Aderemi R. Oki

Manganese(II) complex of the ‘tripod’ ligand tris(2-benzimidazolylmethyl)amine. Five-coordinate and six-coordinate Mn(II) in the crystal structure

Abstract From the reaction of manganese dichloride with tris(2-benzimidazolylmethyl)amine (L) in ethanol, golden yellow crystals of compound 1 were obtained upon slow evaporation of the solvent. The structural assignments of 1 that were made in part by elemental analysis and FAB mass spectroscopy were confirmed by single crystal X-ray diffraction studies. The crystal structure reveals that compound 1 crystallizes in the triclinic space group P 1 with two independent molecules in a cell of dimensions a = 13.805(4), b = 14.185(4), c = 18.176(5) A , α = 81.23(2), β = 70.32(2), γ = 61.45(2)° . The structure has been refined to an R factor of 0.060 based on 4822 observed reflections. Two independent manganese containing molecules were found in the unit cell. Molecule 1a is cis-dichloro(tris(2-benzimidazolylmethyl)amine)manganese(II), with a distorted octahedral geometry. The ClMnCl bond angle in the molecule is 96.8(1)° showing a severe steric constraint imposed by the ligand which may lead to the elongation of the fifth and the sixth axial bond lengths, (Mn(1)Cl(1) and Mn(1)N(1) bond lengths of 2.538(2) and 2.515(7) A, respectively). The other molecule in the unit cell is a chloro(tris(2-benzimidazolylmethyl)-amine)manganese(II) cation (1b), in which the geometry around the manganese atom could best be described as a distorted trigonal bipyramid. The trigonal plane is occupied by the ligating nitrogen atoms from the benzimidazolyl functions with bond lengths of 2.135(8), 2.145(6) and 2.147(4) A. The axial positions are occupied by the ligating sp3 nitrogen and chlorine atoms with bond lengths of 2.514(6) and 2.316(2) A, respectively. This Mn(II) complex shows a remarkable resistance toward oxidation to higher metal oxidation states even with 30% hydrogen peroxide.

Synthesis and Characterization of a C-Functionalized Chelating Carboranyl Ligand and Its Chromium(III) Complex

Abstract The reaction of l,2-dicarba-o-carborane with two equivalents of t-butyllihum in THF followed by the addition of 2chloromethylpyndinc produced 1-(-CH2C5H4N)-1,2-C2B10H11, (1), in 65% yield. Cage degradation of (1) using potassium hydroxide in 95% ethanol followed by the addition of cesium iodide produced [7-(CH2C5H4N)-7,8- C2R9H11],Cs∗. (2). Reaction of compound (2) with NaH, followed by 1 equiv. of anhydrous chromium(III) chloride afforded the chromacarborane [7-(CH2C5H4N)-7,8-C2B9H10CrCI], (3). Compound (3) was characterized by elemental analyses, IR and mass spectra. Compounds (1) and (2) were characterized by elemental analyses, IR, and NMR. In addition, compound (1) was also characterized by single crystal X-ray diffraction.

SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF BIS[3,5-DIMETHYLPYRAZOLE (1-METHOXY,3,5-DIMETHYL PYRAZOLE) COPPER(II) PERCHLORATE]

Abstract The reaction of anhydrous copper nitrate with 1-hydroxy-methyl-3,5-dimethyl pyrazole in the presence of 3,5-dimethyl pyrazole in methanol gave a deep green colored solution, which upon addition of excess sodium perchlorate afforded dark green crystals of bis[3,5-dimethylpyrazole(1-methoxy,3,5-dimethyl pyrazole) Cu(II) perchlorate] (1) upon slow evaporation of the solvent. The structural assignment of (1) was made in part by elemental analysis and electronic spectroscopy and was confirmed by single crystal X-ray diffraction studies. The crystal structure reveals that compound (1) crystallizes in the monoclinic space group P21 In with four molecules in the unit cell of dimensions a = 8.927(3), b = 19.019(9), and c = 9.794(3)A, and β = 112.65(3)∗. The structure has been refined to an R(F) factor of 0.029 based on 2110 observed reflections. The geometry around each Cu(II) center is best described as a square pyramid, with the basal plane occupied by two ligating nitrogen atoms with an average Cu-N di...

The first discrete half-sandwich samaracarborane of a C2B4-carborane ligand system

Abstract The reaction between THF-solvated dilithiacarborane, closo-exo-4,5-Li(THF)2-1-Li(THF)2-2,3-(SiMe3)2C2B4H4, and anhydrous SmCl3 in 1:1 stoichiometry in dry benzene at 0°C, followed by extraction and crystallization of the product from a solution containing 80% dry n-hexane, 10% dry tert-butanol and 10% dry THF resulted in the isolation of pale-yellow crystals of {1,1-(t-C4H9OH)2-1-(t-C4H9O)-2,3-(SiMe3)2-4,5-[Li(THF)Cl]-closo-η5-1-Sm-2,3-C2B4H4}·THF (2) in 78% yield.

Manganese(II) complex of the ‘tripod’ ligand tris(2-benzimidazolylmethyl)amine. Seven-coordinate Mn(II) in the crystal structure

Abstract Mn(II) coordination compounds with tripodal N,N,N-tris-(2-benzimidazolylmethyl)amine (TMBA) have been synthesized and spectroscopically characterized. The crystal structure of [Mn(TMBA)(NO3)(CH3OH)](NO3)H2O has been determined. The compound crystallizes in the monoclinic space group P21/c with four formula units in a cell of dimensions a = 11.3825(2), b = 13.4338(2), c = 17.9548(3) A , β = 100.026(1)° ; final R = 0.0299, based on 4745 independent reflections. The structure indicates the complex ion has a heptacoordinate metal center with a coordination polyhedron best described as a capped octahedron. The octahedron is defined by three nitrogen atoms from the benzimidazole moieties (N(1A), N(1C) and N(1B)), the oxygen atom of the methanol O(41), and two oxygen atoms from the coordinating nitrate group O(11) and O(12). The capping ligating atom is the bridging N(1) from the TMBA ligand with a longer MnN distance of 2.551(1) A.

SYNTHESIS AND CHARACTERIZATION OF A LINEAR μ-OXO DIIRON(III) COMPOUND AND A COPPER(II) NITRITE COMPLEX CONTAINING, A TRIPODAL POLYBENZIMIDAZOLE LIGAND

Abstract Iron(III) and copper(II) complexes of the polybenzimidazole ligand, tris((benzimidazol-2-yl)methyl)amine (tmba) have been synthesized and structurally characterized. The mononuclear complex [Cu(tmba)(NO2)]+[CH3OH][NO− 2], 1, has been isolated and characterized by X-ray crystallography. The complex crystallizes in the triclinic space group P1 with two molecules in the unit cell of dimension a = 8.891(5), b = 11.775(6), and c = 13.702(8)Å, and α = 67.76(1), β = 71.79(2) and γ = 88.96(1)°, and volume = 1253.0(12)Å3. The structure was refined to a final agreement factor R = 0.0901 using 4134 observed reflections. The complex consists of cationic copper(tmba) complex covalently bonded to a nitrite, and a pair of these cations is dibridged by a pair of nitrite anions. The gap between this dimer is occupied by a methanol molecule. The coordination environment around each copper can be described as trigonal bipyramidal, with the tertiary amine, a benzimidazole nitrogen and an oxygen from the nitrite providing the ligating atoms of the trigonal plane. The μ-oxo bridged binuclear complex [Fe2O(tmba)2Cl2](H2O)(EtOH)2·Cl2, 2, was also characterized by single crystal X-ray diffraction and magnetic susceptibility. The complex crystallizes in the triclinic space group P1 with one molecule in the unit cell of dimensions, a = 11.5791(7), b = 13.3369(8), and c = 13.7002(9) Å, and α = 103.904(1), β = 108.903(2) and γ = 112.845(1)°, and volume = 1674.1(2) å3. The structure was refined to a final agreement factor R = 0.073 using 5597 observed reflections. The complex is a centrosymmetric dimer, with the two iron(III) atoms bridged by an oxygen atom, with an Fe—O—Fe angle of 180°, and a Fe—Fe distance of 3.61(1)Å. The coordination around each iron(III) is best described as octahedral, with the bridging oxygen trans to one end of the benzimidazole group, and a chlorine atom trans to the tertiary amine nitrogen of the ligand.

HIGH-SPIN FOUR AND SIX-COORDINATE COBALT(II) COMPLEXES WITH 3,5-DIMETHYL PYRAZOLE

Abstract The reaction of cobalt dichloride hexahydrate with two equivalents of 3,5-dimethyl pyrazole under reflux in THF gave a deep blue solution of Co(3,5-dimethylpyrazole) dichloride. Suitable crystals for X-ray structural determination were grown in THF. The structural assignment of (1) was made by elemental analysis and electronic spectroscopy and confirmed by single crystal X-ray diffraction studies. The crystal structure reveals that compound (1) crystallizes in the monoclinic space group C2/c with eight molecules in the unit cell of dimensions a = 15.012(2), b = 8.275(1), and c = 24.047(2)A, and β = 96.05 (1)°. The structure has been refined to an R(F) factor of 0.045 based on 1670 observed reflections. The geometry around the Co(II) center is best described as tetrahedral. The four ligating atoms consist of two chlorine atoms and two nitrogen atoms from the 3,5-dimethyl pyrazole. The solution electronic spectra of (1) in acetone and THF are consistent with the solid state crystal structure. Howev...

Sandwiched Metallacarboranes of f-Block Elements

Abstract The dilithium complexed “carbons adjacent” nido-carborane anions of the type [2-(SiMe3)-3-(R)-2,3-C2B4H4]2- [R = SiMe3, Me, H], as well as the disodium and dilithium complexed “carbons apart” nido-carborane anions [2-(SiMe3)-4-(R)-2,4-C2B4H4]2- [R = SiMe3, Me] have exhibited different reactivity patterns toward various lanthanide halides, depending upon the solvents used in the reactions and the nature of the group 1 metal. Both the tetrahydofuran (THF) and N,N,N,N-tetramethylethylenediamine (TMEDA)-solvated closo-dilithiacarboranes have been found to be important synthons in the production of novel metallacarboranes of f-block elements. Several unprecedented examples of lanthanide-carborane complexes have been synthesized, their structures determined and reactivity studied.

Synthesis and crystal structure of a neutral open framework cobalt(II) phosphate Co6(PO4)4·7H2O with a channel structure

Using tri-ethyl phosphate as a phosphate source, the hydrothermal reaction of cobalt(II) oxalate di-hydrate, zinc oxide and 1,8 di-amino octane at 200°C gave purple crystals of Co6(PO4)4 · 7H2O (1), along with a mixture of open-framework zinc–cobalt phosphates Co–Zn–HPO4, and Co3(HPO4)2(2OH). Compound 1, has been characterized by thermal analysis, FTIR and single crystal X-ray diffraction. The single crystal structure of Co6(PO4)4 · 7H2O reveals cobalt in four, five and six-fold coordination with linkages through the bridging water molecules and the oxygen atoms of the phosphate in the subunits. Four subunits are connected together through the oxygen atoms (PO4), to form the three dimensional open framework structure, with a 20-member ring channel that hosts two uncoordinated water molecules. Thermal removal of the water molecules occurs between 400–600°C, with the collapse of the structure above 600°C.

A novel cesium–carborane cluster: synthesis and structure of [Cs 5 –(C 2 B 9 H 12 ) 4 Cl] n

Abstract The cage degradation reaction of closo 1,2-C2B10H12 carborane in the presence of 2-chloromethyl-4-nitro-phenol in alcoholic potassium hydroxide, followed by the addition of excess cesium chloride, produced a novel cesium carborane cluster, [Cs5–(C2B9H12)4Cl]n, 1. The compound crystallizes in the tetragonal space group I-4 with a=16.817(1) A, b=16.817(1) A, c=7.601(1) A, V=2149.6(3) A 3 , Z=8 and calculated density of 1.906 Mg/m3. The final refinement converged at R=0.018, based on 1142 unique reflections. There are two distinguishable type of cesium ions, Cs(1) is surrounded by four carborane cages and two Cl(1) ion, and Cs(2) is surrounded by five carborane cages and one Cl(1). The Cl occupies the center of a slightly distorted octahedral site Cs6Cl, with two Cl(1)–Cs(1) average distance of 3.84 A and four Cl(1)–Cs(2) average distance of 3.64 A. Each unit is then linked to another through a Cs(1)–Cl–Cs(1)–Cl repeating unit forming a polymeric chain.