Charmaine Arderne

Branched Selectivity in the Pd‐Catalysed Methoxycarbonylation of 1‐Alkenes

The methoxycarbonylation of alkenes by palladium(II) complexes with P,O‐donor ligands [(2‐methoxyphenyl)diphenylphosphine (L‐2), bis(2‐methoxyphenyl) phenyl phosphine (L‐3) and tris(2‐methoxyphenyl) phosphine (L‐4)] has been investigated. The results show that the Pd complexes derived from these ligands provide high regioselectivity for the branched esters from 1‐pentene and 1‐hexene (>80 %). Various parameters (including temperature, pressure, acid concentration) were optimized to improve the performance of the catalyst system. Higher temperatures afforded higher regioselectivity; but effected rapid catalyst decomposition. Acceptable turnover frequencies, conversions as well as catalyst stability could be obtained at higher L/Pd ratios. The dramatic change in regioselectivity is rationalised on the basis of the hemi‐lability of the o‐methoxy moiety, which may lead to ligand dissociation from L2PdX2 (L=ligand, X=Cl) rather than the expected dissociation of X. In support of our hypothesis, direct evidence for the coordination of the o‐methoxy to the Pd centre was demonstrated by the crystal structure. To the best of our knowledge, this work provides the first reported route to valuable branched esters through the methoxycarbonylation of alkenes at suitable rates.

Charge-assisted hydrogen bonding in salts of 2-amino-1H-benzimidazole with 3-phenylpropynoic acid and oct-2-ynoic acid.

The 100 K structures of two salts, namely 2-amino-1H-benzimidazolium 3-phenylpropynoate, C7H8N3(+)·C9H5O2(-), (I), and 2-amino-1H-benzimidazolium oct-2-ynoate, C7H8N3(+)·C8H11O2(-), (II), both have monoclinic symmetry (space group P21/c) and display N-H...O hydrogen bonding. Both structures show packing with corrugated sheets of hydrogen-bonded molecules lying parallel to the [001] direction. Two hydrogen-bonded ring motifs can be identified and described with graph sets R(2)(2)(8) and R(4)(4)(16), respectively, in both (I) and (II). Computational chemistry calculations performed on both compounds show that the hydrogen-bonded ion pairs are more energetically favourable in the crystal structure than their hydrogen-bonded neutral molecule counterparts.

Bis(acetonitrile-κN)dichlorido(η4-cyclo­octa-1,5-diene)ruthenium(II) acetonitrile monosolvate

In the title RuII complex, [RuCl2(C8H12)(C2H3N)2]·CH3CN, the metal ion is coordinated to the centers of each of the double bonds of the cyclooctadiene ligand, to two chloride ions (in cis positions) and to two N-atom donors (from MeCN molecules) that complete the coordination sphere for the neutral complex. The coordination about the RuII atom can thus be considered to be octahedral with a slightly trigonal distortion. There is also one acetonitrile solvent molecule per molecule which is outside the coordination sphere of the ruthenium atom.

Butane-1,4-diammonium bis(perchlorate)

The butane-1,4-diammonium cation of the title compound, C4H14N2 2+·2ClO4 −, lies on a special position of site symmetry 2/m, whereas the perchlorate anion is located on a crystallographic mirror plane. An intricate three-dimensional hydrogen-bonding network exists in the crystal structure with each H atom of the ammonium group exhibiting bifurcated interactions to the perchlorate anion. Complex hydrogen-bonded ring and chain motifs are also evident, in particular a 50-membered ring with graph-set notation R 10 10(50) is identified.

(Acetato-κ2O,O′)[2′-(di-tert-butyl­phosphanyl)-1,1′-biphenyl-κ2P,C2]palladium(II)

The structure of the title compound, [Pd(C2H3O2)(C20H26P)], shows a distorted square-planar geometry for the PdII atom, with significant deviations being evident owing to the asymmetric coordination mode of the acetate ligand. A weak intramolecular C—H⋯O interaction is noted. The crystal studied was a racemic twin.

Heptane-1,7-diaminium sulfate mono-hydrate.

The crystal structure of the title compound, C7H20N2 2+·SO4 2−·H2O, is presented, with particular focus on the packing arrangement in the crystal structure and selected hydrogen-bonding interactions that the compound forms. The crystal structure exhibits parallel stacking of the diammonium dication in its packing arrangement, together with inorganic–organic layering that is typical of these n-alkyldiammonium salts. An intricate three-dimensional hydrogen-bonding network exists in the crystal structure where the hydrogen bonds link the cation and anion layers together through the sulfate anions and the water molecules.

The crystal structure of 3-aminopropan-1-aminium iodide, C3H11N2I

Abstract C3H11N2I, monoclinic, P21/n (no. 14), a = 5.0152(2) Å, b = 10.1470(4) Å, c = 14.1852(5) Å, β = 96.501(2)°, V = 717.23(5) Å3, Z = 4, Rgt(F) = 0.0174, wRref(F2) = 0.0411, T = 100 K.

Deciphering composition and connectivity of a natural product with the assistance of MS and 2D NMR

A complementary application of three analytical techniques, viz. multidimensional nuclear magnetic resonance spectroscopy (NMR), mass spectrometry (MS), and single-crystal X-ray diffractometry was required to identify and refine two natural products isolated from Millettia versicolor and solvent of crystallization. The two compounds, namely 3-(2H-1,3-benzodioxol-5-yl)-6-methoxy-8,8-dimethyl-4H,8H-pyrano[2,3-h]chromen-4-one, or durmillone, (I), and (2E)-1-(4-{[(2E)-3,7-dimethylocta-2,6-dien-1-yl]oxy}-2-hydroxyphenyl)-3-(4-hydroxyphenyl)prop-2-en-1-one, (II), could not be separated by routine column chromatography and cocrystallized in a 2:1 ratio with 0.13 molecules of ethanol solvent. Compound (II) and ethanol could not be initially identified by single-crystal X-ray analysis due to complex disorder in the aliphatic chain region of (II). Mass spectrometry ensured that (II) represented only one species disordered over several positions in the solid state, rather than several species cohabitating on the same crystallographic site. The atomic identification and connectivity in (II) were established by several 2D (two-dimensional) NMR techniques, which in turn relied on a knowledge of its exact mass. The derived connectivity was then used in the single-crystal analysis to model the disorder of the aliphatic chain in (II) over three positions and allowed identification of a partially occupied ethanol solvent molecule that was disordered over an inversion center. The disordered moieties were refined with restraints and constraints.

Bis[(1,1′-biphenyl-2,2′-di­yl)di-tert-butyl­phospho­nium] di-μ-chlorido-bis­[dichlorido­palladate(II)]

In the title compound, (C20H26P)2[Pd2Cl6], the PdII atom within the hexachloridodipalladate(II) dianion has a square-planar geometry. It resides on a centre of inversion with the asymmetric unit containing half of the dianion and one phosphonium cation. Only weak C—H⋯π interactions are present in the crystal structure.

Decane-1,10-diaminium dinitrate

The crystal structure of the title compound, C10H26N2 2+·2NO3 −, exhibits a back-to-back paired double-stacked packing arrangement culminating in an overall double zigzag pattern of the dications. Each pair of double-stacked dications is surrounded by a ring of ten nitrate anions. An intricate three-dimensional N---H...O and N---H...(O,O) hydrogen-bonding network exists in the crystal structure.