Synthesis, chemical bonding and reactivity of new medium-sized polyarsenides

Gaining an understanding of the growth mechanism from single atoms to clusters and bulk materials continues to present a challenge. Thus, it is important to explore the evolving trends of clusters in the structure and properties during the size evolution. In this work, we report the synthesis and characterization of two medium-sized chain-like polyarsenic anions. [As21]3– represents a trimeric example of polyarsenic anion assembled through oxidative coupling of As73– anions. The anion As184– included in [As18Mo2(CO)8]4– is regarded as formed by two realgar-type As8 subunits connected by a dinuclear As-As dumbbell. The As18 cluster was previously predicted by theory, and this is the first time successfully synthesized using wet chemistry method. Besides, small-sized polyarsenides As22– and As102– were found in compound [K(18-crown-6)]3[As10]0.5[As4{Mo(CO)3}2]0.5·2en. Among these, the former exhibits coordination with metal atoms. Single-crystal X-ray diffraction combined with quantum chemical calculations revealed the formation of double bonded As22– stabilized by metal carbonyl groups. This work demonstrates a novel synthetic approach for the preparation of new polyarsenides and highlights their intriguing bonding characteristics, laying the foundation for the synthesis of such compounds and paving the way for their potential applications.