Multinuclear NMR studies of molybdenum and tungsten carbonyl isocyanide complexes
Multinuclear NMR studies of molybdenum and tungsten carbonyl isocyanide complexes
复制标题
钼和羰基异氰化钨配合物的多核核磁共振研究
DOI：
10.1021/ic00314a016
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发表时间：
1989
影响因子：
4.6
通讯作者：
W. Maley
中科院分区：
文献类型：
--
作者：
M. Minelli;W. Maley
合成了M（CO）_n（CNR）_n（= 0-6）配合物（M= Mo，W; R= 2，6-二甲基苯基，叔丁基，环己基，异丙基）.根据异氰化物配体的R基团，M（CO）6中的四个或六个羰基可以被取代。研究了这些配合物中原子的NMR性质。用95 Mo或183 W NMR观察到的金属中心表明，随着羰基配体被异腈配体取代，金属中心的去屏蔽作用增强。95 Mo NMR是鉴定这些化合物混合物的极好工具，并可用于监测反应。通过14 N NMR光谱法观察到的异氰化物配体中的氮在异氰化物配位到金属中心时变得更加去屏蔽，但是随着进一步的取代，氮再次变得更加屏蔽。异氰化物配体反式到羰基配体的14 N化学位移与四取代络合物中异氰化物配体反式到另一异氰化物配体的化学位移略有不同。CNR碳的13 C NMR信号随着络合物中异氰化物数量的增加而变得更加去屏蔽。与羰基反式的CNR碳比与异氰化物反式的CNR碳更受保护。随着异氰化物对羰基的连续取代，紫外可见光区的电子吸收带向更长的波长移动;即化合物的颜色从白色变为橙红色。
M (CO) j_ „(CNR)„(= 0-6) complexes (M= Mo, W; R= 2, 6-dimethylphenyl, iert-butyl, cyclohexyl, isopropyl) have been synthesized. Depending on the R group of the isocyanide ligand, four or six carbonyl groups inM (CO) 6 can be replaced. The NMR properties of the atoms in these complexes have been studied. The metal centers, observed by 95Mo or 183W NMR, show increased deshieldingwith the substitution of carbonylligands by isocyanide ligands. 95Mo NMR serves as an excellent tool for the identification of mixtures of these compounds and was useful to monitor the reactions. The nitrogen in the isocyanide ligand, observed by 14N NMR spectroscopy, gets more deshielded when the isocyanide is coordinated to the metal center, but with further substitution, the nitrogen becomes more shielded again. The 14N chemical shift of an isocyanide ligand trans to a carbonyl ligand differs slightly from the chemical shift of an isocyanide ligand trans to another isocyanide ligand in the tetrasubstituted complex. The 13C NMR signal of the CNR carbon becomes more deshielded with an increasing number of isocyanides present in the complex. CNR carbons trans to carbonyl groups are more shielded than CNR carbons trans to isocyanides. With the successive substitution of carbonyl groups by isocyanides, the electronic absorption bands in the UV-vis region shift toward longer wavelengths; ie, the color of the compounds changes from white to orange-red.