. Angew. Chem.
1999, 111, 512-515; Angew. Chem., Int. Ed. 1999, 38, 557-559. (e)
Albrecht, M.; Schneider, M.; Fro¨hlich, R. New J. Chem. 1998, 753-754.
(f) Albrecht, M. Chem.sEur. J. 2000, 6, 3485-3489. (g) Albrecht, M.;
Schneider, M. Eur. J. Inorg. Chem. 2002, 1301-1306. (h) Albrecht, M.;
Janser, I.; Houjou, H.; Fro¨hlich, R. Chem.sEur. J. 2004, 10, 2839-2850.
(5) (a) Lehn, J.-M.; Rigault, A.; Siegel, J.; Harrowfield, J.; Chevrier, B.; Moras,
D. Proc. Natl. Acad. Sci. U.S.A. 1987, 84, 2565-2569. (b) Kra¨mer, R.;
Lehn, J.-M.; Marquis-Rigault, A. Proc. Natl. Acad. Sci. U.S.A. 1993, 90,
5394-5398. (c) Hasenknopf, B.; Lehn, J.-M.; Baum, G.; Fenske, D. Proc.
Natl. Acad. Sci. U.S.A. 1996, 93, 1397-1400.
9
11808
J. AM. CHEM. SOC. 2006, 128, 11808-11819
10.1021/ja063655u CCC: $33.50 © 2006 American Chemical Society

Bis(benzene-o-dithiolato) Ligands
A R T I C L E S
Scheme 1. Double- and Triple-Stranded Helicates Formed by Dicatecholato Ligands
benzene-1,2-dithiol that led to the preparation of the first bis-
(benzene-o-dithiol) ligands.9 Some dinuclear, nonhelical nickel
complexes10 and a tetranuclear metallacycle11 have been de-
scribed with this type of ligand. A triple-stranded helicate with
a directional benzene-o-dithiolato/catecholato ligand has also
been described.12
Besides triple-stranded helicates, two other structural motifs
have been obtained with dicatechol ligands. Depending on the
topology of the ligands, tetrahedral M4L6 clusters13 or dinuclear
double-stranded complexes7a,14 can be formed. Stack et al.
reported the dicatechol ligand H4-A (Scheme 1) that forms a
triple-stranded helicate [Fe2(A)3]6- or a dinuclear double-
stranded complex [Fe2(A)2(OH)2]4-, depending on the metal/
ligand ratio used for the complex preparation.7a Albrecht et al.
prepared a series of amino acid bridged dicatechol ligands H4-B
that exclusively form dinuclear double-stranded complexes
[Ti2(B)2(OR)2]2- (R ) CH3, H) with the two coligands OR-
bridging the titanium atoms. With ligands of type B4- no triple-
stranded helicates have been obtained.14
We present here the synthesis and coordination chemistry of
a series of bis(benzene-o-dithiol) ligands that are able to form
either dinuclear triple-stranded helicates or double-stranded
helical complexes with titanium(IV) ions, depending on the
ligand backbone. The ligands H4-1 and H4-2 (Figure 1) form
racemic mixtures of dinuclear triple-stranded helicates, while
the enantiomerically pure ligand H4-3 leads to a chirality transfer
to the metal centers in a triple-stranded helicate. A dinuclear
double-stranded complex is obtained with ligand H4-4 and TiIV.
For a comparison of dicatechol and bis(benzene-o-dithiol)
ligands we prepared the dicatechol ligand H4-5, which exhibits
the same topology as H4-4, and studied its coordination
chemistry with TiIV. A preliminary report on the coordination
chemistry of H4-1 has already appeared.15
(9) (a) Hahn, F. E.; Seidel, W. W. Angew. Chem. 1995, 107, 2938-2941;
Angew. Chem., Int. Ed. Engl. 1995, 34, 2700-2703. (b) Huynh, H. V.;
Seidel, W. W.; Lu¨gger, T.; Fro¨hlich, R.; Wibbeling, B.; Hahn, F. E. Z.
Naturforsch. 2002, 57b, 1401-1408.
(10) Huynh, H. V.; Schulze Isfort, C.; Seidel, W. W.; Lu¨gger, T.; Fro¨hlich, R.;
Kataeva, O.; Hahn, F. E. Chem.sEur. J. 2002, 8, 1327-1335.
(11) Hahn, F. E.; Kreickmann, T.; Pape, T. Eur. J. Inorg. Chem. 2006, 535-
539.
(12) Hahn, F. E.; Schulze Isfort, C.; Pape, T. Angew. Chem. 2004, 116, 4911-
4915; Angew. Chem., Int. Ed. 2004, 43, 4807-4810.
(13) (a) Caulder, D. L.; Powers, R. E.; Parac, T. N.; Raymond, K. N. Angew.
Chem. 1998, 110, 1940-1943; Angew. Chem., Int. Ed. 1998, 37, 1840-
1843. (b) Caulder, D. L.; Bru¨ckner, C.; Powers, R. E.; Ko¨nig, S.; Parac, T.
N.; Leary, J. A.; Raymond, K. N. J. Am. Chem. Soc. 2001, 123, 8923-
8938. (c) Leung, D. H.; Fiedler, D.; Bergman, R. G.; Raymond, K. N.
Angew. Chem. 2004, 116, 981-984; Angew. Chem., Int. Ed. 2004, 43, 963-
966. (d) Fiedler, D.; Bergman, R. G.; Raymond, K. N. Angew. Chem. 2004,
116, 6916-6919; Angew. Chem., Int. Ed. 2004, 43, 6748-6751. (e) Fiedler,
D.; Pagliero, D.; Brumaghim, J. L.; Bergman, R. G.; Raymond, K. N. Inorg.
Chem. 2004, 43, 846-848.
Results and Discussion
Ligand Synthesis. The synthesis of the ligands H4-1, H4-2,
H4-3, and H4-4 is depicted in Scheme 2 and was carried out
according to previously reported methods.10 2,3-Di(isopropyl-
(14) (a) Albrecht, M.; Napp, M.; Schneider, M.; Weis, P.; Fro¨hlich, R. Chem.
Commun. 2001, 409-410. (b) Albrecht, M.; Napp, M.; Schneider, M.; Weis,
P.; Fro¨hlich, R. Chem.sEur. J. 2001, 7, 3966-3975.
(15) Hahn, F. E.; Kreickmann, T.; Pape, T. Dalton Trans. 2006, 769-771.
9
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A R T I C L E S
Kreickmann et al.
complexes M4[Ti2(1)3], M4[Ti2(2)3], and M4[Ti2(3)3] (M ) Li+,
Na+, K+) could not be isolated in analytically pure form. The
alkali metal cations were therefore exchanged for large organic
cations. Addition of 4 equiv of (PNP)Cl (PNP+ ) bis(triphenyl-
phosphoranylidene)ammonium) or (Ph4As)Cl, respectively, to
the methanol solutions of Li4[Ti2(2)3] and Li4[Ti2(3)3] leads to
the precipitation of the red-brown solids (PNP)4[Ti2(2)3] ((PNP)4-
[14]) and (Ph4As)4[Ti2(3)3] ((Ph4As)4[15]). These salts are only
soluble in DMF. In contrast to this, the addition of 4 equiv of
(PNP)Cl to a solution of Li4[Ti2(1)3] in methanol yields Li-
(PNP)3[Ti2(1)3] (Li(PNP)3[13]) as a brown precipitate. We have
not been able to exchange the fourth lithium cation in Li(PNP)3-
[13], even when using a large excess of (PNP)Cl (10 equiv).
The use of the larger cations allowed the isolation of the salts
Li(PNP)3[13], (PNP)4[14], and (Ph4As)4[15] in analytically pure
form after recrystallization from DMF/diethyl ether in 60-80%
yield. The composition of the salts was established by elemental
analysis and ESI mass spectroscopy. Characteristic peaks with
correct isotopic patterns were detected for Li(PNP)3[Ti2(1)3] at
m/z ) 424 [M - 3PNP - Li + H]3- and 604 [M - 2PNP -
Li]3-, for (PNP)4[Ti2(2)3] at m/z ) 652 [M - 3PNP]3- and
1247 [M - 2PNP]2-, and for (Ph4As)4[Ti2(3)3] at m/z ) 478
[M - 4Ph4As + H]3- and 606 [M - 3Ph4As]3-
1H NMR Studies. The triple-stranded helical anions [13]4-
.
,
[14]4-, and [15]4- show very simple 1H NMR spectra with only
one set of signals for the protons for the three ligand strands,
indicating C3 symmetry for the complex anions in solution. For
each complex, the signals for the aromatic protons of the
benzene-o-dithiolato units appear as two doublets of doublets
and a triplett, typical for an AMX spin system.
Figure 1. Ligands investigated in this study.
mercapto) benzoic acid 6 was prepared as we have described
earlier.9,10 Treatment of 6 with oxalyl dichloride in benzene
yields within 60 min the acid chloride 7. The bridging of two
molecules of 7 with different diamines in the presence of
triethylamine affords the S-alkylated compounds 8-11 in yields
of 80-95%. The protection groups at the sulfur atoms were
removed by treatment of 8-11 with sodium/naphthalene fol-
lowed by acid hydrolysis. Ligands H4-1-H4-4 were obtained
as off-white powders.
The dicatechol ligand H4-5 was prepared according to a
method developed by Raymond et al. (Scheme 3).6c,13b 1,2-
Dimethoxybenzoic acid chloride (2 equiv) was reacted with 1,2-
phenylenediamine (1 equiv) to form the O-methylated compound
12. The methyl protection groups were removed with BBr3
followed by hydrolysis to afford H4-5 in 90% yield as a white
solid.
Preparation of Triple-Stranded Helicates. The formation
of dinuclear titanium complexes with bis(benzene-o-dithiolato)
ligands requires the use of reactive metal precursors such as
[Ti(OC2H5)4]. Less reactive compounds such as [TiO(acac)2],
which have been used successfully by Albrecht et al. for the
preparation of dinuclear complexes with dicatecholato ligands,8,14
do not lead to defined products. Treatment of 3 equiv of the
ligands H4-1, H4-2, or H4-3 with 2 equiv of [Ti(OC2H5)4] in
methanol in the presence of Li2CO3 under an argon atmosphere
yields deep red solutions that contain the compounds Li4[Ti2-
(L)3] (L ) 14-, 24-, 34-) (Scheme 4). In the presence of Na2-
CO3 and K2CO3 instead of Li2CO3, the corresponding complexes
Na4[Ti2(L)3] and K4[Ti2(L)3] are formed, indicating that the type
of alkali metal cation does not have an influence on the
composition of the assembled complex anion. However, the
The signals for the protons attached to the benzene-o-
dithiolato groups in complexes [14]4- and [15]4- are shifted
highfield compared to the free ligands H4-2 and H4-3 (range
∆δ ) -0.54 to -0.25 ppm). We assume that the observed
highfield shift is due to the quadruple negative charge of the
helical anions. The resonances for the protons of the benzene-
o-dithiolato units in [13]4- are shifted downfield (range ∆δ )
0.29 to 0.51 ppm) relative to H4-1. This observation can be
attributed to the formation of a cation-anion pair Li+[13]4-
with a reduced overall negative charge. Precisely this type of
interaction occurs in the solid state and was observed in the
crystal structure of Li(PNP)3[Ti2(1)3] (Figure 4, vide infra). The
exact binding site of the lithium cation at [13]4- in solution
remains unknown. However, it is reasonable to assume that the
lithium cation is coordinated by carbonyl functions of the ligands
in a fashion similar to that found in the crystal structure (Figure
4). However, the three ligand strands 14- in one anion [Ti2(1)3]4-
cannot coordinate simultaneously to one lithium cation. This
geometric limitation should actually rule out the observed C3
symmetry in solution. We believe that a fast exchange of the
lithium cation between the carbonyl functions of the ligand
strands and probably the solvent (DMF) occurs in solution. 1H
NMR investigations at -60 °C did not lead to the observation
of more than one set of signals which in turn corroborates the
assumption of a labile coordinated lithium cation.
1
We have recently shown that H NMR spectroscopy is a
powerful method to detect N-H‚‚‚S hydrogen bonds in
complexes with amide substituted benzene-o-dithiolato ligands.15
The signals for the amide protons in the complex anions [13]4-
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Bis(benzene-o-dithiolato) Ligands
A R T I C L E S
Scheme 2. Preparation of the Bis(benzene-o-dithiol) Ligands
Scheme 3. Preparation of the Ligand H4-5
In contrast to the signals observed for the amide proton in
[13]4- and [14]4-, the signal for the amide protons in complex
anion [15]4- is shifted only slightly downfield relative to the
free ligand H4-3 (∆δ ) 0.17 ppm). Since the absence of Ns
H‚‚‚S hydrogen bonds normally leads to a highfield shift of
the signal for the amide proton (vide infra), another kind of
interaction must be responsible for this observation. So far we
were unable to determine the molecular structure of (Ph4As)4-
[15]. Therefore a DFT modeling study (BP86/SV(P)) was carried
out for the [Ti2(3)3]4- anion in order to gain information about
the conformation and the hydrogen bonds possible within the
three ligands strands. The calculated molecular structure of the
helical anion [Ti2(3)3]4- reveals that interligand CdO‚‚‚HsN
hydrogen bonds (H‚‚‚O 2.011 Å) are most likely formed instead
of intraligand NsH‚‚‚S hydrogen bonds (Figure 2). The
observed slight downfield shift for the amide protons in [15]4-
can therefore be ascribed to these interligand CdO‚‚‚HsN
hydrogen bonds. The formation of intraligand NsH‚‚‚S hydro-
gen bonds is effectively prevented by the bulky cyclohexyl rings
which are arranged nearly perpendicular to the TisTi axis.
Within this conformation steric interactions between the cyclo-
hexyl rings and the rest of the complex anion are minimized.
The signal for the CH protons of the cyclohexyl rings is
observed as a broad doublet at δ ) 4.34 ppm due to coupling
with the enantiotopic protons of the adjacent methylene groups.
Only unresolved multipletts are observed for the methylene
protons of the cyclohexyl ring, which is typical for such chiral
rings.
and [14]4- are shifted downfield relative to H4-1 (∆δ ) 0.85
ppm) and H4-2 (∆δ ) 0.53 ppm), respectively. This indicates
the presence of strong N-H‚‚‚S hydrogen bonds in a six-
membered ring between the amide protons and the o-thiolato
atoms. So far, similarly strong N-H‚‚‚S hydrogen bonds have
only been observed in more stable five-membered rings,16 while
N-H‚‚‚O hydrogen bonds in six-membered rings are common
in catechoylamido complexes12 where they can have a structure
determining influence.17
(16) (a) Kato, M.; Okamura, T.; Yamamoto, H.; Ueyama, N. Inorg. Chem. 2005,
44, 1966-1972. (b) Ueyama, N.; Inohara, M.; Onoda, A.; Ueno, T.;
Okamura, T.; Nakamura, A. Inorg. Chem. 1999, 38, 4028-4031. (c)
Okamura, T.; Takamizawa, S.; Ueyama, N.; Nakamura, A. Inorg. Chem.
1998, 37, 18-28. (d) Ueno, T.; Ueyama, N.; Nakamura, A. J. Chem. Soc.,
Dalton Trans. 1996, 3859-3863. (e) Ueyama, N.; Taniuchi, K.; Okamura,
T.; Nakamura, A.; Maeda, H.; Emura, S. Inorg. Chem. 1996, 35, 1945-
1951. (f) Ueyama, N.; Yamada, Y.; Okamura, T.; Kimura, S.; Nakamura,
A. Inorg. Chem. 1996, 35, 6473-6484. (g) Ueyama, N.; Okamura, T.;
Nakamura, A. J. Am. Chem. Soc. 1992, 114, 8129-8137.
(17) (a) McMurry, T. J.; Hosseini, M. W.; Garrett, T. M.; Hahn, F. E.; Reyes,
Z. E.; Raymond, K. N. J. Am. Chem. Soc. 1987, 109, 7196-7198. (b)
Garrett, T. M.; McMurry, T. J.; Hosseini, M. W.; Reyes, Z. E.; Hahn, F.
E.; Raymond, K. N. J. Am. Chem. Soc. 1991, 113, 2965-2977. (c) Stack,
T. D. P.; Karpishin, T. B.; Raymond, K. N. J. Am. Chem. Soc. 1992, 114,
1512-1514. (d) Karpishin, T. B.; Stack, T. D. P.; Raymond, K. N. J. Am.
Chem. Soc. 1993, 115, 182-192. (e) Karpishin, T. B.; Dewey, T. M.;
Raymond, K. N. J. Am. Chem. Soc. 1993, 115, 1842-1851.
Crystal Structure Analyses. We recently communicated the
crystal structure of Li(PNP)3[13]‚3DMF‚H2O.15 Single crystals
of (PNP)3[14]‚3DMF suitable for an X-ray diffraction analysis
have been obtained by slow diffusion of benzene or diethyl ether
into a solution of (PNP)4[14] in DMF. Compound (PNP)4[14]‚
3DMF crystallizes such as Li(PNP)3[13]‚3DMF‚H2O as a
racemic mixture of the Λ,Λ and ∆,∆ isomers in the centrosym-
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A R T I C L E S
Kreickmann et al.
Scheme 4. Preparation of Triple-Stranded Helicates Li(PNP)3[13], (PNP)4[14], and (Ph4As)4[15]
metrical space group R3hc (Z ) 12). The titanium atoms reside
on a crystallographic 3-fold axis.
bond lengths to the sulfur atoms in ortho-position to the amide
functions are elongated (2.4404(10)-2.4592(11) Å for [Ti2(1)3]4-
and 2.4288(15)-2.4358(14) Å for [Ti2(2)3]4-), while the Ti-S
bond lengths to the sulfur atoms in meta-position are shorter
(2.3478(10)-2.3766(10) Å for [Ti2(1)3]4- and 2.3810(14)-
2.3831(15) Å for [Ti2(2)3]4-).
The lithium cation in crystals of compound Li(PNP)3[13]‚
3DMF‚H2O is coordinated by two carbonyl groups of two
different anions [13]4- and by the water and one DMF molecule
in the asymmetric unit. This leads to indefinite polymeric chains
Li-[13]4--Li-[13]4- in the crystal lattice (Figure 4). In contrast
to this, the [Ti2(2)3]4- anions in compound (PNP)4[14]‚3DMF
are well separated with no interactions between cations and
anions. The helical twist angles18 in both complex anions differ
significantly. The rigid ligand 24- in complex anion [14]4- leads
to a twist angle of 60°, while the more flexible ligand 14- in
complex anion [13]4- causes a comparatively small twist angle
of only 12°.
The molecular structures of the anions [Ti2(1)3]4- (∆,∆
isomer) and [Ti2(2)3]4- (Λ,Λ isomer) are depicted in Figure 3.
They confirm the formation of dinuclear triple-stranded heli-
cates. The titanium atoms in both complex anions are coordi-
nated by six thiolato donors in a slightly distorted octahedral
fashion. The Ti‚‚‚Ti separation measures 10.704 Å in complex
[Ti2(1)3]4- and 12.954 Å in complex [Ti2(2)3]4- (Table 1). The
molecular structure of the anion [Ti2(2)3]4- resembles the one
reported for the dinuclear triple-stranded helicate with the
corresponding dicatecholato ligand reported by Raymond et al.6c
Short nonbonding intraligand N‚‚‚S distances between the
amide nitrogen atoms and the ortho-sulfur atoms of the adjacent
benzene-o-dithiolato groups are found in both helical anions
(N‚‚‚S nonbonding distances of 2.992-3.050 Å for [Ti2(1)3]4-
and 3.008-3.029 Å for [Ti2(2)3]4-). The benzene-o-dithiolato
and the amide subunits are arranged in a nearly coplanar fashion
(dihedral angles 0.89°-27.02° for [Ti2(1)3]4- and 24.84°-
28.59° for [Ti2(2)3]4-). This small dihedral angle supports the
presence of strong N-H‚‚‚S hydrogen bonds which are also
indicated by the 1H NMR spectra. As a consequence, the Ti-S
CD Spectroscopic Investigation of (Ph4As)4[Ti2(3)3]. The
triple-stranded helicate (Ph4As)4[Ti2(3)3] ((Ph4As)4[15]), as-
(18) Kepert, D. L. Inorganic Stereochemistry: Inorganic Chemistry Concept
6; Springer-Verlag: Berlin, 1982.
9
11812 J. AM. CHEM. SOC. VOL. 128, NO. 36, 2006

Bis(benzene-o-dithiolato) Ligands
A R T I C L E S
Figure 2. Calculated molecular structure of [Ti2(3)3]4- [15]4- showing all six interligand CdO‚‚‚HsN hydrogen bonds (left) and one selected pair of these
hydrogen bonds (right). Only two of the three ligand strands are depicted in the picture on the right.
Figure 3. ORTEP diagrams of the anions [Ti2(1)3]4- and [Ti2(2)3]4-. Hydrogen atoms have been omitted for clarity.
sembled from the chiral ligand H4-4 and TiIV, has been
investigated by a circular dichroism (CD) spectroscopy. The
electronic spectrum of (Ph4As)4[15] (Figure 5, left) exhibits three
absorption bands at 335 (ꢀ ) 52.000 M-1 cm-1), 428 (ꢀ )
23.500 M-1 cm-1) and 546 nm (ꢀ ) 15.500 M-1 cm-1). Similar
absorptions have been reported for the related mononuclear
complex [NH2(CH3)2]2[Ti(S2C6H4)3].19 The corresponding tran-
sitions can be assigned to ligand-to-metal charge-transfer bands
due to the large absorption coefficients. These absorptions are
useful for the detection of chirality located at the metal center.
The CD spectrum of (Ph4As)4[15] was measured between 300
and 700 nm, and it shows an intensive absorption with a positive
Cotton effect at 546 nm (∆ꢀ ) 37.3 M-1 cm-1) and a less
intensive absorption with a negative Cotton effect at 428 nm
(∆ꢀ ) -27.8 M-1 cm-1) (Figure 5, right). No Cotton effect
was observed at 335 nm, the region with the most intensive
absorption in the electronic spectrum. We assume that this
absorption might be caused by a nonmetal-centered transition
or by a dipole forbidden transition. The large values for ∆ꢀ for
the absorptions exhibiting a Cotton effect indicate that the
chirality is transferred from the ligands to the titanium centers.
Preparation of Dinuclear Double-Stranded Bis(µ-meth-
oxy) Bridged Complexes. The reaction of 1 equiv of H4-4 with
1 equiv of [Ti(OC2H5)4] in the presence of Li2CO3 under an
argon atmosphere in methanol yields a deep red solution of Li2-
[Ti2(4)2(µ-OCH3)2] (Scheme 5, top). As was observed during
the preparation of the triple-stranded helicates, an analytically
pure compound (Ph4As)2[Ti2(4)2(µ-OCH3)2] could be isolated
by addition of (Ph4As)Cl. Addition of 2 equiv of (Ph4As)Cl to
the methanol solution of Li2[Ti2(4)2(µ-OCH3)2] yields a brown
precipitate of (Ph4As)2[Ti2(4)2(µ-OCH3)2] ((Ph4As)2[16]) that
is soluble in DMF and dimethyl sulfoxide. Negative ion ESI
mass spectrometry of (Ph4As)2[16] in acetonitrile reveals a
characteristic signal at m/z ) 519 for the [Ti2(4)2(µ-OCH3)2]2-
dianion with the correct isotope pattern.
Attempts to synthesize a dinuclear triple-stranded helicate
[Ti2(4)3]4- from H4-4 and TiIV failed. When the reaction among
H4-4, [Ti(OC2H5)4], and Li2CO3 is carried out with a metal-to-
(19) Ko¨nemann, M.; Stu¨er, W.; Kirschbaum, K.; Giolando, D. M. Polyhedron
1994, 13, 1415-1425.
9
J. AM. CHEM. SOC. VOL. 128, NO. 36, 2006 11813

A R T I C L E S
Kreickmann et al.
Table 1. Selected Bond Lengths (Å) and Angles (deg) in Complex
Anions [Ti2(1)3]4- and [Ti2(2)3]4-
The ESI mass spectrum of (PNP)2[17] reveals a characteristic
peak at m/z ) 455 for the [Ti2(5)2(µ-OCH3)2]2- dianion with
the correct isotope pattern.
parameter
Li(PNP)3[Ti2(1)3]
(PNP)4[Ti2(2)3]
1H NMR Studies of (Ph4As)2[16] and (PNP)2[17]. Complex
[16]2- shows a simple 1H NMR spectrum with only one set of
signals which indicates C2 symmetry of the complex anion in
solution (Figure 6). Signals for the aromatic protons of the
benzene-o-dithiolato groups are detected as a triplet at δ ) 6.79
ppm and two doublets of doublets at δ ) 6.92 and 7.11 ppm.
The protons of the o-phenylenediamide spacer form an AA“XX”-
spin system and two doublets of doublets are observed at δ )
7.15 and 8.32 ppm. The singlet at δ ) 4.60 ppm belongs to the
protons of the bridging methoxy group. The resonance for the
amide protons appears as a singlet at δ ) 9.77 ppm. Compared
to the free ligand H4-4, this resonance is shifted highfield (∆δ
) -0.31 ppm). The signals for the amide protons in complex
anions [13]4- and [14]4-, where intrastrand N-H‚‚‚S hydrogen
bonds exist, are shifted downfield relative to the free ligands.
We take the observation of the highfield shift for the amide
protons in complex [Ti2(4)2(µ-OCH3)2]2- as an indication that
no N-H‚‚‚S hydrogen bonds are formed in the complex anion
in solution.
Ti1-S1a(S1)
2.3650(11)
2.4503(10)
2.3757(10)
2.4520(11)
2.3655(10)
2.4478(10)
2.4500(10)
2.3766(10)
2.4404(10)
2.3665(11)
2.4592(11)
2.3478(10)
10.704
81.57(3)
82.27(3)
80.83(3)
81.27(3)
81.11(3)
81.32(4)
2.3810(15)
2.4358(14)
Ti1-S2a(S2)
Ti1-S1b
Ti1-S2b
Ti1-S1c
Ti1-S2c
Ti2-S3a(S3)
Ti2-S4a(S4)
Ti2-S3b
2.4288(15)
2.3831(15)
Ti2-S4b
Ti2-S3c
Ti2-S4c
Ti1‚‚‚Ti2
12.954
81.80(4)
S1a(S1)-Ti1-S2a(S2)
S1b-Ti1- S2b
S1c-Ti1-S2c
S3a(S3)-Ti2-S4a(S4)
S3b-Ti2-S4b
S3c-Ti2-S4c
81.83(4)
1
The H NMR spectrum of [17]2- also consists of only one
set of signals and resembles the spectrum for complex anion
[16]2- except that the signal for the amide protons is shifted
downfield compared to the free ligand H4-5 (∆δ ) 0.28 ppm).
We take this as an indication for the expected formation of
strong N-H‚‚‚O hydrogen bonds in the anion [17]2-
.
Molecular Structures of [16]2- and [17]2-. Single crystals
of (Ph4As)2[Ti2(4)2(µ-OCH3)2]‚4DMF which were suitable for
an X-ray diffraction study have been obtained by slow vapor
diffusion of diethyl ether into a solution of (Ph4As)2[Ti2(4)2(µ-
OCH3)2] in DMF within 2 weeks. The complex crystallizes in
the triclinic space group P1h with Z ) 1. Figure 7 displays the
molecular structure of the anion [Ti2(4)2(µ-OCH3)2]2-. The
structure analysis confirms that a dinuclear double-stranded
complex had formed. The two titanium atoms in [16]2- are
bridged by two ligand strands 44- in addition to two methoxy
groups, which form a central four-membered [Ti(µ-OCH3)]2
ring. The coordination geometry at the metal centers is best
described as strongly distorted octahedral with the oxygen atoms
in a cis arrangement. The Ti‚‚‚Ti* separation of 3.1991(8) Å
(Table 2) is characteristic for dinuclear titanium complexes with
two µ-methoxy bridging groups and has been reported by
Albrecht14 and Stack7a for related complexes.
Figure 4. Partial view of the polymeric chains in the crystal lattice of
Li(PNP)3[13]‚3DMF‚H2O.
ligand ratio of 2:3, only the double-stranded complex Li2[Ti2-
(4)2(µ-OCH3)2] can be isolated. An increased rection temperature
of 60 °C also did not lead to the formation of a triple-stranded
helicate. Upon heating of the reaction mixture, the color changes
from red to yellow, indicating the decomposition of the initially
formed double-standed dinuclear complexes. The reaction of 1
equiv of Li2[Ti2(4)2(µ-OCH3)2] or (Ph4As)2[Ti2(4)2(µ-OCH3)2]
with 1 equiv of ligand 44- again leads only to the isolation of
the double-stranded complex.
The coordination chemistry of the related dicatechol ligand
H4-5 resembles the behavior observed for H4-4. Only the orange
double-stranded complex Li2[Ti2(5)2(µ-OCH3)2] is formed in
the reaction of 1 equiv of H4-5 with 1 equiv of [TiO(acac)2]
(acac ) acetonylacetonato anion) and Li2CO3 in methanol under
an argon atmosphere (Scheme 5, bottom). As was observed in
the reaction of H4-4 with TiIV, no dinuclear triple-stranded
helicate [Ti2(5)3]4- could be obtained from H4-5 and [TiO-
(acac)2]. Addition of 2 equiv of (PNP)Cl to the methanol
solution of Li2[Ti2(5)2(µ-OCH3)2] leads to the formation of
(PNP)2[Ti2(5)2(µ-OCH3)2] ((PNP)2[17]) as an orange precipitate.
The complex anion [Ti2(4)2(µ-OCH3)2]2- [16]2- resides on
a crystallographic inversion center. The two titanium atoms
assume different configurations (∆ and Λ), which leads to the
formation of a meso complex. As concluded from the 1H NMR
spectrum no N-H‚‚‚S hydrogen bonds are observed in the solid
state. The nonbonding N‚‚‚S distances are relatively long (3.577
and 3.643 Å), compared to the helical complexe anions [13]4-
(2.992-3.050 Å) and [14]4- (3.008-3.029 Å) where strong
N-H‚‚‚S hydrogen bonds exist. In addition, the amide group
and the benzene-o-dithiolato group are not coplanar in the anion
[16]2- (dihedral angles 95.47° and 89.69°) which also prevents
the formation of N-H‚‚‚S hydrogen bonds. The absence of
N-H‚‚‚S hydrogen bonds in [16]2- leads to nearly uniform
(2.4036(7)-2.4104(8) Å) Ti-S bond distances, which is in
contrast to the triple-stranded helical anions [13]4- and [14]4-
,
9
11814 J. AM. CHEM. SOC. VOL. 128, NO. 36, 2006

Bis(benzene-o-dithiolato) Ligands
A R T I C L E S
Figure 5. Electronic and CD spectra of (Ph4As)4[15], measured in DMF.
Scheme 5. Preparation of Complexes (Ph4As)2[16] and (PNP)2[17]
where the Ti-S distances to the thiolato donors involved in
hydrogen bonding are longer than those not involved in N-H‚
‚‚S hydrogen bonds.
The nonbonding N‚‚‚Oortho distances (2.650(8)-2.721(8) Å)
and the coplanarity of the catecholato ring and the amide
function (dihedral angles 5.22° and 21.40°) reveal that the amide
proton is engaged in a strong N-H‚‚‚O hydrogen bond. This
Single crystals of (PNP)2[Ti2(5)2(µ-OCH3)2]‚2CH3CN‚2CH3-
OH have been grown by slow diffusion of diethyl ether into a
solution of (PNP)2[Ti2(5)2(µ-OCH3)2] in acetonitrile/methanol
(4:1). The complex crystallizes in the triclinic space group P1h
with Z ) 1. The molecular structure of the anion [Ti2(5)2(µ-
OCH3)2]2- (Figure 8) resembles that of the anion [Ti2(4)2(µ-
OCH3)2]2-. Again the complex anion resides on an inversion
center, so that a meso complex with opposite configurations at
the titanium atoms is formed. The Ti‚‚‚Ti* distance (3.158 Å,
Table 2) and the geometry of the [Ti(µ-OCH3)]2 ring are
1
confirms the conclusions drawn from the H NMR spectrum.
Strong N-H‚‚‚O hydrogen bonds have previously been ob-
served in complexes obtained from amide bridged dicatecholato
ligands.6c,7a,12,17 As a consequence of the strong N-H‚‚‚O
hydrogen bond, the Ti-O bond lengths within the catecholato
group differ significantly.
The Ti-O bonds to the oxygen atoms in ortho-position to
the amide group are elongated (1.959(5)-1.961(5) Å) while the
Ti-O bonds to the oxygen atoms in meta-position are shorter
(1.917(5)-1.921(5) Å). The comparison of the complex anions
comparable to the corresponding parameters in complex [16]2-
.
9
J. AM. CHEM. SOC. VOL. 128, NO. 36, 2006 11815

A R T I C L E S
Kreickmann et al.
Figure 8. ORTEP diagram of the anion [Ti2(5)2(µ-OCH3)2]2-. Hydrogen
atoms have been omitted.
Figure 6. 1H NMR spectrum of (Ph4As)2[16].
with TiIV similar to those described for dicatecholato ligands.
The type of bridging group between the benzene-o-dithiolato
donor groups is responsible for the formation or absence of
N-H‚‚‚S hydrogen bonds. The bridging group also determines
the composition of the reaction product, e.g., the formation of
triple- or double-standed complexes.
It has been shown that benzene-o-dithiolato complexes of
type [M(bdt)3]n- (bdt ) benzene-o-dithiolato anion, M ) W,20
n ) 0, 1, 2 and M ) Mo,21 n ) 0, 1, 2) can adopt a trigonal-
prismatic (WVI and MoVI) or octahedral (WV and MoV)
coordination geometry. Incorporation of these metals into triple-
standed dinuclear complexes with benzene-o-dithiolate ligands
could lead to helicates (two octahedal metal centers) or
nonhelical complexes (two trigonal-prismatic metal centers).
Redox reactions could be used to interconvert the nonhelical
complexes (two MVS6 polyhedra) into helical (two MIVS6
polyhedra), which in principle would allow switching on and
off the helicity of a dinuclear triple-stranded complex with a
bis(benzene-o-dithiolato) ligand. We are currently studying the
preparation and properties of triple-standed dinuclear tungsten
and molybdenum complexes with bis(benzene-o-dithiolato)
ligands.
Figure 7. ORTEP diagram of the anion [Ti2(4)2(µ-OCH3)2]2-. Hydrogen
atoms have been omitted.
Table 2. Selected Bond Lengths (Å) and Angles (deg) in Complex
Anions [16]2- and [17]2-
-
-
parameter
[Ti2(4)2(
µ
-OCH3)2]2
[Ti2(5)2(µ
-OCH3)2]2
Ti-S1(O1)
2.4036(7)
2.4071(7)
2.4073(7)
2.4104(8)
2.006(2)
2.012(1)
3.577
1.921(5)
1.961(5)
1.959(5)
1.917(5)
1.992(5)
1.992(5)
2.721
Ti-S2(O2)
Ti-S3(O3)
Ti-S4(O4)
Ti-O99
Ti-O99*
N1‚‚‚S2(O2)
N2‚‚‚S3(O3)
3.643
2.650
Experimental Section
S1(O1)-Ti-S2(O2)
S1(O1)-Ti-S3(O3*)
S1(O1)-Ti-S4(O4*)
S1(O1)-Ti-O99
S1(O1)-Ti-O99*
S2(O2)-Ti-S3(O3*)
S2(O2)-Ti-S4(O4*)
S2(O2)-Ti-O99
S2(O2)-Ti-O99*
S3(O3*)-Ti-S4(O4*)
S3(O3*)-Ti-O99
S3(O3*)-Ti-O99*
S4(O4*)-Ti-O99
S4(O4*)-Ti-O99*
O99-Ti1-O99*
Ti-O99-Ti*
81.72(2)
89.13(3)
100.66(3)
95.11(5)
158.73(5)
167.07(3)
90.64(3)
106.57(5)
83.59(5)
82.06(2)
83.22(5)
107.54(5)
158.19(5)
94.79(5)
74.48(7)
105.52(7)
80.2(2)
92.0(2)
100.2(2)
159.5(2)
95.0(2)
168.8(2)
93.5(2)
84.9(2)
104.5(2)
79.9(2)
104.6(2)
84.1(2)
94.7(2)
158.3(2)
75.1(2)
104.9(2)
General. 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. NMR
spectra were recorded on Bruker AC 200 (200 MHz), Bruker AMX
400 (400 MHz), or Varian Inova 500 (500 MHz) and are reported
relative to TMS as an internal standard or relative to the solvent signal.
IR spectra were recorded on a Bruker Vector 22 infrared spectrometer.
Mass spectra were measured on a Varian MAT 212 (EI), on a
Micromass Quattro LC-Z (ESI), and on a Bruker Reflex IV spectrometer
(MALDI). Elemental analyses were performed with a Vario EL III
CHNS Elemental Analyzer. The electronic spectrum was recorded on
a Varian Cary 50. 2,3-Di(isopropylmercapto)benzoic acid (6),9b 1,2-
bis(2,3-di(isopropylmercapto)benzamido)ethane 8,10 1,2-bis(2,3-dimer-
captobenzamido)ethane H4-1,10 and Li(PNP)3[Ti2(1)3] Li(PNP)3[13]15
have been prepared as previously described.
[Ti2(4)2(µ-OCH3)2]2- and [Ti2(5)2(µ-OCH3)2]2- demonstrated
that the substitution of the oxygen atoms for sulfur atoms leads
to identical structural motifs but different ligand conformations.
1,2-Bis(2,3-di(isopropylmercapto)benzamido)ethane 8.10 1H NMR
(200 MHz, [d6]DMSO): δ ) 8.21 (s, br, 2H, CONH), 7.36 (d, 4H,
Conclusion
(20) Huynh, H. V.; Lu¨gger, T.; Hahn, F. E. Eur. J. Inorg. Chem. 2002, 3007-
3009.
With this contribution we have shown that bis(benzene-o-
dithiolato) ligands form triple- and double-stranded helicates
(21) Schulze Isfort, C.; Pape, T.; Hahn, F. E. Eur. J. Inorg. Chem. 2005, 2607-
2611.
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11816 J. AM. CHEM. SOC. VOL. 128, NO. 36, 2006

Bis(benzene-o-dithiolato) Ligands
A R T I C L E S
ArH), 7.10 (t, 2H, ArH), 3.60 (m, 3JH,H ) 6.3 Hz, 2H, SCH), 3.38 (m,
3JH,H ) 6.5 Hz, 2H, SCH), 3.34 (s, 4H, CH2), 1.30 (d, 3JH,H ) 6.5 Hz,
diamine (756 mg, 7.0 mmol) and NEt3 (2.2 mL, 15.0 mmol) in THF
(40 mL). The suspension obtained was stirred for 12 h at ambient
temperature and NEt3‚HCl was filtered off. The solvent was removed
in vacuo, and the resulting solid was washed with water and recrystal-
lized from CH2Cl2/hexane to yield a white powder (2.90 g, 6.65 mmol,
95%). 1H NMR (200 MHz, CDCl3): δ ) 9.97 (s, 2H, CONH), 7.85-
7.76 (m, 4H, ArH), 7.28 (dd, 3JH,H ) 6.2 Hz, 4JH,H ) 3.3 Hz, 2H, ArH),
3
12H, CH(CH3)2), 1.11 ppm (d, JH,H ) 6.3 Hz, 12H, CH(CH3)2). 13C
NMR (50 MHz, [d6]DMSO): δ ) 168.2 (CONH), 145.5, 144.6, 128.8,
127.8, 126.4, 123.2 (ArC), 34.7 (CH(CH3)2), 22.9 (CH(CH3)2), 22.3
ppm (CH(CH3)2); one of the (CH(CH3)2) signals and the CH2 signal of
the bridge are obscured by the solvent peaks. MS (70 eV, EI): m/z
(%) ) 564 (46, M+), 521 (100, M+-C3H7), 253 (21), 211 (29), 43 (3,
C3H7+). IR (KBr): ν˜ ) 3355, 3257 (st, N-H), 2960, 2923, 2863 (m,
SCsH), 1677 (st, CdO), 1550 (st, NsH), 1638, 1571, 1519 (m, Ars
CdC), 1442 cm-1 (m, CH2). Anal. Calcd for C28H40N2O2S4: C, 59.54;
H, 7.14; N, 4.96; S, 22.70. Found: C, 59.35; H, 7.00; N, 4.81; S, 22.73.
1,4-Bis(2,3-di(isopropylmercapto)benzamido)benzene (9). 2,3-Di-
(isopropylmercapto)-benzoic acid 6 (3.82 g, 14.15 mmol) and DMF (2
drops) were dissolved in benzene (20 mL) and cooled to 5 °C. Oxalyl
dichloride (1.85 mL, 21.23 mmol) was added, and the solution was
stirred for 1 h at 5 °C. The solvent was removed in vacuo. The residue
was dissolved in THF (20 mL) and added to a solution of 1,4-
diaminobenzene (725 mg, 6.72 mmol) and NEt3 (2.0 mL, 14.15 mmol)
in THF (40 mL). The suspension obtained was stirred for 12 h at
ambient temperature. NEt3‚HCl was filtered off, and the solvent was
removed in vacuo. The resulting solid was washed with water and
diethyl ether to give an off-white powder (3.38 g, 82%). 1H NMR (200
MHz, CDCl3): δ ) 10.24 (s, 2H, CONH), 7.65 (s, 4H, ArH), 7.44 (m,
4H, ArH), 7.21 (m, 2H, ArH), 3.65 (m, 2H, SCH), 3.44 (m, 2H, SCH),
1.33 (d, 3JH,H ) 6.4 Hz, 12H, CH(CH3)2), 1.13 ppm (d, 3JH,H ) 6.4 Hz,
12H, CH(CH3)2). 13C NMR (50 MHz, CDCl3): δ ) 166.5 (CONH),
145.4, 144.8, 134.9, 129.2, 127.8, 126.4, 123.2, 119.8 (ArC), 36.2 (CH-
(CH3)2), 34.7 (CH(CH3)2), 23.0 (CH(CH3)2), 22.4 ppm (CH(CH3)2).
MS (70 eV, EI): m/z (%) ) 612 (100, M+), 360 (28), 270 (20), 211
(46), 108 (89), 41 (28). IR (KBr): ) 3307 (st, NsH), 3051 (s, Ars
H), 2960, 2923, 2863 (m, SCsH), 1665 (st, CdO), 1607, 1514 cm-1
(m, ArsCdC). Anal. Calcd for C32H40N2O2S4: C, 62.71; H, 6.58; N,
4.57; S, 20.92. Found: C, 62.29; H, 6.43; N, 4.44; S, 20.88.
3
3
4
7.17 (t, JH,H ) 8.4 Hz, 2H, ArH), 7.06 (dd, JH,H ) 8.4 Hz, JH,H
)
1.8 Hz, 2H, ArH), 3.87 (s, 6H, CH3), 3.86 ppm (s, 6H, CH3). 13C NMR
(200 MHz, CDCl3): δ ) 164.2 (CONH), 152.5, 147.7, 131.0, 126.3,
126.1, 125.4, 124.2, 122.9, 115.9 (ArC), 61.5, 56.0 ppm (CH3). Anal.
Calcd for C24H24N2O6: C, 66.05; H, 5.54; N, 6.42. Found: C, 65.83;
H, 5.59; N, 6.22.
1,2-Bis(2,3-dimercaptobenzamido)ethane (H4-1).10 1H NMR (200
MHz, [d7]DMF): δ ) 8.00 (s, br, 2H, CONH), 6.83 (dd, 2H, ArH),
6.71 (dd, 2H, ArH), 6.32 (t, 2H, ArH), 5.17 (s, br, 4H, SH), 2.87 ppm
(t, 4H, CH2). 13C NMR (50 MHz, [d7]DMF): δ ) 170.0 (CONH),
135.1, 134.0, 132.0, 126.3, 125.4 (ArC), 40.0 ppm (CH2), only 5 of
the expected 6 ArC signals were observed. MS (70 eV, EI): m/z (%)
) 396 (31, M+), 364 (3, M+sSH), 228 (100), 199 (45), 168 (87), 78
(9, C6H6+), 34 (87, H2S+). IR (KBr) ν˜ ) 3285 (st, NsH), 3057, 2945
(s, ArsH), 2528 (m, SsH), 1633 (st, CdO), 1572 (st, NsH), 1536
(st, ArsCdC), 1442 cm-1 (m, CH2). Anal. Calcd for C16H16N2O2S4:
C, 48.46; H, 4.07; N, 7.06; S, 32.34. Found: C, 48.43; H, 4.37; N,
6.80; S, 31.46.
1,4-Bis(2,3-dimercaptobenzamido)benzene (H4-2). Compound 9
(3.150 g, 5.14 mmol) and naphthalene (3.294 g, 25.70 mmol) were
dissolved in THF (80 mL), and pieces of sodium (1.20 g, 52.17 mmol)
were added. The mixture was stirred for 12 h at ambient temperature,
and then methanol (10 mL) was added dropwise. After 10 min, the
solvent was removed in vacuo, and the residue was dissolved in
degassed water (40 mL) and washed with diethyl ether (3 × 20 mL).
After the aqueous phase was filtered, hydrochloric acid (37%) was
added dropwise to afford a white solid. The precipitate was filtered
off, washed with water (2 × 20 mL) and diethyl ether (2 × 20 mL),
1,2-(R,R)-Bis(2,3-di(isopropylmercapto)benzamido)-
cyclohexane (10). Compound 10 was prepared as described for 9. Yield
1
and dried in vacuo to yield an off-white powder (1.98 g, 87%). H
1
1.57 g (2.54 mmol, 78%) of a bright yellow powder. H NMR (200
NMR (200 MHz, [d7]DMF): δ ) 10.65 (s, 2H, CONH), 7.99 (s, 4H,
3
4
MHz, CDCl3): δ ) 7.29-7.19 (m, 6H, ArH), 6.87 (d, br, 2H, CONH),
3.94 (s, br, 2H, NCH), 3.53-3.39 (m, 4H, SCH), 2.28 (s, br, 2H, CH2),
1.83 (s, br, 2H, CH2), 1.38 (dd, 12H, CH3), 1.22 (m, 4H, CH2), 1.19
ppm (t, 12H, CH3). 13C NMR (50 MHz, CDCl3): δ ) 169.0 (CONH),
145.7, 143.2, 129.2, 128.8, 127.8, 124.6 (ArC), 54.0 (NCH), 40.2
(SCH), 36.0 (SCH), 32.2 (CH2), 24.7 (CH2), 23.2 (CH3), 22.9 (CH3),
22.6 ppm (CH3). MS (MALDI): m/z ) 619 [M+]. IR (KBr): ν˜ ) 3285
(st, N-H), 2960, 2926, 2861 (m, SC-H), 1639 (st, CdO), 1529 (m,
NsH), 795 cm-1 (m, ArsH). Anal. Calcd for C32H46N2O2S4: C, 62.10;
H, 7.49; N, 4.53; S, 20.72. Found: C, 61.65; H, 8.01; N, 4.58; S, 20.56.
1,2-Bis(2,3-di(isopropylmercapto)benzamido)benzene (11). Com-
pound 11 was prepared as described for 9. Yield 2.61 g (4.25 mmol,
96%) of an off-white powder. 1H NMR (200 MHz, CDCl3): δ ) 8.88
(s, br, 2H, CONH), 7.76-7.80 (m, 2H, ArH), 7.27-7.45 (m, 8H, ArH),
ArH), 7.77 (dd, JH,H ) 7.8 Hz, JH,H ) 1.0 Hz, 2H, ArH), 7.59 (dd,
JH,H ) 7.8 Hz, 4JH,H ) 1.0 Hz, 2H, ArH), 7.28 (t, 3JH,H ) 7.8 Hz, 2H,
3
ArH), 5.38 ppm (s, br, 4H, SH). 13C NMR (50 MHz, [d7]DMF): δ )
167.9 (CONH), 137.1, 136.2, 134.7, 133.8, 131.9, 126.2, 125.7, 121.0
ppm (ArC). MS (70 eV, EI): m/z (%) ) 444 (1, M+), 276 (100), 244
(54), 108 (88). IR (KBr): ν˜ ) 3279 (st, NsH), 3145, 3048 (s, Ars
H), 2521 (m, SsH), 1641 (st, CdO), 1542 (st, NsH), 1608, 1571,
1516 cm-1 (m, ArsCdC). Anal. Calcd for C20H16N2O2S4: C, 54.03;
H, 3.63; N, 6.30; S, 28.84. Found: C, 54.38; H, 3.97; N, 6.00; S, 27.88.
1,2-(R,R)-Bis(2,3-dimercaptobenzamido)cyclohexane (H4-3). Com-
pound 10 (2.27 g, 3.67 mmol) and naphthalene (2.35 g, 18.35 mmol)
were dissolved in THF (60 mL). Pieces of sodium (850 mg, 36.7 mmol)
were added, the solution was stirred for 12 h at ambient temperature,
and then methanol (10 mL) was added. After 10 min, the solvent was
removed in vacuo, and the residue was dissolved in degassed water
(40 mL). The aqueous phase was washed with diethyl ether (3 × 20
mL), filtered, and acidified with hydrochloric acid (37%) to afford a
white solid. The precipitate was filtered off and washed with water (2
× 20 mL) and diethyl ether (2 × 20 mL). Drying in vacuo yielded
H4-3 as a white powder (1.40 g, 3.11 mmol, 85%). 1H NMR (200 MHz,
3
3.40-3.54 (m, 4H, SCH), 1.40 (d, JH,H ) 6.8 Hz, 12H, CH(CH3)2),
3
1.15 ppm (d, JH,H ) 7.0 Hz, 12H, CH(CH3)2). 13C NMR (50 MHz,
CDCl3): δ ) 167.6 (CONH), 146.0, 142.9, 130.4, 129.1, 128.3, 126.4,
126.3, 125.2, 125.0 (ArC), 40.8 (CH(CH3)2), 36.2 (CH(CH3)2), 23.0
(CH(CH3)2), 22.7 ppm (CH(CH3)2); MS (EI, 70 eV): m/z (%) ) 612
(3, M+), 569 (25, M+-C3H7), 360 (69), 253 (58), 211 (73), 169 (49),
108 (100), 43 (3, C3H7+). IR (KBr): ν˜ ) 3261 (st, NsH), 2962, 2924,
2863 (m, SCsH), 1660 (st, CdO), 1599, 1512 (m, ArsCdC), 755
cm-1 (s, ArsH). Anal. Calcd for C32H40N2O2S4: C, 62.71; H, 6.58; N,
4.57; S, 20.92. Found: C, 61.74; H, 6.38; N, 4.53; S, 20.83.
3
[d7]DMF): δ ) 8.46 (d, JH,H ) 7.6 Hz, 2H, CONH), 7.56 (dd, 2H,
ArH), 7.34 (dd, 2H, ArH), 7.03 (t, 2H, ArH), 5.80 (s, br, 4H, SH),
4.04 (s, br, 2H, NCH), 2.03 (d, br, 2H, CH2), 1.78 (d, br, 2H, CH2),
1.68 (d, br, 2H, CH2), 1.39 ppm (d, br, 2H, CH2). 13C NMR (50 MHz,
[d7]DMF): δ ) 169.5 (CONH), 135.6, 133.8, 131.8, 126.3, 125.3
(ArC), 53.6 (NCH), 32.5 (CH2), 25.4 ppm (CH2), only 5 of the expected
6 ArC resonances were observed. MS (MALDI): m/z ) 451 [M+]. IR
(KBr): ν˜ ) 3265 (st, NsH), 3060 (s, ArsH), 2930, 2857 (m, CH2),
2529 (m, SsH), 1617 (st, CdO), 1572 (m, CdC), 1530 cm-1 (m, Ns
1,2-Bis(2,3-dimethoxybenzamido)benzene (12). 2,3-Dimethoxy-
benzoic acid (2.73 g, 15.0 mmol) and DMF (2 drops) were dissolved
in SOCl2 (10 mL). The solution was stirred for 12 h, and the volatiles
were removed in vacuo to afford a white powder. The powder was
dissolved in THF (20 mL) and added to a solution of 1,2-phenylene-
9
J. AM. CHEM. SOC. VOL. 128, NO. 36, 2006 11817

A R T I C L E S
Kreickmann et al.
Table 3. Crystallographic Data for Li(PNP)3[13], (PNP)4[14], (Ph4As)2[16], and (PNP)2[17]
parameter
Li(PNP)3[13]
‚
3DMF
‚
H20
(PNP)4[14]
‚3DMF
(Ph4As)2[16]
‚
4DMF
(PNP)2[17]‚2CH3CN‚2CH3OH
formula
fw
T (K)
C
165H149LiN12O10P6S12Ti2
C
213H177N13O9P8S12Ti2
C
102H98As2N8O10S8Ti2
C120H104N8O16P4Ti2
2133.79
153(2)
0.12 × 0.04 × 0.02
red-brown
P1h
0.710 73
14.038(3)
15.014(3)
15.241(3)
105.879(4)
100.689(4)
110.322(4)
2753.8(10)
1
1.287
0.272
1.46-23.50
19 230
3133.24
150(2)
3790.96
100(2)
0.38 × 0.16 × 0.14
dark red
R3hc
1.541 78
24.546(2)
24.546(2)
112.885(10)
90
90
120
58900(7)
12
1.283
2098.00
153(3)
crystal size (mm3)
color of crystal
space group
wavelength (Å)
a (Å)
0.50 × 0.07 × 0.07
0.23 × 0.06 × 0.06
dark red
dark red
P21/c
P1h
1.541 84
17.8522(4)
23.0986(5)
37.9215(9)
90
99.417(2)
90
15426.6(6)
4
1.349
3.495
2.36-70.17
89 879
0.710 73
8.4004(10)
16.498(2)
17.952(2)
80.544(2)
76.820(2)
85.068(3)
2386.6(5)
1
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
F
calcd (Mg m-3
)
1.460
1.095
1.84-30.08
28 266
µ (mm-1
θ range (deg)
)
2.989
2.22-70.05
88 221
reflections coll.
Rint
0.078
0.125
0.0399
0.1019
data/restr./param.
GOF
27 800/0/1922
0.938
0.0522, 0.1330
0.0786, 0.1427
+1.737/-0.438
12 393/21/786
1.040
0.0886, 0.2439
0.1258, 0.2790
+1.723/-0.723
13 819/0/608
1.007
0.0464, 0.1013
0.0746, 0.1107
+0.798/-0.459
8128/0/681
0.977
0.0877, 0.2141
0.1717, 0.2654
+1.432/-0.399
R1, wR2 [I g 2σ(I)]
R1, wR2 (all data)
max. peak/hole (e A-1
)
H). Anal. Calcd for C20H22N2O2S4: C, 53.31; H, 4.92; N, 6.22; S, 28.46.
Found: C, 53.15; H, 4.77; N, 5.85; S, 28.59.
(m, 64H, PNPH), 7.34 (dd, 3JH,H ) 7.6 Hz, 4JH,H ) 1.5 Hz, 6H, ArH),
3
4
3
7.00 (dd, JH,H ) 7.6 Hz, JH,H ) 1.5 Hz, 6H, ArH), 6.66 (t, JH,H
)
7.6 Hz, 6H, ArH), 3.46 ppm (t, 12H, CH2). 13C NMR (100 MHz, [d7]-
DMF): δ ) 169.3 (CONH), 156.3, 151.1, 135.3, 134.4, 133.8, 131.9,
129.2, 129.1, 125.1, 122.3, 121.9 (ArC), 40.1 ppm (CH2). MS (ESI,
neg. ions): m/z ) 424.1 ((H[Ti2(1)3])3-), 604.1, ((PNP)[Ti2(1)3]3-).
Anal. Calcd for solvent-free Li(PNP)3[Ti2(1)3] C156H126LiN9O6P6S12-
Ti2: C, 64.70; H, 4.39; N, 4.35; S, 13.28. Found: C, 65.04; H, 4.54;
N, 4.39; S, 13.72.
1,2-Bis(2,3-dimercaptobenzamido)benzene (H4-4). Compound 11
(2.50 g, 4.08 mmol) and naphthalene (3.42 g, 20.40 mmol) were
dissolved in THF (60 mL), and pieces of sodium (938 mg, 40.80 mmol)
were added. The solution was stirred for 12 h at ambient temperature,
and then methanol (10 mL) was added. After 10 min, the solvent was
removed in vacuo, and the residue was dissolved in degassed water
(40 mL). The aqueous phase was washed with diethyl ether (3 × 20
mL), filtered, and acidified with hydrochloric acid (37%) to afford a
white solid. The precipitate was filtered off and washed with water (2
× 20 mL) and diethyl ether (2 × 20 mL). Drying in vacuo yielded
H4-4 as a white powder (1.47 g, 3.30 mmol, 81%). 1H NMR (200 MHz,
[d7]DMF): δ ) 10.08 (s, 2H, CONH), 7.81-7.10 (m, 10H, ArH), 5.04
ppm (s, br, 4H, SH). 13C NMR (50 MHz, [d7]DMF): δ ) 187.9
(CONH), 132.3, 131.8, 129.6, 128.4, 126.4, 126.3, 126.2, 126.1, 125.9
ppm (ArC). MS (MALDI): m/z (%) ) 444 (100, M+). IR (KBr): ν˜ )
3348, 3201 (st, NsH), 2518 (m, SsH), 1662 (st, CdO), 1508 (m,
ArsCdC), 753 cm-1 (st, ArsH). Anal. Calcd for C20H16N2O2S4: C,
54.03; H, 3.63; N, 6.30; S, 28.84. Found: C, 54.21; H, 3.84; N, 5.94;
S, 28.29.
(PNP)4[Ti2(2)3] (PNP)4[14]. A sample of [Ti(OC2H5)4] (17 mg, 0.075
mmol) was added to a solution of H4-2 (50 mg, 0.113 mmol) and Li2-
CO3 (6 mg, 0.075 mmol) in degassed methanol (20 mL). The solution
was stirred for 12 h at ambient temperature and filtered. Addition of
(PNP)Cl (86 mg, 0.15 mmol) to the filtrate yields a brown precipitate,
which was isolated by filtration, washed with methanol, and dried in
vacuo. Yield 98 mg (0.027 mmol, 73%) of red-brown powder. 1H NMR
(500 MHz, [d7]DMF): δ ) 11.18 (s, 6H, CONH), 7.82 (s, 12H, ArH),
7.77-7.68 (m, 72H, PNP-H), 7.60-7.56 (m, 48H, PNP-H), 7.48 (dd,
4
3
3JH,H ) 7.5 Hz, JH,H ) 1.5 Hz, 6H, ArH), 7.10 (dd, JH,H ) 7.5 Hz,
4JH,H ) 1.5 Hz, 6H, ArH), 6.74 ppm (t, 3JH,H ) 7.5 Hz, 6H, ArH). 13
C
NMR (125 MHz, [d7]DMF): δ ) 166.5 (CONH), 155.9, 150.3, 135.5,
133.9, 133.3, 132.6, 132.5, 129.7, 129.7, 128.5, 128.0, 127.2, 125.0,
121.2, 119.7 ppm (ArC). MS (ESI, neg. ions): m/z ) 651.3
([(PNP)[Ti2(2)3]]3-), 1248.0 ([(PNP)2[Ti2(2)3]]2-). Anal. Calcd for
solvent-free (PNP)4[Ti2(2)3] C204H156N10O6P8S12Ti2: C, 68.60; H, 4.40;
N, 3.92; S, 10.77. Found: C, 68.21; H, 4.73; N, 4.33; S, 10.38.
1,2-Bis(2,3-dihydroxybenzamido)benzene (H4-5). Compound 12
(1.50 g, 3.43 mmol) was dissolved in CH2Cl2 (60 mL), and BBr3 (4.30
g, 17.15 mmol) was added at 0 °C. The suspension was stirred for 12
h at room temperature, and the volatiles were removed in vacuo. The
resulting solid was suspended in water (50 mL) and refluxed for 2 h.
A white precipitate formed, which was filtered off, washed with water
and diethyl ether, and dried in vacuo to give H4-5 as a white powder
(1.13 g, 2.98 mmol, 87%). 1H NMR (400 MHz, [d7]DMF): δ ) 10.35
(Ph4As)4[Ti2(3)3] (Ph4As)4[15]. A sample of [Ti(OC2H5)4] (17 mg,
0.074 mmol) was added to a solution of H4-3 (50 mg, 0.111 mmol)
and Li2CO3 (6 mg, 0.074 mmol) in degassed methanol (20 mL). The
solution was stirred for 12 h at ambient temperature and filtered.
Addition of (Ph4As)Cl (63 mg, 0.15 mmol) to the filtrate yielded a
brown precipitate, which was isolated by filtration, washed with
methanol, and dried in vacuo. Yield 69 mg (0.022 mmol, 60%) of a
red-brown powder. 1H NMR (400 MHz, [d]7DMF): δ ) 8.63 (d, 3JH,H
) 6.2 Hz, 6H, CONH), 7.97-7.80 (m, 20H, Ph4As-H), 7.31 (dd, 3JH,H
3
4
(s, 2H, CONH), 7.72 (dd, JH,H ) 5.9 Hz, JH,H ) 3.4 Hz, 2H, ArH),
7.44 (dd, 3JH,H ) 8.2 Hz, 4JH,H ) 1.4 Hz, 2H, ArH), 7.30 (dd, JH,H
5.9 Hz, JH,H ) 3.4 Hz, 2H, ArH), 6.97 (dd, JH,H ) 8.2 Hz, JH,H
)
)
3
4
3
4
1.4 Hz, 2H, ArH), 6.75 (t, 3JH,H ) 8.2 Hz, 2H, ArH), 4.98 ppm (s, 4H,
OH). 13C NMR (100 MHz, [d7]DMF): δ ) 169.1 (CONH), 149.2,
146.6, 136.4, 131.0, 118.8, 117.3, 115.3, 110.9 ppm (ArC), only 8 of
the expected 9 ArC resonances were observed. Anal. Calcd for
C20H16N2O6: C, 63.16; H, 4.24; N, 7.37. Found: C, 62.65; H, 4.73; N,
7.52.
) 7.5 Hz, 4JH,H ) 1.4 Hz, 6H, ArH), 7.08 (dd, 3JH,H ) 7.5 Hz, 4JH,H
)
3
1.4 Hz, 6H, ArH), 6.68 (t, JH,H ) 7.5 Hz, 6H, ArH), 4.34 (s, br, 6H,
CH), 2.13-1.19 ppm (m, br, 24H, CH2). 13C NMR (100 MHz,
[d]7DMF): δ ) 165.2 (CONH), 157.3, 151.1, 139.6, 139.2, 138.7,
131.5, 130.0, 129.4, 128.8, 125.2, 124.1, 122.7 (ArC), 53.6. (CH), 34.4,
Li(PNP)3[Ti2(1)3] Li(PNP)3[13].15 1H NMR (400 MHz, [d7]DMF):
δ ) 8.85 (s, 6H, CONH), 7.98-7.91 (m, 16H, PNP-H), 7.89-7.82
9
11818 J. AM. CHEM. SOC. VOL. 128, NO. 36, 2006

Bis(benzene-o-dithiolato) Ligands
A R T I C L E S
26.8 ppm (CH2). MS (ESI, neg. ions): m/z ) 478 ([H[Ti2(3)3]]3-), 606
([(Ph4As)[Ti2(3)3]]3-), 718 ([H2[Ti2(3)3]]2-). Anal. Calcd for solvent-
free (Ph4As)4[Ti2(3)3] C166H164As4N6O6S12Ti2: C, 63.11; H, 4.55; N,
2.83; S, 12.96. Found: C, 63.35; H, 4.27; N, 3.03; S, 13.54.
X-ray Crystallography. X-ray diffraction data (Table 3) were
collected on a Bruker AXS diffractometer equipped with a rotating
anode generator and with Mo KR ((Ph4As)2[16]‚4DMF, (PNP)2[17]‚
2CH3CN‚2CH3OH), or Cu KR radiation (Li(PNP)3[13]‚3DMF‚H2O,
(PNP)4[14]‚3DMF). All raw data were corrected for absorption. The
structure solutions were found with SHELXS,22 and the refinement was
carried out with SHELXL23 using anisotropic thermal parameters for
all non-hydrogen atoms (see below for exceptions). Hydrogen atoms
were added to the structure models on calculated positions and were
refined as rigid atoms or were unrefined. One PNP cation in (PNP)4-
[14]‚3DMF is disordered around a special position. The positional
parameters of this molecule were refined with one common isotropic
thermal parameter. The solvent molecules in (PNP)2[17]‚2CH3CN‚
2CH3OH are disordered, and the corresponding positional parameters
have been refined with isotropic thermal parameters.
(Ph4As)2[Ti2(4)2(OCH3)2] (Ph4As)2[16]. A sample of [Ti(OC2H5)4]
(26 mg, 0.113 mmol) was added to a solution of H4-4 (50 mg, 0.113
mmol) and Li2CO3 (6 mg, 0.075 mmol) in degassed methanol (20 mL).
The solution was stirred for 12 h at ambient temperature and filtered.
Addition of (Ph4As)Cl (54 mg, 0.113 mmol) to the filtrate yielded a
brown precipitate, which was isolated by filtration, washed with
methanol (3 × 20 mL), and dried in vacuo. Yield 45 mg (0.025 mmol,
67%). 1H NMR (400 MHz, [d]7DMF): δ ) 9.77 (s, 4H, CONH), 8.32
3
4
3
(dd, JH,H ) 6.2 Hz, JH,H ) 3.7 Hz, 4H, ArH), 7.15 (dd, JH,H ) 6.2
4
3
4
Hz, JH,H ) 3.7 Hz, 4H, ArH), 7.11 (dd, JH,H ) 7.5 Hz, JH,H ) 1.4
3
4
Hz, 4H, ArH), 6.92 (dd, JH,H ) 7.5 Hz, JH,H ) 1.4 Hz, 4H, ArH),
6.79 (t, 3JH,H ) 7.5 Hz, 4H, ArH), 4.60 ppm (s, 6H, CH3O). 13C NMR
(100 MHz, [d7]DMF): δ ) 168.3 (CONH), 155.6, 144.8, 135.6, 135.1,
134.4, 134.2, 131.7, 130.4, 130.3, 130.2, 124.4, 124.1, 123.8 (ArC),
69.3 ppm (CH3O). MS (ESI, neg. ions): m/z ) 519 ([Ti2(4)2(OCH3)2]2-).
Anal. Calcd for solvent-free (Ph4As)2[Ti2(4)2(OCH3)2] C90H70As2N4O6S8-
Ti2: C, 59.87; H, 3.91; N, 3.10; S, 14.20. Found: C, 60.33; H, 3.84;
N, 2.87; S, 14.54.
Acknowledgment. Funding from the Deutsche Forschungs-
gemeinschaft (IRTG 673) and the NRW Graduate School of
Chemistry, Mu¨nster (predoctoral grant to T.K.) is acknowledged.
We thank Dr. Klaus Bergander and Dr. Alexander Hepp for
measuring the NMR spectra and Dr. Heinrich Luftmann for
measuring the ESI mass spectra. We also thank Dr. Roland
Fro¨hlich for help with the crystal structure analyses.
(PNP)2[Ti2(5)2(OCH3)2] (PNP)2[17]. A sample of H4-5 (50 mg,
0.132 mmol) was suspended in methanol (20 mL). Li2CO3 (5 mg, 0.066
mmol) and [TiO(acac)2] (35 mg, 0.132 mmol) were added, and the
obtained orange solution was stirred for 12 h at room temperature.
(PNP)Cl (76 mg, 0.132 mmol) was added, and the resulting precipitate
was filtered off, washed with methanol, and dried in vacuo to afford
an orange solid (89 mg, 0.045 mmol, 68%). 1H NMR (400 MHz, [d7]-
Supporting Information Available: X-ray crystallographic
files for Li(PNP)3[13]‚3DMF‚H2O, (PNP)4[14]‚3DMF, (Ph4-
As)2[16]‚4DMF, and (PNP)2[17]‚2CH3CN‚ 2CH3OH (four CIF
files). This material is available free of charge via the Internet
at http://pubs.acs.org.
3
4
DMF): δ ) 10.63 (s, 2H, CONH), 7.87 (dd, JH,H ) 5.8 Hz, JH,H
)
3.6 Hz, 4H, ArH), 7.78-7.71 (m, 36H, PNP-H), 7.63-7.58 (m, 24H,
3
PNPH), 7.26-7.23 (m, 8H, ArH), 6.53 (t, JH,H ) 7.8 Hz, 4H, ArH),
JA063655U
6.34 (dd, 3JH,H ) 7.5 Hz, 4JH,H ) 1.5 Hz, 4H, ArH), 4.43 (s, 6H, CH3O).
MS (ESI, neg. ions): m/z ) 455 ([Ti2(5)2(OCH3)2]2-). Anal. Calcd for
solvent-free (PNP)2[Ti2(5)2(OCH3)2] C114H90N6O14P4Ti2: C, 68.89; H,
4.56; N, 4.23. Found: C, 69.44; H, 4.59; N, 5.02.
(22) SHELXS-97: Sheldrick, G. M. Acta Crystallogr. Sect. A 1990, 46, 467-
473.
(23) Sheldrick, G. M. SHELXL-97; Universita¨t Go¨ttingen: Germany, 1997.
9
J. AM. CHEM. SOC. VOL. 128, NO. 36, 2006 11819