Addition von Phosphanen an das Cα-Atom von Allenyliden(pentacarbonyl)chrom und Umlagerung in Phosphan-Komplexe

Abstract

The allenylidene(pentacarbonyl)chromium complex (CO)5Cr[C=C=C(C6H4NMe2-p)2] (1a) adds phosphines PR3 at the Cα atom to give ylide complexes, (CO)5Cr-[C(PR3=C=C(C6H4NMe2-p)2] (PR3 = PMe3 (3), PHPh2 (3), PH2Mes (7) (Mes = C6H2Me3-2,4,6)). At room temperature complex 3 slowly rearranges to the allenylphosphine complex (CO)5Cr-PPh2[CH=C=C(C6H4NMe2-p)2] (4). The structure of 4 was established by an X-ray structure analysis. The adduct 7 obtained from 1a and PH2Mes, however, could not be detected. It immediately isomerizes to the alkynylphosphine complex (CO)5Cr-PH(Mes)[C≡C-CH(C6H4NMe2-p)2] (8). At room temperature the ylide complex 5, formed by addition of PHPh2 to the Cα atom of the allenylidene complex (CO)5Cr=C=C=C(o-C6H4)2O (1b), rearranges in CH2Cl2 in the presence of excess PHPh2 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.