Three new coordination complexes of cobalt(III), manganese(II), and copper(II) with N,N,O-donor hydrazone ligands: syntheses and structural characterizations

Three new coordination complexes, 2{[Co(L¹)₂]ClO₄} · 0.5CH₃OH (1), [Mn(L²)₂] (2), and [Cu(HL²)(L²)]ClO₄ · 2H₂O (3) have been synthesized from two tridentate N,N,O-donor hydrazone ligands HL¹, 2-acetylpyridine-salicyloylhydrazone, and HL², 2-benzoylpyridine-salicyloylhydrazone, respectively and thoroughly characterized by elemental analysis, FT-IR, UV–Vis, electrochemical, and room temperature magnetic susceptibility measurements. Structures of the complexes have been unequivocally established by single crystal X-ray diffraction technique. Structural analysis reveals that 1 consists of two chemically similar but crystallographically independent cationic [Co(L¹)₂]⁺ units and 2 consists of a neutral [Mn(L²)₂] molecule while 3 consists of a cationic [Cu(HL²)(L²)]⁺ unit. Metal ions display distorted octahedral geometry in 1 and 2 while in 3 it shows a distorted square pyramidal geometry. Ligand conformations around the metal ions are stabilized by the presence of intra-ligand hydrogen bonding in all the complexes. Structure of 3 reveals that a perchlorate ion linked to the complex by hydrogen bonding via a water molecule.     

Rhenium(V) Complexes with Bidentate N,O-Donor Imidazole Derivatives

The reaction of a two-fold molar excess of the potential N,O-donor ligand 2-(hydroxymethyl)-1-methylimidazole (Hmi) with trans-[ReOCl₃(PPh₃)₂] led to the isolation of cis-[ReOCl₂(mi)(PPh₃)]. An X-ray structure determination indicated that the complex has distorted octahedral geometry, and that mi coordinates as a bidentate with the alcoholate oxygen trans to the oxo group. A similar reaction with 2-(1-ethyloxomethyl)-1-methylimidazole (eomi), the ethyl substituted analogue of Hmi, led to the formation of the oxo-bridged dinuclear complex [(μ-O){ReOCl₂(eomi)₂}₂]. The ligand eomi coordinates as a monodentate via the imidazole nitrogen, with the "hard" ether oxygen uncoordinated. An X-ray crystal structure indicates that the chlorides are trans to each other in the ReN₂Cl₂ planes, which are orthogonal to the O=Re-O-Re=O backbone.     

Synthesis and Structural Characterization of Dinuclear Oxorhenium(V) Complexes with Bidentate Imidazole Derivatives

The oxo-bridged dinuclear complexes [(μ-O){ReOCl₂(L)}₂] [L = 2-(1-ethylaminomethyl)-1-methylimidazole (eami); 2-(1-methylaminomethyl)-1-methylimidazole (mami); 2-(1-ethylthiomethyl)-1-methylimidazole (etmi)] were prepared by reaction of trans-[ReOCl₃(PPh₃)₂] with L in acetone. X-ray crystallographic studies of the eami and etmi complexes show that these ligands coordinate in a bidentate manner, and that the cis, cis-N₂Cl₂ and cis, cis-NSCl₂ equatorial planes are nearly orthogonal to the O=Re-O-Re=O backbone.     

A trigonal-bipyramidal oxorhenium(V) complex with a bidentate nitrogen-donor ligand

The oxorhenium(V) complex [ReO(Hapb)(apb)] (1) (H₂apb =?2-(2-aminophenyl)-1-benzimidazole) was prepared by reaction of trans-[ReO₂(py)₄]Cl with a twofold molar amount of H₂apb. The complex was characterized by spectroscopy and X-ray crystallography. The results show that the rhenium atom lies in a distorted trigonal-bipyramidal environment, with the two imidazole nitrogen atoms in apical positions, and the oxo and two amido nitrogens in the trigonal plane.     

Monodentate imido and bidentate aminophenolate coordination of 2-aminophenol in rhenium(V) complexes

Reactions of trans-[ReOCl₃(PPh₃)₂] and trans-[ReO(OEt)I₂(PPh₃)₂] with 2-aminophenol (H₂ap) in acetonitrile led to the formation of cis-[ReOCl₂(Hap)(PPh₃)] (1) and trans-[Re(ap)(Hap)I(PPh₃)₂]I (2), respectively. The X-ray crystal structures show that Hap is coordinated as a bidentate chelate via the neutral amino nitrogen and deprotonated phenolate oxygen, and ap is coordinated as a monodentate through the imido nitrogen. The complexes have been characterized by IR spectroscopy, NMR spectrometry and X-ray crystallography. The bite angle of the Hap chelate is 76.9(1)° and 76.0(1)° in 1 and 2, respectively.     

Synthesis and characterization of a neutral rhenium(V) complex containing a tridentate chelate with an imido donor atom

The six-coordinate complex cis-[Re(mps)Cl₂(PPh₃)] (1) (H₃mps?=?N-(2-amino-3-methylphenyl)-salicylideneimine) was prepared the reaction of trans-[ReOCl₃(PPh₃)₂] with a twofold molar excess of H₃mps in benzene. The compound was characterized by spectroscopy and single-crystal X-ray crystallography. Mps coordinates as a tridentate chelate via the doubly deprotonated 2-amino nitrogen (which is present in 1 as an imide), the neutral imino nitrogen and the phenolate oxygen atoms. The imide and phenolate oxygen atoms coordinate trans to each other in a distorted octahedral geometry around the rhenium(V) centre, with the two chlorides in cis positions.     

Synthesis,characterization, crystal structure,and reactivity of heterobimetallic dioxovanadium(V) complexes containing multidentate hydrazone ligands

Two new heterobimetallic complexes of the composition [(VO₂)₂(μ₃-slsch){Na₂(μ-H₂O)₂(H₂O)₂}]_n (1) and [(VO₂)₂(μ₃-npsch){Na₂(μ-H₂O)₂(H₂O)₂}(DMF)]_n (2) were obtained by reaction of the ligand and vanadium pentoxide in a 1:1 molar ratio in methanol in the presence of Na₂CO₃ (2 equivalents). The complexes obtained were characterized using various spectroscopic studies. The structures of both the complexes were established by single crystal X-ray crystallographic study. We have also explored the catalytic behavior of the complexes in oxidative bromination of phenol red, which is the bio-inspired reaction catalyzed by an enzyme haloperoxidase.     

Synthesis and crystal structure of a rhenium(V) complex containing a tridentate imido-coordinated Schiff base

The complex salt trans-[Re(mps)Cl(PPh₃)₂](ReO₄) (1) (H₃mps?=?N-(2-amino-3-methylphenyl)salicylideneimine) was prepared by reaction of trans-[ReOCl₃(PPh₃)₂] with a twofold molar excess of H₃mps. The compound was characterized by spectroscopy and X-ray crystallography. The results show that the trianionic ligand mps acts as a tridentate chelate via the doubly deprotonated amino nitrogen (which is present in 1 as an imide), the neutral imino nitrogen and the deprotonated phenolic oxygen atoms. The imido nitrogen and phenolate oxygen atoms coordinate trans to each other in a distorted octahedral geometry around the rhenium(V) centre.     

Oxorhenium(V) Complexes with Thiosemicarbazones

Neutral oxorhenium(V) complexes with thiosemicarbazones derived from 2‐pyridine formamide, HL¹, are formed when [ReOCl₃(PPh₃)₂] reacts with equimolar amounts of the ligands. Reduction of the metal and the formation of rhenium(III) complexes of the composition [Re(L¹)₂]⁺ occurs when an excess of thiosemicarbazones is used and the reaction is performed in boiling toluene for a prolonged period of time. The thiosemicarbazones deprotonate and act as tridentate ligands as has been confirmed by an X‐ray structure of [ReOCl₂(L^1b)], where HL^1b is 2‐pyridineformamide‐N(4)‐ethylthiosemicarbazone and the ligand occupies the equatorial coordination sphere of the complex together with one of the chloro ligands.     

Syntheses, characterization, X-ray crystal structures and emission properties of five oxovanadium(V) complexes with pyridyl/pyrimidyl-pyrazole derived ditopic ligands

Four oxovanadium(V) complexes of heterocycle based ditopic ligands PyPzOAP (N-[amino(pyridin-2-yl)methylidene]-5-methyl-1-(pyridin-2-yl)-1H-pyrazole-3-carbohydrazonic acid), PyPzOAPz (N-[amino(pyrazin-2-yl)methylidene]-5-methyl-1-(pyridin-2-yl)-1H-pyrazole-3-carbohydrazonic acid), PymPzOAP (N-[amino(pyridin-2-yl)methylidene]-1-(4,6-dimethylpyrimidin-2-yl)-5-methyl-1H-pyrazole-3-carbohydrazonic acid) and PyPzCAP (5-methyl-1-(pyridin-2-yl)-N′-[1-(pyridin-2-yl)ethylidene]-1H-pyrazole-3-carbohydrazide) and a binuclear (di-μ-oxo) oxovanadium(V) complex of the ligand PymPzCAP (1-(4,6-dimethylpyrimidin-2-yl)-5-methyl-N′-[1-(pyridin-2-yl)ethylidene]-1H-pyrazole-3-carbohydrazide) have been investigated. The ligands act as uninegative NNO tridentates donors for the VO₂⁺ ion exhibiting their monotopicity. The ligands show varying emission properties due to the presence of fluophoric groups like 1-(2-pyridyl)pyrazole or 1-(2-pyrimidyl)pyrazole. The vanadium(V) complexes show fluorescence quenching with respect to the used ligands to a varying extent. The complexes were characterized by UV-Vis, IR, cyclic voltammetry and X-ray crystallography.     

Synthesis,structures, and spectroscopic properties of Hg(II) complexes of bidentate NN and tridentate NNO Schiff-base ligands

Reactions of HgX₂ (X?=?Cl, N₃, NO₃) with (E)-2-methoxy-N-(pyridin-2-ylmethylene)aniline (L¹) and (E)-4-methoxy-N-(pyridin-2-ylmethylene)aniline (L²) in ethanol gave two monomers, [HgL¹(Cl)₂] (1) and [HgL²(NO₃)₂(DMSO)] (5), and three coordination polymers, {[HgL¹(N₃)₂]₂·Hg(N₃)₂}_n (2), [HgL²(Cl)₂]_n (3), and [HgL²(NO₃)₂]_n·nCH₃CN (4). Compounds 1–5 were characterized by elemental analysis, IR, NMR spectroscopy, and single-crystal X-ray diffraction. The common feature of monomeric 1 and 5 is the presence of intra- and intermolecular Hg–O bonds. In the absence of these, polymeric structures arise as a result of azide, chloride, and nitrate bridging in 2, 3, and 4, respectively. Fluorescent properties of 1–5 were also investigated.     

Synthesis,crystal structure and catalytic performance of bis (imino)pyridyl nickel complexes

Two new Ni(II) complexes of 2,6-bis[1-(2,6-diethylphenylimino)ethyl]pyridine (L¹), 2,6-bis[1-(4-methylphenylimino)ethyl]pyridine (L² ) have been synthesized and structurally characterized. Complex Ni(L¹)Cl₂?·?CH₃CN (1), exhibits a distorted trigonal bipyramidal geometry, whereas complex Ni(L¹)(CH₃CN)Cl₂ (2), is six-coordinate with a geometry that can best be described as distorted octahedral. The catalytic activities of complexes 1, 2, Ni{2,6-bis[1-(2,6-diisopropyl-phenylimino)ethyl]pyridine} Cl₂?·?CH₃CN (3), and Ni{2,6-bis[1-(2,6-dimethylphenylimino) ethyl]pyridine}Cl₂?·?CH₃CN (4), for ethylene polymerization were studied under activation with MAO.     

Coordination of a tridentate imido-amino-phenolate chelate to rhenium(V)

The complex cis-[Re(apa)Cl₂(PPh₃)] (1) (H₃apa?=?N-(2-aminophenyl)salicylideneamine) was prepared by reaction of trans-[ReOCl₃(PPh₃)₂] with H₃apa in ethanol. Apa acts as a tridentate chelate ligand via the doubly deprotonated amino nitrogen (which is coordinated as an imide), the amino nitrogen and the deprotonated phenolic oxygen atoms. The two chlorides lie cis to each other in a distorted octahedral geometry around the rhenium(V) centre.     

Synthesis,spectral characterization,properties and structures of copper(I) complexes containing novel bidentate iminopyridine ligands

Four new ligands, (4-methyl-phenyl)-pyridin-2-ylmethylene-amine (A), (2,3-dimethyl-phenyl)-pyridin-2-ylmethylene-amine (B), (2,4-dimethyl-phenyl)-pyridin-2-ylmethylene-amine (C) and (2,5-dimethyl-phenyl)-pyridin-2-ylmethylene-amine (D), and their corresponding copper(I) complexes, [Cu(A)₂]ClO₄ (1a), [Cu(B)₂]ClO₄ (1b), [Cu(C)₂]ClO₄ (1c), [Cu(D)₂]ClO₄ (1d), [Cu(A)(PPh₃)₂]ClO₄ (2a), [Cu(B)(PPh₃)₂]ClO₄ (2b), [Cu(C)(PPh₃)₂]ClO₄ (2c) and [Cu(D)(PPh₃)₂]ClO₄ (2d), have been synthesized and characterized by CHN analyses, ¹H and ¹³C NMR, IR and UV–Vis spectroscopy. The crystal structures of [Cu(B)₂]ClO₄ (1b), [Cu(C)₂]ClO₄ (1c) and [Cu(A)(PPh₃)₂]ClO₄ · 1/2CH₃CN (2a) were determined from single crystal X-ray diffraction. The coordination polyhedron about the copper(I) center in the three complexes is best described as a distorted tetrahedron. A quasireversible redox behavior is observed for the complexes.     

Complexes of Oxorhenium(V) with Aromatic 2-Amino-Alcohols

Monooxo complexes of rhenium(V) with 2-aminophenol and some of its derivatives (H₂nod), containing the N,O donor-atom set, have been synthesized. Square-pyramidal complexes [ReO(nod)₂]^? were isolated by reaction with (n-Bu₄N) [ReOCl₄] in ethanol. In benzene the neutral species [ReOCL(Hnod)₂] were obtained. In the presence of hydrochloric acid in ethanol, the anionic complexes (n-Bu₄N) [ReOCl₃(Hnod)] were produced. Trans-[ReOCl₃(PPh₃)₂] was also reacted with some of the H₂nod ligands to yield [ReOCL₂(Hnod)(PPh₃]. The crystal structure of [ReOCl₂(Hmap)(PPh₃)] (H₂map = 2-aminobenzylalcohol) was determined; crystals are monoclinic, P2₁/n, with a = 15.065(6), b = 11.253(7), c = 15.850(7) Å, β = 94.27(4)°, U = 2680(2) &Aringsup3; and Z = 4. The structure was solved by the Patterson method and refined by full-matrix least-squares techniques to R = 0.042. The monoanionic Hmap^? ligand is coordinated as a bidentate through a neutral amino nitrogen and an anionic alcoholate oxygen atom, with the latter trans to the oxo group.     

Organosilicon backbone containing pyridyl/quinolyl ligands: Synthesis, complexation reactions and single crystal structures of metallamacrocyclic Pd(II) and Cu(II) complexes

Organosilicon backbone containing ligands 1,2-bis(dimethyl(2-pyridyl)silyl)ethane (L¹) and 1,2-bis(dimethyl(3-quinolyl)silyl) ethane (L²) have been synthesized by treating 2-bromopyridine and 3-bromoquinoline with n-butyllithium and reacting the resulting lithiated products with 1,2-bis(chlorodimethylsilyl)ethane. The ligation of L¹ and L² with Pd(II), Ag(I) and Cu(II) has been investigated. The single crystal structures of L², [Pd(L¹)Cl₂] (1), [Cu(L¹)Br₂] (3) and [PdCl₂(L²)]₂ (4) have been solved. All the three complexes are metallamacrocyclic in nature. The last one is 22-membered and the first example which has ligands containing organosilicon backbone. The geometry of Pd as well as Cu is very close to square planar. The Pd–N, Pd–Cl, Cu–N and Cu–Br bond distances (2.010(1)–2.027(3), 2.3063(10)–2.3114(4), 2.004(4)–2.018(5) and 2.4137(10)–2.4172(10) Å) are very close to sum of covalent radii, indicating strong ligation of L¹ and L² with the metal ions.     

Nucleophilic addition of water to coordinated dipyridylethylene in rhenium(V) complexes

Complexes of general formula [ReOX₂{(C₅H₄N)CH(O)CH₂(C₅H₄N)}] (X?=?Cl,?I) were prepared by reaction of trans-[ReOCl₃(PPh₃)₂] and trans-[ReOI₂(OEt)(PPh₃)₂] with cis-1,2-di-(2-pyridyl)ethylene (DPE) in ethanol and benzene in air. The coordinated DPE ligand undergoes addition of water at the ethylenic carbon atoms, and the (C₅H₄N)CH(O)CH₂(C₅H₄N) moiety acts as a uninegative terdentate N,O,N-donor ligand. X-ray crystal structures of both complexes have been determined and show distorted octahedral geometry at the rhenium(V) centre.