Alkyl- and aryl-substituted corroles. 5. Synthesis, physicochemical properties, and X-ray structural characterization of copper biscorroles and porphyrin-corrole dyads

The synthesis and characterization of cofacial copper biscorroles and porphyrin-corroles linked by a biphenylenyl or anthracenyl spacer are described. The investigated compounds are represented as (BCA)Cu(2) and (BCB)Cu(2) in the case of the biscorrole (BC) derivatives and (PCA)Cu(2) and (PCB)Cu(2) in the case of porphyrin (P)-corrole (C) dyads, where A and B represent the anthracenyl and biphenylenyl bridges, respectively. A related monomeric corrole (Me(4)Ph(5)Cor)Cu and monomeric porphyrin (Me(2)Et(6)PhP)Cu that comprise the two halves of the porphyrin-corrole dyads were also studied. Electron spin resonance (ESR), (1)H NMR, and magnetic measurements data demonstrate that the copper corrole macrocycle, when linked to another copper corrole or copper(II) porphyrin, can be considered to be a Cu(III) complex in equilibrium with a Cu(II) radical species, copper(III) corrole being the main oxidation state of the corrole species at all temperatures. The cofacial orientation of (BCB)Cu(2), (BCA)Cu(2), and (PCB)Cu(2) was confirmed by X-ray crystallography. Structural data: (BCB)Cu(2)(C(110)H(82)N(8)Cu(2).3CDCl(3)), triclinic, space group P, a = 10.2550(2) A, b = 16.3890(3) A, c = 29.7910(8) A, alpha = 74.792(1) degrees , beta = 81.681(1) degrees , gamma = 72.504(2) degrees , Z = 2; (BCA)Cu(2)(C(112)H(84)N(8)Cu(2).C(7)H(8).1.5H(2)O), monoclinic, space group P 2(1)/c, a = 16.0870(4) A, b = 35.109(2) A, c = 19.1390(8) A, beta = 95.183(3) degrees , Z = 4; (PCB)Cu(2)(C(89)H(71)N(8)Cu(2).CHCl(3)), monoclinic, space group P2(1)/n, a = 16.7071(3) A, b = 10.6719(2) A, c = 40.8555(8) A, beta = 100.870(1) degrees , Z = 4. The two cofacial biscorroles, (BCA)Cu(2) and (BCB)Cu(2), both show three electrooxidations under the same solution conditions. The reduction of (BCA)Cu(2) involves a reversible electron addition to each macrocycle at the same potential of E(1/2) = -0.20 V although (BCB)Cu(2) is reversibly reduced in two steps to give first [(BCB)Cu(2)](-) and then [(BCB)Cu(2)](2)(-), each of which was characterized by ESR spectroscopy as containing a Cu(II) center. These latter electrode reactions occur at E(1/2) = -0.36 and -0.51 V versus a saturated calomel reference electrode. The half-reduced and fully reduced (BCB)Cu(2) show similar Cu(II) ESR spectra, and no evidence of a triplet signal is observed. The two well-separated reductions of (BCB)Cu(2) to give [(BCB)Cu(2)](2)(-) can be attributed to a stronger pi-pi interaction between the two macrocycles of this dimer as compared to those of (BCA)Cu(2). The copper porphyrin-corrole dyads, (PCA)Cu(2) and (PCB)Cu(2), show five reversible oxidations and two reversible reductions, and these potentials are compared with corresponding values for electrochemical reactions of the porphyrin and corrole monomers under the same solution conditions.     

Alkyl and aryl substituted corroles. 3. Reactions of cofacial cobalt biscorroles and porphyrin-corroles with pyridine and carbon monoxide

The synthesis and characterization of three new cofacial biscorroles and three new linked Co(II) porphyrins and Co(III) corroles with the same face to face orientation are described. The biscorroles are represented as (BCS)Co(2), (BCO)Co(2), (BCX)Co(2) while the porphyrin-corrole dyads are represented as (PCA)Co(2), (PCB)Co(2), (PCO)Co(2) where BC represents the Co(III) cofacial biscorroles and PC represents the porphyrin-corrole complexes which are linked to each other by a dibenzothiophene (S), dibenzofuran (O), or 9,9-dimethylxanthene (X) bridge in the case of the corroles and an anthracene (A), biphenylene (B), or dibenzofuran (O) bridge in the case of the mixed macrocycle derivatives. The electrochemical and spectroscopic data on these new bismacrocycles are compared to those of previously reported biscorroles of the type (BCA)Co(2) and (BCB)Co(2). The CO and/or pyridine binding properties of each biscorrole and porphyrin-corrole in CH(2)Cl(2) are also presented. Only one CO ligand is bound axially to each corrole unit of the bismacrocycle but five- and six-coordinate pyridine complexes can be generated for the same compounds, with the exact stoichiometry depending upon the concentration of pyridine in solution. In all cases, the six-coordinate bispyridine corrole complex can be unambiguously identified by a strong diagnostic marker band located at 598-601 nm. The formation constants for pyridine binding to the biscorroles range from log K(1) = 3.14 to 5.08 while log K(2) ranges from 1.10 to 2.61 depending upon the specific spacer. Carbon monoxide binding constants range from log K = 3.6 to 4.0 in the case of the biscorroles and from log K = 3.4 to 4.1 in the case of the porphyrin-corrole dyads. These values also depend on the specific spacer in the complex and, like the pyridine binding constants, decrease in the order BCO > BCA > BCB for the biscorroles and PCO > PCA > PCB for the porphyrin-corrole complexes.     

Alkyl and aryl substituted corroles. 1. Synthesis and characterization of free base and cobalt containing derivatives. x-ray structure of (Me(4)Ph(5)Cor)Co(py)(2)

The synthesis, spectroscopic properties, and electrochemistry of six different alkyl- and aryl-substituted Co(III) corroles are presented. The investigated compounds contain methyl, ethyl, phenyl, or substituted phenyl groups at the eight beta-positions of the corrole macrocycle and four derivatives also contain a phenyl group at the 10-meso position of the macrocycle. Each cobalt corrole undergoes four reversible oxidations in CH(2)Cl(2) containing 0.1 M tetra-n-butylammonium perchlorate and exists as a dimer in its singly and doubly oxidized forms. The difference in potential between the first two oxidations is associated with the degree of interaction between the two corrole units of the dimer and ranges from an upper value of 0.62 V, in the case of (Me(6)Et(2)Cor)Co, to a lower value of about 0.17 V, in the case of four compounds which have a phenyl group located at the 10-meso position of the macrocycle. These Co(III) corroles strongly coordinate two pyridine molecules or one carbon monoxide molecule in CH(2)Cl(2) media, and ligand binding constants were evaluated using spectroscopic and electrochemical methods. The structure of (Me(4)Ph(5)Cor)Co(py)(2) was also determined by X-ray diffraction. Crystal data: (Me(4)Ph(5)Cor)Co(py)(2).3CH(2)Cl(2).H(2)O, orthorhombic, a = 19.5690(4) A, b = 17.1070(6) A, c = 15.9160(6) A, V = 5328.2(5) A(3), space group Pna2(1), Z = 2, 35 460 observations, R(F) = 0.069.     

Alkyl- and aryl-substituted corroles. 4. Solvent effects on the electrochemical and spectral properties of cobalt corroles

Solvent effects on the electrochemistry and spectroscopic properties of alkyl- and aryl-substituted corroles in nonaqueous media are reported. The oxidation and reduction of six compounds containing zero to seven phenyl or substituted phenyl groups on the macrocycle were studied in four different nonaqueous solvents (CH(2)Cl(2), PhCN, THF, and pyridine) containing 0.1 M tetra-n-butylammonium perchlorate. Dimers were formed upon oxidation of all corroles in CH(2)Cl(2), but this was not the case in the other three solvents, where either monomers or dimers were formed upon oxidation depending upon the solvent Gutmann donor number and the number or location of aryl substituents on the macrocycle. The half-wave potentials were analyzed as a function of the number of aryl substituents on the macrocycle as well as the concentration of added pyridine to PhCN solutions of the compound, and these data were combined with data from the spectroelectrochemistry experiments to determine the stoichiometry of the species actually in solution after the first oxidation or first reduction of each compound. The results of these experiments indicate that reduction of the bispyridine adduct (Cor)Co(III)(py)(2) proceeds via the monopyridine complex (Cor)Co(III)(py) to give in each case the unligated cobalt(II) corrole [(Cor)Co(II)](-). In contrast, pyridine remains coordinated after electrooxidation, and the final product was characterized as [(Cor)Co(III)(py)(2)](+).     

Electrochemistry and spectroelectrochemistry of heterobimetallic porphyrin-corrole dyads. Influence of the spacer, metal ion, and oxidation state on the pyridine binding ability

Combined electrochemical and UV-visible spectroelectrochemical methods were utilized to elucidate the prevailing mechanisms for electroreduction of previously synthesized porphyrin-corrole dyads of the form (PCY)H2Co and (PCY)MClCoCl where M = Fe(III) or Mn(III), PC = porphyrin-corrole, and Y is a bridging group, either biphenylenyl (B), 9,9-dimethylxanthenyl (X), anthracenyl (A), or dibenzofuranyl (O). These studies were carried out in pyridine, conditions under which the cobalt(IV) corrole in (PCY)MClCoCl is immediately reduced to its Co(III) form, thus enabling direct comparisons with the free-base porphyrin dyad, (PCY)H2Co(III) under the same solution conditions. The compounds are all reduced in multiple one-electron-transfer steps, the first of which involves the M(III)/M(II) process of the porphyrin in the case of (PCY)MClCoCl and the Co(III)/Co(II) process of the corrole in the case of (PCY)H2Co. Each metal-centered redox reaction may be accompanied by the gain or loss of pyridine axial ligands, with the exact stoichiometry of the exchange process depending upon the specific combination of metal ions in the dyad, their oxidation states, and the particular spacer in the complex. Before this study was started, it was expected that the porphyrin-corrole dyads with the largest spacers, namely, O and A, would readily accommodate the formation of cobalt(III) bis-pyridine adducts because of the larger size of the cavity while dyads with the smallest B spacer would seem to have insufficient room to add even a single pyridine within the cavity, as was structurally seen in the case of (PCB)H2Co(py). This is clearly not the case, as shown in the present study. A reversible Co(III)/Co(II) reaction is seen for (PCB)MnClCoCl at -0.62 V, which when combined with spectroscopic data, leads to the assignment of (PCB)Mn(III)(py)2Co(III)(py) as the species in pyridine. The reduction of (PCB)Mn(III)(py)2Co(III)(py) to (PCB)Mn(II)(py)Co(III)(py) is accompanied on the slower spectroelectrochemical time scale by the appearance of a 603 nm band in the UV-vis spectra and is consistent with the addition of a second pyridine ligand to the Co(III)(py) unit of the dyad as one ligand is lost from the electrogenerated manganese(II) porphyrin, thus maintaining one pyridine ligand within the cavity. A different change in the coordination number is observed in the case of (PCB)FeClCoCl. Here the initial Fe(III) complex can be assigned as (PCB)Fe(III)ClCo(III)(py), which has no pyridine molecule within the cavity and the singly reduced form is characterized as (PCB)Fe(II)(py)2Co(III)(py)2, which contains two pyridine ligands inside the cavity. A following one-electron reduction of the Fe(II)/Co(III) complex then gives [(PCB)Fe(II)(py)2Co(II)]-.     

Composition Space of the (CuO, (1)/(2)Nb(2)O(5))/(HF)(x)().pyridine/H(2)O System. Structure and Synthesis of [pyH(+)](2)[CuNb(2)(py)(4)O(2)F(10)](2-) and CuNb(py)(4)OF(5)

Single crystals of [pyH(+)](2)[CuNb(2)(py)(4)O(2)F(10)](2)(-) and CuNb(py)(4)OF(5) were synthesized in a (HF)(x)().pyridine/pyridine/water solution (150 degrees C, 24 h, autogeneous pressure) using CuO and Nb(2)O(5) as reagents. The compound [pyH(+)](2)[CuNb(2)(py)(4)O(2)F(10)](2)(-) contains clusters of [CuNb(2)(py)(4)O(2)F(10)](2)(-) anions linked through N-H(+).F hydrogen bonds to the [pyH(+)] cations. In contrast CuNb(py)(4)OF(5) is a unidimensional compound consisting only of chains, perpendicular to the c axis, of alternating [Cu(py)(4)(O/F)(2/2)](0.5+) and [NbF(4)(O/F)(2/)(2)](0.5)(-) octahedra. The chains change direction between the [110] and [1&onemacr;0] every c/2. Crystal data for [pyH(+)](2)[CuNb(2)(py)(4)O(2)F(10)](2)(-): tetragonal, space group I4(1)22 (No. 98),with a = 11.408(3) ?, c = 30.36(1) ?, and Z = 4. Crystal data for CuNb(py)(4)OF(5): monoclinic, space group C2/c (No. 15), with a = 10.561(3) ?, b = 13.546(6) ?, c = 16.103(4) ?, beta = 97.77(2) degrees, and Z = 4.     

Structural characterization of the picket fence (TpivPP) porphyrins Co(TpivPP), Co(TpivPP)(NO2)(1-MeIm), and Co(TpivPP)(NO2)(1,2-Me2Im)

The compounds Co(TpivPP) (1), Co(TpivPP)(NO2)(1-MeIm) (2), and Co(TpivPP)(NO2)(1,2-Me2Im) (3) have been synthesized (TpivPP = meso-tetrakis(alpha, alpha, alpha, alpha-o-pivalamidophenyl)porphyrinato dianion), and their structures have been determined with single-crystal X-ray diffraction methods. 1: a = 17.578(1) A, b = 17.596(1) A, c = 20.639(1) A, beta = 115.03(1) degrees, P2(1)/c, Z = 4, T = -120 degrees C. 2: a = 18.522(4) A, b = 18.942(4) A, c = 18.177(4) A, beta = 90.68(3) degrees, C2/c, Z = 4, T = -70 degrees C. 3: a = 18.998(4) A, b = 19.187(4) A, c = 18.000(4) A, beta = 90.96(3) degrees, C2/c, Z = 4, T = -120 degrees C. Compounds 2 and 3 have crystallographically imposed 2-fold axes. In 2 and 3, which represent R-state (relaxed) and T-state (tense) models, respectively, for hemoglobin, the NO2 ligand is bound on the "picket" side to the Co atom, and either 1-MeIm (for 2) or 1,2-Me2Im (for 3) is bound to the Co atom at the sixth coordination site on the sterically unhindered side of the molecule. The average deviations of atoms from the 24-atom porphyrin core are 0.031, 0.129, and 0.117 A for 1, 2, and 3, respectively. The Co atom is -0.043(1) A out of the mean 24-atom porphyrin plane toward the 1-MeIm ligand in 2 and -0.089(1) A out of the plane toward the 1,2-Me2Im ligand in 3. The bonds of both axial ligands in the R-state model 2, 1.898(4) A for Co-N(O2) and 1.995(4) A for Co-N(base), are shorter than the corresponding bonds in the T-state model 3, 1.917(4) A for Co-N(O2) and 2.091(4) A for Co-N(base).     

New coordination polymers with extended arm cyclotriguaiacyclene ligands: 1D chains, and interpenetrating or polycatenating 2D (4(2).6(2))(4.6(2))2 networks

A series of new 1D chain and 2D coordination polymers with cyclotriguaiacylene-type ligands are reported. A zig-zag 1D coordination chain is found in complex [Cd(2)(4ph4py)(NO(3))(3)(H(2)O)(2)(DMA)(2)]·(NO(3))·(DMA)(4), where 4ph4py = tris[4-(4-pyridyl)benzoyl]-cyclotriguaiacylene and DMA = dimethylacetamide, while complex [Zn(4ph4py)(2)(CF(3)COO)(H(2)O)]·(CF(3)COO)(NMP)(7), where NMP = N-methylpyrrolidone, has a doubly bridged coordination chain structure. Complexes [M(3ph3py)(NO(3))(2)]·(NMP)(4) where M = Co or Zn, 3ph3py = tris[3-(3-pyridyl)benzoyl]cyclotriguaiacylene, are isostructural and feature 1D ladder coordination chains. Complexes [Cd(2)(4ph4py)(2)(NO(3))(4)(NMP)]·(NMP)(9)(H(2)O)(4) and [Co(4ph4py)(H(2)O)(2)]·(NO(3))(2)·(DMF)(2), where DMF = dimethylformamide, both have (3,4)-connected 2D coordination polymers with a rare (4(2).6(2))(4.6(2))(2) topology. A 2D coordination polymer with this topology is also found in complex [Co(2)(3ph4py)(2)(NO(3))(H(2)O)(5)]·(NO(3))(3)·(DMF)(9) where 3ph4py = tris[3-(4-pyridyl)benzoyl]cyclotriguaiacylene. All 2D coordination polymer complexes are interpenetrating or polycatenating. [Co(2)(3ph4py)(2)(NO(3))(H(2)O)(5)](3+)polymers form a 2D→3D polycatenation showing self-complementary "hand-shake" interactions between the host-type ligands.     

Synthesis of Arenethiolate Complexes of Divalent and Trivalent Lanthanides from Metallic Lanthanides and Diaryl Disulfides: Crystal Structures of [{Yb(hmpa)(3)}(2)(&mgr;-SPh)(3)][SPh] and Ln(SPh)(3)(hmpa)(3) (Ln = Sm, Yb; hmpa = Hexamethylphosphoric Triamide)

A convenient and one-pot synthetic method of lanthanide thiolate compounds was developed. An excess of metallic samarium, europium, and ytterbium directly reacted with diaryl disulfides in THF to give selectively Ln(II) thiolate complexes, [Ln(SAr)(&mgr;-SAr)(thf)(3)](2) (1, Ln = Sm; 2, Ln = Eu; Ar = 2,4,6-triisopropylphenyl), Yb(SAr)(2)(py)(4) (3, py = pyridine), and [{Ln(hmpa)(3)}(2)(&mgr;-SPh)(3)][SPh] (6, Ln = Sm; 7, Ln = Eu; 8, Ln = Yb; hmpa = hexamethylphosphoric triamide). Reaction of metallic lanthanides with 3 equiv of disulfides afforded Ln(III) thiolate complexes, Ln(SAr)(3)(py)(n)()(thf)(3)(-)(n)() (9a, Ln = Sm, n = 3; 9b, Ln = Sm, n = 2; 10, Ln = Yb, n = 3) and Ln(SPh)(3)(hmpa)(3) (11, Ln = Sm; 12, Ln = Eu; 13, Ln = Yb). Thus, Ln(II) and Ln(III) thiolate complexes were prepared from the same source by controlling the stoichiometry of the reactants. X-ray analysis of 8 revealed that 8 has the first ionic structure composed of triply bridged dinuclear cation and benezenethiolate anion [8, orthorhombic, space group P2(1)2(1)2(1) with a = 21.057(9), b = 25.963(7), c = 16.442(8) ?, V = 8988(5) ?(3), Z = 4, R = 0.040, R(w) = 0.039 for 5848 reflections with I > 3sigma(I) and 865 parameters]. The monomeric structures of 11 and 13 were revealed by X-ray crystallographic studies [11, triclinic, space group P&onemacr; with a = 14.719(3), b = 17.989(2), c = 11.344(2) ?, alpha = 97.91(1), beta = 110.30(2), gamma = 78.40(1) degrees, V = 2751.9(9) ?(3), Z = 2, R = 0.045, R(w) = 0.041 for 7111 reflections with I > 3sigma(I) and 536 parameters; 13, triclinic, space group P&onemacr; with a = 14.565(2), b = 17.961(2), c = 11.302(1) ?, alpha = 97.72(1), beta = 110.49(1), gamma = 78.37(1) degrees, V = 2706.0(7) ?(3), Z = 2, R = 0.031, R(w) = 0.035 for 9837 reflections with I > 3sigma(I) and 536 parameters]. A comparison with the reported mononuclear and dinuclear lanthanide thiolate complexes has been made to indicate that the Ln-S bonds weakened by the coordination of HMPA to lanthanide metals have ionic character.     

An Approach to Heterometallic Complexes with Selenolate and Tellurolate Ligands: Crystal Structures of cis-[Mn(CO)(4)(SePh)(2)](-), [(CO)(3)Mn(&mgr;-SeMe)(3)Mn(CO)(3)](-), (CO)(4)Mn(&mgr;-TePh)(2)Co(CO)(&mgr;-SePh)(3)Mn(CO)(3), and (CO)(3)Mn(&mgr;-SePh)(3)Fe(CO)(3)

Oxidative addition of diorganyl diselenides to the coordinatively unsaturated, low-valent transition-metal-carbonyl fragment [Mn(CO)(5)](-) produced cis-[Mn(CO)(4)(SeR)(2)](-). The complex cis-[PPN][Mn(CO)(4)(SePh)(2)] crystallized in triclinic space group P&onemacr; with a = 10.892(8) ?, b = 10.992(7) ?, c = 27.021(4) ?, alpha = 101.93(4) degrees, beta = 89.79(5) degrees, gamma = 116.94(5) degrees, V = 2807(3) ?(3), and Z = 2; final R = 0.085 and R(w) = 0.094. Thermolytic transformation of cis-[Mn(CO)(4)(SeMe)(2)](-) to [(CO)(3)Mn(&mgr;-SeMe)(3)Mn(CO)(3)](-) was accomplished in high yield in THF at room temperature. Crystal data for [Na-18-crown-6-ether][(CO)(3)Mn(&mgr;-SeMe)(3)Mn(CO)(3)]: trigonal space group R&thremacr;, a = 13.533(3) ?, c = 32.292(8) ?, V = 5122(2) ?(3), Z = 6, R = 0.042, R(w) = 0.041. Oxidation of Co(2+) to Co(3+) by diphenyl diselenide in the presence of chelating metallo ligands cis-[Mn(CO)(4)(SePh)(2)](-) and cis-[Mn(CO)(4)(TePh)(2)](-), followed by a bezenselenolate ligand rearranging to bridge two metals and a labile carbonyl shift from Mn to Co, led directly to [(CO)(4)Mn(&mgr;-TePh)(2)Co(CO)(&mgr;-SePh)(3)Mn(CO)(3)]. Crystal data: triclinic space group P&onemacr;, a = 11.712(3) ?, b = 12.197(3) ?, c = 15.754(3) ?, alpha = 83.56(2) degrees, beta = 76.13(2) degrees, gamma = 72.69(2) degrees, V = 2083.8(7) ?(3), Z = 2, R = 0.040, R(w) = 0.040. Addition of fac-[Fe(CO)(3)(SePh)(3)](-) to fac-[Mn(CO)(3)(CH(3)CN)(3)](+) resulted in formation of (CO)(3)Mn(&mgr;-SePh)(3)Fe(CO)(3). This neutral heterometallic complex crystallized in monoclinic space group P2(1)/n with a = 8.707(2) ?, b = 17.413(4) ?, c = 17.541(4) ?, beta = 99.72(2) degrees, V = 2621(1) ?(3), and Z = 4; final R = 0.033 and R(w) = 0.030.     

Fluoride-bridged {Ln(2)Cr(2)} polynuclear complexes from semi-labile mer-[CrF(3)(py)(3)] and [Ln(hfac)(3)(H(2)O)(2)

The trifluorido complex mer-[CrF(3)(py)(3)] (py = pyridine) reacts with 1 equiv. of [Ln(hfac)(3)(H(2)O)(2)] and depending on the solvent forms the tetranuclear clusters [Cr(2)Ln(2)(μ-F)(4)(μ-OH)(2)(py)(4)(hfac)(6)], 1Ln, and [Cr(2)Ln(2)(μ-F)(4)F(2)(py)(6)(hfac)(6)], 2Ln, in acetonitrile and 1,2-dichloroethane, respectively (Ln = Y, Gd, Tb, Dy, Ho, and Er; hfacH = 1,1,1,5,5,5-hexafluoroacetylacetone). Reaction with [Dy(hfac)(3)(H(2)O)(2)] in dichloromethane produces the dinuclear cluster [CrDy(μ-F)F(OH(2))(py)(3)(hfac)(4)], 3Dy. All the clusters feature fluoride bridges between the chromium(iii) and lanthanide(iii) centres. Fits of susceptibility data for 1Gd and 2Gd reveal the fluoride-mediated chromium(iii)-lanthanide(iii) exchange interactions to be 0.43(5) cm(-1) and 0.57(7) cm(-1), respectively (in the convention). Heat capacity measurements on 2Gd reveal a moderate magneto-caloric effect (MCE) reaching -ΔS(m)(T) = 11.4 J kg(-1) K(-1) for ΔB(0) = 9 T → 0 T at T = 4.1 K. Out-of-phase alternating-current susceptibility (χ') signals are observed for 1Dy, 2Dy and 2Tb, demonstrating slow relaxation of the magnetization.     

Sandwich-type phosphotungstates: structure,electrochemistry, and magnetism of the trinickel-substituted polyoxoanion [Ni(3)Na(H(2)O)(2)(PW(9)O(34))(2)](11-)

The novel nickel-substituted, dimeric phosphotungstate [Ni(3)Na(H(2)O)(2)(PW(9)O(34))(2)](11-) (1) has been synthesized and characterized by IR spectroscopy, elemental analysis, and electrochemistry. X-ray single-crystal analysis was carried out on Na(11)[Ni(3)Na(H(2)O)(2)(PW(9)O(34))(2)].21.25H(2)O, which crystallizes in the triclinic system, space group P1, with a = 12.2467(6) A, b = 16.6031(7) A, c = 22.4017(12) A, alpha = 73.9870(10) degrees, beta = 87.6060(10) degrees, gamma = 79.344(2) degrees, and Z = 2. The polyanion consists of two lacunary B-alpha-[PW(9)O(34)](9-) Keggin moieties linked via three nickel(II) centers and a sodium ion. The structure of 1 is composed of two fused Keggin fragments that represent different Baker-Figgis isomers (alpha- vs beta-type). Electrochemical studies show that 1 exhibits a stable and reproducible voltammetric pattern, with a first wave featuring a chemically reversible four-electron/four-proton process. An investigation of the magnetic properties indicates that the three nickel centers exhibit ferromagnetic exchange interaction.     

Clusters as Ligands. 4. Synthesis, Structure, and Characterization of the Tungsten(II)-Tungsten(III) Cluster Carboxylate {[Na][W(2){OOCCCo(3)(CO)(9)}(2)(OOCCF(3))(4)(THF)(2)]}(2)

The reaction of W(2)(OOCCF(3))(4) with (CO)(9)Co(3)CCOOH and Na[OOCCF(3)] in a nonpolar solvent mixture leads to the formation of the cluster of clusters {[Na][W(2){OOCCCo(3)(CO)(9)}(2)(OOCCF(3))(4)(THF)(2)]}(2), 1, in 40% yield. The structure of 1.3C(6)H(5)CH(3) in the solid state corresponds to a dimer of W(2) dinuclear complexes (monoclinic P2(1)/c, a = 15.234(6) ?, b = 23.326(11) ?, c = 20.658(7) ?, beta = 102.46(3) degrees; V = 7,168(5) ?(3); Z = 4; R(F)() = 8.39%). Each W(2) unit is bridged by two cis cluster carboxylates, and the remaining four equatorial sites are occupied by monodentate [OOCCF(3)](-) ligands. The axial positions contain coordinated THF. The W(2) carboxylate is opened up (W-W distance of 2.449(2) ?) so that the free ends of the [OOCCF(3)](-) ligands on both W(2) carboxylate units can cooperate in chelating two Na(+) ions thereby forming a dimer of W(2) complexes. A distinctive EPR spectrum with g = 2.08 is consistent with each W(2) carboxylate being a mixed-valent W(II)-W(III) species. The reaction of W(2)(OOCCF(3))(4) with (CO)(9)Co(3)CCOOH in THF in the absence of Na[OOCCF(3)] leads to the expected diamagnetic W(II)-W(II) cluster carboxylate W(2){OOCCCo(3)(CO)(9)}(3)(OOCCF(3))(THF)(2), 3.     

Electrochemistry, spectroelectrochemistry, chloride binding, and O2 catalytic reactions of free-base porphyrin-cobalt corrole dyads

Three face-to-face linked porphyrin-corrole dyads were investigated as to their electrochemistry, spectroelectrochemistry, and chloride-binding properties in dichloromethane or benzonitrile. The same three compounds were also investigated as to their ability to catalyze the electroreduction of dioxygen in aqueous 1 M HClO4 or HCl when adsorbed on a graphite electrode. The characterized compounds are represented as (PCY)H2Co, where P = a porphyrin dianion; C = a corrole trianion; and Y = a biphenylenyl, 9,9-dimethylxanthenyl, or anthracenyl spacer, which links the two macrocycles in a face-to-face arrangement. An axial binding of one or two Cl- ligands to the cobalt center of the corrole is observed for singly and doubly oxidized (PCY)H2Co, with the exact stoichiometry of the reaction depending upon the spacer size and the concentration of Cl- added to solution. No Cl- binding occurs for the neutral or reduced forms of the dyad, which contrasts with what is seen for the monocorrole, (Me4Ph5Cor)Co, where a single Cl- ligand is added to the Co(III) corrole in PhCN. The Co(III) form of the corrole in (PCY)H2Co also appears to be the catalytically active species in the electroreduction of dioxygen, which occurs at potentials associated with the Co(IV)/Co(III) reaction, that is, 0.35 V in 1 M HClO4 as compared to 0.31-0.42 V for the same three dyads in PhCN and 0.1 M TBAP. The potential for the catalytic electroreduction of O2 in HCl shifts negatively by 60 to 70 mV as compared to E(1/2) values in 1 M HClO4, consistent with the binding of Cl- to the Co(IV) form of the corrole and its rapid dissociation after electroreduction to Co(III) at the electrode surface.     

Synthesis, characterization, and reactivity of trans-[PtCl(R'R'SO)(A)2]NO3 (R'R'SO = Me2SO, MeBzSO, MePhSO; A= NH3, py, pic). Crystal structure of trans-[PtCl(Me2SO)(py)2]+

Trans complexes such as trans-[PtCl(2)(NH(3))(2)] have historically been considered therapeutically inactive. The use of planar ligands such as pyridine greatly enhances the cytotoxicity of the trans geometry. The complexes trans-[PtCl(R'R'SO)(A)(2)]NO(3) (R'R'SO = substituted sulfoxides such as dimethyl (Me(2)SO), methyl benzyl (MeBzSO), and methyl phenyl sulfoxide (MePhSO) and A = NH(3), pyridine (py) and 4-methylpyridine or picoline (pic)) were prepared for comparison of the chemical reactivity between ammine and pyridine ligands. The X-ray crystal structure determination for trans-[PtCl(Me(2)SO)(py)(2)]NO(3) confirmed the geometry with S-bound Me(2)SO. The crystals are orthorhombic, space group P2(1)2(1)2(1), with cell dimensions a = 7.888(2) A, b = 14.740(3) A, c =15.626(5) A, and Z = 4. The geometry around the platinum atom is square planar with l(Pt-Cl) = 2.304(4) A, l(Pt-S) = 2.218(5) A, and l(Pt-N) = 2.03(1) and 2.02(1) A. Bond angles are normal with Cl-Pt-S = 177.9(2) degrees, Cl-Pt-N(1) = 88.0(4) degrees, Cl-Pt-N(2) = 89.3(5) degrees, S-Pt-N(1) = 93.8(4) degrees, S-Pt-N(2) = 88.9(4) degrees, and N(1)-Pt-N(2) = 177.2(6) degrees. The intensity data were collected with Mo Kalpha radiation with lambda = 0.710 69 A. Refinement was by full-matrix least-squares methods to a final R value of 3.80%. Unlike trans-[PtCl(2)(NH(3))(2)], trans-[PtCl(2)(A)(2)] (A = py or pic) complexes do not react with Me(2)SO. The solvolytic products of cis-[PtCl(2)(A)(2)] (A = py or pic) were characterized. Studies of displacement of the sulfoxide by chloride were performed using HPLC. The sulfoxide was displaced faster for the pyridine complex relative to the ammine complex. Chemical studies comparing the reactivity of trans-[PtCl(R'R'SO)(amine)(2)]NO(3) with a model nucleotide, guanosine 5'-monophosphate (GMP), showed that the reaction gave two principal products: the species [Pt(R'R'SO)(amine)(2)(N7-GMP)], which reacts with a second equivalent of GMP, forming [Pt(amine)(2)(N7-GMP)(2)]. The reaction pathways were different, however, for the pyridine complexes in comparison to the NH(3) species, with sulfoxide displacement again being significantly faster for the pyridine case.     

Synthesis and characterization of iron(III)-substituted, dimeric polyoxotungstates, [Fe(4)(H(2)O)(10)(beta-XW(9)O(33))(2)](n-) (n = 6, X = As(III), Sb(III); n = 4, X = Se(IV), Te(IV))

Interaction of the lacunary [alpha-XW(9)O(33)](9-) (X = As(III), Sb(III)) with Fe(3+) ions in acidic, aqueous medium leads to the formation of dimeric polyoxoanions, [Fe(4)(H(2)O)(10)(beta-XW(9)O(33))(2)](6-) (X = As(III), Sb(III)) in high yield. X-ray single-crystal analyses were carried out on Na(6)[Fe(4)(H(2)O)(10)(beta-AsW(9)O(33))(2)] x 32H(2)O, which crystallizes in the monoclinic system, space group C2/m, with a = 20.2493(18) A, b = 15.2678(13) A, c = 16.0689(14) A, beta = 95.766(2) degrees, and Z = 2; Na(6)[Fe(4)(H(2)O)(10)(beta-SbW(9)O(33))(2)] x 32H(2)O is isomorphous with a = 20.1542(18) A, b = 15.2204(13) A, c = 16.1469(14) A, and beta = 95.795(2) degrees. The selenium and tellurium analogues are also reported, [Fe(4)(H(2)O)(10)(beta-XW(9)O(33))(2)](4-) (X = Se(IV), Te(IV)). They are synthesized from sodium tungstate and a source of the heteroatom as precursors. X-ray single-crystal analysis was carried out on Cs(4)[Fe(4)(H(2)O)(10)(beta-SeW(9)O(33))(2)] x 21H(2)O, which crystallizes in the triclinic system, space group P macro 1, with a = 12.6648(10) A, b = 12.8247(10) A, c = 16.1588(13) A, alpha = 75.6540(10) degrees, beta = 87.9550(10) degrees, gamma = 64.3610(10) gamma, and Z = 1. All title polyanions consist of two (beta-XW(9)O(33)) units joined by a central pair and a peripheral pair of Fe(3+) ions leading to a structure with idealized C(2h) symmetry. It was also possible to synthesize the Cr(III) derivatives [Cr(4)(H(2)O)(10)(beta-XW(9)O(33))(2)](6-) (X = As(III), Sb(III)), the tungstoselenates(IV) [M(4)(H(2)O)(10)(beta-SeW(9)O(33))(2)]((16)(-)(4n)-) (M(n+) = Cr(3+), Mn(2+), Co(2+), Ni(2+), Zn(2+), Cd(2+), and Hg(2+)), and the tungstotellurates(IV) [M(4)(H(2)O)(10)(beta-TeW(9)O(33))(2)]((16-4n)-) (M(n+) = Cr(3+), Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), and Hg(2+)), as determined by FTIR. The electrochemical properties of the iron-containing species were also studied. Cyclic voltammetry and controlled potential coulometry aided in distinguishing between Fe(3+) and W(6+) waves. By variation of pH and scan rate, it was possible to observe the stepwise reduction of the Fe(3+) centers.     

The satellite-shaped Co-15 Polyoxotungstate, [Co6(H2O)30{Co9Cl2(OH)3(H2O)9(beta-SiW8O31)3}]5-

The 15-cobalt-substituted polyoxotungstate [Co(6)(H(2)O)(30){Co(9)Cl(2)(OH)(3)(H(2)O)(9)(beta-SiW(8)O(31))(3)}](5-) (1) has been characterized by single-crystal XRD, elemental analysis, IR, electrochemistry, magnetic measurements, and EPR. Single-crystal X-ray analysis was carried out on Na(5)[Co(6)(H(2)O)(30){Co(9)Cl(2)(OH)(3)(H(2)O)(9)(beta-SiW(8)O(31))(3)}].37H(2)O, which crystallizes in the hexagonal system, space group P6(3)/m, with a = 19.8754(17) A, b = 19.8754(17) A, c = 22.344(4) A, alpha= 90 degrees, beta = 90 degrees, gamma = 120 degrees, and Z = 2. The trimeric polyanion 1 has a core of nine Co(II) ions encapsulated by three unprecedented (beta-SiW(8)O(31)) fragments and two Cl(-) ligands. This central assembly {Co(9)Cl(2)(OH)(3)(H(2)O)(9)(beta-SiW(8)O(31))(3)}(17-) is surrounded by six antenna-like Co(II)(H(2)O)(5) groups resulting in the satellite-like structure 1. Synthesis of 1 is accomplished in a simple one-pot procedure by interaction of Co(II) ions with [gamma-SiW(10)O(36)](8-) in aqueous, acidic NaCl medium (pH 5.4). Polyanion 1 was studied by cyclic voltammetry as a function of pH. The current intensity of its Co(II) centers was compared with that of free Co(II) in solution. Our results suggest that 1 keeps its integrity in solution. Magnetic susceptibility results show the presence of both antiferro- and ferromagnetic coupling within the (Co(II))(9) core. A fully anisotropic Ising model has been employed to describe the exchange-coupling and yields g = 2.42 +/- 0.01, J(1) = 17.0 +/- 1.5 cm(-1), and J(2) = -13 +/- 1 cm(-(1). Variable frequency EPR studies reveal an anisotropic Kramer's doublet.     

Orientation and Restricted Rotation of Lopsided Aromatic Ligands. Octahedral Complexes Derived from cis-RuCl(2)(Me(2)SO)(4)

The solution and solid state structures of two octahedral Ru(II) complexes, cis,cis,cis-RuCl(2)(Me(2)SO)(2)(py)(Me(3)Bzm) (Me(3)Bzm = 1,5,6-trimethylbenzimidazole, py = pyridine) (1) and cis,cis,cis-RuCl(2)(Me(2)SO)(2)(Me(3)Bzm)(2) (2), were compared. 2, the subject of a preliminary report, is described in more detail here. 1 has two possible geometric isomers with py trans to Cl in one (position "a") and trans to Me(2)SO in the other (position "b"), Me(3)Bzm occupying the other position in each isomer. The X-ray structure of 1 revealed that py is at "a". Since Me(3)Bzm is lopsided, each Me(3)Bzm has two possible orientations related by a rotation of approximately 180 degrees about the Ru-N3 bond; there are two possible atropisomers for each geometric isomer of 1 and four for 2. For 1, the solid state structure shows that Me(3)Bzm adopts the orientation with H2 (H on C between the two N's) pointing between the two cis Cl ligands, the same disposition as Me(3)Bzm "b" in 2 in the solid. For 1, the py signals (two broad py alpha and beta signals, a sharp gamma signal) in CDCl(3) show that py "a" is rotating on the NMR time scale and that only one atropisomer is present. This interpretation was supported by ROESY and EXSY (1)H NMR spectra. The (1)H NMR shift pattern and the NOE data can be understood best if Me(3)Bzm "b" remains primarily in the orientation found in the solid. The solution data for 1, with the nonlopsided and sterically less demanding py ligand, provide insight into the more complicated properties of 2. For 2, there is a marked dispersion of (1)H NMR signals of Me(3)Bzm "a" between the two atropisomers, which have nearly equal stability. One atropisomer is a head-to-head (HH) and the other a head-to-tail (HT) species. Me(3)Bzm "a" flips between the two species. Thus, ligand "a" is fluxional in both complexes. The dispersion of Me(3)Bzm "a" signals is due to the effect of Me(3)Bzm "b" anisotropy. For 1 and both atropisomers of 2, Me(3)Bzm "b" prefers one orientation, which appears to be the most hindered orientation. We postulate that the H2 of Me(3)Bzm "b" is electrostatically attracted to the two cis halides, accounting for this surprising result. Crystallographic details for 1 are as follows: C(19)H(29)Cl(2)N(3)O(2)RuS(2), P2(1)/c, a = 10.947(1) ?, b = 9.046(1) ?, c = 24.221(2) ?, D(calcd) = 1.580 g cm(-)(3), Z = 4, R = 0.026 for 4627 independent reflections.     

Chemistry of cobalt acetate. 7. Electrochemical oxidation of mu3-oxo-centered cobalt(III) acetate trimers

Electrochemical and spectroelectrochemical properties of five cobalt(III) acetate complexes [CoIII3(mu3-O)(CH3CO2)5(OR)(py)3][PF6] are described, where py=pyridine and R=OCCH3 (A), H (B), CH3 (C), CH2CH=CH2 (D), and CH2C6H5 (E). Each is reduced irreversibly as observed by cyclic voltammetry at room temperature and at -40 degrees C in acetonitrile at scan rates up to 20 V s(-1), but oxidized reversibly to a mixed-valence Co(III)2Co(IV) species at approximately 1.23 V vs the ferrocenium/ferrocene couple. Controlled potential coulometry confirmed a one-electron-oxidation process. Spectroelectrochemical oxidation of A at 5 degrees C showed isosbestic points in the electronic absorption spectrum that showed the oxidized complex to be stable in solution for at least 1 h.     

Reactions and reactivity of Co-bpdc coordination polymers (bpdc = 4,4'-biphenyldicarboxylate)

By choosing a suitable metal center, ligand, and solvents, we have revealed several structural transformations involving a polymer precursor. infinity 1[Co(bpdc)(H2O)2].H2O (1) was prepared by reaction of Na2bpdc and Co(NO3)2 in aqueous solution. Immersing 1 in pyridine/water solutions of (2:1) and (8:1) ratios yielded a second one-dimensional structure infinity 1[Co(bpdc)(py)2(H2O)2].2py (2) and a two-dimensional structure infinity 2[Co(bpdc)(py)2].H2O (3), respectively. After heating 1 under N2 to remove all water within the structure, the compound Co(bpdc) (IR) was obtained. When IR was immersed in solutions of pyridine/water (5:4) and in pure pyridine (in air), a third one-dimensional structure of infinity 1[Co(bpdc)(py)2(H2O)2].2py.H2O (4) and 3, respectively, were obtained. Compounds 2-4 easily transformed to 1 when immersed in water. Crystal data for 1: monoclinic, space group C2/c with a = 6.950(1), b = 31.585(6), and c = 6.226(1) A, beta = 95.84(3) degrees, Z = 4. Crystal data for 2: triclinic, space group P1 with a = 9.646(2), b = 10.352(2), and c = 17.031(3) A, alpha = 79.02(3) degrees, beta = 86.88(3) degrees, gamma = 77.16(3) degrees, Z = 2. Crystal data for 3: triclinic, space group P1 with a = 9.137(2), b = 10.480(2), and c = 12.254(2) A, alpha = 102.10(3) degrees, beta = 100.80(3) degrees, gamma = 99.43(3) degrees, Z = 2. Crystal data for 4: orthorhombic, space group Pbcn with a = 13.468(3), b = 16.652 (3), and c = 14.977(3) A, Z = 4.