β,β′-fused metallocenoporphyrins

Article abstract of DOI:10.1039/b107732e

The syntheses of a β,β′-fused ruthenocenoporphyrin (9) and a ferrocenoporphyrin dimer (11) are described.

Full text of DOI:10.1039/b107732e

b,bA-Fused metallocenoporphyrins†
Hong J. H. Wang, Laurent Jaquinod, Daniel J. Nurco, M. Graça H. Vicente and Kevin M. Smith*‡
Department of Chemistry, University of California, Davis, California 95616, USA
Received (in Corvallis, OR, USA) 28th August 2001, Accepted 22nd October 2001
First published as an Advance Article on the web 4th December 2001
The syntheses of a b,bA-fused ruthenocenoporphyrin (9) and
a ferrocenoporphyrin dimer (11) are described.
1-yl acetate for two days at 90 °C in the presence of an in situ
prepared palladium(0) catalyst, to form nitrochlorins 3 and 4,
respectively (as shown by the appearance of an intense Q
absorption band at 602 nm). Further heating of the reaction
mixture at 100 °C for two days gave, upon elimination of nitrous
acid, porphyrins 5 and 6 in 80–88% yields. While the
cycloaddition reaction took place smoothly also on the copper
complexes, the corresponding zinc(II) complexes required
harsher reaction conditions and gave low yields (5%) of the
b,bA-fused cyclopentenylporphyrins. Acid-catalyzed double
bond migration on 5 and 6 afforded, respectively, porphyrins 7
and 8. Addition of LDA to a solution of 8 in THF caused a color
change from red to green which strongly suggested that two of
the porphyrin p-electrons are delocalized into the aromatic
Molecular systems incorporating porphyrins and metallocenes
have great potential as catalysts, chemical sensors, and in
porphyrin-assisted electron-transfer processes.1,2 In recent
years, molecules containing both porphyrin and ferrocene
fragments have emerged as candidates for self-assembled
monolayers in light energy conversion systems.3 In most of
these cases, the metallocene fragment is linked to the porphyrin
meso- or b-positions through various spacers,2–4 or directly to a
central metal ion.5 Direct linkages through a single C–C bond at
the meso-positions have been reported6 and it has also been
5
shown that metalloporphyrins can form h -pyrrolyl–p-metal
complexes with ruthenocyl moieties.7 Our goal was to synthe-
size metallocenoporphyrins fused through the porphyrin b-
positions, in order to enhance intramolecular electronic inter-
actions in these systems.
In order to incorporate a five-membered ring (precursor of
Cp2) onto the porphyrin periphery, we investigated novel
functionalizations of readily available 2-nitro-tetraarylporphyr-
ins.8 The remarkable ability of the nitro group to activate
tetraarylporphyrins towards [3 + 2] cycloaddition reactions and
its propensity to subsequently act as a leaving group was
demonstrated by our synthesis of pyrroloporphyrins.9 We now
report two novel b,bA-fused metallocenoporphyrins (9 and 11)
prepared via a key palladium(0)-catalyzed [3 + 2] cycloaddition
reaction, previously applied to 1-nitronaphthalene.10
Using strict air-free conditions, nickel(II) 2-nitroporphyrins 1
and 211 were treated with 2-[(trimethylsilyl)methyl]-2-propen-
† Electronic supplementary information (ESI) available: molecular struc-
Fig. 1 The molecular structure of 9; hydrogens have been omitted for
ture of 10. See http://www.rsc.org/suppdata/cc/b1/b107732e/
clarity.
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Chem. Commun., 2001, 2646–2647
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b107732e

Fig. 2 The molecular structure of 10 in stereoview; 3,5-di-tert-butylphenyl rings and hydrogens, except for those on the bridging carbons, have been omitted
for clarity.
SHELXL-97). Hydrogen atom positions were refined with riding models.
system of the newly formed cyclopentadienide anion. Deproto-
Final R factors were R1 = 0.0773 (observed data) and wR2 = 0.192 (all
nated 8 reacted with Cp*RuCl2 at room temperature for 2–5
data). CCDC 165704.
¶ Crystals of 10 were grown from MeOH–toluene [C160H190N8Ni2·2(to-
luene), FW = 2527.0]. The selected crystal (0.30 3 0.20 3 0.08 mm) was
monoclinic, space group P21/c, with cell dimensions a = 26.7781(15), b =
days to give air-stable ruthenocenoporphyrin 9 in 25% yield.12
The formation of 9 was confirmed by LDI–ToF mass spectrom-
etry (m/z = 1408.0) and by 1H NMR spectroscopy (which
showed a characteristic singlet at 3.90 ppm corresponding to the
fused cyclopentadienide protons).
15.9648(8), c = 36.499(2) Å, b = 101.885(3)°, V = 15269.2(14) Å3, and
Z = 4. Diffraction data were collected and absorption corrected as for 9
(215487 total reflections for 2q = 63°). A 2q cutoff of 50° was applied to
give 28066 total, 26858 unique, and 13378 observed ( > 2s(I)) reflections
[Rint = 0.169, Tmin = 0.916, Tmax = 0.976, rcalc = 1.101 gcm23, m =
0.299 mm21]. The structure was solved by direct methods and refined as for
9 with 1685 parameters. Hydrogen atom positions were refined with riding
models. Final R factors were R1 = 0.0839 (observed data) and wR2 = 0.270
(all data). CCDC 165703. See http://www.rsc.org/suppdata/cc/b1/
b107732e/ for crystallographic files in .cif or other electronic format.
The molecular structure of 9 was determined by X-ray
crystallography (Fig. 1).§ The porphyrin macrocycle was
lightly saddled13 with a MDPMP (macrocyclic atom mean
deviation from the porphyrin mean plane) of 0.108 Å. The Ni–N
bond lengths averaged 1.965[9] Å, which is longer than in most
reported nickel(II) porphyrin crystal structures.14 The rutheno-
cenyl rings were aligned in an eclipsed orientation, as is
typically observed for this moiety.14 A porphyrin dimer (10)
was also isolated (in 15% yield) along with ruthenocenopor-
phyrin 9 and its structure confirmed by X-ray crystallography
(Fig. 2).¶ The use of a ruthenium(III) complex may account for
the oxidative dimerization leading to the formation of 10.
Similar dimerizations using FeCl3 as the oxidant have been
reported for substituted cyclopentadienides.15 Both macro-
cycles in dimer 10 displayed saddle/ruffle hybrid non-planar
distortions,13 had MDPMPs of 0.375 and 0.315 Å, and average
Ni–N bond lengths of 1.915[13] and 1.913[6] Å.
1 (a) A. C. Benniston, Chem. Soc. Rev., 1996, 25, 427; (b) C. D. Hall, G.
J. Kirkovits, N. K. Diedovic, T. K. U. Truong and J. R. H. Tucker, Pure
Appl. Chem., 1998, 70, 2359.
2 (a) H. Imahori, H. Yamada, Y. Nishimura, I. Yamazaki and Y. Sakata,
J. Phys. Chem. B, 2000, 104, 2099; (b) M. Fujitsuka, O. Ito, H. Imahori,
K. Yamada, H. Yamada and Y. Sakata, Chem. Lett., 1999, 721; (c) M.
Yanagida, T. Kanai, X. Zhang, T. Kondo and K. Uosaki, Bull. Chem.
Soc. Jpn., 1998, 71, 2555.
3 (a) A. K. Burrell, W. M. Campbell, D. L. Officer, S. M. Scott, K. C.
Gordon and M. R. McDonald, J. Chem. Soc., Dalton Trans., 1999, 3349;
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Chem. Soc., Chem. Commun., 1991, 1463; (c) H. Imahori, H. Yamada,
S. Ozawa, K. Ushida and Y. Sakata, Chem. Commun., 1999, 1165; (d)
H. Imahori, H. Norieda, H. Yamada, Y. Nishimura, I. Yamazaki, Y.
Sakata and S. Fukuzumi, J. Am. Chem. Soc., 2001, 123, 100.
4 (a) S. W. Rhee, Y. H. Na, Y. Do and J. Kim, Inorg. Chim. Acta, 2000,
309, 49; (b) S. W. Rhee, B. B. Park, Y. Do and J. Kim, Polyhedron,
2000, 19, 1961.
5 G. B. Maiya, J.-M. Barbe and K. M. Kadish, Inorg. Chem., 1989, 28,
2524.
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1996, 46.
7 K. K. Dailey, G. P. A. Yap, A. L. Rheingold and T. B. Rauchfuss,
Angew. Chem., Int. Ed. Engl., 1996, 35, 1833.
8 L. Jaquinod, in The Porphyrin Handbook, ed. K. M. Kadish, K. M.
Smith and R. Guilard, Academic Press, Boston, MA, 2000, Vol. 1, p
201.
Deprotonation of 8 at 0 °C using LDA followed by addition
of FeCl2 did not produce the desired bisporphyrinatoferrocene,
probably due to the bulkiness of the meso-substituents.
However under the same conditions, 7 produced the air-stable
bisporphyrinatoferrocene 1116 in 30% yield. While the UV–
visible spectrum of 9 displayed a split Soret band and relatively
intense Q bands, that of 11 showed a broad Soret band and no
1
well-defined Q bands. Using variable temperature H NMR
spectroscopy, two distinct conformational processes could be
observed for 11, arising from hindered adjacent meso-phenyls
and ferrocene rotations. The b- and cyclopentadienide protons
of 11 were found upfield-shifted by 0.5–1 ppm relative to those
of 9. The methyl protons on the fused cyclopentadienide ring of
11 appeared at 1.82 ppm, while the methyl protons on the Cp*
ring of ruthenocene 9 gave a singlet at 0.91 ppm. This suggests
a partial overlap of the two porphyrin macrocycles with
staggered meso-phenyl rings.
9 L. Jaquinod, C. Gros, M. M. Olmstead, M. Antolovich and K. M. Smith,
Chem. Commun., 1996, 1475.
10 C. W. Holzapfel and T. L. van der Merwe, Tetrahedron Lett., 1996, 37,
This work was supported by grant CHE-99-04076 from the
US National Science Foundation and grant HL-22252 from the
US National Institutes of Health.
2307.
11 (a) M. M. Catalano, M. J. Crossley, M. M. Harding and L. G. King, J.
Chem. Soc., Chem. Commun., 1984, 1535; (b) K. M. Shea, L. Jaquinod
and K. M. Smith, J. Org. Chem., 1998, 63, 7013.
12 9: UV/Vis (THF): lmax 412 nm (e, 103,000), 450 (77,000), 534
(18,100), 576 (16,100), 640 (18,500). 1H NMR (CDCl3): d 8.57 (d, 2H),
8.47 (s, 2H), 8.48 (d, 2H), 7.81 (m, 8H), 7.67 (t, 2H), 7.64 (t, 2H), 3.90
(s, 2H), 1.75 (s, 3H), 1.45 (s, 72H), 0.91 (s, 15H); MS (LDI-ToF), m/z
1408.0.
Notes and references
‡ Present address: Department of Chemistry, Louisiana State University,
Baton Rouge, LA 70803. E-mail: kmsmith@lsu.edu
§ Crystals of 9 were grown from MeOH–THF–H2O [C90H110N4Ni-
Ru·2(THF), FW = 1551.8]. The selected crystal (0.40 3 0.28 3 0.16 mm)
was monoclinic, space group P21/m, with cell dimensions a = 9.3626(5), b
= 30.748(2), c = 14.5245(8) Å, b = 99.7930(10)°, V = 4120.5(4) Å3, and
Z = 2. Data were collected with w-scans on a Bruker SMART 1000
diffractometer with a sealed tube source [l(Mo-Ka) = 0.71073 Å] at 90(2)
K. Diffraction data were collected to 2q = 63° affording 56880 total
reflections. A 2q cutoff of 55° was applied to give 46122 total, 9601 unique,
and 7078 observed ( > 2s(I)) reflections [Rint = 0.0898, Tmin = 0.837, Tmax
= 0.930, rcalc = 1.251 gcm23, m = 0.464 mm21]. An empirical absorption
correction was applied [SADABS 2.0 (Sheldrick, 2000)]. The structure was
solved by the Patterson method and refined based on F2 using all data by full
matrix least-squares methods with 492 parameters (Bruker SHELXS-97,
13 W. Jentzen, X.-Z. Song and J. A. Shelnutt, J. Phys. Chem. B, 1997, 101,
1684.
14 3D Search and Research Using the Cambridge Structural Database
(April 2001 release), F. H. Allen and O. Kennard, Chemical Design
Automation News, 1993, 8, (1), 31.
15 J. Okuda, E. Herdtweck and E. M. Zeller, Chem. Ber., 1991, 124,
1575.
16 11: UV/Vis (THF): lmax 416 nm (e, 170,000), 530 (broad). No well-
defined Q bands. 1H NMR (CDCl3): d 8.40 (s, 4H), 8.01 (d, 4H), 7.44
(d, 4H), 7.84 (d, 16H), 7.70 (m, 24H), 3.01 (s, 4H), 1.82 (s, 6H); MS
(LDI-ToF), m/z 1499.9.
Chem. Commun., 2001, 2646–2647
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