Strain‐Release Driven Arsenium Ion Bond Insertion

Abstract

Abstract Although it marks a cornerstone of pnictogenium ion [R 2 Pn] + reactivity, the insertion of arsenium ions [R 2 As] + into non‐polar bonds remains highly challenging. Herein, a synthetic approach is developed, which circumvents the limitations of insertion reactivity of [R 2 As] + (e.g., formal redox state of +V at As) via alleviation of ring strain in the substrate. Thus, unlocking arsenium ion bond insertion delivers the ring‐expanded complexes [{L n M}(η 3 ‐Pn 3 AsCy 2 ][TEF] ({L n M} = Cp ‴ Ni, Pn = P ( 1 ); {L n M} = {CpMo(CO) 2 }, Pn = P ( 2 ), As ( 5 ); Cp ‴  = 1,2,4‐ t Bu 3 C 5 H 2 , [TEF] −  = [Al{OC(CF 3 ) 3 } 4 ] − ). Computational analysis of the reaction mechanism and quantum crystallographic investigation of 1 highlight the release of ring strain as the crucial driving force for this reactivity. This rational is corroborated by the isolation of the arsenium ion coordinated [{CpMo(CO) 2 } 2 (μ,η 2:2 ‐P 2 AsCy 2 )][TEF] ( 3 ) as well as the phosphenium ion inserted [{CpMo(CO) 2 }(η 3 ‐As 3 PPh 2 )][TEF] ( 4 ).