The phenomenon of conglomerate crystallization. XVIII. Clavic dissymmetry in coordination compounds. XVI

The x-ray crystal structure of {[Co(NH₃)₄(CO₃)]NO₃}₂ · H₂O has been determined as part of a study of the intra- and interionic interactions present in crystals of several transition-metal-amine complexes chosen to examine the occurrence and causes of conglomerate crystallization. {[Co(NH₃)₄(CO₃)]NO₃}₂ · H₂O crystallizes in the monoclinic space group P2₁/n with cell constantsa=7.4960(9)Å,b=22.673(6),c=10.513(1), and=91.41(1)°;V=1786.12 ų, andd(calc;Z=4)=1.915 g cm^–3. In all, 5333 data were collected over the range of 4° 2 60°; of these, 3395 [independent and with /3(1)] were used in the structural analysis. Data were corrected for absorption (=19.361 cm^–1) and the relative transmission coefficients ranged from 0.9987 to 0.8013. The data were of a quality such that both ammonia and water hydrogens were found in difference Fourier maps. The finalR(F) andR _w(F) residuals were, respectively, 0.0333 and 0.0332. A trans effect is observed for both cations of {[Co(NH₃ (CO₃)]NO₃}₂ · H₂O. The equatorial nitrogens, trans to the carbonato oxygens, have shorter Co-N distances than the axial nitrogens, trans to one another. The carbonato ligands are not symmetrically bonded to their respective metal centers. The Co-O distances for cation 1 are 1.913(1) and 1.903(1) Å and those for cation 2 are 1.916(1) and 1.896(1) Å. The structure reveals the existence of an intricate array of hydrogen bonds, involving both the chelating and nonchelating oxygens of the carbonato ligands as hydrogen bond acceptors of the amine hydrogens. The amine hydrogens are also involved in significant hydrogen-bonding interactions with the nitrate oxygens and water of crystallization, although they are generally weaker than those of the carbonato oxygens.     

The phenomenon of conglomerate crystallization. XIX. Clavic dissymmetry in coordination compounds. XVII

[Co(NH₃)₄(oxalato)]NO₃·H₂O (1) crystallizes as a conglomerate in space groupP2₁2₁2₁ with unit cell constants ofa=7.944(3),b=9.904(11), andc=12.700(2) Å;V=999.15 ų;d(calc.;z=4)=1.968 g cm^–3. [Co(NH₃)₄(oxalato)]¦·H₂O (2) crystallizes in space groupP2₂/n with cell constants ofa=7.285(1),b=9.959(3),c=15.410(5) Å;=102.63(2)° andV=1090.98 ų; d(calc;z=4) = 2.192 g cm^–3. Data were collected over the ranges of 4°270° and 4°255°, respectively for compounds1 and2. This resulted in a total of 2515 and 2823 data for the solution and refinement of the structures of compounds1 and2, respectively. When the refinements converged, the finalR(F) andR _w (F) values were, respectively, 0.073 and 0.080 for1 and 0.0378 and 0.0353 for2.Since neither data set was sufficiently good to give a sensible set of positions for all of the hydrogens, the stereochemistry of the two cations could only be defined by the positions of the heavy atoms. In the absence of reliable amine hydrogen positions, N(amine)-O(nitrate and oxalate) distances were examined. Close N(amine)-O(nitrate and oxalate) contacts indicate the presence of a network of significant hydrogen bonds in1. The N-O distances for compound2 also show the presence of hydrogen bonding between the amines and the oxalate ligand and water; however, the bonds are not of the same magnitude as the interactions involving the nitrate oxygens in1. Despite the similarity between the cations of1 and2, the Co-N distances in the two do not exhibit the same pattern. In1, the Co-N distances for amines trans to one another are shorter than the Co-N distances for amines trans to oxalate oxygens; this effect is reversed in2.     

The phenomenon of conglomerate crystallization: Part 52. Stereochemical control of the crystallization pathway by small alterations of ligands

The X-ray structure analysis of mer-trans-[Co(aepn)Cl₂(OH₂)](ClO₄)·H₂O (1) (aepn=N-(2-aminoethyl)-1,3-propanediamine) reveals that the compound crystallizes in an enantiomorphic space group P2₁2₁2₁ implying a spontaneous resolution of its racemic solution, known as conglomerate crystallization. Substitutions of the two chloride ligands with bromides result in the isostructural compound mer-trans-[Co(aepn)Br₂(OH₂)](ClO₄)·H₂O (2), which also crystallizes as a conglomerate in the space group P2₁2₁2₁. Meanwhile, a substitution of the coordinated OH₂ of 1 with NH₃ gives mer-trans-[Co(aepn)Cl₂(NH₃)](ClO₄) (3), which crystallizes as a simple racemate in P2₁/n space group. When N-(3-aminopropyl)-1,3-propanediamine (dpt) is used instead of aepn in the preparation of 1, it gives racemic crystals of mer-trans-[Co(dpt)Cl₂(OH₂)](ClO₄) (4) whose molecular packing pattern is identical to that of 3. In the conglomerate structures, the protons of coordinated water ligand are strongly hydrogen-bonded to the oxygen of a water of crystallization to form a spiral packing structures. In the packing structures of 3 and 4, two molecules of opposite chirality are brought together around a crystallographic center of inversion by hydrogen bonds of the protons of the corresponding tridentate amine ligand with oxygens of perchlorate anion.     

The phenomenon of conglomerate crystallization of organic compounds. Part 4. The structures of 2,2′-biphenyldisulfide (I) and 2,2′-biphenyldisulfide monoxide (II)

A racemic solution of 2,2′-biphenyldisulfide ( I ), C₁₂H₈S₂, produces conglomerate crystals of ( I ) belonging in space group P3₂21 (no. 154) with lattice constants: a = 7.38 (3) Å, b = 7.38 (3), c = 16.20 (2) Å; V = 766.6 ų and d(calc; M.W. = 216.32, z = 3) = 1.406 g-cm⁻³, d(meas) = 1.47 g-cm⁻³. A total of 1150 data were collected over the range of 4° ≤ 2θ ≤ 60° using film data (Weissenberg); of these, 448 [independent and with I ≥ 3σ(I)] were used in the structural analysis. Refinement converged to final residuals of 0.080 and 0.082 for R(F) and R_W(F), respectively. The molecule is located at the twofold axis of the space group. A solution of 2,2′-biphenyldisulfide mono-oxide ( II ), C₁₂H₈S₂O, produces centrosymmetric crystals of II belonging in space group P2₁/c with lattice constants: a = 9.947 (1) Å, b = 7.162 (2), c = 15.420 (3) Å, and β = 107.56 (1)°; V = 107.56 (1) ų and d(calc; M.W. = 232.31, Z = 4) = 1.473 g-cm⁻³. A total of 2114 data were collected over the range of 4° ≤ 2θ ≤ 50°; of these, 1089 [independent and with I ≥ 2.5σ(I)] were used in the structural analysis. Data were corrected for absorption (μ = 4.539 cm⁻¹), and the relative transmission coefficients ranged from 0.9198 to 0.9998. Refinement converged to final residuals of 0.0313 and 0.0300 for R(F) and R_w(F), respectively. For I , the central six-membered ring C₄S₂ contains a helical C₂S₂ fragment whose conformational chirality is defined by a torsional angle of 59.98°. The benzene rings are the expected, planar hexagons characteristic of aryl rings. By comparison with I , the torsional angle of the C₂S₂ fragment of the mono-oxide is diminished (52.9°) by the introduction of the S=O fragment. We believe alteration of molecules (such as functionalization) causing large changes in torsional angles of helical fragments of molecules may play a role in the selection of their crystallization mode; however, it is not the only factor dictating that choice, which is also affected by steric hindrance to the formation of short intermolecular contacts leading, in the solid state, to the formation of homochiral, infinite helical strings, as we shall demonstrate in the text. This study clearly shows the influence of those contacts on the formation of the strings. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:65–74, 1998     

Oganoboron compounds : XVIII. Chlorodiualkylaminophenylboranes

The synthesis and properties of a series of chlorodialkylaminophenylboranes, PhB(NR₂)CL, are reported and their ¹H and ¹³C NMR spectra discussed     

Conglomerate crystallization in organic compounds II. The conformation,configuration, and spontaneous resolution of 1-phenyl-2-cyano-cyclopropane

The crystal structure of 1 -phenyi-2-cyano-cyclopropane was investigated to probe the stereochemical effects of placing different groups at the 2-position of the phenylcyclopropane moiety. The substance crystallized in space group P2₁2₁2₁ with cell constants a=16.921(3), b=7.699(2), and c=6.251(2) Å; V=814.33 ų and D (calc; z=4) =1.168 g·cm^–3. Final R(F)=0.04, using unit weights. The phenyl substituent is almost exactly in the bi-secting conformation with respect to the C-C-C angle at the point of attachment to cyclopropane. The average value of the C-C distances in the three-membered ring is 1.501 Å, which is on the low side of the ranges cited in previous studies. When we apply the additivity principle to our measured geometrical data and calculate the asymmetry parameters, the value of _cns [0.012(3)] is a little low, but within experimental error it is in accord with the value (0.017) given by Allen. However, our value of _cns (0.006(3)] is substantially lower than Allen's, which is surprising, since the bisecting phenyl ring can exert its maximum effect on the asymmetry of cyclopropane. The substance undergoes spontaneous resolution into a conglomerate of chiral crystals. Unfortunately, in the absence of anomalous scatterers, the absolute configuration could not be determined; nonetheless, the space group in which the compound crystallizes is P2₁2₁2₁, which leaves no ambiguity to the fact that the crystals are a conglomerate.     

Spontaneous resolution among chiral glycerol derivatives: crystallization features of ortho-alkoxysubstituted phenyl glycerol ethers

Five chiral arylglycerol ethers 2-R-C₆H₄-O-CH₂CH(OH)CH₂OH (R = OMe, OEt, OPrⁿ, OPrⁱ, OBu^t) have been prepared in racemic and enantiopure form. The melting points and enthalpies of fusion of every species were measured by differential scanning calorimetry. Binary phase diagrams were reconstructed for the whole family, the entropies of the mixing of the enantiomers in the liquid state, and Gibbs free energy of formation of the racemic compound, as well as Pettersson i-values were derived from the thermal data. The differences in the phase behavior of the investigated compounds were associated with the conformations of the alkoxy fragments.     

Studies on thermal stabilities of coordination compounds by gas chromatography: XVIII. Activation and hydrogenation of coordinated CN−

Various metal (Cr, Mn, Fe, Co, Ni, Cu, Zn, Ag, Sn, La) ferrocyanides and ferricyanides may be considered as a multibond activation model of bimetal coordination, since CN^? acts as a typical ambident ligand bonded at the two ends with two metal ions. In accordance with hydrogenation reactions of CN^? taking place during thermal decomposition in hydrogen, the activation effect of bimetal coordination and the mechanism of hydrogenation reaction of CN^? are discussed from the viewpoint of the crystal structure and the electron structure of the complexes. The activation degree of CN^? bonded with various metal ions has been investigated. It was found that the temperature at which the triple bond of CN^? breaks with top speed to evolve NH₃ correlates closely with the standard electrode potential, and d electron configuration of the metal ions.     

Preferential crystallization in an unusual case of conglomerate with partial solid solutions

Ethanolamine mandelate (E.M.) crystallizes as a stable conglomerate and has been found to form partial solid solutions. The crystal structure of the pure enantiomer has been solved from single-crystal X-ray diffraction. In order to determine the extreme compositions of the partial solid solutions in equilibrium (87% ee), the isothermal ternary section in the system [(+)-E.M.–(−)-E.M.–(ethanol–water azeotropic mixture)] was established at 25 °C. Several consecutive preferential crystallization attempts (AS3PC method) were undertaken between T_B = 41 °C (starting temperature) and T_F = 25 °C (final temperature) on a 2-L scale.We initially expected to obtain crude crops whose enantiomeric purities would be close to that defined by the isothermal ternary phase diagram (T_F). In fact, the filtered solid phases are of lower enantiomeric excesses: ca. 62% ee. The monitoring of the mother liquor composition over the course of the entrainment shows that the enantiomeric composition of the filtered solid is related to the metastable equilibria involved in the preferential crystallization.     

The isolation of a metastable conglomerate using a combined computational and controlled crystallization approach

While the use of additives to control the crystallization of polymorphs is well known, similar methodology to promote the crystallization of a metastable conglomerate over a stable racemic compound in enantiomeric systems has not been reported. Here we demonstrate this phenomenon in the case of 2-chloromandelic acid.     

Spontaneous resolution of a novel chiral coordination polymer through supramolecular interactions and solvent symmetry breaking

The spontaneous resolution reaction of racemic trans-2,3-dihydro-2,3-dipyridyl-benzo[e]indole 1 with Cd(ClO₄)₂·6H₂O in the presence of 2-butanol under solvothermal reaction conditions favors the formation of crystal 2 [P-Cd(R,R,-1)₂(ClO₄)₂], while a similar reaction in the presence of ethanol only favors the formation of crystal 3 [M-Cd(S,S,-1)₂(ClO₄)₂]. The crystal structural determination shows that both 2 and 3 crystallize in chiral enantiomorphous space groups (P6₁22 and P6₅22) and their structures are 1D infinite chain, and are just enantiomorphous pairs most like. The spontaneous resolution process displays estimated ee values of ca. +0.6 for 2-butanol and ca. −0.4 for ethanol. Enantiomerically pure (S,S)-trans-2,3-dihydro-2,3-dipyridyl-benzo[e]indole (S,S,-1) can be obtained through the decomposition of mechanically separated 3. Additionally (S,S,-1) also crystallizes in a chiral space group (P2₁). The CD (circular dichroism) spectra of both 2 and 3 in the solid state are also approximately enantiomorphous pairs. However, their fluorescent spectra in the solid state display a moderate difference in maximum emission peaks (Δλ = 19 nm). Crystal data for 2: C₄₄H₃₄Cl₂N₆O₈Cd, M = 958.07, hexagonal, P6₁22, a = 10.5488(5), c = 68.256(4) Å, α = γ = 90°, β = 120°, V = 6577.8(6) Å³, Z = 6, D_c = 1.451 mg m⁻³, R₁ = 0.0498, wR₂ = 0.1124, μ = 0.679 mm⁻¹, S = 0.623, Flack χ = −0.02(6). For space group P6₅22, R₁ = 0.0670, wR₂ = 0.1602, S = 0.725 with a Flack value of 1.03(7); Crystal data for 3, C₄₄H₃₄Cl₂N₆O₈Cd, M = 958.07, hexagonal, P6₅22, a = 10.5446(3), c = 68.265(3) Å, V = 6573.3(4) Å³, Z = 6, D_c = 1.452 mg m⁻³, R₁ = 0.0444,wR₂ = 0.1002, μ = 0.679 mm⁻¹, S = 0.558, Flack χ = 0.01(5). For space group P6₁22, R₁ = 0.0501, wR₂ = 0.1178, S = 0.599 with a Flack value of 1.00(5). The low Flack parameter indicates that the absolute configurations of 2 and 3 are stated; Crystal data for (S,S)-1, C₂₂H₁₇N₂, M = 323.39, orthorhombic, P2₁2₁2₁, a = 9.2598(7), b = 9.4617(8), c = 19.1452(16) Å, V = 1677.4(2) Å³, Z = 4, D_c = 1.281 mg m⁻³, R₁ = 0.0417, wR₂ = 0.1191, T = 293 K, μ = 0.077 mm⁻¹, S = 0.862.     

Spontaneous chiral resolution of a coordination polymer with distorted helical structure consisting of achiral building blocks

Reaction of achiral 2,5-diphenyl-3,4-di(3-pyridyl)cyclopenta-2,4-dien-1-one (2) with ZnCl2 and HgBr2, respectively, afforded the helically chiral coordination polymers [(2)ZnCl2]infinity and [(2)HgBr2]infinity, which show spontaneous chiral resolution, forming colonies of homochiral crystals.     

Electrochemistry of coordination compounds: Part XVIII. Electrochemical behaviour of d8 iron and osmium nitrosyl complexes a comparison with their ruthenium analogue

A detailed study of the electrochemical behaviour of the d⁸ complexes [Fe(NO)(Ph₂PCH₂CH₂PPh₂)₂]⁺ and [Os(NO)(Ph₂PCH₂CH₂PPh₂)₂]⁺, with emphasis on the properties of the reduced species, has been made and the results compared with those obtained in the reduction of the corresponding ruthenium derivative. the reduction proceeds in two reversible one-electron steps leading to d¹⁰ anionic complexes through an intermediate which, in the case of iron, is labile towards the loss of one phosphorus ligand. A tentative interpretation of this behaviour is suggested.     

Studies in the heterocyclic series. XX. 1,4-Diazaphenoxazine and related compounds

As part of our program on the synthesis of new psychotropic agents, the parent rings of two diazaphenox-azines are described. The reaction of 2-aminophenol and 2,3-dichloropyrazine in alkaline media gave good yields of 1,4-diazaphenoxazine. Replacement of 2,3-dichloropyrazine with 2,3-dichloroquinoxaline gave on the other hand the heterocycle, 1,4-diazabenzo[b]phenoxazine. Nitration and S-oxide formation were achieved by reaction with mixed nitric and sulfuric acids. Mechanistic pathways to these compounds were also discussed.