Oxidative dehydrodimerization of rhenium vinylidene complex (η5-C5H5)(CO)2Redouble bond; length as m-dashCdouble bond; length as m-dashC(H)Ph: two competitive routes of coupling of σ-phenylethynyl intermediate [(η5-C5H5)(CO)2Resingle bondCtriple bond; len

The oxidation of the rhenium vinylidene complex (η5-C5H5)(CO)2Redouble bond; length as m-dashCdouble bond; length as m-dashC(H)Ph (2) with one equivalent of AgBF4 or (C5H5)2FeBF4 leads to the radical cation [(η5-C5H5)(CO)2Redouble bond; length as m-dashCdouble bond; length as m-dashC(H)Ph]+radical dot (2+radical dot) which undergoes dehydrodimerization only in the presence of triethylamine affording a mixture of the binuclear compounds (η5-C5H5)(CO)2Redouble bond; length as m-dashCdouble bond; length as m-dashC(Ph)C(Ph)double bond; length as m-dashCdouble bond; length as m-dashRe(CO)2(η5-C5H5) (6, 55%) and [(η5-C5H5)(CO)2Re]2(μ2-Cdouble bond; length as m-dashC(Ph)Ctriple bond; length of mdashCPh) (9, 22%). Both 6 and 9 are believed to arise via competitive Cβ–Cβ and Cβ–Re couplings of the intermediate σ-phenylethynyl radicals [(η5-C5H5)(CO)2Resingle bondCtriple bond; length of mdashCPh]radical dot (5radical dot). The former process directly yields 6and the latter one produces 9 after reductive elimination and a 1,2-shift of the metal containing moiety. The enthalpies of Cβ–Cβ (−30.3 kcal/mol) and Cβ–Re (+0.3 kcal/mol) coupling processes estimated by DFT calculations are in accordance with the 6:9 ratio observed. The electrochemical behavior of 2, 6, 9 was studied by cyclic voltammetry. The X-ray structures of 2 and 9 are reported.