title: Yttrium Siloxide Complexes Bearing Terminal Methyl Ligands: Molecular Models for Ln-CH3 Terminated Silica Surfaces.
abstract: Surface organometallic chemistry (SOMC) on silica materials is a prominent approach for the generation of highly active heterogenized polymerization catalysts. Despite advanced methods of characterization, the elucidation of the catalytically active surface species remains a challenging task. Alkylated rare-earth metal siloxide complexes can be regarded as molecular models of respective covalently bonded alkylated surface species, primarily used for 1,3-diene polymerization. Here, we performed both salt metathesis reactions of [Y(MMe4 )3 ] (M = Al, Ga) with [K{OSi(OtBu)3 }] and alkylation reactions of [Y{OSi(OtBu)3 }3 ]2 with AlMe3 . The obtained complexes [Y(CH3 )[(AlMe2 ){OSi(OtBu)3 }2 ](AlMe4 )]2 , [Y(CH3 )[(AlMe2 ){OSi(OtBu)3 }2 ]-{OSi(OtBu)3 }], [Y{OSi(OtBu)3 }3 (μ-Me)Y(μ-Me)2 Y{OSi(OtBu)3 }2 (AlMe4 )], and [Y(CH3 )(GaMe4 ){OSi(OtBu)3 }]2 represent rare examples of organoyttrium species with terminal methyl groups. The formation and purity of the mixed methyl/siloxy yttrium complexes could be enhanced by treating [Y(MMe4 )3 ] with [K(MMe2 ){OSi(OtBu)3 }2 ]n (M=Al: n=2; M=Ga: n=∞). Complexes [K(MMe2 ){OSi(OtBu)3 }2 ]n were obtained by addition of [K{OSi(OtBu)3 }] to [Me2 M{OSi(OtBu)3 }]2 . Deeper insight into the fluxional behavior of the mixed methyl/siloxy yttrium complexes in solution was gained by (1) H and (13) C NMR spectroscopic studies at variable temperature and (1) H-(89) Y HSQC NMR spectroscopy.
authors: Institute of Inorganic Chemistry, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18, 72076, Tübingen, Germany.
authors: Nicole
authors: N
authors: Dettenrieder
authors: Institute of Inorganic Chemistry, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18, 72076, Tübingen, Germany.
authors: H Martin
authors: HM
authors: Dietrich
authors: Institute of Inorganic Chemistry, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18, 72076, Tübingen, Germany.
authors: Cäcilia
authors: C
authors: Maichle-Mössmer
authors: Institute of Inorganic Chemistry, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18, 72076, Tübingen, Germany. reiner.anwander@uni-tuebingen.de.
authors: Reiner
authors: R
authors: Anwander
keywords: aluminum; gallium; methyl; siloxy; yttrium