Interactions of tertiary phosphines with p-benzoquinones; X-ray structures of [HO(CH2)3]3P+C6H2(O-)(OH)(MeO) and Ph3P+C6H3(O-)(OH).

Phosphonium zwitterions of a known type were obtained in high yield via a 1:1 reaction of p-benzoquinone or methoxy-p-benzoquinone with the tertiary phosphines R3P [R = (CH2)3OH, Ph, Et, Me] and Ph2MeP, in acetone or benzene at room temp. In all cases, attack of the P-atom occurs at a C-atom rather than at an O-atom. The products were characterized to various degrees by elemental anal., 31P{1H}, 1H and 13C NMR spectroscopies, and mass spectrometry, and two of the zwitterions, the new [HO(CH2)3]3P+C6H2(O-)(OH)(MeO) and the known Ph3P+C6H3(O-)(OH), were structurally characterized by x-ray anal. The PEt3 reaction also produces small amts. of the dimeric’, μ-oxo coproduct Et3P+C6H2(O-)(OH)-O-C6H3(O-)P+Et3 that is tentatively characterized by 1-dimensional- and 2-dimensional-NMR data. 2,5-Di-tert-butyl- and 2,3,5,6-tetramethyl-p-benzoquinone do not react with [HO(CH2)3]3P under the conditions noted above. Heating D2O solns. of the water-sol. zwitterions R3P+C6H3(O-)(OH) [R = (CH2)3OH, Et] at 90° for 72 h leads to complete H/D exchange of the H-atom in the position ortho to the phosphonium center. [on SciFinder(R)]