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

Abstract

The title compound, [cis-Co(en)2(NO2)2](N02) (1), crystallizes in the polar, nonenantiomorphic, monoclinic space group, Cc, with lattice constants: a = 9.198(2) •, b = 12.444(2), c = 9.963(3), and /3 = 96.76(2)~ V= 1132.39 ,~3 and d(calc; Z= 4) = 1.860 g cm 3. Thus, with NO2-as the counteranion, [cis-Oo(en)2(N02)2] crystallizes in a heterochiral lattice containing racemic pairs of cations, A total of 2699 data were collected over the range of 4 ~ -< 20 -< 70~ of these, 1859 (independent and with / -> 3~r (/)) were used in the structural analysis. Data were corrected for absorption (/~ = 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 final R(F) and Rw(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(N02)2] +, which are found to have a pair of oppositely configured en rings [i.e., ~(AB) or A(BA)], we find that in 1 the cations are in the lowest energy conformation and configuration; i.e., ~(AA) or A(8~). 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 *To whom correspondence should be addressed.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.

Stable Heterometallic Cluster Ions based on Werner's Hexol

“…Integration allowed for the assignment of the downfield signals to protons on the two types of ammine ligands ( cis and trans to the hydroxide bridges) and the upfield signal was assigned to the bridging hydroxide protons. The spectrum obtained for CoAl had many similarities to what is observed for the all‐cobalt hexol cluster, showing that they adopt a similar structure in solution. Surprisingly, the same spectrum could be collected in D 2 O with similar integration ratios to that in [D 6 ]DMSO and confirmed the stability of the cluster at ca.…”

“…The data from single‐crystal XRD shows that the aluminum analog adopts a similar structure as the original hexol cluster that contained only cobalt . At the center is a six‐coordinate Al 3+ ion, bound with bridging hydroxide ligands that connect it to the outer [Co(NH 3 ) 4 ] 3+ units.…”

Second-sphere coordination in anion binding:trans-bis(ethylenediamine-κ2N,N′)dinitrocobalt(III) periodate

“…The [Co(en) 2 (NO 2 ) 2 ] + cation has also been characterized in the crystal structures of numerous other complex salts. The cis isomer of the cation is most prevalent among these, having been observed, for example, in combination with halide anions (Bernal, 1985;Frederiksen et al, 1988), polyatomic anions, such as nitrite (Bernal et al, 1990;Marsh, 1997), and organic anions, such as malate and tartrate (Sun et al, 1998;Frederiksen et al, 1988;Sun et al, 2000). The trans isomer has been observed less frequently, in combination with iodide and thiocyanate (Bernal & Cetrullo, 1986), and with nitrate (Bortin, 1976).…”

Anion Effect on the Binary and Ternary Phase Diagrams of Chiral Medetomidine Salts and Conglomerate Crystal Formation

“…The effect of anions as conglomerators on the crystal structure of racemates was studied, mostly concerning racemic coordination complexes and limited types of organic racemates were investigated from this point of view …”

“…However, even now, the mechanism of conglomerate formation is insufficiently understood and, actually, most conglomerates have been discovered by trial-and-error rather than by design. 13 The effect of anions as conglomerators on the crystal structure of racemates was studied, mostly concerning racemic coordination complexes [14][15][16][17][18][19] and limited types of organic racemates were investigated from this point of view. [20][21][22][23][24][25][26] The structural and thermoanalytical investigations of the rac-α-phenylethylammonium salts have proved that the hydrogen phthalate and hydrogen malonate anions form racemic compounds, while the hydrogen succinate anion forms a conglomerate, the latter being the only one which could be resolved by preferential crystallization.…”