J. N. Cooper

Structural trans effects in some bis(ethylenediamine)cobalt(III) complexes

Abstract The crystal structures of seven bis(ethylenediamine) cobalt(III) complexes with monodentate oxalato, azido, nitro, sulfito and thiosulfato ligands have been determined by single-crystal X-ray diffraction methods. The complexes, space groups, cell constants, number of molecules per unit cell, Z , calculated and experimental densities and final reliability factors are as follows: cis [en 2 Co(NO 2 )- (C 2 O 4 )]·2H 2 O, P 1 , a = 6.925(3), b = 8.055(3), c = 12.158(4)A, α = 80.16(2)°, β = 77.87(2)°, γ= 87.90(2)°, V = 653 A 3 Z = 2, ϱ exp = 1.78 g cm −3 , ϱ calc = 1.76 g cm −3 , R 1 = 5.5, R 2 = 9.4; trans [en 2 - Co(NO 2 )(C 2 O 4 )]·2H 2 O, P 2 1 / n , a = 8.218(2), b = 15.613(1), c = 10.694(1) A, β = 101.49(1)°, V = 1344 A 3 , Z = 4, ϱ exp = 1.73 g cm −3 , ϱ calc = 1.74 g cm −3 , R 1 = 3.5, R 2 = 5.6; cis [en 2 Co(N 3 )(C 2 O 4 )]· H 2 O, P 2 1 / c , a = 8.379(1), b = 15.548(4), c = 9.736(3) A, β = 97.44(2)°, V = 1258 A 3 , Z = 4, ϱ exp = 1.73 g cm −3 ϱ calc = 1.69 g cm −3 , R 1 = 4.3, R 2 = 4.8; trans [en 2 Co(N 3 )(C 2 O 4 )]·2H 2 O, I 4 1 / a , a = 26.684(2), c = 7.625(2) A, V = 5429 A 3 , Z = 16,ϱ exp = 1.69 g cm −3 , ϱ calc = 1.69 g cm −3 , R 1 = 6.6, R 2 = 7.9; cis -NH 4 [en 2 Co(S 2 O 3 )(SO 3 )]·3H 2 O, P 2 1 / n , a = 10.094(9), b = 12.205(12), c = 13.358(3) A, β = 90.19(4)°, V = 1646 A 3 , Z = 4, ϱ exp = 1.79 g cm −3 , ϱ calc = 1.78 g cm −3 , R 1 = 7.6, R 2 = 9.2; cis [en 2 - Co(N 3 )(SO 3 )]·1.5H 2 O, P 2 1 / n , a = 7.749(1), b = 10.701(2), c = 15.101(4) A, β = 102.80(2)°, V = 1221 A 3 , Z = 4, ϱ exp = 1.78 g cm −3 , ϱ calc = 1.78 g cm −3 , R 1 = 3.2, R 2 = 4.0; cis [en 2 Co(NO 2 )(SO 3 )]· 1H 2 O, P 2 1 / c , a = 6.629(2), b = 11.429(4), c = 15.156(4) A, β = 93.27(2)°, V = 1146 A 3 , Z = 4, ϱ exp = 1.87 g cm −3 , ϱ calc = 1.86 g cm −3 , R 1 = 3.5, R 2 = 4.4. Additionally, the previously reported structure of cis [en 2 Co(N 3 ) 2 ]NO 3 has been redetermined: Pnma , a =11.903(3), b =23.566(6), c = 8.877(2) A, V = 2493 A 3 , Z = 8, ϱ exp = 1.73 g cm −3 , ϱ calc = 1.73 g cm −3 , R 1 = 4.8, R 2 = 5.9. The structural trans effect, STE , the difference between the CoN(en) bond length trans to a ligand and the average of the two CoN(en) bond lengths that are both cis to that ligand and trans to each other, decreases in the series SO 3 2− [0.059(7) A]> SSO 3 2− [0.036(9) A]> NO 2 − [0.019 (10) A]> N 3 − [0.005(6) A]> C 2 O 4 2− [0.000(6) A].

Complexes of thiosulfate and disulfanemonosulfonate with cis-bis(ethylenediamine)cobalt(III)

Preparation de cis-[(en) 2 Co(SO 3 )(S 2 O 3 )] − et cis-[(en) 2 Co(S 2 O 3 ) 2 ] − et de cis-[(en) 2 (Co)(NO 2 )(S 3 O 3 )]. Structure cristalline

The oxidation of americium(V) and other reductants by aqueous acidic Np(VII)

Abstract The oxidation of Am(V) by Np(VII) proceeds by the rate-law: −d[Np(VII)]/dt = βc[Np(VII)][Am(V)][H+]/1 + c[H+] where at 25°, μ = 1.00 M, β = (4.42 ± 0.10) × 105 M−1 s−1, c = 1.30 ± 0.12 M −1 ; ΔH β ∗ = 5.58 ± 0.76, ΔH c o = −1.8 ± 1.0 kcal / mole ; ΔS β ∗ = −14.1 ± 2.6, ΔS c o = −5.5 ± 3.3 e.u. Reactions between Np(VII) and H2C2O4, HN3, SCN−, H2TeO3, H2SO3, H3PO3, Fe(III), Ni(II), (NH3)5CoBr2+, Ce(III), Cr(III) and Pd(II) are also noted.

An electron spin resonance study of the reactivity of organotin and organolead radicals

Tri-n-butyltin radicals were prepared by photolysis of mixtures of t-butyl peroxide and hexa-n-butylditin. E.s.r. competition experiments gave activation energy differences for the abstraction of the halogen atom from 15 organic halides by the tri-n-butyltin radical. The results indicate that polar as well as enthalpy effects are important. Qualitative work on trimethyl-lead radicals, prepared by photolysis of hexamethyldilead, shows that ease of removal of halogen from organic halides by the trimethyl-lead radical decreases in the order allyl bromide > carbon tetrachloride > alkyl bromides > alkyl and allyl chlorides. SH2 Displacements by t-butoxyl radicals of an alkyl radical from trialkyltin bromides, chlorides, and acetates, but not the hydrides, were observed.

An electron spin resonance study of the reactions of organosilicon, organogermanium, and organotin radicals with carbonyl compounds

Addition of organosilyl, organogermyl, organotin, and organolead radicals to the oxygen atom of carbonyl compounds has been investigated by e.s.r. spectroscopy. Ease of addition, to a given carbonyl compound, falls in the order R3Si· > R3Ge·∼ R3Sn· > R3Pb·, and for a given Group IVB radical, diketones > oxalates > ketones > trifluoroacetates > formates > acetates. The results are rationalized in terms of bond energy differnces, stabilization of radicals formed, and polar effects. Tris(trimethylsilyl)silyl is less reactive than triethylsilyl. Organotin radicals react with α-diketones, oxalates, to give spectra which are best interpreted as being due to radical anions.

Co-ordination stabilization of reactive molecules: preparation of trans-[(en)2Co(OH2)(S3O3)]+, a cobalt(III) complex containing disulphane monosulphonate

cis-[(en)2Co(S2O3)2]– is oxidized by aqueous iodine to yield free sulphate and trans-[(en)2Co(OH2)(S3O3)]+, a moderately stable complex containing the very reactive ligand, disulphane monosulphonate.