Ring-opening reactions induced by gold(i) of five- and four-coordinate palladium(ii) and platinum(ii) complexes containing tripodal or linear polyphosphines

Abstract

The tripodal ligands NP₃ (tris[2-(diphenylphosphino)ethyl]amine) and PP₃ (tris[2-(diphenylphosphino)ethyl]phosphine), form five-coordinate [Pd(NP₃)X]X [X = Cl (1), Br (2)], [M(PP₃)X]X [M = Pd: X = Cl (4), Br (5), I (6); M = Pt, X = Cl (7), Br (8), I (9)] and four-coordinate[Pd(NP₃)I]I (3) complexes containing three fused rings around the metal. The interaction between Au(tdg)X (tdg = thiodiglycol; X = Cl, Br) or AuI and the respective ionic halo complexes 1–9 in a 1∶1 stoichiometric ratio occurs via a ring-opening reaction with formation of the heterobimetallic systems PdAu(NP₃)X₃ [X = Cl (11), Br (12), I (13)], [MAu(PP₃)X₂]X [M = Pd: X = Cl (14), Br (15), I (16); M = Pt: X = Cl (17), Br (18), I (19)]. The cations of complexes 17 and 18 were shown, by X-ray diffraction, to contain a distorted square-planar Pt(II) arrangement (Pt(P₂P)X) where PP₃ is acting as tridentate chelating ligand and an almost linear PAuX moiety bearing the dangling phosphorus formed in the ring-opening process. PPh₃ coordinates to Au(I) and not to M(II) when added in excess to 14 and 17. Complexes 14–17 and [Pt(P₄)](BPh₄)₂ (10) (P₄ = linear tetraphosphine) also react with A(I), via chelate ring-openings to give MAu₂(PP₃)X₄ [M = Pd: X = Cl (20), Br (21), I (22); M = Pt: X = Cl (23)] and [Pt₂Au₂(μ-Cl)₂(μ-P₄)₂](BPh₄)₄ (24), respectively.