meso-Porphyrinylphosphine Oxides: Mono- and Bidentate Ligands for Supramolecular Chemistry and the Crystal Structures of Monomeric {[10,20-Diphenylporphyrinatonickel(II)-5,15-diyl]-bis-[P(O)Ph2] and Polymeric Self-Coordinated {[10,20-Diphenylporphyrinatozinc(II)-5,15-diyl]-bis-[P(O)Ph2]}

Inorg. Chem., 45 (16), 6479 -6489, 2006. 10.1021/ic060372u S0020-1669(06)00372-7
Web Release Date: July 14, 2006

meso-Porphyrinylphosphine Oxides: Mono- and Bidentate Ligands for Supramolecular Chemistry and the Crystal Structures of Monomeric {[10,20-Diphenylporphyrinatonickel(II)-5,15-diyl]-bis-[P(O)Ph₂] and Polymeric Self-Coordinated {[10,20-Diphenylporphyrinatozinc(II)-5,15-diyl]-bis-[P(O)Ph₂]}

Farzad Atefi, John C. McMurtrie, Peter Turner, Martin Duriska, and Dennis P. Arnold*

Synthesis and Molecular Recognition Program, School of Physical and Chemical Sciences, Queensland University of Technology, GPO Box 2434, Brisbane 4001, Australia, Crystal Structure Analysis Facility, School of Chemistry, University of Sydney, NSW 2006, Australia and School of Chemistry, Monash University, Victoria 3800, Australia

Received March 6, 2006

Abstract:

A series of porphyrins substituted in one or two meso positions by diphenylphosphine oxide groups has been prepared by the palladium-catalyzed reaction of diphenylphosphine or its oxide with the corresponding bromoporphyrins. Compounds {MDPP-[P(O)Ph₂]_n} (M = H₂, Ni, Zn; H₂DPP = 5,15-diphenylporphyrin; n = 1, 2) were isolated in yields of 60-95%. The reaction is believed to proceed via the conventional oxidative addition, phosphination, and reductive elimination steps, as the stoichiometric reaction of ¹-palladio(II) porphyrin [PdBr(H₂DPP)(dppe)] (H₂DPP = 5,15-diphenylporphyrin; dppe = 1,2-bis(diphenylphosphino)ethane) with diphenylphosphine oxide also results in the desired mono-porphyrinylphosphine oxide [H₂DPP-P(O)Ph₂]. Attempts to isolate the tertiary phosphines failed due to their extreme air-sensitivity. Variable-temperature ¹H NMR studies of [H₂DPP-P(O)Ph₂] revealed an intrinsic lack of symmetry, while fluorescence spectroscopy showed that the phosphine oxide group does not behave as a "heavy atom" quencher. The electron-withdrawing effect of the phosphine oxide group was confirmed by voltammetry. The ligands were characterized by multinuclear NMR and UV-visible spectroscopy, as well as mass spectrometry. Single-crystal X-ray crystallography showed that the bis(phosphine oxide) nickel(II) complex {[NiDPP-[P(O)Ph₂]₂} is monomeric in the solid state, with a ruffled porphyrin core and the two P=O fragments on the same side of the average plane of the molecule. On the other hand, the corresponding zinc(II) complex formed infinite chains through coordination of one Ph₂PO substituent to the neighboring zinc porphyrin through an almost linear P=O···Zn unit, leaving the other Ph₂PO group facing into a parallel channel filled with disordered water molecules. These new phosphine oxides are attractive ligands for supramolecular porphyrin chemistry.

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