Mai Jonathan, Rösch Bastian, Patel Neha, Langer Jens, Harder Sjoerd
Inorganic and Organometallic Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg Egerlandstraße 1 Erlangen 91058 Germany
Chem Sci. 2023 Apr 13;14(18):4724-4734. doi: 10.1039/d3sc00909b. eCollection 2023 May 10.
DFT-Calculations predict that a low-valent complex (BDI)Mg-Ca(BDI) with bulky β-diketiminate (BDI) ligands is thermodynamically stable. It was attempted to isolate such a complex by salt-metathesis between [(BDI*)MgNa] and [(BDI)CaI] (BDI = HC[C(Me)N-DIPeP]; BDI* = HC[C(Bu)N-DIPeP]; DIPeP = 2,6-CH(Et)-phenyl). Whereas in alkane solvents no reaction was observed, salt-metathesis in CH led to immediate C-H activation of benzene to give (BDI*)MgPh and (BDI)CaH, the latter crystallizing as a THF-solvated dimer [(BDI)CaH·THF]. Calculations suggest reduction and insertion of benzene in the Mg-Ca bond. The activation enthalpy for the subsequent decomposition of CH into Ph and H is only 14.4 kcal mol. Repeating this reaction in the presence of naphthalene or anthracene led to heterobimetallic complexes in which naphthalene or anthracene anions are sandwiched between (BDI*)Mg and (BDI)Ca cations. These complexes slowly decompose to their homometallic counterparts and further decomposition products. Complexes in which naphthalene or anthracene anions are sandwiched between two (BDI)Ca cations were isolated. The low-valent complex (BDI*)Mg-Ca(BDI) could not be isolated due to its high reactivity. There is, however, strong evidence that this heterobimetallic compound is a fleeting intermediate.
密度泛函理论（DFT）计算预测，具有庞大β-二酮亚胺（BDI）配体的低价配合物（BDI）Mg-Ca（BDI）在热力学上是稳定的。尝试通过[(BDI*)MgNa]与[(BDI)CaI]之间的盐复分解反应来分离这样的配合物（BDI = HC[C(Me)N-DIPeP]；BDI* = HC[C(Bu)N-DIPeP]；DIPeP = 2,6-CH(Et)-苯基）。虽然在烷烃溶剂中未观察到反应，但在CH中进行盐复分解反应会导致苯立即发生C-H活化，生成(BDI*)MgPh和(BDI)CaH，后者以THF溶剂化二聚体[(BDI)CaH·THF]的形式结晶。计算结果表明苯在Mg-Ca键中发生了还原和插入反应。随后CH分解为Ph和H的活化焓仅为14.4千卡/摩尔。在萘或蒽存在下重复此反应会生成异双金属配合物，其中萘或蒽阴离子夹在(BDI*)Mg和(BDI)Ca阳离子之间。这些配合物会缓慢分解为它们的同金属对应物和进一步的分解产物。分离出了萘或蒽阴离子夹在两个(BDI)Ca阳离子之间的配合物。由于其高反应活性，无法分离出低价配合物(BDI*)Mg-Ca(BDI)。然而，有强有力的证据表明这种异双金属化合物是一种短暂的中间体。
