Hydrogen-bonding association model tris

C3+ complex cation always favors the homochiral combination (A-A or A-A) with the complex anion, while the C2 " complex cation always favors the heterochiral combination (A-A or A-A) with the complex anion. This tendency is explained by assuming that straight N-H--0 hydrogen bonds are formed in such a favorable pair. This hydrogen bonding association model has made possible the highly efficient optical resolution of electrically neutral tris(aminoacidato)cobalt( III). 

Pyrrole also acts as a -electron donor in association with tri-halomethanes to form weak 1 1 CH-7T complexes (20).141 Similarly pyrrole appears to form (pyrrole) 7T-H-0 bonds with phenol instead of an NH-O hydrogen bond or NH-v (phenol) bonds.112 The association between pyrrole and nitriles has been described both as NH-N132 (21) and as NH-n-146,156 (22) hydrogen-bonded complexes. No definite conclusion has been reached but the NH frequency difference between the bonded and nonbonded vibration is more compatible with a NH-7r-bonded model (Table IV). 

---