Electrochemical and structural studies of organometallic acetylide complexes

Abstract

This thesis describes the synthesis and properties of systems of the general type ML(_x)-bridge- ML(_x), and related 'mixed-valence' derivatives. The efficacy of the l.l'-ferrocenediyl unit (Fc') as a bridge between two redox-active metal centres, is investigated by examination of the properties of a series of complexes, 1,1'-(_2)Fc’, and the related binuclear model systems Ru(C=CFc)(PP)Cp'. Whilst interactions through an ethyndiyl bridge occur between one Ru(PP)Cp' moiety and a ferrocenyl centre, in the l,l'-(_2)Fc' systems no interaction between the terminal Ru(PP)Cp' groups is observed. A comparative study of the redox and spectroscopic properties of the family of complexes [(_2)(u-C≡CXC≡C)](^n+) [ = Ru(PPh(_3))(_2) Cp, Ru(dppe)Cp*; X = 1,4- C(_6)H(_4), l,4-C(_10)H(_6), 9,10-C(_14)H(_8); n = 0, 1, 2] is presented, together with those of the related mononuclear compounds. Comparison of the results with DFT calculations of the electronic structure allows the properties of the diethynylaryl-bridged, bimetallic complexes to be rationalised in terms of a significant contribution of the diethynylaryl bridging ligand to the SOMO. The electronic properties of the 1,12-diethynyl carborane-bridged species 1,12- (_2)(u-C≡C-CB(_10)H(_10)C-C≡C), and the related mononuclear complex Ru(C≡C-CB(_10)H(_10)H)(dppe)Cp*, are assessed by a combination of electrochemical and spectroscopic techniques. The results allow a comparison of the 'three-dimensional' aromatic spacer l,12-C(_2)BH(_10) with the phenylene analogue. Explorations of the acetylide chemistry of the Fe(dppe)’_n’ fragment are described. The resulting air stable complexes provide a convenient entry point to the acetylide chemistry of the octahedral iron fragment. The details of additional crystal structures obtained by single crystal X-ray diffraction methods, together with a brief description of the chemistry associated with them, are presented in the appendix.