Coordination chemistry of a phosphadiazonium Lewis acceptor.
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Date
2005
Authors
Spinney, Heather Anne.
Journal Title
Journal ISSN
Volume Title
Publisher
Dalhousie University
Abstract
Description
The two most common oxidation states for phosphorus are phosphorus(III) and phosphorus(V). Although the ability of phosphorus(V) centres to behave as electron pair acceptors (Lewis acids) is well established, the exploitation of the Lewis acidity of phosphorus(III) represents a more recent and developing area. Phosphorus(III) centres (or phosphines) have a lone pair of electrons, are formally electron rich, and are generally recognized as effective electron donors (Lewis bases). Nevertheless, it has been demonstrated that coordinatively unsaturated phosphorus(III) centres have the potential to exhibit electron acceptor behaviour even with the presence of a non-bonding pair of electrons at the acceptor site.
The synthesis and comprehensive characterization (NMR, FT-IR, FT-Raman, X-ray) of a series of coordination complexes in which an electron-rich (lone pair bearing) phosphorus(III) centre acts as a Lewis acceptor is presented. Previous work has shown that iminophosphines of the type Mes*NPX (Mes* = 2,4,6-tri- t-butylphenyl, X = Cl, OSO2CF3) react with a variety of ligands (e.g., imidazol-2-ylidene, amine, phosphine), which effect nucleophilic displacement of X as an anion. The resulting cations are best described as 1:1 adducts of a neutral ligand on a phosphadiazonium Lewis acceptor (Mes*NP+). This chemistry has now been extended to include complexes of the phosphadiazonium cation with both bidentate- and bidentate-chelating ligands, as well as donor-rich adducts where more than one monodentate ligand coordinates to the acceptor. In a similar fashion, dicationic, acceptor-rich phosphadiazonium complexes have been synthesized through the use of bridging ligands. The isolation and characterization of these coordination complexes has resulted in the observation of a number of novel bonding environments for phosphorus, including hypervalent phosphorus(III) species. The coordination of neutral donors to the phosphadiazonium cation represents a new synthetic methodology in phosphorus chemistry, where phosphorus-element (element = C, N, O, S, Se, P) bonds are formed through donor-acceptor interactions.
Thesis (Ph.D.)--Dalhousie University (Canada), 2005.
The synthesis and comprehensive characterization (NMR, FT-IR, FT-Raman, X-ray) of a series of coordination complexes in which an electron-rich (lone pair bearing) phosphorus(III) centre acts as a Lewis acceptor is presented. Previous work has shown that iminophosphines of the type Mes*NPX (Mes* = 2,4,6-tri- t-butylphenyl, X = Cl, OSO2CF3) react with a variety of ligands (e.g., imidazol-2-ylidene, amine, phosphine), which effect nucleophilic displacement of X as an anion. The resulting cations are best described as 1:1 adducts of a neutral ligand on a phosphadiazonium Lewis acceptor (Mes*NP+). This chemistry has now been extended to include complexes of the phosphadiazonium cation with both bidentate- and bidentate-chelating ligands, as well as donor-rich adducts where more than one monodentate ligand coordinates to the acceptor. In a similar fashion, dicationic, acceptor-rich phosphadiazonium complexes have been synthesized through the use of bridging ligands. The isolation and characterization of these coordination complexes has resulted in the observation of a number of novel bonding environments for phosphorus, including hypervalent phosphorus(III) species. The coordination of neutral donors to the phosphadiazonium cation represents a new synthetic methodology in phosphorus chemistry, where phosphorus-element (element = C, N, O, S, Se, P) bonds are formed through donor-acceptor interactions.
Thesis (Ph.D.)--Dalhousie University (Canada), 2005.
Keywords
Chemistry, Inorganic.