The reaction of [NBu4](2)[(C6F5)(2)Pt(mu-PPh2)(2)Pt(mu-PPh2)(2)Pt(C6F5)(2)] (1a) with [AgPPh3](+) results in the oxidation of two bridging diphenylphosphanides to give the 46e species [(PPh3)(C6F5)(2)Pt-2(eta-(PPh2)-Ph-2)Pd(mu-PPh2)(mu-Ph2P4-(PPh2)-Ph-3)Pt-1(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 angstrom) dative Pt-2 -> Pd bond. Complex 3 is also obtained when [(R-F)(2)Pt(mu-PPh2)Pd(mu-PPh2)(mu-Ph2P-PPh2)Pt(R-F)(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)(2)Pt-2(mu-(PPh2)-Ph-2)pd(mu-PPh2)(mu-Ph2P4-(PPh2)-Ph-3)Pt-1(C6F5)(2)] (L = PPh2Et, 4; L = CO, 6; L = pyridine, 7). The geometry around Pt-2 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 mu-P-2, and in 6 (L = CO), the ligand L occupies the cis position with respect to mu-P-2. 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 oil the Pt-2-P-2-Pd cycle with formation of the saturated 48e species [(PPh2Et)(C6F5)(2)Pf(mu-PPh2)Pd(MeCN)-(mu-PPh2)(mu-Ph2P-PPh2)Pt(C6F5)(2)] (8). The saturated 48e complex [(CO)(C6F5)(2)Pt(mu-PPh2)Pd(MeCN)-(mu-PPh2)(mu-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-Pt-1-P-P ring observed at low T, a rotation about the Pt-2-P-2 bond and a P-C oxidative addition/reductive elimination process occur for 3 and 4 at room temperature. A "through-space" F-19-P-31 spin spin coupling between an ortho-F and the P-4 is observed for complexes 3 and 4, having the C6F5 groups bonded to Pt-2 in mutually trans position. The XRD structures of complexes 3, 6, 7-trans, 7-cis, 8, and 9 are described.
|Titolo:||Synthesis, Dynamic Behavior, and Reactivity of New Unsaturated Heterotrinuclear 46 Valence Electron Complexes|
|Data di pubblicazione:||2011|
|Digital Object Identifier (DOI):||10.1021/ic101934t|
|Appare nelle tipologie:||1.1 Articolo in rivista|