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Title: Reactivity of a ruthenium bis(dinitrogen) complex
Author: Lau, Samantha
ISNI:       0000 0004 9356 682X
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2018
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This thesis investigated the reactivity of the ruthenium bis(dinitrogen) complex [Ru(H)2(N2)2(PCy3)2] (1), an analogue of the ruthenium bis(dihydrogen) complex [Ru(H)2(η2-H2)2(PCy3)2]. It was demonstrated that 1 was able to effect the sp2C–X (X= H, O) bond cleavage of acetophenone substrates to generate 5 membered organometallic intermediates. The by-products from the C–O cleavage reactions were identified as alcohols which also react with 1 at a faster or equal rate to the substrates. The mechanism of these C–X cleavage reactions were probed experimentally and computationally to show that the C–H bond cleavage pathway was operating through a σ-complex assisted metathesis pathway whereas the C–O cleavage pathway was operating through a Ru(II)/Ru(IV) redox mechanism. In addition, the reactivity of 1 with main group hydrides (aluminium, zinc and magnesium) was presented with the formation of a series of new ruthenium main group heterobimetallic hydride complexes, M•Ru (M = Al, Zn, Mg). These heterobimetallic hydride complexes contain either dinitrogen or dihydrogen ligated at the ruthenium centre depending on the partial pressure of N2 and H2 in the atmosphere. It was shown that the main group fragment can subtly tune the degree of dinitrogen activation in these M•Ru N¬2¬ complexes, Mg > Zn > Al. This trend was rationalised by probing the bonding and frontier molecular orbitals of these complexes. Furthermore, 27Al solid state NMR spectroscopy was implemented to analyse the ruthenium aluminium heterobimetallic hydride complexes and it was determined that that there was no linear correlation between the isotropic chemical shift obtained in the 27Al solid state NMR spectra and the oxidation state of the complex.
Supervisor: Crimmin, Mark Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral