Grigorii G. Skvortsov

Bisborohydride yttrium complexes containing amidinate ligands [o-Me2NC6H4CH2C(NR)2]Y(BH4)2Ln (R = Pri, L = DME, n = 1; R = Cy, L = THF, n = 2). Synthesis, structure, and catalytic activity in polymerization of rac-lactide and isoprene

A reaction of o-N,N-dimethyltoluidine lithium derivative (o-Me2NC6H4CH2Li) with carbodiimides (RN=C=NR, where R = Pri, Cy) in THF at room temperature leads to lithium complex of the general formula [{o-Me2NC6H4CH2C(NR)2}Li(THF)2]2 (R = Pri (1), Cy (2)) containing a new tridentate amidinate ligand. X-ray diffraction studies showed that complexes 1 and 2 are dimeric due to the coordination of the nitrogen atoms of the amidinate group with different lithium atoms. The nitrogen atoms of the aminobenzyl fragment are not involved in the complexation. The exchange reactions of Y(BH4)3(THF)3 with lithium amidinates 1 and 2 carried out with the equimolar ratio of reagents in solution in THF proceeded with the formation of neutral amidinatebisborohydride complexes of the general formula [o-Me2NC6H4CH2C(NR)2]Y(BH4)2Ln (3: R = Pri, L = DME (with added DME), n = 1; 4: R = Cy, L = THF, n = 2). According to the X-ray diffraction data, compounds 3 and 4 are monomeric, borohydride ligands are coordinated to the rare-earth metal atom by the η3- and η2-type. The donor NMe2 groups of the amidinate ligands are not involved in the metal—ligand interaction. Yttrium complexes 3 and 4 exhibit catalytic activity in polymerization of rac-lactide and isoprene.

Amidinate bisborohydride complexes of rare-earth metals [6-Me-C5H3N-2-CH2C(NPri)2]Ln(BH4)2THF2 (Ln = Y, Nd): synthesis, structure, and catalytic activity in isoprene polymerization

Reactions of equimolar amounts of RN=C=NR (R = Pri, Cy) and 6-Me-C5H3N-2-CH2Li prepared in situ by metallation of 2,6-dimethylpyridine with n-butyllithium afforded corresponding lithium amidinates [Li{6-Me-C5H3N-2-CH2C(NPri)2}]•1/3THF (1) and [Li{6-MeC5H3N-2-CH2C(NCy)2}]4 (2) containing new tridentate amidinate ligands. The salt metathesis reactions of Ln(BH4)3(THF)3 (Ln = Y, Nd) with 1 (1: 1 molar ratio, THF) result in neutral amidinate bisborohydride complexes [Ln{6-Me-C5H3N-2-CH2C(NPri)2}(BH4)2(THF)2} (Ln = Y (3), Nd (4)). According to X-ray data, both compounds are monomeric, terminal borohydride ligands being coordinated to the rare earth metal atom in η3-fashion. Nitrogen atoms of the pyridine fragments of amidinate ligands are not involved in complexation with metal cations. Complexes 3 and 4 in combination with [Ph3C][B(C6F5)4] and AlBu3i (1: 1: 10 molar ratio) exhibit catalytic activity in isoprene polymerization.

Triketiminate bis(borohydride) complexes of rare-earth metals [(2,6-Me 2 C 6 H 3 N=CMe) 2 C(2,6-Me 2 C 6 H 3 N=CBu t )]Ln(BH 4 ) 2 (THF) 2 (Ln = Y, Nd): synthesis, structure, and catalytic activity in polymerization of rac -lactide, ε-caprolactone, and isoprene

A new triketimine (2,6-Me2C6H3N=CMe)2CH(2,6-Me2C6H3N=CBut) (1) was synthesized by the reaction of imidoyl chloride 2,6-Me2C6H3N=CClBut with lithium diketiminate (2,6-Me2C6H3N=CMe)2CHLi. In the crystalline state, compound 1 exists in the diimineenamine form; in solution, in the triimine form. The metalation of triketimine 1 with n-butyllithium in THF at 0 °C produced lithium triketiminate [(2,6-Me2C6H3N=CMe)2C(2,6-Me2C6H3N=CBut)]Li(THF)2 (2). The metathesis reactions of Ln(BH4)3(THF)3 (Ln = Y, Nd) with compound 2 (1: 1 molar ratio, THF) gave the neutral triketiminate bis(borohydride) complexes [(2,6-Me2C6H3N=CMe)2C(2,6-Me2C6H3N=CBut)]Ln(BH4)2(THF)2 (Ln = Y (3), Nd (4)). As opposed to the complexes with neutral triketimine, the monoanionic triketiminate ligand is coordinated to Li and Y or Nd cations in a bidentate fashion. Complexes 3 and 4 catalyze the polymerization of rac-lactide and ε-caprolactone; in combination with [Ph3C][B(C6F5)4] and AlBu3i (1 : 1 : 10 molar ratio), these compounds exhibit catalytic activity in the polymerization of isoprene.

CCDC 1537909: Experimental Crystal Structure Determination

Related Article: Grigorii G. Skvortsov, Aleksei O. Tolpygin, Georgy K. Fukin, Jerome Long, Joulia Larionova, Anton V. Cherkasov, Alexander A. Trifonov|2017|Eur.J.Inorg.Chem.||4275|doi:10.1002/ejic.201700639

CCDC 1537908: Experimental Crystal Structure Determination

Related Article: Grigorii G. Skvortsov, Aleksei O. Tolpygin, Georgy K. Fukin, Jerome Long, Joulia Larionova, Anton V. Cherkasov, Alexander A. Trifonov|2017|Eur.J.Inorg.Chem.||4275|doi:10.1002/ejic.201700639

CCDC 1537910: Experimental Crystal Structure Determination

Related Article: Grigorii G. Skvortsov, Aleksei O. Tolpygin, Georgy K. Fukin, Jerome Long, Joulia Larionova, Anton V. Cherkasov, Alexander A. Trifonov|2017|Eur.J.Inorg.Chem.||4275|doi:10.1002/ejic.201700639

Yttrium complexes containing heteroscorpionate ligands [(3,5-But2C3HN2)2CHC(Ph)2O]– and [o-Me2NC6H4CH2C(NCy)2]–

A reaction of benzophenone with bis(3,5-di-tert-butylpyrazolyl)methyllithium (3,5-But2C3HN2)2CHLi (obtained in situ by metallation of (3,5-But2C3HN2)2CH2 with n-butyllithium in THF at–70 °C) led to the synthesis of alkoxide lithium complex [(3,5-But2-C3HN2)2CHCPh2O]Li(THF) (1) containing a new monoanionic heteroscorpionate ligand [(3,5-But2C3HN2)2CHCPh2O]–. Hydrolysis of complex 1 gave 2,2-bis(3,5-di-tert-butylpyrazolyl)-1,1-diphenylethanol (2) in 90% yield. The structure of alcohol 2 was established by X-ray crystallography. A reaction of anhydrous YCl3 with two molar equivalents of lithium alkoxide 1 in THF furnished yttrium monochloride complex [(3,5-But2C3HN2)2CHCPh2(μ-O)]2-YCl(THF)[(μ-Cl)Li]2 (3). According to X-ray diffraction data, chloride 3 is a monomeric ate-complex with one terminal and two bridging chloride ligands. The nitrogen atoms of the pyrazole rings are not involved in the coordination of the ligand with the yttrium ion. The bisalkyl complex [(3,5-But2C3HN2)2CHCPh2O]Y(CH2SiMe3)2(THF)2 (4) obtained by the reaction of alcohol 2 with an equimolar amount of Y(CH2SiMe3)3(THF)2 turned out to be unstable and completely decomposed in solution in C6D6 at 25 °C within two hours. An exchange reaction of equimolar amounts of YCl3 and {[o-Me2NC6H4CH2C(NCy)2]Li(THF)2}2 (5) (Cy is the cyclohexyl) in THF led to the formation of a neutral monochloride complex [o-Me2NC6H4CH2C(NCy)2]2YCl(THF)2 (6). A reaction of complex 6 with an equimolar amount of o-Me2NC6H4CH2Li in toluene led to the synthesis of a new yttrium aminobenzyl complex [o-Me2NC6H4CH2C(NCy)2]2Y[CH2C6H4-o-NMe2] (7). X-ray diffraction studies showed that in complexes 6 and 7 the donor NMe2 groups of amidinate ligands are not involved in the metal—ligand interaction. Yttrium complexes 4 and 7 exhibited catalytic activity in polymerization of isoprene.