Reactivity of Dioxoosmium(VI) Porphyrins toward Arylhydrazine. Isolation of Hydrazidoosmium and Amidoosmium Porphyrins

Abstract

Reactions of dioxoosmium(VI) porphyrins [OsVI(Por)O 2] with excess 1,1-diphenylhydrazine in tetrahydrofuran at ca. 55 °C for 15 min afforded bis(hydrazido(1-))osmium(IV) porphyrins [Os IV(Por)(NHNPh2)2] (1a, Por = TPP (mesotetraphenylporphyrinato dianion); 1b, Por = TTP (meso-tetrakis(p-tolyl)porphyrinato dianion)), hydroxo(amido)-osmium(IV) porphyrins [OsIV(Por)(NPh2)(OH)] (2a, Por = TPP; 2b, Por = TTP), and bis(hydrazido(2-))osmium(VI) porphyrin [Os VI(Por)(NNPh2)2] (3c, Por = TMP (meso-tetramesitylporphyrinato dianion)). The same reaction under harsher conditions (in refluxing tetrahydrofuran for ca. 1 h) gave a nitridoosmium(VI) porphyrin, [OsVI(Por)(N)(OH)] (4b, Por = TTP). Oxidation of 1a,b with bromine in dichloromethane afforded bis(hydrazido(2-)) complexes [Os VI-(TPP)(NNPh2)2] (3a) and [Os VI(TTP)(NNPh2)2] (3b), respectively. All the new osmium porphyrins were identified by 1H NMR, IR, and UV-vis spectroscopy and mass spectrometry; the structure of 2b was determined by X-ray crystallography (Os-NPh2 = 1.944(6) Å, Os-OH = 1.952(5) Å).