Department of Chemistry and Biochemistry, University of North Carolina at Wilmington, Wilmington, North Carolina 28403, USA.
Inorg Chem. 2009 Dec 21;48(24):11724-33. doi: 10.1021/ic9017618.
A dimercury(I) 18-crown-6 complex is isolated, and its possible role in the hydrothermal preparation of the mercuric nitrite complex is discussed. The reported structures are of Hg(2)(18-crown-6)(2)(H(2)O)(2)(2) (1), monoclinic, C2/c, a = 21.0345(9), b = 12.1565(5), c = 16.8010(7) A, beta = 113.2000(10) degrees , V = 3948.7(3) A(3), Z = 16, R = 0.0230; Hg(18-crown-6)(2) (2), monoclinic, P2(1)/c, a = 8.027(5), b = 14.437(9), c = 7.827(5) A, beta = 95.165(11) degrees , V = 905.6(10) A(3), Z = 2, R = 0.0175. The complex cation in compound 1 consists of a mercurous dimer exhibiting a Hg-Hg bond length of 2.524(2) A. Non-bonding interactions between adjacent crown ether macrocycles across the Hg-Hg bond result in large variations in mercury to oxygen distances within equatorial coordination sites. At low pH compound 1 is proposed to be preferentially formed under hydrothermal conditions affording compound 2 upon disproportionation. Nitrite ions ligate via a unidentate nitrito (cis to metal) coordination mode as interpreted using vibrational (infrared) spectroscopy. The conformation adopted by 18-crown-6 in compounds 1 and 2 is closely related to a D(3d) conformation as evidenced by X-ray crystallography. Band splitting readily observed in vibrational spectra of the metal free crown ether, attributed to vibrational modes of oxyethylene fragments, is absent in spectra of 1 and 2 confirming a regular D(3d) macrocyclic orientation. Short Hg-O bonds observed for axially coordinated water molecules in 1 and coordinated nitrite ligands in 2, illustrate the prevalence of relativistic effects commonly observed in mercury complexes.
分离得到一个二汞（I）18-冠-6 配合物，并讨论了其在亚硝汞酸配合物的水热合成中的可能作用。报道的结构为 Hg(2)(18-冠-6)(2)(H(2)O)(2)(2)（1），单斜晶系，C2/c，a = 21.0345(9)，b = 12.1565(5)，c = 16.8010(7) A，β = 113.2000(10)°，V = 3948.7(3) A(3)，Z = 16，R = 0.0230；Hg(18-冠-6)(2)（2），单斜晶系，P2(1)/c，a = 8.027(5)，b = 14.437(9)，c = 7.827(5) A，β = 95.165(11)°，V = 905.6(10) A(3)，Z = 2，R = 0.0175。配合物 1 中的配合阳离子由一个二价亚汞组成，其 Hg-Hg 键长为 2.524(2) A。相邻冠醚大环之间的非键相互作用导致赤道配位位点处的汞氧距离发生很大变化。在低 pH 值下，配合物 1 被认为是在水热条件下优先形成的，然后通过歧化反应生成配合物 2。亚硝酸根离子通过一个单齿的硝酰配位模式（顺式配位）与金属配位，这可以通过振动（红外）光谱来解释。18-冠-6 在配合物 1 和 2 中采用的构象与 D(3d)构象密切相关，这可以通过 X 射线晶体学得到证明。在无金属冠醚的振动光谱中容易观察到的带分裂，归因于氧亚乙基片段的振动模式，在 1 和 2 的光谱中不存在，这证实了规则的 D(3d)大环取向。在 1 中轴向配位的水分子和 2 中配位的亚硝酸根配体中观察到的短 Hg-O 键表明，在汞配合物中常见的相对论效应普遍存在。
