Addition von Phosphanen an das C α-Atom von allenyliden(pentacarbonyl)chrom und umlagerung in phosphan-komplexe

Abstract

The allenylidene(pentacarbonyl)chromium complex (CO) 5Cr[C=C=C(C 6H 4NMe 2- p) 2] ( 1a) adds phosphines PR 3 at the C α atom to give ylide complexes, (CO) 5Cr-[C(PR 3=C=C(C 6 H 4NMe 2- p) 2] (PR 3 = PMe 3 ( 3), PHPh 2 ( 3), PH 2Mes ( 7) (Mes = C 6H 2Me 3-2,4,6)). At room temperature complex 3 slowly rearranges to the allenylphosphine complex (CO) 5Cr-PPh 2[CH=C=C(C 6H 4NMe 2- p) 2] ( 4). The structure of 4 was established by an X-ray structure analysis. The adduct 7 obtained from 1a and PH 2Mes, however, could not be detected. It immediately isomerizes to the alkynylphosphine complex (CO) 5Cr-PH(Mes)[C≡C-CH(C 6H 4NMe 2- p) 2] ( 8). At room temperature the ylide complex 5, formed by addition of PHPh 2 to the C α atom of the allenylidene complex (CO) 5Cr=C=C=C( o-C 6 H 4) 2O ( 1b), rearranges in CH 2Cl 2 in the presence of excess PHPh 2 to give a binuclear bisphosphine complex ( 6). 6 corresponds to the product of the chemo-, regio- and stereo-selective dimerization of the allenylphosphine complex analogous to 4.