Direct Access to Chemistry and Catalytic Behavior of the Zero-Valent MoL4 Fragment

This dissertation describes investigations in the reactivity of mixed carbonyl-isocyanide complexes of molybdenum. A primary challenge in isolating functional surrogates of low-coordinate, zero-valent Group 6 carbonyls, e.g. M(CO)2, M(CO)3, M(CO)4 has been the tendency of these compounds form intramolecular h6-arene interactions with the flanking rings of supporting ligands. In this work, a screening of catalysts for hydrostannation provided insight into stabilization of four-coordinate, zero-valent metal centers. Accordingly, reduction of MoI2(CO)2(CNArDipp2)2 with two equivalents of HSnBu3 in the presence of weakly coordinating Lewis bases (e.g. diisopropyl amine [HNiPr2], Et2O) provided access to masked sources of ML4. The unprecedented reactivity and β-(E)-regioselectivity of MoI2(CO)2(CNArDipp2)2 in hydrostannation of alkynes is discussed in Chapter 2. Chapter 3 describes the use of MoI2(CO)2(CNArDipp2)2 and the CH-agostic complex, Mo(κ2-N,CH)-HNiPr2)(CO)2(CNArDipp2)2 in the activation of elemental phosphorus (P4). The tetravalent product, (h4-P4)MoI2(CO) (CNArDipp2)2 was found to undergo photolytic reductive elimination of white phosphorus. In Chapter 4, the synthesis of two dianionic cyclo-P4 complexes is discussed. Investigations with these compounds revealed cyclo-P4 ligand to be isolobal to benzene in Fischer's classic half-sandwich complex Mo(CO)3(h6-C6H6). Chapter 5 further explores the redox chemistry of cyclo-P4 complexes by cyclic voltammetry. Chapter 6 describes the functionalization of cyclo-P4, including the stoichiometric release of [P-I] by treatment of (h4-P4)Mo(CO)2(CNArDipp2)2 upon treatment with 1 equiv I2