Base hydrolysis and aquation of trans-methyl-substituted acidopenta-amminecobalt(III) complexes

Aquation and Base Hydrolysis of trans-Tetraammine(methylamine)sulfatocobalt(III) Complex Ion

“…This result parallels earlier observations for the frans-[Co(NH3)4(NH2-CH3)L] 2+ complexes (see Table III) [22], In both cases the rate enhancement is originated in AH # rather than in AS*. In fact, AS*H for the transsulfato complex is quite small and definitely lower than the activation entropy shown by the frans-[Co(NH3)4(NH2CH3)L] 2+ ions, which falls in the "normal" range [3].…”

“…The percentage of cis-[Co(NH3)4-( 15 NH3)(OH2)] 3+ product of the base hydrolysis of fra«s-[Co(NH3)4( 15 NH3)L]" + ions was 29 for L = 0S03, 47 for L = C1 and Br, and 50 for L = 0N02. These trends were discussed elsewhere [22], A similar pattern has been found for the competition ratios of fra«s-[Co(NH3)4(NH2CH3)L] 2+ ions (L = 0S03, CI, Br and 0N02) with N02 as competitor [31 ], i.e. the competition ratios depend on the nature and charge of the leaving group.…”

“…Comparable rate enhancement observed for ira«s-[Co(NH3)4(NH2CH3)L] 2+ complexes has been assigned to an inductive effect of the methyl substituent [22]. This assumption has now further support since the crystal structure of the trans-[Co(NH3)4(NH2CH3)Cl](C104)2 complex has been determined [25] and it shows that substitution of a NH3 group by a NH2CH3 ligand (trans position) does not produce a relevant steric crowding.…”

“…The percentage of ris-[Co(NH3)4(NH2CH3)(OD2)] 3+ in the products of the base hydrolysis (after acidification) calculated from the resonance integrals was 9% (±2%). The corresponding literature values for the frarcs-[Co(NH3)4(NH2CH3)L] 2+ ions with L = CI, Br and 0N02 are 11%, 13% and 17% respectively [22]. Therefore, there is a slight, but significant, dependence of the product distribution of the base hydrolysis of the irans-methylamine complexes on the nature of the leaving group.…”

“…bond breaking substantially precedes bond making [4][5][6][7][8][9][10]. For base hydrolysis, a conjugate-base mechanism seems well defined, although there is still some controversy on whether the process is entirely dissociative, Deb, or if it is partly concerted, Idcb [11][12][13][14][15][16][17][18][19][20][21][22], In the course of our research on the aquation and base hydrolysis reactions of fra«s-[Co(NH 3 )4(NH2CH3)L] 2+ ions, where the leaving group, L, was an uninegative ligand [22], it seemed useful to study some complex in which L is a binegative group, in order to extend the study to irans-[Co(NH3)4(NH2CH3)L] + ions. Here we report the base hydrolysis and aquation of frans-[Co(NH3)4(NH2CH3)(OS03)] + ion.…”