A selected ion flow tube study of the ion-molecule reactions of monochloroethene, trichloroethene and tetrachloroethene

Data for the rate coefficients and product cations of the reactions of a large number of atomic and small molecular cations with monochloroethene, trichloroethene and tetrachloroethene in a selected ion flow tube at 298 K are reported. The recombination energy of the ions range from 6.27 eV (H$_3$O$^+$) through to 21.56 eV (Ne$^+$). Collisional rate coefficients are calculated by modified average dipole orientation theory and compared with experimental values. Thermochemistry and mass balance predict the most feasible neutral products. Together with previously reported results for the three isomers of dichloroethene (J. Phys. Chem. A., 2006, 110, 5760), the fragment ion branching ratios have been compared with those from threshold photoelectron photoion coincidence spectroscopy over the photon energy range 9-22 eV to determine the importance or otherwise of long-range charge transfer. For ions with recombination energy in excess of the ionisation energy of the chloroethene, charge transfer is energetically allowed. The similarity of the branching ratios from the two experiments suggest that long-range charge transfer is dominant. For ions with recombination energy less than the ionisation energy, charge transfer is not allowed; chemical reaction can only occur following formation of an ion-molecule complex, where steric effects are more significant. The products that are now formed and their percentage yield is a complex interplay between the number and position of the chlorine atoms with respect to the C=C bond, where inductive and conjugation effects can be important

Germanium(II) and tin(II) complexes of a sterically demanding phosphanide ligand

The reaction between PhPCl2 and 1 equiv of RLi, followed by in situ reduction with LiAlH4 and an aqueous workup yields the secondary phosphane PhRPH [R = (Me3Si)2CH]. Treatment of PhRPH with n-BuLi in diethyl ether generates the lithium phosphanide (RPhP)Li(Et 2O)n [15(Et2O)], which may be crystallized as the tetrahydrofuran (THF) adduct (RPhP)Li(THF)3 [15(THF)]. Compound 15(Et2O) reacts with 1 equiv of either NaO-tBu or KO-tBu to give the corresponding sodium and potassium phosphanides (RPhP)Na(Et2O) n (16) and (RPhP)K(Et2O)n (17), which may be crystallized as the amine adducts [(RPhP)Na(tmeda)]2 [16(tmeda)] and [(RPhP)K(pmdeta)]2 [17(pmdeta)], respectively. The reaction between 2 equiv of 17 and GeCl2(1,4-dioxane) gives the dimeric compound [(RPhP)2Ge]2'Et2O (18'Et2O). In contrast, the reaction between 2 equiv of 15 and SnCl2 preferentially gives the ate complex (RPhP)3SnLi(THF) (19) in low yield; 19 is obtained in quantitative yield from the reaction between SnCl2 and 3 equiv of 15. Crystallization of 19 from n-hexane/THF yields the separated ion pair complex [(RPhP)3Sn][Li(THF)4] (19a); exposure of 19a to vacuum for short periods leads to complete conversion to 19. Treatment of GeCl2(1,4-dioxane) with 3 equiv of 15 yields the contact ion pair (RPhP)3GeLi(THF) (20), after crystallization from n-hexane/THF. Compounds 15(THF), 16(tmeda), 17(pmdeta), 18'Et2O, 19a, and 20 have been characterized by elemental analyses, multielement NMR spectroscopy, and X-ray crystallography. While 15(THF) is monomeric, both 16(tmeda) and 17(pmdeta) are dimeric in the solid state. The diphosphagermylene 18'Et2O adopts a dimeric structure in the solid state with a syn,syn-arrangement of the phosphanide ligands, and this structure appears to be preserved in solution. The ate complex 19a crystallizes as a separated ion pair, whereas the analogous ate complex 20 crystallizes as a discrete molecular species. The structures of 19 and 20 are retained in non-donor solvents, while dissolution in THF yields the separated ion pairs 19a and [(RPhP)3Ge][Li(THF)4] (20a). © 2010 American Chemical Society