Unsymmetrically substituted triazacyclohexanes and their chromium complexes

The unsymmetrically N-substituted N,N′-Ar₂-N″-R-1,3,5-triazacyclohexanes 1–4 (Ar = ortho- or para-fluorophenyl, R = n- or iso-propyl) can be obtained in good yields from a one-step condensation reaction with excess amine. Solid state structures of 1–4 resemble closely those of their triaryl-substituted analogues. The condensation reaction to 4 was looked at by detailed NMR investigations and revealed that amine/aniline exchange is occurring in solutions containing free aniline even at ambient conditions setting up an equilibrium between all possible symmetrical and unsymmetrical triazacylcohexanes. Selective crystallisation of 4 from the solution drives the reaction to high yields of 4. Complexes 1–4 react readily with CrCl₃ or CrCl₃(THF)₃ to form the corresponding CrCl₃ complexes. The complexes are insoluble in non-polar solvents and decompose under decomplexation in coordinating solvents.     

Unsymmetrically substituted benzothiazolyl-hydrazines

New unsymmetrically substituted hydrazines containing benzothiazole residues with substituents in the 6-position were obtained by the oxidative cyclization of substituted 1,4-diphenylthiosemicarbazides with potassium ferricyanide in alkaline aqueous alcoholic media. The reaction of these new hydrazines with trichloromethyl mercaptan gave N-(6-R-2-benzothiazolyl)-N-[p-(trichloromethylthioamidosulfonyl)phenyl]hydrazines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 765–766, June, 1971.     

Structural and mechanistic investigations of the oxidation of dimethylplatinum(II) complexes by dioxygen

The oxidation of (tmeda)Pt(II)(CH(3))(2) (1, tmeda = N,N,N',N'-tetramethylethylenediamine) to (tmeda)Pt(IV)(OH)(OCH(3))(CH(3))(2) (3) by dioxygen in methanol proceeds via a two-step mechanism. The initial reaction between (tmeda)Pt(CH(3))(2) and dioxygen yields a hydroperoxoplatinum(IV) intermediate, (tmeda)Pt(OOH)(OCH(3))(CH(3))(2) (2), which reacts with a second equivalent of (tmeda)Pt(CH(3))(2) to afford the final product 3. Both 2 and 3 have been fully characterized, including X-ray crystallographic structure determinations. The effect of ligand variation on the oxidation of several dimethylplatinum(II) complexes by 2 as well as by dioxygen has been examined.     

Platinum(II) and palladium(II) complexes with substituted pyrimidines

Summary Platinum(II) and Palladium(II) complexes with 2-mercaptopyrimidine, 2-thiocytosine (4-aminopyrimidine 2-thione), and isocytosine (2-amino-4-hydroxy pyrimidine) were prepared and characterised by elemental analysis, conductivity data, i.r.,¹H n.m.r. and¹³C n.M.r. spectral studies. 2-Mercaptopyrimidine and 2-thiocytosine are coordinated to the metal ion through N(3) and C₂S, thus forming a four-membered chelate ring. Isocytosine acts as a monodentate ligand and coordinates to the metal ion through N(1). All the complexes are non-electrolytes.     

Metallation of tris(1-pyrazolyl)methane by dimethylplatinum(II)

Tris(1-pyrazolyl)methane (HCpz₃) reacts with Pt(CH₃)₂(COD) to form Pt(CH₃)₂(HCpz₃), and when this complex is heated in pyridine metallation of the pyrazole ring at C(5) occurs to form Pt(CH₃)(HCpz₂(pzH_₁))(py). A triphenylphosphine derivative, Pt(CH₃)(HCpz₂(pzH_₁))(PPh₃)₂, when slowly heated to 185°C forms Pt(HCpz₂(pzH_₁))(C₆H₄PPh₂); this complex has both the nitrogen and phosphorus donor ligands metallated to form six and four-membered rings, respectively.     

Unsymmetrically substituted N-heterocyclic phosphenium ions

Reduction of an unsymmetrically substituted α-diimine followed by condensation with PCl₃ yielded a P-chloro-N-aryl-N′-alkyl diazaphospholene which was further converted into an unsymmetrical diazaphospholium triflate by reaction with trimethylsilyl triflate. Reaction of tetramers of N-H- or N-alkyl-benzo-1,3,2-diazaphospholes with methyl triflate or triflic acid led in one step to triflate salts of unsymmetrically substituted benzo-1,3,2-diazaphospholium cations. Determination of the crystal structures of two of these derivatives by single-crystal X-ray diffraction studies revealed that individual cations and anions in the crystal lattice interact via specific electrostatic, π-stacking, or van-der-Waals type interactions to form supramolecular assemblies. Thermoanalytical measurements disclosed that benzo-diazaphospholium triflates with medium length alkyl chains melt below 100 °C and exhibit a strong tendency to form supercooled liquids.     

Ruthenium(II) and iron(II) complexes of N-pyridyl substituted imidazolin-2-ylidenes

N-mesityl-N′-pyridyl-imidazolium chloride 1a and the corresponding bromide salt 1b have been deprotonated with NaH in THF giving the free N-heterocyclic carbene N-mesityl-N′-pyridyl-imidazolin-2-ylidene 2 in 80% yield (starting from 1a). Imidazolium salt 1a reacts with RuCl₃ · xH₂O to give a racemic mixture of dinuclear di-μ-chloro bridged ruthenium complexes [(κ²-2)₂Ru(μ-Cl)₂Ru(κ²-2)₂]²⁺ [3a]²⁺. The carbene carbon atoms as well as the halides are arranged in cis-positions to each other whereas the nitrogen atoms adopt a trans-configuration. The di-μ-bromo bridged derivative [(κ²-2)₂Ru(μ-Br)₂Ru(κ²-2)₂]²⁺ [3b]²⁺ was obtained from RuCl₃ · xH₂O and 1b. The bridging halide ligands can be removed by the reaction with silver or sodium salts of bidentate Lewis acids. Complex [3a]²⁺ reacts with silver pyridylcarboxylate to give a racemic mixture of the mononuclear complex [4]⁺. Reaction of [3a]²⁺ with the sodium salt of l-proline resulted in a diastereomeric mixture of complexes [5]⁺. The free N-heterocyclic carbene 2 reacts with [FeCl₂(PPh₃)₂] to give after anion exchange with NaBPh₄ cis/cis/trans coordinated [Fe(κ²-2)₂(MeCN)₂](BPh₄)₂ [6](BPh₄)₂. The molecular structures of [3b](PF₆)₂, [4]PF₆ and [6](BPh₄)₂ · H₂O are reported.     

Application of variable-temperature kinetic experiments to oxidative addition reactions of dimethylplatinum(II) complexes with alkyl halides

Rate constants and activation parameters of oxidative addition reactions of [PtMe₂(2,2′-bipyridine)] with EtI and [Pt(p-MeC₆H₄)₂ (2,2′-bipyridine)] with MeI in solvents acetone and benzene have been obtained very easily and with good accuracy from variable-temperature spectrophotometric kinetic data using a method based on nonisothermal analysis. The results are compared with those obtained by the traditional isothermal method. It is shown that there are significant advantages to measuring the reaction rates under variable-temperature kinetic conditions, as compared to the constant-temperature kinetic method.     

The electrochemical reduction of some substituted π-cyclopentadienylnickel(II) complexes

The electrochemical reduction of the complexes [CpNi(PR₃)₂]⁺, where R = C₂H₅, C₃H₇, C₄H₉ or [C₆Ni,(diphos)]⁺ and [CpNi(diars)⁺ in acetonitrile is described and the data are compared with those for the complexes Cp₂Ni, [Ni(PR₃)₄]²⁺ and Ni(diphos)²⁺₂.     

Spectral studies on cobalt(II), nickel(II) and copper(II) complexes of naphthaldehyde substituted aroylhydrazones

A series of new coordination complexes of cobalt(II), nickel(II) and copper(II) with two new aroylhydrazones, 2-hydroxy-1-naphthaldehyde isonicotinoylhydrazone (H(2)L(1)) and 2-hydroxy-1-naphthaldehyde-2-thenoyl-hydrazone (H(2)L(2)) have been synthesized and characterized by elemental analysis, conductance measurements, magnetic susceptibility measurements, (1)H NMR spectroscopy, IR spectroscopy, electronic spectroscopy, EPR spectroscopy and thermal analysis. IR spectra suggests ligands acts as a tridentate dibasic donor coordinating through the deprotonated naphtholic oxygen atom, azomethine nitrogen atom and enolic oxygen atom. EPR and ligand field spectra suggests octahedral geometry for Co(II) and Ni(II) complexes and a square planar geometry for Cu(II) complexes.     

Unsymmetrically substituted furoxans. VIII. Chloromethylfuroxans

The two isomeric chloromethylfuroxans have been prepared. Their structures, thermal equilibration and reaction toward thiophenoxide ion are discussed. Kinetics of the 4-methyl — 3-methyl isomer thermal conversion are also reported.     

Mesophase behaviour and thermal stability of octa-alkoxy substituted phthalocyaninatocobalt (II) complexes

Cobalt (II) phthalocyanines substituted with eight alkoxy chains in the peripheral (2, 3, 9, 10, 16, 17, 23, 24) positions were prepared. The alkoxy chain length was varied between n-butyloxy (C₄H₉O) and n-octadecyloxy (C₁₈H₃₇O). Studies by polarizing optical microscopy and high temperature X-ray diffraction revealed that all the complexes are liquid crystalline and that they exhibit a hexagonal columnar mesophase (Col_h). Transition enthalpies were determined by differential scanning calorimetry. The clearing point could only be observed for compounds with a chain length longer than C₁₃H₂₇O. Both the melting and clearing points decrease with increasing chain length. The transition temperatures of these discotic metallomesogens are higher than those of the corresponding metal-free phthalocyanines, but are comparable with those of the corresponding copper (II) compounds. The thermal decomposition of the compounds was studied by thermogravimetry.     

Mesophase behaviour and thermal stability of octa-alkoxy substituted phthalocyaninatocobalt (II) complexes

Cobalt (II) phthalocyanines substituted with eight alkoxy chains in the peripheral (2, 3, 9, 10, 16, 17, 23, 24) positions were prepared. The alkoxy chain length was varied between n-butyloxy (C₄H₉O) and n-octadecyloxy (C₁₈H₃₇O). Studies by polarizing optical microscopy and high temperature X-ray diffraction revealed that all the complexes are liquid crystalline and that they exhibit a hexagonal columnar mesophase (Col_h). Transition enthalpies were determined by differential scanning calorimetry. The clearing point could only be observed for compounds with a chain length longer than C₁₃H₂₇O. Both the melting and clearing points decrease with increasing chain length. The transition temperatures of these discotic metallomesogens are higher than those of the corresponding metal-free phthalocyanines, but are comparable with those of the corresponding copper (II) compounds. The thermal decomposition of the compounds was studied by thermogravimetry.     

Electronic and structural variation among copper(II) complexes with substituted phenanthrolines

A series of copper(II) complexes with substituted phenanthroline ligands has been synthesized and characterized electronically and structurally. The compounds that have been prepared include the monosubstituted ligand complexes of the general formula [Cu(5-R-phen)(2)(CH(3)CN)](BF(4))(2), where R = NO(2), Cl, H, or Me, and the disubstituted ligand complex [Cu(5,6-Me(2)-phen)(2)(CH(3)CN)](BF(4))(2). The complexes [Cu(5-NO(2)-phen)(2)(CH(3)CN](BF(4))(2) (1), [Cu(5-Cl-phen)(2)(CH(3)CN)](BF(4))(2) (2), [Cu(o-phen)(2)(CH(3)CN)](BF(4))(2) (3), and [Cu(5-Me-phen)(2)(CH(3)CN)](BF(4))(2) (4) each crystallize in the space group C2/c with compounds 1, 2, and 4 comprising an isomorphous set. The disubstituted complex [Cu(5,6-Me(2)-phen)(2)(CH(3)CN)](BF(4))(2) (5) crystallizes in the space group P2(1)/c. Each structure is characterized by a distorted trigonal bipyramidal arrangement of ligands around the central copper atom with approximate or exact C(2) symmetry. The progression from electron-withdrawing to electron-donating substituents on the phenanthroline ligands correlates with less accessible reduction potentials for the bis-chelate complexes.     

Halogen substituted quadridentate schiff bases,their nickel(II) and cobalt(III) complexes

Summary Electrophilic substitutions have been performed on the methyne carbon of NiL and [CoL,2py]ClO₄ [L=N,N-bis(acetylacetone) ethylenediiminato-]. The effects of substituents (H, Cl, Br and I) on the electron distribution within the cobalt(III) complexes have been investigated through¹H and¹³C n.m.r., i.r. spectroscopy and half-wave potential measurements     

Spectroscopic studies of preferential and asymmetric solvation in substituted cyanoiron(II) complexes

The solvatochromism observed for substituted cyanoiron complexes depends on the acceptor properties of the solvents, according to v = v_o + a(AN), where ν is the measured spectral charge transfer energy and AN refers to the acceptor number scale. The parameter a was found to be strongly influenced by the solvation characteristics of the ligands compared with those of the cyanides. In H₂O+S mixed solvents, preferential solvation by water was observed where S was acetone or acetonitrile, but not when S was methanol, dimethylsulfoxide, dimethylformamide or related solvents.     

The gas chromatography of higher substituted tetradentate β-ketoamine copper(II) complexes

The preparation of the Schiff's bases derived from 1,2-diaminoethane and a series of 5-alkyl substituted-1,1,1-trifluoropentan-2:4-diones is described, including the elusive compound obtained from 1,1,1-trifluoro-5,5,5-trimethylpentan-2:4-dione, and trivially denoted as H₂[en(TPM)₂]. Gas chromatography of the copper complexes of these ligands shows increasing retention times as the size of the alkyl substituent is increased, with the exception of Cu[en(TPM)₂] which is unusually volatile and has a much reduced retention time. It is most probable that this graat difference in properties occurs because of the considerable steric hindrance of the tert-butyl groups in the original β-diketone, which prevents the normal condensation reaction with 1,2-diaminoethane taking place. The properties of the metal complexes of H₂[en(TPM)₂] make them ideally suited to quantitative gas chromatography.     

Magnetic properties of copper(II) complexes with some hydrazones of substituted salicylaldehydes

A series of novel mono-and binuclear copper(II) complexes with substituted salicylaldehyde acylhydrazones H₂L of the formula CuL · xH2O (x = 0 and 1) and [Cu(HL)](ClO₄)(CH₃OH) were synthesized. The isolated dimeric complexes of copper acetate were found to exist as isomers with different bridging atoms. In dimers showing a superexchange between the paramagnetic centers through bridging phenoxide O atoms, the antiferromagnetic exchange couplings were much stronger than those in complexes with bridging O atoms of the a-oxyazine fragment.