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

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