Linkage isomerism of organoplatinum(II) compounds coordinated by two 1,3‐di­methyl­barbiturate anions

In two linkage isomers, bis[1,3‐di­methyl‐2,4,6(1H,3H,5H)‐pyrimidine­trionato]‐C⁵,O⁴‐(ethyl­enedi­amine‐N,N′)platinum(II), [Pt(C₆H₇N₂O₃)₂(C₂H₈N₂)], (I), and bis[1,3‐di­methyl‐2,4,6(1H,3H,5H)‐py­rim­idine­tri­on­ato‐C⁵](ethyl­enediamine‐N,N′)­plati­num(II) di­hyd­rate, [Pt(C₆H₇N₂O₃)₂(C₂H₈N₂)]·2H₂O, (II), crystal­lized from the same aqueous solution containing [Pt(en)(OH)₂] and 1,3‐di­methyl­barbituric acid (Hdmbarb) in a 1:2 molar ratio, a pair of monodentate dmbarb^? anions coordinate to the Pt atom at tetrahedral C atoms for (II), while one dmbarb^? anion coordinates at the carbon and the other at a deprotonated enol oxy­gen for (I). The Pt—C distances in (I) and (II) are comparable: 2.112 (4) Å for (I), and 2.114 (4) and 2.117 (4) Å for (II).     

[Bis­(di­phenyl­phosphino)­alkane](pentane‐2,4‐di­thionato) complexes of nickel(II)

The structures of a series of four‐coordinate nickel(II) complexes of the form [Ni(sacsac)L] PF₆ (sacsac = pentane‐2,4‐di­thione anion; L = (Ph₂P)₂(CH₂)_n, n = 1,2,3) have beendetermined. These are [bis­(di­phenyl­phosphino)­methane](pentane‐2,4‐di­thionato‐S,S′)­nickel(II) hexa­fluoro­phosphate, [Ni(C₂₅H₂₂P₂)(C₅H₇S₂)]PF₆, [1,2‐bis­(di­phenylphosphino)­ethane](pentane‐2,4‐di­thionato–S,S′)­nickel(II) hexa­fluoro­phosphate, [Ni(C₂₆H₂₄P₂)(C₅H₇S₂)]PF₆, and [1,3‐bis­(di­phenyl­phosphino)­propane](pentane‐2,4‐di­thionato‐S,S′)­nickel(II) hexa­fluoro­phosphate, [Ni(C₂₇H₂₆P₂)(C₅H₇S₂)]PF₆. All have a distorted square‐planar arrangement about Ni with angles around Ni varying with the length of the hydro­carbon chain.     

Two stereoisomeric pentacyclic oxin­dole alkaloids from Uncaria tomentosa: uncarine C and uncarine E

The chloro­form solvate of uncarine C (pteropodine), (1′S,3R,4′aS,5′aS,10′aS)‐1,2,5′,5′a,7′,8′,10′,10′a‐octa­hydro‐1′‐methyl‐2‐oxospiro­[3H‐indole‐3,6′(4′aH)‐[1H]­pyrano­[3,4‐f]indolizine]‐4′‐carboxyl­ic acid methyl ester, C₂₁H₂₄N₂O₄·CHCl₃, has an absolute configuration with the spiro C atom in the R configuration. Its epimer at the spiro C atom, uncarine E (isopteropodine), (1′S,3S,4′aS,5′aS,10′aS)‐1,2,5′,5′a,7′,8′,10′,10′a‐octahydro‐1′‐methyl‐2‐oxospiro[3H‐indole‐3,6′(4′aH)‐[1H]pyrano[3,4‐f]indolizine]‐4′‐carboxylic acid methyl ester, C₂₁H₂₄N₂O₄, has Z′ = 3, with no solvent. Both form intermolecular hydrogen bonds involving only the ox­indole, with N?O distances in the range 2.759 (4)–2.894 (5) Å.     

The diastereoisomers methyl 5‐(S)‐[2‐(R)/(S)‐methoxycarbonyl)‐2,3,4,5‐tetrahydropyrrol‐1‐ylcarbonyl]‐1‐(4‐methylphenyl)‐4,5‐dihydropyrazole‐3‐carboxylate

The title diastereoisomers, methyl 5‐(S)‐[2‐(S)‐methoxy­carbonyl)‐2,3,4,5‐tetra­hydro­pyrrol‐1‐yl­carbonyl]‐1‐(4‐methyl­phenyl)‐4,5‐di­hydro­pyrazole‐3‐carboxyl­ate and methyl 5‐(S)‐[2‐(R)‐methoxycarbonyl)‐2,3,4,5‐tetrahydropyrrol‐1‐ylcarbonyl]‐1‐(4‐methyl­phenyl)‐4,5‐di­hydro­pyrazole‐3‐carboxylate, both C₁₉H₂₃N₃O₅, have been studied in two crystalline forms. The first form, methyl 5‐(S)‐[2‐(S)‐methoxy­carbonyl)‐2,3,4,5‐tetrahydropyrrol‐1‐ylcarbonyl]‐1‐(4‐methylphenyl)‐4,5‐di­hydro­pyrazole‐3‐carboxyl­ate–methyl 5‐(S)‐[2‐(R)‐methoxy­carbonyl)‐2,3,4,5‐tetra­hydro­pyrrol‐1‐yl­carbonyl]‐1‐(4‐methylphenyl)‐4,5‐dihydropyrazole‐3‐carboxylate (1/1), 2(S),5(S)‐C₁₉H₂₃N₃O₅·2(R),5(S)‐C₁₉H₂₃N₃O₅, contains both S,S and S,R isomers, while the second, methyl 5‐(S)‐[2‐(S)‐methoxycarbonyl)‐2,3,4,5‐tetrahydro­pyrrol‐1‐ylcarbonyl]‐1‐(4‐methyl­phenyl)‐4,5‐di­hydro­pyrazole‐3‐carboxyl­ate, 2(S),5(S)‐C₁₉H₂₃N₃O₅, is the pure S,S isomer. The S,S isomers in the two structures show very similar geometries, the maximum difference being about 15° on one torsion angle. The differences between the S,S and S,R isomers, apart from those due to the inversion of one chiral centre, are more remarkable, and are partially due to a possible rotational disorder of the 2‐­(methoxycarbonyl)tetrahydropyrrole group.     

Intermolecular stacking in pyrazolo[3,4‐d]pyrimidine‐based pentamethylene‐linked flexible ­molecules

The crystal structures of 1‐{5‐[4,6‐bis­(methyl­sulfanyl)‐2H‐py­razolo­[3,4‐d]­pyrimidin‐2‐yl]­pentyl}‐6‐methyl­sulfanyl‐4‐(pyr­rolidin‐1‐yl)‐1H‐pyrazolo­[3,4‐d]­pyrimidine, C₂₂H₂₉N₉S₃, and 6‐methyl­sulfanyl‐1‐{5‐[6‐methyl­sulfanyl‐4‐(pyrrolidin‐1‐yl)‐2H‐pyrazolo­[3,4‐d]­pyrimidin‐2‐yl]­pentyl}‐4‐(pyrrolidin‐1‐yl)‐1H‐pyrazolo­[3,4‐d]­pyrimidine, C₂₅H₃₄N₁₀S₂, which differ in having either a pyrrolidine substituent or a methylsulfanyl group, show intermolecular stacking due to aromatic π–π interactions between the pyrazolo­[3,4‐d]­pyrimidine rings.     

Ten‐vertex rhodadithiaborane ­chemistry: [8‐{I(CH2)5}‐3‐(η5‐C5Me5)‐arachno‐3,7,8‐RhS2B8H9]

Neutral 8‐(5‐iodo‐n‐pentyl)‐3‐(η⁵‐penta­methyl­cyclo­pentadi­enyl)‐arachno‐3‐rhoda‐7,8‐di­thia­undecaborane, [Rh(C₅H₁₉B₈­IS₂)­(C₁₀H₁₅)], obtained from the [arachno‐7,8‐S₂B₉H₁₀]^? anion by treatment with I(CH₂)₅I followed by [Rh(C₅Me₅)Cl₂]₂ and N,N,N′,N′‐tetra­methyl‐1,8‐di­amino­naphthalene, has the 11‐vertex cluster geometry of [arachno‐7,8‐S₂B₉H₁₀]^?, but with an {Rh(C₅Me₅)} unit in the 3‐position instead of a {BH} unit, and with a –(CH₂)₅I chain attached exo to an S atom.     

The molecular and supramolecular structures of four 1,5,6,10b‐tetrahydropyrazolo[1,5‐c]quinazolines

The supramolecular structures of the title compounds, 2‐phenyl‐5‐p‐tolyl‐1,5,6,10b‐tetra­hydro­pyrazolo­[1,5‐c]quinazoline, C₂₃H₂₁N₃, (I), 5‐(4‐bromo­phenyl)‐2‐phenyl‐1,5,6,10b‐tetra­hydro­pyrazolo­[1,5‐c]­quinazoline, C₂₂H₁₈BrN₃, (II), 2‐(4‐chlorophenyl)‐5‐phenyl‐1,5,6,10b‐tetrahydropyrazolo[1,5‐c]quinazoline, C₂₂H₁₈ClN₃, (III), and 5‐(4‐bromo­phenyl)‐2‐(4‐chlorophenyl)‐1,5,6,10b‐tetrahydropyrazolo[1,5‐c]quinazoline, C₂₂H₁₇BrClN₃, (IV), are of two general types. Compounds (I), (II) and (III) form base‐paired dimers via N—H?N hydrogen bonds, where (I) and (II) are isomorphous, while in (IV), there are no conventional hydrogen bonds.     

[N,N′‐Bis(3‐aminopropyl)ethylenediamine‐κ4N,N′,N′′,N′′′](trithiocyanurato‐κ2N,S)zinc(II) ethanol solvate

In the crystal structure of the title compound, [N,N′‐bis(3‐­amino­propyl)­ethyl­enedi­amine‐κ⁴N,N′,N′′,N′′′][1,3,5‐triazine‐2,4,6(1H,3H,5H)‐tri­thionato(2−)‐κ²N,S]­zinc(II) ethanol sol­vate, [Zn(C₈H₂₂N₄)₂(C₃HN₃S₃)]·C₂H₆O, the Zn^II atom is octa­hedrally coordinated by four N atoms [Zn—N = 2.104 (2)–2.203 (2) Å] of a tetradentate N‐donor N,N′‐bis(3‐­amino­propyl)­ethyl­enedi­amine (bapen) ligand and by two S and N atoms [Zn—S = 2.5700 (7) Å and Zn—N = 2.313 (2) Å] of a tri­thio­cyanurate(2−) (ttcH²⁻) dianion bonded as a bidentate ligand in a cis configuration. The crystal structure of the compound is stabilized by a network of hydrogen bonds.     

2′,3′‐Dehydrosalannol

The title compound, methyl (2aS,3R,5R,5aS,6S,6aS,8R,9aS,10aR,10bR,10cS)‐8‐(3‐furyl)‐2a,4,5,5a,6,6a,8,9,9a,10a,10b,10c‐dodeca­hydro‐3‐hydroxy‐2a,5a,6a,7‐tetra­methyl‐5‐(3‐methylbut‐2‐enoyl­oxy)‐2H,3H‐cyclo­penta­[4′,5′]­furo­[2′,3′:6,5]benzo[cd]­isobenzo­furan‐6‐acetate, C₃₂H₄₂O₈, was isolated from uncrushed green leaves of Azadirachta indica A. Juss (neem) and has been found to possess antifeedant activity against Spodptera litura. The conformations of the functional groups are similar to those of 3‐des­acetyl­salannin, which was isolated from neem kernels. The mol­ecules are linked into chains by intermolecular O—H?O hydrogen bonds.     

Novel heterocyclic inhibitors of matrix metalloproteinases: three 6H‐1,3,4‐thiadiazines

The title compounds, (2S)‐N‐[5‐(4‐chloro­phenyl)‐2,3‐di­hydro‐6H‐1,3,4‐thia­diazin‐2‐yl­idene]‐2‐[(phenyl­sulfonyl)­amino]­pro­pan­amide, C₁₈H₁₇ClN₄O₃S₂, (I), (2R)‐N‐[5‐(4‐fluoro­phenyl)‐6H‐1,3,4‐thia­diazin‐2‐yl]‐2‐[(phenyl­sulfonyl)amino]­propan­amide, C₁₈H₁₇FN₄O₃S₂, (II), and (2S)‐N‐[5‐(5‐chloro‐2‐thienyl)‐6H‐1,3,4‐thia­diazin‐2‐yl]‐2‐[(phenyl­sulfonyl)­amino]­propan­amide, C₁₆H₁₅ClN₄O₃S₃, (III), are potent inhibitors of matrix metalloproteinases. In all three compounds, the thia­diazine ring adopts a screw‐boat conformation. The mol­ecules of compound (I) show a short intramolecular N_Ala—H?N_exo hydrogen bond [N?N 2.661 (3) Å] and are linked into a chain along the c axis by N_endo—H?S_endo and N_endo—H?O_Ala hydrogen bonds [N?S 3.236 (3) and N?O 3.375 (3) Å] between neighbouring mol­ecules. In compound (II), the mol­ecules are connected antiparallel into a chain along the a axis by N_exo—H?O_Ala and N_Ala—H?N_endo hydrogen bonds [N?O 2.907 (6) and N?N 2.911 (6) Å]. The mol­ecules of compound (III) are dimerized antiparallel through N_exo—H?N_endo hydrogen bonds [N?N 2.956 (7) and 2.983 (7) Å]. The different hydrogen‐bonding patterns can be explained by an amido–imino tautomerism (prototropic shift) shown by different bond lengths within the 6H‐1,3,4‐thia­diazine moiety.     

A mixed‐valence diacetate‐bridged MnII–MnIII complex incorporating a bridging phenolate ligand

The synthesis and characterization of a new unsymmetrical dinucleating N,O‐donor ligand, 2‐[N,N‐bis­(2‐pyridyl­methyl)­amino­methyl]‐6‐[N‐(3,5‐di‐tert‐butyl‐2‐oxidobenzyl)‐N‐(2‐pyridyl­amino)­aminomethyl]‐4‐methyl­phenol (H₂Ldtb), as well as the X‐ray crystal structure of its corresponding mixed‐valence diacetate‐bridged manganese complex, di‐μ‐acetato‐μ‐{2‐[N,N‐bis­(2‐pyridylmethyl)amino­methyl]‐6‐[N‐(3,5‐di‐tert‐butyl‐2‐oxidobenzyl)‐N‐(2‐pyridyl­amino)­aminomethyl]‐4‐methylphenolato}dimanganese(II,III) tetra­phenyl­borate, [Mn^IIMn^III(C₄₂H₄₉N₅O₂)(C₂H₃O₂)₂](C₂₄H₂₀B), are reported. The complex may be regarded as an inter­esting structural model for the mixed‐valence Mn^II–Mn^III state of manganese catalase.     

Disappearance of intramolecular stacking due to one‐atom movement or increment of a `propyl­ene linker' in pyrazolo­[3,4‐d]­pyrimidine‐based ­flexible models

In the crystal structures of 4,6‐di­methyl­thio‐1‐[3‐(4,6‐di­methyl­thio‐2H‐pyra­zolo­[3,4‐d]­py­rimi­din‐2‐yl)­propyl]‐1H‐py­ra­­zolo­[3,4‐d]­py­rimi­dine, C₁₇H₂₀N₈S₄, and 1‐[4‐(4‐meth­oxy‐6‐methyl­thio‐1H‐pyra­zolo­[3,4‐d]py­rimi­din‐1‐yl)­butyl]‐5‐meth­yl‐6‐methyl­thio‐4,5‐di­hydro‐1H‐pyra­zolo­[3,4‐d]py­rimi­din‐4‐one, C₁₈H₂₂N₈O₂S₂, only intermolecular stacking due to aromatic π–π interactions between pyrazolo­[3,4‐d]­pyrimidinerings is present.     

Two new conformationally restricted 4,5‐dihydroxynorvaline analogues with a norbornane skeleton

The structures of two conformationally restricted 4,5‐di­hydroxy­norvaline analogues with a norbornane skeleton, namely methyl (1S,2S,3R,4R)‐2‐benz­amido‐3‐(1,2‐di­hydroxy­ethyl)­bi­cyclo[2.2.1]­heptane‐2‐carboxyl­ate, C₁₈H₂₃NO₅, and methyl (1R,2S,3R,4S)‐2‐benz­amido‐3‐(1,2‐di­hydroxy­ethyl)­bi­cyclo[2.2.1]­heptane‐2‐carboxyl­ate, C₁₈H₂₃NO₅, exhibit a conformation in the helical region of the ?,ψ map but their handedness is opposite. In both cases, the torsion angles (χ^1,1) giving the relative orientation of the 1,2‐di­hydroxy­ethyl group of the amino acid side chain and the benz­amide group of the peptide chain indicate that these groups adopt a nearly eclipsed conformation. Both compounds show a complex hydrogen‐bonding pattern.     

Three new enanti­omerically pure ferrocenylphosphole compounds

The absolute configurations of three new enanti­omerically pure ferrocenylphosphole compounds, namely (2S,4S,S_Fc)‐4‐methoxy­methyl‐2‐[2‐(9‐thioxo‐9λ⁵‐phosphafluoren‐9‐yl)­ferro­cenyl]‐1,3‐dioxane, [Fe(C₅H₅)(C₂₃H₂₂O₃PS)], (III), (S_Fc)‐[2‐(9‐thioxo‐9λ⁵‐phosphafluoren‐9‐yl)ferrocenyl]methanol, [Fe(C₅H₅)(C₁₈H₁₄OPS)], (V), and (S_Fc)‐diphenyl[2‐(9‐thioxo‐9λ⁵‐phosphafluoren‐9‐yl]ferrocenylmethyl]phosphine, [Fe(C₅H₅)(C₃₀H₂₃P₂)], (VIII), have been unambiguously established. All three ligands contain a planar chiral ferrocene group, bearing a dibenzo­phos­phole and either a dioxane, a methanol or a diphenyl­phosphino­methane group on the same cyclopentadienyl. In compound (V), the occurrence of O—H⋯S and C—H⋯S hydrogen bonds results in the formation of a two‐dimensional network parallel to (001). The geometry of the ferrocene frameworks agrees with related reported structures.     

A comparison of the ring conformational properties of two derivatives prepared from the same diene ­diacetate precursor

Results of single‐crystal X‐ray experiments performed for the title compounds, (1S,2R,3S,4R,5R)‐4‐benzyl­oxy‐2‐[1‐(benzyl­oxy)­allyl]‐5‐hydroxy­methyl‐2,3,4,5‐tetra­hydro­furan‐3‐ol, C₂₂H₂₆O₅, (I), and (3R,5S,6S,7S,8S)‐3,6‐bis­(benzyl­oxy)‐5‐iodo­methyl‐2,3,4,5‐tetra­hydro­furo­[3,2‐b]­furan‐2‐one, C₂₁H₂₁IO₅, (II), demonstrate that the tetra­hydro­furan ring that is common to both structures adopts a different conformation in each mol­ecule. Structural analyses of (I) and (II), which were prepared from the same precursor, indicate that their different conformations are caused by hydrogen‐bonding interactions in the case of (I) and the presence of a fused bicyclic ring system in the case of (II). Density functional theory calculations on simplified analogs of (I) and (II) are also presented.     

Diphenyl(2‐thioxo‐1,3‐dithiole‐4,5‐di­thiolato‐S,S′)plumbane at 295 K and diphenyl(2‐thioxo‐1,3‐dithiole‐4,5‐di­thiolato‐S,S′)stannane at 150 K

Molecules of di­phenyl(2‐thio­xo‐1,3‐di­thiole‐4,5‐di­thiol­ato‐S,S′)­plumbane, [Pb(C₃S₅)(C₆H₅)₂], are linked into sheets via two intermolecular Pb?S_thione interactions of 3.322 (4) and 3.827 (4) Å; the Pb centre has a distorted octahedral geometry. In contrast, mol­ecules of ­di­phenyl(2‐thio­xo‐1,3‐di­thiole‐4,5‐di­thiol­ato‐S,S′)­stannane, [Sn(C₃S₅)(C₆H₅)₂], are linked into chains via a single intermolecular Sn—S_thione interaction of 2.8174 (9) Å; the Sn centre has a distorted trigonal‐bipy­ramidal geometry.     

The lithium chloride complex of the anti isomer of the bridged spherand C50H48O6

The structure of (11,12,24,25‐tetra­hydro‐28,34‐di­methoxy‐3,6,16,19,31,37‐hexa­methyl‐1,21[1′,3′]:8,14[1′′,3′′]‐di­benzeno‐10H,23H‐tetrabenzo­[f,h,o,z][1,5,10,14]­tetraoxa­cyclo­octa­decane)­lithium chloride monohydrate, anti‐[Li(C₅₀H₄₈O₆)]Cl·H₂O, at 100 K reveals that the host is less strained than that of the syn‐bridged isomer. There are two independent complex cations, each lying on a center of symmetry. Four short [1.944 (2)–1.998 (2) Å] and two long [2.381 (2) and 2.455 (2) Å] Li⁺?O distances provide six‐coordination in a distorted octahedral environment.     

Conformational change induced by hydration: trans‐dichloro­bis­[(1R,2R,3R,5S)‐(–)‐isopinocampheylamine]palladium(II) and trans‐dichloro­bis[(1S,2S,3S,5R)‐(+)‐isopinocampheylamine]palladium(II) hemihydrate

The title compounds, trans‐dichloro­bis[(1R,2R,3R,5S)‐(−)‐2,6,6‐trimethyl­bicyclo­[3.1.1]heptan‐3‐amine]palladium(II), [PdCl₂(C₁₀H₁₉N)₂], and trans‐dichloro­bis[(1S,2S,3S,5R)‐(+)‐2,6,6‐trimethyl­bicyclo­[3.1.1]heptan‐3‐amine]palladium(II) hemihydrate, [PdCl₂(C₁₀H₁₉N)₂]·0.5H₂O, present different arrangements of the amine ligands coordinated to Pd^II, viz. antiperiplanar in the former case and (−)anticlinal in the latter. The hemihydrate is an inclusion compound, with a Pd coordination complex and disordered water mol­ecules residing on crystallographic twofold axes. The crystal structure for the hemihydrate includes a short Pd⋯Pd separation of 3.4133 (13) Å.     

5‐n‐Butylpyridine‐2‐carboxylate–copper(II) and –iron(III) complexes

In trans‐bis(5‐n‐butyl­pyridine‐2‐carboxyl­ato‐κ²N,O)­bis­(methanol‐κO)copper(II), [Cu(C₁₀H₁₂NO₂)₂(CH₄O)₂], the Cu atom lies on a centre of symmetry and has a distorted octahedral coordination. The Cu—O(methanol) bond length in the axial direction is 2.596 (3) Å, which is much longer than the Cu—­O(carboxylate) and Cu—N distances in the equatorial plane [1.952 (2) and 1.977 (2) Å, respectively]. In mer‐tris(5‐n‐bu­tyl­pyridine‐2‐carboxyl­ato‐κ²N,O)­iron(III), [Fe(C₁₀H₁₂NO₂)₃], the Fe atom also has a distorted octahedral geometry, with Fe—O and Fe—N bond‐length ranges of 1.949 (4)–1.970 (4) and 2.116 (5)–2.161 (5) Å, respectively. Both crystals are stabilized by stacking interactions of the 5‐n‐butyl­pyridine‐2‐carboxyl­ate ligand, although hydrogen bonds also contribute to the stabilization of the copper(II) complex.     

5‐Fluoro‐1‐octanoyl­uracil

The crystal structure of 5‐fluoro‐1‐octanoyl­uracil [5‐fluoro‐1‐octanoyl­pyrimidine‐2,4(1H,3H)‐dione, C₁₂H₁₇FN₂O₃], a lipophilic prodrug of 5‐fluoro­uracil, is described. The 5‐fluoro­pyrimidine‐2,4(1H,3H)‐dione moiety is similar to the known structure of 1‐acetyl‐5‐fluoro­uracil. The 1‐octanoyl group and the 5‐fluoro­uracil moiety are essentially coplanar, with the octanoyl carbonyl group oriented towards the the ring C—H group and away from the nearer ring carbonyl group. The torsion angle C—N—C—O (from the ring CH group to the octanoyl carbonyl group) of 9.2 (2)° is similar to the corresponding torsion angles reported for 1‐acetyl‐5‐fluoro­uracil (17.3 and 1.6°) and 1,3‐di­acetyl‐5‐fluoro­uracil (8.8°).