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A study of novel ferrocenyl-phosphorus compounds

The intent of this investigation was to use the distinctive characteristics of hydroxymethylphosphine chemistry in order to create new ferrocenyl-phosphorus compounds, as well as carry out investigations into both their electrochemistry and their potential for the production of ferrocene-containing polymers. The compound FcCH₂P(CH₂OH)₂ 1 (Fe = ferrocenyl) was prepared by the reaction of P(CH₂OH)₃ with [FcCH₂NMe₃]I, and FcCH₂PPh₂ 2 was prepared by a similar reaction. The compounds FcCH₂P(O)(CH₂OH)₂ 3, FcCH₂P(S)(CH₂OH)₂ 4, FcCH₂P(CH₂CH₂CN)₂ 5, FcCH₂P(CH₂NEt₂)₂ 6, FcCH₂P(O)(CH₂Net₂)₂ 7, [FcCH₂P(Me)(CH₂OH)₂]I 8, FcCH₂P(Me)CH₂OH 9, [(FcCH₂)₂P(CH₂OH)₂]Cl 10, (FcCH₂)₂PCH₂OH 11, FcCH₂P(H)PPh₂ 14 and FcCH₂P(O)PPh₂ 15 were prepared and characterised, and the compounds [FcCH₂P(Bz)(CH₂OH)₂]Br (Bz = benzyl) 12 and FcCH₂P(Bz)CH₂OH 13 were investigated though not fully characterised. The ferrocenylphosphine complexes cis- PtCl₂[FcCH₂P(CH₂OH)₂]₂ 16, PdCl₂[FcCH₂P(CH₂OH)₂]₂ 17, [Au{FcCH₂P(CH₂OH)₂}₂]Cl 18, RuCl₂(η⁶-C₁₀H₁₄)[FcCH₂P(CH₂OH)₂] 19 and RuCl₂ (η⁶-C₁₀H₁₄)(FcCH₂PPh₂) 20 were also prepared. X-ray crystal structure determinations were carried out for the compounds 1, 2, 4, 8, 18 and 20, and the solid-state hydrogen-bonding interactions present in the case of 1, 4, 8 and 18 were deduced. Hydrogen-bonding in the crystal structures of compounds Ph₂P(O)CH₂OH 21, Ph₂P(S)CH₂OH 22 and Ph₂P(Se)CH₂OH 23 was also investigated. Results were explained in terms of the positioning of hydrogen bonds in line with the direction of lone-pairs on the phosphine chalcogenide heteroatoms. The reaction of 1 with sodium metabisulfite in varying amounts was used to produce the compounds FcCH₂PH₂ 24, FcCH₂P(H)CH₂OH 25 and FcCH₂P(O)(OH)CH₂OH 26. The primary phosphine 24 was found to be remarkably air-stable, and was used to prepare the complexes Mo(CO)₅(FcCH₂PH₂) 27, Mo(CO)₄(FcCH₂PH₂)₂ 28, RuCl₂(η⁶-C₁₀H₁₄)(FcCH₂PH₂) 29, Ru₃(μ²-H)₂(CO)₉(μ³-PCH₂Fc) 30 and Ru₄(CO)₁₀(μ²-CO)(μ³-PCH₂Fc)₂ 31. Confirmation of the structures of 24, 27, 28 and 30 was obtained using X-ray crystallography. Cyclic voltammetric analysis of the electrochemical behaviour of 1, 2, 5, 24, 2S and FcCH(Me)P(CH₂OH)₂ 32 showed that these compounds exhibit a reversible one-electron oxidation followed by a chemical reaction, which leads to formation of a product which undergoes another reversible one-electron oxidation at higher potential. The rate-determining step for the reaction is intermolecular. BE (bulk electrolysis) of 1, 2 and 5 gave similar results in each case, with one-electron oxidation appearing to initially oxidise the ferrocene centre; in the case of 2 and 5 a green colour characteristic of ferrocenium species is seen during BE, but disappears with time. The conclusion was reached that this initial ferrocenium charge is transferred to another part of the molecule. Evidence from NMR and electrospray mass spectrometric analysis of BE products for 1 and 2 suggests the formation of unusual dimeric species is the end result of oxidation. The ferrocenylphosphine 11 shows simpler electrochemical behaviour consistent with previous literature. Compounds 3, 4, 8, 10, 14, 15, 16, 17, 18 and 30 showed very simple electrochemical behaviour consistent with one chemically and electrochemically reversible ferrocene redox couple. Cyclic voltammetry of the complexes 19, 20 and 29 showed both ferrocene and ruthenium redox processes. The electrochemistry of 7 was complex and not intensively investigated. Reaction of 1 with multi-functional secondary amines was used to produce a number of polymeric materials which were investigated using cyclic voltammetry of DMF solutions carbon paste electrodes and drop-coated electrodes. Attempts to covalently bind one of these, polymers to a glassy carbon electrode were unsuccessful. The most electrochemically stable form of electrode investigated was the carbon paste electrode, although the materials did not appear to show great promise for use in such applications, due to irreversible chemical changes in the polymers and quick decay of the ferrocene redox signal upon subjection to cyclic voltammetry.
Type of thesis
The University of Waikato
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