C. M. Perkins, N. J. Rose, R. Stenkamp
Jun 1, 1990
Citations
0
Influential Citations
10
Citations
Journal
Inorganica Chimica Acta
Abstract
Abstract Methylmalonato-2,2′,2″-triaminotriethylaminecobalt(III) chloride was synthesized by two methods, the first involving the addition of 2,2′,2″-triaminotri- ethylamine (tren) to a basic solution of cobalt(II) methylmalonate prepared from methylmalonic acid and cobalt(II) chloride and the second involving the addition of disodium methylmalonate to a solution of [Co(tren)C12] C1·H2O. Crystals of the complex are monoclinic, space group P21/c, a=8.438(2), b = 22.770(7), c = 9.913(3) A, β = 114.6(1)°, Z = 4. The asymmetric unit consists of one complex, a chloride counter ion and three water molecules. A protonated complex was generated in an acidic solution of the first compound and was also characterized crystallographically. The crystals are again monoclinic, space group P21/n, a=9.112(3), b=16.587(4), c= 12.610(4) A, β = 99.32(2)°, Z = 4. In this case, the asymmetric unit contains the complex, two chloride ions, a water molecule and half of an ethanol molecule. A strong hydrogen bond involving one of the carboxylate oxygens not bound to the metal allows the methylmalonate ion to serve as a uninegative, bidentate ligand. This mode of binding suggests a model for how proteins with two adjacent γ-carboxyglutamic acid residues might bind one Ca2+ without causing severe charge balance problems.