Organorhodium chemistry

Organorhodium chemistry is the chemistry of organometallic compounds containing a rhodium-carbon chemical bond, and the study of rhodium and rhodium compounds as catalysts in organic reactions.

Stable organorhodium compounds and transient organorhodium intermediates are used as catalyst such as in olefin hydroformylation, olefin hydrogenation, olefin isomerization and the Monsanto process

Organometallic rhodium compounds share many characteristics with those of cobalt (see organocobalt compounds), which is also in group 9. Rhodium can exist in oxidation states of -III to +IV, but rhodium(I) and rhodium(III) are the most common. Rhodium(I) compounds (d⁸ configuration) can occur with square planar or trigonal bipyramidal geometries, while rhodium (III) compounds (d⁶ configuration) typically have an octahedral geometry.

Important homoleptic rhodium compounds are tetrarhodium dodecacarbonyl Rh₄(CO)₁₀ and hexadecacarbonylhexarhodium Rh₆(CO)₁₆. The hexarhodium compound is less preferred due to poor solubility. Both are important catalysts in hydroformylation of alkenes often accompanied by a phosphine ligand:

Nitrobenzene reduction is another reaction catalysed by this compound type:

Cyclooctadiene rhodium chloride dimer [RhCl(COD)]₂ is investigated for its use in C-H bond activation. Sandwich compounds of rhodium, such as rhodocene, and half-sandwich compounds like [(η⁵-Cp)Rh(CO)₂] are well known.

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