Redox‐Controlled, Reversible Rearrangement of a Tris(2‐pyridylthio)methyl Ligand on Nickel to an Isomer with an “ N , S ‐Confused” 2‐Pyridylthiolate Arm

Interchange between the nickel +2 and +3 oxidation states precisely controls the reversible rearrangement of the tris(2‐pyridylthio)methanide (tptm) ligand in the organometallic nickel(II) complex [{Ni(μ‐Br)(tptm)} 2 ] ( 2 ). Oxidation of 2 first gives the corresponding Ni III complex [{Ni(μ‐Br)(tptm)} 2 ][PF 6 ] 2 ( 4 ). However, in solution the tptm ligand in 4 slowly undergoes a rearrangement, in which the N and S atoms of one of the pyridylthiolate arms exchange Ni and C bonding partners, thereby resulting in an “ N , S ‐confused” isomer of tptm in the product, [NiBr(bpttpm)]PF 6 ( 5 ; bpttpm=bis(2‐pyridylthio)(2‐thiopyridinium)methyl). Reduction of 5 reverses this ligand rearrangement and 2 is reformed quantitatively. The individual steps involved in these unusual ligand rearrangements were investigated by a number of methods, including voltammetric analysis, and a mechanism for this process is proposed. X‐ray crystal structure determinations of the key compounds 2 , 4 and 5 have been obtained.