# Isoselenocyanates with Sterically Encumbered SubstituentsSynthesis, Structures, and Spectroscopic Properties

## TL;DR

This paper describes the synthesis and properties of isoselenocyanates with various bulky organic groups.

## Contribution

A new synthetic method for isoselenocyanates with sterically encumbered substituents is presented.

## Key findings

- Isoselenocyanates with diverse organic residues were successfully synthesized.
- X-ray and NMR studies confirmed structural and spectroscopic properties.
- The influence of substituents on 77Se NMR shifts aligns with DFT calculations.

## Abstract

A series of isoselenocyanates,
SeCNR, spanning over a
variety of
organic residues in terms of steric encumbrance and electronic effects,
was synthesized by reactions of corresponding isocyanides with elemental
selenium. The residues range from tertiary butyl (
t
Bu), phenyl (Ph), 2,4,6-trimethylphenyl (Mesityl), 2,6-diisopropylphenyl
(
i‑Prop2Ph), 2,6-di­(2,4,6-trimethylphenyl)­phenyl
(ArMes2), 2,6-di­(2,6-diisopropylphenyl)­phenyl (ArDipp2), 2,6-di­(2,4,6-triisopropylphenyl)­phenyl (ArTripp2),
and 4-fluorophenyl (PhF) to 2,6-di­{3,5-di­(trifluoromethyl)­phenyl}­4-fluorophenyl
(p-FArDarF2). They were formed as crystalline
solids or viscous oils in medium to good yields, which recommends
this synthetic approach as generally suitable. The products were studied
by X-ray diffraction and spectroscopic methods, including 77Se NMR spectroscopy. The influence of the organic substituents on
the 77Se NMR chemical shifts of the isoselenocyanates is
in good accordance with DFT-modeled values. Experimental 77Se–13C couplings of 280 Hz could be derived for
Se13CNArDipp2 prepared from a sample of 13CNArDipp2 (isotopic enrichment: 99%). A small
amount of a selenourea-type product, (i-Prop)2NC­(Se)­NHp-FArDarF2, was isolated
from a reaction mixture of CNp-FArDarF2 with selenium and diisopropylamine as the supporting base, which
indicates an influence of the supporting base used for the course
of the reaction.