Synthesis and Molecular Structure of a Palladium Complex Containing a λ<sup>5</sup>-Phosphinine-Based SPS Pincer Ligand

2,6-Bis(diphenylphosphino)-3,5-diphenylphosphinine (<b>1</b>) reacts with elemental sulfur to yield the corresponding 2,6-bis(diphenylphosphine sulfide)-3,5-diphenylphosphinine (<b>2</b>). Reaction of ligand <b>2</b> with [Pd(COD)Cl<sub>2</sub>] affords the square planar complex <b>4</b> resulting from the displacement of one chloride ligand. An X-ray crystal study reveals that complex <b>4</b> features a λ<sup>4</sup>-1-<i>P</i>-chlorophosphinine ligand which is bound to the palladium atom through the phosphorus atom. Reaction of <b>4</b> with methanol gives the corresponding P−OMe complex resulting from the nucleophilic substitution of the P−Cl bond. DFT calculations suggest that the formation of <b>4</b> results from the internal attack of the chloride counteranion onto the highly electrophilic P atom of the transient λ<sup>3</sup>-phosphinine complex [Pd(<b>2</b>)Cl]<sup>+</sup> (<b>3</b>).