Synthesis and electrochemistry of dialkylosmium-(IV) and -(V) porphyrins. Crystal structure of [Os(ttp)(CH2SiMe3)2][H2ttp = 5,10,15,20-tetra(p-tolyl)porphyrin]

Abstract

Reaction of [Os(por)O2][por = 5,10,15,20-tetra(p-tolyl)porphyrinate (ttp) or 2,3,7,8,12,13,17,18-octaethylporphyrinate (oep)] with thionyl chloride gave [Os(por)Cl2] in good yields. The dichloride compounds are paramagnetic with µeffca.2.7 µB and display temperature-independent contact-shifted 1H NMR spectra. Reaction of [Os(por)Cl2] with an excess of LiR (R = Ph or Me3SiCH2) gave air-stable diamagnetic dialkyl compounds [Os(por)R2]. The structure of [Os(ttp)(CH2SiMe3)2] has been established by X-ray crystallography. Cyclic voltammograms of the diphenyl compounds exhibit reversible metal-centred OsV–OsIV and OsIV–OsIII couples. Treatment of [Os(ttp)Ph2] with CeIV or AgBF4 afforded the diphenylosmium(V) compound [Os(ttp)Ph2]BF4, which is paramagnetic with µeffca. 1.7 µB.