The Reactivity of [Zn2Cp*2]: Trapping Monovalent {ZnZnCp*} in the Metal-Rich Compounds [(Pd,Pt)(GaCp*)_a(ZnCp*)_(4-a)(ZnZnCp*)_(4-a)] (a = 0,2)

摘要

Carmona's synthesis of [Zn2Cp*2] (Cp* = pentamethylcyclo-pentadienyl), the first molecular compound exhibiting a covalent Zn—Zn bond, has generated much interest and stimulated research on low-coordinate (main-group) metal compounds. Other derivatives with the formula [M2L2], such as [Zn2{HC(CMeNAr)2}2] (Ar = 2,6-iPr2C6H3) or [Zn2Ar2] (Ar = 2,6-(2,6-iPr2C6H3)2C6H3) were subsequently obtained, and even magnesium analogues, such as [Mg2(DippNacnac)2] (DippNacnac = [(2,6-iPr2C6H3)N= CMe]2CH) have been reported. Notably, Robinson's concept of using N-heterocyclic carbenes (NHCs) as neutral, soft, and very bulky ligands for stabilizing unusual bonding states, for example, [L:E=E:L] (E = Si, Ge; L—C[N(2,6-iPr2-C6H3)CH]2) relates to this progress. The quite well-developed coordination chemistry of the carbenoid Group 13 metal analogues of NHC ligands, ER (E = Al, Ga, In; R = Cp* and other bulky substituents) to metal centers complements this progress. Nevertheless, not much is known on the chemistry of the compounds [M2L2] in general, and only very few reports have appeared for reactions of the zinc dimers in particular.