Polymeric multideck sandwich complex of trimeric perfluoro-o-phenylenemercury with bromide anion

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1466–1467, June, 1991.     

Crown compounds for anions: sandwich and half-sandwich complexes of cyclic trimetric perfluoro-o-phenylenemercury with polyhedral closo-[B10H10]2- and closo-[B12H12]2- anions

It has been shown by IR and NMR spectroscopy that cyclic trimeric perfluoro-o-phenylenemercury (o-C6F4-Hg)3 (1) is capable of binding closo-[B10H10]2- and closo-[B12H12]2- anions to form complexes [[(o-C6F4Hg)3](B10-H10)]2- (2), [[(o-C6F4Hg)3]2(B10H10)]2-(3), [[(o-C6F4Hg)3](B12H12)]2- (4), and [[(o-C6F4Hg)3]2(B12H12)]2- (5). According to IR data, the bonding of the [B10H10]2- and [B12H12]2- ions to the macrocycle in these complexes is accomplished through the formation of B-H-Hg bridges. Complexes 2, 3, and 5 have been isolated in analytically pure form and have been characterized by spectroscopic means. X-ray diffraction studies of 3 and 5 have revealed that these compounds have unusual sandwich structures, in which the polyhedral di-anion is located between the planes of two molecules of 1 and is bonded to each of them through two types of B-H-Hg bridges. One type is the simultaneous coordination of a B-H group to all three Hg atoms of the macrocycle. The other type is the coordination of a B-H group to a single Hg atom of the cycle. According to X-ray diffraction data, complex 2 has an analogous but half-sandwich structure. The obtained complexes 2-5 are quite stable; their stability constants in THF/acetone (1:1) at 20 degrees C have been determined as 1.0 x 10(2)Lmol(-1), 2.6 x 10(3)L(2)mol(2), 0.7 x 10(2)Lmol(-1), and 0.98 x 10(3)L(2)mol(-2), respectively.     

Crown compounds for anions. The nature of chemical bonds in the complexes of halide anions with cyclic trimeric perfluoro-o-phenylenemercury and some of its analogs

Geometries and electronic structures of the complexes of halide anions with cyclic trimerico-phenylenemercury, (o-C₆H₄Hg)₃, perfluoro-o-phenylenemercury, (o-C₆F₄Hg)₃, vinylenemercury, (C₂H₂Hg)₃, and perfluorovinylenemercury, (C₂F₂Hg)₃, were modelled by the MNDO method. Calculations were performed for [L-X]^– semisandwich complexes, [X-L-X]^2– bipyramidal complexes, and [L-X-L]^– sandwich complexes (where X=Hal,L is a mercury-containing macrocycle). Based on the results of calculations, we concluded that it was advantageous to describe the chemical bonding between halide anions and mercury-containing macrocycles in terms of generalized chemical bonds, which were successfully used for -complexes of transition metals. In the [L-X]^– semisandwich complexes, the halide anion and the metallacycle are involved in the formation of three generalized chemical bonds: one headlight-shaped -bond and two two-lobe -bonds. In the [X-L-X]^2– bipyramidal complexes, each halide anion forms three generalized chemical bonds with the macrocycle. It is possible because the macrocycleL has unoccupied molecular orbitals suitable for the formation of such bonds; these MOs consist mainly of the orbitals of mercury atoms directed toward both the upper and lower halogen atoms. In the [L-X-L]^– sandwich complexes, the halide anion cannot be bonded to each ringvia three bonds, and, hence, an unsymmetrical structure is formed, in which the rings are located at different distances from the central atom: the [L-X]^– semisandwich complex solvated by macrocycleL.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1035–1042, June, 1995.The authors are grateful to V. I. Faustov for valuable remarks.This work was supported by the Russian Foundation for Basic Research (Project No. 93-03-18342).     

Crown compounds for anions. MNDO calculations of complexes of halide anions with cyclic pentameric difluoromethylidenemercury

Molecular and electronic structures of complexes of halide anions with cyclic pentameric difluoromethylidenemercury [CF₂Hg]₅ have been studied by the MNDO method. Calculations have been performed for [L-X]^– halfsandwich complexes and bipyramidal complexes [X-L-X]^2– having a shape of a spinning top (L is the mercury-containing macrocycle; X = F, Cl, Br, or 1). It has been shown that in complexes of both types, halide anions are bonded to the mercury-containing macrocycle via three generalized chemical bonds: one headlightshaped -bond and two two-lobe n-bonds. The complexes studied have been compared with the analogous complexes of the macrocycles containing three mercury atoms. The similarity and differences in the character of the generalized chemical bonds in relation to the size of the cycle have been considered.V. B. Shur, I. A. Tikhonova, F. M. Dolgushin, A. I. Yanovsky, Yu. T. Struchkov, A. Yu. Volkonsky, and E. V. Solodova, Unpublished results.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 44–48, January, 1996.     

Crown compounds for anions. Sandwich complexes of cyclic trimeric perfluoro-o-phenylenemercury with hexacyanoferrate(III) and nitroprusside anions

Cyclic trimeric perfluoro-o-phenylenemercury (o-C₆F₄Hg)₃ (1) is able to bind hexacyanoferrate(III) and nitroprusside anions to form complexes {[(o-C₆F₄Hg)₃]₂[Fe(CN)₆]}³⁻ and {[(o-C₆F₄Hg)₃]₂[Fe(CN)₅NO]}²⁻, respectively, which contain one anionic species per two macrocycles. According to X-ray diffraction data, the complexes have unusual sandwich structures wherein the anionic guest is located between the planes of two molecules of 1 and is coordinated to each of these through two types of Fe-C-N-Hg bridges. One type is the simultaneous coordination of a cyanide ligand to all three Hg centres of the cycle. The other type is the coordination of a cyanide group to a single Hg atom of the macrocycle. In both types, the bonding of the anionic guest with the macrocyclic host is accomplished with the participation of π-electrons of the cyanide ligands. The synthesized compounds are the first examples of host-guest complexes of a macrocyclic multidentate Lewis acid with anionic metal complexes.     

Molecular structure of the complex of hexano-6-lactam with calcium bromide

A complex of hexane-6-lactam (ε-caprolactam, CL) with calcium bromide was prepared and characterized. According to TGA analyses its thermal stability is distinctly lower than those of the analogous complex of CL with magnesium bromide. The molecular structure of the complex was studied by IR and NMR spectroscopy. Based on interpretations of NMR and vibrational spectra and well-corresponding quantum mechanical calculations, six molecules of CL are arranged in the complex around the central CaBr₂ molecule in almost exactly equivalent positions. The complex molecule CaBr₂(CL)₆ is quite compact but the coordination bonds are markedly weaker in comparison with the recently studied MgBr₂(CL)₆ complex. In solution, a concentration dependent dynamic equilibrium between bound and free CL with fast exchange between both forms was observed.     

Structure of radical anions of organosilicon compounds. INDO calculations of the radical anions of some organosilicon compounds

M. V. Lomonosov Moscow Institute of Fine Chemical Engineering. Translated from Zhurnal Strukturnoi Khimii, Vol. 29, No. 2, pp. 24–30, March–April, 1988.     

Synthesis,structure and cytotoxicity of a zinc(II) bromide complex with caffeine

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Unusual Regioselectivity in the Reactions of Chlorocyclophosphazene-Containing Crown Ethers with Dinucleophiles

Abstract

New macrocyclic ligands with cyclophosphazene sub-units, representing geminally diamino-bridged derivatives of BINO-crown type (III), and bisansa-cyclosubstituted ones of chiral PNP cryptand type (IV) have been obtained by the regioselective substitution reactions of monoansa(oxytetraethylenoxy) reactive PNP-crown, N₃P3CI₄[O(CH₂CH20)₄] (II) with the dinucleophiles, like alkylenediamines or sodium diarylates. The supramolecular control of these processes is discussed.     

The structure of the dinitromethyl anion in aromatic and heterocyclic compounds

It is shown experimentally that in salts of dinitromethyl derivatives of aromatic and heterocyclic compounds the nitro groups are equivalent, and participate equally in anion formation. It is shown that both in the free state, and as an anion, the dinitromethyl group in aromatic and heterocyclic compounds has just the same spectral characteristics as in aliphatic compounds. These characteristics can be utilized for analytical purposes. The IR spectra do not reveal conjugation between the mono- or dinitromethyl group and the benzene ring. Judging by the UV spectra the benzene ring is not conjugated with the dinitromethyl anion. It is found that in the solid state 2-dinitromethylpyridine is an internal salt.     

Unusual structure of the dimeric 4-bromocalcimycin-Zn2+ complex

The X-ray structure of [Zn(4-bromocalcimycin)2 x H2O] complex shows two highly different conformations of the ligand in the dimeric association, unusual in this ionophore family.