Ethynyl porphyrins bridging bis(phosphine)platinum(II) centers: molecular models for conjugated organometallic porphyrin polymers

Linear ethynylporphyrin-bridged platinum(II) complexes, [X(R3P)(2)Pt-C=C-Zn (por)-C=C-Pt(PR3)(2)Y] [Zn(por) is a non-ethynylated porphyrin 1a] and rela ted oligomers have been synthesized. Di- and tri-nuclear platinum centers a re linked to different porphyrin arrays; the end groups Pt(PR3)(2)X and Pt( PR3)(2)Y (R = n-Bu or Ph; X = Y = Cl or I; X = Cl, Y = I) show that a ligan d exchange Cl--> I also occurs. The compounds containing PBu3 as the ligand are more stable than the corresponding PPh3 ones. The dinuclear platinum d imers containing one bridging porphyrin have been isolated and characterize d by IR, UV/VIS, H-1 NMR and MALDI (matrix assisted laser desorption/ioniza tion) mass spectroscopies. The mixture of longer oligomers was separated fr om the crude reaction products and could be identified by MALDI. The cis-tr ans isomerization of the porphyrin complexes with respect to the platinum p recursor complexes, ie. trans-[PtCl2(PBu3)(2)], cis-[PtCl2(PPh3)(2)] and tr ans-[PtH(Cl)(PPh3)(2)], was observed. The dimers and oligomers are expected to be model molecules for long chain organometallic polymers.