PREPARATION, STRUCTURE AND REACTIVITY OF AMINOCARBENE COMPLEXES OF CHROMIUM AND MOLYBDENUM DERIVED FROM PRIMARY AMINES

The synthesis and reactivity towards diphenylacetylene of a series of aminocarbene complexes of general structure (CO)5M = C(NHR')R (M = Cr, R = CH3, Ph, R' = cyclohexyl, cyclopropyl, benzyl) are described: they lead by alkyne insertion followed by a 1,4 hydrogen shift, to imine complexes, which, upon hydrolysis, give the corresponding ketones. When R' = CH2Ph, along with the expected imine, a tetraphenylcyclopentadiene resulting from the coupling of two PhC = CPh and of a carbene moiety, is formed; its structure has been determined by an X-ray study. In the case of aminopyridine, bidentate carbene complexes (the structure of which was confirmed by an X-ray study of (CO)4Cr = C-(CH3)NHNC5H5) are formed, and these also react with PhC = CPh to give, for M = Mo, new pyrrolinones through alkyne/CO insertion followed by a 1,2 hydrogen shift.