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Fe3(CO)12 is a dark green solid, which vacuum-sublimes with significant decomposition at elevated temperatures. It is soluble in nonpolar organic solvents to give intensely green solutions. Most low nuclearity clusters are pale yellow or orange. Heating solutions of Fe3(CO)12 affords iron mirrors, which can be pyrophoric in air. The solid decomposes slowly in air, and thus samples are typically stored cold under an inert atmosphere.
It was occasionally obtained from the thermolysis of Fe(CO)5:
Traces of the compound are easily detected because of its characteristically deep green color. UV-photolysis of Fe(CO)5 produces Fe2(CO)9, not Fe3(CO)12.
An efficient synthesis of Fe3(CO)12 proceeds via the reaction of Fe(CO)5 with base:
followed by oxidation of the resulting hydride with acid:
Fe3(CO)12 features a triangle of Fe atoms surrounded by 12 CO ligands. Ten of the CO ligands are terminal and two span an Fe---Fe edge, resulting in an overall C2v point group symmetry. In contrast, Ru3(CO)12 and Os3(CO)12 adopt D3h-symmetric structures, wherein all 12 CO ligands are terminally bound to the metals. Overall, it can be appreciated that these three clusters formally arise from condensation of three 16-electron M(CO)4 fragments, akin to the condensation of CH2 into cyclopropane.
Elucidation of the structure of Fe3(CO)12 proved to be challenging because the CO ligands are disordered in the crystals. Early evidence for its distinctive C2v structure came from Mößbauer spectroscopic measurements that revealed two quadrupole doublets with similar isomer shifts but different (1.13 and 0.13 mm/s) quadrupole coupling constants.
Like most metal carbonyl, Fe3(CO)12 undergoes substitution reactions, making, for example, Fe3(CO)11(P(C6H5)3.
Fe3(CO)12 reacts with 1,3-propanedithiol to air-stable µ-(1,3-Propanedithiolato)-hexacarbonyldiiron in which both thiol sulfur atoms form a bridge between two iron atoms. This compound is a model compound for certain all-iron dehydrogenases .
Fe3(CO)12, like all metal carbonyls is hazardous as a source of volatile iron and as a source of carbon monoxide. Solid samples, especially when finely divided, and residues from reactions can be pyrophoric, which can ignite the organic solvents used for such reactions.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Triiron_dodecacarbonyl". A list of authors is available in Wikipedia.|