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Structure of Noble Metal Porphyrins

As already mentioned, the coordination type of the Ru, Os, Rh and Ir porphyrins is C (Fig. 2), i.e. distorted octahedral about the metal which is in most cases a d6 system occasionally, d5, d4, or d2 systems are encountered. Table 2 gives a compilation of compounds the molecular structures of which have been determined by X-ray crystallography. The numbers of entries given for the individual noble metals approximately reflects the intensity of research done for the respective metal. For details and special structural aspects, the reader is referred to the original literature and a previous review by Scheidt and Lee [143]. Here, just a few general notes will be made. Phthalocyanine systems are not incorporated. [Pg.20]

Only a few compounds containing Ru, Os, Rh or Ir do not possess type C. Notable are the metalloporphyrin dimers with Ru = Ru (entry 3) or Rh-In bonds (entry 34), the alkyl or acyl rhodium(III) (entries 31, 36, 38), alkyl-iridium(III) (entry 39) or arylruthenium(III) compounds (entry 12). All these species contain pentacoordinate noble metal ions, Type B. A reason for this unusual behavior of the metal ions is seen in the strong trans effect of the axial ligand L in these systems which is a strong o-donor (metalloporphyrinyl, alkyl, aryl, acyl) which precludes further coordination in the trans position of L. The reluctance of RhMe(OEP) to accept an axial ligand is shown by its crystallization as a re-dimer from n-hexane in presence of the base 1-Meim. [Pg.20]

An exception is found with alkyl iridium porphyrins and re-acceptor ligands. In the n-propyl iridium complex, Ir(C3H7)(OEP)L with L = PPh3 (entry 41) and DMSO, type C is found. The sulfoxide is S-bound in the DMSO complex. [Pg.20]

The bidentate bis(diphenylphosphino) alkane ligands (entries 8 and 42) are not capable of forcing the porphyrin ligand to leave the equatorial position of noble metal porphyrins. Either two bidentates are bound in a monodentate fashion, or a bidentate bridges two metalloporphyrin entities. [Pg.20]

The d8 and d9 metal ions, Pd(II), Pt(II), and Ag(II), as in other complexes, prefer the square-planar coordination type given as A in Fig. 2 (entries 44-50). [Pg.22]


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