Passage: Iridium forms compounds in oxidation states between −3 and +9; the most common oxidation states are +3 and +4. Well-characterized examples of the high +6 oxidation state are rare, but include IrF6 and two mixed oxides Sr2MgIrO6 and Sr2CaIrO6. In addition, it was reported in 2009 that iridium(VIII) oxide (IrO4) was prepared under matrix isolation conditions (6 K in Ar) by UV irradiation of an iridium-peroxo complex. This species, however, is not expected to be stable as a bulk solid at higher temperatures. The highest oxidation state (+9), which is also the highest recorded for any element, is only known in one cation, IrO+4; it is only known as gas-phase species and is not known to form any salts.Iridium dioxide, IrO2, a blue black solid, is the only well-characterized oxide of iridium. A sesquioxide, Ir2O3, has been described as a blue-black powder which is oxidized to IrO2 by HNO3. The corresponding disulfides, diselenides, sesquisulfides, and sesquiselenides are known, and IrS3 has also been reported. Iridium also forms iridates with oxidation states +4 and +5, such as K2IrO3 and KIrO3, which can be prepared from the reaction of potassium oxide or potassium superoxide with iridium at high temperatures.Although no binary hydrides of iridium, IrxHy are known, complexes are known that contain IrH4−5 and IrH3−6, where iridium has the +1 and +3 oxidation states, respectively. The ternary hydride Mg6Ir2H11 is believed to contain both the IrH4−5 and the 18-electron IrH5−4 anion.No monohalides or dihalides are known, whereas trihalides, IrX3, are known for all of the halogens. For oxidation states +4 and above, only the tetrafluoride, pentafluoride and hexafluoride are known. Iridium hexafluoride, IrF6, is a volatile and highly reactive yellow solid, composed of octahedral molecules. It decomposes in water and is reduced to IrF4, a crystalline solid, by iridium black. Iridium pentafluoride has similar properties but it is actually a tetramer, Ir4F20, formed by four corner-sharing octahedra. Iridium metal dissolves...

Question: What are the electrons that the ternary hydride Mg6lr2H11 are believed to contain?
the IrH4−5 and the 18-electron IrH5−4 anion