Coordination of Zn(II), Cd(II), Hg(II), and Ag(I) by Bis(benzimidazole) Ligands
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- 作者：Craig J. Matthews ; William Clegg ; Sarah L. Heath ; Nicola C. Martin ; M. N. Stuart Hill ; and Joyce C. Lockhart
- 刊名：Inorganic Chemistry
- 出版年：1998
- 出版时间：January 26, 1998
- 年：1998
- 卷：37
- 期：2
- 页码：199 - 207
- 全文大小：364K
- 年卷期：v.37,no.2(January 26, 1998)
- ISSN：1520-510X
文摘
The coordinating environments provided by the1-(5,6-dimethylbenzimidazolyl)-3-benzimidazolyl-2-thiapropane(1),1-(5,6-dimethylbenzimidazolyl)-3-benzimidazolyl-2-oxapropane(2),1-(N-methyl)benzimidazolyl-3-benzimidazolyl-2-oxapropane (3), and1,7-bis(benzimidazol-2-yl)-2,6-dithiaheptane (4)ligands for a series of soft-to-borderline metal ions have been demonstrated by crystallographicstructure determination in the solid state,supplemented by multinuclear NMR studies in solution. Structuresof[Zn(3)(H2O)(MeCN)](ClO4)2([C19H21N5O2Zn](ClO4)2, monoclinic, space groupP21/c, a =10.3247(11) Å, b = 11.0320(12) Å, c= 20.761(2) Å, 
=96.465(3)
, V = 2349.7(4) Å3,Z = 4),[Zn(1)Cl2]·CH3OH([C18H18Cl2N4SZn]·CH4O,triclinic, space group P
,a = 9.0917(9) Å, b = 9.9186(10)Å, c = 12.2079(12) Å, 
= 99.710(3), = 94.252(2), 
= 95.598(3), V=1075.3(2) Å3, Z = 2),[Hg(1)Br2]·CH3OH([C18H18Br2HgN4S]·CH4O,triclinic, space group P, a =9.1956(12)Å, b = 9.9775(13) Å, c =12.462(2) Å, = 99.239(3), = 97.676(3), = 94.036(3), V = 1113.4(3)Å3, Z= 2), [Cd(1)Cl2]([C18H18CdCl2N4S],monoclinic, space group P21/n,a = 14.5219(11) Å, b = 8.5315(7)Å, c =15.6182(12) Å, = 92.063(2), V =1933.7(3) Å3, Z = 4), and[Ag(4)](NO3)([C19H20AgN4S](NO3),monoclinic,space group C2/c, a =13.7339(3) Å, b = 17.2710(1) Å, c= 9.8866(2) Å, = 115.399(1), V =2118.4(1) Å3,Z = 4) have been determined. Ligand 3provided the expected N2O donor set to Zn(II) formingpart of a pseudo-trigonal bipyramidal coordinating environment, tentatively extrapolatedto the Zn(II), Cd(II), and Hg(II) complexesof ligand 2 from 1H NMR studies. Thethioether-bridged ligands (1 and 4) displayed astrikingly differentcoordination mode; in none of these structures was the thioether foundto be coordinated to the central metal ion,resulting in pseudotetrahedral structures for the Zn(II) andHg(II) complexes of ligand 1, abis(chloro)-bridgeddimeric five-coordinate complex of Cd(II) with ligand1, and a near-linear coordination mode for the Ag(I)complexof ligand 4. No significant distinction in geometricparameters around the metal ions could be observedresultingfrom the introduction of asymmetry and a change ofpKa within the bis(benzimidazole) ligands.Using 199HgNMR spectroscopy, it was demonstrated that the thioether of ligand1 did not coordinate in solutions of the 1:1HgBr2 complex; negligible shifts of the signalscorresponding to the aliphatic bridging protons in the 1HNMRspectra of ligand 1 when coordinated to Zn(II),Cd(II), and Hg(II) also suggested a noncoordinatingbehavior.Exchanges occurring in mixtures of HgBr2 and ligand1 were examined using 199Hg,13C, and 1H NMR. It isconsidered that there is little or no exchange occurring in a region ofexcess mercury on the 199Hg NMR timescale, and in a region of excess ligand 1 the 1/1 complexpredominates.
=96.465(3), V = 2349.7(4) Å3,Z = 4),[Zn(1)Cl2]·CH3OH([C18H18Cl2N4SZn]·CH4O,triclinic, space group P,a = 9.0917(9) Å, b = 9.9186(10)Å, c = 12.2079(12) Å, = 99.710(3), = 94.252(2), = 95.598(3), V=1075.3(2) Å3, Z = 2),[Hg(1)Br2]·CH3OH([C18H18Br2HgN4S]·CH4O,triclinic, space group P, a =9.1956(12)Å, b = 9.9775(13) Å, c =12.462(2) Å, = 99.239(3), = 97.676(3), = 94.036(3), V = 1113.4(3)Å3, Z= 2), [Cd(1)Cl2]([C18H18CdCl2N4S],monoclinic, space group P21/n,a = 14.5219(11) Å, b = 8.5315(7)Å, c =15.6182(12) Å, = 92.063(2), V =1933.7(3) Å3, Z = 4), and[Ag(4)](NO3)([C19H20AgN4S](NO3),monoclinic,space group C2/c, a =13.7339(3) Å, b = 17.2710(1) Å, c= 9.8866(2) Å, = 115.399(1), V =2118.4(1) Å3,Z = 4) have been determined. Ligand 3provided the expected N2O donor set to Zn(II) formingpart of a pseudo-trigonal bipyramidal coordinating environment, tentatively extrapolatedto the Zn(II), Cd(II), and Hg(II) complexesof ligand 2 from 1H NMR studies. Thethioether-bridged ligands (1 and 4) displayed astrikingly differentcoordination mode; in none of these structures was the thioether foundto be coordinated to the central metal ion,resulting in pseudotetrahedral structures for the Zn(II) andHg(II) complexes of ligand 1, abis(chloro)-bridgeddimeric five-coordinate complex of Cd(II) with ligand1, and a near-linear coordination mode for the Ag(I)complexof ligand 4. No significant distinction in geometricparameters around the metal ions could be observedresultingfrom the introduction of asymmetry and a change ofpKa within the bis(benzimidazole) ligands.Using 199HgNMR spectroscopy, it was demonstrated that the thioether of ligand1 did not coordinate in solutions of the 1:1HgBr2 complex; negligible shifts of the signalscorresponding to the aliphatic bridging protons in the 1HNMRspectra of ligand 1 when coordinated to Zn(II),Cd(II), and Hg(II) also suggested a noncoordinatingbehavior.Exchanges occurring in mixtures of HgBr2 and ligand1 were examined using 199Hg,13C, and 1H NMR. It isconsidered that there is little or no exchange occurring in a region ofexcess mercury on the 199Hg NMR timescale, and in a region of excess ligand 1 the 1/1 complexpredominates.