The isomerization of the branched 2M3BN to the linear 3PN by a DPEphosNi species has been investigated by means of variable-temperature NMR spectroscopy, and activation parameters have been determined. An intermediate in this reaction, which is formed via C-C bond activation, could be trapped by addition of ZnCl2, and the molecular structure of the corresponding Ni(II) complex has been determined by X-ray crystallography.