Selective Functionalization with Organophosphite Ligands of Atomically Precise Platinum Chini Clusters

Heteroleptic [Pt-3n(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 [Pt-3n(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 [Pt-3n(CO)(6n-x){P(OPh)(3)}(x)](2-) (n = 3-5; x = 1, 2) has been spectroscopically characterized. In contrast, by using the stronger sigma-bases P(OMe)(3) and P(OEt)(3), it has been possible to identify only the species [Pt-12(CO)(22){P(OR)(3)}(2)](2-), [Pt-9(CO)(17){P(OR)(3)}](2-) and [Pt-9(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 [Pt-3n(CO)(6n)](2-) (n = 3-5) clusters, whereas the addition of a third P(OR)(3) ligand results in the elimination of a Pt-3-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, H-1 and P-31{H-1} NMR spectroscopy. The molecular structures of [PMePh3](2)[Pt-9(CO)(17){P(OPh)(3)}]& centerdot;CH3COCH3, [PMePh3](2)[Pt-12(CO)(22){P(OPh)(3)}(2)]& centerdot;solv, [PMePh3](2)[Pt-12(CO)(22){P(OMe)(3)}(2)], [PMePh3](2)[Pt-15(CO)(28){P(OPh)(3)}(2)]& centerdot;2CH(3)COCH(3)& centerdot;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 [Pt-12(CO)(22){P(OR)(3)}(2)](2-) (R = Me, Ph) and the positional isomers of [Pt-9(CO)(18-x){P(OMe)(3)}(x)](2-) (x = 1-3) and related species.