Synthesis of zwitterionic phosphapalladacycles: unusual reactivity pattern of six-membered P,N-chelates

A cyclometalation motif has been discovered in the unprecedented reaction of Pd(II) precursors with simple pentane-2,4-diyl based aminoalkyl-phosphines. The unique six-membered zwitterionic palladacycles can easily be synthesized in the presence of 1 molar equiv of oxidant in high yields in a pure form. A comparison between the analogous ligands of different tether lengths revealed that the formation of the zwitterionic palladacycles is the exclusive privilege of the six-membered rings.