We use cookies to ensure that we give you the best experience on our website. By continuing to browse this repository, you give consent for essential cookies to be used. You can read more about our Privacy and Cookie Policy.

Durham e-Theses
You are in:

Transition metal imido complexes: synthesis and applications to polymerisation catalysis

Coles, Martyn Paul (1995) Transition metal imido complexes: synthesis and applications to polymerisation catalysis. Doctoral thesis, Durham University.



This thesis describes studies into Group 5 and Group 6 transition metal imido complexes, with particular emphasis on the development of complexes which can be applied to catalytic processes. Chapter 1 highlights the electronic and structural aspects of the imido and alkylidene ligands. The isolobal analogy between Group 4 bent metallocene. Group 5 half-sandwich imido and Group 6 bis(imido) metal fragments is outlined. In addition, Ziegler-Natta type a-olefin polymerisation and Ring Opening Metathesis Polymerisation (ROMP) are briefly reviewed. Chapter 2 describes initial screening of half-sandwich vanadium imido and chromium bis((^t)butylimido) dichloride complexes as catalyst precursors. Synthesis of the chromium bis(imido) dialkyl complex Cr(N(^t)Bu)(_2)(CH(_2)Ph)(_2) (1) is described, its conversion to a cationic alkyl species is probed and the polymerisation activity associated with the resultant compound is addressed. Finally this chapter details the synthesis and characterisation of a range of bis(adamantylimido) chromium complexes. Chapter 3 presents a synthetic entry point into the bis(arylimido) chemistry of chromium. The complex Cr(NAr)(_2)(NH(^t)Bu)Cl (12) is described (Ar = 2,6-(^i)Pr(_2)C(_6)H(_3)) and its conversion to the dichloride complex Cr(NAr)(_2)Cl(_2) (14) is examined. 14 forms the stable monoadduct with pyridine, the X-ray crystallographic study of which reveals a distorted square based pyramidal geometry about the chromium atom. The inclusion of the arylimido ligand at the metal centre allows stabilisation of the chromium bis- phosphine complexes Cr(NAr)(_2)(PMe(_3))(_2) (18) and Cr(NAr)(_2)(PMe(_2)Ph)(_2) (19). The reactivity of 18 towards unsaturated hydrocarbon substrates is briefly investigated. Chapter 4 focuses on the organometallic chemistry of the [Cr(NAr)(_2)] moiety. A range of dialkyl derivatives are isolated and the molecular structures of a selection are solved. The generation of the nascent species [Cr(NAr)(_2)(=CHCMe(_3))] is investigated and the conversion of Cr(NAr)(_2)(CH(_2)CMe(_3))(_2) (24) to Cr(NAr)(-2)(CHDCMe(_3))(C(_6)D(_5)) (25) is the subject of a kinetic study. In chapter 5, the ROMP of a series of amino acid derived norbomene monomers is studied. The resultant polymers are fully characterised and a brief molecular modelling study is carried out on representative polymers chain lengths. Chapter 6 contains experimental details to chapters 2-5.

Item Type:Thesis (Doctoral)
Award:Doctor of Philosophy
Thesis Date:1995
Copyright:Copyright of this thesis is held by the author
Deposited On:09 Oct 2012 11:51

Social bookmarking: del.icio.usConnoteaBibSonomyCiteULikeFacebookTwitter