Oligodentate Phosphine Ligands with Phospholane End Groups: New Synthetic Access and Application to Molybdenum-Based Synthetic Nitrogen Fixation

Abstract

A new synthetic access to oligodentate phosphine ligands with phospholane end groups, starting from lithium phospholanide, is established. Based on this building block, the tridentate ligand prPP(Ph)P-pln was synthesized and used for the synthesis of [MoX3{prPP(Ph)P-pln}] (X = Cl, Br, I) precursors. Sodium amalgam reduction in the presence of N2 and either mono- or bidentate ligands leads to several molybdenum(0) mono- and bis(dinitrogen) complexes, respectively. With the diphosphine dppm a mixture of facial and meridional isomers of [Mo(N2){prPP(Ph)P-pln}(dppm)] is formed. Using the monophosphines PMePh2 and PMe2Ph mer-[Mo(N2){prPP(Ph)P-pln}(PMe2Ph)2] and trans-[Mo(N2)2{prPP(Ph)P-pln}(PMePh2)] could be obtained. The spectroscopic properties and reactivity of the latter towards protonation was investigated, and a hydrazido complex could be obtained and characterized.