Dx2-y2 Ground State Research Articles

EPR Investigation of the Activation of N2O on Mo/SiO2Catalysts via Electron Transfer: From N2O as a Ligand to Adsorbed O-Ion

EPR spectroscopy has been used to monitor changes occurring at the molecular level upon adsorption of N2O on grafted Mo/SiO2 catalysts using naturally abundant and 95Mo-enriched molybdenum. The tetracoordinated Mo4c5+ surface species produced upon reduction with dx2-y2 SOMO coordinates N2O at 298 K and rearranges into a pentacoordinated complex of apparent C4v symmetry with dxy ground state indicating attachment of the N2O ligand in equatorial position. Upon temperature-induced metal to ligand electron transfer (MLET) between 3π* and dxy redox orbitals, O- radicals are produced with an activation energy of 20 ± 4 kJ/mol measured in the 323−393 K range. The mechanism of this process and the hindrance to electron transfer are discussed in terms of intrinsic barriers and within the framework of potential energy surfaces. From the spin Hamiltonian parameters of O-, the unpaired electron density on molybdenum and the splitting of energy levels of O- species were calculated to be 4.3% and ΔEx,y-z = 1.5 eV, resp...

Electrochemical and structural studies of nickel(II) complexes with N 2O 2 Schiff base ligands 2. Crystal and molecular structure of N,N′-l,2-ethane-1,2-diyl-bis(2- hydroxyacetophenonylideneiminate)nickel(II), N, N′-1,2- cis cyclohexane-1,2-diyl-bis(2-hydroxyacetophenonylideneiminate)- nickel(II) and N,N′-1,2-benzene-1,2-diyl-bis(3,5-dichlorosalicylideneiminate)nickel(II)

Reductive and oxidative chemistry of three complexes of formula [Ni(L)], where L represents a N 2O 2 Schiff base pseudomacrocyclic ligand based on salicylaldehyde derivatives and three different diamines, was studied in (CH 3) 2SO: N,N′-1,2-ethane-1,2-diyl-bis(2-hydroxyacetophenonylideneiminate)nickel(II) ( 1); N,N′-1,2-cis-cyclohexane-1,2-diyl-bis(2-hydroxyacetophenonylideneiminate)nickel(II) ( 2); N,N′-1,2-benzene-1,2-diyl-(bis(3,5-dichlorosalicylideneiminate)nickel(II) ( 3). Electrochemical behavior of the complexes was determined by cyclic voltametry, and EPR spectroscopy was used to characterize the one-electron reduced/oxidized species. Reduction of the complexes 1 and 2 yielded Ni(I) complexes with a dxy ground state ( g z > g x , g y ), but the reduction of 3 is ligand-centered as suggested from the pseudo-isotropic radicalar EPR signal of frozen electrolyzed solutions. Oxidation of all three complexes is metal-centered and the oxidized products are low spin hexacoordinate Ni(III) species with two solvent molecules coordinated axially, with a d z 2 ground state ( g x , g y > g z ). The crystal structures of the three Ni(II) complexes were determined from single crystal X-ray diffraction data collected with the use of Mo Kα radiation. 1: space group C2/ c with a = 25.963(3), b = 7.2973(4), c = 17.357(2) Å, β = 107.085(5)°, Z = 8 (R = 0.061); 2: space group P2 1/ a with a = 9.645(6), b = 19.149(16), c = 10.743(5) Å, β = 94.66(2)°, Z = 4 ( R = 0.085); 3: space group P2 1/ n with a = 13.372(5), b = 8.785(2), c = 16.534(5) Å, β = 101.60(3)°, Z = 4 ( R = 0.054). Crystal packing of 1 and 3 involves the pairing of two centrosymmetrical related molecules in dimers, but that of 2 shows no systematic parallel orientation of any part of the molecules. X-ray structural data have provided a rationale for the E 1 2 values obtained for the reduction and oxidation processes.

Copper(II)-disulphide interaction in copper complexes containing salicylaldimine and pyridylaldimine ligands: synthesis, spectra and redox behaviour

Copper(II) complexes of Schiff base ligands formed by the condensation of cystamine (cys) or 2,2′-diaminodiphenyl-disulphide (ddds) with salicylaldehyde (sal) or pyridine-2-carboxaldehyde (pal), and also their C=N reduced analogues, have been isolated and characterised. The e.p.r. spectra of the complexes reveal a dx2-y2 ground state and exhibit low A∥ and g∥ values. The spectral results suggest equatorial coordination of disulphide in a square-based geometry. The π-delocalisation, unsaturation and flexibility in the ligands affect the ligand field, charge transfer and e.p.r. spectral parameters as well as the redox behaviour.

EPR of dynamic Jahn-Teller distortion in CuII doped magnesium Tutton's salt

The dynamic Jahn-Teller distortion in single crystals of CuII doped magnesium Tutton's salt, MgK2(SO4)2·6H2O was studied by EPR spectroscopy. The directions of the g tensor axes were found to coincide with those of A at room temperature as well as at 113 K and were correlated with the MgO directions in the lattice. Two spatially distinct sites of copper were detected in the crystal. The g and A values were also calculated from the polycrystalline samples at various temperatures. A dx2-y2 ground state has been assigned for CuII, as in the isomorphous zinc Tutton's salt. The Silver and Getz model was applied to understand the dynamics of Jahn-Teller (JT) activity. The system was found to undergo dynamic JT distortion at all temperatures. At low temperatures, the [Cu(H2O)6]2+ ion has three possible degenerate vibronic states corresponding to three possible directions for the long axis of the octahedron. The energy separations between the three inequivalent JT valleys were estimated as δ1,2 = 90 and δ1,3 = 370 cm−1. The lattice strain parameter V2 and the JT stabilization energy EJT were also estimated as 19,140 and 1030 cm−1 respectively. From the EJT value, the JT distortion present in the system was classified as a case of “strong” coupling.

ESR investigation of some copper(II)-dioxime-dichloride compounds

The following copper(II)-dioxime-dichloride compounds: [Cu(G)Cl2]2, [Cu(P)Cl2]2, [Cu(DMG)Cl2]2 and [Cu(O)Cl2]2 (where G=C2H4O2N2, P=C3H6O2N2, DMG=C4H8O2N2, O=C8H14O2N2) were investigated by ESR method. Spectra of powder samples obtained in the g≃2 region suggest the presence of triplet ground state (S=1) realized by a weak ferromagnetic exchange coupling. In liquid and frozen solutions the monomeric species (S=1/2) prevail. Some delicate changes in the coordination polyhedra symmetry in terms of ligand molecules and solvents nature were evidence. A 4p-admixture degree of 2% in the dxy ground state was estimated for pseudotetrahedral (Td) species in frozen solutions.

Synthesis, Spectral Studies and Reactivity of Nickel(II), Copper(II) and Zinc(II) Mixed Ligand Complexes with 2-Formyl-, 2-Acetyl- and 2-Benzoyl- Cyclohexanones and Acetylacetone

Abstract Mixed ligand metal(II) complexes of the type [ML{XC(COCH3)2} (H2O)n] [M = Cu(II), Ni(II) and Zn(II); L = 2-formyl-, 2-acetyl- or 2-benzoyl- cyclohexanone; X = H, Cl, Br, CONHPh; n = 0,1,2] have been prepared and characterized by elemental analyses, magnetic measurements, infrared, 1H NMR, EPR and electronic spectral studies. The halogenation of the parent complexes with N-bromosuccinimide and N-chlorosuccinimide caused substitution at the τ -positionintheacetylacetonering. Reactionsofthe complexes with phenylisocyanate produced monoamides. The UV and IR spectra of the products and the 1H NMR spectra of the complexes are all consistent with τ-substitution. The copper(II) complexes are anhydrous and square-planar whereas thedihydratednickel(II)complexesareoctahedral. Zinc (II) complexes are monohydrated. In the mixed ligand complexes ν(C=O). is sensitive to the metal coordinated to it in contrast to that observed in bisacetylacetonates. EPRspectralstudiesofcopper(II)complexesindicatethat they are square-planar with dx2-y2 ground state. MO coefficientsderived from EPR parametersshowthat the mixed ligand complexes are more covalent then the corresponding bis-chesates.

Electron paramagnetic resonance studies of the oxygenated and non-oxygenated LaBa2Cu3O7- delta compounds

The EPR spectra of polycrystalline oxygenated and non-oxygenated (large oxygen deficiency) LaBa2Cu3O7- delta compounds, obtained at various temperatures, were studied and analysed. The oxygenated samples showed a transition temperature Tc at about 50 K. The EPR spectrum of the Cu2+ ions in the orthorhombic local symmetry was observed. It was found that these spectra are essentially influenced by an oxygen deficiency and thermal treatment. In the non-oxygenated samples, at a certain stage of the annealing process an EPR spectrum was detected at low temperatures. After the final anneal, this EPR spectrum showed significant changes. Changes were also observed in the corresponding XRD spectra indicating reductions in the concentrations of the CuO and BaCuO2 impurity phases. Additionally, the EPR spectrum of divalent copper ions in the axial local symmetry in the dx2-y2 ground state was observed.

Copper(II) complexes with anti-inflammatory drugs as ligands. Solution behaviour and electrochemistry of mono- and bi-nuclear complexes

The copper complexes of 1-methyl-5-(p-toluoyl)-1H-pyrrole-2-acetic acid (tolmetin, HL1), α-methyl-4-(2-methylpropyl)benzeneacetic acid (ibuprofen, HL2) and 6-methoxy-α-methylnaphthalene-2-acetic acid (naproxen, HL3) common anti-inflammatory drugs, were prepared and characterized. The available evidence supports a dimeric structure for the dimethyl sulfoxide adducts, [Cu2L4(dmso)2], and monomeric for the pyridine (py) analogues, [CuL(py)2(H2O)]. The solution behaviour of the dimers in dimethylformamide (dmf) shows that the complexes are converted into monomeric compounds by addition of more than 25% of pyridine. The cyclic voltammograms of the dimers of dmf suggest that the complexes retain the dimeric structure in solution. The EPR spectra of the monomers as CH2Cl2–dmf (4 : 1) glasses confirm the monomeric structure, having a dx2–y2 ground state. Paramagnetic 1H NMR studies have shown that the H2O molecule of the monomeric form remains co-ordinated to CuII in CD3Cl, (CD3)2CO or CD3CN. The crystal structure of [CuL32(py)2(H2O)] has been determined: space group P21, a= 16.112(3), b= 5.8692(9), c= 18.130(3)A, β= 75.818(7)°. In this complex the copper atom is five-co-ordinate. The atoms N(1) and N(2) of the two pyridine molecules and one carboxylate oxygen atom from each of the two ligands form the basal plane of a square pyramid with a water molecule at its apex.

Synthesis and characterisation of sulfur-rich manganese(III) and vanadium(IV) complexes containing dithioacid ligands

The chemistry of the bidentate (S,S′)– donor ligand 2-aminocyclopent-1-ene-1-carbodithioic acid (Hacda) and its N-alkylated derivatives [R = Et (Heacda), Prn(Hpacda), or Bun(Hbacda)] with vanadium(IV) and manganese(III) has been studied. The vanadium(IV) complexes [V(aacda)4]1a–1d are all eight-co-ordinated non-oxo species containing a VS8 chromophore. Their ESR spectra in frozen solution (140 K) exhibit axial anisotropy with a 16-line 51V hyperfine pattern. The observed order in spin-Hamiltonian parameters (g‖≈ 1.932, g⊥≈ 1.985, A‖≈ 175 × 10–4 cm–1 and A⊥≈ 74 × 10–4 cm–1) indicates a dx2–y2 ground state with a dodecahedral (D2d) structure. Electrochemical studies of 1a–1d show a quasi-reversible one-electron VIV–VIII reduction at ≈–0.7 V vs. saturated calomel electrode (SCE). The manganese(III) complexes [Mn(aacda)3]2a–2c are all high-spin species (µeff 5.01–5.10) and exhibit two ligand-to-metal charge-transfer bands at ≈ 610 and 530 nm. Their cyclic voltammograms reveal the presence of two quasi-Nernstian couples: E½(ox)= 0.1 V and E½(red)=–0.33 V vs. SCE due to MnIV–MnIII and MnIII–MnII electron transfers respectively.

EPR of VO2+ in Zn(antipyrine)2(NO3)2: On the orientation of vanadyl doped in a low symmetry crystal field

Single crystal EPR of VO2+ doped in Zn(antipyrine)2(NO3)2 is reported. The orientation of substitutionally incorporated vanadyl in relation to the geometry of the ligand field in the host lattice is examined. The preferential orientation of vanadyl is analyzed in terms of factors that are known to effect the energy of the complex such as steric hindrance and molecular in plane bonding. Our results indicate that, for VO2+ in Zn(antipyrine)2(NO3)2, while the V–O bond is not oriented along any metal–ligand bond, it is close to the principal z direction of g for Cu2+ (with a formal dx2–y2 ground state) in the same host lattice. Based on this it is concluded that molecular in-plane bonding is probably the determining factor for the orientation of vanadyl in the present case.

Synthesis and Structural Studies of Some First Row Transition Metal Complexes of N-Benzoylglycine Hydrazide

Abstract N-Benzoylglycine hydrazide(BzGH) has been found to react with bivalent 3d-metal ions forming complexes of the types M(BzGH)2Cl2, M'(BzGH-H)2·nH2O and M' (BzGH-2H)·3H2O [M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II); M' = Co(II), Ni(II) and Cu(II); n = 1 or 2]. Molar conductance studies in 0.001 M DMSO solutions have indicated the non-ionic nature of the complexes. High-spin octahedral geometry for Mn(II), Co(II) and Ni(II) complexes has been suggested on the basis of magnetic and/or electronic spectral studies. IR spectra suggest neutral bidentate, uninegative bidentate and dinegative tridentate behaviour of the ligand in the complexes. ESR spectra of Cu(II) complexes indicate a dx2-y2 ground state of the metal atom with a very weak metal-metal interaction in Cu(BzGH-H)2·H2O and Cu(BzGH-2H)·3 H2O.

Synthetic, Structural and Antifungal Studies of Some 3d-Metal Complexes of Salicylaldehyde-2-furanthiocarboxyhydrazone

Abstract Salicylaldehyde-2-furanthiocarboxyhydrazone (H2L) forms the adducts Ni(H2L)2Cl2 and Cu(H2L)Cl2 and deprotonated complexes having a 1:1, 1:2 and/or 1:3 metal-to-ligand ratio. Magnetic and electronic spectral studies suggest octahedral geometry for VOL. 2H2O, Cr(HL)3, Ni(H2L)2Cl2, Co(HL)3, Co(HL) (L) and Cu(HL)2 and square planar geometry for all other Ni(II) and Cu(II) complexes. ESR spectral studies indicate a dxy ground state for VOL. 2H2O and dX2−y2 for Cu(II) complexes. Further the ESR data also suggest one and two nitrogen(s) are coordinated to the metal ion. 1H NMR studies of Zn(HL)2 suggest the deprotonation of the phenolic proton and the presence of a coordinated ethanol molecule in ZnL. EtOH. Infrared spectral studies show that H2L behaves as a neutral bidentate in the adducts, as a uninegative bidentate in 1:2 and 1:3 deprotonated complexes and as a binegative tridentate in 1:1 deprotonated complexes. The ligand and its 1:2 deprotonated complexes of Mn(II), Co(III) and Cu(II) have been t...

ChemInform Abstract: CRYSTAL STRUCTURE AND ELECTRONIC PROPERTIES OF BIS(2,2′‐BIPYRIDYL)THIOCYANATOCOPPER(II) TETRAFLUOROBORATE

The crystal structure of the title compound, [Cu(bipy)2(NCS)][BF4](1)(bipy = 2,2′-bipyridyl), has been determined by X-ray analysis. It crystallises in the monoclinic space group C2/c with a= 12.791 (3), b= 24.641 (4), c= 15.456(3)A, β= 107.4(1)°, and Z= 8. The five-co-ordinate CuN2N′2N″ chromophore has a distorted bipyramidal stereochemistry related to a regular trigonal-bipyramidal stereochemistry by a distortion towards square pyramidal. The single-crystal e.s.r. spectra involve rhombic g values, R= 1.21 [(g2–g1)/(g3–g2) where g1 < g2 < g3], and cannot be used to distinguish between a dz2 or dx2–y2 ground state, but the direction of the highest g value establishes that it correlates with the elongated Cu–N direction of the square-pyramidal distortion of the CuN2N′2N″ chromophore. This, together with the twin-peaked electronic reflectance spectra (11 170 and 14 120 cm–1), suggests that the structure of (1) is best described as square-pyramidal distorted trigonal bipyramidal.

Transition Metal Chemistry of Oxims Containing Ligands, Part XVII Copper (II) Complexes of Quinoline-2-Aldoxime and Isoquinoline-3-Aldoxime

Abstract Some copper(II) complexes of the types [Cu(HL)(L)(X)] (where HL = quinoline-2-aldoxime, Hqox, or isoquinoline-3-aldoxime, Hiqox, L = qox− or iqox− and X = C1−, Br−, I−, NO− 3, SCN− or SeCN−), [Cu(HL)2(SO4)]:3H2O (where HL = Hqox or Hiqox) and [Cu(HL)(X)2] (where HL = Hqox or Hiqox and X = Cl−, Br−, NO− 3, NCS−, NCSe− or SO− 4) were synthesized and characterized by analysis, X-ray powder diffraction patterns, e.s.r. reflectance and IR spectral studies. [Cu(HL)(L)(X)] contain cis-square-coplanar [Cu(HL)(L)]+ units, linked by weakly coordinated anions giving infinite polymeric highly distorted octahedral chain structures, whereas [Cu(HL)2(SO4)] complexes have a cis-distorted octahedral structure with two ligand molecules and a bidentate sulphate group. The remaining complexes appear to have less tatragonally polymeric distorted octahedral structures. The polyerystalline e.s.r. spectra indicate the presence of a dx2-y2 ground state in a distorted octahedral ligand field stereochemistry for all the present copper(II) complexes. By using e s r and reflectance spectral data the orbital reduction parameters k¶ and k⊥ are calculated and interpreted in terms of molecular orbital coefficients.

Electron spin resonance of Cr5+ in YPO4 and YVO4

The ESR of CrO3−4 has been studied at 4.2 K in single crystal YPO4 and YVO4. The g values and 53Cr hyperfine constants are g∥ = 1.9772, g⊥ = 1.9525, A∥ = 8.5×10−4 cm−1, A⊥ = 19.6×10−4 cm−1 for YPO4 and g∥ = 1.9773, g⊥ = 1.9511, A∥ = 8.6×10−4 cm−1, A⊥ = 18.7×10−4 cm−1 for YVO4. The resonances show an isotropic superhyperfine splitting due to the two nearest neighbor yttrium ions. The PO4 and VO4 tetrahedra are distorted to D2d symmetry by a c axis stretch and a crystal field model predicts a dx2–y2 ground state for the d1 electron on CrO4 in these hosts. But a dz2 state is observed. We attribute the inversion to strong covalency. The g and A values cannot be explained with D2d symmetry and the width of the superhyperfine lines is orientation and magnetic field dependent. We believe these anomalies are due to motional effects.

Crystal structure and electronic properties of bis(2,2′-bipyridyl)-thiocyanatocopper(II) tetrafluoroborate

The crystal structure of the title compound, [Cu(bipy)2(NCS)][BF4](1)(bipy = 2,2′-bipyridyl), has been determined by X-ray analysis. It crystallises in the monoclinic space group C2/c with a= 12.791 (3), b= 24.641 (4), c= 15.456(3)A, β= 107.4(1)°, and Z= 8. The five-co-ordinate CuN2N′2N″ chromophore has a distorted bipyramidal stereochemistry related to a regular trigonal-bipyramidal stereochemistry by a distortion towards square pyramidal. The single-crystal e.s.r. spectra involve rhombic g values, R= 1.21 [(g2–g1)/(g3–g2) where g1 < g2 < g3], and cannot be used to distinguish between a dz2 or dx2–y2 ground state, but the direction of the highest g value establishes that it correlates with the elongated Cu–N direction of the square-pyramidal distortion of the CuN2N′2N″ chromophore. This, together with the twin-peaked electronic reflectance spectra (11 170 and 14 120 cm–1), suggests that the structure of (1) is best described as square-pyramidal distorted trigonal bipyramidal.

The electronic structure of MnO42− as determined by ESR in K2SO4

The electron spin resonance of MnO42− has been studied at 4.2 K in single crystal K2SO4. The principal values of the g and A tensors are gx=1.9757, gy=1.9696, gz=1.9445, Ax=−21.0×10−4 cm−1, Ay=−25.5×10−4 cm−1, and Az=−147.6×10−4 cm−1. Az and gz make an angle of 7.8° and the only element of symmetry in the MnO42− tetrahedron is a xz mirror plane. The ground state is dxy similar to that of MnO2−4 in K2CrO4 but different from the dxy ground state of MnO2−4 in BaSO4 and BaSeO4. It is suggested that a dz22 ground state will be stabilized whenever the host XO4 tetrahedron is distorted so that the angle O(1)–X–O(2) is greatly different from the angle O(3)–X–O(3′) where O(1) and O(2) lie in the mirror plane.

Fine structure due to magnetic dipole coupling in the low temperature EPR spectrum of Rb2Cu(SO4)2⋅6H2O

A study of the EPR spectrum of single crystals of Rb2Cu(SO4)2⋅6H2O over the temperature range 290 to 115 K is reported. Below ∼240 K unusual fine structure occurs for certain orientations of the magnetic field H, consisting of eight equally spaced lines when H is approximately along the z molecular axis and five equally spaced lines when H lies along the y molecular axis of the Cu(H2O)62+ ion. The fine structure may be explained largely in terms of a magnetic dipole coupling with four neighboring copper (II) ions, each of which produces an approximately equal splitting of the EPR lines at the central copper (II) ion; the five line pattern occurs when the hyperfine interaction with the copper nucleus is small, while the eight line pattern results from a hyperfine interaction which is essentially equal to the magnetic dipole interactions (these each being ∼120 G). Spectra were simulated by considering the point magnetic-dipole interactions with the ten nearest Cu(H2O)62+ ions using the expression K̂=g1g2β2 (1–3 cos2ϑ)/r3, where g1 and g2 are the g values of the two interacting ions, r is the distance between them, ϑ is the angle between the internuclear vector and the magnetic field, and β is the Bohr magneton. The resulting line shapes are in reasonable agreement with experiment for most orientations of the magnetic field in the (001) and (010) crystal planes. The agreement is significantly improved if the interaction with the two nearest copper (II) ions is ∼20% greater than that calculated using the simple magnetic dipole model, and it is shown that this is consistent with the unpaired electron density being represented as a quadrupole, as is required by the shape of the dx2y2 ground state orbital, rather than as a point charge. Further improvement occurs if a weak exchange coupling of J=+30 and J=−15 G takes place with the nearest and next-nearest copper ions, respectively, and if an anisotropic component to the background half-width is introduced.

Dissimilarity between hypertensives: VA study vs. general population: Michael H. Alderman, Cornell University Medical College, New York, New York, U.S.A.; Kathryn F. Miller

Reactions of 2-thiosemicarbazido-1,4-naphthoquinone (NQTSC) with iron (II), iron (III), cobalt (II) and copper (II) chloride yield different complexes depending on the synthetic conditions. Under acidic medium, thionato coordination is favored with the formation of cationic complexes (A-1 to A-4) while neutral (B-1, B-3 and B-4) and cationic (B-2) complexes are isolated with thiolato binding under basic conditions. IR spectral data indicates that NQTSC acts as both a neutral and a mono-anionic tridentate ligand, bonding through thione, thiol or both as observed in the case of iron (III) and cobalt (III) complexes. The magnetic and Mössbauer measurements of iron (II) complexes reveal the presence of an unusual (S = 1) spin state possessing small zero-field splitting (ZFS). Reaction of NQTSC with iron (III) chloride results in the stabilization of the spin-triplet state (S = 3/2) with negligible contribution from ZFS components while cobalt complexes exhibit different magnetic properties displaying diamagnetic (A-3) cobalt (III) and low-spin cobalt (II) states (B-3). Evaluation of ESR covalency parameters for A-4 and B-4 indicates considerable delocalization of the unpaired electron present in the dx2-y2 ground state of the tetragonally distorted octahedral geometry over the entire chelate rings formed by the NQTSC ligands. Electrochemical behavior of the complexes exhibit mostly metal-centered redox changes with the iron (III) complexes having a reversible Fe(III)/Fe(II) couple at relatively positive potentials while the copper (II) compounds display quasi-reversible Cu(II)/Cu(I) as well as Cu(III)/Cu(II) redox processes. Thiolato binding probably exerts a pronounced effect on the oxidation processes while thionato coordination seems to influence reduction steps in these complexes.

Spectroscopic investigation of the structure of a novel zerovalent cobalt nitrosyl in zeolite matrices

Cobalt (II) hexahydrate introduced in synthetic zeolites by conventional ion-exchange was shown to give up readily five of its water molecules upon evacuation at room temperature. Subsequently the cobalt ion was coordinated by three lattice oxide ions from the zeolite lattice and by a single water molecule so as to acquire a slightly distorted tetrahedral symmetry. This tetrahedral CoII species readily reacted at room temperature with nitric oxide to yield a zerovalent paramagnetic cobalt dinitrosyl within the zeolite framework. The complex was identified on the basis of its i.r., u.v. and e.p.r. spectra as a C2h distorted octahedral complex with a dx2–y2 ground state with a coordination sphere made up of three lattice oxide ions [possibly O(4) ions], a water molecule and two NO ligands which transferred their odd electrons to the cobalt d orbitals.