Transition metal arene complex
Metal arene complexes are
Synthesis
Fischer–Hafner synthesis
Also known as reductive Friedel–Crafts reaction, the Fischer–Hafner synthesis entails treatment of metal chlorides with arenes in the presence of
Direct synthesis
By metal vapor synthesis, metal atoms co-condensed with arenes react to give complexes of the type M(arene)2. Cr(C6H6)2 can be produced by this method.[1]
Cr(CO)6 reacts directly with benzene and other arenes to give the
- BrMn(CO)5 + Ag+ + C6R6 → [Mn(C6R6)(CO)3]+ + AgBr + 2 CO
From hexadienes
Few Ru(II) and Os(II) complexes react directly with arenes. Instead, arene complexes of these metals are typically prepared by treatment of M(III) precursors with
Alkyne trimerization
Metal complexes are known to catalyze
Structure
In most of its complexes, arenes bind in an η6 mode, with six nearly equidistant M-C bonds. The C-C-C angles are unperturbed vs the parent arene, but the C-C bonds are elongated by 0.2 Å. In the fullerene complex Ru3(CO)9(C60), the fullerene binds to the triangular face of the cluster.[5]
η4- and η2-Arene complexes
In some complexes, the arene binds through only two or four carbons, η2 and η4 bonding, respectively. In these cases, the arene is no longer planar. Because the arene is dearomatized, the uncoordinated carbon centers display enhanced reactivity. A well studied example is [Ru(η6-C6Me6)(η4-C6Me6)]0, formed by the reduction of [Ru(η6-C6Me6)2]2+. An example of an [Os(η2-C6H6)(NH3)5)]2+.[6]
Reactivity
When bound in the η6 manner, arenes often function as unreactive
Particularly from the perspective of organic synthesis, the decomplexation of arenes is of interest. Decomplexation can often be induced by treatment with excess of ligand (MeCN, CO, etc).[4]
References
- ^ .
- .
- .
- ^ ISBN 978-3-540-01604-5.
- .
- PMID 29064228.