BIS(2,4,6-TRI-TERT-BUTYLPHENYL)GERMYLENE REINVESTIGATED - CRYSTAL-STRUCTURE, LEWIS-ACID CATALYZED C-H INSERTION, AND OXIDATION TO AN UNSTABLE GERMANONE

Bis(2,4,6-tri-tert-butylphenyl)germylene (1), which had been reported to undergo an insertion of the germanium atom into a C-H bond of an o- tert-butyl group at room temperature, was found to be quite Stable. Su ch a C-H insertion does occur in solution, forming germaindane 2, but only in the presence of a Lewis acid such as the starting material GeC l2. 1 can be stored unchanged at -30 degrees C for months; at 20 degre es C it decomposes within several weeks under release of 1,3,5-tri-ter t-butylbenzene. Compound 1 was characterized by X-ray diffraction meth ods. The X-ray structure of 1 shows that the two aryl ligands have ver y different geometries: one aryl group is greatly distorted to give a ''boat'' form and the Ge atom is remote from any of the ring planes, w hile the second aryl group is only slightly deformed and the Ge atom L ies in the ring plane. UV/vis spectra exhibit an intense absorption at 430 nm in solution and at 405 nm in the solid state, which represents an enormous hypsochromic shift compared to other germylenes with bulk y aryl ligands. Oxidation of 1 with trimethylamine N-oxide leads to a germanone, which rearranges very rapidly by a C-H insertion process yi elding the germaindanol 3.