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The synthesis of colloidal Pt particles obtained from the reaction between platinum acetylacetonate (Pt(acac) 2 ) and Al(CH 3 ) 3 was monitored, and the formation of the Pt colloid via "reductive stabilization" was established by a combination of techniques including NMR, anomalous small-angle X-ray scattering (ASAXS), X-ray absorption spectroscopy (XAS), density functional theory (DFT) computations, and transmission electron microscopy (TEM). For the first time, a defined organometallic compound was identified as the common intermediate in the formation of an organometallic Pt complex or a Pt colloid, depending on the type of ligands or stabilizers present. During the decomposition of this intermediate state, stable colloidal particles of just one size are observed the number of which increases with time.

59Co chemical shifts were computed at the GIAO-B3LYP level for [Co(CN)6]3-, [Co(H2O)6]3+, [Co(NH3)6]3+, and [Co(CO)4]- in water. The aqueous solutions were modeled by Car-Parrinello molecular dynamics (CPMD) simulations, or by propagation on a hybrid quantum-mechanical/molecular-mechanical Born-Oppenheimer surface (QM/MM-BOMD). Mean absolute deviations from experiment obtained with these methods are on the order of 400 and 600 ppm, respectively, over a total delta(59Co) range of about 18,000 ppm. The effect of the solvent on delta(59Co) is mostly indirect, resulting primarily from substantial metal-ligand bond contractions on going from the gas phase to the bulk. The simulated solvent effects on geometries and delta(59Co) values are well reproduced by using a polarizable continuum model (PCM), based on optimization and perturbational evaluation of quantum-mechanical zero-point corrections.

What's new about complexes 1 and 2, textbook examples of coordination compounds? Quantum‐chemical simulations reveal an exceptionally strong sensitivity of their 57Fe NMR spectroscopy chemical shifts to the FeC bond length, which, in turn, changes noticeably on going from the gas phase to aqueous solution.

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