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

The reactivity of the mixed dipnictogen complexes [{CpMo(CO)(2)}(2)(mu,eta(2:2)-PE)] (E= P, As, Sb) towards different group 14 electrophiles is reported. The resulting library of cationic compounds [{CpMo(CO)2}2(mu,eta(2:2)-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)(mu,eta(2:2)-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)}(mu,eta(2:1)-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.