Neutral and Cationic Rare Earth Metal Alkyl and Benzyl Compounds with the 1,4,6-Trimethyl-6-pyrrolidin-1-yl-1,4-diazepane Ligand and Their Performance in the Catalytic Hydroamination/Cyclization of Aminoalkenes

A new neutral tridentate 1,4,6-trimethyl-6-pyrrolidin-1-yl-1,4-diazepane ( L ) was prepared. Reacting L with trialkyls M(CH 2 SiMe 3 ) 3 (THF) 2 (M = Sc, Y) and tribenzyls M(CH 2 Ph) 3 (THF) 3 (M = Sc, La) yielded trialkyl complexes ( L )M(CH 2 SiMe 3 ) 3 (M = Sc, 1; M = Y, 2 ) and tribenzyl complexes ( L )M(CH 2 Ph) 3 (M = Sc, 3; M = La, 4 ). Complexes 1 and 2 can be converted to their corresponding ionic compounds [( L )M(CH 2 SiMe 3 ) 2 (THF)][B(C 6 H 5 ) 4 ] (M = Sc, 5; M = Y, 6 ) by reaction with [PhNMe 2 H][B(C 6 H 5 ) 4 ] in THF. Complexes 3 and 4 can be converted to cationic species [(L)M(CH 2 Ph) 2 ] + by reaction with [PhNMe 2 H][B(C 6 F 5 ) 4 ] in C 6 D 5 Br in the absence of THF. The neutral complexes 1 − 4 and their cationic derivatives were studied as catalysts for the hydroamination/cyclization of 2,2-diphenylpent-4-en-1-amine and N -methylpent-4-en-1-amine reference substrates and compared with ligand-free Sc, Y, and La neutral and cationic catalysts. The most effective catalysts in the series were the cationic L -yttrium catalyst (for 2,2-diphenylpent-4-en-1-amine) and the cationic lanthanum systems (for N -methylpent-4-en-1-amine). For the La catalysts, evidence was obtained for release of L from the metal during catalysis.