Jahn-Teller Switching of a Redox-Active Nickel(III) Center in a Homoleptic Thiolato Metalloligand Environment

The thermally stable trinuclear complex[Ni{Ir(3-aminopropanethiolate)(3)}(2)](3+) having an octahedral Ni-III center surrounded by thiolatodonors, together with its one-electronreduced and oxidized species, was newly synthesized, isolated, andstructurally characterized. The octahedral Ni-III centershowed a Jahn-Teller distortion that is reversibly convertedto a different distortion on dehydration/rehydration in the solidstate. Treatmentof nickel(II) nitrate with the iridium(III)metalloligand fac-[Ir(apt)(3)] (apt = 3-aminopropanethiolate)gave the trinuclear complex [Ni{Ir(apt)(3)}(2)](NO3)(3) ([1 ( Ir )](NO3)(3)), in which the nickel center has a formal oxidationstate of +III. Chemical or electrochemical oxidation and reductionof [1 ( Ir )](NO3)(3) generated the corresponding trinuclear complexes [Ni{Ir(apt)(3)}(2)](NO3)(4) ([1 ( Ir )](NO3)(4)) and [Ni{Ir(apt)(3)}(2)](NO3)(2) ([1 ( Ir )](NO3)(2)) with one-electronoxidated and reduced states, respectively. Single-crystal X-ray crystallographyrevealed that the nickel center in [1 ( Ir )](NO3)(3) is situated in a highly distortedoctahedron due to Jahn-Teller effect, while the nickel centerin each of [1 ( Ir )](NO3)(4) and [1 ( Ir )](NO3)(2) adopts a normal octahedral geometry. Crystalsof [1 ( Ir )](NO3)(3)center dot 2H(2)O are dehydrated on heating while retainingtheir single-crystallinity. The dehydration induces temperature-dependentdynamic disorder of the Jahn-Teller distortion at the nickel(III)center, which is largely quenched upon rehydration of the crystal.