Mechanisms of Reactions of Open-Shell, Heavier Group 14 Derivatives with Small Molecules: n-Ï€* Back-Bonding in Isocyanide Complexes, C-H Activation under Ambient Conditions, CO Coupling, and Ancillary Molecular Interactions
Mechanisms of Reactions of Open-Shell, Heavier Group 14 Derivatives with Small Molecules: n-Ï€* Back-Bonding in Isocyanide Complexes, C-H Activation under Ambient Conditions, CO Coupling, and Ancillary Molecular Interactions
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DOI：
10.1021/ic4007058
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发表时间：
2013-06-03
影响因子：
4.6
通讯作者：
Power, Philip P.
中科院分区：
文献类型：
--
作者：
Brown, Zachary D.;Power, Philip P.
本文综述了锗和锡的卡宾类似物与异腈、CO、氨及相关分子的反应机理。Ge（Ar-Me 6）（2）（Ar-Me 6 = C6 H3 - 2，6（C6 H2 - 2，4，6-Me-3）（2））与MeNC或（BuNC）-N-t反应得到1：1的配合物，但锗上电子密度的增加导致异腈甲基或叔丁基取代基上的CH活化。对于MeNC，初始加合物形成之后是MeNC碳迁移插入到芳基取代基的Ge-C（ipso）键中。过量MeNC的添加导致连续插入另外两个MeNC分子。（BuNC）-N-t配合物（Ar-Me_6）（2）GeCNBut自发地转化为（Ar-Me_6）（2）Ge（H）CN和异丁烯。锗烯基Ge（Ar-Me 6）（Ar-Pr 4 i）[Ar-Pr 4 i = C6 H 3 - 2，6（C6 H 3 - 2，6-Pr-2（i））（2）]与CO反应，得到α-锗烯基芳基酮。初始步骤是形成11络合物，随后迁移插入Ar-Pr 4 i配体的Ge-C键中以得到（ArGeC）-Ge-Me 6（O）Ar-Pr 4 i。插入第二个CO得到（ArGeC）-Ge-Me 6（O）C（O）Ar-Pr 4 i，其重排得到α-香叶基氧基酮。Sn（Ar-Me 6）（2）与RNC没有反应（R = Me，Bu-t）或CO.光谱（IR）结果和密度泛函理论（DFT）计算表明，反应性可以在Ge-C的基础上合理化Ge（Ar-Me 6）（2）和Sn（Ar-Me 6）（2）与氨或肼的反应最初得到1：1加合物。然而，DFT计算表明，存在辅助的N-H中心点N与第二个氨或肼的相互作用，其稳定过渡态以形成氢化锗（IV）（酰胺基或肼基）产物。对于锡，芳烃消除是有利的电子密度在锡的积累，以及更大的极性的Sn-C（ipso）键。Ge（Ar-Me 6）（2）与酸反应时观察到锗（IV）产物，而Sn（Ar-Me 6）（2）与酸反应不产生锡（II）产物。与与NH3反应相反，在质子化时锡上没有负电荷积累，其随后与共轭碱反应容易得到锡（IV）产物。
The main themes of this review are the mechanisms of the reactions of germanium and tin analogues of carbenes with isocyanides, CO, ammonia, and related molecules. The treatment of Ge(Ar-Me6)(2) (Ar-Me6 = C6H3-2,6(C6H2-2,4,6-Me-3)(2)) with MeNC or (BuNC)-N-t afforded 1 :1 complexes, but the increase in the electron density at germanium leads to C H activation at the isocyanide methyl or tert-butyl substituents. For MeNC, the initial adduct formation is followed by a migratory insertion of the MeNC carbon into a Ge-C(ipso) bond of an aryl substituent. The addition of excess MeNC led to sequential insertions of two further MeNC molecules. The third insertion led to methylisocyanide methyl group C-H activation, to afford an azagermacyclopentadienyl species The (BuNC)-N-t complex (Ar-Me6)(2)GeCNBut spontanously transforms into (Ar-Me6)(2)Ge(H)CN and isobutene with C-H activation of the Bu-t substituent. The germylene Ge(Ar-Me6)(Ar-Pr4i) [Ar-Pr4i = C6H3-2,6(C6H3-2,6-Pr-2(i))(2)] reacted with CO to afford alpha-germyloiryketones. The initial step is the formation of a 11 complex, followed by migratory insertion into the Ge-C bond of the Ar-Pr4i ligand to give (ArGeC)-Ge-Me6(O)Ar-Pr4i. Insertion of a second CO gave (ArGeC)-Ge-Me6(O)C(O)Ar-Pr4i, which rearranges to afford alpha-germyloxyketone. No reaction was observed for Sn(Ar-Me6)(2) with RNC (R = Me, Bu-t) or CO. Spectroscopic (IR) results and density functional theory (DFT) calculations showed that the reactivity can be rationalized on the basis of Ge-C (isocyanide or CO) Ge(n) -> pi* (ligand) back bonding The reaction of Ge(Ar-Me6)(2) and Sn(Ar-Me6)(2) with ammonia or hydrazines initially gave 1:1 adducts. However, DFT calculations show that there are ancillary N-H center dot center dot center dot N interactions with a second ammonia or hydrazine, which stabilizes the transition state to form germanium(IV) hydride (amido or hydrazido) products. For tin, arene elimination is favored by a buildup of electron density at the tin, as well as the greater polarity of the Sn-C(ipso) bond. Germanium(IV) products were observed upon reaction of Ge(Ar-Me6)(2) with acids, whereas reactions of Sn(Ar-Me6)(2) with acids did not give tin (II) products In contrast to reactions with NH3, there is no buildup of negative charge at tin upon protonation, and its subsequent reaction with conjugate bases readily affords the tin(IV) products.