Methyl 1H-pyrrole-2-carboxyl­ate

The title compound, C6H7NO2, is essentially planar with a dihedral angle of 3.6 (3)° between the pyrrole ring and the methoxy­carbonyl O/C/O/C plane. In the crystal structure, the N atom is a hydrogen-bond donor to the carboxylate C=O O atom of the neighboring mol­ecule. These inter­molecular hydrogen bonds lead to the formation of helical chains along the b axis

4-Ethyl­phenol

The title compound, C8H10O, crystallizes with three mol­ecules in the asymmetric unit. O—H⋯O hydrogen bonds form cooperative chains connecting the mol­ecules along [100]. On the unitary graph level, this pattern is assigned a DDD descriptor. The ternary descriptor is C 3 3(6)

Bond Strength of a Diatomic Acceptor Ligand: A Reliable Measure of Its Antibond Occupation and Its Charge?

A nitrosyl ligand is bonded to a central metal mainly via a mostly covalent normal bond and a coordinative metal-to-NO pi-backbond. A recent analysis had unravelled similar bonding characteristics of both linear and bent CoNO moieties in terms of ligand charge and antibond occupation. Thus, there should be no justification for the usual assignment of an NO+ ligand to a linear MNO unit and a singlet-NO- ligand to a bent one. This claim seems to contradict that bending an MNO unit weakens the N-O bond with a marked red-shift of the N-O stretch as one indicator. In this work, the failure of Dewar-Chatt-Duncanson-derived conclusions is demonstrated for linear/bent isomer couples by the analysis of M-N and N-O bond strengths. Instead of DCD behavior, lateral electrostatic influence on NO and other diatomic ligands modulates the intraligand bond strength in a similar way as has been shown in former work for polar interaction of a charge with CO in the 'non-classical' carbonyls. Methodologically, local-mode analysis is used to determine bond strengths. Oxidation states are determined by the effective-oxidation-state (EOS) method

(Cyclo­pentane-1,1-di­yl)dimethanol

In the title compound, C7H14O2, co-operative eight-membered homodromic rings of O—H⋯O hydrogen bonds connect the mol­ecules into strands along [100]. According to graph-set analysis, the descriptor of these cycles is R 4 4(8). The cyclo­pentane-ring adopts an envelope conformation (C4 E)

Poly[[μ-1,4-anhydro­erythritolato-di-μ-aqua-sodium(I)] monohydrate]

In the title compound, {[Na(C4H7O3)(H2O)2]·H2O}n, the sodium ion is octa­hedrally coordinated by two bridging 1,4-anhydro­erythritolate ligands, unexpectedly coordinated by the ring oxygen and four water ligands. This bonding pattern leads to one-dimensional anti­tactical polymeric chains along [010]. One of the exocyclic O atoms of the anhydro­erythritolate group is an acceptor in four hydrogen bonds, giving further evidence that it is deprotonated

m-Phenyl­enediamine

In the title compound, C6H8N2, there are four mol­ecules in the asymmetric unit, with each mol­ecule, including the H atoms on the N atoms of the amino groups, showing local C2 symmetry. In the crystal structure, all except one of the NH2 groups participate in N—H⋯O hydrogen bonding. The identified hydrogen bonds furnish a three-dimensional network. N—H⋯π contacts are observed with H⋯π distances ranging from 2.516 (17) to 2.815 (16) Å. No π-stacking of the aromatic rings is observed

2,3,4,5,6-Penta­bromo­phenol

The title compound, C6HBr5O, is the perbrominated derivative of phenol. The mol­ecule shows non-crystallographic mirror symmetry. Bond lengths between the C and Br atoms are normal. In the crystal structure, O—H⋯O hydrogen bonds connect the mol­ecules into infinite strands. Dispersive Br⋯Br contacts are observed. No significant π–π stacking is obvious

“Brown‐Ring”‐Related Coordination Polymers of the Quartet‐{FeNO}7 Chromophore

A conspicuous detail of the so‐called brown‐ring test (the analytical test on nitrate) is the reddish color of the bottom layer of concentrated sulfuric acid, which develops upon the bleeding of the brown layer into the acid. Crystals of the same color form from a solution of ferrous sulfate in concentrated sulfuric acid on saturation with gaseous nitric oxide. The structure of this H3O[{Fe(NO)(μ4‐SO4)(μ2‐SO4)0.5}n/n] (1a) is made up from infinite chessboard‐type layers with sulfur on the field junctions and Fe(NO) moieties below the black and above the white fields. An Fe–N–O angle of about 160° causes disorder in the tetragonal space group I4/mmm. A similar crystal pathology was found in the related [{Fe(MeOH)(NO)(μ4‐SO4)}n/n] (1b) in the same crystal class. A one‐dimensional coordination polymer is formed in crystals of a third compound that comprises the Fe(NO)O5 coordination pattern, namely the brown oxalato species [{Fe(H2O)(NO)(μ2‐ox)}n/n·H2O] (2). A still larger NO tilt of about 156° is not obscured by disorder in the triclinic crystals of 2

2-Bromo­benzaldehyde cyano­hydrin

The title compound [alternatively called (2-bromo­phen­yl)­(hydr­oxy)acetonitrile], C8H6BrNO, is the reaction product of 2-bromo­benzaldehyde and hydrogen cyanide. Bond lengths and angles are normal. In the crystal structure, an intermolecular hydrogen bond between the hydr­oxy group and the nitrile N atom is established. In agreement with bonding considerations, a linear C—N⋯H acceptor geometry is observed. Each mol­ecule is a single donor and a single acceptor; extended hydrogen-bonded chains are formed along [100]

tert-Butyl imidazole-1-carboxyl­ate

In the title compound, C8H12N2O2, mol­ecules are inter­connected by weak C—H⋯O contacts with H⋯O distances of 2.30 Å, resulting in the formation of chains along [100]. According to graph-set analysis, the unitary descriptor of these chains is C(5). In addition, there are π–π stacking inter­actions between pyrazole rings (centroid distance = 3.878 Å and ring plane distance = 3.26 Å)