The chemistry of the tetraimidophosphate trianion and related species: Synthesis and characterization of a novel series of main group radicals.

摘要

The work described in this thesis focuses on the synthesis of polyimido analogues of orthophosphate [P04]3- and orthosilicate [SiO4]4-, where the oxo [O]2- units have been replaced by imido [NR]2- (R = alkyl, aryl) groups. These species are of interest as they are isoelectronic with these ubiquitous oxo-anions; in addition, they are multidentate ligands which may possess interesting and extensive coordination chemistries.; A new method for the synthesis of tetraimidophosphates was developed by first reacting Cl3PNSiMe3 with LiHNR, then treating the resultant trisamino(imino)phosphoranes (RNH)3PNSiMe3 with nBuLi to yield the unsymmetrical tetraimido-phosphates {lcub}Li3[P(NR)3(NSiMe3)]{rcub} (R = Cy, tBu, Ad).; Only monodeprotonation of (RNH)3PNSiMe3 can be achieved using other metallating agents; however, two different pathways are possible for reactions with AlMe3, with imido analogues of ortho- or meta-phosphate produced, depending on the identity of the NHR-group. The reactivities of the trisaminophosphates EP(NHR)3 (E = O, S, NSiMe 3) toward MgBu2, ZnMe2, and AlMe3 decrease on moving from oxygen to the heavier chalcogen sulfur, and still further upon replacement of S with NSiMe3. The reverse trend in reactivity is observed for n-butyllithium, where three-fold deprotonation is readily accomplished for E = NSiMe3 but is not possible for E = O: the [OP(NR)3]3- trianion is only formed from reactions with ZnMe2.; The lithiated tetraimidophosphate {lcub}Li3[P(NtBU) 3(NSiMe3)]{rcub}2 possesses a unique coordination chemistry, exhibiting the ability to trap rare trimeric alkali metal alkoxide units as six-membered M3O3 rings (M = Li, K). Oxidation of tile tetraimidophosphate trianions {lcub}Li3[P(NR)3(NSiMe 3)]{rcub}2 (R = tBu, Ad) with halogens yields a new class of stable inorganic radicals. These species exist as distorted PN 3Li3X (X = Cl, Br, I) cubes both in the solid state and in solution. Similar reactions of the heterobimetallic lithium/aluminum tetraimidophosphates produce persistent spirocyclic radicals, as does oxidation of the symmetrical tetraimidophosphate {lcub}[Li3[P(NtBU)4]{rcub}. Analogous chemistry can be done with lithiated polyimidosilicates, where persistent radicals in both cubic and spirocyclic geometries are observed.; All novel compounds have been characterized in solution by either multinuclear NMR spectroscopy or EPR spectroscopy (paramagnetic species only); the solid-state structures of several compounds have also been definitively established by X-ray crystallography.