A novel triangulo complex was generated by heating, in vacuo, a racemic C-2-symmetric octahedral nickel(II) diamine complex. The trinuclear species was identified by single-crystai X-ray diffraction, which revealed a 2:1 ligand stereochemistry relationship in each unit. This solid-state structure evidences the hypothesis that a 1:2 stereochemical relationship lies at the heart of the strong positive nonlinear effect observed in enecarbamate aldol-like reactions catalyzed by nickel(II) diamine complexes.