Pentacoordinate cobalt(III) thiolate and nitrosyl tropocoronand compounds

Reaction of [Co(TC-n,m)](+) with (Me4N)(SC6F5), where (TC-n,m) is a tropoco ronand with n and m linker chain methylene groups, yielded the thiolate com plexes [Co(SC6F5)(TC-3,3)] (1a), and [Co(SC6F5)(TC-4,4)] (2a), which were s tructurally characterized. Use of more electron-releasing thiolates afforde d the [Co(TC-n,m)] reduction product and the corresponding disulfide. The b ent nitrosyl complexes [Co(NO)(TC-3,3)] (1b) and [Co(NO)(TC-4,4)] (2b) were synthesized from [Co(TC-n,m)] and NO and their structures were also determ ined. Compounds 2a and 1b have square-pyramidal geometry like all other str ucturally characterized [MX(TC-3,3)] complexes. Compounds 2a and 2b have tr igonal-bipyramidar stereochemistry, formerly rare for Co(III). Although 1a, 1b, and 2a are paramagnetic, 2b is diamagnetic due to the strong antibondi ng pi -interaction between the metal and NO pi* orbitals. in the presence o f excess NO, [Co(TC-4,4)] exhibited novel reactivity in which a putative Co (N-2) adduct formed.