Effects of Axial Solvent Coordination to Dirhodium Complexes on the Reactivity and Selectivity in C–H Insertion Reactions: A Computational Study

Abstract

Density functional theory calculations were used to systematically explore the effects of axial ligation by solvent molecules on the reactivity and selectivity of dirhodium tetracarboxylates with diazo compounds in the context of C-H insertion into propane.Insertions on three types of diazo compounds-acceptor/acceptor, donor/acceptor, and donor/donor-promoted by dirhodium tetraformate were tested with and without axial solvent ligation for no surrounding solvent, dichloromethane, isopropanol, and acetonitrile. Magnitudes, origins, and consequences of structural and electronic changes arising from axial ligation were characterized. The results suggest that axial ligation affects barriers for N2 extrusion and C-H insertion, the former to a larger extent.

Elucidating the Electronic Nature of Rh‐based Paddlewheel Catalysts from 103Rh NMR Chemical Shifts: Insights from Quantum Mechanical Calculations

“…As a consequence, solvent molecules do not coordinate to the metal centers in solution in this case. This steric hindrance is expected to diminish or even cancel the catalytic activity of this complex, as previously suggested in the literature [111] …”

“…This steric hindrance is expected to diminish or even cancel the catalytic activity of this complex, as previously suggested in the literature. [111] Correlation between charge density and 103 Rh NMR chemical shifts Qualitatively, ligands upon increasing donor ability are expected to increase the electron density around the metal centers, resulting in increased shielding. Reducing the ligand donor power, on the other hand, should cause deshielding due to more positive partial charge at Rh.…”

Reactivity of a fluorine-containing dirhodium tetracarboxylate compound with proteins

“…43 The origin of the effects of axial ligand coordination to dirhodium centre is related to structural and electronic changes of the Rh–Rh core arising from axial ligation. 44…”

Effect of Tethered, Axially Coordinated Ligands (TACLs) on Dirhodium(II,II) Catalyzed Cyclopropanation: A Linear Free Energy Relationship Study

“…For example, using additives such as tetramethyl urea or Hünig’s base resulted in improvements in O–H insertion reactions, but the use of 4-dimethylaminopyridine (DMAP) in cyclopropanation reactions resulted in significantly slower reactions. , On the other hand, DMAP is instrumental for high yield and stereoselectivity in the rhodium-nitrenoid mediated amination of thioethers. − Recently, Davies and co-workers reported improved asymmetric cyclopropanation of heteroaryl carboxylates using a 2-chloropyridine additive that binds to the axial site, though the exact effect this additive has on enantioselectivity was not extensively explored . Lately, there have been renewed efforts to pursue an increased understanding on the role of axial coordination in carbene transfer reactions …”

“…Downward curving Hammett plots are associated with a shift in the rate-determining step (RDS) in the mechanism. , In dirhodium­(II,II)-catalyzed cyclopropanations, the nitrogen extrusion step to make carbenoid 19 is considered the RDS (Figure ). ,,− Axial coordination likely contributes to destabilizing the diazo addition step, but kinetic experiments are needed to confirm whether formation of species 18 becomes the new slow-step (Figure ).…”