Synthesis and Reactivity of Hetero‐Pnictogen Diazonium Analogs Stabilized by Transition Metal Units

Abstract

AbstractThe reactivity of the mixed dipnictogen complexes [{CpMo(CO)2}2(μ,η2 : 2‐PE)] (E=P, As, Sb) towards different group 14 electrophiles is reported. The resulting library of cationic compounds [{CpMo(CO)2}2(μ,η2 : 2‐EPR)]+ (R=Mes (2,4,6‐C6H2Me3), CH3, CPh3, SnMe3) represents formally inorganic diazonium homologs which are stabilized by transition metal units. Modifying the steric and electronic properties of the electrophile drastically impacts the respective P−R bond lengths and is accompanied by increasing (SnMe3>CPh3>CH3) dynamic behavior in solution. In contrast to the well‐studied organic analogs, the prepared compounds are stable at room temperature. The subsequent reaction of the model substrate [{CpMo(CO)2}2(μ,η2 : 2‐P2Me)][OTf] ([OTf]−=[CF3SO3]−) with different N‐heterocyclic carbenes (NHCs) leads to an addition at the unsubstituted P atom which is also predicted by computational methods. NMR spectroscopy confirms the formation of two isomers sync/gauche‐[{CpMo(CO)2}(μ,η2 : 1‐P(NHC)PMe){CpMo(CO)2}][OTf]. X‐ray crystallographic characterization and additional DFT calculations shed light on the spatial arrangement as well as on the possible formation pathways of the isomers.