Oxalate-bridged complexes of dimolybdenum and ditungsten supported by pivalate ligands: ((t)BuCO(2))(3)M(2)(mu-O(2)CCO(2))M(2)(O(2)C(t)Bu)(3). Correlation of the solid-state, molecular, and electronic structures with Raman, resonance Raman, and electronic spectral data.
Oxalate-bridged complexes of dimolybdenum and ditungsten supported by pivalate ligands: ((t)BuCO(2))(3)M(2)(mu-O(2)CCO(2))M(2)(O(2)C(t)Bu)(3). Correlation of the solid-state, molecular, and electronic structures with Raman, resonance Raman, and electronic spectral data.
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新戊酸配体支持的二钼和二钨的草酸桥配合物：((t)BuCO(2))(3)M(2)(mu-O(2)CCO(2))M(2)(O(2)
DOI：
10.1021/ja011786j
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发表时间：
2002
影响因子：
15
通讯作者：
J. Zaleski
中科院分区：
文献类型：
--
作者：
B. Bursten;M. Chisholm;R. Clark;S. Firth;C. Hadad;A. Macintosh;P. Wilson;P. Woodward;J. Zaleski
化合物（（t）BuCO（2））（3）M（2）（μ-O（2）CCO（2））M（2）（O（2）C（t）Bu）（3）（M（4）OXA）（其中M = Mo或W）通过粉末X射线衍射数据分析显示具有扩展的晶格结构，其中来自一个M（4）OXA分子的草酸盐和新戊酸盐配体的氧原子与相邻分子的金属原子连接。拉曼，共振拉曼，电子吸收（2-325 K，在2-MeTHF），和发射光谱，连同相应的光谱的μ-O（2）（13）C（13）CO（2）同位素。为了帮助指认，还记录了K（2）C（2）O（4）·H（2）O和K（2）（13）C（2）O（4）·H（2）O的拉曼光谱。可见光区的电子光谱是由强烈的，完全允许MLCT过渡，M（2）δ草酸盐π *，这表明明显的热致变色和广泛的电子振动进展与草酸盐配体在低温下。随着激发进入这些电荷转移带，对于归属于草酸盐nu（1）（a（g））模式的拉曼带，以及在较小程度上归属于nu（2）（a（g））模式的拉曼带，观察到强的共振增强。模型化合物（HCO（2））（3）M（2）（mu-O（2）CCO（2））M（2）（O（2）CH）（3）的电子结构计算（梯度校正和时间依赖性）与高斯98和ADF 2000包，预测平面草酸盐D（2 h）构型是有利的，这使M（2）δ与草酸盐π * 背键最大化，并且表明围绕草酸根C-C键旋转的低势垒（<8 kcal mol（-1））。
The compounds ((t)BuCO(2))(3)M(2)(mu-O(2)CCO(2))M(2)(O(2)C(t)Bu)(3) (M(4)OXA), where M = Mo or W, are shown by analysis of powder X-ray diffraction data to have extended lattice structures wherein oxygen atoms from the oxalate and pivalate ligands of one M(4)OXA molecule are linked to metal atoms of neighboring molecules. Raman, resonance Raman, electronic absorption (2-325 K in 2-MeTHF), and emission spectra are reported, together with corresponding spectra of the mu-O(2)(13)C(13)CO(2) isotopomers. To aid in the assignment, the Raman spectra of K(2)C(2)O(4).H(2)O and K(2)(13)C(2)O(4).H(2)O have also been recorded. The visible region of the electronic spectra is dominated by intense, fully allowed MLCT transitions, M(2) delta to oxalate pi*, which show pronounced thermochromism and extensive vibronic progressions associated with the oxalate ligand at low temperatures. With excitation into these charge-transfer bands, strong resonance enhancement is seen for Raman bands assigned to the oxalate nu(1)(a(g)) and, to a lesser extent, nu(2)(a(g)) modes. Electronic structure calculations for the model compounds (HCO(2))(3)M(2)(mu-O(2)CCO(2))M(2)(O(2)CH)(3), employing density functional theory (gradient corrected and time-dependent) with the Gaussian 98 and ADF 2000 packages, predict the planar oxalate D(2h) configuration to be favored, which maximizes M(2) delta to oxalate pi* back-bonding, and indicate low barriers (<8 kcal mol(-1)) to rotation about the oxalate C-C bonds.