1,2,4-Diazaphosphole und 1,2,4-DiazaarsoIe: Ringstruktur und Struktur wasserstoffbrücken-gebundener Paare und Helices/1,2,4-Diazaphospholes and 1,2,4-Diazaarsoles: Ring Structure and Structure of Hydrogen-Bonded Pairs and Helices

Abstract

Among the large family of azaphospholes 1,2,4-diazaphospholes feature a particularly stable ring system. 3,5-Unsubstituted and 3,5-equally substituted 1,2,4-diazaphospholes and -diazaarsoles are best made from 1,3-bis(dimethylamino)-2-phospha/arsaallyl chlorides and hydrazines. This way four examples for single crystal X-ray structure investigations were prepared: The unsubstituted 1,2,4-diazaphosphole 2 and -diazaarsole 4, the N-substituted 1 -(2-pyridyl) 1.2.4-diazaphosphole 1, and the C-substituted 3,5-di-tert-butyl 1,2,4-diazaphosphole 3. They all possess planar rings with small angles at P (86°) and As (81°). The N-unsubstituted molecules are connected to each other by NH···N hydrogen bonds forming in case of the isotypic compounds 2 and 4 a helix along a crystallographic axis and in case of compound 3 for steric reasons a dimer. The structures of the aggregates found are compared to those of pyrazoles.