Tris(imidazolin-2-ylidene-1-yl)borate Complexes of the Heavier Alkaline Earths: Synthesis and Structural Studies
Tris(imidazolin-2-ylidene-1-yl)borate Complexes of the Heavier Alkaline Earths: Synthesis and Structural Studies
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DOI：
10.1021/om9003994
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发表时间：
2009-08-10
期刊：
影响因子：
2.8
通讯作者：
Kociok-Koehn, Gabriele
中科院分区：
文献类型：
--
作者：
Arrowsmith, Merle;Heath, Alex;Kociok-Koehn, Gabriele
在 Cal(2)、Srl(2) 或 BaI2 存在下，通过硼盐配体前体与 [KN(SiMe3)(2) 去质子化，合成了较重碱土元素钙、锶和钡的杂配体三(咪唑啉-2-亚基-1-基)硼酸盐配合物。复合物的形成总是涉及配体前体的部分 B-N 键断裂。导致形成甲硅烷基酰胺络合物 [{HB(Im'Bu)(3)}M{N(SiMe3)(2)(N-Im'Bu)n] (M = Ca, n = 0; Sr, n = 1; Ba, n = 1.5)。所有三种甲硅烷基酰胺配合物在溶液中对于 Schlenk 型配体重新分布都是稳定的，并且在氨基烯烃的分子内加氢胺化中表现出催化活性。在 M = Ca 的情况下，尝试合成含杂配卤化物物质，在 Cal(2) 存在下用 [KN(SiMe3)(2)] 使硼盐配体前体去质子化后，得到单体 [{HB-(Im'BU)(3)}Cal(THF)] 和 [{HB(Im'Bu)(3)}Cal(N-Im'Bu)] 的 1:9 混合物或二聚体[{HB(Im'Bu)(3)}CaBr](2) 当使用 [Ca{N(SiMe3)(2)}(THF)(2)] 作为碱源和钙源时。然而，M = Sr 的类似反应导致仅形成同配体 [{HB(Im'Bu)(3)}(2)Sr]，这可能是由于所有化合物的 X 射线衍射分析在每种情况下都证明单阴离子硼酸盐配体通过三个 N-杂环卡宾 (NHC) σ 供体以 C-3 对称面 K-3 结合模式与碱土金属中心配位。
Heteroleptic tris(imidazolin-2-ylidene-1-yl)borate complexes of the heavier alkaline earth elements calcium, strontium, and barium have been synthesized by deprotonation of boronium Salt ligand precursors with [KN(SiMe3)(2) in the presence of Cal(2), Srl(2),, or BaI2,. Complex formation invariably involved partial B-N bond cleavage of the ligand precursors. leading to the formation of the silylamide complexes [{HB(Im'Bu)(3)}M{N(SiMe3)(2)(N-Im'Bu)n] (M = Ca, n = 0; Sr, n = 1; Ba, n = 1.5). All three silylamide complexes are stable toward Schlenk-type ligand redistribution in solution and show catalytic activity in the intramolecular hydroamination of aminoalkenes. In the case of M = Ca attempts to synthesize heteroleptic halide-containing species led to a 1:9 mixture of monomeric [{HB-(Im'BU)(3)}Cal(THF)] and [{HB(Im'Bu)(3)}Cal(N-Im'Bu)] following deprotonation of the boronium salt ligand precursor with [KN(SiMe3)(2)] in the presence of Cal(2) or to dimeric [{HB(Im'Bu)(3)}CaBr](2) when using [Ca{N(SiMe3)(2)}(THF)(2)] as both base and calcium Source. However, Similar reactions, with M = Sr resulted in the formation of only homoleptic [{HB(Im'Bu)(3)}(2)Sr] probably due to the X-ray diffraction analyses of all compounds demonstrated in each case that the monoanionic borate ligand coordinates to the alkaline earth metal center in a C-3-symmetric facial K-3-binding mode via the three N-heterocyclic carbene (NHC) sigma-donors.