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

制备了几种不同阴离子的亚硝基五胺铬（III）配合物[Cr(NO)(NH_3)_5]^<2+> (A)，并对其进行了广泛的表征，报道了含A的化合物的固相颜色在很大程度上取决于反阴离子的种类。然而，没有一种晶体结构被确定，颜色变化的原因在很长一段时间内都不清楚。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。然而，配合物的颜色、邻阳离子O(NO)-H（NH_3）的最短距离（Å）、反射光谱峰位置（nm）、N-O伸缩振动波数（cm^<-1>）变化较大：A(PF_6)_2（红色，2.399,579,1693,180）、ACl_2（红橙色，2.749,588,1683）、ACl(ClO_4)（棕色，3.127,598,1710）、ACl(PF_6)（棕色，3.258,603,1713）和A(ClO_4)_2（绿色，3.595,623,1728）。通过对五种晶体结构的比较，得出了O（亚硝基）和H（氨）原子之间存在强氢键形成红色的A(PF_6)_2晶体，而没有氢键形成绿色的A(ClO_4)_2晶体的结论。在B3LYP/6-31G^★（6-31+G为NO）理论水平上，通过从头计算得到了络合物A在三种不同自旋倍数下的优化结构，即双重态（A2）、四重态（A4）和六重态（A6）。该配合物在最低自旋多重态（双重态）下最稳定，这与A(ClO_4)_2中A的x射线结构和A(ClO_4)_2的磁性测量结果（μ_<eff> = 1.8 BM）一致。优化结构的配合物,[Cr (NO) (CN) _5] ^ < 3 - >, (Cr (CN) (NH_3) _5) ^ < 2 + >, (Cr(甲烷)(NH_3) _5) ^ < 3 + >, (Cr(有限公司)(NH_3) _5) ^ < 3 + >, (Cr(成分)(NH_3) _5) ^ < 3 + >了,只有x射线结构(Cr (NO) (CN) _5) ^ < 3 - >已确定。

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.