Cobalt dichlorobis -, trans

The dichlorobis(ethylenediamine)cobalt(II) ion can exist in two geometrical isomers. For the trans isomer, there is a plane of symmetry that bisects the cobalt ion and the ethylenediamine ligands, leaving one Cl on either side of the plane. However, the cis isomer has no plane of symmetry so two optical isomers exist. This is also the case for [Co(en)3]3+ as is illustrated in Figure 16.3. 

The cw-dichlorobis(ethylenediamine)cobalt(III) ion is optically active. The two optical isomers are drawn below. The trans-isomer is not optically active the ion and its mirror image are superimposable. 

Lithium tetranitrodiamminecobaltate(III) Trans-dichlorobis(ethylenediamine)cobalt(III) chloride... 

The traditional method of isolating the trans-dichlorobis-(ethylenediamine)cobalt(III) chloride salt by evaporation of the reaction mixture to dryness in the steam bath gives some reduction to cobalt(II). To avoid this, the chloride salt in the following procedure is isolated by saturation of the reaction mixture with hydrogen chloride gas and by precipitation with standing at room temperature. As an alternative method, the reaction mixture from the preparation of (carbonato)bis(ethylene-diamine)cobalt(III) chloride can be used as the starting material. 

Table 10.1. Symmetry of the dipole moment matrix elements in trans-dichlorobis(ethylenediamine)cobalt(III) in D4h symmetry.

Dichlorobis (ethy lenediamine) cobalt-(III) chloride, cis- and trans-, 2 222, 223... 

A large majority of diacidobis(l, 2-ethanediamine)cobalt(III) complexes can be synthesized from the (carbonato)bis(l, 2-ethanediamine)cobalt(III) ion. This is now readily available in high yield and purity.1 cis- and trans-Dichlorobis(l, 2-ethanediamine)cobalt(III) chlorides are obtained from the carbonato complex with hydrochloric acid using appropriate conditions. These isomeric dichloro salts are widely used starting materials for further syntheses. In this respect, the analogous dibromo complexes can be more convenient starting materials because bromide is substituted from the cobalt center more readily than is chloride ion. The milder conditions minimize the production of cobalt(II), a common side reaction. 

Figure 22.13 shows the cis and trans isomers of dichlorobis(ethylenediamine)-cobalt(lll) ion and their images. Careful examination reveals that the trans isomer and its mirror image are superimposable, but the cis isomer and its mirror image are not. Therefore, the cis isomer and its mirror image are optical isomers. 

FIGURE 22.13 The foj cis and (bj trans isomers of dichlorobis-(ethylenediamine)cobalt(lll) ion and their mirror images. If you could rotate the mirror image in (b) 90° clockwise about the vertical position and place it over the trans isomer, you would find that the two are superimposable. No matter how you rotated the cis isomer and its mirror image, however, you could not superimpose one on the other. 

C0CI2, Cobalt dichloride, 28 322,29 110 CoCljN4C4H,g, Cobaltail), dichlorobis(U-ethanediamine)-, trans-, chloride, 29 167... 

The crystal structure of dichlorobis(pyrazine)cobalt(n) contains polymeric sheets in which the metal atoms are linked by bidentate pyrazine groups (10). An octahedral configuration at each cobalt atom is completed by four coplanar nitrogen atoms at 2.18(1) A from the metal and two mutually trans chlorine atoms at 2.405(6) A. ... 

A considerable amount of kinetic and mechanistic data has been reported for the base hydrolysis of cis- and trans-dihalobis(ethylenediamine)-cobalt(III) cations/ On the other hand, the only chromium(III) analogs which have been studied are cis- and trans-dichlorobis(ethylenediamine)-chromium(III) cations/ The present study was undertaken to gain additional base hydrolysis data for dihalobis(ethylenediamine)chromium(III) complexes, which will permit a more meaningful comparison with their cobalt(III) analogs. 

In contrast, as shown in Figure 22.10B, the two structures of the trans-dichlorobis(ethylenediamine)cobalt(III) ion are not optical isomers rotate structure I 90° around a vertical axis and you obtain III, which is superimposable on II. 

C7H28CI3C0N10S3, trans-Dichlorobis(ethylenediamine)cobalt III) chloride - tris(thiourea), 39B, 440 C8H6K3M0N6O3S6 r Potassium hexaisothiocyanatomolybdate(lII) hydrate-acetic acid, 33B, 422... 

Cl2Ni,Pd, Bis(ethylenediamine)palladium(II) chloride, 31B, 375 C Hi gClaCoNi, trans-Dichlorobis(ethylenediamine)cobalt (III) chloride, 23, 572... 

C4H21CI4C0N4O2, trans Dichlorobis(ethylenediamine)cobalt(III) hydrochloride dihydrate, 16, 457 42B, 717 C4H2iCl4CrN402, trans-Dichlorobis(ethylenediamine)chromium(lll) chloride hydrochloride dihydrate, 24, 596 C4H2 aClCoNeOeSa, Tris(ammine)diethylenetriaminecobalt(111) chloride dithionate, 44B, 797... 

C6H24NeNi06, Trisethylenediaminenickel nitrate, 24, 605 C6H25ClaCoN202, trans-Dichlorobis(l-propylenediamine)cobalt(III) chloride hydrochloride dihydrate, 27, 833 CgH26AU2N6O12S4, Ethylenediammonium bis-cis-(ethylenediamine-disulf itoauratedll)), 41B, 941... 

CaH,aCl2N2PdS2, Dichlorobis(thiomorpholine)palladium(II), 44B, 9l1 CaH1aCoNgNaOi0 f Sodium trans-dinitro(dimethylglyoximato)(dimethylglyoxime )cobaltate (111) dihydrate, 44B, 912 CaHiaCuNgS2, Thiocyanatotriethylenetetraminecopper(11) thiocyanate, 40B, 1119... 

Ci2H28Cl2NnPd, Dichlorobis(azoisopropane)palladium(II), 44B, 947 Cl2H28C0N13, trans-Diazido(C-meso-5,12-dimethyl-1,4,8,11-tetraaza-cyclotetradecane)cobalt(III) azide, 44B, 922 Cl2H2gCuNgOg, Bis(2-imino-4-amino-4-methylpentane)copper(II) ni-... 

C20H3 2AS4CI3C0O1, trans-Dichlorobis- (o-phenylene(bisdimethy 1-arsine))cobalt(III) perchlorate, 35B, 869 C20H32AS4Cl3Ni, Dichlorobis(o-phenylenebis(dimethylarsine))nickel chloride, 38B, 1035... 

C52H48CI2M0P4 CH2Cl2f trans-Dichlorobis(1,2-bis(diphenylphos-phino)ethano)molybdenum(II) dichloromethane solvate, 46B, 1298 C52H4eCli CoP4Sn, Chlorobis( 1,2-bis(diphenylphosphino)ethane)cobalt-(II) trichlorostannatedi), 38B, 1051 39B, 871 C5 2H4 8Cl4P4Re2 f Tetrachlorobis(1,2-bis(diphenylphosphino)ethane)dir-henium, 44B, 1084... 

It is important to underline the fact that a tetrahedral complex, which would have the same global formula as the preceding one, cannot exhibit this isomerism. Hence, for example, the isolation of two isomers of the diamminedichloroplatinum(II) complex [Pt (Cl)2(NH3)2] has been a very strong argument in favor of its planar stmcture. The octahedral hexacoordinated complex dichlorobis(ethylenediamine)cobalt(III) [Co (Cl2)(en)2]+ exists in the cis and trans forms (Fig. 23.4). 

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