The versatile chemistry of arene manganese carbonyl complexes

This research has focused on the complexation of the manganese tricarbonyl moiety to arenes thus rendering the arene ring susceptible to nucleophilic attack. For example, biphenylene is a thermally stable molecule, which upon complexation to manganese was found to undergo facile nucleophilic addition reactions with hydride, phosphorous and carbon donors at a bridgehead carbon to afford cyclohexadienyl complexes. Polyarenes and the class of molecules known as the centropolyindans have also been complexed and functionalized via nucleophilic addition and reductive activation pathways.;It was further discovered that chemical reduction of polyarene complexes led to the formation of novel syn-facial bimetallic complexes coordinated to naphthalene type ligands. Bimetallic complexes are of interest because of their useful physical and chemical properties related to metal-metal interactions and electron delocalization. Extension of this work resulted in the formation of a syn-facial hetero-bimetallic.;Lastly, this thesis is concerned with organometallic complexes containing thiophenic substrates. It was discovered that chemical reduction of the benzothiophene (BT) manganese tricarbonyl ion led to the first ever cleavage of a carbon(aryl)-sulfur bond, where a negatively charged manganese tetracarbonyl unit had inserted into the thiophene ring. This reaction is a model for the largest volume chemical reaction in the world--hydrodesulfurization (HDS).;Benzothiophenes occurring in petroleum are generally highly substituted and extremely resistant to HDS. In order to probe these important "substituent" effects on carbon-sulfur bond cleavage, the reduction chemistry of complexes substituted in the 7 position of benzothiophene was investigated. Methyl and ethyl substituents caused the C(aryl)-S bond cleaved product to isomerize to the corresponding vinyl insertion product, followed by spontaneous metallathiacycle ring contraction to form a five-membered metallathiacycle--both reactions are unprecedented and possibly highly relevant to HDS. Hydrogenation of the metallathiacycles led to manganese-carbon bond hydrogenolysis and ultimate desulfurization. Similar chemistry was found to occur with thiophene. Finally, precoordination of the carbocyclic ring in BT, activated the C-S bonds towards insertion by platinum nucleophiles.