Metal-ligand cooperativity provides avenues for altering the electronic structure, reactivity, and spectroscopic properties of metal cations. In the context of separations chemistry, metal-ligand cooperativity may allow for differential reactivity and separation of otherwise similarly behaving metal cations, such as niobium (Nb) and tantalum (Ta). Niobium and tantalum are always found together in their naturally-occurring ores and require separation before use. Current industrial processes use hydrofluoric acid (HF) in the solvent extraction separation process, a hazardous and toxic reagent. Through tailored ligand design and characterization of novel, isostructural Nb/Ta coordination complexes, new methodologies for greener, fluoride-free Nb/Ta separations are expected. In Chapter 2, a set of [Na(CH3CN)3(Et2O)][MV(BINOLate)3] (M = Nb, Ta; BINOL = (S)-(−)-1,1′-bis-(2-naphthol)) aryloxide-complexes are described. Through selective reduction of the [NbV(BINOLate)3]- species, the first redox-based, molecular Nb/Ta separations strategy is reported. In Chapter 3, amidophenoxide-type Nb/Ta coordination complexes in two oxidation states, [Na(DME)3][(MVClamp)] and MVClamp (DME = dimethoxyethane; M = Nb, Ta; Clamp = tris-(2-(3′,5′-di-tert-butyl-2′-oxyphenyl)amidophenyl)amine), are described. Their characterization revealed differences in metal-ligand covalency and associated properties, such as redox and photo-excited-state lifetimes. In Chapter 4, two strategies for Nb/Ta pentachloride differentiation are described. An electrochemical separation strategy employs the mild reductant, ferrocene, to selectively reduce monomeric NbVCl5(CH3CN) in acetonitrile, representing an improvement on the separation described in Chapter 2. A photochemical separation strategy comprises selective excitation of the putative, dimeric species: NbV2Cl10 in toluene, allowing for subsequent selective precipitation of a photoreduced “NbIVCl4” product, representing the first reported light-driven Nb/Ta separation strategy. From the perspective of electronic structure studies, metal-ligand cooperativity also allows for significantly altered ground-state electronic properties of metal cations by mechanisms such as σ-donation from a ligand or π-backbonding to a metal cation. In the context of silver (Ag+), coordination of the metal center with alkynes allows for metal-ligand covalency and observable π-backbonding to the alkyne moiety. In Chapter 5, the synthesis of a novel tris-alkyne ligand, tris-(2-(trimethylsilyl)ethynyl-4-tert-butyl-benzyl)amine, and associated Ag+ chelating tris-alkyne complex, [Ag-tris-(2-(trimethylsilyl)ethynyl-4-tert-butyl-benzyl)amine][PF6], are presented, and the ground state electronic properties and luminescent properties of the complex are described.