Cyclometallated Ir(III), Rh(III) and Ru(II) complexes as catalysts for the cyclotrimerisation of 1,6-diynes with monoynes

Abstract

A new series of Rh, Ir and Ru precatalysts for the [2+2+2] cyclotrimerisation of 1,6-diynes with monoynes is reported. The precatalysts are reduced in situ to the active catalysts by reduction with alcohols. The precatalysts activity is in the order Ru>Rh>Ir which reflects the ease of this reduction. The Rh and Ir precatalysts require temperature in excess of 140 oC allowing their preparation in 2-methoxymethanol at 125 oC. The mechanism of this process is discussed.