Triazenide complexes of the heavier alkaline earths:: Synthesis, characterization, and suitability for hydroamination catalysis
Triazenide complexes of the heavier alkaline earths:: Synthesis, characterization, and suitability for hydroamination catalysis
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DOI：
10.1021/ic800789x
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发表时间：
2008-08-18
影响因子：
4.6
通讯作者：
Procopiou, Panayiotis A.
中科院分区：
文献类型：
--
作者：
Barrett, Anthony G. M.;Crimmin, Mark R.;Procopiou, Panayiotis A.
采用质子分解法和盐复分解法合成了一系列重碱土金属Ca、Sr和Ba的三氮烯配合物。虽然形式[（Ar 2N 3）M（N（SiMe 3）（2））（THF）（n）]的络合物（M = Ca，n = 2; M = Sr，n = 3; Ar = 2，6-二异丙基苯基）和[{Ar 2N 3}Ca（I）（THF）（2）]（2）可以分离并通过X射线晶体学表征，溶液研究揭示了这些物种经历Schlenk样再分布的倾向，形成[（Ar 2N 3）（2）M（THF）（n）]（M = Ca，n = 1; M = Sr，n = 2）。后一种化合物是独立合成的。在大的钡二价阳离子的情况下，合成该系列中最重的类似物[{Ar 2N 3}（2）Ba（THF）（n）}的尝试失败了，而是导致分离出重晶石钾络合物[K{Ar 2N 3）Ba{N（SiMe 3）（2）}（2）（THF）（4）]。单晶X-射线衍射研究表明，尽管在所有上述情况下，三氮烯配体通过对称的κ（2）-N，N-螯合物与亲电族2金属中心结合，但在后一种化合物中观察到前所未有的桥接模式，其中三氮烯配体通过末端和内部氮中心配位。一系列的密度泛函理论计算实验已经进行，以帮助我们理解这一现象。在进一步的实验中，钙和锶的酰胺衍生物[{Ar 2N 3}M（N（SiMe 3）（2）}（THF）（n）]（M = Ca，n = 2; M = Sr，n = 3）被证明对1-氨基-2，2-二苯基-4-丁烯的分子内氢胺化形成2-甲基-4，4-二苯基吡咯烷具有催化活性，其中钙物质表现出比锶类似物更高的转换数（2a，TOF = 500 h（-1）; 2b，TOF = 75 h（-1））。在这些情况下，由于溶液中预催化剂的结构表征的不明确性，这种定量几乎没有价值，并且没有进行详细的催化研究。
A series of triazenide complexes of the heavier alkaline earths, Ca, Sr and Ba, have been synthesized by either protonolysis or salt metathesis routes. Although complexes of the form [{Ar2N3)M(N(SiMe3)(2))(THF)(n)] (M = Ca, n = 2; M = Sr, n = 3; Ar = 2,6-diisopropylphenyl) and [{Ar2N3}Ca(I)(THF)(2)](2) could be isolated and characterized by X-ray crystallography, solution studies revealed the propensity of these species to undergo Schlenk-like redistribution with the formation of [{Ar2N3)(2)M(THF)(n)] (M = Ca, n = 1; M = Sr, n = 2). The latter compounds have been synthesized independently. In the case of the large barium dication, attempts to synthesize the heaviest analogue of the series, [{Ar2N3}(2)Ba(THF)(n)}, failed and led instead to the isolation of the potassium barate complex [K{Ar2N3)Ba{N(SiMe3)(2)}(2)(THF)(4)]. Single crystal X-ray diffraction studies demonstrated that, although in all the aforementioned cases the triazenide ligand binds to the electrophilic group 2 metal centers via symmetrical kappa(2)-N,N-chelates, in the latter compound an unprecedented bridging mode is observed in which the triazenide ligand coordinates through both terminal and internal nitrogen centers. A series of density-functional theory computational experiments have been undertaken to assist in our understanding of this phenomenon. In further experiments, the calcium and strontium amide derivatives [{Ar2N3}M(N(SiMe3)(2)}(THF)(n)] (M = Ca, n = 2; M = Sr, n = 3) proved to be catalytically active for the intramolecular hydroamination of 1-amino-2,2-diphenylpent-4-ene to form 2-methyl-4,4-diphenylpyrrolidine, with the calcium species demonstrating a higher turnover number than the strontium analogue (2a, TOF = 500 h(-1); 2b, TOF = 75 h(-1)). In these instances, because of ambiguities in the structural charcterization of the precatalyst in solution, such quantification holds little value and detailed catalytic studies have not been conducted.