⁷⁷Se NMR Spectroscopy As a Sensitive Probe for Hammett σ Constants

Herein we showcase the use of a combination of ¹H, ¹³C, and ⁷⁷Se NMR spectroscopy as a sensitive tool for correlation analysis. A series of substituted <i>O</i>-aryl selenocarbamates [ArOC­(Se)­N­(CH₃)₂] and <i>Se</i>-aryl selenocarbamates [ArSeC­(O)­N­(CH₃)₂] have been investigated by means of ¹H, ¹³C, and ⁷⁷Se NMR spectroscopy. We have determined the ¹H, ¹³C, and ⁷⁷Se chemical shift values as well as both one- and two-bond heteronuclear ¹³C–⁷⁷Se coupling constants, and the changes in both the chemical shift values and the coupling constants were found to obey linear free energy relationships with Hammett’s σ_p and σ_p^– constants. For the eight studied <i>O</i>-aryl selenocarbamates, we observe linear free energy correlations with two of the ¹³C and ⁷⁷Se chemical shift values and as well as one ¹³C–⁷⁷Se coupling constant. With the five examples of <i>Se</i>-aryl selenocarbamates, linear correlations are observed with three different ¹³C–⁷⁷Se coupling constants. The strong internal consistency validates the use of ⁷⁷Se NMR spectroscopy for correlation analysis