Reaction paths in the cyclopalladated NN-dialkylbenzylamine–substituted styrene system in acetic acid as solvent. The structure of palladated 2-dialkylaminomethylstilbenes

Abstract

The reaction between di-µ-chlorobis(NN-dialkylbenzylamine-2C,N)dipalladium(II)(1) and a para-substituted styrene at 50°C in 1 : 1 benzene–acetic acid affords 2-dialkylaminomethylstilbene (2) and its ring-palladated derivative di-µ-chlorobis(2-dialkylaminomethylstilbene-6C′,N)dipalladium(II)(3). The structure of (3) was established on the basis of ¹H n.m.r. measurements. The relative amounts of (2) and (3) formed are strongly dependent both on the atmosphere and the presence of alkali-metal perchlorates. Free (2) dominates under argon, but (3) under oxygen. The salts MClO₄(M = Na, Li) accelerate the reaction markedly. Formation of (2) is a Fujiwara–Moritani or Heck-type reaction, but at least two paths contribute to the appearance of (3) : (i) direct metallation of (2) by reoxidized palladium(II) and (ii) an exchange reaction between (1) and (2) affording (3).