Stable heterocyclopentane-1,3-diyls

Abstract

Diphosphadiazanediyl, [(μ-NR)P]2 (R = Ter = 2,6-dimesitylphenyl), is known to readily activate small molecules with multiple bonds. CO is an especially intriguing species for activation, because either 1,1- or 1,2-bridging mode would lead to a [1.1.1]bicycle or a carbene, respectively. The activation of CO with diphosphadiazanediyl already occurs at ambient temperatures (1 bar, 25°C). However, CO is involved in an unprecedented ring expansion reaction under preservation of the biradical character, which leads to the formation of the first stable cyclopentane-1,3-diyl analogue displaying photochromic molecular switch characteristics.