Synthesis and Reactivity of Dipalladated Derivatives of Terephthalaldehyde.

The polynuclear complex [{μ-1,4,,″-CH{C(H)=N(Bu)}-2,5}{Pd(μ-OAc)}] () reacts with tbbpy (4,4'-di--butyl-2,2'-bipyridine) and TlOTf to form the dinuclear complex [{μ-1,4,,″-CH{C(H)=N(Bu)}-2,5}{Pd(tbbpy)}] (). The hydrolysis of with acetic acid in a 5:1 acetone/water mixture, in the presence of two equivalents of tbbpy and excess NaX (X = Br, I), yields the dipalladated terephthalaldehyde complexes [CH{PdX(tbbpy)}-1,4-(CHO)-2,5] [X = Br (), X = I ()], which are the first fully characterized complexes of this type. The reaction of with CO results in the insertion of CO into both aryl-Pd bonds, forming [CH{C(O){PdX(tbbpy)}}-1,4-(CHO)-2,5] [X = Br (), X = I ()], which are the first examples of complexes with CO inserted into two separate aryl-metal bonds involving the same ligand. The bromo complex reacts with excess XylNC in acetone, causing the precipitation of the dinuclear complex 2,3,6,7-tetrahydrobenzo[1,2-:4,5-']dipyrrole-1,5-dione-2,6-dixylyl-3,7-bis{=C(NHXyl)-C(=NXyl)-[PdBr(CNXyl)]} (), which is the result of the insertion of three molecules of the isocyanide into each aryl-Pd bond and the nucleophilic attack of one of them at each formyl group. When complex reacts with TlOTf and residual water in 1,2-dichloroethane at 70 °C, depalladation occurs, and the organic compound 2,3,6,7-tetrahydrobenzo[1,2-:4,5-']dipyrrole-1,5-dione-2,6-dixylyl-3,7-bis{=C(NHXyl)-C(O)NHXyl} () can be isolated. The crystal structures of ·4CHCl, ·2CHCl·3hexane, and ·2CDCl have been determined by X-ray crystallography.