Lithium Di- and Trimethyl Dimolybdenum(II) Complexes with Mo鈥揗o Quadruple Bonds and Bridging Methyl Groups
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- 作者：Natalia Curado ; Mario Carrasco ; Eleuterio 脕lvarez ; Celia Maya ; Riccardo Peloso ; Amor Rodr铆guez ; Joaqu铆n L贸pez-Serrano ; Ernesto Carmona
- 刊名：Journal of the American Chemical Society
- 出版年：2015
- 出版时间：September 30, 2015
- 年：2015
- 卷：137
- 期：38
- 页码：12378-12387
- 全文大小：649K
- ISSN：1520-5126
文摘
New dimolybdenum complexes of composition [Mo2{渭-Me}2Li(S)}(渭-X)(渭-N^N)2] (3a鈥?b>3c), where S = THF or Et2O and N^N represents a bidentate aminopyridinate or amidinate ligand that bridges the quadruply bonded molybdenum atoms, were prepared from the reaction of the appropriate [Mo2{渭-O2CMe}2(渭-N^N)2] precursors and LiMe. For complex 3a, X = MeCO2, while in 3b and 3c, X = Me. Solution NMR studies in C6D6 solvent support formulation of the complexes as contact ion pairs with weak agostic Mo鈥揅H3路路路Li interactions, which were also evidenced by X-ray crystallography in the solid-state structures of the molecules of 3a and 3b. Samples of 3c enriched in 13C (99%) at the metal-bonded methyl sites were also prepared and investigated by NMR spectroscopy employing C6D6 and THF-d8 solvents. Crystallization of 3c from toluene:tetrahydrofuran mixtures provided single crystals of the solvent separated ion pair complex [Li(THF)4] [Mo2(Me)2(渭-Me){渭-HC(NDipp)2}2] (4c), where Dipp stands for 2,6-iPr2C6H3. A computational analysis of the Mo2(渭-Me)2Li core of complexes 3a and 3b has been developed, which is consistent with a small but non-negligible electron-density sharing between the C and Li atoms of the mainly ionic CH3路路路Li interactions.