Coordination chemistry of phosphenium centers.
Date
1995
Authors
Losier, Pierre.
Journal Title
Journal ISSN
Volume Title
Publisher
Dalhousie University
Abstract
Description
Low coordinate and unsaturated non-metal centers offer attractive sites for oxidative addition and coordination chemistry. The phosphenium cations (analogues of carbenes) $\lbrack\rm\overline{N(Me)CH\rm\sb2CH\sb2N(Me)P}\rbrack\sp+$ and (($\rm\sp{i}Pr\sb2N)\sb2P\rbrack\sp+$ are stable in CH$\rm\sb2Cl\sb2$ solutions due to the coordinative interactions of the counterion (GaCl$\sb4$) $\sp_$ with the phosphorus center which is referred to as "anionic protection". However, in the presence of the weakly coordinating anion (BPh$\sb4$) $\sp-$, the reactivity of the phosphenium cations is enhanced and oxidative addition of a CH$\rm\sb2Cl\sb2$ molecule or phenyl transfer to the phosphorous center is observed. The neutral phosphenium derivative $\rm\overline{N(SiMe\sb3)AlCl\sb2N(SiMe\sb3)P}$ undergoes a one-atom oxidative addition with elemental chalcogens to give a dimer with a P$\rm\sb2E\sb2$ ring (E = S and Se) in a bis(spiro)tricyclo framework. Amine, ether and phosphine bases react with the zwitterion to give the first examples of coordination complexes involving a neutral phosphorus center. Phosphenium species typically possess at least one electron-rich substituent (e.g. NR$\sb2,$ SR) which is responsible for stabilizing the electron deficient phosphorus site through $\pi$-donation. Attempts to synthesize a series of dialkylphosphenium cations $\lbrack\rm R\sb2P\rbrack\sp+$ via halide abstraction from R$\sb2$PCl (R = Me, Et, Ph, $\rm\sp{i}$Pr, $\rm\sp{t}$Bu) with GaCl$\sb3$ lead to phosphinophosphonium cations $\lbrack\rm R\sb2PPR\sb2Cl\rbrack\sp+$ or covalent adducts R$\rm\sb2PCl{\cdot}GaCl\sb3.$ Moreover, the methyl derivative $\lbrack\rm Me\sb2PPMe\sb2Cl\rbrack\sp+$ complexes to an equivalent of GaCl$\sb3$ to give the first examples of "base induced" coordination.$\sp*$ ftn$\sp*$Please refer to the dissertation for diagrams.
Thesis (Ph.D.)--Dalhousie University (Canada), 1995.
Thesis (Ph.D.)--Dalhousie University (Canada), 1995.
Keywords
Chemistry, Inorganic.