摘要：

J. CHEM. SOC. DALTON TRANS. 1990 Synthesis and Characterization of Novel Metal(iii) Complexes of Corrole. Crystal and Molecular Structure of (2,3,7,8,12,13,17,18-Octamethyl- corrolato) (triphenylarsine)rhodium( 1 1 1 ) * Dipartimento di Scienze e Tecnologie Chimiche I/ Universita ' di Roma 'Tor Vergata ' 00 1 73 Rome Italy Giancarlo Pelizzi and Francesca Vitali Tristano Boschi," Silvia Licoccia Roberto Paolesse Pietro Tagliatesta and Massoud Azarnia Tehran lstituto di Chimica Generale Universita di Parma and Centro di Studio per la Strutturistica Diffratometrica del CNR Viale delle Scienze 43100 Parma Italy Transition-metal complexes of 2,3,7,8,12,13,17,18-octamethylcorrole (H,omc) have been prepared in high yield by means of three different synthetic procedures.The macrocycle acts as a trianionic ligand leading to the formation of neutral species. The crystal and molecular structure of the compound [Rh(AsPh,) (omc)] has been determined by X-ray diffraction methods. The crystals are orthorhombic space group P2,2,2, with unit-cell dimensions a = 20.1 7 2 ( 7 ) b = 12.468(5) c = 14.893(5) A and Z = 4. The structure was solved by the heavy-atom technique and refined to R = 0.0353 for 1 436 independent reflections. The rhodium atom has a distorted square-pyramidal environment the basal positions being occupied by the four nitrogen atoms from the corrole ligand and the apex by the arsenic atom from the triphenylarsine molecule. Transition-metal complexes of tetrapyrrolic macrocycles have been widely studied for numerous reasons including their similarity to biologically important systems their use as dyestuffs and their applications in catalysis and photocataly- sis.'*2 Among the various macrocycles a very interesting one is corrole which can be considered as intermediate in structure between porphyrin and corrin (Figure 1) it has a direct link between the A and D pyrrole rings thus resembling the corrin skeleton and an 18-electron x system involving porphyrin-like conjugation hence it is aroma ti^.^ Corrole bears obvious relation to corrin the chromophore (as its cobalt complex) of vitamin BI2 and its peculiar structure allows one to study the extent to which modifications of the porphyrin nucleus are possible while still retaining aromatic character and co-ordination ability towards metal ions.The aromaticity of corrole is confirmed by its electronic spectrum which is characterized by two strong absorptions centred at about 400 and 600 nm. These bands have been attributed to n to x* transitions similar to the Soret and Q bands observed in the spectra of porphyrins. The lower symmetry of corrole is reflected by the fact that the higher- energy band is broader than the corresponding one for por- phyrins so that it probably consists of two more unresolved transition^.^ Calculations of the x-electron distributions have been re- ported indicating that a proton hole is located at N(22) and that the D ring is tilted out of the mean plane of the other three pyrrole rings. An X-ray study performed on 8,12-diethyl- ( C ) N HN (dl 2,3,7,13,17,18-hexamethylcorrole has indeed shown that the molecule is not strictly planar the distortion being probably caused by short N N contacts brought about by the direct C(l)-C(19) link and by steric repulsion between the 2- and 18- methyl groups.Ring D is rotated by 8-10" but conjugation stabilization is still important since only small rotations of rings A-C are observed. The n.m.r. spectrum of corrole is a further proof of the * Supplementary data available see Instructions for Authors J. Chem. SOC. Dalton Trans. 1990 Issue 1 pp. xix-xxii. 463 Figure 1. The structural formulae of 1,19-dideoxybiladiene-a~ (a) corrole (b) corrin (c) and porphyrin ( d ) existence of an aromatic system all resonances show a strong upfield shift which has been attributed to the macrocycle ring current. * As far as co-ordination with transition-metal ions is con- cerned corrole having three amino-like nitrogens should act as a trianionic ligand stabilizi

展开