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Dibenzotropylidene Substituted Ligands for Early Main Group Metal‐Alkene Bonding
European Journal of Inorganic Chemistry ( IF 2.3 ) Pub Date : 2020-06-04 , DOI: 10.1002/ejic.202000524
Johannes Martin 1 , Jens Langer 1 , Michael Wiesinger 1 , Holger Elsen 1 , Sjoerd Harder 1
Affiliation  

New N‐ligands with TROP‐substituents are introduced (TROP = [5H ]dibenzo[a,d ]cyclohepten‐5‐yl): (TROP)(DIPP)N (DIPP = 2,6‐diisopropylphenyl), TROPBDI (HC[C(Me)N‐TROP]2) and the β‐diketiminate ligand TROP–DIPPBDI with TROP and DIPP substituents at N. Several Li, Mg, Ca and Zn complexes with these ligands have been isolated and were characterized by X‐ray diffraction. While TROP‐substituents in the protonated ligands show endoexo exchange, TROP‐substituents in the metal complexes are in endo‐conformation due to metal··· alkene bonding. Short contacts between the metal and the TROP alkene unit are observed and some of these are the shortest reported; (TROPBDI)Li: Li··· C 2.416(3) Å, [(TROP)(DIPP)N]2Ca: Ca··· C 2.742(2) Å. TROPBDI shows superior metal shielding properties to the Li complex with a buried volume of V B = 78.7 %. DFT calculations on [(TROP)(DIPP)N]2Mg show a minimum with asymmetric Mg··· alkene bonding. Symmetric Mg··· alkene bonding is a transition state 1.9 kcal/mol higher in energy. Asymmetry in alkene‐Mg bonding is explained by an ion‐induced polarization of the C=C bond and electrostatic Mg2+··· (δ‐)C=C(δ+) attraction. The TROP‐substituent stabilizes low valent radical species but attempts to isolate (TROPBDI)Mg· or (TROPBDI)Zn· by reduction of the iodide precursors failed. Intensely black coloured raw products hint towards formation of radical species. Several radical decomposition products have been structurally characterized.

中文翻译:

早期主族金属-烯烃键合的二苯并亚苄基取代配体

引入了具有TROP取代基的新N-配体(TROP = [5 H ]二苯并[ a,d ]环庚烯-5-基):(TROP)(DIPP)N(DIPP = 2,6-二异丙基苯基),TROP BDI( HC [C(Me)N-TROP] 2)和β-二酮配体TROP-DIPP BDI在N处具有TROP和DIPP取代基。已分离出几种具有这些配体的Li,Mg,Ca和Zn配合物,并用X表征射线衍射。虽然在质子化的配体TROP-取代基示出内切-交换,TROP-取代基在金属配合物在-conformation由于金属···烯烃键。观察到金属与TROP烯烃单元之间的短接触,其中一些是最短的。(TROP BDI)Li:Li ··· C 2.416(3)Å,[(TROP)(DIPP)N] 2 Ca:Ca ··· C 2.742(2)·。TROP BDI具有比Li配合物更好的金属屏蔽性能,埋入量V B = 78.7%。在[(TROP)(DIPP)N] 2 Mg上的DFT计算显示具有不对称Mg ···烯烃键合的最小值。对称的Mg ···烯烃键是能量高1.9 kcal / mol的过渡态。烯烃-镁键的不对称性可以通过离子诱导的C = C键极化和静电镁来解释2 + ···(δ‐)C = C(δ+)吸引力。TROP取代基可稳定低价基团,但尝试通过还原碘化物前体来分离(TROP BDI)Mg ·或(TROP BDI)Zn ·失败。强烈的黑色生料暗示了自由基的形成。几种自由基分解产物已在结构上得到了表征。
更新日期:2020-07-16
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