Preparation of the palladium(II) dimethylamide Pd(2,6-(Ph2PCH2)(2)C6H3)(NMe2) at low temperatures and its ligand exchange with the dicyclohexylamide

Abstract

The title complex Pd(2,6-(Ph2PCH2)(2)C6H3)(NMe2) (2) has been prepared from deprotonation of [Pd(2,6-(Ph2PCH2)(2)C6H3)(NHMe2)]OTf (1) by a stoichiometric amount of dicyclohexylamide anion at low temperatures. VT NMR experiments showed that 2 was stable below -10 degrees C, and slowly underwent decomposition to give a couple of unidentified species at elevated temperatures. However, the reaction of 1 with an excess of lithium dicyclohexylamide (> ten equivalents) generated the monomeric palladium(II) hydride (2,6-(Ph2PCH2)(2)C6H3)PdH (3). The reaction of (Ph2PCH2)(2)C6H3)Pd(OTf) with an excess of lithium dicyclohexylamide also produced the hydride. A d(8)-THF solution of 3 was stable for 16 h at ambient temperature. However, an attempt to isolate 3 resulted in the formation of a small amount of the hydride-bridged dipalladium [(Pd(2,6-(Ph2PCH2)(2)C6H3))(2)(mu-H)(+)] (4) and mostly decomposed species. (C) 1999 Elsevier Science S.A. All rights reserved.