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Neutral and Cationic Alkyl and Amido Group 3 Metal Complexes of Amidine‐Amidopyridinate Ligands: Synthesis, Structure, and Polymerization Catalytic Activity
Author(s) -
Rad'kov Vasily,
Roisnel Thierry,
Trifonov Alexander,
Carpentier JeanFrançois,
Kirillov Evgeny
Publication year - 2014
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201402362
Subject(s) - chemistry , cationic polymerization , hydroamination , aminolysis , medicinal chemistry , polymerization , scandium , agostic interaction , amine gas treating , amidine , ring opening polymerization , lanthanum , stereochemistry , alkyl , lanthanide , metal , yttrium , catalysis , polymer chemistry , organic chemistry , polymer , ion , oxide
Alkane and amine elimination reactions between the amidine‐aminopyridine proligands (N R1 NN R1 C Me N R2 )H [R 1 = R 2 = Me ( 1a ), R 1 = H, R 2 = Me ( 1b ), R 1 = Me, R 2 = i Pr ( 1c )] and the precursors [Ln(CH 2 SiMe 3 ) 3 (thf) 2 ] (Ln = Sc and Y) and [Ln{N(SiHMe 2 ) 2 } 3 (thf) x ] (Ln = Sc, Y, and La) have been investigated. Bulky 1c and [Ln(CH 2 SiMe 3 ) 3 (thf) 2 ] (Ln = Sc and Y) selectively afforded dialkyl complexes 2c‐Sc and 2c‐Y . Yttrium and lanthanum diamido complexes 3a‐Y , 3b‐Y , 3c‐Y , and 3c‐La were synthesized and isolated in high yields; however, similar aminolysis reactions to prepare the scandium analogues were unsuccessful. Detailed 29 Si NMR spectroscopic studies combined with X‐ray crystallography revealed the presence of β‐Si–H ··· Ln agostic interactions in the diamido complexes. Cationic monoamido complex 4a‐Y was obtained from the reaction of 3a‐Y with [Et 3 NH] + [BPh 4 ] – . Both the dialkyl and diamido complexes, activated with [Ph 3 C] + [B(C 6 F 5 ) 4 ] – /Al i Bu 3 or [PhNMe 2 H] + [B(C 6 F 5 ) 4 ] – /Al i Bu 3 , were found to be moderately active at 60 °C in the trans ‐1,4‐selective polymerization of isoprene, and the diamido complexes promoted the ring‐opening polymerization of rac ‐lactide with moderate activities.