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Synthesis, Dynamic Behavior, and Reactivity of New Unsaturated Heterotrinuclear 46 Valence Electron Complexes†Polynuclear Homo- or Heterometallic Palladium(II)−Platinum(II) Pentafluorophenyl Complexes Containing Bridging Diphenylphosphido Ligands. 27. For part 26, see ref .

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posted on 2011-01-03, 00:00 authored by Juan Forniés, Consuelo Fortuño, Susana Ibáñez, Antonio Martín, Pilar Romero, Piero Mastrorilli, Vito Gallo
The reaction of [NBu4]2[(C6F5)2Pt(μ-PPh2)2Pd(μ-PPh2)2Pt(C6F5)2] (1a) with [AgPPh3]+ results in the oxidation of two bridging diphenylphosphanides to give the 46e species [(PPh3)(C6F5)2Pt2(μ-P2Ph2)Pd(μ-PPh2)(μ-Ph2P4−P3Ph2)Pt1(C6F5)2] (3). Complex 3 displays two tetracoordinated terminal platinum centers and a central Pd atom that is bonded to three P atoms and that completes its coordination sphere by a rather long (3.237 Å) dative Pt2 → Pd bond. Complex 3 is also obtained when [(RF)2Pt(μ-PPh2)Pd(μ-PPh2)(μ-Ph2P-PPh2)Pt(RF)2] (2) is reacted with PPh3. Analogously, the addition of PPh2Et, CO or pyridine to 2 affords the 46e complexes of general formula [(L)(C6F5)2Pt2(μ-P2Ph2)Pd(μ-PPh2)(μ-Ph2P4−P3Ph2)Pt1(C6F5)2] (L = PPh2Et, 4; L = CO, 6; L = pyridine, 7). The geometry around Pt2 is determined by the bulkiness of L bonded to Pt. Thus, in complexes 3 (L = PPh3) and 4 (L = PPh2Et), the ligand L occupies the trans position with respect to μ-P2, and in 6 (L = CO), the ligand L occupies the cis position with respect to μ-P2. Interestingly, for 7 (L = py), both isomers 7-trans and 7-cis, could be isolated. Although 4 did not react with an excess of PPh2Et, the reaction with the less sterically demanding CH3CN ligand resulted in the opening of the Pt2−P2−Pd cycle with formation of the saturated 48e species [(PPh2Et)(C6F5)2Pt(μ-PPh2)Pd(MeCN)(μ-PPh2)(μ-Ph2P-PPh2)Pt(C6F5)2] (8). The saturated 48e complex [(CO)(C6F5)2Pt(μ-PPh2)Pd(MeCN)(μ-PPh2)(μ-Ph2P-PPh2)Pt(C6F5)2] (9) was obtained by acetonitrile addition to 6. Beside the hindered rotation of the pentafluorophenyl groups and a flip-flop motion of the Pd−P−Pt1−P−P ring observed at low T, a rotation about the Pt2−P2 bond and a P−C oxidative addition/reductive elimination process occur for 3 and 4 at room temperature. A “through-space” 19F−31P spin−spin coupling between an ortho-F and the P4 is observed for complexes 3 and 4, having the C6F5 groups bonded to Pt2 in mutually trans position. The XRD structures of complexes 3, 6, 7-trans, 7-cis, 8, and 9 are described.