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Abstract
The development of new catalytic processes for the selective activation and transformation of C-H bonds could have tremendous environmental and economic impact. This thesis describes the synthesis and reactivity studies of a variety of late transition metal complexes relevant to C-H bond activation and functionalization. New five-coordinate platinum(IV) complexes bearing the AnIm ligand (AnIm = [o-C6H4(N(C6H3 iPr2))(CH=NC6H 3iPr2)]-) and related ligands have been prepared and characterized. For (AnIm)Pt(CH 3)3 and the related (nacnac)Pt(CH3)3 (nacnac = [((o-iPr2 C6H3)NC(CH3))2CH] -), deuterium labeling studies show competitive C-H bond activation and β-hydride elimination reaction pathways. The known cationic iridium(III) phenyl hydride complex [(PNP)Ir(C6H5)H]PF6 (3) (PNP = 2,6-bis-(di-tert-butyl-phosphinomethyl)-pyridine) has been prepared, and shown to undergo stereoselective decarbonylation of methanol to form the iridium(III) trans-dihydride complex trans-[(PNP)Ir(CO)H2PF6. In experiments designed to model the first step of platinum(II) Shilov chemistry, the deprotonation of 3 to form the iridium(I) phenyl complex (PNP)Ir(C6H 5) (8) has been studied. However, in contrast to most platinum(II) complexes, the iridium(I) complex 8 is readily oxidized by methanol and water. In addition, new PNP rhodium(I) aryloxide and acetate complexes have been prepared and found to catalyze H-D exchange between arenes and water. Mechanistic studies of the H-D exchange reaction support a pathway involving dissociation of aryloxide or acetate ligand. The new pincer ligand PONOP (PONOP = [2,6-(OPtBu2)2C 6H4]) has been prepared, which is a neutral analogue of the POCOP ligand (POCOP = [1,3-(OPtBu2)2C6H4]) used in the iridium-catalyzed dehydrogenation of alkanes. Synthesis of PONOP iridium and rhodium complexes allows for a reactivity comparison with related PNP complexes. Finally, the reactivity of the palladium(II) dimethyl complex (bipy)PdMe2 (bipy = 2,2'-bipyridyl) with oxygen has been studied in a variety of different solvents. In benzene, the product of this reaction is a new palladium(II) methylperoxide complex. This is the first example of the direct insertion of oxygen into a palladium-carbon bond.
