N,N'-Bridged Porphyrins. Novel Synthesis, Metal Complexes, and Conversion into N-Monosubstituted Porphyrins. Crystal Structure of (N,N'-((Benzyloxy)methylene)tetraphenylporphyrin-N'',N''')dibromopalladium(II)

Article abstract of DOI:10.1021/ja00369a021

Formation of a one-carbon bridge between vicinal pyrrolic nitrogen atoms of porphyrins was easily achieved by using CHCl3/NaOH/ROH in the presence of a phase-transfer agent.Alkylation of a third nitrogen atom of the resulting bases and acid-catalyzed hydrolysis of the bridge allowed the preparation of various N-monosubstituted porphyrins.The bridged bases acted as a bidentate ligand toward palladium(II) and mercury(II) to give sitting-atop metal complexes.The crystal and molecular structure of (N,N'-((benzyloxy)methylene)tetraphenylporphyrin-N'',N''')dibromopalladium(II), PdBr2(N4OC52H36)-CH2Cl2, have been determined from three-dimensional single crystal X-ray diffraction data, collected by counter techniques.The dark purple crystals are triclinic of space group P1 (No. 1) with one formula unit in the unit cell of dimensions a = 10.591(2) Angstroem, b = 10.706(1) Angstroem, c = 12.650(1) Angstroem, α = 118.82(1) deg, β = 114.63(1) deg, and γ = 77.68(1) deg.The structure has been refined by least-squares methods to R = 0.051 (R_w = 0.067) for 3569 unique reflections having F² > 3?(F²).The (benzyloxy)methylene moiety bridges two adjasent nitrogen atoms and the PdBr2 group bridges the two other nitrogen atoms leading to a very distorted porphyrin ring.The palladium atom is out of the 4N mean plane by 1.460 Angstroem, and the individual pyrrole rings make dihedral angles with the 4N plane between 8.2 and 21.3 deg.