Sounding out the Reactivity of Trimethylyttrium

The fundamental reactivity of amorphous [YMe3]n was representatively examined:  toward GaMe3 as
a Lewis acid, 9-fluorenone as a carbonyl substrate, and tetramethyldisilazane (HN(SiHMe2)2) as a Brønsted
acid. The products obtained from the 3-equiv reactions were spectroscopically and X-ray crystallographically identified. Y(GaMe4)3 shows Y- - -Ga distances of 3.0393(4) and 3.0502(3) Å, which are significantly
shorter than the Y- - -Al distances in Y[AlMe4]3[Al2Me6]0.5 (av 3.068 Å). The homoleptic alkoxide
[Y(OC14H11)3]x bearing sterically demanding 9-Me-fluorenoxy ligands documents high methyl group
transfer economy via the 1,2-addition reaction of [YMe3]n to 9-fluorenone; it was obtained in single-crystalline form in a minor byproduct, the asymmetric dimer [Y(OC14H11)2(μ-OC14H11)]2(9-fluorenone).
The previously elusive unsolvated complex {Y[N(SiHMe2)2]3} also shows a dimeric molecular
composition, {Y[N(SiHMe2)2]2[μ-N(SiHMe2)2]}2, featuring asymmetrically bridging silylamide ligands
and Y- - -SiH multi-β-agostic interactions in the solid state [(Y- - -Si)min 3.0521(7) Å, (Y- - -H)min 2.41(3) Å, ν(Si−H)agostic 1931 cm-1].

本研究对无定形三甲基钇聚合物（[YMe₃]ₙ）的基础反应活性进行了代表性研究：分别以三甲基镓（GaMe₃，路易斯酸（Lewis acid））、9-芴酮（9-fluorenone，羰基底物）与四甲基二硅氮烷（tetramethyldisilazane，HN(SiHMe₂)₂，布朗斯特酸（Brønsted acid））作为研究对象。通过3当量反应得到的产物，经光谱学与X射线晶体学（X-ray crystallography）方法完成结构鉴定。
三(四甲基镓基)钇（Y(GaMe₄)₃）的钇-镓间距分别为3.0393(4) Å与3.0502(3) Å，显著短于三(四甲基铝基)钇·0.5倍六甲基二铝（Y[AlMe₄]₃[Al₂Me₆]₀.₅）中的钇-铝间距（平均值3.068 Å）。带有位阻较大的9-甲基芴氧基配体的均配型烷氧基配合物[Y(OC₁₄H₁₁)₃]ₓ，证实了[YMe₃]ₙ与9-芴酮经1,2-加成反应可实现优异的甲基转移经济性；该配合物以次要副产物——不对称二聚体[Y(OC₁₄H₁₁)₂(μ-OC₁₄H₁₁)]₂(9-fluorenone)的单晶形式获得。
此前难以分离得到的无溶剂化配合物三(四甲基二硅氮基)合钇（{Y[N(SiHMe₂)₂]₃}）同样呈现二聚分子结构，即{Y[N(SiHMe₂)₂]₂[μ-N(SiHMe₂)₂]}₂，其固态结构中存在不对称桥连硅酰胺配体与钇-硅氢键的多中心β-agostic相互作用（agostic interaction）：[(Y---Si)最小值为3.0521(7) Å，(Y---H)最小值为2.41(3) Å，agostic作用下Si-H伸缩振动波数ν(Si−H)agostic为1931 cm⁻¹]。