Doctor of Philosophy
Prof. Paul J. Ragogna
Synthetic metallopolymers have acquired ample attention recently due to their potential applications as precursors to functional soft materials. Organometallic polymers combine the best of both organic and inorganic polymers. Polyferrocenes comprise the major portion of organometallic polymers. Therefore, quest for new monomeric precursors to organometallic polymers has expediated. One efficient method for obtaining main-chain metallopolymers is by the ring opening polymerization (ROP) of strained cyclic metallacylophanes(MCPs). Organometallic polymers containing cyclopentadienyl-cobalt-cyclobutadiene (CpCoCb) have been targeted since early 1990’s due to their isoelectronic nature (cf. ferrocene) with three major groups working in this area. The early CpCoCb containing polymers were prepared by alkyne dimerization of a bis-alkyne at the Co(I) centre, which did not provide good control over the molecular weights of the polymers generated.
In search of novel Co(I) monomers for ROP, synthesis of sila- and germa- cobaltoarenophanes was undertaken via. unprecedented direct dilthiation of (CpCoCb*) (Cb* = tetramethylcyclobutadiene) and subsequent treatment with the main group dihalides. However, attempts to ring open the CH2-SiMe2 bridged cobaltoarenophanes were unsuccessful, which was attributed to the lower degree of strain in these molecules. An alternative route to cobaltoarenophanes was proposed taking advantage of alkyne dimerization at a substituted CpCo(I) complex featuring a coordinated pendent alkyne. In this regard, alkyne-appended cyclopentadienyl ligands were developed and their utility was explored in reaction with early and late transition metals such as Ti, Fe, Co and Ni. This resulted in the formation of bis-alkynyl metallocenes of Ti and Co and half sandwich Ni complexes featuring a pendent alkyne.
Synthesis of side chain cobalt(I) polymers demonstrating the CpCoCb framework has also been explored, using pre-functionalized Cp ligands incorporating a polymerizable vinyl moiety.
Chadha, Preeti, "Exploring the Chemistry of Cyclopentadienyl-Cobalt-Cyclobutadiene (CpCoCb) Complexes and Synthesis of Side-Chain CpCoCb Polymers" (2011). Electronic Thesis and Dissertation Repository. 186.