Unexpected reactions of NHC*—CuI and —AgI bromides with potassium thio- or selenocyanate

The reactions of N-heterocyclic carbene CuI and AgI halides with potassium thio- or selenocyanate gave unexpected products. The attempted substitution reaction of bromido(1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene)silver (NHC*—Ag—Br) with KSCN yielded bis[bis(1,3-dibenzyl-4,5-diphenylimidazol-2-ylidene)silver(I)] tris(thiocyanato)argentate(I) diethyl ether disolvate, [Ag(C29H24N2)2][Ag(NCS)3]·2C4H10O or [NHC*2Ag]2[Ag(SCN)3]·2Et2O, (1), while reaction with KSeCN led to bis(μ-1,3-dibenzyl-4,5-diphenyl-2-selenoimidazole-κ2 Se:Se)bis[bromido(1,3-dibenzyl-4,5-diphenyl-2-selenoimidazole-κSe)silver(I)] dichloromethane hexasolvate, [Ag2Br2(C29H24N2Se)4]·6CH2Cl2 or (NHC*Se)4Ag2Br2·6CH2Cl2, (2), via oxidation of the NHC* fragment to 2-selenoimidazole. This oxidation was observed again in the reaction of NHC*—Cu—Br with KSeCN, yielding catena-poly[[[(1,3-dibenzyl-4,5-diphenyl-2-selenoimidazole-κSe)copper(I)]-μ-cyanido-κ2 C:N] acetonitrile monosolvate], {[Cu(CN)(C29H24N2Se)]·C2H3N} n or NHC*Se—CuCN·CH3CN, (3). Compound (1) represents an organic/inorganic salt with AgI in a linear coordination in each of the two cations and in a trigonal coordination in the anion, accompanied by diethyl ether solvent molecules. The tri-blade boomerang-shaped complex anion [Ag(SCN)3]2− present in (1) is characterized by X-ray diffraction for the first time. Compound (2) comprises an isolated centrosymmetric molecule with AgI in a distorted tetrahedral BrSe3 coordination, together with dichloromethane solvent molecules. Compound (3) exhibits a linear polymeric 1 ∞[Cu—C[triple-bond]N—Cu—] chain structure with a selenoimidazole moiety additionally coordinating to each CuI atom, and completed by acetonitrile solvent molecules. Electron densities associated with an additional ether solvent molecule in (1) and two additional dichloromethane solvent molecules in (2) were removed with the SQUEEZE procedure [Spek (2015). Acta Cryst. C71, 9–18] in PLATON.

Crystal structure of diaquabis(N,N-diethylnicotinamide-κN1)bis(2,4,6-trimethylbenzoato-κO1)cobalt(II)

The centrosymmetric molecule in the monomeric title cobalt complex, [Co(C10H11O2)2(C10H14N2O)2(H2O)2], contains two water molecules, two 2,4,6-trimethylbenzoate (TMB) ligands and two diethylnicotinamide (DENA) ligands. All ligands coordinate to the CoIIatom in a monodentate fashion. The four O atoms around the CoIIatom form a slightly distorted square-planar arrangement, with the distorted octahedral coordination sphere completed by two pyridine N atoms of the DENA ligands. The dihedral angle between the planar carboxylate group and the adjacent benzene ring is 84.2 (4)°, while the benzene and pyridine rings are oriented at a dihedral angle of 38.87 (10)°. The water molecules exhibit both intramolecular (to the non-coordinating carboxylate O atom) and intermolecular (to the amide carbonyl O atom) O—H...O hydrogen bonds. The latter lead to the formation of layers parallel to (100), enclosingR44(32) ring motifs. These layers are further linkedviaweak C—H...O hydrogen bonds, resulting in a three-dimensional network. One of the two ethyl groups of the DENA ligand is disordered over two sets of sites with an occupancy ratio of 0.490 (13):0.510 (13).

Bis(acetato-κO)bis{2-[4-(pyridin-2-yl)phenyl]-1H-imidazo[4,5-f][1,10]phenanthroline-κ2N,N′}cadmium(II)

The asymmetric unit of the title compound, [Cd(CH3COO)(C24H15N5)], comprises one-half of the centrosymmetric molecule. The CdIIion, situated on a centre of inversion, is coordinated by two O atoms from two acetate ligands and four N atoms from two 2-[4-(pyridin-2-yl)phenyl]-1H-imidazo[4,5-f][1,10]phenanthroline (L) ligands in a distorted octahedral geometry. In theLligand, the terminal phenyl and pyridine rings are turned away from the mean plane of the imidazo[4,5-f][1,10]phenanthroline fragment in opposite directions, at 11.1 (1) and 10.5 (1)°, respectively. In the crystal, N—H...O hydrogen bonds link molecules related by translation along theaaxis into linear chains, and weak C—H...N interactions link these chains into layers parallel to the (011) plane.

Salen ligand complexes as electrocatalysts for direct electrochemical reduction of gaseous carbon dioxide to value added products

CO2, being a linear and centrosymmetric molecule, is very stable, and the electrochemical reduction of CO2 requires energy. However, the salen complexes are found to be very efficient to minimize overpotential as compared to their metal counterparts.

The polyoctahedral silsesquioxane (POSS) 1,3,5,7,9,11,13,15-octaphenylpentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane (octaphenyl-POSS)

Solvent-free single crystals of 1,3,5,7,9,11,13,15-octaphenylpentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane (abbreviated as octaphenyl-POSS), C48H40O12Si8, were obtained by dehydration/condensation of the tetrol Si4O4(Ph)4(OH)4. The powder pattern generated from the single-crystal data matches well with the experimentally measured powder pattern of commercial octaphenyl-POSS. The geometry of the centrosymmetric molecule in the crystal was compared with that in the gas phase, and had shorter Si—O bond lengths and a broader range of Si—O—Si bond angles. The average Si—O bond length [1.621 (3) Å], and Si—O—Si and O—Si—O bond angles [149 (5) and 109 (1)°, respectively] were within the same range measured previously for octaphenyl-POSS solvates.

A list of organic kryptoracemates

A list of 181 organic kryptoracemates has been compiled. This class of crystallographic oddities is made up of racemic compounds (i.e. pairs of resolvable enantiomers) that happen to crystallize in Sohnke space groups (i.e. groups that include only proper symmetry operations). Most (151) of the 181 structures could have crystallized as ordered structures in non-Sohnke groups. The remaining 30 structures do not fully meet this criterion but would have been classified as kryptoracemates by previous authors. Examples were found and checked with the aid of available software for searching the Cambridge Structural Database, for generating and comparing InChI strings, and for validating crystal structures. The pairs of enantiomers in the true kryptoracemates usually have very similar conformations; often the match is near-perfect. There is a pseudosymmetric relationship of the enantiomers in about 60% of the kryptoracemate structures, but the deviations from inversion or glide symmetry are usually quite easy to spot. Kryptoracemates were found to account for 0.1% of all organic structures containing either a racemic compound, a meso molecule, or some other achiral molecule. The centroid of a pair of enantiomers is more likely (99.9% versus 99% probability) to be located on an inversion center than is the centroid of a potentially centrosymmetric molecule.