Functionalization of Carbon Dioxide and Carbon Disulfide Using a Stable Uranium(Ⅲ) Alkyl Complex

摘要

A rare uranium(III) alkyl complex, Tp~*_2U-(CH_2Ph) (2) (Tp~* = hydrotris(3,5-dimethylpyrazolyl)-borate), was synthesized by salt metathesis from Tp~*_2UI (1) and KCH_2Ph and fully characterized using ~1H NMR, infrared, and electronic absorption spectroscopies as well as X-ray crystallography. This complex has a uranium-carbon distance of 2.57(2) A, which is comparable to other uranium alkyls reported. Treating this compound with either carbon dioxide or carbon disulfide results in insertion into the uranium-carbon bond to generate Tp~*_2U(K~2-O_2CCH_2Ph) (3)and Tp~*_2U(SC(S)CH_2Ph)(4), respectively. These species, characterized spectroscopically and by X-ray crystal- lography, feature new carboxylate and dithiocarboxylate ligands. Analysis by electronic absorption spectroscopy supports the trivalent oxidation state of the uranium center in both of these derivatives. Addition of trimethylsilylhalides (Me_3SiX; X = CI, I) to 3 results in the release of the free silyl ester, Me_3SiOC(O)CH_2Ph, forming the initial uranium monohalide species, Tp~*_2UX, which can then be used over multiple cycles for the functionalization of carbon dioxide.