Unsymmetrical PNP-Pincer Type Phosphaalkene Ligands Protected by a Fused-Ring Bulky Eind Group: Synthesis and Applications to Rh(I) and Ir(I) Complexes

作者：Taguchi Hiro omi; Sasaki Daichi; Takeuchi Katsuhiko; Tsujimoto Shota; Matsuo Tsukasa; Tanaka Hiromasa; Yoshizawa Kazunari; Ozawa Fumiyuki^*

来源：Organometallics, 2016, 35(10): 1526-1533.

DOI：10.1021/acs.organomet.6b00113

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.

• 出版日期2016-5-23