Synthesis, crystal structure and in vitro antitumor activity of di-n-butyltin 4′-(7-oxabicyclo [2,2,1]-5-heptane-2,3-dicarboximide) benzoates

Dibutyltin(IV) oxide reacts with the cantharidin analogue, 4′-(7-oxabicyclo [2,2,1]-5-heptane-2,3-dicarboximide) benzoic acid, A, to give the complexes [(p-C₈H₈NO₃-C₆H₄-COOBu₂Sn)₂O]₂ (1) and (p-C₈H₈NO₃-C₆H₄-COO)₂SnBu₂ (2) which had been characterized by IR and ¹H, ¹³C, ¹¹⁹Sn NMR. Single X-ray crystal structure analysis has been determined for compound (1), which was analogue to most other [(RCOOBu₂Sn)₂O]₂. The dimer features central of Bu₄Sn₂O₂ unit with the two Bu₂Sn groups being linked via bridging oxygen atom. Each tin atom adopts distorted trigonal bipyramidal structures via two carbons from a dibutyl moiety and three oxygen atoms from cantharidin derivative and bridging oxygen atom. In vitro tests show compounds 1 and 2 exhibit high cytotoxicity against P388 and HL-60.     

Formation and structure specifics of the SnCl<Subscript>4</Subscript> complex with pyridine-3-carboxylic acid chloride by ab initio calculations

Feasible structures of the SnCl₄ complex with pyridine-3-carboxylic acid chloride were calculated by the MP2/LANL2DZ method. The results of calculations were compared to experimental ³⁵Сl nuclear quadrupole resonance (NQR) data. The coordination site of the ligand was found to be the nitrogen atom and not the carbonyl oxygen atom. The partial negative charge of the electron-donating center and the positive charge of the electron-drawing center increase appreciably upon complex formation.     

An ab initio study of the p,π interaction: IV. Interaction of an ether oxygen atom with a carbonyl group

RHF/6-311G(d) calculations were performed for the H₃COCOH molecule with full geometry optimization and at varied angles of rotation of the methoxy group about the C-O bond, with all the other geometric parameters optimized. The molecule can exist in two stable conformations with the dihedral angle O¹C¹O²C² of 0.00° and 179.99°. The influence of the rotation angle on the population of the p _y orbital of the carbonyl oxygen atom in compounds with different types of the adjacent bond is essentially similar. The results obtained are inconsistent with the concept of the p,π conjugation involving the p _y orbitals of the planar molecular fragment (orbitals whose symmetry axes are perpendicular to this fragment).     

Acid–base equilibria of the aqua adducts of Ru(II) arene complexes with functionalised pyridines

Acid?Cbase equilibria of the aqua adducts of Ru(II) arene complexes, general formulae [(??⁶-p-cymene)Ru (L^1?3)Cl₂] where L¹?=?3-acetylpyridine (1), L²?=?4-acetylpyridine (2) and L³?=?2-amino-5-chloropyridine (3), then [(??⁶-p-cymene)Ru(HL⁴)Cl₂] with HL⁴?=?isonicotinic acid (4); [(??⁶-p-cymene)Ru(HL^5?8)Cl] where H₂L⁵?=?2,3-pyridine dicarboxylic acid (5), H₂L⁶?=?2,4-pyridine dicarboxylic acid (6), H₂L⁷?=?2,5-pyridine dicarboxylic acid (7) and H₂L⁸?=?2,6-pyridine dicarboxylic acid (8) have been studied. pK _a values were determined by potentiometry at 25?°C and constant ionic strength of 0.1?M NaNO₃. The assumed equilibria were confirmed by UV and ¹H-NMR spectroscopy.     

Rare configuration of tautomeric benzimidazolecarboxylate ligands in cadmium(II) and copper(II) coordination polymers

Two Cd(HBimc)-based isomers, [Cd(HBimc^N)(HBimc^T)(H₂O)]·3.5H₂O·EtOH (1a·3.5H₂O·EtOH, H₂Bimc=1H-benzimidazole-5-carboxylic acid) and [Cd(HBimc^N)(HBimc^T)(H₂O)] (1b), and two Cu(HMBimc)-based coordination polymers, [Cu(HMBimc^N)₂(H₂O)]·1/2H₂O (2·1/2H₂O, H₂MBimc=2-methyl-1H-benzimidazole-5-carboxylic acid) and [Cu(HMBimc^T)₂]·2THF·H₂O (3·2THF·H₂O), were self-assembled from Cd(ClO₄)₂·6H₂O/H₂Bimc and Cu(ClO₄)₂·6H₂O/H₂MBimc systems, respectively. Compound 1a adopts a ladder-like chain structure, comprised of a hydrogen-bond-stabilized Cd₂(HBimc^N)₂-metallocyclic stair and a 1D straight -(Cd-HBimc^T)_n- edge, whereas compound 1b exhibits a 2D (4,4)-rhombus layered structure, intercrossed by 1D -(Cd-HBimc^N)_n- chains and -(Cd-HBimc^T)_n- chains. Compound 2 shows a 1D double-stranded wave-like chain from two single-stranded wave-like -(Cu-HMBimc^N)_n- chains and compound 3 adopts a 2D (4,4)-topological layer structure, intercrossed by subunits of 1D -(Cu-HMBimc^T)_n- chains. Interestingly, a pair of tautomeric HBimc building blocks—normal (N or HBimc^N) and tautomer (T or HBimc^T)—is simultaneously included in the structures of 1a and 1b, whilst the N- and T-configured HMBimc building blocks are present as separate entities in Cu species, 2 and 3, respectively. The existence of only a tautomer (T) mode of the benzimidazolecarboxylate-based ligand in a Cu(II) network is observed for the first time.     

Geminal interactions in ClZ(CH3)2X molecules (Z = C, Si, Ge) according to ab initio calculations

The structure and electronic parameters of ClZ(CH₃)₂X molecules (Z = C, Si, Ge, X = CH₃, OCH₃) were calculated by the RHF/6–31G(d) and RHF/6–311G(d,p) methods with full geometry optimization; calculations of ClZ(CH₃)₂OCH₃ molecules were also performed by the RHF/6–31G(d) method with partial geometry optimization. The ³⁵Cl NQR frequencies calculated from the populations of less diffuse 3p constituents of valence p orbitals of chlorine [RHF/6–31G(d)] were in agreement with the experimental values. The ³⁵Cl NQR frequencies for molecules with X = OCH₃ are lower than those for molecules with X = CH₃ (the Z atom being the same), due mainly to direct through-field polarization of the Z-Cl bond, induced by the effect of unshared electron pair of the oxygen atom in the trans position with respect to that bond. The difference in the ³⁵Cl NQR frequencies decreases in going from Z = C to Z = Si, Ge, in parallel with variation of the Z-Cl bond polarization as the size of Z increases.     

Kinetics and mechanism of the oxidation of acrylic acid and methyl methacrylate

The kinetics of the initiated oxidation of acrylic acid and methyl methacrylate in the liquid phase were studied volumetrically by measuring oxygen uptake during the reaction. Both processes proceed via the chain mechanism with quadratic-law chain termination. The oxidation rate is described by the equation w = k ₂/(2k ₆)^1/2[monomer]w _i ^1/2 , where w _i is the initiation rate and k ₂ and k ₆ are the rate constants of chain propagation and termination. The parameter k ₂/(2k ₆)^1/2 is 7.58 × 10^?4 (l mol^?1 s^?1)^1/2 for acrylic acid oxidation and 2.09 × 10^?3 (l mol^?1 s^?1)^1/2 for the oxidation of methyl methacrylate (T = 333 K). For the oxidation of acrylic acid, k ₂ = 2.84 l mol^?1 s^?1 (T = 333 K) and the activation energy is E ₂ = 54.5 kJ/mol; for methyl methacrylate oxidation, k ₂ = 2.96 l mol^?1 s^?1 (T = 333 K) and E ₂ = 54.4 kJ/mol. The enthalpies of the reactions of RO ₂ ^? with acrylic acid and methyl methacrylate were calculated, and their activation energies were determined by the intersecting parabolas method. The contribution from the polar interaction to the activation energy was determined by comparing experimental and calculated E ₂ values: ΔE _μ = 5.7 kJ/mol for the reaction of RO ₂ ^? with acrylic acid and ΔE _μ = 0.9 kJ/mol for the reaction of RO ₂ ^? with methyl methacrylate. Experiments on the spontaneous oxidation of acrylic acid provided an estimate of the rate of chain initiation via the reaction of oxygen with the monomer: w _i,0 = (3.51 ± 0.85) × 10^?11 mol l^?1 s^?1 (T = 333 K).     

Pentacoordinate iron(III) porphyrin carboxylates: Synthesis,physicochemical characteristics and x-ray crystal structure of acetato(5, 10, 15, 20-tetraparatolylporphyrinato) iron(III)

Carboxylatoiron(III) porphyrins have been synthesised by the action of carboxylic acids on the [(por)Fe]₂O dimers. ¹H NMR and ESR data of the isolated products are in accordance with pentacoordinate high spin 5/2 ferric complexes, the iron atom being displaced out of the plane of the porphyrin ligand. IR spectra show ν(CO) and ν(CO) bands separated by 356–409 cm^?1. The magnitude of this separation suggests coordination between the metal centre and the carboxylate group via one oxygen atom. Magnetic susceptibility measurements from 5 to 120 K lead to the value of μ = 5.88 B.M.. The X-ray structure of acetato (5, 10, 15, 20-tetra p-tolyporphyrinato) iron(III) confirms the above deductions. (tp MePP) Fe(CO₂CH₃). 0.5 CH₃COOH crystallises in the I2/c space group with unit cell parameters a = 24.464(8), b = 9.332(3), c = 37.174(4) Å, β = 90.49(2)°, V = 8485 ų, D_c = 1.27 g · cm^?3 and Z = 8. The crystal structure was refined to a conventional R(F) = 0.0584 and R_w(F) = 0.0653 for 5132 unique reflections with F₀ > 3σ(F₀). The iron atom is pentacoordinated by the four nitrogen atoms and one oxygen atom of the acetate group. It lies at 0.520(1) Å out of the porphinato plane and 0.485(1) Å out of the four nitrogen plane. The FeO bond length is 1.898(4) Å.     

Photophysical Properties of Rufloxacin in Neutral Aqueous Solution

The photophysical properties of rufloxacin, 9-fluoro-2_r3-dihydro-10-(4-methyl-l-pyrazinyl)-7-oxo-7-H-pyri-do[l,2,3-de]-l,4-benzothiazin-6-carboxylic acid, a fluoroquinolone antibacterial drug exhibiting photosensitizing action toward biological substrates, were studied in aqueous solutions at neutral pH. The lowest excited electronic states of the zwitterion were characterized by both experimental techniques and theoretical methods. Steady-state and time-resolved emission, triplet-state absorption and singlet oxygen production were investigated. The results indicate that the lowest excited singlet is a fluorescent, relatively long-lived state (φ_r= 0.075, T_r? 4.5 ns) with an efficient intersystem crossing to the triplet manifold (φ_isc? 0-⁷)- The lowest triplet is a long-lived state (T_T? 10 μs at 295 K in 0.01 M phosphate buffer), with properties that make it a good candidate for being the precursor of the photodecarboxylation of the drug. It is quenched by oxygen at a rate of 1.7 times 10⁹M^-1 s-¹ and singlet oxygen is formed with a quantum yield of 0.32 in air-saturated solutions.     

Photophysics and photochemistry of sterically strained α-haloanthraquinones: The bromo and/or chloro substituted compounds

The steric hindrance between the oxygen and halogen atoms results in the structural deformation of α-haloanthraquinones and their lowest excited triplet (T₁) states are of mixed nπ ^*-ππ ^* or ππ ^* character with unusually short lifetimes. Moreover, the rates of hydrogen-atom abstraction from ethanol by the T₁ states decrease with their increasing ππ ^* character, and the proximity of the halogen atom to the hydroxy group causes the photochemical intramolecular elimination of hydrogen halide from the initial photoproducts (α-haloanthrahydroquinones) yielding α-haloanthraquinones (or anthraquinone) with one less halogen atom than the original molecule; the final product is anthrahydroquinone. The remarkably large structural deformation of 1,8-dihaloanthrasemiquinone radicals which gives rise to the simultaneous formation of 1,8-dihaloanthrahydroquinones and the original anthraquinones. Of particular interest is observation of the absorption band(s) attributable to the second excited triplet (T₂) states of 1,8-dihaloanthraquinones. However, the electron transfer from triethylamine (TEA) to these T₂ states generating the radical anions is observed only in acetonitrile, while that to the T₁ states generating their exciplexes with TEA is observed not only in acetonitrile but also in toluene and ethanol.     

Low-dimensional compounds containing cyano groups. XV. Preparation,crystal structure and spectral properties of three copper(II) nitrosodicyanomethanide complexes

We describe the preparation and crystal structures of the ionic complexes [Cu(bipy)₂{ONC(CN)₂}]CF₃SO₃ (1b), [Cu(phen)₂{ONC(CN)₂}]PF₆ (2p) and [Cu(bipy)₂{ONC(CN)₂}]PF₆ (2b). In the complex cations [Cu(L)₂{ONC(CN)₂}]⁺ (L is 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen)) the two molecules of bipy or phen coordinate to the copper atom through two nitrogen atoms along with the oxygen atom of the nitrosodicyanomethanide anion, ONC(CN) ₂ ^? , to form a {CuN₄O} chromophore with a distorted square pyramidal coordination sphere in (1b) and (2b) and a distorted trigonal bipyramidal geometry in (2p). The basal plane in (1b) and (2b) is formed by an oxygen atom coordinated at the Cu1–O1 distance of 1.990(2) and 2.002(2) Å, respectively, and three nitrogen atoms coordinated to the copper atom at similar distances with the average of 2.01(2) and 2.00(3) Å, respectively. The axial position is occupied by the fourth N atom at the longer distance of 2.222(2) and 2.185(2) Å, respectively. The trifluoromethanesulfonate anion (triflate), CF₃SO ₃ ^? , in (1b) might be considered as very weakly coordinated in the opposite axial position (Cu1–O2 = 2.719(2) Å). The equatorial plane in (2p) is formed by an oxygen atom coordinated at the Cu1–O1 distance of 1.975(3) Å, and two nitrogen atoms from different phen molecules coordinated to the copper atom at the same distance within 2 σ with the average distance of 2.124(2) Å. The axial positions are occupied by remaining two nitrogen atoms coordinated at shorter distance (average Cu–N = 1.99(3) Å). The hexafluorophosphate anions, PF ₆ ^? , in (2p) and (2b) remain uncoordinated. Besides the ionic forces, the structures of (2p) and (2b) may be stabilized by very weak C–H···F whereas the structure of (1b) by very weak C–H···F, C–H···O and C–H···N hydrogen bonds. The structural–spectral correlations are also discussed.     

A quantum-chemical study of the interaction of the HeT<Superscript>+</Superscript> ion with cycloalkanes and their oxidation products

The RHF/6-311G*(3d), RHF/6-311++G**(3df, 3p) and MP2/6-311G*(3d) ab initio methods were used to calculate the equilibrium structure of the products of the ion-molecular reaction of tritium ion transfer from HeT⁺ to cyclopentane and cyclohexane. Similar reactions with cyclopentanol and cyclopentanone were calculated at the RHF/6-311G*(3d) level. The interaction of HeT⁺ with cycloalkanes was found to produce onium ions with cyclic structures, in which the tritium atom held neighboring methylene groups together. With the alcohol and ketone, not only cyclic but also stabler linear cations could be formed, and the addition of the tritium ion directly to the oxygen atom was possible. The suggestion was made that the chain of tritium ion transfer reactions was the mechanism of the accumulation of tritium by hydrocarbon oxidation products when T₂ was dissolved in mineral oils.     

The standard molar enthalpies of formation of chromone-3-carboxylic acid, 6-methylchromone-2-carboxylic acid,and 6-methyl-4-chromanone determined by micro-combustion calorimetry

The energies of combustion of chromone-3-carboxylic acid (C3CA), 6-methylchromone-2-carboxylic acid (6MCC), and 6-methyl-4-chromanone (6M4C) were determined using an isoperibolic micro-combustion calorimeter. The calorimeter used in the present work has been assembled, calibrated, and tested in our laboratory with the desired results. Prior to the measurement of the energies of combustion, the purities, heat capacities (C _p), fusion temperatures (T _fus), and enthalpies of melting (Δ_fus H) for each compound were determined by differential scanning calorimetry. The values of the energies of combustion were used to derive standard molar enthalpies of combustion ( \( \Delta _{{\text{c}}} H_{{\text{m}}}^{\circ } \) ) and standard molar enthalpies of formation ( \( \Delta _{{\text{f}}} H_{{\text{m}}}^{\circ } \) ) in the crystalline phase at T = 298.15 K. The values found for the \( \Delta _{{\text{f}}} H_{{\text{m}}}^{\circ } \) of C3CA, 6MCC, and 6M4C were ?(619.5 ± 2.6), ?(656.2 ± 2.2), and ?(308.9 ± 3.0) kJ mol^?1, respectively.     

Mechanism of the reaction of N-p-tosylsulphilimine and related compounds with thiophenolate ion

The reaction of alkyl aryl N-p-tosylsulphilimines with thiophenolate ion was found to afford quantitatively the sulphide that arises by an S_N2 like reaction on the carbon atom adjacent to the tri-valent sulphur atom. This reaction was also found to proceed smoothly with such compounds as sulphoxides and sulphones and sulphoxmanes. The kinetic study on the reaction between aryl methyl N-p-tosylsulphilimine with thiophenolate ion in DMF reveals that the reaction is of second order, namely, first order with respect to each thiophenolate ion and the sulphilimine. The enthalpy and entropy of activation for the reaction are ΔH^≠ = ?17· kcal/mol and ΔS^≠ = ?5·7 eu respectively. The effect of substituents in the reaction, p-XC₆H₄⁺(^?SO₂C₆H₄Y-p)CH₃ + p-ZC₆H₄SK is nicely correl with Hammett σ values giving ?_x = + 2·4, ?_y = + 1·2 and ?_z = ?1·8 respectively. Meanwhile, a marked steric retardation by a bulky alkyl group in alkyl phenyl N-p-tosylsulphilimine is observed. Furthermore, from the stereochemical study of the reaction using an optically active sec-octyl phenyl N-p-tosylsulphilimine with thiophenolate ion it is concluded that the reaction proceeds via a typical S_N2 process on α-carbon atom attached to the tri-valent sulphur atom.     

Spin-resolved orientation,depolarization and left-right asymmetry in electron-lithium scattering

A two-potential localised exchange (TPLE) approach is used to study the role of spin dependence in the inelastic scattering of electrons by lithium atoms at intermediate energies. Results are presented for the spin-resolved orientation parameters (L _⊥ ^S ,L _⊥ ^T , andL _⊥) in the polarized-electron impact resonant (2s–2p) excitation of polarized-lithium atom. Results are also obtained for the depolarization (P′ _e /P _e) in the polarized-electron impact resonant (2s–2p) and nonresonant (2s–3p) transition in unpolarized lithium atom. Further in the case when the fine structure splitting of the target is resolved, we also investigate the left-right scattering asymmetryS _A (1/2) for the polarized-electron superelastically scattered from unpolarized 2p _1/2 and 3p _1/2 states.     

Vitamin C: an experimental and theoretical study on the gas‐phase structure and ion energetics of protonated ascorbic acid

In order to investigate the gas‐phase mechanisms of the acid catalyzed degradation of ascorbic acid (AA) to furan, we undertook a mass spectrometric (ESI/TQ/MS) and theoretical investigation at the B3LYP/6‐31 + G(d,p) level of theory. The gaseous reactant species, the protonated AA, [C₆H₈O₆]H⁺, were generated by electrospray ionization of a 10^?3 M H₂O/CH₃OH (1 : 1) AA solution. In order to structurally characterize the gaseous [C₆H₈O₆]H⁺ ionic reactants, we estimated the proton affinity and the gas‐phase basicity of AA by the extended Cooks's kinetic method and by computational methods at the B3LYP/6‐31 + G(d,p) level of theory. As expected, computational results identify the carbonyl oxygen atom (O2) of AA as the preferred protonation site. From the experimental proton affinity of 875.0 ± 12 kJ mol^?1 and protonation entropy ΔS_p 108.9 ± 2 J mol^?1 K^?1, a gas‐phase basicity value of AA of 842.5 ± 12 kJ mol^?1 at 298 K was obtained, which is in agreement with the value issuing from quantum mechanical computations. Copyright © 2016 John Wiley & Sons, Ltd.     

Experimental study on the energetics of two indole derivatives

The standard (p ^o = 0.1 MPa) molar energies of combustion, $ \Updelta_{\text{c}} H_{\text{m}}^{\text{o}} $ , for indole-2-carboxylic acid and indole-3-carboxaldehyde, in the crystalline state, were determined, at T = 298.15 K, using a static bomb combustion calorimeter. For both compounds, the vapour pressures as function of temperature were measured, by the Knudsen effusion technique, and the standard molar enthalpies of sublimation, $ \Updelta_{\text{cr}}^{\text{g}} H_{\text{m}}^{\text{o}} $ , at T = 298.15 K, were derived by the Clausius–Clapeyron equation. From the experimental results, the standard (p ^o = 0.1 MPa) molar enthalpies of formation in the condensed and gaseous phases, at T = 298.15 K, of indole-2-carboxylic acid and indole-3-carboxaldehyde were derived. The results are analysed in terms of structural enthalpic increments.     

Magnetic properties and structure of a CuDy heterodinuclear Schiff base complex

The crystal structure of a new heterodinuclear lanthanide complex, L²Cu(Me₂CO)Dy(NO₃)₃ (L²=N,N′-bis(2-hydroxy-3-methoxy-benzylidene)-ethylenediamine) has determined and the magnetic properties of the complex investigated. (C₁₈H₁₈N₂O₄)Cu(C₃H₆O)Dy(NO₃)₃, monoclinic, space group P2₁/c, with a=9.875(2), b=18.870(7), c=15.675(8) Å, β=95.45(3)°, V=2908(2) Å³, Z=4. The structure consists of ordered dinuclear units with Cu^II and Dy^III ions bridged by two phenolato oxygen atoms of the Schiff base ligand. The Cu^II ion has a square-pyramidal geometry involving the basal N₂O₂ donor atoms of the Schiff base ligands and one oxygen atom of the acetone molecule at the apex position. The Dy^III ion is decacoordinated by the four oxygen atoms of L² and six oxygen atoms from the three bidentate nitrate ions. The Cu?Dy separation is 3.461(2) Å. The χT versus T plots, χ being the molar magnetic susceptibility per Cu^IIDy^III unit and T the temperature, has been measured in the 4.5-300 K temperature range. The magnetic properties of the compound are dominated by the crystal field effect on the Dy^III site, masking the magnetic interaction between the paramagnetic centers.     

Spectkophotometric determination of the dissociation constants of n,n'-bis(3-hydroxypropyl)dithiooxamide and n,n'-bis(2-hydroxypropyl)dithiooxamide

The dissociation constants of N,N'-bis(3-hydroxypropyl)dithiooxamide and N,N'-bis(2-hydroxypropyl)dithiooxamide were determined by a spectrophotometric method using a weighted least squares technique for the calculations. For N,N'-bis(3-hydroxypropyl) dithiooxamide a thermodynamic constant pK₁^T of 11.37 was found. At ionic strength μ = 1, pK₁ = 11.27 and pK₂ = 14.29. For N,N'-bis-(2-hydroxypropyl) dithiooxamide, these values were respectively: pK₁^T = 11.11; pK₁ = 10.99 and pK₂ = 13.75.     

Trichloro- and methyldichlorogermyl monochelates and dibromo- and dichlorogermyl bischelates derived from N,N-disubstituted amides of 2-hydroxycarboxylic acids

The reactions of GeCl₄, GeBr₄, and MeGeCl₃ with O-trimethylsilyl derivatives of N,N-disubstituted amides of 2-hydroxycarboxylic acids afforded pentacoordinate and hexacoordinate neutral (O,O)-mono- and (O,O)-bischelates. The reactions of glycolic acid derivatives with GeX₄ produced bischelates X₂Ge[OCH₂C(O)NR²R³]₂ 7a,c,d (X = Cl, R² = R³ = Me (a), (CH₂)₅ (c), (CH₂CH₂)₂O (d)) and 8a (X = Br). By contrast, the reactions of lactic and mandelic acid derivatives with GeCl₄ and MeGeCl₃ gave monochelates Cl₃Ge[OCH(R¹)C(O)NR²R³] (S)-9a–c (R¹ = Me) and Cl₂MeGe[OCH(R¹)C(O)NR²R³] 10a (R¹ = H), (S)-11a,b (R¹ = Me), and (S)-12a (R¹ = Ph) (R²R³ = (CH₂)₄ (b)), respectively. According to the X-ray diffraction data, the Ge atom in bischelates 7c,d and 8a has a coordination number 6, and its coordination polyhedron can be described as a slightly distorted octahedron. In monochelates (S)-9a-c, 10a, (S)-11a,b, and (S)-12a, the Ge atom has a coordination number 5, and its coordination polyhedron can be described as a trigonal bipyramid with two halogen atoms or one halogen atom and one ethereal oxygen atom in equatorial positions and the halogen atom and the amide oxygen atom in the axial positions. The bonds in the axial positions are somewhat longer than the corresponding bonds in tetracoordinate Ge compounds.