“…In this case, the two vacant σ hybrids of the L 2 M fragment lie high in energy for having exclusive s/p character without any d contribution. In general, the known Ni, Pd, Pt tetrahedra are stabilized by strong σ donors such as four COs42 or 2COs + 2R 3 P ligands 43,44. Since some complex is known with a dinitrogen chelate,45 we used the species (CO) 2 Ni(NH 3 ) 2 as a model reactant for the reaction with P n , reported in eqn (4).…”