Redox-Active Germylene Based on 2,4,6,8-Tetra-tert-butylphenoxazin-1-one: Synthesis, Structure, and Chemical Properties.

New complex of low-valent germanium PhenoxAPGe (I) based on the redox-active ligand 2,4,6,8-tetra-tert-butylphenoxazin-1-one is synthesized and structurally characterized. Its versatile reactivity is demonstrated for the acid-base and redox transformations. The reaction of germylene I with Ni(COD)2 is found to result in the substitution of both cyclooctadiene molecules, coordination of four germylene fragments to zero-valent nickel, and formation of compound (PhenoxAPGe)4Ni (II). The reaction of compound I with [CpNi(CO)]2 in a toluene solution affords complex (PhenoxAPGe)2(NiCp)2 (III), being the substitution product of two carbonyl groups by two isolobal germylene fragments. The reaction with the one-electron oxidant (3,6-di-tert-butyl-2-methoxyphenoxyl radical) generates labile paramagnetic germylene IV characterized by EPR spectroscopy. Digermylene oxide V synthesized by the hydrolysis of the starting germylene Iin situ reacts with N-heterocyclic carbene and KC8 to form ionic derivatives VI and VII containing the Ge(II)–O–Ge(II) fragment. Germylene I is tested as a catalyst for the hydroboration of benzaldehyde. The molecular structures of the compounds are determined by X-ray diffraction (СIF files CCDC nos. 2117783 (I), 2124277 (II), 2125357 (III), and 2118393 (VII)). [ABSTRACT FROM AUTHOR]