Electrochemical synthesis and magnetic studies of neutral transition metal imidazolates and pyrazolates

Summary The single-step electrochemical synthesis of neutral transition metal complexes of imidazole, pyrazole and their derivatives has been achieved at ambient temperature. The metal was oxidized in an Me₂CO solution of the diazole to yield complexes of the general formula: [M(Iz)₂] (where M = Co, Ni, Cu, Zn; Iz = imidazolate); [M(MeIz)₂] (where M = Co, Ni, Cu, Zn; MeIz = 4-methylimidazolate); [M(PrⁱIz)₂] (where M = Co, Ni, Cu, Zn; PrⁱIz = 2-isopropylimidazolate); [M(pyIz)_n] (where M = Co^III, Cu^II, Zn^II; pyIz = 2-(2-pyridyl)imidazolate); [M(Pz)_n] (where M = Co^III, Ni^II, Cu^II, Zn^II; Pz = pyrazolate); [M(ClPz)_n] and [M(IPz)_n] (where M = Co^III, Ni^II, Cu^II, Zn^II; ClPz = 4-chloropyrazolate; IPz = 4-iodopyrazolate); [M(Me₂Pz)_n] (where M = Co^II, Cu^I, Zn^II; Me₂Pz = 3,5-dimethylpyrazolate) and [M(BrMe₂Pz)_n] (where M = Co^II, Ni^II, Cu^I, Zn^II; BrMe₂Pz = 3,5-dimethyl-4-bromopyrazolate). Vibrational spectra verified the presence of the anionic diazole and electronic spectra confirmed the stereochemistry about the metal centre. Variable temperature (360-90 K) magnetic measurements of the cobalt and copper chelates revealed strong antiferromagnetic interaction between the metal ions in the lattice. Data for the copper complexes were fitted to a Heisenberg (S= ) model for an infinite one-dimensional linear chain, yielding best fit values of J=–62––65cm^–1 andg = 2.02–2.18. Data for the cobalt complexes were fitted to an Ising (S= ) model with J=–4.62––11.7cm^–1 andg = 2.06–2.49.     

Preparation of chiral diimino- and diaminodiphosphine ligands and their Cu and Ag complexes. X-ray crystal structures of [Cu(1S,2S-cyclohexyl-P2N2)][PF6] and [Ag(1R,2R-cyclohexyl-P2N2H4)][BF4]

The interaction of optically pure 1R,2R-diammoniumyclohexane mono-(+)-tartrate and 1S,2S-diammoniumcyclohexane mono-(−)-tartrate with 2 equiv. of o-(diphenylphosphino)benzaldehyde in the presence of 2 equiv. of potassium carbonate in a refluxing ethanol/water mixture gave the optically pure condensation products N,N′-bis[o-(diphenylphosphino)benzylidene]-1R,2R-diiminocyclohexane[1R,2R-cyclohexyl-P₂N₂, (R,R)-I] and N,N′-bis[o-(diphenylphosphino)benzylidene]-1S,2S-diiminocyclohexane [1S,2S-cyclohexyl-P₂N₂, (S,S)-I], respectively, in good yield. Reduction of optically pure (R,R)-I and (S,S)-I with NaBH₄ in ethanol gave the optically pure reduced products N,N′-bis[o-(diphenylphosphino)benzylidene]-1R,2R-diaminocyclohexane[1R,2R-cyclohexyl-P₂N₂H₄, (R,R)-II] and N,N′-bis[o-diphenylphosphine)benzylidene]-1S,2S-diaminocyclohexane[1S,2S-cyclohexyl-P₂N₂H₄, (S,S)-II], respectively, in good yield. The coordination behaviour of I and II toward salts of Cu^I and Ag^I have been examined. The interaction of [Cu(C)₃CN)₄][X] (X = ClO₄⁻, PF₆⁻) with 1 equiv. of optically pure L₄ [L₄ = (R,R)-I, (S,S)-I, (R,R)-II and (S,S)-II] gave the corresponding optically pure [CuL₄][X] complexes, III–VI IIIa, L₄ = (R,R)-I, X = PF₆⁻ IIIb, L₄ = (R,R)-I, X = ClO₄⁻ IV, X = PF₆⁻; Va, L₄ = (R,R)-II, X = PF₆⁻, Vb L₄ = (R,R)-II, X= ClO₄⁻, VI L₄ = (S,S)-II, X = PF₆⁻, in good yield. For the Cu^I complexes, the L₄ ligand acted as a tetradentate ligand. However, a variable-temperature ³¹P[¹H] NMR study of IIIb shows that at ambient temperature one of the imino groups of the tetradentate ligand undergoes rapid dissociation to form a tridentate ligand. The interaction of AgBF₄ with 1 equiv. of otpically pure L₄ [L₄ = (R,R)-I, (S,S)-I, (R,R)-II and (S,S)-II gave the corresponding optically pure [AgL₄][BF₄] complexes, VII–X VII L₄ = (R,R)-I; VIII, L₄ = (S,S)-I; IX,L₄ = (R,R)-II; X, L₄ = (S,S)-II], in good yield. For the Ag^I complexes, the L₄ ligand acted as a tetradentate ligand with the two amino groups coordinated unsymmetrically to the silver. A variable temperature ³¹P [¹H] NMR study of VII suggests that at high temperature the complex exists as a tri-coordinated complex. The structurers of IV and IX were established by X-ray diffraction studies.     

New complexes of iron(III), cobalt(II), nickel(II) and copper(II) with 2-phenyl-1,2,3-triazole-4-carboxalidene-2-aminophenol

Summary Fe^III, Co^II, Ni^II and Cu^II complexes of a new Schiff base, 2-phenyl-1,2,3-triazole-4-carboxalidene-2-aminophenol (PTCAP), have been synthesized and characterized by elemental analyses, molar conductance and magnetic susceptibility measurements, and by u.v.-vis., i.r. and e.p.r. spectral observations. The studies indicate an octahedral structure for the complexes with the general formula [ML₂] (M = Co^II, Ni^II or Cu^II.; L = PTCAP) or [M′(OH)L₂] (M′ = Fe^III). The i.r. spectra suggest that the ligand acts as a tridentate (NNO) donor towards Co^II, Ni^II and Cu^II, and, in the Fe^III complex, one of the two ligand molecules acts as a bidentate (NO) donor and the other as a tridentate donor. The M?ssbauer spectrum of the Fe^III complex suggests the presence of a spin equilibrium at room temperature. Cyclic voltammograms are also recorded for the Cu^II and Fe^III complexes.     

Preparation,characterization and antifungal properties of transition metal ion complexes of quadridentate N3S ligands

Summary New metal complexes [M(NNNS)X] (M = Ni^II, Cu^II, Zn^II and Cd^II; NNNS^– = anion of the quadridentate ligands formed from S-methyl--N-(2-aminophenyl)-methylenedithiocarbazate and pyridine-2-aldehyde or 6-methylpyridine-2-aldehyde; X = Cl, NCS, NO₃ or I) and [Co(NNNS)Cl₂]·2H₂O have been prepared and characterized by elemental analysis and conductance measurements. Magnetic and spectroscopic evidence support a five-coordinate structure for [M(NNNS)X] (M = Ni^II, Cu^II, Zn^II and Cd^II; X = Cl, NCS) and a squareplanar structure for [Ni(NNNS)]X (X = NO₃ or I). The [Co(NNNS)Cl₃]·2H₂O complex is low-spin and octahedral. The Schiff bases and some of their metal complexes were tested against three pathogenic fungi, Alternaria alternata, Curvularia geniculata and Fusarium palidoroseum. The metal complexes are less fungitoxic than the free ligands.     

Reaction of (±)-1,1′-binaphthyl-2,2′-diyl hydrogen phosphate {(±)-phosH} with copper(II), cobalt(II) and iron(II) compounds; Identification by x-ray diffraction of [Co(CH3OH)4(H2O)2][(+)-phos][(−)-phos]. 2CH3OH·H2O

[Cu₂(μO₂CCH₃)₄(H₂O)₂], [CuCO₃·Cu(OH)₂], [CoSO₄·7H₂O], [Co((+)-tartrate)], and [FeSO₄·7H₂O] react with excess racemic (±)- 1,1′-binaphthyl-2,2′-diyl hydrogen phosphate {(±)-PhosH} to give mononuclear Cu^II, Co^II and Fe^II products. The cobalt product, [Co(CH₃OH)₄(H₂O)₂]((+)-Phos)((−)-Phos) ·2CH₃OH·H₂O (7), has been identified by X-ray diffraction. The high-spin, octahedral Co^II atom is ligated by four equatorial methanol molecules and two axial water molecules. A (+)- and a (−)-Phos⁻ ion are associated with each molecule of the complex but are not coordinated to the metal centre. For the other Co^II, Cu^II and Fe^II samples of similar formulation to (7) it is also thought that the Phos⁻ ions are not bonded directly to the metal. When some of the Cu^II and Co^II samples are heated under high vacuum there is evidence that the Phos⁻ ions are coordinated directly to the metals in the products.     

Cobalt(II) complexes with aminopolycarboxylate 1,3-pdta-type ligands: synthesis and characterization of trans(O6)-[Mg(H2O)6][CoII(1,3-pddadp)]·H2O

Starting from Ba₂(1,3-pddadp)·8H₂O (1,3-pddadp=1,3-propanediamine-N,N′-diacetate-N,N′-di-3-propionate ion) and CoSO₄, a new hexadentate [Co^II(1,3-pddadp)]²⁻ complex has been prepared. The trans(O₆) geometry of this complex was confirmed by comparison of its i.r. and u.v.–vis. spectra with those of [Co^II(1,3-pdta)]²⁻ (1,3-pdta is the 1,3-propanediaminetetraacetate ion) and trans(O₆)-[Co^III(1,3-pddadp)]⁻ complexes of known X-ray crystal structure. Magnetic and electrolytic conductivity properties of these complexes have also been discussed.     

Macrocyclic complexes of transition metals with divalent polyaza units

A new series of 14–16-membered hexaazamacrocyclic complexes [ML¹X₂] and [ML²X₂] (M = Co^II, Ni^II, Cu^II and Zn^II; X = Cl or NO₃) have been synthesized by template condensation of phenylenediamine, primary diamines and formaldehyde solution 35% in MeOH and have been characterized by i.r., 1H-n.m.r., e.p.r., and u.v. spectroscopy as well as by magnetic susceptibility and conductivity measurements. An octahedral geometry has been suggested for all the complexes.     

Metallo-guanines and metallo-guanosines

Metallo-guanines of the type [M(G)₂·2H₂O] [M = Ni^II, Fe^II, Cu^II and UO₂ ^II; G = anionic guanine], [M(G)₂(GH)· H₂O] (M = Co^II and Mn^II; GH = neutral guanine), [Pd(G)₂]·2H₂O and [Zn(G)Cl]₂ have been isolated and characterised. Anionic guanine functions as a bidentate ligand and links through N(3) and N(9). E.p.r. data indicate that the Cu^II complex has a highly distorted octahedral structure. The magnetic susceptibility data suggest that the Co^II and Ni^II complexes possess pseudooctahedral geometry. Neutral guanines are probably unidentate and coordinate either through N(3) or N(9). The isolated guanosine complexes are of the types: [M(Gs)₂·H₂O] [M = Ni^II and Cu^II, Gs = anionic guanosine] [Pd(Gs)₂]·2H₂O and [UO₂(Gs)₂]. I.r. data indicate that guanosine also functions as a bidentate ligand, but coordinates through N(1) and C₂ — NH₂. The electronic absorption spectra of the complexes indicate that guanine is a stronger ligand than guanosine.     

Synthesis and characterization of half-sandwich iridium(III) and rhodium(III) complexes bearing organochalcogen ligands

Reactions of [Cp*M(μ-Cl)Cl]₂ (M = Ir, Rh; Cp* = η⁵-pentamethylcyclopentadienyl) with bi- or tri-dentate organochalcogen ligands Mbit (L1), Mbpit (L2), Mbbit (L3) and [Tm^Me]⁻ (L4) (Mbit = 1,1′-methylenebis(3-methyl-imidazole-2-thione); Mbpit = 1,1′-methylene bis (3-iso-propyl-imidazole-2-thione), Mbbit = 1,1′-methylene bis (3-tert-butyl-imidazole-2-thione)) and [Tm^Me]⁻ (Tm^Me = tris (2-mercapto-1-methylimidazolyl) borate) result in the formation of the 18-electron half-sandwich complexes [Cp*M(Mbit)Cl]Cl (M = Ir, 1a; M = Rh, 1b), [Cp*M(Mbpit)Cl]Cl (M = Ir, 2a; M = Rh, 2b), [Cp*M(Mbbit)Cl]Cl (M = Ir, 3a; M = Rh, 3b) and [Cp*M(Tm^Me)]Cl (M = Ir, 4a; M = Rh, 4b), respectively. All complexes have been characterized by elemental analysis, NMR and IR spectra. The molecular structures of 1a, 2b and 4a have been determined by X-ray crystallography.     

Cobalt(II), nickel(II) and copper(II) complexes withN-cyano-N′-methyl-N″(2-[(5-methyl-1H-imidazol-4-yl)methylthio]ethyl)guanidine

Summary N-Cyano-N-methyl-N(2-[(5-methyl-1H-imidazol-4-yl)-methylthio] ethyl) guanidine cimetidine (CM), complexes with Co^II, Ni^II and Cu^II are described. The compounds are of stoichiometry [M(CM)₂]SO₄ · nH₂O [M = Co^II, Ni^II or Cu^II; n = 3,3 or 4, respectively], [M(CM)₂](ClO₄)₂ [M = Co^II or Ni^II], [M(CM)₂]Cl₂ · nH₂O [M=Co^II, Ni^II or Cu^II; n = 1, 2, or 2, respectively] and [Cu(CM)SO₄] · 2H₂O. The electronic spectra of the compounds in solid state, magnetic susceptibilities and i.r. and e.p.r. spectra were studied. Octahedral environments are proposed for the complexes: [M(CM)₂]SO₄·nH₂O, [M(CM)₂](ClO₄)₂, [Ni(CM)₂]Cl₂ · 2H₂O, [Cu(CM)₂]Cl₂ · 2H₂O and [Cu(CM)SO₄] · 2H₂O and a tetrahedral structure for [Co(CM)₂]Cl₂ · H₂O.     

Magnetic properties of biacetyldihydrazone complexes

Summary Magnetic susceptibilities of the biacetyldihydrazone (BdH) complexes [M(BdH)₃](NO₃)₂ (M = Co^II, Ni^II, Cu^II or Zn^II), [Fe(BdH)₃](NO₃)₃, [M(BdH)₃](Ni(dto)₂] (M = Co^II, Ni^II or Zn^II; dto = dithiooxalate), [(BdH)₂Cu(dto)Ni(dto)] and [Fe(BdH)₃]₂[Ni(dto)₂]₃ have been studied in the 4.2–295 K range. Zn^II complexes are diamagnetic, and complexes of Ni^II, Cu^II and Fe^III obey the Curie-Weiss law. The Co^II complexes behave anomalously and the results are interpreted in terms of a high spinlow spin equilibrium.     

Three new copper(II)–nickel(II) heterodinuclear complexes with the <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N′</Emphasis>-bis(2-pyridyl-ethyl)oxamide dianion. Syntheses,spectra, and magnetic properties

Three new Cu(II)–Ni(II) heterodinuclear complexes: [Cu(PMoxd)Ni(phen)₂](ClO₄)₂ (1), [Cu(PMoxd)Ni(NO₂-phen)₂](ClO₄)₂ (2), [Cu(PEoxd)Ni(Me₂-bpy)₂](ClO₄)₂ (3), [where Cu(PMoxd)=N,N′-bis(pyridyl-methyl)oxamidatocopper(II), Cu(PExod)=N,N′-bis(2-pyridyl-ethyl)oxamidatocopper(II), phen=1,10-phenanthroline and NO₂-phen=5-nitro-1,10-phenanthroline and bpy=2,2′-bipyridine] were prepared and characterized by i.r. and electronic spectra, and by magnetic properties. The magnetic analysis was carried out by means of the theoretical expression of the magnetic susceptibility deduced from the spin Hamiltonian H=−2JS₁S₂, leading to J=−70.83 cm⁻¹ (1); −56.23 cm⁻¹ (2); −57.30 cm⁻¹ (3), indicating a weak antiferromagnetic spin–exchange interaction between Cu(II) and Ni(II) ions within three complexes.     

Studies on the stereochemistry of diphenyl diketone monothio-semicarbazone and its transition metal complexes

Summary The stereochemistry and complexation behaviour of diphenyl diketone monothiosemicarbazone (DKTS) with Cu^II, Co^II, Ni^II, Cd^II, Zn^II, Pd^II, Pt^II, Ru^III, Rh^III and Ir^III have been investigated by means of chemical, magnetic and spectral (i.r., Raman, ¹H- and ¹³C-n.m.r. and electronic) studies. The ligand forms complexes of the M(DKTS)₂ type with Ni^II, Cu^II and Co^II having a distorted octahedral geometry. The absence of a v(M—X) band in the i.r. spectra, coupled with their 1:1 electrolytic conductances, suggests that Ru^III, Rh^III and Ir^III form octahedral complexes of the [M(DKTS)₂]Cl type. A four-coordinate structure involving bridging halides is proposed for the Zn^II, Cd^II, Pd^II and Pt^II complexes, which have relatively low v(M—X) vibration modes.     

1, 1-Dithiolato-bridged heterobimetallic complexes containing a transition metal ion and oxouranium(VI)

Summary Anionic complexes [UO₂(1, 1-dithiolate)₂]^2– interact strongly with transition metal ions to yield a new class of dithiolato-bridged heterobimetallic complexes MUO₂(1, 1-dithiolate)₂ (M=Co^II, Ni^II, Cu^II, Zn^II or Pb^II, 1, 1-dithiolate = isomaleonitrile dithiolate (i-MNT^2–) and trithiocarbonate (CS ₃ ^2– )). (Et₄N)₂[UO₂(i-MNT)₂] and (Et₄N)₂[UO₂(CS₃)₂] have also been prepared. The complexes have been characterized by elemental analysis, i.r., u.v.-vis. and e.s.r. spectral studies. The heterobimetallic complexes are non-electrolytic, whereas (Et₄N)₂-[UO₂ (i-MNT)₂] and (Et₄N)₂[UO₂(CS₃)₂] are 21 electrolytes. The i.r. data indicate symmetrical bidentate bridging behaviour for the dithiolate ligands. Magnetic moments, electronic spectra and e.s.r. studies are commensurate with a square planar environment around Co^II, Ni^II and Cu^II.     

2-Aminoacetophenone-2-thenoylhydrazone complexes of bivalent 3d metal ions

Summary 2-Aminoacetophenone-2-thenoylhydrazone, Haath, C₄H₃SC(O)NHN=C(Me)C₆H₄NH₂-o, forms complexes with metal(II) salts of empirical compositions [VO(Haath)₂SO₄], [M(Haath)₂Cl₂] [M=Co^II, Ni^II, Cu^II or Zn^II] and [M(aath)₂] [M=V^IVO, Co^II, Ni^II, Cu^II or Zn^II] which have been characterized by elemental analyses, molar conductance, magnetic susceptibility, electronic, e.s.r., i.r. and n.m.r. (¹H and¹³C) spectral studies. X-ray and electron diffraction patterns have been obtained in order to elucidate the structure of the Cu^II complexes. Photoacoustic spectra of powder Ni^II complexes have been recorded and interpreted in the light of u.v./vis. spectra.     

N-Phthaloylglycinate ternary complexes with cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) metal ions and aromatic mono,bi and tridentate amines

Complexes of N-phthaloylglycinate (N-phthgly) and Co^II, Ni^II, Cu^II, Zn^II and Cd^II containing imidazole (imi), N-methylimidazole (mimi), 2,2-bipyridyl (bipy) and 1,10-phenanthroline (phen), and tridentate amines such as 2,2,2-terpyridine (terpy) and 2,4,6-(2-pyridyl)s-triazine (tptz), were prepared and characterized by conventional methods, i.r. spectra and by thermogravimetric analysis. For imi and mimi ternary complexes, the general formula [M(imi/mimi)₂(N-phthgly)₂]·nH₂O, where M = Co^II, Ni^II, Cu^II and Zn^II applies. For Cd^II ternary complexes with imi, [Cd(imi)₃(N-phthgly)₂]·2H₂O applies. For the bi and tridentate ligands, ternary complexes of the formula [M(L)(N-phthgly)₂]·nH₂O were obtained, where M = Co^II, Ni^II, Cu^II and Zn^II; L = bipy, phen, tptz and terpy. In all complexes, N-phthgly acts as a monodentate ligand, coordinating metal ions through the carboxylate oxygen, except for the ternary complexes of Co^II, Ni^II and Cu^II with mimi and Cu^II and Zn^II with imi, where the N-phthgly acts as a bidentate ligand, coordinating the metal ions through both carboxylate oxygen atoms.     

Nitrates and bis(dithiooxalato)nickelates(II) of biacetyldihydrazone complexes

Summary Biacetyldihydrazone (BdH) complexes [M(BdH)₃](NO₃)₂ (M=Co^II, Ni^II, Cu^II or Zn^II); [Fe(BdH)₃](NO₃)₃; [M(BdH)₃][Ni(dto)₂] (M=Co^II, Ni^II or Zn^II; dto=dithiooxalate); [Cu(BdH)₂][Ni(dto)₂] and [Fe(BdH)₃]₂[Ni(dto)₂]₃ have been prepared and characterized by chemical analysis, conductance measurements, electronic and i.r. spectral studies and cyclic voltammetry.A mononuclear octahedral configuration is proposed for all cationic complexes, excepting [Cu(BdH)₂][Ni(dto)₂, which is probably a dithiooxalate bridged dimer.     

Synthesis, EPR spectrum and X-ray structure of tetra-n-butylammonium bis(benzene-1,2-dithiolato(2−)-κS,S′)platinate(III)

The new salt, tetra-n-butylammonium bis(benzene-1,2-dithiolato(2−)-κ²S,S′)platinate(III), [NBu₄][Pt(C₆H₄S₂)₂] (1), has been synthesized in ethanol/water, and fully characterized by single crystal X-ray structure determination. The central platinum in the complex ion [Pt(bdt)₂]⁻ is tetracoordinated by the S atoms of the bdt²⁻ ligands (bdt²⁻ is benzene-1,2-dithiolate) in a square-planar geometry. The well-resolved frozen solution EPR spectrum exhibits rhombic symmetry. The room temperature effective magnetic moment (μ_eff = 1.80 Bohr magneton) is in line with this spectrum and strongly supports the Pt(III) oxidation state in 1. This observation is in excellent agreement with previous results reported on closely related Ni(III), Pd(III) and Pt(III) species.     

Structural studies of 4-benzamido-1-o-aminoacetophenone-3-thiosemicarbazone complexes

Summary Complexes of Cu^II, Ni^II, Co^II, Zn^II, Cd^II and Hg^II with 4-benzamido-1-o-aminoacetophenone-3-thiosemicarbazone (H₂BATS) are reported and have been characterized by elemental analyses, molar conductivities, magnetic moments, spectral (visible, i.r.) and thermal (d.t.a., t.g., d.t.g.) measurements. I.r. spectra show that H₂BATS behaves as a dianionic, monoanionic or neutral tetradentate ligand or as a monoanionic tridentate ligand. [Cu₂(H₂BATS)Cl₂]·2H₂O and [Cu₂(H₂BATS)Ac₂]·2H₂O complexes are diamagnetic while [Co(HBATS)OH]·2H₂O and [Ni(HBATS)OH]·2H₂O are octahedral. All the complexes are non-electrolytes. Generally, the solid metal acetate complexes have a unique decomposition exotherm profile which can be used as a rapid and sensitive tool for the detection of acetate-containing complexes.     

Preparation and electrical conductivity of organoheterobimetallic-maleonitriledithiolates

The new complexes [PhHg]₂[M(mnt)₂] [M = Ni^II, Cu^II, Zn^II or Pd^II; mnt^2– = 1,2-dicyano-1,2-ethylenedithiolate (maleonitriledithiolate)] have been characterized spectroscopically and magnetically and their solid phase conductivity measured. All compounds exhibit solid phase _rt in the 1.29 × 10^–12–5.68 × 10^–10 S cm^–1 range and semiconduct in the 313–383 K range.