Peripherally-metallated porphyrins: synthesis and spectra of meso-eta(1)-palladio- and platinioporphyrins and the crystal structures of cis-{PtBr[l 0,20-diphenylporphyrinatonickel(II)-5-yl](PPh3)(2)} and trans-{PtBr[10,20-diphenylporphyrin-5-yl](PPh3)(2)}center dot 0.25CH(2)Cl(2)

A series of meso-eta(1)-palladio(II)- and platinio(II)porphyrins containing either monodentate Group 15 ligands (PPh3, AsPh3) or chelating diphosphine s (dppe, dppp, dppf) has been prepared by oxidative addition of mono- and d ibromo derivatives of 5,15-diphenylporphyrin (H2DPP) to Pd(0) and Pt(0) pre cursors. The products were characterized by their H-1- and P-31-NMR, visibl e absorption, and mass spectra and the X-ray crystal structures of trans-[P tBr(H2DPP)(PPh3)(2)] (14) (as a 0.25CH(2)Cl(2) solvate) and cis-[PtBr(NiDPP )(PPh3)(2)] (15) were determined. The structures show approximately square planar geometry about the Pt atoms, although there are distortions due to c rowding of the PPh3 ligands in 15. The NiDPP ring in 15 suffers ruffling ty pical of peripherally-crowded Ni(II) porphyrins, the pairs of opposite meso carbons being displaced alternately > +/- 0.4 Angstrom out of the C20N4 me an plane The conformations of the phenyl groups of the PPh3 ligands indicat e the presence of non-covalent phenyl-porphyrin pi-pi interactions. These d erivatives are the first isolated examples of peripheral organometallic por phyrins with direct transition metal to porphyrin sigma-bonds, and they rep resent a new class of superstructured porphyrins with one or both faces of the macrocycle heavily shielded by the phenyl groups on the auxiliary ligan ds. (C) 2000 Elsevier Science S.A. All rights reserved.