3(µ3-) group was confirmed by the NMR at 20 °C [ -1.04, septet, 2 3*/(PH) = 4.5, '/(PtH) = 598 Hz] and by the -coupled l95Pt NMR spectra,14 and the presence of CO was confirmed by the IR spectrum [¡-(CO) = 1982 cm"1, cf. ¡-(CO) for 1 = 1750 cm'1].8 At -60 °C the '/(PtH) coupling was reduced to 573 Hz and the chemical shift was -1.47. Further characterization was obtained by treating 3 with 13CO to give 2* (* = 13CO labeled). At -90 °C, the hydride signal was at -1.67 ('/(PtH) = 558 Hz and a doublet splitting with /(13CH) = 40 Hz was also observed), and in the 13C NMR spectrum the carbonyl resonance was at 191 as a septet with '/(PtC) = 434 Hz [cf. 209, '/(PtC) = 776 Hz for l]18 with the intensities expected for a Pt3^3-CO) group.12 At room temperature only a broad resonance in the 13C NMR spectrum was observed at 191 without 195Pt satellites and the coupling of 13C to the 3(µ3-) resonance in the NMR was also lost. These data strongly indicate that reversible dissociation of CO from 2 occurs rapidly (14) Migration of a proton through a triangle of metal atoms has been suggested to explain the reversible protonation of [Ni12(CO)21]H4_"]"" in which the hydride ligands are interstitial and may also be involved in the protonation of [Co6(CO)15]2-and in the migration of hydrogen atoms through metallic lattices. This appears to be the first direct evidence and the first time that the barrier to inversion has been determined. The data do not rule out transition states with lower symmetry, for example, with hydride bridging one edge, but these are less likely. A complex with an almost planar Er3(q-H) group is known.

ZnO nanorods (NRs) grown by chemical bath deposition (CBD) are among the most promising semiconducting nanostructures currently investigated for a variety of applications. Still, contrasting experimental results appear in literature on the microscopic mechanisms leading to high aspect-ratio and vertically aligned ZnO NRs. Here, we report on CBD of ZnO NRs by using Zn nitrate salt and hexamethylenetetramine (HMTA), evidencing a double role of HMTA in the NRs growth mechanism. Beyond the well-established pH buffering activity, HMTA is shown to introduce a strong steric hindrance effect biasing the growth along the c-axis and ensuring the vertical arrangement. This twofold function of HMTA should be taken into account for avoiding detrimental phenomena such as merging or suppression of NRs, which occur at low HMTA concentration.

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Described is the self-assembly of a monolayer of TiO2 nanocrystallites on a gold substrate by two related methods. In the first of these methods, a crystalline monolayer of the functionalized thiol HS−(CH2)10−COOH is self-assembled at an annealed gold substrate by adsorption from ethanolic solution. The modified gold substrate is then immersed in an ethanolic TiO2 colloid. TiO2 nanocrystallites are adsorbed at the terminal −COOH group of the molecules constituting the monolayer. In the second of these methods, an ethanolic colloid of TiO2 nanocrystallites is prepared in the presence of the functionalized thiol HS−(CH2)10−COOH. The modified nanocrystallites are adsorbed at the surface of an annealed gold substrate. For each method, there is some evidence for short-range ordering of the nanocrystallites constituting the close-packed monolayer adsorbed at the gold substrate. Some potential applications of these methods are considered.

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