The dianion of the bis[l,2,5]thiadiazolo derivative of tetracyanoquinodimethane (BTDA-TCNQ) was isolated as a stable sodium salt; the dihydro derivative of BTDA-TCNQ, containing the benzo[l,2-c: 4,5-~']bis[l,2,5]thiadiazole skeleton, was found to be a strong dibasic acid.Recently we have prepared the bis[ 1,2,5]thiadiazolo derivative of tetracyanoquinodimethane (BTDA-TCNQ) ,i. a new acceptor which forms highly conductive complexes with donors. 1 The presence of thiadiazole rings enlarges the n-electron system and reduces Coulombic repulsion, which is reflected in the smaller log K,,, value (8.10) as compared with that of TCNQ (9.31).1 Therefore, the dianion of BTDA-TCNQ (BTDA2-) was expected to be persistent, in contrast t Benzo[l,2-c : 4,5-c']bis[ 1,2,5]thiadiazole-4,8-diylidenedi(malononitrile).