Date of Award

1993

Publication Type

Doctoral Thesis

Degree Name

Ph.D.

Department

Chemistry and Biochemistry

Keywords

Chemistry, Inorganic.

Supervisor

Tuck, D. G.,

Rights

info:eu-repo/semantics/openAccess

Abstract

This work was undertaken to further develop work carried out in this laboratory in recent years on the oxidation of Main Group 3A and 4A elements, and of compounds of these elements in low oxidation states, by focusing on the oxidation of the Main Group 5A and 6A elements phosphorus, tellurium and antimony, and of their low oxidation states compounds. The phosphorus compounds P(O$\rm\sb2C\sb6R)\sb2$Br (R = Cl$\sb4$, Br$\sb4$ or Bu$\rm\sp t\sb2H\sb2$) have been prepared by the reaction of P$\sb4$, Br$\sb2$ and the substituted o-benzoquinone o-O$\sb2$C$\sb6$R. There is no reaction between o-O$\rm\sb2C\sb6Bu\sp t\sb2H\sb2$ (dbbq), P$\sb4$ and Ph$\rm\sb2Se\sb2$, but in the presence of catalytic quantities of Br$\sb2$ the product is P(dbc)$\sb2$(SePh) (dbc = 3,5-di-Bu$\sp{\rm t}$catecholate). Electron spin resonance (ESR) spectra identify the presence of the corresponding o-semiquinone species in these reactions. The $\sp{13}$C and $\sp{31}$P NMR spectra of these phosphoranes are studied and compared with those of P(O$\rm\sb2C\sb6R)X\sb3$ (X$\sb3$ = Ph$\sb3$, Ph$\sb2$Cl, Br$\sb3$ or Cl$\sb3$) prepared by the reaction of PX$\sb3$ and o-O$\rm\sb2C\sb6$R. The oxidation of elemental tellurium by three o-benzoquinones o-O$\rm\sb2C\sb6$R (R = Cl$\sb4$, Br$\sb4$ or Bu$\rm\sp{t}\sb2H\sb2$) is a direct route to the corresponding tellurium(IV) catecholates Te(O$\rm\sb2C\sb6R)\sb2$. The analogous reaction with organotellurium(II) TeR$\sp\prime\sb2$, (R$\sp\prime\sb2$ = Et$\sb2$, Me$\sb2$, Ph(Et) or Ph(Br)) gives the products Te(O$\rm\sb2C\sb6R)R\sp\prime\sb2$. The reactions proceed in each case by one-electron transfer, since the presence of the semiquinone radical O$\rm\sb2C\sb6$R in the reaction mixture has been demonstrated by ESR spectroscopy. The Te(O$\rm\sb2C\sb6R)\sb2$ species resist further oxidation, and also show weak donor and acceptor properties. The structure of the compounds Te(dbc)$\sb2$(bipy) 3.1 and Te(O$\rm\sb2C\sb6Cl\sb4)\sb2$(18-crown-6) 3.2 have been determined by X-ray crystallography. In both structures, the average Te-O distances (2.012 and 2.015 A respectively) are typical of tellurium(IV) compounds, and the average C-O distances (1.370 and 1.34 A respectively) confirm that the ligands are aromatic diolates. The oxidation of elemental antimony by the tetrahalogeno-o-benzoquinones o-O$\rm\sb2C\sb6$R (R = Cl$\sb4$, or Br$\sb4$) in diethyl ether gives the unusual antimony(v) products Sb(O$\rm\sb2C\sb6R)\sb{2.5} \cdot$ nEt$\sb2$O (R = Cl$\sb4$, n = 1.5; R = Br$\sb4$, n = 1). The same o-benzoquinones, and dbbq, upon treatment with Sb + 1/2X$\sb2$ (X = Br or I) in diethyl ether, give the antimony(III) derivatives Sb(O$\rm\sb2C\sb6$R)X (R = Cl$\sb4$, Br$\sb4$ or Bu$\rm\sp t\sb2H\sb2$). The oxidations are shown by ESR spectroscopy to proceed via the o-semiquinone intermediates. Adducts of Sb(O$\rm\sb2C\sb6$R)I with bidentate neutral donors have been prepared. The structure of Sb(dbc)I(bipy) 4.1 has been shown to be that of a pseudo-octahedral molecule with a stereochemically active lone pair of electrons. The reactions between diphenyl ditelluride and tetrahalogeno-o-benzoquinones o-O$\rm\sb2C\sb6X\sb4$ (X = Cl or Br) give ((X$\rm\sb4C\sb6O\sb2)TeC\sb6H\sb5\rbrack\sb2$O. The structure of ((Cl$\rm\sb4C\sb6O\sb2)TeC\sb6H\sb5\rbrack\sb2$O 5.1 has been established crystallographically. The reactions between Ph$\rm\sb2Te\sb2$ and other oxidants have also been studied. Preliminary results are also presented on the reaction between o-quinones with tin, and with tin dichloride, as well as the preparation of a novel Schiff-base biquinone lead(II) complex Ph(Cat-N-BQ)$\sb2$ (Cat-N-Bq = 3,5-di-Bu$\sp{\rm t}$-1,2-quinone 1-(2-hydroxy-3,5-di-Bu$\sp{\rm t}$phenyl) 7.1. The structure of 7.1 has been determined by X-ray crystallography. It shows significantly different features in comparison with the known structures of transition metal elements with the same ligand. (Abstract shortened by UMI.)Dept. of Chemistry and Biochemistry. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1993 .T533. Source: Dissertation Abstracts International, Volume: 55-05, Section: B, page: 1843. Adviser: D. G. Tuck. Thesis (Ph.D.)--University of Windsor (Canada), 1993.

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