Synthesis of bis(phosphinomethyl)amines via bis(hydroxymethyl)phosphonium salts. Isolation of 9,9-bis(hydroxymethyl)-9-phosphoniabicyclo[3.3.1]nonane hydrogensulfate and chloride salts, and the crystal structures of [PPh2(CH2OH)2]+ Cl– and [(C6H11)2PCH2]2NCHMePh

Abstract

Phosphines of the type PR₂H reacted readily with formaldehyde in the presence of acid to afford high yields of bis(hydroxymethyl)phosphonium salts [PPh₂(CH₂OH)₂]⁺X^–, [P(C₆H₁₁)₂(CH₂OH)₂]⁺X^–, [[graphic omitted]H₂]⁺X^–, and [[graphic omitted]H₂]⁺X^–(X = Cl or HSO₄). Treatment of the mixed isomers of the bicyclononane phosphonium cation [P(C₈H₁₄)(CH₂OH)₂]⁺ in boiling H₂SO₄ gave a [3.3.1] isomer, the [4.2.1] isomer undergoing decomposition. A single-crystal X-ray diffraction study has been carried out on the phosphonium salt [PPh₂(CH₂OH)₂]⁺Cl^–. The geometry around phosphorus is essentially tetrahedral, and there is hydrogen bonding between the hydroxyl groups and the chloride anion. Treatment of these phosphonium salts with triethylamine and a primary or secondary amine afforded aminomethylphosphines (R₂PCH₂)₂NR′(R = Ph, R′= CHMePh, CHMeCO₂Me, CHMeCO₂Et, [graphic omitted]CMe₂, CH₂CH₂OH or CH₂CHCH₂; R = C₆H₁₁, R′= CHMePh or CHMeCO₂H; R₂= C₈H₁₄, R′= CHMePh) or C₈H₁₄PCH₂NEt₂ in good yields. A single-crystal X-ray diffraction study has been carried out on [(C₆H₁₁)₂PCH₂]₂NCHMePh.