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From molecular to macromolecular and back : investigation of hexacoordinated phosphorus(v) anions and poly(methylenephosphine)s

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Title: From molecular to macromolecular and back : investigation of hexacoordinated phosphorus(v) anions and poly(methylenephosphine)s
Author: Siu, Paul Wai-Man
Degree Doctor of Philosophy - PhD
Program Chemistry
Copyright Date: 2012
Publicly Available in cIRcle 2013-07-31
Abstract: Alkali metal salts of tris(benzenediolato)phosphate [1]–, K[1] and Na[1], were prepared and examined as halide abstraction reagents. Compound K[1] reacts with (dppp)PdCl₂ [dppp = 1,3-bis(diphenylphosphino)propane] (1:1 ratio) or [(cod)RhCl]₂ (2:1 ratio) to afford [(dppp)Pd(μ-Cl)]₂[1]₂ and (cod)Rh[1], respectively. Brønsted acids H(DMSO)₂[1] and H(DMF)₂[1] were isolated as crystalline solids. The basicity of [1]– was examined using IR spectroscopy and determined to be comparable to [BF4]–. Brønsted acid H(DMF)₂[1] is effective in the protonolysis of late transition metal-alkyl bonds. Its stoichiometric reaction with (dppe)PdMe₂ [dppe = 1,2-bis(diphenylphosphino)ethane] affords either [(dppe)Pd(NCMe)Me][1] (1:1 ratio) or [(dppe)Pd(NCMe)₂][1]₂ (1:2 ratio). Brønsted acid H(DMF)₂[1] initiates the cationic polymerization of n-butyl vinyl ether at 17 °C to afford moderate molecular weight poly(n-butyl vinyl ether) (Mn = 10,000 g mol-¹, PDI = 2.80). Brønsted acids of tris(tetrachlorobenzenediolato)phosphate [2]–, H(OEt₂)₂[2] and H(OEt₂)(NCMe)[2], were isolated as crystalline solids. Brønsted acid H(OEt₂)₂[2] was shown to be an effective initiator for the cationic polymerizations of n-butyl vinyl ether, styrene and isoprene. High molecular weight poly(n-butyl vinyl ether) was isolated from polymerization at –78 °C (Mn = 122,000 g mol-¹, PDI = 1.19). Atactic polystyrene of moderate molecular weight was isolated from polymerization at –50 °C (Mn = 55,400 g mol-¹, PDI = 1.62). Moderate molecular weight trans-polyisoprene was isolated from polymerization at –38 °C (Mn = 77,000 g mol-¹, PDI = 1.34). Poly(methylenephosphine) and poly(methylenephosphine) oxide were coated onto paper sheets made from thermomechanical pulp. TAPPI (Technical Association of Pulp and Paper Industry) Standard Method T461 cm-00 was used to evaluate the flame retardant properties of the polymers. Paper samples coated with the phosphorus-based polymers exhibited a higher degree of charring when compared to untreated paper and were comparable to paper treated with the monobasic ammonium phosphate standard. The microstructure of the 1-(2,2,6,6-tetramethylpiperidinyloxy)-1-phenylethane initiated poly(methylenephosphine) was examined by NMR spectroscopy. Evidence suggests the occurrence of 1,5-hydrogen abstraction rearrangement during the propagation step of polymerization. The unexpected microstructure was modeled using PhCH₂P(Mes)CHPh₂.
URI: http://hdl.handle.net/2429/42895
Scholarly Level: Graduate

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