sp-Hybridized Seesaw Ge⁰ Complexes via Germylone-to-Seesaw Isomerization in a Four-Electron Cyclic N₂Ge₂ Ligand

We report the first examples of two linear trigermanium complexes (μ-Ge)(κ²-<b>N</b>_<b>2</b><b>Ge</b>_<b>2</b>^<b>Ar</b>) (Ar = 2,4,6-Me₃C₆H₂ (<b>4</b>), 2,6-Et₂C₆H₃ (<b>5</b>)), in which each central Ge⁰ atom displays a seesaw geometry enforced by a four-electron cyclic <b>N</b>_<b>2</b><b>Ge</b>_<b>2</b>^<b>Ar</b> ligand. The pyridine-stabilized sp-hybridized Ge⁰ center is a four-electron donor and two terminal germylenes are electron-acceptors. Comparative studies show that the N₂Ge₂ scaffold uniquely stabilizes the Ge⁰ atom. This work not only introduces a new class of main-group seesaw complexes but also demonstrates ligand-driven control over hybridization and donor-acceptor dynamics. Compound <b>5</b> underwent one-electron reduction, followed by ligand rearrangement and dimerization, to afford a novel hexanuclear homounivalent germanium cluster, <b>10</b>, featuring a snake-like Ge₆ core. In <b>10</b>, each Ge atom in the central Ge^I-Ge^I unit is solely stabilized one amido ligand, while each of the remaining four Ge atoms is supported by one amido and one pyridyl donor. The isolation of a bulkier analogue (<b>11</b>) and a heteronuclear Ge₄Sn₂ cluster (<b>16</b>) further underscores the crucial role of ligand sterics in stabilizing these assemblies. These findings expand the structural diversity of low-valent group 14 compounds and establish a new paradigm for constructing multinuclear tetrel clusters.