241489-02-1Relevant articles and documents
Synthesis of cis-dichloride complexes of Group 6 transition metals bearing alkyne and chalcogen-bridged chelating bis(aryloxo) ligands as catalyst precursors for ring-opening metathesis polymerization
Takashima, Yoshinori,Nakayama, Yuushou,Yasuda, Hajime,Nakamura, Akira,Harada, Akira
, p. 74 - 82 (2002)
Dichlorotungsten complexes, W(η2-RC≡CR)(R2′tbp)Cl2 (1-Cs: R = Ph, R2′tbp = 2,2′-thiobis(4-methyl-6-tert-butylphenoxo) (tBu2tbp); 2-Cs: R = Et, R2′tbp = 2,2′-thiobis(4,6-dimethylphenoxo) (Me2tbp); 3-C1: R = Et, R2′tbp = tBu2tbp; 4-C1: R = SiMe3, R2′tbp = tBu2tbp), 2,2′-tellurobis(4-methyl-6-tert-butylphenol). The Cs symmetric complex 1-Cs isomerized to the C1 isomer 1-C1 in solution at room temperature. The molecular structures of 1-C1, 3-C1, 5-C1 and 6-Cs were determined to reveal their six coordinated pseudo-octahedral geometry by X-ray crystallography. The M-C(alkyne) bond distances in the Cs complexes 2-Cs and 6-Cs ranging from 2.014(7) to 2.035(6) A? are apparently shorter than those in the corresponding C1 complexes 1-C1, 3-C1 and 5-C1 ranging from 2.04(1) to 2.09(1) A?. In accordance with the structural data, the resonances of the alkyne carbons of the Cs complexes in 13C-NMR spectra appeared at 233.1-244.5 ppm, typical for four electron donating alkynes, and those of the C1 complexes appeared at 198.6-215.4 ppm, typical for two electron donating alkynes. The substituent effects of the ligands on the catalytic behavior of the complexes for the ring-opening metathesis polymerization of norbornene derivatives were studied in the presence of Mg(CH2SiMe3)2 as a cocatalyst. The catalytic activities of the sulfur-bridged complexes tend to increase with increasing the bulkiness of acetylene ligand. The tellurium-bridged complex 5-C1 was found to be remarkably more active than the corresponding sulfur-bridged complexes.
