om900702y_si_005.cif (34.35 kB)

Rare-Earth-Metal/Platinum Heterobinuclear Complexes Containing Reactive Ln-alkyl groups (Ln = Y, Lu): Synthesis, Structural Characterization, and Reactivity

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posted on 28.12.2009, 00:00 by Yumiko Nakajima, Zhaomin Hou
A series of Ln/Pt heterobinuclear complexes, (C5Me4XCH2PPh2)Ln(CH2SiMe3)2(OC4H8)PtMe2 (3a: Ln = Y, X = SiMe2; 3b: Ln = Lu, X = SiMe2; 4a: Ln = Y, X = CH2; 4b: Ln = Lu, X = CH2), were prepared by the reaction of (C5Me4XCH2PPh2)Ln(CH2SiMe3)2(OC4H8) with PtMe2(COD) (COD = 1,5-cyclooctadiene). Single-crystal X-ray diffraction studies revealed that these complexes possess a binuclear framework, in which the two metal centers are bridged by a μ-CH2SiMe3 ligand in addition to the coordination of the phoshpine side arm of the cyclopentadienyl ligand to the Pt atom. Variable-temperature NMR spectroscopic studies revealed the fluxional behavior of the μ-CH2SiMe3 ligand in solution. These complexes underwent intramolecular C−H bond cleavage at the SiMe3 group of the μ-CH2SiMe3 ligand at elevated temperatures. In the thermolysis of 3b, a silyl-bridged bidentate alkyl Lu/Pt complex, (C5Me4SiMe2CH2PPh2)Lu(μ-CH2SiMe2CH2)(OC4H8)PtMe2 (6), was isolated and structurally characterized. The reaction of the Y/Pt complex 3a, which bears the silylene-linked Cp-phosphine ligand, with [Ph3C][B(C6F5)4] or H2 led to fragmentation (C−Si bond cleavage) of the ligand to give several unidentified products including Me2Si(CH2PPh2)PtMe2 (5). In combination with [Ph3C][B(C6F5)4]/AliBu3, the Y/Pt complex 4a, which bears the ethylene-linked Cp-phosphine ligand, showed moderate activity for the polymerization of isoprene to yield polyisoprene with isotactic-rich 3,4-microstructures.