One Electron Changes Everything: Synthesis, Characterization, and Reactivity Studies of [Re(NCCH 3 ) 6 ] 3 .

Oxidation of [Re(NCCH 3 ) 6 ] 2+ with the thianthrene radical cation results in the formation of [Re(NCCH 3 ) 6 ] 3+ , one of the very rare cases of a fully solvated +3 complex. It was fully characterized by spectroscopy and X-ray structure analysis. In contrast to its reduced analogue, [Re(NCCH 3 ) 6 ] 3+ exhibits a much faster CH 3 CN exchange. Hence, substitution reactions proceed at 20 °C within minutes. Its potential as a versatile precursor for Re III chemistry was examined with a series of substitution reactions. The more lipophilic analogue [Re(NCPh) 6 ] 3+ was synthesized by nitrile exchange in benzonitrile (NCPh). The Re(II) analogue of [Re(NCPh) 6 ] 3+ , [Re(NCPh) 6 ] 2+ , forms by Ag I -mediated oxidation of in situ formed [Re(η 6 -C 6 H 6 )(NCPh 3 ) 3 ] + in NCPh. The same synthetic strategy is feasible for the synthesis of [Re(NCCH 3 ) 6 ] 2+ as well. [Re(NCCH 3 ) 6 ] 3+ reacts with 1,4,7-trithiacyclononane (C 6 H 12 S 3 ) to yield sevenfold-coordinated [Re(κ 3 -C 6 H 12 S 3 ) 2 (NCCH 3 )] 3+ . The reaction of [Re(NCCH 3 ) 6 ] 3+ with 1 equiv of (NBu 4 )X produces the Re III monohalide complexes [ReX(NCCH 3 ) 5 ] 2+ (X = Cl, Br, I). Mixed Re III dihalides ( trans -[ReXY(NCCH 3 ) 4 ] + ) were obtained by treating [ReX(NCCH 3 ) 5 ] 2+ with a second equivalent of (NBu 4 )Y (if X = Cl, Y = Br, I; if X = Br, Y = I). Because of this fast CH 3 CN exchange, [Re(NCCH 3 ) 6 ] 3+ is a very suitable precursor for new Re III complexes.