Synthese der ersten quadratisch-planaren Vinyliden-Komplexe des Vaska-Typs. Kristall- und Molekülstruktur von trans-[RhCl(=C=CHMe)(PPri 3)2] / Synthesis of the First Square-planar Vinylidene Complexes of the Vaska Type. Crystal and Molecular Structure of trans-[RhCl(=C=CHMe)(PPri 3)2

Abstract

Square-planar vinylidene rhodium complexes trans-[RhCl( = C=CHR)(PPri 3)2] (X-XII) are prepared either by isomerization of trans-[RhCl(RC≡CH)(PPri 3)2] in hexane at 50 °C or by elimination of pyridine from RhHCl(C≡CR)(py)(PPri 3)2 in benzene at room temperature. The Xray structural analysis of XI (R = CH3) reveals that the CI-Rh=C=C fragment is almost linear, and that the planes formed by these atoms and C3 (carbon atom of the CH3 substituent) and by these atoms and P1 , P2 are perpendicular to each other. The Rh = C bond length is surprisingly short (177.5(6) pm) and supports the assumption that vinylidenes like CO are strong π-acceptor ligands.