Group 3 Metal Complexes Supported by Tridentate Pyridine- and Thiophene-Linked Bis(naphtholate) Ligands: Synthesis, Structure, and Use in Stereo-selective Ring-Opening Polymerization of Racemic Lactide and beta-Butyrolactone

International audienceScandium, yttrium and lanthanum amido complexes supported by tridentate bis(ortho-silyl-substituted naphtholate)-donor ligands ({ONOSiPh3}2− and {ONOSitBuMe2}2−, donor = 2,6-pyridine; {OSOSiPh3}2−, donor = 2,5-thiophene) have been prepared in high yields (72-96%) by reaction of the corresponding pro-ligand {OZOSiR3}H2 and Ln[N(SiHMe2)2]3(THF)n precursor. The solid-state structures of {ONOSiPh3}La[N(SiHMe2)2](THF) (3), {ONOSitBuMe2}Ln[N(SiHMe2)2](THF) (Ln = Sc, 4; Y, 5) and {OSOSiPh3}Ln[N(SiHMe2)2](THF) (Ln = Sc, 7; La, 9) have been determined by single-crystal X-ray diffraction studies. In all five complexes, the naphtholate rings twist in the same direction from the plane of the pyridine or thiophene linker, to give rise to Cs-symmetric (non crystallographic) structures. Compounds 1-9 are single-site initiators for the ring-opening polymerization (ROP) of racemic lactide (rac-LA) at 20 °C, affording poly(lactides)s (PLAs) with relatively narrow polydispersities and molecular weights in good agreement with calculated values. When carried out in THF, the polymerizations afforded heterotactic-enriched PLAs (Pr up to 0.93), while atactic polymers are formed in toluene. Compounds 1-3 and 7-9, having o-SiPh3 substituents on the naphtholate rings, are also active for the ROP of racemicβ-butyrolactone at 20-50 °C, to form syndiotactic-enriched poly(3-hydroxybutyrate)s (PHBs) (Pr up to 0.87) when using toluene as the solvent, whereas atactic polymers were obtained in THF. The nature of the metal center (Sc, Y, La), the central linker in the ligand framework (pyridine, thiophene), and the ortho-silyl substituent (SiPh3, SiMe2tBu) significantly affect the degree of stereocontrol in those polymerizations

MEASUREMENT OF THE SURFACE FORCES IN A HIGHLY DISPERSED SYSTEMS

Scientifically justified and worked out methods for determining the energy characteristics of the surface of highly-dispersed raw rocks. The values of the energy density of the samples of rocks were calculated. The calculation of the surface activity for the highly-dispersed raw materials of rocks obtained by dispersing was suggested

OPTIMIZATION OF BUILDING MORTAR COMPOSITION CONTAINING HIGHLY DISPERSED COMPOSITES

The influence of the highly dispersed rock components on the properties of building mortars was investigated. It was proved that it is possible to produce building mortars with the use of raw mate­rials resources from Arkhangelsk region through introducing highly dispersed composite based on basalt and silica-containing rocks. Us­ing highly dispersed composites, the efficient building mortar was de­signed