Substitution of labile triflate in [(triphos)Re(CO)₂(OTf)]: a new synthetic route to mononuclear and dinuclear Re^I complexes

New synthetic routes to the neutral complex [(triphos)Re(CO)₂(OTf)] [triphos=MeC(CH₂PPh₂)₃, OTf=CF₃SO₃^-] (3) are reported. The triflate ligand in 3 is labile and can be easily replaced by different halides and pseudohalides (CN^-, N₃^-, SCN^-, SeCN^-, OCN^-) to give new mononuclear octahedral Re^I complexes of formula [(triphos)Re(CO)₂(X)] (X=Cl^-, Br^-, I^-, CN^-, N₃^-, SCN^-, SeCN^-, OCN^-). In some cases, when a double proportion of 3 is treated with the appropriate pseudohalide, rare examples of binuclear Re^I complexes featuring a single bridging pseudohalide ligand, [{(triphos)Re(CO)₂}₂(µ-X)]Y (X=CN^-, N₃^-, SCN^-, SeCN^-; Y=OTf, BPh₄^-), have been obtained. All of the new Re^I complexes have been characterized by conventional spectroscopic methods and by electrochemical and spectroelectrochemical techniques. Selected examples of regioselective electrophilic alkylations of both halide and pseudohalide ligands are also reported. Noticeably, selective methylation of [(triphos)Re(CO)₂(η¹-X-XCN)] (X=S, Se) affords the complexes [(triphos)Re(CO)₂{η¹-X-X(Me)(CN)}]OTf, which contain the unprecedented methylsulfocyanate and methylselenocyanate ligands.