24669-77-0Relevant academic research and scientific papers
Evidence for a Single Electron Shift in a Lewis Acid-Base Reaction
Dong, Zhaowen,Cramer, Hanna H.,Schmidtmann, Marc,Paul, Lucas A.,Siewert, Inke,Müller, Thomas
supporting information, p. 15419 - 15424 (2018/11/03)
The Lewis acid-base reaction between a nucleophilic hafnocene-based germylene and tris-pentafluorophenylborane (B(C6F5)3) to give the conventional B-Ge bonded species in almost quantitative yield is reported. This reaction is surprisingly slow, and during its course, radical intermediates are detected by EPR and UV-vis spectroscopy. This suggests that the reaction is initiated by a single electron-transfer step. The hereby-involved germanium radical cation was independently synthesized by oxidation of the germylene by the trityl cation or strong silyl-Lewis acids. A perfluorinated tetraarylborate salt of the radical cation was fully characterized including an XRD analysis. Its structural features and the results of DFT calculations indicate that the radical cation is a hafnium(III)-centered radical that is formed by a redox-induced electron transfer (RIET) from the ligand to the hafnium atom. This valence isomerization slows down the coupling of the radicals to form the polar Lewis acid-base product. The implications of this observation are briefly discussed in light of the recent finding that radical pairs are formed in frustrated Lewis pairs.
Pentamethyldisilyl Radical: Absolute Rate Constants for Its Formation and for Some Halogen Abstraction and Addition Reactions
Lusztyk, J.,Maillard, B.,Ingold, K. U.
, p. 2457 - 2460 (2007/10/02)
Pentamethyldisilane is a better hydrogen donor than Et3SiH toward tert-butoxyl (k's for the overall reaction are 17 and 5.7 * 106 M-1 s-1, respectively, at ca. 27 deg C) and toward primary alkyl radicals (k's for Si-H bond cleavage are ca. 10 and 1.0 * 104 M-1 s-1, respectively, at 120 deg C).Absolute rate constants for various reactions of the Me3SiSiMe2 radical have been measured by laser flash photolysis at room temperature.In halogen atom abstractions, for example, the Me3SiSiMe2 radical is slightly less reactive than Et3Si, but it is more reactive than n-Bu3Ge and n-Bu3Sn.Pentamethyldisilane would appear to offer an attractive alternative to n-Bu3SnH and n-Bu3GeH in radical chain reactions in which the desired product is formed by a hydrogen transfer not to the organic radical formed initially but to a second radical formed by a slow β-scission or rearrangement of the initial radical.
