Synthesis of Tetrahedranes Containing the Unique Bridging Hetero-Dipnictogen Ligand EE' (E ≠ E'=P, As, Sb, Bi).

In order to improve and extend the rare class of tetrahedral mixed main group transition metal compounds, a new synthetic route for the complexes [{CpMo(CO)2 }2 (μ,η2 :η2 -PE)] (E=As (1), Sb (2)) is described leading to higher yields and a decrease in reaction steps. Via this route, also the so far unknown heavier analogues containing AsSb (3 a), AsBi (4) and SbBi (5) ligands, respectively, are accessible. Single crystal X-ray diffraction experiments and DFT calculations reveal that they represent very rare examples of compounds comprising covalent bonds between two different heavy pnictogen atoms, which show multiple bond character and are stabilised without any organic substituents. A simple one-pot reaction of [CpMo(CO)2 ]2 with ME(SiMe3 )2 (M=Li, K; E=P, As, Sb, Bi) and the subsequent addition of PCl3 , AsCl3 , SbCl3 or BiCl3 , respectively, give the complexes 1-5. This synthesis is also transferable to the already known homo-dipnictogen complexes [{CpMo(CO)2 }2 (μ,η2 :η2 -E2 )] (E=P, As, Sb, Bi) resulting in higher yields comparable to those in the literature reported procedures and allows the introduction of the bulkier and better soluble Cp' (Cp'=tert butylcyclopentadienyl) ligand.