Trinuclear alkyl hydrido rare-earth complexes supported by amidopyridinato ligands: synthesis, structures, C–Si bond activation and catalytic activity in ethylene polymerization†
Abstract
The reaction of Ap9MeLu(CH2SiMe3)2(thf) (Ap9Me = (2,4,6-trimethylphenyl)[6-(2,4,6-triisopropylphenyl)pyridine-2-yl]amido ligand) with two molar equivalents of PhSiH3 affords a trinuclear alkyl-hydrido cluster [(Ap9MeLu)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2]. The analogous reactions with Ap9MeLn(CH2SiMe3)2(thf) (Ln = Y, Yb) are more complex and result in the formation of mixtures of two types of trinuclear alkyl-hydrido complexes [(Ap9MeLn)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2] and [(Ap9MeLn)3(μ2-H)3(μ3-H)2(CH2SiH2Ph)(thf)2] differing in the alkyl group. The DFT calculations of [(Ap*Y)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2] (Ap* = (2,6-diisopropylphenyl)[6-(2,4,6-triisopropylphenyl)pyridine-2-yl]amido ligand) confirm localization of the HOMO on the Ap*–Y(1A)–CH2SiMe3 fragment, thus explaining its enhanced reactivity. Analysis of the electron density distribution reveals the Y–H and H–H bonding interactions in the (Y)3(μ2-H)3(μ3-H)2 moiety. The NMR studies of diamagnetic complexes [(Ap9MeLu)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2] and [(Ap*Y)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2] demonstrated that the trinuclear cores are retained in the solution and revealed exchange between μ3- and μ2-bridging hydrido ligands. Complexes [(Ap*Ln)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2], the cationic yttrium hydrido cluster [(Ap*Y)3(μ2-H)3(μ3-H)2(thf)3]+[B(C6F5)4]− as well as [(Ap9MeLn)3(μ2-H)3(μ3-H)2(CH2SiMe3)(thf)2] proved to be active in catalysis of ethylene polymerization under mild conditions.
- This article is part of the themed collection: New Expeditions in Polar Organometallic Chemistry
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