Formation of a P₁₆^2– Ink from Elemental Red Phosphorus in a Thiol–Amine Mixture

A P₁₆^2– polyphosphide dianion ink was produced by the reaction of red phosphorus with a binary thiol–amine mixture of ethanethiol (ET) and ethylenediamine (en). The polyphosphide was identified by solution ³¹P NMR spectroscopy and electrospray ionization mass spectrometry. This solute was compared to the reaction products of white phosphorus (P₄) and other elemental pnictides in the same solvent system. The reaction of P₄ with ET and en gives the same P₁₆^2– polyphosphide; however, the easier handling and lower reactivity of red phosphorus highlights the novelty of that reaction. Elemental arsenic and antimony both give mononuclear pnictogen–sulfide–thiolate complexes upon reaction with ET and en under otherwise identical conditions, with this difference likely resulting from the greater covalency and tendency of phosphorus to form P–P bonds.