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

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.

一系列Ln/Pt异双核配合物（Ln为镧系元素，lanthanide），即(C5Me4XCH2PPh2)Ln(CH2SiMe3)2(OC4H8)PtMe2（3a：Ln=钇(Y)，X=SiMe2；3b：Ln=镥(Lu)，X=SiMe2；4a：Ln=Y，X=CH2；4b：Ln=Lu，X=CH2），通过(C5Me4XCH2PPh2)Ln(CH2SiMe3)2(OC4H8)与PtMe2(COD)（COD=1,5-环辛二烯，1,5-cyclooctadiene）的反应制备得到。单晶X射线衍射(Single-crystal X-ray diffraction)研究表明，此类配合物具有双核骨架，其中两个金属中心不仅通过μ-CH2SiMe3配体桥联，环戊二烯基(Cp, cyclopentadienyl)配体的膦侧臂还与Pt原子配位。变温核磁共振(NMR, nuclear magnetic resonance)光谱研究揭示，溶液中的μ-CH2SiMe3配体具有流变行为。此类配合物在升温条件下，会在μ-CH2SiMe3配体的SiMe3基团处发生分子内C-H键断裂。在3b的热解过程中，一种硅基桥联双齿烷基Lu/Pt配合物(C5Me4SiMe2CH2PPh2)Lu(μ-CH2SiMe2CH2)(OC4H8)PtMe2（6）被分离得到并完成了结构表征。带有硅烯连接的Cp-膦配体的Y/Pt配合物3a，与三苯基碳鎓四(五氟苯基)硼酸盐([Ph3C][B(C6F5)4])或氢气反应后，会发生配体断裂（C-Si键断裂），生成包括Me2Si(CH2PPh2)PtMe2（5）在内的多种未鉴定产物。带有亚乙基连接的Cp-膦配体的Y/Pt配合物4a，与三苯基碳鎓四(五氟苯基)硼酸盐([Ph3C][B(C6F5)4])/三异丁基铝(AliBu3)复配后，对异戊二烯聚合表现出中等活性，可得到富含等规结构的3,4-微观构型聚异戊二烯。