Structurally-defined potassium-mediated regioselective zincation of amino- and alkoxy-substituted pyridines

摘要

The new synergic base [PMDETA K(TMP)(Et)Zn(Et)] selectively zincates 4-(dimethylamino)pyridine at the 2-position and 4-methoxypyridine at the 3-position, to afford bimetallic potassium pyridylzinc complexes each displaying a novel, but remarkably different, structure.rnA senior citizen of the organometallic world, potassium zincate chemistry first emerged 150 years ago through Wank-lyn's epochal report of the synthesis of "potassium ethyl", (KZnEt_3), and its sodium congener.1'2 The first structural determination of a potassium zincate, a powder diffraction study of the tetraethynyl zincate salt, [K_2Zn(C ≡ CH)_4], by Weiss and Wolfrum, also appeared early in the history of organometallic structural chemistry in 1968. Surprisingly, in the intervening years to the present, conspicuously few potassium zincates have been crystallographically characterised.4 Underlining this underdevelopment, potassium cyclopenta-dienylzincate, [KZn(C_5H_5)_3], which one might have thought (erroneously) was a known, classical zincate compound was actually only synthesised and its crystal structure elucidated as recently as 2007.