# Are there any significant uses of the compound formed by magnesium and anthracene?

In an unusual reaction, magnesium reacts with anthracene in THF to form a grignard-like compound called, prosaically, magnesium anthracene:

I remember using it briefly in the 1980s. At the time there was speculation about its potential use in both synthesis and as a starting material for hydrogen-storage systems.

Are there any significant current uses of the the unusual complex?

It seems like an idea of using magnesium anthracene systems for the $\ce{MgH2}$ production persisted since 1980s [1] till late 2000s, when new more efficient method with better scalability for industrial use was established.

One of the recent reviews in hydrogen-storage applications [2, p. 220] compares the older two-step process of $\ce{MgH2}$ synthesis:

First, metallic magnesium is dissolved in anthracene to form Mg-anthracene solution. Then, the hydrogenation of the Mg-anthracene solution produces $\ce{MgH2}$ with $\ce{CrCl3}$ or $\ce{TiCl4}$ catalyst.

with the most recent direct synthesis from Mg powders and tablets [3]. Their experimental trial involved the following:

Powder and tablet Mg were placed on trays inside a 50 kg hydrogenation furnace. After purging with Ar, the furnace was ﬁlled with 99.9999% hydrogen with a pressure of less than 2 MPa. The temperature of the process was controlled so as to remain near the boundary between the regions $\ce{\{MgH2\}}$ and $\ce{\{Mg + H2\}}$ in the thermal equilibrium diagram, and maintained for 30–45 h. The hydrogen consumption behavior was monitored by a pressure gauge. Afterward, the furnace was gradually cooled down to room temperature. The hydrogenation yield (%) was calculated via the weight difference of Mg samples before/after the process.

$\ce{MgH2}$ obtained with this method showed a hydrogen yield of around 96% with great reproducibility and scalability, and was proved as industry-ready.

But still, magnesium-anthracene · 3THF is used at a lab-scale in fine organic, organometallic, and inorganic syntheses [4, pp. 300-307]:

• as a source of soluble zerovalent magnesium;
• in preparation of finely-divided metal powders and transition metal complexes;
• catalytic synthesis of Grignard compounds.

### Bibliography

1. Bogdanovic, B. Acc. Chem. Res. 1988, 21 (7), 261–267. DOI 10.1021/ar00151a002.
2. Sasaki, K.; Li, H.-W.; Hayashi, A.; Yamabe, J.; Ogura, T.; Lyth, S. M. Hydrogen Energy Engineering: A Japanese Perspective; Springer Japan: Tokyo, 2016. ISBN 978-4-431-56042-5.
3. Uesugi, H.; Sugiyama, T.; Nii, H.; Ito, T.; Nakatsugawa, I. Journal of Alloys and Compounds 2011, 509, S650–S653. DOI 10.1016/j.jallcom.2010.11.047.
4. Fürstner, A. Active metals: preparation, characterization, applications; VCH: Weinheim; New York, 1996. ISBN 978-3-527-61517-9.
• I don't think it's zerovalent. Jan 23, 2019 at 18:30
• It isn't. Magnesium anthracene has a structure in which the middle ring where the magnesium is attached has lost its planarity, as if it were no longer aromatic. Transferring electrons from the magnesium into the anthracite would do that. Jul 22 at 2:00