Synthesis and catalytic applications of ruthenium(ii)–phosphino-oxime complexes

Abstract

In this work, the preparation of the first ruthenium complexes containing a phosphino-oxime ligand is presented. Thus, the reaction of cis-[RuCl₂(DMSO)₄] (3) with 2.4 equivalents of 2-Ph₂PC₆H₄CHNOH (1) in refluxing THF led to the clean formation of the octahedral ruthenium(II) derivative cis,cis,trans-[RuCl₂{κ²-(P,N)-2-Ph₂PC₆H₄CHNOH}₂] (5), whose structure was unambiguously confirmed by means of a single-crystal X-ray diffraction study. Complex 5 could also be synthesized from the reaction of the dimer [{RuCl(μ-Cl)(η⁶-p-cymene)}₂] (4) with an excess of 1 in refluxing toluene. Treatment of 4 with 2 equivalents of 1, in CH₂Cl₂ at r.t., allowed also the preparation of the half-sandwich Ru(II) derivative [RuCl{κ²-(P,N)-2-Ph₂PC₆H₄CHNOH}(η⁶-p-cymene)][PF₆] (6). In addition, complexes 5 and 6 proved to be active catalysts for the rearrangement of aldoximes to primary amides, as well as for the α-alkylation/reduction of acetophenones with primary alcohols, with the former showing the best performances in both processes.