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 i n 33-48% isolated yields by the formal trans-addition of the precursor alky l thionitrites (RSNO) across the metal center in (OEP)Os(CO). The nitrosyl thiolate compounds have been characterized by IR, H-1 NMR, and UV-vis spect roscopy, and by FAB mass spectrometry. Their IR spectra display bands in th e 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)(SCH2CH2S H) complex has been prepared in 70% isolated yield from the reaction of (OE P)Os(NO)(O-i-C5H11) with ethane-1,2-dithiol. Nitrosation of the free -SH gr oup in (OEP)Os(NO)(SCH2CH2SH) with t-BuONO, followed by reaction with (TTP) Ru(CO) gave [(OEP)Os(NO)](mu -SCH2CH2S-S,S')[Ru(NO)(TTP)] in 70% yield by H -1 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). The solid-state molecula r structures of the precursor RSNO thionitrite (for R' = Me) and the metall oderivative have been determined by single-crystal X-ray crystallography. P rotonation of these (OEP)Os(NO)(SCR'2CH2NHC(O)Me) complexes gave the amide- bound [(OEP)Os(NO)(O=C(Me)NHCH2CR'2SH)]BF4 derivatives. The latter cationic compounds were also obtained by the sequential reaction of (OEP)Os(CO) wit h nitrosonium tetrafluoroborate, followed by addition of the amide-thiol re agent.