Neutral and cationic (pyrazolylmethyl)pyridine palladium(II) complexes: kinetics and chemoselectivity studies in hydrogenation of alkenes and alkynes

作者：Ojwach Stephen O^*; Ogweno Aloice O

来源：Transition Metal Chemistry, 2016, 41(5): 539-546.

DOI：10.1007/s11243-016-0050-7

Reactions of (3,5-dimethylpyrazolylmethyl)pyridine (L1) and (3,5-diphenylpyrazolylmethyl)pyridine (L2) with either [PdCl2(NCMe)(2)] or [PdClMe(COD)] afforded the respective neutral palladium complexes, [PdCl2(L1)] (1), [PdCl2(L2)] (2) and [PdClMe(L1)] (3). Treatment of complex 1 with equimolar amounts of PPh3 or PPh3/NaBAr4 produced the corresponding cationic complexes [Pd(L1)ClPPh3]Cl (4) and [Pd(L1)ClPPh3]BAr4 (5), respectively. Complexes 1-5 formed active catalysts in hydrogenation of alkenes and alkynes. Isomerization reactions were predominant in the hydrogenation reactions of terminal alkenes, while hydrogenation of alkynes involved a two-step process via alkene intermediates prior to the formation of the respective alkenes. The lack of induction periods in the hydrogenation reactions in addition to pseudo-first-order kinetics with respect to the substrates established the homogeneous nature of the active species.

• 出版日期2016-8