The behaviour of the metal complex anion salts (R+)2[Ni(dmit)2]2-, (R+)2[Ni(mnt)2]2- and R+[Ni(dmit)2]- where R+ = (CH3)2(C12H25)2N+ at the air-water interface has been investigated. Reproducible isotherms are obtained only by leaving the salts on the water surface for over an hour. This time is reduced at higher subphase temperatures. From surface pressure isotherms it is concluded that the limiting area at collapse is governed mainly by the dodecyl chains of the cation, with some contribution from vertically stacked anions. Surface potential measurements suggest that the ionic charges of the salt are coplanar. LB deposited films of the pure salts all show a large increase in conductivity when exposed to bromine vapour.