Geng-Lin Wang

Synthesis, magnetism and structure of μ-oxamido heterobinuclear Cu(II)Ni(II) complexes

Abstract Three heterobinuclear complexes have been synthesized, namely [Cu(oxpn)Ni(L) 2 ](ClO 4 ) 2 · x H 2 O (L=2,2′-bipyridyl (bpy), 1,10-phenanthroline (phen), and 5-nitro-1,10-phenanthroline (NO 2 -phen)), where oxpn is N,N′ -bis(3-aminopropyl)oxamido. The crystal structure of [Cu(oxpn)Ni(phen) 2 ](ClO 4 ) 2 ·CH 3 OH·H 2 O has been determined. Crystal data: triclinic, space group P 1 , with a =9.661(3), b = 13.522(2), c =17.143(3) A, α=86.39(2), β= 82.09(2) and γ=71.73(2)° at room temperature, Z =2. The copper(II) ion is in a square environment and the nickel(II) is in an octahedral environment. The dihedral angle between the two metal equatorial planes is 5.40°. The CuNi distance is 5.338 A. The temperature dependence of the magnetic susceptibility of [Cu(oxpn)Ni(phen) 2 (ClO 2 ) 2 ·H 2 O has been studied, giving the exchange integral J =−47.22 cm −1 . This indicates an antiferromagnetic interaction among the metal ions.

A New Class of Heterobinuclear Complexes: Crystal Structure and Magnetism of Copper(II)-Nickel(II) Complexes Incorporating Two Different Macrocyclic Ligands

Three novel oxamido-bridged heterobinuclear copper(II)-nickel(II) complexes incorporating two different tetraazamacrocyclic compounds were synthesized and characterized by IR, ESR, and electronic spectra. They are of the formulas [(CuL1)Ni(rac-cth)](ClO)42⋅H2O (1), [Cu(L2)Ni(rac-cth)](ClO4)2⋅0.5 EtOH (2), and [(CuL3)Ni(rac-cth)](ClO4)2⋅H2O (3). L1, L2, and L3 are the dianions of diethyl 5,6,7,8,16,17-hexahydro-6,7-dioxo-15H-dibenzo[e,n][1,4,8,12]tetraazacyclopentadecine-13,19-dicarboxylate, diethyl 5,6,7,8,15,16-hexahydro-6,7-dioxodibenzo[1,4,8,11]tetraazacyclotetracine-13,18-dicarboxylate, and diethyl 5,6,7,8,15,16-hexahydro-15-methyl-6,7-dioxodibenzo[1,4,8,11]tetraazacyclotetradecine-13,18-dicarboxylate, respectively, and rac-cth is rac-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane. The crystal structures of 1 and 2 were determined by single-crystal X-ray analysis. The NiII ion is pseudooctahedrally coordinated. The coordination geometry around the CuII ion in 2 is slightly distorted square planar, while that in 1 shows significant distortion towards a tetrahedral structure. The temperature dependence of the magnetic susceptibility for 1 and 2 was analyzed by means of the Hamiltonian Hˆ=−2JSˆ1⋅Sˆ2, leading to J=−63.9 and −67.4 cm−1 for 1 and 2, respectively.

A dinuclear cyano-bridged complex based on hexacyanoferrate(III) and samarium(III) nitrate : Synthesis and crystal structure

A new complex, [Sm(DMF)4(H2O)4Fe(CN)6]·H2O (DMF = N, N-dimethylformamide), has been synthesized and characterized by X-ray single crystal structure and thermogravimetric analyses. The complex crystallizes in the P21/n space group, with lattice parameters a = 17.583(4) Å, b = 8.870(2) Å, c = 19.845(6) Å, β = 95.98(3)°, V = 3078(1) Å3, Dx = 1.679 Mg m−3, Dm = 1.65(1) Mg m−3, Z = 4. The molecular structure shows that a cyano-bridged bimetallic structure is obtained. The Sm atom is coordinated by eight oxygen atoms of four water molecules and four DMF molecules and one nitrogen atom of the bridging cyanide ligand. The iron atom assumes approximately an octahedral environment surrounded by six CN ligands. The hydrate water molecule is hydrogen-bonded to one of the O atoms bound to Sm. Each terminal CN ligand of the Fe(CN)63− entity is hydrogen-bonded to some O atoms of water molecules. An infrared spectrum is also reported.

Magnetic interaction in the keto and enol forms of binuclear copper (II) complexes with a Robson-type ligand. X-ray crystal structure of [Cu2 (HL) (μ-N3) (H2O) (C2H5OH) (ClO4)]

Abstract Three dicopper(II) complexes, [Cu2(H2L) (μ-N3)] (ClO4)2 · 1 2 C 2 H 5 OH ( 1 ) , [Cu2(HL) (μ-N3) (H2O) (C2H5OH) (ClO4)] (2) and [Cu2(L) (μ-N3)] · DMF (3) have been synthesized and characterized, where H3L is the pentadentate binucleating ligand 2,6-diformyl-4-methylphenol di(benzoylhydrazone). Because of the existence of a hydrazide structure in the lateral chain, the ligand H3L can lose one, two or three hydrogen atoms to form the keto form (1) or enol form (3) of the binuclear copper (II) complexes, respectively. The crystal structure of 2 has been determined. Crystal dta for 2: monoclinic, space group P21/c, a = 10.967(4), b = 7.684(2), c = 35.724(7) A , β = 90.08°, Z = 4 . The analysis of variable-temperature magnetic susceptibility data indicates that there is an antiferromagnetic interaction between the copper(II) ions in these complexes with the exchange parameters (2J) of −86.8 cm−1 for 1, −132.4 cm−1 for 2 and −176.7 cm−1 for 3. The effect of a tautomeric isomeride on the magnetic interaction was discussed in relation to molecular mechanics and CNDO/2 methods.

Alternating ferromagnetic and antiferromagnetic interactions in the azido-bridged copper(II) chain compound [Cu(phen)(N3)2]n

Single crystals of a copper(II) chain compound**, [Cu(phen)(N3)2]n (phen = 1,10-phenanthroline), were obtained and its crystal structure was determined by X-ray diffraction methods. The complex crystallizes in the space group P1¯ and is made up of neutral chains of copper(II) ions bridged by two azide groups exhibiting an asymmetrical tri-dentate μ(1,1,3) coordination mode. The copper atoms have a distorted CuN6 octahedral environment: the basal plane is built of two nitrogen atoms from a chelating phen molecule and two azide nitrogens from one bridging and one terminal azide, whereas two nitrogens from two bridging azides fill the axial positions. The intrachain copper(II)–copper(II) separation is 3.396(1) and 5.700(1) Å. The magnetic behavior was investigated in the 5–300 K range. Weak intrachain alternating antiferromagnetic (J = −6.56 cm−1) and ferromagnetic (αJ = 12.76 cm−1) interactions were observed.

Unexpected assembly of a cyanide-bridged one-dimensional nickel(II) complex with alternating [Ni(TIM)]2+ and [Ni(CN)4]2- ions (TIM=2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene)

Abstract Crystals of a cyanide-bridged nickel(II) complex [Ni(TIM)][Ni(CN)4] (1) (TIM=2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene) were formed by diffusion of [Ni(TIM)](ClO4)2 in MeCN and K3[Cr(CN)5(NO)] in H2O for two months. Complex 1 crystallized in the triclinic space group P-1 with a=7.610(2), b=8.096(2), c=9.392(2) A, α=69.56(1), β=71.44(1), γ=84.66(2)°. The crystal structure confirmed the presence of cyanide-bridged nickel(II) chains. The [Ni(CN)4]2− moieties were shown to derive from the dissociation of [Cr(CN)5(NO)]3− and [Ni(TIM)]2+ owing to the stability of the [Ni(CN)4]2− ion. The coordination geometry around the six-coordinate nickel(II) ion is axially elongated octahedral with four nitrogen atoms of the macrocycle (Ni–N=2.008(2) A) and two nitrogen atoms of the bridging cyanides (Ni–N=2.123(2) A). The four-coordinate nickel(II) groups are square-planar with the Ni–C bond distances ranging from 1.858(2) to 1.861(3) A.

Synthesis and magnetic studies of copper(II)-lanthanide(III) complexes with N,N′-bis (2-aminopropyl)oxamidocopper(II)

Abstract Seven novel μ-oxamido heterodinuclear complexes, namely Cu(oxap)Ln(L)2 (ClO4)3, where oxap denotes the N,N′-bis(2-aminopropyl)oxamido dianion, L represents 1,10-phenanthroline (phen) and Ln denotes La, Nd, Gd, Tb, Dy, Ho, Er, have been synthesized and characterized. The magnetic susceptibility measurements (4.2–300 K) of Cu(oxap)Gd(phen)2(ClO4)3 indicate a weak ferromagnetic interaction between the copper(II) and gadolinium(III) ions, with the exchange integral JCuGd = 2.25 cm−1.

Weaker magnetic interactions of oxalato-copper(II) binuclear compounds: synthesis, spectroscopy, crystal structure and magnetism

Abstract Two binuclear copper(II) compounds, Cu2(tacn)2(μ-ox)(ClO4)2 (I) and [Cu2(bdpm)2(H2O)2(μ-ox)](ClO4)2·H2O (II), where tacn=1,4,7-triazacyclononane, ox=oxalate dianion, bdpm=bis(3,5-dimethylpyrazol-1-yl)methane, have been synthesized and characterized by X-ray diffraction. Each copper atom of compound I has a 4+1+1 elongated pseudo-octahedral environment; the copper atoms have distorted square pyramidal geometry in compound II. The magnetic susceptibilities (300–4 K) indicated that the binuclear copper(II) cores were antiferromagnetically coupled (2J=−41 cm−1 for compound I, 2J=−102 cm−1 for compound II). The weakness of the interactions for both compounds is discussed on the basis of the structural features.

Transition metal complexes with nitronyl nitroxides part 2. Crystal structure and magnetism of manganese(II) compounds including radicals and their reduced derivatives

Abstract Four complexes, Mn(hfac) 2 (NITPhCl) ( 1 ), [Mn(hfac) 2 (NITPhCH 3 )] 6 ( 2 ), [Mn(hfac) 2 (IMHF)] 2 ( 3 ), and Mn(hfac) 2 (NITF) 2 ·2H 2 O ( 4 ) (Hfac = hexafluoroacetylacetonate, NITPhX = 2-(4-X-phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (X = chloro (NITPhCl), X = methyl (NITPhCH 3 ), IMHF = 1-hydroxo-2-furfural-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole, NITF = 2-furfural-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) have been prepared and studied. IR, EPR and variable-temperature magnetic susceptibility studies of 1–4 indicate a variety of structural types. Complexes 1 and 4 are probably mononuclear while 2 is hexanuclear. Complex 3 resulting, together with complex 4 , from the reaction of Mn ( hfac ) 2 · 1 2 ) H 2 O with NITF is dinuclear and includes the reduced amidino-oxide form of NITF. The structure of 3 was solved by X-ray diffraction and refined to conventional agreement indices R = 0.051 and R w = 0.052. It crystallizes in the triclinic. P 1 space group with a = 10.463(1), b = 10.316(2), c = 13.224(2) A , α = 108.45(2), β = 106.48(2), γ = 103.80(2)°, Z = 1 . Two IMHF ligands bridge the two manganese(II) ions of 3 through their amidino-oxide oxygen atoms affording a small intramolecular antiferromagnetic inteaction.

Synthesis and Magnetic Properties of μ-Terephthalato Binuclear Cobalt(II) Complexes

Abstract Three Co(II)-Co(II) binuclear complexes have been synthesized, namely [CO2(TPHA)(L)4](ClO4)2 (L = 2,2′-bipyridyl (bpy), 1,10-phenanthroline (phen) and 4,4′-dimethy1-2,2′-bipyridyl (Me2bpy)), where TPHA is the terephthalato dianion. Based on IR, elemental analyses, conductivity measurements and electronic spectra, these complexes are proposed to have extended TPHA-bridged structures and to consist of two cobalt(II) ions in a distorted octahedron evironment. The temperature dependence of the magnetic susceptibility of [Co2(TPHA)(bpy)4](ClO4)2 H2O and [Co2(TPHA)(phen)4](ClO4)2 H2O has been studied giving the exchange integral J = -0.96 cm−1 and J = -0.93 cm−1, respectively. This indicates a weak antiferromagnetic interaction between the metal ions.