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Fernandez-Anca D, Garcia-Seijo MI, Castineiras A, Garcia-Fernandez ME: Novel chelate ring-opening induced by silver (I) of five-coordinate palladium (II) and platinum (II) complexes containing tripodal polyphosphines. Inorg Chem. 2008 Jul 7;47(13):5685-95. Epub 2008 May 29.
The ionic complexes [Pd (NP 3) X] X [NP 3 = tris [2-(diphenylphosphino) ethyl] amine, X = Cl (1), Br (2)] and [M (PP 3) X] X [PP 3 = 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, NO 3) an unexpected ring-opening reaction occurs with formation of the heteronuclear species PdAg (NP 3) X 3 [X = Cl (7), Br (8)], MAg (PP 3) X 3 [M = Pd, X = Cl (9), Br (10), NO 3 (13);M = Pt, X = Cl (11), Br (12), NO 3 (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 PP 3 (the central and two terminal atoms) and to one chloride (9) or one oxygen atom of NO 3 (13). The resultant dangling phosphorus of the ring opening is bound to Ag (I) that completes the three- [PAgCl 2 ( 9)] and four-coordination [PAg (ONO 2)(O 2NO) (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 [Pd 4Ag 2 (PP 3) 2 Br 9] Br ( 10a) whose X-ray crystal structure indicates the presence of cations with a Pd (mu-Br) 3Pd unit that connects via bromide bridges two BrPdP 2PPAg 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 (PdBr 5) with a distorted trigonal bipyramidal geometry. The ionic system [Pt 2Ag 2 (PP 3) 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 ClPtP 3 units bridged by one PAgCl (mu-Cl) 2AgP fragment that is bearing tetrahedral (PAgCl 3) and trigonal planar PAgCl 2 silver (I) centers. Further additions of the corresponding AgX salts to complexes 7- 14 did not give rise to any new ring-opening reaction. |
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