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

Treatment of nickel(II) nitrate with the iridium(III) metalloligand fac -[Ir(apt) 3 ] (apt = 3-aminopropanethiolate) gave the trinuclear complex [Ni{Ir(apt) 3 } 2 ](NO 3 ) 3 ([ 1 Ir ](NO 3 ) 3 ), in which the nickel center has a formal oxidation state of +III. Chemical or electrochemical oxidation and reduction of [ 1 Ir ](NO 3 ) 3 generated the corresponding trinuclear complexes [Ni{Ir(apt) 3 } 2 ](NO 3 ) 4 ([ 1 Ir ](NO 3 ) 4 ) and [Ni{Ir(apt) 3 } 2 ](NO 3 ) 2 ([ 1 Ir ](NO 3 ) 2 ) with one-electron oxidated and reduced states, respectively. Single-crystal X-ray crystallography revealed that the nickel center in [ 1 Ir ](NO 3 ) 3 is situated in a highly distorted octahedron due to Jahn-Teller effect, while the nickel center in each of [ 1 Ir ](NO 3 ) 4 and [ 1 Ir ](NO 3 ) 2 adopts a normal octahedral geometry. Crystals of [ 1 Ir ](NO 3 ) 3 ·2H 2 O are dehydrated on heating while retaining their single-crystallinity. The dehydration induces temperature-dependent dynamic disorder of the Jahn-Teller distortion at the nickel(III) center, which is largely quenched upon rehydration of the crystal.