Isomers of the Dichlorobis(l-cyclohexanediamine)cobalt(III) Ion

Abstract

Titration of [Nb&l,,] 2+ Solutions with Iz and FeS&.--Xn aqueous solution (approximately M ) of [r\-b&l12] 2+ was prepared by dissolving Xb~b6Cl14.7HzO in water. Aliquots of this solution were titrated using an aqueous solution of iron( 111) ammonium sulfate and a methanol solution of iodine. Polarographic Study of [ N~~C~I Z ]~+ Oxidation.-Approximately X solutions of P\'bsC11~.7H~o with 1 ,M KC104 as supporting electrolyte were used, with a standard calomel electrode (s.c.e.) as the reference electrode. An oxidation wave was found with El/* = +O.426 v. on the hydrogen scale; the maximum accessible potential is about 0.60 v. Results and DiscussionSolutions of [Ta6Xl2I2+ in which the ionized halide had been exchanged for nitrate or perchlorate proved to be unsuitable for quantitative studies of the oxidation. The nitrate solutions were unstable with respect t o oxidation of [Ta6X12I2+ by nitrate ion, and a perchlorate solution, evaporated to near dryness on a hot plate, detonated. Therefore, sulfate-exchanged solutions were chosen for study. Nitrate solutions of [Nbs-C1l2I2+ were also found to be unstable, decomposing to liberate C1-.Direct titrations of the [TasX12]2+ solutions were unsatisfactory because the disulfate which precipitated during the titration formed an impervious coating on the platinum electrode, producing erratic results. Indirect titrations allowed removal of this product by filtration and so were free of interference. However, direct titrations of the [NbeC112l2+ ion in the presence of C1ion were carried out with both aqueous Fe(II1) and methanolic 12.The titration of aged solutions (ca. 1 week) of [Tae-C112]2f and [Ta&rl2l2+ with iron(II1) gave Fe/Ta&12 ratios in the range of 1.90 to 1.81. However, on passing these solutions through a Jones reductor or titrating freshly prepared solutions Fe/Ta&12 ratios in the range 1.97 to 2.03 were obtained. Direct titrations of [Nbs-

1,4-Phenylene-bridged 1,3,2,4,6-thia- and 1,3,2,4,6-selenaphosphatriazinyl diradicals: preparation, spin distributions, and solid-state structures

“…Se(l) 0.00512 (8) 0.26175 (8) 0.03526 ( 14) 3.2 (2) Se(2) -0.32080 (8) 0.16227 (9) 0.20687 ( 16) 4.5 (2) P(l) C(l) -0.0503 (7) 0.2554 (7) 0.1482 (13) 2.4 ( 5) C(2) -0.2339 (7) 0.1974 (7) 0.2449 (13) 3.1 ( 5) C(3) -0.0976 (7) 0.2393 (7) 0.1749 (13) 2.5 ( 5) C(4) -0.1088 (7) 0.2394 (7) 0.2495 (12) 2.8 ( 5) C( 5) -0.1523 (7) 0.2265 (6) 0.2720 (11) 2.2 ( 5) C( 6) -0.1855 ( 6) 0.2138 ( 6) 0.2187 (11) 1.7 (4) C( 7) -0.1745 (7) 0.2152 (7) 0.1420 (12) 2.9 ( 5) C( 8) -0.1313 (7) 0.2278 (7) 0.1182 (13) 3.5 ( 5) C( 11) 0.0572 (8) 0.3454 (7) 0.2126 (12) 3.3 ( 5) C( 12) 0.1028 (10) 0.3724 (10) 0.2088 (16) 6.5 (7) C( 13) 0.1248 (9) 0.4205 (9) 0.2273 (15) 5.7 (7) C( 14) 0.0990 (9) 0.4376 (8) 0.2456 (15) 5.1 ( 6) C( 15) 0.0546 (9) 0.4119 (9) 0.2526 (15) 5.6 (7) C( 16) 0.0321 (9) 0.3665 (10) 0.2338 (16) 5.9 (7) C( 21) 0.0560 (8) 0.2685 (7) 0.2560 (14) 3.8 ( 6) C( 22) 0.0872 (10) 0.2575 (10) 0.2312 (17) 7.5 (8) C( 23) 0.1077 (12) 0.2401 (13) 0.2854 (25) 11.1 (11) C( 24) 0.0957 (12) 0.2369 (12) 0.3613 ( 22) 9.8 (10) C( 25) 0.0634 (11) 0.2477 (10) 0.3831 (18) 8.0 (9) C( 26) 0.0429 (9) 0.2624 (8) 0.3286 (16) 5.3 (7) C(31) -0.2810 (7) 0.1425 (7) 0.4342 (12) 2.5 ( 5) C(32) -0.2421 (8) 0.1433 (7) 0.4513 (13) 4.0 ( 6) C(33) -0.2388 (9) 0.1213 (9) 0.5155 ( 16) 5.4 (7) C(34) -0.2747 (10) 0.0965 (9) 0.5628 (16) "C(S1)-C(S6) and N(S1) are the atoms of disordered solvent molecules located from Fourier and difference maps. These were included in the final stages of least-squares refinement.…”

Circular Dichroism of the Copper(II) N,N′-Bis(alanyl)stilbenediamine Complexes

“…81-83', lalD +87" (0.049 g, 5 ml ether). L-alanine was obtained from Nutritional Biochemicals Corp., lalD + 14.25" (2 M, 2 N HCI), and converted to phthaloyl L alanine by standard methods (6).…”

Correlations of Nuclear Magnetic Resonance and Optical Rotatory Dispersion Spectra for Establishing the Absolute Configurational Assignment of Cobalt(III)-Chelated Optically Active Triethylenetetramine Homolog-α-Amino Acid Adducts

“…The fact that optically active molecules which can act as ligands coordinate in a stereoselective manner is well known.1•2 The original concept of this stereopreference was based partly on the apparent stereospecific coordination of D-cyclohexanediamine,3 but part of this work has been shown to be incorrect. 4 The conclusions drawn by Jaeger, however, have some merit but must be updated in light of the theoretical predictions of Corey and Bailar1 which were confirmed experimentally by Dwyer, et a!. '°Most of the work on ligand stereospecificity so far has involved bidentate molecules.…”