TY - JOUR
T1 - Ring opening metathesis polymerization of norbornene and derivatives by the triply bonded ditungsten complex na[w2(μ-cl3cl4(thf)2]·(thf)3
AU - Floros, Georgios
AU - Saragas, Nikolaos
AU - Paraskevopoulou, Patrina
AU - Psaroudakis, Nikolaos
AU - Koinis, Spyros
AU - Pitsikalis, Marinos
AU - Hadjichristidis, Nikos
AU - Mertis, Konstantinos
PY - 2012
Y1 - 2012
N2 - In this study, the reactions of the bimetallic compound Na[W2(μ-Cl)3Cl4(THF)2]·(THF)3 (1, (W3W)6+, a'2e'4) with norbornene (NBE) and some of its derivatives (5-X-2-NBE; X = COOH (NBE-COOH), OH (NBE-OH), CN (NBE-CN), COOMe (NBE-COOMe), CH=CH2 (VNBE); norbornadiene (NBD)) are described. Complex 1 contains a tungsten-tungsten triple bond, bearing three halide bridges and two labile THF ligands, in a cisoidal relationship along the metal-metal axis. The complex was found to be a highly efficient room temperature homogeneous and heterogeneous unicomponent initiator for the catalytic ring opening metathesis polymerization (ROMP) of most substrates. NBE provides polynorbornene (PNBE) of high molecular weight (Mw) in high yields, soluble in organic solvents. The reaction proceeds with high cis-stereoselectivity (80%-86% cis), independently of the reaction conditions. Strongly coordinating pendant groups (-COOH, -OH, -CN) deactivate 1, whereas substrates bearing softer ones (-COOMe, -CH=CH2) are quantitatively polymerized. NBD gives quantitatively insoluble PNBD. The polymers have been characterized by 1H, 13C NMR and Size Exclusion Chromatography (SEC). Monitoring the reactions in situ by 1H NMR (1/NBD or NBE) provides direct evidence of the metathetical nature of the polymerization with the observation of the active tungsten alkylidene propagating polymeric chains. Mechanistic aspects of the reactions are discussed.
AB - In this study, the reactions of the bimetallic compound Na[W2(μ-Cl)3Cl4(THF)2]·(THF)3 (1, (W3W)6+, a'2e'4) with norbornene (NBE) and some of its derivatives (5-X-2-NBE; X = COOH (NBE-COOH), OH (NBE-OH), CN (NBE-CN), COOMe (NBE-COOMe), CH=CH2 (VNBE); norbornadiene (NBD)) are described. Complex 1 contains a tungsten-tungsten triple bond, bearing three halide bridges and two labile THF ligands, in a cisoidal relationship along the metal-metal axis. The complex was found to be a highly efficient room temperature homogeneous and heterogeneous unicomponent initiator for the catalytic ring opening metathesis polymerization (ROMP) of most substrates. NBE provides polynorbornene (PNBE) of high molecular weight (Mw) in high yields, soluble in organic solvents. The reaction proceeds with high cis-stereoselectivity (80%-86% cis), independently of the reaction conditions. Strongly coordinating pendant groups (-COOH, -OH, -CN) deactivate 1, whereas substrates bearing softer ones (-COOMe, -CH=CH2) are quantitatively polymerized. NBD gives quantitatively insoluble PNBD. The polymers have been characterized by 1H, 13C NMR and Size Exclusion Chromatography (SEC). Monitoring the reactions in situ by 1H NMR (1/NBD or NBE) provides direct evidence of the metathetical nature of the polymerization with the observation of the active tungsten alkylidene propagating polymeric chains. Mechanistic aspects of the reactions are discussed.
KW - Catalysis
KW - Metal-metal bonds
KW - Norbornenes
KW - Romp
KW - Tungsten
UR - http://www.scopus.com/inward/record.url?scp=84904626303&partnerID=8YFLogxK
U2 - 10.3390/polym4041657
DO - 10.3390/polym4041657
M3 - Article
AN - SCOPUS:84904626303
SN - 2073-4360
VL - 4
SP - 1658
EP - 1673
JO - Polymers
JF - Polymers
IS - 4
ER -