From alkenylphosphane aminoallenylidene ruthenium(II) complexes to highly unsaturated ruthenaphosphabicycloheptene complexes

The alkenylaminoallenylidene complex [Ru(η5-C9H7){CCC(NEt2)[C(Me)CPh2]}{κ(P)-Ph2PCH2CHCH2}(PPh3)][PF6] (2) has been prepared by the reaction of the allenylidene [Ru(η5-C9H7)(CCCPh2){κ(P)-Ph2PCH2CHCH2}(PPh3)][PF6] (1) with the ynamine MeCCNEt2. The reaction proceeds regio- and stereoselectively, and the insertion of the ynamine takes place exclusively at the CβCγ bond of the unsaturated chain. The secondary allenylidene [Ru(η5-C9H7){CCC(H)[C(Me)CPh2]}{κ(P)-Ph2PCH2CHCH2}(PPh3)][PF6] (3) is obtained, in a one-pot synthesis, from the reaction of aminoallenylidene 2 with LiBHEt3 and subsequent treatment with silica. Moreover, the addition of an excess of NaBH4 to a solution of the complex 2 in THF at room temperature gives exclusively the alkynyl complex [Ru(η5-C9H7){CCCH2[C(Me)CPh2]}{κ(P)-Ph2PCH2CHCH2}(PPh3)] (5). The heating of a solution of allenylidene derivative 3 in THF at reflux gives regio- and diastereoselectively the cyclobutylidene complex [Ru(η5-C9H7) (PPh3)][PF6](4) through an intramolecular cycloaddition of the CC allyl and the CαCβ bonds in the allenylidene complex 3. The structure of complex 4 has been determined by single crystal X-ray diffraction analysis.

Novel unsaturated allenylidene and aminoallenylidene alkenylphosphane ruthenium(II) complexes are reported. A highly unsaturated ruthenaphosphabicycloheptene system, bearing an exocyclic butadienyl group, is synthesized by the diastereoselective intramolecular [2+2] cycloaddition between the allyl CC and CαCβ bonds of the allenylidene precursor.Figure optionsDownload as PowerPoint slide