We recently reported that 2-(phospholanylmethyl)-6-(2-phosphaethenyl)pyridine (PPEP) with a 2,4,6-tri-tert-butylphenyl group (Mes*) as steric protection of the P=C bond serves as a noninnocent ligand on leading to extremely high reactivity toward metal ligand cooperative activation of ammonia and acetonitrile. The high reactivity is largely due to the strong pi-accepting properties of the P=C bond. However, PPEP had a stability problem that provokes the loss of the P=C bond on other transition metals, including Rh(I), and restricts its utilization. This paper describes the synthesis of Eind-PPEP protected by an octaethyl-s-hydrindacen-4-yl group (Eind) instead of Mes*. The fused ring bulky Eind group successfully prevents the loss of the P=C bond and enables us to compare the reactivity of Rh(I) and Ir(I) complexes toward ammonia. The complex K[RhCl(Eind-PPEP*)], bearing a dearomatized Eind-PPEP* ligand, undergoes simple ligand displacement to give [Rh(NH3)(Eind-PPEP*)], whereas the iridium analogue K[IrCl(Eind-PPEP*)] causes N-H bond cleavage to form [Ir(NH2)(Eind-PPEP)]. DFT calculations indicate a thermodynamic cause of the metal-dependent product change.
The Pt0 complex [Pt(PPh3)(Eind2‐BPEP)] with a pyridine‐based PNP‐pincer‐type phosphaalkene ligand (Eind2‐BPEP) has a highly planar geometry around Pt with ∑(Pt)=358.6°. This coordination geometry is very uncommon for formal d10 complexes, and the Pd and Ni homologues with the same ligands adopt distorted tetrahedral geometries. DFT calculations reveal that both the Pt and Pdcomplexes are M0 species
π-conjugated phosphasilenes stabilized by fused-ring bulky “Rind” groups
作者:Tsukasa Matsuo、Baolin Li、Kohei Tamao
DOI:10.1016/j.crci.2010.07.005
日期:2010.8
π-conjugated phosphasilenes stabilized by bulky protecting groups based on a fused-ring octa-R-substituted s-hydrindacene skeleton (Rindgroups) is reviewed. The phosphasilenes with a variety of aryl substituents at the silicon atom are covered in detail. The X-ray crystallography analysis showed the highlycoplanar π-framework reinforced by the perpendicularly-fixed Rindgroups. Strong π–π* absorptions have been