title: Yttrium complexes supported by linked bis(amide) ligand: synthesis, structure, and catalytic activity in the ring-opening polymerization of cyclic esters.
abstract: A series of new yttrium complexes supported by the bulky enediamido dianionic ligand DAB(2-) (DAB(2-) = (2,6-C(6)H(3)iPr(2))NC(Me)=C(Me)N(2,6-C(6)H(3)iPr(2))(2-)), that is, {DAB}Y(THF)(2)(mu-Cl)(2)Li(THF)(2) (1), {DAB}Y(OtBu)(THF)(DME) (2), and {{DAB}Y(BH(4))(2)}{Li(DME)(3)} (3), was synthesized by salt metathesis. The complexes were isolated after recrystallization in 73, 66, and 52% yield, respectively, and characterized in solution by NMR and in the solid state by single-crystal X-ray diffraction studies. In complex 1, the DAB(2-) ligand is bonded to the metal center via two covalent YN bonds, while in complexes 2 and 3 additional eta(2)-coordination of the C=C bond to the metal atom is observed, both in solution and in the solid state. The tert-butoxide and borohydride complexes 2 and 3 act as monoinitiators for the room temperature ring-opening polymerization of racemic lactide and beta-butyrolactone, providing atactic polymers with controlled molecular weights and relatively narrow polydispersities (M(w)/M(n) = 1.15-1.82). Effectively immortal ROP of lactide with as many as 50 equiv of isopropanol per metal center was performed using complex 2 as the catalyst.
authors.affiliation: G.A. Razuvaev Institute of Organometallic Chemistry of Russian Academy of Sciences, Tropinina 49, GSP-445, 603950 Nizhny Novgorod, Russia.
authors.forename: Tatyana V
authors.initials: TV
authors.lastname: Mahrova
authors.forename: Georgy K
authors.initials: GK
authors.lastname: Fukin
authors.forename: Anton V
authors.initials: AV
authors.lastname: Cherkasov
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Trifonov
authors.forename: Noureddine
authors.initials: N
authors.lastname: Ajellal
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Carpentier
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D000577:Amides / Q000138:chemical synthesis / Q000737:chemistry*; D002070:Butadienes / Q000138:chemical synthesis / Q000737:chemistry; D002384:Catalysis; D018360:Crystallography, X-Ray; D004146:Dioxanes / Q000138:chemical synthesis* / Q000737:chemistry; D008024:Ligands; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D011108:Polymers / Q000138:chemical synthesis* / Q000737:chemistry; D015019:Yttrium / Q000737:chemistry*
chemical_list: D000577:Amides; D002070:Butadienes; D004146:Dioxanes; D008024:Ligands; D009942:Organometallic Compounds; D011108:Polymers; C013426:beta-butyrolactone; D015019:Yttrium; C091880:dilactide; C031763:1,3-butadiene; D015107:4-Butyrolactone