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Title: Physico-chemical studies on organo-transition metal complexes
Author: Lindsell, W. E.
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 1968
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After a short preface, in which the object of the work reported in this dissertation is explained, the chemistry of bis-π-cyclopentadienyl compounds of transition metals, other than pure metallocenes, is briefly reviewed. The preparations of the new pseudo-halide complexes, (π-C5-H5)2H(N3)2, (M = Mo, W), (π-C5H5)2W(OR)CN, (R = C2H5, CH3), [(π-C5H5)2W(OC2H5)(CN)H]PF6, (π-C5H5)2M(NCS)2, (M = Mo, W), a complex of proposed formula, (π-C5H5)2W(NCS)(SCN) and (π-C5H5)2W(NCS)Cl are reported and these have been characterised by analysis and various physical measurements. Other reactions and attempts to form related complexes are also discussed. The cyano-complex (π-C5-H5)2W(OC2H5)CN is hygroscopic and this has been shown by the use of infra-red spectroscopy and deuterium oxide. The bonding of the thiocyanato complexes is discussed in the light of infra-red spectra, ultra-violet spectra and other data and the evidence suggests that all the complexes except one, (π-C5H5)2W(NCS)(SCN), contain only N-bonded thiocyanate groups. The products of oxidation by nitric of all complexes have been investigated and a paramagnetic salt, [(π-C5H5)2W(NCS)Cl]PF6, has been characterised. Other paramagnetic products were either, not stable enough or, obtained pure enough for complete characterisation but their nature is discussed. The reaction of (π-C5-H5)2MCl2, (M = Mo, W), with cyanates gave hygroscopic products having the formula, (π-C5H5)2M(OCONH2)2, formed by hydrolysis of cyanate. However a hygroscopic cyanato complex, (π-C5H5)2W(OCN)2. ~1H20 is also reported. The novel pentafluorophenyl hydrido complexes, (π-C5H5)(π-C5H4C6F5)MH(C6F5), (M = Mo, W), are described. Both complexes have been characterised by analysis, proton magnetic resonance spectra, mass spectra, molecular weight measurements and infra-red spectra. The fluorine magnetic resonance spectra of the molybdenum complex is also reported. The results indicate the presence of a sterically hindered pentafluorophenyl group, attached to the metal, which has non equivalent orthofluorine atoms and one of these fluorine atoms interacts with the metal hydrogen causing a splitting of the metal hydride nuclear resonance signal. Both complexes react with carbon tetrachloride to give the complexes (π-C5H5)(π-C5-H4C6F5)MCl(C6F5) and these complexes oxidise to give cations that can be isolated as the salts, [(π-C5H5)(π-C5H4C6F5)MCl(C6F5)]PF6. These salts in solution, at room temperature, have well resolved electron spin resonance spectra showing ligand and metal hyperfine splitting. A related bromo-complex [(π-C5H5)(π-C5H4C6F5)WBr(C6F5)]PF6 is mentioned and its electron spin resonance spectrum reported. The reaction of (π-C5H5)2MCl2, (M = Mo, W), with LiC6H5 gave unstable products that are discussed in the light of analytical, mass spectral, proton magnetic resonance and infra-red spectral results. The new complexes (π-C5H5)2M(NHC6H4Y), (M = Mo, W, Y = S; M = Mo, Y = 0), (π-C5H5)2W(O2C14H8), (π-C5H5)2Mo(O2C5H7)Cl.H2O, [(π-C5H5)2Mo(O2C5H7)]BF4, and (π-C5H5)2M(OCOR)2, (M = Mo, W; R = CF3, C6H5), have been prepared and characterised by analysis and physical techniques. Chemical reactions of some of these complexes are discussed and, in particular, the reactions of iodine and nitric acid. The reaction of alkyl halides with sulphur ligand complexes of and molybdenum are reported. The complexes (π-C5H5)2W(SCH2)2RX, (R = CH2C6H5, X = Cl, PF6; R = CH2CHCH2, X = Br, PF6; and R = CH3, X = I, PF6), and a related complex (π-C5H5)2W(SCH2)2HgCl2 have been prepared. The complex (π-C5H5)2Mo(SC6H5)2 was shown to give (π-C5H5)2MoI2 by reaction with CH3I but, in a similar reaction, (π-C5H5)2Mo(SCH3)2 gave the new complex, [(π-C5H5)5Mo(S(CH3)2)I]I. The related salt, [(π-C5H5)2MoS(CH3)2Br]PF6, reacted with LiCl to give (π-C5H5)2MoClBr and this, on oxidation gave the salt [(π-C5H5)2MoClBr]PF6 as the major product. Oxidation of (π-C5H5)2W(S2C6H3CH3) by nitric acid gave the paramagnetic complex [(π-C5H5)2W(S2C6H3CH3)]PF6, which was characterised, and related oxidation products of (π-C5H5)2Mo(S2C6H3CH3) and (π-C5H5)2W(SCH2)2 are discussed. Electron spin resonance spectra, in solution, of the isolable paramagnetic compounds mentioned above, mixed halide complexes formed by exchange in strong acids and unstable species formed by electrolytic oxidation are reported. The trends in the isotropic and a parameters are discussed in a general manner. Frozen solution spectra of some complexes are also recorded.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available