Phenomenon Of Conglomerate Crystallization Research Articles

The phenomenon of conglomerate crystallization. Part 56. The crystallization behavior of [(tren)Co(N 3) 2]X (X = Br, I): centrosymmetric to Sohnke space group phase transition caused by cooling

[(tren)Co(N 3) 2]Br ( I) and [(tren)Co(N 3) 2]I ( III) was prepared and its crystal structure determined at 293 and at 120 K. At room temperature (293 K), ( I) crystallizes as a conglomerate in space group P2 12 12 1 and remains so at 120 K, (data sets Ia and Ib, respectively). The iodide crystallizes as a racemate, space group P2 1/n ( z=4), data set ( IIIa); but, cooling to 120 K results in a phase change whereby the crystal is enantiomorphic ( IIIb) + ( IIIc), space group P2 1( z=4). There is no damage to the crystal upon undergoing the phase transition ( IIIa) → ( IIIb) + ( IIIc). In fact, the same crystals were used to collect the data sets which were cycled as follows: 293 → 120 → 293 K. The two molecules in the asymmetric unit of ( IIIb and IIIc) are homochiral demanding that the phase transition observed causes the inversion of the axial chirality of one of the five-membered rings of the iodide. This result is reproducible and was observed for all crystals cooled to 120 K. Differential scanning calorimetry confirms the existence of phase changes in the crystalline material as a result of cooling.

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)Cl 2(OH 2)](ClO 4)·H 2O ( 1) (aepn= N-(2-aminoethyl)-1,3-propanediamine) reveals that the compound crystallizes in an enantiomorphic space group P2 12 12 1 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)Br 2(OH 2)](ClO 4)·H 2O ( 2), which also crystallizes as a conglomerate in the space group P2 12 12 1. Meanwhile, a substitution of the coordinated OH 2 of 1 with NH 3 gives mer- trans-[Co(aepn)Cl 2(NH 3)](ClO 4) ( 3), which crystallizes as a simple racemate in P2 1/ 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)Cl 2(OH 2)](ClO 4) ( 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)

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

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) A, b = 7.38 (3), c = 16.20 (2) A; V = 766.6 A3 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 RW(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) A, b = 7.162 (2), c = 15.420 (3) A, and β = 107.56 (1)°; V = 107.56 (1) A3 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 Rw(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

The phenomenon of conglomerate crystallization in coordination compounds. XXIII: The crystallization behavior of [cis-Co(en)2(N3)(SO3)] � 2H2O (I) and of [cis-Co(en)2(NO2)(SO3)] � H2O (II)

A room temperature water solution of (I) crystallizes as a racemate, space groupP21/n with lattice constantsa=7.737(6),b=10.694(5),c=15.097(6) A, andβ=102.83(5)°;V=1218.05 A3 andd (calc; M.W.=337.24, Z=4) = 1.642 g cm−3. A total of 2381 data were collected over the range 4° ≤ 2θ < 50°; of these, 1452 (independent and withI ≥ 3σ(I)) were used in the structural analysis. Data were corrected for absorption (μ = 15.76 cm−1), and the relative transmission coefficients ranged from 0.8976 to 0.9984. Refinement led to the finalR(F) andRw(F) residuals of 0.0858 and 0.1116. A room temperature water solution of (II) crystallizes as a racemate in space group P21/c with lattice constantsa=6.638(3),b=11.425(8),c=15.147(16) A, andβ=93.27(6)°; F=1146.8 A andd (calc; M.W.=323.2,Z=4) = 1.872 g cm−3. A total of 2200 data were collected over the range 4° ≤ 2θ < 50°; of these, 1918 (independent and withI ≥ 3σ(I)) were used in the structural analysis. Data were corrected for absorption (μ=16.94 cm−1), and the relative transmission coefficients ranged from 0.9049 to 0.9967. Refinement led to the finalR(F) andRw(F) residuals of 0.0231 and 0.0279. The chirality symbol for the particular enantiomer of (I) refined here is ∧ (δδ), while for (II) the chirality symbol is ∧(δλ), which means that in the latter compound one of the en rings is in a higher energy conformation. We attribute this result to competitive intramolecular hydrogen-bonded interactions between the — NH2 hydrogens of the en ligands and the oxygens of the -NO2 and -SO3 ligands, strengths which are enhanced by coercing a change in sign of the torsional angle of one en ringa motion which permits both oxo ligands to form stronger hydrogen bonds while retaining proper O ⋯ O contacts. This phenomenon is not observed in (I) since the azide ligand does not compete with -SO3 for such hydrogen-bonded interactions, and nonbonded pair repulsions can be minimized without affecting the ability of — SO3 oxygens to form strong intramolecular hydrogen bonds.

The phenomenon of conglomerate crystallization. XX. Spontaneous resolution in coordination compounds. XVIII.

The title compound, [cis-Co(en)2(NO2)2](NO2) (1), crystallizes in the polar, nonenantiomorphic, monoclinic space group, Cc, with lattice constants:a=9.198(2) A,b=12.444(2),c=9.963(3), andβ=96.76(2)°;V=1132.39 A3 andd(calc;Z=4) =1.860 g cm−3. Thus, with NO2− as the counteranion, [cis-Co(en)2(NO2)2] crystallizes in a heterochiral lattice containing racemic pairs of cations. A total of 2699 data were collected over the range of 4°≤2θ≤70°; of these, 1859 (independent and withI≥3σ(I)) were used in the structural analysis. Data were corrected for absorption (μ=15.465 cm−1) and the relative transmission coefficients ranged from 0.9934 to 0.7112. Refinement was carried out for both lattice polarities and the finalR(F) andR w (F) residuals were, respectively, 0.0242 and 0.0202 for (−−−) and 0.0264 and 0.0243 for (+++). Thus, the former was selected as correct for our specimen. Unlike all previous X-ray diffraction studies of the structural properties of the cation [cis-Co(en)2(NO2)2]+, which are found to have a pair of oppositely configured en rings [i.e., Δ(λδ) or Λ(λδ)], we find that in1 the cations are in the lowest energy conformation and configuration; i.e., Δ(λλ) or Λ(δδ). We attribute this change in configuration to the formation of strong interionic hydrogen bonds between nitrite anion oxygens and the axial—NH2 hydrogens, which markedly weaken the intermolecular and intramolecular hydrogen bonds between ligand—NO2 oxygens and the hydrogens of those same amine moieties. Thus, the nitrite anions behave exactly as nitrate anions, except that the hydrogen bonds found here are stronger than those formed by the latter. This is as expected since the negative charge is delocalized over two, instead of three, oxygens.

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)A,b=22.673(6),c=10.513(1), andβ=91.41(1)°;V=1786.12 A3, andd(calc;Z=4)=1.915 g cm−3. In all, 5333 data were collected over the range of 4°≤ 2θ≤ 60°; of these, 3395 [independent and with /≥3σ(1)] were used in the structural analysis. Data were corrected for absorption (μ=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) A and those for cation 2 are 1.916(1) and 1.896(1) A. 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) A;V=999.15 A3;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) A;β=102.63(2)° andV=1090.98 A3; d(calc;z=4) = 2.192 g cm−3. Data were collected over the ranges of 4°≤2Θ≤70° and 4°≤2Θ≤55°, 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. XVII. Clavic Dissymmetry in Coordination Compounds. XV. The Effect of the Charge Compensating Ions on the Phenomenon of Conglomerate Crystallization

Abstract In this report, we discuss the effect of the counter ion on the crystallization behaviour of chiral ions which may produce racemic or conglomerate crystals. We demonstrate that the counter ion is often capable of influencing the crystallization pathway and provide examples of substances in which the same chiral ion produces enantiomorphic crystals or racemic crystals depending on the nature of the counter ion. Moreover, we demonstrate that the crystal structures of such species amply demonstrate the reasons for such differences in crystallization pathway. In the species selected for the illustrations, the underlying phenomenon being influenced by the choice of counter ion is hydrogen bonding. This summary provides examples of counter ion pairs as varied as halides vs NO3 −, halides vs NO2 −, K+1 vs Ag+, etc., influencing the choice of crystallization pathway. Also, we illustrate the fact that the same ion (i.e., NO3 −) can play either a positive or a negative role in such a selection.

The phenomenon of conglomerate crystallization. XV. Spontaneous resolution in coordination compounds. XIII. The crystallization behaviour and the crystal and molecular structure of Δ(λδ)- cis-Rh(en) 2(NO 2) 2]Cl

The title compound, I, crystallizes in the monoclinic space group P2 1 with cell constants: a = 6.599(3), b = 11.121(2), c = 8.375(1) Å and β = 106.35(2)°; V = 589.74 Å 3 and D(calc; Z = 2) = 1.974 g cm −3. The compound is isomorphous and isostructural with its Co analogue. A total of 2982 data were collected over the range of 4°  20  70°; of these, 2537 (independent and with I ⩾ 3σ( I)) were used in the structural analysis. Data were corrected for absorption (μ = 16.6 cm −1) and the relative transmission coefficients ranged from 1.000 to 0.9504. Refinement was carried out for both enantiomeric configurations and the crystal used was found to contain cations with Δ(λδ) absolute configuration. The final R( F) and R w( F) residuals were, respectively 0.0220 and 0.0239 for (−−−; i.e.Δ(λδ)) and 0.0231 AND 0.0317 FOR (+++; i.e.Λ(δλ)). Thus, the former was selected as correct for our specimen. In the case of I, as well as in the Co derivative [ cis-Co(en) 2(NO 2) 2]Cl ( II), the conformation of one of the rings is opposite that expected for the lowest energy conformation, which in the current case should be Δ(λλ)). The RhN(NO) 2 distances are 2.020(2) and 2.010(2) Å, while the RhN(amine) distances, trans to the NO 2 ligands are 2.085(2) and 2.093(1) Å, values distinctly longer than the other two RhN distances (2.064(1) and 2.068(1) Å). The latter are the RhN distances to the terminalNH 2 ligands located trans to each other. Thus, we observe a trans effect, which is more pronounced in I than in II, and which is of comparable magnitude to that observed in the case of the trien derivative, [ cis-α-Rh(trien)(NO 2) 2]Cl( III). Parallel with an increase in metalN distances in going from [ cis-α-Co(trien)NO 2) 2]Cl·H 2) ( IV) to ( III) is an increase in the torsional angles of the outer rings (NCCN) of about 10°. Comparison of these parameters in I and II reveal that this change is not so marked for this pair since in I they are −54.9° and 52.8° while in II they are 50.2° and −48.1°; i.e. a change of only 4°. This important difference between trien and en derivatives is caused by the presence of the central five-membered ring, which for compounds III and IV remains largely unchanged, except for the metalN distances. The NO bond lengths are 1.244(3), 1.220)(2), 1.237(2) and 1.211(2) Å, which are similar to those found for the analogous Co isomer. The CN bond lengths are 1.492(3), 1.474(2), 1.486(2) and 1.475(2) Å, while the CC bonds are 1.509(3) and 1.524(3) Å. These values are also comparable with those obtained for the Co isomer and, in fact, the pattern of the bonds is nearly identical in both, including the common feature of having a longer CC bond for the en ring with the conformation opposite that expected. As was the case with the Co analogue, the Cl − anion is associated with the hydrogens of the secondary nitrogen ( trans to the −NO 2) ligands, the Cl…H7 distance being 2.18(3) Å and the <Cl…H7N2 = 163°.

The phenomenon of conglomerate crystallization. XIII. Spontaneous resolution in coordination compounds. X. The effect of intramolecular hydrogen bonding on ring conformations of polyamine ligands

The phenomenon of conglomerate crystallization. XIII. Spontaneous resolution in coordination compounds. X. The effect of intramolecular hydrogen bonding on ring conformations of polyamine ligands

The phenomenon of conglomerate crystallization. XI. Clavic dissymmetry in coordination compounds. VIII. An investigation of the crystallization, conformational and configurational behaviour of [ mer-Co(1,5-diamino-3-azapentane)(NO 2) 3

[ mer-Co(dien)(NO 2) 3] does not form conglomerates when crystallized from water at a variety of temperatures; instead, it crystallizes in the racemic space group Pbca. Crystals obatined at 21 °C, and studied by X-ray diffraction at 16 °C, crystallize with unit cell parameters of a = 13.030(3), b = 12.688(2) and c = 13.172(3) Å; V = 2177.66 Å 3, D(calc; M = 300.12 g mol −1; Z = 8) = 1.831 g cm −3. Data were collected with Mo Kα (4° ⩽ 20 ⩽ 50°; 2268 data), corrected for absorption (μ = 16.01 cm −1; relative transmission coefficients range from 0.9026 to 1.0000) producing a reduced set of 1556 reflections for which I ⩾ 3σ (I). The structure was solved by the Patterson method and refined to R(F) = 0.0282 and R w( F) = 0.0330, using as weights w = [σ( F o)] −2. The Co(dien) fragment has the shape of pleated sheet in which the conformation of the two (NHCH 2CH 2NH 2) fragments are δ and λ or their inverse. The two CoN(H 2) distances are identical (1.942(1) and 1.944(1) Å) and shorter than the CoN(H) distance of 1.952(1) Å. The two mutually trans CoN(O 2) bonds are 1.97(1) and 1.931(1) Å, reflecting an interesting molecular asymmetry; the effect in question being the bending of one of the NO 2 ligands towards the NH 2CoNH 2 edge of the molecule so as to maximize the strength of the ▪ bonds. The bent NO 2(N4) is the one with the long CoN distance. Finally, the unique CoN(O 2) distance is 1.914(1) Å, shorter than either of the previous ones and a clear example of the trans effect. The geometry at Co is a distorted octahedron, as expected. The largest distortion being the angle N1CoN3(169.9(6)°) defined by the two terminalNH 2 ligands. Other angular distortions are smaller. The NC distances range from 1.473(2) to 1.493(2) Å and the two CC distances are 1.505(2) and 1.498(2) Å. Refined NH (terminal) distances range from 0.81(2) to 0.88(2) Å and the secondary NH distance is 0.90(1) Å. CH distances range from 0.90(2) to 1.05(2) Å.

The phenomenon of conglomerate crystallization. X. New classes of clavic coordination compounds crystallizing as conglomerates and enumeration of further factors relevant to conglomerate behaviour

Octahedral Co(III) compounds of the sulfenyl and sulfinyl families, as well as their Se counterparts, have been found to readily undergo spontaneous resolution into crystalline conglomerates. Examples of octahedral compounds of Co(III) containing −S 2O 3 and −SO 3 ligands have also been found to do so. In fact, despite their superficial chemical differences sulfenyls and sulfinyls share with these latter species simple stereochemical fragments which render both of them clavic. An example of a clavic Ru-π-olefin, [Ru(NH 3) 5(fumarate)] 2+ cation, is discussed also. From the variety of compounds discussed in this report, it is clear that the phenomenon described previously is not the province of a narrow class of compounds best classified as an interesting oddity.

ChemInform Abstract: The Phenomenon of Conglomerate Crystallization. Part 9. Clavic Dissymmetry in Coordination Compounds. Part 7. An Investigation of the Crystallization Behaviour of (trans‐Co(en)2(ONO)X)Y, (trans‐Co(en)2(NO2)X)Y, with (X: NO‐ 2, NCS‐) and (Y: I‐, ClO‐ 4, NO‐ 3, NCS‐) and the Crystal Structures of Racemic (trans‐Co(en)2(NO2)2)I and of Racemic (trans‐Co(en)2(NO2)2)NCS. Why Are Some Conglomerates and Some Racemic?

AbstractThe compound (Ia) crystallizes in the space group C2/c with Z=4 and (Ib) in P1, Z=2.

ChemInform Abstract: The Phenomenon of Conglomerate Crystallization. Part 8. Spontaneous Resolution in Coordination Compounds. Part 6. The Chiral Behaviour of (trans‐(P, or M)‐Co(NH3)2(NO2)4)‐ Anions, Dissymmetric by Virtue of Their Propeller Conformation.

AbstractThe study of salts of the title anion reveals that its gross stereochemistry is largely independent of the compensating cation and to variations in packing forces.

The phenomenon of conglomerate crystallization. IX. Clavic dissymmetry in coordination compounds. VII. An investigation of the crystallization behaviour of [ trans-Co(en) 2(ONO)X]Y, [ trans-Co(en) 2(NO 2)X]Y, With (X = NO 2−, NCS −) and (Y = I −, ClO 4−, NO 3−, NCS −) and the crystal structures of racemic [ trans-Co(en) 2(NO 2) 2]I (VII) and of racemic [

The compounds [ trans-Co(en) 2(NO 2) 2]X (X = I, NCS) will, hereafter, be referred to as VII and VIII. Compound VII crystallizes in space group C2/ c with cell constants a=10.743(2), b=9.179(3), c= 13.432(3) Å, β=112.28(2)°; V=1225.56 Å 3, d calc=2.157 g cm −3 and Z=4. Chemical formula for VII= C 4H 16N 6O 4CoI; M R = 398.05 and μ= 39.012 cm t̄1; absorption corrections were made and the relative values of the transmission coefficients were 99.96 to 77.38. Compound VIII crystallizes in the triclinic system, space group P 1 , a=6.496(2), b=9.192(3), c=10.956(8) Å, a=89.58(5)°, β= 79.70(5)°, γ=75.7t(2)°; V=623.26 Å 3, d calc= 1.754 g cm −3 and Z=2. Chemical formula for VIII = C 5H 16N 7O 4SCo; M R = 329.22, μ = 15.532 cm −1 and transmission coefficients ranged from 99.99 to 73.36. Total data collected for VII: 1238 of which 1048 were independent and had I> 3σ( I) and VIII: 3840 of which 657 were symmetry related forms which were averaged ( R=0.012). The remaining 3183 were above 3σ( I) and were, thus considered observed. Both structures were solved by Patterson methods and refined to R and R f factors of 0.0284 and 0.0350 for VII and 0.0216 and 0.0276 for VIII. Both molecules crystallize in centrosymmetric space groups. The cation of VII sits at a crystallographic inversion center while that of VIII is located at a general position; nonetheless, it has a nearly perfect, molecular, inversion center. In both compounds, the cations have a λ and a δ conformed ethylenediamine which in the case of VII is required by the inversion center. Comparison of the stereo- chemical parameters of the Co(en) 2 fragments in VII and VIII reveal them to be nearly identical. However, the −NO 2 ligands in VII are bent towards the terminal −NH 2 of the basal plane in what is, obviously, an attempt to form as strong NH···ON intramolecular hydrogen bonds as possible. This is not the case with the −NO 2 ligands of VIII which are almost exactly orthonormal to the CoN 4 base. This phenomenological difference in behaviour of the −NO 2 ligands is due to the difference in hydrogen bonding ability of the two compensating anions. Bond lengths and angles compare favorably with literature results on relevant substances.

The phenomenon of conglomerate crystallization. VIII. Spontaneous resolution in coordination compounds. VI. The chiral behaviour of [ trans-( P, or M)-Co(NH 3) 2 (NO 2) 4] − anions, dissymmetric by virtue of their propeller conformation

Octahedral coordination compounds chiral by virtue of having fixed propeller conformations are, apparently, quite rare. Despite the fluxionality of the anion [ trans-( P, or M)-Co(NH 3) 2(NO 2) 4] −, it is possible to establish its chiroptical properties in the solid. Our studies of its salts suggest that, conformationally, it is relatively impervious to the nature of the compensating cation and to variations in packing forces. Consequently, a useful method of determining the chiral symbol of this anion is proposed based on that of stereochemically rigid cations with which it forms diastereoisomeric salts. In the case of solutions of the ions [ cis-Co(en) 2(NO 2) 2] + and [ trans-Co(NH 3) 2(NO 2) 4] −, the crystals obtained from a conglomerate are expected to contain Λ(δλ)-(−) 589-[ cis-Co(en) 2(NO 2) 2][ trans-( P)- Co(NH 3) 2(NO 2) 4] and Λ(δλ)-(+) 589-[ cis-Co(en) 2(NO 2) 2][ trans-( M)-Co(NH 3) 2(NO 2) 4].

The phenomenon of conglomerate crystallization. VII. Clavic dissymmetry in coordination compounds.V. An investigation of the crystallization behavior of [ cis-β-Co(triethylenetetramine)(NO 2) 2]X (X = I, NO 3) and the crystal structure of racemic [ cis-β-Co(trien)(NO 2) 2]NO 3

[ cis-β-Co(trien)(NO 2) 2]X (X=I −, NO 3 −) were prepared and examined crystallographically to ascertain whether or not they undergo conglomerate crystallization. As predicted earlier, the nitrate crystallizes as a racemate: space group P2 1/ n with cell constants of a = 7.604(3), b = 13.019(2), c = 14.472- (3) Å, β = 98.13(3)°, V = 1418.26 Å 3, D c = 1.682g cm −3, Z = 4. The bonding parameters and overall stereochemistry of the [ cis-β-Co(trien)] fragment of the cation are essentially identical with that of resolved and racemic salts sharing this common fragment, proving that lattice forces do not play a major role in shaping its geometrical features. The iodide crystallizes in the monoclinic space group Cc, with cell constants of a = 15.65(1), b = 6.53(3), c = 13.095(7) Å, β = 100.59(5)°, V = 1314.72 Å 3, D c=2.142 g cm −3, Z = 4. The crystals of the iodide are not only extremely small but of poor quality, allowing only a qualitative solution of the structure which, nonetheless, is sufficient to establish that this salt also crystallizes as a racemate - a surprise in view of the fact that the α isomer crystallizes as a conglomerate; thus, there is a major difference in the crystallization behaviour of this pair of geometrical isomers.

ChemInform Abstract: The Phenomenon of Conglomerate Crystallization. Part 5. Clavic Dissymmetry in Coordination Compounds.

The title compound crystallizes in the space group P212121 with Z=4.

The Phenomenon of Conglomerate Crystallization. V. Clavic Dissymmetry in Coordination Compounds. IV. A Neutron Diffraction Study of K[ trans-Co(NH 3) 2(NO 2) 4

The structure of K[ trans-Co(NH 3) 2(NO 2) 4] has been determined by neutron diffraction data collected at room temperature ( ca. 21 °C). The substance crystallizes as a conglomerate of antipodal crystals, many large enough for neutron diffraction work. The space group and cell constants are: P2 12 12 1; a = 11.275(3), b = 12.806(5) and c = 6.696(3) Å. The cell volume is 966.82 Å 3 and given the M r of 316.12 g mol −1, the D(calc; Z = 4) is 2.170 g cm −3. The data (1553 unique reflections) were corrected for absorption (μ = 79.533 cm −1) and there was no decay during data collection, as expected from the X-ray study. All heavy atoms were initially placed at the positions found with X-rays, refined isotropically and, after locating the hydrogens in a difference map, all atoms were refined isotropically. Conversion to anisotropic motion was followed by 12 cycles of least-squares fitting (200 variables), at which point the structural refinement converged to its final R and R w factors of 0.056 and 0.056, respectively. The goodness of fit was 1.133. The positional parameters of the two studies are in close agreement, as expected. For example, the average value of the CoN(NH 3) bonds in the X-ray and neutron studies are, respectively, 1.958(3) Å and 1.949(9) Å. The average value of the CoN(NO 2) distances for the X-ray and neutron studies are 1.956(3) Å and 1.948(9) Å, while the average NO distances are 1.230(4) and 1.222(6) Å for the former and latter, respectively. The most important result derived from this study is the accurate location of the hydrogens of the −NH3 ligands which had caused problems in two previous X-ray studies of salts of this anion. In this analysis, we found that −N1(NH 3) is well behaved thermally while −N2(NH 3) is much less so, the reason being that the three hydrogens of the amines attempt to form hydrogen bonds with the adjacent oxygens of the basal plane −NO 2 ligands — which is impossible while satisfying all of them equally well. One of the two amino ligands manages better than the other one, as we shall demonstrate below.