Selective white phosphorus activation and functionalization with inorganic Grignard reagents

Abstract

We describe the targeted and selective functionalization of white phosphorus (P₄) using ‘inorganic Grignard reagents’. Reactions of the Fe–Mg complexes [(^DippBDI)Mg(THF)_xFp] (Fp = CpFe(CO)₂, 1: x = 0; 1-THF: x = 1, ^DippBDI = 2,6-diisopropylphenyl-1,3-diketiminate)) and [(^DippBDI)MgFp*] (2, Fp* = Cp*Fe(CO)₂) afford the compounds [(^DippBDI)Mg(THF)_xFp(µ-P₄)] (3: x = 0; 3-THF: x = 1) and [(^DippBDI)MgFp*(µ-P₄)] (4) featuring P₄²⁻ ligands with a ‘butterfly’ structure bridging Fe and Mg. The coordination of the β-diketiminate magnesium cations [(DippBDI)Mg]⁺ plays a key role in stabilizing these reactive ‘P₄-butterfly’ anions through non-covalent Mg–P bonds and dispersion forces. Thermolysis or photolysis of 3-THF and 4 afforded rare tetraphosphacyclopentadienolate complexes 7 and 8. Complex 4 exhibits unmitigated reactivity towards a wide range of main group element electrophiles (ⁱPrNCNⁱPr, Ph₂BCl, Ph₃SnCl, (Me₃Si)₃SiCl and Mes₂PCl), furnishing rare examples of stable, mixed-substituted tetraphosphanes 9–13 as well as an octaphosphane 14 featuring a Sn₂P₈ core.