Reactivity of [Cp∗Rh(η6-C6H3NH2-2,6-i-Pr2)](OTf)2 toward phosphines and alkynes

The cationic aniline complex [Cp∗Rh(η6-2,6-(Me2CH)2C6H3NH2)](OTf)2 (1) was prepared from either [Cp∗Rh(η2-NO3)(η1-OTf)] or [Cp∗Rh(OH2)3](OTf)2 and 2,6-diisopropylaniline. Complex 1 underwent substitution with phosphines or phosphites, indicating the labile character of the η6-aniline ligand. Complex 1 mediated cycloaddition reactions of several alkynes in refluxing ethanol: the [2 + 2] dimerization for Phsingle bondCtriple bond; length of mdashCsingle bondPh and the [2 + 2 + 1] trimerization for Phsingle bondCtriple bond; length of mdashCsingle bondH and CH3C6H4single bondCtriple bond; length of mdashCsingle bondH. The unexpected cyclobutadiene complex [Cp∗Rh(η4-C4(C(O)CH3)2H(SiMe3))] was obtained from complex 1 and Me3Sisingle bondCtriple bond; length of mdashCsingle bondCtriple bond; length of mdashCsingle bondSiMe3 and structurally characterized by X-ray diffraction.