Metal-Assisted Unusual Hydroxylation at the Carbon Atom of the Triazine Ring in Dinuclear Ruthenium(II) and Osmium(II) Complexes Bridged by 2,4,6-Tris(2-pyridyl)-1,3,5-triazine: Synthesis, Structural
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- 作者：Parimal Paul ; Beena Tyagi ; Anvarhusen K. Bilakhiya ; Parthasarathi Dastidar ; and Eringathodi Suresh
- 刊名：Inorganic Chemistry
- 出版年：2000
- 出版时间：January 10, 2000
- 年：2000
- 卷：39
- 期：1
- 页码：14 - 22
- 全文大小：187K
- 年卷期：v.39,no.1(January 10, 2000)
- ISSN：1520-510X
文摘
The reaction of cis-[M(bpy)2Cl2] (M = Ru(II), and Os(II)) with 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz) in refluxingethanol-water resulted in the formation of dinuclear complexes of the composition [{M(bpy)2}2(tptz-OH)](PF6)3·nH2O (n = 1 for Ru and n = 0 for Os). In this reaction an unusual metal-induced hydroxylation at the carbonatom of the triazine ring of bridged tptz occurred. However, hydroxylation did not occur in the correspondingmononuclear complexes under similar reaction condition. A comparative study revealed that sufficientelectrophilicity on the carbon atom and free movement of the attached pyridyl ring promoted the hydroxylationreaction. The hydroxylated dinuclear complexes exist in two stereoisomeric forms, a rac form (
/
) and ameso form (/). Both diastereoisomers have been isolated in pure form and characterized. The molecularstructures of the rac form of Ru(II) complex (3-II) and meso form of the Os(II) complex (4-I) have been establishedby single-crystal X-ray studies. Crystal data: complex 3-II, monoclinic, C2/c, a = 24.584(7) Å, b = 14.309(4)Å, c = 41.044(13) Å, 
= 92.84(2)
, V = 14420.0(7) Å3, Z = 8, R = 0.179, wR2 = 0.479; complex 4-I, triclinic,P
, a = 13.444(7) Å, b = 14.576(5) Å, c = 19.641(7) Å, 
= 98.21(3), = 101.67(4), 
= 105.80(4), V =3546.0(3) Å3, Z = 2, R = 0.093, wR2 = 0.279. The poor data quality of 3-II did not allow anisotropic refinementof non-hydrogen atoms except Ru and P. A PLUTO drawing of this compound is given only to support themolecular structure. 1H NMR data have been used to characterize the diastereoisomers. The dinuclear complexesexhibit unusual electrochemical behavior; cathodic shifts of the metal-centered oxidations and ligand-based firstreduction compared to mononuclear complexes have been observed. There is a splitting in the metal-centeredoxidation potentials, indicating strong electronic communication between the metal centers. Comproportionationconstants (Kcom) of the mixed-valence species have been calculated; the values are in the range 6.03 × 104-4.7× 106. It appears that a metal-metal interaction occurred by an electron-transfer mode across the low-lying 
*orbital of the bridged tptz.
/) and ameso form (/). Both diastereoisomers have been isolated in pure form and characterized. The molecularstructures of the rac form of Ru(II) complex (3-II) and meso form of the Os(II) complex (4-I) have been establishedby single-crystal X-ray studies. Crystal data: complex 3-II, monoclinic, C2/c, a = 24.584(7) Å, b = 14.309(4)Å, c = 41.044(13) Å, = 92.84(2), V = 14420.0(7) Å3, Z = 8, R = 0.179, wR2 = 0.479; complex 4-I, triclinic,P, a = 13.444(7) Å, b = 14.576(5) Å, c = 19.641(7) Å, = 98.21(3), = 101.67(4), = 105.80(4), V =3546.0(3) Å3, Z = 2, R = 0.093, wR2 = 0.279. The poor data quality of 3-II did not allow anisotropic refinementof non-hydrogen atoms except Ru and P. A PLUTO drawing of this compound is given only to support themolecular structure. 1H NMR data have been used to characterize the diastereoisomers. The dinuclear complexesexhibit unusual electrochemical behavior; cathodic shifts of the metal-centered oxidations and ligand-based firstreduction compared to mononuclear complexes have been observed. There is a splitting in the metal-centeredoxidation potentials, indicating strong electronic communication between the metal centers. Comproportionationconstants (Kcom) of the mixed-valence species have been calculated; the values are in the range 6.03 × 104-4.7× 106. It appears that a metal-metal interaction occurred by an electron-transfer mode across the low-lying *orbital of the bridged tptz.