Formation and Reactivity of a C-P-N-Sc Four-Membered Ring: H2 , O2 , CO, Phenylsilane, and Pinacolborane Activation

Abstract

Reaction of scandium dimethyl complex LScMe₂ (L=[2-{N(DIPP)C(Ph)N}C₆ H₄ CH=N(DIPP)]^- , DIPP=2,6-(iPr)₂ C₆ H₃ ) (2) with bulky phosphine ArPH₂ (Ar=2,6-{3,5-(Me)₂ C₆ H₃ }₂ C₆ H₃ ) gives an unprecedented scandium 2,3-azaphosphametallacyclobutane complex L'Sc (L'=[2-{N(DIPP)C(Ph)N}C₆ H₄ C(H)P(2,6-{3,5-(CH₃ )₂ C₆ H₃ }₂ C₆ H₃ )N(DIPP)]^3- ) (3) that contains a C-P-N-Sc four-membered ring. Complex 3 was characterized by X-ray crystallography, revealing a short distance between the Sc and P atoms (2.786(1) Å), but without a direct Sc-P bonding interaction. The formation of 3 involves a complete cleavage of the imino bond of the tridentate ligand L and C-P and N-P bond coupling. Complex 3 not only activates H₂ under mild conditions to give a H-H bond cleavage product, but also reacts with O₂ , CO, phenylsilane, and pinacolborane to produce novel products through cleavage and formation of various bonds.

Keywords: Lewis acids; Lewis bases; insertion; phosphorus; scandium.