Synthesis and Reactivity of Multiply-Bonded Ditungsten Complexes

• Main Author: 林展民
• Other Authors: 蔡易州
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/95087476236012851597

碩士 === 國立清華大學 === 化學系 === 101 === The cation exchange between [Li(THF)4]{W2Cl4[μ-η2-HC(N-2,6-iPr2 C6H3)2]2} (1a) and KI in the presence of 18-crown-6 ether affords [K(18-c-6)]{W2Cl4[μ-η2-HC(N-2,6-iPr2C6H3)2]2} (2). Subsequent reduction of 2 gives the quadruply-bonded ditungsten(II) complex W2H2[μ-K(OEt2)]2[μ-η2-HC(N-2,6-iPr2C6H3)(N-2-iPr2-6-CH(1-CH2)CH3-C6H3)]2 (3), which is arisen from double intramolecular C-H bond activation and features two potassium counter-cations. Dissolution of 2 in THF affords W2(μ-H)2(THF)[μ-η2-HC(N-2,6-iPr2C6H3)(N-2-iPr2-6-CH(1 -CH2)CH3-C6H3)]2 (1e), which displays a gem conformation with two hydrido ligands unsymmetrically bridging two tungsten centers. Complexes 1e and 3 are chemically interconvertible. Reduction of 1e by KC8 gives back to 3. Treatment of 1e or 3 with 2 equiv of mesityl nitrile yields W2(μ-H)2 [1-NC(Mes)]2[μ-η2-HC(N-2,6-iPr2C6H3)(N-2-iPr2-6-CH(1-CH2)CH3 -C6H3)]2 (4), where the nitrogen donor atom of mesityl nitrile coordinates tungsten centers. Reaction of 1e or 3 with 2 equiv of diphenylzinc generates the hetero tetranuclear complex W2H2[μ-ZnC6H5]2[μ-η2-HC(N- 2,6-iPr2C6H3)(N-2-iPr2-6-CH(1-CH2)CH3-C6H3)]2 (5), whereby phenyl zinc bridges two tungsten atoms. Addition of 1 equiv of AlEt2Cl to 3 yields [K(OEt2)4]W2H2(μ-AlEt2)[μ-η2-HC(N-2,6-iPr2C6H3)(N-2-iPr2-6-CH (1-CH2)CH3-C6H3)]2 (6), whereby diethyl aluminum group bridges two tungsten centers. Reactions of WCl4(DME) with 2 equiv of lithiated amidinate Li[HC(N-2,6-Et2C6H3)2] in different time periods afford two mononuclear complexes W[η3-Cl2Li(OEt2)N(2,6-Et2C6H3)C(H)N(2,6- Et2C6H3)]2 (7) and WCl2[η2-HC(N-2,6-Et2C6H3)2]2 (8). Complex 8 can be thought of LiCl extrusion from 7. Upon treatment of 8 with 1 equiv of WCl4(DME), the mononuclear penta-valent tungsten complex WCl3[η2- HC(N-2,6-Et2C6H3)2]2 (9) is obtained. On the other hand, the reaction of WCl3(DME) with 1 equiv of Li[HC(N-2,6-Et2C6H3)2] affords the dinuclear “-ate” complex W2Cl2 (μ-O)(μ-Cl)[η2-ClLi(OEt2)2Cl][η2-HC(N-2,6-Et2C6H3)2] [μ-η2-HC(N- 2,6-Et2C6H3)2] (10), which features an oxygen atom bridging two tungsten centers. Subsequent reduction of 10 gives the methylidyne complex W2(μ-Cl)(μ-CH)(1-N-2,6-Et2C6H3)2[η2-HC(N-2,6-Et2C6H3)2]2 (11) and the tetranuclear complex W4(μ-Cl)4[μ-η2-HC(N-2,6-Et2C6H3)2]4 (12). Complex 11 is formed through a three-atom 6e reductive cleavage of the amidinate to give a bis-terminal imido and bridging methylidyne ditungsten complex. Complex 12 is the quadruply-bonded complex, which has four tungsten(II) centers with four chloride atoms bridging to the tungsten centers. Further reaction of 10 with 1 equiv of Li[HC(N-2,6-Et2C6H3)2] affords W2Cl2(μ-O)(μ-Cl)[η2-HC(N-2,6-Et2C6 H3)2]2[μ-η2-HC(N-2,6-Et2C6H3)2] (13). Subsequent reduction of 13 also induces the cleavage of the amidinato ligand to give the methylidyne complex W2[μ-O(KOEt2)](μ-CH)(1-N-2,6-Et2C6H3)2[η2-HC(N-2,6-Et2 C6H3)2]2 (14).