CHLOROMETAL(III) COMPLEXES OF A NEW CHIRAL QUINQUEDENTATE POLYAMINO ACID-BASED ON (SS)-TRANS-CYCLOHEXANE-1,2-DIAMINE

The potentially quinquedentate ligand lamino)-2-(2-aminocyclohexyl-ami nomethyl)propionic acid (HL(1)), prepared via a metal-directed condens ation reaction, readily formed a (carboxylatotetraamine) chtorocobalt( III) complex cation;as well as the rhodium(III) and chromium(III) anal ogues. The compound SS,SS-[CoL(1)(Cl)] [ClO4]. 0.75HClO(4) . 2H(2)O cr ystallizes in the orthorhombic space group P2(1)2(1)2(1), a=7.825(2). b=16.566(6), c=19.737(11) Angstrom. and the crystal structure determin ed by X-ray diffraction methods refined to a residual of 0.066 for 147 5 independent observed reflections. The co-ordinated chloride has a tr ans disposition relative to the carboxylate group of the ligand. the t wo pairs of nitrogen donors from the cyclohexane-1,2-diamine residues being coplanar with the cobalt ion. The NHCH2CH(CO2-)CH2NH core of the ligand necessarily occupies an octahedral face. Metal-nitrogen distan ces [Co-N 1.920(11)-1.982(11) Angstrom] are slightly longer than in th e 3-(2-aminoethylamino)-2- (2-aminoethylaminomethyl)propionic acid ana logue although the metal-oxygen distance [1.916(10) Angstrom] is compa rable to that in the analogue, as is the Co-Cl distance [2.223(4) Angs trom]. Comparisons of structures and kinetics of base hydrolysis with related systems are drawn.