Journal of the American Chemical Society, Vol.130, No.28, 8904-8904, 2008
Divalent dirhodium imido complexes: Formation, structure, and alkyne cycloaddition reactivity
Dirhodium amido complexes [(Cp*Rh)(2)(mu(2)-NHPh)(mu(2)-X)] (X = NHPh (2), Cl(3), OMe(4); Cp* = eta(5)-C5Me5) were prepared by chloride displacement of [Cp*Rh(mu(2)-Cl)](2) (1) and have been used as precursors to a dirhodium imido species [Cp*Rh(mu 2-NPh)RhCp*]. The imido species can be trapped by PMe3 to give the adduct [Cp*Rh(mu(2)-NPh)Rh(PMe3)Cp*] (5) and undergoes a formal [2 + 2] cycloaddition reaction with unactivated alkynes to give the azametallacycles [Cp*Rh(mu(2)-eta(2):eta(3)-(RCCRNPh)-C-1-N-2)RhCp*] (R-1 = R-2 = Ph (6a), R-1 = H, R-2 = t-Bu (6b), R-1 = H, R-2 = p-tol (6c)). Isolation of a relevant unsaturated imido complex [Cp*Rh(mu(2)-NAr)RhCp*] (7) was achieved by the use of a sterically hindered LiNHAr (Ar = 2,6-diisopropylphenyl) reagent in a metathesos reaction with 1, X-ray structures of 2, 6a, 7 and the terminal isocyanide adduct [Cp*Rh(mu(2)-NAr)Rh(t-BuNC)Cp*] (8) are reported.