Electron-Deficient Group 4 Metal Complexes of Sulfur-Bridged Dialkoxide Ligands: Synthesis, Structure, and Polymerization Activity Studies
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- 作者：Laurent Lavanant ; Anca Silvestru ; Anne Faucheux ; Loic Toupet ; Richard F. Jordan ; and Jean-Franç ; ois Carpentier
- 刊名：Organometallics
- 出版年：2005
- 出版时间：November 7, 2005
- 年：2005
- 卷：24
- 期：23
- 页码：5604 - 5619
- 全文大小：439K
- 年卷期：v.24,no.23(November 7, 2005)
- ISSN：1520-6041
文摘
Coordination of the sulfur-bridged dialkoxide ligands {OCR2CH2SCH2CR2O}2- ({OSOR}2-,R = Me, p-tolyl) on titanium and zirconium centers has been studied. A variety of complexeshaving one or two ancillary {OSOMe}2- ligands, viz., M(OR)2{OSOMe} (M = Zr, OR = OtBu,4; M = Ti, OR = OiPr, 5), M{OSOMe}2 (M = Zr, 6; Ti, 7), Zr(CH2Ph)2{OSOMe} (8), and MCl2{OSOMe}(THF)n (M = Zr, n = 0, 9; n = 1, 10; n = 2, 11; M = Ti, n = 0, 12; n = 2, 13), havebeen prepared in good yields by alcohol or alkane elimination from {OSOMe}H2 (1a) or bysalt metathesis routes from alkali metal salts M{OSOMe} (M = K, 2a; M = Li, insitu-generated). Coordination of the p-tolyl-substituted ligand by these and other routesproved to be much more difficult, and only TiCl2{OSOtol} (14) was obtained. Crystallographicstudies showed that dichloro complexes 11 and 13 and bis-ligand complex 7 adopt in thesolid state mononuclear structures with no bonding interaction between the sulfur atomand metal centers. The crystal structure of 4 contains two independent dinuclear moleculesthat interconvert formally by exchange of tBuO and chelating {OSOMe} ligands betweenterminal and bridging modes and feature normal Zr-S bonds. NMR data for 4 and 12 areconsistent with dinuclear C1-symmetric structures in toluene solution, while dibenzyl complex8 has a mononuclear structure. Variable-temperature NMR studies combined with line-shape analysis established that the fluxional behavior of 8 results from the exchange between
2/ 1-benzyl ligands (
H
= 10.6 ± 1 kcal·mol-1; S = -2.7 ± 2 cal·mol-1·K-1). Abstractionof one benzyl ligand of 4 with 1 equiv of [Ph3C][B(C6F5)4] or B(C6F5)3 proceeds cleanly togive the corresponding thermally unstable, ionic species [Zr(CH2Ph){OSOMe}]+[BX(C6F5)3]-(X = C6F5, 15; CH2Ph, 16), which have been characterized by 1H, 11B, 13C, and 19FNMR spectroscopy and show Cs symmetry in solution. The decomposition of 16 proceeds viaC6F5/benzyl exchange from Zr to B and generates the stable [Zr(C6F5){OSOMe}]+[6-(PhCH2)B(CH2Ph)(C6F5)2]- (17). Cationic species in situ-generated from Zr chlorocomplexes and MAO are highly active but very unstable ethylene polymerization catalysts.
2/ 1-benzyl ligands (H = 10.6 ± 1 kcal·mol-1; S = -2.7 ± 2 cal·mol-1·K-1). Abstractionof one benzyl ligand of 4 with 1 equiv of [Ph3C][B(C6F5)4] or B(C6F5)3 proceeds cleanly togive the corresponding thermally unstable, ionic species [Zr(CH2Ph){OSOMe}]+[BX(C6F5)3]-(X = C6F5, 15; CH2Ph, 16), which have been characterized by 1H, 11B, 13C, and 19FNMR spectroscopy and show Cs symmetry in solution. The decomposition of 16 proceeds viaC6F5/benzyl exchange from Zr to B and generates the stable [Zr(C6F5){OSOMe}]+[6-(PhCH2)B(CH2Ph)(C6F5)2]- (17). Cationic species in situ-generated from Zr chlorocomplexes and MAO are highly active but very unstable ethylene polymerization catalysts.