Novel chelate ring-opening induced by silver(I) of five-coordinate palladium(II) and platinum(II) complexes containing tripodal polyphosphines

The ionic complexes [Pd(NP3)X]X [NP3 = tris[2-(diphenylphosphino)ethyl]amine, X = Cl (1), Br(2)] and [M(PP3)X]X [PP3 = tris[2-(diphenylphosphino)ethyl]phosphine, M = Pd, X = Cl (3), Br(4); M = Pt, X = Cl (5), Br (6)] contain square pyramidal (1, 2) and trigonal bipyramidal (3-6) cations with three fused chelate rings to M and one M-X bond. By addition of AgX salts (X = Cl, Br, NO3) an unexpected ring-opening reaction occurs with formation of the heteronuclear species PdAg(NP3)X-3 [X = Cl (7), Br (8)], MAg(PP3)X-3 [M = Pd, X = Cl (9), Br (10), NO3 (13); M = Pt, X = Cl (11), Br (12), NO3 (14)]. The complexes have been characterized in the solid state and solution. The X-ray crystal structures of 9 and 13 reveal a distorted square-planar arrangement to Pd(II) that is coordinated to three P Of PP3 (the central and two terminal atoms) and to one chloride (9) or one oxygen atom of NO3 (13). The resultant dangling phosphorus of the ring opening is bound to Ag(I) that completes the three- [PAgCl2 (9)] and four-coordination [PAg(ONO2)(O2NO) (13)] through the donor atoms of the anions with the nitrates in 13 unusually acting as both mono- and bidentate ligands. Complexes 7, 8, 10, and 11 undergo oligomerization in solution. Complex 10 oligomerizes giving rise to the ionic compound [Pd4Ag2(PP3)(2) Br-9]Br (10a) whose X-ray crystal structure indicates the presence of cations with a Pd(mu-Br)(3)Pd unit that connects via bromide bridges two BrPdP2PPAg Br-2 fragments containing distorted square-planar and trigonal-planar Pd(II) and Ag(I) centers, respectively. The palladium(II) metal centers in the central unit afford the five-coordination (PdBr5) with a distorted trigonal bipyramidal geometry. The ionic system [Pt2Ag2(PP3)(2) Cl-5]Cl (11a) consists of chloride anions and heteronuclear monocations. The X-ray crystal structure reveals that the cations contain two distorted square-planar ClPtP3 units bridged by one PAgCl(mu-Cl)(2)AgP fragment that is bearing tetrahedral (PAgCl3) and trigonal planar PAgCl2 silver(l) centers. Further additions of the corresponding AgX salts to complexes 7-14 did not give rise to any new ring-opening reaction.