Stereochemical non-rigidity of a metal polyhedron; carbon-13 and platinum-195 fourier transform nuclear magnetic resonance spectra of [Ptn(CO)2n]2- (n = 3, 6, 9, 12 or 15)

The inter-conversions of platinum carbonyl dianionic clusters, [Pt3(CO)6]n2− (n = 2–5), in THF and acetonitrile. A combined in situ FTIR spectroscopic and BTEM study leading to the characterization of the new [H4−xPt15(CO)19]x− (x = 2–4) clusters

“…They can be obtained by various reduction reactions from several platinum substrates such as Na 2 [PtCl 6 [PtCl 4 ] and Pt(CO) 2 Cl 2 . The reducing agents include alkali hydroxide under CO, Fe(CO) 5 , cobaltocene and alkali metals etc. The dianionic cluster, [Pt 6 (CO) 12 ] 2-, can be prepared by either reductive carbonylation by sodium hydroxide and CO (1 atm) in methanol or DMF 3 or by the reduction of [Pt 3 (CO) 6 ] n 2-(n = 5, 4, 3) with lithium metal in THF.…”

“…2 They have been studied in solution by FTIR spectroscopy and 13 C and 195 Pt NMR spectroscopy. [4][5] It is also known that the presence (or absence) of hydrogen can promote the inter-conversions of the platinum dianionic clusters [Pt 3 (CO) 6 ] n 2-(n = 3-5) in THF via the general equilibrium shown in eqn (1).…”

Heterometallic Ni–Pt Chini-Type Carbonyl Clusters: An Example of Molecular Random Alloy Clusters

“…CO migration has been previously observed for [Ni 6 (CO) 12 ] 2– but not [Pt 6 (CO) 12 ] 2– . 9 , 26 Variable-temperature (VT) 195 Pt and 13 C NMR experiments (see Figures S47–S50 in the Supporting Information) confirm that [Pt 6 (CO) 12 ] 2– is static, whereas all other species present in the solutions of [Pt 6– x Ni x (CO) 12 ] 2– ( x = 1–6) are somewhat fluxional, even if the spectra are too complicated to be easily interpreted. As reported by Longoni and Heaton, 26 the CO exchange process of lowest activation energy involves a bridge–terminal carbonyl exchange, which results in randomization of the ligands of [Ni 6 (CO) 12 ] 2– .…”

“…Conversely, intramolecular rotation of the two M 3 triangles has been proposed on the basis of multinuclear VT NMR and liquid X-ray scattering studies for both [Ni 6 (CO) 12 ] 2– and [Pt 6 (CO) 12 ] 2– . 8 , 9 , 13 …”

“…Such intermolecular processes have been previously evidenced for Pt Chini clusters through VT 195 Pt NMR experiments. 8 , 9 In principle, the intermolecular exchange of M 3 (CO) 6 units in solution may occur via either a dissociative or an associative mechanism. The latter should require the shuttling of M 3 (CO) 6 units between [M 6 (CO) 12 ] 2– anions.…”