Formation and Reactivity of a C‐P‐N‐Sc Four‐Membered Ring: H 2 , O 2 , CO, Phenylsilane, and Pinacolborane Activation

Reaction of scandium dimethyl complex LScMe 2 (L=[2‐{N(DIPP)C(Ph)N}C 6 H 4 CH=N(DIPP)] − , DIPP=2,6‐( i Pr) 2 C 6 H 3 ) ( 2 ) with bulky phosphine ArPH 2 (Ar=2,6‐{3,5‐(Me) 2 C 6 H 3 } 2 C 6 H 3 ) gives an unprecedented scandium 2,3‐azaphosphametallacyclobutane complex L′Sc (L′=[2‐{N(DIPP)C(Ph)N}C 6 H 4 C(H)P(2,6‐{3,5‐(CH 3 ) 2 C 6 H 3 } 2 C 6 H 3 )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 H 2 under mild conditions to give a H−H bond cleavage product, but also reacts with O 2 , CO, phenylsilane, and pinacolborane to produce novel products through cleavage and formation of various bonds.