Studies on synthesis and reactions of anionic <em>P</em>-NR₂/P-OR organophosphane complexes

Abstract

This thesis was focused on the studies of synthesis and reactivity of the first Li/OR phosphinidenoid complexes, in pursuit of the boundary between phosphanide complex and phosphinidenoid complex chemistry. <br /> First, the three modified methodologies were used to generate the precursors – <em>P</em>-functional phosphane complexes. Then subjection of <em>P</em>-functional phosphane complexes to LDA (lithium diisopropylamide) in presence of 12-crown-4 at –78°C led to the Li/OR phosphinidenoid complexes: bearing a downfield ³¹P chemical shift, combined with a small tungsten-phosphorus coupling constants. But an unexpected decomposition product was observed in the deprotonation of <em>P</em>-acetyl phosphane complex, in which a P–H and a P–O–Li moiety were contained in one molecule. Again, the deprotonation of <em>P</em>-acetyl phosphane complex without 12-crown-4 gave rise to the first observation of phosphorus-lithium coupling (quart, <em>δ</em> = 220 ppm, ¹<em>J</em>_(P,Li) = 40.7 Hz). <br /> Moreover, the effects of reaction conditions (e.g. different bases, different co-ligands, etc) on the NMR signature and thermal stability of Li/OR phosphinidenoid complexes were investigated. However, in all of cases, the ³¹P NMR signature showed little (or no) difference, therefore it was deduced that the Li/OR phosphinidenoid complexes might be an ion pair complex, in which metal cations bear the co-ligand (such as 12-crown-4 or cryptand[2.1.1]) or solvents and <em>P</em>-OR phosphanide complexes as anions. This assumption was confirmed additionally by the single-crystal X-ray analysis of [<em>N,N</em>-di-tert-butyl-imidazolium] stabilized phosphinidenoid complex. <br /> In the chapter 7, reactivity studies of Li/OR phosphinidenoid complexes were introduced. In most cases, the “phosphanide-type” reactivity was displayed. Only in the thermal reaction of Li/OPh derivative, the “phosphinidene-type” reactivity was revealed, which was explained by the observation of cyclotriphosphane compound, although the mechanism was not clear. Besides, for Li/OMe phosphinidenoid complex, the redox reactivity was observed and also confirmed by the ESR measurement.