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A new class of sulfur bridged ruthenium–molybdenum complexes, (L)2RuII(μ-S)2MoIV(OH)2 [L=NC5H4N=NC6H4(R), R=H, o-Me/Cl, m-Me/Cl]. Synthesis, spectroscopic and electron-transfer properties

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Title A new class of sulfur bridged ruthenium–molybdenum complexes, (L)2RuII(μ-S)2MoIV(OH)2 [L=NC5H4N=NC6H4(R), R=H, o-Me/Cl, m-Me/Cl]. Synthesis, spectroscopic and electron-transfer properties
 
Creator SAMANTA, RAMAPATI
MUNSHI, PRADIP
SANTRA, BIDYUT KUMAR
LAHIRI, GOUTAM KUMAR
 
Subject ruthenium-molybdenum complexes
sulfur bridging
electron transfer
 
Description The reaction of (NH4)2MoVIS4 with the complexes ctc-RuII(L)2Cl2 (1a–1e) [L=NC5H4N=NC6H4(R), R=H, o-Me/Cl, m-Me/Cl; ctc=cis–trans–cis with respect to chlorides, pyridine and azo nitrogens respectively] in MeOH–H2O (1:1) resulted in a group of stable sulfur bridged ruthenium–molybdenum complexes of the type (L)2RuII(μ-S)2MoIV(OH)2 (2a–2e). In complexes 2 the terminal Mo=S bonds of the MoVIS42− unit get hydroxylated and the molybdenum ion is reduced from the starting MoVI in MoS42− to MoIV in the final product 2. The cis–trans–cis (with respect to sulfurs, pyridine and azo nitrogens respectively) configuration of the RuL2S2 fragment in 2 has been established by the 1H NMR spectroscopy. In dichloromethane solution the complexes 2 exhibit a strong dπ(RuII)→Lπ* MLCT transition near 550 nm, a strong sulfur to molybdenum LMCT transition near 500 nm and intra ligand π–π* transition in the UV region. In dichloromethane solution the complexes display reversible RuII⇌RuIII oxidation couples in the range 1.15–1.39 V, irreversible MoIV→MoV oxidations in the range 1.68–1.71 V vs SCE. Four successive reversible ligand (–N=N–) reductions are observed for each complex in the ranges −0.37→−0.67 V (one-electron), −0.81→−1.02 V (one-electron) and −1.48→−1.76 V (simultaneous two-electron reduction) vs SCE respectively. The presence of trivalent ruthenium in the oxidized solutions 2+ is evidenced by the rhombic EPR spectra. The EPR spectra of the coulometrically oxidized species 2+ have been analyzed to furnish values of axial (Δ=4590–5132 cm−1) and rhombic (ν=1776–2498 cm−1) distortion parameters as well as energies of the two expected ligand field transitions (γ1=3798–4022 cm−1) and (γ2=5752–6614 cm−1) within the t2 shell. One of the ligand field transitions has been observed experimentally at 6173 cm−1 and 6289 cm−1 for the complexes 2b+ and 2d+ respectively by near-IR spectra which are close to the computed γ2 values.
 
Publisher Elsevier
 
Date 2009-04-03T09:05:03Z
2011-11-25T20:38:01Z
2011-12-26T13:08:34Z
2011-12-27T05:56:31Z
2009-04-03T09:05:03Z
2011-11-25T20:38:01Z
2011-12-26T13:08:34Z
2011-12-27T05:56:31Z
1999
 
Type Article
 
Identifier Polyhedron 18(7), 995-1004
0277-5387
http://dx.doi.org/10.1016/S0277-5387(98)00385-4
http://hdl.handle.net/10054/1123
http://dspace.library.iitb.ac.in/xmlui/handle/10054/1123
 
Language en