4 `-(Oxodiphenylphosphino)-2,2 `: 6 `,2 ``-terpyridine - crystal structure and complexes of cobalt(II) and cobalt(III)

The complex [Co(2)(2)](2+) (2 = 4`-(oxodiphenylphosphino)-2,2`:6`,2``-terpyridine) has been prepared either by the direct reaction of 2 with Co(II) or by careful oxidation of [Co(1)(2)](2+)(1 = 4`-(diphenylphosphino)-2,2`:6`,2``-terpyridine). Further oxidation with H2O2 leads to [Co(2)(2)](3+). The H-1 NMR spectra of the paramagnetic and diamagnetic [Co(2)(2)](2+) and [Co(2)(2)](3+) are reported. The crystal structure of ligand 1 has been determined; in the solid-state, 1 exhibits extensive intermolecular pi-pi stacking.