A Modern Twist to a Classic Synthetic Route: Ph3Bi-Based Redox Transmetalation Protolysis (RTP) for the Preparation of Barium Metalorganic Species

摘要

This paper reports advances in redox transmetalation/protolysis (RTP) utilizing the readily available Ph3Bi for the synthesis of a series of barium metal-organic species. On the basis of easily available starting materials, an easy one-pot procedure, and workup, we have obtained BaL2 compounds (L = bis(trimethylsilyl)amide, phenyl(trimethylsilyl)amide, pentamethylcyclopentadienide, fluorenide, 2,6-diisopropylphenolate, and 3,5-diphenylpyrazolate) quantitatively by sonication of an excess of barium metal with triphenylbismuth and HL in perdeuterotetrahydrofuran, as established by NMR measurements. Rates of conversion are affected by both pk(a) and bulk of HL. Competition occurs from direct reaction of Ba with HL, thereby enhancing the overall conversion, the effect being pronounced for the less bulky and more acidic ligands. Overall, the method significantly adds to the synthetic armory for barium metal-organic/organometallic compounds.