The preparation and reactivity of late transition-metal complexes in low oxidation states with nondative-heteroatomic ligands (e.g., amido, hydroxo, alkoxo, and aryloxo ligands) are described. For such complexes the disruption of ligandto-metal π-donation because of a filled dπ manifold can enhance the nucleophilic and/or basic reactivity at the nondative-heteroatomic ligand relative to transition-metal complexes in high oxidation states. The chemistry of five-and six-coordinate Ru complexes with amido, hydroxo, methoxo, and aryloxo ligands is described including Brønsted acid/ base reactions, coordination, and activation of polar sub-