Synthesis, Characterization, and Reactivity of an N-Heterocyclic Germanium(II) Hydride: Reversible Hydrogermylation of a Phosphaalkyne

The β-diketiminato germanium(II) chloride complex [(ButMesNacnac)GeCl] (ButMesNacnac = [{N(Mes)C(But)}2CH]−, Mes = mesityl) has been prepared and spectroscopically characterized. Treating this compound and a less bulky system, [(MeMesNacnac)GeCl] (MeMesNacnac = [{N(Mes)C(Me)}2CH]−), with K[HBEt3] led to differing outcomes, namely, the formation of the novel diamido germylene [(ButMesNacnacH)Ge:] (ButMesNacnacH = [N(Mes)C(H)(But)C(H)C(But)N(Mes)]2‑) and the germanium(II) hydride [(MeMesNacnac)GeH], both of which were crystallographically characterized. The former product forms via a 1,3-hydrogen migration reaction involving [(ButMesNacnac)GeH] as an unstable reaction intermediate. Reactions of [(MeMesNacnac)GeH] with CO2 and PCBut proceed at or below ambient temperature, in the absence of a catalyst, to give the crystallographically characterized hydrogermylation products [(MeMesNacnac)GeOC(O)H] and [(MeMesNacnac)GeC(But)PH], with complete regioselectivity. When a solution of the latter was gently heated, the hydrogermylation reaction was partially reversed, regenerating [(MeMesNacnac)GeH] and PCBut. Heating to higher temperatures led to the irreversible isomerization of [(MeMesNacnac)GeC(But)PH] to (E)-[(MeMesNacnac)GePC(H)(But)], theoretical studies of which indicate is the thermodynamic product of the original hydrogermylation reaction.

β-二酮亚胺基(II)氯化锗配合物[(ButMesNacnac)GeCl]（其中ButMesNacnac = [{N(Mes)C(But)}₂CH]⁻，Mes = 均三甲苯基(mesityl)）已被合成，并通过光谱学手段完成表征。将该配合物与位阻更小的体系[(MeMesNacnac)GeCl]（MeMesNacnac = [{N(Mes)C(Me)}₂CH]⁻）一同与三乙基氢硼酸钾(K[HBEt₃])反应，得到了两种不同产物：分别为新型二酰胺基锗烯[(ButMesNacnacH)Ge:]（ButMesNacnacH = [N(Mes)C(H)(But)C(H)C(But)N(Mes)]²⁻）以及锗(II)氢化物[(MeMesNacnac)GeH]，两种产物均通过晶体学手段完成表征。前述产物通过以不稳定反应中间体[(ButMesNacnac)GeH]参与的1,3-氢迁移(1,3-hydrogen migration)反应生成。[(MeMesNacnac)GeH]分别与二氧化碳(CO₂)以及叔丁基磷炔(P≡CBut)在无催化剂、室温及更低温度下发生反应，以完全的区域选择性(regioselectivity)得到经晶体学表征的氢锗化(hydrogermylation)产物[(MeMesNacnac)GeOC(=O)H]与[(MeMesNacnac)GeC(But)=PH]。将后者的溶液进行温和加热时，该氢锗化反应会部分逆向进行，重新生成[(MeMesNacnac)GeH]与P≡CBut。当升温至更高温度时，[(MeMesNacnac)GeC(But)=PH]会发生不可逆异构化，得到(E)-[(MeMesNacnac)GeP=C(H)(But)]，理论研究表明该产物为原始氢锗化反应的热力学产物。