Structures of three cis-beta(1) and three cis-beta(2) isomers of [Co(trien)(aminoacidato)](2+) complexes

The crystal structures and absolute configurations of three cis-beta (1) an d three cis-beta (2) isomers of [Co(trien)(L-aminoacidato)](2+), namely bet a (1)-Lambda (SSS)(lambda lambda delta)/(lambda delta delta)-[Co(trien)(L-i soleucinato)](ClO4)2, L-isoleucinato(triethylenetetramine)cobalt(III) diper chlorate (1), beta (1)-Delta (SRS)(lambda delta lambda)-[Co(trien)(L-valina to)](ClO4)(2), L-valinato(triethylenetetramine)cobalt(III) diperchlorate (2 ), beta (2)-Delta (RSS)(delta delta lambda)-[Co(trien)(L-pyroglutamato)]ClO 4, L-pyroglutamato(triethylenetetramine)cobalt(III) perchlorate (3), beta ( 2)-Delta (RRS)(delta delta lambda)-[Co(trien)(L-isoleucinato)]I-2.H2O, L-is oleucinato(triethylenetetramine)cobalt(III) diiodide monohydrate (4), beta (2)-Delta (RRS)(delta delta lambda)-[Co(trien)(L-isoleucinato)](ClO4)(2). - 2H(2)O L-isoleucinato(triethylenetetramine)cobalt(III) diperchlorate dihydr ate (5), and beta (2)-Lambda (SSS)(delta lambda lambda)[Co(trien)(L-leucina to)](ClO4)(2). 2H(2)O, L-leucinato(triethylenetetramine)cobalt(III) diperch lorate dihydrate (6), have been determined. Both beta (1) and beta (2) isom ers form inter-cation hydrogen-bonding interactions through double or tripl e hydrogen bonds which link the cations into helices. However, the motifs o f the interactions are different in beta (1) and beta (2) isomers, resultin g in different packing structures. A localized hydrophobic area is observed in the packing structure of (1), a unique feature amongst these six struct ures. This work describes the first synthesis of the beta (1) isomer by dir ect reaction between amino acids and cis-alpha-[Co(trien)Cl-2]Cl in mildly basic solution.