A Two-Coordinate Neutral Germylene Supported by a β‑Diketiminate Ligand in the Radical State

Using the new β-diketimine 1a (PhCH­(PhCN-Dip)2, Dip = 2,6-iPr2C6H3), which
possesses three phenyl groups at the ligand backbone, we synthesized
the β-diketiminato germylene chloride 2 (LGeCl,
L = [PhC­(PhCN-Dip)2]−). The β-diketiminato
germanium radical complex 3 (•LGe:, •L = •[PhC­(PhCN-Dip)2]2–) has been isolated by reduction of LGeCl with sodium/naphthalene
in 64% yield. X-ray diffraction, HR-MS, and electron paramagnetic
resonance analyses together with DFT calculations reveal that 3 exhibits a remarkably different structure in comparison
with the reported Ge­(I) radical C (L′•Ge:, L′ = [HC­(tBuCN-Dip)2]−). The inductive effect of three phenyl groups
leads to the backbone of ligand 1 being more electron
deficient, and therefore the singly occupied molecular orbital (SOMO)
of radical 3 is mainly composed of a π-antibonding
orbital between the N and C atoms. This results in ca. 0.14 Å
shorter N–Ge bonds and ca. 0.1 Å longer C–N bonds
in 3 in comparison to those observed in C. Thus, the radical 3 is a two-coordinate germylene
stabilized by an N-heterocyclic radical ligand.