¹⁰³Rh NMR spectroscopy and its application to rhodium chemistry

Abstract

Rhodium is used for a number of large processes that rely on homogeneous rhodium-catalyzed reactions, for instance rhodium-catalyzed hydroformylation of alkenes, carbonylation of methanol to acetic acid and hydrodesulfurization of thiophene derivatives (in crude oil). Many laboratory applications in organometallic chemistry and catalysis involve organorhodium chemistry and a wealth of rhodium coordination compounds is known. For these and other areas, 103Rh NMR spectroscopy appears to be a very useful analytical tool. In this review, most of the literature concerning 103Rh NMR spectroscopy published from 1989 up to and including 2003 has been covered. After an introduction to several experimental methods for the detection of the insensitive 103Rh nucleus, a discussion of factors affecting the transition metal chemical shift is given. Computational aspects and calculations of chemical shifts are also briefly addressed. Next, the application of 103Rh NMR in coordination and organometallic chemistry is elaborated in more detail by highlighting recent developments in measurement and interpretation of 103Rh NMR data, in relation to rhodium-assisted reactions and homogeneous catalysis. The dependence of the 103Rh chemical shift on the ligands at rhodium in the first coordination sphere, on the complex geometry, oxidation state, temperature, solvent and concentration is treated. Several classes of compounds and special cases such as chiral rhodium compounds are reviewed. Finally, a section on scalar coupling to rhodium is provided.

Probing the stereo‐electronic properties of cationic rhodium complexes bearing chiral diphosphine ligands by 103Rh NMR

“…[8] Given the advances in high-field NMR and the development of reverse detection methods, acquisition of NMR data of the so-called low-γ nuclei has been greatly facilitated. This is peculiarly true for 103 Rh NMR where improvement in NMR probe and detection field has allowed a better comprehension [9] of the 103 Rh chemical shifts. A pioneer in this field is von Philipsborn.…”

Applications of heteronuclear NMR spectroscopy in biological and medicinal inorganic chemistry

“…Unfortunately, low receptivity, negative magnetogyric ratio and very long relaxation times (>50 s) are major drawbacks. A recent survey of 103 Rh NMR spectroscopy has been published [178], but no studies of biological relevance appear to have been reported.…”

Nuclear Magnetic Resonance Spectroscopy in Homogeneous Hydrogenation Research

“…This makes it difficult to relate, for example, the geometry around a metal with its chemical shift [13]. It is this local effect that makes it possible to use NMR as a structural characterization tool.…”

“…For example, the magnitude of the 1 J RhH coupling constant provides information about the degree of s-character of the bond [13]. Both the magnitude of the coupling constant and the multiplicity (which reflects the number of (equivalent) nuclei that couple) are important.…”