Pentacoordinate Cobalt Research Articles

Slow magnetic relaxation in penta-coordinate cobalt(II) field-induced single-ion magnets (SIMs) with easy-axis magnetic anisotropy.

Two penta-coordinate complexes of the general formula [Co(Ln)(NCS)]ClO4, where L1 = {bis[(3,5-dimethyl-1H-pyrazol-1-yl)ethyl]-[(3,4-dimethoxypyridin-2-yl)methyl]}amine and L2 = {bis[(3,5-dimethyl-1H-pyrazol-1-yl)ethyl]-[(4-methoxy-3,5-dimethylpyridin-2-yl)methyl]}amine, have been synthesized and thoroughly characterized. Each of the cobalt(ii) atoms is penta-coordinated in the {CoN5} donor set with a distorted square-pyramidal geometry in [Co(L1)(NCS)]ClO4·MeOH (1), while the vicinity of the central atom can be described as a distorted trigonal-bipyramidal geometry in [Co(L2)(NCS)]ClO4 (2) as revealed using the SHAPE analysis. Differences in interatomic parameters among the cobalt(ii) and donor atoms in 1 and 2 have definite impact on the magnetic features of both compounds. The complexes show an easy-axis magnetic anisotropy (D = -38.5 cm-1 for 1 and D = -8.5 for 2), and both complexes reveal a large rhombicity with E/D = 0.21 for 1 and E/D = 0.29 for 2. The ZFS parameters (g, D and E) were also calculated using CASSCF/NEVPT2 methods and they are in good agreement with those determined from experimental data. A frequency dependent out-of-phase susceptibility has been observed in external magnetic field (Bdc = 0.1 T) revealing the following parameters of slow relaxation of magnetization for 1: energy of the spin reversal barrier, Ueff = 16.0 cm-1 (Ueff/kB = 23.0 K) and the relaxation time, τ0 = 1.28 × 10-6 s. In the case of complex 2, no maxima of frequency dependent out-of-phase susceptibility have been observed and thus, the value of Ueff = 17 cm-1 has been estimated using the expression Ueff = |D| × (S2 - 1/4). It has been demonstrated that the degree of substitution and the type of substituents on the pyridyl moieties of the tripodal ligands (L1 and L2) used in these penta-coordinate cobalt(ii) complexes have significant impact on structural and magnetic features.

Cobalt Superoxo and Alkylperoxo Complexes Derived from Reaction of Ring-Cleaving Dioxygenase Models with O2.

The syntheses and O2 reactivities of active-site models of cobalt-substituted ring-cleaving dioxygenases are presented. The pentacoordinate cobalt(II)-aminophenolate complex, [Co(TpMe2)(tBu2APH)], gives rise to two distinct dioxygen adducts at reduced temperatures. The first is a paramagnetic (S = 1/2) cobalt(III)-superoxo species that was characterized with spectroscopic and computational techniques. The identity of the second Co/O2 adduct was elucidated by X-ray crystallography, which revealed an unprecedented cobalt(III)-alkylperoxo structure generated by O2 addition to the metal ion and ligand. These results provide synthetic precedents for proposed intermediates in the catalytic cycles of O2-activating cobalt enzymes.

Pentacoordinate cobalt(II) complexes with neutral tripodal N-donor ligands: Zero-field splitting for a distorted trigonal bipyramidal geometry

Abstract A series of pentacoordinate Co(II) complexes of the composition [Co(bpdmpz)Cl]ClO4 (1), [Co(bpdmpz)Cl]PF6 (2), [Co(bdmpzp)Cl]ClO4·H2O (3), [Co(bdmpzp)Cl]PF6 (4), [Co(tdmpza)Cl]ClO4 (5) and [Co(tdmpza)Cl]PF6 (6) (bpdmpz = bis[(2-pyridylmethyl)-(di(3,5-dimethyl-1H-pyrazolyl)methyl)]amine, bdmpzp = bis[(di(3,5-dimethyl-1H-pyrazolyl)methyl))-(2-pyridylmethyl)]amine and tdmpza = tris[di(3,5-dimethyl-1H-pyrazolyl)methyl)]amine) was prepared and thoroughly characterized. Single-crystal X-ray analyses of complexes 1–5 revealed that they possess very close molecular structures with a distorted trigonal bipyramidal geometry. The static DC magnetic experiments revealed the ZFS parameters pointing out small magnetic anisotropy (with the |D| values lying in a relative narrow range of 4.4–5.7 cm−1) and rhombicity (with the E/D parameters in the range of 0–0.26). The dynamic magnetic data revealed that AC susceptibility is temperature and frequency-dependent for 1, 2 and 3, and thus, these compounds belong to a group of field-induced pentacoordinate Co(II) single-molecule magnets (SMMs). The evaluation of magnetic data was also supported by the CASSCF/NEVPT2 calculations.

Spin Changes Accompany Ultrafast Structural Interconversion in the Ground State of a Cobalt Nitrosyl Complex

AbstractUltrafast, reversible intersystem crossing (ISC) is reported under ambient conditions for the electronic ground state of the pentacoordinate cobalt nitrosyl complexes, [CoX2(NO)(PMePh2)2] (X=Cl, Br), in solution. ISCs on such short timescales are more typically observed in electronically excited states reached by absorption of ultraviolet or visible light. Singlet and triplet electron spin states of the complex, corresponding to two different isomers, are populated at room temperature, and the two isomers exchange on a timescale of a few picoseconds. Ultrafast two‐dimensional infrared spectroscopy observes the change in wavenumber of the NO ligand band accompanying the isomerization and associated ISC on the (spin) adiabatic ground potential energy surface. Comparison of the dynamics of the chloro‐ and bromo‐complexes shows that inertial effects of the ligand motion have a greater effect than spin–orbit coupling on determining the forward and reverse isomerization and ISC rates.

Spin Changes Accompany Ultrafast Structural Interconversion in the Ground State of a Cobalt Nitrosyl Complex

Ultrafast, reversible intersystem crossing (ISC) is reported under ambient conditions for the electronic ground state of the pentacoordinate cobalt nitrosyl complexes, [CoX2 (NO)(PMePh2 )2 ] (X=Cl, Br), in solution. ISCs on such short timescales are more typically observed in electronically excited states reached by absorption of ultraviolet or visible light. Singlet and triplet electron spin states of the complex, corresponding to two different isomers, are populated at room temperature, and the two isomers exchange on a timescale of a few picoseconds. Ultrafast two-dimensional infrared spectroscopy observes the change in wavenumber of the NO ligand band accompanying the isomerization and associated ISC on the (spin) adiabatic ground potential energy surface. Comparison of the dynamics of the chloro- and bromo-complexes shows that inertial effects of the ligand motion have a greater effect than spin-orbit coupling on determining the forward and reverse isomerization and ISC rates.

Single-molecule magnetism in a pentacoordinate cobalt(II) complex supported by an antenna ligand.

Pentacoordinate complex [CoL(3)Cl2] with a tridentate antenna-like ligand L(3) forms a dimer held by short π-π stacking with head-to-head contacts at 3.4 Å. The direct-current (dc) magnetic susceptibility and magnetization data confirm weak ferromagnetic interaction and a large-magnetic anisotropy, D/hc = 150 cm(-1) and E/hc = 11.6 cm(-1). The system shows superparamagnetic behavior at low temperature that depends upon the applied magnetic field. At Bdc = 0.2 T, a low-frequency peak at the out-of-phase susceptibility is seen (ν ∼ 0.3 Hz), whereas the onset of the second peak appears at ν > 1500 Hz, indicating the existence of two slow relaxation processes.

Preparation of organocobalt complexes through C[sbnd]F/C[sbnd]H bond activation of polyfluoroaryl imines

In this paper, we reported the CF and CH bond activation of polyfluoroimine ligands induced by CoMe(PMe3)4. The reaction of pentafluorophenylmethylidene-2,6-diisopropylaniline 1 with CoMe(PMe3)4 afforded an ortho-chelated cobalt(I) complex [Co(PMe3)3(C6F4-ortho-CH=N-C6H3(iso-Pr)2(ortho, ortho))] (5) via CF bond activation and subsequent elimination of methyl fluoride. Under similar reaction conditions, the reactions of polyfluoroaryl imines 2–4 with CoMe(PMe3)4 afforded the penta-coordinate cobalt(I) complexes 6–8 via CH bond activation and subsequent elimination of methane [Co(PMe3)3(C6H2F2(meta, meta)-ortho-(CH=N-C6H4Clpara)] (6), [Co(PMe3)3(C6H2F2(meta, para)-ortho-(CH=N-C6H4Clpara)] (7), and [Co(PMe3)3(C6HF3(meta, meta, para)-ortho-(CH=N-C6H4Clpara)] (8). Complexes 5–8 were characterized through IR, 1H NMR, 31P NMR, 19F NMR and elemental analyses. The crystal and molecular structures of complexes 5, 6 and 8 were determined by X-ray single crystal diffraction. The reactions of 8 with MeI and EtBr afforded organic fluorides 9–10. A proposed formation mechanism of 9–10 with the oxidative addition of RX at the cobalt(I) center of 8 and reductive elimination via C,C-coupling was discussed.

Reactivity of mer-hydrido(2-mercaptobenzoyl)tris(trimethylphosphine)cobalt(iii) complex

The reactivity of mer-hydrido(2-mercaptobenzoyl)tris(trimethylphosphine)cobalt(III) complex 1 was intensively studied. A series of sulfur-coordinated organocobalt complexes (2-8) were obtained through the reactions of 1 with RX (RX = HCl, C2H5Br and CH3I), 2-(diphenylphosphanyl)phenol, 2-(diphenylphosphino)benzenethiol, and CO. The reaction of complex with ethynyltrimethylsilane under 1 bar of CO afforded a penta-coordinate cobalt(I) complex 11 via insertion reaction of C≡C bond of ethynyltrimethylsilane into Co-H bond and subsequent C,C-coupling reaction (reductive elimination). The formation mechanism of 11 was proposed and partly-experimentally verified. As an intermediate, the tetra-coordinate cobalt(I) complex 13 was isolated through the reaction of complex 1 with ethynyltrimethylsilane in the absence of CO. The crystal structures of complexes 2-4, 8, and 11 were determined by X-ray diffraction.

C–Cl bond activation of ortho-chlorinated benzamides by nickel and cobalt compounds supported with phosphine ligands

The C-Cl bonds of ortho-chlorinated benzamides Cl-ortho-C(6)H(4)C(=O)NHR (R = Me (1), nBu (2), Ph (3), (4-Me)Ph (4) and (4-Cl)Ph (5)) were successfully activated by tetrakis(trimethylphosphine)nickel(0) and tetrakis(trimethylphosphine)cobalt(0). The four-coordinate nickel(II) chloride complexes trans-[(C(6)H(4)C([double bond, length as m-dash]O)NHR)Ni(PMe(3))(2)Cl] (R = Me (6), nBu (7), Ph (8) and (4-Me)Ph (9)) as C-Cl bond activation products were obtained without coordination of the amide groups. In the case of 2, the ionic penta-coordinate cobalt(II) chloride [(C(6)H(4)C(=O)NHnBu)Co(PMe(3))(3)]Cl (10) with the [C(phenyl), O(amide)]-chelate coordination as the C-Cl bond activation product was isolated. Under similar reaction conditions, for the benzamides 3-5, hexa-coordinate bis-chelate cobalt(III) complexes (C(6)H(4)C(=O)NHR)Co(Cl-ortho-C(6)H(4)C(=O)NR)(PMe(3))(2) (11-13) were obtained via the reaction with [Co(PMe(3))(4)]. Complexes 11-13 have both a five-membered [C,N]-coordinate chelate ring and a four-membered [N,O]-coordinate chelate ring with two trimethyphosphine ligands in the axial positions. Phosphonium salts [Me(3)P(+)-ortho-C(6)H(4)C(=O)NHR]Cl(-) (R = Ph (14) and (4-Me)Ph (15)) were isolated by reaction of complexes 8 and 9 as a starting material under 1 bar of CO at room temperature. The crystal and molecular structures of complexes 6, 7 and 9-12 were determined by single-crystal X-ray diffraction.

Thermodynamics of Cobalt(III) Schiff base complexes in various solvents

The electronic and steric effects of some Schiff bases and the solvent on the thermodynamic parameters of the pentacoordinate Co(III) Schiff base complexes were studied. The formation constants and the thermodynamic parameters were measured spectrophotometrically for 1:1 adduct formation of the complexes as acceptors with tributylphosphine (PBu3) as donor, in some solvents (acetonitrile, tetrahydrofuran, butanol, ethanol and N,N-dimethylformamide) in constant ionic strength (I = 0.01 M, sodium perchlorate) and at various temperatures. The trend of the reactivity of the pentacoordinate cobalt(III) Schiff base complexes toward tributylphosphine according to the solvent is as follows: acetonitrile > tetrahydrofuran > butanol > ethanol > N,N-dimethylformamide. The trend of the reactivity of pentacoordinate cobalt(III) Schiff base complexes toward the donor in a given solvent according to the equatorial Schiff base is as follows: BBE > BAE > Salen.

Spectrophotometric Study of Adduct Formation Between [Co(Salen)PPh3]ClO4.H2O and [Co(7,7′‐Dimethylsalen)PPh3]ClO4.H2O with Amines Donors in Acetonitrile

The equilibrium quotient of the adduct formation of [Co(Salen)PPh3]ClO4.H2O and [Co(7,7′‐dimethylSalen)PPh3]ClO4.H2O, as acceptor with amines donors are studied by spectrophotometer. Thermodynamics of these pentacoordinate cobalt(III) Schiff‐base complexes have been examined with n‐butylamine, sec‐butylamine, tert‐butylamine, benzylamine and diethylamine in constant ionic strength of 0.1 M sodium perchlorate and acetonitrile solvent at room temperature. We aimed to investigate the effects of different electronic and steric situations of donor and acceptor by comparing their equilibrium quotient for any adduct.

Synthesis, characterization, and thermodynamic studies of cobalt Schiff base complexes with amines

The [ N, N′-bis(Salicyliden)-2,3-diaminopyridine]tributylphosphinecobalt(III) perchlorate monohydrate, [Co(Salpyr)(PBu 3)]ClO 4 · H 2O, was synthesized and characterized. For the new five coordinate complex and some others, such as [ N, N′-bis(Salicyliden)-1,2-phenylenediamine]tributylphosphinecobalt(III) perchlorate monohydrate, [Co(Saloph)(PBu 3)]ClO 4 · H 2O, [ N, N′-bis(4-methylSalicyliden)-1,2-phenylenediamine]tributylphosphine cobalt(III) perchlorate monohydrate, [Co(4-MeSaloph)(PBu 3)]ClO 4 · H 2O, [ N, N′-bis(4-nitroSalicyliden)-1,2-phenylenediamine]tributylphosphinecobalt(III) perchlorate monohydrate, [Co(4-NO 2Saloph)(PBu 3)]ClO 4 · H 2O, and [ N, N′-bis(Salicyliden)-1,2-phenylenediamine]dimethylphenylphosphinecobalt(III) perchlorate monohydrate, [Co(Saloph)(PMe 2Ph)]ClO 4 · H 2O, the formation constants and the thermodynamic parameters of the interaction of Co(III) Schiff bases with amines were measured spectrophotometrically. Furthermore, the formation constant of these 1:1 adducts in 96% ethanol solvent and in constants ionic strength ( I = 0.1 M NaClO 4) and at different temperatures were determined using the Ketelaar equation. Also the adduct formation of [Co(Saloph)(PBu 3)]ClO 4 · H 2O, with Imidazol, 2-MeImidazol, 4-MeImidazol, 2-EtImidazol, and BzImidazol in 96% ethanol was studied. The formation constants and the thermodynamic parameters for [Co(Salpyr)(PBu 3)]ClO 4 · H 2O as an acceptor with some aliphatic amines, such as n-butylamine, sec-butylamine, tert-butylamine, benzylamine, and diethylamine as donors were determined in DMA. The comparison of formation constants and the thermodynamic parameters show that the trend of formation constants of pentacoordinate cobalt(III) Schiff base complexes toward a given donor at lower temperature of the range used (283 and 293) K is as follows: 4 -MeSaloph > Saloph > 4 - NO 2 Saloph > Salpyr. Also the following binding trend of the donors toward a given cobalt(III) Schiff base complex is in sequence: Im > 4-MeIm > 2-MeIm > 2-EtIm > BzIm and for aliphatic amines is as follows: Benzylamine > sec-butylamine ∼ n-butylamine > tert-butylamine > diethylamine. The formation constants for a given donor change according to the following trend for phosphine axial ligands: PBu 3 < PMe 2Ph.

Structure of a five-coordinate mononuclear cobalt(II) complex: chlorobis([N,N-(1,1′-biphenyl-2,2′-dimethylene)]-2-aminomethyl) pyridine)cobalt(II) bromide

A penta-coordinate mononuclear cobalt(II) complex, [Co(BP)2(Cl−)](Br−), 1 with a novel, biphenyl-appended N,N-bidentate ligand, BP ([N,N-(1,1′-biphenyl-2,2′-dimethylene)]-2-aminomethyl) pyridine) was synthesized and characterized by elemental analysis, UV-Vis, electro-spray ionization mass spectrum and single crystal XRD. The title complex crystallizes in the monoclinic space group C2/c with cell dimensions a = 11.389(2), b = 25.627(3), c = 12.276(3) A, β = 100.419(18)° and Z = 2. The cobalt atom has a distorted trigonal bipyramidal (tbp) geometry and is surrounded by 4Ns of two BP, and a Cl−/Br− at the 5th coordination site. This is the first report of a mononuclear tbp cobalt complex with biphenyl appended bidentate ligand containing amino-pyridyl moiety.

A novel 3D coordination polymer containing pentacoordinate cobalt(II) dimers with antiferromagnetic ordering

A novel three dimensional (3D) polymer, [Co2(hypa)2(4,4′-bipy)] (1) (H2hypa = hydroxy-phenyl-acetic acid, 4,4′-bipy = 4,4′-bipyridine), featuring pentacoordinate, dimeric cobalt(II) as subunits have been prepared, which shows low-dimensional antiferromagnetic ordering blow 15.2 K (TN).

A Unique Two-Dimensional Terephthalate-Bridged Structure with Alternate Tetra- and Penta-Coordinate Cobalt(II) Sites. Synthesis, Crystal Structure and Magnetic Properties of [{Co3(tp)2(OH)2(phen)2}n

Abstract A two-dimensional (2D) cobalt coordination polymer [{Co3(tp)2(OH)2(phen)2}n] (1), bridged by the terephthalate (tp) ligand, was synthesized under hydrothermal conditions, and its structure was determined by single-crystal X-ray diffraction. Complex 1 crystallized in the triclinic space group P1- with a = 8.2620(11) Å, b = 10.4409(12) Å, c = 11.0840(10) Å, α = 111.332(8)°, β = 91.394(10)°, γ = 91.638(10)°, Z = 2, V = 889.65(18) Å3. A structure refinement showed that complex 1 is the first example of a two-dimensional (2D) framework with both carboxylate bridges and μ-hydroxo bridges, in which cobalt atoms adopt square-pyramidal and square-planar geometries. Complex 1 exhibited a interesting magnetic behavior: the shape of the μeff curve indicates a ferrimagnetic-like behavior between 300–41.0 K, immediately followed by a strong decay of the magnetic moment. Moreover, complex 1 was characterized by IR spectroscopy, inductively coupled plasma (ICP), elemental and thermogravimetric (TGA) analyses.

Regiospecific Cyclometalation of Diphenyl(2‐substituted phenyl)phosphane with Methyltetrakis(trimethylphosphane)cobalt(I)

AbstractThe pre‐chelate molecules 2‐(diphenylphosphanyl)‐N,N‐dimethylaniline, [2‐(diphenylphosphanyl)benzyl]dimethylamine, 1‐(diphenylphosphanyl)‐2‐ethylbenzene, 1‐(diphenylphosphanyl)‐2‐isopropylbenzene, and 2‐(diphenylphosphanyl)benzonitrile, in a reaction with [CoMe(PMe3)4], eliminate methane to afford the selectively 6‐ortho‐metalated complexes 1−5 that contain four‐membered metallacycles. The molecular structure of 3 shows a tbp‐coordinated cobalt atom, with axial C and PMe3 donor groups. Metalation in the aliphatic side‐chain occurs with 2‐(diphenylphosphanyl)toluene, giving complex 6 that contains a five‐membered metallacycle. Benzyldiphenylphosphane is selectively ortho‐metalated in the benzyl group, affording 7. As shown by the molecular structures, complex 7 is a true ligand isomer of 6. Substitution of a trimethylphosphane group in compounds 4 and 6 by ethene gives the pentacoordinate complexes 8 and 9, respectively. The ethene ligand is π‐coordinated in the equatorial plane of a trigonal bipyramid. Under 1 bar of CO, complex 6 forms monocarbonyl complex 10. Carbonylation of complexes 3 and 4 proceeds by insertion of CO into the Co−C bond under ring expansion, affording the aroylcobalt complexes 11 and 12, respectively. Complex 6 reacts with iodomethane in an oxidative substitution reaction yielding a structurally characterized octahedral complex mer‐13, which eliminates a methyl group in THF at 20 °C to form a pentacoordinate cobalt(II) complex 14. Complex 3 oxidatively adds iodomethane in a stereoselective cis addition to give the cobalt(III) complex mer‐15, which retains its four‐membered metallacycle and the CoCH3 group. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2003)

Pentacoordinate cobalt(III) thiolate and nitrosyl tropocoronand compounds.

Reaction of [Co(TC-n,m)]+ with (Me4N)(SC6F5), where (TC-n,m) is a tropocoronand with n and m linker chain methylene groups, yielded the thiolate complexes [Co(SC6F5)(TC-3,3)] (1a), and [Co(SC6F5)(TC-4,4)] (2a), which were structurally characterized. Use of more electron-releasing thiolates afforded the [Co(TC-n,m)] reduction product and the corresponding disulfide. The bent nitrosyl complexes [Co(NO)(TC-3,3)] (1b) and [Co(NO)(TC-4,4)] (2b) were synthesized from [Co(TC-n,m)] and NO and their structures were also determined. Compounds 1a and 1b have square-pyramidal geometry like all other structurally characterized [MX(TC-3,3)] complexes. Compounds 2a and 2b have trigonal-bipyramidal stereochemistry, formerly rare for Co(III). Although 1a, 1b, and 2a are paramagnetic, 2b is diamagnetic due to the strong antibonding pi-interaction between the metal and NO pi* orbitals. In the presence of excess NO, [Co(TC-4,4)] exhibited novel reactivity in which a putative Co(N2) adduct formed.

X-ray Structure, Magnetic and Catalytic Properties of a Cyclic Trinuclear CoII/CoIII/CoIII Complex with a μ3-Hydroxy Anion

The mixed-valent cyclic trinuclear cobalt(II)/cobalt(III)/cobalt(III) complex tris(dibenzoylmethanato-1κ2O,O′;2κ2O,O′;3κ2O,O′)(μ3-hydroxo-1:2κ2O;1:3κ2O;2:3κ2O)tetrakis(μ-pyrazolato-1:2κ4N1N2;1:3κ2N1N2;2:3κ2N1N2)-1,2-dicobalt(III)-3-cobalt(II) with four bridging pyrazolate anions and a μ3-hydroxy anion has been synthesized and its molecular structure has been elucidated on the basis of X-ray crystallographic, magnetic, NMR, and EPR studies. The remaining coordination sites of the pentacoordinate cobalt(II) and hexacoordinate cobalt(III) centers are occupied by oxygen donor atoms of dibenzoylmethanate anions, rendering the complex soluble in most organic solvents. The complex has been found to effectively catalyze the decomposition of tert-butyl hydroperoxide (TBHP) in chlorobenzene with a short induction period and a half-life of 80 min and to catalyze the oxidation of cyclohexene to 2-cyclohexen-1-one with oxygen and to 2-cyclohexen-1-ol with TBHP.

A unique open inorganic–organic framework with alternate hexa- and penta-coordinate cobalt(ii) sites. Synthesis, crystal structure and magnetic properties of [Co3(C4H4O4)2.5(OH)]n·0.5nH2O

A three-dimensional open-framework with unprecedented alternate hexa- and penta-coordinate cobalt(II) sites was obtained from the hydrothermal reaction of cobalt nitrate and succinate in a basic solution. Of the four crystallographically independent Co(II) atoms in the crystal structure of this compound, three are hexa-coordinated and one penta-coordinated. The cobalt(II) atoms are linked by edge-sharing CoOn (n = 5 or 6) polyhedrons. The temperature dependence of the magnetic susceptibility of this compound shows strong antiferromagnetic interaction between the metal atoms.

Synthesis and characterization of polymer supported vitamin B12 model compounds

A series of polymer supported cobalt complexes have been synthesized by the reaction of Co(II)-SALEN (salicylaldehyde ethylenediimine) and other variations thereof with the chelating resin containing vinyl pyridine. The polymer supported complexes have been characterized by electronic and infrared spectra. The presence of polymer supports has a marked influence on the UV-visible bands observed in the electronic spectra of cobalt complexes. These polymer supported complexes are also investigated by cyclic voltammetry. The electronic spectral data and cyclic voltammetric data for free complexes and polymer supported complexes are compared. The discernible differences in the spectral and electrochemical data suggest the presence of pentacoordinate cobalt in the polymer matrix.