Rhodium carbonyl complexes containing pyridine carboxylic acid ligands: Reactivity towards various electrophiles and catalytic activity

Review of Acetic Acid Synthesis from Various Feedstocks Through Different Catalytic Processes

“…A phosphine ligand is preferentially chosen in most of these studies because the phosphorous ligands have some capabilities to change the characteristics of transition metals with a lower oxidation state and to the softness of the incorporated phosphorous atoms, which are well-known in a field of coordination chemistry [38][39][40][41][42]. In addition, some ligands containing nitrogen atoms have been also attracted for the preparation of rhodium-based homogeneous catalysts due to their facile adjustment of binding energy in both high and low oxidation states [43].…”

“…Therefore, the nitrogen containing metal ligands with a strong r-donor capability can enhance the nucleophilicity of the Rh(I) center which in turn increases the catalytic activity of the rhodium complexes for a carbonylation of methanol to AA. Based on these characteristics, some investigations of the rhodium complexes containing pyridine (Py) species such as Py-2-COOH, Py-3-COOH, Py-4-COOH ligands and the different types of benzyl pyridine ligands have been largely investigated to verify the ligand effects for a liquid-phase carbonylation of methanol to AA [38,40]. By using those modified rhodium-based homogeneous catalysts, a reasonable catalytic performance was observed as summarized in Table 3.…”

Dicarbonylrhodium(I) Complexes of Bipyridine Ligands with Proximate H‐Bonding Substituents and Their Application in Methyl Acetate Carbonylation

“…[37][38][39] Noteworthy, Dutta and co-workers have recently reported improved catalytic behaviour of rhodium catalysts for methanol carbonylation, when monodentate pyridine ligands with carboxylic acid substituents were employed. [40] The coordination chemistry of ligands with proximate acidic or basic functionalities and their application in homogeneous catalysis has been an ongoing theme in our laboratory. Previously, we have reported on the application of such ligands in the context of alkane oxidation, [41][42][43] and very recently we have communicated our first results on methyl acetate carbonylation.…”

Rhodium(I) carbonyl complexes of quinoline carboxaldehyde ligands and their catalytic carbonylation reaction

“…Since nitrogen atoms have no low lying vacant d-orbital available to accept back donation from the metal centre and thus, nitrogen donor ligands use only s-donor electrons. This imparts more ionic character to the metal-ligand bonds [17] and hence makes the metal centre more susceptible to oxidative addition, which is the key step in carbonylation reaction [17e19]. The oxygen atom, being hard donor, confers stability to metal at high oxidation state in the oxidative addition reaction [17].…”

“…This imparts more ionic character to the metal-ligand bonds [17] and hence makes the metal centre more susceptible to oxidative addition, which is the key step in carbonylation reaction [17e19]. The oxygen atom, being hard donor, confers stability to metal at high oxidation state in the oxidative addition reaction [17]. Thus, the different hardness and donor properties of ligands containing N and O donor sites may offer advantages in catalysis.…”