Synthesis, reactivity, and X-ray crystallographic characterization of mono-, di-, and tetranuclear palladium(II)-metalated species

The reactivity of the tetranuclear metallated palladium compound {Pd[mu (2) -(C6H4)PPh2]Br}(4) (1) with different ligands has been investigated with th e aim of evaluating the influence of the entering ligand on the nature of t he reaction products. The results confirmed the ability of the ligand [(C6H 4)PPh2](-) to expand a bridging [mu (2)-] or a chelating [eta (2)-] coordin ation mode, depending on the auxiliary Ligands present in the complex. Bulk y phosphines stabilize mononuclear species of formula {Pd[eta (2)-(C6H4)PPh 2]Br[P]}, with a four-atom metallocycle, while small phosphines give dinucl ear compounds. The molecular structures of three different metalated pallad ium compounds have been determined by single-crystal X-ray crystallography; the tetranuclear {Pd[mu (2)-(C6H4)PPh2]Cl}(4) (2), the dinuclear-{Pd[mu (2 )-(C6H4)PPh2]Br[PMe3]}(2) (3), and the mononuclear {Pd[eta (2)-(C6H4)PPh2]B r[PCBr]}, (PCBr = P(o-BrC6H4)-Ph-2) (9) were obtained, the first one by hal ogen exchange reaction and the others by frame degradation of 1.