NEW [PT3(MU-3-CO)(MU-PH2PCH2PPH2)3L]2+ CLUSTERS, L = PHOSPHINE OR PHOSPHITE LIGAND, CONTAINING AN ASYMMETRIC PT3(MU-3-CO) GROUP AND THE CRYSTAL-STRUCTURE OF THE COMPLEX WITH L = P(OPH)3

The complex [Pt3(µ3-CO)(µ-dppm)3]2+ (1; dppm = Ph2PCH2PPh2) adds phosphorus donors L to give the adducts [Pt3(µ3-CO)(µ-dppm)3L]2+ (2), where L = P(OMe)3 (2a), P(OEt)3 (2b), P(OPh)3 (2c), PMe2Ph (2d), PMePh2 (2e), PPh3 (2f), PF3 (2g). Complexes 2a–d are thermally stable, but 2e–g readily dissociate the phosphorus donor ligand to regenerate 1. Complex 2c has been characterized crystallographically. The phosphite ligand binds as a terminal ligand to a single platinum center, and the triply bridging carbonyl ligand is bound most strongly to the same platinum atom. The same structure is believed to be present in solutions of 2a–f at low temperature, but the complexes 2a–e exhibit a new type of fluxionality at higher temperatures in which the phosphorus donor ligand migrates around the Pt3 triangle. The “time-averaged” structure therefore appears to have a μ3-PX3 ligand. For complex 2g, the fluxional process was not frozen out at -90 °C and it is possible that the Pt3(µ3-PF3) group is present in the ground state. © 1990, American Chemical Society. All rights reserved.