Fluorophosphoranes containing the perfluoropinacolyl ring system. Part 5. Estimates of two-step exchange barriers in some amino-derivatives

Abstract

Low-temperature n.m.r. spectra have confirmed the presence of a two-step intramolecular exchange process in aminodifluoro(perfluoropinacolyl)phosphoranes, PF₂(NR¹R²)(pfp)(R¹= H, R²= H or Bu^t; R¹= Bu^t or SiMe₃, R²= SiMe₃; R¹= R²= Me or Et; R¹R²= Me₂C[CH₂]₃CMe₂). Energy barriers for these processes have been estimated. Analysis of the spectra confirms the expected ground-state configurations. Rotational effects are observed in a highly hindered asymmetrically substituted amino-derivative. The compound PF₂(NH₂)(pfp) has been synthesised by cleavage of the bis(trimethylsilyl)amino-precursor with hydrogen chloride. Intramolecular hydrogen-bonding effects are suspected in this compound and in PF₂(NBu^tH)(pfp).