Reactivity of [CpRh(η-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 PhCCPh and the [2 + 2 + 1] trimerization for PhCCH and CH₃C₆H₄CCH. The unexpected cyclobutadiene complex [Cp^∗Rh(η⁴-C₄(C(O)CH₃)₂H(SiMe₃))] was obtained from complex 1 and Me₃SiCCCCSiMe₃ and structurally characterized by X-ray diffraction.