Two tautomeric forms of 2-amino-5,6-dimethylpyrimidin-4-one

Derivatives of 4-hydroxypyrimidine are an important class of biomolecules. These compounds can undergo keto-enol tautomerization in solution, though a search of the Cambridge Structural Database shows a strong bias toward the 3H-keto tautomer in the solid state. Recrystallization of 2-amino-5,6-dimethyl-4-hydroxypyrimidine, C6H9N3O, from aqueous solution yielded triclinic crystals of the 1H-keto tautomer, denoted form (I). Though not apparent in the X-ray data, the IR spectrum suggests that small amounts of the 4-hydroxy tautomer are also present in the crystal. Monoclinic crystals of form (II), comprised of a 1:1 ratio of both the 1H-keto and the 3H-keto tautomers, were obtained from aqueous solutions containing uric acid. Forms (I) and (II) exhibit one-dimensional and three-dimensional hydrogen-bonding motifs, respectively.

Monoanionic bis(carbene) pincer complexes featuring cobalt(I–III) oxidation states

The synthesis and characterization of a series of cobalt complexes featuring a pincer bis(carbene) ligand of the meta-phenylene-bridged bis-N-heterocyclic carbene (^ArCCC, Ar = 2,6-diispropylphenyl or mesityl) are reported.

Crystal structure of 1,3-bis-(2,3-di-methyl-quinoxalin-6-yl)benzene

The title compound, C26H22N4 (I), was synthesized by C-H iridium-catalyzed borylation followed by Suzuki coupling. The mol-ecular structure of (I) consists of a central benzene ring with 3-di-methyl-quinoxalin-6-yl groups at the 1 and 3 positions. These 2,3-di-methyl-quinoxalin-6-yl groups twist significantly out of the plane of the benzene ring. There are inter-molecular π-π inter-actions which result in a two-dimensional extended structure. The layers extend parallel to the ab plane and stack along the c axis.

Crystal structure of 9,10-bis-(1,3-di-thiol-2-yl-idene)-9,10-di-hydro-anthracene

The crystal structure of the well-studied 9,10-bis-(1,3-di-thiol-2-yl-idene)-9,10-di-hydro-anthracene mol-ecule, C20H12S4, (I), also known as exTTF, is reported. The mol-ecular structure of (I) consists of a di-hydro-anthracene moiety with two 1,3-di-thiol-2-yl-idene substituents. This is a saddle-shaped mol-ecule, which inter-acts with a close neighbor through various π-π and C-H⋯π contacts to form a 'dimer'. These 'dimers' inter-act through a series of C-H⋯S and C-H⋯π contacts to construct a complex three-dimensional extended structure.

Crystal structure of [μ2-3,3-dimethyl-4-(propan-2-yl-idene)thietane-2,2-dithiol-ato-κ(4) S:S':S:S']bis[tricarbonyl-iron(I)](Fe-Fe)

The title complex, [Fe2(C8H12S3)(CO)6] or [{Fe(CO)3}2(μ-L)] [L = 3,3-dimethyl-4-(propan-2-yl-idene)thietane-2,2-bis-(thiol-ato)], consists of two Fe(CO)3 moieties double-bridged by a di-thiol-ate ligand. Each of the two Fe(I) atoms has a distorted anti-prismatic coordination environment consisting of three carbonyl groups, two S atoms of the di-thiol-ate ligand and the neighboring Fe(I) atom [Fe-Fe = 2.4921 (4) Å]. Weak C-H⋯O inter-molecular inter-actions result in the formation of dimers. This is the second crystal structure reported with the 3,3-dimethyl-4-(propan-2-yl-idene)thietane-2,2-bis-(thiol-ate) ligand and the first in which it bridges two metal atoms.

Crystal structure and absolute configuration of (3S,4aS,8aS)-N-tert-butyl-2-[(S)-3-(2-chloro-4-nitro-benzamido)-2-hy-droxy-prop-yl]deca-hydro-isoquinoline-3-carboxamide and (3S,4aS,8aS)-N-tert-butyl-2-{(S)-2-[(S)-1-(2-chloro-4-nitro-benzoyl)pyrrolidin-2-yl]-2-hy-droxy-eth-yl}deca-hydro-iso-quinoline-3-carboxamide

The crystal structure and absolute configuration of the two new title nelfinavir analogs, C24H35ClN4O5, (I), and C27H39ClN4O5, (II), have been determined. Each of these mol-ecules exhibits a number of disordered moieties. There are intra-molecular N-H⋯O hydrogen bonds in both (I) and (II). In (I) it involves the two carboxamide groups, while in (II) it involves the N-tert-butyl carboxamide group and the 2-hydroxyl O atom. The inter-molecular hydrogen bonding in (I) (O-H⋯O and N-H⋯O) leads to two-dimensional sheets that extend parallel to the ac plane. The inter-molecular hydrogen bonding in (II) (O-H⋯O) leads to chains that extend parallel to the a axis.

Crystal structure of bis-(acetyl-acetonato-κ(2) O,O')(tetra-hydro-furan-κO)(tri-fluoro-methane-sulfonato-κO)iron(III)

The mononuclear title complex, [Fe(CF3O3S)(C5H7O2)2(C4H8O)] or [Fe(acac)2(OTf)(THF)] (acac = acetyl-acetonate; OTf = tri-fluoro-methane-sulfon-ate; THF = tetrahydrofuran), (I), consists of one six-coordinate Fe(3+) atom in a slightly distorted octa-hedral environment [Fe-O bond-length range = 1.9517 (11)-2.0781 (11) Å]. The triflate ligand was found to be disordered over two sets of sites, with a site-occupancy ratio of 0.622 (16):0.378 (16). Weak inter-molecular C-H⋯O and C-H⋯F hydrogen-bonding inter-actions generate a two-dimensional supra-molecular structure lying parallel to (100). This is only the second crystal structure reported of a mononuclear bis-(acetyl-acetonato)iron(III) complex.

Crystal structure of tetrakis-(acetyl-acetonato)di-chloridodi-μ3-methano-lato-tetra-μ2-methano-lato-tetra-iron(III)

The title complex, [Fe4(C5H7O2)4(CH3O)6Cl2] or [Fe4(acac)4(μ2-OMe)4(μ3-OMe)2Cl2] (acac = acetyl-acetonate), crystallizes in the ortho-rhom-bic Pbca space group with one half of the mol-ecule per asymmetric unit, the other half being completed by inversion symmetry. The core structure consists of a face-sharing double pseudo-cubane entity with two opposite corners missing. Weak C-H⋯Cl inter-molecular inter-actions result in a two-dimensional layered structure parallel to the ac plane.

Crystal structure of di-μ-hydroxido-κ(4) O:O-bis[bis(acetyl-acetonato-κ(2) O,O')cobalt(III)]

The dinuclear title complex, [Co2(C5H7O2)4(μ-OH)2] or [Co(acac)2(μ-OH)]2, where acac is acetyl-acetonate, is centrosymmetric with half of the mol-ecule per asymmetric unit. The mol-ecular structure is a dimer of octa-hedrally coordinated Co(III) atoms with four O atoms from two chelating acac ligands and two O atoms from bridging hydroxide ligands. The crystal packing features weak C-H⋯O inter-actions between neighboring mol-ecules, leading to the formation of chains normal to the ac plane. The hydroxide H atoms are not involved in hydrogen bonding because of the bulky acac ligands. This is the first crystal structure reported of a dimeric transition metal bis-acac complex with OH(-) as the bridging group.

Synthesis and characterization of M(ii) (M = Mn, Fe and Co) azafulvene complexes and their X3− derivatives

Structural and electronic flexibility in a tripodal ligand platform featuring a secondary coordination sphere.