Related Products of 492-08-0, The reaction rate of a catalyzed reaction is faster than the reaction rate of the uncatalyzed reaction at the same temperature.492-08-0, Name is (+)-Sparteine, molecular formula is C15H26N2. In a Article£¬once mentioned of 492-08-0
Characterization of a rhodium-sparteine complex, [((-)-sparteine) Rh(eta4-COD)]+: Crystal structure and DNMR/DFT studies on ligand-rotation dynamics
A cationic rhodium-sparteine complex, [((-)-sparteine)Rh(eta4- COD)]+ (1+; COD = 1,5-cyclooctadiene) was obtained, isolated as its tetrafluoroborate salt (1BF4), and characterized using X-ray crystallography and multinuclear (1H, 13C) NMR spectroscopy. This is the first structurally characterized sparteine complex of rhodium. The Rh-N bonds are unusually long (2.214(3) and 2.242(3) A), apparently due to steric repulsion between COD and sparteine. 1H NMR exchange experiments (EXSY) demonstrate a dynamic process that results in an overall 180 rotation of the COD methine protons in solution (CD 2Cl2) with a first-order rate constant of 460 s -1 at the coalescence temperature (314 K) and interpolated rate constant of 150 s-1 at 298 K. Temperature-dependent NMR studies yield DeltaH? = 13.0 ¡À 0.3 kcal mol-1, DeltaS? = -5 ¡À 1 cal mol-1 K-1, such that DeltaG?298 = 14.3 ¡À 0.3 kcal mol-1. DFT studies (B3LYP) indicate that the loosely bound (-)-sparteine ligand rotates through a pseudo-tetrahedral transition state where both ligands are rotated approximately 90 relative to each other. While both ligands remain bound (eta4-COD, kappa2-sparteine), bonding to sparteine is weakened much more than bonding to COD in the transition state. DFT computed DeltaG?298 and DeltaS? values (15.55 kcal mol -1 and -2.67 cal mol-1 K-1, respectively) agree very well with the experimental values. Attempts to find alternative mechanisms involving partial dechelation of COD and (-)-sparteine yielded slightly higher barriers along with positive DeltaS values for intermediate formation.
We¡¯ll also look at important developments in the pharmaceutical industry because understanding organic chemistry is important in understanding health, medicine, the role of 492-08-0, and how the biochemistry of the body works.Related Products of 492-08-0
Reference£º
Chiral nitrogen ligands in late transition metal-catalysed asymmetric synthesis¡ªI. Addressing the problem of ligand lability in rhodium-catalysed hydrosilations,
Nitrogen-Containing Ligands for Asymmetric Homogeneous and Heterogeneous Catalysis