Stereochemistry of base hydrolysis of Co(NH3)5X2+ and Co(en)2LXn+ ions

Abstract

FRANCIS K. XOKDMEYEKInorgunic Cizem.istry radii, namely, C(1) e . . 0 ( 3 ) = 2,911 (8) A. 'The tion of the crystals and in the X-ray work and to distances between the different hydrogen-bonded Mrs. M, Hillberg for excellent technical assistance. chains are all somewhat larger than this sum. )~X'~ and Co(en)2LXrz+ IonsThe stereoclieriiistry of base liytirolysis of eo( SH3):X2 and Co(cii)nL>iZ6-+ coinpleses is esatniiied in terms of thc SNICU mechanism. Stereochemical results reported for the [Co( N H -h ( 16SHa)X] a -complexes support the conclusion that thc leaving group, X-, leaves from a position cis to an amido groul) to form a trigonal-bipyramidal intermediate and that H,O enters the intermediate by the microscopic reverse of this process. It is argued that for the base hydrolysis reactions of Co(en)JX" + complexes only two of a possible four (or three of a possible five where L = SHa) trigonal-bipyramidal intermediates will be important. Assuming that only these two intermediates are important, the retention of optical activity i n the base hydrolysis of active c-is-Co(en)2LX7'+ can be predicted from the yield of trens product from cis-and from tians-Co( en)pLX"+.

Mechanism of chiral asymmetry generation by chiral autocatalysis in the preparation of chiral octahedral cobalt complex

“…19 The absolute configuration, however, changes in the ligand exchange reactions, since the reaction proceeds through an achiral transition state. [19][20][21][22][23] In this reaction system, an optically active final product was produced from racemic intermediate, indicating the presence of an achiral transition state. We, therefore, postulated that the rate constant for each enantiomer of the final product is independent of the handedness of the intermediate.…”

Synthesis, characterization and some reactions of trans‐[Co(NH3)4(CH3NH2)Br]2+ and trans‐[Co(NH3)4(CH3NH2)(NO3)]2+ complexes

“…Close to 50% cis and 50% trans aquo product was observed for all the substrates. Later on NORDMEYER [19] explained such result assuming a trigonal bipyramidal structure for the five-coordinated intermediate with the amido group cis to the leaving group. This cis-amido group was supposed to have a cis-directing influence on the entering water.…”

Substitution Reactions of Octahedral Complexes

“…(1) there should be a "flat" nitrogen for example, the sec-NH in a mer-dien arrangement Nordmeyer [10] first noted the cw-effect, that is non-terminal amine groups provide the best labilisation, especially when they are cis to the leaving group. On the basis of the above criteria it is clear that ?ra«j-macrocyclic complexes of the type trans-[Co(MAC)X 2 ] (MAC = a tetra-aza macrocycle) will be very labile in base as they fulfil most of the Hendersen-Tobe requirements.…”

“…10 Rate constants for the base hydrolysis of some ruthenium(III) acido-amine complexes at 25°C Base Hydrolysis, Comparisons of Different Metal Centres A summary of some of the significant feature of the base hydrolysis of Co(III), Cr(III), Rh(III) and Ru(III) acido-amine complexes is given in…”