Schädle Dorothea, Meermann-Zimmermann Melanie, Maichle-Mössmer Cäcilia, Schädle Christoph, Törnroos Karl W, Anwander Reiner
Institut für Anorganische Chemie, Universität Tübingen, Auf der Morgenstelle 18, D-72076 Tübingen, Germany.
Dalton Trans. 2015 Nov 7;44(41):18101-10. doi: 10.1039/c5dt02936h. Epub 2015 Sep 29.
Trinuclear rare-earth metal methylidene complexes with a Ln3(μ3-CH2)(μ3-Me)(μ2-Me)3 structural motif were synthesized by applying three protocols. Polymeric [LuMe3]n (1-Lu) reacts with the sterically demanding amine H[NSiMe3(Ar)] (Ar = C6H3iPr2-2,6) in tetrahydrofuran via methane elimination to afford isolable monomeric [NSiMe3(Ar)]LuMe2(thf)2 (4-Lu). The formation of trinuclear rare-earth metal tetramethyl methylidene complexes [NSiMe3(Ar)]3Ln3(μ3-CH2)(μ3-Me)(μ2-Me)3(thf)3 (7-Ln; Ln = Y, Ho, Lu) via reaction of [LnMe3]n (1-Ln; Ln = Y, Ho, Lu) with H[NSiMe3(Ar)] is proposed to occur via an "intermediate" species of the type [NSiMe3(Ar)]LnMe2(thf)x and subsequent C-H bond activation. Applying Lappert's concept of Lewis base-induced methylaluminate cleavage, compounds [NSiMe3(Ar)]Ln(AlMe4)2 (5-Ln; Ln = Y, La, Nd, Ho) were converted into methylidene complexes 7-Ln (Ln = Y, Nd, Ho) in the presence of tetrahydrofuran. Similarly, tetramethylgallate complex [NSiMe3(Ar)]Y(GaMe4)2 (6-Y) could be employed as a synthesis precursor for 7-Y. The molecular composition of complexes 4-Ln, 5-Ln, 6-Y and 7-Ln was confirmed by elemental analyses, FTIR spectroscopy, (1)H and (13)C NMR spectroscopy (except for holmium derivatives) and single-crystal X-ray diffraction. The Tebbe-like reactivity of methylidene complex 7-Nd with 9-fluorenone was assessed affording oxo complex [NSiMe3(Ar)]3Nd3(μ3-O)(μ2-Me)4(thf)3 (8-Nd). The synthesis of 5-Ln yielded [NSiMe3(Ar)]2Ln(AlMe4) (9-Ln; Ln = La, Nd) as minor side-products, which could be obtained in moderate yields when homoleptic Ln(AlMe4)3 were treated with two equivalents of K[NSiMe3(Ar)].
通过三种方法合成了具有Ln3(μ3-CH2)(μ3-Me)(μ2-Me)3结构单元的三核稀土金属亚甲基配合物。聚合的[LuMe3]n（1-Lu）在四氢呋喃中与空间位阻较大的胺H[NSiMe3(Ar)]（Ar = C6H3iPr2-2,6）通过消除甲烷反应，得到可分离的单体[NSiMe3(Ar)]LuMe2(thf)2（4-Lu）。通过[LnMe3]n（1-Ln；Ln = Y、Ho、Lu）与H[NSiMe3(Ar)]反应生成三核稀土金属四甲基亚甲基配合物[NSiMe3(Ar)]3Ln3(μ3-CH2)(μ3-Me)(μ2-Me)3(thf)3（7-Ln；Ln = Y、Ho、Lu），推测是通过[NSiMe3(Ar)]LnMe2(thf)x类型的“中间体”物种以及随后的C-H键活化发生的。应用拉珀特提出的路易斯碱诱导甲基铝酸盐裂解的概念，在四氢呋喃存在下，化合物[NSiMe3(Ar)]Ln(AlMe4)2（5-Ln；Ln = Y、La、Nd、Ho）被转化为亚甲基配合物7-Ln（Ln = Y、Nd、Ho）。类似地，四甲基镓酸盐配合物[NSiMe3(Ar)]Y(GaMe4)2（6-Y）可作为7-Y的合成前体。配合物4-Ln、5-Ln、6-Y和7-Ln的分子组成通过元素分析、傅里叶变换红外光谱、（1）H和（13）C核磁共振光谱（钬衍生物除外）以及单晶X射线衍射得到证实。评估了亚甲基配合物7-Nd与9-芴酮的类似特贝反应，得到了氧代配合物[NSiMe3(Ar)]3Nd3(μ3-O)(μ2-Me)4(thf)3（8-Nd）。5-Ln的合成产生了少量副产物[NSiMe3(Ar)]2Ln(AlMe4)（9-Ln；Ln = La, Nd），当用两当量的K[NSiMe3(Ar)]处理均配型Ln(AlMe4)3时，可以中等产率得到这些副产物。
