Synthesis, structure, and redox properties of the extremely crowded triarylpnictogens: Tris(2,4,6-triisopropylphenyl)phosphine, arsine, stibine, and bismuthine

A Series of the extremely crowded triarylpnitogens, tris(2,4,6-triisopropylphenyl)phosphine (1), arsine (2), stibine (3), and bismuthine (4), were synthesized by the reaction of 2,4,6-triisopropylphenylcopper(I) with the corresponding pnictogen trichlorides. Introducion of the three bulky aryl groups resulted in the unusual structures and redox properties, which were studied by X-ray crystallography and cyclic voltammetry. The triarylpnictogens 1, 2, and 3 had extremely large bond angles around pnictogen atoms (1: 111.5°, 2:°, 3: 106.7°), and not only 1 and 2, but also stibine 3 displayed a reversible redox wave in the cyclic voltammograms at very low potentials (1: 0. 16 V, 3: 0.57 V vs Ag/Ag⁺), Whic suggests considerable stability of the corresponding cation radicals.