Reversible complexation of acetylene with (perchlorato)cobalt(III) porphyrins to form a novel dicobalt(II) bis (porphyrin) with a vinylene-N,N′ linkage

Article abstract of DOI:10.1021/om960339n

(Perchlorato)cobalt(III) porphyrins bind acetylene reversibly in anhydrous CH₂Cl₂. The ¹H NMR and UV-vis spectra of the acetylene adduct at room temperature are characteristic of a Co^II N-substituted porphyrin. The ESR spectra of the acetylene adduct in CH₂Cl₂ at 4.2 and 77 K showed signals due to a π-cation radical and low-spin Co^II. These spectroscopic data show that one acetylene combines with two cobalt porphyrins to generate a vinylene-N,N′-linked bis(porphyrin) dicobalt(II) structure reversibly via an acetylene π-complex of Co^II porphyrin π-cation radical. When coordinating anionic axial ligands (Cl^-, SCN^-) were attached, the vinylene-N,N′ bis(tetraarylporphyrin) dicobalt(II) complexes were stabilized enough to be isolated and fully characterized.

Full text of DOI:10.1021/om960339n

Organometallics 1997, 16, 597-605
597
Rever sible Com p lexa tion of Acetylen e w ith
(P er ch lor a to)coba lt(III) P or p h yr in s To F or m a Novel
Dicoba lt(II) Bis(p or p h yr in ) w ith a Vin ylen e-N,N′ Lin k a ge
J un-ichiro Setsune,*,†,‡ Shoji Ito,† Hirokazu Takeda,† Yoshihiro Ishimaru,†
Teijiro Kitao,§ Masaaki Sato,| and Hiroaki Ohya-Nishiguchi
Department of Chemistry, Faculty of Science, Kobe University, Nada, Kobe 657, J apan,
Coordination Chemistry Laboratory, Institute for Molecular Science, Myodaiji,
Okazaki 444, J apan, Department of Applied Chemistry, College of Engineering, and
Department of Chemistry, Faculty of Integrated Arts and Sciences, University of Osaka
Prefecture, Sakai, Osaka 591, J apan, and Department of Chemistry, Faculty of Science,
Kyoto University, Sakyo, Kyoto 606, J apan
Received May 7, 1996X
(Perchlorato)cobalt(III) porphyrins bind acetylene reversibly in anhydrous CH2Cl2. The
1H NMR and UV-vis spectra of the acetylene adduct at room temperature are characteristic
of a CoII N-substituted porphyrin. The ESR spectra of the acetylene adduct in CH2Cl2 at
4.2 and 77 K showed signals due to a π-cation radical and low-spin CoII. These spectroscopic
data show that one acetylene combines with two cobalt porphyrins to generate a vinylene-
N,N′-linked bis(porphyrin) dicobalt(II) structure reversibly via an acetylene π-complex of
CoII porphyrin π-cation radical. When coordinating anionic axial ligands (Cl-, SCN-) were
attached, the vinylene-N,N′ bis(tetraarylporphyrin) dicobalt(II) complexes were stabilized
enough to be isolated and fully characterized.
In tr od u ction
π-complexes except for (η5-cyclopentadienyl)ScIII.5 Coll-
man’s group prepared stable ethylene π-complexes of
RuII and OsII porphyrins,4 and Weiss and co-workers
reported a MoII alkyne π-complex.6 Wayland and co-
workers have shown 1H NMR evidence indicating the
formation of an ethylene π-complex of RhIII through the
acidification of (σ-â-hydroxyethyl)RhIII porphyrin.7 While
a CoIII porphyrin π-complex with vinyl ether has been
postulated as an intermediate leading to the formation
of (σ-formylmethyl)CoIII porphyrin,9 a π-complex of CoIII
porphyrin has never been found thus far. We have
recently shown that CoIII porphyrins react with alkynes
in the presence of 2,6-lutidine, probably via a CoIII
alkyne π-complex intermediate, to give (σ-vinyl)CoIII
porphyrins with the 2,6-lutidine nitrogen bound at the
â-vinylic carbon of the σ-vinyl moiety.10 This reaction
is mechanistically analogous to that of CoIII porphyrin
with vinyl ether in the presence of ethanol. Thus, the
present study is aimed at elucidating the basic reaction
behavior of cationic CoIII porphyrins toward acetylene.
Not only has the spectroscopic evidence indicating the
reversible formation of a CoIII acetylene π-complex been
obtained here but also novel vinylene-N,N′-linked bis-
(porphyrin) dicobalt(II) complexes have been isolated
and characterized as the end products.
A number of organometallic porphyrin complexes
have recently been synthesized, and their properties and
reactivities have been studied with the aim of elucidat-
ing metabolic processes governed by heme and related
metalloenzymes and also at developing new methodol-
ogy for organic transformations.1,2 Syntheses of carbene
complexes,3,4 π-complexes,4-7 and σ-complexes8 of met-
alloporphyrins have been reported so far. As far as
metalloporphyrin π-complexes are concerned, only a few
examples have been isolated or observed directly, and
all of them are second- and third-row transition-metal
* To whom correspondence should be addressed at Kobe University.
E-mail: setsunej@icluna.kobe-u.ac.jp.
† Kobe University.
‡ Institute for Molecular Science.
§ University of Osaka Prefecture (College of Engineering). Deceased
J an 4, 1992.
| University of Osaka Prefecture (Faculty of Integrated Arts and
Sciences).
Kyoto University. Present address: Institute for Life Support
Technology, Yamagata Technopolis Foundation, Kurumanomae 683,
Numagi, Yamagata 990, J apan.
X Abstract published in Advance ACS Abstracts, J anuary 15, 1997.
(1) (a) Brothers, P. J .; Collman, J . P. Acc. Chem. Res. 1986, 19, 209.
(b) Setsune, J .; Dolphin, D. Can. J . Chem. 1987, 65, 459. (c) Mansuy,
D. Pure Appl. Chem. 1987, 59, 759.
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A. J . Chem. Soc., Chem. Commun. 1992, 328.
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J pn. 1976, 49, 2529. (d) Peree-Fauret, M.; Gaudemer, A.; Boucly, P.;
Devynek, J . J . Organomet. Chem. 1976, 120, 439. (e) Maureen, K. G.;
Halpern, J . J . Am. Chem. Soc. 1987, 109, 1238. (f) Gridnev, A. A.; Ittel,
S. V.; Fryd, M.; Wayland, B. B. Organometallics 1993, 12, 4871. (g)
Setsune, J .; Ishimaru, Y.; Moriyama, T.; Kitao, T. J . Chem. Soc., Chem.
Commun. 1991, 555.
(9) Sugimoto, H.; Ueda, N.; Mori, M. Bull. Chem. Soc. J pn. 1981,
54, 3425.
(7) Wayland, B. B.; Van Voorhees, S. L.; Del Rossi, K. J . J . Am.
Chem. Soc. 1987, 109, 6513.
(10) Setsune, J .; Saito, Y.; Ishimaru, Y.; Ikeda, M.; Kitao, T. Bull.
Chem. Soc. J pn. 1991, 65, 639.
S0276-7333(96)00339-1 CCC: $14.00 © 1997 American Chemical Society

598 Organometallics, Vol. 16, No. 4, 1997
Setsune et al.
1
the temperature was lowered, these paramagnetic H
NMR signals broadened and an ESR signal became
apparent as noted later.
The rhodo-type spectral pattern (398, 544, 592, and
629 nm) in the UV-vis and the molecular symmetry
and the range of chemical shifts observed in the
paramagnetic 1H NMR spectrum of the adduct are
consistent with a CoII complex of N-substituted por-
phyrin. The similarity in the spectroscopic properties
between the acetylene adduct and (N-(γ-IPr)OEP)-
CoIICl (2)11 is indicated in Table 1. It is remarkable that
the Soret band of this acetylene adduct is blue-shifted
by ca. 30 nm in comparison with ordinary N-substituted
(OEP)CoII complexes. We had proposed in a preliminary
communication that this acetylene adduct might be a
d6 high-spin CoIII complex with a vinylene-Co,N bridge.12a
However, all the Co,N-bridged porphyrin complexes
reported so far have a CoIII d6 low-spin (S ) 0) state,13
and there seems to be no special demand for a high-
spin state to be preferred in such a hypothetical etheno-
Co,N-bridged CoIII complex.
It has been noted that the complex 1a is a CoII
porphyrin π-cation radical and is ESR silent in dry
CH2Cl2 solution in the temperature range 173-298 K,
because the two unpaired electrons in the CoII porphyrin
π-cation radical structure are spin-coupled.14 The acety-
lene adduct of 1a , however, showed a strong ESR signal
(g ) 2.002; line width 14 G) in frozen CH2Cl2 (1 mM) at
77 K (see Figure 2a). This g value is indicative of a
porphyrin π-cation radical. Whereas the intensity of
this ESR signal was diminished to ca. 1% when the
temperature was raised to 250 K, it was restored as the
temperature was cooled down again to 77 K. The ESR
spectrum of the acetylene adduct of 1a at 4.2 K in a
polycrystalline state showed the signals due to the
unpaired electron at CoII in addition to the signal due
to the porphyrin π-cation radical (Figure 2b). Thus, the
CoII porphyrin π-cation radical structure was clearly
evidenced by the ESR spectrum, since two spins do not
interact with each other in this acetylene adduct, in
contrast to the case for 1a .
F igu r e 1. UV-vis spectral changes recorded at 1 min
intervals after the dissolution of (a) the acetylene adduct
C2H2-(1a ) in CH2Cl2 (dotted line; after 30 min) and (b) the
acetylene adduct C2H2-(1b).
It was indicated that 1a exists in dry CH2Cl2 as a form
Resu lts a n d Discu ssion
of CoII porphyrin π-cation radical where a Co dz orbital
2
Acetylen e Ad d u ct of (OEP )CoIII(H2O)2ClO4 (1a ).
Introduction of purified acetylene gas into a CH2Cl2
solution of (OEP)CoIII(H2O)2ClO4 (1a ; OEP ) octaethyl-
porphyrin) caused an immediate color change from
reddish brown to green. This color change is reversible.
That is, rapid dissociation of acetylene to regenerate 1a
was observed by the UV-vis spectral change, giving
four isosbestic points (387, 471, 570, and 633 nm) as
shown in Figure 1a when the acetylene adduct C2H2-
(1a ), which was obtained by the precipitation with
and a porphyrin π-orbital (a2u) are singly occupied.14
This was evidenced by the UV-vis spectrum (a blue-
shifted Soret band and a broad and featureless Q-band)
and the resonance Raman spectrum, both characteristic
of porphyrin π-cation radicals. Addition of water or
methanol gives rise to the normal CoIII porphyrin
structure with two molecules of water (or MeOH)
coordinating to the axial sites. The axial coordination
2
of σ-donor ligands to Co would lift the energy of the dz
orbital to the extent enough to exceed the energy level
of the porphyrin HOMO a2u π-orbital, making a diradi-
1
n-hexane, was dissolved in CH2Cl2 (Scheme 1). The H
NMR spectrum of a mixture of 1a with excess acetylene
in CD2Cl2 at 0 °C showed two 2H signals due to the
meso protons at δ 11.6 and -9.0, the assignment of
which was confirmed by using a meso-octaethylpor-
phyrin-d4 analogue. Eight 2H signals due to the
peripheral CH2 protons at 38.1, 30.9, 30.3, 28.1, 23.0,
20.3 (overlapped), and 19.3 ppm and four 6H signals
due to the CH3 protons at 10.2, 10.0, 9.5, and 3.9 ppm
were also observed to indicate Cs symmetric molecular
structure with a mirror plane containing a N(21)-Co-
N(23) axis. Signals derived from acetylene could not
be detected over the spectral range of (200 ppm. As
(11) Setsune, J .; Takeda, H. Tetrahedron Lett. 1995, 36, 5903.
(12) (a) Setsune, J .; Ikeda, M.; Ishimaru, Y.; Kitao, T. Chem. Lett.
1989, 667. (b) Setsune, J .; Ishimaru, Y.; Saito, Y.; Kitao, T. Chem. Lett.
1989, 671.
(13) (a) J ohnson, A. W.; Ward, D.; Batten, P.; Hamilton, A. L.;
Schelton, G.; Elson, C. M. J . Chem. Soc., Perkin Trans. 1 1975, 2076.
(b) Callot, H. J .; Schaeffer, E. Nouv. J . Chim. 1980, 4, 307. (c) Setsune,
J .; Dolphin, D. Organometallics 1984, 3, 440. (d) Setsune, J .; Iida, T.;
Kitao, T. Chem. Lett. 1989, 885. (e) Setsune, J .; Iida, T.; Kitao, T.
Tetrahedron Lett. 1988, 29, 5677. (f) Setsune, J .; Ikeda, M.; Kishimoto,
Y.; Kitao, T. J . Am. Chem. Soc. 1987, 109, 6515.
(14) (a) Salehi, A.; Oertling, W. A.; Babcock, G. T.; Chang, C. K. J .
Am. Chem. Soc. 1986, 108, 5630. (b) Oertling, W. A.; Salehi, A.; Chung,
Y. C.; Leroi, G. E.; Chang, C. K.; Babcock, G. T. J . Phys. Chem. 1987,
91, 5887.

Complexation of Acetylene with Co(III) Porphyrins
Organometallics, Vol. 16, No. 4, 1997 599
Sch em e 1
Ta ble 1. 1H NMR a n d UV-Vis Da ta for th e
Acetylen e Ad d u ct C2H2-(1a ) of
(OEP )CoIII(H2O)2ClO4 (1a ) a n d
has a negative slope. The A value decreases from 400
G (in the case of four-coordinate complexes) to 100 G
(in the case of five-coordinate complexes) and to -50 G
(in the case of six-coordinate complexes) as the strength
of the axial ligand field increases. Although ESR
parameters for a parallel component have not been
clearly determined in the present case (probably g| )
∼2 and A| ) 160 G), the values of a perpendicular
component (g ) 3.1; A ) 290 G) conform well to this
linear relationship and are in the range indicative of
tetragonal CoII coordination with a very weak axial
ligand effect. This is consistent with the formation of
an acetylene π-complex of a CoII porphyrin π-cation
radical.
(CH2CH2CH2I-N)(OEP )CoIICl (2)
1H chem shifts (δ)a
meso-H
-CH2-
-CH3
N-R
λmax (nm)b
C2H2-(1a )
11.6
-9.0
38.1 23.0 10.2
30.9 20.3 10.0
n.d.
398
544
592
629
30.3 20.3
28.1 19.3
9.5
3.9
2
8.6
-5.9
34.8 19.1
26.3 18.4
24.1 16.5
19.4 15.2
9.7 -117.5 (R)
428
543
584
627
6.5
5.8
2.6
-44.5 (â)
-23.2 (γ)
a
Measured at 0 °C for C2H2-(1a ) in CD2Cl2 and 23 °C for 2 in
Thus, the acetylene adduct of 1a takes the form of a
CoII N-substituted porphyrin or the form of a CoII
porphyrin π-cation radical π-complexed with an axial
acetylene, depending on temperature (Scheme 2).
Acetylen e Ad d u cts of (TP P )CoIII(H2O)2ClO4 (1b)
a n d (TTP )CoIII(H2O)2ClO4 (1c). The adduct forma-
tion of (TPP)CoIII(H2O)2ClO4 (1b) with acetylene oc-
curred similarly to the case of 1a . The reaction is also
reversible, but the acetylene adduct, C2H2-(1b), went
back much more slowly to 1b than in the case of 1a
under the same reaction conditions. The UV-vis
spectrum of the adduct is that of a rhodo-type charac-
teristic of N-substituted porphyrin metal complexes
showing absorption maxima at 443 (Soret), 568, 622,
b
CDCl3. In CH2Cl2.
cal structure unfavorable. Coordination of acetylene to
Co, however, would not change the CoII porphyrin
π-cation radical structure, probably because the energy
2
level of the singly occupied dz orbital is not raised,
owing to the π-acceptor character of acetylene. Mag-
netic properties of various metalloporphyrin π-cation
radicals have been interpreted in terms of the occupancy
and symmetry of the orbitals on the metal and on the
ligand that contain an unpaired electron.15 It is not
clear why coordination of acetylene disrupts the interac-
tion between spins at CoII and at the porphyrin π-sys-
tem. Such a noninteracting two S ) 1/2 spin system has
been reported for RuIII porphyrin π-cation radical, where
1
and 667 nm (see Table 2 and Figure 1b). While the H
1
1
ESR signals from the S ) /2 ruthenium and S ) /2
porphyrin π-cation radical are observed at 77 K.16
One of us previously studied the ESR spectra of a
number of CoII porphyrins with different axial ligations
and found that there is a linear relationship between g
values and hyperfine splittings (A).17 The g -A cor-
relation has a positive slope, while the g|-A| correlation
NMR spectrum at room temperature did not show
discrete signals, an ESR signal due to a π-cation radical
was also observed in frozen CH2Cl2 (1 mM) at 77 K (g
) 1.99; line width 35 G). When a saturated NaSCN or
NaCl aqueous solution was added to a CH2Cl2 solution
of the acetylene adduct, stable N-substituted CoII por-
phyrins (3b) and (4b) were obtained in 48-56% yield
after chromatographic purification on silica gel. The
FAB MS spectrum of the TTP analogue 4c showed a
peak at the exact mass number (m/ e 1553) correspond-
ing to the molecular ion of a dimeric structure, (CHdCH-
(15) (a) Erler, B. S.; Scholz, W. F.; Lee, Y. J .; Scheidt, W. R.; Reed,
C. A. J . Am. Chem. Soc. 1987, 109, 2644. (b) Gans, P.; Buisson, G.;
Duee, E.; Marchon, J .-C.; Erler, B. S.; Scholtz, W. F.; Reed, C. A. J .
Am. Chem. Soc. 1986, 108, 1223. (c) Spreer, L. O.; Maliyackel, A. C.;
Holbrook, S.; Otvos, J . W.; Calvin, M. J . Am. Chem. Soc. 1986, 108,
1949.
(16) Barley, M.; Becker, J . Y.; Domazetis, G.; Dolphin, D.; J ames,
B. R. Can. J . Chem. 1983, 61, 2389.
(17) Kohno, M.; Ohya-Nishiguchi, H.; Yamamoto, K.; Sakurai, T.
Bull. Chem. Soc. J pn. 1984, 57, 932.

600 Organometallics, Vol. 16, No. 4, 1997
Setsune et al.
Ta ble 2. 1H NMR a n d UV-Vis Da ta for th e
Acetylen e Ad d u ct C2H2-(1b) of
(TP P )CoIII(H2O)2ClO4 (1b),
(CHdCH-N,N′)(TP P CoIISCN)2 (3b), a n d
(CHdCHCl-N)(TP P CoIISCN) (5) a n d Th eir F r ee
Ba ses 6b a n d 7
1H chem shifts (δ)a
py â-H
o-H
m-H p-H
N-R
λmax (nm)b
C2H2-(1b)
n.d.
443
568
622
667
3b
6b
41.8
40.2
33.8
-3.4
20.8
16.3
9.5
15.4 8.7 -178c
442
567
618
661
13.9 9.9
11.8
-0.6
5.8
8.86
8.27
7.96
6.12
8.5-5.4
-5.32c
415
531
571
623
683
5
7
44.2
44.2
35.9
-1.9
23.3
19.6
2.5
13.5 9.5
12.2 7.6
7.3
-69.6c
-95.1d
447
569
618
667
-3.0
7.1
8.99
8.91
8.61
8.46
8.4-7.6
2.30d
433
529
569
617
672
-1.45c
F igu r e 2. ESR spectra of (a) the acetylene adduct C2H2-
(1a ) in frozen CH2Cl2 at 77 K and (b) its polycrystalline
sample at 4.2 K.
a
Measured at room temperature in CDCl3. b In CH2Cl2. c NCHd.
d
NCdCHCl.
two porphyrin planes) ortho protons of the inner (region
close to the N,N′ linkage) meso-aryl groups with respect
to the center of the dimeric structure, and this deviation
from a theoretical linear relationship should be at-
tributed to the rotational barrier for a porphyrin nitro-
gen bond to a linking vinylene carbon, as will be
discussed later. The signal assignment of 3b was made
in comparison with the spectra of a TPP-d8 (deuteriated
at the pyrrole â-positions) analogue (d8-3b) and a TTP
(tetra-p-tolylporphyrin) analogue (3c) and with the aid
of line-width analysis (Figure 4) and a 1H-1H COSY
spectrum (Figure 5).19 Of special interest is the 2H
absorption at -178 ppm due to the vinylene-N,N′
protons. This chemical shift is quite close to the
summation of the chemical shifts of the R- (-69.6 ppm)
and the â-vinyl (-95.1 ppm) protons of the N-trans-â-
chlorovinyl moiety of 5.18 This means that the vinylene-
N,N′ proton of 3b is subject to isotropic shifts from the
two chemically equivalent but magnetically nonequiva-
lent CoII atoms of the trans-vinylene-N,N′-linked bis-
(porphyrin) structure. This chemical shift is not con-
sistent with a cis-vinylene-N,N′-linked bis(porphyrin)
structure, since a geometric factor is quite important
in the isotropic shifts for protons in the proximity of a
paramagnetic center. The analysis of the diamagnetic
1H NMR spectrum of the corresponding free base 6b,
which was readily obtained by the demetalation of 3b
with trifluoroacetic acid, is also consistent with the
trans-vinylene-N,N′-linked dimeric structure. A 2H
proton singlet at -5.32 ppm is associated with the
vinylene-N,N′ protons, and a rough estimation of the
ring current term for this signal (∆δ ) ca. -10 ppm,
taking a reference chemical shift as δ 5 for vinylic
Sch em e 2
N,N′)(TTPCoIICl)2. A similar treatment of the mixture
of 1a and acetylene with aqueous NaSCN or NaCl,
however, resulted in the complete disappearance of the
acetylene adduct to give a monomeric CoIII porphyrin.
This means that the rates of the equilibrium for
acetylene adduct formation and decomposition in the
case of 1a are fast enough to undergo exclusive axial
ligation of water and halide to the monomeric CoIII
porphyrin.
The complexes 3b and 4b retain the UV-vis spectral
feature of the acetylene adduct which is virtually the
same as that of (N-(trans-ClC(H)dCH)TPP)CoIISCN
(5),18 as summarized in Table 2. The similarity in the
1H NMR spectra of 3b and 5 is also indicated in Table
1
2. A very sharp paramagnetic H NMR spectrum was
observed for 3b, and the Curie plot (Figure 3) in the
temperature range between 50 and -55 °C shows
straight lines except for the highest field signal. This
signal is assignable to the inside (region between the
(18) Setsune, J .; Ikeda, M.; Kishimoto, Y.; Ishimaru, Y.; Fukuhara,
K.; Kitao, T. Organometallics 1991, 10, 1099.
(19) Keating, K. S.; de Ropp, J . S.; La Mar, G. N.; Balch, A. L.; Shiau,
F.-Y.; Smith, K. M. Inorg. Chem. 1991, 30, 3258.

Complexation of Acetylene with Co(III) Porphyrins
Organometallics, Vol. 16, No. 4, 1997 601
F igu r e 5. 1H-1H COSY spectrum of (CHdCH-N,N′)-
(TPPCoIICl)2 (4b) in CDCl3 at room temperature.
that these protons are in the shielding regions of the
other half-porphyrin moiety of the dimeric structure.
The FAB MS ion peak at m/ e 1367 ((M + H)+) provided
evidence in support of the dimeric structure of the TTP
analogue, (CHdCH-N,N′)(TTPH)2 (6c).
F igu r e 3. Curie plots of paramagnetic chemical shifts in
CDCl3 against temperature (15 °C intervals between 50
and -55 °C) for the signals of (CHdCH-N,N′)(TPPCoII-
SCN)2 (3b).
Therefore, 3b should have trans-vinylene-N,N′-linked
bis(porphyrin) dicobalt(II) structure. Since the spec-
troscopic properties of the acetylene adducts derived
from 1a and 1b at room temperature are best rational-
ized in terms of the N-substituted CoII porphyrin, the
reversibility between the formal trivalent complex 1 and
its divalent acetylene adduct complex without apparent
redox counterparts necessitates a dimeric structure for
these acetylene adducts. It is remarkable that the
vinylene-N,N′-linked bis(tetraarylporphyrin) dicobalt(II)
structure is stabilized by the axial coordination of
chloride and thiocyanate. The axial ligand coordination
causes deviation of Co atom out of the porphyrin plane
toward axial ligands,20 and this would weaken the
interaction between cobalt and the vinylene-N,N′ moi-
ety, which leads to the scission of the N-C bond. In
fact, treatment of 3c with AgClO4 in CH2Cl2 resulted
in the complete degradation of the dimeric structure,
probably by way of replacement of chloride in the axial
coordination site by perchlorate (Scheme 3).
A number of the layered bis(porphyrin) structures
have recently been prepared for the purpose of creating
molecular systems effective for electron transfer and
bimetallic catalysis.21-23 They include bis(porphyrins)
linked through the peripheral substituents,21 axial
ligation,22 and metal elements.23 While the coordination
F igu r e 4. 1H NMR spectra of (CHdCH-N,N′)(TPPCoII-
SCN)2 (3b) (bottom), d8-3b (middle), and (CHdCH-N,N′)-
(TTPCoIISCN)2 (3c) (top) at room temperature.
(20) Lavallee, D. K. The Chemistry and Biochemistry of N-Substi-
tuted Porphyrins; VCH: Weinheim, Germany, 1987.
protons) is in good accordance with the summation of
the ring current terms at the R-vinylic proton (∆δ ) ca.
-6.5 ppm) and the â-vinylic proton (∆δ ) ca. -2.7 ppm)
of the N-trans-â-chlorovinyl moiety of the free base 7
derived from 5, which were observed at δ -1.45 and
2.30, respectively (see Table 2). The unusually upfield
shifted signals due to the â-pyrrole protons at 6.06 ppm
and the meso-phenyl ortho protons at 5.51 ppm imply
(21) (a) Collman, J . P.; Hutchison, J . E.; Lopez, M. A.; Tabard, A.;
Guilard, R.; Seok, W. K.; Ibers, J . A.; L’Her, M. J . Am. Chem. Soc.
1992, 114, 9869. (b) Chang, C. K.; Abdalmuhdi, I. J . Org. Chem. 1983,
48, 5388. (c) Dolphin, D.; Hiom, J .; Paine, J . B., III. Heterocycles 1981,
16, 417. (d) Karaman, R.; Blasko, A.; Almarsson, O¨ .; Arasasingham,
R.; Bruice, T. C. J . Am. Chem. Soc. 1992, 114, 4889. (e) Borovkov, V.
V.; Sugiura, K.; Sakata, Y.; Shul’ga, A. M. Tetrahedron Lett. 1993, 34,
2153. (f) Osuka, A.; Kobayashi, F.; Maruyama, K. Bull. Chem. Soc.
J pn. 1992, 64, 1213.

602 Organometallics, Vol. 16, No. 4, 1997
Setsune et al.
Sch em e 3
Sch em e 4
of porphyrin N-oxide to a metalloporphyrin has been
reported to provide a bis(porphyrin) system joined with
a M-O-N link as the first bis(porphyrin) system
utilizing N-substituted porphyrins,24 the present vinyl-
ene-N,N′-linked bis(porphyrin) system is of wide ap-
plication because its covalently bound unique dimeric
structure allows one to make various homo- and het-
erobimetallic complexes (Scheme 4).
Mech a n ism of t h e Dim er F or m a t ion . We have
already reported that an electrophilic CoIII and a nu-
cleophilic nitrogen base add across a C-C triple bond
of methyl propiolate to give organocobalt(III) com-
plexes.10 That is, intermolecular attack of a 2,6-lutidine
nitrogen gives a (σ-vinyl)CoIII complex, (Por)CoIII(C(CO2-
Me)dCHN(C7H9))ClO4 (8), while intramolecular attack
of a porphyrin nitrogen affords the etheno-C,N-bridged
CoIII complex (C(CO2Me)dCH-Co,N)(Por)CoIIIClO4 (9)
(Scheme 5). These reactions suggest that an acetylene-
π-coordinated cobalt intermediate, (π-C2H2)CoII(Por•+)-
ClO4, undergoes σ-π rearrangement to generate a (σ-
vinyl)CoIII structure (A) in which a â-carbon atom with
respect to CoIII is cationic (see Scheme 6). Therefore,
an etheno-Co,N-bridged CoIII intermediate (B) would be
formed and it should undergo homolytic cleavage of a
CoIII-C σ-bond to provide a vinyl radical species (C)
attached at the nitrogen of the cobalt porphyrin. As it
is well-known that the rate of the CoIII-C bond-forming
reaction between low-spin CoII complexes and alkyl
radicals is generally on the order of diffusion control,25
this vinyl radical (C) would be immediately captured
by complex 1, since it takes a CoII π-cation radical
structure. Thus, the generated bis(porphyrin) with (σ-
vinyl)CoIII porphyrin π-cation radical structure (D)
would automatically undergo Co-to-N migration of the
σ-vinyl group to provide vinylene-N,N′-linked bis(por-
phyrin) dicobalt(II) complexes. A (σ-alkyl)CoIII por-
phyrin π-cation radical has long been thought to be a
key intermediate in the reversible Co-to-N migration of
a σ-alkyl group upon one-electron oxidation of (σ-alkyl)-
CoIII porphyrins.1,26 A recent study has indicated that
the migration of an alkyl and an aryl group from Co to
nitrogen will only occur after the initial formation of a
transient σ-bonded CoIV derivative rather than a σ-bond-
ed CoIII porphyrin π-cation radical, on the basis of the
ESR evidence.27 That is, the isotropic g values (∼2.02)
observed at 77 K for the one-electron-oxidized interme-
diates from (σ-alkyl)CoIII porphyrins are reported to
agree well with those for organocobalt(IV) species.28
Thus, the bis(porphyrin) intermediate with a (σ-vinyl)-
CoIII porphyrin π-cation radical structure (D) in the
present case might better be described as a form of (σ-
vinyl)CoIV structure, (Por)CoIVsCHdCHN(Por)CoII(ClO4)2
(D′).
(22) (a) Mansuy, D.; Lecomte, J .-P.; Chottard, J .-C.; Bartoli, J . F.
Inorg. Chem. 1981, 20, 3119. (b) Summerville, D. A.; Cohen, I. A. J .
Am. Chem. Soc. 1976, 98, 1747. (c) Hoffman, A. B.; Collins, D. M.; Day,
V. W.; Fleischer, E. B.; Srivastava, T. S.; Hoard, J . L. J . Am. Chem.
Soc. 1972, 94, 3620. (d) Masuda, H.; Taga, T.; Osaki, K.; Sugimoto,
H.; Mori, M.; Ogoshi, H. J . Am. Chem. Soc. 1981, 103, 2199. (e) Scheidt,
W. R.; Cheng, B.; Safo, M. K.; Cukiernik, F.; Marchon, J .-C.; Debrun-
ner, P. G. J . Am. Chem. Soc. 1992, 114, 4420. (f) Balch, A. L.; Latos-
Grazynski, L.; Noll, B. C.; Olmstead, M. M.; Safari, N. J . Am. Chem.
Soc. 1993, 115, 9056. (g) Goff, H. M.; Scheidt, W. R. Inorg. Chem. 1984,
23, 315.
(23) (a) Buchler, J . W.; De Cian, A.; Fischer, J .; Kihn-Botulinski,
M.; Paulus, H.; Weiss, R. J . Am. Chem. Soc. 1986, 108, 3652. (b)
Buchler, J . W.; Hu¨ttermann, J .; Lo¨ffler, J . Bull. Chem. Soc. J pn. 1988,
61, 71. (c) Collman, J . P.; Arnold, H. J .; Fitzgerald, J . P.; Weissman,
K. J . J . Am. Chem. Soc. 1993, 115, 9309. (d) Collman, J . P.; Garner, J .
M.; Woo, L. K. J . Am. Chem. Soc. 1989, 111, 8141. (e) Collman, J . P.;
Prodolliet, J . W.; Leidner, C. R. J . Am. Chem. Soc. 1986, 108, 2916. (f)
Wayland, B. B.; Woods, B. A.; Coffin, V. L. J . Am. Chem. Soc. 1988,
110, 6063. (g) Setsune, J .; Yoshida, Z.-I.; Ogoshi, H. J . Chem. Soc.,
Perkin Trans. 1 1982, 983. (h) Yang, C.-H.; Dzugan, S. J .; Goedken,
V. L. J . Chem. Soc., Chem. Commun. 1986, 1313.
Since the ESR g value (2.002) observed at 77 K for
the acetylene adduct C2H2-(1a ) is not consistent with
the CoIV structure as noted above, the observed ESR
signal is not associated with the structure D′. We
(25) Halpern, J . Acc. Chem. Res. 1982, 15, 238.
(26) Dolphin, D.; Halko, D. J .; J ohnson, E. Inorg. Chem. 1981, 20,
4348.
(27) Miyamoto, K.; Suenobu, T.; Itoh, S.; Fukuzumi, S. Abstracts of
42nd Symposium on Organometallic Chemistry, Higashi-Hiroshima,
J apan; Kinki Chemical Society: Osaka, J apan, 1995; p 166.
(28) (a) Halpern, J .; Chan, M. S.; Hanson, J .; Roche, T. S.; Topich,
J . A. J . Am. Chem. Soc. 1975, 97, 1606. (b) Collins, T. J .; Powell, R.
D.; Slebodnick, C.; Uffelman, E. S. J . Am. Chem. Soc. 1991, 113, 8419.
(c) Will, S.; Lex, J .; Vogel, E.; Adamian, V. A.; Caemelbecke, E. V.;
Kadish, K. M. Inorg. Chem. 1996, 35, 5577.
(24) Arasasinghem, R. D.; Balch, A. L.; Olmstead, M. M.; Renner,
M. W. Inorg. Chem. 1987, 26, 3562.

Complexation of Acetylene with Co(III) Porphyrins
Organometallics, Vol. 16, No. 4, 1997 603
Sch em e 5
Sch em e 6
consider the acetylene π-complex intermediate (π-C2H2)-
CoII(Por•+)ClO4 to be responsible for the ESR signal.
Furthermore, the ESR parameters due to CoII of the
acetylene adduct are those of a low-spin (S ) 1/2) type17
and are not consistent with those for CoII N-substituted
groups of 6c are broadened uniformly with increasing
temperature, signals due to the inner meso-tolyl groups
(δ 7.3-5.1) showed unusual dynamic behavior with the
same temperature change. While the signal due to the
inside ortho proton at δ 5.10 is extremely broadened at
25 °C, the other aromatic protons appear as sharp
signals at ∼7.2 ppm at this temperature. Therefore, the
specific broadening of the ortho proton signal at 5.10
ppm would be ascribable to the restricted rotation
around the bond between the porphyrin nitrogen and
the linking vinylene carbon but not to the hindered
rotation of the tolyl groups. The above observation
shows that the dynamic molecular motion of the vi-
nylene-N,N′-linked bis(porphyrins) is greatly influenced
by the metalation, which changes and fixes the shape
of porphyrin planes.
3
porphyrins, which generally show a high-spin (S ) /2)
type ESR (g ) 4.4, g| ) 2.04 for (N-MeOEP)-
CoII(OAc)).29 Therefore, the ESR spectra of the acety-
lene adduct are not explainable in terms of the hypo-
thetical bis(porphyrin) intermediate D or D′, which
3
must have an S )
/
spin at the CoII site even if a
2
noninteracting two-spin system might be possible in
such a bis(porphyrin) framework.
It is remarkable that acetylene is reversibly com-
plexed with cobalt porphyrin as a vinylene-N,N′ linkage
and that an acetylene-π-complexed CoII porphyrin π-cat-
ion radical structure and a vinylene-N,N′ bis(porphyrin)
dicobalt(II) structure are thermally equilibrated, as
evidenced by the ESR and NMR spectroscopy.
Dyn a m ic Beh a vior . Figure 6 shows temperature-
dependent 1H NMR spectra of the aromatic regions of
6c and its dizinc complex (10c). The aromatic region
of the dizinc complex shows two sets of four doublets
associated with the outer meso-tolyl groups (δ 7.95-7.5)
and the inner meso-tolyl groups (δ 7.35-5.1). The
extremely upfield shifted doublet at δ 5.10 is assigned
to the inside (region between the two porphyrin planes)
ortho protons of the inner (region close to the N,N′
linkage) meso-aryl groups, because these protons are
located in the strongly shielding region due to the
porphyrin ring current effect from the other half-moiety.
The signal broadening of all the aromatic protons of 10c
takes place simultaneously with increasing tempera-
ture, and this is explained in terms of the hindered
rotation of the meso-aryl groups (Figure 6; right side).
The coalescence temperature is similar to that observed
for an N-methylated tetraarylporphyrin reported re-
cently.30 The aromatic protons due to the outer meso-
tolyl groups of the free base 6c appear as a set of four
doublets between 8.7 and 7.4 ppm (Figure 6; left side).
Comparison of the temperature-dependent line-broad-
ening behavior of these signals with that of 10c indi-
cates that the rotation of meso-tolyl groups of the free
base is more hindered than that of the zinc complex.
Whereas the four doublets due to the outer meso-tolyl
Con clu sion
We have delineated a novel reaction behavior of
cationic CoIII porphyrins with acetylene. Spectroscopic
measurements showed that acetylene is reversibly com-
plexed with (perchlorato)CoIII porphyrin in dry CH2Cl2
solution. This acetylene adduct underwent a reversible
structural change depending on temperature between
(π-C2H2)CoII(Por•+)ClO4 at low temperature and CoII-
(Por)(CHdCH-N,N′)(Por)CoII(ClO4)2 at room tempera-
ture. The presence of two noninteracting S ) 1/2 spins
at Co and at the porphyrin π-system was evidenced by
the ESR signals at 4.2 K, while a paramagnetic NMR
spectrum characteristic of CoII complexes of N-substi-
tuted porphyrins was observed at room temperature.
The vinylene-N,N′-linked bis(porphyrin) dicobalt(II)
complexes have been isolated in moderate yields by the
addition of an axially coordinating ligand such as a
chloride ion. The free base bis(porphyrins) with a
vinylene-N,N′ linkage obtained here by a convenient
procedure are of wide application because their co-
valently bound dimeric structure allows easy access to
a novel face-to-face bis- and poly(porphyrin) metal
complexes. An extensive study in this regard is under
way in our laboratory.
(29) Fukui, K.; Ohya-Nishiguchi, H.; Hirota, N.; Aoyagi, K.; Ogoshi,
H. Chem. Phys. Lett. 1987, 140, 15.
(30) Lavallee, D. K.; Xu, Z.; Pina, R. J . Org. Chem. 1993, 58, 6000.

604 Organometallics, Vol. 16, No. 4, 1997
Setsune et al.
F igu r e 6. Variable-temperature 1H NMR spectra in the aromatic region of (CHdCH-N,N′)(TTPH)2 (6c) (left) and (CHdCH-
N,N′)(TTPZnIICl)2 (10c) (right) in CDCl3.
raphy with CH2Cl2-acetone (10:1) and recrystallization from
CH2Cl2-methanol or CH2Cl2-diethyl ether. 3b: 1H NMR (δ,
in CDCl3) 41.8, 40.2, 33.8, -3.4 (4H × 4, pyrrole â-H), 20.8,
16.3, 9.5, -0.6 (4H × 4, Ph o-H), 15.4, 13.9, 11.8, 5.8 (4H × 4,
Ph m-H), 9.5, 8.7 (4H × 2, Ph p-H); UV-vis (λmax (log ꢀ) in
CH2Cl2) 442 (5.33), 567 (4.07), 618 (4.22), 661 (4.00) nm. Anal.
Calcd for C92H58N10S2Co2‚H2O: C, 73.49; H, 4.02; N, 9.32.
Found: C, 73.55; H, 3.52; N, 9.22. 3c: 1H NMR (δ, in CDCl3)
41.5, 40.3, 34.3, -3.3 (4H × 4, pyrrole â-H), 20.4, 15.9, 8.8,
-0.6 (4H × 4, Ar o-H), 15.2, 13.7, 11.6, 5.6 (4H × 4, Ar m-H),
7.9, 3.6 (12H × 2, Ar p-Me); UV-vis (λmax (log ꢀ) in CH2Cl2)
445 (5.29), 570 (4.06), 621 (4.21), 666 (4.03) nm. Anal. Calcd
for C100H74N10S2Co2‚H2O: C, 74.09; H, 4.74; N, 8.67. Found:
C, 74.09; H, 4.40; N, 8.60. 4b: 1H NMR (δ, in CDCl3) 48.6,
39.4, 37.0, -8.5 (4H × 4, pyrrole â-H), 20.5, 18.5, ∼6.3, 1.2
(4H × 4, Ph o-H), 14.4, 14.1, 11.9, 6.3 (4H × 4, Ph m-H), 9.7,
9.0 (4H × 2, Ph p-H); UV-vis (λmax (log ꢀ) in CH2Cl2) 445 (5.22),
569 (3.95), 617 (4.12), 663 (3.94) nm. Anal. Calcd for
C90H58N8Cl2Co2‚C4H10O: C, 74.55; H, 4.53; N, 7.40. Found:
C, 74.43; H, 4.62; N, 7.41. 4c: 1H NMR (δ, in CDCl3) 48.1,
39.5, 36.8, -8.4 (4H × 4, pyrrole â-H); 20.1, 18.1, 5.4, 1.1 (4H
× 4, Ar o-H), 14.3, 14.0, 11.7, 6.1 (4H × 4, Ar m-H), 7.7, 3.8
(12H × 2, Ar p-Me), -178 (2H, NCHdCHN). FAB MS m/ e
1553 ((M + H)+), 1454 ((TTPCo)2+), 727 ((TTPCo)+); UV-vis
(λmax (log ꢀ) in CH2Cl2) 447 (5.27), 575 (4.06), 618 (4.13), 665
(3.95) nm. Anal. Calcd for C98H74N8Cl2Co2: C, 74.10; H, 4.95;
N, 7.05. Found: C, 73.97; H, 4.50; N, 7.03.
Exp er im en ta l Section
Dichloromethane was dried by distilling from calcium
hydride and stored over 4A molecular sieves. Extra-pure
acetylene gas (99.99%) was courteously supplied by Nichigo
Acetylene Co. Ltd. Osaka, J apan. (TPP)H2, (TTP)H2, and
(OEP)H2 and their deuteriated analogues were prepared
according to the literature.31,32 (Perchlorato)cobalt(III) por-
phyrins were prepared according to the literature.9,14
1H NMR spectra were measured on J EOL GX-270 (270
MHz) and Bruker AC-250 (250 MHz) spectrometers, and the
chemical shifts are referenced to tetramethylsilane as an
internal standard. A J EOL FE-3X X-band spectrometer
equipped with an Air Product Model LTR-3-110 Heli-Tran
liquid-helium-transferring refrigerator was used for ESR
measurement at liquid-helium temperature. FAB MS spectra
were obtained at the acceleration voltage of 8 kV (Xe, 7 kV)
using m-nitrobenzyl alcohol as a matrix on a Shimadzu/Kratos
CONCEPT IS mass spectrometer.
Vin ylen e-N,N′ Bis(p or p h yr in ) Dicoba lt(II) Com p lexes
(3b,c a n d 4b,c). Purified acetylene gas was introduced into
a
flask containing (tetraarylporphyrinato)cobalt(III) per-
chlorate 1b or 1c (150 mg; 0.186 mmol for 1b or 0.174 mmol
for 1c) in dry CH2Cl2 (50 mL) with stirring at room temper-
ature. The color of the solution changed rapidly to bright
green. After the mixture was stirred for 15 min, saturated
NaSCN or NaCl aqueous solution (50 mL) was added at once
with vigorous stirring. The organic layer was separated,
washed with water, and dried over anhydrous Na2SO4. It was
then condensed with a rotary evaporator and chromatographed
on silica gel (Wakogel C-300, Wako J unyaku). The first green
band eluted with CH2Cl2 was evaporated to dryness, and the
residue was recrystallized from CH2Cl2-methanol to give
(CHdCH-N,N′)(TPPCoIISCN)2 (3b ) and (CHdCH-N,N′)-
(TTPCoIISCN)2 (3c) in yields of 48-56%. (CHdCH-N,N′)-
(TPPCoIICl)2 (4b) and (CHdCH-N,N′)(TTPCoIICl)2 (4c) were
obtained similarly after purification by silica gel chromatog-
Vin ylen e-N,N′ Bis(p or p h yr in ) F r ee Ba ses (6b,c). Tri-
fluoroacetic acid (4 mL) was added to a dry CH2Cl2 solution
(50 mL) of (CHdCH-N,N′)(TPPCoIISCN)2 (3b) or (CHdCH-
N,N′)(TTPCoIISCN)2 (3c) (150 mg; 0.101 mmol for 3b or 0.094
mmol for 3c), and the mixture was stirred for 15 min at room
temperature. Aqueous ammonia (28%) sufficient to neutralize
CF3COOH was added cautiously until the green solution
turned brown. Fine crystals formed in the organic layer were
filtered, washed with water, and dried under vacuum. The
organic layer was separated, dried over Na2SO4, and con-
densed. Hexane was added to this residue to afford precipi-
tates. The combined precipitates were recrystallized from
CH2Cl2-hexane to afford (CHdCH-N,N′)(TPPH)2 (6b) and
(31) Bonnett, R.; Gale, I. A. D.; Stephenson, G. F. J . Chem. Soc. C
1967, 1169.
(32) Boersma, A. D.; Goff, H. M. Inorg. Chem. 1982, 21, 581.

Complexation of Acetylene with Co(III) Porphyrins
Organometallics, Vol. 16, No. 4, 1997 605
(CHdCH-N,N′)(TTPH)2 (6c) in 79-95% yields. 6b: 1H NMR
(δ, in CDCl3) 8.86, 6.12 (s × 2, 4H × 2, pyrrole â-H), 8.27, 7.96
(d × 2, 4H × 2, pyrrole â-H), 8.5-5.4 (m, 40H, Ph H), -3.1
(bs, 2H, NH), -5.32 (s, 2H, bridge NCHd); UV-vis (λmax (log
ꢀ) in CH2Cl2) 415 (5.39), 531 (4.15), 571 (4.17), 623 (3.80), 683
(3.82) nm. Anal. Calcd for C90H60N8‚CH2Cl2: C, 81.66; H,
4.67; N, 8.37. Found: C, 81.60; H, 4.39; N, 8.05. 6c: 1H NMR
(δ, in CDCl3) 8.86, 6.08 (s × 2, 4H × 2, pyrrole â-H); 8.26, 7.96
(d × 2, 4H × 2, pyrrole â-H); 8.3-5.4 (m, 32H, Ar H), 2.79,
2.57 (s × 2, 12H × 2, Ar p-Me), -3.1 (bs, 2H, NH), -5.33 (s,
2H, bridge NCHd); FAB MS m/ e 1367 ((M + H)+), 695 ((M -
(TTP)H2)+), 683, 670 ((TTPH)+); UV-vis (λmax (log ꢀ) in CH2Cl2)
425 (5.52), 532 (4.04), 576 (4.26), 625 (4.10), 680 (4.10) nm.
Anal. Calcd for C98H76N8‚CH2Cl2: C, 81.96; H, 5.42; N, 7.72.
Found: C, 82.58; H, 5.20; N, 7.73.
(CHdCH-N,N′)(TTPZnIICl)2 (10c) in 90-96% yield. 10b: 1H
NMR (δ, in CDCl3) 8.92, 6.84 (s × 2, 4H × 2, pyrrole â-H),
8.66, 8.15 (d × 2, 4H × 2, pyrrole â-H), 7.9-5.4 (m, 40H, Ar
H), -5.86 (s, 2H, bridge NCHd); FAB MS m/ e 1452 ((M)+),
1417 ((M - Cl)+), 676 ((TPPZn)+); UV-vis (λmax (log ꢀ) in
CH2Cl2) 437 (5.90), 566 (4.24), 613 (4.48), 663 (4.22) nm. Anal.
Calcd for C90H58N8Cl2Zn2‚H2O: C, 73.48; H, 4.11; N, 7.62.
Found: C, 73.45; H, 4.59; N, 7.43. 10c: 1H NMR (δ, in CDCl3)
8.92, 6.78 (s × 2, 4H × 2, pyrrole â-H), 8.66, 8.16 (d × 2, 4H
× 2, pyrrole â-H), 8.0-5.2 (m, 32H, Ar H), 2.78, 2.60 (s × 2,
12H × 2, Ar p-Me), -5.86 (s, 2H, bridge NCHd); UV-vis (λmax
(log ꢀ) in CH2Cl2) 438 (5.65), 565 (4.12), 615 (4.35), 664 (4.21)
nm. Anal. Calcd for C98H74N8Cl2Zn2: C, 75.19; H, 4.76; N,
7.16. Found: C, 74.10; H, 4.78; N, 6.80.
Ack n ow led gm en t. This work was supported by a
Grant-in-Aid for Scientific Research on Priority Area
from the Ministry of Education, Science, and Culture
of J apan. A part of this work was performed for the
photonics material laboratory of the graduate school of
science and technology of Kobe University. We are
grateful to Nichigo Acetylene Co. Ltd. (Osaka, J apan)
for a gift of extra-pure grade acetylene gas, to Ms. S.
Nomura (IMS) for FAB MS analysis, and to Ms. M.
Nishinaka (Kobe University) for microanalysis.
N,N′-Vin ylen e Bis(p or p h yr in ) Dizin c(II) Com p lexes
(10b,c). To the free base 6b or 6c (50 mg; 0.037 mmol for 6b
or 0.034 mmol for 6c) dissolved in CH2Cl2 (30 mL) was added
a saturated MeOH solution (5 mL) of ZnII(OAc)2‚2H2O. After
a slight excess amount of 2,6-lutidine was added, the green
solution was stirred at room temperature for 1 h. The
resulting solution was evaporated to dryness, and the residue
was extracted with CH2Cl2. The CH2Cl2 solution was vigor-
ously shaken with saturated NaCl aqueous solution for 1 h,
dried over Na2SO4, and then evaporated to dryness. The green
residue was chromatographed on silica gel with CH2Cl2-
acetone (10:1) to give (CHdCH-N,N′)(TPPZnIICl)2 (10b) and
OM960339N