Embracing ligands. A synthetic strategy towards new nitrogen-thioether multidentate ligands and characterization of the cobalt(III) complexes

Article abstract of DOI:10.1039/b304914k

The synthesis of the hexadentate ligand 2,2,9,9-tetra(methyleneamine)-4,7-dithiadecane (EtN₄S₂amp) is reported. The ligand is of a type in which bifurcations of the chain occur at atoms other than donor atoms. The cobalt(III) complex

Full text of DOI:10.1039/b304914k

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Embracing ligands. A synthetic strategy towards new nitrogen–
thioether multidentate ligands and characterization of the
cobalt(III) complexes
Clint A. Sharrad, Stefan R. Lüthi† and Lawrence R. Gahan*
Chemistry Department, The University of Queensland, Brisbane, QLD 4072, Australia.
E-mail: gahan@mailbox.uq.edu.au
Received 1st May 2003, Accepted 19th August 2003
First published as an Advance Article on the web 5th September 2003
The synthesis of the hexadentate ligand 2,2,9,9-tetra(methyleneamine)-4,7-dithiadecane (EtN4S2amp) is reported.
The ligand is of a type in which bifurcations of the chain occur at atoms other than donor atoms. The cobalt()
complex [Co(EtN4S2amp)]3ϩ (1) was isolated and characterized. The synthetic methodology also results in a number
of by-products, notably 2,9,9-tris(methyleneamine)-9-methylenehydroxy-4,7-dithiadecane (Et(HO)N3S2amp) and an
eleven-membered pendant arm macrocyclic ligand 6,10-dimethyl-6,10-bis(methyleneamine)-1,4-dithia-8-azaacyclo-
undec-7-ene (dmatue). The complexes [Co(Et(HO)N3S2amp)]3ϩ (2), in which the alcohol is coordinated to the metal
ion, and [Co(dmatue)Cl]2ϩ (4) were isolated and characterized. Et(HO)N3S2amp also undergoes complexation with
cobalt() to produce two isomers endo-[Co(Et(HO)N3S2amp)Cl]2ϩ (endo-3) and exo-[Co(Et(HO)N3S2amp)Cl]2ϩ
(exo-3), both with an uncoordinated alcohol group. endo-3 has the alcohol positioned cis, and exo-3 trans, to the sixth
metal coordination site. Reaction of 1 with isobutyraldehyde, paraformaldehyde and base in dimethylformamide
results in the encapsulated complex [Co(1,5,5,9,13,13-hexamethyl-18,21-dithia-3,7,11,15-tetraazabicyclo[7.7.6]-
docosa-3,14-diene)](ClO4)3ؒ2H2O ([Co(Me6docosadieneN4S2)]3ϩ (5). All complexes have been characterized by single
crystal X-ray study. The low-temperature (11 K) absorption spectrum of 1 has been measured in Nafion films with
spin-allowed 1A1g
1T1g and 1A1g
1T2g and spin forbidden 1A1g
3T1g and 1A1g
3T2g bands observed. The
octahedral ligand-field parameters were determined (10Dq = 22570 cmϪ1, B = 551 cmϪ1; C = 3500 cmϪ1). For 5 10Dq
and B were determined (20580 cmϪ1; 516 cmϪ1, respectively) and compared with those for similar expanded cavity
complexes [Co(Me8tricosatrieneN6)]3ϩ and [Co(Me5tricosatrieneN6)]3ϩ
.
Introduction
The design and application of hexadentate ligands has been of
interest ever since Lions proposed thirty-six different ligand
topologies for the hexadentate donor set.1,2 Numerous
examples of the hexadentate ligand type have been reported
and in many cases the interest has been their application as
precursors for the synthesis of fully encapsulated complexes.3–14
One ligand topology described by Lions was that in which
bifurcations of the chain occur at atoms other than donor
atoms.1,2 Our interest in this particular ligand topology arises
from the intrinsic chemistry, and that of the metal complexes
formed from them.15,16 The application of this ligand topology
for further synthetic elaboration enabling the synthesis of
encapsulating ligands with larger cavities and a larger variety of
donor groups is also of interest. The synthesis and characteriz-
ation of two new examples of this ligand topology, herein called
amplector ligands (Latin: to embrace) is now reported.
Although the synthetic methodology reported allows for
variations in the donor type and the chelate ring size, the
present work confines itself to the synthesis of a particular
mixed nitrogen–thioether ligand 2,2,9,9-tetra(methylene-
amine)-4,7-dithiadecane (EtN4S2amp) and its cobalt()
complex. Subsequent elaboration to prepare an encapsulating
ligand, as the cobalt() complex, is also reported.
Chart 1
The ligands discussed in this work are shown in Chart 1.
connecting them. Thus, for EtN4S2amp (2,2,9,9-tetra(methyl-
eneamine)-4,7-dithiadecane) the prefix Et denotes the ethyl
hinge and N4S2 refers to the tetraamine–dithioether donor set
of the ligand. The same nomenclature applies for the major
synthetic by-product Et(OH)N3S2amp (2,9,9-tris(methylene-
amine)-9-methylenehydroxy-4,7-dithiadecane) with a possible
chromophore of three primary amines, two thioether donors
and an alcohol. In both cases the final two atoms referred
to (S2) denote the donor atoms of the hinge moiety. The
nomenclature employed to describe the encapsulated complex
Results and discussion
Nomenclature
The abbreviated nomenclature for the amplector (amp) ligand
can be considered in terms of the donor set and a hinge moiety
† Current address: Gemfire Corporation, 1220 Page Avenue, Fremont
CA 94538, USA.
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
D a l t o n T r a n s . , 2 0 0 3 , 3 6 9 3 – 3 7 0 3
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Me6docosadieneN4S2 is similar to that used to describe the
expanded hexaaza cage complexes.17,18
The abbreviation dmatue employed for the eleven-membered
macrocyclic ligand 6,10-dimethyl-6,10-bis(methyleneamine)-
1,4-dithia-8-azacycloundec-7-ene is not systematic.
the reversibility of this protonation process. The average fit to
the data23 for the forward and back titrations provides a pKa of
2.8(1). Similar shifts in the 1A1g
1T1g transition are observed
on the deprotonation of Co() aminoalcohol complexes,24 and
are assigned to the deprotonation of a coordinated alcohol
group to a coordinated OϪ species.
The ligand Et(OH)N3S2amp can function as a pentadentate
ligand (N3S2 chromophore) which can adopt two major con-
formations, the endo isomer, where the unbound alcohol group
is positioned cis to the sixth metal coordination site and the
other, the exo-isomer, where the unbound alcohol group is
positioned trans. endo-[Co(Et(HO)N3S2amp)Cl]2ϩ (endo-3)
where the coordination sphere is completed by a bound ClϪ
ligand, was found to be the predominant product in the initial
fractions eluted from Sephadex cation exchange resin with 0.2
M NaCl. The exo-[Co(Et(HO)N3S2amp)Cl]2ϩ (exo-3) complex
was isolated in extremely low yield from the tail of the same
band. The formation of the endo- and exo-3 complexes can be
understood in terms of the possible sequence of steps involved
in the complexation. In the case of a multidentate ligand with
an amine donor at the apex (e.g. tren; tris(2-aminoethyl)amine),
the nitrogen can readily invert to accommodate the sequence of
chelation. For ligands with a carbon apex such ready inversion
is not possible once two donors are attached. Chelation of the
OH in endo-3 would result in the OH trans to the thioether. The
observed structure of endo-3 (vide infra) suggests that the
thioether donor labilises this site leading to replacement of OH
by chloride.
Synthesis of ligands and complexes
The potentially hexadentate ligand EtN4S2amp was synthesized
by a reaction sequence (Scheme 1) in which 1,3-(dimethylmeth-
ylenedioxy)-2-methyl-2-(methylene-p-tolylsulfonyl)propane19 is
reacted with the sodium salt of 1,2-ethanedithiol. Removal of
the acetal protecting groups, under acidic conditions, resulted
in the tetrahydroxy product. Conversion to the corresponding
sulfonyl ester and reaction with potassium phthalimide in
diglyme at 150 ЊC resulted in the tetraphthalimide.20,21 The
phthalimide groups were removed as described previously.20 We
have found that multidentate ligands of this type cannot easily
be purified; distillation invariably results in pyrolysis and
chromatographic methods are relatively inefficient.9,10,14 The
most convenient manner in which to produce a pure sample
of the ligand is to prepare and characterize the cobalt()
complex.9,10,14
The complex [Co(dmatue)Cl]2ϩ (4) was isolated in low yield
from the first fractions of the eluent from Sephadex cation
exchange resin (0.2 M NaCl). The ligand is an eleven-
membered pendant arm macrocycle containing an imine in the
ring. One proposal as to the origin of this ligand arises from an
intramolecular reaction between an aldehyde and a neigh-
bouring amine. Cobalt() nitrate has been shown to act as a
mild oxidising agent in the low yielding (9%) conversion of
cyclodecanol to cyclodecanone.25 Thus, formation of the
aldehyde may arise from Et(HO)N3S2amp by reaction with
Co2ϩ prior to, or in association with, complexation and
subsequent reaction with a neighbouring primary amine.
The metal complex 1 presents opportunities for further syn-
thetic elaboration about the pseudo-C2 axis, through the four
primary amine donors, in a similar manner to the encapsulation
reactions of [Co(tame)2]3ϩ.17,18 These encapsulation reactions
are different to those reported for hexaamine complexes, and
the mixed thioether/amine analogues where the reaction occurs
around the (pseudo) C3 axis.9,10,14,26 The imine cage complex
[Co(Me6docosadieneN4S2)]3ϩ (5) was synthesized from a metal
template strategy using 1 with paraformaldehyde in the
presence of isobutyraldehyde and base. The imine complex
proved difficult to reduce cleanly to the saturated analogue
using previously described methodologies.17,18 Invariably the
reactions were low yielding and the products obtained
indicative of ligand decomposition under the conditions
employed (NaBH4, base).17,18
Scheme 1 Synthetic strategy for the formation of EtN4S2amp. (a)
HSCH2CH2SH (0.5 eq.)/Na (1 eq.)/ethanol; (b) Hϩ, ethanol; (c)
toluenesulfonyl chloride (4.4 eq.)/pyridine; (d) potassium phthalimide
(4.4 eq.)/diglyme/150 ЊC; (e) hydrazine hydrate (excess)/ethanol/HCl.
Reaction of EtN4S2amp with cobalt() and oxygen resulted
in the major product [Co(EtN4S2amp)]Cl3 (1ؒCl3), isolated as an
orange band after chromatographic purification. The chrom-
atography also resulted in the elution of a series of coloured
bands preceding the major product. A red–brown band was
identified by microanalysis, NMR spectroscopy and X-ray crys-
tallography as [Co(Et(HO)N3S2amp)]Cl(ClO4)2 (2ؒCl(ClO4)2), a
complex with a N3OS2 chromophore where the HO is bound to
the metal ion. The precursor for the Et(HO)N3S2amp ligand
is most likely formed in the reaction between 2,2,9,9-tetra-
(methylene-p-toluenesulfonyl)-4,7-dithiadecane and potassium
phthalimide in diglyme. A similar by-product leading to 2,2-
bis(aminomethyl)propan-1-ol was isolated in the synthesis of
tame (1,1,1-tris(aminomethyl)ethane).22 A spectrophotometric-
pH titration of 2 in water (0.1 M Et4NClO4; pH 2–5) showed
that the position of λmax shifts to higher wavelengths with
increasing pH (476 nm at pH 2; 494 nm at pH 5). Titration with
acid (0.1 M Et4NClO4; pH 5–2) using the same solution shows
Structures
The structures of 1 and 2 consist of the complex cation (Figs. 1
and 2, respectively), a single chloride anion and two perchlorate
anions. For 1 the cobalt atom is coordinated to four primary
amine and two thioether donors in an octahedral geometry;
the cobalt atom lies on a two-fold axis. In 2 the cobalt is
coordinated to three amine, one alcohol and two thioether
donors. Attempts to crystallize 2 in its deprotonated form were
not successful. The complex cations 1 and 2 have a conform-
ation with the C–C bond of the five-membered dithio-chelate
ring parallel (lel )27 to the pseudo-C3 axis and the remaining six-
membered chelate rings all adopt the unsymmetrical skew boat
conformation.
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Table
2
Selected interatomic distances (Å) and angles (Њ) for
1ؒCl(ClO4)2
Co(1)–N(1)
Co(1)–S(1)
1.987(4)
2.2159(13)
Co(1)–N(2)
1.981(4)
N(1)–Co(1)–N(1)#1 88.8(2)
N(2)–Co(1)–N(1)#1 89.00(16)
N(2)–Co(1)–S(1)#1 90.04(11)
N(2)#1–Co(1)–N(2) 177.5(2)
S(1)–Co(1)–S(1)#1 89.72(7)
N(1)–Co(1)–S(1)
90.79(12)
N(1)–Co(1)–S(1)#1 177.13(12)
N(2)–Co(1)–N(1)
N(2)–Co(1)–S(1)
92.80(16)
88.17(12)
Fig. 1 ORTEP plot of the complex cation 1, with crystallographic
numbering. Probability ellipsoids of 30% are shown.
Fig. 2 ORTEP plot of the complex cation 2, with crystallographic
numbering. Probability ellipsoids of 30% are shown.
For 1 (crystal data, Table 1) the Co–N and Co–S bond
lengths (1.987(4) and 1.981(4) Å; 2.2159(13) Å, respectively
(Table 2)) are similar to those reported for the hexadentate
complex [Co(N4S2)]3ϩ (N4S2
methyl-3,7-dithianonane-1,9-diamine)
=
5-(4-amino-2-azabutyl)-5-
(Co–N: 1.985(5),
1.975(5), 1.979(5),1.993(5) Å; Co–S: (2.218(2), 2.205(2) Å)13
and appear typical of the normal range of Co–N and Co–S
bond lengths for cobalt() complexes of this type
(Co–N:1.94–2.01 Å; Co–S: 2.194(5)–2.275(3) Å).12–14,28
For 2 the Co–N bond lengths (Table 3) for the bonds trans to
the sulfur atoms (1.975(7), 1.989(6) Å) are similar to the Co–N
bond lengths for 1 but that trans to the oxygen atom (1.946(7)
Å) is slightly shorter. The Co–O bond length (1.955(7) Å) falls
within the range for Co() bonds with alcohol groups in multi-
dentate ligands (1.898(1)–1.979(8) Å).29–31 The similar ranges
D a l t o n T r a n s . , 2 0 0 3 , 3 6 9 3 – 3 7 0 3
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Table
3
Selected interatomic distances (Å) and angles (Њ) for
2ؒCl(ClO4)2
Table 4 Selected interatomic distances (Å) and angles (Њ) for endo-
3ؒCl(PF6)ؒ½H2O
Co(1)–N(1)
Co(1)–N(2)
Co(1)–N(3)
1.975(7)
1.946(7)
1.989(6)
Co(1)–S(1)
Co(1)–S(2)
Co(1)–O(1)
2.228(2)
2.219(2)
1.955(7)
Co(1)–N(1)
Co(1)–N(2)
Co(1)–N(3)
1.973(5)
1.968(6)
1.986(6)
Co(1)–S(1)
Co(1)–S(2)
Co(1)–Cl(1)
2.202(2)
2.2348(19)
2.281(2)
N(1)–Co(1)–N(3)
N(1)–Co(1)–S(1)
N(1)–Co(1)–S(2)
N(2)–Co(1)–N(1)
N(2)–Co(1)–N(3)
N(2)–Co(1)–S(1)
N(2)–Co(1)–S(2)
N(2)–Co(1)–O(1)
88.8(2)
90.3(2)
178.2(2)
89.7(3)
94.5(3)
90.0(2)
N(3)–Co(1)–S(1)
N(3)–Co(1)–S(2)
S(2)–Co(1)–S(1)
O(1)–Co(1)–N(1)
O(1)–Co(1)–N(3)
O(1)–Co(1)–S(1)
O(1)–Co(1)–S(2)
175.4(3)
91.8(2)
89.28(6)
92.1(3)
87.8(3)
87.7(2)
89.60(19)
N(1)–Co(1)–N(3)
N(1)–Co(1)–S(1)
N(1)–Co(1)–S(2)
N(2)–Co(1)–N(1)
88.7(2)
89.90(18)
175.00(17)
87.1(2)
N(3)–Co(1)–S(2)
S(1)–Co(1)–S(2)
N(1)–Co(1)–Cl(1)
N(2)–Co(1)–Cl(1)
N(3)–Co(1)–Cl(1)
S(1)–Co(1)–Cl(1)
S(2)–Co(1)–Cl(1)
95.92(15)
88.10(7)
93.03(17)
86.96(17)
88.65(17)
176.92(8)
89.06(7)
N(2)–Co(1)–N(3) 173.7(2)
N(2)–Co(1)–S(1)
N(2)–Co(1)–S(2)
N(3)–Co(1)–S(1)
94.15(17)
88.47(16)
90.47(18)
88.6(2)
177.08(19)
for Co()–amine and Co()–alcohol bond lengths means that
the oxygen atom in 2 cannot be distinguished from the nitrogen
atoms based on coordination bond lengths alone. However, the
oxygen atom can be distinguished by comparing the C–O bond
length (1.463(9) Å) with the C–N bond lengths (1.485(3) Å
average). The Co–S bond lengths (2.228(2), 2.219(2) Å) are
similar to those for 1 (2.2159(13) Å).
The structures of the complex cations of endo-3 and exo-3
(Figs. 3 and 4(a) and (b), respectively) show a N3S2Cl donor set
with the alcohol group not coordinated. The amine donors are
Table 5 Selected interatomic distances (Å) and angles (Њ) for exo-
3ؒCl(ClO4)
Co(1)–N(1)
Co(1)–N(2)
Co(1)–N(3)
1.969(4)
1.973(4)
1.980(4)
Co(1)–S(1)
Co(1)–S(2)
Co(1)–Cl(1)
2.2012(11)
2.2272(12)
2.2771(11)
N(1)–Co(1)–N(2)
N(1)–Co(1)–N(3)
N(1)–Co(1)–S(1)
N(1)–Co(1)–S(2)
87.72(16)
88.14(16)
90.91(11)
176.51(12)
N(3)–Co(1)–S(2)
S(1)–Co(1)–S(2)
N(1)–Co(1)–Cl(1)
N(2)–Co(1)–Cl(1)
N(3)–Co(1)–Cl(1)
S(1)–Co(1)–Cl(1)
S(2)–Co(1)–Cl(1)
95.27(11)
88.39(4)
93.02(11)
87.65(12)
88.61(12)
175.65(5)
87.80(4)
N(2)–Co(1)–N(3) 174.27(14)
N(2)–Co(1)–S(1)
N(2)–Co(1)–S(2)
N(3)–Co(1)–S(1)
94.39(12)
88.92(11)
89.64(11)
arranged meridonially as opposed to 2 where the amine donors
adopt a facial conformation. The structure of endo-3 consists
of the complex cation, a chloride anion, a hexafluorophosphate
anion and a water molecule positioned on a site of symmetry
such that it has a unit cell occupancy of 50%. exo-3 was crystal-
lized as a mixed chloride/perchlorate salt, and the structure
shows the complex cation disordered, with each form having a
∼50% occurrence within the unit cell. In one structure, the six-
membered chelate ring at the alcohol apex has a boat conform-
ation while in the second form the same chelate ring has a chair
conformation. The structures of endo- and exo-3 are otherwise
identical with the five-membered dithio-chelate rings having the
lel form. As might be expected, the coordination spheres for
endo- and exo-3 exhibit very few differences in terms of bond
lengths and bond angles (Tables 4 and 5, respectively). The Co–
N bond lengths for both endo (1.973(5), 1.968(6), 1.986(6) Å)
and exo (1.969(4), 1.973(4), 1.980(4) Å) isomers fall within the
expected range for Co()–amine bonds (1.94–2.01 Å).12–14,28
The Co–S bond length for the thioether trans to the chloride
group (endo, 2.202(2) Å; exo, 2.2012(11) Å) is found to be
slightly shorter in comparison to the Co–S bond for the
thioether trans to an amine (endo, 2.2348(19) Å; exo, 2.2272(12)
Å). These Co–S bonds are still within the typical range
for Co()–thioether bond lengths (2.194(5)–2.275(3) Å).12–14
The Co–Cl bond lengths for the endo (2.281(2) Å) and exo
(2.2771(11) Å) isomers are in reasonable agreement with
Co()–Cl bonds of similar complexes (2.237(4)–2.305(4)
Å).32,33
Fig. 3 ORTEP plot of the complex cation endo-3 with crystallo-
graphic numbering. Probability ellipsoids of 30% are shown.
Complex 4 (Fig. 5) consists of a coordinated chloride and a
pentadentate macrocyclic ligand coordinated to the cobalt
centre through two primary amines, two thioethers and one
imine donor. Two perchlorate anions and a water molecule
make up the structure. The dmatue ligand has a cis arrange-
ment with both methyleneamine arms positioned on the same
side of the average plane of the macrocycle. The primary amine
donors are coordinated trans to the thioether donors. The
donors within the eleven-membered macrocyclic ring are co-
ordinated facially and the chloride ion is positioned trans to the
imine nitrogen. The imine bond is located between atoms N1
and C9. The Co–Nimine bond (1.919(3) Å) (Table 6) is seen to
be significantly shorter than the Co–Namine bonds (1.974(3),
Fig. 4 (a) ORTEP plot of the complex cation exo-3 – boat form, with
crystallographic numbering. Probability ellipsoids of 30% are shown.
(b) ORTEP plot of the complex cation exo-3 – chair form, with
crystallographic numbering. Probability ellipsoids of 30% are shown.
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Table
6
Selected interatomic distances (Å) and angles (Њ) for
4ؒ(ClO4)2ؒH2O
Co(1)–N(1)
Co(1)–N(2)
Co(1)–N(3)
1.919(3)
1.974(3)
1.975(3)
Co(1)–S(1)
Co(1)–S(2)
Co(1)–Cl(1)
2.2244(12)
2.2345(12)
2.2658(12)
N(1)–Co(1)–N(2)
N(1)–Co(1)–N(3)
N(1)–Co(1)–S(1)
N(1)–Co(1)–S(2)
N(2)–Co(1)–N(3)
N(2)–Co(1)–S(1)
N(2)–Co(1)–S(2)
N(3)–Co(1)–S(1)
90.67(13)
88.22(13)
92.60(10)
94.45(10)
94.16(14)
88.48(10)
174.34(10)
177.23(11)
N(3)–Co(1)–S(2)
S(1)–Co(1)–S(2)
N(1)–Co(1)–Cl(1) 177.83(9)
N(2)–Co(1)–Cl(1)
N(3)–Co(1)–Cl(1)
S(1)–Co(1)–Cl(1)
S(2)–Co(1)–Cl(1)
88.42(11)
88.88(5)
88.22(10)
90.00(10)
89.23(5)
86.75(4)
Table
7
Selected interatomic distances (Å) and angles (Њ) for
5ؒ(ClO4)3ؒ2H2O
Co(1)–N(1)
Co(1)–N(2)
Co(1)–N(3)
N(1)–C(7)
N(3)–C(16)
2.026(10)
1.991(9)
1.989(9)
1.274(14)
1.422(13)
Co(1)–N(4)
Co(1)–S(1)
Co(1)–S(2)
N(2)–C(8)
N(4)–C(17)
2.025(8)
2.248(3)
2.225(3)
1.232(14)
1.439(14)
Fig. 6 ORTEP plot of the complex cation 5 with crystallographic
numbering. Probability ellipsoids of 30% are shown.
N(1)–Co(1)–S(1)
N(1)–Co(1)–S(2)
N(2)–Co(1)–N(1)
N(2)–Co(1)–N(4)
N(2)–Co(1)–S(1)
N(2)–Co(1)–S(2)
N(3)–Co(1)–N(1)
N(3)–Co(1)–N(2)
83.6(3)
166.5(3)
85.3(4)
91.6(4)
97.2(3)
86.2(3)
90.9(4)
175.2(4)
N(3)–Co(1)–N(4)
N(3)–Co(1)–S(1)
N(3)–Co(1)–S(2)
N(4)–Co(1)–N(1)
N(4)–Co(1)–S(1)
N(4)–Co(1)–S(2)
S(2)–Co(1)–S(1)
86.6(4)
85.2(3)
98.0(3)
105.2(4)
168.0(3)
85.5(3)
distorted octahedron. Encapsulation of the coordination
sphere shows a slight increase in both the Co–Namine (1.989(9)
and 2.025(8) Å) and Co–S (2.225(3) and 2.248(3) Å) bond
lengths in comparison with the precursor 1. The Co–Nimine
bond lengths (1.991(9) and 2.026(10) Å) are similar to those
reported for its N6 analogue17,18 and are distinctly longer than
Co–Nimine bonds of 1.90 Å in relatively unstrained ligand
87.04(12)
environments.34,35 The Co–Namine,
bonds trans to the
imine
thioether donors are ∼0.03 Å longer than the corresponding
Co–Namine, bonds trans to nitrogen donors indicating a
imine
possible trans influence exerted by the thioethers. This is not
observed in 1 and may be a result of the strained nature of the
macrobicyclic ligand. The six-membered amine/imine-chelate
rings of 5 have a distorted chair conformation while those at
the apices adopt the unsymmetrical skew boat conformation,
as observed for 1. Superimposition of the structures of 1 and
5 (Fig. 7) suggests that the amplector structure undergoes
minimal rearrangement on encapsulation.
Fig. 5 ORTEP plot of the complex cation 4 with crystallographic
numbering. Probability ellipsoids of 30% are shown.
1.975(3) Å). This is typical for cobalt()–imine bonds in rel-
atively unstrained systems (1.905(5)–1.924(7) Å) consisting of
linear or branched ligands.34,35 However, Co()–Nimine distances
have been observed as long as 2.011 Å in a strained macro-
bicyclic system.17 This suggests that there is little strain for the
complex upon chelation. The Co–Namine (1.974(3), 1.975(3) Å),
Co–S (2.2244(12), 2.2345(12) Å) and Co–Cl (2.2658(12) Å)
distances are all within the typical ranges for these type of
bonds.32,33 The bond angles about the coordination sphere also
suggests there is little coordinative strain as there is minimal
distortion of donor atoms from octahedral geometry.
The structure of 5 consists of the molecular cation, three
perchlorate anions and two water molecules. The complex
cation (Fig. 6; selected bond lengths and angles Table 7) has a
lel3 conformation (defined as the vectors between C7 and C16,
C8 and C17, C6 and C15). Two cis imine bonds are located
between atoms N1 and C7, and N2 and C8. The position of the
donor atoms in the complex can be considered as a slightly
Fig. 7 An overlay of the structures of the complex cations of 1 and 5
(b) perpendicular and (b) parallel to the pseudo-C3 axis. The S–Co–S
bonds are overlaid.
13C and 1H NMR
The 13C NMR spectrum of 1 displays a six-line spectrum with a
single resonance for the methyl carbons and the quaternary
carbons whilst two resonances are observed for the methylene
carbons adjacent to the coordinated primary amines (δC
∼
Ϫ21 ppm) and the coordinated thioethers (δC ∼ Ϫ28 ppm).9,13,14
Complex 2 displays a twelve-line 13C NMR spectrum. The
resonance at δC Ϫ43.5 ppm for 2 can be assigned to the methyl
group at the amine and thioether donor apex by comparison
with the resonance for the methyl peaks in 1 (δC Ϫ43.2 ppm)
while that at δC Ϫ45.3 ppm can be assigned to the methyl group
at the oxygen donor apex. Similarly, the quaternary carbon
resonances at the N2S and NOS apices (δC Ϫ26.5 and Ϫ25.4
D a l t o n T r a n s . , 2 0 0 3 , 3 6 9 3 – 3 7 0 3
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ppm, respectively) can be assigned by comparison with 1 (Cq:
δC Ϫ26.5 ppm). The 13C resonance for the methylene carbon
adjacent to the coordinated oxygen (δC Ϫ1.0 ppm, pH 1.3) is
shifted downfield relative to the resonances for the methylene
carbons adjacent to primary amine donors, reflecting the higher
electronegativity of oxygen compared to nitrogen. The reson-
ance position is also dependent on pH. The 1H NMR spectrum
of 2 also shows the unsymmetric nature of the complex with
distinct resonances observed for the methyl groups.
reduction of the Co() to Co() on replacement of an amine
with a alcohol donor. The redox behaviour of 2 was found to be
pH dependent where increasing the pH incrementally to 5.5
caused a decrease in the intensity of the Co3ϩ/2ϩ cathodic peak
until no metal-based cathodic peak was observed within the
limits of the solvent.
The cyclic voltammogram of 5 (aqueous 0.1 M NaCl, pH
1.4, glassy carbon working electrode) exhibited quasi-reversible
behaviour (∆E = 77 mV, 10 mV sϪ1, ic/ia = 1.0; ∆E = 165 mV, 500
mV sϪ1, ic/ia = 1.0). The quasi-reversible behaviour is in contrast
to the irreversible redox characteristics of 1 under the same
conditions, reflecting the enhanced stability of the macro-
bicyclic complexes (Fig. 8). The potential of the 53ϩ/2ϩ couple
(E1/2 ϩ245 mV, vs. SHE) falls between those reported for
the cobalt complexes of Me8tricosatrieneN6 and Me5tricosa-
trieneN6 (ϩ400 mV and Ϫ160 mV, vs. SHE, respectively).17,18
Replacement of N donors with thioethers in the case of the
sarcophagine complexes causes a positive shift in metal centred
redox potentials ([Co(MeN6sar)]3ϩ/2ϩ Ϫ484 mV; [Co(MeN3-
S3sar)]3ϩ/2ϩ Ϫ104 mV; vs. SHE).36 For the complexes of the
enlarged encapsulating ligands, Me6docosadieneN4S2, Me8tri-
cosatrieneN6 and Me5tricosatrieneN6, the position of the metal
centred redox potential is predominantly influenced by steric
factors due to the methyl substituents on each encapsulating
arm rather than the composition of the donor set.17,18
The 13C NMR spectrum of endo-3 exhibits twelve reson-
ances, similar to the 13C spectrum of 2 with only minor shifts
observed for analogous resonances. For the exo-3 complex the
13C NMR spectrum exhibits ten resonances of a possible
twelve with resonances due to methylenes adjacent to thio-
ethers degenerate (δC Ϫ30.1 ppm). The resonance due to the
methyl group at the NOS apex (δC Ϫ48.5 ppm) is shifted
upfield in comparison to the analogous resonance for endo-3
(δC Ϫ45.8 ppm) while that at the N2S apex (δC Ϫ43.1 ppm)
is similar to those of 1, 2 and endo-3 (δC Ϫ43.2, Ϫ43.5,
Ϫ43.5 ppm, respectively). The resonances for the quaternary
carbons for exo-3 (δC Ϫ27.0, Ϫ26.6 ppm) and endo-3 (δC Ϫ27.9,
Ϫ24.3 ppm) cannot be readily distinguished on the basis of
proximity to the oxygen donor. For each of these compounds
there is no quaternary carbon chemical shift that is distinctly
closer to that for 1 (δC Ϫ26.5 ppm) than the other quaternary
carbon resonance. The resonance for the methylene carbon
adjacent to the unbound alcohol group in endo- and exo-3
(δC ϩ3.1 and ϩ 2.6 ppm, respectively) display a downfield
shift in comparison with the resonance of the methylene
carbon adjacent to the coordinated alcohol group in 2
(δC Ϫ1.0 ppm, pH 1.3). The 13C chemical shifts of the methyl-
ene carbons adjacent to coordinated primary amines and
coordinated thioethers in both the endo- and exo-3 complexes
are typical for nitrogen–thioether complexes.12–14 1H NMR
spectra, obtained in D2O, give no indication of the formation
of an aqua species by substitution of the coordinated chloride
ion.
Complex 4 displays a resonance in the twelve-line 13C NMR
spectrum assigned to the imine carbon (δC ϩ121.8 ppm).17,18
The resonance attributed to the methylene carbon adjacent to
the imine nitrogen (δC Ϫ5.8 ppm) is shifted markedly downfield
relative to that assigned to the coordinated primary amines
(δC Ϫ24.4, Ϫ20.6 ppm). The resonance at δC Ϫ18.5 ppm is due
to the quaternary carbon in proximity to the imine bond while
the other quaternary carbon is assigned to the resonance at
δC Ϫ25.9 ppm. The resonances for the methyl (δC Ϫ44.4, Ϫ43.6
ppm) and methylene carbons adjacent to thioethers (δC Ϫ31.4,
Ϫ29.2, Ϫ27.9, Ϫ26.5 ppm) do not shift substantially from those
Fig. 8 Cyclic voltammograms of 5 (pH 1.4, I = 0.1 M NaCl) and 1 (pH
1.5, I = 0.1 M NaClO4) 100 mV sϪ1, glassy carbon working electrode, vs.
Ag/AgCl.
1
observed for 1. The H NMR spectrum of 4 displays two dis-
tinct methyl resonances (δH 1.19, 1.57 ppm) and an α-imine
proton resonance at δH 7.98 ppm.
UV-Visible spectroscopy
The encapsulated complex 5 displays a twenty-line 13C NMR
spectrum indicative of an unsymmetric molecule in solution.
The resonances observed for the methyl carbons (δC Ϫ43.0,
Ϫ42.9, Ϫ42.8, Ϫ42.6, Ϫ42.4 ppm; two accidentally degenerate),
methylene carbons adjacent to thioethers (δC Ϫ29.1, Ϫ28.7,
Ϫ27.0 ppm; degenerate δC Ϫ29.1 ppm), methylene carbons
adjacent to secondary amines (δC Ϫ9.5, Ϫ8.1, Ϫ6.5, Ϫ6.3 ppm),
imine nitrogens (δC ϩ0.7, ϩ1.0 ppm) and methine carbons
(δC ϩ123.6, ϩ125.6 ppm) appear typical.9,13,14,17,18
The room-temperature solution visible absorption spectra of
Co() low-spin d6 systems characteristically exhibit two spin-
1
allowed transitions. For 1 the A1g
1T1g transition is clearly
observed (21140 cmϪ1) whilst the higher energy 1A1g
1T2g d–d
transition was observed as a clearly defined shoulder (28800
cmϪ1) on a much more intense charge-transfer band. The spin-
forbidden transitions were not observed in the room-temper-
ature solution spectra. At 14 K in a Nafion film the higher
1
energy A1g
1T2g absorption becomes more pronounced. In
order to locate the spin-forbidden transitions (1A1g
3T1g
Redox behaviour
(13800 cmϪ1) and A1g
3T2g (17400 cmϪ1)) at 11 K highly
1
The cyclic voltammogram of 1 (aqueous 0.1 M NaClO4, glassy
carbon working electrode) showed metal-based irreversible
redox processes (Ϫ0.37 V). For 2 under the same conditions
metal based irreversible redox couples were observed although
the cathodic peak for the Co3ϩ/2ϩ redox couple (Ec Ϫ96 mV: 100
mV sϪ1) was shifted to less negative potentials in comparison to
1 (Ec Ϫ330 mV: pH 1.5, 100 mV sϪ1) reflecting the more facile
concentrated solutions and stacked Nafion films were required
(Fig. 9).
The perturbation expressions corrected for configuration
interaction which can be used to uniquely determine the
spectroscopic parameters 10Dq, B and C when the spin for-
bidden transitions are observed, and assuming Oh symmetry
are,13,37
D a l t o n T r a n s . , 2 0 0 3 , 3 6 9 3 – 3 7 0 3
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Fig. 9 Nafion film UV-visible absorption spectrum of 1 spin allowed
bands at room temperature and 14 K with calculated fit for the 1A1g
1T2g transition at 14 K. (Inset (a) 1A1g
3T1g transition with calculated
fit at 14 K. Inset (b) 1A1g
3T2g transition with calculated fit at 14 K.)
E(1A1g
E(1A1g
E(1A1g
E(1A1g
1T1g) = 10Dq Ϫ C ϩ (5BC ϩ 7B2 ϩ C2)/5Dq
1T2g) = 10Dq Ϫ C ϩ 16B ϩ (3BC Ϫ 27B2 ϩ C2)/5Dq
3T1g) = 10Dq Ϫ 3C ϩ (5BC Ϫ 11B2 ϩ C2)/5Dq
3T2g) = 10Dq – 3C ϩ 8B ϩ (3BC Ϫ 21B2 ϩ C2)/5Dq
(1)
For 1 the best fit parameters for 10Dq (22570 cmϪ1), B (551
cmϪ1) and C (3500 cmϪ1; C/B = 6.4) were obtained from the
observed band positions in the low-temperature spectra. The
values obtained may be compared with the values determined
from a complete d6 ligand field calculation for 1 (10Dq ∼ 23400
cmϪ1, B = 553 cmϪ1, C = 3680 cmϪ1), assuming C2v symmetry.38
The results C ≈ 6B and 10Dq ∼ 22000 cmϪ1 are consistent with
those obtained previously for mixed donor thioether–nitrogen
ligands (Table 8) and consistent with arguments that C/B ratio
is approximately 6 compared with 4.8 for the free ion.4,13,14,39
The magnitude of 10Dq for 1 supports previous observations
that this parameter is relatively insensitive for mixed nitrogen–
thioether cobalt() complexes.4,13,14
The UV-visible absorption spectra of 2 were obtained in
aqueous solution at room temperature, and Nafion films at
room temperature and at ∼14 K. The absorption due to the 1A1g
1T1g transition is clearly observed in solution (pH 2.05:
1
21000 cmϪ1) but the A1g
1T2g transition is completely
obscured by a charge-transfer band and cannot be resolved
even with low temperature studies (∼14 K). The Nafion film
UV-visible absorption spectra at low temperature (∼14 K) did
not resolve bands due to the 1A1g
3T1g and 1A1g
3T2g spin-
forbidden transitions, hence a complete analysis of ligand field
parameters for 2 was not possible. Splitting of the 1A1g 1T1g
transition due to the low symmetry of the complex was not
observed, although the band was found to exhibit a pH
dependence in aqueous solution.
The room-temperature solution UV-visible absorption spec-
1
trum of endo-3 shows the lower energy d–d transition A1g
1T1g at 18760 cmϪ1. The higher energy 1A1g
1T2g transition is
observed as a distinct shoulder on an intense charge-transfer
band and band analysis of the spectrum suggests that the
band maximum occurs at 26880 cmϪ1. No spin-forbidden bands
were observed in the room-temperature solution absorption
spectrum. The ligand field parameters 10Dq and B determined
from the perturbation expressions for the energies of the d–d
D a l t o n T r a n s . , 2 0 0 3 , 3 6 9 3 – 3 7 0 3
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transitions, corrected for configuration interaction and assum-
ing C = 6B, were 10Dq = 19650 cmϪ1 and B = 619 cmϪ1. The
10Dq for endo-3 is somewhat less than the 10Dq values for
mixed donor nitrogen–thioether complexes. The Racah par-
ameter B for endo-3 is greater than those of 1 and [Co(N4S2)]3ϩ
(551 and 516 cmϪ1, respectively)4 suggesting greater ionic char-
acter of the Co–Cl bond and the higher covalent character of
the Co–S bond relative to the cobalt()-amine bond.
positive downfield of the internal reference sodium 2,2-di-
methyl-2-silapentane-5-sulfonate. The chemical shifts of 13C
NMR spectra (D2O) are reported in parts per million (δ) as
positive downfield and negative upfield of the internal reference
1,4-dioxane.10,13,14 13C NMR spectra recorded in CDCl3 and d4-
methanol were referenced to the CDCl3 resonance at 77 ppm or
the d4-methanol resonance at 49 ppm. For NMR assignments
quaternary and aromatic carbons are denoted by Cq and Ar,
respectively. The tosyl and phthalimide groups are abbreviated
at tos and phth, respectively.
Low-resolution ESI mass spectra were obtained using a
Finnigan MAT 900 XL mass spectrometer and methanol–water
(40 : 60) solutions of the metal complexes. Spectra were
recorded varying the capillary and skimmer potentials (50–
200 V) so as to optimize the intensity of the signals obtained.
Cyclic voltammetry was performed with a Metrohm 757VA
Computrace electrochemical analyzer using a standard three-
electrode system with a glassy carbon or platinum working
electrode, a platinum auxillary electrode and a Ag/AgCl/KCl
reference electrode. Aqueous solutions (metal complex, 5 ×
10Ϫ3 M; 0.1 M NaClO4) were employed. Scan rates were varied
from 5 to 600 mV sϪ1.
The solution UV-visible absorption spectrum of 4 in aque-
ous solution shows both spin allowed d–d transitions (1A1g
1
1T2g, 26880 cmϪ1; A1g
1T1g, 20660 cmϪ1) expected for low
spin Co() complexes. Spin-forbidden transitions were not
1
observed under these conditions. The A1g
1T1g band is
asymmetric and can be fitted to two band components at 21000
cmϪ1 and 18830 cmϪ1, with the intensity of the former approx-
imately twice that of the latter. The low symmetry of 4 causes
1
the triply degenerate T1g state to be split into its three lower
symmetry components. The observation of only two bands
within the 1A1g
1T1g transition, one being twice the intensity
of the other, suggests that two of the lower symmetry states
1
derived from the T1g state are degenerate or near-degenerate.
When the weighted average of the energies of the band com-
ponents for the 1A1g
1T1g (20285 cmϪ1) transition is used for
Solution and Nafion film UV-visible spectra were recorded as
described previously.4 Where necessary, peak positions were
determined using Peakfit40 obtaining a correlation coefficient
(R2) greater than 0.997.
the determination of ligand field and Racah parameters of 4,
10Dq is determined as 21610 cmϪ1 and B as 472 cmϪ1.
The room-temperature solution UV-visible absorption spec-
trum of 5 shows two spin-allowed transitions with the higher
1
energy A1g
1T2g clearly seen as a shoulder on an intense
Syntheses
charge-transfer band. The Nafion film spectrum at low temper-
ature shows the spin-allowed transitions at 19380 and 26450
cmϪ1; no spin-forbidden transitions were detected. The
electronic spectrum of 5 is similar to that of [Co(Me8tricosa-
trieneN6)]3ϩ with spin allowed transitions at 19310 and 27250
cmϪ1, but is markedly different in comparison to [Co(Me5tri-
cosatrieneN6)]3ϩ (21370 and 29150 cmϪ1), the latter thought
to have optimal CoIIIN6 geometry.16,17 Assuming C = 6B, gives
10Dq = 20580 cmϪ1 and B = 516 cmϪ1 for 5. In comparison with
the spectrophotometric parameters of other N6 expanded
encapsulated Co() complexes, ([Co(Me8tricosatrieneN6)]3ϩ, B
= 597 cmϪ1; [Co(Me5tricosatrieneN6)]3ϩ, B = 568 cmϪ1) B is dis-
tinctly lower for 5 (516 cmϪ1) reflecting the higher covalency of
Co–thioether bonds. The ligand field parameter 10Dq may
correlate to the size of the encapsulating cavity of these large
macrobicyclic ligands. Thus the larger encapsulating cavities
Me6docosadieneN4S2, Me8tricosatrieneN6 give 10Dq values of
similar magnitude (20580 and 20330 cmϪ1, respectively) while
the smaller cavity of Me5tricosatrieneN6 has a larger 10Dq
value (22700 cmϪ1).16,17
1,3-(Dimethylmethylenedioxy)-2-methyl-2-hydroxymethyl-
propaneand1,3-(dimethylmethylenedioxy)-2-methyl-2-(methyl-
ene-p-tolylsulfonyl)propane were prepared as described previ-
ously.19
2,9-Bis(3,3-dimethyl-2,4-dioxocyclohexanyl)-4,7-dithiadecane.
To a solution of sodium metal (10.72 g, 0.47 mol) dissolved in
dry ethanol (600 cm3) was added 1,2-ethanedithiol (20.0 g, 0.21
mol) and the solution stirred for five minutes. 1,3-(Dimethyl-
methylenedioxy)-2-methyl-2-(methylene-p-toluenesulfonyl)-
propane (133.6 g, 0.42 mol) was added and the solution heated
at reflux for 6 h. Upon cooling, the white precipitate of sodium
tosylate was removed by filtration and the solvent was removed
from the filtrate under reduced pressure. The residue was dis-
solved in CHCl3 (300 cm3) and the solution was washed with
water (3 × 100 cm3). The organic layer was separated, dried
over Na2SO4, filtered and the solvent removed under reduced
pressure leaving a yellow oil (86.9 g, quantitative). 13C NMR
(CDCl3): δC 19.1 (–CH3); 20.5, 26.8 (CH3–CqO); 34.0, 38.6
1
(–CH2–S); 34.0 (Cq); 67.9 (–CH2–O); 97.8 (Cq–O). H NMR
(CDCl3): δH 0.86 (–CH3, s); 1.40, 1.42 (CH3–CqO, s); 2.78
(–CH2–S, s); 3.64 (–CH2–O, dd).
Conclusion
A relatively versatile synthetic methodology has been developed
for the synthesis of a ligand in which bifurcations of the chain
occur at atoms other than donor atoms. A range of by-products
has also been characterized. The cobalt() complex has
been characterized and elaborated to form a new encapsulated
complex. Subsequent work will report the development of the
synthetic strategy resulting in a range of amplector and
encapsulating type ligands.
2,2,9,9-Tetra(hydroxymethyl)-4,7-dithiadecane. 2,9-Bis(3,3-
dimethyl-2,4-dioxocyclohexanyl)-4,7-dithiadecane (86.9 g) was
dissolved in ethanol (400 cm3) and heated at reflux. Concen-
trated HCl (20 cm3) was added and the reflux continued for
10 min. Upon cooling the solvent was removed under reduced
pressure. The black residue was allowed to stand overnight to
solidify. The solid was triturated in ethanol and filtered to give
a white solid (41.5 g, 60.6%). The filtrate was retained, the
solvent removed, and the trituration repeated until no further
product was obtained. Analysis. Calc. for C12H26O4S2: C, 48.3;
H, 8.78%. Found: C, 48.2; H, 9.11%. 13C NMR (d4-methanol):
δC 18.9 (–CH3); 34.9, 38.3 (–CH2–S); 42.2 (Cq); 67.1 (–CH2–O).
1H NMR (d4-methanol): δH 0.90 (–CH3, s); 2.61 (–CH2–S, s);
2.74 (–CH2–S, s); 3.45 (–CH2–O, s).
Experimental
Physical measurements
1H, 13C[1H] and 13C DEPT NMR spectra were recorded with
a Bruker AC200F 200 MHz or a Bruker AV400 400 MHz
spectrometer on internal lock. Chemical shifts for the 1H NMR
spectra (CDCl3 and d4-methanol) are reported in parts per
million (δ) as positive downfield of the internal reference tetra-
methylsilane. In D2O, the chemical shifts are reported as
2,2,9,9-Tetra(methylene-p-toluenesulfonyl)-4,7-dithiadecane.
2,2,9,9-Tetra(hydroxymethyl)-4,7-dithiadecane (32.5 g, 0.11
mol) was dissolved in dry pyridine (200 cm3) and cooled in an
D a l t o n T r a n s . , 2 0 0 3 , 3 6 9 3 – 3 7 0 3
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ice-bath. To this stirred solution, p-toluenesulfonyl chloride
(93.6 g, 0.49 mol) dissolved in dry pyridine (250 cm3) was added
dropwise over 2 h. The reaction mixture was allowed to warm
to room temperature and stirring maintained for 48 h. The mix-
ture was poured into a solution of concentrated HCl (275 cm3),
water (350 cm3) and methanol (700 cm3) to precipitated an off-
white solid which was extracted in CHCl3 (3 × 300 cm3) and the
extracts combined and washed with water (2 × 300 cm3). The
CHCl3 solution was separated, dried over Na2SO4, filtered and
the solvent was removed under reduced pressure leaving an
orange oil. The oil was triturated with boiling ethanol, the solu-
tion cooled to 5 ЊC for 24 h and filtered to give a white solid
(79.8 g, 80.0%). Analysis. Calc. for C40H50O12S6: C, 52.5; H,
5.51%. Found: C, 52.6; H, 5.61%. 13C NMR (CDCl3): δC 18.1
(–CH3); 21.5 (CH3-tos); 33.8, 36.3 (–CH2–S); 39.5 (Cq); 71.4
products. The major red band was eluted with 3 M HCl. The
solvent was removed from the eluent under reduced pressure to
give a red solid which was dissolved in water (750 cm3) and
loaded onto Sephadex C-25 cation exchange resin (Naϩ form).
The column was washed with water, then 0.2 M NaCl to elute a
large rose coloured band which was collected in fractions. Elu-
tion with 0.3 M NaCl resulted in a major orange band. The
orange eluent was collected and loaded onto Dowex cation
exchange resin, and the column washed with water and 1 M
HCl. The orange band was eluted with 3 M HCl and the solvent
was removed under reduced pressure to yield an orange solid
(1.7 g, 12%). The solid was dissolved in a minimum of water
and NaClO4 added until an orange precipitate formed. The
precipitate was filtered and crystallised from warm water.
Analysis. Calc. for [C12H30N4S2Co]Cl(ClO4)2: C, 24.5; H, 5.14;
N, 9.53%. Found: C, 24.2; H, 5.12; N, 9.31. UV-visible spec-
trum [λmax/nm (εmax/L molϪ1 cmϪ1) in H2O]: 479 (346), 359 (304),
287 (16600), 237 (14600). 13C NMR (D2O): δC Ϫ43.2 (–CH3);
Ϫ28.4, Ϫ27.5 (–CH2–S); Ϫ26.5 (Cq); Ϫ22.1, Ϫ20.1 (CH2–N).
1
(–CH2–O); 127.8, 129.9 (Ar–H); 132.0, 145.1 (Ar–). H NMR
(CDCl3): δH 0.91 (–CH3, s); 2.45 (CH3-tos, s); 2.49, 2.54 (–CH2–
S, s); 3.83 (–CH2–O, dd); 7.54 (Ar–H, dd).
1H NMR (D2O): δH 1.05 (–CH3, s); 2.2–3.9 (–CH2–, m). ESI-
2,2,9,9-Tetra(methylenephthalimido)-4,7-dithiadecane.
Ϫ
MS: Calc. for [Co(EtN4S2amp)]3ϩ Ϫ Hϩ
ϩ
35ClO4 , m/z 451;
2,2,9,9-Tetra(methylene-p-toluenesulfonyl)-4,7-dithiadecane
(40.0 g, 0.044 mol) and potassium phthalimide (35.6 g, 0.19
mol) were suspended in diethylene glycol dimethyl ether
(150 cm3) and the mixture heated at 150ЊC for 18 h. The cooled
solution was poured into water (600 cm3) to precipitate a brown
oil. The mixture was allowed to stand for 24 h and was filtered
to yield a pale brown solid. The solid was dissolved in CHCl3
(600 cm3), dried over Na2SO4, filtered and the solvent removed
under reduced pressure to give a pale brown oil. The oil was
triturated in warm ethanol and the solution filtered to yield an
off-white solid (20.5 g, 57.2%). 13C NMR (CDCl3): δC 21.0
(–CH3); 34.4 (–CH2-phth); 41.2, 45.2 (–CH2–S); 43.0 (Cq);
Found, m/z 451 (100%). Calc. for [Co(EtN4S2amp)]3ϩ Ϫ 2Hϩ,
m/z 351; Found, m/z 351 (80%).
[Co(Et(HO)N3S2amp)]Cl(ClO4)2 (2ؒCl(ClO4)2). During the
purification of the crude product from the synthesis of 1
[Co(EtN4S2amp)]3ϩ on Sephadex cation exchange resin with
0.2 M NaCl a final red–brown fraction was collected. The red–
brown eluent was loaded on Dowex cation exchange resin (50W
× 2 (200–400 mesh) Hϩ form) and the column was washed with
1 M HCl. The product was eluted with 3 M HCl to separate two
bands, a minor initial band and a larger second band. The sol-
vent removed from the eluent under reduced pressure to yield a
red solid. The solid was dissolved in a minimum volume of
aqueous NaClO4 solution. Slow evaporation over several days
resulted in dark red–brown crystals (0.3 g, 1.7%). Analysis.
Calc. for [C12H29N3OS2Co]Cl(ClO4)2: C, 24.5; H, 4.96; N,
7.14%. Found: C, 23.9; H, 4.87; N, 6.89%. UV-visible spectrum
(H2O, pH 2.05) [λmax/nm (εmax/L molϪ1 cmϪ1)]: 476 (287). 13C
NMR (D2O, pH 1.3): δC Ϫ45.3 (–CH3, N/O donor apex); Ϫ43.5
(–CH3, N/N donor apex); Ϫ28.7, Ϫ27.4, Ϫ27.4, Ϫ26.6 (–CH2–
S); Ϫ26.5 (Cq, N/N donor apex); Ϫ25.4 (Cq, N/O donor apex);
123.4, 134.1(Ar–H); 131.9 (Ar–); 168.9 (C᎐O). 1H NMR
᎐
(CDCl3): δH 1.07 (–CH3, s); 2.69, 2.72 (–CH2–S, s); 3.79 (–CH2-
phth, s); 7.78 (Ar–H, m).
2,2,9,9-Tetra(methyleneamine)-4,7-dithiadecane
(EtN4S2amp). 2,2,9,9-Tetra(methylenephthalimido)-4,7-dithia-
decane (12.5 g) was suspended in ethanol (200 cm3) and heated
at reflux. Hydrazine hydrate (31 cm3) was added to the refluxing
solution. Over a period of 5 min the solution became clear then
a dense white precipitate formed. The reflux was maintained for
2 h. The solution was cooled in an ice-bath and concentrated
HCl (40 cm3) was added dropwise. The mixture was heated at
reflux for a further 40 min, then cooled and the solvent removed
under reduced pressure. The residue was dissolved in water (200
cm3) and the solution filtered. The filtrate was made strongly
alkaline with KOH and the product was extracted in CHCl3
(3 × 100 cm3). The CHCl3 extracts were combined, dried over
Na2SO4, filtered and the solvent was removed under reduced
pressure to yield a yellow oil (4.22 g, 96%). The product was
used for preparation of the cobalt() complex without further
purification.
1
Ϫ22.8, Ϫ20.1, Ϫ19.7 (–CH2–N); Ϫ1.0 (–CH2–O). H NMR
(D2O, pH 2.1): δH 0.97, 1.06 (–CH3); 1.8–4.0 (–CH2–, m). ESI-
Ϫ
MS: Calc. for [Co(Et(HO)N3S2amp)]3ϩ Ϫ Hϩ
ϩ
35ClO4 , m/z
452; Found, m/z 452 (77%). Calc. for [Co(Et(HO)N3S2amp)]3ϩ
Ϫ 2Hϩ, m/z 352; Found, m/z 352 (99%).
endo-[Co(Et(HO)N3S2amp)Cl]Cl(ClO4) (endo-3ؒCl(ClO4)).
From the purification of the crude product from the [Co(EtN4-
S2amp)]3ϩ eluted from Sephadex cation exchange resin with 0.2
M NaCl the initial section of the rose coloured band was col-
lected. The rose coloured eluent was loaded onto Dowex cation
exchange resin (50W × 2 (200–400 mesh) Hϩ form) and the
column washed with water and 1 M HCl. Elution with 3 M HCl
resulted in the separation of minor red/pink bands and the sep-
aration of two bands, a pink/purple band followed by a red/
pink band (see below) which were collected separately. The sol-
vent was removed from the pink/purple eluent and the purple
residue was dissolved in a minimum of water and NaClO4
was added. Purple crystals formed within 24 h. Analysis. Calc.
for [C12H29N3OS2ClCo]Cl(ClO4): C, 26.55; H, 5.76; N, 7.74%.
Found: C, 26.35; H, 5.41; N, 7.51%. The sample was recrystal-
lised in water with the addition of NH4PF6 resulting in a purple
product (0.3 g, 1.7%). UV-visible spectrum (H2O) [λmax/nm
(εmax/L molϪ1 cmϪ1) ]: 533 (345), 290 (12600), 217 (12500). 13C
NMR (D2O): δC Ϫ45.8 (–CH3, O apex); Ϫ43.5 (–CH3, N/N
donor apex); Ϫ33.3, Ϫ32.8, Ϫ30.0, Ϫ26.5 (–CH2–S); Ϫ27.9,
Ϫ24.3 (Cq); Ϫ23.1, Ϫ22.6, Ϫ21.4 (–CH2–N); ϩ3.1 (–CH2–O).
1H NMR (D2O): δH 1.04, 1.08 (–CH3, s), 3.38 (–CH2–O, dd),
Metal complex syntheses
CAUTION: Although the perchlorate salts described in this
work do not appear to be sensitive to shock or heat these
materials, like all perchlorates, should be treated with caution.
[Co(EtN4S2amp)]Cl(ClO4)2 (1ؒCl(ClO4)2). Cobaltous nitrate
hexahydrate (9.0 g) in methanol (200 cm3) was added dropwise
to the stirred crude EtN4S2amp (9.0 g) dissolved in methanol
(200 cm3). A stream of air was bubbled through the ligand
solution for the duration of the addition and continued for a
further 3 h. The solvent was removed under reduced pressure,
the residue dissolved in water and the solution filtered. The
filtrate was diluted to 2 L and loaded onto Dowex cation
exchange resin (50W × 2 (200–400 mesh) Hϩ form). The
column was washed with water, then 1 M HCl to elute minor
D a l t o n T r a n s . , 2 0 0 3 , 3 6 9 3 – 3 7 0 3
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View Article Online
2.0–3.7 (–CH2–, m). ESI-MS Calc. for [Co(Et(HO)N3S2amp)]3ϩ
Ϫ 2Hϩ, m/z 352; Found, m/z 352 (100%).
Crystal structure determinations
For diffractometry the crystals were mounted onto glass fibres
with Supa Glue. Lattice parameters were determined by least
squares fits to the setting parameters of 25 independent reflec-
tions, measured and refined with an Enraf-Nonius CAD4 dif-
fractometer using graphite-monochromated Mo-Kα radiation.
The structures were solved by heavy-atom methods (direct
methods) and refined using full-matrix least squares on F 2.
Programs used were SHELXS-8641 or SIR-9242 for solution,
SHELXL-9343 for refinement and ORTEP44 for plotting. Crys-
tal data are given in Table 1. The geometries of the molecules
are shown in Figs. 2–6 together with atomic numbering
schemes. Selected bond lengths and bond angles are given in
Tables 2–7.
exo-[Co(Et(HO)N3S2amp)Cl]Cl(ClO4) (exo-3ؒCl(ClO4)). The
solvent was removed from the red/pink eluent under reduced
pressure. The red solid was dissolved in a minimum of water
and NaClO4 was added. The solution was allowed to slowly
evaporate over several days to give red crystals (<0.01 g,
<0.01%). Analysis. Calc. for [C12H29N3OS2ClCo]Cl(ClO4): C,
27.46; H, 5.57; N, 8.00%. Found: C, 26.29; H, 5.61; N, 7.59%.
13C NMR (D2O): δC Ϫ48.5 (–CH3, O apex); Ϫ43.1 (–CH3, N/N
donor apex); Ϫ30.1, Ϫ26.9 (–CH2–S); Ϫ27.0, Ϫ26.6 (Cq);
Ϫ22.2, Ϫ21.8, Ϫ20.4 (–CH2–N); ϩ2.6 (–CH2–O).
[Co(dmatue)Cl](ClO4)2ؒH2O (4ؒ(ClO4)2ؒH2O). The first frac-
tion of the rose coloured solution eluted from Sephadex with
0.2 M NaCl was collected and loaded onto Dowex cation
exchange resin (50W × 2 (200–400 mesh) Hϩ form). The Dowex
column was washed with 1 M HCl and elution with 3 M
HCl gave a red–pink solution first followed by some minor
bands. The red-pink eluent was collected separately and the
solvent was removed under reduced pressure to give a red
residue. The residue was dissolved in a minimum of water
and NaClO4 was added to afford red crystals (<0.01 g,
<0.01%). Analysis. Calc. for [C12H25N3S2ClCo](ClO4)2ؒH2O: C,
24.56; H, 4.64; N, 7.16%. Found: C, 24.27; H, 4.60; N, 7.01%.
UV-visible spectrum (H2O) [λmax/nm (εmax/L molϪ1 cmϪ1)]:
484 (280), 372 (390), 281 (13000), 256 (12000). 13C NMR (D2O):
δC Ϫ44.4, Ϫ43.6 (–CH3); Ϫ31.4, Ϫ29.2, Ϫ27.9, Ϫ26.5 (–CH2–
CCDC reference numbers 209636–209641.
See http://www.rsc.org/suppdata/dt/b3/b304914k/ for crystal-
lographic data in CIF or other electronic format.
References and notes
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S); Ϫ25.9 (Cq); Ϫ24.4, Ϫ20.6 (–CH2–N); Ϫ18.5 (Cq (imine));
1
Ϫ5.8 (–CH –N᎐); ϩ121.8 (–CH᎐N). H NMR (D O): δ 1.19,
᎐
᎐
2
2
H
1.57 (–CH , s), 2.4–3.7 (–CH –, m), 7.98 (–CH᎐N, s). ESI-MS:
᎐
3
2
Calc. for [Co(dmatue)]3ϩ
ϩ
35ClϪ, m/z 184; Found, m/z 184
(100%).
[Co(Me6docosadieneN4S2)](ClO4)3ؒ2H2O (5ؒ(ClO4)3ؒ2H2O). 1
(as its chloride salt) (1.0 g) was dissolved in dimethylformamide
(70 cm3) with an excess of NaClO4 with stirring. The solution
was filtered. To the filtrate was added isobutyraldehyde (10
cm3), paraformaldehyde (0.32 g) and triethylamine (7.6 cm3) in
quick succession with stirring. After stirring for 1 h, the reac-
tion was quenched with acetic acid. The solution was poured
into water (1 L) and filtered. The filtrate was diluted to 2 L and
loaded onto Dowex cation exchange resin (50W × 2 (200–400
mesh) Hϩ form). The column was washed with water and 1 M
HCl to elute a minor pink band. The major band was eluted
with 3 M HCl. The solvent was removed from the eluent under
reduced pressure. The residue was dissolved in water (1 L) and
loaded onto Sephadex C-25 cation exchange resin (Naϩ form).
The column was washed with water slightly acidified with HCl
(pH 4). A major pink band was eluted with 0.2 M NaCl
acidified with HCl (pH 4) followed by a series of minor orange
bands. The pink eluent was loaded onto Dowex cation
exchange resin. The column was washed with 1 M HCl and the
product was eluted with 3 M HCl. The solvent was removed
from the eluent to yield a dark pink solid (0.15 g, 11.6%). The
solid was dissolved in a minimum of water and NaClO4 was
dissolved in the solution. The solution was allowed to stand
to produce dark pink crystals. Analysis. Calc. for [C22H42N4-
S2Co](ClO4)3ؒ2H2O: C, 32.27; H, 5.65; N, 6.83%. Found: C,
31.80; H, 5.25; N, 6.24%. UV-visible spectrum [λmax/nm (εmax/L
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molϪ1 cmϪ1) in H2O]: 515 (630), 378 (450, sh), 310 (15000). 13
C
NMR (D2O, acidified with HCl): δC Ϫ43.0, Ϫ42.9, Ϫ42.8,
Ϫ42.6, Ϫ42.4 (–CH3); Ϫ29.1, Ϫ28.7, Ϫ27.0 (–CH2–S); Ϫ28.2,
Ϫ27.2, Ϫ25.6, Ϫ24.3 (Cq); Ϫ9.5, Ϫ8.1, Ϫ6.5, Ϫ6.3 (–CH2–N),
1
ϩ0.7, ϩ1.0 (–CH –N᎐); ϩ123.6, ϩ125.6 (–CH᎐N). H NMR
᎐
᎐
2
(D2O, acidified with HCl): δH 1.21, 1.27, 1.32, 1.34, 1.38 (–CH3,
s); 2.1–3.9 (–CH –, m); 7.83, 8.30 (–CH–N᎐, s). ESI-MS: Calc.
᎐
2
for [Co(Me6docosadieneN4S2)]3ϩ Ϫ 2Hϩ, m/z 483; Found, m/z
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483 (100%).
D a l t o n T r a n s . , 2 0 0 3 , 3 6 9 3 – 3 7 0 3
3702

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D a l t o n T r a n s . , 2 0 0 3 , 3 6 9 3 – 3 7 0 3
3703