Low valent magnesium compounds
A number of stable low valent magnesium compounds containing a metal-metal, Mg-Mg, bond, where magnesium exhibits the formal oxidation state of +1 are known. These compounds generally have the formula L2Mg2, where L represents a bulky ligand.[1] The first examples of these stable magnesium(I) compounds were reported in 2007.[2] The chemistry of Mg is dominated by the +2 oxidation state and prior to 2007 only examples of crystalline compounds with short Mg-Mg distances that may indicate an Mg-Mg bond were known, such as the ternary metal hydrides Mg2RuH4, Mg3RuH3, and Mg4IrH5 and magnesium diboride,[3] Calculations had also indicated the stability of the Mg22+ cation[4]
The preparation of the first compounds made involved the reduction of MgII iodine complexes with potassium metal and the bulky ligands were:[2]
- a guanidinate, "priso", [(Ar)NC(NPri2)N(Ar)]− where Ar = 2,6-diisopropylphenyl and Pri = iso-propyl
- a ketiminate, "nacnac", {[(Ar)NC(Me)]2CH}−,- where Ar = 2,6-diisopropylphenyl and Me = methyl
Both examples have the formula L2Mg2, where L represents the bulky anionic bidentate ligand.[2] X-ray crystallographic studies showed an Mg-Mg bond length of 285.1 pm and 284.6 pm.[2] Theoretical studies indicate an essentially ionic formulation Mg22+(L−)2.[2] 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).
Since then a variety of stable Mg(I) compounds have been prepared, some melting over 200 °C, some colorless, others colored, but all involving very bulky ligands.[1] Also complexes of the LMgMgL with monodentate ligands have been prepared and in these the coordination of the Mg atom increases from three to four.[1] The magnesium(I) dimers have proved to be useful reducing agents, for example in the preparation of tin(I) compounds.[5]
References
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- ↑ 2.0 2.1 2.2 2.3 2.4 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found. – via ScienceDirect (Subscription may be required or content may be available in libraries.)
- ↑ .Lua error in package.lua at line 80: module 'strict' not found. – via ScienceDirect (Subscription may be required or content may be available in libraries.)
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
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