Coordination Features of the 1,3,5‐Triazapentadienyl Ligand in Alkyl Complexes of Rare‐Earth Metals

The reactions of 1,3,5‐triazapentadiene 2,6‐iPr 2 C 6 H 3 NC(Ph)NC(Ph)NHC 6 H 3 iPr 2 ‐2,6 ( 1 ) with Ln(CH 2 SiMe 3 ) 3 (THF) 2 (Ln=Y, Lu) in hexane afford bis(alkyl) complexes [2,6‐iPr 2 C 6 H 3 NC(Ph)NC(Ph)NC 6 H 3 iPr 2 ‐2,6]Ln(CH 2 SiMe 3 ) 2 (THF) (Ln=Y ( 2 ), Lu ( 3 )) in 58 ( 2 ) and 62 ( 3 ) % yields. The X‐ray diffraction study revealed that in 3 the triazapentadienyl ligand coordinates with the Lu 3+ ion in “amidinate” fashion resulting in the formation of a four‐membered metallocycle. In contrast, the reaction of 1 with the scandium analogue Sc(CH 2 SiMe 3 ) 3 (THF) 2 in toluene proceeds with the cleavage of C−N bond of 1,3,5‐triazapentadiene and leads to the formation of a dinuclear monoalkyl complex [{μ 2 ‐2,6‐iPr 2 C 6 H 3 NC(Ph)N}Sc(CH 2 SiMe 3 )(THF)] 2 ( 4 ) in 43 % yield. Complex 4 features κ 2 ‐N,N‐coordination of the residual dianionic {μ 2 ‐2,6‐iPr 2 C 6 H 3 NC(Ph)N} 2− ligand μ‐bridging two Sc 3+ centers. Alkyl complexes 2 – 4 were evaluated as pre‐catalysts for isoprene polymerization and hydrosilylation of unsaturated substrates with PhSiH 3 .