Selective Functionalization with Organophosphite Ligands of Atomically Precise Platinum Chini Clusters

Heteroleptic [Pt3n(CO)6n–x{P(OR)3}x]2– (n = 3–5; x = 1, 2; R = Me, Et, Ph) Chini clusters have been obtained upon reaction of homoleptic [Pt3n(CO)6n]2– (n = 3–5) species with increasing amounts of P(OR)3. In the case of P(OPh)3, the whole series of clusters [Pt3n(CO)6n–x{P(OPh)3}x]2– (n = 3–5; x = 1, 2) has been spectroscopically characterized. In contrast, by using the stronger σ-bases P(OMe)3 and P(OEt)3, it has been possible to identify only the species [Pt12(CO)22{P(OR)3}2]2–, [Pt9(CO)17{P(OR)3}]2– and [Pt9(CO)16{P(OR)3}2]2– (R = Me, Et). Generally speaking, 1–2 CO ligands may be selectively replaced by P(OR)3 ligands in homoleptic [Pt3n(CO)6n]2– (n = 3–5) clusters, whereas the addition of a third P(OR)3 ligand results in the elimination of a Pt3-triangle and the concomitant formation of a smaller [Pt3(n–1)(CO)6(n–1)]2– cluster that may be further substituted. The nature in solution of all the species has been elucidated by means of FT-IR, ESI-MS, 1H and 31P{1H} NMR spectroscopy. The molecular structures of [PMePh3]2[Pt9(CO)17{P(OPh)3}]·CH3COCH3, [PMePh3]2[Pt12(CO)22{P(OPh)3}2]·solv, [PMePh3]2[Pt12(CO)22{P(OMe)3}2], [PMePh3]2[Pt15(CO)28{P(OPh)3}2]·2CH3COCH3·C6H14 have been determined by single-crystal X-ray diffraction (SC-XRD). Computational studies have been carried out to get insights into the torsional isomers of [Pt12(CO)22{P(OR)3}2]2– (R = Me, Ph) and the positional isomers of [Pt9(CO)18–x{P(OMe)3}x]2– (x = 1–3) and related species.