The new pincer ligand 1,6-bis((tert-butylphosphino)methyl)-1,3,5-cycloheptatriene is metalated by Ir(CO) x Cl at the 7-position to give a pincer complex. This complex when treated with LiBEt 3 H gives a mixture of products which result from the unusual migration of both an ethyl group and the replacement of the chlorine atom with a hydride. Individual components of the mixture can be prepared separately by treatment of the pincer complex with NaH to give dehydrochlorination followed by a prototopic rearrangement and NaBEt 4 , which generates the corresponding ethyl derivative.

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Selenophosphinito complexes (OC)4Mn(η2‐Se\documentclass{article}\usepackage{amsmath}\pagestyle{empty}\begin{document}$ \dddot - $\end{document}PR21) (2a, b) [R1 = cyc‐Hex (a), tBu (b)] are formed by the reaction of BrMn(CO)5 with the phosphane selenides R21HPSe (1a, b) in the presence of the auxiliary base Et(iPr)2N. According to an X‐ray structural analysis, 2a crystallizes in the space group \documentclass{article}\pagestyle{empty}\begin{document}$ P\bar 1 $\end{document} with Z = 2. The dimeric complex [(OC)4Mn(μ‐Se\documentclass{article}\usepackage{amsmath}\pagestyle{empty}\begin{document}$ \dddot - $\end{document}PMe2)]2 (4c) is not obtained in a straightforward way. Compound 4c is only obtained via the intermediate Br(OC)4Mn–Se\documentclass{article}\usepackage{amsmath}\pagestyle{empty}\begin{document}$ \dddot - $\end{document}P(H)Me2 (3c) by HBr elimination with nBuLi. Complex 3c is formed by replacement of carbon monoxide in BrMn(CO)5 by Me2HPSe (1c). A dissociative equilibrium between [(OC)4 Mn(μ‐Se\documentclass{article}\usepackage{amsmath}\pagestyle{empty}\begin{document}$ \dddot - $\end{document}PMe2)]2 (4c) and the monomeric species (OC)4Mn(\documentclass{article}\usepackage{amsmath}\pagestyle{empty}\begin{document}$ \dddot - $\end{document}2‐Se\documentclass{article}\usepackage{amsmath}\pagestyle{empty}\begin{document}$ \dddot - $\end{document}PMe2) was not observed. The cyclocotrimerization of the >P\documentclass{article}\usepackage{amsmath}\pagestyle{empty}\begin{document}$ \dddot - $\end{document}Se function with the activated alkynes ZCCZ [Z = CO2R2; R2 = Me (d), Et (e), iPr (f), cyc‐Hex (g)] was successful only in the case of the cyclohexyl derivative 2a to give the selenaphosphamanganabicycloheptadienes 5d – g. An X‐ray structural analysis proved that 5d crystallizes in the space group \documentclass{article}\pagestyle{empty}\begin{document}$ P\bar 1 $\end{document} with Z = 2. Under CO pressure 5d was degraded to the selenophene 6.