Pentammine cobalt

Reductions of monosubstituted iron(iii) complexes have been studied, the reactions being inner sphere with rates in the order Br > Cl > F" in contrast to the corresponding europium(ii) systems. The order does, however, parallel that for the Cr reduction of pentammine-cobalt(m) halide complexes. Reactions with platinum(iv) complexes have been studied, and in the case of [Pt(NH3)sa] + and [Pt(NH3)sOH] + a two-electron change is involved with intermediate formation of Cr and subsequent production of dimeric Cr" complexes ... 

Electron-transfer reactions between Co-complexes and reductants are being studied in this laboratory. As was noted by Gould [17] earlier, who studied electron-transfer reactions between pentammine cobalt complexes and Cr(II), the main factor in determining the acceleration is the valencies of the oxidants and reductants, as shown... 

A considerable amount of controversy appears to exist in the literature (1) regarding the mechanism of base hydrolysis of acido-pentammine-cobalt(III) complexes. Detailed investigations on the kinetics of base hydrolysis of several complexes of this type, [Co(NHj) X] , where X = Cl , Br" or N , have been reported by earlier investigators (2-4). It is known (5) that in [Co(NH ) (S20 )] the thiosulphate is so firmly bound that on treating with potassium cyanide all the ammonia are displaced leading to the formation of [Co(CN)g(S20 )l ". 

C3 KINETICS AND MECHANISM OF NUCLEOPHILIC SUBSTITUTION IN AN ACIDO-PENTAMMINE-COBALT(III) COMPLEX IN AQUEOUS SOLUTION, D. Banerjea and T.P. Das Gupta... 

As with rhodium (and cobalt), introduction of five ammonia molecules is relatively straightforward, but the sixth substitution is difficult, requiring more forcing conditions. One versatile route involves the formation of the pentammine triflate complex ion [Ir(NH3)5(03SCF3)]2+, where the labile triflate group is readily replaced by water, then by a range of anionic ligands [148]. 

C. P. Rammelsberg prepared what appears to be nickel tetrammino-iodate, Ni(I03)2.4NH3, as a pale blue crystalline powder, by the addition of alcohol to a soln. of nickel iodate in ammonia he also prepared a similar cobalt tetrammino-iodate, Co(I03)2.4NH3. P. Ephraim and A. Jahnsen prepared trihydrated nickel pentammino-iodate, Ni(I03)2.5NH3.3H20, in reddish-violet columnar crystals, and from it they obtained pale violet crystals of nickel pentammino-iodate, Ni(I03)2.5NH3, of sp. gr. 2-97, and with a dissociation press, of 179 mm. at 53° 365 min. at 65° 670 at 77° and 905 mm. at 79°. The ammino-iodates do not explode when heated in open tubes, but they do so in closed tubes between 210° and 219°. The mol. vol. of the pentammino-salt is 166 2, and the mol. vol. of each NH3 is 17 1. The heat of formation of the pentammine is 12-5 Cals. 

J. Sand and 0. Genssler15 obtained a series of complex salts by the action of nitric oxide on ammoniaeal soln. of cobalt salts. They considered the products to be formed by the addition of two mols. of the cobalt pentammines. Thus, cobalt nitrosylpentamminodichloride, [Co(N0)(NH3)5]C12, furnishes black crystals supposed to be constituted Cl2[(NH3)5Co.NO.NO.Co(NH3)5]C12 or [Co2(N2O2)(NH3)10]C14. 

SAFETY PROFILE A poison. An irritant. Mutation data reported. Flammable liquid when exposed to heat or flame can react vigorously with oxidizing materials. Has exploded when stirred with (cobalt pentammine triazoperchlorate + nitrosyl perchlorate). When heated to decomposition it emits toxic fumes of CN and NOx. See also CYANATES. 

The nickel, cobalt, and zinc in the reduction end solution are precipitated as metal ammonium double salts after solution evaporation to 500 gm/liter ammonium sulfate. The double salts containing the nickel and cobalt centrifuged from the solution are then dissolved in water. Nickel and cobalt are separated by formation of cobaltic pentammine sulfate solution. The cobaltic pentammine solution is reduced at 350°F under hydrogen at 500 psig to produce cobalt powder. The ammonium sulfate by-product is prepared by stripping out the metal values with hydrogen sulfide. 

Ogawa and coworkers have examined peptide y -strand mimics of the general type 24 (R = CH(CH3)2, n = 1-3), consisting of a ruthenium(II) polypyridyl electron donor tethered to a cobalt(III) pentammine electron acceptor by an polyvaline peptide chain [107]. A related parallel ) -sheet mimic has also been studied [108]. These compounds adopt the conformational properties found within the individual strands of a y -pleated sheet in both aqueous and methanol solutions. Emission lifetime measurements and HPLC product analyses suggest that the binuclear donor-acceptor compounds undergo photoinduced electron transfer. The values of et decrease with increasing donor acceptor distance according to y = 1.1 A, which is observed for electron transfers both in water at 298 K and in ethanol-... 

For the compound represented by the formula [Co(NH3)5S04]Br the name pentammine-sulfatocobalt(III) bromide indicates clearly that the sulfate group is monocoordinated if a maximum coordination number of six is accepted for cobalt. 

Ammonia forms complex derivatives with all three classes of iridium compounds. When added to iridious chloride, IrCl2, or to iridic chloride, IrCl4, the complex salts formed are analogous to the series of platinous and platinic ammine derivatives. When ammonia is added to the trichloride, many complex derivatives are formed which are similar to rhodic, cobaltic, and chromic compounds. For example, when ammonia acts upon ammonium iridiochloride a compound is produced having the formula [Cl(NHj)5lr]Cl2, and called chloro-pentammine-iridium dichloride. 

A. PENTAMMINE(TRIFLUOROMETHANESULFONATO)COBALT(III) TRIFLUOROMETHANESULFONATE, [Co(NH3)sOS02CF3 ](CF3SO)2... 

Induced electron transfer has been investigated in the action of one-electron oxidants on pyridinemethanolpentammine-cobalt(iii) complexes. The direct [and silver(i)- and cobalt(ii)-catalysed] oxidations of pentammine-(pyridine-4-methanol)cobalt(iii) (G) and the corresponding pyridine-3-methanol complex by cerium(iv) yield aldehydic complexes of cobalt(iii)... 

Cobalt can also be separated from nickel in alkaline conditions, by first adding ammonia and H2O2 to form cobalt(III) pentammine complex, at ambient temperature and pressure ... 

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