Homobinuclear Complexes Research Articles

Transition metal complexes with ‘end-off’ compartmental Schiff bases containing sulphonic or phosphonic groups

Nickel(II), manganese(II) and copper(II) complexes with ‘end-off’ compartmental ligands derived from 2,6-diformyl-4-chlorophenol and α or β-amino-sulphonic or aminophosphonic acids, have been prepared. The mono- and homobinuclear complexes, obtained by template or step by step procedures, have been characterized by IR, UV, scanning electron microprobe analysis and magnetic susceptibility measurements. The electrochemical behaviour of some complexes has been also examined. The crystal structure of {[Cu 2(C 10H 8ClN 2O 7S 2)(OH)](DMSO(H 2O)} 2 has been determined by X-ray crystallography. The compound is orthorhombic, space group Pbca, with a=17.071(5), b=11.751(5), c=20.464(4) Å, Z=4. The molecule of the compound is centrosymmetric. One five-coordinate square pyramidal and one four-coordinate square planar copper atom are present in the asymmetric unit, and the four coordinate copper also makes a contact of 2.58 Å with a DMSO molecule. Selected bond distances are: CuO (bridging) 1.95 Å (mean), CuO (base) 2.00 Å, CuN (base) 1.96 Å (mean), CuO (axial) 2.25 Å. The organic ligand is pentadentate; the hydroxo oxygen atom is bridging two copper atoms of the same asymmetric unit and is axially bonded to one copper atom of the centrosymmetric unit. The clathrate water molecules are hydrogen bonded to the compound.

Iridium(III)cis-dihydrido complexes with 3,6-bis(2′-pyridyl)pyridazine. Crystal structure of the pyridazinyl complex [{IrH2(PPh3)2}2{µ-C4HN2(C5H4N)2-3,6}]PF6

The complexes [IrH2(Me2CO)2(PPh3)2]X (X = PF6 or SbF6) react with 3,6-bis(2′-pyridyl)pyridazine, dppn, in dichloromethane at 20 or 0 °C. At 20 °C the resulting products are the mononuclear species [IrH2(dppn)(PPh3)2]X only, while at 0 °C, in addition the salts dppn·HX (X = PF6 or SbF6) and the homobinuclear complexes [{IrH2(PPh3)2}2{µ-C4HN2(C5H4N)2-3,6}]X form. The structure of the dichloromethane solvate of the latter (X = PF6) has been determined by X-ray diffraction methods. Crystals are triclinic, space group P, with a= 14.014(4), b= 22.781(8), c= 14.328(3)A, α= 108.58(4), β= 68.79(5), γ= 99.04(5)°, and Z= 2. The structure has been solved from diffractometer data by Patterson and Fourier methods and refined by full-matrix least squares to R= 0.052 for 6 725 observed reflections. The structure consists of binuclear cationic complexes, of PF6– anions, and of dichloromethane molecules of solvation. The cation has imposed Ci symmetry, so that the organic ligand, chelating on its opposite sides both metals through three nitrogen and one carbon atoms, must be disordered and statistically distributed in two positions with the carbon atom bonded to both metals. The distorted octahedral co-ordination around each Ir atom is completed by two P atoms from PPh3 ligands in trans positions and by two terminal hydrides in cis positions.

Mono- and bi-nuclear four-membered methanide auracycles; synthesis and reactivity. X-Ray structure of cis-[Au(C6F5)2(SPPh2O)(CH2PPh2Me)

The complexes [Au(C6F5)2Cl(SPh2PCH2PPh2CH2R)]ClO4(R = H or Ph) react with Na2CO3 or NaH to give four-membered methanide auracycles [[graphic omitted]HPPh2CH2R)]ClO4 or [[graphic omitted]PPh2CH2R)], respectively; these complexes can be interconverted by reaction with with NaH or HClO4. The neutral derivatives can be used to form homobinuclear complexes [[graphic omitted]C(AuX)PPh2Me}](X = C6F5 or Cl) and [[graphic omitted](AuPPh3)PPh2Me}]BF4 and react with water to give [Au(C6F5)2(SPPh2O)(CH2PPh2CH2R)]. The structure of [Au(C6F5)2(SPPh2O)(CH2PPh2Me)] has been solved by X-ray crystallography.

Binucleating N624- and 26-membered macrocyclic ligands. Part 2. Transition-metal homo- and hetero-binuclear complexes: X-ray crystallographic structure determination of a lead–manganese heterobinuclear complex

Template condensation products of 1,5-diaminopentane and 1,6-diaminohexane with 2,6-diacetylpyridine on Pb(NCS)2 have been transmetallated with CoII and CuII to yield homobinuclear complexes of the 24- and 26-membered macrocycles, L1 and L2 respectively. In the dicobalt(II) complex of the smaller macrocycle, L1, a thermally populated spin equilibrium exists lying well to the low-spin side at 93 K. E.s.r. spectra indicate the complex has an equatorially compressed tetragonal geometry. The dicobalt(II) complex of the larger macrocycle, L2, is effectively high-spin, down to 93 K. Dicopper(II) complexes of L1 display a weak antiferromagnetic interaction, absent in analogous complexes of L2. Heterobinuclear complexes [PbML1(NCS)2(MeCN)2][ClO4]2 of the 24-membered macrocycle have been prepared for M = NiII and FeII, as confirmed by fast-atom bombardment (f.a.b.) mass spectra. An X-ray crystallographic structure determination on the heterobinuclear complex PbMnL1(NCS)4 reveals a Pb–Mn distance of 4.857(2)A and confirms that the metal centres are bridged by two 1,3-µ–NCS–bridges, as inferred from i.r. spectroscopy for the other thiocyanato complexes studied. However, the X-ray structure shows that in this case the thiocyanate bridges present both S-donors to Pb and both N-donors to Mn.

The formation and synthetic applications of new acetonitrile derivatives of cycloheptatrienyl-molybdenum and -tungsten complexes; synthesis of binuclear [M(CO) 3(η-C 5R 5)M(CO) 2(η-C 7H 7)] (M = Mo, R = H or Me; M = W, R = H)

Reaction of [WI(CO) 2(η-C 7H 7)] with Ag[BF 4] in acetonitrile yields the trihaptocycloheptatrienyl complex [W(CO) 2(NCCH 3) 3(η 3-C 7H 7)][BF 4] which affords [W(CO) 2(NCCH 3)(η-C 7H 7)][BF 4] ( 1a) on stirring in CH 2Cl 2. A similar reaction sequence is observed starting from [MoI(CO) 2(η-C 7H 7)] but a mixture of [Mo(CO) 2(NCCH 3) 3(η 3-C 7H 7)][BF 4] ( 2b) and [Mo(CO) 2(NCCH 3)(η-C 7H 7)][BF 4] ( 1b) is formed in CH 3CN. Treatment of [M(CO) 2(NCCH 3)(η-C 7H 7)] + (M = Mo, W) with Li[M(CO) 3(η-C 5R 5)] (M = Mo, R = H or Me; M = W,R = H) affords asymmetric homobinuclear complexes [M(CO) 3(η-C 5R 5)M(CO) 2(η-C 7H 7)] ( 4). Ultraviolet irradiation of [Mo(CO) 2(NCCH 3)(η-C 7H 7)][BF 4] in CH 3CN forms [Mo(CO)(NCCH 3) 2(η-C 7H 7)][BF 4] ( 5) whilst irradiation of [Cr(CO) 3(η-C 7H 7)][PF 6] in CH 3CN followed by addition of P(OMe) 3 gives [Cr(CO){P(OMe) 3} 2(η-C 7H 7)][PF 6].

SYNTHESIS, STRUCTURE AND SPECTROSCOPIC STUDIES OF ETHYLENEDIAMINE-N, N-BIS[1′-METHYL-3′-OXO-3′-(2′'-HYDROXY-5′'-METHYLPHENYL)PROPENYL] AND ITS MONO AND HOMOBINUCLEAR COMPLEXES WITH NICKEL(II) AND COPPER(II)

Abstract The title compound and its mono and homobinuclear complexes with Ni(II) and Cu(II) have been prepared. Spectroscopic and magnetic studies and crystal X-ray structure determinations show a slightly distorted square planar geometry for the mononuclear Cu(II) and Ni(II) complexes with the metals in the N2O2 compartment. Both compounds crystallize in the monoclinic space group P21 n, with a = 8.382(1), b = 15.435(1), c = 17.216(1)A, β = 100.62(1)° R = 0.077, with 1228 reflections for the Ni(II) complex and a = 8.405(1), b = 15.324(2), c = 17.483(2)A, β = 101.96(10)° R = 0.075, with 1255 reflections for the Cu(II) complex. The presence of Cu(II) causes slight changes in the structure and conformation of the complex. The spectroscopic and magnetic study for the dinuclear Ni(II) complex is consistent with an octahedral environment for the metal occupying the O2O2 site and a square planar geometry for that occupying the N2O2 site, whereas the spectroscopic and magnetic data for the dinuclear Cu(II) compl...

Strongly luminescing ruthenium(II)/ruthenium(II) and ruthenium(II)/platinum(II) binuclear complexes

Two strongly luminescing complexes, ruthenium(II)/ruthenium(II) homobinuclear complex and ruthenium(II)/platinum(II) heterobinuclear complex, have been prepared and characterized. The organic part of the complex is 4,4'-dimethyl-2,2' bipyridine dimer. The luminescence behavior of the homobinuclear and heterobinculear complexes was found to be comparable to that of Ru(bpy)/sub 3//sup 2 +/, although the luminescence maxima were shifted from 615 to 620 nm. These complexes exhibit good stability due to the bidentate chelating capability of the bridging ligand. These new complexes can provide the opportunity for detailed photophysical studies related to donor-acceptor interactions and to the possibility of two simultaneous single-electron transfer events. 17 references, 2 figures.

Lanthanide complexes of compartmental ligands

Abstract Schiff base ligands having available adjacent, dissimilar coordination sets have been termed collectively compartmental ligands [1]. Such ligands may be prepared from the reaction of an α, ω-diamine with one terminal keto-function of a β-triketone or β-ketophenol (Fig. 1). The ligands are capable of forming mononuclear positional isomers, homobinuclear and heterobinuclear metal complexes (Fig. 2). The application of such ligands to the area of ‘d’ block transition metal chemistry has been recently reviewed [1]. We here describe some lanthanide complexes of compartmental ligands derived from the β-ketophenol, 2-proprionoacetylphenol. The reaction of 2-proprionoacetylphenol, (H 2 -pap), with α, ω-diamines leads to the Schiff bases I and II in Fig. 3. The ligands are readily characterised by i.r., m.s. and 1 H n.m.r. spectroscopy. Metal complexation reactions have been carried out using both the Schiff base ligands and the β-ketophenol precursor. Complexes of the β-Ketophenol The reaction of H 2 - pap with LN(NO 3 ) 3 ·xH 2 O (Ln = La, Pr, Eu) in methanol in the presence of LiOH gave fine powdery products. The products analysed as Ln 2 (pap) 2 (NO 3 )OH), nH 2 O (n = 2 for La, 3 for Eu and 6 for PR), and are assigned the cis binuclear structure, III, by analogy with transition metal analogues [2]. Mononuclear Complexes of the Schiff Bases The reaction of a chloroform solution of the Schiff base with a methanolic solution of Ln(NO 3 ) 3 · nH 2 O gave fine, powdery products. For I complexes were available for Ln = La→ Eu, and for II complexes were of the form Ln(H 2 −L)NO 3 ·xH 2 O and are assigned structure IV. Outer compartment occupancy is indicated by the absence, in the i.r., of v OH for the phenol and the presence of v NH . 1 H n.m.r. spectra of the La derivatives also support this proposition. The preference of lanthanide ions for oxygen donor environments would also suggest such an occupancy. Binuclear Complexes of the Schiff Bases Attempts to obtain homobinuclear lanthanide complexes have so far been unsuccessful as have been attempts to prepare heterobinuclear complexes by the reaction of the mononuclear lanthanum complexes with metal salts such as VO(IV), Th(IV), UO 2 (VI) - all metals with strong -O 2 o 2 preferences. The reaction of copper(II) ethanoate with IV gave the homobinuclear copper(II) derivative. The reaction of the mononuclear copper(II) complex of I having -N 2 O 2 occupancy with Ln(NO 3 ) 3 , nH 2 O gave no heterobinuclear product but reaction of the corresponding nickel(II) complex with Ln(NO 3 , nH 2 O did give heterobinuclear complexes of I (Ln = La, Pr, Eu).

Acyclic and macrocyclic schiff base complexes of lanthanides and actinides

Acyclic and macrocyclic schiff base complexes of lanthanides and actinides

Investigation of the possible pathways for magnetic exchange interactions in homobinuclear chelates of naphthazarin

Homobinuclear complexes of the binucleating naphthazarinato ligand of the general formula [Formula: see text] where M = Cu, Ni, and Zn, C10H4O4 = naphthazarinato ligand, and C10H8N2 = 2,2′-bipyridyl, have been prepared and studied. In these complexes the naphthazarinato ligand, acting as a bridging unit between the two metal centers, supports the propagation of magnetic exchange interactions through its extensive π-electron system. The spectroscopic and magnetic data of the compounds showed that each metal ion is surrounded by two oxygen and two nitrogen donor atoms in a nearly tetrahedral configuration (C2v point group) with the naphthazarinato ligand adopting a centrosymmetrical structure of C2h symmetry. The room-temperature magnetic data of the copper(II) and nickel(II) homobinuclear chelates (1.32 and 1.73 BM per metal ion at 8000 G, respectively), as well as the slight decrease of the magnetic moments as the magnetic field strength decreases are indicative of the operation of antiferromagnetism in these chelates. Quantum mechanical calculations of the Hückel LCAO-MO type improved by ω-technique have been used to provide a qualitative guide to the possible pathways for the superexchange processes observed in the tetrahedral copper(II) and nickel(II) chelates, as well as to explain qualitatively why there is no antiferromagnetic interactions propagated by the bridging naphthazarinato ligand in analogous homobinuclear chelates with other coordination geometries such as square planar, square-pyramidal, trigonal bipyramidal, and octahedral.

Binuclear complexes of tetraketones

The tetraketones 1,1′-(1,3-phenylene)-bis-1,3-butanedione (H 2L a) and 1,1′-(1,4-phenylene)-bis-1,3-butanedione (H 2L b have been isolated and characterised. They are potentially tetradentate ligands and H 2L a could act as binucleating agent. The reaction of the tetraketones with different metal ions has been investigated. Homobinuclear complexes of the type (ML) 2nS (S = H 2O, MeOH or pyridine; n = 0, 1, 2, 4) have been prepared and characterised on the basis of analytical, i.r. and visible spectra, and magnetic susceptibility data. Metal complexes of 1,4-bis(acetoacetyl)-piperazine (H 2L c) have also been prepared.

Synthesis and characterization of homobinuclear complexes with 4-substituted-2,6-diformylphenol bis-aroylhydrazones

Synthesis and characterization of homobinuclear complexes with 4-substituted-2,6-diformylphenol bis-aroylhydrazones

Preparation and crystal structure of a copper(II) homobinuclear chelate

The structure of the homobinuclear complex Cu2(aapen)H2O, where aapen is the tetraanionic ligand derived from the condensation of 1,2-diaminocthane witho-acetoacetylphenol, has been determined from diffractometer data and refined to R = 6.1%. The crystals are monoclinic,P21/c, witha = 12.991(5),b = 8.530(4),c = 18.546(6) A, andβ = 104.10(4)°; Z = 4. The ligand employed has two different coordination sets of atoms, N2O2 and O2O2, two oxygen atoms being common to both donor sets. In the complex, one copper atom is retained in the plane of the inner N2O2 chamber whilst the other, which is incorporated in the outer O2O2 chamber, is five-coordinate, being axially bonded to a water molecule.

Compartmental ligands. Part 2. Mononuclear transition-metal complexes of acyclic Schiff bases derived from 1,3,5-triketones

A series of acyclic Schiff bases (1) derived from 1,3,5-triketones and α,ω-alkanediamines has been prepared, and their mononuclear complexes with CuII, NiII, UO2, and VO are described. Phenyl-substituted alicyclic bases are prepared by the reaction of 1-p-X-phenylhexane-1,3,5-trione (X = H, Br, Me, or OMe)(2 mol) and ethane-1,2-diamine (en)(1 mol) in ethanol; the condensation of 7,7-dimethyloctane-2,4,6-trione with en similarly yields 2,2,7,12,17,17-hexamethyl-8,11-diazaoctadeca-6,12-diene-3,5,14,16-tetraone (1 I). 6, 11-Dimethyl-7,10-diazahexadeca-5,11-diene-2,4,13,15-tetraone, (1 a), is prepared by acid hydrolysis of the macrocyclrc Schiff base 5,9,14,18-tetramethyl-1,4,10,13-tetra-azacyclo-octadeca-5,8,14,17-tetraene-7,16-dione (2a). Treatment of the alicyclic bases with metal acetates gives the corresponding mononuclear complexes. The ligands (1) are potentially tetra-anionic and have two available dissimilar compartments for complex formation, one comprising N2O2 and the other O2O2 donor sites. The co-ordination selectivity of (1) is established as a necessary prerequisite for the formation of pure heterobinuclear chelates of these ligands. The reaction of Cu[O2CMe]2 with (1a) gives three products: the two N2O2 and O2O2 positional isomers, (5a) and (6a)·H2O, and a homobinuclear complex. The mononuclear complexes of Ni, UO2, and VO show N2O2, O2O2, and O2O2 site occupancy respectively. The preference of Ni for the N2O2 site is reinforced in its reaction wth the phenyl-subsmuted bases, but here Cu shows a preference for O2O2 as do VO and UO2. The site selectivity of Ni is further exemplified in the reaction of (5a; M = Cu) with Ni[O2CMe]2 in which the Ni replaces the Cu in the ligand. The complexes have been characterised by chemical analysis and spectral measurements, and the potential role of magnetic studies in establishing the site occupancy has been investigated.