Shun'ichiro Ooi

Synthesis and solution behavior of mononuclear palladium(II) and platinum(II) complexes containing pyridine-2-thiolate as a ligand. Crystal structure of chloro(pyridine-2-thiolato)- (triphenylphosphine)palladium(II)

Abstract Various types of mononuclear pyridine-2-thiolato (pyS) complexes [M(pyS)2(PPh3)2], [MCl(pyS)(PPh3)], [M(pyS)2(PPh3)] (M=Pd(II), Pt(II)) and [PdCl(pyS)(PPh3)2]·CH2Cl2, and the complex of pyridine-2-thiol [PdCl2(pySH)(PPh3)] have been prepared. The solution behavior of these complexes has been examined by 1H and 31P{1H} NMR measurements as well as the determination of the molecular weights. The coordination modes of the pyS ligand in the complexes, including chelation, S-unidentate, and the fast exchange between them, have been elucidated. The crystal structure of [PdCl(pyS)(PPh3)] has been determined. The complex crystallizes in the triclinic space group P1, Z=2, a=12.969(6), b=10.246(5), c=9.493(3) A, α=114.53(3), β=72.57(3), γ=105.71(3)°. The structure has been determined using conventional heavy atom methods, final Rw=0.067 based on 2546 significant (I>;3σ(I)) reflections. The Pd atom is four-coordinated by the Cl, P, S and N donor atoms, constituting a square-planar, trans-(P,N) structure; the pyS ligand is chelated with a small bite angle. In the crystals, there are two independent molecules, the structures of which differ from one another in the disposition of the pyridine ring folded in opposite directions on the plane defined by the Pd, Cl, P and S atoms.

A mixed valence binuclear complex of vanadium(IV) and vanadium(V). X-Ray crystal structure of (NH4)3[V2O3(nitrotriacetate)2]·3H2O

A deep blue mixed valence complex [VO(nta)–O–VO(nta)]3–(nta = nitrilotriacetate) was found to be in equilibrium with [VIVO(nta)(H2O)]– and [VVO2(nta)]2– in aqueous solution; the crystal structure of its ammonium salt trihydrate has been determined.

Copper(II) complexes with tripodal imidazole-containing ligands. Structure-electrochemistry relationship

Mono- and dimeric copper(II) complexes of tris- (benzimidazol-2-ylmethyl)amine (L1) and of its derivatives with the imidazole NH protons substituted by a methyl (L2), ethyl (L3), benzyl (L4) or o-methylbenzyl (L5) group were prepared and characterized based on magnetic susceptibility, conductivity, cyclic voltammetric half-wave potential (E12), infrared, electronic and ESR spectra. The complexes containing H2O, NO3−, Cl−, Br−, N3−, and N-methylimidazole with L1–L5 were mononuclear copper(II) complexes, while the complexes with NCS− or NCO− and L1–L3 [except [Cu(L1)NCS](NO3)] were dinuclear ones, which dissociate to monomeric complexes in DMF solution. The E12 values of copper(II) in a series of complexes containing H2O or NO3− decrease in the order L5 > L1 > L2 > L3 > L4, whereas those in complexes with Br− and N-methylimidazole decrease in the orders L4 ≳ L5 > L1 > L2 > L3 and L5 > L1 > L4 ≳ L2 > L3, respectively. The relationship between the structure of the complexes and the E12 values are discussed in some detail.

X-Ray crystal structures and magnetic properties of azide-bridged binuclear copper(II) complexes containing the Schiff-base ligand derived from 2-pyridinecarbaldehyde and histamine. Structure–magnetism relationship

The structures of the complexes [Cu2(L1)2(N3)2][ClO4]2(1){ L1= 1-(imidazol-4-yl)-2-[(2-pyridylmethylene)amino]ethane} and [Cu2(L1)2(N3)3]Cl·2H2O (2) have been determined by X-ray methods. Complex (1) contains discrete [Cu2(L1)2(N3)2]2+ cations which are located at centres of inversion. The geometry around each copper(II) ion is square pyramidal. The two basal planes in the complex cation are parallel and separated by 2.64 A. The two azide ions which are parallel to each other bridge in an end-on fashion between a basal position of one square pyramid and an apical position of the other. Magnetic susceptibility data for (1) show a ferromagnetic interaction (Weiss constant θ=+23 K) above 200 K. On the other hand, below 200 K, it is considered that there is a weaker exchange interaction than that above 200 K. In differential scanning calorimetry curves for (1), small thermal anomalies have been observed over the temperature range 150–250 K. Complex (2) contains an azide-bridged, centrosymmetric copper(II) dimeric cation. The five-coordinate geometry around each copper(II) ion is square pyramidal. An azide ion bridges in an endto-end fashion between the two apical positions of two square pyramids. A very weak antiferromagnetic exchange interaction is found for (2)(0 J–0.5 cm–1, where J denotes the exchange integral defined by the Hamiltonian ℋ=–2JS1S2).

Mixed oxidation state trinuclear cobalt complexes with bridging sulphito and Schiff-base ligands. Part 1. Preparation of the complexes [CoII(µ-SO3)2(µ-L)2COIII2(ROH)2](L = Schiff base anion, R = alkyl) and structure determination of [CoII(µ-SO3)2(µ-α,α′-Me2-salpd)2CoIII2(PrnOH)2]·2PrnOH

Mixed-valence complexes of the type [CoII(µ-SO3)2(µ-L)2CoIII2(H2O)n(ROH)2–n](n= 0, 1, or 2; R = Me or Prn) have been prepared and characterized, where the deprotonated Schiff-base ligands L2– are either symmetrical, such as N,N′-ethylenebis(salicylideneiminate)(salen), N,N′-ethylenebis(α-methylsalicylideneiminate)(α,α′-Me2-salen), propane-1,3-diylbis(salicylideneiminate)(salpd), and propane-1,3-diylbis(α-methylsalicylideneiminate)(α,α′-Me2-salpd), or unsymmetrical such as propane-1,3-diyl(α-methylsalicylideneiminate)(salicylideneiminate)(α-Me-salpd). An X-ray structure determination of [COII(µ-SO3)2(µ-α,α′Me2-salpd)2CoIII2(PrnOH)2]·2PrnOH showed the presence of bridging phenolic oxygens and sulphite ions. The mixed-valence state CoIII(S= 0)–CoII(S=)–CoIII(S= 0) in these trinuclear complexes has been demonstrated by cryomagnetic measurements because the effective magnetic moments (4.40–5.00) at room temperature correspond to the monomeric complex of a cobalt(II) ion in a high-spin state. Down to 77 K, no spin-exchange interaction was observed between the cobalt(III) and cobalt(II) ions. I.r. spectra and thermal gravimetric-differential thermal analysis data have been obtained and discussed with regard to the co-ordination modes of the solvent molecules water, methanol, ethanol, and propan-1-ol.

Synthesis and cyclic voltammetry of trinuclear selenido and tellurido clusters of nickel(II), palladium(II) and platinum(II) with 1,2-bis(diphenylphosphino)ethane and crystal structure of the tellurido cluster of platinum(II)

Abstract Reaction of M2+ (M=Ni, Pd or Pt) with 1,2-bis(diphenylphosphino)ethane (dppe) and NaSeH or NaTeH in acetonitrile (MeCN) and/or N,N-dimethylformamide (DMF) gives rise to [Pd3Se2(dppe)3][PF6]2 (2), [Pt3Se2(dppe)3][BPh4]2 (3), [Ni3Te2(dppe)3][BPh4]2 (4), [Pd3Te2(dppe)3][BPh4]2 (5) and [Pt3Te2(dppe)3][BPh4]2 (6). The X-ray structure of 6 was determined and cyclic voltammograms of 2-6 at 293 and 255 K were recorded. The structure of [Pt3Te2(dppe)3]2+ comprises three square-planar PtTe2P2 coordination planes sharing two μ3- Te2− ligands. Interatomic distances are Te ··· Te 3.432(2), Pt ··· Pt 3.456, PtTe 2.634 and PtP 2.263 A. Cyclic voltammograms of the reduction process of complex 4 in DMF at 293 K give two chemically reversible couples, while those of 2, 3, 5 and 6 show one reversible couple at 255 K.

Monomeric and dimeric copper(II) complexes composed of some terdentate schiff bases and oxalate, oxamate, azide, thiocyanate or cyanate ions

Abstract Monomeric and dimeric copper(II) complexes containing the Schiff bases derived from 2-pyridinecarbaldehyde and histamine (2-PcaHist), 2-(2-aminoethyl)pyridine (2-Pca2-Aep), or β-alanine (2-Pcaβ-Ala), and oxalate (ox), oxamate (om), azide, thiocyanate, or cyanate ions have been prepared and characterized based on their electronic, infrared and electron spin resonance spectra, and magnetic susceptibilities. The structure of the monomeric copper(II) complex, [Cu(2-PcaHist)(N3)2] has been determined by the X-ray diffraction method. The crystal of [Cu(2-PcaHist)(N3)2] is triclinic, with a = 10.262(8), b = 9.177(6), c = 7.688(5) A, α = 104.42(4), β = 94.09(4), γ = 92.64(4)°, Z = 2, and space group P 1 . The five-coordinate geometry around copper(II) ion is intermediate between trigonal-bipyramid and square-pyramid. The half-field absorption in the ΔMs = 2 region of powdered X-band ESR spectra was scarcely observed for [Cu(2-Pca2-Aep)(N3)2], [Cu(2-Pca2-Aep)(NCS)2], [Cu(2-Pca2-Aep)(NCO)2] and [Cu(2-PcaHist(N3)2]. The compounds [Cu2(2-PcaHist)2(N3)3]Cl·2H2O and [Cu2(2-PcaHist)2(N3)2](ClO4)2 which are considered to have a dimeric structure exhibited the half-field absorption in the same region. However, an exchange interaction was hardly observed down to 4.2 °K in the magnetic susceptibility measurement for [Cu2(2-PcaHist)2(N3)3](Cl·2H2O. The susceptibility of an oxalate-bridged copper(II) complex, [Cu2(2-PcaHist)2(ox)](ClO4)2, showed an antiferromagnetic interaction (J = −21.5 cm−1) and the X-band ESR spectrum for the powdered sample showed a very weak absorption for the triplet state of such a dimer in the ΔMs = 2 region.

Crystal and molecular structure of sodium µ-(imidazol-1-yl-NN′)-bis-[(glycylglycinato-NN′O)cuprate(II)] hexahydrate: structure–magnetism relationship in imidazolate-bridged binuclear copper(II) complexes

The structure of the title complex, Na[Cu2(Gly-GlyO)2(im)]·6H2O [Gly-GlyO = glycylglycinate(2–), im = imidazolyl), has been determined from X-ray diffractometer data, to give final discrepancy indices of R= 0.0302, and R′= 0.0391. The complex crystallizes in the triclinic space group P with unit-cell dimensions a= 11.246(4), b= 10.464(3), c= 10.858(4)A, α= 109.99(3), β= 115.05(3), γ= 85.05(3)°, and Z= 2. Each copper(II) atom has square-planar co-ordination by amino-nitrogen, deprotonated amide nitrogen, carboxylate oxygen of the glycylglycinate ligand, and by nitrogen of bridging imidazolate, to form altogether a binuclear copper(II) complex. The complex is almost planar and has an approximate two-fold axis which is coincident with that of the imidazolate ring. Variable-temperature magnetic susceptibility data measured down to 4.2 K show an antiferromagnetic exchange interaction with a coupling constant J=–19 cm–1. The bridging imidazolate plane and copper(II) co-ordination planes make an angle of 5.8° for Cu(1) and 10.4° for Cu(2). The relative orientation of the bridging imidazolate and the copper(II) co-ordination planes does not seem to be responsible for the magnitude of the magnetic exchange coupling constant (J=–19 cm–1) in this case. It is concluded that a π-exchange mechanism is not important in the imidazolate-bridged binuclear copper(II) complexes.

The mono- and dinuclear copper(II) complexes containing tripodal ligand and pyridine, imidazole or pyrazole

Abstract Monomeric and dimeric copper(II) complexes containing tris(2-benzimidazylmethyl)amine (L 1 ) or its derivatives (L 2 , L 3 , L 4 and L 5 ) and pyridine (Py), imidazole (ImH) or pyrazole (Pz) have been prepared and characterized by their magnetic susceptibilities, electric conductivities, cyclic voltammetric half-wave potentials, and visible absorption and ESR spectra. The compounds made of L 2 , L 3 or L 4 and imidazole are dinuclear copper(II) complexes bridged by imidazolate, while other complexes are mononuclear ones. The susceptibility of [Cu 2 (L 2 ) 2 (Im)](ClO 4 ) 3 ·3H 2 O shows an antiferromagnetic interaction ( J = −30 cm −1 ) and the X-band ESR spectrum for the powdered sample of this complex exhibits the triplet state of such a dimer in the Δ M s = 2 region. Likewise, the signals due to the Δ M s = 2 transition were also observed for the complexes [Cu 2 (L 3 ) 2 (Im)](ClO 4 ) 3 ·2H 2 O and [Cu 2 (L 4 ) 2 (Im)](ClO 4 ) 3 ·2H 2 O. From the comparison of half-wave potentials ( E 1 2 ) in a series of monomeric copper(II) complexes, the E 1 2 values for the reduction of Cu(II) to Cu(I) decrease in the order Py > Pz > ImH in DMF and CH 3 CN solutions.

Crystal structure and X-ray photoelectron spectroscopy of bis(o-amidothiophenolato)platinate(II)

Abstract The deep blue [Pt(S(NH)C6H4)2] has been synthesized and characterized by X-ray structure analysis and X-ray photoelectron spectroscopy. The compound crystallizes in the monoclinic space group P21/c with a = 12.691(7), b = 5.916(2), c = 8.125(4) A, β = 96.10(4)° and Z = 2. The Pt atom has a trans- planar coordination by 2S and 2N atoms. The PtS and PtN bond lengths are 2.278(2) and 1.938(5) A, respectively. The o-amidothiophenolato ligand assumes o-thionequinoneimine structure as indicated from short SC(1) [1.713(7) A], NC(2) [1.344(8) A], C(3)C(4) [1.369(10) A] and C(5)C(6) [1.368(12) A] bond lengths. The Pt 4f7/2 binding energy (73.9 eV) for the complex is slightly higher than those for usual Pt(II) compounds, but lies within the highest limit for Pt(II) 4f7/2 binding energies.