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The reaction of 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz) with RhCl 3 ‚3H 2 O has been studied under different experimental conditions. This reaction in ethanol resulted in the formation of [Rh(tptz)Cl 3 ]‚2H 2 O (1), whereas the bis-chelate complex [Rh(tptz) 2 ][ClO 4 ] 3 ‚2H 2 O (2) was obtained in a two-step reaction in acetone; the chlorides from RhCl 3 were removed in the first step using AgClO 4 , and the ligand tptz was added in the second step. Complexes 1 and 2, when refluxed in ethanol-water (1:1), resulted in metal-promoted hydrolysis of tptz to bis-(2-pyridylcarbonyl)amide anion (bpca) and 2-picolinamide (pa), yielding the complexes [Rh(bpca)(pa)Cl][PF 6 ]‚ H 2 O (3) and [Rh(bpca) 2 ][ClO 4 ] (6), respectively. A mixed-ligand complex, [Rh(bpca)(tpy)][PF 6 ] 2 ‚CH 3 CN (4), was obtained by the reaction of either 1 with tpy or [Rh(tpy)Cl 3 ] (5) with tptz in ethanol-water medium. The crystal structures of complexes 1 and 4 have been determined. Crystal data: complex 1, monoclinic, P2 1 /c, a ) 11.642(2) Å, b ) 7.302(2) Å, c ) 24.332(3) Å, β ) 96.420(10)°, Z ) 4, R ) 0.040, and wR2 ) 0.117; complex 4, triclinic, P1 h, a ) 9.581(1) Å, b ) 12.933(2) Å, c ) 14.493(2) Å, R ) 82.480(10)°, β ) 71.810(10)°, γ ) 75.100(10)°, Z ) 2, R ) 0.030, and wR2 ) 0.082. The two water molecules of complex 1 make short contacts with the carbon atoms adjacent to the metal-bound nitrogen atom of the triazine ring; this observation provides some insight about the "intermediate" of the hydrolysis. X-ray and NMR data suggest that the electron-withdrawing effect of the metal ion is the major responsible factor for the hydrolysis of tptz. The cyclic voltammograms of the complexes exhibit a metal-based 2e reduction (Rh(III) f Rh(I)) at the potential range -0.42 to -0.98 V vs SCE, followed by ligand-based redox couple(s). These novel complexes show effective catalytic properties for the electrocatalytic reduction of carbon dioxide in the potential range -1.26 to -1.44 V.

Removal of color and reduction of chemical oxygen demand (COD) in an industrial azo dye effluent containing chiefly reactive dyes were investigated under single-pass conditions at a dimensionally stable anode (DSA) in a thin electrochemical flow reactor at different current densities, flow rates, and dilutions. With 50% diluted effluent, decolorization was achieved up to 85-99% at 10-40 mA/ cm2 at 5 mL/min flow rate and 50-88% at 30-40 mA/ cm2 at high (10-15 mL/min) flow rates. The COD reduction was maximum (81%) at 39.9 mA/cm2 or above when solution-electrode contact time (Ct) was as high as 21.7 s/cm2 and decreased as Ct declined at a given current density. Cyclic voltammetric studies suggesting an indirect oxidation of dye molecules over the anode surface were carried out at a glassy carbon electrode. The effect of pH on decolorization and COD reduction was determined. An electrochemical mechanism mediated by OCl- operating in the decolorization and COD reduction processes was suggested. The effluent was further treated with NaOCI. The oxidized products from the treated effluents were isolated and confirmed to be free from chlorine-substituted products by IR spectroscopy. From the apparent pseudo-first-order rate data, the second-order rate coefficients were evaluated to be 2.9 M(-1) s(-1) at 5 mL/ min, 76.2 M(-1) s(-1) at 10 mL/min, and 156.1 M(-1) s(-1) at 15 mL/ min for color removal, and 1.19 M(-1) s(-1) at 5 mL/min, 1.79 M(-1) s(-1) at 10 mL/min, and 3.57 M(-1) s(-1) at 15 mL/min for COD reduction. Field studies were also carried out with a pilot-scale cell at the source of effluent generation of different plants corresponding to the industry. Decolorization was achieved to about 94-99% with azo dye effluents at 0.7-1.0 L/min flow costing around Indian Rupees 0.02-0.04 per liter, and to about 54-75% in other related effluents at 0.3-1.0 L/min flow under single-pass conditions.

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Mixtures of NaBr and NaBrO 3 in two different ratios have been used for highly stereoselective bromination of alkenes and alkynes, and regioselective bromine substitution at the a-carbon of ketones and at the benzylic position of toluene derivatives. The reactions were conducted in an aqueous acidic medium under ambient conditions. The solid reagents were prepared from the intermediate obtained in the ''cold process'' of bromine manufacture and are stable, nonhazardous and inexpensive to prepare. This procedure provides an efficient and practical alternative to conventional procedures using liquid bromine directly or indirectly.

Facile bromination of various organic substrates has been demonstrated with a 2 : 1 bromide:bromate reagent prepared from the alkaline intermediate of the conventional bromine recovery process. The reagent is acidified in situ to generate HOBr as the reactive species, which effects bromination. Aromatic substrates that have been successfully brominated under ambient conditions without use of any catalyst include phenols, anilines, aromatic ethers and even benzene. Non-aromatic compounds bearing active methylene group were monobrominated selectively with the present reagent and olefinic compounds were converted into the corresponding bromohydrins in moderate yields. By obtaining the present reagent from the liquid bromine precursor, the twin advantages of avoiding liquid bromine and producing the reagent in a cost-effective manner are realised. When coupled with the additional advantage of high bromine atom efficiency, the present protocol becomes attractive all the way from ''cradle to grave''.

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