Chapter One introduces two classes of late-transition metal ethylene polymerization catalysts. The first class are Pd(II)-alkyl complexes supported by phosphine-arenesulfonate (PO) ligands. (PO)PdRL catalysts are unique in their ability to copolymerize ethylene and a wide variety of polar vinyl monomers to highly linear functionalized polyethylene. The ability to produce new types of functionalized polymers with enhanced properties motivates the development of new PO-type Pd catalysts and new strategies for enhancing the catalytic performance of these catalysts. The second class are the pyridine-diimine (PDI) Co and Fe catalysts which produce highly linear polyethylene with high activity. (PDI)Co and (PDI)Fe complexes have also been shown to versatile catalysts for a wide variety of organic transformations such as CO2/ethylene coupling, hydroboration, hydrosilylation, and [2+2] cycloaddition. Chapter Two describes the ethylene polymerization behavior of new PO-type zwitterionic electronically-unsymmetrical Pd(II)-Me complexes supported by phosphino-perchloro-closo-decaborane ligands (PR2CB9Cl9). The κ2-P,Cl-(PR2CB9Cl9)PdMe(THF) (R = iPr, Ph) complexes and the κ2-P,O-(P(o-OMe-Ph)2CB9Cl9)PdMe(THF) complex were synthesized and characterized in solution and solid state. Reaction of κ2-P,O-(P(o-OMe-Ph)2CB9Cl9)PdMe(THF) with excess ethylene in situ generates the κ2-P,O-(P(o-OMe-Ph)2CB9Cl9)PdMe(ethylene) adduct. Ethylene insertion kinetics of the κ2-P,O-(P(o-OMe-Ph)2CB9Cl9)PdMe(ethylene) are described in addition to bulk polymerization studies for all three complexes. Chapter Three describes the the template-free synthesis a bis-(pyridine-dieanamine) proligand, which was metalated to synthesize a variety of bis-(pyridine-diimine) (bis-PDI) and bis-(pyridine-dienamido) (bis-PDE) metal complexes, in the hopes of synthesizing dinuclear bis-PDI complexes to exploit metal-metal cooperativity effects to engender new reactivity. Three five-coordinate dinuclear (bis-PDI)M2Cl4 (M = Zn, Co, Fe) complexes were synthesized and characterized in solution and the solid state for M = Zn and Co. A four-coordinate square-planar dinculear [(bis-PDI)Pd2Br2][BArF4]2 was synthesized in solution and the solid state. The bis-(pyridine-dienamine) form of the proligand allowed for the facile synthesis of a (bis-PDE)Zr2(NMe2)4 complex, which was subsequently alkylated to synthesize (bis-PDE)Zr2Me4 and (bis-PDE)Zr2(CH2SiMe3)2(NMe2)2 complexes, the latter of which was characterized in the solid state.