Abstract Dichloro[4-(dimethylamino)phenyl]arsine (1) and tris[4-(dimethylamino)phenyl]arsine (2) were synthesized and characterized using single crystal X-ray diffraction studies, NMR spectroscopy, IR spectroscopy and elemental analyses techniques. The X-ray structure analysis of 1 ( P 1 ¯ , triclinic, Z = 4; R1 = 0.0478) revealed two crystallographically independent molecules in the asymmetric part of the unit cell. The average As Cl bond (220.6 p.m.) is found to be slightly longer than that of arsenic(III) chloride (216.1 or 216.2 p.m.), but to be rather similar to that in the orthorhombic modification of chlorobis[2,4,6-tris(trifluoromethyl)phenyl]arsine (219.2 p.m.). Mean As–Caryl (191.7 p.m.) and Caryl–N bond lengths (135.9 p.m.) suggest extended electronic interactions between the dichloroarsanyl group, the π-electron system of the arene ring and the nitrogen lone pair. In both molecules the nitrogen atoms are found in a planar coordination sphere; the sums of bond angles vary only slightly between 359.1° for 1a and 359.9° for 1b. In contrast to these observations, sums of bond angles of 292.7° for 1a and 293.98° for 1b indicate a pyramidal coordination sphere at arsenic. As well, the X-ray structure analysis of 2 ( P 1 ¯ , triclinic, Z = 2; R1 = 0.0347) reveals bond lengths and angles at arsenic (As C 194.9 p.m., C As C 99.3°, As C C 121.3°) as to be expected and obtained for similar compounds such as triphenyl arsine or triphenyl arsine derivatives. The sums of angles at two of the nitrogen atoms amount to values of 353.6° and 356.1° and deviate significantly from the value of the third (348.1°). Hence, two of three dimethylamino groups are found to be almost planar, whereas the third group shows a coordination sphere which has to be classified as an intermediate between trigonal planar and trigonal pyramidal. The molecule shows a high degree of C3 pseudosymmetry; the sum of angles at arsenic amounts to 298.0°. The average Caryl–N bond length (139.0 p.m.) suggests an interaction of the nitrogen lone pair with the π-system of the arene ring but it turns out to be much weaker than in dichloro[4-(dimethylamino)phenyl]arsine (1). Additionally, quantum chemical calculations were performed on several para substituted dichlorophenyl arsine compounds in order to ascertain optimized structural data and to shed some light onto these phenomena. Indeed, the aforementioned shortening of the N–Cipso bond to 135.9 p.m. can only in part be attributed to the well-known electronic interaction between the lone pair at nitrogen and the antibonding π∗ orbitals of the adjacent Cipso–Cortho bonds – on an average, these two distances are significantly elongated by 1.7 p.m. with respect to the standard value (140 p.m.).

中文翻译：

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二氯[4-(二甲氨基)苯基]胂和三[4-(二甲氨基)苯基]胂的晶体结构和量子化学计算

摘要 二氯[4-(二甲氨基)苯基]胂(1)和三[4-(二甲氨基)苯基]胂(2)被合成并使用单晶X射线衍射研究、核磁共振光谱、红外光谱和元素分析技术表征。 . 1 (P 1¯ , 三斜晶系, Z = 4; R1 = 0.0478) 的 X 射线结构分析揭示了晶胞的不对称部分中有两个晶体学独立的分子。发现平均 As Cl 键 (220.6 pm) 比氯化砷 (III) 的平均键长（216.1 或 216.2 pm），但与氯双 [2,4,6-三（三氟甲基）苯基]胂（219.2 pm）。平均 As-Caryl (191.7 pm) 和 Caryl-N 键长 (135.9 pm) 表明二氯砷基之间的电子相互作用扩展，芳烃环和氮孤对电子的π-电子系统。在两个分子中，氮原子都位于平面配位球中；键角总和仅在 1a 的 359.1° 和 1b 的 359.9° 之间略有不同。与这些观察结果相反，1a 为 292.7° 的键角和 1b 为 293.98° 的键角总和表明砷的金字塔配位球。同样，2（P 1 ¯ ，三斜晶系，Z = 2；R1 = 0.0347）的 X 射线结构分析揭示了砷的键长和角度（As C 194.9 pm，C As C 99.3°，As CC 121.3°）预期和获得的类似化合物，如三苯基胂或三苯基胂衍生物。两个氮原子的角度总和为 353.6° 和 356.1°，与第三个 (348.1°) 的值显着不同。因此，发现三个二甲氨基中的两个几乎是平面的，而第三组显示了一个配位球，必须将其归类为三角平面和三角锥体之间的中间体。该分子表现出高度的C3假对称性；砷的角度总和为 298.0°。平均 Caryl-N 键长 (139.0 pm) 表明氮孤对与芳烃环的 π 系统相互作用，但结果证明它比二氯[4-（二甲氨基）苯基]胂弱得多（1 ）。此外，还对几种对位取代的二氯苯基胂化合物进行了量子化学计算，以确定优化的结构数据并阐明这些现象。事实上，前面提到的 N-Cipso 键缩短到 135.9 pm