A reversible solid–solid phase transition Z′ = 1 to Z′ = 6 in [Ni(OAc)(PNPtBu)]OTf

At ambient temperature, the complex [Ni(OAc)(PNPtBu)]OTf has one independent molecule in the asymmetric unit of the crystal structure with very large anisotropic displacement parameters. During cooling a fully reversible solid–solid phase transition occurs at a discrete temperature in the range 210–230 K. The low-temperature phase has six independent, well ordered molecules in the asymmetric unit. The P21/a space group symmetry of the high-temperature phase changes to P21/n for the low-temperature phase and the c-axis increases by a factor of six. The acetate ligand is shown to be coordinated in a η1-fashion through one of the oxygen atoms, with the sterically encumbered, tridentate PNPtBu ligand completing the square planar geometry around the NiII ion. The synthesis and full characterization of the complex is reported.

The pincer complex [Ni(OAc)(PNPtBu)]OTf has a room temperature structure with Z′ = 1, which shows signs of disorder. During a phase transition between 230 and 210 K the unit cell volume increases by a factor of six, accompanied by large structural changes, resulting in a well ordered structure with Z′ = 6.Figure optionsDownload as PowerPoint slide