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Review | Regular issue | Vol 87, No. 1, 2013, pp.31-54
Published online, 16th November, 2012
DOI: 10.3987/REV-12-757
Boron and Phosphorus Complexes of meso-Aryl Expanded Porphyrins

Tomohiro Higashino and Atsuhiro Osuka*

*Department of Chemistry,, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan

Abstract

Our recent efforts in the boron and phosphorus insertion reactions into meso-aryl expanded porphyrins are reviewed. Boron insertion into [28]hexaphyrin(1.1.1.1.1.1) 19 triggered a skeletal rearrangement to bis-boron complex of [28]hexaphyrin(2.1.1.0.1.1) 20. Boron-insertion into quadruply N-fused heptaphyrin 23 with BBr3 and EtNiPr2 followed by treatment with an alcohol gave corresponding boron complex 24-OR. Treatment of non-fused heptaphyrin mono-Cu(II) complex 25 with BBr3 and EtNiPr2 induced a splitting reaction to B(III) subporphyrin 26 and Cu(II) porphyrin 27. Phosphorus insertion to N-fused [24]pentaphyrin 30 led to the formation of multiply fused P(V) complex 31, which was reduced to P(III) complex 33 with BH3·Me2S as a rare P(III) porphyrinoid. Phosphorus insertion to 19 proceeded in a stepwise manner to give mono-P(V) complex 38 and bis-P(V) complex 39, which were, respectively, identified to be Möbius aromatic and antiaromatic molecules. Phosphorus insertion into [34]heptaphyrin 40 gave Möbius antiaromatic P(V) complex 43 and Hückel aromatic P(V) complex 44. Upon heating in acetonitrile, 43 was cleanly converted to 44, indicating that 43 was a kinetically formed Möbius antiaromatic product as the first case. Phosphorus insertion into [36]octaphyrin 5 led to the formation of [38]octaphyrin mono-P(V) complex 47 and [40]octaphyrin bis-P(V) complex 48. The latter complex is a fully reduced octaphyrin, hence representing the first example of expanded isophlorins, but is stable under ambient conditions.