Rh(I) Complexes in Catalysis: A Five-Year Trend

Abstract

Rhodium is one of the most used metals in catalysis both in laboratory reactions and industrial processes. Despite the extensive exploration on “classical” ligands carried out during the past decades in the field of rhodium-catalyzed reactions, such as phosphines, and other common types of ligands including N-heterocyclic carbenes, ferrocenes, cyclopentadienyl anion and pentamethylcyclopentadienyl derivatives, etc., there is still lively research activity on this topic, with considerable efforts being made toward the synthesis of new preformed rhodium catalysts that can be both efficient and selective. Although the “golden age” of homogeneous catalysis might seem over, there is still plenty of room for improvement, especially from the point of view of a more sustainable chemistry. In this review, temporally restricted to the analysis of literature during the past five years (2015–2020), the latest findings and trends in the synthesis and applications of Rh(I) complexes to catalysis will be presented. From the analysis of the most recent literature, it seems clear that rhodium-catalyzed processes still represent a stimulating challenge for the metalloorganic chemist that is far from being over.

Overview of the Synthesis and Catalytic Reactivity of Transition Metal Complexes Based on C═P Bond Systems

“…This group includes metals whose complexes often find many applications, including those involving catalytic − and biological , processes. Their phosphaalkene variants also exhibit many properties.…”

Hydroformylation of Alkenes over Phosphorous-Free Rhodium Supported on N-Doped Silica

“…Hydroformylation (oxo process), discovered by Otto Roelen as far back as 1938, is still widely used to produce aldehydes, which can further be converted into alcohols, ethers and esters, carboxylic acids, aliphatic amines, and other derivatives with high added value [1]. The modern industrial hydroformylation process is based on homogeneous rhodium systems [2][3][4][5]. However, one of the main problems of homogeneous hydroformylation has long been the difficulty of the recovery of the catalyst from the reaction mixture and the purification of the catalyst.…”

Rhodium(I)-Catalyzed Formate-Mediated Domino Heck/1,4-Hydride Addition toward Oxindoles

“…For these reasons, we were interested in further investigating rhodium-catalyzed Heck-type cyclization processes, with an emphasis on utilizing inexpensive, safe, and abundant formate salts. Development of such reactions is potentially challenging due to the necessity of controlling the selectivity of the insertion into the C­(sp 2 )–X, or the conjugated olefin, suggesting that ligand choice would be crucial . Furthermore, the presence of a hydride source could result in the irreversible and unproductive reductive processes at various points in the catalytic cycle .…”