2,4,6-Tris(2-pyridyl)-1,3,5-triazine (tptz)-Derived [RuII(tptz)(acac)(CH3CN)]+ and Mixed-Valent [(acac)2RuIII{(
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- 作者：Sandeep Ghumaan ; Sanjib Kar ; Shaikh M. Mobin ; B. Harish ; Vedavati G. Puranik ; and Goutam Kumar Lahiri
- 刊名：Inorganic Chemistry
- 出版年：2006
- 出版时间：March 20, 2006
- 年：2006
- 卷：45
- 期：6
- 页码：2413 - 2423
- 全文大小：361K
- 年卷期：v.45,no.6(March 20, 2006)
- ISSN：1520-510X
文摘
Mononuclear [RuII(tptz)(acac)(CH3CN)]ClO4 ([1]ClO4) and mixed-valent dinuclear [(acac)2RuIII{(
-tptz-H+)-}RuII(acac)(CH3CN)]ClO4 ([5]ClO4; acac = acetylacetonate) complexes have been synthesized via the reactions ofRuII(acac)2(CH3CN)2 and 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz), in 1:1 and 2:1 molar ratios, respectively. In[1]ClO4, tptz binds with the RuII ion in a tridentate N,N,N mode (motif A), whereas in [5]ClO4, tptz bridges the metalions unsymmetrically via the tridentate neutral N,N,N mode with the RuII center and cyclometalated N,C- state withthe RuIII site (motif F). The activation of the coordinated nitrile function in [1]ClO4 and [5]ClO4 in the presence ofethanol and alkylamine leads to the formation of iminoester ([2]ClO4 and [7]ClO4) and amidine ([4]ClO4) derivatives,respectively. Crystal structure analysis of [2]ClO4 reveals the formation of a beautiful eight-membered water clusterhaving a chair conformation. The cluster is H-bonded to the pendant pyridyl ring N of tptz and also with the O atomof the perchlorate ion, which, in turn, makes short (C-H- - - - -O) contacts with the neighboring molecule, leadingto a H-bonding network. The redox potentials corresponding to the RuII state in both the mononuclear {[(acac)(tptz)RuII-N
C-CH3]ClO4 ([1]ClO4) 
[(acac)(tptz)RuII-NH=C(CH3)-OC2H5]ClO4 ([2]ClO4) > [(acac)(tptz)RuII-NH2-C6H4(CH3)]ClO4 ([3]ClO4) > [(acac)(tptz)RuII-NH=C(CH3)-NHC2H5]ClO4 ([4]ClO4)} and dinuclear {[(acac)2RuIII{(-tptz-H+)-}RuII(acac)(NC-CH3)]ClO4 ([5]ClO4), [(acac)2RuIII{(-tptz-H+(N+-O-)2)-}RuII(acac)(NC-CH3)]ClO4([6]ClO4), [(acac)2RuIII{(-tptz-H+)-}RuII(acac)(NH=C(CH3)-OC2H5)]ClO4 ([7]ClO4), and [(acac)2RuIII{(-tptz-H+)-}RuII(acac)(NC4H4N)]ClO4 ([8]ClO4)} complexes vary systematically depending on the electronic nature of the coordinated sixth ligands. However, potentials involving the RuIII center in the dinuclear complexes remain more or lessinvariant. The mixed-valent RuIIRuIII species ([5]ClO4-[8]ClO4) exhibits high comproportionation constant (Kc) valuesof 1.1 × 1012-2 × 109, with substantial contribution from the donor center asymmetry at the two metal sites. Complexes display RuII- and RuIII-based metal-to-ligand and ligand-to-metal charge-transfer transitions, respectively, inthe visible region and ligand-based transitions in the UV region. In spite of reasonably high Kc values for [5]ClO4-[8]ClO4, the expected intervalence charge-transfer transitions did not resolve in the typical near-IR region up to2000 nm. The paramagnetic RuIIRuIII species ([5]ClO4-[8]ClO4) displays rhombic electron paramagnetic resonance(EPR) spectra at 77 K (<g> ~ 2.15 and 
g ~ 0.5), typical of a low-spin RuIII ion in a distorted octahedral environment.The one-electron-reduced tptz complexes [RuII(tptz
-)(acac)(CH3CN)] (1) and [(acac)2RuIII{(-tptz-H+)2-}RuII(acac)(CH3CN)] (5), however, show a free-radical-type EPR signal near g = 2.0 with partial metal contribution.
-tptz-H+)-}RuII(acac)(CH3CN)]ClO4 ([5]ClO4; acac = acetylacetonate) complexes have been synthesized via the reactions ofRuII(acac)2(CH3CN)2 and 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz), in 1:1 and 2:1 molar ratios, respectively. In[1]ClO4, tptz binds with the RuII ion in a tridentate N,N,N mode (motif A), whereas in [5]ClO4, tptz bridges the metalions unsymmetrically via the tridentate neutral N,N,N mode with the RuII center and cyclometalated N,C- state withthe RuIII site (motif F). The activation of the coordinated nitrile function in [1]ClO4 and [5]ClO4 in the presence ofethanol and alkylamine leads to the formation of iminoester ([2]ClO4 and [7]ClO4) and amidine ([4]ClO4) derivatives,respectively. Crystal structure analysis of [2]ClO4 reveals the formation of a beautiful eight-membered water clusterhaving a chair conformation. The cluster is H-bonded to the pendant pyridyl ring N of tptz and also with the O atomof the perchlorate ion, which, in turn, makes short (C-H- - - - -O) contacts with the neighboring molecule, leadingto a H-bonding network. The redox potentials corresponding to the RuII state in both the mononuclear {[(acac)(tptz)RuII-NC-CH3]ClO4 ([1]ClO4) [(acac)(tptz)RuII-NH=C(CH3)-OC2H5]ClO4 ([2]ClO4) > [(acac)(tptz)RuII-NH2-C6H4(CH3)]ClO4 ([3]ClO4) > [(acac)(tptz)RuII-NH=C(CH3)-NHC2H5]ClO4 ([4]ClO4)} and dinuclear {[(acac)2RuIII{(-tptz-H+)-}RuII(acac)(NC-CH3)]ClO4 ([5]ClO4), [(acac)2RuIII{(-tptz-H+(N+-O-)2)-}RuII(acac)(NC-CH3)]ClO4([6]ClO4), [(acac)2RuIII{(-tptz-H+)-}RuII(acac)(NH=C(CH3)-OC2H5)]ClO4 ([7]ClO4), and [(acac)2RuIII{(-tptz-H+)-}RuII(acac)(NC4H4N)]ClO4 ([8]ClO4)} complexes vary systematically depending on the electronic nature of the coordinated sixth ligands. However, potentials involving the RuIII center in the dinuclear complexes remain more or lessinvariant. The mixed-valent RuIIRuIII species ([5]ClO4-[8]ClO4) exhibits high comproportionation constant (Kc) valuesof 1.1 × 1012-2 × 109, with substantial contribution from the donor center asymmetry at the two metal sites. Complexes display RuII- and RuIII-based metal-to-ligand and ligand-to-metal charge-transfer transitions, respectively, inthe visible region and ligand-based transitions in the UV region. In spite of reasonably high Kc values for [5]ClO4-[8]ClO4, the expected intervalence charge-transfer transitions did not resolve in the typical near-IR region up to2000 nm. The paramagnetic RuIIRuIII species ([5]ClO4-[8]ClO4) displays rhombic electron paramagnetic resonance(EPR) spectra at 77 K (<g> ~ 2.15 and g ~ 0.5), typical of a low-spin RuIII ion in a distorted octahedral environment.The one-electron-reduced tptz complexes [RuII(tptz-)(acac)(CH3CN)] (1) and [(acac)2RuIII{(-tptz-H+)2-}RuII(acac)(CH3CN)] (5), however, show a free-radical-type EPR signal near g = 2.0 with partial metal contribution.