The Study of Lewis Acidity and Catalytic Activity of Zero Valent Tungsten Complexes

• Main Authors: ZiFang Shi, 施子方
• Other Authors: ShuChun Yu
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/56008958472923074587

碩士 === 國立中正大學 === 化學研究所 === 87 === The treatment of C3v ligands, AB3（A = HOC，MeC，N，P；B = pyridine N，CH2PPh2）with W(CO)6 in refluxing CH3CN gives complexes of the type, AB3W(CO)3 (A = C, N, P ; B = N, P ). The AB3 ligand coordinates to the W matel center via three nitrogen or phosphine atoms at facial-position of the octahedron. The complexes, HOC(2-py)3W(CO)3（5）, P(2-py-5-Me)3W(CO)3（6）and H3CC(CH2PPh)3W(CO)3（11）, are syn- thesized by the reactions of HOC(2-py)3, P(2-py-5-Me)3 and H3CC(CH2PPh)3 with W(CO)6 at reflux in CH3CN. Substitution of the CO ligands of complex（5）by one or two equiv. of NOBF4 lead to the formation of singly and doubiy charged complexes, [HOC(2-py)3W(CO)3-n(NO)n](BF4)n (n= 1, 2). The facile loss of CO in [HOC(2-py)3W(CO)(NO)2](BF4)2（8）generates the 16-electron speces [HOC(2-py)3W(NO)2](BF4)2. The 1H-NMR chemical shift difference of crotonaldehyde before and after coordinated to Lewis acid can be used as a qualitative assessment of relative Lewis acidity. The acidity of the tungsten species, [HOC(2-py)3W(NO)2](BF4)2, is found to be comparable to those of BF3and AlCl3. Due to the methyl group on the C-5 of the pyridine ring, only the singly charged complexe, [P(2-py-5-Me)3W(CO)2(NO)](BF4), can be isolated. Treatments of HOC(2- py)3W(CO)3 with one or two equiv. of NOBF4 fail to generate the singlyor doubly charged complexes because of the phosphine oxidation by NO +. With a high Lewis acid loading（catalyst / solvent = 20 mg / 0.5 mL）, the Mukaiyama reaction of TMSCNand Benzaldehyde can be catalyzed by Lewis acid, [HOC(2-py)3W(NO)2](BF4)2.