α-Diimines as nitrogen ligands for ruthenium-catalyzed allylation reactions and related (pentamethylcyclopentadienyl) ruthenium complexes

The new Cp*Ru(II) (Cp*: pentamethylcyclopentadienyl) complexes Cp*(dab-R)RuCl, [Cp*(dab-R)(MeCN)Ru][PF6] (dab-R: RNdouble bond; length as m-dashCH–CHdouble bond; length as m-dashNR; R: iso-propyl, mesityl), and [Cp*(cod)(MeCN)Ru][PF6], are synthesized in high yields by reacting the corresponding α-diimine or 1,5-cyclooctadiene with [Cp*RuCl]4 and [Cp*(MeCN)3Ru][PF6], respectively. The α-diimine ligands are strongly bonded to the ruthenium centre as shown by the subsequent formation of the alkynyl derivatives Cp*(dab-R)RuCtriple bond; length of mdashCR′ (R′ = tert-butyl or phenyl) and of the cationic derivatives [Cp*(dab-R)(L)Ru][PF6] (L = CO, PMe3). The neutral and cationic α-diimine or 1,5-cyclooctadiene ruthenium complexes are compared as catalyst precursors for the ruthenium-catalyzed allylation of diethyl-sodiomalonate and diethylamine with cinnamyl acetate or ethyl cinnamyl carbonate.