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B O Patrick

Publications and source records attributed to B O Patrick.

12 recordsLinked to original sources
PubMed2001

Gold-gold interactions as crystal engineering design elements in heterobimetallic coordination polymers.

A series of coordination polymers containing Cu(II) and [Au(CN)(2)](-) units has been prepared. Most of their structures incorporate attractive gold-gold interactions, thus illustrating that such "aurophilic" interactions can be powerful tools for increasing structural dimensionality in supramolecular systems. [Cu(tren)Au(CN)(2)][Au(CN)(2)] (1, tren = tris(2-ethylamino)amine) forms a cation/anion pair, which is weakly linked by hydrogen bonds but not by aurophilic interactions. [Cu(en)(2)Au(CN)(2)][Au(CN)(2)] (2-Au, en = ethylenediamine) is a 2-D system composed of a chain of [Au(CN)(2)](-) anions and another chain of [(en)(2)Cu-NCAuCN](+) cations; short Au-Au bonds of 3.1405(2) A connect the anions. This bond is shorter than that observed in the analogous silver(I) structure, 2-Ag. The average M-C bond lengths of 1.984(8) A in 2-Au are significantly shorter than those found in 2-Ag, suggesting that Au(I) is smaller than Ag(I). Cu(dien)[Au(CN)(2)](2) (3, dien = diethylenetriamine) forms a 1-D chain of tetranuclear [Au(CN)(2)](-) units that are bound to [Cu(dien)] centers. Aurophilic interactions of ca. 3.35 A hold the tetramer together. Cu(tmeda)[Au(CN)(2)](2) (4, tmeda = N,N,N',N'-tetramethylethylenediamine) forms a 3-D network by virtue of aurophilic interactions of 3.3450(10) and 3.5378(8) A. Altering the Cu:Au stoichiometry yields Cu(tmeda)[Au(CN)(2)](1.5)(ClO(4))(0.5) (5), which has an unusual 2-D rhombohedral layer structure (space group R32). Complex 5 is composed of three mutually interpenetrating Cu[Au(CN)(2)](1.5) networks which are interconnected by aurophilic interactions of 3.4018(7) and 3.5949(8) A. Weak antiferromagnetic coupling is observed in 2 and 5.

Journal Article↗
PubMed2001

Electropolymerization of Pd(II) complexes containing phosphinoterthiophene ligands.

A series of Pd complexes of 3'-diphenylphosphino-2,2':5'2' '-terthiophene (1a, dppterth) in which the metal is coordinated in three different modes have been prepared and electropolymerized, resulting in the formation of conductive thin films. In [Pd2(mu-Cl2)(dppterth-P,C3)2] (3a) the metal is P,C-coordinated, in [PdCl2(dppterth-P)2] (4a) the coordination is monodentate via the phosphine, and in [Pd(dppterth-P,C3)(dppterth-P,S1)][PF6] (5a) both P,C- and P,S-coordination modes are found. In 5a, the coordinated thiophene is hemilabile and may be displaced by reaction with more strongly coordinating ligands such as isocyanides. To probe the effect of blocking the alpha-position of the terthienyl moiety with methyl groups, 3'-diphenylphosphino-5-methyl-2,2':5'2' '-terthiophene (1b, Me-dppterth) and 3'-diphenylphosphino-5,5' '-dimethyl-2,2':5'2' '-terthiophene (1c, Me2-dppterth) were prepared, and the corresponding series of Pd complexes was synthesized. One of these complexes, [Pd(Me2-dppterth-P,C3)(Me2-dppterth-P,S1)][PF6] (5c), has been crystallographically characterized. The electropolymerized films prepared from 5a react with isonitriles, and shifts in the absorption spectra of the electropolymerized materials are observed upon reaction. A Pd complex has also been prepared from 5-diphenylphosphino-2,2':5'2' '-terthiophene (2, 5dppterth), and this complex has been electropolymerized. All the electropolymerized thin films have been characterized using EDX analysis, which demonstrates good correspondence with the elemental analysis of the respective monomers, and the maximum conductivities of the films are near 10(-4) S x cm(-1). Comparing the electropolymerization behavior of the complexes, along with their electrochemical and spectroscopic data, allows conclusions to be drawn regarding the involvement of pi-delocalization and the metal group in the conductivity of the materials.

Journal Article↗
PubMed2001

Two fluoradene derivatives: pseudosymmetry, eccentric ellipsoids and a phase transition.

Structures of two derivatives of the curved fluoradene ring system (C(19)H(12)) have been determined. Both have phases that are highly pseudosymmetric. At room temperature crystals of 7b-triisopropylsilylfluoradene (C(28)H(32)Si) have a P1 cell that contains two independent molecules (Z' = 2) and that is almost centered. Crystals of 7b-(2,4-dinitrophenyl)fluoradene (C(25)H(14)N(2)O(4)) have both a P2(1)/c cell with Z' = 1 and a P2(1)/c cell with Z' = 2. The molecular volumes in these two P2(1)/c structures differ by 0.7%, but the structures are otherwise virtually the same; the two independent molecules in the larger cell are related by a pseudotranslation. Some of the atomic ellipsoids in the P2(1)/c, Z' = 1 structure are very large and eccentric, and there are some hints in the diffraction pattern of an incipient phase transition, but the Z' = 1 and Z' = 2 phases are clearly different. The P2(1)/c, Z' = 2 crystal at 295 K probably contains some volume fraction of the Z' = 1 phase; when the temperature is lowered to 273 K this fraction is decreased markedly. The pronounced pseudosymmetry in the P1 and P2(1)/c structures that have Z' = 2 has been investigated by analysing the atomic coordinates, by performing refinements in the smaller pseudocells and by making separate Wilson plots for the classes of reflections which are systematically strong and systematically weak. All three approaches are informative, but they reveal different information. Least-squares fits of coordinates of corresponding atoms measure the similarity of the molecular conformations. The Wilson plots allow a quantitative comparison of the intensities of the strong and weak reflections and thus an assessment of the deviations of the true structure from the smaller pseudocell structure. Comparison of the atomic displacements obtained in the full and pseudocell refinements shows where the structural distortions are largest and provides an indication of their directions.

Journal Article↗
PubMed2001

New mode of coordination for the dinitrogen ligand: formation, bonding, and reactivity of a tantalum complex with a bridging N(2) unit that is both side-on and end-on.

The reaction of a mixture of 1 equiv of PhPH(2) and 2 equiv of PhNHSiMe(2)CH(2)Cl with 4 equiv of Bu(n)Li followed by the addition of THF generates the lithiated ligand precursor [NPN]Li(2).(THF)(2) (where [NPN] = PhP(CH(2)SiMe(2)NPh)(2)). The reaction of [NPN]Li(2).(THF)(2) with TaMe(3)Cl(2) produces [NPN]TaMe(3), which reacts under H(2) to yield the diamagnetic dinuclear Ta(IV) tetrahydride ([NPN]Ta)(2)(mu-H)(4). This hydride reacts with N(2) with the loss of H(2) to produce ([NPN]Ta(mu-H))(2)(mu-eta(1):eta(2)-N(2)), which was characterized both in solution and in the solid state, and contains strongly activated N(2) bound in the unprecedented side-on end-on dinuclear bonding mode. A density functional theory calculation on the model complex [(H(3)P)(H(2)N)(2)Ta(mu-H)](2)(mu-eta(1):eta(2)-N(2)) provides insight into the molecular orbital interactions involved in the side-on end-on bonding mode of dinitrogen. The reaction of ([NPN]Ta(mu-H))(2)(mu-eta(1):eta(2)-N(2)) with propene generates the end-on bound dinitrogen complex ([NPN]Ta(CH(2)CH(2)CH(3)))(2)(mu-eta(1):eta(1)-N(2)), and the reaction of [NPN]Li(2).(THF)(2) with NbCl(3)(DME) generates the end-on bound dinitrogen complex ([NPN]NbCl)(2)(mu-eta(1):eta(1)-N(2)). These two end-on bound dinitrogen complexes provide evidence that the bridging hydride ligands are responsible for the unusual bonding mode of dinitrogen in ([NPN]Ta(mu-H))(2)(mu-eta(1):eta(2)-N(2)). The dinitrogen moiety in the side-on end-on mode is amenable to functionalization; the reaction of ([NPN]Ta(mu-H))(2)(mu-eta(1):eta(2)-N(2)) with PhCH(2)Br results in C-N bond formation to yield [NPN]Ta(mu-eta(1):eta(2)-N(2)CH(2)Ph)(mu-H)(2)TaBr[NPN]. Nitrogen-15 NMR spectral data are provided for all the tantalum-dinitrogen complexes and derivatives described.

Journal Article↗
PubMed2001

Chemistry of re with N,N'-bis(2-pyridylmethyl)ethylenediamine (H2pmen): hydrolysis, dehydrogenation, and ternary complexes.

A number of Re complexes with N,N'-bis(2-pyridylmethyl)ethylenediamine (H2pmen) have been made from [NH4][ReO4]. [ReOCl2(H2pmen)]Cl, [ReOCl(Hpmen)][ReO4], and [ReO2(H2pmen)][ReO4] are related by hydrolysis/HCl substitution. [ReOCl(Hpmen)][ReO4] was structurally characterized and found to contain a water-stable amido-Re bond. Dehydrogenation of the N-donor ligand from each amine to imine with concomitant two-electron reduction of the Re center occurs readily in these systems. With suitable 3-hydroxy-4-pyrones, ternary complexes such as [ReIIICl(ma)(C14H14N4)][ReO4].CH3OH, 5, were made from [NH4][ReO4], H2pmen.4HCl and pyrones in one-pot syntheses. 5, a seven-coordinate ReIII complex, was structurally characterized.

Crystallography, X-Ray↗
PubMed2001

Expanding cavitand chemistry: the preparation and characterization of [n]cavitands with n>=4.

The preparation of cavitands composed of 4, 5, 6, and 7 aromatic subunits ([n]cavitands, n=4-7) is described. The simple, two-step synthetic procedure utilized readily available starting materials (2-methylresorcinol and diethoxymethane). The two cavitand products having 4 and 5 aromatic subunits exhibited highly symmetric cone conformations, while the larger cavitands (n = 6 and 7) adopt conformations of lower symmetry. 1H NMR spectroscopic studies of [6]cavitand and [7]cavitand revealed that these hosts undergo exchange between equivalent conformations at room temperature. The departure of these two cavitands from cone conformations is related to steric crowding on their Ar-O-CH2-OAr bridges and is predicted by simple molecular mechanics calculations (MM2 force field). X-ray diffraction studies on single crystals of the [4]cavitand, [5]cavitand, and [6]cavitand hosts afforded additional experimental support for these conclusions.

Ethers, Cyclic↗
PubMed2001

Conformational preferences in glycosylamines. implications for the exo-anomeric effect.

The conformational preferences about the C-N bond in N-(4-methoxyphenyl)-2,3,4,6-tetra-O-acetyl-alpha (1) and beta-D-glucopyranosylamine (2), in the solid state and in solution, have been investigated. The crystal structure of the axially substituted alpha anomer (1) indicates a conformational preference about the C-1-N bond in which nN-->sigma*C-O exo-anomeric interactions may be expressed, although this conformational preference is not displayed in solution. The solution conformation relieves steric interactions that result from expression of the exo-anomeric effect in the solid-state conformation. The conformational preference in the equatorially substituted beta anomer (2) both in solution and in the solid state is similar and permits expression of nN-->sigma*C-O exo-anomeric interactions. The structural data for 1 and 2 indicate significant differences in O-5-C-1-N-1 bond angles but insignificant differences in each of the O-5-C-1 or C-1-N-1 bond lengths. The J(C-1-H-1 coupling constants in 1 and 2 indicate a greater coupling constant for the alpha anomer that is consistent with a dominant nO-->sigma*C-H orbital interaction in the beta anomer that weakens the C-1-H-1 bond.

Acetylation↗
PubMed2000

Seven-coordinate [ReVON4X2]+ complexes (X = O and Cl).

The oxorhenium(V) complexes with ligands containing N4 (H2pmen) and N4O2 (H2bbpen, H2Clbbpen, and H2bped) donor atom sets have been synthesized. X-ray crystallographic analyses of the [ReO(H2pmen)Cl2]+, [ReO(bbpen)]+, and [ReO(bped)]+ complexes showed that all three cations share a rare seven-coordinate structure with a distorted pentagonal bipyramidal geometry, which represents a novel and potentially general structural motif in ReV = O complexes. 1H NMR spectroscopy shows that the structures of the complexes are retained in the solution.

Crystallography, X-Ray↗
PubMed2000

Coaggregation of paramagnetic d- and f-block metal ions with a podand-framework amine phenol ligand.

This report covers initial studies in the coaggregation of nickel (Ni2+) and lanthanide (Ln3+) metal ions to form complexes with interesting structural and magnetic properties. The tripodal amine phenol ligand H3tam (1,1,1-tris(((2-hydroxybenzyl)amino)methyl)ethane) is shown to be particularly accommodating with respect to the geometric constraints of both transition and lanthanide metal ions, forming isolable complexes with both of these ion types. In the solid-state structure of [Ni(H2tam)(CH3CN)]PF6.2.5CH3CN.0.5CH3OH (1), the Ni(II) center has a distorted octahedral geometry, with an N3O2 donor set from the [H2tam]- ligand and a coordinated solvent (acetonitrile) occupying the sixth site. The reaction of stoichiometric amounts of H3tam with the Ni(II) ion in the presence of lanthanide(III) ions provides [LnNi2(tam)2]+ cationic complexes which contain coaggregated metal ions. These complexes are isolable and have been characterized by a variety of analytical techniques, with mass spectrometry proving to be particularly diagnostic. The solid-state structures of [LaNi2(tam)2(CH3OH)1/2(CH3CH2OH)1/2(H2O)]ClO4.0.5CH3OH.0.5CH3CH2OH.4H2O (2), [DyNi2(tam)2(CH3OH)(H2O)]ClO4.CH3OH. H2O(6), and [YbNi2(tam)2(H2O)]ClO4.2.58H2O(9) have been determined. Each complex contains two octahedral Ni(II) ions, each of which is encapsulated by the ligand tam3- in an N3O3 coordination sphere; each [Ni(tam)]-unit caps the lanthanide(III) ion via bridging phenoxy oxygen donor atoms. In 2, La3+ is eight-coordinated, while in 6, Dy(III) is seven- (to "weakly eight-") coordinated, and Yb(III) in 9 has a six-coordination environment. The complexes are symmetrically different, 2 possessing C2 symmetry and 6 and 9 having C1 symmetry. Magnetic studies of 2, 6, and 9 indicate that antiferromagnetic exchange coupling between the Ni(II) and Ln(III) ions increases with decreasing ionic radius of Ln(III).

Amines↗