Synthesis of Tungsten Oxo Alkylidene Biphenolate Complexes and Ring-Opening Metathesis Polymerization of Norbornenes and Norbornadienes
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https://figshare.com/articles/dataset/Synthesis_of_Tungsten_Oxo_Alkylidene_Biphenolate_Complexes_and_Ring-Opening_Metathesis_Polymerization_of_Norbornenes_and_Norbornadienes/9252773
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资源简介：
We
have synthesized and characterized tungsten oxo alkylidene biphenolate
complexes with the formulas W(O)(CHR)(rac-biphenolate)(PPhMe2) and (R,S)-[W(μ-O)(CHR)(biphenolate)]2 (R = CMe2Ph; biphenolate = L1 or L2 in the text). They behave as initiators for the stereoselective
(cis,isotactic) polymerization of 2,3-dicarbomethoxy-5-norbornadiene
and eight enantiomerically pure 5-substituted norbornenes with a cis,isotactic precision of 95–98% in most cases.
The active initiators are 14e W(O)(CHR)(biphenolate) complexes, which
are formed through either dissociation of PPhMe2 from the
phosphine adducts or scission of the heterochiral dimer. Addition
of B(C6F5)3 (one per W) to (R,S)-[W(μ-O)(CHR)(L1)]2 led
to formation of what we propose to be monomeric W[OB(C6F5)3](CHR)(L1) in equilibrium
with B(C6F5)3 and (R,S)-[W(μ-O)(CHR)(L1)]2. This mixture
decomposed over a period of 1–2 h, was much slower to initiate
polymerization than (R,S)-[W(μ-O)(CHR)(L1)]2, and was much less stereoselective. Polymerization
of five of the monomers with the imido alkyidene initiator, W(N-2,6-Me2C6H3)(CHCMe2Ph)(rac-L1), gave virtually identical results compared to the
results obtained with oxo complexes.
创建时间：
2019-08-05
