119743-70-3Relevant articles and documents
Five-coordinate olefin complexes of platinum(II) containing σ-bonded carbon ligands. Coordination environment and stability
Cucciolito, Maria Elena,De Felice, Vincenzo,Panunzi, Achille,Vitagliano, Aldo
, p. 1180 - 1187 (2008/10/08)
Using three different procedures, trigonal-bipyramidal complexes of the type PtClR(N-N′)(η2-olefin) have been prepared containing a variety of alkyl or aryl ligands (R), bidentate nitrogen (N-N′), and olefinic ligands. In contrast to other previously known five-coordinate complexes of platinum (II), the dissociation of the olefin from these species is reversible. The equilibria PtClR(N-N′) (olefin) ?K PtClR(N-N′) + olefin have been investigated through qualitative observations and through the determination of the dissociation constants by 1H NMR analysis of equilibrium mixtures. The main ligand effects may imply a variation of Kdiss of several orders of magnitude and are the following: (a) A dominating factor is the steric hindrance present on both sides of the N-N′ ligand. If properly oriented in the coordination plane, this stabilizes the bipyramidal complexes through a corresponding destabilization of the square-planar species. (b) Electron-releasing substituents on the olefinic double bond destabilize the five-coordinate complexes while electron-withdrawing groups stabilize them. This trend is opposite to that observed for square-planar species and provides direct evidence for the relative importance of π-back-donation in five-coordinate Pt(II) olefin complexes.
