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Thiophene-NPN Ligand Supported Rare-Earth Metal Bis(alkyl) Complexes. Synthesis and Catalysis toward Highly trans-1,4 Selective Polymerization of Butadiene.
- Source :
-
Organometallics . Dec2008, Vol. 27 Issue 24, p6531-6538. 8p. - Publication Year :
- 2008
-
Abstract
- A series of new rare-earth metal bis(alkyl) complexes [L1â3Ln(CH2SiMe3)2(THF)n] (L1= MeC4H2SCH2NC6H4(Ph)2Pî»NC6H2Me3-2,4,6: Ln = Sc, n= 1 (1a); Ln = Lu, n= 1 (1b); L2= MeC4H2SCH2NC6H4(Ph)2Pî»NC6H3Et2-2,6: Ln = Sc, n= 1 (2a); Ln = Lu, n= 1 (2b); Ln = Y, n= 1 (2c); L3= MeC4H2SCH2NC6H4(Ph)2Pî»NC6H3iPr2-2,6: Ln = Sc, n= 0 (3a)) and L4Sc(CH2SiMe3)2(THF) (4a) (L4= C6H5CH2NC6H4(Ph)2Pî»NC6H3Et2-2,6) have been prepared by reaction of rare-earth metal tris(alkyl)s with the corresponding HL1â4ligands via alkane elimination. Complexes 1a, 1b, 2aâ2c, and 4aare monomeric with a coordinating THF molecule. Each metal ion is coordinated by a NPN ligand, two trans-located alkyl groups, and a THF molecule, forming a distorted trigonal-bipyramidal geometry. Complex 3ais THF-free, adopting a distorted tetrahedron geometry. In combination with AlR3and borate, these complexes have shown medium activity and good trans-1,4 selectivity for the polymerization of butadiene. The resultant polymer has moderate molecular weight (Mn= 10â000â18â000) with narrow molecular weight distribution (Mw/Mn< 1.6) and trans-1,4 regularity varying from 49.2% up to 91.3%. The catalyst performances are strongly dependent on the orthosubstituent of the N-aryl ring and the presence of the thiophene moiety of the ligands and the type of aluminum alkyls and the lanthanide metal used. The scandium complex 2adisplays the highest trans-1,4 selectivity. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 02767333
- Volume :
- 27
- Issue :
- 24
- Database :
- Academic Search Index
- Journal :
- Organometallics
- Publication Type :
- Academic Journal
- Accession number :
- 35912032
- Full Text :
- https://doi.org/10.1021/om800660j