Ruthenium mediated halogenation of white phosphorus: synthesis and reactivity of the unprecedented P4Cl2 moiety

Abstract

The transition metal mediated functionalization of P₄ is an approach to develop a more sustainable production of organophosphorus compounds. In this paper a ruthenium complex is presented, in which the P₄ unit can be selectively converted into new P₄R₂ molecules in a two-step synthesis. The unsaturated 16 electron species [RuX(Cp*)(PCy₃)] (Cp* = C₅Me₅, X = Cl, Br) reacts with a half equivalent of P₄ affording a bimetallic complex bearing a planar P₄X₂ moiety as a ligand. The latter eliminates chloride anions under reduction with magnesium. In this process the butadiene-like P₄Cl₂ ligand is converted into two weakly bound P₂ units which bridge the ruthenium centers. In the presence of n-BuLi, the P₄Cl₂ unit can be selectively alkylated, yielding the planar organophosphorus ligand P₄ⁿBu₂. A detailed analysis of the electronic properties and solid state structures of the compounds combined with DFT calculations and AIM analyses demonstrate that the P₄ unit in all complexes acts as an electronically highly flexible, non-innocent ligand.