N-acetyl-DL-leucinate cobalt(II), nickel(II) and zinc(II) complexes

Summary Complexes of the type M(AcLeu)₂ · B₂ (M = Co^II, Ni^II or Zn^II; B = H₂O, py, 3-pic, 4-pic; AcLeu =N-acetyl-DL-leucinate ion) and M(AcLeu)₂ B (M = Co^II or Zn^II and B = o-phen) were prepared and investigated by means of magnetic and spectroscopic measurements. The i.r. spectra of all the complexes are consistent with bidentate coordination of the amino acid to the metal ion. The room temperature solid state electronic spectra indicate that the symmetry of this species is closer toD _4h and that MO₆ and MO₄N₂ chromophores are present in the M(AcLeu)₂ · 2 H₂O and M(AcLeu)₂B_n · x H₂O (B = py, 3-pic, 4-pic, n=2 and x=0 for M = Ni^II; B = o-phen, n=1 and x=0 for M = Co^II; B = py, 3-pic, 4-pic, n=1 and x=1 for M = Co^II) complexes, respectively. By comparing the Dq values of the amino acid and those of other N-substituted amino acids previously studied, a spectrochemical series of the the cobalt(II) and nickel(II) complexes is proposed. The¹ H n.m.r. spectra of the zinc(II) complexes confirm the proposed stereochemistry.     

Isomorphous replacement of M(II) ions in M(II)-Gd(III) dimers (M(II) = Cu(II), Mn(II), Ni(II), Co(II), Zn(II)): magnetic studies of the products

Complexes [M(II)Gd(III){pyCO(OEt)pyC(OH)(OEt)py}?](ClO?)?·EtOH [M(II) = Cu(II) (1), Mn(II) (2), Ni(II) (3), Co(II) (4) and Zn(II) (5)] crystallize in the monoclinic Cc space group and contain one hexacoordinate M(II) ion and one enneacoordinate Gd(III) ion, bridged by three {pyCO(OEt)pyC(OH)(OEt)py}? ligands. Magnetic susceptibility measurements indicate a ferromagnetic interaction for 1 and antiferromagnetic interactions for 2-4. Using the ? = -J?(Gd(III))?(M(II)) spin Hamiltonian formalism, fits to the magnetic susceptibility data yielded J values of +0.32 cm?1 for 1, -1.7 cm?1 for 2, and -0.22 cm?1 for 3. In complex 4, the orbital contributions of Co(II) precluded the determination of the magnetic coupling. The complex follows the Curie-Weiss law with θ = -2.07 K (-1.44 cm?1).     

Mono{hydrotris(mercaptoimidazolyl)borato} complexes of manganese(II), iron(II), cobalt(II), and nickel(II) halides

A series of [Tm(Me)M(mu-Cl)]2 and Tm(R)MCl (Tm(R) = tris(mercaptoimidazolyl)borate; R = Me, tBu, Ph, 2,6-iPr2C6H3 (Ar); M = Mn, Fe, Co, Ni) complexes have been prepared by treatment of NaTm(Me) or LiTm(R) with an excess amount of metal(II) chlorides, MCl2. Treatment of Tm(R)MCl (R = tBu, Ph, Ar) with NaI led to a halide exchange to afford Tm(R)MI. The molecular structures of [Tm(Me)M(mu-Cl)]2 (M = Mn, Ni), [Tm(Me)Ni(mu-Br)]2, Tm(tBu)MCl (M = Fe, Co), Tm(Ph)MCl (M = Mn, Fe, Co, Ni), Tm(Ar)MCl (M = Mn, Fe, Co, Ni), Tm(Ph)MI (M = Mn, Co), and Tm(Ar)MI (M = Fe, Co, Ni) have been determined by X-ray crystallography. The Tm(R) ligands occupy the tripodal coordination site of the metal ions, giving a square pyramidal or trigonal bipyramidal coordination geometry for Tm(Me)M(mu-Cl)]2 and a tetrahedral geometry for the Tm(R)MCl complexes, where the S-M-S bite angles are larger than the reported N-M-N angles of the corresponding hydrotris(pyrazolyl)borate (Tp(R)) complexes. Treatment of Tm(Ph)2Fe with excess FeCl2 affords Tm(Ph)FeCl, indicating that Tm(R)2M as well as Tm(R)MCl is formed at the initial stage of the reaction between MCl2 and the Tm(R) anion.     

The infrared spectra (3500—150 cm-1) of aniline complexes of cobalt(II), nickel(II), copper(II) and zinc(II) halides

The IR spectra (3500—150 cm^?1) of the complexes [M(aniline)₂,X₂ (M = Co, Ni, Cu, Zn; X = Cl, Br), [Zn(aniline)₂I₂] are discussed. Assignments of the internal ligand vibrations are based on the band shifts which result from ¹⁵N-labelling of the amino group. The metal—ligand stretching frequencies, ν(M—N) and ν(M—X), are assigned on the basis of the band shifts which occur on ¹⁵N-labelling and metal ion and halogen substitution. Two bands within the range 350–450 cm^?1 are assigned to ν(M—N) while the ν(M—X) bands occur within the range 170–320 cm^?1. The effects of structure and coordination number on ν(M—N) and ν(M—X) are discussed. The spectra of two ethanol adducts, [M(aniline)₂-(ethanol)₂Cl₂] (M = Co, Ni) compared with those of the unsolvated species [M(aniline)₂-Cl₂], exhibit a unique band near 480 cm^?1 which is insensitive to ¹⁵N-labelling and is assigned to ν(M—O).     

New biimidazole and bibenzimidazole derivatives: mono and binuclear palladium(II) or platinum(II) complexes and heterobinuclear palladium(II)-rhodium(I) or platinum(II)-rhodium(I) complexes

Novel neutral biimidazolate or bibenzimidazolate palladium(II) and platinum(II) complexes of the type M(NN)₂(dpe) [M = Pd, Pt; (NN)₂^2? = BiIm^2?, BiBzIm^2?. dpe = 1,2-bis(diphenylphosphino) ethane] have been obtained by reacting MCl₂(dpe) with TI₂(NN)₂. Complexes M(NN)₂(dpe) which are Lewis bases react with HClO₄ or [M(dpe)(Me₂CO)₂](ClO₄)₂ to yield, respectively, mononuclear cationic complexes of general formula [M{H₂(NN)₂](dpe) (M = Pd, Pt; H₂(NN)₂ = H₂BiIm, H₂BiBzIm) and homobinuclear palladium(II) or platinum(II) cationic complexes of the type [M₂{μ - (NN)₂}(dpe)₂](ClO₄)₂. Reactions of M(BiBzIm)(dpe) with [Rh(COD) (Me₂CO)_X](ClO₄) render similar heterobinuclear palladium(II)-rhodium(I) and platinum(II)-rhodium(I) cationic complexes, of general formula [(dpe)M(μ-BiBzIm)Rh(COD)](ClO₄) (M = Pd, Pt; COD = 1,5-cyclooctadiene). Di- and mono-carbonyl derivatives [(dpe)M(μ-BiBzIm)Rh(CO)L](ClO₄) (M = Pd, Pt; L = CO, PPh₃) have also been prepared. The structures of the resulting complexes have been elucidated by conductance studies and IR spectroscopy.     

Electrochemistry of platinum(II) coordination compounds II. Electroreduction of trimetallic dimetalliobis(isocyanide)platinum(II) complexes

Linear trimetallic MPPt^IIL₂M complexes (M = Cr(CO)₃(η-C₅H₅), Mo(CO)₃- (η-C₅H₅), W(CO)3(η-C₅-H₅), Mn(CO)₅, Fe(CO)₃NO, Co(CO)₄; L = t-BuNC, cyclo- C₀H₁₁ NC) are reduced on platinum and gold electrodes in non-aqueous medium. All these complexes undergo irreversible one electron reductions, which result in the rupture of one Ptmetal bond and the liberation of one M^? ion per mole reduced. Coupled ESR spectroscopy and coulometry show that a radical is generated during the reduction of the trimetallic complexes. The several ESR signals obtained for these paramagnetic Pt¹ species exhibit no hyperfine structure.The electrochemical behaviour of MPtL₂M complexes is compared with that of the following linear trimetallic complexes: MHgM and (MAuM)^?.     

Formation of copper(II), zinc(II), silver(I) and lead(II) ferrocyanides

The factors influencing the formation of metal hexacyano-ferrate(II) complexes have been examined and the experimental conditions leading to formation of M(2)Fe(CN)(6), and K(2)M(3)[Fe(CN)(6)](2) have been studied, where M is Cu(II) or Zn(II); Ag(I) yields Ag(4)Fe(CN)(6). and KAg(3)Fe(CN)(6) and Pb(II) yields only Pb(2)Fe(CN)(6). Measurements made at constant ionic strength obtained by addition of K(2)SO(4) show how the potassium ion affects the stabilization of the complexes. The free energy changes and K(sp) values for the complexes have been calculated.     

Chelate complexes of some NNO tridentate Schiff bases with iron(II), cobalt(II), nickel(II) and copper(II)

Summary The Schiff bases a-(C₅H₄N)CMe=NNHCOR (R = Ph, 2-thienyl or Me), prepared by condensation of 2-acetylpyridine with the acylhydrazines RCONHNH₂, coordinate in the deprotonated iminol form to yield the octahedral complexes, M[NNO]₂ M = Co or Ni; [NNOH] = Schiff base and the square-planar complexes, Pd[NNO]Cl. The Schiff bases also coordinate in the neutral keto form yielding the octahedral complexes (M[NNOH]2)Z2 (M = Ni, Co or Fe; Z = C104, BF₄ or N03) and complexes of the type M[NNOH]X2 (M = Ni, Co, Fe or Cu; X = Cl, Br or NCS). Spectral and x-ray diffraction data indicate that the complexes M[NNOH]X2 (M = Ni or Fe) are polymeric octahedral, as are the corresponding cobalt complexes having R = 2-thienyl. However, the cobalt complexes Co[NNOH]X2 (X = CI or Br; R = Ph or Me) and the copper complexes Cu[NNOH]CI₂ (R = Ph, 2-thienyl or Me) are five-coordinate, while the thiocyanato complex Co[NNOH](NCS)₂ (R = 2-thienyl) is tetrahedral.     

Metallatriazadiphosphorines of zinc(II), cadmium(II) and mercury(II)

Metallatriazadiphosphorine complexes corresponding to [{N(PPh₂NR)₂}M(OAc)] and [{N(PPh₂NR)₂}₂M], (R = Ph or SiMe₃; M = Zn, Cd or Hg) have been synthesized under strictly anhydrous and inert conditions by the reaction of the acyclic bis-silylated phosphazene ligand, [HN(PPh₂NSiMe₃)₂], or the bis-phenylated phosphazene ligand, [HN(PPh₂NPh)₂], with Zn, Cd and Hg acetate in 1:1 and 2:1 molar ratios. These complexes are highly soluble in common organic solvents, but unstable hydrolytically as well as thermally, even under reduced pressure. Molecular weight determinations in benzene indicated the monomeric nature of these complexes. Further, they have been characterized on the basis of elemental analysis and spectral studies: i.r. and n.m.r. (¹H, ¹³C and ³¹P) that plausibly reveal a trigonal planar and tetrahedral geometry around the metal atom in the complexes.     

A spectroscopic and magnetic study of complexes of bis(2-benzothiazolyl)methanate and bis(2-benzoxazolyl)methanate with Co(II), Ni(II), Cu(II) and Zn(II)

The co-ordination geometry of the complexes M(bbtm)2 and M(bbom)2 (M: Co, Ni, Cu, Zn; bbtm, bis(2-benzothiazolyl)methanate; bbom, bis(2-benzoxazolyl)methanate) are discussed on the basis of their IR, Raman, resonance Raman, electronic and ESR spectra. Compounds of Ni, Co, Zn with both ligands and Cu(bbom)2 resulted to have a distorted tetrahedral geometry. The distortion towards a square planar geometry is more marked for the M(bbtm)2 series than for the M(bbom)2 one. It has been impossible to suggest a co-ordination geometry for Cu(bbtm)2, that probably has a polymeric structure.     

Carbamoyl and alkoxycarbonyl complexes of palladium(II) and platinum(II)

Carbamoyl and alkoxycarbonyl complexes of palladium(II) and platinum(II) of the type M(pnp)(CONHR)Cl (pnp = 2,6-bis(diphenylphosphinomethyl)pyridine; M Pd, R  C₆H₅, p-CH₃C₆H₄, p-CH₃OC₆H₄, C₆H₁₁, t-Bu; M  Pt, R  C₆H₅), Pd(pnp)[CON(Pr)₂]Cl (Pr = propyl), M(pnp)(COOR)Cl (M  Pd, R  C₆H₅, CH₃; M  Pt, R  CH₃), Pd(pnp)(COOCH₃)₂ result from reaction of M(pnp)Cl₂ with carbon monoxide and amines or alkoxides at room temperature and atmospheric pressure.The carbamoyl complexes react with bases to give urethane or diphenylurea depending upon the experimental conditions.     

Palladium(II)-, Platin(II)-, Ruthenium(II)-, Rhodium(III)- und Iridium(III)-Komplexe von Desoxyfructosazin

Metal Complexes of Biologically Important Ligands. CIII. [1] Palladium(II), Platinum(II), Ruthenium(II), Rhodium(III), and Iridium(III) Complexes of Desoxyfructosazine The reactions of the pyrazine derivative desoxyfructosazin(pz) with K₂PtCl₄ and with the chlorobridged [M(PR₃)Cl₂]₂ (M = Pd, Pt), [(η⁵-C₅Me₅)MCl₂]₂ and [(η⁶-p-Cymol)RuCl₂]₂ give the watersoluble complexes cis-Cl₂Pt(pz)₂, (R₃P)(Cl)M(pz)M(Cl)(PR₃) (M = Pd, Pt), (η⁵-C₅Me₅)(Cl)₂M(pz)M(Cl)₂(η⁵-C₅Me₅) (M = Rh, Ir), (η⁶-p-Cymol)(Cl₂)Ru(pz)Ru(Cl)₂(η⁶-p-Cymol).     

Ni(II), Pd(II) and Pt(II) complexes of PNP and PSP tridentate amino-phosphine ligands

The ligands D((CH(2))(2)NHPiPr(2))(2) (D = NH 1, S 2) react with (dme)NiCl(2) or (PhCN)(2)MCl(2) (M = Pd, Pt) to give complexes of the form [D((CH(2))(2)NHPiPr(2))(2)MX]X (X = Cl, I; M = Ni, Pd, Pt) which were converted to corresponding iodide derivatives by reaction with Me(3)SiI. Reaction of 1 or 2 with (COD)PdMeCl affords facile routes to [κ(3)P,N,P-NH((CH(2))(2)NHPiPr(2))(2)PdMe]Cl (8a) and [κ(3)P,S,P-S((CH(2))(2)NHPiPr(2))(2)PdMe]Cl (9a) in high yields. An alternative synthetic approach involves oxidative addition of MeI to a M(0) precursor yielding [κ(3)P,N,P-HN(CH(2)CH(2)NHPiPr(2))(2)NiMe]I (10), [κ(3)P,N,P-HN(CH(2)CH(2)NHPiPr(2))(2)MMe]I (M = Pd 8b Pt 11) and [κ(3)P,S,P-S(CH(2)CH(2)NHPiPr(2))(2)MMe]I (M = Pd 9b, Pt 12). Alternatively, use of NEt(3)HCl in place of MeI produces the species [κ(3)P,N,P-HN(CH(2)CH(2)NHPiPr(2))(2)MH]X (X = Cl, M = Ni 13a, Pd 14a, Pt 16a). The analogs containing 2; [κ(3)P,S,P-S((CH(2))(2)NHPiPr(2))(2)MH]X (M = Pd, X = PF(6)15: M = Pt, X = Br, 17a, PF(6)17b) were also prepared in yields ranging from 74-93%. In addition, aryl halide oxidative addition was also employed to prepare [κ(3)P,N,P-HN(CH(2)CH(2)NHPiPr(2))(2)MC(6)H(4)F]Cl (M = Ni 18, Pd 19) and [κ(3)P,S,P-S((CH(2))(2)NHPiPr(2))(2)Pd(C(6)H(4)F)]Cl (20). Crystal structures of 3a, 4a, 5a, 6a, 8a, 9a, 14b and 16b are reported.     

Electro-oxidation and electro-reduction of some iron (II), cobalt(II) and nickel(II) polypyridyl complexes in acetonitrile

Cyclic voltammetry and controlled potential coulometry studies of 2,2′-bipyridyl, 4,4′-dimethyl-2,2′-bipyridyl and 2,2′, 2″-terpyridyl complexes of Fe(II), Co(II) and Ni(II) in acetonitrile are described. E_1/2 values for M(III)/M(II) and M(II)/M)I) couples are compared and crystal field effects discussed. A series of M(I) and M(III) polypyridyl complexes have been prepared by controlled potential electrolysis; these include a number of 3+ and 1+ oxidation state complexes of nickel which have not previously been isolated — [Ni(bipy)₃]-(ClO₄)₃, [Ni(dimbipy)₃](ClO₄)₃, [Ni(terpy)₂](ClO₄)₃ and [Ni(bipy)₂]ClO₄.     

3,6-bis(2′,-pyridyl)pyridazine dinuclear complexes: Palladium(II), platinum(II) and first row transition metal(II) mixed complexes

New Pd(II) and Pt(II) 3,6-bis(2′-pyridyl)pyridazine (dppn) mononuclear complexes of the type M(dppn)Cl₂ were prepared and characterized. From M(dppn)Cl₂, the bimetallic homonuclear complexes M(dppn)MCl₄ were prepared by reaction with Pd(PhCN)₂Cl₂ or K₂PtCl₄. Bimetallic heteronuclear species of the type M(dppn)M′Cl₄, were prepared reacting the mononuclear complexes with the stoichiometric amount of M′Cl₂ (M′ = Cu, Co, Ni). All the described reaction give product in high yield. The isolated compounds, almost completely insoluble in most organic solvents, were characterized by elemental analysis, IR, ESR, reflectance spectra, and magnetic moment measurements. On the basis of these data the geometries around the metals are discussed.     

Electrochemical, spectroscopic, and photophysical properties of structurally diverse polyazine-bridged Ru(II),Pt(II) and Os(II),Ru(II),Pt(II) supramolecular motifs

Five new tetrametallic supramolecules of the motif [{(TL)(2)M(dpp)}(2)Ru(BL)PtCl(2)](6+) and three new trimetallic light absorbers [{(TL)(2)M(dpp)}(2)Ru(BL)](6+) (TL = bpy = 2,2'-bipyridine or phen = 1,10-phenanthroline; M = Ru(II) or Os(II); BL = dpp = 2,3-bis(2-pyridyl)pyrazine, dpq = 2,3-bis(2-pyridyl)quinoxaline, or bpm = 2,2'-bipyrimidine) were synthesized and their redox, spectroscopic, and photophysical properties investigated. The tetrametallic complexes couple a Pt(II)-based reactive metal center to Ru and/or Os light absorbers through two different polyazine BL to provide structural diversity and interesting resultant properties. The redox potential of the M(II/III) couple is modulated by M variation, with the terminal Ru(II/III) occurring at 1.58-1.61 V and terminal Os(II/III) couples at 1.07-1.18 V versus Ag/AgCl. [{(TL)(2)M(dpp)}(2)Ru(BL)](PF(6))(6) display terminal M(dπ)-based highest occupied molecular orbitals (HOMOs) with the dpp(π*)-based lowest unoccupied molecular orbital (LUMO) energy relatively unaffected by the nature of BL. The coupling of Pt to the BL results in orbital inversion with localization of the LUMO on the remote BL in the tetrametallic complexes, providing a lowest energy charge separated (CS) state with an oxidized terminal Ru or Os and spatially separated reduced BL. The complexes [{(TL)(2)M(dpp)}(2)Ru(BL)](6+) and [{(TL)(2)M(dpp)}(2)Ru(BL)PtCl(2)](6+) efficiently absorb light throughout the UV and visible regions with intense metal-to-ligand charge transfer (MLCT) transitions in the visible at about 540 nm (M = Ru) and 560 nm (M = Os) (ε ≈ 33,000-42,000 M(-1) cm(-1)) and direct excitation to the spin-forbidden (3)MLCT excited state in the Os complexes about 720 nm. All the trimetallic and tetrametallic Ru-based supramolecular systems emit from the terminal Ru(dπ)→dpp(π*) (3)MLCT state, λ(max)(em) ≈ 750 nm. The tetrametallic systems display complex excited state dynamics with quenching of the (3)MLCT emission at room temperature to populate the lowest-lying (3)CS state population of the emissive (3)MLCT state.     

Synthesis and structural studies of 2-acetylthiophene-2-thenoylhydrazone complexes of oxovanadium(IV), manganese(II), cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II) and mercury(II)

Complexes with chemical compositions VO(Hatth)₂SO₄, VO(Hatth)₂SO₄·py, [M(Hatth)₂Cl·H₂O]Cl [M = Mn(II), Co(II) and Ni(II)], [Cu(Hatth)₂Cl]₂Cl₂, [Cu(Hatth)₂· Cl·py]Cl, [Cd(Hatth)₂Cl]Cl, M(Hatth)₂Cl₂ [M = Zn(II) and Hg(II)], VO(atth)₂, VO(atth)₂py, M(atth)₂(py)₂ [M = Mn(II) and Cu(II)], M(atth)₂(H₂O)₂ [M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)], Hatth = 2-acetylthiophene-2-thenoylhydrazone, and atth, its deprotonated form, have been prepared and characterized by analytical data, molar conductance, magnetic susceptibility, electronic and photoacoustic, ESR, IR and NMR spectral studies. X-ray diffraction study has been used to determine the shape and the dimensions of the unit lattice of copper(II) complexes.     

Complexes of Cobalt(II), Nickel(II) and Copper(II) Chloroacetates with Quinoline N-Oxide

Some 1:1 and 1:2 adducts of cobalt(II), nickel(II) and copper(II) chloroacetates with quinoline N -oxide have been isolated by the interaction of the appropriate metal chloroacetate with quinoline N -oxide (QuinNo). The complexes isolated are of 1:1 stoichiometry of formula (M(CH_3-xCl_xCOO)₂QuinNO) (when M=Co(II), Ni(Il); X=l, 2 and 3 and when M=Cu(II), X=1 and 2) except copper(II) trichloroacetate which yields an adduct of 1:2 stoichiometry of formula[Cu(CCl₃COO)₂ (QuinNO)₃]. The adducts isolated are soluble in common organic solvents.     

Cobalt(II), nickel(II) and copper(II) with 2-substituted benzimidazole complexes

Summary Complexes of stoichiometries M(Acbim)₂X₂·nH₂O and M(Bzbim)₂X₂·nH₂O (M = Co, Ni or Cu; Acbim = 2-acetylbenzimidazole, Bzbim = 2-benzoylbenzimidazole; X = Cl, Br, NO₃ or ClO₄; n = 0, 1 or 2) have been prepared and characterised by spectroscopic and physicochemical methods. The ligands coordinate through carbonyl oxygen and tertiary nitrogen.     

Complexes of Cobalt(II), Nickel(II) and Copper(II) Chloroacetates with Quinoline N-Oxide

Some 1:1 and 1:2 adducts of cobalt(II), nickel(II) and copper(II) chloroacetates with quinoline N -oxide have been isolated by the interaction of the appropriate metal chloroacetate with quinoline N -oxide (QuinNo). The complexes isolated are of 1:1 stoichiometry of formula [M(CH₃_xClxCOO)₂QuinNO] (when M=Co(II), Ni(II); X=1,2 and 3 and when M=Cu(II), X=l and 2) except copper(II) trichloroacetate which yields an adduct of 1:2 stoichiometry of formula[Cu(CCI₃COO)₂(QuinNO)₂]. The adducts isolated are soluble in common organic solvents.