Magnesium iron hexahydride

Magnesium iron hexahydride
Names
	Other names dimagnesium iron hexahydride
Identifiers
CAS Number	89959-23-9 ;
3D model (JSmol)	Interactive image;
	InChI InChI=1S/Fe.2Mg.6H/q3* 2;6*-1 Key: VJOPJGZJJZUMMB-UHFFFAOYSA-N;
	SMILES [Mg 2].[Mg 2].[FeH6-4];
Properties
Chemical formula	FeH6Mg2
Molar mass	110.503 g·mol−1
Appearance	green solid
Density	2.74 g/cm3
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Magnesium iron hexahydride is an inorganic compound with the formula Mg₂FeH₆. It is a green diamagnetic solid that is stable in dry air. The material is prepared by heating a mixture of powdered magnesium and iron under high pressures of hydrogen:^[1]

2 Mg Fe 3 H₂ → Mg₂FeH₆

Structure

Interaction between one (of four) MgBr(thf)₂ centers and FeH₆^4-.

The compound is isomorphous with K₂PtCl₆, i.e., their connectivities and structures are the same. The [FeH₆]⁴⁻ centre adopts octahedral molecular geometry with Fe-H distances of 1.56 Å. The Mg² centres are bound to the faces of the octahedron, with Mg-H distances of 2.38 Å. Several related compounds are known including salts of [RuH₆]⁴⁻, [OsH₆]⁴⁻, and [PtH₆]²⁻ anions.^[2]

Soluble derivatives

Although Mg₂FeH₆ is not soluble in ordinary solvents, related derivatives are. For example, the related salt Mg₄Br₄(THF)₄FeH₆ is soluble as are related alkoxides. Measurements on such compounds suggest that the hydride ligand exerts a weaker crystal field than cyanide.^[3]

References

^ J. J. Didisheim, P. Zolliker, K. Yvon, P. Fischer, J. Schefer, M. Gubelmann, A. F. Williams "Dimagnesium iron(II) hydride, Mg₂FeH₆, containing octahedral FeH₆⁴⁻ anions" Inorganic Chemistry 1984, vol. 23, pp 1953–1957. doi:10.1021/ic00181a032.
^ Robert Bau, Mary H. Drabnis "Structures of transition metal hydrides determined by neutron diffraction" Inorganica Chimica Acta 1997, vol. 259, 27ff.doi:10.1016/S0020-1693(97)89125-6
^ R.B. King "Structure and bonding in homoleptic transition metal hydride anions" Coordination Chemistry Reviews, 2000, vol. 200–202, p. 813–829. doi:10.1016/S0010-8545(00)00263-0

[1] J. J. Didisheim, P. Zolliker, K. Yvon, P. Fischer, J. Schefer, M. Gubelmann, A. F. Williams "Dimagnesium iron(II) hydride, Mg₂FeH₆, containing octahedral FeH₆⁴⁻ anions" Inorganic Chemistry 1984, vol. 23, pp 1953–1957. doi:10.1021/ic00181a032.

[2] Robert Bau, Mary H. Drabnis "Structures of transition metal hydrides determined by neutron diffraction" Inorganica Chimica Acta 1997, vol. 259, 27ff.doi:10.1016/S0020-1693(97)89125-6

[3] R.B. King "Structure and bonding in homoleptic transition metal hydride anions" Coordination Chemistry Reviews, 2000, vol. 200–202, p. 813–829. doi:10.1016/S0010-8545(00)00263-0

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