Reduction-induced o-C–H bond activation of pyridine with decamethylzirconocene dichloride
摘要:
Treatment of decamethylzirconocene dichloride (eta(5)-Cp*)(2)ZrCl2 with amalgamated magnesium in pyridine results in formation of the o-C-H bond activation product [eta 5-C5Me5](2)ZrH[eta(2)-KC,N-C5H4N] (1). X-ray diffraction analysis (solid state) and NMR spectroscopy data (solutions) reveal the lateral positioning of the nitrogen atom in 1. At elevated temperatures, complex I smoothly rearranges into its isomer 2 with medial positioning of the N-atom. The parameters of equilibrium between 1 and 2 were measured at different temperatures. A reaction of I or a mixture of 1 and 2 (ca. 1:10) with CDCl3 smoothly and under mild conditions leads to one and the same eta(2)-pyridyl chloride complex [eta(5) -C5Me5](2)ZrCl[eta(2)-kappa C,N-C5H4N] (3) with medial positioning of the N-atom. The thermodynamic and mechanistic concepts of the paper are discussed with application of the DFT computational data. (C) 2007 Elsevier Ltd. All rights reserved.
Reduction-induced o-C–H bond activation of pyridine with decamethylzirconocene dichloride
摘要:
Treatment of decamethylzirconocene dichloride (eta(5)-Cp*)(2)ZrCl2 with amalgamated magnesium in pyridine results in formation of the o-C-H bond activation product [eta 5-C5Me5](2)ZrH[eta(2)-KC,N-C5H4N] (1). X-ray diffraction analysis (solid state) and NMR spectroscopy data (solutions) reveal the lateral positioning of the nitrogen atom in 1. At elevated temperatures, complex I smoothly rearranges into its isomer 2 with medial positioning of the N-atom. The parameters of equilibrium between 1 and 2 were measured at different temperatures. A reaction of I or a mixture of 1 and 2 (ca. 1:10) with CDCl3 smoothly and under mild conditions leads to one and the same eta(2)-pyridyl chloride complex [eta(5) -C5Me5](2)ZrCl[eta(2)-kappa C,N-C5H4N] (3) with medial positioning of the N-atom. The thermodynamic and mechanistic concepts of the paper are discussed with application of the DFT computational data. (C) 2007 Elsevier Ltd. All rights reserved.