title: Group II metal complexes of the germylidendiide dianion radical and germylidenide anion.
abstract: The two-electron reduction of a Group 14-element(I) complex [RË⋅] (E=Ge, R=supporting ligand) to form a novel low-valent dianion radical with the composition [RË:]˙(2-) is reported. The reaction of [LGeCl] (1, L=2,6-(CH=NAr)2C6H3, Ar=2,6-iPr2C6H3) with excess calcium in THF at room temperature afforded the germylidenediide dianion radical complex [LGe]˙(2-)⋅Ca(THF)3(2+) (2). The reaction proceeds through the formation of the germanium(I) radical [LGe⋅], which then undergoes a two-electron reduction with calcium to form 2. EPR spectroscopy, X-ray crystallography, and theoretical studies show that the germanium center in 2 has two lone pairs of electrons and the radical is delocalized over the germanium-containing heterocycle. In contrast, the magnesium derivative of the germylidendiide dianion radical is unstable and undergoes dimerization with concurrent dearomatization to form the germylidenide anion complex [C6H3-2-{C(H)=NAr}Ge-Mg-6-{C(H)-NAr}]2 (3).
authors.affiliation: Division of Chemistry and Biological Chemistry, Nanyang Technological University, 21 Nanyang Link, Singapore 637371 (Singapore).
authors.forename: Siew-Peng
authors.initials: SP
authors.lastname: Chia
authors.forename: Emma
authors.initials: E
authors.lastname: Carter
authors.forename: Hong-Wei
authors.initials: HW
authors.lastname: Xi
authors.forename: Yongxin
authors.initials: Y
authors.lastname: Li
authors.forename: Cheuk-Wai
authors.initials: CW
authors.lastname: So
keywords: Group 14 elements; anions; calcium; germanium; magnesium; radicals