New Oligophosphines and (Hydroxymethyl)phosphonium Chlorides

The new oligophosphines [H2P(CH2)2]2PH, [H2P(CH2)2P(H)CH2]2, and{[(H2P(CH2)2]2PCH2}2 have been made by
hydrophosphination of diethyl vinylphosphonate (2) with H2P(CH2)2PH2 (1), using different ratios of 2/1, followed by
LiAlH4 reduction of the phosphonate intermediates; the three phosphonate precursors were obtained as oils of
varying purity (∼90−95%) in low (∼20%) to almost quantitative yield. The tri-, tetra-, and hexaphosphines were
then treated with formaldehyde in the presence of hydrochloric acid to generate the corresponding water-soluble
(hydroxymethyl)phosphonium chlorides {(HOCH2)3P[(CH2)2P(CH2OH)2]n(CH2)2P(CH2OH)3}Clm (n = 1, m = 3; n =
2, m = 4) and {[(HOCH2)3P(CH2)2]2P(CH2OH)CH2}2Cl6 that were characterized by NMR spectroscopy and elemental
analysis. The known (hydroxymethyl)bisphosphonium chloride [(HOCH2)3P(CH2)2]2Cl2 was similarly prepared from
H2P(CH2)2PH2, and the determined crystal structure revealed strong hydrogen bonding between the chloride anions
and the hydrogen atoms of the hydroxymethyl groups.