Thermodynamic Studies on the Complexation Reactions of Copper(II) Macrocyclic Tetramine Complexes with Monodentate Ligands: Part II. A Spectrophotometric Study on the Reactions of Meso-5, 7, 7, 12, 14, 14-Hexamethyl-1, 4, 8, 11-Tetraazacyclotetradecane-Copper(II) (Blue) with Halide Ions

The stability constants for the formation of [Cu(tet a)X]⁺(blue) from [Cu(tet a)]²⁺(blue) and X- (where X=Cl, Br, I) were determined by spectrophotometric method at 15°, 25° and 35°C. The corresponding ΔH° and ΔS° values were obtained from the variations of the stability constants between 15° and 35°C. For the same halide ion, the stability constant of [Cu(tet b)X]⁺ (blue) is larger than that of [Cu(tet a)X]⁺(blue).     

Molecular Structure of the Macrocyclic Ligand Complex (5, 7, 12, 14-Tetraethyl-7, 14-Dimethyl-1, 4, 8, 11-Tetraazacyclotetra Decane) Nickel (II) Perchlorate

The structure of macrocyclic ligand complex, (5, 7, 12, 14-tetraethyl-7, 14-dimethyl-1, 4, 8, 11-tetraazacyclotetra decane)·Ni^II·(ClO₄)₂ has been determined by X-ray diffraction with three dimensional counter data. This compound, C₂₀H₄₄N₄Ni^II·(ClO₄)₂, crystallizes in orthorhombic space group Pbca, with cell parameters a=14.369, b=11.752, c=16.207 A, V=2736.8 A³, determined from Syntex Pl autodiffractomter. The formula weight (598.21) and a measured density of 1.45 gm cm^?3 (by flotation) indicate the presence of four molecules per unit cell (D_c=1.452 gm cm^?3). The structure was solved, using Patterson and Fourier methods and refined by full-matrix least-squares techniques to a reliability index, R(F) of 0.09, based on 1480 independent observed data corrected for absorption, L-p factors. In this molecule, in addition to the usual covalent and ionic bonds, there exist two hydrogen bonds between the perchlorate ions and the amine groups. The Ni and the four N atoms are coplanar. The six membered ring subtends a larger angle (93.5(3)°) over the Ni atom than the five membered ring (86.5(3)°) does. The former belongs to the chair form and the latter pertains to the gauche form.     

Structures of Nickel(II) and Copper(II) Complexes of 14-Membered Macrocyclic Quadridentate Ligands

The structures of 41 Ni(II) and 17 Cu(II) complexes of macrocyclic quadridentate ligands have been analyzed, and are discussed about bond lengths, bond angles, conformations, and configurations, upon which many conclusions are formed. The inter- or intra-molecular hydrogen bonds exist among ligands and hydrates in many compounds and play an important role in the structures. There are exhibited two distinct peaks on the histogram of the average Ni-N distances, corresponding to four coordination and six coordination; these average Ni-N distances are 1.95(4) Å and 2.10(5) Å, respectively. The most probable structures of Ni(II) macrocyclic compounds have coordination number six for the metal ion, chair forms for six-membered rings, planar structure for the metal ion and the four donor atoms of the quadridentate ligand and an inversion center at the central metal ion.     

Stereoselective Effects in Reactions of Metal Complexes III. Asymmetric hydrogenation of 5, 7, 7, 12, 14, 14-hexamethyl-1, 4, 8, 11-tetraazacyclotetradeca-4, 11-diene-nickel (II)

The catalytic hydrogenation in acidic solution (pH ～ 2) of the title compound

1 In order to represent this and the related compounds by meaningful abbreviations, we shall adopt the numerotation system proposed in the literature [8] [12]. The complete abbreviation of the title compound is [Ni(5, 7, 7, 12, 14, 14-Me₆-[14]-4, 11-diene-1, 4, 8, 11-N₄)]²⁺. As in the present work the 14-membered ring system with six methyl groups remains unchanged, we shall use [Ni(4, 11-dieneN₄)]²⁺ and [Ni(4, 11-aneN₄)]²⁺ and [Ni(4, 11-aneN₄)]²⁺ for the complex with the unsaturated and saturated ligand, respectively.

[Ni(4, 11-dieneN₄)]²⁺ (I) has been studied. The reaction yields only C-meso- 5, 7, 7, 12, 14, 14-hexa-methyl-1, 4, 8, 11-tetraaza-cyclotetradecane-nickel (II) (C-meso-[Ni(4, 11-aneN₄)]²⁺), when meso-[Ni(4, 11-dieneN₄)]²⁺ is the starting material. Rac-[Ni(4, 11-dieneN₄)]²⁺ yields the unstable α-C-rac-[Ni(4, 11-aneN₄)]²⁺. When optically active [Ni(4, 11-dieneN₄)]²⁺ is reduced, optically active α-[Ni(4, 11-aneN₄)]²⁺ is obtained, which in neutral or basic solution shows mutarotation due to conversion into optically active β-[Ni(4, 11-aneN₄)]²⁺ no racemization is observed. Reaction with cyanide ions yields the optically active free tetramine ligand. The reaction mechanism of this asymmetric synthesis is discussed.     

Crystal and Molecular Structure of the Macrocyclic Nickel (II) Complex Ni(C22H22H4): Dibenzo[b,i][5, 7, 12, 14] Tetramethyl [1, 4, 8, 11] Tetraazacyclotetradeca-2, 4, 7, 9, 12, 14-Hexaeneatonickel (II)

The crystal and molecular structure of the four-coordinate complex Ni(C₂₂H₂₂N₄) containing the tetramethyldibenzotetraaza[14] annulene ligand has been determined from three-dimensional X-ray diffraction data. The complex crystallized in the monoclinic space group C_2h⁵-P2₁/n with cell dimensions a=14.7967(10), b=11.2169(6), c=11.4510(6) Å, and β=98.467(5)° with Z=4. The final agreement indices from the least-square refinement of 245 variables with 3111 observations F>3σ(F), are R=0.050, R_w=0.037. The structure has a pronounced saddle-shaped conformation with Ni atom at the saddle point coordinated to four nitrogen atoms. The average Ni-N distance is 1.866(3) Å. The delocalized propane-1,3-diiminato chelate rings and the benzene rings are linked by nominally single C-N bonds.     

Metal Complexes with Macrocyclic Ligands. Part XLI. Nickel(II) and copper(II) complexes with mono-N-functionalized dithiadiazamacrocycles

Three N₂S₂ macrocycles ( 3, 10, 12 ) carrying an amino group as a pendant arm have been synthesized and their complexation properties towards Ni²⁺ and Cu²⁺ studied. The crystal structures of the Cu²⁺ complexes with 10-methyl-1,4-dithia-7,10-diazacyclododecane-7-ethanamine ( 3 ) and 11-methyl-1,4-dithia-8,11-diazacyclotetradecane-8-ethanamine ( 10 ) show that, in both cases, the Cu²⁺ is pentacoordinated by the four donor atoms of the macrocycle and the amino group of the side chain. In aqueous solution, however, two forms of the complexes with stoichiometries [MLH] and [ML] (M = Cu²⁺ or Ni²⁺) have been observed. In [MLH], the amino group is protonated and does not bind to the metal ion, whereas in [ML] the amino group is bound, and a pentacoordinated geometry results. The pK_a values for the equilibrium [ML] + H⁺?[MLH]⁺ decrease in the order 12 > 10 > 3 , indicating that the 2-aminoethyl side chain binds better to the Cu²⁺ than the 3-aminopropyl side chain. Cyclic voltammetry for the Cu²⁺/Cu⁺ pair shows that the 2-aminoethyl pendant arm stabilizes the Cu²⁺ oxidation state, when the metal ion is in the 14-membered ring ( 10 ), whereas it stabilizes Cu⁺ for the 12-membered macrocycle ( 3 ).     

Metal Complexes with Macrocyclic Ligands. Part XXXIX. Mono- and binuclear copper(II) complexes of a bridging bis[1, 4, 7-triazacyclononane]

The new bis-macrocycle 1, 1′-[(1H-pyrazol-3], 5-diyl)bis(methylene)bis[1, 4, 7-triazacyclononane] ( 1 ) was synthesized and its complexation with Cu²⁺ studied. Potentiometric and spectrophotometric titrations indicate that, in addition to the mononuclear species [Cu(LH₂)]⁴⁺, [Cu(LH)]³⁺, [CuL]²⁺, and [Cu(LH_?1)]⁺, binuclear complexes such as [Cu₂L]⁴⁺, [Cu₂(LH_?1)]³⁺, and [Cu₂(LH_-2)]²⁺ are also formed in solution. The stability constants and spectral properties of these are reported. The binuclear species [Cu₂(LH_?1)]³⁺ specifically reacts with an azide ion to give a ternary complex [Cu₂(LH_?1)(N₃)]²⁺, the stability and structure of which were determined spectrophotometrically and by X-ray diffraction, respectively. The two Cu²⁺ ions are in a square-pyramidal coordination geometry. The axial ligand is one of the N-atoms of the 1, 4, 7-triazacyclononane ring, whereas at the base of the square pyramid, one finds the other two N-atoms of the macrocycle, one N-atom of the pyrazolide and one of the azide, both of which are bridging the two metal centres. In [Cu₂(LH_?1)(N₃)]²⁺, a strong antiferromagnetic coupling is present, thus resulting in a species with a low magnetic moment of 1.36 B.M. at room temperature.     

Silver(I) Complexes with Nitrogen-Containing Noncyclic, Macrocyclic, and Macrobicyclic Ligands in Propylene Carbonate

Stability constants and thermodynamic data for complex formation of silver(I) with noncyclic, macrocyclic, and macrobicyclic ligands have been measured in propylene carbonate using potentiometric and calorimetric methods. All ligands containing two nitrogen donor atoms form extremely stable complexes. Only if substituents reduce the basicity of the nitrogen donor atoms, the stability of the complexes decreases drastically. However, the cryptand (221) forms the most stable complex of all ligands examined. In this case, the dimensions of the ligand cavity and of the cation are nearly identical.     

Syntheses,Structural, and Spectroscopic Properties of Copper(II) Complexes of Constrained Macrocyclic Ligands

The complexes [Cu(L¹)(H₂O)₂](BF₄)₂ · 2H₂O ( 1 ) [L¹ = 5, 16‐dimethyl‐2, 6, 13, 17‐tetraazatricyclo(14, 4, 0^1.18,0^7.12)docosane] and 0.5[Cu(L²)(NO₃)₂][Cu(L²)](NO₃)₂ ( 2 ) [L² = dibenzyl‐5, 16‐dimethyl‐2, 6, 13, 17‐tetraazatricyclo(14, 4, 0^1.18,0^7.12)docosane] were synthesized and characterized by single crystal X‐ray analyses. In these constrained macrocycles, the central copper(II) atoms are in a tetragonally distorted octahedral environment with four nitrogen atoms of the macrocyclic ligands in equatorial positions and oxygen atoms from either water molecules or nitrato groups in axial positions. The macrocyclic ligands in both complexes adopt the most stable trans‐III conformation. The Cu–N distances [1.999(7)–2.095(7) Å] are typical for such complexes, but the axial ligands are weakly coordinating Cu–OH₂ bonds [2.693(3) Å] and Cu–ONO₂ bonds [2.873(7) Å] due to the combination of the pseudo Jahn–Teller effect and strong in‐plane ligand field. The crystals are stabilized by a three‐dimensional network by hydrogen bonds that are formed among the secondary nitrogen hydrogen atoms, oxygen atoms of water molecules, fluorine atoms of BF₄^–, and oxygen atoms of NO₃^–. The electronic absorption and IR spectroscopic properties are also discussed.     

Thermodynamic Studies on the Complexation Reactions of Copper(II) Complex of o2n2-Donor Macrocycle with Halide and Pseudohalide Ions

Complexation reactions of 5,6,7,8,9,10,16,17-octahydrodibenzo[e, m][1, 4]dioxa-[8, 11]diazacyclotetradecine-copper(II) complex with halide and pseudohalide ions have been studied at 25.0° in three water-methanol mixed solvents by spectro-photometric method. It is found that the equilibrium constants increases in the order of 50 vol.% CH₃OH<75 vol.% CH₃OH<95 vol.% CH₃OH for solvents and I-<Br^?<CI^?<SCN^?, N^?₃ for anions.     

Manganese(II), Cobalt(II), and Nickel(II) Perchlorate Complexes Containing N,O Donor Macrocyclic Ligands

Mononuclear macrocyclic complexes of manganese(II ), cobalt(II ) and nickel(II ) perchlorate using 10 different oxaazamacrocyclic ligands (L¹ — L¹⁰) have been prepared and characterized. The complexation reactions with the diiminic ligands were obtained by template condensation of the appropriate dialdehyde and diamine precursors; the reduced macrocycle complexes were synthesized using a direct route. The complexes have been characterized by elemental analyses, molar conductivity, mass spectrometry, IR, UV‐vis spectroscopy, diffuse reflectance and magnetic susceptibility measurements.     

Synthesis,Characterization, Electrochemical and Antimicrobial Studies of Iron(II) and Nickel(II) Macrocyclic Complexes

Russian Journal of Electrochemistry - Herein, we synthesized [12] membered pyridine based transition metal macrocyclic complexes [MIILCl2] (M = Fe(II) and Ni(II), L = 6,12,5,11-tetraphenyl...     

Thermodynamic and Kinetic Studies on Reactions of Pt(II) Complexes with Pyrazole,Pyridazine, and 1,2,4-Triazole

Summary. Substitution reactions of the complexes [Pt(dien)H₂O]²⁺ and [PtCl(dien)]⁺, where dien = diethylentriamine or 1,5-diamino-3-azapentane, with some nitrogen-donor ligands such as 1,2,4-triazole, pyrazole, and pyridazine, were studied in an aqueous 0.10 M NaClO₄ at pH = 2.5 using variable-temperature spectrophotometry and ¹H NMR spectroscopy. The second-order rate constants indicate that the aqua complex, [Pt(dien)H₂O]²⁺, is more reactive than the corresponding chloro complex, [PtCl(dien)]⁺. The reactivity of the used ligands follows the order: 1,2,4-triazole > pyridazine > pyrazole. Activation parameters were determined for all reactions and the negative entropies of activation (ΔS ^≠) support an associative ligand substitution mechanism.     

Thermodynamic and Kinetic Studies on Reactions of Pt(II) Complexes with Pyrazole, Pyridazine, and 1,2,4-Triazole

Substitution reactions of the complexes [Pt(dien)H₂O]²⁺ and [PtCl(dien)]⁺, where dien = diethylentriamine or 1,5-diamino-3-azapentane, with some nitrogen-donor ligands such as 1,2,4-triazole, pyrazole, and pyridazine, were studied in an aqueous 0.10 M NaClO₄ at pH = 2.5 using variable-temperature spectrophotometry and ¹H NMR spectroscopy. The second-order rate constants indicate that the aqua complex, [Pt(dien)H₂O]²⁺, is more reactive than the corresponding chloro complex, [PtCl(dien)]⁺. The reactivity of the used ligands follows the order: 1,2,4-triazole > pyridazine > pyrazole. Activation parameters were determined for all reactions and the negative entropies of activation (ΔS ^≠) support an associative ligand substitution mechanism.     

Metal Complexes with Macrocyclic Ligands. Part XXXVIII. Steric effects in the copper(II) and nickel(II) complexes with tetra-N-alkylated 1,4,8,11-tetraazacyclotetradecanes

A series of tetra-N-alkylated 1,4,8,11-tetraazacyclotetradecanes have been synthesized and their complexation potential towards Ni²⁺ and Cu²⁺ studied. In the case of sterically demanding alkyl substituents, such as i-Pr, PhCH₂, or 2-MeC₆H₄CH₂, no metal complexes are formed, whereas for substituents such as Me, Et, and Pr, the metal ion is incorporated into the macrocycle. The spectroscopic properties of the Ni²⁺ and Cu²⁺ complexes in aqueous solution indicate that, depending on the sterical hindrance of the N-substituents, the complexes are either square planar or pentacoordinated. All these Ni²⁺ and Cu²⁺ complexes react with N to give ternary species, the stability of which have been determined by spectrophotometric titrations. The tendency to bind N decreases with increasing steric hindrance of the alkyl substituents. The X-ray studies of the Ni²⁺ complex with the macrocycle 11 , substituted by two Me and two Pr groups, and that of the Cu²⁺ complex with the tetraethyl derivative 8 show that in the solid state, the metal ions exhibit square planar coordination with a small distortion towards tetrahedral geometry.     

Metal Complexes with Macrocyclic Ligands. Part XLIII. Tetraazamacrocyclic nickel(II) and copper(II) complexes with aliphatic methylthio- and methoxy-substituted pendant chains

The 14-membered tetraazamacrocyclic Ni²⁺ and Cu²⁺ complexes of 4 (1, 4, 8-trimethyl-11-[(2-methylthio)ethyl]-1, 4, 8, 11-tetraazacyclotetradecane), 5 . (1, 4-dimethyl-8, 11-bis[2-(methylthio)ethyl]-l, 4, 8, 11-tetraazacyclotetradecane), and 7 (1, 4, 8, ll-tetrakis[2-(methylthio)ethyl]-1, 4, 8, 11-tetraazacyclotetradecane), with pne, two, and four methylthio-substituted pendant chains, respectively, and the Ni²⁺ complex of 6 (1, 4-dimethyl-8, 11-bis (2-methoxyethyl)-1, 4, 8, 11-tetraazacyclotetradecane), with two methoxy-substituted pendant chains, were synthesized and their chemistry studied with regard to modelling F430. Solution spectra in H₂O, MeCN, and DMF indicate participation of the side chain in metal coordination when the donor group is a thioether, whereas no coordination with the metal ion is observed with the ether group. Similarly the X-ray structures of the thioether-containing compounds [Ni( 5 )](ClO₄)₂, [Cu( 5 )](ClO₄)₂, and [Cu( 7 )](ClO₄)₂ show a coordination number of 5, whereas that of [Ni( 6 )](ClO₄)₂ with ether pendant chains, shows a coordination number of 4. Cyclic voltammetry of these complexes in MeCN reveals that Ni²⁺ is reversibly reduced to Ni⁺ between ?0.64 and ?0.77 V vs. SCE, the potential being influenced by the nature and number of the pendant chains. At more negative potentials, the thioether is cleaved, whereby a thiol is formed; the thiol is then oxidized at ca. + 0.8 V vs. SCE, when a glassy carbon electrode is used, or at ca. 0 V vs. SCE at a dropping Hg electrode. No cleavage of the ether bond in [Ni( 6 )](ClO₄)₂ is observed under similar conditions.