Progress toward a catalytic alkenation using transition metal alkylidene and oxo complexes

We are seeking to develop a new methodology for the synthesis of alkenes. Our desire is to develop an efficient, versatile and highly atom efficient process that offers an environmentally sound and cost effective alternative for the synthetic and industrial chemist to consider over current, well established methodologies. We have conceived a transition metal mediated hypothetical catalytic cycle, the basis of which is a series of ligand interconversions effected by cycloaddition chemistry. This thesis represents a feasibility study into our hypothetical catalytic cycle. Chapter 1 introduces the established methodologies, our hypothetical catalytic cycle and gives a review of the most relevant chemistry. Chapter 2 details our results. Particular attention is paid to relevant concepts in catalysis and transition metal chemistry. Chapter 2.1 reports our experiences in synthesising ketenes. An efficient synthesis of diphenylketene 13C2 is described. Our hypothetical catalytic cycle requires a chemoselective reaction and Chapter 2.2 describes our preliminary work investigating the feasibility of this. Chapter 2.3 describes the synthesis of [PPN][Cp*MO3] (M=Mo, W) and Chapter 2.4 describes the reactivity of these complexes with ketenes and provides a unique experimental insight into the stepwise cycloaddition mechanism of diphenylketene with [PPN][Cp*WO3). Chapter 2.5 describes the reactivity of mono oxo complexes with ketenes and Chapter 2.6 describes the synthesis and reactivity of stereoelectronically activated dioxo complexes. A formal account of all experimental procedures is presented. (author)