Nucleation Kinetics and Molecular Mechanism in Transition-Metal Nanoparticle Formation: The Intriguing, Informative Case of a Bimetallic Precursor, {[(1,5-COD)IrI·HPO4]2}2–

Following a summary of the relevant literature on nucleation and applicable nucleation and growth models and mechanisms, the kinetics and molecular mechanism of nucleation are investigated in detail starting from [(1,5-COD)IrI(NCCH3)2][BF4], 1, which upon addition of HPO42– to 1 forms a neutral, phosphate-bridged species, {[(1,5-COD)IrI(NCCH3)]2·HPO4}0, 2, en route to {[(1,5-COD)IrI·HPO4]2[Bu4N]2}, 3. Post a list of the seven advantages of the {[(1,5-COD)IrI·HPO4]2}2– precatalyst as a novel bimetallic precursor for kinetic and mechanistic studies of nucleation, six important, previously unanswered questions are raised about the ill-understood but exceedingly broad and important topic of nucleation. 1H NMR solution speciation and Signer apparatus solution molecular weight studies establish that in situ prepared {[(1,5-COD)IrI·HPO4]2}2–, 3, exists predominantly in its indicated, dimeric form. The NMR studies also identify {[(1,5-COD)IrI(NCCH3)]2·HPO4}0, 2, as an important, metastable species with one less H...