Low valent magnesium compounds

Two low valent magnesium compounds have been discovered that are the first examples of stable magnesium(I) compounds.[1] Both examples have the formula L2Mg2, where L represents a bulky anionic ligand.[1] X-ray crystallographic studies show an Mg-Mg bond length of 285.1 pm and 284.6 pm.[1] Theoretical studies indicate an essentially ionic formulation Mg22+(L−)2.[1] The Mg22+ ion is the group 2 analogue of the group 12 Hg22+ (present in e.g. mercury(I) chloride) and Cd22+ ions (present in cadmium(I) tetrachloroaluminate). The preparation involved the reduction of MgII iodine complexes with potassium metal and the bulky ligands were[1]:

The chemistry of Mg is dominated by the +2 oxidation state and up to this point the ternary metal hydrides Mg2RuH4, Mg3RuH3, and Mg4IrH5 and magnesium diboride,[2] MgB2 with short Mg-Mg bonds (293 pm, 303 pm, 275 pm, 308pm respectively)[2] [3] had been assumed to contain an Mg2 unit. Calculations had also indicated the stability of the Mg22+ cation[4]

References

  1. ^ a b c d e Green, S. P.; Jones C.; Stasch A. (December 2007). "Stable Magnesium(I) Compounds with Mg-Mg Bonds". Science 318 (5857): 1754–1757. doi:10.1126/science.1150856. PMID 17991827. 
  2. ^ a b King, R. Bruce (October 2002). "Chemical bonding topology of superconductors. 5. The similarities between magnesium diboride and cuprate superconductors and the role of subvalent magnesium". Polyhedron 21 (23): 2347–2350. doi:10.1016/S0277-5387(02)01183-X. 
  3. ^ R. Bruce King,(1994),"Hydrides: Solid state transition metal complexes" in Encyclopedia of Inorganic chemistry,John Wiley & Sons, ISBN 0-471-93620-0
  4. ^ .Hogreve, H. (August 2004). "Mg22+: a long-lived metastable dication". Chemical Physics Letters 394 (1–3): 32–36. doi:10.1016/j.cplett.2004.06.099.