Free germylenes r2ge and their synthetic application

Abstract

Free singlet Me2Ge is used as pilot germylene to explore the reactions of this group of heavy carbene analogs. After a short review on the known state, new results from the authors’ laboratory are compiled. Insertions into O-H and other acidic X-H bonds depend on the acidity of the proton, but also on the donor quality of R-O-H resp. R-X-H (X = S, N). Acidic C-H bonds don’t insert. A reversible complex Me2Ge.D is concluded as reactive intermediate, exhibiting an individual chemistry. It slows down the usual reactions of Me2Ge, but opens, e. g., new cycloadditions to different alkynes including those not reactive toward Me2Ge itself, and nucleophilic 1,4- as well as 1,6-additions to open-chained or cyclic en-3-ones or l,3-dien-5-ones of the Michael or super-Michael type. - The formation, structure and reactions of the exotic 1,2,3-trigermacyclopent-4-enes are studied, starting from Me2Ge. - Chemical and physical investigations on the photoinduced degradation of 7-dimethylgerma-1,2,3,4-Ph4- norbornadiene reveal a rapid one-step splitting of its (fluorescing) excited singlet into Me2Ges and ground-state Ph4-naphthalene without any further intermediate. © 1994, Walter de Gruyter. All rights reserved.