Facile Formation of Stable Tris(imido)phosphate Trianions as Their Tri- and Hexanuclear Pd(II) Complexes in Protic Solvents

Employing Pd­(OAc)2, a facile deprotonation route to access the highly basic tris­(alkylimido)­phosphate trianions, [(RN)3PO]3– (R = tBu, cHex, or iPr), analogous to the orthophosphate (PO43–) ion in polar and in protic solvents has been achieved. Trinuclear and prismatic Pd­(II) clusters of these imido trianions having the formula {Pd3[(NR)3PO]­(OAc)3}n (n = 1 or 2) or as mixed-bridged clusters of the type {Pd3[(NiPr)3PO]­(OAc)2(OR′)}2 (R′ = Me or H) were isolated exclusively in all these reactions in which the trianionic species acts as a tripodal chelating ligand to the trinuclear Pd3 unit. Reactivity studies aiming at the Pd­(II) atoms in these clusters with nucleophilic reagents, such as primary amines (R″NH2), have led to a new trimeric cluster with the formula {Pd3[(NR)3PO]­(OAc)3(R″NH2)3} in which the tripodal coordination of the Pd–Nimido moieties remained unaffected, exemplifying the robustness of the Pd3 unit in all these clusters. We have also shown the catalytic activity of these Pd­(II) complexes in Mizoroki–Heck type coupling reactions in the presence of Cu­(OAc)2.