Synthesis, characterization, and protonation of octaethylporphyrin osmium nitrosyl complexes containing axial thiolate ligands - X-ray structures of an alkyl thionitrite (RSNO) and its (OEP)Os(NO)(SR) addition product

The (OEP)Os(NO)(SR) compounds (R = Me, Et, i-Pr, t-Bu) have been prepared in 33-48% isolated yields by the formal trans-addition of the precursor alkyl thionitrites (RSNO) across the metal center in (OEP)Os(CO). The nitrosyl thiolate compounds have been characterized by IR, 1H NMR, and UV-vis spectroscopy, and by FAB mass spectrometry. Their IR spectra display bands in the 1751-1755 cm-1 (KBr) range, which is indicative of terminal N-bound NO ligands in this class of compounds. The thiolate-thiol (OEP)Os(NO)(SCH2CH2SH) complex has been prepared in 70% isolated yield from the reaction of (OEP)Os(NO)(O-i-C5H11) with ethane-1,2-dithiol. Nitrosation of the free -SH group in (OEP)Os(NO)(SCH2CH2SH) with t-BuONO, followed by reaction with (TTP)Ru(CO) gave [(OEP)Os(NO)](µ-SCH2CH2S-S,S')[Ru(NO)(TTP)] in 70% yield by 1H NMR spectroscopy. The (OEP)Os(NO)(SCR'2CH2NHC(O)Me) compounds have also been prepared either by an alkoxide-thiolate exchange reaction (for R' = H) or by RSNO addition to (OEP)Os(CO) (for R' = Me). ...