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Creating new chemical reactions remains one of the key objectives of modern synthetic chemistry. In particular, transition-metal catalysis has been instrumental in enabling challenging transformations. Although late transition metals allow for elegant and highly efficient transformations, they are often precious, expensive and toxic while group IV earth abundant transition metals offer a more sustainable alternative. In this context, zirconium (IV) complexes represent excellent candidates, distinguished by their unique reactivity, enabling both functionalization and cleavage reactions.The aim of this thesis is to develop new catalytic methodologies based on zirconocene dichloride complexes with a particular focus on identifying a mild activation method for the in situ generation of the active zirconium dihydride species. Two projects were conducted in this context.The first one focused on the development of a new zirconium catalyzed hydrosilylation reaction of terminal and internal alkenes. This method employs a commercially available zirconium precatalyst together with LiOMe and silanes as mild catalyst activators, offering an interesting and practical alternative to late transition-metal based methods, which generally require complex ligand synthesis or strong organometallic activators. By exploiting the “chain-walking” ability of zirconocene hydride complexes, even internal alkenes could be efficiently converted into the corresponding terminal hydrosilylated product. Mechanistic investigations support a pathway involving a zirconium(IV) species (Appendix: Manuscript). The second one, which is still ongoing, focuses on the development of a new C-C bond cleavage reaction of alkenylcyclopropanes. The substrate scope has been explored using LiAlH4 as activator for the zirconocene precatalyst; however preliminary results demonstrate that a combination of LiOMe and hexylsilane enables both cyclopropane opening and hydrosilylation of the product. While the opening of alkylidenecyclopropanes and cyclopropylamides followed by hydroboration has already been reported using various transition metals, this transformation is much less explored. Several tested substrates demonstrate that the opening of cyclopropane located in remote position to the double bond anchor point is feasible. Reports of such remote cyclopropane opening are scarce.Notably in both projects LiOMe and silane emerged as unifying strategy for accessing the catalytically active zirconium species under mild and operationally simpleconditions.

Our current day quality of life would be impossible without organic chemical materials. One important group of materials are organosilanes, which are used in electronics, construction, and medical products of example. Synthetic methods to make these materials efficiently are thus of great importance. Yet,the current industrial methods, based on precious late-transition metals, arecostly in both economic and environmental terms. The use of earth abundant metals for the synthesis of organosilanes has gained popularity in recent years, but most methods require complex ligand synthesis and difficult handling.Bench-stable zirconocene dichloride can catalyse the hydrosilylation of both terminal and internal alkenes using LiOMe as a mild activation agent. In this licentiate thesis the scope and mechanism of this reaction is explored.

Another class of widely used materials are fluorinated chemicals and per- andpolyfluoroalkyl substances (PFAS). These compounds exhibited remarkable thermal stability, hydrophobicity and chemical resistance. However, these properties make them extremely resistant to degradation. There is a dire need for efficient and safe disposal and degradation methods for these compounds. Current methods have many drawbacks, like the formation of green house gases. In this licentiate thesis, the development, scope and mechanism of a perdefluorinative-monoborylation is explored. Via the iterative removal offluorine, alkene-bound longer perfluoroalkyl chains and gem-difluorocompounds are converted into linear pinacolboronates. Fluoride can be recovered in the form of lithium fluoride salt.

Catalysis based on earth-abundant early transition metals has emerged as a sustainable alternative to traditional late transition-metal catalysis. In this context, zirconium(IV) complexes stand out for their unique reactivity, enabling both functionalization and cleavage reactions. 

This thesis describes the development of two zirconocene-catalyzed methodologies together with the identification of a practical strategy for the in situ generation of the active zirconium hydride catalyst.

The first project focuses on the development of a new zirconium-catalyzed C-C bond cleavage reaction of unactivated alkenylcyclopropanes. Depending on the hydride source and conditions, the reaction yields either the corresponding open-chain product or its hydrosilylated derivative. By exploiting the “chain-walking” ability of zirconocene hydride complexes, cyclopropanes distant up to eight carbons from the alkene unit could be successfully converted into the corresponding products. 

The second project involves the development of a new zirconium catalyzed hydrosilylation reaction of terminal and internal alkenes. This method employs the commercially available precatalyst Cp₂ZrCl₂ together with LiOMe and silanes as mild catalyst activators, providing a practical alternative to existing late transition-metal based methods. Mechanistic investigations support a pathway involving a zirconium(IV) species. 

Interestingly, in both projects LiOMe and silane emerged as unifying activation strategy for accessing the catalytically active zirconocene hydride species, enabling both bond-forming and bond-cleavage transformations under operationally simple conditions.