or a compound cation such as ammonium (NH4+), methylammonium (CH3NH3+), hydroxylammonium (HONH3+) or hydrazinium (N2H5+), B is a trivalent metal ion, such as aluminium , chromium , titanium , manganese , vanadium , iron (III) , cobalt(III) , gallium , molybdenum , indium , ruthenium , rhodium , or iridium .