Synthesis and properties of group 9 metal complexes bearing a β-ketophosphenato ligand

A novel β-ketophosphenato ligand bearing a bulky substituent, Tbt(2,4,6-tris[bis(trimethylsilyl)methyl]phenyl), on the phosphorus atom was newly designed and synthesized as a heavier congener of a β-ketoiminato ligand. Rhodium and iridium complexes bearing this new β-ketophosphenato ligand have been synthesized and fully characterized by spectroscopic and elemental analyses together with X-ray crystallographic analyses. The results of NMR spectroscopic studies and the X-ray structural analyses suggested that the β-ketophosphenato ligand has unique electronic features due to the low-coordinated phosphorus atom. Comparison of properties between rhodium β-ketophosphenates 2a,b and rhodium β-ketoiminate 7 revealed the character of the β-ketophosphenato ligand, where the trans influence of the phosphorus atom should be stronger than the nitrogen atom of the β-ketoiminato ligand.