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Title: Mixed valency in redox-active, all-carbon bridged bimetallic complexes of iron and molybdenum
Author: Tarhuni, Sarah
ISNI:       0000 0004 6495 1665
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2016
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This thesis describes the development of new procedures for the synthesis of homo- and hetero-bimetallic complexes [M-(C≡C-C≡C)-M*] linked by a butadiyndiyl (-C≡C-C≡C-) bridge (where M, M* = Mo(dppe)(η-C7H7) and Fe(dppe)Cp) and also of the diethynyl-anthracenyl bridged complex [{Mo(dppe)(-C7H7)}2(μ-C≡CC14H8C≡C)] in which an anthracenyl group is inserted into the butadiyndiyl bridge. The redox chemistry and mixed valence character of these systems are investigated by a range of synthetic, electrochemical and spectroscopic techniques. Chapter 1: (Introduction) presents a literature review related to all-carbon bridged bimetallics including their synthesis, redox chemistry and mixed valence properties. Chapter 2: describes the synthesis of the key precursor [FeI(dppe)Cp] in multi-gram quantities. A new synthetic protocol has been developed to vinylidene [Fe(C=CH2)(dppe)Cp][PF6] and acetylide [Fe(C≡CH)(dppe)Cp] complexes starting from the iodo precursor [FeI(dppe)Cp] which can be conveniently used in place of the chloro precursor [FeCl(dppe)Cp]. We also identified the carbene species [Fe{C(OMe)Me}(dppe)Cp][PF6], which is formed as a by-product from the reaction of the vinylidene with a molecule of methanol solvent. Chapter 3: describes the synthesis and characterisation of butadiyndiyl bridged [{Fe(dppe)Cp}2(-CCCC)]n+ (n = 0, 1, 2). The electronic structure of [{Fe(dppe)Cp}2(-CCCC)]n+ has been investigated in all thermally accessible oxidation states (0, 1, 2, 3) and compared directly with the closely related ruthenium analogue [{Ru(dppe)Cp}2(-CCCC)]n+. Particular focus was given to the formally 'mixed valent' radical cations [{Fe(dppe)Cp}2(-CCCC)]+ and [{Ru(dppe)Cp}2(-CCCC)]+, where the spectroscopic data highlight significant differences between the iron and ruthenium complexes. Furthermore, in this chapter the heterobimetallic complex [{Fe(dppe)Cp}(µ-C≡C-C≡C){Mo(dppe)(C7H7)}] was successfully synthesised and characterised by microanalysis, IR, mass spectrometry and cyclic voltammetry. Chapter 4: discusses the synthesis of the diethynyl-anthracene bridged complexes [{Mo(dppe)(-C7H7)}2(μ-C≡CC14H8C≡C)]n+ (n = 0, 1, 2). The focus of the investigation is to determine the effect of a diethynyl-benzene vs. diethynyl-anthracene bridge in bimetallics supported by the Mo(dppe)(C7H7) end cap. In the mixed valence (n = +1) state, the odd electron should be more localised on the ligand bridge of the anthracene derivative and this principle was investigated by EPR spectroscopy.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Molybdenum Carbon Chain Bimetallic Redox Chemistry