A family of polynuclear cobalt complexes upon employment of an indeno-quinoxaline based oxime ligand

The reaction of Co(OAc) 2 ·4H 2 O with LH (LH = 11 H -indeno[1,2- b ]quinoxalin-11-one oxime) in MeOH in the presence of NEt 3 forms the complex [Co III 2 Co II O(OAc) 3 L 3 ]·0.5MeOH·0.2H 2 O ( 1 ·0.5MeOH·0.2H 2 O), while repeating the reaction under solvothermal conditions yielded the heptanuclear cluster [Co II 7 L 9 (OH) 2 (OAc) 2.7 (MeO) 0.3 (H 2 O)]·4.6MeOH·3.3H 2 O ( 2 ·4.6MeOH·3.3H 2 O). Changing the starting metal salt to Co(ClO 4 ) 2 ·6H 2 O and upon the reaction with LH in the presence of NEt 3 under high temperature and pressure, we managed to isolate the decanuclear cluster [Co II 10 L 14 (OH) 3.6 (MeO) 0.4 ](ClO 4 ) 2 ·8.5MeOH·5.75H 2 O ( 3 ·8.5MeOH·5.75H 2 O), while under normal bench conditions and upon employment of pivalates in the reaction mixture complex [Co II 4 L 4 (piv) 4 (MeOH) 2 ]·MeOH·H 2 O ( 4 ·MeOH·H 2 O) was formed. Furthermore, the reaction of Co(ClO 4 ) 2 ·6H 2 O with LH and aibH (2-amino-isobutyric acid) in the presence of NEt 3 in MeOH gave the mononuclear complex [Co III L(aib) 2 ]·3H 2 O ( 5 ·3H 2 O), while upon increasing the metal–ligand ratio cluster [Co III 2 Co II L 4 (aib) 2 (OH) 2 ]·7.9MeOH ( 6 ·7.9MeOH) was isolated. Finally, repeating the reaction that yielded the mononuclear complex 5 ·3H 2 O under solvothermal conditions, gave the octanuclear cluster [Co II 8 L 10 (aib) 2 (MeO) 2 ](ClO 4 ) 2 ·6.8MeOH·7H 2 O ( 7 ·6.8MeOH·7H 2 O). Variable temperature dc magnetic susceptibility studies for complexes 2 , 3 , 4 and 7 , reveal that all clusters display dominant antiferromagnetic interactions leading to small or diamagnetic ground-states, S.