Alkyl-heteroatom Bond Forming Reactions from the Late Transition Metals
Stevens, Tyler Eugene
MetadataShow full item record
C(sp3)-N bond formation is a potential high value reaction in transition metal catalysis, however, only a handful of examples of this fundamental coupling reaction step have been reported. Presented in this thesis are new efforts to promote this challenging reaction. Group 9 and 10 metals bound by the pincer ligands Pybox and PCP, respectively, were initially investigated. Evidence suggests the Ir-Et complex ([(dmPybox)Ir(Et)(OAc)][PF6] (12)) undergoes a β-H deprotonation, similar to an E2 type elimination in organic chemistry, rather than the desired SN2 nucleophilic attack. Use of strong nucleophiles, i.e. sulfur nucleophiles, resulted in the ring opening of the pybox ligand. Ir-Et complexes bound by the MeBPA ligand ([(MeBPA)Ir(OOCR)Et][PF6] (20 and 21)), however, did undergo the desired reaction to form C-N bonds upon reaction with neutral nitrogen nucleophiles. A computational investigation of the mechanism revealed that rather than the direct attack at the Ir-Et (generally observed for high valent Pd and Pt) the complex first undergoes β-hydrogen elimination to form an Ir ethylene complex. Nucleophilic attack by amine at the olefin then forms the C-N bond. In the final chapter the synthesis and characterization of new a new Rh-Me complex ((DPEphos)RhMe(I)2 (25)), which undergoes C(sp3)-I reductive elimination, is described. A kinetic investigation of the mechanism indicated two competing mechanisms involving SN2 attack by iodide at both cationic and neutral Rh-Me species. The demonstration of bond formation via nucleophilic attack at the Rh-Me allowed for the room temperature functionalization of the methyl ligand with both nitrogen and sulfur nucleophiles.
- Chemistry