Aluminum Adducts of NHC‐Silylphosphinidenes and Their Isosteric Analogy to NHC‐Disilylsilylene Complexes

Aluminum‐silicon adducts of N‐heterocyclic carbene (NHC) phosphinidenides have been synthesized and structurally characterized. Their bonding and electronic structures were compared with those of isosteric NHC‐disilylsilylene complexes using DFT, NBO, and QTAIM analyses. The results reveal striking structural analogies, in particular similar pyramidalization at the exocyclic main‐group center, while also highlighting clear differences between the covalent SiSi and PSi bonds and the more polar, coordinative P–Al interaction. Extension to an arsenic analog further underlines the generality of this approach and emphasizes the significance of isosterism as a guiding principle in main‐group organometallic chemistry.