Jay H. Worrell

CsOH-promoted chemoselective mono-N-alkylation of diamines and polyamines

Abstract Selective N -alkylation of diamines and polyamines was carried out using cesium hydroxide, 4 A molecular sieves, and DMF. This protocol was highly chemoselective, favoring mono- N -alkylation over overalkylations.

High-resolution NMR analysis of cobalt(III) complexes with 1,8-diamino-3,6-dithiaoctane

Abstract This article summarizes NMR data obtained for cobalt(III) complexes derived from linear and tripodal tetradentate or pentadentate ligands containing nitrogen and/or sulfur donor atoms, and not complexes of large Schiff-base macrocycles, porphyrins or corrins. The review is supplemented with recent NMR work on complexes that had their origin in the laboratories of Professor Busch at a time when the use of NMR spectroscopy as an inorganic structural tool was in its infancy. The more recent capabilities and uses of nuclear magnetic resonance spectroscopy for assisting in metal complex structure assignments and isomeric identification are illustrated by the following work. Cobalt(III) complexes containing the quadridentate ligand 1,8-diamino-3,6-dithiaoctane (eee) were examined by high resolution one and two-dimensional NMR techniques. The spectra acquired using conventional pulse sequences include proton, carbon, DEPT, COSY and heteronuclear correlation. [Co(eee)(NO 2 ) 2 ]Cl and [Co(eee)Cl 2 ]Cl both give rise to carbon-13 spectra which contain only three signals and 1 H-proton spectra which contain a highly pronounced A 2 B 2 pattern. This data is supportive of the symmetrical cis geometry. Assignments in the proton spectra were assisted by the use of the COSY experiment. Carbon-13 signals were assigned by heteronuclear chemical shift spectroscopy. The DEPT spectra confirmed all carbon signals arise from methylene carbons. The study highlights the power of 1 H and 13 C NMR spectroscopic techniques for the structural characterization of inorganic complexes.

Syntheses, properties and reactions of nickel(II) complexes derived from 1,8-bis(2-pyridyl)-3,6-dithiaoctane

Abstract The preparation, properties and reactions of several new nickel(II) complexes derived from 1,8-bis(2-pyridyl)-3,6-dithiaoctance (Ligand A) are presented. The complexes NiAX 2 (X = Cl − , Br − , I − , SCN − ) are typically octahedral in the solid state, methanol and nitromethane. [NiA(H 2 O) 2 ] (ClO 4 ) 2 , also octahedral, undergoes a very unique solid state reaction when exposed to low energy near infrared radiation, producing a red 5-coordinate species [NiAClO 4 ]ClO 4 . Also reported is a square-planar diamagnetic [NiA] (ClO 4 ) 2 complex. The compounds are characterized by elemental analyses, magnetic moments, IR vibrational spectra, solid and liquid electronic spectra and interconversion reactions. Available evidence suggests that the NSSN tetradentate ligand occupies an equatorial square-planar arrangement around nickel(II) with coordinating anions or solvent occupying the fifth and/or sixth positions above and/or below the ligand plane.

The phenomenon of conglomerate crystallization. XXXVI: The crystal and molecular structure of racemic [CIS-α-dinitro(1,8-diamino-3,6-dithiaoctane)cobalt(III)]Cl (I) and the absolute configuration of (+)546-Λ(δλδ)[cis-α-dinitro-1,8-diamino-3,6-dithiaoctane)cobalt(III)]ClO4 (II)

Abstract Compound I crystallizes as a racemate, as suggested earlier.3,5,14 Crystals of II were prepared from externally resolved material. In both, the organic ligand is quadridentate with two trans-axial nitrogen and two cis sulphur donor atoms located trans to the two basal NO2 ligands. Likewise, in both, the counter-anion is hydrogen bonded to the terminal NH2 hydrogens and the cations are in the cis-α configuration, with those of the former having Λ(δλδ) and Δ(λδλ) pairs related by the inversion centre; those of the (+)546 enantiomer of II are Λ(δλδ). These results fix the absolute configuration of II and establish the fact that the synthetic procedure for the preparation of the precursors of this compound, [Co(C6H16N2SP2)(XY)]A (X  Y  NO2−; X  Y  Cl; X  Cl, Y  H2O, etc. and A = an anion), contain exclusively racemic Δ(δλδ) and Δ(λδλ) pairs and no cis-β or trans isomers. Packing in the case of I consists of infinite strings of chloride-linked cations which are formed such that a given string contains [Co(1)Cl(1)Co(1)Cl(1)]n and of another string of [Co(2)Cl(2)Co(2)Cl(2)]n, and each chloride has three hydrogen bonds, two intra-string and a third linking adjacent strings. All Co(1) cations within the string defined by the current coordinates are Λ(δλδ); torsional angles = 42.3, −33.9 and 48.3°) and all Co(2) cations within the string defined by the current coordinates are Δ(λδλ); torsional angles = −27.1, 39.8 and −42.1°). Given the space group and the contents of the cell, it is clear that enantiomorphic pairs of infinite strings are present in the crystals. Crystals of enantiomorphic II were studied in order to show the relationship between the CD spectrum and the absolute configuration of the cation.

An examination of the relationship between the x-ray diffraction-derived molecular structure of chloro (1,11-diamino-3,6,9-trithiaundecane)cobalt(III) cation and its inner sphere reduction by iron(II)

Abstract The crystal structure of racemic [Co(NSSSN)Cl](ClO4)Cl was determined by X-ray diffraction methods. It crystallizes in the monoclinic system, space group P21/c, with cell constants of a = 9.795(3), b = 10.412(3) and c = 16.323(8) A, and β = 93.87(4)°; V = 1661 A3 d (meas.; flotation) = 1.85 gm-cm−3, d (calc.; Z = 4 molecules/unit cell) = 1.88 gm-cm−3. The molecules, a racemic mixture, have the absolute configurations λλδλ or δδλδ at each of the four five-membered rings and resemble, in general, the so called αα conformer already described by Snow1 in his study of the Co(tetraen)Cl2+ cation. However, the torsional angles at C2, C3 and C8, C9 in the two terminal C-C-NH2 fragments are quite different in the two systems. For Co(tetraen)Cl2+ they are 44.7° and −20.2° respectively, whereas for Co(NSSSN)C2+ the values –52.3° and –44.6° obtain. Also, the ring Co-S1-C3-C2-N1 does not have the classical, low energy conformation found in Co(tetraen)Cl2+. The presence of the larger Co-S bonds causes the two terminal -NH2 groups to be pushed toward each other, and to minimize steric hindrance between adjacent -NH2 hydrogens and ligand twists C2 down and staggers the terminal hydrogens. We visualize the propagation of these distortion effects in solution as being transferred from one side to the other across the entire ligand chain with concomittant effects on the activation of the precursor complex in electron transfer reactions, resulting in ~107 rate enhancement over the Co(tetraen)Cl2 system. Kinetic data for the reduction of Co(NSSSN)X2+ and Co(NSNSN)X2+ (X = Cl−, Br−) by Fe(II) is also presented and discussed.

The synthesis of a stereospecific pentadentate ligand and its bromo cobalt(III) complex

Abstract The synthesis of 7 - methyl - 4,10 - dithia - 1,7,13 - triazatridecane, NH2CH2CH2SCH2CH2N(CH3) CH2CH2SCH2CH2NH2, a flexible, linear pentadentate ligand is reported. The preparation of its bromo cobalt(III) complex is reported and its stereospecific attachment to cobalt(III) is discussed.

PREPARATION, ISOLATION, AND CHARACTERIZATION OF COBALT (III) COMPLEXES DERIVED FROM A NEW LINEAR, FLEXIBLE PENTADENTATE LIGAND 1, 11-DIAMINO-3, 6, 9-TRITHIAUNDECANE

Abstract The reaction of bis(2-mercaptoethyl)sulfide with N-(β-bromoethyl)phthalimide followed by hydrolysis using hydrazine hydrate afforded 1,11-diamino-3,6,9-trithiaundecane, NH2CH2CH2 -S-CH2CH2 -S-CH2 CH2 -S-CH2-CH2 NH2, (QS). The preparations and interconversions of Cobalt(III) complexes of the type Co(QS)Xn+ where X=Cl−, Br−, N3 −, NO2 − and SCN− are presented and discussed. Considerations are presented supporting the αα geometry for this series of complexes.

Synthesis and NMR Characterization of Cobalt(III) Complexes with 1,8-diamino-3,6-dithiaoctane, 2,2-Bipyridine, and 1,10-phenanthroline

The complexes [Co(eee)(bipy)]Cl3 and [Co(eee)(phen)]Cl3 (eee, 1,8-diamino-3,6-dithiaoctane) were synthesized and characterized by two-dimensional NMR spectroscopy. The presence of the bidentate aromatic ligands 2,2-bipyridine and 1,10-phenanthroline caused the 1H resonances to be spread into a wider spectral width than previously observed for [Co(eee)(NO2)2]Cl and [Co(eee)Cl2]Cl. Separate multiplets were observed for the four protons in the terminal ethylene linkage. It was possible to positively assign each multiplet and to determine the relative spatial orientations of the corresponding protons.

USING TWO DIMENSIONAL NMR TECHNIQUES TO ASSIGN PROTON AND CARBON SPECTRA FOR COBALT(III) COMPLEXES DERIVED FROM LINEAR QUINQUEDENTATE LIGANDS CONTAINING NITROGEN AND SULFUR DONOR ATOMS

Abstract High resolution NMR spectroscopy was used to study the structure of a cobalt(III) complex derived from the linear quinquedentate ligand, 7-methyl-4, 10-dithia-l, 7, 13-tria-zatridecane, NH2-CH2CH2-S-CH2CH2-N(CH3)-CH2CH2-S-CH2CH2-NH2. The flexibility of this ligand allows it theoretically to form four distinct structural isomers with metal ions. The one dimensional proton spectrum exhibited by [Co(NSNSN)Cl]Cl2, is complicated and does not provide structural insight. A combined utilization of proton, carbon, DEPT, COSY, NOESY and HETCOR spectra was employed to establish geometric structure type, make individual proton assignments, identify proton-proton connectivities that result from scalar coupling, and distinguish interactions occurring as a result of through-space interactions. Information about the five-membered chelate ring orientations was also obtained. Two groups of signals were shown to correlate with each carbon signal, exhibiting a definite nonequivalence between geminal protons. Gemina...

Kinetics of Substitution and Isomerization of Nitrite Ion on Aqua(7-Methyl-4,10-Dithia-1,7,13-Triazatridecane)Cobalt(III) and the Structure of the Product

Abstract The influence of placing a CH3N- linkage trans to a site of nitro substitution and spontaneous nitrito-to-nitro isomerization is reported for the Co(NSNSN)H2O3+ cation where NSNSN is 7-methyl-4,10-dithia-1,7,13-triazatridecane, NH2CH2CH2-S-CH2CH2-N(CH3)-CH2CH2-S-CH2CH2NH2. Preparation and characterization is described for the aqua and nitrito complexes. Co(NSNSN)H2O3+ is 435 times more reactive than Co(NH3)5H2O3+ under identical conditions. Nitrito-to-nitro isomerization is much slower than the conversion of Co(NSNSN)H2O3+ to Co(NSNSN)ONO2+. The isomerization was studied at a number of wavelengths, temperatures and at various concentrations of acid and nitrite ion at ionic strengths of 0.11–0.60 m. Isomerization rate constants are 1.10±0.11 × 10-5sec-1 at 20.0[ddot]C, 5.24 ± 0.83 × 10-5sec-1 at 30.0[ddot]C, and 18.1 ± 1.1 × 10-5 sec-1 at 39.0[ddot]C. Thermodynamic activation parameters are ΔHΔ = 109.3 kJ mol-1, ΔSΔ = + 33 J mol-1 K-1 and ΔGΔ = 99.4 kJ mol-1. Single-crystal X-ray diffraction data ...