A simple synthesis of trans-RuCl(CCR)(dppe)2 complexes and representative molecular structures

The five-coordinate complex [RuCl(dppe)₂]OTf ([2]OTf) is obtained in high yield by the sequential reduction of RuCl₃ · nH₂O to RuCl₂(PPh₃)₃, subsequent phosphine substitution to give trans-RuCl₂(dppe)₂ (trans-1) and finally chloride abstraction (AgOTf, CH₂Cl₂). The use of [2]OTf as an entry point to mono-acetylide complexes trans-RuCl(CCC₆H₄R-4)(dppe)₂ (3) is described, and represents an alternative route to the long-standing methods based on cis-RuCl₂(dppe)₂ (cis-1), which is always prepared as a mixture with the more thermodynamically stable trans isomer when prepared by phosphine substitution reactions of RuCl₂(dmso)₄. The molecular structures of [2]OTf, trans-RuCl(CCC₆H₄OMe-4)(dppe)₂ (3b), trans-RuCl(CCC₆H₄Me-4)(dppe)₂ (3c) and trans-RuCl(CCC₆H₄CO₂Me-4)(dppe)₂ (3e) are described. A facile and reproducible synthesis of cis-1 is also reported.