Donorsubstituierte Cyclobutenyliden–Komplexe und Cyclobutenone aus Vinyliden–Komplexen und elektronenreichen Alkinen

Abstract

Donor–Substituted Cyclobutenylidene Complexes and Cyclobutenones from Vinylidene Complexes and Electron–Rich AlkynesPentacarbonyl(vinylidene) complexes of chromium and tungsten, (CO)5MCC(R1)R2 (1) [MW: R1R2Ph (a), R1  tBu, R2Et (b), Me (c); MCr: R1tBu, R2Me (d)] react with 1‐(diethylamino)‐1–propyne by regiospecific addition of the CC bond of the alkyne to the CαCβ bond of the vinylidene ligand to form the cyclobutenylidene complexes 2a–d. Oxidative cleavage of the cyclobutenylidene ligand from 2a–d gives the corresponding cyclobutenones. The reactions of 1b with bis(diethylamino)acetylene and of 1a with 1–ethoxy–1‐propyne afford the cyclobutenylidene complexes 3b and 4a, respectively. In contrast, 1a reacts with diorganylcyanamides, NCNR2 (RMe, Et, iPr), by ligand displacement and formation of tetraphenylbutatriene and diorganyl–cyanamide complexes. The structures of 2c and 4a were established by X–ray analyses.