With the volume and accessibility of scientific research increasing across the world, it has never been more important to continue building the reputation for quality and ethical publishing we’ve spent the past two centuries establishing. Formula: C7H9N
Synthetic and kinetic studies of the reactions between (Fe(1-5-eta-C6H7)(CO)3)+ (1) and X-substituted pyridines (X=H, 2-Me, 3-Me, 4-Me, 4-Ph, 2-Cl, 3-CN, 2,5-Me2, 2,6-Me2, 3,5-Me2, or 2,4,6-Me3) in CH3CN provide the first quantitative information on the importance of basicity and steric properties in controlling amine nucleophilicity towards co-ordinated ?-hydrocarbons.The products are pyridinium adducts of tricarbonyl(hexa-1,3-diene)iron.Similar pyridinium adduct formation occurs with cations (Fe(1-5-eta-2-MeOC6H6)(CO)3)+ (2) and (Fe(1-5-eta-C7H9)(CO)3)(BF4) (3).The general rate law rate = k1(Fe)(amine) is observed, except for the equilibrium reaction of (1) with 3-cyanopyridine which gives rate = k1 (Fe)(amine) + k-1 (Fe).The rate trend C6H7 > 2-MeOC6H6 > C7H9 found with several pyridines and the low DeltaH1<*> and large negative DeltaS1<*> values are consistent with direct addition to the dienyl rings.For attack of non-sterically crowded pyridines on (1), a Bronsted plot of log k1 versus pKa of the amine conjugate acid has a high slope alpha of 1.0, indicating a very marked dependence of rate on amine basicity.Successive blocking of the 2- and 6-positions of pyridine by methyl groups leads to marked non-additive steric retardation.
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Reference：
Chiral nitrogen ligands in late transition metal-catalysed asymmetric synthesis—I. Addressing the problem of ligand lability in rhodium-catalysed hydrosilations,
Nitrogen-Containing Ligands for Asymmetric Homogeneous and Heterogeneous Catalysis