The porphyrinogen-porphodimethene relationship leading to novel synthetic methodologies focused on the modification and functionalization of the porphyrinogen and porphodimethene skeletons

Article abstract of DOI:10.1021/ja000253s

The general synthetic methods presented in this paper make available, on a preparative scale, unprecedented porphyrinogen-derived skeletons, including their functionalization at the meso positions. The stepwise dealkylation of meso-octaalkylporphyrinogen R₈N₄H₄ [R = Et, 1; R = Bu(n), 2] was chemically, mechanistically, and structurally followed until the formation of porphomethene and porphodimethene derivatives 5-13, obtained with a sequential use of SnCl₄. In particular, the porphodimethene derivative [(Et₆N₄)SnCl₂], 9, was reductively transmetalated using Li metal to Et₆N₄Li₂, 14, subsequently hydrolyzed to Et₆N₄H₂, 15. The porphodimethene-nickel complex [(Et₆N₄)Ni], 16, was used for studying the reactivity and the ligand modification of the porphodimethene skeleton. The reactivity of 16 toward nucleophiles led to otherwise inaccessible meso- substituted-meso-functionalized porphyrinogens [(Et₆N₄R₂)NiLi₂], [R = H, 18; R = Bu(n), 19; R = CH₂CN, 20], thus exemplifying a general methodology to meso-functionalized porphyrinogens. In addition, when [NMe₂]^- was used as the nucleophile, 16 was converted into mono- and bis- vinylideneporphyrinogen derivatives [{Et₄(=CHMe)N₄}NiLi], 21, and [{Et₅(=CHMe)₂N₄}NiLi₂], 22, through the intermediacy of meso- (dimethylamino)-porphyrinogens undergoing an α-H elimination from the meso positions. Such intermediates were isolated and characterized in the stepwise reaction of 14 with LiNMe₂ leading to [{Et₆(NMe₂)₂N₄}Li₄], 23, and [{Et₅(NMe₂)(=CHMe)N₄}Li₄], 25. Both compounds, as a function of the reaction solvent, undergo the thermal elimination of HNMe₂ with the formation of [{Et₄(=CHMe)₂N₄}Li₄], 24, which is then protonated to [{Et₄(=CHMe)₂N₄}H₄], 27. Transmetalation from 23 to 24 can be used as the methodology for the synthesis of a remarkable variety of meso-substituted and functionalized porphyrinogen complexes. The deprotonation of 16 is reversible, therefore 22 and 23 can be protonated back to their starting materials. We took advantage of the nucleophilicity of the vinylidene carbon in 21 and 22 for establishing a general synthetic method to produce meso- functionalized porphodimethenes. This approach was exemplified with the alkylation and the benzoylation of 22 and 21 leading to [{Et₄Pr(i)₂N₄}Ni], 28, [Et₄{CH(Me)(PhCO)}₂N₄Ni], 29, and [Et₅{CH(Me)(PhCO)}N₄Ni], 30, respectively. Complex 21 displays a bifunctional behavior, as shown by the formation of 30, whereas in the reaction with LiBu, led to [{Et₅(Bu(n))(=CHMe)N₄}NiLi₂], 31.

Full text of DOI:10.1021/ja000253s

5312
J. Am. Chem. Soc. 2000, 122, 5312-5326
The Porphyrinogen-Porphodimethene Relationship Leading to Novel
Synthetic Methodologies Focused on the Modification and
Functionalization of the Porphyrinogen and Porphodimethene
Skeletons
Lucia Bonomo,† Euro Solari,† Rosario Scopelliti,† Carlo Floriani,*,† and Nazzareno Re‡
Contribution from the Institut de Chimie Mine´rale et Analytique, BCH, UniVersite´ de Lausanne,
CH-1015 Lausanne, Switzerland, and Facolta` di Farmacia, UniVersita` degli Studi “G. D’Annunzio”,
I-66100 Chieti, Italy
ReceiVed January 24, 2000
Abstract: The general synthetic methods presented in this paper make available, on a preparative scale,
unprecedented porphyrinogen-derived skeletons, including their functionalization at the meso positions. The
stepwise dealkylation of meso-octaalkylporphyrinogen R8N4H4 [R ) Et, 1; R ) Bun, 2] was chemically,
mechanistically, and structurally followed until the formation of porphomethene and porphodimethene derivatives
5-13, obtained with a sequential use of SnCl4. In particular, the porphodimethene derivative [(Et6N4)SnCl2],
9, was reductively transmetalated using Li metal to Et6N4Li2, 14, subsequently hydrolyzed to Et6N4H2, 15.
The porphodimethene-nickel complex [(Et6N4)Ni], 16, was used for studying the reactivity and the ligand
modification of the porphodimethene skeleton. The reactivity of 16 toward nucleophiles led to otherwise
inaccessible meso-substituted-meso-functionalized porphyrinogens [(Et6N4R2)NiLi2], [R ) H, 18; R ) Bun,
19; R ) CH2CN, 20], thus exemplifying a general methodology to meso-functionalized porphyrinogens. In
addition, when [NMe2]- was used as the nucleophile, 16 was converted into mono- and bis-vinylidenepor-
phyrinogen derivatives [{Et4(dCHMe)N4}NiLi], 21, and [{Et5(dCHMe)2N4}NiLi2], 22, through the interme-
diacy of meso-(dimethylamino)-porphyrinogens undergoing an R-H elimination from the meso positions. Such
intermediates were isolated and characterized in the stepwise reaction of 14 with LiNMe2 leading to [{Et6-
(NMe2)2N4}Li4], 23, and [{Et5(NMe2)(dCHMe)N4}Li4], 25. Both compounds, as a function of the reaction
solvent, undergo the thermal elimination of HNMe2 with the formation of [{Et4(dCHMe)2N4}Li4], 24, which
is then protonated to [{Et4(dCHMe)2N4}H4], 27. Transmetalation from 23 to 24 can be used as the methodology
for the synthesis of a remarkable variety of meso-substituted and functionalized porphyrinogen complexes.
The deprotonation of 16 is reversible, therefore 22 and 23 can be protonated back to their starting materials.
We took advantage of the nucleophilicity of the vinylidene carbon in 21 and 22 for establishing a general
synthetic method to produce meso-functionalized porphodimethenes. This approach was exemplified with the
alkylation and the benzoylation of 22 and 21 leading to [{Et4Pri2N4}Ni], 28, [Et4{CH(Me)(PhCO)}2N4Ni], 29,
and [Et5{CH(Me)(PhCO)}N4Ni], 30, respectively. Complex 21 displays a bifunctional behavior, as shown by
the formation of 30, whereas in the reaction with LiBu, led to [{Et5(Bun)(dCHMe)N4}NiLi2], 31.
Introduction
redox2b and acid-base chemistry.3 This paper deals with the
genesis of porphodimethene, the skeleton paving the way from
porphyrinogen to porphyrin,4 and its chemistry, which revealed
the interesting relationship with the porphyrinogen skeleton.
Chart 1 displays the stepwise oxidation of meso-octaalkylpor-
phyrinogen to porphomethene and porphodimethene, which is
formally the four-electron oxidized form of porphyrinogen. The
novelty in the present synthesis of porphodimethene rests in
two major facts: (i) its generation from the porphyrinogen
skeleton using a metal-assisted transformation; and (ii) the large
amount of porphodimethene derivatives produced out of this
Porphyrinogen, namely the meso-tetrahydro-tetraalkyl(aryl)-
porphyrin, a keystone in the scenario of chemically and bio-
logically relevant molecules, still remains a mysterious molecule
due to its instability toward spontaneous autoxidation to por-
phyrin.1 The recent modeling studies performed using the much
more stable meso-octaalkyl derivative2 disclosed, however, a
number of so-far unforeseen but fundamental features of its
* To whom correspondence should be addressed.
† Universite´ de Lausanne.
‡ Universita` degli Studi “G. D’Annunzio”.
(1) (a) Lindsey, J. S. In The Porphyrin Handbook; Kadish, K. M., Smith,
K. M., Guilard, R., Eds.; Academic: Burlington, MA, 1999; Vol. 1, Chapter
2. (b) Kim, J. B.; Adler, A. D.; Longo, F. R. In The Porphyrins; Dolphin,
D., Ed.; Academic: New York, 1978; Vol. I, Chapter 3. (c) Paine, J. B.,
III. In The Porphyrins; Dolphin, D., Ed.; Academic: New York, 1978; Vol.
I, Chapter 4. (d) Scheer, H. In The Porphyrins; Dolphin, D., Ed.;
Academic: New York, 1978; Vol. II, Chapter 1. (e) Scheer, H.; Inhoffen,
H. H. In The Porphyrins; Dolphin, D., Ed.; Academic: New York, 1978;
Vol. II; Chapter 2. (f) Mauzerall, D. In The Porphyrins; Dolphin, D., Ed.;
Academic: New York, 1978; Vol. II; Chapter 3. (g) Smith, K. M.
Porphyrins and Metalloporphyrins; Elsevier: Amsterdam, 1975.
(2) Floriani, C.; Floriani-Moro, R. In The Porphyrin Handbook; Kadish,
K. M., Smith, K. M., Guilard, R., Eds.; Academic: Burlington, MA; 1999;
Vol. 3: (a) Chapter 24 and references therein, (b) Chapter 25 and references
therein.
(3) Bonomo, L.; Solari, E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. J.
Am. Chem. Soc. 1998, 120, 12972.
(4) (a) Mauzerall, D.; Granick, S. J. Biol. Chem. 1958, 232, 1141. (b)
Woodward, R. B. Angew. Chem. 1960, 72, 651. (c) Treibs, A.; Ha¨berle, H.
Justus Liebigs Ann. Chem. 1968, 718, 183. (d) Dolphin, D. J. Heterocycl.
Chem. 1970, 7, 275. (e) Montforts, F.-P.; Gerlach, B.; Ho¨per, F. Chem.
ReV. 1994, 94, 327.
10.1021/ja000253s CCC: $19.00 © 2000 American Chemical Society
Published on Web 05/18/2000

Porphyrinogen-Porphodimethene Relationship
J. Am. Chem. Soc., Vol. 122, No. 22, 2000 5313
Chart 1
Chart 2
methodology. Two less interesting synthetic approaches have
been avoided, namely the reductive alkylation of the porphyrin5
or the stepwise synthesis from dipyrromethane.6 None of these
synthetic approaches would have even a vague relationship with
any natural genesis of the porphodimethene skeleton. In addition,
only small amounts of compounds are available from such syn-
thetic routes.5,6 The reactivity studies carried out on the free or
metal-bonded porphodimethenes revealed the access, via the nu-
cleophilic attack to the meso position, to a variety of unprec-
edented porphyrinogens, including those containing heteroatoms
in the meso positions. Particularly relevant, in this context, was
the formation of meso-bisvinyilidene porphyrinogens. The latter
allowed the establishment of a quite general synthetic methodol-
ogy for acceding to functionalizable porphodimethenes. Partial
preliminary results have been communicated.7
1
of tetrahydrofuran (THF)/n-hexane. H NMR (C6D6, 200 MHz, 298
K, ppm): δ 6.37 (s, 8H, C4H2N); 3.13 (m, 8H, THF); 1.96 (q, J ) 7.4
Hz, 16H, CH2); 1.08 (m, 8H, THF); 0.90 (t, J ) 7.4 Hz, 24H, CH3).
Anal. Calcd for 5, C44H64N4O2Sn: C, 66.08; H, 8.07; N, 7.01. Found:
C, 66.12; H, 8.51; N, 7.04.
A few of the species reported in this paper have some ana-
logues in the literature, though the later species were generated
through convoluted pathways and only in very limited quantities.
They appear more like chemical curiosities than starting ma-
terials appropriate for synthetic purposes. We took care to un-
cover not only the porphyrinogen-porphodimethene relation-
ship, but also to establish a synthetic methodology which makes
available to the users the skeletons listed in Chart 2 and their
derivatives containing functionalities in the meso positions.
Synthesis of 6. SnCl4(THF)2 (17.8 g, 44.0 mmol) was slowly added
to a solution of 4 (50.2 g, 44.0 mmol) in toluene (700 mL). The reaction
mixture was refluxed overnight. The undissolved white solid, LiCl,
was filtered off and the resulting violet solution was evaporated to
dryness. n-Pentane (200 mL) was added to the residue to give a light
violet powder which was collected and dried in vacuo (31.0 g, 69%).
1H NMR (C5D5N, 200 MHz, 298 K): δ 6.43 (s, 8H, C4H2N); 3.67 (m,
8H, THF); 1.66 (t, J ) 6.8 Hz, 16H, CH2); 1.3-0.9 (m, 32H, CH2);
0.77 (t, J ) 7.4 Hz, CH3 overlapping with m, THF, 32H). Anal. Calcd
for 6, C60H96N4O2Sn: C, 70.37; H, 9.45; N, 5.47. Found: C, 69.95; H,
9.33; N, 5.12.
Experimental Section
Synthesis of 7. A solution of SnCl4 (1.0 g, 3.8 mmol) in toluene
(50 mL) was added dropwise at -40 °C to a solution of 5 (12.2 g,
15.2 mmol) in toluene (200 mL). The reaction mixture was warmed to
room temperature, stirred overnight, and heated for 2 h at 80 °C to
complete the reaction. It was evaporated to dryness and the collected
liquid was analyzed with the GC-MS technique. H2SnEt2, HSnEt3,
and SnEt4 were identified. To the solid residue n-hexane (70 mL) was
added to give a red powder which was collected and dried in vacuo
(9.3 g, 61%). Crystals suitable for X-ray diffraction were grown in
All operations were carried out under an atmosphere of purified
nitrogen. All solvents were purified by standard methods and freshly
distilled prior to use. NMR spectra were recorded on a 200-AC or DPX-
400 Bruker instrument; IR spectra were recorded with a Perkin-Elmer
FT 1600 spectrophotometer. GC-MS analyses were carried out using
a Hewlett-Packard 5890A GC system. Elemental analyses were
performed using an EA 1110 CHN elemental analyzer by CE
Instruments. The meso-octaalkylporphyrinogens and their lithium
derivatives were synthesized according to the literature.2a
1
toluene. H NMR (C6D6, 400 MHz, 298 K): δ 7.10 (d, J ) 4.4 Hz,
Synthesis of 5. SnCl4(THF)2 (28.5 g, 70.4 mmol) was added
portionwise to a solution of 3 (60.0 g, 70.4 mmol) in toluene (700
mL). The reaction mixture was refluxed overnight. The undissolved
white solid, LiCl, was filtered off and the resulting pink-violet solution
was evaporated to dryness. n-Hexane (300 mL) was added to the residue
to give a pink powder which was collected and dried in vacuo (40.0 g,
71%). Crystals suitable for X-ray diffraction were grown in a mixture
2H, C4H2N); 6.43 (d, J ) 2.93 Hz, 2H, C4H2N); 6.38 (d, J ) 4.4 Hz,
2H, C4H2N); 6.31 (d, J ) 2.93 Hz, 2H, C4H2N); 3.63 (m, 4H, THF);
3.15 (q, J ) 7.34 Hz, 2H, CH2); 2.70 (q, J ) 7.34 Hz, 2H, CH2); 2.53
(q, J ) 7.34 Hz, 2H, CH2); 2.24 (dq, Jgem ) 14.2 Hz, Jvic ) 7.34 Hz,
2H, CH2); 2.02 (dq, Jgem ) 14.2 Hz, Jvic ) 7.34 Hz, 2H, CH2); 1.95-
1.75 (dq, Jgem ) 14.2 Hz, Jvic ) 7.34 Hz, 2H, CH2 overlapping with
dq, Jgem ) 14.2 Hz, Jvic ) 7.34 Hz, 2H, CH2); 1.5 (m, 4H, THF); 1.33
(t, J ) 7.34 Hz, 3H, CH3); 1.30 (t, J ) 7.34 Hz, 3H, CH3); 0.92 (t, J
) 7.34 Hz, overlapping with t, J ) 7.34 Hz, 9H, CH3); 0.12 (t, J )
7.34 Hz, 6H, CH3). Anal. Calcd for 7, C38H51ClN4OSn: C, 62.18; H,
7.00; N, 7.63. Found: C, 62.12; H, 7.23; N, 7.32.
Synthesis of 8. A solution of SnCl4 (1.9 g, 7.3 mmol) in toluene
(50 mL) was added dropwise at -30 °C to a solution of 6 (30.0 g,
29.3 mmol) in toluene (300 mL). The reaction mixture was warmed to
room temperature and stirred overnight. To complete the reaction, this
dark red solution was heated for 4 h at 80 °C. It was evaporated to
dryness and n-hexane (100 mL) was added to give a red powder which
was collected and dried in vacuo (15.4 g, 56%). 1H NMR (C5D5N, 400
MHz, 298 K): δ 7.84 (d, J ) 4.4 Hz, 2H, C4H2N); 6.99 (d, J ) 4.4
Hz, 2H, C4H2N); 6.51 (d, J ) 2.8 Hz, 2H, C4H2N); 6.27 (d, J ) 2.8
Hz, 2H, C4H2N); 3.63 (m, 4H, THF); 3.35 (t, J ) 6.85 Hz, 2H, CH2);
3.12 (t, J ) 6.85 Hz, 2H, CH2); 2.97 (t, J ) 6.85 Hz, 2H, CH2); 2.6-
(5) (a) Botulinski, A.; Buchler, J. W.; Wicholas, M. Inorg. Chem. 1987,
26, 1540. (b) Buchler, J. W.; Puppe, L. Justus Liebigs Ann. Chem. 1970,
740, 142. (c) Buchler, J. W.; Lay, K. L.; Smith, P. D.; Scheidt, W. R.;
Ruppzecht, G. A.; Kenny, J. E. J. Organomet. Chem. 1976, 110, 109. (d)
Buchler, J. W.; Dreher, C.; Lay, K. L.; Lee, Y. J. A.; Scheidt, W. R. Inorg.
Chem. 1983, 22, 888. (e) Buchler, J. W.; Lay, K. L.; Lee, Y. J. A.; Scheidt,
W. R. Angew. Chem., Int. Ed. Engl. 1982, 21, 432. (f) Dwyer, P. N.; Buchler,
J. W.; Scheidt, W. R. J. Am. Chem. Soc. 1974, 96, 2789. (g) Mauzerall, D.
J. Am. Chem. Soc. 1962, 84, 2437. (h) Renner, M. W.; Buchler, J. W. J.
Phys. Chem. 1995, 99, 8045. (i) Dwyer, P. N.; Puppe, L.; Buchler, J. W.;
Scheidt, W. R. Inorg. Chem. 1975, i, 1782. (j) Botulinski, A.; Buchler, J.
W.; Lee, Y. J. A.; Scheidt, W. R. Inorg. Chem. 1988, 27, 927. (k) Botulinski,
A.; Buchler, J. W.; Tonn, B.; Wicholas, M. Inorg. Chem. 1985, 24, 3239.
(6) Bonomo, L.; Solari, E.; Floriani, C. Unpublished work.
(7) (a) Benech, J.-M.; Bonomo, L.; Solari, E.; Scopelliti, R.; Floriani,
C. Angew. Chem., Int. Ed. Engl. 1999, 38, 1957. (b) Bonomo, L.; Solari,
E.; Scopelliti, R.; Latronico, M.; Floriani, C. Chem. Commun. 1999, 2227.

5314 J. Am. Chem. Soc., Vol. 122, No. 22, 2000
Bonomo et al.
2.2 (m, 4H, CH2); 2.1-1.9 (m, 12H, CH2); 1.9-1.6 (m, 4H, CH2); 1.6
(m, 4H, THF); 1.4-1.0 (m, 16H, CH2); 0.90 (t, J ) 7.3 Hz, 3H, CH3);
0.85-0.60 (t, J ) 7.34 Hz, 3H, CH3 overlapping with t, J ) 7.34 Hz,
6H and t, J ) 7.34 Hz, 3H, CH3); 0.4 (t, J ) 7.34 Hz, 6H, CH3). Anal.
Calcd for 8, C52H79ClN4OSn: C, 67.13; H, 8.56; N, 6.02. Found: C,
67.52; H, 8.62; N, 5.97.
Synthesis of 9. SnCl4(THF)2 (72.8 g, 0.179 mol) was added to a
solution of 5 (47.8 g, 0.06 mol) in toluene (400 mL). The reaction
mixture was refluxed overnight and after cooling, a red crystalline solid
precipitated. This product was collected, washed by extraction with
diethyl ether (500 mL), and then dried in vacuo (21.3 g, 53%). Crystals
suitable for X-ray diffraction were grown in toluene. 1H NMR (C5D5N,
400 MHz, 298 K): δ 7.73 (d, J ) 4.4 Hz, 4H, C4H2N); 6.83 (d, J )
4.4 Hz, 4H, C4H2N); 2.98 (q, J ) 7.32 Hz, 4H, CH2); 2.29 (q, J )
7.32 Hz, 8H, CH2); 1.25 (t, J ) 7.32 Hz, 6H, CH3); 0.93 (t, J ) 7.32
Hz, 12H, CH3). Anal. Calcd for 9, C32H38Cl2N4Sn: C, 57.51; H, 5.73;
N, 8.38. Found: C, 57.41; H, 5.84; N, 7.80.
in a mixture of toluene/n-hexane and contained n-hexane of crystal-
lization. 1H NMR (C5D5N, 400 MHz, 298 K): δ 7.59 (d, J ) 4.4 Hz,
1H, C4H2N); 6.79 (d, J ) 4.4 Hz, 1H, C4H2N); 6.65 (s, 1H, C4H2N);
6.31 (d, J ) 2.93 Hz, 1H, C4H2N); 6.30 (d, J ) 2.93 Hz, 1H, C4H2N);
6.20 (d, J ) 2.93 Hz, 1H, C4H2N); 6.19 (d, J ) 2.93 Hz, 1H, C4H2N);
3.63 (m, 4H, THF); 3.2-3.1 (m, 2H, CH2); 2.78 (m, 2H, CH2); 2.67
(m, 4H, CH2); 2.58 (m, 2H, CH2); 2.48 (m, 2H, CH2); 2.41 (m, 2H,
CH2); 2.34 (m, 2H, CH2); 2.24 (m, 2H, CH2); 1.92 (m, 8H, CH2); 1.83
(m, 4H, CH2 overlapping with m, 4H, THF); 1.54 (m, 2H, CH2). Anal.
Calcd for 13, C40H47ClN4OSn: C, 63.72; H, 6.28; N, 7.43. Found: C,
63.52; H, 6.23; N, 7.32.
Synthesis of 14. Li (0.37 g, 52.8 mmol) and naphthalene (1.0 g, 7.8
mmol) were added under argon to a solution of 9 (8.5 g, 13.2 mmol)
in THF (200 mL). The reaction mixture was stirred overnight and the
metallic residue was filtered off. The resulting orange solution was
evaporated to dryness and benzene (200 mL) was added to remove the
undissolved LiCl. The solution was evaporated to dryness and the
residue washed with n-pentane (100 mL). An orange powder was
collected and dried in vacuo (4.2 g, 50%). Crystals suitable for X-ray
diffraction were grown in a mixture of THF/n-hexane. 1H NMR (C5D5N,
400 MHz, 298 K, ppm): δ 7.41 (d, J ) 4.4 Hz, 4H, C4H2N); 6.67 (d,
J ) 4.4 Hz, 4H, C4H2N); 3.63 (m, 8H, THF); 3.14 (q, J ) 7.32 Hz,
4H, CH2); 2.42 (q, J ) 7.32 Hz, 8H, CH2); 1.59 (m, 8H, THF); 1.44
(t, J ) 7.32 Hz, 6H, CH3); 1.05 (t, J ) 7.32 Hz, 12H, CH3). Anal.
Calcd for 14, C40H54N4Li2O2: C, 75.45; H, 8.55; N, 8.76. Found: C,
74.8; H, 8.48; N, 8.60.
Synthesis of 10. SnCl4(THF)2 (71.5 g, 176 mmol) was added to a
solution of 6 (60.0 g, 58.6 mmol) in toluene (400 mL). The reaction
mixture was refluxed overnight and after cooling, a white solid residue
was filtered off. The solution was evaporated to dryness and n-hexane
(200 mL) was added. The resulting brown solid was collected, dried,
and finally it was redissolved in benzene (200 mL).The white
undissolved solid was filtered off and the solution was evaporated to
dryness. n-Pentane (150 mL) was added to give a dark red-violet product
which was collected and dried in vacuo (27.1 g, 55%). Suitable crystals
1
for X-ray analysis were obtained from a THF-isooctane solution. H
Synthesis of 15. Water (100 mL) was added to a solution of 14
(1.0 g, 1.6 mmol) in diethyl ether (100 mL). After 1 h stirring at room
temperature, the organic phase was removed and the aqueous phase
was washed twice with 100 mL Et2O. Et2O was evaporated to dryness
and the orange residue dissolved in THF (100 mL). The product was
dried by azeotropic distillation, and then the solution was evaporated
to dryness. An orange powder was obtained which was collected and
dried in vacuo (0.52 g, 68%). Crystals suitable for X-ray diffraction
were grown in a mixture of Et2O/n-hexane. 1H NMR (C6D6, 400 MHz,
298 K, ppm): δ 14.86 (s, 2H, NH); 6.90 (d, J ) 4.4 Hz, 4H, C4H2N);
6.35 (d, J ) 4.4 Hz, 4H, C4H2N); 2.56 (q, J ) 7.34 Hz, 4H, CH2 over-
lapping with s broad, 4H, CH2); 2.53 (s broad, 4H, CH2); 1.01 (t, J )
7.34 Hz, 18H, CH3). 1H NMR (C7D8, 400 MHz, 310 K, ppm): δ 14.97
(s, 2H, NH); 7.01 (d, J ) 4.4 Hz, 4H, C4H2N); 6.34 (d, J ) 4.4 Hz,
4H, C4H2N); 2.63 (q, J ) 7.34 Hz, 4H, CH2); 2.51 (q, J ) 7.34 Hz,
8H, CH2); 1.03 (t, J ) 7.34 Hz, 6H, CH3); 0.99 (t, J ) 7.34 Hz, 12H,
CH3). 1H NMR (C7D8, 400 MHz, 263 K, ppm): δ 14.65 (s, 2H, NH);
6.78 (d, J ) 4.4 Hz, 4H, C4H2N); 6.37 (d, J ) 4.4 Hz, 4H, C4H2N);
2.62 (q, J ) 7.34 Hz, 4H, CH2); 2.55 (q, J ) 7.34 Hz, 4H, CH2); 2.50
(q, J ) 7.34 Hz, 4H, CH2); 1.02 (t, J ) 7.34 Hz, 6H, CH3); 1.0 (t, J
) 7.34 Hz, 6H, CH3); 0.97 (t, J ) 7.34. Hz, 6H, CH3). Anal. Calcd for
15, C32H40N4: C, 79.96; H, 8.39; N, 11.65. Found: C, 79.8; H, 8.03;
N, 11.53.
NMR (C5D5N, 400 MHz, 298 K): δ 7.94 (d, J ) 4.4 Hz, 4H, C4H2N);
7.08 (d, J ) 4.4 Hz, 4H, C4H2N); 3.02 (t, J ) 7.8 Hz, 4H, CH2); 2.33
(t, J ) 8.3 Hz, 8H, CH2); 1.52 (m, 4H, CH2); 1.45 (m, 8H, CH2); 1.15
(m, 4H, CH2); 1.07 (m, 8H, CH2); 0.59 (t, J ) 7.34 Hz, 6H, CH3);
1
0.52 (t, J ) 7.34 Hz, 12H, CH3). H NMR (CD2Cl2, 400 MHz, 308
K): δ 7.60 (d, J ) 4.4 Hz, 4H, C4H2N); 6.69 (d, J ) 4.4 Hz, 4H,
C4H2N); 3.12 (t, J ) 7.8 Hz, 4H, CH2); 2.21 (t, J ) 8.8 Hz, 8H, CH2);
1.88 (m, 4H, CH2); 1.56 (m, 4H, CH2); 1.22 (m, 8H, CH2); 1.17 (m,
8H, CH2); 0.59 (t, J ) 7.34 Hz, 6H, CH3); 0.52 (t, J ) 7.34 Hz, 12H,
1
CH3). H NMR (CD2Cl2, 400 MHz, 263 K): δ 7.69 (d, J ) 4.4 Hz,
4H, C4H2N); 7.53 (d, J ) 4.4 Hz, 4H, C4H2N); 6.77 (d, J ) 4.4 Hz,
4H, C4H2N); 6.62 (d, J ) 4.4 Hz, 4H, C4H2N); 3.08 (t, J ) 7.8 Hz,
4H, CH2 overlapping with t, J ) 7.8 Hz, 4H, CH2); 2.24 (t, J ) 8.8
Hz, 4H, CH2); 2.14 (t, J ) 8.8 Hz, 8H, CH2 overlapping with m, 4H,
CH2); 1.83 (m, 4H, CH2); 1.78 (m, 4H, CH2); 1.51 (m, 4H, CH2
overlapping with m, 4H, CH2); 1.30 (m, 4H, CH2); 1.15 (m, 8H, CH2);
1.13 (m, 4H, CH2); 1.07 (m, 8H, CH2); 0.97 (t, J ) 7.34 Hz, 6H, CH3,
overlapping m, 4H, CH2); 0.97 (m, 4H, CH2); 0.82 (t, J ) 7.34 Hz,
6H, CH3); 0.74 (t, J ) 7.34 Hz, 12H, CH3 overlapping with t, J )
7.34 Hz, 6H, CH3); 0.70 (t, J ) 7.34 Hz, 6H, CH3). Anal. Calcd for
10, C44H62N4SnCl2: C, 63.17; H, 7.47; N, 6.70. Found: C, 64.42; H,
6.17; N, 6.78.
Synthesis of 11. SnCl4(THF)2 (19.2 g, 47.3 mmol) was slowly added
to a solution of [{(CH2CH2)2}4N4Li4 (THF)2] (40.0 g, 47.3 mmol) in
toluene (700 mL). The reaction mixture was refluxed overnight. The
undissolved white solid, LiCl, was filtered off and the resulting pink
solution was evaporated to dryness. n-Pentane (200 mL) was added to
the residue to give a light pink powder which was collected and dried
in vacuo (29.0 g, 77%). 1H NMR (C6D6, 400 MHz, 298 K): δ 6.41 (s,
8H, C4H2N); 3.54 (m, 8H, THF); 1.85 (m, 16H, CH2); 1.63 (m, 16H,
CH2); 1.41 (m, THF, 8H). Anal. Calcd for 11, C60H96N4O2Sn: C, 66.77;
H, 7.13; N, 7.08. Found: C, 66.91; H, 7.31; N, 7.12.
Synthesis of 13. SnCl4 (52.8 mL, 0.17 M in toluene, 8.96 mmol)
was added dropwise at -40 °C to a solution of 11 (7.1 g, 8.97 mmol)
in toluene (200 mL). The reaction mixture was warmed to room
temperature and stirred overnight. A yellow-brown solid precipitated
which was collected and dried in vacuo. Elemental analysis was
consistent with the adduct 12. Anal. Calcd for 12, C40H48Cl4N4OSn2:
C, 49.02; H, 4.94; N, 5.72. Found: C, 48.74; H, 4.72; N, 5.51. This
product was then suspended in toluene (200 mL) and refluxed for 24
h. The reaction mixture became red-violet. A white precipitate was
filtered off and the solution was evaporated to dryness. n-Hexane (100
mL) was added to give a red powder which was collected and dried in
vacuo (5.2 g, 77%). Crystals suitable for X-ray diffraction were grown
Synthesis of 16. [NiCl2(DME)] (1.03 g, 4.69 mmol) was added to
a solution of 14 (3.04 g, 4.69 mmol) in THF (200 mL). The red solution
obtained was stirred overnight at room temperature. The solvent was
evaporated and benzene (200 mL) allowed to dissolved the residue.
LiCl was removed by filtration. The solution was evaporated to dryness
and the residue triturated with n-pentane (100 mL) to give a red-violet
1
powder which was collected and dried in vacuo (2.1 g, 76.6%). H
NMR (C6D6, 400 MHz, 298 K, ppm): δ 7.07 (d, J ) 4.4 Hz, 4H,
C4H2N); 6.30 (d, J ) 4.4 Hz, 4H, C4H2N); 3.44 (s broad, 4H, CH2);
2.65 (q, J ) 7.34 Hz, 4H, CH2); 1.96 (s broad, 4H, CH2); 1.07 (m,
1
18H, CH3). H NMR (C6D6, 400 MHz, 318 K, ppm): δ 7.13 (d, J )
4.4 Hz, 4H, C4H2N); 6.24 (d, J ) 4.4 Hz, 4H, C4H2N); 2.95 (q, J )
7.34 Hz, 4H, CH2); 2.45 (q, J ) 7.34 Hz, 8H, CH2); 1.20 (t, J ) 7.34
Hz, 6H, CH3); 1.04 (t, J ) 7.34 Hz, 12H, CH3). Anal. Calcd for 16,
C32H38N4Ni: C, 71.52; H, 7.13; N, 10.43. Found: C, 71.49; H, 7.15;
N, 10.6.
Synthesis of 17. Activated magnesium (0.73 g, 30.0 mmol) was
added to 9 (10 g, 15.0 mmol) in THF (300 mL). The red mixture was
stirred at room temperature for 24 h until it became violet. The metallic
residue was filtered off. The red solution was evaporated to dryness.
The residue was dissolved in 150 mL of dichloromethane and the
solution was evaporated to dryness. Upon a further addition of

Porphyrinogen-Porphodimethene Relationship
J. Am. Chem. Soc., Vol. 122, No. 22, 2000 5315
dichloromethane (150 mL), a white solid precipitated which was filtered
off. The solution was then evaporated to dryness and n-pentane was
added to give an orange powder which was collected and dried in vacuo
(6.5 g, 67%). Crystals suitable for X-ray diffraction were grown in a
mixture of THF/n-hexane. 1H NMR (C5D5N, 200 MHz, 298 K, ppm):
δ 7.61 (d, J ) 4.4 Hz, 4H, C4H2N); 6.58 (d, J ) 4.4 Hz, 4H, C4H2N);
3.67 (m, 8H, THF); 3.33 (q, J ) 7.4 Hz, 4H, CH2); 1.98 (q, J ) 7.4
Hz, 8H, CH2); 1.98 (t, J ) 7.4 Hz, 6H, CH3 + m, 8H, THF); 0.18 (t,
J ) 7.4 Hz, 12H, CH3). Anal. Calcd for 17, C40H54N4MgO2: C, 74.23;
H, 8.41; N, 8.66. Found: C, 74.8; H, 8.23; N, 8.53.
3.34 (s, 2H, CH2CN); 2.72 (q, J ) 7.34 Hz, 2H, CH2); 2.45 (q, J )
7.34 Hz, 4H, CH2); 1.64 (m, 16H, THF); 1.45 (t, J ) 7.34 Hz, 3H,
CH3); 1.40 (t, J ) 7.34 Hz, 6H, CH3); 1.10 (t, J ) 7.34 Hz, 6H, CH3);
1.01 (t, J ) 7.34 Hz, 3H, CH3).
Synthesis of 21. To a solution of 16 (4.0 g, 7.59 mmol) in THF
(200 mL) a solution of LiNMe2 (0.39 g, 7.59 mmol) in THF (100 mL)
was dropwise added at T ) 0 °C. The reaction mixture was warmed to
room temperature and stirred for 2 h. The solution was evaporated to
dryness. The red solid was collected with n-hexane (100 mL) and dried
in vacuo (4.28 g, 82%). 1H NMR (C5D5N, 400 MHz, 298 K, ppm): δ
7.09 (d, J ) 4.4 Hz, 1H, C4H2N); 7.07 (d, J ) 4.4 Hz, 1H, C4H2N);
6.57 (d, J ) 2.93 Hz, 1H, C4H2N); 6.54 (d, J ) 2.93 Hz, 1H, C4H2N);
6.41 (d, J ) 4.4 Hz, 1H, C4H2N); 6.38 (d, J ) 2.93 Hz, 1H, C4H2N
overlapping with d, J ) 4.4 Hz, 1H, C4H2N); 6.28 (d, J ) 2.93 Hz,
1H, C4H2N); 6.03 (q, J ) 6.85 Hz, 1H, CH); 3.86 (m, 8H, THF); 2.7
(q, J ) 7.3 Hz, 2H, CH2); 2.32-2.28 (m, 8H, CH2); 2.14 (d, J ) 6.85
Hz, 3H, CH3); 1.61 (m, 8H, THF); 1.30 (t, J ) 7.34 Hz, 3H, CH3);
1.28 (t, J ) 7.34 Hz, 3H, CH3); 1.18 (t, J ) 7.34 Hz, 3H, CH3); 1.10
(t, J ) 7.34 Hz, 3H, CH3); 1.07 (t, J ) 7.34 Hz, 3H, CH3). Anal.
Calcd for 21, C40H53LiN4NiO2: C, 69.88; H, 7.77; N, 8.15. Found: C,
69.93; H, 8.12; N, 7.97. Reprotonation of 21 with 1 eq of PyHCl in
toluene at room temperature gave 16.
Synthesis of 22. Method A. LiNMe2 (0.74 g, 14.4 mmol) was added
in one portion at room temperature to a stirred solution of 16 (3.8 g,
7.22 mmol) in THF (250 mL). The reaction was monitored by NMR
and the mixture was stirred until the product 21 was entirely converted
(≈ 60 h). The solution was evaporated to dryness. The violet solid
was collected with n-hexane (100 mL) and dried in vacuo (4.28 g,
71%). Crystals suitable for X-ray diffraction were grown in DME and
the X-ray analysis was carried out on the solvated form [{Et4(d
CHMe)2}Ni][Li(DME)3]2. 1H NMR for the two isomers of 22 (C5D5N,
400 MHz, 298 K, ppm): δ 6.55 (m, 8H, C4H2N); 6.39 (d, J ) 3.2 Hz,
2H, C4H2N); 6.38 (d, J ) 3.2 Hz, 2H, C4H2N); 6.26 (d, J ) 2.8 Hz,
2H, C4H2N); 6.25 (d, J ) 2.8 Hz, 2H, C4H2N); 5.87 (q, J ) 6.85 Hz,
2H, CH); 5.86 (q, J ) 6.85 Hz, 2H, CH); 4.25-3.75 (m, 8H, CH2);
3.58 (m, 32H, THF); 2.5 (m, 8H, CH2); 2.18 (d, J ) 6.85 Hz, 6H, CH3
overlapping with d, J ) 6.85 Hz, 6H, CH3); 1.68 (m, 32H, THF); 1.5
(m, 12H, CH3); 1.19 (t, J ) 7.6 Hz, 12H, CH3). Anal. Calcd for 22,
C48H68Li2N4NiO4: C, 68.8; H, 8.18; N, 6.69. Found: C, 68.54; H, 8.02;
N, 6.83. Reprotonation of 22 with 1 eq of PyHCl in toluene at room
temperature gave 21. Reprotonation of 22 with 2 eq of PyHCl in toluene
at room temperature gave 16.
Synthesis of 18. LiHBEt3 (7.58 mL, 1.0 M in THF, 7.58 mmol)
was added at room temperature to a solution of 16 (2.0 g, 3.79 mmol)
in THF (100 mL). The reaction mixture turned immediately violet, was
stirred overnight, and then was evaporated to dryness. The pink solid
residue was collected with Et2O (60 mL) and dried in vacuo (2.3 g,
1
72%). Analysis H NMR of reaction mixture and collected product
showed that a mixture of syn and anti isomers in a 1:4 ratio was formed.
1H NMR (C5D5N, 400 MHz, 298 K, ppm): δ 6.25 (d, J ) 2.9 Hz, 8H,
C4H2N); 6.24 (d, J ) 2.9 Hz, 4H, C4H2N); 6.23 (d, J ) 2.9 Hz, 8H,
C4H2N); 6.21 (d, J ) 2.9 Hz, C4H2N overlapping with d, J ) 2.9 Hz,
C4H2N, 12H); 6.19 (d, J ) 2.9 Hz, 8H, C4H2N); 4.94 (t, J ) 5.87 Hz,
4H, Hendo); 4.59 (t, J ) 5.87 Hz, 2H, Hendo); 4.09 (t, J ) 7.34 Hz, 4H,
Hexo); 3.69 (dq, Jgem ) 14.2 Hz, Jvic ) 7.34 Hz, 8H, CH2); 3.60 (dq,
Jgem ) 14.2 Hz, Jvic ) 7.34 Hz, 8H, CH2 overlapping with m, 80H,
THF and q, J ) 7.34 Hz, 4H, CH2); 3.28 (q, J ) 7.34 Hz, 4H, CH2);
2.95 (m, 8H, CH2); 2.6-2.45 (m, 28H, CH2); 1.61 (m, 80H, THF);
1.49 (t, J ) 7.34 Hz, 12H, CH3); 1.47 (t, J ) 7.34 Hz, 24H, CH3
overlapping with t, J ) 7.34 Hz, 6H, CH3); 1.43 (t, J ) 7.34 Hz, 6H,
CH3); 1.16 (t, J ) 7.34 Hz, 24H, CH3 overlapping with t, J ) 7.34 Hz,
6H, CH3); 1.10 (t, J ) 7.34 Hz, 12H, CH3). Anal. Calcd for 18,
C48H72N4Li2NiO4: C, 68.5; H, 8.62; N, 6.66. Found: C, 68.37; H, 8.53;
N, 6.24.
Synthesis of 19. BunLi (4.17 mL, 1.63 M in THF, 6.8 mmol) was
added at room temperature to a solution of 16 (1.78 g, 3.4 mmol) in
THF (100 mL). A light yellow solution was obtained which was stirred
overnight and evaporated to dryness. Et2O (60 mL) was added to give
a yellow solid which was collected and dried in vacuo (2.43 g, 74%).
1
Analysis H NMR of reaction mixture and collected product showed
1
that the syn isomer only was formed. H NMR (C5D5N, 400 MHz,
298 K, ppm): δ 6.25 (d, J ) 2.9 Hz, 4H, C4H2N); 6.23 (d, J ) 2.9 Hz,
4H, C4H2N); 3.79 (t, J ) 7.8 Hz, 4H, CH2); 3.66 (m, 16H, THF); 2.57
(q, J ) 7.34 Hz, 4H, CH2); 2.50 (q, J ) 7.34 Hz, 4H, CH2); 1.64 (m,
4H, CH2 overlapping with m, 16H, THF); 1.50 (t, J ) 7.34 Hz, 6H,
CH3 overlapping with m, 4H, CH2); 1.46 (t, J ) 7.34 Hz, 6H, CH3);
1.21 (m, 4H, CH2); 1.08 (t, J ) 7.34 Hz, 6H, CH3); 0.61 (t, J ) 7.34
Hz, 6H, CH3). Anal. Calcd for 19, C56H88Li2N4NiO4: C, 70.51; H, 9.30;
N, 5.87. Found: C, 70.62; H, 9.27; N, 5.55. The crystals used for the
X-ray analysis contain only 3 THF per molecule.
Synthesis of 20. Complex 16 (2.91 g, 5.52 mmol) was added at
room temperature to a solution of LiCH2CN (11.04 mmol) in THF (300
mL). The reaction mixture was stirred for 2 h and then was evaporated
to dryness. The pink solid residue was collected with n-hexane and
dried in vacuo (3.82 g, 75%). Anal. Calcd for 20, C52H74Li2N6NiO4:
C, 67.91; H, 8.11; N, 9.14. Found: C, 68.12; H, 8.06; N, 8.99. Analysis
1H NMR of reaction mixture and collected product showed that the
syn isomer only was formed. 1H NMR (C5D5N, 400 MHz, 298 K,
ppm): δ 6.29 (d, J ) 2.4 Hz, 4H, C4H2N); 6.23 (d, J ) 2.4 Hz, 4H,
C4H2N); 4.63 (s, 4H, CH2CN); 3.66 (m, 16H, THF); 3.61 (q, J ) 7.3
Hz, 4H, CH2); 2.72 (q, J ) 7.3 Hz, 4H, CH2); 2.45 (q, J ) 7.3 Hz, 4H,
CH2); 1.64 (m, 16H, THF); 1.45 (t, J ) 7.3 Hz, 6H, CH3); 1.40 (t, J
Synthesis of 22. Method B. LiNMe2 (0.33 g, 6.54 mmol) was added
in one portion at room temperature to a stirred solution of 21 (4.5 g,
6.54 mmol) in THF (250 mL). 1H NMR spectrum of reaction mixture
showed the meso-vinylidene-dimethylamino derivative to be present.
1H NMR (C5D5N, 400 MHz, 298 K, ppm): δ 6.35 (d, J ) 3.4 Hz, 1H,
C4H2N); 6.34 (d, J ) 2.9 Hz, 1H, C4H2N); 6.32 (d, J ) 2.9 Hz, 1H,
C4H2N); 6.31 (d, J ) 2.9 Hz, 1H, C4H2N); 6.29 (d, J ) 3.4 Hz, 1H,
C4H2N); 6.27 (d, J ) 3.4 Hz, 1H, C4H2N); 6.25 (d, J ) 3.4 Hz, 1H,
C4H2N); 6.11 (d, J ) 2.9 Hz, 1H, C4H2N); 5.34 (q, J ) 7.3 Hz, 1H,
CH); 4.1 (dq, Jgem ) 14.2 Hz, Jvic ) 7.3 Hz, 1H, CH2); 3.9 (dq, Jgem
14.2 Hz, Jvic ) 7.3 Hz, 1H, CH2); 3.66 (m, 8H, THF); 3.41 (dq, Jgem
) 14.2 Hz, Jvic ) 7.3 Hz, 1H, CH2); 3.33 (dq, Jgem ) 14.2 Hz, Jvic
)
)
7.3 Hz, 1H, CH2); 2.5 (m, 4H, CH2); 2.31 (q, J ) 7.3 Hz, 2H, CH2);
2.28 (s broad, 6H, N(CH3)2); 1.75 (d, J ) 7.3 Hz, 3H, CH3); 1.65 (m,
8H, THF); 1.41 (t, J ) 7.3 Hz, 6H, CH3); 1.2 (t, J ) 7.3 Hz, 3H,
CH3); 1.1 (t, J ) 7.3 Hz, 3H, CH3); 1.05 (t, J ) 7.3 Hz, 3H, CH3). The
reaction mixture was stirred for 60 h until only 22 was present. The
solution was then evaporated to dryness and the violet solid was
collected with n-hexane (100 mL) and dried in vacuo (4.34 g, 79%).
Anal. Calcd for 22, C48H68Li2N4NiO4: C, 68.8; H, 8.18; N, 6.69.
Found: C, 69.12; H, 8.32; N, 6.45.
) 7.3 Hz, 6H, CH3); 1.07 (t, J ) 7.3 Hz, 6H, CH3). IR (Nujol νmax
/
cm-1): 2256 (s). The X-ray analysis was performed on the solvated
form of 20, namely [{Et6(CH2CN)2N4}Ni][Li(DME)2]2 recrystallized
slowly at low temperature from 1,2-dimethoxyethane (DME), and it
showed to be the anti isomer. After 1 week in deuterated pyridine, all
Synthesis of 23. A solution of LiNMe2 (0.32 g, 6.28 mmol) in THF
(50 mL) was added dropwise at room temperature to a solution of 14
(2.0 g, 3.14 mmol) in THF (100 mL). The reaction mixture was stirred
for 2 h and then was evaporated to dryness. The solid residue was
triturated with n-hexane to give a light pink powder which was collected
and dried in vacuo (2.03 g, 73%). Crystals suitable for X-ray diffraction
were grown in a mixture of THF/n-hexane. 1H NMR (C5D5N, 400 MHz,
298 K, ppm): δ 6.46 (d, J ) 2.4 Hz, 4H, C4H2N); 6.27 (d, J ) 2.4 Hz,
1
the product was converted in the anti isomer. H NMR (C5D5N, 400
MHz, 298 K, ppm): δ 6.35 (d, J ) 2.9 Hz, 2H, C4H2N); 6.27 (d, J )
2.9 Hz, 2H, C4H2N); 6.24-6.22 (d, J ) 2.9 Hz, 2H, C4H2N overlapping
with d, J ) 2.9 Hz, 2H, C4H2N); 4.86 (s, 2H, CH2CN); 3.75 (dq, Jgem
) 14.2 Hz, Jvic ) 7.3 Hz, 2H, CH2); 3.66 (m, 4H, CH2 overlapping
with m, 16H, THF); 3.61 (dq, Jgem ) 14.2 Hz, Jvic ) 7.3 Hz, 2H, CH2);

5316 J. Am. Chem. Soc., Vol. 122, No. 22, 2000
Bonomo et al.
4H, C4H2N); 3.70 (m, 16H, THF); 3.25 (q, J ) 7.3 Hz, 4H, CH2); 2.99
(q, J ) 7.3 Hz, 4H, CH2); 2.17 (q, J ) 7.3 Hz, 4H, CH2); 1.93 (s, 12H,
CH3); 1.62 (m, 16H, THF overlapping with t, J ) 7.3 Hz, 6H, CH3);
1.05 (t, J ) 7.3 Hz, 6H, CH3); 0.83 (t, J ) 7.3 Hz, 6H, CH3). Anal.
Calcd for 23, C52H82Li4N6O4: C, 70.73; H, 9.36; N, 9.52. Found: C,
70.62; H, 9.17; N, 9.35. Hydrolysis gave 15.
Hz, 12H, CH3). Anal. Calcd for 26, C48H77Li3N4O8: C, 67.12; H, 9.03;
N, 6.52. Found: C, 67.28; H, 9.15; N, 6.74.
Synthesis of 27. H2O (1.0 mL) was added to a solution of 24 (5.0,
7.71 mmol) in benzene (100 mL). The reaction mixture was stirred at
room temperature for 1 h and the LiOH precipitate was filtered off.
The solution was evaporated to dryness and benzene (100 mL) was
added again, completely eliminating LiOH. The solvent was evaporated
and pentane (50 mL) was added to give a light yellow microcrystalline
solid which was collected and dried in vacuo (2.5 g, 67%). Crystals
suitable for X-ray diffraction were obtained in n-heptane. 1H NMR of
the 1:1 mixture of the two isomers (C6D6, 400 MHz, 298 K, ppm): δ
9.43 (s broad, 4H, NH); 9.32 (s broad, 2H, NH); 9.17 (s broad, 2H,
NH); 6.39 (t, J ) 2.93 Hz, 2H, C4H2N); 6.36 (t, J ) 2.93 Hz, 2H,
C4H2N); 6.25 (t, J ) 2.93 Hz, 2H, C4H2N); 6.20 (t, J ) 2.93 Hz, 2H,
C4H2N); 6.10 (t, J ) 2.93 Hz, 2H, C4H2N); 6.08-6.05 (t, J ) 2.93 Hz,
2H, C4H2N overlapping with t, J ) 2.93 Hz, 2H, C4H2N); 6.04 (t, J )
2.93 Hz, 2H, C4H2N); 6.00 (q, J ) 7.34 Hz, 2H, CH); 5.94 (q, J )
7.34 Hz, 2H, CH); 1.87 (d, J ) 7.34 Hz, 6H, CH3); 1.82 (d, J ) 7.34
Hz, 6H, CH3 overlapping with m, 16H, CH2); 0.72-0.66 (t, J ) 7.34
Hz, 12H, CH3 overlapping t, J ) 7.34 Hz, 6H, CH3 and t, J ) 7.34
Hz, 6H, CH3). Anal. Calcd for 27, C32H40N4: C, 79.96; H, 8.39; N,
11.65. Found: C, 79.42; H, 8.02; N, 11.33.
Synthesis of 24. LiNMe2 (0.63 g, 12.3 mmol) was added at room
temperature to a solution of 14 (3.93 g, 6.15 mmol) in benzene (300
1
mL). After 1 h, H NMR showed that 14 was entirely converted into
23. The reaction mixture was then refluxed for 12 h and was then
evaporated to dryness. The light yellow solid residue was collected
with n-pentane (60 mL) and dried in vacuo (2.8 g, 70%). Anal. Calcd
for 24, C40H52Li4N4O2: C, 74.07; H, 8.08; N, 8.64. Found: C, 74.33;
1
H, 8.13; N, 8.45. H NMR for the two isomers of 24 (C5D5N, 400
MHz, 298 K, ppm): δ 6.91 (d, J ) 2.45 Hz, 2H, C4H2N); 6.86 (d, J
) 2.45 Hz, 2H, C4H2N); 6.74 (d, J ) 2.45 Hz, 2H, C4H2N); 6.69 (d,
J ) 2.45 Hz, 2H, C4H2N); 6.47 (d, J ) 2.45 Hz, 2H, C4H2N overlapping
with d, J ) 2.4 Hz, 2H, C4H2N); 6.36 (d, J ) 2.45 Hz, 2H, C4H2N
overlapping with d, J ) 2.4 Hz, 2H, C4H2N); 5.95 (q, J ) 6.85 Hz,
2H, CH); 5.88 (q, J ) 6.85 Hz, 2H, CH); 3.70 (m, 16H, THF); 2.4-
2.2 (m, 16H, CH2); 2.15 (d, J ) 6.85 Hz, 6H, CH3 overlapping with d,
J ) 6.85 Hz, 6H, CH3); 1.62 (m, 16H, THF); 1.00 (m, 24H, CH3).
Anal. Calcd for 23, C52H82Li4N6O4: C, 70.73; H, 9.36; N, 9.52.
Found: C, 70.62; H, 9.17; N, 9.35. The X-ray analysis was performed
on the polymeric form, [Et4(dCHMe)2N4Li4(dioxane)3.5]n‚dioxane‚C6H6,
obtained from dioxane/C6H6.
Synthesis of 28. A solution of 22 (1.78 g, 2.32 mmol) in THF
(150°mL) was added dropwise at 0 °C to a solution of MeI (0.66 g,
4.65 mmol) in THF (150 mL). The reaction mixture was then warmed
to room temperature and stirred overnight. The red-orange solution was
evaporated to dryness and benzene (100 mL) was added. The white
undissolved solid was filtered off and the solvent evaporated. n-Pentane
(50 mL) was added to give a red-violet solid which was collected and
dried in vacuo (0.9 g, 68%). 1H NMR (C5D5N, 400 MHz, 298 K,
ppm): δ 7.21 (d, J ) 4.4 Hz, 4H, C4H2N); 6.39 (d, J ) 4.4 Hz, 4H,
C4H2N); 3.50 (q, J ) 7.34 Hz, 2H, CH); 3.42 (q, J ) 7.34 Hz, 4H,
CH2); 2.08 (q, J ) 7.34 Hz, 4H, CH2); 1.33 (d, J ) 7.34 Hz, 12H,
CH3); 1.05 (t, J ) 7.34 Hz, 12H, CH3). Anal. Calcd for 28, C34H42N4-
Ni: C, 72.22; H, 7.49; N, 9.91. Found: C, 72.43; H, 7.63; N, 9.34.
Synthesis of 29. PhCOCl (1.68 g, 11.9 mmol) was added at room
temperature to a solution of 24 (5.0 g, 5.95 mmol) in THF (300 mL).
The reaction mixture was stirred overnight and then evaporated to
dryness. Benzene (100 mL) was added and the white undissolved solid
was filtered off. The solvent was evaporated and n-pentane (50 mL)
was added to give a bright red solid which was collected and dried in
vacuo (3.7 g, 83%). Anal. Calcd for 29, C44H46N4NiO2: C, 74.10; H,
6.22; N, 7.51. Found: C, 74.34; H, 6.42; N, 7.24. ν(C-O) (Nujol),
1684 cm-1. 1H NMR spectrum for the two isomers of 29 (C5D5N, 400
MHz, 298 K, ppm): δ 8.33 (d, J ) 7.34 Hz, 2H, ArH); 8.31 (d, J )
7.34 Hz, 2H, ArH); 7.70 (s broad, 4H, C4H2N); 7.33 (t, J ) 7.34 Hz,
2H, ArH); 7.26 (t, J ) 7.34 Hz, 2H, ArH); 7.12 (m, 4H, ArH); 7.05
(m, 4H, ArH); 6.59 (m, 4H, ArH); 5.14 (q, J ) 6.85 Hz, 2H, CH);
5.10 (q, J ) 6.85 Hz, 2H, CH); 3.5-3.2 (s broad, 16H, CH2); 1.71 (d,
J ) 6.85 Hz, 6H, CH3); 0.98 (s broad, 12H, CH3); 0.90 (s broad, 12H,
Synthesis of 25. Method A. LiNMe2 (0.21 g, 4.12 mmol) was added
at room temperature to a solution of 14 (1.31 g, 2.06 mmol) in THF
1
(150 mL). After 1 h, H NMR showed that 14 was entirely converted
into 23. The reaction mixture was then refluxed for 12 h and evaporated
to dryness. The solid residue was dissolved in n-pentane (100 mL)
and DME was added dropwise until a yellow microcrystalline solid
precipitated. The product was then collected and dried in vacuo (2.0 g,
60%). Crystals suitable for X-ray diffraction were obtained in a mixture
of DME/n-heptane and have a different solvation, namely [Et5-
(NMe2)(dCHMe)N4Li4(DME)3]. 1H NMR (C5D5N, 400 MHz, 298 K,
ppm): δ 6.54 (d, J ) 2.9 Hz, 1H, C4H2N); 6.52 (d, J ) 2.9 Hz, 1H,
C4H2N); 6.45 (m, 3H, C4H2N); 6.42 (d, J ) 2.9 Hz, 1H, C4H2N); 6.39
(d, J ) 2.9 Hz, 1H, C4H2N); 6.30 (d, J ) 2.9 Hz, 1H, C4H2N); 5.41 (q,
J ) 7.3 Hz, 1H, CH); 3.49 (s, 48H, DME); 3.26 (s, 72H, DME); 2.9-
2.68 (m, 2H, CH2); 2.62 (m, 1H, CH2); 2.57-2.33 (m, 4H, CH2); 2.30
(m, 1H, CH2); 2.26 (q, J ) 7.3 Hz, 2H, CH2); 2.02 (s, 3H, CH3); 1.99
(s, 3H, CH3); 1.75 (d, J ) 7.3 Hz, 3H, CH3); 1.33 (t, J ) 7.3 Hz, 3H,
CH3 overlapping with t, J ) 7.3 Hz, 3H, CH3); 1.19 (t, J ) 7.3 Hz,
3H, CH3); 0.77 (t, J ) 7.3 Hz, 3H, CH3 overlapping with t, J ) 7.3
Hz, 3H, CH3). Anal. Calcd for 25, C82H163Li4N5O24: C, 60.39; H, 10.07;
N, 4.29. Found: C, 60.32; H, 10.13; N, 4.34. Refluxing in benzene
gave 24.
Synthesis of 25. Method B. LiNMe2 (0.10 g, 1.96 mmol) was added
at room temperature to a solution of 26 (1.68 g, 1.96 mmol) in DME
1
1
(100 mL). After 1 h stirring, H NMR showed that 26 was entirely
CH3). H NMR (C5D5N, 400 MHz, 353 K, ppm): δ 8.22 (d, J ) 7.34
converted into 25. The reaction mixture was concentrated and n-pentane
(100 mL) was added to give 25, which was collected and dried in vacuo
(1.82 g, 57%).
Hz, 2H, ArH); 8.20 (d, J ) 7.34 Hz, 2H, ArH); 7.43 (d, J ) 4.4 Hz,
4H, C4H2N); 7.42 (d, J ) 4.4 Hz, 4H, C4H2N); 7.36 (t, J ) 7.34 Hz,
2H, ArH); 7.30 (t, J ) 7.34 Hz, 2H, ArH); 7.13 (m, 8H, ArH); 6.42
(d, J ) 4.4 Hz, 8H, C4H2N); 5.04 (m, 4H, CH); 2.75 (q, J ) 7.34 Hz,
16H, CH2); 1.77 (d, J ) 6.85 Hz, 12H, CH3); 1.07 (t, J ) 7.34 Hz,
6H, CH3); 1.00 (t, J ) 7.34 Hz, 12H, CH3); 0.93 (t, J ) 7.34 Hz, 6H,
CH3). Anal. Calcd for 28, C34H42N4Ni: C, 72.22; H, 7.49; N, 9.91.
Found: C, 72.43; H, 7.63; N, 9.34.
Synthesis of 26. LiNMe2 (0.4 g, 7.84 mmol) was added at room
temperature to a solution of 5 (2.50 g, 3.92 mmol) in DME (300 mL).
After 1 h, 1H NMR showed that 5 was entirely converted into 24. The
reaction mixture was then refluxed for 12 h. A white crystalline solid
precipitated and n-pentane (200 mL) was added to completely eliminate
the excess of LiNMe2 which was filtered off. The solution was then
cooled to -20 °C for 12 h and a red crystalline solid precipitated. The
product was then collected and dried in vacuo (1.75 g, 52%). Crystals
suitable for X-ray diffraction were obtained in a mixture of DME/n-
Synthesis of 30. PhCOCl (0.55 g, 3.91 mmol) was added at room
temperature to a solution of 23 (2.69 g, 3.91 mmol) in THF (100 mL).
The reaction mixture was stirred overnight and then evaporated to
dryness. Benzene (100 mL) was added and the white undissolved solid
was filtered off. The solvent was evaporated and n-pentane (50 mL)
was added to give a red-orange solid which was collected and dried in
vacuo (2.13 g, 85%). Anal. Calcd for 30, C39H42N4NiO: C, 73.02; H,
1
pentane. H NMR (C5D5N, 400 MHz, 298 K, ppm): δ 7.25 (d, J )
3.2 Hz, 1H, C4H2N); 7.22 (d, J ) 4.0 Hz, 1H, C4H2N); 6.89 (d, J )
2.8 Hz, 1H, C4H2N); 6.77 (d, J ) 2.8 Hz, 1H, C4H2N); 6.66 (d, J )
4.0 Hz, 1H, C4H2N); 6.63 (d, J ) 4.0 Hz, 1H, C4H2N); 6.61 (d, J )
4.0 Hz, 1H, C4H2N); 6.51 (d, J ) 3.2 Hz, 1H, C4H2N); 5.65 (q, J )
6.85 Hz, 1H, CH); 3.49 (s, 16H, DME); 3.28 (s, 24H, DME); 2.83 (q,
J ) 7.6 Hz, 2H, CH2); 2.50 (m, 4H, CH2); 2.25 (m, 4H, CH2); 1.95 (d,
J ) 6.85 Hz, 3H, CH3); 1.23 (t, J ) 7.6 Hz, 3H, CH3); 0.85 (t, J ) 7.3
1
6.60; N, 8.73. Found: C, 73.15; H, 6.40; N, 8.47. H NMR (C5D5N,
400 MHz, 330 K, ppm): 8.17 (d, J ) 7.34 Hz, 2H, ArH); 7.51 (d, J
) 4.4 Hz, 2H, C4H2N); 7.13 (m, 1H, ArH); 7.06 (d, J ) 4.4 Hz, 2H,
C4H2N); 7.01 (m, 2H, ArH); 6.49 (d, J ) 4.4 Hz, 2H, C4H2N); 6.32 (d,
J ) 4.4 Hz, 2H, C4H2N); 5.13 (q, J ) 6.85 Hz, 1H, CH); 2.72 (q, J )

Porphyrinogen-Porphodimethene Relationship
J. Am. Chem. Soc., Vol. 122, No. 22, 2000 5317
7.34 Hz, 2H, CH2 overlapping with m, 8H, CH2); 1.78 (d, J ) 6.85
Hz, 3H, CH3); 1.25 (t, J ) 7.34 Hz, 3H, CH3); 1.11 (t, J ) 7.34 Hz,
6H, CH3); 1.06 (t, J ) 7.34 Hz, 6H, CH3).
Synthesis of 31. BunLi (1.0 mL, 1.78 M in n-hexane, 1.78 mmol)
was added at room temperature to a solution of 21 (1.22 g, 1.78 mmol)
in THF (100 mL). A light yellow solution was obtained which was
stirred overnight and evaporated to dryness. N-pentane (60 mL) was
added to give a yellow solid which was collected and dried in vacuo
1
(1.33 g, 83%). H NMR (C5D5N, 400 MHz, 298 K, ppm): δ 6.57 (d,
J ) 2.93 Hz, 1H, C4H2N); 6.55 (d, J ) 2.93 Hz, 1H, C4H2N); 6.37 (d,
J ) 2.93 Hz, 1H, C4H2N); 6.36 (d, J ) 2.93 Hz, 1H, C4H2N); 6.35 (d,
J ) 2.93 Hz, 1H, C4H2N); 6.23 (d, J ) 2.93 Hz, 1H, C4H2N); 6.22 (d,
J ) 2.93 Hz, 1H, C4H2N); 6.19 (d, J ) 2.93 Hz, 1H, C4H2N); 6.03 (q,
J ) 6.85 Hz, 1H, CH2); 4.25 (dq, Jgem ) 15.6 Hz, Jvic ) 7.34 Hz,
1H,CH2); 4.19 (dq, Jgem ) 15.6 Hz, Jvic ) 7.34 Hz, 1H, CH2); 3.67 (m,
CH2, overlapping with THF, 33H); 3.54 (dq, Jgem ) 15.6 Hz, Jvic
)
7.34 Hz, 1H, CH2); 3.06 (m, 1H, CH2); 2.9 (m, 1H, CH2); 2.65-2.50
(m, 4H, CH2); 2.46 (q, J ) 7.34 Hz, 2H, CH2); 2.34 (d, J ) 6.85 Hz,
3H, CH3); 1.62 (m, 16H, THF); 1.58 (t, J ) 7.34 Hz, CH3 overlapping
with m, CH2, 5H); 1.55 (t, J ) 7.34 Hz, 3H, CH3); 1.39 (t, J ) 7.34
Hz, 3H, CH3); 1.19 (t, J ) 7.34 Hz, 3H, CH3); 1.16 (t, J ) 7.34 Hz,
3H, CH3); 0.7 (m, 2H, CH2); 0.34 (t, J ) 7.34 Hz, 3H, CH3). Anal.
Calcd for 31, C52H78Li2N4NiO4: C, 69.72; H, 8.78; N, 6.25. Found:
C, 70.12; H, 8.67; N, 5.95.
X-ray Crystallography for Complexes 14, 15, 16, 20, 22, 23, and
30. Suitable crystals of 14, 15, 16, 20, 22, 23, and 30 were mounted in
glass capillaries and sealed under nitrogen. Data concerning crystals,
data collection, and structure refinement are listed in Table 1. Data for
complexes 16, 22, and 30 were collected at 143 K on a mar345 Imaging
Plate Detector and reduced with marHKL release 1.9.1.8 Diffraction
data for compounds 14, 15, 20, and 23 were collected at 143 K on a
KUMA diffractometer, having a kappa geometry, equipped with a
charge-coupled device (CCD) area detector and reduced using CrysAlis
RED release 1.6.2.9 No absorption correction of any kind was ap-
plied to any data set. Structure solutions were determined with SIR97.10
All structures were refined using the full-matrix least-squares on F2
with all non-H atoms anisotropically defined. Hydrogen atoms were
placed in calculated positions using the “riding model” with Uiso ) a
* Ueq(C) (where a is 1.5 for methyl hydrogens and 1.2 for others, while
C is the parent carbon atom). Some particular problems were
encountered during the refinement of compound 15 and 22. In
compound 15 the two hydrogens belonging to the nitrogens are
disordered over the four nitrogen atoms [the occupancy factor for the
hydrogens linked to N2 and N4 is 0.64861, whereas those linked to
the other pair of nitrogen (N1 and N3) have an occupancy factor of
0.35139] and the N-H bond distance has been refined (0.96715 Å).
In compound 22 a disorder problem, affecting the CHCH3 groups, was
solved by finding two different sites (A and B) for the methyl carbon
atom (C12) and including them into the structure refinement (occupancy
factor for site A ) 0.78930). Structure refinement, molecular graphics,
and geometrical calculations were carried out on all structures with
the SHELXTL software package, release 5.1.11 Final atomic coordinates,
thermal and geometrical parameters, and hydrogen coordinates are listed
in the Supporting Information.12
Results and Discussion
A. Metal-Assisted Dealkylation of meso-Octaalkylporphy-
rinogen. During the metalation of meso-octaalkylporphyrino-
gens using early transition metals, some degree of dealkylation
of the meso positions was observed.13 This kind of metal-
(8) Otwinowski, Z.; Minor, W. Methods in Enzymology, Volume 276:
Macromolecular Crystallography; Carter, C. W., Jr., Sweet, R. M., Eds.;
Academic: New York, 1997; Part A; pp 307-326.
(9) Kuma Diffraction Instruments GmbH, PSE-EPFL module 3.4, CH-
1015, Lausanne, Switzerland, 1999.
(10) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.;
Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna,
R. J. Appl. Crystallogr. 1999, 32, 115.
(11) Bruker AXS, Inc., Madison, WI, 1997.
(12) See paragraph at the end of this paper regarding Supporting
Information.

5318 J. Am. Chem. Soc., Vol. 122, No. 22, 2000
Bonomo et al.
Scheme 1
Scheme 2
induced dealkylation was hardly understandable and never of a
synthetic utility for producing porphomethenes and por-
phodimethenes. The same synthetic difficulties are encountered
using the literature methods, i.e., the reductive alkylation of
porphyrins.5 Therefore, we devised a completely new approach
in the field. The synthetic sequence is given in Scheme 1. The
metalation of meso-octaalkylporphyrinogen R8N4H4 [R ) Et,
Bun] was carried out using SnCl4‚THF2. In this context, the use
of SnCl4‚THF214 is particularly appropriate because it is a solid
containing a Lewis acid weaker than SnCl4. The latter property
is particularly suitable for carrying the metalation of the
porphyrinogen tetraanion. The stannation reaction of 3 and 4
led to 5 and 6, which contain an octahedral tin(IV) bonded to
a porphyrinogen showing a folded and very distorted 1,3
alternate conformation. The reaction of 5 and 6 with SnCl4 in
the 4:1 molar ratio led to the formation of the porphomethene-
Sn complexes 7 and 8, which undergo a further meso-
dealkylation to 9 and 10 when reacted in one-pot reaction with
an excess of SnCl4‚THF2. Although the X-ray structure analyses
are available on 5, 7, 9, and 10, they are not reported here,
because a number of significant structures of metal complexes
issued from the same skeletons are discussed in detail in the
following sections. The reaction sequence in Scheme 1 can be
formally viewed as the halogenation of the central metal ion
and the corresponding elimination of R-SnCl3.
Some significant understanding of the mechanism of such a
reaction came from the nature of the meso substituents, the
presence of â-hydrogens in the meso substituents being the
prerequisite for the easy occurrence of the reaction. Such
observations are in agreement with the fact that we were able
neither to run the reaction with the meso-octamethyl derivative,
nor to intercept any R-SnCl3 derivative from the solution. Note
that H-SnCl3 was intercepted when the final solution was
treated with PhCtCH or PhCtCPh, thus obtaining the corre-
sponding vinyl-tin derivatives.15 We reached the conclusion
that the reactions in Scheme 1 proceeds in the case of R ) Et
or Bun with the elimination of H-SnCl3 and the corresponding
olefin, namely ethylene or 1-butene. The latter can eventually
reinsert into the Sn-H bond. To confirm further this hypothesis,
the reaction in Scheme 1 was run with the meso-tetracyclopentyl
derivative, 11, which might not lose the olefin residue. The
reaction led to the formation of 13, through a plausible
mechanism displayed in Scheme 2. We suppose in a preliminary
step the binding of SnCl4 by 11 via a bridging chloride and by
the use of the electron-rich pyrrolyl anion.2a We found spec-
troscopic and synthetic support for 12, the later from the reaction
of 11 with Ph3SnCl.16 We also have a variety of examples where
pyrrolyl anions function as η3 or η5 binding sites for main group
and transition metals.2a The conversion of an η3-η5 to an η1
bonding mode and the formation of the σ Sn-C bond (see A
in Scheme 2) parallels what has been observed for lithium
derivatives.17 The intermediacy of A is further supported by
the 1H NMR spectrum of the reaction solution, where a singlet
appears at 5.83 ppm, typical for the proton in the R position of
the pyrrole.3 The elimination of HSnCl3 from A gives rise to a
potential free radical coupling with the â position of the pyrrole
forming the bicyclic pyrrolyl moiety in 13. This type of
cyclization of the meso substituent, which has some precedent
in zirconium-porphyrinogen chemistry with carbon monoxide
and isocyanide,18 has been further confirmed by the use of meso-
tetracyclohexyl-porphyrinogen-tin in the reaction with SnCl4.19
The structural support for 13 is given in the Supporting
Information.
(16) Reaction of 11 with Ph3SnCl: Ph3SnCl (1.46 g, 3.79 mmol) was
added to a solution of 11 (3.0 g, 3.79 mmol) in toluene (100 mL). The
reaction mixture was refluxed for 24 h. The solvent was evaporated to
dryness and Et2O (100 mL) was added to give a light orange solid, which
was collected and dried in vacuo (2.57 g, 61%). 1H NMR spectrum and
elemental analysis revealed a product with Ph3SnCl, where one of the axial
THF at the metal is replaced by the chloride from PH3SnCl. 1H NMR (C6D6,
400 MHz, 298 K, ppm): δ 7.81 (m, 6H, ArH); 7.14 (m, 9H, ArH); 6.33 (s,
8H, C4H2N); 3.54 (m, 4H, THF); 2.5 (m, 8H, CH2); 1.81 (m, 8H, CH2);
1.77 (m, 8H, CH2); 1.59 (m, 8H, CH2); 1.41 (m, 4H, THF). Anal. Calcd
for C58H63ClN4OSn2: C, 63.04; H, 5.75; N, 5.07. Found: C, 62.98; H,
5.81; N, 5.13.
(17) Bonomo, L.; Solari, E.; Latronico, M.; Scopelliti, R.; Floriani, C.
Chem. Eur. J. 1999, 5, 2040.
(18) (a) Jacoby, D.; Isoz, S.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. J.
Am. Chem. Soc. 1995, 117, 2805. (b) Floriani, C. Pure Appl. Chem. 1996,
68, 1.
(13) Solari, E.; Musso, F.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. J.
Chem. Soc., Dalton Trans. 1994, 2015.
(14) SnCl4‚THF2 can be made simply by addition of a small amount of
THF to a toluene solution of SnCl4. Its X-ray structure has been determined.
(15) (a) Pereyre, M.; Quintard, J.-P.; Rahm, A. Tin in Organic Synthesis;
Butterworth: London, 1987. (b) Davies, A. G. Organotin Chemistry;
VCH: Weinheim, Germany, 1997; p 88.
(19) Bonomo, L.; Solari, E.; Floriani, C. Unpublished work.

Porphyrinogen-Porphodimethene Relationship
J. Am. Chem. Soc., Vol. 122, No. 22, 2000 5319
Figure 1. Ball-and-stick representation of complex 14 showing the
adopted labeling scheme [hydrogens omitted for clarity]. Prime denotes
the following symmetry transformation: -x, -y, -z.
Figure 2. Ball-and-stick representation of compound 15 showing the
adopted labeling scheme [only NH hydrogens with the highest
occupancy factor are shown].
Scheme 3
The formation of porphomethenes and porphodimethenes, as
reported in Scheme 1, becomes of practical utility under the
conditions to find an efficient method for removing the tin ion
from the macrocycles. The reductive demetalation of 9 was
easily achieved in the reaction with lithium metal in THF. The
reaction produces a mirror of tin metal and the lithium
porphodimethene. This latter compound is the most appropriate
for the entry into the metalated form of porphodimethene, as
exemplified by the synthesis of the Ni(II)-porphodimethene
complex, 16, and the protic form, 15 (see Scheme 3). The use
of other powerful reducing metals as demetalating agents led
instead to the formation of too stable complexes, so that the
reaction of 9 with magnesium metal gave the corresponding
magnesium-porphodimethene derivative, 17. The structural
analysis of the porphodimethene derivatives in their metalated
and nonmetalated form has been examined both in solution and
in the solid state by 1H NMR and X-ray analysis, respectively.
Structures of 14, 15, and 16 are shown in Figures 1-3,
respectively, whereas a selection of the conformational and
structural parameters is listed in Tables 2 and 3.
Figure 3. Ball-and-stick representation of complex 16 showing the
adopted labeling scheme [hydrogens omitted for clarity].
Significant Ni-H axial interactions, which are probably
responsible for minimizing the out-of-plane of Ni, have been
observed in the case of 16 between the central metal and the
C23 and C31 methylenes [Ni‚‚‚H, 2.69 and 2.66 Å].20 The
structural parameters in Table 3 support the bonding sequence
proposed in Scheme 3. The two lithium cations are squeezed
to a very short distance [Li‚‚‚Li, 2.142(8) Å], because of their
binding inside of the N4 core.21 The two lithium cations lie on
the opposite sides of the N4 average plane, and they bind two
nitrogens at close distances [Li1-N1, 2.113(5); Li1-N2, 2.156-
(5) Å] and the other two nitrogens at longer distances (Li1-
N1′, 2.523(5); Li1-N2′, 2.465(5) Å].
1H NMR spectra of porphomethenes always show two sets
of two doublets for the â protons of the pyrroles with one J
value in the range 4.0-4.5 and the other J value e3. The relative
assignment to the different hydrogens (see D in Chart 3) was
(20) Similar interactions have been observed in some meso-octaalkyl-
porphyrinogens: (a) De Angelis, S.; Solari, E.; Floriani, C.; Chiesi-Villa,
A.; Rizzoli, C. J. Am. Chem. Soc. 1994, 116, 5691 and 5702. (b) Crescenzi,
R.; Solari, E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. J. Am. Chem. Soc.
1999, 121, 1695.
(21) For the binucleating binding ability of meso-octaalkylporphyrinogen
tetraanion, see: (a) Bonomo, L.; Solari, E.; Floriani, C.; Scopelliti, R. Angew.
Chem., Int. Ed. Engl. 1999, 38, 913.
The skeleton of the ligand is almost planar for the lithium
derivative and saddle-shaped for compounds 15 and 16. As
expected, in 14 the lithium cations show a very pronounced
deviation from the N4 average plane [(1.031(4) Å], whereas
in compound 16 the deviation of the nickel atom from the N4
core is small [0.072(2) Å].

5320 J. Am. Chem. Soc., Vol. 122, No. 22, 2000
Bonomo et al.
Table 2. Comparison of Relevant Structural Parameters within the Metal-Ligand or Free Ligand Units
14
15
16
20
22
23
30
deviations form the N4 core, Å
N1
N2
N3
N4
Mb
0
0
0
0
-0.003(2)
0.003(2)
-0.003(2)
0.003(2)
-
0.009(2)
-0.009(2)
0.009(2)
-0.009(2)
0.072(2)
16.8(1)
63.4(2)
60.8(2)
57.5(2)
62.8(2)
0.007(2)
-0.007(2)
0.007(2)
-0.007(2)
-0.012(2)
38.5(3)
65.8(2)
43.2(3)
51.1(2)
65.2(2)
48.0(3)
-
-0.006(3)
0.006(3)
-0.006(3)
0.006(3)
0.011(3)
40.5(2)
63.0(2)
44.4(2)
44.4(2)
60.3(2)
-0.013(2)
0.013(2)
-0.013(2)
0.013(2)
-0.377(8)
32.3(2)
79.0(2)
73.7(2)
68.3(2)
76.9(2)
24.5(2)
-
-0.013(2)
0.013(2)
-0.013(3)
0.013(2)
-0.046(3)
30.0(3)
58.5(3)
46.3(3)
53.6(3)
58.1(3)
(1.031(4)
12.0(2)
0
12.0(2)
12.0(2)
0
angle between ABa, °
4.6(2)
angle between ACa, °
64.7(1)
61.0(1)
65.2(1)
60.8(1)
8.8(2)
angle between ADa, °
angle between BCa, °
angle between BDa, °
angle between CDa, °
12.0(2)
0
24.1(2)
63.6(2)
40.5(2)
93.2(3)
26.8(4)
49.9(3)
angle between meso C sp2 moieties, °
58.1(1)
a A, B, C, and D define the pyrrole rings containing N1, N2, N3, and N4. b M ) Li in compound 14 and 23, M ) Ni in compound 16, 20, 22,
and 30.
Table 3. Selected Bond (Å) for Compounds 14, 16, 20, 22, 23,
and 30
recorded in C7D8 at a lower temperature (263 K) show three
quartets and three triplets of equal intensity for the ethyl groups.
This is probably due to the presence of two meso-sp3 carbons
giving rise to a pseudo saddle-shaped conformation with
different endo-exo ethyl groups. 1H NMR spectra of the butyl-
porphodimethene-Sn complex, 10, in deuterated pyridine at
room temperature is similar to the corresponding ethyl deriva-
tive with a D2h symmetry. When the spectrum is recorded in
CD2Cl2 at room temperature, all the signals are broad, while at
higher temperature (308 K) two doublets for the â protons of
the pyrroles and two sets of signals for the butyl groups appear.
At lower temperatures (263 K), four doublets for the â protons
of the pyrroles and five sets of signals for the butyl group appear,
because of the two different conformers shown as E and F in
Chart 3. One is consistent with a C2h symmetry with only two
sets of signals for the butyl groups. The other one displays three
sets of signals of equal intensity for the butyl groups, in
agreement with a C2V symmetry.
B. The Electrophilic Reactivity of Porphodimethenes at
the meso-Carbon: The Synthesis of Meso-Functionalized
Porphyrinogens. The porphodimethene skeleton displays a
quite interesting and unprecedented reactivity in its metalated
or metal-free form. In both cases the porphodimethene skeleton
is quite sensitive to the attack by nucleophiles at the monosub-
stituted meso-positions.22 Such a methodology has been recently
and successfully used for the meso-functionalization of
porphyrins,22d though with few nucleophiles. The reactivity of
porphodimethene toward nucleophiles, depending on the pres-
ence of the metal and the nature of the nucleophile, led to quite
interesting synthetic results with the formation of novel forms
of porphyrinogen. The electrophilic reactivity of the por-
phodimethene skeleton was explored using 14 and 16 as starting
materials. The reactivity of 16 is displayed in Scheme 4, where
three different nucleophiles were used to prove the versatility
of such a class of reactions. The reaction of 16 with LiHBEt3
led to a quite unusual meso-dehydro-hexaethylporphyrinogen-
nickel complex, 18, which shows a quite unexpected stability.
Note that porphyrinogens bearing hydrogens in the meso
positions show a high tendency to autooxidize to the corre-
14
16
20
22
23
30
M-N1a
2.113(5) 1.893(3) 1.858(5) 1.889(4) 2.145(7) 1.889(5)
2.156(5) 1.896(3) 1.889(4) 1.884(4) 2.213(7) 1.872(5)
2.523(5) 1.891(3) 1.871(5) 1.889(5) 2.261(7) 1.879(5)
2.465(5) 1.893(3) 1.878(4) 1.884(4) 2.195(7) 1.864(5)
M-N2a
M-N3a,b
M-N4a,b
C22-N5
C30-N6
N6-Li1
C10-C11
Li2-N1
Li2-N2
Li2-N5
Li3-N3
Li3-N4
Li3-N6
Li4-η5(Pyr)c
C29-O1
1.146(9)
1.141(8)
2.128(12)
1.316(11)
2.025(6)
2.077(7)
2.103(7)
2.136(8)
2.061(7)
2.172(7)
1.994(9)
1.236(7)
a M is lithium for complex 14 and 23, whereas it corresponds to
nickel for complex 16, 20, 22, and 30. b For complexes 14 and 22, N3
and N4 correspond to N1′ and N2′ obtained by the following symmetry
operations: -x, -y, -z (14); -x, y, -z+1/2 (22). c η5(Pyr) indicates
the centroid.
Chart 3
based on coupling constant analysis. The observed multiplicity
(d, J ∼ 4.4 Hz) of the Ha or Hb protons is consistent with an
Ha-Hb torsion angle of approximately 2°. The observed
multiplicity of Hc or Hd (d, J ∼ 2.9 Hz,) is in agreement with
a minor torsion angle Hc-Hd (1°). 1H NMR spectra of
porphodimethenes with a single set of doublets for the â protons
of the pyrroles (J ∼ 4.4 Hz) support what has been mentioned
above. Moreover, porphodimethenes generally are expected to
have very simple 1H NMR spectra with only two sets of signals
for the ethyl groups. For the Ni complex 16 and the nonmeta-
lated derivative 15, however, this is only true at relatively high
temperatures (> 310 K). Note that their 1H NMR spectra
(22) (a) Vicente, M. D. G. H. In The Porphyrin Handbook; Kadish, K.
M., Smith, K. M., Guilard, R., Eds.; Academic: Burlington, MA, 1999;
Vol. 1, Chapter 4. (b) Jacquinot, L. In The Porphyrin Handbook; Kadish,
K. M., Smith, K. M., Guilard, R., Eds.; Academic: Burlington, MA, 1999;
Chapter 5. (c) Fhurhop, J.-H. In The Porphyrins, Dolphin, D., Ed.;
Academic: New York, 1978; Vol. II, Chapter 5. (d) Kalisch, W. W.; Senge,
M. O. Angew. Chem., Int. Ed. Engl. 1998, 37, 1107 and references therein.
(e) Krattinger, B.; Callot, H. J. Tetrahedron Lett. 1996, 37, 7699. (f)
Krattinger, B.; Callot, H. J. Tetrahedron Lett. 1998, 39, 1165. (g) Krattinger,
B.; Callot, H. J. Chem. Commun. 1996, 1341. (h) Sugimoto, H. J. Chem.
Soc., Dalton Trans. 1982, 1169. (i) Segawa, H.; Azumi, R.; Shimidzu, T.
J. Am. Chem. Soc. 1992, 114, 7564.

Porphyrinogen-Porphodimethene Relationship
J. Am. Chem. Soc., Vol. 122, No. 22, 2000 5321
Chart 4
-CH2CN group [Li1-N6, 2.128(12) Å]. A further common
interesting structural feature of 19 (Supporting Information) and
20 is the presence in the axial position of four hydrogens from
the meso-methylenes in a tetrahedral arrangement around the
central metal ion. Three sets of Ni‚‚‚H interactions can be
singled out: (1) Ni1‚‚‚H (owned by a CH2CN group), 2.67 Å;
(2) Ni1‚‚‚H (owned by CH2CH3 groups), 2.83, 2.84 Å; and (3)
Ni‚‚‚H (owned by a CH2CH3 group facing the CH2CN group
which interacts with the lithium and the nickel cations), 3.06
Å.20 The macrocyclic ligand shows the usual saddle-shaped
conformation, with opposite meso sp3 carbon atoms facing each
other. The very distinctive structural feature between 19 and
20 is the difference in the stereoisomer present in the solid state,
being the syn for 19 and the anti for 20. The analysis in solution
of 19 and 20 by means of 1H NMR allowed us to establish the
solid state-solution structural relationship. Within this context
it should be clarified that the structures drawn in the schemes
refer to the solvated forms obtained from the synthesis and they
differ slightly from those recrystallized to produce suitable
crystals for X-ray analysis. Regardless of the type of solvation,
when the ion-pair forms are examined by NMR in solution of
strongly coordinating solvents such as Py, they are present in
the ion-separated forms, so we refer to the analysis of the anions
drawn in the schemes.
Figure 4. Ball-and-stick representation of the dianion of complex 20
showing the adopted labeling scheme [hydrogens and Li(DME)2
cations omitted for clarity].
+
Scheme 4
The 1H NMR analysis indicates that the meso-dihydro-
hexaethylporphyrinogen-nickel complex, 18, was obtained as
a mixture of syn and anti isomers in a 1:4 ratio. The relative
chemical assignment of the two stereoisomers was based on
symmetry considerations. The syn isomer has a C2V symmetry
with a set of two doublets for the â-pyrrole protons and one
triplet for the meso-protons. The 1H NMR spectrum of the anti
isomer with four doublets for the â pyrrole protons and two
triplets for the two different endo-exo hydrogens was consistent
with a Cs symmetry. The stereochemistry of the two isomers
was also confirmed by a two-dimensional (correlation spec-
troscopy) (COSY), nuclear Overhauser enhancement spectors-
copy (NOESY) NMR spectral analysis. For the anti isomer only,
large nuclear Overhauser effect (NOE) between the Hexo and
the â protons was observed (Chart 4). The absence of NOE in
the case of the syn isomer suggests that the predominant
conformation is that shown in Chart 4 with the hydrogens endo
sponding porphodimethene or porphyrin.1,22 The other two
reactions in Scheme 4 were carried out in a similar way using
LiBu and LiCH2CN as nucleophiles. The reactions led to the
formation of 19 and 20, respectively. The η3-η5 binding of
the lithium countercation is the same as that which we found
in several meso-octaethylporphyrinogen-metal complexes,2a
though the ion-pair can be crystallized as the ion-separated form
in the presence of strongly binding solvents. This structural
feature was further confirmed with X-ray analyses (see below).
Two stereoisomers issued from a syn or anti attack at the meso
positions are expected in the case of compounds 18-20.
Because of such a possibility, the solid state-solution relation-
ship has been carefully analyzed both for the crude and the
crystallized compounds. A short summary is given, first, on the
common structural features in the solid state of complexes 18-
20. They have a very similar structure, which is reported in
detail only for the anion in 20 (Figure 4), whereas the structure
of 19 is given in the Supporting Information. The X-ray analysis
on 20 was performed on the ion-separated form recrystallized
from DME. The overall structure of the anion in 20 is quite
reminiscent of the meso-octaalkylporphyrinogens,2 albeit the
presence of the two CH2CN functionalities. The conformational
parameters in Table 2 are informative about the saddle-shaped
conformation of the ligand, with the out-of-plane of the metal
distance, -0.012(2) Å, being similar to that in meso-octaalkyl-
porphyrinogen-metal derivatives. The two lithium cations are
fully solvated by DME, one of them interacting also with the
1
in the meso positions. Examination of the H NMR spectra of
19 and 20 (reaction mixture and isolated product) indicates for
both only the syn isomer. For 19 this spectral evidence is in
agreement with the solid-state structure, whereas 20 crystallized
as the anti isomer. To accommodate this apparent discrepancy
between solid state and solution for 20, it should be assumed
that the syn stereoisomer is the kinetic product, whereas the
anti isomer is the thermodynamic product. The conversion of
the syn into the anti isomer was followed by 1H NMR
spectroscopy. The 1H NMR spectrum of 20 in deuterated
pyridine, carried out immediately after dissolution of the solid,
showed the presence of the syn isomer exclusively, whereas 1
day later the appearance of the anti isomer with four doublets
for the pyrrole â-protons and two singlets for the two different
endo-exo-CH2CN groups was observed. The syn f anti

5322 J. Am. Chem. Soc., Vol. 122, No. 22, 2000
Bonomo et al.
Chart 5
Scheme 5
Figure 5. Molecular orbitals of the porphodimethene-nickel complex.
transformation was complete in a week. This type of isomer-
ization is only possible if one admits the reversibility of the
nucleophilic attack by the [CH2CN]- group at the meso positions
of the porphodimethene skeleton, such a reversibility being
impossible in the case of alkyl or hydrido nucleophiles. Further
examples of reversible nucleophilic reactions at the meso
positions of porphodimethenes are reported in the next section.
Note that the three reactions reported in Scheme 4 represent
a synthetic methodology to meso-functionalized porphyrinogens,
exemplified particularly by 20, whereas the formation of 18
shows a synthetic access to a potentially unstable porphyrino-
gen.1,22 The high and selective reactivity with nucleophiles at
the meso positions prompted us to analyze such a behavior with
a qualitative theoretical approach.
complex. To understand the factors which determine the
observed regioselectivity of the nucleophilic attack on the meso
carbon atoms of the macrocyclic ligand, we analyzed both the
atomic charges and the frontier orbitals localization. The gross
atomic charges derived for the nickel porphodimethene show
that the two meso carbons are less positive (+0.07) than the
pyrrole â-carbons (+0.32) and the metal (+0.58), thus indicating
that the nucleophilic attack is not charge-controlled. On the other
hand, the two low-lying empty orbitals 2b2 and 3a1 are purely
ligand-based and mostly localized on the two meso carbons see
(Chart 5), thus suggesting that the regioselectivity of the
nucleophilic attack on these atoms is controlled by frontier
orbitals factors. Note that the 2b2 and 3a1 are essentially the
unaltered LUMO and LUMO + 1 of the free porphodimethene
dianion see (Figure 5), and thus determine also the regioselec-
tivity of the nucleophilic attack on the latter species, as
exemplified by the synthetic approach in Scheme 6.
The molecular orbitals of the nickel-hexaethylporphodi-
methene fragment are built in a step-by-step approach, using
the extended Hu¨ckel method.23 The hexaethylporphodimethene
ligand was simplified by replacing the six ethyl groups with
hydrogen atoms. We first considered the macrocyclic ligand of
C. Deprotonation of Porphodimethene to bis-Vinylidene-
Porphyrinogen. The addition of dimethylamino anions to the
meso positions of porphodimethene led, through the interme-
diacy of C and D (Scheme 5), to the deprotonation of the ethyl
group and the formation of the meso-vinylidene-porphyrinogen
derivatives 21 and 22. The proposed pathway involving
intermediates C and D is based on the analogous structure
displayed by complexes 18-20 in Scheme 4, and on spectro-
scopic evidence for the existence of D (see Experimental
Section, compound 24). Such an assumption is further supported
(see below) by the isolation of intermediates in the reaction of
14 with LiNMe2 (Scheme 6). The vinylidene functionality is a
quite good spectroscopic probe, thus the stepwise conversion
C2V symmetry whose molecular orbitals are reported in the first
column of Figure 5. We then added the nickel atom and the
resulting molecular orbitals (MOs) diagram of this d8 metal
complex is reported in the second column of Figure 5. Upon
coordination, the d orbitals mix strongly with the ligand frontier
orbitals, but five MOs with large metal d character can be
2
2
2
identified. These are the four occupied orbitals 1a1(dz ), 2a1(dx -y ),
1b1(dxz), and 1b2(dyz). The a2(dxy) pointing more closely toward
the nitrogen atoms of the ligand, is pushed higher in energy.
The two lowest unoccupied (LUMO) (a1 and b2) and the two
highest occupied (HOMO) (b1 and a2) orbitals of the por-
phodimethene ligand are left essentially unperturbed by the
interaction with the metal and remain, respectively, the LUMO
and LUMO + 1 and the HOMO and HOMO - 1 for the nickel
1
of 16 into 22 can be followed in the H NMR spectrum. For
22, the 1H NMR spectrum revealed the presence of an equimolar
mixture of the two possible geometrical isomers, with the two
methyls cis or trans to each other. The spectrum, in fact, has
(23) (a) Hoffmann, R.; Lipscomb, W. N. J. Chem. Phys. 1962, 36, 2179.
(b) Hoffmann, R. J. Chem. Phys. 1963, 39, 1397.

Porphyrinogen-Porphodimethene Relationship
J. Am. Chem. Soc., Vol. 122, No. 22, 2000 5323
Scheme 6
Figure 6. Ball-and-stick representation of the dianion of complex 22
showing the adopted labeling scheme [hydrogens, Li(DME)3+ cations
and disorder omitted for clarity]. Prime denotes the following symmetry
1
operation: -x, y, -z + /2.
oxidized or functionalizable forms. The closest relationship we
found for the bis-vinylidene-porphyrinogen is the 5,15-dioxo-
porphyrinogen reported several years ago and never structurally
characterized.24 The novel form of porphyrinogen in 22, which
may have considerable synthetic potential, can be available
either from transmetalation or demetalation of 22. We achieved,
however, a much better synthetic approach to the bis-vinyl-
idene-porphyrinogen tetraanion from the direct deprotonation
of 14. In addition, such a reaction shed light on the deprotonation
mechanism of the porphodimethene skeleton as a function of
the metal and the reaction solvent (Scheme 6). The addition of
LiNMe2 to 14 gave, regardless of the solvent used (THF, DME,
benzene), the bisdimethylamino-porphyrinogen derivative 23,
which, upon heating, underwent HNMe2 elimination to give
different porphyrinogen derivatives, according to the solvent,
namely 24 in benzene, 25 in THF, and 26 in DME. Scheme 6
displays also the relationship between 24, 25, and 26. This
relationship reveals the fundamental role of the reaction solvent.
The complete elimination of HNMe2 from 23 or 25 to form 24
occurs exclusively in a poorly coordinating solvent, which
prevents from either 23 or 25 the loss of LiNMe2 promoted by
a polar solvent binding alkali cations. Thus, the thermal
decomposition of 23 in THF, followed by the crystallization in
DME, gave the elimination of a single HNMe2 molecule and
the formation of meso-vinylidene-dimethylamido derivative 25,
which undergoes the loss of a second HNMe2 molecule to 24
exclusively in benzene. By running the reaction in DME, it has
been shown how a coordinating solvent could affect the thermal
evolution of 23. In a preliminary step we isolated 26, derived
from the loss of HNMe2 and LiNMe2. Such a finding proves
that the reaction of LiNMe2 at the meso carbons of por-
phomethene or porphodimethene is reversible. Note that the
addition of LiNMe2 in DME at room temperature allowed the
isolation of 25. We mapped the entire transformation of the
porphodimethene in vinylidene-porphyrinogen by analyzing the
solid-state structure of complexes 23-26. The structural inves-
tigation of the compounds displayed in Scheme 6 revealed three
major characteristics: (i) the possible presence of geometrical
isomers of 23 and 24; (ii) the occurrence, as a function of the
two quartets and two doublets of equal intensity for the
vinylidene groups and eight doublets for the â-protons of the
pyrroles. The simultaneous presence of the two possible isomers
has been confirmed even in the solid state by the X-ray analysis,
which reveals a statistical distribution of the Me and H groups
around the vinylidene carbon in a ratio close to that observed
in solution. An X-ray analysis was performed on crystals
obtained from the recrystallization of 22 from DME. From this
solvent the ion-separated form of 22 was obtained and the
picture of the corresponding anion is reported in Figure 6.
The presence of two vinylidene substituents in the meso
positions does not affect very much the overall conformation
of the ligand, which displays the usual saddle-shaped form with
a slight out-of-plane of the Ni ion (see Table 2). Both
geometrical isomers, namely those having the two methyl groups
C12 and C12′ cis or trans to each other, are present in the solid
state in a ratio which is nearly the same as that in solution (1:
1). The bonding sequence within the pyrrolyl anion is as
expected, and the C10-C11 distance [1.32(1) Å] is in agreement
with the presence of a double bond. Short Ni‚‚‚H contacts [2.92
Å] from two meso-ethyl groups from the same side of the N4
coordination plane were found. Although the ligand has two
meso sp2 carbon atoms, the ruffling around them is very high,
thus minimizing the steric hindrance between the hydrogens of
the pyrrolyl moieties and the CHMe groups.
Both 21 and 22 were obtained with good yield (>70%) in a
multigram scale, and therefore the reactions reported (see the
Experimental Section) can be used conveniently at the prepara-
tive level. The protonation of 21 and 22 (Scheme 6) leading to
16 reveals the nucleophilic reactivity of the vinylidene-
porphyrinogen derivatives, a topic which will be discussed in
the following. Complex 22 contains a novel form of porphy-
rinogen, which opens the synthetic access to a variety of
(24) (a) Inhoffen, H. H.; Fuhrhop, J. H.; von der Haar, F. Justus Liebig
Ann. Chem. 1966, 700, 92. (b) Fischer, H.; Treibs, A. Justus Liebig Ann.
Chem. 1927, 451, 209.

5324 J. Am. Chem. Soc., Vol. 122, No. 22, 2000
Bonomo et al.
Scheme 7
Figure 7. Ball-and-stick representation of complex 23 showing the
adopted labeling scheme [hydrogens and solvent molecules omitted
for clarity].
reaction or crystallization solvent, of an ion-pair or an ion-
separated form for the same compound; and (iii) the solid state-
solution structural relationship.
dimethylamino and meso-vinylidene porphyrinogens. The meso-
functionalization and the formation of vinylidene derivatives
can be performed equally well on transition metal, i.e. Ni(II),
or alkali cation, i.e. Li, derivatives, the latter being much more
suitable for any kind of metalation or protonation. The question
at this stage concerns the possibility of converting the novel
porphyrinogens to their protic form. The protonation of 23 is
essentially occurring at the more basic sites, namely the
diethylamino groups, thus causing the elimination of HNMe2
and the formation of 15. In contrast, under very controlled
conditions, we were able to achieve the protonation of 24 with
the formation of 27. Following the procedure given in the
Experimental Section, the selective protonation of the nitrogen
occurred, without any protonation at the vinylidene functionality.
The porphyrinogen 27 was isolated and fully characterized both
in solution and in the solid state. A preliminary X-ray analysis
supported the proposed structure.19
The latter aspect will be analyzed in detail comparing the
1
structural information from the H NMR spectra of 23 and 24
with their structures in the solid state. The structures of 24, 25,
and 26 are available in the Supporting Information. The structure
of 23 (Figure 7) differs considerably from that of 20, which is
also a doubly meso-functionalized porphyrinogen. The differ-
ence in the overall conformation is due to the presence of four
lithium cations in the structure. The central cation has a distorted
square pyramidal coordination, with an N4 out-of-plane of
-0.377(8) Å. Two adjacent pyrrole-nitrogen and one of the
amino groups act as an N3 tridentate ligand for the two lithium
cations bonded to the periphery of the porphyrinogen, while
the fourth lithium cation is η5-bonded to one of the pyrrolyl
anions. The lithium cations at the periphery force the syn
arrangement of the dimethylamino groups. A selected list of
the structural parameters is given in Table 3, whereas the
conformational parameters are listed in Table 2. The ligand
displays a dome conformation, and each lithium cation com-
pletes its coordination sphere with a THF molecule.
The three sets of signals for the ethyl groups in the 1H NMR
spectrum of 23 are in agreement with the presence of the syn
isomer, which does not isomerize on standing in solution.
Compound 24 is an equimolar mixture of the cis and trans
isomers, as we found for the nickel derivative 22, and this fact
is supported by the equal intensity of the two quartets and the
two doublets relative to the vinylidene groups. Coalescence of
the two sets of signals was not observed even at high
temperature. Compound 25 displays a C1 symmetry in deuter-
ated pyridine at room temperature. The possible rotation around
the double bond was not observed on the NMR time scale at
room temperature, as confirmed by the presence of eight
doublets for the â hydrogens of the pyrroles in the spectrum.
When the temperature of the deuterated pyridine or toluene
solution of 25 was increased, its conversion into 26 and 24,
respectively, was observed. The 1H NMR spectrum of 26, with
eight doublets for the â hydrogens of the pyrroles and two sets
of dq for the meso-methylenes, supports the Cs symmetry, both
at room and higher temperature.
D. The Nucleophilic Reactivity of the Vinylidene-Por-
phyrinogen: The Meso-Functionalization of Porphodimethene.
The reversible deprotonation-protonation sequence of the
porphodimethene skeleton in Scheme 5 reveals the synthetic
potentiality of the vinylidene-porphyrinogen derivatives. The
reactions of 22 with the electrophiles listed in Scheme 7 give a
glimmering of such a potentiality. The stepwise protonation of
22 using PyHCl led to 21, then to 16. The reaction of 22 with
MeI parallels the protonation with the formation of the meso-
bis-isopropyltetraethylporphodimethene-nickel, 28. Such an
unusual meso-substituted porphodimethene is hardly accessible
from any other synthetic route. The reaction of 22 with PhCOCl
shows how the introduction of a reactive functional group in
the meso positions of porphodimethene can be achieved. The
reaction led to the formation of the functionalized por-
phodimethene-Ni complex, 29. The presence of two stereogenic
centers in 29 reveals the possible use of 22 in the synthesis of
chiral porphodimethenes.19 Detailed characterization of 28 and
1
29 is discussed in the Experimental Section. The H NMR
spectra did not reveal any characteristics different from those
of the other porphodimethenes so far reported.
Because of the synthetic relevance of the reaction of bis-
vinylidene-porphyrinogens with electrophiles, a theoretical
analysis on the electronic properties of the bis-vinylidene-
porphyrinogen was carried out. The molecular orbitals of the
Some major synthetic achievements reported in this section
have to be emphasized: they are the formation of meso-

Porphyrinogen-Porphodimethene Relationship
J. Am. Chem. Soc., Vol. 122, No. 22, 2000 5325
Figure 9. Ball-and-stick representation of complex 30 showing the
adopted labeling scheme [hydrogens omitted for clarity].
Scheme 8
Figure 8. Molecular orbitals of the bis-vinylidene-porphyrinogen-
nickel complex.
Chart 6
thus suggesting that the regioselectivity of the electrophilic attack
could be directed by charge and orbital factors in concert. This
agrees with the experimental evidence that the same regiose-
lectivity is shown by both hard (H+) and soft (PhCOCl)
electrophiles.
bis-vinylidene-porphyrinogen-nickel were built similarly to
those of the nickel-porphodimethene fragment, and are dis-
played in Figure 8. The bis-vinylidene-porphyrinogen ligand
was simplified by replacing the four ethyl groups on the meso
carbons and the two methyl groups on the vinylidene unit with
hydrogens. A comparison of Figures 5 and 8 shows that the
modification from a hydrogen to a vinylidene group at the
periphery of the model macrocyclic ligand affects neither the
character nor the energy ordering of the metal orbitals. The main
difference with the molecular orbital diagram of the por-
phodimethene complex consists of the presence of two high-
lying occupied orbitals, 3a1 and 2b2, which are the HOMO and
HOMO - 1 of the bis-vinylidene-porphyrinogen-Ni complex.
These are ligand-centered orbitals mostly localized on the
â-carbon atoms of the vinylidene groups (see Chart 6). It is
therefore the presence of such orbitals that determines the
observed regioselectivity of the electrophilic attack toward the
vinylidene â-carbon atoms, which seems to be again frontier-
orbital-controlled. An analysis of the gross atomic charges
derived for the nickel bis-vinylidene-porphyrinogen show a
significant negative charge on the vinylidene â-carbon atoms
(-0.35) only slightly lower than for the nitrogen atoms (-0.51),
In the scenario so far presented on the meso-reactivity of the
porphodimethene and bis-vinylidene-porphyrinogen, the chem-
istry of complex 21 deserves to be discussed and proved by a
few examples such as those collected in Scheme 8. Complex
21 contains at the same time a nucleophilic and an electrophilic
center in the meso-positions. Such a kind of bifunctionality is
synthetically very attractive. The reaction with PhCOCl led to
the monofunctionalized porphodimethene complex 30, whereas
the reaction with a nucleophile, i.e., LiBu, gave the nonsym-
metric substituted porphyrinogen 31. The structure of 30 is
displayed in Figure 9. Complex 30 has structural features similar
to those of complex 16, nickel(II) being -0.046(3) Å out of
the plane, while the ligand shows the usual saddle-shaped
conformation. The metal is protected by the hydrogen from the
methylenes of the meso-sp3-ethyl groups (Ni1‚‚‚H23B, 2.65;
Ni1‚‚‚H36B, 2.77). The dihedral angle between the phenyl ring
and the -CH-(CdO)-CPh fragment is 14.0(4)°. The torsion
angles [O1-C29-C30-C31, -13(1)°; O1-C29-C30-C35,
166.6(7)°] give a picture of the orientation of the benzoyl
substituent.

5326 J. Am. Chem. Soc., Vol. 122, No. 22, 2000
Bonomo et al.
Scheme 9
to porphyrins, but are the key for entering novel and function-
alized forms of porphyrinogen. The electrophilic reactivity of
the monosubstituted meso-positions of the porphodimethene
leads to meso-functionalized porphyrinogens by the use of a
large variety of nucleophiles. Among them, the dimethylamido
anion causes the deprotonation of the meso-alkyl substituents,
thus forming meso-vinylidene porphyrinogens. These latter
compounds, very easily undergoing attack by electrophiles,
generate functionalized porphodimethenes. The synthetic path-
way from meso-octaalkylporphyrinogen to porphodimethene,
functionalized porphyrinogen, and functionalized porphodimethene
is depicted in Scheme 9.
Acknowledgment. We thank the “Fonds National Suisse de
la Recherche Scientifique” (Bern, Switzerland, Grant No. 20-
53336.98), Action COST D9 (European Program for Scientific
Research, OFES No. C98.008), and Fondation Herbette (Uni-
versite´ de Lausanne, N.R.) for financial support.
Supporting Information Available: ORTEP drawings
(Figures S1-S7); details of the X-ray data collection, structure
solution and refinement, tables giving crystal data and structure
refinement, atomic coordinates, isotropic and anisotropic dis-
placement parameters, and bond length and angles (Tables S1-
S35) for 14, 15, 16, 20, 22, 23, and 30. Crystal data (Tables
S36-S60) and ball-and-stick drawings (Figures S8-S13) for
13, 19, 24, 25, and 26 (PDF). This material is available free of
charge via the Internet at http://pubs.acs.org.
Conclusions
A novel synthetic methodology was established, which leads,
through an unprecedented pathway, from porphyrinogen to
porphomethene and porphodimethene. Such molecules, which
were so far almost curiosities, become available in large quan-
tities for synthetic and mechanistic purposes. Porphomethene
and porphodimethene not only pave the way from porphyrinogen
JA000253S