Robert T. Stibrany

Synthesis, structure, and spectroscopic properties of (nitrito-O,O′)[tris[2-(1-methyl)imidazolyl]methoxymethane]copper(II), Cu(II)(TIMM)(NO2)21

The nitrito-O,O′ complex, Cu(II)(TIMM)(NO2)2, (1) has been characterized by X-ray crystallography, UV-vis, IR, and EPR spectroscopy. CuC14H18N8O5 crystallizes in the monoclinic space group P21/n, with a = 7.7068(6), b = 17.933(1), c = 13.615(1) A, β = 95.334(8)° and Z = 4. The structure was refined to an R value of 0.031 based upon 2150 observed reflections. The distorted tetragonal N2O4 coordination is supplied by two TIMM imidazole groups and two anisobidentate nitrito-O,O′ groups, resulting in a dx2-y2 ground state for the Cu(II). Methanolic 1 exhibits an electronic absorption at 352 nm (shoulder, e &2∼ 900) assigned as the lowest energy nitrite → Cu(II) CT absorption (it obscures the weak (ϵ ∼ 30) lowest energy localized nitrite absorption at ∼ 360 nm). The nitrite → Cu(II) CT absorption appears as a shoulder (∼405 nm) in the mineral oil mull spectra of polycrystalline 1. The relationship between the observed bond distances and nitrite stretching frequencies is discussed.

Complexes exhibiting non-conventional solubility: synthesis and characterization of trans-Pt[(CF3(CF2)5(CH2)2)3P]2Cl2 ☆

Abstract Synthetic approaches have been developed for preparing fluorocarbon solvent and liquid and supercritical CO 2 (sc CO 2 ) soluble organometallic complexes. To explore solubility in these media, the synthesis of a number of organometallic complexes containing the phosphine ligand (CF 3 (CF 2 ) 5 (CH 2 ) 2 ) 3 P 2 , is reported. The platinum(II) complex, trans -Pt[(CF 3 (CF 2 ) 5 (CH 2 ) 2 ) 3 P] 2 Cl 2 1 , has been synthesized, isolated, and characterized by X-ray crystallography and 31 P-NMR spectroscopy. Complex 1 , PtC 48 H 24 Cl 2 F 78 P 2 crystallizes in the triclinic space group P 1 , with a =11.632(2), b =16.970(2), c =20.838(3) A; α =71.67(1), β =80.22(2), γ =88.18(2)°; Z =2, and R F ( R WF 2 )=0.0789 (0.108) for 8095 reflections. The Pt coordination is trans square planar with the long fluoroalkyl chains of the (CF 3 (CF 2 ) 5 (CH 2 ) 2 ) 3 P ligands being nearly perpendicular to the coordination plane.

Dimethyl(2-methylphenyl)ammonium hydroxotris(pentafluorophenyl)borate.

In the title compound, [(CH(3))(2)(C(7)H(7))NH][(C(6)F(5))(3)B(OH)] or C(9)H(14)N(+).C(18)HBF(15)O(-), the distorted tetrahedral borate anions are strongly hydrogen bonded to the substituted ammonium cations. The N.O separation in the N-H.O hydrogen bond is 2.728 (3) A.

Isostructural trigonal-bipyramidal CuII and nominally 1% CuII-doped ZnII complexes with N5 ligation.

[Cu(C6H18N4)(C10H10N2)](ClO4)2, (1-benzylimidazole)[N,N-bis(2-aminoethyl)-1,2-ethanediamine]copper(II) diperchlorate (1), M(r) = 566.88, monoclinic, P2(1)/c, a = 10.549 (1), b = 9.2465 (9), c = 25.256 (2) A, beta = 101.42 (1) degrees, V = 2415 (1) A3, Z = 4, Dm = 1.54 (1), Dx = 1.559 Mg m-3, lambda (Mo K alpha) = 0.71073 A, mu = 1.18 mm-1, F(000) = 1172, T = 296 (1) K, R = 0.048, wR = 0.069 for 3063 reflections. [Zn0.99Cu0.01(C6H18N4)(C10H10N2)](ClO4)2, 1% CuII-doped (1-benzylimidazole)[N,N-bis(2-aminoethyl)-1,2-ethanediamine]zinc(II) diperchlorate (2), M(r) = 568.72, monoclinic, P2(1)/c, a = 10.708 (1), b = 9.229 (2), c = 25.205 (2) A, beta = 101.867 (8) degrees, V = 2438 (1) A3, Z = 4, Dm = 1.54 (1), Dx = 1.549, lambda (Mo K alpha) = 0.71073 A, mu = 1.30 mm-1, F(000) = 1176, T = 295 (1) K, R = 0.041, wR = 0.055 for 3282 reflections. The isostructural distorted trigonalbipyramidal MN5 cations are separated by perchlorate anions. Equatorial M--N distances are similar in both cations [range 2.083 (3) to 2.105 (3) A for (1); 2.073 (3) to 2.084 (3) A for (2)]. In contrast, the axial M--N distances differ substantially [2.043 (3) and 1.971 (3) A for (1); 2.255 (4) and 2.054 (3) A for (2)]. Axial contraction in the copper complex (1) is consistent with a dz2 ground state.

Structures of 1-hydrophenanthroimidazoles: building blocks in the synthesis of expanded-ring bis(imidazoles).

The structures of 1H-phenanthro[9,10-d]imidazole, C15H10N2, (I), and 3,6-dibromo-1H-phenanthro[9,10-d]imidazole hemihydrate, C15H8Br2N(2).0.5H2O, (II), contain hydrogen-bonded polymeric chains linked by columns of pi-pi stacked essentially planar phenanthroimidazole monomers. In the structure of (I), the asymmetric unit consists of two independent molecules, denoted (Ia) and (Ib), of 1H-phenanthro[9,10-d]imidazole. Alternating molecules of (Ia) and (Ib), canted by 79.07 (3) degrees, form hydrogen-bonded zigzag polymer chains along the a-cell direction. The chains are linked by pi-pi stacking of molecules of (Ia) and (Ib) along the b-cell direction. In the structure of (II), the asymmetric unit consists of two independent molecules of 3,6-dibromo-1H-phenanthro[9,10-d]imidazole, denoted (IIa) and (IIb), along with a molecule of water. Alternating molecules of (IIa), (IIb) and water form hydrogen-bonded polymer chains along the [110] direction. The donor-acceptor distances in these N(imine)...H-O(water)...H-N(amine) hydrogen bonds are the shortest thus far reported for imidazole amine and imine hydrogen-bond interactions with water. Centrosymmetrically related molecules of (IIa) and (IIb) alternate in columns along the a-cell direction and are canted by 48.27 (3) degrees. The present study provides the first examples of structurally characterized 1H-phenanthroimidazoles.

An alternating copolymer containing trigonal planar homocoordinated copper(I) ions: catena-poly[[[bis­[μ-(E)-1,2-bis­(1-ethyl-1H-benzimidazol-2-yl)ethene-κ2N3:N3′]dicopper(I)]-μ-(E)-1,2-bis­(1-ethyl-1H-benzimidazol-2-yl)ethene-κ2N3:N3′] bis­(perchlorate) acetonitrile disolvate]

The structure of the title salt, {[Cu(2)(C(20)H(20)N(4))(3)](ClO(4))(2) x 2 CH(3)CN}(n), consists of linear [Cu(I)(2)L(3)] polymer chains [L is (E)-1,2-bis(1-ethyl-1H-benzimidazol-2-yl)ethene], which extend along the c cell direction, interspersed with disordered perchlorate ions and acetonitrile solvent molecules. In a given chain, each Cu(I) ion exhibits distorted trigonal planar coordination to three L ligands; two of these are linked to adjacent Cu(I) ions to form dimeric units containing 14-membered rings that adopt a twisted-loop configuration, stabilized by pi-pi interactions between the ethene fragments of the two ligands. The dimeric units exhibit diad symmetry (twofold axis sites in I2/a) and are linked by a third, centrosymmetric, S-shaped L ligand (inversion centers in I2/a) to form the copolymer chain. When viewed along the b cell direction, the 14-membered rings appear as vacant ellipses that form channels parallel to the b axis. The walls of the channels are formed by the benzimidazole fragments of the dimeric units. This study of a novel alternating copolymer containing homocoordinated Cu(I) ions demonstrates further the usefulness of bis(benzimidazoles) as versatile bidentate ligands.

Three structures containing (E)-1,2-bis(benzimidazol-2-yl)ethene groups.

Two of the title compounds, namely (E)-1,2-bis(1-methylbenzimidazol-2-yl)ethene, C18H16N4, (Ib), and (E)-1,2-bis(1-ethylbenzimidazol-2-yl)ethene, C20H20N4, (Ic), consist of centrosymmetric trans-bis(1-alkylbenzimidazol-2-yl)ethene molecules, while 3-ethyl-2-[(E)-2-(1-ethylbenzimidazol-2-yl)ethenyl]benzimidazol-1-ium perchlorate, C20H21N4+.ClO4-, (II), contains the monoprotonated analogue of compound (Ic). In the three structures, the benzimidazole and benzimidazolium moieties are essentially planar; the geometric parameters for the ethene linkages and their bonds to the aromatic groups are consistent with double and single bonds, respectively, implying little, if any, conjugation of the central C=C bonds with the nitrogen-containing rings. The C-N bond lengths in the N=C-N part of the benzimidazole groups differ and are consistent with localized imine C=N and amine C-N linkages in (Ib) and (Ic); in contrast, the corresponding distances in the benzimidazolium cation are equal in (II), consistent with electron delocalization resulting from protonation of the amine N atom. Crystals of (Ib) and (Ic) contain columns of parallel molecules, which are linked by edge-over-edge C-H...pi overlap. The columns are linked to one another by C-H...pi interactions and, in the case of (Ib), C-H...N hydrogen bonds. Crystals of (II) contain layers of monocations linked by pi-pi interactions and separated by both perchlorate anions and the protruding ethyl groups; the cations and anions are linked by N-H...O hydrogen bonds.

Bioinspired Catalysis: Hydroperoxidation of Alkylaromatics

Upgrading the value of raw materials by the selective conversion of organic molecules to oxygenated derivatives using air as an oxidant represents a worthy goal and challenge. Industrially, oxygenates are prepared at a rate of 109 to 1010 lbs/year, mostly using high temperature (above 100°C) processes.1 Since, in general, the oxygenated products are more reactive then the starting hydrocarbons, secondary reactions which lower the selectivity occur.

{Bis[5-methyl-3-(trifluoro­meth­yl)pyrazol-1-yl]borato}{tris­[5-methyl-3-(trifluoro­meth­yl)pyrazol-1-yl]borato}cobalt(II): a structure containing a B—H⋯Co agostic inter­action

The title compound, [Co(C10H10BF6N4)(C15H13BF9N6)], is a neutral CoII complex which contains one each of the anionic ligands, bis(3-trifluoromethyl-5-methylpyrazol-1-yl)borate (Bp) and tris(3-trifluoromethyl-5-methylpyrazol-1-yl)borate (Tp). A distorted octahedral coordination geometry results from ligation of an H atom, which is part of an agostic B—H⋯Co interaction (H⋯Co = 2.17 Å), and by five imine N atoms, two from a Bp ligand and three from a Tp ligand. In the crystal, molecules form layers parallel to the (10) planes, and the layers are linked along the a axis by C—H⋯F hydrogen bonds. An intramolecular C—H⋯F interaction also occurs.

Solid-State Changes in Ligand-to-Metal Charge-Transfer Spectra of (NH3)5RuIII(2,4-dihydroxybenzoate) and (NH3)5RuIII(xanthine) Chromophores

Five distorted-octahedral complexes containing (NH3)5Ru(III)L ions, where L = 2,4-dihydroxybenzoate or a xanthine, have been studied using a combination of X-ray crystallography, solution and polarized single-crystal electronic absorption spectroscopy, and first principles electronic structure computational techniques. Both yellow (2) and red (3) forms of the complex (NH3)5Ru(III)L, where L = 2,4-dihydroxybenzoate, as well as three xanthine complexes in which L = hypoxanthine-kappaN(7) (4), 7-methylhypoxanthine-kappaN(9) (5), and 1,3,9-trimethylxanthine-kappaN(7) (6) were examined. In the solid state, some of these complexes exhibit split low-energy ligand-to-metal charge-transfer (LMCT) bands. Traditional solid-state effects, such as ligand pi-pi overlap or hydrogen bonding that might lead to splitting of electronic absorption bands, were probed in an attempt to identify the origins of these unusual observations. For comparison, companion studies were carried out for spectroscopically normal reference complexes of the same ligands. Time-dependent density-functional theory (TD-DFT) calculations, employing modified B3LYP-type functionals with increased contributions of exact exchange, attribute the color change in the crystalline complexes 2 and 3 to pi(ligand) --> Ru[d(pi)] LMCT bands which, in the red form (3), arise from ligand donor pi-orbitals split by strongly overlapping phenyl moieties in centrosymmetric (NH3)5Ru(III)(2,4-dihydroxybenzoate) dimers. Complex 5 does not show split visible absorptions, whereas both the polarizations and energies of the split visible absorptions shown by 4 and 6 also suggest assignment as LMCT. No support is found for relating the split absorptions of 4 and 6 to the details of pi-pi xanthine overlap in the solid state; indeed, complex 4 enjoys considerably less pi-stacking overlap than does 5. We feel compelled to attribute the split absorptions in crystalline 4 and 6 to the emergence of a LMCT transition originating in the carbonyl lone pair, potentially deriving intensity from the significant intramolecular N-H...O hydrogen bonding present in both 4 and 6 (but not in 5). The electronic structure calculations suggest an O(n) --> Ru[d(sigma*)] LMCT transition; however, this novel assignment must be considered tentative.