The N 2 O 2 Porphyrinogen Skeleton: Access to a Novel Class of Coordinatively Unsaturated Transition Metal Ions Raffaella Crescenzi, † Euro Solari, † Carlo Floriani,* ,† Angiola Chiesi-Villa, ‡ and Corrado Rizzoli ‡ Institut de Chimie Mine ´rale et Analytique, BCH, Universite ´ de Lausanne, CH-1015 Lausanne, Switzerland, and Dipartimento di Chimica, Universita ` di Parma, I-43100 Parma, Italy ReceiVed December 28, 1995 The porphyrinogen skeleton, which is stable when fully alkylated, 1,2 provides a variety of tridimensional binding cavities for metal ions. The binding peculiarities depend on (i) the sp 3 meso carbons whereby the bonding to the metal can vary from η 1 to η 51 and (ii) the nature of the heteroatoms, allowing one to tune the binding ability of the cavity. meso-Octaalkylporphyrinogen skeletons are known with different sets of heteroatoms; 3 two of them, 1 1,2 and 2, 3,4 will be considered here as reference compounds. The former was recently exploited in its tetraanionic form as a strong binder of a variety of early and late transition metals because of its special redox properties. 1,2 The meso-octaalkylporphyrinogen 2 has been largely unable to bind any cation because of the electro- philic nature of the furan oxygens. 4b,d,e The binding properties of 1 and 2 allowed us to design a cavity which would strongly bind atoms in a linear arrangement, using the NH moieties, while the two oxygens would have the role of weakly binding spectators, as illustrated by the meso-octaalkyldioxaporphyrino- gen R 8 O 2 N 2 H 2 , 3. The core of 3 seems particularly appropriate for protecting a linear dicoordinate unsaturated metal ion in the presence of weakly binding electron-poor oxygens. The synthesis of 3 (R ) Me) was performed using an improved published procedure based on the conversion of furan to pyrrole. 5 The metal complexation by 3 6 was achieved via its lithium or sodium derivative, 7 which can engage in metathesis reactions with metal halides. The structure and the most relevant structural parameters of 5 8 are shown in Figure 1. The planar rhombic Na 2 O 2 array forms a dihedral angle of 86.01° with the N 2 O 2 core, and each sodium cation has a tetrahedral coordination. The dioxapor- * To whom correspondence should be addressed. † University of Lausanne. ‡ University of Parma. (1) Villa, A.; Rizzoli, C. J. Chem. Soc., Chem. Commun. 1991, 790; J. Am. Chem. Soc. 1993, 115, 3595, 7025. Rosa, A.; Ricciardi, G.; Rosi, M.; Sgamellotti, A.; Floriani, C. J. Chem. Soc., Dalton Trans. 1993, 3759. Jacoby, D.; Isoz, S.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. J. Am. Chem. Soc. 1995, 117, 2793, 2805. Jacoby, D.; Isoz, S.; Schenk, K.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. Organometallics 1995, 14, 4816. (2) Angelis, S.; Solari, E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. J. Am. Chem. Soc. 1994, 116, 5691, 5702; J. Chem. Soc., Dalton Trans. 1994, 2467; Angew. Chem., Int. Ed. Engl. 1995, 34, 1092. Solari, E.; Musso, F.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. J. Chem. Soc., Dalton Trans. 1994, 2015. (3) Newkome, G. R.; Sauer, J. D.; Roper, J. M.; Hager, D. C. Chem. ReV. 1977, 77, 513. (4) (a) Ackman, R. G.; Brown, W. H.; Wright, G. F. J. Org. Chem. 1955, 20, 1147. (b) Chastrette, M.; Chastrette, F. J. Chem. Soc., Chem. Commun. 1973, 534. (c) Kobuke, Y.; Hanji, K.; Horiguchi, K.; Asada, M.; Nakayama, Y.; Furukawa, J. J. Am. Chem. Soc. 1976, 98, 7414. (d) de Sousa Healy, M.; Rest, A. J. J. Chem. Soc., Perkin Trans. 1 1985, 973. (e) Vogel, E.; Haas, W.; Knipp, B.; Lex, J.; Schmickler, H. Angew. Chem., Int. Ed. Engl. 1988, 27, 406. (f) Musau, R. M.; Whiting, A. J. Chem. Soc., Chem. Commun. 1993, 1029. (g) Kretz, C. M.; Gallo, E.; Solari, E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. J. Am. Chem. Soc. 1994, 116, 10775. (5) (a) Paal, C. Chem. Ber. 1885, 18, 367, 2254. (b) Knorr, L. Chem. Ber. 1885, 18, 299, 1568 and references therein. (c) Nozaki, H.; Koyama, T.; Mori, T.; Noyori, R. Tetrahedron Lett. 1968, 2181. (d) Nozaki, H.; Koyama, T.; Mori, T. Tetrahedron 1969, 25, 5357. (e) Wasserman, H. H.; Bailey, D. T. J. Chem. Soc., Chem. Commun. 1974, 119. (f) Haley, J. F.; Keehn, P. M. Tetrahedron Lett. 1973, 4017. (g) Rosenfeld, S. M.; Keehn, P. M. J. Chem. Soc., Chem. Commun. 1974, 119. (h) Haley, J. F.; Keehn, P. M. Tetrahedron Lett. 1975, 1675. (i) Williams, P. D.; LeGoff, E. J. Org. Chem. 1981, 46, 4143. (j) Brown, W. H.; French, W. N. Can. J. Chem. 1958, 36, 371. (6) Procedure for 3: See Supporting Information. (7) Procedure for 5: 3 (5.0 g, 11.6 mmol) and NaH (0.72 g, 30.0 mmol) were combined in THF (100 mL). The orange solution was refluxed overnight and excess NaH then removed by filtration. The solvent was evaporated and the resulting solid triturated with n-hexane (100 mL) to give a beige solid, which was then filtered off and dried in vacuo (82%). Anal. Calcd for 5‚THF, C 28H32N2Na2O2‚C4H8O: C, 70.31; H, 7.38; N, 5.12. Found: C, 70.25; H. 7.40; N, 5.09. 1 H NMR (C 5D5N, 298 K): δ 6.45 (s, 4 H, C4H2O), 5.70 (s, 4 H, C4H2N), 3.64 (m, 4 H, THF), 1.77 (s, 24 H, CH 3), 1.60 (m, 4 H, THF). White crystals suitable for X-ray analysis were obtained by recrystallization from DME. Anal. Calcd for 5‚2DME, C 28H32N2Na2O2‚C8H20O4: C, 70.31; H, 7.38; N, 5.12. Found: C, 70.25; H, 7.40; N, 5.09. 1 H NMR (C5D5N, 298 K): δ 6.45 (s, 4 H, C 4H2O), 5.70 (s, 4 H, C4H2N), 3.64 (m, 4 H, DME), 1.77 (s, 24 H, CH 3), 1.60 (m, 4 H, DME). (8) Crystal data for 5‚2DME: C36H52N2Na2O6, M ) 654.8, monoclinic, space group P2 1/n, a ) 11.688(2) Å, b ) 12.300(2) Å, c ) 12.585(2) Å,  ) 97.41(1)°, V ) 1794.1(5) Å 3 , Z ) 2, Dcalcd ) 1.212 g/cm 3 , F(000) ) 704, λ(Cu KR) ) 1.541 78 Å, µ(Cu KR) ) 8.32 cm -1 , crystal dimensions 0.23 × 0.29 × 0.52 mm. The structure was solved using SHELX86 and anisotropically refined for all the non-hydrogen atoms. For 1466 unique observed reflections [I > 2σ(I)] collected at T ) 295 K (6 < 2θ < 140°), the current R is 0.056 (R2w ) 0.136). For details see the Supporting Information. 2413 Inorg. Chem. 1996, 35, 2413-2414 0020-1669/96/1335-2413$12.00/0 © 1996 American Chemical Society