Huang Deguang, Zhang Xiaofeng, McInnes Eric J L, McMaster Jonathan, Blake Alexander J, Davies E Stephen, Wolowska Joanna, Wilson Claire, Schröder Martin
School of Chemistry, University of Nottingham, Nottingham NG9 2RD, UK.
Inorg Chem. 2008 Nov 3;47(21):9919-29. doi: 10.1021/ic8010037. Epub 2008 Oct 2.
The mononuclear macrocyclic complexes [Au(I)([9]aneS2O)2]BF4 x MeCN 1a, Au(II)([9]aneS2O)22 x 2 MeCN 2a, and Au(III)([9]aneS2O)26(H5O2)(H3O)2 3 ([9]aneS2O = 1-oxa-4,7-dithiacyclononane) have been prepared and structurally characterized by single crystal X-ray crystallography. The oxidation of Au([9]aneS2O)2 to Au([9]aneS2O)2 involves a significant reorganization of the co-ordination sphere from a distorted tetrahedral geometry in Au([9]aneS2O)2 [Au-S 2.3363(12), 2.3877(12), 2.6630(11), 2.7597(13) A] to a distorted square-planar co-ordination geometry in Au([9]aneS2O)2. The O-donors in Au([9]aneS2O)2 occupy the axial positions about the Au(II) center [Au...O = 2.718(2) A] with the S-donors occupying the equatorial plane [Au-S 2.428(8) and 2.484(8) A]. Au([9]aneS2O)2 shows a co-ordination sphere similar to that of Au([9]aneS2O)2 but with significantly shorter axial Au...O interactions [2.688(2) A] and equatorial Au-S bond lengths [2.340(4) and 2.355(6) A]. The cyclic voltammogram of 1 in MeCN (0.2 M NBu4PF6, 253 K) at a scan rate of 100 mV s(-1) shows an oxidation process at E(p)(a) = +0.74 V and a reduction process at E(p)(c) = +0.41 V versus Fc(+)/Fc assigned to the two-electron Au(III/I) couple and a second reduction process at E(p)(c) = +0.19 V assigned to the Au(I/0) couple. This electrochemical assignment is confirmed by coulometric and UV-vis spectroelectrochemical measurements. Multifrequency EPR studies of the mononuclear Au(II) complex Au([9]aneS2O)2 in a fluid solution at X-band and as frozen solutions at L-, S-, X-, K-, and Q-band reveal g(iso) = 2.0182 and A(iso) = -44 x 10(-4) cm(-1); g(xx) = 2.010, g(yy) = 2.006, g(zz) = 2.037; A(xx) = -47 x 10(-4) cm(-1), A(yy) = -47 x 10(-4) cm(-1), A(zz) = -47 x 10(-4) cm(-1); P(xx) = -18 x 10(-4) cm(-1), P(yy) = -10 x 10(-4) cm(-1), and P(zz) = 28 x 10(-4) cm(-1). DFT calculations predict a singly occupied molecular orbital (SOMO) with 27.2% Au 5d(xy) character, consistent with the upper limit derived from the uncertainties in the (197)Au hyperfine parameters. Comparison with Au([9]aneS3)2 reveals that the nuclear quadrupole parameters, P(ii) (i = x, y, z) are very sensitive to the nature of the Au(II) co-ordination sphere in these macrocyclic complexes. The observed geometries and bond lengths for the cations Au([9]aneS2O)2 reflect the preferred stereochemistries of d(10), d(9), and d(8) metal ions, respectively, with the higher oxidation state centers being generated at higher anodic potentials compared to the related complexes Au([9]aneS3)2.
单核大环配合物[Au(I)([9]aneS2O)2]BF4·MeCN 1a、Au(II)([9]aneS2O)22·2MeCN 2a和Au(III)([9]aneS2O)26(H5O2)(H3O)2 3（[9]aneS2O = 1-氧杂-4,7-二硫杂环壬烷）已通过单晶X射线晶体学进行了制备和结构表征。Au([9]aneS2O)2氧化为Au([9]aneS2O)2涉及配位球从Au([9]aneS2O)2中扭曲的四面体几何结构[Au-S 2.3363(12)、2.3877(12)、2.6630(11)、2.7597(13) Å]到Au([9]aneS2O)2中扭曲的平面正方形配位几何结构的显著重组。Au([9]aneS2O)2中的O供体占据Au(II)中心周围的轴向位置[Au...O = 2.718(2) Å]，S供体占据赤道平面[Au-S 2.428(8)和2.484(8) Å]。Au([9]aneS2O)2显示出与Au([9]aneS2O)2类似的配位球，但轴向Au...O相互作用明显更短[2.688(2) Å]，赤道Au-S键长[2.340(4)和2.355(6) Å]。1在MeCN（0.2 M NBu4PF6，253 K）中以100 mV s(-1)的扫描速率的循环伏安图显示相对于Fc(+)/Fc，在E(p)(a) = +0.74 V处有一个氧化过程，在E(p)(c) = +0.41 V处有一个还原过程，这归因于双电子Au(III/I)偶合，在E(p)(c) = +0.19 V处有第二个还原过程，归因于Au(I/0)偶合。这种电化学归属通过库仑法和紫外可见光谱电化学测量得到证实。在X波段的流体溶液中以及在L-、S-、X-、K-和Q波段的冷冻溶液中对单核Au(II)配合物Au([9]aneS2O)2进行的多频EPR研究表明，g(iso) = 2.0182，A(iso) = -44×10(-4) cm(-1)；g(xx) = 2.010，g(yy) = 2.006，g(zz) = 2.037；A(xx) = -47×10(-4) cm(-1)，A(yy) = -47×10(-4) cm(-1)，A(zz) = -47×10(-4) cm(-1)；P(xx) = -18×10(-4) cm(-1)，P(yy) = -10×10(-4) cm(-1)，P(zz) = 28×10(-4) cm(-1)。DFT计算预测一个单占据分子轨道（SOMO）具有27.2%的Au 5d(xy)特征，与从(197)Au超精细参数的不确定性得出的上限一致。与Au([9]aneS3)2比较表明，核四极参数P(ii)（i = x、y、z）对这些大环配合物中Au(II)配位球的性质非常敏感。阳离子Au([9]aneS2O)2观察到的几何结构和键长分别反映了d(10)、d(9)和d(8)金属离子的优选立体化学，与相关配合物Au([9]aneS3)2相比，更高氧化态的中心在更高的阳极电位下生成。
