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首页> 美国政府科技报告 >Preparation and Reactions of Tantalum Alkylidene Complexes Containing Bulky Phenoxide or Thiolate Ligands. Controlling Ring-Opening Metathesis Polymerization Activity and Mechanism Through Choice of Anionic Ligand
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Preparation and Reactions of Tantalum Alkylidene Complexes Containing Bulky Phenoxide or Thiolate Ligands. Controlling Ring-Opening Metathesis Polymerization Activity and Mechanism Through Choice of Anionic Ligand

机译：含大量酚盐或硫醇盐配体的亚钽基亚砜配合物的制备及反应。通过选择阴离子配体控制开环易位聚合活性及机理

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We have reported a variety of high oxidation state, electronically unsaturated alkylidyne and (more recently) alkylidene complexes of tungsten and molybdenum that contain bulky alkoxide ligands. We decided to test whether some of the principles we had uncovered in tungsten and molybdenum chemistry could be used to advantage in tantalum chemistry, especially since Ta(CH1Bu)(THF)2Cl3 can be prepared in high yield in two relatively easy steps from TaCl. Tantalum alkylidene complexes have been useful for outlining the principles of olefin metathesis, but none has been long-lived enough to be practical for metathesis of ordinary olefins. Therefore we felt we had a better chance of preparing reagents for Wittig-like reactions or catalysts for the controlled ring-opening of strained cyclic olefins. We also wanted to compare various other supporting ligand systems with alkoxides in order to uncover major differences that might be useful in controlling metathesis activity. In this paper we report the preparation and a comparison of the reactivity of complexes of the type Ta(CH1Bu)X3(THF) where X is a bulky phenoxide or phenyl thiolate ligand. We have found that differences between phenoxide and phenyl thiolate systems are dramatic; the choice determines both activity and mechanism. Yellow Ta(CH1Bu)(DIPP)3(THF) (1; equation 1; DIPP = 2,6-diisopropylphenoxide) is formed in high yield upon treating isolated Ta(CH1Bu)(THF)2Cl3 with 3 eq of LiDIPP. It also can be prepared from Ta(CH1Bu)(THF)2Cl3 that has been generated in situ in ether by addition of excess THF to Ta(CH2(t)Bu)2Cl3. (aw)

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