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Issue 12, 1992
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Bis(N,N) chelated rhenium(III): the [ReL2Cl2]Cl family [L = 2-(arylazo)pyridine]


The reaction of mer-[Re(MeCN)(PPh3)2Cl3] with 2-(arylazo)pyridines (L) affords dark green, diamagnetic, 1 : 1 electrolytes [ReL2Cl2]Cl (aryl of L = Ph, m-MeC6H4 or p-ClC6H4). The ReCl2 moiety is cis(two Re–Cl stretches) and the cation has an overall two-fold symmetry axis (1H NMR spectra). The co-ordinated pyridine-nitrogen atoms and azo-nitrogen atoms of each ligand are assigned relative trans and cis geometries respectively. The N[double bond, length half m-dash]N stretching frequencies are low (1280–1290 cm–1) implying significant Re(t2)–azo(π*) back bonding. In MeCN solution three nearly reversible redox couples occur with E½ values of ≈ 0.9 V [rhenium(IV)–rhenium(III)] and ≈–0.4, ≈–0.8 V (azo redox)vs. the saturated calomel electrode (SCE). A metal-to-ligand charge-transfer (m.l.c.t.) absorption is observed near 600 nm. The reduction potentials and m.l.c.t. frequencies are mutually consistent. The remarkable spectral and electrochemical similarities between [ReIIIL2Cl2]Cl and [OsIIL2Cl2] are noted and rationalised.

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Article type: Paper
DOI: 10.1039/DT9920001883
Citation: J. Chem. Soc., Dalton Trans., 1992,0, 1883-1886
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    Bis(N,N) chelated rhenium(III): the [ReL2Cl2]Cl family [L = 2-(arylazo)pyridine]

    P. Ghosh, A. Pramanik, N. Bag and A. Chakravorty, J. Chem. Soc., Dalton Trans., 1992, 0, 1883
    DOI: 10.1039/DT9920001883

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