PPh₃‑Derivatives of [Pt_3<i>n</i>(CO)_6<i>n</i>]^2– (<i>n</i> = 2–6) Chini’s Clusters: Syntheses, Structures, and ³¹P NMR Studies

The reaction of the [Pt3n(CO)6n]2– (n = 2–6) Chini’s clusters with increasing amounts of PPh3 has been investigated in detail by combined FT-IR, 31P­{1H} NMR, and electrospray ionization-mass spectrometry (ESI-MS) studies, showing that up to three CO ligands are gradually substituted by PPh3, resulting in isonuclear phosphine-substituted anionic clusters of general formula [Pt3n(CO)6n−x(PPh3)x]2– (n = 2–6; x = 1–3). Further addition of PPh3 results in the elimination of the neutral Pt3(CO)3(PPh3)3 species and formation of lower nuclearity anionic clusters. [Pt12(CO)22(PPh3)2]2– and [Pt9(CO)16(PPh3)2]2– have been structurally characterized, and they maintain the trigonal prismatic structures of the parent homoleptic clusters, with the two PPh3 ligands bonded to different external Pt3-triangles in relative cis-position. Conversely, the crystal structure of [Pt6(CO)10(PPh3)2]2– shows that its metal cage is transformed from trigonal prismatic to trigonal antiprismatic after CO/PPh3 exchange.