A simple synthesis of trans-RuCl(Ctriple bond; length of mdashCR)(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(Ctriple bond; length of mdashCC6H4R-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(Ctriple bond; length of mdashCC6H4OMe-4)(dppe)2 (3b), trans-RuCl(Ctriple bond; length of mdashCC6H4Me-4)(dppe)2 (3c) and trans-RuCl(Ctriple bond; length of mdashCC6H4CO2Me-4)(dppe)2 (3e) are described. A facile and reproducible synthesis of cis-1 is also reported.