Spiros P. Perlepes

The vibrational spectra of complexes with planar monothio-oxamides—I. The Ni(II), Pd(II), Pt(II), Cu(II) and Zn(II) complexes of N,N′-dimethylmonothio-oxamide

Abstract The new complexes M(LH) 2 (M = Pd,Pt), ML(M = Pd,Cu) and ML · H 2 O (M = Ni,Zn), where LH 2 = N , N ′-dimethylmonothio-oxamide, have been prepared. The complexes were characterized by metal analyses, thermal methods and spectral (i.r., Raman, u.v.—vis.) studies. The vibrational analyses of the complexes are given using NH/ND, CH 3 /CD 3 and metal isotopic substitutions. The Ni(II), Pd(II), Pt(II) and Cu(II) compounds are square planar. The monoanion LH − shows a chelated bidentate S,O-coordination, while the doubly deprotonated L 2− acts as a bridging S,N/N,O-tetradentate ligand giving polymeric structures.

Coordination chemistry of corrosion inhibitors of the benzotriazole type: Preparation and characterization of cobalt(II) complexes with 1-methylbenzotriazole (Mebta) and the crystal structures of [CoCl2(Mebta)2], trans-[Co(NCS)2 (Mebta)4], trans-[Co(NCS)2(MeOH)2(Mebta)2] and cis-[Co(NO3)2(Mebta)2]

Abstract An inorganic model approach to the corrosion inhibition of metals by benzotriazoles has been initiated. The preparation and characterization of monomeric cobalt(II) complexes of the types [CoX2(Mebta)2](X = Cl, Br, NCS, NO 3), (MebtaH)[CoCl3(Mebta)], (MebtaH)2[CoCl4], [Co(NCS)2(Mebta)4], [Co(NCS)2 (MeOH)2(Mebta)2] and [Co(NO3)2 L2(Mebta)2] (L = H2O, MeOH), where Mebta = 1-methylbenzotriazole, are described. Four representative complexes have been structurally characterized by single-crystal X-ray diffraction studies; [CoCl2(Mebta)2] (1), trans- [Co(NCS)2(Mebta)4] (5), trans-[Co(NCS)2 (MeOH)2(Mebta)2] (6) and cis-[Co(NO3)2(Mebta)2] (8). Mebta acts as a monodentateligand binding through N(3). The geometry about cobalt in 1 is tetrahedral, while complexes 5, 6 and 8 have octahedral stereochemistries. The new complexes were also characterized by elemental and thermogravimetric analyses, conductivity measurements, variable-temperature magnetochemistry and spectroscopic (IR, ligand field, low-temperature ESR) methods. The data are discussed in terms of the nature of bonding and known structures.

Preparation and properties of complexes of lanthanide(III) salts with n-(2-pyridyl) pyridine-2′-carboxamide

New complexes of the general formulae [Ln(LH)2(NCS)3(H2O)] (Ln = La-Eu), [Ln(LH)2(NCS)3] (Ln = Gd-Yb), [Ln(LH)3(OClO3)](ClO4)2 (Ln = La-Gd), [Ln(LH)3] (ClO4)3 (Ln = Tb-Yb), [Ln(LH)2(ONO2)2](NO3) (Ln = La-Yb) and [Ln(LH)(ONO2)3] (Ln = La, Pr, Nd, Sm, Eu), where LH = N-(2-pyridyl)pyridine-2′-carboxamide, have been isolated. The complexes were characterized by elemental analyses, conductivity measurements, X-ray powder patterns, thermal methods, magnetic susceptibilities and spectroscopic (IR, 1H NMR, electronic diffuse reflectance and solid state emission f-f spectra) studies. All the data are discussed in terms of the nature of the bonding and the possible structural types. The 1:2 and 1:3 complexes appear to be monomeric, while polymeric structures are assigned for the 1:1 nitrato compounds. The LH molecule behaves as a bidentate ligand in the monomeric complexes, bonding through the amide oxygen and N(l′). The amide oxygen and both pyridine residues are coordinated in the 1:1 nitrato complexes.

The coordination chemistry ofN, N′-ethylenebis(2-acetylpyridine imine) andN, N′-ethylenebis(2-benzoylpyridine imine); two potentially tetradentate ligands containing four nitrogen atoms

SummaryNew complexes of the general formulae [MLA(H2O)2]-Cl2 (M=Ni or Cu), [MLAX2] (M=Co or Cu; X=Cl or Br), [NiLABr2]·H2O, [MLA] [MCl4] (M=Pd or Pt), [NiLB(H2O)2]Cl2·2H2O, [MLBCl2] (M=Co, Ni, Cu, Pd or Pt; X=Cl or Br) and [MLB] [MCl4] (M=Pd or Pt), where LA=N,N′-ethylenebis(2-acetylpyridine imine) and LB=N, N′-ethylenebis(2-benzoylpyridine imine), have been isolated. The complexes were characterized by elemental analyses, conductivity measurements, t.g./d.t.g. methods, magnetic susceptibilities and spectroscopic (i.r., far-i.r., ligand field,1Hn.m.r.) studies. Monomeric pseudo-octahedral stereochemistries for the CoII, NiII and CuII complexes andcis square planar structures for the compounds [MLBX2] (M=Pd or Pt; X=Cl or Br) are assigned in the solid state. The molecules LA and LB behave as tetradentate chelate ligands in the CoII, NiII, CuII and Magnus-type PdII and PtII complexes, bonding through both the pyridine and methine nitrogen atoms. A bidentateN-methine coordination of the Schiff base LB is assigned in the [MLBX2] complexes (M=Pd or Pt; X=Cl or Br). The anomalous magnetic moment values of the CoII complexes are discussed.

The Coordination Chemistry of N-(3-Carboxylphenyl) Pyridine-2′-Carboxamide

Abstract New complexes of the general compositions M(LH2)2X2 (M = Co, Ni, Cu, Zn; X = Cl, NCS, NO3), M(LH2)2Cl2. EtOH (M = Ni, Cu; EtOH = ethanol), M(LH)2.nH2O (M = Co, Ni, Cu, Zn, Pt; n = 1, 2, 3), Pd(LH)Cl·H2O, CuL·3H2O and Zn(LH) (OH) ·2H2O, where LH2 = N-(3-carboxylphenyl)pyridine-2′-carboxamide, have been isolated. The complexes were characterised by elemental analyses, conductivity measurements, TG patterns, magnetic susceptibilities and spectral (1H-NMR, IR, electronic) studies. Distorted octahedral and square planar stereochemistries are assigned in the solid state. Coordination of the neutral carboxylic group is not observed for the complexes of LH2; the carboxylate ion exhibits monodentate coordination in the compounds of LH− and L2-. The neutral amide group of LH2 and LH− is coordinated to Co(II), Ni(II), Cu(II) and Zn(II) through oxygen, while nitrogen and oxygen amide coordination is observed for CuL·3H2O. The secondary amide bond shows the rare iminol type of coordination in Pd(LH)Cl·H2O.

The vibrational spectra of complexes with planar monothio-oxamides—II. Complexes of N(s)-methylmonothio-oxamide

Abstract The new complexes Pd(SH 2 ) 2 · H 2 O, M(SH) · H 2 O (M = Ni, Pd, Pt) and M(SH) · 0.5H 2 O (M = Cu, Zn), where SH 3 = N ( s ) -methylmonothio-oxamide, have been prepared. The complexes were characterized by metal analyses, thermal methods and i.r., Raman and u.v./vis spectroscopic studies. The vibrational analyses of the complexes are given using NH/ND, CH 3 /CD 3 and metal isotopicsubstitutions. The Ni(II), Pd(II), Pt(II) and Cu(II) compounds are square planar. The vibrational spectra show that in Pd(SH 2 ) 2 · H 2 O the coordination occurs via the sulphur atom of the deprotonated thioamide group and the oxygen atom of the neutral primary amide group, in a bidentate chelated fashion. The doubly deprotonated SH 2− ion behaves as a bridging bis -bidentate ligand giving polymeric structures.

The infrared spectra of complexes with planar dithio-oxamides—VII. The Cu(LH2)1X2 and Cu(LH2)2X2 complexes

Cu(II) gives square planar complexes, Cu(LH2)1X2 (X = Cl, Br) and Cu(LH2)2X2 (X = Cl, Br, ClO4), with planar dithio-oxamides, LH2 = dithio-oxamide (DTO), N-methyldithio-oxamide (MDTO) and NN′-dimethyldithio-oxamide (NN′DMDTO) in acid media [1]. The ligands act as bidentates with S, S′-coordination. A thorough investigation of the i.r. spectra of these complexes is presented, and special attention has been given to the low frequency region and to the influence of hydrogen bonding in the spectra. The hydrogen bonding ability is found to increase following the series DTO < MDTO < NN′DMDTO and ClO4 < Br < Cl. This difference in hydrogen bond strength is much more pronounced for the Cu(LH2)2X2 complexes than for the Cu(LH2)1X2 complexes.

Synthesis, spectroscopy and thermal properties of the nickel(II), palladium(II) and copper(II) complexes of bis(aminoalkyl)-oxamides (= LH2) including the crystal structure of Cu2L(NO3)2

SummaryThe synthesis of the NiII, PdII and CuII complexes of N, N′-bis(aminoalkyl)oxamides (LH2) is described and structures are proposed on the basis of their physical and spectroscopic properties. With NiII and PdII only one complex is formed with general formula NiL or PdL, characterised by coordination through two deprotonated amide N-atoms and two terminal NH2 groups. With CuII it proved possible to obtain three structurally different compounds, depending on the pH, with general formulae Cu(LH2)X2, Cu2(L)X2 and CuL in which X=Cl, Br or NO3. The structure of [Cu2(C8O2N4H16](NO3)2 was solved by means ofx-ray diffraction; Mr=451.33, monoclinic, space group P21/n, a=9.503(4), b=7.614(1), c=10.407(3) Å, β=98.43(3)°, V=744.3(7)Å3, Z=2, Dx=1.202 g cm−3, μ=1.33 cm−1, γ(MoKα)=0.71073 Å, F(000)=520, room temperature, R=0.043, wR=0.047 for 1080 observed [I>-3σ(I)] not systematically absent reflections out of 1423 measurements and 137 variables. The compound has a conformational chair/boat disorder with 82% in the more stable chair form.

Syntheses, solid state electronic and infrared spectra of the Ni(II), Pd(II) and Cu(II) complexes of N-(2-hydroxyethyl) and N-(3-hydroxypropyl) oxamide

The new complexes K2[Ni(Hheo)2], K2[Cu(Hheo)2]·H2O, K2[Ni(Hhpo)2]·H2O, K2[M(Hhpo)2]·0.5H2O (M = Cu, Pd) and K2[Cu2(hpo)2·0.5H2O, where H3heo = N-(2-hydroxyethyl)oxamide and H3hpo = N-(3-hydroxypropyl)oxamide, have been prepared. Several synthetic routes were investigated and the complexes were characterized by analyses, conductivity measurements, thermogravimetry, magnetic susceptibility and spectroscopy (i.r. and far i.r., diffuse reflectance u.v.). Monomeric square planar structures are found for the [M(Hheo)2]2− and [M(Hhpo)2]2− complex anions, while the hpo3− Cu(II) complex appears to be a square planar dimer. The doubly deprotonated Hheo2− and Hhpo2− ions exhibit a bidentate N(secondary amide), N′(tertiary amide)-coordination with the OH-group remaining uncoordinated, while the triply deprotonated hpo3− ion behaves as a bridging N(secondary amide), N′(tertiary amide), O(deprotonated) ligand, while two Cu(II) centres are bridged by two alkoxide-O atoms. The vibrational analysis of the dehydrated complexes is carried out, using NH/ND, OH/OD, 58Ni/62Ni and 63Cu/65Cu substitutions.

Lanthanide(III) Complexes of N-(2- and N-(3-Carboxylphenyl)Pyridine-2-Carboxamide

Abstract New complexes of the general compositions Ln(o-LH)3·2H2O (Ln=La, Ce, Pr, Nd, Sm), Er(o-LH)3·2.5H2O, Ln(o-LH)3·3H2O (Ln=Eu, Gd, Tb, Dy, Ho, Tm, Yb), Ln(m-LH)3·2H2O (Ln=Pr, Nd, Sm, Gd, Er), Ln(m-LH)3·3H2O (Ln=La, Ce, Eu, Tb) and Ln(m-LH)3·4H2O (Ln=Dy, Ho, Tm, Yb), where o-LH2=N-(2-carboxylphenyl) pyridine-2′ -carboxamide and m-LH2=N-(3-carboxylphenyl)pyridine-2′ -carboxamide, have been isolated. The complexes, which are probably polymeric, were characterised by elemental analyses, conductivity measurements, thermal (TG, DTG, DTA, DSC) methods, X-ray powder patterns, magnetic moments and spectral (IR, Raman, 1H-NMR, electronic diffuse reflectance and emission f-f spectra) studies. All the data are discussed in terms of the nature of the bonding and the possible structural types. The neutral secondary amide group and the ring N-atom of o-LH−and m-LH− are not coordinated to the metal ions. The carboxylate