Structures and Dynamics of Secondary and Tertiary Alkylphosphine Oxides Adsorbed on Silica

: The three secondary phosphine oxides [CH2 =CH(CH2 )4 ]2 HPO (1), [CH2 =CH(CH2 )5 ]2 HPO (2), and [CH2 =CH(CH2 )6 ]2 HPO (3), and two diphosphine dioxides, {[CH2 =CH(CH2 )6 ]2 PO(CH2 )7 }2 (4) and {[CH2 =CH(CH2 )6 ]2 PO(CH2 )4 }2 (5), incorporating long methylene chains, are described. The single crystal X-ray structures of 1, 2, and 5 have been determined. The phosphine oxides 3, 4, and 5 have been adsorbed on silica in submonolayer quantities to give 3 a-5 a. The 1 H, 13 C, and 31 P solid-state NMR spectra of polycrystalline 3-5 have been analyzed and compared with those of 3 a-5 a. The changes of the solid-state NMR characteristics upon adsorption and the surface mobilities of the phosphine oxides are discussed.