The new diphosphanylphosphido complexes of tungsten(vi) and molybdenum(vi). Their synthesis, structures and properties

Abstract

We report on the reactivity of R₂P–P(Li)–PR′₂ (R = tBu, iPr, R′ = NEt₂, iPr) towards diimido complexes [(dippN)₂MCl₂·dme] (M = Mo, W and dipp = 2,6-iPr₂C₆H₃). A series of new complexes with diphosphanylphosphido ligands R₂P–P–PR′₂ were isolated. The solid-state structures of [(dippN)₂M(Cl)(1,2-η-iPr₂P–P–PiPr₂)] (2Mo and 2W) and [(dippN)₂M(Cl){1,2-η-tBu₂P–P–P(NEt₂)₂}] (3Mo and 3W) were established by single-crystal X-ray diffraction analysis and indicate a side-on geometry of the R₂P–P–PR′₂ moiety. 3W and 3Mo are the first triphosphorus complexes with the amido ligand NEt₂ on the P atom. [(dippN)₂M(Cl)(1,2-η-tBu₂P–P–PtBu₂)] (1Mo and 1W) and 3Mo and 3W display similar side-on geometry in solution and in the solid state. By contrast, 2Mo and 2W reveal a dynamic behavior in solution. For the first time, the reactivity of diphosphanylphosphido complexes towards different nucleophiles was studied. The complexes react with the phosphorus nucleophile Ph₂PLi, yielding phosphanylphosphinidene complexes [(dippN)₂M(Cl)(η²-P-PR₂)]⁻ Li⁺ (M = Mo, W) together with related diphosphanes R′₂P–PPh₂. Carbon nucleophile MeLi does not yield [(dippN)₂M(Cl)(η²-P-PR₂)]⁻ Li⁺ but substitutes a Cl ligand at the metal center. Moreover, we compare the coordination of the R₂P–P–PR′₂ moiety to different metal centers based on DFT methods.