99770-94-2Relevant academic research and scientific papers
Rapid phosphorus(III) ligand evaluation utilising potassium selenocyanate
Muller, Alfred,Otto, Stefanus,Roodt, Andreas
, p. 650 - 657 (2008/09/17)
Oxidative addition of SeCN- to tertiary phosphine ligands has been investigated in methanol at 298 K by use of UV-Vis stopped-flow and conventional spectrophotometry. In most cases kobsvs. [SeCN -] plots were linear with zero intercepts corresponding to a rate expression of kobs = k1[SeCN-]. Reactions rates are dependent on the electron density of the phosphorus centre with k 1 varying by five orders of magnitude from 1.34 ± 0.02 × 10-3 to 51 ± 3 mol-1 dm3 s-1 for P(2-OMe-C6H4)3 to PCy3 respectively. Activation parameters range from 27 ± 1 to 49.0 ± 1.3 kJ mol-1 for ΔH? and -112 ± 9 to -140 ± 3 J K-1 mol-1 for ΔS ? supporting a SN2 mechanism in which the initial nucleophilic attack of P on Se is rate determining. Reaction rates are promoted by more polar solvents supporting the mechanistic assignment. Reasonable linear correlations were observed between log k1vs. pKa, 1JP-Se and χd values of the phosphines. The reaction rates are remarkably sensitive to the steric bulk of the substituents, and substitution of phenyl rings in the 2 position resulted in a decrease in the reaction rate. The crystal structures of SePPh2Cy and SePPhCy2 have been determined displaying Se-P bond distances of 2.111(2) and 2.1260(8) respectively. The Royal Society of Chemistry 2008.
Remarkable ligand effect in Ni- And Pd-catalyzed bisthiolation and bisselenation of terminal alkynes: Solving the problem of stereoselective dialkyldichalcogenide addition to the C≡C bond
Ananikov, Valentine P.,Gayduk, Konstantin A.,Beletskaya, Irina P.,Khrustalev, Victor N.,Antipin, Mikhail Yu.
body text, p. 2420 - 2434 (2009/04/08)
We have developed two new catalytic systems based on Ni and Pd complexes to solve the challenging problem of dialkyldichalcogenide (Alk2E 2; E = S, Se) addition to alkynes. A comparative study of two catalytic systems - Ni/PMe2Ph and Pd/PCy2Ph - has revealed that the Ni catalyst is superior with respect to high catalytic activity and more general scope relative to the Pd system. A novel synthetic methodology was developed for the preparation of (Z)-bis(alkylthio)alkenes and (Z)-bis(alkylseleno)alkenes from terminal alkynes with excellent stereoselectivity and high yields.
