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首页> 外文OA文献 >Beyond alkyl transfer: synthesis of main group metal (Mg, Ca, Zn) silyl and tris(oxazolinyl)borato complexes and their stoichiometric and catalytic reactions with borane Lewis acids and carbonyls
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Beyond alkyl transfer: synthesis of main group metal (Mg, Ca, Zn) silyl and tris(oxazolinyl)borato complexes and their stoichiometric and catalytic reactions with borane Lewis acids and carbonyls

机译：超越烷基转移：主族金属（Mg，Ca，Zn）甲硅烷基和三（恶唑啉基）硼酸盐络合物的合成及其与硼烷路易斯酸和羰基化合物的化学计量和催化反应

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Recently, the fundamental knowledge of main group metal chemistry has grown. This progress is crucial for the further development of main group metal compounds in silicon chemistry and catalysis and for advancing their applications as green alternatives to many rare earth and transition metal compounds. This thesis focuses on reactivity beyond the well-documented alkyl-transfer applications for main group metals, and it highlights examples of reactions with Lewis acids and the reduction of carbonyls.A series of magnesium, calcium, and zinc organometallic compounds are synthesized, and their characterization, stoichiometric reactions, and catalytic activity are described. A novel silyl ligand, -Si(SiHMe2)3, and the ancillary ligand ToM (tris(4,4-dimethyl-2-oxazolinyl)phenylborate) are employed in the synthesis of these homoleptic and heteroleptic species. The silyl anion, KSi(SiHMe2)3, is prepared from the reaction of KOtBu and Si(SiHMe2)4. A single crystal X-ray diffraction study shows that the structure is made up of a chain of alternating potassium cations and Si(SiHMe2)3 anions with K coordinated to the central Si atoms and the three Si-H moieties oriented toward the next K atom.This unique silyl ligand incorporating beta-SiH functionality undergoes salt metathesis reactions with main group metal halides (MgBr2, CaCl2, ZnCl2) to afford disilyl compounds. While the disilyl magnesium and calcium compounds are THF adducts, the disilylzinc compound is free of coordinating solvent. All three compounds undergo coordination by N-donor ligands, and zinc is also stabilized by the N-heterocyclic carbene 1,3-di-t-butylimidazol-2-ylidene (ImtBu). Interestingly, spectroscopic characterization and X-ray analysis reveal that all of the main group metal silyl compounds contain classic 2-center-2-electron bonding, and the beta-SiH groups do not show evidence of nonclassical interactions. Yet they undergo beta-hydrogen abstraction with the Lewis acids PhB(C6F5)2 or B(C6F5)3.The monomeric magnesium and zinc silyl complexes containing an ancillary ligand are also synthesized via salt metathesis with ToMMgBr or ToMZnCl, and similarly give classical interactions between the metal center and the silyl ligand. However, ToMMg-Si(SiHMe2)3 and ToMZn-Si(SiHMe2)3 react with the Lewis acids B(C6F5)3 and CO2 via contrasting pathways and yield different products. The reactivity of ToMZn-Si(SiHMe2)3 was also compared to the analogous compounds ToMZn-CH(SiHMe2)2 and ToMZn-N(SiHMe2)2 in order to explore some of the similarities and differences in reactivity among Zn-element bonds.The cationic complex ToMMgHB(C6F5)3, which is accessible from the reaction noted above between ToMMg-Si(SiHMe2)3 and B(C6F5)3 or from the reaction of ToMMgMe, PhSiH3, and B(C6F5)3, is an effective precatalyst for the 1,4-hydrosilylation of unsaturated esters. Silyl ketene acetals are isolated in high yield from a range of alpha,beta-unsaturated esters and hydrosilanes. However, an alpha-alkyl group in the ester is essential. In the presence of an alpha-proton, rapid polymerization is observed as a competing pathway with 1,4-hydrosilylation.The precursor to ToMMgHB(C6F5)3, ToMMgMe, is also an efficient precatalyst for the reduction of carbonyls. Under catalytic conditions, tertiary and secondary amides are reduced to amines using pinacolborane (HBpin) as a reductant. The optimized reaction conditions reveal that excess HBpin gives reduction at room temperature in excellent yield. Interestingly, this system is the first example of a hydroboration of amides to amines and the first magnesium-catalyzed amide reduction.
机译：近来，主要族金属化学的基本知识已经增长。这一进展对于进一步发展硅化学和催化中的主族金属化合物以及促进其作为许多稀土和过渡金属化合物的绿色替代品的应用至关重要。本论文着眼于主要文献报道的烷基转移应用以外的反应性，并重点介绍了与路易斯酸反应和羰基还原反应的实例。合成了一系列镁，钙和锌有机金属化合物，描述了表征，化学计量反应和催化活性。一种新型的甲硅烷基配体-Si（SiHMe2）3和辅助配体ToM（三（4,4-二甲基-2-恶唑啉基）苯基硼酸酯）用于合成这些均配和杂配物种。甲硅烷基阴离子KSi（SiHMe2）3由KOtBu与Si（SiHMe2）4反应制备。 X射线单晶衍射研究表明，该结构由交替的钾阳离子和Si（SiHMe2）3阴离子的链组成，其中K与中心Si原子配位，并且三个Si-H部分朝向下一个K原子配位。这种具有β-SiH官能团的独特甲硅烷基配体与主要金属卤化物（MgBr2，CaCl2，ZnCl2）进行盐复分解反应，生成二甲硅烷基化合物。虽然二甲硅烷基镁和钙化合物是THF加合物，但二甲硅烷基锌化合物不含配位溶剂。所有这三种化合物均通过N供体配体进行配位，并且锌也通过N杂环卡宾1,3-二叔丁基咪唑-2-亚烷基（ImtBu）稳定。有趣的是，光谱表征和X射线分析表明，所有主要的金属甲硅烷基化合物都包含经典的2中心2电子键，而β-SiH基团未显示非经典相互作用的证据。然而，它们会与路易斯酸PhB（C6F5）2或B（C6F5）3进行β氢提取。还通过与ToMMgBr或ToMZnCl的盐复分解反应合成了含有辅助配体的单体镁和锌甲硅烷基配合物，并进行了经典相互作用在金属中心和甲硅烷基配体之间。但是，ToMMg-Si（SiHMe2）3和ToMZn-Si（SiHMe2）3通过相反的途径与路易斯酸B（C6F5）3和CO2反应并产生不同的产物。还比较了ToMZn-Si（SiHMe2）3的反应性与类似化合物ToMZn-CH（SiHMe2）2和ToMZn-N（SiHMe2）2的反应性，以探讨锌元素键之间反应性的某些相似之处和不同之处。阳离子络合物ToMMgHB（C6F5）3是有效的，可从上述ToMMg-Si（SiHMe2）3与B（C6F5）3之间的反应或ToMMgMe，PhSiH3和B（C6F5）3的反应中获得。 1，4-氢化硅烷化不饱和酯的催化剂。从一系列α，β-不饱和酯和氢硅烷中高产率地分离出甲硅烷基乙烯酮缩醛。但是，酯中的α-烷基是必需的。在α-质子的存在下，快速聚合被认为是与1,4-氢硅烷化反应的竞争途径.ToMMgHB（C6F5）3的前体ToMMgMe也是减少羰基的有效预催化剂。在催化条件下，使用频哪醇硼烷（HBpin）作为还原剂将叔酰胺和仲酰胺还原为胺。优化的反应条件表明，过量的HBpin在室温下以极好的收率被还原。有趣的是，该系统是酰胺加氢硼化成胺的第一个实例，也是镁催化的酰胺还原的第一个实例。

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    Lampland, Nicole Lynn;

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  • 年度 2015
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