Date of Award

12-17-2015

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Chemistry and Biochemistry

First Advisor

Rawson, Jeremy

Keywords

bis-triamide, cationic ring-opening polymerization of THF, diazaphosphole, dithiaphosphole, dithiazolyl, phosphenium

Rights

CC BY-NC-ND 4.0

Abstract

This thesis commences with an introduction to the chemistry and materials properties of dithiazolyl radicals and a review of previous research on the isolobal heterocyclic phosphorus-containing derivatives, particularly dithiaphospholes and diazaphospholes. P-chloro-1,3,2-benzo-dithiaphospholes were prepared from the condensation of PCl3 and 1,2-benzodithiols in good yield. Reduction afforded 2c,2e- P-P s-bonded dimers containing a formal PII oxidation state which were characterised by X-ray diffraction. Re-oxidation generates the crystallographically characterised Phalogeno- 1,3,2-benzo-dithiaphospholes. The synthesis and structural characterisation of the isolobal P-chloro-1,3,2-benzodiazaphospholes, C6H4(NR)2PCl (R = H, Me, Et, COMe, COOMe) is described. The outcome of attempted reductive coupling was found to be sensitive to reaction conditions, affording the PII dimer alongside other decomposition products characterised by Xray diffraction. Functionalisation of the P-chloro group by salt metathesis and/or condensation was used to prepare a series of poly-cyclic structures containing two or more diazaphosphole, dithiaphosphole and dithia-arsole rings linked via bridging units which were characterised by X-ray diffraction. The paddle-wheel molecules N(C7H6S2Pn)3 (Pn = P, As) were prepared by a stepwise condensation of Li[N(SiMe3)2] with P-chloro-dithiaphosphole and As-chloro-dithia-arsole whereas the bis-triamide C6H4(NR[C6H4(NR)2P])2 was prepared from condensation of the P-chloro-diazaphosphole with ortho-C6H4(NHR)2. Treatment of P-chloro-dithiaphospholes or P-chlorochloro-benzodiazaphospholes with MCl3 (M = Al, Ga) generated a series of two-coordinate phosphenium cations whose structures were determined by X-ray crystallography. This methodology was extended to prepare the heavier dithia-arsenium and dithia-stibenium cations and the structure of the first benzodithia-arsenium cation is reported. These cations are Lewis acidic and form a series of 1:1 complexes with Ph3E (E= P, As, Sb) which are characterised by multinuclear NMR. The dithiaphosphenium cation (as its GaCl4 - salt) also forms adducts with dioxane and propylene oxide but is an efficient catalyst for the cationic ring opening polymerisation (CROP) of THF to form poly(THF), [O(CH2)4]n. The conversion rate and yield is sensitive to reaction conditions. Notably the corresponding AlCl4 - salt did not polymerise THF due to reformation of the P-chloro-dithiaphosphole and formation of the adduct, AlCl3·2THF. The related arsenium and stibenium cations show limited activity as reagents for the CROP of THF.

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