Coordination Moieties Research Articles

Synthesis, crystal structure and spectroscopic characterization of a hydrogen-bonded 1D copper(II) complex

Novel 1:2 and 1:1 (M:L) copper(II) complexes have been prepared from the tridentate ligand 2-(1-methyl-2-aza-5-oxapentyl)phenol (H2L1). The crystal structure of [Cu(HL1)2] (1) exhibits a noncentrosymmetric square-planar geometry with a slightly tetrahedral distortion. The CuII atom is coordinated by two amino N and two phenoxo O atoms of two (HL1)− ligands. The phenoxo and the alkoxy groups are involved in two strong intramolecular hydrogen bonds. The coordination moieties are further connected to a 1D linear structure by the action of intermolecular hydrogen bonds between the alkoxyl and the amino groups. The importance of steric hindrance introduced by the methyl group in the molecular structure and the packing of the complex molecules has been demonstrated. The e.p.r. parameters of (1) have been obtained: g∥ = 2.231, g⊥ = 2.005, giso = 2.080, A∥ = 185.0 G, Aiso = 86.5 G, A⊥ = (3Aiso − A∥)/2 = 37.3 G. These results confirm a distorted square planar stereochemistry with a (\({\text{d}}_{x^2 - y^2 }\))1 ground state.

Tris(Trifluoroacetylacetonato)(4,4′-bipyridyl-N,N′-dioxido)Lanthanum(III)∶ A One-dimensional Polynuclear Complex

A novel one-dimensional polynuclear complex, tris(trifluoroacetylacetonato)(4,4'-bipyridyl- N , N '-dioxido)lathanum(III), was synthesized and characterized by elemental analysis and IR spectroscopy. X-ray structure analysis revealed that the complex has an infinite one-dimensional polynuclear structure with the 4,4'-bipyridyl- N , N '-dioxide as a bridge. La(III) is coordinated to eight oxygen atoms, six from three trifluoroacetylacetonate anions and two from two 4,4'-bipyridyl- N , N '-dioxide molecules to form a slightly distorted square antiprismatic coordination polyhedron. The coordination moiety was linked through 4,4'-bipyridyl- N , N '-dioxide forming a one-dimensional chain.

Bis{methylNβ-[4-(dipropylamino)benzylidene]dithiocarbazato}nickel(II)

The Schiff base ligand in the title complex, [Ni(C15H22N3S2)2], lost a proton from its tautomeric thiol form and coordinated to Ni(II) via the mercapto S and β-N atoms. The geometry around the Ni atom is square planar with two equivalent Ni—N and Ni—S bonds. The two phenyl rings and the coordination moieties are in one plane forming an extensive electronic delocalization system. The structure is governed by C—H⋯S and C—H⋯N hydrogen bonds, leading to the formation of centrosymmetric dimers.

Bis[S-methyl 3-(2-bromobenzylidene)dithiocabazato-N3,S]platinum(II)

The Schiff base ligand in the title complex, [Pt(C9H8BrN2S2)2], is deprotonated from its tautomeric thiol form and coordinated to PtII via the mercapto S and β–N atoms. The configuration about PtII is a perfect square-planar, with two equivalent Pt—N [2.023 (3) Å] and Pt—S [2.293 (1) Å] bonds. The phenyl ring is twisted against the coordination moiety Pt1/N1/N1′/S2′/S2 by 31.8 (2)°, due to the steric hindrance induced by ortho-substituted bulky Br atom.

SYNTHESIS, CRYSTAL STRUCTURE AND THIRD-ORDER NONLINEAR OPTICAL PROPERTIES OF COPPER(II) COMPLEXES WITH SCHIFF-BASE LIGAND DERIVATIVES FROM DITHIOCARBAZATE

The synthesis and spectroscopic characterization of D-M-D type neutral Cu(II) chelates with Schiff base ligands, R‒C6H4CHNNHCSSCH3 (R = ‒N(CH3)2, ‒CH3O) are reported. Spectroscopic data suggest that the Schiff base ligands act as single negatively charged bidentate ligands forming stable neutral metal complexes. Single crystal X-ray structure determinations of the Cu(II) chelates established that the coordination geometry of Cu(II) is square planar with two equivalent Cu-N and Cu-S bonds. The Schiff base ligands lost a proton from their tautomeric thiol form and coordinated to Cu(II) via the mercapto sulfur and β-nitrogen as expected. The two phenyl rings and the coordination moieties are almost in one plane forming an extensive electronic delocalization system. Magnetic properties and ESR data support the square-planar coordination geometry for both of the Cu(II) chelates. Nonlinear optical properties were measured using z-scan methods in CH3CN solution.

Bis(4-methoxybenzaldehyde thiosemicarbazonato-S,N4)copper(II)

The Schiff base ligand in the title complex, [Cu(C9H10N3OS)2], lost a proton from its tautomeric thiol form and coordinated to CuII via the mercapto S and β-N atoms. The geometry around CuII is square-planar with two equivalent Cu-N and Cu-S bonds. The two phenyl rings and the coordination moieties are in one plane forming an extensive electronic delocalization system.

Mono- and polynuclear schiff base complexes derived from polyoxadiamines

New compartmental macroacyclic and macrocyclic Schiff bases have been prepared by reaction of the formyl precursors 2,3-dihydroxy-benzaldehyde, 3-methoxy-2-hydroxy-benzaldehyde and 2,6-diformyl-4-chlorophenol with 1,2-diaminoethane, 1,3-diaminopropane and the polyethyleneoxy-diamine H 2N(CH 2) 2[O(CH 2) 2] nNH 2 ( n = 1, 2, 3) also with the presence of a templating ion. In these ligands the shape of one or borh compartments has progressively been enlarged and the denticity increased in order to link up to four metal ions into the coordination moiety. These ligands react with copper(II), nickel(II) or lanthanide(III) salts to form mononuclear, homo- and heterodinuclear, homotrinuclear or homotetranuclear complexes. The ligands and the complexes were characterized by elemental analysis, IR, 1H and 13C NMR, mass spectrometry, magnetic susceptibility and SEM investigations.

Mononuclear and polynuclear complexes containing f ions

Dinuclear and tetranuclear uranyl(VI) complexes ((UO 2) 2(L A)·2H 2O and (UO 2) 4(LB)· nS, n=2; S=H 2O, dmf, dmso), where H 4L A and H 8L B are the Schiff bases obtained by condensation of 1,4-bis- [bis(2-aminoethyl)aminomethyl]benzene with salicylaldehyde or 2,3-dihydroxybenzaldehyde, respectively, have been prepared by template procedure or by reaction of the preformed ligands with uranyl(VI) salts. The ligands and the complexes have been characterized by physicochemical data, particularly by IR and NMR spectroscopy. Their properties have been compared with those of the similar mono-, homo- and heterodinuclear complexes containing uranyl(VI) and/or lanthanide(III) ions with the potentially heptadentate compartmental Schiff bases H 4L c and H 4L D, derived by condensation of 2,3-dihydroxybenzaldehyde with 1,5-diamino-3-azapentane and 1,5-diamino-3-thiapentane, respectively. The X-ray structure of the dinuclear uranyl complex (UO 2) 2(L A)·dmso·C 6H 6 has been determined by X-ray diffractometry and compared with that of UO 2(H 2L c)·dmf, (UO 2) 2(L c)(dmf) and (UO 2) 2(L c)(dmso). The crystals of (UO 2) 2(L A)·dmso·C 6H 6 grown from a dmso/C 6H 6 solution are triclinic, space group P 1 with a=13.459(4), b=13.179(3), c=11.418(4) Å, α=75.80(4), β=108.30(4)m γ=116.77(5)°, U=1704(1) Å 3, D c=1.38 g cm −3 for Z=1. The asymmetric unit is half of the molecule, this being centrosymmetric. The structure was refined to the final R of 4.9%. The compound forms a centro-symmetric binuclear complex as the benzene ring, bridging the two macroacyclic coordination moieties, is centered on inversion point 1 2 , 0, 1 2 The uranium atom is in the usual, slightly distorted, bipyramidal pentagonal configuration; the quasi linear (175°) uranyl UO 2 2+ ion is equatorially coordinated by the O 2N 3 donor set of the Schiff base ligand forming an irregular puckered pentagon. Selected bond distances for this compound are: UO (uranyl) 1.77 (mean), UO (ligand) 2.22 (mean) and UN 2.61 Å (mean). The two uranium atoms displace 1.20 Å above and below the central benzene ring plane and are 12.686(1) Å apart (the shortest intermolecular U···U distance is 6.954(1) Å. One dmso and one benzene molecule are present, as clathrate solvents, in disordered positions and do not present any type of interaction with the remaining cell content.

Nickel(II), palladium(II) and cobalt(II) complexes of the substituted tritertiary arsine, 2-chloroethylbis(3-dimethylarsinopropyl)arsine

The substituted tritertiary arsine, 2-chloroethyl-bis(3-dimethylarsinopropyl)arsine, forms Ni(trias)X 2 (X = Cl, Br, I), which are assigned tetragonal pyramidal pentacoordinate structures. The Pd(trias)Cl 2 species is best assigned as a planar [Pd(trias)Cl]Cl coordination moiety. Both [Co(trias)Br] 2[CoBr 4] and [Co(trias)Br]ClO 4 contain pseudotetrahedral cations, but [Co(trias) 2](ClO 4) 2 is unlike any four-coordinate or six-coordinate cobalt(II) entity and is assigned a pentacoordinate structure containing a tridentate and a bidentate ligand. The donor properties of trias are compared to that of similar tridentate ligands.

Metal complexes of amino acids and derivatives—XIII Some nickel(II) complexes of L-arginine zwitterions or L-argininate anions. A novel ionic → bidentate perchlorate rearrangement brought about by pressure[1–5

Nickel(II) complexes have been isolated in which the ligand coordinates as an anion (Arg −) or a zwitterion (ArgH). These complexes, Ni(Arg) X· nH 2O ( X = Cl, Br, NO 3, ClO 4) and Ni(ArgH) x X 2· nH 2O ( X = Cl, NO 3, ClO 4, OH), are six-coordinate and contain a NiN 2O 4 coordination moiety. Only in the cases of Ni(ArgH) 2(NO 3) 2·H 2O and Ni(ArgH)(OH) 2·H 2O are X − groups coordinated. However, it has also been found that the complexes containing ionic perchlorate, when put under pressure, rearrange to form complexes containing bidentate perchlorato groups. The complexes have been characterised by magnetic measurements and by infrared and visible reflectance spectral methods.