Organic protecting ligands impart stability to metal-oxide nanocrystals (NCs) but block access to reactive NC surfaces in catalysis and prevent electronic coupling or the emergence of optoelectronic properties. in response, we use inorganic polyoxometalate (POM) ligands that coordinatively bind metal-oxide cores. The POMs bind directly to a limited fraction of atoms of the NC cores, leaving their reactive surfaces exposed. The negative charges of POMs and their alkali-metal, or alternatively,organic counter-cations, render POM-complexed NCs soluble and stable in water or organic solvents.