P--P bond cleavage of tetraphenyltetraphosphane-1,4-diide facilitated by nickel(0)

One equivalent of Na2(thf)5-(P4Ph4)] (1) reacts with one equivalent of Ni(cod)2] (cod=1,5-cyclooctadiene) to give the unexpected ionic compound Na(Et2O)3]Na3(Et2O)2Ni3(micro-P2Ph2)2-(P2Ph2)3] (2), whereas the reaction of Ni(cod)2] with the less reactive K2(pmdeta)2(P4Ph4)] (3) leads to the formation of K(pmdeta)]2Ni(P4Ph4)-(P2Ph2)] (4) (PMDETA=NMe(CH2CH2NMe2)2), in which K--Ni interactions are observed. The calculations for 4 confirm the structural parameters obtained by X-ray diffraction studies. A shared electron number (SEN) analysis was applied to investigate the K...Ni interactions. These studies indicate a SEN value of a typical three-center, two-electron bond for K1-Ni-K2 indicating a covalent contribution in the interaction between nickel and potassium.