STERIC TRANS INFLUENCE OF AMINOMETHANE LIGAND IN TRANS-AMINOMETHANECHLOROBIS(1,2-DIAMINOETHANE)COBALT(III)

The trans isomer of aminomethanechlorobis (1,2-diaminoethane) cobalt(III), trans-[CoCl(NH(2)Me)(en)(2)](2+), was prepared from trans-[CoCl(NO2)(en)(2)](+) by a two-step reaction in which Cl- was replaced with an NH(2)Me and then the remaining NO2- was replaced with a Cl-. The configuration was confirmed by X-ray crystal analysis, and structural comparison was made with its cis isomer. The crystals have the formulae, trans-[CoCl(NH(2)Me)(en)(2)]Cl(ClO4) and cis-[CoCl(NH(2)Me)(en)(2)]Cl-2. The crystallographic data are as follows; Monoclinic, P2(1)/c, a=11.515(1), b=7.421(2), c=17.257(1) Angstrom, beta=99.220(8)degrees, V=1455.6(5) Angstrom(3), Z=4, and R=0.043 for the former, and Orthorhombic, Fdd2, a=26.64(1), b=27.26(1), c=7.570(2) Angstrom, V=5497(3) Angstrom(3), Z=16, and R=0.057 for the latter. The Co-Cl bond of the trans complex is longer than that of the cia complex. It was found that the bulkiness of the Me group effects the trans Co-Cl bond through one of the two flexible equatorial en chelate rings. The kinetic data of an aquation reaction of the trans and the cia complexes show that the Cl- of the trans complex is substituted more readily than that of the cis is.