ニトロシル錯体の合成・構造決定とab initio計算による物性解釈

合成了几种含不同阴离子的硝基五胺铬(III)配合物[Cr(NO)(NH_3)_5]^&lt；2+&Gt；(A)，并对其进行了表征。据报道，含A‘s的化合物的固相颜色与反阴离子的种类有很大关系。然而，所有的晶体结构都没有确定，颜色变化的原因长期以来也不清楚。我们成功地对五种配合物进行了X射线结构测定，发现阳离子的尺寸差异很小。而颜色、最短O(NO)-H(邻阳离子中的NH3)距离(Å)、反射光谱的峰位(Nm)、N-O伸缩振动的波数(cm^&lt；-1&gt；A(PF_6)_2(红色，2.399,579,1693,180)，Acl_2(红橙，2.749,588,1683)，Acl(ClO_4)(棕色，3.127,598,1710)，ACL(PF_6)(棕色，3.258,603,1713)，A(ClO_4)_2(绿色，3.595,623,1728)。5种晶体结构的比较结果表明，O(亚硝基)和H(相邻络合阳离子中的氨)原子之间存在较强的氢键，形成红色的A(PF_6)_2晶体，而没有氢键的A(ClO_4)_2形成绿色晶体A(ClO_4)_2。通过从头计算，在B3LYP/6-31G、★(6-31+G，NO)水平上得到了配合物A在三种不同自旋多重数下的优化结构。配合物在最低自旋多重数(DOBLET)处最稳定，这与A(ClO_4)_2中A的X-射线结构和A(ClO_4)_2的磁性测量(μ_&lt；ff&gt；=1.8BM)相一致。，[Cr(N_2)(NH_3)_5]^&lt；3+&gt；，[Cr(CO)(NH_3)_5]^&lt；3+&gt；，[Cr(O_2)(NH_3)_5]^&lt；3+&gt；，而其中只确定了[Cr(NO)(CN)_5]^&lt；3-&gt；。

Several kinds of nitrosylpentaamminechromium (III) complexes [Cr(NO)(NH_3)_5]^<2+> (A) with different anions were prepared and widely characterized, and it was reported that the colors in the solid states of the compounds containing A's depended very much on the kinds of counter anions. None of the crystal structures, however, were determined, and the cause of the color change was unclear for a long time.We have succeeded in the X-ray structural determination of five kinds of the complexes, and found very little dimensional differences of the cations. However, the color, shortest O(NO)-H(NH_3 in the adjacent cation) distance (Å), peak position of reflection spectra (nm), wave number of N-O stretching vibration (cm^<-1>) of the complex compounds change considerably : A(PF_6)_2 (red, 2.399, 579, 1693, 180), ACl_2 (red-orange, 2.749, 588, 1683), ACl(ClO_4) (brown, 3.127, 598, 1710), ACl(PF_6) (brown, 3.258, 603, 1713), and A(ClO_4)_2 (green, 3.595, 623, 1728). Comparison of the five crystal structures has led to the conclusion that the existence of the strong hydrogen bonds between the O (nitrosyl) and H (ammonia in adjacent complex cations) atoms gives red crystals of A(PF_6)_2, while the absence of hydrogen bonds results in the formation of green crystals of A(ClO_4)_2.Optimized structures of the complex A at three different spin multiplicities, doublet (A2), quartet (A4), and sextet (A6), were obtained by ab initio calculation at B3LYP/6-31G^★(6-31+G for NO) level of theory. The complex was most stable at the lowest spin multiplicity (doublet), which is in harmony with the X-ray structure of A in A(ClO_4)_2 and with the previous magnetic measurement (μ_<eff> = 1.8 BM) of A(ClO_4)_2.Optimized structures of the complexes, [Cr(NO)(CN)_5]^<3->, [Cr(CN)(NH_3)_5]^<2+>, [Cr(N_2)(NH_3)_5]^<3+>, [Cr(CO)(NH_3)_5]^<3+>, [Cr(O_2)(NH_3)_5]^<3+> were obtained, while only the X-ray structure of [Cr(NO)(CN)_5]^<3-> has been determined among them.