Hepta-coordinate halocarbonyl molybdenum(II) and tungsten(II) complexes as heterogeneous polymerization catalysts
authors Gimenez, J; Nunes, CD; Vaz, PD; Valente, AA; Ferreira, P; Calhorda, MJ
nationality International
journal JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL
author keywords molybdenum; tungsten; MCM-41; polymerization; DAB ligands; hepta-coordination; catalysis
keywords RING-OPENING POLYMERIZATION; MCM-41 MOLECULAR-SIEVES; RAY CRYSTAL-STRUCTURE; 7-COORDINATE MOLYBDENUM(II); METATHESIS POLYMERIZATION; MESOPOROUS MCM-41; NORBORNENE; NORBORNADIENE; DERIVATIVES; NITROGEN
abstract [MX2(CO)(3)(DAB)] (M=Mo, W; X=I, Br) (5-8) complexes bearing the 1,4-diazobutadiene (DAB) ligand RN=C(Ph)-C(Ph)=NR [R=(CH2)(3)Si(OEt)(3)] were immobilized in MCM-41 mesoporous silica. The tethering, stepwise procedure started with treatment of the MCM-41 mesoporous material with a toluene solution of the 1,4-diazobutadiene ligand, under reflux. The molybdenum and tungsten organometallic cores were subsequently introduced into the ligand-silicas by pore volume impregnation of a solution of the complexes [MX2(CO)(3)(NCMe)(2)] (M=Mo, W; X=Br, I). The modified materials were extensively characterized by several techniques, such as FTIR, solid-state MAS and CP MAS NMR (C-13, Si-29), powder XRD, and nitrogen adsorption-desorption measurements. These new materials (containing 2.6-2.9 wt.% Mo or 0.4-0.6 wt.% W) catalyze the ring-opening metathesis polymerization (ROMP) of norbornene (NBE) and norbornadiene at 328 K, in contrast with the very low activity exhibited by the precursor complexes and with their behavior at lower temperature. Addition of AlCl3 as a co-catalyst enhanced the catalytic performance of the material MCM-DAB-MoBr2 (12) in the ROMP of NBE. (c) 2006 Elsevier B.V All rights reserved.
publisher ELSEVIER SCIENCE BV
issn 1381-1169
year published 2006
volume 256
issue 1-2
beginning page 90
ending page 98
digital object identifier (doi) 10.1016/j.molcata.2006.04.023
web of science category Chemistry, Physical
subject category Chemistry
unique article identifier WOS:000240365800012
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