The four phosphorus atoms are at the corners of a tetrahedron surrounding the palladium(0) center. This structure is typical for four-coordinate 18 e complexes. The corresponding complexes Ni(PPh) and Pt(PPh) are also well known. Such complexes reversibly dissociate PPh ligands in solution, so reactions attributed to Pd(PPh) often in fact arise from Pd(PPh) or even Pd(PPh).