General and Inorganic Chemistry

Abstract

Fig. 1.-Rotatory dispersion curves: (1) L-[Co(Z-pn)2C03]I; (2) L-[Co(en)2C03]I. iodide was dissolved in water and acetone was added until the salt was on the point of precipitating. The solution so obtained was kept at 30° for 1 week, during which time practically all the complex iodide had separated out as orange-pink crystals. Analyses showed that this was the anhydrous iodide and the rotatory dispersion curve indicated that it was pure l-[Co(/-pn)2-CO,]I. Figure 1 shows the rotatory dispersion curve for this isomer and compares it with that for pure L-carbonato-bis-(ethylenediamine)-cobalt(III) iodide. The difference is similar to that between l-[Co(Z-pn)2C204]I and l-[Co(en)2C2C>4]L4 The equilibrium which exists between d-and l-[Co(/-pn)2C03] + ions and the lower solubility of the iodide of the levorotatory isomer in aqueous acetone enabled this stereospecific synthesis to be achieved. This investigation indicates that the isomers obtained previously1,2 were about 75% pure. Subsequent stereospecific reactions5,6 might be improved by using the product of the present investigation. Experimental d,L-Carbonatobis-(Z-prop.ylenediamine)-cobalt(III) Chloride 1-Hydrate.-Carbon dioxide gas was bubbled through an aqueous solution of cobalt(II) chloride hexahydrate (40 g.) and Z-pro-pylenediamine (86.3 ml., 28.5% aqueous solution) was added slowly while the temperature was raised to 80°. The carbon dioxide flow then was stopped and lead(IV) oxide (30 g.) was added slowly while stirring the mixture to prevent caking. Vigorous stirring was continued for 3 hr. at 80° and the mixture was filtered while hot. Lithium carbonate (29 g.) was added to the filtrate, which was stirred at 60° for 8 hr., filtered, and evaporated in the presence of small amount of lithium carbonate (2 (4) T., ibid., 74, 4820 (1952). g.) to 250 ml., and again filtered (pH 10). Calcium chloride hexahydrate (10 g.) was added to the cooled solution, which then was stirred for 3 min. and filtered through a Whatman 542 paper. Ethanol (51.) was added to the filtrate and the flocculent precipitate was stirred for 5 hr., collected at the pump, washed with ethanol and then acetone, and air-dried at 70°. The filtrate was cooled in a refrigerator overnight to give further product. The total yield was 34 g. (64%); [a]v-40°. Anal. Caled, for [Co(C3HioN2)2C03]C1 H20: C, 26.25; H, 6.88; N, 17.50. Found: C, 26.59; , 6.81; N, 17.45. L-Carbonatobis-(/-propylenediamine)-cobalt(III) Iodide.-The above chloride (20 g.) was dissolved in a small volume of water and precipitated almost completely with excess solid sodium iodide. The crude iodide was collected at the pump, washed with acetone, and air-dried. It then was dissolved in a minimum volume of water and acetone was added until the solution was slightly cloudy. The flask was stoppered and kept at 30° for 1 week. The crystalline precipitate which formed gradually in the course of the week was filtered off and washed with acetone. It w'as recrystallized twice from water by adding acetone, collected at the pump, washed with acetone, and air-dried. The rotatory dispersion curve of a 0.04% solution in a 1-dm. tube was obtained using a Shimadzu manual spectrophotometer with a photo-electric polarimeter attachment. It is shown in Fig. 1 and is there compared wdth the curve for L-[Co(en)2C03]I. Anal. Ternary compound formation in the system chromium -boron-oxygen has previously been sought without success. Keith and Roy1 found that heating of equimolar mixtures of Cr203 and B203 at 1000° yielded only Cr203 as a crystalline phase. Prolonged heating (7 days) at 1000° caused gradual evaporation of B203. The originally fine-grained Cr203 grew into larger crystals up to 0.1 mm. in size. Earlier, Partington2 referred to recrystallization of Cr203 by fusion with B203 and CaC03. However, no details are given concerning ratios, temperatures, or duration of heating; the CaC03 is presumably included to act as a "mineralizer." In this Laboratory chromium borate, CrB03, has been prepared by reaction between Cr203 and B203 in molten B203 at 1100°. The crystal structure is rhombohedral. Based on a hexagonal cell the dimensions are a0 = 4.5775 A.., c0-14.25s A.; space group R3c (D3a6). DTA studies show that decomposition to Cr203 and B203 occurs at 1220°.