Ahmed El-Toukhy

Coordination compounds of hydrazine derivatives with transition metals—XV Electronic and 1H NMR spectra of some diamagnetic metal(II) chelates with bidentate Schiff bases derived from hydrazine-S-methyl-dithiocarboxylate and thiosemicarbazide

Abstract A series of diamagnetic bis ligand Zn(II), Cd(II), Hg(II), Ni(II) and Pd(II) chelates with some Schiff bases derived from hydrazine-S-methyldithiocarboxylate(III) and the corresponding acid amide(IV) were prepared and characterized. The H NMR spectral studies showed that the Schiff base ligands derived from aromatic aldehydes as well as their metal(II) chelates exist only in one configuration with the aldehydic hydrogen syn to the NN bond. The ligand (III) derived from asymmetric ketones exist as a mixture of syn and anti configurations. The H NMR spectra of the corresponding Zn(II), Cd(II), Hg(II) and Ni(II) chelates indicate the presence of a trans isomer in syn and anti configurations. The spectra of Pd(II) chelates with ligand (III) show the possible existence of both cis and trans isomers in both syn and anti configurations. Besides, the syn and anti configurations, the Zn(II) and Ni(II) chelates with (III, R1 = CH3, R2 = CH2C6H5) appear to exist in different conformations. Ni(II) chelates derived from acetophenone derivatives exist predominantly in cis-syn configuration.

Transmetalation: A New Route to Heteropolymetallic Molecules and Materials

Abstract The newly discovered transmetalation of polymetallic molecules by mononuclear transmetalators is an excellent source of a wide variety of related heteropolyatomic molecules and materials that cannot be obtained by other means. The systems discussed involve easily obtained reactants, stoichiometric reactions and easily separated products. Among the factors that affect specific transmetalation patterns are target structure, transmetalator identity and relative stability, redox phenomena, intramolecular ligand transfer and specific types of primary product fragmentation. A feature of reported transmetalation systems that make them excellent candidates for the production of new materials is that they are stoichiometric and flexible. Prospects for extending known systems to new targets and elements are discussed.

Coordination compounds of hydrazine derivatives with transition metals—VII: Metal(II) complexes with hydrazine s-methyl dithiocarboxylate Schiff bases and their pyridine adducts

Abstract Metal(II) chelates of general formula M ( R 1 R 2 CN−NCSSCH 3 ) 2 ( M Ni( II ), Co(II) and Cu(II); R 1 = R 2 = CH 3 ; R 1 , R 2 = C 5 H 10 − and R 1 = CH 3 , R 2 = C 6 H 5 ) were prepared and investigated. Magnetic and spectral data indicated square planar Ni(II) complexes while Co(II) afforded tetrahedral complexes. All the Cu(II) chelates probably possessed a dimeric pentacoordinate geometry. The reaction of pyridine with the bis metal (II) complexes were discussed. Monopyridinate adducts were isolated with the bis (N-isopropylidene hydrazine-S-methyldithiocarboxylate) cobalt (II) and nickel (II) chelates.

Coordination compounds of hydrazine derivatives with transition metals. V. Square planar nickel(II) complexes with hydrazine-S-methyl dithiocarboxylate schiff bases

Abstract Schiff bases derived from the condensation of hydrazine-S-methyl dithiocarboxylate with substituted benzaldehyde and heterocyclic aldehydes were prepared. Their reactions with Ni II chloride and acetate were investigated. Magnetic and spectral data have shown that square planar Ni II complexes resulted from all the Schiff bases. Bis neutral complexes were obtained with the Schiff bases acting as monobasic bidentate ligands. In addition, 1:1 complexes were isolated with salicylaldehyde and pyridine-2-carbaldehyde derivatives where the Schiff bases functioned as dibasic tridentate and monobasic tridentate ligands respectively. The interaction of the square planar Ni II complexes with pyridine was also investigated.

Coordination compounds of hydrazine derivatices with transition metals—XIX: Redox reactions of Cu(II) salts with thiosemicarbazide and hydrazine-S-methyl dithiocarboxylate schiff bases

Abstract Schiff base ligands derived from hydrazine-S-methyl dithiocarboxylate (R1R2CNNH·CSSMe) can react with Cu(II) salts to give either Cu(I) or Cu(II) chelates depending on the anion of the salt used, the nature of R1 and R2 in the ligand molecule and the temperature of the reaction medium. A tentative mechanism for the reduction of Cu(II) salts by these ligands was proposed. From the magnetic measurements, electronic and ESR spectral data the structure of the Cu(II) chelates was assigned.

The kinetics of primary events in the reactions of L2Cu2X2 complexes (L is an N,N,N′N′-tetraalkyldiamine; X is Cl or Br) with M(NS)2 reagents

Abstract The rate laws for the earliest events in the transmetalation of dimeric copper(I) complexes L 2 Cu 2 X 2 (L = N,N,N′N′ -tetraalkyldiamine; X = Cl or Br) by M(NS) 2 reagents (M = Co, Ni, Cu, Zn; NS is a monoanionic S -methylhydrazinecarbodithioate Schiff base ligand) depend on L, X, M and NS and the aprotic solvent. The kinetic data are compared with those for monotransmetalation of copper(II) complexes (μ 4 -O)N 4 Cu 4 X 6 by M(NS) 2 . Different kinetic behavior is particularly marked for cobalt(II) reactants. Unexpectedly high rates of reactions with Cu(NS) 2 are attributed to electron transfer. The results provide a basis for discussion of transmetalation specificity.

Stoichiometry and products of transmetalation of dimeric copper(I) complexes L2Cu2X2 (L is an N,N,N′,N′-tetraalkylethylenediamine; X = Cl or Br) by M(NS)2 reagents in aprotic solvents

Abstract Dimeric copper(I) complexes L 2 Cu 2 X 2 react with 1 and 2 mol of M(NS) 2 reagents in aprotic solvents to give quantitative yields of products LMX 2 and (NS)M(X,X)M(NS), respectively. Here, L = N,N,N′N′ -tetraethylethylenediamine, X = Cl or Br, M = Co, Ni, Cu and Ns = S -methylisopropylidenehydrazinecarbodithioate. Dimers (NS)Cu(X,X)Cu(NS) are oxidatively unstable. LCoCl 2 crystallizes in the monoclinic space group P 2 1 / c (C 2h 5 ): a = 7.345(1), b = 11.801(1), c = 17.478(2) A, β = 104.98(1)°, Z = 4. The electronic spectra of LMX 2 and (NS)M(X,X)M(NS) complexes are discussed.

Crystal and molecular structure of racemic fac-tris-(S-methylisopropylidene-hydrazinecarbodithioato)cobalt(III), Co(NS)3, and the kinetics of its isomerization in aprotic solvents

Abstract The crystal and molecular structure of fac-tris- (S-methylisopropylidenehydrazinecarbodithioato)cobalt (III) is reported. The dark olive-green Co(NS)3 crystallizes in the monoclinic space group P21/c with Z = 4 in a cell of dimensions a = 17.876(2), b = 9.792(2), c = 14.816(2) A and β = 108.63(1)°. The coordination sphere is relatively undistorted but the cobalt atom does not lie in the center of this sphere. Kinetic studies have shown the fac to mer isomerization to have a very large (⩾100) equilibrium constant and to proceed by a trigonal twist mechanism.

Transmetalation of μ-carbonatodicopper(II) complexes with M(NS)2 reagents

Abstract Well characterized binuclear μ-carbonatodicopper( II ) complexes III can be partially and completely transmetalated with Ni(NS) 2 reagents I or II (NS are mononegative anions of S-methyl hydrazinecarbodithioate Schiff bases) to give hetero- and homobinuclear species and Cu(NS) 2 coproducts. The neutral ligand HNS stoichiometrically demetalates III , showing that a major driving force for transmetalation is the formation of stable Cu(NS) 2 coproducts. All nickel-containing products were found to have a strong affinity for water and a tendency to lose their bidentate amine ligands. Products (H 2 O) 6 Ni 2 Cl 2 (CO 3 ) and (Py) 6 Ni 2 (OH)Cl(CO 3 )·6H 2 O have been obtained by direct transmetalation of III using different experimental conditions. Nickel( II ) complexes, Ni(NS) 2 , effectively inhibit the oxidation of 2,6-dimethylphenol by dioxygen initiated by complexes III .

Coordination compounds of hydrazine derivatives with transition metals. Part 24. Coordination chemistry of hydrazine-S-methyl carbodithioate schiff bases derived from β-dicarbonyl compounds

SummaryThe reactions of β-diketones and β-ketoaldehydes with hydrazine-S-methyl carbodithioate, hydth, have been studied in the absence and presence of metal(II) ions. A series of dimeric monoligand chelates [Ni(β-dikhydth-2H)]2 have been isolated. The reaction of these chelates with monodentate Lewis bases yields square planar [Ni(β-dikhydth2H)B] chelates. Bisligand chelates of benzoylacetone monohydrazones [M(Bzachydth-H)2] (M=Cu or Zn) have been also synthesized, as have a series of NiII and ZnII chelates of β-diketone bishydrazones of the type [M(β-dik(hydth)2-2H)].