Stabilization of the tervalent nickel complex with meso-5, 7, 7, 12, 14, 14-hexamethyl-1, 4, 8, 11-tetraazacyclotetradecane by axial coordination of anions in aqueous … (original) (raw)
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Inorganic Chemistry, 1982
The electrochemical oxidation of NiL2+ (where L = meso-5,7,7,12,14,14-hexamethyl-1,4,8,1l-tetraazacyclotetradecane) in aqueous solutions in the presence of sulfate, phosphate, chloride, and phthalate yields Ni111LX2. The stability constants for the axial coordination of the anions X are estimated from the observed redox potentials and from kinetic measurements. The complexes [Ni111L(S04)H20]C104 and [Ni111L(H2P04)2]C104 were precipitated. The crystal structure of the latter complex was determined. The complex crystallizes in the triclinic space group Pi with a = 11.074 (3) A, b = 9.386 (2) A, c = 14.299 (2) A, a = 88.55 (1)O, @ = 106.33 (2)O, y = 1 1 1.46 (2)O, and two molecules in the unit cell; least-squares refinement based on 4282 reflections led to a conventional R of 0.046. The nickel is located in the plane determined by the four ligating nitrogen atoms, and the configuration of the remainder of the macrocyclic ligand is essentially identical with that reported for the divalent nickel complex with this ligand. The kinetics of decomposition of the complexes were studied and found to be complicated. The results indicate that the complexes Ni111L(S04)2-and Ni11'L(H2P04-)2+ decompose via Nim1L3+ and perhaps also partially via Ni111LS04+ and Ni"'LH2P0:+.
Inorganic Chemistry, 1996
Two nickel(II) complexes of formula (H 3 dien) 2 [Ni 2 (ox) 5 ]‚12H 2 O (1) and [Ni 2 (dien) 2 (H 2 O) 2 (ox)]Cl 2 (2) (dien ) diethylenetriamine and ox ) oxalate dianion) have been synthesized and characterized by single-crystal X-ray diffraction. 1 crystallizes in the orthorhombic system, space group Abnn, with a ) 15.386(4) Å, b ) 15.710(4) Å, c ) 17.071(4) Å, and Z ) 4. 2 crystallizes in the monoclinic system, space group P2 1 /c, with a ) 10.579(1) Å, b ) 7.258(1) Å, c ) 13.326(1) Å, ) 93.52(3)°, and Z ) 2. The structures of 1 and 2 consist of dinuclear oxalato-bridged nickel(II) units which contain bidentate oxalate (1) and tridentate dien in the fac-conformation (2) as terminal ligands. Both features, oxalato as a peripheral ligand and dien in the fac-conformation (instead of its usual mer-conformation), are unprecedented in the coordination chemistry of nickel(II). The nickel atom is six-coordinated in both compounds, the chromophores being NiO 6 (1) and NiN 3 O 3 (2). The Ni-O(ox) bond distances at the bridge (2.072(4) Å in 1 and 2.11(1) and 2.125(9) Å in 2) are somewhat longer than those concerning the terminal oxalate (2.037 and 2.035(3) Å in 1). Magnetic susceptibility data of 1 and 2 in the temperature range 4.2-300 K show the occurrence of intramolecular antiferromagnetic coupling with J ) -22.8 (1) and -28.8 (2) cm -1 (J being the parameter of the exchange Hamiltonian H ) -JS A ‚S B ). The observed value of -J in the investigated oxalato-bridged nickel(II) complexes, which can vary from 22 to 39 cm -1 , is strongly dependent on the nature of the donor atoms from the peripheral ligands. This influence has been analyzed and rationalized through extended Hückel calculations. Bossek, U.; Nuber, B.; Weiss, J.; Bonvoisin, J.; Corbella, M.; Vitols, S. E.; Girerd, J. J. J. Am. Chem. Soc. 1988, 110, 7398. (c) Deguenon, D.; Bernardelli, G.; Tuchagues, J. P.; Castan, P. Inorg. Chem. 1990, 29, 3031. (d) De Munno, Ruiz, R.; Lloret, F.; Faus, J.; Sessoli, R.; Julve, M. Inorg. Chem. 1995, 34, 408. (9) Kahn, M. I.; Chang, Y. D.; Chen, Q.; Salta, J.; Lee, Y. S.; O'Connor, C. J.; Zubieta, J. Inorg. Chem. 1994, 33, 6340. (10) (a) Verdaguer, M.; Julve, M.; Michalowicz, A.; Kahn, O. Inorg. Chem. 1983, 22, 2624. (b) Julve, M.; Verdaguer, M.; Charlot, M. F.; Claude, R. Inorg. Chim. Acta 1984, 82, 5. (c) Pei, Y.; Journaux, Y.; Kahn, O. Inorg. Chem. 1989, 28, 100. (d) Tamaki, H.; Zhong, Z. J.; Matsumoto, N.; Kida, S.; Koikawa, M.; Achiwa,.N.; Hashimoto, Y.; Okawa, H. J. Am. Chem. Soc. 1992, 114, 6974. (e) Ohba, M.; Tamaki, H.; Matsumoto, N.; Okawa, H. Inorg. Chem. 1993, 32, 5385. (f) Decurtins, S.; Schmalle, H. W.; Oswald, H. R.; Linden, A.; Ensling, J.; Gütlich, P.; Hauser, A. Inorg. Chim. Acta 1994, 216, 65. (g) Cortés, R.; Urtiaga, M. K.; Lezama, L.; Arriortua, M. I.; Rojo, T.
A nickel(III) complex with a NiO6 coordination sphere
Inorganic Chemistry, 1986
Constant-potential electrolysis of a solution of tris(2,2'-bipyridine 1,l'-dioxide)nickel(II) perchlorate dihydrate, [Ni(b~yO,)~]-(C104)2.2H20, in acetonitrile on a platinum electrode at 1.7 V (vs. SCE) affords a violet solution of Ni(bpy0,):' having the low-spin (d', S = I/,) Ni"'06 coordination sphere. In frozen (77 K) acetonitrile solution Ni(bpy02)33t displays rhombic EPR spectra (fitted to g components: g,, = 2.220, gyy = 2.155, and g,, = 2.060) suggestive of sizable Jahn-Teller distortion and a (d: )' ground state. The cation, which shows allowed optical transitions at 370 and 495 nm with a shoulder at 580 nm in acetonitrile solution, is relatively unstable and decomposes, producing a yellow species in which nickel(I1) and bpyOz are present in a 1:2 ratio. The formal potential (Eoz9*) of the couple Ni(bpy02)?-Ni(bpy02)32' measured cyclic voltammetrically in acetonitrile at platinum with use of solutions of either ion is 1.47 V vs. SCE. The values of the corresponding couples for other 3d elements are as follows (V vs. SCE): Cr, -0.84; Mn, 0.79; Fe, 0.13; Co, 0.87. It is shown that these values vary linearly with the values of the corresponding M(H20)2+-M(Hz0)62t couples. From this linear correlation it is estimated that the formal potential of the experimentally inaccessible aquo couple Ni(H20)2'-Ni(H20)62' is 2.26 f 0.12 V vs. SCE. (9) Oxime complexes: (a) Lappin, A. G.; Laranjeira, M. C. M.; Youde-Owei, L. J. Chem. SOC., Dalton Trans. 1981, 721. (b) Lappin, A. G.; Laranjeira, M. C. M.
Journal of the Korean Chemical Society
The geometry structures of hexa-coordinated [NiLX]X complexes (X = Cl−, Br−, I−) {L = 8,9,18,19-tetrahydro- 7H,17H-dibenzo[f,o] [1,5,9,13]dioxadiaza cyclohexadecine-8,18-diol} are optimized by density functional theory (DFT) using B3LYP/LANL2DZ. The calculated geometric parameters are in good agreement with the corresponding experimental values. Calculation results about these complexes show that dipole moment decreases, and the energy levels of HOMOs descend from iodo-complex to chloro-complex. The energy levels of HOMOs descend gently from iodo-complex to chloro-complex, while the energy levels of LUMOs in the present complexes are almost similar; therefore the energy gapes between HOMOs and LUMOs increased from iodo-complex to chloro-complex.
Nickel(II) complexes bonded to 12-membered macrocyclic ligands
Inorganica Chimica Acta, 1995
Information has been obtained on how ring size, steric factors and the mode of coordination of tetraaza macrocycles will affect the field strength of the macrocycle and how these parameters affect the equilibrium in water or in a water-ethanol mixture between the five-coordinate nickel(II) complexes containing the macrocycle, R4[12]aneN4, where R is CH3 and CH2C6Hs, and the planar [Ni(R4[12]aneN,)] 2+ species. On the basis of spectral data it is concluded that steric factors influence the ligand field strength more than the size of the macrocycle for macrocycles that do not bond in a planar manner to the nickel(II). However, for square planar complexes both the size of the macrocyclic ligand and the steric factors play significant roles in the ligand field strength. The equilibrium between the high spin, five-coordinate, [Ni(R4[12]aneNa)H20] 2+ complexes and the planar or nearly planar [Ni(l~[12]aneN4)] 2+ is dominated by the solvation properties of these complexes. The more carbon atoms on the R group, the larger the K, AS and AH values for the above equilibrium. In the presence of excess chloride ions, [Ni(Me4[12]aneN4)H20] 2÷ is converted to [Ni(Me4[12]aneN4)Cl] +. By increasing the percentage of ethanol in an ethanol-water mixture of [Ni(Me4[12]aneNa)Cl2, the equilibrium shifts to produce more [Ni(Me4[12]aneN,)Cl] + and less [Ni(Me4[12]aneN,)H20] 2+. The tetrabenzyl[12]aneN4 nickel(II) complex is more difficult to oxidize and easier to reduce than the tetramethyl[12]aneN4 nickel(II) complexes and the chloride complexes are easier to oxidize than the nitrate complexes in CH3CN. In water and in ethanol-water mixtures the [Ni(Me4[12]aneN4)H20]2+/[Ni(Me4[12]aneN4)H20] + couple is quasireversible but in CH3CN only the cathodic reaction is observed.
Inorganica Chimica Acta, 2012
Complexes of nickel(II) chloride with homologous tetradentate aminopyridine ligands 1,8-bis(2-pyridyl)-3,6-dimethyl-3,6-diazaoctane (pdao) and 1,6-bis(2-pyridyl)-2,5-dimethyl-2,5-diazahexane (bpmen) were prepared in the crystalline state and characterized by elemental analysis and X-ray diffraction as [Ni(pdao)(H 2 O) 2 ]Cl 2 ÁH 2 O (1) and [Ni(bpmen)Cl 2 ]ÁH 2 O (2). In the solid state, both complexes are bluegreen and contain octahedral Ni(II) with a cis-a-coordinated tetramine. In aqueous solution, both complexes are strong electrolytes as follows from the measurements of electrical conductivity: complex 2 is hydrated and forms purple [Ni(bpmen)(H 2 O) 2 ] 2+ (aq). Complex 1 displays thermochromic behavior in solution (it is blue-green at low temperatures and yellow at high temperatures) due to a temperature sensitive equilibrium [Ni(pdao)(H 2 O) 2 ] 2+ (aq) ¢ [Ni(pdao)] 2+ (aq) + 2H 2 O(l), DH°= +30(1) kJ/mol and DS°= +80(3) J/mol K in 0.1 M NaClO 4 (aq). Complex 1, but not 2, can be reversibly reduced to the Ni(I) species (E 1/2 = À0.9 V versus SHE in aqueous solution and À1.37 V versus Fc + /Fc in acetonitrile). The relative stabilization of nickel(I) by ligand pdao can be attributed to an optimal size of the ligand bite and to the presence of the pyridine and tertiary amine N-donors.
Transition Metal Chemistry
The reaction of Rh&O& with two equivalents of Me,NO in the presence of a substituting ligand (L = NCMe, Py, P(OPh),) affords a mixture of isomers of the general formula Rh,(CO),,L,. The substituting ligands occupy two terminal sites in the structure of the parent cluster. For L = P(OPh), three isomers (I-III) were separated from the reaction mixture. The structure of the first isomer (I) has been established by X-ray analysis. This compound crystallizes in two polymorphic modifications, monoclinic and triclinic; both of which consist of identical molecules and differ only in the packing of the molecules in the crystals. It should be noted that both polymorphic forms contain in the unit cells the racemic mixture (RR and SS) of the Rh&CO),,(P(OPh),), molecules. This octahedral cluster may be considered as a derivative of the parent Rh&CO),, cluster with two terminal CO groups in tram positions at Rh(l) and Rh(2) atoms substituted by phosphite ligands. The structures of two other disubstituted clusters, (II) and (III) were established by "P NMR spectroscopy. Phosphite ligands in these compounds occupy the terminal sites at the adjacent rhodium atoms of the Rh, octahedron but differ in their mutual orientation. Other disubstituted derivatives (L = NCMe, Py) are labile compounds and exist in solution as inseparable mixtures of the isomers characterized by 'H and 13C NMR spectroscopy. A mechanism of interconversion of the isomers is proposed.