A Study of the Reactivity of Iminopyridinium Compounds with Metal Ions

  • Shelton A. Dias

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

Several known resonance-stabilized carbonyl ylides of general formula A - BCOAr (where A = C5H5N, (CH3)3N, or (C6 H5)3P; B = N or CH; and Ar = C6H5 or m or p C6H4-CH3) and their salts (some of them previously unknown) have been prepared and fully characterized. Reported literature methods were used for their synthesis but in some cases modifications were incorporated. Detailed spectroscopic data for these ylides are presented and are discussed.All the available literature on the reactions of these ylides with metal salts are described and a comprehensive literature survey on the well-known ortho-metallation reaction is presented and the available data are critically reviewed.N-aminopyridinium perchlorate, like the corresponding chloride, bromide and iodide in solution behaves as a 1:1 electrolyte and shows no sign of any association. However, in the solid form, under the influence of high pressure, the anion and cation of N-aminopyridinium perchlorate interact via hydrogen bonding possibly to give chain polymers or cyclic oligomers. Ample spectroscopic evidence is presented to support this interaction.Attempts to use N-iminopyridinium imine as a donor molecule towards some transition metal salts have failed and resulted in the protonation of the free ylide. This behaviour of the N-iminopyridinium imine is in direct contrast to that of isoelectronic pyridine-N-oxideand a possible explanation for its greater tendency for protonation rather than co-ordination is the very much higher basicity as reflected by its pka, value (=13.4).The reaction of the carbonyl ylides mentioned above, with halidesalts of palladium (II), platinum (II), rhodium (III) and iridium (111) affords products containing metallated betaines. Spectroscopic data (i.r. 'H and 13C.n.m.r) show unambiguously that the aryl group (Ar) has become metallated in a position ortho to the carbonyl group and also that the ylide is bidentate via the group B (N or CH). There is good evidence to indicate that the mechanism of the reaction involves preliminary co-ordination of the ylide followed by intramolecular electrophilic attack by the metal.
Palladium tends to di-μ-halogeno-complexes; [Pd(LH)Hal]2, whereas in the case of platinum it is possible to prepare [Pt(L-H)2] which has cis Pt-C bonds. Reaction with rhodium (III) affords jonic compounds cis [Rh(L-H)2(H20)2] (equation please see thesis) (where X = Cl,Br,I, BPh4) which with 2,2'-bipyridy1 give [Rh (L-H)2(bipy)]+C⌉. Iridium gives a non-ionic derivative [Ir(L-H)2(H20)C1]3H2,0. Reactions of the complexes with Ph3P or Bu3p [Pd(L-H)(PhP0)C1], [Pt(L-H)(Ph,P0)C1],[Rh(L-H)(BugP0)C1]and[Ir(L-H))(Ph,P0)C1].The Pd-ClandPt-Cl bondsaretranstonitrogenP give new compounds containing phosphine oxide such as+when L = CeH_N-NCOPh with which most of the metallation reactions have been done.
Date of Award1974
Original languageEnglish

Keywords

  • Reactivity
  • iminopyridinium compounds
  • metal ions

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