Reactions of phosphorus fluorides and ortho-carborane ditertiary aminophosphines

Fluorophosphine bidentate ligands containing o-carborane as backbone can be prepared by the reaction of the lithium-o-carboranes and PF₂X derivatives to give only two species: the unsymmetrical (C₆H₅)₂PB₁₀H₁₀C₂]PF₂ and the cyclic FPB₁₀H₁₀C₂]₂PF, both in low yield. However, exchange of F and NMe₂ groups by use of PF₅ or PF₃ provides a facile way to produce several new fluorophosphines.Phosphorus pentafluoride forms solid adducts with the o-phosphino derivatives (C₆H₅)₂PB₁₀H₁₀C₂]P(NMe₂)₂, (Me₂N)₂PB₁₀H₁₀C₂]P(NMe₂)₂ and (C₆H₅)₂PB₁₀H₁₀C₂]H. All the adducts contain a phosphorus-phosphorus bond as evidenced from i.r., NMR and stoichiometry. The stability of the adducts reflects the strength of the PP bond formed upon complexation. When suspensions or solutions of the adducts are heated they exchange F and NMe₂ groups and no redox occurs. The products (C₆H₅)₂PB₁₀H₁₀C₂]P(F)NMe₂(I) and Me₂N(F)PB₁₀H₁₀C₂]P(F)NMe₂(II) react further with PF₅ giving (C₆H₅)₂PB₁₀H₁₀C₂]PF₂(III) and F₂PB₁₀H₁₀C₂]PF₂(IV).The precursors also react with phosphorus trifluoride to produce only (I) and (Me₂N)₂PB₁₀H₁₀C₂]P(F)NMe₂(V) regardless of the reaction conditions. All the products I–V have been identified by ¹H, ¹⁹F, and ³¹P NMR and i.r. spectroscopy, mass spectrometry, and elemental analysis. The NMR spectra of the novel (IV) have been analysed as X₂AA¹X¹₂ spin system.