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.