Synthesis and characterization of novel phosphinoketone and phosphinoenolato rhenium(v) nitrido complexes. Crystal structure of ReNCl2{iPr2PCH2C(Ph)O}2

Abstract

Refluxing ReNCl₂(PPh₃)₂ with phosphinoketone ligands (P∼CO) of the type R₂PCH(R′)C(R″)O (R = phenyl, isopropyl; R′ = H, methyl; R″ = phenyl, tert-butyl) in toluene or ethanol yields selectively the octahedral nitrido-rhenium(V) complexes ReN(PR₃)(P∼O)₂, where the P atoms of two deprotonated P∼O⁻ ligands occupy cis positions and an oxygen donor lies trans to the ReN bond. The sixth coordination site is filled by a monodentate phosphine, either PPh₃ or non-deprotonated P∼CO, depending on the metal-to-ligand ratio. When ⁱPr₂PCH₂C(Ph)O is refluxed for 1 h (2/1 L/Re ratio), ReNCl₂{ⁱPr₂PCH₂C(Ph)O}₂ (1) precipitates as the only species. X-Ray diffraction shows that the Re(V) centre of 1 is six-coordinated with a distorted octahedral geometry, being bonded to the nitrido N atom, two trans chlorides, two trans P atoms and the oxygen of one of the phosphinoketones lying trans to the N³⁻ ligand. The short ReN bond (1.629(4) Å) and the long trans Re–O bond (2.466(5) Å) reflect the large trans influence of the nitrido ligand. The mono- and bi-dentate phosphinoketones in this compound are involved in an intramolecular interchange process.