Selective oxygenation of amphiphilic thiacalix[3]pyridine Rh(I) diene complexes in both water and organic solvents

Article abstract of DOI:10.1039/b503924j

Thiacalix[3]pyridine (Py₃S₃) reacted with [Rh(diene)(μ-Cl)]₂ (diene = 1,5-cyclooctadiene (cod), 2,5-norbornadiene (nbd)) to give amphiphilic trigonal bipyramidal complexes, [Rh(Py₃S₃)(diene)]Cl. Sulfu

Full text of DOI:10.1039/b503924j

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F U L L P A P E R
Selective oxygenation of amphiphilic thiacalix[3]pyridine Rh(I) diene
complexes in both water and organic solvents
Takanori Nishioka,* Yusuke Onishi, Kunio Nakajo, Jin Guo-Xin, Rika Tanaka and
Isamu Kinoshita*
Department of Material Science, Graduate School of Science, Osaka City University, Sugimoto,
Sumiyoshi-ku, Osaka, 558-8585, Japan. E-mail: nishioka@sci.osaka-cu.ac.jp;
Fax: 81-6-6690-2753; Tel: 81-6-6605-2569
Received 17th March 2005, Accepted 27th April 2005
First published as an Advance Article on the web 11th May 2005
Thiacalix[3]pyridine (Py3S3) reacted with [Rh(diene)(l-Cl)]2 (diene = 1,5-cyclooctadiene (cod), 2,5-norbornadiene
(nbd)) to give amphiphilic trigonal bipyramidal complexes, [Rh(Py3S3)(diene)]Cl. Sulfur bridges of the Py3S3 ligand
in these complexes were selectively oxygenated by m-chloroperoxybenzoic acid in dichloromethane to give
sulfinylcalix[3]pyridine complexes, [Rh{Py3(SO)3}(diene)]+, in which all three oxygen atoms of the SO groups occupy
the equatorial positions. Structures of the complexes were analysed by X-ray crystallography and the oxidation
reaction was investigated using 1H NMR spectroscopy and electrospray ionisation mass spectrometry showing that
the oxygenation of the sulfur atoms in the ligand proceeded stepwise and further oxygenation of the SO moiety
occurred only for the nbd complex having the smaller diene ligand resulting in [Rh{Py3(SO)2(SO2)}(nbd)]+. On the
other hand, the oxidation of [Rh(Py3S3)(cod)]+ by H2O2 in water did not result in oxygenation of the sulfur bridges
4
but the cod ligand is hydroxygenated to give 1,4,5,6-g -2-hydroxycycloocta-4-ene-1,6-di-yl.
Introduction
Results and discussion
Macrocyclic polypyridines are potentially powerful ligands
which can promote significant functionalities such as C–H
bond activation by the platinum complex of pyridinophane.1
However, only limited examples of macrocyclic polypyri-
dine complexes have been reported.2 We have prepared the
first example of a transition metal complex of a macro-
cyclic polypyridine ligand with threefold rotational symmetry,
bis(thiacalix[3]pyridine)dicopper(I), [Cu(Py3S3)]22+, which has
a dimeric structure through the compensatory coordination
of one of the sulfur atoms in the ligand to another copper
ion.3 Another facial coordinating N tridentate ligand, triaza-
cyclononane (tacn) can stabilise higher oxidation states such
as NiIII.4 This property of the tacn ligand also stabilised an
intermediate with a higher oxidation state of the metal centre
in the case of the selective oxidation of [Rh(Me3tacn)(cod)]+
(Me3tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane) by H2O2.
In this system, the rhodium(I) cod complex was oxidised by H2O2
to afford the rhodium(III) oxabicyclononadiyl complex which
rearranged to the rhodium(III) hydroxycyclooctenediyl complex.
A rhodaoxetane was suggested to be the key intermediate
of these oxygenation reactions.5 For the [Rh(Py3S3)(diene)]+
complexes, there are some possible sites for oxygenation, for
example, the diene ligand (the same as in the Me3tacn system)
and the bridging sulfur of the Py3S3 ligand. In this paper, we
describe the oxidation reaction of newly synthesised amphiphilic
thiacalix[3]pyridine Rh complexes, [Rh(Py3S3)(diene)]Cl (di-
ene = 1,5-cyclooctadiene (cod), 2,5-norbornadiene (nbd)) using
H2O2 in water or m-chloroperoxybenzoic acid (m-CPBA) in
CH2Cl2.
Formation of complexes
[Rh(Py3S3)(cod)]Cl (1a) was synthesised by the reaction of
[Rh(cod)(l-Cl)]2 and Py3S3 in methanol with a 1 : 2 molar ratio
of the starting materials.
[Rh(diene)(l-Cl)]2 + 2 Py3S3 → 2[Rh(Py3S3)(diene)]Cl
The 1H NMR spectrum of an in situ reaction mixture revealed
only the signals corresponding to one Py3S3 and one cod ligand
and the electrospray ionisation (ESI) mass spectrum showed
only the complex cation peak at m/z = 538. These results show
that the reaction proceeded quantitatively. The BPh4 salt (1b)
was easily isolated by the addition of NaBPh4 to the reaction
mixture owing to the low solubility of the salt in methanol.
[Rh(Py3S3)(nbd)]X (X = Cl, 2a; BPh4, 2b) was also synthesised
in a similar manner. Complexes 1a and 2a were soluble in both
water and organic solvents such as CH2Cl2. X-Ray diffraction
studies were performed for the BPh4 salts 1b and 2b and the
structures of the cationic complexes are shown in Fig. 1.
Oxidation of [Rh(Py3S3)(cod)]+ and [Rh(Py3S3)(nbd)]+
The cod complex 1 was oxidised by m-chloroperoxybenzoic acid
(m-CPBA) in CH2Cl2 for 24 h to give a sulfinylcalix[3]pyridine
complex [Rh{Py3(SO)3}(cod)]+ in high yield.
X-Ray structure analysis of the BPh4 salt (3b) revealed that
all three oxygen atoms of the SO groups in the complex occupy
equatorial positions as shown in Fig. 2. The Py3S3 ligand in
1 adopts the cone shape conformation and the oxygenation
occurred on the opposite side to the {Rh(cod)} unit. The ESI
mass spectrum of the reaction mixture of 1 and 10 eq. of m-
CPBA after 3.5 h, Fig. 3(b), showed a dominant peak at m/z =
554 for [Rh(Py3S3O)(cod)]+ beside the much smaller peaks of 1
2 1 3 0
D a l t o n T r a n s . , 2 0 0 5 , 2 1 3 0 – 2 1 3 7
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 5
©

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four oxygen atoms were observed after generation of the
trioxygenated complex 3 shown in Fig. 3(d) meaning that the
oxygenation stopped at this stage. In contrast to the oxidation
of the complex, the oxidation of the free Py3S3 ligand by 10 eq. of
m-CPBA for 24 h gave a mixture of Py3S3O3, Py3S3O4, Py3S3O5
and Py3S3O6 confirmed by the ESI mass spectrum showing
peaks at m/z = 398, 414, 430 and 446 ([M + Na]+) with 48%,
100%, 21% and 5% relative intensities, respectively, Fig. 4(b). The
result apparently indicates that the oxidation of the free ligand
produced not only sulfinyl but also sulfonyl. In the case of the
oxidation of 1, molecules of m-CPBA could approach the Py3S3
ligand in the complex only from the less hindered side of the
ligand with the help of the p–p interaction between the benzene
ring of m-CPBA and the pyridine rings of the ligand. It means
that the selectivity of the oxygenation reaction is attributed to the
steric hindrance of the cod ligand. Similar oxygenation of sulfur
bridges was reported for thiacalix[4]arenes.6 The oxidation of
p-tert-butylthiacalix[4]arene afforded several stereoisomers of p-
tert-butylsulfinylcalix[4]arene due to the existence of conformers
and unselective oxygenation. Separation of each conformer
before oxidation became possible by introducing the bulky
O-benzylester groups and oxygenation occurred on the other
side of the O-benzylester groups, for example, the oxidation
of its separated cone conformer by NaBO3 gave only one
stereoisomer due to steric hindrance.6 In the case of oxidation of
1, coordination of the Py3S3 ligand to the {Rh(cod)} unit has an
important role in limiting the approach direction of the oxidising
agent and in fixing the cone conformation of the Py3S3 ligand,
which adopts an alternate conformation as a free ligand.7
Fig. 1 ORTEP drawing of the cationic moieties of (a) [Rh(Py3S3)-
(cod)](BPh4) 1b and (b) [Rh(Py3S3)(nbd)](BPh4) 2b. All hydrogen atoms
have been deleted for clarity.
Fig. 4 ESI mass spectra of the reaction mixture of Py3S3 and 10 eq. of
m-CPBA after (a) 1 h and (b) 24 h.
Fig. 2 ORTEP drawing of the cationic moiety of [Rh{Py3(SO)3}-
(cod)](BPh4) 3b. All hydrogen atoms have been deleted for clarity.
Mono- and di-oxygenated complexes were also observed
in the 1H NMR spectrum during the reaction of 1 with
m-CPBA. The 1H NMR spectrum of the oxygenated com-
plexes showed complicated patterns in the pyridine region and
downfield-shifted cod signals, Fig. 5(b). The complicated signals
were observed in the pyridine region and they are attributed
to the overlap of two sets of AB2 and ABBꢀ signals of the
oxygenated Py3S3 ligands. The signal patterns of the cod ligands
were unchanged after oxidation. These results mean that the cod
Fig. 3 ESI mass spectra of (a) 1b and the reaction mixture of complex
1b and 10 eq. of m-CPBA after (b) 3.5 h, (c) 6.5 h and (d) 24 h.
Fig. 5 The cod ligand region of the 1H NMR spectra in CDCl3 of (a)
complex 1, (b) the oxidation product of 1 by m-CPBA for 2 h and (c)
complex 3. The peak marked with * is the signal of the CH3 group of
toluene used for crystallisation.
and [Rh(Py3S3O2)(cod)]+ at m/z = 538, 570, respectively. This
result suggests that the oxygenation of 1 proceeds stepwise.
No peaks corresponding to the complex having more than
D a l t o n T r a n s . , 2 0 0 5 , 2 1 3 0 – 2 1 3 7
2 1 3 1

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ligand was not oxygenated but that the Py3S3 ligand was oxidised
to give S-oxygenated Py3S3 complexes, [Rh(Py3S3O)(cod)]+ and
[Rh(Py3S3O2)(cod)]+ consistent with the result of the ESI-
MS. Because the structure of the final product was confirmed as
[Rh{Py3(SO)3}(cod)]+, the dioxygenated complex does not con-
tain SO2 groups and these mono- and di-oxygenated complexes
should be [Rh{Py3S2(SO)}(cod)]+ and [Rh{Py3S(SO)2}(cod)]+,
respectively. A set of 1H NMR signals for the cod ligand in the
dioxygenated Py3S3 complex appeared at lower field than that in
the monooxygenated one. It means less electron density on the
cod ligand in the dioxygenated complex, and oxidation of the
Py3S3 ligand withdraws electrons from the Rh centre. Because
the oxygen atoms in 3b sit on the equatorial positions, the oxygen
atoms in the mono- and di-oxygenated complexes should occupy
the equatorial positions.
The norbornadiene complex 2 was also oxidised by m-
CPBA resulting in the S oxygenated complexes. However, ESI-
MS showed that the oxygenation proceeded until four oxygen
atoms were added to the complex, Fig 6. The mono- and di-
oxygenated complexes were crystallised as mixed-crystals by
addition of NaBPh4 to a methanol solution of the mixture of
these complexes. X-Ray analysis of the mixed-crystal revealed
that the O(2) atom had less than 1.0 occupancy meaning that
the crystal contained both mono- and di-oxygenated complexes,
[Rh{Py3S2(SO)}(nbd)]+ (4) and [Rh{Py3S(SO)2}(nbd)]+ (5), and
only the S atoms of the Py3S3 ligands were oxygenated, Fig. 7(a).
The result of ESI-MS of the crystal also supported the fact
that it was a mixed-crystal, Fig. 7(b). 1H NMR spectra of
a mixture of tri- and tetra-oxygenated complexes (Fig. 8(b))
showed the signal pattern of the nbd ligand to be unchanged
after oxygenation implying that third and forth oxygenation also
occurred at the sulfur bridges, but not at the nbd ligands, to give
[Rh{Py3(SO)3}(nbd)]+ (6) and [Rh{Py3(SO)2(SO2)}(nbd)]+ (7),
respectively. Since the nbd ligand consists of a six-membered ring
(if the bridge-head CH2 is not taken into account) and is smaller
than the cod ligand which has an eight-membered ring. As a
result, steric hindrance at the Rh-diene side of the Py3S3 ligand
in the nbd complex is less than that in the cod complex causing
the fourth oxygenation reaction. Isolation of pure 7 has not been
successful because of the instability of 7 in the presence of m-
CPBA or m-chlorobenzoic acid and comparably slow reaction
rate.
Fig. 7 (a) ORTEP drawing of the cationic moiety of the oxygenated nbd
complex. All hydrogen atoms have been deleted for clarity. The disorder
of the O(2) atom suggested that the crystal contained both di- and
mono-oxygenated complexes. (b) ESI-MS of the crystal used for X-ray
analysis clearly showed the signals for both mono- and di-oxygenated
complexes.
Fig. 8 (a) ESI mass and (b) 1H NMR spectra of the mixture of
[Rh(Py3S3O3)(nbd)](BPh4) 6b (*) and [Rh(Py3S3O4)(nbd)](BPh4) 7b (᭹).
of 8b shown in Fig. 11 clearly showed that the sulfur bridges
remained unoxygenated and the cod ligand was hydroxygenated
4
to 1,4,5,6-g -2-hydroxycycloocta-4-ene-1,6-di-yl, so the peak at
m/z = 554 in the ESI mass spectrum was assigned to the
complex with a hydroxygenated cod ligand whose structure has
eleven inequivalent protons and is consistent with the 1H NMR
spectrum in Fig. 10. The same hydroxygenation of the cod ligand
was reported for the oxidation of rhodium and iridium cod
complexes.5b,8 These Rh cod complexes were oxidised by H2O2
to afford oxabicyclononadiyl complexes which were converted
to hydroxycyclooctenediyl ones by heating at 80 ◦C. In the Py3S3
system, only the hydroxycyclooctenediyl complex was isolated
in the oxidation by H2O2 at room temperature. Additionally, no
oxidation reaction occurred when the same reaction time (1 h)
as the Me3tacn complexes was applied.
Fig. 6 ESI mass spectra of the reaction mixture of complex 2b and 10
eq. of m-CPBA after (a) 2 h, (b) 7 h, (c) 8 h and additional 2 h after
further addition of 20 eq. of m-CPBA.
Although oxygenation occurred only at the sulfur bridges
of Py3S3 using m-CPBA, oxidation by H2O2 afforded the
monooxygenated complex, 8b, in which the cod ligand was
hydroxygenated. ESI mass spectrum of the reaction mixture
of 1a and H2O2 in H2O dominantly revealed the peaks of the
monooxygenated complex, Fig. 9. The 1H NMR spectrum of the
product obtained by addition of NaBPh4 to the reaction mixture
showed a complicated pattern over 1–6 ppm beside the signals
for the unoxygenated starting material 1, Fig. 10. X-Ray analysis
In the ESI mass spectrum of the reaction mixture of H2O2
oxidation (Fig. 9(b)), a small signal for the dioxygenated
complex was observed. It is unclear whether the sulfur bridge
2 1 3 2
D a l t o n T r a n s . , 2 0 0 5 , 2 1 3 0 – 2 1 3 7

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or was very slow if it occurred. This is probably attributed
to the lack of p–p interactions with the pyridine ring of the
Py3S3 ligand supposed for m-CPBA oxidation. Oxygenation of
rhodium and iridium complexes with N3 ligands afforded the cod
ligands oxygenated via oxygen-coordinated intermediates.5 In
the case of the oxygenation of 1 by H2O2, a similar intermediate
containing RhIII–O could be concerned. On the other hand, such
intermediates were not involved in m-CPBA oxygenation.
Fig. 9 ESI mass spectra of the reaction mixture of [Rh(Py3S3)(cod)]+
and H2O2 after (a) 4 h and (b) 24 h.
Structures of the complexes
X-Ray crystal structure analyses were performed for 1b, 2b,
3b, 6b (see Fig. 12), 8b and the mixed crystal 4b/5b, but 8b
is excluded from the structural discussion because of the poor
quality of the data due to the poor quality of the crystal used
for the analysis. Selected bond lengths and angles are listed in
Table 1. The coordination geometry around the Rh atom in
1b is trigonal bipyramidal similar to the 1,4,7-trimethyl-1,4,7-
triazacyclononane (Me3tacn) analogue.6 In complex 1b, the axial
˚
Rh–C(olefin) bond lengths (av. 2.167(4) A) are longer than the
˚
equatorial ones (av. 2.081(5) A) and these values and trends
were the same as those found in the Me3tacn complex (av.
˚
˚
2.164(6) A for axial, av. 2.080(4) A for equatorial). While the
arrangement of the cod ligands around the Rh atoms in 1b and
the Me3tacn complex are almost the same, the Rh–N distances
˚
˚
(Rh–Nax, 2.092(3) A; Rh–Neq, 2.293(3) and 2.314(3) A) and N–
Rh–N angles (Nax–Rh–Neq, 84.9(1) and 83.2(1)◦; Neq–Rh–Neq,
79.7(1)◦) in 1b were shorter and wider than those found in the
˚
Me3tacn complex (Rh–Nax, 2.198(2) A; Rh–Neq, 2.339(2) and
◦
˚
2.335(2) A; Nax–Rh–Neq, 80.09(9) and 78.91(9) ; Neq–Rh–Neq,
76.77(9)◦).
Fig. 10 1H NMR spectrum (400 MHz, cod region) of the mixture of
[Rh(Py3S3)(cod)]+ (᭹) and the H2O2 oxygenated complex 8. The signals
marked with * are of solvents.
Fig. 12 ORTEP drawing of the cationic moiety of [Rh{Py3(SO)3}-
(nbd)](BPh4) 6b. All hydrogen atoms have been deleted for clarity.
The coordination geometry around the Rh atom in each
unoxygenated complex, 1b or 2b, is very similar to the cor-
responding trioxygenated complex, 3b or 6b, and the Rh–
N distances and the N–Rh–N angles are almost the same.
Between the structures of the unoxygenated and corresponding
trioxygenated complexes, significant differences appear around
the bridging sulfur atoms. The S–C bond lengths are in the
Fig. 11 ORTEP drawing of the cationic moiety of 8b. Although X-ray
crystallography showed two independent cations of the complex in the
asymmetric unit, one of them is shown because they have almost the
same structures.
˚
range 1.764(4)–1.777(4) A in 1b and 2b and become longer
˚
after oxidation (1.808(3)–1.822(2) A in 3b and 6b). The C–
S–C angles in the unoxygenated complexes (98.9(2), 102.8(2)
and 104.3(2)◦ in 1b, 101.3(1), 101.4(1) and 102.4(1)◦ in 2b)
become smaller after oxidation (91.4(1), 93.6(1) and 94.4(1)◦
for 3b, 94.0(1), 94.1(1) and 95.4(1)◦ for 6b). Similar structural
or the carbon atom in the cod moiety was oxygenated and the
second oxygenation seems to be slower. In the case of oxidation
by H2O2, oxygenation of the sulfur bridges did not proceed
D a l t o n T r a n s . , 2 0 0 5 , 2 1 3 0 – 2 1 3 7
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◦
˚
Table 1 Selected bond lengths (A) and angles ( ) in 1b, 2b, 3b, 6b and the mixed crystal 4b/5b
1b
2b
3b
4b/5b
6b
Rh–Nax
Rh–Neq
Rh–Cax
Rh–Ceq
Rh–Ctr(C C)ax
Rh–Ctr(C C)eq
2.092(3)
2.120(2)
2.078(2)
2.069(3)
2.086(2)
2.293(3), 2.314(3)
2.164(4), 2.170(4)
2.076(4), 2.085(4)
2.055(4)
2.233(2), 2.242(2)
2.138(3), 2.149(4)
2.075(3), 2.086(3)
2.035(4)
2.294(2), 2.326(2)
2.188(2), 2.208(2)
2.092(3), 2.100(3)
2.088(2)
2.232(2), 2.262(3)
2.167(4), 2.170(4)
2.062(5), 2.066(4)
2.059(4)
2.265(2), 2.271(2)
2.172(3), 2.187(3)
2.080(3), 2.085(3)
2.070(3)
a
a
=
=
1.954(4)
1.961(3)
1.970(3)
1.940(4)
1.958(3)
C–S
1.764(4), 1.770(4)
1.774(4), 1.774(4)
1.776(4), 1.777(4)
1.771(3), 1.772(3)
1.774(3), 1.775(3)
1.776(3), 1.777(3)
1.811(3), 1.811(3)
1.811(3), 1.814(3)
1.821(2), 1.822(2)
1.478(2), 1.485(2)
1.487(2)
1.372(4)
1.429(4)
1.776(4), 1.778(4)
1.791(4), 1.806(4)
1.807(4), 1.809(4)
1.419(4), 1.483(3)
1.808(3), 1.813(3)
1.814(3), 1.814(3)
1.816(3), 1.817(3)
1.456(2), 1.478(2)
1.481(2)
1.366(4)
1.417(4)
S–O
=
C
C
Cax
Ceq
1.375(6)
1.426(6)
1.350(6)
1.394(5)
1.357(7)
1.408(7)
=
Nax–Rh–Neq
Neq–Rh–Neq
Nax–Rh–Ctr(C C)ax
Nax–Rh–Ctr(C C)eq
Neq–Rh–Ctr(C C)ax
Neq–Rh–Ctr(C C)eq
C–S–C
83.2(1), 84.9(1)
79.7(1)
176.1(1)
85.02(8), 85.31(8)
82.08(8)
167.6(1)
83.72(7), 84.20(7)
78.34(7)
175.60(9)
85.6(1), 85.64(9)
81.1(1)
167.4(2)
85.24(8), 85.35(8)
80.55(8)
167.5(1)
a
a
a
a
=
=
90.1(2)
96.7(1)
91.09(10)
97.5(1)
97.24(10)
=
97.8(1), 100.0(1)
137.3(2), 141.8(2)
98.9(2), 102.8(2)
104.3(2)
103.2(1), 104.8(1)
138.4(1), 139.6(1)
101.3(1), 101.4(1)
102.4(1)
96.12(9), 100.65(9)
137.04(10), 143.67(10)
91.4(1), 93.6(1)
94.4(1)
102.1(1), 105.3(2)
136.4(2), 142.4(2)
95.7(2), 98.0(1)
99.9(2)
103.92(9), 104.37(10)
137.62(10), 141.81(10)
94.0(1), 94.3(1)
95.4(1)
=
C–S–O
104.8(1), 105.6(1)
105.7(1), 106.2(1)
106.5(1), 106.9(1)
105.5(2), 105.8(1)
108.3(2), 111.3(2)
105.8(1), 106.6(1)
107.1(1), 107.7(1)
107.9(1), 108.6(1)
a
=
Ctr(C C): Central position between olefin carbon atoms.
changes upon oxygenation of the bridging S atoms were
observed in p-tert-butylthiacalix[4]arene tetra-O-be◦nzylester (S–
˚
C, 1.781(4)–1.785(4) A; C–S–C, 99.4(2) and 99.7(2) ) and p-tert-
butylsulfinylcalix[4]arene tetra◦-O-benzylester (S–C, 1.810(5)
6
˚
and 1.814(5) A; C–S–C, 97.4(2) ). Although the C–S–C values
in 1b vary widely, the distribution of those found in 3b is much
smaller. The large distribution of the C–S–C angles in 1b is
probably attributed to steric repulsion caused by the cod ligand
around the metal ion. On the other hand, the distributions of the
C–S–C values of both 2b and 6b are smaller than those of the cod
complexes. The flexible C–S–C bonds in the Py3S3 ligand allows
changes in its conformation to reduce the steric hindrance in 1b.
These structural features probably affect the reactivity upon the
fourth oxygenation of the sulfur bridges which occurs only for
the less hindered nbd complex.
Conclusions
We have synthesised the amphiphilic thiacalix[3]pyridine
rhodium cod and nbd complexes and have demonstrated their se-
lective oxidation by m-CPBA to give the sulfinylcalix[3]pyridine
rhodium complexes. The selectivity of the oxygenation is at-
tributed to steric hindrance of the diene ligands and to the fixed
conformation of the ligand by coordination to a Rh ion. Oxida-
tion of the cod complex by H2O2 did not result in oxygenation of
the sulfur bridges in the Py3S3 ligand but hydroxygenation of the
Scheme 1
General procedures
1H and 13C NMR spectra were recorded on JEOL Lambda300
and 400 and Bruker AVANCE600 FT-NMR spectrometers, and
chemical shifts were referenced to tetramethylsilane. Electro-
spray ionisation (ESI) mass spectrometry measurements were
performed on an Applied Biosystem Mariner spectrometer using
HPLC grade solvents. Elemental analyses were performed by the
Analytical Research Service Centre at Osaka City University on
Perkin Elmer 240C or FISONS Instrument EA108 elemental
analysers.
4
cod ligand to give a 1,4,5,6-g -2-hydroxycycloocta-4-ene-1,6-di-
yl rhodium(III) complex. The reactions reported in this paper
are summarised in Scheme 1.
Experimental
Materials
All solvents were purchased from Nacalai Tesque for the
reactions and from Sigma-Aldrich Japan or Merck for the
measurements and used without further purification. Thia-
calix[3]pyridine was synthesised by the literature procedure.3a
m-Chloroperoxybenzoic acid was purified by washing with
phosphate buffer (1/15 mol l−1, pH 7.0). All other reagents were
used as received.
Synthesis of [Rh(Py3S3)(diene)]+ (diene = cod, nbd) complexes
Synthesis of [Rh(Py3S3)(cod)]Cl (1a). Thiacalix[3]pyridine
(Py3S3, 327 mg, 1.00 mmol) and [Rh(cod)(l-Cl)]2 (247 mg,
0.50 mmol) were stirred in 20 ml of methanol for 10 min
2 1 3 4
D a l t o n T r a n s . , 2 0 0 5 , 2 1 3 0 – 2 1 3 7

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resulting in a yellow orange solution. After a small amount
insoluble solid was filtered off, the solvent of the filtrate was
removed under reduced pressure to give a yellow solid of
[Rh(Py3S3)(cod)]Cl (1a) (546 mg, 95%). The crude product was
recrystallised from an aqueous solution by slow evaporation
of the solvent to afford orange crystals of the hydrated com-
plex, [Rh(Py3S3)(cod)]Cl·2.5H2O (Found: C, 44.79; H, 4.07; N,
6.73. C23H26N3O2.5RhS3 requires C, 44.63; H, 4.23; N, 6.79%);
dH(300 MHz, CD3OD, TMS) 7.94 (9H, AB2 multiplet, pyridyl),
of 1a (42 mg, 0.073 mmol) in 5 ml of CH2Cl2. After stirring
for 12 h, a solution of NaBPh4 (48 mg, 0.15 mmol) in 15 mL
methanol was added and the solution was concentrated to ca.
10 mL under reduced pressure to give a yellow precipitate
of [Rh{Py3(SO)3}(cod)](BPh4) (3b) which was collected by
filtration (55 mg, 83%) (Found C, 62.07; H, 4.57; N, 4.54.
C47H41BN3O3RhS3 requires C, 62.32; H, 4.56; N, 4.64%);
dH(600 MHz, CDCl3, TMS) 8.30–8.38 (9H, AB2 multiplet,
3
pyridyl), 7.27 (8H, m, o-phenyl), 6.95 (8H, t, JH–H = 7.2 Hz,
4.03 (4H, br, –CH ), 2.47 (4H, m, exo –CH2–), 1.80 (4H, m,
m-phenyl), 6.79 (4H, t, 3JH–H = 7.2 Hz, p-phenyl), 4.28 (4H, br,
=
endo –CH2–); ESI-MS m/z = 538 ([M − Cl]+).
–CH ), 2.62 (4H, br, exo –CH2–), 2.02 (4H, dd, JH–H = 16.4,
2
=
2JH–Rh = 7.9 Hz, endo –CH2–); dC(150 MHz, CDCl3, TMS) 165.2
(m, i-phenyl), 157.1 (s, 2,6-pyridyl), 142.1 (s, 4-pyridyl), 136.5 (s,
Synthesis of [Rh(Py3S3)(cod)](BPh4) (1b). A solution of
Py3S3 (327 mg, 1.00 mmol) in 60 mL of methanol was added
to a suspension of [Rh(cod)(l-Cl)]2 (247 mg, 0.50 mmol) in
40 ml of methanol and the mixture was stirred for 2 h to
give a yellow orange solution. Slow addition of a solution of
NaBPh4 (420 mg, 1.23 mmol) in methanol (20 ml) afforded
a yellow microcrystalline solid of [Rh(Py3S3)(cod)](BPh4) (1b).
After further stirring for 1 h, the solid was collected by filtration
and washed with methanol and diethyl ether (853 mg, 99%)
(Found: C, 65.71; H, 4.74; N, 4.85. C47H41BN3RhS3 requires C,
65.81, H, 4.82; N, 4.90%); dH(600 MHz, CDCl3, TMS) 7.60 (6H,
o-phenyl), 126.7 (s, 3,5-pyridyl), 126.1 (s, m-phenyl), 122.2 (s,
1
=
p-phenyl), 81.4 (d, JC–Rh = 12.3 Hz, –CH ), 30.8 (s, –CH2-);
ESI-MS m/z = 586 ([M − BPh4]+).
Oxidation of [Rh(Py3S3)(nbd)]Cl by m-chloroperoxybenzoic
acid. Oxidation reaction of 2a (216 mg, 0.387 mmol) by m-
CPBA (668 mg, 3.87 mmol) in 50 ml of CH2Cl2 was examined in
a similar manner to that of 1a as mentioned above to afford the
sulfinylcalix[3]pyridine complex, [Rh{Py3(SO)3}(nbd)](BPh4)
(6b) (234 mg, 68%) (Found: C, 62.14; H, 4.10; N, 4.70.
C46H37N3BO3RhS3 requires C, 62.10; H, 4.19; N, 4.72%);
dH(300 MHz, CD2Cl2, TMS) 8.21 (9H, AB2 multiplet, pyridyl),
3
3
d, JH–H = 7.8 Hz, 3,5-pyridyl), 7.49 (3H, t, JH–H = 7.8 Hz, 4-
3
pyridyl), 7.32 (8H, m, o-phenyl), 6.82 (8H, t, JH–H = 7.2 Hz,
m-phenyl), 6.68 (4H, t, 3JH–H = 7.2 Hz, p-phenyl), 3.82 (4H, br,
3
7.26 (8H, m, o-phenyl), 6.97 (8H, t, JH–H = 7.5 Hz, m-
=
3
–CH ), 2.35 (4H, m, exo –CH2–), 1.68 (4H, m, endo –CH2–
phenyl), 6.81 (4H, t, JH–H = 7.2 Hz, p-phenyl), 3.93 (4H,
); dC(150 MHz, CDCl3, TMS) 166.5 (m, i-phenyl), 155.7 (s,
=
dd, J = 2.1 and 5.0 Hz, –CH ), 3.79 (2H, m, –CH–),
3
2,6-pyridyl), 141.3 (s, 4-pyridyl), 136.2 (s, o-phenyl), 128.9 (s,
1.39 (2H, t, JH–H = 1.6 Hz, H-bridge-head); ESI-MS m/z =
570 ([M − BPh4]+). Prolonged reaction time (3 weeks) gave
the tetraoxygenated complex, [Rh{Py3(SO)2(SO2)}(nbd)](BPh4)
(7b), as a mixture with 6b. dH(300 MHz, CD2Cl2, TMS) 8.53
(2H, d, J = 8.1 Hz, pyridyl), 8.38 (2H, d, J = 7.7 Hz, pyridyl),
8.25 (2H, d, J = 7.9 Hz, pyridyl), 8.05 (3H, AB2 multiplet,
3,5-pyridyl), 125.4 (s, m-phenyl), 121.6 (s, p-phenyl), 76.5 (br,
+
=
–CH ), 30.7 (s, –CH2–); ESI-MS m/z = 538 ([M − BPh4] ).
Synthesis of [Rh(Py3S3)(nbd)]Cl (2a). [Rh(Py3S3)(nbd)]Cl
was prepared in a manner similar to that of the cod com-
plex [Rh(Py3S3)(cod)]Cl (1a) using [Rh(nbd)(l-Cl)]2 (230 mg,
0.50 mmol) instead of [Rh(cod)(l-Cl)]2. Yield 520 mg, 93%.
The crude product was recrystallised from an aqueous solution
by slow evaporation of the solvent to afford orange crystals of
the hydrated complex, [Rh(Py3S3)(nbd)]Cl·1.5H2O (Found: C,
45.37; H, 3.40; N, 7.06. C22H20N3O1.5RhS3 requires C, 45.17; H,
3.45; N, 7.18%); dH(300 MHz, CD3OD, TMS) 7.95 (9H, AB2
3
pyridyl), 7.26 (8H, m, o-phenyl), 6.95 (8H, t, JH–H = 7.4 Hz,
3
m-phenyl), 6.79 (4H, t, JH–H = 7.2 Hz, p-phenyl), 4.04 (4H,
=
dd, J = 2.0 and 5.0 Hz, –CH ), 3.72 (2H, br, –CH–), 1.42
(2H, br, H-bridge-head); ESI-MS m/z = 586 ([M − BPh4]+).
Shorter reaction time (2 h) afforded a mixture of monooxy-
genated [Rh{Py3S2(SO)}(nbd)](BPh4) (4b) and dioxygenated
[Rh{Py3S(SO)2}(nbd)](BPh4) (5b) complexes confirmed by ESI
mass spectrometry and X-ray diffraction study.
multiplet, pyridyl), 3.55 (2H, m, –CH–), 3.51 (4H, dd, J = 2.3
3
=
and 4.8 Hz, –CH ), 1.13 (2H, t, JH–H = 1.5 Hz, H-bridge-
head); dC(75 MHz, CD3OD, TMS) 157.3 (s, 2,6-pyridyl), 141.1
(s, 4-pyridyl), 129.9 (s, 3,5-pyridyl), 59.8 (d, JH–Rh = 6.9 Hz,
Oxidation of [Rh(Py3S3)(cod)]Cl by H2O2. To a solution of
1a (115 mg, 0.200 mmol) in 20 mL of H2O, 1 mL of 30%
H2O2 aq was added and the mixture was stirred for 24 h. After
a small amount of precipitate was filtered off, a solution of
NaBPh4 137 mg, 0.400 mmol) in 5 mL of H2O was added
to the filtrate to give a yellow precipitate. After standing for
1 h, the precipitate was collected by filtration, washed with
methanol and recrystallised from CH2Cl2 solution by addition of
methanol. The precipitate contained the BPh4 salt of the starting
material and a small amount of the cod oxygenated complex, 8b
(102 mg). Prolonged reaction times caused decomposition of
the complexes. Pure 8b for X-ray crystallography was obtained
by repeated recrystallisation by slow diffusion of methanol to
a CH2Cl2 solution. dH(600 MHz, CD2Cl2, TMS) Assignment of
bridge-head), 47.7 (d, JH–Rh = 2.9 Hz, –CH–), 41.7 (d, JH–Rh
=
+
=
10.4 Hz, –CH ); ESI-MS m/z = 522 ([M − Cl] ).
Synthesis of [Rh(Py3S3)(nbd)](BPh4) (2b). [Rh(Py3S3)-
(nbd)](BPh4) was prepared in a manner similar to that of the
cod complex [Rh(Py3S3)(cod)](BPh4) (1b) using [Rh(nbd)(l-
Cl)]2 (230 mg, 0.50 mmol) instead of [Rh(cod)(l-Cl)]2. Yield
558 mg, 66% (Found: C, 64.96; H, 4.38; N, 4.72. C46H37BN3RhS3
requires C, 65.64, H, 4.43; N, 4.99%); dH(300 MHz, CD2Cl2,
TMS) 7.64–7.75 (9H, AB2 multiplet, pyridyl), 7.31 (8H, m, o-
3
phenyl), 6.99 (8H, t, JH–H = 7.4 Hz, m-phenyl), 6.83 (4H, t,
3JH–H = 7.2 Hz, p-phenyl), 3.57 (2H, m, –CH–), 3.45 (4H, dd,
3
=
J = 2.2 and 5.0 Hz, –CH ), 1.15 (2H, t, JH–H = 1.6 Hz, H-
the NMR signals follows the numbering scheme in Fig. 10. 7.55
3
bridge-head); dC(75 MHz, CD2Cl2, TMS) 164.4 (m, i-phenyl),
156.0 (s, 2,6-pyridyl), 139.8 (s, 4-pyridyl), 136.3 (s, o-phenyl),
129.1 (s, 3,5-pyridyl), 125.9 (s, m-phenyl), 122.1 (s, p-phenyl),
(9H, br, pyridyl), 7.31 (8H, m, o-phenyl), 6.98 (8H, t, JH–H
=
6.4 Hz, m-phenyl), 6.82 (4H, t, 3JH–H = 7.1 Hz, p-phenyl), 5.95
(1H, q, J = 5.3 Hz, H7), 5.77 (1H, q, J = 5.3 Hz, H5), 4.80
(1H, d, J = 6.4 Hz, H1), 4.39 (1H, t, J = 8.0 Hz, H6), 3.15
(1H, d, J = 0.8 Hz, H2), 1.89 (1H, m, H9), 1.84 (1H, m, H4),
1.82 (1H, m, H11), 1.35 (1H, dt, J = 14.7, 4.7 Hz, H3), 1.10
(1H, m, H8), 1.06 (1H, m, H10); dC(150 MHz, CD2Cl2, TMS)
164.4 (q, JC–B = 49.5 Hz, i-phenyl), 156.5 (s, 2,6-pyridyl), 139.8
(s, 4-pyridyl), 136.3 (s, o-phenyl), 129.2 (s, 3,5-pyridyl), 126.0 (s,
m-phenyl), 122.1 (s, p-phenyl), 96.6 (d, 1JC–Rh = 6.2 Hz, C5), 87.1
(d, 2JC–Rh = 0.8 Hz, C2), 79.5 (d, 1JC–Rh = 11.8 Hz, C6), 73.5 (d,
58.2 (s, bridge-head), 47.0 (d, JH–Rh = 2.9 Hz, –CH–), 41.2 (d,
+
=
JH–Rh = 9.8 Hz, –CH ); ESI-MS m/z = 522 ([M − BPh4] ).
Oxidation of [Rh{Py3S3}(diene)]+ complexes
Oxidation of [Rh(Py3S3)(cod)]Cl by m-chloroperoxybenzoic
acid. A solution of m-chloroperoxybenzoic acid (m-CPBA,
126 mg, 0.73 mmol) in 10 ml of CH2Cl2 was added to a solution
D a l t o n T r a n s . , 2 0 0 5 , 2 1 3 0 – 2 1 3 7
2 1 3 5

View Article Online
2 1 3 6
D a l t o n T r a n s . , 2 0 0 5 , 2 1 3 0 – 2 1 3 7

View Article Online
1JC–Rh = 12.9 Hz, C4), 52.6 (d, 1JC–Rh = 21.4 Hz, C1), 39.9 (s, C8),
35.6 (s, C3), 24.6 (s, C7); ESI-MS m/z = 554 ([M − BPh4]+).
CCDC reference numbers 237066, 237067 and 266664–
266667.
See http://www.rsc.org/suppdata/dt/b5/b503924j/ for cry-
stallographic data in CIF or other electronic format.
Counter anion replacement of S-oxygenated complexes from
BPh4 to Cl
Into an acetone solution of a corresponding BPh4 salt of each S-
oxygenated complex, a small amount of conc. HCl aq was added.
After stirring for 1 h, the solvent was removed under reduced
pressure to give a yellow residue. The residue was re-dissolved in
a small amount of methanol and any insoluble solid was filtered
off. Addition of diethyl ether to the filtrate afforded a yellow
precipitate which was collected by filtration (Yield 60–80%).
References
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8 Crystal Clear, Rigaku Corp., Woodlands, TX, 1999.
9 A. Altomare, M. C. Burla, M. Camalli, G. Cascarano, C. Giacovazzo,
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11 teXsan, Crystal Structure Analysis Package, Molecular Structure
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Crystal growth and X-ray crystallography
Single crystals of 1b, 2b and 8b were obtained by diffusion of
methanol into a solution of the complex in CHCl3 or CH2Cl2,
at room temperature. Single crystals of 3b were obtained by
diffusion of cyclohexane into a solution of the complex in
CH2Cl2. Mixed crystals of 4b/5b were obtained from a solution
of the mixture of the complexes in CH2Cl2 and methanol by
slow evaporation of the solvents. Single crystals of 6b were
obtained by slow diffusion of a NaBPh4 solution in methanol
into a methanol solution of a Cl salt of the complex. Each
single crystal was mounted on a glass fibre. Diffraction data
were collected on an AFC7/CCD Mercury diffractometer using
a rotation method with 0.3 for 8b and 0.5 frame width for
the others and with 5 s for 1b and 6b and 10 s for 2b,
3b, 4b/5b and 8b exposure times per frame. The data were
integrated, scaled, sorted and averaged using CrystalClear9
software. Absorption corrections were applied using Coppens
numerical method. The structures were solved using SIR9710
and refined with SHELXL9711 using teXsan12 as a graphical
interface. Crystallographic data are summarised in Table 2. All
non-hydrogen atoms were refined anisotropically. All hydrogen
atoms except for those in 8b were found in difference Fourier
maps and refined isotropically. Hydrogen atoms in 8b were
located at calculated positions and refined as riding models.
The site occupancy of the disordered oxygen atom in the mixed
crystal 4b/5b was refined.
12 T. C. Flood, M. Iimura, J. M. Perotti, A. L. Reingold and T. E.
Concolino, Chem. Commun., 2000, 1681.
D a l t o n T r a n s . , 2 0 0 5 , 2 1 3 0 – 2 1 3 7
2 1 3 7