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

Abstract

The inter-conversions of platinum carbonyl dianionic clusters, ([Pt(3)(CO)(6)](n)(2-), n = 2-5), have been studied in THF and acetonitrile using in situ FTIR spectroscopy. These inter-conversions were facilitated by the addition (or removal) of molecular hydrogen. The individual reactions, namely reductions and oxidations of [Pt(3)(CO)(6)](n)(2-) were fast and reversible. BTEM analysis of the data provided the pure component spectra of the individual species without the need for physical separation. It is shown, for the first time, that the species [Pt(3)(CO)(6)](n)(2-) (n = 2) can be formed from the reduction of [Pt(3)(CO)(6)](n)(2-) (n = 3-5) by hydrogen alone in acetonitrile. Also, detection of dissolved CO(2) in solution suggests that a room-temperature water gas shift reaction occurs. This has been shown to arise from nucleophilic attack of water on a coordinated CO of [Pt(3)(CO)(6)](n)(2-) which leads to the formation of [HPt(15)(CO)(19)](3-) and [H(2)Pt(15)(CO)(19)](2-). The parent tetraanion, [Pt(15)(CO)(19)](4-), has been isolated in high yields by reaction of [Pt(3)(CO)(6)](n)(2-) (n = 2, 3) with NaOH at 60 °C and has been structurally characterized by X-ray analysis.

Looking at platinum carbonyl nanoclusters as superatoms

“…The two relatively small and non-spherical clusters [Pt 14 (μ-CO) 6 (CO) 12 ] 4− and [Pt 15 (μ-CO) 8 (CO) 11 ] 4− experimentally reported 31,61 (Fig. 4 and Fig.…”

“…This is what happens in [Pd 13 (μ 4 -C 7 H 7 ) 6 ] 2+ (nfe = 2, 1S 2 configuration) 55,56 and Pd 55 (PR 3 ) 12 (μ 3 -CO) 20 (nfe = 20, 1S 2 1P 6 1D 10 2S 2 configuration) for instance. 57,58 In this paper, we move to platinum, which is also remarkable in its propensity to form high nuclearity carbonyl clusters, in particular the socalled family of "platinum browns", 31 which were mainly developed in the past in the group of Longoni and now that of Zacchini in Italy, 31,[59][60][61][62][63][64][65][66] and to a lesser extent, in that of Dahl in the USA. 67,68 So, we explore a large series of this platinum nanocluster family and we demonstrate that, most of the time, it can also be rationalized within the concepts of superatoms and supermolecules.…”

Functionalization, Modification, and Transformation of Platinum Chini Clusters

“…This is due to the fact that the inter‐triangular bonding of Chini clusters may be related to their negative charge to nuclearity ratio. As a matter of fact, the inter‐triangular Pt–Pt bonds become weaker as the nuclearity of the cluster increases , , , , . Thus, the non‐redox substitution is favored over redox fragmentation in the order [Pt 6 (CO) 12 ] 2– > [Pt 9 (CO) 18 ] 2– > [Pt 12 (CO) 24 ] 2– > [Pt 15 (CO) 30 ] 2– .…”

“…Thus, by employing stoichiometric amounts of phosphine ligands, heteroleptic anionic Chini type clusters can be obtained through non‐redox substitution. Conversely, when used in excess, redox fragmentation occurs affording mixtures of lower nuclearity anionic clusters and zero‐valent species such as Pt 3 (CO) 3 (PPh 3 ), Pt 6 (CO) 6 (dppe) 3 , Pt 4 (CO) 4 (dppe) 2 and Pt(dppe) 2 . It must be remarked that, because of the low steric hindrance of PTA (cone angle 103°) compared to PPh 3 (145°), multiple substitutions may occur with PTA (up to one PTA per triangular unit), whereas only two PPh 3 ligands per Chini cluster may be introduced.…”

“…Homoleptic Pt‐CO clusters which do not display the structure of Chini clusters are usually called globular molecular platinum carbonyl nanoclusters (because of their sizes and structures) or platinum browns (because of the color of their solutions) . Compared to Chini clusters (CO/Pt = 2), these are CO‐poorer species (CO/Pt = 1.0–1.3) which are usually obtained by means of two general strategies:, (1) thermal decomposition of [Pt 3 n (CO) 6 n ] 2– ( n = 2–10) Chini clusters; (2) oxidation/reduction of preformed platinum carbonyl nanoclusters. The first examples of Pt browns were reported by Chini and Longoni in the seventies of last century,, but the number of species structurally characterized has considerably increased only in the recent years , …”