Clifford S. Garner

Magnetic Evidence for d3s Bond Hybridization in Chromium (II) Acetate. The Oxidation State of Chromium in a Reported Tris(8‐Hydroxyquinoline) Chromium (II)

Magnetic susceptibilities of solid Cr(OOCCH3)2 and its monohydrate were measured, and these compounds were shown to contain no unpaired electrons. This fact indicates that the four unpaired 3d electrons of the normal Cr++ ion are paired in these compounds, the three 3d orbitals thus made available being utilized in the formation of covalent bonds. The fourth covalent bond probably involves use of the 4s orbital of chromium. This evidence may constitute the first example of d3s bond hybridization postulated by Pauling. Susceptibility measurements were also carried out on tris(8‐hydroxyquinoline) chromium (III) and a reported tris(8‐hydroxyquinoline) chromium (II). The evidence indicates both to be the same compound, with the chromium having a tripositive oxidation state.

MAGNETIC MOMENTS OF SOME OCTAHEDRAL COMPLEXES OF IRIDIUM

Magnetic susceptibilities of Na2IrCl6, Na3IrCl6·2H2O, and (NH4)2Ir(H2O)Cl5 were determined for these solids and for aqueous solutions 0.6f in the complex compound and 1f in HCl by the Gouy method. Na2IrCl6 is paramagnetic in the solid state and in solution, with a magnetic moment corresponding to one unpaired 5d electron and to d2sp3 covalent Ir–Cl bonds. The two iridium (III) complexes are diamagnetic, corresponding likewise to d2sp3 bond formation.

Kinetics of hydrolysis of cis-dichloro- and cis-chloroaquobis(propylenediamine)-chromium(III) cations☆

Abstract In 0·10 F HClO4, cis-Cr(pn)2Cl2+ has been found by spectrophotometric, Cl− release and chromatographic methods to aquate to the previously unreported species cis-Cr(pn)2(OH2)Cl2+; at 25·0°C the first-order constant is k1 = (3·5 ± 0·3) × 10−4 sec−1. At 25·0°C, cis-Cr(pn)2(OH2)Cl2+ hydrolyses in 3·1 F HClO4 with a pseudo first-order rate constant of k2 = (9·7) ± 0·9) × 10−6 sec−1, the product having been tentatively identified as a new complex, cis-Cr(pn)2(OH2)23+. Visible absorption spectra of the complexes are reported.

Transition metal complexes of triethylenetetramine. IV. Synthesis of chloroaquotriethylenetetraminechromium(III) cation, and kinetics of primary and secondary aquation of cis-α- dichlorotriethylenetetraminechromium (III) cation

Abstract The new complex, pink Cr (trien) (OH2)Cl2+ (probably cis-β or cis-β′isomer), has been synthesized and characterized aqueous solution, as have orange Cr(trien) (OH2)23+ (unknown isomers) and a purple species tentatively characterized as Cr(trienH) (OH2)2Cl3+ (unknown isomers), and their visible absorption spectra recorded. The latter two species are directly formed products in the hydrolysis of pink Cr(trien) (OH2Cl2+ in 0.1–3 F HClO4 at 25–35°. Aquation of cis-μ-Cr(trien) Cl2+ follows a first-order rate law with k = (1.02±0.06) × 10−4 sec−1 at 25.00° over the range 0.0001–0.1 F HClO4 (μ = 0.1); Ea = 21.2± 0.7 kcal mole−1 and log PZ = 11.8±0.5 (sec−1). The aquation product is the new pink chloroaquo complex. Reaction schemes and approximate rate constant are presented for the hydrolysis of the chloroaquo complex. Comparison of rates are made with Cr(III)-bis(en) and Co(III)-trien analogs where they are known.

Kinetics of aquation of trans-dichlorobis(ethylenediamine)chromium(III) cation

Abstract The pseudo first-order rate constant for the production of ionic chloride by aquation of trans -dichlorobis(ethylenediamine)chromium(III) cation in 0·1 F HNO 3 at 25·0°C was found to be (2·25±0·03) × 10 −5 sec −1 . The rate is independent of initial concentration of the complex over the range 1·6–11·3 mF, of pH from 0·14 to 2·9, and of ionic strength from 0·016 to 1·0. Added sulphate ion accelerates the aquation, as does light. The Arrhenius activation energy is 23·23±0·17 kcal/mole over the temperature range 15·35°C, slightly less than for the trans -cobalt(III) analogue as predicted by crystal-field theory.

Kinetics of the spontaneous reduction of 1,2,3-triaquodiethylenetriaminecobalt(III) cation in aqueous perchloric acid

Abstract The spontaneous reduction of 1,2,3-Co(dien)(OH 2 ) 3 3+ to Co(II) has been investigated spectrophotometrically in 0·1-2F HClO 4 at 80–100°C. The observed first-order rate constant has the form k obs = k 1 + ( k ′ 2 /[H + ]); the hydrogen ion dependence has been ascribed to reduction of the hydroxodiaquo species. In 3·5M ionic strength (controlled with NaClO 4 ), k 1 = (6·5 ± 2·1) × 10 −8 sec −1 and k ′ 2 = (1·4 ± 0·8) × 10 −7 M sec −1 at 80·7°. The activation parameters for the acid independent ( k 1 ) path are E a = 36 ± 7 kcal mole −1 , log PZ (sec −1 ) = 15·0 ± 4·3.

Kinetics of the spontaneous reduction of triaquotriamminecobalt(III) cation in aqueous perchloric acid

Abstract The spontaneous reduction of Co(NH3)3(OH2)33+ (probably the 1, 2, 3 isomer) to Co(II) has been investigated spectrophotometrically and chromatographically in 0·2-1 F HClO4 (μ = 1·0 M, NaClO4) at 70–99°C and in 0·5 F HClO4 at 90°C. The observed first-order rate constant has the form kobs = k1 + (k′2/[H+]); the hydrogen ion dependence is ascribed to reduction of the hydroxodiaquo species. At 80·3°C and 1·0 M ionic strength, k1 = (1 ± 1) × 10−6 sec−1 and k′2 = (5·07 ± 0·03) × 10−6 M sec−1. The apparent activation parameters for the acid-dependent(k′2) path are Ea = 37·4±1·3 kcal mole−1, log PZ (M sec−1)= 17·8±0·8. Characterization of the triaquo complex is described.

Kinetics of isomerization of 1,2,6-triaquodiethylenetriaminecobalt(III) cation

Abstract The isomerization of 1, 2, 6-Co(dien) (OH 2 ) 3 3+ to the 1, 2, 3 ( cis or facial) isomer has been studied spectrophotometrically in 0·1 − 1 F HClO 4 at 30–40°. The observed first-order rate constant has the form k = k 1 + ( k 2 ′/[H + ]), and the hydrogen ion dependence has been ascribed to isomerization via a hydroxodiaquo species. In 3·5 M ionic strength (controlled with NaClO 4 ), k 1 = (3·73 ± 0·05) × 10 −5 sec −1 and k 2 ′ = (0·33 ± 0·03) × 10 −5 M sec −1 at 25° (by extrapolation). The activation parameters for the acid-independent ( k 1 ) path are E a = 25·9 ± 0·9 kcal/mole and log PZ (sec −1 ) = 14·6 ± 0·7.

Characterization of cis- chloroaquobis(2,2′-dipyridyl)chromium(III) cation, and kinetics of primary and secondary aquation of cis-Dichlorobis(2,2′-dipyridyl)chromium(III) Cation☆☆☆

Abstract Aquation of cis-Cr(dipy)2Cl2+ in 0.1–0.5 F HCl (μ = 0.1–0.5 M, NaCl) has been studied spectrophotometrically at 50–70°. At 70° μ = 0.5 M) the first-older rate constant is (5.4 ± 0.5) X 10−5 sec−1, independent of the acid concentration; Ea = 23.4 ± 0.8 kcal mole−1 and log PZ(sec−1) = 10.62 ± 0.55. The product is the previously not fully characterized cis-Cr(dipy)2(OH2)Cl2+, with no evidence for concurrent aquation via CrN bond rupture. At 70° in 0.13 F HCl or HNO3 (μ = 0.13 M) cis-Cr(dipy)2(OH2)2+ appears to aquate concurrently to cis-Cr(dipy)2(OH2)23+ and to an unidentified species of charge ⩾4 +, perhaps Cr(dipy)(dipyH)- (OH2)34+ (via the intermediate Cr(dipy)(dipyH)(OH2)(2- Cl3+), with a total first-order rate constant of (6.9 ± 0.8) X 10−5 sec−1. The cis-chloroaquo species has been fully characterized, and its visible absorption spectrum is reported. The new pink complex Cr(dipy)(OH2)43+ has been chromatographically isolated from a 0.1 F HCl solution of cis-Cr(dipy)2Cl2+ which had been aged at 70° for 50 days.

Exchange of Radiocobalt between the Hexammines of Cobalt(II) and Cobalt(III) in Liquid Ammonia

Exchange of radiocobalt between Co(NH3)6+2 and Co(NH3)6+3 nitrates in liquid ammonia has been studied at 25° and 45°C. Reactants were separated by distilling off the solvent ammonia and extracting the Co(II) as the thiocyanate complex into a mixture of ether and isoamyl alcohol. Runs were not accurately reproducible, probably because of catalytic effects from traces of oxygen in the system. Rate constants, calculated for an assumed bimolecular rate law, are 6×10—5 and 7×10—4 l·mole—1·sec—1 at 25° and 45°C, respectively. The rate in liquid ammonia is compared with published rates in aqueous ammonia solution and with the rate of exchange of labeled NH3 between solvent liquid ammonia and ligand ammonia in Co(NH3)6+3.